Effect of addition of Zn on the catalytic activity of a Co/HZSM-5 catalyst for the SCR of NOx with CH4

The selective catalytic reduction (SCR) of NOx by methane in the presence of excess oxygen was studied on a Zn-Co/HZSM-5 catalyst. It was found that the addition of Zn could improve effectively the selectivity of methane towards NOx reduction. When prepared by a coimpregnation method, the Zn-Co/HZSM-5 catalyst showed much higher catalytic activity than the two catalysts of a Zn/Co/HZSM-5 and Co/Zn/HZSM-5 prepared by the successive impregnation method. It is considered that there exists a cooperative effect among the Zn, Co and zeolite, which enhances the reduction of NO to NO2 reaction and the activation of methane. (C) 2002 Elsevier Science B.V. All rights reserved.

干旱胁迫对蒙古柞表观资源利用率的影响

比较研究了模拟干旱及自然水分梯度条件下蒙古柞树种光合生理指标 ,模拟干旱处理试验土壤含水量分别控制在田间持水量的 85 %～ 10 0 % (CK)、6 5 %～ 85 % (MW )和 4 5 %～ 6 5 % (LW ) .结果表明 ,干旱胁迫对蒙古柞幼树净光合速率、气孔导度、蒸腾速率、水分利用率、表观CO2 利用率和表观光能利用率等生理指标均产生明显影响 .野外自然条件下水分梯度对蒙古柞大树气孔导度、水分利用率和净光合速率有显著影响 ,但对蒸腾速率、表观CO2 利用率和表观光能利用率的影响不显著 ,中等水分条件可明显提高蒙古柞大树叶片的气体交换和水分利用率 ,说明蒙古柞树种叶片气体交换和表观资源利用率对干旱胁迫的响应程度不同 .蒙古柞树种是干旱可变植物 ,长期水分胁迫可提高树种的耐旱能力 ,特别是中等水分胁迫能保持蒙古柞固有的强劲耐旱能力

Influence of iron promoter on catalytic properties of Rh-Mn-Li/SiO2 for CO hydrogenation

The effect of iron promoter on the catalytic properties of Rh-Mn-Li/SiO2 catalyst in the synthesis Of C-2 oxygenates from syngas was investigated by means of the following techniques: CO hydrogenation reaction, temperature-programmed reduction (TPR), temperature-programmed desorption and reaction of adsorbed CO (CO-TPD and TPSR) and pulse adsorption of CO. The results showed that the addition of iron promoter could improve the activity of the catalysts. Unexpectedly, the yield of C-2 oxygenates increased greatly from 331.6 up to 457.5 g/(kg h) when 0.05% Fe was added into Rh-Mn-Li/SiO2 catalyst, while no change in the selectivity to C-2 oxygenates was observed. However, the activity and selectivity Of C-2 oxygenates were greatly decreased if the Fe amount exceeded 1.0%. The existence of a little iron decreased the reducibility of Rh precursor, while the reduction of Fe component itself became easier. CO uptake decreased with increasing the quantity of Fe addition. This phenomenon was further confirmed by CO-TPD results. The CO-TPD and TPSR results showed that only the strongly adsorbed CO could be hydrogenated, while the weakly adsorbed CO was desorbed. We propose that Fe is highly dispersed and in close contact with Rh and Mn; such arrangements were responsible for the high yield Of C-2 oxygenates. (C) 2002 Elsevier Science B.V. All rights reserved.

