Soda AQ Research Articles

Study on Soda–Ethanol Delignification of Pine Sawdust for a Biorefinery

The soda–ethanol process was conceived as a sulfur-free pulping process, which may also be an alternative to conventional alkaline pulping, such as kraft or soda–AQ in the biorefinery context. An in-depth study using two experimental designs was conducted to establish the viability of soda–ethanol delignification of pine sawdust. At first, a simple factorial design involving the ethanol–water ratio (ethanol:water) and the alkaline load (AL, % over dry wood, odw) was applied to define the levels of these variables and their eventual interaction. Then, a 32 experimental design was performed to evaluate the ability of the process concerning the pulping of pine sawdust. The tested conditions were carefully selected to screen a broad range of cooking times (60, 100, and 140 min) and alkaline loads (19.0, 23.3, and 27.6 %odw) to obtain pulps with different extents of delignification (residual lignin contents). Finally, the kraft, soda–AQ, and soda–ethanol treatments were compared. Soda–ethanol pulping was shown to be a suitable delignification stage for a biorefinery scheme of Pinus elliottii and Pinus taeda sawdust. It has many advantages over traditional processes regarding its environmental impact, harmless chemicals, and selectivity. The tested conditions were similar to those frequently used in conventional pulping at an industrial scale, suggesting the technical feasibility of the soda–ethanol process for pine sawdust processing.

Mechanical Properties for Elephant Dung and its Utilization as a Raw Material Composites Sheet: A Study

Elephant dung is an excellent source of cellulosic fiber that is a basic requirement for paper making. But they contributed to very small percentage production of elephant dung. So, researchers are trying to find a new area of utilization of elephant dung fiber pulp as in reinforcement’s polymer composite. In this experiment element dung fiber pulp in the natural fiber component chemically treated with alkaline and soda AQ solution in this study, it has been aimed to use elephant dung fiber pulp in composite material and to study mechanical properties of the produced material. The produced composite samples were then characterized using tensile test, Izod impact test, thickness test. The fracture surface of the polymer composite sample was also inspected with the help of SEM. The content of elephant dung fiber pulp is varied (35%, 45%, 55%) weight percentage whereas the epoxy resin is varied (50%, 40%, 30%) percentage is kept constant 15% in hardener. The entire sample has been tested in a universal testing machine as per ASTM standard for tensile strength and impact strength. It is observed that composite with 35% fiber pulp is having the highest tensile strength of 4mm 6.445 Mpa and 8mm 11.80 Mpa. The impact strength of composite with 35% fiber pulp washes highest than 45% to 55% dung fiber pulp. This produces composite sheet will be used for the surfboards, sporting goods, building panel this not only reduces the cost but also save from environmental pollution.

The Effects of Sodium Hydroxide and Soda AQ Content on Mechanical and Physical Properties of Waste Flax Fibre Pulp Reinforced Polymer Composite Sheet

The aim of this study is utilized agricultural waste which may be profitable, pollution free and economically viable for the farmer and industries. In this experiment short flax fiber pulp is the natural fiber component chemically treated with alkaline solutions. Six specimens will be prepared in different volume percentage of flax fiber pulp and epoxy resin in order to get more accurate results. In this study it has been aimed to use flax fibres in composite materials and to study the mechanical properties of the produced samples. The mechanical tests results (thickness test, Tensile strength and impact strength tests) and SEM micrographs indicated flax fibres as an alternative natural fibre source for developing reinforced composites for various industries. The content of short flax fiber pulp is varied (35%, 45%, 55%) weight percentage whereas the epoxy resin is varied (50%, 40%, 30%) percentage is kept constant 15% in hardener. All the sample have been tested in universal testing machine as per ASTM standard for tensile strength and impact strength it is observed that composite with 35% flax fiber pulp is having highest tensile strength of 4 mm (4.57 Mpa) and 8 mm (6.04 Mpa). The impact strength of composite with 35% flax fiber pulp was highest than 45% to 55% flax fiber pulp.

