JPS5830915B2 - How to convert synthesis gas to hydrocarbon mixtures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Methods for converting gas mixtures containing hydrogen and carbon oxides are known in the prior art.

Various methods can also be used to produce gas mixtures of this type.

The main methods of interest rely on partial combustion of the fuel with oxygen-containing gases or high temperature reaction of the selected fuel with steam or a combination of these two methods.

Synthesis gas is heated at temperatures ranging from 300°F to about 850'F.
It is known to undergo conversion reactions at pressures from atm. to about 1000 atm. and in the presence of a wide variety of catalysts to produce reduction products of carbon monoxide, such as hydrocarbons.

For example, the Fuscher-Tropsch process produces a range of liquid compositions, some of which have been used as relatively low octane gasolines.

Catalysts used in this and some related methods include catalysts based on iron, cobalt, nickel, rhenium, thorium, rhodium and osmium metals and/or oxides.

On the other hand, Fischer-Tropsch processing technology has suffered from a number of problems, such as catalyst deactivation by sulfur and catalyst regeneration problems.

In addition, we have found specific conditions for producing liquid hydrocarbons that boil in the gasoline boiling point range and contain highly branched paraffins and significant amounts of aromatic hydrocarbons, which are necessary to produce high-quality gasoline. It was difficult to confirm.

A number of publications discuss the current state of Fischer-Tropsch synthesis technology, but few of these publications discuss the range of boiling synthesis gas to gasoline when the catalyst is in continuous or intermittent contact with sulfur. None have given a satisfactory answer to the processing of boiling hydrocarbons into hydrocarbon-containing hydrocarbons.

This invention relates to a recently developed and unexpected process for converting synthesis gas to desired hydrocarbon products containing aromatics in the gasoline boiling range in the presence of sulfur.

Synthesis gas with or without sulfur, such as hydrogen sulfide, is relatively insensitive to sulfur and preserves its activity and selectivity even after continuous exposure to sulfur in the syngas feedstock. It has been found that the syngas can be converted to hydrocarbons by contacting it with special catalyst compositions that have been improved and even improved.

This invention converts synthesis gas into desired hydrocarbon products, including aromatics in the gasoline boiling range, by contacting a catalyst continuously or intermittently with the sulfur component of the synthesis gas, either intentionally or inadvertently. It relates to a method for catalytically converting into.

In particular, the invention provides a method for converting synthesis gas containing hydrogen and carbon oxides derived from, for example, coal, which may or may not contain sulfur, to a specific heterogeneous catalyst that is relatively insensitive to sulfur compounds. The present invention relates to a process for converting said synthesis gas into paraffins and aromatic hydrocarbons, preferably boiling within the gasoline boiling range, by contacting the mixture with a mixture.

More particularly, the invention is typified by ZSM-5, in which a synthesis gas containing carbon monoxide and hydrogen is mixed with a carbon monoxide reducing component containing hafnium and/or zirconium as metal oxides and/or sulfides. The invention relates to a method for converting said synthesis gas into hydrocarbon products by contacting it with a particular class of crystalline zeolites.

Synthesis gas can be produced from fossil fuels by any method known in the prior art, including in situ gasification methods such as underground combustion of coal and oil deposits.

Fossil fuels are intended to include anthracite and sweet coal, as well as charcoal, crude oil, shale oil, oil from tar sands, natural gas, and fuels resulting from the separation or conversion of these materials. .

Synthesis gas produced from fossil fuels often contains various impurities such as particulates, sulfur and metal carbonyl compounds, and the hydrogen to carbon oxide (-carbon oxide and carbon dioxide) ratio, which depends on the fossil fuel used and the specific gasification technology).

In general, conventional methods require purification of compositional synthesis gas to remove these impurities.

However, it has been found that the sulfur in the synthesis gas does not need to be removed if the catalyst according to the invention is used to convert the synthesis gas.

However, under some conditions it may be desirable to partially remove sulfur and completely remove other undesirable impurities.

In the conversion operation of this invention, hydrogen:
The carbon oxidation part volume ratio is 0.2 to about 6.0, more usually 1.
It is preferable to adjust it to :l.

