Nitrogen and hydrogen combine to generate the inorganic substance ammonia, which has the formula NH3. Ammonia is an odorless, colorless gas with a characteristic unpleasant odor. It is a stable binary hydride and the simplest pnictogen hydride. It contributes considerably to the nutritional demands of terrestrial creatures by serving as a precursor to 45 percent of the world's food and fertilizers. Biologically, it is a common nitrogenous waste, especially among aquatic animals. About 70% of ammonia is used to create fertilizers, including urea and diammonium phosphate, in a variety of shapes and compositions. Additionally, pure ammonia is sprayed straight onto the ground. About 40% of the nitrogen in people is thought to have originated from the manufacturing of industrial ammonia. Its significance can therefore hardly be emphasized.
Stereo structural formula of the ammonia molecule.
Ammonia is also a key ingredient in many commercial cleaning solutions and is a building component for the manufacture of numerous medicinal medicines. It is mostly gathered through the displacement of both air and water downward.
Although ammonia is widely used and found in nature on Earth and on the outer planets of the Solar System, it is dangerous and caustic when it is concentrated. Facilities that produce, store, or utilize it in sizable amounts are subject to severe reporting requirements in many nations because it is categorized as an exceedingly hazardous material.
A solution of ammonia in water is referred to as ammonia solution, ammonia water, ammonium hydroxide, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia. You can represent it with the symbols NH3 (aq). It is hard to isolate samples of NH4OH, despite the term ammonium hydroxide suggesting an alkali with composition [NH4+][OH]. Except in extremely diluted solutions, the ions NH4+ and OH do not contribute significantly to the total quantity of ammonia.
The creation of ammonia from the elements hydrogen and nitrogen is challenging for fundamental reasons, requiring high pressures and high temperatures. At the start of the twentieth century, the Haber process—which made industrial production possible—revolutionized agriculture.
NH3 must be stored under pressure or at a low temperature because it boils at 33.34 °C (or 28.012 °F) at a pressure of one atmosphere. NH3 is dissolved in water to form household ammonia, also known as ammonium hydroxide. The density of such solutions is measured in units of the Baumé scale, with 26 degrees Baumé being the usual high-concentration commercial product (about 30% (by weight) ammonia at 15.5 °C or 59.9 °F).
A colorless gas with a distinctively strong smell, ammonia. Due to its lower density (0.589 times that of air), it is lighter than air. The liquid boils at 33.1 °C (27.58 °F), and it freezes to white crystals at 77.7 °C (107.86 °F) because of the strong hydrogen bonds between its molecules.
The crystal has a cubic symmetry with the lattice constant of 0.5125 nm, space group P213 No.198, and Pearson symbol cP16.
Liquid ammonia has potent ionizing properties, as evidenced by its high of 22. Liquid ammonia can be utilized in laboratories in uninsulated vessels without additional cooling since it has a very high standard enthalpy change of vaporization (23.35 kJ/mol vs. water 40.65 kJ/mol, methane 8.19 kJ/mol, and phosphine 14.6 kJ/mol). Ammonia in liquid form is a solvent.
In water, ammonia dissolves easily. It can be boiled out of an aqueous solution to remove it. Ammonia in aqueous solution is basic. The term ".880 ammonia" refers to the highest concentration of ammonia in water (a saturated solution), which has a density of 0.880 g/cm3.
Ammonia breaks down into its component parts at high temperatures and in the presence of a suitable catalyst, or in a pressured vessel with constant volume and high temperatures (for example, 1,100 °C (2,010 °F)). Ammonia decomposition produces hydrogen and nitrogen gas and is a mildly endothermic reaction that requires 23 kJ/mol (5.5 kcal/mol) of ammonia. If the unreacted ammonia can be eliminated, ammonia can also be used as a source of hydrogen for acid fuel cells. It was discovered that supported Ni catalysts were less effective than ruthenium and platinum catalysts.
According to the valence shell electron pair repulsion theory (VSEPR theory), the ammonia molecule has a trigonal pyramidal form with an empirically determined bond angle of 106.7°. With an additional electron from each hydrogen atom, the central nitrogen atom possesses six outside electrons in total. This results in four pairs of tetrahedrally organized electrons, or eight total electrons. One lone pair of electrons remains after three of these electron pairs are employed as bond pairs. The bond angle is not 109.5°, as expected for a typical tetrahedral structure, but rather 106.8° because the lone pair repels more strongly than bond pairs. The molecule becomes polar due to this shape's dipole moment. Ammonia is extremely miscible with water due to the polarity of the molecule and, in particular, its capacity to form hydrogen bonds. Ammonia becomes a base and a proton acceptor due to the lone pair. Ammonia is moderately basic; a 1.0 M aqueous solution has a pH of 11.6, and 99.4% of the ammonia molecules are protonated if a strong acid is added to the solution until it is neutral (pH = 7). The proportion of NH+4 is also influenced by temperature and salt. The latter is isoelectronic with methane and has the form of a standard tetrahedron.
