CO Ratio Research Articles

Response surface optimization of hydrogen-rich syngas production by the catalytic valorization of greenhouse gases (CH4 and CO2) over Sr-promoted Ni/SBA-15 catalyst

Dry reforming of methane (DRM) which utilizes CO2 and CH4, is a more efficient and environmentally friendly syngas production method. However, since the technique is endothermic, catalyst deactivation from sintering and carbon deposition has prevented its industrial implementation. This study investigated the effect of Strontium (Sr) promoter on Ni-based catalyst synthesized on SBA-15 support via the impregnation method. The incorporation of Sr as a promoter has demonstrated distinct advantages, primarily attributed to its remarkable capability to inhibit carbon formation. This property imparts a notable enhancement in the stability of the catalyst, thereby extending its operational lifespan and maintaining consistent catalytic performance. The physicochemical properties of the fresh catalyst were observed by using various characterization techniques such as X-Ray diffraction (XRD) analysis, N2 physisorption analysis, field emission scanning electron microscopy (FESEM), and temperature programmed reduction using hydrogen as the probing gas (TPR-H2). The catalysts were tested in DRM reaction using a tubular fixed bed reactor at 800 °C with an equimolar feed ratio. Overall, 1% Sr promoted Ni/SBA-15 showed enhanced performance having CO2 and CH4 initial conversions of 88.5% and 96.5%, respectively while remaining stable for 320 min on stream. Furthermore, the predicted optimal condition was 713.73 °C and a feed gas ratio (CH4:CO2) of 1.12, with CO2 and CH4 conversion rates of 69.59% and 84.83%, respectively, resulting in an H2:CO ratio of 1.00. Slight differences from the predicted values were considered insignificant, validating the Srb catalyst at a 95% confidence level with a 5% likelihood of error in the RSM model.

Full oxygen blast furnace steelmaking: From direct hydrogen injection to methanized BFG injection

This paper presents a novel concept of Power to Gas in an oxygen blast furnace, through blast furnace gas methanation and direct H2 injection. The PEM electrolyser produces H2, which reacts with the CO and CO2 from the blast furnace gas forming synthetic natural gas. The latter gas is injected into the blast furnace, closing a carbon loop and avoiding CO2 emissions. A parametric analysis is performed to vary the H2:CO2 ratio in the methanation reaction. Different ratios are simulated and compared, among of which the most representative are: (i) 2.5, where unreacted CO2 is directly recycled with the synthetic natural gas; (ii) 4, where stoichiometric conditions are found and the synthetic gas is composed mostly by CH4; and (iii) 8, where an excess of H2 is found in the synthetic gas; and (iv) an infinite ratio, where only H2 is injected in the blast furnace. In the latter, the methanation plant is not required, and no synthetic natural gas is produced. The results show that low H2:CO2 ratios perform poorly, involving high PEM sizes and high costs but only a 5% of CO2 avoidance (compared to conventional blast furnaces). A H2:CO2 ratio of 4 and full H2 injection results in higher reduction of CO2 emissions (33.8 % and 28.6%) with carbon abatement costs of 260 and 245 €/tCO2, respectively.

Tuning magnetic properties of polar magnets (Mn1−xCox)2Mo3O8 (0 ≤ x ≤ 1) with interacted magnetic sublattices

Single crystalline polar magnets (Mn1−xCox)2Mo3O8 (0 ≤ x ≤ 1) have been synthesized, and their magnetic properties have been studied. Magnetic interactions of the samples can be modulated drastically by Co-doping, and a ferrimagnetic to antiferromagnetic phase transition is identified at x = 0.35. For the samples hosting a ferrimagnetic state (0 ≤ x ≤ 0.3), square-like magnetic hysteresis loops are commonly identified, and the remnant magnetization and coercive field are revealed to strongly depend on the Co-content and temperature. The occupation ratio and magnetic nature of Co2+ are key ingredients to dictate the competition of various magnetic exchange couplings in the samples.

