GB316898A - Improvements in effecting gaseous dehydrating reactions - Google Patents

Abstract

316,898. Ewan, T., Roberts, H. M., and Imperial Chemical Industries, Ltd. March 5, 1928. Acetic anhydride ; esters.-Readily reversible gaseous reactions involving the splitting off of water and the use of a dehydrating catalyst are effected in the presence of carbon monoxide and a catalyst promoting the reaction between carbon monoxide and steam. The initial reagents may be mixed with carbon monoxide and the mixture passed under suitable temperature conditions over a dehydrating catalyst mixed with a catalyst promoting the reaction between carbon monoxide and steam. Since, however, the optimum temperature for the dehydration may differ from that for the reaction between carbon monoxide and steam, the catalysts are preferably used in succession, the second catalyst being generally at a lower temperature than the first; the space velocities of the gases may also differ in the two stages. When the catalysts are used in succession, the carbon monoxide may be added after the first stage, or a part may be added before the first stage and further amounts added subsequently, particularly in order to cool the gases. In the example, a mixture of acetic acid vapour with carbon monoxide is passed at 500-600‹ C. over sodium metaphosphate and then at 350‹ C. over a catalyst prepared by heating manganous carbonate in a current of carbon monoxide at 300-500‹ C., a mixture of acetic anhydride and acetic acid almost free from water being obtained ; iron should be excluded from the reaction system. Reference is made also to the formation of esters in the gaseous phase and, in one of the Provisional Specifications, to the production of hydrocyanic acid from formamide. Specification 305,147 is referred to.