Supercritical Water: A Green Solvent: Properties and Uses

214 Pages·1.473 MB·English

by  Yizhak Marcus(auth.)

SUPERCRITICAL WATER
SUPERCRITICAL WATER
A Green Solvent: Properties
and Uses
Yizhak Marcus
Copyright(cid:2)2012byJohnWiley&Sons,Inc.Allrightsreserved
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Marcus,Y.
Supercriticalwater:agreensolvent,propertiesanduses/YizhakMarcus.
p.cm.
Includesindexes.
ISBN978-0-470-88947-3(hardback)
1. Solvents.2. Greentechnology. I.Title.
TP247.5.M2942012
541’.3482–dc23
2011049802
PrintedintheUnitedStatesofAmerica
10 9 8 7 6 5 4 3 2 1
CONTENTS
Preface ix
List ofAcronymsand Symbols xiii
1 Introduction 1
1.1 Phase Diagrams ofSingle Fluids / 1
1.2 TheCritical Point / 3
1.3 Supercritical Fluidsas Solvents / 5
1.4 Gaseous and Liquid Water / 8
1.5 Near-Critical Water / 15
1.6 Summary / 17
2 Bulk Properties ofSCW 22
2.1 Equations of State(EoS) / 22
2.1.1 PVT Data for SCW / 22
2.1.2 Classical Equations of State ofSCW / 24
2.1.3 Scaling Equations of State for SCW / 26
2.1.4 EoS ofSupercritical HeavyWater / 29
2.2 Thermophysical Properties of SCW / 30
2.2.1 Heat Capacity / 30
2.2.2 Enthalpy andEntropy / 32
2.2.3 Sound Velocity / 34
2.3 Electrical andOptical Properties / 34
2.3.1 Static RelativePermittivity / 34
2.3.2 Electrical Conductivity / 37
2.3.3 Light Refraction / 38
2.4 Transport Properties / 39
2.4.1 Viscosity / 39
2.4.2 Self-Diffusion / 41
v
vi CONTENTS
2.4.3 Thermal Conductivity / 42
2.5 Ionic Dissociation ofSCW / 44
2.6 Properties Related tothe SolventPowerofSCW / 47
2.7 Summary / 49
3 Molecular Properties of SCW 57
3.1 Diffraction Studies ofSCW Structure / 60
3.1.1 X-Ray Diffraction Studies ofSCW Structure / 61
3.1.2 NeutronDiffraction Studiesof SCW Structure / 62
3.2 Computer Simulations ofSCW / 66
3.2.1 Monte Carlo Simulations / 67
3.2.2 Molecular Dynamics Simulations / 70
3.3 Spectroscopic Studies ofSCW / 74
3.3.1 InfraredAbsorption Spectroscopy / 74
3.3.2 RamanScattering Spectroscopy / 77
3.3.3 NuclearMagneticResonance / 79
3.3.4 DielectricRelaxation Spectroscopy / 82
3.4 The Extent ofHydrogen Bonding inSCW / 83
3.5 The Dynamics ofWater MoleculesinSCW / 90
3.6 Summary / 92
4 SCW as a“Green” Solvent 100
4.1 Solutionsof Gases in SCW / 101
4.1.1 Phase Equilibria / 101
4.1.2 Interactions inthe Solutions / 104
4.2 Solutionsof OrganicSubstances inSCW / 106
4.2.1 Phase Equilibria / 106
4.2.2 Interactions inthe Solutions / 111
4.3 Solutionsof Salts and Ions in SCW / 115
4.3.1 Solubilities ofSalts andElectrolytes / 115
4.3.2 Thermodynamic Properties / 121
4.3.3 Transport Properties / 123
4.3.4 IonAssociation inSCW / 129
4.3.5 IonHydration in SCW / 134
4.4 Binary Mixtures of Cosolventswith SCW / 138
4.5 Summary / 141
5 Applications ofSCW 151
5.1 ConversionofOrganic Substancesto Fuel / 152
5.1.1 ConversiontoHydrogen and Natural Gas / 152
5.1.2 ConversiontoLiquid Fuel / 156
5.2 Supercritical Water Oxidation / 157
CONTENTS vii
5.2.1 General Aspects ofSCWOProcess / 158
5.2.2 Examplesof SCWOApplications / 160
5.3 Uses of SCWinOrganicSynthesis / 162
5.4 Uses in PowderTechnologyof Inorganic Substances / 164
5.5 Geothermal Aspects ofSCW / 166
5.6 Application ofSCWinNuclear Reactors / 169
5.7 Corrosion Problems with SCW / 171
5.8 Summary / 174
Author Index 183
Subject Index 199
PREFACE
As of the summer 2011, therewere more than 3000 topics dealing in detail
withsupercriticalwater(SCW)intheSciFinderliteraturesearchinstrumentof
the American Chemical Society. However, there were more than 14,000
entriesoutliningthisconcept.Inthe1980ssome100papersandinthe1990s
some900papersonsupercriticalwaterwerepublished,whileatpresentthere
are already more than 2000 papers. As it is impossible to compile all the
published information in a book, an attempt has been made to include the
maximum possible important properties and uses of supercritical water.
