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The combination of traditional reactor and permeable membrane is beneficial to increase the production rate of the target product. How to design a high efficiency and energy saving membrane reactor is one of the key problems to be solved urgently. This paper utilizes finite-time thermodynamics and nonlinear programming to solve the optimal configurations of the membrane reactor of steam methane reforming (MR-SMR) for two optimization objectives, that is, heat exchange rate minimization and power consumption minimization. The exterior wall temperature and fixed hydrogen production rate are regarded as the control variable and constraint, respectively. The results indicate that the hydrogen production rate and heat exchange rate in MR-SMR are increased by 108.58% and 58.42%, respectively, while the power consumption is reduced by 33.44% compared with those in the traditional reactor under the same condition. Compared with the results in reference reactor (MR-SMR obtained with initial values), the heat exchange rate is reduced by 1.40% by optimizing the exterior wall temperature, and the power consumption is reduced by 5.10% by optimizing the exterior wall temperature and molar flow rate of sweep gas. The optimal distributions of exterior wall temperatures in the optimal reactors of minimum heat exchange rate and power consumption have a theoretical guiding significance for the thermal design of the membrane reactors.

The available natural energy sources are insufficient to meet everyone's needs. Due to an increased population, dwindling natural resources, limited natural sources, and environmental issues, it is critical to focus on reproducing, recycling, and reused techniques. Coal is a major source of energy generation in India, but it causes significant environmental pollution. The use of petroleum oil for transportation contributes to global warming, and domestic and industrial waste contributes to pollution. It is critical to consider waste water treatment as well as alternative energy sources such as biofuel. Conventional technology is insufficient in terms of both economics and the environment. Membrane technology is an effective and efficient technology. This paper provides an overview of recent research on membrane technology applications in waste water treatment, biofuel production (such as biodiesel and bioethanol). It also discusses membrane reactors, membrane bioreactors, and mixed matrix membrane reactor applications for biodiesel production, as well as hybrid pervaporization membrane bioreactors, integrated pervaporization membrane bioreactors for bioethanol production, the membrane bioreactors application for waste water treatment.

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.

Photocatalytic membrane reactors (PMRs) are a promising treatment technology for degradation of organic compounds discharged from wastewater treatment facilities. This review presents information about TiO2 nanoparticles, which are the widely used photocatalyst semiconductor in PMRs, and how doping can be used to make TiO2 able to absorb part of the visible spectrum. Then, many examples are presented showing PMR applications for various feedwater types ranging from dyes, oils, pharmaceuticals, and antibiotic resistant bacteria, either in simulated wastewater or water from real matrices. Although the results are dependent on the feed, photocatalyst, and type of reactor, the PMR technology can achieve removal efficiency higher than 95% for some situations. PMRs have also shown antimicrobial properties in removing 99.9% of antibiotic-resistant bacteria in one study presented. Additionally, PMRs have demonstrated antifouling properties due to their surface modification – resulting in their reuse and extended lifespan. Although photocatalytic membrane reactors can achieve quantitative removal in some feed water types, more development is needed before employing them for more widespread wastewater treatment. In this sense, the article ends with a perspective section where some possible advances in the photocatalyst and reactor design are suggested which can expand the range of PMR applications.

Electrocatalytic palladium membrane reactors (ePMRs) use electricity and water to drive hydrogenation reactions without forming H2 gas. In these reactors, a hydrogen-permeable palladium foil physically separates electrochemical proton generation in aqueous media from chemical hydrogenation in organic media. We report herein the use of the ePMR to electrolytically hydrogenate furfural, an important biomass derivative. This system was proven to convert furfural into furfuryl alcohol and tetrahydrofurfuryl alcohol with 84% and 98% selectivities, respectively. To reach these high selectivities, we designed and built an ePMR for high-throughput testing. Using this apparatus, we tested how different solvents, catalysts, and applied currents impacted furfural hydrogenation. We found that bulky solvents with weak nucleophilicities suppressed the formation of side products. Notably, these types of solvents are not compatible with standard electrochemical hydrogenation architectures where electrolysis and hydrogenation occur in the same reaction chamber. This work highlights the utility of the ePMR for selective furfural hydrogenation without H2 gas, and presents a possible pathway for helping to decarbonize the hydrogenation industry.

During the past decade, the growth in membrane research and technology advanced and multiplied in usage for many industries including water and wastewater. A major limitation of the application is due to membrane fouling. In this work, the construction, start-up calibration and testing of a membrane unit as well as an examination into the fouling and cleaning aspect of the ceramic membranes are investigated. An aqueous solution containing precipitate is fed to the unit in order to observe fouling behaviour. Effluent wastewater from a bioreactor, CUBEN, is also tested with the unit and membrane cleaning is performed using various chemical agents. For both chemically enhanced backwash (CEB) and membrane soaking, hydrochloric acid cleaning agent (

Potent carbon-neutral energy carriers bring a vital solution for sustained industrialization and environmental protection. Hydrogen as a novel zero-emission energy carrier offers more than twice energy per unit mass compared to other fuels. Membrane reactor technology transforms gray hydrogen to blue by selective hydrogen separation and carbon dioxide capture from the product mixture. Moreover, improved reactant conversion during reversible steam reforming of methane, methanol, and ethanol; water gas-shift; and dehydrogenation of cyclic and aliphatic hydrocarbons as well as enhanced hydrogen yield are results of selective and distributed hydrogen separation from membrane reactor. In this review applicability of membrane reactor technology for above-mentioned reactions are discussed and effects of different membranes, reactor designs, and operating conditions on performance of membrane reactors are investigated. Finally, impact of membrane reactor technology on reactant conversion, product yield, and overall process are explained and future directions of this technology are outlined.

