【作者】 朱庆才；

【导师】 沈本贤；

【作者基本信息】 华东理工大学 ， 化学工艺， 2010， 博士

【摘要】 过氧化二异丙苯(DCP)是一种最常用的优良有机过氧化物,可作为单体聚合的引发剂、高分子材料的硫化剂、固化剂和阻燃添加剂。在DCP的生产过程中,通过过氧化氢异丙苯(CHP)制备二甲基苄醇(CA)是此生产工艺的关键步骤。目前工业上普遍采用硫化碱还原CHP来制备CA,但是此方法的原子利用率较低,而且会产生大量的含硫废水,造成环境的污染。随着国家环保政策的日益严格,其发展必将受到严格的制约。纵观所有可能的替代工艺,催化加氢技术以其原子经济性、绿色环保性及低运行成本而成为最有可能实现的替代工艺。本文采用常规浸渍法设计和制备了一系列负载型Pd催化剂并在滴流床反应器上进行了活性评价,同时借助N2低温吸附脱附(BET)、电感耦合等离子体发射光谱(ICP-AES)、X-射线衍射(XRD)、透射电镜(TEM)、热重分析(TGA)、紫外可见光谱(UV-vis)、红外光谱(IR)、CO化学吸附、程序升温还原(H2-TPR)等表征手段系统地考察了载体(Al2O3、活性炭、MgO)、Pd前驱体盐(K2PdCl4、Pd(NO3)2、(NH4)2PdCl4)、还原剂(甲醛溶液、氢气)、Pd负载量及制备条件等因素对负载型Pd催化剂物理化学性质及反应性能的影响,研究了催化剂的稳定性及失活原因。研究结果表明,以K2PdCl4水溶液浸渍AlOOH后在空气中600℃焙烧,氢气中300℃还原所得的0.5wt%Pd／Al2O3催化剂的活性及稳定性最好。另外还发现CHP液相加氢是一个结构敏感性反应,催化活性随Pd金属分散度的增大(Pd颗粒尺寸减小)而减小。在排除内扩散影响的前提下考察了滴流床反应器上Pd／Al2O3催化CHP液相加氢的反应动力学行为。研究结果表明,在高的液时体积空速下CHP液相加氢是关于CHP浓度的零级反应,反应活化能为12.4kJ／mol；在低的液时体积空速下CHP液相加氢则是关于CHP浓度的一级反应,反应活化能为10 kJ／mol。在此基础上,建立了不同液时体积空速时CHP液相加氢的Rideal-Eley机理模型并通过计算得到了各参数值。同时,本文借助ICP-AES、XRD、TEM和TGA等表征手段对Pd／Al2O3催化剂的失活原因进行了研究,结果表明活性金属Pd表面在反应中发生氧化是造成催化剂活性下降的主要原因。除此之外,本文还考察了原料气组成、反应温度及氢气压力对催化剂失活的影响并建立了催化剂的失活动力学方程。研究结果表明原料气中若含有CO则可使催化剂的活性快速下降,但通过高纯氢气吹扫可使催化剂活性完全恢复,是一种可逆中毒；反应温度越高,催化剂的剩余活性越小；氢气压力越高,催化剂的剩余活性越大。催化剂的再生研究表明,对失活的催化剂进行原位高温还原可恢复其活性。为了满足工业化生产的需求,本文对滴流床反应器上CHP液相加氢的工艺条件进行了优化。在氢油体积比240、液时体积空速5h-1、反应温度65℃、氢气压力1.5MPa的优化工艺条件下,其加氢产物分布与工业上由硫化碱还原CHP的产物分布基本一致,而且催化剂的寿命大于1000h。最后,本文还对滴流床单管反应器进行了设计及参数敏感性研究,为CHP液相加氢制备CA的工业化生产提供了依据。更多还原

