Optimal synthesis of micro/mesoporous beta zeolite from kaolin clay and catalytic performance for hydrodesulfurization of diesel

To be used as the unique sources of silica and alumina, kaolin clay was pretreated by different kinds of acids including H2SO4, HCl and H3PO4. Through evaluating the synthesis factors of the kaolin clay pretreatment and the crystallization of beta zeolite systematically, the optimal conditions were obtained, i.e., using HCl concentrations of 8.2 mol/L to process kaolin clay at 96 °C for 3 h, and the optimal H2O/SiO2 of 3–4, TEAOH/SiO2 ratio of 0.06, Na2O/SiO2 ratio of 0.05 for crystallizing at 170 °C more than 16 h. The typical physico-chemical properties of samples were characterized by the techniques of XRD, N2-adsorption and FT-IR. The supported NiMo/Beta-Al2O3 series catalysts with different beta contents were prepared and evaluated in a fixed bed microreactor with FCC diesel. HDS results indicated that NiMo/Beta-Al2O3 series catalysts exhibited higher HDS activities compared with the conventional NiMo/Al2O3 catalysts, and S in the best product obtained over the catalyst with beta content of 32% was 8.4 μg g−1 which met the S regulation of ultra clean diesel in Euro-V specification. Combined with the sulfur distributions by GC–PFPD method, it could be found that the incorporation of acidic zeolite in the support could favor the deep removal of sulfur compounds.