Introduction. The article provides a review of technologies for membrane fractionation of various hydrolyzed food substrates in membrane bioreactors (MBR). In food industry, MBRs are popular in functional food production, especially in the processing of whey, which is a very promising raw material due to its physicochemical composition. Study objects and methods. The research was based on a direct validated analysis of scientific publications and featured domestic and foreign experience in MBR hydrolysis of protein raw material. Results and discussion. The MBR hydrolysis of proteins combines various biocatalytic and membrane processes. This technology makes it possible to intensify the biocatalysis, optimize the use of the enzyme preparation, and regulate the molecular composition of hydrolysis products. The paper reviews MBRs based on batch or continuous stirring, gradient dilution, ceramic capillary, immobilized enzyme, etc. Immobilized enzymes reduce losses that occur during the production of fractionated peptides. Continuous MBRs are the most economically profitable type, as they are based on the difference in molecular weight between the enzyme and the hydrolysis products. Conclusion. Continuous stirred tank membrane reactors have obvious advantages over other whey processing reactors. They provide prompt separation of hydrolysates with the required biological activity and make it possible to reuse enzymes.

We introduce a Spin Transfer Automated Reactor (STAR) that produces continuous parahydrogen induced polarization (PHIP), which is stable for hours to days. We use the PHIP variant called signal amplification by reversible exchange (SABRE), which is particularly well suited to produce continuous hyperpolarization. The STAR is operated in conjunction with benchtop (1.1 T), and high field (9.4 T) NMR magnets, highlighting the versatility of this system to operate with any NMR or MRI system. The STAR uses semipermeable membranes to efficiently deliver parahydrogen into solutions at nano to milli Tesla fields, which enables (1)H, (13)C and (15)N hyperpolarization on a large range of substrates including drugs and metabolites. The unique features of the STAR are leveraged for important applications, including continuous hyperpolarization of metabolites, desirable for examining steady-state metabolism in vivo as well as for continuous RASER signals desirable for the investigation of new physics.

In view of its important role as raw materials in various energy and environment fields, pure oxygen has been widely required. The present cryogenic distillation, polymeric membrane and pressure swing adsorption (PSA) air separation methods are either energy-intensive or producing non-high purity oxygen. The comparative analysis of the inorganic dense ceramic-based oxygen transport membranes (OTMs) with these traditional oxygen production technologies and the H2/O2 production by electrolysis of water shows irreplaceable advantages. The oxygen transport mechanism has been elaborated further to reveal the theoretical basis for the development of OTMs. The dual-phase membranes that have been widely studied are divided into three types according to the conduction paths of oxygen ions and electrons. Based on a review of the different types of OTM materials experienced in the past 30 years, its applications such as oxygen-enriched combustion involving H2 and membrane reactors have been discussed. Finally, challenges and future directions are analyzed according to potential industrial design directions and competitive technologies of OTMs.

This paper reports the results obtained in a techno-economic analysis of the Steam Methane Reforming (SMR) technology aided with solar heat, developed and demonstrated in the European FCH JU project CoMETHy: a compact membrane reformer heated with molten salt up to 550 °C allowed to simultaneously carry out methane steam reforming, water-gas-shift reaction and hydrogen separation. This reactor can be integrated with new generation Concentrating Solar Thermal (CST) systems to supply the process heat. Experimental validation of the technology has been successfully achieved in a pilot scale plant and the results recently published. In this paper, we introduce a fully-integrated scheme and operation strategies of a plant on the 1500 Nm3/h hydrogen production scale. Then, techno-economic analysis of this new solar-driven process is presented to evaluate its competitiveness. Considering a plant capacity of 1500 Nm3/h (pure hydrogen production) and today's costs for the methane feed and the CST technology, obtained Hydrogen Production Cost (HPC) are in the range of 2.8–3.3 €/kg for a “solar-hybrid” system with high capacity factor (8000 h/year operation) and 4.7 €/kg for a “solar-only” case, while HPC≅1.7 €/kg can be obtained with the conventional route under equivalent assumptions. However, a sensitivity analysis shows that the expected drop of the cost of the CST technology will bring the HPC around 2.4 €/kg for the “solar-hybrid” case and close to 3.4 €/kg for the “solar-only” case, thus making the cost of solar reforming closer to conventional SMR with CO2 capture and with wind/solar electrolysis in the future. In the “solar-hybrid” case total CO2 production can be reduced by 13–29% with 58–70% of produced CO2 recovered as pure stream (at 1.3 bar); in the “solar-only” case total CO2 production can be reduced by 52% and 100% of produced CO2 recovered as pure stream (at 1.3 bar). However, compared to the conventional route, CO2 avoidance costs are still relatively high (≥137 €/tonCO2) and process optimization measures required. Therefore, optimization measures have been outlined to increase the overall process efficiency and further reduce the HPC.

