Raimo Alén

Formation of the main degradation compound groups from wood and its components during pyrolysis

The thermochemical behavior of pine wood (Pinus sylvestris) and its main structural constituents (cellulose, hemicelluloses, and lignin) was investigated by pyrolysis-gas chromatography with mass-selective detection (Py-GC/MSD). In each case, major GC-amenable pyrolysis products were classified into several compound groups, and changes in the relative mass portions of these monomer-related fragments were monitored in the temperature range 400–1000 °C. The formation of the main products was shown to be characteristically dependent on the reaction temperature. The results also indicated that in the temperature range used, wood appeared to behave as the sum of its constituents.

Thermochemical behavior of Norway spruce (Picea abies) at 180–225 °C

Abstract Norway spruce (Picea abies) was heated for 2–8 h in the temperature range 180–225 °C, under a steam atmosphere. The chemical analyses of the treated feedstock samples indicated that during heating (total mass loss 1.5–12.5% of the initial DS) carbohydrates (hemicelluloses and cellulose) were clearly more amenable to various degradation reactions than lignin. In addition, major water-soluble products released from the feedstock material during the treatments were classified into several compound groups and changes in the relative mass portion of these groups were monitored by GC during a separate experiment.

Catalytic hydrotreatment of some technical lignins

Five kraft lignins from softwood and hardwood and one softwood lignin from the organocell process were converted into an oil-like product by hydrotreatment at 400°C for 40 minutes in the presence of different catalysts. The total oil yields varied in the range 49–71% wt of the original lignin feedstock. The highest yield was obtained for organosolv lignin using a catalyst mixture of sulfided NiMo on aluminosilica (M8–81): Cr2O3 (M9–10) (1:1). Detailed GLC analysis of the low-molecular-weight components in the oil products (the total amounts of 14–38% wt of the original lignin) indicated the presence of various alkyl benzenes, phenols, and polycyclic aromatics.

FTIR Monitoring of Chemical Changes in Softwood During Heating

Abstract A multivariate chemometric method for monitoring the mass loss of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) by IR spectroscopic determination of chemical changes occurring during the heat treatment (160 - 260 °C, 2 - 8 h) of these wood materials was developed. The method was based on the handling of FTIR data on treated and untreated wood powder samples by the partial least squares (PLS) method. In addition, unknown samples (treated and untreated pine and spruce) were classified into separate groups by the principal component analysis (PCA) method. The chemical changes occurring in the wood samples during heating were also briefly discussed.

Laccase-catalysed functionalisation of TMP with tyramine

Abstract Modified wood fibres open new perspectives to create value-added products based on renewable raw materials. An interesting option is the targeted modification of fibre surfaces by oxidative enzymes. This two-stage functionalisation method consists of enzymatic activation of fibre surfaces followed by addition of radicalised compounds reacting preferentially by radical coupling. In this work, the activation of bleached and unbleached softwood TMPs with laccase isolated from Trametes hirsuta was studied. The formation and stability of the radicals were studied by EPR spectroscopy. The reaction of the radicals with 3-hydroxytyramine hydrochloride and the type of chemical linkages were investigated. EPR, ESCA and FTIR spectroscopy were used for analysis. Bleached TMP was radicalised more efficiently than unbleached TMP. The radicals were unstable, as 90% of them were quenched within a few hours. Their lifetime was, however, found to be adequately long for performing coupling reactions. Bonding of new compounds to pulps via radical reactions thus seems to be possible.

Carboxymethylation of alkali extracted xylan for preparation of bio-based packaging films

This study describes the synthesis of carboxymethylxylan (CMX) and investigates its suitability as a film for packaging applications. High-purity polymeric xylan was extracted from commercial bleached birch kraft pulp and converted to CMX with three different degrees of substitution (DSs). The water vapor sorption, mechanical, and barrier properties of the films prepared from CMX were tested. Increasing DS of CMX films resulted in an increase in elongation at break and a decrease in tensile strength and Youngs modulus. The DS also affected the barrier properties of the films. CMX films with higher DS showed improved (reduced) oxygen permeability (OP), and the water vapor permeability (WVP) increased with DS. It was demonstrated that the carboxymethylation of xylan recovered from industrial side-streams and its conversion to packaging films could be a viable option to valorize xylan.

