脱氢与加氢耦合的电化学氢泵双反应过程研究

发布时间：2018-04-11 05:25

  本文选题：电化学氢泵反应器 + 非均相催化加氢　； 参考：《大连理工大学》2016年硕士论文

【摘要】：近年来,生物质作为可持续能源受到广泛关注,越来越多的研究集中于其提质流程中的加氢过程。而电化学氢泵反应器具有在阴极催化剂表面生成原位吸附氢的特殊结构,可使加氢过程在常温常压下进行,避免了传统加氢反应器中高温高压操作带来的一系列设备和操作复杂性。但是目前电化学氢泵加氢反应器的氢源为纯氢或水,纯氢高昂的价格和水电解的巨大电能消耗,阻碍电化学氢泵加氢反应器的进一步发展。本文提出脱氢与加氢耦合的电化学氢泵双反应器解决上述难题,即利用电化学氢泵反应器中质子交换膜的分隔作用,使脱氢反应与加氢反应同时在阳、阴极进行且互不影响,阳极有机物脱氢产生的H+通过质子交换膜传递至阴极催化剂表面,直接供给阴极加氢。与水做氢源相比,有机物具有较低的电化学窗口,可降低脱氢电势和供氢能源成本；脱氢与加氢在同一反应器中完成,提升了反应器的整体效率、降低设备成本。基于电化学氢泵双反应器的设想,本文尝试了异丙醇-苯酚双反应器。阳极异丙醇在常用阳极催化剂Pt催化下脱氢生成氢气和丙酮,通过改进实验条件使脱氢电势稳定在0.85 V。并考察了生物质模型化合物苯酚在电化学氢泵反应器的加氢反应,环已醇选择性可达95.4%,加氢速率达到17.0 nmol cm-2 s-1。在此基础上,成功运行Pt-Nafion-Pt异丙醇-苯酚双反应器,阴极苯酚加氢反应速率9.7 nmol cm-2 s-1,阳极电势约为0.9 V。进而,本文针对上述反应器存在阳极过电势高,环已酮产率低的问题进一步改进。阳极通过使用PtRu催化剂,增大催化剂担载量,脉冲电流以及操作条件优化,将异丙醇脱氢电势进一步降低至0.2 V,并可长时间稳定运行,仅为同条件下水脱氢电势的1-10。同时以苯酚加氢得到更多环已酮为目标,改用Pd催化剂并进行进一步优化,优选扩散层、催化剂担载量、操作条件等,其在80℃时,催化加氢生成环已酮速率达11.0 nmolcm-2 s-1,高于文献报道的Pd-C催化的三相反应速率。并成功运行PtRu-Nafion-Pt/Pd异丙醇-苯酚双反应器,其中PtRu-Nafion-Pt反应器阴极加氢速率达到19.3 nmol cm-2 s-1,阳极电势可稳定在0.2 V,证明双反应器的可行性和精确控制反应的优势。针对前文阴极苯酚渗透导致脱氢电势升高问题,探究了另一种生物质模型化合物乙酰丙酸在电化学氢泵阴极的加氢反应,实验表明PtRu催化乙酰丙酸加氢的活性高于Pt。乙二醇作为阳极反应物,其相比异丙醇,可提供较高的电流密度,80℃可达到130 mAcm-2。并进一步成功运行PtRu-Nafion-Pt/PtRu乙二醇-乙酰丙酸双反应器,其阴极加氢反应速率均高于单独氢泵反应器的加氢速率,整个过程中电压持续稳定在0.5 V。
[Abstract]:In recent years, biomass as a sustainable energy has received extensive attention, and more and more research has focused on the hydrogenation process in the process of improving the quality of biomass.The electrochemical hydrogen pump reactor has a special structure of in-situ hydrogen adsorption on the surface of the cathode catalyst, which can make the hydrogenation process take place at room temperature and atmospheric pressure.A series of equipment and operation complexity caused by high temperature and high pressure operation in traditional hydrogenation reactor are avoided.But at present the hydrogen source of electrochemical hydrogen pump hydrogenation reactor is pure hydrogen or water. The high price of pure hydrogen and the huge electric energy consumption of water electrolysis hinder the further development of electrochemical hydrogen pump hydrogenation reactor.In this paper, an electrochemical hydrogen pump dual reactor coupled with dehydrogenation and hydrogenation is proposed to solve the above problem, that is, by using the separation of proton exchange membrane in the electrochemical hydrogen pump reactor, the dehydrogenation reaction and the hydrogenation reaction are carried out simultaneously in the positive, cathode and without influence on each other.The H produced by the dehydrogenation of anodic organic compounds is transferred to the surface of the cathode catalyst through the proton exchange membrane and directly supplied to the cathode hydrogenation.Compared with water as hydrogen source, organic compounds have lower electrochemical window, which can reduce the potential of dehydrogenation and the cost of hydrogen supply energy, and the dehydrogenation and hydrogenation are completed in the same reactor, which improves the overall efficiency of the reactor and reduces the equipment cost.Based on the assumption of electrochemical hydrogen pump dual reactor, this paper tries to use isopropanol-phenol dual reactor.Anodic isopropanol was dehydrogenated to produce hydrogen and acetone under the catalysis of common anode catalyst Pt. The potential of dehydrogenation was stabilized at 0.85 V by improving the experimental conditions.The hydrogenation of phenol, a biomass model compound, in an electrochemical hydrogen pump reactor was investigated. The selectivity of cyclohexanol was 95.4 and the hydrogenation rate was 17.0 nmol cm-2 s-1.On this basis, the Pt-Nafion-Pt isopropanol-phenol dual reactor was successfully operated. The reaction rate of cathodic phenol hydrogenation was 9.7 nmol cm-2 s-1, and the anode potential was about 0.9 V.Furthermore, the problems of high anode overpotential and low cyclohexanone yield in the above reactors are further improved.By using PtRu catalyst, the catalyst load, pulse current and operation conditions were optimized to further reduce the dehydrogenation potential of isopropanol to 0.2V and to run stably for a long time, which was only 1-10 of the dehydrogenation potential in water under the same conditions.At the same time, more cyclohexanone was obtained by hydrogenation of phenol, PD catalyst was used and optimized, diffusion layer was selected, catalyst loading capacity, operating conditions, etc., at 80 鈩，

本文编号：1734633