Chemical Looping Research Articles

CeO2 enhanced performance of NiFe2O4-CaO for carbon capture and in-situ hydrogenation conversion to CO

NiFe2O4 exhibits excellent redox properties and is widely applied in CaO-NiFe2O4 chemical looping processes. However, rapid sintering of Ni-Fe alloy under reaction conditions limited its industrial applications. The CeO2-NiFe-CaO were synthesized through a physical mixing method with NiFe2O4 as a precursor, and its CO2 capture capacity and in-situ hydrogenation performance were conducted on ICCC-RWGS reaction under different conditions. 20CeO2-NiFe-CaO exhibited a CO yielding of 9.35 mmol/g at 650 °C. During the carbon capture stage, CO2 was adsorbed by CaO, leading to the formation of CaCO3. In the hydrogenation conversion stage, hydroxyl groups were generated on the surface, combining with CaCO3 to produce formate species, further generating H2O and CO. 15CNF-CaO exhibited superior cyclic ICCC-RWGS reaction performance compared to 15NF-CaO, with a CO yield of 1.88 mmol/g after 40 cycles. CeO2 inhibited the sintering of catalytic components, preserving a higher specific surface area and smaller particle size. Furthermore, CeO2 in 15CNF-CaO inhibited carbon deposition and enhanced in-situ hydrogenation performance, exhibiting better CaO regeneration capability and better cyclic stability. These results could provide insight for designing the DFMs for the ICCC-RWGS process.

From lab to industry: Scaling-up Fe-Ni bimetallic nano oxygen carrier for mid-temperature methane chemical looping reforming

Chemical looping methane reforming has emerged as a promising avenue to produce blue hydrogen. Currently, satisfactory CH4 conversion and H2 productivity typically requires reaction temperature above 800 °C, bringing challenges for industrial reactor design and energy conservation. To realize high chemical looping methane reforming performance at low temperature, a Fe-Ni bimetallic nano oxygen carrier was presented, along with the workflow and platform for scaled-up synthesis of the oxygen carrier. On account of the synergy of nanoscale Fe-Ni species, the operating temperature could be lowered to 500–600 °C. The lab-scale oxygen carrier converted >90 % CH4 and produced 3.5 H2 per CH4 molecule with 80–82 % outlet H2 purity at 575–600 °C. The 10-kg scale synthesized oxygen carrier powder exhibited >90 % CH4 conversion, >78 % H2 purity and produced 2.8–3.5 H2 per CH4, with performance penalty from scaling up controlled within 5 %. After shaping and calcination, the 10-kg oxygen carrier beads still produced 2.8 H2 from per CH4 molecule with >70 % H2 purity. Longevity test revealed the 10-kg powder and beads as stable in phase, morphology, and redox activity over 110 cycles. Experiments of variable operating conditions found that the 10-kg oxygen carriers can meet industrial requirements of H2 production at >550 °C, with low steam/carbon ratio favored by 10-kg beads. Further analysis attributed the performance distinction of 10-kg beads to its lower surface area, reduction extent and steam affinity, compared to those of the lab-scale and 10-kg powders. These findings contributed to the mid-temperature chemical looping methane reforming by bridging laboratory practices and industrial application.

Effect of pyrolysis parameters on the biochar reactivity in the N-absorption reaction of chemical looping ammonia generation

Biochar from slow pyrolysis was applied to Chemical Looping Ammonia Generation (CLAG) to avoid the preparation of ammonia from fossil fuels and relatively expensive H2. The effects of pyrolysis atmosphere, temperature, heating rate, and residence time on the biochar reactivity in the N-adsorption reaction were investigated. The relationship between specific surface area, average pore diameter, micropore percentage, and disorder degree of biochar on reactivity was evaluated by simple and multiple linear regression and Analysis of Variance (ANOVA). The results showed that the biochar prepared in a CO2 atmosphere with a pyrolysis temperature of 700 °C, a heating rate of 10 °C/min, and a resident time of 30 min had the highest conversion rate of 57.79 % in the N-absorption reaction. When the pyrolysis temperature was increased from 600 °C to 700 °C, the biochar conversion in the N-adsorption reaction was significantly increased due to the Boudouard reaction during biomass pyrolysis. The linear regression and ANOVA results show that the micropore percentage and disorder degree of biochar significantly positively affected the reactivity, guiding feedstock selection and optimization of the preparation method of the carbon source used for CLAG.

