View source for 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 = V<sub>2</sub>O<sub>5</sub>
| MolarMass = 181.8800 g/mol
| Appearance = Yellow solid
| Density = 3.35 g/cm<sup>3</sup><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 = +128.0·10<sup>−6</sup> cm<sup>3</sup>/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 Mg<sup>2+</sup> insertion into V<sub>2</sub>O<sub>5</sub> single crystals | journal = J. Solid State Chem. | volume = 123 | issue = 2 | pages = 317–23 | doi = 10.1006/jssc.1996.0186| bibcode = 1996JSSCh.123..317S }}.</ref>
| CrystalStruct = [[Orthorhombic crystal system|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/m<sup>3</sup> (cat, 23 min)<br/>70 mg/m<sup>3</sup> (rat, 2 hr)<ref name=IDLH/>

| PEL = C 0.5 mg V<sub>2</sub>O<sub>5</sub>/m<sup>3</sup> (resp) (solid)<ref name="PGCH|0653">{{PGCH|0653}}</ref>
<br/>
C 0.1 mg V<sub>2</sub>O<sub>5</sub>/m<sup>3</sup> (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]] [[oxide]]s
  }}
}}

'''Vanadium(V) oxide''' (''vanadia'') is the [[inorganic compound]] with the [[chemical formula|formula]] [[Vanadium|V]]<sub>2</sub>[[Oxygen|O]]<sub>5</sub>.  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 [[Redox|oxidizing agent]]. From the industrial perspective, it is the most important compound of [[vanadium]], being the principal precursor to [[vanadium alloy|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 [[Hydrate|trihydrate]], V<sub>2</sub>O<sub>5</sub>·3H<sub>2</sub>O, 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>
:V<sub>2</sub>O<sub>5</sub>  +  V<sub>2</sub>O<sub>3</sub>  →   4 VO<sub>2</sub>
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 V<sub>4</sub>O<sub>7</sub> and V<sub>5</sub>O<sub>9</sub> before black V<sub>2</sub>O<sub>3</sub> is reached.

===Acid-base reactions===
V<sub>2</sub>O<sub>5</sub> is an [[amphoteric]] oxide, and unlike most [[transition metal]] oxides, it is slightly water [[Solubility|soluble]], giving a pale yellow, acidic solution. Thus V<sub>2</sub>O<sub>5</sub> reacts with strong non-reducing acids to form solutions containing the pale yellow salts containing [[pervanadyl|dioxovanadium(V)]] centers:
:V<sub>2</sub>O<sub>5</sub> + 2 HNO<sub>3</sub>  →  2 VO<sub>2</sub>(NO<sub>3</sub>) + H<sub>2</sub>O 

It also reacts with strong [[alkali]] to form [[Polyoxometalate|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 (chemistry)|salt]], [[sodium orthovanadate]], Na<sub>3</sub>VO<sub>4</sub>. If acid is slowly added to a solution of Na<sub>3</sub>VO<sub>4</sub>, the colour gradually deepens through orange to red before brown hydrated V<sub>2</sub>O<sub>5</sub> precipitates around pH&nbsp;2. These solutions contain mainly the ions HVO<sub>4</sub><sup>2−</sup> and V<sub>2</sub>O<sub>7</sub><sup>4−</sup> between pH&nbsp;9 and pH&nbsp;13, but below pH&nbsp;9 more exotic species such as V<sub>4</sub>O<sub>12</sub><sup>4−</sup> and HV<sub>10</sub>O<sub>28</sub><sup>5−</sup> ([[decavanadate]]) predominate.

Upon treatment with [[thionyl chloride]], it converts to the volatile liquid [[vanadium oxychloride]], VOCl<sub>3</sub>:<ref>Brauer, p. 1264</ref>
:V<sub>2</sub>O<sub>5</sub> +  3 SOCl<sub>2</sub> → 2 VOCl<sub>3</sub> + 3 SO<sub>2</sub>

===Other redox reactions===
[[Hydrochloric acid]] and [[hydrobromic acid]] are oxidised to the corresponding [[halogen]], e.g.,
:V<sub>2</sub>O<sub>5</sub> +  6HCl + 7H<sub>2</sub>O → 2[VO(H<sub>2</sub>O)<sub>5</sub>]<sup>2+</sup>  +  4Cl<sup>−</sup> + Cl<sub>2</sub>

[[Vanadate|Vanadates]] or [[Vanadyl ion|vanadyl]] compounds in acid solution are reduced by [[zinc amalgam]] through the colourful pathway:

