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The imperative to decarbonize the energy sector has prompted substantial advancements in clean electricity generation, with hydrogen emerging as a promising low-carbon energy carrier. While hydrogen synthesis from renewable sources is crucial, challenges persist, necessitating innovative approaches for efficient and sustainable production. This study leverages diverse artificial neural network (ANN) models to assess and predict system efficiency based on key operational variables in membrane reactor systems. The multilayered perceptron (MLP) and radial basis function (RBF) methodologies are employed, with the MLP models optimized across twelve training algorithms and eight activation functions, exploring up to three hidden layers with variable neuron counts. The MLP model, utilizing the Levenberg-Marquard training algorithm and Tangent-Sigmoid activation function, achieved a high correlation coefficient (R2) of 0.9975 for training and 0.9962 for testing, and a mean squared error (MSE) of 0.00425 for training and 0.23951 for testing, indicating precise and accurate efficiency predictions. The Log-Sigmoid activation function also performed well, with R² values of 0.9971 (training) and 0.9961 (testing), and MSE values of 0.004086 (training) and 0.17694 (testing). Optimization of the RBF network identified the best performance with a spread parameter of 1 and 35 neurons, although the MLP model demonstrated superior accuracy and reduced computational time. Statistical analysis, encompassing correlation coefficient, mean squared error, Root Mean Squared error, absolute average deviation, absolute average relative deviation, and runtime, confirms the network's consistent and accurate estimation of system efficiency across various input variables. The study highlights that applying tansig and logsig activation functions, configured with neuron counts of 20, 17, 6 and 23, 20, 2 at the first, second and third hidden layers, respectively, offers enhanced accuracy and reliability. The MLP model's high performance underscores its potential to identify optimal conditions for H2 generation based on system efficiency, thereby advancing membrane reactor technology for hydrogen production. [ABSTRACT FROM AUTHOR]

This study proposes a combination system consisting of a biogas dry reforming reactor and a solid oxide fuel cell (SOFC). Since biogas dry reforming is an endothermic reaction, this study adopted a membrane reactor operated due to the non-equilibrium state with H2 separation from the reaction space. This study aimed to clarify the performance of the Ni/Cr/Ru catalyst using a biogas dry reforming membrane reactor. Additionally, this study also undertook a comparison of the performance of the Ni/Cr/Ru catalyst with that of the Ni/Cr catalyst. The impact of operation temperature, the molar ratio of CH4:CO2, the differential pressure between the reaction chamber and the sweep chamber, and the introduction of a sweep gas on the performance of the biogas dry reforming membrane reactor using a Pd/Cu membrane and a Ni/Cr/Ru catalyst was examined. The concentration of H2 using the Ni/Cr/Ru catalyst was greater than that using the Ni/Cr catalyst by 2871 ppmV for the molar ratio of CH4:CO2 = 1.5:1 at the reaction temperature of 600 °C and the differential pressure of 0 MPa without a sweep gas in particular. Under this condition, CH4 conversion, H2 yield, and thermal efficiency were 67.4%, 1.77 × 10−2%, and 0.241%, respectively. [ABSTRACT FROM AUTHOR]

Abstract The imperative to decarbonize the energy sector has prompted substantial advancements in clean electricity generation, with hydrogen emerging as a promising low-carbon energy carrier. While hydrogen synthesis from renewable sources is crucial, challenges persist, necessitating innovative approaches for efficient and sustainable production. This study leverages diverse artificial neural network (ANN) models to assess and predict system efficiency based on key operational variables in membrane reactor systems. The multilayered perceptron (MLP) and radial basis function (RBF) methodologies are employed, with the MLP models optimized across twelve training algorithms and eight activation functions, exploring up to three hidden layers with variable neuron counts. The MLP model, utilizing the Levenberg-Marquard training algorithm and Tangent-Sigmoid activation function, achieved a high correlation coefficient (R2) of 0.9975 for training and 0.9962 for testing, and a mean squared error (MSE) of 0.00425 for training and 0.23951 for testing, indicating precise and accurate efficiency predictions. The Log-Sigmoid activation function also performed well, with R² values of 0.9971 (training) and 0.9961 (testing), and MSE values of 0.004086 (training) and 0.17694 (testing). Optimization of the RBF network identified the best performance with a spread parameter of 1 and 35 neurons, although the MLP model demonstrated superior accuracy and reduced computational time. Statistical analysis, encompassing correlation coefficient, mean squared error, Root Mean Squared error, absolute average deviation, absolute average relative deviation, and runtime, confirms the network’s consistent and accurate estimation of system efficiency across various input variables. The study highlights that applying tansig and logsig activation functions, configured with neuron counts of 20, 17, 6 and 23, 20, 2 at the first, second and third hidden layers, respectively, offers enhanced accuracy and reliability. The MLP model’s high performance underscores its potential to identify optimal conditions for H2 generation based on system efficiency, thereby advancing membrane reactor technology for hydrogen production.

This study proposes a combination system consisting of a biogas dry reforming reactor and a solid oxide fuel cell (SOFC). Since biogas dry reforming is an endothermic reaction, this study adopted a membrane reactor operated due to the non-equilibrium state with H2 separation from the reaction space. This study aimed to clarify the performance of the Ni/Cr/Ru catalyst using a biogas dry reforming membrane reactor. Additionally, this study also undertook a comparison of the performance of the Ni/Cr/Ru catalyst with that of the Ni/Cr catalyst. The impact of operation temperature, the molar ratio of CH4:CO2, the differential pressure between the reaction chamber and the sweep chamber, and the introduction of a sweep gas on the performance of the biogas dry reforming membrane reactor using a Pd/Cu membrane and a Ni/Cr/Ru catalyst was examined. The concentration of H2 using the Ni/Cr/Ru catalyst was greater than that using the Ni/Cr catalyst by 2871 ppmV for the molar ratio of CH4:CO2 = 1.5:1 at the reaction temperature of 600 °C and the differential pressure of 0 MPa without a sweep gas in particular. Under this condition, CH4 conversion, H2 yield, and thermal efficiency were 67.4%, 1.77 × 10−2%, and 0.241%, respectively.

Methylcyclohexane (MCH) dehydrogenation is an equilibrium‐limited reaction that requires high temperatures (>300 °C) for complete conversion. However, high‐temperature operation can degrade catalytic activity and produce unwanted side products. Thus, a hybrid zeolite membrane (Z) is prepared on the inner surface of a tubular support and used it as a wall in a membrane reactor (MR) configuration. Pt/C catalysts is packed diluted with quartz sand inside the Z‐coated tube and applied the MR for MCH dehydrogenation at low temperatures (190–250 °C). Z showed a remarkable H2‐permselectivity in the presence of both toluene and MCH, yielding separation factors over 350. The Z‐based MR achieved higher MCH conversion (75.3% ± 0.8% at 220 °C) than the conventional packed‐bed reactor (56.4% ± 0.3%) and the equilibrium state (53.2%), owing to the selective removal of H2 through Z. In summary, the hybrid zeolite MR enhances MCH dehydrogenation at low temperatures by overcoming thermodynamic limitations and improves the catalytic performance and product selectivity of the reaction. [ABSTRACT FROM AUTHOR]

