钯膜反应器柴油重整制氢模拟与验证

为了研究钯膜反应器柴油重整制氢工艺的反应规律,对其进行热力学和动力学建模,并通过实验验证模型的准确性。采用顺序模块法将钯膜反应器分为连续的子反应器和子分离器,模拟钯膜反应器的反应分离耦合过程,通过灵敏度分析,研究钯膜反应器中各反应因素等对氢气收率的影响规律。结果表明,钯膜反应器较无膜反应器可突破热力学平衡的限制,减小反应体积,在低温下可获得较高的氢气产率。在一定条件下模拟结果与实验值误差为8.9%,证明该仿真模型可对实验研究起到预测和指导作用。     

钯膜及钯膜反应器的研究进展

钯基膜具有很高的透氢速率和透氢选择性以及良好的化学和热稳定性,一直是膜技术领域的研究热点。文章综述了钯膜的透氢原理、钯膜制备方法及钯膜反应器的研究进展。重点介绍了钯膜反应器在加氢、脱氢等反应中的应用,并对钯膜反应器的发展趋势进行了展望。     

钯膜及钯膜反应器的研究进展

钯基膜具有很高的透氢速率和透氢选择性以及良好的化学和热稳定性,一直是膜技术领域的研究热点。文章综述了钯膜的透氢原理、钯膜制备方法及钯膜反应器的研究进展。重点介绍了钯膜反应器在加氢、脱氢等反应中的应用,并对钯膜反应器的发展趋势进行了展望。     

利用复合钯膜反应器转化甲烷制取合成气

目前工业上一般都采用甲烷的蒸汽转化和部分氧化制取合成气。但这 2种工艺都受到热力学限制 ,特别是在高压下 ,甲烷的平衡转化率比较低。最近 ,意大利卡拉布里亚大学膜和化学反应器模拟研究院对复合钯膜反应器进行了研究 ,以图克服传统反应器的热力学极限。复合钯膜反应器结合了膜分离器与催化反应器的典型特征 ,它利用钯膜选择性除去催化反应后混合气体中的氢 ,从而使平衡转化率向高于热力学平衡极限的方向移动 ,最终达到提高甲烷转化率的目的。试验采用的传统反应器是一个不锈钢管 ,总长度 2 5cm ,有效长度 1 5cm ,内径 0 .67cm。膜反应器…     

钯膜的应用

介绍了钯膜在制取烯烃和氢气的反应系统中的应用。由于使用了钯膜,在甲烷、甲醇蒸气重整反应中降低了反应温度,在丙烷、异丁烷、乙苯脱氢中均提高了反应物的转化率以及目的产物的选择性。在氨催化分解、水煤气转化、除去水中硝酸盐的反应中使用钯膜也得到了令人满意的效果。     

耦合催化膜反应过程中的最佳催化活性分布

引　言近年来 ,膜反应器研究已经成为化学反应工程领域的热点课题之一 .其中单侧的膜反应过程研究较多 ,而耦合膜反应过程的研究相对较少 .耦合膜反应过程是指在膜反应器中膜两侧都有反应发生 ,一侧反应的产物是另一侧反应的反应物 ,而膜可优先选择该物质透过 .耦合膜反应过程的研究首先是在前苏联开展的 ,主要以Ｇｒｙａｚｎｏｖ等[1,2 ] 对脱氢反应与加氢反应耦合过程的研究为代表 ,有关介绍参见Ｓｈｕ等[3] 、Ｚａｍａｎ和Ｃｈａｋｍａ[4 ] 以及Ｓａｒａｃｃｏ和Ｓｐｅｃｃｈｉａ[5] 的综述 .研究表明 ,耦合膜反应过程有其特殊的优点 :通…     

硅橡胶/陶瓷复合膜反应器中CO2合成甲醇(Ⅲ)过程实验研究

对在由硅橡胶 /陶瓷复合膜所构成的膜反应器中进行的CO₂ 加氢合成甲醇的复杂反应体系CO₂ +3H₂=CH₃ OH +H₂ O与CO₂ +H₂=CO +H₂ O开展实验研究 .考察了硅橡胶 /陶瓷复合膜在合成含氧化合物反应过程中的作用 ,并讨论了CO₂ 与H₂ 合成甲醇反应的膜反应过程参数对反应行为的影响 ,对部分理论分析结果进行验证 .在实验条件下 ,CO₂ 合成甲醇复杂反应体系中的主反应转化率较传统的固定床反应器提高了 2 2 %     

透氢铌基钯合金膜

目前商用的致密型钯合金膜是钯银合金膜,较高的使用成本限制了其大规模的应用。而铌基钯合金膜因其较高的透氢率,机械性能及较低的使用成本等诸多优势受到了广泛关注。本文简要介绍了钯膜的透氢机理和影响钯膜透氢性能的因素,重点综述了以Pd/Nb/Pd复合膜为代表的新型夹层型复合膜透氢性能的研究进展,并对未来铌基钯合金膜的研究方向作出了展望。     

