Volume 13 Issue 4

An efficient and selective process for the conversion of carbohydrates to 5-hydroxymethylfurfural (HMF) was applied over a novel phosphated TiO₂-SiO₂ (P-TiO₂-SiO₂) catalyst. The catalyst, synthesized by a facile sol-gel technique, was characterized by X-ray diffraction (XRD), N₂ sorption, NH₃ temperature-programmed-desorption, and Fourier transform infrared spectroscopy (FT-IR) study of the pyridine adsorbed. The highest HMF yield of 63.0 mol% was achieved at 170 °C for 90 min over P-TiO₂-SiO₂ catalyst in a tetrahydrofuran (THF)/H₂O-NaCl system. The P-TiO₂-SiO₂ catalyst showed a predominant catalytic performance in the synthesis of HMF, a result of its moderate acid density and suitable Brønsted/Lewis (B/L) acid ratio. Additionally, the catalyst was shown to be efficient in the conversion of more complex cellulose with the high HMF yield of 56.0 mol%. More importantly, this mesoporous catalyst exhibited high stability and recyclability, making it a promising choice for the future production of HMF.

The efficacy of five different nanoparticles (zinc-oxide, zinc-borate, silver, copper, and copper-borate) were evaluated after application at different concentrations for protection against Coniophora puteana and Coriolus versicolor. Tests were performed with two different wood species (beech and pine sapwood). Furthermore, tests were done to investigate the resistance of the nanoparticles to leaching. Overall, the results of the efficiency of the investigated nanoparticles against the brown and white rot fungi were diverse. One of the investigated fungi showed a tolerance to the nanoparticles in some cases (zinc-oxide, silver nanocubes, and copper). The most effective nanoparticle treatments were those containing borate. However, only the zinc-oxide, copper, and silver nanoparticles showed a high resistance to leaching. Unfortunately, zinc-borate and copper-borate showed a low resistance to leaching, as the treated samples showed a similar decay compared with that of the control. Thus, only the zinc-oxide at the highest investigated concentration (5% m/m) provided effective protection after leaching for both of the investigated fungi. Also, the copper nanoparticles showed potential as an effective treatment at higher concentrations.

Two hybrid models of cellulose and heat transfer media were designed to simulate changes of cellulose and gas during the heat treatment of wood. The chosen heat transfer media were air and nitrogen, and the range of selected simulation temperature was from 450 to 510 K. The diffusion coefficients of air and nitrogen both increased as the temperature increased, and the diffusion coefficient and amplification of air were larger than that of nitrogen. In addition, the calculation of free volume (fraction) confirmed this conclusion. The mechanical parameters of cellulose were analyzed in terms of the Young’s modulus, Poisson’s ratio, and the ratio of bulk modulus to shear modulus (K/G), which were affected by the temperature and heat transfer medium. Compared with the nitrogen model, the cellulose in the air model decreased in the Young’s modulus and K/G as the temperature increased, while the Poisson’s ratio increased. Young’s modulus and K/G were larger when the heat transfer medium was nitrogen, and the Poisson’s ratio was superior to nitrogen in the air environment. The rate of change of mechanical parameters of cellulose in the air system was greater than that of nitrogen, which was related to the larger diffusion coefficient of air.

The complex supramolecular structure of lignocellulose makes it difficult to clarify the recalcitrance to enzymatic digestibility. As an extensively used model mimicking the plant cell wall, assembled lignocellulosic film was applied to investigate inhibition factors of enzymatic hydrolysis for the first time. Xylan was deposited and then a model lignin compound was synthesized to equip bacterial cellulose films. Scanning electron microscopy and surface contact angle analyses revealed that lignin inhibited enzymatic hydrolysis by reducing cellulase accessibility to the cellulose surface. Moreover, xylan showed a good correlation (R² = 0.969) with the decreased cellulose conversion, although xylan itself did not display inhibitions. The component and surface analyses revealed that xylan enhanced lignin formation on the cellulose surface, and thus increased lignin inhibition. These results highlighted the validity of lignocellulosic films in elucidating inhibitions of cellulose enzymatic hydrolysis. The research could thus open a new avenue for the mechanistic study of the recalcitrance of lignocellulose to enzymatic hydrolysis.

Financial data of barbecue bamboo charcoal plants located in the Fujian province, China with annual productions of 1000 MT, 2000 MT, and 3000 MT was investigated to compare the economic benefits. The project was evaluated based on the time of purchasing bamboo processing residues as the starting point and the sale of barbecue bamboo charcoal as the end point. Calculations of the net present value (NPV), dynamic investment pay-back period (PBP), internal rate of return (IRR), and break-even point (BEP), and a sensitivity analysis were performed. The plant with an annual production of 3000 MT had good economic benefits with an NPV of 3.1 million USD and PBP of 2.89 years. The IRR and BEP of the plant were 44.4% and 63.8%, respectively, indicating that the plant had a good ability to adapt to market changes and resist risks. The sales prices had a greater impact on the sensitivity than the plant operating costs. Thus, high-quality barbecue bamboo charcoal should be produced to increased the price of the product for better economic benefits, even though all of the plants had good market prospects. A large-scale plant should be designed for better economic benefits if there are adequate raw materials.

