Margaret M. Wu

Conversion of methanol to hydrocarbons: II. Reaction paths for olefin formation over HZSM-5 zeolite catalyst

Methanol was converted to hydrocarbons, primarily olefins, and water over a low-activity HZSM-5 zeolite catalyst with a SiO2Al2O3 ratio of 1600/1. Mixtures of methanol and individual C2-C4 olefins were also used to simulate conditions in the catalyst bed at low conversions. Facile methylation of olefins with methanol to produce the next higher olefinic homolog was observed. Ethylene was the major primary hydrocarbon produced from methanol at low conversion. The olefin mixtures isolated under various conditions of reaction were fitted to the chain-growth kinetics as described by the Flory equation. Good to excellent correlation coefficients were found at low and medium conversions of methanol. This is consistent with a stepwise growth in molecular weight of the olefins, starting with propylene, by alkylation of the olefins with methanol. However, since ethylene is produced by a different mechanism, it does not fit the Flory equation. At higher temperatures and conversions, the olefins undergo scrambling or thermodynamic equilibration reactions also producing olefin mixtures with good correlation coefficients. Under the latter conditions, a distinction between the stepwise growth and thermodynamic equilibration reactions cannot be made since both contribute to the product mixture.

Mobil Zeolite Catalysts for Monomers

Abstract It has been about 20 years since Plank, Rosinski, and Hawthorne reported their spectacular results with metal-modified zeolite cracking catalysts for more efficient production of gasoline [1]. This discovery has saved an estimated 200 million barrels of crude oil each year in the United States alone [2]. In 1972, a patent by Argauer and Landolt described the preparation of a member of a generation of new synthetic zeolites, called ZSM- 5. It was unique because of its high silica/alumina ratio and greatly reduced coking rates for reactions with hydrocarbons by comparison with known low silica zeolites [3]. This material was an early member of a series of over 50 synthetic zeolitic substances prepared in Mobil laboratories.