管状钯膜反应器中的脱氢反应与氢气分离

讨论了钯膜反应器的实验装置及环己烷的脱氢反应实验方法。对环己烷的脱氢反应及氢气通过钯膜的渗透建立了扩散模型，使用状态－变量法求解偏微分方程组，得出反应物和生成物的组分浓度分布，进而求出反应转化率。同实验结果对比表明，扩散模型能较好地计算脱氢反应及氢气的分离过程。     

多孔膜反应器中丙烷催化脱氢制丙烯的模拟研究

针对丙烷高效脱氢制丙烯的多孔膜反应器构建了无量纲数学模型并进行了模拟研究,考察了催化剂活性、透氢膜性能、操作条件对多孔膜反应器中丙烷脱氢的转化率、丙烯收率、氢气收率和纯度的影响。结果表明,移走产物氢气可以有效提升膜反应器的性能,其性能的提升程度由不同温压条件下催化剂和透氢膜性能共同决定。高活性催化剂是丙烷高效转化的基础,催化剂活性越高,膜反应器内的产氢速率越快;其次,膜的选择性和渗透通量越高,氢气的移除效率越高,可在最大程度上打破热力学平衡的限制,使反应向生成丙烯的方向移动。当多孔透氢膜的氢气渗透率在10^-7~10^-6 mol·m^-2·s^-1·Pa^-1,H₂/C₃H₈选择性达到100时,其丙烷转化率可以与Pd膜反应器内的转化率相当,但分离的氢气纯度低于Pd膜反应器。与传统的固定床反应器相比,膜反应器由于促进了化学平衡的移动,可以在较低的反应温度下获得相当高的丙烷转化率,且丙烷转化率随着反应压力的增加呈现出一个最大值。该模拟研究可为实际生产过程中膜反应器用于PDH反应的高效强化提供有益的技术指导。     

Isobutane dehydrogenation reaction in a packed bed catalytic membrane reactor

A packed-bed catalytic ceramic membrane reactor (PBCMR) was used for the isobutane dehydrogenation reaction. The experimental results have shown that through the use of the membrane reactor one can attain better conversions and yields than in a conventional reactor operating under the same outlet pressure and temperature, and feed composition conditions.     

Palladium/ceramic membranes for selective hydrogen permeation and their application to membrane reactor

Plating thin Pd or Pd-Ag alloy film on the outer surface of a porous alumina ceramic tube enables very rapid hydrogen permeation with an absolute selectivity based on the solution-diffusion transport mechanism. Effectiveness, such as displacement of thermodynamic equilibrium, selectivity enhancement, is brought forth by incorporating the metal/ceramic composite membrane in the catalytic reactor, as demonstrated in concrete examples of steam and CO₂ reforming of methane and dehydrogenation of isobutane. It is also shown that the membrane reactor occasionally requires its own catalyst which is different from conventional ones.     

Integrated membrane system for pure hydrogen production: A Pd-Ag membrane reactor and a PEMFC

In this work, an integrated system consisting of single stage hydrogen production and a commercial PEMFC was investigated experimentally. The CO-free hydrogen fed to the PEMFC was produced in a Pd-Ag membrane reactor (MR), upgrading a syngas stream with a composition similar to that coming out of a reformer (CO 45%; H₂ 50%; CO₂ 4%; N₂ balance, on dry basis). The performance of the MR was evaluated in terms of CO conversion and H₂ recovery as a function of the feed pressure (up to 600 kPa) and space velocity; no sweep gas was used for promoting the H₂ permeation, since this role was assigned exclusively to the feed pressure.Special attention was paid to the analysis of the integrated system, focusing on the influence of the Pd-Ag MR operating conditions on the electrical performance of the PEMFC. The PEMFC internal crossover was also considered to have an effect on the electrical performance and this was taken into account estimating the PEMFC actual efficiency. Furthermore, the chemical efficiency of the integrated membrane plant was evaluated, considering the H₂ converted into electricity with respect to the total amount of H₂ contained in the feed mixture. An interesting performance was shown by the integrated system since the PEMFC performance was close to the power nominal value.     

