【作者】 焦冬梅；

【导师】 肖天存；

【作者基本信息】 华东理工大学 ， 化学工艺， 2011， 博士

【摘要】 柴油中的硫化物在高温燃烧时形成的SOx排放到大气中,给人体健康和环境带来危害,发达国家制定的几近“零”硫的柴油标准对炼油加工技术提出了极大的挑战。研究者尝试通过改进柴油脱硫工艺、反应器或催化剂等技术实现深度脱硫,大量的实践和研究表明,催化剂的改进仍是实现深度脱硫最经济有效的途径。目前工业装置上所用的加氢脱硫催化剂主要是传统浸渍法制备的催化剂,该催化剂在一般操作条件下,还不易实现深度脱硫的目标,而且抗毒性弱,在处理劣质高硫原料时,会缩短催化剂的使用周期,而少量已工业化的Ti02为载体的加氢脱硫催化剂因价格高、成型难、强度差等原因制约了其工业化应用规模。为此本文从两个方面对加氢脱硫(HDS)催化剂进行改进,首先在活性组分的分布和优化方面,利用制备过程中尿素对催化剂表面结构和晶粒结构的控制作用,采用新型的尿素矩阵燃烧法(UMxC)、尿素螯合剂法(UCA),来负载加氢脱硫的活性组分；另一方面,从载体改性的角度出发,通过在氧化铝载体中分别引入TiO2、MgO制备系列复合载体负载的Co-Mo/Al2O3-TiO2、Co-Mo/Al2O3-MgO加氢脱硫催化剂。采用X射线衍射(XRD)、激光拉曼光谱(LRS)、高分辨率透射电镜(HRTEM)、X射线光电子能谱(XPS)、N2物理吸附法、红外光谱(FT-IR)、程序升温还原(TPR)等技术对催化剂进行表征。在不锈钢管式固定床反应器(管长600mm,φ40mm×10mm)中,以噻吩(T)、苯并噻吩(BT)和(或)二苯并噻吩(DBT)的二甲苯溶液为模型化合物,以3% CS2的环己烷溶液为预硫化剂,对催化剂的活性进行了考评,结合表征结果,从HDS反应机理上探究了制备方法、复合载体组成、反应条件的变化对催化剂活性的影响。在尿素矩阵燃烧法制备的Co-Mo/Al2O3-TiO2催化剂上研究了BT和DBT的加氢脱硫反应动力学。UMxC法的催化剂制备过程简单、省时,减少或避免了在焙烧过程中对催化剂晶粒结构的破坏,而且所制催化剂孔径分布更加均匀、孔体积高、负载的金属组分分散性好,尤其是未形成传统的共浸渍法所制催化剂出现的非活性P-CoMoO4结构和孪晶现象。活性评价表明UMxC法所制Co-Mo/Al2O3催化剂的活性比传统的顺序浸渍法(SI)和共浸渍法(CI)法的高10%左右。与CO-MO/Al2O3催化剂相比,TiO2的加入改变了Co-Mo/Al2O3-TiO2催化剂表面的电子结构、金属组分的多层晶粒结构的Lc/La值变大,Ti02的加入有利于金属组分在硫化后形成更多的高活性Co-Mo-S和MoS2相。在载体中适度引入Ti02可提高催化剂的活性,尤其是提高二苯并噻吩的脱除率,实现深度脱硫的目的。活性评价表明：二苯并噻吩的脱除率受反应温度、LHSV、催化剂组成的影响较大,当反应温度在300-360℃,LHSV为3-6 h-1,Co/Mo摩尔比在0.3-0.5,TiO2添加比例为20%时,Co-Mo/Al2O3-TiO2(UMxC)催化剂脱除三种硫化物的活性均较高。UCA法制备的CO-Mo/Al2O3-TiO2催化剂平均孔径小,负载的金属组分晶粒有单层和多层结构,多层结构的层间距较大,可能有利于大分子与活性组分的接触,因尿素添加顺序和添加量的不同,形成了与UMxC法所制Co-Mo/Al2O3-TiO2催化剂不同的晶粒结构和孔结构,在相同反应条件下,虽然两种方法所制催化剂均呈现出了较高的加氢脱硫活性,但是UCA法所制催化剂的DBT脱除率比UMxC法的低。UCA法制备的Co-Mo/Al2O3-MgO催化剂的研究表明：与Al2O3单载体催化剂相比,MgO的加入对催化剂的结构有显著影响,随着MgO添加量的增加,氧化钼的还原温度升高,Co-O-Mo键物相增多；更多的活性金属以小团簇的形式负载在催化剂表面上,提供了更多不饱和活性位,催化剂硫化后易形成更多的高活性Co-Mo-S相；残炭特征峰减弱,表明MgO有利于抑制催化剂表面的积炭。活性评价表明：与Co-Mo/Al2O3-TiO2-0.2催化剂相比,Co-Mo/Al2O3-MgO-0.8催化剂在较低H2/HC(300)比下可达到更高的DBT脱除率。在催化剂的制备过程中尿素对催化剂表面性质和晶粒结构的控制作用显著,对尿素的控制作用机理进行了推测。尿素矩阵燃烧法制备过程简单,所制Co-Mo/Al2O3-TiO2催化剂的孔径大而均匀、晶粒分散性好、层数多,催化剂的加氢脱硫活性高。在消除了内扩散影响的条件下,获得了粒度为40～60目的该催化剂的加氢脱硫反应动力学数据,建立了BT和DBT的直接加氢脱硫反应动力学模型：其中KH2=更多还原

