A Critical Role for the Presence of Lignocellulosic Material in the Determination of Wood Buffering Capacity

The currently used determinations of wood buffering capacity, which are based on pH-metric titrations of aqueous wood extracts, neglect the effect of lignocellulosic material and the role of its insoluble constituents. This study examined the influence of the presence of wood in a system subjected to titration. A comparison of the results obtained from pine chip extracts and chip suspensions showed that the presence of wood and the wood-to-water ratio were critical factors that affected the measurement of the wood buffering capacity. The evidence showed that the resulting determination may vary by up to six times (0.28–1.99 ml/g), depending upon the conditions of the titration. In addition, it was found that the presence of wood had a neutralizing effect over the course of prolonged pH observations.     

Experimental quantification and modelling of reaction zones in a cyclic watergas shift reactor

The cyclic watergas shift reactor (CWGSR) is a cyclically operated fixed bed reactor for the production of hydrogen. It is based on the alternating reduction of an iron oxide fixed bed with synthesis gas and its subsequent oxidation with steam. We show experimental data of moving reaction zones in a tubular CWGSR. Based on this data and to help further design of these reactors, we propose a dynamic, one-dimensional model of the reactor. The formulated process model was fitted to experimental data by adjusting only two parameters describing the catalytic activity and the oxygen capacity of the fixed bed. Exemplary simulation results are shown.     

Chain Dechlorination of Organic Chlorinated Compounds in Alcohol Solutions by 60Co γ-Rays, (III)

Chlorinated benzenes dissolved in deoxygenated alkaline 2-propanol were dechlorinated by irradiating with ⁶⁰Co γ-rays to produce the lower chlorinated benzenes and chloride ion. The yield of dechlorination was found to depend on the number of chlorine atoms on the benzene ring, the G (CI^?)-values being, for instance, 6,500, 480 and 2.0 for 0.07 M penta-chlorobenzene, 1, 2, 4-trichlorobenzene, and monochlorobenzene, respectively, in 0.2 M KOH-2-propanol solution. In contrast, the values of G(C1^?) differed little between the isomers of trichlorobenzene. The large difference in G (CI^?) according to the number of chlorine atoms can be explained by considering the redox potential of the chlorinated benzenes and the ketyl radical ion.

Trichlorobenzene is dechlorinated to dichlorobenzene and then to monochlorobenzene while producing potassium chloride and acetone, and consuming hydroxide ion. In the experiment, some chlorinated benzene derivatives were observed to be generated in the course of this process—probably dichlorophenyl-2-propanol and monochlorophenyl-2-propanol, judging from observation by gaschromatograph-mass spectrometer and from the path-way of formation. The observation also indicated the presence of dichlorophenyl-2-propanol in predominant amounts in 1, 3, 5-trichlorobenzene solution, but only in a small fraction in 1, 2, 3-trichlorobenzene.     

重铬酸盐法测定水质化学需氧量

在水样中加入已知量的重铬酸钾溶液,并在强酸介质下,经沸腾回流后,以试亚铁灵为指示剂,用硫酸亚铁铵滴定水样中未被还原的重铬酸钾,由消耗的硫酸亚铁铵的量换算成消耗氧的质量浓度。     

Rapid and direct determination of fructose in food: A new osmium-polymer mediated biosensor

This paper describes the development and performance of a new rapid amperometric biosensor for fructose monitoring in food analysis. The biosensor is based on the activity of fructose dehydrogenase (FDH) immobilised into a carbon nanotube paste electrode according to two different procedures. The direct wiring of the FDH in a highly original osmium-polymer hydrogel was found to offer a better enzyme entrapment compared to the immobilisation of the enzyme in an albumin hydrogel. The optimised biosensor required only 5 U of FDH and kept the 80% of its initial sensitivity after 4 months. During this time, the biosensor showed a detection limit for fructose of 1 μM, a large linear range between 0.1 and 5 mM, a high sensitivity (1.95 μA cm⁻² mM), good reproducibility (RSD = 2.1%) and a fast response time (4 s).     

