Dry Wood Basis Research Articles

Optimization of the extraction of galactoglucomannans from Pinus halepensis

Abstract The effectiveness of pressurized hot-water extraction conditions for obtaining galactoglucomannans (GGMs) from Pinus halepensis suitable for applications like coatings and films packaging was investigated. For this purpose, high molar masses with high yields are required, presenting a serious challenge for hot-water extraction processes. The extraction of GGMs was carried out in an accelerated solvent extractor (ASE) and the isolation was performed by precipitation in ethanol. Three temperatures in the range 160–180 °C and five extraction times 5–90 min were tested in order to optimize extraction parameters of GGMs, avoiding thermal and chemical degradation in hot-water. Total dissolved solids (TDS) were determined gravimetrically after freeze-drying and weight average molar masses (Mw) were determined by high-performance size exclusion chromatography (HPSEC). Total non-cellulosic carbohydrates were determined by gas chromatography (GC) after acid methanolysis. Free monomers were additionally analyzed by GC. Lignin in water extracts was measured by an ultraviolet (UV) method. Acetic acid was determined after alkaline hydrolysis of acetyl groups and analyzed by HPSEC. The main parameters influencing the extraction processes of the GGMs, namely, extraction time and temperature were studied. Optimal extraction parameters of GGMs were identified at 170 °C and 20 min extraction time, with average Mw of extracted fraction of 7 kDa leading to a GGM yield of approximately 56 mg g o . d . m − 1 ${\text{mgg}}_{\text{o}.\text{d}.\text{m}}^{-1}$ , corresponding to 6% on dry wood basis.

Influence of Ethanol Organosolv Pulping Conditions on Physicochemical Lignin Properties of European Larch

Over the years, the organosolv pulping process has proven to be a valuable pretreatment method for various lignocellulosic feedstocks. The objective of this study was to characterize and assess the potential applicability of the organosolv lignin fraction from European larch sawdust, as no research has been conducted in this field so far. Eight different samples were prepared from the European larch sawdust under varied reaction conditions and one milled wood lignin sample as reference. The reaction temperature and sulfuric acid loading were varied between 420 and 460 K and 0.00 and 1.10% (w/w on dry wood basis) H2SO4, respectively. The antiradical potential (via DPPH• method), chemical structure (via ATR-FTIR, 1H NMR, 31P NMR, and thioacidolysis), as well as the molecular weight distribution of the isolated lignins were analyzed and compared. Results from thioacidolysis show a direct correlation between the amount of β-ether bonds broken and pulping process severity. Similarly, both antiradical potential and phenolic hydroxyl group content exhibit a direct relationship to reaction temperature and catalyst loading. On the contrary, the content of aliphatic hydroxyl groups and the average molecular weights both decreased with increasing process severity. The high content of phenolic hydroxyl groups and antioxidative potential of the larch organosolv fractions, especially for the sample isolated at 460 K and 1.10% H2SO4 loading, indicate good applicability as antioxidants as well as feedstocks for further downstream valorization and require additional research in this area.

Isolation and Thermal Characterization of Softwood-Derived Lignin with Thermal Flow Properties

A potential alternative biorefinery platform, in which high quality lignin is the main product of the process, is demonstrated. The polyethylene glycol (PEG)-modified softwood lignin (glycol lignin, GL) was isolated from Japanese cedar by acid-catalyzed PEG solvolysis, where liquid PEG with varying polymer chain length was used as the solvolysis reagent with a small amount of acid catalyst. The isolated glycol lignin had the weight-average molecular weight of 4000–7000 and exhibited a viscous thermal flow property, which is impossible for industrial softwood lignin without further processing steps. Thermal analyses, such as thermomechanical analysis (TMA) and capillary flow tester rheometer (CFT), proved to be sensitive techniques for determination of thermal flow behavior. The lignin yield and solid residue (mostly cellulosic residue), respectively, of 28%–31% and 36%–38% (dry wood basis) were obtained from PEG200 solvolysis with 0.5%–0.7% acid catalyst. The results indicated the effectiveness of the one...

