Yuanli Jiang

A structured, chloride‐free Pd–Cu/NaY catalyst was developed for the direct synthesis of dimethyl carbonate (DMC) from syngas‐derived methyl nitrite and CO. The NaY zeolite support stabilizes Pd(II) species via strong electrostatic interactions, while Cu addition enhances durability by suppressing Pd reduction and aggregation, as confirmed by H ₂ ‐TPR and TEM. Using shaped spherical supports improves DMC selectivity by limiting methyl nitrite decomposition side reactions through diffusion constraints. Under optimized conditions (CO/MN = 1/6, 120°C), the catalyst achieves a DMC space‐time yield of 669 g·kg ⁻¹ ·h ⁻¹ with high selectivity. A 1000 h stability test shows sustained activity above 550 g·kg ⁻¹ ·h ⁻¹ after an initial run‐in period. In situ DRIFTS studies identify the ligand exchange step as rate‐determining and elucidate the full reaction pathway. This robust catalytic system demonstrates strong potential for pilot‐scale and industrial syngas‐to‐DMC processes.

Despite recent progress in the coal‐to‐ethylene glycol (EG) technology, some indicators show that the obtained products are still different from those produced by the petroleum route method. Therefore, it is of great significance to improve the thermodynamic performance of the system to obtain an enhanced process technology. In this paper, thermodynamic data related to uncommon substances in coal‐to‐EG reactions were estimated using the Benson group contribution method, and the values of the reaction enthalpy, Gibbs free energy, and the equilibrium constant of each reaction in the system were calculated. We systematically analyzed the temperature influence on the main product, DMO (dimethyl oxalate), and the main by‐product, DMC (dimethyl carbonate), in the DMO synthesis reaction and the influence of the DMC content on the spontaneous formation of EC (ethylene carbonate) in the DMO hydrogenation reaction. The obtained results demonstrated that elevated temperatures are favorable for the generation of DMC. In the DMO hydrogenation reaction, the mass fraction of DMC should be less than 0.05678 % when the feeding proportion is based on industrial data. When pure DMO is fed, the mass fraction of DMC should be less than 0.0335 %. Finally, no special treatment is required for EC separation in these cases.

In order to explore the commercialized applications of the low-grade bauxite in the refractory industry, a calcination integrated with acid leaching method was adopted to remove the potassium (K) and iron (Fe) from the diaspore-illite (DI) type low-grade bauxite. Following calcining the bauxite at different temperatures, the leaching parameters, including the sulfuric acid concentration, temperature, sulfuric acid to bauxite ratio, and reaction time were systematically studied. The appropriate and economical conditions for removing the impurities were found to be calcining the bauxite at 550 °C, and leaching it with a sulfuric acid solution of 1.2 mol/L, sulfuric acid/bauxite ratio of 9 mL/g at a reaction temperature of 70 °C and reaction time of 2 h, under these conditions, the removal efficiency of K and Fe from the bauxite can reach 30.32% and 47.33%, respectively. The treated bauxite was examined by XRD analysis, SEM observations, and chemical analysis. Kinetics of the removing process were calculated by two models, and the results showed that the leaching process was controlled by the mixed shrinking core model, which was affected by both the diffusion through solid layer and the interface transfer. In summary, the approach in this work presents a promising process for comprehensive utilization of the low-grade bauxite.