Hydrogen production from methanol by oxidative steam reforming carried out in a membrane reactor

The aim of this work is to study from an experimental point of view the oxidative steam reforming of methanol by investigating the behaviour of a dense Pd/Ag membrane reactor (MR) in terms of methanol conversion as well as hydrogen production. The main parameters considered are the operating temperature and the O₂/CH₃OH feed ratio. This is a pioneer work in the application of MR to this kind of reaction, whose goal should be to produce a CO-free hydrogen stream suitable for hydrogen fuel cell applications. The experimental results show that the MR gives methanol conversions higher than traditional reactors (TRs) at each temperature investigated, confirming the good potential of the membrane reactor device for this interesting reaction system.     

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.     

Hydrogen generation in a Pd membrane fuel processor: assessment of methanol-based reaction systems

The feasibility of a Pd membrane fuel processor that integrates several methanol-based chemistries and hydrogen purification steps is assessed. The assessment involves membrane reactor simulations to determine the effects of operating and design parameters on performance metrics including hydrogen utilization, hydrogen productivity, device volume, and Pd requirements. Methanol decomposition (direct and oxidative) on Pd/SiO₂, methanol steam reforming (MSR) on Cu/ZnO/Al₂O₃, and methanol partial oxidation (MPOX) on Cu/Al₂O₃ are evaluated. The membrane reactor model includes detailed treatments of the catalytic kinetics from the literature, accounts for reaction on the Pd membrane and hydrogen permeation inhibition by site blockage, among other features. The simulations reveal that a maximum in the hydrogen productivity occurs at an intermediate value of the space velocity, implying a trade-off between reactor size, methanol conversion and hydrogen utilization. The assessment involves a determination of the Pd membrane surface to reactor volume ratio that maximizes productivity and the requisite Pd to realize that productivity. We show that MSR on Cu/ZnO and MPOX on Cu are promising reaction systems to practice the membrane concept for fuel processing, whereas direct methanol decomposition is reaction limited, making it infeasible. Several approaches for improving membrane fuel processor performance are evaluated and discussed. We show that oxygen addition can increase the hydrogen productivity in the Pd system, while water addition is beneficial for the MPOX system. The extent of enhancement in both cases depends on supply rate and kinetic factors.     

Hydrogen production by methanol steam reforming carried out in membrane reactor on Cu/Zn/Mg-based catalyst

The methanol steam reforming (MSR) reaction was studied by using both a dense Pd-Ag membrane reactor (MR) and a fixed bed reactor (FBR). Both the FBR and the MR were packed with a new catalyst based on CuOAl₂O₃ZnOMgO, having an upper temperature limit of around 350 °C. A constant sweep gas flow rate in counter-current mode was used in MR and the experiments were carried out by varying the water/methanol feed molar ratio in the range 3/1–9/1 and the reaction temperature in the range 250–300 °C. The catalyst shows high activity and selectivity towards the CO₂ and the H₂ formation in the temperature range investigated. Under the same operative conditions, the MR shows higher conversions than FBR and, in particular, at 300 °C and H₂O/CH₃OH molar ratio higher than 5/1 the MR shows complete methanol conversion.     

浆态床中二氧化碳加氢合成甲醇

研究了浆态床中自行开发的LP201甲醇合成催化剂上二氧化碳加氢合成甲醇的过程。探讨了不同操作条件,如温度、压力、气体空速、原料气配比等对反应的影响;考察了该催化剂在浆态床二氧化碳加氢合成甲醇过程中的稳定性。实验结果表明,浆态床二氧化碳加氢合成甲醇过程中主要产物为甲醇、CO和水;随温度的增加,CO2的转化率和甲醇产率呈现上升的趋势,但甲醇的选择性明显下降;压力的升高有利于CO2的转化率、甲醇产率以及甲醇的选择性提高;原料气空速的提高会增大甲醇产率,但同时降低CO2的转化率以及甲醇的选择性;CO2的转化率、甲醇收率以及甲醇的选择性在氢碳摩尔比4～5获得极大值。LP201催化剂的寿命考察结果表明,该催化剂具有较好的催化活性和稳定性。     

操作参数对余热回收甲醇水蒸气重整制氢过程的影响

以模拟汽车尾气供热的甲醇水蒸气重整（MSR）制氢反应为研究对象,设计了集余热加热与MSR制氢反应于一体的肋式微反应器,考察了反应器进口热风速度、温度,反应物进口速度、温度、水醇比及顺逆流情况对MSR制氢过程的影响。计算结果表明,逆流、水醇比1.3、热风进口速度1.1 m/s、温度773 K、反应物进口速度0.1 m/s、温度493 K为该反应过程的最佳工况参数,此时甲醇转化率为99.4%,模拟汽车尾气余热的热效率为28%,反应器出口氢气的体积分数为69.6%。研究结果对开展余热综合利用及发动机尾气重整制氢掺氢燃烧的研究有借鉴意义。     

