steamreforming

Steam reforming is a widely used industrial process for producing hydrogen from light hydrocarbons, most commonly methane, by reacting the hydrocarbon with water (steam) over a catalyst at high temperature. The principal reaction is methane steam reforming: CH4 + H2O -> CO + 3 H2. This reaction is endothermic and requires continuous heat input. Typical operating conditions are temperatures around 700–1100°C and pressures from near atmospheric to several tens of bar. Nickel-based catalysts are common, usually supported on materials such as alumina or silica.

In industry, natural gas is the primary feedstock, though other light hydrocarbons can be reformed. A steam-to-carbon ratio (S/C) around 2–3 is commonly used to minimize carbon formation while balancing energy use. The reforming step is often split into a primary reformer and, if needed, a secondary reforming stage to adjust the gas composition and heat balance. The primary reforming step generates synthesis gas containing hydrogen and carbon monoxide and is typically followed by a water–gas shift stage to convert CO and steam into CO2 and additional H2.

Purification and separation of the product gas follow reforming. The gas mixture is cooled and treated to remove CO2 and other impurities, and hydrogen is isolated by processes such as pressure swing adsorption (PSA) or membrane separation to achieve high-purity hydrogen. In refinery and chemical plants, the produced hydrogen is used for hydrodesulfurization, hydrocracking, ammonia synthesis, and other processes.

Variants of steam reforming include autothermal reforming (ATR), which combines reforming with partial oxidation to balance heat input, and dry reforming, which uses CO2 as the oxidant. These methods are chosen based on feedstock, energy considerations, and plant design.