Hydrolysis of pentosans in bagasse pith

Work has been conducted on the hydrolysis of pentosans in bagasse pith as the first part of a study of the chemistry of bagasse processing aimed at establishing an integrated industry. Bagasse pith is the fine part screened out and discarded as waste during the preparation of raw material for bagasse pulping plant. By using dilute sulphuric acid at a concentration less than 2% by weight and at a temperature lower than 165°C, pith is hydrolysed to pentoses in a yield of 80–90% based on potential pentoses in pith. Hydrolysis of pentosans in pith, within the scope of experiment, seems to be a first order reaction. However, the semi-logarithmic time plot for the hydrolysis of potential pentoses in the residue consists of two straight lines of different slope. This may be explained on the assumption that bagasse pith contains two major fractions of pentosans that are hydrolysed at different rates. Saeman's equation for hydrolysis of wood with sulphuric acid may be adapted to represent dependence of rate constant K on acid concentration C and reaction temperature T in hydrolysis of the two major parts of pentosans in bagasse pith. K₁ = 6.4 × 10⁵C^1.02 exp (?6378/T) K₂ = 10.7C^0.363 exp (- 2826/T)     

Saccharification of bagasse pith

Work is reported here on a process for the saccharification of bagasse pith, as the second part of a study of bagasse processing aimed at establishing an integrated industry. A method for pentose preparation from bagasse pith is designed on the basis of the conclusions reached in the first part of the study. It is preferable to Scholler's process in recovery of sugar and in concentration of the sugar solution. A process for glucose production from pentose-exhausted cellulosic residue is also developed to avoid the difficulties encountered in the Udic-Rheinau process. It seems to be a promising continuous process capable of giving a higher yield of glucose with less acid at a higher speed and affording favourable conditions for crystallising the dissolved glucose.     

Nitrogen containing additives in soda pulping of bagasse pith

Unbleached soda pulp was prepared from Egyptian bagasse pith by varying the alkali concentration and the time of heating at the boiling point of the liquor under atmospheric pressure. A linear relationship was observed between the dissolved pith and the dissolved lignin. Pulping with alkali concentration higher than 10% but not exceeding 16% was more effective, since more delignification took place with lower dissolved pith percentage. p- And m-nitrobenzoic acids and also hydroxylamine hydrochloride had a slight or no effect on the yield of the pulps. The alkali solubility percentage of the pulps prepared in the presence of any of the additives was lower than the control pulp. The delignification was enhanced more on the addition of hydroxylamine hydrochloride than p-nitrobenzoic acid, while m-nitrobenzoic acid seemed to have no effect. The yield of the pulps thus prepared, as determined by weighing, showed lower values than those determined by a chemical method. The soda delignification rate was shown to be proportional to the amount of unremoved lignin and the concentration of alkali in the liquor. The delignification reaction was found to follow approximately first-order kinetics.     

Synthesis and studies of egyptian bagasse pith phenol formaldehyde cationic exchangers

The article is concerned with a simple method for preparing cationic resins from polycondensation of Egyptian bagasse pith (as a source of cheap and renewable material) with phenol and paraformaldehyde as a cross-linking agent. Optimum principal reaction conditions of the preparation and properties are determined and compared with resin without bagasse pith content. The Synthesized resins are stable in water, organic solvents, thermal treatment, and mineral acids (1M). The sample having a cation exchange capacity up to 3.92 meq g^?1 of dry resins are being introduced as new cationic exchangers. The synthesized resins are used in the study of the possible separation of univalent cations. The rational thermodynamic equilibrium constants (In K) are calculated for Li⁺ ?Na⁺ exchanges on the resins having a various amount of bagasse pith. The thermodynamic parameters are computed and suitable explanations are described. © 1994 John Wiley & Sons, Inc.     

Adsorption of dyes onto bagasse pith using a solid diffusion model

The adsorption of four dyes (Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114) onto bagasse pith has been studied using an agitated batch adsorber. The variables studied were initial dye concentration and pith mass. A mathematical model has been developed based on external mass transfer and solid-phase diffusion. The model has been used to generate theoretical concentration–time decay curves, and these results were adjusted to experimental data by a best fit approach. The external mass transfer coefficients are 2.0 × 10^?3, 1.5 × 10^?3, 8.0 × 10^?4, and 5.0 × 10^?4 cm s^?1 and the solid diffusivities are 1.1 × 10^?8, 1.0 × 10^?8, 6.0 × 10^?9, and 3.0 × 10^?9 cm² s^?1 for Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114.     

