Preparation and testing of ceasium Brønsted ion-exchanged Al-SBA-15 supported heteropoly acid as heterogeneous catalyst in the fructone fragrancy synthesis

Here we report a new ceasium Brønsted ion-exchanged Al-SBA-15 (Cs/AS15) supported heteropoly acid (HPA) H3PW12O40 (HPA-Cs/AS15) material which can be prepared and used as heterogeneous catalyst for the fructone fragrancy synthesis. It was demonstrated that Cs+ was more effective than NH4+ as counter cation of ion-exchanged AS15 support for preparing HPA/AS15 catalyst with higher acidity and HPA leaching stability. HPA-Cs/AS15 material showed high acidity with the maximum NH3 desorption peak appeared at 759.6 °C in the NH3-TPD spectrum, stronger than pure HPA (635.7 °C) and the ammonium Brønsted ion-exchanged Al-SBA-15 supported HPA (HPA-NH4/AS15) (559.1 °C) materials. The HPA leaching stability test showed that the HPA content of HPA-Cs/AS15 catalyst reduced only by 2.55% after five washing times, much less than that of HPA-NH4/AS15 catalyst (49.22%).

The higher acidity helped improve the HPA-Cs/AS15 catalyst performance in the fructone fragrancy synthesis. The ethyl acetoacetate conversion over this catalyst was 94.82%, better than those over HPA-NH4/AS15 (93.49%) and pure HPA (89.52%) catalysts, although HPA-Cs/AS15 catalyst had lower HPA content (23.16 wt%) than HPA-NH4/AS15 (24.28 wt%). In addition, it was shown that the reaction conditions such as ethyl acetoacetate:ethanediol reactant molar ratio of 1:1.5, ethanediol used as the diol reactant, and toluene used as the solvent, the fructone fragrancy synthesis reaction over HPA-Cs/AS15 catalyst reached the highest ethyl acetoacetate conversion (95.58%). The toluene’s boiling temperature of 110.6 °C can promote the dispersion and contact abilities of the reactants with HPA molecules presented inside the pores of HPA-Cs/AS15 catalyst.