Near-Surface Air Content of CH<sub>4</sub>, СО<sub>2</sub>, СО and δ<sup>13</sup>C–СH<sub>4</sub> in Moscow According to <i>In Situ</i> Observations

Near-surface observations of air mixing ratios of CH4, CO2, CO, benzene, and δ13C–СH4 at the IAP-RAS site in Moscow for years 2018–2020 are analyzed to describe typical interannual, seasonal, and diurnal variations. The highest mixing ratios of CH4, CO2, and CO (above 2.2, 430, and 0.2 ppmv, respectively) are mostly observed in winter as a result of the seasonal maxima in the emissions of these gases from motor transport and energy sectors and the slow removal of the emissions from the near-surface air due to suppressed turbulent vertical mixing in the cold season. The highest impact of local and distant microbial emissions on the CН4 mixing ratios is observed in summer, as follows from the low δ13C–СH4 values from –50 to –60‰. The highest increase in the mixing ratios of all the measured species is associated with air transport from the industrial area located at the east – southeast from the site. The estimated emission ratios CH4/benzene = = 0.52–0.54 ppmv/ppbv, СH4/СО = 0.56–0.75 ppmv/ppmv, СО2/benzene = 77–93 ppmv/ppbv, СО2/СО = = 81–131 ppmv/ppmv, СО/benzene = 0.65–1.11 ppmv/ppbv show the prevailing contribution of emissions from motor transport and energy sectors to the content of trace gases in the near-surface air in Moscow and are consistent with other similar estimates published on the basis of observations in large cities.

Selective Gas Sensing under a Mixed Gas Flow with a One-Dimensional Copper Coordination Polymer.

Structural changes of the coordination polymer associated with gas adsorption (gate opening-type adsorption) can be linked to bulk physical properties such as magnetism, electrical conductivity, and dielectric properties. To enable real-space sensing applications, it is imperative to have a system where the selective adsorption of mixed gases can be correlated with physical properties. In this report, we demonstrate that a crystalline sample of one-dimensional (1D) coordination polymer exhibits selective CO2 adsorption while simultaneously displaying dielectric switching behavior in a mixed N2/CO2 gas environment. In the crystal of {[Cu2(2-TPA)4(pz)]·CH3CN}n (1·CH3CN), where 2-TPA and pz are 2-thiophencarboxylate and pyrazine, respectively, paddle wheel-type units of [Cu2(2-TPA)4] are bridged by pz, forming a 1D chain structure. One of the two crystallographically independent 2-TPA units was interacted with the pz moiety of the adjacent 1D chain by π···π interactions, forming a two-dimensional (2D) layer parallel to the ab plane. Activated 1 shows selective CO2 adsorption by a gate opening-type adsorption mechanism, indicating that the CO2 adsorption process is accompanied by a structural change. The change in the real part of dielectric permittivity (ε') under the mixed N2/CO2 gas flow is a result of the selective CO2 adsorption, which was supported by the enthalpy changes (ΔH) associated with CO2 adsorption in two methods: CO2 adsorption isotherms and temperature-dependent measurements of ε' under a mixed N2/CO2 gas flow. The calculated ΔH values were found to be in good agreement across both methods. The CO2 ratio in the mixed N2/CO2 gas flow increased, and the switching ratio of ε' (Δε') also increased. Notably, Δε' exhibited a marked increase beyond the pressure required for gate opening adsorption.

