Dissolving pulps from Egyptian bagasse. II. Low temperature cooking

Bagasse was pulped by the prehydrolysis-soda process. Increasing the concentration during prehydrolysis or pulping had a favourable effect on pulp properties. Further improvement in these properties was attained when the increase in concentration was accompanied by lowering the temperature. The effects of increasing the concentration and lowering the temperature of prehydrolysis and pulping were compared.     

Acetylation behaviour of cotton and bagasse celluloses. II. Effect of hot alkali refining

The alkali pretreatments of cotton linters, bagasse dissolving pulp, and bagasse kraft pulp increased the accessibility of the cellulose hydroxy groups to acetylating molecules. The pretreatment with hot alkali resulted in a higher degree of esterification than with cold alkali. The filterabilities of cellulose acetates obtained from alkali pretreated samples of cotton linters, dissolving pulp, and kraft pulp were better than in case of the untreated samples. Hot refining resulted in better filterability than cold refining, but resulted in stronger degradation and lower thermal stability than cold refining. The presence of hemicelluloses in the untreated pulp lowered the reactivity towards acetylation but favoured the reactivity towards xanthation. In case of cotton linters both reactivities were improved by the alkaline pretreatments. The increase in reactivity resulting from the depolymerization of the cellulose overcame the increase in inaccessibility resulting from drying after the alkaline treatment. The removal of hemicelluloses from the dissolving and kraft pulps by alkaline extraction deteriorated the reactivities towards xanthation, but had a favourable effect on the reactivity towards acetylation.     

Dissolving pulps from Egyptian bagasse I. Effect of depithing on the chemical,physical and sub-microscopic characteristics of viscose pulps

Egyptian bagasse was pulped by the prehydrolysis-sulphate process. The effects of depithing on certain chemical, physical and sub-microscopic characteristics of the pulp, in particular its reactivity towards xanthation, were investigated. Depithing before and after prehydrolysis was compared. Pulps with a higher degree of chemical purity and higher degree of whiteness showed better reactivity towards xanthation. However, the most important factor affecting the reactivity was the accessibility of the cellulose hydroxyls to reactant molecules.     

Thermal and biological properties of tin-modified cellulosic material derived from cotton

Thermal and biological properties of tin-modified cellulose derived from cotton are described. The inception temperature of degradation for tin-modified cellulosic products is inferior to that of cotton itself, but the heats of degradation in air are less than that of cotton consistent with the modified products being superior in this respect. Degradation of the modified materials in helium as monitored by coupled thermogravimetric analysis–mass spectroscopy shows that degradation occurs through a series of complex steps with the evolution of products characteristic of both the tin-containing and cellulose materials. The tin-modified cellulose was tested against five fungi using disk and protein assays. The fungi tested are typical and widespread, and these tests provide a good indication of the applicability of such products as retarders of fungi-related rot and mildew. Most of the tested samples showed good inhibition of the tested fungi.     

Effect of depithing on pulps from egyptian bagasse

Egyptian bagasse was pulped by the prehydrolysis-soda process followed by multi-state bleaching. Raising the concentration of sodium hydroxide used in the second step of bleaching improved the chemical characteristics of the pulp. Depithing had to be applied to improve the degree of pulping and to reduce the ash content. The minimum ash content (0.07%) was arrived at either by carrying out depithing before prehydrolysis to the extent of 2%, or after prehydrolysis to the extent of 10%. Depithing before prehydrolysis was superior as it resulted in a better yield, higher alpha cellulose, and higher degree of whiteness.     

Graft copolymerization of acrylonitrile onto bagasse and wood pulps

Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50°C than at 30°C or at 40°C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.     

Acetylation behaviour of cotton and bagasse celluloses. III. Upgrading pulps by extraction with sodium hydroxide-borax solutions

The presence of borax during alkali refining of pulps increased the solubility of the short-chain celluloses and hemicelluloses and thus improved their chemical characteristics. Small improvements in the chemical characteristics of cotton linters took place. A stronger effect was observed in case of the dissolving pulp and a more pronounced effect took place in case of the kraft pulp. Cold 20% NaOH refining was more effective than hot 5% NaOH refining. The physical and sub-microscopic characteristics of linters were mainly affected. Refining lowered the D.P., increased the affinities towards water and alkali, decreased the crystallinity, and improved the reactivity towards xanthation. The presence of borax resulted in a more open and accessible fine structure and better reactivity. Cold refining of the dissolving and kraft pulps resulted in lower reactivity than hot refining and the presence of borax improved the reactivity. It also increased the yield of cellulose acetate. The increase in the solubility of the short-chain celluloses and hemicelluloses resulting from the presence of borax resulted in better homogenisation of the pulp. This was reflected in better chemical and physical characteristics of the acetate.     