The features of steam reforming of a hydrocarbon mixture containing 71.8% СН4, 15.6% С2Н6, 10.2% С3Н8, and 2.4% С4Н10 in a membrane reactor with a 30 μm thick Pd–Ru alloy foil and the NIAP-03-01 industrial nickel catalyst have been investigated. The reaction was studied in the temperature range of 723–823 K at a steam/feed ratio of 5 and space velocities of 1800 and 3600 h−1. Comparison with the “nonmembrane” reaction showed that in the membrane reactor, the feedstock conversion to form H2 and CO2 increases and the yield of byproduct methane and carbon deposits decreases. With an increase in the rate of H2 recovery from the reaction mixture by permeate evacuation, the degree of conversion by the water gas shift reaction yielding H2 and CO2 increases. Under optimal conditions (773–823 K, 1800 h−1, permeate evacuation), high purity H2 is formed in an amount of about 0.8 mmol/(min gcat) and more than 80% of H2 is recovered from the reaction mixture. As the feed space velocity increases to 3600 h−1, the yield of hydrogen increases to 1.3 mmol/(min gcat) and 90% of H2 is recovered through the membrane. However, a high conversion of the feedstock into carbon deposits is observed in this case. In general, the results obtained show that it is possible to obtain high-purity hydrogen from associated petroleum gases by optimizing the conditions of steam reforming in a membrane reactor without preliminary isolation of C2+ alkanes from the feedstock.

Comparative analysis of membrane oscillation and aeration in a photocatalytic membrane reactor is conducted. The investigation involved degradation of methylene blue dye as model pollutant using suspended ZnO photocatalyst and UV illumination. The effect of reactor hydrodynamics and design parameters on the system performance and its relation to the membrane-catalyst retention characteristics is evaluated using flat surface membranes roughed with transverse turbulence promoters (TP). The investigation showed that membrane oscillation is more energy efficient than aeration and can provide higher shear rates and better mixing which decreases both the catalyst agglomeration and deposition on the membrane surface. These, in turn, increase both the suspended catalyst concentration in solution and enhance the membrane flux. Compared to oscillation, achieving high shear rates through aeration is limited due to the adverse effects of high gas flow on photocatalytic reactions. Considering the above together with the small effect of aeration on ZnO photocatalytic kinetics, the need for aeration may be relaxed when using membrane oscillation in a ZnO photocatalytic reactor.

Membrane reactors are inherently two-dimensional systems that require complex models for an accurate description of the different transport phenomena involved. However, when their performance is limited by mass transport within the reactor rather than by the selective product permeation across the membrane, the 2D model may be significantly simplified. Here we extend results previously found for methane steam reforming membrane reactors to show that such simplified two-dimensional model admits either a straightforward analytical solution for the cross-section averaged concentration profile, or can be reduced to a 1D model with an enhanced Sherwood number, depending on the stoichiometry of the reaction considered. Interestingly, the stoichiometry does not affect the expression of the enhanced Sherwood number, indicating that a versatile tool has been developed for the determination of membrane reactor performance at an extremely low computational cost and good degree of accuracy.

Methane steam reforming is the most widely used pathway for hydrogen production. In this context, the use of a fixed bed catalytic reactor with a hydrogen-selective membrane is one of the most promising technologies to produce high purity hydrogen gas. In this work, the membrane reactor three-dimensional computational fluid dynamic (CFD) model was developed to investigate the performance. In this model, methane steam reforming global kinetic model has been coupled with the CFD model using User-Defined Function (UDF). Whereas, hydrogen permeation across the membrane is implemented by introducing source and sink formulation. The CFD simulation results were compared to the experimental data, where the developed model successfully captured the experimentally observed trends. We studied the influence of the various operating parameters, as temperature, steam to carbon ratio, sweep gas flow configuration and space velocity on the overall performance. The main observation and attained optimal operation windows from the study was discussed to provide insight into the factors affecting the overall performance.

In this study, a corrosion-stable silica membrane was developed to be used in H2 purification during the hydrogen iodide decomposition (2HI → H2 + I2), which is a new application of the silica membranes. From a practical perspective, the membrane separation length was enlarged up to 400 mm and one end of the membrane tubes was closed to avoid any thermal variation along the membrane length and sealing issues. The silica membranes consisted of a three-layer structure comprising a porous α-Al2O3 ceramic support, an intermediate layer, and a top silica layer. The intermediate layer was composed of γ-Al2O3 or silica, and the top silica layer that is H2 selective was prepared via counter-diffusion chemical vapor deposition of a hexyltrimethoxysilane. To the best of our knowledge, this is the first report of 400-mm-long closed-end silica membranes supported on Si-formed α-Al2O3 tubes produced via chemical vapor deposition method. A 400-mm-long closed-end membrane using a Si-formed α-Al2O3 tube exhibited a higher H2/SF6 selectivity of 1240 but lower H2 permeance of 1.4 × 10−7 mol Pa−1 m−2 s−1 with compared with the membrane using a γ-Al2O3-formed α-Al2O3 tube (907 and 5.6 × 10−7 mol Pa−1 m−2 s−1, respectively). The membrane using the Si-formed α-Al2O3 tube was more stable in corrosive HI gas than a membrane with a γ-Al2O3-formed α-Al2O3 tube after 300 h of stability tests. In conclusion, the developed silica membranes using the Si-formed α-Al2O3 tubes seem suitable for membrane reactors that produce H2 on large scale using HI decomposition in the thermochemical iodine–sulfur process.