The Formation of Carboxylic Acids during Kraft and Kraft-Anthraquinone Pulping of Birch Wood

The formation of carboxylic acids was followed during kraft and kraft-anthraquinone (AQ) pulping of birch wood. In all 26 hydroxy monocarboxylic acids and 16 dicarboxylic acids were identified in addition to acetic and formic acids. Their total amount corresponded to 20% (kraft pulping) and 18% (kraft-AQ pulping) of the wood weight. Five of these acids have not earlier been detected in the black liquors. Acetic acid was formed rapidly at the initial stage of pulping, whereas the amounts of the other acids increased continuously without any distinct culmination period. In the presence of AQ the formation of lactic, 2-hydroxybutanoic and isosaccharinic acids was depressed, whereas increased amounts were recorded for glycolic, 3-deoxytetronic and 3-deoxypentonic acids.

Thermogravimetric behavior of black liquors and their organic constituents

Abstract The slow thermal degradation of various black liquors and their organic components (lignin, aliphatic carboxylic acids, extractives and polysaccharides) was investigated by thermogravimetry in the temperature range 25–700 °C under an inert nitrogen atmosphere and at a heating rate of 20 °C/min. Oven-dried samples of pine and birch black liquors from kraft and soda-anthraquinone pulping were tested. Similar tests with black liquor components were carried out both in the absence and in the presence of alkali. In all cases, the mass loss occurred primarily in the temperature range 250–500 °C. The thermograms of the various black liquors were very similar even though there were significant differences in the thermograms of the individual black liquor components. The possible roles of the individual components in the thermal degradation of black liquor are discussed. During the thermogravimetric runs, the formation of the most prominent gaseous products, carbon dioxide and carbon monoxide, was monitored by Fourier transforminfrared analysis.

Determination of low-molecular-mass aliphatic carboxylic acids and inorganic anions from kraft black liquors by ion chromatography.

An ion chromatographic (IC) method with suppressed conductivity detection (CD) was developed and validated for the quantitative determination of several low-molecular-mass aliphatic mono- and dicarboxylic acids as their carboxylate anions together with some inorganic anions (chloride, sulfate, and thiosulfate) from kraft black liquors. To confirm the identification of some carboxylate anions which lack commercial model substances, a qualitative IC method with suppressed electrospray ionization mass spectrometry (ESI-MS) was also developed. The separations were performed on an IonPac AS 11-HC anion-exchange column operated at 25 degrees C within 25 min by a gradient elution with aqueous potassium hydroxide (suppressed CD in the AutoRegen mode) or sodium hydroxide (suppressed ESI-MS in the pressurized bottle mode). In the validation process a mixture of carboxylic acids and inorganic anions in aqueous media and in seven different types of wood and non-wood black liquor samples were quantitatively analyzed by IC-CD. As a result, calibration lines with correlation coefficients of 1.00 for all analytes were achieved at a concentration range from 0.05 to 105 mg L(-1). In black liquor samples intra-day (n=6) precision values ranged from 0.9 to 5%. Day-to-day (n1=3) and intermediate precision values were less than 5% for all other compounds except sulfate and thiosulfate. The variability in the thiosulfate and sulfate results is due in large part to the oxidation of sulfide and thiosulfate, respectively. Recoveries were close to 100% with standard deviations less than 8%. Depending of the analyte, the limits of detection and quantification were, respectively, between 1 and 8 microg L(-1) and between 3 and 27 microg L(-1) for standard compounds in aqueous media and between 6 and 106 microg L(-1) and between 14 and 148 microg L(-1) for black liquor samples. These validation results clearly indicated that with respect to selectivity, linearity, limits of detection and quantification, precision, and accuracy, the IC-CD method showed good applicability in the determinations described above.

Soda-AQ pulping of reed canary grass

Abstract Delignification of reed canary grass (Phalaris arundinacea L.) was carried out by conventional soda-anthraquinone (AQ) pulping under varying conditions selected according to an orthogonal experimental design with four factors (cooking parameters) at three levels each L9 (34). The influence of these four parameters, i.e. effective alkali, EA (12, 15, and 18% on oven dried (o.d.) reed, as NaOH), maximum temperature (145, 155, and 165°C), time to maximum temperature (70, 90, and 110 min), and time at maximum temperature (0, 15, and 30 min) on the pulp properties (yield, kappa number, and viscosity) was studied. Results indicated that, with respect to delignification, EA was the most important parameter, other parameters having a minor effect. It was also noted that, contrary to wood-based pulping, the viscosity of the reed canary grass pulp prepared in this study increased as the kappa number decreased. This finding might be explained by assuming that variations in hemicellulose content of the pulp resulted in the changes in viscosity, and that cellulose degradation was limited.