席夫碱Mo(VI)功能化介孔SiO2的制备及其催化烯烃环氧化研究

采用共缩聚法制备有机-无机杂化材料,以介孔SiO_2材料为载体,分别嫁接席夫碱配体和配位乙酰丙酮钼,得到Mo(VI)席夫碱修饰的介孔SiO_2(Mo-SB-Cl-SiO_2-0.5-1).所制备的材料采用XRD,SEM,N2吸附-脱附和TEM技术对其结构进行了表征.考察了Mo-SB-Cl-SiO_2-0.5-1催化液相烯烃环氧化性能,结果表明:Mo-SB-Cl-SiO_2-0.5-1催化剂对烯烃环氧化具有高的转化率和优良的催化活性.与后嫁接法制备的催化剂相比,Mo-SB-Cl-SiO_2-0.5-1催化剂催化活性得到明显提高,催化环己烯环氧化的转化率和选择性分别为85%和99%.在不同烯烃的研究中,环辛烯具有最高的转化率和选择性,分别为87%和99%.催化剂重复使用4次后,环己烯的转化率没有明显下降,选择性仍然高达98%,表明Mo-SB-Cl-SiO_2-0.5-1具有较好的催化稳定性.     

CoPc/Al2O3催化剂的制备、表征及其催化氧化性能

用原位合成法,以酸性Al2O3为载体,酞菁类金属大环配合物为活性组分,合成出CoPc/Al2O3新型环氧化催化剂,红外、紫外-可见、热重分析及XPS证实能够利用该法在Al2O3上固载CoPc催化剂,且催化剂稳定性增加,不易流失.以分子氧为氧源,异丁醛为共还原剂考察CoPc/Al2O3催化剂对环己烯的催化环氧化活性及催化剂的重复使用情况.结果表明,与均相催化剂相比,固载后环己烯转化率增加了8%,环氧环己烷选择性增加了23%,催化剂重复使用4次后,活性仅降低4%.     

缺位类型磷钨酸盐催化的烯烃环氧化反应

主要合成了两种杂多磷钨酸盐环氧化催化剂,分别是由单缺位Keggin类型磷钨酸阴离子或者饱和结构的磷钨酸阴离子与十六烷基三甲基季铵盐阳离子构成,即[n-C16H33N(CH3)3]4Na3PW11O39(PW11)以及[n-C16H33N(CH3)3]3PW12O40(PW12),将其与低毒性的乙酸乙酯、30%的双氧水、烯烃构成催化环氧化反应体系,以环辛烯的环氧化反应为模型反应,着重探讨了PW11与PW12的催化性能产生明显差异的原因,并通过傅里叶变换-红外光谱,核磁共振谱以及催化剂溶解性实验给出了合理的解释.首先,在进行环辛烯的环氧化反应的动力学研究中,我们发现相同的反应条件下,PW11的催化活性明显高于PW12的催化活性,当反应进行至10min,以PW11为催化剂的反应体系,环辛烯的转化率已达到89%,而相应的采用PW12为催化剂的反应体系,环辛烯的转化率仅仅为11%.通过核磁磷谱(31PNMR)表征证明:当PW11和PW12与双氧水反应10min时PW11已降解产生大量的活性物种,而PW12的31PNMR谱并没有显示降解产物的谱峰.溶解性实验则更近一步说明,两个催化剂在双氧水的作用下均可降解形成小分子的物...     

三缺位Keggin型磷钨杂多酸盐高选择性催化氧化环己烯

利用三缺位Keggin型杂多酸[A-α-PW9O34]9-和[(FeШ(OH2)2)3(A-α-PW9O34)2]9-的四丁基铵盐做为催化剂,H2O2做为氧化剂催化环己烯氧化反应. 考察了反应时间、H2O2与环己烯的摩尔比,催化剂的用量等因素对反应结果的影响. 结果表明：在1, 2-二氯乙烷为10 mL,H2O2 (30 %)与环己烯的摩尔比为2,反应温度为35 oC,反应时间为6 h,[(C4H9)4N]9[A-α-PW9O34]为催化剂的条件下,环己烯氧化反应的转化率为55 %,主要产物是环氧环己烷,其选择性 ≥ 99 %;而以[(C4H9)4N]9[(FeШ(OH2)2)3(A-α-PW9O34)2]为催化剂时环己烯氧化反应的转化率17 %,主要产物是2-环己烯-1-酮,选择性 ≥ 99 %.     

缺位Dawson型K10Na2H2P2W16O60在环己烯氧化中的催化作用

合成了二缺位杂多化合物K10Na2H2P2W16O60·18H2O,用IR、UV-vis、XRD及TG表征了其结构,考察了该化合物在过氧化氢氧化环己烯反应中的催化作用.研究结果表明,溶剂种类和反应温度对二缺位杂多化合物的催化性能有显著的影响,在叔丁醇中主要生成环己烯酮,在丙酮中主要生成环己二醇.在乙腈中主要生成环氧环己烷,其选择性随着反应温度升高和催化剂用量增加而降低,环己烯酮的选择性则逐步升高.催化剂与产物可通过温控固-液相分离,可以重复使用.     

