Effect of promoter loading for supported silver catalysts used for the epoxidation of 1,3-butadiene with dioxygen.

摘要

The epoxidation of 1,3-butadiene to epoxybutene (EpB) was performed in a plug flow reactor utilizing an Aumina-supported silver catalyst (Ag/Alumina) with molecular oxygen as the oxidant. Alkali metal salts have been established as promoters that enhance the reactivity and useful lifetime of supported-silver catalysts for this reaction; however, the exact role of the alkali is still in question. Unpromoted silver catalysts exhibited optimum catalytic activity at a silver loading of 15-wt%. Using this experimentally determined level of silver, a range of cesium nitrate loadings was incorporated on the Ag/Alumina catalyst to determine which catalyst composition provides the optimum activity. For this study, two catalyst preparations were investigated: (1) simultaneous supporting of silver and cesium nitrate and (2) initial supporting of silver, followed by the sequential supporting of cesium nitrate. Initial results have shown that steady-state EpB formation over those catalysts prepared via simultaneous supporting of silver and cesium nitrate is not significantly enhanced with increasing levels of promoter salt, while the rate achieved over the catalysts prepared via the sequential supporting method is dependent on the promoter salt loading level. Results from adsorption microcalorimetry of carbon dioxide will be presented in an attempt to elucidate the effect of the promoter loading method at the catalyst surface.