Catalyst compositions for converting syngas to produce higher alcohols

Abstract

Catalyst compositions for production of higher alcohols comprise a hydrotalcite or hydrotalcite-like support impregnated with molybdenum and an alkali metal. When the compositions are used to convert syngas, selectivity to higher (C2+) alcohols is increased in comparison to conversions accomplished over many other catalyst systems.

Claims

1. A catalyst composition prepared by a process comprising (a) calcining a hydrotalcite or hydrotalcite-like support by heating it at a temperature ranging from 200 C. to 600 C., under conditions suitable to form a calcined support exhibiting a powder X-ray diffraction pattern obtained using copper K-alpha radiation having d-spacings at angles 2-theta of 43.4, 62.5 and, optionally, 35.1; and (b) impregnating the calcined support with a molybdenum source and an alkali metal source, under conditions suitable to form a catalyst composition.

2. The catalyst composition of claim 1 wherein at least a portion of the molybdenum source is in the form of molybdenum sulfide.

3. The catalyst composition of claim 2 wherein the catalyst composition comprises from 5 weight percent to 20 weight percent of molybdenum sulfide, and from 2.5 weight percent to 2 weight percent of alkali metal from the alkali metal source; both based on the weight of the catalyst composition as a whole.

4. The catalyst composition of claim 1 wherein step (b) occurs under at least one condition selected from a temperature ranging from 30 C. to 120 C., a time ranging from 1 hour to 4 hours, and combinations thereof.

5. The catalyst composition of claim 1 wherein the hydrotalcite or hydrotalcite-like support is prepared by co-precipitation of salt solutions containing divalent magnesium, nickel or cobalt ions and trivalent aluminum or cobalt ions, provided the divalent and trivalent ions represent different elements; alkali metal ions; and at least one carbonate anion; to form a product having the formula:
M.sup.2+.sub.1xM.sup.3+.sub.x(OH).sub.2(CO.sub.3).sub.x/2.mH.sub.2O, wherein M.sup.2+ is a divalent magnesium, nickel or cobalt ion, and M.sup.3+ is a trivalent aluminum or cobalt ion, provided M.sup.2+ and M.sup.3+ represent different elements; x is the number of moles of the trivalent aluminum or nickel ion; m is the number of moles of waters of hydration; and wherein the carbonate anion may optionally be replaced, in whole or part, by an anion selected from the group consisting of phosphate, molydate, sulfate, nitrate, chlorate, chloride, bromide, fluoride, iodide, and combinations thereof.

6. A process for preparing a higher alcohol comprising contacting (a) a catalyst composition prepared by a process comprising (a) calcining a hydrotalcite or hydrotalcite-like support by heating it at a temperature ranging from 200 C. to 600 C., under conditions suitable to form a calcined support exhibiting a powder X-ray diffraction pattern obtained using copper K-alpha radiation having d-spacings at angles 2-theta of 43.4, 62.5 and, optionally, 35.1; and (b) impregnating the calcined support with a molybdenum source and an alkali metal source; under conditions suitable to form a catalyst composition; and (b) a gas mixture, including at least hydrogen gas and carbon monoxide gas; under conditions suitable to form a product comprising at least one higher alcohol.

7. The process of claim 6 wherein the gas mixture is part of a feed that further comprises hydrogen sulfide in an amount ranging from 20 ppm to 250 ppm.

Description

EXAMPLES

Example 1

(1) Preparation of Support #1

(2) First, an amount of 1.60 g of sodium carbonate is dissolved in 25 mL of water in a 500 mL beaker. The solution is heated to 65 C. Then, a quantity of 11.25 g of aluminum nitrate nonahydrate (Al(NO.sub.3).sub.3.9H.sub.2O, 99.sup.+%) and 17.92 g of magnesium nitrate hexahydrate (Mg(NO.sub.3).sub.2.6H.sub.2O, 99.sup.+%) are dissolved in 150 mL of deionized (DI) water. The resulting suspension is added drop-wise to the preheated Na.sub.2CO.sub.3 solution. The pH of the solution is adjusted to approximately 9.50 using 1.5 molar (M) sodium hydroxide (MOH) solution.

(3) After completing addition of the metal nitrate solutions, the resulting suspension is kept at 65 C. with stirring for 24 h. The precipitate is separated from the solution by filtering and washed with 1000 mL of hot DI water. The filter cake is dried in an oven at 105 C. overnight and calcined at 450 C. for 2 hours in air to obtain Support #1.

(4) BET surface area of the uncalcined Support #1 is about 142 m.sup.2/g. XRD of the uncalcined hydrotalcite support, 2-theta: 11.5; 23.1; 27.1; 34.4; 38.2; 45.3; 60.5; 61.9; 64.7. XRD of the calcined support, 2-theta: 43.2; and 62.6.

