NationMaster - Encyclopedia: Haber process

The Haber process, also called the Haber–Bosch process, is the nitrogen fixation reaction of nitrogen and hydrogen, over an iron substrate, to produce ammonia.^[1]^[2]^[3] The Haber process is important because ammonia is difficult to produce on an industrial scale and the fertilizer generated from the ammonia is responsible for sustaining one-third of the Earth's population.^[4] Even though 78.1% of the air we breathe is nitrogen, the gas is relatively unreactive because nitrogen molecules are held together by strong triple bonds. It was not until the early 20th century that this method was developed to harness the atmospheric abundance of nitrogen to create ammonia, which can then be oxidized to make the nitrates and nitrites essential for the production of nitrate fertilizer and munitions. Nitrogen fixation is the process by which nitrogen is taken from its natural, relatively inert molecular form (N2) in the atmosphere and converted into nitrogen compounds (such as, notably, ammonia, nitrate and nitrogen dioxide)[1] useful for other chemical processes. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... This article is about the chemistry of hydrogen. ... For other uses, see Substrate. ... For other uses, see Ammonia (disambiguation). ... Look up air in Wiktionary, the free dictionary. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... For other uses, see Ammonia (disambiguation). ... ed|other uses|reduction}} Illustration of a redox reaction Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... Trinitrate redirects here. ... // Definition The nitrite ion is NO2âˆ’. A nitrite compound is one that contains this group, either an ionic compound, or an analogous covalent one. ... Trinitrate redirects here. ... Fertilizers are chemicals given to plants with the intention of promoting growth; they are usually applied either via the soil or by foliar spraying. ... Materiel (from the French for material) is the equipment and supplies in Military and commercial supply chain management. ...

History

The process was first patented by German chemist Fritz Haber. In 1910 Carl Bosch, while working for German chemical company BASF, successfully commercialized the process and secured further patents. Haber and Bosch were later awarded Nobel prizes, in 1918 and 1931 respectively, for their work in overcoming the chemical and engineering problems posed by the use of large-scale high-pressure technology. Ammonia was first manufactured using the Haber process on an industrial scale in Germany during World War I, to meet the high demand for ammonium nitrate (for use in explosives) at a time when supply of Chile saltpetre from Chile could not be guaranteed because this industry was then almost 100% in British hands. It has been suggested that without this process, Germany would not have fought in the war^[5]. Here is a list of famous Germans: Actors Mario Adorf, (born 1930), actor Hans Albers, actor Moritz Bleibtreu, (born 1971), actor Eric Braeden, (born Hans Gudegast, 1941), actor Horst Buchholz, (1933-2003), actor Marlene Dietrich, (1901-1992), actress Heinz Erhardt, (1909-1979), actor and comedian Gert Fröbe, (1913-1988), actor... This is a list of famous chemists: (alphabetical order) Contents: Top - 0â€“9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Emil Abderhalden, (1877â€“1950), Swiss chemist Richard Abegg, (1869â€“1910), German... Fritz Haber (9 December 1868 â€“ 29 January 1934) was a German chemist, who received the Nobel Prize in Chemistry in 1918 for his development of synthetic ammonia, important for fertilisers and explosives. ... Year 1910 (MCMX) was a common year starting on Saturday (link will display calendar) of the Gregorian calendar (or a common year starting on Friday [1] of the 13-day-slower Julian calendar). ... Carl Bosch (August 27, 1874 â€“ April 26, 1940) was a German chemist and engineer. ... This article is about the German chemical company. ... The Nobel Prize (Swedish: ) was established in Alfred Nobels will in 1895, and it was first awarded in Physics, Chemistry, Physiology or Medicine, Literature, and Peace in 1901. ... â€œThe Great War â€ redirects here. ... Related Compounds Other anions Ammonium nitrite; ammonium perchlorate Other cations Sodium nitrate; potassium nitrate; hydroxylammonium nitrate Related compounds Nitrous oxide Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references The chemical compound ammonium nitrate, the nitrate of... Made of Porn and sex things Inhalation respiratory irritation Skin May cause irritation. ...