Enhancement of ethylene selectivity in chemical looping oxidative dehydrogenation of ethane using manganese-based redox catalysts supported on HY zeolite

As the crucial role of zeolite catalysts becomes increasingly prominent in refining and petrochemical industries, this study introduces a novel application of xMn / HY catalysts in ethane catalytic dehydrogenation via Chemical Looping Oxidative Dehydrogenation (CL-ODH). The synergistic effect of manganese oxides on the HY framework and a moderate amount of acidic sites within the catalyst facilitates the cleavage of C-H bonds and the desorption of olefins, which are vital for advancing ethane CL-ODH. We identified the reasons for maintaining high ethylene selectivity using advanced characterization techniques such as XRD, SEM, TEM, BET, H2-TPR, NH3-TPD, and Py-IR. Notably, under optimized conditions at 700 °C with a gas time-space velocity (GHSV) of 1800 mL·h−1·g−1, the 3Mn/HY catalyst achieved approximately 97.1 % selectivity for ethylene and a 22.7 % conversion of ethane. These findings present a scalable route for ethylene production, showcasing significant industrial relevance by potentially reducing energy costs and improving yield.

Enhanced decomposition of H2S to H2 via iron sulfide nanoparticles: A comprehensive experimental and theoretical evaluation

Hydrogen sulfide (H2S), a common pollutant in both fossil and bio-based fuels, can be transformed into valuable hydrogen (H2) through a two-step thermochemical process known as sulfur looping. This scheme, derived from the chemical looping approach, employs a metal-sulfide-based sulfur carrier as a solid intermediate. Iron sulfide, a benign and abundant material, is a promising candidate as the sulfur carrier; however, it faces challenges related to its poor kinetic activity. In this study, we demonstrate the exceptional performance of nano-sized sulfur carriers for the sulfur looping scheme through comprehensive experimental and theoretical analyses. We synthesized iron sulfide nanoparticles that exhibit a remarkable ∼69% enhancement in reactivity over the bulk-sized sulfur carrier. This enhancement is attributed to the high surface area and the nanoscale effects that enhance intrinsic activity. Furthermore, for the first time, we evaluated the effect of co-feeding carbon dioxide (CO2), a prevalent component in industrial acid gas streams alongside H2S. Our combined thermodynamic, atomistic density functional theory (DFT), and experimental studies indicate that the presence of CO2 enhances the conversion of H2S. Additionally, to gauge the sulfur looping process’s superiority at a larger scale, we conducted comprehensive thermodynamic analyses under industrial acid gas conditions. These analyses reveal an improvement of ∼22 percentage points in energy efficiency and ∼8 percentage points in exergy efficiency over the state-of-the-art Claus process. This study, integrating experiments, atomistic DFT studies, and process simulations, provides valuable guidance in the design of high-performance sulfur carriers for efficient H2S splitting to H2.

