The synthesis of solketal was carried out in a bench scale continuous down-flow tubular reactor (Inconel 316 tubing, 9.55 mm
OD, 6.34 mm ID and 600 mm length) heated with an electric furnace. A schematic diagram of the continuous flow reactor
system is shown inFig. 1. The feed – a homogeneous solution of
reactants (acetone and glycerol) and solvent (ethanol) at a selected
molar ratio, was pumped using a HPLC pump (Eldex) at a specific
flow rate into the reactor maintained at a desired temperature
and pressure (controlled by a temperature controller and a back-pressure controller, respectively). In a typical run, 116.00 g of acetone, 92.00 g of glycerol and 46.00 g of ethanol (corresponding to
2:1:1 molar ratio of acetone:glycerol:ethanol) were mixed, and
the homogeneity of the solution was confirmed by GC–MS analysis. Ethanol was used as solvent mainly to improve the solubility
of glycerol in acetone. In each run, a pre-determined amount of
catalyst was preloaded into the catalytic bed, in which the catalyst
particles were supported on a porous Inconel metal disc (pore size:
100lm) and some quartz wool. The amount of catalyst in each run
was determined by the selected weight hourly space velocity
(WHSV, reciprocal of reaction time) defined as follows