Effect of reduction temperature on the characteristics and catalytic properties of TiO2 supported AuPd alloy particles prepared by one-step flame spray pyrolysis in the selective hydrogenation of 1-heptyne

Abstract

The bimetallic flame spray-synthesized AuPd/TiO2 catalysts (Au:Pd weight ratio 1:1) were reduced for 2h under H2 at two different temperatures (40°C and 500°C) and tested in the liquid phase selective hydrogenation of 1-heptyne under mild conditions (30°C and 4bar H2). Based on TEM-EDX analysis of individual nanoparticles, reduction at 500°C tends to homogenize the composition of the individual AuPd nanoparticles without significant changes of their average particle size and bulk composition. Higher reaction rate (245μmols−1gcat.−1) was obtained on the AuPd/TiO2 R40 than on the AuPd/TiO2 R500 (223μmols−1gcat.−1). Upon reduction at 500°C, the bimetallic AuPd/TiO2 exhibited a similar degree of the strong-metal support interaction (SMSI) effect as the monometallic one. As revealed by XPS results, the ratios of Pd/Ti on both catalysts decreased by ca. 23%, due probably to the migration of TiOx species onto the metals. The highest yield of 1-heptene (∼93%) was obtained over the bimetallic AuPd/TiO2 reduced at 40°C in 20min reaction time under the reaction conditions used. The high temperature reduction is unnecessary for the improvement of catalyst performances when using supported bimetallic AuPd catalysts.