Application Of Membrane Reactor Research Articles

Carbon ceramic composite membranes for catalytic membrane reactor applications

A novel route is described for the production of carbon-ceramic membranes where the structure can be adjusted for use in either multiphase (gas-liquid) or gas phase membrane reactors. The production route allows the deposition of the membrane layer onto a two layer ceramic support (1OO nm top layer) giving potentially significant cost savings. It has also been shown that the route can be readily extended to multichannel monolith supports allowing a simple scale up route. The carbon component also provides an excellent support for the active metal allowing the production of high metal dispersions.

Hydrogen Separation Characteristics of SiC Nanoporous Membrane at High Temperature

Ceramic membranes having less than 1nm size pores have great potential for gas separation at high temperature due to their good thermal stability. Moreover, nanoporous silicon carbide membrane has potential application under hydrothermal condition at high temperature since it is highly stable at high temperature. In this research, nanoporous SiC membrane has been developed on porous alumina support using preceramic polymer. Pore size of the SiC membrane was controlled using polystylene(PS) as the pore forming agent. The SiC membrane having controlled pore size was characterized with SEM, EDS, FT-IR, XRD and pore size measurement. The hydrogen permeability and selectivity toward nitrogen gas of the developed membrane were 0.3 x 10-6 mole/m2.s.pa and 4.1, respectively. The nanoporous hydrogen selective SiC membrane shows promising application in membrane reactor for steam reforming reacti on of natural gas, water gas shift reactions and hydrogen separation from coal gasification such as Integrated Gasification Combined Cycle (IGCC).

Model‐based characterization of an amino acid racemase from Pseudomonas putida DSM 3263 for application in medium‐constrained continuous processes

The amino acid racemase with broad substrate specificity from Pseudomonas putida DSM 3263 was overproduced and characterized with respect to application in an integrated multi-step process (e.g., dynamic kinetic resolution) that--theoretically--would allow for 100% chemical yield and 100% enantiomeric excess. Overexpression of the racemase gene in Escherichia coli delivered cell free extract with easily sufficient activity (20-50 U mg(-1) total protein) for application in an enzyme membrane reactor (EMR) setting. Model-based experimental analysis of a set of enzyme assays clearly indicated that racemization of the model substrates D- or L-methionine could be accurately described by reversible Michaelis-Menten kinetics. The corresponding kinetic parameters were determined from progress curves for the entire suitable set of aqueous-organic mixtures (up to 60% methanol and 40% acetonitrile) that are eligible for an integrated process scheme. The resulting kinetic expression could be successfully applied to describe enzyme membrane reactor performance under a large variety of settings. Model-based calculations suggested that a methanol content of 10% and an acetonitrile content of 20% provide maximum productivity in EMR operations. However product concentrations were decreased in comparison to purely aqueous operation due to decreasing solubility of methionine with increasing organic solvent content. Finally, biocatalyst stability was investigated in different solvent compositions following a model-based approach. Buffer without organic content provided excellent stability at moderate temperatures (20-35 degrees C) while addition of 20% acetonitrile or methanol drastically reduced the half-life of the racemase.

Oxidation in catalytic membrane reactors

This paper presents a series of applications of catalytic membrane reactors (CMR) to oxidation reactions. Four reactions were tested in our group. Alkane activation (C2, C3 and C4) or total oxidation (WAO) is implemented in various membrane reactor modes, using dense, microporous or mesoporous membranes. In some cases, a catalyst bed is associated with a membrane, whereas other applications use an intrinsically active membrane. Progresses in catalyst and membrane design, along with careful operational conditions led to overall higher performances when compared to conventional processes.

LTA zeolite composite membrane preparation, characterization and application in a zeolitic membrane reactor

Abstract An LTA membrane has been crystallized inside a porous ceramic tube and applied to synthesis of methanol from carbon dioxide and hydrogen in a zeolite membrane reactor (ZMR). The results obtained with the ZMR were compared with those gained from one traditional reactor (TR) used under the same operating conditions. CO 2 conversion obtained with the ZMR at 210 °C reached 17% under conditions where the equilibrium value without zeolite membrane (TR) is equal to about 6%.

Application of Artificial Neural Networks Coupled with Sequential Pseudo-Uniform Design to Optimization of Membrane Reactors for Hydrogen Production

Fuel cells with on board reforming require compact and lightweight components. A membrane reactor (MR) that combines hydrogen permeable membranes with a methanol steam reformer promises considerable weight and space savings. Its dense metal membranes produce high purity hydrogen over a wide range of pressure and load. For a real application of MR, there is much incentive to determine optimal operating conditions of a membrane reactor without resorting to the time consuming knowledge-based modeling work. In this work, a Pd membrane reactor (PMR) for carrying out the methanol steam reforming was simulated and adopted as the test process for verification of the applicability of the proposed optimization method. The artificial neural networks (ANN) with back propagation algorithms coupled with the sequential pseudo-uniform design (SPUD) was applied and demonstrated successfully to the modeling of the PMR system using limited but adequate experimental data. The optimum operating conditions determined from the identified ANN model were applied precisely.

