Catalytic Kinetics. Chemistry and Engineering

742 Pages·2016·48.258 MB·English

by  Dmitry Yu Murzin, Tapio Salmi

CATALYTIC KINETICS
CATALYTIC KINETICS
Chemistry and Engineering
Second Edition
DMITRY YU. MURZIN AND TAPIO SALMI
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ABOUT THE AUTHORS
TapioSalmiandDmitryYu.Murzin
DMITRY YU. MURZIN
Education: 1986: MSc (Chemical Engineering) with honors, Mendeleev University of
Chemical Technology, Moscow; 1989: PhD, Karpov Physico-Chemical Institute,
Moscow; 1999: Doctor of Chemical Sciences, Karpov Physico-Chemical Institute.
Career: 1986–1992: Karpov Physico-Chemical Institute; 1992–1994: postdoctoral
experience (Universite´ Louis Pasteur, Strasbourg, France; A˚bo Akademi University,
Turku, Finland); 1995–2000: with BASF; since 2000: Professor in Chemical Technol-
ogy, A˚bo Akademi University, Turku, Finland.
Editorial board member of several journals in catalysis and chemical engineering field.
Vice-president of the European Federation of Catalysis Societies (2009–2013).
An author of textbooks (Engineering Catalysis, DeGruyter, 2013; and Chemical Reaction
Technology, DeGruyter, 2015) and author and co-author of over 650 journal articles
on kinetics and catalysis.
TAPIO SALMI
Education: 1980: MSc (Chemical Engineering), A˚bo Akademi University, Turku,
Finland; 1986: Doctor of Technology, A˚bo Akademi University.
Career: 1985 Researcher at Technical University of Denmark; 1990–1998: Associate
Professor; since 1998: Professor in Chemical Reaction Engineering, A˚bo Akademi
University, Turku, Finland; Academy Professor, Academy of Finland.
A co-author of Chemical Reaction Engineering and Reactor Technology (CRC Press, 2011)
and author and co-author of over 500 journal articles on various aspects of chemical
reaction engineering. Member of the European Federation of Chemical Engineering
Working Party on Chemical Engineering.
ix
PREFACE
Diversity of catalysts, for example, catalysis by mineral acids, complexes of transition
metals, organic molecules, enzymes, and alumosilicates, resulted in fragmentation of
thediscipline.Separatecoursesaregivenbasedontextbookscoveringseparately,despite
all similarities, homogeneous, heterogeneous, and enzymatic catalysis. More general
books on physical chemistry, while discussing some aspects of catalytic kinetics, cannot
go into details to the extent that is often needed.
Although in the chemical industry, the main focus is currently on heterogeneous
catalysis, other fields (homogeneous, enzymatic, photochemical, electrochemical
catalysis)shouldnotbeoverlooked,asveryoftentheindustrialaimistoproduceacertain
chemicalinthemostoptimalway,butnotwithaparticulartypeofcatalyst.Theindustrial
importanceofcatalysisalsodictatesanecessitytohaveabookdevotedtothefundamental
aspects of catalytic kinetics, as well as catalytic engineering and, more specifically,
transport phenomena.
Suchanintegratedapproachtokineticsandtransportphenomenaincatalysis,while
still recognizing the fundamental differences among different types of catalysis, was
applied in the first edition of this book, published in 2005.
Theauthorshavereceivedanumberofencouragingcommentsaswellascritiqueabout
whatwasmissingandsuggestionsforhowthebookcouldbeimproved.Wewerealsovery
happytolearnthatduetoapositiveresponse,Elsevierdecidedtoproceedwiththesecond
editionofthisbookoncatalytickinetics.Theauthorscarefullydiscussedthematerialtobe
includedintherevisedversion.Materialforchapters10.1–10.2,10.4,and11.3–11.6was
preparedbyTapioSalmi,whiletheremainingtextwaswrittenbyDmitryYu.Murzin,
whoalsooversawthesecondeditionandimplementationofallchanges.
