环氧氯丙烷改性稻草的反应机理及表征

稻草秸秆经碱煮预处理后,用环氧氯丙烷在120℃下以甲苯为溶剂反应1~8h,醚化程度用增重率(weight percent gain,WPG)表示。采用元素分析和中性糖分析两种化学方法,以及傅里叶红外变换光谱、固体CP/MAS ~(13)C-NMR,对所制备的环氧氯丙烷改性稻草进行表征,以探讨醚化反应机理。结果显示,醚化反应发生在纤维素C2、C3和C6位置的羟基上。醚化反应后,稻草样品的C和H的质量分数增加,羟基数量减少,O质量分数降低。     

提高接枝淀粉浆料接枝效率的淀粉预处理方法EI北大核心CSCD

一种提高接枝变性淀粉浆料接枝效率的淀粉预处理方法,属于纺织经纱上浆使用的变性淀粉浆料技术领域。本发明包括淀粉烯丙基醚化预处理和自由基接枝共聚合两步。通过对淀粉原料进行醚化预处理,在淀粉大分子上引入含有碳一碳双键的烯丙基原子团,然后将醚化淀粉与乙烯基单体在引发剂作用下进行接枝共聚合反应,引入接枝支链,制得高接枝效率的接枝淀粉浆料。本发明借助于在淀粉大分子上引入含有碳一碳双键的烯丙基侧基;以便在随后进行的淀粉接枝共聚反应过程中部分地将均聚反应转化成接枝共聚合反应,减少均聚物的生成量,从而显著增加接枝淀粉浆料中接枝共聚物的含量,有效提高接枝共聚合反应的接枝效率,降低单体消耗量和生产成本。     

基于环氧氯丙烷醚化改性水杨酸的功能材料的制备

提出了一种改性方法以降低水杨酸的生物毒性。以环氧氯丙烷为反应原料和反应溶剂,在60℃条件下,与水杨酸羧基保护产物搅拌醚化反应5h,获得中间产物,通过去羧基保护反应,得到目标化合物。通过对反应最佳条件的探讨,获得目标化合物的收率为76.3%。同时,目标化合物采用傅里叶变换红外光谱进行结构表征。此研究为水杨酸的改性提供了一种新的方法,将促进水杨酸在医学领域上的应用。     

提高接枝淀粉浆料接枝效率的淀粉预处理方法EI北大核心CSCD

一种提高接枝变性淀粉浆料接枝效率的淀粉预处理方法,属于纺织经纱上浆使用的变性淀粉浆料技术领域。本发明包括淀粉烯丙基醚化预处理和自由基接枝共聚合两步。通过对淀粉原料进行醚化预处理,在淀粉大分子上引入含有碳-碳双键的烯丙基原子团,然后将醚化淀粉与乙烯基单体在引发剂作用下进行接枝共聚合反应,引人接枝支链,制得高接枝效率的接枝淀粉浆料。本发明借助于在淀粉大分子上引入含有碳-碳双键的烯丙基侧基,     

提高接枝淀粉浆料接枝效率的淀粉预处理方法

一种提高接枝变性淀粉浆料接枝效率的淀粉预处理方法，属于纺织经纱上浆使用的变性淀粉浆料技术领域。本发明包括淀粉烯丙基醚化预处理和自由基接枝共聚合两步。通过对淀粉原料进行醚化预处理，在淀粉大分子上引入含有碳一碳双键的烯丙基原子团，然后将醚化淀粉与乙烯基单体在引发剂作用下进行接枝共聚合反应，引入接枝支链，制得高接枝效率的接枝...     

蒸汽爆破预处理对稻草刨花板性能的影响

稻草SiO2含量较高,并且表皮被光滑的斥水性的蜡层所覆盖,无法使用传统的脲醛树脂(UF)制造稻草刨花板。采用蒸汽爆破法预处理稻草,预处理温度分别为160和170℃,时间分别为2,4和6 min。以预处理后的稻草为原料,利用UF为胶粘剂制作稻草刨花板。实验结果表明,经过160℃,停留时间为6 min和170℃,停留时间分别为4与6 min预处理的稻草制备的刨花板的强度性能达到了国标GB/T 4897-2003的要求。     

