Methanol to hydrocarbons over zeolites with MWW topology: Effect of zeolite texture and acidity

Abstract

MCM-36 and MCM-22 zeolites derived from the same precursor with MWW topology were compared for the conversion of methanol to hydrocarbons (MTH) at 450 °C. MCM-36 was found to be a very attractive catalyst, showing a selective formation of C 3+ aliphatic hydrocarbons (about 90% at WHSV = 2 h −1) and a high resistance to the deactivation. Under similar conditions MCM-22 produced higher amount of aromatics and coke. This behavior was mainly related to the textural and acidic properties of catalysts. The dual meso-/microporosity of MCM-36 facilitates the diffusion of bulkier species produced by different reactions in the MTH process which results in lower deactivation rate of this zeolite compared to the purely microporous MCM-22 catalyst. Moreover, the density of the acid sites in MCM-36 (three times lower than that of the MCM-22 sample) is unfavorable to secondary reactions like aromatization and hydrogen transfer which are responsible for the formation of aromatics and coke precursors.