The utilization of ammonia for hydrogen storage relies on the implementation of efficient decomposition techniques, and the membrane reactor, which allows simultaneous ammonia decomposition and hydrogen recovery, can be regarded as a promising technology. While Pd-based membranes show the highest performance for hydrogen separation, their applicability for NH3-sensitive applications, such as proton exchange membrane (PEM) fuel cells, demands relatively thick, and therefore expensive, membranes to meet the purity targets for hydrogen. To address this challenge, this study proposes a solution involving the utilization of a downstream hydrogen purification unit to remove residual ammonia, thereby enabling the use of less selective, therefore more cost-effective, membranes. Specifically, a carbon molecular sieve membrane was prepared on a tubular porous alumina support and tested for ammonia decomposition in a membrane reaction setup. Operating at 5 bar and temperatures ranging from 450 to 500 °C, NH3 conversion rates exceeding 90% were achieved, with conversion approaching thermodynamic equilibrium at temperatures above 475 °C. Simultaneously, the carbon membrane facilitated the recovery of hydrogen from ammonia, yielding recoveries of 8.2–9.8%. While the hydrogen produced at the permeate side of the reactor failed to meet the purity requirements for PEM fuel cell applications, the implementation of a downstream hydrogen purification unit comprising a fixed bed of zeolite 13X enabled the production of fuel cell-grade hydrogen. Despite performance far from being comparable with the ones achieved in the literature with Pd-based membranes, this study underscores the viability of carbon membranes for fuel cell-grade hydrogen production, showcasing their competitiveness in the field. [ABSTRACT FROM AUTHOR]

Globally, the rise in the environmental awareness on the reduction of greenhouse gas emissions has spurred the development of carbon capture and utilization (CCU) technologies, including membrane separation. Among the membrane separation technologies, dual-phase carbonate membrane is feasible for post-combustion carbon capture given its high thermal and chemical stabilities at high temperatures. The integration of carbon capture and dry reforming of methane (DRM) in a catalytic dual-phase carbonate membrane reactor to function as a single device for syngas production is an emerging area of research. This paper aims to provide a comprehensive review on the progress of the dual-phase carbonate membranes and membrane reactors in carbon capture and syngas production. The working mechanism and performance of three types of carbonate membranes in CO2 separation from various aspects (i.e., material selection, membrane configuration, modifications on the materials, and operating conditions) are thoroughly examined. Additionally, an overview of the reactions involved (i.e., DRM, steam reforming of methane (SRM), and partial oxidation of methane (POM)) and catalyst design (i.e., nickel-based supported with metal oxides and zeolites) is provided. A detailed comparison of the performance of the catalytic dual-phase ceramic-carbonate membrane reactor using different types of catalysts for syngas production is presented. Finally, the review is concluded with a discussion of the challenges, recommendations, and future insights on the development of dual-phase carbonate membranes and membrane reactors.

Butyric acid, a four-carbon fatty acid, is an important industrial chemical and feedstock. To produce this chemical, a control fermentation was run with a 126.5 g.L−1 glucose concentration in the feed medium. In this medium, the strain produced 44.8 g.L−1 total acid with a productivity of 0.23 g.L−1h−1 and a yield of 0.41 g.g−1. The strain (Clostridium tyrobutyricum ATCC 25755) was also able to utilize glucose and xylose simultaneously with similar fermentation performance. The culture was also used to produce butyric acid from wheat straw hydrolysate (WSH) employing a hot water pretreatment. In a batch system, the strain resulted in a productivity and yield of 0.27 g.L−1h−1 and 0.44 g.g−1, respectively, which was an improvement over the use of glucose or xylose alone or mixtures of both. To improve reactor productivity, a membrane cell recycle bioreactor was used which resulted in a productivity of 1.89 g.L−1h−1. This productivity was 822% of that achieved in the glucose or xylose batch fermentation. Furthermore, a butyric acid recovery method was developed using XAD-4 adsorbent resin. In this system, up to 206.1 g.L−1 of butyric acid was used in the feed and, as a result of the quick adsorption, the residual butyric acid concentration was 29.5 g.L−1. In this experiment, the rate of acid removal of 1059.4 g.L−1h−1 was achieved. [ABSTRACT FROM AUTHOR]

Abstract Methylcyclohexane (MCH) dehydrogenation is an equilibrium‐limited reaction that requires high temperatures (>300 °C) for complete conversion. However, high‐temperature operation can degrade catalytic activity and produce unwanted side products. Thus, a hybrid zeolite membrane (Z) is prepared on the inner surface of a tubular support and used it as a wall in a membrane reactor (MR) configuration. Pt/C catalysts is packed diluted with quartz sand inside the Z‐coated tube and applied the MR for MCH dehydrogenation at low temperatures (190–250 °C). Z showed a remarkable H2‐permselectivity in the presence of both toluene and MCH, yielding separation factors over 350. The Z‐based MR achieved higher MCH conversion (75.3% ± 0.8% at 220 °C) than the conventional packed‐bed reactor (56.4% ± 0.3%) and the equilibrium state (53.2%), owing to the selective removal of H2 through Z. In summary, the hybrid zeolite MR enhances MCH dehydrogenation at low temperatures by overcoming thermodynamic limitations and improves the catalytic performance and product selectivity of the reaction.

The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational fluid dynamics (CFD) can be used to model reactors based on this concept. In this study, a modelling approach for water splitting is presented in which oxygen transport through the membrane acts as the rate-determining process for the overall reaction. This transport step is implemented in the CFD simulation. Both gas compartments are modelled in the simulations. Hydrogen and methane are used as reducing gases. The model is validated using experimental data from the literature and compared with a simplified perfect mixing modelling approach. Although the main focus of this work is to propose an approach to implement the water splitting in CFD simulations, a simulation study was conducted to exemplify how CFD modelling can be utilized in design optimization. Simplified 2-dimensional and rotational symmetric reactor geometries were compared. This study shows that a parallel overflow of the membrane in an elongated reactor is advantageous, as this reduces the back diffusion of the reaction products, which increases the mean driving force for oxygen transport through the membrane.

The inorganic-carbonate dual-phase membrane represents a class of dense membranes that are fabricated using diverse support materials, ranging from metals to ceramics. This dual-phase membrane consists of a porous metal or ceramic support with an introduced carbonate phase within the support pores. Compared with polymer and zeolite membranes, inorganic-carbonate dual-phase membranes exhibit exceptional CO2 selectivity at elevated temperatures (>500 °C), making them an ideal choice for high-temperature CO2 separation in power plant systems. The present paper provides a comprehensive overview of the separation principle, significant models, and preparation techniques employed in carbonate dual-phase membranes for CO2 separation. The present study aims to discuss key factors that limit the CO2 permeation performance and stability of membranes, while also exploring the potential applications of dual-phase membranes in various fields. The identification of key challenges in the future development of the carbonate dual-phase membrane has been highlighted in this work. The future trajectory of research and development should be directed toward overcoming these challenges, encompassing the synthesis technology of membranes, balance optimization of membrane structure and performance, modification of physical and chemical properties of molten carbonate, and advancement in high-temperature sealing techniques, as well as exploration of diverse membrane reactors based on carbonate dual-phase membranes for prospective applications. [ABSTRACT FROM AUTHOR]

This study explores the optimization of membrane reactor configurations to enhance hydrogen production through CH4 tri-reforming. The investigation employs ceramic membranes for oxygen, vapor, and carbon dioxide distribution within the reactor bed. A differential evolution algorithm is utilized alongside cuckoo search algorithm (CSA) and support vector regression (SVR) to determine optimal values for O2/CH4, H2O/CH4, and CO2/CH4 ratios, membrane thickness, and shell pressure, with hydrogen yield as the objective function. Results demonstrate that the oxygen membrane reactor achieves the highest hydrogen yield, reaching 2.02 and 1.75 for direct methanol synthesis and Fischer–Tropsch processes, respectively, representing a 7.98 % and 10.03 % increase compared to the conventional tri-reforming reactor. Furthermore, CSA and SVR emerge as invaluable tools, facilitating robust optimization and predictive modeling. The CSA efficiently navigates complex solution spaces to identify optimal parameters, while SVR accurately models relationships between input variables and hydrogen yield. Incorporating these methodologies enhances the effectiveness of membrane reactor design and synthesis gas production. This study contributes to advancements in clean energy technologies by providing insights into efficient hydrogen production methods using membrane reactors.

