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
PCH Mitchell Presentation IMOA AGM September 2004
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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
PCH Mitchell Presentation IMOA AGM September 2004
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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
PCH Mitchell Presentation IMOA AGM September 2004
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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
PCH Mitchell Presentation IMOA AGM September 2004
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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
PCH Mitchell Presentation IMOA AGM September 2004
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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
PCH Mitchell Presentation IMOA AGM September 2004
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
PCH Mitchell Presentation IMOA AGM September 2004
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.
PCH Mitchell Presentation IMOA AGM September 2004
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.
PCH Mitchell Presentation IMOA AGM September 2004
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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.
PCH Mitchell Presentation IMOA AGM September 2004
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..
PCH Mitchell Presentation IMOA AGM September 2004
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
PCH Mitchell Presentation IMOA AGM September 2004
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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.