氢等离子体法制备金属磷化物及其加氢脱硫催化性能研究

发布时间：2018-06-14 23:29

本文选题：等离子体 + 金属磷化物　；参考：《大连理工大学》2011年博士论文

【摘要】：过渡金属磷化物作为一类新型半导体材料可广泛应用于光电、磁、催化等领域。金属磷化物作为催化剂常采用程序升温还原法制备,但该法制备温度高,磷物种易损失,且高温制备容易导致催化剂颗粒烧结。本论文用氢等离子体还原法(PR)制备了一系列过渡金属磷化物,考察并优化了磷化镍(Ni2P)、磷化钻(CoP)、磷化钼(MoP)和磷化钨(WP)的制备条件；采用典型含硫化合物二苯并噻吩(DBT)和4,6二甲基二苯并噻吩(4,6-DMDBT),考察了金属磷化物的加氢脱硫催化反应性能；采用XRD、CO化学吸附、TPR、HRTEM、SEM、ICP-AES等对金属磷化物的结构进行了表征,初步研究了氢等离子体还原法制备过渡金属磷化物的反应机理。论文系统考察了电压、放电时间、金属与磷的原子比(M/P)及加入贵金属对体相Ni2P, CoP, MoP和WP制备的影响。结果表明,提高电压和增加还原时间有利于提高所制备的金属磷化物的晶化程度；当金属磷化物存在一种晶型(如WP和MoP)时,氧化物前体中M/P影响其晶化程度；当存在多种晶型时,M/P比决定了金属磷化物的晶体结构；PR法可以按化学计量比制备金属磷化物,而不需要在其前体引入过量的磷；少量引入贵金属(如Ru)可进一步缓和制备条件；采用PR法可制备磷化镓(GaP)、磷化铟(InP)、磷化铁(Fe2P)等重要半导体材料。采用PR法和传统程序升温还原法制备了体相Ni2P、CoP、MoP和WP,比较了不同方法制备的体相磷化物在DBT加氢脱硫反应中的催化性能；研究了制备条件和钝化方法对磷化物晶化度和加氢脱硫催化反应的影响规律。发现PR法制备的催化剂比传统程序升温法制备的活性高；PR法制备的体相磷化物活性顺序为CoPNi2PMoP≈WP。研究发现CoP在四种金属磷化物中制备条件最为苛刻,且易于形成加氢脱硫活性很低的Co2P相,因而采用传统程序升温还原法制备的CoP催化剂在加氢脱硫反应中表现出最低的活性。当在氧化物前体中引入少量Ru时,可以在较温和条件下制备出高结晶度、高活性CoP催化剂。反应评价结果表明,Ru的引入主要促进了CoP的形成,改善了晶粒的分散,但没有明显改变催化反应过程和活性中心本质。用PR法制备了MCM-41担载的WP、MoP和Ni2P催化剂,以DBT和4,6-DMDBT的十氢萘溶液为模拟油考察了其加氢脱硫反应性能。对混合物料HDS活性顺序为：WPMoPNi2P, WP和MoP以加氢脱硫路径为主,Ni2P以直接脱硫路径为主。若将WP/MCM-41与Ni2P/MCM-41机械混合,则可以同时高效脱除DBT和4,6-DMDBT。此外,比较了不同方法制备的Ni-W-P在加氢脱硫反应中的催化活性,其活性顺序顺序为：先硫化后还原法PR法先混合后还原法(MR)共浸渍法。共浸渍法制备的Ni-W-P活性低的主要原因是有杂晶生成。
[Abstract]:As a new type of semiconductor materials, transition metal phosphide can be widely used in the fields of photoelectric, magnetic, catalysis and so on. Metal phosphide is often prepared by programmed temperature reduction as a catalyst, but this method has high temperature, the phosphorus species is easy to lose, and the high temperature preparation is easy to lead to the sintering of the catalyst particles. In this paper, the hydrogen plasma reduction method (PR) is used in this paper. A series of transition metal phosphide was prepared, and the preparation conditions of nickel phosphide (Ni2P), phosphide (CoP), molybdenum phosphide (MoP) and tungsten phosphide (WP) were prepared. The catalytic properties of the hydrodesulfurization of metal phosphide were investigated by using the typical sulfur compounds two benzo thiophene (DBT) and 4,6 two methyl two benzo thiophene (4,6-DMDBT). XRD, CO was used. The structure of metal phosphide was characterized by chemical adsorption, TPR, HRTEM, SEM, ICP-AES and so on. The reaction mechanism of the transition metal phosphide prepared by the hydrogen plasma reduction method was preliminarily studied.
The effects of voltage, discharge time, atomic ratio of metal to phosphorus (M/P) and the addition of precious metals to the bulk phase Ni2P, CoP, MoP and WP are investigated. The results show that increasing the voltage and increasing the reduction time are beneficial to the crystallization of the metal phosphide. When a crystalline form of metal phosphide (such as WP and MoP), the oxidation of metal phosphide is oxidized. M/P affects the crystallization degree of the precursors; when there are various crystalline forms, the M/P ratio determines the crystal structure of the metal phosphide; the PR method can prepare the metal phosphide according to the stoichiometric ratio, without the introduction of the excess phosphorus in its precursor; a small amount of precious metals (such as Ru) can be used to prepare the preparation conditions, and the PR method can be used to prepare the gallium phosphide. GaP), indium phosphide (InP), iron phosphide (Fe2P) and other important semiconductor materials.
The bulk phase Ni2P, CoP, MoP and WP were prepared by the PR method and the traditional temperature programmed reduction method. The catalytic properties of the bulk phase phosphide prepared by different methods in the DBT hydrodesulfurization reaction were compared. The effects of preparation conditions and passivation methods on the crystallinity of phosphide and the catalytic reaction of hydrodesulfurization were studied. It was found that the catalyst prepared by the PR method was specific to the catalyst. The activity prepared by the programmed temperature method is high, and the active phase of the phosphor prepared by PR is CoPNi2PMoP WP..
It is found that the preparation conditions of CoP in four kinds of metal phosphide are most harsh and easy to form Co2P phase with low hydrodesulfurization activity. Therefore, the CoP catalyst prepared by the traditional temperature programmed reduction method has the lowest activity in the hydrodesulfurization reaction. When a small amount of Ru is introduced in the oxide precursor, it can be made under mild conditions. The high crystallinity and high active CoP catalyst were prepared. The results of the reaction evaluation showed that the introduction of Ru mainly promoted the formation of CoP and improved the dispersion of the grain, but did not change the catalytic reaction process and the essence of the active center.
The MCM-41 supported WP, MoP and Ni2P catalysts were prepared by PR method. The hydrodesulfurization reaction properties of the ten hydrogen naphthalene solution of DBT and 4,6-DMDBT were investigated. The order of HDS activity of the mixed materials was WPMoPNi2P, WP and MoP were mainly hydrodesulfurization path, and the Ni2P was mainly desulphurizing path. DBT and 4,6-DMDBT. can be effectively removed at the same time, and the catalytic activity of Ni-W-P in the hydrodesulfurization reaction prepared by different methods is compared. The order of the activity sequence is: first after the vulcanization and the reduction method, the PR method is first mixed with the reduction method (MR) Co impregnation. The main reason for the low viability of Ni-W-P prepared by CO impregnation is the formation of the hetero crystal.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2011
【分类号】：O643.36

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