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Characterization of an in situ chamber for catalytic studies using LIF.

Evertsson, Jonas LU (2011) FYSK01 20111
Department of Physics
Abstract (Swedish)
Populärvetenskaplig sammanfattning.

Katalyskammare för aktivitetsmätning med laser.
Katalysatorer är oumbärliga i såväl livsprocesser som industriella tillämpningar. Bilismen är ett exempel där katalysatorer används vid såväl bränsletillverkning som avgasrening. Med hänsyn till miljön måste mycket ständigt förbättras, också katalytiska processer. I mitt examensarbete har jag karakteriserat en ny typ av reaktorkammare där Laser Inducerad Flourescens (LIF) används för aktivitetsmätning av katalysatorer.

Industriella katalysatorer för oxidering av kolmonoxid och metan, CO och CH4, är mycket komplexa system som ofta består av katalytiskt aktiva nanopartiklar utspridda i ett supportmaterial. Sådana katalysatorer är svåra att undersöka... (More)
Populärvetenskaplig sammanfattning.

Katalyskammare för aktivitetsmätning med laser.
Katalysatorer är oumbärliga i såväl livsprocesser som industriella tillämpningar. Bilismen är ett exempel där katalysatorer används vid såväl bränsletillverkning som avgasrening. Med hänsyn till miljön måste mycket ständigt förbättras, också katalytiska processer. I mitt examensarbete har jag karakteriserat en ny typ av reaktorkammare där Laser Inducerad Flourescens (LIF) används för aktivitetsmätning av katalysatorer.

Industriella katalysatorer för oxidering av kolmonoxid och metan, CO och CH4, är mycket komplexa system som ofta består av katalytiskt aktiva nanopartiklar utspridda i ett supportmaterial. Sådana katalysatorer är svåra att undersöka med ytfysikens metoder. Därför har det under många år använts modeller med enkla kristallprover, ultrahögvakuum och metoder ex situ, tillvägagångssätt som långt ifrån avspeglar industriella katalysatorer.

Under senare år har nya tekniker utvecklats in situ och därmed möjligheter till mer realistiska modeller som i sin tur bidrar till ökad förståelse. I mitt projekt har jag karakteriserat ett experimentsystem med en ny typ av reaktorkammare för in situ undersökning av katalysatorer. Med kammaren ska CO2 producerat från CO- och CH4-oxidering med hjälp av katalysatorer mätas med en laser (LIF), vilket möjliggör jämförelse av flera olika prover samtidigt i kammaren.

Systemet kan användas till både flödesexperiment och stängda experiment för tryck mellan 10-2 och 1000 mbar, men den stora kammaren, 200 ml, gör den mest lämpad för det senare. Förutom LIF mätning av CO2 är andra gaser mätbara med en masspektrometer.

Det gjordes också två reaktionsmätningar med systemet. I det första jämfördes CO oxidering på Pd(100) och PdAg(100) för att se om Pd-atomerna i legeringen segregerar till ytan och ger samma aktivitet som det rena Pd-provet. Försöket visade att aktivitet för PdAg nådde samma nivå eller nästan samma nivå som det rena Pd- provet, men efter längre tid, troligen på grund av att Pd-atomerna behöver segregera upp till ytan av provet.

I det andra experimentet användes LIF för att jämföra reaktiviteten för två mycket reaktiva pulverprover. I samma experiment syntes det vid låga temperaturer att ett prov med 1 % Pd och 2 % Pt i ett aluminiumoxidpulver är mer reaktivt än ett liknande prov med 4 % Pd.

