环己烯合成实验的绿色化改进

以新制的硅钨酸为催化剂,环己醇脱水制备环己烯。考察了催化剂、反应温度、反应时间、分馏柱等因素对实验结果的影响。环己烯产率可达79.3%,纯度为98.8%。与传统方法相比,实验操作简单、产率高、环境友好、催化剂可重复使用,是一条合成环己烯的典型绿色途径。     

Ti4+修饰阳离子交换树脂催化制备环已烯

在Ti^4 修饰阳离子交换树脂催化剂上进行了环己醇脱水制备环己烯的反应，考察了催化剂吸附毗啶的FT-IR，证实了该催化剂表面具有Bronsted酸和Lewis酸性住是催化环己烯脱水反应的物质基础，实验结果表明：修饰树脂具有较高的热稳定性，Ti^4 交换容量对阳离子交换树脂的催化活性存在着明显的影响，催化剂对环己醇脱水制环己烯反应的活性高，并得到该反应的优化条件如下：环己醇40g，催化剂5g，反应温度175℃，反应时问60min，在此条件下，环己烯的产率达89％。     

聚乙二醇稳定的RuB纳米粒子催化苯选择加氢为环己烯的性能研究

PEG稳定的RuB纳米粒子对苯选择加氢制备环己烯显示出良好的催化性能,在不添加硫酸锌的条件下,该体系催化的苯选择性加氢中,环己烯收率高达29%。这一体系的高催化性能是由于PEG稳定的RuB纳米粒子,使催化剂表面的亲水性增强,提高了环己烯的选择性。     

花生壳碳基固体酸催化环己烯与甲酸酯化反应(英文)

碳基固体酸是一种可替代液体质子酸的无定形碳材料,具有酸密度大、催化活性高等优点.花生壳是农业废弃物,以其为原料制备碳基固体酸具有成本低、原料可再生和环境友好等优点.甲酸环己酯是重要的化工产品,可用于香料和涂料工业.传统的甲酸环己酯制备方法是以环己醇和甲酸为原料,在酸催化条件下进行酯化反应而得.近年来,随着环己烯的大规模生产,利用环己烯与甲酸直接酯化制备甲酸环己酯引起广泛关注.此外,甲酸环己酯还可通过水解反应转变为环己醇.环己醇可以进一步转化为己二酸和己内酰胺,从而用于化纤工业中尼龙-6和尼龙-66的生产.目前,工业上采用环己烯水合反应制备环己醇,由于热力学限制,并受到环己烯与水相容性差的影响,环己烯单程转化率仅为~10%,循环量较大,能耗很高.以环己烯为原料,通过甲酸环己酯制备环己醇克服了上述环己烯直接水合的缺点,具有很好的发展前景.我们研究组使用HZSM-5分子筛作为催化剂,采用"一锅法"由环己烯经甲酸环己酯制备环己醇,环己醇收率可达40%.但是环己烯在酸性条件下可发生低聚反应,生成的副产物会堵塞HZSM-5孔道,造成催化剂失活.本文在前述研究基础上,以花生壳为原料,经过碳化、磺化过程制备得到了碳基固体酸PSCSA.采用傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)、X射线衍射(XRD)、拉曼光谱(Raman)、热重分析(TG)、X射线光电子能谱(XPS)和元素分析等方法表征了PSCSA的结构、微观形貌、热稳定性以及酸性质,考察了其催化环己烯与甲酸酯化反应性能,并与几种常见的固体酸催化剂进行了比较.FT-IR结果显示,经磺化后,PSCSA表面出现了–SO3H和–COOH基团.XPS结果则说明PSCSA表面所有的S元素均属于–SO3H,可利用元素分析测定S含量,进而得到–SO3H密度.此外,由于花生壳属于天然物质,成分并不均一,因此PSCSA的SEM照片中不同部位颗粒的微观形貌差异较大.采用PSCSA作为催化剂,考察了其催化环己烯与甲酸酯化反应性能,优化了反应条件.在酸/烯摩尔比为3/1,PSCSA用量0.07 g/mL环己烯,413 K反应1 h,环己烯转化率为88.4%,甲酸环己酯选择性为97.3%;副产物包括环己醇、二聚环己烯和环己基醚等.比较了PSCSA与几种常用固体酸如HZSM-5、离子交换树脂Amberlyst-15和Nafion NR50的催化性能,其中,Amberlyst-15催化性能最优,在393 K下反应,环己烯转化率亦达91.5%,甲酸环己酯选择性98.1%;但是,高昂的价格限制了其在工业上的大规模应用.与HZSM-5相比,PSCSA催化的环己烯与甲酸酯化反应的初始速率较低,反应时间超过30 min后,环己烯转化率迅速增加.在本反应中,PSCSA在甲酸存在条件下发生溶胀,使得大量的甲酸分子插入到碳材料本体中;而环己烯与甲酸具有较好的相容性,因此环己烯可以进入到碳材料本体中,与活性中心–SO3H充分接触,从而具有较高的反应速率.并且,由于溶胀需要一定的时间,在反应初期溶胀不充分时,环己烯、甲酸与活性中心接触有限,因此反应较慢;反应一定时间后,PSCSA充分溶胀,更多的–SO3H参与到反应中,反应速率加快.PSCSA重复使用性较好,第3次使用时环己烯转化率为68.6%;继续使用,催化剂不再失活.PSCSA在反应初期失活是–SO3H流失造成的.构成PSCSA的多环芳香烃可以部分溶解到溶剂中,进而带走其包含的–SO_3H.PSCSA的后期活性稳定则说明可以流失的活性中心是有限的.     

