Chemistry Reference
In-Depth Information
Fig. 8 Equilibrium distribution of products during homologation (cofeeding) of ethanol with
syngas, with no methane formation allowed (H
2
/CO/C
2
H
5
OH
=
2/1/1, 20 bar, calculated
using HSC software); (b) Close-up of (a) to show the distribution of MeOH, EtOH and PrOH.
Fig. 9 Equilibrium distribution of products during homologation (cofeeding) of propanol
with syngas, with no methane formation allowed (H
2
/CO/C
3
H
7
OH
=
2/1/1, 20 bar, cal-
culated using HSC software); (b) Close-up of (a) to show the distribution of MeOH, EtOH
and PrOH.
However the addition of ethanol resulted in a significant change in the
product distribution as can be seen in Fig. 8. A comparison of Figs. 7 and
8 reveals that cofeeding methanol with CO and H
2
produces relatively less
butanol compared to ethanol homologation, which is consistent with the
experimental results reported by Lachowska et al.
27,28
A similar effect may
be observed in the case of recycling methanol and/or ethanol formed
during the course of the reaction.
Propanol homologation has also been studied previously.
104,107
Apesteguia et al. and Minahan et al. reported that propanol addition to
syngas selectively increased isobutanol formation.
104,107
They found that
both n-propanol and isopropanol had a more positive effect in boosting
isobutanol formation compared to ethanol.
104,107
When a thermo-
dynamic analysis was carried out for propanol addition to syngas (Fig. 9),
similar to those on methanol and ethanol addition, butanol formation
increased to 50% under the same reaction conditions, indicating that
cofeeding of propanol has a substantial promoting effect on higher
alcohol formation.
Cofeeding mixtures of lower alcohols has also been reported to
increase higher alcohol formation. Nunan et al. reported that injection of
C
2
þ
C
1
alcohols greatly enhanced the yields of C
3
þ
products, and
