Continuous Flow Membrane Reactor Research Articles

Ozone decomposition on transition-metal-atom anchored graphdiyne: Insights from computation and experiment

Transition-metal-atom anchored graphdiynes (TM@GDY, TM = Mn, Fe, Co, Ni and Cu) have already been synthesized and found applications in hydrogen evolution, nitrogen fixation and etc. By means of first-principle predictions and test experiments, we propose here that Fe@GDY and Co@GDY are efficient catalysts for the sustainable conversion of O3 to O2. These two catalysts can spontaneously chemisorb O3 with zero reaction barrier and have low O3 conversion barriers (0.31 eV and 0.19 eV, respectively). The O3 decomposition experiment in a continuous flow membrane reactor and electron paramagnetic resonance results verify that Fe@GDY and Co@GDY are efficient catalysts under humid conditions. Raman spectra prove the formation of the key Fe-O/Co-O and FeOO and CoOO intermediates. The hydrophobic nature of graphdiyne and the strongest chemisorption of O3 among tested ambient gases, make Fe@GDY and Co@GDY ideal catalysts under both dry and humid conditions. These findings would stimulate future explorations on metal anchored GDY-based catalysts for applications of toxic gas decomposition or fixation.

Multi-Functional Polymer Membranes Enable Integrated CO2 Capture and Conversion in a Single, Continuous-Flow Membrane Reactor under Mild Conditions.

Herein, we present a membrane-based system designed to capture CO2 from dilute mixtures and convert the captured CO2 into value-added products in a single integrated process operated continuously under mild conditions. Specifically, we demonstrate that quaternized poly(4-vinylpyridine) (P4VP) membranes are selective CO2 separation membranes that are also catalytically active for cyclic carbonate synthesis from the cycloaddition of CO2 to epichlorohydrin. We further demonstrate that quaternized P4VP membranes can integrate CO2 capture, including from dilute mixtures down to 0.1 kPa of CO2, with CO2 conversion to cyclic carbonates at 57 °C and atmospheric pressure. The catalytic membrane acts as both the CO2 capture and conversion medium, providing an energy-efficient alternative to sorbent-based capture, compression, transport, and storage. The membrane is also potentially tunable for the conversion of CO2 to a variety of products, including chemicals and fuels not limited to cyclic carbonates, which would be a transformative shift in carbon capture and utilization technology.

Design of continuous flow membrane reactor for in-situ sonophotocatalytic degradation of ciprofloxacin

Antibiotics in the aquatic environments pose a severe threat to global public health. Hence, a sonophotocatalytic membrane reactor (SPMR) of sonophotocatalysis coupled membrane separation was designed to realize continuous and stable degradation of ciprofloxacin (CIP) by Bi2MoO6/FeVO4 in this study. The prepared catalysts were characterized by XRD, SEM, TEM, BET, UV–vis DRS, PL, and EIS. Under the optimal hydraulic retention time (HRT) of 55 min, 93.43% of CIP (10 mg/L) was degraded by Bi2MoO6/FeVO4 (500 mg/L) after 200 min sonophotocatalytic reaction in the presence of H2O2 (20 mM). The synergy index (SI) of sonocatalysis and photocatalysis was calculated to 1.80 during the catalytic process. The SPMR effluent turbidity was basically nil after 10 min separation of catalyst by polyvinylidene fluoride (PVDF) hollow fiber membrane. The changes of PVDF membrane before and after use in SPMR were observed by SEM and FTIR. The membrane fouling behavior in the SPMR was investigated by membrane water flux, flux recovery rate, and membrane resistances. The mechanisms of CIP degradation are attributed to·OH and·holes (h+) generated by Bi2MoO6/FeVO4 under ultrasonic and visible light irradiation. Besides, the solution matrix effects on sonophotocatalytic removal of CIP were investigated. The results proved that SPMR still maintained satisfactory sonophotocatalytic degradation efficiency in typical natural water bodies and simulated water matrices. In this work, the continuous operation process of CIP degradation and catalyst separation was realized, and the membrane fouling was alleviated by ultrasonic.

