Highly Active Ni-Ru Bimetallic Catalyst Integrated with MFI Zeolite-Loaded Cerium Zirconium Oxide for Dry Reforming of Methane

Effect of strontium on the performance of Ni/CBV20A catalyst in partial oxidation of methane for syngas and hydrogen production

Converting methane into syngas via partial oxidation of methane (POM) is a promising energy-efficient technology given its exothermic nature. Active nickel-based catalysts suffer from deactivation by carbon deposition and sintering. This study explores the novel use of mordenite zeolite (CBV20A) as a catalytic support for nickel (Ni) and using strontium (Sr) as a promoter. Ni5Sr x /CBV20A samples with various Sr loadings were prepared and characterized using N2-sorption, X-ray diffraction, H2-temperature programmed reduction, temperature programmed desorption of CO2, and Transmission Electron Microscopy. Sr addition improved NiO reducibility at lower temperature and boosted basicity, enhancing CH4 conversion and H2 yield. The optimal catalyst, Ni5Sr2/CBV20A, exhibited the highest performance with 72% CH4 conversion, 47% H2 yield, and 2.6 H2/CO ratio at 700 °C and 14 400 mL g-1 h-1. Results show that at a high gas hourly space velocity (GHSV) of 72 000 mL g-1 h-1, a combustion and reforming reaction mechanism is preferred, while at a low GHSV of 14 400 mL g-1 h-1, a direct partial oxidation mechanism predominates.

Formate and CO* Radicals Intermediated Atmospheric CO2 Conversion over Co-Ni Bimetallic Catalysts Assembled on Diatomite

There exists an imperative exigency to ascertain catalysts of cost-effectiveness and energy efficiency for the facilitation of industrial CO2 methanation. In this area, the dual metal synergistic enhancement of the metal-support interaction emerges as a highly promising strategy. Here, Diatomite (Dt) was used as the support, and a series of CoyNi/Dt (Co as the first component and Ni as the second component) composite catalysts were constructed using an ultrasound-assisted coimpregnation method. Different Co/Ni molar ratios had a significant impact on the phase structure, chemical properties, morphological characteristics, and NiCo crystal structure of the xCoyNi/Dt materials. When the Co/Ni molar ratio was set to 2.0, a Ni-Co alloy was obtained, which is the key to improve the catalytic activity. Compared to the other xCoyNi/Dt catalysts, the bimetallic catalyst 2Co1Ni/Dt exhibited superior CO2 catalytic performance and stability, achieving a 76% CO2 conversion and 98% CH4 selectivity at 425 °C. The in situ DRIFTS results indicated that CO2 methanation over the 2Co1Ni/Dt catalyst followed the reaction pathway with formate and CO* radicals as the intermediates.

Co Cluster-Modified Ni Nanoparticles with Superior Light-Driven Thermocatalytic CO2 Reduction by CH4

Excessive fossil burning causes energy shortages and contributes to the environmental crisis. Light-driven thermocatalytic CO2 reduction by methane (CRM) provides an effective strategy to conquer these two global challenges. Ni-based catalysts have been developed as candidates for CRM that are comparable to the noble metal catalysts. However, they are prone to deactivation due to the thermodynamically inevitable coking side reactions. Herein, we reported a novel Co-Ni/SiO2 nanocomposite of Co cluster-modified Ni nanoparticles, which greatly enhance the catalytic durability for light-driven thermocatalytic CRM. It exhibits high production rates of H2 (rH2) and CO (rCO, 22.8 and 26.7 mmol min-1 g-1, respectively), and very high light-to-fuel efficiency (ƞ) is achieved (26.8%). Co-Ni/SiO2 shows better catalytic durability than the referenced catalyst of Ni/SiO2. Based on the experimental results of TG-MS, TEM, and HRTEM, we revealed the origin of the significantly enhanced light-driven thermocatalytic activity and durability as well as the novel photoactivation. It was discovered that the focused irradiation markedly reduces the apparent activation energy of CO2 on the Co-Ni/SiO2 nanocomposite, thus significantly enhancing the light-driven thermocatalytic activity.

