Research Articles

Alkali pretreatment is one of the leading pretreatment technologies for biofuel applications. The histochemical and structural characteristics of poplar cell walls were investigated before and after sodium hydroxide pretreatment (121 oC, 2%) to understand the alterations in biomass cellular structure, which were correlated with saccharification yield. Results showed that alkali pretreatment preferentially removed lignin from the S2 of fibers, which was similar to the behaviors of coniferyl alcohol and aldehyde (lignin-CAA), exhibiting a positive correlation between removal of the two structures. Additionally, the cellulose microfibril angle was enlarged as the residence time increased during pretreatment. Scanning electron microscopy (SEM) analysis further suggested that pretreatment caused ultrastructure changes in cell walls with cracks formation on cell wall surface, especially in the areas adjacent to the cell corner middle lamellar (CCML). Accordingly, the cellulose digestibility of residues increased from 32.1% for the raw material to 53.7% for the treated samples obtained in 72 h. It can be concluded that the changes in topochemistry and ultrastructure of poplar cell walls resulting from alkali pretreatment mediated the efficiency of enzymatic hydrolysis of residues.

Wood-plastic composites (WPCs) represent a growing class of durable, low-maintenance construction materials whose use can decrease dependence on petroleum. High-density polyethylene (HDPE), chitosan (CS), wood flour (WF), boric acid (BA), and borax (BX), as well as maleic anhydride grafted polyethylene (MAPE) and polyethylene wax (PE wax), were used to develop a durable wood-plastic composite (WPC) using the extrusion method. The effects of boron compounds (3%, 6%, 9%, or 12% by weight BA/BX) on the mechanical and fire properties of the WPCs were investigated. Mechanical testing indicated that as the percentage weight of boron compounds increased, the flexural modulus, flexural strength, and tensile strength significantly decreased. Cone calorimeter tests were used to characterize the fire performance of the WPCs, and these results suggested that adding BA/BX compounds to WPCs modestly improved the fire performance. As the percentage weight of BA/BX increased from 3% to 9%, the time to ignition (TTI), heat release rate (HRR), total heat release rate (HRR-Total), smoke production rate (SPR), and specific extinction area (SEA) of the WPCs were all reduced.

A series of sulfated zirconia-titanium dioxide (SO₄^2-/ZrO₂-TiO₂) catalysts with different Zr-Ti molar ratios were prepared by a precipitation and impregnation method and characterized by ammonia adsorption/ temperature programmed desorption (NH₃-TPD), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The catalysts were used in the catalytic conversion of a sugar mixture (glucose and xylose) to 5-hydroxymethylfurfural and furfural in a water/n-butanol reaction system. An optimized yield of 26.0 mol% for 5-hydroxymethylfurfural and 47.5 mol% for furfural was obtained within 2 h at 170 °C over the SO₄^2-/ZrO₂-TiO₂ catalyst with a Zr-Al molar ratio of 7:3. Catalysts with higher acidity and moderate basicity were more favorable for the formation of the target product.

The current Chinese Standard (GB5889-86 1986) for wet chemistry determination assumes that there is no temperature degradation of sugars during hot water extraction. There is therefore a need to quantify this level of error and propose possible solutions for future revisions. This research was performed to investigate the thermal resistance of polysaccharides in common fibrous materials. A two-factor, two-level experimental design was employed, in which pre-oven drying and water bath temperature were controlled and changes in extractive content were measured. The thermodynamic equations for polysaccharide thermal degradation in ramie and wood were calculated. High-performance liquid chromatography (HPLC) was employed to identify monosaccharide changes during the process. This study found that polysaccharides in fibrous materials have considerable thermal degradation during oven drying at 100 °C and hot water treatment. Lower temperature combinations are recommended during hot water extractive testing when sugar analysis is to be subsequently performed.

Submerged culture conditions for laccase production by Pleurotus ostreatus were optimized by response surface methodology (RSM). A total of six factors, carbon (glucose), nitrogen sources (urea and peptone), 2,5-xylidine (inducer), wheat bran (lignocellulosic material), and medium pH, were optimized. A total of 50 experiments were conducted, and the obtained data were modeled using a second-order polynomial. The optimized conditions show significant improvement in laccase expression, by approximately 3.5-fold (12,124 U/L).

Wetting of coated papers by isopropyl alcohol (IPA)-based fountain solutions or surfactant solutions was studied in this paper. Additionally, the effect of paper surface properties on wetting was analyzed. To that end, six fountain solutions were prepared. Three solutions had increasing amounts of IPA, and three were made from surfactant-based dampening agents. Eight commercial coated papers were selected and characterized in terms of roughness and surface free energy. Paper resistance to wetting by fountain solutions was evaluated by measuring the static and dynamic contact angles. Static contact angles between the paper surface and the IPA-based fountain solutions decreased as the alcohol concentration increased, whereas the wettability with surfactant-based fountain solutions was highly dependent on their surface tensions. Paper surface free energy strongly affects the static contact angle and only moderately affects the dynamic contact angle.

