Volume 8 Issue 3

The upgrading of bio-oil in supercritical ethanol was investigated using furfural and acetic acid as model compounds with the aim of exploring the reaction pathways. The effects of catalysts, temperature, cold H2 pressure, and the presence of other compounds were studied. Based on products analysis, upgrading with Pt/HZSM-5 improved performance over Pd/HZSM-5 and Ru/HZSM-5. Moreover, the catalytic performance of Pt/HZSM-5 could be enhanced by adding Ni as a second metal. Complete conversion of acetic acid and 83.06% conversion of furfural were achieved at 320 °C and 1.0 MPa of cold H2 pressure. The presence of acetone was found to increase the conversion of furfural. Through gas chromatography–mass spectrometry (GC-MS) analysis, the reaction pathways of furfural and acetic acid were clarified. It was concluded that it is possible to combine different reactions including esterification, hydrogenation, ring opening, isomerization, aldol condensation, and acetalization in supercritical ethanol.

This is the first report on chemical mutagenesis of Trametes versicolor IBL-04 to develop a hyper-producing mutant for overproduction of manganese peroxidase (MnP) using sugarcane bagasse as a substrate. A freshly prepared inoculum of indigenously isolated T. versicolor IBL-04 was treated with 100 µg mL-1 (v/v) ethyl methane sulfonate (EMS) and ethidium bromide (EB) separately for different time periods. The selected mutants and parent strain were cultured in solid-state fermentation (SSF) conditions to select the hyper-producing mutants. After selection of hyper-producing EMS- and EB-treated mutants, the fermentation parameters, including substrate type, incubation time, initial pH of the medium, temperature, moisture level, and carbon-to-nitrogen ratio (C:N), were optimized by adopting the Classical Optimization Strategy. T. versicolor IBL-04 treated for 90 min with EMS (EMS-90 mutant) gave maximum MnP production (935 U mL-1) after 8 days of fermentation. Supplementation with carbon and nitrogen sources significantly enhanced mutant growth, and under optimum conditions, the maximum MnP production by the mutant strain increased to 3045 U mL-1. The results indicated that the random chemical mutagenesis significantly enhanced the MnP production. The increased production of MnP by the EMS-90 mutant strain suggest its potential for commercial-scale enzyme production and biotechnological applications.

To better utilize low-density softwood, a thermo-hydro-mechanical densification process performed in an open system was studied to enable the manufacture of densified wood with a hard surface, strong bonding, and good dimensional stability. This study was aimed at optimizing three densification parameters, i.e., compression ratio (CR), temperature, and time, for balsam fir (Abies balsamea (L.) Mill.). The Brinell surface hardness, bond strength, and thickness recovery ratio of densified fir were examined. It was found that the optimal densification parameters were a CR of 60%, a temperature of 230 ºC, and a time of 20 minutes. The surface hardness and bond strength of optimized densified fir were about 30 and 8 MPa, respectively. The thickness recovery ratio of the densified fir after a 2-hour cold water soaking and another 2-hour boiling treatment was about 10%. Because the densified fir in this study was used for indoor applications only, its thickness recovery ratio could be minimal under conditions of use.

Mechanical properties of the core layer (in-plane) of high density fiberboards (HDF) were analyzed across the width of the board (i.e., across the feed direction). The tests were performed by means of a newly developed double cantilever I beam (DCIB) testing system, with analysis of internal bond strength and bending strength. The specimens were selected from a large-scale experiment in a central European HDF plant, including a completely different machine setting for each sample set. Homogeneous density and property distributions across the feed direction of the boards were generally assumed. During this trial the question arose as to whether processing leads to unequal mechanical properties across the feed direction. In total, 20 sample sets were tested longitudinally and laterally to the feed direction at eight measurement points, revealing 320 test specimens per testing procedure. In contrast to standard testing procedures, the specific fracture energy and the stress intensity factor revealed significant differences between the centre and the edge across the feed direction. This study revealed variations of mechanical properties across the width of the board using the DCIB approach.

The pyrolysis reaction of rice straw under microwave irradiation in bromide 1-ethyl-3-methyl imidazole ([Emim]Br) ionic liquid (IL) was investigated in this work. The effects of reaction temperature, mass ratio of IL to straw, reaction time, and microwave irradiation power on the yield of bio-oil were considered. An orthogonal experimental method was adopted to obtain the optimal technological conditions for pyrolysis: a reaction temperature of 160 °C, a mass ratio of IL to straw of 2:1, a reaction time of 15 min, and a microwave irradiation power of 700 W. The yield of bio-oil reached 28.2% at optimum conditions. The percent recovery of IL ranged from 84% to 87%. The recycled IL could be reused as straw pyrolysis solvent and did not affect the bio-oil yield because its structure was not damaged after being used in pyrolysis as a solvent.

