An elegant synthesis of chitosan grafted hydrotalcite nano-bio composite material and its effective catalysis for solvent-free synthesis of jasminaldehyde

Abstract

A novel nano-bio composite of chitosan and a layered double hydroxide was elegantly synthesized by a co-precipitation method. The nano-bio composite material (CMA) was thoroughly characterized by FTIR, TGA, XRD, SEM and TEM. The composite material CMA showed efficient catalytic activity for selective synthesis of jasminaldehyde under solvent free conditions by condensation of benzaldehyde and 1-heptanal. In typical employed conditions, 39.5 mmol benzaldehyde, 7.9 mmol 1-heptanal, 100 mg catalyst, 160 °C and 700 rpm, a maximum selectivity of 89% with 99% conversion was obtained. The investigations were performed in detail as a function of the amount of catalyst, temperature and molar ratio of 1-heptanal to benzaldehyde to observe the effect of these reaction parameters on the conversion, selectivity and rate of the formation of the condensation products. All these parameters were found to influence the performance of the catalyst. The initial rate of formation of jasminaldehyde was found to be ∼20% more than the rates with individual chitosan and hydrotalcite. The rate of formation of 2-pentyl-2-nonenal with CMA was found to be lower in comparison with individual catalysts, chitosan and hydrotalcite. The determined activation energy was 16.3 kJ mol⁻¹. The catalyst was elegantly separated, washed and dried, and found to be effectively recycled six times without any substantial loss in its activity.