Membrane Reactor Research Articles

Construction of N-Fe-S bridge in atomic iron catalyst for boosting Fenton-like reactions

Constructing the coordination environment of single-atom catalysts (SACs) can be an attractive technical strategy to regulate the generation of reactive oxygen species for Fenton-like reactions. Herein, we have constructed an asymmetric coordination of Fe single-atom catalyst (FeSA-NS-PCNS) with abundant N-Fe-S bridge (FeSA-N3S1) for robust Fenton-like reactions. 82.5 % of singlet oxygen (1O2) selectivity and high turnover frequency of bisphenol A degradation (0.568 min−1) were achieved at mild conditions. Experimental works and theoretical analyses illustrated that S doping breaks the inert environment of the original N-Fe-N symmetric coordination equilibrium and modulates the electron density of the atomic Fe center, which is beneficial for boosting PMS adsorption and reducing the energy barriers of vital *OH and *O intermediates. The coupling between the FeSA-N3S1 interface and peroxymonosulfate molecule boosts in-situ electron transfer through the N-Fe-S bridge, which induces more electron flow from the low valence Fe to OH* on the surface of Fe-*O-H, forming a high yield of 1O2. Moreover, we designed the Fenton-like reactions by FeSA-NS-PCNS membrane reactor for an efficient contaminant removal rate of over 90 % even after 11 cycles. This work provides a novel perspective on developing SACs with asymmetric coordination to regulate reactive oxygen species for the treatment of organic contaminants in water bodies.

Continuous flow-through electro-Fenton membrane reactor with Fe−N4-doped carbon membrane as cathode for efficient removal of dimethylacetamide

Fe − N4-doped conductive carbon membranes (FeCMs) were fabricated through high-temperature carbonization using chitosan and phenolic resin as the raw materials and ammonium ferrous sulfate (NH4Fe(SO4)2) as the dopant. The impact of the NH4Fe(SO4)2 doping rate (0 − 15 wt%) on the structure and performance of the FeCM was investigated. Moreover, a continuous flow-through electro-Fenton membrane reactor (EFMR) was constructed using an FeCM cathode and a Ti plate anode for the efficient removal of dimethylacetamide (DMAC). The resultant carbon membrane with 10 wt% NH4Fe(SO4)2 (M10) exhibited a smaller pore size (40.1 nm), a higher porosity (48.3 %), a larger specific surface area (531.6 m2/g), and a higher mechanical strength (6.7 M Pa) than the other membranes. The removal rate of DMAC by EFMR with M10 as the cathode at 2 V reached 42.1 %, which was much greater than that without NH4Fe(SO4)2 (3.6 %). The electrosynthesis ·OH concentration by EFMR with M10 as the cathode was approximately 89.1 mg/L, which was much greater than that of most carbon-based materials. The intermediates of DMAC degradation (such as N-methylacetamide, acetamide, acetaldehyde, and acetic acid) were determined by gas chromatography–mass spectrometry (GC–MS), and the removal of total organic carbon (TOC) was approximately 3.4 %. Density functional theory (DFT) calculations revealed that the Fe atom served as the active site for dissolved oxygen adsorption and electrogeneration of ·OH. After 5 days of continuous EFMR operation, the DMAC removal rate remained at 88.8 % of the initial value (42.1 %). This study presents a novel approach for designing and fabricating conductive carbon membranes to improve industrial wastewater treatment performance.

Exploiting UPO versatility to transform rutin in more soluble and bioactive products

The discovery of unspecific peroxygenases (UPOs) completely changed the paradigm of enzyme-based oxyfunctionalization reactions, as these enzymes can transform a wide variety of substrates with a relatively simple reaction mechanism. The fact that UPO can exert both peroxygenative and peroxidative activity in either aromatic or aliphatic carbons, represents a great potential in the production of high value-added products from natural antioxidants. In this work, the flavonoid rutin has been considered as possible substrate for UPO from Agrocybe aegerita, and its peroxygenation or its peroxidation and successive oligomerization have been studied. Different experiments were performed in order to reduce the range of process variables involved and gaining insight on the behavior of this enzyme, leading to a multivariable optimization of UPO-based rutin modification. While trying to preserve enzyme activity this optimization aimed for maximizing the production of more soluble antioxidants. Reusability of the enzyme was evaluated recovering UPO using an enzymatic membrane reactor, revealing challenges in enzyme stability due to inactivation during the filtration stages. The influence of the radical scavenger ascorbic acid on product formation was investigated, revealing its role in directing the reaction towards hydroxylated rutin derivatives, hence indicating a shift towards more soluble and bioactive products.

