CN108753342B

CN108753342B - Fischer-Tropsch method in micro-channel reactor

Info

Publication number: CN108753342B
Application number: CN201810323334.0A
Authority: CN
Inventors: S·C·莱文斯; F·达利; L·理查德; S·鲁米尼
Original assignee: Velocys Inc
Current assignee: Velocys Inc
Priority date: 2012-10-22
Filing date: 2013-09-11
Publication date: 2021-05-18
Anticipated expiration: 2033-09-11
Also published as: KR101804283B1; KR101607847B1; CN105451873B; CN105451873A; KR20160040307A; KR20150073158A; CN108753342A

Abstract

The disclosed invention relates to a process for conducting a fischer-tropsch reaction comprising flowing a reactant mixture comprising fresh synthesis gas and tail gas in a microchannel reactor in contact with a catalyst derived from a catalyst precursor comprising cobalt and a surface-modified catalyst support to form at least one hydrocarbon product.

Description

Fischer-Tropsch method in micro-channel reactor

The application is a divisional application of a Chinese patent application with the application date of 2013, 9 and 11, and the application number of 201380042156.X, and the name of the invention is 'Fischer-Tropsch method in a microchannel reactor'.

According to 35 u.s.c. § 119(e), priority is claimed for U.S. provisional application 61/716,772 filed 10, 22/2012. British patent application No.1214122.2, filed 8, 7, 2012, is also claimed in accordance with 35 u.s.c. § 119 (d). These applications are incorporated herein by reference.

Technical Field

The present invention relates to a Fischer-Tropsch process and more particularly to a Fischer-Tropsch process carried out in a microchannel reactor.

Background

The Fischer-Tropsch reaction involves the reaction of a catalyst comprising H₂And CO are converted into one or more hydrocarbon products.

Disclosure of Invention

The present invention relates to a process for carrying out the fischer-tropsch reaction, comprising: flowing the reactant mixture in a microchannel reactor in contact with a catalyst to form a product comprising at least one higher molecular weight hydrocarbon product; the catalyst is derived from a catalyst precursor comprising cobalt, a promoter such as Pd, Pt, Rh, Ru, Re, Ir, Au, Ag and/or Os, and a surface-modified support, wherein the surface of the support is modified by treatment with silica, titania, zirconia, magnesia, chromia, alumina or a mixture of two or more thereof; wherein the products further comprise a tail gas, at least a portion of which is separated from the higher molecular weight hydrocarbon products and combined with fresh syngas to form the reactant mixture in which the volume ratio of the fresh syngas to the tail gas is from about 1:1 to about 10:1, or from about 1:1 to about 8: 1, or from about 1:1 to about 6: 1, or from about 1:1 to about 4:1, or from about 3: 2 to about 7: 3, or about 2: 1; the reactant mixture comprises H₂And CO, in the reactant mixture, H, based on the concentration of CO in the fresh syngas₂A molar ratio to CO of from about 1.4:1 to about 2: 1, or from about 1.5: 1 to about 2.1:1, or from about 1.6: 1 to about 2: 1, or from about 1.7: 1 to about 1.9: 1; wherein the conversion of CO from fresh syngas in the reactant mixture is at least about 70%, or at least about 75%, or at least about 80%, or at least about 85%, or at least about 90%; and the selectivity to methane in the product is from about 0.01 to 10%, or from about 1% to about 5%, or from about 3% to about 9%, or from about 4% to about 8%.

For CO in the reactant mixture (i.e., CO from fresh syngas plus CO from tail gas combined with fresh syngas), the per pass conversion of CO may be from about 70% to about 90%, or from about 70% to about 85%, or from about 70% to about 80%.

For CO in fresh syngas, the conversion of CO may be from about 88% to about 95%, or from about 90% to about 94%, or from about 91 to about 93%.

The support may comprise a refractory metal oxide, carbide, carbon, nitride or a mixture of two or more thereof. The support may comprise alumina, zirconia, silica, titania, or a mixture of two or more thereof.

The support may comprise TiO₂A modified silica support wherein the support contains at least about 11% by weight TiO₂Or from about 11 to about 30 wt% TiO₂Or from about 15 to about 17 weight percent TiO₂Or about 16 wt% TiO₂。

The surface of the surface-modified support may be amorphous.

The catalyst precursor may comprise cobalt oxide. The cobalt oxide may comprise Co₃O₄。

The microchannel reactor may comprise at least one process microchannel in thermal contact with the heat exchanger, the catalyst being in the process microchannel.

A microchannel reactor may comprise a plurality of process microchannels in which a catalyst is located and a plurality of heat exchange channels.

A microchannel reactor may comprise a plurality of process microchannels in which a catalyst is located and a plurality of heat exchange channels, each heat exchange channel in thermal contact with at least one process microchannel; at least one manifold for flowing a reactant mixture into the process microchannels; at least one manifold for flowing product out of the process microchannels; at least one manifold for flowing a heat exchange fluid to the heat exchange channels; and at least one manifold for flowing the heat exchange fluid out of the heat exchange channels.

A plurality of microchannel reactors may be provided in a vessel, each microchannel reactor comprising a plurality of process microchannels and a plurality of heat exchange channels, catalyst being in the process microchannels, each heat exchange channel being in thermal contact with at least one process microchannel, the vessel being equipped with a manifold for flowing a reactant mixture to the process microchannels, a manifold for flowing product out of the process microchannels, a manifold for flowing a heat exchange fluid to the heat exchange channels, and a manifold for flowing the heat exchange fluid out of the heat exchange channels.

The catalyst may be in the form of a particulate solid. A microchannel reactor comprises one or more process microchannels, and a catalyst may be coated on or grown on the interior walls of the process microchannels. The catalyst may be supported on a support having a flow-through configuration, or a serpentine configuration. The catalyst may be supported on a support having the configuration of foam, felt, agglomerate, fin, or a combination of two or more thereof.

The higher molecular weight aliphatic hydrocarbon product may comprise one or more hydrocarbons boiling at a temperature of at least about 30 ℃ at atmospheric pressure. The higher molecular weight aliphatic hydrocarbon product may comprise one or more hydrocarbons boiling at a temperature above about 175 ℃ at atmospheric pressure. The higher molecular weight aliphatic hydrocarbon product may comprise one or more alkanes and/or one or more alkenes of about 5 to about 100 carbon atoms. The higher molecular weight aliphatic hydrocarbon product may comprise one or more olefins, one or more normal paraffins, one or more isoparaffins, or a mixture of two or more thereof. The higher molecular weight aliphatic hydrocarbon product may be further processed using separation, fractionation, hydrocracking, hydroisomerization, dewaxing, or a combination of two or more thereof. The higher molecular weight aliphatic hydrocarbon product may be further processed to form an oil or middle distillate fuel of lubricating viscosity. The higher molecular weight aliphatic hydrocarbon product may be further processed to form a fuel.

A microchannel reactor may comprise at least one process microchannel and at least one heat exchanger comprising at least one heat exchange channel in thermal contact with the at least one process microchannel, the process microchannel having a fluid flowing therein in one direction, the heat exchange channel having a fluid flowing in a co-current, counter-current, or cross-current direction to the flow of fluid in the process microchannel.

A microchannel reactor may comprise at least one process microchannel and at least one heat exchanger, customized heat exchange features being provided along the length of the process microchannel, the localized release of heat generated by reactions taking place in the process microchannel being matched to the cooling provided by the heat exchanger.

The microchannel reactor may comprise a plurality of process microchannels formed by arranging corrugations between planar sheets. The microchannel reactor may also contain a plurality of heat exchange channels in thermal contact with the process microchannels, the heat exchange channels being formed by arranging corrugations between planar sheets.

The microchannel reactor may comprise a plurality of plates in a stack defining a plurality of fischer-tropsch process layers and a plurality of heat exchange layers, each plate having a peripheral edge, the peripheral edge of each plate being welded to the peripheral edge of the next adjacent plate to provide a peripheral seal for the stack.

The deactivation rate of the catalyst may be less than about 0.2% CO conversion lost per day.

The product may comprise higher molecular weight hydrocarbon products, H₂O and H₂H of the product₂Partial pressure of O is about 3 to about 10 bar, H of the product₂O/H₂The molar ratio is from about 1:1 to about 5:1, and the conversion of CO is from about 70 to about 80%, or from about 70 to about 85%, or from about 80 to about 85%, or from about 82 to about 83%, based on the total reactant mixture fed to the reactor (i.e., the sum of the fresh syngas and the recycled tail gas).

In one embodiment, the present invention can provide a combination of the following advantages and unexpected results:

A) very high overall CO conversion in a single stage microchannel process (in one embodiment about 90% or higher);

B) in one embodiment, (a) is achieved with a ratio of recycled tail gas to fresh syngas of about 0.45 to about 0.50.

C) This allows high CO conversion to be tolerated, which can provide high water partial pressures and high water to hydrogen ratios. Generally, cobalt catalysts can be expected to deactivate rapidly under these conditions.

D) Operating sub-stoichiometry H₂Ratio of/CO (i.e. H)₂the/CO ratio is lower than the stoichiometric consumption ratio (probably about 2.12)). In one embodiment, the tail gas H₂the/CO ratio may be less than about 1.0, which is lower than the tail gas H for which a typical cobalt FT catalyst may be capable of operating₂The ratio of/CO. Generally, cobalt catalysts can deactivate rapidly under these conditions.

E) These results were achieved under both: (1) relatively low operating temperatures (in one embodiment, about 200 ℃ C.). about 210 ℃ C.), and (2) high reaction rates (in one embodiment, catalyst productivity is generally at or above 2,000v/v/hr and is just about 1gm C5+/gm catalyst/hour or higher).

F) Low methane (and other light gases) selectivity is achieved, which means high C₅+ liquid selectivity (e.g., in one embodiment, about 90% or higher).

One problem in the art relates to the fact that: in order to achieve relatively high CO conversion, it is often necessary to employ a two-stage fischer-tropsch reactor. This creates waste and expense. With the present invention, on the other hand, it is possible to achieve relatively high levels of CO conversion with a single-stage reactor at relatively low recycle ratios, due to the fact that: at least a portion of the tail gas produced during the fischer-tropsch process is recycled back to the reactor where it is combined with fresh synthesis gas, and relatively high per pass (total reactor feed) CO conversion can be achieved without accelerating catalyst deactivation. The ratio of recycled tail gas to fresh syngas in the reactant mixture can be about 0.8 or higher.

Drawings

In the drawings, like parts and features have like reference numerals. The various drawings are schematic diagrams that may not necessarily be drawn to scale.

FIG. 1 is a flow diagram showing a particular form of the process of the present invention comprising converting a reactant mixture comprising fresh syngas and recycled tail gas to one or more higher molecular weight hydrocarbons in a microchannel reactor.

FIG. 2 is a schematic view of a vessel for containing a plurality of reactors.

FIGS. 3 and 4 are schematic representations of reactor cores for microchannel reactors used in the process of the present invention.

FIGS. 5 and 6 are schematic diagrams of repeating units that may be used in a microchannel reactor. Each of the repeating units shown in fig. 5 and 6 comprises a fischer-tropsch process microchannel comprising a reaction zone containing a catalyst, and one or more adjoining heat exchange channels. The heat exchange fluid flowing in the heat exchange channels shown in fig. 5 flows in a cross-flow direction relative to the flow of the process fluid in the process microchannels. The heat exchange fluid flowing in the heat exchange channels shown in FIG. 6 may flow in a co-current or counter-current direction to the flow of the process fluid in the process microchannels. Each of these embodiments can provide customized heat exchange characteristics by controlling the number of heat exchange channels in thermal contact with different portions of the process microchannels. With these tailored heat exchange features, more cooling channels may be provided in some portions of the process microchannels than in other portions of the process microchannels. For example, more cooling channels may be provided at or near the inlet of the reaction zone than in the downstream portion of the reaction zone. The heat exchange characteristics may be tailored by controlling the flow rate of the heat exchange fluid in the heat exchange channels. For example, a relatively high rate of flow of heat exchange fluid in heat exchange channels in thermal contact with the inlet of the reaction zone may be used in combination with a relatively low rate of flow of heat exchange fluid in heat exchange channels in thermal contact with a downstream portion of the reaction zone.

FIGS. 7-12 are schematic illustrations of catalysts or catalyst supports that may be used in process microchannels. The catalyst shown in figure 7 is in the form of a bed of particulate solids. The catalyst shown in fig. 8 has a flow-through design. The catalyst shown in fig. 9 has a flow-through structure. Fig. 10-12 are schematic illustrations of fin assemblies that may be used to support a catalyst.

Fig. 13 is a flowchart showing the test operation used in example 2.

FIG. 14 is a schematic representation of a catalyst insert that may be used in a microchannel reactor.

Detailed Description

All range and ratio limits disclosed in the specification and claims may be combined in any manner. It is to be understood that, unless specifically stated otherwise, where "a", "an" and/or "the" are mentioned, one or more than one may be included, and that reference to an item in the singular may also include the plural of that item.

The phrase "and/or" should be understood to mean "either or both" of the elements connected, i.e., that the elements exist in some cases connectively and in other cases connectionless. Unless clearly indicated to the contrary, other elements may optionally be present in addition to the elements specifically identified by the "and/or" phrase, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, when used in conjunction with open-ended language such as "comprising," a reference to "a and/or B" may refer in one embodiment to a without B (optionally including elements other than B); in another embodiment, refers to B without a (optionally including elements other than a); in another embodiment refers to a and B (optionally including other elements); and the like.

The word "or" should be understood to have the same meaning as "and/or" as defined above. For example, when items are separated in a list, "or" and/or "should be understood to mean including, i.e., containing at least one of a plurality or series of elements, but also including more than one of a plurality or series of elements, and optionally including additional unlisted items. The terms "a," "an," and "the" are used interchangeably herein to refer to a term that is used to describe a structure that is not a part of a structure. In general, the term "or" as used herein should be understood to mean an exclusive choice (i.e., "one or the other but not both") only when there is an exclusive term in front of, for example, "either," one of.

The phrase "at least one of," when referring to a series of one or more elements, should be understood to mean at least one element selected from any one or more of the series of elements, without necessarily including at least one of each and every element specifically listed in the series of elements and without excluding any combinations of elements in the series of elements. This definition also allows that elements may optionally be present other than those explicitly identified in the series of elements to which the phrase "at least one" refers, whether related or unrelated to those elements explicitly identified. Thus, as a non-limiting example, "at least one of a and B" (or, equivalently, "at least one of a or B," or, equivalently "at least one of a and/or B") can refer, in one embodiment, to at least one a, optionally including more than one a, with no B present (and optionally including other elements in addition to B); in another embodiment, may refer to at least one B, optionally including more than one B, with no a present (and optionally including other elements in addition to a); in yet another embodiment, may refer to at least one a, optionally including more than one a, and at least one B, optionally including more than one B (and optionally including other elements); and so on.

Transitional words or phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "possessing," and the like are to be understood to be open-ended, i.e., to mean including but not limited to.

