Direct synthesis of hydrogen peroxide with no ionic halides in solution

We have studied the direct synthesis of hydrogen peroxide from H-2/O-2 mixtures using a palladium catalyst loaded on a sulfonic acid-functionalized resin in methanol as a solvent and using alternative bromine promoters in the absence of ionic halides in the reaction medium. Three different bromo-organic compounds were tested, 2-bromo-2-methylpropane (t-ButBr), 2-bromopropane (i-PrBr), and bromobenzene (PhBr), and compared to HBr as the reference. The direct synthesis of hydrogen peroxide was tested under 9.5 and 5 MPa overall pressures. The use of t-ButBr and PhBr precursors yielded H2O2 concentrations higher than 9 wt% in less than 3 h of reaction, while the H2O2 concentration obtained in the presence of i-PrBr was very low. A higher concentration of H2O2 and higher selectivity are obtained with t-ButBr than with PhBr, but when using a t-ButBr promoter some hydrolysis is expected to occur in the course of the reaction because bromide ions are detected in the liquid samples, but no bromide ions are detected when PhBr is used.