对苯二甲酸乙二醇酯降解机理密度泛函的理论研究.

Mechanism degradation of ethylene terephthalate momer was investigated by density functional theory B3P86/6-31++G (d, p) method, the possible reaction paths of pyrolysis/hydrolysis/alcoholysis and catalytic degradation were designed, the geometric structures of various intermediates, transition states, and products involved in the reaction were optimized, and their frequencies were calculated to gain the thermodynamic and kinetic parameters. The calculation results show that: When water or methanol is used as a catalyst in the ethylene terephthalate process of thermal degradation, the use water or methanol O-H provides H to the main chain of the ethylene terephthalate ester bond on the carbonyl O atom is form terephthalic acid, and ethyl C off H atoms and (water) hydroxyl (-OH) or (methanol) methoxy group (-OCH3) are combined to form new water or methanol, thereby reducing the reaction energy barriers during the pyrolysis of ethylene terephthalate (251.4 kJ/mol→181.1 kJ/mol (methanol) and 187.5 kJ/mol (water)). When water or methanol is reactant in the thermal degradation process of ethylene terephthalate, H in water or methanol O-H is supplied to the carbonyl O atom of the main chain of ethylene terephthalate to form ethylene glycol. Hydroxy group (-OH) in water or methoxy group (-OCH3) in methanol binds to the carbonyl C atom of the carbonyl group of ethylene terephthalate backbone to form terephthalic acid or mono-methyl terephthalate, it further reduces the reaction energy barriers (156.4 kJ/mol (methanol) and 170.1 kJ/mol (water)) during the pyrolysis of ethylene terephthalate. In the reaction process, either water/methanol as catalysis or water/methanol as reactants can reduce the reaction energy barrier of the main element step to a certain extent, so that the reaction is easy to proceed. [ABSTRACT FROM AUTHOR]