Electro‐induced polymerization of acrylamide initiated by the potassium permanganate–titriplex VI redox system

The polymerization of acrylamide (AAm) was carried out with a potassium permanganate–Titriplex VI redox initiator system with and without electrolysis. Because of the high metal‐ion concentration in general, low‐molecular‐weight polymers were obtained (weight‐average molecular weight = 2600–4000). The effect of potassium permanganate and AAm concentrations and temperature on the polymerization yield was studied and compared with results obtained under the same experimental conditions used for electrolysis. The results of Fourier transform infrared spectroscopy, atomic absorption spectrometry, and scanning electron microscopy (SEM) results are given. SEM micrographs of the polymer obtained by electrochemical methods exhibited smoother surfaces than those obtained by nonelectrolytic methods. In the absence of potassium permanganate, there was no polymerization under experimental conditions. A possible reaction mechanism is suggested. The electro‐induced system resulted in about a 50% increase in the yield. Manganese content in the electro‐induced and chemical polymerization systems were 2.7 and 8.2%, respectively, supporting the yield increase in the electro‐induced system. A graphite electrode was used and resulted in a high yield and a fibrous polymeric structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1526–1534, 2001     

Redox behavior of indium in molten chlorides

An electrochemical study on the redox behavior of indium in the eutectic LiCl-KCl system at 450 °C was carried out with the transient techniques of cyclic voltammetry and chronopotentiometry on an inert molybdenum electrode. The reduction of In(III) was found to be a two-step process involving In(III)/In(I) and In(I)/In couples at the potentials of about ?0.4 and ?0.8 V versus Ag/AgCl, respectively. The redox mechanism was further confirmed by the theoretical evaluation of the number of transferred electrons based on cyclic voltammetry and characterizations of the precipitates generated by the potentiostatic electrolysis. The diffusion coefficients of indium ions in the eutectic LiCl-KCl melt at 450 °C were estimated by cyclic voltammetry and chronopotentiometry. The results obtained through the two methods are in fair agreement, delivering an average diffusion coefficient of approximately 1.8×10^?5 cm²/s for In(III), and 1.4×10^?4 cm²/s for In(I).     

Fe_2O_3含量对MnZn铁氧体中Fe~(2+)量、磁性能及导电机制的影响

通过测量MnZn铁氧体的磁性能及Fe2+、Mn3+含量,考察了MnZn铁氧体中的Fe2+含量与配方中Fe2O3、MnO含量的关系及其对MnZn铁氧体磁性能的影响,并探究了MnZn铁氧体的导电机制。结果表明:随着(Fe2O3)a(MnO)b(ZnO)c主组成配方中a值递增(52.55≤a≤53.35)、b值递减(38.33≥b≥37.52),呈现出Fe2+、Mn3+含量均增加的趋势。随着Fe2+含量增加,Pcv谷底温度向低温方向移动,Pcv(min)先减后增,Pcv(20/70/100℃)均先减后增,均在Fe2+含量=1.55%附近达到最小值;起始磁导率μi(20/70/100℃)均先增后减。根据Pcv-Fe2+含量和μi-Fe2+含量两个关系图在Fe2O3=53.15mol%附近出现极值点这一现象,初步推测铁氧体Znα2+Mnβ-x2+Mnx3+Fey2+Feχ-y3+O4+σ(0.1794≥α≥0.1786,0.754≥β≥0.734,0.0031≤x≤0.0040,0.051≤y≤0.070)的导电机制为:y0.064时小极化子间的束缚能主导,y0.064时电子跃迁主导。     

基于恒功率控制的风电场储能系统研究

风力发电输出功率随风速变化波动较大,对电网的安全稳定运行造成了威胁。采用在风电场并网侧增加大容量电池储能系统,对风电场和电池储能系统结合模型进行了分析,并设计了储能系统变流器的恒功率控制系统。最后,利用MATLAB/Simulink软件对所提策略在风电场储能系统中控制的有效性进行了验证。仿真结果表明,储能系统能对风电场有功、无功进行调节,平稳了风电场输出功率,同时能根据控制输出一定无功功率,有助于风电场和电网稳定。