CO2 In Feed Gas Research Articles

Anionic and cationic co-doping to enhance the oxygen transport property of Bi0.5Sr0.5FeO3-δ as a high-performance air electrode for reversible solid oxide cells

Reversible solid oxide cells (RSOCs) have attracted considerable interest due to their efficient energy conversion. However, the low catalytic activity of air electrodes limits the application of RSOCs. Bi0.5Sr0.5Fe0.9Ta0.1O3-δ developed in our previous work exhibits a comparatively desirable performance and is expected to be further optimized. Herein, a novel strategy of anionic F and cationic Ta co-doped Bi0.5Sr0.5Fe0.9Ta0.1O3-δ-xFx (x = 0, 0.05, 0.10, 0.15, denoted as, BSFTF0, BSFTF5, BSFTF10, BSFTF15) materials are obtained to enhance the oxygen transport property of Bi0.5Sr0.5FeO3-δ for RSOCs. The polarization resistance (Rp) of BSFTF10 (0.017 Ω cm2) decreases by 66 % compared with that of BSFTF0 (0.051 Ω cm2) at 800 °C. In fuel cell mode, the single cell with BSTF10 reaches the maximum power density of 908 mW cm−2, which is approximately 72 % higher than the only Ta-doped BSFTF0 (527 mW cm−2) at 800 °C. In electrolysis mode, the single cell with BSFTF10 exhibits a high electrolysis current density of 1679 mA cm−2, indicating an approximately 90 % increase compared to that of BSFTF0 at 800 °C and 1.5 V with 70 % CO2-30 % CO feed gas. The bulk chemical diffusion (Dchem) of BSFTF10 is up to 5.12 × 10−4 cm2 s−1, which is 4.3 times higher than that of BSFTF0. The superior oxygen transport property of BSFTF10 is attributed to the high electronegativity of F− (4.0) and low electronegativity of Ta5+(1.8), which may weaken the chemical bonding between B-site ions and O2−, generating more oxygen vacancies and accelerating the rate of oxygen transfer. The results indicate that F and Ta co-doping is an effective strategy to develop a highly catalytically active air electrode for RSOCs featuring oxygen transport properties.

3D printing of poly(ethyleneimine)-functionalized Mg-Al mixed metal oxide monoliths for direct air capture of CO2

Direct air capture (DAC) of CO2 plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies. Since large air flows are required to capture the ultradilute CO2 from the air, lab-synthesized adsorbents in powder form may cause unacceptable gas pressure drops and poor heat and mass transfer efficiencies. A structured adsorbent is essential for the implementation of gas-solid contactors for cost- and energy-efficient DAC systems. In this study, efficient adsorbent poly(ethyleneimine) (PEI)-functionalized Mg-Al-CO3 layered double hydroxide (LDH)-derived mixed metal oxides (MMOs) are three-dimensional (3D) printed into monoliths for the first time with more than 90% adsorbent loadings. The printing process has been optimized by initially printing the LDH powder into monoliths followed by calcination into MMO monoliths. This structure exhibits a 32.7% higher specific surface area and a 46.1% higher pore volume, as compared to the direct printing of the MMO powder into a monolith. After impregnation of PEI, the monolith demonstrates a large adsorption capacity (1.82 mmol/g) and fast kinetics (0.7 mmol/g/h) using a CO2 feed gas at 400 ppm at 25 °C, one of the highest values among the shaped DAC adsorbents. Smearing of the amino-polymers during the post-printing process affects the diffusion of CO2, resulting in slower adsorption kinetics of pre-impregnation monoliths compared to post-impregnation monoliths. The optimal PEI/MeOH ratio for the post-impregnation solution prevents pores clogging that would affect both adsorption capacity and kinetics.

Boosting CO2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen.

