Solid Electrolyte Membrane Reactor Research Articles

Electrochemically assisted synthesis of fuels by CO2 hydrogenation over Fe in a bench scale solid electrolyte membrane reactor

The electrochemically assisted synthesis of fuels by CO2 hydrogenation was studied over a cheap, widespread and non-precious Fe catalyst in a bench scale oxygen ion conducting membrane (YSZ) reactor. The studies were performed under conditions representative of potential practical application i.e., under atmospheric pressure, at relatively low temperatures and high gas flow rates, with varying H2/CO2 ratios and using gas compositions typical for postcombustion CO2 capture exit streams and easily scalable catalyst-electrode configurations.The Fe-TiO2 catalyst film was deposited by “dip-coating” and characterised both after pre-reduction and after testing.CO2 conversion and selectivities to CH3OH and C2H6O can be enhanced up to 4, 50 and 1.7 times, respectively, by electrochemically controlled migration of O2− promoting ions to or from the catalyst surface.The optimum temperature for the process was 325°C. Lower gas flow rates favoured the synthesis of CH3OH and C2H6O. CO2 conversion and selectivities to CH3OH and C2H6O showed a maximum for a stoichiometric H2/CO2 ratio of 3. Formation of C3H6 and CO is strongly favoured for a H2/CO2 ratio of 4 and 2, respectively, as a result of the increased and decreased hydrogen availability in the reaction system.

Direct production of flexible H2/CO synthesis gas in a solid electrolyte membrane reactor

The development of novel configurations for the production of synthesis gas (syn-gas) of flexible H2/CO ratio is of great importance to reduce the cost for the synthesis of synfuels and high-value chemicals. In this work, we propose a radically novel approach to the direct production of syn-gas with flexible H2/CO ratio based on the solid electrolyte membrane reactor (SEMR). For that purpose, a single-chamber solid electrolyte membrane reactor based on yttria-stabilized zirconia (YSZ) has been developed (Pt/YSZ/Pt), where both active Pt catalysts–electrodes were exposed to the same reaction atmosphere (C2H5OH/H2O = 0.7 %/2 %). The application of different polarizations at temperature range (600–700 °C) allows to control the H2/CO ratio of the obtained syn-gas, i.e., the ratio was varied between 1.5 and 12 under polarization conditions. Unlike conventional catalytic partial oxidation processes, the H2/CO adjustment was managed without the requirement of external O2 feeding to the reactor. An increase in the applied current or potential caused the H2/CO ratio to increase vs. the open-circuit conditions where ethanol reforming occurred on the Pt catalyst–electrodes which is due to an increase in the rate of the electro-catalytic processes. On the other hand, a decrease in the H2/CO ratio at a fixed potential was achieved at higher temperatures due to the further reaction of the produced H2 with the rest of the species present in the gas phase, leading to a decrease in the faradaic efficiency. The proposed configuration may be of great interest especially for biorefinery applications where H2, syn-gas and electricity may be produced from bioethanol.

Effect of operating conditions on the performance of solid electrolyte membrane reactor for steam and CO2 electrolysis

Solid electrolyte membrane reactor (SEMR) based on the Ni–YSZ (yttria-stabilized zirconia) supported YSZ electrolyte membrane was developed and used in the high-temperature electrochemical reduction of steam, CO2 and a mixture of steam-CO2. Effect of different operating parameters such as temperature, feed gas composition, and operating voltage on the performance of SEMR in a high steam and/or CO2 environment was investigated. Experiments were performed in the temperature range of 750–850°C with 20% H2–80% oxidant as a feed to the Ni–YSZ electrode and air to the LSM electrode. The electrochemical performance was investigated using the current density–voltage (i–V) curves and electrochemical impedance spectra (EIS). A high area-specific resistance (ASR) was observed in a fuel cell mode as compared to the electrolysis mode because of very low fuel content and consequently, a higher concentration polarization. At 850°C and 1.5V, a very high current density of −1.9A/cm2, −1.5A/cm2 and −1.2A/cm2 is observed for steam, steam-CO2 (co-electrolysis) and CO2 electrolysis respectively. The decrease in electrochemical performance with increasing CO2 content was found to be related to the mass transport limitation of the fuel electrode. An equivalent circuit model was used to fit the impedance data and separate the various polarization losses in the cell. EIS results showed that different performance limiting step is involved depending on the operating conditions. At low operating temperature and/or cell voltage, the polarization losses at LSM oxygen electrode contributed significantly to total ASR of the cell, whereas at high operating temperature and cell voltage, the concentration polarization at fuel electrode led to a decrease in the cell performance.