The present study aims to analyze the performance characteristics of the biogas dry reforming process conducted in a membrane reactor using Ni/Cr catalysts and to compare these characteristics with those obtained using pure Ni catalysts. The effect of the pre-set reaction temperature, the molar ratio of CH4:CO2 and the pressure difference between the reaction chamber and the sweep chamber on the characteristics of biogas dry reforming is analyzed. In the present work, the molar ratio of the supplied CH4:CO2 is varied to 1.5:1, 1:1 and 1:1.5. In this case, CH4:CO2 = 1.5:1 simulates a biogas. The pressure difference between the reaction chamber and the sweep chamber is varied to 0 MPa, 0.010 MPa and 0.020 MPa. The reaction temperature is changed to 400 °C, 500 °C and 600 °C. It is revealed that the highest concentration of H2 is achieved using a Ni/Cr catalyst when the molar ratio of CH4:CO2 is 1.5:1 at the differential pressure of 0.010 MPa and the reaction temperature of 600 °C. Under this condition, the H2 yield, H2 selectivity and thermal efficiency are 12.8%, 17.5% and 174%, respectively. The concentration of the H2 produced using a Ni/Cr catalyst is larger than that produced using a Ni catalyst regardless of the pre-set reaction temperature, the molar ratio of CH4:CO2 and the differential pressure.

Hydrogen as an energy vector is going to play an important role in the global energy mix. On the other hand, wastewater management has become a worldwide concern, as urban settlements have been considerably increasing for decades. Consequently, biodigestion to produce biogas (rich in methane) in water treatment plants could be an interesting starting point to obtain a valuable gas that can be converted into hydrogen through steam reforming. The aim of this work was to review the main aspects concerning steam reforming of biogas from wastewater treatment plants. For this purpose, the whole chain, from water treatment to hydrogen production and purification, was considered, paying attention to the main challenges and new technologies for its optimization. Thus, a wide range of possibilities is offered, from direct energy use of syngas to high purification of hydrogen (mainly through pressure swing adsorption or membrane reactors), presenting advantages and disadvantages. In any case, the role of catalysts seems to be essential, and aspects such as hydrogen sulfide and coke deposition control should be addressed. In conclusion, biogas steam reforming applied to wastewater treatment plants is a reality, with serious possibilities for its global implementation at the industrial level, according to techno-economic assessment. [ABSTRACT FROM AUTHOR]

The present study aims to analyze the performance characteristics of the biogas dry reforming process conducted in a membrane reactor using Ni/Cr catalysts and to compare these characteristics with those obtained using pure Ni catalysts. The effect of the pre-set reaction temperature, the molar ratio of CH4:CO2 and the pressure difference between the reaction chamber and the sweep chamber on the characteristics of biogas dry reforming is analyzed. In the present work, the molar ratio of the supplied CH4:CO2 is varied to 1.5:1, 1:1 and 1:1.5. In this case, CH4:CO2 = 1.5:1 simulates a biogas. The pressure difference between the reaction chamber and the sweep chamber is varied to 0 MPa, 0.010 MPa and 0.020 MPa. The reaction temperature is changed to 400 °C, 500 °C and 600 °C. It is revealed that the highest concentration of H2 is achieved using a Ni/Cr catalyst when the molar ratio of CH4:CO2 is 1.5:1 at the differential pressure of 0.010 MPa and the reaction temperature of 600 °C. Under this condition, the H2 yield, H2 selectivity and thermal efficiency are 12.8%, 17.5% and 174%, respectively. The concentration of the H2 produced using a Ni/Cr catalyst is larger than that produced using a Ni catalyst regardless of the pre-set reaction temperature, the molar ratio of CH4:CO2 and the differential pressure. [ABSTRACT FROM AUTHOR]

Butyric acid, a four-carbon fatty acid, is an important industrial chemical and feedstock. To produce this chemical, a control fermentation was run with a 126.5 g.L−1 glucose concentration in the feed medium. In this medium, the strain produced 44.8 g.L−1 total acid with a productivity of 0.23 g.L−1h−1 and a yield of 0.41 g.g−1. The strain (Clostridium tyrobutyricum ATCC 25755) was also able to utilize glucose and xylose simultaneously with similar fermentation performance. The culture was also used to produce butyric acid from wheat straw hydrolysate (WSH) employing a hot water pretreatment. In a batch system, the strain resulted in a productivity and yield of 0.27 g.L−1h−1 and 0.44 g.g−1, respectively, which was an improvement over the use of glucose or xylose alone or mixtures of both. To improve reactor productivity, a membrane cell recycle bioreactor was used which resulted in a productivity of 1.89 g.L−1h−1. This productivity was 822% of that achieved in the glucose or xylose batch fermentation. Furthermore, a butyric acid recovery method was developed using XAD-4 adsorbent resin. In this system, up to 206.1 g.L−1 of butyric acid was used in the feed and, as a result of the quick adsorption, the residual butyric acid concentration was 29.5 g.L−1. In this experiment, the rate of acid removal of 1059.4 g.L−1h−1 was achieved.

Endeavors have recently been concentrated on minimizing the dependency on fossil fuels in order to mitigate the ever-increasing problem of greenhouse gas (GHG) emissions. Hydrogen energy is regarded as an alternative to fossil fuels due to its cleaner emission attributes. Reforming of hydrocarbon fuels is amongst the most popular and widely used methods for hydrogen production. Hydrogen produced from reforming processes requires additional processes to separate from the reformed gases. In some cases, further purification of hydrogen has to be carried out to use the hydrogen in power generation applications. Metallic membranes, especially palladium (Pd)-based ones, have demonstrated sustainable hydrogen separation potential with around 99.99% hydrogen purity. Comprehensive and critical research investigations must be performed to optimize membrane-assisted reforming as well as to maximize the production of hydrogen. The computational fluid dynamic (CFD) can be an excellent tool to analyze and visualize the flow/reaction/permeation mechanisms at a lower cost in contrast with the experiments. In order to provide the necessary background knowledge on membrane reactor modeling, this study reviews, summarizes and analyses the kinetics of different fuel reforming processes, equations to determine hydrogen permeation, and lastly, various geometry and operating condition adopted in the literature associated with membrane-reactor modeling works. It is indicated that hydrogen permeation through Pd-membranes depends highly on the difference in hydrogen pressure. It is found that hydrogen permeation can be improved by employing different pressure configuration, introducing sweep flow on the permeate side of the membrane, reducing retentate side flow rate, and increasing the temperature.

Cinnamic acid is a phenolic compound with the potential to act as a natural antioxidant. Cinnamic acid esterification can be performed by adding a long-chain alcohol to one of its hydroxyl groups to improve its antioxidant activity. In this study, cinnamic esters were synthesized in an enzymatic membrane reactor (EMR) and were carried out continuously. This study aimed to determine the optimum conditions for the synthesis of cinnamic esters using various types of alcohols (e.g., butanol, hexanol, and octanol) as alkyl group donors and the impact of the esterification on the antioxidant activity. The continuous synthesis of cinnamic esters with TL IM lipozyme as the biocatalyst had the highest conversion (20.91%) with 1-butanol as the alkyl donor, in a synthesis strategy of a 12-h batch followed by continuous operation with a residence time of 9 h. The resulting ester increased the antioxidant activities by 2.18 and 3.85-fold, respectively based on the DPPH and FRAP assays. [ABSTRACT FROM AUTHOR]

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.

