Phosphorus on platinum surfaces – from molecular adsorption to catalyst poisoning

Olli Heikkinen

Phosphorus on platinum surfaces – from molecular adsorption to catalyst poisoning

Julkaisun otsikon käännös: Fosfori platinapinnoilla – molekyylien adsorptiosta katalyyttien myrkyttymiseen

Olli Heikkinen

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Platina on katalyyttisesti aktiivinen metalli, jota käytetään laajasti teollisuudessa. Merkittävä sovellus ovat autojen pakokaasukatalysaattorit, joiden tehtävä on vähentää haitallisia päästöjä. Niissä platinaa käytetään esimerkiksi katalysoimaan hiilimonoksidin ja hiilivetyjen hapetusreaktioita. Fosfori puolestaan on katalyyttimyrkky. Se adsorboituu katalyyttipinnalle ja aiheuttaa tämän aktiivisuuden heikentymistä. Fosfori on yleinen ainesosa voiteluöljyissä ja niiden lisäaineissa, ja siksi fosforimyrkyttyminen on pakokaasukatalyyttien todellinen ongelma. Myrkyttymismekanismien yksityiskohtien ymmärtämiseksi voi olla hyödyllistä tutkia teollisten katalyyttimateriaalien ohella myös fosforin adsorboitumista yksittäiskiteisille platinapinnoille. Toistaiseksi tällaista tutkimusta on kuitenkin tehty varsin rajoitetusti. Tässä työssä on tutkittu fosforin adsorptiota platina (111) ja (110) -pinnoille. Toisena tutkimus-kohteena on ollut fosforin sekä rikin vaikutus eräisiin diesel- ja maakaasuajoneuvokäyttöön valmistettuihin hapetuskatalyytteihin. Näiden lisäksi yksi työn osio käsittelee maleiinianhydridin adsorptiota platina (111) -pinnalle. Maleiinianhydridi on orgaaninen molekyyli, jota käytetään yleisesti kemianteollisuudessa esimerkiksi voiteluöljyjen ja biopolttoaineiden valmistuksessa. Työn tutkimus on tehty pintafysiikan tavanomaisilla menetelmillä, kuten röntgenfotoelektroni-spektroskopialla, matalaenergisten elektronien diffraktiolla, tunnelointimikroskopialla ja termisellä desorptiospektroskopialla. Lisäksi työssä esitellään yhteistyökumppanien muilla kokeellisilla sekä laskennallisilla menetelmillä saavuttamia tuloksia. Fosforin adsorption kummallekin yksittäiskidepinnalle havaittiin olevan tehokkaampaa, mikäli pinnan lämpötilaa nostetaan. Pinnan toivutus fosforin annostelun jälkeen tuotti järjestyneitä rakenteita. Näitä löydettiin useampia erilaisia erisuuruisilla fosforipeitoilla. Kyllin suurilla annoksilla peitto saturoitui kummallakin pinnalla. Fosforin havaittiin myös muodostavan moniatomisia klustereita. Hapetuskatalyyttipinnoilla fosfori muodosti fosfaattiyhdisteitä katalyyttien tukiaineiden kanssa. Se aiheutti myös morfologisia muutoksia: esimerkiksi katalyyttipinnan alan huomattiin pienenevän. Katalyyttisen aktiivisuuden väheneminen vaihteli kohtalaisesta merkittävään eri katalyyttien ja hapetusreaktioiden välillä. Rikin puolestaan huomattiin lieventävän fosforimyrkytystä. Maleiinianhydridi muodosti järjestymättömiä usean kerroksen rakenteita platina (111) -pinnalle. Molekyylit desorboituivat pinnalta tai hajosivat jo alle huoneenlämmössä. Hajonneiden molekyylien osien desorptiota havaittiin tätä korkeammissa lämpötiloissa. Työssä saavutetut tulokset tuovat omalta osaltaan lisätietoa fosforin aiheuttamasta katalyyttimyrkytyksestä. Toisaalta tulokset ovat myös osa pintatieteen perustutkimuksen jatkumoa.

