Phosphate-Modified MCM-48-Based Ag Nanoparticle Catalyst for Selective Oxidation of Ethylene Glycol to Glyoxal

Supported silver nanoparticle (Ag NP) catalysts usually have high reactivity for organic oxidation reactions; however, catalyst deactivation caused by the migration, aggregation, and oxidation of Ag NPs during catalytic reactions pose significant challenges in their practical applications. Herein, mesoporous MCM-48 was employed as a carrier to covalently graft phosphoric acid and Ag NPs on its surface, affording supported Ag NP catalyst Ag/MCM-48-H3PO4. A variety of spectral characterizations reveal that there is an electron-donating effect of the grafted phosphoric acid moieties on the MCM-48 surface toward Ag NPs, which induce a higher Ag0/Ag+ ratio in comparison to Ag/MCM-48 without H3PO4 modification. Consequently, Ag/MCM-48-H3PO4 exhibits better activity than Ag/MCM-48 for the selective oxidation of ethylene glycol in a fixed-bed reactor under more energy-efficient reaction conditions. In addition, Ag/MCM-48-H3PO4 can also prevent the migration, aggregation, and oxidation of reactive Ag NP species in the reaction process due to the coordination and molecular fence effect generated by MCM-48 surface phosphoric acid functionalization, thus exhibiting higher stability than Ag/MCM-48.