CA2974159A1 - A catalyst for co hydrogenation to produce synthesis fuel - Google Patents

Abstract

The present invention relates to a process of conversion of synthesis gas to hydrocarbons wherein the process comprises of contacting synthetic gas with a carbon monoxide hydrogenation catalyst composition, comprising an extruded alumina as support;
a cobalt compound as an active metal component; and two promoters, wherein the promoters are a magnesium compound and a ruthenium compound. The present invention also relates to a process for preparation of a carbon monoxide hydrogenation catalyst.

Description

A CATALYST FOR CO HYDROGENATION TO PRODUCE SYNTHESIS FUEL
FIELD OF THE INVENTION
The present invention relates to a Carbon monoxide hydrogenation catalyst composition. The invention, further relates to a process for preparation of carbon monoxide hydrogenation catalyst. The present invention also relates to a process of conversion of synthesis gas to hydrocarbons.
BACKGROUND OF THE INVENTION
Synthesis gas which is containing hydrogen and carbon oxides are important feedstock for the production of valuable range of hydrocarbons, and other chemical products.
Synthesis gas mixtures with accurate ratios of hydrogen to carbon monoxide react catalytically to give hydrocarbons and oxygenated organic compounds. Liquids which are produced by synthesis gas conversion are valuable as fuels, chemical intermediates, and final chemical products.
The cost of generating the synthesis gas usually is the largest part of the total cost of these products.
The well-known Fischer-Tropsch process is described widely in the art, for example in an article entitled "Fischer-Tropsch Synthesis" by B. Bussemeier et al in the Encyclopedia of Chemical Process and Design, 22, p 81-119 (1985). Catalysts which promote the conversion of synthesis gas to hydrocarbons, steam, and carbon dioxide are well-known in the art.
US6835690 A covers the cobalt based Fischer-Tropsch catalyst, the catalyst including a porous catalyst support and metallic cobalt crystallites within the support.
It also discusses about the feed for the preparation of synthesis gas. The limitation of this invention is that the yield is not mentioned anywhere as well as this catalyst system would be suitable only for the CSTR reactor.
US7365040 covers the process for preparing a cobalt-based Fischer-Tropsch synthesis catalyst, which process includes introducing a soluble modifying component precursor of the formula Mc (OR)x, where Mc is a modifying component selected from the group of metal atoms. The limitation of this invention is that the yield conversion is between 50-70% and the catalyst system would be suitable only for the CSTR reactor.

US8067333 covers a supported cobalt-based Fischer-Tropsch synthesis catalyst having a higher hydrocarbon synthesis activity and a process for the preparation of the catalyst system.
The limitation of this invention is that the yield conversion is between 50-70% and the catalyst system would be suitable only for the CSTR reactor.
US20030125201A1 covers a cobalt catalyst precursor which includes a catalyst support impregnated with cobalt, with all reducible cobalt being present in the support as supported cobalt oxide. The limitation of this invention is that the yield conversion is between 34.2 to 62.3 wt% and the catalyst system would be suitable only for the Slurry reactor.
US2007/0099797A1 covers a transition metal-based catalyst having a high surface area, a smooth, homogeneous surface morphology, an essentially uniform distribution of cobalt throughout the support, and a small metal crystallite size. The limitation of this invention is that the yield conversion is not indicated anywhere and the catalyst system would be suitable only for the Slurry reactor.
US7563747 covers a catalyst comprising particles of a cobalt and zinc co-precipitate, having a volume average particle size of less than 150 i.trn and a particle size distribution wherein at least 90% of the volume of the catalyst particles have a size between 0.4 and

