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A unique Taylor‐vortex membrane reactor (TVMR) design for continuous gas‐liquid reactions is presented in this work. The reactor consists of a cylindrical rotor inside a stationary concentric cylindrical vessel, and a flexible system of equispaced baffle rings surrounding the rotor. This restricts the annular cross section to a small gap between the baffles and the rotor, and divides the annulus into 18 mixing zones. The baffles support a 6 m long PFA tubular membrane that is woven around the rotor. At 4 mL/min inlet flow rate, the TVMR showed a plug‐flow behavior and outperformed the unbaffled reactor, having 5–12 times lower axial dispersion. The continuous aerobic oxidation of benzyl alcohol was performed for 7 h using the Pd(OAc)2/pyridine catalyst in toluene at 100 °C and 1.1 MPa oxygen pressure. A stable conversion of 30% was achieved with 85% benzaldehyde selectivity, and no pervaporation of organics into the gas phase. [ABSTRACT FROM AUTHOR]

CO2 methanation is one of the vital reactions to utilize CO2 and realize power to gas process. To decrease the CO2 capture cost and alleviate the hot spots during the strong exothermic methanation reaction, here, we report a coupling of CO2 capture process with in situ CO2 methanation process through a ceramic‐molten carbonate (MC) dual phase membrane reactor over the Ni‐based catalyst. The performance of the membrane reactor was systematically investigated and compared with the traditional fixed‐bed reactor. The results show that the performance of the membrane reactor is higher than that of the fixed‐bed reactor, since the produced steam through the methanation process can be partially removed through the dual‐phase membrane, which promotes the reaction shift to right side. A stability test shows no obvious degradation within 32 h. These results indicate that the membrane reactor is promising for coupling CO2 capture with in situ methanation process. [ABSTRACT FROM AUTHOR]

Precombustion carbon capture is an effective strategy to reduce large‐scale CO2 emissions, which is mainly used in the area of integrated gasification combined cycle (IGCC) power plants. Oxygen transport membranes (OTMs) were suggested as the air separation unit to produce high purity oxygen for the gasifier. However, the improvement in efficiency was limited. Here, a new IGCC process is reported based on a robust OTM reactor, where the OTM reactor is used behind the coal gasifier. This IGCC‐OTM process fulfills syngas oxidation, H2 production, and carbon capture in one unit, thus a significant decrease of the energy penalty is expectable. The membrane reactor does not use noble metal components, and exhibits high hydrogen production rates, high hydrogen separation factor (103–104), and stable performance in a gas mixture mimicking real syngas compositions from a coal gasifier with H2S concentrations up to 1,000 ppm. [ABSTRACT FROM AUTHOR]

Catalytic membrane reactors based on oxygen‐permeable membranes are recently studied for hydrogen separation because their hydrogen separation rates and separation factors are comparable to those of Pd‐based membranes. New membrane materials with high performance and good tolerance to CO2 and H2S impurities are highly desired. In this work, a new membrane material Ce0.85Sm0.15O1.925–Sr2Fe1.5Mo0.5O6‐δ (SDC–SFM) was prepared for hydrogen separation. It exhibits high conductivities at low oxygen partial pressures, which is benefit to electron transfer and ion diffusion. A high hydrogen separation rate of 6.6 mL cm−2 min−1 was obtained on a 0.5‐mm‐thick membrane coated with Ni/SDC catalyst at 900°C. The membrane reactor was operated steadily for 532 h under atmospheres containing CO2 and H2S impurities. Various characterizations reveal that SDC–SFM has good stability in the membrane reactor for hydrogen separation. All facts confirm that SDC–SFM is promising for hydrogen separation in practical applications. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1088–1096, 2019 [ABSTRACT FROM AUTHOR]

