Use Of Membrane Reactor Research Articles

Power-to-ammonia synthesis process with membrane reactors: Techno- economic study

This work aims at investigating the potential of catalytic membrane reactors (CMRs) for ammonia production from renewable hydrogen. To achieve this objective, computer-aided process simulation is deployed using Aspen plus v14 simulation tool. A 1D model is developed to describe the integration of a ruthenium catalyst into a CMR equipped with inorganic membranes that are selective to NH3 over N2 and H2. First, the CMR performance is studied across a broad spectrum of membrane properties and operating conditions. Subsequently, the CMR model is integrated into several Power-to-Ammonia (PtA) process layouts, which are optimized and techno-economically compared against a traditional PEM-based PtA production process, employing condensation for the purification stage. Key findings at the reactor level confirmed that beyond a selectivity threshold towards hydrogen of 10–20, both the degree of conversion and recovery tend to be generally independent of the membrane's selectivity. However, for producing pure ammonia permeate, highly selective membranes (>1000 towards H2) depending on the pressure drop are found essential making this alternative elusive based on existing membranes. At the PtA level, results in terms of efficiency indicates that the use of membrane reactor increases the system efficiency by around ∼8% with respect to reference case while ∼15% enhancement is achieved with this process when using SOEC technology. When examining the final Levelized Cost of Ammonia (LCOA), incorporating a membrane reactor in conjunction with condensation separation results in a cost that nearly matches the reference case. Future research should focus on replacing the condensation process with a method of purification at lower pressures. This could potentially further improve efficiency and reduce the cost of the membrane reactor compared to the traditional one.

Preparation of polymeric-ceramic composite membranes for use in the methanol synthesis reaction

A new kind of ceramic-polymeric membranes has been prepared and characterized towards its use in membrane reactors for synthesis of methanol from CO2 and hydrogen. In this way, PBI membranes were prepared on a ceramic support by varying parameters of the preparation process. The effect of those parameters on the separation of the compounds involved in the reaction was measured under conditions (temperature, pressure and gas composition) simulating those of the reaction. The prepared membranes were able to selectively remove water from a mixture containing hydrogen and CO2. H2O/CO2 and H2O/H2 separation factors over 18 and 12, respectively, were achieved at 160°C. The separation factors decreased by increasing the temperature with a 3-layer membrane but were quite stable with a 4-layer membrane.

Carbon-low, renewable hydrogen production from methanol steam reforming in membrane reactors – a review

The development of sustainable and new technologies based on renewable energy sources is mandatory due to the anthropogenic climate changes and the depletion of fossil fuels. Hydrogen is considered a clean alternative able to produce only water and energy when consumed in fuel cell. However, the main issue for large-scale hydrogen commercialization is its storage and transportation. One way to solve this problem is to use energy carriers, such as methanol, which is liquid at ambient conditions, low reforming temperature, holds relatively highly H/C ratio and can be produced by biomass. So, hydrogen can be later produced on-demand by methanol steam reforming reaction. In order to produce carbon-low hydrogen alternative technologies are considered. In particular, membrane reactors are raising attention. The use of membrane reactor enables to increase the process selectivity, lower the temperature of the reaction while avoiding the formation of coke, and obtain a high pure hydrogen stream. This review provides an overview of the recent progress to produce hydrogen from methanol reforming in convectional and membrane reactors.

Construction of a thermally stable ZIF-8 membrane embedded inside a porous support for H2/CO2 separation: Close interlocking between membrane grains and porous support grains

Zeolitic imidazolate framework-8 (ZIF-8) membranes have emerged as promising wall candidates for use in membrane reactors. These membranes can improve the water gas shift (WGS) reaction performance because of their exceptional thermal stability and marked H2/CO2 sieving ability. Here, we propose a modified counter diffusion scheme to form an unprecedented, thermally stable ZIF-8 membrane: Pre-deposition of a zinc precursor (zinc acetate dihydrate) and subsequent solvothermal reaction with a methanolic solution of the ligand (2-methylimidazole). It appears that the pre-deposition and drying of the Zn precursor on and inside a porous support were key to retarding the diffusion of the Zn source, thus leading to the primary contact between the Zn source and ligand molecules within the porous support. As a result, it is likely that a continuous ZIF-8 layer was formed on the top surface and, more preferentially, at the interface with the grains of the porous support, reaching an infiltration depth of approximately 80 μm. Accordingly, this allowed for the effective blocking of the support pores by ZIF-8 grains, as well as their high dispersion. Notably, the resulting ZIF-8 membrane exhibited a maximum H2/CO2 separation factor of ca. 8.7 at a WGS reaction temperature of 300 °C. Unlike the conventional membrane architecture, ZIF-8 grains were densely embedded inside the porous support, thus reducing the risk of mechanical damage. Furthermore, the unique membrane structure was desirable for securing superior thermal stability for reliable and sustainable H2/CO2 separation at 300 °C for up to 72 h.

