Influence of palladium structural and electronic properties on the activity and selectivity of Pd/Al2O3-, Pd-Co/Al2O3-catalysts for acetylenic hydrocarbons hydrogenation

The influence of structural and electronic characteristics of nonpromoted and cobalt promoted Pd-catalysts in their adsorption and catalytic properties. Shown that the conversion vinylacetylene depends on palladium dispersity for both catalysts, synthesized with acetate and acetylacetonate complexes. Higher conversion vinylacetylene is on catalysts of palladium acetylacetonate, as dispersity of palladium higher compared with samples from the solutions of the acetate complexes. It was established that the selectivity of vinylacetylene transformation to 1,3-butadiene on catalysts from acetate and acetylacetonate palladium is determined by the electronic state of 3d-orbitals of Pd surface atoms. Catalysts from palladium acetate have a higher electron density at the 3d-orbitals in comparison with the acetylacetonate samples, which determines their higher selectivity of the vinylacetylene conversion to 1,3-butadiene. The cobalt introduction in Pd/δ-Al2O3-catalysts, synthesized using acetylacetonate complex, leads to formation of bimetallic Pd-Co-particles with Pd atoms with higher electron density compared to the Pd atom in nonpromoted Pd/δ-Al2O3-catalysts, that is probably due to donation of electron density from the promoter atoms and leads to a decrease in the adsorption capacity of bimetallic particles by 1,3-butadiene and hydrogen. Consequence is an increase of vinylacetylene to 1,3-butadiene conversion selectivity.

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