纳米金功能化复合催化剂的制备、表征及其在选择性氧化中的应用

发布时间：2018-08-07 15:51

【摘要】：有机物选择性氧化涉及到化工生产诸多方面,在化学工业中占有重要的地位。但是有机物的选择性氧化过程由于存在较多的平行反应和串联反应,尤其是在高温条件下因催化剂不佳致副反应发生较为严重,使目标产物选择性降低。因此温和条件下高活性、高选择性催化氧化引起了广泛的重视,但也是一项具有巨大挑战性的课题。为此,本论文展开纳米金功能化复合催化剂的制备、表征及其在选择性氧化中的应用研究。论文分为七章,研究了锰卟啉金属有机骨架负载的纳米金催化剂Au/MnPS的制备、表征及其环己烯选择性氧化的反应性能;研究了以金为中心的金属有机框架催化剂AuBTC的制备、表征及其苯甲醇的选择性氧化性能;研究了内壁涂覆纳米金催化剂Au/Al_2O_3微通道反应器的制备及其环己烷选择性氧化性能。具体结论如下:首先,采用水热合成法和浸渍法成功制备了 Au/MnPS。该催化剂TEM表征显示MnPS晶体为深色立方晶体状结构,部分为浅色无定形絮凝状结构,存在大颗粒的金和粒径小于10nm的纳米金,说明纳米金被成功负载;XRD表征显示MnPS结构与碳酸锰相似,为进一步推测其真实结构提供了可能。Au/MnPS催化环己烯选择性氧化性能表明,反应溶剂,氧化剂,温度,反应时间,反应压力,催化剂用量,金负载量等工艺条件均对反应性能均有影响。对于釜内常压环己烯氧化而言,反应物环己烯量为10mmol,Au/MnPS金负载量为2wt%,催化剂用量为0.2g,乙腈为溶剂,含少量水的叔丁基过氧化氢为氧化剂,反应温度35℃,反应时间15h的工艺条件较佳,此时环己烯转化率最高为76.7%,环氧环己烷选择性为75.1%;对于釜内高压分子氧的环己烯氧化而言,反应物环己烯量为10mmol,Au/MnPS金负载量为0.25%,催化剂用量为0.1g,乙腈为溶剂,4-5滴TBHP为引发剂,反应温度120℃,反应压力1.2MPa,反应时间10h的工艺条件较佳,此时环己烯转化率最高为88.4%,环氧环己烷选择性为83.0%。该催化剂重复使用4次没有明显的活性损失,说明其具有较好的循环催化性能。然后,采用水热合成法成功制备了 AuBTC催化剂。该催化剂XRD表征显示其具有与HKUST-1(CuBTC)相似的晶体结构,金已形成其晶体结构;SEM表征显示,金和均苯三甲酸在水热合成后形成了一种新的晶体,这种晶体具有片层组成的柱状结构。AuBTC用于苯甲醇的分子氧选择性氧化反应性能研究表明,反应时间、反应温度、催化剂用量等工艺条件对反应催化性能均有影响。反应物苯甲醇量为10mmol,乙腈为溶剂,4-5滴TBHP为引发剂,催化剂用量为0.10g,反应时间为15h,反应温度为80℃,反应压力为1.0MPa的工艺条件较佳,此时苯甲醇转化率最高为11.8%,苯甲醛选择性为90.3%。该催化剂循环性能研究表明,催化剂重复使用后苯甲醛的选择性下降较快。最后,采用自主创新的内壁涂覆方法成功制备了内壁涂覆纳米金催化剂Au/Al_2O_3微通道反应器。Au/Al_2O_3催化剂的TEM和XRD表征显示催化剂内纳米金颗粒均匀分散于超细氧化铝载体;催化剂涂覆前后的微管内SEM表征显示酸洗微管内壁对于增强催化剂和管壁之间的结合具有一定的促进作用。反应温度为180℃,反应压力为3MPa,停留时间为4min,氧气和环己烷的气液摩尔比为0.3:1的工艺条件较佳,此时环己烷的转化率为2.09%,环己醇,环己酮,环己基过氧化氢和己二酸的选择性分别为29.4%,39.9%,2.46%和18.9%。实验表明不锈钢微管内涂覆负载型纳米金催化剂是可行的,并且能显著缩短反应的时间和提高反应操作运行过程的安全性。综上所述,纳米金功能化复合催化剂对于有机物的选择性氧化不但具有优良的效果和较大的工业应用潜力,而且具有很高的学术研究价值,值得进一步深入探究。
[Abstract]:Selective oxidation of organic matter is involved in many aspects of chemical industry and occupies an important position in the chemical industry. However, the selective oxidation process of organic compounds is due to the existence of more parallel and series reaction, especially in the high temperature conditions, which causes the adverse reaction of the catalyst to be more serious, so that the target product is selectively reduced. High activity and high selectivity catalytic oxidation under mild conditions have attracted wide attention, but it is also a very challenging task. For this reason, the preparation, characterization and application of nano gold functionalized composite catalysts were studied in this paper. The paper is divided into seven chapters. The load of manganese porphyrin metal organic skeleton is studied. The preparation, characterization of Au/MnPS and the selective oxidation of cyclohexene, the preparation of gold centered metal organic framework catalyst AuBTC, characterization and selective oxidation of benzyl alcohol, the preparation of Au/ Al_2O_3 microchannel reactor and its cyclohexane selection on the inner wall coated gold nanoparticle catalyst were studied. The specific conclusions are as follows: first, Au/MnPS. was successfully prepared by hydrothermal synthesis and impregnation. The TEM characterization of the catalyst showed that the MnPS crystal was a dark cubic crystal structure, part of which was light colored amorphous structure, and the gold and particle size of large particles were less than 10nm, indicating that gold nanoparticles were successfully loaded; XRD table. It shows that the structure of MnPS is similar to manganese carbonate, which provides the possible selective oxidation performance of.Au/MnPS catalyzed cyclohexene. The reaction solvent, oxidizer, temperature, reaction time, reaction pressure, the amount of catalyst, the