Reducing CO2 has been an environmental concern for the past decade due to its greenhouse effect. Chemical fixation of CO2 would not only be environmentally helpful, but would also provide a cheaper source of carbon. The Kolbe-Schmitt reaction offers a direct CO2 fixation on hydroxy-aromatic compounds, producing aromatic hydroxy-carboxylic acids, such as salicylic acid, p-hydroxy-benzoic acid, 2-hydroxy-3-naphthoic acid(2,3-HNPA), and 2-hydroxy-6-naphthoic acid(2,6-HNPA). This study focuses on the use of Rb as an alkali precursor to promote formation of 2,6-HNPA using 2-naphthol as a reactant. In the first step, Rb-naphthoxide was prepared by mixing 2-naphthol (13.6 mmol) and RbOH (13.6 mmol) in water and dried overnight. After then, a catalyst (K2CO3, 6.8mmol) was added into a semi-batch reactor with a solvent of hexadecane. The temperature was then raised to the reaction temperature of 553K, followed by injection of CO2 up to 0.2 MPa, where CO2 was continuously flowed at 18 ml/min in the semi-batch reactor. The reaction was carried out for 3 h. The effects of alkali metals and composition of reactants on the formation of HNPA were examined. Overall, three types of HNPA isomers were identified at the conditions of 553K and 0.2MPa CO2 in a semi-batch reactor, and gave an HNPA yield of 48% with a 2,6-HNPA selectivity of 72%.

Synthesis of 2-hydroxy-6-naphthoic acid (2,6-HNPA) over alkali metal carbonates

2019 Fall National Meeting

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