Homogeneous vs. heterogeneous catalysis · PDF fileHomogeneous vs. heterogeneous catalysis...

Leibniz-Institut für Katalyse e.V.an der Universität Rostock

Homogeneous vs. heterogeneouscatalysis

Dr. habil. Marko Hapke

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Homogeneous vs. heterogeneous catalysis July 2, 2015


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HeterogeneousCatalysis

HomogeneousCatalysis

Biocatalysis

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Catalyst and reactant(s) are in the same phase.

Catalyst and reactant(s) are in different phases.

Definitions

General features:

Different reaction phases possible: „classic“ gas/solid; liquid/solid or liquid/liquid systems.

High industrial relevance (about 85% of all catalytic processes are heterogeneouslycatalysed).

In general wide range of operating conditions(high temperatures/pressures).

Specialised set of analytic methods required(e.g. X-ray methods, Operando spectros.).

Major advantage: Ease of separation ofreactants/products/catalysts.

General features:

Liquid phase reactions dominate the field. Industrially less relevant; but complex orga-

nic or asymmetric transformations possible! Reaction conditions milder than required for

heterogeneous reactions (-78 °C - ~200 °C). Investigation of reactions by spectroscopic

methods (NMR, MS, IR, UV-Vis) directly in solution possible.

Fine-tuning of catalyst properties usingdifferent ligands/additives easy possible.

Major challenge: Separation of productsand catalysts/additives.

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Mechanism:

reactants

products

reactor

catalyst support

active site

substrate

adsorption

reaction desorption

bed ofcatalyst particles

porous carrier (catalyst support)

product

catalyst surface

substrateA

substrateB

productC

catalyst surface

B

A

C

Technical setup:

Langmuir-Hinshelwood Eley-Rideal

Source: Gadi Rothenberg, Catalysis – Concepts and Green Applications, Wiley-VCH, 2008

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Major industrial processes usingheterogeneous catalysis

Process Catalyst Reactants Products Application

Haber-Bosch process Magnetite (Fe) H2, N2 NH3 Fertiliser, explosives

Methanol synthesis Cu/ZnO/Al2O3 CO, CO2, H2 Methanol Bulk chemicals, fuel

Fischer-Tropsch process Co, Fe Coal, natural gas C5-C11 hydrocarbons Automotive fuel

Cracking Clays Long alkanes, C12+ C7-C9 alkanes Fuel, detergents

Alkylation Zeolites, Clays, Silicates

C3-C5 alkanes C7-C9 isoalkanes High-octane fuel

Dehydrogenation/Reforming

Pt/Al2O3 Alkanes Alkenes Polymers, bulkchemicals

Polymerisation Ti, Ziegler-Natta Ethylene Polyethylene Polymers

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Major industrial processes usingheterogeneous catalysis

catalytic converter

ceramicmonolith

1 mm 1 m

-aluminawashcoat

Pt/Pd/Rh catalyst

CO + 1/2O2 CO2Pt, Pd

HC's + O2 CO2 + H2OPt, Pd

CO + NO CO2 + 1/2N2

H2 + NO H2O + 1/2N2

Rh

Rh

An example from daily life: the three-way catalyst

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Source: Gadi Rothenberg, Catalysis – Concepts and Green Applications, Wiley-VCH, 2008

RhCOH

LL

CO

H2

aqueous phase

organic phase

reactants

productsaqueous phase recycle

The Ruhrchemie/Rhône-Poulenc Hydroformylation(the oxo process)

Setup:

P

SO3Na

SO3Na

NaO3S

Ligand L is "tppts":

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Solvent

Substrates

Additives

Precatalyst

h

Reactionmixture

General procedure:

Mechanism forPd-cataysedreactions – cross-coupling andcarbonylation:

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Major industrial processes usinghomogeneous catalysis

The Shell Higher Olefins Process(SHOP)Oligomerization of ethen to medium and long-chain -olefins (C4-C20)Catalysts: Ni(II)-complexes

The Wacker Oxidation ProcessOxidation of olefins to carbonyl compoundsCatalyst system: Pd(II)- and Cu(I)-salts, oxygen

The DuPont Adiponitril SynthesisHydrocyanation of butadiene tohexanedinitrileCatalyst system: Ni(0)-complexes

The Ciba-Geigy Metolachlor ProcessEnantioselective Hydrogenation of an imineCatalyst system: Josiphos-Ir complexes

The Monsanto process /Cativa ProcessAcetic acidCatalyst system: Rh / Ir complexes

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IrI

I CO

CO

IrI

I CO

CO

CH3

IrI

I CO

CO

CH3

CO

IrI

I CO

CO

O CH3

CH3I

I

CO

I

O Me

I

H2OCH3COOH

Reactionmechanism


The Cativa process: Synthesis of acetic acid

Source: http://www.catalysis-ed.org.uk/ethacid/ethacid9.htm

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Gadi Rothenberg, Catalysis – Concepts and Green Applications, Wiley-VCH, 2008

Interplay: homogeneous and heterogeneous catalysis

Traditionalsynthesis

BHC process



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Biocatalysis

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Merging the advantages of different types of catalysis – here:enzymatic and transition metal catalysis

Final example: Artificial metalloenzymes

Highlight: M. Hapke, C. C. Tzschucke, Angew. Chem. 2013, 52, 3317

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Manuskript der Vorlesung unter:

http://www.catalysis.de/Cycloadditionen.42.0.html

Homogeneous vs. heterogeneous catalysis · PDF fileHomogeneous vs. heterogeneous catalysis...

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