Natural gas can be reformed to syngas (CH4 + H2O = CO + 3H2), at temperatures above 850°C. Membrane catalytic reformers can provide high CH4 conversions at temperatures below 650°C, by separating H2 from the reactive mixture. Traditional Ni‐based catalysts suffer from low activity at low temperatures and deactivate rapidly by coking, particularly at low steam/carbon ratios. In this study, an ultralow loading (0.15 wt %) Ru/γ‐Al2O3 catalyst was implemented in a lab‐scale membrane reformer, using a supported 5μm Pd‐Ag film membrane. Methane conversions above 90% were achieved at 650°C, 8 bar, and H2O/CH4 = 2, 3 with contact times of ca. 10 s. The system generated up to 3.5 mol of ultrapure H2 per mol of CH4 fed, with a maximum power density of 0.9 kW/L. No significant deactivation was observed after 200 h time on stream, even when using low H2O:CH4 ratios. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3101–3108, 2018 [ABSTRACT FROM AUTHOR]

We report a detailed modeling analysis of membrane reactor systems for propane dehydrogenation (PDH), by integrating a two-dimensional (2-D) nonisothermal model of a packed bed membrane reactor (PBMR) with ASPEN process simulations for the overall PDH plant including downstream separations processes. PBMRs based on ceramic hollow fiber membranes-with catalyst placement on the shell side-are found to be a viable route, whereas conventional tubular membranes are prohibitively expensive. The overall impact of the PBMR on the PDH plant (e.g., required dimensions, catalyst amount, overall energy use in reaction and downstream separation) is determined. Large savings in overall energy use and catalyst amounts can be achieved with an appropriate configuration of PBMR stages and optimal sweep/feed ratio. Overall, this work determines a viable design of a membrane reactor-based PDH plant and shows the potential for miniaturized hollow-fiber membrane reactors to achieve substantial savings. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4519-4531, 2017 [ABSTRACT FROM AUTHOR]

This article introduces a novel operability-based approach for process design and intensification of energy systems described by nonlinear models. This approach is applied to a membrane reactor (MR) for the direct methane aromatization (DMA) conversion to benzene and hydrogen. The proposed method broadens the scope of the traditional path of the operability approaches for design and control, mainly oriented to obtain the achievable output set (AOS) from the available input set, and compare the computed AOS to a desired output set. In particular, an optimization algorithm based on nonlinear programming tools is formulated for the calculation of the desired input set that is feasible considering process constraints and intensification targets. Results on the application of the operability method as a tool for process intensification show reduction of the DMA-MR footprint (≈77% reactor volume and 80% membrane area reduction) for an equivalent level of performance, when compared to the base case. This case study indicates that the novel approach can be a powerful tool for process intensification of membrane reactors and other complex chemical processes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 975-983, 2017 [ABSTRACT FROM AUTHOR]

In this article, we report a detailed study on co-production of H2 and syngas on La0.9Ca0.1FeO3−δ (LCF-91) membranes via water splitting and partial oxidation of methane, respectively. A permeation model shows that the surface reaction on the sweep side is the rate limiting step for this process on a 0.9 mm-thick dense membrane at 990°C. Hence, sweep side surface modifications such as adding a porous layer and nickel catalysts were applied; the hydrogen production rate from water thermolysis is enhanced by two orders of magnitude to 0.37 μmol/cm2•s compared with the results on the unmodified membrane. At the sweep side exit, syngas (H2/CO = 2) is produced and negligible solid carbon is found. Yet near the membrane surface on the sweep side, methane can decompose into solid carbon and hydrogen at the surface, or it may be oxidized into CO and CO2, depending on the oxygen permeation flux. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4427-4435, 2016 [ABSTRACT FROM AUTHOR]

The planar membrane reactor configuration was explored for partial oxidation of methane (POM) to syngas. A supported membrane composed of yttria-stabilized zirconia and La0.8Sr0.2Cr0.5Fe0.5O3-δ was sealed to a stainless holder, and a Ni/Al2O3 catalyst bed was placed under the membrane plane with a small slit between them. This reactor configuration would facilitate the POM reaction via oxidation-reforming mechanism: the oxidation reaction occurring at the membrane surface and the reforming reaction taking place in the catalyst bed. At 800°C and a methane feed rate of 32 mL min−1, the reactor attained methane throughput conversion over 90%, CO and H2 selectivity both over 95%, and an equivalent oxygen permeation rate 1.4 mL cm−2 min−1. The membrane and catalyst remained intact after the POM testing. The planar membrane reactor configuration explored in this study may lead to the development of a compact reactor for syngas production. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2170-2176, 2016 [ABSTRACT FROM AUTHOR]