Integration of catalytic methane oxy-reforming and water gas shift membrane reactor for intensified pure hydrogen production and methanation suppression over Ce0.5Zr0.5O2 based catalysts

The production of pure hydrogen from methane or biomethane is a multistep process that can be intensified by the use of membrane reactors. In this study we have synthetized by microemulsion technique Rh and Pt supported over Ce0.5Zr0.5O2 to be applied to the catalytic methane oxy-reforming and water gas shift (WGS) reaction respectively. At first the reformate produced by the reforming process at 750 °C was purified using and hydrogen selective empty Pd-based membrane operated at 400 °C. This led to pure hydrogen production but it resulted also in a not-fully exploitation of the membrane performances. Thus, the Pt-based catalyst was loaded in the membrane reactor configuration leading to in situ hydrogen production that helped to increase the separation driving force. The water gas shift reaction downstream oxy-reforming was also studied on the Pt/Ce0.5Zr0.5O2 catalyst and evidenced the consumption of hydrogen by methanation at high H2/H2O ratio. Comparing the WGS membrane reactor with a classical fixed bed demonstrated that removing hydrogen led to increased CO conversion over the equilibrium of an analogous fixed bed, higher H2 yield and suppression of the methanation reaction, even at high inlet H2/H2O ratio. Optimizing the reaction conditions allowed to reach high hydrogen recoveries (89 %) for the integrated oxy-reforming/membrane water gas shift at high GHSV and without the need of a sweep gas.

Catalytic membrane reactor based on Pd-Sn supported on nanocarbons for the reduction of nitrate in water

This work studies the reduction of NO3- in water using a catalytic membrane reactor in flow-through configuration (FTCMR) for enhanced control of H2 availability and generation of NH4+. The catalytic membrane was prepared with metal catalysts supported on carbon materials with different structural and physicochemical properties (graphite, carbon nanofibers, reduced graphene oxide, activated carbon and carbon black). The catalysts were firstly tested in a batch reactor for screening and assessing influence of regime control on activity and selectivity. Pd-Sn catalysts showed higher production of NH4+ under chemical control than Pd-Cu ones, but equivalent performance was reached for Pd-Sn supported on carbon nanofibers and carbon black in conditions of H2 mass transfer control. Catalytic membranes were prepared with Pd-Sn catalyst according to higher impact of H2 availability in NH4+ generation. FTCMR was less selective to NH4+ compared to the batch reactor due to better control of H2 mass transfer. Reduction of NH4+ generation was achieved at the expense of activity due to lower availability of H2. However, membranes based on Pd-Sn supported on carbon nanofibers and carbon black were able to operate at higher H2 concentration with low selectivity to NH4+, making possible the use of membrane reactors at advantageous conditions.

Polymer-Ceramic Composite Membranes for Water Removal in Membrane Reactors.

Methanol can be obtained through CO2 hydrogenation in a membrane reactor with higher yield or lower pressure than in a conventional packed bed reactor. In this study, we explore a new kind of membrane with the potential suitability for such membrane reactors. Silicone–ceramic composite membranes are synthetized and characterized for their capability to selectively remove water from a mixture containing hydrogen, CO2, and water at temperatures typical for methanol synthesis. We show that this membrane can achieve selective permeation of water under such harsh conditions, and thus is an alternative candidate for use in membrane reactors for processes where water is one of the products and the yield is limited by thermodynamic equilibrium.

Extraction of Valuable Components from Man-made Waters

The results of experimental studies on isolation of poly-charged metals cations from man-made waters, which are valuable components, are presented. For their isolation and concentration, the method of homogenous sedimentation was used, which provides self-purification of water bodies in natural conditions and is responsible for the formation of bottom sediments. To implement these processes, energy-consuming low-pressure membrane methods were used- nanofiltration and dialysis, which creates conditions for the formation of solid solutions inside the composite membrane and do not require additional dosage of reagents. With the help of such combination, it was possible to obtain conditionally clean water for technical and household use, to divert environmentally friendly waste waters to the hydrographic network of the region. In addition, the shape of resulting original “ore body” simplifies its processing into individual components. It is noted the use of membrane reactors makes it possible to implement the homogenous deposition regime, which ensures the isolation of transition metals in the form of solid solutions with natural components of surface waters.