The term "microchannel" refers to a channel having at least one internal dimension of a height or width of up to about 10 millimeters (mm), and the height or width is in one embodiment up to about 5mm, and in one embodiment up to about 2mm, and in one embodiment up to about 1 mm. The microchannel may comprise at least one inlet and at least one outlet, wherein the at least one inlet is different from the at least one outlet. The microchannels may not only be holes. The microchannels may not only be channels through the zeolite or mesoporous material. The length of the microchannel may be at least about twice the height or width, and in one embodiment at least about five times the height or width, and in one embodiment at least about ten times the height or width. The internal height or width of the microchannel may be from about 0.05 to about 10mm, or from about 0.05 to about 5mm, or from about 0.05 to about 2mm, or from about 0.05 to about 1.5mm, or from about 0.05 to about 1mm, or from about 0.05 to about 0.75mm, or from about 0.05 to about 0.5mm, or from about 1 to about 10mm, or from about 2 to about 8mm, or from about 3 to about 7 mm. Other internal dimensions of height or width may be any dimension, for example, up to about 3 meters, or about 0.01 to about 3 meters, and in one embodiment, about 0.1 to about 3 meters, or about 1 to about 10mm, or about 2 to about 8mm, or about 3 to about 7 mm. The length of the microchannel may be any dimension, for example, up to about 10 meters, and in one embodiment, from about 0.1 to about 10 meters, and in one embodiment, from about 0.2 to about 6 meters, and in one embodiment, from 0.2 to about 3 meters. The microchannels may have any shape in cross-section, e.g., square, rectangular, circular, semi-circular, trapezoidal, etc. The shape and/or size of the cross-section of the microchannel may vary over its length. For example, the height or width may taper from a relatively large dimension to a relatively small dimension, or vice versa, over the length of the microchannel.

The term "microchannel reactor" refers to an apparatus comprising one or more process microchannels in which a reaction process is carried out. The process may be a fischer-tropsch reaction process. The microchannel reactor may comprise one or more slots for receiving one or more catalyst inserts (e.g., one or more fins or fin assemblies, one or more corrugated inserts, etc.), wherein the process microchannels comprise slots, are disposed in the catalyst inserts, and/or comprise openings formed by the walls of the slots and the inserts. When two or more process microchannels are used, the process microchannels may be operated in parallel. The microchannel reactor may include a header or manifold assembly for providing flow of fluid into one or more process microchannels; and a footer (footer) or manifold assembly to provide for the flow of fluid exiting the one or more process microchannels. The microchannel reactor may comprise one or more heat exchange channels adjacent to and/or in thermal contact with one or more process microchannels. The heat exchange channels can provide cooling to the fluid in the process microchannels. The heat exchange channels may be microchannels. The microchannel reactor may include a main tube or manifold assembly for providing flow of heat exchange fluid into the heat exchange channels; and a tailpipe or manifold assembly providing flow of heat exchange fluid out of the heat exchange channels.

The term "process microchannel" refers to a microchannel in which the process is carried out. The process may be a fischer-tropsch (FT) reaction process.

With respect to the volume within a process microchannel, the term "volume" may include all volumes in the process microchannel through which the process fluid may flow or flow. The volume may comprise a volume within a surface feature that may be disposed in a process microchannel and adapted for flow of a fluid in a flow-through or flow-through manner.

The term "abutting" when referring to the position of one channel relative to another channel may refer to direct abutment such that one or more walls separate the two channels. In one embodiment, both channels may have a common wall. The thickness of the common wall may vary. However, channels that are "contiguous" may not be separated by intervening channels that may interfere with heat transfer between the channels. One channel may be adjacent to the other channel over only a portion of its dimensions. For example, the process microchannels may be longer than and extend beyond one or more adjacent heat exchange channels.

The term "thermal contact" refers to two bodies, e.g., two channels, which may or may not be in physical contact with or abut each other, but still exchange heat with each other. The thermal contact of one body with another may heat or cool the other body.

The term "fluid" refers to a gas, a liquid, a mixture of gas and liquid, or a gas or liquid containing dispersed solids, droplets, and/or gaseous bubbles. The droplets and/or bubbles may have irregular or regular shapes and may be of similar or different sizes.

The terms "gas" and "vapor" may have the same meaning and are sometimes used interchangeably.

The term "residence time" or "average residence time" refers to the internal volume of a space within a channel occupied by a fluid flowing in the space divided by the average volumetric flow rate of the fluid flowing in the space at the temperature and pressure used.

The terms "upstream" and "downstream" refer to positions within a channel (e.g., a process microchannel) or in a process flow diagram relative to the direction of flow of a fluid in the channel or process flow diagram. For example, a channel or a location within a process flow diagram where a portion of a stream flowing toward that location has not yet been reached will be downstream of that portion of the stream. A channel or portion of a process flow diagram that has been traversed by a stream flowing away from a location will be upstream of that portion of the stream. The terms "upstream" and "downstream" do not necessarily refer to a vertical position, as the channels used herein may be oriented horizontally, vertically, or at an oblique angle.

The term "plate" refers to a planar or substantially planar sheet or plate. The plate may be referred to as a shim (shim). The thickness of the plate may be the smallest dimension of the plate and may be up to about 4mm, or from about 0.05 to about 2mm, or from about 0.05 to about 1mm, or from about 0.05 to about 0.5 mm. The plate may have any length and width.

The term "surface features" refers to depressions in the channel walls and/or protrusions of the channel walls that interfere with flow within the channel. The surface features can be circular, spherical, frusto-conical, oblong, square, rectangular, angled rectangular, lattice (checks), V-shaped, blade-shaped, airfoil-shaped, wave-shaped, and the like, as well as combinations of two or more thereof. The surface features may contain sub-features where the main walls of the surface features also contain smaller surface features that may be in the form of notches, waves, scores, voids, burrs, lattices, scallops, or the like. The surface features may have a depth, a width, and for non-circular surface features, a length. Surface features may be formed on or in one or more interior walls of the process microchannels, heat exchange channels and/or combustion channels used in accordance with the methods of the present invention. The surface features may be referred to as passive surface features or passive hybrid features. Surface features can be used to disrupt flow (e.g., disrupt laminar streamlines) and create convective flow at an angle to the general flow direction.

The term "heat exchange channel" refers to a channel having a heat exchange fluid therein that provides heat and/or absorbs heat. The heat exchange channels may absorb heat from or provide heat to adjacent channels (e.g., process microchannels) and/or one or more channels in thermal contact with the heat exchange channels. The heat exchange channels may absorb heat from or provide heat to channels that are adjacent to each other but not adjacent to the heat exchange channels. In one embodiment, one, two, three or more channels may be adjacent to each other and disposed between two heat exchange channels.

The term "heat transfer wall" refers to a common wall between a process microchannel and an adjacent heat exchange channel where heat is transferred from one channel to the other channel through the common wall.

The term "heat exchange fluid" refers to a fluid that can emit heat and/or absorb heat.

The term "wave-shaped" refers to a contiguous piece of material (e.g., thermally conductive material) that is transformed from a planar object to a three-dimensional object. The waveform may be used to form one or more microchannels. The waveform may comprise a right angle corrugated insert which may be sandwiched between opposed planar sheets or shims. The right angle corrugated insert may have rounded edges. In this manner, one or more microchannels may be defined by the waveform on three sides and on the fourth side by one of the planar sheets or shims. The waveforms may be made from any of the materials disclosed herein that may be used to make microchannel reactors. These materials may include copper, aluminum, stainless steel, and the like. The thermal conductivity of the waveform may be about 1W/m-K or higher.

The term "general flow direction" may refer to the vector in a channel through which fluid in an open path may travel.

The term "bulk flow region" may refer to an open area within a microchannel. The contiguous bulk flow region may allow rapid fluid flow through the microchannel without significant pressure drop. In one embodiment, the flow in the bulk flow region may be laminar. The bulk flow region may comprise at least about 5% of the internal volume and/or cross-sectional area of the microchannel, or from about 5% to about 100%, or from about 5% to about 99%, or from about 5% to about 95%, or from about 5% to about 90%, or from about 30% to about 80% of the internal volume and/or cross-sectional area of the microchannel.

The term "open channel" or "flow-through channel" or "open path" refers to a channel (e.g., microchannel) having a gap of at least about 0.01 mm that extends through the entire channel such that fluid can flow through the channel without encountering an obstruction to flow. The gap may extend up to about 10 mm.

The term "cross-sectional area" of a channel (e.g., a process microchannel) refers to the area measured perpendicular to the direction of the overall bulk flow of fluid in the channel and may include all areas within the channel, including any surface features that may be present, but not the channel walls. For a channel that is curved along its length, the cross-sectional area can be measured perpendicular to the direction of bulk flow at a selected point along a line parallel to the length and located at the center of the channel (area center). The height and width dimensions may be measured from one channel wall to the opposite channel wall. These dimensions may not be altered by the application of a coating to the surface of the wall. These dimensions may be averages that take into account variations caused by surface features, surface roughness, and the like.

The term "open cross-sectional area" of a channel (e.g., a process microchannel) refers to the area in the channel that is open to the bulk fluid flow, measured perpendicular to the direction of the bulk flow of the fluid flow in the channel. The open cross-sectional area may not include internal obstructions such as surface features that may be present, and the like.

The term "superficial velocity" with respect to the velocity of a fluid flowing in a channel refers to the velocity of the fluid at the inlet temperature and pressure of the channel divided by the cross-sectional area of the channel.

The term "free stream velocity" refers to the velocity at which the stream flows in the channel at a sufficient distance from the side walls of the channel such that the velocity is at a maximum. If no sliding boundary conditions apply, the velocity of the flow flowing in the channel is zero at the side wall, but increases with increasing distance from the side wall until a constant value is reached. This constant value is the "free stream velocity".

The term "process fluid" as used herein refers to reactants, products and any diluents or other fluids that may flow in a process microchannel.

The term "reaction zone" refers to a space within a microchannel in which a chemical reaction occurs or in which a chemical conversion of at least one substance occurs. The reaction zone may contain one or more catalysts.

The term "contact time" refers to the volume of the reaction zone within a microchannel divided by the volumetric feed flow rate of the reactants at a temperature of 0 ℃ and a pressure of one atmosphere.

The term "fresh synthesis gas" refers to synthesis gas that flows into the microchannel reactor and is used as a reactant for the fischer-tropsch reaction.

The term "tail gas" refers to the gaseous products produced during the fischer-tropsch reaction. The tail gas may contain CO and H₂。

The term "reactant mixture" refers to fresh synthesis gas and tail gas or tail gas components (e.g., CO and H) recycled from the Fischer-Tropsch reaction₂) A mixture of (a).

The term "conversion of CO" refers to the change in moles of CO between the fresh synthesis gas and the product in the reactant mixture divided by the moles of CO in the fresh synthesis gas.

The term "per pass conversion of CO" refers to the conversion of CO from the overall reactant mixture (i.e., fresh syngas plus recycled tail gas or recycled tail gas components) after a single pass through the microchannel reactor.

The term "methane selectivity" refers to the moles of methane in the product minus the moles of methane in the reactant mixture divided by the moles of CO consumed in the reaction.

The term "yield" refers to the moles of product exiting the microchannel reactor divided by the moles of reactants entering the microchannel reactor.

The term "recycle" refers to a single pass of reactants through the microchannel reactor.

The term "staged catalyst" refers to a catalyst having one or more gradients of catalytic activity. The staged catalysts may have different concentrations or surface areas of catalytically active metals. The staged catalyst may have different turnover rates of the catalytically active sites. The staged catalyst may have physical properties and/or form that vary with distance. For example, the staged catalyst may have an active metal concentration of: which is relatively low at the inlet of the process microchannel and increases to a higher concentration near the outlet of the process microchannel, or vice versa; or the concentration of the catalytically active metal is lower nearer the center (i.e., midpoint) of the process microchannel and higher near the walls of the process microchannel, or vice versa, and so forth. The thermal conductivity of the staged catalyst can vary from one location to another within the process microchannels. The surface area of the staged catalyst can be varied by varying the size of the catalytically active metal sites on the constant surface area support, or by varying the surface area of the support, for example by varying the type or particle size of the support. The staged catalyst may have a porous support with a surface area to volume ratio of the support being higher or lower in different sections of the process microchannels, and then the same catalyst coating applied throughout. Combinations of two or more of the foregoing embodiments may be used. The staged catalyst can have a single catalytic component or multiple catalytic components (e.g., a bimetallic or trimetallic catalyst). The staged catalyst may gradually change its properties and/or composition with distance from one location to another within the process microchannels. The graded catalyst may comprise framed particles having a catalytically active metal in an "eggshell" distribution within each particle. The staged catalyst may be staged axially or laterally along the length of the process microchannels. The staged catalysts may have different catalyst compositions, different loading amounts, and/or number of active catalytic sites, which may vary from one location to another within the process microchannel. The number of catalytically active sites may be varied by varying the porosity of the catalyst structure. This can be achieved by using a wash coating process that is capable of depositing varying amounts of catalytic material. One example would be to use different porous catalyst thicknesses along the length of the process microchannels, leaving thicker porous structures where greater activity is desired. Varying porosity can also be applied to fixed or variable porous catalyst thicknesses. A first pore size may be used in the vicinity of the open area or gap for flow, while at least a second pore size may be used in the vicinity of the process microchannel walls.

The term "chain growth" refers to the growth of a molecule resulting from the following reaction: in this reaction, the molecule grows with the addition of a new molecular structure (e.g., in fischer-tropsch synthesis, methylene groups add to the hydrocarbon chain).

The term "aliphatic hydrocarbon" refers to aliphatic compounds such as alkanes, alkenes, alkynes, and the like.

The term "higher molecular weight aliphatic hydrocarbon" refers to an aliphatic hydrocarbon having 2 or more carbon atoms, or 3 or more carbon atoms, or 4 or more carbon atoms, or 5 or more carbon atoms, or 6 or more carbon atoms. The higher molecular weight aliphatic hydrocarbon may have up to about 200 carbon atoms or more, or up to about 150 carbon atoms, or up to about 100 carbon atoms, or up to about 90 carbon atoms, or up to about 80 carbon atoms, or up to about 70 carbon atoms, or up to about 60 carbon atoms, or up to about 50 carbon atoms, or up to about 40 carbon atoms, or up to about 30 carbon atoms. Examples may include ethane, propane, butane, pentane, hexane, octane, decane, dodecane, and the like.

The term "fischer-tropsch" or "FT" refers to a chemical reaction represented by the following equation:

n CO+2n H₂→(CH₂)_n+n H₂O

the reaction is exothermic. n can be any number, for example, 1 to about 1000, or about 2 to about 200, or about 5 to about 150.

The term "fischer-tropsch product" or "FT product" refers to a hydrocarbon product produced by the fischer-tropsch process. The FT liquid product may have a boiling point of about 30 ℃ or above at atmospheric pressure.

The term "FT tail gas" or "tail gas" refers to the gaseous products produced by the fischer-tropsch process. The tail gas may have a boiling point of less than about 30 ℃ at atmospheric pressure. The tail gas may contain H₂And CO.

The term "Co loading" may refer to the weight of Co in the catalyst divided by the total weight of the catalyst, i.e., the total weight of Co plus any Co-catalyst or promoter and any support. If the catalyst is supported on an engineered support structure (such as a foam, felt, mass, or fin), the weight of the engineered support structure may not be included in the calculation. Similarly, if the catalyst is attached to the channel walls, the weight of the channel walls may not be included in the calculation.

The term "mm" may refer to millimeters. The term "nm" may refer to nanometers. The term "ms" may refer to milliseconds. The term "mus" may refer to microseconds. The term "μm" may refer to microns (micrometer or micrometer). The terms "micron" and "micrometer" have the same meaning and are used interchangeably.

