Hot Water Pre-extraction Research Articles

Integrated biorefinery for production of biodegradable film, bioethanol, and soda pulp from corn stalks

In traditional pulping, black liquor is burned in an alkali recovery system to produce energy. According to the integrated forest biorefinery (IFBR) concept, hemicellulose is partially pre-extracted prior to pulp production to generate value-added products. Corn stalks have a remarkable carbohydrate content (75% w/w), and thus were examined in this study in terms of the IFBR concept. The hemicelluloses were pre-extracted with hot water (90, 120, 135, and 150 °C), NaOH, and NaOH + NaBH4 (50, 70, and 90 °C) for 4 h. NaOH charges of 16.7, 26.7, and 33.3% were explored. The extracts were utilized to produce bioethanol and biodegradable films, and papermaking pulps were produced from the solid fractions. Differences among groups were identified via analysis of variance, and the Duncan’s test was applied to determine those differences that were significant. The results showed that the alkaline pre-extraction (26.7% NaOH at 50 °C) removed 35.6% of the xylose from the stalk structure. The liquid fraction collected from the hot water pre-extraction at 150 °C gave a 14.7% (g/100 g soluble material) yield of bioethanol. Moreover, the theoretical ethanol yield was calculated as 89.4%. The addition of gluten and nanocellulose to the xylan enabled the production of high-quality biodegradable films. Furthermore, the pulps produced from the hot water pre-extracted solid fractions were comparable in yield and pulp properties to the control soda pulp.

Production and Characterization of High Value Prebiotics From Biorefinery-Relevant Feedstocks.

Hemicellulose, a structural polysaccharide and often underutilized co-product stream of biorefineries, could be used to produce prebiotic ingredients with novel functionalities. Since hot water pre-extraction is a cost-effective strategy for integrated biorefineries to partially fractionate hemicellulose and improve feedstock quality and performance for downstream operations, the approach was applied to process switchgrass (SG), hybrid poplar (HP), and southern pine (SP) biomass at 160°C for 60 min. As a result, different hemicellulose-rich fractions were generated and the chemical characterization studies showed that they were composed of 76–91% of glucan, xylan, galactan, arabinan, and mannan oligosaccharides. The hot water extracts also contained minor concentrations of monomeric sugars (≤18%), phenolic components (≤1%), and other degradation products (≤3%), but were tested for probiotic activity without any purification. When subjected to batch fermentations by individual cultures of Lactobacillus casei, Bifidobacterium bifidum, and Bacteroides fragilis, the hemicellulosic hydrolysates elicited varied responses. SG hydrolysates induced the highest cell count in L. casei at 8.6 log10 cells/ml, whereas the highest cell counts for B. fragilis and B. bifidum were obtained with southern pine (5.8 log10 cells/ml) and HP hydrolysates (6.4 log10 cells/ml), respectively. The observed differences were attributed to the preferential consumption of mannooligosaccharides in SP hydrolysates by B. fragilis. Lactobacillus casei preferentially consumed xylooligosaccharides in the switchgrass and southern pine hydrolysates, whereas B. bifidum consumed galactose in the hybrid poplar hydrolysates. Thus, this study (1) reveals the potential to produce prebiotic ingredients from biorefinery-relevant lignocellulosic biomass, and (2) demonstrates how the chemical composition of hemicellulose-derived sources could regulate the viability and selective proliferation of probiotic microorganisms.

Xylan and xylose decomposition during hot water pre-extraction: A pH-regulated hydrolysis

One of the key issues in the development of biofuels using lignocellulosic feedstocks is to increase the yield of fermented sugar, and simultaneously decrease the generation of fermentation inhibitors. Therefore, it is essential to understand the degradation mechanism of xylan during hot-water pretreatment. We analyzed the hydrothermal degradation products of xylan and xylose under different conditions. Results showed that furfural and formic acid formed from xylose reached a maximum value of 32.56 % and 35.14 %, respectively. By increasing the initial pH of the xylan solution, the furfural concentration can be reduced effectively to 2% and the formation of formic acid was preferred under alkaline conditions. On this basis, we proposed a new hydrothermal degradation pathway of xylan in alkaline solution. The in-depth understanding of xlyan degradation during hot water pre-treatment will be beneficial for improving the efficiency of biofuel production.