Design of Continuous Flow Membrane Reactor for In-Situ Sonophotocatalytic Degradation of Ciprofloxacin

Design of Continuous Flow Membrane Reactor for In-Situ Sonophotocatalytic Degradation of Ciprofloxacin

Design methodology for mass transfer-enhanced large-scale electrochemical reactor for CO[formula omitted] reduction

The electrochemical conversion of CO2 using a continuous flow membrane reactor is a promising technology. This is because the membrane reactor can achieve high productivity and selectivity by enhancing the mass transfer of CO2. In an industrial-scale reactor, the extrinsic properties that facilitate the mass transfer rate are crucial because the uniform flow distribution and high production rate can only be achieved when the interface and flow patterns are properly designed. Herein, we experimentally measured the production rate of CO in a large-scale electrochemical CO2 reduction reactor by varying the pH, interface, and flow pattern. The result indicated that optimization of the flow pattern alone can improve the production rate of CO by 28% indicating that a high convection rate through gas diffusion electrode (GDE) results in a high production rate. A three-dimensional computational fluid dynamic model was developed to quantify the effect of the new flow pattern on the mass transfer. From the model, the Peclet number increased by 28%, which is consistent with the CO partial current increment. This result indicates that the convective mass transfer improves the production rate. Additionally, we proposed a general guideline for the flow pattern design for a large-scale electrochemical CO2 reduction reactor that maximizes convective mass transfer through a GDE.

Asymmetric synthesis with cinchona-decorated cyclodextrin in a continuous-flow membrane reactor

This work presents a cyclodextrin-enhanced organocatalytic method from molecular to process design. Cinchona-thiourea and -squaramide catalysts were covalently anchored to inherently large, stable and well-defined permethyl-β-cyclodextrins. The asymmetric catalysis was successfully demonstrated on the Michael reaction of 1,3-diketones and trans-β-nitrostyrene. Both emerging green and conventional solvents were screened for the asymmetric addition (up to 99% ee), and the Kamlet–Taft solvent parameters were correlated to the enantioselectivity. Quantum chemical modelling revealed that the catalyst anchoring resulted in favorable structural changes, and stronger intermolecular interactions between the catalyst and the reagents. Continuous organocatalysis was performed in coiled tube flow reactor coupled with a membrane separation unit, which allowed complete recovery of the catalyst and 50% solvent (2-MeTHF) recycling. The 100% conversion, 98% purity, 99% ee, 100% in-line catalyst recovery, and 80 g L−1 h−1 productivity makes it an attractive catalytic platform.

CO2 conversion in a photocatalytic continuous membrane reactor

CO2 was photocatalytically reduced over TiO2–Nafion membranes in a continuous flow membrane reactor. MeOH production is considered as a relevant advance over the existing literature results which mostly propose CH4 as the reaction product.

Characterization of incubation experiments and development of an enrichment culture capable of ammonium oxidation under iron-reducing conditions

Abstract. Incubation experiments were conducted using soil samples from a forested riparian wetland where we have previously observed anaerobic ammonium oxidation coupled to iron reduction. Production of both nitrite and ferrous iron was measured repeatedly during incubations when the soil slurry was supplied with either ferrihydrite or goethite and ammonium chloride. Significant changes in the microbial community were observed after 180 days of incubation as well as in a continuous flow membrane reactor, using 16S rRNA gene PCR-denaturing gradient gel electrophoresis, 454 pyrosequencing, and real-time quantitative PCR analysis. We be Acidimicrobiaceae bacterium A6), belonging to the Acidimicrobiaceae family, whose closest cultivated relative is Ferrimicrobium acidiphilum (with 92% identity) and Acidimicrobium ferrooxidans (with 90% identity), might play a key role in this anaerobic biological process that uses ferric iron as an electron acceptor while oxidizing ammonium to nitrite. After ammonium was oxidized to nitrite, nitrogen loss proceeded via denitrification and/or anammox.

Analysis of a Chemostat Model with Variable Yield Coefficient and Substrate Inhibition: Contois Growth Kinetics

We analyze the steady-state operation of a generalized reactor model that encompasses a continuous flow bioreactor and an idealized continuous flow membrane reactor as limiting cases. The biochemical reaction kinetics is governed by a Contois growth model subject to noncompetitive substrate inhibition with a variable substrate yield coefficient. The steady-state performance of the reactor is predicted and stability of the steady-state solutions as a function of dimensionless residence time reported. Our results identified two cases of practical interest. The first feature corresponds to the case where solutions to both no-washout and washout conditions are bistable. The second feature identifies the parameter region in which periodic solutions can occur when the yield coefficient is not constant. Both these features are often undesirable in practical applications and must be avoided. Scaling of the model equations reveals that both the second-bifurcation parameters are functions of the influent concentration. Our results predict how the reactor behavior varies as a function of influent concentration and identify the range of influent concentrations where the reactor displays neither periodic nor bistable behavior.

