【作者】 张海涛；

【导师】 王延吉；

【作者基本信息】 河北工业大学 ， 化学工艺， 2004， 硕士

【摘要】 针对铂炭催化剂存在难以分离和回收问题，分别采用等体积浸渍和微乳液法制备了SiO₂负载的Pt金属催化剂，并将其用于硝基苯催化加氢合成对氨基苯酚反应。同时研究了用醋酸溶液代替硫酸溶液的对氨基苯酚合成新工艺。初步探讨了由硝基苯直接制备对乙酰氨基酚反应工艺过程。 对于等体积浸渍法制备的Pt/SiO₂催化剂，考察了具有不同纹理组织的SiO₂载体、浸渍液pH值、干燥过程、焙烧温度及还原条件等制备因素对催化剂结构及合成对氨基苯酚反应性能的影响规律。由此确定了适宜的Pt/SiO₂催化剂制备条件。XRD和TEM表征结果表明，经焙烧再还原的催化剂Pt晶粒的粒径明显大于直接还原催化剂的Pt粒径，后者的催化活性高于前者。研究了Co、Mo、Ru、Ba等金属助剂对Pt/SiO₂催化剂性能的影响，发现Pt-Co/SiO₂催化剂具有较高的活性，对氨基苯酚收率为81.4％。 采用微乳液法制备出了Pt-SiO₂超细粒子催化剂。考察了微乳液体系、制备温度、氨水比例、负载量及水与表面活性剂比值等制备因素对Pt-SiO₂催化剂结构与催化性能的影响规律。确定了适宜的制备条件，其对氨基苯酚的收率为55.7％，此催化剂单位表面积的比活性高于浸渍法制备的Pt/SiO₂催化剂。并且通过XRD、TEM表征发现微乳液法制备的Pt-SiO₂催化剂具有较高的热稳定性，高温下抗烧结能力强。 考察了Pt/SiO₂催化剂上硝基苯催化加氢合成对氨基苯酚反应的工艺条件。选择十六烷基三甲基溴化铵为相转移催化剂，其适宜用量为硝基苯用量为0.8wt％；催化剂适宜的Pt负载量为3wt％，催化剂与原料用量比为1：20（质量比）；适宜的反应条件：反应温度为85℃，反应时间为4h，H₂SO₄浓度为17.5wt％，原料与H₂SO₄用量比为1：20（体积比）。在此条件下，Pt/SiO₂催化剂上对氨基苯酚收率为78.8％。催化剂使用后有失活现象，经原子吸收、XPS、SEM及比表面分析确定了失活原因。对催化剂进行再生处理后，套用5次，活性没有下降。 基于清洁化工生产的要求，提出了取代硫酸，在醋酸溶液中进行硝基苯催化加氢合成对氨基苯酚新工艺。考察了醋酸浓度、助剂等因素对对氨基苯酚收率的影响，其收率最高为50.2％。并探讨了硝基苯直接合成对乙酰氨基酚新工艺过程，其收率目前仅为7.6％，但工艺本身简化了分离过程。更多还原

【Abstract】 In order to resolve the problem of separation and recovery of Pt/AC catalyst, impregnation and microemulsion methods were used to prepare SiO2-support metal Pt catalysts, which were used in the hydrogenation of nitrobenzene to prepare p-aminophenol (PAP). Meanwhile, the new technology of synthesizing PAP from nitrobenzene by employing acetic acid solution instead of sulfuric acid solution was studied. An preliminary exploration of the reaction from nitrobenzene directly to p-acetamidophenol (APAP) in acetic acid solution was made.As for Pt/SiO2 catalysts which were prepared by incipient impregnation, effects of various factors during the preparation precess, such as SiO2 supports with different texture, pH value of impregnation solution, drying process, calcination temperature and reduction conditions, on the structures and catalytic performances were investigated. The suitable conditions for preparing the catalysts were confirmed. The characterisation results of XRD and TEM indicated that the size of Pt particle directly reduced without calcination was obviously smaller than that calcined before reduction, and the activity was higher. In addition, the effects of different promoters such as Ru, Mo, Ba, Co on the performance of Pt/SiO2 catalyst were investigated. The results showed that performance of Pt-Co/SiO2 catalyst was better, and the yield of PAP was 81.4%.A series of ultrafine Pt-SiO2 catalysts were prepared by microemulsion method. Effects of different microemulsion systems, preparation temperature, NH4OH aqueous solution amount, Pt loading and the molar ratio of water to surfactant on the structures and catalytic performances of Pt-SiO2 catalysts were investigated. The optimal conditions for preparing the catalysts were confirmed, and the yield of PAP could reach 55.7%. The specific activity on per-unit surface of the Pt-SiO2 catalysts was higher than that of the Pt/SiO2 catalysts prepared by incipient impregnation. The characterisation results of XRD and TEM showed that the Pt-SiO2 catalyst prepared by microemulsions method had higher heat stability and the resistance to sintering in high temperature than the Pt/SiO2 catalysts prepared by incipient impregnation.The reaction conditions for catalytic hydrogenation of nitrobenzene to p-aminophenol wasinvestigated. CTAB was chosen as the phase transfer catalyst, whose optimal amount was 0.8(wt) percent of nitrobenzene. The optimal loading of Pt was 3wt%, and the weight ratio of the catalyst to nitrobenzene was 1:20. The optimal reaction conditions were as follows: reaction temperature 85 ℃, reaction time 4h, concentration of sulfuric acid 17.5wt%, the volume ratio of nitrobenzene to sulfuric acid 1:20. Under the above-mentioned conditions, the yield of PAP reached 78.8%. The catalyst showed a partial deactivation after reaction. The characterisation results showed that the reason for deactivation might attribute to the active centers on the surface of the catalyst being partially encapsulated by organic substances in the course of reaction. However the activity of the catalyst which had been regenerated did not drop after employed for five runs.For the sake of clean chemical production, the new technology of synthesizing PAP from nitrobenzene by employing acetic acid instead of sulfuric acid solution was studied. Effects of concentration of acetic acid solution, promoters on the reaction were investigated, and the maximal yield of PAP reached 50.2%. A preliminary exploration of directly synthesizing p-acetamidophenol from nitrobenzene in acetic acid solution was made. Although the yield of APAP was only 7.6% at present, the new technology simplified the separating operation.更多还原