What is Steam Methane Reforming?
Steam methane reforming (SMR) is a process in which methane from natural gas is heated, with steam, usually with a catalyst, to produce a mixture of carbon monoxide and hydrogen used in organic synthesis and as a fuel1. In energy, SMR is the most widely used process for the generation of hydrogen2.
In SMR, methane reacts with steam under 3-25 bar pressure (1 bar= 14.5 psi) in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide. Steam reforming reaction is endothermic, i. e. heat must be supplied to the process for the reaction to proceed.
In a “water-gas shift reaction,” the carbon monoxide and steam are reacted using a catalyst to produce carbon dioxide and more hydrogen. In a final process step called “pressure-swing adsorption,” carbon dioxide and other impurities are removed from the gas stream, leaving essentially pure hydrogen. Steam reforming can also be used to produce hydrogen from other fuels, such as ethanol, propane, or even gasoline3.
Steam-Methane Reforming Reaction
CH4 + H2O (+heat) → CO + 3H2
Water-Gas Shift Reaction
CO + H2O → CO2 + H2 (+small amount of heat)
Steam methane reforming is the most widely used process for the generation of hydrogen. This is largely due to its cost effectivness in obtaining a high level of purity in its produced hydrogen. The hydrogen obtained from SMR can be used in industrial processes and in fuel cells because of its purity.
Although hydrogen itself is an emission free fuel, the feedstock to produce the hydrogen often comes from natural gas which results in the emissions of greenhouse gases. Additionally, the SMR process requires vast amounts of heat and is therefore highly energy intensive.
As the world continues to consider a hydrogen economy, SMR technology will remain a critical piece of that puzzle.
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