Intensified energetically enhanced steam methane reforming through the use of membrane reactors

AbstractThis work focuses on the implementation of membrane reactors (MRs) in the production of hydrogen through steam–methane reforming (SMR). A novel equilibrium MR model featuring Gibbs Free Energy Minimization is introduced and applied to the SMR‐MR process. In addition, the concept of “energetically enhanced steam methane reforming (EER),” which allows for the use of a hybrid (methane combustion/renewable energy) energy supply in the production of hydrogen, is intensified. The UNISIM software (Honeywell™) is used to create a range of intensified flowsheets depicting the proposed IEER‐MR process as well as two baseline flowsheets depicting “a standard SMR‐MR process” and “a fully exothermic EER process.” Heat integration studies are carried out on the developed flowsheets, and the baseline designs are compared to the IEER‐MR designs to identify energetic intensification.

Methanol Steam Reforming in Membrane Reactors

A brief review of recent scientific publications concerning the steam reforming of methanol in membrane reactors for the production of pure hydrogen is presented. The use of membrane reactors makes it possible to lower the temperature of this process by 100°C, increase the selectivity of the process, and practically eliminate the effect of catalysts’ carbonization. A substantial advantage of the use of membrane reactors is the possibility for removing a stream of high-purity hydrogen from the permeate zone. First of all, this applies to CO impurities, whose presence is critical for the use of hydrogen in low-temperature fuel cells based on proton-conducting membranes. The use of metallic membranes based on Pd makes it possible to directly use the hydrogen produced in the fuel cells.

Biochemical properties of a novel chitosanase from Bacillus amyloliquefaciens and its use in membrane reactor

Chitooligosaccharides are widely used in functional food, medicaments and agriculture. Controllable conversion of chitosan to chitooligosaccharides with desired degree of polymerization (DP) is of great value. Herein, a novel glycoside hydrolase family 46 chitosanase (BaCsn46A) was cloned and expressed from Bacillus amyloliquefaciens. BaCsn46A exhibited good enzymatic properties with high specific activity (1031.2 U/mg) under optimal hydrolysis conditions of pH 6.0 and 50 °C. BaCsn46A is an endo-type chitosanase, which could be utilized to yield abundant chitooligosaccharides. Furthermore, the preparation of high degree of polymerization chitooligosaccharides (DP 5–10) was investigated by BaCsn46A in an enzymatic reactor with a subsequent series of membranes. The maximum concentration of total chitooligosaccharides (DP 2–10) was 28.11 g/L (93.70% yield). The proportion of high degree of polymerization chitooligosaccharides (DP 5–10) occupied 56.17% (w/w) of total chitooligosaccharides. This study provided a cleaner production process for the controllable preparation of chitooligosaccharides with specific degree of polymerization.

Dynamic operation of water gas shift reaction over Fe2O3/Cr2O3/CuO catalyst in Pd/Al2O3 membrane reactor

Hydrogen has been considered as promising energy carrier that can be produced from renewable resources, such as biomass through gasification. This process results in producer gas containing CO, CO2, H2, N2, and CH4. The conventional enhancement of hydrogen is typically conducted using several unit operations such as water gas shift reactor (WGSR) and separation unit such as Pressure Swing Adsorption (PSA). Process intensification offers a new method to integrate both WGSR and separation unit into single membrane reactor. This research aimed to investigate the influence of dynamic operation on membrane reactor performance. The steady state fixed bed reactor and membrane reactor were used as base case to judge the performance of dynamic membrane reactor. The water gas shift reaction over Fe2O3/Cr2O3/CuO was carried out at 350°C and 1 atm by varying the feed composition and gas residence time. The feed composition ratio of H2O/CO consisted of 2 and 3 on mole basis, while the gas residence times were 1.2 s and 2.3 s. The membrane reactor consists of shell and tube sides made of Pd/Al2O3 material with technical specification of 10 mm inner diameter, 20 μm Pd thickness supported by alumina, and 10 cm reactor length. The compositions of the feed gas and products were measured using gas analysers such CO gas detector (Bacharach PCA® 3) and H2 gas detector (Cosmos XP-3140). The dynamic operation was performed following the square wave perturbation of the feed gas at switching time of 15 s. The experiment results showed that increasing the feed composition ratio and gas residence time increased the conversion of CO and hydrogen production in the fixed bed reactor and membrane reactor. Higher production of hydrogen also improved the recovery of hydrogen in membrane reactor. The use of membrane reactor increased significantly the conversion of CO when compared to fixed bed reactor. Moreover, the dynamic membrane reactor would give much better performance in term of CO conversion and hydrogen recovery. The stability of the Pd/Al2O3 membrane reactor was proven for at least 10 h operation.