Configuration optimization of a biomass chemical looping gasification (CLG) system combined with CO2 absorption

Biomass chemical looping gasification (CLG) combined with CO2 absorption in a dual circulating fluidized bed (DCFB) has emerged as an advanced technology for clean and efficient biomass utilization, yet the reactor design for achieving higher gasification performance and the in-depth understanding of physical-thermal-chemical characteristics is still lacking. This study presents an optimized design aimed at enhancing hydrogen production and carbon reduction in the biomass CLG process with a DCFB reactor by employing the multiphase particle-in-cell (MP-PIC) method integrated with thermochemical sub-models. The proposed reactor is comprehensively compared with the original reactor from the experimental setup in terms of particle mixing, heat transfer, and gasification behaviors. The results indicate that compared to the original setups, the proposed CLG system demonstrates: (i) an improved gas-solid mixing, as evidenced by the particle mixing index rising from 0.23 to 0.34; (ii) an enhanced particle heat transfer coefficient, which boosts heat and mass transfer process; (iii) a 10.11 % increase in H2 concentration alongside a 23.71 % decrease in CO2 concentration; (iv) a particle distribution characterized by higher concentration at the bottom and lower concentration at the top, along with intensified particle back-mixing. The pressure drop inside the combustor is higher than that in the gasifier. A smaller absorbent mean particle diameter and lower-positioned biomass feeding port contribute to the improvement of the CLG performance.

Reaction kinetics of Ni-Fe oxygen carriers with high performance for chemical looping hydrogen production

The chemical looping hydrogen production (CLHP) process utilizing iron-based oxygen carriers holds promise for practical hydrogen generation applications. However, challenges persist in developing iron-based carriers that are easy to prepare and demonstrate effective reactivity. Our research focuses on evaluating the CLHP reaction performance using bimetallic Ni-Fe oxygen carrier particles, synthesized by a scalable mechanical mixing method. This study unravels the role of Ni in bimetallic Ni-Fe oxygen carriers and investigates the influence of varying nickel-doping ratios on enhancing the reduction reactivity of iron-based oxygen carriers. Compared to the undoped sample, the 20 wt% nickel-doped Fe2O3/Al2O3 (20NiFe) particles enabled a reduction in the reaction temperature by at least 50 K. With the dopant, the methane conversion rate at 923 K is 500% higher than that of carriers without the dopant. Heterogeneous kinetic analysis demonstrates that the global reduction reaction data for the Ni-Fe oxygen carriers fit with the nucleation-nuclei growth model. Through redox reactivity tests and reduction kinetic analysis, 20NiFe shows the lowest apparent activation energy at 53.93 kJ/mol. Furthermore, the kinetic study and quasi in-situ XRD analysis aid in proposing the evolution process of methane reduction reaction for nickel-doped iron-based oxygen carriers, clarifying the role of doping in improving chemical looping reactivity from a kinetic perspective. This work provides valuable guidance for the design and optimization of oxygen carriers, thus accelerating the readiness for industrial deployment of hydrogen production via chemical looping process.

Investigation and optimization of syngas generation during chemical looping gasification of municipal sludge using Fe/Al oxygen carrier

To contribute to the reduction of carbon emissions, municipal sludge has to be utilized as a resource instead of being disposed of, especially since current sludge disposal methods encounter problems such as high dehydration energy consumption and secondary pollution. In this study, Fe/Al composite oxygen carriers (FOCs) were prepared using Al2O3 particles as carriers and Fe(NO3)3·9H2O as a precursor. Chemical looping gasification (CLG) of wet municipal sludge was conducted in a FOC-loaded fixed bed reactor, and the effect of reaction parameters and conditions on FOCs and syngas generation characteristics were analyzed by various methods. The results showed that the participation of water vapor in the gasification reaction significantly improved the hydrogen production rate of sludge gasification and avoided the over-reduction of the FOC. The vapor released from sludge significantly improved the thermal conversion efficiency of the sludge. Higher temperatures were conducive to the gasification reaction in the first stage, but when the reaction temperature reached 900 °C, the FOC slightly sintered, the reaction atmosphere was affected, and the hydrogen ratio in syngas started decreasing. Controlling the mixing ratio of FOC to sludge (O/H) was an important influencing factor for preparing high-quality syngas. When O/H was higher than 0.25, the quality of syngas decreased significantly. The conclusions obtained in this study can guide the selection of reaction conditions for the CLG of wet sludge using FOCs to prepare hydrogen-rich syngas.

