Elina Orblin

Topochemical pretreatment of wood biomass to enhance enzymatic hydrolysis of polysaccharides to sugars

The surface chemistry of milled birch and pine wood pretreated by ionic liquid, hydrothermal and hydrotropic methods, followed by enzymatic hydrolysis was studied in this work. Surface coverage by lignin was measured by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to describe the surface chemical composition after pretreatment in detail, and the morphology after pretreatment was investigated by FE-SEM. Ionic liquid (1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride) pretreatment at room temperature made the samples swell but did not dissolve the wood. Comparing the surface coverage by lignin, both in the case of birch and pine wood, hydrotropic worked best to remove the lignin hampering enzymatic hydrolysis. ToF-SIMS supported this finding, and showed that in birch, the carbohydrates were degraded more than in pine after hydrotropic pretreatment. The glucose yield of birch was improved by hydrotropic pretreatment from 5.1% to 83.9%, more significantly than in case of pine.

Probing the chemical and surface chemical modification of vessel cell walls during bleaching of eucalyptus pulp

Abstract Eucalyptus pulp is increasingly used for the manufacture of printing papers. However, its major drawback, the vessel picking, is still waiting for a solution. The detailed features and the characteristic behaviour of vessel elements (VEs) in pulp and paper processes are poorly understood. This study focusses on the chemistry, surface chemistry and morphology of eucalyptus VEs. These properties were followed through the changes introduced by different stages of elemental chlorine-free (ECF) bleaching, by studying separated VEs. Microprobe X-ray photoelectron spectroscopy (μ-XPS) and field emission-scanning electron microscopy (FE-SEM) were applied to elucidate the surface chemical composition and morphological ultrastructure, respectively. The bulk chemical composition was investigated among others by Py-GC/MS. Lignin was detected in vessels still after completed bleaching sequence, whereas the fibres were lignin-free. The vessel lignin was mainly composed by syringyl-type units. Surface coverage by lignin and amount of surface anionic groups were practically unaffected by bleaching. The vessel cell wall structure was observed to be layered in a complex way with no particular orientation of cellulose fibrils, and the different layers seemed to be exfoliated during different bleaching stages.

Surface chemistry of vessel elements by FE-SEM, mu-XPS and ToF-SIMS

Abstract Separation of vessel elements and fibers was carried out for Eucalyptus kraft and recycled pulp as raw materials. A new separation method is presented. The surface morphology, surface chemical characteristics and chemistry of individual vessel elements were studied using field emission scanning electron microscopy (FE-SEM), microbeam X-ray photo-electron spectroscopy (μ-XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). By FE-SEM it could be seen that vessel elements in recycled pulp were almost intact or only partly broken via the pits. They were also detected on the surface of newsprint paper. The chemical composition of vessel element surfaces was similar to that of fibers. The surface coverage by lignin in vessels showed scattered results by μ-XPS. However, normalized lignin peak intensities of ToF-SIMS indicated that vessels had lower surface lignin counts than fibers. Vessel elements in recycled pulp were rich in phthalates and other hydrocarbons originating probably from printing ink and paper chemicals. Fillers, sizes, and other paper chemicals were not completely removed from the recycled vessel surfaces during the de-inking.

Topochemical activation of pulp fibres

A new concept for topochemical activation of mechanical pulp fibres was investigated. The activation concept was based on attachment of precursors of peracids onto the surface of the fibres prior to hydrogen peroxide bleaching. The activators used in this work were: tetraacetylethylenediamine (water soluble), lactose octaacetate (LOA, colloidal particles, and low water solubility) and sucrose octaacetate (partially soluble in water). LOA showed promising results for application in the surface activation concept due to attachment of colloidal particles on the outmost surface of the fibres, simultaneously contributing to a brightness increase. Surface coverage by lignin on fibres had decreased after the bleaching process with activators, which was detected by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry.