Zeolite based catalysts for linear alkylbenzene production: Dehydrogenation of long chain alkanes and benzene alkylation

Linear alkylbenzenes (LAB) obtained by alkylation of benzene with linear C10-14 olefins. In the present work we have investigated the dehydrogenation of long chain alkanes over Pt-based catalysts. For convenience n-octane dehydrogenation was used to probe the dehydrogenating properties of the catalysts. The catalysts for dehydrogenation of n-octane are constituted by Pt or Pt-In alloys supported on alumina, NaY, KL zeolites and on silicalite. The metal particles were characterized by STEM-EDX, H-2 adsorption, and IR of adsorbed CO. The main conclusions are: In Pt-In/silicalite system, very small metal particles, less than 1 nm, are formed that are localized in the silicalite pores and Pt is alloyed with In. These Pr-In particles show unexpected high dehydrogenating activity and very high stability against coking even in the absence of added hydrogen. The alkylation of benzene with 1-dodecene over H-form zeolites was investigated. The reaction temperature was in the range 373-473 K. Batch reactor was chosen for this study. The results indicate that dealuminated HY zeolites are apparently the most suitable catalysts. H-ZSM-5, H-ZSM-12 showed almost no activity for the production of LAB, due to the small size of the channels. The reaction was influenced considerably by diffusion. While H-mordenite also showed very low catalytic activity, dealuminated H-mordenite exhibited a significant activity and a very high selectivity for the production of 2-phenyldodecane which is the less bulky among the other phenyldodecane isomers. The mesoporosity generated within dealuminated mordenite is responsible for these observations.