稀土超强酸SO42-/TiO2-Nd2O3催化合成环己烯

环己烯是重要的一种有机合成中间体,具有活泼的双键,作为有机化工原料,可广泛应用于医药、农药、农用化学品、饲料添加剂、聚酯和其他精细化学品的生产。人们曾对环己醇脱水制环己烯反应使用过多种酸性催化剂及固体催化剂,固体超强酸就是其中之一,虽然已有许多关于固体超强酸应     

第23届全国高中学生化学竞赛实验试题

顺-4-环己烯-1, 2-二羧酸的制备及纯度分析 一、实验内容 1. 产品制备:先由环丁烯砜和顺丁烯二酸酐反应得到顺-4-环己烯-1, 2-二酸酐(用A表示),再水解得到产品顺-4-环己烯-1, 2-二羧酸(用B表示). 2. 产品纯度分析:通过酸碱滴定法测定自制产品B的纯度.     

8-羟基喹啉对V2O5催化氧化环己烯的调变作用

研究了8-羟基喹啉对丙酮中V2O5催化氧化环己烯合成环己烯酮的调变作用,考察了8-羟基喹啉的用量、反应温度、反应时间、溶剂和催化剂用量对环己烯氧化反应的影响,发现在该催化体系中生成的环己烯醇和环氧环己烷可转化成环己烯酮,在适当的反应条件下可抑制环己烯醇和环氧环己烷的生成.结果表明,当五氧化二钒的用量为1%,五氧化二钒与8-羟基喹啉之比为1∶2,在20℃以下反应时,过氧化氢几乎定向地将环己烯氧化成环己烯酮.认为是8-羟基喹啉与钒的配位作用促进了环己烯酮的生成.     

用Diels-Alder反应合成顺-4-环己烯-1,2-二羧酸及产品纯度分析——小综合实验推荐

推荐了一个适合在化学及非化学专业开设的涉及有机合成、化学分析等操作的小综合实验。采用环丁烯砜加热分解释放出的丁二烯与顺丁烯二酸酐进行Diels-Alder反应来制备六元环化合物顺-4-环己烯-1,2-二酸酐,再经水解得到顺-4-环己烯-1,2-二羧酸。采用酸碱滴定法分析产品纯度,测定产物熔点,并通过红外光谱、核磁共振谱进行化合物结构表征。     

五氧化二钒催化环己烯烯丙位氧化

 研究了以五氧化二钒为催化剂,以过氧化氢水溶液为氧源氧化环己烯. 考察了溶剂种类、溶剂用量、催化剂用量和反应温度等因素对催化剂性能的影响. 结果表明,常温下环己烯在此催化体系中主要发生烯丙位氧化反应生成环己烯酮. 溶剂的种类对催化活性和烯丙位酮式氧化的选择性具有较大的影响,丙酮是该反应的合适溶剂. 在丙酮与环己烯的体积比为4, 五氧化二钒与环己烯的质量比为1∶40, 过氧化氢与环己烯的摩尔比为3和反应温度为20 ℃的条件下,反应24 h后的环己烯转化率可达60%以上,环己烯酮选择性可达85%. 催化反应过程中丙酮可能与过氧化氢作用生成过氧化酮,从而进行氧转移,催化剂则经过V5+/V4+物种的循环使环己烯氧化成为环己烯酮等产物.     