Rational design double S-scheme heterosystem based Photo-Electrocatalytic membrane device for continuous phytotoxin remediation

Today, the escalating contamination of water sources with phytotoxins poses a significant danger to both ecosystems and human health. Consequently, the implementation of advanced and sustainable remediation technologies becomes imperative for the effective removal of toxins. This study introduces a pioneering method for continuous phytotoxin remediation by integrating a photoelectrocatalytic membrane reactor, which utilizes a ZnCdFeSe heterojunction photocatalyst with a double S-scheme, is derived from the ZnCd prussian blue analog. This design capitalizes on the unique electronic structure and synergistic effects of the catalyst enabling efficient photo-electrocatalysis in the device. The proposed system attains an impressive phytotoxin rejection efficiency of 98.39%, accompanied by enhanced membrane permeation and anti-fouling performance. The obtained results are noteworthy for an emerging process that combines the simultaneous degradation and separation of toxic species, enabling prolonged and uninterrupted remediation processes. Experimental and density function theory (DFT) results demonstrate that, under optimal conditions, the well-stabilized double S-scheme ZnCdFeSe heterojunction achieves a mineralization rate of 85.67%. Even after six cycles of the photocatalytic membrane, the removal rate of ricin remains high at 78.96%, indicating the membrane’s commendable reusability and stability. This research not only contributes to the advancement of innovative environmental remediation strategies but also provides valuable insights for designing and optimizing photoelectrocatalytic systems for the persistent removal of toxins in water treatment applications.

Stabilizing Bicontinuous Emulsions with Sub-Micrometer Domains Solely by Nanoparticles.

Nanoparticle-stabilized, bicontinuous interfacially jammed emulsion gels (bijels) find potential applications as battery, separation membrane, and chemical reactor materials. Decreasing the liquid domain sizes of bijels to sub-micrometer dimensions requires surfactants, complicating bijel synthesis and postprocessing into functional nanomaterials. This work introduces surfactant-free bijels with sub-micrometer domains, solely stabilized by nanoparticles. To this end, the covalent surface functionalization of silica nanoparticles is characterized by thermogravimetric analysis, mass spectrometry, Fourier-transform infrared spectroscopy, and contact angle measurements. Bijels are generated with the functionalized nanoparticles via solvent transfer induced phase separation (STrIPS), enabling the optimization of nanoparticle functionalization and surface ionization. Nanoparticles of intermediate functionalization and controlled negative surface charge stabilize bijels with sub-micrometer liquid domains. This remarkable control over bijel synthesis provides urgently needed progress to facilitate the widespread implementation of bijels as nanomaterials in research and applications.

An “all-in-one” and confined self-enhancing Fenton-like membrane reactor for multiple antibiotic treatment in aquatic environment at natural pH

Conventional Fenton oxidation technique utilized for the treatment of antibiotics is plagued by issues such as extra H2O2 requirement and harsh reaction conditions. In this work, an “all-in-one” membrane reactor with H2O2 self-supply and self-catalysis at natural pH conditions for multiplex antibiotic residues degradation was developed by loading bifunctional composite Pt/CuO2 Janus nanoparticles (Pt/CuO2 JNPs) on the surface of the PVDF membrane. Specifically, the Fenton reagents H2O2, which was generated from the decomposition of the functional material CuO2 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.

Self-stabilizing economic nonlinear model predictive control applied to modular systems

Recent advances have been made in self-stabilizing Economic Nonlinear Model Predictive Control (eNMPC) formulation without pre-calculated setpoints, which leverages norm-based steady-state optimality conditions to enhance system robustness. To enable practical implementation, a generalized time-domain formulation is proposed, accommodating the discrete-time nature of control instrumentation and the continuous-time nature of first-principles models. A case study involving a modular membrane reactor illustrates the applicability of self-stabilizing eNMPC in real-world industrial scenarios.

