本文選題：磷化鎳　切入點(diǎn)：水熱合成　出處：《東南大學(xué)》2017年碩士論文

【摘要】：過(guò)渡金屬磷化物作為一種新型催化劑,在光學(xué)、電磁學(xué)等多個(gè)領(lǐng)域均表現(xiàn)出卓越性能,使其一度成為熱門的研究課題。磷化鎳,作為一種重要的過(guò)渡金屬磷化物,在多類涉氫反應(yīng)中均表現(xiàn)出較高的活性和穩(wěn)定性。磷化鎳具有多種可調(diào)節(jié)的組成比,如Ni2P、Ni12P5、Ni3P和Ni5P2等,這就使得制備單一晶相組成的磷化鎳成為一個(gè)難題。而本文另一個(gè)重要的研究物質(zhì)——三氯乙烯(TCE),作為脫脂劑、干洗劑和制冷劑等,廣泛用于生產(chǎn)生活中。正因?yàn)槿绱?三氯乙烯是當(dāng)前環(huán)境中分布最廣的污染物之一。在各種降解方法中,加氫脫氯被證明是一種最安全有效的降解方法。本文采用水熱法制備出一系列不同組成的磷化鎳,并在制備過(guò)程中加入表面活性劑聚乙二醇(PEG)或聚乙烯吡咯烷酮(PVP),得到四方晶型和六方晶型兩種晶型的磷化鎳。同時(shí),通過(guò)各種表征手段(X射線衍射、掃描電鏡、透射電鏡和比表面積測(cè)定等),探討了磷化鎳不同晶型結(jié)構(gòu)的形成機(jī)理,并將磷化鎳應(yīng)用于三氯乙烯的加氫脫氯反應(yīng)中,來(lái)測(cè)定其催化性能,得到以下結(jié)論:(1)磷化鎳的制備條件(反應(yīng)物初始配比(Ni/P)、反應(yīng)溫度、反應(yīng)時(shí)間和溶劑)直接影響其最終組成。實(shí)驗(yàn)表明:在Ni/P≥1/2、T彡180℃或者t≥48h時(shí),有利于Ni12P5生成,反之,更有利于Ni2P生成;而溶劑中乙二醇的加入會(huì)使部分Ni2P 轉(zhuǎn)變成 Ni12P5。(2)PEG和PVP對(duì)磷化鎳的晶型結(jié)構(gòu)具有調(diào)控作用,但兩者的作用機(jī)理完全不同。當(dāng)溶液中PEG的濃度達(dá)到臨界膠束濃度時(shí),其親水性一端會(huì)按一定優(yōu)先次序吸附在Ni2P晶面上,被吸附的晶面就停止生長(zhǎng),這種擇優(yōu)吸附改變了晶體在各個(gè)方向上的生長(zhǎng)率,最終導(dǎo)致六方晶型的Ni2P逐漸轉(zhuǎn)變成四方晶型的Ni12P5;而PVP具有還原性,濃度增大,還原能力增強(qiáng),最終形成了氧化性更弱的Ni12P5°(3)PVP對(duì)磷化鎳的粒徑具有調(diào)節(jié)作用。在其作用下,磷化鎳由不規(guī)則大塊狀轉(zhuǎn)變成由均一小顆粒聯(lián)接而成的三維孔道結(jié)構(gòu)。(4)磷化鎳中加入表面活性劑進(jìn)行改性后,加氫脫氯活性比原來(lái)可提高2-3倍,同時(shí),最佳活性溫度降低,活性溫度區(qū)間變寬。
[Abstract]:As a new type of catalyst, transition metal phosphates have shown excellent performance in many fields, such as optics, electromagnetics and so on. Nickel phosphide has a variety of adjustable composition ratios, such as Ni _ 2P, Ni _ (12) P _ (5) Ni _ (3P) and Ni5P2, etc. This makes the preparation of single crystalline nickel phosphide a difficult problem. Another important research substance in this paper, trichloroethylene (TCE), is widely used in production and life as degreasing agent, dry cleaning agent and refrigerant. Trichloroethylene (trichloroethylene) is one of the most widely distributed pollutants in the environment. Hydrodechlorination has been proved to be the safest and most effective degradation method in various degradation methods. A series of nickel phosphide with different compositions were prepared by hydrothermal method in this paper. The tetragonal and hexagonal forms of nickel phosphide were obtained by adding the surfactant PEG (polyethylene glycol) or polyvinylpyrrolidone (PVP) in the preparation process. At the same time, X-ray diffraction and scanning electron microscopy were used to characterize the nickel phosphide. The formation mechanism of different crystalline structure of nickel phosphide was discussed by transmission electron microscope and specific surface area measurement. The catalytic activity of nickel phosphide was determined by applying it to hydrodechlorination of trichloroethylene. The following conclusion is drawn: the preparation conditions of nickel phosphide (the initial ratio of reactants, reaction temperature, reaction time and solvent) directly affect the final composition of nickel phosphide. The experimental results show that when Ni/P 鈮，

本文編號(hào)：1674288