Effective CO2 Thermocatalytic Hydrogenation with High Coke Resistance on Ni-CZ/Attapulgite Composite

Converting CO2 into methane is considered a promising and economically viable technology for global transportation and utilization of this greenhouse gas. This study involves the preparation of a Ni-CZ (CeO2-ZrO2)/ATP (attapulgite) catalyst through the co-precipitation and impregnation methods. XRD, SEM, TEM, N2 absorption-desorption isotherms, XPS, H2-TPR, CO2-TPD, TG/DSC, and Raman were adapted to characterize the obtained samples. Real-time GC was used to measure the catalytic performances and to intensively study the impact of Ni loading content and ATP to CZ ratio on the catalytic performance of the products. DRIFTs was used to monitor the interstitial radicals in the catalytic reactions and to deduce the catalytic mechanisms. The results indicate that the composite catalytic matrix composed of CZ assembled on ATP demonstrated higher CO2 methanation stability and better carbon deposition resistance ability than the single CZ or ATP as the carrier, which should be attributed to the improved specific surface area and pore volume of the ATP assembled matrix and the enhanced dispersibility of the CZ and Ni species. The adoption of CZ solid solutions improves the oxygen storage capability of the catalyst, thereby providing continued mobile O2- in the matrix and accelerating the molecular exchange rate in the catalytic reactions. The ideal loading quantity of nickel contents on the CZA matrix is 15%, as the CO2 conversion decreases at elevated temperatures when the Ni loading content reaches 20%. Among the tested samples, the 15Ni-0.8CZA sample showed the best catalytic performance of 75% CO2 conversion and 100% CH4 selectivity at 400 °C. After 50 h of stability tests, the CO2 conversion rate still remained 70.84%, and the CH4 selectivity obtained 97.46%. No obvious coke was detected according to the Raman spectra of the used catalyst. The in situ DRIFTS experiment showed that formate is the main intermediate of the CO2 hydrogenation reaction on the 15Ni-0.8CZA catalyst.

Rh/InGaN1-xOx nanoarchitecture for light-driven methane reforming with carbon dioxide toward syngas

Light-driven dry reforming of methane toward syngas presents a proper solution for alleviating climate change and for the sustainable supply of transportation fuels and chemicals. Herein, Rh/InGaN1-xOx nanowires supported by silicon wafer are explored as an ideal platform for loading Rh nanoparticles, thus assembling a new nanoarchitecture for this grand topic. In combination with the remarkable photo-thermal synergy, the O atoms in Rh/InGaN1-xOx can significantly lower the apparent activation energy of dry reforming of methane from 2.96 eV downward to 1.70 eV. The as-designed Rh/InGaN1-xOx NWs nanoarchitecture thus demonstrates a measurable syngas evolution rate of 180.9 mmol gcat-1 h-1 with a marked selectivity of 96.3% under concentrated light illumination of 6 W cm-2. What is more, a high turnover number (TON) of 4182 mol syngas per mole Rh has been realized after six reuse cycles without obvious activity degradation. The correlative 18O isotope labeling experiments, in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and in-situ diffuse reflectance Fourier transform infrared spectroscopy characterizations, as well as density functional theory calculations reveal that under light illumination, Rh/InGaN1-xOx NWs facilitate releasing *CH3 and H+ from CH4 by holes, followed by H2 evolution from H+ reduction with electrons. Subsequently, the O atoms in Rh/InGaN1-xOx can directly participate in CO generation by reacting with the *C species from CH4 dehydrogenation and contributes to the coke elimination, in concurrent formation of O vacancies. The resultant O vacancies are then replenished by CO2, showing an ideal chemical loop. This work presents a green strategy for syngas production via light-driven dry reforming of methane.

Interfacial Metal-Support Interaction and Catalytic Performance of Perovskite LaCrO3-Supported Ru Catalyst

Interfacial metal-support interaction (MSI) significantly affects the dispersion of active metals on the surface of the catalyst support and impacts catalyst performance. Understanding MSI is crucial for developing highly active and stable catalysts with a low metal loading, particularly for noble metal catalysts. In this work, we synthesized LaRuxCr1-xO3 catalysts with low Ru loading (x = 0.005, 0.01, and 0.02) using the sol-gel self-combustion method. We found that all of the Ru atoms immediately above or below the metal-support interface are closely bonded to the perovskite LaCrO3 surface lattice through Ru-O bonds, enhancing the MSI via interfacial reaction and charge transfer mechanisms. We identified a variety of Ru species, including small 3D Ru nanoparticles, 2D dispersed Ru surface atoms, and even 0D Ru single atoms. These highly dispersed Ru species exhibit high activity and stability under dry reforming of methane (DRM) conditions. The LaRu0.01Cr0.99O3 catalyst with very low Ru loading (0.42 wt %) was stable over a 50 h DRM test and the carbon deposition was negligible. The CH4 and CO2 conversions at 750 °C reached 83 and 86%, respectively, approaching the theoretical thermodynamic equilibrium values.