WO2022243212A1

WO2022243212A1 - Process for conversion of biological feedstocks to middle distillates with catalytic inhibitor removal

Info

Publication number: WO2022243212A1
Application number: PCT/EP2022/063118
Authority: WO
Inventors: Dominic DEBONIS
Original assignee: Axens
Priority date: 2021-05-18
Filing date: 2022-05-16
Publication date: 2022-11-24
Also published as: EP4341363A1; CN117460806A; BR112023023478A2

Abstract

The invention relates to an improved apparatus and methods for removing carbon dioxide during the hydroprocessing and/or hydrotreatment of biological feedstocks in the making of middle distillates. The improved apparatus and methods eliminates the need for multiple auxillary processes to support it including, for example, an amine regeneration unit, thus significantly decreasing not only the cost of constructing such a facility, but also the energy intensity and by extension the carbon footprint required to make the renewable fuel.

Description

Process for Conversion of Biological Feedstocks to Middle Distillates with Catalytic

Inhibitor Removal FIELD OF THE INVENTION

The invention relates to an improved apparatus and methods for removing carbon dioxide during the hydrotreatment and/or hydroprocessing of biological feedstocks in the making of middle distillates. BACKGROUND

Recent years have been marked by the rapid growth in need of fuels, in particular diesel fuel bases in the European community and also by the importance of the problems related to global warming and the emission of greenhouse gases. The result is a desire to reduce energy dependence on fossil- based raw materials and on reducing C02 emissions. In this context, the search for new methods to manufacture fuels from renewable sources that can be easily integrated into the traditional pattern of refining and fuel production is an issue of increasing importance. As such, the integration into the refining process of new products of plant origin, resulting from the conversion of lignocellulosic biomass or from the production of vegetable oils or animal fats, has in recent years experienced a growing interest due to the rising cost of fossil fuels. In addition, such processes known to date using vegetable oils or animal fats are responsible for significant emissions of C02, known for its negative effects on the environment. A more efficient and effective processing method of these bio-resources that reduces the emissions of C02, prior to their integration in the fuel pool would therefore be a definite advantage.

The production of fuel bases is therefore increasingly identified as an attractive new outlet for the agricultural world, especially for vegetable oil producers, who grind oilseeds such as rapeseed, soya beans or sunflower seeds. In fact, these vegetable oils consist of fatty acids, primarily in the form of triglycerides having long alkyl chains whose structure corresponds to the normal paraffins of the gas oil and kerosene cuts (chain length of 12 to 24 carbon atoms, depending on the nature of the vegetable oil). Unsuitable in its unprocessed form as fuel in modern diesel engines, these vegetable oils must be transformed beforehand. Two chemical pathways for the conversion of these biological feedstocks to middle distillate fuels is commonly used: transesterification and hydrotreating. The transesterification reaction utilizes an alcohol such as methanol leading to methyl esters of vegetable oils (VOME) commonly called biodiesel. This path is now widely used in Europe since the production of VOME has increased dramatically in the last ten years, reaching 1.5 Mt in 2003 (the average annual growth rate was 35% between 1992 and 2003). This production is supported in particular by the European directive on the promotion of biofuels (2003/30 / EC), which sets increasing targets for biofuel consumption in the transport sector. These consumptions will have to represent at least 20/0 in 2005, 5,750 / 0 in 2010 and 8% (percentages measured in energy) in 2015 of the global consumption of gasoline and diesel fuel used in transport. However, this type of process is relatively expensive and requires limiting the type of vegetable oils to meet biodiesel specifications. In addition, the charges for this type of process must be carefully selected, so that a number of vegetable oils can not be treated in this way. Finally, the cold properties of these products are also a limiting factor.

As mentioned above, another approach consists in directly exploiting vegetable oils via their transformation into elemental fatty acid derivatives, by means of hydrotreatment or hydroconversion processes whose catalysts are also well known to those skilled in the art for their hydrodeoxygenation properties. (E. Lawrence, Delmon B., Catal.App., 1994, 109, 1, 77 and 97).

