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在中学、技工校、中等专业学校以及大学的化学教材和有关教学参考资料里,都是以铜与浓硫酸反应为例来分析说明浓硫酸的强氧化性的。有些教材还把铜与浓硫酸反应作为课堂演示实验和学生实验来加以证实浓硫酸的氧化性,并强调:应仔细观察有关现象,或要求从铜片表面、溶液和所放出气体等几方面描述现象。 相似文献
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提高乙醇与浓硫酸制乙烯产率的实验研究 总被引:4,自引:0,他引:4
我们知道,实验室用乙醇脱水制乙烯的反应主要利用了浓硫酸的强酸性,而副反应的发生是由浓硫酸的强氧化性引起的。笔者设想,对浓硫酸作适当稀释,使之既能保持其强酸性(即催化作用),又能降低其氧化性,从而从根本上有效地减少副反应的发生,提高乙烯产率。为此,提出如下实验方案进行对比研究,寻找最佳稀释点。1实验方案及报告1.1实验装置(如图所示)1.2实验操作在烧瓶里,混合液按实验报告要求依次加入。加浓硫酸时,使烧瓶倾斜,沿瓶口缓慢倒入,塞上配有温度计和导管的橡皮塞,轻轻摇晃,使之混均,立即固定在铁架台上加热… 相似文献
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对教材中"证明海带中存在碘元素"实验的灼烧法进行进一步研究,对灰化过程的细节提出坩埚灼烧不要加盖或使用蒸发皿的建议,并尝试用微波炉灰化干海带。提出了冷水1 min浸泡检验法和干海带浓硫酸直接氧化法2种直接证明方法。通过对3种不同实验方法在教学中所起作用的反思,提出了对教材实验的使用建议。 相似文献
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氧化条件下NOx催化的甲烷均相部分氧化 总被引:2,自引:0,他引:2
考察了没有固体催化剂时NOx对甲烷气相氧化的促进作用.实验结果表明,即使在强氧化条件下(O2/CH4=5),NOx对甲烷部分氧化制一氧化碳仍然有明显的催化活性.在CH4-O2体系中加入0.005%~0.2%的NO后,反应温度可降低200-300 ℃.在反应产物中还可观察到甲醛和乙烯,通过改变反应条件可以控制它们的相对浓度. 相似文献
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针对乙酸乙酯制备实验中的不足,以海藻酸钠-铁凝胶球(SA-Fe)为催化剂,降低了使用浓硫酸操作的危险性,便于反应残液的后处理,同时方便催化剂回收和再生。使该课堂演示实验简单化、安全化、绿色化。 相似文献
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采用“科学问题为目标导向”的实验教学指导原则,将邻硝基苯甲醛的绿色合成工艺开发为有机化学基础实验,丰富了绿色氧化反应在实验教学中的应用。本新创实验以水溶性2-(2,2,6,6-四甲基-4-亚哌啶基-1-氧化物)乙酸(简称TEMPO-COOH)为催化剂,在摩尔分数0.1%用量下,催化次氯酸钠氧化邻硝基苄醇,实现了重要有机合成中间体邻硝基苯甲醛的高选择性绿色催化合成,产率达93%,纯度>99%。作为本科生基础教学实验,本案例不仅涉及多种有机化学实验基本操作,还包含反应监测、结构表征、纯度分析等重要环节,同时还融入了绿色化学理念和有机合成方法学研究的实验探究过程。该新创实验所用试剂环境友好,安全性高,教学时长约为3–4 h,非常适合用于有机化学基础实验教学。以本实验方案为蓝本,结合有关氧化反应研究进展的微课学习和拓展练习,实现了理论知识与合成实践之间的有效互动,提升了化学专业本科生解决较为复杂有机合成问题的综合能力,提高了化学类人才的培养质量。 相似文献
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利用工业上应用广泛的铝阳极氧化电解实验及其着色工艺,阐述该实验原理及着色机理,用食用色素对阳极氧化后的铝片着色,得到色彩丰富的铝片,并制备出一种可以检验气体酸碱性的简易气体酸碱性检测器。该实验可以用于拓展课堂的实验教学,简便易行、原料易得、成本低、趣味性强。 相似文献
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Laboratory scale experiments were carried out in order to get more information about the oxidation of SO2 by OH radicals (homogeneous reaction) and the oxidation of SO2 at aerosol surfaces (heterogeneous reaction). For the experiment of homogeneous reaction, SO2 was added to synthetic flue gas without initial NO and without ammonia and the mixture was irradiated with electron beam. The SO2 removal was measured as a function of temperature and water vapour concentration at constant dose. For the experiment of heterogeneous reaction, SO2 was added to nucleating sulfuric acid aerosol. No SO2 removal was observed in this case. So, it can be concluded that the heterogeneous oxidation of SO2 is negligible in the absence of ammonia. Therefore, the oxidation of SO2 must be interpreted merely by homogeneous gas phase chemistry. The gas phase kinetics are derived from comparison of experimental results and computer modelling. 相似文献
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Depanjan Sarkar Soujit Sen Gupta Rahul Narayanan Thalappil Pradeep 《Journal of the American Society for Mass Spectrometry》2014,25(3):380-387
