Modulation of Electrochemical Oscillations by Specific Adsorption of Cl- during the Electrooxidation of Methanol on Pt Electrode

Potential oscillation during the electrocatalytic oxidation of methanol can be modulated by the specific adsorption of Cl- on the platinum electrode, which suppresses the electrocatalytic oxidation of methanol, and makes the cross cycle in the cyclic voltammogram become smaller and finally disappear with the increase of Cl- concentration. The method is also applicable to the electrocatalytic oxidation of other small organic molecules.

Chemical oscillation in electrochemical oxidation of methanol on Pt surface

Based on dual path reaction mechanism, a nonlinear dynamics model reflecting the potential oscilla- tion in electrooxidation of methanol on Pt surface was established. The model involves three variables, the electrode potential (e), the surface coverage of carbon monoxide (x), and adsorbed water (y). The chemical reactions and electrode potential were coupled together through the rate constant ki = exp(ai(e ? ei)). The analysis to the established model discloses the following: there are different kinetics be- haviors in different ranges of current densities. The chemical oscillation in methanol electrooxidation is assigned to two aspects, one from poison mediate CO of methanol electrooxidation, which is the in- duced factor of the chemical oscillation, and the other from the oxygen-containing species, such as H2Oa. The formation and disappearance of H2Oa deeply depend on the electrode potential, and directly cause the chemical oscillation. The established model makes clear that the potential oscillation in methanol electrooxidation is the result of the feedback of electrode potential e on the reactions in- volving poison mediates CO and oxygen-containing species H2Oa. The numerical analysis of the estab- lished model successfully explains why the potential oscillation in methanol galvanostatic oxidation on a Pt electrode only happens in a certain range of current densities but not at any current density.

甲醇混合气自燃的压力振荡特性研究

以一台增压中冷压燃式发动机为试验样机,在其第1缸进行甲醇混合气自燃试验,分析甲醇自燃的压力振荡特性,研究超级爆震中破坏性压力波形成的规律。研究结果表明:随着过量空气系数的减小,甲醇自燃的概率有上升的趋势;而在同一过量空气系数下,上止点前着火的循环最高燃烧压力和压力振荡幅度远大于上止点后着火的循环,振荡频率也较高,并且随着着火时刻靠近上止点,最高燃烧压力和压力振荡的幅度与频率均增大;自燃时刻位于上止点前附近时,压力振荡的破坏性最大;甲醇自燃与超级爆震类似,具有间歇性。

甲醇预混合气F-T柴油引燃发动机压力振荡研究

为有效降低预混引燃双燃料发动机的压力振荡,对甲醇预混合气F-T柴油引燃发动机的爆震和粗暴燃烧及循环变动进行研究。试验结果表明:缸压信号的功率谱密度曲线并结合带通滤波方法可以很好地反映爆震和粗暴燃烧的结果;当甲醇占能比为0.62,较大压缩比下,发动机压力波动较小;随甲醇占能比增加或压缩比降低,爆发压力循环变动均会出现先升后降趋势,供油推迟有利于降低爆发压力循环变动。协调甲醇占能比、供油提前角、压缩比,对有效降低预混引燃发动机压力振荡具有重要意义。

振荡天平结合微反研究程序升温条件下SAPO-34催化的甲醇转化

利用结合振荡天平的固定床微反装置,对甲醇转化的气相产物和催化剂相的有机物种沉积进行实时在线监测,由此建立程序升温过程中多相催化甲醇转化完整的碳资源走向图谱.

