PROCESS FOR SYNTHESIS OF COBALT MOLYBDENUM SULFIDE CATALYSTS This invention generally relates to preparation of catalysts used to convert synthesis gas ("syngas", a mixture of carbon monoxide (CO) and hydrogen (H ₂ ) to an alcohol (e.g. ethanol (EtOH) and propanol (PrOH)). This invention particularly relates preparation of such catalysts from a combination of cobalt (Co) precursor and molybdenum (Mo) precursor and the use of such catalysts to convert syngas to an alcohol.

United States Patent (USP) 4,752,623 to Stevens et al. discloses a process for selectively producing mixed alcohols from syngas using a catalyst that contains (1) a catalytically active metal selected from Mo, tungsten (W) or rhenium (Re) in free or combined form, (2) a co-catalytic metal selected from Co, nickel (Ni) or iron (Fe), (3) a Fischer- Tropsch promoter, and (4) an optional support. Stevens et al. prefers Mo and Co in their sulfided form and teach use of precursors such as ammonium tetrathiomolybdate and cobaltous acetate tetrahydrate. In several comparison catalyst preparations, Stevens et al. teaches calcining for one hour at 500 degrees centigrade (°C) in an inert atmosphere such as nitrogen.

USP 4,825,013 to Quarderer et al. presents teachings about homologation of alcohols using a heterogeneous catalyst consisting of (1) a Mo metal, sulfide, oxide, carbide or mixture thereof, (2) an alkali or alkaline earth metal element or a mixture thereof in free or combined form, (3) optionally a Co, Ni or Fe metal, sulfide, oxide or carbide or a mixture thereof, and (4) optionally an alumina, silica or carbon support. Quarderer et al. defines "in free or combined form" as a metal, an alloy or a compound of an element (e.g. Mo). Quarderer et al. also teaches calcining for one hour at 500 °C in an inert atmosphere such as nitrogen.

In some embodiments, this invention is an improved process for preparing catalysts such as those taught by Stevens et al. and Quarderer et al., especially a cobalt- molybdenum sulfide catalyst, the process comprising heating a catalyst precursor in an inert gaseous atmosphere, the improvement comprising heating the catalyst precursor for a first period of time at a first temperature within a range of from greater than 250 °C to less than or equal to 450 °C and then for a second period of time at a second temperature within a range of from 450 °C to less than 600 °C. The catalyst precursor is preferably a product of a reaction among cobalt acetate, ammonium heptamolybdate and ammonium sulfide. The first temperature is preferably within a range of from 300 °C to 450 °C, more preferably from 350 °C to 450 °C. The second temperature is preferably less than 600°C, more preferably less than or equal to 550 ° C. Each of the first and second periods of time is independently and preferably within a range of from one minute to 60 minutes. When ranges are stated herein, as in a range of from 2 to 10, both end points of the range (e.g. 2 and 10) and each numerical value, whether such value is a rational number or an irrational number, are included within the range unless otherwise specifically excluded.

Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percents are based on weight.

Example 1:

Prepare a reaction mixture by combining 467 pounds (lbs) (211.8 kilograms (kg) of cobalt acetate, 662 lbs (300.3 kg) of ammonium heptamolybdate and 2311 lbs (1048.2 kg) of ammonium sulfide (aqueous (aq.)) (44.2 wt%) and 2666 lbs (1209.3 kg) of glacial acetic acid and 10664 lbs (4837.1 kg) of distilled water in a 4000 gallon (15.1 cubic meter) reactor. Allow the reaction mixture components to react at a temperature of 50.6 to 64.4 °C for a period of 1 hr and then hold at 60 °C for 1 hr to yield a product solution. Pump the product solution to a Komline Sanderson filter press that contains 10 plates and convert the product solution into filter cakes that have a thickness of 17 millimeters (mm) and a moisture content of 49.6 wt , based upon filter cake weight. Transfer the filter cake of catalyst precursor complex to a 100 liter (L) Vrieco-Nauta vacuum dryer that has a jacket preheated with oil to a set point temperature of 70 °C. Increase the set point temperature to 77 °C and dry the filter cake under vacuum (pressure of 100 mm mercury) to a moisture content of 47 wt . Store the dried filter cake (catalyst precursor complex) under nitrogen until use.