Morphological and anatomical characterization of bleached soda, soda-AQ and kraft pulps from essential oil isolated citronella grass

Morphology and anatomy of pulp fibres are very crucial in determining the physical and strength properties of paper sheets prepared from them. This study reports the morphological and anatomical features of bleached soda, soda-AQ (Soda-anthraquinone) and kraft pulp fibres obtained from solid residues left after extraction of essential oil from Citronella grass (Cymbopogon winterianus Jowitt) using hydro-distillation. Their surface morphology and structural properties were also analyzed using SEM (Scanning electron microscope) and FTIR (Fourier transform infrared) spectroscope. The pulps exhibited mean length-weighted length ∼709–736 µm, average fibre width ∼13.5–14.4 µm, average fibre curl ̴ 8%, average fines length ∼49–51 µm and average fines area ∼1001–1058 µm. The parenchyma length, parenchyma width, vessels length, vessels width, lumen diameter and cell wall thickness of the bleached soda–AQ pulp were found to be 205.92 µm, 96.62 µm, 515.84 µm, 35.28 µm, 4.45 µm and 4.53 µm respectively. SEM analysis of paper hand sheets revealed a dense network of well bounded fibres within the matrix while FTIR analysis demonstrated presence of characteristic bands of cellulose, lignin and hemicellulose in pulp samples. Comparison of morphological and anatomical features of these pulps with those of other grasses and non-woody raw materials confirmed the suitability of essential oil isolated Citronella grass as potential raw material for pulp and paper industry.

Optimization of Alkaline Pulp Extraction from Napier Grass Using Response Surface Methodology

Napier grass which has several types of them has been studied by researchers for few applications such as biofuel, sugar and pulp production. This research focused on specific type of Napier grass which is the Dwarf Napier due to high cellulose content to produce pulp. Delignification of Dwarf Napier grass was carried out by soda anthraquinone pulping under varying conditions selected according to experimental design software with three factors. The influence of these three factors including concentration of sodium hydroxide (15%, 17.5% and 20%), concentration of anthraquinone (0.05% and 0.1%) and duration of cooking time (30, 60 and 90 min) on pulp yield was studied. 18 runs of experiment were conducted and the result obtained was used to analyse the optimized condition for pulp extraction by using RSM. Results indicated that the optimized response obtained while Napier grass stem is treated with 17.5% sodium hydroxide and 0.05% AQ with 66 mins of cooking time meanwhile the predicted yield is 34.87 %. However, the actual pulp yield obtained (36.38%) is higher than the predicted yield. The pulp which extracted with optimized condition is then bleached with hydroxide peroxide. Fourier transform infrared spectroscopy (FTIR) was used to characterize the raw grass fiber and pulp obtained. Napier grass is successfully demonstrated to be an effective alternative source for producing paper pulp. In the this study Dwarf Napier grass fibres were successfully pulped applying soda AQ process although the obtained pulp is not as high as the studied done before due to the limitations. FTIR analysis also confirmed the removal of lignin as well as most of the hemicellulose during the pulping process. Therefore, the abundance and fast growth of Napier grass are an added advantage as an alternative non-wood source for papermaking

Alkaline Delignification of Cactus Fibres for Pulp and Papermaking Applications

Stable aqueous suspensions with high cellulosic contents and low fractions of lignin have been prepared from Cactus fibres via chemical delignification of the Cactus biomass feedstock with a sodium hydroxide–anthraquinone (soda–AQ) mixture. In order to optimize the reaction parameters, various temperatures between 120 and 170 °C and reaction times between 60 and 180 min were examined. The optimal yield of the resulting alkaline pulps (corresponding to the complete reaction of the raw materials) was equal to 41.4%, while the morphological parameters of individual cellulose fibres (such as length, width, and fraction of fine elements) were determined using a MorFi analyser. The estimated degree of polymerization, water retention value, total charge, and drainability of the produced pulps confirmed their suitability for papermaking applications; as a result, paper sheets were manually prepared using a Rapid-Kothen sheet former apparatus. The morphological analysis of the produced paper was conducted using a scanning electron microscopy technique, and its structural and mechanical properties were evaluated with the standard laboratory testing equipment. The obtained results indicate that the paper fabricated from Cactus fibres via the soda–AQ delignification process exhibits homogenous morphology as well as satisfactory mechanical and structural properties.

