Catalytic Membrane Microreactor Research Articles

MnO2@CS modified catalytic membrane for simultaneous organics removal and membrane fouling mitigation via peroxymonosulfate activation

The integration of advanced oxidation process and ultrafiltration membrane has been regarded as an effective method to improve pollutants removal and mitigate membrane fouling simultaneously in the field of wastewater treatment. Hence, a novel catalytic membrane microreactor, referred to as MnO2@CS-UF, was synthesized via coupling MnO2 modified carbon spheres (MnO2@CS) with membrane. The mesoporous structure of MnO2@CS guaranteed adequate water transfer channels and also contributed to more exposure of active sites. With MnO2@CS uniformly dispersed, the MnO2@CS-UF membrane showed increased hydrophilicity, higher permeability and superior peroxymonosulfate (PMS)-activation capability. With synergistic effect of pore interception and catalytic degradation, MnO2@CS-UF showed excellent organic pollutants removal (MB removal of about 100 % in 5 min), and had a prominent mitigation effect on membrane fouling caused by model NOM. In addition, MnO2@CS-UF/PMS system showed excellent catalytic filtration performance in the treatment of actual secondary effluent (SE). MnO2@CS-UF/PMS system could effectively remove fluorescent organics, and the removal rates of I-V region were 36.3 %, 72.3 %, 67.7 %, 73.5 % and 71.4 %, respectively. The permeance decline of MnO2@CS-UF was also effectively alleviated, with irreversible and reversible resistances reduced by 61.0 % and 23.2 % than UF membranes, individually. High-valent manganese-oxo species and singlet oxygen played a leading role in contaminants elimination, whereas radical oxidation acted as auxiliary contributors. Standard blocking became the dominant fouling pattern for MnO2@CS-UF/PMS, demonstrating that the MnO2@CS catalytic layer ensured the synthesis of vast active substances, prevented foulant adhesion on pore walls and alleviated the growth of cake layer. These results illustrated that the integration of MnO2@CS catalytic degradation and membrane filtration was feasible to improve the permeate quality and mitigate membrane fouling in wastewater reclamation.

A flow-through catalytic membrane micro-reactor for hydrogen production by methanol steam reforming

A flow-through catalytic membrane micro-reactor (CMR) with Cu/ZnO/Al2O3 nanoparticles immobilized in porous membrane pores has been developed for hydrogen production by methanol steam reforming (MSR). The characteristics for CMR demonstrated Cu/ZnO/Al2O3 nanoparticles with almost 200 nm were successfully in situ immobilized in membrane pores. During MSR for hydrogen production in CMR by flow-through mode, hydrogen yield of 500 mmol h−1 g−1 and selectivity of 100% can be achieved under the condition of temperature being 360℃, molar ratio of water to methanol of 8.8 and weight hourly space velocity (WHSV) of 9.28 h−1. Compared with the commercial fixed bed reactor, the hydrogen productivity in CMR is one order of magnitude higher, owing to MSR confined in the space of membrane pore with micro-scale. The methanol conversion rate of over 95% can be expected, if five sheets of CMR with thickness of 5 mm were assembled in series.

Catalytic membrane micro-reactor with nano Cu/ZIF-8 assembly in membrane pores by flowing synthesis combining partial ion-exchange

A catalytic membrane micro-reactor (CMMR) is fabricated, with nano Cu/ZIF-8 particles immobilized in the pores of the microfiltration membrane for flow-through catalysis. Nano ZIF-8 is firstly assembled in polyethersulfone (PES) membrane pores by flowing synthesis and then Cu nanoparticles (NPs) are synthesized in-situ in ZIF-8 by the partial ion-exchange reaction. Cu/ZIF-8 nanoparticles are distributed evenly throughout the whole direction of membrane thickness while Cu NPs are dispersed well in ZIF-8. The 4-nitrophenol (4-NP) reduction is used to test the performance of the CMMR. The 4-NP reduction rate being 99.3% is achieved when the membrane flux is 2293 L m −2 h −1 . The CMMR has good stability for over 210 min and presents a surprisingly high apparent reaction rate constant ( K app , 837.43 min −1 ) at room temperature with the loading of ZIF-8 being 85 mg g −1 (PES) and Cu loading cycle number being 1. Compared with batch catalysis by powder catalysts, the K app is increased by 4 orders of magnitude via flow-through catalysis mode using CMMR. The nanoscale configuration of ZIF-8 and Cu NPs assembled inside pores of the membrane enhances remarkably the catalytic activity owing to the enhanced contact and mass transfer in the confined space of membrane pores. A catalytic membrane micro-reactor (CMMR) with nano Cu/ZIF-8 immobilizing in membrane pores was fabricated by flowing synthesis combining partial ion-exchange. This structure provides excellent activities due to the synergistic effect of membrane pores, ZIF-8, and nano Cu. Cu/ZIF-8 catalytic membrane micro-reactor fabricated by flowing synthesis method Cu/ZIF-8 assembled throughout membrane thickness with high loading and dispersity Synergistic effect between membrane pores, ZIF-8 and nano Cu enhances 4-NP reduction Reduction rate of 4-NP over 99.3% achieved with stability over 210 min Apparent reaction rate constant improved by 4 orders of magnitude via flow-through catalysis

