几种典型国产活性炭吸附各种烃类的NMR研究——Ⅱ. 苯、环己烷、正戊烷和正己烷吸附的1H NMR研究

活性炭吸附苯、环己烷、正戊烷和正已烷的测量表明, 在同一种活性炭中各烃的饱和吸附体积相同, 四种烃的吸附量与其摩尔体积成反比。同一种被吸附物在不同活性炭中的吸附量与各活性炭的比孔容和孔径分布有关。活性炭的比孔容大, 且孔径小于3.0 nm的微孔比例大时, 其吸附和解吸容量也大。这些体系的~1H NMR研究进一步证实了孔径小于3.0 nm的微孔中发生毛细管凝聚, 导致吸附和解吸的容量增大。被吸附分子的自旋晶格弛豫时间几乎不随被吸附物的种类而异。他们与活性炭表面上酸性基团总量有较好的曲线关系。

NMR STUDY OF THE ADSORPTION OF HYDROCARBONS ON SEVERAL TYPICAL NATIVE CHARCOALS Ⅱ. 1H NMR Study of Adsorbed Benzene,Cyclohexane, n-Pentane and n-Hexane

Adsorption and desorption of benzene, cyclohexane, n-pentane and n-hexane on four native charcoals were measured. The adsorption behavior of the charcoals was interpreted with respect to the specific pore volume and pore size distribution by the ~1H NMR parameters measured, which showed that capillary condensation takes place in the micropores with radius less than 3.0 nm. The degree of high field shift of the adsorbed hydrocarbons gives a measure of the ratio between specific surface and specific pore volume, which may influence the adsorption capacity of the charcoal. Spin lattice relaxation time of the adsorbed hydrocarbons is independent on their species, but closely related to the total amount of the surface acid groups of the charcoal.