Volume 9 Issue 3

Lignin is one of the main components of corncob acid hydrolysis residue (CAHR). It can be used as a feedstock for biomaterial and biochemical production via biorefining. In this study, CAHR lignin was extracted, and enzymatic/mild acidolysis lignin (EMAL) was produced to ensure efficient lignin recovery. Next, hydrothermal conversion of the EMAL was carried out. The influences of process conditions including the temperature, time, and mass ratio of deionized water to EMAL on the hydrothermal conversion were thoroughly investigated to quantify analysis of the aromatics. EMAL produced from CAHR had a structure of the G-S-H type, in which the p-hydroxyphenyl unit was the primary structural unit, followed by the guaiacyl structural unit. The syringyl structural unit was less common. The yields (wt. %) of phenol, guaiacol, and 4-ethyl-phenol reached maxima of 1.26%, 0.75%, and 1.16%, respectively, at a reaction temperature of 310 °C and time of 30 min with a mass ratio of 80:1.

The final features of natural fiber composites (NFCs) depend on the integrated characteristics of their constituents. In the industry today, natural agro waste fibers are evaluated using a limited number of criteria. In this work, a combined multi-criteria evaluation stage technique (CMCEST) is introduced as a simple efficient systematic indicator to enhance evaluation of the available natural agro wastes for polymeric composites. In this proposed technique, criteria affecting the proper selection of natural agro waste fibers were combined and divided into sequence stages as follows: single-evaluation-criterion (SEC), combined-double-evaluation-criterion (CDEC), combined-triple-evaluation-criterion (CTEC), etc. These stages are based on combined physical, mechanical, and economic evaluation criteria and can be extended to several further stages to include other beneficial characteristics. The effectiveness of this technique was demonstrated by evaluating coir, date palm, jute, hemp, kenaf,and oil palm fibers simultaneously. This combined evaluation criteria can lead to more informative decisions regarding selection of the most suitable fiber type for polymeric composites. The CMCEST enhancements can reveal new potential fiber types through better evaluation schemes, help achieve clearer indications of the capabilities of available agro wastes to enhance composites, and determine proper ecological waste management practices. Utilizing the proposed technique, the date palm fiber type was found to be quite promising due to beneficial characteristics revealed in CTEC, which provides a reasonable, cheap, and eco-friendly alternative material suitable for different applications.

A novel two-step process for pretreatment of corn stover was investigated with the goal of increasing sugar recovery and decreasing the capital cost. In the process, corn stover was first treated with dilute hydrochloric acid to maximize xylan recovery, and then the residue was treated with aqueous ammonia to alter the lignin structure and swell the cellulose surface. The optimal conditions were 110 °C and 40 min for 1% dilute hydrochloric acid pretreatment with a liquid to solid ratio of 10:1 followed by aqueous ammonia pretreatment at 37% NH3, 130 °C, 30 min, and liquid to solid ratio of 6:1. Under these pretreatment conditions, the glucan and xylan recoveries were 83.2% and 97.3%, respectively, with cellulase dosage at 15 FPU/g of substrate. When the cellulase dosage was decreased from 15 FPU/g to 10 FPU/g of substrate, the glucan recovery only dropped to 70%, while the xylan recovery remained high at 95.1%. The results show that this two-step pretreatment was effective for achieving high sugar recovery from corn stover by enzymatic hydrolysis.

The effects of CaCl2, MgCl2, FeCl3, NaCl, and AlCl3 on the solubility of lignin in the prehydrolysis kraft black liquor of Masson pine were studied using a focused-beam reflectance measurement (FBRM) instrument and UV spectra. The results showed that NaCl and AlCl3 have no obvious effects on the coagulation or solubility of lignin in the prehydrolysis kraft black liquor at high effective alkalinity. However, CaCl2, MgCl2, and FeCl3 have significant effects on the solubility of lignin in the black liquor. According to the reduction rate of UV absorbance, the effects of these chloride salts on the black liquor lignin solubility at high alkali content were as follows: AlCl3≈NaCl＜MgCl2＜CaCl2＜FeCl3.

The curing kinetics of foam prepared from the tannin of spruce tree bark was investigated using differential scanning calorimetry (DSC) and the advanced isoconversional method. An analysis of the formulations with differing amounts of components (furfuryl alcohol, glycerol, tannin, and a catalyst) showed that curing was delayed with increasing proportions of glycerol or tannins. An optimum amount of the catalyst constituent was also found during the study. The curing of the foam system was accelerated with increasing temperatures. Finally, the advanced isoconversional method, based on the model-free kinetic algorithm developed by Vyazovkin, appeared to be an appropriate model for the characterisation of the curing kinetics of tannin-based foams.

