Heterogeneous Catalysis in Industrial Practice

Charles N. Satterfield

2nd edition

McGraw-Hill

Chapter 1. Introduction and Basic Concepts

1.1 introduction1.1 introduction1.1 introduction1.1 introduction

1.2 industrial heterogeneous catalysts1.2 industrial heterogeneous catalysts1.2 industrial heterogeneous catalysts1.2 industrial heterogeneous catalysts

1.3 definitions1.3 definitions1.3 definitions1.3 definitions

1.3.1 catalyst1.3.1 catalyst1.3.1 catalyst1.3.1 catalyst

1.3.2 catalyst activity1.3.2 catalyst activity1.3.2 catalyst activity1.3.2 catalyst activity

1.3.3 catalyst selectivity and functionality1.3.3 catalyst selectivity and functionality1.3.3 catalyst selectivity and functionality1.3.3 catalyst selectivity and functionality

1.3.4 negative catalyst1.3.4 negative catalyst1.3.4 negative catalyst1.3.4 negative catalyst

1.3.5 1.3.5 1.3.5 1.3.5 heterohomogeneousheterohomogeneousheterohomogeneousheterohomogeneous catalystscatalystscatalystscatalysts

1.3.6 sites1.3.6 sites1.3.6 sites1.3.6 sites

1.3.7 turnover number1.3.7 turnover number1.3.7 turnover number1.3.7 turnover number

1.3.8 naming of catalysts and catalyst structures1.3.8 naming of catalysts and catalyst structures1.3.8 naming of catalysts and catalyst structures1.3.8 naming of catalysts and catalyst structures

1.3.9 catalyst deactivation1.3.9 catalyst deactivation1.3.9 catalyst deactivation1.3.9 catalyst deactivation

1.4 thermodynamics and 1.4 thermodynamics and 1.4 thermodynamics and 1.4 thermodynamics and energeticsenergeticsenergeticsenergetics

1.4.1 reaction pathways1.4.1 reaction pathways1.4.1 reaction pathways1.4.1 reaction pathways

1.5 classification and selection of catalysts1.5 classification and selection of catalysts1.5 classification and selection of catalysts1.5 classification and selection of catalysts

1.6 homogeneous catalysts 1.6 homogeneous catalysts 1.6 homogeneous catalysts 1.6 homogeneous catalysts

The origin of term “catalysis”

FriherreFriherreFriherreFriherre JJJJönsnsnsns JakobJakobJakobJakob BerzeliusBerzeliusBerzeliusBerzelius

((((20 August20 August20 August20 August 1779177917791779 – 7 August7 August7 August7 August 1848184818481848) ) ) )

Swedish chemist. He invented the modern chemical notation.He is together with John Dalton, Antoine Lavoisier, and Robert Boyle considered a father of modern chemistry.

In 1835In 1835In 1835In 1835“catalytic forcecatalytic forcecatalytic forcecatalytic force”decomposition of bodies by this forcedecomposition of bodies by this forcedecomposition of bodies by this forcedecomposition of bodies by this force

Theories on Catalysis

• The chemical approach

• The geometrical theories

• The electronic theories

Chemical approach

Paul Sabatier

a French chemist

the Nobel Prize winner in Chemistry in 1912.

SabatierSabatierSabatierSabatier reactionreactionreactionreaction

CO2 + 4H2 → CH4 + 2H2O

It regards the catalyst as a chemical intermediate that form an It regards the catalyst as a chemical intermediate that form an It regards the catalyst as a chemical intermediate that form an It regards the catalyst as a chemical intermediate that form an unstable, unstable, unstable, unstable,

surface, transitory complex with the reactantssurface, transitory complex with the reactantssurface, transitory complex with the reactantssurface, transitory complex with the reactants

Geometrical theories

AlekseiAlekseiAlekseiAleksei AleksandrovichAleksandrovichAleksandrovichAleksandrovich BalandinBalandinBalandinBalandin

Russian/Soviet chemist.

MultipletMultipletMultipletMultiplet hypothesishypothesishypothesishypothesis

Bravais lattice

• an infinite set of points generated by a set of discrete translation operations.

• there are 14 possible Bravais lattices that fill three-dimensional space.

FICP

orthorhombic

CP

monoclinic

P

triclinic

The 14 The 14 The 14 The 14 BravaisBravaisBravaisBravais latticeslatticeslatticeslatticesThe 7 Crystal The 7 Crystal The 7 Crystal The 7 Crystal systemssystemssystemssystems

FIP

cubic

A

hexagonal

P

rhombohedral(trigonal)

IP

tetragonal

Miller index

• a notation system in crystallography for planes and directions in crystal (Bravais) lattices.

Planes with different Miller indices in cubic crystals

Examples of directions

Examples of determining indices for a plane using intercepts with axes; left (111), right (221).

Miller-Bravais index

With hexagonal and rhombohedral crystal systems, it is possible to use the Bravais-Miller index which has 4 numbers (h k i l)

i = −h − k. Here h, k and l are identical to the Miller index, and i is a redundant index.