At ambient temperature, the ammonia molecule easily undergoes nitrogen inversion; an umbrella turning inside out in a strong wind serves as a helpful comparison. The resonance frequency for this inversion is 23.79 GHz, which corresponds to microwave radiation with a wavelength of 1.260 cm, and the energy barrier is 24.7 kJ/mol. The first maser exploited the absorption at this frequency, which was the first microwave spectrum to be detected.
Ammonia's basicity is one of its most distinguishing qualities. It is thought that ammonia is a weak base. It reacts with acids to generate salts, such as ammonium chloride (sal ammoniac) with hydrochloric acid and ammonium nitrate with nitric acid. It takes moisture to cause the interaction between perfectly dry hydrogen chloride gas and perfectly dry ammonia gas.
As a demonstration experiment, opened bottles of concentrated ammonia and hydrochloric acid solutions produce a cloud of ammonium chloride, which appears "out of nothing" as the salt aerosol forms where the two diffusing clouds of reagents meet between the two bottles. The experiment is conducted in an environment with ambient moisture.
NH3 + HCl → [NH4]Cl
The ammonium ion (NH4+) is present in all of the salts created when ammonia reacts with acids. These compounds are referred to as "ammonium salts."
Ammonia is frequently thought of as a weak base, however it can also function as a very weak acid. It is a protic chemical that can produce amides, which are molecules that contain the NH2 ion. Lithium, for instance, dissolves in liquid ammonia to produce a blue solution of lithium amide (solvated electron):
2 Li + 2 NH3 → 2 LiNH2 + H2
Ammonia in liquid form goes through molecular autoionization to create its conjugates for acids and bases.
NH4+ + NH2 = 2 NH3
Ammonia has some buffering properties since it frequently serves as a weak base. Ammonium cations (NH+4) and amide anions (NH2) will fluctuate in concentration in response to pH changes. K equals [NH4+] minus [NH2-] at standard pressure and temperature, or 10-30.
4 NH3 + 3 O2 → 2 N2 + 6 H2O(g), ΔH°r = −1267.20 kJ (or −316.8 kJ/mol if expressed per mol of NH3)
The standard enthalpy change of combustion, ΔH°c, expressed per mole of ammonia and with condensation of the water formed, is −382.81 kJ/mol. Dinitrogen is the thermodynamic product of combustion: all nitrogen oxides are unstable with respect to N2 and O2, which is the principle behind the catalytic converter. Nitrogen oxides can be formed as kinetic products in the presence of appropriate catalysts, a reaction of great industrial importance in the production of nitric acid:
4 NH3 + 5 O2 → 4 NO + 6 H2O
A subsequent reaction leads to NO2:
2 NO + O2 → 2 NO2
The combustion of ammonia in air is very difficult in the absence of a catalyst (such as platinum gauze or warm chromium(III) oxide), due to the relatively low heat of combustion, a lower laminar burning velocity, high auto-ignition temperature, high heat of vaporization, and a narrow flammability range. However, recent studies have shown that efficient and stable combustion of ammonia can be achieved using swirl combustors, thereby rekindling research interest in ammonia as a fuel for thermal power production. The flammable range of ammonia in dry air is 15.15–27.35% and in 100% relative humidity air is 15.95–26.55%. For studying the kinetics of ammonia combustion, knowledge of a detailed reliable reaction mechanism is required, but this has been challenging to obtain.
Synthesis of different chemicals
A direct or indirect precursor to the majority of synthetic nitrogen-containing molecules is ammonia.
Ammonia can function as a nucleophile in substitution reactions in organic chemistry. Ammonia can react with alkyl halides or alcohols to produce amines as a byproduct. As a result, secondary and tertiary amines are frequently formed because the resulting NH2 group is also nucleophilic. An overabundance of ammonia helps minimize such multiple replacement when it is not wanted. For instance, the creation of methylamine involves the reaction of ammonia with methanol or chloromethane. Dimethylamine and trimethylamine are jointly synthesized in both situations. By initiating a ring-opening reaction with ethylene oxide, ethanolamine is created. If the reaction is allowed to continue, diethanolamine and triethanolamine are produced. Racemic alanine has been produced with a 70% yield by reacting ammonia with 2-bromopropanoic acid.
Ammonia and derivatives of carboxylic acids can be combined to create amides. For instance, when heated, ammonia combines with formic acid (HCOOH) to produce formamide (HCONH2). Acyl chlorides are the most reactive, but to neutralize the hydrogen chloride produced, ammonia must be present in at least a twofold excess. Ammonia and esters and anhydrides both combine to generate amides. If no thermally sensitive groups are present, ammonium salts of carboxylic acids can be dehydrated to amides by heating to 150–200 °C.