Schiff碱铁配合物催化环己烯环氧化

合成了一种吡啶甲醛类Schiff碱铁配合物[Fe(PA2OPd)C12]Cl,并考察了配合物对环己烯绿色环氧化反应的催化活性及反应条件,结果表明:吡啶甲醛类Schiff碱铁配合物对环己烯的环氧化反应有比较高的催化活性及选择性.以过氧化氢为氧源、[Fe(PA2OPd)C12]Cl为催化剂、在pH=5.0左右的乙酸乙酯溶液中25℃反应6.0 h,环己烯转化率可达90.5%,环氧环己烷选择性可达97.2%.     

离子液体中锰卟啉催化双氧水氧化烯烃的研究

研究了离子液体中Mn(TFPP)Cl(meso-tatrakis(pentafluoropheyl)porphinato)manganese(Ⅲ)cloride锰卟啉催化烯烃的氧化反应.在离子液体-CH2C12混合溶剂中,以价廉、环境友好的H2O2为氧源,考察了离子液体结构、反应条件等对环氧化反应的影响.当氧化剂/环己烯/催化剂/咪唑=450∶150∶1∶75(摩尔比)时,室温下,在MMISM-CH2Cl2的混合溶剂中,环己烯的转化率和环氧环己烷的选择性可分别达到94.8%和95.5%,远高于在纯CH2Cl2中的实验结果.并在最优反应条件下考察了该催化剂体系对烯烃底物的适用性.此外,反应结束后,产物可以由正己烷萃取出来,考察了混合溶剂中Mn(TFPP)Cl催化剂的重复使用情况.     

离子液体中Mn(salen)催化环己烯环氧化反应

 研究了离子液体中Mn(salen)络合物催化环己烯的环氧化反应,考察了反应介质、 Mn(salen)络合物催化剂结构和反应条件等对环氧化反应的影响. 在离子液体-CH2Cl2混合溶剂中,以相对廉价的H2O2为氧化剂,得到了高的环己烯转化率和环氧环己烷选择性. 当以邻苯二胺和水杨醛制备的Mn(salen)络合物为催化剂,反应温度为273 K时,在［bmim］BF4-CH2Cl2的混合溶剂中,环己烯的转化率和环氧环己烷选择性分别可达100%和94.0%. 此外,反应结束后,产物可以由正己烷萃取出来,解决了传统均相催化体系中催化剂与产物不易分离的问题.     

离子液体中V2O5催化环己烯选择氧化合成 2-环己烯酮

研究了以V2O5为催化剂,H2O2为氧化剂,在室温离子液体中环己烯氧化制备2-环己烯酮的反应.考察了离子液体种类、反应温度、催化剂用量和氧化剂用量等因素对2-环己烯酮产率的影响.结果表明,在H2O2用量为110 mmol,V2O5/环己烯摩尔比为2%,反应温度为313 K的条件下,在[bmim]BF4离子液体中反应10 h后,环己烯的转化率和2-环己烯酮选择性分别为88.7%和91.1%.对含离子液体的催化体系的重复使用性能进行了考察.结果发现,随着使用次数的增加,环己烯的转化率以及2-环己烯酮的选择性有所下降.     

CoPc/Al2O3催化分子氧环氧化环己烯的研究

常使用均相催化剂[1-4]催化氧化剂对烯烃进行环氧化来制备环氧环己烷,但均相催化剂存在分离回收难,易二聚失活的缺点.近年来对均相催化剂的固载开展了广泛的研究,如郑岩等[5]使用溶胶 -凝胶包容乙酰丙酮镍,M.Salavati-Niasari等[6]用Al2O3固载Mn(Salen)、Mn(en)2和Mn(acac)2金属配合物用于烯烃环氧化,由于Al2O3廉价易得,酞菁具有不易二聚、降解等较稳定的优点[3],本文以酸性Al2O3为载体,固载酞菁钴金属配合物制备CoPc/Al2O3新型环氧化催化剂,并对其结构进行表征,同时以分子氧为氧源,异丁醛为还原剂考察CoPc/Al2O3催化剂对环己烯的催化环氧化活性,探索了环己烯环氧化的较佳工艺参数.     

