Research progress in carboxylation of coal-based aromatic compounds with CO2

Abstract

Burning fossil fuels is an effective way to obtain energy at present, but the emitted carbon dioxide has seriously affected the earth’s ecological environment. Meanwhile, CO2 itself is a low toxicity, nonflammable, abundant and cheap carbon resource. The resource utilization of CO2 through chemical methods not only provides some useful ideas for the fixation of CO2, but also obtains some high value-added products. Among them, the direct carboxylation of CO2 has attracted much attention because of its advantages in the step economy and the atom economy. The commonly used catalysts in such reactions include metal complexes, Lewis acids and bases, while most of the metal complexes face complex synthesis steps and high price. Aromatics and heterocyclic compounds are important products of coal chemical industry. Expanding the downstream utilization of coal-based chemicals is an important way to promote the transformation and upgrading of coal chemical industry. Aromatic acid is a kind of very important chemical products. At present, the production process of most aromatic acids involves multi-step reaction, with low atomic utilization and high cost. This paper reviews the research progress in the synthesis of aromatic acids catalyzed over Lewis acid or base, using coal-based aromatic compounds as substrates and cheap and easily available CO2 as carboxylation raw materials. Compared with the traditional synthesis method of aromatic acid, the CO2 carboxylation method is a green and economic synthesis method with short reaction process, low cost, high product selectivity and yield. Taking coal-based aromatic compounds as raw materials, the technology of preparing aromatic acids by carboxylation with CO2 has broad development prospects. Through comparison, the supported carbonate catalyst has good safety and stability, and can be regenerated, but the yield and selectivity of the target compound are low. In the subsequent development, the performance and safety of the catalyst need to be continuously improved for promoting the application of the reaction in a large-scale industrial production.

Keywords

• carbon dioxide
• carboxylation
• coal-based aromatic compounds
• lewis acid catalyst
• alkali catalyst