Effects of Hot Water Pre-Extraction on Energy Consumption and Brightness of Bamboo Alkaline Peroxide Mechanical Pulp

The main purpose of this paper was to investigate the effects of hot water pre-extraction (HWP) on the refining energy consumption and the brightness of bamboo alkaline peroxide mechanical pulp (APMP). It was found that compared with un-extraction, the refining energy consumption dropped by about one-third after HWP. The reduction of energy consumption was proved through enhancing the channel of water and chemicals into inferior fiber based on the surface characterization of bamboo. Scanning electron microscope (SEM) images showed that the HWP made the fibers' structure loose and porous. Both pore volume and specific surface area were increased significantly after HWP, by 260.00% and 1804.76%, respectively. A decrease in pulp brightness was mainly due to the formation of new chromophore groups during the HWP process. The results of 13C nuclear magnetic resonance spectroscopy (13C-NMR) illustrated that some structures of milled wood lignin (MWL), such as guaiacyl, etherificated guaiacyl, and aromatic units, were increased during the HWP process. However, some lignin-links units of α-O-4, β-O-4, and some carbohydrate structures such as xylan, α- and β-glucose, and β-and β-mannose in lignin-carbohydrate complex (LCC) were evidently degraded. Additionally, most of the lignin and LCC were degraded under the simulative conditions of HWP bamboo. Furthermore, the analysis of UV spectrophotometry indicated that HWP was conductive to the generation of chromophore groups such as conjugated carbonyl, catechol, and o-benzoquinone.

Lignin isolation from spruce wood with low concentration aqueous alkali at high temperature and pressure: influence of hot-water pre-extraction

Lignin was successfully isolated from spruce wood with an accelerated solvent extractor using low concentration aqueous NaOH as an extraction solvent. The biorefinery concept was also applied.

Hydrogen Ion Catalytic Kinetic Model of Hot Water Preextraction for Production of Biochemicals Derived from Hemicellulose using Moso Bamboo (Phyllostachys pubescens)

A kinetic model was developed for predicting the time-dependent behavior of xylo-oligomer, xylose, arabinose, and furfural in hydrolysates during hot water preextraction of moso bamboo at various elevated temperatures. Due to the poor performance of conventional kinetic models for describing the autohydrolysis of moso bamboo, this model introduces the time dependence of the hydrogen ion concentration as an essential influencing factor. For each reaction, the activation energies and effect factor of hydrogen ion concentration on reaction rate coefficients were calculated using the proposed kinetic model. This model is helpful in the investigation of the dissolution and degradation of hemicellulose during hot water preextraction of moso bamboo and thus provides guidance for process control and optimization.

Effect of chitosan and cationic starch on the surface chemistry properties of bagasse paper

The use of non-wood fibers in the paper industry has been an economical and environmental necessity. The application of dry–strength agents has been a successful method to enhance the strength properties of paper. The experimental results evidencing the potential of chitosan and cationic starch utilization in bagasse paper subjected to hot water pre-extraction has been presented in this paper. The research analyzes the surface properties alterations due to these dry–strength agents. Inverse gas chromatography was used to evaluate the properties of surface chemistry of the papers namely the surface energy, active sites, surface area as well as the acidic/basic character. The results of the study revealed that the handsheets process causes surface arrangement and orientation of chemical groups, which induce a more hydrophobic and basic surface. The acid–base surface characteristics after the addition of dry–strength agents were the same as the bagasse handsheets with and without hot water pre-extraction. The results showed that the dry–strength agent acts as a protecting film or glaze on the surfaces of bagasse paper handsheets.

Effects of hot water pre-extraction on surface properties of bagasse soda pulp

In this work, the effects of hot water pre-extraction of depithed bagasse on the soda pulping and surface properties were studied. The conditions of hot water pre-extraction were: maximum temperature 170°C, heat-up time 90min, time at maximum temperature 10min, and solid to liquor ratio (S:L) 1:8. Consequently, the pre-extracted and un-extracted bagasse chips were subjected to soda pulping at 160°C for 1h with 11, 14 and 17% active alkali charge and an S:L of 1:5. The results showed that the hot water pre-extraction increased bagasse surface texture porosity by hemicellulose degradation. Therefore, the delignification was faster for pulping of pre-extracted samples. At a certain charge of alkali, pre-extracted samples showed higher screened yield and lower Kappa number. For instance, at 17% alkali charge, pre-extracted bagasse gave 11.3% higher pulp yield compared with the un-extracted ones. Inverse gas chromatography (IGC) results showed that the hot water pre-extraction changed the active sites on the bagasse surface, decreasing the dispersive energy and the basicity character, and affected the particle morphology. The pulping process decreased the hydrophobicity and the basicity of the bagasse surface. The surfaces of un-extracted and pre-extracted bagasse pulps had similar properties but different morphology. The pulps present higher surface area and permeability with more reactive capacity.

