The oxidation coupling of methane (OCM) has received attention as a direct route to produce C-2 chemicals. Although the OCM is energetically more efficient than the conventional process, however, it provides relatively low C-2 yield and CH4 conversion at lower temperatures. In this study, TiO2 and Ce were used as a support and a promoter to facilitate CH4 conversion by providing more available oxygen species in the Mn/Na2WO4-based catalysts. Additionally, the performance of TiO2-supported catalysts was compared with that of the conventional Mn/Na2WO4/SiO2 catalyst. Various techniques including X-ray diffraction, X-ray photoelectron spectroscopy, and H-2 temperature-programmed reduction were conducted to evaluate the effect of TiO2 and Ce. The 1.9 % Mn-5% Na2WO4-5% Ce/TiO2 showed the best performance, with a maximum C-2 yield of 26.1% at 775 degrees C and the CH4/O-2 ratio of 2. This yield was higher than that of the Mn/Na2WO4-based catalysts examined in this study, indicating that TiO2 is a promising support for OCM catalysts.
In this study, the divergent behaviors were elucidated for CH2Cl2 and CH3Br oxidation over TiO2 and Ru/TiO2. Possible reaction mechanisms were elucidated. It was concluded that the adsorption and activation of halogenated volatile organic compounds were strongly dependent on the hard-soft acid-base theory.
Plasma-catalytic conversion of CO2 and H2O into energy gases at room temperature was studied in a dielectric barrier discharge reactor. CO, H-2 , and traces of CH4 were observed as the products in an argon atmosphere. Moreover, NiO with different morphologies was prepared and loaded on cordierite as catalysts. Compared with NiO-grain and NiO-sheet, NiO-sphere showed higher catalytic performance; the yields of H-2, CO, and CH4 were 354.3, 21.0, and 0.061 mu mol.h(-1).g(cat)(-1), respectively. Characterization indicated that highly dispersed NiO nano- clusters, chemical adsorption of CO2, and defect formation may be the factors that promoted the catalytic performance. Subsequently, a kinetic analysis was performed for further understanding the reaction process.
CeMnOx catalyst was synthesized by the combustion method, and the supported Ti/CeMnOx catalyst was subsequently prepared by wetness impregnation. Ti/CeMnOx catalyst exhibited higher N-2 selectivity than CeMnOx catalyst in the selective catalytic reduction of NO by NH3 (NH3-SCR), and the generation of side products including in N2O and NO2 were discussed. N-2 adsorption/desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H-2 temperature-programmed reduction (TPR), NH3 temperature-programmed desorption (TPD), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were carried out to reveal the promotion effect of TiO2 on the N-2 selectivity of CeMnOx catalyst. Results indicated that loading TiO2 weakened the redox ability and enhanced the NH3 adsorption ability of CeMnOx catalyst, and thus inhibited NO/NH3 oxidation and facilitated the Eley-Rideal reaction pathways even at higher temperature.
MXenes are two-dimensional metal carbides with promising applications in energy storage and sensors. Guidelines for safe, scalable MXene synthesis are important due to ongoing efforts to scale-up production of these novel nanomaterials. Hazard identification before scale-up will allow for inherently safer designs prior to actual implementation. Here, we investigate hazards associated with MXene production, including MAX phase synthesis from raw materials, etching of the MAX phase to MXene clay, exfoliation to MXene nanosheets, and postprocessing of MXenes with Ti3C2Tx as a model species. The major hazards in MXene synthesis are the potential for dust ignition, runaway reactions, and toxic chemical exposure. Because the synthesis of MXenes is a multistep process, safety guidelines for each step are evaluated, including preventive and mitigating measures, best practices, and emergency procedures and responses. This includes handling of combustible powders, exothermic reactions, and harsh chemical etchants. This study is intended to facilitate safer MXene synthesis across various levels of scale-up, from large laboratory batches to commercial production.
