Research Articles

The purpose of this study was to determine the pyrolysis characteristics and gas properties of woody biomass and coal. The main gases from the pyrolysis of biomass, coal, and mixtures of different ratios of the two were identified using TGA-FTIR. The evolution of gases and their characteristics were investigated in real time. Thermal analysis demonstrated that the biomass sources decomposed easily and that most of their weight was lost under lower temperatures than those of coal. TGA-FTIR analysis indicated that H2, CO2, CH4, and CO were the dominant gases released during the pyrolysis of biomass and mixtures. The results indicated that woody biomass could enhance coal pyrolysis or gasification and different types of biomass could have different influences on the thermal behavior of coal.

Statistical models and optimization of Eucalyptus globulus Labill. wood and bark delignification were achieved using response surface methodology (RSM). A central composite design was outlined to model the simultaneous influence of active alkali (AA), reaction temperature (T), and reaction time (t) on pulp yield (η) and kappa number (k) during the kraft pulping of wood and bark. Experimental results were fitted to a second-order polynomial with linear interaction of factors. The statistical models showed high coefficients of determination for both wood (R2η = 0.991, R2k = 0.975) and bark (R2η = 0.993, R2k = 0.984). Using these models, the optimum conditions to attain a pulp with the highest yield at an acceptable kappa number (below 17) were determined. For wood, the pulp yield was 51.6% (51.5% predicted) and the kappa number was 16.1 (16.9 predicted) under optimized conditions (AA = 21%, T = 151 ºC, and t = 118 min). For bark, the pulp yield was 51.3% (51.0% predicted) and the kappa number was 19.4 (16.9 predicted) under optimized conditions (AA = 15%, T = 166 ºC, and t = 114 min). The degree of polymerization (DP) of the carbohydrates for the optimized pulps, 1430 and 1151 for wood and bark, respectively, suggests low levels of polysaccharide degradation. The bark delignification showed similar behavior to wood.

Binderless fiberboards were made from oil palm (Elaeis guineensis) empty fruit bunches with two treatments: steam explosion and Fenton reagent oxidation. Fiberboards were prepared with a targeted density of 1.20 g/cm³ and a thickness of 4 mm. A factorial experimental design 22 with two center repetitions and one repetition was applied for each treatment. The oil palm waste was oxidized with Fenton reagent using a H2O2/Fe²⁺ ratio of 2%/0.2% to 4%/0.4% and a pressing temperature of 170 to 190 °C. Steam explosion was carried out at a severity factor of 3.5 to 4.0 at the same pressing temperature. Both treatments were examined under two major response variables: mechanical properties (modulus of rupture, MOR, and modulus of elasticity, MOE) and physical properties (thickness swelling, TS, and water absorption, WA). Steam-exploded samples developed better physico-mechanical properties than those that underwent Fenton reagent oxidation. The best results were obtained from fiberboards treated with the highest steam explosion design conditions (severity 4 and pressing temperature 190 °C) to give optimum values of MOE 3100.09 MPa, MOR 28.49 MPa, TS 11.80%, and WA 22.74%. Binderless fiberboards made from steam explosion-treated pulp satisfied favorably well the Colombian Standard NTC 2261.

A detailed study was undertaken to examine the color and chemistry changes of pine wood flour when its extractives are removed and when it is delignified. The solvent systems employed were toluene/ethanol (TE), acetone/water (AW), and hot-water (HW), while sodium chlorite/acetic acid were used for delignification (i.e., lignin removal (LR)). Samples were analyzed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, Fourier transform Raman (FT-Raman) spectroscopy, and colorimetry. The study demonstrated that color parameters (i.e., CIE L*a*b*) were only slightly affected by the removal of extractives, but changed noticeably when extractions were followed by delignification. TE extraction was more effective at removing the yellow colored substances, whereas AW mostly removed red colored substances that contained C=O groups. Inclusion of a HW extraction step after extraction with AW (AW-HW) removed components that contained conjugated C=O structures. Inclusion of a delignification step after extraction with AW followed by HW extraction (AW-HW-LR) was effective at removing yellow substances that contained non-conjugated C=O groups.

A wood-based composite was prepared via simple electroless Ni-Cu-P plating on birch veneer for EMI shielding. The effects of CuSO4·5H2O concentration on the metal deposition, elemental composition, phase structure, surface morphology, wettability, surface resistivity, and shielding effectiveness of coatings were investigated. The coatings were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). When the CuSO4·5H2O concentration was increased from 0.6 g/L to 2.2 g/L, the metal deposition was decreased from 79.61 g/m2 to 66.44 g/m2. Elemental composition showed that the copper content in the coating increased significantly, whereas the nickel content was reduced significantly and the phosphorus content was slightly reduced. The crystallinity of coatings increased, and fine-grain structure was observed, with higher copper content. Ni-Cu-P deposition improved the hydrophobic properties when the maximum static contact angle increased from 77.5° to 116.5°/cm2, and the EMI shielding effectiveness of Ni-Cu-P-coated veneers was higher than 60 dB in frequencies ranging from 9 kHz to 1.5 GHz.

