Sökning: "carbonyl groups"

Visar resultat 1 - 5 av 30 avhandlingar innehållade orden carbonyl groups.

  1. 1. Fenton Pre-treatment of a Birch Kraft Pulp for MFC preparation

    Detta är en avhandling från Karlstad : Karlstads universitet

    Författare :Pia Hellström; Karlstads universitet.; [2015]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Microfibrillated cellulose; Fenton chemistry; carbonyl groups; surface charge; total charge; Enzymatic hydrolysis; Tensile strength; z-directional strength; Chemical Engineering; Kemiteknik;

    Sammanfattning : The potential to use acidic hydrogen peroxide in the presence of ferrous ions (Fenton’s reagent) as a pre-treatment when producing microfibrillar cellulose (MFC) from a fully bleached birch (Betula verucosa) kraft pulp was investigated and the properties of the produced MFC was compared to the properties of a MFC produced with enzymatic pre-treatment with a monocomponent endoglucanase (FiberCare® R). The mechanical treatment to MFC was performed in a laboratory colloid mill or in a pilot high-pressure homogeniser and the pre-treated pulps as well as the produced MFCs were chemically and morphologically characterised. LÄS MER

  2. 2. Transition metal-catalyzed reduction of carbonyl compounds Fe, Ru and Rh complexes as powerful hydride mediators

    Detta är en avhandling från Stockholm : Department of Organic Chemistry, Stockholm University

    Författare :Elina Buitrago; Stockholms universitet.; [2012]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Asymmetric catalysis; amino acid; N-heterocyclic carbene; iron; ruthenium; rhodium; mechanistic investigation; kinetic study; asymmetric transfer hydrogenation; hydrosilylation; Organic Chemistry; organisk kemi;

    Sammanfattning : A detailed mechanistic investigation of the previously reported ruthenium pseudo-dipeptide-catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones was performed. It was found that the addition of alkali metals has a large influence on both the reaction rate and the selectivity, and that the rate of the reaction was substantially increased when THF was used as a co-solvent. LÄS MER

  3. 3. Long-term properties of polyethylene films efficiency of a natural antioxidant

    Detta är en avhandling från Stockholm : KTH

    Författare :Clara Strandberg; KTH.; [2006]
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Polymer Technology; alfa-tocopherol; Polyethylene PE ; Thermal aging; Infrared Spectroscopy FT-IR ; Chemiluminescence CL ; Solid-phase microextraction SPME ; NATURAL SCIENCES Chemistry; NATURVETENSKAP Kemi;

    Sammanfattning : There is a growing awareness of the risks of pollution in biological systems and one potential problem is the synthetic antioxidants, used for e.g. the stabilisation of polymeric materials. Natural antioxidants are an interesting alternative, if the high efficiency and thermal stability of the synthetic compounds can be reached. LÄS MER

  4. 4. Electrical properties of thermally aged polyethylenes and of polyethylenes containing voltage stabilisers

    Detta är en avhandling från Institutionen för polymerteknologi

    Författare :Patrik A. Roseen; KTH.; [1998]
    Nyckelord :;

    Sammanfattning : The use of polyethylene (PE) in electrical applications athigh voltages requires a certain resistance of the material topartial discharges (PDs). The space charge behaviour of PE isof great importance when PE is used as insulator inhigh-voltage DC cables. LÄS MER

  5. 5. Poly (3-hydroxybutyrate) from a moderate halophile: production and modification for new applications

    Detta är en avhandling från Institutionen för polymerteknologi

    Författare :Marlene Munoz; Lund University.; Lunds universitet.; [2011]
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Biopolymers; polyhydroxyalkanoates; polyhydroxybutyrate; moderate halophile; Halomonas boliviensis; fermentation; recovery; thermally induced phase separation; scaffolds; covalent modification; hydrophobic ion pairing; polyethylenemine; lysozyme.;

    Sammanfattning : Polyhydroxybutyrate (PHB) is a homopolymer belonging to the family of biopolyesters, polyhydroxyalkanoates (PHA) produced by different bacteria and archaea as intracellular granules often under conditions of metabolic stress due to a limited supply of essential nutrients. The properties of the PHAs are similar to those of polyethylene and polypropylene and can hence replace these fossil based polymers in a large variety of applications. LÄS MER