Abstract
Abstract The hydrogenolysis of n -butane was studied over silica-supported ruthenium and a series of ruthenium-copper catalysts of varying copper content. The catalytic activity and the product selectivities were determined in the temperature range of 413–493 K. The turnover frequency based on the amount of ruthenium at the surface did not vary with copper content, indicating that geometric or ensemble effects were absent. Reaction products were formed via terminal, internal, and multiple carbon-carbon bond scission reactions of the parent molecule. Multiple carbon-carbon bond scission reactions of the adsorbed intermediate which increase the selectivity for lower hydrocarbons have been noted even at the lowest temperature studied. With higher reaction temperatures, the rate of the multiple scission reactions dominated the product selectivities. It is proposed that copper deposited on the ruthenium particles changes the product selectivities by two mechanisms. First, copper decreases the number of multiple splitting reactions by enhancing the desorption rate of the hydrogenolysis products. Second, copper increases the propensity of the hydrogenolysis reaction for a single internal scission reaction, favoring the formation of ethane. The first mechanism is suggested to involve weakly bound hydrogen on the surface which is affected by the presence of copper at the surface of the metal particle. The second mechanism is proposed to involve either a minor electronic interaction between ruthenium and copper or the unique ability of copper to interact strongly with hydrogen but only weakly with carbon, or both.
Published Version
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