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)(O3PCH2CH2–4,4′-bipyridinium–CH2CH2PO3)]F·2H2O with Pd–metal nanoaggregates, has been attempted. In addition to the development of a novel technique for making this catalyst by hydrothermal incorporation, an extensive optimization of the process conditions to make hydrogen peroxide from H2 and O2 has been carried out. The optimal reaction medium for this process was methanol in conjunction with sulfuric acid. Under atmospheric conditions, over 3.5 M H2O2 has been produced in 50 h. A technique has also been developed to measure the water formed from the undesirable 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 external mass transfer (at the liquid–gas interface) because the resistance due to it is the rate-determining step.