Well-known water gas production reactions can be used to increase the hydrogen ratio, if necessary, by adding carbon monoxide and/or carbon dioxide in the case of hydrogen-rich synthesis gas to increase the hydrogen:hydrocarbon volume ratio. Can be adjusted.

The heterogeneous catalyst mixture used in this invention consists of at least two components intimately mixed together and shall be referred to as a sulfur-insensitive or sulfur-tolerant catalyst mixture.

The sulfur-resistant component may or may not lose some of its activity due to the presence of sulfur, but at least it can be substantially completely removed by simply removing or reducing the presence of sulfur in the syngas feedstock. It can reinvigorate itself.

Thus, in the method of this invention, the carbon monoxide reducing component is selected from a class of substantially sulfur-insensitive inorganic substances that are active for the reduction of carbon monoxide in the presence of hydrogen, thereby producing hydrocarbons; a zeolite selected from a particular class of crystalline aluminosilicates characterized by a pore size greater than about 5 angstroms, a silica:alumina ratio greater than 12, and a constraint factor within the range of 1-12. is specifically intended for use.

The classes of crystalline zeolites classified in this way and defined in this specification are ZSM-5, ZSM-11, ZS
A class of crystalline zeolites represented by M-12, ZSM-35 and ZSM-38.

A sulfur-resistant inorganic substance that does not or may lose its activity in the presence of sulfur, but which substantially reactivates itself upon removal of the sulfur, The crystalline zeolite defined in this specification is used either as a separate particle and intimately mixed, or combined with the crystalline zeolite as a single catalyst particle.

Inorganic substances suitable for the purposes of this invention are
Contains elements from groups IB and IVB.

Elements from these groups that have been found to be particularly sulfur resistant are zirconium and hafnium.

Sulfur is even used as a promoter for these materials.

Known Fischer-Tropsch synthesis catalysts other than thoria are substantially deactivated by contact with sulfur or sulfur compounds, and there is a satisfactory method of restoring the activity and selectivity of catalysts deactivated by such sulfur. In the case of these catalysts, it is necessary to remove sulfur or sulfur compounds from the synthetic operation, since regeneration operations have not yet been discovered.

The inorganic material can be used in an amount of from about 0.1% to about 80%, preferably less than 60% by weight of the active components of the intimately mixed catalyst.

The acidic crystalline aluminosilicate component of the heterogeneous catalyst is approximately 5
It is characterized by a pore size larger than angstroms, ie it is capable of adsorbing paraffins with one branched methyl group as well as straight-chain paraffins, and it has a silica to alumina ratio of at least 12.

For example, zeolite A with a silica to alumina ratio of 2.0 cannot be used in this invention.

Zeolite A also has no pores with pore sizes greater than about 5 angstroms.

Crystalline aluminosilicates, referred to herein and known as zeolites, are a unique class of naturally occurring and synthetic minerals.

They have a rigid crystalline framework consisting of an assembly of silicon and aluminum atoms, each silicon and aluminum atom being surrounded by a tetragonal body that shares an oxygen atom, and a precisely defined pore structure. characterized by.

Exchangeable cations reside within the pores.

The catalyst involved in this invention uses a special class of zeolites that exhibit unique properties.

These zeolites convert aliphatic hydrocarbons to aromatic hydrocarbons in industrially desirable yields and are generally highly effective in alkylation, isomerization, disproportionation and other reactions involving aromatic hydrocarbons. .

Although they have an unusually low alumina content, ie, a high silica to alumina ratio, they are very active even when the silica to alumina ratio exceeds 30.

This activity is surprising since the catalytic activity of zeolites is based on the aluminum atoms of the framework and the cations bound to these aluminum atoms.

These zeolites maintain their crystallinity over long periods of time even at high temperatures despite the presence of steam (which causes an irreversible collapse of the crystal framework of other catalysts such as zeolites X and A). Hold.

Additionally, if carbonaceous precipitates form, they can be removed by combustion at temperatures higher than those normally used to restore activity.

In many environments, this class of zeolites has very low coke-forming potential, making them useful for very long reaction run times between combustion regeneration treatments.

The important features of the crystal structure of this class of zeolites are about 5
Pore size larger than angstrom and 1 of oxygen atom
By having a pore opening of approximately the same size as that created by a zero-membered ring, entry into and exit from the free space within the crystal is restricted (constrained).

