Vanadium(V) oxide (''vanadia'') is the
inorganic compound with the
formula V2 O5. Commonly known as vanadium pentoxide, it is a brown/yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because of its high
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
, it is both an
amphoteric
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used.
One type of amphoteric species are amphipro ...
oxide and an
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...
. From the industrial perspective, it is the most important compound of
vanadium, being the principal precursor to alloys of vanadium and is a widely used industrial catalyst.
[
The mineral form of this compound, shcherbinaite, is extremely rare, almost always found among ]fumaroles
A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...
. A mineral trihydrate
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was underst ...
, V2O5·3H2O, is also known under the name of navajoite.
Chemical properties
Reduction to lower oxides
Upon heating a mixture of vanadium(V) oxide and vanadium(III) oxide, comproportionation
Comproportionation or synproportionation is a chemical reaction where two reactants containing the same element but with different oxidation numbers, form a compound having an intermediate oxidation number. It is the opposite of disproportionation. ...
occurs to give vanadium(IV) oxide, as a deep-blue solid:
:V2O5 + V2O3 → 4 VO2
The reduction can also be effected by oxalic acid, 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 ...
, and sulfur dioxide. Further reduction using hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
or excess CO can lead to complex mixtures of oxides such as V4O7 and V5O9 before black V2O3 is reached.
Acid-base reactions
V2O5 is an amphoteric
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used.
One type of amphoteric species are amphipro ...
oxide. Unlike most metal oxides, it dissolves slightly in water to give a pale yellow, acidic solution. Thus V2O5 reacts with strong non-reducing acids to form solutions containing the pale yellow salts containing dioxovanadium(V) centers:
:V2O5 + 2 HNO3 → 2 VO2(NO3) + H2O
It also reacts with strong alkali to form polyoxovanadates, which have a complex structure that depends on pH.[.] If excess aqueous sodium hydroxide is used, the product is a colourless salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
, sodium orthovanadate
Sodium orthovanadate is the inorganic compound with the chemical formula . It forms a dihydrate . Sodium orthovanadate is a salt of the oxyanion. It is a colorless, water-soluble solid.
Synthesis and structure
Sodium orthovanadate is produced by ...
, Na3VO4. If acid is slowly added to a solution of Na3VO4, the colour gradually deepens through orange to red before brown hydrated V2O5 precipitates around pH 2. These solutions contain mainly the ions HVO42− and V2O74− between pH 9 and pH 13, but below pH 9 more exotic species such as V4O124− and HV10O285− ( decavanadate) predominate.
Upon treatment with thionyl chloride
Thionyl chloride is an inorganic compound with the chemical formula . It is a moderately volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a chlorinating reagent, with approximately per year bein ...
, it converts to the volatile liquid vanadium oxychloride, VOCl3:
:V2O5 + 3 SOCl2 → 2 VOCl3 + 3 SO2
Other redox reactions
Hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
and hydrobromic acid
Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains 47.6% HBr by mass, which is 8.77 mol/L. ...
are oxidised to the corresponding halogen, e.g.,
:V2O5 + 6HCl + 7H2O → 2 2O)5">O(H2O)5sup>2+ + 4Cl− + Cl2
Vanadates Vanadates can refer to:
* Ammonium vanadate (disambiguation) Ammonium vanadate may refer to:
* Ammonium metavanadate (ammonium trioxovanadate(V)), NH4VO3
* Ammonium orthovanadate (ammonium tetraoxovanadate(V)), (NH4)3VO4, a compound related to ...
or vanadyl
The vanadyl or oxovanadium(IV) cation, VO2+, is a functional group that is common in the coordination chemistry of vanadium. Complexes containing this functional group are characteristically blue and paramagnetic. A triple bond is proposed to ex ...
compounds in acid solution are reduced by zinc amalgam through the colourful pathway:
The ions are all hydrated to varying degrees.
Preparation
Technical grade V2O5 is produced as a black powder used for the production of vanadium metal and ferrovanadium
Ferrovanadium (FeV) is an alloy formed by combining iron and vanadium with a vanadium content range of 35–85%. The production of this alloy results in a grayish silver crystalline solid that can be crushed into a powder called "ferrovanadium ...
. A vanadium ore or vanadium-rich residue is treated with sodium carbonate and an ammonium salt to produce sodium metavanadate, NaVO3. This material is then acidified to pH 2–3 using H2SO4 to yield a precipitate of "red cake" (see above). The red cake is then melted at 690 °C to produce the crude V2O5.
Vanadium(V) oxide is produced when vanadium metal is heated with excess oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
, but this product is contaminated with other, lower oxides. A more satisfactory laboratory preparation involves the decomposition of ammonium metavanadate at 500–550 °C:
:2 NH4VO3 → V2O5 + 2 NH3 + H2O
Uses
Ferrovanadium production
In terms of quantity, the dominant use for vanadium(V) oxide is in the production of ferrovanadium
Ferrovanadium (FeV) is an alloy formed by combining iron and vanadium with a vanadium content range of 35–85%. The production of this alloy results in a grayish silver crystalline solid that can be crushed into a powder called "ferrovanadium ...
(see above). The oxide is heated with scrap iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
and ferrosilicon
Ferrosilicon is an alloy of iron and silicon with a typical silicon content by weight of 15–90%. It contains a high proportion of iron silicides.
Production and reactions
Ferrosilicon is produced by reduction of silica or sand with coke in t ...
