Abstract: A process for making a dianhydride product, said process comprising reacting two moles of maleic anhydride and one mole of a vinyl benzene compound in a reaction mixture comprising about 1.5 to 2.0 moles of the vinyl benzene compound per mole of maleic anhydride at reaction temperature in the range from 105.degree. to 125.degree. C. for time to complete the reaction, adding a polar organic liquid to the reaction product mixture and refluxing the mixture, cooling the mixture following reflux and adding a hydrocarbon liquid to precipitate the product, separating the solid dianhydride product by filtration, washing the solids on the filter and drying the solids to make the finished dianhydride product.