定义Definition
接触法是工业制硫酸的方法：硫磺或硫化物矿燃烧得到 SO₂，在五氧化二钒催化剂上被氧化为 SO₃，SO₃ 用约 98% 的浓硫酸吸收生成发烟硫酸，再稀释为硫酸。
The contact process is the industrial route to sulfuric acid: SO₂ from burning sulfur or sulfide ores is oxidised to SO₃ over a vanadium(V) oxide catalyst, and the SO₃ is absorbed in ~98 % sulfuric acid to form oleum, which is diluted to acid.
关键反应与条件Key reaction and conditions
2SO₂ + O₂ ⇌ 2SO₃，ΔH ≈ −198 kJ/mol。按勒夏特列原理低温有利于平衡，但速率太慢，所以取约 400–450 °C 和略高于常压，并分段转化、段间冷却；转化率可超过 99.5%。
2SO₂ + O₂ ⇌ 2SO₃, ΔH ≈ −198 kJ/mol. Le Chatelier favours low temperature, but rates are then too slow, so plants run at about 400–450 °C and slightly above 1 atm in several catalyst beds with inter-bed cooling, reaching over 99.5 % conversion.
为何不直接用水吸收Why not absorb in water
SO₃ 与水反应剧烈放热，会形成难以捕集的硫酸酸雾，因此用浓硫酸吸收：SO₃ + H₂SO₄ → H₂S₂O₇，再加水 H₂S₂O₇ + H₂O → 2H₂SO₄。
SO₃ reacts with water so exothermically that an uncatchable acid mist forms, so it is absorbed in concentrated sulfuric acid to give oleum (H₂S₂O₇), which is then diluted.
历史History
1831 年英国人皮里格林·菲利普斯申请用铂催化的专利；19 世纪后期德国巴斯夫实现工业化，替代了铅室法。20 世纪 20 年代起钒催化剂取代昂贵且易中毒的铂。“双接触双吸收”工艺显著减少 SO₂ 排放。
Peregrine Phillips patented a platinum-catalysed process in 1831; BASF industrialised it in the late nineteenth century, displacing the lead-chamber process. From the 1920s vanadium catalysts replaced costly, easily poisoned platinum. Double-contact double-absorption plants greatly cut SO₂ emissions.
反应Reactions
V₂O₅/K₂SO₄ 催化剂，400–450 °C，1–2 atm，多段转化
V₂O₅/K₂SO₄ catalyst, 400–450 °C, 1–2 atm, multiple beds
制取并净化 SO₂（除尘、干燥，防止催化剂中毒）。
Make and purify SO₂ (dust removal and drying to protect the catalyst).
SO₂ 在钒催化剂上氧化为 SO₃。
Oxidise SO₂ to SO₃ over vanadium catalyst.
浓硫酸吸收 SO₃ 得发烟硫酸。
Absorb SO₃ in concentrated acid to give oleum.
稀释得到所需浓度的硫酸。
Dilute to the required strength.
平衡与速率的折中。
A compromise between equilibrium and rate.
年表Timeline
- 1831
菲利普斯取得接触法专利
Phillips patents the contact process
- 1875
工业规模生产开始（德国）
Industrial production begins in Germany
- 1920s
钒催化剂取代铂
Vanadium catalysts replace platinum