Preparation of Pure Methyl Esters from Corresponding Alkali Metal Salts of Carboxylic Acids Using Carbon Dioxide and Methanol

Abstract

In the present article, for the first time, we report the synthesis of alkyl esters by direct esterification of alkali metal salts of carboxylic acids using carbon dioxide and alcohol. Methyl acetate, methyl benzoate, methyl salicylate, and methyl lactate have been synthesized by esterification of sodium acetate, sodium benzoate, sodium salicylate, and calcium lactate, respectively. The esterification reaction was carried out in a batch as well as in a semicontinuous mode of operation. A detailed study on the esterification of calcium lactate using methanol and carbon dioxide was carried out to record the effects of various operating parameters (like CO2 pressure, reaction temperature, moisture content in the calcium lactate, and initial concentrations of calcium lactate) on the esterification reaction. This synthesis route produces highly pure methyl lactate by direct esterification of calcium lactate with calcium carbonate as byproduct. The byproduct calcium carbonate was characterized for its crystallinity, surface area, and pore volume. The process route has the advantage that the synthesized byproduct can be recycled into the fermenter to make corresponding alkali metal lactate or the finely precipitated calcium carbonate can be used for various other applications. Thus, the recovery and recycle of alkali metal is possible providing a pollution free process for synthesis of pure methyl lactate.

C−H Carboxylation of Aromatic Compounds through CO2 Fixation

“…The metal salt MCl could then be processed by electrodialysis to regenerate M 2 CO 3 and the acid HCl (Scheme 10 b). [21] In this regard,t his whole cycle would effectively transform CÀHi nto CÀCO 2 Hu sing only CO 2 and no other stoichiometric reagents. This protocolw ould be classifiedw ithin the CÀHd eprotonation class by ab ase-type pathway.…”

Tandem catalytic conversion of glycerol using solid catalysts followed by transesterification to produce alkyl lactate

“…Fig. 27 ANOVA analysis for the obtained models for methyl lactate production in Tables 2 also suggests that the molar ratio of methanol to glycerol has more effect on the methyl lactate yield than on the other two factors. From Fig.…”

“…Barve et al pointed out how the low concentration of calcium lactate in the methanol favors the conversion of calcium lactate to methyl lactate, which gives the high yield of methyl lactate obtained at the high molar ratio of methanol to glycerol. 27 ANOVA analysis for the obtained models for methyl lactate production in Table 2 also suggests that the molar ratio of methanol to glycerol has more effect on the methyl lactate yield than on the other two factors. Methyl lactate shows great change with an increase of methanol to glycerol molar ratio at a constant reaction temperature or time (Fig.…”

“…27 They proposed a reaction mechanism of esterification of calcium lactate using CO 2 and methanol made up of three steps: 1) the formation of carbonic acid by the reaction of water with CO 2 , 2) the formation of lactic acid and CaCO 3 by the reaction of calcium lactate with carbonic acid, and 3) the esterification of lactic acid with methanol. 27 They proposed a reaction mechanism of esterification of calcium lactate using CO 2 and methanol made up of three steps: 1) the formation of carbonic acid by the reaction of water with CO 2 , 2) the formation of lactic acid and CaCO 3 by the reaction of calcium lactate with carbonic acid, and 3) the esterification of lactic acid with methanol.…”

“…Barve et al investigated methyl lactate production from alkali metal salts of carboxylic acids using carbon dioxide and alcohol. 27 They proposed a reaction mechanism of esterication of calcium lactate using CO 2 and methanol made up of three steps: (1) the formation of carbonic acid by the reaction of water with CO 2 , (2) the formation of lactic acid and CaCO 3 by the reaction of calcium lactate with carbonic acid, and (3) the esterication of lactic acid with methanol. However, in our process, CaO used was excessive, which might also induce methanol to form methoxy anion, which further reacts with CO 2 to form intermediates.…”