Synthesis And Separation Of Dicarboxylic Acid Esters

Dicarboxylic acids (DBA), also so-called nylon acids, are byproducts of cyclohexane oxidation. The main components are adipic acid(ADA), glutanic acid(GA) and succinic acid(SA). Development of down stream products of dicarboxylic acids such as dicarboxylic acid esters and separation of dicarboxylic acid esters can not only enlarge application range of dicarboxylic acids and significantly increase added value of three dicarboxylic acid esters but also extend industrial chain, which means great economic and social benefit.In chapter two, silica supported sodium hydrogen sulfate (NaHSO₄·SiO₂) has been found to be an efficient heterogeneous catalyst for the esterification of dicarboxylic acids compounds with alcohols(methanol, ethanol, butanol, benzyl alcohol, dodecanol and hexadecanol) to give the corresponding dicarboxylic acid esters. This method has high yields, convenient post-treatment and the catalyst could be easily recovered from the reaction mixtures.In chapter three, phosphotungstic acid(HPW) catalysts supported on SiO₂ and bentonite(BN) were prepared with and without ultrasonic treatment during the impregnation step. Structural and physical properties of the catalysts were characterized by X-ray diffraction, fourier transform infrared absorption, and scanning electron microscopy. The results show that the activity of the supported catalysts prepared with ultrasonictreatment for the esterification of dicarboxylic acids is higher than those without ultrasonic treatment. Compared with the HPW/SiO₂ catalyst, the supported catalyst HPW/BN prepared under the same condition of ultrasonic treatment during the impregnation step has higher catalytic activity in the esterification of dicarboxylic acids.In chapter four, the method of qualitative analysis of dicarboxylic acid esters such as dimethyl adipate, dimethyl glutarate, dimethyl succinate was established by gas chromatography. Furthermore, the separation of dicarboxylic acid esters was attempted by distillation in tooth profile fractionating column which has seven layers.