(661f) Direct carboxylation of thiophene and CO2 in the cesium carbonate system
AIChE Annual Meeting
2021
2021 Annual Meeting
Catalysis and Reaction Engineering Division
Poster Session: Catalysis and Reaction Engineering (CRE) Division - Virtual
Monday, November 15, 2021 - 10:30am to 12:00pm
Based on green chemistry and atomic economy principles, the direct carboxylation of thiophene and CO2 is an important research direction in the field of CO2 utilization. The main carboxylate products have been widely applied in the fields of medicine and materials. However, it is difficult for both substrates to achieve the carboxylation reaction under mild conditions due to the relatively stable CO2 and less active thiophene. The highly active organometallic reagents are generally employed to promote the carboxylation reaction accompanied by the potential environment and safety problems. The direct carboxylation of thiophene is primarily achieved in the batch reactor with Cs2CO3 and simple carboxylates (cesium acetate, formate and oxalate and pivalate) as the reaction medium. The synergistic effect of Cs2CO3 and simple carboxylates is observed, and the cesium pivalate is the most efficient additive in the carboxylation reaction. The effects of different reaction factors (reaction temperature, Cs2CO3 proportion, CO2 pressure, total salt amount, substrate amount and reaction period) are investigated. Meanwhile, high temperature in-situ X-ray diffraction (in-situ XRD) characterization technique indicates that the direct carboxylation is carried out in the heterogeneous system with Cs2CO3-CsOPiv eutectic phase and Cs2CO3 solid phase. The carboxylation mechanism is further speculated in this system. The complex [Cs2CO3-CsOPiv] is primarliy formed through the interaction of Cs2CO3 and CsOPiv, which can activate and further break the C-H bond of thiophene, and the CO2 insertion is easily conducted to form C-C bond of carboxylate products.
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