Comparative Study of Toluene and Hexane Adsorption on Activated Carbons From Gas and Liquid Phase. Enthalpy and Isotherms

Abstract

Activated carbons with different chemical and textural properties were used to carry out the adsorption of toluene and hexane from gas phase and from liquid phase for toluene-hexane solutions where toluene was used as a solute and hexane as the solvent, complementing the process with the evaluation of the immersion enthalpy for the pure components and toluene-hexane mixtures at different molar fractions. The adsorption capacities for the gas phase were between 3.40 and 0.05 mmol g −1 , being higher for toluene because of the π-π interaction with the solid; when evaluating the liquid phase, the adsorption capacities were 0.24 and 0.74 mmol g −1 , where the adsorption of toluene decreased compared to the gas phase because of the solute-solute, solvent-solvent, solute-solvent interaction. The immersion enthalpies for the pure solvents were between −40.87 and −126.10 J g −1 being higher also for toluene confirming a greater interaction compared to hexane; for the mixtures, immersion enthalpy was higher than hexane enthalpies, but lower than toluene enthalpies with values between −59.79 and −107.95 J g −1. It was found that there was a greater interaction between the sample with a lower content of acid groups and a greater surface area with toluene due to the high electron density of carbon and London-type as π-π interactions with the aromatic compound. For mixtures, hexane decreased the adsorption capacity and interaction with respect to toluene because there was competition for adsorption sites and subsequent displacement of hexane molecules when the amount of toluene on the surface increased.

Mild hydrotreatment of biocrude derived from hydrothermal liquefaction of agriculture waste: improving biocrude miscibility with vacuum gas oil to aid co‐processing

“…For example, run UR#3 without solvent gave an oxygen removal of 46.0%, whereas run UR#7 40.5%. A possible explanation is that toluene might have affected deoxygenation rates through competitive adsorption on the catalyst surface 30 . Therefore, although adding a solvent helped easing feed and product handling, there is indication that it affected oxygen removal.…”

Effects of Processing‐Induced Contamination on Organic Electronic Devices

“…This difference in adsorption efficiency likely derives from π–π interactions between solvents and activated carbon: a recent experimental study found that the gas phase adsorption capacity of activated carbon was two orders of magnitude higher for toluene as compared to hexane, an effect attributed to π–π interactions. [ 47 ] Furthermore, in toluene‐hexane mixtures, the adsorption capacity of hexane dropped further due to competition for adsorption sites. Together these findings suggest that aliphatic compounds, even relatively nonvolatile, long chain materials such as SAM precursors and pump oils, are likely to be the primary contaminants in typical research gloveboxes when the solvent filter is not exchanged regularly.…”