Mesoporous Sn(IV) doping MCM-41 supported Pd nanoparticles for enhanced selective catalytic oxidation of 1,2-propanediol to pyruvic acid

The conversion of biomass derivative 1,2-propanediol (PDO) to value-added chemicals by selective catalytic oxidation is of great research interest. Herein, we provide an alternative and effective strategy for selectively catalyzing the PDO oxidation to pyruvic acid using Sn(IV) doping MCM-41 (SnM) supported Pd nanoparticles (2%Pd/SnM) as catalyst, in which the SnM with the Si/Sn ratios ranging from 6 to 50 are prepared by direct hydrothermal synthesis (DHS) method and the Pd nanoparticles are in situ reduced on the SnM surfaces. When the Si/Sn ratios are above 12, decreasing the Si/Sn ratio favors the incorporation of more Sn(IV) species into the framework, the formation of smaller Pd nanoparticles with higher distribution and the increment of basicity, contributing to the significant enhancement in the selective oxidation of PDO to pyruvic acid, but if the ratio is further reduced to 6, larger Pd nanoparticles are formed in the 2%Pd/SnM6 with less ordered mesostructure due to excess Sn(IV) resulting in the formation of SnO2 crystallites, displaying much lower catalytic activity than the 2%Pd/SnM12. The Sn(IV) species incorporated into MCM-41 can be used as effective promoter for enhancing the selective oxidation of PDO to pyruvic acid over the Pd/SnM catalyst.