Direct Non-Oxidative Methane Conversion and Hydrogen Co-Production in a Proton Conducting Membrane Reactor

Direct Non-oxidation Methane Conversion (DMNC) has been recognized a promising technology for the upgrading of cheap and abundant methane to higher hydrocarbons (C2+) and H2, but this technology has not been commercialized yet because of the low methane equilibrium conversion and severe carbon deposition.1-3 Here, we present our effort to develop a proton conducting membrane reactor (SrCe0.7Zr0.2Eu0.1O3- ⴃ) combined with the catalysts (Fe©SiO2) to circumvent the equilibrium limitations of the DMNC reaction and solve the coking (i.e., solid carbon deposition) problem. By coupling the Fe©SiO2 catalysts with H2 permeable membrane reactor, part of produced H2 during the catalytic conversion can be extracted from the effluent gas, which not only provides a one-step hydrogen production without additional separation process, but also shifts the equilibrium of the reaction to the product side and achieves an improved methane conversion and higher C2+ yield when compared to the traditional fixed-bed reactor. In addition, an air sweep outside the reactor results in O-permeation into catalyst to oxidize any deposited carbon to CO thus preventing coking.The membranes were fabricated using tape casting of the support layer followed by dip coating process to form the dense membrane layer. Using this method, we obtained 25 µm for the thickness of the dense layer and around 700 µm for the thickness of the support layer (see Fig. 1a and 1b). The catalyst was synthesized by a simple sol-gel method followed by fusing process, and then was crushed into 40-80 mesh and loaded inside of membrane reactor to test.The performance metrics include methane conversion, selectivity, and product yield. Our membrane reactor achieved single-pass methane conversion of 17.5%, and a C2+ yield of 15% (see Fig. 1c) at 1323K.Finally, our membrane reactors were stable for over 350 hours, which, along with the aforementioned performance metrics, constitutes a major advance in the development of commercial DMNC technology. References Guo, X.; Fang, G.; Li, G.; Ma, H.; Fan, H.; Yu, L.; Ma, C.; Wu, X.; Deng, D.; Wei, M.; Tan, D.; Si, R.; Zhang, S.; Li, J.; Sun, L.; Tang, Z.; Pan, X.; Bao, X., Direct Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen. Science 2014, 344 (6184), 616-619.Thyssen, V. V.; Vilela, V. B.; de Florio, D. Z.; Ferlauto, A. S.; Fonseca, F. C., Direct Conversion of Methane to C2 Hydrocarbons in Solid-State Membrane Reactors at High Temperatures. Chemical Reviews 2022, 122 (3), 3966-3995.Sakbodin, M.; Schulman, E.; Cheng, S.; Huang, Y.-L.; Pan, Y.; Albertus, P.; Wachsman, E. D.; Liu, D., Direct Nonoxidative Methane Conversion in an Autothermal Hydrogen-Permeable Membrane Reactor. Advanced Energy Materials 2021, 11 (46), 2102782. Figure 1

Covalent organic framework membrane reactor for boosting catalytic performance

Membrane reactors are known for their efficiency and superior operability compared to traditional batch processes, but their limited diversity poses challenges in meeting various reaction requirements. Herein, we leverage the molecular tunability of covalent organic frameworks (COFs) to broaden their applicability in membrane reactors. Our COF membrane demonstrates an exceptional ability to achieve complete conversion in just 0.63 s at room temperature—a benchmark in efficiency for Knoevenagel condensation. This performance significantly surpasses that of the corresponding homogeneous catalyst and COF powder by factors of 176 and 375 in turnover frequency, respectively. The enhanced concentration of reactants and the rapid removal of generated water within the membrane greatly accelerate the reaction, reducing the apparent activation energy. Consequently, this membrane reactor enables reactions that are unattainable using both COF powders and homogeneous catalysts. Considering the versatility, our findings highlight the substantial promise of COF-based membrane reactors in organic transformations.

