Adipic Acid Green Catalytic Synthesis Kinetic Study

Adipic acid is a very important dibasic acid and is widely used in industry. The main industrial production process of adipic acid is nitric acid oxidation process, which generates large volumes of N₂O, NOx, and other harmful gases and waste acid, causing serious environmental pollution. With the increasing of environmental protection pressure, the development of green synthesis process for adipic acid have become an important subject in chemical industry.With the green adipic acid synthesis technologies of adipic acid proposed and researched deeply, technology that hydrogen peroxide oxidize cyclohexene to synthesize adipic acid has been widely concerned. Based on the previous research, our lab successfully developed a new technology, in which cyclohexene was directly oxidized with 30% H₂O₂ in homogenous system, without organic solvent, ligands and phase-transfer agents. This technology was very simple and caused no environmental pollution, and the purity of adipic acid could be increased by this method. The recycle of catalyst and scale-up reaction were both studied. In this thesis, the reaction kinetics and mechanism were investigated deeply.1. Study on the reaction mechanismThermodynamic energy data of the main reaction and all the possible reactions was estimated with the Gaussian 03 program, Lange's Handbook of Chemistry and the group adding method, meanwhile the tendency of each reaction was analyzed. The main reaction is prior to the others in thermodynamics. Then, thermodynamic energy data of each step of the proximate reaction path introduced by Noyori was calculated by the Gaussian 03 program in order to confirm its feasibility.2. Study on reaction kineticsThe reaction kinetics study of hydrogen peroxide under various acidic conditions and temperatures was performed. There was a parallel reaction mechanism in the green synthesis process of adipic acid, in which the hydrogen peroxide either oxidized cyclohexene or decomposed into water and oxygen, and the two reaction paths were competed with each other. The reaction order of hydrogen peroxide is 0 at low temperature.At pH = 0.3 and T = 72℃, utilization of hydrogen peroxide reached the maximum, which is the most favorable conditions to epoxidation of Cyclohexene.The kinetics behavior of cyclohexene under various acidity conditions and temperatures was studied, and the reaction order and rate constant was estimated. At pH = 0.3, which is the best reaction condition, the reaction order is the 2^nd and the activation energy is 95.628 kJ/mol.The kinetics behavior of adipic acid in the reaction was studied, too. As a result, both the reaction constant and the reaction order are increased as the temperature rises. Finally, we proposed coordination catalytic reaction mechanism that involved Tungsten-dioxygen complex catalyst.