CO2 Reforming Of CH4 Research Articles

Direct carbon dioxide-methane solid oxide fuel cells integrated for high-efficiency power generation with La0.75Sr0.25Cr0.5Fe0.4Ni0.1O3–δ-based dry reforming catalyst

Solid oxide fuel cell (SOFC) can directly convert carbon-based fuels to power with low environmental impact and high energy efficiency, while there is still one of the key challenges that carbon deposition over Ni-based cermet anodes causes serious performance degradation. Herein, a Ni-doped perovskite, La0.75Sr0.25Cr0.5Fe0.4Ni0.1O3–δ (LSCFN), is prepared to design exsolution systems and evaluated as the dry reforming catalyst for direct carbon dioxide-methane SOFCs. It is demonstrated that the reducing atmosphere in anode effectively induce the NiFe alloy nanoparticles exsolution from LSCFN, and provide abundant active sites for dry reforming. Anode supported single cells with LSCFN-Ce0.9Gd0.1O2–δ (LSCFN-GDC) composite reforming catalyst show excellent electrochemical performance in both H2 and CH4-CO2, and the peak power densities of 686.05 and 684.83 mW·cm−2 are obtained at 800 ℃, respectively. The dry reforming of 50 %CH4-50 %CO2 integrated with LSCFN-GDC reforming catalyst is sustained for 100 h stable performance at 700 ℃ without any degradation, which are further confined by the experimental verification and thermodynamic calculation. These results demonstrate that additional dry reforming catalyst is an effective strategy to effectively manipulate CH4-CO2 reforming and electrochemical performance for energy purposes.

In situ generated oxygen vacancy on Nb2O5 for boosted catalytic activities of M/Nb2O5 in photothermal CO2 reforming of CH4

Photothermal synergistic CO2 reforming of CH4 (CRM) is a promising avenue to convert the greenhouse gases (CO2 and CH4) into valuable chemicals and store the abundant clean solar energy into chemical energy simultaneously. Developing photothermal catalysts that could drive CRM efficiently at low temperatures remains as a challenge. In the present study, Nb2O5 supported group VIII metal catalysts (M/Nb2O5) were synthesized, with the typical catalyst Rh/Nb2O5 recording a CO2 conversion rate of 50.6 mmol gRh−1 min−1 in CRM at 500 °C under visible light irradiation, about double fold higher than that achieved under the thermal-driven reaction condition. Mechanism study disclosed that oxygen vacancy was generated in situ over M/Nb2O5 under the CRM reaction atmosphere. The oxygen vacancy promoted CO2 adsorption and enhanced the light harvesting capacities of M/Nb2O5 catalysts, which ultimately boosted their activities in photothermal CRM. This study provides a promising pathway for the rational design of efficient catalysts by tailoring the properties of the catalysts under the reaction atmosphere.

Promotion of microwave discharge over carbon catalysts for CO2 reforming of CH4 to syngas

The discharge (microplasma) of carbon materials in microwave fields can activate reaction molecules and promote the reaction process. This paper studied the microwave discharge characteristics under different carbon materials, particle sizes, particle structures, and microwave electric/magnetic fields. Combining microwave short-term pulse reaction experiments and spectroscopic experiments, the effect of discharge on reforming reactions was analyzed. The results show that: different carbon materials had different discharge intensities, but they all produced star-shaped sparks. Particles with cis-fiber structure and tips placed in opposition to each other were easier to discharge in microwave electric fields. In the same type of activated carbon, the 0.6 mm coconut shell activated carbon has many discharge sites and high discharge frequency, so the reaction effect was the best. The reactant conversions reached more than 80 %, the syngas yield was 92 %, and the H2/CO was about 1.1. The discharge could promote the activation and decomposition of reaction gas and improve the conversion of reactants.

