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

CrMCM-41 catalyst gave a good conversion of geraniol ( X = 53%) and high selectivity of citral ( S = 98%) in scCO 2 media at 80 °C for 6 h. [Display omitted] ▶ CrMCM-41 gave high selectivity (98%) and good yield (52%) of citral in scCO 2. ▶ Conversion of geraniol is enhanced in scCO 2. ▶ Activity of CrMCM-41 is higher than PtMCM-41 and PdMCM-41. Selective catalytic oxidation of geraniol to citral with molecular oxygen in supercritical carbon dioxide (scCO 2) 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 CO 2 pressure and reaction temperature geraniol oxidation was studied with CrMCM-41. Supercritical CO 2 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.