Composition regulation of bimetallic RuPd catalysts supported on porous alumina spheres for selective hydrogenation

The fabrication of heterogeneous bimetallic catalysts has been of greatly continuous significance, considering the demands of economy and efficiency in the field of practical applications. Here, we report the preparation of a series of supported bimetallic RuPd catalysts with relatively low constant loading amounts of two metals (0.3 wt%), but varying the Ru:Pd ratio, by progressively blending the cheaper Ru with the sole Pd source on porous alumina spheres for selective hydrogenation of dimethyl terephthalate (DMT) to dimethyl cyclohexane-1,4-dicarboxylate (DMCD), one prominent modification reagent and intermediate in the polymer industry. As a consequence, bimetallic RuPd catalysts behaved the superior catalytic activity over monometallic ones, and arrived at the highest value in the optimized sample 1.5Ru1.5Pd under the employed conditions for interested reaction of DMT to DMCD. The HRTEM and STEM-EDX characterizations demonstrated the contribution of bimetallic RuPd samples toward morphological and structural features especially for the smaller nanoparticle size, narrower distribution, less marked aggregation and the formation of bimetallic nanoparticles with homogeneous distribution of Ru and Pd. The H-2-TPR analysis revealed that bimetallic candidates could create the remarkable alterations for reduction behaviors, typically showing the intermediate characteristic of two monometallic ones; and, their surface properties were greatly dependent on the metal component ratios. The H-2-TPD investigation disclosed a more facile release of larger amounts of hydrogen derived from bimetallic families, as compared with monometallic ones; and, 1.5Ru1.5Pd exhibited the largest hydrogen desorption amount. DFT calculations provided further potential interpretations for the structure-property relationship from the standpoint of moderate d-band center. (C) 2014 Elsevier B.V. All rights reserved.