Recent Advances in Photothermal COxConversion

Recognizing the emergency of the global climate issue, the current fossil fuel‐based economic structure with massive carbon emission is urgent to be transformed. Catalytic conversion of COx, as an emerging alternative technology to produce advanced chemicals and fuels, has received enormous attention. Particularly, photothermal COxconversion, combining the advantages of high efficiency and low pollution, has shown the potential for the production of solar fuels and chemicals, and the progress of this field is accelerating. This review summarizes the fundamentals of photothermal catalysis as well as the state‐of‐the‐art advances of the photothermocatalytic COxconversion in the three main parts that involve COxhydrogenation, water–gas shift reaction, and CO2reforming of CH4. Moreover, the challenges and perspectives are also briefly discussed, which proposes guidance for future investigation of photothermal C1 conversion and anthropogenic carbon cycle.

A highly efficient solar-driven CO2 reforming of methane on Ni/MgAlOx-LDH loaded Ni foam reactors with heat recovery: Experimental measurements and numerical simulations

By converting two greenhouse gases into fuels, CO2 reforming of CH4 via free and clean solar energy is a promising solution to the energy shortage and global warming problems simultaneously. However, serious challenges such as limited light-to-fuel efficiency, severe catalyst aggregation, and deactivation still exist for reactors employing traditional catalyst powders. Here, Ni/MgAlOx-LDH catalysts loaded Ni foam reactor with heat recovery is proposed for highly efficient and stable CO2 reforming under direct concentrated solar irradiation. The temperature nonuniformity is reduced by 84.3% compared to powdered systems, which benefits from the high thermal conductivity of nickel foams. Overheating is also prevented, which leads to much less carbon deposition and relieved active sites aggregation. Ultrahigh light-to-fuel efficiency of 36.51% is achieved, which is much higher than that of traditional powdered systems (23.87%). Numerical simulation results have an excellent agreement with experiments and demonstrate that heat recovery can greatly improve CRM rates by 23.8%. This work opens new routes to achieve highly efficient, stable, and scalable solar-driven CO2 reforming via Ni/MgAlOx-LDH catalysts loaded Ni foam reactors with heat recovery.

CO2 reforming of CH4 over Ni supported on SiO2 modified by TiO2 and ZrO2: Effect of the support synthesis procedure

Two series of catalysts containing nickel supported on silica modified by TiO2 and ZrO2 were tested in the dry (CO2) reforming of methane (DRM). The two series of catalysts with 10 wt% Ni and with Ti(Zr)/Si = 1 were obtained by using two different support preparation procedures. One series had the support synthesized by sol-gel and the other series the support obtained by grafting a home-made SiO2 with zirconium and titanium alkoxides. According to XRD, TPR, NH3 -TPD and XPS analyses, the two series of catalysts and supports had different structural, acidic, and surface chemistry properties. The promoter effect was evaluated with respect to the nickel supported on bare silica. DRM reaction was conducted in a fixed-bed reactor at atmospheric pressure in the low temperature range of 450–650 °C with a feed gas mixture containing CH4 and CO2 in a 1:1 ratio in He. As compared to the unpromoted nickel catalyst, doping silica with titanium oxide increased the methane conversion in the entire range of the tested temperature, and the catalytic stability at 650 °C during 24 h of time on stream. The effect was quite remarkable in the case of the nickel on the sol-gel prepared support exhibiting at 650 °C a stable 65 % CH4 conversion during 24 h. On the contrary, regardless the support preparation method, the presence of zirconium affected only slightly the methane conversion and the catalytic stability. After catalytic test, all the catalysts formed carbon but to a less extent the ones with the grafted supports. The structural characterizations before and after the reaction confirmed a better structural stability of the nickel particles supported on the sol-gel doped silica, explaining the improvement of the catalytic stability during the DRM reaction.

Dual site contiguity study for CO2 catalytic activation and CO2 reforming of CH4 over Ni and NiM2 catalysts with MgO-spinel support

