Selective catalytic oxidation of geraniol to citral with molecular oxygen in supercritical carbon dioxide

Selective catalytic oxidation of geraniol to citral with molecular oxygen in supercritical carbon dioxide (scCO2) has been investigated. The catalyst used was a chromium containing mesoporous molecular sieve catalyst viz. CrMCM-41. Comparison studies were performed with CoMCM-41, PtMCM-41 and PdMCM-41 catalysts. Among the various catalysts studied, CrMCM-41 showed a high conversion of geraniol and an excellent selectivity for citral. In contrast CoMCM-41, PtMCM-41 and PdMCM-41 catalysts exhibited low conversion of geraniol. However all three catalysts compared showed similar citral selectivity to CrMCM-41. The effect of CO2 pressure and reaction temperature geraniol oxidation was studied with CrMCM-41. Supercritical CO2 medium was found to enhance the conversion of geraniol and/or yield of citral. It was noticed that the catalyst can be recycled with negligible loss of conversion.

CrMCM-41 catalyst gave a good conversion of geraniol (X = 53%) and high selectivity of citral (S = 98%) in scCO2 media at 80 °C for 6 h.Figure optionsDownload high-quality image (111 K)Download as PowerPoint slideResearch highlights▶ CrMCM-41 gave high selectivity (98%) and good yield (52%) of citral in scCO2. ▶ Conversion of geraniol is enhanced in scCO2. ▶ Activity of CrMCM-41 is higher than PtMCM-41 and PdMCM-41.