(673g) Application of Monoatomic Cu Modified ZSM-5 Molecular Sieve in Cracking of Light Olefins to Propylene

In the field of petrochemical industry, there are a lot of low-carbon olefin by-products in MTO process and FCC gasoline process at present. With the implementation of the Sixth National standard, it is imperative to reduce the content of low-carbon olefins in gasoline. Therefore, it will be a promising work to convert this kind of light olefins into other valuable products. At the same time, with the development of domestic propylene downstream industries such as acrylonitrile and propylene oxide Market, the demand for propylene is also increasing. It will be a promising work to develop a molecular sieve with high propylene selectivity, high reaction activity and high stability for olefin catalytic cracking reaction [2]. In this work, monoatomic Cu modified ZSM-5 catalysts with common morphology and square shape were prepared. The catalytic performance of the catalysts for C₄-C₈ light olefins to propylene was evaluated using 1-hexene as model substrate. It was found that although the acidity of the zeolites was reduced, the hydrothermal stability and carbon deposition resistance of the zeolites were greatly improved. The selectivity of propylene to the ratio of propylene to ethylene in the reaction process was greatly improved, and the selectivity of propylene in gas reached 70%. Bet, TPD and other characterization confirmed that although the addition of copper atoms can reduce the pore volume of the catalyst to a certain extent, it will have a significant impact on the acidity of the catalyst. The amount of L acid is inhibited to a certain extent, while the amount of B acid is greatly improved. In the process of catalytic cracking reaction, L acid will adsorb unsaturated hydrocarbon to produce dehydrogenation reaction, and finally generate coke, while B acid can only be cracked through positive carbon ion mechanism, and is not easy to coking [3].