Hydrogen

Hydrogen is a chemical element with symbol H and atomic number 1. Hydrogen is the lightest element and in standard conditions, it is a diatomic gas with the formula H_2. Hydrogen gas is colorless, odorless, tasteless, non-toxic and highly flammable. Hydrogen is the most abundant chemical in the world. Most of the hydrogen on Earth exists in molecular form such as water and organic compounds. The most common isotope of hydrogen (symbol (1) H) has one proton, one electron and no neutrons in each atom.

Combustion:

Hydrogen gas (dihydrogen or molecular hydrogen) is highly flammable:

2 H2(g) + O2 (g) → 2H2O(l) + 286 kJ/mol

 

Its combustion enthalpy is 286 kJ/mol.

Hydrogen gas forms explosive mixtures with air in concentrations of 4-74% and with chlorine in concentrations of 5-95%. Sparks, heat, or sunlight may cause explosive reactions. The autoignition temperature of hydrogen, the autoignition temperature in air, is 500 °C (932 °F).

Flame

Pure hydrogen-oxygen flames emit ultraviolet light and with the high oxygen composition are almost invisible to the naked eye. Hydrogen flames are blue in other conditions and resemble blue natural gas flames. The destruction of the airship Hindenburg was an infamous example of hydrogen combustion, and its cause is still debated.

Reactants

H2 is inactive compared to diatomic elements such as halogen or oxygen. The thermodynamic basis of this low reactivity is the very strong H-H bond, with a bond dissociation energy of 435.7 kJ/mol. The kinetic basis of low reactivity is the non-polar nature of H2 and its weak polarizability. It spontaneously reacts with chlorine, fluorine, forms hydrogen chloride, and hydrogen fluoride, respectively. The reaction of H2 is strongly influenced by the presence of metal catalysts. Thus, while mixtures of H2 with O2 or air burn readily when heated by a spark or flame to at least 500°C, they do not react at room temperature in the absence of a catalyst.

Phase

  • Compressed hydrogen
  • Liquid hydrogen
  • Hydrogen slurry
  • Solid hydrogen
  • Metallic hydrogen

 

Isotopes

Hydrogen has three natural isotopes, which are represented by (1) H, (2) H and (3) H. Other highly unstable nuclei ((4-H) to (7-H) have been synthesized in the laboratory but not observed in nature.

(1) H is the most common isotope of hydrogen with an abundance of more than 99.98%. Because the nucleus of this isotope consists of only one proton, it is given the descriptive but rarely used formal name of protium. Among all the stable isotopes, only H (^1) has no neutrons.

    (2)H, another stable isotope of hydrogen, is known as deuterium and contains one proton and one neutron in the nucleus. All the deuterium in the universe is thought to have been produced at the time of the Big Bang and has persisted ever since. Deuterium is not radioactive and does not pose a significant toxicity risk. Water enriched with molecules that contain deuterium instead of ordinary hydrogen is called heavy water. Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for H (_^1).

 Heavy water is used as a neutron moderator and coolant for nuclear reactors. Deuterium is also a potential fuel for nuclear fusion.

(3)H is known as tritium and has one proton and two neutrons in its nucleus. It is radioactive and decays through beta decay into helium-3 with a half-life of 12.32 years. It is so radioactive that it can be used in bright colors and is useful in things like watches. Small amounts of tritium are produced naturally from the interaction of cosmic rays with atmospheric gases. Tritium has also been released during nuclear weapons tests. It is used in nuclear fusion reactions, as a tracer in isotope geochemistry, in specialized automatic lighting devices. Tritium has also been used as a radiolabel in chemical and biological labeling experiments.

Among the unique elements, distinctive names have been assigned to its isotopes, which are in common use today. During the early study of radioactivity, the various heavy radioactive isotopes had their own names, but these names are no longer used except for deuterium and tritium. Symbols D and T (instead of (_ ^2) H and (_ ^3) H) is sometimes used for deuterium and tritium, but the symbol P is currently used for phosphorus and is therefore not available for protium.

History

In 1671, Robert Boyle discovered and explained that the reaction between iron and a dilute acid produces hydrogen gas. After him, in 1766, Henry Cavendish was the first to recognize hydrogen gas as a separate substance. A substance that is the result of a chemical reaction between metal and acid, and of course, it is also flammable, that is why he named it "flammable air". He thought that "flammable air" is actually the same legendary "flammable" substance or phlogiston. Experiments after that in 1781 showed that burning this gas produces water. Cavendish is known as the one who first recognized hydrogen as an element. In 1783, Lavazier and Laplace, when they tested Cavendish's findings and saw that water is produced from the burning of this gas, they chose the name hydrogen for it at Lavazier's suggestion. Hydrogen, meaning water maker, is derived from the Greek word hydro meaning "water" and genes meaning "creator".

