【作者】 于雪；

【导师】 张文祥； 王振旅；

【作者基本信息】 吉林大学 ， 物理化学， 2014， 博士

【摘要】 缩合反应在化学工业中是一类非常重要的反应，通过缩合反应获得的产物在日常生活及工业生产等领域中也都有非常广泛的应用，例如：乙酸乙酯和异戊二烯。乙酸乙酯是目前工业中重要的有机溶剂和化工原料，常应用于香料工业、食品工业、纺织工业中。异戊二烯是合成橡胶(SR)的重要单体，主要用于合成异戊橡胶(IR)、丁基橡胶(IIR)和苯乙烯-异戊二烯-苯乙烯嵌段共聚物(SIS)等。在缩合反应的工业生产中，主要选用液体酸作为催化剂，但是液体酸催化剂存在诸多缺陷，如：腐蚀设备，污染环境，分离和循环使用困难等。为了解决这些问题，人们尝试选用无腐蚀性、环境友好、可重复利用的金属氧化物及固体酸催化剂来取代液体酸催化剂。但是对于缩合反应在金属氧化物及固体酸催化剂上的催化性能、反应活性中心及机理以等方面还有待进一步改善和研究。基于上述情况，本论文主要开展了金属氧化物和固体酸催化剂的制备及表征等研究工作，并尝试将催化剂分别用于乙醇一步法合成乙酸乙酯反应以及异丁烯和甲醛气相缩合制备异戊二烯反应当中。同时通过各种表征手段研究了催化剂的结构及性质，并结合催化测试结果对反应活性中心及机理进行了研究和探讨。论文的主要研究内容和结果如下：一．Cu/SiO2催化剂在乙醇一步法合成乙酸乙酯反应中的研究采用氨蒸发法制备了一系列含有页硅酸铜物种的Cu/SiO2催化剂。表征结果发现，页硅酸铜物种的存在不仅可以提高铜物种的分散度、减小铜粒径，而且在还原过程中还可以还原为Cu+，为催化剂表面提供一定的L酸中心。在乙醇一步法合成乙酸乙酯反应中，乙醇转化率以及乙酸乙酯选择性都随着铜含量的增加呈现先增加后减小的趋势，当铜含量为23.7wt%时，乙醇的转化率和乙酸乙酯的选择性达到最大值，分别为65.3%，48.9%。将氨蒸发法与传统的浸渍法做对比，催化反应结果发现在氨蒸发法制备的Cu/SiO2催化剂上催化性能要高于传统的浸渍法。实验结果表明氨蒸发法制备的催化剂上Cu0的分散度以及Cu+物种的数目都要高于浸渍法制备的催化剂。结合文献和实验结果，我们认为Cu0和L酸中心之间的协同作用在反应中起到关键作用。二．Zr改性的Cu基催化剂在乙醇一步法合成乙酸乙酯反应中的研究采用浸渍法将Zr以助剂的形式加入到Cu/SiO2催化剂中，考察锆助剂对乙醇一步法合成乙酸乙酯反应催化性能的影响。实验结果发现，加入助剂Zr后，乙醇的转化率和乙酸乙酯的选择性都显著提高。当Zr含量达到15.3wt%时，乙醇的转化率和乙酸乙酯的选择性都达到最大值。表征结果表明，Zr的加入不仅能够提高CuO的分散度，限制Cu粒径的增长，还能为催化剂表面提供一定量的L酸和B酸中心(L: Zr4+, B: Zr-OH)。结合实验结果，我们对L酸和B酸中心上乙醇一步法合成乙酸乙酯的反应机理做了推测，认为Cu0和适量的酸性位相互配合有利于反应的进行。以ZrO2为载体，制备了Cu/ZrO2催化剂。并向Cu/ZrO2催化剂中加入碱金属Na、K以及碱土金属Mg，实验发现Mg助剂的加入可以提高乙酸乙酯选择性。但是Na、K对乙醇一步法合成乙酸乙酯反应并没有促进作用。NH3-TPD结果表明，碱金属和碱土金属的加入，会导致催化剂表面中心的酸强度有所降低，酸量也有所减少。我们认为Mg助剂可以中和催化剂表面一部分中等强度酸中心，减少副反应发生，进而提高乙酸乙酯的选择性。而Na、K的加入不仅中和了副反应所需的活性中心同时也减少了酯化中心，因此导致乙酸乙酯的选择性下降。三．改性的HZSM-5分子筛在异丁烯和甲醛气相缩合制备异戊二烯反应中的研究将高硅铝比的HZSM-5分子筛应用到异丁烯和甲醛气相缩合反应中。实验结果发现分子筛的硅铝比对催化剂的性能有一定的影响。随着硅铝比的提高，强酸中心逐渐减少，异戊二烯的选择性逐渐提高。我们认为催化剂表面上的强酸中心不利于异戊二烯的生成。经过P改性后，HZSM-5表面上的强酸中心消失，弱酸中心增加，异丁烯的转化率和异戊二烯的选择性显著提高。但是，过量的酸中心并不利于缩合反应的进行。选用其他金属对HZSM-5分子筛进行改性，发现催化剂表面的弱酸中心和强酸中心数目都有所提高，但是催化剂的催化性能并没有明显改善。我们认为催化剂表面酸量和酸强度与异丁烯的转化率和异戊二烯的选择性有关。适量的弱酸中心有利于异丁烯和甲醛缩合反应的进行。实验还将H-Y、H-beta、TS-1分子筛应用到异丁烯和甲醛反应当中。实验结果进一步说明适量的弱酸中心有利于异丁烯和甲醛缩合反应的进行，同时还证明，催化剂表面的酸类型与催化剂的催化性能没有直接关联。四．负载型杂多酸催化剂在异丁烯和甲醛气相缩合制备异戊二烯反应中的研究采用浸渍法制备了一系列负载型杂多酸催化剂，并将它们应用到了异丁烯和甲醛气相缩合制备异戊二烯反应中。通过对杂多酸种类和载体种类的考察，发现硅钨酸和SiO2分别为性能最佳的活性组分和最优的载体。实验还考察了硅钨酸/SiO2催化剂中硅钨酸负载量对催化性能的影响。结果得出，当硅钨酸负载量达到5wt%时，异丁烯的转化率和异戊二烯的选择性达到了最大值，分别为10.1%和89.8%。异丁烯的转化率和异戊二烯的选择性随着硅钨酸负载量的增加而增加，但当硅钨酸负载量达到一定值之后，异戊二烯的选择性反而有所下降，我们认为，催化异丁烯和甲醛缩合制备异戊二烯反应所需的酸量存在一个范围的定值，当高于这个范围的定值时，过多的酸量不一定有利于反应的进行。又以HSiW-10催化剂为例，考察了反应时间与催化剂表面酸量、酸强度变化及催化剂积碳变化情况之间的关系，实验结果发现，随着反应时间的延长，催化剂表面上的中强酸中心的数目逐渐减少，同时，催化剂的表面上伴有积碳形成。在反应1h内，催化剂的失重量最大，并随反应时间的延长失重量逐渐减小。我们认为，在反应初期，由于催化剂表面大量的中强酸中心存在，会导致一些副反应的发生，同时在催化剂表面形成积碳。而随着时间的延长，积碳又会覆盖中强酸中心，从而减少了副反应的发生，提高了主产物的选择性。更多还原