Sulfuric acid decomposition is the critical reaction in sulfur-iodide thermochemical cycle to produce oxygen. Sulfuric acid can decompose spontaneously into sulfur trioxide (SO3) and water, and SO3 continues to decompose into oxygen and sulfur dioxide. The application of membrane reactor can effectively improve the conversion rate of SO3 and thermal efficiency of sulfur-iodide cycle. The decomposition of SO3 requires the absorption of a large amount of heat due to its highly endothermic properties, and there are many irreversible processes such as heat transfer, mass transfer, chemical reaction and friction flow in the SO3 membrane reactor. Therefore, it is necessary to conduct thermodynamic analysis and optimization of the decomposition process to reduce the irreversible loss of the membrane reactor system. In this paper, a finite time thermodynamic model of SO3 decomposition membrane reactor is established, and the kinetic parameters of decomposition reaction are deduced and calculated based on experimental data. Firstly, the membrane reactor heated by hot helium gas is solved and used as reference reactor. Secondly, optimal control theory is used to optimize the reference reactor under fixed reactant inlet conditions and outlet conversion rate with total entropy generation rate minimization as optimization objective. The total entropy generation rate of Opt-1 reactor is reduced by 32.7% compared with the reference value. For variable reactor length, the total entropy generation rate of Opt-2 reactor is quadratic optimum at L=0.72m, which is 34.7% less than the reference value. It is found that the reduction of total entropy generation rate in optimal reactors is mainly achieved by minimizing the entropy generation rate in heat transfer process. The distribution of local entropy generation rate is relatively uniform in the middle position, approximately consistent with the principle of equalization of entropy production rate. The conclusions obtained herein can provide guidelines for the energy-saving design of SO3 decomposition membrane reactors.

In order to promote the engineering application of ammonia-based solar thermal storage systems, a one-dimensional model of an ammonia decomposition endothermic membrane reactor based on actual light condition is established by applying finite time thermodynamics. The reactor is heated by a trough solar collector and equipped with a regenerative preheater, and effects of four parameters including ammonia molar flow rate, ammonia preheated temperature, permeation zone pressure and light intensity on the total heat absorption rate, entropy generation rate and system efficiency are analyzed. The results show that the permeate pressure and light intensity affect the system performance significantly. When the permeate pressure reduces from 1 bar to 0.1 bar, the total heat absorption rate, the system efficiency and the entropy generation rate increase by 32.3%, 22.3% and 16.4%, respectively. When the light intensity increases from 800 W/m2 to 1200 W/m2, the heat absorption rate and the entropy generation rate increase by 53.8% and 38.2%, respectively. The results obtained in this paper provide some guidance for the practical engineering application of ammonia decomposition heat endothermic membrane reactors.

The present review focuses on the current progress on harnessing the potential of hydrogen production by Methane Steam Reforming (MSR). First, based on the prominent literature in last few years, the overall research efforts of hydrogen production using different feed stocks like ethanol, ammonia, glycerol, methanol and methane is presented. The presented data is based on reactor type, reactor operating conditions, catalyst used and yield of hydrogen to provide a general overview. Then, the most widely used process [steam methane reforming (SMR)/methane steam reforming (MSR)] are discussed. Major advanced reactors, the membrane reactors, Sorption Enhanced methane steam reforming reactors and micro-reactors are evaluated. The evaluation has been done based on parameters like residence time, surface area, scale-up, coke formation, conversion, space velocity and yield of hydrogen. The kinetic models available in recently published literature for each of these reactors have been presented with the rate constants and other parameters. The mechanism of coke formation and the rate expressions for the same have also been presented. While membrane reactors and sorption enhanced reactors have lot of advantages in terms of process intensification scale-up to industrial scale is still a challenge due to factors like membrane stability and fouling (in membrane reactors), decrease in yield with increasing WHSV (in case of Sorption Enhanced Reactors). Micro-reactors pose a higher potential in terms of higher yield and very low residence time in seconds though the volumes might be substantially lower than present industrial scale conventional reactors. [ABSTRACT FROM AUTHOR]

This work investigates numerically the characteristics of the two process, hydrogen separation and steam methane reforming (SMR), in a palladium-based (Inconel-supported Pd–Ag film) membrane reactor (MR) of porous reformer (30% Ni/Al2O3) shell and multi-tube design. Still parameters like reactor design and temperature, feed gas concentration and pressure, and flow configuration need more investigation to figure out their impact on hydrogen production rate at lower energy cost and minimum possible volume. This work targets optimization of reactor performance for higher hydrogen yield and coming up with a scalable optimized reactor design for industrial applications. First, an optimization study is performed under non-reforming (separation-only) conditions to optimize the MR design and operating parameters for higher hydrogen production. Then, the study is extended to consider hydrogen separation under SMR conditions to come up with a MR design for hydrogen production at the industrial scale. Hydrogen permeation is limited to small zone near the membrane surface with no effect of feed pressure, inlet gas temperature, and feed hydrogen concentration on widening such zone that necessitates reducing the pitch distance between membrane tubes below 22 mm. The results showed reduced hydrogen permeation rate under SMR conditions compared to the separation-only cases.

Clean methanol can play an important role in achieving net zero emission targets by decarbonizing the energy and chemical sectors. Conventionally, methanol is produced by using fossil fuel as raw material, which releases a significant amount of greenhouse gases (GHGs) into the environment. Clean methanol, which is produced by hydrogen (H2) from renewable sources (green H2) and captured carbon dioxide (CO2), is totally free from the influence of fossil fuel. Due to its vast applications, clean methanol has potential to substitute for fossil fuels while preventing further GHGs emissions. This review addresses the feasibility of producing clean methanol from renewable resources, i.e., green H2 and captured CO2. Availability of these raw materials is the main factor involved in establishing the circular economy of methanol, therefore, their potential sources and the possible pathways to access these sources are also summarized. Renewable energy sources such as solar, wind and biomass should be utilized for producing green H2, while CO2 captured from air, and more likely from point emission sources, can be recycled to produce clean methanol. After producing methanol from CO2 and H2, the removal of by-product water by distillation is a big challenge due its high energy consumption. An alternative approach for this methanol-water separation is membrane technology, which is an energy saving option. Water-selective zeolite membranes can separate water post-synthesis, as well as during the synthesis. Production efficiency of methanol can be enhanced by utilizing zeolite membranes inside the methanol synthesis reactor. Furthermore, CO2 conversion as well as methanol selectivity, purity and yield can also be increased significantly by selectively removing by-product water using a zeolite membrane reactor. [ABSTRACT FROM AUTHOR]

Hydrogen is rapidly gaining popularity as an energy carrier, largely expected to replace fossil fuels for many applications. As the hydrogen economy grows and the need for high purity hydrogen increases, better materials for high selectivity, high temperature hydrogen separation will be needed. In this theoretical investigation, InVO 4 was explored for use as a novel high temperature dense hydrogen separation membrane. The kinetics of hydrogen transport through an indium vanadate membrane (as it would be utilized in a membrane reactor) were modeled by leveraging density functional theory calculations. Structural features that control the kinetics were identified, from which material selection and modification for future experiments requiring high temperature hydrogen transport through solids can be better informed. The results of this investigation bring to light the importance of surface effects and reinforce the idea that surface and subsurface interactions must not be neglected when investigating hydrogen transport through solids. [Display omitted] • Kinetic modeling demonstrates InVO 4 shows promise as a hydrogen separation membrane. • Surface and subsurface effects determine the kinetics of hydrogen transport. • Proton tunneling only plays a significant role in the kinetics of hydrogen transport at temperatures less than 900 K. [ABSTRACT FROM AUTHOR]

