Integrated Membrane Reactor Research Articles

Modeling of an ammonia decomposition membrane reactor including purity with complex geometry and non-isothermal behavior

A fully coupled mass, momentum, and heat balance model was constructed in axisymmetric 2D for an ammonia decomposition packed bed membrane reactor using computational fluid dynamics and compared to experimental results for a Pd/YSZ membrane surrounded by Ru/Al2O3 catalyst. In addition to the complex geometry of the fittings used to seal the membrane, a total of 16 design variables were found to be required to fully specify the tubular integrated membrane reactor. Aside from emissivity, all input variables were experimentally determined or obtained from tabulated material property data, and no correlation fitting was performed. Experimental data were obtained for temperatures of 450 °C–530 °C, trans-membrane pressures of 0 MPa–0.4 MPa, and gas hourly space velocity feed rates of 375 h−1 to 620 h−1, chosen such that the ammonia conversion and hydrogen recovery spanned a broad range with maximum values of 99.9 % conversion or 88 % recovery with greater than 99.8 % purity. The model was able to successfully determine the ammonia conversion and hydrogen recovery of the experimental results to within an average error of −0.31 % and −2.4 %, respectively. The purity was determined within +0.0071 %, but experimental detection limitations of the impurities affected the fit between experiment and model of the N2 and NH3 in the permeate. The sensitivity of the model to various assumptions and input variables was explored. Notably, the inclusion of purity is a rarity in published models and this study adds to the discussion on the ability of modeling to predict high purity results. Compared to the relatively minimal effects of using the full geometry, the inclusion of heat transfer and radial diffusion were critical in successfully predicting the experimental results.

Catalytic membrane reactors for alkane dehydrogenation applications: an integration of catalysis and separation process

Abstract Catalytic dehydrogenation of saturated hydrocarbons to corresponding alkenes by the release of the stoichiometric amount of hydrogen is the paramount solution for safe storage of hydrogen. The utilization of a catalytic membrane reactor for this process enhances the reaction yield beyond thermodynamic equilibrium by selectively and simultaneously removing the produced H2 during the reaction. To this end, the present review is focused on the integration of H2 permeable membranes with the catalysts for dehydrogenation of lighter alkanes for coproduction of olefins and high-purity hydrogen in a single step. Besides, this review also covers dehydrogenation of liquid organic hydrogen carriers for safe storage of hydrogen. Herein, different types of H2 perm-selective membranes used for the dehydrogenation reaction are highlighted and the effect of hydrocarbon on H2 permeation through these membranes are discussed in detail. Furthermore, the simulation studies along with the experimental investigation performed on the membrane reactors for dehydrogenation of linear and cyclic alkanes are critically reviewed to find the coherence between simulation and experimental findings. Systematic discussion is done on the different types of alkane dehydrogenation reactions and the parameters affecting the reaction performance. Finally, directions are provided to prepare a cheaper and large industrial scale membrane reactor for dehydrogenation reaction. The concept of coupling an exothermic reaction with the endothermic dehydrogenation reaction is provided as a future direction study to enhance the overall yield and energy efficiency of the integrated membrane reactor.

Energy and exergy analyses of an integrated membrane reactor and CO2 capture system to generate decarbonized hydrogen

