CO Conversion Rate Research Articles

Modulating nickel precursors to construct highly active Ni/Y2O3 catalysts for CO2 methanation

Constructing the interface of Ni/Y2O3 heterogeneous catalyst is a feasible strategy for efficient catalyst design in CO2 methanation, which can create the active Y–O–Ni interfacial sites by utilizing the interaction between Ni and Y2O3. In this work, the strategy of using different nickel precursors (nickel nitrate, nickel acetate, basic nickel carbonate and nickel citrate) was used to prepare various Ni-based catalysts supported on Y2O3, which were estimated for their catalytic performance on CO2 methanation. The catalysts were characterized based on BET, XRD, TEM, H2-TPR, XPS and CO2-TPD, etc. The results indicated a close correlation between the metal dispersion and particle size of Ni/Y2O3 catalysts and the nickel precursor employed. The Y–O–Ni interface structure in Ni/Y2O3 catalysts, associated with basic sites, provides a richer source of basic sites, offering more active sites for CO2 adsorption and activation. Ni/Y2O3 catalyst prepared with nickel nitrate as the precursor exhibited characteristics such as a highly enhanced nickel dispersion, a smaller nickel particle size, and more abundant metallic Ni0 sites. Moreover, nickel nitrate-derived Ni/Y2O3 catalyst exhibited optimal catalytic activity, achieving a CO2 conversion rate of up to 92 % at 300 °C, with 100 % selectivity to CH4, and displaying good stability over 30 h. Therefore, the dispersion of Ni and the size of Ni particles could be controlled by adjusting the precursor, which is closely associated with the catalytic activity of Ni/Y2O3 catalyst. This work unveils the interface-property relationship of Ni/Y2O3 catalysts and provides a new insight into strategy of constructing more effective Ni-based catalyst for CO2 methanation through the controlled nickel precursor.

Continuous biogas production and ex-situ biomethanation in a trickling bed bioreactor under mesophilic and thermophilic conditions

The utilization of biogas as a renewable energy source necessitates a reduction in its CO2 content. "Ex-situ biomethanation" is employed to convert CO2 in biogas to CH4 through hydrogenotrophic methanogens. In this study, a biogas stream (32–36 % CO2) originating from cow manure digestion was subjected to treatment in a trickle bed bioreactor (4 liters). The presence of microorganisms on the packing material was confirmed by using a 16 S rRNA test and SEM images. This study stands out by considering all four combinations of thermophilic and mesophilic conditions, monitoring the transition and steady-state phases in a two-reactor series setup. The mesophilic-thermophilic mode yielded the highest purity (92 %) with an 86 % CO2 conversion rate and an energy density of 13,870 kJ/m3. Additionally, the performance consistency was also assessed using a larger TBB (8 liters). Extending the residence time, the thermophilic-thermophilic mode yielded the highest CH4 concentration at 98 %. The 16 S rRNA results revealed that, influenced by the designated growth conditions encompassing culture media, pH, temperature, and reactor retention time, an enrichment of hydrogenotrophic methanogens occurred. Furthermore, promising results in terms of CH4 concentration and process efficiency were demonstrated by the trickled bed bioreactor employing liquid-in-gas dispersion.

Preparation of catalyst for CO2 hydrogenation reaction based on the idea of element sharing and preliminary exploration of catalytic mechanism.

Under the background of the continuous rise of CO2 annual emissions, the development of CO2 capture and utilization technology is urgent. This study focuses on improving the catalytic capacity of the catalyst for CO2 hydrogenation, improving the efficiency of CO2 conversion to methanol, and converting H2 into chemical substances to avoid the danger of H2 storage. Based on the concept of element sharing, the ASMZ (Aluminum Shares Metal Zeolite catalysts) series catalyst was prepared by combining the CuO-ZnO-Al2O3 catalyst with the ZSM-5 zeolite using the amphoteric metal properties of the Al element. The basic structural properties of ASMZ catalysts were compared by XRD, FTIR, and BET characterization. Catalytic properties of samples were measured on a micro fixed-bed reactor. The catalytic mechanism of the catalyst was further analyzed by SEM, TEM, XPS, H2-TPR, and NH3-TPD. The results show that the ASMZ3 catalyst had the highest CO2 conversion rate (26.4%), the highest methanol selectivity (76.0%), and the lowest CO selectivity (15.3%) in this study. This is mainly due to the fact that the preparation method in this study promotes the exposure of effective weakly acidic sites and medium strength acidic sites (facilitating the hydrogenation of CO2 to methanol). At the same time, the close binding of Cu-ZnO-Al2O3 (CZA) and ZSM-5 zeolite also ensures the timely transfer of catalytic products and ensures the timely play of various catalytic active centers. The preparation method of the catalyst in this study also provides ideas for the preparation of other catalysts.