Cu-Ag Bimetallic Core-shell Nanoparticles in Pores of a Membrane Microreactor for Enhanced Synergistic Catalysis.

A bimetallic catalytic membrane microreactor (CMMR) with bimetallic nanoparticles in membrane pores has been fabricated via flowing synthesis. The bimetallic nanoparticle is successfully immobilized in membrane pores along its thickness direction. Enhanced synergistic catalysis can be expected in this CMMR. As a concept-of-proof, Cu-Ag core-shell nanoparticles have been fabricated and immobilized in membrane pores for p-nitrophenol (p-NP) hydrogenation. Transmission electron microscopy (TEM) for the characterization of the bimetallic core-shell nanostructure and X-ray photoelectron spectroscopy (XPS) for the characterization of the electron transfer behavior between Cu-Ag bimetal have been performed. The Ag shell on the core of Cu can improve the utilization of Ag atoms, and electron transfer between bimetallic components can promote the formation of high electron density active sites as well as active hydrogen with strong reducing properties on the Ag surface. The dispersed membrane pore can prevent nanoparticle aggregation, and the contact between the reaction fluid and catalyst is enhanced. The enhanced mass transfer can be achieved by the plug-flow mode during the process of hydrogenation catalysis. The p-NP conversion rate being over 95% can be obtained under the condition of a membrane flux of 1.59 mL·cm-2·min-1. This Cu-Ag/PES CMMR has good stability and has a potential application in industry.

Synergistic enhanced catalysis of micro-reactor with nano MnO2/ZIF-8 immobilized in membrane pores by flowing synthesis

A catalytic membrane micro-reactor (CMMR) with nano MnO2/ZIF-8 immobilized in membrane pores has been fabricated by flowing synthesis and formaldehyde degradation was used to test its catalytic performance. The CMMR with deep-permeation nano structure (DPNS) has good stability, uniform nano MnO2/ZIF-8 dispersion and higher loading capacity. The MnO2 coated on the surface of nano ZIF-8 with the size in the range of 100–150 nm was obtained. The contact between formaldehyde and MnO2 is enhanced by the effect of even disperse of membrane pores. The enhanced mass transfer can be achieved in the micro-scale pores of the membrane by the confined space effect. A higher amount of MnO2 loading and higher formaldehyde absorption rate can be achieved by the effect of ZIF-8 in membrane pores. The formaldehyde degradation rate was increased from 82.6% to 94.0%, if the MnO2 loading capacity was increased from 98 mg g−1 to 344 mg g−1.

Enhanced Catalytic Performance of a Membrane Microreactor by Immobilizing ZIF-8-Derived Nano-Ag via Ion Exchange

A catalytic membrane microreactor (CMMR) was fabricated by immobilizing ZIF-8-derived nano-Ag in membrane pores via ion exchange. ZIF-8 was first in situ assembled in polyethersulfone (PES) membran...

Catalytic membrane micro-reactor with nano ZIF-8 immobilized in membrane pores for enhanced Knoevenagel reaction of Benzaldehyde and Ethyl cyanoacetate

A novel catalytic membrane micro-reactor (CMMR) is assembled with ZIF-8 in situ immobilized in polyethersulfone (PES) membrane pores. In this structure, ZIF-8 is evenly distributed on pore walls throughout membrane thickness. The size of ZIF-8 particles is lower than 50 nm. Loading of ZIF-8 can be achieved in the range of 10–180%. This CMMR exhibits high catalytic performance during the Knoevenagel reaction of Benzaldehyde and Ethyl cyanoacetate. The apparent reaction rate constant can be increased by 140.9% at 20 °C, catalyzed by the CMMR than that by ZIF-8 powders under batch catalysis mode. The apparent reaction rate constant can be increased further by 35.9%, with the value being 0.072 ± 0.006 min−1, if plug-flow reaction mode is adopted. High catalytic stability can be achieved, and this CMMR can be recycled and reused over 10 repeating cycles and 300 min without significant decrease in the conversion rate. The conversion rate is 99.5 ± 0.2% at 80 °C, with loading of ZIF-8 being 85% and the membrane flux being 960 mL m−2h−1. Increasing loading of ZIF-8 and temperature can both improve the conversion rate and the apparent reaction rate constant. The apparent activation energy is halved catalyzed by the CMMR than that by ZIF-8 powders.

