Methyl chloride is an important industrial product with a global capacity of ca. 900 ktonne. It is a valuable starting material in the production of higher chlorinated products, silicones, and methyl cellulose. The industrial scale manufacture of methyl chloride is typically achieved via the hydrochlorination of methanol over an alumina-based catalyst (Equation 1), although the formation of dimethyl ether as a by-product (Equation 2) leads to an unwelcome reduction in the atom efficiency of the process. CH3OH + HCl --&gt; CH3Cl + H2O (1) 2 CH3OH --&gt; CH3OCH3 + H2O (2) We have recently outlined a catalyst design strategy that has led to the development of a highly selective methyl chloride synthesis catalyst based on h-alumina that has been modified by the addition of a Group 1 salt [1]. This presentation will show how the chemical modifier affects the h-alumina acid site distribution that is responsible for controlling the product distribution over the solid acid catalyst. Pyridine is used as a probe molecule; the adsorption characteristics of which are followed by a combination of temperature-programmed infrared spectroscopy and temperature-programmed desorption. This series of spectroscopic data establishes how the concentration of the chemical modifier can be used to selectively ‘cap’ specific Lewis acid sites; this action preferentially attenuates dimethyl ether production and, consequently, enhances product selectivity.

Investigating the acid site distribution of a new generation methyl chloride synthesis catalyst

256th National Meeting (2018)

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