Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol, and it is combustible and can be used as a fuel. Syngas is produced by steam reforming or partial oxidation of natural gas or liquid hydrocarbons, or coal gasification. The chemical composition of syngas varies based on the raw materials and the processes. Syngas produced by coal gasification generally is a mixture of 30 to 60% carbon monoxide, 25 to 30% hydrogen, 5 to 15% carbon dioxide, and 0 to 5% methane. It also contains lesser amounts of other gases.

There are different ways to prepare syngas, and the process depends on the raw material used. Some of the methods include:

• Steam reforming: This is a process where steam reacts with a hydrocarbon to produce syngas. For example, methane can be reacted with steam to produce syngas.

• Partial oxidation: This is a process where a hydrocarbon is partially oxidized with oxygen or air to produce syngas. For example, natural gas can be partially oxidized to produce syngas.

• Coal gasification: This is a process where coal is reacted with steam and oxygen to produce syngas. The syngas produced by coal gasification generally has a different composition than that produced by steam reforming or partial oxidation.

The preparation of syngas can also involve the compression of a concentrated stream of carbon dioxide, followed by admixing with FT off-gas, and hydrogen. The chemical composition of syngas and proportion of its molecules is highly dependent on the raw material characteristics and conditions of the treatment process. Syngas can be produced from many sources, including natural gas, coal, biomass, or virtually any hydrocarbon feedstock, by reaction with steam or oxygen.