Structural Changes of Lignin in the Soda-AQ Pulping Process Studied Using the Carbon-13 Tracer Method

To reveal the structural changes of lignin during the soda–AQ cooking process and chemical bonds between lignin and xylan of wheat straw, 13C isotope-labeled technology was used in this study. First, 13C isotope-labeled xylose was injected into the living wheat straw. The success of 13C isotope-labeling was confirmed by the results of 13C abundance determination. Then, milled wood lignin-13C was extracted from wheat straw. The wheat straw, which had already been labeled by xylose-13C, was cooked by the soda-AQ process. Soda-AQ Lignin-13C and Residual Lignin-13C were extracted from black liquor and residual pulp. FT-IR, 13C-NMR, and 2D HSQC NMR analyses indicated that all lignin preparations were HGS-type lignin. The main lignin linkages were β-O-4’ units, β-β’ units, β-5’ units, and β-1 units, with the highest content of β-O-4’. Furthermore, 82.8% of β-O-4’ units, 77.2% of β-β’ units, 75.4% of β-5’ units, and 75.4% of β-1 units were degraded during the cooking process. LC bonds between lignin and xylan were at C2 and C5 positions of xylan. It was found that the C-2 position of xylan in wheat straw could be mainly connected to lignin by γ-ester bonds, and C-5 position of xylan in wheat straw was possibly linked with lignin by benzyl ether bonds.

KRAFT PULPING CHARACTERISTICS OF THREE MOROCCAN EUCALYPTI. PART 2. COMPARISON OF THE GUAIACYL FRACTION OF THE NATIVE LIGNINS BY A NOVEL METHOD

In Part 1 of this series it was observed that one of the eucalypti (EGC 39) was more reactive than the other two in kraft and soda-AQ (SAQ) cooking. However, the lignin in EGC 39 contained equal or less syringyl (S) units than the other two eucalypti. In the present research an attempt was made to compare the guaiacyl (G) fraction of the three lignins. The approach was to use SAQ treatment to cleave β-O-4 bonds in dimeric units containing uncondensed guaiacyl A-rings (those rearranging to quinone methides). The coniferyl alcohol, vinylguaiacol and isoeugenol generated from β-O-4 cleavage are then trapped as dimers by ethylguaiacol that is included in the SAQ liquor. Research with sugar maple (Acer saccharum) showed that the estimate of these structures (uncondensed G-β-O-4) by this approach was in close agreement with traditional but more tedious methods such as permanganate oxidation and 31P NMR. It was also shown that the lignin in the EGC 39 hybrid contained a higher concentration of uncondensed G-β-O-4 structures than the other two eucalypti lignins.

Preliminary Results on an Approach for the Quantification of Lignin-Carbohydrate Complexes (LCC) in Hardwood Pulps

The literature on biomass research contains many references to lignin-carbohydrate complexes (LCC) decreasing the rate of delignification in chemical pulp production, decreasing the yield of cellulosic ethanol via fermentation, and decreasing forage digestibility. However, it is difficult to find correlations between rates of the processes above and initial LCC concentration. One of the main reasons for the lack of such correlations is the absence of methods for accurate quantification of LCC. In this investigation, repeatable and reproducible determinations of bound sugars at monomeric concentrations as low as 0.3 wt% on enzymatic lignin (EL) have been achieved. The bound sugars are hydrolyzed by H2SO4, most likely as low molecular weight oligomers. In the same H2SO4 treatment, the oligomers are hydrolyzed to monomers which are subsequently quantified by 1H NMR analyses. A significant enrichment of bound arabinan was previously reported when a crude milled wood lignin (MWL) was compared to the starting wood meal. A similar arabinan enrichment was observed for ELs from kraft and soda-AQ (SAQ) pulps in the present study. Also, well-resolved cross-peaks have been obtained in 2D HSQC NMR analyses of ELs. It has so far been confirmed that the EL from a 30.6 kappa number SAQ pulp from sugar maple contained ∼30% more benzyl ethers linked to primary-OH groups in sugar units than the corresponding EL from a 33.7 kappa number kraft pulp.