The Influence of the Reaction Conditions on the Photocatalytic Gas‐Phase Conversion of Methanol with Water Vapor over Pt/SrTiO3 in a Continuously Operated Flow Reactor

AbstractContinuous methanol photooxidation in the gas phase is a promising method to produce valuable chemicals like formaldehyde or methyl formate in addition to hydrogen under mild conditions. The influence of the reaction conditions on the selectivity of methanol oxidation to formaldehyde is studied using a heated flat‐plate flow photoreactor illuminated by an LED array (λmax = 368 nm) and Pt‐modified SrTiO3. A combination of online analytical methods allowed to quantify all gaseous products during extended time‐on‐stream (> 48 h TOS). The selectivity to formaldehyde is found to be primarily determined by the residence time and the process temperature. At a low methanol to water ratio, methanol conversion and evolution of CO2 are favored, whereas the light intensity primarily influenced the apparent quantum yield from 5.1 to 1.8% at 9.36 to 52.93 mW cm−2, respectively, and the methanol conversion thus determining the economic efficiency of the process. Operation temperatures higher than 110 °C resulted in a strong deactivation of the catalyst while simultaneously the formation of CO at the expense of formaldehyde selectivity is favored. This study demonstrates the importance of understanding the influence of relevant reaction conditions and the potential of selective photocatalytic gas‐phase oxidation of small molecules.

Investigating the role and impact of N2 as a blowing agent in the fabrication of thermoplastic polyurethane foams

Fabricating low-density elastomeric foams with a homogenous cell structure has been challenging because of foam shrinkage. The low modulus of the elastomers and the high diffusivity of blowing agents lead to foam shrinkage and poor surface quality. Using N2 as a physical blowing agent (PBA) is an eco-friendly foaming method to overcome foam shrinkage. In this study, PTMEG-MDI/BD-based TPU with a hardness of 85A, 90A, and 95A were foamed using N2. Nitrogen as a blowing agent created a homogeneous cell structure with an expansion ratio of more than five times, an average cell size of less than 25 μm, and a cell density of more than 109 cells/cm3. The shrinkage ratio and cellular morphology of CO2- and N2-blown TPU foam were compared at their maximum expansion ratio. At the maximum expansion ratio, the N2-blown foams exhibited a fine cell structure with a shrinkage ratio of less than 4%. However, the CO2-blown TPU foam showed a shrinkage ratio of 12.7% with significant cracks in the sample. The results demonstrate that using N2 as a blowing agent can achieve an expansion ratio similar to that of CO2-blown foam, and the shrinkage problems of elastomeric foams can be significantly eliminated, which may help to maintain the physical properties of the foam.

Dynamic-cycle simulation of power-to-methanol-to-power system with reversible solid oxide cells: Multi-physics and techno-economic analysis

Power-to-Methanol-to-Power System (PMPS) has a great potential for fluctuating renewable power storage and flexible power generation. In this study, a dynamic-cycle model of PMPS is developed by coupling reversible solid oxide cells with methanol synthesis process. The system stores energy from fluctuating photovoltaic power in the form of methanol during the day and generates electricity at night using the methanol fuel generated in the daytime. It is found that reducing the CO2 ratio in co-electrolysis from 60% to 30% increases CH3OH production by 64% and doubles electricity efficiency due to the increased H2 supply to methanol synthesis section. While in the fuel cell, reducing methanol supply rate from 500 to 200 SCCM increases power generation capacity by 110% with longer generating duration, and the electricity efficiency is improved from 30% to 61%. Besides, the optimized PMPS presents a round-trip efficiency of 78%, along with high conversion rates of carbon (97%) and hydrogen (84%), significantly exceeding that of the Power-to-Hydrogen-to-Power System (PHPS, the round-trip efficiency of 45%) under similar cell’s inputs. Furthermore, our techno-economic analysis shows that the levelized fuel cost (0.49$ t−1 CH3OH) and levelized generating capacity cost (0.22 $/kWh) of PMPS are about 10% (4.8$ t−1 H2) and 74% of the PHPS, mainly due to the 16% lower capital expenditure of PMPS.

