Direct production of hydrogen peroxide with palladium supported on phosphate viologen phosphonate catalysts

The optimization of porous hafnium phosphate viologen phosphonate (HfPOPV(X )) catalyst, [(HfF)(2)(PO4)(P3PCH2CH2-4,4'-bipyridinium-CH2CH2PO3)]F . 2H(2 )O with Pd-metal nanoaggregates, has been attempted. In addition to the dev elopment of a novel technique for making this catalyst by hydrothermal inco rporation, an extensive optimization of the process conditions to make hydr ogen peroxide from H-2 and O-2 has been carried out. The optimal reaction m edium for this process was methanol in conjunction with sulfuric acid. Unde r atmospheric conditions, over 3.5 M H2O2 has been produced in 50 h. A tech nique has also been developed to measure the water formed from the undesira ble H2O2 reduction step that occurs in series-parallel. to the desired H2O2 production step. The selectivity toward the production of H2O2 in the case of the hydrothermally incorporated catalysts is over 70% under atmospheric conditions. The maximum rate of production of H2O2, achieved in anhydrous methanol-H2SO4 media and hydrothermally incorporated Pd-HfPOPV(X) is about 4.1 mmol/(g min). However, the rate measured here is probably that of exter nal mass transfer (at the liquid-gas interface) because the resistance due to it is the rate-determining step. (C) 2000 Academic Press.