Promotion of the acidity and textural properties of NiMo/γ-Al2O3 catalyst by applying fluorine, boron and phosphorus in hydrodesulfurization of diesel fuel

Abstract

Phosphorus, boron and fluorine were employed as promoters to synthesize the optimized γ-Al2O3 support and NiMo/γ-Al2O3 catalyst. Based on Response Surface Methodology, supports were synthesized with specified contents of promoters using wet impregnation method. Characterization and properties of the samples were determined through BET, TPD, XRD, TGA and EDX analyses. Moreover, the catalytic performance of the NiMo/γ-Al2O3 catalysts was evaluated at the temperature, pressure and LHSV of 350°C, 4.5 MPa and 1.1 h − 1, respectively. The results of experimental design indicated the effects of the promoters on the responses including pore volume, BET surface area and acidity. Based on the results, a model was designed to predict the optimal condition of synthesis. Then, the optimal support was synthesized using 3.99 wt.% of fluorine, 1.7 wt.% of phosphorus and its properties including acidity, BET surface area and pore volume were 1.28 mmolNH3/g, 276.95 m2/g and 0.63 cm3/g, respectively. Based on the developed model, it was concluded that boron-fluorine and phosphorus-fluorine interactions mostly affected the acidity and BET surface area, respectively. Then, properties and catalytic performance of catalyst were evaluated in the HDS process through diesel fuel feeding (sulfur content: 12,100 ppm) and its acidity was 2.2 mmolNH3/g and the efficiency of desulfurization and the coke of catalyst were 81% and 3%, respectively, which confirms better performance in comparison to a commercial catalyst.