The process

The bulk of the chemical technology consists of isolating hydrogen from methane (natural gas) using heterogeneous catalysis and then reacting it with atmospheric nitrogen. This article is about the chemistry of hydrogen. ... Methane is a chemical compound with the molecular formula . ... For other uses, see Natural gas (disambiguation). ... Heterogeneous catalysis is a chemistry term which describes catalysis where the catalyst is in a different phase (ie. ...

Synthesis gas preparation

First, the methane is cleaned, mainly to remove sulfur impurities that would poison the catalysts. This article is about the chemical element. ...

The clean methane is then reacted with steam over a catalyst of nickel oxide. This is called steam reforming: For other uses, see Steam (disambiguation). ... This article is in need of attention from an expert on the subject. ... Steam reforming, hydrogen reforming or catalytic oxidation, is a method of producing hydrogen from hydrocarbons. ...

Secondary reforming then takes place with the addition of air to convert the methane that did not react during steam reforming.

The gas mixture is now passed into a methanator, which converts any remaining CO₂ into methane for recycling:

Ammonia synthesis

The final stage is the synthesis of ammonia using magnetite, iron oxide, as the catalyst: Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ...

This is done at 150 - 250 atmospheres (atm) and between 300 and 550 °C, passing the gases over four beds of catalyst, with cooling between each pass to maintain a reasonable equilibrium constant. On each pass only about 15% conversion occurs, but any unreacted gases are recycled, so that eventually an overall conversion of 98% can be achieved. The iron catalysis of ammonia synthesis is complete; see below The mole (symbol: mol) is the SI base unit that measures an amount of substance. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... In chemistry, the equilibrium constant is a quantity characterizing a chemical equilibrium in a chemical reaction. ...

Reaction rate and equilibrium

There are two opposing considerations in this synthesis: the position of the equilibrium and the rate of reaction. At room temperature, the reaction is slow and the obvious solution is to raise the temperature. This may increase the rate of the reaction but, since the reaction is exothermic, it also has the effect, according to Le Chatelier's Principle, of favouring the reverse reaction and thus reducing equilibrium constant, given by: Iron rusting - a chemical reaction with a slow reaction rate. ... In chemistry, an exothermic reaction is one that releases heat. ... In chemistry, Le Chateliers principle, also called the Le Chatelier-Braun principle, can be used to predict the effect of a change in conditions on a chemical equilibrium. ... In chemistry, the equilibrium constant is a quantity characterizing a chemical equilibrium in a chemical reaction. ...

As the temperature increases, the equilibrium is shifted and hence, the constant drops dramatically according to the van't Hoff equation. Thus one might suppose that a low temperature is to be used and some other means to increase rate. However, the catalyst itself requires a temperature of at least 400 °C to be efficient. Look up equilibrium in Wiktionary, the free dictionary. ... The Vant Hoff equation in chemical thermodynamics relates the change in temperature to the change in the equilibrium constant given the enthalpy change. ...

Pressure is the obvious choice to favour the forward reaction because there are 4 moles of reactant for every 2 moles of product (see entropy), and the pressure used (around 200 atm) alters the equilibrium concentrations to give a profitable yield. This article is about pressure in the physical sciences. ... For other uses, see: information entropy (in information theory) and entropy (disambiguation). ...

Economically, though, pressure is an expensive commodity. Pipes and reaction vessels need to be strengthened, valves more rigorous, and there are safety considerations of working at 200 atm. In addition, running pumps and compressors takes considerable energy. Thus the compromise used gives a single pass yield of around 15%.

Another way to increase the yield of the reaction would be to remove the product (i.e. ammonia gas) from the system. In practice, gaseous ammonia is not removed from the reactor itself, since the temperature is too high; but it is removed from the equilibrium mixture of gases leaving the reaction vessel. The hot gases are cooled enough, whilst maintaining a high pressure, for the ammonia to condense and be removed as liquid. Unreacted hydrogen and nitrogen gases are then returned to the reaction vessel to undergo further reaction.