Factual information is given in numerous tables along with suggested
references for more details on the subject. Where appropriate, the reader is
referred to several reviews relevant to the topics included in this book.
Priorto1980,onlyafewdozenpapersdealtwithSCW,consideringSCW
mainly within the broad subject of high-pressure steam in the context of
electricpowergeneration.Thepapersdealtprincipallywiththeheattransfer
inSCW,mineralsolubilitiesinit,andcorrosionbyit.E.U.Franck,apioneer
in the study of supercritical fluids, however, published in 1968 a review
(Endeavour,22,55)thathighlightedsomeofthepropertiesofthisfluidandits
possibleuses.Thepropertiescontrastedwiththoseofwatervaporandofthe
liquidwateratambientcondition.Theyincludedthecompletemiscibilityof
SCW with nonpolar fluids, the very high mobility of ions from electrolytes
dissolved in SCW, and the water itself acquiring appreciable electrical
conductivity.Knowledgeofthechemicalbehaviorofhigh-temperaturewater,
inthepurestateandwhenservingasasolvent,ledtotheunderstandingofthe
structuralfeaturesofSCWandofhydrationphenomenainit.Thepropertiesof
geochemically important “hydrothermal” solutions could also be explained
and possible technical applications were suggested.
Thepropertiesofdensesteamorcompressedhotwaterbelowthecritical
pointandsolutionsinsuchmediacanbeofinterest,astheseareabletoactas
“green” solvents. In the present book, the so-called near-critical water is
howeveronlycursorilydealtwith,asitismainlydevotedtothepropertiesand
ix
x PREFACE
usesofsupercriticalwater.SCWinitselfcanalsobedeemedtobea“green”
solvent, that is, environment-friendly.
Havingdealtformanyyearswithliquidsandsolutions,theauthor’sinterest
in SCW was raised by the proposal he received in the late 1990s from the
INTAS agency for his participation in an international collaboration on this
subject.Duringtheperiodof3yearsoftheprojectthatinvolvedthreegroups
from Russia, one from Greece, one from Germany, and the present author,
“experimentalandtheoreticalstudiesofsupercriticalaqueoussolutionsasa
mediumfornewenvironmentallyfriendlyandenergyefficienttechnologiesof
pollutioncontrol” were carried out. Asa further result of this collaboration,
one of the participants, A. Kalinichev, was invited together with the present
authorbyR.Ludwig,theeditorofthebookWater:FromHydrogenBonding
toDynamicsandStructure,towriteachapteronSCWforit.Thisprovidedthe
initialimpetustothewritingofthepresentbook,seeingthatnoneexistedsofar
thatsummarizedthestateoftheartandinviewoftheincreasinginterestinthe
subject as reflected by the increasing number of published papers.
The book is divided into five chapters. Chapter 1 introduces supercritical
fluidsintermsofthephasediagramsofthefluidsandtheircriticalpoints.A
brief description of a variety of supercritical fluids that have been used as
solvents is given. Attention is then turned toward thewater substance, in its
gaseousstate(watervapor)andordinaryliquidwaterandtheirproperties.As
waterisheatedtowardthecriticalpoint,near-criticalwaterisreached,anda
shortdiscussionofthisstateofwater(thathasfoundsomeapplicationsasa
“green”solvent)ispresented.Chapter2dealswiththemacroscopicmeasur-
able properties. Foremost of these are the temperature–pressure–density or
volume(PVT)relationshipsdescribedbymeansofequationsofstate.Other
important thermophysical properties of SCWare the heat capacity and the
enthalpyandentropy.Theelectricalandopticalpropertiesincludethestatic
dielectricconstant,thelightrefraction,andtheelectricalconductivityofneat
SCW.Thetransportpropertiesinvolvetheviscosity,theself-diffusion,andthe
thermal conductivity. The ionic dissociation of SCWis then discussed, and
finally the properties of SCW relevant to the solubility of solutes in it are
brieflydescribed.Chapter3dealswiththestructureanddynamicsasinferred
fromexperimentaldataandcomputersimulations.DiffractionofX-raysand
in particular of neutrons provides information on the molecular structure of
SCW.Computersimulationsprovideinformationonboththestructure(bythe
Monte Carlo method) and the dynamics (the molecular dynamics method).
