Performance assessment and evaluation of catalytic membrane reactor for pure hydrogen production via steam reforming of methanol

The steam reforming of methanol was investigated in a catalytic Pd–Ag membrane reactor at different operating conditions on a commercial Cu/ZnO/Al₂O₃ catalyst. A comprehensive two-dimensional non-isothermal stationary mathematical model has been developed. The present model takes into account the main chemical reactions, heat and mass transfer phenomena in the membrane reactor with hydrogen permeation across the PdAg membrane in radial direction. Model validation revealed that the predicted results satisfy the experimental data reasonably well under the different operating conditions. Also the impact of different operating parameters including temperature, pressure, sweep ratio and steam ratio on the performance of reactor has been examined in terms of methanol conversion and hydrogen recovery. The modeling results have indicated the high performance of the membrane reactor which is related to continuous removal of hydrogen from retentate side through the membrane to shift the reaction equilibrium towards formation of hydrogen. The obtained results have confirmed that increasing the temperature improves the kinetic properties of the catalyst and increase in the membrane's H₂ permeance, which results in higher methanol conversion and hydrogen production. Also it is inferred that the hydrogen recovery is favored at higher temperature, pressure, sweep ratio and steam ratio. The model prediction revealed that at 573 K, 2 bar and sweep ratio of 1, the maximum hydrogen recovery improves from 64% to 100% with increasing the steam ratio from 1 to 4.     

Modelling of the ethanol steam reforming over Rh-Pd/CeO2 catalytic wall reactors

Existing literature data have been used to model the steam reforming of ethanol on catalytic honeycombs coated with Rh-Pd/CeO₂, which have shown an excellent performance and robustness for the production of hydrogen under realistic conditions. In this article, a fully 3D non-isothermal model is presented, where the reactions of ethanol decomposition, water gas shift, and methane steam reforming have been modelled under different operational pressures (1–10 bar) and temperatures (500–1200 K) at a steam to carbon ratio of S/C = 3 and a space time of W/F between 2·10⁻³ and 3 kg h L_liq⁻¹. According to the modelling results, a maximum hydrogen yield of 80% is achieved at a working temperature of 1150 K and a pressure of 4 bar at S/C = 3.     

Methanol and ethanol steam reforming in membrane reactors: An experimental study

In this work a comparison between methanol steam reforming (MSR) reaction and ethanol steam reforming (ESR) reaction to produce hydrogen in membrane reactors (MRs) is discussed from an experimental point of view.     

Recent trends in the development of reactor systems for hydrogen production via methanol steam reforming

Hydrogen is currently receiving significant attention as an alternative energy resource, and among the various methods for producing hydrogen, methanol steam reforming (MSR) has attracted great attention because of its economy and practicality. Because the MSR reaction is inherently activated over catalytic materials, studies have focused on the development of noble metal-based catalysts and the improvement of existing catalysts with respect to performance and stability. However, less attention has been paid to the modification and development of innovative MSR reactors to improve their performance and efficiency. Therefore, in this review paper, we summarize the trends in the development of MSR reactor systems, including microreactors and membrane reactors, as well as the various structured catalyst materials appropriate for application in complex reactors. In addition, other engineering approaches to achieve highly efficient MSR reactors for the production of hydrogen are discussed.     

RuRh based catalysts for hydrogen production via methanol steam reforming in conventional and membrane reactors

Results of hydrogen production study in methanol steam reforming (MSR) process with the use of Ru_0.5–Rh_0.5 catalysts supported on different carbon materials: synthetic graphite-like material Sibunit, carbon black Ketjenblack EC600DJ, detonation nanodiamonds (DND) and ZrO₂-based material with fluorite structure, doped with ceria, have been described. The samples have been tested in conventional flow reactor and membrane (MR) reactor, containing Pd-based membranes with different composition, thickness and surface architecture. It has been shown that the catalytic activity of the composites depends on the support nature. The RuRh/DND catalyst exhibits the highest activity, whereas RuRh/Ce_0.1Zr_0.9O_2–δ is the most selective. The use of PdAg (23%) foil with the surface modified by palladium black showed great advantages comparing to the smooth dense membrane. The use of the MR with the PdAg membrane improves the MSR reaction and provides almost 50% increase in the hydrogen yield. The hydrogen produced with the use of the MR is ultra pure.     

