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

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.