活性炭的孔隙结构和表面酸性对其香料吸附性的影响

Effects of Porosity Property and Acid Functional Groups of Activated Carbons on Adsorption of Three Flavors

本文主要研究两种活性炭吸附材料SY-1和SY-11对薄荷醇,呋喃酮和2-环戊烯酮三种香料的吸附性能。使用ASAP2010M测定了活性炭SY-1和SY-11的孔隙结构,用Boehm滴定测定了活性炭表面化学性质的含氧基团的浓度,用静态吸附法测试了三种香料在两种活性炭上的吸附动力学,采用程序升温脱附技术测定了三种香料在两种活性炭上的脱附活化能。结果表明,两种活性炭SY-1和SY-11的比表面积分别为928 m2/g、1065 m2/g,平均孔径分别为2.3和2.6 nm,表面酸性基团总含量分别为0.5498 mmol/g,0.5289 mmol/g。SY-1对三种香料的平衡吸附量均大于SY-11,这主要由于SY-1的平均孔径小于于SY-11,SY-1表面的酸性基团含量高于SY-11。较小的孔径则有利于孔壁表面对香料分子形成较强的吸附作用,较丰富的表面基团含量,有助于形成更多吸附位,从而提高吸附量。三种香料在两种活性炭上的脱附活化能大小顺序均为:薄荷醇>呋喃酮>2-环戊烯酮,这主要是由于三种香料分子的分子直径大小的顺序也是:薄荷醇>呋喃酮>2-环戊烯酮,较大直径的分子易受到孔壁表面更强的吸附作用力,与表面吸附就更牢,相应的分子的脱附活化能就越大。

The adsorption property of two kinds of activated carbons （SY-1 and SY-11） for menthol, furanone and 2-cyclopentenone was investigated. Textural parameters of pore structure and the concentration of acid functional groups were measured by ASAP 2010M and Boehm titration, respectively. The adsorption kinetics of the activated carbons for flavors were determined by static adsorption method, and the desorption activation energies of flavors on the activated carbons were estimated by means of temperature programmed desorption technique （TPD）. Results showed that the specific surface areas, average pore sizes, acid functional group contents of SY-1 and SY-11 were 928 and 1065 mE/g 2.3 and 2.6 nm and 0.5498 and 0.5289mmol/g, respectively. The adsorption capacities of SY-1 for three flavors were higher than that of SY-11, for smaller pores was benefit to form stronger force fields for adsorption of flavors and more surface acidic groups provided more adsorption sites for the flavors. The sequence of desorption activation energy for the flavors was： menthol 〉 furanone 〉 2-cyclopentenone, which was coincident with their molecular diameters. The molecule with larger diameter needed stronger adsorptive force fi＇om the pore surface, and thus the higher activation energy was required.