All pressures are expressed as absolute pressures unless otherwise indicated.

Method

The term "fresh synthesis gas" refers to a gaseous mixture containing CO and H₂And is not part of the recycled off-gas used during the process of the present invention. The synthesis gas may be referred to as syngas. During the process according to the invention, the fresh synthesis gas is mixed with a gas which also contains H₂And CO to form a reactant mixture for use in the process of the invention. The reactant mixture may comprise H₂And CO, wherein H₂The molar ratio to CO may be from about 1.4:1 to about 2.1:11, or about 1.5: 1 to about 2: 1, or about 1.6: 1 to about 2: 1, or about 1.7: 1 to about 1.9: 1. The fresh synthesis gas may comprise H₂And CO, wherein H₂The molar ratio to CO is from about 1.9: 1 to about 2.1:1, or from about 1.95: 1 to about 2.05: 1, or from about 1.98: 1 to about 2.02: 1. The tail gas generated during the process of the present invention and combined with fresh synthesis gas to form the reactant mixture may be referred to as recycled tail gas. The recirculated tail gas may comprise H₂And CO, wherein H₂The molar ratio to CO is from about 0.5: 1 to about 2: 1, or from about 0.6: 1 to about 1.8: 1, or from about 0.7: 1 to about 1.2: 1. The volume ratio of fresh syngas to tail gas in the reactant mixture may be from about 1:1 to about 10:1, or from about 1:1 to about 8: 1, or from about 1:1 to about 6: 1, or from about 1:1 to about 4:1, or from about 3: 2 to about 7: 3, or about 2: 1.

In an exemplary embodiment, the method of the present invention will first be described with reference to fig. 1. Referring to FIG. 1, a process 100 employs a microchannel reactor 110. The microchannel reactor 110 may be referred to as a fischer-tropsch microchannel reactor. In operation, fresh syngas 120 is combined with recycled tail gas 130 to form reactant mixture 140. The fresh syngas can be combined with the recirculated tail gas upstream of the microchannel reactor 110 (as shown in fig. 1), or combined in the microchannel reactor 110.

In the microchannel reactor 100, a reactant mixture flows through one or more process microchannels, contacting a catalyst to form a product. The catalyst may be referred to as a fischer-tropsch catalyst and the product formed by contact with the fischer-tropsch catalyst may comprise one or more higher molecular weight aliphatic hydrocarbons as well as a tail gas. The reaction is exothermic. The reaction may be controlled using heat exchange fluid flowing through the microchannel reactor 110 as indicated by

arrows

170 and 180. In one embodiment, the heat exchange fluid may comprise steam. The resulting product exits the microchannel reactor 110 as indicated by arrow 150. The tail gas is separated from the product, as indicated by arrow 130, and recycled to be combined with the fresh syngas. If it is desired to adjust the ratio of fresh syngas to tail gas in the reactant mixture, a portion of the tail gas can be separated from the process as indicated by arrow 135. In the case where the tail gas is separated from the products, the remainder of the products (which comprise the higher molecular weight hydrocarbon product(s) and are indicated by arrow 160) are suitable for further processing.

One or more microchannel reactor cores 110 may be housed within the vessel 200. The container 200 has the configuration shown in fig. 2. Referring to FIG. 2, a vessel 200 contains three Fischer-Tropsch microchannel reactor cores 110. Although three microchannel reactor cores are disclosed, it should be understood that any desired number of microchannel reactor cores may be provided in vessel 200. For example, the vessel 200 may contain from 1 to about 100 microchannel reactors 110, or from 1 to about 10, or from 1 to about 3 microchannel reactors 110. The container 200 may be a pressurizable container. The vessel 220 includes inlet and outlet ports 112 that allow reactant flow into the microchannel reactor 110, product flow out of the microchannel reactor 110, and heat exchange fluid flow into and out of the microchannel reactor.

When the vessel 200 is used with a fischer-tropsch microchannel reactor 110, one of the inlets 112 is connected to a manifold provided for flowing the reactant mixture to the fischer-tropsch process microchannels in the microchannel reactor 110. One of the inlets 112 is connected to a manifold provided for flowing a heat exchange fluid (e.g., steam) to the heat exchange channels in the microchannel reactor 110. One of the inlets 112 is connected to a manifold provided for product to flow out of the fischer-tropsch process microchannels in the microchannel reactor 110. One of the inlets 112 is connected to a manifold provided to flow heat exchange fluid out of the heat exchange channels in the microchannel reactor 110.

The vessel 200 may be constructed using any suitable material sufficient to operate at the pressures and temperatures required to operate the fischer-tropsch microchannel reactor 110. For example, the housing 202 of the vessel 200 may be constructed of cast steel. The flange 204, coupling, and piping may be constructed from 316 stainless steel. The container 200 may have any desired diameter, for example, from about 10 to about 1000cm, or from about 50 to about 300 cm. The axial length of the vessel 200 may be any desired value, for example, from about 0.5 to about 50 meters, or from about 1 to about 20 meters.

The microchannel reactor 110 may contain a plurality of fischer-tropsch process microchannels and heat exchange channels stacked or juxtaposed to one another. The microchannel reactor 110 may be in the form of a cube block. This is shown in fig. 3 and 4. These cube blocks may be referred to as microchannel reactor cores 111. Each cube block can have a length of about 10 to about 1000cm, or about 20 to about 200 cm. The width may be from about 10 to about 1000cm, or from about 20 to about 200 cm. The height may be from about 10 to about 1000cm, or from about 20 to about 200 cm.

The microchannel reactor 110 and vessel 200 may be small enough and compact to be easily transportable. Thus, these reactors and vessels, as well as other equipment used in the process of the invention, can be readily transported to remote locations, such as military bases and the like. These reactors and vessels may be used on ships, oil rigs, and the like.

The microchannel reactor 110 may contain a plurality of repeating units, each repeating unit comprising one or more fischer-tropsch process microchannels and one or more heat exchange channels. The repeating units that may be used include repeating

units

210 and 210A shown in fig. 5 and 6, respectively. The microchannel reactor 110 may contain from 1 to about 1000 repeating units 230 or 230A, or from about 10 to about 500 such repeating units. The catalyst used in the

repeat units

210 and 210A can be in any form, including a bed of particulate solids and the various structured forms described below.

Repeat unit 210 is shown in fig. 5. Referring to fig. 5, process microchannels 212 are disposed adjacent to a heat exchange layer 214 containing heat exchange channels 216. The heat exchange channels 216 may be microchannels. A common wall 218 separates the process microchannels 212 from the heat exchange layer 214. Catalyst is disposed in the reaction zone 220 of the process microchannel 212. The reactant mixture (i.e., fresh syngas and recirculated tail gas) flows into the reaction zone 220 in the process microchannels 212 in the direction indicated by arrow 222, contacts the catalyst in the reaction zone, and reacts to form products. The product (i.e., the one or more higher molecular weight aliphatic hydrocarbons and the tail gas) flows out of the process microchannels 210 as indicated by arrow 224. The heat exchange fluid flows through the heat exchange channels 216 in a cross-current direction to the flow of the reactant mixture and product in the process microchannels 212. The fischer-tropsch reaction carried out in the process microchannels 212 is exothermic and the heat exchange fluid provides cooling for the reaction.

Alternatively, the process microchannels and heat exchange channels may be aligned as provided in repeat unit 210A. The repeating unit 210A shown in fig. 6 is the same as the repeating unit 210 shown in fig. 5, except that: the heat exchange channels 216 are rotated 90 and the heat exchange fluid flowing through the heat exchange channels 216 flows in a direction that may be counter current to the flow of reactants and products in the process microchannels 212 or co-current with respect to the direction of reactants and products in the process microchannels 212.

The process microchannels 212 may have any shape in cross-section, for example, square, rectangular, circular, semi-circular, and the like. It is believed that the internal height of each process microchannel 212 is less than the internal dimension perpendicular to the direction of flow of the reactants and products through the process microchannels. Each process microchannel 212 may have an internal height of up to about 10mm, or up to about 6mm, or up to about 4mm, or up to about 2 mm. The height may be from about 0.05 to about 10mm, or from about 0.05 to about 6mm, or from about 0.05 to about 4mm, or from about 0.05 to about 2 mm. The width of each process microchannel 212 can be considered to be the other internal dimension perpendicular to the direction of flow of reactants and products through the process microchannels. The width of each process microchannel 212 can be any dimension, for example, up to about 3 meters, or from about 0.01 to about 3 meters, or from about 0.1 to about 3 meters. The length of each process microchannel 210 can be any dimension, for example, up to about 10 meters, or from about 0.1 to about 10 meters, or from about 0.2 to about 6 meters, or from about 0.2 to about 3 meters, or from about 0.5 to about 2 meters.

The heat exchange channels 216 may be microchannels or they may have large dimensions that may not classify them as microchannels. Each heat exchange channel 216 may have any shape in cross-section, such as, for example, square, rectangular, circular, semi-circular, and the like. It is believed that the internal height of each heat exchange channel 216 is less than the internal dimension perpendicular to the direction of flow of the heat exchange fluid in the heat exchange channel. Each heat exchange channel 216 may have an internal height of up to about 10mm, or up to about 5mm, or up to about 2mm, or from about 0.05 to about 10mm, or from about 0.05 to about 5mm, or from about 0.05 to about 2mm, or from about 0.05 to about 1.5 mm. The width of each of these channels (which would be the other internal dimension perpendicular to the direction of flow of the heat exchange fluid through the heat exchange channels) may be any dimension, for example, up to about 3 meters, or from about 0.1 to about 3 meters. The length of each heat exchange channel 216 may be any dimension, for example, up to about 10 meters, or from about 0.1 to about 10 meters, or from about 0.2 to about 6 meters, or from 0.5 to about 3 meters, or from about 0.5 to about 2 meters.

The number of repeating

units

210 or 210A in the microchannel reactor 110 may be as many as desired, e.g., one, two, three, four, six, eight, ten, hundreds, thousands, tens of thousands, hundreds of thousands, millions, etc.

In the design of a fischer-tropsch microchannel reactor, it may be advantageous to provide tailored heat exchange characteristics along the length of the process microchannels in order to optimize the reaction. This can be achieved by matching the local release of heat evolved by the fischer-tropsch reaction carried out in the process microchannels with the heat removal or cooling provided by the heat exchange fluid in the heat exchange channels in the microchannel reactor. The extent of the fischer-tropsch reaction and the subsequent heat release provided by the reaction may be higher in the front or upstream portion of the reaction zone in the process microchannels than in the rear or downstream portion of the reaction zone. Thus, the matched cooling requirements may be higher in an upstream portion of the reaction zone as compared to a downstream portion of the reaction zone. Customized heat exchange can be achieved by providing more heat exchange or cooling channels, and thus more flow of heat exchange or cooling fluid, in thermal contact with an upstream portion of the reaction zone in the process microchannels than a downstream portion of the reaction zone. Alternatively or additionally, customized heat exchange characteristics may be provided by varying the flow rate of the heat exchange fluid in the heat exchange channels. The flow rate of the heat exchange fluid may be increased in areas where additional heat exchange or cooling is required as compared to areas where less heat exchange or cooling is required. For example, a higher flow rate of heat exchange fluid may be advantageous in heat exchange channels in the process microchannels that are in thermal contact with an upstream portion of the reaction zone as compared to heat exchange channels that are in thermal contact with a downstream portion of the reaction zone. Thus, for example, referring to FIG. 5, a higher flow rate may be used in heat exchange channels 216 near the inlet of the process microchannels 212 or reaction zone 220 than in heat exchange channels 216 near the outlet of the process microchannels 212 or reaction zone 220, which may have a lower flow rate. For optimum performance, the heat transfer from the process microchannels to the heat exchange channels may be designed by selecting the optimum heat exchange channel size and/or flow rate of the heat exchange fluid for each individual heat exchange channel or group of heat exchange channels. Other design alternatives for custom heat exchange may involve the selection and design of a fischer-tropsch catalyst at a particular location within the process microchannels (e.g., particle size, catalyst formulation, packing density, use of a staged catalyst, or other chemical or physical properties). These design alternatives can affect the heat release from the process microchannels and the heat transfer to the heat exchange fluid. The temperature differential between the process microchannels and heat exchange channels, which may provide a driving force for heat transfer, may be constant or may vary along the length of the process microchannels.

The fischer-tropsch process microchannels and heat exchange channels may have rectangular cross-sections and are aligned in side-by-side vertically oriented planes or horizontally oriented stacked planes. These planes may be inclined at an inclination angle to the horizontal. These configurations may be referred to as parallel plate configurations. These channels may be arranged in modular compact units for scaling up. These may be in the form of cube blocks as shown in figures 3 and 4.

The microchannel reactor 110 may be made of any material that provides sufficient strength, dimensional stability, and heat transfer characteristics to allow operation of the desired process. These materials may include aluminum; titanium; nickel; platinum; (ii) rhodium; copper; chromium; alloys of any of the foregoing metals; brass; steel (e.g., stainless steel); quartz; silicon; or a combination of two or more thereof. Each microchannel reactor may be constructed of stainless steel with one or more copper or aluminum corrugations used to form the channels.

Microchannel reactor 110 can be fabricated using known techniques, including electrical discharge machining, conventional machining, laser cutting, photochemical machining, electrochemical machining, die casting, water jet, embossing, etching (e.g., chemical, photochemical, or plasma etching), and combinations thereof.

The microchannel reactor 110 may be constructed by forming a gasket, portions of which are removed to allow flow therethrough. The stack of shims may be assembled via diffusion bonding, laser welding, diffusion brazing, and similar methods to form an integrated device. The microchannel reactor may be assembled using a combination of shims or sheets and partial sheets or strips. In this method, channels or void areas may be formed by assembling strips or partial sheets to reduce the amount of material required.

The microchannel reactor 110 may contain a plurality of plates or gaskets in a stack to define a plurality of fischer-tropsch process layers and a plurality of heat exchange layers, each plate or gasket having a peripheral edge that is welded to the peripheral edge of the next adjacent plate to provide a peripheral seal for the stack. This is shown in us application 13/275,727 filed on 18/10/2011, which is incorporated herein by reference.

The microchannel reactor 110 may be constructed using a wave form in the form of a right angle corrugated insert. These right angle corrugated sheets may have rounded edges rather than sharp edges. These inserts may be sandwiched between opposing planar sheets or shims. This is illustrated in fig. 4. In this way, the microchannels may be defined on three sides by the corrugated inserts and on the fourth side by one of the planar sheets. The process microchannels and heat exchange channels may be formed in this manner. Microchannel reactors prepared using waveforms are disclosed in WO 2008/030467, which is incorporated herein by reference.

