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This work investigated the changes in the physical structure of autohydrolyzed poplar sapwood chips and the effect on the subsequent alkali liquor diffusion properties for chemi-mechanical pulping (CMP). An alkali impregnation process was conducted by using the autohydrolyzed poplar sapwood with different levels of autohydrolysis intensity. The results showed that the volume porosity, water constraint capacity, and saturated water absorption of the autohydrolyzed poplar sapwood chips increased. Also, the effective capillary cross-sectional area (ECCSA) in the radial direction and the diffusion coefficients of NaOH solution in both the radial and axial directions all increased. Autohydrolysis pretreatment enhanced the alkali liquor diffusion properties in poplar sapwood chips, and the diffusion coefficient was increased more greatly in the radial direction than that in the axial direction. [ABSTRACT FROM AUTHOR]

Poplar sapwood chips were autohydrolyzed at three severity levels and subsequently treated with alkali for the production of chemi-mechanical pulp (CMP). The aim was to study the variation of the principal pathways for sodium hydroxide solution and the alkali concentration and distribution inside the autohydrolyzed chips as a function of autohydrolysis (AH) severity. The tyloses in the vessels and some pit membranes were partly dissolved after AH, while the skeletal structure of the fiber and vessel cell walls remained intact. AH had a positive influence on the diffusion and the uniform distribution of NaOH solution both in the axial and radial direction of the chips, but the axial direction was more favored than the radial one. [ABSTRACT FROM AUTHOR]

This work is aimed at investigating the influence of changes in the content of hemicelluloses of the autohydrolyzed poplar sapwood on the subsequent alkali impregnation for chemi-mechanical pulping (CMP). An alkali impregnation process was conducted using the autohydrolyzed poplar sapwood with different content of hemicelluloses as raw materials. The results showed that both the amount of NaOH consumption and swelling degree of poplar sapwood increased with the removal of hemicelluloses, thus enhancing the alkali impregnation effectiveness. The hemicelluloses removal can also shorten the alkali impregnation time for the autohydrolyzed poplar sapwood to achieve the similar impregnation effectiveness of unautohydrolyzed poplar sapwood. All of these can be attributed to the fact that the hemicelluloses removal would result in the exposure of more free hydroxyl groups on the cellulose and an increase in the porosity of the fiber cell walls. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystal (CNC), as a natural/sustainable material, has attracted considerable attention, and its preparation from the sulfuric acid hydrolysis process has attained the precommercial demonstration stage. In this study, the process was further characterized by following the alkali solubility in an 18 % sodium hydroxide solution (S) and the degree of polymerization (DP) of the cellulosic substrate during the sulfuric acid hydrolysis of cotton fibers. The results showed that the S increased as the hydrolysis progressed until reaching a nearly constant level at about 45 min, while the DP exhibited a decrease and approached a nearly constant level at 55 min. The emergence of the constant S coincided with the formation/appearance of CNC; thus, a 'critical stage' with irregular CNC particle size but high yield was identified during the hydrolysis. The optimization of the CNC preparation process was realized under a shortened reaction time with 41.7 % yield (with a CNC size of <150 nm). Therefore, the amount of S can be used as a new characterization method for the preparation of CNC or other cellulose-derived products during the acid hydrolysis process with the advantage of a favorable product yield. [ABSTRACT FROM AUTHOR]

Pretreatmentof biomass is expected to improve the pulp propertiesand facilitate the main components in the raw materials to be betterused. In this work, the refining energy consumption and propertiesof the poplar chemithermomechanical pulp (CTMP) from different autohydrolysispretreatment intensities of wood chips were investigated, and thepulp bleaching ability was also studied. The results showed that theCTMP with autohydrolysis pretreatment at a severity factor of 3.47could have a 26% energy reduction in pressurized refining, a 60% energysaving in PFI refining, and 44% and 46% increases in tensile and tearindices, respectively. Autohydrolysis pretreatment prior to pulpingcould result in CTMP with a higher water retention value, higher finescontent, better strength properties, lower shives content, and lowerbulk and ISO brightness after PFI refining. The brightness of CTMPcan be improved by alkaline peroxide bleaching. [ABSTRACT FROM AUTHOR]

