The influence of modification methods on the catalytic cracking of LPG over lanthanum and phosphorus modified HZSM-5 catalysts

Abstract

In the present study, the effect of various modification methods on the activity of ZSM-5 modified catalysts has been studied in catalytic cracking (CC) of LPG. Lanthanum (La) has been loaded in HZSM-5 catalyst using ion exchange, and wet impregnation, and phosphorus (P) has been introduced by wet impregnation and dry impregnation methods. Physico-chemical properties of modified samples were evaluated by using XRF, ICP-OES, XRD, FT-IR, physical N2 adsorption and NH3-TPD characterization methods. Studying the catalytic performance of the samples revealed that wet impregnation could result in better efficiency than dry impregnation and ion-exchange methods. Afterwards, the dual site catalysts containing both La and P have been prepared using wet impregnation and physical mixture processes. It was found that HZSM-5 catalyst modified by successive wet impregnation of La and P could led to the higher conversion and yield of light olefins (ethylene + propylene) compared to the other samples. At the reaction temperature of 650 °C and GHSV of 433 ml min−1/gcat over the mentioned catalyst (in the presence of N2) yield of total light olefins and selectivity was acquired to be 51% and 62%, respectively.