Research Articles

Corncob was calcined within a temperature range of 300 °C to 700 °C to prepare a series of corncob residue catalysts for the transesterification of glycerol with dimethyl carbonate (DMC) to synthesize glycerol carbonate (GC). Among the catalysts, the corncob residue catalyst obtained through calcination of corncob at 500 °C (CCR-500) showed a relatively high basicity and satisfactory catalytic activity. The structural investigation results indicated that CCR-500 was composed of carbon material and some alkaline mineral salts. Using CCR-500 as the catalyst, a glycerol conversion of 98.1% and a GC yield of 94.1% were achieved when the reaction was performed at 80 °C for 90 min, with a catalyst amount of 3 wt% and glycerol to DMC molar ratio of 1:3. The comparison of CCR-500 with the reported catalysts indicated that the CCR-500 was a low-cost, high-active, and easily-accessible catalyst for the transesterification of glycerol with DMC.

To improve their hygroscopicity, kenaf fibers were thermally modified by saturated steam at 180 °C for 5, 10, 20, and 40 min. The chemical structure, cellulose crystallinity, cell-wall mechanics, and moisture sorption properties of kenaf fibers were analyzed to evaluate the modification effectiveness. Mass loss and Fourier transform infrared spectroscopy spectra (FTIR) changes indicated that the lignin content and cellulose crystallinity (CrI) increased with the reduction in hemicellulose after a steam treatment, especially for a long duration. The increased CrI and relative lignin content resulted in an increased elastic modulus (Er) and hardness (H) of fiber cell walls after the steam treatment. The reduction in hydrophilic groups and increased stiffness of the cell wall after the steam treatment caused an obvious reduction in the equilibrium moisture content (EMC) at the given relative humidity (RH). It also reduced the moisture increment/decrement and sorption hysteresis during the adsorption and desorption process.

This study evaluated the combined effects of rosin and aluminum sulfate (alum) on the leachability of boron, the color stability, and the decay resistance of poplar (Populus ussuriensis) wood treated with boron compounds. After leaching, the boron content in the leachates was analyzed via the azomethine-H method. Results showed the amount of boron released from the rosin-alum-boron solution treated samples was reduced by approximately 30% when compared to the samples treated with boric acid alone. All samples treated with rosin-alum-boron formulations exhibited greater color stability than that of the untreated controls after being exposed to natural weathering. The decay resistance of the treated wood blocks was measured via a soil-block culture. The results revealed that after being treated with the rosin-alum-boron formulations, the decay resistance of the leached wood was markedly improved. The average weight loss of the samples degraded by both fungi tested was less than 20%. Notably, scanning electron microscopy equipped with an energy dispersive X-ray analysis showed that the B element was still in the cell lumens of the leached and decayed wood blocks. This signified that the use of rosin combined with aluminum sulfate as a fixative agent may reduce boron leachability and could increase the usage of wood treated with boron preservatives.

Pretreatment of Salix gracilistyla Miq. with 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) together with N,N-dimethylacetamide (DMAc) as a co-solvent achieved an improvement in enzymatic saccharification yield in comparison to the raw material without pretreatment. The effects of the [EMIM]Ac/DMAc ratio (7:3, 5:5, and 3:7), pretreatment temperature (80 to 140°C), and pretreatment time (1 to 3 h) on enzyme saccharification were investigated. Acremonium cellulase and Optimash BG were used as the enzyme cocktail. With addition of DMAc to [EMIM]Ac, the viscosity of the co-solvent was drastically decreased. With increasing pretreatment temperature and time, the water soluble fraction increased at all [EMIM]Ac/DMAc ratios. The cellulose crystallinity also increased with increasing amount of DMAc in the co-solvent but decreased with increasing pretreatment temperature. The yields of glucose and xylose increased with increasing [EMIM]Ac amounts in the co-solvent, varying from 72.8% to 84.3% and 75.3% to 88.1%, respectively, for all [EMIM]Ac/DMAc ratios. These values were markedly higher than the glucose and xylose yields of 25.7% and 8.4%, respectively, obtained with DMAc alone and comparable to the 86.7% and 83.9% yields, respectively, obtained with [EMIM]Ac alone. The highest glucose and xylose yields obtained under the investigated pretreatment conditions were 84.3% and 88.1%, respectively.

Three fast-growing wood species in Romania, namely birch, willow, and poplar, were considered in this work. These species may have potential to replace softwoods or mixtures of wood species frequently used in the production of oriented strand boards (OSB). This study evaluated some physico-mechanical properties of these wood species that influence the performance of OSB boards made using 100% of strands from each individual species. Wood strands were cut, dried, screened, and sorted in order to form the core and surface layers of OSB boards. They were blended with a polymeric diphenyl methane diisocyanate adhesive (pMDI) and compressed with the help of a hydraulic press. The mechanical tests were performed under standard laboratory conditions. The obtained OSB boards made of each of the wood species met the EN standard of minimum requirements for OSB/2 properties, except the MOE of poplar-OSB, while its MOR was higher than that obtained for OSB made of birch even for small differences in board density. The birch-OSB presented superior elastic properties. Results of this experimental work can have industrial applications for an efficient use of low-grade raw material.