High pressure adsorption, permeation and swelling of carbon membranes – Measurements and modelling at up to 20 MPa

A unique feature of inorganic membranes is the ability to operate at high temperature and pressure. Even supercritical solvents can be processed by these membranes, whereas polymer membranes tend to swell and consequently suffer from reduced selectivity and mechanical strength. Carbon membranes open new possibilities, e.g. the processing of high pressure, high temperature fluid streams directly in place or the use in membrane reactors for chemical reactions like H2-synthesis by dehydrogenation. This work investigates high pressure adsorption of carbon membrane material for different gases at up to 12MPa, the selectivity and permeance for CO2/N2 mixtures in a pressure range from 0.1 to 20MPa and the swelling of carbon material exposed to Oxygen at up to 10MPa. A model based on Maxwell-Stefan diffusion with parameters gained from measured adsorption and fluxes has been implemented to improve the understanding of the behaviour of high pressure separation with carbon membranes.

Application of NaA Membrane Reactor for Methanol Synthesis in CO2 Hydrogenation at Low Pressure

Abstract The process of CO2 hydrogenation into methanol has recently attracted more attention for reducing CO2, a main green-house gas in the atmosphere. In addition, methanol can be used as fuel or a basic chemical to satisfy the growing demand for energy in the world. In this study, the performance of NaA membrane reactor on the methanol yield and methanol selectivity obtained from the CO2 hydrogenation process was evaluated at different reaction conditions by varying the temperature, pressure, gas hourly space velocity (GHSV) and H2/CO2 ratio. The results show that the methanol yields and methanol selectivities obtained from the membrane reactor (MR) at all reaction conditions are higher than those from the traditional reactor (TR). The ratio of methanol yield in MR over methanol yield in TR are varied from 1.4 to 1.7 depending on the operating conditions. It is also observed that the use of membrane reactor is more efficient at low GHSV and the temperature in the range of 220–240°C.

Development of an active, selective and durable water-gas shift catalyst for use in membrane reactors

Rh(0.6%)/La2O3 and Rh(0.6%)/La2O3(27wt%)·SiO2were assayed for the WGS reaction at 673K and 1 atm. They were both more active than industrial Cr-Fe based catalysts. Rh(0.6%)/La2O3 was the most active but it progressively deactivated. To investigate its deactivation and the stability of the Rh(0.6%)/La2O3(27wt%)·SiO2, the WGS reaction was carried out in a DRIFTS cell in operando mode. The deactivation of the former was due to the strong adsorption of intermediate oxygenates. Another disadvantage of the Rh formulations was their methanation activity. Therefore, a series of formulations containing 0.1 wt% through 1.2 wt% Pt supported on La2O3(27wt%)·SiO2 were synthesized and catalytically evaluated in a fixed-bed reactor. The activity, methane formation and stability were carefully checked. The fresh and used catalysts were characterized through a battery of techniques including XRD, LRS and XPS. The Pt(0.1wt%) formulation resulted the most active one per gram of platinum and negligible methanation occurred. It maintained the activity and selectivity after 155h on stream. This catalyst was tested in a Pd-Ag membrane reactor to produce ultrapure H2 (<10ppm of CO) that can be used to feed a low temperature PEM fuel cell. Comparing our results with those already published, it is concluded that our system is one of the best ones reported so far.

Structural and functional properties of SrTi1−xFexO3−δ (0 ⩽ x ⩽ 1) for the use as oxygen transport membrane

Perovskitic oxides are widely investigated as oxygen transport membrane materials for the efficient generation of pure oxygen or the use in membrane reactors. However, most of high performance perovskites suffer from low stability in operation conditions. Therefore, solid solutions of SrTi1−xFexO3−δ (STF) are investigated due to the initial high stability of the strontium titanate host lattice. Self-synthesized powders with substitution of Ti by 0%, 25%, 35%, 50%, 75%, and 100% Fe were studied. Crystal structure, functional properties i.e., diffusion coefficient, surface exchange rates, and oxygen permeation rates as well as membrane fabrication and operation related material properties i.e. sintering behaviour and thermal/chemical expansion were investigated. Substitution of Ti by Fe increases oxygen mobility and, hence, oxygen permeation rates, but reduces stability in operation relevant atmospheres such as Ar/4%H2 or CO2. At the same time thermal/chemical expansion increases. This makes the fabrication of supported thin membranes and their integration into membrane modules more challenging. It turned out that 25–35% Fe substituting Ti seems to be a good compromise between structural and functional properties. Oxygen permeation rates achieved are comparable to that of standard materials such as La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF). At the same time stability is higher and thermal expansion coefficients lower compared to LSCF, which makes STF with limited Fe-content (max. 35%) a promising oxygen transport membrane material.

