Adsorption isotherms were measured for thiophenic sulfur compounds, thiophene (T), benzothiophene (BT), 2-methylbenzothiophene (2-MBT), and dibenzothiophene (DBT), from their binary solutions in n-octane. Two sulfur-selective, π-complexation sorbents were studied:  Cu(I)-Y zeolite and PdCl2 impregnated on activated carbon (PdCl2/AC). Vapor-phase isotherms of n-octane and thiophene were also measured. The selectivity of adsorption from liquid solutions followed the order, T < BT < 2-MBT < DBT for PdCl2/AC, and T < DBT < 2-MBT < BT for Cu(I)-Y zeolite. The adsorption bond energies, which approximate the heats of vapor-phase adsorption, followed the order, T < BT < 2-MBT < DBT. This order was not followed for adsorption from liquid solutions on Cu-Y zeolite. The heats of adsorption were obtained by the temperature dependence of the isotherms. A simple theory was proposed for estimating the relationship between the heat of adsorption from liquid solution and that from vapor phase. The experimental results were in fair agreement with the theory.

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A study of adsorption of thiophenic sulfur compounds, thiophene (T), benzothiopnene (BT), and dibenzothiophene (DBT), in normal alkane solvents (n-octane and hexadecane) on NaY and 13X zeolites was performed. Adsorption isotherms of pure-component n-octane, hexadecane, and T from the vapor phase were also measured. Analysis of the heats of adsorption (including differential and integral heats) calculated by using the Clausius−Clapeyron equation were in agreement with the results obtained by Ng et al. using flow calorimetry for the same systems. The simple theory estimating the relationship between the heat of adsorption from liquid solution and that from the vapor phase proposed in our previous work was tested using the experimental data. The enthalpies of solvation for T−octane and T−hexadecane were also used to validate the simple theory. The theoretical predictions were in close agreement with experiments. The simple theory is easy to use and can explain and provide insight into adsorption from liquid solution.

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