Hydrotreating has been used more frequently commercially due to its ability to produce hydrocarbon product with greater stability and ease of blending with hydrocarbons derived from mineral oil. In this case, the triglycerides are converted into mainly paraffinic and saturated derivatives, thus constituting excellent hydrocarbon bases for the diesel fuel pool because of their high cetane numbers.

In a typical renewable diesel plant configuration, hydrogen from a hydrogen plant is fed along with pretreated biological feedstock for hydroprocessing, including a hydrotreatment step and an isomerization step. The biological feedstock generally needs to be pretreated because, contaminants contributing to the presence of trace elements in animal fats and/or plant oils, hinder the ability to catalytically convert these feedstocks to hydrocarbons during hydroprocessing. For example, certain elements and compounds containing these elements (e.g., phosphorous, phosphorous-containing compounds, and metals such as calcium and magnesium) poison or reduce the activity of hydroprocessing catalysts, thereby shortening their useful life and consequently increasing the overall cost of biofuel production. Treating methods to reduce certain contaminants of the fatty acid- or triglyceride-containing component (and therefore contaminants of the feedstock), to the greatest extent possible, therefore provide important commercial advantages in the hydroprocessing of biological feedstocks to middle distillate products. A wide variety of different pretreatment schemes have been reported, each offering different advantages and disadvantages. The hydrotreatment of triglycerides includes several different reactions. In the first reaction, hydrogen is added to saturate the double bonds of the unsaturated vegetable oil triglycerides. In the second reaction, hydrogen is added to remove the propane backbone, hereby converting the saturated vegetable oil triglycerides to fatty acids. Finally, the fatty acids either undergo hydrodeoxygenation (by addition of more hydrogen the oxygen leaves as FbO) or decarboxylation (oxygen leaves as CO2 without further addition of hydrogen), or a combination of these two. The result is a mixture of straight chain paraffinic hydrocarbons. Shown below is the reaction pathway for the hydrotreatment process.

Decarboxylation The alkane isomerisation and cracking step thereafter brings the biofuel to a quality that equals or surpasses specifications for conventional petroleum fuels. A major drawback of the hydrotreating pathway however is that it requires multiple auxiliary processes to support it; these additional processes increase not only the cost of constructing such a facility, but also increase the energy intensity and by extension the carbon footprint required to make the renewable fuel. One such example is the amine regeneration unit. Amine is often used in current state of the art processes for hydrotreating triglycerides and fatty acids to remove carbon dioxide. To adequately remove carbon dioxide, often a specialty amine is required; most conventional amines either do not readily remove carbon dioxide or result in other operational issues such as severe fouling. The amine regeneration itself also represents an additional investment cost and requires significant energy input. Prior art also suggests conventional pressure-driven membranes can be used to remove carbon dioxide from the hydrotreating section. For these membranes however, the hydrogen rich side is the permeate, resulting in significant pressure losses that require additional compression to be recovered. Pressure-driven membranes then effectively separate hydrogen from hydrocarbon gasses and carbon monoxide, but they do not effectively separate hydrogen gas from carbon dioxide.

In light of the above, Applicants have disclosed an invention comprising an efficient and effective processing scheme that can be used to remove carbon dioxide from the hydrotreating section using a membrane. These and other features of the present invention will be more readily apparent from the following description with reference to the accompanying drawings.

SUMMARY OF THE INVENTION It is an object of the invention to create an efficient and effective processing scheme that can be used to remove carbon dioxide from the hydrotreating section of a biomass processing facility using a membrane instead of amine absorption processes.

It is another object of the invention to create an efficient and effective processing scheme to remove carbon dioxide from the hydrotreating section of a biomass processing facility using a membrane wherein the recycle gas in the hydrotreating section is routed through a membrane and wherein the membrane has a higher permeability for carbon dioxide than for hydrogen gas.