The process microchannel may contain one or more surface features in the form of depressions and/or projections on one or more interior walls of the process microchannel. The surface features may be used to disrupt the flow of fluid flowing in the channel. These disturbances to the flow may enhance mixing and/or heat transfer. The surface features may be in the form of a patterned surface. The microchannel reactor may be made by pressing a plurality of shims together. One or both major surfaces of the gasket may contain surface features. Alternatively, the microchannel reactor may be assembled using some sheets or shims and some strips or partial sheets to reduce the total amount of metal required to construct the device. A shim containing surface features may be mated (on opposite sides of the microchannel) to another shim containing surface features. The pairing may result in better mixing or enhancement of heat transfer compared to channels having surface features on only one major surface. The patterning may comprise grooves with diagonal lines, the grooves being provided over substantially the entire width of the surface of the microchannel. The patterned surface feature region of the wall may occupy a portion of or the entire length of the surface of the microchannel. The surface features may be disposed at least about 10%, or at least about 20%, or at least about 50%, or at least about 80% of the length of the channel surface. Each of the diagonal depressions may include one or more angles relative to the flow direction. Features of successive recesses may contain similar or alternating angles relative to surface features of other recesses.

The fischer-tropsch process microchannels may be characterized as having a bulk flow path. The term "bulk flow path" refers to an open path (contiguous bulk flow area) within a process microchannel or combustion channel. The contiguous bulk flow area allows rapid fluid flow through the channel without a large pressure drop. In one embodiment, the flow of fluid in the bulk flow region is laminar. The cross-sectional area of the bulk flow region within each process microchannel or combustion channel may be from about 0.05 to about 10,000mm²Or from about 0.05 to about 5000mm²Or from about 0.1 to about 2500mm². The total flow area may comprise from about 5% to about 95%, or from about 30% to about 80% of the cross-section of the process microchannels or combustion channels.

The contact time of the reactants with the fischer-tropsch catalyst may be up to about 2000 milliseconds (ms), or from about 10 to about 2000ms, or from about 10ms to about 1000ms, or from about 20ms to about 500ms, or from about 200 to about 400ms, or from about 240 to about 350 ms.

Space velocity of flow of fluid (or gas per unit of Fischer-Tropsch) in Fischer-Tropsch microchannelsHourly Space Velocity (GHSV)) may be at least about 1000hr^-1(Standard liters of feed/hour/liter of volume in the process microchannels), or from about 1000 to about 1,000,000hr^-1Or from about 5000 to about 20,000hr^-1。

The pressure in the fischer-tropsch process microchannels may be up to about 100 atmospheres, or from about 1 to about 75 atmospheres, or from about 2 to about 40 atmospheres, or from about 2 to about 10 atmospheres, or from about 10 to about 50 atmospheres, or from about 20 to about 30 atmospheres.

When flowing in a fischer-tropsch process microchannel, the pressure drop of the fluid may be at most about 30 atmospheres (atm/m), or at most about 25atm/m, or at most about 20atm/m, per meter of channel length. The pressure drop may be from about 10 to about 20 atm/m.

The reynolds number for the fluid flow in the fischer-tropsch process microchannels may be in the range of from about 10 to about 4000, or from about 100 to about 2000.

The average temperature in the fischer-tropsch process microchannels may be in the range of from about 150 to about 300c, or from about 175 to about 225 c, or from about 190 to about 220 c, or from about 195 to about 215 c.

The heat exchange fluid entering the heat exchange channels of the microchannel reactor 110 may be at a temperature of from about 100 ℃ to about 400 ℃, or from about 200 ℃ to about 300 ℃. The heat exchange fluid exiting the heat exchange channels may be at a temperature of from about 150 ℃ to about 450 ℃, or from about 200 ℃ to about 350 ℃. The residence time of the heat exchange fluid in the heat exchange channels may be about 1 to about 2000ms, or about 10 to about 500 ms. The pressure drop of the heat exchange fluid when flowing through the heat exchange channels may be up to about 10atm/m, or about 1 to about 10atm/m, or about 3 to about 7atm/m, or about 5 atm/m. The heat exchange fluid may be in the form of a vapor, a liquid, or a mixture of vapor and liquid. The heat exchange fluid may flow in the heat exchange channels at a reynolds number of from about 10 to about 4000, or from about 100 to about 2000.

The heat exchange fluid used in the heat exchange channels in the microchannel reactor 110 can be any heat exchange fluid suitable for cooling a fischer-tropsch exothermic reaction. These fluids may include air, steam, liquid water, gaseous nitrogen, other gases including inert gases, carbon monoxide, oils such as mineral oil, and heat exchange fluids such as Dowtherm a and Therminol available from Dow-Union Carbide.

The heat exchange channels used in the microchannel reactor 110 may comprise process channels in which endothermic processes are conducted. These heat exchange process channels may be microchannels. Examples of endothermic processes that may be carried out in the heat exchange channels include steam reforming and dehydrogenation reactions. Steam reforming of alcohols, which occurs at temperatures of about 200 ℃ to about 300 ℃, is an example of an endothermic process that may be used. Combining simultaneous endothermic reactions to provide improved cooling can achieve typical heat fluxes roughly an order of magnitude higher than convective cooling.

When flowing in the heat exchange channels of the microchannel reactor 110, the heat exchange fluid may undergo a partial or complete phase change. This phase change may provide additional heat removal from the process microchannels beyond that provided by convective cooling. For a vaporized liquid heat exchange fluid, the additional heat transferred from the Fischer-Tropsch process microchannels may be due to the latent heat of vaporization required by the heat exchange fluid. In one embodiment, about 50 wt% of the heat exchange fluid may be vaporized, or about 35 wt% may be vaporized, or about 20 wt% may be vaporized, or about 10 wt%, or about 5 wt% may be vaporized, or about 2 to about 3 wt% may be vaporized.

In a microchannel reactor, the heat flux of the heat exchange in the microchannel reactor 110 can be about 0.01 to about 500 watts (W/cm) per square centimeter of surface area of the heat transfer wall or walls of the process microchannels²) Or from about 0.1 to about 250W/cm²Or from about 1 to about 125W/cm²Or from about 1 to about 100W/cm²Or from about 1 to about 50W/cm²Or from about 1 to about 25W/cm²Or from about 1 to about 10W/cm². Can range from about 0.2 to about 5W/cm²Or from about 0.5 to about 3W/cm²Or from about 1 to about 2W/cm²。

Controlling the heat exchange during the fischer-tropsch reaction process may be advantageous in controlling the selectivity to the desired product due to the fact that: this additional cooling may reduce or eliminate undesirable byproducts formed by undesirable parallel reactions with higher activation energies.

Passive structures (e.g., obstructions), holes, and/or mechanisms upstream of or in the heat exchange channels may be used to control the pressure within each individual heat exchange channel in the microchannel reactor 110. By controlling the pressure in each heat exchange channel, the temperature in each heat exchange channel can be controlled. For each heat exchange channel, a higher inlet pressure may be used, with passive structures, holes, and/or mechanisms reducing the pressure to the desired pressure. By controlling the temperature within each heat exchange channel, the temperature in the fischer-tropsch process microchannels can be controlled. Thus, for example, each Fischer-Tropsch process microchannel can be operated at a desired temperature by using a particular pressure in a heat exchange channel that is adjacent to or in thermal contact with the process microchannel. This provides the advantage of precise control of the temperature of each Fischer-Tropsch process microchannel. The use of precise control of the temperature of each fischer-tropsch process microchannel provides the advantage of tailored temperature characteristics and an overall reduction in energy requirements for the process.

In scaled-up devices, for some applications, it may be desirable to have a uniform distribution of the mass of the process fluid within the microchannels. The application may be when the process fluid needs to be heated or cooled together with the adjacent heat exchange channels. Uniform mass flow distribution from one parallel microchannel to another microchannel can be achieved by varying the cross-sectional area. The uniformity of the mass flow distribution can be defined by the quality index factor (Q-factor) shown below. A Q-factor of 0% means an absolutely uniform distribution.

The change in cross-sectional area may result in a difference in shear stress on the wall. In one embodiment, the Q-factor of the microchannel reactor 110 may be less than about 50%, or less than about 20%, or less than about 5%, or less than about 1%.

The superficial velocity of the fluid flowing in the Fischer-Tropsch process microchannels may be at least about 0.01 meters per second (m/s), or at least about 0.1m/s, or from about 0.01 to about 100m/s, or from about 0.01 to about 10m/s, or from about 0.1 to about 10m/s, or from about 1 to about 100m/s, or from about 1 to about 10 m/s.

The free stream velocity of the fluid flowing in the Fischer-Tropsch process microchannels may be at least about 0.001 m/s, or at least about 0.01m/s, or from about 0.001 to about 200m/s, or from about 0.01 to about 100m/s, or from about 0.01 to about 200 m/s.

The conversion of CO of the fresh syngas in the reactant mixture may be about 70% or more, or about 75% or more, or about 80% or more, or about 90% or more, or about 91% or more, or about 92% or more, or about 88% to about 95%, or about 90% to about 94%, or about 91% to about 93%. For CO in the reactant mixture (i.e., fresh syngas plus recycled tail gas), the per pass conversion of CO can be from about 65% to about 90%, or from about 70% to about 85%.

The selectivity to methane in the fischer-tropsch (FT) product may be from about 0.01 to about 10%, or from about 1% to about 5%, or from about 1% to about 10%, or from about 3% to about 9%, or from about 4% to about 8%.

The fischer-tropsch product formed in the microchannel reactor 110 can comprise a gaseous product fraction and a liquid product fraction. The gaseous product fraction may comprise hydrocarbons boiling below about 350 ℃ at atmospheric pressure (e.g., tail gas passing through the middle distillate). The liquid product fraction (condensate fraction) may include hydrocarbons boiling above about 350 ℃ (e.g., vacuum gas oil (vacuum gas oil) passed through heavy alkanes).

The fischer-tropsch product fraction boiling below about 350 c may be separated into a tail gas fraction and a condensate fraction, for example normal paraffins and high boiling hydrocarbons of from about 5 to about 20 carbon atoms, using for example high pressure and/or low temperature vapor-liquid separators, or low pressure separators or combinations of separators. After removal of one or more fractions having a boiling point above about 650 ℃, the fraction having a boiling point above about 350 ℃ (the condensate fraction) may be separated into a wax fraction having a boiling point between about 350 ℃ and about 650 ℃. The wax fraction may contain straight chain alkanes having from about 20 to about 50 carbon atoms, as well as relatively small amounts of high boiling, branched chain alkanes. Fractionation may be used to achieve separation.

The fischer-tropsch products formed in the microchannel reactor 110 may include methane, waxes, and other heavy, high molecular weight products. The products may include olefins such as ethylene, normal and iso-alkanes, and combinations thereof. These may include hydrocarbons in the distillate fuel range, including jet or diesel fuel ranges.

In particular, branching can be advantageous for a variety of end-uses when it is desired to increase octane number and/or reduce pour point. The degree of isomerization may be greater than about 1 mole of isoparaffin per mole of normal paraffin, or about 3 moles of isoparaffin per mole of normal paraffin. When used in a diesel fuel composition, the product may comprise a hydrocarbon mixture having a cetane number of at least about 60.

The fischer-tropsch product may be further processed to form a lubricating base oil or diesel fuel. For example, the product produced in the microchannel reactor 110 may be hydrocracked, then subjected to fractionation and/or catalytic isomerization to provide a lubricating base oil, diesel fuel, aviation fuel, and the like. The fischer-tropsch product may be hydroisomerized using the processes disclosed in U.S. Pat. nos. 6,103,099 or 6,180,575; hydrocracking and hydroisomerization are carried out using the methods disclosed in U.S. Pat. nos. 4,943,672 or 6,096,940; dewaxing was performed using the method disclosed in U.S. patent No. 5,882,505; or hydroisomerization and dewaxing using the processes disclosed in U.S. Pat. Nos. 6,013,171, 6,080,301, or 6,165,949. The disclosures of the processes for treating Fischer-Tropsch synthesized hydrocarbons and the resulting products made using these processes in these patents are incorporated herein by reference.

The hydrocracking reaction may be carried out in a hydrocracking microchannel reactor, and may involve reaction between hydrogen and the fischer-tropsch product effluent from the microchannel reactor 210, or one or more hydrocarbons separated from the fischer-tropsch product (e.g., one or more liquid or waxy fischer-tropsch hydrocarbons). The fischer-tropsch product may comprise one or more long chain hydrocarbons. In the hydrocracking process, C can be added₂₃₊Cracking the fraction to C₁₂To C₂₂Middle range of carbon number ofIncreasing for example the desired diesel fraction. The wax fraction produced by the fischer-tropsch microchannel reactor 110 may be fed to a hydrocracking microchannel reactor with excess hydrogen for a three-phase reaction. Under the reaction conditions of elevated temperature and pressure, a portion of the liquid feed may be converted to the vapor phase, while the remaining liquid portion may flow along the catalyst. In conventional hydrocracking systems, a liquid stream is formed. The use of microchannel reactors for hydrocracking reactions can achieve unique advantages in several respects. These may include kinetics, pressure drop, heat and mass transfer.

The fischer-tropsch hydrocarbon product that can be hydrocracked in the hydrocracking microchannel reactor can comprise any hydrocarbon that can be hydrocracked. These hydrocarbons may include hydrocarbons containing one or more C-C bonds that can be broken during hydrocracking. Hydrocarbons that may be hydrocracked may include saturated aliphatic compounds (e.g., alkanes), unsaturated aliphatic compounds (e.g., alkenes, alkynes), hydrocarbyl (e.g., alkyl) substituted aromatics, hydrocarbylene (e.g., alkylene) substituted aromatics, and the like.

The feed composition to the hydrocracking microchannel reactor may include one or more diluent materials. Examples of such diluents may include non-reactive hydrocarbon diluents and the like. The concentration of diluent may be from zero to about 99 wt%, or from zero to about 75 wt%, or from zero to about 50 wt%, based on the weight of the fischer-tropsch product. Diluents may be used to reduce the viscosity of the viscous liquid reactants. The viscosity of the feed composition in the hydrocracking microchannel reactor may be from about 0.001 to about 1 centipoise, or from about 0.01 to about 1 centipoise, or from about 0.1 to about 1 centipoise.

The ratio of hydrogen to Fischer-Tropsch product in the feed composition to the hydrocracking microchannel reactor may be from about 10 to about 2000 standard cubic centimeters (sccm) of hydrogen per cubic centimeter (ccm) of Fischer-Tropsch product, or from about 100 to about 1800sccm/ccm, or from about 350 to about 1200 sccm/ccm. The hydrogen feed may also comprise water, methane, carbon dioxide, carbon monoxide and/or nitrogen.

H in hydrogen feed₂It can be derived from another method of the invention,for example, steam reforming method (H)₂Product stream with a molar ratio/CO of about 3), partial oxidation process (H)₂Product stream with a molar ratio of CO/about 2), autothermal reforming process (H)₂Product stream with a molar ratio of CO of about 2.5), CO₂Recombination method (H)₂Product stream with a molar ratio of CO of about 1), coal gasification process (H)₂Product stream having a mole ratio of CO of about 1), and combinations thereof. For each of these feed streams, H can be subjected to conventional techniques (e.g., membrane separation or adsorption)₂Separated from the remaining components.

The Fischer-Tropsch product of hydrocracking may comprise an intermediate distillate having a boiling point of about 260-700 ℃ F. (127-371 ℃ C.). The term "middle distillate" is intended to include diesel, jet fuel and kerosene boiling range fractions. The terms "kerosene" and "jet fuel" boiling point ranges are intended to refer to the temperature range of 260-550 deg.F (127-288 deg.C), and the "diesel" boiling point range is intended to refer to the hydrocarbon boiling point of about 260 to about 700 deg.F (127-371 deg.C). The fischer-tropsch product of hydrocracking may comprise a gasoline or a naphthalene fraction. These may be considered as C₅To 400 ℃ F. (204 ℃ C.) end point.