An attempt to application of continuous recycle membrane reactor for hydrolysis of oxidised derivatives of potato starch

Oxidised starches E 1404 are the most popular food grade modified starches but the process of their enzymatic hydrolysis was not investigated, and the functionality of the products of this processing is unknown. The aim of the work was to study the possibility of the application of continuous recycle membrane reactor (CRMR) for the hydrolysis of oxidised starches as well as the estimation of the surface properties of the obtained products. It was found that the application of CRMR for the enzymatic hydrolysis of oxidised starches allowed products to be obtained which reveal surface activity. The effectiveness of the membrane process is strongly influenced by the rheological properties of the raw material, which determines fouling phenomena in reaction system. The presence of carboxyl groups in starch macromolecules did not inhibit their enzymatic hydrolysis. The surface properties of enzymatic hydrolysis products do not depend on the degree of oxidation of the investigated starches. Substantial differences of the surface activity for the permeate and retentate fractions were observed.

Zeolite based films, membranes and membrane reactors: Progress and prospects

The integration of reaction and separation in catalytic membrane reactors has received increasing attention during the past 30 years. The combination promises to deliver more compact and less capital-intensive processes with substantial savings in energy consumption. With the advent of new inorganic materials and processing techniques, there has been renewed interest in exploiting the benefits of membranes in many industrial applications. Zeolite membranes, however, have only recently been considered for catalytic membrane reactor applications. Despite the significant recent interest in these types of membranes there are relatively few reports of the application of such membranes in high-temperature catalytic membrane reactor applications. This can be attributed to a number of limitations that still need to be addressed such as the relatively high price of membrane units, the difficulty of controlling the membrane thickness, permeance, high-temperature sealing, reproducibility and the dilemma of upscaling. A number of research efforts, with some degree of success have been directed to finding solutions to the remaining challenges. This review makes a critical assessment of what has been achieved in the past few years in terms of hurdles that still stand in the way of the successful implementation of zeolite membrane reactors in industry.

Application of a catalytic membrane reactor to catalytic wet air oxidation of formic acid

A series of Pt-doped, tubular ceramic membranes were prepared by the evaporation–crystallization technique. The activity of these membranes was measured in the process of liquid-phase oxidation of aqueous formic acid solutions (0.2–10 g L −1), carried out in a semi-batch three-phase reactor system by using air or oxygen. An influence of trans-membrane pressure difference, reaction temperature, catalyst loading, and re-circulation rate on the extent of formic acid removal was measured in a wide range of operating conditions. A mathematical model that captures essential physics of the process, was developed to predict concentration profiles of reactants within the membrane wall and the thickness of reaction zone. The calculations show that the productivity of membrane contactor is influenced by the concentration of dissolved oxygen in the reaction zone as well as by the molar ratio of reactants, the latter being dependent on formic acid conversion.

Zeolite Membranes: From the Laboratory Scale to Technical Applications

Current trends and novel concepts in R&D of zeolite membranes like the seeding supported crystallization and the preparation of Al-containing zeolite membranes are discussed. The influences of adsorption and diffusion on the permeation properties of zeolite membranes are considered. Dehydration of ethanol by steam permeation and pervaporation as the first zeolite membrane based industrial separation is presented. Membrane supported dehydrogenation and esterification are discussed as possible applications of a catalytic membrane reactors.

A dense Pd/Ag membrane reactor for methanol steam reforming: Experimental study

This paper focuses on an experimental study of the methanol steam reforming (MSR) reaction. A dense Pd/Ag membrane reactor (MR) has been used, and its behaviour has been compared to the performance of a traditional reactor (TR) packed with the same catalyst type and amount. The parameters investigated are reaction time, temperature, feed ratio and sweep gas flow rate. The few papers dealing with MR applications for the MSR reaction mainly analyse the effect of temperature and pressure on the reaction system. The investigation of new parameters permitted to better understand how the fluid-dynamics of the MR influences the hydrogen separation effect on methanol conversion and product selectivity. The comparison between MR and TR in terms of methanol conversion shows that the MR gives a higher performance than the TR at each operating condition investigated. Concerning hydrogen production, the experiments have shown that the overall selectivity towards hydrogen is identical for both MR and TR. However, the MR produces a free-CO hydrogen stream, which could be useful for direct application in proton exchange membrane fuel cells. A comparison, in terms of methanol conversion versus temperature, with literature data is also included.