Long time behaviour of a stochastic model for continuous flow bioreactor

The global dynamics of a deterministic model in wastewater treatment has been investigated in Zhang (J Math Chem 50:2239–2247, 2012). The stochastic version, which can be used for continuous flow bioreactor and membrane reactor is presented in this study. Precisely, we assume there is some uncertainty in the part describing the recycle, which results in a set of stochastic differential equations with white noise. We first show that the stochastic model has always a unique positive solution. Then long time behavior of the model is studied. Our study shows that both the washout equilibrium and non-washout equilibrium are stochastically stable. At the end, we carry out some numerical simulations, which support our theoretical conclusions well.

Global analysis of continuous flow bioreactor and membrane reactor models with death and maintenance

The aim of the paper is to investigate the global dynamics of mathematical models for a continuous flow bioreactor and a membrane reactor. It assumes that the models include terms representing death of the microorganism and maintenance energy, respectively. By carrying out a qualitative analysis of the models, we give the classification of the equilibria and show that an unstable limit cycle can exist when the non-washout equilibrium is a focus.

A FUNDAMENTAL ANALYSIS OF CONTINUOUS FLOW BIOREACTOR AND MEMBRANE REACTOR MODELS WITH TESSIER KINETICS

In this research we analyze the steady-state operation of a continuous flow bioreactor, with or without recycle, and an idealized or nonidealized continuous flow membrane reactor. The model extends to include a fixed bed reactor where a fraction of the biomass is detached by the flow. The reaction is assumed to be governed by Tessier growth kinetics. We show that a flow reactor with idealized recycle has the same performance as an idealized membrane reactor and that the performance of a nonidealized membrane reactor is identical to that of an appropriately defined continuous flow bioreactor with nonidealized recycle. The performance of all three reactor types can therefore be obtained by analyzing a flow reactor with recycle. The steady states of the recycle model are found and their stability determined as a function of the residence time. The performance of the reactor at large residence times is obtained.

A fundamental analysis of continuous flow bioreactor and membrane reactor models with noncompetitive product inhibition

AbstractWe analyze the steady‐state production of a product produced through the growth of microorganisms in both a continuous flow bioreactor and in an idealized continuous flow membrane reactor. The reaction is assumed to be governed by Monod growth kinetics subject to noncompetitive product inhibition. Although this reaction scheme is often mentioned in textbooks, a stability analysis does not appear in the literature.The steady‐state solutions of the model are found and their stability determined as a function of the residence time. The performance of the reactor at large residence times is obtained. Knowledge of the steady‐state solutions and their asymptotic limits may be useful to estimate parameter values from experimental data. The key dimensionless parameter that controls the degree of noncompetitive product inhibition is identified and we quantify the effect that this has on the reactor performance in the limit when product inhibition is 'small' and 'large'. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

Palladium Nanoparticles in Allylic Alkylations and Heck Reactions: The Molecular Nature of the Catalyst Studied in a Membrane Reactor

AbstractA series of palladium nanoparticles stabilized by five chiral sugar‐based oxazolinyl‐phosphite ligands, containing various substituents at the oxazoline and phosphite moieties has been synthesized. They were characterized by transmission electron microscopy (TEM), X‐ray powder diffraction (XRD), infrared spectroscopy (IR) and elemental analysis. These nanoparticles were applied in Pd‐catalyzed asymmetric allylic alkylation and Heck coupling reactions. A detailed study to elucidate the nature of the active species using a continuous‐flow membrane reactor (CFMR), accompanied by TEM observations, classical poisoning experiments, and kinetic measurements have been carried out. Conclusive evidence of the nature of the species involved in the use of PdNPs in asymmetric catalytic reactions has been obtained. The CFMR experiments proved the molecular nature of the true catalysts and all conversions can be justified by the amount of molecular palladium that leached as measured by ICP‐AES.

Hydrogen purification from carbon monoxide by means of selective oxidation using zeolite catalytic membranes

The focus of the present work is on the analysis of CO selective oxidation using catalytic zeolite (Pt/Na-Y) membranes in a continuous flow membrane reactor. A series of membranes with different permeation properties, prepared by secondary growth, Pt-loaded by ion exchange and reduced was used for this study. Catalytic tests were carried out with a simulated dry reformate shifted gas mixture with an operative O 2/CO stoichiometric equivalent feed ratio of two, at a temperature of 200–220 °C and reaction pressure up to 600 kPa. The best performance was achieved by the lowest permeance membrane considered in this work that showed also stable catalytic activity over many hours of testing. The catalytic membranes effectively reduced the CO content from 10,000 ppm down to 10–50 ppm, depending on the operating conditions.