Electrooxidation of Poly(methyl-methacrylate) and Poly(ethylene glycol): Hydrogen Production from Plastic Wastes Electrolysis

Introduction. Green H2 production by water electrolysis at low temperature has some bottlenecks mostly dealing with the anodic reaction, the oxygen evolution reaction (OER), given its thermodynamic and kinetic limitations [1]. One strategy to reduce the energy requirements for this H2 production route is the replacement of the conventional OER (with a thermodynamic potential of 1.23 V vs. Reversible Hydrogen Electrode (RHE)) by a less-energy intensive reaction like the electrooxidation of organic molecules (in some cases presenting a thermodynamic potential as low as c.a. 0 V vs RHE). This approach also addresses the possibility of converting organic wastes into value-added chemicals avoiding the CO2 emissions derived from conventional treatments (e.g., incineration) [2, 3]. Our research group is focused on the electrochemical valorization of several organic wastes like polyethylene glycol (PEG) or poly(methyl-methacrylate) (PMMA). Both are commonly found in urban and industrial water effluents and concern has been raised about the true fate of these polymers in the environment. Herein, the possibility of generating H2 and value-added organic molecules from these plastic wastes has been explored. Experimental. A binary solvent strategy was followed to dissolve the PMMA polymer, by using 1 M H2SO4 in 80% v/v 2-propanol/water electrolyte. Then the electrooxidation of PMMA was studied in a 2-electrode batch cell at 70ºC with different PMMA concentrations (0.1-2 wt.%). On the other hand, the electrooxidation of ethylene glycol (EG) and PEG with various molecular weights (from 200 to 4000 g mol-1), which are soluble in water, was carried out in aqueous solutions (PEG concentrations from 1 to 20 g/L) between 30 and 80 °C by using a Polymer Electrolyte Membrane (PEM) reactor. Pt/C electrodes were used in all cases. A commercial Pt cathode was employed and the anode material was prepared by the spray-deposition of a Pt(20 wt.%)/C catalyst powder onto a carbon paper gas-diffusion layer. The liquid products at the anodic compartment were analysed by size-exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy while the production of hydrogen in the cathodic compartment was online monitored with a mass spectroscopy. Results and discussion. In the case of PMMA electrooxidation, despite the dissolution challenge, polymer macromolecules showed to partially block the accessibility of the Pt active sites on the electrode and strongly degraded its electrochemical performance [4]. In the case of PEG, it was much more easily electrooxidised, at low cell voltages, from around 0.4 V at 80°C (Figure 1a), near to values recorded with EG, suggesting a first step linked with the electrooxidation of the terminal groups of the macromolecules chain. Current densities larger than 100 mA.cm-2 at 0.8 V and 80°C were achieved for low molecular mass molecules (200 and 400 g/mol). A decrease of the PEG molecular weight in the anodic solution was demonstrated by SEC, confirming that the electro-oxidation process likely follows two main mechanisms, involving the consumption of terminal –OH or intermediate -C-O-C- bonds cleavage (Figure 1b), depending on the polymer molecular weight. This study demonstrates the proof-of-concept of the low-temperature electro-oxidation of polymers containing C-O bonds in their main chain. Conclusions. With a further macroporous electrode enegineering and catalyst development, the electrolysis of plastic wastes stands as a promising technology not only for the production of hydrogen from macromolecules by electrochemical means, but also as a potential pathway to depolymarize plastic wastes, thus increasing their degradability. References. [1]. Y. Cheng, S.P. Jiang, Advances in electrocatalysts for oxygen evolution reaction of water electrolysis-from metal oxides to carbon nanotubes, Prog. Nat. Sci.: Mater. 25 (2015) 545-553.[2]. M. Simões, S. Baranton, C. Coutanceau, Electrochemical valorisation of glycerol, ChemSusChem. 5 (2012) 2106–2124[3]. Y.X. Chen, A. Lavacchi, H.A. Miller, M. Bevilacqua, J. Filippi, M. Innocenti, et al. Nanotechnology makes biomass electrolysis more energy efficient than water electrolysis. Nat. Commun. 5 (2014) 1-6.[4]. N. Grimaldos-Osorio, F. Sordello, M. Passananti, J. González-Cobos, A. Bonhommé, P. Vernoux, A. Caravaca. From plastic-waste to H2: A first approach to the electrochemical reforming of dissolved Poly(methyl methacrylate) particles. Int. J. Hydrogen Energy. 48 (2023) 11899-11913. Acknowledgments The authors gratefully acknowledge the French institution “Ecole Urbaine de Lyon” (EUL - Institut de Convergences) for funding a PhD grant of Dr. N. Grimaldos-Osorio. Figure 1

