Fischer higher alcohols synthesis

Studies in these laboratories have resulted in the synthesis and catalytic evaluations on a wide range of perovskites and ion modified homogeneous solid solutions for Fischer-Tropsch catalysis, copper modified spinels for higher alcohol synthesis, ion substituted perovskites for methane activation, alkali modified metal... 

Carbon monoxide may be hydrogenated to produce either alcohols or hydrocarbons, depending on the catalysts used and the reaction conditions. Temperatures ranging from 100-400°C and pressures as high as 1,000 atm have been studied. Different catalysts yield radically different types of products. Important processes for uch reactions consist of the methanol synthesis, the higher-alcohol synthesis (or the variation termed the iso synthesis), the Fischer-Tropsch reaction (or the version called hydrocarbon synthesis), and the methanation reaction. These syntheses were discovered in the period 1920-1925, at which time the methanol and higher-alcohol syntheses developed rapidly. A brief summary of processes and conditions used for the hydrogenation of carbon monoxide is presented in Table 10-17. 

The Fischer-Tropsch (FT) synthesis leads to a broad range of products, i.e. hydrocarbons, alcohols, acids, esters, etc. The increasingly stringent regulations on the sulfur and aromatics content in fuels are the reasons for renewed interest in this reaction [1]. More efficient catalysts are required to improve FT activity and selectivity to the desired products. Cobalt catalysts have been found to be most suitable for the production of higher hydrocarbons [2]. Optimization of the metal function (Co, Fe, Ru, Mo) in supported FT catalysts has been studied in a large number of papers [3-6]. 

In principle also the possibility should be considered that CO is dissociated, as in Fischer-Tropsch synthesis of hydrocarbons, and thereafter partially hydrogenated. A metal carbene would then produce, upon addition of H2O, a molecule of methanol. However, one would expect that with a metal like Rh, which can dissociate CO, the isotopically labelled atoms from C 0 would be scrambled with C 0 atoms in the methanol product but this has not been found.With metals which dissociate CO even more reluctantly, like Pd and Cu, this mechanism is even less likely than with Rh. This does not however exclude the possibility that higher alcohols can be formed by H2O addition to a carbene-like intermediate. 

Except for cobalt systems, other metals also demonstrate activity in the Fischer-Tropsch process. Mo/HZSM-5 turned out to be active in FT synthesis [98], The catalysts were tested at a low H /CO molar ratio 1.0, this composition being typical for biomass gasification. Liquid hydrocarbons obtained on Mo/HZSM-5 at 573 K were presented by alkylaromatics and lower branched and cyclic alkanes. The formation of aliphatic hydrocarbons was close to zero. The gas products included Cj-C alkanes. Higher alcohols and carboxylic acids (C,-Cg) were observed in the aqueous phase. The formation of hydrocarbons on Mo/zeolite is accounted for by the bifunctional zeolite acidity and molybdenum metal activities via alcohols as intermediates. The zeolite Y was also found to be a good support for Mo in the FT reaction. 

Hudson, C. S., The Fischer Cyanohydrin Synthesis and the Configurations of Higher-carbon Sugars and Alcohols, I, 1-36... 

The oxo reaction (31) is carried out in the liquid phase at high pressure using a cobalt catalyst. A mixture of aldehyde isomers is always produced, each isomer being one carbon number higher than the starting olefin. As a group the oxygenated products of the hydrocarbon synthesis (Fischer-Tropsch) process and the oxo process are primary compounds and thus (except, of course, the methyl and ethyl derivatives) differ fundamentally from the products based on alcohols made by the hydration of olefins, which are always secondary or tertiary in structure. 

How, M. J., Brimacombe, J. S., and Stacey, M., The Pneumococcal Polysaccharides, 19, 303-357 Hudson, C. S., Apiose and the Glycosides of the Parsley Plant, 4, 57-74 Hudson, C. S., The Fischer Cyanohydrin Synthesis and the Configurations of Higher-carbon Sugars and Alcohols,... 

Transition metal carbonyls and their derivatives are remarkably effective and varied in their ability to catalyze reactions between unsaturated molecules (e.g., CO and olefinic compounds) or between certain saturated and unsaturated molecules (e.g., olefins and H2 or H20). The carbonyl derivatives of cobalt are particularly active catalysts for such reactions and have been put to use in the industrial synthesis of higher aliphatic alcohols. In fact, much of the growth in knowledge concerning catalysis by metal carbonyls has been stimulated by the industrial importance of the Fischer-Tropsch synthesis, and by the economically less important, but chemically more tractable, hydroformylation reaction. 

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