【摘要】：催化劑被廣泛應(yīng)用于各種化學(xué)品的生產(chǎn),從原子尺度了解整個(gè)催化反應(yīng)體系有利于合理設(shè)計(jì)新型催化劑.參與氣固相反應(yīng)的催化劑主要有貴金屬催化劑和過(guò)渡金屬催化劑.近年來(lái),Ru基催化劑由于在低溫低壓下表現(xiàn)出良好的催化活性而廣泛應(yīng)用于一些氣固相反應(yīng).本文對(duì)Ru的基本性質(zhì)、氧化行為以及Ru基催化劑的理論研究進(jìn)行綜述.介紹了釕基催化劑參與的氣固相反應(yīng),包括揮發(fā)性有機(jī)物的催化氧化、一氧化碳優(yōu)先氧化(PROX)、氨合成、氯化氫氧化以及甲烷部分氧化,分析了催化性能與理化性質(zhì)之間的構(gòu)效關(guān)系,提出了釕基催化劑在相關(guān)反應(yīng)中存在的問(wèn)題以及未來(lái)發(fā)展趨勢(shì).Ru具有多種氧化態(tài),在Ru基催化劑參與的氣固相反應(yīng)中,金屬Ru和/或RuO_2被認(rèn)為是活性物種,通常反應(yīng)溫度在400oC以下.Ru(0001)晶面在O_2存在條件下,隨著氧氣含量的不同會(huì)從中間態(tài)過(guò)渡到氧化態(tài),實(shí)驗(yàn)證明該晶面屬于RuO_2.理論研究證實(shí)了在反應(yīng)過(guò)程中RuO_2的存在,并提出了核殼結(jié)構(gòu),對(duì)于其它氣固相反應(yīng)的機(jī)理研究有一定啟發(fā).揮發(fā)性有機(jī)物(VOC)的催化氧化主要集中烷烴、烯烴、芳烴以及鹵代烴的催化氧化,催化劑的理化性質(zhì)包括顆粒粒徑、價(jià)態(tài)和晶體結(jié)構(gòu)等對(duì)催化活性有很大影響,并且Ru基催化劑對(duì)鹵代烴的催化氧化表現(xiàn)出良好的抗鹵性,同時(shí)多鹵代副產(chǎn)物低于其它貴金屬體系.Ru基催化劑在低溫條件下對(duì)PROX具有高的活性和選擇性,并且可以有效抑制H_2氧化、CO甲烷化和CO_2甲烷化等副反應(yīng)發(fā)生.氨合成的難點(diǎn)在于N≡N具有很強(qiáng)的解離能,許多研究表明,氨合成使用的Ru基催化劑的催化性能與載體性質(zhì)密切相關(guān),Ru與載體之間強(qiáng)的相互作用使得電子可以迅速地從載體轉(zhuǎn)移到Ru顆粒上,摻雜其它有效元素可能會(huì)提供更多的氧空位和有效防止高溫焙燒導(dǎo)致催化劑燒結(jié).對(duì)于HCl氧化雖然研究較少,但是Over等人對(duì)HCl氧化機(jī)理進(jìn)行了深入研究,并且日本住友化工設(shè)計(jì)的Ru基催化劑已經(jīng)商業(yè)化.Ru基催化劑可以有效降低甲烷部分氧化的反應(yīng)溫度和壓力,并具有高的選擇性和穩(wěn)定性,避免副產(chǎn)物生成.現(xiàn)有催化系統(tǒng)以及新型催化劑開(kāi)發(fā)仍面臨諸多挑戰(zhàn),例如:對(duì)于單一VOC氧化過(guò)程和多元VOCs催化氧化的機(jī)理和動(dòng)力學(xué)需要進(jìn)一步研究;對(duì)于氨合成需要尋求具有高電導(dǎo)率的載體,從而將電子快速轉(zhuǎn)移到Ru顆粒表面,使得氨合成在更低溫度下進(jìn)行;為了避免副產(chǎn)物生成,需確保新型Ru基催化劑上PROX和甲烷部分氧化在低溫低壓條件下進(jìn)行;Ru基催化劑理化性質(zhì)對(duì)活性的影響以及失活等問(wèn)題需要進(jìn)一步研究.
[Abstract]:Catalysts are widely used in the production of various chemicals. Understanding the whole catalytic reaction system at atomic scale is beneficial to the rational design of new catalysts. The catalysts involved in the gas-solid reaction are mainly noble metal catalyst and transition metal catalyst. In recent years, Ru catalysts have been widely used in some gas-solid reactions due to their good catalytic activity at low temperature and low pressure. In this paper, the basic properties, oxidation behavior and theoretical study of Ru based catalysts are reviewed. The gas-solid reactions of ruthenium based catalysts, including catalytic oxidation of volatile organic compounds, (PROX), ammonia synthesis, hydrogen chloride oxidation and partial oxidation of methane, were introduced. The structure-activity relationship between catalytic performance and physicochemical properties was analyzed, and the problems and future trends of ruthenium based catalysts in the related reactions were put forward. Ru has a variety of oxidation states and is involved in the gas-solid reactions of Ru based catalysts. Metal Ru and / or RuO_2 are considered to be active species, usually at the reaction temperature below 400oC (. Ru (0001) in the presence of O _ 2, the transition from intermediate state to oxidized state varies with the oxygen content. The experimental results show that the crystal plane belongs to RuO_2.. The existence of RuO_2 in the reaction process was confirmed by theoretical study, and the core-shell structure was proposed, which has some implications for the study of the mechanism of other gas-solid reactions. The catalytic oxidation of volatile organic compounds (VOC) is mainly concentrated on alkanes, alkenes, aromatics and halogenated hydrocarbons. The physicochemical properties of the catalysts, including particle size, valence state and crystal structure, have great influence on the catalytic activity. Moreover, Ru based catalysts exhibited good halogen-resistance to halogenated hydrocarbons, and polyhalogenated by-products were lower than other noble metal systems. Ru based catalysts had high activity and selectivity to PROX at low temperature. And the side reactions such as H _ 2 oxidation, CO methanation and CO_2 methanation can be effectively inhibited. The difficulty of ammonia synthesis lies in the strong dissociation energy of N 鈮，

本文編號(hào)：2389898