New Concept for the Effect of Metal Particle Size on the Catalyst Activity in the Reactions Involving Oxygen

Abstract

Carbon monoxide oxidation, steam reforming of methanol, C₃H₆ oxidation, and oxidation of the copper catalyst itself were performed by a flow method using copper catalysts with varying copper particle sizes ranging from 3.6 to 1700 nm in diameter. The specific rate of CO oxidation increased with a decreasing copper particle size. The specific rate of steam reforming of methanol increased with an increasing particle size in the small range within a 4-10 nm range, but this reaction was insensitive to increases in copper particle sizes greater than 10 nm. The selectivity for acrolein formation from C₃H₆ oxidation was maximum when the copper particle sizes were on the order of 20-80 nm in diameter, where the oxidation state of the copper during the reaction was near that of cuprous oxide. From these results, the following new concept was derived. The metal particle size in metallic catalysts controls the balance between the oxidation of copper and the reducing action of reactants or products during reactions involving oxygen.