【作者】 顾颖颖；

【导师】 单永奎；

【作者基本信息】 华东师范大学 ， 物理化学， 2007， 博士

【摘要】 苯酚是重要的化工原料，它是制双酚A、酚醛树脂、尼龙—6及其它许多化合物的前驱体，因此工业需求量非常大。目前工业合成苯酚的最主要方法是异丙苯法，此法经过三个步骤：以苯和丙烯为原料，在酸催化下生成异丙苯，异丙苯经氧化生成过氧化氢异丙苯，再用硫酸或树脂分解，同时得到等摩尔的苯酚和丙酮。但是丙酮的市场需求量的增长远小于苯酚，因此以此法合成苯酚受丙酮市场的制约。由于多步合成苯酚的方法需要加入酸及多种有机试剂，这不仅浪费了大量资源，还造成了环境污染等问题，不符合可持续发展的战略。所以近年来作为一条比较经济的路线，以苯为原料经过一步氧化，直接羟基化生产苯酚的反应吸引了各国研究者的广泛关注，这也是催化化学中最为艰难、最具有挑战性的研究课题之一。为了实现苯酚合成过程的绿色化，本文选择了最具有经济效益和环境效益的一步合成法，在液相条件下以苯为原料合成苯酚。并且选择了来源最为广泛、最为廉价、不会对环境造成任何污染的分子氧作为氧化剂。本文设计合成了一系列多相催化剂，研究了这些催化剂对苯羟基化反应的催化性能，并寻找出苯羟基化反应的最佳条件。这种一步合成法不仅大大简化了目前的工业合成途径，可以大量节省原材料，从而有效地降低生产成本；而且使用分子氧的苯羟基化反应的苯酚选择性几乎能达到100％，所以对环境造成伤害非常小。所合成的这些多相催化剂在这种一步苯羟基化反应中具有很高的催化活性和选择性，因此具有一定的工业应用前景。通过水热法合成了铁、钒双金属取代的SBA-15分子筛。经过XRD、TEM、N₂吸附-脱附的表征，证实了该材料具有高度有序的二维六方介孔结构；ESR和紫外可见光谱结果证明了在SBA-15分子筛中所参杂的Fe和V物种都以高度分散的四配位状态存在于分子筛的骨架中。通过对苯的催化羟基化反应的研究发现FVS分子筛在用分子氧为氧化剂，抗坏血酸为还原剂的液相苯羟基化反应体系中是非常高效的催化剂，当反应温度为70℃，反应时间为5小时，其选择性为100％，苯酚的产率达到了14.5％。以水热法合成的负载型VOx／CuSBA-15分子筛作为催化剂，以分子氧为氧化剂，抗坏血酸为还原剂对苯的羟基化反应进行了研究。实验证明VOx／CuSBA-15分子筛是非常高效的苯羟基化反应的催化剂，在其作用下，苯酚的产率能达到约27％，苯酚的选择性高于99.6％。VOx／CuSBA-15催化剂对苯的羟基化反应具有两个专一性：（1）对反应底物具有专一性，它能选择性地催化苯的氧化使之生成为苯酚，却不能进一步催化氧化苯酚生成相应的醌或二酚；（2）对氧化剂具有专一性，它能够催化分子氧的活化使之与苯发生反应，但是不能使双氧水有效地与苯发生反应。同时负载了铜和钒的催化剂比单组分负载的催化剂或其他过度金属负载的催化剂有更高的催化活性，这表明铜和钒的氧化物可能存在协同催化作用。在VOx／CuSBA-15分子筛催化的苯羟基化反应中生成了羟基自由基，而羟基自由基是由分子氧直接活化而得到的，并且催化活化分子氧的反应可能是该反应的速控步骤。尝试了三种不同的配合物作为苯羟基化反应的催化剂，均表现出了很高的催化活性和对苯酚的选择性。在[Fe^Ⅱ（edta）]的催化作用下苯酚的产率达到18.8％，选择性为100％；在这三种配合物中VO（phen）的催化活性最高，苯酚的产率能达到20.8％，选择性为99.0％；Fe^Ⅱ酞菁和SBA-15负载的V，Cu酞菁催化剂在金属酞菁类催化剂中的活性最高，苯酚的产率分别为12.9％和12.4％，选择性均为100％。金属酞菁催化剂由于活性组分不会流失，易于与反应体系分离和重复利用等特性，表现出较好的工业应用前景。用高真空浸渍法成功地合成了Keggin结构的杂多酸纳米粒子。通过透射电镜、XRD、BET、红外、核磁等表征证明了杂多酸纳米颗粒的粒径大约为20nm。这些纳米粒子保持了很完整的Keggin结构，比普通杂多酸晶体拥有更高的酸度和更多的酸位。但是通过高真空浸渍法不能很有效地在大孔SBA-15分子筛孔道内定向制备杂多酸纳米粒子。利用定向自组装法合成策略成功地在大孔SBA-15分子筛的孔道内定向制备了平均粒径大约为20nm的杂多酸纳米粒子。通过表征证明了该方法利用杂多酸醚合物的水解反应作为运送纳米粒子构建单元的推动力定向原位自组装合成了高纯度的Keggin结构杂多酸纳米颗粒。利用定向自组装法合成的Keggin结构的磷钼钒杂多酸纳米粒子对苯的羟基化反应表现出了很高的催化活性，所得到的苯酚产率为16.2％，是普通磷钼钒杂多酸活性的3倍。磷钼钒杂多酸有机盐纳米粒子具有和杂多酸纳米粒子相当的催化活性，并且杂多酸有机盐不溶于水，催化剂的活性组分不发生流失。使用过渡金属作为磷钼钒酸盐的阳离子能进一步提高杂多化合物纳米催化剂的活性，MnPMo₁₀V₂／SBA-15催化该反应将苯酚的产率提高到了18.1％，这个结果高于已报道杂多化合物催化剂的2倍以上。更多还原

