Pretreatment of biomass is expected to improve the pulp properties and facilitate the main components in the raw materials to be better used. In this work, the refining energy consumption and properties of the poplar chemithermomechanical pulp (CTMP) from different autohydrolysis pretreatment intensities of wood chips were investigated, and the pulp bleaching ability was also studied. The results showed that the CTMP with autohydrolysis pretreatment at a severity factor of 3.47 could have a 26% energy reduction in pressurized refining, a 60% energy saving in PFI refining, and 44% and 46% increases in tensile and tear indices, respectively. Autohydrolysis pretreatment prior to pulping could result in CTMP with a higher water retention value, higher fines content, better strength properties, lower shives content, and lower bulk and ISO brightness after PFI refining. The brightness of CTMP can be improved by alkaline peroxide bleaching.

Pre-extracting part of hemicelluloses in wood can not only realize a high value-added utilization of hemicelluloses but also ensure the production of traditional pulping using the extracted wood raw materials, which benefits the highly efficient utilization of bioresources. In this work, this concept was applied to the poplar chemi-thermomechanical pulping. 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 dissolution of carbohydrate were also evaluated. The results show that the content of the sugars (xylose, glucose, and arabinose), acetic acid, and furfural increased with the increase of autohydrolysis pretreatment temperature and time, and the dissolved sugars in the AHL were mostly in a polymeric form. The release of acetic acid played an important role in the dissolution of carbohydrate and the pH value of the AHL.

•Xylan and 2-(methacryloyloxy) ethyl trimethylammonium chloride were copolymerized.•The best copolymer had a charge density of 2.6 meq/g and Mw of 102,250 g/mol.•The hydrodynamic diameter and viscosity of the copolymer solution were analyzed.•98% Dye removal obtained via having 160 mg/L copolymer in dye solution (100 mg/L).Xylan is a part of hemicelluloses of woody materials and can be converted to value-added products such as flocculants for the textile industry. To assess the production of flocculants from hemicelluloses of woody materials, xylan was selected as a model and rendered cationic via copolymerization. In this study, the copolymerization reaction of xylan and [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was optimized. The optimum parameters were 3 mol/mol METAC/xylose, 3 h reaction time, 80 °C reaction temperature, pH 7 and 25 g/L xylan concentration. The copolymer was characterized by a charge density analyzer, viscometer, gel permeation chromatography (GPC), light scattering instrument, Fourier transform infrared spectroscopy (FTIR) and an elemental analyzer. The application of the cationic xylan copolymer as a flocculant to decolorize the simulated reactive orange 16 azo-dye wastewater was evaluated. The results confirmed that, by having 160 mg/L xylan–METAC concentration in the dye solution with the concentration of 100 mg/L, 97.8% of dye could be removed.

The oxidation of cellulose nanocrystal (CNC) by sodium periodate can generate aldehyde functions for crosslinking reactions or for further modification, which can extend the range of applications of CNC. In this paper, the effects of reaction conditions during the periodate oxidation of CNC, such as oxidant concentration, pH, temperature and oxidation time on the oxidized CNC yield and the aldehyde content, were investigated and an optimized reaction condition was identified. The generation of aldehyde groups on the CNC was confirmed by Fourier transform infrared spectroscopy analysis, and the decreased crystalline index was observed by X-ray diffraction. The transmission electron microscope observation showed the morphological changes of CNC after the oxidation. The oxidized CNC was used as a strength additive to paper, and the results showed that the dry tensile index was 32.6 % higher than the control sample, and the wet tensile index was reached to 3.08 N.m/g, at the oxidized CNC dosage of 1.2 %.

•Cellulose nanocrystals (CNC) are used as carriers for spirooxazine (SO) to make it be compatible in the aqueous system.•Photochromatism is applied in cellulose paper by impregnating CNC-dispersed SO.•The photochromic efficiency of CNC-dispersed SO can be improved obviously.•The CNC-dispersed SO impregnated paper shows enhanced color stability and fatigue resistance.Nanocrystalline cellulose (CNC) as a renewable/sustainable material, has received much attention. Herein we studied CNC as carriers for a hydrophobic spirooxazine (SO)-based dye, 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]naphtha[2,1-b][1,4]oxazine], which may have potential applications in reversible memory photo-devices, textiles, photo-sensitive paper coatings, and inkjet printing inks. Due to the high cost and water-insolubility of this dye, it is desirable to improve its coloration efficiency and water-dispersibility. The experimental approach was to use CNC as carriers for the SO dye, thus obtaining a stable photochromic dye in aqueous systems. Transmission electron microscope (TEM) observation confirmed that the SO dye adsorbed on the surface of the CNC, which functioned as carriers for the photochromic dye. An impregnation process was adopted to anchor the dye onto cellulosic paper. It was found that the use of CNC resulted in a significant improvement in the SO coloration efficiency. The color stability and fatigue resistance were also studied. The use of CNC as carriers for a hydrophobic compound, its enhancement of associated properties, and its subsequent application were demonstrated.