2.5 times the average particle size.
US8258195 covers the process for converting carbon containing products, such as natural gas, to liquid hydrocarbons or fuels, and more particularly, to methods for catalytically converting synthesis gas or "Syn-gas" (carbon monoxide (CO) and hydrogen (H2)) into hydrocarbon products utilizing Fischer-Tropsch (F-T) reactions. The limitation of this invention is that the conversions of CO and hydrogen were about 60% and 65%, respectively and the catalyst system would be suitable only for the Fixed Bed reactor.
EP1042067A1 covers the process for the preparation of a cobalt-containing catalyst or catalyst precursor, comprising (a) mixing (1) titania or a titania precursor, (2) a liquid, and (3) a cobalt compound, which is at least partially insoluble in the amount of liquid used, to form a mixture, (b) shaping and drying of the mixture thus-obtained, and (c) calcination of the composition thus-obtained. The limitation of this invention is that the yield, conversion are not mentioned anywhere and the catalyst system would be suitable only for the Fixed Bed reactor.
EP0190307A1 covers Fischer-Tropsch catalyst comprises cobalt or iron on a support which is carbon having a BET surface area of at least 100 m2/g, ratio of BET to basal plane surface area not greater than 4:1 and a ratio of basal plane surface area to edge surface area of at least 10:1. The limitation of this invention is that the catalyst system would be suitable only for the slurry reactor.
However, there is a need to provide an improved process for carbon monoxide hydrogenation employing an efficient catalyst composition.
OBJECT OF THE INVENTION
It is the primary objective of the invention to provide a process of conversion of synthesis gas to hydrocarbons wherein the process comprises of contacting synthesis gas with a carbon monoxide hydrogenation catalyst composition.
The other objective of the invention is to provide a carbon monoxide hydrogenation catalyst composition comprising of a support, an active metal component and two different promoters wherein one of the promoters is a magnesium compound.
The other objective of the present invention relates to a process for preparation of carbon monoxide hydrogenation catalyst.
SUMMARY OF THE INVENTION
The present invention relates to a carbon monoxide hydrogenation catalyst composition comprising of a support, an active metal component and two promoters wherein one of the promoters is a magnesium compound.
The present invention further relates to a carbon monoxide hydrogenation catalyst composition wherein said composition comprises of:
(a) an extruded alumina;
(b) a cobalt compound;
(c) a ruthenium compound; and

3 (d) a magnesium compound.
In the above catalyst composition, the extruded alumina is the support, cobalt compound is the active metal component and ruthenium compound and the magnesium compound are the two promoters.
In a preferred embodiment, the carbon monoxide hydrogenation catalyst composition comprises of:
(a) a cobalt compound in an amount of 10-20 wt% of the catalyst composition;
(b) alumina in an amount of 79.00-89.44 wt% of the catalyst composition;
(c) a ruthenium compound in an amount of 0.1-0.50 wt%;
(d) a magnesium compound in an amount of 0.1-1.00 wt%
wherein the wt % of cobalt compound, ruthenium compound and magnesium compound is based on weight of metal.
Present invention further provides a process for preparation of carbon monoxide hydrogenation catalyst wherein said process comprises the steps of:
(a) impregnating extruded alumina with cobalt;
(b) soaking cobalt impregnated alumina and drying;
c. calcining the cobalt impregnated alumina;
d. impregnating with ruthenium;
e. soaking, drying and calcining ruthenium and cobalt impregnated alumina;
f. impregnating with magnesium; and g. soaking, drying and calcining to get carbon monoxide hydrogenation catalyst.
Present invention furthermore provides a process of conversion of synthesis gas to hydrocarbons wherein the process comprises of contacting synthetic gas with a carbon monoxide hydrogenation catalyst composition comprising an extruded alumina impregnated with cobalt compound, ruthenium compound and magnesium compound in fixed bed operation.
The present invention further relates to a carbon monoxide hydrogenation catalyst composition wherein said catalyst composition possess carbon selectivity to LPG(C3+C4) and C5+ respectively, and less than 10% of carbon selectivity to off gas comprising Ci+C2 carbon.