This article presents a theoretical study on the integration of a membrane reactor (MR) for carbon capture into an integrated gasification combined cycle (IGCC) plant. First-principles, simplified systems-level models for the individual IGCC units and the MR are introduced for their subsequent plantwide integration. The integrated plant model is then used for simulation studies that assume different MR characteristics. Using this model, an optimization problem is formulated to analyze the MR effects when adding it to the IGCC plant, while satisfying all of the process constraints in streams and performance variables. The solution of this optimization problem indicates improvements in the original case studies, including capital cost savings as high as $18 million for the optimal case under nominal process conditions. To determine the cost implications of inserting the MR into the IGCC plant, a differential cost analysis is performed taking into account major plant capital and operating costs. This analysis considers the same amount of coal and power generation for cases with and without the MR. The results of this analysis based on a present value of annuity calculation show break even costs for the MR within the feasible range for membrane fabrication, even for short membrane lifetimes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1568-1580, 2016 [ABSTRACT FROM AUTHOR]

Hollow fiber MFI zeolite membranes were modified by catalytic cracking deposition of methyldiethoxysilane to enhance their H2/CO2 separation performance and further used in high temperature water gas shift membrane reactor. Steam was used as the sweep gas in the MR for the production of pure H2. Extensive investigations were conducted on MR performance by variations of temperature, feed pressure, sweep steam flow rate, and steam-to-CO ratio. CO conversion was obviously enhanced in the MR as compared with conventional packed-bed reactor (PBR) due to the coupled effects of H2 removal as well as counter-diffusion of sweep steam. Significant increment in CO conversion for MR vs. PBR was obtained at relatively low temperature and steam-to-CO ratio. A high H2 permeate purity of 98.2% could be achieved in the MR swept by steam. Moreover, the MR exhibited an excellent long-term operating stability for 100 h in despite of the membrane quality. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3459-3469, 2015 [ABSTRACT FROM AUTHOR]

To accelerate the commercial application of mixed-conducting membrane reactor for catalytic reaction processes, a robust mixed-conducting multichannel hollow fiber (MCMHF) membrane reactor was constructed and characterized in this work. The MCMHF membrane based on reduction-tolerant and CO2-stable SrFe0.8Nb0.2O3-δ (SFN) oxide not only possesses a good mechanical strength but also has a high oxygen permeation flux under air/He gradient, which is about four times that of SFN disk membrane. When partial oxidation of methane (POM) was performed in the MCMHF membrane reactor, excellent reaction performance (oxygen flux of 19.2 mL min−1 cm−2, hydrogen production rate of 54.7 mL min−1 cm−2, methane conversion of 94.6% and the CO selectivity of 99%) was achieved at 1173 K. And also, the MCMHF membrane reactor for POM reaction was operated stably for 120 h without obvious degradation of reaction performance. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2592-2599, 2015 [ABSTRACT FROM AUTHOR]

The mechanistic modeling of biodiesel production process in membrane reactor with the consideration of chemical reaction, phase equilibrium, and ultrafiltration is important for the membrane reactor design. In part II of this work, the chemical and phase equilibrium (CPE) model for crude palm oil transesterification reaction in the membrane reactor developed in part I is extended to an integration of CPE with modified Maxwell-Stefan model, which considers multicomponent mass transport phenomena of concentration polarization and intramembrane. A good fit of simulated permeate fluxes and apparent solute rejection to the experimental data shows that the model has a good prediction capability. Reversible fouling was found to be the major fouling and no pore plugging was observed. Simulation results verified that micelles were retained by the membrane at CPO:MEOH molar ratio of 1:24 and catalyst concentration of 0.5 wt %. However, phase inversion happened when catalyst concentration of 0.05 and 0.1 wt % were used. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1981-1996, 2015 [ABSTRACT FROM AUTHOR]

