This article addresses a general feasibility evaluation method for quaternary reactive distillation based on a feasibility study of isomolar reactions. With an arbitrary reaction stoichiometry and feed ratio, the general algorithm can be applied to evaluate the feasibility of a double-feed reactive distillation column. The feasibility evaluation relies on the desired directions of column composition profiles for reaching pure products or achieving complete reaction conversion without performing rigorous stage calculations. Critical composition regions (CCRs) are defined as the areas in which thermodynamic constraints force composition profiles to travel in infeasible directions. After the CCRs have been identified, material balance is imposed to determine whether composition profiles can move in desired directions in terms of upper and lower bounds of the internal reflux ratio. If the upper and lower bounds permit composition profiles to approach a desired boundary, then a double-feed column can achieve almost 100% reaction conversion and produce pure products.