不同种类SiO_2对NiMo催化剂加氢脱硫性能的影响

分别以白炭黑、气凝胶和普通SiO2粉末为硅源,采用混捏与浸渍相结合的方法制备了NiMo/SiO2-γ-Al2O3催化剂;用SEM,TG,XRD,BET,TEM,NH3-TPD,UV-Vis DRS等手段表征了催化剂的结构和物理化学特性;同时对二苯并噻吩(DBT)-正辛烷模拟体系和常压直馏柴油进行了加氢脱硫性能评价。实验结果表明,白炭黑能很好地减弱活性组分与载体之间的相互作用,形成更多的微晶层数为2～6层、长度为8～15 nm的Ⅱ型加氢脱硫活性中心,使催化剂中含有20 nm以上的大孔,同时具有合适的表面酸性。将白炭黑改性催化剂用于初始硫含量为4.00×10-3(w)的DBT-正辛烷模拟体系,在300℃、氢分压2.5 MPa、液态空速3.0 h-1、氢气流量与原料流量的比(简称氢油比)为200的条件下,出口处硫含量降至3.00×10-5(w);对初始硫含量为1.05×10-3(w)的常二线直馏柴油,在350℃、氢分压2.6 MPa、液态空速1.8 h-1、氢油比200的条件下,出口处硫含量为3.48×10-5(w)。

Effect of Different Silica on the Hydrodesulfurization Performance of NiMo Catalyst

A NiMo catalyst with γ-Al2O3 as the support was modified by adding different kinds of silica,namely amorphous silica hydrate with high specific surface area,aerogel silica with high pore volume and silica powder with low specific surface area.The modified catalysts were characterized by means of SEM,TG,XRD,BET,TEM,NH3-TPD and UV-Vis DRS.The catalyst activity in the hydrodesulfurization of dibenzothiophene(DBT)-n-octane system or atmospheric straight-run diesel oil was evaluated.The results showed that adding amorphous silica hydrate could weaken the interaction between the support and the active components,improve the surficial acidity of the catalysts,and form appropriate active centers for the hydrodesulfurization and larger mesopore than 20 nm.The outlet sulfur concentration was 3.00×10-5(w) under the conditions of DBT-n-octane as the experimental system,the initial sulfur concentration 4.00×10-3(w),reaction temperature 300 ℃,LHSV 3.0 h-1,hydrogen pressure 2.5 MPa and the ratio of hydrogen to oil 200.For the atmospheric straight-run diesel oil with an initial sulfur concentration 1.05×10-3(w),under the conditions of reaction temperature 350 ℃,LHSV 1.8 h-1,hydrogen pressure 2.6 MPa and the ratio of hydrogen to oil 200,the outlet sulfur concentration was 3.48×10-5(w).