A hybrid adsorbent-membrane reactor (HAMR) system for hydrogen production

Design characteristics and performance of a novel reactor system, termed a hybrid adsorbent-membrane reactor (HAMR), have been investigated for hydrogen production. The recently proposed HAMR concept couples reactions and membrane separation steps with adsorption on the membrane feed-side or permeate-side. Performance of conventional reactors has been significantly improved by this integrated system. In this paper, an HAMR system has been studied involving a hybrid-type packed-bed catalytic membrane reactor undergoing methane steam reforming through a porous ceramic membrane with a CO₂ adsorption system. This HAMR system is of potential interest to pure hydrogen production for fuel cells for various mobile and stationary applications. Reactor behaviors have been investigated for a range of temperature and pressure conditions. The HAMR system shows enhanced methane conversion, hydrogen yield, and product purity, and provides good promise for reducing the hostile operating conditions of conventional reformers, and for meeting the product purity requirements.     

Experimental studies of a hybrid adsorbent-membrane reactor (HAMR) system for hydrogen production

An experimental study of the performance of a novel reactor system—termed the hybrid adsorbent-membrane reactor (HAMR)—is described. In the HAMR the reaction and membrane separation steps are coupled with adsorption. It was shown previously by our group for esterification reactions that this system results in significantly improved performance. The focus in this paper is on the use of the HAMR for hydrogen production. We present experimental investigations of the HAMR for the water-gas-shift (WGS) reaction using layered double hydroxides as adsorbents for CO₂ and nanoporous H₂-selective carbon molecular sieve membranes. The reactor characteristics are investigated for a range of temperatures and pressures relevant to the WGS application, and are compared with the predictions of a mathematical model previously developed by our group.     

Kinetics and Reactor Modeling of Hydrogen Production from Glycerol via Steam Reforming Process over Ni/CeO2 Catalysts

As a result of skyrocketing prices, environmental concerns and depletion associated with fossil fuels, renewable fuels are becoming attractive alternatives. In this respect, the demand for biodiesel has increased tremendously in recent years. Increased production of biodiesel has resulted in a glut of glycerol that has reduced the demand for this once valuable commodity. Consequently, finding alternative uses for glycerol is a timely proposition. One alternative is producing renewable hydrogen from this cheap commodity. Only a handful of studies have been conducted on producing hydrogen from glycerol. Previous studies have mainly focused on finding effective catalysts for glycerol steam reforming. This paper extends previous knowledge by presenting kinetic parameters in relation to glycerol steam reforming over Ni/CeO₂ and a reactor modeling. The study found that the activation energy and the reaction order for the glycerol steam reforming reaction over Ni/CeO₂ catalyst were 103.4 kJ/mol and 0.233, respectively.     

用于分布式制氢的甲烷蒸汽重整膜反应器的数值模拟

采用反应-分离集成的膜反应器进行分布式制氢,对简化工艺、降低能耗、提升技术经济性至关重要。本文采用数学模型对甲烷蒸汽重整制氢过程膜反应器进行模拟,系统分析了渗透侧操作策略、反应压力、反应温度、钯基膜性能、催化剂性能对反应器行为的影响;并以1m³/h甲烷最大程度转化为目标进行分布式制氢案例分析,详细比较膜反应器技术与“常规反应器+膜分离”工艺技术。结果表明,膜反应器在反应压力30atm（1atm=101325Pa）、反应温度500℃下操作可实现紧凑设计,比“常规反应器+膜分离”工艺技术具有明显优势,但是亟需研发更佳活性（10倍）的钯基膜和催化剂以实现显著的过程强化。模拟结果可为不同规模分布式制氢膜反应器的操作与设计及进一步的性能强化提供指导。     

Sorbent-enhanced/membrane-assisted steam-methane reforming

Thermodynamic equilibrium and kinetic reactor models are used to simulate a fluidized bed membrane reactor with in situ or ex situ hydrogen and/or CO₂ removal for production of pure hydrogen by steam methane reforming. In the equilibrium model, the membranes and CO₂ removal are located in separate vessels downstream of the reformer. As the recycle ratio increases, the overall performance approaches that where membranes are located inside the reactor. Whether located in situ or ex situ, hydrogen removal by membranes and CO₂ capture by sorbents both enhance hydrogen production. In the kinetic reactor model, a circulating fluidized bed membrane reformer is coupled with a catalyst/sorbent regenerator. Sorbent enhancement combined with membranes could provide very high hydrogen yields. In addition, since carbonation is exothermic, with its heat of reaction similar in magnitude to the endothermic heat of reaction of the net reforming reactions, sorbent enhancement can provide much of the heat needed in the reformer. The overall heat needed for the process would then be provided in a separate calciner, acting as a sorbent regenerator. While the technology is promising, several practical issues need to be examined.     

