Volume 11 Issue 2

This work has established the optimum reaction conditions in a biphasic system using microcrystalline cellulose as the raw material, an ionic liquid as the solvent, metal chloride as a catalyst, and an organic solvent as the extraction reagent. The optimum reaction conditions were microcrystalline cellulose:ionic liquid – 1:10 (mass ratio), chromium(III) chloride (CrCl3) – 6.8 mol% (based on the glucose unit of cellulose molecule), reaction time – 3 h, temperature – 130 °C, and mass ratio of 1-butyl-3-methyl-imidazolium chloride ([BMIM]Cl) to methylbenzene – 1:4.4]. Under these conditions, the yields of glucose and 5-(hydroxymethyl)furfural (5-HMF) were 27% and 55%, respectively. The solvent [BMIM]Cl could be reused twice. The first recovery rate of [BMIM]Cl was approximately 70.9%. The product 5-HMF was obtained in 64.7% yield, which decreased after the first [BMIM]Cl recycling. The second recovery rate of [BMIM]Cl was 45%. The yield of 5-HMF was 39.6%, which decreased after the second recycling of [BMIM]Cl. In this paper, the energy consumption, operation, reutilization of [BMIM]Cl, and product yields of a one-phase system and a biphasic system were compared. Experimental results demonstrated that the biphasic solvent system was suitable for the degradation of cellulose to glucose and 5-HMF.

A bacterial endo-polygalacturonase (endo-PGase) gene from the plant pathogen Pectobacterium carotovorum was cloned into pGAPZαA vector and constitutively expressed in Pichia pastoris. The recombinant endo-PGase secreted by the Pichia clone showed a 1.7 fold increase when the culture medium included glycerol in replacement of glucose as the carbon source. The enzyme had optimum activity at pH 5.5 and 40 °C with stability between pH 5.0 and 8.0 and at temperatures up to 50 °C. The enzyme activity was enhanced by 41% with the addition of 1 mM Co++, and inhibited by Fe++ with a 63% reduction. The mode of the enzyme action showed internal cleavage of α-1,4 glycoside bonds of polygalacturonic acid and citrus peel pectin. Trigalacturonate and hexagalacturonate were the main hydrolysis products, with a yield of 0.44±0.01 and 0.21±0.01 mg released per mg polygalacturonic acid substrate, respectively. This represents the first report of a microbial endo-PGase that produced trimer and hexamer uniquely as the end products of hydrolysis, in contrast to mixtures of mono-, di-, and trigalacturonates commonly observed for the action of fungal enzymes. Pectic oligosaccharides generated from native carbohydrate polymers offer the potential application as building blocks for value-added products.

A novel fire-resistant adhesive made from polyvinyl alcohol, urea, phosphoric acid, and starch was demonstrated for use as a binder and fire retardant to produce ultra-low density fibreboard (ULDF) with clear environmental benefits. The results from Fourier transform infrared spectroscopy showed the presence of chemical bonding between fire-resistant adhesives and ULDFs. The limiting oxygen index (LOI), combustion behaviour, and thermal stability were characterized using a LOI text, cone calorimeter, and thermal analyzer, respectively. The results demonstrated that the LOI value of the fire-retardant ULDF can reach up to 34.2 with 300 mL of fire-resistant adhesive. It was established that the additive noticeably reduced the peak of heat release rate, total heat release, and total smoke release of ULDF. Their morphologies after combustion were elucidated using a scanning electron microscope, and a char layer in the condensed phase was observed. Thermal analysis showed that the thermal stability of ULDF improved dramatically and the residual weight increased 4-fold, to 48.32%. Therefore, such ULDFs will be tremendously attractive as renewable, sustainable, and bio-based insulating materials.

Pinus pinaster Aiton is the pine with the largest natural area of distribution in Spain and the species that sustains the country’s resin industry, with an annual average production of 3.2 to 3.5 kg per tree. After trees have been tapped, their wood has a high resin content and is of little use because of machining difficulties. For the first time, resinous wood of this species was characterized to compare its physico-mechanical properties with those of non-resinous wood. Significant differences were found in all the properties studied except modulus of elasticity. The resin produced by tapping decreased swelling, probably by reducing accessibility to the –OH groups and decreasing the available spaces during the capillary condensation phase. Similarly, tapping caused an increase in wood density and therefore in hardness, at the same time improving the mechanical properties.

