**2.3. Oxy-fuel combustion capture**

This technology is employed only in combustion conversions that generate flue gas rich in CO2 but free from N2 and NOx products. The energy demands are lower in this capture process, but the expenses majorly stem from the need of using pure oxygen in the combustion process to avoid generating the coproducts and their separation afterward.

Carbon dioxide is indeed an extremely valuable molecule that can be utilized in diverse ben-

Carbon dioxide is commonly used in fire extinguishers and photosynthesis as well as a car-

temperature (304.25 K) and pressure (7.39 MPa). In processes at high pressure (at or above

pounds and as a greener alternative for multiphase catalytic reactions, where it is employed as a promoter or modifier of liquid-phase organic reactions although not as a reactor. The

chemical properties is modulated by its interactions with the functional groups of substrates and/or intermediates (whether gases or not), as proved by the *in situ* high-pressure Fourier transform infrared spectroscopy. Hence, it acts here as a "modifier" to the reactivity of these groups and, thereby, to the selectivity of the reaction (e.g., Heck reactions). It is worth noting

natural gas (ECBM), respectively, from oil fields and coal deposits represent an attractive option to obtain the otherwise unrecoverable fossil fuels. These methods have been tested successfully and are being extensively researched to reduce the costs, optimize the CCS and

the viscosity and consequently increasing the extraction yields by 5–15%. The ECBM employs

adsorbs onto the carbon at twice the rate of methane, leading to its faster displacement and enhanced recovery. It is worth noting that surfactants and other gases as well as varied meth-

 represents an abundant and a safe resource of C and O, which can be employed in the synthesis of variety of useful products conforming to the principles of Green Chemistry.

is attracting huge attention. The types of transformations of carbon dioxides along with

ods like thermal energy processes are also applied in EOR and ECBM processes.

 **into chemicals and fuels**

in the organic phase acts as a "promoter" by altering the physical properties

, thereby accelerating the involved reactions such as oxidation,

Introductory Chapter: An Outline of Carbon Dioxide Chemistry, Uses and Technology

in the extraction processes of crude oil (EOR or tertiary recovery) and

under supercritical conditions allows an efficient mixing with oil, decreasing

is a fluid state of CO<sup>2</sup>

hydroformylation, and hydrogenation, respectively. In contrast, the impact of scCO2

) has found indispensable applications in super-

is used in sustainable extractions of bioactive com-

where it is held at or above its critical

http://dx.doi.org/10.5772/intechopen.79461

can fill the volume as a

on the

7

state that can dissolve gaseous

emission streams of high purity

to the environment. In EOR, the

occupies the porous spaces of the coal bed and

as an alternative to toxic reactants such as phosgene and CO

eficial ways, as illustrated in **Figure 1** and detailed herein.

bonating agent and preservative in food and drink industries.

of the solvent from pure organic phase into high-density CO2

that most of the abovementioned uses are limited to CO2

CCU conditions, and thus to avoid the reemission of CO2

**4.2. Enhanced oil (EOR) and coal-bed methane recovery (ECBM)**

, CO, H2

(from ammonia production, for instance) [10, 12].

a similar technique in which the injected CO2

the critical parameters), the density drastically increases, so scCO2

In addition, *supercritical carbon dioxide* (scCO2

gas but with a density like a liquid. scCO2

**4.1. Direct utilization of CO2**

critical fluid technology. scCO<sup>2</sup>

dissolved CO2

reactants such as O2

The injection of CO2

injection of CO2

**4.3. Conversion of CO2**

For instance, employing CO2

CO2