Soda/AQ Pulping of a Hardwood with Trapping of the Generated Coniferyl Alcohol

Coniferyl alcohol is generated from the cleavage of β-O-4 bonds during alkaline pulping of hardwoods and softwoods. Once formed, some of the coniferyl alcohol (CA) is transformed into vinylguaiacol (VG) and isoeugenol (IE). All three of these compounds (CA, VG, and IE) can rearrange to quinone methides (QMs) under alkaline conditions and become involved in condensation reactions with lignin and carbohydrate moieties. The aim of this investigation was to see if ethylguaiacol (EG) addition to soda-AQ (SAQ) pulping systems would lead to its reaction with the QMs from CA, VG, and IE to form dimers that are unreactive towards further condensation. Sugar maple wood meal was delignified by the SAQ process with EG added at 5.0 wt% on wood meal. Three dimers were detected in the pulping effluent and identified as a combination of EG with CA, VG, and IE. The total yield of the three dimers corresponded to ∼80% of the estimated CA that would have been generated. Conventional kraft, SAQ, and SAQ+EG pulping of the maple chips were then performed. The bleachability of the SAQ+EG pulp was significantly improved as compared to the SAQ pulp and it was estimated to be superior to the kraft pulp as well.

Inclusion of a pressurized acidolysis stage in chemical pulp bleaching

Hardwood soda-AQ pulps are believed to be rich in benzyl sugar ethers (BSE) that can be partially cleaved by aqueous acidic treatments. The aim of this investigation was to evaluate the effect of acidolysis on final bleached brightness for kraft and soda-AQ (SAQ) hardwood pulps. The increase in final brightness due to acidolysis at 110 °C was twice as high for a eucalyptus SAQ pulp as compared to the kraft pulp. An oxygen delignified maple C-SAQ pulp (carbonate pre-treated SAQ) was acidolyzed at 120 °C and pH 2.6 for 30 min. When 1.60% ClO2 + 0.25% H2O2 on pulp was used in DEPD final bleaching of the control sample a brightness of 91.5% was achieved. When only 1.00% ClO2 + 0.25% H2O2 on pulp was used for the acidolyzed sample a brightness of 92.0% was attained. Analyses of the maple pulp after the acidolysis showed no major change in lignin content, brightness, or pulp yield. The minor changes suggest that a facile reaction such as benzyl ether cleavage was responsible for the improved bleachability. Preliminary research involving a lignin model compound and commercial birch xylan showed that lignin-carbohydrate condensation products were generated under SAQ cooking conditions. Furthermore, a fraction of these lignin-carbohydrate moieties were subsequently cleaved by acidolysis at pH 2.5 and 105 °C.

Bio-conventional bleaching of wheat straw soda–AQ pulp with crude xylanases from SH-1 NTCC-1163 and SH-2 NTCC-1164 strains of Coprinellus disseminatus to mitigate AOX generation

Two novel cellulase-poor xylanases from Coprinellus disseminatus SH-1 NTCC-1163 (enzyme-A) and SH-2 NTCC-1164 (enzyme-B) produced under solid-state fermentation mitigated kappa number of wheat straw soda-AQ pulps by 24.38 and 27.94% respectively after XE stages. The release of reducing sugars and chromophores was highest for both the enzymes at 10IU/g and reaction time 180min for 55°C at variable consistencies that is, 10% for enzyme-A and 5% for enzyme-B. (A)XECEHH and (B)XECEHH sequences improved brightness by 5.17 and 2.58% respectively at 4.5% chlorine charge. AOX in (A)XECEHH and (B)XECEHH sequences reduced by 56.11 and 55.75% respectively at 4.5% chlorine charge and 68.34 and 67.98% respectively at 2.25% chlorine charge respectively compared to control. Both the enzymes showed improvement in double fold and tear index with a decrease in burst and tensile index. SEM showed peeling, cracking and delamination in fibers due to enzyme treatment thus facilitating the penetration of bleach chemicals.