Numerous substituents have the ability to substitute the hydrogen in ammonia. Dry ammonia gas is converted to sodamide, NaNH2, when heated with metallic sodium. Monochloramine is created by combining chlorine.
Ammonium hydride or 5-amine are other names for pentavalent ammonia. This crystalline solid disintegrates back into trivalent ammonia and hydrogen gas under normal circumstances but is only stable under high pressure. In 1966, this material was looked into as a potential solid rocket fuel.
Approximately 88% of ammonia in the US as of 2019 was utilized as fertilizers, either as its salts, solutions, or anhydrously. It contributes to higher crop yields for crops like wheat and maize when applied to the soil. Anhydrous ammonia accounts for 30% of the agricultural nitrogen sprayed in the US, where 110 million tonnes are applied annually.
Liquid ammonia has a raw energy density of 11.5 MJ/L, or about one-third that of diesel. Ammonia can either be used directly in high-temperature solid oxide direct ammonia fuel cells to produce effective power sources without producing greenhouse gases, or it can be converted back to hydrogen and utilized to power hydrogen fuel cells.
It is feasible to use ammonia as fuel for a proton exchange membrane fuel cell or to convert it to hydrogen using the sodium amide method. The catalytic breakdown of ammonia using solid catalysts is another technique. In contrast to 5% for gaseous hydrogen under pressure, conversion to hydrogen would enable storage of hydrogen at over 18 wt%.
There have been suggestions for and sporadic uses of ammonia engines or ammonia motors that employ ammonia as the operating fluid. The idea is the same as in a fireless locomotive, except instead of using steam or compressed air, ammonia is used as the working fluid. In the 19th century, ammonia engines were tested by Goldsworthy Gurney in the UK, the St. Charles Avenue Streetcar line in New Orleans in the 1870s and 1880s, and ammonia was also used to power buses in Belgium during World War II.
On occasion, ammonia is suggested as a workable substitute for fossil fuel in internal combustion engines.
The utilization of high compression ratios without suffering from high NOx production is made possible by the fuel's high octane rating of 120 and low flame temperature. Ammonia does not contain carbon, so when it is burned, no carbon dioxide, carbon monoxide, hydrocarbons, or soot are produced.
1.8% of the world's CO2 emissions are currently produced via ammonia production. Green hydrogen (hydrogen created through electrolysis) is used to produce "green ammonia," whereas blue hydrogen is used to produce "blue ammonia" (hydrogen produced by steam methane reforming where the carbon dioxide has been captured and stored).
There are several obstacles preventing ammonia from being widely used in automobiles, including the fact that it has a relatively narrow flammability range. In order to boost production levels of raw ammonia, factories would need to be erected, which would need a substantial investment in money and energy sources. Despite being the second most manufactured chemical (after sulfuric acid), ammonia production is still a tiny portion of global petroleum consumption. It could be produced by nuclear power, coal, or renewable energy sources. Since 1913, the 60 MW Rjukan dam in Telemark, Norway, has produced ammonia, which has been used as fertilizer throughout most of Europe.
Nevertheless, numerous tests have been conducted. A 1981 Chevrolet Impala was modified by a Canadian business to run on ammonia as gasoline. As part of a demonstration, a University of Michigan pickup running on ammonia traveled from Detroit to San Francisco in 2007, needing just one fill-up in Wyoming.
Ammonia is much more energy-efficient than hydrogen as a fuel and could be produced, stored, and delivered for a lot less money than hydrogen, which needs to be kept compressed or as a cryogenic liquid.
Ammonia has also been used as fuel for rocket engines. Liquid ammonia was utilized in the Reaction Motors XLR99 rocket engine that propelled the X-15 hypersonic research aircraft. Although it wasn't as strong as other fuels, it didn't leave any soot in the reusable rocket engine, and its density was close to that of the liquid oxygen oxidizer, simplifying the design of the aircraft.
Early in August 2018, researchers from Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) reported the development of a method to extract hydrogen from ammonia with an ultra-high purity and use it as a vehicle fuel had been successful. This makes advantage of a unique membrane. The technology is present in two demonstration fuel cell cars, the Hyundai Nexo and Toyota Mirai.
40 metric tons of liquid "blue ammonia" from Saudi Arabia were sent to Japan in 2020 to be used as fuel. It may be burned without emitting greenhouse gases and was created as a byproduct of petrochemical companies. Compared to liquid hydrogen, it has roughly double the energy density per volume. If the production of green ammonia can be scaled up using only renewable resources, it might significantly reduce the likelihood of climate change. A green hydrogen and ammonia plant will be built in Neom in 2020, according to announcements from the companies ACWA Power and Neom.
