Process for producing methanol and catalyst therefor

Details Process for producing methanol and catalyst therefor Process for producing methanol and catalyst therefor

1998-06-10

2000-04-25

Geist, Gary

Chemistry: fischer-tropsch processes; or purification or recover

Group ib metal containing catalyst utilized for the...

518700, 502307, 502344, 502345, 502349, C07C 2700, B01J 2300, B01J 2302, B01J 2370

Patent

active

06054497&

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a process for preparing methanol by reacting a gas mixture containing hydrogen and carbon monoxide and/or carbon dioxide over a catalyst.
2. Background Art
It is known that methanol can be prepared from H and CO and/or CO.sub.2 over copper-containing catalysts. It is also known that catalysts containing not only copper but also zinc oxide, zirconium oxide and, if desired, further oxides can be used for this purpose (GB-A 2 151 498, U.S. Pat. No. 5,254,520, Y. Nitta et al., Catal. Lett. 1994, 26, 345-354). Although the catalysts known hitherto do give usable space-time yields in the synthesis of methanol, it is desirable to increase these further. Moreover, the known catalysts frequently contain additives which make it more difficult to dispose of or reprocess the used catalyst. It is therefore an object of the invention to provide, by use of an improved catalyst, a methanol-preparation process having a higher space-time yield, where the catalyst should if possible contain no toxic or otherwise harmful components.


BROAD DESCRIPTION OF THE INVENTION

According to the invention, this object is achieved by the process of the invention. It has surprisingly been found that good results can be achieved even with a catalyst having the simple composition of 10-70% of Cu, 10-50% of Zn and 20-80% of Zr if it is essentially X-ray-amorphous. The percentages indicate the relative proportions of the metallic elements Cu, Zn and Zr, i.e. the sum of the three values is always 100% regardless of whether further elements are present. Indicating the composition in per cent by weight of the metals (and not the metal oxides) is advantageous here because changes in the oxidation state during the course of preparation, activation or use of the catalyst can have no influence on these figures. Here and in the following, the catalyst in the context of all indications of the composition is only the catalytically active substance. This can, of course, be applied to a support or be converted into a ready-to-use form in another way. For the purposes of the present invention, the term "essentially X-ray-amorphous" refers to a catalyst whose X-ray diffraction pattern has, like that of a liquid or a glass, no discrete diffraction lines.
The catalyst used according to the invention preferably contains 20-50% of Cu, 10-40% of Zn and 30-60% of Zr.
The catalyst is preferably prepared by precipitating a precursor from a solution of water-soluble copper, zinc and zirconium salts by coprecipitation. This is washed and dried and subsequently calcined at 300-500.degree. C. In this temperature range, no appreciable crystallization of the amorphous catalyst precursor takes place. Before use in the synthesis of methanol, the catalyst is advantageously activated. This is achieved by heating in a hydrogen-containing atmosphere to a final temperature of from 200 to 350.degree. C. Preferably, the catalyst is first held at a low temperature in an inert atmosphere, for example under nitrogen or argon, and then subjected stepwise or continuously to slowly increasing temperatures and hydrogen concentrations until the final temperature is reached.
As water-soluble copper, zinc and zirconium salts, preference is given to using the chlorides or nitrates.
The coprecipitation is preferably effected by adding an alkali metal hydroxide solution to the solution of the water-soluble copper, zinc and zirconium salts. The coprecipitation can be carried out continuously or batchwise and, in any case, intensive mixing of the reactants has to be ensured.
The methanol synthesis itself can be carried out under the customary temperature and pressure conditions. The temperature is advantageously from 200 to 320.degree. C., preferably from 220 to 280.degree. C. The pressure is advantageously in the range from 1 to 10 MPa, preferably from 3 to 7 MPa.
The methanol synthesis using the catalysts of the invention is preferably carried out at a gas hourly space velocity (GHSV) of from 3200 to 40

REFERENCES:
patent: 4149009 (1979-04-01), Yoneoka et al.
patent: 4780481 (1988-10-01), Courty et al.
patent: 5254520 (1993-10-01), Sofianos
Y. Nitta et al. Catal. Lett., 26, (1994) 345-354.

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