Bimetallic Nanoparticles for Catalytic HydrogenationsRichard D. Adams

Department of ChemistryUniversity of South Carolina

Columbia, SC 29208

Aromatization (Dehydrogenation) - Important Reforming Reactions

Catalyst Particle Sizes: 1-5 nm in diameter

1140Octane ratings

Commerical Catalysts are Pt-Sn or Pt-Re on Al2O3

Bimetallic NanoCatalysts in Petroleum Reforming

C7H16 + 4 H2

+ 3 H2

+ 3 H2

Ru-Ru = 2.854(3) Åin Ru3(CO)12

Ru Ru

Ru

MeC N

N CMe

+3 Ph3SnH

Ru Ru

RuPh3Sn

SnPh3

MeC N

N CMe

SnPh3

Ru Ru

RuPh3Sn

SnPh3

SnPh3

H

H H

H

H H + 2CO

-2 NCMe- 2CO

Ru1-Ru2 = 2.9629(4)ÅRu1-Ru3 = 2.9572(4)Ru2-Ru3 = 2.9906(4)

125 oC

Ru Ru

Ru SnPh2Ph2Sn

SnPh2

- 3C6H6

Ruthenium-Tin Clusters for Catalytic HydrogenationsMultiple Additions of HSnPh3 to Ru3(CO)10(NCMe)2

Oxidative-Addition of Ph3SnH to Ru5(CO)12(η6-C6H6)(µ5-C)

CRu Ru

Ru Ru

Ru+ Ph3SnH

68 °C

Ru Ru

Ru Ru

Ru

Ph3Sn

H

C- CORu Ru

Ru Ru

Ru

SnPh3

SnPh3

HH

C+

Ru5(CO)11(η6-C6H6)(SnPh3)(µ5-C)(µ-H) Ru5(CO)10(η6-C6H6)(SnPh3)2(µ5-C)(µ-H)2

Up to 5 Tin Ligands can be added to Ru5(CO)12(C6H6)(µ5-C), four SnPh2 and one SnPh3

Ru5(CO)7(η6-C6H6)(µ-SnPh2)4(SnPh3)(µ5-C)(µ-H)

CRu Ru

Ru Ru

Ru+ 5 Ph3SnH

127 °CC

Ru Ru

Ru Ru

Ru

SnPh2Ph2Sn

SnPh2

Ph2Sn

SnPh3

- 5 CO- 4 C6H6

H

PtRu5(CO)15(µ-XPh2)(µ6-C)

Pt-Sn = 2.631 ÅRu1-Sn = 2.607 Å

Pt-Ge = 2.470 ÅRu1-Ge = 2.446 Å

PtRu5(CO)16(µ6-C)

SnPh2 and GePh2 Groups can be introduced into Platinum-Ruthenium Carbonyl Cluster Complexes

Ru Ru

Ru Ru

Pt

Ru

Ru Ru

Ru Ru

Pt

Ru

XPh

Ph

(i) Ph3SnH, rtC C

(ii) Ph3GeH, 68 °CX = Sn or Ge

J. M. Thomas et al. Accts. Chem. Res. 2003, 36, 20.

HO2C

CO2H

H2CO2H

CO2H

trans,trans-muconic acid adipic acid

Pt2Ru10 nanoclusterson mesoporous silica

Bimetallic Clusters can be good precursors to Heterogeneous NanoCluster Catalysts on Supports

x-ray emission spectrum of nanoparticle

Activated trimetallic PtRu(CO)14(C)(SnPh2) cluster on Mesoporous silica yields trimetallic PtRu5Sn nanoparticles

Energy (keV)

Cou

nts

2520151050

60

40

20

0

Pt

PtPt

Pt

Sn

SnSn

Sn

RuRu

Ru

RuRu

Ru

Ru

Cu

CuCu

1.0 ± 0.2Sn

1.0 ± 0.1Pt

5.0 ± 0.3Ru

Atom ratio

200 oC

H2 ,2h38 Å mesoporous silica

Activated trimetallic PtRu(CO)14(C)(SnPh2) cluster on Mesoporous silica yields trimetallic PtRu5Sn nanoparticles

Hydrogenation of Dimethylterephthalate. Comparison of Activites for some metallic nanoparticle catalysts

COMe

OC

MeO

OC

OMe

OC

MeO

OCH2OHHOH2C

dimethyl terephthalate (DMT)

dimethyl hexahydroterephthalate (DMHT)

1,4-cyclohexanedimethanol (CHDM)

* Pd0 170oC H2 400 atm

* CuCr 200oC H2 40 atm

* Eastman ProcessPtRu5Sn 100oC H2 20 atm

0

10

20

30

40

50

60

70

80

90

100

Ru5PtSn [a]Ru5PtGe [a]Ru5Pt [a]Ru6Sn [b]

