Bromide-free TEMPO-mediated oxidation of cellulose by hypochlorite - fundamental and practical aspects

Timo Pääkkönen

Bromide-free TEMPO-mediated oxidation of cellulose by hypochlorite - fundamental and practical aspects

Julkaisun otsikon käännös: Selluloosan bromidivapaa TEMPO-hapetus hypokloriittia käyttäen - perusluonteisia ja käytännöllisiä näkökulmia

Timo Pääkkönen

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Selluloosan TEMPO-katalysoitua hapetusta käytetään esikäsittelymenetelmänä TEMPO-hapetettujen selluloosananokuitujen (TOCN) tuotannossa. Kyseinen tuote voisi soveltua tutkimusten mukaan raaka-aineeksi esimerkiksi elektro-optisiin kalvoihin, mikroelektroniikkaan, kaasua eristäviin kalvoihin, kosmetiikkaan, palonkestäviin materiaaleihin sekä muihin korkean arvon käyttökohteisiin. Olemassa olevan TOCN:n valmistusmenetelmän haittapuoli on runsas bromidin käyttö. Bromidia pidetään hankalana yhdisteenä teollisissa jätevesissä sekä ongelmallisena lisääntyneen korroosioriskin takia. Tämä väitöstyö keskittyy teollisen mittakaavan bromidivapaan TEMPO-hapetusmenetelmän kehittämiseen. Kyseistä menetelmää sovelletaan TOCN-kuitujen valmistukseen valkaistusta koivusellusta. TEMPO-radikaalin konversio varsinaisena hapettimena toimivaksi TEMPO+-kationiksi on prosessin toiminnan kannalta aliarvostettu ja riittämättömästi tutkittu reaktiovaihe perinteisissä TEMPO-hapetusprosesseissa. Tässä työssä kehitettiin kaksi erilaista aktivointimenetelmää TEMPO+-kationin tuottamiseksi. TEMPO aktivoitiin suljetussa astiassa klooridioksidin tai hypokloriitin avulla ennen aktivoidun katalyyttiliuoksen lisäämistä hapetusreaktoriin. Tämän jälkeen valkaistun koivusellun TEMPO-hapetus tapahtui riittävällä nopeudella teollisen toiminnan näkökulmasta. Lopulta pitkälle hapetettu sellumassa fluidisoitiin TOCN-kuiduiksi, jotka muodostavat tyypillisesti läpinäkyvän geelin. Myöhemmin työssä kehitettiin tehokas esikäsittely valkaistuille koivusellumassoille. Koivumassan alkalikäsittelyllä saatiin sellun TEMPO-hapetuksen reaktioaika putoamaan muutamasta tunnista puoleen tuntiin hapetuksessa käytettävällä keskitasoisella hypokloriittiannoksella. TEMPO-hapetettujen sellumassojen karboksylaattipitoisuuden maksimitaso oli selvästi korkein massoilla, jotka oli alkalikäsitelty ennen hapetusta. Atomivoimamikroskooppi-topografiaa ja reologista karakterisointia käytettiin apuna tutkittaessa TOCN-näytteiden sarjaa ksylaanipitoisuuden funktiona. TEMPO+-pitoisuuden määrittämiseksi katalyyttiliuoksista ja reaktioseoksista kehitettiin jodometrinen titrausmenetelmä. Tätä uutta tutkimusmenetelmää hyödynnettiin TEMPO-hapetuksen reaktiomekanismin ja -kinetiikan tutkimuksessa. TEMPO-radikaalin konversiota Cl(+1) ja Br(+1) kanssa varsinaisena hapettimena toimivaksi TEMPO+-kationiksi tutkittiin kineettisesti. Erillisen aktivointivaiheen oleellinen merkitys bromidivapaissa prosesseissa voitiin todistaa tällä titrausmenetelmällä. Väitöskirjatutkimuksen tuloksia voidaan soveltaa teollisen TOCN tuotannon kehittämisessä.

Julkaisun otsikon käännös	Selluloosan bromidivapaa TEMPO-hapetus hypokloriittia käyttäen - perusluonteisia ja käytännöllisiä näkökulmia
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Vuorinen, Tapani, Vastuuprofessori Vuorinen, Tapani, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-7626-3
Sähköinen ISBN	978-952-60-7625-6
Tila	Julkaistu - 2017
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

alkalikäsittely
koivusellu
bromidivapaa
klooridioksidi
hypokloriitti
jodometrinen titraus
nanofibrilloitu selluloosa
TEMPO hapetus
ksylaani

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-7625-6Lisenssi: Määrittelemätön

Biotalousinfrastruktuuri
Seppälä, J. (Manager)
Kemian tekniikan korkeakoulu
Laitteistot/tilat: Facility