Eucalyptus was applied to investigate the influence of extractives on thermo-degradation of wood during heat treatment. Degradation characteristics, specifically the thermal degradation kinetics and volatile products during the heat treatment, were studied. A kinetic analysis was performed based on the Arrhenius equation and the time-temperature superposition principle. A devolatilization analysis was then conducted according to the chromatography identification. The results showed that the extractives facilitated the thermo-degradation and initiated the degradation at a lower temperature. An earlier degradation starting point was detected, and a lower activation energy of 65.7 kJ/mol was calculated for the non-extracted Eucalyptus. The VOCs collected in this research were primarily acetates, furans, terpenes, and other compounds. The non-extracted specimen released more VOCs than the extracted specimen. Compared with extracted samples, further hemicellulose degradation was identified for the non-extracted samples at the whole stage of 180 °C and a temperature-elevating period of 200 °C, as well as lignin decomposition at the temperature-holding section of 220 °C. However, only hemicellulose degradation was observed in extracted samples. This research could be helpful for the mechanism explanation of wood heat treatments and to promote the process to be more efficient and environmentally friendly.

Kraft pulp and alkali peroxide mechanical pulp were prepared with aspen and wheat straw and bleached with chlorine dioxide, an alkali extraction strengthened by hydrogen peroxide, hydrogen peroxide, or peroxyacetic acid. Eight different bleaching effluents were obtained, and a Coomassie brilliant blue G-250 method was applied to determine the lignin content in each of the bleaching effluents. The visible light spectra indicated that the alkali-soluble lignin and the alkali bleaching effluent could increase the absorbance of Coomassie brilliant blue G-250 at 640 nm, but the acidic soluble lignin and the acidic bleaching effluent did not increase absorbance. Thus, the Coomassie brilliant blue G-250 method applied to alkali bleaching effluents but did not apply to acidic bleaching effluents. An analysis of the pH, particle size, zeta potential, and visible light spectra determination showed the Coomassie brilliant blue G-250 absorbed on lignin particles, which caused the absorbance increase at 640 nm. With the actual measured value of the lignin content obtained via the Klason lignin method, the relative error of the results obtained via the Coomassie brilliant blue G-250 method was less than or equal to 3.8%.

Mesoporous heteropolyacid (HPA) nanorods having a composition of [C16H33N(CH3)3]xH3-xPW12O40 ((CTA)xH3-xPW, x = 1, 2, and 3) were synthesized by surfactant encapsulation and were evaluated for their catalytic activity in cellulose hydrolysis. The (CTA)H2PW nanorods were found to be most active with 57.2% yield of 5-hydroxymethylfurfural (5-HMF) at ~100% conversion in water/methyl isobutyl ketone (MIBK) biphase, which was higher than (CTA)H2PW nanosphere at 140 °C for 11 h. The yields of 5-HMF and glucose were obtained as 4.5% and 54.3% at 160 °C for 8 h in water system, respectively. (CTA)H2PW nanorods showed higher tolerance to such feedstocks as lignocellulose, i.e. corn straw with 19.8% and 8.3% yields for glucose and xylose at 35.4% conversion in water. Moreover, (CTA)H2PW nanorods showed higher stability and long duration with ten times reuse. (CTA)H2PW nanorods presented higher efficiency and reusability in conversion of cellulosic biomass.

Diatomite is extensively used as a natural environmental material because of its biogenic origin and stable structure. The zeolitic imidazolate framework (ZIF-8) is a prototypical metal-organic frame (MOF) that is well known for its high surface areas and chemical stability. Herein, a facile method for the generation of diatomite in situ loaded by ZIF-8 (D/Z) was reported. The results of powder x-ray diffraction (PXRD) analysis confirmed the successful loading of ZIF-8 on the diatomite. The ZIF-8 were distributed uniformly on the surface of the diatomite from the scanning electron microscope (SEM) images. The specific surface of the D/Z increased due to the loading of the ZIF-8. Methylene orange (MO-) in an aqueous form was efficiently separated and removed through a simple mixture and filtration process where the D/Z was employed as an absorbent, and the removal rate of the MO- increased in the case of the sample with more ZIF-8 loaded on the diatomite. In addition, the D/Z was reused after several regenerations by washing out the adsorbed dye.

Old books suffer from aging and deterioration spurred by acidification, oxidation, and other factors. To preserve these important historical documents, it is important to implement deacidification and reinforcement methods to extend their durability. In this study, microdroplets of 75 g/L sodium hydroxide solution were atomized before being utilized to neutralize acidity in the paper. As well, styrene acrylic latex was diluted to 10 times for atomization to function as a reinforcing agent. In addition to studying these methods individually, the effects of simultaneous deacidification and reinforcement were also studied.