Co‐current and Countercurrent Configurations for a Membrane Dual Type Methanol Reactor

A dynamic model for a membrane dual‐type methanol reactor was developed in the presence of catalyst deactivation. This reactor is a shell and tube type where the first reactor is cooled with cooling water and the second one with feed synthesis gas. In this reactor system, the wall of the tubes in the gas‐cooled reactor is covered with a palladium‐silver membrane which is only permeable to hydrogen. Hydrogen can penetrate from the feed synthesis gas side into the reaction side due to the hydrogen partial pressure driving force. Hydrogen permeation through the membrane shifts the reaction towards the product side according to the thermodynamic equilibrium. Moreover, the performance of the reactor was investigated when the reaction gas side and feed gas side streams are continuously either co‐current or countercurrent. Comparison between co‐current and countercurrent mode in terms of temperature, activity, methanol production rate as well as permeation rate of hydrogen through the membrane shows that the reactor in co‐current configuration operates with lower conversion and also lower permeation rate of hydrogen but with longer catalyst life than does the reactor in countercurrent configuration.     

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.     

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。     

Investigation of mini-reformer for hydrogen production

以解决小功率燃料电池氢源问题为目的,研制了集原料预热、甲醇水蒸气重整（MSR）、催化燃烧、水汽变换（WGS）于一体的自热式重整制氢反应器。通过条件实验考察了操作温度、甲醇气体空速、水醇比（W/M）等操作条件对重整反应的影响,并在苛刻条件下进行了稳定性研究。实验证明,反应器最大净产氢量可达90 L/h,可为百瓦级质子交换膜燃料电池提供氢源。     

Ignition of methanol partial oxidation over supported platinum catalyst

Supported platinum catalysts were prepared by precipitation of H₂PtCl₆ on powders of different metal oxides. Catalytic activity of the prepared catalysts was tested with reaction of partial oxidation of methanol (POM) for hydrogen production. Most of the prepared catalysts can ignite POM at the ambient temperature. The conversion of methanol and the selectivity of hydrogen and carbon monoxide, however, increased with the reaction temperature and varied with the kind of support and platinum loading. A 1 wt% Pt/ZnO catalyst exhibited optimized methanol conversion and selectivity at a low reaction temperature of 150 °C. The reactor may reach this temperature within 2 min after a start of the exothermic reaction.     

Application of hydrogen-permselective Pd-based membrane in an industrial single-type methanol reactor in the presence of catalyst deactivation

This work presents application of palladium-based membranes in a conventional single-type methanol reactor. A novel reactor configuration with hydrogen-permselective Pd and Pd–Ag membrane are proposed. In this configuration the reacting synthesis gas is fed to the shell side of reactor while the high pressure product is routed from recycle stream through tubes of the reactor in a co-current mode with reacting gas. The reacting gas is cooled simultaneously with recycle gas in tube and saturated water in outer shell. The permselective palladium layer on inner tube allows hydrogen to penetrate from the tube side to the reaction side. In this work, the results of two types of novel membrane reactors are compared with a conventional methanol synthesis reactor at identical process conditions. Also the effect of key parameters such as membrane thickness, reaction and tube side pressure, ratio of tube side flow rate to reaction side flow rate on performance of reactor are investigated. The steady-state and quasi-steady-state simulations results show that there are favorable profiles of temperature and methanol mole fraction along the reactor in proposed reactor relative to conventional reactor system. Therefore using this novel configuration in industrial single-type methanol reactor improves methanol production rate.     

Methyl tert-butyl ether decomposition over heteropoly acid catalyst in a cellulose acetate membrane reactor

In this study the methyl tert-butyl ether (MTBE) decomposition over H₃PW₁₂O₄₀ was carried out in a cellulose acetate membrane reactor. The permeability of methanol through the cellulose acetate membrane was about 30 and 300 times higher than that of either isobutene or MTBE, respectively. The isobutene selectivity in the fixed bed reactor was only slightly higher than the methanol selectivity due to the side reaction. In the cellulose acetate membrane reactor, however, the isobutene selectivity in the rejected stream was 68% and the methanol selectivity in the permeated stream was up to 97%. The MTBE conversion in the membrane reactor was about 7% higher than that in the membrane-free fixed bed reactor under the same reaction conditions. The enhanced performance of the membrane reactor in this reversible reaction was mainly due to the selective permeation of methanol which resulted in a methanol-deficient condition suppressing MTBE synthesis reaction.     

