Carbon supported cobalt and molybdenum catalyst

Abstract

The present invention relates to a catalyst composition comprising cobalt molybdenum and optionally one or more elements selected from the group consisting of alkali metals and alkaline earth metals on a carbon support wherein said cobalt and molybdenum are in their metallic form. It was surprisingly found that the selectivity for alcohols can be increased by using the carbon supported cobalt molybdenum catalyst as described herein in a process for producing alcohols from a feed stream comprising hydrogen and carbon monoxide. Furthermore, it was found that the catalyst of the present invention has a decreased selectivity for CO.sub.2 and can be operated at relatively low temperature when compared to conventional catalysts. Moreover, a method for preparing the carbon supported cobalt molybdenum catalyst composition and a process for producing alcohols using said carbon supported cobalt molybdenum catalyst composition is provided.

Claims

1. A catalyst composition comprising formula Co.sub.aMo.sub.bM.sub.cC, wherein M is one or more elements selected from the group consisting of alkali metal and alkaline earth metal and C is an activated carbon support, wherein the relative molar ratios of the elements in the formula are as follows: a is 1E3-0.3; b is 1E3-0.9; c is 0-1E2; and wherein the Co and Mo are in their metallic form and wherein the catalyst composition has a BET surface area of at least 320 m.sup.2/g.

2. The catalyst composition according to claim 1, wherein M is present and is selected from the group consisting of potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg).

3. The catalyst composition according to claim 1, wherein: a is 1E2-0.3; and b is 5E3-0.9.

4. The catalyst composition according to claim 1, wherein the catalyst composition has a BET surface area of 350-1200 m.sup.2/g.

5. The catalyst composition according to claim 1, wherein the Co and/or Mo are not in sulphide form.

6. The catalyst composition according to claim 1, wherein said catalyst composition further comprises an inert binder.

7. The catalyst composition according to claim 1, wherein the catalyst composition has a BET surface area of 350-800 m.sup.2/g.

8. The catalyst composition according to claim 1, wherein b is 1E2-0.3.

9. The catalyst composition according to claim 1, wherein b is 5E3-0.2.

10. The catalyst composition according to claim 1, wherein c is >0-1E2.

11. The catalyst composition according to claim 1, wherein the molar ratio of Co:Mo is 1.2-4.

12. The catalyst composition according to claim 1, wherein the molar ratio of Co:Mo is 2.0-2.5.

13. The catalyst composition according to claim 1, wherein M is present and is selected from the group consisting of calcium (Ca), and magnesium (Mg).

14. A catalyst composition comprising a formula consisting essentially of Co.sub.aMo.sub.bM.sub.cC, wherein M is one or more elements selected from the group consisting of alkali metal and alkaline earth metal and C is an activated carbon support, wherein the relative molar ratios of the elements in the formula are as follows: a is 1E3-0.3; b is 1E3-0.9; c is 0-1E2; and wherein the Co and Mo are in their metallic form and wherein the catalyst composition has a BET surface area of at least 320 m.sup.2/g.

Description

MODE(S) FOR CARRYING OUT THE INVENTION

(1) The present invention will now be more fully described by the following non-limiting Examples.

EXAMPLE 1 (COMPARATIVE)

(2) CoMoS.sub.2

(3) A co-precipitated cobalt/molybdenum sulfide is prepared with a Mo/Co atomic ratio of about 2:1. Fifteen grams of (NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O (0.085 Moles Mo) is dissolved in 106 cm.sup.3 of 22% (NH.sub.4).sub.2S in water and stirred at 60 C. for one hour to form (NH.sub.4).sub.2MoS.sub.4. A solution of 10.5 grams of Co (CH.sub.3CO.sub.2).sub.2 (0.042 moles Co) in 200 ml of water was prepared. The two solutions were then added simultaneously, drop wise to a stirred solution of 30% aqueous acetic acid in a baffled flask at 50 C. over a one hour period. After stirring for an additional hour the reaction mixture is filtered and the filter cake dried at room temperature and then calcined for one hour at 500 C. in an inert atmosphere such as nitrogen. The calcined Co/Mo Sulfide is ground together with 2.0 g of bentonite clay, 1.0 g of K.sub.2CO.sub.3 and 0.4 g of sterotex lubricant in a mortar and pestles and used for catalyst testing.