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@phdthesis{a89f17ed24b94063ab44b9641d7ed635,

title = "Bromide-free TEMPO-mediated oxidation of cellulose by hypochlorite - fundamental and practical aspects",

abstract = "TEMPO-mediated oxidation of pulp is a pretreatment procedure which is applied to produce TEMPO-oxidized cellulose nanofibers (TOCN). TOCN is proposed to be a raw material for many applications such as electro-optical films, microelectronics, gas-barrier films, cosmetics, flame-resistant materials and other high-tech applications. The drawback in the traditional procedure, which is effective enough for industrial purposes, is the use of bromide in high quantities. Thus, bromide is considered to be highly undesired in the waste water due to the environmental and corrosion concerns. This thesis focused on the development of an industrially feasible bromide-free TEMPO-mediated oxidation procedure of birch kraft pulp which can be applied with the production of the TOCN. TEMPO conversion to TEMPO+ is an underestimated and uncharted process step in the conventional TEMPO-oxidation processes. Here, two separate TEMPO activation steps were developed. TEMPO was activated with ClO2 or NaOCl in the closed vessel prior to the addition in the reactor. Then, the bromide-free TEMPO-mediated oxidations of bleached birch kraft pulp were conducted with the industrially feasible reaction rate. Finally, the oxidized pulps with the adequate carboxylate content were fluidized to TOCN, which is typically a transparent gel. Later, an effective alkali pretreatment of bleached birch kraft pulp was developed to enhance the reaction rate of bromide-free TEMPO-mediated oxidation of the pulp. The TEMPO-oxidation time of alkali treated birch pulp reduced drastically from few hours to half an hour when an adequate hypochlorite addition was used with TEMPO-oxidation. The reached carboxylate content of the TEMPO-oxidized pulp by a high hypochlorite addition was clearly higher with the alkali treated pulps than with the untreated pulps. Atomic force microscopy topography and rheological characterization was applied to study alkali treated TOCN gels as a function of decreased xylan content. An iodometric titration method was developed to monitor TEMPO+ content of catalyst and pulp solutions. This novel analytical method was applied with studying the reaction mechanisms and kinetics of TEMPO-mediated oxidation. The kinetics of the TEMPO conversion to TEMPO+ with Cl(+1) and Br(+1) was examined with the titration method. The importance of the separate TEMPO activation step was found to be an essential part of bromide-free TEMPO-oxidation. Once TEMPO is converted to TEMPO+, which can be conducted with Cl(+1), ClO2 or Br(+1), the reaction rate is dependent on the reaction rate with TEMPO+ and primary hydroxyls or reoxidation of the reduced catalyst (TEMPOH) to TEMPO+. The results of the thesis facilitates the development of industrially feasible TOCN production.",

keywords = "alkali treatment, birch pulp, bromide-free, chlorine dioxide, hypochlorite, iodometric titration, nanofibrillated cellulose, TEMPO-mediated oxidation, xylan, alkalik{\"a}sittely, koivusellu, bromidivapaa, klooridioksidi, hypokloriitti, jodometrinen titraus, nanofibrilloitu selluloosa, TEMPO hapetus, ksylaani, alkali treatment, birch pulp, bromide-free, chlorine dioxide, hypochlorite, iodometric titration, nanofibrillated cellulose, TEMPO-mediated oxidation, xylan",

author = "Timo P{\"a}{\"a}kk{\"o}nen",

year = "2017",

language = "English",

isbn = "978-952-60-7626-3",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "180",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Bromide-free TEMPO-mediated oxidation of cellulose by hypochlorite - fundamental and practical aspects

