Influence of the pore architecture on the selective conversion of ethene to propene and butenes over medium pore zeolites

This contribution focuses on the conversion of ethene to propene and butenes over medium pore zeolites with different pore architectures and similar nSi/nAl-ratios. The aim of this systematic study was to explore the factors which govern the yield/selectivity of propene/butenes from ethene and to optimize the catalytic properties for this reaction. All used zeolites were prepared by hydrothermal synthesis and characterized by various techniques. Their catalytic properties (with respect to increased propene yield/selectivity) were explored in a fixed-bed flow-type reactor operating under atmospheric pressure. One major result of these investigations is that medium pore zeolites with a one-dimensional channel system offer catalytic properties superior to the well-known zeolite ZSM-5 with its three-dimensional pore system. Selectivities to propene of 43% and to butenes of 24% could be achieved over zeolite HZSM-23 used as the catalyst at medium conversions. This demonstrates the effective suppression of by-product formation over a wide range of reaction conditions due to shape selectivity effects in the tubular pore structure of HZSM-23.