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PCH Mitchell Presentation IMOA AGM September 2004

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Philip C.H. Mitchell

School of Chemistry

University of Reading

Reading RG6 6AD UK

Chemical Applications of Molybdenum

Understanding

molybdenum chemistry

and applications


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The purpose of the presentation is to show how technical applications of molybdenum compounds exploit fundamental molybdenum chemistry.


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MoS2

MoO3

Mo

Mo2C

MoCl5

(NH4)2MoS4

[(RS2)2Mo2OxSy]

Mo2N

Na2MoO4

(NH4)2Mo2O7

(NH4)6Mo7O24

Mo(CO)6

roast air

Aq NaOH, aq NH3

Calcine/sublime

H2/CO 1000 C

H2

1000 CNH3

1000 C

C+H2

1500 CNH3

1100 C

Cl2CO 70 barEtMgBrice

H2S

RS2

Molybdenum Chemistry


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Molybdenum Compounds Applications

Application Partner

C N O Si P S

Mo2NMoO3

molybdateMoSi2 MoP MoS2

Catalysis

Lubrication

Corrosion inhibition

Pigments

Smoke suppression

Ceramics

Nanomaterials

Mo2C


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Molybdenum CatalystsUS Patents

Molybdenum and catalysis US Patents

0

10

20

30

40

50

60

70

80

90

1981-1985 1986-1990 1991-1995 1996-2001

Num

ber

of pate

nts

s

Oxide

Sulfide

Carbide

Nitride


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Molybdenum Catalysts

Hydrotreatment of petroleum

Remove S = hydrodesulfurisation = HDS

Remove N, O compounds

Selective oxidation

Methanol to formaldehyde

Propene to acrolein and acrylontrile

For polymers and plastics


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Thiophene Desulfurisation

S

+ 4H2 + 4H2S

350 °C100 bar


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MolybdenumHydrodesulfurisation

Catalyst

Mo(9%)O3Co(3)%O

g-Al2O3

Mo(9%)S2Co(3)%S

g-Al2O3

Pre-cursor

Oxide form

Active catalyst

Sulfide


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MoS2 CatalystThiophene Hydrodesulfurisation

S H

H

H2

H2S


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CH

H

+ H2OCH

H H

O H

+ O2

Selective OxidationMethanol

Iron molybdate Fe2(MoO4)3

methanol formaldehyde


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Selective Oxidation of Propene

C C

C

H

H

HH

HH

O2

O2

NH3

+propene

acrolein

C

C

H

HH

H

C

O

acrylonitrile

C

C

H

H

H

CN

Bismuth molybdate Bi2(MoO4)3


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removes H

Step 3

C C

C

H

H

HH

HH

How Selective Oxidation Works

activates CH

removes H

inserts O

Mo(VI)O2 Mo(IV)O + O

BiOStep 1

Step 4

Step 2

Mo

O

O


13Molybdenum―sulfur Compounds in Lubrication

Molybdenum disulfide

Used in e.g. greases, dispersions, friction materials and bonded coatings.

Dry lubricant

Molybdenum complexesantiwear and extreme pressure additives

friction modifiers in lubricating oils and greases.

soluble in petroleum oils and other organic solvents

Decompose at hot metal surface Protective filmMoS2 layer


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MoS2 Structure


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MoS2 Lubricating Action

No MoS2

With MoS2

Reproduced with permission of Acheson Industries http://www.achesonindustries.com/doc/guides/HowDoSolidLubricantsFunction.pdf


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From R.T. Vanderbilt Company, Inc. Lubricants Information Brochure http://www.rtvanderbilt.com/petro/p981.pdf


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Molybdenum ComplexesAnti-friction, Anti-wear, Anti-oxidant

S

SN Mo2OxSy

2

S

PSO

Mo2O2S2

2

O

dithiocarbamate

dithiophosphate


18Corrosion Inhibitors and Pigments

Automobile engine coolant

Central heating systems

Zinc, calcium, strontium molybdate

Molybdenum orange: lead molybdate + lead chromate

Phosphomolybdates

Paints

plastics

rubber

ceramics

Sodium molybdate

Steel, Al, Cu

Application

Replace toxic chromate by molybdate


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Calcium Zinc PhosphomolybdateCorrosion Test

Reproduced with permission from Paint and Coatings Industry magazine 2001Industry Update: Molybdate Corrosion InhibitorsBy Charles Simpson Moly-White Pigments Group, Cleveland, OHhttp://www.pcimag.com.


20Mechanism of Protective Action of

Molybdate

Interacts with the metallic substrate

― adsorption.

Fills gaps and promotes the formation of an adherent oxide layer.

Prevents corrosion of the underlying substrate ― passivation.


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Molybdates as Smoke Suppressants

Ammonium octamolybdate

MoO3

PVC

cable

carpet backing

building materials

Application Compound

Non-volatile Mo oxide remains in char.


22Mechanism of Smoke Suppression

by Molybdate

Plasticizers ― greatly enhance the polymer combustibility.

Molybdate reduces smoke from burning PVC.

The char produced from the AOM containing compound was MoO2.

Cross-links the plastic to form a surface char..


23Molybdenum DisilicidesCeramics, advanced materials, composites

Aerospace gas turbine engines blade outer seal

Molten metal lances

Diesel engine glow plugs

Gas burner

Heating elements air furnaces

Application Properties

•High melting point 2030 C

•Excellent oxidation resistance

•Moderate density 6.24 g cm-3


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Molybdenum Carbide CatalystNanotubes

From U.S. Department of Energy 2002http://www.oit.doe.gov/chemicals/factsheets/nanoscale.pdf


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Vibrational Spectroscopy with NeutronsWith Applications in Chemistry, Biology,

Materials Science and Catalysis

PCH Mitchell, SF Parker, AJ Ramirez-Cuesta and J Tomkinson

World Scientific

Series on Neutron Techniques and Applications –Vol. 3


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0

2000

4000

6000

8000

10000

12000

steels alloys

chemicals

Molybdenum UsageUnited States 2002

metric tonnes

80%

20%

US Geological Survey Minerals Division


27Molybdenum Chemicals UsageUnited States 2002

metric tonnes

0

200

400

600

800

1000

1200

1400

other

catalysts

lubrication

pigments

percent

40 89

US Geological Survey Minerals Division


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Challenges 1Discovery

new

old

newold

Mo compoundsApplications

The hydrogen economy


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Challenges 2

Organics?Pigments

and coatings

Ashless additives ―

to eliminate sulfur, phosphorus and ash

Lubrication

Vanadium?

Iron?

Catalysts

Substitution


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OptimismU.S. Geological Survey

Mineral Commodity SummariesJanuary 2004

The variety of uses for molybdenum materials, few of which afford acceptable substitution, has resulted in a doubling of demand in the Western World to about 136,000 metric tons per year (t/yr) (300 million pounds per year) in 2000 from about 68,000 t/yr (150 million poundsper year) in 1983.


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WHY USE MOLYBDENUM?

Chemical versatility

Low toxicity

ALWAYS WORTH THINKING MOLYBDENUM


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Disclaimer

• This presentation is based on information in the open research literature and in the public domain generally.

• Any particular product is mentioned for illustrative purposes only. Its mention is not intended as a recommendation over any other product.

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