【Abstract】 The reactions for condensation are very important, and their products of ethylacetate and isoprene have a wide range of applications in various fields. Ethylacetate is an important chemical materials and a useful solvent that is widely used inperfume industry, food industry, textile industry, etc. Isoprene is the importantmonomer for synthetic rubber (SR), and it is mainly used for synthesis isoprenerubber (IR), butyl rubber (IIR) and styrene-isoprene-styrene block copolymer (SIS)etc.The liquid acid catalysts have many defects in reactions for condensation, suchas: corrosion of equipment, pollution of the environment, separation and recyclingdifficulties. A lot of research works have been carried out to solve these problems.The the metal oxides and solid acid catalysts have been used to replace liguid acidcatalysts, due to their advantages of non-corrosive, environmentally friendly,reusable. However, for the condensation reaction, the catalytic properties, activecenter, reaction mechanism over the solid acid catalysts still need furtherimprovement and research.The reaction of ethanol one-step synthesis to ethyl acetate and the vapor phasecondensation of isobutene and formaldehyde reactions have been investigated overmetal oxides and solid acid catalysis. The structure and surface texture of thecatalysts were studied with different characterization means. The active sites on thecatalysts and the reaction mechanism were also discussed combining with thecatalytic performance of catalysts. The main experimental results and conclusionsare as follows:1. Cu/SiO2catalysts for ethanol one-step synthesis to ethyl acetate Cu/SiO2catalysts, which contain copper phyllosilicate, were successfullyprepared using the ammonia-evaporation method. The formation of the copperphyllosilicate species significantly affected the structural properties and caused theCuO nanoparticles to become highly dispersed, and they would also provide accessto the Lewis acidic Cu+species. The Cu/SiO2catalyst with a23.7wt%copperloading exhibited the best ethanol conversion and ethyl acetate selectivity.Compared to the IM catalyst, the AE catalysts exhibited a much higherdispersion, a smaller copper particle size and a larger surface area, in addition to theformation of copper phyllosilicate, which could be reduced to Cu+. The AE catalystsexhibited superior ethanol conversion and selectivity for ethyl acetate formation inthe reaction of ethanol one-step synthesis to ethyl acetate. We proposed that thesynergistic effect of Cu0and appropriate amount of Lewis acidic sites generatedfrom Cu+cause this effect.2. The one-step synthesis of ethanol to ethyl acetate over Cu-based catalystsmodified by ZrA series of Cu/Zr/SiO2catalysts have been prepared through impregnationmethod. The introduction