Fabrication of cobalt-zinc bimetallic oxides@polypyrrole composites for high-performance electromagnetic wave absorption

Composite materials that combine magnetic and dielectric losses offer a potential solution to enhance impedance match and significantly improve microwave absorption. In this study, Co3O4/ZnCo2O4 and ZnCo2O4/ZnO with varying metal oxide compositions are successfully synthesized, which are achieved by modifying the ratios of Co2+ and Zn2+ ions in the CoZn bimetallic metal–organic framework (MOF) precursor, followed by a high-temperature oxidative calcination process. Subsequently, a layer of polypyrrole (PPy) is coated onto the composite surfaces, resulting in the formation of core–shell structures known as Co3O4/ZnCo2O4@PPy (CZCP) and ZnCo2O4/ZnO@PPy (ZCZP) composites. The proposed method allows for rapid adjustments to the metal oxide composition within the inner shell, enabling the creation of composites with varying degrees of magnetic losses. The inclusion of PPy in the outer shell serves to enhance the bonding strength of the entire composite structure while contributing to conductive and dielectric losses. In specific experimental conditions, when the loading is set at 50 wt%, the CZCP composite exhibits an effective absorption bandwidth (EAB) of 5.58 GHz (12.42 GHz-18 GHz) at a thickness of 1.53 mm. Meanwhile, the ZCZP composite demonstrates an impressive minimum reflection loss (RLmin) of −71.2 dB at 13.04 GHz, with a thickness of 1.84 mm. This study offers a synthesis strategy for designing absorbent composites that possess light weight and excellent absorptive properties, thereby contributing to the advancement of electromagnetic wave absorbing materials.

(Cu3-x Nix)Co2-Layered Double Hydroxide Nanosheets for Enhanced Electrocatalytic Activity Towards Overall Water Splitting

The exploration of transition metal based electrocatalyst for overall water splitting is becoming important as hydrogen becomes integral part of energy landscape. Recently, a new class of compounds i.e. layered double-hydroxides (LDHs), also known as anionic clays, are have shown tremendous promise for use as electrocatalyst. The lamellar morphology of LDHs accommodates higher active sites, that contributes to the facile electron transfer and thus attracts a great deal of interest in catalysis application. Moreover, the high catalytic activity of LDHs are also linked to their facile anion exchange, specific electronic structures, and versatile chemical compositions.Herein, we have developed a series of ternary layered double hydroxide (LDH) using pH-adjusted co-precipitation method with varying ratio of Cu, Ni and Co, which are used as an electrocatalyst for overall water splitting. (CuxNi1)Co1-LDHs (x = 0.5 1, 1.5, and 2 ) were systematically characterized using XRD, XPS, SEM, FTIR, TEM and BET techniques. The synergistic contributions from the electrocatalytically active metals and lamellar morphology of LDHs promotes water dissociation, facilitates faster release of H2-O2 gas bubbles, ameliorate electrolyte ion diffusion and improves electron transfer rate. It is further observed that the (CuxNi1)Co1-LDHs showed excellent electrocatalytic activity for both hydrogen evolution (HER) and oxygen evolution reaction (OER) with an overpotential of 147 and 218 mV for HER and OER, respectively at 10 mA cm-2. Tafel slope was found to be lowest for (Cu1Ni1)Co1-LDH. Further, the durability of the materials was also analysed by performing chronoamperometry for over 12 h. The overall water electrolytic cell using (Cu1Ni1)Co1-LDH as both electrodes can reach 50 mA cm−2 at 1.9V with outstanding durability.

Phase Evolution in (La0.6Sr0.4)0.95Co0.2Fe0.8O3-Δ Oxygen Electrodes after SOEC Operation