Electrocatalytic Upgrading of CO2 to Light Olefins in Protonic Ceramic Electrochemical Cells

Light olefins (ethylene, propylene, butylene) are primary building blocks for chemical manufacturing of large volume products including organic chemicals, plastics, and even sustainable aviation fuels. Currently, the dominant commercial process for olefin production is steam cracking of naphtha or ethane, which is highly energy intensive and accounts for a large fraction of global CO2 emissions. To decarbonize olefin production processes, electrochemical CO2-to-olefin conversion coupled with renewable or low-emission energy sources including electricity and heat offers an attractive alternative. Previously, extensive research efforts have been devoted to low temperature electrochemical CO2 reduction in aqueous media, i.e., occurring below 100 °C. This approach, however, still faces enormous scientific and technological challenges in improving CO2 utilization, energy efficiency, and product selectivity. In this work, we have developed a new electrochemical process for direct conversion of CO2 to ethylene at intermediate temperatures (350-500°C) in an electrochemical membrane reactor. This process is based on high-performance protonic ceramic electrochemical cells (PCECs) that integrate CO2 hydrogenation reaction to produce olefins in the cathode and concurrent hydrogen generation reaction in the anode to provide hydrogen for CO2 conversion. Highly active and selective catalysts for CO2-to-olefin conversion have been identified and integrated into the PCECs. Both the catalytic and electrochemical performances of the integrated reactor system are evaluated and optimized. In contrast to the use of molecular H2 in conventional thermal catalytic pathways, the active hydrogen in PCECs could be sourced from different feedstocks including H2O, light alkanes, and ammonia, etc. This work also provides valuable insights into the selection and design of efficient catalysts for electrochemical CO2 conversion at elevated temperatures.

Thin Film Based Membrane Electrode Assemblies for Solid-State Ammonia Synthesis

Ammonia is the of the most crucial chemicals and currently primarily produced through the Haber-Bosch process causing the industrial ammonia production to emit more CO2 than any other chemical-making reaction. While the current primary function of ammonia lies within the fertilizer production, it can also be directly used as a fuel for power generation or in the maritime industry. Compared to hydrogen, ammonia has superior storage and transportation capabilities due to its greater volumetric energy density and mild conditions for liquefication. Given the need of reducing global carbon emissions, ammonia could be synthesized electrochemically using air, water and electricity by the Solid-State Ammonia Synthesis (SSAS). Protonic ceramic cells operate within an intermediate temperature regime of around 450 - 550 °C which is well suited for this process. Within our work, we present a tubular membrane electrode unit entirely made of ceramic components based on a barium zirconate thin film electrolyte. An ammonia production rate of 9.06 × 10-10 mol s-1 cm-2 and a Faradaicefficiency of 6.58% were achieved using a NiO-BaZr0.7Ce0.2Y0.1O3- δ | BaZr0.8Y0.2O3- δ | Ru@Ba0.5Sr0.5TiO3-δ cell.A key innovation lies in the production of dense BaZr0.8Y0.2O3-δ electrolyte layers, ranging from 1 to 5 µm in thickness, utilizing a Closed-Field Unbalanced Magnetron Sputtering (CFUMS) process. This technique allows precise adjustments of stoichiometric ratios within the perovskite structure, offering improved sputtering yields compared to conventional methods. Furthermore, the crystallinity, phase purity, and microstructure of sputter-deposited thin films are enhanced through selective laser annealing (SLA), resulting in high-density films composed of single-phase BaZr0.8Y0.2O3-δ with average crystallite sizes of 200 nm while avoiding substrate damage from thermal stress. Electrochemical performance was evaluated through impedance spectroscopy, half-cell tests and full cell tests providing insights into the efficacy of the developed tubular membrane reactor for the electrochemical synthesis of ammonia. The results demonstrate the feasibility of utilizing ceramic proton conductors in SSAS, particularly highlighting the potential of high-pressure operation up to 80 bars in tubular cells at relatively low temperatures around 450 °C, thereby achieving attractive NH3 production rates.This research contributes to the evolving landscape of sustainable ammonia synthesis by presenting a novel approach that integrates advanced materials and manufacturing techniques. Electrification and decentralization of the ammonia supply chain will expand the market by supporting its current use as fertilizer source and enable a new route as green energy carrier paving the way for an ammonia-based economy. Figure 1

