Molecular simulations using quantum chemical techniques were carried out to characterize the acid strengths of functional groups on mesoporous silica. RHF and MP2 techniques were used to simulate the sorption of pyridine and collidine on different types of acid functional groups. Desorption energy values obtained from pyridine sorption studies showed that butylcarboxylic acid was the weakest acid, while propylsulfonic acid was the strongest acidic group. The simulation results did not show any significant effect of the presence of the arene group. The experimental values obtained from XPS studies corroborated well with the theoretical calculations. This is an abstract of a paper presented at the AIChE Annual Meeting (Salt Lake, UT 11/4-9/2007).