[Display omitted] • A recycle reactor combined with membrane separator was used to produce green NH 3. • Aquivion/ceramic composite and sulfonated MPTMS membranes were used to system. • NH 3 mole fraction was increased from equilibrated 0.01 to 0.1–0.45 in permeate stream. • A mathematical model was proposed to simulate the recycle membrane reactor. With the increasing demand for ammonia (NH 3) and the environmental benefits, green and sustainable NH 3 production has been urgently developed and is expected to replace the traditional Haber-Bosch (HB) process with high energy consumption and CO x emission. In this work, a recycle membrane reactor (RMR) process where a catalytic reactor relates to a membrane separator in series and the retentate stream is recycled to the reactor was designed and executed to produce NH 3 , in which a Ru (10 wt%)/Cs/MgO catalyst and two membranes with different permeation properties and NH 3 selectivity were used. By independently controlling the temperature of the reactor and membrane separator, the synthesized NH 3 was selectively extracted from feed side to permeate side by Aquivion/ceramic composite and sulfonated (3-mercaptopropyl)trimethoxysilane membranes. Impressively, NH 3 mole fraction was greatly increased from 0.01 of equilibrium state to 0.1–0.45 in permeate stream, which is ascribed to the permeation properties and NH 3 selectivity of membrane at different temperatures. Moreover, a one-dimensional, isothermal, and plug-flow model was proposed to simulate RMR, which can be successfully applied to deeply understand the mechanism of RMR. Furthermore, a green NH 3 production process based on RMR was simulated to give rationalized suggestions for the NH 3 synthesis under mild conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The membrane fouling was effectively alleviated at low voltage of 0.1 V/cm. • Electric field decreased the EPS content and extended the service time. • Electric field reduced the irreversible fouling and enhanced effluent quality. • Increased Patescibacteria and decreased Bacteroidetes mitigated membrane fouling. The electrical assisted MBR (EMBR) has been employed to improve the water quality and solve the fouling problem. However, advanced material-based electrodes or high operation voltage bring difficulties for the practical application of EMBR. Herein, a weak electric field generated by titanium electrodes was employed to establish an EMBR and the fouling mechanism was investigated in detail. The results showed that introduction of a weak electric field at voltage of 0.1 V/cm and current density of 7 μA/cm2 efficiently decreased the extracellular polymeric substances (EPS) content by over 40 % as such extended the service time of MBR by more than 20 %. Specifically, the weak electric field reduced the relative abundance of Bacteroidetes , known for secreting proteinaceous EPS, by 38.61 %, and increased relative abundance of Patescibacteria with EPS decomposition by 6.73 times, thus effectively reducing the EPS concentration. Further KEGG pathway analysis revealed that electric field accelerated enzymatic reactions and promoted microbial metabolism of carbohydrate and amino acid. Furthermore, this weak field reduced the sludge deposition on membrane by increase of the electrostatic repulsion and the irreversible fouling was mediated. According to the composition of the fouling layer, a corresponding cleaning scheme was applied. This EMBR consistently produced high-quality effluent in all cycles, with 99.31 % COD, 98.73 % NH 4 +-N, 85.87 % TP and 92.66 % TN removals. In conclusion, the weak electric field endow EMBR exceptional anti-fouling ability and superior effluent quality under lower energy consumption. [ABSTRACT FROM AUTHOR]

Membrane technology has been embraced as a feasible and suitable substitute for conventional time- and energy-intensive biodiesel synthesis processes. It is ecofriendly, easier to run and regulate, and requires less energy than conventional approaches, with excellent stability. Therefore, the present study involved the synthesis and application of a highly reactive and recyclable Titania-based heterogeneous nanocatalyst (TiO2) for biodiesel production from nonedible Azadhiracta indica seed oil via a membrane reactor, since Azadhiracta indica is easily and widely accessible and has a rich oil content (39% w/w). The high free fatty acids content (6.52 mg/g KOH) of the nonedible oil was decreased to less than 1% via two-step esterification. Following the esterification, transesterification was performed using a heterogeneous TiO2 nanocatalyst under optimum conditions, such as a 9:1 methanol–oil molar ratio, 90 °C reaction temperature, 2 wt.% catalyst loading, and an agitation rate of 600 rpm, and the biodiesel yield was optimized through response surface methodology (RSM). Azadhiracta indica seed oil contains 68.98% unsaturated (61.01% oleic acid, 8.97% linoleic acid) and 31.02% saturated fatty acids (15.91% palmitic acid, 15.11% stearic acid). These fatty acids transformed into respective methyl esters, with a total yield up to 95% achieved. The biodiesel was analyzed via advanced characterization techniques like gas chromatography–mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR), whereas the catalyst was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Fourier transform infrared spectroscopy (FT-IR). Due to its physicochemical properties, Azadirachta indica seed oil is a highly recommended feedstock for biodiesel production. Moreover, it is concluded that the Titania-based heterogeneous nanocatalyst (TiO2) is effective for high-quality liquid fuel synthesis from nonedible Azadirachta indica seed oil in a membrane reactor, which could be an optional green route to cleaner production of bioenergy, eventually leading to sustenance, robustness, and resilience that will aid in developing a holistic framework for integrated waste management.

Butyl acetate (BuAc) is widely used as a solvent in many applications, mainly in the food and pharmaceutical industries. The conventional process for BuAc production is both capital and energy intensive. The purification process involves the separation of BuAc from the azeotropic mixture of water and n-butanol, which is difficult to accomplish using a simple distillation unit. In this study, a membrane reactor (MR) for BuAc production via the esterification of n-butanol was investigated. The MR using the Amberlyst-15 catalyst was modeled and validated with previously reported experimental data, and a good agreement was achieved. The ultimate conversion of n-butanol using the MR was 92.0%, compared to 69.8% for the conventional reactor. This study is the first to propose an intensified MR-based process for butyl acetate production. The MR-based process was developed and rigorously simulated using Aspen Plus for an annual plant capacity of 92,500 metric tons of BuAc. The MR-based process is environmentally friendly regarding CO2 emissions, with a reduction of 80% compared to the conventional process. The economic analysis of the MR-based process shows a payback period of 2.7 years and a return on investment (ROI) of 23.1%. The MR-based process for BuAc production is a promising technology that provides similar key benefits as compared to the reactive distillation (RD) process. [ABSTRACT FROM AUTHOR]

The utilization of oxygen transport membranes enables the production of high-purity hydrogen by the thermal decomposition of water below 1000 °C. This process is based on a chemical potential gradient across the membrane, which is usually achieved by introducing a reducing gas. Computational fluid dynamics (CFD) can be used to model reactors based on this concept. In this study, a modelling approach for water splitting is presented in which oxygen transport through the membrane acts as the rate-determining process for the overall reaction. This transport step is implemented in the CFD simulation. Both gas compartments are modelled in the simulations. Hydrogen and methane are used as reducing gases. The model is validated using experimental data from the literature and compared with a simplified perfect mixing modelling approach. Although the main focus of this work is to propose an approach to implement the water splitting in CFD simulations, a simulation study was conducted to exemplify how CFD modelling can be utilized in design optimization. Simplified 2-dimensional and rotational symmetric reactor geometries were compared. This study shows that a parallel overflow of the membrane in an elongated reactor is advantageous, as this reduces the back diffusion of the reaction products, which increases the mean driving force for oxygen transport through the membrane.

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.

The hydrogen economy is expected to dominate in the nearest future. Therefore, the most hydrogen-containing compounds are considered as potential pure hydrogen sources in order to achieve climate neutrality. On the other hand, alkanes are widely used to produce industrially important monomers via various routes, including dehydrogenation processes. Hydrogen is being produced as a by-product of these processes, so the application of efficient separation of hydrogen from the reaction mixture can give double benefits. Implementation of the dehydrogenation processes in the catalytic membrane reactor is that case. Since the use of dense metal membranes, which possess the highest perm-selectivity towards hydrogen, is complicated in practice, the present research is aimed at the optimization of the porous membrane characteristics. By means of a mathematical modeling approach, the effects of pore diameter on the hydrogen productivity and purity for the cases of ethane and propane dehydrogenation processes were analyzed. The pore size value of 0.45 nm was found to be crucial as far as the diffusion of both the alkane and alkene molecules through the membrane takes place.