Catalyst and process for preparing same

Catalyst precursor

A catalyst precursor is a material that can be activated to form a catalyst. The terms "catalyst" and "catalyst precursor" are used interchangeably herein and will be understood in accordance with their specific context.

The catalyst precursor comprises at least one catalyst metal, for example cobalt, which may be present in the form of an oxide, as an elemental metal, in the form of its carbide or as a mixture of any of these. In particular, the catalyst precursor may comprise from about 10 to about 60% cobalt (as a percentage of the total weight of the catalyst precursor based on the weight of the metal), or from about 35 to about 50% cobalt, or from about 40 to about 44% cobalt, or about 42% cobalt. The cobalt can be used as CoO and/or Co₃O₄Are present.

The catalyst precursor may comprise a noble metal on a support, which may be one or more of Pd, Pt, Rh, Ru, Re, Ir, Au, Ag and Os. The noble metal can be one or more of Pd, Pt, Rh, Ru, Ir, Au, Ag and Os. The noble metal may be one or more of Pt, Ru and Re. The noble metal may be Ru. Alternatively, or in addition, the noble metal may be Pt. The catalyst precursor may comprise a total of about 0.01 to about 30% of the noble metal (as a percentage of the total weight of the catalyst precursor based on the total weight of all noble metals present), or a total of about 0.05 to about 20% of the noble metal, or a total of about 0.1 to about 5% of the noble metal, or a total of about 0.2% of the noble metal.

If desired, the catalyst precursor may include one or more other metal-based components as promoters or modifiers. These metal-based components may also be present at least partially in the catalyst precursor as carbides, oxides or elemental metals. Suitable metals for the one or more other metal-based components may be one or more of Zr, Ti, V, Cr, Mn, Ni, Cu, Zn, Nb, Mo, Tc, Cd, Hf, Ta, W, Re, Hg, Tl and the 4 f-block lanthanide. Suitable 4 f-block lanthanides can be La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu. The metal for the one or more other metal-based components may be one or more of Zn, Cu, Mn, Mo and W. The metal for the one or more other metal-based components may be one or more of Re and Pt. The catalyst precursor may comprise a total of about 0.01 to about 10% of other metals (as a percentage of the total weight of the catalyst precursor based on the total weight of all other metals), or a total of about 0.1 to about 5% of other metals, or a total of about 3% of other metals.

The catalyst precursor may contain up to 10% carbon (as a percentage of the total weight of the catalyst precursor based on the weight of carbon (regardless of form) in the catalyst), or from about 0.001 to about 5% carbon, or from about 0.01% to about 1% carbon. Alternatively, the catalyst precursor may be characterized by the absence of carbon.

Optionally, the catalyst precursor may contain nitrogen-containing organic compounds, such as urea; or an organic ligand, for example ammonia or a carboxylic acid such as citric acid or acetic acid (which may be in the form of a salt or ester).

The precursor may be activated to produce a fischer-tropsch catalyst, for example, by heating the catalyst precursor in hydrogen and/or a hydrocarbon gas or in hydrogen diluted with another gas (e.g., nitrogen and/or methane) to convert at least some of the carbides or oxides to elemental metal. In the active catalyst, the cobalt may optionally be at least partially in its carbide or oxide form.

Reducing agent

The use of a carboxylic acid as the reducing agent can minimize or reduce cracking and fragmentation of the catalyst precursor, thereby allowing more catalyst precursor to be incorporated into the activated catalyst to be used in the fischer-tropsch reaction, as less catalyst precursor particles are produced than the smallest particle size criteria for achieving an acceptable reactor pressure drop, for example <340kPa (or 50 psi). In some cases, the need for screening catalyst precursors to remove particles below a threshold particle size limit (e.g., about 125 microns) may be eliminated. Without wishing to be bound by theory, it is believed that this is because the reaction between the carboxylic acid and the catalyst metal precursor is less vigorous than other reducing agents (e.g., urea), but the reaction is still effective in providing a highly active, stable and selective catalyst.

The carboxylic acid may be selected such that it minimizes cracking of the catalyst precursor, but still ultimately results in an effective catalyst. Mixtures of two or more carboxylic acids may be used. The carboxylic acid may be an alpha-hydroxycarboxylic acid, such as citric acid, glycolic acid, lactic acid or mandelic acid.

The term "reducing agent" as used herein may also include agents that additionally act as complexing agents.

Catalyst metal precursor

The catalyst metal precursor may be a cobalt-containing precursor. Suitable cobalt-containing precursors may include cobalt benzoylacetonate, cobalt carbonate, cobalt cyanide, cobalt hydroxide, cobalt oxalate, cobalt oxide, cobalt nitrate, cobalt acetate, cobalt acetylacetonate, and cobalt carbonyl. These cobalt precursors may be used alone or may be used in combination. These cobalt precursors may be in the form of hydrates or anhydrous forms. In some cases, where the cobalt precursor is insoluble in water, such as cobalt carbonate or hydroxide, a small amount of nitric acid or carboxylic acid may be added to enable the precursor to be completely dissolved in solution or suspension. The solution or suspension may contain little or no water, in which case the drying step may be omitted in the process of forming the catalyst precursor.

The catalyst metal precursor may be cobalt nitrate. Cobalt nitrate may react with a reducing agent during calcination to produce Co₃O₄。

The solution or suspension may contain at least one primary catalyst metal precursor, such as one of the cobalt-containing precursors described above or a mixture of cobalt-containing precursors, and at least one secondary catalyst metal precursor. Such secondary catalyst metal precursors may be present to provide promoters and/or modifiers in the catalyst. Suitable secondary catalyst metals may include noble metals such as Pd, Pt, Rh, Ru, Ir, Au, Ag, and Os; transition metals such as Zr, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Tc, Cd, Hf, Ta, W, Re, Hg and Ti; and 4 f-block lanthanides, such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and/or Lu.

The secondary catalyst metal may be one or more of Pd, Pt, Ru, Ni, Co (if not the primary catalyst metal), Fe (if not the de-grading catalyst metal), Cu, Mn, Mo, Re and W.

Catalyst support

The catalyst may be dispersed on a surface modified support to anchor the catalyst particles and provide mechanical strength. The support may comprise a refractory metal oxide, carbide, carbon, nitride, or a mixture of two or more thereof. The support may comprise alumina, zirconia, silica, titania, or a mixture of two or more thereof. The surface of the support may be modified by treating it with silica, titania, zirconia, magnesia, chromia, alumina, or a mixture of two or more thereof. The material used for the support and the material used for the modified support may be different. Without wishing to be bound by theory, it is believed that the surface treatment provided herein helps Co avoid sintering during operation of the fischer-tropsch process of the invention.

The support may comprise silica and the surface of the silica may be coated with an oxide refractory solid oxide, particularly titanium dioxide. The catalyst support may be in the form of a structured shape, pellets or powder.

The support may comprise a titania-modified silica support. Titanium dioxide (TiO)₂) Can be used to increase the stability of the silica-supported catalyst (e.g., by reducing deactivation).

Thus, the rate of deactivation of the catalyst may be such that: it may be used in fischer-tropsch synthesis, for example, for greater than about 300 hours, or greater than about 3,000 hours, or greater than about 12,000 hours, or greater than about 15,000 hours, all before regeneration of the catalyst is required.

At elevated temperatures, the catalyst material may react with surface Si-OH groups on the silica support to produce silicate species that are not fischer-tropsch active and may not be readily reduced. This can lead to a loss of active surface area of the catalyst and thus to a decrease in FTS activity.

Without wishing to be bound by theory, it is believed that through the consumption of surface Si-OH groups, dispersion of the titania on the silica surface occurs, followed by the formation of bridged Ti-O-Si bonds. Thus, modifying the silica support with a layer of titanium dioxide can remove the Si — OH groups and thus prevent the formation of silicates.

TiO₂May comprise at least 11 wt%, or greater than 11 wt% of the total weight of the catalyst support. In particular, the catalyst support may be in Silica (SiO)₂) 11-30 wt%, 11-25 wt%, 11-20 wt%, or 12-18 wt%, or 15-17 wt%, or about 16 wt% of TiO₂。

In one embodiment, the catalyst precursor may comprise from about 40 to about 44 wt% Co, from about 0.1 to about 0.3 wt% Re, and from about 0.01 to about 0.05 wt% Pt (all expressed as a percentage of the total weight of the catalyst precursor); and TiO₂-a modified silica catalyst support comprisingAbout 11 to about 30 weight percent TiO₂(expressed as a percentage of the total weight of the catalyst support).

The catalyst precursor may comprise 42 wt% Co, 0.2 wt% Re and 0.03 wt% Pt (all expressed as a percentage of the total weight of the catalyst precursor); and TiO₂-a modified silica catalyst support comprising 16 wt% of TiO₂(expressed as a percentage of the total weight of the catalyst support).

The catalyst may be in the form of a particulate catalyst having a particle size distribution such that d10 is greater than 90 μm and d90 is less than 325 μm. The average particle size distribution may be about 180 to about 300 μm.

Because titania is more acidic than silica, the effectiveness of the dispersion of titania on the silica surface can be characterized by a measurement of the surface acidity of the modified support. In addition, four coordinate Ti at the interface of silicon dioxide/titanium dioxide⁴⁺The presence of ions may further generate particularly strong lewis acid sites.

The surface acidity of the modified support can be measured using a Temperature Programmed Desorption (TPD) experiment with a lewis base such as ammonia.

In one embodiment, the surface acidity of the catalyst support may be: neutralization requires 0.20. mu. mol of NH₃/m²Or more, e.g. 0.22. mu. mol NH₃/m²Or more.

Another method for measuring the replacement of the Si-OH bond by Ti-O-Si on the modified support is by using FT-IR spectroscopy. In FT-IR, the band of Si-OH groups is expected to be around 980cm^-1At the frequency of (c). In addition, bands for Ti-O-Si groups are expected to be around 950cm^-1At the frequency of (c). Thus, 980cm when a certain number of Si-OH bonds are replaced by Ti-O-Si groups^-1The intensity of the treatment band is reduced and 950cm^-1The intensity of the spectral band increases. 980cm^-1And 950cm^-1The ratio of the intensities of the bands indicates how many Si-OH groups have been replaced by Ti-O-Si groups.

The FT-IR spectrum can be corrected by subtracting the spectrum of the silica. Therefore, in these proofingsIn the positive spectrum, 980cm^-1The band at (d) may appear as a dip (dip). The "FT-IT intensity ratio" can be used with 980cm observed in the corrected spectrum^-1And 950cm^-1The intensity of the band, where 950cm is used^-1The intensity of the maximum of the spectral band divided by 980cm^-1The intensity of the band minimum.

The modified catalyst support was 950: 980cm^-1The FT-IR intensity ratio at (a) may be 1.2 or higher, such as 1.3 or higher, 1.4 or higher or 1.5 or higher.

Rate of deactivation

The catalyst may be used for extended periods of time (e.g., > 300 hours) and has a deactivation rate of less than about 1.4%/day, or less than about 1.2%/day, or from about 0.1% to about 1.0%/day, or from about 0.03 to about 0.15%/day.

In a fixed bed combinatorial reactor or a high throughput screening reactor, the deactivation rate of the catalyst can be measured as a percentage loss of CO conversion per 24 hours, where the CO conversion can be greater than about 70%, or greater than about 75%, or greater than about 80%, where the loss is measured over a period of 200 hours or more, and where the period of 200 hours begins at a Time of Operation (TOS) of less than 500 hours.

In a microchannel reactor, the catalyst may be used for extended periods of time (e.g., > 300 hours) and at a deactivation rate of less than about 0.25%/day, or from about 0.001% to about 0.20%/day, or from about 0.01 to about 0.10%/day, or about 0.08%/day.

In a microchannel reactor, the deactivation rate of the catalyst can be measured as a percent loss of CO conversion per 24 hours of less than about 0.25, wherein the CO conversion is greater than about 70%, or greater than about 75%, or greater than about 80%, wherein the loss is measured over a period of 200 hours or more, and wherein the period of 200 hours begins at a Time of Operation (TOS) of less than 500 hours.

Co₃O₄Average particle diameter and particle diameter distribution

The activity and selectivity of cobalt-based catalysts may be affected by the density of active sites, with very small particle sizes being advantageous. However, the deactivation mechanism of cobalt catalysts may generally follow the opposite trend, with the largest particles being likely to be the most stable.

Co₃O₄May be less than about 12nm (as determined by powder X-ray diffraction, e.g., using a Siemens D5000 θ/θ powder diffractometer and CuK_αRadiation). The cobalt oxide particle size distribution may affect catalyst activity and stability, so that a particle size distribution as narrow as possible may be useful. The width of the particle size distribution can be measured by the c-value of the log-normal particle size distribution. c is a dimensionless ratio and characterizes the width of the particle size distribution. Co₃O₄The c-value of the lognormal size distribution of the particles may be less than about 0.31. Co₃O₄May be less than about 11nm, or from about 8 to about 10 nm. The c value may be from about 0.19 to about 0.31, or less than about 0.25, or from about 0.19 to about 0.25. In Co₃O₄C may be less than 0.31 in the case where the number average particle diameter of (a) is from about 8 to about 10 nm.

The number average particle size may be from about 8 to about 10nm, and the c-value may be about 0.31 or less, such as 0.29 or less, 0.26 or less, or 0.25 or less. Alternatively or additionally, the c-value may be about 0.19 or more, such as 0.20 or more or 0.235 or more. The value of c-can be about 0.19. ltoreq. c.ltoreq.0.31; c is more than or equal to 0.19 and less than or equal to 0.29; c is more than or equal to 0.19 and less than or equal to 0.26; c is more than or equal to 0.19 and less than or equal to 0.25; c is more than or equal to 0.20 and less than or equal to 0.31; c is more than or equal to 0.20 and less than or equal to 0.29; c is more than or equal to 0.20 and less than or equal to 0.26; c is more than or equal to 0.20 and less than or equal to 0.25; c is more than or equal to 0.235 and less than or equal to 0.31; c is more than or equal to 0.235 and less than or equal to 0.29; c is more than or equal to 0.235 and less than or equal to 0.26; or c is more than or equal to 0.235 and less than or equal to 0.25.

In a sample of calcined catalyst (assuming spherical particles equivalent to crystallites or crystallites having a lognormal monomodal distribution), the form of the particle size distribution can be written as:

wherein

Equation 1

Wherein R is_oAre number average particlesRadius, and c (which is known as a dimensionless ratio) characterizes the width of the particle size distribution. R_oMultiply by 2 to obtain the number average particle size.

Characterization of Co₃O₄Another way of relating the particle size distribution to the activity and stability of the catalyst is by the D-value. The D-value may be referred to as a reorganization of the particle size distribution described by the c-value and does not represent any new data. Thus, the c-value and the D-value are mathematically related, but an improved correlation can be seen between the D-value and the activity and stability of the catalyst.

D-value is represented by Co₃O₄The particle size distribution of the particles in the fresh, unreduced catalyst (i.e. in the catalyst precursor) is parametrically calculated.

