introduction of heterogeneous catalysis
TRANSCRIPT
低温等离子体在催化过程中的应用和机理研究
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Project Training Workshop – Catalyst Characterisation
Introduction of Heterogeneous Catalysis and Characterisations
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Shaojun xu
School of Chemistry, Cardiff University
UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Labs
Email: : [email protected]
Bioenergy – Carbon capture and utilisation – Energy Storage
EU RISE – BIOMASS-CCU
Marie Skłodowska-Curie Actions
Harwell Science and Innovation Campus
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UK Catalysis Hub
Diamond Light Source
Contents
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1. Introduction of Heterogeneous Catalysis
2. Kinetics of Heterogeneous Catalysis
3. Preparation of Heterogeneous catalysts
4. Characterisations of Catalysis
Bioenergy – Carbon capture and utilisation – Energy Storage
EU RISE – BIOMASS-CCU
Marie Skłodowska-Curie Actions
1. Introduction of Heterogeneous Catalysis
a phenomenon in which a small quantity of a substance (the catalyst) increases the rate of a chemical reaction without being consumed
What is Catalysis?
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Catalysis is a cycle of elementary steps
(at least three); catalytic sites are
regenerated
M. Shahinuzzaman et al. Renewable and Sustainable Energy Reviews 77 (2017) 1375–1384
1. Introduction of Heterogeneous Catalysis
Reactants: gas / liquid phaseCatalyst: molecule
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1. Introduction of Heterogeneous Catalysis
Heterogeneous Catalysis?
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Reactants: gas / liquid phaseCatalyst: solid
The reaction inside the catalytic particle1. Transport of reactants (A, B, …) from the
fluid bulk to the catalyst surface2. Transport of reactants inside catalyst pores3. Adsorption or reactants to the catalytic site4. Surface reaction among molecules or
atoms adsorbed5. Desorption of products (R, S, . )6. Transport of products from pores to the
catalyst surface7. Transport of products from the catalyst
surface to the fluid bulk
Froment, G. F.; Bischoff, K. B.; De Wilde, J., Chemical reactor analysis and design. Wiley New York: 1990; Vol. 2.
Unsupported/supported catalystnanometer particles + support
Typical heterogeneous catalytic process
Why is the catalytic reaction faster?
1. Introduction of Heterogeneous Catalysis
Svante Arrhenius
1859 - 1927
Nobel Prize 1903
Energy barrier of the catalytic route much lower
Activation energy lowerReaction temperature lower
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Arrhenius Equation
How to translate the catalysis into kinetics?
2. Kinetics of Heterogeneous Catalysis
Surface concentration of adsorbed species
↕Gas phase pressure
The adsorption isotherm: a curve of the amount of adsorbed molecules to the adsorbent surface as a function of the partial pressure or concentration of the adsorbate at a constant temperature.
Monolayer Multilayer
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Langmuir adsorption isotherm
2. Kinetics of Heterogeneous Catalysis
Assumption:
➢ A fixed number of surface sites➢ Sites are either occupied or empty➢ All sites are equivalent➢ Adsorbates do not interact➢ Molecules and atoms adsorb on these sites
A: gas phase molecules,
S: vacant surface sites,SA: occupied surface sites,
Irving Langmuir 1881 - 1957
Nobel Prize 1932
An equilibrium constant, K:
Fraction occupied θA (0 < θ < 1)
𝐾 =𝜃
1 − 𝜃 𝑃
𝜃 =𝐾𝑃
1 + 𝐾𝑃9
Langmuir adsorption isotherm
2. Kinetics of Heterogeneous Catalysis
𝐾 =𝜃
1 − 𝜃 𝑃𝜃 =
𝐾𝑃
1 + 𝐾𝑃
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At low concentration, adsorption is linearly proportional to P
At high concentration, it reaches a monolayer.
Larger value of K means
stronger binding, larger θ
K depend on T
Balance the catalyst-adsorbate interaction?
2. Kinetics of Heterogeneous Catalysis
Paul Sabatier1854 - 1941
Nobel Prize 1912
The Sabatier Effect
optimum interaction
catalyst - adsorbate:
• not too strong
• not too weak A volcano plot for the decomposition of formic acid
using different transition metals as catalysts 11
Optimum coverage at right surface
Multilayer Adsorption and Condensation
2. Kinetics of Heterogeneous Catalysis
The famous BET Isotherm first introduced in the 1930s by Brunauer, Emmett and Teller now considers also the possibility of multilayer adsorption and condensation as shown below.
Koduru, J. R, et al. In Rare-Earth Metal Recovery for Green Technologies, 2020; pp 87-109.
