Branched-Chain Higher Alcohols - Biotechnology in China: Biofuels and Bioenergy - page 107

The current market for isobutanol is about 500,000 t/year. The traditional
strategy for isobutanol production is carbonylation of propylene. Two processes
are commonly used in the chemical industry. The major process is hydroformyl-
ation, which generates a mixture of isobutanol and isobutyraldehyde. Another
process is Reppe carbonylation. However, these petrochemical pathways are not
sustainable, and great concerns have been raised regarding environmental

pollution.
In recent years, with the rapid growth of the construction of new carbonyl
alcohol production facilities [ 23 ], the production capacity of isobutanol (one of the
main by-products of carbonyl alcohol production) in China has been increased. In
2006, the total domestic production capacity of isobutanol was 81,500 t/y. In 2010,
China National Offshore Oil Corporation (CNOOC) initiated a 1.5 billion tons per
year oil refinery project to use heavy crude oil from the Bohai Sea Oil Field, and
Bohai Chemical Group will construct a 230,000 t/year butanol/octanol production
facility as the CNOOC project's downstream support unit, which will significantly
increase China's isobutanol production capacity. However, with the rapid devel-
opment of the country's chemical industry, it will be difficult to be self-sufficient in
raw materials for the domestic market, and the dependence on imports of isobu-
tanol will persist for quite a long time. In 2008, China's isobutanol consumption
was 260,000 t, and more than half of the isobutanol was imported. Therefore, the
development of alternative isobutanol production processes has great potential.

2.4 2-Methyl-1-butanol, and 3-Methyl-1-butanol

3-Methyl-1-butanol and 2-methyl-1-butanol are normally used as apple or banana
flavoring agents for wine. They can also be used as chemical intermediates and
solvents in pharmaceutical products. The market consumption of 3-methyl
-1-butanol and 2-methyl-1-butanol is increasing continuously: however, the pro-
duction capacity is still low. The domestic market for 3-methyl-1-butanol and
2-methyl-1-butanol is more than 100,000 t/year, but China's production capacity
is only around 30,000 t [ 24 ].
3-Methyl-1-butanol and 2-methyl-1-butanol were first isolated from fusel oils,
by-products of ethanol fermentation by yeast [ 25 ]. These compounds can also be
derived from the chlorination of pentane followed by hydrolysis [ 26 ]. Another
alternative process is the oxo process, a general strategy for the manufacture of C 4
and higher alcohols [ 27 ]. Both the chlorination process and the oxo process are
current commercial processes for the production of 3-methyl-1-butanol and
2-methyl-1-butanol, but the oxo process via the hydroformylation reaction is the
more popular. Two main technologies are used for the process. The first was
brought on stream by Ruhrchemie in Germany and Exxon in USA in the 1940s and
is generally referred to as ''high-pressure cobalt catalyst technology.'' The active
catalyst species is cobalt hydrocarbonyl, and a pressure of 200-300 atm is required
to maintain the stability of the catalyst. In the early 1960s, Shell commercialized a