Effect of the presence of light hydrocarbon mixtures on hydrogen permeance through Pd–Ag alloyed membranes

The production of light olefins by alkane dehydrogenation is limited by the thermodynamic equilibrium. The use of membrane reactors for this process enhances alkane conversion by a selective removal of hydrogen from the reaction media. This hydrogen removal results in an equilibrium shift towards the production of olefins. However, hydrogen permeance through Pd-based membranes may be affected by the presence of light olefins. This work evaluates the effect of the composition of propane/propylene mixtures on the hydrogen permeation through Pd–Ag alloyed membranes for propane dehydrogenation. It has been observed that the transient hydrogen permeation decreases in the presence of C3 species due to coke deposition over the Pd–Ag layer. The permeation decrease has been characterized and quantified as a function of propane/propylene contents in the feed gas and of operation temperature.

Modeling of ethylbenzene dehydrogenation in catalytic membrane reactor with porous membrane

AbstractThe modeling of ethylbenzene dehydrogenation in a catalytic membrane reactor has been carried out for porous membrane by means of two-dimensional, non-isothermal stationary mathematical model. A mathematical model of the catalytic membrane reactor was applied, in order to study the effects of transport properties of the porous membrane on process performance. The performed modeling of the heat and mass transfer processes within the porous membrane, allowed us to estimate the efficiency of its use in membrane reactors, in comparison with a dense membrane (with additional oxidation of the hydrogen in shell side). The use of a porous ceramic membrane was found to cause an increase of the ethylbenzene conversion at 600°C, up to 93 %, while the conversion in the case of conventional reactor was 67%. In this work, we defined the key parameter values of porous membrane (pore diameter and thickness) for ethylbenzene dehydrogenation in catalytic membrane reactor, at which the highest conversion of ethylbenzene and styrene selectivity can be reached.

Preparation of BTESE-derived organosilica membranes for catalytic membrane reactors of methylcyclohexane dehydrogenation

High-performance organic–inorganic hybrid silica membranes were developed for use in membrane reactors for methylcyclohexane (MCH) dehydrogenation to toluene (TOL). The membranes were prepared via sol–gel processing using bis(triethoxysilyl)ethane (BTESE). In particular, the effect of hydrolysis conditions (H2O/BTESE molar ratio) on membrane performance was extensively investigated. Characterization based on TG-MASS, FTIR, N2 adsorption and positron annihilation lifetime (PAL) measurements of BTESE-derived silica gels revealed that the ethoxides of BTESE were almost completely hydrolyzed and the silica networks became dense by increasing the H2O/BTESE molar ratio from 6 to 240. BTESE-derived silica membranes showed a hydrogen permeance that was higher than 1×10−6mol/(m2sPa). H2/TOL selectivity increased from 100 to 10,000 by increasing the H2O/BTESE molar ratio from 6 to 240, while keeping a hydrogen permeance of more than 1×10−6mol/(m2sPa).In MCH dehydrogenation, a BTESE-derived silica membrane reactor with a Pt/γ-Al2O3/α-Al2O3 bimodal catalytic layer achieved MCH conversion of 75% that was higher than the equilibrium conversion of 60%, and a hydrogen purity in the permeate stream of more than 99.9% at 230°C.

Low Temperature Methane Steam Reforming: Catalytic Activity and Coke Deposition Study

Low temperature steam reforming combined with hydrogen-selective membrane offers significant advantages in terms of energy conservation, reduction of GHG emissions and low cost operation. In this study, Ni supported on La/CeO2-ZrO2 is evaluated under steam reforming at temperature <550 C. The catalyst is highly active in steam reforming of methane and water gas shift reaction. Stability test at simulated biogas steam reforming was conducted and the catalyst showed extremely stable performance for long time on stream (90 h) and very low amount of carbonaceous deposits, as determined by TPO and TPH. The above characteristics demonstrate that this catalyst is a potential candidate for use in membrane reactors operating at low temperature for the one-step production of pure hydrogen.