Bimetallic gold/palladium catalysts for the selective liquid phase oxidation of glycerol

Abstract

A new methodology for the preparation of single phase bimetallic Au-Pd on activated carbon (AC) has been recently developed and now used for preparing Au/Pd catalysts at different atomic ratio. The bimetallic catalysts have been tested in the liquid phase oxidation on glycerol in water using oxygen as the oxidant and compared with monometallic Au and Pd catalysts. We observed that strong synergistic effect is present in a large range of Au/Pd ratio, being maximized for Au 90 -Pd 10 composition. Gold-rich composition showed an increased durability compared to palladium-rich alloy.

Selective Oxidation of Raw Glycerol Using Supported AuPd Nanoparticles

“…One percent Au6Pd4/AC resulted in the most active catalysts with an initial activity (3205 mol/mol h) at least three-times more active than 1% Au6Pd4/N-CNFs (1076 mol/mol h) and 1% Au6Pd4/CNTs (815 mol/mol h), despite a similar AuPd particle size (3.4-3.7 nm). This result is in agreement with the findings that AuPd homogeneous alloys are more active than inhomogeneous phases in the alcohol oxidation due to a synergistic effect [24][25][26]29]. One percent Au6Pd4/CNFs and 1% Au6Pd4/TiO2 resulted in less activity (675 and 628 mol/mol h, respectively), probably due the presence of bigger particle sizes (4.5 and 4.1 nm) ( Table 2).…”

“…As already highlighted in the literature, these results confirmed the beneficial effect of the presence of heteroatoms on the carbon nanofibers' surface in terms of stabilization of the metal nanoparticles with a better particle size distribution. In the case of AuPd on activated carbon, alloyed AuPd nanoparticles with a uniform composition and homogeneity were obtained [24][25][26]. In the other cases, most of the nanoparticles were alloyed, but the Au/Pd ratio was inhomogeneous from cluster to cluster.…”

“…AuPd catalysts were synthesized by impregnation of preformed metal nanoparticles using polyvinyl alcohol as a protective agent. We reported on a two-step procedure for the preparation of activated carbon-supported AuPd alloy nanoparticles (NPs) [24][25][26]. In this procedure, after immobilization of a preformed gold sol on activated carbon, a sol of palladium was generated in the presence of Au/AC using H2 as the reducing agent.…”

“…This result can be justified by the better selectivity to glyceric acid evidenced in the presence of the pure AuPd alloy, instead of the inhomogeneous phases [24][25][26]. One percent Au6Pd4/N-CNFs showed the lowest selectivity to glyceric acid (66%) with the formation of a high amount of tartronic acid, which is the product of the consecutive reaction of glycerol to tartronate.…”

Au–Pd/AC as catalysts for alcohol oxidation: Effect of reaction parameters on catalytic activity and selectivity

“…The effect of the Au-Pd ratio on the conversion and selectivity was observed and a synergistic effect is present in a large range of the Au-Pd ratio, being maximized for Au80-Pd20 composition instead of Au90-Pd10 shown in glycerol oxidation [1]. Moreover the enhancement of conversion observed by adding a base resulted greater for gold-rich catalysts rather than for palladium-rich ones.…”