Study on a catalytic membrane reactor for hydrogen production from ethanol steam reforming

Ethanol steam reforming in a membrane reactor with catalytic membranes was investigated to achieve important aims in one process, such as improvement in ethanol conversion and hydrogen yield, high hydrogen recovery and CO reduction. In order to confirm the efficiency of reaction and CO reduction, an ethanol reforming-catalytic membrane reactor with water–gas shift reaction (ECRW) in the permeate side was compared with a conventional reactor (CR) and an ethanol reforming-catalytic membrane reactor (ECR). In comparison with the CR, ethanol conversion improvement of 11.9–19% and high hydrogen recovery of 78–87% were observed in the temperature range of 300–600 °C in the ECRW. Compared with CR and ECR, the hydrogen yield of ECRW increased up to 38% and 30%, respectively. Particularly, the ECRW showed higher hydrogen yield at high temperature, because Pt/Degussa P25 loaded in the permeate side showed catalytic activity for the methane steam reforming as well as WGS reaction. Moreover, CO concentration was reduced under 1% by the WGS reaction in the permeate side in the temperature range of 300–500 °C.     

An analytical and experimental investigation of high-pressure catalytic steam reforming of ethanol in a hydrogen selective membrane reactor

The objective of this work was to explore the benefits of high-pressure steam reforming of ethanol for the production of hydrogen needed to refuel the high-pressure tanks of fuel cell (polymer electrolyte) vehicles. This paper reports on the potential efficiency benefits and challenges of pressurized reforming and options for dealing with the challenges; it reports the results from experiments in a micro-reactor, followed by a modeling study of the reactor to project the dependence of the hydrogen yields on process parameters. The experiments were conducted in the range of approximately 7–70 atm, 600–750 °C, steam-to-carbon molar ratios of 3–12, and gas hourly space velocities of 8500–83,000 per hour. By placing a hydrogen-transporting palladium-alloy membrane within the catalyst zone, this study quantified the beneficial effect of hydrogen extraction from the reforming zone. The model was used to explore the parameter space to define the reactor and conditions that would be needed to approach the efficiency targets for distributed hydrogen production plants. The results indicate that the tested catalyst was sufficiently active, and the hydrogen yield achieved with the experimental membrane reactor was limited by the low hydrogen flux of the tested membrane. The reactor model predicts that a membrane with at least 20 times higher flux than currently evaluated would be sufficient to generate hydrogen yields to match efficiency targets of 72%.     

Performance evaluation of PdAg membrane reactor in glycerol steam reforming process: Development of the CFD model

In the present paper, a CFD modeling of palladium membrane reactor, in which hydrogen produced through glycerol steam reforming, is presented. A comprehensive and precise kinetic and permeation model was used. On the basis of the equations and assumptions, an excellent agreement between model prediction and experimental data was achieved. Pressure, velocity and concentration distribution of various component within the Membrane Reactor (MR) were predicted. Moreover, the performance of both a Traditional Reactor (TR) and a MR was compared in various condition. The effects of some operating conditions such as temperature, pressure, feed flow rate and flow pattern on the glycerol conversion, hydrogen recovery and CO selectivity were evaluated. The most effective parameter was pressure: increasing it from 1 to 10 bar in co-current MR, the glycerol conversion, H2 recovery and CO selectivity were shifted from 46%, 17% and 6.6%–81%, 56% and 0.8%, respectively. The CFD model indicates that the performance of glycerol steam reforming improves when MR is used instead of TR. At various operating conditions the glycerol convertion enhanced 10–64% and CO selectivity reduced 7.5–99.0% in the MR when compared with the TR.     

Hydrogen production from biogas reforming and the effect of H2S on CH4 conversion

Biogas produced during anaerobic decomposition of plant and animal wastes consists of high concentrations of methane (CH₄), carbon dioxide (CO₂) and traces of hydrogen sulfide (H₂S). The primary focus of this research was on investigating the effect of a major impurity (i.e., H₂S) on a commercial methane reforming catalyst during hydrogen production. The effect of temperature on CH₄ and CO₂ conversions was studied at three temperatures (650, 750 and 850 °C) during catalytic biogas reforming. The experimental CH₄ and CO₂ conversions thus obtained were found to follow a trend similar to the simulated conversions predicted using ASPEN plus. The gas compositions at thermodynamic equilibrium were estimated as a function of temperature to understand the intermediate reactions taking place during biogas dry reforming. The exit gas concentrations as a function of temperature during catalytic reforming also followed a trend similar to that predicted by the model. Finally, catalytic reforming experiments were carried out using three different H₂S concentrations (0.5, 1.0 and 1.5 mol%). The study found that even with the introduction of small amount of H₂S (0.5 mol%), the CH₄ and CO₂ conversions dropped to about 20% each as compared to 65% and 85%, respectively in the absence of H₂S.     