Fractionation of wood polymers by carboxymethylation: Exploring the strategy

We explored the feasibility of fractionating wood polymers in situ by carboxymethylation to yield the carboxymethyl derivatives of cellulose (CMC), hemicelluloses, and lignin for potential industrial applications. The initial water-soluble materials formed were a mixture of hemicelluloses and cellulose derivatives, and also contained some lignin (3%–5%). Interestingly, the water-insoluble residue after another carboxymethylation treatment gave essentially a CMC product containing less than 1% of residual lignin. Thus, the bulk of wood lignin is less reactive than the polysaccharide components under typical carboxymethylation conditions. Also, a hot water pre-extraction or dilute acid pre-treatment of wood samples was found to significantly enhance the reactivity of the cellulose component. A preextraction approach would facilitate CMC preparation and also provide the flexibility to convert the extracted hemicelluloses to other bio-based fuels or materials.

Effect of Hot Water Extraction on Hardwood Kraft Pulp fibers (Acer saccharum, Sugar Maple)

This study focuses on the properties of fibers obtained from the kraft pulping of pre-extracted sugar maple wood chips. Hot-water pre-extraction was carried out for different times characterized by P-factors in the range of 12 and 600 h. It was found that pre-extraction of the chips significantly accelerates delignification during Kraft pulping such that the H-factors necessary to obtain equivalent delignification (i.e., the same k numbers) were substantially smaller than control cooks (i.e., with unextracted chips). Unbleached pulps of k numbers of 35, 25, and 15 were prepared, and their papermaking properties were tested. The hemicellulose content of the pulps decreased with pretreatment, whereas the cellulose contents increased. Pretreatment also resulted in an increase in the pulp viscosity. The fiber lengths showed no change, but the fines content was reduced. The kink index of pre-extracted pulps showed large increases. The porosity of the cell wall also increased with extraction severity as did the mean pore size. The water retention values (WRV) also increased with extraction probably because of the increased fiber porosity. The ζ potential of the fines remained unaffected, whereas the total charge (cationic) demand of the pulps decreased with pre-extraction. Thereisalsoasignificantlossoftensileandburststrengthsofhandsheetsmadewithextractedpulpspossiblyasaconsequenceofthe increased kink and curl index and decreased interfiber bonding ability.

Effect of Hot Water Pre-Extraction on APMP Pulping Process of Pink Sheets Bamboo

In this paper, the technology of pressurized hot water extraction of hemi-cellulose and the effects of the pre-extraction on APMP pulping process of the Pink Sheets bamboo are investigated. The results show that the yields of pentosan and bamboo chip are the highest under the conditions of the maximum temperature 170 °C, liquid ratio 1:5, holding time 2h. And the yield of bamboo chip is lowered generally, the color of bamboo is deepened, the pulp strength is degraded, but the refining energy is reduced largely after pre-extraction.

Effect of Hot-Water Pre-Extraction on Alkaline Pulping Properties of Wheat Straw

The alkaline pulping properties of wheat straw, which had been hemicelluloses pre-extracted with hot water, were studied. In this work, the process of hot-water extraction at various temperatures, reaction time and other conditions were investigated. The straws pre-extracted or not were made into pulp with NaOH-AQ at same conditions. Then the effects of pre-extraction on properties of straw pulp were studied. The results show that the yield, Kappa number and viscosity of the pulp are affected significantly by hemicelluloses pre-extraction process. The chemicals charge of the extracted straw in the pulping process is lower and shorter cooking time needed, the maximum pulping temperature reduced. These effects indicate that the action of hot-water pre-extraction before alkaline pulping is able to reduce effluent discharge and chemical demand to pulp, and it would be energy-saving. In this experiment, the optimum conditions of hot-water pre-extraction were: maximum temperature 140°C, heat-up time 30min, time at maximum temperature 60min and liquor ratio 1:10. The optimal pulping conditions were: alkali charge 12%, maximum temperature 155°C, heat-up time 90min, and holding time at maximum temperature 60min.

Kraft pulping and papermaking properties of hot-water pre-extracted loblolly pine in an integrated forest products biorefinery

Our objective in this research was to investigate the effect of hot-water pre-extraction of softwood on the behavior and papermaking properties of kraft pulp. Loblolly pine wood chips were treated with pressurized hot water at an elevated temperature of 170°C until the H-factor reached 200 and 500 hours. Kraft pulping of the extracted wood chips, performed at 15% effective alkali charge and 30% sulfidity, showed significantly improved delignification rates with 40% to 60% higher rate constants than corresponding kraft control cooks. The total pulp yield based on the original wood at a given kappa number was 3% and 6% lower than the control at the pre-extraction H-factors of 200 and 500 hours, respectively. The water pre-extracted kraft pulps showed a reduced refining response to PFI mill refining. The handsheets prepared from bleachable-grade pulps, after kraft pulping of hot-water pre-extracted wood chips for 400 H-factor hours, showed reduced tensile strength because of the lower percentage of hemicelluloses, compared to the control; but comparable pulp viscosity, zero-span wet tensile strength and tear resistance.