The fermentation for the production of succinic acid (SA) outperforms other methods by low energy consumption and environmental benignity, with the resulted products mainly as disodium succinate (DSA). By the direct esterification of DSA using CO2 and CH3OH, it is expected to avoid the use of inorganic acids in downstream industrial esterification of bio-based DSA. By high-resolution mass spectrometry analysis and theoretical calculation,this study establishes that the direct esterification of DSA consists of three steps by first forming 3-carboxypropanoate,then monomethyl succinate (MMS),and finally DMS. The reaction kinetics of DSA direct esterification is also investigated by experiment and simulation with MATLAB, and the reaction kinetics equation along with reaction rate constant are obtained. The activation energy for the generation of MMS from DSA is 37.15 kJ/mol,and the one for the generation of DMS from MMS is 85.80 kJ/mol,indicating the latter one is the rate-determining step for the direct esterification of DSA.

The fermentation method for preparing SA is distinguished by low energy consumption and environmental friendliness, but the resulting products mainly exist in form of disodium succinate (DSA). Direct esterification of DSA using CO2 and CH3OH as esterification reagent to produce dimethyl succinate (DMS) can avoid use of inorganic acids in downstream esterification industry of bio-based DSA. On basis of high-resolution mass spectrometry analysis and quantum theoretical calculation, the process of DSA direct esterification involved sequentially forming 3-carboxypropanoate, monomethyl succinate (MMS), and DMS. Furthermore, the reaction kinetics of DSA direct esterification was investigated by experiment and numerical simulation method, where the reaction kinetics equation and reaction rate constant were obtained. The activation energy for the generated process of MMS by DSA was 37.15 kJ/mol, while the one for the formed process of DMS from MMS was 85.80 kJ/mol, indicating the latter was the speed control step of DSA direct esterification.

The use of organic solvents to remove SO2 from flue gas has the advantages of low investment cost, convenient operation, high efficiency, and reusability. We prepared three absorbents in this paper, namely tetraethylenetetramine (TETA), triethylenetetramine /triethylene glycol dimethyl ether (TriEDGME), and triethylenetetramine/triethylene glycol dimethyl ether/H2O. The atmospheric bubbling method absorbs SO2. The experimental results show that the three kinds of absorbents formed white precipitates after adsorbing SO2. The infrared spectra analysis and element analysis of the three types of precipitate showed that their chemical structures were basically the same. The structural formula is NH2(CH2)2NH(CH2)2NH3SO3NH2·2H2O; the product was determined to be a shaped crystal structure by XRD and SEM. In addition, the thermal stability analysis of the product revealed that the product sublimed at 123 °C and decomposed at about 185 °C.