The conversion of methanol to hydrocarbons over zeolite H-beta

The conversion of methanol to hydrocarbons over an H-beta zeolite catalyst at 400 degrees C has been investigated. The experiments were carried out at a methanol pressure of about 150 mbar, using a WHSV of 0.8 or 7.2 h(-1). With WHSV = 0.8 h(-1) the methanol conversion was still 30% after 16 h on stream. There was a preponderance of saturated and aromatic hydrocarbons in the product. Ethene, propene, propane, isobutane, hexamethylbenzene and some pentamethylbenzene were the dominant products. Methane was initially a rather minor product, but with progressive catalyst deactivation it became a major product. Methanol was also converted over dealuminated H-mordenite and H-ZSM-5 under identical conditions. The aromatic products over these zeolites are quite different. Zeolite beta is selective for hexamethylbenzene and mordenite is selective for pentamethylbenzene, while ZSM-5 gives mostly di- and trimethylbenzenes and some small amounts of the slimmest tetramethylbenzene, i.e. durene. The product compositions are compared and discussed. (C) 1999 Elsevier Science B.V. All rights reserved.