This study investigated the autohydrolysis pre-treatment prior to chemi-thermomechanical pulping (CTMP) process including the effects of autohydrolysis pretreatment with a lower severity on characteristics of the autohydrolysis liquor and hydrolyzed chips. The intensity of autohydrolysis, characterized by the severity factor, increased from 1.76 to 3.54, the hydrolyzed chips yield decreased from 99.0% to 86.7% and the xylose extraction yield increased from 0.8% to 44.0%. The content of holocellulose, pentosan and acid soluble lignin remained in the hydrolyzed chips decreased dramatically with increasing the treatment severity. After the autohydrolysis pretreatment, the resultant poplar chemi-thermomechanical pulp with a severity factor of 2.37 could obtain a 15.3 N m/g tensile index, 58.6% ISO brightness and a 2.39 cm 3 /g bulk. [ABSTRACT FROM AUTHOR]

Alkenyl succinic anhydride (ASA) is a reactive sizing agent that can impart good water repellence to paper by decreasing the wettability of the cellulose fibers. However, ASA can undergo hydrolysis, which is detrimental to the ASA sizing efficiency. In order to improve the ASA emulsion stability and ASA sizing efficiency, we used cationically modified cellulose nanocrystals (CNCs) to stabilize the cationic starch-emulsified ASA. Transmission electron microscope observation revealed that ASA droplets were well shielded by both the cationic CNCs and cationic starch, which may be responsible for the improved stabilization of ASA. The Hercules size test sizing degree, contact angle and particle size measurements demonstrated that cationic CNCs-ASA sized paper exhibited improved results in comparison with the control (without cationic CNCs under otherwise the same conditions). Furthermore, the resulting cationic CNCs-ASA system can improve the tensile index and burst index of the sized paper. [ABSTRACT FROM AUTHOR]

Dilute acid pre-extraction enhanced the mechanically refined poplar pulp substrates’ enzymatic hydrolysis efficiency obviously. The results showed that the surface lignin distribution was changed significantly in residual wood chips and pulp substrates, and the surface lignin distribution showed important impact on the following enzymatic hydrolysis. Acid pre-extraction can lead to a redistribution of lignin in fiber cell walls, i.e., the lignin was degraded and migrated to fiber surface in the form of re-deposited lignin and pseudo-lignin. However, higher pre-extraction intensity was not desired due to the formation of redeposited lignin and pseudo-lignin. This study will help to reach a deeper understanding on the lignin distribution in the view of molecular and ultrastructure, and promote the development of a cost-efficient pretreatment strategy for biomass processing. [ABSTRACT FROM AUTHOR]

Autohydrolysis with different severity factors was performed on poplar wood chips prior to pulping, and the wettability, absorbility and the following impregnation of NaOH solution for the poplar wood chips were then investigated. The results showed that after autohydrolysis pretreatment the porosity, shrinkage and fiber saturation point (FSP) of the poplar wood chips were increased, while the surface contact angle decreased as the severity factor was increased. The autohydrolyzed chips absorbed more NaOH in impregnation that resulted in a low NaOH concentration in the bulk impregnation liquor (i.e., the impregnation liquor outside wood chips), while the concentration in the entrapped liquor (i.e., the impregnation liquor inside wood chips) was increased. Autohydrolysis substantially improved the effectiveness of alkali impregnation. [ABSTRACT FROM AUTHOR]

The hardwood bleached kraft pulp (HBKP) fibers were pretreated by PFI mill to obtain the substrates, the effects of fibrillation on HBKP fibers’ enzymatic hydrolysis was studied. The results showed that the enzymatic hydrolysis efficiency was enhanced obviously by mechanical refining. The mechanical refining alterated the fibers’ characteristics such as fibrillation degree, specific surface area, swelling ability, crystallinity, fiber length and fines content. All these factors correlating to the enzymatic hydrolysis were evaluated through mathematical analysis. Among these factors, the fibrillation degree has the profoundest impact on the enzymatic hydrolysis of wood fibers. Consequently, the mechanical refining aiming for a high fibrillation degree was feasible to enhance the enzymatic hydrolysis of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Autohydrolysis pretreatment with different severity factors was performed on poplar chips prior to chemi-thermomechanical pulping (CTMP) in order to investigate the change in pH value and its effect on the autohydrolysis pretreatment. The results showed that the dissolution amount of acetic acid increased with raising the severity factor of the pretreatment and declining the size of poplar chips, respectively. Besides, a logarithmic relationship between the amount of acetic acid released in the autohydrolysis liquor (AHL) and pH value of the AHL was observed. The amounts of glucose and xylose (including those in the form of monomers, oligomers, and polysaccharides) as well as furfural and hydroxymethylfurfural (HMF) also depended on the pH value of the AHL to some extent. [ABSTRACT FROM AUTHOR]