Upgrading of a syngas mixture for pure hydrogen production in a Pd-Ag membrane reactor

Water gas shift (WGS) is a thermodynamics limited reaction and CO equilibrium conversion of a traditional reactor is furthermore reduced owing to the presence of H₂ (ca. 50%) in the feed stream coming from a reformer.The upgrading of a simulated reformate stream was experimentally investigated as a function of temperature (280-320 °C), feed pressure (up to 600 kPa), gas hourly space velocity (GHSV), etc. using a Pd-alloy membrane reactor (MR) packed with a commercial catalyst CuO/CeO₂/Al₂O₃; no sweep gas was used. The MR performance was also evaluated using new parameters such as conversion index, H₂ recovery and extraction index, etc., which evidence the advantages with respect to a traditional reactor.A Pd-based MR operated successfully overcoming the thermodynamic constraints of a traditional reactor and, specifically, the drawback introduced by the hydrogen presence. In fact, a CO conversion of 90% significantly exceeded (three times) the thermodynamics upper limit (<36%) of a traditional reactor owing to ca. 80% of hydrogen permeated through the membrane.The overall process performance was significantly improved by the presence of the Pd-based membrane and, thus, by the high reaction pressure which allowed and drove the hydrogen permeation.     

Pure Hydrogen and Propylene Coproduction in Catalytic Membrane Reactor-Assisted Propane Dehydrogenation

Propane dehydrogenation on a commercial Pt-Sn/Al₂O₃ catalyst in a Pd-Ag membrane reactor is considered. A mathematical model is developed to evaluate the performance of the catalytic membrane reactor for the process of propane dehydrogenation. Design and operating conditions are systematically evaluated for key performance metrics such as propane conversion, propylene selectivity, hydrogen selectivity, and hydrogen recovery under different operating conditions. The results confirm that the high performance of the membrane reactor is related to the continuous removal of hydrogen from the reaction zone to shift the reaction equilibrium towards the formation of more propylene and hydrogen.     

异丁烷脱氢过程催化剂结焦与焦性质研究

在固定床反应装置上,采用YBD型Cr/Al_2O_3催化剂催化异丁烷脱氢,通过热分析技术研究结焦催化剂,考察反应条件对催化剂结焦量及焦性质的影响。结果表明,Cr/Al_2O_3催化剂对异丁烷脱氢有较好的催化活性,当反应温度580℃,空速800 h^(-1)时,异丁烷转化率60%以上,异丁烯选择性90%以上,异丁烯收率约60%。反应温度、空速以及异丁烯对结焦催化剂的焦含量有明显影响,当反应温度超过580℃,随着原料气中异丁烯含量的增加,催化剂的结焦量迅速增加。     

糠醛在Pd-Cu膜反应器中催化加氢合成糠醇

以糠醛催化加氢合成糠醇作为模型反应,采用共沉淀法制备的Cu/MgO-K₂O作为催化剂,考察了Pd-Cu膜反应器的加氢性能.膜反应器由双套管组成,采用分别进料的方式操作.即糠醛气化后由载气带入中心膜管的催化床层,而氢气则进入管壳层通过Pd-Cu合金膜渗透到反应区.在不同条件下分别进行糠醛催化加氢反应,考察了糠醛转化率、产品糠醇选择性和收率,并与传统的共进料填充床反应器进行比较.研究结果显示,膜反应器比传统的填充床反应器具有产品收率高、选择性好和副产物少的特点.此外,本文结合催化剂的组成、结构和表面形貌的表征对催化剂的催化活性和失活行为进行了讨论.     

Contribution to emission reduction of CO2 by a fluidized-bed membrane dual-type reactor in methanol synthesis process

In this work, a fluidized-bed membrane dual-type reactor was evaluated for CO₂ removal in methanol synthesis process. The feed synthesis gas is preheated in the tubes of the gas-cooled reactor and flowing in a counter-current mode with reacting gas mixture in the shell side. Due to the hydrogen partial pressure driving force, hydrogen can penetrate from feed synthesis gas into the reaction side through the membrane. The outlet synthesis gas from this reactor is fed to tubes of the water-cooled packed-bed reactor and the chemical reaction is initiated by the catalyst. The methanol-containing gas leaving this reactor is directed into the shell of the gas-cooled reactor and the reactions are completed in this fluidized-bed side. A two-phase dynamic model in bubbling regime of fluidization was developed in the presence of long-term catalyst deactivation. This model is used to compare the removal of CO₂ in a FBMDMR with a conventional dual-type methanol synthesis reactor (CDMR) and a membrane dual-type methanol synthesis reactor (MDMR). The simulation results show a considerable enhancement in the CO₂ conversion due to have a favourable profile of temperature and activity along the fluidized-bed membrane dual-type reactor relative to membrane and conventional dual-type reactor systems.     

Vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor with Cu/SiO2/ ceramic composite membrane

The Cu/SiO₂/ceramic composite membrane was prepared on the SiO₂/ceramic mesoporous membrane by an ion exchange method, and vapor phase dehydrogenation of methanol to methyl formate in the catalytic membrane reactor was investigated. It showed much better performance in the catalytic membrane reactor than that in the fixed-bed reactor under the same reaction conditions. At 240 °C, 57.3% conversion of methanol and 50.0% yield of methyl formate were achieved in the catalytic membrane reactor and only 43.1% conversion of methanol and 36.9% yield of methyl formate were achieved in the fixed-bed reactor.