(335j) Synthesis Technics of Aliphatic Dicarboxylic Acid Alkoxy Ethyl Ester

Synthesis Technics of Aliphatic dicarboxylic acid alkoxy ethyl ester

CHEN Muhua^1,2,  WANG Junxiang¹,ZHANG Xiaoxiang¹, ZHU Xinbao^1,2

(1.    College of Chemical Engineering,Nanjing Forestry University,Nanjing 210037,ChinaG2.Engineering Research Center for Alcohol Ether of Jiangsu Province,Wuxi 214441,China)

CHEN Muhua :simonzrh@163.com

AbstractFAliphatic dicarboxylic acid alkoxy ethyl ester is a kind of cold resistant plasticizer with good performances. This kind of dibasic ester has high plasticizing effectiveness with PVC and PVA, and provides excellent low temperature flexibility, a certain light stability and water resistance. So it has been widely used in nitrile rubber,polychloroprene, acrylic rubber, polyvinyl chloride,cellulose acetate resin,and other fields. In the present research, Aliphatic dicarboxylic acid ester was synthesized from aliphatic dicarboxylic acid and ethyle glycol monoalkyl ether,by using hetergeneous acid as the catalyst, butyl ether as the dehydrant. Followed by filtration and distillation, the high purity product was obtained easily. Some commercial (ZSM-5 and HZSM-5) and homemade catalysts (SO₄^2-/AC and SO₄^2-/TiO₂-ZrO₂) were investigated by esterification and characterized using gas adsorption analysis (BET), X-ray diffraction (XRD), X-ray fluorescence (XRF), temperature-programmed decomposition (TPD) and electron spin resonance (ESR) techniques. The weight-based activity of the heterogeneous catalysts decreases in the following order: SO₄^2-/TiO₂-ZrO₂>SO₄^2-/AC>HZSM-5≈ZSM-5. It was unexpected that the esterification rate of ZSM-5 was up to 92% and the good catalytic activity was maintained during recycling tests. According to the characterization results, it was revealed that the exchange between hydrogen ion (from aliphatic dicarboxylic acid) and sodium ion (on the catalyst surface) plays an important role during the reaction. Upon optimizing the catalyst preparation conditions and reaction parameters, both SO₄^2-/TiO₂-ZrO₂ and SO₄^2-/AC exhibited 99% initial esterification rate. For SO₄^2-/TiO₂-ZrO₂, it was possible to recycle the catalyst without visible loss of activity because of the big amount of the acid sites and its strange acidity on the catalyst surface. However, the results also indicated that loss of sulfonic acid groups and pore blockage in activated carbon channels was two main reasons for catalyst deactivation. In addition, apparent rate constants for those acid-catalyzed homogeneous esterification reactions were obtained,and apparent kinetics models were established. The results showed that the synthesis of dibasic esters (between 453.15-473.15K) was the third order irreversible reaction. Activation energy values (Ea) of those solid catalysts were all in the range from 110-140 kJ/mol, which was obviously lower than comparative data in homogeneous reactions (220 to 250 kJ/mol).