Example 2

(5) Preparation of Support #2

(6) First, an amount of 2.50 g of sodium carbonate is dissolved in 25 mL of water in a 500 mL beaker. The solution is heated to 65 C. Then, a quantity of 18.76 g of aluminum nitrate nonahydrate (Al(NO.sub.3).sub.3.9H.sub.2O, 99.sup.+%) and 12.82 g of magnesium nitrate hexahydrate (Mg(NO.sub.3).sub.2.6H.sub.2O, 99.sup.+%) are dissolved in 150 mL of DI water. The resulting suspension solution is added drop-wise to the preheated Na.sub.2CO.sub.3 solution. The pH of the solution is adjusted to approximately 9.50 using 1.5 M sodium hydroxide solution.

(7) After complete addition of the metal nitrate solutions, the resulting suspension is kept at 65 C. with stirring for 24 h. The precipitate is separated from solution by filtering, washed with 1000 mL of hot DI water. The filter cake is dried in an oven at 105 C. overnight and calcined at 450 C. for 2 h in air to obtain Support #2.

(8) BET surface area of the uncalcined Support #2 is about 80 m.sup.2/g. XRD of the uncalcined hydrotalcite support, 2-theta: 11.7; 18.4; 20.2; 23.3; 27.1; 34.7; 39.2; 39.4 45.3; 60.7; 62.1. XRD of the calcined support, 2-theta: 43.2; 62.6.

Example 3

(9) Preparation of Catalyst Composition A

(10) First, 5.34 g of Support #1 described in Example 1 and 0.73 g of ammonium heptamolybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O) are added in 10 g of isopropanol. The resulting suspension is stirred at 65 C. for 2 h before evaporation in an oven at 105 C. overnight. The resultant solid is calcined in a inch diameter quartz tube at 500 C. for 2 h at a ramp of 5 C./min in a flow of 50 mL/min of N.sub.2. The calcined solid is then added into 10 g of DI water containing 0.28 g of K.sub.2CO.sub.3 at room temperature. The slurry is dried in an oven at 105 C. overnight. The dried solid is calcined in the quartz tube at 400 C. for an hour at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The molybdenum loading calculated as molybdenum trioxide is about 10 wt %, and the K.sub.2CO.sub.3 loading is about 5 wt %.

(11) BET surface area of the calcined catalyst composition is 69 m.sup.2/g. XRD: Mg(Al)O.sub.x oxide (2-theta): 43.4; 62.6.

Example 4

(12) Preparation of Catalyst Composition B

(13) First, 5.67 g of Support #1 described in Example 1 and 1.74 g of ammonium heptamolybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O) are added in 11.5 g of isopropanol. The resulting suspension is stirred at 65 C. for 2 hours before evaporation in an oven at 105 C. overnight. The resultant solid is calcined in a inch diameter quartz tube at 500 C. for 2 h at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The calcined solid is then added into 11.5 g of DI water containing 0.68 g of K.sub.2CO.sub.3 at room temperature. The slurry is dried in an oven at 105 C. overnight. The dried solid is calcined in the quartz tube at 400 C. for an hour at a ramp of 5 C./min in a flow of 50 mL/min of N.sub.2. The molybdenum loading calculated as molybdenum trioxide is about 20 wt %, and the K.sub.2CO.sub.3 loading is about 10 wt %.

(14) The BET surface area of the catalyst composition is from 9 to 47 m.sup.2/g. XRD: K.sub.2Mo.sub.2O.sub.7 (2-theta): 18.8; 29.3; 30.6; K.sub.2Mo.sub.4O.sub.6 (2-theta): 25.5; 39.7; MoO.sub.2 (2-theta): 26.2; 28.1; Mg(Al)O.sub.x oxide (2 theta): 43.1; 62.4.

Example 5

(15) Preparation of Catalyst Composition C

(16) First, 4.58 g of Support #1 described in Example 1 and 2.4 g of ammonium heptamolybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O) are added in 9.0 g of isopropanol. The resulting suspension is stirred at 65 C. for 2 h before evaporation in an oven at 105 C. overnight. The resultant solid is calcined in a inch diameter quartz tube at 500 C. for 2 h at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The calcined solid is then added into 9.0 g of DI water containing 0.94 g of K.sub.2CO.sub.3 at room temperature. The slurry is dried in an oven at 105 C. overnight. The dried solid is calcined in the quartz tube at 400 C. for an hour at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The molybdenum loading calculated as molybdenum trioxide is about 30 wt %, and the K.sub.2CO.sub.3 loading is about 15 wt %.