At present, most of the world hydrogen production comes from the steam reforming of natural gas, carried out in conventional reactors, which show some disadvantages such as thermodynamic equilibrium limitation, harsh operating conditions, and are responsible for huge CO2 emission in the atmosphere. To overcome these disadvantages and meet the pressing requests of the hydrogen energy decarbonisation, the interest in membrane reactors, able to provide both hydrogen generation and separation in the same unit and at milder conditions, is increasing. Indeed, in these devices, the produced hydrogen in the reaction side is removed for permeation through a membrane continuously, and it is collected as a decarbonized stream in the permeate side, meanwhile overcoming the thermodynamic equilibrium limitation of the conventional reactors, and contributing to the intensification of the process and to the CO2 capture and storage. In this study, firstly, a one-dimensional model of a membrane reactor is developed and validated. The changes in the molar flow rates of each species and the temperature through the membrane reactor length are investigated. Furthermore, the effects of some operating parameters (the operating temperature, the steam-to-carbon ratio, and the inlet pressure on the reaction side of the membrane reactor) on the system performance (methane conversion, hydrogen yield, CO2 yield, and thermal efficiency based on lower heating value) are examined. Successively, the membrane reactor model is integrated into a system-level model, taking into account further a CO2 capture unit and the plant components (compressor, boiler, burner, pump, blower, and two mixers) in order to analyze theoretically the potentiality of this integrated membrane reactor based system to generate decarbonized hydrogen (high grade hydrogen production combined to the full CO2 capture to avoid its release in the environment). The novelty of this work deals with the application for the first time of a system-level modeling is based on the principles of electrochemistry and thermodynamics to develop a detailed energy and exergy analysis, calculating further the rate of exergy destruction of each component of the proposed membrane reactor based integrated system. At the baseline simulation conditions (773 K, 9 bar, and S/C = 3/1), thermal efficiency (based on lower heating value), methane conversion of the system, hydrogen yield, CO2 yield are equal to 51 %, 67 %, 22 %, and 66 %, respectively. Furthemore, the exergy destructions distribution is 49 % for the burner, 36 % for the boiler, 14 % for the membrane reactor, and 1 % others.

Foam structured membrane reactor for distributed hydrogen production

Membrane reactor is one of the most potential methods for methane steam reforming process to achieve distributed hydrogen production. Mass, heat transfer and catalyst cost are the main hurdles to achieve its scaleup and practical applications. Here, we adopt structured foam SiC to construct Foam Structured Membrane Reactor (FSMR) and conduct systematic experimental study including catalytic reaction, membrane separation and integrated membrane reactor. The results indicate that FSMR can significantly intensify radial heat transfer (e.g., increase membrane side temperature about 20 °C) and radial mass transfer (e.g., faster H2 transfer to membrane) compared to conventional particles-packed membrane reactor (PMR). The mechanism is related to 3D continuous skeleton, cellular structure, and high thermal conductivity of structured solid foam. Also, FSMR can save more than 78% catalyst amount and achieve nearly 100% catalyst utilization efficiency.

Thermodynamic Assessment of a Solar-Driven Integrated Membrane Reactor for Ethanol Steam Reforming.

To efficiently convert and utilize intermittent solar energy, a novel solar-driven ethanol steam reforming (ESR) system integrated with a membrane reactor is proposed. It has the potential to convert low-grade solar thermal energy into high energy level chemical energy. Driven by chemical potential, hydrogen permeation membranes (HPM) can separate the generated hydrogen and shift the ESR equilibrium forward to increase conversion and thermodynamic efficiency. The thermodynamic and environmental performances are analyzed via numerical simulation under a reaction temperature range of 100–400 °C with permeate pressures of 0.01–0.75 bar. The highest theoretical conversion rate is 98.3% at 100 °C and 0.01 bar, while the highest first-law efficiency, solar-to-fuel efficiency, and exergy efficiency are 82.3%, 45.3%, and 70.4% at 215 °C and 0.20 bar. The standard coal saving rate (SCSR) and carbon dioxide reduction rate (CDRR) are maximums of 101 g·m−2·h−1 and 247 g·m−2·h−1 at 200 °C and 0.20 bar with a hydrogen generation rate of 22.4 mol·m−2·h−1. This study illustrates the feasibility of solar-driven ESR integrated with a membrane reactor and distinguishes a novel approach for distributed hydrogen generation and solar energy utilization and upgradation.

A mid/low-temperature solar-driven integrated membrane reactor for the dehydrogenation of propane – A thermodynamic assessment

Solar thermochemical conversion is an effective method for solar energy storage, and propane dehydrogenation is one popular technology to generate propylene and hydrogen, while the high temperature required in the reaction limits its efficiency and utilization. In this research, a solar–driven hydrogen permeation membrane reactor system for propane dehydrogenation is proposed for efficiently generating pure hydrogen and propylene in a mild temperature range, which can decrease the heat loss and increase the conversion rate, thereby converting low–grade solar thermal energy into high–grade chemical energy. Using the method of numerical simulation, the thermodynamic, kinetic, and environmental performances of the system are analyzed at different temperatures (250–500 °C) and H2 permeate pressures (10–5–10–2 bar). The C3H8 conversion rate, C3H6 selectivity, and C3H6 yield can achieve 99.2%, 99.1%, and 98.3% at 400 °C, 10–5 bar with the assistance of hydrogen separation. The first–law thermodynamic efficiency, solar–to–fuel efficiency, and exergy efficiency of the system are calculated to be 93.1%, 33.6%, and 73.4% (400 °C, 10–4 bar), respectively. The annual standard coal savings and carbon dioxide reduction rates are calculated to be 279.8 kg/(m2·year) and 685.5 kg/(m2·year) (400 °C, 10–5 bar). This study demonstrates the feasibility of a solar collector integrated with a membrane reactor for efficient solar energy storage via C3H8 dehydrogenation and provides guidance for further experimental research.

