This work presents a continuous, easy-to-scale-up esterification system with 100% conversion of glycerol in acetic acid with a high selectivity to DA and TA and no byproducts under industrially applicable reaction conditions. The main emphasis is to obtain TA from glycerol esterification in acetic acid without using any acetic anhydride or harsh conditions. The effects of reaction parameters, including the acetic acid-to-glycerol mole ratio (1–9), temperature (66–134 °C), and pressure (1–199 bar) with a 0.5 mL·min–1 feed flow rate, on the glycerol conversion and selectivities to monoacetin, diacetin, triacetin, and byproducts were investigated. Under the optimum conditions of an acetic acid-to-glycerol mole ratio of 7, a temperature of 100 °C, and a pressure of 1 bar, over 3 g of Amberlyst 36, the glycerol conversion and monoacetin, diacetin, and triacetin selectivities reached 100%, 43%, 44%, and 13%, respectively. The formation of byproducts was not detected under these optimum conditions. Amberlyst 36 remained stable after 25 h on-stream. The recovered catalyst was reused with no significant deactivation after three cycles. This continuous system also can be used for monoacetin synthesis with 85% selectivity and 95% glycerol conversion with an acetic acid-to-glycerol mole ratio of 1, a temperature of 100 °C, and a pressure of 100 bar.

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Glycerol esterification with acetic acid was carried out in a continuous, easy-to-scale-up system using toluene as the entrainer. A water separation system was designed and coupled to an optimized continuous system. The continuous system operated at a temperature of 100 °C, an acetic acid-to-glycerol mole ratio of 7, a pressure of 1 bar, and a feed flow rate of 0.5 mL min–1 over 3 g of Amberlyst 36. Under these conditions, the glycerol conversion was 100% with 43%, 44%, and 13% selectivities to monoacetin, diacetin, and triacetin, respectively. Formation of byproducts was not observed under these conditions. When this continuous system was coupled to the designed simultaneous reactor and water separation system, containing 3 g of Amberlyst 36, these values changed to 0%, 15%, and 80%, respectively. Byproduct formation was observed with a selectivity of only 5% after the feed was passed from the water separation system. Continuous removal of the water formed in the reaction was done with toluene. As a result of this process, the chemical equilibrium shifted toward the TA production. The maximum selectivities obtained from experiments were 85% for MA, and 65% for DA. Amberlyst 15 and Purolite PD206 also was used for esterification reaction. Amberlyst 15 and Amberlyst 36 exhibited similar performances. A mixture of MA and DA was obtained through esterification of glycerol with trapped acetic acid in a Dean–Stark apparatus.

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