Thermal behavior of ungrafted and grafted bagasse and wood pulps

The effect of grafting of methyl methacrylate (MMA) and acrylonitrile (AN) on the thermal behavior of the pulp of sugar cane loaded with CaCO₃ and the pulp of a broad-leaved tree has been studied by thermal methods. Different experimental conditions of grafting AN onto the eucalyptus pulp have been used, including both water and organic solvent systems as the medium of reaction. To optimize the grafting of MMA onto wood pulp, the effect of pulp swelling and the contact time of the monomer with the pulp have been examined. Ungrafted as well as grafted cellulose samples with different levels of grafting were characterized by differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA). The CaCO₃ filler makes the pulp of bagasse thermally more stable. The grafting of MMA onto the bagasse or the wood pulps improves their thermal stability. This is not the case for wood grafted with poly(AN). The thermal stability of the grafted and ungrafted samples varies after a few weight percent has been lost. The glass transition temperature (T_g) of the copolymers have been measured and they are in good agreement with the calculated data. © 1993 John Wiley & Sons, Inc.     

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。     

A comparison of methods to quantify cationization of cellulosic pulps

Fibers resulting from pulping of wood are negatively charged by nature. This charge might be reversed by chemical modification for different applications. In this study, different options to determine the degree of substitution (DS) with cationic groups introduced using 2,3-epoxypropyltrimethylammonium chloride, a common cationization reagent, are compared. Classical analytical methods for this purpose include elemental analysis, which is unspecific, and titration, which is sensitive toward impurities and highly elaborate. These are complemented by fast and robust approaches based on infrared spectroscopy or thermogravimetric analysis. The absorption increase at 1480 cm^?1 is specific for the introduced R-NMe₃ and linearly correlated with the DS. For bleached Kraft pulps, cationization splits the thermal degradation of cellulose in two phases, their ratio being roughly proportional to the DS. Both methods require virtually no sample preparation. Infrared spectroscopy is particularly easy to apply and allows a quantification of pulp cationization in short time.     

虫白蜡的碱炼脱酸

参考油脂碱炼理论，提出了虫白蜡碱炼脱酸精炼的实施方案，实践证明，在熔化的虫白蜡中加入计算量的碱液，于93℃碱炼30min，可得到符合国家部颁标准的虫白蜡产品。     

Permeability of alkali chlorides through charged cellulosic membranes

The permeation of alkali chlorides through charged cellulosic membranes was investigated. The membranes used were partially carboxymethylated and carboxyethylated cellulose with various degrees of substitution. The permeability coefficients were found to increase in a sequence of LiCl < NaCl < CsCl < KCl. This sequence is explained by considering the partition and the hydration of the ions in these hydrophilic membranes. The dependence of the permeability on the salt concentration was interpreted by means of Teorell-Meyer-Sievers (TMS) theory. The effectiveness of the charged groups in the membranes is explained by the counterion binding mechanism.     

Chemical celluloses derived from Pinus radiata wood pulps for nitrocellulose preparation

The nitration capabilities of a range of chemical celluloses, including some containing the cellulose-II polymorph, were examined. The cellulose samples, derived from Pinus radiata wood by bisulphite, prehydrolysis-kraft or kraft pulping, were compared with a commercial nitration-grade cellulose and two bleached cotton linters samples. All samples on nitration gave nitrocelluloses (degree of substitution ≈ 2–45) which had satisfactory stabilities and solubilities, with the exception of a P. radiata bisulphite cellulose which had a high pentosan value. The presence of cellulose-II in the samples was not an impediment to the nitration. High performance size exclusion chromatography of the nitrocelluloses showed that the molecular weight distributions of samples derived from the P. radiata celluloses were generally similar to that derived from a commercial nitration-grade cellulose.     

Factors affecting the enzymic susceptibility of alkali and acid pretreated sugar-cane bagasse

Acid and alkali pretreatments were studied to identify those factors which are critical in determining the susceptibility of a lignocellulosic substrate (bagasse) to enzymic hydrolysis. The different effects of each treatment on the structure of the bagasse affected the subsequent susceptibility to enzymic attack in different ways. The acid treatments appeared to act by disrupting the lignin structure, probably by hydrolysing the carbohydrate chains attached to the lignin, as well as the lignin itself. The attack on the carbohydrate content removed outlying material in the cell wall (i.e. hemicellulose and amorphous cellulose) to expose a ‘core’ of more resistant regions. The alkali treatments appeared to produce a more open structure by penetrating the inner layers and selectively removing hemicellulose molecules as well as breaking some lignin—carbohydrate bonds. The different treatments resulted in structural changes which were found to affect the hydrolysis mechanism.     

盐水精制过程中过碱量的自动调节

在盐水精制工艺中,增设了过碱量自动检测设备,并通过编程,实现了根据过碱量检测结果自动调节两碱流量的目标.由于控制更精确,氢氧化钠和碳酸钠的消耗均降低.     

