Understanding the enhancement of catalytic performance for olefin cracking: Hydrothermally stable acids in P/HZSM-5

Enhanced catalytic performance for C4 olefin cracking to propene and ethene was observed on phosphorus-modified HZSM-5 treated in steam at 1073 K. Combining the results of 31P and 27Al MAS NMR, D2/OH exchange, NH3-TPD, and catalytic performance of the catalysts, it seems reasonable to conclude that new and hydrothermally stable acid sites are formed during the steam treatment through the interaction of phosphorus species with silanol nests exposed on the zeolite due to dealumination. It is tentatively suggested that the incorporated phosphorous species stabilized by some nonframework aluminum species are responsible for both the enhanced acid stability and the significantly improved catalytic performance for the cracking of C4 olefin.