In catalytic CO2 reforming of CH4 reaction, CO2 is activated by the basic sites and CH4 by the metallic sites on the catalysts. The contiguity of the dual sites, i.e., how the two kinds of sites neighbor to each other and how the adsorption species form and interact with each other, determines the activity, selectivity, and stability of the reaction. Following our earlier studies, catalysts with different ratios of Mg/Al and the different second metal (Co, Cu, Fe, or Mn) to the primary metal Ni were prepared using the coprecipitation method. Extensive characterizations showed the catalysts had basic sites of various basicity strength and metallic particles of different sizes. The pulse adsorption experiments showed that the ability of CO2 activation on the basic sites was varying with not only the site basicity itself (pushing effect) but also the pulling effect from the neighbor metallic sites. On the other hand, the ability of CH4 dissociation on the metallic site was determined by the metallic sites themselves and the basic sites that burned the carbon and made the metallic sites recovered. The correlation between the turnover frequency of CO2 and CH4 based on the number of metallic sites indicated that the size of metallic particles was the main factor that determined the catalyst performance once the two kinds of sites were made neighbor to each other with proper Mg/Al ratio. Studies with the catalysts reduced at a higher temperature confirmed these observations. Further analysis of the catalyst deactivation revealed that the decrease in H2/CO ratio (selectivity) in the CO2 reforming of CH4 may be caused by the C–Hx species from the incomplete dissociation of CH4 on the weakened metallic sites and their interaction with the activated CO2 on the basic sites.

Effect of preparation methods of CeO2 on the properties and performance of Ni/CeO2 in CO2 reforming of CH4

CO2 reforming of CH4 (CRM) is not only beneficial to environmental protection, but also valuable for industrial application. Different CeO2 supports were prepared to investigate the matching between Ni and CeO2 over Ni/CeO2 and its effect on CRM. The physicochemical properties of Ni/CeO2-C (commercial CeO2), Ni/CeO2-H (hydrothermal method) as well as Ni/CeO2-P (precipitation method) were characterized by XRD, N2 adsorption at − 196 °C, TEM, SEM–EDS, H2-TPR, NH3-TPD and XPS. Ni0 with good dispersion and CeO2 with more oxygen vacancies were obtained on Ni/CeO2-H, proving the influence on Ni/CeO2 catalysts caused by the preparation methods of CeO2. The initial conversion of both CO2 and CH4 of Ni/CeO2-H was more than five times that of Ni/CeO2-P and Ni/CeO2-C. The better matching between Ni and CeO2 on Ni/CeO2-H was the reason for its best catalytic performance in comparison with the Ni/CeO2-C and Ni/CeO2-P samples.

Evidence for redispersion of Ni on LaMnO3 films following high-temperature oxidation

LaMnO3 films, 0.5-nm thick, were deposited by atomic layer deposition (ALD) onto γ-Al2O3 that had been modified with 15- wt% CaO. The CaO was shown to be effective in preventing formation of LaAlO3 that formed when La2O3 was deposited directly onto γ-Al2O3. Lattice fringes on the resulting CaAl2O4/γ-Al2O3 substrate were weakly resolved, allowing a detailed characterization of the LaMnO3 films. High-resolution transmission electron microscopy (HR-TEM) images showed that the LaMnO3 formed two-dimensional crystallites, ∼10–15 nm wide, that covered most of the surface. Crystallites with (001) and (111) orientation were clearly identified. High-temperature oxidation caused Ni to spread over the LaMnO3 film, suggesting there is a reaction of the Ni2+ cations with the perovskite lattice. Ni formed by high-temperature reduction on these films remained well dispersed and significantly more active for CO2 reforming of CH4 compared to Ni on MgAl2O4, even after repeated oxidation and reduction cycles at 1073 K. The implications of these results for understanding metal-support interactions between Ni and LaMnO3 are discussed.

Oxygen defective bimodal porous Ni-CeO2−x-MgO-Al2O3 catalyst with multi-void spherical structure for CO2 reforming of CH4

Ni-CeO2-MgO-Al2O3 catalysts with bimodal meso-macropores have been synthesized by one-pot spray pyrolysis using dextrin as a structuring agent for dry reforming of methane. The formation of macropores originating from phase segregation and the decomposition of dextrin positively affects both the physical and chemical features of the catalysts, and therefore, the bimodal porous catalysts outperform the dense catalysts in catalytic activity and stability. The volume and size of macropores in a bimodal porous catalyst are dependent on the concentration of dextrin. Based on diverse characterization results, this morphological change has been revealed to induce the distortion of the CeO2 lattice and embedding of Ni nanoparticles, resulting in the strong interaction between the metal and support/promoter and high oxygen storage capacity. The catalyst with balanced bimodal pore structures and optimized physicochemical parameters showed the best performance, considering both catalytic activity and stability with high sintering/coking resistance in the dry reforming of methane.