Influence of Si/Al ratio, pre-treatment and measurement conditions on permeation properties of MFI membranes on metallic and ceramic supports

MFI membranes with Si/Al ratios between 57 and ∞ were prepared on metallic and ceramic supports as part of ongoing work to develop membranes for membrane reactor applications. The membranes were characterized by H 2 and SF 6 single gas permeation measurements under various conditions, by mixture permeation studies of H 2:SF 6 = 1:1, and of n-pentane: i-pentane = 1:1 as well as by permporosimetry in order to estimate the relative contributions of inter- and intracrystalline membrane transport. The permeation properties are mainly influenced by the Al content in the MFI layers but not by the type of the support. From permporosimetry and the n/ i-pentane and H 2/SF 6 mixture permeation it follows that the intercrystalline permeance increases with increasing Al content and therefore the mixture selectivities are low for Al-rich MFI membranes. The ZSM-5 membrane with the highest Al content (Si/Al = 57) behaves exceptionally since it separates H 2/SF 6 mixtures but not n/ i-pentane mixtures. The permeation results depend strongly on the measurement conditions such as the pressure difference across the membrane and are influenced by the calcination parameters of the membrane.

Hydrogen production from methanol by oxidative steam reforming carried out in a membrane reactor

The aim of this work is to study from an experimental point of view the oxidative steam reforming of methanol by investigating the behaviour of a dense Pd/Ag membrane reactor (MR) in terms of methanol conversion as well as hydrogen production. The main parameters considered are the operating temperature and the O 2/CH 3OH feed ratio. This is a pioneer work in the application of MR to this kind of reaction, whose goal should be to produce a CO-free hydrogen stream suitable for hydrogen fuel cell applications. The experimental results show that the MR gives methanol conversions higher than traditional reactors (TRs) at each temperature investigated, confirming the good potential of the membrane reactor device for this interesting reaction system.

A new photocatalytic membrane reactor (PMR) for removal of azo-dye Acid Red 18 from water

A very promising method for solving problems concerning separation of photocatalyst as well as products and byproducts of photodecomposition from the reaction mixture is application of photocatalytic membrane reactors (PMRs). The PMRs described in literature combine photocatalysis with pressure-driven membrane techniques, such as nanofiltration (NF), ultrafiltration (UF) and microfiltration (MF). A serious problem with application of these membrane techniques is membrane fouling, which is especially observable with MF and UF. The presented paper describes the results of the investigation on the possibility of coupling photocatalysis and membrane distillation (MD) for degradation of organic pollutants in aqueous solution. Acid Red 18 was applied as a model dye and titanium dioxide Aeroxide® P25 (Degussa, Germany) was used as a photocatalyst. In the first step of the research, the effect of the presence of TiO2 in a feed on the permeate flux was investigated. It was found that the addition of TiO2 P25 did not affect the distillate flux, regardless of the catalyst concentration applied. In order to select the best process conditions in terms of photocatalyst concentration and temperature of feed solution the batch tests were performed. On the basis of these experiments, the TiO2 concentration was set on a level of 0.3g/dm3 and the feed temperature in the reactor amounted to 333K. The hybrid process photocatalysis – MD – was conducted in a simultaneous mode. After 5h of the processes performance, the model dye was removed completely, whereas TOC concentration was lowered for ca. 80%.

Enzymatic membrane reactor for the kinetic resolution of racemic ibuprofen ester: modeling and experimental studies

The production of (S)-ibuprofen acid was studied in a hollow fiber membrane reactor, with the aim to develop a clean and ecofriendly technology. The modeling and simulation of enzymatic membrane reactor was studied for lipase-catalyzed hydrolysis of racemic ibuprofen ester in hollow fiber membrane reactor. Mathematical model was developed to simulate the behavior of enzymatic reaction in the membrane matrix region. The model equation was derived considering reaction over immobilized enzyme in the membrane porous support with the substrate flowing along the shell side. The model was simulated on the basis of experimental operating conditions, physical and hollow fiber geometrical parameters. The model equation was a nonlinear second-order differential equation and solved numerically using Matlab. The parameters studied were Thiele Modulus ( Φ 2 ) , Bodenstein number ( B 0 ) , transmembrane pressure (TMP) and intrinsic enzyme kinetic constants ( V max and K m ). Simulation results showed that a satisfactory product separation was achieved with 60% conversion of (S)-ester, enantiomeric excess of substrate, ee s in the range 35–43%, enantiomeric excess of product, ee p in the range 80–85%, and enantiomeric ratio ( E value) of 11.2–15.3 at 4.34 < B 0 < 13.89 and Φ 2 < 1 . The simulated results agreed with the experimental data within an error of ± 7.5 % . The reaction–separation functionality of EMR system has shown the potential of membrane reactor application for kinetic resolution of racemic compounds especially in overcoming the difficulties associated with conventional technology particularly in downstream separation and enzyme recovery.