These 10-membered rings are formed by a regular array of tetrahedra that frame the anionic framework of the crystalline aluminosilicate, and the oxygen atoms themselves are bonded to silicon or aluminum atoms at the center of the tetrahedron. It should be understood that

Briefly, preferred zeolites useful in the Type B catalysts of this invention are those that combine a silica to alumina ratio of at least about 12 and a structure that restricts crystal free space intrusion.

The silica to alumina ratio referred to herein is determined by conventional analysis.

This ratio is meant to represent as accurately as possible the silica to alumina ratio in the rigid anionic framework of the zeolite crystal, excluding aluminum in the binder or in cationic form or other forms within the crystal slots. It means that.

Zeolites with a silica to alumina ratio of at least 12 are useful, although it is preferred to use zeolites with a higher ratio of at least about 30.

Such zeolites obtain an intracrystalline sorption capacity for normal hexane that is greater than the intracrystalline sorption capacity for activated water withdrawal, and therefore they exhibit hydrophobicity.

This hydrophobicity is believed to be advantageous in this invention.

Zeolites useful as catalysts in this invention are free to sorb normal hexane and have pore sizes greater than about 5 angstroms (1).

Moreover, this structure must restrain larger molecules from entering the paired pores.

Whether entry into such pores is restricted can sometimes be determined from known crystal structures.

For example, if the pore openings in the crystal are shaped by eight-membered ring oxygen atoms, entry into the pores by molecules with a cross section larger than normal hexane is virtually excluded, and the zeolite is not of the desired type.

Zeolites with 10-ring pores are preferred, but excessive shrinkage or pore blockage can render these zeolites substantially ineffective.

Zeolites with 12-membered ring pores are generally not believed to produce sufficient restraint to produce the advantageous conversions desired in this invention, but these structures can be used due to pore blockage or other causes. It is speculated that this may be the case.

Instead of determining from the crystal structure whether the zeolite restricts pore entry as required by this invention, an equal weight mixture of n-hexane and 3-methylpentane is added to the zeolite in an amount of about 1 or less. The "restraint factor" is determined by continuously passing atmospheric pressure over a small sample according to the following procedure.
can make simple decisions.

Specifically, samples of zeolite in the form of pellets or extrudates were ground to coarse sand-sized particle sizes and placed in glass tubes.

Test 1 Prior to testing, treat the zeolite at 1000'F in a stream of air for at least 15 minutes, then flush the helium to wash the zeolite, and adjust the temperature between 550°F and 950°F to remove 10% to 60% It now gives a total conversion rate of .

The hydrocarbon mixture was diluted with helium to give a helium:total hydrocarbon molar ratio of 4:1 and passed over the zeolite at a liquid weight hourly space velocity of 1 liquid (i.e. 1 volume of liquid hydrocarbon per hour per volume of catalyst). .

After 20 minutes of flowing the hydrocarbon mixture, samples of the effluent were taken and analyzed, most conveniently by gas chromatographic analysis, to determine the proportion remaining unchanged for each of the two hydrocarbons.

The "restraint index" was calculated as follows.

This constraint coefficient approximates the ratio of cracking rate constants for the two types of hydrocarbons.

Catalysts suitable for this invention are those using zeolites with a constraint index of 1.0 to 12.0.

Constraint index (CI) values for some representative zeolite catalysts, including some that do not fall within the range of zeolites used in this invention, are as follows.

Zeolite CI Acid Form Mordenite 0.5 RE Y 0.4 Amorphous Silica-Alumina 0.6 The above-mentioned constraint factors are important and even critical definitions of the zeolite useful for exhibiting catalytic action in the process of this invention. be.

However, the very nature of this parameter and the technique for determining the constraint factor allows that a given zeolite may be tested under slightly different conditions and thus have a different constraint factor.

The restraint index appears to vary somewhat with the severity of the conversion operation.

Therefore, for a particular given zeolite,
It will be appreciated that it is possible to choose test conditions to establish many restraint indices within and outside the specified range of 12.

Therefore, when using such values in this specification, it should be understood that "constraint coefficient" is not a single 0 value, but a comprehensive value.