Electronic theories

Simplified diagram of the electronic band structure Simplified diagram of the electronic band structure Simplified diagram of the electronic band structure Simplified diagram of the electronic band structure

the valence bandvalence bandvalence bandvalence band is the highest range of electron energies where electrons are normally present at absolute zero.

the conduction bandconduction bandconduction bandconduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current.

Industrial Heterogeneous Catalysts

Johann Wolfgang Döbereiner

a German chemist

He worked on the use of platinum as a catalyst, and invented a lighter, known as Döbereiner's lamp.

invented in 1823

contact action

Sir Humphry Davy

a Cornish chemist and physicist.

He invented the Davy lamp and discovered the use of platinum in catalysis.

Davy lamp

It was created for use in coal mines, allowing deep seams to be mined despite the presence of methane and other flammablegases, called firedamp or minedamp.

Sulfuric acid

Lead chamber processLead chamber processLead chamber processLead chamber process

In 1746, John Roebuck began producing sulfuric acid in lead-lined chambers

The reaction2SO2 + O2 → 2SO3

is catalysed by oxides of nitrogen through the intermediate formation of HOSO2ONO. The SO3 produced is dissolved in water contained in the chamber.Concentrations ranged from 35%-40%, and after numerous refinements up to 78%.

Nitric acidThe OstwaldOstwaldOstwaldOstwald processprocessprocessprocess is chemical process for producing nitric acid, which was developed by Wilhelm Ostwald (patented 1902).

4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)

2NO(g) + O2(g) → 2NO2(g)

3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g)

4NO2(g) + O2(g) + 2H2O(l) → 4HNO3(aq)

ammoniaThe HaberHaberHaberHaber processprocessprocessprocess, also called the HaberHaberHaberHaber–Bosch processBosch processBosch processBosch process, is the reaction of

nitrogen and hydrogen, over an iron substrate, to produce ammonia

In the Haber Process, nitrogen (N2) and hydrogen (H2) gases are reacted over an iron catalyst (Fe3+) in which aluminium oxide (Al2O3) and potassium oxide (K2O) are used as promoters. The reaction is carried out under conditions of 150-250 atmospheres (atm), 450-500 °C; resulting in a yield of 10-20%:

N2(g) + 3H2(g) → 2NH3(g)

Synthetic fuelsThe FischerFischerFischerFischer----TropschTropschTropschTropsch processprocessprocessprocess is a catalyzed chemical reaction in which carbon monoxide and hydrogen are converted into liquid hydrocarbons of various forms.

(2n+1)H2 + nCO → CnH(2n+2) + nH2O

Catalyst

Friedrich Wilhelm Friedrich Wilhelm Friedrich Wilhelm Friedrich Wilhelm OstwaldOstwaldOstwaldOstwald

Catalysts can be defined as the substance

that accelerates the rate of chemical reactions

without being consumed.

He received the Nobel Prize in Chemistry in 1909 for his work on catalysis, chemical equilibria and reaction velocities.

Catalyst activity

• Space-time yield (STY):

– The quantity of product formed per unit time per unit volume of reactor

Catalyst selectivity and functionality

CCCC2222HHHH5555OHOHOHOH

CHCHCHCH3333CHO + HCHO + HCHO + HCHO + H2222

CCCC2222HHHH4444 + H+ H+ H+ H2222OOOO

CuCuCuCu

aluminaaluminaaluminaalumina

Negative catalyst

• A substance that decreases the rate of reaction

• This is usually found only when the reaction proceeds by the formation and disappearance of free redicals

Heterohomogeneous catalysis

• A catalyst may act by generating free radicals, which A catalyst may act by generating free radicals, which A catalyst may act by generating free radicals, which A catalyst may act by generating free radicals, which

desorbdesorbdesorbdesorb from the surface and initiate a chain reaction from the surface and initiate a chain reaction from the surface and initiate a chain reaction from the surface and initiate a chain reaction

in the bulk of the reacting fluidin the bulk of the reacting fluidin the bulk of the reacting fluidin the bulk of the reacting fluid

• LiquidLiquidLiquidLiquid----phase reactionphase reactionphase reactionphase reaction

• GasGasGasGas----phase reaction at high temperaturesphase reaction at high temperaturesphase reaction at high temperaturesphase reaction at high temperatures

Sites

• Where reaction takes place on the catalyst

• active center

• Structure-insensitive

– The rate is independent of the size, shape, or other physical characteristics of the metal crystallite and is proportional only to the total number of metal atoms exposed to the reactant.

• Structure-sensitive

Turnover number

• Turnover frequency

• the number of molecules that react per site per unit time

Catalyst deactivation

• Poisoning

• Fouling

• Reduction of active area by sintering or migration

• Loss of active species

Poisoning

• Catalyst poisoningCatalyst poisoningCatalyst poisoningCatalyst poisoning refers to the effect that a catalyst can be 'poisoned' if it reacts with another compound that bonds chemically(similar to an inhibitor) but does not release, or chemically alters the catalyst. This effectively reduces the usefulness of the catalyst, (i. e. the number of active sites) as it cannot participate in the reaction with which it was supposed to catalyze.

