建立绿色化学理念深化化工工艺学教学改革

为保证21世纪我国的可持续发展战略的实施,必须进行绿色化学教育.文章分析了"化工工艺学"课程中开展绿色化学教育的必要性与可行性;介绍了化工工艺学教学中开展绿色化学教育的改革与实践,以及绿色化学教育在培养和提高人才的全面素质与综合能力等方面的积极作用.绿色化学教育既是21世纪化学教育所面临的时代挑战,也是化工教育发展的一大机遇,关系着我国可持续发展战略目标的实现.     

己内酰胺绿色生产技术

中国石化石油化工科学研究院历经20年,成功开发出己内酰胺绿色生产技术,建成3套20万t/a工业生产装置、多套工业装置正在建设中.己内酰胺绿色生产技术包括:钛硅分子筛与浆态床集成用于环己酮氨肟化合成环己酮肟;纯硅分子筛与移动床集成用于环己酮肟气相重排;非晶态合金催化剂与磁稳定床集成用于己内酰胺精制.工业实施后,装置投资下降70%、生产成本下降10%、原子利用率由60%提高到90%以上、三废排放是已有技术路线的1/200、无副产物硫酸铵.己内酰胺绿色生产技术产生了重大的经济效益和社会效益,践行了绿色化学的理念,是绿色化学的成功范例.     

硅纳米线阵列的制备及其光电应用

近年来,硅纳米线阵列在宽波段、宽入射角范围内优异的减反射性能及其在光电领域的巨大应用前景引起了相关研究者的广泛关注。本文综述了国内外硅纳米线阵列的制备及其在光电应用方面的最新研究进展。关于硅纳米线阵列的制备方法,主要从"自下而上"和"自上而下"两大类出发,分别阐述了模板辅助的化学气相沉积法、化学气相沉积结合Langmuir-Blodgett技术法和金属催化化学刻蚀法,其中重点介绍了目前使用最为广泛且操作简单的金属催化化学刻蚀法的步骤、机理及控制参数。关于硅纳米线阵列在光电领域的应用,主要阐述了硅纳米线阵列在光电探测器、常规太阳能电池、光电化学太阳能电池、光催化分解水制氢、光催化降解有机污染物方面的应用。最后,从硅纳米线阵列在实际应用中面临的提高光电转换效率和避免硅纳米线阵列腐蚀以提高器件的稳定性等问题出发,展望了硅纳米线阵列的表面修饰及修饰后的性能研究是未来硅纳米线阵列光电应用研究的主要方向之一。     

大学化学实验教学中构建绿色化学思维的探索与实践

依据绿色化学的基本原理,分析了在大学化学实验教学中构建绿色化学思维的重要性与必要性。结合多年的教学实践,从实验教学理念、教学内容和教学管理三方面,探研了在大学化学实验教学过程中构建绿色化学思维的途径;并从实验教学内容绿色化的角度,重点探讨了如何在大学化学实验教学过程中构建绿色化学思维。     

己内酰胺绿色生产技术

绿色化学的理想是实现反应的＂原子经济＂性,生产环境友好的绿色产品,这就要求原料中的每一个原子进入产品,不产生废物和副产品,并采用无毒无害的原料、催化剂和溶剂。根据绿色化学的理念,中国石化石油化工科学研究院历经20年,开发成功己内酰胺绿色生产技术,建成20万t/a工业生产装置。这项技术包括：单釜连续淤浆床与钛硅分子筛集成...     

硅能与氢氟酸发生化学反应吗?

