To synthesize mesoporous magnesium oxide (MgO) with a high surface area and pore volume, a calcination procedure was developed for hydrated MgO prepared by the same aerogel method. The sorption capacities of as-prepared MgO compounds were evaluated by breakthrough experiments to remove methylmercaptan (291 mu mol/mol) from methane. The surface area of nanosized MgO varied from 296.6 to 503.5 m(2)/g, depending on the calcination procedure. The physical properties and sorption capacity of MgO were affected by the final temperature, step, and heating rate during calcination, but the sorption capacity could not be evaluated only by the surface area and pore volume. MgO prepared by the four-step calcination method, which had two additional steps in the significant decomposition temperature range, had 2-11 times higher sorption capacity than MgO by other calcination methods. This suggests that optimizing the calcination method is as important as searching for a new synthesis route.