Model‐based simulation studies of integrated membrane reactor concepts of various complexity for the oxidative dehydrogenation of propane to propene

Model‐based simulation studies of integrated membrane reactor concepts of various complexity for the oxidative dehydrogenation of propane to propene

ANOVA analysis of an integrated membrane reactor for hydrogen production by methane steam reforming

Steam methane reforming is an endothermic reaction and it used to produce hydrogen and syngas. In this research, a factorial design is developed for an integrated Pd-based membrane reactor, producing hydrogen by methane steam reaction. In literature, no analogous works are present, because a simple sensitivity analysis is carried out without finding significant factors for the process. The reactor is modelled in MATLAB software using the Numaguchi kinetic. The reactor does not use conventional catalysts, but a Ni(10)/CeLaZr catalyst supported on SSiC ceramic foam. In ANOVA analysis, inlet temperature (550 K-815 K), methane flow rate in the feed (0.1 kmol/h-1 kmol/h), hydrogen permeability (1000 m3μmm−2hrbar0.5–3600 m3μmm−2hrbar0.5), the thickness of membrane (0.003 m-0.02 m) are the chosen factors. The analyzed responses are: hydrogen yield, carbon dioxide conversion and methane conversion. Results show that only inlet temperature, methane flow rate, their interaction and the thickens of membrane are significant. Also, the optimal operating conditions are obtained with inlet temperature, methane flow rate, hydrogen permeability and thickness of membrane equal to 550 K, 0.1 kmol/h, 3600 m3μmm−2hrbar0.5 and 0.003 m.

Integrated Design and Control of Various Hydrogen Production Flowsheet Configurations via Membrane Based Methane Steam Reforming.

This work focuses on the development and implementation of an integrated process design and control framework for a membrane-based hydrogen production system based on low temperature methane steam reforming. Several alternative flowsheet configurations consisted of either integrated membrane reactor modules or successive reactor and membrane separation modules are designed and assessed by considering economic and controller dynamic performance criteria simultaneously. The design problem is expressed as a non-linear dynamic optimization problem incorporating a nonlinear dynamic model for the process system and a linear model predictive controller aiming to maintain the process targets despite the effect of disturbances. The large dimensionality of the disturbance space is effectively addressed by focusing on disturbances along the direction that causes the maximum process variability revealed by the analysis of local sensitivity information for the process system. Design results from a multi-objective optimization study, where only the annualized equipment and operational costs are minimized, are used as reference case in order to evaluate the proposed design framework. Optimization results demonstrate the controller’s ability to track the imposed setpoint changes and alleviate the effects of multiple simultaneous disturbances. Also, significant economic improvements are observed by the implementation of the integrated design and control framework compared to the traditional design methodology, where process and controller design are performed sequentially.

Investigating the simultaneous process design and control of a membrane reactor for hydrogen production via methane steam reforming

In the present work, the simultaneous process design and control of a membrane reactor for H2 production via methane steam reforming (MSR) is performed. The problem is stated as a non-linear optimization problem with non-linear constraints, which includes economic and controllability criteria in the objective function. A linear model predictive controller (MPC) is implemented to enforce the desired dynamic performance. Utilizing this methodology two pre-defined process flowsheets for H2 production through the low temperature MSR, utilizing palladium-based membranes, are optimally designed based on economic criteria in the form of annualized capital and operating cost, and controllability criteria, in the form of the sum of squared errors during dynamic transitions. The first flowsheet is consisted of an integrated membrane reactor (IMR), whereas the second flowsheet under consideration is consisted of a cascaded arrangement between a reactor and a membrane module in series (CRM). Several other auxiliary processes such as heat exchangers, splitters, and mixers are employed. Rigorous nonlinear dynamic models have been developed assuming one dimensional transport and pseudo-homogenous conditions in the reaction zone in order to emulate the plant dynamics, whereas a linearized version of it is used by the MPC algorithm. Optimization results demonstrate the ability of the integrated process and control design framework to achieve a superior operating performance for a range of several factors affecting the operating conditions of the reactor.