In his famous experiments on the survival of matter, Lavazier achieved the production of hydrogen from the reaction between water vapor and iron metal that was extremely hot and irradiated in a fire.

Zirconium and many other metals will produce hydrogen again if they have the same process with water.

For the first time in 1898, James Dewar was able to recover hydrogen in the cooling process and liquefy it with the help of several of his own innovations such as the vacuum flask. A year later, he was able to solidify hydrogen. In December 1931, Harold Urey was able to obtain deuterium, followed by Ernest Rutherford, Mark Oliphant and Pavel Hartek in 1934. Next, Harold Urey’s group obtained heavy water made of deuterium instead of ordinary hydrogen in 1932. In 1806, Francois Isaac de Rivaz built the first internal combustion engine with a mixture of hydrogen and oxygen, and Edward Daniel Clarke made hydrogen-blowing tubes in 1819. Calcium lighting and Dubrynner's lamp were first made in 1823.

Jacques Charles created the first hydrogen balloon in 1783, but Henri Giffard was the first person who could use these hydrogen balloons to make a means of transportation in the sky and rise high enough in the air. He achieved this success in 1852. After that, German Ferdinand Zeppelin proposed to build a flying ship and in 1900, the first Zeppelin flew in the sky. With the advent of this tool, air travel became possible, so much so that from 1910 to 1914, when the First World War began, 35,000 passengers were transported in the sky without any serious incident. During the war, this tool was used as a lookout or bomber.

British R34 airships built in 1919 could cross the Atlantic Ocean non-stop. After that, in the 1920s, regular flights were provided for passengers. With the detection of helium gas by the Americans, it was hoped that these trips would be more secure. However, the US government refused to sell helium for this purpose. For this reason, these spaceships were still working with hydrogen. The Hindenburg airship, which caught fire in the sky of New Jersey on May 6, 1937, was also flying with H2 gas. The event was broadcast live on the radio and filmed. It was believed that the fire was caused by a hydrogen gas leak, but later investigations showed that a spark between the aluminum wires caused by static electricity caused the fire. It became hydrogen gas.

In 1977, nickel-hydrogen batteries were used for the first time in the Navy's satellite tracking system. For example, nickel-hydrogen batteries are used in the International Space Station, Mars Odyssey and the Mars Surveyor. The Hubble space telescope also uses nickel hydrogen batteries in parts of its orbit where the space is dark. However, these batteries were replaced in May 2009.

Applications

Hydrogen is widely used in chemical and petrochemical industries. Its biggest application is in fossil fuel processing and ammonia production. The key consumers of H2 in petrochemical plants are hydrodealkylation, hydrodesulfurization and cracking. Of course, hydrogen has several other important uses. Hydrogen is used in hydrogenation, especially in increasing the saturation level of unsaturated fats and producing solid oil, oil seeds and methanol production. Its other use is as a source of hydrogen in the production of hydrochloric acid. In addition, hydrogen works as a reducing agent in the recovery of metal ores.

Hydrogen is well soluble in many rare earth elements and transition metals. It is also soluble in amorphous metals and nano crystals.

Apart from the chemical reactions in which hydrogen can participate, this substance has many uses in engineering and physics. For example, it is needed as a shielding gas in various welding methods such as atomic hydrogen welding. Another application of hydrogen is in cooling the electric generator of power plants. This application is because hydrogen has the highest thermal conductivity among gases. In cryological researches, such as the study of superconductivity, liquid hydrogen is also used. The density of hydrogen gas is close to 1/15 of air. For this reason, it was used as a lifting gas in balloons and airships in the past.

Recently, pure hydrogen or a mixture of hydrogen and nitrogen has been used to detect tiny leaks and very small holes in power plants, chemical industries, aerospace, automotive and telecommunications. Hydrogen is an allowed food additive, with its help, food packaging can be tested for leaks and holes, and it prevents food from oxidizing. The temperature of hydrogen at its triple point is 13.8033 K.

Rare hydrogen isotopes each have a special use. Deuterium (hydrogen-2) works as a moderator in nuclear fission reactions to reduce the motion of neutrons and is used in nuclear fusion reactions. Deuterated compounds (containing deuterium) are needed in biological and chemical researches on the effects of isotopes. Tritium (Hydrogen-3), which is produced in nuclear reactors, is needed to make hydrogen bombs. Tritium is a classified isotope in the life sciences and is used as a source of beta particles (eg in radioluminescence).

Energy carrier

Hydrogen is not an energy source by itself. Unless it produces energy for power plants with the help of nuclear fusion reactions in deuterium or tritium; of course, this technology is very advanced. The energy of the sun is also obtained from the nuclear fusion of hydrogen, but on earth, it is difficult to achieve this process in a controlled manner. Hydrogen obtained from the sun, biological or electrical processes, the energy required for its production is more than the energy obtained from its combustion, therefore, in these situations, and hydrogen is treated as an energy carrier, like a battery. Hydrogen can be obtained from fossil fuels (such as methane), but such sources are not permanent and sustainable.

