The 50 °C temperature of the catalyst was measured at the exterior of the catalyst and the exact temperature of the interior of the catalyst was not known. The ring opened product, diethyl maleate (18), was isolated in 86% yield. This conversion likely begins with a protonation of the maleic anhydride carbonyl group -forming a carboxonium ion intermediate which reacts with ethanol. Finally, a Fischer esterification was accomplished using terephthalic acid (19) and methanol (eq 8). The conversion was carried out by dissolving the terephthalic acid in methanol and passing it through the preheated catalyst. The product dimethyl terephthalate 20 was isolated in 78% yield from the reaction.