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Institute of Paper Science and Technology / Thesis (Ph. D) -- Institute of Paper Science and Technology, 1998.

Renewable energy sources, such as lignocellulosic biomass, are environmentally friendly because they emit less pollution without contributing net carbon dioxide to the atmosphere. Among lignocellulosic biomass, corn stover is a very useful feedstock to economically produce environmentally friendly biofuels. Corn stover was pretreated with an excess of calcium hydroxide (0.5 g Ca(OH)2/g raw biomass) in non-oxidative and oxidative conditions at 25, 35, 45, and 55oC. The optimal condition is 55oC for 4 weeks with aeration, determined by yields of glucan and xylan. The overall yields of glucose (g glucan hydrolyzed/100 g original glucan) and xylose (g xylan hydrolyzed/100 g original xylan) were 91.3 and 51.8 at 15 FPU/g cellulose, respectively. Furthermore, when considering the dissolved fragments of glucan and xylan in the pretreatment liquors, the overall yields of glucose and xylose were 93.2 and 79.5 at 15 FPU/g cellulose, respectively. The pretreatment liquor has no inhibitory effect on ethanol fermentation using Saccharomyces cerevisiae D5A. At the recommended condition, only 0.073 g Ca(OH)2 was consumed per g of raw corn stover. Under extensive delignification conditions, 87.5% of the initial lignin was removed. Extensive delignfication required oxidative treatment and additional lime consumption. Deacetylation quickly reached a plateau within 1 week. Delignification highly depended on temperature and the presence of oxygen. Lignin and hemicellulose were selectively removed, but cellulose was not affected by lime pretreatment in mild temperatures (25 ?? 55oC). The delignification kinetic models of corn stover were empirically determined by three simultaneous first-order reactions. The activation energies for the oxidative delignification were estimated as 50.15 and 54.21 kJ/mol in the bulk and residual phases, respectively. Crystallinity slightly increased with delignification because amorphous components (lignin, hemicellulose) were removed. However, the increased crystallinity did not negatively affect the 3-d sugar yield of enzyme hydrolysis. Oxidative lime pretreatment lowered the acetyl and lignin contents to obtain high digestibility, regardless of crystallinity. The enzymatic digestibility of lime-treated biomass was affected by the change of structural features (acetylation, lignification, and crystallization) resulting from the treatment. The non-linear models for 3-d hydrolysis yields of glucan and xylan were empirically established as a function of the residual lignin fraction for the corn stover pretreated with lime and air.

Renewable energy sources, such as lignocellulosic biomass, are environmentally friendly because they emit less pollution without contributing net carbon dioxide to the atmosphere. Among lignocellulosic biomass, corn stover is a very useful feedstock to economically produce environmentally friendly biofuels. Corn stover was pretreated with an excess of calcium hydroxide (0.5 g Ca(OH)2/g raw biomass) in non-oxidative and oxidative conditions at 25, 35, 45, and 55oC. The optimal condition is 55oC for 4 weeks with aeration, determined by yields of glucan and xylan. The overall yields of glucose (g glucan hydrolyzed/100 g original glucan) and xylose (g xylan hydrolyzed/100 g original xylan) were 91.3 and 51.8 at 15 FPU/g cellulose, respectively. Furthermore, when considering the dissolved fragments of glucan and xylan in the pretreatment liquors, the overall yields of glucose and xylose were 93.2 and 79.5 at 15 FPU/g cellulose, respectively. The pretreatment liquor has no inhibitory effect on ethanol fermentation using Saccharomyces cerevisiae D5A. At the recommended condition, only 0.073 g Ca(OH)2 was consumed per g of raw corn stover. Under extensive delignification conditions, 87.5% of the initial lignin was removed. Extensive delignfication required oxidative treatment and additional lime consumption. Deacetylation quickly reached a plateau within 1 week. Delignification highly depended on temperature and the presence of oxygen. Lignin and hemicellulose were selectively removed, but cellulose was not affected by lime pretreatment in mild temperatures (25 ?? 55oC). The delignification kinetic models of corn stover were empirically determined by three simultaneous first-order reactions. The activation energies for the oxidative delignification were estimated as 50.15 and 54.21 kJ/mol in the bulk and residual phases, respectively. Crystallinity slightly increased with delignification because amorphous components (lignin, hemicellulose) were removed. However, the increased crystallinity did not negatively affect the 3-d sugar yield of enzyme hydrolysis. Oxidative lime pretreatment lowered the acetyl and lignin contents to obtain high digestibility, regardless of crystallinity. The enzymatic digestibility of lime-treated biomass was affected by the change of structural features (acetylation, lignification, and crystallization) resulting from the treatment. The non-linear models for 3-d hydrolysis yields of glucan and xylan were empirically established as a function of the residual lignin fraction for the corn stover pretreated with lime and air.

The purpose of the study was to investigate how different types of filtrates (oxidized and unoxidized) would effect on oxygen delignification for softwood pulp, as well as study its impact on yield final-pH, viscosity and kappa number.