Comparison of alkali treated sugarcane bagasse and softwood cellulose/polypropylene composites

ABSTRACT

In this study, composite materials from agricultural biomass and polypropylene (PP) thermoplastic were produced by melt compounding using a melt mixer. The chemical interaction of sugarcane bagasse (SCB)-PP and soft wood (SW)-PP composites and corresponding cellulose were verified by Fourier-transform infrared spectroscopy (FTIR) analysis, X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The cellulose composites were more crystalline than PP, trailed by PP/SCB and PP/SW composites. It was found that among composite materials, PP/SCB were least thermally stable compared to PP/SW. The addition of extracted cellulose decreased the thermal stability of PP/SCB composites at higher filler content due to poor interfacial bonding as compared to PP/SW composites. SEM results confirmed a rough morphology and the presence of many voids resulting from fibre pull-out in composites, especially for the ones with higher fibre content. Dynamic mechanical analysis (DMA) of both PP/SCB and PP/SW composites indicated improvement in the storage modulus compared with neat PP.     

Effects of plant‐scale alkali refining and physical refining on the quality of rapeseed oil

The physical refining of soybean oil was introduced as an energy saving and environmentally friendly procedure alternative to the traditional alkali refining, and the process was successfully applied to other vegetable oils. We had compared the two procedures in industrial refining under conditions, which enable a clear comparison. In nine plant‐scale experiments, crude rapeseed oil, taken from the same tank of crude oil, was processed on the same day both by alkali refining and by physical refining. Quality changes (free fatty acids, peroxide value, conjugated fatty acids, polar lipids, minor constituents) were determined, and also their stability against oxidation (Rancimat and Schaal Oven Test), and the fatty acid composition. In refined oils, the sensory acceptabilities and the sensory profiles were assayed. Finally deodorized oils, produced by the two methods, did not appreciably differ in their sensory characteristics and chemical composition, excepting slightly higher concentration of isomeric polyunsaturated fatty acids in physically refined oils. During storage for one year in commercial packagings at 15 °C, oxidative and sensory changes were negligible.     

Action of alkali metal hydroxides on cotton

The swelling of cotton increased continuously as the concentration of LiOH solution was raised progressively to saturation. In contrast, the swelling of cotton treated with NaOH or KOH leveled off at higher concentrations after increasing initially. The maximum swelling achieved with NaOH was higher than that obtained with LiOH, which was higher than that given by KOH. Accessibility of cotton treated with LiOH solutions, as indicated by sorption ratios, was lower than that of cotton treated with NaOH or KOH solutions of similar concentrations. The level-off degree of polymerization (LODP) of cotton treated with similar concentrations of alkali decreased in the order LiOH, NaOH, KOH. The reactivity, as indicated by acetylation, of cotton treated with alkali metal hydroxides, washed with water, and never dried was measured. At concentrations between 5.5.N and 8.2N, the rate of increase of reactivity was relatively low for cotton treated with NaOH, and no increase was observed for cotton treated with KOH. The reactivity of LiOH-treated cotton continued to increase sharply up to treatment with a saturated solution of the alkali. A limited number of observations were also made on cotton treated with CsOH and RbOH. Accessibility, reactivity, extent of swelling, and LODP values, together with x-ray data, are discussed in relation to the fine structure of the alkali-treated fiber.     

Speciation and distribution of alkali,alkali earth metals and major ash forming elements during gasification of fuel cane bagasse

Gasification of fuel cane bagasse, the waste residue from fuel cane, a hybrid of wild and commercial clones of sugar cane, was carried out in a novel 50 kWe air-blown autothermal downdraft gasifier. The speciation and distribution of alkali, alkali earth metals and major ash forming elements during gasification were investigated to evaluate the extent of volatilisation of these elements into the syngas and to determine the likely impact on syngas fuelled solid oxide fuel cell systems. Also assessed was the potential for defluidisation of the fuel bed due to agglomerate and deposit formation. Chemical fractionation studies showed that 30% of the potassium was captured by aluminosilicates and was retained in the ash, thereby reducing the alkali loading in the syngas and that more than 50% of the alkali earth metals were released to the syngas. In contrast, although the major ash forming elements were transformed from acid insoluble to acid soluble forms during gasification they remained hard bound in the ash and less than 30% of each one was released into the gas phase. The composition of clinkers and agglomerates produced during gasification was investigated by SEM-EDX and XRD which confirmed the presence of the eutectic systems KAlSi₂O₆–SiO₂, KAlSi₂O₆–CaMgSi₂O₆–SiO₂ and CaMgSi₂O₆–NaAlSi₃O₈. A preliminary model of the distribution behaviour during gasification of the ash forming elements has been developed.