The effect from the P2O5 introduction on the activity of Co(Ni)-Mo/Al2O3 catalysts in hydrotreating reactions of petroleum feedstock was examined. As support served γ-Al2O3, prepared from aluminum hydroxide AlOOH powder TH-60 (Sasol), with the following textural characteristics: SBET = 205 m2/g, Vpore = 0.682 cm3/g, Reff = 48 Å. In order to optimize the amount of the modifier the catalyst samples were modified with 0.5, 1.0, 2.0, and 5.0 wt % P2O5. The support was impregnated with an aqueous solution of H3PO4, and this was followed by drying and calcination. The modified supports were impregnated with an aqueous solution of the active phase precursors. The catalyst samples were examined by temperature-programmed desorption (TPD) of ammonia; they were sulfided before the tests. Their catalytic properties were studied in a micro-flow bench-scale reactor under hydrogen pressure in the hydrotreating reactions of mixtures of straight-run diesel fraction with light coker gas oil and of straight-run diesel fraction with catalytically cracked light gas oil. The activities of the catalysts were determined in hydrodesulfurization and hydrogenation reactions. After the test the catalysts were subjected to differential thermal analysis in combination with thermogravimetry (DTA-TGA). The relationship between the acidity of the oxide form of the catalysts and the catalyst activity in hydrogenation reactions was demonstrated. The influence of the amount of the modifier introduced on the catalyst activity and the content of coke on the catalysts after the test was elucidated.