Microwave plasma-assisted hydrogen production via conversion of CO2–CH4 mixture

A method concerning re-use of the main greenhouse gases: CO2 and CH4 at the same time producing value-added chemicals (H2 + CO) is presented in this paper. The method involves the methane dry reforming using an atmospheric pressure operated 915 MHz microwave plasma source with a swirl gas flow. The effect of the CO2 to CH4 flow rates ratio, the total gas flow rate and the absorbed microwave power on the volume concentration of the gaseous plasma component in the outlet gas (%), CO2 and CH4 conversion rate (%), hydrogen production rate (g h−1) and energy yield of hydrogen production (g kWh−1) was investigated experimentally. The recorded results of the CO2 and CH4 conversion rate were about 82% and 88%, respectively. The best results in terms of the hydrogen production rate and energy yield of hydrogen production were equal to 156 g h−1 and 24 g kWh−1, respectively.

Water–Gas Shift Activity over Ni/Al2O3 Composites

The water–gas shift (WGS) performance of 10%Ni/Al2O3, 20%Ni/Al2O3 and 10%Ni/CaO-Al2O3 catalysts was studied to reduce CO concentration and produce extra hydrogen. Ni was added onto the Al2O3 support by an impregnation method. The physicochemical properties of nickel catalysts that influence their catalytic activity were examined. The most influential factors in increasing the CO conversion for the water–gas shift reaction are Ni dispersion and surface acidity. Ni metal sites were identified as the active sites for CO adsorption. The main effect of nickel metal was reducing the adsorbed CO amount by reducing the active site concentration. The 10%Ni/Al2O3 catalyst was more active for the WGS reaction than other catalysts. This catalyst presents a high CO conversion rate (75% CO conversion at 800 °C), which is due to its high Ni dispersion at the surface (6.74%) and surface acidity, thereby favoring CO adsorption. A high Ni dispersion for more surface-active sites is exposed to a CO reactant. In addition, favored CO adsorption is related to the acidity on the catalyst surface because CO reactant in the WGS reaction is a weak base. The total acidity can be evaluated by integrating the NH3-Temperature-Programmed Desorption curves. Therefore, an enhancement of surface acidity is identified as the favored CO adsorption.

Efficient synthesis of CO and H2O2 via nanosecond pulsed CO2 bubble discharge

In the context of escalating global efforts to mitigate carbon emissions and explore sustainable energy resources, the transformation of CO2 into valuable chemicals and fuels via plasma technology has garnered significant attention. This study demonstrated a new pathway of CO2 conversion into CO and H2O2 via the bubble-enabled gas-liquid discharge driven by a nanosecond pulse. Results showed that the increased discharge frequency and larger pulse widths could enhance CO2 conversion rates and H2O2 yields, albeit potentially at the cost of reduced energy efficiency. Conversely, the rising time of pulse showed negligible impact on the process, whereas varying gas flow rates significantly altered CO and H2O2 yields, underscoring the nuanced influence of these parameters on the efficiency and selectivity of conversion processes. Through illuminating the dynamics of bubble discharge-assisted CO2 transformation, this study contributes to the broader understanding of gas-liquid discharge driven by nanosecond pulse, underlining its potential for addressing environmental and energy challenges.