Two-Stage Hot-Water Extraction of Galactoglucomannans from Spruce Wood

In order to preserve the polymeric structure and the acetylation degree of extracted galactoglucomannans and, at the same time, achieve high yield, ground spruce wood was subjected to a series of sequential two-stage extractions with an Accelerated Solvent Extraction (ASE) apparatus using plain water at 170°C. The total combined extraction time was one hour in all the extractions. The total yield of the dissolved material after 1 h extraction was almost the same, about 25% of the wood, irrespective of the time ratios between the first and the second extractions. The yield of hemicellulose high polymers with the weight average molar mass of 8–10 kDa during the first extraction had a maximum at 20 min extraction time, amounting to about 7% on dry wood basis, and comprising about half of the total extract. Along with the progress of the extraction, the molar mass of the hemicelluloses decreased and hemicellulose-derived low polymers with the weight average molar mass of 6–2 kDa became dominating. The extracted substances were fractionated, mainly according to their molar mass, by sequential precipitation with ethanol, acetone, and methyl tert-butyl ether (MTBE). The hemicelluloses with some amount of pectins comprised 83–90% of the precipitated polymeric material and the content of galactoglucomannans was about 80%.

Condensed lignin structures and re-localization achieved at high severities in autohydrolysis of Eucalyptus globulus wood and their relationship with cellulose accessibility.

Eucalyptus globulus wood was subjected to autohydrolysis pretreatment at different severity factors. The pretreated materials were enzymatically saccharified at a substrate load of 10% (w/v) using a cellulase enzyme complex. Around 82-95% of original glucans were retained in the pretreated material, and the enzymatic hydrolysis yields ranged from 58% to 90%. The chemical and structural changes in the pretreated materials were investigated by microscopic (SEM, LSCM) and spectroscopic (2D-HSQC NMR and FT-IR) techniques. 2D-NMR results showed a reduction in the amounts of β-O-4 aryl-ether linkages and suggested the presence of newly condensed structures of lignin in the biomass pretreated at the more severe conditions. Furthermore, the microscopic analysis showed that lignin migrates out of the cell wall and re-deposits in certain regions of the fibers at the more severe conditions to form droplet-like structures and expose the cellulose surface. These changes improved the glucose yield up to 69%, on dry wood basis.

Improved yield parameters in catalytic steam gasification of forestry residue; optimizing biomass feed rate and catalyst type

The catalytic gasification (900 °C) of forestry industry residue ( Eucalyptus saligna) was laboratory-studied. Biomass feed rate and type and amount of catalyst were assayed for their effect on the gasified product composition and the overall energy yield of the gasification reaction. The use of a calcined dolomite catalyst resulted in a combustible gas mixture of adequate calorific power (10.65 MJ m −3) for use as fuel, but neither the product gas composition nor the energy yield varied significantly with widely different amounts of the catalyst (2 g and 20 g). The use of NiO-loaded calcined dolomite catalysts did not affect the product gas composition significantly but led to a 30% increase in the total product gas volume and to a reduction in the rate of tar and char formation. The catalyst loaded with the smallest amount of NiO studied (0.4 wt%. Ni/Dol) led to the highest energy yield (21.50 MJ kg −1 on a dry-wood basis) based on the use of the gasified product as fuel. The gasified product was found to have an adequate H 2/CO molar ratio and H 2 content for use as synthesis gas source and partial source of H 2.

The calculation of EMC for the analysis of wood/water relations in Fagus sylvatica L. modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea

Beech wood (Fagus sylvatica L.) was modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU). The equilibrium moisture content (EMC) of wood modified with DMDHEU calculated on a dry modified basis is reduced. Previous results have shown that the modification with DMDHEU does not alter the capillary condensation; therefore, the reduction in EMC seems exaggerated. The equilibrium constants of the Hailwood–Horrobin model (Kd and Kh) and the molecular weight of a hypothetical polymer of modified wood capable of adsorbing one molecule of water (Wi) were calculated from the EMC on a dry modified wood basis (M) and on a dry wood basis (MR). The hypothetical polymer was also calculated by stoichiometry (Wc) and compared to Wi to estimate the number of operative OH groups. The number of operative OH groups decreased when M was used, in contradiction with the previously obtained results of differential heat of adsorption (∆Hs). Therefore, the use of MR is recommended for the analysis of moisture sorption in wood modified with DMDHEU.

