The photocatalytic oxidative coupling of methane (OCM) on metal-loaded one-dimensional TiO₂ nanowires (TiO₂ NWs) was performed. With metal loading, the electric and optical properties of TiO₂ NWs were adjusted, contributing to the improvement of the activity and selectivity of the OCM reaction. In the photocatalytic OCM reaction, the 1.0 Au/TiO₂ NW catalyst exhibits an outstanding C₂H₆ production rate (4901 μmol g⁻¹ h⁻¹) and selectivity (70%), alongside the minor production of C₃H₈ and C₂H₄, achieving a total C₂–C₃ hydrocarbon selectivity of 75%. In contrast, catalysts loaded with Ag, Pd, and Pt show significantly lower activity, with Pt/TiO₂ NWs producing only CO₂, indicating a propensity for the deep oxidation of methane. The O₂-TPD analyses reveal that Au facilitates mild O₂ adsorption and activation, whereas Pt triggers excessive oxidation. Spectroscopic and kinetic studies demonstrate that Au loading not only enhances the separation efficiency of photogenerated electron–hole pairs, but also promotes the generation of active oxygen species in moderate amounts, which facilitates the formation of methyl radicals and their coupling into C₂H₆ while suppressing over-oxidation to CO₂. This work provides novel insights and design strategies for developing efficient photocatalysts.

Microwave heating has excellent potential for applications in wastewater treatment. This study proposes a highly efficient continuous liquid-phase microwave heating system to overcome the problems of low treatment capacity, low dynamic range of loads, and insufficient heating uniformity of the existing equipment. First, a quarter-wavelength impedance-matching layer improves heating efficiency, and the heating uniformity has been enhanced by horn antennas. Second, an experimental system is developed. The simulation and experimental results are consistent, with the microwave system achieving over 90% energy utilization for different thicknesses and concentrations of salt water. Finally, simulations are performed to analyze microwave efficiency and heating uniformity at different flow rates, salinities, dielectric properties, and sawtooth structures. The system can efficiently heat loads with a wide range of dielectric properties, including saline water. Generally, when the permittivity varies from 10 to 80, and the loss tangent varies dynamically from 0.15 to 0.6, more than 90% of microwave efficiency and excellent temperature distribution (The coefficient of temperature variation COV < 0.5) can be achieved. The system’s modular design enables scaling up to further boost processing capacity. Overall, the system provides high-throughput, high-efficiency, high-uniformity, and large-dynamic-range microwave water treatment, which has promising applications in industrial water treatment.

Microwave radiation has become an effective catalytic combustion method, especially in the degradation of volatile organic compounds (VOCs) such as toluene using catalysts like MnO₂. In this study, a spine waveguide microwave reactor was designed to investigate the influence of different microwave processing conditions on the degradation of toluene catalyzed by MnO₂. An experimental system for microwave-assisted catalytic degradation of toluene was established to explore the relationship between microwave power, catalyst conductivity, and toluene degradation rate. The results showed that the efficiency of MnO₂ catalyzing toluene degradation had a nonlinear relationship with microwave power, first increasing to a peak and then decreasing. Additionally, the experiment found that the degradation rate of toluene was positively correlated with the conductivity of MnO₂. Subsequent characterization analyses using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) further verified the changes in the microstructure and properties of MnO₂ under microwave heating. The characterization results showed that with the increase in microwave power, the relative content of Mn³⁺ on the surface of MnO₂ increased, and the relative content of adsorbed oxygen also increased accordingly. At a microwave power of 100 W, the treated MnO₂ displayed the optimal ratio of manganese oxidation state and oxide, both close to 1:1, which was more conducive to the degradation of toluene. Based on these findings, this study hypothesized that the microwave-enhanced catalytic degradation of toluene by MnO₂ may be attributed to changes in the surface electron transfer kinetics of MnO₂, providing new insights into the field of microwave-enhanced catalysis.

Traditional microwave heating faces challenges such as low efficiency and uneven heating, hindering its industrial application. Sweep frequency microwave heating is an effective way to improve uniformity. Larger cavity sizes result in better heating uniformity due to the generation of more resonant modes. However, in industrial applications, large cavities occupy significant space, making them less flexible and limiting their usability. This paper introduces a method to enhance sweep frequency microwave heating uniformity by adding a dielectric substance to cavity walls. First, the impact of increasing cavity size on the uniformity of sweep frequency microwave heating was studied, with the theoretical analysis showing that filling the cavity with dielectric materials can be equivalent to enlarging the cavity size. Subsequently, a multiphysics simulation model for sweep frequency microwave heating was established to analyze the effects of dielectric substance thickness and permittivity on heating uniformity. A high-efficiency, high-uniformity microwave multimode cavity was designed, and the accuracy of the simulation model was validated through experiments. Finally, the effects of sweep frequency range and load variations on the heating performance were analyzed. This method effectively addresses the uniformity issues in industrial microwave heating and aids in promoting the application of microwave energy in industry.

Cylindrical loads are commonly found in microwave heating. However, cylindrical loads tend to have a thermal focus, leading to uneven microwave heating. In this paper, a novel microwave heating method was proposed by employing resonant rings to mitigate the thermal focus of cylindrical loads. Firstly, a multiphysics simulation model for microwave heating of a cylindrical tube is established, and the influence of the resonant ring around the cylindrical tube on the temperature distribution of load was analyzed. Subsequently, microwave heating experiments of agar gels with and without resonant rings were carried out. In agreement with the simulation results, the use of resonant rings reduces the coefficient of temperature variation (COV) from 1.064 to 0.793. In addition, the parameters affecting the heating uniformity of the cylindrical tube were discussed through simulations.

In order to improve the uniformity of microwave heating, moving components are often added to the cavity. For higher uniformity or greater industrial processing capacity, samples often perform large-scale movements such as rotating and lifting motion or translational motion on a conveyor belt. The microwave heating algorithm based on the ray-casting method (RCM), as proposed in previous studies, can calculate moving complex-shaped samples, but the calculation efficiency is low when the sample moves on a large scale due to the large refined mesh area. To solve this problem, this study introduced a moving mesh combined with the RCM for calculation purposes. A microwave oven model with a rotating and lifting turntable was selected for the analysis. First, the calculation area was divided into a sliding mesh and a telescopic mesh area. The telescopic mesh area was stretched or compressed at different times, which was equivalent to the translational motion of the sample. Then, the electromagnetic parameters were assigned to each mesh point in combination with the boundary recognition algorithm based on the ray-casting method, and the horizontal motion was calculated while calculating the large-scale translation. The proposed method only needs to refine the mesh in the horizontal motion area, which reduces the number of overall meshes. The electromagnetic field distribution obtained by the model during the heating process was verified by the discrete position method. The surface temperature distribution and the real-time curve of the center point temperature were further compared with the RCM. The results show that the average error of the sample center temperature is 2.5% and the calculation time was reduced to 9.8%, which verified the accuracy and efficiency of the proposed method. Finally, the influence of different lifting and rotating speeds on the heating effect was further explored.