Cr as a promoter for the In2O3-catalyzed hydrogenation of CO2 to methanol

The utility of Cr as a promoter for In2O3 catalysts in the hydrogenation of CO2 to methanol is investigated. Uniform precursors to binary CrOx-In2O3 and ternary NiO-CrOx-In2O3 catalysts are prepared by flame spray pyrolysis. For the CrOx-In2O3 samples, the highest methanol rate is obtained at a Cr content of 2 mol%, exceeding the methanol rate of In2O3 by 55 %. With increasing Cr content, the CO2 conversion rate does not increase, albeit the methanol selectivity decreases. Characterization of the samples supported by density functional theory calculations provides insight into the role of Cr. At low content, Cr is mainly doped into the lattice of In2O3, which leads to more oxygen vacancy (Ov) sites. The In2O3 surface sites close to Cr-oxide clusters present on the surface are also activated towards Ov formation, offsetting the decrease in Ov due to coverage of the In2O3 surface by Cr-oxide with increasing Cr content. Cr2O3 dispersed on the surface of the In2O3 particles suppresses sintering of In2O3 under reducing conditions, which is especially evident at a Cr content above 2 mol% and higher reaction temperatures. Introducing Ni to the CrOx-In2O3 catalysts results in a higher methanol formation rate compared to CrOx-In2O3. The methanol rate increases with the Ni content with the highest activity obtained at Ni and Cr contents of 22 mol% and 8 mol%, respectively. The optimum Ni(22)-Cr(8)-In2O3 catalyst displays twice the methanol rate of a Ni(22)-In2O3 reference. Ni and Cr play different promoting roles in achieving an increased and more stable rate of methanol formation compared to In2O3: Ni promotes the hydrogenation of formate and methoxy surface intermediates to methanol, while Cr results in more Ov sites and suppresses sintering of In2O3.

Co–N–C anchored g-C3N4 plate enhancing surface activity for efficient visible-light photocatalytic rhodamine-B elimination and CO2 conversion

Poor light-harvesting, fast recombination of photo-induced charge carriers, and unfavorable surface adsorption remain the major issues restricting the photocatalytic activity of g-C3N4. In this study, the Co-N-C decorated g-C3N4 (Co-N-C/g-CN) plate was developed by constructing Co-N-C on the surface of g-CN plate to improve photocatalytic rhodamine-B (RhB) degradation and CO2 conversion. The as-prepared 0.5Co-N-C/g-CN plate exhibited an exceptionally high efficiency in photocatalytic RhB degradation, with a rate of 99.5 % achieved in mere 30 min. Besides, the 0.5Co-N-C/g-CN plate also demonstrated an outstanding photocatalytic CO2 conversion rate of 33.7 μmol g−1cat h−1 within 4 h, which was more than 3.4-fold that of g-CN (9.9 μmol g−1cat h−1). Experiments demonstrated that the surface-constructed Co-N-C enhanced the visible light-harvesting and the separation of photo-induced charge carriers, boosting the optical property. Moreover, the density functionalized theory (DFT) calculations verified that the Co-N-C cocatalyst optimized O2 adsorption for the generation of superoxide radicals (·O-2), accelerating the photocatalytic RhB removal. Meanwhile, the Co-N-C was advantageous for the adsorption and activation of CO2, facilitating the photocatalytic CO2 conversion. This study provides a perspective on the surface engineering of g-CN toward enhanced photocatalytic performance.

Synthesized high performance UV-cured wood wax oil using Irgacure 2959 modified thistle oil and linseed oil

With the reduction of petroleum resources and the intensification of environmental pollution, the development and application of bio-based coatings using renewable resources have become increasingly important in the wood working industry. Wood wax oil is a new bio-based natural coating that provides an environmentally friendly solution for wood preservation. The main challenges related to wood wax oil are slow drying speed and poor liquid resistance. To address this issue, wood wax oil was modified using Irgacure 2959, and the effects of the different concentrations (0, 0.5, 1.0, 1.2 and 1.5 %) of Irgacure 2959 on the properties of ultraviolet (UV) wood wax oil were explored. X-ray photoelectron of spectroscopy analysis indicated that in a wood wax oil film containing 1.2 wt% Irgacure 2959, the C–C and CO conversion rates are 15.62 % and 25.30 %, respectively. Compared with regular wood wax oil films, the 1.2 % Irgacure 2959 wood wax oil film exhibited a notable 14.2 % decrease in surface roughness. The surface of the UV wood wax oil film exhibits hydrophobic properties, which are positively correlated with its roughness. 1.2 wt% Irgacure 2959 UV-cured wood wax oil with a hardness level of 3 H, an adhesion level of 1, a viscosity of 24.87 s, and a reduction in drying time from 1 h to 20 min. The weather resistance is better than that of the commercial wood wax oil. These findings underscore the potential and versatility of UV wood wax oil, capable of forming a low-roughness and high-gloss wax film on the surface of wooden materials, thus providing an environmentally friendly and non-toxic alternative.

