【作者】 罗云；

【导师】 毛建新；

【作者基本信息】 浙江大学 ， 化学， 2011， 硕士

【摘要】 Friedel-Crafts反应是一类重要的酸催化反应,传统催化工艺通常是以液体酸为催化剂的均相反应体系。虽然传统液体酸的催化效果很好,但是却不符合绿色化学的要求。因此,人们致力于研究无污染、可反复使用的催化剂来代替它。固体酸是一类环境友好型催化剂,研究其在Friedel-Crafts反应中的应用具有重要的理论意义和应用前景。近年来,含铌催化材料逐渐受到研究者们的重视。含铌固体酸具有高活性、高选择性和高稳定性,并能有效提高催化剂的疏水作用从而可以应用于含水的反应体系,是固体酸材料开发的一个新的研究方向。尽管人们对含铌催化剂表现了极大的兴趣,并作了大量的研究,但到目前为止,人们对铌的理解和认识还不多。本论文主要研究含铌负载型分子筛及含铌杂多酸催化剂分别在对甲氧基苯酚与甲基叔丁基醚间的反应、对苯二酚与叔丁醇间的反应中的应用,对催化剂的性质作了系统的表征,并探讨了酸催化作用下的反应规律。主要的研究内容和结果如下：1.制备得到两个系列含铌元素的固体酸催化剂。一个系列是用浸渍法将不同含量的Nb205负载到H-DAY分子筛上；另一个系列是通过焙烧和酸处理方法合成了H1-xNb1-xM1+xO6 (M=Mo、W)固体酸催化剂。利用BET, XRD, Raman, NH3-TPD, SEM, TG等分析手段,对催化剂进行了表征。结果表明：①利用浸渍法将Nb205负载到H-DAY分子筛上,经高温焙烧后Nb205以正交型存在。负载型Nb205/DAY的比表面积、孔容和总酸量均随着负载量的增加而下降。②催化剂HNbWO6表现出明显的层状结构,而H1-xNb1-xMo1+xO6呈不规则的层状结构。层状结构有利于反应物和催化剂之间的插层效应。焙烧和酸处理过程对催化剂结构和性质具有重要影响,H1-xNb1-xMo1+xO6系列催化剂的总酸量随着元素Nb的含量增加而增加,但是当元素Nb的量增加到一定程度时酸量反而下降。2.H-DAY分子筛在对甲氧基苯酚(MOP)和甲基叔丁基醚(MTBE)反应中具有明显的催化作用,文中详细讨论了反应条件对转化率、得率或选择性的影响,并研究了铌负载型分子筛催化本反应的情况。对这一反应主要的研究结果如下：①分子筛的孔大小和酸量是影响反应的关键因素。若分子筛的孔径大于反应物分子和产物分子直径,催化剂的酸量越大,反应活性越高；而当分子筛的孔径小于反应物分子和产物分子直径时,催化剂的活性取决于外表面的酸中心。②H-DAY催化作用下,过量的催化剂会增大再烷基化的程度,不利于3-叔丁基羟基茴香醚(3-TBHA)的生成；3-TBHA的选择性与原料MTBE/MOP摩尔比成反比。通常较低的反应温度和较短的反应时间对于生成3-TBHA的选择性较高,但是此时反应的转化率不高,因此为了得到较高得率的3-TBHA,可以适当提高温度并缩短反应时间。③Nb205的负载量对主产物3-TBHA的选择性有很大影响,当负载量为59%时,主产物3-TBHA的选择性和得率最高。3.分别以对甲氧基苯酚及对苯二酚(HQ)的烷基化为模型反应,系统地研究了H1-xNb1-xM1+xO6 (M=Mo、W)催化剂催化上述两种反应的变化规律。主要的结果为：①在H1-xNb1-xM1-xO6 (M=Mo、W)催化作用下,对苯二酚的叔丁化反应比对甲氧基苯酚的更容易进行,叔丁醇(TBA)作为烷基化试剂的反应效果比MTBE更好。对苯二酚和叔丁醇反应主要生成2-叔丁基-1,4-对苯二酚和2,5-二叔丁基-1,4-对苯二酚,以及4-叔丁氧基苯酚。②H1-xNb1-xMo1+xO6 (x=-0.1～0.3)系列催化剂催化上述两个反应的活性规律相同,其中当x=-0.05时,即H1.05Nb1.05Mo0.95O6,其催化活性最高。③在HNbWO6催化作用下,对苯二酚和叔丁醇反应主要生成醚类产物4-叔丁氧基苯酚,在某些条件下会生成较少量的2-叔丁基-1,4-对苯二酚和2,5-二叔丁基-1,4-对苯二酚。④进一步考察了在HNbWO6催化作用下,反应温度、反应物摩尔比和酸处理对对苯二酚叔丁基化反应的影响规律,发现低温有利于O-烷基化产物生成,高温有利于C-烷基化产物生成；HQ/TBA摩尔比为5时,HQ的转化率最高；酸处理中的酸种类对催化剂影响不大。更多还原