Modification of Fagus sylvatica L. with 1,3-dimethylol-4,5-dihydroxy ethylene urea (DMDHEU). Part 2: Pore size distribution determined by differential scanning calorimetry

Abstract The enthalpy of melting and the freezing point depression of European beech (Fagus sylvatica L.) wood modified with 0.8, 1.3, and 2.3 M 1,3-dimethylol-4,5-dihydroxy ethylene urea (DMDHEU) were determined at different levels of moisture content above the fibre saturation point by differential scanning calorimetry. The results permitted estimations of the amount of water bound to the cell wall, non-freezing water (NFW), and pore size distribution. The NFW of wood modified with DMDHEU, calculated on a dry wood basis, was not significantly lower than that of the control. The ratio of bound to total water present in the sample was higher in unmodified than in DMDHEU-modified samples. The proportion of pores with a diameter ≤30 nm was 70% of the total cell wall voids for wood modified with 2.3 M DMDHEU and 18% for unmodified wood. These results indicate that DMDHEU reduced the pore size of the samples by occupying the void space present in the cell wall.

Thermal and catalytic decomposition of wood impregnated with sulfur- and phosphorus-containing ammonium salts

The decomposition of fir wood, impregnated with diammonium sulfate and diammonium phosphate, has been investigated with a laboratory scale reactor together with gas-chromatographic analysis of gas and condensable organics. The dependence of products and other process variables on the salt concentration in the wood (from 0 to about 20% on a dry wood basis) and the heating temperature (650–900 K) is qualitatively similar for the two cases. Given heating temperatures of about 650–750 K and using as a reference water-extracted wood, diammonium sulfate and diammonium phosphate concentrations of about 1% are apt to cause a small increase (factors of 1.2–2) in the yields of levoglucosan, 5-methyl-2-furaldehyde and 2-acetylfuran, whereas values in the range 2–5% highly augment the yields of levoglucosenone and 2-furaldehyde (factors of 14–16 and 3–2, respectively). Salt concentrations above 10% confer excellent fire retardance properties of wood with total yields of water and char up to about 70 and 85% and ratio values of non-combustible to combustible volatile products up to 3.5 and 6.5, respectively. The displacement of the reaction process at lower temperatures, the higher exothermicity associated with the enhanced char formation, the reduced convective cooling and the endothermicity of salt decomposition also highly affect the conversion times and the overall rates of volatile species release.

Products and Global Weight Loss Rates of Wood Decomposition Catalyzed by Zinc Chloride

Motivated by the production of fine chemicals and the improvement of flame retardance properties, experiments have been performed with a fixed-bed reactor to investigate the catalytic action exerted by zinc chloride on fir wood pyrolysis (catalyst concentrations between 0 and 16% on a dry wood basis and heating temperatures between 650 and 900 K). It has been observed that this Lewis acid acts as a dehydrating and cross-linking agent promoting the formation of char and water with total yields up to about 73%. As a consequence, the majority of organic condensable products generated from uncatalyzed pyrolysis of wood (hydroxyacetaldehyde, hydroxypropanone, levoglucosan, and other minor carbohydrates, phenols, and guaiacols) is rapidly reduced to low values. However, zinc chloride is a particularly effective catalyst (concentrations of 1–6% and temperatures of 700–800 K) to maximize the yields of levoglucosenone, acetylfuran, 5-methyl-2-furaldehyde, and, especially, 2-furaldehyde which is augmented by a fact...

Oxidation characteristics of chars generated from wood impregnated with (NH 4) 2HPO 4 and (NH 4) 2SO 4

Thermogravimetric analysis (heating rates between 5 and 15 K/min up to 873 K) has been carried out in air of chars, generated from the pyrolysis of wood and wood impregnated with (NH 4) 2HPO 4 and (NH 4) 2SO 4 (5%, dry wood basis) which are widely used as flame retardants. Salts significantly alter the char reactivity, but a mechanism consisting of three parallel reactions always provides a good description of the measurements. The estimated activation energy and reaction order of the most important combustion reaction, which causes the release of about 71–80% of the volatile matter, are nearly the same for untreated and (NH 4) 2SO 4 impregnated samples (about 190–200 kJ/mol and 0.86). A lower activation energy (about 150 kJ/mol) and a higher reaction order (1.35) are obtained for (NH 4) 2HPO 4 treatments. Scanning electronic microscope (SEM) images show significant modifications in the morphological structure of both wood and char as a consequence of salt impregnation.