Hydrolysis of sweet sorghum bagasse hemiceilulose with liquid hot water and its mechanism

引 言木质纤维素类生物质的生化转化过程包括预处理过程、水解液发酵过程和产物分离过程,而预处理过程是减少整个生化转化成本和提高生化转化效率的关键[1-3].与其他预处理方法相比,高温液态水处理(liquid hot water)(温度在170～250℃,压力高于饱和蒸气压)是一种绿色处理方法,它可以将木质纤维素类生物质中的半纤维素转化为木糖及其低聚糖,同时提高了残渣的纤维素酶解效率[4-7].该糖化工艺由于产生发酵毒性副产物少、不需要添加任何化学试剂、设备成本低等优点而受到广泛关注[8-12].就目前国内外相关报道来看,高温液态水预处理研究大都采用间歇(batch)搅拌反应器,该反应器的缺陷是反应中生成的糖类不能被及时排出从而被进一步降解.浙江大学吕秀阳等[13-16]主要针对葡萄糖、木糖、果糖和纤维素等在高温液态水中的水解动力学进行了深入研究,而针对真实生物质中的半纤维素水解机理报道比较少.     

Hydrolysis of sugar cane bagasse with hydrochloric acid,promoted by metallic cations

Lithium chloride, in combination with commercial grade hydrochloric acid, is very effective in the hydrolysis of prehydrolysed sugar cane bagasse. After 10 min at 50°C the holocellulosic portion is completely dissolved and after 20 min most of the sugar oligomers are hydrolysed to monomers, making the time-and energy-consuming post-hydrolysis unnecessary. With longer reaction times the sugars start to reoligomerise and decompose. Zinc chloride is a milder promoter, requiring post-hydrolysis even after reaction for 30 min at 50°C. On the other hand, it does not decompose the sugars giving the highest sugar yields after prolonged reaction time and post-hydrolysis. Ferric chloride is mostly ineffective in the hydrolysis of cellulose but is a good promoter of the hydrolysis of the sugar oligomers, under the reaction conditions.     

Maximizing the yield of water-soluble cellouronic acid sodium salt with high carboxyl content by 4-acetamide-TEMPO mediated oxidation of parenchyma cellulose from bagasse pith

Parenchyma cellulose, isolated from bagasse pith BP, was utilized as an alternative resource for preparation of soluble cellouronic acid sodium salt (SCA) by selective oxidation with the catalytic amounts of 4-acetamide-TEMPO and NaClO, in which NaClO₂ was used as a primary oxidant in an aqueous condition. The yield and carboxyl content of SCA were measured as a function of NaClO₂ content, 4-acetamide-TEMPO loading, oxidation temperature, initial pH, and reaction time, and optimized by an orthogonal test with the objective of achieving a maximum yield with high carboxyl content. An optimal SCA yield of 71.0 % with 32.92 % carboxyl content was found under the conditions of NaClO₂ dosage of 16 mmol/g, 4-acetamide-TEMPO loading of 0.20 mmol/g, and oxidation temperature of 50 °C in acetate buffer at pH 5.5 for 72 h. The structure and morphology of both parenchyma cellulose and its oxidized product were further characterized by means of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectronic spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). These techniques confirmed that parenchyma cellulose from bagasse pith was successively modified by an effective TEMPO-derivative-catalyzed oxidation process. The finding of this study might provide guidance in maximizing the yield of SCA from parenchyma cells utilizing the 4-acetamide-TEMPO/NaClO/NaClO₂ system. Considering the simple preparation process and favorable SCA property, this BP parenchyma cellulose showed unique characteristics with a great promise for high-valued modification and application in the areas of advanced and functional materials.     

Hydrolysis of sugar cane bagasse with hydrochloric acid: Separation of the acid by pervaporation. Evaluation of the bergius process

Polyester reinforced PTFE membranes with a nominal pore size of 0.02 μm are very effective in pervaporating HCl gas from hydrochloric acid solutions and cellulose hydrolysates. The efficiency of such membranes, which may be as high as 1.8x10^?2 mmol HCl min^?1 cm^?2 at 40°C, is almost independent of the flow rate and the static pressure of the acidic solution but depends strongly on the acid concentration. At an acid concentration of 26% (w/v) the pervaporation of HCl is negligible at 40°C, but can be accelerated by increasing the temperature. A slow increase of temperature during the pervaporation process is proposed, as this promotes post-hydrolysis of the sugars. Lithium chloride induces structural changes in the membrane which increase efficiency without compromising performance. The use of this new technology in conjunction with the original Bergius process could improve the performance of the latter and reduce its overall costs. The use of the improved process for the hydrolysis of sugar cane bagasse could double the yields of sugar or alcohol per hectare of planted sugar cane.     