EXAMPLE 2

(4) Co.sub.0.159Mo.sub.0.079C

(5) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 15 g of ammonium molybdate tetrahydrate [(NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH.sub.3 precipitating solution (200 ml of 11.6 M NH.sub.3 solution) was also preheated to 80 C. 6.4 g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-8.00. The duration of reaction was 1 h. This solution was immediately filtered through a preheated funnel and washed (using 500 ml of warm distilled water). The precipitates were dried at 110 C. for 16 h followed by calcinations at 500 C. under continuous flow of helium for 24 h. The calcined catalysts were pelleted and sieved (0.65-0.85 mm).

EXAMPLE 3

(6) Co.sub.0.159Mo.sub.0.079C

(7) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 15 g of ammonium molybdate tetrahydrate [(NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH.sub.3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 6.4 g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was approximately 1 h. This solution was immediately filtered through a preheated funnel and washed (using 500 ml of warm distilled water). The precipitates were dried at 110 C. for 16 h followed by calcinations at 500 C. under continuous flow of helium for 24 h. The calcined catalysts were pelleted and sieved (0.65-0.85 mm).

EXAMPLE 4

(8) Co.sub.0.126Mo.sub.0.766C

(9) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 45.08 g of ammonium molybdate tetrahydrate [(NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH.sub.3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 4 g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was approximately 1 h. This solution was immediately filtered through a preheated funnel and washed (using 500 ml of warm distilled water). The precipitates were dried at 110 C. for 16 h followed by calcinations at 500 C. under continuous flow of helium for 24 h. The calcined catalysts were pelleted and sieved (0.65-0.85 mm).

EXAMPLE 5

(10) Co.sub.0.177Mo.sub.0.547C

(11) 100 ml each of Co and Mo solutions was prepared by dissolving 14.7 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 32.2 g of ammonium molybdate tetrahydrate [(NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH.sub.3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 4 g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was approximately 1 h. This solution was immediately filtered through a preheated funnel and washed (using 500 ml of warm distilled water). The precipitates were dried at 110 C. for 16 h followed by calcinations at 500 C. under continuous flow of helium for 24 h. The calcined catalysts were pelleted and sieved (0.65-0.85 mm).

(12) Catalyst Testing

(13) Catalyst material (0.5 g) were loaded in a reactor and reduced with H.sub.2 at 350-400 C. for several hours. Pressure was increased to 75 bar. All catalysts were tested under similar reaction conditions (T=250 C.; p=75 bar; and WHSV=1225 h.sup.1). The composition of the feed stream was CO:H.sub.2:N.sub.2=47.5:47.5:5. Accordingly, the feedstream comprised syngas having CO:H.sub.2 molar ratio of 1.

(14) Analysis of gaseous product was achieved by an online gas chromatograph (GC, Varian 3800). A 5 m* inch stainless steel Porapak-Q column (mesh size 80-100) was used to separate the reactants and products. Concentrations of hydrogen, carbon monoxide, carbon dioxide and nitrogen were analyzed by a thermal conductivity detector (TCD). The TCD compares the conductivity of the analyzed gas to that of a reference gas. Conversion was determined using an internal standard, nitrogen. Organic compounds such as hydrocarbons and oxygenates were determined by a flame ionization detector (FID). By using a hydrogen and air flame, the FID burns the organic compounds into ions whose amounts are roughly proportional to the number of carbon atoms present. Liquid products from alcohols reactor were collected and identified by gas chromatography mass spectrometer (GC-MS, Perkin Elmer TurboMass). Quantification of liquid products was determined by an offline GC equipped with a Chrompack capillary column (CP-Sil 8CB, 30 m, 0.32 mm, 1 m) and an FID detector.

