(1) Steam Methane Reforming (SMR)
Steam reforming is the endothermic conversion of methane and steam into H₂ and CO.
The chemical reaction is:
CH₄ + H₂O + heat → CO + 3H₂
The heat required for the reaction is supplied by the combustion of methane. The process takes place at 700–850 °C, producing CO and H₂, with CO accounting for approximately 12% of the total product. CO is further converted into CO₂ and H₂ through the water‑gas shift reaction, as shown in the chemical equation.
(2) Partial Oxidation (POX)
Hydrogen production via partial oxidation of natural gas involves the partial combustion of methane with oxygen to release CO and H₂.
The chemical reaction is:
CH₄ + 1/2O₂ → CO + 2H₂ + heat
This process is exothermic and requires careful design. The reactor does not need an external heat source, and the outlet temperature can reach 950–1100 °C. The CO produced is further converted into H₂ through the water‑gas shift reaction. Hydrogen from the autothermal reforming process requires purification, which significantly increases the cost of hydrogen production.
Table 3-2 compares the advantages and disadvantages of the above three hydrogen production methods.
| Hydrogen Production Technology | Advantages | Disadvantages |
| Steam Methane Reforming | Most widely applied; no oxygen required; suitable process temperature; favorable H₂/CO ratio for hydrogen production | Usually requires excessive steam; high capital investment in equipment; high energy demand |
| Autothermal Reforming | Low energy requirement; lower process temperature than partial oxidation; H₂/CO ratio easily adjusted by CH₄/O₂ ratio | Limited commercial application; usually requires oxygen |
| Partial Oxidation | Direct desulfurization of feedstock; no steam required; natural low H₂/CO ratio beneficial for applications with ratio < 20 | Natural low H₂/CO ratio unfavorable for applications requiring ratio > 20; very high operating temperature; usually requires oxygen |