Homogeneous Catalysts for C-H Activation and Other Approaches to Shale Gas Utilization

Homogeneous Catalysis for C-H Activation and

Other Approaches to Shale Gas Utilization

!

Shannon S. Stahl

!

University of Wisconsin–Madison

!

CH₄

H₂/CO

H₂C CH₂

R CH₃OH

[O]

(existing)!

What will be the source of aromatics, C4s and propylene?!

Bruijnincx and Weckhuysen! ACIE2013, 52, 11980!

Why Homogeneous Catalysis?

!

• _!Homogeneous catalysts are used in numerous major industrial processes_!

!_- !_{olefin oligomerization, polymerization (ethylene)} !

! ! !_{• metallocenes and other single-site Ti/Zr/Hf}!

! ! !_{• [(P,O)Ni–H]}+ _{(SHOP catalysts)!}

! ! !_{• Cr(EH)}

3/Me2pyrrole/AlR3!

!_- !_{hydroformylation (syngas)}!

! ! !_{• Rh/phosphine, HCo(CO)}

4 ± phosphine!

!_- !_{aerobic oxidation - Wacker and Mid-Century processes (O}

2)!

!_- !_{many others…}! !

• _!Is Homogeneous vs. Heterogenous Catalysis an appropriate dividing line? _!

!_{Is this an artifact of US academic science (Chemistry vs. Chem. Engr. departments and}

associated language barriers)?!

!_- !_{Molecular vs. Nanoparticle vs. Bulk Heterogeneous}! !_- !_{Liquid phase vs. gas phase chemistry}!

!_- !_{How should single-site supported catalysts (e.g., metallocene and related olefin}!

! !_{polymerization catalysts) and MOFs be classified?}!

!

• _!This presentatiion will emphasize "molecular" processes and/or concepts_!

!_- !_{biological transformations/oxidations reflect this perspective}!

! !_{(enzymes are molecules)}!

!_- !_{molecular/atomistic concepts are increasingly relevant and applied to} !

α

_{-Olefin Synthesis and Applications}

!

Alpha Olefins Market Analysis By Product (1-Butene, 1-Hexene, 1-Octene), By Application (Polyethylene, Detergent Alcohol, Synthetic Lubricant) And Segment Forecasts To 2020!

Published: March 2015 | ISBN Code: 978-1-68038-356-0!

“Increasing 1-hexene usage in LLDPE

production is expected to drive the market growth over the forecast period.”_!

Major Applications_!

•  _LLDPE! •  _HDPE!

•  _{Detergent Alcohols!} •  _{Synthetic Lubricants!}

α-Olefin Synthesis_!

•  _{Shell Higher Olefin Process (oligomerization/methathesis) - ethylene!} •  _{Oligomerization (INEOS) - ethylene!}

•  _{Fischer-Tropsch (Sasol) - syngas!}

•  _{Butadiene telomerization (Dow) – naphtha cracking!} •  _{Ethylene trimerization/tetramerization - ethylene}

(Chevron Phillips, Sasol)_!

Homogeneous Catalysts_!

Selective for primarily_! a single alpha olefin_!

5.2M tons! 3.7M _!

tons_!

Discovered in 1930s (Co)

& 1960s (Rh)

– Oxo Process –

Hydroformylation: (

α

-)Olefins and Syngas

!

Linear (and branched) Aldehydes > 18 billion lbs/year

R + H2/CO _{R H}

O H

Discovered in 1955

– Mid-Century and Related Autoxidations –

Radical Chain (Liquid Phase) Aerobic Oxidation of Hydrocarbons

!

H₃C

CH₃ + 3 O₂

Co/Mn/Br

-HO₂C

CO₂H + 2 H₂O

Radical-Chain (Catalytic) Aerobic Oxidation_!

> 100 billion lbs/year

In₂

In RH

R O₂ RH R

RO₂

RO₂ RO₄R 2 RO₂

InH

RO2H

2 In

RO₂R RO₂

R

R

Initiation Propagation

Termination

R_i

+ +

+

+ +

+

nonradical products + O₂

also…_!

air

OOH

decomposition

OH O

+

H₂C CH₂ + 1/2 O₂

H₃C H O [Pd, Cu]

H₂O _{2 Cu}2+

2 Cu+

H O

CH₃

PdII

PdII

OH PdII

H+

H₂O

CH₂

CH₂

2+

+ 2 H+

+

+ H+ Pd0

1/2 O₂

CH₂ CH₂

Discovered in 1959

Wacker Process: Ethylene to Acetaldehyde

!

