. Materials and methods
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 use.
2.2. Catalyst characterization
The surface area, total pore volume and average pore diameter
of the selected catalysts were determined by nitrogen isothermal
(at196C) adsorption with a Micromeritics ASAP 2010 BET apparatus. The catalysts zeolite, and montmorrilonite were degassed at
120C and amberlyst was dried at 90C overnight under vacuum
prior to the surface area measurements. The acidity of the catalysts
were measured by ammonia temperature programmed desorption
(NH3-TPD) test using Micromeritics AutoChem II analyzer. Thermal
stability of the catalysts was evaluated using thermogravimetric
analyser (TA Q500) at a heating rate of 10C/min in N2 flow of
30 ml/min. Fourier Transform Infrared Spectroscopy (FTIR) (Thermo scientific-Nicolet 6700) was used to identify the functional
groups present in the catalysts