Application of a forced-flow catalytic membrane reactor for the dimerisation of isobutene

A forced-flow catalytic membrane reactor was applied for dimerisation of isobutene to isooctene. Several catalysts, such as silica supported Nafion ® (Nafion ® SAC-13), Nafion ® NR50, Amberlyst™ 15, and silica supported phosphotungstic acid were mixed in solution with a polymeric binder. Teflon ® AF, Hyflon ® AD, polytrimethylsilylpropyne, and polydimethylsiloxane (PDMS) were applied as binder to form a porous, reactive layer on top of a porous, polymeric, supporting membrane. An optional intermediate PDMS film acted as flow regulator and enabled selective product removal. Isobutene was fed to the reactive membrane, the reaction started immediately and a pressure of around 4 bar built-up on the feed side. Liquid product was collected on the permeate side in an iced trap. Depending on the type of binder high conversions up to 98% at 22% selectivity to isooctene (binder = Hyflon ® AD) and space velocity of 530 g i−C4 /g cat h, or high selectivities of >80% at 45% conversion of isobutene and space velocity of 275 g i−C4 /g cat h (binder = Teflon ® AF) were achieved. Catalyst poisoning was not observed during operation for at least 1 week.

Preparation and reactive applications of nanoporous silicon carbide membranes

SiC nanoporous membranes have been prepared by chemical-vapor deposition/chemical-vapor infiltration of two different precursors, namely tri-isopropylsilane (TPS) and 1,3-disilabutane (DSB). Both precursors produce nanoporous membranes. The TPS-derived membranes are hydrothermally stable, while the DSB membranes produced, so far, are not. SiC nanoporous membranes have also been prepared by conventional dip-coating techniques using a novel pre-ceramic polymeric precursor allyl-hydridopolycarbosilane (AHPCS), a partially allyl-substituted hydridopolycarbosilane (HPCS). These membranes are stable in air-treatment at 450 °C, but have, so far, also proven unstable to high-temperature steam. The nanoporous hydrogen selective SiC membranes show promise for application in membrane reactors for the water gas shift and steam reforming reactions.

Application of an electrochemical membrane reactor to the thermochemical water splitting IS process for hydrogen production

The Bunsen reaction (SO 2 + I 2 + 2H 2O = H 2SO 4 + 2HI) in the thermochemical IS process to produce hydrogen was successfully employed using an electrochemical membrane reactor. H 2SO 4 and HI were concentrated in the anode side and the cathode side of the reactor, respectively. I 2 is the dominant bulk of the recycling chemicals in this process, and I 2 concentration at the outlet of the reactor was reduced ca. 93% by using this technique. The electric energy consumption for the reaction was about 50% smaller by reducing the concentration of I 2 indicating that the IS process can be operate efficiently at low I 2 concentration. The reaction was carried out for 4 h, and the HI concentration was increased by 26%. This amount was the same within 10% as the values calculated from the total loaded electricity. In order to decrease the overpotential at the anode side, small amount of HI was added to the anode side solution. The total voltage was reduced by 0.03 V by the addition of HI.

High-temperature membranes in power generation with CO 2 capture

A survey is made of high-temperature membranes and several possible applications of membrane reactors for integration in power generation cycles with CO 2 capture. Current performance and limitations of relevant inorganic membranes are presented and discussed. Integrated H 2, O 2 or CO 2 membrane separation is analysed and it is concluded that development of power plant concepts including membrane technology is not yet fully explored. Significant design optimisation would be required in order to identify efficient, feasible and environmentally sound technical solutions. In addition, further development and validation of performance of membranes in real applications are needed.

Application of a carbon membrane reactor for dehydrogenation reactions

This research tests a membrane reactor, equipped with a molecular-sieve carbon membrane, using isobutane dehydrogenation on a chromia alumina catalyst as a model reaction. Most pores of the carbon membrane employed are 6– 8 A in size and previous independent transport studies show that the permeability ratio of hydrogen to isobutene is larger than 100. These features make the membrane an excellent highly selective low-cost candidate for application in a membrane reactor. The novelty of this study is in the proposed application at relatively high temperatures (450°C and 500°C); only a few studies have tested carbon membrane reactors. Two types of operation modes were studied, using either nitrogen as a sweeping gas in counter current flow or using vacuum as a driving force for membrane transport. As expected, higher conversions were achieved with decreasing feed flow rate. The conversion achieved in the counter-current flow operation method was higher than in all other modes achieving a maximum of 85% at 500°C. While this result is much higher than in the corresponding PFR, the obtained improvement is a result of nitrogen transport and dilution. The conversions obtained in the vacuum mode show modest gains above the ones received in the PFR (40% vs. 30% at 500°C). These results were compared with simulations that used the experimentally determined transport parameters.