Organometallic Aerobic Oxidation Chemistry > 1 billion lbs/year

Regioselective Alkane Activation by Transition Metal Complexes

!

Activation of 1° C-H bond is favored!!_! but…_!

reactions generally stoichiometric and incompatible with oxidants

or other reagents needed to functionalize the metal-alkyl_!

Labinger & Bercaw Nature 2002, 417, 507-514. ! Ir

Me₃P

H H

Ir Me₃P

H hν

– H₂

+ Ir

Me₃P

H 110 °C, 14h

1.5:1 +

for M = Rh, only 1° C–H activation

+ CH₄ Zr NR

R(H)N R(H)N

R = SiBut 3

Zr

N(H)R R(H)N

R(H)N

CH₃

Sc CH₃ + 13_CH

4 Sc 13CH3 + CH4

Oxidative Addition (Bergman, Graham, Jones, …)!

Sigma-Bond Metathesis (Bercaw, Watson, Marks, …)!

1,2-Addition (Wolczanski, Bergman, …)!

Selective "C–H Functionalization"

!

2000s – Applications to organic chemistry, pharmaceutical synthesis…_!

DG H₃C

H3C CH3 O

H₃C

H₃C O

O

O O OH

OH

Jiadifenolide Huw Davies

Emory University

120° C

CH₃OH + PtCl₄2- + 2 HCl CH₄ + PtCl₆2- + H₂O

PtCl₄

2-!

[O]

_!

The

Oxidant

Problem

_!

Organometallic Methane Oxidation

!

The Shilov System (1971)

_!

PtII Cl Cl

Cl Cl

PtII

Cl Cl

CH₃ Cl

PtIV Cl Cl

Cl Cl

2-CH₃

Cl

2-CH₃OH + H+

CH₄ HCl

PtIVCl₆

2-PtIICl₄ 2-H₂O

Shilov System

!

+ 25%

conversion

80%

OH HO OH Cl OH

CH

₄

vs. CH

₃

OH

k1 k2

k1 ~ k2

cf. H atom abstraction: k1

k2

~ 10-6

C

₂

H

₆

vs. C

₂

H

₅

OH

H–CH₂CH₃ > H–CH₂CH₂OH > H–CH(OH)CH₃

→ direct oxidation of ethane to ethylene glycol!

Propanol Oxidation

Biological Methane Oxidation

!

CH₄ + O₂ + NADH + H+ MMO CH₃OH + H₂O + NAD+ 45 °C

!

e

–

The

Reductant

Problem

_!

Methane Monooxygenase (Fe)

_!

Graphic:_!

Biological Methane Oxidation

!

CH₄ + O₂ + NADH + H+ MMO CH₃OH + H₂O + NAD+ 45 °C

The

Reductant

Problem

_!

Methane Monooxygenase (Fe)

_!

CH₄ + H₂O₂ → CH₃OH + H₂O _! O₂ + 2 H+ _{+ 2 e}– _{→ H}

2O2 !

CH₄ + 2 H₂O → CO₂ + 8 H+ _{+ 8 e}– _!

x 4

_!

5 CH₄ + 4 O₂ → 4 CH₃OH + 2 H₂O + CO_{2 !}

Biological Aerobic Oxidation

Mn+

H₂O SubH₂

Subox 1/2 O₂

M(n+2)+

+ 2 H+ + 2 H+

S(O) S

O

Mn+

O₂

H₂O

+ 2 H+ + 2 e

-M(n+2)+

L

N N

N N

CO₂- CO₂

-Fe

O _•+

Fe O O Fe O_Glu O_Glu

N_{His N}

His OH₂ O_Glu O O Glu Cu O O Cu N_His

N_His NHis

NN_HisHis

N_His

Oxidases

substrate oxidation and

!

dioxygen reduction occur

in

independent

steps

Oxygenases

substrate oxidation coupled

!

to

oxygen atom transfer

!

from dioxygen

!

H₂O or!

HgX

₂

& Pt(bpym)-Catalyzed Oxidation of Methane

!

A. Sen! CH₃CH₃ + O₂ + CO 5% Pd/C CH₃CO₂H + CO₂

H₂O (0.1 M HCl)

500 psi 100 psi 100 psi 2.7% yield 1138 TOs

References:_!