Using a membrane reactor for reversible transesterification reaction involves reaction and product separation within a single unit. However, a pseudohomogeneous reaction and heterogeneous separation must be maintained for successful membrane reactor operation. Present research is aimed to develop an integrated model of chemical and phase equilibrium (CPE) and modified Maxwell-Stefan equation that describes the simultaneous CPE and mass transport phenomena of biodiesel production from crude palm oil (CPO) using a membrane reactor. In the first part of this work, a systematic approach describing simultaneous CPE of CPO transesterification in the membrane reactor was developed with the reconciliation of transesterification reaction and phase equilibrium that involves six-component. The results revealed that regressed apparent equilibrium constant [ABSTRACT FROM AUTHOR]

The dehydrogenation of methylcyclohexane (MCH) to toluene (TOL) for hydrogen production was theoretically and experimentally investigated in a bimodal catalytic membrane reactor (CMR), that combined Pt/Al2O3 catalysts with a hydrogen-selective organosilica membrane prepared via sol-gel processing using bis(triethoxysilyl) ethane (BTESE). Effects of operating conditions on the membrane reactor performance were systematically investigated, and the experimental results were in good agreement with those calculated by a simulation model with a fitted catalyst loading. With H2 extraction from the reaction stream to the permeate stream, MCH conversion at 250°C was significantly increased beyond the equilibrium conversion of 0.44-0.86. Because of the high H2 selectivity and permeance of BTESE-derived membranes, a H2 flow with purity higher than 99.8% was obtained in the permeate stream, and the H2 recovery ratio reached 0.99 in a pressurized reactor. A system that combined the CMR with a fixed-bed prereactor was proposed for MCH dehydrogenation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1628-1638, 2015 [ABSTRACT FROM AUTHOR]

A modeling-based approach is presented to understand physically realistic and technologically interesting material properties and operating configurations of packed-bed membrane reactors (PBMRs) for propane dehydrogenation (PDH). PBMRs composed of microporous or mesoporous membranes combined with a PDH catalyst are considered. The influence of reaction and membrane transport parameters, as well as operating parameters such as sweep flow and catalyst placement, are investigated to determine desired 'operating windows' for isothermal and nonisothermal operation. Higher Damköhler (Da) and lower Péclet (Pe) numbers are generally helpful, but are much more beneficial with highly H2-selective membranes rather than higher-flux, lower-selectivity membranes. H2-selective membranes show a plateau region of conversion that can be overcome by a large sweep flow or countercurrent operation. The latter shows a complex trade-off between kinetics and permeation, and is effective only in a limited window. H2-selective PBMRs will greatly benefit from the fabrication of thin (∼1 µm or less) membranes. © 2014 American Institute of Chemical Engineers AIChE J, 61: 922-935, 2015 [ABSTRACT FROM AUTHOR]

A catalytic membrane reactor, which was immobilized with palladium-loaded nanogel particles (NPs), was developed for continuous-flow Suzuki coupling reaction. Palladium-loaded membranes were prepared by immobilization of NPs, adsorption of palladium ions, and reduction into palladium(0). The presence of palladium in the membrane was confirmed by the scanning electron microscopy; palladium aggregation was not observed. The catalytic activity of the membrane reactor in continuous-flow Suzuki coupling reaction was approximately double that of a comparable reactor in which palladium ions were directly adsorbed onto an aminated membrane. This was attributed to the formation of small palladium particles. The reusability in the continuous-flow system was higher than that in a batch system, and the palladium-loaded membrane reactor had high long-term stability. © 2014 American Institute of Chemical Engineers AIChE J, 61: 582-589, 2015 [ABSTRACT FROM AUTHOR]