Julkaisun otsikon käännös	Fosfori platinapinnoilla – molekyylien adsorptiosta katalyyttien myrkyttymiseen
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Liljeroth, Peter, Vastuuprofessori Lahtinen, Jouko, Vastuuprofessori
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-7349-1
Sähköinen ISBN	978-952-60-7348-4
Tila	Julkaistu - 2017
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

platina
palladium
fosfori
rikki
maleiinianhydridi
adsorptio
desorptio
hapetus
katalyysi
katalyyttimyrkky

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-7348-4Lisenssi: Määrittelemätön

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@phdthesis{74bb07b908fa40b3a940647d2a089229,

title = "Phosphorus on platinum surfaces – from molecular adsorption to catalyst poisoning",

abstract = "Platinum is a catalytically active metal widely used in technology. An important application is automotive exhaust gas catalysis, aiming at reducing combustion engine emissions. Platinum is used to catalyse oxidation reactions of carbon monoxide and hydrocarbons, for instance. On the other hand, phosphorus is a catalyst poison. It is adsorbed on catalyst surfaces, causing decrease in the catalytic activity. In practice, phosphorus is commonly found in lubricant oils and additives, which makes phosphorus poisoning a true problem in exhaust gas catalysis. In addition to real catalysts, studying phosphorus adsorption on platinum single crystal surfaces may give insight into the mechanism of poisoning. However, so far the number of such studies has remained relatively limited.In this work, molecular phosphorus adsorption on platinum (111) and (110) surfaces has been investigated. In addition, effects of phosphorus as well as sulfur on real platinum and platinum-palladium catalysts for diesel and natural gas oxidation have been studied. Furthermore, one section is devoted to maleic anhydride adsorption on platinum (111). Maleic anhydride is an organic molecule, used as an intermediate in many large-scale chemical manufacturing processes, related for instance to lubricant oils and biofuels. The studies featured in this work have been carried out with standard techniques of surface science, such as X-ray photoelectron spectroscopy, low-energy electron diffraction, scanning tunnelling microscopy and temperature-programmed desorption. Furthermore, results acquired with additional experimental and computational methods by collaborators are also reported. Phosphorus adsorption on both single crystal surfaces was found to be more efficient on elevated temperatures. Annealing the surface after deposition resulted in formation of ordered structures. Several different superstructures were found, depending on the phosphorus coverage which eventually saturated on both surfaces. Phosphorus was observed to have a tendency towards forming large clusters. On the real catalyst surfaces, phosphorus was found to form phosphate compounds with particles in the catalyst support. It also induced morphological changes, such as decreasing the specific surface areas. The magnitude of deactivation varied from moderate to severe depending on the catalyst and the reaction. Sulfur was found to mitigate the poisoning effect caused by phosphorus. Maleic anhydride formed unordered multilayer structures on platinum (111). All molecules desorbed or dissociated below room temperature, above which desorption of molecule fragments was observed in a wide temperature range. The results gained in this work give insight into how catalyst poisoning induced by phosphorus takes place. Moreover, they also give answers to some previously uncharted problems in fundamental surface science.",

keywords = "platinum, palladium, Pt(111), Pt(110), phosphorus, sulfur, maleic anhydride, adsorption, desorption, oxidation, catalysis, catalyst poison, platina, palladium, fosfori, rikki, maleiinianhydridi, adsorptio, desorptio, hapetus, katalyysi, katalyyttimyrkky, platinum, palladium, Pt(111), Pt(110), phosphorus, sulfur, maleic anhydride, adsorption, desorption, oxidation, catalysis, catalyst poison",

author = "Olli Heikkinen",

year = "2017",

language = "English",

isbn = "978-952-60-7349-1",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "53",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Phosphorus on platinum surfaces – from molecular adsorption to catalyst poisoning

