Catalytic cracking of 1-butene to propylene using modified H-ZSM-5 catalyst: A comparative study of surface modification and core-shell synthesis

Surface modification of ZSM-5 catalyst was carried out by silica deposition using chemical liquid deposition (CLD) method as well as core-shell silicalite composite material by hydrothermal method. The modified ZSM-5 catalyst was characterized using various physiochemical methods such as XRD, TPD, N₂adsorption-desorption and SEM analysis. Catalytic cracking of 1-butene was carried out using modified ZSM-5 catalysts. The propylene yield was higher for core-shell silicalite composite as compared to silica deposition through CLD method. Silica deposited using CLD method showed propylene-to-ethylene (P/E) ratio of 1.7, whereas core-shell silicalite composite resulted in P/E ratio of 3.0. The higher selectivity to light olefins using core-shell silicalite composite to be attributed to weak acid sites and effective control of external acid sites, which reduces the hydrogen transfer reactions that form alkanes and aromatics. The effective external surface passivation was verified using catalytic cracking of triisopropyl benzene. The core-shell silicalite composite showed excellent stability over 50 h for the cracking of 1-butene stream.