High-temperature CO2 selective membranes offer potential for use to separate flue gas and produce a warm, pure CO2 stream as a chemical feedstock. The coupling of separation of CO2 by a ceramic-carbonate dual-phase membrane with dry reforming of CH4 to produce syngas is reported. CO2 permeation and the dry reforming reaction performance of the membrane reactor were experimentally studied with a CO2-N2 mixture as the feed and CH4 as the sweep gas passing through either an empty permeation chamber or one that was packed with a solid catalyst. CO2 permeation flux through the membrane matches the rate of dry reforming of methane using a 10% Ni/γ-alumina catalyst at temperatures above 750°C. At 850°C under the reaction conditions, the membrane reactor gives a CO2 permeation flux of 0.17 mL min−1 cm−2, hydrogen production rate of 0.3 mL min−1 cm−2 with a H2 to CO formation ratio of about 1, and conversion of CO2 and CH4, respectively, of 88.5 and 8.1%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2207-2218, 2013 [ABSTRACT FROM AUTHOR]

Recently, membrane reactor technology was used to produce high-quality biodiesel because of its advantage of simultaneous transesterification and separation. As the transesterification reaction involves two immiscible phases of methanol ( MeOH) and oil ( TG), a thorough investigation on the membrane reactor for biodiesel production with the consideration of chemical phase equilibrium ( CPE) via modeling analysis, was conducted in this study. A mathematical model was developed based on the modified Maxwell- Stefan model with the incorporation of CPE. The formation of TG rich micelles dispersed in the continuous phase of MeOH was the most important hypothesis in the model development. The preliminary experiment results show that the permeate compositions from the membrane reactor were closely related to CPE of the system, which was highly depending on the MeOH to TG molar ratio. TG free permeate can only be obtained if the continuous phase of MeOH was free from TG and the TG rich micelles were retained by the membrane. The model verification further confirmed the formation of micelles dispersed in the continuous MeOH phase within the feed side of the membrane reactor and the model was able to predict the performance of the membrane reactor for biodiesel production at an acceptable accuracy. © 2012 American Institute of Chemical Engineers AIChE J, 59: 258-271, 2013 [ABSTRACT FROM AUTHOR]

Equilibrium shifts of methane steam reforming in membrane reactors consisting of either tetramethoxysilane-derived amorphous hydrogen-selective silica membrane and rhodium catalysts, or hexamethyldisiloxane-derived membrane and nickel catalysts is experimentally demonstrated. The hexamethyldisiloxane-derived silica membrane showed stable permeance as high as 8 × 10 mol m s Pa of H after exposure to 76 kPa of vapor pressure at 773 K for 60 h, which was a much better performance than that from the tetramethoxysilane-derived silica membrane. Furthermore, the better silica membrane also maintained selectivity of H/N as high as 10 under the above hydrothermal conditions. The degree of the equilibrium shifts under various feedrate and pressure conditions coincided with the order of H permeance. In addition, the equilibrium shift of methane steam reforming was stable for 30 h with an S/C ratio of 2.5 at 773 K using a membrane reactor integrated with hexamethyldisiloxane-derived membrane and nickel catalyst. © 2010 American Institute of Chemical Engineers AIChE J, 2011 [ABSTRACT FROM AUTHOR]

The article describes a study which examined the oxidative dehydrogenation (DH) of propane in a Perovskite membrane reactor with multi-step oxygen insertion to produce propene. It cites that propene is being used in a commercial scale to produce polymers, particularly polypropylene, as well as cumene, acrylonitrile and acrylic acid/acrolein or propylene oxide. Several technologies for the DH of propane to propene are also cited, including the logy from UOP and the Catofin technology from Air Products and Chemicals.

The article analyzes the design and performance of mixed conducting ceramic membrane reactors for the partial oxidation of methane to syngas using a two-dimensional mathematical model. It evaluates kinetic parameters including material balance, heat balance and the momentum balance for the shell and tube phase and determines the reaction capacity of the reactor via oxygen permeation rate as well as the problem with pressure drop. It also looks at the regulation of the methane feed velocity for the operation of mixed conducting membrane reactors.

The article investigates the use of BaCoxFeyZrzO3 (BCFZ) perovskite oxygen selective ceramic hollow fiber membranes as construct reactors for partial oxidation of methane (POM) to syngas. It examines the performance of the BCFZ fibers in the POM and its operational stability for the different catalyst arrangements. It also proposes a stable reactor concept with an arrangement of the reforming catalyst behind the oxygen permeation zone.