Study on K-modified Ca-based dual-functional materials for carbon capture and in-situ methane dry reforming

Integrated carbon capture and in-situ methane dry reforming (ICCU-DRM) is a promising technology for chemical looping transformation, this process involves the sequential switching of feedstocks within a single reactor, allowing CO2 capture to occur before methane dry reforming without direct CO2-CH4 contact. However, a significant challenge in the ICCU-DRM process is the disparity between the optimal temperatures required for carbon capture and dry reforming, with the latter necessitating considerably higher temperatures. This could lead to substantial CO2 losses when the reaction temperature is elevated to the optimal level for dry reforming. To address this issue and improve CO2 conversion efficiency, this study explores K doping in synthesizing a dual-functional material, NiCa1.6K0.4@Al2O3, through extrusion-spheronization. The synthesized material exhibits a stable pore structure and a large internal surface area, crucial for enhancing CO2 capture. The optimum temperature for DRM is around 800 °C. Notably, the formation of K2Ca(CO3)2 during the calcination of NiCa1.6K0.4@Al2O3, with a thermal decomposition temperature of approximately 800 °C, plays a crucial role in minimizing CO2 release during the heating process, thereby significantly improving the CO2 conversion. To evaluate the impact of K doping on the material, the samples were subjected to carbon capture at 650 °C and dry reforming of methane at 750 °C. The results showed that the CO2 conversion rate of NiCa1.6K0.4@Al2O3 reached 52.8 %, compared to only 18.9 % for NiCa2@Al2O3 under the same conditions. Moreover, this study also investigates the impact of carbon capture temperature, dry reforming temperature, and catalytic metal loading on the performance of the ICCU-DRM process.

Perovskite Oxide Materials for Solar Thermochemical Hydrogen Production from Water Splitting through Chemical Looping.

Solar-driven thermochemical hydrogen (STCH) production represents a sustainable approach for converting solar energy into hydrogen (H2) as a clean fuel. This technology serves as a crucial feedstock for synthetic fuel production, aligning with the principles of sustainable energy. The efficiency of the conversion process relies on the meticulous tuning of the properties of active materials, mostly commonly perovskite and fluorite oxides. This Review conducts a comprehensive review encompassing experimental, computational, and thermodynamic and kinetic property studies, primarily assessing the utilization of perovskite oxides in two-step thermochemical reactions and identifying essential attributes for future research endeavors. Furthermore, this Review delves into the application of machine learning (ML) and density functional theory (DFT) for predicting and classifying the thermochemical properties of perovskite materials. Through the integration of experimental investigations, computational modeling, and ML methodologies, this Review aspires to expedite the screening and optimization of perovskite oxides, thus enhancing the efficiency of STCH processes. The overarching objective is to propel the advancement and practical integration of STCH systems, contributing significantly to the realization of a sustainable and carbon-neutral energy landscape.

A cradle-to-gate life cycle assessment for clean hydrogen gas production pathway using the CeO2/Ce2O3-based redox thermochemical cycle

The present study is conducted to develop a two-steps redox thermochemical cycle based on combined ceria reduction and methane reforming through the CeO2/Ce2O3 redox pair. This cycle incorporates simultaneous water splitting for hydrogen production. To enhance the accuracy and reliability of the inventory data, the system is simulated using the Aspen Plus software package. Also, the goal of this work is to evaluate the carbon footprint of thermochemical based hydrogen production under different scenarios and to compare it with traditional technologies like steam methane reforming (SMR). The analysis takes into account both the plant manufacturing line (reactors), fuel processing (H2 production), redox particles oxygen carrier manufacturing (OC), H2 compression (power consumption) and H2 storage (pipeline manufacturing). The openLCA software with the European database environmental footprint is employed to compute the total carbon emissions of this thermochemical cycle during its overall life cycle. The study concludes that the base case scenario of this system has an overall GWP of 1751.14 g CO2 eq./kg H2 respectively. In the overall GWP, the share of plant construction and OC production was found to be around 1.67%, and 15.78% respectively. The conventional steam methane reforming is loaded with an overall GWP of 4472.83 g CO2 eq./kg H2. In terms of renewable energy input, the base case scenario of this hydrogen production system results in 1465.73 g CO2 eq./kg H2 with thermal energy produced from renewable sources. Comparative life cycle assessment (LCA) demonstrates that base case of CeO2/Ce2O3 has an 85.41% lower GWP emphasizing its environmental advantages over the SMR and Fe3O4/FeO redox pair carries an 84.06% lower GWP as compared to the conventional SMR with 1483.55 g CO2 eq./kg H2. The present study concludes that the combined ceria reduction and methane reforming chemical looping process with simultaneous water splitting may be a more promising option to produce hydrogen using renewable energy.

