四种香气物质在MCM-41分子筛上的脱附活化能

Desorption Activation Energy of Four Aroma Substances on MCM-41 Zeolite

本文研究了苯乙醇、大马酮、乙基香兰素和乙酸乙酯香气物质在存储材料MCM-41分子筛上的吸附结合力。采用程序升温脱附(TPD)实验测定了这四种香气物质分子在MCM-41上的程序升温脱附曲线,估算了它们的脱附活化能。同时还采用从头计算(abinition)法分别计算了它们的电负性。研究结果表明:苯乙醇、大马酮、乙基香兰素和乙酸乙酯在MCM-41上的脱附活化能分别为86.16、71.13、55.47和46.09 kJ/mol。苯乙醇、大马酮、乙基香兰素和乙酸乙酯的电负性分别为2.386、2.664、3.064和3.521。按照Pearson碱类物质软硬划分标准,苯乙醇和大马酮均属于软碱物质,乙基香兰素和乙酸乙酯均属于硬碱物质。苯乙醇和大马酮在MCM-41上吸附结合力要明显强于乙基香兰素和乙酸乙酯在MCM-41上的吸附结合力,根据软硬酸碱理论(HSAB),可以推定MCM-41的表面具有软酸的性质。

In this work, the interactions of aroma substances including benzyl alcohol, damascenone, ethyl vanillin and ethyl acetate with the surfaces of MCM-41 zeolite were investigated. Temperature programmed desol^0tion （TPD） experiments were conducted separately to determine the TPD curves of these four kinds of aroma molecules on the MCM-41, and then estimate their desorption activation energies. Their electronegativity was calculated using abinitio calculation. Results showed that desolation activation energies of benzyl alcohol, damascenone, ethyl vanillin and ethyl acetate on the MCM-41 separately were 86.16, 71.13, 55.47 and 46.09 kJ/mol, respectively. The electronegativity of benzyl alcohol, damaseenone, ethyl vanillin and ethyl acetate were 2.386, 2.664, 3.064 and 3.521, respectively. According to the HSAB theory, benzyl alcohol and damascenone belonged to the software base substances, and ethyl vanillin and ethyl acetate were the hard base substances. The interactions of benzyl alcohol and damascenone with the MCM-41 were much stronger than those of ethyl vanillin and ethyl acetate with the MCM-41, suggesting that the surfaces of the MCM-41 had the nature of soft acid substance.