Phosphate-Modified MCM-48-Based Ag Nanoparticle Catalyst for Selective Oxidation of Ethylene Glycol to Glyoxal
Weibiao Li, Cheng Liu, Qianfan Yang, Yanwei Ren, Huanfeng Jiang
Abstract
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-H 3 PO 4 . 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 Ag 0 /Ag + ratio in comparison to Ag/MCM-48 without H 3 PO 4 modification. Consequently, Ag/MCM-48-H 3 PO 4 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-H 3 PO 4 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.