Three different pre-extraction methods (i.e., acetic acid, sulfuric acid and sodium hydroxide) were used for the pretreatment followed by chemi-thermomechanical treatments and then enzymatic hydrolysis of wheat straw to produce fermentable sugars. The performance of enzymatic hydrolysis by the synergistic effect of pre-extractions and chemi-thermomechanical treatments was remarkable. Results showed that the pre-extraction combining with the chemi-thermomechanical treatments shorten the enzymatic hydrolysis time and improved the glucose yield at the same enzyme loadings. The chemical components, swelling ability, and crystallinity, as well as the surface morphology of the substrates were changed obviously. All of these changes can affect the accessibility of enzymes to cellulose in the substrates to a certain extent. [ABSTRACT FROM AUTHOR]

Pre-extracting part of hemicellulosesin wood can not only realizea high value-added utilization of hemicelluloses but also ensure theproduction of traditional pulping using the extracted wood raw materials,which benefits the highly efficient utilization of bioresources. Inthis work, this concept was applied to the poplar chemi-thermomechanicalpulping. The chemical components of the autohydrolysis liquor (AHL)at different autohydrolysis pretreatment conditions were studied,and the formation of acetic acid and its effect on the dissolutionof carbohydrate were also evaluated. The results show that the contentof the sugars (xylose, glucose, and arabinose), acetic acid, and furfuralincreased with the increase of autohydrolysis pretreatment temperatureand time, and the dissolved sugars in the AHL were mostly in a polymericform. The release of acetic acid played an important role in the dissolutionof carbohydrate and the pH value of the AHL. [ABSTRACT FROM AUTHOR]

Highlights • The pretreatment using MgCl 2 had a strong degradation effect on hemicellulose. • For enzymatic hydrolysis, the CYC could come up to 99.5% in some cases. • Hemicellulose degradation kinetics followed a first-order homogeneous reaction. Abstract Pretreatment using an acid salt is a novel technology for biomass conversion, which not only improves the following enzymatic efficiency but also decreases the equipment corrosion. In the present work, MgCl 2 was used as a pretreatment for enzymatic saccharification. After pretreatment, the solid substrate (SS) and pretreatment liquor (PL) were characterized, and the SS was enzymatically hydrolyzed to evaluate the conversion yield of cellulose (CYC). The results showed that the pretreatment using MgCl 2 had a strong degradation effect on hemicellulose, whose removal rate was nearly 100% in certain cases. After pretreatment, the efficiency of the enzymatic SS saccharification increased, such that the CYC was as high as 99.5%. The degradation kinetics of hemicellulose and cellulose both followed first-order homogeneous reactions, and the reaction activation energies E a were 46.63 kJ/mol and 82.26 kJ/mol, respectively. The suitable pretreatment conditions were as follows: 0.2 mol/L MgCl 2 at 210 °C for 20 min. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal & chemi-mechanical pretreatment greatly improved enzymatic hydrolysis. • Different combined pretreatments on enzymatic hydrolysis efficiency were compared. • HFM pretreatment showed the highest enzymatic hydrolysis performance. • Adsorption kinetics of enzymes on different substrates were investigated. • Adsorption mechanism of enzymes on different substrates was summarized. An integration of different pretreatments is important to overcome recalcitrance and realize efficient bioconversion of lignocellulosic biomass. This study aims at the effects of combination of hydrothermal pretreatment and different chemi-mechanical pretreatments on enzymatic hydrolysis, and understanding the enzymes adsorption mechanism. The combination of hydrothermal and chemi-mechanical pretreatments effectively improved the enzymatic hydrolysis of poplar substrates, in which the enzymatic hydrolysis of substrates pretreated by hydrothermal pretreatment + Fenton pretreatment + mechanical refining (HFM) was the highest (92.39% of glucose conversion yield, and 20.88 g/L of glucose concentration). The substrates' main characteristics were obviously changed after combined pretreatments, such as swelling ability and specific surface area of substrates were increased. The Langmuir adsorption model (R2 > 0.98) and pseudo second-order adsorption kinetic model (R2≈1) were well suitable to describe the adsorption of enzymes on substrates, meanwhile the adsorption mechanism was summarized. [ABSTRACT FROM AUTHOR]