That is, a zeolite that has a restraint index of 1-12 when tested under the combination of conditions within the test specifications set forth in this specification will have a restraint index of 1-12 when that same zeolite is tested under other specified conditions. Regardless of the constraint index given, it is included within the definition of the catalyst used in the present invention.

The class of zeolite defined in this specification is ZSM-5
, ZSM-11, ZSM-12, ZSM-21 and other similar materials.

Recently issued U.S. Patent No. 3,702,886 is ZS
M-5 is described.

ZSM-11 is detailed in U.S. Patent No. 3,709,979.
No. 3,832, the ZSM-12 is described in detail in U.S. Pat.
It is described in the specification of No. 449.

French Patent Application No. 74-12078 describes a zeolite composition designated ZSM-21 useful in this invention and a method for its preparation.

The particular zeolites described herein when prepared in the presence of organic cations are substantially catalytically inactive, probably because the free space within the crystals is occupied by organic cations from the crystal formation solution. .

These can be heated, for example, at 1000° F. for 1 hour in an inert atmosphere, followed by base exchange with an ammonium salt, followed by 1 hour.
Can be activated by firing in air at 000'F.

The presence of organic cations in the crystallization solution is not absolutely necessary to form this particular type of zeolite.

However, the presence of these cations appears to favor the formation of this particular type of zeolite.

More commonly, this type of zeolite is base exchanged with an ammonium salt and then heated at about 1000°F for about 15 minutes to about 2 hours.
Activation is preferably performed by baking in air for 4 hours.

Naturally occurring zeolites can sometimes be converted to this type of zeolite by various activation operations or other treatments, such as base exchange, steaming, alumina extraction and calcination, alone or in combination.

Naturally occurring minerals that can be treated in this way include ferrierite;
bluestellite, stilbite, dachialdite,
Includes epistilbite, hyurandite and clinoptilolite.

A suitable crystalline aluminosilicate is ZSM-5゜ZSM
-11, ZSM-12 and ZSM-21, ZSM-5
is particularly suitable.

The zeolites used as catalysts in this invention are in the hydrogen form or they are base exchanged or impregnated to contain ammonium cations or metal cations compensating valves.

It is desirable to calcin the zeolite after base exchange.

Metal cations that can be present include any of the metals from Groups I to II of the Periodic Table.

However, in no case should the Group IA metal have such a large cation content as to substantially eliminate the catalytic activity of the zeolite used in this invention.

For example, fully sodium-exchanged H-ZSM-5 appears to be nearly inert to the shape-selective conversion required in this invention.

In a preferred aspect of this invention, the zeolite useful as a catalyst in this invention is in dry hydrogen form substantially about 169/c
selected from those having a crystal framework density of rit or higher.

Zeolites that meet all three of these criteria have been found to be most desirable.

Accordingly, preferred catalysts of this invention are those having a constraint factor as defined above of about 1-12, a silica:alumina ratio of at least about 12, and a dry crystal density not substantially less than 1.6 g/i.

The dry density of crystal structures with known crystal structures is determined by, for example, D. M. Meyer (W.M.
) can be calculated from the total number of silicon and aluminum per 1000 cubic angstroms, as described on page 19 of the paper on zeolite structure.

This paper (the entire contents of which are hereby incorporated by reference) is therefore published by The Society of Chemical Industry London (th
e 5ociety of Chemical In
Proceedings of the Conference Molecular Thieves, London (1968)
Ro-ceedings of the Conference
ence molecule-1ar 5ieves,L
ondon) April 1967.

When the crystal structure is unknown, the crystal framework density can be measured by classical hydrometer techniques.

For example, it can be measured by soaking the dry hydrogen form of the zeolite in an organic solvent that is not absorbed by the crystals.

The unusually long-lasting activity and stability of this class of zeolites can be related to the high crystalline anionic framework density of about 1.697- or higher.

This high density must of course be related to the relatively small amount of free space within the crystal, which is expected to result in a more stable crystal structure.

However, this free space appears to be important as the active center of the catalyst.

Listed below are some representative zeolite crystal framework densities, including some that are not within the scope of Yuko's invention.

This heterogeneous catalyst can be made in a variety of ways.

For example, the two components may be formed separately in the form of catalyst particles, such as pellets or compacts, and simply mixed in the required proportions.

The particle size of the individual component particles is quite small, for example from about 20 to about 150 microns when intended for use in fluidized bed operations.

