Adsorption of benzene and cyclohexane on faujasite-type zeolites. Part 2.—Adsorption site efficiency and zeolite field influence at high coverage

Abstract

Adorption of benzene and cyclohexane at high coverage (θ= 1) has been studied on Y zeolites with various Na⁺, K⁺ and Al atom contents and on several NaHX materials. The amounts adsorbed, which depend on cation and aluminium atom contents, define an efficiency of adsorption sites which is similar to the efficiency of acidic sites previously described. Secondly, integral heats of adsorption and integral changes in entropy per mole adsorbed allow integral heats of adsorption per cation and changes in entropy per cation to be obtained. These values do not depend on cation (content and nature). For a given hydrocarbon ΔĤ/cation and ΔŜ/cation characterize X or Y type. Hence adsorption at high surface coverage is related more to a zeolite field due to a long range influence of AlO^–₄ charges than to specific cation field. Results are consistent with the lower reactivity of X type zeolites.