【Abstract】 Phenol is an important chemical in industry, as an intermediate for biphenol A, phenol-aldehyde resins, nylon-6, etc. It’s mainly produced by cumene peroxidation process, which requires three steps of reactions and is limited by the market requirement of equimolar byproduct acetone. Because it needs many kinds of acid and organic reagents, cumene peroxidation process brings the problems of wasting materials and environment pollution. For economical and ecological environment reasons, the one-step direct hydroxylation of benzene with cleaner and cheaper oxidants becomes one of the most exciting challenges of catalytic chemistry.In this dissertation, we studied the one-step hydroxylation of benzene to form phenol with an environmentally safer and cheaper oxidant, molecular oxygen. Several heterogeneous catalysts were designed and thus synthesized for benzene hydroxylation using molecular oxygen in presence of ascorbic acid. These catalysts performed highly catalytic activation and nearly 100% phenol selectivity was obtained in all the cases. Therefore, this catalytic process is environmentally benign, which may be a prospective chemical process in industry.Iron and vanadium substituted SBA-15 was synthesized to catalyze hydroxylation reaction of benzene. Well ordered hexagonal arrays of 1D mesoporous channels and 2D P6mm hexagonal structure was confirmed by XRD, TEM, N₂ adsorption-desorption and the existing of highly dispersive tetrahedral coordinated Fe and V species were proved by ESR and UV-vis spectrum. This material possessed highly catalytic activity for benzene hydroxylation using molecular oxygen as oxidant. The yield and the selectivity of phenol were obtained of 14.5% and 100%, respectively.The VOx/CuSBA-15 catalyst was synthesized to catalyze hydroxylation of benzene. A high yield of phenol was achieved at 27% with the selectivity of nearly 100%. The VOx/CuSBA-15 possessed two specialties: （1） it selectively catalytically activated dioxygen molecules rather than H₂O₂, （2） it selectively catalyzed benzene hydroxylation to form phenol, but phenol could hardly react under certain reaction condition. Both copper and vanadium oxide supported catalyst had a prominently catalytic performance toward the benzene hydroxylation comparing to other bi-transition metal oxides or monometallic supported catalysts, which suggested there might be a cooperation between copper and vanadium oxide on the support. It is believed that benzene hydroxylation over V0x/CuSBA-15 catalyst occured through the hydroxyl radical pathway without the participation of H₂O₂, and catalytic activation of molecular oxygen to form hydroxyl radical would be a rate determingstep.Three complex catalysts were studied for benzene hydroxylation. The benzene conversion and phenol selectivity were obtained of 18.8% and 100%, respectively, over [Fe^II（edta）] catalyst using molecular oxygen as an oxidant. VO（phen） performed very high catalytic activation toward benzene hydroxylation, over which benzene conversion and phenol selectivity were obtained of 20.8% and 99.0%, respectively. The metallophthalocyanines were the most prospective catalysts. Although the benzene conversions were not higher than 13%, the metallophthalocyanines did not dissolve in the reaction solution and the catalytic activation did not decrease after being reused 3 times.Heteropoly acid nanoparticles were successfully assembled by the novel vacuum impregnation method. High vacuum (10^-7Torr) pretreatment was applied for clearing water molecules, nitrogen and other contaminations from the pores of the SBA-15 in order to provide more capacity and to finish crystallization of heteropoly acid at relatively low temperature. Highly pure Keggin structural heteropoly acid nanoparticles with diameter around 20nm both inside and outside the pores of SBA-15 were obtained.Another novel method was developed to get heteropoly acid nanocrystals controlled directionally self-assembled in large-pore SBA-15 successfully, in which the chemical reaction of hydrolysis was used as main driving force for transportation of the guest. The utilization of the large-pore SBA-15 as a host, the method of high vacuum (10^-7Torr) and the water saturated channels of SBA-15 ensure that the number of heteropoly acid molecules incorporated in the pores would be plenty enough for the formation of nanoparticles. The selection of an appropriate extraction solvent guaranteed the higher purity of heteropoly acid nanoparticles within the channels of mesoporous silica SBA-15. Through this method, highly pure Keggin structural heteropoly acid nanoparticles with diameter around 20nm inside the channels of SBA-15 were obtained.The nano-heteropoly compounds possessed highly catalytic activation toward benzene hydroxylation using molecular oxygen as an oxidant. Phenol yield of 16.2% was obtained over nano-molybdovanadophosphoric acid, which was 3 times of that over bulk molybdovanadophosphoric acid. The MnPMo₁₀V₂/SBA-15 catalyst promoted the phenol yield to 18.1% with the selectivity of 100%. The catalytic activation was much higher than the reported heteropoly compounds.更多还原