DMC production

Palladium chloride (PdCl2) based catalyst has been widely investigated and been verified to be highly selective toward dimethyl carbonate (DMC) yielding. 

Theoretical calculations and structural analysis have been performed by Zhi-Shen Huang and colleagues^[1] to explore the catalytic mechanism and the evolutions of active sites on PdCl2/α-Al2O3 for CO oxidative esterification. Defective PdCl2 (140) surface is identified as the active plane for CO and MN association. The formation of DMC probably abides by L–H mechanism and the Clvac acts as the active sites. Researhcers proposed a plausible chlorine loss mechanism on PdCl2 (140) surface using the DFT calculations.

The results show that chlorine prefers to run away from palladium chloride surface as HCl instead of CH3OCl or CH3OOCCl. It is important to note that the chlorine species continue to drain during the reaction and the product evolves from DMC to DMO simultaneously. Researchers proposed that preserving a proper amount of chlorine is of significant importance to maintain the activity of the catalyst for the production of DMC. Based on this perspective, future studies will focus on how to stabilize the defective palladium chloride structure with the proper amount of chlorine and their locations, which would contribute much to improve the stability of the catalysts.

Salicylonitrile synthesis

The synthesis of salicylonitrile is primarily conducted through the salicylamide dehydration method, which commonly employs toxic dehydrating agents for non-catalytic amide dehydration. However, the homogeneous palladium chloride offers a simple and green reaction process with outstanding activity and selectivity towards nitrile. Its high cost and non-recyclability, however, limit its industrial applicability. In this research^[2], the conversion of salicylamide to salicylonitrile was successfully achieved using a heterogeneous PdCl2/AC catalyst, prepared via a simple impregnation method with a high specific surface area activated carbon as the support.

References

[1] Huang, Z.-S., Zhou, Z.-F., Qiao, L.-Y., Zeng, Y.-Y., Zong, S.-S., & Yao, Y.-G. (2024). Mechanistic Investigation of Dimethyl Carbonate Synthesis Over Palladium Chloride Catalyst. Catalysis Letters, 155 1. https://doi.org/10.1007/s10562-024-04855-z

[2] Lan, G., Shi, T., Lin, D., Zhou, J., Cheng, Z., Sun, X., Qiu, Y., & Li, Y. (2024). A green process for the dehydration of salicylamide to salicylonitrile utilizing a heterogeneous carbon supported PdCl2 catalyst. Molecular Catalysis, 563, Article 114258. https://doi.org/10.1016/j.mcat.2024.114258