壳聚糖席夫碱钴催化环己烯烯丙位氧化反应的研究

制备了壳聚糖(CS)水杨醛席夫碱钴配合物,利用X射线粉末衍射(XRD)、红外(IR)等方法对其结构特征进行了分析,并以氧气为氧化剂,评价了该配合物的环己烯氧化催化性能,初步考察了催化剂用量、反应温度以及反应时间等因素对氧化反应的影响。实验结果表明:CS-席夫碱钴配合物具有良好的环己烯催化氧化活性和较高的烯丙位氧化选择性,在较优条件下,环己烯转化率和烯丙位氧化选择性分别达到85.3%和81.3%;催化剂具有较好的稳定性,易分离可多次重复使用。     

Investigating the oxidation of alkenes by non-heme iron enzyme mimics

Iron is emerging as a key player in the search for efficient and environmentally benign methods for the functionalisation of C-H bonds. Non-heme iron enzymes catalyse a diverse array of oxidative chemistry in nature, and small-molecule complexes designed to mimic the non-heme iron active site have great potential as C-H activation catalysts. Herein we report the synthesis of a series of organic ligands that incorporate key features of the non-heme iron active site. Iron(ii) complexes of these ligands have been generated in situ and their ability to promote hydrocarbon oxidation has been investigated. Several of these systems promote the biomimetic dihydroxylation of cyclohexene at low levels, when hydrogen peroxide is used as the oxidant; allylic oxidation products are also observed. An investigation of ligand stability reveals formation of several breakdown products under the conditions of the oxidative turnover reactions. These products arise via oxidative decarboxylation, dehydration and deamination reactions. Taken together these results indicate that competing mechanisms are at play with these systems: biomimetic hydroxylation involving high-valent iron species, and allylic oxidation via Fenton chemistry and Haber-Weiss radical pathways.     

Experimental Design for Modeling and Multi‐response Optimization of Catalytic Cyclohexene Epoxidation over Polyoxometalates

An experimental design methodology was applied to optimize cyclohexene epoxidation with hydrogen peroxide in the presence of acid‐activated montmorillonite clay supported on 11‐molybdovanado‐phosphoric acid, with the Keggin structure H₄[PVMo₁₁O₄₀] · 13H₂O (PVMo) as catalyst. The statistical study of the process was achieved through a two‐level, full‐factorial experimental design with five process parameters. The significant input variables (key factors) that influenced the performance of cyclohexene oxidation are the catalyst weight, catalyst loading, temperature, H₂O₂ concentration, and the reaction time. The effect of the individual parameters and their interaction effects on the cyclohexene conversion, as well as the selectivity of cyclohexane‐1,2‐diol, was determined, and a statistical model of the process was developed. The process was optimized by considering the two responses simultaneously, which allows defining the optimal regions for the significant process variables. The optimal conditions were obtained for the catalyst weight of 0.05 g, temperature of 70°C, and reaction time of 9 h, with 20% PVMo as the active phase and hydrogen peroxide as oxidant.     

Investigation of catalytic conversions of isopropanol and cyclic hydrocarbons on titanium dioxide (anatase) by means of a differential thermocouple

Summary With the aid of a differential thermocouple it was possible to show that the gradual carbonization of the anatase surface occurring during an experiment completely suppressed the dehydrogenation of isopropanol and promoted its dehydration with the total activity of the catalyst remaining unchanged, suppressed the irreversible catalytic reaction of cyclohexene and cyclohexadiene, and promoted the dehydrogenation of cyclohexene, cyclohexadiene, and cyclohexane.     

Following Solid‐Acid‐Catalyzed Reactions by MAS NMR Spectroscopy in Liquid Phase—Zeolite‐Catalyzed Conversion of Cyclohexanol in Water

A microautoclave magic angle spinning NMR rotor is developed enabling in situ monitoring of solid–liquid–gas reactions at high temperatures and pressures. It is used in a kinetic and mechanistic study of the reactions of cyclohexanol on zeolite HBEA in 130 °C water. The ¹³C spectra show that dehydration of 1‐¹³C‐cyclohexanol occurs with significant migration of the hydroxy group in cyclohexanol and the double bond in cyclohexene with respect to the ¹³C label. A simplified kinetic model shows the E1‐type elimination fully accounts for the initial rates of 1‐¹³C‐cyclohexanol disappearance and the appearance of the differently labeled products, thus suggesting that the cyclohexyl cation undergoes a 1,2‐hydride shift competitive with rehydration and deprotonation. Concurrent with the dehydration, trace amounts of dicyclohexyl ether are observed, and in approaching equilibrium, a secondary product, cyclohexyl‐1‐cyclohexene is formed. Compared to phosphoric acid, HBEA is shown to be a more active catalyst exhibiting a dehydration rate that is 100‐fold faster per proton.     

Facile redbrick clay as splendid catalyst for selective dehydration of alcohols

Research on Chemical Intermediates - Excellent catalytic activity of activated redbrick clay (ARB) for dehydration and highly selective conversion of cyclohexanol to cyclohexene and 1-phenylethanol...     

