Structure and Performance of Selective Hydrogenation Catalysts 

C. Martin LokCatalok Consultancy

Topsoe Catalysis Forum, August 27‐28, 2015

Main MessageCatalysts for Petrochemicals

• Choice of main metal extremely critical

• Ìn many reactions (multple) promoters are essential

• Most existing catalysts have been optimized in the traditional way. Few promoter combinations have been studied in a wideconcentration range, if at all. Few ternary and quarternary metal systems have been explored.

• Now– Better understanding allows a more judcious selection of promoters– High‐throughput screening will accelerate the development of new and 

improved catalysts. Many combination of promoters can be studied – Modelling becomes more predictive

Jacques Coenen:“Catalyst preparation is like tightrope walking: one wrong step and there is a steep drop”

Murray Raney:"It is in the preparation of catalysts that the chemist is most likely to employ alchemical methods. The work should be approached with humility and supplication and the production of a good catalyst received with rejoicing and thanksgiving.” 

CitationsCitations

Outline of Talk

• Reactions• Main metals• Promoters/additives• Examples• Modern research in selective hydrogenation

Selective HydrogenationSome Reaction Types

• One or more C=C double bonds in dienes and polyenes

• Acetylenes to olefins

• C=C‐C=O,  either C=C or C=O hydrogenation

• Nitriles to primary, secondary or tertiary amines

• Benzene to cyclohexane, minimize byproducts

• Syngas to methanol, olefins

Choice of MetalActivity and Selectivity Ranking Depends on Application

• Activity– Often pgms > Ni > Co > Cu

• Selectivity– Often pgms < Ni < Co < Cu

• Costs – Pt > Rh > Pd > Ru > Co > Ni > Cu

Ranking may change by additionof promoters

Choice of MetalActivity and Selectivity Ranking Depends on Application

• Activity– Often pgms > Ni > Co > Cu                                                                                           

• Selectivity– Often pgms < Ni < Co < Cu

• Cost– Pt>Rh>Pd>Ru>Co>Ni>Cu

World production (tpa)

Price (US $/kg)

nickel 1,600,000 10

cobalt 61,000 29

copper 20,000,000 5

ruthenium 20 1,400

platinum 180 33,000

palladium 202 20,000

rhodium 30 27,000

Choice of MetalActivity and Selectivity Ranking Depends on Application

• Activity– Often pgm>Ni>Co>Cu

• Selectivity– Often pgms < Ni < Co < Cu

• Cost– Pt > Rh > Pd>Ru>Co>Ni>Cu

• Loading pgms (0.1‐5 wt%) typically much lower than for base metals (5‐90 wt%)• Pgms can be recycled 

World production (tpa)

Price (US $/kg)

nickel 1,600,000 10

cobalt 61,000 29

copper 20,000,000 5

ruthenium 20 1,400

platinum 180 33,000

palladium 202 20,000

rhodium 30 27,000

Choice of Main Metal• Nickel

– Poly‐olefins to mono‐olefins, cis‐trans isomerization, double bond migration– Full saturation (white oil)– Nitriles to amines

• Copper– Syngas to methanol– Carboxylic acids/acids to saturated alcohols (200 bar, 250 C)– Aldehydes to alcohols

• Cobalt– Nitriles to primary amines

• Iron– Syngas to olefins, alcohols, alkanes– Dinitriles to diamines (HMDA)

• Palladium – Acetylenes to ethylenes

Choice of Main Metal• Nickel (Mg, S, K)

– Poly‐olefins to mono‐olefins, cis‐trans isomerization– Full saturation (white oil)– Nitriles to amines

• Copper (Cr) – Syngas to methanol– Carboxylic acids/acids to saturated alcohols (200 bar, 250 C)– Aldehydes to alcohols

• Cobalt (Mn, Re, Pt, Ru)– Nitriles to primary amines

• Iron (Cu, K)– Syngas to olefins, alcohols, alkanes– Dinitriles to diamines (HMDA)

• Palladium (Re, Pb)– Acetylenes to ethylenes

Often these catalystscontain promoters

Promoters

A promoter is an additive which itself is mostly inactive butwhich improves the activity/selectivity and/or stability and/orprocessability of the metallic catalyst

– Electronic: Sn/Pt (alloy)

– Structural/textural: Mg/Ni (improves Ni surface area)

– Process: Cu/Ni, Cu/Fe, Pt/Co, Ru/Co (reduction promoters)

Wikipedia: The effect of a catalyst may vary due to the presence of other substances known as inhibitorsor poisons (which reduce the catalytic activity) orpromoters (which increase the activity) (I?)

Olefins Value Chain

SteamCracking of LPG, naphtha, gas oil

acetylene

methylacetylene

ethyleneethylene

propylenepropadiene

C4 acetylenes butadienebutadiene butene

pyrolysis gasoline aromatics

Overhydrogenation to saturates should be preventedModified after Johnson Matthey brochure

Acetylene Conversion

• Acetylene poisons ethylene polymerization catalyst• Requirement: <1 ppm acetylene in ethylene

• Avoid saturation to alkane, temperature runaway

• Activity ranking: Pd>Pt>Ni, Rh>Co>Fe>Cu>Ru

• Pd most selective

• Catalysts: Ag/Pd or eggshell 0.015‐0.05% Pd/alumina

• Other promoters: Pb, Cu, Rh, Zn, Cr, V, K, Ce,………..

