Boosting Dimethyl Carbonate Production from CO2 and Methanol using Ceria-Ionic Liquid Catalyst.

As a crucial strategy towards a sustainable chemical industry, the direct synthesis of dimethyl carbonate (DMC) from renewable carbon dioxide (CO2) and methanol (MeOH) is studied using CeO2 nanoparticles modified with 1-butyl-3-methylimidazolium hydrogen carbonate ([BMIm][HCO3]) devoid of stoichiometric dehydrating agents. The synthesized CeO2@[BMIm][HCO3] catalyst having high thermal stability harnesses the unique physicochemical properties of CeO2 and the ionic liquid to exhibit a DMC yield of 10.4 % and a methanol conversion of 16.1 % at optimal conditions (pressure of CO2=5 MPa; temperature=130 °C). The catalytic behavior of CeO2@[BMIm][HCO3] studied with a detailed XRD, XPS, CO2 and NH3-TPD, Raman spectroscopy, TGA, FTIR, SEM and TEM suggests that the synergy between the two catalytic components originating from an increased surface oxygen vacancies boosts the overall catalytic performance. After several recycling tests, the catalyst demonstrated no significant reduction in DMC yield and methanol conversion. This platform is an attractive approach to synthesize thermally stable nanoparticle@ionic liquid that retains and merges the physical attributes of both materials for producing useful bulk chemicals from readily available chemical resources.

Synthesis of C2+ Chemicals from CO2 and H2 via C-C Bond Formation.

ConspectusThe severity of global warming necessitates urgent CO2 mitigation strategies. Notably, CO2 is a cheap, abundant, and renewable carbon resource, and its chemical transformation has attracted great attention from society. Because CO2 is in the highest oxidation state of the C atom, the hydrogenation of CO2 is the basic means of converting it to organic chemicals. With the rapid development of H2 generation by water splitting using electricity from renewable resources, reactions using CO2 and H2 have become increasingly important. In the past few decades, the advances of CO2 hydrogenation have mostly been focused on the synthesis of C1 products, such as CO, formic acid and its derivatives, methanol, and methane. In many cases, the chemicals with two or more carbons (C2+) are more important. However, the synthesis of C2+ chemicals from CO2 and H2 is much more difficult because it involves controlled hydrogenation and simultaneous C-C bond formation. Obviously, investigations on this topic are of great scientific and practical significance. In recent years, we have been targeting this issue and have successfully synthesized the basic C2+ chemicals including carboxylic acids, alcohols, and liquid hydrocarbons, during which we discovered several important new reactions and new reaction pathways. In this Account, we systematically present our work and insights in a broad context with other related reports.1.We discovered a reaction of acetic acid production from methanol, CO2 and H2, which is different from the well-known methanol carbonylation. We also discovered a reaction of C3+ carboxylic acids syntheses using ethers to react with CO2 and H2, which proceeds via olefins as intermediates. Following the new reaction, we realized the synthesis of acetamide by introducing various amines, which may inspire the development of further catalytic schemes for preparing a variety of special chemicals using carbon dioxide as a building block.2.We designed a series of homogeneous catalysts to accelerate the production of C2+ alcohols via CO2 hydrogenation. In the heterogeneously catalyzed CO2 hydrogenation, we discovered the role of water in enhancing the synthesis of C2+ alcohols. We also developed a series of routes for ethanol production using CO2 and H2 to react with some substrates, such as methanol, dimethyl ether, aryl methyl ether, lignin, or paraformaldehyde.3.We designed a catalyst that can directly hydrogenate CO2 to C5+ hydrocarbons at 200 °C, not via the traditional CO or methanol intermediates. We also designed a route to couple homogeneous and heterogeneous catalysis, where exceptional results are achieved at 180 °C.

Synthesis of ethanol from aryl methyl ether/lignin, CO2 and H2.

Currently, ethanol is produced via hydration of ethene or fermentation of foods. Lignin and CO2 are abundant, cheap and renewable feedstocks. Synthesis of ethanol using the lignin or its derivatives is of great importance, but is a great challenge and has rarely been reported. Herein, we propose a route to synthesize ethanol from CO2, H2, and lignin or various aryl methyl ethers, which can be derived from lignin. The reaction could be effectively conducted using Ru-Co bimetallic catalyst and the TON of ethanol could reach 145. Interestingly, ethanol was the only liquid product when lignin was used. A series of control experiments indicate that ethanol was formed via cleavage of aryl ether bond, reverse water gas shift (RWGS) reaction, and C-C bond formation. This protocol opens a way to produce ethanol using abundant renewable resources.