Chemistry Reference
In-Depth Information
promotion of higher alcohol formation (mainly propanol, butanol and
pentanol).
27,28
C
n
H
2n
þ
1
OH
þ
CO
þ
2H
2
2
CH
3
(CH
2
)
n
OH
þ
H
2
O
(5)
CH
3
OH
þ
nCO
þ
2nH
2
2
C
n
þ
1
H
2n
þ
3
OH
þ
nH
2
O
(6)
C
2
H
5
OH
þ
nCO
þ
2nH
2
2
C
n
þ
2
H
2n
þ
5
OH
þ
nH
2
O
(7)
Lachowska et al. reported that the addition of methanol and/or ethanol
to syngas increased the yields of all C
3
þ
alcohols.
27,28
They also reported
that the addition of methanol to CO and H
2
enhanced butanol formation,
however it was less ecient and produced relatively less butanol com-
pared to ethanol addition.
27,28
In contrast, Majocchi et al. found that the
addition of methanol to syngas did not cause any significant change in
higher alcohol formation, but ethanol addition resulted in a significant
promotion of propanol formation.
106
Minahan et al. also reported that
the addition of methanol had little or no effect on higher alcohol
synthesis and hence methanol feed/recycle is not a viable option for
improving higher alcohol production.
107
They also found that the add-
ition of ethanol to syngas feed increased the yields of n-propanol and
isopropanol and an excess of ethanol doubled the isobutanol rate with
concurrent formation of ethane.
107
Figures 7 and 8 show the result of a thermodynamic analysis of
methanol and ethanol homologation with syngas as a function of tem-
perature, in the absence of methane formation and assuming a stoi-
chiometric mixture of reactants at 20 bar, respectively. In both cases,
butanol formation is higher at lower temperatures and decreases with
increasing temperatures, whereas that of propanol and ethanol go
through a maximum (see close-up views in Figs. 7b and 8b). Figure 7
appears to the same as Fig. 3b, which was calculated for the hydrogen-
ation of CO in the absence of methane formation under the same con-
ditions. This indicates that addition of methanol to syngas did not
change the equilibrium distribution of products significantly, thus con-
sistent with Majocchi et al. and Minahan et al.
106,107
Fig. 7 Equilibrium distribution of products during homologation (cofeeding) of methanol
with syngas, with no methane formation allowed (H
2
/CO/CH
3
OH
=
2/1/1, 20 bar, calculated
using HSC software); (b) Close-up of (a) to show the distribution of MeOH, EtOH and PrOH.