Microbial photosynthesis in the harnessing of solar energy

The shortage of fossil fuels restricts the world supply of reduced carbon compounds and energy sources. Biotechnology offers the most feasible route to renewing the supplies of reduced carbon compounds. This involves recycling of CO₂ through photosynthesis. Conventional agriculture has little or no potential for supplying biomass and its derivatives on sufficient scale to offer an alternative to the fossil fuels. The agricultural wastes, on the whole, are intractable to conversion into useful carbon and energy sources and in any case are not available in amounts to provide a significant alternative to the fossil fuels. In contrast, microbial photosynthesis, optimised in photobioreactors, has vast potential to provide organic matter on a scale to match the consumption of fossil fuels. The quantitative study of microbial photosynthesis as a biotechnological route to biomass has been neglected. As a result there is a chaos of conflicting data on fundamental parameters, for example, the photosynthetic efficiency of biomass production. New photosynthetic biotechnology with fully controlled continuous-culture systems is providing unequivocal values for the parameters. For the scale-up of microbial photosynthesis a tubular-loop reactor is proposed.     

Review: Microstructured reactors for distributed and renewable production of fuels and electrical energy

The current paper provides an overview of recent and past research activities in the field of microreactors for energy related topics. The main research efforts in this field are currently focussing on fuel processing as hydrogen source, mostly for distributed consumption through fuel cells. Catalyst development, reactor design and testing for reforming and removal of carbon monoxide through water-gas shift, preferential oxidation, selective methanation and membrane separation are therefore under investigation. An increasing number of integrated complete micro fuel processors has been developed for a large variety of fuels, assisted by static and dynamic simulation of these systems. The synthesis of liquid fuels is another emerging topic, namely Fischer-Tropsch synthesis, methanol and dimethylether production from synthesis gas and biodiesel production.     

A novel slurry bubble column membrane reactor concept for Fischer–Tropsch synthesis in GTL technology

Fischer–Tropsch synthesis (FTS) plays an important role in the production of ultra-clean transportation fuels, chemicals, and other hydrocarbon products. In this work, a novel combination of fixed-bed and slurry bubble column membrane reactor for Fischer–Tropsch synthesis has been proposed. In the first catalyst bed, the synthesis gas is partially converted to hydrocarbons in a water-cooled reactor which is fixed bed. In the second bed which is a membrane assisted slurry bubble column reactor, the heat of reaction is used to preheat the feed synthesis gas to the first reactor. Due to the decrease of H₂/CO to values far from optimum reactants ratio, the membrane concept is suggested to control hydrogen addition. A one-dimensional packed-bed model has been used for modeling of fixed-bed reactor. Also a one-dimensional model with plug flow pattern for gas phase and an axial dispersion pattern for liquid-solid suspension have been developed for modeling of slurry bubble column reactor. Proficiency of a membrane FTS reactor (MR) and a conventional FTS reactor (CR) at identical process conditions has been used as a basis for comparison in terms of temperature, gasoline yield, H₂ and CO conversion as well as selectivity. Results show a favorable temperature profile along the proposed concept, an enhancement in the gasoline yield and, thus a main decrease in undesirable product formation. The results suggest that utilizing this type of reactor could be feasible and beneficial. Experimental proof of concept is needed to establish the validity and safe operation of the proposed reactor.     

Hydrogen production from liquid hydrocarbon fuels for PEMFC application

Lack of efficient hydrogen storage intermediate has boosted the development of fuel processor or economic onsite hydrogen production techniques for application to proton exchange membrane fuel cell promptly. Aiming to develop onsite hydrogen production techniques for proton exchange membrane fuel cell application using nickel-based reforming catalysts and stainless steel reactors, in this paper, a novel process for H₂ production from liquid hydrocarbon fuels was proposed and experimentally demonstrated on a lab scale. The main operations involved prereforming, autothermal reforming, high temperature water gas shift, low temperature water gas shift and H₂ enrichment by Pd membrane. The results indicated that prereforming introduction prior to autothermal reforming suppressed undesired gas phase reactions efficiently and made reforming reactions perform catalytically and smoothly, which was confirmed by a stable 500 h time-on-stream test of both prereforming and autothermal reforming catalysts. The air distributed feed applied in autothermal reforming reactor coupled the endothermic steam reforming and exothermic catalytic combustion reactions over the catalyst closely, maintaining an appropriate temperature distribution curve for autothermal reforming catalyst bed. During the process of H₂ enrichment by highly H₂ permeable Pd composite membrane, concentration polarization played an important role.     