Stacked Catalytic Membrane Microreactor for Nitrobenzene Hydrogenation

In the present study, a novel stacked catalytic membrane microreactor assembled by microfluidic sheets and gas-permeable membranes was developed for gas–liquid–solid multiphase catalytic reactions....

Catalytic Membrane Microreactors with an Ultrathin Freestanding Membrane for Nitrobenzene Hydrogenation.

A catalytic membrane microreactor is a potential tool for the application in multiphase catalytic reactions. Currently, the installation of a permeable ultrathin membrane to separate the reactants with different phases and the grafting of a catalyst layer on the membrane in a microreactor remain challenging. In this work, a catalytic ultrathin membrane microreactor with an ultrathin freestanding supporting membrane was developed for nitrobenzene hydrogenation, which was formed by the interfacial polycondensation reaction with parallel laminar flow in a microchannel, followed by catalyst layer immobilization on one side of the ultrathin membrane surface using the layer-by-layer self-assembly technique and in situ reduction. The ultrathin freestanding membrane ensured a stable gas/liquid contact interface and good hydrogen permeability. The developed membrane microreactor could exhibit high catalytic performance under mild conditions, demonstrating its superior mass transport. In addition, the effects of the thickness of the ultrathin freestanding membrane, flow rates, and inlet nitrobenzene concentration were investigated to obtain the optimum operating conditions. The experimental results demonstrate that this newly developed membrane microreactor is a promising candidate for multiphase catalytic reactions.

Rational Design of High-Performance Continuous-Flow Microreactors Based on Gold Nanoclusters and Graphene for Catalysis

In this work, we rationally designed a high-performance microreactor system for continuous-flow catalysis. The membrane consists of ultrasmall gold nanoclusters (AuNCs) and two-dimensional graphene. The Au cores of the NCs act as catalysts, while their ligands have two functions: (1) protecting the Au cores to avoid agglomeration and (2) providing a well-defined surfactant assembly to disperse graphene in aqueous solution. Hydrogenation of 4-nitrophenol (4-NP) was employed as model reaction to evaluate catalytic activity. The catalytic membrane microreactor demonstrated excellent catalytic activity and stability, where complete 4-NP conversion was readily achieved via a single pass through the membrane. This desirable performance was maintained over 12 h of continuous operation, although a certain amount of organic buildup on the membrane was observed. The catalytic membrane microreactor outperforms conventional batch reactors due to its improved mass transport. 4-NP-spiked real water samples were also co...

Tube-in-tube hollow fiber catalytic membrane microreactor for the hydrogenation of nitrobenzene

The miniaturization of membrane reactors aims to improve the mass transfer efficiency. A tube-in-tube hollow fiber catalytic membrane microreactor that contains dual characteristics of a catalytic membrane reactor and a microreactor was developed in this study. For a gas-liquid-solid (G-L-S) reactor, the immobilization of solid catalysts on a hollow fiber membrane (HFM) via layer-by-layer (LBL) self-assembly enables the model reaction of nitrobenzene hydrogenation to occur. The unique structure of the novel catalytic membrane microreactor separates the gas and liquid reactants and shortens the transfer distance. The experimental results showed that the nitrobenzene conversion was high during 30 h of continuous operation. The effects of the flow rates and inlet nitrobenzene concentration were also investigated. At a given gas flow rate, the nitrobenzene conversion and concentration of the product aniline decreased with increasing the liquid flow rate. Meanwhile, at a given liquid flow rate, an increase in the gas flow rate led to an increase in the pressure of the gas phase. Sufficient hydrogen promoted the reaction, increasing the nitrobenzene conversion and aniline concentration. In addition, the inlet nitrobenzene concentration affected the conversion. Higher concentration not only enhanced the reaction rate but also caused catalyst poisoning. Based on these results, the newly designed catalytic membrane microreactor is feasible to improve the performance towards multiphase reaction.