of Zr could not only improve the dispersion of CuO andrestrict the growth of Cu particle, but also provide a certain amount of acid L and Bacid sites for the surface of catalysts. We suggested that the synergistic effect of Cu0and amount of acidic sites was beneficial for the reaction.The Cu/ZrO2catalysts were modified by alkali metal and alkaline earth metal,the introduction of Mg could neutralize the medium strength acid sites, and inhibitthe occurrence of side reactions, enhance the selectivity of ethyl acetate. But, theaddition of Na, K decreased the selectivity of ethyl acetate, which may be due to thestrong basicity of Na and K, and reduced esterification center.3. Modified HZSM-5molecular sieves for the condensation of isobutene andformaldehydeThe high silica of HZSM-5zeolite applied in the vapor phase condensation reaction isobutylene and formaldehyde. Experimental results showed that Si/Al ratiohave a certain impact on the catalytic performance the catalysts. The selectivity ofisoprene increased gradually with the silica to alumina ratio increasing. We proposedthat the strong acid sites were not conducive to the generation of isoprene.The HZSM-5molecular sieves modified with transition metal and nonmetalwere prepared and successfully applied to the condensation of isobutene andformaldehyde. We found that the sample with P content of5wt%showed the bestcatalytic performance. The results suggested that appropriate amount of the weakacid sites could improve the condensation of isobutene with formaldehyde.Other acidic zeolites such as HY, H-beta, TS-1were also applied in the vaporphase condensation reaction isobutylene and formaldehyde. The results furtherillustrated that a appropriate amount of weak acids were in favor of the condensationreaction, and confirmed that the acid type was not related with the catalyticperformance directly.4. Supported heteropoly acid catalysts for the condensation of isobutene andformaldehydeThe type of heteropoly acids and supports had been filtered, and it was foundthe SiO2supported heteropoly acid catalysts showed high catalytic performance. Theconversion and selectivity were related with the concentration and strength of acidsites. Appropriate amount of the weak Lewis acid sites could improve thecondensation of isobutene with formaldehyde.The relationship between acidity of the surface catalyst and the coke depositshas been investigated. The side effects and coke deposits were caused by themedium-strong acid sites. The coke deposits could cover the moderately strong acidsites as the reaction continued which inhibited the side reactions and enhanced theselectivity to isoprene.更多还原