This work aims to evaluate the microstructural and compositional changes in (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) electrodes in solid oxide electrolysis cells (SOEC) before and after testing at 750°C for 2800 hours at 1.3V. Scanning electron microscopy (SEM) examination of the LSCF electrodes before and after SOEC operation was conducted. In untested LSCF electrodes, LSCF perovskite was a predominant phase with very minor presence of La(Fe,Co) oxide, and Fe,Co spinel phases. The post-tested electrodes exhibited a change where the La(Fe,Co) oxide phase exhibited a broader composition range, most notably with respect to the La/Fe ratio and potential loss of Co, and there was a noticeable increase in the volume fraction of Fe,Co spinel from 1.5% in the untested cell to over 3% after testing. To better understand the phases and their compositions, a transmission electron microscopy (TEM) study of tested and untested electrodes was undertaken using an aberration (Cs) corrected JEM-ARM200CF microscope operated at 200 kV. TEM confirmed the presence of cubic spinel particles with a composition of 26 at.% Fe and 13-15 at.% Co, with little to no Sr or La present. The composition of the La(Fe,Co) phase was more variable in agreement with the SEM analysis, with the Co/Fe ratio higher in the untested cell versus the cell tested at 2800 hours.

An Analysis of Capacitive Contributions of the Cell Impedance during High-Temperature CO2 and Co-Electrolysis

High-temperature electrolysis is often studied by electrochemical impedance spectroscopy (EIS). The EIS spectra are analyzed using equivalent circuit models (ECM). In many cases, these models use basic elements such as resistor, capacitances or inductances. The discussion of the modelling results is often limited to resistances [e.g. 1-4]. Only some rare papers discuss capacitances as well [e.g. 5-7]. A detailed analysis of all capacitive contributions of the overall cell impedance in electrolysis mode in dependence on temperature, current and composition is missing in literature.The present study provides this detailed analysis of the capacitive contributions, which in the models are usually represented by constant phase elements (CPEs). Impedance spectroscopy measurements of high-temperature CO2 and co-electrolysis on conventional fuel electrode supported cells were performed. The cells consisted of a Ni/YSZ fuel electrode, a YSZ electrolyte, a GDC barrier layer and a (La,Sr)CoO3 air electrode. The spectra were analyzed by an ECM consisting of an inductance, a serial resistance and four RQ elements (resistance and constant phase element in parallel). The dependences of the resistances on operating conditions were already reported elsewhere [1,8].The variation of the parameters temperature, current and composition showed different trends for the single elements. For example, the capacitive contribution of processes 1 – 3 (high to middle frequency range) increases with temperature while it decreases for process 4 (low frequency range). The low frequency process had been assigned to a gas phase diffusion process according to the dependence of the corresponding resistance [1]. The CPE element of process 4 also shows a prominent dependence on the current density. This might correlate with the changing ratio of CO2 to CO in the gas phase and thus support the assignment. Further results of the dependencies of the elements will be presented and discussed.[1] S. Foit, L. Dittrich, T. Duyster, I. Vinke, R.-A. Eichel, L.G.J. de Haart, Processes 2020, 8, 1390.[2] S.E. Wolf, L. Dittrich, M. Nohl, T. Duyster, I.C. Vinke, R.-A. Eichel, L.G.J. de Haart, J. Electrochem. Soc. 2022, 169, 034531.[3] S.D. Ebbesen, X. Sun, M. B. Mogensen, Faraday Discuss. 2015, 182, 393–422.[4] A. Leonide, V. Sonn, A. Weber, E. Ivers-Tiffée, J. Electrochem. Soc. 2008, 155, B36.[5] S. Primdahl, M. Mogensen, J. Electrochem. Soc. 1997, 144, 3409.[6] E.-C. Shin, J. Ma, P.-A. Ahn, H.-H. Seo, D. T. Nguyen, J. S. Lee, Electrochim. Acta 2016, 188, 240-253.[7] X. Ge, C. Fu, S. H. Chan, Phys. Chem. Chem. Phys. 2011, 13, 15134-15142.[8] L. Dittrich, Tailoring of the Synthesis Gas Composition during High-Temperature Co-Electrolysis (Aachen, Germany) (2021).

