关键词: 超/亚临界CO2, 邻甲酚, 邻甲基水杨酸, 一步法合成, 无水K2CO3

Abstract: The synthesis of 3-methyl salicylic acid in supercritical or subcritical carbon dioxide has important meaning for the green synthesis of 3-methyl salicylic acid and resourcization of carbon dioxide. After comparing the catalytic activity of anhydrous potash，anhydrous sodium carbonate and so on，anhydrous potash was chosen as the best catalyst to synthesize 3-methyl salicylic acid directly from o-cresol by one-pot method in supercritical or subcritical carbon dioxide. At the condition of reaction time from 1—6 hours，catalyst′s relative dosage（nK2CO3/ nO-Cresol）from 0.05—1.25，reaction temperature from 130—270 ℃ and reaction pressure from 4—10MPa，o-cresol’s carboxylic reaction was studied in supercritical or subcritical carbon dioxide. The result showed that the conversion of o-cresol and the yield of 3-methyl salicylic acid both increased at first with the increase of time，and then the conversion became stable，but the yield decreased slightly in the end. The conversion and the yield increased rapidly at first and then increased slowly with the increase of catalyst′s relatively dosage. The conversion and the yield increased rapidly at first but then decreased with the increase of reaction pressure or reaction temperature. The conversion is about 19.7% and the yield is about 17.5% under the optimal condition that reaction time was 3 hours，catalyst′s relatively dosage was 0.5，reaction temperature was 190 ℃ and reaction pressure was 8 MPa. In addition，a possible reaction mechanism was proposed.

Key words: supercritical or subcritical carbon dioxide, o-cresol, 3-methyl salicylic acid, one-pot synthesis, anhydrous potash