Alternatively, it may be larger, such as up to about 7 inches for fixed bed operations.

Alternatively, the two components may be mixed as powders into pellets or extrudates, each pellet or extrudate containing the two components in substantially the required proportions.

A binder such as a viscosity can be added to this mixture.

Alternatively, the component having catalytic activity for carbon monoxide reduction may be acidified by conventional means such as impregnating an acidic crystalline aluminosilicate solid with a solution of a salt of the desired carbon monoxide reduction catalytically active metal, followed by drying and calcination. It can also be formed on crystalline aluminosilicate.

In some selected cases, some or all of the carbon monoxide reducing component can be introduced by base exchange of the acidic crystalline aluminosilicate component.

Other methods such as precipitation of carbon monoxide reducing components in the presence of acidic crystalline aluminosilicate to create an intimate mixture, electroless deposition of metals on zeolites or precipitation of metals from the vapor phase Means can also be used.

Various combinations of the catalyst preparation methods described above will be obvious to those skilled in the art of catalyst manufacture.

However, care must be taken to avoid techniques that reduce the crystallinity of the acidic crystalline aluminosilicate.

From the foregoing description it will be seen that the heterogeneous catalysts used in the process of this invention, ie the intimate mixtures mentioned above, are of varying degrees of intimacy.

In one extreme case, such as when using the carbon monoxide reducing components of 10,000-inch pellets mixed with the acidic crystalline aluminosilicate of Finch's pellets, the substance in at least one of these components All positions above are within about 7 inches of some of the other components, regardless of the proportions in which the two components are used.

In the case of pellets of different sizes, such as 1-inch and 4-inch pellets, again substantially all of the locations within at least one of the four components are within about ± inches of the other component.

These examples illustrate the lower limits of tightness required to practice this invention.

At the other extreme, acidic crystalline aluminosilicate particles of about 0.1 micron particle size and colloidal zinc oxide of similar particle size are ball milled together and then pelletized.

In this case, substantially all of the locations within at least one of these components are within about 0.1 microns of the other component.

This is an example of maximum closeness in practice.

The compactness of a physical mixture can also be expressed as the minimum separation distance between the center points of each particle of the two components.

This is expressed, on average, by the sum of the average particle sizes for the two components.

In the above example case 2, which thus illustrates the highest degree of tightness,
The center of a particle of one of the seed components is separated from the nearest particle of the other component by an average distance of at least about 0.1 micron.

The compactness of a heterogeneous catalyst is determined to a large extent by its method of preparation, but can be independently verified by physical methods such as visual observation, examination with a common or electron microscope, or electron microprobe analysis. .

In the process of this invention, synthesis gas is combined with a heterogeneous catalyst at temperatures of from about 400°F to about 1000°F, preferably from about 500°F to
from about 500 to about 50,000 volumes of synthesis gas at a temperature of about 850°F, a pressure of about 1 to about 1000 atmospheres, preferably about 3 to about 200 atmospheres, and a volume of catalyst per volume of catalyst per hour. Contact is carried out at a space velocity or, if a fluidized bed is used, at an equivalent contact time.

The heterogeneous catalyst may be contained as a fixed bed or a fluidized bed may be used.

The product stream containing hydrocarbons, unreacted gases and steam is recovered by techniques known in the art, which do not form part of this invention.

The recovered hydrocarbons may be further separated by distillation or other means to produce high octane gasoline, propane fuel, benzene, toluene, xylene or other aromatic hydrocarbons.
Collecting the seeds or more products.

Example 1 Pure Zr was produced by thermally decomposing zirconium oxalate.
A sample of O2 was made and a composite catalyst was made by ball milling and pelletizing.

Synthesis gas (H2//C0=1) was heated over zirconia and zirconia-ZSM-5 crystalline zeolite composite catalyst at 120%
0psig, 800°F, 1.3-1.5VH8V (
Gas at standard temperature and pressure based on ZrO2) or 720-750VH8V (based on total reaction volume).

The effect of ZSM-5 crystalline zeolite on zirconia on reaction products appeared to be similar to that observed with the zeolite on thoria.

The main effect observed is a reductive effect on methane production.