Inthisedition,thecontentwasexpandedtocoverinmoredepthseveralareas,suchas
organocatalysis; enzymatic kinetics; nonlinear dynamics; solvent effects; nanokinetics
(structure sensitivity); kinetic isotope effects; and polynomial kinetics, to name a few.
In addition, a separate chapter on cascade catalysis has been written.
Each and every chapter in the second edition also contains examples and exercises,
which facilitates understanding and mastering of the underlying concepts.
Inordertostaymorefocusedonthecoreofcatalytickinetics,asectionongas-liquid
mass transfer, which was present in the first edition, was not included.
Inadditiontothesechanges,unfortunatemisprintswerecorrectedandgeneraledit-
ing of the text, introducing new figures and examples, was performed.
xi
xii Preface
Similar to the previous edition, the authors limited themselves to the main mono-
graphs, review articles, and key references without extensive coverage of original
literature.
Itisthepleasureoftheauthorstoacknowledgemanycolleaguesfromacademiaand
industry who, through the years, shared their knowledge and expertise in fundamental
andappliedaspectsofcatalytickinetics.ThelateProfessorM.I.Temkindeservesaspecial
mentionasarolemodelofanexemplarypersonandscientistfortheauthorofthesewords.
The authors hope that the second edition will beuseful for students and researchers
working in the field of catalytic kinetics.
Dmitry Yu. Murzin
Turku/A˚bo, November 2015
CHAPTER 1
Setting the Scene
1.1. HISTORY
Allprocessesoccuroveratimerangingfromfemtosecondtobillionsofyears.Thesame
holds for chemical and biochemical transformations. Kinetics (derived from the Greek
word κινητιχοζ meaning dissolution) is a science which investigates rates of processes.
Chemical kinetics is the study of reaction rates.
However complex a process is, it can be, in principle, divided into a number of
elementary processes which can be studied separately.
Chemicalkineticsemergedasabranchofphysicalchemistryinthe1880s,withsem-
inalworksofHarcourtandEssondemonstratingthedependenceofreactionratesonthe
concentrationsofreactants.ItwasGermanscientistK.Wenzelwhostatedthattheaffin-
ity of solid materials towards a solvent is inversely proportional to dissolution time.
100years after that Guldberg and Waage (Norway) formulated a law, which was later
coined the “law of mass action,” meaning that the reaction “forces” are proportional
to the product of the concentrations of the reactants.
When the rate of a certain process is measured, especially if it is of practical impor-
tance, a curious mind is always eager to know if it is possible to accelerate its velocity.
Moreover,onecouldevenimagineasituationthatforasystemdemonstratingcomplete
inertness, the introduction of a foreign substance could enhance the rate dramatically.
Conversion of starch to sugars in the presence of acids, combustion of hydrogen over
platinum, decomposition of hydrogen peroxide in alkaline and water solutions in the
presence of metals, etc., were critically summarized by Swedish scientist J.J. Berzelius
in1836,whoproposedtheexistenceofacertainbody,which“effectingthe(chemical)
changesdoesnottakepartinthereactionandremainsunalteredthroughthereaction.”
He called this unknown force catalytic force and defined catalysis as decomposition of
bodies by this force.
ThisnewconceptwasimmediatelycriticizedbyLiebig,asthisnotionwasputting
catalysis somewhat outside other chemical disciplines. A catalyst was later defined by
Ostwald as a compound, which increases the rate of a chemical reaction, but which
CatalyticKinetics ©2016ElsevierB.V.
http://dx.doi.org/10.1016/B978-0-444-63753-6.00001-4 Allrightsreserved. 1
2 CatalyticKinetics
JönsJakobBerzelius WilhelmOstwaldandSvanteArrhenius
is not consumed by the reaction. This definition allows for the possibility that small
amountsofthecatalystarelostinthereactionorthatthecatalyticactivityisslowlylost.
1.2. CATALYSIS
Already from these definitions, it is clear that there is a direct link between chemical
kineticsandcatalysis;accordingtotheverydefinitionofcatalysis,itisakineticprocess.
There are different views, however, on the interrelation between kinetics and catalysis.