[[File:Vanadium oxidation states.jpg|none|300px|thumb|
{{center|{{underset|yellow|VO<sub>2</sub><sup>+</sup>}} → {{underset|blue|VO<sup>2+</sup>}} → {{underset|green|V<sup>3+</sup>}} → {{underset|purple|V<sup>2+</sup>}}<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==
[[File:V2O5powder.jpg|thumb|140px|left|The orange, partly hydrated form of V<sub>2</sub>O<sub>5</sub>]]
[[File:V2O5 hydrous.jpg|thumb|140px|left|Precipitate of "red cake", which is hydrous V<sub>2</sub>O<sub>5</sub>]]
Technical grade V<sub>2</sub>O<sub>5</sub> 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]], NaVO<sub>3</sub>. This material is then acidified to pH&nbsp;2–3 using [[Sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]] to yield a precipitate of "red cake" (see [[#Chemical properties|above]]). The red cake is then melted at 690&nbsp;°C to produce the crude V<sub>2</sub>O<sub>5</sub>.

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 NH<sub>4</sub>VO<sub>3</sub>  →  V<sub>2</sub>O<sub>5</sub> +  2 NH<sub>3</sub> + H<sub>2</sub>O

==Uses==

===Ferrovanadium production===
In terms of quantity, the dominant use for vanadium(V) oxide is in the production of [[ferrovanadium]] (see [[#Preparation|above]]). The oxide is heated with scrap [[iron]] and [[ferrosilicon]], with [[Lime (material)|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===
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&nbsp;million tonnes in 2001, with an approximate value of US$8&nbsp;billion. Vanadium(V) oxide serves the crucial purpose of [[catalyst|catalysing]] the mildly [[exothermic reaction|exothermic]] [[Redox|oxidation]] of sulfur dioxide to [[sulfur trioxide]] by air in the [[contact process]]:
:2 SO<sub>2</sub>  +  O<sub>2</sub>  {{eqm}}  2 SO<sub>3</sub>

The discovery of this simple reaction, for which V<sub>2</sub>O<sub>5</sub> 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&nbsp;°C; below 400&nbsp;°C the V<sub>2</sub>O<sub>5</sub> is inactive as a catalyst, and above 620&nbsp;°C it begins to break down. Since it is known that V<sub>2</sub>O<sub>5</sub> can be reduced to VO<sub>2</sub> by SO<sub>2</sub>, one likely catalytic cycle is as follows:
:SO<sub>2</sub>  +  V<sub>2</sub>O<sub>5</sub>  →  SO<sub>3</sub>  +  2VO<sub>2</sub>
followed by
:2VO<sub>2</sub> +½O<sub>2</sub>  →  V<sub>2</sub>O<sub>5</sub>

It is also used as catalyst in the [[selective catalytic reduction]] (SCR) of [[Nitrogen oxide#NOx|NO<sub>''x''</sub>]] emissions in some [[power plant]]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===
[[File:V2O5OxNaphth.svg|thumb|left|464px|Proposed early steps in the vanadium-catalyzed oxidation of naphthalene to [[phthalic anhydride]], with V<sub>2</sub>O<sub>5</sub> 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 V<sub>2</sub>O<sub>5</sub>-catalysed oxidation of butane with air:
:C<sub>4</sub>H<sub>10</sub>  +  4 O<sub>2</sub>   →   C<sub>2</sub>H<sub>2</sub>(CO)<sub>2</sub>O  +  8 H<sub>2</sub>O
Maleic anhydride is used for the production of [[polyester]] resins and [[Alkyd#Manufacture|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 V<sub>2</sub>O<sub>5</sub>-catalysed oxidation of [[ortho-xylene|''ortho''-xylene]] or [[naphthalene]] at 350–400&nbsp;°C.  The equation for the vanadium oxide-catalysed oxidation of ''o''-xylene to phthalic anhydride:
:C<sub>6</sub>H<sub>4</sub>(CH<sub>3</sub>)<sub>2</sub>  +  3 O<sub>2</sub>   →   C<sub>6</sub>H<sub>4</sub>(CO)<sub>2</sub>O +  3 H<sub>2</sub>O
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>
:C<sub>10</sub>H<sub>8</sub> + 4½ O<sub>2</sub>   →   C<sub>6</sub>H<sub>4</sub>(CO)<sub>2</sub>O + 2CO<sub>2</sub> + 2H<sub>2</sub>O
Phthalic anhydride is a precursor to [[plasticiser]]s, 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 [[bolometer]]s 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 battery|Vanadium redox batteries]] are a type of [[flow battery]] used for [[energy storage]], including large power facilities such as [[wind farm]]s.<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>

==Biological activity==
[[Image:V2o5label.jpg|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 LD<sub>50</sub> 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]] ({{chem|VO|4|3-}}), formed by hydrolysis of V<sub>2</sub>O<sub>5</sub> at high pH, appears to inhibit [[enzyme]]s that process [[phosphate]] (PO<sub>4</sub><sup>3−</sup>). 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 = 227–92 | 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 = 3400–4 | 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]]