The effects of wear on the performance of sanding belts were determined for European beech (Fagus sylvatica L.) and English oak (Quercus robur). These measurements are presented as a function of the defined sanding time of 480 min on a manual sanding belt machine. Sanding belt pressure on the piece surface (6600, 10400, 14700, and 18600 Pa), sanding direction (cutting speed vector with reference to wood fibers equal to 0°, 60° and 90°), wood hydrothermal treatment, and sanding belts from various manufacturers were the variables. The sanding belt wear was monitored by means of specific wood removal rate (g/cm2.min) in 20-min intervals by the means of reference samples with size of 50 x 50 x 50 mm, which were sanded for 1 min. The resulting curves for the sanding belts, as well as the statistical models of the wood removal rate, decreased as a function of the sanding time, described by the function y = a + b.e–ct. This work also describes the impact of wood species, optimum pressure, and grinding time on the characteristics to abrasion.

The effect of biochar addition and turning frequency was examined relative to biochar-chicken manure co-composting and its associated methane (CH4) and carbon dioxide (CO2) emissions. The results demonstrated that biochar addition was more effective in accelerating the composting process, which was indicated by a 5.2% increase in peak pile temperature and a 148% increase in peak CO2 emission with 20% biochar amended-compost, compared with the control that had no biochar. The compost pH increased and moisture content decreased significantly over the whole course of composting with the biochar amendment. The addition of 20% biochar also resulted in a 54.9% decrease in peak CH4 emission compared with the control. More frequent turning (daily vs. every 3 or 7 days) accelerated the composting process and reduced the CH4 emission.

Thermal modification of spruce wood (Picea abies L.) was conducted at three different temperatures (160, 200, and 240 °C) and treatment times (1, 3, and 5 h). The cyclic sorption experiments were performed for relative humidity changes of 30 to 85%. The equilibrium moisture content of the thermally modified wood was reduced up to 50% after treatment at 240 °C for 5 h. The sorption isotherms were described with the Guggenheim, Anderson, and De Boer (GAB) model. Cyclic sorption increased the monolayer capacity. Thus, the monolayer sorption was increased, while the multilayer sorption was limited. The dependence of the mass loss, hysteresis loop, and the maximum difference of equilibrium moisture content on the modification temperature and duration was modeled by response surface methodology. There was a very strong correlation between the modification temperature and mass loss, while the relationship between treatment time and mass loss was insignificant. The correlations between the modification parameters and the descriptors of sorption hysteresis were stronger after cyclic sorption. The sorption hysteresis decreased after cyclic sorption. This result was mainly caused by the increase of the monomolecular sorption for the adsorption processes.

This paper describes preparation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mediated oxidized cellulose nanofibers (TOCNs) from corn husk. The process adopted for this work included alkaline treatment, TEMPO/NaBr/NaClO-mediated oxidation, and homogenization. The morphological investigation of TOCNs was performed using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The chemical composition and structure of the material obtained after each stage of the treatments was characterized through Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. The thermal stability of the samples was investigated by thermogravimetric analysis (TGA). The obtained TOCNs possessed a narrow width, ranging from 8 to 10 nm, and a high aspect ratio (> 300). The crystallinity type of TOCNs was found to be cellulose-Iβ. Compared with the original fibers, the crystallinity of TOCNs gradually increased because of the removal of hemicellulose and lignin, while the thermal stability decreased.

The alkyl-alkoxysilane (AAS) pre-impregnation method and thermal modification were combined to improve the water-related properties of southern yellow pine (Pinus spp.) sapwood. Four types of AAS with varied alkyl chain lengths, including butyltrimethoxysilane (BTMOS), octyltrimethoxysilane (OTMOS), dodecyltrimethoxysilane (DTMOS), and cetyltrimethoxysilane (CTMOS), were used to pre-impregnate wood samples at a concentration of 5% or 15% mass fraction, and the subsequent thermal modification was processed at either 180 °C or 200 °C. The water absorption, dimensional stability, equilibrium moisture content (EMC), mechanical properties (modulus of rupture (MOR), and modulus of elasticity (MOE)), and mold resistance of the treated wood were evaluated. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to reveal the mechanism of the combined treatments in improving the properties of wood. Compared with thermal modification alone, the AAS combined treatment improved the water repellency, mechanical properties, and mold resistance of the modified wood. The study also identified the penetration of AAS into the wood cell wall and its reaction with the chemical components of the cell wall.

Co-polymer systems of methylene diphenyl diisocyanate (MDI) and phenol-formaldehyde (PF) resins with different molecular weights were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The FTIR and TGA coupled with differential thermogravimetric (DTG) results showed that higher molecular weight of PF resins not only promoted the reaction of isocyanate and PF co-polymer system, but also resulted in a better thermal property of prepared co-polymers. The XRD results revealed that higher molecular weight led to a higher proportion of ordered or crosslinking structures in the hybrid resin system. The relationship between the thermal resistance, mechanical properties and the molecular weights of phenolic resins needs further study.