title: High-temperature liquid water: a viable medium for terephthalic acid synthesis.
abstract: We report new information concerning the effect of oxygen concentration and catalyst concentration and identity [MnBr2, CoBr2, ZrBr4, and Mn(OAc)2] on the partial oxidation of p-xylene in dense water from 250 to 380 degrees C. Water is a more environmentally benign replacementfor the acetic acid solvent used commercially. We used a 440 mL Hastelloy batch reactorfor all experiments and monitored O2 consumption and product (including COx) formation. Increasing the catalyst concentration at 300 degrees C significantly increased terephthalic acid yields. MnBr2 was the most active catalyst of those we assessed. Increasing the initial O2 concentration beyond a modest excess did not significantly alter the terephthalic acid yield, but it increased the CO2 yield. Injecting supplemental 02 midreaction, however, did cause the terephthalic acid yield to increase. The highest terephthalic acid yields (>80%) occurred at 300 degrees C, [p-xylene]0 = 0.02 M, [O2]0 = 0.10 M, [Br] = 0.014 M, and t = 5-15 min. These yields are the highest reported to date from this reaction in high-temperature liquid water. Moreover, under these conditions and t=15 min, COx yields were below 2% and reaction intermediates were not detected.
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, USA.
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: Dunn
authors.forename: Phillip E
authors.initials: PE
authors.lastname: Savage
mesh_terms: D002384:Catalysis; D010084:Oxidation-Reduction; D010100:Oxygen; D010795:Phthalic Acids / Q000138:chemical synthesis*; D013696:Temperature; D014867:Water / Q000737:chemistry; D014992:Xylenes / Q000737:chemistry*
chemical_list: D010795:Phthalic Acids; D014992:Xylenes; D014867:Water; C011363:terephthalic acid; C031286:4-xylene; D010100:Oxygen