Vanadium(V) oxide

{{Short description|Precursor to vanadium alloys and industrial catalyst}} {{chembox | Verifiedfields = changed | Watchedfields = | verifiedrevid = 470628838 | Name = Vanadium(V) oxide | ImageFile1 = Vanadium pentoxide powder.jpg | ImageName1 = Vanadium(V) oxide | ImageSize1 = 150px | ImageFile = Vanadium-pentoxide-monolayer-3D-balls.png | ImageName = Vanadium pentoxide monolayer | ImageSize = 250px | IUPACName = Divanadium pentaoxide | OtherNames = Vanadium pentoxide<br/>Vanadic anhydride<br/>Divanadium pentoxide |Section1={{Chembox Identifiers | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 30045 | SMILES = O=[V](=O)O[V](=O)=O | CASNo = 1314-62-1 | CASNo_Ref = {{cascite|correct|CAS}} | UNII_Ref = {{fdacite|correct|FDA}} | UNII = BVG363OH7A | UNNumber = 2862 | EINECS = 215-239-8 | RTECS = YW2450000 | PubChem = 14814 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 14130 | InChI = 1/5O.2V/rO5V2/c1-6(2)5-7(3)4 | InChIKey = GNTDGMZSJNCJKK-HHIHJEONAP | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/5O.2V | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = GNTDGMZSJNCJKK-UHFFFAOYSA-N | KEGG_Ref = {{keggcite|changed|kegg}} | KEGG = C19308 }} |Section2={{Chembox Properties | Properties_ref = <ref>{{RubberBible62nd|page=B-162}}.</ref> | Formula = V₂O₅ | MolarMass = 181.8800 g/mol | Appearance = Yellow solid | Density = 3.35 g/cm³<ref name=CRC>Haynes, p. 4.94</ref> | Solubility = 0.7 g/L (20&nbsp;°C)<ref name=CRC/> | MeltingPtC = 681 | MeltingPt_ref =<ref name=CRC/> | BoilingPtC = 1750 | BoilingPt_notes = (decomposes) | BoilingPt_ref =<ref name=CRC/> | MagSus = {{val|+128.0e-6|u=cm³/mol}}<ref>Haynes, p. 4.131</ref> }} |Section3={{Chembox Structure | Structure_ref = <ref>{{citation | last1 = Shklover | first1 = V. | last2 = Haibach | first2 = T. | last3 = Ried | first3 = F. | last4 = Nesper | first4 = R. | last5 = Novak | first5 = P. | year = 1996 | title = Crystal structure of the product of Mg²⁺ insertion into V₂O₅ single crystals | journal = J. Solid State Chem. | volume = 123 | issue = 2 | pages = 317–323 | doi = 10.1006/jssc.1996.0186| bibcode = 1996JSSCh.123..317S }}.</ref> | CrystalStruct = Orthorhombic | SpaceGroup = Pmmn, No. 59 | Coordination = Distorted trigonal bipyramidal (V) | LattConst_a = 1151 pm | LattConst_b = 355.9 pm | LattConst_c = 437.1 pm }} | Section4 = {{Chembox Thermochemistry | DeltaGf = −1419.5 kJ/mol | DeltaHc = | DeltaHf = −1550.6 kJ/mol | Entropy = 131.0 J/(mol·K) | HeatCapacity = 127.7 J/(mol·K) | Thermochemistry_ref=<ref>Haynes, p. 5.41</ref> }} |Section7={{Chembox Hazards | ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0596.htm ICSC 0596] | GHSPictograms = {{GHS08|Muta. 2; Repr. 2; STOT RE 1}}{{GHS06|Acute Tox.4; STOT SE 3}}{{GHS09|Aquatic Chronic 2}} | GHSSignalWord = DANGER | HPhrases = {{H-phrases|341|361|372|332|302|335|411}} | NFPA-H = 4 | NFPA-F = 0 | NFPA-R = 0 | FlashPt = Non-flammable | LD50 = 10 mg/kg (rat, oral)<br/>23 mg/kg (mouse, oral)<ref name=IDLH>{{IDLH|vandust|Vanadium dust}}</ref> | LCLo = 500 mg/m³ (cat, 23&nbsp;min)<br/>70 mg/m³ (rat, 2&nbsp;hr)<ref name=IDLH/>

