Conversion of refined and crude glycerol to ethyl lactate using the
integrated process was also investigated and the results are shown in
Fig. 6. The ethyl lactate yield achieved using refined glycerol as starting
material was about 45 mol% with glycerol conversion of 98 mol%. The
conversion of crude glycerol CG1 showed similar glycerol conversion
and ethyl lactate yield. In the case of CG2, glycerol conversion was
similar, but ethyl lactate yield was slight higher than that in the case
of converting refined glycerol. The LA yields from CG1 and CG2 were
lower than those in the case of converting refined glycerol, but the PG
yields from CG1 and CG2 were close to those in the case of converting
refined glycerol. Comparing with methyl lactate production, the
reaction temperature for ethyl lactate production was much higher
(220 °C for ethyl lactate production and 180 °C for methyl lactate
production). The high reaction temperature might change reaction kinetics,
alleviating the negative effects of impurities in crude glycerol
on glycerol conversion and ethyl lactate yield.