Study on Gas–Solid Flow Characteristics in Fluidized Bed Membrane Reactors with Different Membrane Tube Arrangements Using X-ray Computed Tomography

Study on Gas–Solid Flow Characteristics in Fluidized Bed Membrane Reactors with Different Membrane Tube Arrangements Using X-ray Computed Tomography

Comparative analysis of hydrogen production from ammonia decomposition in membrane and packed bed reactors using diluted NH3 streams

Ammonia decomposition is a key technology for its use as a hydrogen carrier and in the recovery of H2 from waste streams containing ammonia. The coupling of the catalytic decomposition of ammonia with an H2 permeoselective membrane improves the process by mitigating thermodynamic constraints and producing a flux of high-purity hydrogen, not requiring further separation/purification. In this study, we compare the behaviour of an eggshell catalyst 1.3 wt % Ru/Al2O3 catalyst in a packed bed reactor (PBR) and a packed bed membrane reactor (PBMR) using an ultrathin Pd membrane (3.4 μm). Tests were made at 11 bar(a) with a weight hourly space velocity of NH3 in the 0.560–1.68 Lꞏg−1ꞏh−1 range and temperatures of 350–400 °C, e.g. milder conditions than the conventional ammonia cracking catalysts. Under optimised conditions (0.56 Lꞏg−1ꞏh−1, 400 °C, sweep gas flow 0.55 L min−1), the PBMR shows excellent performance, achieving NH3 conversion, H2 productivity and recovery factor of 99%, 47 mmolH2·gRu−1·min−1, and 94.9%, respectively. PBMR increases by ∼50% the conversion rate compared to PBR. Without a sweep gas, PBMR performances are lower, even still higher than in PBR. For the first time, superior or comparable performance was demonstrated compared to similar systems using pure ammonia in terms of conversion, hydrogen recovery, H2 productivity, and Ru utilisation. These results can be further enhanced with vacuum systems to convert diluted ammonia streams into high-purity hydrogen for small-scale distributed systems and can be extended to other reactions.

Zeolite Membrane-Based Low-Temperature Dehydrogenation of a Liquid Organic Hydrogen Carrier: A Key Step in the Development of a Hydrogen Economy.

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.

Novel Ni–Ru/CeO2 catalysts for low-temperature steam reforming of methane

Upgrading of biogas and biomethane into H2-rich streams by steam reforming is regarded as an effective strategy to reduce fossil fuel consumption contributing to the transition towards a green energy system. In this context, novel reactor configurations such as membrane reactors appear a promising route for process intensification, but they require novel catalysts more active at low temperatures, stable, and resistant to coke formation. In this work, we prepared and tested structured catalysts characterized by a low Ni content (7 wt%) and a very low Ru content (≤1 wt%) supported on ceria and deposed onto SiC monoliths. Catalysts were tested at low temperatures (<600 °C), i.e. at temperatures suitable for applications in Pd-based membrane reactors. Fresh and used catalysts were characterized by ICP-MS, N2 physisorption, XRD, TEM, SEM-EDS, XPS and H2-TPR to identify the physicochemical properties affecting the catalytic activity. The catalysts showed good activity towards methane reforming, stable performance, and good resistance to coke formation. Ruthenium affects both the intrinsic catalytic activity and the resistance to the inhibiting effect of steam on the reaction rate. This is related to improved redox properties due to the intimacy between the active metals and their strong-metal-support-interaction with the ceria. Finally, our catalysts show self-activation under reaction conditions, which is an interesting property for applications.