Thermal characteristics of bagasse

Bagasse is a solid waste that remains after crushing sugarcane. Since bagasse is used as a fuel in sugar mills, characterization of its thermal degradation is rather important in order to use it efficiently. Thermal analysis of bagasse was carried out using differential thermal analysis (DTA) and thermogravimetry (TG) under oxidizing and inert atmospheres. Kinetic studies were based on weight loss obtained from TG analysis. Thermal degradation of bagasse takes place in two stages: volatilization and carbonization. The reaction rate, activation energy, entropy change, enthalpy change, and Gibbs free energy for the two thermal stages were calculated. The results indicated that activation energy for the volatilization stage is higher than that of decarbonization stage, and that both the rate constant and activation energy for combustion are higher than those of pyrolysis. © 1996 John Wiley & Sons, Inc.     

Microstructure and water sorption mechanism of coconut pith

The water sorption isotherm of coconut pith is studied in order to get an insight into the nature of the sorption process. The surface area available for adsorption, heat of adsorption and approximate size of possible capillaries are computed from the isotherm. A considerable hysteresis effect is observed. The cell structure of coconut pith is studied using an optical microscope. On the basis of the computations and microscopic observations, the similarity of the sorption process with that of woody materials is established.     

A study of biogas generation from coconut pith

Biogas production from cowdung is well studied. Coconut pith is an agricultural waste available in large quantities in Kerala: the possibility of using coconut pith for biogas production was studied. It was found that coconut pith in combination with cowdung gives considerable amount of biogas, while alone it did not produce any gas. The optimum combination was found to be 60% pith and 40% cowdung. Study of dilution effect on the slurry showed that the optimum solid-liquid ratio is 1:20. Partial removal of lignin from pith increased the rate of biogas production. Gas produced from a mixture of cowdung and pith was found to have a higher methane content than that produced from cowdung only.     

Characterization of unburned carbon in bagasse fly ash

Bagasse is one of the important biomass sources, which is used as a fuel in the sugar industry in India. As a result, large quantities of fly ash are generated and create a serious disposal problem. This is further aggravated by the presence of unburned bagasse mainly as carbonised fibre. In this study, the unburned carbon in bagasse fly ash is characterized by thermal analysis, electron microscopy and adsorption. The carbon particles can be separated from oxide fraction of fly ash by floating it in water. This process increases the loss on ignition from 20–30% to 80%. N₂ adsorption measurements give BET surface areas of ～200 m²/g for the separated carbons. Analysis of the isotherms indicates a large fraction of pores in the size range of 10–12 Å. Scanning and transmission electron microscopy studies show that the unburned carbon is amorphous and the morphology retains the cellular characteristics of the parent bagasse fibres.     

Characterization of sugarcane bagasse powders

Sugarcane bagasse is a promising renewable lignocellulosic feedstock. Hence, proper characterization of bagasse powders is important for the development of novel technologies based on this resource. In this work, bagasse powders are prepared by sieve fractionation followed by cutting milling and rotor milling (which acts by impact, shear, and friction). The generated powders are characterized by techniques commonly applied to other particulate systems, namely scanning electron microscopy, light scattering particle sizing, and nitrogen adsorption. Particle size distribution, envelope density, specific surface areas, and effective cell wall thickness are determined. Results obtained from different techniques are compared. Finally, the applicability of the analytical techniques to sugarcane bagasse powders is discussed.     

Production of cellulases from coconut coir pith in solid state fermentation

Coconut coir pith, available in abundance especially in tropical countries, was studied as a substrate for the production of cellulase[1,4(1,3;1,4)-β-D -glucan 4-glucanohydrolase, EC 3.2.1.4] and β-D -glucosidase(β-D -glucoside glucohydrolase, EC 3.2.1.21) in solid state fermentation. The effects of fermentation time, nutrient level, substrate particle size and inoculum size have been examined for optimal production of these enzymes by the fungal strain Aspergillus niger NCIM 1005. The highest filter paper activity (FPA) of 4.11 IU g^?1, carboxyl methyl cellulose (CMCase) activity of 15·55 IU g^?1 and cellobiase activity of 9·31 IU g^?1 were obtained after 7 to 8 days of fermentation. Reese and Mandel's mineral solution in the substrate to mineral solution ratio of 1:10 (w/v) supported high cellulase and cellobiase activities. An inoculum size of 20–50% (v/v) based on the volume of mineral medium and substrate average particle size of 375 μm were optimum for enzyme production.     