A slight increase in activity was evident, and the distribution of aromatics was similar to that observed when using the Th02728M-5 catalyst.

WH8V is the weight of feedstock per weight of catalyst per hour using time as the unit of time.

VH8V is the volume of gas per volume of catalyst per time using hours as the unit of time.

STP represents the standard temperature of 0° C. and the condition of 760 rrutH&.

The effect of H, S on Z r 02 / Z SM 5 catalyst activity was determined and listed in Table 1 below.

The first part of the test (Test A) was conducted without H2O to serve as a baseline test.

Test conditions were 600 psig, 800°F and 1.3
It was WH8V (based on Zr02).

Approximately 3 wt% H2S was added to H2/CO after 20 hours of testing.
It was introduced into continuous technology together with the syngas feedstock.

A mass balance was taken after continuous aeration with H2S for 26 hours (Test B).

The catalytic activity was quite unexpectedly and surprisingly not impaired.

The slightly higher conversion observed in Test B than Test A is due to the lower WH8V for this test.

The main effect attributed to H2S is an increase in methane yield (3,
6% to about 11.2%).

Significant amounts of C05 (carbonyl sulfide) were found, indicating that the catalyst activity was not affected by this material.

The space velocity was then reduced to 0.26WH8V (Test C) and another mass balance after another 24 hours test (Test C).
I took it.

The material balance shows that there is little change in the three times higher conversion and selectivity.

At the end of Test C, the H2S was removed from the feed and the product was analyzed after an additional 22 hours of testing.

This analysis showed that methane production was reduced and the catalyst selectivity for aromatics production was restored (see test results).

This analysis also showed a low conversion rate which was partially attributable to the use of a slightly higher WH8V total 8V degree for mass balance during this period.

Changes in the catalyst over time are also one of the contributing factors.

The H2S in the feedstock can even be described as acting as a promoter.

In any case, the production of aromatics in the tests is higher than that obtained in tests B and C.

Example 2 Synthesis gas containing up to 2.5% H2O
Converted to aromatic hydrocarbons on HzSM-5.

This catalyst was found to be resistant to the poisonous effects of sulfur.

This is shown in attached Table 2. Sulfur (2,5% H20)
was added to the syngas feedstock (LPA130B).

The results obtained showed that the catalyst could work even in the presence of sulfur.

As previously observed for the Th02/H2SM-5 catalyst, the presence of sulfur tends to slightly increase methane production while concomitantly reducing aromatics.

A catalyst containing 3.5% T 102 / 65% Hz SM-5 gave a syngas conversion of about - obtained using ZrO2 and a syngas conversion of about -1 obtained using HfO2. Gave.

Part of the reason for this low conversion is the low Tie2 content (35%).

The data for this T io 2 are listed in Table 2.

Table 2 also lists experiments in which 0.5% by weight of a rare earth metal was added as a promoter to ZrO2/HzSM-5.

Claims (1)

[Scope of Claims] 1. A method for converting synthesis gas to hydrocarbon components in the gasoline boiling range, wherein the synthesis gas is converted to a silica:alumina ratio of 12-=-3000 at a temperature of 400 to 1000'F.
Metals, oxides and/or mixed with crystalline aluminosilicate zeolites with a restraint factor in the range of ~12
A method comprising contacting a carbon monoxide reduction catalyst containing hafnium and/or zirconium as sulphides. 2. Process according to claim 1, in which hafnium and/or zirconium are used in sulfurized form. 3. A process according to claim 1, wherein the carbon oxide reduction catalyst is initially zirconium in oxide form. 4 Crystalline aluminosilicate zeolite is ZSM-5
4. A method according to any one of claims 1 to 3, wherein the zeolite is a type of zeolite. 5. A process according to any one of claims 1 to 4, wherein the conversion is carried out at a temperature of 500 to 850<0>F. 6. Any of claims 1 to 5, wherein a substance in the gasoline boiling range containing aromatics is produced at a pressure greater than 3 atmospheres and a space velocity of 500 to 50,000 volumes of gas per hour. The method described in item 1. 7. The method according to any one of claims 1 to 6, wherein the mixture contains an excess volume amount of crystalline aluminosilicate compared to the carbon monoxide reduction catalyst. 8. The method according to any one of claims 1 to 7, wherein the feedstock contains sulfur.