A potential fuel for future container ships is green ammonia. The development of an ammonia-powered ship was announced by the businesses DSME and MAN Energy Solutions in 2020; DSME intends to make it available for purchase by 2025. Ammonia is also being investigated as a potential replacement fuel for jet engines in aviation.
As part of efforts to help domestic and other Asian utilities accelerate their transition to carbon neutrality, Japan is aiming to present a plan to develop ammonia co-firing technology that can increase the use of ammonia in power generation. The first International Conference on Fuel Ammonia (ICFA2021) took place in October 2021.
In June 2022, IHI Corporation achieved entirely CO2-free power generation by lowering greenhouse gases by approximately 99% during the combustion of liquid ammonia in a 2,000 kilowatt-class gas turbine. At the security grouping's first energy meeting in July 2022, the Quad nations of Japan, the U.S., Australia, and India decided to support technological advancement for clean-burning hydrogen and ammonia as fuels.
The most popular and extensively researched nonaqueous ionizing solvent is liquid ammonia. Its capacity to dissolve alkali metals into vividly colored, electrically conductive solutions with solvated electrons is its most notable characteristic. A lot of the chemistry in liquid ammonia can be categorized by analogy with related reactions in aqueous solutions, aside from these remarkable solutions. When NH3's physical characteristics are compared to those of water, it is discovered that NH3 has lower melting, boiling, density, viscosity, dielectric constant, and electrical conductivity. This is at least partially because NH3 has weaker hydrogen bonds and because these bonds cannot form cross-linked networks because each NH3 molecule only has one lone pair of electrons, whereas each H2O molecule has two. The ionic self-dissociation constant of liquid NH3 at −50 °C is about 10−33.
Ammonium hydroxide, also known as household "ammonia," is an NH3 solution that is used as a multipurpose cleanser for numerous surfaces. Ammonia is frequently used to clean glass, porcelain, and stainless steel because it produces a comparatively streak-free gloss. Additionally, it is widely used to clean ovens and soak objects to remove baked-on filth. The weight-based concentration of household ammonia ranges from 5 to 10% ammonia. The material safety data sheet for the product, which includes the concentration used, must be made available by cleaning product manufacturers in the United States.
Ammonia solutions (5–10% by weight) are used as cleaning agents around the house, especially for glass. These solutions irritate the skin less so than they do the mucous membranes of the respiratory and digestive systems, eyes, and mucous membranes. Due to the risk of harmful gas, experts advise using caution to make sure the chemical is not put into any liquid that contains bleach. Chloramines can be produced by mixing with chlorine-containing chemicals or potent oxidants like home bleach.
Experts also advise against using ammonia-based cleaners on car touchscreens because they run the risk of damaging the screens' anti-glare and anti-fingerprint coatings.
In the fermentation industry, solutions of ammonia in the range of 16% to 25% are utilized as a source of nitrogen for microorganisms and to alter pH during fermentation.
Antimicrobial agent for food products
Ammonia was recognized as being "highly antibacterial" and "needs 1.4 grams per litre to preserve beef tea (broth)" as early as 1895. Anhydrous ammonia in one study killed 99.999% of zoonotic bacteria in three different kinds of animal feed, but not silage. Currently, commercial use of anhydrous ammonia to lessen or get rid of microbial contamination of beef. The beef industry produces lean finely textured beef (often referred to as "pink slime") from fatty beef scraps (around 50–70% fat) by centrifuging and heating the fat to remove it, then treating the remaining fat with ammonia to kill E. coli. The US Department of Agriculture approved the procedure after a research shown that it lowers E. coli levels to undetectable levels. Along with consumer complaints about the flavor and odor of ammonia-treated beef, there have been safety concerns about the procedure.
What prospects does green ammonia have?
Additional possibilities for the transition to net-zero carbon dioxide emissions may be provided by the manufacture of green ammonia. These consist of:
Ammonia is easily kept in large quantities as a liquid at low pressures (10–15 bar) or chilled to –33 °C. It is therefore the perfect chemical storage system for renewable energy. Ammonia is currently distributed around the world via a network of pipes, road tankers, and ships to transfer it from massive chilled tanks.
Ammonia is a zero-carbon fuel that may be burned in an engine or converted into power in a fuel cell. The only by-products of ammonia use are water and nitrogen. The maritime sector is most likely to replace the use of fuel oil in marine engines as an early adopter.
Hydrogen carrier - although hydrogen gas is employed in some applications (such as PEM fuel cells), it is difficult and expensive to store in large quantities (needing cryogenic tanks or high-pressure cylinders). Ammonia is simpler to store, transport, and purify, and it can easily be "cracked" when needed to produce hydrogen gas.
Green Ammonia (docx)