Catalytic membrane microreactor with Pd/γ-Al2O3 coated PDMS film modified by dopamine for hydrogenation of nitrobenzene

Conventional gas–liquid–solid reactors usually face the gaseous reactant transport issues in association with the interface and liquid phase to immobilized solid catalysts. To resolve this problem, a catalytic membrane microreactor (CMMR) with the catalytic membrane formed by coating the catalysts on a thin PDMS film modified by dopamine was developed in this study, which not only eliminated the issues in the conventional gas–liquid–solid reactors but also provided a large surface-area-to-volume ratio to enhance the mass transport. The performance of the developed CMMR was evaluated by hydrogenation of nitrobenzene. It was found that the nitrobenzene conversion and operation stability was greatly improved by the CMMR as a result of enhanced mass transport of hydrogen. Parametric study was also performed in this work to explore how the operation conditions and reactor design affected the performance. It was shown that low liquid flow rate and high gas flow rate benefited for the improvement in the nitrobenzene conversion due to the increased residence time and hydrogen permeation rate through the membrane. The results on the effect of the inlet nitrobenzene concentration showed that an increase in the inlet nitrobenzene concentration increased the aniline concentration because of enhanced catalytic reaction rate but lowered the nitrobenzene conversion because of the overloaded liquid reactant. Besides, it was also shown that thinner membrane could enhance the hydrogen permeation through the membrane, thereby yielding higher nitrobenzene conversion. This study fully demonstrates the feasibility and superiority of the developed CMMR for the gas–liquid–solid reaction system.

Mathematical Modeling, Verification and Optimization for Catalytic Membrane Esterification Micro-reactor

AbstractAnalysis of efficient production of ethyl acetate utilizing aCatalyticMembraneMicro-Reactor(CMMR)was theoretically investigated and verified using published results for the esterification reaction. Grafted sulfonic groups in the pores of a polyethersulfone membrane catalyzed the reaction. Theoretical analysis of the catalytic membrane reactor was achieved through development of a lumped parameter model to describe the CMMR behavior and performance. The developed model was solved numerically for different design and operating conditions using MATLAB Simulink software. The model parameters were verified and validated using the experimental results to achieve a reliable tool for design, replication, scaling-up, and optimization. The approach to maximum conversion was simulated. Cumulative yield per unit time was investigated to determine the optimum process time. Membrane regeneration was conducted and the regeneration time was determined as well in order to reuse the membrane for other cycles. Reactor scaling-up was studied using the model for process design.

A novel catalytic membrane microreactor for COx free H2 production

A novel catalytic hollow fibre membrane microreactor (CHFMMR), consisting of a thin Pd layer and a 30%CuO/CeO2 catalyst supported on an asymmetric Al2O3 hollow fibre has been developed. In the preparation of the CHFMMR, the Pd layer was deposited on outer surface of the hollow fibre substrate by electroless plating first, followed by impregnation of 30%CuO/CeO2 catalyst in the finger pores located in the inner surface of the hollow fibre lumen by sol–gel coating. The catalytic activity of the CHFMMR was tested using water–gas shift (WGS) reaction and compared to that of a catalytic hollow fibre microreactor (CHFMR) and a conventional fixed-bed reactor. The catalytic activity tests were performed at 1 atm and from 200 °C to 500 °C using different flow rates of sweep gas (from 50 to 75 ml/min). The ratio between CO and H2O in the feed was 1 to 0.5 with a space velocity of 80 l g−1 h−1. The conversion obtained in the CHFMMR is 35% higher than that in the conventional fixed-bed reactor. Furthermore, a conversion which was 17% higher than the corresponding thermodynamic equilibrium conversion was achieved in the CHFMMR, at 500 °C with a sweep gas flow rate of 75 ml/min.

Modelling a novel miniaturised reactor/separator system

AbstractThe use of microreactors for industrially relevant chemical production processes has been investigated. Recent research has shown that miniaturised reactors support process intensification and successful applications involve the synthesis of unit operations. Following a study of candidate processes for miniaturisation, this investigation focussed on the direct fluorination that consists of a complex set of reactions. A novel catalytic membrane microreactor configuration has been developed to address the contacting of the gas/liquid/solid phases. The membrane separates the gas phase from the liquid phase, presenting a well‐defined interface to the catalyst. A simplified model has been developed to study the advantages of the catalytic membrane for an isothermal parallel reaction system, where an electrophilic reaction leads to the desired product but competes with a fast radical reaction mechanism. If no catalyst is used the selectivity can be improved by limiting the fluorine concentration. The separation of the reactants results in higher selectivities at higher conversion compared with a mixed feed process (ie bubble column).© 2003 Society of Chemical Industry