Comparative Example A

Replicate Example 1 with changes to prepare precipitate for use as a catalyst. Change the reaction mixture to 198 lbs (89.8 kg) of cobalt acetate, 280 lbs (127.0 kg) of ammonium heptamolybdate and 982 lbs (445.4 kg) of ammonium sulfide (aq.) (44 wt ) and 1129 lbs (512.1 kg) of acetic acid and 5834 lbs (2646.2 kg) of distilled water and the reactor to a 4000 L reactor. The filter cakes have a moisture content of 42.8 wt -49.6 wt , based upon filter cake weight. Place the cakes on trays in a heated enclosure at 70 ° Fahrenheit (°F) (21° C) overnight and then transfer the cakes to a second oven and dry them for 16 hrs at 158 °F (70° C) before storing dried cakes in drums with two plastic liners under a nitrogen atmosphere.

Feed 1 kg/ hr of dried filter cake to a rotary furnace (Harper International Rotary Furnace, Model HOU-D60-RTA-24) that has a diameter of six inches (in.) (15.2 centimeters (cm)) and a length of 120 in. (304.8 cm) and three heated zones, all configured to a set point temperature of 550 °C. The dried filter cake, which has a residence time of 48 minutes in the heated zones, converts to a powder.

Blend the powder with 10 wt of potassium carbonate (K ₂ CO ₃ ) and 20 wt of Bentolite L clay and 4 wt Sterotex lubricant and press the blend into tablets using a 51 station tabletting machine.

Example 2

Replicate Comparative Example A, but use the powder from Example 1 and set heated zone 1 to a set point temperature of 450 °C and heated zones 2 and 3 to a set point temperature of 500 °C,

Example 3

Load ¼ inch (0.64 cm) inner diameter tubes with 3 grams (g) of tablets from either Comparative Example A or Example 2. Plumb the tubes into a reaction system with freed gas delivery at 3000 pounds per square inch (psi) (20.7 megapascals (MPa), and heat applied with a sand bath. The feed gas contains 5 volume percent (vol ) nitrogen and 95 vol of a 1:1 molar ratio of carbon monoxide and hydrogen, each vol being based upon total feed composition volume. Summarize productivity results in Table 1 below.

Table 1

Table 1

Comparative Examples B-E and Examples 4-8

Form a catalyst batch for each of the Comparative Examples and Examples by placing 3 g of dried filter cake prepared in Example 1 in a platinum boat (½ inch by 1 inch by ½ inch (1.3 cm by 2.5 cm by 1.3 cm) and move the boat into a pre-heated static furnace under a nitrogen flow of 200 standard cubic centimeters per minute (seem) for a period of 15 minutes at a zone 1 temperature (Table 2). Move the boat outside of the furnace's heated zone. Adjust the furnace temperature to a zone 2 temperature (Table 2), then move the boat into the furnace for a second period of 15 minutes. Allow the furnace to cool to ambient temperature before removing the boat from the furnace and compounding the contents with 20 wt clay and 10 wt K2CO ₃ , each wt being based upon combined weight of clay, K2CO ₃ and boat contents. Press the compounded materials into a slug, then fracture the slug and sieve it into 20 mesh (0.841 millimeter (mm) sieve opening) by 40 mesh (0.373 mm sieve opening) particles for testing in the laboratory scale reactor used in Example 3. Table 2

Using the same reactor as in Example 3, pass the feedstream used in Example 3 through the reactor at a gas hourly space velocity (GHSV) of 11,300 hr ^"1 taking data between 270 °C and 360 °C and fitting it to a line to compare performance at constant conversion. Summarize test results in Table 3 below.

Table 3

The data presented in Table 3 shows that use of two different temperatures, temperature of 350 °C (Example 6) or 450 °C (Example 7) for Zone 1 and 500 °C for the

Zone 2, provides better results in terms of ethanol productivity at temperatures of 340 °C and 360 °C than a single temperature both Zone 1 and Zone 2 of 500 °C (Comparative Example B), 550 °C (Comparative Example C) or 600 °C (Comparative Example D) zones, or use of two zones where Zone 1 is 250 °C (Example 4). If one desires a single temperature for both zones, one should use a temperature less than 500 °C as in Example 8 (450 °C). In addition, a temperature of 600 °C for Zone 2 provides the lowest ethanol productivity irrespective of the temperature in Zone 1.