It is yet a further object of the invention to efficient and effective processing scheme to remove carbon dioxide from the hydrotreating section of a biomass processing facility using a membrane that requires significantly less compression than a typical processing scheme utilizing a membrane to remove carbon dioxide. More particularly, the present invention provides a method and apparatus for efficiently and effectively removing carbon dioxide from the hydroprocessing reactor section of a biomass feedstock processing facility comprising: a) contacting a biological feedstock with hydrogen gas and a solid catalyst in a hydroprocessing reactor to produce a vapor hydroprocessing effluent stream and a liquid hydroprocessing effluent stream; and b) feeding said vapor hydroprocessing effluent stream to a membrane separator of which the permeability of carbon dioxide is greater than the permeability of hydrogen wherein a substantial portion of the carbon dioxide in said vapor hydroprocessing effluent stream diffuses through said membrane separator to create a permeate stream and wherein a substantial portion of the hydrogen in said vapor hydroprocessing effluent stream remains on the other side of said membrane separator to create a residue stream; and c) recycling at least a portion of said residue stream back to said hydroprocessing reactor where the hydrogen in said residue stream is utilized as a reactant for hydrodeoxygenation, hydrogenation, hydrodesulfurization, and/or hydrodenitrification of said biological feedstock in said hydroprocessing reactor.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a particular embodiment of Applicant’s scheme for removal of carbon dioxide using a membrane in a renewable middle distillate and/or diesel processing plant.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a particular embodiment of Applicant’s scheme for removal of carbon dioxide using a membrane in a renewable middle distillate and/or diesel processing plant.

As used herein “for efficiently and effectively removing carbon dioxide” means that the carbon dioxide removal step allows to remove at least 50% of the initial carbon dioxide (in volume), preferably between 50% and 90% of the initial carbon dioxide (in volume), depending on the sizes of the membrane.

As used herein “hydrotreating or hydrotreatment” means chemical reactions between the hydrocarbon feedstock and hydrogen including hydrodenitrification, hydrodesulfurization, hydrodeoxygenation, hydrogenolysis, alkene saturation, and olefin saturation; this term will also be used herein to include decarboxylation and decarbonylation, as these reactions occur simultaneously as a competing reaction to hydrogenolysis under the given reaction conditions.

As used herein “hydroprocessing” means a process in which the hydrotreatment reactions occur between the hydrocarbon feedstock and hydrogen when contacted with the catalyst bed. The hydroprocessing process may also include, in addition to the catalyst bed(s), one or more of the following: separation of liquid stream(s) and vapor stream(s) downstream of the catalyst bed(s), a recycle gas loop, recycle liquid loop(s). Further, the hydroprocessing process may also include an isomerization and/or hydrocracking step with different catalyst(s) to facilitate isomerization/hydrocracking of paraffinic hydrocarbons.

As used herein “middle distillates” means hydrocarbon fuels generally comprising primarily of hydrocarbon components boiling above 150°C including, for example, kerosene, diesel, or gasoil.

As used herein “biological feedstocks” means vegetable oils, animal fats, tall oil, and derived material such as fatty acid alkyl esters, or combinations thereof. Vegetable oils include, but are not limited to, rapeseed oil, soybean oil, corn oil, coconut oil, olive oil, linseed oil, sunflower oil, palm oil, jatropha oil, mustard oil, peanut oil, hemp oil, and cottonseed oil. Animal fats include, but are not limited to, pork fat, poultry fat, lard, butter and tallow.

As used herein, the term light ends or light hydrocarbons means chemical compounds lighter than pentane including methane, ethane, propane, n-butane, or isobutane. Such light hydrocarbons or “light ends” are often used in some hydrocarbon processing schemes as a feedstock and/or as a fuel.

