Steam reforming

Steam reforming, also called steam methane reforming (SMR), is the main way that industries produce hydrogen today.^[1] In this process, fuels like natural gas, naphtha, or even biogas are mixed with very hot steam, between 700 and 1,100 °C. This mixture passes over a special nickel-based catalyst, which helps the chemical reaction happen. The result is a mix of hydrogen, carbon monoxide, and a little carbon dioxide. The main reaction is when methane (CH₄) from natural gas reacts with steam (H₂O) to form carbon monoxide (CO) and hydrogen (H₂). Because this reaction needs a lot of heat, extra fuel is usually burned to keep the temperature high.^[2]

The process usually happens inside strong reformer furnaces that can handle the extreme heat. Once the first reaction produces hydrogen and carbon monoxide, another step is used to make even more hydrogen. This is called the water–gas shift reaction, where carbon monoxide reacts with more steam to create carbon dioxide and extra hydrogen.^[3] This happens in two stages: one at high temperature and another at lower temperature to get the most hydrogen possible.^[4]

After that, the gas mixture is cleaned up. One of the most common methods is called pressure swing adsorption (PSA). This step removes leftover carbon dioxide, carbon monoxide, methane, and other impurities, leaving behind very pure hydrogen, up to 99.999%.^[5] This pure hydrogen can then be used in important industries, such as making ammonia for fertilizers, refining petroleum, producing methanol, or powering fuel cells.^[6]

Even though SMR is very efficient and provides over half of the world’s hydrogen, it has a big downside: it releases a lot of carbon dioxide. In fact, producing just one kilogram of hydrogen this way can release 9 to 12 kilograms of CO₂.^[7] To lower these emissions, some SMR plants add carbon capture and storage (CCS), creating what is called “blue hydrogen.”^[8] There are also variations of SMR, such as autothermal reforming (ATR), which combines steam reforming with a small amount of burning to reduce outside heating needs,^[9] and biogas reforming, which uses renewable sources like landfill gas.^[10]

Running an SMR plant also requires care. If carbon builds up on the nickel catalyst, it can block the reaction, a problem called coking.^[11] Also, sulfur in the fuel must be removed beforehand because it can damage the catalyst.^[12] As the world looks for cleaner energy, scientists are trying to improve SMR with new ideas like membrane reactors, sorption-enhanced reforming, and ways to combine it with renewable electricity. This could make hydrogen production cleaner while still using SMR’s well-developed technology.^[13]