4 DDETAILED DESCRIPTION OF THE INVENTION
While the invention is susceptible to various modifications and alternative forms, specific embodiment thereof will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the scope of the invention as defined by the appended claims.
According to the main embodiment, the present invention provides a carbon monoxide hydrogenation catalyst composition comprising of a support, an active metal component and two types of promoters wherein one of the promoters is a magnesium compound.
In detailed embodiment, the support is an extruded alumina and the active metal component comprises of cobalt compound. Cobalt compounds which are used in the catalyst composition are selected from Cobalt nitrate and cobalt acetate. The addition of promoter elements to cobalt-based FT (Fishcher Trosph) catalysts can affect directly the formation and stability of the active cobalt phase by altering the cobalt-support interfacial chemistry, directly affect the elementary steps involved in the turnover of the cobalt active site by altering the electronic properties of the cobalt nanoparticles and indirectly the behavior of the active cobalt phase, by changing the local reaction environment of the active site as a result of chemical reactions performed by the promoter element itself. Therefore, promoters enhance the activity &
change selectivity of the products. Cobalt range falls between 10-20 wt% of catalyst composition. More than 20 wt% of Cobalt on alumina support in the catalyst composition will lower the dispersion on support surface. Also, higher amount of cobalt in catalyst will increase the cost of production of catalyst.
Role of Ru: Ruthenium promoted cobalt catalysts exhibit exceptionally high selectivity towards C5+ products and higher activity compared to unpromoted Co catalysts.
Role of Magnesium: Reduces the interaction of active component cobalt with alumina support 8z reduces the methane selectivity and increases the C4 and C5 hydrocarbons selectivity. Among the two types of the promoters, one is magnesium compound thermally decomposable to oxide and the other promoter is a ruthenium compound thermally decomposable to oxide. Broad range of Ruthenium (Ru) metal: 0-0.5 wt %; Broad range of Magnesium metal (Mg): 0-1 wt %. .
According to embodiment, Magnesium compounds which are used in the catalyst composition are selected from Magnesium nitrate and Magnesium acetate.
Ruthenium compound, which is used in the catalyst composition is Ruthenium nitrosylnitrate.
According to the other main embodiment, the present invention provides a carbon monoxide hydrogenation catalyst composition wherein said composition comprises of:
a. an extruded alumina;
b. a cobalt compound;
c. a ruthenium compound; and d. a magnesium compound.
Further detailed embodiment, the extruded alumina contains less than 100 ppm of sodium.
Broad range of sodium: 0-99.5 ppm. Above 100 ppm, activity of the catalyst will be decreased. The aforesaid cobalt compound, ruthenium compound and magnesium compound are thermally decomposable to oxides.
This catalyst composition after pretreatment with hydrogen, converts synthesis gas into 7.5%
and 81% of carbon selectivity to LPG(C3+C4) and C5+ respectively, and less than 10% of carbon selectivity to off gas comprising C 1+C2 carbon. Broad range: LPG
(C3+C4): 7.5 ¨
13.60%; C5+: 60 -81.60% & Off gas (Ci+C2): 9.60- 25%.
According to the other main embodiment, the present invention provides a process for preparation of carbon monoxide hydrogenation catalyst wherein said process comprises the steps of:
a. impregnating extruded alumina with cobalt;
b. drying cobalt impregnated alumina;
c. calcining the cobalt impregnated alumina;
d. impregnating with ruthenium;
e. drying and calcining ruthenium and cobalt impregnated alumina;
f. impregnating with magnesium; and g. drying and calcining to get carbon monoxide hydrogenation catalyst.
In detailed embodiment, the extruded alumina has spherical size from 0.5 mm to 1.5 mm.

