【作者】 周永华；

【导师】 叶红齐；

【作者基本信息】 中南大学 ， 化学工艺， 2008， 博士

【摘要】 多相催化选择加氢是石油化工、精细化学品合成中的重要反应。对于保持高催化活性的同时,也具有更高中间产物选择性的催化剂的研究,具有重大的工业应用价值。整体式催化剂由于其载体的结构化、相间传质效率高、孔内扩散路径短的特点,与传统的颗粒催化剂相比,在提高串联反应选择性方面表现出巨大潜力。本研究以整体式催化剂的特点为基础,探讨了以W/O微乳液合成的Pd纳米微粒为前驱物的Pd负载技术,实现了Pd纳米微粒在具有微米级孔径的多孔α-Al₂O₃陶瓷管上的直接负载,发展出了新型Pd整体式催化剂制备技术。以此为基础,将新型Pd整体式催化剂,应用于1,5-环辛二烯选择加氢制备环辛烯的研究,并考察了反应动力学。（1）微乳液体系与Pd纳米微粒的合成研究。考察了表面活性剂HLB值、含量、温度对Tween80-Span80及O13/80微乳液体系W/O相区的影响及微乳液稳定性随时间的变化,利用稳定的W/O微乳液合成并表征了Pd纳米微粒。结果表明,表面活性剂HLB为13、含量γ为0.20、水与表面活性剂的摩尔比ω₀为3-8、完全混合3小时之后,两种微乳液体系均为稳定的W/O微乳液。在反应温度30℃条件下,两种稳定的W/O微乳液中合成的Pd纳米微粒,粒径为3-10 nm,呈球形或近似球形,高度分散。O13/80微乳液采用含还原剂微乳液还原的方式,3分钟内即可反应完全;而Tween80-Span80微乳液则需采用还原剂水溶液还原的方式,才能实现较完全、快速的反应。（2）微乳液中Pd纳米微粒的化学破乳沉积研究。对Tween80-Span80、O13/80两种含Pd微乳液体系的化学破乳过程的研究表明,具有短链、强亲水性的甲醇、乙醇、四氢呋喃、丙酮,都可以使两种含Pd微乳液体系破乳,从而使Pd纳米微粒沉积。对Tween80-Span80微乳液体系而言,随着破乳剂用量的增大,混合体系依次呈现均相、分层及再均相的变化。破乳剂能显著降低内聚能比（R）,使W/O微乳液向双连续型微乳液转变。破乳剂使R降低的幅度顺序为:甲醇>乙醇>THF>丙酮。对O13/80微乳液体系而言,随着破乳剂用量的增大,混合体系一直为均相体系。不同破乳剂使Pd沉积速率顺序为:THF>丙酮>甲醇>乙醇。破乳剂作用下O13/80微乳液的两亲因子（f_α）逐渐降低,微乳液向无序混合物转变。与Tween80-Span80微乳液相比,O13/80微乳液体系合成Pd纳米微粒,是微乳液之间的还原反应,有利于保持整个体系的稳定性;化学破乳无明显相变,从高度有序的微乳液结构到无序混合物呈渐变过程,使得Pd微粒的沉积速率易于控制,为实现后续研究中Pd微粒在载体表面的均匀负载提供了条件。（3）Pd纳米微粒在载体上的负载研究。将含Pd纳米微粒的O13/80微乳液,对多孔α-Al₂O₃陶瓷管载体同时进行循环浸渍与化学破乳,实现了Pd纳米微粒在多孔α-Al₂O₃陶瓷管上的负载,制备了新型Pd整体式催化剂。考察了浸渍-破乳过程载体通量的下降与恢复,以及浸渍-破乳方式、焙烧温度对整体式催化剂上Pd形态、分布及负载量的影响。结果表明,乙醇与水交替洗涤、400℃焙烧,可以使由于浸渍-破乳造成的多孔载体下降的通量恢复95%。结合粉状α-Al₂O₃载体上负载的Pd微粒的TEM、XPS表征结果,对Pd整体式催化剂的SEM、XRD、AAS分析表明,负载后的Pd虽形成团簇,团簇中的Pd微粒还是基本保持了其在微乳液中的原始粒径;以Pd单质晶体形态均匀分布于载体孔结构中。微乳液浸渍-破乳技术制备的整体式催化剂上Pd负载量可达0.312%,10次负载量的方差小于0.06844。（4）Pd整体式反应器中的1,5-COD加氢反应研究。为便于比较,首先通过浆态床反应器优化了反应条件:正辛烷作溶剂、搅拌速率1600min^-1、反应压力1.0MPa、反应温度47℃、1,5-COD初始浓度0.4kmol.m^-3。接着重点考察了Pd整体式催化剂的制备条件与整体式反应器操作条件对催化活性与选择性的影响。结果表明,当载体孔径1.9μm、循环浸渍的同时缓慢递加乙醇使微乳液破乳、400℃焙烧、Pd负载量0.151%、流量420 ml/min条件下,Pd整体式催化剂具有最高的催化活性与选择性。进一步将Pd整体式反应器与浆态床、固定床反应器中的1,5-COD加氢反应效果进行了比较。结果表明,当1,5-COD完全转化时,整体式反应器与浆态床反应器中的COE选择性很接近（94.08%、95.10%）,都远远高于固定床反应器（70.04%）。这表明,与固定床反应器相比,Pd整体式反应器在提高选择性方面效果显著。理论分析显示,中间产物选择性的提高,源于整体式催化剂Pd分布层中停留时间及中间产物局部浓度的降低,从而使表观两步反应速率常数之比k_1eff/k_2eff著提高。（5）1,5-COD加氢反应动力学研究。针对浆态床反应器与整体式反应器中1,5-COD加氢反应实验结果,借鉴Santacesaria E的间接处理方法,提出了包含内、外效率因子的反应速率方程式模型很好地拟和了实验数据。采用空间自适应性粒子群优化算法（LAPSO）估算出了模型参数:k₁₀=14729.05; k₂₀=84.248; E₁=33.7 kJ.mol^-1;E₂=31.438 kJ.mol^-1。更多还原

【Abstract】 The multiphase selective hydrogenation is widely used in petrochemical and fine chemical industries. An important aim is to achieve high selectivity of intermediate product with an accepteable conversion rate. The monolithic catalyst shows great potential on the improvement of selectivity of series reactions campared with tranditional pellet catalyst in view of the structured support, high efficiency of intra-phase mass transfer and short diffusion path. Based on the feature of monolithic catalyst, the Pd immobilization technique with Pd nano particles synthesized by W/O microemulsion as precursor was investigated. The direct immobilization of Pd nano particles in porousα-Al₂O₃ ceramic tube was realized and a new preparation technique of Pd monolithic catalyst was developed in this study. In addition, the selective hydrogenation of 1,5-cyclooctadiene to cyclooctene was performed over the Pd monolithic catalyst.