• Common poisons for these two metals are sulfur and nitrogen-heterocycles like pyridine and quinoline.

Catalyst poisoning to enhance selectivity

• In the classical "In the classical "In the classical "In the classical "RosenmundRosenmundRosenmundRosenmund reductionreductionreductionreduction" of " of " of " of acylacylacylacylchlorideschlorideschlorideschlorides to to to to aldehydesaldehydesaldehydesaldehydes, the , the , the , the palladiumpalladiumpalladiumpalladium catalyst (over catalyst (over catalyst (over catalyst (over barium sulfatebarium sulfatebarium sulfatebarium sulfate or or or or calcium carbonatecalcium carbonatecalcium carbonatecalcium carbonate) is poisoned by ) is poisoned by ) is poisoned by ) is poisoned by the addition of the addition of the addition of the addition of sulfursulfursulfursulfur or or or or quinolinequinolinequinolinequinoline. . . .

• Lindlar'sLindlar'sLindlar'sLindlar's catalystcatalystcatalystcatalyst is another example is another example is another example is another example — palladiumpalladiumpalladiumpalladiumpoisoned with poisoned with poisoned with poisoned with leadleadleadlead salts. salts. salts. salts.

RosenmundRosenmundRosenmundRosenmund reductionreductionreductionreduction

• The RosenmundRosenmundRosenmundRosenmund reductionreductionreductionreduction is a chemical reaction that reduces an acid halide to an aldehyde using hydrogen gas over palladium-on-carbon poisoned with barium sulfate

• The catalyst must be poisoned because otherwise the catalyst is too active and will reduce the acid chloride to a primary alcohol.

Lindlar catalyst

The catalyst is used for the The catalyst is used for the The catalyst is used for the The catalyst is used for the hydrogenationhydrogenationhydrogenationhydrogenation of of of of alkynesalkynesalkynesalkynes to to to to alkenesalkenesalkenesalkenes. . . .

Thermodynamics and Energetics

Classification and selection of catalysts

• Selection among known catalysts

– For known reactions

– For reactions analogous to known catalytic reactions

– For new reactions

• Search for new catalysts– For well-known catalytic reactions

– For reactions analogous to those well known

– For reactions of new types, having no analogous among well-known reactions

Homogeneous catalysts

Wacker process

• The The The The WackerWackerWackerWacker process or the Hoechstprocess or the Hoechstprocess or the Hoechstprocess or the Hoechst----WackerWackerWackerWacker process process process process (named after the chemical companies of the same (named after the chemical companies of the same (named after the chemical companies of the same (named after the chemical companies of the same name) originally referred to the oxidation of name) originally referred to the oxidation of name) originally referred to the oxidation of name) originally referred to the oxidation of ethyleneethyleneethyleneethyleneto to to to acetaldehydeacetaldehydeacetaldehydeacetaldehyde by by by by oxygenoxygenoxygenoxygen in water in the presence of in water in the presence of in water in the presence of in water in the presence of a palladium tetrachloride a palladium tetrachloride a palladium tetrachloride a palladium tetrachloride catalystcatalystcatalystcatalyst. . . .

Monsanto processMonsanto processMonsanto processMonsanto process

• The Monsanto processMonsanto processMonsanto processMonsanto process is an important method for the manufacture of acetic acid.

• This process operates at a pressure of 30-60 atm and a temperature of 150-200 °C and gives a selectivity greater than 99%.

• The Monsanto process has largely been supplanted by the Cativa process, a similar iridium-based process developed by BP Chemicals Ltd which is more economical and environmentally friendly.

HydroformylationHHHH2222 + CO + CH+ CO + CH+ CO + CH+ CO + CH3333CH=CHCH=CHCH=CHCH=CH2222 →→→→ CHCHCHCH3333CHCHCHCH2222CHCHCHCH2222CHO ("normal") CHO ("normal") CHO ("normal") CHO ("normal")

vs. vs. vs. vs.

HHHH2222 + CO + CH+ CO + CH+ CO + CH+ CO + CH3333CH=CHCH=CHCH=CHCH=CH2222 →→→→ (CH(CH(CH(CH3333))))2222CHCHO ("CHCHO ("CHCHO ("CHCHO ("isoisoisoiso") ") ") ")

HCo(CO)HCo(CO)HCo(CO)HCo(CO)4444

CoCoCoCo2222(CO)(CO)(CO)(CO)8888 + H+ H+ H+ H2222 →→→→ 2 HCo(CO)2 HCo(CO)2 HCo(CO)2 HCo(CO)4444

HRh(CO)HRh(CO)HRh(CO)HRh(CO)2222(PPh(PPh(PPh(PPh3333))))2222