In the current study, the energy and exergy efficiencies of three hydrogen production systems from ammonia decomposition using dielectric barrier discharge plasma (DBD) were comparatively evaluated. The hydrogen gas was separated in a cylindrical plasma membrane reactor (PMR) using the Pd–Cu40% membrane with a thickness of 20 μm. The pre-catalytic reactor (CR) is added to the second system (CR-PMR), additionally, the CR is filled with the catalytic material type of 2%Ru/Al2O3 and the CR temperature is raised to 450 °C. Furthermore, the zeolite material type of SA-600 A was added to the PMR in the third H2 production system (PMR) to enhance the hydrogen permeation through the Pd–Cu membrane. The hydrogen production rate was enhanced by combining the plasma and zeolite material in the third system (CR-CPMR). Moreover, the maximum obtained hydrogen production rates were 2.66, 81.6, and 96.6% in PMR, CR-PMR, and CR-CPMR or catalytic PMR, respectively. Also, it was observed that the energy efficiency increased by adding the CR to the system, while, the exergy efficiency values of all ammonia decomposition systems were still low due to the effect of system irreversibility. Additionally, the maximum energy efficiencies values were 0.8, 16.1, 44.1%, while the maximum exergy efficiencies values were 0.156, 4.91, and 6.344% for PMR, CR-PMR, and CR-CPMR, respectively. The exergy destruction rate of all NH3 decomposition systems was still high although using the modified systems. The depletion factor is enhanced with the feeding ammonia flow rate increased while the sustainability index decreased at the same flow rates. Moreover, it was seen that the depletion factor results of PMR only were higher than other systems due to the exergy destruction rate was high.

This paper is a numerical study about ethylbenzene (EB) dehydrogenation and nitrobenzene (NB) hydrogenation in a membrane reactor. Both sides of the membrane reactor were filled with an appropriate catalyst. Effect of different parameters in the dehydrogenation side including inlet temperature, pressure, catalyst porosity, and initial ethylbenzene concentration was investigated on temperature distribution and ethylbenzene and nitrobenzene conversion in the membrane reactor. Generally, the results showed that an increase in all parameters except the catalyst porosity can improve ethylbenzene and nitrobenzene conversion. The temperature was firstly decreased in the dehydrogenation side as the reactions were endothermic but there was an increase in temperature after a shorter distance from the entrance because of transferring heat from hydrogenation side into dehydrogenation side. Change in pressure has a considerable effect on the hydrogen transferring from dehydrogenation side into hydrogenation side. The styrene yield was not improved by increasing the initial ethylbenzene concentration from 5 to 20 mol/s but it has a positive influence on the yields of benzene and toluene. It was possible to achieve 0.97 of ethylbenzene conversion at 950 K.

The objective of this study is to develop ceramic supports employed in the preparation of catalytic membrane reactor using less catalyst and lower temperature and enabling H-2 production and separation together through the dry reforming of methane. For this reason, nine different ceramic supports are fabricated by using three different types of activated alumina (acidic, basic and neutral) and three different Si/Al molar ratios at two different calcination temperatures in order to investigate the surface acidity and basicity effect of supports to be used with impregnated Rh catalyst for rising the activity to CH4, CO2 and sensitivity to coke formation encountered with Ni-based catalysts. Subsequently, the effect of those variations on supports is determined by using XRD, SEM and BET instruments, in addition to this, H-2 permeability test of five supports having high BET surface areas is also performed with using constant volume-variable pressure technique at the temperatures of between 25 and 250 degrees C. Acidic alumina sintered at 600 degrees C and containing Si/Al ratio of 0.648 represented the highest hydrogen permeability with higher activity, whereas, neutral alumina calcined at the temperature of 600 degrees C having Si/Al ratio of 0.555 gave the highest activity with the lower hydrogen permeability, while basic alumina sintered at the temperature of 600 degrees C and including Si/Al ratio of 0.648 imparted lower activity with higher hydrogen permeability. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Scientific Research Projects Foundation of HITIT UNIVERSITY [MUH03.11.011, MUH03.13.001, MUH19002.15.003]; METU (Middle East Technical University) Central Laboratory; ERCIYES UNIVERSITY Technology Research and Application Center The authors would like to thank the Scientific Research Pro-jects Foundation of HI_TI_T UNIVERSITY for the financial sup-port given in the projects with the numbers of MUH03.11.011, MUH03.13.001, MUH19002.15.003 and METU (Middle East Technical University) Central Laboratory, the ERCI_YES UNI-VERSITY Technology Research and Application Center. Also, we thank the HI_TI_T UNIVERSITY Scientific and Technical Application and Research Center that contributed to the measurements of SEM, BET, XRD and DSC results and prepa-ration of this work. We appreciate the Cambridge Editing and Proofreading for editing and proofreading service of the manuscript as well. WOS:000684993300009 2-s2.0-85090865203