An experimental and theoretical approach for the biogas steam reforming reaction

An experimental and theoretical study for the biogas steam reforming reaction over 5%Ru/Al₂O₃ catalyst have been performed. An apparatus was constructed for the conduction of the experiments, the core of which was a tube reactor, filled with the catalyst in form of pellets. The inlet gas mixture consisted of CH₄ and CO₂ in various composition ratios as a model biogas and steam. A theoretical model of the process was developed. The experimental reactor was modelled as an isothermal pseudo homogeneous fixed bed reactor. Internal and external transport phenomena were neglected and appropriate effectiveness factors were employed instead. A physical properties model was used for the calculation of the physicochemical properties of the real mixture. Five reactant species, CH₄, CO₂, H₂O, CO and H₂, were included in the model, whereas the feed consisted of the first three. Steam reforming and water gas shift were the main reactions. Experimental results and theoretical predictions match closely, stability of the catalyst was assured and an optimal operational window was identified, at GHSV = 10,000–20,000 h⁻¹, T = 700–800 °C, CH₄/CO₂ = 1.0–1.5 and H₂O/CH₄ = 3.0–5.0.     

Oxidative steam reforming of ethanol over a Pt/Al2O3 catalyst in a Pd-based membrane reactor

In this study, the ability of a Pd-Ag membrane reactor of producing ultrapure hydrogen via oxidative steam reforming of ethanol has been evaluated. A self supported Pd-Ag tube of wall thickness 60 μm has been filled with a commercial Pt-based catalyst and assembled into a membrane module in a finger-like configuration. In order to evaluate the hydrogen yield behavior under different operating conditions, experimental tests have been performed at temperatures of 400 and 450 °C and pressures of 150 and 200 kPa. The oxidative steam reforming of ethanol has been carried out by feeding the membrane reactor with a gas stream containing a dilute water-ethanol mixture and air. Different water/ethanol feed flow rates (5, 10, 15 g h⁻¹), several water/ethanol (4, 10, 13) and oxygen/ethanol (0.3, 0.5, 0.7) feed molar ratios have been tested. The results pointed out that the highest hydrogen yield (moles of permeated hydrogen per mole of ethanol fed) corresponding to almost 4.1 has been attained at 450 °C and 200 kPa of lumen pressure by using a water/ethanol/oxygen feed molar ratio of 10/1/0.5.The results of these tests have been compared with those reported for the ethanol steam reforming in a Pd-Ag membrane reactor filled with the same Pt-based catalyst. This comparison has shown a positive effect on the hydrogen yield of small oxygen addition in the feed stream.     

H2 production in silica membrane reactor via methanol steam reforming: Modeling and HAZOP analysis

The main aim of this work is the presentation of both qualitative safety and quantitative operating analyses of silica membrane reactor (MR) for carrying out methanol steam reforming (MSR) reaction to produce hydrogen. To perform the safety analysis, HAZOP method is used. Before the HAZOP analysis, a comprehensive investigation of most important operating parameters effects on silica MR performance is required. Therefore, for a quantitative analysis, a 1-dimensional and isothermal model is developed for evaluating the reaction temperature, reaction pressure, feed molar ratio (steam/methanol) and feed flow rate effects on silica MR performance in terms of methanol conversion and hydrogen recovery. The model validation results show good agreement with experimental data from literature. As a consequence, simulation results indicate that the reaction pressure and feed molar ratio have dual effect on silica MR performance. In particular, it is found that methanol conversion is decreased by increasing the reaction pressure from 1.5 to 4.0 bar, whereas over 4.0 bar, it is improved. Moreover, the hydrogen recovery is decreased by increasing the feed molar ratio from 1 to 5, while over 5, it was approximately constant. After the evaluation of modeling results, the HAZOP analysis for silica MR is carried out during MSR reaction. The analysed operating parameters in the modeling study have been considered as key parameters in the HAZOP analysis. The safety assessment results are presented in tables as check list. By considering the HAZOP results, safety pretreatment works are recommended before or during the experimental tests of MSR reaction in silica MR. According to different parameters consequences, reaction temperature is the most critical parameter in MSR reaction for the silica MR studied in this work. In particular, to avoid the consequences of temperature deviation, it is recommended to use a PID temperature controller in the silica MR for MSR reaction.     