Coupling catalysis and electrocatalysis for hydrogen production in a solid electrolyte membrane reactor

This study reports the production of H2 via catalytic methane decomposition on Pt supported on yttria-stabilized zirconia together with its electrochemical regeneration in a solid electrolyte membrane reactor. Hence, a Pt-YSZporous/YSZ/Pt double-chamber solid electrolyte cell was prepared and tested under two reaction regimes. In the first regime, under open-circuit conditions, hydrogen and carbon are produced on the catalytically active Pt-YSZ porous catalyst via methane decomposition reaction (CH4 (g) → C (s)+2H2 (g)). In the second regime, under polarization conditions, steam is electrolyzed at the Pt cathode of the cell (H2O+2e−→H2+O2−) and the produced O2− ions were simultaneously electrochemically pumped to the Pt/YSZ porous catalyst (anode), thereby allowing removal of the previously deposited carbon (C (s)+O2−→CO2 (g)) and finally regenerating the Pt/YSZ porous catalyst film. We demonstrated that the carbon generated in the methane decomposition step serves as a depolarizating agent in the steam electrolysis process, thus decreasing the electrical energy input required for electrochemically producing pure H2. In addition, during the regeneration step, C2 hydrocarbons (e.g., ethane and ethylene) were obtained as a result of the electrocatalytic methane oxidative coupling on the Pt/YSZ porous catalyst film. The performance and durability of the system was also verified for long operation times in view of the possible practical application of this novel reactor configuration, which combines gas-phase catalysis and electrocatalysis for hydrogen production.

Electro-reduction of nitrogen oxides using steam electrolysis in a proton conducting solid electrolyte membrane reactor (H +-SEMR)

A double chamber SrCe 0.95Yb 0.05O 3 − a proton conducting membrane reactor was used in order to explore N 2O and NO cathodic reduction, over Pd cathodes, by hydrogen generated from steam electrolysis at the anode. Non-Faradaic enhancement of N 2O decomposition was observed at cathodic overpotentials, and |Λ| values above unity were achieved. Electrochemically transferred protons not only liberated the active sites from oxygen ad-atoms but also activated inactive, at open circuit, sites to adsorb and dissociate N 2O. In the NO-containing reactant mixtures the NO reduction rate was always negligible at open circuit since Pd was essentially inactive towards NO dissociation. Nevertheless, Pd became active at cathodic overpotentials, and |Λ| values equal to unity revealed a Faradaic enhancement according to the “decomposition” mechanism. In presence of C 3H 8 and O 2 data suggested a “reduction” type of mechanism.

Oxidative dehydrogenation of ethane in an electrochemical packed-bed membrane reactor: Model and experimental validation

Abstract A model was developed for the electrochemical oxidative dehydrogenation of ethane to ethylene in a solid electrolyte membrane reactor. Experimental data from the process with oxygen being supplied either electrochemically or gaseously were used in the model validation. In the model description, the converse axial distribution of the oxygen concentration in the reactor operated in the co-feed modus as well as in the electrochemical membrane modus was taken into account. The conversion of ethane and the selectivity to the desired product ethylene were well predicted with the model that included the kinetic equations based upon the Mars-van-Krevelen or the Langmuir-Hinshelwood mechanisms for investigations in the co-feed modus with gaseous dioxygen. This model was not directly applicable for the conditions of an electrochemical membrane reactor. The kinetics of the oxygen reduction on the cathode, the transfer of oxygen ions from the cathode to the anode, as well as the formation of the gaseous dioxygen on the anode, were therefore included in the model. Furthermore, the model for the electrochemical operation was extended by two additional side reactions that describe the electrochemically induced oxidation of the intermediate ethylene. After this, the experimental data measured in the temperature range of 540–620 °C agreed well with the predictions of the extended model.