This study proposes the steam reforming of a synthetic biogas stream containing 200 ppm of H2S, carried out in a non-commercial supported Pd-Au/Al2O3 membrane reactor (7-8 mu m selective layer thickness) at 823 K and 150 kPa over a non-commercial Rh(1%)/MgAl2O4/Al2O3 catalyst. This system is able to recover almost 80% of the total hydrogen produced during the reaction and shows good resistance to the H2S contamination, as confirmed by stable methane conversions for more than 400 h under operation. For comparison, the same reaction was carried out in a commercial self-supported Pd-Ag membrane (150 mu m wall thickness), yielding a hydrogen recovery equal to 40% at 623 K and 200 kPa, and presenting stable methane conversions for less than 200 h under operation due to the effect of the H2S contamination. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Biomass is an abundant source of energy, and its utilization will increase in the near future. One of the promising ways to recapture energy from biomass is by the gasification process. The primary product from biomass gasification (synthesis gas) can be used for a wide range of applications. By-products such as tar are also produced along with synthesis gas, which needs to be removed or converted catalytically. In recent times, a tremendous effort has been made to develop efficient and cheap catalysts for catalytic conversion of tar. Among many kinds of catalysts, the catalysts derived from natural minerals (olivine or dolomite) and solid waste (incinerated bottom ash or biochar) will make the process more sustainable. Therefore, in this review, the development of natural minerals and waste-derived catalysts for the biomass-derived tar reforming reaction was summarized. Besides tar conversion by thermal catalytic processes, the tar conversion is also highlighted using a low-temperature plasma process combined with catalysts. Furthermore, the possible process intensification by applying selective gas separable membranes was also summarized. The selective O2 permeable membrane at the tar reforming zone improves the stability of the catalyst and quality of syngas by gasifying the deposited coke during the reforming reaction. Finally, a conclusion section covering possible challenges associated with biomass tar reforming technology, membranes, and plasma catalysis was provided.

Hydrogen (H2) is currently receiving significant attention as a sustainable energy carrier. Steam methane reforming (SMR) accounts for approximately 50% of H2 production methods worldwide. However, SMR is concern because of the prodigious carbon dioxide (CO2) emissions that have resulted in a global climate emergency. CO2 emissions remain, although some efforts have been made in a membrane reactor (MR) coupled with membranes to improve the H2 yield. A sorption-enhanced membrane reactor (SEMR) has been proposed as a next-generation process for simultaneous H2 production and CO2 capture. In this study, the thermodynamic and economic evaluation of SEMR were implemented using a process simulation, an itemized cost estimation, a sensitivity analysis (SA), and an uncertainty analysis (UA). The thermodynamic analysis results revealed that unit H2 production costs of 4.53, 1.98, and 3.04 $ kgH2−1 were obtained at 773 K for a conventional packed-bed reactor (PBR), a MR, and a SEMR, respectively. The SA results identified PSA as the most critical economic parameter for a unit H2 production cost for a PBR, whereas natural gas is determined to be the most influential parameter for a MR and a SEMR. The UA results from a Monte-Carlo simulation provided a broad range of unit H2 production costs, with 4.26–5.44 $ kgH2−1 for a PBR, 1.61–2.94 $ kgH2−1 for a MR, and 2.83–4.19 $ kgH2−1 for an SEMR. This indicates that using a SEMR for next-generation H2 production and CO2 capture is beneficial.

Process intensification in a membrane reactor is an efficient and compact way to produce hydrogen. A methane-rich gas mixture that simulated the composition of pre-reformed naphtha (PRN; with a steam-to-carbon ratio of 2.7) was reformed at temperatures of 550 °C–625 °C and pressures up to 40 barg. The reactor contained commercial steam reforming catalyst and a 14.8 cm long, 2.6 μm thick Pd-1.8Au (wt. %) membrane on a porous alumina support. Methane conversions approaching 90% were obtained in the membrane reactor at a gas-hourly space velocity of 676 h−1, compared to ≤30% conversion at the same conditions in conventional reactor mode (CM) without withdrawing hydrogen through the membrane. The results were compared to steam methane reforming (SMR) in the membrane reactor at similar conditions. The nitrogen leak through the membrane increased slowly during the testing, because of both pinhole formation and some leakage through the end seals.

Formaldehyde-based chemistry plays a significant role in the production of different materials. In this work, attempts have been made to revamp a silver catalyzed formaldehyde plant by applying membrane technology. The conventional silver catalyst packed bed reactor was replaced by a shell and tube membrane reactor. A steady-state one-dimensional model was applied to evaluate the performance of the proposed membrane process. The model was validated with experimental results from the plant. The effects of various parameters including reactor pressure, feed temperature, and membrane thickness on the membrane reactor were investigated. Results showed that the effect of feed temperature on production rates was negligible. The increase in pressure and decrease in membrane thickness, however, leads to increase products. The simultaneous production of 100 tonnes/day of formalin 37% (37 wt% formaldehyde in water) and 500 kg/day pure hydrogen achieved by the proposed process. Furthermore, the exiting reactor temperature can be reduced to 420 °C which is significantly lower than the conventional method (650 °C).

A microwave (MW) heating system induced by a magnetic field was designed and applied for uniform heating of a Pd membrane selectively through hydrogen. This system aimed to control the temperature of the membrane and the hydrogen permeation rate. Although the conventional dielectric heating by MWs is not suitable for metal membranes because of the reflection of MWs, a magnetic field can excite the surface current (eddy current) and causes Joule heating. First, this was successfully achieved for thin metal films in a frequency-variable single-mode MW reactor system with a cylindrical cavity. The temperature of the surface was controlled precisely by a resonance frequency autotracking function. Then, for the control of the hydrogen permeation rate through the Pd membrane, this system was applied to a pore-filling-type Pd membrane where the Pd nanoparticles were filled in the nanospace void of the Al2O3 support tube, suggesting high durability. The temperature of Pd membrane could be quickly and precisely controlled due to direct heating by this MW system. Hydrogen permeation rate was well controlled associated with the temperature of the membrane.

