The influence of B and P in the impregnating solution on the properties of NiMo/gamma-delta-Al2O3 catalysts for VGO hydrotreating

Abstract

The effect of the addition of boric and phosphoric acids to impregnating solutions on the structure and properties of NiMo catalysts for VGO hydrotreating was studied. The catalysts contained a wide-porous support on the basis of a mixture of γ- and δ-Al 2 O 3 phases. The catalysts were studied by XRD, HRTEM, IR CO, ATR-FTIR, XPS. The catalytic activity was evaluated in hydrotreating of heavy VGO. It is established that the NiMo-citrate complex is formed in impregnating solutions. At the same time, the introduction of phosphoric and boric acids into NiMo-citrate complex solution does not lead to a distortion of the complex compound structure. It has been found that calcining of the support at 900 °C makes it possible to obtain a mixture of gamma and delta phases. It was determined that phosphoric and boric acids react with OH groups of the support, but the introduction of phosphoric acid leads to the formation of P–OH groups on the surface. The presence of P and/or B in a catalyst composition results in an increase in the number of MoS 2 layers in a slab. However, with the introduction of B, a small decrease in the amount of Mo on the surface of a catalyst in the form of Mo 4+ is observed. The change in textural and acid characteristics allows us to conclude that bulk particles of BO 3 are formed. Testing of catalysts in hydrotreating of heavy VGO made it possible to establish that the introduction of B into composition of the impregnating solution significantly reduces the activity of the catalysts in hydrotreating, while the introduction of phosphorus leads to an increase in the activity of a catalyst. The introduction of phosphoric and boric acids into the impregnating solution simultaneously increased the activity of the catalyst as compared to the sample containing boron only.