Thermodynamic performance analysis of a new air energy storage multigeneration system

This paper proposes a chemical looping hydrogen generation-solid oxide fuel cell combined cooling, heating, and power system that utilizes compressed air energy storage and liquefied natural gas, aiming to address the issues of instability in renewable energy power generation and waste of liquefied natural gas cold energy. The scheme achieves CO2 capture and efficient power generation while also addressing grid fluctuations and the utilization of waste cold energy. The compressed air energy storage system is employed to supply air centrally, eliminating the power consumption of traditional air compressors while improving discharging efficiency. Aspen Plus software and embedded Fortran are used for system simulation. The system is comprehensively evaluated through energy analysis, exergy analysis, and sensitivity analysis. The results indicate that the discharging efficiency, energy round-trip efficiency, and round-trip electrical efficiency are 87.56%, 81.57%, and 67.82%, respectively. The purity of CO2 capture is 99.72%. Sensitivity analysis indicates that the outlet pressure of the air storage tank and fuel flow are the main influencing parameters for system performance. Increasing the fuel flow can effectively enhance system power output, but efficiency will decrease. The outlet pressure primarily influences the power output of the gas turbine and discharging time. Overall, this system provides theoretical guidance and new ideas for efficient energy utilization.

Development of a CFD-DEM Model for a 1 MWth Chemical Looping Gasification Pilot Plant Using Biogenic Residues as Feedstock.

Chemical looping gasification (CLG) is a novel dual fluidized bed gasification process that enables the conversion of solid feedstocks to a nitrogen-free syngas through in situ air separation, avoiding a costly air separation unit. While there have been recent advances in experimental studies, modeling of CLG is almost exclusively restricted to lab-scale units or 1D models. In this study, a 3D CFD-DEM model of a 1 MWth fuel reactor for the conversion of solid biomass was developed. Due to the high computational demand of the DEM method, a coarse-grained approach was used in combination with a simplified reaction network. The hydrodynamics were modeled with an EMMS drag model. Simulations were conducted for two woody biomasses and wheat straw based on experimental data of a 1 MWth CLG reactor. The model was able to predict the pressure profile over the reactor accurately, with a mean error below 10%. Carbon conversion and oxygen carrier oxidation were in good agreement with the experimental data with mean deviations below 5%, while reasonable values below 8 mol % mean error were achieved for the gas composition. Discrepancies in the gas composition as well as temperature profile indicate that further work is needed in the pyrolysis step of the model.

Effect of Cu doping on morphology and properties of calcium ferrite and its application as oxygen carrier in chemical looping hydrogen production