An Overview of Heterogeneous Transition Metal-Based Catalysts for Cyclohexene Epoxidation Reaction

Cyclohexane epoxide, which contains highly active epoxy groups, plays a crucial role as an intermediate in the preparation of fine chemicals. However, controlling the epoxidation pathway of cyclohexene is challenging due to issues such as the allylic oxidation of cyclohexene and the ring opening of cyclohexane epoxide during the cyclohexene epoxidation process to form cyclohexane oxide. This review focuses on the structure-activity relationships and synthesis processes of various heterogeneous transition metal-based catalysts used in cyclohexene epoxidation reactions, including molybdenum(Mo)-based, tungsten(W)-based, vanadium(V)-based, titanium(Ti)-based, cobalt(Co)-based, and other catalysts. Initially, the mechanism of cyclohexene epoxidation by transition metal-based catalysts is examined from the perspective of catalytic active centers. Subsequently, the current research of cyclohexene epoxidation catalysts is summarized based on the perspective of catalyst support. Additionally, the differences between alkyl hydroperoxide, hydrogen peroxide (H₂O₂), and oxygen (O₂) as oxidants are analyzed. Finally, the main factors influencing catalytic performance are summarized, and reasonable suggestions for catalyst design are proposed. This work provides scientific support for the advancement of the olefin epoxidation industry.     

Reaction cells and collision cells for ICP-MS: a tutorial review

This paper reviews the literature published to September 2001 relating to the history, design, operation and application of linear radio-frequency (r.f.)-driven multipole collision cells and reaction cells in combination with inductively coupled plasma mass spectrometry. The available material is supplemented with original experimental data that demonstrates the principles presented. The relation of these devices to collision cells for organic mass spectrometry and to the three-dimensional ion trap is discussed in its historical context. A general tutorial on the fundamentals of ion collision and reaction, including thermochemistry, energy transfer and reaction kinetics, is given. Consideration is given to some of the fundamental aspects of operation and design of linear r.f. devices. This historical and fundamental framework then allows the tutorial to focus on the promotion and control of ion–molecule chemistry in linear r.f.-multipole cells for elemental analysis. Vacuum requirements are considered in some detail, and deal in particular with the issue of contamination of the reaction gas. Special attention is paid to the thermal characteristics of the ions in the cell, as this has important implications for the application of the available databases of thermochemical and thermal kinetic data to the development of analytical methods. Calculation and experimental validation of the efficiency of the ion–molecule chemistry leads to the recognition that secondary, sequential chemistry can play a limiting role in the realization of the potential of the cell method. The two principal means of controlling the analytical impact of the secondary chemistry, through post-cell kinetic energy discrimination and through in-cell mass-bandpassing are discussed and contrasted through spectral data acquired for different reaction gas types and pressures. The available literature on the application of collision cells and reaction cells for the analysis of samples of high purity, environmental, geological and biological materials is critically reviewed.     

Oxodiperoxo tungsten complex-catalyzed synthesis of adipic acid with hydrogen peroxide

An amphiphilic oxodiperoxo complex of tungsten using 8-quinolinol (QOH) as ligand has been synthesized and characterized by elemental analyses, gravimetry, chemistry titration, TG/DSC, IR and UV-vis spectroscopy. Oxidation of cyclohexene, cyclohexanol, cyclohexanone, cyclohexene oxide and 1,2-cyclohexane-diol to adipic acid in one-step was conducted by this complex catalyst using 30 wt.% hydrogen peroxide in the absence of organic solvent and phase-transfer catalyst. The effect of the reaction conditions on the oxidation of cyclohexene was studied by varying the amount of the catalyst, reaction temperature, reaction time and the amount of hydrogen peroxide. The results showed that oxodiperoxo tungsten complex with QOH as ligand could achieve 89.8% yield of adipic acid at 90°C by refluxing for 20 h.     

有机化学实验线上课程之扬长避短教学设计与实践篇

It has been two months since a boom of online education triggered by the epidemic in China. At present, we are keeping focus on how to optimize our online class. In the case of chemistry laboratory courses, there's not much that can be done to experimental operations through online teaching. While for the traditional teaching procedure, there is still room for improvement in terms of integrating research to teaching, interactivity, etc. This paper will present some design strategies for improving teaching the organic chemistry laboratory online. To be specific, it describes how teaching materials like the lesson plan and virtual lab were coordinated into the online teaching. And we will also discuss the holistic approach to a better outcome for students' active learning and integration research into teaching by redesigning multiple phases, such as the pre-laboratory preparation, live online class, experimental operations.