Further Studies on How the Nature of Zeolite Cavities That Are Bounded by Small Pores Influences the Conversion of Methanol to Light Olefins.

Abstract

A series of small-pore zeolites are synthesized and investigated as catalysts for the methanol-to-olefins (MTO) reaction. Small-pore zeolites SSZ-13, SSZ-16, SSZ-27, SSZ-28, SSZ-52, SSZ-98, SSZ-99, SSZ-104, SSZ-105 and an ITQ-3-type material are synthesized, and the results from their use as catalytic materials in the MTO reaction compared to those obtained from SAPO-34. The production of propane that tends to correlate with catalytic material lifetime (higher initial propane yields lead to shorter lifetimes) declines with increasing Si/Al (as has been observed previously for SSZ-13), and a larger cage dimension leads to higher propane yields at a fixed Si/Al. Data from these materials and others reported previously, for example, SSZ-39 and Rho, that were tested at the same reaction conditions, revealed four different patterns of light olefin selectivities: 1) ethylene greater than propylene with low butene, for example, SSZ-17, SSZ-98, SSZ-105, 2) ethylene equal to propylene and low butene, for example, SAPO-34, SSZ-13, SSZ-16, SSZ-27, SSZ-52, SSZ-99, SSZ-104, 3) propylene greater than ethylene with butene similar to ethylene, for example, SSZ-28, SSZ-39, and 4) ethylene equal to propylene equal to butene, for example, Rho. No clear relationships between zeolite cage architecture and light olefin selectivity emerged from this investigation, although several trends are presented as suggestions for further study.