TiO 2 supported Au-Pd and Cu-Pd catalysts were prepared by strong electrostatic adsorption (SEA) of Pd followed by electroless deposition (ED) of a second metal with incremental surface coverages of Au or Cu. High dispersion of small Pd particles on the Pd/TiO 2 prepared by SEA led to the high amount of second metal deposition on Pd surface. The Cu addition by ED increased the relative ratio of linear CO adsorption mode indicating the presence of higher amount of isolated Pd atoms. The ensemble effect of the Cu-Pd/TiO 2 catalysts resulted in the improved catalytic performances in the selective hydrogenation of acetylene to ethylene. However, as revealed by the blue shift of CO-IR and XPS results, Au addition by ED rather exhibited the electronic modification. The highest catalytic activity was obtained on the 1.10% Au-Pd/TiO 2 catalyst; however, the Cu addition (0.12% Cu-Pd/TiO 2 , θCu = 0.37) showed interesting results as only a small amount of Cu was used to improve the catalyst performances. The bimetallic catalysts were also prepared by conventional impregnation for comparison purposes. These catalysts exhibited several drawbacks such as low Pd dispersion, formation of second metal aggregates, and blockage of isolated Pd atoms.
The objective of this study is to fabricate the polyoxymethylene (POM)/microcrystalline cellulose (MCC) and poly(lactic acid) (PLA)/MCC composites, and to compare the effect of MCC on the morphology and mechanical properties of POM and PLA. The polymer composites were prepared by melt mixing in an internal mixer and molded by compression molding. The MCC concentrations were 1, 3, 5, 7, 10, 15 and 10% by weight. From scanning electron microscopy study observes the fracture surface of POM and PLA composites is much rough and the roughness increases with increasing MCC content. This observation indicates MCC induces the ductile fracture characteristic of POM and PLA. The addition of MCC can improve the impact strength of PLA composite and improve Young’s modulus of both POM and PLA composites. While the tensile strength and strain at break decrease after adding MCC. In summary, MCC can enhance the morphology and mechanical properties of PLA composites is better than POM composites.
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