Embedded catalysts prepared by grinding crystallization and their catalytic performance in dry reforming of methane: Domain-limited nanostructures for high activity and stability

Dry reforming of methane (DRM) takes advantage of greenhouse gases (CH4 and CO2) and mitigates their eco-environmental consequences. However, the biggest obstacle for DRM reactions has been the design of catalysts with high resistance to sintering and carbon deposition. In this paper, the embedded bimetallic nickel-cobalt@ silicalite-1 (S1) catalysts (NiCo@S1), with high resistance to sintering and lower carbon deposition, were prepared by grinding crystallization method. The physicochemical characterizations demonstrated that the embedded catalyst for NiCo@S1 could effectively control the size and dispersion of the active metal Ni–Co in the catalyst compared to the supported catalysts for 10Ni/SiO2 and 10Ni/S1, which further enhance the interaction between the active metal phase and the carrier S1, and greatly minimize the amount of carbon accumulation on the catalysts. After being subjected to a reaction at 700 °C for 6 h, the 10Ni2.5Co@S1 exhibited a significant performance improvement. The instantaneous conversion rate of CH4 increased from 63.17% to 86.39% (an increase of 23.22%), and the instantaneous conversion rate of CO2 rose from 70.20% to 88.62% (an increase of 18.42%). Additionally, carbon deposition reduced from 14.58% to 0.82% (a decrease of 13.76%). Therefore, the conceptual design provided a new perspective for designing Ni-based dry reforming catalysts.

MOF-derived carbon-based catalysts with enhanced anti-coking property for the dry reforming of methane

To avoid sintering and carbon deposition of conventionally loaded catalysts, a spatial confinement strategy was employed to design a high-performance catalyst for the dry reforming of methane (DRM) reaction. With tri-metallic Ni-Co-Mg metal-organic framework (MOF-74) as a precursor, a novel nanostructured NiCoMg@C catalyst was synthesized, where the active metals Ni and Co were confined within the carbon framework derived from MOF pyrolysis. Characterization results indicate that the catalyst synthesized with MOF as template has a high specific surface area, well-dispersed metals, and strong metal-support interactions. The introduction of a high content of Mg promoted the dispersion of active metal Ni and Co and increased the number and strength of surface basic sites. Among the catalysts, NiCoMg20@C exhibited optimal catalytic activity, with initial CH4 and CO2 conversion rates reaching 75.13 % and 85.29 %, respectively. More importantly, the catalyst showed high stability during 100 h DRM reaction at 700 °C without significant carbon deposition. This research provides a new perspective for the development of DRM catalysts.

Engineering Single Cu Atoms Anchored via N‐Heterocyclic Carbene in COF Mesopores for Modulating Electron Kinetics of CO2 Photoconversion

AbstractCharge transfer and carbon dioxide (CO2) adsorption/activation are critical factors for the electron kinetics during CO2 photoconversion. Herein, high‐loading and robust single Cu atoms (7.8 wt.%) are anchored via N‐heterocyclic carbene ligands derived from imidazolium ionic liquid motifs, precisely bonding to the acceptors of mesoporous donor‐acceptor pyridine‐covalent organic framework (pCOF) nanosheets. By engineering the valance and coordination structure, atomic Cu(I)‐CO2 sites, superior to Cu(II)‐CN2OCl ones, enable a 22‐fold increase of CO2 conversion rate compared to pCOF in pure water, ≈100% selectivity toward CO, and an apparent quantum yield of 1.7% (420 nm). The photoactivity outperforms analogous COF‐based photocatalysts under similar conditions. Experimental results prove single Cu(I) atoms possess more improved electron capture and CO2 adsorption/activation capacities than single Cu(II) ones. Combining fs‐ and µs‐transient absorption spectroscopy, the electron kinetics mechanism is investigated on the single‐atom pCOF photocatalyst model. The fs‐transient absorption spectra confirm single Cu(I) atoms can rapidly and precisely extract electrons from the electron‐rich region of pCOF along N‐heterocyclic carbene, exhibiting an electron transfer rate of 3 × 109 s−1. Using in situ µs‐transient absorption spectroscopy, the electron transfer efficiency is quantified to reach 60.4% under photocatalytic reaction conditions. This work provides a rational design strategy for advanced single‐atom photocatalysts.