In this study, bio-oil was analyzed by gas chromatography mass spectrometry (GC-MS), and the evaporation characteristics of bio-oil were studied at different heating rates (10, 20, and 30 °C/min) from 35 °C to 250 °C by a thermal analyzer (TG-DSC). The TG-DSC results of bio-oil showed that the heat requirement of bio-oil during the evaporation process ranged from 2.072´103 to 2.299´103 J/g, and the bio-oil activation energy ranged from 1.22×104 to 3.34×104 J/mol. Moreover, four models with five compounds (methanol, water, ethanol, furfural, and phenol) were established to study the bio-oil evaporation process. By comparing the TG-DSC results of bio-oil and its models at 30 °C/min, it was shown that the optimal model was model 2, which has the following chemical composition: methanol (27.10 wt.%), water (44.96 wt.%), ethanol (16.24 wt.%), furfural (4.40 wt.%), and phenol (7.30 wt.%). Model 2 exhibited a minimal relative error in dynamic parameters and characteristic curve parameters. The errors for activation energy of the TG, activation energy of the DSC, maximum endothermic rates, and the total of the heat absorption were 3.04%, 5.88%, 2.49%, and 1.06%, respectively.

Three different types of recycled polyurethane (PUR) material, two in powder form from a pulverizing process (one < 50 µm and one < 250 µm) and one in polyol form from a glycolysis process, were used as substitutes for polymeric methylene diphenyl diisocyanate (pMDI) resin at 5%, 15%, and 30% ratio, respectively, to replace the pMDI resin for particleboard manufacturing at 8% resin loading. The reactions between pMDI resin and recycled PUR powder and polyol were investigated with Fourier transform infrared (FT-IR) spectroscopy. It was found that 5% substitution of pMDI with recycled PU powder of < 50 µm resulted in significantly higher panel internal bonding (IB) strength than pure pMDI resin, which also tended to increase panel modulus of rupture (MOR), and modulus of elasticity (MOE). Polyol did not show advantages over PUR powder in particleboard application. Increasing the size of recycled PUR powder from < 50 µm to < 250 µm decreased the panel IB, which also tended to decrease MOR and MOE. Recycling PUR materials in either powder or polyol form in particleboard manufacturing did not improve panel thickness swelling, but did appear to improve panel water absorption.

Hydrophobically modified celluloses were prepared by the esterification of monocarboxycellulose (MCC) and carboxymethylcellulose (CMC) with methanol, followed by the amino-de-alkoxylation of the methyl esters with n-octadecylamine. These cellulose derivatives were fed at 30 and 60 g/kg for 4 weeks to female rats. The diets were supplemented with palm fat (60 or 50 g/kg) and cholesterol (0 or 10 g/kg). There was no significant effect of amidated celluloses on the feed intake or body weight of rats. Both MCC and CMC derivatives significantly decreased the concentrations of cholesterol present in the serum and liver. The supplementation of diets with hydrophobically modified celluloses tended to increase fecal concentrations of cholesterol and coprostanol and significantly increased fecal concentrations of total neutral sterols. In rats fed diets containing cholesterol, the total serum cholesterol correlated negatively with the fecal concentrations of neutral sterols. It can be concluded that MCC-C18 and CMC-C18 are effective cholesterol-lowering agents.

Larix spp., a wood species of low dimensional stability, was heat-treated in nitrogen at 180 to 210 °C for 6 h. Changes in the thermal decomposition and combustion behaviors of the wood after heat treatment were investigated by TGA, SEM, FTIR, and cone calorimetry. TGA confirmed the loss of hemicellulose from heat-treated Larix spp. Small cracks in the cell wall and loss of resin from the vessels of heat-treated wood were observed by SEM. Hemicellulose degradation within the heat-treated samples was indicated by decreased intensities of typical O-H and C=O stretching vibration peaks in the FTIR spectra. The HRR and MLR curves of treated wood were much lower than those of the untreated ones, which is preferable for fire safety. However, the time to ignition of treated samples decreased from 22 to 13 s and the total smoke production increased by 4.76 and 43.3% for 180- and 210 °C-treated samples, respectively, a detrimental effect on fire safety. To determine the influence of heat treatment on the combustion behaviorof Larix spp., the fire safety properties of heat-treated wood (such as wood structure building, furniture, and floors) must be studied further.