Combination of CH4 oxidative coupling reaction with C2H6 oxidative dehydrogenation by CO2 to C2H4

A new process has been suggested for converting natural gas to ethylene by combining oxidative coupling of methane with ethane dehydrogenation to provide an efficient method for the utilization of thermicity and CO2. From their thermodynamics, it is clear that the exothermicity from CH4 oxidative coupling reaction (DeltaH(800degreesC) = -174.3 kJ mol(-1)) can support C2H6 dehydrogenation by CO2 (DeltaH(800degreesC) = + 180.2 kJ mol(-1)). Meanwhile, the two reactions can be conducted under the same reaction conditions, such as the reaction temperature and reaction pressure as well as space velocity. In addition, the CO2 yielded from CH4 oxidative coupling reaction can be directly used for C2H6 dehydrogenation. Two kinds of catalyst are developed for this combined process with an achievement, from which C2H4 content in tail gas can reach attractively 16.4%, which can be used directly to produce ethylbenzene by the alkylation of benzene. (C) 2002 Elsevier Science Ltd. All rights reserved.

Direct decomposition of NO by microwave heating over Fe/NaZSM-5

Catalytic decomposition of NO was studied over Fe/NaZSM-5 catalyst. Novel results were observed with the microwave heating mode. The conversion of NO to N-2 increased remarkably with the increasing of Fe loading. The effects of a series of reaction parameters, including reaction temperature, O-2 concentration, NO concentration, gas flow rate and H2O addition, on the productivity of N-2 have been investigated. It is shown that the catalyst exhibited good endurance to excess O-2 in the microwave heating mode. Under all reaction conditions, NO converted predominantly to N-2. The highest conversion of NO to N-2 was up to 70%. (C) 2002 Elsevier Science B.V. All rights reserved.

模拟水分胁迫对水曲柳光合速率及水分利用效率的影响

经过 3年人工模拟水分胁迫 ,研究了不同水分处理下水曲柳光合特征及其水分利用效率的变化 .结果表明 ,在中度水分胁迫 (MW )下 ,水曲柳的光合速率和水分利用效率比对照组均有所提高 ,而在重度水分胁迫 (LW )下则分别降低了 7 2 6 %和 1 1 3% .长期的中度水分胁迫使水曲柳的光合潜力得到充分发挥 ,其适应性也好于重度水分胁迫 .对照组水曲柳的光合速率日变化呈单峰曲线 ,MW组和LW组则均呈“双峰”曲线 ;对照组水曲柳水分利用率的日变化呈现双峰曲线 ,而MW组和LW组则呈现波动趋势 ,无明显的波峰和波谷 .这与水曲柳在不同水分处理下的生理特性和环境因子的日进程密切相关 .

千烟洲人工林主要树种地上生物量的估算

利用不同参数和函数,模拟了千烟洲人工林主要树种马尾松、湿地松和杉木的枝条、叶生物量和总生物量及单株各器官生物量,选择最佳函数计算生物量在各树种不同器官中的分配,估算不同林型的地上生物量.结果表明,不同树种的枝条基径(d)和枝条生物量(BW)、叶生物量(LW)之间,当d3为自变量时,相关系数最高,湿地松利用线性函数、马尾松和杉木利用幂函数模拟效果最佳;单木总生物量以利用D2H(胸径2×树高)为自变量的幂函数模拟相关系数最高;3个树种叶和枝生物量各有不同的最佳自变量和函数类型,但同一树种的叶、枝生物量最佳拟合方程的自变量和函数类型一致.马尾松林、湿地松林和杉木林的地上生物量分别为83·6、72·1和59t·hm-2,其中树干生物量所占比重最大,叶生物量最小.根据前人的研究结果推算3种林分地下生物量分别为10·44、9·42和11·48t·hm-2,其固碳量分别为47·94、45·14和37·52t·hm-2.