(15) The provided values have been calculated as follows:

(16) Conversion:

(17) An indication of the activity of the catalyst was determined by the extent of conversion of the carbon monoxide or for more active catalysts by the extent of volume reduction of the reagent gases (using nitrogen as internal standard). The basic equation used was:
Conversion %=Moles of CO.sub.inmoles of CO.sub.out/moles of CO.sub.in*100/1

(18) Selectivity

(19) First of all, the varying response of the detector to each product component was converted into % v/v by, multiplying them with online calibration factors. Then these were converted into moles by taking account the flow out of internal standard, moles of feed in and time in hours. Moles of each product were converted into mole-% and selectivity-% was measured by taking carbon numbers into account.

(20) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 Catalyst CoMoS.sub.2 Co.sub.0.159Mo.sub.0.079C Co.sub.0.159Mo.sub.0.079C Co.sub.0.126Mo.sub.0.766C Co.sub.0.177Mo.sub.0.547C Co/Mo/C 14./47.85/37.57 14.58/47.85/37.57 13.92/70.05/16.05 7.5/79.50/12.99 (wt-%) BET 400 415 350 340 surface area (m.sup.2/g) pH 8 9 9 9 Precipitant 11.6 5.6 5.6 5.6 conc (M) H.sub.2:CO 1 1 1 1 1 CO 41 23 28 21 17 Conversion (mole-%) CO.sub.2 35.46 0.58 3.8 7.5 11.5 CH.sub.4 9.19 2.7 1.27 12 15.3 C.sub.2-C.sub.6 26.89 2.45 1 15.5 25 Methanol 10.6 19.68 26.21 17.5 13.5 ethanol 20.56 21.4 30.7 21 16.3 propanol 21.56 24.9 33.6 22 15 1-butanol 5.37 24.96 2 2.5 1.5 higher 9.16 3.33 3.8 2 1.9 alcohols total 67.26 94.27 96.31 65 48.2 ALCOH

(21) Table 1 clearly shows that the catalyst of the present invention has a significantly increased selectivity for methanol when compared to a conventional carbon supported cobalt molybdenum catalyst. In addition thereto, a decrease in CO.sub.2 formation could be observed, which is an undesired side-products produced in F-T synthesis. The selectivity pattern of alcohols also depends on the pH of precipitation mixture and the concentration of precipitant, wherein the selectivity for methanol, ethanol and propanol is increased in case the pH of the precipitation mixture is increase from 8 to 9.

(22) FIGS. 1 and 2 show XRD pattern of two catalysts prepared at different pH 8 (Example 2) and pH 9 (Example 3). The pH difference and concentration of the precipitant also affects the morphology of catalyst material. The catalyst prepared at pH 8 precipitated with more concentrated solution of ammonium hydroxide was found to be more crystalline and the one prepared at pH 9 with less concentrated solution of ammonium hydroxide showed an amorphous morphology. The XRD data were obtained using standard X-ray diffraction meter at 2 theta value from 1 to 100 within 1 hr.

EXAMPLE 6

(23) Co.sub.0.126Mo.sub.0.255C

(24) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 15 g of ammonium molybdate tetrahydrate [(NH.sub.4)6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 4g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was ca. 1 h. This solution was filtered and washed. The precipitates were dried at 110 C. for 16 h followed by thermal cooking and activation of catalyst at 400 C. under continuous flow of helium/nitrogen for 12 to 24 hrs and used for syngas conversion.

EXAMPLE 7

(25) Co.sub.0.126Mo.sub.0.255C

(26) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 15 g of ammonium molybdate tetrahydrate [(NH.sub.4)6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 4g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was ca. 1 h. This solution was filtered and washed. The precipitates were dried at 110 C. for 16 h followed by thermal cooking and activation of catalyst at 500 C. under continuous flow of helium/nitrogen for 12 to 24 hrs and used for syngas conversion.

EXAMPLE 8 (COMPARATIVE EXAMPLEWO 2010/002618 A1)

(27) Co.sub.0.126Mo.sub.0.255C

(28) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 15g of ammonium molybdate tetrahydrate [(NH.sub.4)6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 4 g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was ca. 1 h. This solution was filtered and washed. The precipitates were dried at 110 C. for 16 h followed by thermal cooking and activation of catalyst at 600 C. under continuous flow of helium/nitrogen for 12 to 24 hrs and used for syngas conversion.

EXAMPLE 9 (COMPARATIVE EXAMPLEWO 2010/002618 A1)

(29) CO.sub.0.126Mo.sub.0.255C

(30) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 15 g of ammonium molybdate tetrahydrate [(NH.sub.4)6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 4 g of activated carbon (derived from coconut shell having a BET surface area of 800 m.sup.2/g) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was ca. 1 h. This solution was filtered and washed. The precipitates were dried at 110 C. for 16 h followed by thermal cooking and activation of catalyst at 700 C. under continuous flow of helium/nitrogen for 12 to 24 hrs and used for syngas conversion.

EXAMPLE 10 (COMPARATIVE EXAMPLEWO 2010/002618 A1)

(31) Co.sub.0.126Mo.sub.0.255C

(32) 100 ml each of Co and Mo solutions was prepared by dissolving 10.5 g of cobalt acetate [Co(CH.sub.3CO.sub.2).sub.2] and 15 g of ammonium molybdate tetrahydrate [(NH.sub.4)6Mo.sub.7O.sub.24.4H.sub.2O] in distilled water. Both solutions were premixed and heated to 80 C. The NH3 precipitating solution (200 ml of 5.6M NH.sub.3 solution) was also preheated to 80 C. 4 g of activated carbon (derived from coconut shell) was added into 100 ml of distilled water in the precipitation vessel. Both reagents (mixed metal salts solutions and NH.sub.3 solution) were combined together in the reaction vessel at 80 C. at a combined pumping rate of 6.7 ml/min (3.3 ml/min NH.sub.3 solution, 3.3 ml/min metals solution). The reagents were combined in the reaction vessel (80 C.) containing activated carbon in 100 ml of water. The pH was varied from 4.35-9.00. The duration of reaction was ca. 1 h. This solution was filtered and washed. The precipitates were dried at 110 C. for 16 h followed by thermal cooking and activation of catalyst at 800 C. under continuous flow of helium/nitrogen for 12 to 24 hrs and used for syngas conversion.

(33) Catalyst Testing

(34) The comparative catalysts were tested under similar reaction conditions as the catalysts according to the present invention (T=250 C.; p=75 bar; and WHSV=1225 h.sup.1). The composition of the feedstream was CO:H.sub.2:N.sub.2=47.5:47.5:5. Accordingly, the feedstream comprised syngas having CO:H.sub.2 molar ratio of 1.

(35) TABLE-US-00002 TABLE 2 Example 6 7 8 9 10 Catalyst Co.sub.0.126Mo.sub.0.255C Co.sub.0.126Mo.sub.0.255C Co.sub.0.126Mo.sub.0.255C Co.sub.0.126Mo.sub.0.255C Co.sub.0.126Mo.sub.0.255C Co/Mo/C (wt-%) 15.88/56.42/27.69 15.88/56.42/27.69 15.88/56.42/27.69 15.88/56.42/27.69 15.88/56.42/27.69 pH 9 9 9 9 9 Precipitant 5.6 5.6 5.6 5.6 5.6 conc (M) H.sub.2:CO 1 1 1 1 1 BET (m.sup.2/g) 366 351 311 267 210 CO Conversion 39.8 36.5 24.3 19 11 (mole-%) CO.sub.2 5 8.3 11.5 21.6 35 CH.sub.4 15.5 11 5.2 5.4 2.3 C.sub.2-C.sub.6 21 13 32 36 41 Methanol 21 18.5 19 19.7 11.2 ethanol 25.3 30.1 22 9.6 5.4 propanol 9 16.6 9.1 4.5 5.1 1-butanol 3.2 2.5 1.2 3.2 0 total alcohols 59.1 67.7 51.3 37 21.7

(36) Table 2 clearly shows that the catalyst of the present invention has a dramatically improved CO conversion in combination with a significantly increased selectivity for alcohols when compared to a carbon supported carbon supported cobalt molybdenum catalyst having a lower BET surface area, like the catalyst suggested in WO 2010/002618 A1. Moreover, it is evident from Table 2 that a lower calcination temperature is to be selected when preparing the carbon supported cobalt molybdenum catalyst.