基于水杨酸的新型两性离子水凝胶单体的制备

以水杨酸、环氧氯丙烷和甲基丙烯酸二甲氨乙酯为基本原料,经过羧基保护、开环醚化和季铵化等反应制备了一种新型的含有可聚合双键的两性离子水凝胶单体。单体结构中的水杨酸和季铵盐结果均对细菌具有很好的杀灭作用,且经聚合后可覆盖于医疗器械的表面,进一步防止细菌的侵蚀。考察了制备这种两性离子水凝胶单体的反应条件如反应溶剂、反应时间和反应温度对原料转化率的影响,进而获得了最佳制备工艺条件,在此条件下获得目标化合物的总收率为51.6%,终产物使用傅里叶变换红外光谱对特征基团进行了表征。     

淀粉与2-氯乙醇醚化反应的研究

对在水溶液中不同反应条件下淀粉与2-氯乙醇醚化的反应进行了研究.考察的因素包括碱处理时间与温度、氢氯化钠及2-氯乙醇的用量以及醚化时间与温度.结果表明,碱处理时间超过40min,摩尔取代度没有明显的变化.摩尔取代度随氢氧化纳用量的增加而提高,但达到最大值后则会降低.随醚化时间的延长,摩尔取代度增大,但10h以后则变化不大.醚化温度在53℃时可以得到较高的摩尔取代度.     

Span-80合成工艺的改进

加入醚化催化剂VA,采用先醚化后酯化的工艺,合成结构合理、性能优良的Span-80.讨论催化剂浓度、反应温度、反应时间等因素对合成反应的影响,并确定了最佳反应条件.较理想的醇酸比为0.56;催化剂VA的浓度取1.1%;醚化温度150℃;酯化温度为200℃;反应时间3 h.     

环氧氯丙烷对淀粉热解行为的影响及其交联机理

首先制备了环氧氯丙烷交联的玉米淀粉,然后经稳定化和炭化得到淀粉基类球形炭材料。通过TG-MS分析玉米淀粉在环氧氯丙烷影响下的热解行为;采用扫描电镜(SEM)、X射线粉末衍射仪(XRD)对淀粉基类球形炭材料的微观形貌和晶型结构进行表征;利用原位红外(in situ FTIR)对淀粉热解过程中表面化学演化进行表征;最后,通过以上表征及分析探究环氧氯丙烷对淀粉热解行为的影响并深入探究了环氧氯丙烷与淀粉的交联反应机理。结果表明,淀粉交联环氧氯丙烷后,热稳定性得到有效提高,最大热失重温度提前,热解过程相对温和,避免淀粉在剧烈反应时基本骨架结构遭到破坏和炭收率显著降低,同时,交联淀粉在后续的热解过程中更趋向于向芳香族结构转化,在相同温度下比纯淀粉热解产物炭化程度高,得到的最终产物炭收率高;环氧氯丙烷与淀粉在热解过程中与淀粉发生交联反应,形成稳定的网状结构稳定淀粉炭骨架从而减少淀粉中挥发性小分子物质的产生。     

苄基化改性杉木粉的制备表征及对PP复合材料力学性能的影响

以甲苯为溶荆、NaOH为催化剂,使用氯化苄对杉木粉进行改性,制备了增重率(WPG)不同的改性木粉;用双辊筒炼塑机将改性木粉与聚丙烯(PP)共混,制备了木粉/PP复合材料.研究了工艺条件对改性木粉增重率的影响.通过红外光谱(FT-IR)、X射线衍射(XRD)和热重分析(TG)等方法,研究了改性木粉的结构和热性能.并研究了...     

Analyzing the pyrolysis kinetics of rice straw,bagasse, and mixtures thereof and product energy yield

In Taiwan, rice straw and bagasse are major agricultural wastes that are produced in extremely large quantities and volumes and contain high moisture content. Current processing methods remain inadequate; therefore, this study focused on the pyrolysis and relevant analyses of rice straw, bagasse, and mixtures thereof to investigate the feasibility of copyrolyzing rice straw and bagasse for renewable energy generation. Mixtures containing various ratios of bagasse and rice straw were examined through physical, chemical, thermogravimetric, and reaction kinetics analyses. Pyrolysis experiments were conducted to investigate the energy yield of the reaction products. Both bagasse and rice straw contained low ash content, and thermal processing effectively reduced the waste volume and cost of final disposal. A mixture content containing approximately 30 wt% rice straw (potassium content reaching 8.50 g/kg) substantially reduced the activation energies required for copyrolysis reactions, subsequently reducing energies required for thermal processing. The solid char generated from pyrolyzing the bagasse and rice straw mixtures did not decay easily and exhibited high storability and transportability. Moreover, volumetric energy densities substantially increased after pyrolysis. Therefore, copyrolysis is arguably a feasible and effective alternative biofuel conversion method for countries that process large quantities of bagasse and rice straw.     