If hydrogen can be used as a fuel in transportation, this fuel burns cleaner than other fuels and produces little NOx. However, it burns without producing carbon.

Cooler

Hydrogen is used in power plants as a generator coolant. This is due to the very high heat capacity of this gas, which is higher than all other gases.

In semiconductors

Hydrogen is used to saturate the broken bonds of amorphous silicon and amorphous carbon and helps stabilize the properties of the material. It also works as an electron donor in many material oxides.

Other uses

A large amount of hydrogen is involved in the Haber process. Other uses of hydrogen include:

In rocket fuels

Hydrogen can be burned in internal combustion engines or generate electrical energy in hydrogen batteries. So far, several automobile companies, including BMW (thermal engine) and Benz, Toyota, Apple have produced several test cars, etc. (hydrogen battery). Hydrogen fuel cells have been considered as a way to produce cheap and pollution-free potential power.

Biological reactions

H2 is a product of some anaerobic reactions made by several types of microbes. These reactions are usually facilitated by iron or nickel present in enzymes called hydrogenases. These enzymes work as facilitators in reversible oxidation and reduction reactions between H2 and its components, two protons and two electrons. Hydrogen gas is formed during the transfer of reducing balances caused by the fermentation of pyruvic acid with water.

Breaking the water molecule into its component parts, protons, electrons and oxygen, happens every day in the photosynthetic reaction in living organisms. Some organisms, such as cyanobacteria and the algae Chlamydomonas Reinhartii, enter a second step in the reaction, which is related to the reactions in the dark, in which protons and electrons are reduced and with the help of special enzymes present in the chloroplast, H_2 gas is made. Attempts have been made to genetically correct cyanobacterial enzymes and produce hydrogen gas with their help even in the presence of oxygen. Attempts have also been made to modify the algae genes of a bioreactor.

Nitrogen production methods

The main methods of nitrogen production in the industry are:

Cryogenic method (COLD BOX)

In this method, nitrogen with a purity of 99.99% and oxygen with a purity of 99.6% are produced in the normal state, and it is possible to produce nitrogen and oxygen with very high purity for special uses. Liquid nitrogen is produced only by this method. In this method, the compressed air temperature is reduced by about ten degrees by the water chiller and enters the drive, where the moisture, oil and impurities are taken inside it, it is completely dried, and after entering the COLD BOX, its temperature is up to 196 degrees Celsius. It decreases and turns into liquid air. When this liquid air enters the lower part of the tower, due to the difference between the dew point of nitrogen and oxygen, its pressure is reduced, and first, upon reaching the boiling temperature, nitrogen leaves the upper part of the tower as a gas with high purity, and part of it also After passing through the condenser, it turns into liquid nitrogen and enters special liquid nitrogen storage tanks for storage. While the oxygen has not yet reached the boiling point to turn into a gas phase, it has accumulated as a liquid at the bottom of the tower.

 Surface absorption method (PSA (Pressure Swing Absorption))

In this method, which is one of the most common methods of nitrogen production. First, after passing through the dryer and the water trap, the compressed air absorbs a high percentage of the moisture and suspended oil in the air, and then passing through two series micro filters of 1 micron and 0.01 micron, the remaining moisture and oil from the compressed air is completely removed. It is absorbed and then the completely dry and compressed air enters the nitrogen generating filter containing special carbons called Sieve molecular carbon with perfectly regular porous surfaces with a hole diameter of 4 angstroms, which considering that the molecular diameter of oxygen is 3.8 angstroms and the molecular diameter of nitrogen is 4. It is 2 angstroms, only the smaller oxygen molecules find the ability to penetrate into the carbon 4 angstrom tiny holes and get trapped in it, and therefore, the nitrogen molecules come out of the carbon material with a certain purity from the top of the filter, and then After a certain period of time, depending on the size of the filter and the output flow rate, the CMSs are saturated with oxygen and must come out of the carbon pores when the compressed air inside is emptied and exit from the bottom exhaust of the filter, and because the regeneration process creates wasted time in the nitrogen production process slow Two filters are used so that when one filter is being regenerated, the second filter produces nitrogen, and this process continues in an oscillatory manner by the continuous control circuit with the control of solenoid valves. In this processing method, the dryness of the incoming compressed air is very important, and if proper microfilters are not used, which are also expensive, the moisture and especially the suspended oil in the compressed air coming out of the compressor will quickly cover the carbon pores and prevent oxygen absorption. In fact, it destroys the CMS material and greatly reduces the output nitrogen purity. Currently, most nitrogen tire generators work with this system.

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