Enzymic Hydrolysis Of Lignin—Carbohydrate Complexes Isolated From Kraft Pulp

Four carbohydrate samples extracted from kraft pulps are used as model substrates for studying the mechanism by which xylanase enhances subsequent bleaching of kraft pulp. Fourier transform infrared spectroscopy confirms that small amounts of aromatic molecules, probably lignin, remain associated with these carbohydrate samples. When the extracts are hydrolyzed with xylanase or acid, size exclusion chromatography shows a decrease in the molecular mass of their UV-absorbing constituents, as well as their carbohydrate constituents as determined by pulsed amperometric detection. The results are consistent with the hypothesis that xylanase prebleaching hydrolyzes the xylan portion of lignin-carbohydrate complexes to leave smaller lignin-containing macromolecules in pulp fiber, thus facilitating the removal of lignin components by bleaching chemicals.     

谐势阱中玻色气体的有限尺度和相互作用的叠加效应

基于半经典近似(kB T>>hω),提出了考虑有限尺度和相互作用叠加效应条件下新的态密度解析表达式.在各项异性势阱中,基于新的态密度公式,计算了玻色-爱因斯坦凝聚临界温度、凝聚比率、原子平均能等热力学量.计算表明:所得的理论值与实验测量数据相吻合,也与其他理论计算结果相一致.     

Airside fin efficiencies for finned-tube heat exchangers with forced convection

The heat transfer and mass transfer fin efficiencies were analyzed numerically to show that popular models for heat transfer fin efficiency for circular fins are not always reasonable.The numerical results show that the effective heat transfer area of a circular fin increases several times faster than that of a straight fin for the same tube radius.Then,a simple but accurate heat transfer fin efficiency model was developed and verified by numerical results for a wide range of fin designs.This model predicts...     

Simulation of thermophysical flow in axisymmetric nozzle with expansion chamber

Axisymmetric nozzle flows with a free‐jet expansion are simulated considering several substances and several flow conditions, and the thermophysical properties in the nozzle and the free‐jet region are predicted. The present numerical method is based on the preconditioning method developed by Yamamoto and the mathematical models of thermophysical properties of the substances. As numerical examples show, gas flows of carbon dioxide, water, and nitrogen under a subcritical pressure condition are first calculated. Calculated distances to the Mach disk are compared with the experimental results, and also the density distributions are compared among these three substances. Second, carbon dioxide flows while changing the pressure from subcritical to supercritical values are calculated and the effect of pressure on the flow field is investigated. Third, flows of water vapor with and without nonequilibrium condensation are calculated and the effect of condensation on the flow field is investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

不饱和聚酯树脂生产中"三废"治理探讨

分析了不饱和聚酯树脂生产过程中废水、废气和废渣的产生及治理措施、治理效果,并尝试提出改进措施。     

SO42-TiO2/Al2O3固体超强酸催化合成呋喃酚中间体

通过直接浸渍焙烧法等过程，制备了SO4^2--TiO2／Al2O3新型固体超强酸催化剂，用Hammett指示剂法测定了其酸强度；以邻苯二酚和异丁醛为原料合成了呋喃酚中间体2-异丙基-1,3-苯并二氧五环；考察了催化剂的活化温度、TiO2的担载量、催化剂用量、原料配比和带水剂等因素对反应的影响。结果表明，在425℃～575℃温度范围内焙烧的SO4^2--TiO2／Al2O3样品可以形成固体超强酸体系，且在邻苯二酚与异丁醛的缩合反应中具有较高的催化活性、化学稳定性好、无环境污染。在最佳反应条件下，产品收率可达91.5％。     

腰果树脂漆的制备

采用工业腰果壳液(CNSL)和甲醛缩聚反应合成具有良好性价比的腰果酚甲醛树脂，并以此配制了腰果树脂漆。着重讨论CNSL和甲醛的摩尔比及反应保温时间对树脂性能的影响，同时提供了各种腰果漆的配方及其性能指标。     

表面活性剂对肉桂醛和巴比妥酸缩合反应的影响

研究了以环境友好介质 -水溶液为溶剂 ,不同种类的表面活性剂对肉桂醛和巴比妥酸缩合反应的催化作用以及表面活性剂的浓度和反应温度对缩合反应的影响。实验结果表明 :肉桂醛和巴比妥酸在水溶液中用阳离子长碳链的表面活性剂十六烷基三甲基溴化铵为催化剂 ,催化剂的浓度为其临界胶束浓度十八倍时 ,缩合反应的得率最高。产物的结构用 mp,IR,1H NMR验证     

一类含查尔酮结构的光敏性二胺的合成研究

以醛、酮为原料经羟醛缩合反应合成了具有一类含查尔酮结构的光敏性二胺:1-(3-氨基苯基)-3-(4-氨基苯基)-2-丙烯-1-酮与对-二(间氨基肉桂酰)苯.通过优化实验得到最佳的合成工艺为:醛、酮在温度为0℃下,以乙醇为溶剂,氢氧化钠为催化剂,进行羟醛缩合反应3h.收率可达到86%,经液相色谱分析其纯度分别为99.92%,99.91%,紫外可见最大吸收波长分别为349nm、361nm.所得方法操作简便,收率较高,原料易得.并用元素分析、核磁共振、红外光谱等手段对产物的结构进行了表征.     

聚乳酸的直接合成研究(Ⅱ)

研究了以乳酸单体为原料的直接熔融缩聚的工艺条件,包括工艺路线、原料含水率、催化剂种类、温度及余压对合成的影响。结果表明:采用适当的工艺能通过熔融缩聚法制备出高分子质量的聚乳酸,且具有良好的生物降解性能。