The present work inspects the preparation of bio-composites of cassava starch with particles of eucalyptus wood through the application of a novel method of thermal compression. Bio-composites with different amounts of wood particles (5 to 30%), with particle sizes of 4 and 8 mm, were obtained. Chemical and mechanical evaluation of these samples was carried out using optical microscopy, infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the moisture absorption effect. The effect of the amount and size of the wood particles was tested by comparison with a thermoplastic matrix sample. Results from these evaluations demonstrated that the thermo-compression method produced bio-composites with a distribution of particles in the matrix that contributed to an increase in their tensile strength. This mechanical property is also enhanced by interfacial adhesion between the matrix and particles, as confirmed by SEM. Furthermore, the maximum amount of particles in the bio-composites (30%) showed the maximum resistance to moisture absorption. Temperature and time parameters contributed to the formation of diffraction patterns VH and EH as a consequence of the structural disruption of native starch. Finally, FTIR showed the chemical compatibility between the starch, glycerol, and wood particles.

The effects of assembly time on the properties of plywood were investigated in detail in this study. Three-layer plywood was fabricated, and its wet shear strength and formaldehyde emission were measured. The assembly time was varied to create three different assembly conditions (A, B, and C). The assembly condition A consisted of UF resin mixed with NH4Cl and kept for 0 to 8 h before gluing; the assembly condition B consisted of glued veneer kept in the open air for 0 to 8 h; and the assembly condition C consisted of glued veneer pre-pressed for 0 to 8 h before hot-pressing. The thermal behavior of the adhesive applied through varying assembly times was tested by differential scanning calorimetry (DSC). Results showed that the plywood prepared under condition C exhibited the highest wet shear strength, which was 37% and 18% higher than those under conditions A and B, respectively. The plywood prepared under condition C exhibited the lowest formaldehyde emission, which was 32% and 16% lower than those under conditions A and B, respectively. The DSC results indicated that the curing process consisted of three sections and that the rate of the curing reaction was the fastest in the first section and was similar in the latter two sections.

A superabsorbent resin (SAR) synthesized from carboxymethyl cellulose (CMC) by grafting acrylic acid (AA) was studied using single-factor analysis. The optimum preparation conditions were as follows: plasma discharge power of 250 W, processing time of 90 s, pressure of 300 Pa, m(CMC):m(AA) ratio of 1:9, m(K2S2O8):m(CMC) ratio of 1:4, and neutralization degree of 40%. Under these conditions, the resin has a salt water absorbency of 38.5 g/g and a stable chlorine dioxide solution absorbency of 27.2 g/g. The structural characterization of the SAR was also studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning colorimetry (DSC). The results showed that the resin was synthesized by grafting copolymerization of CMC and AA, and the water absorbency and thermal stability of the resin were greatly improvedcompared to CMC alone. This method may provide a new way for high value-added utilization of bagasse.

Hydrothermal pretreatment of corncobs in aqueous media under non-isothermal conditions is an effective means for solubilizing hemicellulose fractions and improving cellulose hydrolysis. The effects of a range of pretreatment severities (temperatures of 170 to 230 °C) on the conversion of corncobs into fermentable sugars were examined. The major differences between the conversions of untreated and pretreated corncobs were the dissolution of hemicelluloses into the prehydrolyzate and the partial removal and relocation of lignin on the external surface of biomass particles (in the form of recondensed droplets) in the pretreated corncobs. Hemicellulose dissolution increased with pretreatment temperature. The maximum sugar recovery (272.3 g/kg raw material) and the minimum accumulation of inhibitory compounds in the prehydrolyzate were observed following treatment at 190 °C. While the fibrils of the untreated raw material remained largely intact, serious disruption of the cell wall was observed in SEM images of the surfaces of pretreated samples. Accordingly, the cellulose digestibilities of residues increased from 26.8% for the raw material to almost 100% for the 190 °C-treated sample. It was concluded that low severity hydrothermal pretreatment can be successfully applied to corncobs to obtain high cellulose digestibility while operating at low enzyme charges.

Autohydrolysis of Eucalyptus globulus both with and without the addition of 5 g/L formic acid was explored for different liquid-to-solid (L/S) ratios at 150 ºC for 100 min. The L/S ratio has an impact on the dissolution of wood components during prehydrolysis. The extraction yield of wood components other than lignin decreased with increasing L/S ratio, while lignin removal increased with increasing L/S ratio, irrespective of acid reinforcement. The molecular weight (Mw) of dissolved hemicelluloses and lignin remained relatively constant. The average degree of polymerization of hemicelluloses isolated from the hot water extract was between 7 and 8 over a L/S ratio range from 3:1 to 50:1. The cellulose to glucose conversion yield of pretreated wood samples improved during prehydrolysis with 5 g/L formic acid. Although the conversion yield of autohydrolyzed wood meal stayed relatively constant, the conversion yield of dilute acid-pretreated wood samples increased with increasing L/S ratio.