Cyclization of Pseudoionone into α-Ionone Over Heteropolyacid Supported on Mesoporous Silica SBA-15

Abstract

Cyclization of pseudoionone into a-ionone was performed over the series heteropolyacid supported on SBA-15 in liquid-phase at 363 and 373 K using a batch reactor. It has been demonstrated that the liquid-phase synthesis of a-ionone by pseudoionone cyclization can be efficiently achieved on heteropolyacid/SBA-15 materials. The high catalytic performance of PW 12 /SBA-15 materials is due to their strong Brønsted acidity, high dispersion of active phase and also to absence of steric constraints for pseudoionone cyclization. PW 12 /SBA-15 catalysts are specially active and selective for this reaction giving predominantly a-ionone, as the main product, with high yield (about 60% at 373 K after 2 h) close to that obtained via the homogeneous synthesis. This catalytic system is more active and efficient in comparison with heteropolyacid supported on commercial silica. In order to achieve comparable amount of a-ionone, as is got for PW 12 /SBA-15, belongs to apply five times more of the catalyst based on classical SiO 2 .

Kinetic and mechanistic study of the synthesis of ionone isomers from pseudoionone on Brønsted acid solids

“…Those results showed that at PS isoconversion the contribution of α-ionone increases from 35 to 45.2% at the expense of γ-ionone as the reaction temperature increases from 343 to 383 K. Thus, at high reaction temperatures α-ionone is the main product on HPAS-59. A similar result was obtained by Rachwalik et al [17] using HPA/SiO 2 and HPA/SBA-15 catalysts. The analysis of the dependence of β isomer concentration with reaction temperature showed that β-ionone contribution remains almost constant at increasing temperatures taking values around 20%; that result confirmed that β-ionone is a primary and terminal product on HPA-based samples and that isomer interconversion is limited to isomerization of the γ isomer toward α-ionone.…”