Hemicelluloses dissolved in the pre-hydrolysis liquor (PHL) of kraft-based dissolving pulping processes can potentially be used to produce high value-added products such as fuel ethanol and xylitol. However, the isolation of lignin in PHL is a problem that remains unsolved and obstructs the utilization of those parts of hemicelluloses. Based on the principle of lignin isolation by acidification, the feasibility of using polyethylene oxide (PEO) to enhance the removal of lignin from PHL was tested in this work. The formation of lignin/PEO complexes was confirmed by means of turbidity, particle size, Fourier transform infrared spectroscopy (FTIR), and thermo-gravimetric analysis (TGA). The removal rate is affected by lignin content, chemical oxygen demand (COD), and decolorizing, and the results show that sulfuric acid acidification or PEO flocculation alone do not have an obvious effect on lignin removal from PHL. However, a much higher removal rate, compared to 2.81% (only acidification at pH 2) and 1.2% (only PEO on original PHL), of 22.75% is obtained by the sequential process of acidification and addition of PEO (pH 2 and PEO 350 mg/L in PHL).

A pretreatment in tandem composed of sunlight or sun-like UV-irradiation, freezing-thawing, soda swelling, and boiling (never drying between treatments), was applied to a slurry of ground-up Lupinus rotundiflorus, followed by enzymatic hydrolysis. The effects were studied through an experimental design in which the factors were employed cumulatively to statistically evaluate the effect of each factor on enzymatic saccharification. Results showed that swelling and physical disarrangement of the lignocellulosic complex probably occurred with little or no delignification and soda consumption. The disarrangement of the cell wall and tissue structures generated by the combined effects of UV-light, freezing-thawing, soda swelling, and boiling contributed to a yield of up to 67.0% of fermentable sugars with respect to hydrolyzed material (82.8% of theoretical fermentable sugars). This yield was comparable to that obtained in control samples using Whatman No.1 paper, which produces a very high yield of fermentable sugars after hydrolysis. Finally, the acceptable overall results showed that improved saccharification of lignocellulosic materials by means of natural agents is feasible.

The effects of press pressure on laboratory-made parallel strand lumbers (PSLs) that were manufactured from fast-growing rotary-peeled I-77/51(Populus deltoides) hybrid poplar clones’ veneer strands with a urea formaldehyde (UF) adhesive using press pressures ranging from 7.5 to 15 kg cm-2 in increments of 2.5 kg cm-2 were investigated. The physical and mechanical properties of PSL were affected by the press pressures. However, press pressures did not affect the combustion properties. Results indicated that higher press pressures lead to higher densification or compaction rates and specific gravities (SGs). For improved physical and mechanical properties, higher press pressures were found to be necessary. A press pressure of 12.5 kg cm-2 was found to be the optimum press pressure in relation to PSL properties. There are positive correlations among SG and mechanical properties as well as press pressures. The results may provide valuable information to assess the behavior of structural composite lumbers, including PSLs, that are manufactured using low and high press pressures. Utilization of fast-growing tree species is possible because their strength properties are improved through pressing.

The color and appearance of timber is influenced by a variety of physical and chemical effects. Especially the chemical composition and the surface structure play a major role. In particular, the influence of chromophore extractives and the effect of thermal degradation processes on the color of wood are widely discussed in the literature. The present study deals with the influence of the surface nanostructure on the visual appearance of wood. This new perspective should generally demonstrate various influences on the appearance of natural inhomogeneous surfaces. Therefore, two methods were used to change the nanoroughness of lignocellulose materials. With different oil coatings and UV-irradiation, the surface structures of the samples were changed, and the measured roughness using atomic force microscopy was then correlated with the collected brightness differences. The results show that a clear correlation exists between the nanoroughness altered by oil coatings or UV irradiation and the brightness of the wood surface. Due to various other influences, such as chemical changes and light refractions of the treated wood structure which also influence the color of wood, no quantification can be given at this point.

Fibers obtained from dissolved air flotation rejects were oxidized using a TEMPO oxidation system to prepare oxidized recovered fibers. The effects of oxidization time on carboxyl content, water retention value, and physical properties of handsheets were evaluated. The effects of pH, amount of oxidized recovered fibers, and aluminum sulfate on paper properties were also considered. The results showed that carboxyl content and water retention values increased with the increasing of oxidized time. FTIR analysis indicated that carboxyl groups were connected to the surface of fibers. SEM micrographs showed that fibers were integrated more closely in the paper sheet, benefiting from the addition of the oxidized recovered fibers. Tensile index, burst index, and folding endurance were respectively increased by 71.7%, 38.5%, and 600% when 3% of oxidized recovered fibers was added to the pulp at pH 5, with 0.5% aluminum sulfate addition, based on the original pulp. Tensile index and folding endurance were increased by 40.2% and 433.3%, respectively, when 1% oxidized recovered fibers (the oxidized time was 60 min) were added into pulp for recycled pulp. This finding may lay the foundation for greater re-use of fiber obtained from dissolved air flotation rejects.