Our Conditions: 24h at 100oC,20 atm H2 Support: mesoporous Davison 923 Silica with 38 Å pores

conversion DMHT CHDM SP X SP Y

25 oC 1h

Pt(COD)2+2 HSnPh3

25 oC 30 min

Ru3(CO)10(NCMe)2+2 HSnPh3

New bis-SnPh3 Compounds are Precursors to excellent new Heterogeneous Nanoscale Hydrogenation Catalysts

(COD)Pt(SnPh3)2

Ru(CO)4(SnPh3)2

+H2 +H2 +H2

CDT CDD CDE CDA

The Effect Tin on Selective Hydrogenation of Cyclododecatriene CDT

* “RhSn2” was derived from Rh3(CO)6(SnPh2)3(SnPh3)3

The monoene, Cyclododecene,is the most valuable product

Conversion(disappearance of CDT)

R. D. Adams et al. Angew. Chem., 2007, 46, 8182.

More on The Tin EffectReaction of H4Ru4(CO)12 with HSnPh3 has provided a new

Series RuSn cluster complexes Ru4(CO)12-x(µ4-SnPh)2(µ -SnPh2)xx=0,2,3,4 for use as Catalyst Precursors

RuRu

SnPh

RuRu

PhSn

Ph2Sn

Ph2SnCO

SnPh2

RuRu

SnPh

RuRu

PhSn

Ph2Sn

Ph2SnCO

CO

H4Ru4(CO)12

Ph3SnH

125o C+

RuRu

SnPh

RuRu

PhSn

Ph2Sn

Ph2SnSnPh2

SnPh2

+RuRu

SnPh

RuRu

PhSn

+

Ru4Sn2 Ru4Sn4 Ru4Sn5 Ru4Sn6

Ru4Sn2

Ru4Sn6

10 nm

Ru4(CO)12(µ4-SnPh)2(µ-SnPh2)4

The Tin EffectRu4Snx Nanoparticles obtained from Ru4(CO)12(µ4-SnPh)2(µ-

SnPh2)x clusters are excellent catalysts

10 nm

200 oC

H2 ,2h38 Å mesoporous silica

Ru4Sn6 nanoparticles

Ru4Sn6 Ru4Sn4 Ru4Sn2 Ru6Sn PtRu5Sn

Solvent free conditions 2% metal loading H2 ≅ 30 bar, T = 373 K, t = 8h

With Ru4Sn6 the only product Is cyclododecene after 10 h.

Ru3Sn3

All Ru4Snx Catalysts exhibit high selectivity for Cyclododecene.Selectivity increases with the increasing tin content

0 5 10 15 20 25

0

10

20

30

40

50

60

conversion 1,9-cyclododecadiene cyclododecene cyclododecanen/

mol

%

time (h)

0

10

20

30

40

50

60

70

80

90

100n/m

ol%

Ru Sn Ru SnRu SnRu Sn Ru Sn Ru SnPt

0

10

20

30

40

50

60

70

80

90

100n/m

ol%

Ru Sn Ru SnRu SnRu Sn Ru Sn Ru SnPt

conversion

1,9-cyclododecadiene

cyclododecene

cyclododecane

conversion

1,9-cyclododecadiene

cyclododecene

cyclododecane

Nanoparticle on top is slightly larger than 2nm

Nanoparticles move in the during imaging.The two below the group of four fuse at the end.

High Resolution Scanning Transmission Electron Microscopy Images of Ru3Sn3 Nanoparticles on 38 Å silica mesopore

High Resolution Scanning Tunneling Microscopy STM Images of Ru3Sn3 on ultrathin SiO2/Mo(112) at +1.5 volts

SiO2/Mo(112)

200 oC

RuRu

RuPh2Sn SnPh2

Ph2Sn

J. Phys. Chem. 2008, 112, 14233

15 nm × 15 nm

SiO4 tetrahedra on Mo(112)

White triangles are Ru3Sn3 clusters

Individual Ru3Sn3 Clusters are revealed at higher resolutions

a

b6 nm × 6 nm

6 nm × 4 nm

[1 11]

[110]

c

d

3 D image

Ru-Sn≅ 2.7Å

Ru3Sn3 Clusters in close proximity

4.5 nm x 4.5 nm at 1.5 v

[-1-11]

[-1-10]

Yang - TAMU Grönbeck - Chalmers

1) Ph3SnH and Ph2SnH2 are good reagents forintroducing tin ligands into polynuclear metalcluster complexes

2) Clusters containing tin ligands can be precursors tobi- and trimetallic heterogeneous hydrogenationnanocatalysts

3) Tin containing nanocatalysts exhibit better reactionselectivity than the pure metals for some catalytichydrogenation reactions.

Conclusions

• Drs. Burjor Captain, Doug Blom, Ms. Eszter Trufan

• Prof. D. Wayne Goodman and Dr. Fan Yang at TAMU, STM measurements

• Prof. Sir John Meurig Thomas, Dr. Paul Midgley, Dr. Ana Hungria, Cambridge University (TEM)

• Dr. Robert Raja University of Southampton (catalysis)

$$$National Science Foundation

Acknowledgements