Palladium catalysts supported on H3PW12O40 heteropolyacid incorporated into MCF silica (Pd/HPW-MCF-X (X= 1.0, 4.8, 9.1, 13.0, 16.7, 20.0, 23.1, and 25.9)) were prepared with a variation of H3PW12O40 content (X, wt.%). The prepared catalysts were then applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Conversion of hydrogen over Pd/HPW-MCF-X catalysts showed no great difference, while selectivity for hydrogen peroxide and yield for hydrogen peroxide over the catalysts showed volcano-shaped curves with respect to H3PW12O40 content. Acidity of Pd/HPW-MCF-X catalysts also showed a volcano-shaped trend with respect to H3PW12O40 content. It was observed that yield for hydrogen peroxide increased with increasing acidity of Pd/HPW-MCF-X catalyst. Thus, acidity of Pd/HPW-MCF-X catalyst played an important role in determining the catalytic performance in the direct synthesis of hydrogen peroxide. HPW-MCF-X support efficiently served as an alternate acid source in the direct synthesis of hydrogen peroxide. (C) 2011 Elsevier B.V. All rights reserved.