ANALYSIS OF THE MECHANISM OF THE DECOMPOSITION-EXTRACTION PROCESS

In our last paper (Hu, L.; Adeyiga, A. A. 1997, 36 (6), 2375), we repo rted the extraction of formic acid from the reaction of sodium formate with carbon dioxide by organic tertiary amine. The process can be des cribed by the reactions HCOONa(w) + CO2(g) + H2O(w) === NaHCO3(s,w) HCOOH(w) and HCOOH(w) + NR3(o) === HCOOHNR3(o). We defined the above p rocess as a decomposition-extraction process. The studies investigated the mechanism of the decomposition-extraction process. By engineering analysis of the process, it was found that the mass transfer of carbo n dioxide from the gas phase to the aqueous phase (the aqueous solutio n of sodium formate or calcium chloride) proceeded essentially through the organic phase (organic tertiary amine with diluent 2-ethylhexyl a lcohol) rather than directly. Then carbon dioxide in the organic phase reacted with salt in the aqueous solution to form MHCO3 and complex N R3-HOOCH. The organic phase was both the extractant of formic acid and the transporter of carbon dioxide. This mechanism has been identified through our experimentation for the first time.