An efficient and low-cost approach to preparing CNFs with succinic acid hydrolysis and NaClO 2 oxidation is explored. High-temperature-short-time hydrolysis can depolymerize the cellulose, whereas the dispersibility of the CNFs is hugely enhanced by NaClO 2 oxidation under alkaline condition. The degradation of cellulose in succinic acid hydrolysis follows first-order reaction kinetics and is severely influenced by the hydrolysis temperature, moreover, the molecular chains of the cellulose are seriously cracked under the optimized condition. The NaClO 2 oxidation greatly improves the zeta potential (−36.2 mV) and the dispersibility of the CNFs. The obtained CNFs have an ultimate yield of 94.6%, and the diameter distribution is mainly within 20–40 nm. In addition, some amount of carboxyl groups in the cellulose will be instead of the hydroxyl groups, and the crystallinity of the CNFs is significantly increased. • Succinic acid hydrolysis and NaClO 2 oxidation were utilized to prepare CNFs. • High-temperature-short-time hydrolysis could control the cellulose degradation. • NaClO 2 oxidation greatly improves the dispersibility of CNFs. • The yield of CNFs was about 94.6%, with a diameter distribution of 20–40 nm. [ABSTRACT FROM AUTHOR]

• Hydrothermal and Fenton pretreatment synergistically promote enzymatic hydrolysis. • Fenton pretreatment can help to solve inhibition of pseudo lignin problem. • Pre-hydrolysates provide additional revenues such as XOS, GOS, and xylose. • Main substrates' characteristics were changed by combined pretreatments. The combination of different pretreatment methods can effectively overcome recalcitrance of lignocellulosic biomass to ensure its highly efficient conversion into bio-based products. In this study, the combined pretreatments of chemical methods (hydrothermal treatment and Fenton treatment) with mechanical refining were used to improve the enzymatic hydrolysis efficiency of poplar branches. The results indicated that hydrothermal pretreatment and Fenton pretreatment can effectively improve the enzymatic hydrolysis of poplar substrates, e.g., the maximum glucose conversion yield and glucose concentration reached 92.4% and 20.8 g/L, respectively. The pre-hydrolysates contained some valuable components such as monosaccharides, oligosaccharides, acetic acid, furfural, and hydroxymethylfurfural. The main characteristics (specific surface area, water retention value, fines content, and surface lignin concentration) of poplar substrates were obviously changed by the combined pretreatment, which benefit the enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

• Three methods on enzymatic hydrolysis of corncob residues were compared. • Corncob residues substrate's main characteristics were changed by pretreatment. • Enzymatic hydrolysis efficiency were significantly enhanced by wet grinding. Under the situation of increasingly severe challenge of energy consumption, it is of great importance to make full use of bioresources such as forestry and agricultural residues. Herein, the corncob residues generated after processing corncob were enzymatically hydrolyzed to yield fermentable sugars. To overcome the recalcitrance of corncob residues, three kinds of pretreatment methods, i.e., sulfonation, PFI refining, and wet grinding, were applied; their effects on enzymatic hydrolysis and main characteristics of corncob residues substrate were investigated. The results showed that the enzymatic digestibility of the substrate was greatly enhanced by employing each method. The wet grinding exhibited obvious advantages, e.g., the conversion yield of cellulose to glucose and glucose concentration reached 96.7% and 32.2 g/L after 59 h of enzymatic hydrolysis, respectively. The improvement in enzymatic hydrolysis was mainly attributed to the altered characteristics of the substrate such as swelling ability, specific surface area, and particle size and distribution. [ABSTRACT FROM AUTHOR]