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The Haber process relies on catalysts that accelerate the scission of these bonds. Two opposing considerations are relevant: the equilibrium position and the reaction rate . At room temperature, the equilibrium is in favor of ammonia, but the reaction does not proceed at a detectable rate due to its high activation energy.
Abiological nitrogen fixation describes chemical processes that fix (react with) N 2, usually with the goal of generating ammonia. The dominant technology for abiological nitrogen fixation is the Haber process, which uses iron-based heterogeneous catalysts and H 2 to convert N 2 to NH 3. This article focuses on homogeneous (soluble) catalysts ...
The Born–Haber cycle is an approach to analyze reaction energies. It was named after two German scientists, Max Born and Fritz Haber , who developed it in 1919. [ 1 ] [ 2 ] [ 3 ] It was also independently formulated by Kasimir Fajans [ 4 ] and published concurrently in the same journal. [ 1 ]
The production of 90% of chemicals (by volume) is assisted by solid catalysts. [2] The chemical and energy industries rely heavily on heterogeneous catalysis. For example, the Haber–Bosch process uses metal-based catalysts in the synthesis of ammonia, an important component in fertilizer; 144 million tons of ammonia were produced in 2016. [5]
Later, he established that uranium could also act as a catalyst. [51] Haber also obtained good results with iron, nickel, manganese and calcium. [52] In the chemical equation shown above, the direct reaction is exothermic. This heat can be used to heat the reagents before they enter the chemical reactor. [53]
An illustrative example is the effect of catalysts to speed the decomposition of hydrogen peroxide into water and oxygen: . 2 H 2 O 2 → 2 H 2 O + O 2. This reaction proceeds because the reaction products are more stable than the starting compound, but this decomposition is so slow that hydrogen peroxide solutions are commercially available.
The main finding of Haber and Weiss was that hydrogen peroxide (H 2 O 2) is decomposed by a chain reaction. [2] The Haber–Weiss reaction chain proceeds by successive steps: (i) initiation, (ii) propagation and (iii) termination. The chain is initiated by the Fenton reaction: Fe 2+ + H 2 O 2 → Fe 3+ + HO – + HO • (step 1: initiation)
The following is an example: The final stage, which is the actual Haber process, is the synthesis of ammonia using an iron catalyst promoted with K 2 O, CaO and Al 2 O 3: [citation needed] N 2 (g) + 3 H 2 (g) ⇌ 2 NH 3 (g) (ΔH = −92.22 kJ· mol −1 )