Chemical looping hydrogen production with inherent CO2 capture has been widely recognized as a clean and efficient approach to high-purity hydrogen production because of the ultra-pure H2 product without any purification facilities. It is crucial to develop oxygen carriers with better performance to improve fuel conversion and hydrogen production efficiency. The potential of Ca2Fe2O5 in steam converting has been confirmed. However, its lower oxygen transfer capacity, that is, it tends to produce lower fuel conversion in fuel reactors, which will limit its practical application. Here, we report the development of Cu-doped Ca2Fe2O5-based oxygen carriers using sol-gel technology. The effects of B-site substitution of Cu element on the morphological properties and redox properties of Ca2Fe2-xCuxO5 (x = 0, 0.1, 0.25, 0.5, 1) oxygen carriers were evaluated based on experiments and density functional theory calculations. The results show that Cu doping not only elevated the surface oxygen content and enhanced the oxygen activity of the oxygen carriers, but also increased the Fe3+ at the B-site, thus enhanced their binding ability with oxygen molecules. Vacancy formation was a rate-determining step in the chemical looping hydrogen production (CLH), and Cu-doped Ca2Fe2O5 reduced the energy of oxygen vacancy formation. In the CLH process, the doping of Cu significantly improved the hydrogen productivity and fuel conversion rate. The fuel conversion rate was positively correlated with the doping amount of Cu. When x = 1, Ca2Fe2-xCuxO5 had the maximum fuel conversion rate, and its average conversion was 54.2% more than that of undoped Ca2Fe2O5. Ca2Fe2-xCuxO5 with x = 0.25 was the most suitable for CLH with the highest H2 yield, which was 20.3% more than that of Ca2Fe2O5. Moreover, its properties remained stable over multiple redox cycles with high activity and stability for CO-CLH.

Insights into the role of A/B-site substitution in chemical looping gasification of cotton stalk for enhanced syngas production over La-Co-O based perovskite oxygen carriers

Biomass chemical looping gasification (BCLG) is an emerging technology for efficient and clean utilization of cotton stalk (CS) to produce high-quality syngas. Among various oxygen carriers, perovskite oxides are holding an ever-increasing position in BCLG due to their unique structural properties and compositional flexibilities. However, research on perovskite-type oxygen carriers mostly focused on Fe-based oxides, and there is little in-depth investigation of Co-based perovskite and the role of A/B site substitution in the BCLG process. Herein, the LaCoO3 perovskite is selected as the basic oxygen carrier, and Sr, Fe are further doped on the A/B-site to form LaCo1-xFexO3 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) and La1-ySryCoO3 (y = 0, 0.2, 0.4, 0.6, 0.8) series. Effects of perovskite type, gasification temperature, steam volume fraction and oxygen carrier mass fraction of the BCLG performance are investigated. Results indicate that La0.6Sr0.4CoO3 and LaCo0.2Fe0.8O3 exhibit enhanced syngas production with the maximum of 1.304 m3/kg and 1.188 m3/kg, respectively, and outstanding cyclic stability at optimal reaction conditions. Further characterizations including H2-TPR, XPS and EPR analysis reveal that Sr substitution facilitate the formation of oxygen vacancies and adsorbed oxygen species, while Fe doping leads to the increasing concentration of oxygen vacancies and surface lattice oxygen species. Combined with the experimental and characterization results, it is deduced that the oxygen vacancies which promote the adsorption of reactants and accelerate the migration of bulk lattice oxygen, play the key role in the enhanced BCLG performance.

Ca- and Ba-Decorated CuO Oxygen Carriers for In Situ Dechlorination in Chemical Looping Combustion

Ca- and Ba-Decorated CuO Oxygen Carriers for In Situ Dechlorination in Chemical Looping Combustion

Oxygen vacancy modulation for enhanced hydrogen production via chemical looping water-gas shift