（1） Microemulsion systems and the synthesis of Pd nano particles therein. The effects on the W/O phase region of HLB value, content of surfactants and temperature as well as the stability of Tween80-Span80 and O13/80 microemulsion syetems were investigated. Then the Pd nano particles were synthesized in the stable W/O microemulsion. The results show that the stable W/O microemulsion can be obtained with the HLB value 13 and content 0.20 of surfactant, the mole ratio of water to surfactant 3 to 8 and 3 hours after completely mixing. The spherical or near spherical, with size 3-10 nm, well dispersed Pd nano particles can be synthesized at 30℃in the two types of microemulsion. To make reaction proceed rapidly and completely, the reductant-contaning microemulsion is adopted for O13/80 microemulsion. whereas the reductant solution must be adopted for Tween80-Span80 microemulsion.（2） Deposition of Pd nano particles in microemulsion by chemical-demulsifying. The chemical-demulsifying processes of Tween80-Span80 and O13/80 microemulsion systems contaning Pd nano particles were investigated. The results show that such agents as methanol, ethanol, THF and acetone can demulsify microemulsion and make Pd nano particles deposite because of their short chain structure and high hydrophilicity. As for Tween80-Span80 microemulsion system, the above demulsifying agents can greatly decrease the cohesion energy ratio（R） of microemulsion and lead to the transition to co-continuous structure in a sequence of methanol>ethanol>THF>acetone. As for O13/80 microemulsion system, the mixture of microemulsion and demulsifying agent remains homogeneous with the increase of the amount of demulsifying agents. The sequence of deposition rate of Pd nano particles from microemulsion is: THF>acetone>methanol>ethanol. The amphilicity of O13/80 microemulsion decreases gradually and is transformed into disordered mixture under the action of demulsifying agents.Compared with Tween80-Span80 microemulsion, during the process of Pd synthesis, it is more beneficial to maintain the stability of microemulsion in view of the reducing pattern. Meanwhile, no obvious phase transition is observed during the demulsifying process and it is a gradual process from highly ordered microemulsion to disordered mixture in O13/80 microemulsion Therefore it is easy to control the deposition rate of Pd particles, and more beneficial to the follwing Pd immobilization step on the support.