| PEL = C 0.5&nbsp;mg V₂O₅/m³ (resp) (solid)<ref name="PGCH|0653">{{PGCH|0653}}</ref> <br/> C 0.1&nbsp;mg V₂O₅/m³ (fume)<ref name="PGCH|0653"/> }} |Section8={{Chembox Related | OtherAnions = Vanadium oxytrichloride | OtherCations = Niobium(V) oxide<br />Tantalum(V) oxide | OtherFunction = Vanadium(II) oxide<br />Vanadium(III) oxide<br />Vanadium(IV) oxide | OtherFunction_label = vanadium oxides }} }}

'''Vanadium(V) oxide''' (''vanadia'') is the inorganic compound with the formula V₂O₅. Commonly known as '''vanadium pentoxide''', it is a dark yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because of its high oxidation state, it is both an amphoteric oxide and an oxidizing agent. 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.<ref name=Ullmann/>

The mineral form of this compound, shcherbinaite, is extremely rare, almost always found among fumaroles. A mineral trihydrate, 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 occurs to give vanadium(IV) oxide, as a deep-blue solid:<ref>Brauer, p. 1267</ref> :V₂O₅ + V₂O₃ → 4 VO₂ The reduction can also be effected by oxalic acid, carbon monoxide, and sulfur dioxide. Further reduction using hydrogen 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 oxide, and unlike most transition metal oxides, it is slightly water soluble, giving 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.<ref name="G&E">{{Greenwood&Earnshaw1st|pages=1140, 1144}}.</ref> If excess aqueous sodium hydroxide is used, the product is a colourless salt, sodium orthovanadate, 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&nbsp;2. These solutions contain mainly the ions {{chem2|HVO4(2-)}} and {{chem2|V2O7(4-)}} between pH&nbsp;9 and pH&nbsp;13, but below pH&nbsp;9 more exotic species such as {{chem2|V4O12(4-)}} and {{chem2|HV10O28(5-)}} (decavanadate) predominate.

Upon treatment with thionyl chloride, it converts to the volatile liquid vanadium oxychloride, VOCl₃:<ref>Brauer, p. 1264</ref> :V₂O₅ + 3 SOCl₂ → 2 VOCl₃ + 3 SO₂

===Other redox reactions=== Hydrochloric acid and hydrobromic acid are oxidised to the corresponding halogen, e.g., :V₂O₅ + 6 HCl + 7 H₂O → 2 [VO(H₂O)₅]²⁺ + 4 Cl⁻ + Cl₂

Vanadates or vanadyl compounds in acid solution are reduced by zinc amalgam through the colourful pathway:

none|300px|thumb| {{center|{{underset|yellow|{{chem2|VO2+}}}} → {{underset|blue|VO²⁺}} → {{underset|green|V³⁺}} → {{underset|purple|V²⁺}}<ref>{{Cite web|url=https://edu.rsc.org/resources/the-oxidation-states-of-vanadium/2003.article|title=The oxidation states of vanadium|website=RSC Education|language=en|access-date=2019-10-04}}</ref>}} The ions are all hydrated to varying degrees.

==Preparation== thumb|140px|left|The orange, partly hydrated form of V₂O₅ thumb|140px|left|Precipitate of "red cake", which is hydrous V₂O₅ Technical grade V₂O₅ is produced as a black powder used for the production of vanadium metal and ferrovanadium.<ref name="G&E"/> 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&nbsp;2–3 using H₂SO₄ to yield a precipitate of "red cake" (see above). The red cake is then melted at 690&nbsp;°C to produce the crude V₂O₅.

Vanadium(V) oxide is produced when vanadium metal is heated with excess oxygen, but this product is contaminated with other, lower oxides. A more satisfactory laboratory preparation involves the decomposition of ammonium metavanadate at 500–550&nbsp;°C:<ref>Brauer, p. 1269</ref> :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 (see above). The oxide is heated with scrap iron and ferrosilicon, with lime added to form a calcium silicate slag. Aluminium may also be used, producing the iron-vanadium alloy along with alumina as a byproduct.