(17) BET surface area of the catalyst composition is about 14 to 18 m.sup.2/g. XRD: MoO.sub.2 (2-theta): 26.1; 37.0; Mg(Al)O.sub.x oxide (2-theta): 43.2; 62.6.

Example 6

(18) Preparation of Catalyst Composition D

(19) First, an amount of 4.58 g of Support #1 described in Example 1 and 0.62 g of ammonium heptamolybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O) are added in 9.0 g of isopropanol. The resulting suspension is stirred at 65 C. for 2 hours before evaporation in an oven at 105 C. overnight. The resultant solid is calcined in the inch quartz tube at 500 C. for 2 h at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The calcined solid is then added into 9.0 g of DI water containing 0.74 g of K.sub.2CO.sub.3 at room temperature. The slurry is evaporated and dried in an oven at 105 C. overnight. The dried solid is calcined in the quartz tube at 400 C. for an hour at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The molybdenum loading calculated as molybdenum trioxide is about 10 wt %, and the K.sub.2CO.sub.3 loading is about 15 wt %.

(20) BET surface area of the catalyst is about 47 m.sup.2/g. XRD: K.sub.2Mo.sub.2O.sub.7 (2-theta): 18.9; 23.3; 29.3; 30.6; K.sub.2Mo.sub.4O.sub.6 (2-theta): 26.3, 39.7; Mg(Al)O.sub.x oxide (2-theta): 43.2; 62.7.

Example 7

(21) Preparation of Catalyst Composition E

(22) First, 4.76 g of Support #2 described in Example 2 and 2.51 g of ammonium heptamolybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O) are added in 9.0 g of isopropanol. The resulting suspension is kept at 65 C. with stirring for 2 h before evaporation in an oven at 105 C. overnight. The resultant solid is calcined in a inch diameter quartz tube at 500 C. for 2 h at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The calcined solid is then added into 9.0 g of DI water containing 0.98 g of K.sub.2CO.sub.3 at room temperature. The slurry is dried in an oven at 105 C. overnight. The dried solid is calcined in the quartz tube at 400 C. for an hour at a ramp of 5 C./min in flow of 50 mL/min of N.sub.2. The molybdenum loading calculated as molybdenum trioxide is about 30 wt %, and the K.sub.2CO.sub.3 loading is about 15 wt %.

(23) The BET surface area of the catalyst is about 8.0 m.sup.2/g. XRD: MoO.sub.2 (2-theta): 26.1; 36.7; Mg(Al)O.sub.x oxide (2-theta) 43.6; 62.7.

Example 8

(24) Preparation of Catalyst F

(25) First, 3.71 g of Support #2 described in Example 2 and 0.51 g of ammonium heptamolybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4O.sub.2O) are added in 7.0 g of isopropanol. The resulting suspension is kept at 65 C. with stirring for 2 hours before evaporation in an oven at 105 C. overnight. The resultant solid is calcined in a inch diameter quartz tube at 500 C. for 2 hours at a ramp of 5 C./min in a flow of 50 mL/min of N.sub.2. The calcined solid is then added into 7.0 g of DI water containing 0.19 g of K.sub.2CO.sub.3 at room temperature. The slurry is dried in oven at 105 C. overnight. The dried solid is calcined in the quartz tube at 400 C. for an hour at a ramp of 5 C./min in a flow of 50 mL/min of N.sub.2. The molybdenum loading calculated as molybdenum trioxide is about 10 wt %, and the K.sub.2CO.sub.3 loading is about 5 wt %.

(26) The BET surface area of the catalyst is about 77 m.sup.2/g. XRD, Mg(Al)O.sub.x oxide (2-theta): 43.1; 62.8.

Example 9

(27) Preparation of Catalyst G

(28) First, 1.027 g of ammonium heptamolybdate ((NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O) is added to 28.8 g dimethyl sulfoxide and stirred for 4 hours at 23 C. The solution is then added to a beaker containing 7.59 g of support similar to that described in Example 2 and heated to 135 C. for 12 hours in air. The resultant solid is calcined in a inch diameter quartz tube first at 200 C. for 4 hours at a ramp of 5 C./min in a flow of 50 mL/min of N.sub.2 and then at 450 C. for 2 hours at a ramp of 5 C./min in a flow of 50 mL/min of N.sub.2. Finally, the calcined solid is combined with 0.42 g K.sub.2CO.sub.3 and ground in a mortar and pestle at 23 C. for 15 minutes. The molybdenum loading calculated as molybdenum trioxide is about 10 wt %, and the K.sub.2CO.sub.3 loading is about 5 wt %.

(29) The BET surface area of the catalyst is about 143 m.sup.2/g. XRD, Mg(Al)O.sub.x oxide (2-theta): 43.4; 62.6.