• Ternary systems: Cu2.75Ni0.25Fe 

Winterbottom (1981)Bailey, King (2001)Sorbier et al. (2012)Handbook of Commercial Catalysts (2000)Bailey et al. US2006217579 to Johnson MattheyBridier 2012

Acetylene >ethylene ‐42kcal/moleethylene ‐> ethane ‐33 kcal/mole

90

95

100

0 50 100

Surface area (m2/g)

Ethylene yield (%)

200 ‐ 400 μm thick palladium crust and a totalpalladium amount of about 0.3 to 0.5 wt%

Lindlar: Pd/Pb on CaCO3:Cis‐hydrogenation

Selectivity by “Poisoning”

• Inactivation of sites– Promoter is chemisorbed onto sites active for unwanted reactions

• Influences adsorption of reactants

• Ensemble control– Promoter reduces ensemble size

Promotion of Nickel by Partial Sulphur Poisoning

• Suppresses monoene hydrogenation– but promotes cis‐trans isomerization

• Saturation concentration– 0.4‐ 0.5 sulphur atom per surface nickel atom

• Fully S saturated Ni catalyst inactive– becomes gradually active under sulphur‐free hydrogen– to maintain selectivity feed should contain some sulphur

Lok, Catalysis,  course manual, University of  Liverpool, 1996

Pyrolysis Gasoline (Pygas) Hydrogenation

• Hydrogenated pygas contains olefins and aromatics– High octane gasoline– Source of aromatics

• Hydrogenation– Removes polyenes– Improves colour and gum content in gasoline– Reduces fouling in downstream hydrotreating

• Industrial catalysts– Pd‐on‐alumina

• Cleaner feeds– Sulphided Ni‐on‐alumina

• Order of magnitude higher tolerance for heavy metals and sulphur than Pd‐catalysts

Promotion by Sulphur:Pyrolysis Gasoline Hydrogenation

0

20

40

60

80

100

120

feed Ni

Polyenemonoenearomaticsaturated

Lok, Catalysis,  course manual, University of  Liverpool, 1996

Nickel Catalysed Pyrolysis Gasoline Hydrogenation

0

20

40

60

80

100

120

feed Ni

Polyenemonoenearomaticsaturated

Highly exothermic: temperaturerunaway (750 C): risk of explosion(pre)sulphiding required(Goossens et al. 1997)

Lok, Catalysis,  course manual, University of  Liverpool, 1996

Nickel Catalysed Pyrolysis Gasoline HydrogenationPromotion by Sulphur

0

20

40

60

80

100

120

feed Ni Ni S promoted

Polyenemonoenearomaticsaturated

Lok, Catalysis,  course manual, University of  Liverpool, 1996

Adding Sn has a similar effect US2011166398 (A1) ― 2011‐07‐07 to IFP 

Phenylacetylene Hydrogenation

• C8 cut from steam cracking: mostly styrene and up to 1% phenylacetylene

• Styrene spec: < 300 ppm phenylacetylene

• Catalysts– Presulphided nickel, mostly for high‐sulphur and high contaminant

feeds– Palladium, higher selectivity in cleaner feeds

Ensemble Control by SulphurBenzene to Cyclohexane

Undesired byproducts: linear alkanes, methylcyclopentane

Ensemble size– Hydrogenation: 3‐4 Ni surface atoms– Hydrogenolysis to linear alkanes: 15‐22 Ni surface atoms

Low dosage of S– Selectivity to cyclohexane increases to 100%– Breaks up nickel surface in smaller ensembles

Martin (1988)Rekker et al. US5856603 (1994) to Engelhard

Sulphiding Procedures1. Reduction of the oxidic catalyst followed by sulphiding

2. Simultaneous reduction and sulphiding of the oxidic catalyst

3. Sulphiding of the oxidic catalyst followed by reduction

Sulphiding agents:  H2S, DMDS, polysulphides, etc.

B. W. Hoffer et al. Fuel 83 (2004) 1‐8B. W. Hoffer et al. J. Catalysis 209 (2002) 245‐255

Sulphiding Procedures

• TPR studies showed thatpresulphided oxidic catalystscan be reduced at a lowertemperature than the originalnon‐sulphided catalyst

B. W. Hoffer et al. Fuel 83 (2004) 1‐8B. W. Hoffer et al. J. Catalysis 209 (2002) 245‐255

• No significant difference in nickel surface area orhydrogenation activity

Nitrile Hydrogenation to Primary Amines

• Secondary and tertiary amines as byproducts suppressed by NH3

• Co much more selective than Ni; Sponge Ni more selective than supported Ni

• Promotion of Ni and Co with bases– Ca, Mg, Na, K, improves selectivity

• Adiponitrile to hexamethylenediamine (HMDA), high pressure– Co/Cu – fused iron catalyst with a range of promoters: Fe 72, Mn 0.17, Al 0.08, Ca 0.03, Mg 0.05, Si 0.12, Ti 0.01