Exposure of Elderly People to Indoor Air Pollutants in Wanxia Nursing Home

The elderly residing in nursing homes are typically more advanced in age, have more health issues, and spend more time indoors than other elderly people. This study explored the indoor air quality in the Wanxia nursing home, the largest private nursing home in Chengdu, China, based on long-term measurement data. Air pollutant sensors measured the level of air pollution in the Wanxia nursing home from March 2021 to February 2022. This study obtained several important results: (1) The indoor air quality index (IAQI) of the Wanxia nursing home was at a low pollution level in spring, summer, and autumn, and at a moderate pollution level in winter. PM concentration played the most important role in determining indoor air quality; (2) During winter, the 24 h mean indoor concentrations of PM2.5 and PM10 were close to or even exceeded the standard limits. During winter and summer nights, indoor CO2 levels were very close to or greater than 1000 ppm. During spring and summer nights, the indoor TVOC concentrations exceeded the limit (0.45 mg/m3); (3) Apart from HCHO concentrations in autumn, the levels of other indoor air pollutants were significantly influenced by their outdoor levels. In addition, the seasonal indoor/outdoor (I/O) ratios of CO2 and TVOCs exceeded 1; and (4) Indoor CO2 levels were closely related to indoor temperature (Ta) and relative humidity (RH) in each season. PM10 concentration correlated with Ta and RH in summer, while PM2.5 concentration did not correlate with Ta and RH in winter. The indoor TVOC level positively correlated with RH. Lastly, the indoor HCHO level was minimally influenced by changes in Ta and RH. Due to the above results, this study proposes targeted strategies for improving indoor air quality in nursing homes.

Effect of gaseous pollutant and greenness exposure on mortality during treatment of newly treated tuberculosis patients: a provincial population-based cohort study.

Previous studies addressing the impact of environmental factors on TB prognosis are scarce, with only some studies examining the effect of particulate pollutants on TB mortality. Moreover, few studies have evaluated the effects of multiple gaseous pollutants and greenness exposures on newly treated TB patients on a large population scale. Through the Centers for Disease Control and Prevention, data were collected from January 1, 2015 to December 31, 2020 for newly treated TB patients in Anhui Province, China. Data on gaseous pollutants sulfur dioxide, nitrogen dioxide, carbon monoxide, and ozone were collected through the National Earth System Science Data Center of China. Normalized vegetation index data were obtained through NASA. The Cox proportional risk model was also applied to calculate the hazard ratios of SO2, NO2, CO, O3, and NDVI with 95% confidence intervals for mortality among newly treated TB patients. Multifactorial Cox regression analysis showed that for every 0.10μg/m3 increase in SO2, the risk of death among newly treated TB patients increased by 13.2% (HR = 1.132, 95% CI: 1.045-1.1.225), for every 10μg/m3 increase in NO2, the risk of death among newly treated TB patients increased by 11.4%, and for each 0.1 mg/m3 increase in CO, the risk of death among newly treated TB patients increased by 5.8%. For each 0.1 increase in NDVI 250m-buffer and 500m-buffer, the risk of death among newly treated TB patients decreased by 8.5% and 6.4%, respectively. The effect of gaseous pollutants on mortality decreased progressively with elevated greenness exposure when greenness exposure was grouped from low to high. Gaseous pollutants are a risk factor during the treatment of newly treated TB patients and greenness exposure is a protective factor. Higher greenness exposure reduces the risk of death due to exposure to gaseous pollutants.

