This report presents a cost analysis of Phthalic Anhydride production from o-xylene. The process examined is a catalytic oxidation in vapor phase with Low Air Ratio (LAR). In the process examined, the fixed-bed catalytic oxidation occurs with air/o-xylene weight ratio of 9.5:1. This report was developed based essentially on the following reference(s): Keywords: Unsaturated Polyester, UPR, Phthalic Acid, Orto-Xylene, LAR, Low Air Ratio, Fixed-Bed Reactor