制备条件对Co-Mo/nano-TiO_2-Al_2O_3催化剂HDS性能的影响

Effect of Preparation Conditions on Hydrodesulfurization Performance of Co-Mo/nano-TiO_2-Al_2O_3 Catalysts

采用TiCl4水解法制备了一系列纳米TiO2粉体,用机械混捏法制备了nano-TiO2-Al2O3二元复合载体,进而采用等体积浸渍法制备了Co-Mo-P-CA(柠檬酸)/nano-TiO2-Al2O3汽油选择性加氢脱硫催化剂;对TiO2粉体进行了TEM、XRD表征,对nano-TiO2-Al2O3二元复合载体进行了吡啶吸附红外光谱分析(Py-IR)。以FCC汽油重馏分(>80℃)为原料,重点考察了不同条件下制得的TiO2对催化剂选择性加氢脱硫性能的影响。结果表明,锐钛矿相的nano-TiO2有利于使载体表面生成L酸中心,提高催化剂的选择性加氢脱硫活性;锐钛矿相nano-TiO2的适宜制备条件为温度85℃,pH=5.0,Ti4+/H+=15/1;在温度270℃、压力1.4 MPa、空速4 h?1时,FCC汽油重馏分脱硫率为92.4%,烯烃饱和度为28.8%;与TiCl4常规sol-gel法制备的TiO2粉体相比,在相同脱硫率下,所制备催化剂的加氢油的烯烃饱和度低10%左右。

The nanometer TiO2 powders were prepared by the hydrolysis of TiCl4, nano-TiO2-Al2O3 binary oxide complex supports were prepared by using kneading method, and the Co-Mo-P-Citric Acid （CA）/ nano-TiO2-A12O3 catalysts for FCC gasoline hydrodesulfurization （HDS） were prepared finally by incipient impregnation. The prepared TiO2 powders were characterized by TEM and XRD, respectively, and the nano-TiO2-Al2O3 binary oxide complex supports were characterized by Py-IR. The effects of TiO2 preparation conditions on the selective HDS performance of the prepared catalysts for FCC gasoline heavy fraction （〉 80℃） hydrodesulfurization were examined. The results show that the anatase nano-TiO2 is beneficial to form Lewis acid sites in supports and improve the selective HDS performance of the catalysts. The suitable preparation conditions of forming anatase nano-TiO2 was found as follows： pH=5.0, T=-85℃ and Ti4＋/H＋=15/1. After hydrodesulfurizing with the prepared catalyst under the conditions of 270℃, 1.4 MPa and LHSV of 4 h-1, the desulfurization ratio and olefins saturation degree of the FCC gasoline heavy fraction （〉80℃） are 92.4% and 28.8%, respectively. Under the same hydrodesulfurization ratio, using the prepared catalyst, the olefin saturation degree is 10% lower than that obtained by using catalyst with TiO2 prepared by the conventional TICl4 sol-gel method.