Introductory Chapter: Methanol Fuel – New Developments and Applications

1. Introduction

Climate change is a major threat that the world is dealing with today, and more efforts are needed in all economic sectors to reduce greenhouse gas (GHG) emissions. Especially in the transport sector, thus fossil-free fuels are required to reduce the negative impact caused by climate change. The most effective fuels are those with minimum GHG emissions and minimum pollutants, while compatible with common internal combustion engines and fuel infrastructure. There are various alternative fuel options including methanol, ethanol, and ammonia [1]. Comparing the three fuels, methanol has the advantage of being similar to traditional fuels. It is a hydrocarbon and a liquid. With stronger commitments to address climate change, the focus is on methanol as one of the fuels to be considered, especially for maritime engines, as it is making it easier to allow dual-fuel engines to be used in the marine sector [2]. Methanol is also used as fuel in other applications including fuel cells and the motor industry. This book reports on various developments in using methanol as a fuel for transportation and direct methanol fuel cells.

Methanol is a clear, colorless, neutral, and polar liquid at ambient conditions, with boiling and freezing points of 64.6°C and −97.6°C, respectively [3]. Methanol is produced using fossil fuels (i.e., natural gas, coal, and petrochemicals); it can also be produced from renewable sources such as biomass raw materials, agricultural raw materials (i.e., sugar cane, cereals, and rice), timber, and urban waste. More research is focusing on producing methanol from renewable sources as its production from fossil fuels results in a greenhouse emission. The growing demand for green methanol in the maritime industry has led to a growing number of project announcements for green methanol around the globe. It is predicted that the green methanol market will increase by 39.6%, which will have a significant improvement in climate change (Figure 1) [4].

Figure 1.

Green Methanol Market, $Million, 2021, 2022, and 2031 [4].

2. Methanol in the transport sector

Methanol possesses some interesting properties that make it more performing compared to conventional fuels for internal combustion engines, including high latent heat, fast-burning velocity, no carbon-to-carbon bonds, and high octane rating, and hence higher compression ratios and higher knock resistance for an increased engine efficiency [5].

Moreover, methanol is a fuel of choice due to its clean-burning and less explosive nature, which results in less gas emission (GHG) compared to other fuels, which has a significant effect on bettering the environment. When used as fuel transportation, it can be used straight for a gasoline component called Methyl tert-butyl ether (MTBE), as a blending component of fuel, or for the production of fuel components including a diesel component called fatty acid methyl ester FAME [4]. Countries like China and the United States use methanol-gasoline blends due to high demand for fuel and also its benefit in reducing GHG emissions impact and its use has been increasing in other regions like Asia and Europe [5].

Recently, more research focused on using methanol in the marine sector has grown rapidly, leading to commitments from some of the world’s largest shipping companies due to several advantages including being the lowest-cost carbon-neutral shipping fuel, by total cost of ownership (TCO), across a wide range of vessels and applications when compared to a suit of fuels including ammonia, liquefied biogas, electricity and hydrogen [6].

3. Methanol in fuel cells

Methanol is used as a fuel in direct methanol fuel cells, which is a variant of proton exchange membrane fuel cells where the mixture of methanol and water is used instead of hydrogen and indirectly via steam reforming into a hydrogen-rich gas mixture in HT-PEMFCs. Methanol is used as a fuel in direct methanol due to several advantages including its easy handling as a liquid mixture compared to the hydrogen storage required for low-temperature fuel cells or the added reforming system needed in HT-PEMFC. Methanol as fuel in fuel cells still faces challenges like the costs due to the Pt-based catalysts used, methanol crossover, low efficiency of below 30%, and poor electrode kinetics [7].

Methanol in fuel cells converts the liquid fuel, i.e. methanol into electricity in combination with oxygen producing only waste heat, water vapour and small amount of carbon dioxide [8].

$$\text{Anode}:\text{C}{\text{H}}_3\text{O}\text{H}+{\text{H}}_2\text{O}\to 6{\text{H}}^{+}+6{\text{e}}^{-}+\text{C}{\text{O}}_2(\text{oxidation})$$E1

$$\text{Cathode}:\frac{3}{2}{\text{O}}_2+6{\text{H}}^{+}+6{\text{e}}^{-}\to 3{\text{H}}_2(\text{reduction})$$E2

$$\text{Overall reaction}:\text{C}{\text{H}}_3\text{O}\text{H}+\frac{3}{2}{\text{O}}_2\to 2{\text{H}}_2\text{O}+\text{C}{\text{O}}_2\text{ (redox reaction)}$$E3

Pt is used as a catalyst for both half reactions. This contributes to the loss of the cell voltage potential, as any methanol that is present in the cathode chamber will oxidize. If another catalyst could be found for the reduction of oxygen, the problem of methanol crossover would likely be significantly lessened [9]. It is necessary to develop other low-cost, durable, safe and efficient alternatives to replace Pt catalysts in DMFC [10].