非负载过渡金属硫化物热解法制备及催化性能

发布时间：2018-07-07 16:03

本文选题：过渡金属硫化物 + 程序升温热解　；参考：《大连理工大学》2010年硕士论文

【摘要】： 负载型过渡金属硫化物催化剂广泛应用于油品的加氢精制过程以及化学品的选择加氢等领域。然而由于活性中心与载体的强相互作用降低了负载型过渡金属硫化物催化剂的催化性能,因此,研发高比表面积的非负载过渡金属硫化物催化材料对于提高加氢精制反应活性,降低油品中硫氮含量具有重要的理论和应用意义。本文采用单源前体程序升温直接热解的方法制备得到了一系列过渡金属硫化物催化材料。常温常压下成功合成了四硫代钼酸铵、四硫代钨酸铵、四甲基四硫代钼酸铵、四甲基四硫代钨酸铵、十六烷基三甲基四硫代钼酸铵和十六烷基三甲基四硫代钨酸铵等单源硫代过渡金属盐前体。采用单源前体直接热解法制备了具有不同的比表面积和孔道特征的非负载MoS2、WS2和Ni/MoS2催化材料。其中四甲基四硫代钼酸铵、十六烷基三甲基四硫代钼酸铵和十六烷基三甲基四硫代钨酸铵热解得到的MoS2和WS2的比表面积在100m2/g以上,以十六烷基三甲基四硫代钨酸铵或钼酸铵热解得到的催化剂以微孔为主,而四甲基四硫代钨酸铵或钼酸铵热解得到的催化剂以中孔为主。所制备的过渡金属硫化物催化剂具有典型MoS2或WS2特征峰,但晶化程度弱,而WS2的晶化程度明显高于MoS2。Ni的掺杂进一步降低MoS2晶化程度,但仍保留了MoS2的衍射峰,观察不到NiS的衍射峰,表明NiS粒子很小且Ni元素在样品中的分布均匀。透射电镜照片显示了明显的MoS2粒子(002)晶面的晶格条纹。杂乱无章的MoS2粒子主要由3-4层组成,层长度约为3-8nm。随Ni含量的增加,MoS2粒子相互交联生成片层状的MoS2。非负载MoS2、WS2和Ni/MoS2催化剂在喹啉选择加氢中显示出较高的催化活性和对1,2,3,4-四氢喹啉的高选择性。通过MCM-41模板剂十六烷基三甲基溴化铵和四硫代钼酸铵反应,在MCM-41孔道内合成了十六烷基三甲基四硫代钼酸铵,直接热分解制备得到的MoS2/MCM-41催化材料。BET、XRD、TEM和EDS等表征显示,MCM-41有序中孔结构没有被破坏,但MoS2纳米粒子的形成改变了载体的孔径分布,减小了载体的孔容。MoS2粒子的分布位置主要在MCM-41载体的端部和孔道内部。随着MoS2担载量的增加,MoS2/MCM-41催化剂对DBT加氢脱硫活性呈现先增加后减小的趋势,而MoS2/MCM-41只有直接脱硫途径,表明此MoS2/MCM-41催化剂主要是通过氢解过程达到脱硫目的的。
[Abstract]:Supported transition metal sulphide catalysts are widely used in the hydrofining process of oil products and the selective hydrogenation of chemicals. However, because the strong interaction between the active center and the support reduces the catalytic performance of the supported transition metal sulphide catalyst, therefore, the development of non-supported transition metal sulfide catalyst material with high specific surface area can improve the hydrofining reaction activity. It is of great theoretical and practical significance to reduce the content of sulfur and nitrogen in oil. In this paper, a series of transition metal sulphide catalytic materials were prepared by single source precursor programmed pyrolysis. Ammonium tetrathiomolybdate, ammonium tetrathioate, ammonium tetramethylammonium tetrathiomolybdate and ammonium tetramethyl tetrathiotungstate were successfully synthesized at room temperature and atmospheric pressure. Single source transition metal salts such as cetyltrimethyl ammonium tetrathiomolybdate and cetyltrimethylammonium tetrathiotungstate were used. Unloaded MoS _ 2W _ 2 and Ni / MoS _ 2 catalytic materials with different specific surface area and pore characteristics were prepared by direct pyrolysis of single precursor. The specific surface areas of MoS2 and WS2 obtained by pyrolysis of ammonium tetramethyl tetrathiomolybdate, cetyltrimethylammonium tetrathiomolybdate and cetyltrimethyl ammonium tetrathioate are above 100m2/g. The catalysts obtained by pyrolysis of cetyltrimethylammonium tetrathiotungstate or ammonium molybdate are mainly microporous, while the catalysts obtained by pyrolysis of tetramethyl ammonium tetrathioate or ammonium molybdate are mesoporous. The transition metal sulphide catalysts prepared have typical MoS2 or WS2 characteristic peaks, but the degree of crystallization is weak, and the degree of crystallization of WS2 is significantly higher than that of MoS2.Ni doping, but the diffraction peak of MoS2 is retained. The diffraction peaks of NIS were not observed, which indicated that the particles of NiS were very small and the distribution of Ni elements in the samples was uniform. Transmission electron microscopy (TEM) photographs show the lattice stripes of the (002) surface of the MoS2 particles. The disordered MoS2 particles are mainly composed of 3-4 layers, the length of which is about 3-8 nm. With the increase of Ni content, MoS _ 2 particles crosslinked each other to form lamellar MoS _ 2. The unsupported MoS _ 2W _ 2 and Ni / MoS _ 2 catalysts showed high catalytic activity and high selectivity for 1H _ 2N _ 3H _ 3H _ 4H _ 4 quinoline in the selective hydrogenation of quinoline. Cetyltrimethylammonium tetrathiomolybdate was synthesized in MCM-41 pore channel by the reaction of cetyltrimethylammonium bromide with ammonium tetrathiomolybdate. The characterization of MoS _ 2 / MCM-41 catalyst material. BETN XRDX TEM and EDS showed that the ordered mesoporous structure of MCM-41 was not destroyed, but the formation of MoS2 nanoparticles changed the pore size distribution of the support. The distribution of MoS2 particles is mainly located in the end and inside of MCM-41 carrier. With the increase of MoS _ 2 loading, the activity of MoS _ 2 / MCM-41 catalyst for DBT hydrodesulfurization increased first and then decreased, while MoS _ 2 / MCM-41 had only direct desulfurization pathway, which indicated that the MoS _ 2 / MCM-41 catalyst was mainly desulphurized by hydrogenolysis.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2010
【分类号】：O643.36

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