Herein, we propose an oxygen-containing species coordination strategy to boost CO2 electroreduction in the presence of O2. A two-dimensional (2D) conjugated metal-covalent organic framework (MCOF), denoted as NiPc-Salen(Co)2-COF that is composed of the Ni-phthalocyanine (NiPc) unit with well-defined Ni-N4-O sites and the salen(Co)2 moiety with binuclear Co-N2O2 sites, is developed and synthesized for enhancing the CO2RR under aerobic condition. In the presence of O2, one of the Co sites in the NiPc-Salen(Co)2-COF that coordinated with the intermediate of *OOH from ORR could decrease the energy barrier of the activation of CO2 molecules and stabilize the key intermediate *COOH of the CO2RR over the adjacent Co center. Besides, the oxygen species axially coordinated Ni-N4-O sites can favor in reducing the energy barrier of the intermediate *COOH formation for the CO2RR. Thus, NiPc-Salen(Co)2-COF exhibits high oxygen-tolerant CO2RR performance and achieves outstanding CO Faradaic efficiency (FECO) of 97.2 % at -1.0 V vs. the reversible hydrogen electrode (RHE) and a high CO partial current density of 40.3 mA cm-2 at -1.1 V in the presence of 0.5 % O2, which is superior to that in pure CO2 feed gas (FECO=94.8 %, jCO=19.9 mA cm-2). Notably, the NiPc-Salen(Co)2-COF achieves an industrial-level current density of 128.3 mA cm-2 in the flow-cell reactor with 0.5 % O2 at -0.8 V, which is higher than that in pure CO2 atmosphere (jCO=104.8 mA cm-2). It is worth noting that an excellent FECO of 86.8 % is still achieved in the presence of 5 % O2 at -1.0 V. This work provides an effective strategy to enable the CO2RR under O2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO2 electroreduction.

Boosting CO2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen

AbstractHerein, we propose an oxygen‐containing species coordination strategy to boost CO2 electroreduction in the presence of O2. A two‐dimensional (2D) conjugated metal‐covalent organic framework (MCOF), denoted as NiPc‐Salen(Co)2‐COF that is composed of the Ni‐phthalocyanine (NiPc) unit with well‐defined Ni−N4−O sites and the salen(Co)2 moiety with binuclear Co−N2O2 sites, is developed and synthesized for enhancing the CO2RR under aerobic condition. In the presence of O2, one of the Co sites in the NiPc‐Salen(Co)2‐COF that coordinated with the intermediate of *OOH from ORR could decrease the energy barrier of the activation of CO2 molecules and stabilize the key intermediate *COOH of the CO2RR over the adjacent Co center. Besides, the oxygen species axially coordinated Ni−N4−O sites can favor in reducing the energy barrier of the intermediate *COOH formation for the CO2RR. Thus, NiPc‐Salen(Co)2‐COF exhibits high oxygen‐tolerant CO2RR performance and achieves outstanding CO Faradaic efficiency (FECO) of 97.2 % at −1.0 V vs. the reversible hydrogen electrode (RHE) and a high CO partial current density of 40.3 mA cm−2 at −1.1 V in the presence of 0.5 % O2, which is superior to that in pure CO2 feed gas (FECO=94.8 %, jCO=19.9 mA cm−2). Notably, the NiPc‐Salen(Co)2‐COF achieves an industrial‐level current density of 128.3 mA cm−2 in the flow‐cell reactor with 0.5 % O2 at −0.8 V, which is higher than that in pure CO2 atmosphere (jCO=104.8 mA cm−2). It is worth noting that an excellent FECO of 86.8 % is still achieved in the presence of 5 % O2 at −1.0 V. This work provides an effective strategy to enable the CO2RR under O2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO2 electroreduction.

Coke formation pathway under various reaction conditions during the production of syngas in a dielectric barrier discharge plasma environment using CeO2 nanorods supported Ni catalysts

