Electronic Regulation and Hydrophobic Improvement of the Fe-Pd Alloys by an Ionic Liquid and an Amino Group Achieve High Selectivity of Methane for Methanol.

Selective oxidation of methane to methanol by in situ-generated hydrogen peroxide (H2O2) from H2 and O2 is a promising alternative to the current industrial methods. However, it still faces the dilemma that the slow formation of the hydroxyl radical (•OH) leads to a low efficiency of partial oxidation of methane to methanol. In order to solve this problem, we constructed an Fe-Pd/SIL-NH2 composite catalyst synergistically modified by amino and [BMIM]PF6. Comprehensive characterization and experimental results show that the electron transfer path between Pd and Fe is regulated. Fe2+ and Pd2+ species are mainly distributed in Fe-Pd alloy catalysts. The Fe-Pd/SIL-NH2 catalyst not only successfully coupled the in situ synthesis and efficient decomposition of H2O2 to produce •OH radicals but also changed the local hydrophobic microenvironment of the active sites, thereby promoting the rapid desorption of hydrophilic products. These factors work together to weaken the adsorption energy of HOOH* (from 0.78 to 0.49 eV) and greatly promote the dissociation of HOOH*, thereby greatly improving the efficiency of generation of •OH radicals, which lays a foundation for the efficient synthesis of methanol. The final CH3OH yield and selectivity were as high as 73.42 mmol gFePd-1 h-1 and 87.4%, respectively, which were 2.52 and 1.67 times those of of Fe-Pd/SBA-15-NH2 and 4.87 and 2.11 times those of Fe-Pd/SIL, respectively. This study highlights the surface modification of Fe-Pd alloy catalysts for bimetallic catalysis.