Catalytic Performance of Phosphorus Modified HZSM-5 Zeolite Catalysts in the Co-cracking Reaction of n-Hexane and Methanol

Co-cracking reaction of hydrocarbons and methanol combines hydrocarbon endothermic cracking with the exothermic MTO process, and also is a promising technique to produce light olefins. High selectivity for light olefins and stable catalytic activity of the catalysts are fundamental and crucial factors for practical application. Herein, we prepared diverse phosphorus-modified HZSM-5 (0-2 wt%) samples by an ultrasonic impregnation approach. The activities of the prepared catalysts in catalyzing the co-cracking reaction at 600 degrees C under the pressure of 0.1 MPa were then examined. XRF, FTIR, XRD, SEM, N-2 adsorption-desorption, NH3-TPD, pyridine-absorbed FTIR and Al-27 MAS NMR were also performed for characterizing sample structure, texture, and acidic property. As a result, HZSM-5 zeolite had weakened acidic property with the increase in phosphorus loadings. In comparison with the unmodified HZSM-5, phosphorus was found to be a great promoter for the catalytic stability and light olefins selectivity. 100% n-hexane initial conversion and 70.1% light olefins selectivity were obtained on 1P/HZSM-5 (phosphorus content of 1 wt%). Carbon deposition was inhibited due to the reduction of strong Lewis acid site quantity.