Chemical looping water gas shift (CL-WGS)is prospective to generate high-purity hydrogen with integrated CO2 capture. However, this technology is impeded by the lack of active oxygen carriers at mid-temperatures. Here, we synthesized several Ni-doped CoFe2O4-δ to modulate oxygen vacancies and investigate its effect on promoting hydrogen production reaction via chemical looping water gas shift at 650 °C. The findings delineate that doping Ni considerably lowers the energy barriers associated with the oxygen vacancies formation, thereby augmenting their concentration. The underlying mechanism elucidates that within the CL-WGS process, the transfer of lattice oxygen acts as the rate-limiting step. NixCo1-xFe2O4 lowers the formation energy of oxygen vacancies and facilitates the bulk lattice oxygen diffusion through the bulk. Hence, Ni0.5Co0.5Fe2O4 demonstrates the most reduction depth and reversibility via redox reactions, resulting in an elevated hydrogen yield (∼15.5 mmol g−1) at 650 °C, which surpasses the yield from undoped CoFe2O4 by 1.4 times. This performance remains consistently high with only a minimal decline over 100 cycles. The findings introduce a promising approach to promote the reactivity of oxygen carriers, particularly for mid-temperature applications.

Thermodynamic evaluation on the chemical looping co-gasification performances of Cr-containing tannery sludge and waste surgical mask

Thermodynamic evaluation on the chemical looping co-gasification performances of Cr-containing tannery sludge and waste surgical mask

High selectivity syngas generation by double perovskite oxygen carriers La2Fe2-xCoxO6 for chemical looping steam methane reforming

The generation of high-quality syngas combined with high-purity hydrogen is an essential challenge in the chemical looping steam methane reforming (CL-SMR) process, in which the design of oxygen carriers (OCs) is crucial. In this study, La2FeBO6 (BCr, Ni，Co) and La2Fe2-xCoxO6 (x = 0.2, 0.4, 0.6, 0.8, 1.0) double perovskites have been investigated as OCs in the CL-SMR process. Various analytical techniques (BET, XPS, XRD, H2-TPR, Raman.) have been deployed to characterize the OCs' specific surface area, crystal structure, and surface oxygen species. The fixed-bed experiments revealed that the Cr-modified perovskite had the lowest reactivity, which was attributed to the creation of LaCrO3 limiting the oxygen release rate of the OC. Meanwhile, Ni doping exhibited the maximum methane conversion (99.15 %), but it resulted in more carbon deposition due to methane cracking, and its carbon deposition was four times than that of Co doping. Whereas, the Co doped double perovskite OCs showed excellent overall performance, in which La2Fe1.8Co0.2O6 (L2F1.8Co0.2) exhibited the optimum CO selectivity (90.72 %), H2 selectivity (96.91 %), and H2 purity (96.84 %), as well as the lowest carbon deposition. Moreover, the L2F1.8Co0.2 also exhibited outstanding stability in 10 cycles, and it could be a prospective material for CL-SMR, enabling the simultaneous generation of high-quality syngas and high-purity hydrogen.

Performance of a novel CLOU oxygen carrier (CuO/ZrO2/TiO2/MgO) in the combustion of high-rank coal: Anthracite and bituminous

Coal is the largest contributor to global CO2 emissions, and current reserves are projected to last approximately 150 years, with 71.6 % being high-rank coals (anthracite and bituminous). Chemical looping combustion is an economical CO2 capture method that uses oxygen carrier materials to supply oxygen for combustion. Copper is the most reactive due to its oxygen uncoupling capability, though it has poor stability. In our research, we developed a novel modified copper-based oxygen carrier with enhanced stability in oxygen uncoupling cycles by increasing the ZrO2 ratio at the expense of TiO2 to reduce phase interactions. The modified oxygen carrier (40 % CuO, 30 % ZrO2, 15 % TiO2, 15 % MgO) was used to combust bituminous and anthracite coal in a fixed-bed system. While bituminous coal had a high combustion rate, its efficiency was 63 %, yielding 18 mol/kg of CO2, compared to 90 % efficiency and 56 mol/kg CO2 for anthracite. The lower efficiency for bituminous was due to the rapid release of volatiles. Adding steam improved bituminous combustion efficiency to 75 % and CO2 yield to 21 mol/kg, with no significant change for anthracite. A blend of 25 % bituminous and 75 % anthracite showed better combustion efficiency, rate, and CO2 yield. This blend test was stable over 10 cycles, as confirmed by SEM, XRD, and BET analyses.