535
reactions, photoexcited electrons are used to reduce the coenzyme NADP+ to
NADPH as well as create the high-energy molecule ATP. In the second set of reactions, called the light-independent reactions, these reduced molecules are used to
convert CO 2 to organic compounds that can then be used by algae as a source of
energy. The oils produced by algae which are used for biofuel production contain
the carbon that was fixed in the Calvin cycle. [17].
2.4 Catalytic Conversion of CO 2
Synthesis routes involving CO 2 have been developed for the catalytic conversion to
methanol, methane, formaldehyde, formic acid, synthesis gas and polymers [16]. In
general, these processes involve the reduction of carbon dioxide at high temperatures over a catalyst. The catalytic conversion mainly involves the conversion into
polymers and reduction of carbon dioxide into higher valued products or intermediate (synthesis gas) using hydrogen or methane. Carbon dioxide reduction to synthesis gas or other higher valued products are energy-intensive processes due to the
very low energy content and stable nature of CO 2 . A significant amount of energy is
required to activate carbon dioxide for subsequent reaction. The intermediate, synthesis gas is further used for the synthesis of commodity or fine chemicals. Major
routes for CO 2 catalytic conversion involve the hydrogenation of CO 2 and the
reforming of methane with CO 2 .
Carbon dioxide utilization by conversion into chemicals and fuels has immense
potential to transform CO 2 into an important feedstock for the chemical industry.
However, this can only be realised if these processes can be implemented in large
industrial scales.
3 Importance of Scale for CO 2 Sources and Conversion
Sources of CO 2 include point sources from industrial processes, and distributed
sources such as from the transportation sector and agriculture. Distributed sources
of carbon dioxide do not provide a continuous, high-volume and reliable supply of
carbon dioxide and are not effective sources for large-scale CO 2 utilization projects.
Even though the atmosphere is ubiquitous and free, the concentration of CO 2 in the
atmosphere is very low (400 ppm) which significantly increases the cost and energy
penalty associated with CO 2 capture to obtain concentrated streams. Pilot plant
studies have shown that the cost of CO 2 capture from atmospheric air can range
from USD94 to USD232 per ton [19]. Industrial sources of CO 2 provide reliable
supply of CO 2 at much lower cost (USD14 to USD51 per ton) depending on stream
purity [9]. The focus of the rest of this section is therefore on the utilization of CO 2
captured from industrial point sources.
Synthesis of Novel Catalysts for Carbon Dioxide Conversion to Products of Value
reactions, photoexcited electrons are used to reduce the coenzyme NADP+ to
NADPH as well as create the high-energy molecule ATP. In the second set of reactions, called the light-independent reactions, these reduced molecules are used to
convert CO 2 to organic compounds that can then be used by algae as a source of
energy. The oils produced by algae which are used for biofuel production contain
the carbon that was fixed in the Calvin cycle. [17].
2.4 Catalytic Conversion of CO 2
Synthesis routes involving CO 2 have been developed for the catalytic conversion to
methanol, methane, formaldehyde, formic acid, synthesis gas and polymers [16]. In
general, these processes involve the reduction of carbon dioxide at high temperatures over a catalyst. The catalytic conversion mainly involves the conversion into
polymers and reduction of carbon dioxide into higher valued products or intermediate (synthesis gas) using hydrogen or methane. Carbon dioxide reduction to synthesis gas or other higher valued products are energy-intensive processes due to the
very low energy content and stable nature of CO 2 . A significant amount of energy is
required to activate carbon dioxide for subsequent reaction. The intermediate, synthesis gas is further used for the synthesis of commodity or fine chemicals. Major
routes for CO 2 catalytic conversion involve the hydrogenation of CO 2 and the
reforming of methane with CO 2 .
Carbon dioxide utilization by conversion into chemicals and fuels has immense
potential to transform CO 2 into an important feedstock for the chemical industry.
However, this can only be realised if these processes can be implemented in large
industrial scales.
3 Importance of Scale for CO 2 Sources and Conversion
Sources of CO 2 include point sources from industrial processes, and distributed
sources such as from the transportation sector and agriculture. Distributed sources
of carbon dioxide do not provide a continuous, high-volume and reliable supply of
carbon dioxide and are not effective sources for large-scale CO 2 utilization projects.
Even though the atmosphere is ubiquitous and free, the concentration of CO 2 in the
atmosphere is very low (400 ppm) which significantly increases the cost and energy
penalty associated with CO 2 capture to obtain concentrated streams. Pilot plant
studies have shown that the cost of CO 2 capture from atmospheric air can range
from USD94 to USD232 per ton [19]. Industrial sources of CO 2 provide reliable
supply of CO 2 at much lower cost (USD14 to USD51 per ton) depending on stream
purity [9]. The focus of the rest of this section is therefore on the utilization of CO 2
captured from industrial point sources.
Synthesis of Novel Catalysts for Carbon Dioxide Conversion to Products of Value