An efficient method for preparation of propyl gallate using Brønsted acidic ionic liquid N-methyl pyrrolidonium hydrosulfate [Hnmp]HSO4

The synthesis of propyl gallate using Brønsted acidic ionic liquid N-methyl pyrrolidonium hydrosulfate [Hnmp]HSO4 as an efficient catalyst with gallic acid and n-propanol as materials was studied. The influence factors, such as the selection of water-carrying agent, reaction temperature, molar ratio of reactants, the dosage of catalyst, and the reaction time were also investigated. The results showed the optimum reaction conditions were as follows: the molar ratio of n-propanol and gallic acid and catalyst was 5:1:0.3, reaction time was 5 h and the yield of propyl gallate was up to 89.8% without water-carrying agent at 95–105 °C.

► Green synthesis of propyl gallate with an environmentally friendly catalyst without poisonous water-carrying agent.
► The mechanism for the synthesis using [Hnmp]HSO4 as catalyst.
► Influence of the reaction conditions on the synthesis of propyl gallate.