5-hydroxymethylfurfural (HMF) is an important bio-based platform chemical, and its aerobic selective oxidation to 2,5-diformylfuran (DFF) still remains a challenge. This work dealt with active manganese dioxide (AMD) and efficiently catalyzed HMF oxidation to DFF with a yield of ~73% at 393 K and 60 bar O2 in N,N-Dimethylformamide (DMF). Through analysis of liquid products and the catalyst characterization using X-ray diffraction (XRD), a scanning electron microscope (SEM), a transmission electron microscope (TEM), and an elemental analyzer, it can be seen that this AMD catalyst is a low-cost, efficient, and environmentally benign heterogeneous catalyst for the aerobic selective oxidation of HMF to DFF in a one-pot technique. These research results may provide guidance for the development of more efficient catalysts for the future industrial production of high-value added DFF.

In a previous study, a soybean meal-based adhesive was developed by mixing soybean meal flour with a self-made cross-linking agent. The objective of this study was to investigate the effects of retention agents on the properties of the adhesive. Soybean meal flour (together with a cross-linking agent) and two kinds of additives (SDS and cationic PAM) were used to develop the soybean meal-based adhesive. The water resistance of the adhesive was measured by testing the wet shear strength of the resulting three-ply plywood samples and the residual rate of the different adhesives themselves. The apparent viscosities of the adhesives were also measured. Cross sections of the cured adhesives were imaged with a scanning electron microscope (SEM). Results showed that adding 0.5% SDS to the adhesive formulation improved its wet shear strength by 38.6%, from 0.83 to 1.15 MPa, and increased the residual rate by 1.3%, from 76.5 to 77.5%. Adding 0.01% PAM improved the water resistance of the adhesive by 38.6%, from 0.83 to 1.15 MPa, and increased the residual rate by 2.2%, from 76.5 to 78.2%. Adding 0.2% SDS and 0.01% PAM together improved the water resistance of the adhesive by 55.4%, from 0.83 to 1.29 MPa. The plywood bonded with the soybean meal/SDS/PAM adhesive met interior plywood requirements. SEM results showed fewer holes and cracks on the cross section of the cured adhesive with the addition of SDS and PAM.

Ground calcium carbonate (GCC) was modified with a starch/sodium stearate complex and used to prepare different coating weights by controlling the starch dosages. Modified GCC was characterized by scanning electron microscopy (SEM) and particle size analysis. The effects of starch dosage (based on the dry weight of GCC) on the size of modified GCC, the coating weight of modified GCC, and the utilization rate of starch were evaluated. Four kinds of modified GCC with different coating weights obtained by controlling the starch dosage were studied in the last part of this paper. The starch dosage was found to play an important role in the coating weight of starch/sodium stearate complex used in preparing the modified GCC and the utilization rate of starch, but did not have as much of an effect on the size of modified GCC. The higher coating weight was beneficial for retention of the filler retention and for enhancing paper strength properties at the same ash content. The higher coating weight, however, caused a decrease in the paper ash content at the same initial added filler.

The objective of this work was to investigate the possibility of using Na-bentonite as a raw material to produce aluminum salt-modified bentonite (AlMB) for desilication of green liquor. Batch experiments were carried out by varying the experimental parameters to find the optimum conditions. The optimum adsorbent dose was 20 g/L. The maximum adsorptions of 96.37% and 87.22% took place at pH 7.4 when the initial concentrations of silicate in green liquor were 4 and 6 g/L, respectively. The kinetic models showed that the process included physical adsorption and chemical adsorption. Finally, this study showed that the extent of desorption was 56.78% for silicate after desorption of AlMB in 2 M NaOH solution. The AlMB is an efficient and novel adsorbent for desilicating that can provide a good reference for the “silicon influence” in a papermaking mill.

Acetic acid-catalyzed steam explosion pretreatment was applied to wheat straw at temperatures of 190 and 210 °C for 2, 6, and 10 min of residence time. The effects of pretreatment conditions on the total gravimetric recovery, hemicellulose sugars, glucose content, and yield of the enzymatic hydrolysis of cellulose were studied. The results indicated that the total gravimetric recovery decreases while the solubility of hemicellulose and the yield of cellulose enzymatic hydrolysis increase as the pretreatment severity increases. Pretreatment at 190 °C with a 2-min residence time resulted in the highest total gravimetric recovery, 58.9%. The optimum defiberation, glucose content, and enzymatic hydrolysis yields of 70.4 and 79.6%, respectively, occurred following pretreatment at 210 °C with a 10-min residence time. The optimal pretreatment condition was determined to be 190 °C for 10 min. Under the optimum conditions, the recovery yield of all sugars reached 42.7%. This pretreatment resulted in the highest recovery yield of all sugars.