Feasibility of rice straw as a raw material for the production of soda cellulose pulp

The main objective of this work is to evaluate the suitability of rice straw and soda–anthraquinone (soda–AQ) pulping process to produce pulp and paper. To reach this aim, it was used a central composite factorial design to study the influence of operational variables (temperature (155–185 °C), cooking time (30–90 min), soda concentration (10–20%), anthraquinone concentration (0–1%) and liquid/solid ratio (6–8)), in soda–anthraquinone cooking of rice straw on pulps and paper sheets properties obtained. Based on the yield values obtained, nearly one half of the raw material can be efficiently converted into cellulose pulp and paper sheets. Also, the Kappa number/viscosity ratio of the pulp facilitates its efficient bleaching. Finally, based on the values for above-described physical properties, the pulp can be used to obtain paper or board and recycled paper (as % virgin fibre). In Spain are produced annually 757,000 t of rice straw. If we considered an average yield process of 45%, it would be possible to obtain 340,000 tons of pulp. These tons would be absorbed by the market taking into account the necessities in cellulosic pulp consumption.

Mechanistic Differences Between Kraft and Soda/AQ Pulping. Part 2: Results from Lignin Model Compounds

Data accumulated in our laboratory from the cooking of chips and bleaching of resulting pulps consistently pointed to a higher rate of lignin condensation during soda-AQ (SAQ) as compared to kraft pulping. The data also appear to indicate that the rate of condensation was higher at lower alkalinity and that the higher concentration of condensed structures in SAQ pulps is likely responsible for their poorer bleachability. Alkaline condensation reactions were investigated with four commercially available lignin model compounds: apocynol (AP), ethylguaiacol (EG), homovanillyl alcohol (HVA), and vinylguaicol (VG). The investigation of lignin model compounds (LMCs) indicated mechanistic differences that would explain the higher rate of lignin condensation for SAQ pulping as compared to the kraft pulping. Several research groups have reported that the rate of formation of coniferyl alcohol (CA) is 4–5 times higher for SAQ or kraft/AQ as compared to kraft pulping. The present investigation showed that secondary quinone methides from CA degradation products, such as vinylguaicol, participate in condensation reactions. A higher rate of condensation was observed in 0.1 M NaOH as compared to 0.6 M NaOH. Evidence was also found for carbohydrate-rich materials condensing with quinone methides.

Mechanistic Differences Between Kraft and Soda/AQ Pulping. Part 1: Results from Wood Chips and Pulps

Soda pulping catalyzed by anthraquinone (AQ) or 2-methylanthraquinone (MAQ) can produce hardwood chemical pulps similar to kraft pulps in all respect but for bleachability. Results accumulated in our laboratory suggest that the residual lignin in pulps from anthraquinone catalyzed processes is less reactive toward bleaching chemicals than that in kraft pulps. Analyses of pulps by periodate and permanganate oxidations suggest that the residual lignin from the non-sulfur processes contained more condensed structures than kraft residual lignin. The low reactivity of these structures is believed to be responsible for the lower brightness of bleached soda-AQ (SAQ) pulps. Pulping and bleaching trials with hardwood chips demonstrated that shortening of the cooking time and/or increasing the alkalinity is one strategy for improving bleachability of SAQ pulps. When sugar maple (Acer saccharum) chips were SAQ cooked for 1.0 and 2.0 h at 165°C, the higher kappa number pulp produced after 1.0 h of cooking bleached to a significantly higher brightness with a small increase in the chlorine dioxide application.

Soda-AQ delignification of poplar wood. Part 2: Further degradation of initially dissolved lignins

