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  本文選題：KIT-6 + 介孔材料��； 參考：《華南理工大學(xué)》2015年碩士論文

【摘要】：環(huán)氧苯乙烷是重要的精細化工中間體,工業(yè)上通常以苯乙烯為原料制備,該工藝存在能耗高,污染嚴重等弊端。目前科研界通過苯乙烯催化環(huán)氧化制備環(huán)氧苯乙烷探索中,負載型金屬催化劑長期屬于研究熱點,而介孔分子篩通常被用作該反應(yīng)的催化劑載體。作為一種以二氧化硅為骨架的新型立方介孔有序分子篩材料,KIT-6除了比表面積大,孔容孔徑均勻規(guī)整等常規(guī)分子篩優(yōu)點外,還具備獨特的孔道內(nèi)部連通性,并且孔道系統(tǒng)可根據(jù)水熱溫度適當(dāng)調(diào)控。在上述基礎(chǔ)上,本論文選用低溫水熱合成的KIT-6作為催化劑載體,銅鈷氧化物為活性組分,通過浸漬法建立催化劑體系,考察其在叔丁基過氧化氫(TBHP)為氧化劑、反應(yīng)溫度為70 oC時苯乙烯環(huán)氧化中的催化性能并借助相關(guān)表征手段闡明影響催化劑活性的要素。本文探討了焙燒溫度(550 oC和250 oC)對催化劑活性的影響并分析了其原因。結(jié)果表明,銅物種是催化劑活性主要來源,而單獨的鈷物種活性較差。同時,550 oC焙燒的催化劑較250 oC具有更優(yōu)越的性能。綜合XRD、N2吸脫附、TEM、Raman光譜、XPS、AAS表征手段結(jié)果,揭示了在比表面積、孔道結(jié)構(gòu)、金屬含量等物理結(jié)構(gòu)基本類似的情況下,較高溫度焙燒的催化劑因Cu(II)進入Co3O4晶格從而提高了催化劑的性能,這也表明電子結(jié)構(gòu)(electron structure)是影響該催化劑在反應(yīng)中活性的主導(dǎo)因素。本文還考察了去除KIT-6的催化劑以及以MCM-41和SBA-15為載體的銅鈷氧化物催化劑在苯乙烯環(huán)氧化中的催化性能。結(jié)果表明,催化劑在失去載體KIT-6支撐或者更換另兩種載體后,活性急劇下降。借助上述表征方法則進一步確定了KIT-6有利于催化劑維持有序結(jié)構(gòu)和金屬氧化物均勻分散,因而保障其較高的催化活性。該結(jié)果證明了催化劑質(zhì)構(gòu)特性(textural properties)是影響其催化活性的重要因素。本文也優(yōu)化了氧化劑TBHP用量、反應(yīng)時間等反應(yīng)條件。研究表明,在其他條件不變情況下,氧化劑用量或者反應(yīng)時間的延長均可以提高苯乙烯轉(zhuǎn)化率,但是目標產(chǎn)物環(huán)氧苯乙烷的選擇性則呈下降趨勢。反應(yīng)最佳條件為反應(yīng)物苯乙烯:TBHP物質(zhì)的量比例為1:1,反應(yīng)時間為8 h,可達53.8%的苯乙烯轉(zhuǎn)化率和82.6%的環(huán)氧苯乙烷選擇性。此外,本文還初步推測了反應(yīng)機理。
[Abstract]:Epoxy-phenylene ethane is an important fine chemical intermediate, which is usually prepared from styrene in industry. This process has many disadvantages such as high energy consumption, serious pollution and so on. At present, supported metal catalysts have long been a hot topic in the research of epoxidation of epoxy-phenylethane from styrene, and mesoporous molecular sieve is usually used as catalyst carrier for this reaction. As a new ordered cubic mesoporous molecular sieve material with silica framework, KIT-6 has many advantages, such as large specific surface area, uniform pore volume and uniform pore size. And the pore system can be adjusted according to the hydrothermal temperature. On the basis of the above, KIT-6, synthesized by hydrothermal synthesis at low temperature, was used as the catalyst carrier and CuCo oxide as the active component. The catalyst system was established by impregnation method, and the catalyst system was investigated in the presence of tertiary Ding Ji hydrogen peroxide (TBHP) as oxidant. The catalytic properties of styrene epoxidation at 70 OC and the factors affecting the activity of the catalyst were elucidated by means of related characterization. The effect of calcination temperature (550 OC and 250 OC) on the activity of the catalyst was studied and the reasons were analyzed. The results showed that copper species were the main source of catalyst activity, while cobalt species had poor activity. At the same time, the catalyst calcined at 550oC has better performance than that of 250oC. By synthesizing the results of the Raman spectra of XRD- N _ 2 desorption and desorption, and the results of XPS-AAS characterization, it is found that the physical structures of XRDX N _ 2 adsorption and desorption have similar physical structures, such as specific surface area, pore structure, metal content, and so on. Due to Cu (II) entering the lattice of Co _ 3O _ 4, the catalyst calcined at a higher temperature improves the catalyst performance, which indicates that the electronic structure of (electron structure) is the dominant factor affecting the activity of the catalyst in the reaction. The catalytic properties of KIT-6 removal catalyst and copper-cobalt oxide catalysts supported on MCM-41 and SBA-15 in styrene epoxidation were also investigated. The results showed that the activity of the catalyst decreased sharply after losing the support of KIT-6 or replacing the other two kinds of support. With the help of the above characterization methods, it was further confirmed that KIT-6 was conducive to the maintenance of the ordered structure of the catalyst and the uniform dispersion of the metal oxides, thus ensuring its higher catalytic activity. The results show that (textural properties) is an important factor affecting the catalytic activity. The reaction conditions such as the amount of oxidant TBHP and the reaction time were also optimized. The results show that the conversion of styrene can be increased by the addition of oxidant or the prolongation of reaction time under the same conditions, but the selectivity of the target product epoxy-phenylethane is decreasing. The optimum reaction conditions are as follows: the molar ratio of styrene to TBHP is 1: 1, the reaction time is 8 h, the conversion of styrene is 53.8% and the selectivity of epoxy-phenylethane is 82.6%. In addition, the reaction mechanism was preliminarily speculated.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB383.1;O621.251

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本文編號：2089225