Under försöket syntes tydligt tre aktivitetsfaser och hur de skilde sig åt i de olika proverna i reaktorn. Slutsatsen är att systemet fungerade bra och genom att förbättra noggrannheten kommer det i framtiden troligtvis vara användbart. (Less)
Abstract
Industrial catalysts are very complex systems, often produced of nanoparticles dispersed in a so-called support material to maximize the surface area and minimize the cost. These catalysts are very difficult to study in surface science. Therefore industrial catalysts have been developed in a trial-and-error approach, with the loss of the fundamental understanding of the reactions.
In surface science, CO and CH4 oxidation have been studied for many years in model systems using single crystal samples, ultra high vacuum and ex situ techniques, which means that many of the properties of real industrial catalysts will be lost. For a few years, better in situ methods operating in higher vacuum have been developed to get closer to the real... (More)
Industrial catalysts are very complex systems, often produced of nanoparticles dispersed in a so-called support material to maximize the surface area and minimize the cost. These catalysts are very difficult to study in surface science. Therefore industrial catalysts have been developed in a trial-and-error approach, with the loss of the fundamental understanding of the reactions.
In surface science, CO and CH4 oxidation have been studied for many years in model systems using single crystal samples, ultra high vacuum and ex situ techniques, which means that many of the properties of real industrial catalysts will be lost. For a few years, better in situ methods operating in higher vacuum have been developed to get closer to the real systems.
In this project I have characterized a new type of in situ system with both industrial and surface science applications. The idea is that the CO2, produced in an oxidation reaction, should be measured with Laser-Induced Fluorescence (LIF), directly giving a spatially resolved image of the CO2 produced over each of several samples in the reactor. This makes it possible to compare different catalysts in a live mode. The system can be used for both flow and batch experiments for pressures
between 102 - 1000 mbar, but the rather large reactor, 200 ml, makes it best suited for the later. In addition to the LIF measured CO2, also other gases are measurable with a Quadrupole Mass Spectrometer. The sample temperature is controlled by a bohr electric heater and measured with a thermocouple.
Performance and some catalysis measurements were used to characterize the system and find possible improvements. In a test experiment using LIF the results were good. Together with some improvements the next measurement could give more accurate results, making it possible to compare different catalytic samples.
In this thesis two measurements are presented. The first compares CO oxidation on Pd(100) and PdAg(100) to see if the Pd atoms can segregate to the surface of the alloy and give the same activity as the pure Pd sample. The result showed that the activity of the PdAg reached the same or almost the same level as the Pd sample, but after longer time probably due to the time it took for the Pd atoms to segregate to the surface.
The second experiment was on two very reactive Powder samples where also LIF was used. In the same experiment it was found that the sample with 1 % Pd + 2 % Pt was more reactive then the 4 % Pd, at least at low temperatures. Three different activity phases of the samples were very clearly seen in the LIF signal. Also the exothermic effect of the CO oxidation, which is an interesting property, could easily be seen in the experiment. (Less)
Please use this url to cite or link to this publication:
author
Evertsson, Jonas LU
supervisor
organization
course
FYSK01 20111
year
type
M2 - Bachelor Degree
subject
keywords
Catalysts, aktivitetsmätning katalysatorer, reaktorkammare, katalytiska processer, Katalysatorer, catalytic processes, reactor chamber, activity measurements
language
English
id
2219790
date added to LUP
2011-11-29 17:09:43
date last changed
2015-12-14 13:33:08
@misc{2219790,
  abstract     = {Industrial catalysts are very complex systems, often produced of nanoparticles dispersed in a so-called support material to maximize the surface area and minimize the cost. These catalysts are very difficult to study in surface science. Therefore industrial catalysts have been developed in a trial-and-error approach, with the loss of the fundamental understanding of the reactions.
In surface science, CO and CH4 oxidation have been studied for many years in model systems using single crystal samples, ultra high vacuum and ex situ techniques, which means that many of the properties of real industrial catalysts will be lost. For a few years, better in situ methods operating in higher vacuum have been developed to get closer to the real systems.
In this project I have characterized a new type of in situ system with both industrial and surface science applications. The idea is that the CO2, produced in an oxidation reaction, should be measured with Laser-Induced Fluorescence (LIF), directly giving a spatially resolved image of the CO2 produced over each of several samples in the reactor. This makes it possible to compare different catalysts in a live mode. The system can be used for both flow and batch experiments for pressures
between 102 - 1000 mbar, but the rather large reactor, 200 ml, makes it best suited for the later. In addition to the LIF measured CO2, also other gases are measurable with a Quadrupole Mass Spectrometer. The sample temperature is controlled by a bohr electric heater and measured with a thermocouple.
Performance and some catalysis measurements were used to characterize the system and find possible improvements. In a test experiment using LIF the results were good. Together with some improvements the next measurement could give more accurate results, making it possible to compare different catalytic samples.
In this thesis two measurements are presented. The first compares CO oxidation on Pd(100) and PdAg(100) to see if the Pd atoms can segregate to the surface of the alloy and give the same activity as the pure Pd sample. The result showed that the activity of the PdAg reached the same or almost the same level as the Pd sample, but after longer time probably due to the time it took for the Pd atoms to segregate to the surface.
The second experiment was on two very reactive Powder samples where also LIF was used. In the same experiment it was found that the sample with 1 % Pd + 2 % Pt was more reactive then the 4 % Pd, at least at low temperatures. Three different activity phases of the samples were very clearly seen in the LIF signal. Also the exothermic effect of the CO oxidation, which is an interesting property, could easily be seen in the experiment.},
  author       = {Evertsson, Jonas},
  keyword      = {Catalysts,aktivitetsmätning katalysatorer,reaktorkammare,katalytiska processer,Katalysatorer,catalytic processes,reactor chamber,activity measurements},
  language     = {eng},
  note         = {Student Paper},
  title        = {Characterization of an in situ chamber for catalytic studies using LIF.},
  year         = {2011},
}