JACS1992, 114, 7307.! Nature1994, 368, 613.! JACS1997, 119, 6048.!

Acc. Chem. Res.1998, 31, 550.!

in situ H₂O₂!

production with!

heterogeneous catalyst!

Catalytic "monooxygenase" pathway for ethane oxidation:_!

See also:!

R. NeumannJACS2004, 126, 10236.! Methane to Methanol/Acetaldehyde!

Alternative coupled process for methane to acetic acid ("oxidase"-type reactivity): _!

Science2003, 301, 814-818._! PdSO₄, 180 °C in H₂SO₄!

H₂C CH₂ + 1/2 O₂

H₃C H O [Pd, Cu]

H₂O _{2 Cu}2+

2 Cu+

H O

CH₃

PdII

PdII

OH PdII

H+

H₂O

CH₂

CH₂

2+

+ 2 H+

+

+ H+ Pd0

1/2 O₂

CH₂ CH₂

Discovered in 1959

Wacker Process: Ethylene to Acetaldehyde

!

Organometallic Aerobic Oxidation Chemistry > 1 billion lbs/year

N O N O NO₂ NO

1/2 O₂ H₂O

e

-cathode e

-2 H+

2 2

Homogeneous "Oxidase" Reactions

O₂ + 4 H+ _{+ 4 e}- _{→ H} 2O!

2 H+ _{+ 2 e}- _{→ H2!}

O₂ + 2 H+ _{+ 2 e}- _{→ H} 2O2!

0 .0 0 ! 1 .2 3 ! 0 .6 8 !

Redox couples can facilitate oxidation reactions with O

₂

_!

•

_A!

_!

•

_B

_!

_!

Gerken & Stahl, ACS Cent. Sci., 2015, 1, 234-243. ! 2 H₂

2 H2O

cathode anode

O2 + 4 H+

e- _e

-e

-e- _e

-e

-H+

membrane 4 H+

(CH₃OH)

(CO2)

η

= 0.3 V

_!

Slow steps avoided through the use of synergistic mediators! (Also Fast)!

Fast_!

Electrochemical_! Kinetics!

Fast _! Aerobic_! Oxidation! Slow! Aerobic! Oxidation_! ! Slow! Electrochemical_! Kinetics!

Electrocatalysis provide unique opportunities to address catalyst development and characterization_!

Low Temperature, Direct Conversion of

Natural Gas to Alcohols Using Commercial

Wacker Plant Design

N₂

Low pressure Air  (O₂/N₂) Natural Gas

(CH₄+ C₂H₆+ C₃H₈)

ROH (Methanol + Ethanol + Ethylene glycol + Isopropanol + propylene glycol) Ox + HOP H₂Ox

H₂Ox + HOP ROP

H₂O

Separator  (SP) Vent STY = ~50 lbs/L.hr Hydrocarbon oxidizer (HO) Ox Regenerator (OR)

~200o_C

bubble‐column  reactors are among  the least expensive  reactors

No O2plant required

Inherently Safe

Modified, Commercial Wacker Process

New main group chemistry Enables, new low cost process Methanol Ethanol Ethylene Glycol Isopropanol Propylene Glycol Natural Gas Air

Courtesy of T.B. Gunnoe!

IO₃- _{-based C-H activation reagent/oxidant:}

Gunnoe, Groves et al. J. Am. Chem. Soc. 2014, 136, 8393₋8401!

TlIII_{, Pb}IV_{, Bi}V_{, I}III_{-based C-H activation reagent/oxidant:}

Periana, Ess et al. Science2014, 343, 1232-1237

T. Brent Gunnoe!

Radical Chain (Aerobic) Oxidation of Hydrocarbons

!

Bromine as a recyclable "chain carrier"_!

(CH

₄

, C

₂

H

₆

, …)

_!

Lorkovic, et al. !

Radical Chain (Aerobic) Oxidation of Hydrocarbons

!

Bromine as an

O

₂

-recyclable

"chain carrier"

_!

McFarland, Science, 2012, 338, 340-342. ! Alkane bromination:!

Alkyl bromide conversion !

to valuable products:!

Pt(bpym)-Catalyzed Oxidation of Methane vs. Ethane

!

Periana et al.!

Science1998, 280, 560-564._! CH4 + H2SO4 + SO3 CH3OSO3H + H2O + SO2

[Pt(bpym)X₂] 180° C

HgX

₂

& Pt(bpym)-Catalyzed Oxidation of Methane

!