As used herein LHSV is the liquid hourly space velocity, which is the ratio of liquid volume flow per hour to catalyst volume. For example, a system with a flow rate 2 m³/h and lm³ of catalyst would have an LHSV of 2. (The units are 1/hr). LHSV is inversely proportional to residence time.

A biological feedstock (preferably pretreated) 10 is fed along with a hydrogen treat gas 15 to a hydroprocessing reactor section 12 for hydrotreating. The hydrogen treat gas 15 may include a hydrogen feed stream 11 and/or a recycle hydrogen stream 31 from the membrane separation section 30. Although not shown in Figure 1, the hydrogen feed stream 11 and the recycle feed stream 31 may be separately sent to the hy droproces sing reactor section 12 in lieu of being combined and sent as a treat gas stream 15.

The hydrogen feed stream 11 may come from any number of sources including Steam Methane Reforming (SMR), Autothermal Reforming, Partial Oxidation or any other hydrogen production technology known to those skilled in the art. In the hydroprocessing reactor section 12, hydrogen from the treat gas stream 15 is added to saturate the double bonds of the unsaturated vegetable oil triglycerides from the biological feedstock 10 and remove the propane backbone, thereby converting the saturated vegetable oil triglycerides to fatty acids. Finally, the fatty acids either undergo hydrodeoxygenation (by addition of more hydrogen the oxygen leaves as FhO) or decarboxylation (oxygen leaves as CO2 without further addition of hydrogen), or a combination of these two. The result is a liquid hydroprocessing effluent stream 14 comprising a mixture of paraffinic hydrocarbons and light ends and a vapor hydroprocessing effluent stream 13 comprising carbon dioxide, carbon monoxide, water vapor, hydrogen, and hydrocarbon lightends. This hydroprocessing reactor section 12 utilizes a solid catalyst to catalyze the hydrotreatment reactions.

Catalysts known in the art often use metals from group VIII such as nickel or cobalt alone or in combination with metals from group VIB such as molybdenum or tungsten. Catalyst types well known in the art (all in solid form) are sulfided forms of NiMo, C0M0, and NiW on an alumina support as well as reduced nickel. Depending upon the specific biological feedstock, the reaction typically operates at reaction temperatures generally between 180 °C and 400 °C, a pressure between 10 bar to 150 bar, and a LHSV of between 0.1 to 10 h^"1. The hydroprocessing reactor section 12 may also include catalyst that allow the straight chain paraffinic hydrocarbons to undergo alkane isomerization and cracking after the hydrotreatment reactions have taken place. The isomerization/cracking catalyst may be present in stage independent of the hydrotreatment reactions or share a common stage with the hydrotreatment reactions.

Optionally, the liquid hydroprocessing effluent stream 14 comprising a mixture of paraffinic hydrocarbons may thereafter be fed to a separation section 20. The optional separation section 20 typically may use a single vessel with multiple stages, such as a distillation column, but may use multiple vessels, particularly if it is desirable to achieve production of multiple hydrocarbon liquid products of varying boiling ranges.

The optional separation section 20 is operated at low pressure, and separates the liquid hydroprocessing effluent stream 14 into a hydrocarbon liquid product stream 22 and a vent gas stream 21. The hydrocarbon liquid product stream 22 typically comprises paraffinic hydrocarbons and is thereafter suitable for further processing by any number of methods known to those skilled in the art into saleable products including diesel fuel, kerosene, jet fuel, gas oil, and/or naphtha. The vapor hydroprocessing effluent stream 13 , which comprises carbon dioxide, carbon monoxide, water vapor, hydrogen, and hydrocarbon lightends, is thereafter sent to a membrane separation section 30. It is imperative that carbon dioxide is removed from the hydroprocessing reactor section 12; if the carbon dioxide removal is not accomplished, then there will be an accumulation of carbon dioxide and carbon monoxide, which will eventually cause an unacceptable level of inhibition in the catalyst beds of the hydroprocessing reactor section 12. The effects of this inhibition cascade to the rest of the scheme. Moreover, when the solid catalyst of the hydroprocessing reactor section 12 is severely inhibited, it cannot successfully remove the organic nitrogen or organic oxygen atoms, thus inhibiting possible downstream catalytic processes such as isomerization as well.

Carbon dioxide from the vapor hydroprocessing effluent stream 13 then diffuses through the membrane separation section 30 and is concentrated on the permeate side 30a. The permeate stream 32 is then removed from the membrane separation section 30 and may be routed to a fuel gas system to be burned; alternatively, the permeate stream may be sent to a destination wherein any hydrogen gas in the permeate stream 32 may be recovered, such as a PSA. Hydrogen is more favorably kept on the residue side 30b of the membrane separation section 30, to obtain a residue stream 31. In a preferred embodiment, the residue stream which comprises hydrogen is sent to the suction of a recycle compressor (not shown); the recycle compressor routs the hydrogen-rich residue stream 31 back to the hydroprocessing reactor section 12 either by itself or in combination with the hydrogen feed stream 11 , wherein the hydrogen is used as a reactant for hydrodeoxygenation, hydrogenation, hydrodesulfurization, and hydrodenitrification. Although not shown, make-up hydrogen may optionally be mixed into the recycle compressor suction if additional compression is required for the stream.

The membrane separation section 30 may operate between -20°F and 150°F (i.e. between -29°C and 66°C). The pressure at the process inlet of the feed side may operate between 1,500 psig and 300 psig (i.e. between 10,4 MPa and 2,2 MPa); the permeate side may operate from 500 psig to 0 psig (i.e. between 3,5 MPa and 0,1 MPa), but may preferably operate at a lower pressure than that of the membrane process inlet.

A significant advantage of this invention over amine absorption is that it does not require an amine supply in order to function. The invention also offers an advantage over conventional membrane separation because the hydrogen rich side is the membrane residue, substantially reducing the required compression required on the hydrogen rich stream as well as the level of pressure required to facilitate the separation thus saving costs as increased amounts of compression required to a system increases costs substantially. Due to the nature of the membrane separation section 30, the permeate stream 32 may still contain appreciable amounts of hydrogen gas. For this reason, it would be practical to send the permeate stream 32 to a hydrogen recovery system such as a PSA. If the amount of lightends is significant, it is possible to send the permeate stream as feedstock to a hydrogen production process such as a Steam Methane Reformer, to both recapture the hydrogen and convert the lightends to hydrogen, thus reducing the required amount of natural gas feed.

Figure 1 is one embodiment of the present invention. Although not shown on Figure 1, there are several other possible configurations of Applicants invention. First, while it is possible to recover any hydrogen in the permeate stream 32 as indicated above, it is still desirable to limit the amount of hydrogen in the permeate stream 32 so that the flowrate of hydrogen sent to the hydrogen recovery section is minimized. The invention described herein has been disclosed in terms of a specific embodiment and application. However, these details are not meant to be limiting and other embodiments, in light of this teaching, would be obvious to persons skilled in the art. Accordingly, it is to be understood that the drawings and descriptions are illustrative of the principles of the invention, and should not be construed to limit the scope thereof.

Claims

We claim:

1. A process for efficiently and effectively removing carbon dioxide from the hydroprocessing reactor section of a biomass feedstock processing facility comprising: a) contacting a biological feedstock with hydrogen gas and a solid catalyst in a hydroprocessing reactor to produce a vapor hydroprocessing effluent stream and a liquid hydroprocessing effluent stream; and b) feeding said vapor hydroprocessing effluent stream to a membrane separator of which the permeability of carbon dioxide is greater than the permeability of hydrogen wherein a substantial portion of the carbon dioxide in said vapor hydroprocessing effluent stream diffuses through said membrane separator to create a permeate stream and wherein a substantial portion of the hydrogen in said vapor hydroprocessing effluent stream remains on the other side of said membrane separator to create a residue stream; and c) recycling at least a portion of said residue stream back to said hydroprocessing reactor where the hydrogen in said residue stream is utilized as a reactant for hydrodeoxygenation, hydrogenation, hydrodesulfurization, and hydrodenitrification of said biological feedstock in said hydroprocessing reactor.