Life Cycle Assessment of Improved Oil Recovery While Helping to Achieve Net Zero Emissions from Shale Reservoirs

Summary Shale reservoirs will help to meet oil demand that is forecasted to continue increasing for several years. Oil recovery from shales is low and has been reported to range between 5% and 10%. The objective of this paper is to show how oil recovery from shale can be improved while simultaneously reducing CO2 emissions, thus contributing to the goal of a net-zero future. The proposed methodology shows how oil recovery from shales can be increased while simultaneously storing CO2 in undepleted (as opposed to depleted) shale oil reservoirs and consequently contributing to a future with net-zero emissions. The methodology is developed with the use of reservoir simulation and is achieved by performing the following procedure: (1) Start huff ’n’ puff CO2 injection 2 or 3 years after the well goes on oil production so the shale reservoir is essentially undepleted, and (2) store CO2 gradually in the shale reservoir during the huff periods, and continuously once the huff ’n’ puff project is finalized. The simulation model includes a history match period with actual production data from a pilot horizontal well and a forecast period with huff ’n’ puff CO2 injection. Two cases, one with diffusion and one without diffusion, are conducted for evaluating the molecular diffusion effect. The initial reservoir pressure is never exceeded during the life cycle of the project as a safeguard against the possible creation of new fractures or reactivation of faults. Life cycle assessment (LCA) indicates that the ratio of cumulative stored CO2 to cumulative equivalent CO2 emissions during the project is approximately 31.3%, helping us consequently in the goal to eventually achieve a future with net-zero emissions. A careful literature survey indicates that the methodology proposed in this paper that includes enhanced oil recovery (EOR) by huff ’n’ puff CO2 injection and the simultaneous storage of CO2 in the shale reservoir is novel and has not been considered previously in geoscience or petroleum engineering literature.

Optimization of Discharge Plasma Reactor for Dry Reforming of Methane using Response Surface Methodology

This research provides a study of the dry reforming of methane (DRM), which converts two main greenhouses gases (CO2 and CH4) to synthesis gas (H2 and CO) by a Dielectric Barrier Discharge (DBD) plasma reactor at atmospheric pressure. The Box-Behnken Design (BBD) method based on the Response Surface Methodology (RSM) was applied to determine the optimum experimental conditions on the plasma stability and the synthesis gas production. The synergistic effects of input power (P), CO2/CH4 ratio (R), and flow rate (FR) on the CO2, CH4 conversions, H2, CO yields, and the syngas ratio of H2 to CO were studied. With the desirability value of 0.97, the optimum values of 10.05 W (P), 1.03 (R), and 1.58 L.min−1 FR were identified with CO2 conversion of 48.56% and CH4 conversion of 86.67%; H2 and CO yields of 45.87% and 39.43% respectively; and syngas ratio of H2 to CO of 0.88. The study shows that both P and FR have a major significant effect on the reactant conversions and syngas ratio, followed by R. Meanwhile, the value of R has a significant impact on the H2, CO yields followed P and FR. In contrast, the synergistic effects between P-R, P-FR, and R-FR had a weak significant on the CO2 and CH4 conversions, H2 and CO yields, and H2 to CO ratio respectively. The quadratic term coefficients of P, R, and FR had a remarkable effect on all responses. Thus, the synergistic effect of the most important parameters improves the process efficiency. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Direct methanol fuel cell with enhanced oxygen reduction performance enabled by CoFe alloys embedded into N-doped carbon nanofiber and bamboo-like carbon nanotube

The exploration of cost-effective electrocatalysts with high catalytic activity and methanol tolerance to replace precious metal catalysts in the oxygen reduction reaction (ORR) is highly desirable for direct methanol fuel cells (DMFCs). Herein, we report a novel complex composed of a CoFe alloy with a modulated electronic structure confined to nitrogen-doped carbon nanofiber (NCNF) and bamboo-like carbon nanotube (BCNT) by tuning the molar ratio of Co and Fe (CoFe@NCNF/BCNT). The synthetized catalysts possess one-dimensional (1D) mesoporous structure, high specific surface area, and rich pyridinic-N content. Notably, the Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT (Co:Fe ≈ 1:1 and 1:3) exhibited enhanced oxygen reduction activity and methanol tolerance, compared to unmodified samples. In addition, alkaline DMFCs containing Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT presented high power density (29.10 and 31.11 mW cm−2), exceeding that of Pt/C-modified DMFC (27.23 mW cm−2). Furthermore, the Co1Fe1@NCNF/BCNT-catalyzed DMFC exhibited high stability. This improved catalytic activity can be attributed to the rich surface area, controllable alloy composition, optimized N configuration, and favorable electronic interaction. The as-developed CoFe@NCNF/BCNT with multifunctional components may open a new avenue for designing highly active cathode catalysts for various fuel cells.