Thermo-Catalytic decomposition (TCD) of methane can be regarded as a cornerstone towards the development of greenhouse gas-free processes for pure hydrogen production. Most studies of TCD focused on process schemes where the extraction of hydrogen from the gaseous CH 4 − H 2 mixture is accomplished in a unit separated from the reaction environment. In this article, we investigate numerically a different setup that involves the use of a semi-batch annular fixed-bed membrane reactor. The permeselective membrane allows to lower the reaction temperature, overcoming equilibrium limitations. The intrinsic time-dependency of the process (induced by catalyst deactivation due to massive deposition of the solid carbon product), together with spatial concentration gradients triggered by hydrogen permeation through the membrane give rise to a non-trivial dynamical behavior of the reactor. Specifically, we observe that a localized reaction front develops near the membrane at the early stage of the process. At later times, the front moves away from the membrane zone throughout the bed as larger and larger portions of the catalyst become inactive. The front thickness and dynamics are found to have a strong influence upon the overall timescales of the reaction. A dimensionless analysis of the dependence of the reactor efficiency on the pressure and on the catalyst activity (here quantified by the Damkohler number) is carried out by assuming 550 °C as a working temperature. An optimal working pressure is found at relatively high Damkohler value. Qualitatively different operating modes of the membrane reactor in different regions of the pressure-Damkohler parameter space are identified and interpreted.

Monolithic membrane reactors based on supported ionic liquid phase (SILP) materials – Hydroformylation and water-gas shift case studies

In this paper, a novel membrane reactor (MR) for methanol steam reforming is modeled to produce fuel cell grade hydrogen, which can be used as the inlet fuel for a later developed 500-W horizon polymer electrolyte fuel cell (PEFC) stack. The backpropagation (BP) neural network algorithm is employed to develop the mapping relation model between the MR's prime operational parameters and fuel cell output performance for future integration system design and control application. Simulation results showed that the MR model performs well for hydrogen production and the developed PEFC system presents good agreement with experimental results. Finally, the BP method captures an accurate mapping relation model between the MR inputs and PEFC output, for example, predicts the system's behavior well. (Less)

A membrane reactor (MR) combines reaction and separation phenomena in a single unit and offers an energy-efficient, cost-effective, compact, modular, and sustainable design compared to conventional designs. A systematic design framework can yield such benefits of MRs and increase their adoption in the chemical process industry. To this end, we present SPICE_MARS (synthesis and process intensification of chemical enterprises involving membrane-assisted reactive separations), a software prototype for conceptual design, simulation, synthesis, and optimization of MRs for different process applications. At the conceptual level, we can determine whether MR is desired or not and select which species to convert/separate. At the equipment level, we obtain optimal MR configurations considering different flow arrangements, intensification strategies, membrane types, sweep gases, reactor lengths, membrane areas, and catalyst amounts. Additionally, we can generate rank-ordered lists of optimal reactor configurations for different design objectives. These enabling capabilities are demonstrated using two case studies involving methanol synthesis and methane partial oxidation. In both cases, novel MR designs—achieving drastic improvement compared to current industrial practice—are found.

Side-arm hydrogenation (SAH) by homogeneous catalysis has extended the reach of the parahydrogen enhanced NMR technique to key metabolites such as pyruvate. However, homogeneous hydrogenation requires rapid separation of the dissolved catalyst and purification of the hyperpolarised species with a purity sufficient for safe in-vivo use. An alternate approach is to employ heterogeneous hydrogenation in a continuous-flow reactor, where separation from the solid catalysts is straightforward. Using a TiO2 -nanorod supported Rh catalyst, we demonstrate continuous-flow parahydrogen enhanced NMR by heterogeneous hydrogenation of a model SAH precursor, propargyl acetate, at a flow rate of 1.5 mL/min. Parahydrogen gas was introduced into the flowing solution phase using a novel tube-in-tube membrane dissolution device. Without much optimization, proton NMR signal enhancements of up to 297 (relative to the thermal equilibrium signals) at 9.4 Tesla were shown to be feasible on allyl-acetate at a continuous total yield of 33 %. The results are compared to those obtained with the standard batch-mode technique of parahydrogen bubbling through a suspension of the same catalyst.

A model of steam methane reforming in a catalytic reactor has been developed the working part of which is two cylindrical chambers separated by a membranous wall. The upper chamber is evacuated while the lower one is maintained at atmospheric pressure. With a uniform supply of raw materials along the outer perimeter of the lower chamber, the problem is reduced to finding the average flows of CH4, H2O, CO2, CO, and H2 from the solution of a system of five nonlinear ordinary differential equations of the first order. The calculations were carried out for a Pd–6% Ru membrane in the temperature range of 673 K < T < 973 K at a steam/methane inlet flow ratio of 3 and a feed rate of 1800–9600 L/h. As a result of comparing the calculations with experimental data, a theoretical substantiation of the main regularities of the process observed in practice was obtained.

