蒸汽重整Steam reforming

主反应 CH₄ + H₂O ⇌ CO + 3 H₂ 强烈吸热（ΔH° = +206 kJ/mol）且气体分子数增加，因此高温低压有利；工业上在装满 Ni/Al₂O₃ 催化剂的炉管中于 800–900 °C、2–3 MPa 下进行，炉管外用燃料燃烧供热。随后进行水煤气变换 CO + H₂O ⇌ CO₂ + H₂（放热，在较低温度下进行），最后用变压吸附提纯氢气。

The main reaction, CH₄ + H₂O ⇌ CO + 3 H₂, is strongly endothermic (ΔH° = +206 kJ/mol) and increases the moles of gas, so high temperature and low pressure favour it; plants run it at 800–900 °C and 2–3 MPa in tubes packed with Ni/Al₂O₃ catalyst, heated by burners outside. The water–gas shift, CO + H₂O ⇌ CO₂ + H₂, which is exothermic and run cooler, follows, and pressure-swing adsorption purifies the hydrogen.

1920 年代巴斯夫开始研究烃类水蒸气转化，1930 年美国标准石油公司建成首套工业装置。二战后天然气供应增加，蒸汽重整逐渐取代煤气化成为合成氨的主要氢源。镍催化剂易因积碳和硫中毒失活，因此进料必须先脱硫，并保持足够的水碳比。

BASF investigated steam reforming of hydrocarbons in the 1920s, and Standard Oil of New Jersey built the first industrial unit in 1930. As natural gas became widely available after the Second World War, steam reforming displaced coal gasification as the main hydrogen source for ammonia. Nickel catalysts are deactivated by coking and sulfur, so feeds are desulfurised first and a sufficient steam-to-carbon ratio is maintained.

每生产 1 kg 氢气约排放 9–12 kg CO₂，这种氢被称为“灰氢”；若配套碳捕集，称为“蓝氢”。用可再生电力电解水得到的“绿氢”、甲烷热解制氢和自热重整是降低碳排放的研究方向。

Each kilogram of hydrogen releases roughly 9–12 kg of CO₂, so the product is called grey hydrogen; with carbon capture it becomes blue hydrogen. Green hydrogen from renewable-powered electrolysis, methane pyrolysis and autothermal reforming are being developed to cut emissions.