Hydrogen production from ethanol steam reforming: energy efficiency analysis of traditional and membrane processes

The ethanol steam reforming reaction has been considered for producing pure hydrogen to be used for feeding a PEM fuel cell of power 4 kW. As an innovative technology, Pd–Ag thin wall membranes are proposed for building membrane reactors: accordingly, the energy efficiency analysis of the processes producing hydrogen from ethanol steam reforming has been carried out and, particularly, the comparison among a traditional process and different membrane processes is reported.     

Evaluation of silica membrane reactor performance for hydrogen production via methanol steam reforming: Modeling study

The aim of this work is to analyze the potential application of microporous silica membrane reactor carrying out methanol steam reforming reaction for hydrogen production. As a further study, a comparison with dense Pd–Ag membrane reactor and a traditional reactor, working at the same operating conditions of silica membrane reactor, is realized.     

Methane steam reforming in a Pd-Ag membrane reformer: An experimental study on reaction pressure influence at middle temperature

In this experimental work, methane steam reforming (MSR) reaction is performed in a dense Pd-Ag membrane reactor and the influence of pressure on methane conversion, CO_x-free hydrogen recovery and CO_x-free hydrogen production is investigated. The reaction is conducted at 450 °C by supplying nitrogen as a sweep gas in co-current flow configuration with respect to the reactants. Three experimental campaigns are realized in the MR packed with Ni-ZrO catalyst, which showed better performances than Ni-Al₂O₃ used in a previous paper dealing with the same MR system. The first one is directed to keep constant the total pressure in both retentate and permeate sides of the membrane reactor. In the second case study, the total retentate pressure is kept constant at 9.0 bar, while the total permeate pressure is varied between 5.0 and 9.0 bar. As the best result of this work, at 450 °C and 4.0 bar of total pressure difference between retentate and permeate sides, around 65% methane conversion and 1.2 l/h of CO_x-free hydrogen are reached, further recovering 80% CO_x-free hydrogen over the total hydrogen produced during the reaction. Moreover, a study on the influence of hydrogen-rich gas mixtures on the hydrogen permeation through the Pd-Ag membrane is also performed and discussed.     

Comparative study of propane steam reforming in vanadium based catalytic membrane reactor with nickel-based catalysts

The performance of catalytic membrane reactor with Pd-coated V membrane was examined for steam reforming of propane. The long term reforming experiment confirmed the stability of the V membrane with high hydrogen selectivity and permeability. The effect of types of hydrogen permeable membranes on the performance of the catalytic membrane reactor was studied by comparing Pd-coated V, Pd–23Ag, and Pd–10Ag membranes. The types of hydrogen separation membranes (i.e. hydrogen removal rates) did not have a marked effect on the propane conversion rates, while the product compositions were largely influenced by the hydrogen removal rate. Varying metal oxide supports of Ni-catalysts resulted in significant differences in the product compositions. Further, the evaluation of various catalyst-support systems (9wt%Ni–1wt%M/CeO₂, M = Co, Pt, Ag, Ru) revealed that hydrogen yield was the highest when 1wt%Ag was added to Ni/CeO₂. However, it was also found that excessive secondary metal additions can have negative impact on the catalytic behaviour of parent catalysts.     

Co-current and counter-current modes for methanol steam reforming membrane reactor

In this simulation study, methanol steam reforming reaction to produce synthesis gas has been studied in a membrane reactor when shell side and lumen side streams are in co-current mode or in counter-current mode. The simulation results for both co-current and counter-current modes are presented in terms of methanol conversion and molar fraction versus temperature, pressure, _H2O/_CH3OH${\mathrm{H}}_2\mathrm{O}/{\mathrm{CH}}_3\mathrm{OH}$ molar feed flow rate ratio and axial co-ordinate.     

Techno-economic analysis: Ethane steam reforming in a membrane reactor with H2 selectivity effect and profitability analysis

With the increased production of shale gas through a new drilling technology of hydraulic fracturing, much attention has been directed to various utilization methods for ethane accounting for about 7% of shale gas. As an efficient utilization method for ethane, ethane steam reforming in a membrane reactor is proposed in this paper to provide improved reactant conversions and product yields thus leading to a reduced operating temperature. To assess techno-economic feasibility of ethane steam reforming in a membrane reactor, parametric studies focusing on a H₂ selectivity and economic analysis predicting profitability from cash flow diagrams based on a purified hydrogen in Korea were performed simultaneously providing very useful design and economic guidelines to implement a membrane reactor for ethane steam reforming.