Propene partial oxidation over Au–Ag Alloy and Ag catalysts using electrochemical oxygen

The partial oxidation of propene over Au–Ag alloy (14 mol%) and monometallic Ag supported over a dense Solid Electrolyte Membrane Reactor (SEMR) was studied and compared under electro-catalytic reaction conditions. Two partial oxidation products, namely acrolein and 1,5-hexadiene, in addition to carbon dioxide were detected. It was observed that the Au–Ag alloy was more selective towards acrolein formation, possibly promoted by oxygen adsorbed molecularly on exposed Ag surfaces whereas 1,5-hexadiene formation is promoted by oxygen species adsorbed atomically on silver surfaces. Taking into account that gold has no ability to dissociate molecular oxygen, and that acrolein and 1,5-hexadiene were not observed under open circuit conditions it is suggested that oxide ions are reduced at the triple phase boundary to form an active oxygen species which spills onto the catalyst surface to react with adsorbed propene. Differences in selectivity can only be explained by a difference in oxygen type and surface population of the catalysts based, for example, on a sufficiently large change in the work function of the catalysts.

Hydrogen Production in Solid Electrolyte Membrane Reactors (SEMRs)

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Methane Conversion to C2 Hydrocarbons in Solid Electrolyte Membrane Reactors

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Steady-state and forced-periodic operation of solid electrolyte membrane reactors for selective oxidation of [formula omitted]-butane to maleic anhydride

Experimental results obtained with a bilayer-solid electrolyte membrane reactor (bilayer-SEMR) are analysed based on a 1D+1D reactor model and attainable yields in steady-state and forced-periodic operation modes are determined. Optimal steady-state operation conditions are predicted in the range of high Damköhler numbers and oxidizing conditions. Forced-periodic operation of bilayer-SEMRs, which is easily established via the electric current, leads to a significant selectivity enhancement, but has to be critically rated with respect to energy expenses needed under electrochemical-oxygen-pumping conditions.

Hydrogen production in solid electrolyte membrane reactors (SEMRs)

In the present work, the prospects and trends of solid electrolyte membrane reactors (SEMRs) towards hydrogen production, are discussed. Initially, an overview of the principles, the properties and the techniques related to the usage of the SEMRs, are presented. In the following, a literature survey covering earlier and recent developments of the various methods (e.g. reforming or partial oxidation or dehydrogenation of hydrocarbons, steam electrolysis) employed in the SEMRs for the production of hydrogen, is performed. Finally, the current status of this research field is analyzed and future research topics are proposed.

Methane conversion to C2 hydrocarbons in solid electrolyte membrane reactors

Solid electrolyte membrane reactors (SEMRs) have been used to both study and influence catalytic reaction rates. Methane coupling is the reaction most thoroughly and intensively studied in these membrane reactors. In the last 20 years, oxygen ion (O2−), proton (H+) and mixed (O2−-e−, H+-e−) conducting membranes have been tested in order to maximize the conversion of methane to C2 compounds. The present review contains the fundamental operating principles of the various SEMR types and their applications in this reaction. The difficulties that should be overcome in order to promote this SEMR process to an industrial scale are discussed.

Partial Oxidation of n-Butane in a Solid Electrolyte Membrane Reactor: Influence of Electrochemical Oxygen Pumping

The partial oxidation of -butane to maleic anhydride (MA) in a solid electrolyte membrane reactor was studied in three different operation modes: electrochemical membrane reactor (EMR), cofeed membrane reactor (CR), and mixed-feed membrane reactor (MMR). The EMR operation exhibited lower selectivity to MA but higher conversion of oxygen than the CR operation. The electrochemical oxygen pumping in the MMR operation led to decrease in the MA selectivity compared to the CR operation. By means of comparing the three operation modes, the electrochemically pumped oxygen was found to be more reactive but less selective to MA than gas-phase oxygen, which is directly related to the different reaction mechanisms between the CR and EMR operations. The butane oxidation occurred in the EMR involved not only the same catalytic reaction mechanism as in the CR but also an electrocatalytic reaction. A simplified catalytic and electrocatalytic reaction-mechanism scheme was proposed for the butane oxidation carried out in the EMR.

Solid Electrolyte Membrane Reactors: Status and Trends

AbstractFor Abstract see ChemInform Abstract in Full Text.