四种生物质废弃物环氧树脂的合成及表征

分别以四种生物质废弃物———木粉、榛子壳、稻草和玉米秆苯酚液化物为原料,与环氧氯丙烷反应,制备出以四种生物质液化物为基材的环氧树脂,采用凝胶渗透色谱(GPC)对比分析了四种生物质液化物及其环氧树脂的相对分子量分布。以聚酰胺(PA-650)为固化剂进行固化,并利用热失重分析(TGA)、差热分析(DSC)和剪切强度测试等手段对固化物的热力学性能进行了测试。结果表明,木粉液化物及其树脂的-Mw和-Mn最高分别为532、759和249、308,木粉基树脂胶粘剂的剪切强度最大为5.7MPa,且它的热稳定性最好。     

Enhanced malachite green removal from aqueous solution by citric acid modified rice straw

In this paper, rice straw was thermochemically modified with citric acid (CA) as esterifying agent. Two introduced free carboxyl groups of esterified rice straw were further loaded with sodium ion to yield potentially biodegradable cationic sorbent. In order to investigate the effect of chemical modification on the cationic dye sorption of rice straw, the removal capacities of native and modified rice straw sorbing a cationic dye (malachite green) from aqueous solution were compared. The effects of various experimental parameters (e.g. initial pH, sorbent dose, dye concentration, contact time) were investigated. For modified rice straw (MRS), the malachite green (MG) removal percentage came up to the maximum value beyond pH 4. For the 250 mg/l of MG solution, the 1.5 g/l or up of MRS could almost completely remove the dye from aqueous solution. Under the condition of 2.0 g/l sorbent used, the percentage of MG sorbed on MRS kept above 93% over a range from 100 to 500 mg/l of MG concentration. The sorption isotherms fitted the Langmuir or Freundlich models. The sorption equilibriums were reached at about 10 h. The sorption processes followed the pseudo-first-order rate kinetics. After chemical modification, the intraparticle diffusion rate constant (k(id)) was obviously increased. The results in this study indicated that MRS was an excellent sorbent for removal of MG from aqueous solution.     

可循环混合溶剂分离水稻秸秆纤维素

粉碎的水稻秸秆经水煮和抽提预处理后,采用乙二醇(EG)和水的混合体系(体积比9∶1)为溶剂,在酸或碱催化作用下,分离得到纤维素,同时回收木质素和半纤维素;对所得样品的组分含量、晶体结构、微观形貌等进行了分析。结果表明:经水煮和抽提预处理后,秸秆纤维束状结构变得疏松;在0.1mol/L的硫酸催化下,经混合溶剂处理所得样品的综纤维素含量达到86.59%(其中纤维素含量为83.09%),酸不溶木质素含量为3.70%;相同条件下,以0.1mol/L氢氧化钠为催化剂,所得样品中酸不溶木质素含量为4.21%。研究还发现,混合溶剂可高效回收并循环使用。基于实验结果和结论分析,对催化剂可能的作用机理解释为:在适当浓度的酸或碱作用下,木质素的重聚合被有效抑制,从而促进了其在混合溶剂中溶解,并使其从秸秆组织中分离。     

Optimization of Amorphous Silica Nanoparticles Synthesis from Rice Straw Ash Using Design of Experiments Technique

In this study, a chemical method of dissolution-precipitation was applied to produce amorphous silica nanoparticles from rice straw ash (RSA; the waste material of rice cultivation. The morphology, particle size, structure, and area of specific surface of synthesized amorphous silica nanoparticles were evaluated using transmission electron microscopy (TEM), x-ray diffraction analysis (XRD), and BET method to measure the specific surface area of materials. In addition, chemical composition of RSA used and the synthesized silica nanoparticles was studied by x-ray fluorescence (XRF) spectroscopy. The atomic concentration of synthesized silica was determined by x-ray photoelectron spectroscopy (XPS). The effects of sodium hydroxide concentration, precipitation reaction temperature, and precipitation reaction duration on the area of specific surface were determined through design of experiments (DOE) technique. Results depicted that silica nanoparticles with particle size of 10–15 nm were successfully synthesized. Average area of specific surface and purity were 327 m2/gr and 99.5%, respectively. The interactive influence of temperature and duration had the highest effect on the average area of specific surface.     