Novel lignocellulosic composite films (LCFs) based on poplar wood flour (PWF) and waste filter paper (WFP) were developed with 1-allyl-3-methylimidazolium chloride ([Amim]Cl) as green solvent. Scanning electron microscopy revealed that the dissolved part acted as the matrix that combined with the insoluble part and reinforced the LCFs. Under the same preparation conditions, there was an increased amount of the insoluble part with an increased amount of PWF. The PWF and WFP mass ratio was a key parameter that influenced the solubility of the raw materials. The differences in the grammage, thickness, and mechanical properties among the groups were related to the dissolution extent of the raw materials. Group A (100 wt% WFP) had the best mechanical properties because of the highest dissolution of cellulose. When the PWF and WFP mass ratio increased, the mechanical properties of the samples decreased and surface bonding became poor. Consequently, the TS of group F (100 wt% PWF) was the lowest. The elongation and elastic modulus showed the same trend as that of the TS.

Microfibrillated cellulose (MFC) was isolated from the byproduct of soymilk, tofu, and okara (soybean residue) using a chemi-mechanical technique. Initially, petroleum ether treatment at 50 °C for 8 h and protease treatment at 50 °C for 2 h were used to remove fat and protein, respectively. A 6 wt% hydrochloric acid solution at a 20 mL/g acid-to-cellulose ratio was applied at 88 °C for 60 min to remove the residual hemicellulose and degrade cellulose. Finally, the sample was gently homogenized at 60 MPa to aid in individualization of the fibers to nano dimension; homogenization for 5 and 25 passes resulted in fibers labeled as MFC-5 and MFC-25, respectively. The amorphous region of okara cellulose was higher than other non-wood fibers. The average diameters of MFC-5 and MFC-25 were within the range of 13 nm to 93 nm and 9 nm to 55 nm, respectively. MFC obtained from okara has potential to reinforce ecofriendly cellulosic nanofibrillated for diverse applications.

Autocatalyzed isopropanol-water extraction is a potentially high-value lignin isolation methodology. A solution of isopropanol-water (2-PrOH/ H₂O, 7:3, v/v) was used on willow powder (Salix matsudana cv. Zhuliu), at varying temperatures (160 °C to 210 °C) and reaction times (6 h to 12 h). The highest yield (61 wt%) and purity (93.7%) with low weight/number average molecular weight (1681/1061 g/mol) was observed at a treatment temperature and time of 190 °C and 10 h, respectively. Fourier-transform infrared (FTIR) and two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy indicated that the lignin was composed of syringyl (S) and guaiacyl (G) units that were not severely damaged. More specifically, ³¹P-NMR showed that S units were dominant. Finally, a majority of glucan was preserved.

With the advent of surface modification procedures for the production of fibrillated cellulose, it has become evident that some procedures have a limited negative impact on the cellulose surface chemistry. In the case of TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl)-mediated oxidation, this is evident from the residual aldehyde groups present on the surface and the impact on the colour stability of the resulting material under conditions of high temperature drying. In this paper, an alternative is presented for the common procedure for the oxidation of aldehydes on TEMPO oxidized cellulose using an acidified solution of sodium chlorite. By using potassium peroxymonosulfate, residual aldehyde groups were converted to carboxylic groups, and the colour stability of the modified cellulose fibers was increased. The post-oxidation procedure takes place under mildly alkaline conditions, which preserves the surface charge on the TEMPO modified cellulose fibers, and this in turn helps with fibrillation of the material into a nanofibrillar form.

Wood-based activated carbon microspheres (WACMs) were successfully prepared from Chinese fir. However, the weak thermal stability of the precursors resulted in melting at high activation temperatures, which led to a lower yield and poor adsorption properties. To promote the thermal stability of the precursors in the process without chemicals, this paper focused on the effects of the pre-oxidation before activation on the thermal stability and chemical structure of the precursors and the pore structure of the activated samples. The results showed that during the pre-oxidation process, the O/C ratio increased noticeably and the intensity of oxygen-containing functional groups, such as carbonyl, carboxyl, and ester groups, were enhanced, which contributed to the improvement of the thermal stability. Moreover, the etching effect of oxygen on the structure of the precursors was verified when the porous structure was enriched by activation. The activated sample pre-treated at pre-oxidation temperature 250 °C had the maximum micropore specific surface area and pore volume. As the temperature was raised to 280 °C, the mesopore specific surface area and pore volume increased, which indicated that the optimization of the pre-oxidation parameters contributed to the formation of the mesopore structure.