电催化析氢催化剂研究进展

氢能热值高和环境友好性强等特点使其成为未来能源界最具发展潜力的能源之一。电催化析氢反应（hydrogen evolution reaction,HER）作为一种绿色、可持续的产氢方法成为近年来广泛研究的主题。发展高性能、低成本、高活性的析氢催化剂是目前该领域面临的主要挑战。本文总结了近年来高性能催化剂用于HER反应的进展,重点介绍HER反应的基本原理,评估HER催化剂催化性能的典型方法,过渡金属以及化合物、非金属催化剂以及单原子催化剂等电催化析氢催化剂的最新研究进展,系统讨论了催化活性与催化剂形态、结构、组成和合成方法之间的联系,并对催化剂的合成策略、活性位点的固有活性、如何提高活性中心的内在活性和活性位点的数量进行了展望。     

Large-Scale Hydrogen Production

There is a growing need for hydrogen in processing heavier and dirtier fossil fuels and a future hydrogen economy is widely suggested as the next generation fuel/energy source once fossil fuels diminish in availability. Sustainable fuels are still regarded as too expensive given the large amounts of natural gas and a projected, ample supply of fossil fuels beyond the next twenty-plus years. Today, the steam reforming of hydrocarbons is the most favorable route to H₂. If CO₂ sequestration were ever to become widely practiced, fossil fuels would continue to play an important role in the future hydrogen economy.     

Methanol production in an optimized dual-membrane fixed-bed reactor

Coupling reaction and separation in a membrane reactor improves the reactor efficiency and reduces purification cost in the following stages. This paper focuses on modeling and optimization of methanol production in a dual-membrane reactor. In this configuration, conventional methanol reactor is supported by Pd/Ag membrane tubes for hydrogen permeation and alumina–silica composite membrane tubes for water vapor removal from the reaction zone. A steady state heterogeneous one-dimensional mathematical model is developed to predict the performance of this novel configuration. In order to verify the accuracy of the model, simulation results of the conventional reactor is compared with available industrial plant data. The main advantages of the optimized dual-membrane reactor are: higher CO₂ conversion, the possibility of overcoming the limitation imposed by thermodynamic equilibrium, improvement of the methanol production rate and its purity. Genetic algorithm as an exceptionally simple evolution strategy is employed to maximize the methanol production as the objective function. This configuration has enhanced methanol production rate by 13.2% compared to industrial methanol synthesis reactor.     

Hydrogen production from methanol through dielectric barrier discharge

The hydrogen fuel cell is a promising option as a future energy resource and the production of hydrogen is mainly depended on fossil fuels now. In this paper, methanol reforming to produce H₂ through dielectric-barrier discharge (DBD) plasma reaction was studied. Effects of the power supply parameters, reactor parameters and process conditions on conversion of methanol and distribution of products were investigated. The best reaction conditions were following: input power (45 W), material of inner electrode (stainless steel), discharge gap (3.40 mm), length of reaction zone (90.00 mm), dielectric thickness (1.25 mm), and methanol content (37.65%). The highest conversion of methanol and the yield of H₂ were 82.38% and 27.43%, respectively.     

A review on production,storage of hydrogen and its utilization as an energy resource

Energy price is rising due to rapid depletion of fossil fuels. Development of renewable and non-polluting energy resources is necessary for reducing pollution level caused by those conventional fuels. Researchers have recognized hydrogen (H₂) as such an energy source. Hydrogen is a potential non-carbon based energy resource, which can replace fossil fuels. Hydrogen is considered as the alternative fuel as it could be generated from clean and green sources. Despite many advantages, storage of hydrogen is a serious problem. Due to high inflammability, adequate safety measures should be taken during the production, storage, and use of H₂ fuel. This review article elucidates production methods and storage of hydrogen. Besides this safety related to H₂ handling in refilling station, and automobiles has also been discussed. Study shows that safety program and awareness could be fruitful for increasing the acceptance of hydrogen as fuel.     