高级中学课本（甲种本）“化学”第二册及原十年制高中课本"化学"第二册,在阐明硅的化学性质时都说：“硅的化学性质不活泼。在常温下,除氟气、氢氟酸和强碱溶液外,其他物质如氧气、氯气、硫酸和硝酸等都不跟硅起反应……。”其中肯定了硅在常温下能与氢氟酸发生化学反应。     

绿色化学原则在发展*

从源头上减少或消除化学污染是绿色化学的理想,而绿色化学原则是对绿色化学内涵的最好诠释。自Anastas等人在1998年提出12条绿色化学原则以来,Anastas本人和Winterton又从技术、经济和商业等角度出发,分别提出了另12条绿色化学补充原则。但这些原则中缺乏清晰地反映与环境影响高度相关的概念,绿色工程的概念和绿色工程原则由此应运而生。Tang等人随后将Anastas等人提出的绿色化学原则和绿色工程原则简化为“IMPROVEMENTS PRODUCTIVELY”中字母表示的24条原则,以便于记忆、交流和推广。然而,上述原则主要是直觉和常识的结晶,难以清晰地反映绿色化学的目标和相关研究领域的内在联系。预计,从绿色的认定,原子经济性和有效质量收率等的兼顾,生命周期评价数据的采集,催化剂的性质及其反应、分离和循环使用的一体化以及绿色程度评价指标和评价方法的优化与平衡等几方面发展和凝炼绿色化学原则将是长期的研究课题。     

美国Beyond Benign推进高中绿色化学教育的实践与启示

Beyond Benign是美国的一个推进绿色化学教育的非盈利性组织。从什么是绿色化学、工业中的绿色化学和绿色化学替代实验练习3个方面概述了该组织针对高中师生开展的绿色化学教学方案;从先进绿色化学模块素材开发、志愿者推广、暑期实习生研习、网络研讨会或专题论坛、在线课程培训、绿色化学训练营或实地考察等方面探讨了该组织推进高中绿色化学教育的举措;针对国内中学的绿色化学教育,提出了引导民间力量和民间组织参与绿色化学教育、构建较系统的高中绿色化学教学方案、对高中教师进行绿色化学多样化培训以及引导学生在课外活动和第二课堂中开展绿色化学训练等建议。     

消防相关专业化学教学策略研究

针对消防相关专业化学教学中存在的问题,探讨了消防相关专业化学的教学策略,如紧密联系消防实际选择教学内容;采用案例教学模式;通过典型化合物性质及其制备方法,引入化学工艺知识、化学灾害事故评估方法和危险化学品灾害事故控制方法;通过典型火灾事故原因调查展开分析化学知识教学;教学中渗透"绿色化学"和"绿色消防"的理念;将新成果应用于课堂教学等。     

绿色化学理念在高分子化学实验教学中的渗透

绿色化学是促进人类与自然和谐发展的化学,培养绿色化学意识是实现社会可持续发展的基本要求。高分子化学实验是高等院校高分子材料专业或材料化学高分子方向本科生开设的一门必修课,对学生进行绿色化学教育具有非常有利的条件。文章分析了在高分子化学实验课程中开展绿色化学教育的必要性与可行性;介绍了高分子化学实验教学中开展绿色化学教育的具体措施。通过绿色化学理念在高分子化学实验教学中渗透,在提高学生动手能力的同时,又增强了学生的绿色化学意识。     

Efficient production of nanoporous silicon carbide from rice husk at relatively low temperature

Nanoporous silicon carbide with a specific surface area of up to 186.45 m² g⁻¹ has been efficiently synthesized from waste rice husk using a magnesiothermic reduction at 950 °C as a key step. Throughout the entire process, the recovery rates of silicon, potassium and phosphorus from rice husk can reach 88.46, 91.5 and 65.5%, respectively. Turning rice husk waste into a real treasure, this promising method for producing porous SiC protects the environment and brings economic benefits.     

Thermal kinetics and morphological investigation of alkaline treated rice husk biomass

Agro waste bio mass are creating challenges for environment in term of air pollution due to improper disposal. Rice milling is the process in which rice husk is produced as by-product. The agro-waste rice husk has tremendous potential to be used either in its raw form or in ash form. The inherent component of this waste cellulose provides enhanced properties in a reinforced composite when used as filler. Rice husk is the hard outer layer and covering rice seed, which makes reinforcement challenging in its original form. Fiber surface treatment significantly improves adhesion with matrix and various thermo chemical properties of filler as well as of composites. NaOH treatment is cost-effective and it ensures the adhesion with matrix by removal of hemicellulose and lignin. The chemical treatment of agro-waste (rice husk) is performed with 5% alkali solutions of NaOH in water. Results are compared with the properties of untreated rice husk for thermal and morphological characterizations. In the present work, we are trying to quantify the impact of chemical treatment on rice husk thermal decomposition and its kinetics. Thermogravimetric analysis and kinetics study of thermal degradation, provide key input towards pyrolysis pattern of rice husk, while FTIR and SEM analysis provide the prospects of this bio filler using a reinforcing agent to develop green composite and productive disposal. The FTIR data helps to find the possibilities of blending different bio fillers and natural fibers to find suitable reinforcing substances. The average activation energy of treated fiber is noted as 137.95 by KAS method and 108.08 by FWO method as compared to 55.56 by KAS method & 54.26 by FWO method for untreated rice husk.     