For Co having substantially the same number average particle diameter₃O₄The particles, a trend between c-value and deactivation rate can be seen. The D-value may be an improvement over the c-value, since the Co is still considered although the D-value₃O₄Width of particle size distribution and number average particle size, but log average Co₃O₄The particle sizes are more heavily weighted so that it is not necessary to maintain substantially the same number average particle size in order to observe the trend of the data. This allows a single scale (D-value) to be recorded and compared, rather than two scales (c-value and number average particle size).

The D-value can be calculated by plotting a lognormal particle size distribution using equation 1 (see above). The frequency (f) in the lognormal distribution mode can be set_Mode(s)) Considered as a measure of the width of the distribution. To illustrate the dependence of the FTS catalyst stability on the number average particle size, the following formula can be used, where f_Mode(s)Weighted by the median particle size distribution to generate a "particle size-weighted distribution width" or D-value:

D＝f_mode(s) ^yxR_ox2

Equation 2

Wherein f is_Mode(s)Frequency in the mode of lognormal distribution, R_OIs the number average particle radius, and y is an empirical value based on experimental observations. Selected (at least about 5 to 10) via comparison to have substantially similar compositions but at Co₃O₄The value of y is determined for the stability of the catalyst with small variations in particle size and particle size distribution width. These changes can be achieved via minor modifications to the synthesis method, such as increasing dilution of the impregnation solution (in one example, this is shown to result in a subtle change in the particle size distribution). FTS stability data for these catalysts were then collected under the same test conditions. Then, within this group of similar catalysts, y is manually adjusted to generate a spread of D-values so that FTS-stabilized catalysts can be distinguished from unstable catalysts. For the catalyst composition: 16% TiO₂/SiO₂42% Co-0.2% Re-0.03% Pt on top, with a y value of 1.15.

Thus, an increase in the D-value may represent a narrowing of the particle size distribution or an increase in the number average particle size.

Co₃O₄The particle size distribution can affect the FTS activity and stability of the catalyst, so that preferably, Co₃O₄The D-value of the lognormal particle size distribution of the particles is about 19 or more. A D-value of 19.2 corresponds to a particle size distribution with a c-value of about 0.31 and a number average particle size of about 10 nm. A D-value of 19.8 corresponds to a particle size distribution with a c-value of about 0.31 and an average particle size of about 8 nm. In either of these cases, a decrease in c (e.g., a narrowing of the particle size distribution) will result in an increase in D. Thus, a specification of c ≦ 0.31 in the average particle size range of 8-10nm corresponds to a particle distribution defined by a D-value greater than or equal to about 19.

In one embodiment, the D-value can be about 19 or greater, such as 19.2 or greater, 20.4 or greater, 21.0 or greater or 21.35 or greater, or 21.4 or greater. Alternatively or additionally, the D-value may be 23.5 or less, such as 22.2 or less. Within the scope of this application, any of these upper and lower limits are combined such that the D-value can be about 19 ≦ D ≦ 23.5; d is more than or equal to 19 and less than or equal to 22.2; d is more than or equal to 19.2 and less than or equal to 23.5; d is more than or equal to 19.2 and less than or equal to 22.2; d is more than or equal to 20.4 and less than or equal to 23.5; dc is more than or equal to 20.4 and less than or equal to 22.2; d is more than or equal to 21.0 and less than or equal to 23.5; dc is more than or equal to 21.0 and less than or equal to 22.2; d is more than or equal to 21.35 and less than or equal to 23.5; or D is more than or equal to 21.35 and less than or equal to 22.2.

The catalyst or catalyst precursor may comprise 16% TiO₂Modified silica support comprising Co on the support₃O₄Which is flatA mean particle diameter of about 9.6nm, a c-value of about 0.31 and a D-value of about 19.2. Alternatively, the catalyst or catalyst precursor may comprise 16% TiO₂Modified silica support comprising Co on the support₃O₄Having an average particle size of about 6.2nm, a c-value of about 0.14 and a D-value of about 29.1.

Co₃O₄The characteristics of the particles may be influenced by the synthesis method used to produce the catalyst precursor and the catalyst.

In particular, the catalyst comprises TiO₂In the case of a modified silica support, modifying the support with a titanium alkoxide (such as titanium isopropoxide) may provide a support comprising Co having the above-mentioned properties₃O₄The catalyst of (1). In this embodiment, the catalyst precursor may contain less than 10%, or less than 5%, or preferably less than 1% crystalline TiO₂(in all TiO form)₂The percentage in the catalyst precursor). Alternatively, all TiO present in the catalyst precursor₂And may be amorphous or amorphous (at most detectable limit).

Alternatively, the catalyst comprises TiO₂In the case of a modified silica support, the support may be modified using an aqueous method, such as using bis (2-hydroxypropionic acid) diammonium titanium (IV) dihydroxide, without using a titanium alkoxide. Preferred aqueous methods are described below in the section entitled "aqueous treatment of catalyst supports". The resulting modified support can also provide a support comprising Co having the above properties₃O₄The catalyst of (1).

Similarly, using citric acid as a fuel/reductant in the preparation of the catalyst precursor, it is possible to provide a catalyst comprising Co having the above-mentioned properties₃O₄A catalyst precursor and a catalyst.

In addition, the number of impregnations used to form the catalyst may affect the particle size distribution, and thus the c-value. Specifically, an increase in the number of impregnations may result in an increase in the c-value and an increase in the deactivation rate of the catalyst. Therefore, it is preferable that the number of impregnation steps be reduced. Three impregnation steps may be used.

In one embodimentIn one embodiment, the catalyst may be formed using 4 impregnations, resulting in a c value of 0.25, preferably Co₃O₄Has a number average particle size of about 8 to about 10 nm.

In one embodiment, the catalyst may be formed using 6 impregnations, resulting in a c value of 0.27, preferably Co₃O₄Has a number average particle size of about 8 to about 10 nm.

In one embodiment, the catalyst may be formed using 8 impregnations, resulting in a c value of 0.30, preferably Co₃O₄Has a number average particle size of about 8 to about 10 nm.

Preparation of catalyst precursor

The catalyst precursor may be prepared by the method defined above or by any of the methods discussed in WO 2008/104793. The solution or suspension is applied to the catalyst support by spraying, dipping or dipping. If the solution or suspension is completely free of water, it may not be necessary to perform a drying step and a calcination step immediately after the deposition step.

However, if a catalyst metal precursor that is a hydrate is used, the solution or deposit may contain some water of hydration. The water may be sufficient to dissolve some components of the solution or suspension, such as the carboxylic acid (if solid at room temperature). However, in some cases, it may be necessary to add some water to the solution or suspension to ensure that the catalyst metal precursor and other components are able to dissolve or become suspended. In this case, the amount of water used is generally the minimum amount necessary to allow the catalyst metal precursor and other components to be dissolved or suspended.

The deposition, drying and calcination steps may be repeated one or more times. The solution or suspension used in the deposition step may be the same or different for each repetition. If the solution or suspension in each iteration is the same, the repetition of the steps allows the amount of catalyst metal to be brought to the desired level on the catalyst support in steps in each iteration. If the solution or suspension in each iteration is different, the repetition of the steps allows for a plan to bring the amount of different catalyst metals to the desired level in the series of steps to be performed.

A programmed heating scheme may be used during drying and calcination that gradually increases the temperature in order to control the generation of gas and heat from the catalyst metal precursor and other components of the solution or suspension.

During the heating process, the catalyst support may reach a maximum temperature of no greater than about 500 ℃, or no greater than about 375 ℃, or no greater than about 250 ℃ at atmospheric pressure.

The temperature may be ramped (ramp) at a rate of about 0.0001 to about 10 ℃/minute, or about 0.1 to about 5 ℃/minute. The rate may be from about 10 to about 30 deg.c/minute.

An illustrative programmed heating protocol may comprise:

(a) heating the catalyst support, having the solution or suspension deposited thereon, at a rate of about 1 to about 5 ℃/minute, or about 2 ℃/minute, to a temperature of about 80 to about 120 ℃, or about 100 ℃, and maintaining it at that temperature for about 1 to about 10 hours, or about 5 hours;

(b) it is heated at a rate of about 1 to about 5 deg.c/minute, or about 2 deg.c/minute, to a temperature of about 150 to about 400 deg.c, or about 200 to about 350 deg.c, or about 250 deg.c, and maintained at that temperature for about 0.5 to about 6 hours, or about 1 to about 6 hours, or about 3 hours.

The heating step may be carried out in a rotary oven, in a static oven or in a fluidized bed.

Once the calcination step has been completed, either after the step is first performed or at the end of the repetition, additional catalyst metals may optionally be loaded onto the catalyst support.

The calcination step may be carried out in an oxygen-containing atmosphere (e.g., air), particularly if the metal catalyst oxide is to be formed.

Catalyst activation

The catalyst precursor may be activated by any conventional activation method. For example, the catalyst precursor may be activated using a reducing gas such as hydrogen, a gaseous hydrocarbon, a mixture of hydrogen and a gaseous hydrocarbon (e.g., methane), a mixture of gaseous hydrocarbons, a mixture of hydrogen and a plurality of gaseous hydrocarbons, a mixture of hydrogen and nitrogen, syngas, or a mixture of syngas and hydrogen.

The pressure of the gas may be from 1 bar (atmospheric pressure) to about 100 bar, or less than about 30 bar. The pressure may be from about 5 to about 20 bar, or from about 10 to about 15 bar.

The catalyst precursor may be heated to its activation temperature at a rate of from about 0.01 to about 20 c/min. The activation temperature may be no greater than about 600 deg.C, or no greater than about 400 deg.C. The activation temperature may be from about 300 ℃ to about 400 ℃, or from about 325 ℃ to about 375 ℃, or about 350 ℃.

The catalyst precursor may be maintained at the activation temperature for about 2 to about 24 hours, or about 8 to about 12 hours.

After activation, the catalyst may be cooled to the desired reaction temperature.

After activation, the catalyst may be used in the fischer-tropsch process described above.

In a fischer-tropsch reaction conducted in a microchannel reactor comprising a catalyst using the disclosed catalyst or a catalyst derived from the disclosed catalyst precursor, the performance of the catalyst can be substantially maintained for a reaction time of about 5000 hours or greater without catalyst regeneration, such that the contact time can be less than 500 milliseconds, the CO conversion can be greater than about 70% and the methane selectivity can be less than about 10%.

By "performance of the catalyst is substantially maintained" it is meant that the average contact time, average CO conversion and average methane selectivity parameters may be within the above ranges over each data collection interval of 24 hours. The duration of the data collection interval may be 12 hours, 6 hours, 3 hours, or 1 hour. In this way, while there may be small variations in these parameters, the overall performance of the catalyst in terms of contact time, CO conversion and methane selectivity can be maintained.

The reaction time may be about 8000 hours or more. In a fischer-tropsch reaction comprising a catalyst using the disclosed catalyst or derived from the disclosed catalyst precursor, the rate of deactivation of the catalyst, measured as a percentage of CO conversion loss per day, can be about 0.09% or less over a reaction time of about 5000 hours or more.

The catalyst may be of any size and suitable geometry within the process microchannels. The catalyst may be in the form of a particulate solid (e.g., pellets, powder, fiber, etc.) having a median particle size of from about 1 to about 1000 μm (microns), or from about 10 to about 500 μm, or from about 25 to about 250 μm. The median particle size may be from about 125 to about 400 μm, or from about 170 to about 300 μm. In one embodiment, the catalyst may be in the form of a fixed bed of particulate solid.

The catalyst may be in the form of a fixed bed of particulate solid (as shown in figure 7). Referring to fig. 7, a catalyst 261 in the form of a bed of particulate solid is contained within the process microchannels 260. The reactants enter the fixed bed, undergo reaction, as indicated by arrow 262, and the product exits the fixed bed, as indicated by arrow 263.

The catalyst may be supported on a catalyst support structure, such as a foam, felt, agglomerate, or combination thereof. The catalyst support structure may comprise a fin assembly or corrugated insert adapted to be inserted into slots in a microchannel reactor. The cobalt loading of the catalyst may be at least about 20 wt.%, or at least about 25 wt.%, or at least about 28 wt.%, or at least about 30 wt.%, or at least about 32 wt.%, or at least about 35 wt.%, or at least about 38 wt.%.

The term "foam" as used herein refers to a structure having continuous walls that define pores that extend through the structure. The term "felt" as used herein refers to a structure of fibers having void spaces therebetween. The term "mass" as used herein refers to the structure of tangled strands, such as steel wool. The catalyst may be supported on a honeycomb structure. The catalyst may be supported on a flow-through support structure such as a felt with adjacent gaps, a foam with adjacent gaps, a fin structure with gaps, any wash coat (washcoat) inserted on the substrate, or a gauze parallel to the direction of flow and having corresponding gaps for flow.

An example of a flow-through configuration is shown in fig. 8. In FIG. 8, catalyst 266 is contained within process microchannels 265. The open channels 267 allow fluid flow through the process microchannels 265 as indicated by

arrows

268 and 269. The reactants contact the catalyst and undergo reaction to form the product.

The catalyst may be supported on a flow-through support structure, such as a foam, a briquette, a pellet, a powder, or a gauze. An example of a flow-through structure is shown in fig. 9. In fig. 9, a flow-through catalyst 271 is contained within a process microchannel 270, as indicated by

arrows

272 and 273, the reactants flow through the catalyst 271 and undergo reaction to form a product.

The support structure for the flow-through catalyst may be formed from a material comprising silica gel, copper foam, sintered stainless steel fibers, steel wool, alumina, or a combination of two or more thereof. The support structure may be made of a thermally conductive material, such as a metal, to enhance heat transfer to or from the catalyst.

The catalyst may be supported on a fin assembly comprising one or more fins disposed within the process microchannel. Examples are shown in fig. 10-12. Referring to FIG. 10, fin assembly 280 includes fins 281 that are mounted on fin supports 283, which fin supports 283 cover the base wall 284 of process microchannel 285. Fins 281 protrude from fin supports 283 into the interior of process microchannels 285. The fins 281 may extend to and contact the inner surface of the upper wall 286 of the process microchannel 285. The fin channels 287 between the fins 281 provide passageways for the flow of reactants and products through the process microchannel 285 parallel to the length of the process microchannel 285. Each fin 281 has an outer surface on each side thereof. The outer surface provides a support substrate for the catalyst. The reactants may flow through the fin channels 287, contact the catalyst supported on the outer surface of the fins 281, and react to form products. The fin assembly 280a shown in FIG. 11 is similar to the fin assembly 280 shown in FIG. 10, except that the fins 281a do not extend all the way to the inner surface of the upper wall 286 of the microchannel 285. The fin assembly 280b shown in fig. 12 is similar to the fin assembly 280 shown in fig. 10, except that the fins 281b in the fin assembly 280b have a cross-sectional shape in the form of a trapezoid. The height of each fin may be from about 0.02mm to about multiple workThe height of the process microchannels 285 may be from about 0.02 to about 10mm, or from about 0.02 to about 5mm, or from about 0.02 to about 2 mm. The width of each fin may be about 0.02 to about 5mm, or about 0.02 to about 2mm, or about 0.02 to about 1 mm. The length of each fin can be any length up to the length of the process microchannels 285, or up to about 10m, or from about 0.5 to about 6m, or from about 0.5 to about 3 m. The gap between the fins can be any value and can be about 0.02 to about 5mm, or about 0.02 to about 2mm, or about 0.02 to about 1 mm. The number of fins in the process microchannel 285 can be about 1 to about 50 fins per cm of the width of the process microchannel 285, or about 1 to about 30 fins per cm, or about 1 to about 10 fins per cm, or about 1 to about 5 fins per cm, or about 1 to about 3 fins per cm. Each fin may have a cross section in the form of a rectangle or a square as shown in fig. 10 or 11, or a cross section in the form of a trapezoid as shown in fig. 12. Each fin may be straight, tapered or have a serpentine configuration when viewed along its length. The fin assembly may be made of any material that provides sufficient strength, dimensional stability, and heat transfer characteristics to allow the intended operation of the process microchannel. These materials include: steel (e.g., stainless steel, carbon steel, etc.); aluminum; titanium; nickel; platinum; (ii) rhodium; copper; chromium; alloys of any of the foregoing metals; monel alloy; inconel alloys; brass; polymers (e.g., thermosetting resins); a ceramic; glass; quartz; silicon; or a combination of two or more thereof. The fin assembly may be made of Al₂O₃Or Cr₂O₃A forming material in which Al is formed on the surface of the fin assembly when the fin assembly is heat-treated in air₂O₃Or Cr₂O₃Of (2) a layer of (a). The fin assembly may be made of an alloy containing Fe, Cr, Al, and Y, or an alloy containing Ni, Cr, and Fe.

