Study On The Reaction Kinetics Of Propylene Glycol Monomethyl Ether Propionate

Propylene glycol monomethyl ether propionate (PMP) is new member cf P series solvent of glycol ethers, it not only has the excellent solubility, but also has the lowest genital toxicity among the all of glycol ethers, as a result it is called "green solvent". PMP was manufactured by esterification of propylene glycol monomethyl ether and propionic acid in the presence of acid catalysts. However, the liquid acid catalyst, water-entrainment and traditional technology — "reaction - separation - recycling" were adopted in current processing, which let out great waster water and consumed lots of energy. In this paper, a reactive distillation was brought forward to the synthesis of PMP, and the major research was focused on the reaction kinetics model, which was necessary for the process modeling of reactive distillation.The pseudo-homogeneous second-order kinetics model was established and the batch stir reactor was built for measuring kinetics data in this paper. The concentration target function and the temperature target function were carried on the estimating of model parameters.Taking toluene-p-sulfonic acid as the catalyst synthesizes PMP, when the dosage of catalysts for 0.7% of the raw materials, the reaction balance was reached after 60 minutes. The parameters of the kinetics model by concentration target function was as following: the pre-exponential factor of positive reaction and reverse reaction respectively was 4.292×104 L²(mol·g·min)^-1 and 38.18 L²(mol·g·min)^-1, and the active energy respectively was 58.13 kJ·mol-1 and 34.34 kJ·mol-1. The parameters of the kinetics model by temperature target function was as following: the pre-exponential factor of positive reaction and reverse reaction respectively was 1.388 × 10⁶ L²(mol·g·min)¹ and 13.29 L²(mol·g·min)^-1, and the active energy respectively was 69.68 kJ·mol-1 and 31.47 kJ-mol-1.Macroporous strong acid ion exchange resin was adopted to synthesize PMP for the first time, when the dosage of catalysts for 9% of the raw materials, the reaction balance was reached after 60 minutes. The parameters of the kinetics model using macroporous strong acid ion exchange resin as catalysts by concentration target function was obtained, the pre-exponential factor of positive reaction and reverse reaction respectively was .081× 10⁶ L²(mol·g·min)^-1 and 8.988× 10⁷ L²(mol·g·min)^-1,and the active energy respectively was 80.12 kJ-mol"1 and 89.49 kJ-mol"1. The influence of particle size of catalysts on the reaction was investigated, the result showed that the internal diffusion resistance of catalysts could be neglected.