Chemistry Reference
In-Depth Information
injection of C
3
þ
C
1
alcohol mixture greatly enhanced the yields of C
4
þ
products.
29
Apesteguia et al. also studied the effect of cofeeding mixtures
of methanol/1-propanol and methanol/ethanol with syngas.
104
It was
found that methanol/1-propanol mixtures led to the selective formation
of isobutanol, while the methanol/ethanol mixture mainly increased the
productivity to 1-butanol.
104
Thermodynamic calculations show that
adding a methanol/ethanol mixture to syngas is the same as adding only
ethanol to syngas (the results are the same as in Fig. 8), and adding a
methanol/propanol mixture is the same as that of adding only propanol.
4 Scope for further work in this area
The most interesting and effective methods for isobutanol synthesis
appear to be the Guerbet reaction and the homologation or cofeeding of
lower alcohols, especially propanol, with syngas. Thermodynamics also
suggests that propanol homologation results in a higher butanol yield
compared to ethanol or methanol homologation.
The typical catalysts used for higher alcohol synthesis consist of
methanol synthesis components such as Cu, Zn, Mn, Cr, etc. and alkali
promoters such as Cs or K. Since higher temperatures and higher pres-
sures are required for isobutanol synthesis compared to methanol,
careful selection of catalysts is essential to avoid undesired by-products,
hydrocarbon formation (which is highly favorable at higher tempera-
tures) as well as deactivation. An alkali promoter (like K or Cs) which can
provide both basic sites for higher alcohol synthesis and neutralize acid
sites responsible for hydrocarbon formation is recommended. A catalyst
that can rapidly transfer the hydrogen between adsorbed species is found
to be essential for high yield and selectivity toward higher alcohol
formation via the Guerbet reaction. The solid base which catalyzes the
condensation steps also has to be carefully selected in order to achieve
the desired performance.
References
1 N. D. Subramanian, G. Balaji, C. Kumar and J. J. Spivey, Catal. Today, 2009,
147(2), 100-106.
2 DOE/EIA-0384(2009), Annual Energy Review 2009, U.S. Energy Information
Administration, U.S. Department of Energy, Washington, D.C., August 2010.
Available from: www.eia.gov/aer.
3 DOE/EIA-0484(2010), International Energy Outlook 2010, U.S. Energy
Information Administration, U.S. Department of Energy, Washington, D.C.,
July 2010. Available from: www.eia.gov/oiaf/ieo.
4 X. L. Pan, Z. L. Fan, W. Chen, Y. J. Ding, H. Y. Luo and X. H. Bao, Nat. Mater.,
2007, 6(7), 507-511.
5 S. Velu, N. Satoh, C. S. Gopinath and K. Suzuki, Catal. Lett., 2002, 82(1-2),
145-152.
6 G. A. Deluga, J. R. Salge, L. D. Schmidt and X. E. Verykios, Science, 2004,
303(5660), 993-997.
7 S. Velu, C. Song, Royal Society of Chemistry, London, 2007, vol. 20.
8 J. J. Spivey and A. Egbebi, Chem. Soc. Rev., 2007, 36(9), 1514-1528.
9 V. Subramani and S. K. Gangwal, Energy Fuels, 2008, 22(2), 814-839.