（3） Immobilization of Pd nano particles in porousα-Al₂O₃ ceramic tube. To prepare Pd monolithic catalyst, the Pd nano particles were immobilized in porousα-Al₂O₃ ceramic tube by cycle-impregnating and chemical-demulsifying simultaneously. The decrease and recover of support flux during impregnation-demulsifying process as well as the effects on the phase, distribution and Pd loading amount of demulsifying pattern, and calcination temperature were investigated. The results show that the support flux can be recoved 95% through washing by water and ethanol alternatively and calcination at temperature 400℃. Combined with the results of TEM and XPS of Pd onα-Al₂O₃ powder and the results of SEM, XRD and AAS of Pd onα-Al₂O₃ monolithic support, it is demonstrated that, on the monolithic support, Pd nano particles form clusters which is composed of nano particles with original size in microemulsion. And Pd particles are well distributed in Pd crystalline phase in the pore structure of support. The Pd loading amount of monolithic catalyst can reach 0.312% and the square difference of ten times loading amount is lower than 0.06844.（4） Hydrogenation reaction of 1,5-COD over Pd monolithic catalyst. Firstly the optimized reaction conditions were obtained in SR（slurry reactor）: n-heptane as solvent, agitating rate 1600min^-1, reaction pressure 1.0MPa, reaction temperature 47℃and initial concentration 0.4 kmol.m^-3. The effects on activity and selectivity of preparation parameters and operating parameters were investigated. The results show that Pd monolithic catalyst exhibites the highest activity and selectivity with Pd loading amount 0.151%, dripping ethanol slowly at the same time cycle impregnation, calcination temperature 400℃, support with pore size 1.9μm and flow rate 420 ml/min.Comparing the catalytic performance in MR（monolithic reactor）, SR and FBR（fixed bed reactor） shows that the selectivity for COE in MR（94.08%） is near to that in SR（95.10%） and much higher than that in FBR（70.04%）. The theoretical analysis shows that the improvement of selectivity can be contributed to the decrease of staying time and the local concentration of intermediate product in active layer. Therefore the ratio of two step apparent reaction constants k_1,（eff）/k_2,（eff） is fairly increased.（5） Kinetics of hydrogenation reaction of 1,5-COD. The model of reaction rate equation including the intra- and inter-porous efficiencies was presented based on the experimental data in SR and MR and using the indirect method from Santacersaria E for reference. The model（?） can fitthe expenmental data well, The parameters in model were evaluated byLandscape adaptive particle swarm optimization（LAPSO） method k₁₀=14729.05; k₂₀=84.248; E₁=33.7 kJ.mol^-1;E₂=31.438 kJ.mol^-1.更多还原