, with lime
Lime commonly refers to:
* Lime (fruit), a green citrus fruit
* Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide
* Lime (color), a color between yellow and green
Lime may also refer to:
Botany ...
added to form a calcium silicate slag. Aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
may also be used, producing the iron-vanadium alloy along with alumina as a
Sulfuric acid production
Another important use of vanadium(V) oxide is in the manufacture of sulfuric acid, an important industrial chemical with an annual worldwide production of 165 million tonnes in 2001, with an approximate value of US$8 billion. Vanadium(V) oxide serves the crucial purpose of catalysing the mildly exothermic oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
of sulfur dioxide to sulfur trioxide by air in the contact process:
:2 SO2 + O2 2 SO3
The discovery of this simple reaction, for which V2O5 is the most effective catalyst, allowed sulfuric acid to become the cheap commodity chemical it is today. The reaction is performed between 400 and 620 °C; below 400 °C the V2O5 is inactive as a catalyst, and above 620 °C it begins to break down. Since it is known that V2O5 can be reduced to VO2 by SO2, one likely catalytic cycle is as follows:
:SO2 + V2O5 → SO3 + 2VO2
followed by
:2VO2 +½O2 → V2O5
It is also used as catalyst in the selective catalytic reduction
Selective catalytic reduction (SCR) is a means of converting nitrogen oxides, also referred to as with the aid of a catalyst into diatomic nitrogen (), and water (). A reductant, typically anhydrous ammonia (), aqueous ammonia (), or a urea () ...
(SCR) of NO''x'' emissions in some power plant
A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the electricity generation, generation of electric power. Power stations are generally connected to an el ...
s and diesel engines. Due to its effectiveness in converting sulfur dioxide into sulfur trioxide, and thereby sulfuric acid, special care must be taken with the operating temperatures and placement of a power plant's SCR unit when firing sulfur-containing fuels.
Other oxidations
Maleic anhydride
Maleic anhydride is an organic compound with the formula C2H2(CO)2O. It is the acid anhydride of maleic acid. It is a colorless or white solid with an acrid odor. It is produced industrially on a large scale for applications in coatings and pol ...
is produced by the V2O5-catalysed oxidation of butane with air:
:C4H10 + 4 O2 → C2H2(CO)2O + 8 H2O
Maleic anhydride is used for the production of polyester resins and alkyd resins.
Phthalic anhydride
Phthalic anhydride is the organic compound with the formula C6H4(CO)2O. It is the anhydride of phthalic acid. Phthalic anhydride is a principal commercial form of phthalic acid. It was the first anhydride of a dicarboxylic acid to be used commer ...
is produced similarly by V2O5-catalysed oxidation of ortho-xylene or naphthalene at 350–400 °C. The equation for the vanadium oxide-catalysed oxidation of o-xylene to phthalic anhydride:
:C6H4(CH3)2 + 3 O2 → C6H4(CO)2O + 3 H2O
The equation for the vanadium oxide-catalysed oxidation of naphthalene to phthalic anhydride:
:C10H8 + 4½ O2 → C6H4(CO)2O + 2CO2 + 2H2O
Phthalic anhydride is a precursor to plasticiser
A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture.
Plasticize ...
s, used for conferring pliability to polymers.
A variety of other industrial compounds are produced similarly, including adipic acid
Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2. From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion kilograms of this white crystalline powder are produced annuall ...
, acrylic acid
Acrylic acid (IUPAC: propenoic acid) is an organic compound with the formula CH2=CHCOOH. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a ...
, oxalic acid, and anthraquinone
Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula . Isomers include various quinone derivatives. The term anthraquinone however refers to the isomer, 9,10-anthraquinone (IUPAC: 9,10-dioxoan ...
.[
]
Other applications
Due to its high coefficient of thermal resistance
Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance.
* (Absolute) thermal resistance ''R'' in kelvi ...
, vanadium(V) oxide finds use as a detector material in bolometer
A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley.
Principle of operation
A bolometer ...
s and microbolometer
A microbolometer is a specific type of bolometer used as a detector in a thermal camera. Infrared radiation with wavelengths between 7.5–14 μm strikes the detector material, heating it, and thus changing its electrical resistance. This resista ...
arrays for thermal imaging
Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared i ...
. It also finds application as an ethanol sensor in ppm levels (up to 0.1 ppm).
Vanadium redox batteries are a type of flow battery
A flow battery, or redox flow battery (after reduction–oxidation), is a type of electrochemical cell where chemical energy is provided by two chemical components dissolved in liquids that are pumped through the system on separate sides of a ...
used for energy storage, including large power facilities such as wind farm
A wind farm or wind park, also called a wind power station or wind power plant, is a group of wind turbines in the same location used to produce electricity. Wind farms vary in size from a small number of turbines to several hundred wind turb ...
s. Vanadium oxide is also used as a cathode in lithium ion batteries.
Biological activity
Vanadium(V) oxide exhibits very modest acute toxicity to humans, with an LD50
In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is the ...
of about 470 mg/kg. The greater hazard is with inhalation of the dust, where the LD50
In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is the ...
ranges from 4–11 mg/kg for a 14-day exposure. Vanadate (), formed by hydrolysis of V2O5 at high pH, appears to inhibit enzymes that process phosphate (PO43−). However the mode of action remains elusive.
References
Cited sources
*
*
Further reading
*.
*.
External links
How Vanadium Oxide Is Used In Energy Storage
*
*
*
( Concise International Chemical Assessment Document 29)
*
*
{{DEFAULTSORT:Vanadium(V) Oxide
Vanadium(V) compounds
Catalysts
Infrared sensor materials
IARC Group 2B carcinogens
Oxidizing agents
Transition metal oxides