Economic Evaluation of Flexibility in the Design of IGCC Plants with Integrated Membrane Reactor Modules

ABSTRACTIntegrated Gasification Combined Cycle with embedded membrane reactor modules (IGCC‐MR) represents a new technology option for the coproduction of electricity and pure hydrogen endowed with enhanced environmental performance capacity. It is viewed as an alternative to conventional coal‐ and gas‐fired power generation technologies. An IGCC‐MR power plant needs to be techno‐economically evaluated in the presence of irreducible regulatory and fuel market uncertainties for the potential deployment of an initial fleet of demonstration plants at the commercial scale. This paper applies a systematic methodological framework to assess the economic value of flexible alternatives in the design and operation of an IGCC‐MR plant under the aforementioned sources of uncertainty. The main objective is to demonstrate the potential value enhancements associated with the long‐term economic performance of flexible IGCC‐MR project investments, by managing the uncertainty associated with future environmental regulations and fuel costs. The paper provides an overview of promising design flexibility concepts for IGCC‐MR power plants and focuses on operational and constructional systems flexibility. Operational flexibility is realized through temporary plant shutdown with considerations of regulatory and market uncertainties. Constructional flexibility is realized by considering the installation of a Carbon Capture and Storage (CCS) unit at three strategic periods: (1) installation at the initial construction phase, (2) retrofitting at a later stage, and (3) retrofitting at a later stage with preinvestment. Monte Carlo simulations and financial analysis demonstrate that, in the presence of irreducible uncertainty, the most economically advantageous flexibility option is to install CCS in the initial IGCC‐MR construction phase.

Reaction integrated separation of homogenous catalysts in the hydroformylation of higher olefins by means of organophilic nanofiltration

Discovered in 1938, hydroformylation is one of the most important reactions using homogeneous precious metal catalysts. In the process, olefins react to aldehydes using hydrogen and carbon monoxide (synthesis gas). The main problem for the sensitive and expensive catalyst system, however, is the downstream processing of the reaction products, typically done by thermal separation, by which the catalyst system deactivates and is lost by clustering. In contrast, organophilic nanofiltration allows the catalyst to be separated under stabilizing conditions in a gentle and also energy saving way. As a first step to an integrated membrane reactor concept for homogeneous catalysis, two different membranes and the influence of CO on the separation were investigated for the Rh catalysed hydroformylation of octene and dodecene as examples. Catalyst rejections in excess of 99% in a single stage membrane separation combined with a high CO partial pressure that prevents the catalyst from deactivation and losses through the formation of clusters during the separation shows that organophilic nanofiltration can be a benchmark setting separation technology in homogeneous catalysis.

Energy efficiency of membrane-based fuel processors – PEM fuel cell systems

This work presents a simulative energy efficiency analysis performed on fuel processor – PEMFC systems, considering methane as fuel and steam reforming or autothermal reforming as processes to produce hydrogen. Computation of energy efficiency takes into account the power required by the auxiliary units, coupling of the fuel processor with the fuel cell as well as heat recovery and integration. Two system configurations were simulated and compared: an innovative configuration, based on an integrated membrane reactor directly coupled with the fuel cell, and a conventional configuration, based on a classic reforming reactor followed by a conventional CO clean-up section, constituted by water gas shift and preferential CO oxidation reactors. Reforming temperature, plant pressure, steam to methane and oxygen to methane inlet ratios were considered as process parameters. The effect of the addition of steam as sweep gas is also presented and discussed.