Dry reforming of methane over embedded Ni nanoparticles in CeZrO2: Effect of Ce/Zr ratio and H2O addition

Biogas has emerged as renewable source of CH4 towards energy decarbonization in recent years. Among the biogas valorization routes, the dry reforming of methane (DRM) process is particularly interesting for H2 production. However, the development of new catalysts with high metal dispersion and coke resistance is a significant challenge, particularly under industrial condition. Therefore, this work studies the performance of Ni@CexZr1-xO2 catalysts with different Ce/Zr molar ratios for the dry reforming and bi-reforming of methane reactions. The addition of Zr promotes the Ni dispersion and the oxygen mobility of the support, leading to enhanced resistance to coke formation. Additionally, H2O suppresses coke formation under high CH4/CO2 molar ratio, but catalyst deactivation is still observed. Finally, an optimal Ce/Zr molar ratio (i.e., 4.0) is achieved, demonstrating remarkable resistance to coke formation and high CH4 and CO2 conversion rates through the control of Ni particle size and the promotion of oxygen mobility.

Enhanced CO2 methanation over LaNiO3/CeO2 derivative catalyst with high activity and stability

The conversion of CO2 into synthetic natural gas offers a promising approach for the long-term storage of renewable energy, addressing the challenge of its intermittent supply. This study successfully developed a catalyst comprised of LaNiO3 supported by CeO2, synthesized via a citric acid-aided impregnation method. This catalyst demonstrated efficiency and stability as a precursor for the CO2 methanation reaction. Upon reduction, it transforms into a Ni–La2O3/CeO2 configuration, featuring dispersed Ni nanoparticles. Characterization through hydrogen temperature-programmed reduction (H2-TPR) revealed that this catalyst exhibits enhanced reducibility and smaller particle sizes, which promote hydrogen activation at lower temperatures. X-ray photoelectron spectroscopy (XPS) analysis further clarified that the increased catalytic activity results from electron transfer interactions between Ni, CeO2, and La2O3. Moreover, the catalyst displayed an augmented count of weak to medium basic sites, which, along with improved hydrogen activation, elevated the CO2 conversion rate to 83.8% within the kinetic control region. The collaborative effect of Ni, La2O3, and CeO2 substantially outperformed the conventional Ni/CeO2 catalyst in CO2 methanation efficiency. Additionally, in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analysis revealed that the methanation process predominantly follows the HCOO* pathway. Notably, the LaNiO3/CeO2 catalyst exceeded the performance of Ni–La/CeO2 in CO2 adsorption, HCOO* intermediate decomposition, and CHO* conversion, significantly enhancing low-temperature methanation activity.

Exceptional stability of spinel Ni–MgAl2O4 catalyst with ordered mesoporous structure for dry reforming of methane