Solid electrolyte membrane reactors: Status and trends

A survey of recently published research work on solid electrolyte (SE) membrane reactors is given, with focus on high-temperature oxygen ion conductors, high-temperature proton conductors and low-temperature proton conductors. In these three material classes, the current status and the future trends of membrane reactor development are briefly elucidated. SE membrane reactor principles are realized in gas sensors, fuel cells, electrolyzers and reactors for partial oxidation. In all these fields SE membranes are in contact with porous electrolyte layers at which anodic or cathodic electrochemical reactions take place. In the area of membrane reactors using high-temperature oxygen ion conductors, there is a trend towards lower operating temperatures on order to ensure stable long-term operation of the membrane materials, and to match the optimal temperature window of the applied catalysts. As a younger generation of ion conducting ceramics, high-temperature proton conductors offer new possibilities for the implementation of electrochemical membrane reactors. Finally, current trends in the application of low-temperature proton conductors being based on polymeric materials are discussed. These materials can not only be used for fuel cells but also as membranes in hydrogenation or oxidation reactors.

Solid electrolyte membrane reactor for controlled partial oxidation of hydrocarbons: Model and experimental validation

A mathematical model of a solid electrolyte membrane reactor is presented which accounts for the prevailing physical phenomena of the electrochemical partial oxidation of n-butane to maleic anhydride. From an analysis of characteristic dimensionless numbers it was concluded that the reactor behaviour can be described by a one-dimensional pseudo-homogeneous approach with respect to the anodic gas channel and a one-plus-one-dimensional electrochemical model. Beside mass and charge transport processes, electrochemical charge transfer reactions as well as heterogeneously catalysed oxidation reactions are considered. As kinetic model a modified Mars–van Krevelen approach is suggested. Experimental results of oxygen pumping and butane oxidation experiments were used to determine kinetic parameters and to validate the model.

Partial oxidation of n-butane in a solid electrolyte membrane reactor: Periodic and steady-state operations

An electrochemical membrane reactor using yttria-stabilized zirconia as a solid electrolyte membrane was applied to the selective partial oxidation of n-butane to maleic anhydride over a vanadium phosphorus oxide (VPO) catalyst. In this reactor, the oxygen required for anodic butane oxidation was generated by electrical oxygen pumping, i.e. by imposing an external current to the membrane reactor from anode to cathode. Periodic redox experiments, in which electrical oxygen pumping and butane oxidation were carried out sequentially, confirmed that the reduced activity of the VPO catalyst in the butane oxidation could be regenerated by electrical oxygen pumping. A series of steady-state experiments were carried out to assess the influence of operating conditions such as imposing current, reaction temperature, butane concentration and flow rate on the catalytic performance, where the electrochemical oxygen pumping and butane oxidation were performed simultaneously. The studied membrane reactor gave maleic anhydride yield of 10% with maleic anhydride selectivity up to 53% at reaction temperature of 753 K.

Fabrication of novel type solid electrolyte membrane reactors for exhaust gas purification

Three kinds of membrane reactors with different electrodes, LSCF, LSCF–GDC, and LSCF–Pt were fabricated for the purpose of application to a de-NOx device, and the electrocatalytic characteristic and NO decomposition behaviors of the reactors were investigated. Both the LSCF–GDC and LSCF–Pt composite electrodes seemed to have a better affinity against oxygen than LSCF. When electric current was applied to the membrane reactors, oxygen-gas reduction preferably occurred at the LSCF and composite electrodes rather than NO decomposition. Once oxygen in the reactant gas was completely pumped out from cathode to anode, the membrane reactors could decompose NO. The onset current for NO decomposition of the LSCF–Pt electrode was slightly lower than that required by the other two membrane reactors, which indicating that Pt shows better selectivity against NO than LSCF or LSCF–GDC electrode.

Solid-Electrolyte Membrane Reactors: Current Experience and Future Outlook

This review article covers the research work that has been conducted in solid-electrolyte membrane reactors (SEMR). An overview of the types of solid electrolytes and their applications in heterogeneous catalysis is first presented, followed by a survey of SEMR studies published until 1998. Earlier and recent developments are discussed. The technoeconomic aspects and the requirements to be met for further development into industrial practice are presented and discussed.