Gas-phase epoxidation of butadiene: Effect of the concentration and distribution of cesium on the properties of the Ag/α-Al₂O₃ catalyst

Abstract

Using the well-known patent methods, we have synthesized 1,3-butadiene epoxidation α-Al₂O₃ supported catalysts containing 15 wt % of Ag and 250–1500 ppm of Cs (Johnson Matthey, H16P07). The physicochemical properties of samples are systematically studied by varying the dispersion of supported silver, the amount of an introduced promoter, and its distribution over the surface of a catalyst. Catalytic tests of samples show that the optimum amount of a promoter depends directly on the surface of a catalyst. With optimum promotion, the steady-state activity of catalysts is determined by the dispersion of supported silver. In the course of catalytic tests, it is established that the shape of kinetic curves is governed by the excess or lack of Cs in a catalyst, thus providing a method for optimizing the concentration of the promoter. An analysis of the energy dispersion spectra (EDS) is applied for the first time to study the distribution of Cs over the surface of promoted catalysts. It is shown that thermal treatment favors the uniform distribution of a promoter over the surface of a catalyst and shortens the time required to attain its steady-state activity in catalytic tests. In our work, the steady-state productivity of catalysts reaches 0.5 g of 3,4-epoxy-1-butene per gram of the catalyst per hour, thus exceeding the claimed patent values.