The choice of an optimal composition and preparation method of non-promoted Pd/Al2O3 and promoted Pd-Co/Al2O3 catalysts for the selective hydrogenation of vinylacetylene

For the purpose of optimizing the chemical composition and technology of synthesis of the catalyst for the acetylene hydrocarbons hydrogenation in industrial streams of butadiene and ethyl-vinylacetylene fractions, the influence of the palladium initial compound nature, the active component concentration, the promotion by cobalt, the molar ratio of palladium to cobalt, the phase composition of the supporter on physical chemical properties, and the activity and selectivity to 1,3-butadiene of the catalysts was studied. The effect of acidic-base characteristics of the supporter on its ability to oligomerize unsaturated hydracarbons has been investigated. It has been established, than the δ-Al2O3 supporter is characterized by a low concentration of Bronsted and Lewis acidic sites, decreasing the quantity of oligomers formed on its surface. The optimal composition of the non-promoted KGV-07 catalyst, recommended for the raw butadiene fraction hydrogenation, is 0.5% of Pd deposited from palladium acetate on δ-Al2O3 with palladium particles of 16 nm in size, on which the vinylacetylene conversion of 100% and the selectivity to 1,3-butadiene of 69.9% are reached at a temperature of 20°C at the reactor input, hourly space velocity (HSV) of hydrocarbon raws of 700 h−1, molar ratio of hydrogen to ethyl-vinylacetylenes of 4: 1, summary concentration of 49% of acetylene hydrocarbons, and 1.5% of 1,3-butadiene in hydrocarbon raws. The synthesis of the cobalt-promoted KGVP-07 catalyst with 0.5% of Pd deposited from palladium acetylacetonate on δ-Al2O3 and molar ratio of Pd: Co = 1: 1 has been developed for the hydrogenation of an ethyl-vinylacetylene fraction with a concentration of acetylene hydrocarbons to 6 wt %, with the vinylacetylene conversion of 100% and the selectivity to 1,3-butadiene of 61.3%, at HSV of the hydrocarbon stream of 700 h−1, temperature of 6°C at the reactor input, and molar ratio of hydrogen to ethyl-vinylacetylene admixtures of 4: 1. Promotion by cobalt leads to the formation of palladium particles at the zero oxidation level and to an increase in their average size from 11 to 14 nm in comparison with the non-promoted Pd-catalyst. In the work, IR-spectroscopy, transmission electron microscopy (TEM), and physicochemical methods have been used to characterize the catalysts texture and supporter phase composition. Pilot tests of the KGV-07 and KGVP-07 catalysts on the Etilen plant unit have proven the correctness of the choice for the catalysts’ optimal chemical composition.