本文選題：甲硫醇 + 催化分解�。� 參考：《昆明理工大學(xué)》2017年博士論文

【摘要】：甲硫醇(CH3SH)是一種典型的含硫揮發(fā)性有機(jī)污染物(SVOC),其來(lái)源廣泛,具有較強(qiáng)的毒性和揮發(fā)性,直接排放到大氣中,會(huì)對(duì)自然環(huán)境和人體健康造成一定危害,因而開(kāi)展甲硫醇尾氣的治理和減排研究工作具有重要的現(xiàn)實(shí)意義。本論文主要合成系列鈰基稀土復(fù)合型氧化物及稀土氧化物改性復(fù)合型分子篩催化劑,進(jìn)行甲硫醇?xì)怏w催化分解的研究。通過(guò)對(duì)合成的催化劑進(jìn)行相關(guān)表征,詳細(xì)探究甲硫醇催化分解反應(yīng)過(guò)程及反應(yīng)機(jī)理。主要結(jié)果歸納如下:(1)利用微波輔助溶膠-凝膠法快速合成納米顆粒Ce02催化劑,將其應(yīng)用于甲硫醇的催化分解反應(yīng)研究。研究表明,相比于傳統(tǒng)溶膠-凝膠法,該方法合成的催化劑具有較多的氧空位和較小的晶體粒徑,可為催化轉(zhuǎn)化甲硫醇反應(yīng)提供較多的反應(yīng)活性位點(diǎn),因而表現(xiàn)出良好的甲硫醇催化轉(zhuǎn)化反應(yīng)活性。通過(guò)對(duì)合成條件(焙燒溫度、焙燒時(shí)間、鈰鹽與檸檬酸的配比以及微波處理時(shí)間等)進(jìn)行優(yōu)化,獲得高性能的催化劑材料。通過(guò)對(duì)比分析反應(yīng)前后催化劑的變化情況,探究氧化鈰催化劑催化分解甲硫醇過(guò)程中的失活原因。其中氧化鈰催化劑催化分解甲硫醇反應(yīng)過(guò)程中,易消耗催化劑上的表面晶格氧,導(dǎo)致低價(jià)態(tài)鈰硫物種(如Ce2S3)的累積,引起催化劑失活。在此基礎(chǔ)上,對(duì)失活的催化劑進(jìn)行再生處理,結(jié)果表明,失活的催化劑在450℃反應(yīng)條件下通過(guò)空氣處理,可在較短的時(shí)間內(nèi)(10 min)恢復(fù)其原來(lái)性能,論文研究中還分析了該催化劑的再生反應(yīng)過(guò)程。(2)在氧化鈰催化劑研究基礎(chǔ)上,通過(guò)向氧化鈰中添加系列稀土(Y,Gd,Sm,Nd和La),合成鈰基稀土復(fù)合氧化物。不同稀土的添加對(duì)合成的催化劑堿性強(qiáng)度及氧空位含量等性能有著不同的影響作用,并最終影響其催化分解甲硫醇的性能。其中,氧化鈰中摻雜較小離子半徑的稀土元素(Y和Gd等)時(shí),合成的催化劑堿性強(qiáng)度得到適度的增強(qiáng),氧空位濃度顯著增加,晶格氧遷移能力增強(qiáng),因而其催化分解甲硫醇的反應(yīng)穩(wěn)定性能得到改善:而氧化鈰中摻雜較大離子半徑的稀土元素(Nd和La等)時(shí),一方面由于合成的復(fù)合氧化物晶胞參數(shù)增大,導(dǎo)致催化劑晶格的過(guò)度扭曲,使得其氧空位含量降低,另一方面較大離子半徑的金屬元素結(jié)合更多的陰離子氧,使得催化劑上含有更多的堿性位點(diǎn),從而導(dǎo)致催化劑上吸附累積更多的酸性含硫物種,引起催化劑的失活。(3)為了進(jìn)一步分析稀土的摻雜對(duì)氧化鈰基催化劑性能的影響。論文中詳細(xì)分析了鈰-釔(Ce-Y)稀土氧化物的氧空位濃度及其晶格氧遷移轉(zhuǎn)化過(guò)程,并將該性質(zhì)與甲硫醇催化分解反應(yīng)的活性進(jìn)行關(guān)聯(lián)。結(jié)果表明,隨著稀土 Y添加量的增加,合成的催化劑的表面晶格氧含量降低,其催化分解甲硫醇活性下降,說(shuō)明晶格氧含量對(duì)其催化分解甲硫醇的活性有著重要的影響作用。而Ce0.75Y0.25O和Ce0.5Y0.5O催化劑催化分解甲硫醇的穩(wěn)定性能優(yōu)于Ce02,主要是由于Y添加的稀土復(fù)合氧化物中含有較多的氧空位,有利于催化劑中晶格氧的遷移轉(zhuǎn)化,反應(yīng)過(guò)程中,更多的體相晶格氧遷移補(bǔ)充反應(yīng)過(guò)程中消耗的表面晶格氧,繼續(xù)為反應(yīng)提高活性氧位點(diǎn),鈰基催化劑的氧遷移轉(zhuǎn)化過(guò)程(體相晶格氧向表面晶格氧的遷移)對(duì)維持催化劑的表面活性氧位點(diǎn)、提高催化劑的穩(wěn)定性能有著重要的作用。(4)探究稀土的添加對(duì)HZSM-5沸石分子篩的酸堿性的調(diào)控作用及其對(duì)催化劑催化性能的改善作用。Ce、Pr、Nd和Sm改性的HZSM-5沸石分子篩催化劑催化分解甲硫醇時(shí),反應(yīng)活性均有一定程度提高,其中Sm改性的HZSM-5分子篩表現(xiàn)出最佳的反應(yīng)活性。一方面,稀土 Sm添加后,HZSM-5中的堿性增強(qiáng),有利于酸性甲硫醇?xì)怏w分子的吸附和活化,從而提高了催化劑的反應(yīng)活性;另一方面,HZSM-5中添加稀土 Sm,可部分取代沸石分子篩中的骨架鋁物種,使催化劑上的B酸量降低,強(qiáng)酸性活性位點(diǎn)數(shù)量減少,反應(yīng)過(guò)程中有利于減少積碳的產(chǎn)生,進(jìn)而顯著提高了催化劑催化分解甲硫醇的反應(yīng)穩(wěn)定性能。開(kāi)展稀土改性HZSM-5沸石分子篩催化劑的失活原因及再生過(guò)程研究,結(jié)果表明,積碳的累積是導(dǎo)致HZSM-5沸石分子篩催化劑失活的主要原因,失活的催化劑在550℃的空氣中可以較容易實(shí)現(xiàn)多次再生。
[Abstract]:Methyl mercaptan (CH3SH) is a typical sulfur containing volatile organic pollutant (SVOC). It has a wide range of sources and has strong toxicity and volatility. It is directly discharged into the atmosphere and will cause certain harm to the natural environment and human health. Therefore, it is of great practical significance to carry out the research on the treatment and emission reduction of methyl thiol tail gas. Synthesis of a series of cerium based rare earth complex oxides and rare earth