Saadi, R. et al. Korean J. Chem. Eng. 2015, 32 (5), 787-799. 12
M. Shahinuzzaman et al. Renewable and Sustainable Energy Reviews 77 (2017) 1375–1384United States Patent Nos. 8,062,521 (“the ‘521 Patent”) and 9,101,863 (“the ‘863 Patent”)
Multiple length and time
scales
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3. Preparation of Heterogeneous catalysts
3. Preparation of Heterogeneous catalysts
Application of a Heterogeneous Catalyst
Natural: Clay/Zeoliters
Synthetic:
Crystalline aluminosilicatesMetal–organic frameworksMetal clusters/alloy
Bravo-
Suárez, J.
J.; et al,
ACS: 2013;
Vol. 1132, pp 3-68.
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3. Preparation of Heterogeneous catalysts
Components of a Heterogeneous Catalyst Function:Chemical activityTypes:MetalsSemiconductor oxides and sulfidesInsulator oxides and sulfides
Function:High surface areaPorosityMechanical propertiesStabilityDual functionalActivityModification of active componentTypesOxides/Clays/Carbon
Function:On support:StructuralActivity inhinitiionActivity promotionOn active componentElectronicMorphologyPoisoning
Arsalanfar, M, etal, Journal of Industrial and Engineering Chemistry 2014, 20 (4), 1313-1323. 15
3. Preparation of Heterogeneous catalysts
Preparation of a Heterogeneous Catalyst
Precipitation:To form non-soluble precipitate by desired reactions at certain pH and temperature
Adsorption & ion-exchange:Cationic: S-OH+ + C+ → SOC+ + H+
Anionic: S-OH- + A- → SA- + OH-
I-exch. S-Na+ + Ni 2+ ↔ S-Ni 2+ + Na+
Impregnation:Fill the pores of support with a metal salt solution of sufficient concentration to give the correct loading.
Dry mixingPhysically mixed, grind, and fired
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Lifecycle of Prepared Catalysts
3. Preparation of Heterogeneous catalysts
Further treatment of prepared catalysts:Calcined to decompose the precursor and to receive desired thermal stability.
Commonly used Pre-treatmentsReduction: elemental metal is the active phaseSulphidation: a metal sulphide is the active phaseActivation: for the best performance.
Typical catalyst life span:Can be many years or a few mins.
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3. Preparation of Heterogeneous catalysts
M. Shahinuzzaman et al. Renewable and Sustainable Energy Reviews 77 (2017) 1375–1384 18
4. Characterisations of Catalysis
Variables in Catalytic Process
Known / Controllable Variables
Reactor system
Temperature Pressure
Catalyst system
Specific surface
area
Porosity
Surface roughness
Metal loading
Interaction
between
metal andsupport
Diagnostic system
In line
/
In situ
Multivariable Control DesignSingle Variable Control 19
4. Characterisations of Catalysis
Hyphenated Methods for Species Analysis
Sarker, S. D.; Nahar, L., Hyphenated Techniques and Their Applications in Natural Products Analysis. pp 301-340. 20
4. Characterisations of Catalysis
Sarker, S. D.; Nahar, L., Hyphenated Techniques and Their Applications in Natural Products Analysis. pp 301-340.
Information from Hyphenated Techniques
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4. Characterisations of Catalysis
Hyphenated Methods for Species Analysis
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4. Characterisations of Catalysis
Characterization for Heterogeneous Catalysts
A.Alshammari and V.N. Kalevaru. Catalytic Application of Nano-Gold Catalysts, Chapter 3, P65P. Lanzafame,; et al., Catalysis Science & Technology 2017, 7 (22), 5182-5194.
Operando characterisations(Simultaneous Reaction + Catalyst
diagnostics)
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4. Characterisations of Catalysis
Fundamental Research on Catalysts
A.Alshammari and V.N. Kalevaru. Catalytic Application of Nano-Gold Catalysts, Chapter 3, P65
The overall concept follows the deep characterisation of the catalytically active sites,
detailed kinetic analysis, determination of the rate determining step and based on this knowledge the targeted design of advanced catalysts for process optimisation.
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4. Characterisations of Catalysis
Dual functional catalytic materials of Ni over Ce-modified CaO
sorbents for integrated CO2 capture and conversion
Sun, H.; et al., Appl. Catal., B. 2019, 244, 63-75. 25
Diffuse reflectance infrared fouriertransform spectroscopy (DRIFTS)
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Project Training Workshop – Catalyst Characterisation
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Shaojun xu
School of Chemistry, Cardiff University
UK Catalysis Hub, Research Complex at Harwell, Rutherford Appleton Labs
Email: : [email protected]
Bioenergy – Carbon capture and utilisation – Energy Storage
EU RISE – BIOMASS-CCU
Marie Skłodowska-Curie Actions
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