Catalytic synthesis of higher α-olefins by paraffin cracking

Abstract

Catalysts for the synthesis of higher α-olefins by the atmospheric-pressure cracking of paraffins in the temperature range of 450–570°C have been proposed. Natural zeolite from the Shankanay deposit in Almaty oblast was modified with inorganic and organic acids and a tungsten 12-heteropoly acid (HPA). The modification enhances the paraffin cracking ability; the best result was achieved with the tungstic 12-HPA. The strength and concentration of acid sites of the catalysts were determined by the IR measurement of CO adsorption. The HPA-promoted catalysts were found to contain a large amount of strong acid sites. The modification of natural zeolite with HPA leads to an increase in the total surface area from 22 to 257 m2/g. TEM images show the presence of ordered HPA structures of a few nanometers in size in zeolite pores. The abnormal rise in catalytic activity is associated with the emergence of new nanosized HPA structures on the zeolite surface.