Whilesomeauthorsstatethatcatalysisisapartofkinetics,otherstreatkineticsasapartof
a broader phenomenon of catalysis.
Despitethefactthatcatalysisisakineticphenomenon,therearemanyissuesincatal-
ysis which are not related to kinetics. Mechanisms of catalytic reactions, elementary
reactions, surface reactivity, adsorption of reactants on the solid surfaces, synthesis
and structure of solid materials, enzymes or organometallic complexes, not to
mention engineering aspects of catalysis, are obviously outside the scope of chemical
kinetics.
Some discrepancy exists whether chemical kinetics include also the mechanisms of
reactions.Infact,ifreactionmechanismsareincludedinthedefinitionofcatalytickinet-
ics, it will be an unnecessary generalization, as catalysis should cover mechanisms.
Catalysisisofcrucialimportanceforthechemicalindustry.Thenumberofcatalysts
applied in industry is very large, and catalysts come in many different forms, from het-
erogeneous catalysts in the form of porous solids to homogeneous catalysts dissolved in
the liquid reaction mixture to biological catalysts in the form of enzymes. Catalysis is a
multidisciplinary field requiring efforts of specialists in different fields of chemistry,
SettingtheScene 3
physicsandbiologytoworktogethertoachievethegoalssetbymankind.Knowledgeof
inorganic, organometallic, organic chemistry, materials and surface science, solid state
physics,spectroscopy,reactionengineeringandenzymologyisrequiredfortheadvance-
ments of the discipline of catalysis.
Despitethefundamentaldifferencesbetweenelementarystepsincatalyticprocesson
surfaces,therearestrikingsimilaritiesalsointermsofchemicalkineticswithenzymesor
homogeneous organometallic complexes. Although superficially it is difficult to find
somethingincommonbetweenthereactionofnitrogenandhydrogenformingammo-
niaonasurfaceofiron,D-fructose6-phosphatereactionwithATPinvolvinganenzyme
phosphofructokinaseorozonedecompositionintheatmosphereinthepresenceofNOx,
allthesetransformationsrequirethatthecatalystformsbondswiththereactingmolecules.
Suchacomplexthenreactstoproducts,leavingthecatalystunalteredandreadyfortaking
part in a next catalytic cycle.
Fig.1.1isanexampleofacatalyticreactionbetweentwomoleculesAandBwiththe
involvement of a catalyst.
In order to understand how a catalyst can accelerate a reaction, a potential energy
diagram should be considered.
Fig. 1.2 represents a concept for a non-catalytic reaction. Arrhenius suggested that
reactions should overcome a certain barrier before a reaction can proceed.
ThechangeintheGibbsfreeenergybetweenthereactantsandtheproductsΔGdoes
not change in case of a catalytic reaction; however, the catalyst provides an alternative
path for the reaction (Fig. 1.3).
ct START A
u
d
o
Pr
Reagent A
Catalyst
on to catalyst
Product
leaves
st C A
duct ataly ataly
o C s
Pr t
B
Reaction
Catalyst Reagent B
occurs on catalyst
on to catalyst
B A
Fig.1.1 Catalyticcycle.
4 CatalyticKinetics
X‡
ΔG‡
G
A + B
Δ G
reaction
P + Q
Reaction coordinate
Fig.1.2 Potentialenergydiagram.
X ‡
Uncatalyzed ΔΔG‡
cat
(the reduction
in ΔG‡ by the
catalyst)
G
Catalyzed
A + B
P + Q
A + B GP + Q
Reaction coordinate
Fig.1.3 Potentialenergydiagramforcatalyticreactions.
Ingeneral,reactionratesincreasewithincreasingtemperature.Kooijandvan’tHoff
(1893) proposed an equation for the temperature dependence of reaction rates:
k¼ATme(cid:2)Ea=RT (1.1)
where A is pre-exponential factor and activation energy, E , is related to the potential
a
energybarrier.Thisequation,whichcouldbederivedonthebasisoftransitionsatethe-
ory, in a slightly simplified form
k¼koe(cid:2)Ea=RT (1.2)