Plasma-assisted dry reforming of methane (DRM) was investigated using CeO2 nanorods (NR) supported Ni catalysts in a fixed-bed coaxial dielectric barrier discharge (DBD) reactor. This study individually examined the catalyst support, packing material, and 10 wt% Ni-CeO2 NR catalyst under pure thermal and plasma-assisted thermal DRM environments to explore the plasma-thermal synergy. Support and packing material displayed no discernible reactivity under thermal DRM within 450 °C; however, the catalyst exhibited reactivity beginning around 350 °C. Alternatively, plasma-assisted DRM experiments revealed a distinct reaction occurrence at significantly lower temperatures across all sample types. Introducing plasma demonstrated a significant enhancement in CH4 conversion compared to CO2 conversion. The 10 wt% Ni-CeO2 NR catalyst in plasma-assisted DRM testing showed increasing conversions of CH4 and CO2 with rising temperatures, peaking at 52.1 % and 46.1 %, respectively, at 450 °C. The catalyst’s improved performance in the plasma environment can be attributed to the enhanced metal-support interaction between NiO and the CeO2 NR support, a consequence of the rich surface oxygen vacancy concentration. However, this increase in conversion was accompanied by an escalation in carbon deposition. Considering contributions from the thermal DRM process, the optimal operating temperature was determined as 350 °C. Increasing plasma power at this temperature led to enhanced conversion. However, beyond a threshold of 23.8 W power, the reaction path altered, resulting in reduced syngas output. Increasing the CH4:CO2 feed gas flow ratio, while maintaining constant plasma power and temperature, elevated H2/CO generation. Moreover, increasing the total flow rate under identical conditions, with a constant feed gas flow ratio, reduced both conversions due to decreased chemical residence time. Consequently, under a constant feed gas ratio, a higher syngas yield is achievable with lower overall flow rates.

Low-Temperature Plasma-Assisted Catalytic Dry Reforming of Methane over CeO2 Nanorod-Supported NiO Catalysts in a Dielectric Barrier Discharge Reactor.

Nonthermal plasma (NTP)-assisted catalytic dry reforming of methane (DRM) is considered a powerful single-stage reaction mechanism because of its ability to activate normally stable CO2 and CH4 at a low temperature under ambient conditions. The thermodynamic barrier of DRM requires a high operating temperature (>700 °C), which can be reduced by nonequilibrium plasma. Herein, we present a method for the wet-impregnation synthesis of CeO2 nanorod (NR)-supported 5 and 15 wt % NiO catalysts for efficient NTP-promoted DRM with an applied power in the range of 24.9-25.8 W (frequency: 20 kHz), a CH4:CO2 feed gas ratio of 100:250 sccm, and a total flow rate of 350 sccm. The presence of NTP dramatically increased the reaction activity, even at 150 °C, which is usually inaccessible for thermally catalyzed DRM. The CH4 and CO2 conversion reaches a maximum of 66 and 48%, respectively, at 500 °C with the 15 wt % NiO/CeO2 NR catalyst, which are much higher than the values obtained for the 5 wt % NiO/CeO2 NR catalyst under the same conditions. According to the X-ray photoelectron spectroscopy profile for 15 wt % NiO/CeO2 NR, a higher concentration of NiO on CeO2 increases the proportion of Ce3+ in the catalyst, suggesting enhanced oxygen vacancy concentration with an increased amount of NiO loading. Additionally, a higher NiO loading promotes a higher rate of replacement of Ce4+ with Ni2+, which generates more oxygen vacancies due to the induced charge imbalance and lattice distortion within the CeO2 lattice. As a result, it can be inferred that the incorporation of Ni ions into the CeO2 structure resulted in inhibited growth of CeO2 crystals due to the creation of a NixCe1-xO2-α solid solution and the production of oxygen vacancies.