The article presents a study which developed a novel inorganic hollow fiber membrane reactor (iHFMR) which was applied to the catalytic dehydrogenation of propane to propene. Aluminum oxide hollow fiber substrates were prepared through a combined phase inversion/sintering technique. It was found that the advantage of using iHFMR compared to fixed bed reactor (FBR) is lessened after 40 minutes of operation because of the deactivation of the catalyst and the low equilibrium conversion of propane.

This article describes the development of a membrane reformer for the production of hydrogen with methane steam. This process is described as a thermally balanced packed bed membrane reactor (PBMR) that uses a methane steam reformer and an exothermic oxidation compartment. Diagrams outlining the optimal organization of these reactors are presented. Strategies for ensuring the thermal balance of these processes are considered. Issues relating to the maintenance of temperature boundaries within the fuel cell are described.

The article presents a study which investigated the performance of heptane reforming in three dense ceramic membrane reactors, where the membranes were modified differently with reforming catalyst. The authors report that each reactor displayed distinctive catalytic behavior. According to the result of their investigation, the reactor with a bare membrane showed low catalytic activity and low oxygen permeation flux, but gave stable performance. The authors propose a reaction pathway of hydrocarbon reforming in dense ceramic membrane reactor.

The article details a study which investigated the partial hydrogenation of 1,5-cyclooctadiene in a pore-flow-through membrane reactor at 50°C and 1 MPa hydrogen pressure with single capillary membranes and a bundle of 27 capillaries. It describes the preparation method for and the characteristics of the catalytically active membranes. The authors suggest that the conversion rate of 1,5-cyclooctadiene in the membrane reactor was mainly affected by the Pd amount and the mass flow rate of the reaction mixture through the membrane.

In this study, we proposed coupling the thermal decomposition of carbon dioxide (CO2 → CO + 1/2O2) with the partial oxidation of methane (POM) to syngas (CH4 + 1/2O2 → CO + 2H2) in a dense mixed-conducting membrane reactor, in which the reaction of CO2 decomposition took place in one side of the membrane and the POM reaction occurred in the other side of the membrane simultaneously (or methane reacted with oxygen that was permeated through the membrane from the CO2 decomposition, to produce H2 and CO over supported transition metal catalysts). A perovskite-type oxygen-permeable membrane of SrCo0.4Fe0.5Zr0.1O3.δ (SCFZ) was used for the membrane reactor. The effects of temperature and the feedflow rates of CO2 and CH4 on the reaction performance of the SCFZ membrane reactor were investigated. It was found that the CO2 conversion increased with increasing the temperature and decreased with increasing the feed fldw rates of CO2 or with decreasing the feed flow rates of CH4. At 1173 K, the CO2 conversion reached about 11.1%, and the CH4 conversion, CO selectivity, and the ratio of H2/CO were 84.5%, 93%, and 1.8, respectively. [ABSTRACT FROM AUTHOR]

A new approach for analyzing and understanding the dynamics of combined reaction separation processes with fast chemical reactions was proposed recently. The approach is based on transformed concentration variables which were first introduced by Doherty and co-workers for the steady-state design of reactive distillation processes. Application was demonstrated for reactive distillation processes and fixed bed, as well as moving-bed chromatographic reactors. The focus was on simple reactions of type 2A ⇌ B + C. This approach is further extended and applied to some real--fairly complex--multireaction systems. Applications to be considered are a reactive enantiomeric separation process in a fixed-bed chromatographic reactor, and an industrial reactive distillation column. Finally, application to membrane reactors is discussed. [ABSTRACT FROM AUTHOR]

This article discusses a process for the partial oxidation of methane (POM). This process was developed using a membrane reactor to separate oxygen in the POM process. Problems relating to membrane permeability are noted. A self-catalytic mixed-conducting membrane is described and the testing process developed for it is outlined. The advantages of this reactor are discussed in terms of its thin membrane and the rapidity with which surface oxygen is exchanged. The fact that a nickel oxide redox, or reduction oxidation, reaction sustains equilibrium among the catalysts in the membrane reactor is also noted.