MTO reaction over SAPO-34 catalysts synthesized by combination of TEAOH and morpholine templates and different silica sources

Abstract

The SAPO-34 catalyst was synthesized by the combination of TEAOH and morpholine templates, and colloidal silica and silicic acid, as the silica source under hydrothermal conditions. The effect of the template molar ratio and silica source on the physicochemical properties of each catalyst was studied by XRD, SEM, BET and TPD techniques. XRD patterns revealed the significant effect of gel composition on the crystallinity and particle size of the samples. SEM photos showed that all the catalysts have cubic morphology, but their particle size was different. According to the XRD and SEM of the catalyst prepared by silicic acid, this catalyst showed low crystallinity and large crystal size. TPD analysis indicated that the acidity reduced by increasing the morpholine content in the reaction mixture. The catalytic performance of the synthesized catalysts was tested in MTO reaction. The catalyst produced by the TEAOH/morpholine ratio of 0.5:1.5 exhibited the highest light olefins yield, as well as the longest catalyst lifetime. The maximum yield of ethylene and propylene was determined to be 94 wt%, with 100% methanol conversion.