The dry reforming of methane reaction holds significant importance for the comprehensive utilization of CO2 and CH4, contributing to carbon neutrality. However, due to the high reaction temperatures, catalyst deactivation due to carbon deposition and sintering remains a challenge. In this study, a one-pot method was employed to improve the solvent evaporation self-assembly process for the preparation of Ni–MgAl2O4 catalysts. The impact of calcination temperature (600 °C, 800 °C, and 1000 °C) on the ordered mesoporous structure of the catalyst was investigated. Catalysts without an ordered mesoporous structure, such as Ni–MgAl2O4-1000, suffered deactivation due to carbon deposition caused by the large size of Ni grains, while Ni–MgAl2O4-600 deactivated due to sintering caused by the lack of confinement effect of the support on Ni. Conversely, Ni–MgAl2O4 catalysts with an ordered mesoporous structure exhibited confinement effects on Ni metal, resulting in excellent resistance to carbon deposition and sintering. Further investigation into the effect of different loading methods of Ni on methane dry reforming was conducted. A comparison was made between Ni–MgAl2O4 (800 °C) prepared by the one-pot method and Ni/MgAl2O4 (800 °C) prepared by the impregnation method. It was observed that Ni–MgAl2O4 catalysts, with Ni incorporated into the support, exhibited strong interaction between Ni and the support. During a 500-h long-term reaction, both CO2 and CH4 conversion rates remained at 90% for Ni–MgAl2O4 catalysts, with less carbon deposition and slower grain growth rate, demonstrating excellent reaction activity and stability. In contrast, the performance of Ni/MgAl2O4 catalysts gradually declined after 260 h. Ni–MgAl2O4 catalysts with ordered mesopores and strong interaction between Ni and the support displayed superior resistance to carbon deposition and sintering.

Distributed electrified heating for efficient hydrogen production

This study introduces a distributed electrified heating approach that is able to innovate chemical engineering involving endothermic reactions. It enables rapid and uniform heating of gaseous reactants, facilitating efficient conversion and high product selectivity at specific equilibrium. Demonstrated in catalyst-free CH4 pyrolysis, this approach achieves stable production of H2 (530 g h−1 L reactor−1) and carbon nanotube/fibers through 100% conversion of high-throughput CH4 at 1150 °C, surpassing the results obtained from many complex metal catalysts and high-temperature technologies. Additionally, in catalytic CH4 dry reforming, the distributed electrified heating using metallic monolith with unmodified Ni/MgO catalyst washcoat showcased excellent CH4 and CO2 conversion rates, and syngas production capacity. This innovative heating approach eliminates the need for elongated reactor tubes and external furnaces, promising an energy-concentrated and ultra-compact reactor design significantly smaller than traditional industrial systems, marking a significant advance towards more sustainable and efficient chemical engineering society.

Doping Pd2+ into NinCeOx nanofibers promotes low-temperature CO2 methanation

CO2 methanation at low temperatures is still a challenge. Herein, NinCeOx (n = 1–3) and Ni2.5Pd0.1CeOx nanofibers by electrospinning is reported. The main advantage of this method is to obtain the highly dispersed precursor of palladium, nickel, and cerium, overcoming the difficulty of uniform mixing in conventional preparation methods. The Ni2.5Pd0.1CeOx nanofiber catalyst exhibited outstanding catalytic performance at low temperatures (CO2 conversion rate = 90.4 %, CH4 selectivity = 99.6 % at 230 °C) along with exceptional stability over 300 h. EPR, Raman, and O 1s XPS confirmed that Pd2+ doping increased oxygen vacancy concentration. In-situ infrared spectroscopy indicated that CO2 methanation on Ni2.5CeOx and Ni2.5Pd0.1CeOx catalysts followed the formate pathways. Pd2+ doping increased the number of surface oxygen vacancies and hydroxyl groups, thus increasing the amount of bicarbonates and formates. DFT calculations suggested that Pd2+ doping increased CO2 adsorption energy, and confirmed surface hydroxyl groups and bicarbonate being beneficial for CO2 methanation, consequently enhancing the activity of Ni2.5Pd0.1CeOx catalyst especially at low temperatures.