CH₄ + 2 Hg(O₃SCF₃)₂ CH₃O₃SCF₃ + HO₃SCF₃ + Hg₂O₃SCF₃)₂

alternative solvents: H₂SO₄ and CF₃CO₂H

CH₄ + 2 H₂SO₄ CH₃OSO₃H + 2 H₂O + SO₂ 180 °C

100% !!

50% conversion, 85% selectivity: 43% yield

180 °C HO₃SCF₃

HgII

Periana/Catalytica, 1993_!

50% conversion, 85% selectivity: 43% yield!

90% conversion, 81% selectivity: 70% single-pass YIELD !!_! CH₄ + 2 H₂SO₄ CH₃OSO₃H + 2 H₂O + SO₂

200 °C PtII

Periana/Catalytica, 1998_!

N N

N N

PtII X

X PtII =

Periana et al. Science1993, 259, 340-343.! Periana et al. Science1998, 280, 560-564.

!

Notes!

• H₂SO₄ is the oxidant!

• the organic ligand remains stable in hot, fuming sulfuric acid! • the Pt(II) complex is thermodynamically stable!

HgX

₂

& Pt(bpym)-Catalyzed Oxidation of Methane

!

Step 1: CH₄ + 2 H₂SO₄

Step 2: CH₃OSO₃H + H₂O

Step 3: SO₂ + 1/2 O₂ + H₂O

Net Rxn: CH₄ + 1/2 O₂

CH₃OSO₃H + 2 H₂O + SO₂

CH3OH + H2SO4 H2SO4

In principle. . .

CH₃OH

multi-stage aerobic oxidation of alkanes... _!

Step 1: 2 CH₄ + 5 H₂SO₄

Step 2: CH₃CO₂SO₃H + H₂O Step 3: 4 SO₂ + 2 O₂ + 4 H₂O Net Rxn: 2 CH₄ + 2 O₂

CH₃CO₂SO₃H + 7 H₂O + 4 SO₂

CH3CO2H + H2SO4

4 H2SO4

CH₃CO₂H + 2 H₂O

Catalytica/Periana Pt(bpym) Catalyst

!

++_!! +! +! +! +_! +_! +_! +_! +! ++!! +_! +! +_! +! +_! +_! +! +_! +! +! +! +! +! +! +!_{++! !} +!+! +_! +_! +! +! +! +_! +_! +! +! +_! +_! +! +_! +_! +_! ++_!! +_! +! +_! +!++!! +_! +_! +_! ++!! +! +! +_! +_! +! +! +_! +_! +_! +_! +! " " "

10! 20! 30! 40! 50! 60! 70! 100! 80! 60! 40_! 20! 0!

0_{! 80! 90! 100!}

% One-Pass RH Conversion_!

% Pr o d u c t Se le c ti v ity ! " " " +! +! " "

 CH₃OH!

These catalysts all generate radicals

k₁ << k₂

+ OCM!

 Methane Sulfonation_!

Economic Window: k₁ >> k₂

  _ 

  _{      } 

 

   

courtesy of R. A. Periana!

R–H

R–OH

+ 1/2 O

₂

+

_n

O

₂

CO

₂

k

₁

_!

k

₂

_!

N N

N N

PtII X

X PtII =H

First-generation

Pt(bpym)-Catalyzed Oxidation of Methane vs. Ethane

!

Periana and coworkers!

J. Am. Chem. Soc.2014, 136, 10085−_10094!

CH₃–CH₃ + H₂SO₄ + SO₃ CH₃ OSO₃H HO3S OSO₃H [Pt(bpym)X₂]

CH4 + H2SO4 + SO3 CH3OSO3H + H2O + SO2

[Pt(bpym)X₂] 180° C

Gunnoe, Herring, Trewyn; J. Am. Chem. Soc. _{2016, 138, 116-125.}!

Low Temperature Electrocatalytic

Oxidation of CH

₄

OMC-4Bp-Pt-Cl_{2 Electrocatalysis provides a unique opportunity}

Oxidative C–C Coupling

_!

H

[Pd], O₂

O O O O O O N O O N O O n NH2 NH2 polyimide +

Upilex

(UBE)!

#2 polyimide resin!

!

high thermal and chemical resistance, high electrical insulating properties

and high mechanical strength!

