Combined Effects of EDTA and Heteroatoms (Ti, Zr, and Al) on Catalytic Activity of SBA-15 Supported NiMo Catalyst for Hydrotreating of Heavy Gas Oil

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• 作者：Sandeep Badoga ; Ajay K. Dalai ; John Adjaye ; Yongfeng Hu
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2014
• 出版时间：February 12, 2014
• 年：2014
• 卷：53
• 期：6
• 页码：2137-2156
• 全文大小：1093K
• ISSN：1520-5045

文摘

M-SBA-15 (M = Ti, Al, and Zr) materials with a Si/M ratio of 20 were synthesized using a direct synthesis method. M-SBA-15 supported NiMo hydrotreating catalysts with and without EDTA was prepared by an incipient wetness impregnation method. A EDTA/Ni molar ratio of 2 was used for catalysts with EDTA. The hydrotreating activities of these catalysts were measured using Athabasca bitumen derived heavy gas oil, and comparison was done with the performance of NiMo/SBA-15 and NiMo/纬-Al₂O₃ catalysts. All catalysts were thoroughly characterized by BET, TPR, TPD, CO-chemisorption, XRD, XANES, HRTEM, ICP-MS, and ¹³C NMR. Incorporation of Ti, Al, and Zr in SBA-15 framework results in an increase in the surface acidity and metal support interactions in otherwise neutral SBA-15 material. This increases the dispersion, and HDS, HDN and HDA activity of a NiMo/SBA-15 catalyst increases by 12%, 70%, and 22%, respectively, as in the case of a NiMo/Ti-SBA-15 (Cat-Ti) catalyst. EDTA addition helps in better redispersion of molybdenum during sulfidation/activation as indicated by HRTEM and CO chemisorption studies. A XANES Mo LIII-edge study for the oxide state of catalysts reveals that EDTA helps in the formation of a greater number of molybdenum in octahedral structures which are easily reducible during sulfidation as compared to molybdenum in tetrahedral structures. A power law based kinetic study indicates that addition of EDTA lowers the activation energy, which could be due to formation of a more favorable Type II NiMoS active site. The activity studies show that using EDTA increases the HDS, HDN, and HDA activity of a NiMo/M-SBA-15 catalyst by 18%, 36%, and 22%, respectively, as in the case of a NiMo/Ti-SBA-15/2EDTA (Cat-TiE) catalyst. Based on the results from different characterization techniques, the schematic is presented related to the effect of EDTA-Mo-support interactions on dispersion of active metals in catalysts. The results from characterization techniques are in parallel with catalytic activity which follows the order Cat-TiE > Cat-AlE > Cat-ZrE > Cat- Ti. However, the catalytic activity of Cat-TiE is almost comparable to that of a NiMo/纬-Al₂O₃ catalyst and has the potential for superior hydrotreating catalyst.