2. The process of claim 1 wherein said permeate stream from step b) is thereafter further processed in a pressure swing adsorption step to recover and purify any remaining hydrogen gas in said permeate stream.

3. The process of claim 1 wherein said permeate stream from step b) is thereafter further processed in a steam methane reformer or autothermal reformer to recapture hydrogen from said permeate stream and to convert any lightends in said permeate stream to hydrogen.

4. The process of claim 1 wherein said permeate stream from step b) is thereafter sent to a fuel gas processing system.

5. The process of one of the preceding claims wherein said membrane separator uses multiple membrane stages to produce multiple permeate streams.

6. The process of one of the preceding claims wherein said hydroprocessing reactor includes a hydrotreatment step and an isomerization step.

7. The process of claim 6 wherein said hydroprocessing reactor includes a hydrotreatment step and an isomerization step and wherein said hydrotreatment step utilizes at least one solid catalyst that is different from the solid isomerization catalyst used in said isomerization step and further wherein said solid catalyst used in said hydrotreatment step comprises a hydrodeoxygenation function comprising at least one metal from group VIII selected from cobalt and nickel, at least one metal from group VIB selected from molybdenum and tungsten, or a mixture of at least one metal from group VIII selected from cobalt and nickel and at least one metal from group VIB selected from molybdenum and tungsten, on a support comprising alumina, silica, silica-alumina, magnesia, clays, or a mixture of at least two of these minerals.

8. The process of claim 6 wherein said hydroprocessing reactor includes a hydrotreatment step and an isomerization step and wherein said isomerization step utilizes at least one solid isomerization catalyst that is different from the solid catalyst used is said hydrotreatment step and further wherein said solid isomerization catalyst comprises an isomerization function comprising at least one metal selected from palladium (Pd) and platinum (Pt), and a support comprising zeolite, alumina, silica, silica-alumina, magnesia, clays, or a mixture of at least two of these minerals.

9. The process of claim 6 wherein said hydroprocessing reactor includes a hydrotreatment step and an isomerization step and wherein said isomerization step utilizes at least one solid isomerization catalyst that is different from the solid catalyst used in said hydrotreatment step and further wherein said solid isomerization catalyst comprises at least one metal from group VIB selected from molybdenum and tungsten, at least one metal in from group VIII selected from nickel and cobalt, or a combination of at least one metal from group VIB selected from molybdenum and tungsten and at least one metal from group VIII selected from nickel and cobalt, on a support comprising zeolite, alumina, silica, silica-alumina, magnesia, clays and mixtures of at least two of these minerals.

10. The process according to one of claims 6 to 9 wherein said hydroprocessing reactor includes a hydrotreatment step and an isomerization step and wherein said isomerization step operates at an LHSV of between 0.1 to 10 h^"1.

11. The process of one of the preceding claims wherein said biological feedstock is selected from the group comprising: rapeseed oil, soybean oil, corn oil, coconut oil, olive oil, linseed oil, sunflower oil, palm oil, jatropha oil, mustard oil, peanut oil, hemp oil, cottonseed oil, pork fat, poultry fat, lard, butter, tallow, or any combination thereof.

12. The process of one of the preceding claims wherein said membrane separator operates between -20°F and 150°F (i.e. between -29°C and 66°C).

13. The process of one of the preceding claims wherein the residue side of said membrane separator operates at a pressure of between 1,500 psig to 300 psig (i.e. between 10,4 MPa and 2,2 MPa) and the permeate side operates at a pressure lower than that of the residue side.