Optimization of glycerol etherification with ethanol in fixed bed reactor under various pressures

The objective of this paper was to study the glycerol etherification with ethanol in a fixed bed reactor catalyzed by Amberlyst 15. We analyzed through a four factor central composite design the influence of independent process variables including pressure (7–103 MPa), temperature (180–290 °C), ethanol/glycerol molar ratio (4–30/1) and amount of catalyst (0–0.95 g). Special interest was taken in evaluating the effect of pressure, since this reaction mixture can be one or two phase depending on this variable. The results showed that for this system it is not necessary to keep all the reaction mixture in just one phase to obtain good results in terms of glycerol conversions and ether yields. For the glycerol conversion, a maximum of 97% was obtained and the optimum conditions were temperature (269 °C), ethanol/glycerol molar ratio (12:1), catalyst amount (0.78 g) and pressure (2.5 MPa). In terms of ether yield, the optimization study using canonical analysis predicted the following optimal levels were predicted: pressure (7.1 MPa), temperature (242 °C), ethanol/glycerol molar ratio of (22:1) and catalyst amount (0.63 g). Under these operating conditions, the experimental value for ether yield obtained was 69%, confirming the result predicted by the optimization study. These results indicated that the equations were effective in describing the actual experimental data. Reaction conditions in which glycerol-ethanol form two phase mixtures still presented excellent results on the responses.