纳米SnO2的制备条件及其光催化活性

纳米粒子;光催化降解;纳米SnO2的制备条件及其光催化活性     

壳聚糖的γ射线辐射降解研究

动力学;无规降解;断链机理;壳聚糖的γ射线辐射降解研究     

Fe~(3 )/TiO_2/SiO_2复合纳米微粒的合成及光催化降解NO_2~-

采用溶胶 -凝胶法制备了 Ti O2 / Si O2 和不同浓度 Fe3 掺杂的 Fe3 / Ti O2 / Si O2 复合纳米粉末 ,并利用XRD、BET、UV-vis等手段研究了 Ti O2 / Si O2 及掺铁形成的 Fe3 / Ti O2 / Si O2 复合微粒的表面结构形态变化 ,以及对污染物 NO- 2 光催化降解的影响 .结果表明 ,Fe3 / Ti O2 / Si O2 (ω( Fe3 ) =1 .5 % ,m( Ti)∶ m( Si) =2∶ 1 )具有最佳活性 ,样品呈晶化度较低的锐钛矿结构 .Fe3 掺杂导致晶粒的增大 ,稳定性降低 ,大大提高了半导体的光催化活性 ,有利于对低浓度 NO- 2 的光催化降解     

TiO_2制备方法对光催化分解十二烷基苯磺酸钠的影响

本文以TiCl4 为前体 ,采用沉淀法、气相沉积法和溶胶 凝胶法分别制备了TiO2 光催化剂 ,比较了它们在十二烷基苯磺酸钠 (SDBS)光解反应中的催化活性。结果表明 ,以日光灯作光源时 ,气相沉积法获得的催化剂效果最好 ;以 5 0 0W紫外线高压汞灯作光源时 ,沉淀法获得的催化剂活性最高 ,10 0ml初始化学需氧量 (COD)为381mg/L的SDBS溶液 ,在 0 .1g催化剂作用下 ,室温光照 8h ,COD去除率可达 98 8%。在沉淀法制备的催化剂上 ,SDBS溶液的催化光解为一级反应     

聚氧化乙烯/苯乙烯-马来酸钠共聚物共混体系性能研究

用热分析（DSC、TG）和FTIR对聚氧化乙烯（PEO）/苯乙烯-马来酸钠（St-alt-MANa,简称SMANa)共聚物共混体系的相容性、分子间作用、热失重等性质进行了研究。结果表明,共混物可以任意比互溶,它们之间的相互作用是PEO的醚键“-O-”和共聚物盐中的“-COOH”之间形成了氢键。TG分析结果表明,随温度的升高,首先形成了酸酐,这可由FTIR光谱确定。热降解产如CO2作为酸酐和共聚物中羧基的降解产物。与不饱和结构相关的谱带（1774cm^-1、1449cm^-1)在350℃和450℃的红外光谱中可观察到,这可能是主要的碳-碳链断裂的结果。共混体系的Tg随SMANa含量的增加而增加,而体系结果温度Tc、熔融温度Tm却略有下降,这说明两组分间具有良好的溶混性。     

Flash pyrolysis of polystyrene wastes in a free-fall reactor under vacuum

Plastic waste minimization and recycling are important for both economical and environmental reasons. In this flash pyrolysis study, polystyrene wastes were degraded in a free-fall reactor under vacuum to regain the monomer. A set of experiments varied the temperature between 700 and 875°C and determined its effects on the phase yields, the benzene, styrene, toluene, and naphthalene distribution of the liquid output and C1–C4 content of the gaseous output. The liquid yield maximized around 750°C and the styrene yield at 825°C. In general, operating at higher temperatures lessened the solid residue and increased the gaseous yield and total conversion. Employing waste particles in four size ranges, a second set of runs indicated that the finer the waste particles fed the higher the gaseous yield and total conversion. This recycling method can be made more promising if the feed particles are allowed more time for degradation and the removal of the primary products speeded up thereby preventing their decomposition. Ways are suggested to obviate these residence time problems.     

TiO2光催化降解4-氯苯酚过程中的电分析监测

采用循环伏安法和紫外光谱法对有机物的光催化降解进行机理研究和在线监测.以标准光催化剂DegussaP25在紫外光照射下催化降解4-氯苯酚,发现在降解过程中至少有两对氧化还原中间产物对苯二酚-苯醌和羟基氢醌-羟基苯醌.由4-氯苯酚及中间产物的电极响应,可以观测到它们在光催化降解过程中的含量变化,从而对整个过程实现在线监测,并由此全面了解光催化反应机理.从不同反应时间后测得的紫外光谱可以看到,苯环特征峰逐渐消失.这表明4-氯苯酚的苯环逐渐被打开,直至被彻底降解.     

Production of oxychemicals from precipitated hardwood lignin

Lignin is a major byproduct in the biomass-to-ethanol process. The lignin produced from acid treatment of biomass has characteristics suitable for further conversion to organic chemicals. It is free of contaminants and has a relatively low molecular weight. In this study, catalytic oxidative conversion of the acid-soluble lignin precipitated from acid hydrolysates of hardwood was investigated. The process is based on aqueous alkaline oxidation of lignin with dissolved O₂ in the presence of Fe³⁺ and Cu²⁺ catalysts at moderate reaction temperatures (160–180°C). Aromatic aldehydes, ketones, and organic acids are found to be the primary products identifiable on extraction with ether. The combined weight yield of the total ether extractable products is about 20–25% of the initial lignin. The yield of the aldehydes (vanillin + syringaldehyde) is in the vicinity of 15% with an additional 3 to 4% of aromatic ketones. The yields of aldehydes plus ketones observed in this work far exceeded those obtainable from the conventional alkaline air oxidation of spent sulfite liquors. This article also provides comprehensive batch reaction data on conversion and product distribution.     

Study on the Thermal Behaviour and Flammability of the Modified Polyacrylonitrile Fibers

The effects of some kinds of metal ions used as chemical modifications on the thermal properties of the modified polyacrylonitrile (PAN) fibers were studied by DTA, TG, GC and cone calorimetry. The apparent activation energies for the decomposition of the unmodified and modified PAN fibers were determined using Kissinger equation and Broido equation. This revised version was published online in August 2006 with corrections to the Cover Date.     

基于韧性耗散模型的损伤定量分析方法

材料的静力韧性便于工程测量,对疲劳损伤较其它宏观损伤变量更敏感。本文以材料静力韧性为宏观损伤变量,依据疲劳过程中金属材料韧性随疲劳循环加载而变化的实验结果的规律分析,得到了应力和循环数表达的损伤演化方程和损伤累积模型。该模型能较好地反映加载顺序的影响。推导出该疲劳损伤累积模型在多级加载下的递推公式。经四种金属材料疲劳试验数据验证结果表明,该模型预测疲劳寿命是较为满意的。由于疲劳试验数据分散性大,结果有待进一步验证。