Higher Alcohols Synthesis

The alkalized zinc oxide—chromia process developed by SEHT was tested on a commercial scale between 1982 and 1987 in a renovated high pressure methanol synthesis plant in Italy. This plant produced 15,000 t/yr of methanol containing approximately 30% higher alcohols. A demonstration plant for the lEP copper—cobalt oxide process was built in China with a capacity of 670 t/yr, but other higher alcohol synthesis processes have been tested only at bench or pilot-plant scale (23). 

Isobutyl alcohol [78-83-1] forms a substantial fraction of the butanols produced by higher alcohol synthesis over modified copper—zinc oxide-based catalysts. Conceivably, separation of this alcohol and dehydration affords an alternative route to isobutjiene [115-11 -7] for methyl /-butyl ether [1624-04-4] (MTBE) production. MTBE is a rapidly growing constituent of reformulated gasoline, but its growth is likely to be limited by available suppHes of isobutylene. Thus higher alcohol synthesis provides a process capable of supplying all of the raw materials required for manufacture of this key fuel oxygenate (24) (see Ethers). 

TABLE II METHAWOL-HIGHER ALCOHOLS SYNTHESIS ON COPPER-COBALT BASED CATALYSTS... 

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... 

Advances in higher alcohol synthesis that need to be made include improving productivity and selectivity. Higher spacetime yields are also required which may be achieved by dual catalyst bed reactors, the use of slurry phase synthesis process to increase CO conversion levels, and injection of lower alcohols into the reactant stream to increase the rate of higher alcohol formation.630... 

Moser, W. R., and Connolly, K. E., Synthesis and characterization of copper modified zinc chromites by the high-temperature decomposition (HTAD) process for higher alcohol synthesis, Chem. Eng. J. 64,239 (1996). 

Applications of HT-type catalysts, prepared by the above methods, have been reported in recent years for basic catalysis (polymerization of alkene oxides, aldol condensation), steam reforming of methane or naphtha, CO hydrogenation as in methanol and higher-alcohol synthesis, conversion of syngas to alkanes and alkenes, hydrogenation of nitrobenzene, oxidation reactions, and as a support for Ziegler-Natta catalysts (Table 2). 

Hu and co-workers have developed an expert system especially for the optimization of higher alcohol synthesis catalysts [27, 28]. The knowledge base contains data about experimental work and heuristic rules about... 

Appropriate catalysts are necessary for all fuel and chemical synthesis. The basic concept of a catalytic reaction is that reactants adsorb onto the catalyst surface and rearrange and combine into products that desorb from the surface. One of the fundamental functional differences between various syngas synthesis catalysts is whether the adsorbed CO molecule dissociates on the catalyst surface. For FTS and higher alcohol synthesis, CO dissociation is a necessary reaction condition. For methanol... 

Hu, X.D. Scientific Basis for Design of Heterogeneous Catalysts—A Study of Higher Alcohol Synthesis Catalysts, Ph.D dissertation. University of Delaware, 1989. 

Methanol synthesis from CO and H2. Higher alcohol synthesis from CO and H2 are also included in this subclass. .. 

Finally, it should be noted that different reaction engineering approaches are being investigated to further increase the activities and selectivities of higher alcohol synthesis. A review of these approaches has recently been published by Herman.99... 

The mechanism generally accepted at the present for higher alcohol synthesis is by the direct condensation of the lower alcohols through the elimination of water. Thus,... 

It is possible to analyze the mechanism for the higher alcohol synthesis. This may be typified by... 

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. 

Recently, a group of authors from the Institut Franfais du Petrole disclosed that Co catalysts can be used to produce a mixture of various alcohols (Ci-Cg) when certain rules are followed during the preparation of the catalysts. The authors stressed the importance of crystal chemistry in the strong interaction between the support and the precursor of the metal phase. Only precursor materials of certain phase composition and crystallographic structure lead to catalysts active in higher alcohol synthesis. 

It is known that ZnO alone is a methanol synthesis catalyst [8,9,10], however, the impurities (for example, alkaline residues) introduced to the catalyst during the preparation accelerate side reactions including higher alcohol synthesis and hydrocarbon synthesis [9], In this paper, the support and the gold catalysts were prepared in a similar way, which enables us to investigate the function of gold over the supported catalysts. The results above show that the catalytic behaviour is improved with the addition of Au to the catalyst, since the Au/ZnO selectivity produces alcohols as products and there is a distinct increase in the selectivity for higher alcohols for Au/ZnO when compared with ZnO alone. 

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