Characterization of rice husks and the products of its thermal degradation in air or nitrogen atmosphere

Rice husk is a by-product of rice milling process and are a major waste product of the agricultural industry. They have now become a great source as a raw biomass material for manufacturing value-added silicon composite products, including silicon carbide, silicon nitride, silicon tetrachloride, pure silicon, zeolite, fillers of rubber and plastic composites, adsorbent and support of catalysts. The bulk and true densities of raw rice husk with different moisture and sizes were determined. The rice husk was subjected to pyrolysis in fluidized-bed reactor in air or nitrogen atmosphere. The products obtained were characterized by thermogravimetric and X-ray powder analysis, IR-spectroscopy, scanning electron microscopy and nitrogen adsorption at 77 K. The specific surface area of the products is comparable with this of γ-Al₂O₃. The kinetics of H₂SeO₃ adsorption out of aqueous solutions at 298 K was studied. The adsorption capacity of white rice husks ash was found to be higher than that of black rice husk ash and the adsorption kinetics obeyed the second order kinetic equation.     

Study by X-ray photoelectron spectroscopy of rice husk and the products of its processing

The rice floral glume (husk) and its processing products were studied using X-ray photoelectron spectroscopy. We established that the rice husk contained silica in two non-equivalent forms in 1:3 ratio. The predominating form is silicon dioxide, while the minor component contains the silicon bound with the organic component which is stable up to ∼350°C.     

Effects of active silicon uptake by rice on 29Si fractionation in various plant parts

Rice (Oryza sativa L.) accumulates large amounts of silicon which improves its growth and health due to enhanced resistance to biotic and abiotic stresses. Silicon uptake and loading to xylem in rice are predominantly active processes performed by transporters encoded by the recently identified genes Lsi1 (Si influx transporter gene) and Lsi2 (Si efflux transporter gene). Silicon deposition in rice during translocation to upper plant tissues is known to discriminate against the heavier isotopes ²⁹Si and ³⁰Si, resulting in isotope fractionation within the plant. We analyzed straw and husk samples of rice mutants defective in Lsi1, Lsi2 or both for silicon content and δ²⁹Si using isotope ratio mass spectrometry (IRMS) and compared these results with those for the corresponding wild‐type varieties (WT). The silicon content was higher in husk than in straw. All the mutant rice lines showed clearly lower silicon content than the WT lines (4–23% Si of WT). The δ²⁹Si was lower in straw and husk for the uptake defective mutant (lsi1) than for WT, albeit δ²⁹Si was 0.3‰ higher in husk than in straw in both lines. The effect of defective efflux (lsi2) differed for straw and husk with higher δ²⁹Si in straw, but lower δ²⁹Si in husk while WT showed similar δ²⁹Si in both fractions. These initial results show the potential of Si isotopes to enlighten the influence of active uptake on translocation and deposition processes in the plant. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermogravimetric analysis of composites obtained from sintering of rice husk-scrap tire mixtures

Summary The disposal of used automotive tires has caused many environmental and economical problems to most countries. We propose the use of rice husk as filler for increasing the value of recycled tire rubber. Thermal degradation of both components and their sintering mixtures is presented in this paper. Thermal decomposition of rice husk occurs in various steps in the temperature range between 150 and 550°C. This complex process is the result of the overlapping of thermal decomposition of the three major constituents common in all lignocellulosic materials, i.e., hemicellulose, lignin and cellulose. Hemicellulose is degraded at temperatures between 150 and 350°C, cellulose from 275 to 380°C and lignin from 250 to 550°C. The degradation process of major constituents of scrap tires or their composites is observed at temperatures between 150 and 550°C. For composites, the addition of rice husk (maximum 25%) produces an increase in the mass loss rate. This effect is higher as the amount of rice husk increases. However, the degradation initial temperature of elastomeric matrix is not affected with addition of rice husk. Apparent kinetic parameters were also studied by the isoconversional Friedman method. We observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed.     

Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica

Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials.     

Simplified Synthesis of Biomass-Derived Si/C Composites as Stable Anode Materials for Lithium-Ion Batteries

Synthesis of silicon/carbon (Si/C) composites from biomass resources could enable the effective utilization of agricultural products in the battery industry with economical as well as environmental benefits. Herein, a simplified process was developed to synthesize Si/C from biomass, by using a low-cost agricultural byproduct “rice husk (RH)” as a model. This process includes the calcination of RH for SiO₂/C and the reduction of SiO₂/C by Al in molten salts at a moderate temperature. This process does not need the removal of carbon before thermal reduction of SiO₂, which is thought to be necessary to avoid the formation of SiC at elevated temperatures. Thus, carbon derived from biomass can be directly used for Si/C composites for anode materials. The resultant Si/C shows a high reversible capacity of 1309 mAh g⁻¹ and long cycle life (300 cycles). This research advocates a new and simplified strategy for the synthesis of RH-based biomass-derived Si/C, which is beneficial for low-cost, environmentally friendly, and green energy storage applications.     

Characterization and comparative study of pyrolysis kinetics of the rice husk and the elephant grass

A comparative evaluation of different biomasses allows the choice that presents the best potential as fuel for energy production. The knowledge of the thermal and kinetics parameters of the biomass in the process of thermal conversion is fundamental as their chemical and physical characterization. Various methodologies have been developed for the determination of kinetic parameters as apparent activation energy and reaction order from the thermogravimetric analysis. In this work, the apparent activation energy needed to break the bonds of hemicelluloses and cellulose of rice husk and elephant grass during the thermal conversion was evaluated according to the kinetics models of Flynn and Wall and Model Free Kinetics developed by Vyazovkin. The biomass elephant grass and rice husk were characterized for moisture, ash and volatile matter by ASTM E871, ASTM E1755, ASTM E872, respectively, and fixed carbon by difference. The percentage of carbon, hydrogen, nitrogen, and oxygen were determined by ultimate analysis. The elephant grass showed to be more suitable for production of bio-oil through pyrolysis due to the higher percentage of volatile, less ash content and less energy required to break the bonds of hemicellulose and cellulose than rice husk in the thermal conversion process.     

Enhanced Antioxidant,Hyaluronidase, and Collagenase Inhibitory Activities of Glutinous Rice Husk Extract by Aqueous Enzymatic Extraction

In this research, we aimed to compare the biological activities related to cosmeceutical applications of glutinous rice husk extracted by aqueous enzymatic extraction (AEE) and conventional solvent extraction. Cellulase enzymes were used to assist the extraction process. The vanillic and ferulic acid contents of each extract were investigated by high-performance liquid chromatography, and their antioxidant and anti-aging activities were investigated by spectrophotometric methods. The irritation effects of each extract were investigated by the hen’s egg test on chorioallantoic membrane. The rice husk extract from AEE using 0.5% w/w of cellulase (CE0.5) contained the significantly highest content of vanillic and ferulic acid (p < 0.05), which were responsible for its biological activities. CE0.5 was the most potent antioxidant via radical scavenging activities, and possessed the most potent anti-skin wrinkle effect via collagenase inhibition. Aside from the superior biological activities, the rice husk extracts from AEE were safer than those from solvent extraction, even when 95% v/v ethanol was used. Therefore, AEE is suggested as a green extraction method that can be used instead of the traditional solvent extraction technique given its higher yield and high quality of bioactive compounds. Additionally, CE0.5 is proposed as a potential source of natural antioxidants and anti-aging properties for further development of anti-wrinkle products.