Monte Carlo simulations are used to predict the adsorption isotherms at 300 and 600 K for binary and ternary mixtures of linear, branched, and cyclic alkanes in silicalite-1, AlPO4-5, and the recently synthesized ITQ-22. The theoretical binary and ternary adsorption isotherms predicted by Ideal Adsorption Solution Theory (IAST) agree well with the simulated isotherms. Increasing the temperature altered the adsorption hierarchy, with the adsorption of cyclic molecules increasing as the linear and, to a greater extent, branched molecules decreased. A microscopic analysis of the adsorption locations and molecular conformations provides an explanation for the change in the selectivity of adsorption with temperature.