The Simulation And Experiment Study For The Catalyst And Mass Transfer Process Of Pd-Activated Carbon And Pd-Graphene

Activated carbon has developed micro channel and its specific surface area is as large as 1000 m2/g. As the catalyst carrier it can effectively disperse the active particles, but just because of its micro channel, the diffusion resistance is relatively large when reactants touch catalytic active site, which has a negative effect on catalytic activity. Since graphene was successfully prepared in 2004, its application in catalysis has attracted people's attention. This is because graphene has good stability under the condition of high temperature, strong acid and strong alkali, while its specific area is 2630 m2/g with the single layer structure. Because of these characteristics graphene can disperse the active site better as the catalyst carrier in the reaction process without the effects of internal diffusion. In this work, the effect of intrinsic reaction rate, diffusion rate and catalyst size on activated carbon and graphene catalyst process has been investigated, and the reduction of p-nitrophenol by sodium borohydride indicated that the catalytic activity of graphene based catalysts in better than that of activated carbon based catalyst.In this work, the catalytic reaction process was simulated with COMSOL Multiphysics. For the activated carbon based catalyst, intrinsic reaction rate, diffusion rate and catalytic were changed to study the change of reactant concentration along the radius direction in the catalytic process. The results showed that for the rapid reaction, the decrease of the reactant diffusion rate or the increase of catalyst size in not conducive to utilization of the active site inside activated carbon particles. For the graphene based catalyst, the change of reactant concentration on the surface of the graphene in catalytic mass transfer process was studied by changing intrinsic reaction rate. The results showed that there was almost no accumulation of reactants on the surface of graphene for the rapid reaction, while the concentration of reactants on the surface of graphene was same as the concentration of the ambient fluid for the slow reaction. Meanwhile, graphene based catalysts was proved to be more efficient than activated carbon based catalyst through the simulation of activated carbon/graphene based catalyst to catalyze the reduction of p-nitrophenol by sodium borohydride.In this work, the reduction of p-nitrophenol by sodium borohydride catalyzed by the palladium nanoparticles on the activated carbon/graphene was conducted to prove the simulation results. The reactions were conducted in parallel, results showed that the catalytic efficiency of palladium nanoparticles catalyst based on graphene is higher than that of catalyst based on activated carbon and it is consistent with simulation results.