Characterization of Cr(VI) removal from aqueous solutions by a surplus agricultural waste--rice straw

The removal of Cr(VI) from aqueous solution by rice straw, a surplus agricultural byproduct was investigated. The optimal pH was 2.0 and Cr(VI) removal rate increased with decreased Cr(VI) concentration and with increased temperature. Decrease in straw particle size led to an increase in Cr(VI) removal. Equilibrium was achieved in about 48 h under standard conditions, and Cr(III), which appeared in the solution and remained stable thereafter, indicating that both reduction and adsorption played a part in the Cr(VI) removal. The increase of the solution pH suggested that protons were needed for the Cr(VI) removal. A relatively high level of NO(3)(-) notably restrained the reduction of Cr(VI) to Cr(III), while high level of SO(4)(2-) supported it. The promotion of the tartaric acid modified rice straw (TARS) and the slight inhibition of the esterified rice straw (ERS) on Cr(VI) removal indicated that carboxyl groups present on the biomass played an important role in chromium remediation even though were not fully responsible for it. Isotherm tests showed that equilibrium sorption data were better represented by Langmuir model and the sorption capacity of rice straw was found to be 3.15 mg/g.     

Novel lignocellulosic hybrid particleboard composites made from rice straws and coir fibers

Novel lignocellulosic hybrid particleboard composites with low cost and high performance using the mixture of rice straws and coir fibers were developed in this work. NaOH (sodium hydroxide) aqueous solution was used to remove the wax and silica layer of rice straw surface. The effects of rice straws/coir fibers (R/C) mass ratios on the physical (thickness swelling) and mechanical (modulus of rupture, modulus of elasticity and internal bond strength) properties of particleboard composites were investigated. The results show that NaOH treatment was an effective method for improving wettability of rice straw surface with smaller contact angles and larger diffusivity–permeability constant. The SEM (scanning electron microscope) observation also gave some evidences such as more rough surface and less number of silica cells after NaOH treatment for improving wettability of rice straw surface. The coir fibers content had a significant negative linear effect on the bending properties and thickness swelling, but a significant positive linear effect on the internal bonding strength due to the lower wax and holocellulose content of coir fiber. When no diisocyanate resin applied, the particleboard composites made with only phenol formaldehyde resin at the optimal R/C ratio satisfied the requirements for load-bearing boards used in dry conditions based on Chinese Standard, indicated that the mixture of rice straws and coir fibers to make high quality particleboard composites was a cost-effective and environment friendly approach.     

Artificial neural network (ANN) modeling of dynamic adsorption of crystal violet from aqueous solution using citric-acid-modified rice (Oryza sativa) straw as adsorbent

Rice straw, an abundant, lignocellulosic agricultural residue worldwide, was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The morphological and chemical characteristics of rice straw and acid-modified rice straw were investigated by scanning electron microscopy, surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared spectroscopy. The modification process leads to the increase in the specific surface area and pore size of rice straw. In order to investigate the application potential of the prepared adsorbent to remove a cationic dye (Crystal violet) from its aqueous solution, a continuous adsorption study was carried out in a laboratory scale fixed-bed column packed with acid-modified rice straw. Effect of different flow rates and bed heights on the column breakthrough performance was investigated. Results show that with increasing bed height and decreasing flow rate, the breakthrough time was delayed. In order to determine the most suitable model for describing the adsorption kinetics of Crystal violet in the fixed-bed column system, the Bed Depth Service Time model as well as the Thomas model was fitted to the experimental data. An artificial neural network (ANN) based model for determining the dye concentration in the column effluent was also developed. An extensive error analysis was carried out between experimental data and data predicted by the models using the following error functions: correlation coefficient (R ²), average relative error (ARE), sum of the absolute error (SAE), and χ² statistic test. Based on the values of the error functions, the ANN model was most appropriate for describing the dynamic dye adsorption process.     

Composition and structure of amorphous silica produced from rice husk and straw

We have studied amorphous silica samples prepared by a thermal method and precipitation from rice processing waste: straw and grain shells (husk and peelings). We have determined their true and bulk densities, silica content, and sorbed water vapor content. The porosity of the samples has been evaluated by different techniques: nitrogen desorption (Barrett-Joyner-Halenda method) and adsorption (BET analysis), water vapor adsorption, sorption of organic dyes (methylene blue and brilliant green), and positron annihilation spectroscopy. The effect of the nature of raw materials and processing procedure on the physicochemical properties of amorphous silica is examined.