Enhancing the catalytic performance and coke reduction using low-cost Ni-based promoted catalyst for hydrogen production

Dry reforming of methane (DRM) is a highly promising reforming technology that facilitates converting CO2-rich natural gas into synthesis gas. However, the commercial application of DRM has concerns such as carbon deposition and sintering of the catalyst at high temperatures, leading to catalyst deactivation. This study aimed to determine the effect of an alkaline promoter addition on the amount of carbon deposited and activity test of alkaline-promoted nickel-based catalysts. Alkaline-promoted nickel-based catalysts were prepared using the incipient wetness impregnation method, followed by characterization using X-ray diffraction, N2 physisorption, H2-TPR, CO2-TPD, and thermogravimetric analysis. The performances of the catalysts were tested in a fixed-bed reactor under atmospheric pressure at 700 °C for 240 min. The Mg-promoted catalyst yielded the highest CH4 conversion (78%), CO2 conversion (64%), and H2 to CO ratio (1.52) compared to the non-promoted nickel-based and other alkaline-promoted catalysts. Furthermore, the thermogravimetric analysis revealed the Mg and Na-promoted catalyst produced 1.2 and 3.5 times less carbon than a commercial steam reforming catalyst.

Insights into syngas-fueled Wankel rotary engine performance from varied CO/H2 ratio

Syngas is a fuel with a huge market and low carbon emission, which has been proven to be well applied to internal combustion engines. WRE with high power density can effectively improve the power characteristic when syngas is employed as fuel in engines, however, which has not been reported publicly. This work aims to provide insights into the performance of syngas-fueled WRE under different CO/H2 ratios and thus gives theoretical guidance for its application. The test is done at 1500 r/min and part load. It is found that with the increase of the volumetric ratio of CO in syngas (CO%), the efficiency, torque and carbon emissions are deteriorated, however, the NO emission is significantly improved and the knock level is also reduced. In addition, on the premise of constant CO%, a high brake thermal efficiency, low NO emission and knock intensity can be achieved at lean combustion. In particular, when CO% is 10%, the combustion efficiency of CO is independent of the excess air ratio, while when CO% is 20%, that is decreased with increasing excess air ratio. In summary, the syngas-fueled WRE is recommended to adopt the qualitative control and the syngas with low CO%.

Ni-Co alloy catalyst derived from NixCoy/MgAl2O4 via exsolution method for high coke resistance toward dry reforming of methane

The dry reforming methane (DRM) reaction, which directly utilizes the two major greenhouse gases as reactants and produces syngas (a mixture of H2 and CO), is a promising method to achieve carbon neutrality. In this study, we developed a series of Ni–Co alloy catalysts with varying ratios using the exsolution method and explored the optimal Ni/Co ratio for DRM. By incorporating Co as a secondary metal and precisely controlling its proportion, the catalysts exhibited improved activation balance in CH4 and CO2, excellent resistance to coking, and the efficiency of the reaction pathway. Notably, the Ni4Co1 catalyst exhibited excellent coke resistance with the lowest coking rate of 0.2 μgcoke·gcat−1h−1, which was only 0.34% of the monometallic Ni catalyst. The origin of coke resistance of catalysts was investigated through in-situ DRIFT and found that the appropriate ratio of Co leads to the formate-intermediate dominant pathway that is more favorable for anti-coking. Furthermore, the catalysts exhibited reversible exsolution properties, as confirmed by cyclic of calcination–reduction. The findings of this study offer valuable insights into the fabrication of high-performance DRM catalysts utilizing the exsolution-driven alloying technique.