Dominant Reaction Pathways in the Catalytic Partial Oxidation of CH4 on Rh

Reforming technologies are at the heart of converting fossil fuels and biofuels to syngas and hydrogen for novel energy applications and, among reforming technologies, catalytic partial oxidation is appealing for decentralized energy production due to the compactness of reactors. Yet, the mechanisms of these reactions are poorly understood. Here we combine fundamental surface chemistry and detailed reactor models to elucidate the pathways leading to syngas and propose strategies for optimizing the process.     

生物质热化学法制氢技术的研究进展

介绍木质生物质热化学法生产氢气的四条主要技术路线,分别是生物质气化制氢、生物质热解油制氢、生物质超临界水气化制氢、源于生物质的小分子有机物催化重整制氢方法,着重从化学反应机理、热力学模拟、催化剂种类、工艺开发、工业化进展等方面总结生物质热化学制氢技术的最新研究进展,分析了各类小分子制氢的热力学规律,并指出工业化过程存在...     

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.     

Komplementäre Dekarbonisierung der Erzeugung von Elektroenergie und Gewinnung synthetischer Kraftstoffe durch Erneuerbare Energien und fossile Energieträger

The concept of complementary decarbonisation of power generation from renewable energy sources and fossil fuels consists of their integration in one system. A technology network in the form of a CCU‐combined power plant is proposed for the energy generation from fossil fuels by a coal power plant with CO₂ recovery from the exhaust gases and a pyrolysis of natural gas to hydrogen and carbon as a basic technology. This technology network is completed by a reverse water‐gas shift reaction for the conversion of the CO₂ to CO, which will react with the hydrogen in a Fischer‐Tropsch synthesis for synthetic diesel. The recovered energy from the exothermic Fischer‐Tropsch synthesis meets the energy needs of CO₂ scrubbing. The carbon from the pyrolysis can replace other fossil carbon or can be sequestered.     

Modelling of packed bed membrane reactors for autothermal production of ultrapure hydrogen

The conceptual feasibility of a packed bed membrane reactor for the autothermal reforming (ATR) of methane for the production of ultrapure hydrogen was investigated. By integrating H₂ permselective Pd-based membranes under autothermal conditions, a high degree of process integration and intensification can be accomplished which is particularly interesting for small scale H₂ production units. A two-dimensional pseudo-homogeneous packed bed membrane reactor model was developed that solves the continuity and momentum equations and the component mass and energy balances. In adiabatic operation, autothermal operation can be achieved; however, large axial temperature excursions were seen at the reactor inlet, which are disadvantageous for membrane life and catalyst performance. Different operation modes, such as cooling the reactor wall with sweep gas or distributive feeding of O₂ along the reactor length to moderate the temperature profile, are evaluated. The concentration polarisation because of the selective hydrogen removal along the membrane length was found to become significant with increasing membrane permeability thereby constraining the reactor design. To decrease the negative effects of mass transfer limitations to the membrane wall, a small membrane tube diameter needs to be selected. For a relatively small ratio of the membrane tube diameter to the particle diameter, the porosity profile needs to be taken into account to prevent overestimation of the H₂ removal rate. It is concluded that autothermal production of H₂ in a PBMR is feasible, provided that the membranes are positioned outside the inlet region with large temperature gradients.     

CFD analysis of water gas shift membrane reactor

Fuel cell based modular power generation can be achieved by miniaturization and process intensification of equipments in the process. Fuel cells require hydrogen rich gas which can be generated through reforming and water gas shift reaction. The water gas shift reactor being kinetically limited occupies more volume to achieve the required CO conversion. A membrane reactor integrates the reaction and hydrogen separation stages and hence reduces the volume requirement. Computational Fluid Dynamics offers virtual prototyping of the reactor and thus helps in design, optimization and scale up of reactors. In this study customized User Defined Functions (UDFs) were developed to analyze the performance of low temperature water gas shift membrane reactor. The models were validated using literature data for the parameters – synthesis gas compositions, time factor, sweep flow rate and steam to CO ratio. The effect of all these parameters on the reactor was analyzed for CO conversion, H₂ recovery, DaPe, concentration polarization, concentration profiles and conversion index. The simulations have showed that the UDFs developed were capable of simulating the membrane reactor and this can be used for the design and optimization of the membrane reactor for any process conditions.