===Sulfuric acid production=== thumb|left|Proposed mechanism for the oxidation of sulfur dioxide over vanadium oxide catalysts Vanadium(V) oxide is used as the oxygen-transfer catalyst in the contact process, the only process now used for the industrial production of sulfuric acid.<ref name="Lapina">O.B. Lapina, B.S. Bal'zhinimaev, S. Boghosian, K.M. Eriksen, R. Fehrmann: ''Progress on the mechanistic understanding of SO₂ oxidation catalysts'', in: ''Catalysis Today'', 1999, 51, pp.&nbsp;469–479, doi:10.1016/S0920-5861(99)00034-6.</ref> The catalyst phase is a molten salt formed from vanadium(V) oxide and added alkali metal sulfates acting as co-catalysts. In this melt, the reactive complex [(VO)₂O(SO₄)₄]⁴⁻, which is regarded as the actual catalytic species, is formed. Oxygen and sulfur dioxide coordinate to this complex and react to form sulfur trioxide without a change in the oxidation state of vanadium.<ref name="Lapina" />

:The overall reaction is: :2 SO₂ + O₂ {{eqm}} 2 SO₃

The reaction is carried out at about 420 to 620&nbsp;°C; at lower temperatures the catalyst is deactivated by formation of vanadium(IV) compounds, while at higher temperatures it begins to decompose.<ref name="Lapina" /> Industrial conversion is performed in multi-bed contact furnaces, in which the catalyst is arranged in four superposed layers and the process gas is cooled between the beds to maintain the required temperature range.

===Other oxidations=== [[File:V2O5OxNaphth.svg|thumb|left|464px|Proposed early steps in the vanadium-catalyzed oxidation of naphthalene to phthalic anhydride, with V₂O₅ represented as a molecule vs its true extended structure<ref>{{cite book|doi=10.1002/9780470638859.conrr270|chapter=Gibbs-Wohl Naphthalene Oxidation|title=Comprehensive Organic Name Reactions and Reagents|year=2010|pages=1227–1229 |isbn=978-0-470-63885-9}}</ref>]] Maleic anhydride 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.<ref>{{citation | title = Basic Organic Chemistry: Part 5, Industrial Products | editor1-first = J. M. | editor1-last = Tedder | editor2-first = A. | editor2-last = Nechvatal | editor3-first = A. H. | editor3-last = Tubb | publisher = John Wiley & Sons | location = Chichester, UK | year = 1975}}.</ref>

Phthalic anhydride is produced similarly by V₂O₅-catalysed oxidation of ''ortho''-xylene or naphthalene at 350–400&nbsp;°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:<ref>{{cite book | last1=Conant | first1=James | last2=Blatt | first2=Albert | title=The Chemistry of Organic Compounds | publication-place=New York, New York | publisher=The Macmillan Company | edition=5th | year=1959 | page=511}}</ref> :C₁₀H₈ + {{frac|4|1|2}} O₂ → C₆H₄(CO)₂O + 2 CO₂ + 2 H₂O Phthalic anhydride is a precursor to plasticisers, used for conferring pliability to polymers.

A variety of other industrial compounds are produced similarly, including adipic acid, acrylic acid, oxalic acid, and anthraquinone.<ref name=Ullmann/>

===Other applications=== Due to its high coefficient of thermal resistance, vanadium(V) oxide finds use as a detector material in bolometers and microbolometer arrays for thermal imaging. It also finds application as an ethanol sensor in ppm levels (up to 0.1&nbsp;ppm).

Vanadium redox batteries are a type of flow battery used for energy storage, including large power facilities such as wind farms.<ref>{{cite web|last=REDT Energy Storage|title=Using VRFB for Renewable applications|url=http://www.redtenergy.com/applications/renewable-energy|access-date=2014-01-21|archive-date=2014-02-01|archive-url=https://web.archive.org/web/20140201171818/http://www.redtenergy.com/applications/renewable-energy|url-status=dead}}</ref> Vanadium oxide is also used as a cathode in lithium-ion batteries.<ref>{{cite journal |last1=Sreejesh |first1=M. |last2=Shenoy |first2=Sulakshana |last3=Sridharan |first3=Kishore |last4=Kufian |first4=D. |last5=Arof |first5=A. K. |last6=Nagaraja |first6=H. S. |title=Melt quenched vanadium oxide embedded in graphene oxide sheets as composite electrodes for amperometric dopamine sensing and lithium ion battery applications |journal=Applied Surface Science |date=2017 |volume=410 |pages=336–343 |doi=10.1016/j.apsusc.2017.02.246|bibcode=2017ApSS..410..336S }}</ref>