According to the other main embodiment, the present invention provides a process of conversion of synthesis gas to hydrocarbons wherein the process comprises of contacting synthetic gas with a carbon monoxide hydrogenation catalyst composition comprising an extruded alumina impregnated with cobalt compound solution, ruthenium compound and magnesium compound. In the detailed embodiment, the aforesaid process is carried out by fixed bed operation.
Method-I:
Extruded alumina was first impregnated by desired quantity of Co using Co based compound and followed by soaking at room temperature for 2-4 hrs. Impregnated sample was dried at 50-100 C for 3-6 hrs. Subsequently, catalyst precursor was again impregnated by desired quantity of Ru using Ru based compound and followed by same previous procedure as adopted for soaking & drying. Similarly, desired quantity of Mg was impregnated using Mg based compound followed by same previous procedure as adopted for soaking &
drying.
Finally, prepared catalyst was calcined at 400-500 C for 4 to 8 hrs.
Method-II:
Extruded alumina was first impregnated by desired quantity of Co using Co based compound and followed by soaking at room temperature for 2-4 hrs. Impregnated sample was dried at 50-100 C for 3-6 hrs. Subsequently, Co impregnated sample was calcined at 400-500 C for 4 to 8 hrs. Catalyst precursor was again impregnated by desired quantity of Ru using Ru based compound and followed by same previous procedure as adopted for soaking, drying &
calcination. Similarly, desired quantity of Mg was impregnated using Mg based compound followed by same previous procedure as adopted for soaking, drying &
calcination.
Cat-1 & 2 was prepared by Method-1. Method -II was used for preparation of Cat-3 to Cat-10. Ten different types of alumina supported catalysts with different composition of Co, Ru and Mg were prepared by impregnation method. The composition of the catalysts is as follows:
Table-1: Catalyst compositions (wt.%) Catalyst Name Alumina Co Ru Mg Cat-1 89.44 10.56 0.00 0.00 Cat-2 89.14 10.56 0.30 0.00 Cat-3 89.14 10.56 0.30 0.00 Cat-4 84.70 15.00 0.30 0.00 Cat-5 79.70 20.00 0.30 0.00 Cat-6 79.60 20.00 0.40 0.00 , Cat-7 79.25 20.00 0.50 0.25 Cat-8 78.50 20.00 0.50 1.00 Cat-9 79.00 20.00 0.50 0.50 Cat-10 81.00 18.00 0.50 0.50 Experimental Conditions The experiments were designed to evaluate each catalyst under fixed and representative conditions. Their catalytic activity (CO conversion) and selectivity or product distribution are compared. The catalysts to be evaluated were diluted by mixing with inert material like silicon carbide and loaded in a fixed bed micro-reactor. Each catalyst was activated in-situ in a flow of high purity hydrogen at 350 to 400 C for 12-18 hrs under atmospheric pressure. The flow rate of hydrogen was maintained at 3000 cc /hr/ cc of catalyst. The syngas feed of composition given in Table-2 was then contacted with catalyst under conditions given in Table-3. The CO hydrogenation reaction was carried out for about 90 -100 hours.

Table-2: Syngas feed composition used for the study Component mor/0 Hydrogen (H2) 57 Carbon monoxide (CO) 28.5 Methane (CH4) 12.5 Carbon dioxide (CO2) 1 Nitrogen (N2) 0.9 Carbonyl sulfide ( COS), Hydrogen sulfide ( H2S), ppb Trace amounts Table-3: CO-hydrogenation conditions Reactor Type Fixed Bed Micro reactor Temperature 220 C
GHSV (hr') 3000 CO Conversion and product selectivity Different catalysts as mentioned above were tested in fixed bed micro reactor as above conditions (Table-3) using synthesis gas composition (Table-2). The gaseous products were analyzed by off line GC. The H2, Cj, C2, C3, C4 and C5 lump was determined quantitatively.
The liquid products were analyzed by ASTM 2887 procedure in a Simulated Distillation Analyzer. The carbon balance for each run was determined. CO conversion and product selectivity on carbon basis was calculated. CO conversion and selectivity towards offgas, LPG and C5+ hydrocarbons and CO2 obtained from each catalyst (Cat-1 to Cat-10) is depicted in Table-4.
Table 4: Comparison of CO conversion and product selectivity Catalyst % CO Selectivity (%) Conversion DG(C1+C2) C3-C4 C5+ CO2 Cat-1 10.15 25.22 12.17 60.16 2.45 Cat-2 17.13 19.48 9.95 68.17 2.40 Cat-3 24.71 18.50 9.73 70.01 1.76 Cat-4 58.94 12.95 13.57 71.79 1.69 Cat-5 81.08 12.70 9.33 74.63 3.34 Cat-6 86.5 12.13 8.22 76.29 3.36 Cat-7 95.1 9.59 7.52 81.62 1.27 Cat-8 100.00 19.75 12.80 63.07 4.38 Cat-9 99.27 14.50 10.84 69.49 5.17 Cat-10 98.12 13.25 10.95 71.68 4.12 Table 4 depicts comparison of CO conversion and product selectivity. With increasing active metal component (Cobalt) as well as Ruthenium as a promoter, activity (CO
conversion), dry gas (C1+C2) decreases & C5+ selectivity increases from Cat-2 to Cat-6. With addition of 2nd promoter (magnesium), activity increases further with increased magnesium concentration from 0.25% to 1.0% (Cat-7 to Cat-9). However, undesirable drygas (C 1 +C2) increases. In case of Cat-10, active ingredient Cobalt concentration has decreased, as a result drygas as well as activity slightly decreases.
Advantages 1. The present invention is advantageous as the catalyst composition is prepared by employing impregnation technique for further use in fixed mode operation to enhance the yields of high value hydrocarbons.