CO2Me

CO2Me

+ MeOH [Pd], O2 MeO2C CO2Me

MeO2C CO2Me

CO2H

HO2C

HO₂C CO₂H

- H2O

O O O O O O

- H2O

[V], O2

O O O

+ H2O

- MeOH

CH₄ + CH₄ CH₃–CH₃ CH₂=CH₂ Pd/O₂ Pd/O₂

Oxidative Dehydrogenation of Saturated C–C Bonds

!

R R' _{+ H}

2O cat. PdII

+ 1/2 O₂

H H

R' R

O

₂

as the hydrogen acceptor

_!

R

R'

X

L

_n

Pd

II

H

Hydride

Elimination

β

-L

_n

Pd

II

X

₂

HX

X

L

_n

Pd

II

R

R'

H

H

R

R'

H

C–H

Activation

L

_n

Pd

L

_n

Pd

0

HX

2 HX

O

O

O

₂

H

₂

O

₂

Oxidative Dehydrogenation

!

Pd-Catalyzed Dehydrogenation of Cyclohexanones to Phenols!

Izawa, Pun, Stahl Science, 2011,333, 209.!

catalyst!

Pd(TFA)₂ /

N NMe₂

O O OH

R _{R R}

[Pd], O₂ [Pd], O2

– H2O – H2O

"Interrupted" Dehydrogenation of Cyclohexanones:_!

Diao, Stahl JACS 2011, 133, 14566.! catalyst!

Pd(DMSO)₂(TFA)_2!

O O OH

R _{R R}

[Pd], O₂ [Pd], O2

– H2O – H2O

O O

O OH

Molecular PdII_!

Species_{! Nanoparticles}Soluble Pd! _! Heterogeneous Pd_Aggregates! !

fast! moderate! inactive!

slow! moderate! inactive!

(kinetic burst)!

(induction period)!

(steady-state! turnover)!

(steady-state! turnover)!

X

_!

Non-Oxidative Hydrocarbon Conversion

!

Activation of 1° C-H bond is favored!!_! but…_!

reactions generally stoichiometric and incompatible with oxidants

or other reagents needed to functionalize the metal-alkyl_!

Labinger & Bercaw Nature 2002, 417, 507-514. ! Ir

Me₃P

H H

Ir Me₃P

H hν

– H₂

+ Ir

Me₃P

H 110 °C, 14h

1.5:1 +

for M = Rh, only 1° C–H activation

+ CH₄ Zr NR

R(H)N R(H)N

R = SiBut 3

Zr

N(H)R R(H)N

R(H)N

CH₃

Sc CH₃ + 13_CH

4 Sc 13CH3 + CH4

Oxidative Addition (Bergman, Graham, Jones, …)!

Sigma-Bond Metathesis (Bercaw, Watson, Marks, …)!

1,2-Addition (Wolczanski, Bergman, …)!

Sadow & Tilley!

A NSF Center for Chemical Innova=on CHE‐1205189  Karen I. Goldberg, University of Washington, Principal Inves=gator  www.nsfcentc.org  OO O O O OH OH OH OH OH OH O H

H3CO

O OH OH O OH O O OH O H3CO

OH OH

H3CO _OH

HO OCH3 O HO O OCH3 OH O OH H3CO O

OH OH OCH3 O O OH OCH3 O O OH OCH3 O OH OCH3 OCH3 HO O OH H3CO

HO lignin lignin CO + H₂  CO₂  cellulose hemicellulose lignin waste oil O O HO OH O OH O HO OH O OH O O O O O O R R R

CO + H

₂

n

-alkanes

Stochas(c Distribu(on  Fischer ‐

Tropsch 

GAS

FUEL (Diesel)

C

_n

X

(not useful

as

fuel) _HIGH-MW

3 9 19

Alkane Metathesis:



Diesel from Any Carbon Source

_!

Gas, Coal, Shale, Tar Sands, Biomass…

hydrocracking alkane

metathesis

n-Alkanes are ideal transportation fuel (C₁₀-C₁₉ diesel): !

  _{Burns more cleanly than oil-based fuels. Reduces CO}


emissions and particulate matter!

  _{Diesel engines 30 - 40% more efficient than} !

Alkane Methathesis via Tandem Catalysis

_!

Goldman, A. S. et al, Science, 2006, 312, 257.!

U.S. Patent 7,902,417, issued March 8, 2011!