催化剂颗粒形状对甲烷水蒸气重整反应的影响及工业反应器模拟

甲烷水蒸气重整工艺是现阶段最主要的工业制氢技术,催化剂颗粒形状和反应器操作条件是影响重整反应器性能和产物组成的重要因素。首先从颗粒尺度研究催化剂形状对甲烷水蒸气重整反应的影响,在不同的反应温度和压力下,计算并比较了球形、柱形和环形催化剂的效率因子,其大小顺序为:柱形 < 球形 < 环形。其次,将反应器床层的质量、热量和动量传递与环形催化剂颗粒的扩散-反应方程相结合,建立了用于描述甲烷水蒸气重整工业反应器的一维轴向数学模型。计算并分析了反应器进口温度和压力对反应器床层的温度和压力分布、催化剂效率因子以及甲烷转化率和各组分浓度分布的影响,确定了适宜的工业反应器进口温度和压力,分别为773 K和3 MPa。     

Simulation of CO2 hydrogenation with CH3OH removal in a zeolite membrane reactor

A thermodynamic analysis of the CO₂ hydrogenation to methanol where competitive reactions take place is presented for a membrane reactor (MR) where methanol was selectively removed. A non-isothermal mathematical model was written to simulate a micro-porous MR. Zeolite membranes with different values of the CH₃OH and H₂O permeances were considered in the MR modelling. The effect of temperature, pressure and species permeation on the conversion, selectivity and yield was analysed. A higher CO₂ conversion and CH₃OH selectivity can be reached by the use of an MR. An increased CH₃OH yield allows to reduce the consumption of reactant and also to operate at lower pressures and higher temperatures, a fact, which favours the kinetics reducing the residence time and the reactor volume. The MR with the highest CH₃OH/H₂O permeance ratio resulted in better selectivity and yield of CH₃OH with respect to the other MR characterised by a higher conversion.     

Theoretical Investigation of a Pd‐membrane Reactor for Methanol Synthesis

A numerical study is performed in order to evaluate the performance and optimal operating conditions of a palladium membrane reactor for methanol synthesis. A novel reactor configuration with a Pd wall, which is perm‐selective to hydrogen, has been proposed. In this configuration the reactants are added to the tube side while pure hydrogen is added to the shell side, as a result, the hydrogen diffuses across the membrane from the shell side to the tube side. In this membrane reactor, hydrogen penetrates to the reaction side in order to maintain a suitable hydrogen level in the whole length of the reactor and shift the equilibrium reaction. The effects of different parameters on the methanol output mole fraction were investigated in the co‐current mode. These parameters were membrane thickness, reaction side flow rate, reaction side pressure, shell side pressure and H₂/CO₂ ratio in the feed.     

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.     

CO‐Free Hydrogen Production by Ethanol Steam Reforming in a Pd–Ag Membrane Reactor

In this work, the ethanol steam reforming (ESR) reaction has been studied by using a dense Pd–Ag membrane reactor (MR) by varying the water/ethanol molar ratio between 3:1 and 9:1 in a temperature range of 300–400 °C and at 1.3 bar as reaction pressure. The MR was packed with a commercial Ru‐based catalyst and a constant sweep gas flow rate in counter current mode was used. The influence of the temperature and the feed molar ratio on different parameters such as the ethanol conversion, the hydrogen production, the hydrogen yield and the CO‐free hydrogen recovery has been evaluated.     

Effect of incipient removal of hydrogen through palladium membrane on the conversion of methane steam reforming: Experimental and modeling

This paper presents a mathematical model based on the reaction rate expressions to describe the displacement of methane conversion in the steam reforming. The effect of several parameters including weight hourly space velocity (WHSV), load-to-surface ratio, reaction pressure, hydrogen partial pressure in permeate side and reaction temperature were investigated. Simulation and experimental results showed that a conversion higher than 80% could be achieved in a palladium membrane reactor at reaction temperature of 500 °C relative to 850 °C in a conventional fixed bed reactor (FBR). Besides, the yield of CO (<2%) in membrane reactor was much lower than that (>50%) in the FBR, which indicated the significant depression of CO production in use of membrane reactor.     

Performance evaluation of a novel reactor configuration for oxidative dehydrogenation of ethane to ethylene

A one-dimensional non-isothermal steady state model was developed to simulate the performance of three-reactor configurations for the oxidative dehydrogenation of ethane (ODHE) to ethylene. These configurations consist of side feeding reactor (SFR), conventional fixed bed reactor (CFBR) and membrane reactor (MR). The performance of these reactors was compared in the terms of C₂H₆ conversion, C₂H₄ and CO₂ selectivity and temperature profiles. The use of sectional air injections on the wall of SFR with a limited number of injection points showed that the performance of reactor significantly improves and optimum pattern of oxygen consumption is also obtained. Moreover, our SFR with a liquid coolant medium operates in an effectively controlled temperature profile that is comparable with that of the MR, which is cooled by a coolant stream of air. Hence, an enhancement in the level of selectivity is obtained for the SFR configuration. Consequently, the side feeding procedure can decrease the high operating temperature problem and low ethylene selectivity in the ODHE process. According to obtained results, the SFR would be a proper alternative for both the MR and CFBR.