2.1. Materials
Glycerol and acetone (both >99 wt% purity) were purchased
from Sigma Aldrich and used as received. Reagent grade anhydrous
ethanol was supplied from Commercial Alcohols Inc. Solketal (1,2-isopropylidene glycerol, 99 wt%), for GC calibration was also obtained from Sigma Aldrich. The catalysts of Amberlyst 35 Dry and
Amberlyst 36 Wet were obtained from Rohm and Hass Co. (USA)
and used as received. Zeolite beta (CP 814 C) in the acid form
was procured from Zeolyst International (USA) and was calcined
at 500C for 6 h before use. Montmorillonite (K-10) was obtained
from Sigma-Aldrich and was dried at 120C for 3 h before use. Zirconium sulphate was prepared according to literature[24] from
zirconium sulfate hydrate purchased from Sigma–Aldrich. Polymax
(845) was provided by Sud Chemie group and was dried at 120C
for 2 h prior to us