Plasma-assisted CO2 and N2 conversion to plant nutrient

Colossal research on CO2 and N2 conversion using non-thermal plasma (NTP) technology has been ongoing since many years. The primary focus is on CO and NH3 production through CO2 and N2 conversion, respectively, with high conversion efficiency and low energy consumption with or without catalysts. Although in the present study, we propose that the NTP can assist in converting CO2 and N2 to plant nutrients in the form of plasma-treated/activated water. We used a homemade streamer plasma device and produced plasma-activated water (PAW) using CO2 and N2 feed gas, CO2-activated water (CAW) and N2-activated water (NAW). Later, we used CAW and NAW to treat the radish seeds and evaluate the germination rate, germination percentage, and seeding growth. To understand the chemical changes in PAW after the NTP treatment, we performed a chemical analysis to detect NO2¯, NO3¯, NH4+, and H2O2 along with the PAW pH and temperature shift. Additionally, to understand the other species produced in the gas phase, we simulated chemical reactions using COMSOL Multiphysics® software. Our results show that NOx and NHx species are less produced in CAW than in NAW, but CO2-generated PAW offers a significantly more substantial effect on enhancing the germination rate and seeding growth than NAW. Therefore, we suggested that CO and H2O2 formed during CAW production trigger early germination and growth enhancement. Furthermore, the total plasma reactor energy consumption, NO3¯ and NH4+ selective production percentage, and N2 conversion percentage were calculated. To our best knowledge, this is the first study that uses plasma-assisted CO2 conversion as a nutrient for plant growth.

Effect of Y0.25Bi0.75O1.5 electrolyte composite on the performance of La1.4Bi0.1Sr0.5Ni0.5Mn0.5O4+δ air electrode for solid oxide electrolysis cells

In the present study, in order to further improve the electrochemical performance of La1.4Bi0.1Sr0.5Ni0.5Mn0.5O4+δ (LBSNM) air electrode for solid oxide electrolysis cells (SOECs), Y0.25Bi0.75O1.5 (YSB) electrolyte composite for LBSNM (LBSNM-xYSB, x = 0, 20, 30, 40 wt%) air electrode is systematically investigated to obtain the optimal performance. The effect of sintering temperature on the microstructure and polarization impedance (Rp) of the air electrode is also examined. Among the samples with different YSB contents, the half cell with LBSNM-30YSB composite electrode exhibits the lowest Rp value of about 0.041 Ω cm2 at 800 °C, which is 88.1% lower than that of LBSNM electrode. The single cell with LBSNM-30YSB air electrode obtains a current density as high as 1188 mA cm−2 at 800 °C and 1.4 V for 70%CO2+30%CO feed gas; this value is 46.5% higher than that of LBSNM under the same conditions. No degradation is observed after the single cell is operated continuously at 1.4 V for 50 h at 800 °C, indicating its relatively good long-term stability. Thus, LBSNM-30YSB is a potential air electrode for SOECs.

Utilizing fly ash from a power plant company for CO2 capture in a microchannel

The separation of carbon dioxide by mineral waste with alkaline properties is an innovative technology for storing carbon dioxide. This experiment utilized an aqueous solution containing seawater and fly ash in a microchannel to investigate CO2 absorption. In all experiments, the concentration of CO2 in feed gas was 10.5% at atmospheric pressure. A number of variables were examined, including temperature (10–50 °C), inlet solvent flow rate (50–300 ml/h), inlet gas flow rate (50–250 ml/min), as well as fly ash to seawater ratios (1:25, 1:50, 1:75, 1:100, 1:125,1:150, 1:175 and 1:200 gr/ml). The study found that an increase in the concentration of fly ash in the solution and a higher flow rate of the solvent led to a noteworthy improvement in both the absorption percentage and volume transfer coefficient of gas-based gas. The increase in gas flow rate led to a decrease in the percentage of CO2 removal and an increase in the gas-based volumetric mass transfer coefficient. Under optimal operating conditions, absorption percentages were 96.25% and gas-based volumetric mass transfer coefficients were 63.21 (kmol h −1m−3 kPa−1) were achieved even though the temperature in the range of (10–50 °C) has a negative impact on the absorption rate. According to the overall gas-based volumetric mass transfer coefficient, microchannel reactors provide higher absorption efficiency than other mass transfer devices.