Photocatalytically active silicon carbide (SiC)-based mesoporous layers (pore sizes between 5 and 30 nm) were synthesized from preceramic polymers (polymer-derived ceramic route) on the surface and inside the pores of conventional macroporous α-alumina supports. The hybrid membrane system obtained, coupling the separation and photocatalytical properties of SiC thin films, was characterized by different static and dynamic techniques, including gas and liquid permeation measurements. The photocatalytic activity was evaluated by considering the degradation efficiency of a model organic pollutant (methylene blue, MB) under UV light irradiation in both diffusion and permeation modes using SiC-coated macroporous supports. Specific degradation rates of 1.58 × 10−8 mol s−1 m−2 and 7.5 × 10−9 mol s−1 m−2 were obtained in diffusion and permeation modes, respectively. The performance of the new SiC/α-Al2O3 materials compares favorably to conventional TiO2-based photocatalytic membranes, taking advantage of the attractive physicochemical properties of SiC. The developed synthesis strategy yielded original photocatalytic SiC/α-Al2O3 composites with the possibility to couple the ultrafiltration SiC membrane top-layer with the SiC-functionalized (photocatalytic) macroporous support. Such SiC-based materials and their rational associations on porous supports offer promising potential for the development of efficient photocatalytic membrane reactors and contactors for the continuous treatment of polluted waters.

Biogas is a valuable renewable energy source that can help mitigate greenhouse emissions. The dry reforming of methane (DRM) offers an alternative hydrogen production route with the advantage of using two main greenhouse gases, CO2 and CH4. However, its real application is limited mainly due to catalyst deactivation by coke formation and the reverse water gas shift (RWGS) reaction that can occur in parallel. Additionally, the typical dry reforming temperature range is 700–950 °C, often leading to catalyst sintering. A low-temperature DRM process could be in principle achieved using a membrane reactor (MR) to shift the dry reforming equilibrium forward and inhibit the RWGS reaction. In this work, biogas reforming was investigated through the simulation of MRs with thin (3.4 µm) and thick (50 µm) Pd-Ag membranes. The effects of the feed temperature (from 450 to 550 °C), pressure (in the range of 2–20 bar), and biogas composition (CH4/CO2 molar ratios from 1/1 to 7/3) were studied for the thin membrane through the calculation and comparison of several process indicators, namely CH4 and CO2 conversions, H2 yield, H2/CO ratio and H2 recovery. Estimation of the CO-inhibiting effect on the H2 molar flux through the membrane was assessed for a thick membrane. Simulations for a thin Pd-Ag MR show that (i) CO2 and CH4 conversions and H2 yield increase with the feed temperature; (ii) H2 yield and average rate of coke formation increase for higher pressures; and (iii) increasing CH4/CO2 feed molar ratio leads to higher H2/CO ratios, but lower H2 yields. Moreover, simulations for a thick Pd-Ag MR showed that the average H2 molar flux decreases due to the CO inhibiting effect (ca. 15%) in the temperature range considered. In conclusion, this work showed that for the considered simulation conditions, the use of an MR leads to the inhibition of the RWGS reaction and improves H2 yield, but coke formation and CO inhibition on H2 permeation may pose limitations on its practical feasibility, for which proper strategies must be explored.

Mixed ionic-electronic conducting oxygen transport membranes have demonstrated high oxygen permeability, which can be coupled with other oxidation reactions. The membrane reactor coupling water splitting with partial oxidation of methane reaction has great practical potential as it produces valuable feedstocks such as ammonia syngas and liquid fuel syngas. However, the existing membrane materials often exhibit structural stability issue and/or unsatisfactory oxygen permeability. In this work, copper-doped LCF 1-x Cu x O 3-δ (x = 0.05–0.1) hollow fiber membranes were used for hydrogen production by coupling the oxygen separation with water splitting and partial oxidation of methane. A small amount of copper doping could effectively reduce the sintering temperature of the membrane and increase the conductivity of the material, where a maximum oxygen flux of 0.55 mL min−1 cm−2 was achieved on LCFCu 0.05 membrane under the experimental conditions. In the water splitting test, a maximum hydrogen production rate of 3.7 mL min−1 cm−2 was achieved by using steam as the raw gas (driven by nitrogen) at the shell side and hydrogen/helium mixture as the sweep gas at the lumen side of the LCFCu 0.05 hollow fiber membrane with 10 wt.% Ni/SDC catalyst coated on the shell side. As pure methane gas was introduced at the lumen side coated with Ni/LaNiO 3 /γ-Al 2 O 3 catalyst, the H 2 production rate was further increased to its highest of 4.4 mL min−1 cm−2. In addition, the membrane reactor could be stably operated for 300 h under three different flow conditions without performance degradation. These results paves the development of robust membrane reactor for integrated water splitting and partial oxidation of methane. [Display omitted] • New Cu-doped La 0.9 Ca 0.1 Fe 0.95 Cu 0.05 O 3-δ (LCFC) hollow fibre membrane. • LCFC demonstrated high O 2 flux of 0.55 mL min−1 cm−2 at 950 °C with He sweep gas. • Coupled water splitting and partial oxidation of methane for more than 310 h. • Co-production of H 2 /N 2 and H 2 /CO syngas through the coupled reactions. • The achieved H 2 flux was 3.7 mL min−1 cm−2 with catalyst. [ABSTRACT FROM AUTHOR]

Advancements in isotope separation are both essential and challenging. The separation of water isotopes is vital in industrial production, biopharmaceuticals, and healthcare applications. This process is energy-intensive and complex due to the similarity of the isotopes. Pure polyacrylonitrile (PAN) is resistant to proton permeability, but neutral hydrogen radicals are capable of penetration. In this study, we report a novel approach using PAN macroscopic hybrid micro-/nanofibers in combination with a photocatalyst to separate hydrogen ion isotopes. Application of photocatalytic water splitting to generate protons results in significantly slower deuteron permeation in these fibers relative to protons, resulting in a separation factor of approximately 15 at room temperature. The composite PAN fibers exhibit a conductivity of 17.5 mS cm−1 at 25 °C and 95 % relative humidity. Our approach not only converts sunlight directly into storable hydrogen, but also enriches heavy water from H₂O/D₂O by H/D isotope separation. This study provides new insights into proton transport mechanisms in acidic media and demonstrates the significant potential of high molecular weight polymers for hydrogen isotope separation. [Display omitted] • The separation of hydrogen isotopes (separation factor: 15) was realized for the first time in heavy and light water using a functional PAN membrane. We have shown that the photocatalytic sieving effect of hydrogen isotopes is related to the zero-point oscillation effect. • The proposed Pt NC@CZS-GAF membranes transformed PAN into proton-conductive materials. Pt nanoclusters were introduced into the PAN matrix, allowing proton conductivity to reach 17.5 mS cm⁻1 at 25 °C and 95 % relative humidity. The membranes also exhibited a higher H₂ generation rate of 12.3 mmol‧m⁻2‧h⁻1 under visible light. • We propose that the coordination of N and Cd mediates electron transfer from the catalyst to PAN. [ABSTRACT FROM AUTHOR]