AU - Heikkinen, Olli

PY - 2017

Y1 - 2017

N2 - Platinum is a catalytically active metal widely used in technology. An important application is automotive exhaust gas catalysis, aiming at reducing combustion engine emissions. Platinum is used to catalyse oxidation reactions of carbon monoxide and hydrocarbons, for instance. On the other hand, phosphorus is a catalyst poison. It is adsorbed on catalyst surfaces, causing decrease in the catalytic activity. In practice, phosphorus is commonly found in lubricant oils and additives, which makes phosphorus poisoning a true problem in exhaust gas catalysis. In addition to real catalysts, studying phosphorus adsorption on platinum single crystal surfaces may give insight into the mechanism of poisoning. However, so far the number of such studies has remained relatively limited.In this work, molecular phosphorus adsorption on platinum (111) and (110) surfaces has been investigated. In addition, effects of phosphorus as well as sulfur on real platinum and platinum-palladium catalysts for diesel and natural gas oxidation have been studied. Furthermore, one section is devoted to maleic anhydride adsorption on platinum (111). Maleic anhydride is an organic molecule, used as an intermediate in many large-scale chemical manufacturing processes, related for instance to lubricant oils and biofuels. The studies featured in this work have been carried out with standard techniques of surface science, such as X-ray photoelectron spectroscopy, low-energy electron diffraction, scanning tunnelling microscopy and temperature-programmed desorption. Furthermore, results acquired with additional experimental and computational methods by collaborators are also reported. Phosphorus adsorption on both single crystal surfaces was found to be more efficient on elevated temperatures. Annealing the surface after deposition resulted in formation of ordered structures. Several different superstructures were found, depending on the phosphorus coverage which eventually saturated on both surfaces. Phosphorus was observed to have a tendency towards forming large clusters. On the real catalyst surfaces, phosphorus was found to form phosphate compounds with particles in the catalyst support. It also induced morphological changes, such as decreasing the specific surface areas. The magnitude of deactivation varied from moderate to severe depending on the catalyst and the reaction. Sulfur was found to mitigate the poisoning effect caused by phosphorus. Maleic anhydride formed unordered multilayer structures on platinum (111). All molecules desorbed or dissociated below room temperature, above which desorption of molecule fragments was observed in a wide temperature range. The results gained in this work give insight into how catalyst poisoning induced by phosphorus takes place. Moreover, they also give answers to some previously uncharted problems in fundamental surface science.

AB - Platinum is a catalytically active metal widely used in technology. An important application is automotive exhaust gas catalysis, aiming at reducing combustion engine emissions. Platinum is used to catalyse oxidation reactions of carbon monoxide and hydrocarbons, for instance. On the other hand, phosphorus is a catalyst poison. It is adsorbed on catalyst surfaces, causing decrease in the catalytic activity. In practice, phosphorus is commonly found in lubricant oils and additives, which makes phosphorus poisoning a true problem in exhaust gas catalysis. In addition to real catalysts, studying phosphorus adsorption on platinum single crystal surfaces may give insight into the mechanism of poisoning. However, so far the number of such studies has remained relatively limited.In this work, molecular phosphorus adsorption on platinum (111) and (110) surfaces has been investigated. In addition, effects of phosphorus as well as sulfur on real platinum and platinum-palladium catalysts for diesel and natural gas oxidation have been studied. Furthermore, one section is devoted to maleic anhydride adsorption on platinum (111). Maleic anhydride is an organic molecule, used as an intermediate in many large-scale chemical manufacturing processes, related for instance to lubricant oils and biofuels. The studies featured in this work have been carried out with standard techniques of surface science, such as X-ray photoelectron spectroscopy, low-energy electron diffraction, scanning tunnelling microscopy and temperature-programmed desorption. Furthermore, results acquired with additional experimental and computational methods by collaborators are also reported. Phosphorus adsorption on both single crystal surfaces was found to be more efficient on elevated temperatures. Annealing the surface after deposition resulted in formation of ordered structures. Several different superstructures were found, depending on the phosphorus coverage which eventually saturated on both surfaces. Phosphorus was observed to have a tendency towards forming large clusters. On the real catalyst surfaces, phosphorus was found to form phosphate compounds with particles in the catalyst support. It also induced morphological changes, such as decreasing the specific surface areas. The magnitude of deactivation varied from moderate to severe depending on the catalyst and the reaction. Sulfur was found to mitigate the poisoning effect caused by phosphorus. Maleic anhydride formed unordered multilayer structures on platinum (111). All molecules desorbed or dissociated below room temperature, above which desorption of molecule fragments was observed in a wide temperature range. The results gained in this work give insight into how catalyst poisoning induced by phosphorus takes place. Moreover, they also give answers to some previously uncharted problems in fundamental surface science.

KW - platinum

KW - palladium

KW - Pt(111)

KW - Pt(110)

KW - phosphorus

KW - sulfur

KW - maleic anhydride

KW - adsorption

KW - desorption

KW - oxidation

KW - catalysis

KW - catalyst poison

KW - platina

KW - palladium

KW - fosfori

KW - rikki

KW - maleiinianhydridi

KW - adsorptio

KW - desorptio

KW - hapetus

KW - katalyysi

KW - katalyyttimyrkky

KW - platinum

KW - palladium

KW - Pt(111)

KW - Pt(110)

KW - phosphorus

KW - sulfur

KW - maleic anhydride

KW - adsorption

KW - desorption

KW - oxidation

KW - catalysis

KW - catalyst poison

M3 - Doctoral Thesis

SN - 978-952-60-7349-1

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Phosphorus on platinum surfaces – from molecular adsorption to catalyst poisoning

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

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