Is Direct DME Synthesis Superior to Methanol Production in Carbon Dioxide Valorization? From Thermodynamic Predictions to Experimental Confirmation

CO2 valorization is a key measure to reach climate neutrality. Thermodynamics suggest direct conversion of CO2 into dimethyl ether (DME) to have greater potential than the indirect route via methanol synthesis, followed by purification of methanol and then a separate dehydration into DME. In this work, we introduce heteropoly acids as a capable class of dehydration catalysts for direct DME synthesis from CO2 and H2. To clarify if direct DME synthesis is in fact superior to sole MeOH synthesis, accurate thermodynamic equilibrium calculations are performed and pose as the base of our argumentation. An efficient Cu/ZnO/ZrO2 (CZZ) methanol catalyst is used to compare the methanol synthesis using a feedstock with stoichiometric CO2/3H2 mixture against bifunctional catalysts, containing CZZ and a dehydration component. The dehydration components include a commercial ferrierite (FER) and heteropoly acid (HPA) coated alumina and zirconia. For direct DME synthesis, the CO2 feed gas at gas hourly space velocities (GHSVs) between 1,250 and 158,400 NL kgcat–1 h–1, at temperatures of 210–270 °C and 40 bar pressure, was investigated. Based on the wide parameter window investigated, the following can be concluded at 250 °C: under a thermodynamic regime, CO2 conversion is close to the theoretical limit (30%exp/32%theo) and the direct DME synthesis is superior to sole methanol synthesis (+20%exp/+33%theo). The amount of valuable products (methanol, DME) profits significantly more (+70%exp/+88%theo) from the direct DME synthesis than CO2 conversion indicates. Under a kinetic regime, HPA-coated catalysts show superior apparent activation energies for DME production than the widely used ferrierite (HPA: 45 kJ mol–1/FER: 80 kJ mol–1), making HPA coatings a great option for highly capable dehydration catalysts under CO2- and water-rich conditions.

Toward a Stackable CO2-to-CO Electrolyzer Cell Design─Impact of Media Flow Optimization

Aqueous CO2-to-CO electrolysis is a promising technology for closing the carbon cycle and defossilizing industrial processes. Considering the technological readiness, consensus has been achieved about using silver as a stable and selective electrocatalyst for the CO2-to-CO reduction reaction in aqueous electrolyte. On the other hand, challenges such as media flow management, component stability, and force distribution are still associated with improving the process performance and developing a stackable cell concept to meet industrially relevant levels. We therefore report on a promising stack concept with continuous flowcells operated with gas diffusion electrodes (GDEs). To enhance the CO2-to-CO conversion efficiency, dedicated media flow chambers were developed on two levels. In the gas chamber, which touches the GDE from the far side of the anode, the feed gas flow and distribution over the GDE were controlled by introducing various gas path architectures in a modular flowcell. In addition, an ionically conductive spacer was implemented in the catholyte chamber, which is adjacent to the opposite side of the GDE. The effect of these modifications on the cell voltage, selectivity, and overall conversion was investigated at 100 mA/cm2 with varying CO2 feed gas flow and concentration. Noteworthy, an optimized feed gas distribution generated an increase of the Faraday efficiency for CO under reduced CO2 supply. Furthermore, the implementation of the spacer enhanced the process stability by suppressing gas-bubble-induced noise in the cell voltage measurements. By functioning as support structures to the GDE, the combined modifications provided the cell with mechanical integrity and allowed an ionic and electric contact over the full active cell area, which is required for both stacking and upscaling of the cell. The corresponding performance was demonstrated by a two-cell short-stack.

Highly active Pt/In2O3-ZrO2 catalyst for CO2 hydrogenation to methanol with enhanced CO tolerance: The effects of ZrO2

The supported Pt catalyst is normally not active for CO2 hydrogenation to methanol at the presence of CO. Herein, ZrO2 is added into Pt/In2O3 for CO2 hydrogenation to methanol with CO as a co-feed gas. High activity with enhanced CO tolerance is achieved on Pt/In2O3-ZrO2. For example, the space-time yield of methanol reaches 0.569 gmethanol gcat−1 h−1 at 300 °C and 5 MPa under feed gas containing 4% CO of 21,000 cm3·h−1·gcat−1. With the addition of ZrO2, a stronger electron transfer occurs between Pt and the In2O3-ZrO2 solid solution support. This leads to weaker CO adsorption, which suppresses over-reduction of In2O3 and enhances CO tolerance of the Pt catalyst. The oxygen vacancy of In2O3 modified by ZrO2 promotes CO2 activation. The synergy between Zr-modified oxygen vacancy (In-Ov-Zr) and Pt catalyst facilitates methanol synthesis from CO2 hydrogenation via formate route. This is different from Pt/In2O3, which takes CO hydrogenation route.