oxide modified composite zeolite catalysts for catalytic decomposition of methyl mercaptan is carried out. The catalytic decomposition process and reaction mechanism of methyl mercaptan are investigated in detail through the related characterization of the synthesized catalysts. The main results are as follows: (1) the use of microwave assisted sol - The rapid synthesis of nano particle Ce02 catalyst by gel method is applied to the catalytic decomposition of methyl mercaptan. The study shows that the catalyst has more oxygen vacancy and smaller crystal size than the traditional sol-gel method, which can provide more reactive sites for catalytic conversion of methyl thiol reaction. A high performance catalyst was obtained by optimizing the synthesis conditions (roasting temperature, calcination time, the ratio of cerium salt with citric acid and microwave treatment time) to obtain high performance catalyst materials. By comparing and analyzing the change of the catalyst before and after the reaction, the catalytic decomposition of methyl mercaptan over the cerium oxide catalyst was studied. In the process of catalytic decomposition of methyl mercaptan, cerium oxide catalyzes the breakdown of the surface lattice oxygen on the catalyst, resulting in the accumulation of low valence cerium and sulphur species (such as Ce2S3) and the deactivation of the catalyst. On this basis, the reactivation of the deactivated catalyst is regenerated. The results show that the deactivated catalyst is at 450 centigrade reaction strip. The original performance of the catalyst can be recovered in a short time (10 min) by air treatment. In the paper, the regeneration process of the catalyst is also analyzed. (2) on the basis of the cerium oxide catalyst, a series of rare earth compounds (Y, Gd, Sm, Nd and La) are added to the cerium oxide to synthesize the cerium based rare earth compound oxide. The properties of the catalyst, such as the alkaline strength and the oxygen vacancy content, have different effects and ultimately affect the catalytic decomposition of methyl mercaptan. In the case of rare earth elements (Y and Gd) doped with smaller ionic radius in cerium oxide, the alkaline strength of the synthesized catalyst is enhanced, the oxygen vacancy concentration is significantly increased, and the lattice oxygen migration is increased. As a result, the stability of the catalytic decomposition of methyl mercaptan is improved. While the rare earth elements (Nd and La) doped with the larger ionic radius of the cerium oxide, on the one hand, the crystal lattice of the catalyst is excessively twisted because of the increase of the composite oxide cell parameters, which makes the oxygen vacancy content reduced and the other is the larger ion. The metal element of the radius combined with more anionic oxygen makes the catalyst contain more basic loci, which leads to the accumulation of more acidic sulfur species on the catalyst and the deactivation