On January 5, the phthalic anhydride market in Shandong region showed an upward trend. The mainstream negotiated prices for o-xylene-based phthalic anhydride were 5,800–6,100 yuan/ton, while those for naphthalene-based phthalic anhydride were 5,500–5,800 yuan/ton. The price of raw material o-xylene rose sharply, while the price of industrial naphthalene remained stable. The cost of phthalic anhydride increased, and the downstream plasticizer market experienced a strong upward trend. The operating rates of phthalic anhydride production facilities declined, leading to a decrease in the overall operating rate of phthalic anhydride enterprises. Despite sufficient supply in the phthalic anhydride market, the operating load of plasticizer enterprises also decreased. However, rigid demand for phthalic anhydride remained, and the market outlook for phthalic anhydride is expected to continue its strong upward trend.