Conventional Fenton oxidation technique utilized for the treatment of antibiotics is plagued by issues such as extra H 2 O 2 requirement and harsh reaction conditions. In this work, an "all-in-one" membrane reactor with H 2 O 2 self-supply and self-catalysis at natural pH conditions for multiplex antibiotic residues degradation was developed by loading bifunctional composite Pt/CuO 2 Janus nanoparticles (Pt/CuO 2 JNPs) on the surface of the PVDF membrane. Specifically, the Fenton reagents H 2 O 2 , which was generated from the decomposition of the functional material CuO 2 NPs in a near natural pH condition without extra addition, was synergistic activated by nano-enzyme Pt NPs and Cu2+. This, in turn, greatly improves the practicability of the reactor. Notably, the large number of nanopores present on the surface of the reactor endows it with a confined self-enhancing effect, which could greatly improve its catalytic degradation efficiency of antibiotics. The developed membrane reactor is capable of degradation 97.6 % of chloramphenicol (CAP) residues after several cycles of filtration. The apparent rate constant of the developed membrane reactor for CAP is approximately folded for the bulk reaction system. What's more, the developed membrane reactor features favorable usability and preservability and superior universality for common antibiotics. [Display omitted] • "All-in-one" enables self-supply and auto-catalysis of H 2 O 2. • Fenton-like oxidation is initiated at natural pH condition. • Fenton-like and nanozymes co-promote the production of ROS. • Confined self-enhancing boosts the degradation efficiency of CAP. [ABSTRACT FROM AUTHOR]

Biogas, consisting of CH4 and CO2, is a promising energy source and can be converted into H2 by a dry reforming reaction. In this study, a membrane reactor is adopted to promote the performance of biogas dry reforming. The aim of this study is to investigate the effect of pressure of sweep gas on a biogas dry reforming to get H2. The effect of molar ratio of supplied CH4:CO2 and reaction temperature is also investigated. It is observed that the impact of psweep on concentrations of CH4 and CO2 is small irrespective of reaction temperature. The concentrations of H2 and CO increase with an increase in reaction temperature t. The concentration of H2, at the outlet of the reaction chamber, reduces with a decrease in psweep. It is due to an increase in H2 extraction from the reaction chamber to the sweep chamber. The highest concentration of H2 is obtained in the case of the molar ratio of CH4:CO2 = 1:1. The concentration of CO is the highest in the case of the molar ratio of CH4:CO2 = 1.5:1. The highest sweep effect is obtained at reaction temperature of 500 °C and psweep of 0.045 MPa.

Based on finite time thermodynamic theory, a mathematical model of hydrogen iodide fixed bed membrane reactor is constructed. Considering irreversibilities of chemical reaction, heat transfer, flow and mass transfer processes, basic properties of hydrogen iodide decomposition membrane reactor are analyzed. It is noticed that entropy generation rate due to heat transfer and chemical reaction process in membrane reactor is more significant and irreversibility of reaction system is mainly distributed in front part of membrane reactor. Total entropy generation rates of chemical reaction, heat transfer processes and mass transfer process account for 33.7 %, 37.5 % and 23.8 % of the total, respectively. Effects of some parameters on hydrogen yield, entropy generation rate and specific entropy generation rate are further analyzed. The results show that there are optimal reactor length, inlet flow rate, sweep flow rate and inlet pressure to make the specific entropy generation rate reach a minimum. Multivariate simultaneous optimization is performed to obtain the minimum specific entropy generation rate reactor, and the minimized specific entropy generation rate is reduced by 43.4 % compared to the reference value. Minimum specific entropy generation rate can be used for compact reactor design and scale-up by tube multiplication in hydrogen-iodide decomposition process. [Display omitted] • Hydrogen iodide membrane reactor is modeled using finite time thermodynamics. • Irreversibility is mainly distributed in the front of the membrane reactor. • Optimal reactor length, reaction and sweep flow rates exist for membrane reactor. • Multivariate optimized specific entropy generation rate reduced by 43.4 %. • Optimized design of multi-tube hydrogen iodide membrane reactor. [ABSTRACT FROM AUTHOR]

[Display omitted] • pH activity and long-term stability of alcohol dehydrogenase were improved. • Branched polyamines provided better membrane permeability and enzyme stability. • Correlation between immobilization yield and membrane surface charge was found. • High-MW PEI enhanced stability of ADH, while low-MW PEI showed higher activity. Enzymatic membrane reactor (EMR) is a type of continuous-flow bioreactor offering easy separation and reuse of biocatalyst while giving opportunities to improve its performance. However, simultaneous enhancement of activity and stability of enzyme while retaining high membrane permeability poses a challenge for a single reactor. Herein, we propose a new method to optimize EMR system − by employing cationic polyelectrolytes with selected molecular weight, backbone, and amino group type for modification of membrane surface; after we have evaluated the effect of polyamine chemistry and membrane properties on each aspect of EMR performance. Polydopamine (PDA)-assisted co-deposition of polyamines (polyethyleneimine (PEI), PEI-graft-poly(ethylene glycol) (PEI-g-PEG), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDADMAC)) was used as the modification method; the membranes were characterized by water permeability, water contact angle (WCA), zeta potential (ZP), FTIR spectra, and SEM/EDX; and EMRs were assessed by biocatalytic activity at various pH, flux, immobilization yield and efficiency (activity recovery), enzyme leakage, pH/storage and thermal stability, and reusability. In this work, EMRs with immobilized alcohol dehydrogenase (ADH) showed activities up to 8.9 mU/cm2, retained up to 86 % of initial activity in three conversion cycles without any reduction in flux, and allowed to increase non-optimal pH activity (pH 10) by up to 81 % and improve storage stability by up to 53 % compared to the free enzyme. We discovered statistically significant (p < 0.01) relationships between: (1) polyamine backbone type (linear vs branched) and membrane permeability; (2) membrane isoelectric point and immobilization yield; and (3) membrane WCA and immobilization efficiency. To our knowledge, this is the first systematic study of the effect of polyelectrolyte chemistry on performance of immobilized enzyme − which showed the method's strong potential for customizing properties and maximizing the productivity of EMRs. [ABSTRACT FROM AUTHOR]

• A 2D model was developed for a solar-driven steam methane reforming membrane reactor. • Indices to evaluate reaction and energy storage performances were proposed. • Effect of membrane permeance and diameter of membrane tube were studied. • Structural and operating parameters were recommended based on evaluation indices. When the steam methane reforming membrane reactor is coupled with trough solar collector to achieve solar thermochemical energy storage, the dimension of the membrane reactor is enlarged and the catalyst filling amount increases dramatically. As a results, the hydrogen permeation property should be well addressed to match the permeation and the reaction characteristics for a better energy storage performance. In the present paper, the effect of hydrogen permeation, including the effective permeation area and the membrane permeance was investigated by numerical simulations. Results show that the sensitivity factors of the membrane surface area on CH 4 conversion, H 2 yield and H 2 recovery are 0.379, 0.325 and 2.196 respectively while that of membrane permeance are 0.007, 0.009 and 0.488 respectively. This indicates that influence of membrane surface area is more remarkable and H 2 recovery is the most sensitive to the hydrogen permeation. The reactor with a membrane tube diameter of 50 mm and a permeance of 1.07 × 10−2 mol/(m2·s·Pa0.62) can achieve best reaction performance. Besides the reaction performance, a solar thermochemical system is proposed and a solar-to-fuel efficiency is defined to evaluate the thermochemical performance. Again the aforementioned reactor has the highest solar-to-fuel efficiency which can exceed 70 %. Furthermore, for a better thermochemical performance, lower inlet mass flow rate and higher inlet temperature are recommended, but too small or too high values should be avoided to maintain the operating temperature of the membrane. A suitable combination of pressures in the reaction side and the permeating side is also suggested. The results of the present paper reveal the role of hydrogen permeation and helps the reactor design. [ABSTRACT FROM AUTHOR]