Barley spent grain, the main residue of the brewing industry, is a lignocellulosic material, which could be considered a potential raw material for ethanol production. In this work, spent grains generated in a microbrewery were fractionated by acid hydrolysis and delignification. The investigated sort of barley spent grains had high carbohydrate content, accounting for 60% of the dry matter, while its lignin content was lower than that reported for other sorts of spent grains. Since the used spent grains contained residual starch different treatment approaches were used for separating their main components without affecting the sugars generated by starch hydrolysis. Two kinds of acid hydrolysis processes, namely single-step and two-step hydrolysis, were used for solubilising the carbohydrate fraction. Single-step hydrolysis was performed either at 100oC or at 121oC. In the two-step approach, a second hydrolysis, at 121oC, was performed after the first hydrolysis step. The dilute-acid hydrolysis at 100oC removed all the starch, whereas the hydrolysis at 121oC removed also a part of the hemicelluloses in addition to starch. During the second hydrolysis step, the content of easily hydrolysable polysaccharides decreased from 32.5 to 7.6% in the material pre-hydrolyzed at 100oC and from 20.3 to 10.6% in the material pre-hydrolyzed at 121oC. The amount of easily hydrolysable polysaccharides removed in the second step corresponded to 83% and 81.5% of the total removed matter in the materials pre-hydrolyzed at 100 and 121oC, respectively. In the next step, acetosolv and alkaline delignification, either alone or combined with acid hydrolysis, were used for dissolving the lignin fraction. A higher solubilisation occurred after alkaline delignification, where 83% of the initial material was removed. Only 34% of the initial lignin was removed by direct acetosolv, while the combined acid hydrolysis/acetosolv approach resulted in lignin removal between 70 and 75%. However, the resulted pulp still contained important amount of lignin. The acid prehydrolysis was also beneficial for alkaline delignification, but the effect was less noticeable than for acetosolv. Lignin removal increased from 95% in direct alkaline delignification to nearly 100% in the acid hydrolysis-assisted alkaline treatment. Two different methods were carried out for lignin precipitation. In the liquid fraction obtained by acetosolv, lignin was precipitated by water addition after concentration of the liquors to 75% of the initial volume. Although the visual inspection of the liquors after water addition revealed a relatively good lignin precipitation, the separation by filtration of the precipitated material was difficult, apparently due to the small particle size of precipitated lignin molecules. Some improvement was observed for the combined treatments, especially for those including two-step acid hydrolysis. The best recovery, 54% of the precipitated lignin, occurred for the process including consecutive acid hydrolyses at 100 and then at 121oC before acetosolv. In the alkaline liquors, lignin was precipitated by pH adjustment to 2.0 by HCl. Around 40.5% of the solubilised lignin was precipitated, and it increased to 85-100% when combined treatments were applied. The best results were achieved upon the treatment including acid prehydrolysis at 121oC before alkaline process.

The interest in production of fuel ethanol from lignocellulosic materials is continuouslyincreasing due to the urgency of finding non-food substrates for production of bio-fuels.Marabou (Dichrostachys cinerea) is one of the abundant lignocellulosic bio-resources in Cuba,and it could be useful to produce bio-ethanol. Pre-treatment is an important step to produceethanol from lignocellulosic materials since it allows the separation of cellulose, hemicelluloseand lignin, and activates cellulose towards enzymatic hydrolysis. During the past few years,organosolv methods have been reported for effective separation of the main components oflignocellulosic materials and improvement of the enzymatic hydrolysis of cellulose. By usingacetosolv method lignin is separated under mild conditions and many of the lignin properties arewell preserved.The present work was aimed to perform a chemical characterisation of marabou biomass and toevaluate acetosolv delignification of the material. In this work the content of moisture, ash,extractives, easy-to-hydrolyze polysaccharides, difficult-to-hydrolyze polysaccharides, andKlason lignin of marabou biomass were analyzed. Klason lignin of the marabou biomass was23.4% of the mass. Acetosolv delignification was performed at normal boiling temperature(NBT) and 121oC, using 50-50, 70-30 and 90-10 acetic acid – water mixtures with 10% of solidsload during 1h. Hydrochloric acid (0.2g / 100g of mixture) was used as catalyst. Thedelignification of marabou biomass was also evaluated for the combination of dilute acid prehydrolysis(DAPH) and acetosolv with the same reaction conditions. This investigation provedthat acetosolv pretreatment was effective for solubilizing lignin contained in marabou biomass.The degree of lignin solubilisation increased with increasing acetic acid concentration in thereaction mixture. Lignin removals above 80% were achieved consistently both at NBT and121oC with 90% acetic acid, while only around 44.6 and 6.8% of the initial lignin was removedusing, respectively, 70 and 50% acetic acid at 121oC. The effect of temperature ondelignification was only marginal when acetosolv was conducted with 90% acetic acid, but itwas remarkable for lower acetic acid concentrations. A two-fold decrease of lignin removal wasobserved for the NBT acetosolv compared with the process performed at 121oC using both 70and 50% acetic acid. The insertion of a DAPH step prior to acetosolv considerably improvedlignin removal using 70 and 50% acetic acid at both temperatures, but its effect on the processesusing 90% acetic acid was minimal. High lignin yields were achieved upon its precipitation fromacetosolv liquors.

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A series of laboratory oxygen delignification were performed in this study at constant oxygen pressure and consistency to study the response of the pulp to the different process parameters, i.e. reaction temperature, reaction time, soda addition, and mechanical pretreatment, to the zero span tensile strength loss. The basic chemistry of the oxygen delignified pulps was under study including fiber charge, celluloses/hemicelluloses, and hexenuronic acid. The fiber structure such as curl, kink, fines, and fiber length were also discussed. NaOH charge can be reduced as much as 50 % by applying mechanical pretreatment to obtain the same level of selectivity at the oxygen delignification conditions described in this study.Mechanical pretreatment prior to oxygen delignification promoted a better selectivity for both Acacia mangium and MHW pulps. MHW kraft pulp did not show a significant extractive removal in all pretreatment methods during oxygen delignification. The ultrasonic pretreatment followed by filtering induced the best extractive removal among the other three methods.