amount of gold load and so on all have influence on the reaction performance. In addition, the amount of cyclohexene is 10mmol, the amount of Au/MnPS gold load is 2wt%, the amount of catalyst is 0.2g, acetonitrile is the solvent and the tert butyl peroxide containing a small amount of water is used as oxidant. The reaction temperature is 35 C and the reaction time 15h is better. At this time, the conversion rate of cyclohexene is the highest and the epoxide cyclohexane is 75.1%, and the height of the cyclohexane is 75.1%. As for cyclohexene oxidation, the amount of cyclohexene is 10mmol, the amount of Au/MnPS gold load is 0.25%, the amount of catalyst is 0.1g, the acetonitrile is the solvent, the 4-5 drop TBHP is the initiator, the reaction temperature is 120, the reaction pressure is 1.2MPa, the reaction time 10h is better, the conversion rate of cyclohexene is the highest at this time, and the epoxide cyclohexane is selective. 83.0%. the catalyst was reused for 4 times without obvious loss of activity, indicating that the catalyst had good cyclic catalytic performance. Then, AuBTC catalyst was successfully prepared by hydrothermal synthesis. The catalyst XRD showed that the catalyst had a crystal structure similar to HKUST-1 (CuBTC), and gold had formed its crystal structure; SEM characterization showed gold and average benzene. After hydrothermal synthesis of formic acid, a new crystal has been formed. This crystal has a lamellar structure of columnar structure.AuBTC used in the selective oxidation of benzyl alcohol by molecular oxygen. The reaction time, reaction temperature, and the amount of catalyst have an effect on the catalytic performance. The amount of benzyl alcohol in the reactant is 10mmol, acetonitrile. For the solvent, 4-5 drops of TBHP as an initiator, the amount of catalyst is 0.10g, the reaction time is 15h, the reaction temperature is 80, the reaction pressure is 1.0MPa, the conversion rate of benzyl alcohol is 11.8%, the selectivity of benzaldehyde is 90.3%., the cycle performance of the catalyst is clear, and the selectivity of benzaldehyde after the reuse of the catalyst is better than that of the catalyst. Finally, the TEM and XRD of the Au/Al_2O_3 microchannel reactor.Au/Al_2O_3 catalyst for the inner wall coated nano gold catalyst were successfully prepared by the internal wall coating method of independent innovation. The nano gold particles in the catalyst were uniformly dispersed in the ultrafine alumina carrier, and the inner wall of the acid washing microtubule was displayed by the SEM characterization in the microtubule before the catalyst coating. The reaction temperature is 180 C, the reaction pressure is 3MPa, the retention time is 4min, the gas and liquid molar ratio of oxygen and cyclohexane is better than 0.3:1, and the conversion rate of cyclohexane is 2.09%, cyclohexanol, cyclohexanone, cyclohexyl hydrogen peroxide and adipic acid are selected. The 29.4%, 39.9%, 2.46% and 18.9%. experiments showed that the coated nano gold catalyst coated with the stainless steel microtubule was feasible and could significantly shorten the time of the reaction and improve the safety of the operation process. In summary, the nano gold functionalized composite catalyst not only had good effect on the selective oxidation of organic matter. It has great potential for industrial application, and has high academic research value. It is worth further exploring.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ426

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