A fundamental analysis of continuous flow bioreactor and membrane reactor models with death and maintenance included

AbstractIn this research we analyse the steady‐state operation of a continuous flow bioreactor, with or without recycle, and an idealised, or non‐idealised, continuous flow membrane reactor. The reaction is assumed to be governed by the well‐known Monod growth kinetics. We show that a flow reactor with idealised recycle has the same performance as an idealised membrane reactor and that the performance of a non‐idealised membrane reactor is identical to an appropriately defined continuous flow bioreactor with non‐idealised recycle. The performance of all three reactor types can therefore be obtained by analysing a flow reactor with recycle. The steady‐states of the recycle model are found and their stability determined as a function of the residence time. The performance of the reactor at large residence times is obtained. In the limit, as the residence time becomes very large, all three reactor configurations have identical performances. Thus the main advantage of using a membrane reactor, or a flow reactor with recycle, for the treatment of industrial wastewaters and slurries is to improve the performance at low residence times. This is quantified for the case of an ideal membrane reactor. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.

A fundamental analysis of continuous flow bioreactor models and membrane reactor models to process industrial wastewaters

We analyse the steady-state treatment of industrial wastewaters in a continuous flow bioreactor and in an idealised continuous flow membrane reactor. The reaction is assumed to be governed by Contois growth kinetics, which is often used to model the growth of biomass in wastewaters containing biodegradable organic materials. We show that a flow reactor with idealised recycle has the same performance as an idealised membrane reactor and that the performance of a non-idealised membrane reactor is identical to an appropriately defined continuous flow bioreactor with non-idealised recycle. The performance of all three reactor types can therefore be obtained by analysing a flow reactor with recycle. The steady-states of the model are found and their stability determined as a function of the residence time. The performance of the reactor at large residence times is obtained. In the limit as the residence time becomes very large, all three reactor configurations have identical performances. Thus the main advantage of using a membrane reactor, or a flow reactor with recycle, for the treatment of industrial wastewaters and slurries is to improve the performance at low residence times.

Continuous enzymatic solubilization of alfalfa proteins in an ultrafiltration reactor

Insoluble alfalfa protein concentrate (APC) was solubilised by two proteolytic enzymes (pepsin and Delvolase) in batch and in continuous flow membrane reactor. In a preliminary investigation, the suitable enzyme (Delvolase) was selected and the nitrogen solubility profile of APC was established. The kinetics of APC solubilization was investigated: no product inhibition was noticed and the enzyme was found to be adsorbed on the APC particles. The effect of operating variables such as enzyme and substrate concentrations, permeate flow, reactor volume and residence time were studied.

Palladium Complexes of Phosphane-Functionalised Carbosilane Dendrimers as Catalysts in a Continuous-Flow Membrane Reactor

Phosphane-functionalised carbosilane dendrimers 9, 10, 11, 12, 13, 19 and 20 have been synthesised, and their palladium complexes have been used as catalysts in the allylic substitution reaction. The catalytic sites at the periphery of the dendrimer support are readily accessible to the substrate, which is reflected − also for the larger dendrimeric systems − in the high catalytic activity. Moreover, the higher generations are sufficiently large to be retained by a nanofilter, and dendrimeric catalysts 13 and 20 have been applied in a continuous-flow membrane reactor. The stability of the palladium complexes of the phosphane-functionalised dendrimers is crucial for application in a continuous process of this type, and appeared to be very sensitive to small changes in the dendrimeric structure. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Core-functionalized dendrimeric mono- and diphosphine rhodium complexes; application in hydroformylation and hydrogenation

Three novel series of core-functionalized dendrimeric phosphine ligands were synthesized and their rhodium complexes were studied as catalysts in both hydroformylation and hydrogenation of alkenes. Generally similar activities were obtained for the dendrimeric systems and the parent compounds except in the hydroformylation of a bulky substrate, 4,4,4-triphenylbut-1-ene, which gave a significant decrease in activity when the larger dendrimers were used. The rhodium complexes of the dppf-type dendrimeric ligands were studied in the hydrogenation of dimethyl itaconate in a continuous-flow membrane reactor showing a reasonable constant formation of the product compared to the non-dendrimeric catalyst.