• Magnetic nanoparticles can be produced in a membrane reactor with in situ stabilization. • Stabilization is performed using several polymers as PEG, PAA, PVA, PVP, Chitosan, and alginate. • Temperatures and ultrasound play an important role in situ stabilization of nanoparticles in membrane reactors. Membrane reactors have been proven to be effective in producing nanoparticles with reduced polydispersity indices. Recently, our group has incorporated this technology into the synthesis of ferromagnetic nanoparticles. In the initial phase, we conducted post-synthesis stabilization experiments to assess the performance of various polymeric agents. Polyacrylic acid (PAA) was chosen because of its notable affinity for the functional groups on the nanoparticle surface. Subsequently, in situ stabilization experiments were conducted using a membrane reactor, with variations in PAA addition flow rates ranging from 0.33 to 1.5 mL/min and maturation times in an ultrasonic bath ranging from 0.5 to 2 h. The samples were characterized in terms of their hydrodynamic diameter, polydispersity, and Z-potential. Notably, the smallest particle size was achieved at the intermediate point with a PAA flow rate of 0.66 mL/min. However, the influence of maturation time did not follow a predictable pattern; the most favorable characteristics, based on the analyzed variables, were observed at 1.5 and 2 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • Endo-hydrolytic activity of free dextranase is transformed to exo -hydrolytic after covalent immobilization. • Noncovalent immobilization of dextranase maintains its endo -hydrolysis behavior. • Matching target products generation and separation efficiency can control product molecular weight and mitigate fouling. • A desirable enzyme membrane reactor requires highly active enzyme, strong internal mass transfer and high permselective membrane. • Immobilization is not necessary in enzyme membrane reactor if enzyme has good shear resistance and acceptable stability. Enzyme membrane reactor (EMR) provides an effective strategy for controlling molecular weight (Mw) of oligodextrans. However, the synergistic effect between dextran hydrolysis and product separation as well as continuous operation stability remains still unclear. We observed that covalently immobilized dextranase exhibited more obvious exo -hydrolysis behavior compared to free enzymes probably due to enzyme conformational alterations. Using non-covalently immobilized enzyme, suitable ultrafiltration membrane, optimal substrate/enzyme ratio and matched permeate flux, the yield of the target product reached 62.8%. However, the non-covalently immobilized dextranase exhibited reduced hydrolytic activity and more obvious membrane fouling (caused by high-Mw dextran). When free dextranase with high activity was used together with suitable permeate flux and high shear rate, the yield increased to 72.0%. The obtained EMR maintained stable for 8 h with slight fouling formation because enzymatic hydrolysis and membrane separation were well matched. The polydispersity index of the target product reached 1.3 (analytical grade) following diafiltration purification. [ABSTRACT FROM AUTHOR]

• TEA for our RWGSR/MeS-MCR technology compared to four other competitive processes. • RWGSR/MeS-MCR attains ∼80 % conversion, much higher than the equilibrium conversion. • RWGSR/MeS-MCR outperforms other four processes in energy efficiency and economics. • By 2030, RWGSR/MeS-MCR will match commercial MeOH costs (400–600 $/ton) per U.S. DOE targets. We introduced recently a CO 2 capture and utilization (CCU) technology that produces methanol (MeOH), from waste CO 2 employing a novel configuration combining a reverse water gas shift reactor (RWGSR) with a membrane contactor reactor for MeOH synthesis (MeS-MCR). The integrated RWGSR/MeS-MCR process overcomes the challenges direct CO 2 conversion into MeOH faces and achieves carbon conversions exceeding 80 %, significantly surpassing the equilibrium conversion of ∼ 20–30 % for the MeS reaction. In this study, a techno-economic analysis (TEA) was conducted on the RWGSR/MeS-MCR process along with four other CO 2 -to-MeOH CCU processes. Key economic parameters, as well as the energy efficiency, were analyzed with respect to CO 2 and renewable hydrogen (H 2) costs and plant capacity. The study revealed that the RWGSR/MeS-MCR technology has the highest energy efficiency and the best economic performance among all the technologies investigated. All technologies offer the significant societal benefit of capturing and utilizing waste CO 2 , but under present CO 2 and renewable H 2 costs, they cannot currently compete cost-wise with conventional MeOH production methods. However, under a future scenario whereby government incentives lower the CO 2 cost and technological advances decrease the price of renewable H 2 , the proposed RWGSR/MeS-MCR process and another catalytic technology (CAMERE) become price competitive. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Incorporated FeOOH onto 2D BiOBr nanosheets to modulate built-in electric field. • Optimizing the photocatalytic activity of BiOBr by adjusting Br source amount. • The synergistic effect in BiOBr-1/FeOOH enhances photo-Fenton-like activity. • Discussed the mechanism of charge transfer and tetracycline removal. • Integrating BiOBr/FeOOH with a PVDF membrane to construct continuous-flow reactor. The selection of photosensitizer substrates with high photocatalytic efficiency is crucial for leveraging the advantages of metal-based materials in photo-Fenton-like process. Herein, we report a novel 2D layered BiOBr/FeOOH nanosheets equipped with a built-in electric field (BIEF) to activate peroxymonosulfate (PMS) for the degradation of tetracycline (TC). The photocatalytic efficiency of BiOBr is enhanced by fine-tuning the Br source quantity. Both experimental and theoretical analyses confirm that BIEF at the BiOBr/FeOOH heterointerface expedites the movement of photogenerated electrons, significantly boosting both photocatalytic and photo-Fenton-like activities. The BiOBr/FeOOH + PMS + Vis system exhibits a high TC removal rate of 96 % with only 0.24 mM of PMS and nearly 100 % of PMS utilization. Moreover, affixing BiOBr/FeOOH nanosheets onto a PVDF microfiltration membrane, we establish a continuous flow reactor system for antibiotic wastewater treatment. This system demonstrates a remarkable TC removal efficiency consistently above 97.5 % for 6 h of continuous injection, underscoring its practicality and potential for real-world applications. [ABSTRACT FROM AUTHOR]

Research background. Rice germination is a natural approach to enhance the physical and functional properties of brown rice. Thus, the aim of this study is to investigate the influence of different germination methods on functional properties of germinated brown rice and evaluate the process feasibility. Experimental approach. Brown rice of IPB 3S variety was germinated with three different methods: (i) complete soaking without water replacement, (ii) complete soaking with water replacement every six hours, and (iii) complete soaking with continuous washing in the developed membrane-facilitated soaking reactor. Results and conclusions. The application of the membrane reactor for producing germinated brown rice maintained the pH of the soaking solution relatively constant (i.e. 6.8-7.0). This indicated the circumvention of natural fermentation during brown rice germination. Moreover, the mass fraction of γ-aminobutyric acid in germinated brown rice produced in the membrane reactor was about 4.5-fold higher (169.2 mg/100 mg) than in ungerminated brown rice (36.82 mg/100 mg), and also higher than that of the other two soaking methods. The γ-oryzanol mass fractions and the antioxidant capacity expressed as ascorbic acid equivalents of germinated brown rice obtained with the three soaking methods varied from 32 to 38 mg/100 mg and 18 to 28 mg/100 g, respectively. Within this study, germination could also slightly reduce the transition temperatures of germinated brown rice starch gelatinization (to=73-74 °C, tp=76-77 °C and tc=~80 °C, where to, tp and tc are onset, peak and conclusion (final) temperatures). In conclusion, the production of germinated brown rice in the membrane reactor could enhance its γ-aminobutyric acid mass fraction and reduce wastewater production and is therefore considered more feasible. Novelty and scientific contribution. This study demonstrates the feasibility of germinated brown rice production using a membrane-facilitated soaking reactor with enhancement of bioactive compound content, especially γ-aminobutyric acid, and minimised wastewater production.