AU - Pääkkönen, Timo

PY - 2017

Y1 - 2017

N2 - TEMPO-mediated oxidation of pulp is a pretreatment procedure which is applied to produce TEMPO-oxidized cellulose nanofibers (TOCN). TOCN is proposed to be a raw material for many applications such as electro-optical films, microelectronics, gas-barrier films, cosmetics, flame-resistant materials and other high-tech applications. The drawback in the traditional procedure, which is effective enough for industrial purposes, is the use of bromide in high quantities. Thus, bromide is considered to be highly undesired in the waste water due to the environmental and corrosion concerns. This thesis focused on the development of an industrially feasible bromide-free TEMPO-mediated oxidation procedure of birch kraft pulp which can be applied with the production of the TOCN. TEMPO conversion to TEMPO+ is an underestimated and uncharted process step in the conventional TEMPO-oxidation processes. Here, two separate TEMPO activation steps were developed. TEMPO was activated with ClO2 or NaOCl in the closed vessel prior to the addition in the reactor. Then, the bromide-free TEMPO-mediated oxidations of bleached birch kraft pulp were conducted with the industrially feasible reaction rate. Finally, the oxidized pulps with the adequate carboxylate content were fluidized to TOCN, which is typically a transparent gel. Later, an effective alkali pretreatment of bleached birch kraft pulp was developed to enhance the reaction rate of bromide-free TEMPO-mediated oxidation of the pulp. The TEMPO-oxidation time of alkali treated birch pulp reduced drastically from few hours to half an hour when an adequate hypochlorite addition was used with TEMPO-oxidation. The reached carboxylate content of the TEMPO-oxidized pulp by a high hypochlorite addition was clearly higher with the alkali treated pulps than with the untreated pulps. Atomic force microscopy topography and rheological characterization was applied to study alkali treated TOCN gels as a function of decreased xylan content. An iodometric titration method was developed to monitor TEMPO+ content of catalyst and pulp solutions. This novel analytical method was applied with studying the reaction mechanisms and kinetics of TEMPO-mediated oxidation. The kinetics of the TEMPO conversion to TEMPO+ with Cl(+1) and Br(+1) was examined with the titration method. The importance of the separate TEMPO activation step was found to be an essential part of bromide-free TEMPO-oxidation. Once TEMPO is converted to TEMPO+, which can be conducted with Cl(+1), ClO2 or Br(+1), the reaction rate is dependent on the reaction rate with TEMPO+ and primary hydroxyls or reoxidation of the reduced catalyst (TEMPOH) to TEMPO+. The results of the thesis facilitates the development of industrially feasible TOCN production.

AB - TEMPO-mediated oxidation of pulp is a pretreatment procedure which is applied to produce TEMPO-oxidized cellulose nanofibers (TOCN). TOCN is proposed to be a raw material for many applications such as electro-optical films, microelectronics, gas-barrier films, cosmetics, flame-resistant materials and other high-tech applications. The drawback in the traditional procedure, which is effective enough for industrial purposes, is the use of bromide in high quantities. Thus, bromide is considered to be highly undesired in the waste water due to the environmental and corrosion concerns. This thesis focused on the development of an industrially feasible bromide-free TEMPO-mediated oxidation procedure of birch kraft pulp which can be applied with the production of the TOCN. TEMPO conversion to TEMPO+ is an underestimated and uncharted process step in the conventional TEMPO-oxidation processes. Here, two separate TEMPO activation steps were developed. TEMPO was activated with ClO2 or NaOCl in the closed vessel prior to the addition in the reactor. Then, the bromide-free TEMPO-mediated oxidations of bleached birch kraft pulp were conducted with the industrially feasible reaction rate. Finally, the oxidized pulps with the adequate carboxylate content were fluidized to TOCN, which is typically a transparent gel. Later, an effective alkali pretreatment of bleached birch kraft pulp was developed to enhance the reaction rate of bromide-free TEMPO-mediated oxidation of the pulp. The TEMPO-oxidation time of alkali treated birch pulp reduced drastically from few hours to half an hour when an adequate hypochlorite addition was used with TEMPO-oxidation. The reached carboxylate content of the TEMPO-oxidized pulp by a high hypochlorite addition was clearly higher with the alkali treated pulps than with the untreated pulps. Atomic force microscopy topography and rheological characterization was applied to study alkali treated TOCN gels as a function of decreased xylan content. An iodometric titration method was developed to monitor TEMPO+ content of catalyst and pulp solutions. This novel analytical method was applied with studying the reaction mechanisms and kinetics of TEMPO-mediated oxidation. The kinetics of the TEMPO conversion to TEMPO+ with Cl(+1) and Br(+1) was examined with the titration method. The importance of the separate TEMPO activation step was found to be an essential part of bromide-free TEMPO-oxidation. Once TEMPO is converted to TEMPO+, which can be conducted with Cl(+1), ClO2 or Br(+1), the reaction rate is dependent on the reaction rate with TEMPO+ and primary hydroxyls or reoxidation of the reduced catalyst (TEMPOH) to TEMPO+. The results of the thesis facilitates the development of industrially feasible TOCN production.

KW - alkali treatment

KW - birch pulp

KW - bromide-free

KW - chlorine dioxide

KW - hypochlorite

KW - iodometric titration

KW - nanofibrillated cellulose

KW - TEMPO-mediated oxidation

KW - xylan

KW - alkalikäsittely

KW - koivusellu

KW - bromidivapaa

KW - klooridioksidi

KW - hypokloriitti

KW - jodometrinen titraus

KW - nanofibrilloitu selluloosa

KW - TEMPO hapetus

KW - ksylaani

KW - alkali treatment

KW - birch pulp

KW - bromide-free

KW - chlorine dioxide

KW - hypochlorite

KW - iodometric titration

KW - nanofibrillated cellulose

KW - TEMPO-mediated oxidation

KW - xylan

M3 - Doctoral Thesis

SN - 978-952-60-7626-3

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Bromide-free TEMPO-mediated oxidation of cellulose by hypochlorite - fundamental and practical aspects

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

Sormenjälki

Laitteet

Biotalousinfrastruktuuri

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