Abstract Degraded lignin fragments dissolved in pulping liquor during the soda AQ pulping of poplar (Populus deltoides) wood with a flow through reactor were divided in two fractions. The first one (LF-1) was collected during the heating-up period (100°C until the final temperature t max=170°C); the second one (LF-2) was collected at t max with 60 min cooking time. These two liquors were then treated at 170°C for 70 min (leading to a liquor LF-1A) and 10 min (leading to a liquor LF-2A). By these post-treatments, pulping liquors of batch pulpings were simulated. From the four liquors, lignins were isolated and after purification the chemical and physical properties were characterized by Gel Permeation Chromatography (GPC: to obtain their molecular weight distribution), nitrobenzene oxidation, permanganate oxidation, and 13C NMR spectroscopy. By these means, the reaction mechanisms of dissolved and degraded lignin fragments in pulping liquors was elucidated and insight was gained concerning the effectiveness of the anthraquinone-anthrahydroquinone (AQ-AHQ) redox system using the corresponding batch lignin preparation as reference. The simulated batch fractions LF-1A, LF-2A, and true batch lignin preparations are similar. They have a high content of condensed arylpropane units. Among them, syringylpropane units are most severely degraded, in particular, etherified β-aryl ether bonds are cleaved to a great extent after dissolution in pulping liquor. The structure of the remaining degraded lignin fragments was changed seriously, particularly on their side chains. Oxidation and disproportionation reactions are typical. In the presence of fibers, xylans tend preferentially to simple deposition on fibers instead of grafting with the degraded lignin fragments. Dissolution of carbohydrates is not affected by higher alkali concentration at the end of the pulping, and the yield losses are caused by a better lignin removal.

Recycling of chemical pulp from wheat straw and corn stover

Handsheets produced from corn stalks and wheat straw soda AQ pulps were recycled in the lab. Pulping of corn stalks resulted in a low pulp yield, low bonding strength, and low recyclability. Conversely, wheat straw fiber had a better yield, very good tensile properties, and showed a considerably better response to recycling. The tensile index of wheat straw fibers retained 67% of its original value after four cycles. It could be shown that recycling caused only small changes in chemical compo-sition, but that the crystallinity index increased considerably. To be able to understand the behavior of wheat straw fiber as part of a commercial papermaking furnish, a paper containing 20% wheat straw fiber was produced on a 24 inch pilot paper machine and was recycled using a handsheet mold with white water return. Chemical analysis of the control (no wheat fiber) and the wheat-containing paper demonstrated slightly higher xylan content for the wheat-containing material. Recyclability increased slightly with addition of wheat fibers to a commercial furnish.

Soda–anthraquinone, kraft and organosolv pulping of holm oak trimmings

The operating conditions for an organosolv (ethyleneglycol) and two alkaline (soda–anthraquinone and kraft) processes for obtaining cellulose pulp and paper from holm oak ( Quercus ilex) wood trimmings were optimized. A range of variation for each process variable (viz. temperature, cooking time and soda or ethyleneglycol concentration) was established and a central composite experimental design involving three independent variables at three different variation levels was applied. The results obtained with the three cooking processes used were compared and those provided by the kraft process were found to be the best. Thus, the tensile index values it provided (5.9–16.3 N m/g) were 23.7% and 41.5% better than those obtained with the soda–AQ and ethyleneglycol processes, respectively. Also, the kraft process provided the best burst index, brightness and kappa number values. Based on the optimum working ranges, the temperature and cooking time were the variables resulting in the most and least marked changes, respectively, in pulp properties.

Environmentally friendly pulping and bleaching of bagasse

Depithed Sudanese bagasse was examined for its suitability for pulp production. Bagasse fibre dimensions, morphological and chemical characteristics are reported. The pulping trials were carried out with soda–AQ and alkaline sulphite–AQ (AS–AQ) methods and soda method as reference. The AS–AQ pulping gave the best results in yield, degree of delignification, mechanical and optical pulp properties. Blending of bagasse and bamboo alkaline sulphite–anthraquinone pulps in different ratios gave well-balanced pulp strength characteristics with good tensile and tear indices, widening the range of different end products from bagasse pulp. Totally chlorine free bleaching (Q 1O/PQ 2P) of the best unbleached bagasse pulps gave bleached pulps of 76.9% ISO brightness, suitable for use in writing and printing grades of paper.

直接か性化技術

Research Association of Pulp and Paper Technology is developing Direct Causticizing Technology by using ferric oxide. Pilot plant test has now been done in Kure laboratory.The purposes of this paper are as follows.(1) to define and classify various Direct Causticizing methods, and to make the characteristics of the ferric oxide method clear compared with other causticizing methods.(3) to give a general view of the progress of Direct Causticizing Technology and to grasp the situations of R & D in other countries.(3) to clarify the advantages and the technical problems of ferric oxide method.(4) to elucidate the position of a soda AQ cooking which is requisite for the development of the ferric oxide method.