Chemistry: fischer-tropsch processes; or purification or recover – Liquid phase fischer-tropsch reaction
Patent
1986-07-22
1988-03-15
Mars, Howard T.
Chemistry: fischer-tropsch processes; or purification or recover
Liquid phase fischer-tropsch reaction
502156, C07C 2706
Patent
active
047313862
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the use of specific organic solvents in the catalytic preparation of methanol from carbon monoxide and hydrogen. A mixture of an alkali metal alcoholate and a heterogeneous copper catalyst is used as catalyst. The formation of methanol (CH.sub.3 OH) takes place by reaction of the gases carbon monoxide (CO) and hydrogen (H.sub.2) which are dissolved in the liquid reaction mixture, according to the following reaction:
As will be known the industrial production of methanol today takes place almost solely by bringing synthesis gas (CO, CO.sub.2 and H.sub.2) to reaction over a heterogeneous copper catalyst at a temperature in the range: 200.degree.-270.degree. C. and a pressure in the range: 50-150 bar. In European Patent Application No. 81300344.9 there is described a catalytic preparation of methanol in the presence of an organic solvent in order to obtain a better temperature control in the process. However, the catalysts used are solid and no alkali metal alcoholate is present.
According to German Patent Specification No. 809803 and Norwegian Patent Application No. 81.2279 it is known to prepare methanol in a liquid reaction mixture by reacting CO and H.sub.2 in the presence of catalyst systems consisting of an alkali or alkaline earth metal alcoholate and a hetergeneous copper catalyst. In both the above processes methanol has been preferred as the solvent for the reaction, although others have been mentioned without further illustration, and no particular solvent effects have been described. From the literature it is also known that the catalytic activity of alkali metal alcoholates in general may be substantially increased by means of additions which solvatize the cation such as cyclic polyethers and polyethyleneglycol dimethylethers or by using polar organic solvents such as dimethylformamide and dimethylsulfoxide. (See Ugelstad, J. and Rokstad, O.A. Acta Chemica Scandinavia 18 (1964), 474 and Ugelstad, J., Jenssen, B. and Mork, P.C. Acta Chemica Scandinavia 16 (1962) 323).
The subject matter of the application is characterized by the features given in claim 1.
Thus, according to the present invention it has surprisingly been found that the presence of non-polar organic solvents having weak cation solvatizing properties, in a liquid phase which otherwise consists of methanol and methylformate, to a substantial extent increases the catalytic activity of catalyst systems consisting of an alkali metal alcoholate and a heterogeneous copper catalyst for the reaction of CO and H.sub.2 to methanol.
In order to obtain an essential improvement of reaction rate and selectivity at least 50% (by volume) of the liquid phase must be inert organic solvents which have a lower dielectric constant (polarity) than that of methanol. Information regarding the polarity and dielectric constant of organic substances is given in standard handbooks such as Handbook of Chemistry and Physics 57th Ed. (1976-1977) CRC-Press, Cleveland, Ohio 44128, page E-55 to E-58. According to this reference methanol has a dielectric constant of 32.62 at 25.degree. C. Thus, according to the invention all inert organic solvents which have a lower dielectric constant than 32.62 at 25.degree. C. may be used. Typical examples of such solvents are aliphatic and cycloaliphatic hydrocarbons such as n-hexane, n-decane, cyclohexane and decalin, aromatic compounds such as benzene, toluene, ethylbenzene, xylene and diphenyl, ethers such as diethylether, dibutylether and 1,4 dioxane, esters such as ethylformate, propylformate, butylformate, octylformate, ethylacetate and methylstearate, and alcohols such as ethanol, propanol, n-butanol, iso-butanol, 2-methyl-2-propanol, pentanol, hexanol, 2-ethylhexanol and 1-decanol etc. Such solvents having lower polarity than that of methanol have herein also been designated as "non-polar".
A combination of an alkali metal alcoholate and a copper catalyst is used as catalyst for the process according to the invention. Typical alkali metal alcoholates are lithium methoxide, sodium methoxide, potass
REFERENCES:
patent: 4567204 (1986-01-01), Mednick
Mars Howard T.
Sintef
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