Catalysts

The catalyst has no effect on the position of chemical equilibrium; rather, it provides an alternative pathway with lower activation energy and hence increases the reaction rate, while remaining chemically unchanged at the end of the reaction. The first Haber–Bosch reaction chambers used osmium and uranium catalysts. However, today a much less expensive iron catalyst is used almost exclusively. It has been suggested that this article or section be merged into Catalysis. ... A burette, an apparatus for carrying out acid-base titration, is an important part of equilibrium chemistry. ... The sparks generated by striking steel against a flint provide the activation energy to initiate combustion in this Bunsen burner. ... General Name, Symbol, Number osmium, Os, 76 Chemical series transition metals Group, Period, Block 8, 6, d Appearance silvery, blue cast Standard atomic weight 190. ... This article is about the chemical element. ... Fe redirects here. ...

In industrial practice, the iron catalyst is prepared by exposing a mass of magnetite, an iron oxide, to the hot hydrogen feedstock. This reduces some of the magnetite to metallic iron, removing oxygen in the process. However, the catalyst maintains most of its bulk volume during the reduction, and so the result is a highly porous material whose large surface area aids its effectiveness as a catalyst. Other minor components of the catalyst include calcium and aluminium oxides, which support the porous iron catalyst and help it maintain its surface area over time, and potassium, which increases the electron density of the catalyst and so improves its reactivity. Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ... This article is about the chemical element and its most stable form, or dioxygen. ... For other uses, see Calcium (disambiguation). ... Alumina redirects here. ... General Name, symbol, number potassium, K, 19 Chemical series alkali metals Group, period, block 1, 4, s Appearance silvery white Standard atomic weight 39. ... For other uses, see Electron (disambiguation). ...

The reaction mechanism, involving the heterogeneous catalyst, is believed to be as follows: In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. ...

Reaction 5 occurs in three steps, forming NH, NH₂, and then NH₃. Experimental evidence points to reaction 2 as being the slow, rate-determining step. The rate-determining step is a chemistry term for the slowest step in a chemical reaction. ...

A major contributor to the elucidation of this mechanism is Gerhard Ertl.^[7]^[8]^[9]^[10] Gerhard Ertl (born October 10, 1936) in Stuttgart) is a German chemist, and a Nobel prize winning Professor emeritus at the Department of Physical Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft in Berlin, Germany. ...

Economic and environmental aspects

The Haber process now produces 100 million tons of nitrogen fertilizer per year, mostly in the form of anhydrous ammonia, ammonium nitrate, and urea. 3-5% of world natural gas production is consumed in the Haber process (~1-2% of the world's annual energy supply)^[1],^[11],^[12],^[13]. That fertilizer is responsible for sustaining one-third of the Earth's population, as well as various deleterious environmental consequences.^[14] Generation of hydrogen using electrolysis of water, using renewable energy, is not currently competitive cost-wise with hydrogen from fossil fuels, such as natural gas, and is responsible for only 4% of current hydrogen production. Notably, the rise of this industrial process led to the "Nitrate Crisis" in Chile, when the British industrials left the country -- since the natural nitrate mines were no longer profitable -- closing the mines and leaving a large unemployed Chilean population behind. Fertilizers are chemicals given to plants with the intention of promoting growth; they are usually applied either via the soil or by foliar spraying. ... For other uses, see Ammonia (disambiguation). ... Related Compounds Other anions Ammonium nitrite; ammonium perchlorate Other cations Sodium nitrate; potassium nitrate; hydroxylammonium nitrate Related compounds Nitrous oxide Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references The chemical compound ammonium nitrate, the nitrate of... Urea is an organic compound with the chemical formula (NH2)2CO. Urea is also known by the International Nonproprietary Name (rINN) carbamide, as established by the World Health Organization. ...

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