Magnetic polymer microspheres based on phosphotungstic acid quaternary ammonium salt as an efficient heterogeneous catalyst for epoxidation of cyclohexene

The magnetic polymer microsphere catalysts based on phosphotungstic acid quaternary ammonium salt were designed and prepared in order to improve the performance and reusability of the catalysts during the epoxidation of cyclohexene. The structure, particle size and surface property of the new catalysts were characterized by FTIR, laser particle size analysis and SEM, respectively. And the reactivity of the catalysts was detected in cyclohexene epoxidation. Among the obtained catalysts, PS-double-D-PW4 catalyst exhibited the best catalytic performance and high stability for cyclohexene epoxidation. The results showed that the optimum yield of epoxycyclohexane was 83% with a selectivity above 95% after 7 h. And the catalyst still showed a conversion above 78% after six runs.     

纳米SnO2高效催化烯烃与H2O2环氧化反应研究

构建了用于催化烯烃与过氧化氢环氧化反应的高效、 绿色催化反应体系. 首先, 通过水热合成法制备了纳米SnO₂, 并在320 ℃下煅烧. 随后, 对所有催化剂进行X射线衍射(XRD)、 紫外-可见漫反射光谱(UV-Vis)、 傅里叶变换红外光谱(FTIR)、 扫描电子显微镜(SEM)和透射电子显微镜(TEM)表征. 进一步将催化剂用于以H₂O₂水溶液为氧化剂环氧化各种官能化烯烃(包括环烯烃, 苯乙烯和直链烯烃)的反应, 以高转化率和高选择性得到了环氧化物. 在相似的反应条件下, 发现合成的纳米SnO₂-170催化剂在催化1-甲基环己烯与H₂O₂的环氧化反应中的活性最佳, 在2 h内1-甲基环己烯的转化率达到100%, 环氧化物选择性达到100%.     

Heterogenized peroxopolyoxotungstate catalyst on the surface of clicked magnetite‐graphene oxide nanocomposite: Magnetically recoverable epoxidation catalyst

A new heterogeneous catalyst for the epoxidation of olefins was prepared by immobilization of peroxophosphotungstate anions on the surface of clicked magnetite‐graphene oxide as magnetically recoverable support. To prepare the heterogeneous catalyst, the clicked magnetite‐graphene oxide support was prepared by thiolene click reaction of thiol functionalized graphene oxide with vinyl modified magnetite nanoparticles. The tailored support was then modified with aminopropyl groups followed by electrostatic interaction with peroxophosphotungstate anions to achieve the desired heterogeneous catalyst. Characterization of the catalyst was performed by various physicochemical methods which confirmed the successful immobilization of peroxopolyoxotungstate species on the surface of clicked magnetite‐graphene oxide. Catalytic activity of the catalyst revealed its high catalytic activity and selectivity in the epoxidation of various olefins in the presence of H₂O₂ as green oxidant. This heterogeneous catalyst can be magnetically reused several times without significant loss of activity and selectivity.     

Synthesis of ceria nanoparticles for the catalytic activity of cyclohexene epoxidation and selective detection of nitrite

Based on a few noteworthy features, cerium oxide nanoparticles have gained significance in nanotechnology. The effective microwave combustion method (MCM) and the conventional sol–gel (CRSGM) technologies are used in this study to successfully generate the crystalline CeO₂ nanoparticles (NPs). Additionally, using a variety of spectroscopic and analytical methods, the synthesized CeO₂ NPs are examined to assess to understand their structure and morphology. The XRD patterns of CeO₂ NPs show that the structure exhibits a face-centered cubic lattice. Then, with demonstrated good conversion and selectivity, the impact of the epoxidation reaction of cyclohexene was examined. Finally, it can be said that using CeO₂ nanoparticles is an efficient strategy to increase the catalytic activity toward the epoxidation reaction of cyclohexene. In the presence of acetonitrile as a solvent and H₂O₂ as an oxidant, the catalyst samples utilized in the cyclohexene epoxidation reaction were examined. In this study, the CeO₂ catalyst outperformed all other catalysts in terms of cyclohexene maximal conversion and selectivity. After six prolonged cycles, the conversion of cyclohexene oxidation using CeO₂ NPs shows reasonable recyclability and conversion efficiency, making it the best catalyst for an industrial production application.Additionally, the upgraded CeO₂ nanoparticle electrode for nitrite detection has a linear concentration range (0.02–1200 M), a low detection limit (0.22 M), and a higher sensitivity (1.735 A M⁻¹ cm⁻²). CeO₂ NPs, on the other hand, have a quick response time, excellent sensitivity, and high selectivity. Additionally, the manufactured electrode is used to find nitrite in various water samples. Finally, it can be said that using CeO₂ NPs is an efficient strategy to increase the catalytic activity toward cyclohexene oxidation and nitrite.     

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.     

