Hydrogen

Introduction

Hydrogen is a chemical element. Its atomic number is 1 and the symbol is H. So, it appears as H on the top of the periodic table. However, in nature, it exists as a diatomic molecule (H2) – as an odourless and colourless gas. It was discovered by Henry Cavendish in 1766.

Hydrogen is a vital element for many reasons, especially because it forms water (H2O), ammonia (NH3), hydrocarbons and many other essential industrial compounds, which are necessary for producing daily-use products and medicines.

Properties of Hydrogen

Hydrogen is an odourless, colourless, non-toxic and a highly combustible gas at room temperature. It is also non-metallic in nature. It is the lightest gas among all gases due to its lowest density. It reacts vigorously with oxygen to form water.

2H2 (g) + O2 (g) → 2H2O (l) + energy

Hydrogen powers the sun and stars in the universe. Four hydrogen atoms fuse together to form a helium molecule and produce energy. This reaction is also called nuclear reaction because this reaction takes place among nuclei, not electrons as is the case with most chemical reactions. The reaction of hydrogen atoms that leads to mass production of energy in the sun can be summarised as below:  

4H → He +2e- + energy

The reaction takes place in a controlled temperature and pressure environment.

Uses of Hydrogen

Hydrogen gas has several uses in the industry. Its most notable use includes:

– Production of ammonia (by Haber’s process), cyclohexane, and methanol

– Hydrogenation of oils to form fat

– Use in hydrogen cells

– Used as a protective layer in glass manufacturing plants

– Used as a slushing gas to remove sulphur during oil refining

-Production of Hydrogen

-Hydrogen is produced in the industry in three ways.

Heating natural gas (CH4)/ steam reforming

Most of the hydrogen required in the industry is produced by heating natural gas (CH4) with steam. This process is called Steam Reforming. This process is cost effective and meets the demand for most of the hydrogen around the world.

Natural gas (or methane) is heated with steam at 700-1000 degree celsius in the presence of nickel catalyst. This produces a mixture of carbon monoxide and hydrogen called syngas.

CH4 + H2O → CO + 3H2           (endothermic reaction)

Syngas is then passed over steam at 360 degree Celsius in the presence of iron oxide or other oxides to produce more hydrogen. This reaction is called the water shift reaction.

CO+ H2O  → CO2 + H2               (exothermic reaction)

Nearly 50 percent of the hydrogen in the world is produced by this method. Steam reforming however produces a large quantity of greenhouse gases, including CO2, CO, and more.

Coal Gasification

Coal is heated with steam and oxygen to produce a gaseous mixture containing hydrogen and carbon monoxide. Then, this gaseous mixture is treated at relatively low temperatures to separate hydrogen.

Electrolysis of water (H2O)/ Water Splitting

Electrolysis or water splitting uses electricity to produce hydrogen.

 2H2O → 2H2 +O2

Water splitting is increasingly getting popular as a way to produce hydrogen in the industry especially because it doesn’t produce greenhouse gases. Additionally, the process can be carried out at relatively low temperatures, between 50-60 degree Celsius compared to 700-1000 degree Celsius. Further, the source of energy in case of electrolysis is electricity while for steam reforming it is methane.

Conclusion

Hydrogen is an essential element and is used to produce various essential products. The major portion of Hydrogen on earth exists as water. A very small percentage of hydrogen is present as gas (H2) in the atmosphere. It is also the most abundant element in the universe and is considered as the next source of fuel on earth. Hydrogen cells are increasingly being promoted across the world as a new source of energy to reduce our dependence on coal, petrol, diesel, and other sources of non-renewable energy. Many countries across the world have already started using hydrogen cells to power their cars, buses, and other motor vehicles. Hydrogen fuel cells are primarily used in rockets.