Alan Goldman Maurice Brookhart Richard Schrock

Comparable rates ! but desired ! MW-selectivity achieved with tBu_{PCP, !}

not with tBu_{POCOP. !} (tBu_POCOP)Ir!

!

e.g. for reaction: 2 C₆ → C₁₀ + C_2!

!

PtBu₂ O O P t_Bu 2 Ir H H

Subtle catalyst variations are key:_!

PtBu₂

PtBu₂ Ir

H H

(tBu_PCP)Ir!

with!

Schrock!

catalyst_!

! or!

CHC(CH₃)₂Ph Mo

N RF₆O

RF₆O

Ar

R 2

M MH₂

dehydrogenation X Y Ir PR'₂ PR₂

M = Z

hydrogenation R

2

R R

H₃C CH₃

olefin metathesis R R Mo NAr CHR" R'O R'O Or

Re₂O₇/Al₂O₃ MoO₃/CoO/Al₂O₃ H₂C CH₂

From Ethylene and Alkanes to Aromatics

_!

Lyons, T. W. et al. J. Am. Chem. Soc. 2012, 134, 15707-15711.

Brookhart, et al. “Synthesis of para-xylene and toluene.” (2012) WO 2012061272 A2.

Maurice Brookhart (iPr)₂P Ir P(iPr)₂

Brookhart, Goldman, et al. Nature Chemistry, 2011, 3, 167-171.

(CH₂)_nH

O Pi_Pr 2 Pi_Pr

2 Ir

170 °C (CH2)nH

+ (CH₂)_nH

R R

Alan Goldman Maurice Brookhart

[Cr] Catalyst

Phillips Process

Dehydrogenation

2 H₂

major minor

Feedstock

3

catalyst

250 °C 250 °C

Pd/C or Pt/Al₂O₃

Opportunities for Homogeneous Catalysis

!

1.



Oxygen management and reactivity

_!

a.  _{Sacrificial reductant?}!

b.  _O

2-Recyclable co-oxidant (Br2, NOx, etc.)!

2.



Oxidative vs. Non-Oxidative Transformations

_!

a.  _{Reactions with ethylene (selective oligomerization)}!

b.  _{Dehydrogenative coupling, aromatization}!

c.  _{Methane as a C1 source}!

d.  _{Oxygenation reactions} !

e.  _{Oxidative C–C coupling (fundamentals, practical opportunities?)}!

f.  _{Oxidative dehydrogenation}!

3.



Broader exploration of "Extreme" conditions (homogen. catal. perspective)

_!

a.  _{Strong acid solvents}!

b.  _{"High" temperature (200 °C)}!

c.  _{Stable ligands to prevent catalyst decomp., oxidatively stable} !

!_{(previous examples: pincers, bpym)}!

4.



Electrocatalysis and other tools

_!

a.  _{A (new) tool for catalyst development and understanding}!

b.  _{Practical application opportunites? (smaller scale plants to avoid flaring)}!

5.



Funding – to reinvigorate the field

_!

a.  _{Small-team grants but programmatically interconnected – e.g., req'd participation in}

annual/bi-annual workshop/symposium!

b.  _{Active industrial engagement (consultation, funding?)}!

! !

Non-Oxidative Hydrocarbon Conversion

!

Activation of 1° C-H bond is favored!!_! but…_!

reactions generally stoichiometric and incompatible with oxidants or other reagents needed to functionalize the metal-alkyl_!

Labinger & Bercaw Nature 2002, 417, 507-514. !

Ir Me₃P

H H

Ir Me₃P

H hν

– H₂

+ Ir

Me₃P

H 110 °C, 14h

1.5:1 +

for M = Rh, only 1° C–H activation

+ CH₄ Zr NR

R(H)N R(H)N

R = SiBut 3

Zr

N(H)R R(H)N

R(H)N

CH₃

Sc CH₃ + 13_CH

4 Sc 13CH3 + CH4

Oxidative Addition (Bergman, Graham, Jones, …)!

Sigma-Bond Metathesis (Bercaw, Watson, Marks, …)!

1,2-Addition (Wolczanski, Bergman, …)!

Sadow & Tilley!