The catalyst may be supported on one or more corrugated inserts disposed in slots within the microchannel reactor. This is illustrated in fig. 14, where the microchannel reactor 110 includes a corrugated insert 300 that is inserted into a slot 302. The slot 302 may contain microchannels and have the dimensions shown above for microchannels. Alternatively, the slot 302 may haveMaking it larger than the dimensions of the microchannel. The process microchannels of the microchannel reactor may contain slots 302, or may be disposed in the corrugated insert 300 and/or formed by openings between the inner sidewalls of the slots 302 and the insert 300. The height of each corrugated insert 300 may be about 0.02mm to at most the height of the slots 302, or about 0.02 to about 10mm, or about 0.02 to about 5mm, or about 0.02 to about 2 mm. The width of each corrugated insert 300 may be about 0.02mm to at most the width of the slots 302, or about 0.02 to about 10mm, or about 0.02 to about 5mm, or about 0.02 to about 2 mm. The length of each corrugated insert may be any length up to the length of the slot 302, or up to about 10m, or from about 0.5 to about 6m, or from about 0.5 to about 3 m. The corrugated insert 300 may be made of any material that provides sufficient strength, dimensional stability, and heat transfer characteristics to allow for the intended operation of the microchannel reactor. These materials include: steel (e.g., stainless steel, carbon steel, etc.); aluminum; titanium; nickel; platinum; (ii) rhodium; copper; chromium; alloys of any of the foregoing metals; monel alloy; inconel alloys; brass; polymers (e.g., thermoset resins); a ceramic; glass; quartz; silicon; or a combination of two or more thereof. The corrugated insert 300 may be made of an alloy that, when heat treated in air, forms Al on the surface of the insert₂O₃Or Cr₂O₃Of (2) a layer of (a). The corrugated insert 300 may be made of an alloy containing Fe, Cr, Al, and Y, or an alloy containing Ni, Cr, and Fe.

The catalyst may be wash coated or grown from solution directly on the inner walls of the process microchannels and/or on one or more of the catalyst support structures described above. The catalyst may be in the form of a block of porous continuous (coherent) material, or in the form of a plurality of blocks in physical contact. The catalyst may comprise a continuous material and have a continuous porosity such that molecules may diffuse through the catalyst. In this embodiment, the fluid may flow through the catalyst rather than around it. The cross-sectional area of the catalyst can comprise from about 1 to about 99%, or from about 10 to about 95% of the cross-sectional area of the process microchannel.

The catalyst may comprise a support, an interfacial layer on the support, and a catalyst material on or mixed with the interfacial layer. The support may comprise one or more of the foams, felts, briquettes, fin structures, or corrugated inserts described above. The interfacial layer may be a solution deposited on the support, or it may be deposited by chemical vapor deposition or physical vapor deposition. The catalyst may comprise a support, a buffer layer, an interfacial layer, and a catalyst material. The support may be porous. Any of the above layers may be continuous or discontinuous, e.g. in the form of spots or dots, or in the form of a layer with gaps or holes. The support may have a porosity (as measured by mercury porosimetry) of at least about 5% and an average pore diameter (total number of pore diameters divided by number of pores) of about 1 to about 2000 microns, or about 1 to about 1000 microns. The support may be a porous ceramic or metal foam. Other supports that may be used include carbides, nitrides and composite materials. The support may have a porosity of about 30% to about 99%, or about 60% to about 98%. The support may be in the form of a foam, felt, mass, or combination thereof. The open cells of the metal foam may be from about 20 pores per inch (ppi) to about 3000ppi, and in one embodiment from about 20 to about 1000ppi, and in one embodiment from about 40 to about 120 ppi. The term "ppi" refers to the maximum number of pores per inch (in isotropic materials, the direction of measurement does not matter; however, in anisotropic materials, the measurement is made in the direction that maximizes the number of pores).

When present, the buffer layer may have a different composition and/or density than the support and the interface layer, and in one embodiment has a coefficient of thermal expansion that is intermediate to the coefficients of thermal expansion of the porous support and the interface layer. The buffer layer may be a metal oxide or a metal carbide. The buffer layer may include Al₂O₃、TiO₂、SiO₂、ZrO₂Or a combination thereof. Al (Al)₂O₃May be alpha-Al₂O₃、γ-Al₂O₃Or a combination thereof. The buffer layer may include an oxide layer (e.g., Al) formed by heat-treating the support in air₂O₃Or Cr₂O₃). The buffer layer may be formed from two or more compositionally distinct sub-layers. For example, when the porous support is a metal such as stainless steel foam, a buffer layer consisting of two sub-layers that differ in composition may be used. The first sublayer (in contact with the porous support) may be TiO₂. The second sublayer may be disposed on the TiO₂alpha-Al of (A)₂O₃. In one embodiment, alpha-Al₂O₃The sub-layer is a dense layer that provides protection to the underlying metal surface. A less dense, high surface area interfacial layer, such as alumina, may then be deposited as a support for the catalytically active layer.

The support may have a different coefficient of thermal expansion than the interface layer. In this case, the buffer layer may need to transition between two coefficients of thermal expansion. The buffer layer may be tailored in its coefficient of thermal expansion by controlling its composition to achieve a coefficient of expansion compatible with the coefficients of expansion of the porous support and the interfacial layer. The buffer layer should be free of openings and pinholes to provide excellent protection for the underlying support. The buffer layer may be non-porous. The buffer layer may have a thickness of less than half the average pore size of the porous support. The thickness of the buffer layer may be about 0.05 to about 10 μm, or about 0.05 to about 5 μm.

In one embodiment, sufficient adhesion and chemical stability can be achieved without the need for a buffer layer. In this embodiment, the buffer layer may be omitted.

The interfacial layer may comprise a nitride, carbide, sulfide, halide, metal oxide, carbon, or combinations thereof. The interfacial layer provides a high surface area and/or provides the desired catalyst-support interaction for the supported catalyst. The interfacial layer may be composed of any material conventionally used as a catalyst support. The interfacial layer may comprise a metal oxide. Examples of metal oxides that may be used include alpha-Al₂O₃、 SiO₂、ZrO₂、TiO₂Tungsten oxide, magnesium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, nickel oxide, cobalt oxide, copper oxide, zinc oxide, molybdenum oxide, tin oxide, calcium oxide, aluminum oxide, lanthanide oxide, barium oxide, magnesium oxide, cobalt oxide, copper oxide, zinc oxide, magnesium,Zeolites and combinations thereof. The interfacial layer may act as a catalytically active layer without any other catalytically active material deposited thereon. The interfacial layer may be used in combination with a catalytically active layer. The catalyst may be mixed with the interfacial layer. The interfacial layer may also be formed from two or more compositionally different sublayers. The thickness of the interfacial layer may be less than half the average pore size of the porous support. The interfacial layer thickness may be from about 0.5 to about 100 μm, and in one embodiment from about 1 to about 50 microns. The interfacial layer may be crystalline or amorphous. The BET surface area of the interfacial layer may be at least about 1m²/g。

A catalyst may be deposited on the interfacial layer. Alternatively, the catalyst may be deposited simultaneously with the interfacial layer. The catalyst layer may be intimately dispersed on the interfacial layer. The "dispersion" or "deposition" of the catalyst layer on the interfacial layer includes the general understanding that microscopic catalyst particles are dispersed in: on the surface of the carrier layer (i.e., the interface layer), in the interstices of the carrier layer, and in the open pores of the carrier layer.

The catalyst may be a catalyst bed that is compositionally graded or graded with a material that is inert to heat transfer. A thermally conductive inert material may be dispersed in the active catalyst. Examples of thermally conductive inert materials that may be used include diamond powder, silicon carbide, aluminum oxide, copper, graphite, and the like. The portion of the catalyst bed may range from about 100 wt% active catalyst to less than 50 wt% active catalyst. The portion of the catalyst bed may be from about 10 wt% to about 90 wt% active catalyst, and in one embodiment from about 25 wt% to about 75 wt%. In another embodiment, the heat transfer inert material may be disposed at the center of the catalyst or within the catalyst particles. The active catalyst may be deposited on the outside, inside or between composite structures comprising thermally conductive inert materials. The resulting catalyst composite structure may have an effective thermal conductivity of at least about 0.3W/m/K, in one embodiment at least about 1W/m/K, and in one embodiment at least about 2W/m/K when placed in the process microchannels or combustion channels.

The catalyst bed may be only partially staged within the process microchannels. For example, a process microchannel may contain a catalyst bed having a first reaction zone and a second reaction zone. The top or bottom (or front or back) of the catalyst bed may be graded in composition, thereby using a more or less active catalyst in all or part of the first or second reaction zone. The reduced composition in one reaction zone may result in less heat per unit volume and thereby reduce the potential for hot spots and the production of undesirable by-products, such as methane in a fischer-tropsch reaction. The catalyst may be classified with inert materials in all or part of the first and/or second reaction zones. The first reaction zone may contain a first composition of catalyst or inert material, while the second reaction zone may contain a second composition of catalyst or inert material.

Different particle sizes may be used in different axial regions of the process microchannels to provide a graded catalyst bed. For example, very small particles may be used in the first reaction zone, while larger particles may be used in the second reaction zone. The average particle diameter may be less than half the height or spacing of the process microchannels. Very small particles may be less than one-fourth the height or spacing of the process microchannels. Larger particles can result in lower pressure drop per unit length of the process microchannels and can also reduce catalyst efficiency. For larger sized particles, the effective thermal conductivity of the catalyst bed may be reduced. Smaller particles may be used in areas where improved heat transfer is desired throughout the catalyst bed, or larger particles may be used to reduce the local heat generation rate.

Relatively short contact times, high selectivity to desired products, and relatively low deactivation rates of the catalyst can be achieved by limiting the diffusion path required for the catalyst. This can be achieved when the catalyst is in the form of a thin layer on an engineered support such as a metal foam or on the walls of the process microchannel. This may allow for an increase in space velocity. Chemical vapor deposition methods may be used to produce thin layers of catalyst. The thin layer may have a thickness of up to about 1 micron, and in one embodiment from about 0.1 to about 0.5 micron, and in one embodiment about 0.25 micron. These thin layers can reduce the time of reactants in the active catalyst structure by shortening the diffusion path. This can reduce the time spent by the reactants in the active part of the catalyst. This result may improve selectivity to product and reduce undesirable by-products. An advantage of this mode of catalyst distribution may be that the active catalyst film may be in intimate contact with the walls of the engineered structure or process microchannels, unlike conventional catalysts in which the active portion of the catalyst may be bound to inert, low thermal conductivity binders. This can achieve high heat transfer rates in the microchannel reactor and allows for precise temperature control. This can lead to the ability to operate at elevated temperatures (faster kinetics) without promoting the formation of undesirable by-products, thus resulting in higher productivity and yields and extended catalyst life.

The configuration of the microchannel reactor 110 can be tailored to match the reaction kinetics. The microchannel height or gap may be less near the entrance or top of the first reaction zone of the process microchannels than near the exit or bottom of the process microchannels in the second reaction zone. Alternatively, the reaction zone may be less than half the length of the process microchannel. For example, for the first 25%, 50%, 75%, or 90% of the length of the process microchannels of a first reaction zone, a first process microchannel height or gap may be used, while a second, larger height or gap may be used in a second reaction zone downstream of the first reaction zone. This arrangement may be suitable for carrying out a fischer-tropsch reaction. Other staging schemes for the height or spacing of the process microchannels may be used. For example, a first height or gap may be used near the inlet of the microchannel to provide a first reaction zone, a second height or gap may be used downstream of the first reaction zone to provide a second reaction zone, and a third height or gap may be used to provide a third reaction zone near the outlet of the microchannel. The first and third heights or gaps may be the same or different. The first and third heights or gaps may be less than or greater than the second height or gap. The third height or gap may be less than or greater than the second height or gap. The second height or gap may be greater than or less than the third height or gap.

The catalyst may be regenerated by flowing a regeneration fluid through process microchannel combustion channels in contact with the catalyst. The regeneration fluid may comprise hydrogen or a diluted hydrogen stream. The diluent may comprise nitrogen, argon, helium, methane, carbon dioxide, steam, or a mixture of two or more thereof. The temperature of the regeneration fluid may be from about 50 to about 400 deg.C, and in one embodiment from about 200 to about 350 deg.C. During the regeneration step, the pressure within the channels may be from about 1 to about 40 atmospheres, and in one embodiment from about 1 to about 20 atmospheres, and in one embodiment from about 1 to about 5 atmospheres. The residence time of the regenerating fluid in the channel is from about 0.01 to about 1000 seconds, and in one embodiment from about 0.1 to about 100 seconds.

The catalyst may be regenerated by: h in the reactant composition₂The molar ratio to CO is increased to at least about 2.5: 1, or at least about 3: 1, and the resulting conditioned feed composition is flowed through the process microchannels, contacting the catalyst, at a temperature of from about 150 ℃ to about 300 ℃, or from about 180 ℃ to about 250 ℃, for a period of from about 0.1 to about 100 hours, or in one embodiment from about 0.5 to about 20 hours, to provide a regenerated catalyst. The feed composition can be adjusted by interrupting the flow of all feed gases except hydrogen and passing the hydrogen through the process microchannels into contact with the catalyst. Can increase H₂To provide and contain H₂And the same contact time used for the reactant composition of CO. The conditioned feed composition may comprise H₂And is characterized by the absence of CO. Once the catalyst has been regenerated, it can be prepared by contacting the regenerated catalyst with a catalyst comprising H₂And an initial reactant composition of CO to continue the Fischer-Tropsch process. By removing wax and other hydrocarbons from the catalyst (usually by using H)₂Stripping), with air or other O-containing compounds₂The gas regenerates the catalyst by oxidizing the catalyst at an elevated temperature, re-reducing the catalyst, and then activating the catalyst.

