Ammonia synthesis - Ammonia synthesis

A method of directly synthesizing ammonia from hydrogen and nitrogen in the presence of a catalyst under high temperature and pressure.

3H ₂ + N ₂ → 2NH ₃ + 92 kJ

At the beginning of the 20th century, thermodynamic research by F. Haber and HW Nernst provided clues to successful synthesis. This was the result of the application of the theory of chemical equilibrium to industry. First, Haber succeeded in his basic research and obtained the first patent in 1908. Then in 1913, C. Bosch succeeded in technically solving the problems with the high-pressure equipment, and succeeded in building and operating an ammonia synthesis plant with an annual production of 9,000 tons. Over the next 50 years or so, around 10 new synthesis methods emerged, all of which were essentially modifications of the Haber-Bosch process. Ammonia synthesis methods are classified by reaction conditions, type of catalyst, and type of synthesis tower. Typical synthesis towers include low-temperature low-pressure types, medium-temperature medium-pressure types, high-temperature high-pressure types, and modifications of the Haber process. The main methods used in Japan are shown in the table below.

From the theory of equilibrium, the _NH3 production rate increases with lower temperature and higher pressure. At low temperatures, the reaction rate decreases, and there is an appropriate temperature for the appropriate pressure and space velocity to obtain a high industrial yield. The industrial temperature range is 400-650 °C, the pressure range is 100-1000 atm, _and the production rate is 5-30%. The commonly used catalyst is mainly _Fe3O4 , and is made by the melting method with the addition of _Al2O3 or _K2O . First, a mixture of hydrogen and nitrogen produced by various methods is purified, and then the _N2 : _{H2 ratio} is adjusted to about 1:3 and compressed to high pressure. _The ammonia synthesized in the synthesis tower is condensed in the condenser and stored as liquid ammonia in the high-pressure receiver. The separated unreacted mixed gas is returned to the synthesis tower. One use of ammonia is the production of nitric acid by the ammonia oxidation process.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

水素と窒素から触媒の存在，高温，高圧下でアンモニアを直接合成する方法．

3H₂ ＋ N₂ → 2NH₃ ＋ 92 kJ

20世紀のはじめに，F. Haber(ハーバー)やH.W. Nernst(ネルンスト)の熱力学的研究により，合成の成功への糸口が得られた．これは化学平衡論の工業への応用の成果である．まず，Haberが基礎的研究に成功し，1908年に最初の特許を得，ついで1913年にC. Bosch(ボッシュ)の成功によって高圧装置の問題を技術的に解決し，年産9000 t のアンモニア合成工場の建設，操業に成功した．その後，約50年間に10種類ほどの新合成法が現れたが，いずれも本質的には上記のハーバー-ボッシュ法の改変法である．アンモニア合成の方式は，反応条件，触媒の種類，合成塔の型式などで分けられる．合成塔の典型的なものは，低温低圧型，中温中圧型，高温高圧型，ハーバー法の改変型などである．わが国で行われているおもな諸方式を表に示す．

平衡の理論から，NH₃生成率は温度が低く，圧力が高いほど高くなる．温度が低いと反応速度が小さくなり，工業的に高収率を得るための適当な圧力，空間速度に対して適当な温度がある．工業的な温度範囲は400～650 ℃，圧力範囲は100～1000 atm，生成率5～30％ である．常用されている触媒はFe₃O₄を主体とし，Al₂O₃やK₂Oを添加して融解法でつくる．まず，種々の方法で製造した水素と窒素との混合物を精製後，N₂：H₂ を約1：3に調整し，高圧に圧縮する．合成塔で合成されたアンモニアは凝縮器で凝縮し，高圧受器に液体アンモニアとしてためられる．分離した未反応混合ガスは合成塔へ戻す．アンモニアの用途として，アンモニア酸化法(ammonia oxidation process)による硝酸の製造がある．

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