Investigating the Acid Site Distribution of a New-Generation Methyl Chloride Synthesis Catalyst.

Peter Jones,Christopher C Dudman,John M Winfield,David Lennon,Alastair R Mcinroy

doi:10.1021/acsomega.9b01719

Abstract

The effect of modifying an η-alumina methyl chloride synthesis catalyst by doping with CsCl and KCl over the concentration range of 0.1–1.0 mmol g(cat)–1 is investigated by a combination of pyridine chemisorption coupled with infrared spectroscopy and mass-selective temperature-programmed desorption measurements. The loading of group 1 metal chloride is equivalent to a titrant that enables selective neutralization of Lewis acid sites present at the surface of the reference η-alumina catalyst. Specifically, a loading of 0.1 mmol g(cat)–1 is sufficient to neutralize the strong Lewis acid sites; a loading of 0.6 mmol g(cat)–1 is sufficient to neutralize the strong and medium-strong Lewis acid sites; a loading of 1.0 mmol g(cat)–1 neutralizes all of the strong and medium-strong Lewis acid sites and partially neutralizes the medium-weak Lewis acid site. These deductions connect with a catalyst design program to develop a methyl chloride synthesis catalyst that exhibits minimal formation of the byproduct dimethyl ether.

Highlights

Methyl chloride is an important chemical compound: in 1997, productions within the regions of United States, western Europe, and Japan were 0.51, 0.48, and 0.14 Mton, respectively.[1]
A combination of infrared spectroscopy with temperatureprogrammed desorption studies has allowed an analysis of the effect of group 1 metal salt dopants on the Lewis acidity of reference transition alumina
The loading of a group 1 metal chloride can act as a titrant that enables selective neutralization of the distribution of Lewis acid sites present at the surface of an η-alumina catalyst

Summary

Introduction

Methyl chloride is an important chemical compound: in 1997, productions within the regions of United States, western Europe, and Japan were 0.51, 0.48, and 0.14 Mton, respectively.[1] The global chloromethane market is expected to garner $2171.6 million by 2022, with the market exhibiting a compound annual growth rate of 4.63% over the period 2016− 2022.2 Methyl chloride is used for the methylation of phenols, alcohols, and cellulose It is used in the manufacture of methylchlorosilanes (precursors to silicones) and quaternary ammonium salts.[1] Two principal routes dominate the industrial-scale manufacture of methyl chloride: (i) methane chlorination and (ii) the esterification of methanol with anhydrous hydrogen chloride. The hydrochlorination of methanol is thought to be the most important commercially exploited route to methyl chloride;[1] this article examines aspects of the surface chemistry of this process over η-alumina-based catalysts

Results

Discussion

Conclusion