Controllable Preparation Of Nano-Pd Supported Catalyst And Its Application In Selective Hydrogenation Of Phenylacetylene

Selective hydrogenation of phenylacetylene is a key reaction for recovering styrene from the Cg fraction of pyrolysis gasoline. In this work, a series of nano-Pd/a-Al2O3catalysts were prepared by a two-step technique-reduction-by-solvent and impregnation onto support, and applied to the selective hydrogenation of phenylacetylene. Catalyst characterization showed that the amounts of reducing agent (NaBH4), solvent (C2H5OH) and protective agent of colloid (Polyvinylpyrrolidone, PVP) had great impacts on the Pd particle size. The results of catalyst test demonstrated that the selective hydrogenation of phenylacetylene over nano-Pd/a-Al2O3catalyst was structure-sensitive. With an increase in the Pd particle size, the specific activity (TOF) of catalyst increased accordingly, while the selectivity to styrene first increased and then decreased. During five consecutive reaction cycles, the nano-Pd/a-Al2O3catalyst displayed good stability in the selective hydrogenation of phenylacetylene, and no Pd leaching or agglomeration occurred, showing that the catalyst can be reused several times without loss of activity and selectivity. Moreover, by using the model C8fraction of pyrolysis gasoline as liquid reactant, the effects of operation conditions on the axial backmixing of liquid phase and on the conversion of phenylacetylene and yield of styrene were studied in a trickle bed reactor. The results showed that the particle size of catalyst, liquid flow rate, gas flow rate, temperature and pressure had obvious influence on the axial backmixing of liquid phase and the selective hydrogenation performance of catalyst.