Hopcalite
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Hopcalite is the trade name for a number of mixtures that mainly consist of oxides of
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and
manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...
, which are used as
catalysts Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
for the conversion of
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
to
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
when exposed to the oxygen in the air at room temperature. The name "hopcalite" is derived from
Johns Hopkins University Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...
- "Hop" and the
University of California The University of California (UC) is a public land-grant research university system in the U.S. state of California. The system is composed of the campuses at Berkeley, Davis, Irvine, Los Angeles, Merced, Riverside, San Diego, San Francisco, ...
- "Cal", where basic research into carbon monoxide was carried out during the First World War and these catalysts were discovered in 1918. A variety of compositions are known, such as "hopcalite II" that is approximately 60%
manganese dioxide Manganese dioxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for is for dry-cell ...
and 40%
copper oxide Copper oxide is a compound from the two elements copper and oxygen. Copper oxide may refer to: * Copper(I) oxide (cuprous oxide, Cu2O) * Copper(II) oxide Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black so ...
(the MnO2 : CuO molar ratio is 1.375) and "hopcalite I" that is a mixture of 50%
MnO Manganese(II) oxide is an inorganic compound with chemical formula MnO.Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. It forms green crystals. The compound is produced on a large ...
, 30%
CuO Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black solid, it is one of the two stable oxides of copper, the other being Cu2O or copper(I) oxide (cuprous oxide). As a mineral, it is known as tenorite. It is ...
, 15% Co2O3, and 5% Ag2O. Hopcalite has the properties of a porous mass and resembles
activated carbon Activated carbon, also called activated charcoal, is a form of carbon commonly used to filter contaminants from water and air, among many other uses. It is processed (activated) to have small, low-volume pores that increase the surface area avail ...
in its appearance.


Preparation

While typically hopcalite catalysts are prepared by
calcining Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), genera ...
intimate mixtures of oxides and carbonates, various techniques have been employed for producing hopcalites in the laboratory and on an industrial scale, such as physical mixing of the (finely divided) metal oxides, co-precipitation of the metal oxides from metal salt solutions (see
salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...
), thermal decomposition of mixtures of metal nitrates (see
nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
) and metal carbonates (see
carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
), one-step synthesis via flame spray pyrolysis from organic and inorganic precursor systems, e.g. Nanophase hopcalite catalysts have also been described. Although hopcalite-based catalysts have been used in practice for decades, many questions regarding their mode of action are still open. This is due to their complex structures, which make it difficult to obtain information about the active centers and the mechanisms of catalysis and deactivation.


Applications

Hopcalite is widely used in personal respiratory protective equipment (RPE) and collective protective equipment, among others. Different uses of hopcalite catalysts are listed below: * in some types of gas mask filters designed to protect from carbon monoxide (Soviet-made DP-1, combined filters VK-450, SX (CO) filters, e.g.) * in air filtration systems and breathing apparatus to purify breathing air supplies, for example those utilised in scuba diving, and firefighting. * used as the main filtration ingredient in the self rescue respirators issued to miners (SPP-4) * filtering self-rescuers designed for use in fire conditions (GDZK-EN, GDZK-U, GDZK-A, e.g.) * in devices for monitoring the content of carbon monoxide (CO) in rooms * used as a precaution with submersible air compressors, if they are driven by internal combustion engines (like on ships) In respiratory protective equipment, hopcalite is used to facilitate the rapid oxidation of the toxic carbon monoxide to harmless carbon dioxide with the oxygen from the air, which is then chemically bound to a
sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkali ...
layer, thus eliminating CO from the air stream, (which otherwise is not removed by activated charcoal air filters). Water vapor poisons the hopcalite catalyst, so in order to protect against water vapor, an additional filter based on
Silica gel Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other l ...
is introduced. In addition to that, the hopcalite layer is protected by a mechanical filter and a layer of activated carbon, purify the air of other contaminants. The operation of carbon monoxide (CO) detectors, on the other hand, is based on recording the heat released during the catalytic oxidation of carbon monoxide (CO) to carbon dioxide (CO2). Although primarily used to catalyze the conversion of CO to CO2, hopcalite catalysts are also used to remove
ethylene oxide Ethylene oxide is an organic compound with the chemical formula, formula . It is a cyclic ether and the simplest epoxide: a three-membered Ring (chemistry), ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless a ...
and other
VOCs Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
as well as
ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
from gas streams. In addition, hopcalites catalyze the oxidation of various organic compounds at elevated temperatures (200–500 °C).


See also

*
Gas mask A gas mask is a mask used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft tissues of the face. Most gas mask ...
* breathing apparatus *
Self-contained self-rescue device Self-sustainability and self-sufficiency are overlapping states of being in which a person or organization needs little or no help from, or interaction with, others. Self-sufficiency entails the self being enough (to fulfill needs), and a self-s ...
*
Carbon monoxide detector A carbon monoxide detector or CO detector is a device that detects the presence of the carbon monoxide (CO) gas to prevent carbon monoxide poisoning. In the late 1990s Underwriters Laboratories changed the definition of a single station CO de ...
*
Catalysis Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
*
heterogeneous catalysis In chemistry, heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reactants or products. The process contrasts with homogeneous catalysis where the reactants, products and catalyst exist in the same phase. Ph ...
*
Carbon monoxide poisoning Carbon monoxide poisoning typically occurs from breathing in carbon monoxide (CO) at excessive levels. Symptoms are often described as "flu-like" and commonly include headache, dizziness, weakness, vomiting, chest pain, and confusion. Large e ...


References

{{Underwater diving, divsup Manganese compounds Copper compounds Catalysts Diving support equipment