Spectroscopic studies, involving infrared light absorption, Raman light
scattering,nuclearmagneticresonance,anddielectricrelaxation,complement
theaforementionedstudies.Itis shownthat SCWhasappreciablehydrogen
bondingbetweenitsmoleculesandtheextentofthisisexplored.Finally,the
dynamics of the water molecules in SCW and the lifetime of various
PREFACE xi
configurationsinitarediscussed.Chapter4describesthesolubilitiesofgases,
organic substances, salts, and ions in SCW in terms of the relevant phase
equilibria.Theinteractionsthattakeplacebetweenthewatermoleculesand
thesolutesofthevariouscategoriesarepresented.Inparticular,forionsand
salts, the properties of such solutions are dealt with. In case of ions, their
associationontheonehandandtheirhydrationontheotherdeterminethese
properties.Finally,Chapter5includesthecurrentpracticaluses,whetherona
modestoronafullindustrialscale.Conversionofbiomasstofuel,gaseousor
liquid,isonesuchuse.SCWoxidation(SCWO)ofpollutantsandhazardous
materialsisanotherimportantuse,theproblemsassociatedwithwhichhave
not so far been completely resolved. Some other uses include organic
synthesis,whereSCWisbothareactionmediumandareactant,nanoparticle
production of inorganic substances (mainly oxides), and as a neutron mod-
eratorinnuclearpowerreactorsandatthesametimeasthecoolant,providing
thefluidforturbineoperation.GeochemistryisanotherfieldwhereSCWplays
arole,becausedeepstrataintheearth’scrustprovidethehightemperatureand
pressuretoconvertanywaterderivedfromhydrousmineralstoSCW.Thisis
then evolved inthermalvents, carryingalongsomemineralsdissolved init.
Finally,someofthecorrosionproblemsmetwithinapplicationsofSCWare
briefly dealt with.
Avast amount of information is available on SCWand solutions therein;
thisbookhoweverprovidesthosenumericaldataintablesthathelpthereader
toappreciatethequantitativeaspectsofSCWanditsproperties.Someother
tablesincludeannotatedexamplesoftheusesofSCW,butonthewhole,itis
possibleonlytopointoutwhatvariousauthorshavestudied,tosummarizeit,
andasnecessarytocommentonthis.Thisbookincludesreferencestowhich
the readers interested in having in-depth knowledge of the topics may refer.
It is hoped that the book will help understand the concept of supercritical
water, its properties, and uses.
YIZHAK MARCUS
Jerusalem,2011
LIST OF ACRONYMS
AND SYMBOLS
ACRONYMS
EoS Equation of states
MC Monte Carlo computer simulation
MD Molecular dynamics computer simulation
PVT Pressure–volume–temperature
SAFT Statistical associated fluid theory
SCD Supercritical carbon dioxide
SCF Supercritical fluid
SCW Supercritical water
SCWG Supercritical water gasification
SCWO Supercritical water oxidation
VLE Vapor/liquid equilibrium
SYMBOLS
Symbol Description Units
Universalconstants
e Unit electrical charge:1.602177(cid:2)10(cid:3)19 C
F Faraday’s constant:9.64853(cid:2)104 Cmol(cid:3)1
k Boltzmann’s constant:1.380658(cid:2)10(cid:3)23 JK(cid:3)1
B
N Avogadro’s number: 6.022136(cid:2)1023 mol(cid:3)1
A
R Gas constant:8.31451 JK(cid:3)1mol(cid:3)1
e Permittivityof vacuum: 8.854188(cid:2)10(cid:3)12 C2J(cid:3)1m(cid:3)1
0
Physical quantities
A Helmholtz energy,molar kJmol(cid:3)1
a Attractiveparameter inEoS J2 Pa(cid:3)1mol(cid:3)2
B Virial coefficient m3
xiii