Granulation of alkaline metal nitrate promoted MgO adsorbents and the low-concentration CO2 capture performance in the fixed bed adsorber

Magnesium-based adsorbents with the modification of alkaline metal salts are considered the competitive candidates for CO2 capture at intermedium temperature. In this article, the NaNO3 promoted MgO adsorbents were prepared and granulated, and the characterization methods were used to detect the microstructure of the granular adsorbents, including NaNO3 distribution, BET specific surface area, micropore size and microcrystal aggregation. The thermogravimetric analyzer (TGA) tests were carried out to investigate the optimal CO2 adsorption and desorption temperatures and the cyclic stability of the NaNO3 promoted MgO granules. Moreover, the pretreatment of carbonization and calcination was adopted to improve the cyclic stability of the granular adsorbents. Furthermore, the fixed bed adsorber with 40 g NaNO3-MgO granules was used to capture CO2 from 50% CO2 mixture gas with N2 and from 20% CO2 mixture gas with N2, respectively, and the CO2 breakthrough behaviors in the fixed bed were investigated. It was found that NaNO3-MgO adsorbents were suitable for the middle and high-concentration CO2 capture (such as 50% CO2 feed gas) in fixed bed adsorber with the higher CO2 recovery efficiency, but the CO2 recovery efficiency was lower for the low-concentration CO2 capture (such as 20% CO2 feed gas) at ordinary pressure. Because about 10 kPa CO2 partial pressure in the gas phase was needed to overcome CO2 mass transfer resistance in the molten salt layer on MgO surface during adsorption, the appropriate pressurization would improve the low-concentration CO2 capture efficiency in the fixed bed adsorber.

Performance of Multilayer Composite Hollow Membrane in Separation of CO2 from CH4 in Mixed Gas Conditions.

Composite membranes comprising NH2-MIL-125(Ti)/PEBAX coated on PDMS/PSf were prepared in this work, and their gas separation performance for high CO2 feed gas was investigated under various operating circumstances, such as pressure and CO2 concentration, in mixed gas conditions. The functional groups and morphology of the prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). CO2 concentration and feed gas pressure were demonstrated to have a considerable impact on the CO2 and CH4 permeance, as well as the CO2/CH4 mixed gas selectivity of the resultant membrane. As CO2 concentration was raised from 14.5 vol % to 70 vol %, a trade-off between permeance and selectivity was found, as CO2 permeance increased by 136% and CO2/CH4 selectivity reduced by 42.17%. The membrane produced in this work exhibited pressure durability up to 9 bar and adequate gas separation performance at feed gas conditions consisting of high CO2 content.

Bi-doped La1.5Sr0.5Ni0.5Mn0.5O4+δ as an efficient air electrode material for SOEC

Bi-doped La1.5-xBixSr0.5Ni0.5Mn0.5O4+δ (LBSNM-x, x = 0, 0.05, 0.1, 0.15) was investigated as a potential air electrode for solid oxide electrolysis cell (SOEC). The effect of Bi doping on the structure, electrical conductivity, chemical compatibility with GDC electrolyte, electrochemical performance and thermal expansion coefficients (TECs) were investigated. XRD characterization results show that the solid solution content of Bi is less than or equal to 0.1. XPS characterization results indicate that Bi doping increases the oxygen vacancy content of LBSNM-x air electrode and thus greatly benefits its oxygen evolution reaction. Among the Bi-doped samples, LBSNM-0.1 electrode has the best electrochemical performance with its lowest Rp (polarization resistance) of 0.28 Ω cm2 at 800 °C based on LBSNM-0.1/GDC half-cell. LBSNM-0.1 single cell with 70%CO2 + 30%CO fuel gas feed on the fuel electrode has achieved current density of 811 mA cm−2 at 800 °C and 1.4 V, a 62.2% increase relative to that of LSNM single cell. In addition, LBSNM-0.1 single cell exhibits excellent stability at 800 °C and 1.3 V with 70%CO2 + 30%CO feed gas on the fuel electrode. These results prove that Bi-doped LBSNM-0.1 is an efficient air electrode for SOEC.