【Abstract】 The sulfur in diesel converts into SOX while burning, which is harmful to human being healthy and natural environment. The increasingly strict non-sulfur diesel regulations being implemented by the developed countries bring great challenge to refinery technology. A lot of industrial practice and researches showed that the improvement of catalyst is still the most efficient way to reach deep desulfurization. Nowadays, most industrial catalysts are prepared using traditional method, which is difficult to produce low sulfur diesel and the weak poison resistance shortened the catalyst lifetime while processing high sulfur content feed.The expensive price, difficulty in shaping and weak strength hindered the industrialization scale up of TiO2 supported hydrodesulfurization catalyst or the bulk catalysts.In this work, our aim is to promote the hydrodesulfurization (HDS) catalyst activity from two aspects. Firstly, new Urea Matrix Combustion (UMxC) method and Urea Chelating Agent method (UCA) were used to optimize the active phase dispersion exploiting the controllable function of urea during the preparation. Secondly, the catalyst support is modified by adding TiO2 or MgO using the novel method. The surface properties and morphology were characterized using XRD, LRS, HRTEM, XPS,N2 physorption, FT-IR and TPR technologies.The HDS catalytic activity was tested in a stainless fixed-bed reactor(600mm long,Φ40mm×10mm).The xylene solution of B, BT and (or) DBT was used as the model compound, the 3% CS2 cyclohexane was used as the presulfur agent. Effects of preparation method, support component and reaction conditions on HDS catalytic activity were discussed corresponding to the HDS mechanism. The HDS reaction kinetics of BT and DBT were studied.It showed that the UMxC method had the characters of saving time, simple steps and avoiding the damage of catalyst crystal morphology. The catalyst presented uniform pores, higher pore volume and better dispersion, especially without forming nonactiveβ-CoMoO4 and twins crystal structure compared with that of co-impregnaition method.The HDS activity of Co-Mo/Al2O3 catalyst prepared using UMxC method was about 10% higher than that of prepared using sequential impregnation (SI) and co-impregnaition (CI) methods.Compared with Co-Mo/Al2O3 catalyst, the addition of TiO2 changed the electronic states of catalyst surface and the Lc/La of multi-layer crystal increased, benefited forming more high active Co-Mo-S andMoS2 phase. Proper addition of TiO2 favors improving catalytic activity, especially increasing the removal of DBT.The HDS tests showed that the reaction temperature, LHSV and catalytic component notably affected the removal of DBT. The Co-Mo/Al2O3-TiO2 (UMxC) catalyst with 20% TiO2 addition content and 0.3～0.5 Co/Mo(mole ratio) presented the best removal ratio of the three sulfur compounds at:300-360℃,3～6 h-1 LHSV.Co-Mo/Al2O3-TiO2 catalysts prepared using UCA method had the character of smaller average pore diameter, mono-layer and multi-layer crystal morphology, bigger layer space which may be beneficial to the connection of big molecular DBT with active component. The addition sequence and content of urea resulted in different crystal and pore morphology. The activity of Co-Mo/Al2O3-TiO2 catalyst prepared using UCA method was lower than that of UMxC method, although the catalysts prepared using the two methods both presented high catalytic activity.The results of Co-Mo/Al2O3-MgO catalyst prepared using UCA method showed that MgO greatly affected the morphology of catalyst compared with Al2O3 mono-support. With the rising of MgO content, the reduction temperature of Mo-oxide increased, Co-O-Mo cluster raising, more metal component existed as small clusters on the surface of catalyst forming more unsaturated sites, thus benefited forming more and higher active Co-Mo-S phase after sulfurization. The decrease of residual carbon peak meant the trend of lower accumulation of carbon. The HDS reaction results showed that Co-Mo/Al2O3-MgO catalyst presented higher activity at low H2/HC ratio (300) compared with Co-Mo/Al2O3-TiO2 catalyst.The addition amount and sequence of urea affected the catalyst morphology significantly during the preparation. The control function of urea on catalyst textural properties and crystal morphology was expected. The Co-Mo/Al2O3-TiO2 (UMxC) catalyst presented higher average pore diameter, uniform dispersion and multi-layer crystal morphology and high HDS activity. The HDS reaction kinetics data of 40～60 mesh Co-Mo/Al2O3-TiO2 (UMxC) catalyst gained by the elimination of inner-diffusion, the direct HDS reaction of BT and DBT hyperbolic type kinetics models were:The parameters in the above kinetics models were as following: k2更多还原