Hydrogen production by reforming of liquid hydrocarbons in a membrane reactor for portable power generation—Experimental studies

One of the most promising technologies for lightweight, compact, portable power generation is proton exchange membrane (PEM) fuel cells. PEM fuel cells, however, require a source of pure hydrogen. Steam reforming of hydrocarbons in an integrated membrane reactor has potential to provide pure hydrogen in a compact system. Continuous separation of product hydrogen from the reforming gas mixture is expected to increase the yield of hydrogen significantly as predicted by model simulations. In the laboratory-scale experimental studies reported here steam reforming of liquid hydrocarbon fuels, butane, methanol and Clearlite ® was conducted to produce pure hydrogen in a single step membrane reformer using commercially available Pd–Ag foil membranes and reforming/WGS catalysts. All of the experimental results demonstrated increase in hydrocarbon conversion due to hydrogen separation when compared with the hydrocarbon conversion without any hydrogen separation. Increase in hydrogen recovery was also shown to result in corresponding increase in hydrocarbon conversion in these studies demonstrating the basic concept. The experiments also provided insight into the effect of individual variables such as pressure, temperature, gas space velocity, and steam to carbon ratio. Steam reforming of butane was found to be limited by reaction kinetics for the experimental conditions used: catalysts used, average gas space velocity, and the reactor characteristics of surface area to volume ratio. Steam reforming of methanol in the presence of only WGS catalyst on the other hand indicated that the membrane reactor performance was limited by membrane permeation, especially at lower temperatures and lower feed pressures due to slower reconstitution of CO and H 2 into methane thus maintaining high hydrogen partial pressures in the reacting gas mixture. The limited amount of data collected with steam reforming of Clearlite ® indicated very good match between theoretical predictions and experimental results indicating that the underlying assumption of the simple model of conversion of hydrocarbons to CO and H 2 followed by equilibrium reconstitution to methane appears to be reasonable one.

Hydrogen production by reforming of liquid hydrocarbons in a membrane reactor for portable power generation—Model simulations

One of the most promising technologies for lightweight, compact, portable power generation is proton exchange membrane (PEM) fuel cells. PEM fuel cells, however, require a source of pure hydrogen. Steam reforming of hydrocarbons in an integrated membrane reactor has potential to provide pure hydrogen in a compact system. In a membrane reactor process, the thermal energy needed for the endothermic hydrocarbon reforming may be provided by combustion of the membrane reject gas. The energy efficiency of the overall hydrogen generation is maximized by controlling the hydrogen product yield such that the heat value of the membrane reject gas is sufficient to provide all of the heat necessary for the integrated process. Optimization of the system temperature, pressure and operating parameters such as net hydrogen recovery is necessary to realize an efficient integrated membrane reformer suitable for compact portable hydrogen generation. This paper presents results of theoretical model simulations of the integrated membrane reformer concept elucidating the effect of operating parameters on the extent of fuel conversion to hydrogen and hydrogen product yield. Model simulations indicate that the net possible hydrogen product yield is strongly influenced by the efficiency of heat recovery from the combustion of membrane reject gas and from the hot exhaust gases. When butane is used as a fuel, a net hydrogen recovery of 68% of that stoichiometrically possible may be achieved with membrane reformer operation at 600 °C (873 K) temperature and 100 psig (0.791 MPa) pressure provided 90% of available combustion and exhaust gas heat is recovered. Operation at a greater pressure or temperature provides a marginal improvement in the performance whereas operation at a significantly lower temperature or pressure will not be able to achieve the optimal hydrogen yield. Slightly higher, up to 76%, net hydrogen recovery is possible when methanol is used as a fuel due to the lower heat requirement for methanol reforming reaction, with membrane reformer operation at 600 °C (873 K) temperature and 150 psig (1.136 MPa) pressure provided 90% of available combustion and exhaust gas heat is recovered.

Modeling of a novel membrane reactor to integrate dehydrogenation of ethylbenzene to styrene with hydrogenation of nitrobenzene to aniline

The catalytic dehydrogenation of ethylbenzene to styrene is coupled with the catalytic hydrogenation of nitrobenzene to aniline in a simulated integrated reactor formed of two fixed beds separated by a hydrogen-selective membrane, where both hydrogen and heat are transferred across the surface of membrane tubes. A pseudo-homogeneous model of the two fixed beds predicts the performance of this novel configuration first proposed by Moustafa and Elnashaie [Simultaneous production of styrene and cyclohexane in an integrated membrane reactor. Journal of Membrane Science 178 (1), 171–184]. Both co-current and counter-current operating modes are investigated and the simulation results are compared with corresponding predictions for an industrial adiabatic fixed bed reactor operated at the same feed conditions. The conversion of ethylbenzene and the yield of styrene in the membrane reactor are predicted to exceed by a wide margin those in the industrial adiabatic fixed bed reactor. Aniline is also produced as an additional valuable product in a favorable manner, and autothermality is achieved within the reactor. The results suggest that coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.