Some of the dissolved and colloidal substances (DCS) such as extractives and pectic acids have great negative influence through the whole papermaking process, and their control and understanding would benefit the production, especially in the mills with closed water system. In this work, the DCS from the alkaline peroxide bleaching of poplar chemi-thermomechanical pulp (CTMP) with partial substituting MgO for NaOH were analyzed. The results showed that the amount, pH value, lignin content, conductivity, and cationic demand (CD) of the DCS decreased with increasing substitution percentage of MgO for NaOH. The methyl tert-butyl ether (MTBE) extractives were characterized by a gas chromatograph coupled to a mass spectrometry (GC-MS). The substitution of MgO for NaOH in the bleaching process improves the bulk, light-scattering coefficient, and opacity of the bleached poplar CTMP, reduces the pulp brightness, and decreases the tensile and burst indices.

Magnesium-based alkalis have become an attractive alkali source in the peroxide bleaching process of high-yield pulps. The objective of this work is to evaluate the effect of industrial grade MgO with different particle sizes as the alkali source in the peroxide bleaching process of poplar chemi-thermomechanical pulp (CTMP). The effect of MgO with different particle sizes on pulp properties including strength and optical properties was investigated. With the particle size of MgO decreasing, the peroxide bleaching process produced a bleached CTMP with higher tensile and tear indices, whereas the bulk and light-scattering coefficients were less. The maximum ISO brightness (73.2%) was obtained when the particle size of MgO was 4.3 μm. The possible reason for the brightness change with the variation of particle size of MgO was discussed.

Bleached thermomechanical pulp (TMP) has been applied in the production of newsprint and supercalendered (SC) paper or other paper products. Recent studies on the alkaline peroxide bleaching with magnesium-based alkalis indicated that the bulk and optical properties can be improved, and effluent load can be reduced. In this work, MgO was partially used in alkaline peroxide bleaching process of pine (Pinus massoniana) TMP to investigate the effect of MgO substitution for NaOH on the pulp properties and effluent characteristics. The present research showed that partial substitution of MgO for NaOH could decrease the dissolution of chemical components in pulp fibers, thus, improving the pulp yield and decreasing the effluent load. When the substitution percentage of MgO for NaOH increased from 0% to 50% at 3.5% alkali charge, the bulk of the bleached pine TMP increased from 3.45 cm3/g to 3.69 cm3/g, while the opacity was improved from 84.7% to 89.1%, the cationic demand and CODCr of the effluent decreased by 31% and 22%, respectively. However, the MgO substitution had decreased the brightness and tensile index of the bleached TMP.Highlights► In this work, MgO was partially used in alkaline peroxide bleaching process of pine (pinus massoniana) TMP. ► The bulk of the bleached pine TMP can increase from 3.45 cm3/g to 3.69 cm3/g. ► The opacity of the bleached pine TMP can improve from 84.7% to 89.1%. ► The cationic demand of the effluent can decrease by 31%. ► The CODCr of the effluent can decrease by 22%.

Pre-extraction of hemicelluloses prior to pulping and conversion of the extracted hemicelluloses to other byproducts will provide additional revenue to the traditional pulp and paper industry. The effect of hemicelluloses pre-extraction with dilute sulfuric acid on the properties and bleachability of aspen (Populus tremuloides) chemithermomechanical pulp (CTMP) was investigated. The acid pre-extraction significantly reduced refining energy consumption to a given freeness. However, at the same freeness, the acid pre-extraction resulted in the reduction of bulk, tensile index, and zero-span breaking length, fewer long fibers and more fines, but an increase of the Scott bond strength. Alkaline peroxide bleaching can compensate the strength loss, but the bleachability of pulps with acid pre-extraction was lower than that of the control.

