Acid-Promoted Selective Oxidation of Methane to Formic Acid over Dispersed Rhodium Catalysts under Mild Conditions

Direct oxidation of methane into value-added liquid chemicalsisa promising route for wide applications. However, the efficient conversionof methane with high selectivity under mild conditions is still challenging.Herein, the catalysts of rhodium dispersed on ZSM-5 were synthesizedfor the methane conversion utilizing molecular O-2 as theoxidant together with CO and H2O under a total pressureof 40 bar at <100 & DEG;C. Moreover, the conversion of methaneand the selectivity of formic acid could be improved by increasingacidity over the Rh/ZSM-5 catalysts. Promoted by H+, theactivities of methane oxidation can reach 3.56 mol(HCOOH)/mol(Rh)/h and 23.96 mol(HCOOH)/mol(Rh)/h at 50 and 90 & DEG;C over the 5.0Rh/H-ZSM-5 catalyst, and theselectivity of HCOOH of 98.48% to all organic oxygenates can be acquiredat 90 & DEG;C. Dramatically, the activation of the C-H bondcan even happen at room temperature. Electron paramagnetic resonanceresults showed that acidity can promote the generation of & BULL;OHwith CO, H2O, and O-2 as the reactants, resultingin high catalytic activity under mild conditions.