of the catalyst. (3) in order to further analyze the effect of rare earth doping on the performance of the cerium oxide based catalyst. The paper detailed analysis of the cerium yttrium (Ce-Y The oxygen vacancy concentration and the lattice oxygen migration and transformation process of the rare earth oxides are associated with the activity of the catalytic decomposition reaction of methyl mercaptan. The results show that the surface lattice oxygen content of the synthesized catalyst decreases with the increase of the addition of rare earth Y, and the catalytic decomposition of methyl mercaptan decreases. The decomposition of methyl mercaptan has an important effect. The catalytic decomposition of methyl mercaptan by Ce0.75Y0.25O and Ce0.5Y0.5O catalysts is better than that of Ce02. It is mainly due to the presence of more oxygen vacancies in the rare earth compound oxides added by Y, which is beneficial to the migration and transformation of the MICROTEK lattice oxygen in the catalyst, and more bulk phase lattice oxygen in the reaction process. The surface lattice oxygen consumed in the supplementary reaction process continues to increase the reactive oxygen site, and the oxygen migration and transformation process of the cerium based catalyst (the migration of the lattice oxygen to the surface lattice oxygen of the body phase) plays an important role in maintaining the surface active oxygen site of the catalyst and improving the stability of the catalyst. (4) to explore the addition of rare earth to HZSM- The effects of the acidity and alkalinity of 5 zeolite molecular sieves and the improvement of the catalytic performance of the catalyst.Ce, Pr, Nd and Sm modified HZSM-5 zeolite catalysts for the catalytic decomposition of methyl mercaptan to a certain extent, of which the Sm modified HZSM-5 molecular sieves show the best reaction activity. On the one hand, the addition of rare earth Sm, HZSM The alkaline enhancement in -5 is beneficial to the adsorption and activation of acid methyl mercaptan molecules, thus improving the activity of the catalyst. On the other hand, the addition of rare earth Sm in HZSM-5 can partly replace the skeleton species in the zeolite molecular sieve, reducing the B acid content on the catalyst, reducing the number of strong acid active sites and reducing the number of the strong acid active sites. The production of less carbon has significantly increased the stability of catalytic catalytic decomposition of Methanthiol. The cause of deactivation and regeneration process of the rare earth modified HZSM-5 zeolite catalyst has been studied. The results show that the accumulation of carbon is the main cause of the deactivation of the zeolite catalyst for HZSM-5 zeolite, and the deactivated catalyst is at 550 centigrade. It can be easily regenerated many times in the gas.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：X701;O647.3

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