A portion of hemicelluloses and acetic acid can be pre-extracted with dilute sulfuric acid prior to the aspen chemithermomechanical pulp process. The streams collected from the second press-impregnation stage after acid pre-extraction contain a significant amount of acid pre-extracted hemicelluloses. Most of the total sugars obtained from the pressate were xylan, in which xylan was further hydrolyzed to sugar monomers under the acid pre-extraction condition. To fully understand the characteristics of hemicelluloses yielded prior to pulping, the pre-extracted hemicelluloses were separated and characterized by FT-IR, 1H NMR, and thermogravimetric analysis in this study. Most of the FT-IR bonds from the hemicelluloses agreed well with the other two spectra of birch xylan and CA0050 xylan, except a new absorption at 1734 cm–1 contributed to acetyl groups. The hemicelluloses obtained from acid pre-extraction began to decompose significantly at about 225 °C, slightly lower in comparison with organosolv and alkaline hemicelluloses reported in the literature.

Wheat straw has been used as a pulping resource in China for many years. Wheat straw pulp (WSP) was widely used to substitute high quality chemical pulps such as those made from wood in producing writing and printing paper to reduce production cost of the resultant paper products and to improve paper smoothness without sacrificing paper strength. In this study, the process of co-refining of WSP and bleached hardwood kraft pulp (BHKP) was compared with the traditional separate refining and then blending these two pulps. The differences in refining energy consumption, the resultant pulp morphological and drainage properties, as well as the mechanical properties of the paper handsheets made of the resultant pulps were examined to explore the potential advantages of the co-refining process. The results show that the co-refining process has the potential to reduce refining energy consumption by at least 30% without affecting handsheet tensile and tear strength at a slightly lower re-wet tensile strength.

Magnesium-based alkali is another attractive alkali source in the peroxide bleaching process of high-yield pulps. This work investigated the effluent characteristics in the high-consistency retention stage and pulp properties of triploid poplar P-RC APMP (that is, so-called preconditioning followed by refining chemical treatment, alkaline peroxide mechanical pulp) by partially substituting MgO for NaOH. The results showed that the pH, dissolved and colloidal substances (DCS), chemical oxygen demand (CODCr), cationic demand, and conductivity of the effluent in the high-consistency retention stage decreased with the increase of the substitution percentage of MgO for NaOH. Meanwhile, both the light-scattering coefficient and the bulk of the pulps increased, but the tensile index and internal bond decreased. The tensile index and internal bond had a good linear relationship with bulk.

In the conventional preconditioning followed by refiner chemical treatment, alkaline peroxide mechanical pulping (P-RC APMP) process, sodium hydroxide (NaOH) is used as the alkali source. In this study, magnesium oxide (MgO) was used to partially substitute for NaOH as the alkali source (substitution ratio of up to 50%) in the second-stage impregnation of the triploid poplar P-RC APMP process. The changes in pH values of the residual bleaching liquor, yields, and chemical components of the treated wood chips in the second-stage impregnation and also the physical properties of the resultant P-RC APMP pulps with and without MgO substitution were investigated to explore the potential advantages of the process. The results showed that the partial MgO substitution for NaOH resulted in a lower pH of residual bleaching liquor and a higher treated wood chips yield than those of the NaOH-based process. In addition, the dissolution of benzene alcohol extractives, lignin, pentosans, and carbohydrates were all decreased. The resultantly yielded P-RC APMP pulp has a higher bulk, opacity, and light-scattering coefficient, but lower strength properties and a slightly lower brightness.

•Poplar sapwood with different hemicelluloses content by autohydrolysis was got.•The autohydrolyzed poplar sapwood was subjected to alkali impregnation.•Porosities of the fiber cell walls were increased due to the hemicelluloses removal.•Hemicelluloses removal raised alkali impregnation effectiveness of poplar sapwood.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.

A headspace gas chromatography (HS-GC) method is developed for determination of formic acid (FA) and acetic acid (AA) in biomass hydrolysate. The method is based on the “in-vial” derivatization reaction of alcohols and acids. NaHSO4/ethanol is selected as the preferred derivatization reagent. The method has a reproducibility of RSD <0.87% and recovery of 97.1%–103.1%. The limits of the quantification were 2.02 and 2.38 mg/L for FA and AA, respectively. The GC analysis time only required 12.4 min. The method is rapid, sensitive and suitable for measuring FA and AA in the multifarious biomass hydrolysates in pulping and biorefinery industries.Download high-res image (154KB)Download full-size image