Effective synthesis of cis-3-hexen-1-yl acetate via transesterification over KOH/γ-Al2O3: Structure and catalytic performance

Cis-3-hexen-1-yl acetate is a significant green note flavor compound and widely used in the food and cosmetic industry. In this research, a series of solid base KOH/γ-Al2O3 have been prepared and been utilized for the synthesis of cis-3-hexen-1-yl acetate via transesterification from cis-3-hexen-1-yl and ethyl acetate. The catalysts were also characterized by several physic-chemical techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, N2 adsorption, CO2-temperature-programmed desorption (CO2-TPD), and X-ray fluorescence (XRF). 30%KOH/Al2O3 was suggested to be the best conversion due to the cis-3-hexen-1-ol conversion of 59.3% at a temperature 88 °C within 2 h. Characterization results showed that KOH transformed into Al–O–K and K2O·CO2 species during the calcination process. It was confirmed that K2O·CO2 disappeared and Al–O–K groups existed on the surface of the water-washing 30%KOH/Al2O3 which was inactive for transesterification. K2O·CO2 species might be the major active species on KOH/Al2O3, and Al–O–K groups was inactive for cis-3-hexen-yl acetate synthesis.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (150 K)Download as PowerPoint slideHighlights► Synthesis of cis-3-hexen-1-yl acetate via transesterification catalyzed by KOH/γ-Al2O3. ► Cis-3-hexen-1-yl acetate was synthetized at a low temperature (88 °C). ► The K2O·CO2 species were main active compounds on the surface of KOH/γ-Al2O3. ► The catalyst only containing Al–O–K groups without K2O·CO2 species was inactive for transesterification.