1. Introduction

Nowadays, the demand for energy is rapidly increasing because of the economic growth worldwide. In order to meet this growing demand, an abundant amount of fossil fuel (oil, coal, and natural gas) is needed [1]. Fossil fuel combustion is often considered as one of the main threats to the environment because of the CO2 release in the atmosphere. CO2, which is

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

considered as a primary greenhouse-gas (GHG), is periodically exchanged within land surface, ocean, and atmosphere where a variety of creatures, including animals, plants, and microorganisms absorb and produce it daily. However, the process of releasing and consuming CO2 trends has to be balanced by nature. Since 1750, when the industrial revolution began, so did climate change following the activities related to industries. In order to reduce the greenhouse gas emissions, CO2 sequestration and storage (CSS) processes gained a widespread attention. However, it will increase the amount of available captured CO2 as feedstock of zero cost. Therefore, utilizing CO2 and converting it into fuels and chemicals, which is called carbon capture and recycling (CCR) process, is an active option used worldwide to convert usable products into valuable products, and it is used to mitigate CO2 emissions which is more preferable compared to CSS option [2–5]. During the last years, conversion of CO2 into valueadded chemicals (i.e., ethanol, methanol, and formic acid) using different ways has received a great attention from the researchers as it can be seen as a solution to reduce the global warming [6–8], energy crisis (i.e., fossil fuels depletion) [9–11], and the storage of energy [12] problems. Methanol is a renewable energy source that can be produced from any raw material containing carbon (mainly CO2), as well as it is a clean source of energy that can be used as transportation fuel. In general, for a fuel to satisfy the market demand, it must be sustainable material, clean, and able to be synthesized from available resources. Nowadays, as a matter of fact, most of the production companies around the world use methanol as a raw material to produce different products. Methanol is used in producing solvents like the acetic acid, which represents 10% of the global demand [13]. Methanol can also be used in direct methanol fuel cells (DMFC), which is used for the conversion of chemical energy in methanol directly to electrical power under ambient conditions [14]. Methanol is considered to be one of the most important organic feedstocks that can be used in the industries with an annual production of 65 million tons worldwide [15]. However, "Methanol Economy" term includes an anthropogenic carbon cycle for methanol production as shown in Figure 1, which can be used as a renewable fuel or to

Figure 2. Green methanol production by Carbon Recycling International [18].

Carbon Dioxide Conversion to Methanol: Opportunities and Fundamental Challenges

http://dx.doi.org/10.5772/intechopen.74779

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Figure 3. Outline of chemical conversion processes of CO2.

Figure 1. Anthropogenic carbon cycle for methanol production [20].

Carbon Dioxide Conversion to Methanol: Opportunities and Fundamental Challenges http://dx.doi.org/10.5772/intechopen.74779 43

Figure 2. Green methanol production by Carbon Recycling International [18].

considered as a primary greenhouse-gas (GHG), is periodically exchanged within land surface, ocean, and atmosphere where a variety of creatures, including animals, plants, and microorganisms absorb and produce it daily. However, the process of releasing and consuming CO2 trends has to be balanced by nature. Since 1750, when the industrial revolution began, so did climate change following the activities related to industries. In order to reduce the greenhouse gas emissions, CO2 sequestration and storage (CSS) processes gained a widespread attention. However, it will increase the amount of available captured CO2 as feedstock of zero cost. Therefore, utilizing CO2 and converting it into fuels and chemicals, which is called carbon capture and recycling (CCR) process, is an active option used worldwide to convert usable products into valuable products, and it is used to mitigate CO2 emissions which is more preferable compared to CSS option [2–5]. During the last years, conversion of CO2 into valueadded chemicals (i.e., ethanol, methanol, and formic acid) using different ways has received a great attention from the researchers as it can be seen as a solution to reduce the global warming [6–8], energy crisis (i.e., fossil fuels depletion) [9–11], and the storage of energy [12] problems. Methanol is a renewable energy source that can be produced from any raw material containing carbon (mainly CO2), as well as it is a clean source of energy that can be used as transportation fuel. In general, for a fuel to satisfy the market demand, it must be sustainable material, clean, and able to be synthesized from available resources. Nowadays, as a matter of fact, most of the production companies around the world use methanol as a raw material to produce different products. Methanol is used in producing solvents like the acetic acid, which represents 10% of the global demand [13]. Methanol can also be used in direct methanol fuel cells (DMFC), which is used for the conversion of chemical energy in methanol directly to electrical power under ambient conditions [14]. Methanol is considered to be one of the most important organic feedstocks that can be used in the industries with an annual production of 65 million tons worldwide [15]. However, "Methanol Economy" term includes an anthropogenic carbon cycle for methanol production as shown in Figure 1, which can be used as a renewable fuel or to

42 Carbon Dioxide Chemistry, Capture and Oil Recovery

Figure 1. Anthropogenic carbon cycle for methanol production [20].

Figure 3. Outline of chemical conversion processes of CO2.

produce nearly all products that are derived from fossil fuels [16, 17]. Carbon Recycling International (CRI)'s George Olah plant is considered to be the world's largest CO2 methanol plant. In 2015, Carbon Recycling International (CRI) scaled up the plant from a capacity of 1.3 million liters of methanol per year to more than 5 million liters a year. The plant now recycles 5.5 thousand tons of CO2 a year. All energy used in the plant comes from the Icelandic grid that is generated from geothermal and hydro energy [18]. As shown in Figure 2, the plant uses electricity to make H2 which reacts with CO2 in a catalytic reaction for methanol production. The various pathways and processes for CO2 conversion to methanol are described schematically in Figure 3. There are different CO2 conversion routes such as the catalytic method which comes in the form of conventional, electrocatalytic, photocatalytic, and photoelectrocatalytic conversion [19].
