Research Articles

Microcrystalline cellulose (MCC) was prepared from the residue of the incomplete liquefaction of eucalyptus sawdust; atmospheric liquefaction was carried out using ethylene glycol as the solvent and 1-(4-sulfobutyl)-3-methylimidazolium hydrosulfate as the catalyst. The highest cellulose content in the residue reached 93.9%. The MCC prepared from liquefaction was characterized by various techniques, which included infrared spectroscopy, X-ray diffraction, thermo-gravimetric analysis, and scanning electron microscopy. The results were compared to those of a commercial MCC (cotton linters). The analyses indicated that hemicelluloses and lignin were removed extensively from the MCC produced from the sawdust. The MCC was a cellulose I polymorph with 79.0% crystallinity. The particles were shaped as elongated rods and had good thermal stability. The particle sizes of the produced MCC ranged from 1 µm to 100 µm with a mean of 38.6 µm.

To achieve a deeper and more uniform impregnation of water-soluble phosphorous-based fire retardants (WPFRs), in this work several physical pretreatment methods were developed including kerfing, boring, and the combination of both for structural square-wood posts in wooden buildings. Research was performed on three wood species, sugi (Cryptomeria japonica), larch (Larix olgensis), and Douglas fir (Pseudotsuga menziesii Franco), which are generally recognized as refractory wood species. The effects of pretreatment method on chemical uptake, chemical penetration, and mechanical properties were evaluated. The methods were compared with the incising method, a traditional method used for wood preservation. The results indicated that the pretreatments effectively increased the chemical uptake and penetration, especially in larch wood. Although the traditional incising method also increased the chemical uptake, it decreased the modulus of rupture (MOR) and compressive strength. The boring and combined method with a boring diameter less than 12 mm are recommended for WPFR wood impregnation.

The optimization of the process conditions for fire retardant ultra-low density fiberboards (ULDFs) was investigated using response surface methodology (RSM). Three parameters, namely those of Borax-Zinc-Silicate-Aluminum (B-Zn-Si-Al), chlorinated paraffin (CP), and chloride-vinyl chloride emulsions (PVDC) were chosen as variables. The considerably high R2 value (99.98%) indicated the statistical significance of the model. The optimal process conditions for the limiting oxygen index (LOI) were determined by analyzing the response surface’s three-dimensional surface plot and contour plot, and by solving the regression model equation with Design Expert software. The Box-Behnken design (BBD) was used to optimize the process conditions, which showed that the most favorable dosages of B-Zn-Si-Al, CP, and PVDC were 800 mL, 46.47 mL, and 35.64 g, respectively. Under the optimized conditions, the maximum LOI was 48.4.

Pine wood was pretreated with H2SO4 and NaOH, followed by liquefaction in methanol at temperatures ranging from 200 to 350 °C, to produce bio-oil. Composition analysis and scanning electron microscopy (SEM) observation were performed to study the impact of the pretreatment on the pine wood structure. The SEM images showed that the structures of the samples were destroyed by pretreatment. After being pretreated by H2SO4, the size of holes generated was smaller than that with pretreatment by NaOH. Furthermore, the influences of the temperature, methanol content, and residence time on the yield of the water-soluble fraction (WS), ether-soluble fraction (ES), and bio-oil were determined. Shorter residence time and higher amounts of methanol favored the products of WS, ES, and bio-oil. Gas chromatography-mass spectrometry (GC-MS) analysis showed that phenols, ketones, aromatics, and aldehydes are the main components of bio-oil.

The effect of temperature on the physiochemical characteristics of a solid fuel or biocoal derived from the dried trunk of Adansonia digitata (Baobab) was studied using torrefaction processes. The chemical composition of the solid fuel or char obtained by wet (HTC) and dry torrefaction processes were determined by elemental and thermogravimetric (TGA) analyses. The Brunauer-Emmett-Teller (BET) surface area analyzer measured the porous texture and surface area of the prepared samples. The changes in the surface morphology and crystallinity of the prepared samples were evaluated by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The torrefaction process successfully improved the energy content from 16.8 MJ/kg to 22.0 MJ/kg, which was evidently higher than the starting precursors. The maximum energy yield obtained was 90.0% using dry torrefaction at 250 °C. The energy densification ratio was also higher for the char produced by the dry torrefaction process. However, the char produced by the HTC process at 250 °C showed the highest surface area. The pore diameter was higher for HTC-char produced at the same temperature. Overall the results revealed that the torrefaction of lignocellulosic biomass is beneficial for upgrading the fuel quality and energy densification of char residues.