Decarbonisation Technology - May 2023 Issue

Conversion of CO 2 to methanol CO 2-to-methanol conversion has the potential to play a significant role in reducing greenhouse gas emissions and advancing a more sustainable energy system

Nieves Alvarez MERYT Catalysts & Innovation

M ethanol has many uses, including as the starting feedstock for several high- demand chemicals, such as dimethyl ether oxymethylene ethers, as an additive or as a fuel component for gasoline engines and fuel cells. It is also one of the leading contenders as a renewable fuel for marine engines. Building on the hydrogen economy, the hydrogenation of carbon dioxide (CO 2) to produce methanol could potentially lead to the generation of the ‘methanol economy’. The conversion of CO 2 to methanol is a process known as CO 2 reduction and involves the following steps:  Capture and purification of CO2 : CO 2 is captured from industrial processes or directly from the air, then purified to remove impurities.  Production of low-carbon-intensity hydrogen, initially from the reforming of methane with carbon capture, but over time, increasingly from the electrolysis of water using renewable electricity from solar, wind or hydroelectricity.  Conversion of CO 2 to carbon monoxide (CO): CO 2 is reacted with hydrogen gas (H 2) to produce carbon monoxide (CO) and water (H2O). This is known as the reverse water-gas shift reaction.  Conversion of CO to methanol: The CO produced in the previous step is then reacted with hydrogen in the presence of a catalyst to produce methanol (CH 3OH). E-methanol The cost of producing fossil fuel-based methanol is in the range of $100-250 per tonne. Renewable methanol can be produced using renewable energy and renewable feedstocks via two routes:  CO 2 would most likely be captured from the combustion of fossil fuels in power plants,

or furnaces for industrial steel and glass manufacture. Even though recycled, it originates from non-renewable fossil fuels, making the overall process net CO 2 positive. However, given that the CO 2 from these sources would otherwise be released into the atmosphere, using it to produce methanol with green hydrogen would result in low-carbon methanol. It would also displace a corresponding amount of fossil fuel otherwise required. In the case of cement, the CO 2 is released from the chemical process itself. The cost of producing fossil fuel-based methanol is in the range of $100-250 per tonne. Renewable methanol can be produced using renewable energy and renewable feedstocks via two routes  CO 2 from biogenic sources such as distilleries, fermentation units, municipal solid waste (MSW) incinerators, and power plants that burn biomass or biogas to generate electricity is normally treated as off-gas and emitted to the atmosphere (usually at high CO 2 concentrations but atmospheric pressure). These biogenic sources are considered to be renewable, sustainable, and net CO 2 neutral.  However, when the CO 2 from these biogenic sources is captured for storage or utilisation, the process is usually referred to as bioenergy with carbon capture and storage (BECCS). BECCS and CO 2 obtained from the atmosphere via direct air capture (DAC) are considered net CO2 negative. Bio-methanol is produced from biomass. Potential sustainable biomass feedstocks include forestry and agricultural waste and