A novel electrocatalytic membrane reactor (ECMR), assembled by MnOx/Ti (MT) composite membrane as an anode, was used to degrade phenolic wastewater. The MT composite membrane, MnOx layer with the various crystal forms coated on porous tubular Ti support, was prepared by sol–gel method and then activated further by acidification to obtain acidified MnOx/Ti (AMT) composite membrane. The XRD results showed that the crystallite size of MnOx layer distinctly decreased after acidification. This is because of the Ti support had a great effect on the crystal form and crystallite size of MnOx, especially after acidification. The results of XPS analysis showed that the interaction between Ti support and MnOx layer had great influence on the Mn–O, Ti–O binding energies and active oxygen species of MT and AMT. Treated by ECMR with AMT, the phenol, COD and TOC removal rates of the synthetic phenolic wastewater were 96.45%, 84.97% and 71.26%, which were obviously higher than that of MT, 62.87%, 50.34% and 41.25%, respectively. It was revealed that acidified MnOx as the catalysts in AMT composite membrane, with the specific crystal form, refined crystallite size and active oxygen species, exhibited a great potential in the electrocatalytic oxidative degradation of the phenolic wastewater.

Many of the highly populated and industrialized countries are paying more attention to green fuels. The conventional methods for biodiesel purification processes result in a large quantity of polluted water, leading to serious environmental concerns. To overcome the challenges in the existing process, addressing the membrane technology is a viable solution to direct further research toward sustainable membrane-based green production. The developing membrane technology is an alternative method for eliminating wastewater during biodiesel production from conventional processes. This paper provides a comprehensive review of recent development applications of the catalytic membrane and membrane materials for high-quality biodiesel production. Both polymeric and ceramic membranes result in optimum performance of more than 90% effective conversion and purification. The catalytic membrane reactor integrates chemical reaction and product separation concurrently in a single device system to produce high-quality biodiesel. Glycerol purification of 99% was achieved in the potential membrane distillation process. This review critically summarizes biodiesel production and purification using membrane techniques and membrane reactors. Membrane material and separation efficiency were discussed in a short view. Besides, the significance of catalytic membrane reactor is outlined. Glycerol separation and purification by removal of water and other residual impurities were potentially achieved using membrane technology. Apart from applications of the membrane, the novel attempt of a combined description of influencing factors and limitations of the membrane during biodiesel production was revealed. Therefore, membrane applications in high-grade biodiesel and value-added byproduct production are the predominant green technological approach for next-generation biofuels.

An electrocatalytic palladium membrane reactor (ePMR) uses electricity and water to drive hydrogenation without H2 gas. The device contains a palladium membrane to physically separate the formation of reactive hydrogen atoms from hydrogenation of the unsaturated organic substrate. This separation provides an opportunity to independently measure the hydrogenation reaction at a surface without any competing H2 activation or proton reduction chemistry. We took advantage of this feature to test how different metal catalysts coated on the palladium membrane affect the rates of hydrogenation of C=O and C=C bonds. Hydrogenation occurs at the secondary metal catalyst and not the underlying palladium membrane. These secondary catalysts also serve to accelerate the reaction and draw a higher flux of hydrogen through the membrane. These results reveal insights into hydrogenation chemistry that would be challenging using thermal or electrochemical hydrogenation experiments.

Aims and Objective: In this work, the performance of a sodalite membrane reactor (MR) in the conversion of methanol to olefins (MTO process) was evaluated for ethylene and propylene production with in situ steam removal using 3-dimensional CFD (computational fluid dynamic) technique. Methods: Numerical simulation was performed using the commercial CFD package COMSOL Multiphysics 5.3. The finite element method was used to solve the governing equations in the 3- dimensional CFD model for the present work. In the sodalite MR model, a commercial SAPO-34 catalyst in the reaction zone was considered. The influence of key operation parameters, including pressure and temperature on methanol conversion, water recovery, and yields of ethylene, propylene, and water was studied to evaluate the performance of sodalite MR. Results: The local information of component concentration for methanol, ethylene, propylene, and water was obtained by the proposed CFD model. Literature data were applied to validate model results, and a good agreement was attained between the experimental data and predicted results using CFD model. Permeation flux through the sodalite membrane was increased by an increase of reaction temperature, which led to the enhancement of water stream recovered in the permeate side. Conclusion: The CFD modeling results showed that the sodalite MR in the MTO process had higher performance in methanol conversion compared to the fixed-bed reactor (methanol conversion of 97% and 89% at 733 K for sodalite MR and fixed-bed reactor, respectively).

In this study, tubular titanium membrane (TTM) /SnO2-Sb/SnO2-Sb-CeO2 porous anode was fabricated and used in continuous tubular membrane reactor for electrochemical treatment of dye wastewater. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) were used to evaluate the morphology and microstructure of the different tubular titanium membrane. Linear sweep voltammetry (LSV) and accelerated service life test are employed to illustrate the performance of TTM/SnO2-Sb/SnO2-Sb-CeO2 porous membrane electrode. It is found that TTM/SnO2-Sb/SnO2-Sb-CeO2 active layer on titanium membrane has compact microstructure, high over-potential for oxygen evolution (2.10 V vs saturated calomel electrode). The effects of pore diameter, applied voltage and flow rate on the electro-catalytic property of the tubular porous electrode were investigated. Study shows titanium membrane reactor with an optimized pore diameter of 10 μm has the lowest energy consumption which is important for the practical application of electrochemical technology. The performance of titanium tubular membrane reactor is investigated by treating methylene blue (MB) wastewater under the cell voltage of 3.0–4.5 V and the flow rate of 2.5–3.5 L min−1. This continuous titanium membrane electrochemical reactor using solar cell show excellent performance in treating dye wastewater and the further potential application in electrochemical synthesis.