Mesoporous alumina: A comprehensive review on synthesis strategies, structure, and applications as support for enhanced H2 generation via CO2-CH4 reforming

Lately, the generation of hydrogen out from carbon dioxide (CO2) - methane (CH4) reforming has been touted as a feasible option for reducing two of the most harmful greenhouse gases (CO2 and CH4) in the atmosphere. However, this technology typically suffered from catalyst deactivation triggered by sintering and coke deposition. Therefore, designing a feasible catalyst by making efficient support selections is vital for overcoming this challenge. Mesoporous alumina (MA) has aroused great attraction attributed to their potential applications as catalysis supports resulted from their high surface areas combined with tunable, narrow, and uniform pore size distribution, as well as their ability to constrain active metal from sintered and deactivated during the reaction. These materials' morphology, composition, and pore structure can be directly tailored during synthesis by altering the synthesis parameters like the type of the surfactants/templates employed, pH conditions, or selection of alumina precursors. As a result, this review's major focus is on synthesizing unique MA using a range of synthesis routes and conditions. Apart from that, this review also focuses on the applications and performance of MA as catalyst support during the CO2-CH4 reforming. We believe that this effort provides the complete grasp of MA contribution towards improving the CO2-CH4 reforming activity.

Plasma-assisted CO2 reforming of methane over Ni-based catalysts: Promoting role of Ag and Sn secondary metals

Carbon dioxide (CO2) and methane (CH4) are the primary greenhouse gases (GHGs) that drive global climate change. CO2 reforming of CH4 or dry reforming of CH4 (DRM) is used for the simultaneous conversion of CO2 and CH4 into syngas and higher hydrocarbons. In this study, DRM was investigated using Ag–Ni/Al2O3 packing and Sn–Ni/Al2O3 packing in a parallel plate dielectric barrier discharge (DBD) reactor. The performance of the DBD reactor was significantly enhanced when applying Ag–Ni/Al2O3 and Sn–Ni/Al2O3 due to the relatively high electrical conductivity of Ag and Sn as well as their anti-coke performances. Using Ag–Ni/Al2O3 consisting of 1.5 wt% Ag and 5 wt% Ni/Al2O3 as the catalyst in the DBD reactor, 19% CH4 conversion, 21% CO2 conversion, 60% H2 selectivity, 81% CO selectivity, energy efficiency of 7.9% and 0.74% (by mole) coke formation were achieved. In addition, using Sn–Ni/Al2O3, consisting of 0.5 wt% Sn and 5 wt% Ni/Al2O3, 15% CH4 conversion, 19% CO2 conversion, 64% H2 selectivity, 70% CO selectivity, energy efficiency of 6.0%, and 2.1% (by mole) coke formation were achieved. Sn enhanced the reactant conversions and energy efficiency, and resulted in a reduction in coke formation; these results are comparable to that achieved when using the noble metal Ag. The decrease in the formation of coke could be correlated to the increase in the CO selectivity of the catalyst. Good dispersion of the secondary metals on Ni was found to be an important factor for the observed increases in the catalyst surface area and catalytic activities. Furthermore, the stability of the catalytic reactions was investigated for 1800 min over the 0.5 wt% Ag-5 wt% Ni/Al2O3 and 0.5 wt% Sn-5 wt% Ni/Al2O3 catalysts. The results showed an increase in the reactant conversions with an increase in the reaction time.

Ni/CexZr1-xO2 catalyst prepared via one-step co-precipitation for CO2 reforming of CH4 to produce syngas: role of oxygen storage capacity (OSC) and oxygen vacancy formation energy (OVFE)

Ni/CexZr1-xO2 catalyst prepared via one-step co-precipitation for CO2 reforming of CH4 to produce syngas: role of oxygen storage capacity (OSC) and oxygen vacancy formation energy (OVFE)

CO2 Reforming of CH4 Using Coke Oven Gas over Ni/MgO-Al2O3 Catalysts: Effect of the MgO:Al2O3 Ratio