A review on solar methane reforming systems for hydrogen production

Hydrogen energy is a promising alternative to fossil fuels. Solar hydrogen production through steam and carbon dioxide methane reforming is one of the sustainable and environmentally friendly methods for supplying hydrogen. This review will focus on steam and dry methane reforming. A section on methane reforming catalysts is considered to review different types of catalysts, including noble metals, non-noble metals, and Ni-based catalysts. The catalysts section will focus on the activity and stability of the catalysts. Methane reforming using solar energy is the next main section of this review and will be discussed in detail in different types of reactors, including tubular, volumetric, and membrane reactors. Sorption-enhanced steam methane reforming using solar energy will also be discussed in detail. It should be mentioned that the highly efficient methane reforming systems will be investigated. Finally, some conclusions and future trends will be proposed in the solar methane reforming field.

Development of a hydrogen permselective silica membrane and its application to the thermochemical water splitting method

Abstract The thermochemical water splitting IS process is one of the hydrogen production method to use a heat directly. The temperature of the thermal decomposition of water (4000 K) can be reduced under 700 K by introducing I2 and SO2 as recycling catalysts. One of the problems in the IS process is that the conversion of the HI decomposition reaction is low at about 20%. If a membrane reactor with the H2 permselective membrane is applied to the HI decomposition reaction, the hydrogen can be extracted to improve the HI conversion. We focus on a counter diffusion CVD method for the preparation method of the membranes. Two reactants (e.g. silica precursor and oxidant) are provided at the opposite side of the porous substrates and hybrid silica is deposited inside the pore of the substrate. The pore sizes are controlled by introducing organic functional groups to silica precursor. In this study, the silica hybrid membrane with high H2 permeation performance and high H2/HI selectivity were developed by introducing organic functional groups. Effects of the organic functional groups were summarized by using a pore model. The HI gas and other inorganic gases permeation performance were tested through silica hybrid membranes.

Universal solution to the membrane selectivity challenge: Separation merit and efficiency

Membrane technology holds immense potential across multiple industries, offering sustainable solutions for challenging separations by reducing energy demand and transitioning from thermal to electrical energy. The inherent diversity of membrane technology results in various transport scenarios and phenomena, rendering robust process evaluation and optimization challenging. Addressing this problem, we formulate the cascading selectivity principle (CSP), a universal concept applicable across all membrane separation types, including gas, liquid, and particle filtration. Introducing a distinction between primary and secondary permselectivity, the CSP provides a theoretical basis for novel efficiency indices. We also present the first highly versatile selectivity merit descriptors for true membrane cross-comparison. We demonstrate the advantages of the novel descriptors through a series of real-life nanofiltration, ion separation, gas separation, membrane reactor, and ultrafiltration examples. Facilitated by an online calculator tool, this work offers a standardized framework for academic and industrial professionals to implement pioneering membrane separation systems efficiently across the multiple disciplines of membrane technology.

Study on the synthesis of nanoparticles and their power characteristics in a bubble liquid membrane reactor

Abstract A bubble liquid film reactor is a new type of reactor used for preparing nanoparticles, which has strong inflation ability and dispersion, homogenization, and emulsification effects, especially suitable for preparing loose nanoparticles. In the actual production of enterprises, there is an urgent need to expand production capacity and scale up the reactor. Due to the lack of power characteristic data during the reaction process, it is difficult to select the motor, resulting in unnecessary energy and cost waste. Therefore, the power characteristic data of bubble liquid film reactors urgently needs to be studied. This article investigates the influence of operating conditions such as bubble cap diameter and immersion depth on stirring power and obtains the power characteristics during the operation of a bubble liquid film reactor. The results indicate that the larger the diameter of the bubble cap disk, the stronger the power consumption, but the smaller the power input capacity. The deeper the immersion depth, the higher the power consumption and the stronger the power input capability. Finally, fitting the dimensionless power standard formula provides a mathematical model for reactor amplification, providing theoretical guidance for enterprises to expand production lines and increase production capacity, and providing data support for motor selection.