【Abstract】 Friedel-Crafts reactions are a kind of important acid catalyzed reactions, which usually take place in the presence of homogeneous catalysts. Although these catalysts are effective in catalysis, they do not accord with the principles of green chemistry. Therefore, it is significant to endeavor to investigate new solid acid catalysts which are environment-friendly in Friedel-Crafts reactions.Recently, niobium-containing materials have attracted more and more attention. They are becoming a new research field of solid acid materials due to their strong hydrophobic characteristic which is in favor of those aqueous systems and high acidity, high selectivity, acceptable stability. During the past decades, an increasing interest and large amounts of researches have been brought in niobium-containing materials, but so far, the understanding of the nature of niobium-containing materials is limited.In the present paper, the reaction of p-methoxyphenol with methyl t-butyl ether, hydroquinone with tert-butanol over supported niobium zeolites and niobium-containing metal oxides were investigated, and the catalysts were characterized by various spectral and physicochemical techniques. The effects of reaction conditions and reaction mechanisms catalyzed by solid acid were further discussed.The main contents and results were as follows:1. Nb2O5 supported on H-DAY zeolites and H1-xNb1-xMo1+xO6 (M=Mo, W) catalysts were prepared separately by impregnation and calcination method with subsequent acid treatments respectively. Their physicochemical properties such as dispersion, specific surface area, and so on were characterized by X-ray diffraction (XRD), N2 adsorption BET, Scanning electron microscopy (SEM) and Raman spectrum. The results showed that:①Nb2O5 was successfully supported on H-DAY zeolites by impregnation method, which exhibited orthorhombic crystals. The surface area, pore volume and acid amount of the synthesized Nb2O5/DAY decreased with the niobium content.②HNbWO6 showed obvious layered structures, but there were irregular layered structures observed in H1-xNb1-xMo1+xO6 samples. Layered structure was beneficial to the intercalation effect in the substrates.Calcination and acid treatment influenced the structures and characters of the catalysts. The acid amount increased with increasing Nb concentration in H1-xNb1-xMo1+xO6 samples.2. H-DAY zeolite was effective catalysts for the reaction of p-methoxyphenol with methyl t-butyl ether, this paper focused on discussing of the effect of reaction conditions on the Conversion, Yield or Selectivity. In addition, the alkylation of p-methoxyphenol under supported niobium zeolites was studied. The main results were as follows:①Both the pore size and acid amount were critical to the reaction activity. The more the acid amount, the higher the reactant activity as the pore size of zeolite is bigger than the diameter of products. When the pore size is smaller than the diameter of products, the surface acid site is crucial.②The reaction conditions of p-methoxyphenol over H-DAY zeolite are optimized. It showed that too large amounts of catalysts were not favorable to the forming of 3-TBHA; the selectivity of 3-TBHA decreased with the increasing of the molar ratio of MTBE/MOP; higher selectivity to 3-TBHA was usually obtained at lower temperature and shorter time, whereas a lower conversation was following. Therefore it was better to increase reaction temperature and shorten reaction time in order to obtain a higher yield of 3-TBHA.③The catalytic activity was significantly influenced by the loading of niobium oxide.59% was considered as the appropriate loading when the main product (3-TBHA) had the best selectivity and yield.3. Reaction of p-methoxyphenol and hydroquinone was studied systematically over H1-xNb1-xMo1+xO6 (M=Mo, W). The main results were as follows:①Metal oxide H1-xNb1-xMo1+xO6 samples were recognized as the suitable catalysts for butylation of hydroquinone, and TBA served as a more excellent alkylating agent than MTBE in this condition.②The regulation in butylation of p-methoxyphenol catalyzed by H1-xNb1-xMo1+xO6 (x=-0.1-0.3) was corresponded with that in butylation of hydroquinone. H1.05Nb1.05Mo0.95O6.was found to function as the most active solid acid catalyst among H1-xNb1-xMo1+xO6 compounds.2-tert-butyl-1,4-hydroquinone and 2,5-di-tert-butyl-1,4-hydroquinone with little 4-tert-butoxy-phenol were synthesized via hydroquinone and tert-butyl alcohol.③O-alkylation product 4-tert-butyloxy-phenol was synthesized as the main product via hydroquinone with tert-butyl alcohol over layered HNbWO6. A little 2-tert-butyl-1,4-hydroquinone and 2,5-di-tert-butyl-l,4-hydroquinone were found in some conditions.④lkylation of hydroquinone with TBA was carried out by varying different parameters such as temperature, molar ratio of TBA to HQ, and acid treatment under layered and protonated HNbWO6. It showed that a relatively low reaction temperature was helpful to the formation of O-alkylation product, and a high temperature benifited the C-alkylation products. The maximum conversion of HQ was obtained when the molar ratio of TBA to HQ was 5. The kinds of acids in treatment played an inconsequential role in catalytic activity of catalysts.更多还原