Chemical looping co-conversion of CH4 and CO2 using Fe2O3/Al2O3 pellets as both oxygen carrier and catalyst in a fluidized bed reactor

Chemical looping reforming of CH4 (CH4-CLR) is a safe and efficient CH4 upgrading technology for syngas production. The Fe2O3-based oxygen carriers (OCs) possess a higher potential for CH4-CLR among so many transition metal oxides as high syngas selectivity can be obtained from partial CH4 oxidation by OCs with the step-by-step reduction of Fe3+/Fe2+ to Fe0. However, the impurity CO2 in CH4-source feed gas, when using Fe2O3-based OCs, often causes the inhibition of reaction between CH4 and OCs resulting in no partial CH4 oxidation to syngas. The present work has employed the Fe2O3/Al2O3 pellets as OCs with introducing the fully reduced same pellets as a catalyst in a bubbling fluidized-bed reactor to eliminate the inhibition effect of CO2 during CH4-CLR. It has been demonstrated that the Fe species with low valent, e.g., Fe0, in the catalyst can effectively catalyze the dry CH4 reforming. Thus, the CO2 has been consumed before contacting with Fe2O3-based OCs and the inhibition effect of CO2 has been eliminated. Meanwhile, both CO2 and CH4 can be converted to syngas in the reducer leading to an opportunity for CO2 utilization. With the help of the catalyst of reduced OCs, not only the CO2 in the feed gas but also that formed from full CH4 oxidation by Fe2O3/Al2O3 at the early CH4 reforming stage is converted into syngas of CO and H2. Semi-continuous cyclic CH4-CLR test has demonstrated the good stability of both Fe2O3/Al2O3 OC and counterpart catalyst, which suggests the potential of such OC/catalyst pair in practical applications.

Ni/CGO-Based Electrolyte-Supported Cells During Co-Electrolysis: The Role of Feed Gas Impurities

The electrochemical generation of syngas via simultaneous co-electrolysis of steam and CO2 in high temperature solid oxide cells and its consecutive catalytic upgrade has attracted growing interest over recent years since this pathway offers a sustainable route to the production of synthetic fuels. However, most solid oxide cell technologies have been developed for durable and efficient fuel cell operation and thus, their use in electrolysis mode leads to the emergence of different lifetime-limiting degradation mechanisms. For instance, strongly cathodic polarization of the cermet fuel electrode leads to irreversible Ni migration away from the electrode/electrolyte interface. Furthermore, carbon deposition can become an issue when local non-equilibrium, carbon monoxide-rich gas phase compositions are formed. All of these mechanisms have been shown to be particularly harmful in Ni/YSZ-based fuel-electrode supported cells. Ni/Gadolinium-doped ceria (CGO) electrodes offer a potentially promising alternative to alleviate these issues due the intrinsic high electro-catalytic activity and carbon mitigating effect of the ceria phase. Furthermore, the higher operating temperatures commonly used for electrolyte-supported cell (ESC) architectures may mitigate carbon deposition and impurity adsorption due to thermodynamic considerations. In addition, the thinner electrodes employed in ESC could help to avoid the formation of CO-rich gas phases at the electrode/electrolyte interface due to enhanced porous diffusion and thus, further prevent coking. With regards to durability of the reactor, the purity of the feed gases steam and CO2 becomes of great importance.In the present study durability aspects of industrial Ni/CGO-based ESC are investigated in co-electrolysis mode under various operating conditions by means of current-voltage characteristics and electrochemical impedance spectroscopy. Durability was evaluated at different current densities for times of >=1500 h. Post-mortem analysis was carried out with scanning electron microscopy (SEM) to correlate the observed degradation phenomena with microstructural changes, particularly Ni migration. It is shown that the steam inlet gas has to be carefully purified to avoid the deposition of silica in the fuel electrode. Furthermore, electrochemical measurements performed in dry CO2 electrolysis demonstrate that sulfur impurities in the CO2 feed gas must be removed to achieve low degradation rates.

