Abstract
Transesterification of glycerol with ethyl acetate was performed over acidic catalysts in the batch and semi-batch systems. Ethyl acetate was used as reactant and entrainer to remove the produced ethanol during the reaction, through azeotrope formation. Since the azeotrope of ethyl acetate and ethanol forms at 70 oC, all the experiments were performed at this temperature. Para-toluene sulfonic acid, sulfuric acid, and Amberlyst 36 were used as catalyst. The effect of process parameters including ethyl acetate to glycerol molar ratio (6-12), reaction time (3-9 h), and the catalyst to glycerol weight (2.5-9.0%), on the conversion and products selectivities were investigated. Under reflux conditions, 100% glycerol conversion was obtained with 45%, 44%, and 11% selectivity to monoacetin, diacetin, and triacetin, respectively. Azeotropic reactive distillation led to 100% conversion of glycerol with selectivities of 3%, 48% and 49% for monoacetin, diacetin, and triacetin. During the azeotropic reactive distillation, it was possible to remove ethanol to shift the equilibrium towards diacetin and triacetin. Therefore, the total selectivity to diacetin and triacetin was increased from 55% to 97% through azeotropic distillation.
Highlights
Biodiesel is one of the renewable fuels whose global production is estimated to reach 37 million metric tons in 2020 (Kale et al, 2015)
The major byproduct of the conventional biodiesel process is glycerol which is produced at an approximate rate of 10wt.% (Kale et al, 2015)
Such dramatic rise in the availability of biodiesel glycerol has led to significant price declines in the market and has marked glycerol as attractive feedstock for the synthesis of various valuable chemicals (Corma et al, 2007; Behr et al, 2008)
Summary
Biodiesel is one of the renewable fuels whose global production is estimated to reach 37 million metric tons in 2020 (Kale et al, 2015). The major byproduct of the conventional biodiesel process is glycerol which is produced at an approximate rate of 10wt.% (Kale et al, 2015). Such dramatic rise in the availability of biodiesel glycerol has led to significant price declines in the market and has marked glycerol as attractive feedstock for the synthesis of various valuable chemicals (Corma et al, 2007; Behr et al, 2008). Acetins are mono-, di-, and triacetate esters of glycerol, which are named monoacetin (MA), diacetin (DA), and triacetin (TA), respectively These chemicals have extensive applications especially as fuel additive (Melero et al, 2007; Zhou et al, 2008; Rastegari et al, 2015)
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