哈伯法Haber process

反应放热（ΔH° = −92 kJ/mol）且气体分子数减少，按勒夏特列原理，低温高压有利于平衡转化；但低温下反应太慢。工业上折中采用 400–500 °C、15–25 MPa，配合铁催化剂，单程转化率约 15%，未反应气体冷却分离出液氨后循环使用。N≡N 键能高达 945 kJ/mol，在催化剂表面的解离吸附是决速步。

The reaction is exothermic (ΔH° = −92 kJ/mol) and reduces the number of gas molecules, so by Le Chatelier's principle low temperature and high pressure favour conversion, but at low temperature it is too slow. Plants compromise at 400–500 °C and 15–25 MPa over an iron catalyst, reaching about 15% conversion per pass; ammonia is condensed out and the unreacted gas recycled. The N≡N bond is very strong (945 kJ/mol), and its dissociative adsorption on the catalyst surface is the rate-determining step.

十九世纪末，智利硝石即将耗尽，克鲁克斯在 1898 年警告“氮危机”。德国化学家弗里茨·哈伯在 1909 年用锇催化剂在实验室高压装置中连续制得氨。巴斯夫公司的卡尔·博施解决了高压设备和氢脆问题，米塔施筛选出廉价的铁基催化剂，1913 年奥堡工厂投产。哈伯和博施分别获得 1918 年和 1931 年诺贝尔化学奖。

By the 1890s Chilean saltpetre was running out, and Crookes warned of a nitrogen crisis in 1898. In 1909 the German chemist Fritz Haber produced ammonia continuously in a high-pressure laboratory apparatus using an osmium catalyst. Carl Bosch of BASF solved the problems of high-pressure equipment and hydrogen embrittlement, Alwin Mittasch screened a cheap iron-based catalyst, and the Oppau plant started in 1913. Haber received the 1918 Nobel Prize in Chemistry and Bosch shared the 1931 prize.

氢气来源从水煤气转为天然气蒸汽重整，合成氨消耗全球约 1–2% 的能源，排放约 1% 以上的 CO₂。2007 年埃特尔因阐明铁表面合成氨机理获诺贝尔奖。钌基催化剂、可再生电力制氢的“绿氨”、电化学和光催化固氮是当前研究方向。

The hydrogen source moved from water gas to steam reforming of natural gas; ammonia synthesis now uses about 1–2% of world energy and emits over 1% of global CO₂. Gerhard Ertl received the 2007 Nobel Prize partly for explaining the mechanism on iron surfaces. Ruthenium catalysts, green ammonia from renewable hydrogen, and electrochemical and photocatalytic nitrogen fixation are current research directions.

全球年产氨约 1.8 亿吨，约 80% 用于化肥（尿素、硝酸铵等），其余用于硝酸、炸药、尼龙和制冷。合成氨既让粮食产量大幅提高，也在第一次世界大战中为德国提供了炸药原料；过量施氮还造成水体富营养化等环境问题。

World output is about 180 million tonnes a year; roughly 80% goes into fertilisers such as urea and ammonium nitrate, the rest into nitric acid, explosives, nylon and refrigeration. Synthetic ammonia greatly raised food production but also supplied Germany with explosives in the First World War, and excessive nitrogen use causes environmental problems such as eutrophication.