Acetylation of Glycerol over Mixed Zirconium Phosphate- Sulphate Catalysts

In the present work, the acetylation of glycerol over zirconium phosphates and mixed zirconium phosphate sulphate catalysts was investigated. In details, the catalysts with formula Zr-3(PO4)(4), Zr(SO4)(2), Zr-2(PO4)(2)SO4, Zr-3(PO4)(2)(SO4)(3) and Zr-4(PO4)(2)(SO4)(5) have been prepared. Characterizations by XRD, FT-IR and acid capacity measurements by titration with NaOH aq. were performed. The glycerol acetylation reactions were performed by using a mass ratio of catalyst/glycerol equal to 5wt% and molar ratio acetic acid/glycerol corresponding to 3:1. The products were analyzed by GC-MS. Zr-3(PO4)(2)(SO4)(3), Zr-4(PO4)(2)(SO4)(5) were the best performing catalysts giving full glycerol conversion in 1h only. Then the activity decreased as a function of the phosphate/sulphate groups. A relationship between acid capacity, activity in glycerol acetylation and selectivity to triacetylglycerol was found. Zr-4(PO4)(2)(SO4)(5) showing the highest acid capacity (7.5 mmol g(-1)) exhibited the best catalytic performance and the highest selectivity to triacetin. Recycling experiments up to 5 cycles were performed over such catalyst.