Example 1

The catalyst precursor was prepared using the following reagents:

	suppliers of goods	Encoding	Purity of

Cobalt nitrate hexahydrate	Sigma-Aldrich	230375	98％
				Tetramine platinum hydroxide	Alfa Aesar	38201-97-7	9.3％Pt w/w
Silicon dioxide (SG432)	Grace Davison	(180-300μm)
				Citric acid monohydrate (CA)	Sigma Aldrich	C1909	ACS reagent
Perrhenic acid	Sigma Aldrich	70% by weight solution in water	99.99％

Support preparation

100g of 16% TiO are prepared from₂Modified silica (expressed in weight percentage of the catalyst support):

silicon dioxide (180 ion 300 μm)	84g
		Citric acid monohydrate	25g
Bis (2-hydroxypropionic acid) diammonium dihydroxide titanium (IV) solution (TALH)	118g(97mL)
		Approximate volume of solution	130-135mL

The silica only catalyst support material was dried at 100 ℃ for 2 hours and allowed to cool to room temperature before impregnation. 25g of citric acid was dissolved in a minimum amount of water at 40 to 45 ℃ and cooled to below 30 ℃. The citric acid solution was then added to 118g (97ml) of titanium (IV) bis (2-hydroxypropionic acid) dihydroxide solution (TALH) and made up with water to the desired impregnation volume (which was about 130 to 135 ml). The desired amount of silica (84g, weight measured after drying) was impregnated by spraying with the resulting citric acid-TALH impregnation solution.

Then, drying was performed at 2 ℃/100 ℃/5h (ramp/temperature/hold) and calcination was performed at 2 ℃/250 ℃/5h (ramp/temperature/hold). The yield of the modified catalyst support after drying and calcination was about 120 g. The color of the modified catalyst support was dark brown.

Preparation of the first impregnation solution

25g of cobalt nitrate hexahydrate (Sigma Aldrich, 98% purity) was dissolved in water, and the solution was then heated to 40 to 45 ℃ until the salt was completely dissolved. A minimum amount of water required is used to obtain a clear solution. 0.048g of perrhenic acid (Sigma Aldrich, 70% solution by weight in water, 99.99% purity) was added to the cobalt nitrate solution and mixed. The resulting solution was cooled to room temperature (less than 30 ℃) and made up to 19ml with water.

Impregnation-first step

The first impregnation of the modified catalyst support was carried out by impregnating 20g of the modified catalyst support with 19ml of cobalt nitrate/perrhenic acid solution. The resulting modified catalyst support was then dried by increasing to a temperature of 100 ℃ at a ramp rate of 2 ℃/min. The temperature was maintained at 100 ℃ for 5 hours. The modified support catalyst was then calcined, the temperature was increased to 200 ℃ using a ramp rate of 2 ℃/min and held at 200 ℃ for 3 hours, then the temperature was further increased to 250 ℃ using a ramp rate of 2 ℃/min and held at 250 ℃ for 1 hour.

Preparation of impregnation solution for the second to fourth steps

12g of citric acid monohydrate (Sigma Aldrich, ACS reagent) was dissolved in water. To the clear solution was added 81.4g of cobalt nitrate hexahydrate (Sigma Aldrich, 98% purity), followed by heating the solution to 40 to 45 ℃ until the salts were completely dissolved. A minimum amount of water required is used to obtain a clear solution. 0.14g perrhenic acid (Sigma Aldrich, 70 wt% solution in water, 99.99% purity) was added to the cobalt nitrate and citric acid solution and mixed. The resulting stock solution was cooled to room temperature (less than 30 ℃) and made up to 66 to 67ml with water.

Impregnation-second to fourth step

The second impregnation step was carried out by impregnating the modified catalyst support (27.20g) obtained from the first impregnation step with about 22ml of the stock solution. The modified catalyst support was then dried by increasing the temperature to 100 ℃ at a ramp rate of 2 ℃/min. The temperature was maintained at 100 ℃ for 5 hours. The modified support catalyst was then calcined by increasing the temperature to 250 ℃ using a ramp rate of 2 ℃/min and maintaining the temperature at 250 ℃ for 3 hours.

The third impregnation step was performed by impregnating the modified catalyst support (34.40g) obtained from the second impregnation step with about 22ml of the stock solution. The modified catalyst support was then dried by increasing the temperature to 100 ℃ at a ramp rate of 2 ℃/min. The temperature was maintained at 100 ℃ for 5 hours. The modified support catalyst was then calcined by increasing the temperature to 250 ℃ using a ramp rate of 2 ℃/min and maintaining the temperature at 250 ℃ for 3 hours.

The fourth impregnation step was performed by impregnating the modified catalyst support (41.60g) obtained from the third impregnation step with about 22ml of the stock solution. The modified catalyst support was then dried by increasing the temperature to 100 ℃ at a ramp rate of 2 ℃/min. The temperature was maintained at 100 ℃ for 5 hours. The modified support catalyst was then calcined by increasing the temperature to 250 ℃ using a ramp rate of 2 ℃/min and maintaining the temperature at 250 ℃ for 3 hours.

The four impregnation steps are summarized in Table 1. The total values in table 1 relate only to the total values of steps 2 to 4.

Accelerator addition-fifth impregnation step

Then, using 20g of the catalyst precursor obtained after the four impregnation steps, a promoter addition step was performed. 0.06g of tetraamine platinum hydroxide (Alfa Aesar, 9.3% Pt w/w) was added to 9ml of water to prepare a diluted solution and the solution was used to further impregnate the catalyst precursor. After impregnation, the catalyst was subsequently dried by increasing to a temperature of 100 ℃ at a ramp rate of 2 ℃/min. The temperature was maintained at 100 ℃ for 5 hours. The catalyst was then calcined by increasing the temperature to 250 ℃ using a ramp rate of 2 ℃/min and maintaining the temperature at 250 ℃ for 3 hours. The resulting catalyst had 0.03% Pt.

Example 2

The catalyst of example 1 was used in a series of fischer-tropsch reactions carried out in microchannel reactors using the reactants fresh synthesis gas, or a mixture of fresh synthesis gas and tail gas. Fig. 13 is a process flow diagram illustrating the method used. The results are shown in Table 2. The data in table 2 were generated using a single microchannel reactor. Carbon monoxide (CO), hydrogen (H) using calibrated mass flow controllers₂) And nitrogen (N)₂) Are delivered to the reactor separately so that the flow of each gas can be varied independently to simulate different process settings, such as a single reactor stage with a recycle loop. The reaction temperature was controlled with hot oil flowing concurrently in two adjacent microchannels which were not in fluid communication with the reaction chamber. In a series of three separators with interstage heat exchangers, the reaction products and unreacted gases are separated into a condensed stream and a vapor stream, and each separator vessel is maintained at a decreasing temperature. At the end of the separator train, the tail gas (vapor phase reaction product plus unreacted feed gas) is passed through a pressure control valve (setting)To control the pressure at the reactor inlet) exits the system.

Determining the reaction performance by characterizing the outlet stream; the dried tail gas composition was analyzed using an Agilent 3000A micro gas chromatograph and the outlet flow was measured using a gasometer. The outlet flow of any species is calculated by multiplying the mole percent by the total gas flow, normalized to the same reference conditions used to calibrate the mass flow controller. By conversion of CO and selectivity to methane (plus up to C)₈Other hydrocarbon species) to determine the performance of the reactor. The amount of CO converted is determined by subtracting the outlet CO flow from the calibrated inlet flow. Percent conversion was calculated by converting the amount of CO by the throughput of CO from the reactor inlet. Methane (C)₁) The selectivity is calculated by dividing the amount of methane produced by the amount of CO converted.

Abbreviations

CO flow to reactor: CO 2_Into

Mole% of species in the off-gas, as measured by micro GC: [ substances ], e.g. [ CO ]

Total tail gas outlet flow: flow rate_{Go out}

CO_inSetting by calibrated MFC

CO_out＝[CO]x flow_{Go out}

CO conversion rate 100% (CO)_Into-CO_{Go out})/CO_Into

C1 Selectivity 100% x flow_{Go out}x[C1]/(CO_Into-CO_{Go out})

The condensed FT reaction products were collected from three separators, weighed to determine production rate, and analyzed separately using an Agilent 7890 gas chromatograph using a method derived from ASTM D2887. The GC data was combined in proportion based on the production rate of each phase to generate the full carbon number distribution shown in the relevant file.

While the invention has been described in connection with various embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. It is therefore to be understood that the invention disclosed herein includes any such modifications as may fall within the scope of the appended claims.

Claims

1. A process for carrying out a fischer-tropsch reaction, comprising:

flowing a reactant mixture formed from fresh syngas and tail gas in a microchannel reactor in contact with a catalyst to form a product comprising at least one hydrocarbon product having 5 or more carbon atoms, the microchannel reactor comprising at least one process microchannel and at least one heat exchange channel in thermal contact with the at least one process microchannel, the catalyst being in the at least one process microchannel, the at least one heat exchange channel having a heat exchange fluid therein for heat exchange with the at least one process microchannel, wherein the catalyst comprises from 10 to 60 wt% cobalt based on the weight of metal as a percentage of the total weight of the catalyst;

wherein the product further comprises a tail gas comprising H₂And CO, at least a portion of the tail gas being separated from the hydrocarbon products and combined with fresh syngas to form the reactant mixture in which the volume ratio of the fresh syngas to the tail gas is from 1:1 to 10: 1;

the reactant mixture comprises H₂And CO, in the reactant mixture, H₂The molar ratio to CO is 1.4:1 to 2.1: 1;

wherein the rate of deactivation of the catalyst is less than 1.4%/day;

wherein the conversion of CO is 88% to 95% based on the CO in the fresh syngas in the reactant mixture; and is

The selectivity to methane in the product is from 0.01 to 10%.

2. The process of claim 1 wherein the microchannel reactor comprises a plurality of process microchannels and a plurality of heat exchange channels.

3. The process of claim 1 wherein the microchannel reactor comprises a plurality of process microchannels and a plurality of heat exchange channels, each heat exchange channel being in thermal contact with at least one process microchannel; at least one manifold for flowing the reactant mixture into the process microchannels; at least one manifold for flowing product out of the process microchannels; at least one manifold for flowing a heat exchange fluid into the heat exchange channels; and at least one manifold for flowing the heat exchange fluid out of the heat exchange channels.

4. The process of claim 1 wherein a plurality of the microchannel reactors are disposed in a vessel, each microchannel reactor comprising a plurality of process microchannels and a plurality of heat exchange channels, each heat exchange channel in thermal contact with at least one process microchannel, the vessel being equipped with a manifold for flowing the reactant mixture to the process microchannels, a manifold for flowing product out of the process microchannels, a manifold for flowing a heat exchange fluid to the heat exchange channels, and a manifold for flowing the heat exchange fluid out of the heat exchange channels.

5. The process of claim 4 wherein the vessel contains from 1 to 1000 microchannel reactors.

6. The process of claim 1 wherein the internal dimension of said at least one process microchannel has a width or height of at most 10 mm.

7. The process of claim 1 wherein said at least one process microchannel has a length of at most 10 meters.

8. The process of claim 1 wherein said at least one process microchannel and said at least one heat exchange channel are made from materials comprising: aluminum; titanium; nickel; copper; alloys of any of the foregoing metals; steel; quartz; silicon; or a combination of two or more thereof.

9. The process of claim 1 wherein the reactant mixture flows in the at least one process microchannel and contacts surface features in the process microchannel, the contacting of the surface features imparting an interfering flow to the reactant mixture.

10. The method of claim 1, wherein the at least one heat exchange channel comprises a microchannel.

11. The process of claim 1, wherein the catalyst is in the form of a particulate solid.

12. The process of claim 1 wherein the catalyst is coated on or grown on the interior walls of the at least one process microchannel.

13. The method of claim 1, wherein the catalyst is supported on a support in the form of a fin assembly comprising a plurality of fins.

14. The method of claim 1, wherein the catalyst is supported on corrugated inserts disposed in slots within the microchannel reactor.

15. The process of claim 1 wherein the at least one process microchannel has at least one heat transfer wall and the heat flux for heat exchange within the microchannel reactor ranges from 0.01 to 500 watts per square centimeter of surface area of the at least one heat transfer wall.

16. The process of claim 1 wherein the pressure in the at least one process microchannel is at most 50 atmospheres.

17. The process of claim 1 wherein the temperature in the at least one process microchannel is from 150 to 300 ℃.

18. The process of claim 1 wherein the contact time of said reactant mixture with said catalyst within said at least one process microchannel is at most 2000 milliseconds.

19. The method of claim 1, wherein the at least one hydrocarbon product comprises one or more hydrocarbons boiling at least 30 ℃ at atmospheric pressure.

20. The method of claim 1, wherein the at least one hydrocarbon product comprises one or more hydrocarbons having a boiling point above 175 ℃ at atmospheric pressure.

21. The process of claim 1, wherein the at least one hydrocarbon product comprises one or more alkanes and/or one or more alkenes.

22. The process of claim 1, wherein the at least one hydrocarbon product comprises one or more olefins, one or more normal paraffins, one or more isoparaffins, or a mixture of two or more thereof.

23. The method of claim 1, wherein the at least one hydrocarbon product is further processed using separation, hydrocracking, hydroisomerization, dewaxing, or a combination of two or more thereof.

24. The method of claim 23, wherein the separation is fractional distillation.

25. The process of claim 1 wherein the at least one hydrocarbon product is further processed to form an oil of lubricating viscosity or a middle distillate fuel.

26. The method of claim 1, wherein the at least one hydrocarbon product is further processed to form a fuel.

27. The process of claim 1 wherein the process microchannels have fluid flowing therein in one direction and the at least one heat exchange channel has fluid flowing in a co-current or counter-current direction to the flow of fluid in the at least one process microchannel.

28. The process of claim 1 wherein the at least one process microchannel has a fluid flowing therein in one direction and the at least one heat exchange channel has a fluid flowing therein in a cross-current direction to the flow of fluid in the at least one process microchannel.

29. The process of claim 1 wherein customized heat exchange features are provided along the length of the at least one process microchannel, the localized release of heat generated by the reaction conducted in the at least one process microchannel being matched to the cooling provided by the at least one heat exchange microchannel.

30. The method of claim 1, wherein the catalyst comprises a staged catalyst.

31. The process of claim 1 wherein the superficial velocity of the fluid flowing in the at least one process microchannel is at least 0.01 m/s.

32The process of claim 1 wherein the volumetric space velocity of the fluid flowing in the at least one process microchannel is at least 1000hr^-1。

33. The process of claim 1 wherein the pressure drop of the fluid flowing in the at least one process microchannel is at most 10 atm/m.

34. The process of claim 1 wherein the reynolds number for the flow of fluid in the process microchannels is from 10 to 4000.

35. The method of claim 1 wherein the microchannel reactor comprises a plurality of process microchannels formed by disposing corrugations between planar sheets.

36. The method of claim 35 wherein the microchannel reactor further comprises a plurality of heat exchange channels in thermal contact with the process microchannels, the heat exchange channels formed by arranging corrugations between planar sheets.

37. The process of claim 1 wherein the microchannel reactor comprises a plurality of plates in a stack defining a plurality of fischer-tropsch process layers and a plurality of heat exchange layers, each plate having a peripheral edge, the peripheral edge of each plate being welded to a peripheral edge of the next adjacent plate to provide a peripheral seal for the stack.

38. The method of claim 1, wherein the product comprises H₂O and H₂H of said product₂Partial pressure of O from 3 to 10 bar, H of the product₂O/H₂The molar ratio is 1:1 to 5: 1.