In order to understand the behavior of the low-temperature water gas shift (WGS) reaction membrane reactor system and obtain better performance of the reactor, numerical simulations are performed with a two-dimensional axisymmetric model. Dimensionless analysis is applied to the governing equations, and then a set of dimensionless parameters are established. The effect of the parameters of Damkohler number ( D a ) and membrane permeability ( P p ) over a wide range on the performance of CO conversion and hydrogen recovery is studied, and the discussion of reaction phenomenon is presented. The WGS reaction is simulated under the operating conditions of 2 atm and two temperatures of 200 and 300 °C. The simulation results suggest that D a = 10 − 4 and P p = 10 − 1 are the optimum operating conditions for the reactor system where the conversion reaches nearly 100% exceeding the thermodynamic equilibrium conversion by 11% at 300 °C and the optimal hydrogen recovery is achieved simultaneously. The distribution of components along the axis of the reactor is checked, and then two crucial indicators are raised to assess the extent of reaction and hydrogen separation respectively, for the purpose of guidance for the length design of the reactor. Finally, the analysis of the effect of sweep gas on reactor performance suggests that the optimum flow rate of sweep gas is 0.2–0.5 L/min, and further enhancement of performance can be achieved by using counter-current sweep gas configuration.

Membrane reactors are a potential tool to produce high purity hydrogen on-site but sufferfrom immense losses in hydrogen recovery under reaction conditions. For high-temperature operations, these losses mostly occur due to the presence of lesser permeable gases in the reformate that develop into a concentration polarization barrier around the membrane. Based on our previous findings, a multi-pass design was manifested to alleviate hydrogen losses through the membrane tested with synthetic gas mixtures. The same design is currently employed to establish improvement in hydrogen recovery under reaction conditions. Having a catalyst and membrane integrated into a single unit termed as a membrane reactor, its performance is optimized with varying membrane assembly and catalyst bed configurations. This study shows that a packed bed multi-pass membrane reactor is an optimal design to target high hydrogen recovery. Further, multi-pass membrane reactor design also improves the hydrogen recovery in fluidized bed operations which opens immense scope for future studies.

A microstructured membrane reactor has been developed to overcome the safety and productivity challenge of the direct synthesis of hydrogen peroxide. A single membrane is employed for separate, continuous dosage of the gaseous reactants hydrogen and oxygen to the solid catalyst present in the aqueous solvent. Using a custom OpenFOAM® model, the impact of catalyst‐coated static mixers with different mixer geometries is studied. It is demonstrated that the custom fluid guiding elements outperform the investigated commercial static mixer under the flow conditions relevant to this application.

Hydrogen has a potential to be a clean energy carrier that emits only water after combustion and can be produced from diverse feedstocks. Hydrogen has much better combustion characteristics in conv...

A zeolite membrane reactor can be employed for hydrogenation of CO2 to methanol. The removal of water from the reaction environment would increase the reaction rate and the achievable conversion. The separation of water from mixtures containing CO2, hydrogen and water at suitable temperatures for this reaction was tested with several zeolite membranes (zeolite A, mordenite, zeolite T, chabazite and Ti-Chabazite). Zeolite A provided the best H2O/H2 separation factor. Preliminary experiments comparing a traditional reactor and the combination of a traditional reactor with a membrane reactor show that the yield of methanol was improved, in one case being higher than the limit corresponding to the thermodynamic equilibrium in a conventional reactor.

The hydrogen removal and carbon formation effects in dense palladium (Pd)-based membrane reactors for dry reforming of methane (DRM) performance is numerically analyzed in this study. The steady-state membrane reactor operation is described using a three-dimensional, heterogeneous, non-isothermal mathematical model. Based on the numerical simulation results for reaction temperature and pressure varied in the 400–600 °C and 1–30 atm ranges, methane conversion and hydrogen yield were found enhanced using the membrane reactor. However, carbon formation, which affects catalyst activity and limits the benefits of using a membrane reactor is also enhanced. A parametric study using reaction pressure as the primary parameter for the membrane reactor operation found that the CH4 conversion, hydrogen yield, H2 recovery, and carbon formation can be enhanced by increasing the reaction temperature, inlet CO2/CH4 ratio, and sweep gas flow rate. With the enhanced H2 removal, carbon formation is also enhanced. Because membrane permeance is inversely proportional to the membrane thickness, membrane thickness can be used as a parameter to control the carbon formation under given operating conditions.

Biorefineries enable the conversion of renewable resources to value-added chemicals. The enzymatic hydrolysis of cellulosic poly- or oligomers is often employed, because it is a highly selective conversion. However, the enzymes represent a significant cost factor. This study investigates the alternative depolymerization of cellobiose to glucose via an electro-Fenton process. A membrane separation stage is coupled with the reactor in order to enhance the selectivity towards glucose. OH radicals are formed by the Fenton reaction and convert cellobiose to glucose. However, the selectivity has an upper limit of approximately 25% and decreases over time due to the non-selective nature of the radicals. In this regard, the selectivity mainly depends on the ratio of cellobiose to glucose in the reactor. Experiments and simulations show that the membrane reactor composed of a nanofiltration module coupled with the electrochemical reactor improves the selectivity due to the removal of glucose from the reaction. With 42% retention, glucose mainly permeates through the membrane, while the retention of cellobiose and the catalyst was 90% and 80%, respectively. A viable concept for continuous electro-Fenton processes is introduced. For the cellobiose conversion, it enables an operation close to the highest possible selectivity towards glucose of approximately 25%.