A design of solar-driven thermochemical reactor integrated with heat recovery for continuous production of renewable fuels

To cope with the increasingly serious energy crisis and environmental problems, the transformation from traditional energy to renewable energy is urgent. Solar-driven thermochemical conversion of CO2 and H2O into renewable fuels technology provides a favorable path for alternative energy. However, the temperature/pressure swing required for the reduction and oxidation steps during thermochemical process incurs irreversible energy losses and severe material stresses. Moreover, the two-step redox cycle mode cannot achieve a continuous fuel production in the reactor. To address these issues, this study proposes a novel design of thermochemical reactor integrated with heat recovery for continuous production of renewable fuels. In this design, an oxygen-conducting ceria membrane is employed to conduct oxygen ions, electrons and vacancies induced by the oxygen chemical potential gradient to achieve an isothermal and continuous splitting of CO2 and H2O. At the fuel production side, a counter-flow and tube-in-tube alumina reticulate porous ceramic filling heat exchange design is developed to recover the sensible heat of gas products and excessive reactants. In addition, a comprehensive model is developed by coupling the computational dynamics of flow, radiation, conduction and convection, and is solved by the Monte Carlo method coupled with ANSYS FLUENT software through User-defined Functions. Results indicate that the integrating membrane reactor/heat recovery design can not only realize continuous production of renewable fuels, but also recover sensible heat of gas products, which is beneficial for conversion of solar energy to chemical energy. Optimizing heat recovery design can help reactor achieve a solar-to-fuel efficiency of 10.58%. Moreover, if the theoretical CO2 conversion rate could be achieved, the solar-to-fuel efficiency of reactor can reach as high as 40.43%, which means that such a reactor design has a huge potential in conversion of solar energy into renewable fuels.

Highly dispersed active sites and strong metal-support interaction for boosting CO2 hydrogenation to methanol

As global energy demand continues to increase and global climate change issues caused by greenhouse gas emissions gradually heat up, the effective conversion of carbon dioxide into high value-added methanol has become a key challenge in the energy and environmental fields. However, due to the chemical inertness of CO2 molecules, it is difficult to activate CO2 at low temperatures, resulting in extremely low conversion rates. Although increasing the reaction temperature is beneficial for the conversion of CO2, there is also competition in the reverse water gas reaction, resulting in lower methanol selectivity. Therefore, developing efficient catalysts is the key to improving CO2 conversion rate and methanol selectivity. In this work, we used zirconium-based UIO-66 metal-organic framework as a precursor, replaced the original terephthalic acid ligand with thermally unstable aminoterephthalic acid, and supported Cu on the MOF precursor by equal volume impregnation method. After heat treatment, the Cu/ZrO2-DM catalyst was prepared. The catalyst was compared with Cu/ZrO2 catalyst prepared by co-precipitation method, hydrothermal method and unmodified Cu/ZrO2-D catalyst. The Cu/ZrO2-DM catalyst exhibited the highest CO2 conversion and methanol selectivity in the hydrogenation reaction, reaching 13.95% and 90.78%, respectively. The main reason is attributed to the large specific surface area of the copper-based catalyst derived from MOF materials, the good dispersion of the active center and the strong interaction between Cu and the precursor. This work may provide a new perspective for the design and synthesis of related catalytic materials for efficient CO2 hydrogenation to methanol.

Green catalyst innovation: Enhanced Fischer-Tropsch synthesis using potassium-promoted cobalt catalysts supported on pyrolyzed peanut shells and Cladophora Glomerata modified biochars

This paper explores pyrolysis potential for effective modified biochar (MB) production, serving as a green and novel carbon-based catalyst support in Fischer-Tropsch to olefins synthesis. For this purpose, the MB produced from the pyrolysis of pre-treated Peanut shell (PS) and Cladophora glomerata algae (CG) was used as a high porosity support for cobalt catalyst synthesis. The impregnation technique was applied to prepare the cobalt catalysts, and the catalysts were promoted with potassium. Various methods examine catalysts physico-chemical properties. After 10 h of reduction at 400 °C, the catalysts' activity and selectivity were studied in a fixed-bed reactor. TEM images show that the metal particles are suitably distributed on the porous surface of the modified biochars. The majority of the particles were between 5 and 15 nm in size. Also, TPR results indicate a suitable metal dispersion of about 10% and good catalyst reducibility have been achieved. The cobalt catalysts produced on MBs of CG and PS exhibited FT rates of 0.245 and 0.223 (g HC/g cat.h), with CO conversion rates of 50.25% and 45.68% in each case. Finally, K-promoted cobalt catalysts supported on MBs of CG and PS showed the α-olefins selectivities of 38.67% and 35.49% for C2-C13 hydrocarbons, respectively.