Example 10

(30) Preparation of Higher Alcohols

(31) A series of tests of the six catalyst compositions, designated as Catalyst Compositions A-F as shown in Examples 3-8, is carried out to measure their performance in converting syngas into higher alcohols. The reactor used consists of a quarter-inch stainless steel (SS) tube (316 SS) with a catalyst loading of 1.0 g. Premixed hydrogen, carbon monoxide, and nitrogen feed gases from cylinders are compressed and regulated at the reaction pressure stated in the following tables. The feed gas mixture contains hydrogen and carbon monoxide at the molar ratio of 1/1 with about 10 percent by volume nitrogen, serving as an internal standard. About 50 ppm of H.sub.2S is also present in the feed gas.

(32) The mixed feed gas passes through a bed of molecular sieve 13 held at 170 C. to remove iron carbonyl and any other carbonyl contaminants that may be present. The feed gas then passes, at a pre-determined gas hourly space velocity (GHSV) of 1200, 1750, or 2400 milliliters per gram per hour (mL/g/h), through the fixed bed reactor that is kept at the stated reaction temperature and held at a pressure of 1,500 pounds per square inch gauge (psig) (10.34 megapascals, MPa). The reactor effluent is fed into a gas chromatograph to analyze the gas composition, and the catalytic performance of the solids is summarized in Tables 1-3 hereinbelow. Selectivity, in carbon mole percent, excluding CO.sub.2, is defined as the carbon atom content in each product divided by the sum of carbon atoms in all alcohols, non-alcohol oxygenates, and hydrocarbons. Hydrocarbons are primarily methane, and Oxygenates are the total of oxygen-containing products other than alcohols.

(33) Table 1 shows performance of Catalyst Compositions A-E, with results recorded under the following relevant conditions: Temperature=310 C.; H.sub.2/CO=1; H.sub.2S (ppm)=50; catalyst weight=1.0 g; and GHSV=1200 mL/g/h.

(34) TABLE-US-00001 TABLE 1 CO Selectivity (C, %, Excluding CO.sub.2) Conver- CO.sub.2 Oxy- Hydro- Catalyst sion (%) (%) MeOH C2.sup.+OH genates carbons A 9.9 35.1 3.3 65.5 4.1 27.1 B 7.5 31.1 4.4 49.4 3.6 42.5 C 12.0 23.9 8.1 42.2 1.5 59.5 D 5.8 27.6 8.9 44.3 2.4 44.5 E 13.7 29.9 4.8 44.0 2.3 49.3

(35) Table 2 shows results for the same catalysts, based upon a GHSV of 2400 mL/g/h. All other conditions are the same as those for Table 1.

(36) TABLE-US-00002 TABLE 2 CO Selectivity (C, %, Excluding CO.sub.2) Conver- CO.sub.2 Oxy- Hydro- Catalyst sion (%) (%) MeOH C2.sup.+OH genates carbons A 7.2 31.4 6.1 60.5 2.3 31.6 B 2.6 30.5 12.5 44.0 7.3 36.1 C 4.1 24.3 13.1 37.4 2.4 46.8 D 2.9 28.7 13.9 51.1 5.6 29.4 E 6.8 28.9 8.5 43.6 3.8 44.0

(37) Table 3 shows results for only Catalyst Composition F (Example 8), at temperatures ranging from 260 C. to 335 C. Test conditions include H.sub.2/CO=1; GHSV (mL/g/h)=1750; H.sub.2S (ppm)=50; and weight of catalyst (g)=0.7.

(38) TABLE-US-00003 TABLE 3 CO Selectivity (C, %, Excluding CO.sub.2) Temperature, Conver- CO.sub.2 Oxy- Hydro- C. sion (%) (%) MeOH C2.sup.+OH genates carbons 260 1.9 43.0 3.9 72.6 4.9 18.5 285 3.2 46.3 3.8 76.6 4.4 15.5 310 7.8 47.9 2.3 56.5 1.2 40.0 335 12.3 44.4 1.9 29.9 1.3 66.9

(39) The inventive catalysts (Catalyst Compositions A-F, Examples 3-8) are useful as low-methanol catalysts for the conversion of syngas to non-methanol oxygenate products. In particular, the selectivity to C2.sup.+OH is much higher than to methanol, by a factor ranging from 8 to 15. At a lower loading of MoO.sub.2 precursor (Example 3) and a higher ratio of atomic K to Mo (Example 8), the catalysts show an improved C2.sup.+OH selectivity under typical higher alcohol synthesis conditions. A highest selectivity toward C2.sup.+OH from syngas is seen, in Table 3, at estimated reaction temperatures ranging from approximately 270 C. to 300 C., i.e., at 260 C. C2.sup.+OH is at 72.6%; at 285 C. it increases to 76.6%; and at 310 C. it has dropped to 56.5%.