水分胁迫对长白山阔叶红松林主要树种生长及生物量分配的影响

以长白山阔叶红松林主要树种红松、水曲柳、胡桃楸和椴树为研究对象 ,设置 3个水分处理 ,土壤含水量分别为田间持水量的 85 %～ 10 0 % (对照 )、6 5 %～ 85 % (MW )、4 5 %～ 6 5 %(LW )。对不同树种在不同处理下的生长进行测定 ,结果表明 :土壤水分含量对供试树种的单叶面积、单叶干重、叶片数量、茎干重、根长等生长指标均有显著影响。但各个树种对土壤水分胁迫的响应存在明显差异。在中度水分胁迫下 ,红松和水曲柳在总生物量降低的同时增加了地下生物量的比例 ,地下生物量 /地上生物量值比对照组分别提高了 79 31%和 2 3 91%。而胡桃楸和椴树的地下生物量 /地上生物量分别比对照组降低了 4 2 32 %和 7 92 %。在重度水分胁迫条件下 ,供试树种中只有红松的的地下生物量 /地上生物量比对照组提高了 2 7 5 % ,水曲柳、胡桃楸和椴树均呈下降趋势。由此可见 ,在供试树种中 ,红松对土壤水分胁迫的适应性最强 ,水曲柳仅对中度水分胁迫具有一定的适应性 ,而胡桃楸和椴树均不适宜在干旱的环境中生长。

土壤水分状况对长白山阔叶红松林主要树种叶片生理生态特性的影响

Potted seadlings of Pinus koraiensis , Fraxinus mandshurica,Juglans mandshurica,Tilia amurensis, and Quercus mongolica ,which are five dominant species in the Korean pine broadleaf forest at Changbai mountain,were grown in different soil moistures.We designed three soil moisture scenarios:85%～100%(high water,CK),65%～85% (medium water,MW) and 45%～65% (low water,LW) of field water holding capacity.The results show that characteristics of typical drought resistance on the leaves are significantly developed.The net photosynthetic rate and water use efficiency of F. mandshurica were higher compared with CK at MW.The net photosynthetic rate and water use efficiency of other 4 tree species at CK were lower than those at MW and LW.The transpiration rate of 5 tree species responses differently to various soil water status.

Direct electrochemistry of horseradish peroxidase immobilized in calcium carbonate microsphere doped with phospholipids

Protein electrochemistry affords a direct method to study the biological electron transfer processes. However, supplying a biocompatible environment to maintain the native state of protein is all-important and challengeable. Here, we chose vaterite, one of the crystalline polymorphs of calcium carbonate, with highly porous nature and large specific surface area, which was doped with phospholipids, as the matrix to immobilize horseradish peroxidase (HRP). The integrity of HRP was kept during the simple immobilization procedure. By virtue of this organic/inorganic complex matrix, the direct electrochemistry of HRP was realized, and the activity of HRP for catalyzing reduction of O-2 and H2O2 was preserved.

Direct Electrochemistry and Electrocatalysis of Hemoglobin in Lipid Film Incorporated with Room-Temperature Ionic Liquid

A facile phospholipid/room-temperature ionic liquid (RTIL) composite material based on dimyristoylphosphatidylcholine (DMPC) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) was exploited as a new matrix for immobilizing protein. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were adopted to characterize this composite film. Hemoglobin (Hb) was chosen as a model protein to investigate the composite system. UV-vis absorbance spectra showed that Hb still maintained its heme crevice integrity in this composite film.

The effect of template phase on the structures of As-synthesized silica nanoparticles with fragile didodecyldimethylammonium bromide vesicles as templates

The effect of template phase on the structures of as-synthesized silica nanoparticles with fragile DDAB vesicles as templates is reported. It is found that the template phase plays a critical role in the growth process of silica: the unstable DDAB vesicles in liquid-crystalline phase often lead to the formation of mesostructured solid spheres, and the rather stable DDAB vesicles in gel phase lead to the formation of hollow spheres with less mesostructures.

Biosynthesis of gold nanoparticles assisted by Escherichia coli DH5 alpha and its application on direct electrochemistry of hemoglobin

In this communication, biosynthesis of gold nanoparticles assisted by Escherichia coli DH5 alpha and its application on direct electrochemistry of hemoglobin are reported. The gold nanoparticles formed on the bacteria surface are mostly spherical. The direct electrochemistry of hemoglobin can be achieved by incorporated into the bio-nanocomposite films on a glassy carbon electrode.