柴油机燃用乳化甲醇柴油的燃烧和压力振荡特性研究

在4100QBZL柴油机上上对0#柴油、M10和M15分别进行台架试验,对比分析了三种油品的燃烧和压力振荡特性。试验结果表明:随着乳化甲醇柴油中甲醇比例增加,燃烧压力峰值变大,燃烧始点后移,压力升高率峰值逐渐上升,峰值所对应的相位后移;缸内温度升高,燃烧压力振荡幅值升高,衰减进程变慢;压力振荡频率趋于高频段,压力振荡声压级幅值变大,燃烧更加粗暴。

甲醇电氧化过程中恒电流模式下电位振荡分析

研究了甲醇电氧化体系的交流阻抗与循环伏安响应特征,分析了恒电流电位振荡的特点。循环伏安曲线中,在正扫描方向有三个氧化峰和一个肩峰,反扫时出现一个不对称氧化峰,认为在该氧化峰低电位一侧存在一个隐藏的氧化峰。交流阻抗图谱对施加电位十分敏感,随着频率降低,施加电位为0.1V时Nyquist图上阻抗点以顺时针方式出现,在0.12V时则以逆时针方式出现,即,阻抗实部在非零有限频率下可以变成负值。在0.13V下阻抗的特征更加复杂。恒流模式下发现电极电位振荡现象,先后出现单周期、双周期、四周期、五周期和六周期振荡行为。恒电流早期出现的振荡周期在1～10s数量级,而恒电流测试后期的振荡行为周期达到26s,振幅可达到0.15V以上。

武汉建筑用地三种特征土壤吡虫啉回收率试验

采用甲醇振荡提取-高效液相色谱法测定（HPLC），对白蚁防治药剂吡虫啉在武汉建筑用地3种特征土壤中的残留量进行阳性添加和回收率测定试验。结果表明：吡虫啉在各种土壤中回收率和变异系数分别为潮土73．7％～78．8％，2．2％～3．4％，红棕壤67．8％～72．2％，2．8％～4．5％，黄棕壤66．4％～70．1％，2．5％～3．8％。

Temporal and Oscillatory Behavior Observed during Methanol Synthesis on a Cu/ZnO/Al_{<span style="font-family:Verdana;">2</span>}<span style="font-family:Verdana;">O</span>_{<span style="font-family:Verdana;">3</span>}<span style="font-family:Verdana;">(60:30:10) Catalyst

The rate of Methanol synthesis over a Cu/ZnO/Al2O3 (60:30:10) catalyst has been measured using CO2/H2 (10:90) and CO/CO2/H2 (10:10:80) streams at 433, 443, 453, 463 and 473 K. Using the CO2/H2 stream, it requires 12 × 103 s to achieve steady-state performance;this time reduces to 5.4 × 103 s on increasing the temperature to 463 K. Using the CO/CO2/H2 stream, steady State performance is not achieved even after 14.4 × 103 s at 433 K but is achieved after 9 × 103 s at 463 K. Significant deviations from steady state behavior (~40% of steady state) are observed only at 453 K and only using the CO2/H2 feed when gas chromatography (GC) is the analysis system. When the reactor output is connected directly into a flame ionization detector (FID), oscillation is observed at all temperatures studied using a CO2/H2 stream. Injection of CO into the CO2/H2 stream, which is synthesizing methanol at 473 K, produces a sharply spiked increase in the rate of methanol synthesis followed by an oscillatory relaxation to steady state behavior. At 433 and 443 K, the injection of CO into the CO2/H2 stream again produces the sharply spiked increase in the rater of methanol synthesis, which returns to the baseline value without oscillations.

工业条件下铁钼氧化物催化剂上甲醇氧化反应的复杂振荡

在工业条件下，观察到甲醇在Ｆｅ２（ＭｏＯ４）３－ＭｏＯ３催化剂上的氧化反应发生强烈的自振荡，反应温度及尾气成分呈现周期性变化。振荡参数与反应温度、进料流速以及原料气中甲醇浓度有关，但不受原料气中氧浓度的影响，用原位红外技术检测到ＭｏＯ３及Ｆｅ２（ＭｏＯ４）３中Ｍｏ＝Ｏ双键的振荡有着不同的相位，说明振荡过程伴随着晶格氧的转移及金属离子价态的变化。这些变化造成反应速度的负反馈，从而产生振荡。用多种手段研究了铁和铂之间的协同效应，并提出了协同作用机理及避免振荡的措施。