Improving the accuracy of the Eyring equation by pseudo‐ideal solution model to predict the viscosity of the mono‐ethanol amine‐[Bmim] PF6 ionic liquid blends in a CO2 capturing pilot plant

AbstractThe purpose of the present study was to propose a new simulation model for calculation of the viscosity of the mono‐ethanol amine‐ionic liquid (MEA‐IL) solvent in the CO2‐capturing pilot plant. To do so, a combination of the pseudo‐ideal solution model (PISM) and Eyring's mixture viscosity equation was implemented in MATLAB. Moreover, the various thermodynamic models were used to calculate viscosity, using solvent containing MEA‐IL in the high CO2 feed gas. The present study determined the viscosities of the MEA‐IL blends at different concentrations and various temperatures in the CO2 capturing pilot plant. The results were comparable to those obtained from the Eyring‐PISM model, Eyring‐Wilson method, Cheng and Meisen a previous study equation, and the Aspen Plus and Promax with electrolyte non‐random two‐liquid model that presented the actual viscosity values of the liquid solutions. The calculated solvent viscosity values with the Eyring‐PISM model at different temperature profiles were achieved using an average absolute deviation (AAD) of about 1.164% and 1.422% in absorber and desorber for solvent (MEA = 27 wt% and IL = 34.2 wt%) and 1.578% and 1.868% in absorber and desorber for solvent (MEA = 29 wt% and IL = 37.12 wt%), respectively. The consideration of a suitable model for the determination of viscosity has a significant role in energy consumption in the CO2‐capturing pilot plant. The estimated energy consumption with the Eyring‐PISM model was achieved using an AAD of about 0.652% for solvent (MEA = 27 wt% and IL = 34.2 wt%) and 0.502% for solvent (MEA = 29 wt% and IL = 37.12 wt%), respectively. The results obtained from the Eyring‐PISM simulation model using the experimental data revealed a high degree of accuracy.

Design of absorption process for CO2 capture using cyano based anion ionic liquid

Ionic liquids are regarded as potential candidate for CO2 absorption because of their tunable properties, wide liquid range, negligible vapor pressure and their high CO2 solubility. This work aimed to study the feasibility of CO2 separation from gas containing methane and carbon dioxide using a cyano based anion ionic liquid “1-hexyl-3-methylimidazolium tetracyanoborate” [hmim][TCB] as physical absorbent due to its high CO2 capacity and its low viscosity comparing to the organic solvent DEPG called Selexol. A comparative study among different proposed case studies for CO2 absorption in the both cases of solvent has been carried out to improve the performance of the separation process. Results show that for feed gas containing between 20 and 40mol.% of CO2, it is well favorable to use the IL instead of DEPG. At 5mol.% of CO2 in feed gas it was found that lower solvent flow rate is required for the absorption with [hmim][TCB] than DEPG and the solvent can be regenerated by combining both the pressure and temperature swing process.

Effect of CO2 Concentration and Liquid to Gas Ratio on CO2 Absorption from Simulated Biogas Using Monoethanolamine Solution

In industrial scale, removal of CO2 by chemical absorption from raw biogas represents an imperative treatment and the cutting-edge technology towards improvement of its quality and heat value. In this work, CO2 absorption studies were conducted in an absorption column packed with Sulzer metal gauze packing with simulated biogas absorbed using 30 wt. % of monoethanolamine (MEA) solution. Experimental works were conducted to determine the influence of different CO2 concentrations in feed gas (30 % and 40 %) and L/G ratio (0.6 and 0.7) and subsequently assessed in terms of CO2 absorption efficiency along the column. The results showed that 30 % CO2 in feed gas has higher removal efficiency as compared to 40 % CO2 with the ability to remove 94 % CO2 during the process. In addition, the CO2 absorption studied on the L/G ratio proved that CO2 removal was improved at higher L/G ratio of 0.7.