Adsorption of n-butane and n-heptane on 5A zeolite

Adsorption thermodynamics of n-butane and n-heptane on 5A zeolite was studied by the flow gravimetric-chromatograph technique at temperatures ranging from 533 K to 653 K and over a range of hydrocarbon partial pressures. It is shown that the equilibrium amount of n-heptane adsorbed is much larger than that of n-butane. Adsorption isotherms are modeled satisfactorily by using a modified virial equation and the Dubinin-Astakhov (D-A) equation. It is concluded that the influence of n-butane is very small while the influence of n-heptane is significant in the separation stage of the total isomerization process. Modified virial equation: P = a(n) exp(C-1 + C(2)a + C(3)a(2)) D-A equation: a = a(m) exp{B [ln[(T/T-c)P-2(c)/P]](n)} The adsorption isosteric heat and entropy were calculated, and the results show that the adsorption isosteric heat of n-heptane is larger than that of butane at low loadings.