Borninkhof et al. Patent US5571943, to EngelhardAnsmann et al. Patent DE 10151558, 2003 to BASF

Carbonyl Hydrogenationaldehydes to alcohols

• Primary gas phase hydrogenation mostly with copper catalysts (nickel toounselective)

• Trickle‐bed polishing with nickel to reduce carbonyl number

• Sodium promotion increases selectivity in nickel catalysed hydrogenationof butanal

Nickel catalyst No Na 1wt% Na

butanol 98.9 99.9

acetal 0.3 0

2‐ethylhexanol 0.1 0

dibutylether 0.1 0

Deckers et al., US Patent 5498587 to Hoechst

Unsaturated Carbonyl HydrogenationC=C or C=O 

• The chemoselective hydrogenation to desired unsatd. alcs. is difficult to achieve as the hydrogenation of the C=C bond is thermodynamically preferred over C=O bond

• Acrolein hydrogenation over Pt: > 99% C=C and only <1% C=O hydrogenation

• Over Pt the selectivity to unsaturated alcohols is greatly improved by alloying with Sn, Zn or Fe

– The adsorption modes favourable to the C=C hydrogenation are inhibited– Polarization of the C=O bond– Change in metal dispersion– Sn+ species promoting attack of C=O by hydrogen – Combinations thereof

• In addition, selectivity is improved by various promoters at the Pt surface like K

• Further improvements: process conditions (high T), Pt crystallite size and use of Au and Ag

Maki‐Arvela et al. (2005)Gallezot et al. (1994, 1998)Chen et al. (2005)

Selectivitycrotonaldehyde ‐> crotylalcoholPt/SiO2:  0% Pt‐Sn/SiO2: 78%

Unsaturated Carbonyl Hydrogenationto unsaturated alcohol 

Mebi et al. 2007

Important reactions• Acrolein ‐> allylalcohol

• Crotonaldehyde ‐> crotyl alcohol

• Cinnamonaldehyde ‐> cinnamylalcohol

• Citral ‐> geraniol

Selectivity can be tuned by additives

Hydrogenation of 5‐Ethoxyfurfural ring (1→2) or C=O (1→3), parameter space

The full factorial combination of these parameter results in 576 combinations which were all testedusing high‐throughput techniques

Ras et al. Top. Catal. 53 (2010) 1202.

Hydrogenation of 5‐EthoxyfurfuralRing vs. carbonyl hydrogenation

Ni–Sn‐based alloy catalystsaldehydes to alcohols

• High selectivity to exclusively unsaturatedalcohols. 

• Both the Ni3Sn2 and Ni3Sn alloy phases were found to be responsible for the enhancement of the chemoselectivity. 

• Reusable without anysignificant loss of selectivity.

Rodiansono (2012)

Glycerol Hydrogenation1,3‐ vs. 1,2‐propanediol

Nakagawa et al. (2014)

Glycerol Hydrogenation1,3‐ vs. 1,2‐propanediol

Nakagawa et al. (2014)

Main product

Glycerol to 1,3‐propanediol1,3‐ vs. 1,2‐propanediol

• Key is to quickly hydrogenate 3‐hydroxypropanol before interconversionto more stable acetol

• Polyoxometalates, WOx clusters and Re may stabilise cationic intermediates

• Re/Ir: 70% selectivity to 1,3‐propanediol declining at higher conversion

Nakagawa et al. (2010)

Methanol from CO2 using a NiGa Catalyst

A NiGa catalyst has been discoveredthrough a descriptor‐basedcomputational analysis, and has been shown experimentally to beparticularly active and selective.Studt et al. compared the copper‐zinc‐aluminum catalyst withthousands of other materials in the database. 

The most promising candidate turnedout to be a nickel‐gallium. At high temperatures, nickel‐galliumproduced more methanol than the conventional copper‐zinc‐aluminumcatalyst, and considerably less of the carbon monoxide byproduct.

Studt et al. Nature Chemistry 6 (2014) 320

Turnover frequency (TOF) is plotted as a function of ΔEO, relative to Cu(211).

Ni: darkGa: lightO: red

Catalytic Reaction Guide App

Always useful to check:

The Catalytic Reaction Guide is a free mobile application designed to provide mobile access to catalyst recommendations on over 150 reactions in the area of homogeneous, heterogeneous and asymmetriccatalysis. 

Designed for iPhone and iPad (rated 4.5 based on 19 ratings)

Some emphasis on fine chemicals and pgm catalysts

Available via the web

Conclusions• Choice of main metal extremely critical

• Ìn many reactions (multple) promoters are essential

• Most existing catalysts have been optimized in the traditional way. Few promoter combinations have been studied in a wide concentration range, if at all. Few ternary and quarternary metal systems have been explored.

• Now– Better understanding allows a more judcious selection of promoters– High‐throughput screening will accelerate the development of new and 

improved catalysts. Many combination of promoters can be studied – Modelling becomes more predictive

Thank you for your attention