【Abstract】 Dicumyl peroxide (DCP) is widely applied as a cross-linking agent for polyethylene (PE), ethylene vinyl acetate (EVA) copolymer, ethylene propylene terpolymer (EPT), and as a curing agent for unsaturated polystyrene (PS). Preparation ofα-cumyl alcohol (CA) from cumene hydroperoxide (CHP) is the key reaction in producing DCP. As current technology, sufide sodium (Na2S) or sufite sodium (Na2SO3) was adopted to reduce CHP to CA. It is a simple process with high conversion for CHP and selectivity to CA. However, it is a stoichiometric reaction with low atom-efficiency and generates large amounts of sulfide-containing water. Increasingly stringent legislation on environmental protection has restricted the development of this process. More economical as regards costs and environmental protection is the reduction of CHP by means of hydrogen with the aid of a catalyst.A series of supported Pd catalysts for CHP liquid phase hydrogenation to CA have been designed and prepared by impregnation, using various supports (Al2O3, Activated Carbon, MgO), precursors (K2PdCl4, Pd(NO3)2, (NH4)2PdCl4), reducing agents (formaldehyde, hydrogen), Pd content, calcination and reduction temperatures. All the catalysts were characterized by BET, inductively coupled plasma atomic emission spectrometry (ICP-AES), thermogravimetric analysis (TGA), X-ray diffraction (XRD), CO chemisorption, UV-visible spectroscopy, transmission electron microscory (TEM), temperature-programmed reduction (TPR) to correlate the physico-chemical properties with catalytic performance. The results showed that the 0.5wt%Pd/Al2O3 catalyst prepared by impregnation of AlOOH with K2PdCl4, calcinated at 600℃in air and reduced in hydrogen at 300℃exhibited the best catalytic activity and stability. Moreover, it was found that CHP hydrogenation was a structure-sensitive reaction, its activity can increase with Pd particle size.Kinetics of CHP hydrogenation to CA over Pd/Al2O3 catalyst in a trickle bed reactor was inverstigated. A mechanism was proposed for the hydrogenation of CHP. According to this mechanism, the step of hydrogen activated depends on the redox properties of the catalyst surface. High CHP concentration (LHSV) and low H2 pressure resulted in oxidized surface of Pd, leading to a zero-order with respect to CHP concentration in CHP hydrogenation. Low CHP concentration (LHSV) and high H2 pressure resulted in reduced surface of Pd, leading to a first-order with respect to CHP concentration in CHP hydrogenation. Based on the mechanism, the kinetics model has been established and the related parameters have been estimated. The activated energies were calculated to be 12.4 kJ/mol and 10.0 kJ/mol for zero-order and first-order reactions, respectively.Deactivation of Pd/Al2O3 catalyst in CHP hydrogenation in a trickle bed reactor was studied as well. It was found that the oxidation of Pd surface was the key factor for catalyst deactivation by means of ICP-AES, XRD, TEM and TGA. Moreover, the effect of composition of raw gas, reaction temperature, H2 pressure on the catalyst deactivation was also investigated. The results showed that CO in raw gas could result in catalyst deactication quickly. Luckily, the catalytic activity can be recovered by sweeping the catalyst with high pure hydrogen. Besides, a residual activity can be obtained in CHP hydrogenation, indicating deactivation of Pd/Al2O3 catalyst was reversible. Thus, the catalytic activity can be recovered by treating the spent catalyst in flowing pure hydrogen with relatively high temperature (300℃). Compared with temperature, H2 pressure has a more significant impact on the catalyst deactivation and residual activity. Higher residual activity can be obtained under higher H2 pressure. Kinetics of catalyst deactivation was established and the related parameters have also been evaluated.Based on the kinetics of CHP hydrogenation and catalyst deactivation, the optimized reaction conditions were obtained as follows:volume ratio of hydrogen to CHP solution=240, LHSV=5h-1, reaction temperature=65℃, H2 pressure=1.5MPa. Under the optimized reaction conditions, a similar product distribution was found when comparing hydrogenation and sufide reduction of CHP. Moreover, the catalyst showed a lifetime with 1000h and can be regenerated easily in flowing hydrogen gas. Finally, a one-pipe reactor suitable for industrial production was designed.更多还原