Research is being actively conducted to improve the carbon deposition and sintering resistance of Ni-based catalysts. Among them, the Al2O3-supported Ni catalyst has been broadly studied for the dry reforming reaction due to its high CH4 activity at the beginning of the reaction. However, there is a problem of deactivation due to carbon deposition of Ni/Al2O3 catalyst and sintering of Ni, which is a catalytically active material. Supplementing MgO in Ni/Al2O3 catalyst can result in an improved MgAl2O4 spinel structure and basicity, which can be helpful for the activation of methane and carbon dioxide molecules. In order to confirm the optimal supports’ ratio in Ni/MgO-Al2O3 catalysts, the catalysts were prepared by supporting Ni after controlling the MgO:Al2O3 ratio stepwise, and the prepared catalysts were used for CO2 reforming of CH4 (CDR) using coke oven gas (COG). The catalytic reaction was conducted at 800 °C and at a high gas hourly space velocity (GHSV = 1,500,000 h−1) to screen the catalytic performance. The Ni/MgO-Al2O3 (MgO:Al2O3 = 3:7) catalyst showed the best catalytic performance between prepared catalysts. From this study, the ratio of MgO:Al2O3 was confirmed to affect not only the basicity of the catalyst but also the dispersion of the catalyst and the reducing property of the catalyst surface.

Recent Progress on Photothermal Heterogeneous Catalysts for CO2 Conversion Reactions

Converting the greenhouse gas carbon dioxide into important chemical fuels is promising to alleviate the global warming problem. Photocatalytic CO2 reduction is beneficial for energy storage and environmental protection; however, it suffers from low efficiency. Recently, photothermal catalysis, which merits the advantages of both photocatalysis and traditional thermally driven catalysis, has been extensively studied and proven promising. Herein, the scope of catalyst type within heterogeneous catalysts is discussed, the latest progress of photothermal heterogeneous catalysts designed for CO2 conversion reactions is described, including the reduction of CO2 by H2O, CO2 hydrogenation to CO, CH4, CH3OH, or C2+, CO2 reforming of CH4 (CRM), CO2 cycloaddition reaction, etc. the preparation principles of photothermal catalysts are summarized, the challenges on the design and development of highly efficient photothermal catalysts are pointed out, and the future research directions are prospected.

CO2 reforming of CH4 in single and double dielectric barrier discharge reactors: Comparison of discharge characteristics and product distribution

CO2 reforming of CH4 in a non-thermal plasma process (e.g., dielectric barrier discharge, DBD) possesses dual benefits for our environment and energy needs. However, this process is strongly influenced by the dielectric structure of the DBD. Here, plasma CO2 reforming of CH4 has been performed in both single-dielectric and double-dielectric DBD (DBD-SD and DBD-DD) reactors under atmospheric pressure. Electrical and optical characterization, along with temperature measurements are performed to understand the influence of the DBD-SD and DBD-DD designs. Reactor performance for reforming is compared under different discharge powers. The results show that CO2/CH4 discharges in both DBD-SD and DBD-DD display typical filamentary microdischarges. Compared with the DBD-DD, the DBD-SD reactor exhibits a larger number and higher intensity of current pulses, which leads to a higher electron density and formation of reactive species. The highest conversion of CO2 (24.1 %) and CH4 (49.2 %) are achieved in the DBD-SD at a high discharge power (75 W). Moreover, higher selectivities of gaseous products are obtained in the DBD-DD, while the DBD-SD reactor shows a higher selectivity for liquid products, mainly including methanol and acetic acid. The highest energy efficiencies for reactant conversion (0.34 mmol/kJ), gaseous and liquid production formation (0.26 mmol/kJ and 0.015 mmol/kJ) are achieved in the DBD-SD reactor at a low discharge power (22 W), resulting from the low energy loss to the environment. However, the carbon deposited on the inner electrode surface in the DBD-SD would have an adverse influence on the reactor’s performance. Further research on the optimization of the DBD reactor to establish an efficient plasma-catalysis system is required for industrial applications.