Effects of Diammonium Phosphate on the Yields and Composition of Products from Wood Pyrolysis

The catalytic effects of diammonium phosphate on wood pyrolysis are investigated for applications in specialty chemical production and fire retardance. For a fixed-bed reactor operated at a temperature of 800 K, over a range of salt concentrations of 0−20%, the yields of char and water continuously increase (from 22 and 20%, respectively, to 45%), at the expense mainly of organic liquid products (from 43 to 6%) with only a small reduction in the yields of gases (percentages on a dry wood basis). As for the organic products, the yields of phenols, guaiacols, hydroxyacetaldehyde, hydroxypropanone, and some other minor carbohydrates rapidly attain low values. Major variations are undergone by levoglucosan only for mild treatments of wood, whereas levoglucosenone and 2-furaldehyde remain at the maximum values over a range of salt concentrations of roughly 2−5%. Diminution in the yields of acetic acid is generally slow. The same qualitative trends are preserved for a reactor temperature of 650 K. The ratio of the noncombustible to the combustible volatile products increases from 0.5 up to 5.5 already for a salt concentration of about 10%, thus confirming the fire-retardant action of diammonium phosphate in wood. Conversion times and global devolatilization rates are significantly affected by the modifications in the process energetics caused by salt addition.

Dissolution of fibre material in alkaline pre-treatment and refining of spruce CTMP

Abstract The chemistry of chemithermomechanical pulping (CTMP) was assessed by chemical pre-treatment of spruce chips, followed by laboratory-scale refining. Pre-treatments with alkali, sulfite, alkaline sulfite and alkaline peroxide liquors were carried out at 40°C, 60°C and 80°C. The sodium hydroxide dosages were 1% and 2% and the sodium sulfite and hydrogen peroxide dosages were 2%, 4% and 6% on a dry wood basis. Process water samples were taken before and after refining. Alkali consumption in the pre-treatments and the amount and composition of released wood components were determined. A major part of the alkali was consumed in the alkaline and alkaline sulfite pre-treatments. In the alkaline peroxide pre-treatments, however, alkali consumption was considerably lower. Acetic acid was the main wood component released to the process waters in alkaline pre-treatments. Pectins, determined as galacturonic acid and rhamnose by acid methanolysis, were also released to some extent, as well as easily soluble polysaccharides. After fibre separation in refining, more hemicelluloses and pectins were released. There was a significant difference between the degree of demethylation for pectins and the degree of deacetylation for galactoglucomannans after the pre-treatments. The diffusion of chemicals into the secondary wall layers seemed to be slower than the liquor penetration into the porous middle lamella through the pit pores. Up to 10% of the pectins were dissolved in the process waters as a result of depolymerisation and extensive demethylation. The residual amount of pectins in the fibres, however, was determined to be as low as 65–70% of the initial pectin content.

Analysis of beech wood fatty acids by supercritical acetone extraction

Soxhlet and supercritical fluid extracts of freshly cut oriental beech (Fagus orientalis) have been obtained using acetone. While the yield of the Soxhlet extract was 2.54% the yield of the supercritical acetone extract obtained at 240°C and 6.0–6.5 MPa was 9.55% (dry wood basis). The fatty acids present in the extracts were separated by chemical and Chromatographic methods and analysed by combined gas chromatography and mass spectrometry. Linoleic acid was the major fatty acid in both extracts.

Ammonium sulfide organosolv pulping

The use of ammonium sulfide in aqueous ethanol and methanol was investigated for pulping of wood. Hemlock chips required 21% ammonium sulfide (equivalent to 19% Na2O) at 180°C to become delignified to the kappa range 35–50. The yields exceeded those of conventional kraft pulps by 14% on dry wood basis. Over 75% of the original glucomannan was recovered in the pulp as the consequence of end group stabilization by ammonium sulfide. The intrinsic viscosity of the pulps, measured in cadoxen was 10.65 dl/g — approximately double the value for softwood kraft pulps. The pulps were readily bleached and possessed higher tensile and burst strengths but lower tear strengths than kraft pulps. Ammonium sulfide pulps from cottonwood were likewise obtained in high yields and with adequate strength properties.