Vanadium pentoxide is often used as a component in glazes where it produces a wide range of colours from greens and yellows to blues and grays.<ref>{{Cite web|title=Applications of Vanadium Pentoxide in Ceramic and Glass Manufacturing|url=https://www.dsalloyd.com/applications-of-vanadium-pentoxide-in-ceramic-and-glass-manufacturing/|website=DS Alloyd|date=2025-11-10|access-date=2026-01-31|language=en-US|last=Grvghai}}</ref>

==Biological activity== thumb|right Vanadium(V) oxide exhibits very modest acute toxicity to humans, with an {{LD50}} of about 470&nbsp;mg/kg. The greater hazard is with inhalation of the dust, where the LD₅₀ ranges from 4–11&nbsp;mg/kg for a 14-day exposure.<ref name=Ullmann>{{Cite book|doi = 10.1002/14356007.a27_367|chapter = Vanadium and Vanadium Compounds|title = Ullmann's Encyclopedia of Industrial Chemistry|year = 2000|last1 = Bauer|first1 = Günter|last2 = Güther|first2 = Volker|last3 = Hess|first3 = Hans|last4 = Otto|first4 = Andreas|last5 = Roidl|first5 = Oskar|last6 = Roller|first6 = Heinz|last7 = Sattelberger|first7 = Siegfried|isbn = 3-527-30673-0}}</ref> Vanadate ({{chem2|VO4(3-)}}), formed by hydrolysis of V₂O₅ at high pH, appears to inhibit enzymes that process phosphate ({{chem2|PO4(3-)}}). However the mode of action remains elusive.<ref name="G&E"/>{{better source needed|date=November 2022}}

==References== {{reflist}}

==Cited sources == *{{cite book|editor=Brauer, G. |author=Brauer, G. |chapter=Vanadium, Niobium, Tantalum|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed.|publisher=Academic Press|year=1963|place=NY}} *{{cite book | editor= Haynes, William M. | date = 2016| title = CRC Handbook of Chemistry and Physics | edition = 97th | publisher = CRC Press | isbn = 978-1-4987-5429-3}}

==Further reading== *{{citation | contribution = Vanadium Pentoxide | url = http://monographs.iarc.fr/ENG/Monographs/vol86/mono86-10.pdf | pages = 227–292 | title = Cobalt in Hard Metals and Cobalt Sulfate, Gallium Arsenide, Indium Phosphide and Vanadium Pentoxide | series = IARC Monographs on the Evaluation of Carcinogenic Risks to Humans 86 | publisher = International Agency for Research on Cancer | location = Lyon, France | year = 2006 | isbn = 92-832-1286-X}}. *{{citation | first1 = B. | last1 = Vaidhyanathan | first2 = K. | last2 = Balaji | first3 = K. J. | last3 = Rao | year = 1998 | title = Microwave-Assisted Solid-State Synthesis of Oxide Ion Conducting Stabilized Bismuth Vanadate Phases | journal = Chem. Mater. | volume = 10 | issue = 11 | pages = 3400–3404 | doi = 10.1021/cm980092f}}.

==External links== {{Commons category|Vanadium(V) oxide}} *{{ICSC|0596}} *{{PGCH|0653}} *{{PGCH|0654}} *[http://www.inchem.org/documents/cicads/cicads/cicad29.htm Vanadium Pentoxide and other Inorganic Vanadium Compounds] (Concise International Chemical Assessment Document 29) *{{EHC|81|name=Vanadium}} *{{HSG|042|name=Vanadium and some vanadium salts}}

{{Vanadium compounds}} {{Oxides}}

{{DEFAULTSORT:Vanadium(V) Oxide}} Category:Vanadium(V) compounds Category:Catalysts Category:Infrared sensor materials Category:IARC Group 2B carcinogens Category:Oxidizing agents Category:Transition metal oxides