Epoxidation of cyclohexene with H2O2 over efficient water‐tolerant heterogeneous catalysts composed of mono‐substituted phosphotungstic acid on co‐functionalized SBA‐15

A series of Keggin‐type heteropolyacid‐based heterogeneous catalysts (Co‐/Fe‐/Cu‐POM‐octyl‐NH₃‐SBA‐15) were synthesized via immobilized transition metal mono‐ substituted phosphotungstic acids (Co‐/Fe‐/Cu‐POM) on octyl‐amino‐co‐functionalized mesoporous silica SBA‐15 (octyl‐NH₂‐SBA‐15). Characterization results indicated that Co‐/Fe‐/Cu‐POM units were highly dispersed in mesochannels of SBA‐15, and both types of Brønsted and Lewis acid sites existed in Co‐/Fe‐/Cu‐POM‐octyl‐NH₃‐SBA‐15 catalysts. Co‐POM‐octyl‐NH₃‐SBA‐15 catalyst showed excellent catalytic performance in H₂O₂‐mediated cyclohexene epoxidation with 83.8% of cyclohexene conversion, 92.8% of cyclohexene oxide selectivity, and 98/2 of epoxidation/allylic oxidation selectivity. The order of catalytic activity was Co‐POM‐octyl‐NH₃‐SBA‐15 > Fe‐POM‐octyl‐NH₃‐SBA‐15 > Cu‐POM‐octyl‐NH₃‐SBA‐15. In order to obtain insights into the role of ‐octyl moieties during catalysis, an octyl‐free catalyst (Co‐POM‐NH₃‐SBA‐15) was also synthesized. In comparison with Co‐POM‐NH₃‐SBA‐15, Co‐POM‐octyl‐NH₃‐SBA‐15 showed enhanced catalytic properties (viz. activity and selectivity) in cyclohexene epoxidation. Strong chemical bonding between ‐NH₃⁺ anchored on the surface of SBA‐15 and heteropolyanions resulted in excellent stability of Co‐POM‐octyl‐NH₃‐SBA‐15 catalyst, and it could be reused six times without considerable loss of activity.     

Ti-Beta分子筛的控制合成及高效催化环己烯环氧化

构建了以H₂O₂为氧化剂催化环己烯合成环氧环己烷的高效、 绿色催化反应体系. 在不加入铝源的情况下, 以四乙基氢氧化铵(TEAOH)为模板剂, 通过改进的干胶转化法控制H₂O/SiO₂摩尔比为1.5合成出Ti-Beta分子筛. 实验结果表明, 适宜的酸碱性、 含水量以及模板剂用量显著影响分子筛的结晶度, 同时影响晶粒尺寸和晶粒尺寸的均一性. 通过对Ti-Beta分子筛原粉进行焙烧处理制得Ti-Beta分子筛催化剂, 再通过对反应溶剂、 反应温度和反应时间的筛选和优化, 获得最优催化反应条件, 在该条件下, 环己烯转化率可达33.5%, 环氧环己烷选择性可达99.6%. 实验结果表明该催化剂是一种高效的多相催化剂.     

聚苯乙烯负载席夫碱Mo(Ⅵ)配合物合成、表征及其在环己烯环氧化反应中的催化活性

合成了聚苯乙烯负载乙二胺缩水杨醛席夫碱与Mo(Ⅵ)的配合物,并对其结构进行了表征.该配合物催化环己烯环氧化反应与小分子配合物MoO₂(acac)₂相比,具有更优良的催化活性和选择性;建立了催化剂中Mo分析和环氧环己烷气相色谱分析新方法;探讨了配合物及环氧环己烷合成过程诸因素的影响;优化了环氧环己烷合成条件,即以n(t-BuOOH)=0.1mol计,n(C₆H₁₀)∶n(t-BuOOH)=3∶1,溶剂5mL,反应温度80℃,时间60min.在该条件下,环氧环己烷收率(以t-BuOOH计)99.2%以上,质量分数约99.5%(GC检测).催化剂循环使用5次后,未见活性明显下降,环氧环己烷收率(以t-BuOOH计)仍接近99%.     

非负载型铁催化剂上二氧化碳加氢制低碳烯烃

研究了非负载型铁催化剂上CO₂加氢制低碳烯烃反应.结果显示,添加碱金属可显著提高铁催化剂上的CO₂转化率和烯烃选择性.在经K和Rb修饰的Fe催化剂上,CO₂转化率可达约40%,烯烃选择性达到50%以上,其中C₂~C₄烯烃收率超过10%.催化剂表征结果表明,碱金属促进了催化剂中碳化铁的生成,这可能是催化剂性能提高的一个关键原因.随着K含量由1 wt%增加至5 wt%,CO₂转化率及烯烃选择性均升高.但K含量过高时,催化剂活性降低.这可能是由于催化剂比表面积和CO₂化学吸附量降低所致.当K含量为5%~10%时,K-Fe催化剂上烯烃收率较高; 进一步添加适量的硼可进一步提高烯烃选择性,且CO₂转化率下降不大.