Comparative Study between 2‐Furonitrile and 2‐Cyanopyridine as Dehydrants in Direct Synthesis of Dialkyl Carbonates from CO2 and Alcohols over Cerium Oxide Catalyst

The shift of equilibrium by removing water with nitrile dehydrants is crucial for CeO2‐catalyzed synthesis of dialkyl carbonates from CO2 and alcohols, and two nitriles—2‐cyanopyridine and 2‐furonitrile—were previously found as effective dehydrants. Yet, their detailed comparison as well as exploration of potential of 2‐furonitrile have remained insufficient. In this work, therefore, the performance of 2‐cyanopyridine and 2‐furonitrile was compared in the synthesis of various dialkyl carbonates. 2‐Furonitrile was found to be superior to 2‐cyanopyridine in the synthesis of dialkyl carbonates from CO2 and bulky or long‐chain (≥C3) alcohols. Namely, the yield of diisopropyl carbonate (up to 50%) achieved by the combination of CeO2 and 2‐furonitrile is comparable to or even higher than those ever reported. Meanwhile, 2‐cyanopyridine behaved as a better dehydrant than 2‐furonitrile in the synthesis of dimethyl carbonate and diethyl carbonate. The adsorption experiments and density functional theory calculations have indicated that the better performance of 2‐furonitrile compared to 2‐cyanopyridine in the synthesis of dialkyl carbonates from bulky or long‐chain alcohols is due to the weaker interaction of 2‐furonitrile with the CeO2 surface. Such weak interaction of 2‐furonitrile enables to offer a larger reaction field on the catalyst surface for both CO2 and alcohols.