Dielectric properties of cyanoethylated bagasse composites

Bagasse was converted into a thermo-moldable material by cyanoethylation. The effect of reaction conditions employed during the preparation of cyanoethylated bagasse (CE-B) fibers on dielectric properties of hot-pressed composites was studied. Increase in the nitrogen content of the cyanoethylated fiber, i.e., the nitrile groups resulted in an increase in the dielectric constant and a decrease in the dissipation factor (tan δ) peak of the composites. Increase in the reaction temperature and the alkali concentration resulted in a decrease in the dielectric constant and tan δof the composites. Thickness swelling (TS) and equilibrium moisture content of composites conditioned at different relative humidities (RHs) were studied and the extent of the effect of the absorbed moisture on the dielectric properties was also studied. Increase in the nitrogen content, the alkali concentration, and the reaction temperature during the preparation of cyanoethylated fibers resulted in a decrease in TS and moisture absorption of the composites formed. The dielectric properties of the composites conditioned at 60 or 90% RH deteriorated severely. The effect of temperature on the dielectric constant and tan δof a selected CE-B composite was studied. The dielectric constant and tan δincreased as the temperature increased.     

有机溶剂法纯化蔗渣木质素

采用有机溶剂法对甲酸预处理蔗渣后的蔗渣木质素进行纯化并进行结构表征。纯化后木质素的纯度为92.1%,收率为76.1%。红外图谱分析、热重和核磁共振氢谱分析表明,提纯前后木质素均含有愈创木基和紫丁香基两种结构,其中紫丁香基单元为主要单元。扫描电镜分析表明,纯化后的木质素由1⁵μm的球体颗粒组成,表面结构松散,颗粒产生粘连现象,有利于其在水凝胶、高分子树脂等方面的应用。     

蔗渣碱木素的热裂解特性

利用热重分析法研究了蔗渣碱木素的热解特性,并利用TG-FTIR和Py-GCMS对碱木素的热解产物种类及分布规律进行了分析。结果表明,木素热解呈现宽温度区域,可分为4个阶段,主要裂解温度范围为200～500℃,在400℃左右失重率最大,残余物得率较高。TG-FTIR分析显示了木素热解过程中气体产物的释放规律,300～500℃为主要热解挥发阶段,大部分气体产物在400℃左右产率达到最大。Py-GCMS分析表明,木素的热解产物大致可分为杂环、苯类芳香族、酚类芳香族、酯和酸等化合物,在主要热分解阶段,随着热解温度的升高,苯类和酚类芳香族化合物的含量增多,600℃时酚类物质的含量最高。     

LiCl/DMAc体系对蔗渣的溶解性

LiCl/DMAc体系是近年来日益受到重视的纤维素非水溶剂,但其溶解植物生物质,如蔗渣的情况却鲜有报道。本文从活化时间、固液比、LiCl浓度、加热时间及加热温度5个方面对LiCl/DMAc体系溶解蔗渣的行为进行研究。结果表明最佳溶解条件为:蔗渣160℃活化1h,烘干后取400mg与10%LiCl/DMAc溶液20mL按固液比1:50g/mL混合,160℃加热3h后,蔗渣溶解率可达81.8%。这为均相条件下利用蔗渣进行高效衍生化提供了有前景的发展方向。     

二乙烯三胺基蔗渣碱木质素的制备

以二乙烯三胺和甲醛对蔗渣碱木质素进行改性,对工艺参数进行优化。结果表明,当温度80℃,时间4 h,m(木质素)∶m(二乙烯三胺)=1∶1. 5,n(二乙烯三胺)∶n(甲醛)=1∶3,含氮量最大为7. 1%,二乙烯三胺和甲醛的物质的量之比对含氮量的影响显著。红外光谱和扫描电镜-能谱仪的测试结果表明,改性后亚甲基和胺基被引入木质素结构中,表面形貌由球状变为块状。