Conversion of methane to C2 and C3 hydrocarbons over TiO2/ZSM-5 core–shell particles in an electric field

Integrating Physical Principles with Machine Learning for Predicting Field-Enhanced Catalysis

Field-dipole interactions can tune the energetics of polarized species over catalyst nanoparticles (NPs) for sustainable technologies. This can boost the energy efficiency of desired reactions by several orders of magnitude compared with conventional heating. However, the local electric field accumulation over the NPs sharp points and field-dependent adsorption over NPs are not well studied, and the associated computational expense is immense. To address this challenge, we introduce an innovative approach that combines density functional theory (DFT) calculations, DFT-based CO vibrational Stark effects, and physics principles enhanced machine learning (ML). This approach enables precise mapping of local electric fields and integrates the physical principles of the first-order Taylor expansion as a training input into the ML model for predicting field-dependent adsorption, facilitating rapid prediction of field-dependent adsorption energetics with acceptable accuracies, particularly when training data sets are limited. Our methodology reveals the dominant roles of external electric field (EEF), the generalized coordination number (GCN), and NP size in determining the local electric field (LEF) strength. Low-coordinated sites and small NPs size enhanced the LEF by about 4-fold compared to the flat surfaces. Using ML models, we can predict the field-driven adsorption energetics at a given adsorption site of the NPs with high accuracy and efficiency. The integration of ab initio modeling and ML algorithms offers exceptional possibilities to facilitate catalyst development and create the opportunity to enter a new paradigm in field-enhanced catalysis design based on fundamentals rather than trial and error.

Production of Acetylene from Viable Feedstock: Promising Recent Approaches

The potential of acetylene is extremely high both in chemical industry and synthetic applications due to unsaturated nature and the smallest active C≡C unit. The production of many essential necessities is originated from acetylene; however, the formation of acetylene molecule requires a lot of energy. Currently, the access to acetylene is based on coal processing, methane reforming and calcium carbide hydrolysis. Recently, extensive research has been done to decrease the cost of acetylene. In this review, the routes to acetylene were highlighted, considering the energy consumption in kW ⋅ h/t of the product to evaluate the best approach. Since energy prices depend on various regions, the cost of the product is complicated. The manufacturing of acetylene is usually accompanied by formation of by-products, which may be valuable or not. The review should help to identify current status and not overlook promising approaches.

Kinetics and mechanism study of dyes degradation in electric field-promoting catalytic wet air oxidation process

Wet air oxidation (WAO) is a clean and eco-friendly technology for dyes removal, but the high operating temperature and pressure limit its practical application. In the present work, an electric field-promoting (EF-promoting) catalytic WAO process is developed to degrade dyes under room condition. The oxidation kinetics of four different types of dyes and their degradation pathways are studied. A kinetic model is constructed by including the exogenous electric field into the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism framework, and quantitative structure-activity relationship (QSAR) analysis is conducted to correlate the kinetic parameters to the physicochemical properties of the dyes. A negative linear relationship is found between the adsorption equilibrium constants of the dyes and their first ionization energies, and their surface reaction rate constants are positively linearly associated to E_sum (E_LUMO + E_HOMO). The degradation pathways of the different dyes are proposed according to the degradation intermediates and the activities of the atoms within the dye molecules. The heteroatoms N and S, and the atom C connecting the aromatic rings are identified as the susceptible sites upon the electrophilic attack of O₂. Bond cleavage at these sites gives rise to aromatic fragments which are eventually mineralized via carboxyl acids. The results of this work is helpful for guiding the design and operation of the EF-promoting catalytic WAO process into the treatment of various dye wastewaters.

Plasma-Enhanced Chemical Looping Oxidative Coupling of Methane through Synergy between Metal-Loaded Dielectric Particles and Non-Thermal Plasma

A plasma–catalyst hybrid system has been developed for the direct conversion of methane to C2+ hydrocarbons in dielectric barrier discharge (DBD) plasma. TiO2 presented the highest C2+ yield of 11.63% among different dielectric materials when integrated with DBD plasma, which made us concentrate on the TiO2-based catalyst. It was demonstrated that MnTi catalyst showed the best methane coupling performance of 27.29% C2+ yield with 150 V applied voltage, without additional thermal input. The catalytic performance of MnTi catalyst under various operation parameters was further carried out, and different techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and H2-temperature-programmed reduction were used to explore the effect of Mn loading on methane oxidative coupling (OCM) performance. The results showed that applied voltage and flow rate had a significant effect on methane activation. The dielectric particles of TiO2 loaded with Mn not only synergistically affected the coupling reaction, but also facilitated charge deposition to generate a strong local electric field to activate methane. The synergy effects boosted the OCM performance and the C2+ yield became 1.25 times higher than that of the undoped TiO2 under identical operating conditions in plasma, which was almost impossible to occur even at 850 °C on the MnTi catalyst in the absence of plasma. Moreover, the reaction activity of the catalyst was fully recovered by plasma regeneration at 300 °C and maintained its stability in for at least 30 consecutive cyclic redox tests. This work presents a new opportunity for efficient methane conversion to produce C2+ at low temperatures by plasma assistance.

Oxidative Coupling of Methane for Ethylene Production: Reviewing Kinetic Modelling Approaches, Thermodynamics and Catalysts

Ethylene production via oxidative coupling of methane (OCM) represents an interesting route for natural gas upscaling, being the focus of intensive research worldwide. Here, OCM developments are analysed in terms of kinetic mechanisms and respective applications in chemical reactor models, discussing current challenges and directions for further developments. Furthermore, some thermodynamic aspects of the OCM reactions are also revised, providing achievable olefins yields in a wide range of operational reaction conditions. Finally, OCM catalysts are reviewed in terms of respective catalytic performances and thermal stability, providing an executive summary for future studies on OCM economic feasibility.

Pressure-induced dehydrogenative coupling of methane to ethane by platinum-loaded gallium oxide photocatalyst

Pt/Ga₂O₃ induced photocatalytic dehydrogenative coupling of CH₄ to yield C₂H₆ under high CH₄ pressure.