Ändra sökning
Avgränsa sökresultatet
1 - 5 av 5
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Andersson, Karl
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Lundahl, Carl-Gustav
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Lundmark, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Nordvik, Enar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Pantze, Anna
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Förslag till handlingsplan för utveckling av LTU Skellefteå: Att synas med stolthet2008Rapport (Övrigt vetenskapligt)
  • 2.
    Pantze, Anna
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Studies of ester formation on a cellulose matrix2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work a model system has been developed to quantitatively study esterification of cellulosic material during drying and heating in which solid-state conditions can be said to predominate. The formation of ester cross-links in cellulosic or lignocellulosic composite materials during drying and heating is of interest for production of paper and wood composite boards, for wood modification and in giving cotton materials improved characteristics. The results support the hypothesis that direct ester formation, without anhydride intermediate, occurs between carboxylic acids of suitable structure and cellulosic hydroxyls at elevated temperatures even after such short reaction times as 5 minutes. Ester formation has been observed at temperatures ranging from 90°C to 180°C. Another important conclusion is that a hydroxy or keto group in alpha position of the carboxylic acids seems to favour ester formation. A critical parameter for ester formation is pH, and the results indicate that pH 5-6. In the experiments, low moisture content, higher temperatures and longer reaction times also favour ester formation, with some exceptions. Another interesting finding is that three pyrrolidine structures are produced after esterification and aminolysis of 2- ketobutyric acid. One of the structures indicates that 2-ketobutyric acid is reactive in two positions and could therefore be a potential cross- linker. Esterifications of five structurally different carboxylic acids-2(R)- hydroxybutyric acid, 2-ketobutyric acid, 3-hydroxybutyric acid, hexanoic acid and veratric acid have been studied. The carboxylic acids and moisture were added to ordinary cellulosic filter paper. Samples were heated at temperatures ranging from 22°C to 180°C between 5 and 45 minutes. Quantitative analysis of ester formation, in this case between the monocarboxylic acids and the cellulose's hydroxyl groups, was performed using aminolysis/gas chromatography.

  • 3. Pantze, Anna
    et al.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Westermark, Ulla
    A model system to study esterification reactions in cellulosic or lignocellulosic material2007Ingår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 33, nr 4, s. 177-183Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of natural ester cross-linkages in cellulosic or lignocellulosic composite materials during drying and heating is of interest for the production of paper and of wood composite boards and in giving cotton materials improved characteristics. A model system has been developed to study quantitatively the esterification of cellulosic material during drying and heating when solid-state conditions can be said to predominate. In the experiments, hexanoic acid and 3-hydroxybutyric acid were added to ordinary filter paper. Moisture content was adjusted, and samples were heated to temperatures ranging from 85 degrees C to 180 degrees C for between 15 and 45 minutes. Quantitative analysis of ester,formation, in this case between the monocarboxylic acids and the cellulose's hydroxyl groups, was performed using aminolysis/gas chromatography. The 3-hydroxybutyric acid was surprising v effective in ester formation. The results indicate that direct esterification of monocarboxylic acid can be an important reaction in lignocellulosic material at elevated temperatures.

  • 4. Pantze, Anna
    et al.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Westermark, Ulla
    Esterification of carboxylic acids on cellulosic material: solid state reactions2008Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, nr 2, s. 136-141Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, the formation of ester linkages in cellulosic materials during drying and heating was addressed. The results indicated that direct ester formation, without anhydride intermediate, occurs between carboxylic acids of suitable structure and cellulosic hydroxyls at 180 degrees C, even after reaction times as short as 5 min. The 2(R)-hydroxybutyric acid is most effective in ester formation, followed by 2-ketobutyric acid and 3-hydroxybutyric acid. Hexanoic acid is less effective and veratric acid produces no esters at all. At lower temperatures, 2-ketobutyric acid is the most reactive compound. One conclusion is that a hydroxyl or keto group in alpha position of the carboxylic acids favours ester formation. Another finding is that three pyrrolidine structures are produced after esterification and aminolysis of 2-ketobutyric acid. One of the structures indicates that 2-ketobutyric acid is reactive in two positions and could therefore be a potential cross-linker. A critical parameter for ester formation is pH, and the results indicate that pH < 2 strongly favours esterification, whereas almost no esters are produced at pH > 5-6. All experiments were performed in a solid-state model system (on cellulosic filter paper) with low moisture content. Esterification of five carboxylic acids was studied. Samples were heated constantly at 180 degrees C for 5 min or gradually from 22 degrees C to 180 degrees C over periods ranging from 5 to 45 min. Quantitative analysis of ester formation between the monocarboxylic acids and the hydroxyl groups of cellulose was performed by means of aminolysis and gas chromatography.

  • 5. Pantze, Anna
    et al.
    Westermark, Ulla
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Formation of ester cross linkage in lignocellulosic materials during drying and heating2005Konferensbidrag (Övrigt vetenskapligt)
1 - 5 av 5
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf