A simple central composite design was applied to estimate the activity of V<inf>2</inf>O<inf>5</inf>/TiO<inf>2</inf> catalyst and catalyst life in phthalic anhydride production. Using 1-3 years of simulation data, it was found that the temperature profiles along the catalyst bed and the outlet flow rates of phthalic anhydride and maleic anhydride (main by-product) were less than 8% deviation compared with the plant data. In comparing the simulated optimal conditions to the normal operating conditions, the phthalic anhydride production increased by 1,600ton with the inlet o-xylene-air ratio (w/w) and the coolant temperature, while maleic anhydride decreased by approximately 340ton.
