Formulated Mn-promoted SAPO-34/kaolin/alumina sol micro-size catalyst with a superior performance for methanol to light olefins conversion in a fluidized bed reactor

Abstract

Formulation of zeolite molecular sieves powder is necessary to prepare an excellent micro-size catalyst for methanol conversion to light olefins (MTO) in a fluidized bed reactor. In this work, new fluidizable micro-meso pore catalysts were successfully fabricated by spray drying a slurry containing Mn(x)SAPO-34 powder, kaolin filler, alumina sol binder, and HCl additive. A mixed template of TEAOH/morpholine with different amounts of Mn ion was used in primary gel during hydrothermally synthesis of the crystals. The catalytic samples were characterized utilizing different methods. A moderate acidity reached by catalyst formulation using kaolin and alumina sol as well as through Mn incorporation into the chabazite cages was helpful for MTO performance of the final shape-selective catalyst in terms of selectivity to light olefins and lifetime. The enhancement effect of Mn promoter on ethylene production was much more than propylene because of entering Mn to the micro-pores and imposing restriction on heavier hydrocarbons diffusion. The uniformity and crystalinity were also appeared to be enhanced once Mn(0.05) was introduced into the gel composition. The suggested spray dried catalyst was SD-Mn(0.05)SAPO-34 (70–120 µm) in which provided a superior selectivity up to 88.4% to light olefins and catalytic lifetime of 330 min in a fluidized bed reactor at 450℃, WHSV = 4 h−1, and XMeOH = 0.75 in the feed.