Preparation and Characterization of Alumina-Based Microreactors for Application in Methyl Chloride Synthesis

Anthropogenic emissions of ozone-depleting substance CH3Cl during 2000-2020 in China

Methyl Chloride (CH₃Cl) is the largest source of stratospheric chlorine, which has a significant impact on the depletion of the stratospheric ozone layer. Detailed information on anthropogenic CH₃Cl emissions in China is still lacking. This study establishes a comprehensive bottom-up inventory of anthropogenic CH₃Cl emissions in China during 2000-2020. Results show that China's anthropogenic CH₃Cl emissions have increased significantly, from 34.1 ± 11.6 Gg/yr (gigagrams per year) in 2000 to 128.5 ± 26.5 Gg/yr in 2018 with a slight decrease to 124.9 ± 26.0 Gg/yr in 2020. The main sources of anthropogenic emissions of CH₃Cl in China are chemical production (37.1%), solvent use (35.4%), and coal combustion (13.6%) in 2020. China's contribution to global anthropogenic emissions of CH₃Cl reached almost 50%. Moreover, the ratios of CH₃Cl CFC-11-eq emissions relative to emissions of ozone-depleting substances (ODSs) controlled under the Montreal Protocol in China have increased from 0.8% in 2000 to 11.6% in 2020 and are estimated to continue increasing in the future. In summary, China's anthropogenic CH₃Cl emissions have shown an increasing trend in the past two decades, made a huge contribution to the total global anthropogenic emissions, and presented a potential increasing impact on the depletion of the ozone layer and global warming.

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.

The development of a new generation of methyl chloride synthesis catalyst

In previous work by the authors, aspects of the surface chemistry connected with methyl chloride synthesis over an η-alumina catalyst have been examined. This communication considers a role for Group 1 metal salts to modify the catalytic performance of the well characterised η-alumina catalyst. Firstly, based on a previously postulated mechanism for the reaction of methanol on η-alumina, a mechanism for methyl chloride synthesis over the η-alumina catalyst is proposed. Secondly, the validity of the new mechanism is tested by observing how the (i) type and (ii) loading of the Group 1 metal salt may perturb methyl chloride selectivity. The outcomes of these measurements are rationalised with reference to the postulated mechanism. Overall, this study represents an example of how a proposed reaction mechanism has been used to inform and guide a catalyst development strategy for a large-scale industrial process.

Electrochemically dealloyed platinum with hierarchical pore structure as highly active catalytic coating

Electrochemical dealloying of Pt–Si produces Pt films with hierarchical pore structure and superior performance in butadiene hydrogenation.