Recent advances in fibrous catalysts for CO2 conversion: A short review

In recent years, CO2 conversion reactions such as CO2 reforming of CH4 and CO2 methanation have devoted significant attention on account of their advantages in utilizing greenhouse gases (CO2 and CH4). The development of an excellent catalyst with great properties is a crucial strategy in the catalytic reaction, as it could enhance the efficiency of reaction. Additionally, the tunable characteristics of support materials may influence the distribution of active metal sites, strength of metal-supporting interactions, and amount of oxygen vacancies. To improve metal dispersion on a support, the production of support materials with fibrous morphology and dendrimeric structures is becoming an exciting approach. This short review highlighted recent developments in the preparation of fibrous catalysts and their relation with the physical and chemical properties of catalyst. This article also discussed the governing factor of fibrous morphology in CO2 conversions. Owing to the fascinating physicochemical properties of fibrous catalyst, further research is needed to explore its potential in various applications.

Experimental studies of catalyst deactivation due to carbon and sulphur during CO2 reforming of CH4 over Ni washcoated monolith in the presence of H2S

AbstractThis study presents the CO2 reforming of CH4 over Ni coated monolith catalyst at 800°C and 101.325 kPa. The high CH4 to CO2 ratio employed in this study is similar to the CH4:CO2 ratio of >1 found in biogas. Cordierite monolith samples (0.258 channels per m2) washcoated with alumina are used for the experimental purpose. The study considers the combined deactivation effect due to sulphur poisoning and fouling due to carbon deposition. Four different cases with respect to the introduction and removal of H2S are considered. The rate of deactivation due to simultaneous carbon deposition and sulphur poisoning is much faster than the individual poisoning processes. The catalyst shows almost stable operation for 6 h without the presence of in the feed stream. From the conversion studies, it appears that the pre‐treatment of catalyst samples with H2S leads to negligible sulphur coverage. The sulphur poisoning effect is also found to be reversible.

CO2 utilization by dry reforming of CH4 over mesoporous Ni/KIT-6 catalyst

Abstract The mesoporous Ni/KIT-6 catalysts with different composition were prepared by altering reduction temperatures. In addition, their physicochemical properties were characterized by X-ray diffraction, in-situ X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller techniques. The results shown that the specific surface area, composition and metallic Ni crystallinity of the Ni/KIT-6 catalyst were significantly affected by reduction temperatures. The catalytic performances of the prepared Ni/KIT-6 catalysts were evaluated via the CO2 reforming of CH4 into syngas and followed the order: RT0 < RT250 < RT300 < RT350 < RT400 < RT450 ≈ RT500. The specific surface area, pore volume, pore diameter, and Ni0 content of the most representative RT450 catalyst among of them were 646.7 m2 g−1, 0.92 cm3 g−1, 6.5 nm, and 30.9%, respectively. The CH4 and CO2 conversions of RT450 catalyst reached to 69.0 and 39.4% under a reaction temperature of 600 °C, respectively. The CO selectivity was greater than 49% and the RT450 catalyst had good stability.

Enhanced activity of Co catalysts supported on tungsten carbide-activated carbon for CO2 reforming of CH4 to produce syngas

Carbon materials are widely used as catalysts or supports due to their excellent properties. In this paper, the tungsten carbide-activated carbon (WC-AC) composite support was successfully prepared by in-situ carburizing on AC matrix, which is characterized by the covalent anchoring of WC on the AC support. The active metal Co was supported on WC-AC for dry reforming of methane (DRM). Samples were analyzed by N2 physisorption measurements, XRD, XPS, H2-TPR, H2-TPD, CH4&CO2-TPSR, TG-DTG. The WC-AC stabilizes the disturbance of C in AC, alleviates the gasification effect of CO2 and increases the active sites for CH4 cracking. Moreover, WC provides a resistance-less bridge suitable for the Co3+ → Co2+, resulting in a high Co2+/Co3+ ratio on the catalyst surface. This enhances the interaction between the Co species and the WC-AC, thereby enhancing the CH4 activation. In the process of WC-AC promoting Co3+→Co2+, the catalyst surface is accompanied by the generation of oxygen vacancies. This can enhance the dissociative adsorption of CO2 on surface of the WC-cobalt oxide, and at the same time increase the relative proportion of adsorbed oxygen on the catalyst surface, thereby effectively inhibiting the formation of coke. However, the small amount of graphitic carbon generated due to the strong coupling of WC and Co is the main reason for deactivation of Co/WC-AC.