We report in-situ production and detection of intermediates at graphenic surfaces, especially during alcohol oxidation. Alcohol oxidation to acid occurs on graphene oxide-coated paper surface, driven by an electrical potential, in a paper spray mass spectrometry experiment. As paper spray ionization is a fast process and the time scale matches with the reaction time scale, we were able to detect the intermediate, acetal. This is the first observation of acetal formed in surface oxidation. The process is not limited to alcohols and the reaction has been extended to aldehydes, amines, phosphenes, sugars, etc., where reaction products were detected instantaneously. By combining surface reactions with ambient ionization and mass spectrometry, we show that new insights into chemical reactions become feasible. We suggest that several other chemical transformations may be studied this way. This work opens up a new pathway for different industrially and energetically important reactions using different metal catalysts and modified substrate. Figure
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Surface-enhanced infrared absorption spectroscopy (SEIRAS) combined with cyclic voltammetry or chronoamperometry has been utilized to examine kinetic and mechanistic aspects of the electrocatalytic oxidation of formic acid on a polycrystalline Pt surface at the molecular scale. Formate is adsorbed on the electrode in a bridge configuration in parallel to the adsorption of linear and bridge CO produced by dehydration of formic acid. A solution-exchange experiment using isotope-labeled formic acids (H(12)COOH and H(13)COOH) reveals that formic acid is oxidized to CO(2) via adsorbed formate and the decomposition (oxidation) of formate to CO(2) is the rate-determining step of the reaction. The adsorption/oxidation of CO and the oxidation/reduction of the electrode surface strongly affect the formic acid oxidation by blocking active sites for formate adsorption and also by retarding the decomposition of adsorbed formate. The interplay of the involved processes also affects the kinetics and complicates the cyclic voltammograms of formic acid oxidation. The complex voltammetric behavior is comprehensively explained at the molecular scale by taking all these effects into account. 相似文献
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Os(VIII) catalysis of oxidation of As(III)/Sb(III) by 1-equivalent oxidants like Ce(IV) and Mn(III) in acid medium is studied.
A multistep mechanism involving the intervention of the intermediate oxidation states of osmium is found to apply. Specific
rates of different steps in the mechanism are estimated and used to calculate reaction rates which are in reasonable agreement
with those of experiment. 相似文献
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以氯化铜、钼酸铵、苯酐、氯化铵、尿素和NaY分子筛为原料,采用苯酐-尿素法制备了酞菁铜/分子筛复合物CuPc/Y.采用等体积浸渍法将金属钯担载在CuPc/Y上制备了Pd-CuPc/Y催化剂,并在醋酸水溶液中考察了其催化甲烷选择氧化合成甲醇反应的性能,结果表明,催化性能与反应温度、溶剂中CH3COOH与H2O的混合比例、对苯醌用量、反应时间等因素有关,在0.5%Pd-0.5%CuPc/Y添加量0.5 g、CH3COOH与H2O体积比4∶1、对苯醌用量1 000 μmol、反应时间3 h、反应温度150 ℃的条件下,甲醇的最佳生成量为1 840 μmol.Pd-CuPc/Y催化剂可以多次循环使用,但由于催化剂流失和催化剂表面的钯粒子聚集的原因,循环使用后的催化剂催化活性有所下降.Pd-CuPc/Y在醋酸溶液中催化甲烷选择氧化合成甲醇是亲电取代反应和活性氧物种氧化共同作用的结果. 相似文献
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用H2O2氧化苯乙烯合成苯甲酸 总被引:2,自引:1,他引:1
摘要:以30%H2O2做为氧化剂,钨酸钠与含O双齿有机配体(草酸)形成的络合物为催化剂,在无有机溶剂、无相转移剂的条件下,研究了苯乙烯氧化制苯甲酸的反应。研究结果表明,最佳反应条件为:苯乙烯100.0mmol,n(钨酸钠):n(草酸):n(苯乙烯):n(30%H2O2)=2.0:3.2:100.0:440.0,于92℃反应24h,苯甲酸收率98.6%。用GC—MS跟踪了氧化过程中4种主要物质苯乙烯、1-苯基邻二醇、羟基苯乙酮及苯甲酸含量随反应时间的变化关系,提出了其主要氧化机理为苯乙烯经过环氧化反应、水解生成生成1-苯基邻二醇,1-苯基邻二醇再氧化为羟基苯乙酮、最后氧化为苯甲酸。 相似文献