Center for Enabling New Technologies Through Catalysis 

A NSF Center for Chemical Innova=on CHE‐1205189  Karen I. Goldberg, University of Washington, Principal Inves=gator  www.nsfcentc.org  OO O O O OH OH OH OH OH OH O H

H3CO O OH OH O OH O O OH O H3CO

OH OH

H3CO _OH HO OCH3 O HO O OCH3 OH O OH H3CO O OH OH OCH3 O O OH OCH3 O O OH OCH3 O OH OCH3 OCH3 HO O OH H3CO

HO lignin lignin CO + H₂  CO₂  cellulose hemicellulose lignin waste oil O O HO OH O OH O HO OH O OH O O O O O O R R R

CO + H

₂

n

-alkanes

Stochas(c Distribu(on  Fischer ‐

Tropsch 

GAS

FUEL (Diesel)

C

_n

X

(not useful

as

fuel) _HIGH-MW

3 9 19

Alkane Metathesis:



Diesel from Any Carbon Source

_!

Gas, Coal, Shale, Tar Sands, Biomass…

hydrocracking alkane

metathesis

n-Alkanes are ideal transportation fuel (C₁₀-C₁₉ diesel): !

  _{Burns more cleanly than oil-based fuels. Reduces CO}
 emissions and particulate matter!

  _{Diesel engines 30 - 40% more efficient than} ! gasoline engines!

Alkane Methathesis via Tandem Catalysis

_!

Goldman, A. S. et al, Science, 2006, 312, 257.!

U.S. Patent 7,902,417, issued March 8, 2011!

Alan Goldman Maurice Brookhart Richard Schrock

Comparable rates ! but desired ! MW-selectivity achieved with tBu_{PCP, !}

not with tBu_{POCOP. !} (tBu_POCOP)Ir!

!

e.g. for reaction: 2 C₆ → C₁₀ + C_2!

!

PtBu₂

O

O P

t_Bu

2

Ir H H

Subtle catalyst variations are key:_!

PtBu₂

PtBu₂ Ir

H H

(tBu_PCP)Ir!

with!

Schrock!

catalyst_!

!

or!

CHC(CH₃)₂Ph Mo

N RF₆O

RF₆O

Ar

R 2

M MH₂

dehydrogenation

X

Y Ir PR'₂

PR₂

M = Z

hydrogenation R

2

R R

H₃C CH₃

olefin metathesis

R R

Mo NAr

CHR" R'O

R'O

Or

Re₂O₇/Al₂O₃ MoO₃/CoO/Al₂O₃ H₂C CH₂

From Ethylene and Alkanes to Aromatics

_!

Lyons, T. W. et al. J. Am. Chem. Soc. 2012, 134, 15707-15711.

Brookhart, et al. “Synthesis of para-xylene and toluene.” (2012) WO 2012061272 A2.

Maurice Brookhart (iPr)₂P Ir P(iPr)₂

Brookhart, Goldman, et al. Nature Chemistry, 2011, 3, 167-171.

(CH₂)_nH

O Pi_Pr 2

Pi_Pr 2

Ir

170 °C (CH2)nH

+ (CH₂)_nH

R R

Alan Goldman Maurice Brookhart

[Cr] Catalyst Phillips Process

Dehydrogenation

2 H₂

major minor

Feedstock 3

catalyst

250 °C 250 °C

Pd/C or Pt/Al₂O₃

Opportunities for Homogeneous Catalysis

!

1.



Oxygen management and reactivity

_!

a.  _{Sacrificial reductant?}! b.  _O

2-Recyclable co-oxidant (Br2, NOx, etc.)!

2.



Oxidative vs. Non-Oxidative Transformations

_!

a.  _{Reactions with ethylene (selective oligomerization)}! b.  _{Dehydrogenative coupling, aromatization}!

c.  _{Methane as a C1 source}! d.  _{Oxygenation reactions} !

e.  _{Oxidative C–C coupling (fundamentals, practical opportunities?)}! f.  _{Oxidative dehydrogenation}!

3.



Broader exploration of "Extreme" conditions (homogen. catal. perspective)

_!

a.  _{Strong acid solvents}!

b.  _{"High" temperature (200 °C)}!

c.  _{Stable ligands to prevent catalyst decomp., oxidatively stable} ! !_{(previous examples: pincers, bpym)}!

4.



Electrocatalysis and other tools

_!

a.  _{A (new) tool for catalyst development and understanding}!

b.  _{Practical application opportunites? (smaller scale plants to avoid flaring)}!

5.



Funding – to reinvigorate the field

_!

a.  _{Small-team grants but programmatically interconnected – e.g., req'd participation in} annual/bi-annual workshop/symposium!

b.  _{Active industrial engagement (consultation, funding?)}! !