The preparation of titanium adipate and optimization of its catalytic ester exchange reaction for the synthesis of diisooctyl adipate

Chelated titanium adipate with stable properties was prepared via an ester-exchange reaction using low-carbon alkyl titanate, and it was characterized and analyzed using infrared spectroscopy, thermogravimetry, and scanning electron microscopy. Diisooctyl adipate (DOA) was synthesized via an ester-exchange method using the synthesized novel titanium adipate as a catalyst and isooctanol and dimethyl adipate as raw materials, where dimethyl adipate is the methyl esterification product of the by-product (mixed dicarboxylic acid) in industrial adipic acid production. The process is easy to carry out, green and environmentally friendly, and the methanol by-product can be recycled and utilized. With the objective of optimizing the DOA ester exchange rate, the effects of three factors, namely, catalyst dosage, the molar ratio of isooctanol to dimethyl adipate and the reaction temperature at catalyst addition, on the optimization objective were systematically investigated via one-way and response surface tests. Analysis of variance (ANOVA) and parameter optimization were conducted using Design-Expert software to obtain the optimal parameter combinations and verify the accuracy of the experimental results. The results showed that the optimal reaction conditions were as follows: a catalyst dosage of 2.39%, an isooctanol to dimethyl adipate molar ratio of 2.55 : 1, and a reaction temperature of 117 °C at the time of catalyst addition; this resulted in a high ester exchange rate of 94.23%. Due to the high catalytic efficiency, environmental friendliness and energy saving, and recyclable catalyst, this study provides a feasible process for the effective synthesis of DOA using industrial by-products, which is of significance.