2. The present invention is advantageous due to efficient process and a catalyst composition, which enhances the catalytic activity and selectivity of catalysts.
3. Furthermore, the present invention relates to a product and process for improving selectivity of catalyst.
4. The present invention is advantageous to have a process, by which the Lower cobalt in catalyst is being used, therefore it cost lesser for production of catalyst.

5. Ru is the one of the most costly material in the world. Lower Ru content in catalyst will reduce production cost of catalyst further. Mg & Ru are promoters. They just help to enhance activity & selectivity of catalyst in presence of active ingredient cobalt.

Claims (16)

Claims:

1. A
carbon monoxide hydrogenation catalyst composition wherein said composition comprises of:
(a) an extruded alumina as support, (b) a cobalt compound as an active metal component; and (c) two promoters, wherein one of the promoters is a magnesium compound;
wherein said catalyst composition comprises cobalt in the range of 10-20 wt%.
of the catalyst composition.

2. The catalyst composition as claimed in claim 1, wherein the other promoter is ruthenium compound.

3. The catalyst composition as claimed in claim 1, wherein said support is an extruded alumina containing 0-99.5 ppm of sodium.

4. The catalyst composition as claimed in any of the preceding claims, wherein said cobalt, ruthenium and magnesium are thermally decomposable to oxides.

5. The catalyst composition as claimed in claim 1, wherein said catalyst comprises of ruthenium in the range of 0.3 to 0.5 wt% and magnesium in the range of 0.5 to 1.0 wt% of the catalyst composition.

6. The catalyst as claimed in claim 1, wherein said catalyst possesses 10-100 wt%
carbon monoxide conversion to produce synthesis fuel.

7. The catalyst as claimed in claim 1, wherein said catalyst possess 7.5% and 81% of carbon selectivity to LPG(C3+C4) and C5+ respectively, and less than 10% of carbon selectivity to off gas comprising C1+C2 carbon.

8. A
process for preparation of carbon monoxide hydrogenation catalyst wherein said process comprises the steps of:

a. impregnating extruded alumina with cobalt;
b. soaking cobalt impregnated alumina and drying;
c. impregnating with ruthenium;
d. soaking, and drying ruthenium and cobalt impregnated alumina;
e. impregnating with magnesium; and f. soaking, drying and calcining to get the carbon monoxide hydrogenation catalyst.

9. The process for preparation of catalyst as claimed in claim 8, wherein said extruded alumina has spherical size from 0.5 mm to 1.5 mm.

10. The process for preparation of catalyst as claimed in claim 8, wherein said extruded alumina is first dried at 120 to 150°C before impregnating with cobalt, ruthenium and magnesium.

11. A process of conversion of synthesis gas to hydrocarbons wherein the process comprises of contacting synthetic gas with a carbon monoxide hydrogenation catalyst composition as claimed in claim 1 comprising an extruded alumina impregnated with cobalt compound solution, ruthenium compound and magnesium compound in mode fixed bed operation.

12. The process as claimed in claim 11, wherein said process is carried at a temperature in the range of 210°C to 230°C, pressure in the range of 20 Kg/cm2(g) to 30 kg/cm2(g) and GHSV in the range of 2500 to 4000 cc/gcat/hr.

13. The process as claimed in claim 11, wherein said synthesis gas comprises of impurities;
wherein impurities ranges from 0.01-1 mol% CO2, 0.1-0.9 mol% N2, 0.05-0.15 mol%
of carbonyl sulphide and 0.05-0.15 mol% of hydrogen sulphide of the catalyst composition.

14. The process as claimed in claim 11, wherein said synthesis gas comprises of 25 to 30%
of carbon monoxide, 55 to 60% of hydrogen, 10 to 15% of methane, 0.10 to 1 %
of carbon dioxide, 0.1 to 1% of nitrogen, 0.001 to 0.1 % of carbonyl sulfide and hydrogen sulphide.

15. The process as claimed in claim 11, wherein said alumina comprises of 0-99.5 ppm of sodium.

16. The process as claimed in claim 11, wherein said cobalt, ruthenium and magnesium compounds are decomposable to oxides.