Semicontinuous production of lactic acid from cheese whey using integrated membrane reactor

Semicontinuous production of lactic acid from cheese whey using free cells of Bifidobacterium longum with and without nanofiltration was studied. For the semicontinuous fermentation without membrane separation, the lactic acid productivity of the second and third runs is much lower than the first run. The semicontinuous fermentation with nanoseparation was run semicontinuously for 72 h with lactic acid to be harvested every 24 h using a nanofiltration membrane unit. The cells and unutilized lactose were kept in the reactor and mixed with newly added cheese whey in the subsequent runs. Slight increase in the lactic acid productivity was observed in the second and third runs during the semicontinuous fermentation with nanofiltration. It can be concluded that nanoseparation could improve the lactic acid productivity of the semicontinuous fermentation process.

Integration of H 2-separating membrane technology in gas turbine processes for CO 2 capture

The paper describes the promising possibility to capture CO 2 in natural gas fired power cycles through the use of a high-temperature membrane reactor of the methane-steam reforming type with an integrated H 2-separating membrane. Two types of membranes are investigated: Pd membranes, which could allow for zero-emission power cycles, and microporous membranes, the use of which in the present work means that 20% of the generated CO 2 is emitted to the atmosphere. The membrane reactor is a complex component and much further work is required to find optimum power cycle operating conditions. Combined cycles with an integrated membrane reactor were investigated and the thermal efficiency in some of these non-optimized cases was superior at 47%.

Design and operation of an integrated membrane reactor for enzymatic cellulose hydrolysis

A purposely built membrane reactor with combined reaction and separation zone in a single piece of equipment was tested for heterogeneous enzymatic hydrolysis of a hardwood derived cellulosic material. The design and operation features a process of simultaneous reaction and in situ removal of products (reducing sugars) in order to reduce the effect of product inhibition on the cellulase enzyme. The integrated reactor system differs from the hybrid integration of reaction-separation system where the reaction takes place in a stirred reaction vessel and the separation of the product is carried out in a separate cross-flow membrane filtration unit. Various operating strategies of semi-continuous and continuous product removal and substrate feeding were examined and optimised in respect to their effect on reducing product inhibition and increasing reactor productivity and product yield. The effect of total enzyme concentration and possible enzyme deactivation by shear stress were also investigated. The findings from examining the performance of a well understood enzymatic system in a new integrated reactor system would facilitate the understanding and development of system integration and process intensification in combined reaction-separation process which may alleviate common problems (product inhibition, inefficient interfacial mass transfer, slow kinetics and low reactor productivity) in heterogeneous enzyme catalysis systems. The cellulose substrate conversion ratio was 53% in the continuous operation of reaction with simultaneous product removal. This compares favourably with 35% substrate conversion in traditional batch operations. The improvement in overall reaction rate through adopting an in situ product removal strategy was rather limited, mainly because of the inherent slow reaction kinetics of the heterogeneous cellulose hydrolysis and the complex interfacial interactions between the cellulase enzymes and the solid cellulose substrate.

Simultaneous production of styrene and cyclohexane in an integrated membrane reactor

A rigorous heterogeneous model is used to study the performance of the membrane catalytic reactor for the dehydrogenation of ethylbenzene to styrene. The mathematical model is extended to simulate a novel hybrid configuration which is composed of two catalytic sections separated by hydrogen selective composite membrane for hydrogen separation. One side of the reactor is a dehydrogenation section in which ethylbenzene is dehydrogenated to styrene, while the other catalytic side is a hydrogenation section in which benzene is catalytically converted to cyclohexane. The continuous removal of hydrogen from the dehydrogenation section leads to the shift of equilibrium conversion in this section, thus higher styrene yield is obtained. Detailed parametric investigation has been carried out for the membrane reactor and the hybrid reactor configurations. The effect of co-current and counter-current flow pattern is investigated. Superior performance in terms of ethylbenzene conversion enhancement far above the equilibrium value was observed in the hybrid reactor configuration. The selectivity and styrene yield considerably exceed the industrial values.