Vapor phase carbonylation of methanol was catalyzed by strong solid acids in the absence of halogen promoter under pressurized conditions. Methyl acetate, methyl formate and acetic acid were obtained as carbonylated product with dimethyl ether as main by product. Hydrocarbons were also formed at high temperature.
Dimethyl ether was produced selectively from synthesis gas with hybrid catalysts composed of methanol synthesis catalysts and γ-alumina. It was estimated that methanol, the primary product, was immediately converted in situ to dimethyl ether and water on the γ-alumina and that the water reacted with CO to form CO2 and H2 on the methanol synthesis catalyst.
Vapor phase carbonylation of methanol on supported nickel and other iron group metals was studied under pressurized condiins in the presence of methyl halide promoters. A nickel metal catalyst supported on an activated carbon exhibited an excellent activity to convert most of the methanol to carbonylated Rroducts (acetic acid and methyl acetate) selectively. The typical reaction conditions utilized were 300 "C and 11 bar. However, nickel on a yalumina or a silica gel exhibited quite low activity. Iron and cobalt on activated carbon gave small amounts of carbonylated products with a large amount of dimethyl ether. Methyl iodide exhibited an excellent promoting effect while methyl bromide showed a fairly good effect. With increasing methyl iodide concentration, both conversions of methanol and carbon monoxide increased accompanied by the marked changes in the product selectivity of increasing acetic acid and decreasing methyl acetate. The yields of carbonylated products were markedly increased with a rise in the operating pressure. The role of activated carboq as the carrier and that of methyl halide as the promoter are discussed.
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