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硫酸钙晶须催化合成三羟甲基丙烷三丙烯酸酯 总被引:1,自引:0,他引:1
以三羟甲基丙烷(TMP)、丙烯酸(AA)为原料,硫酸钙晶须为催化剂,环己烷和甲苯混合物为带水剂,合成三羟甲基丙烷三丙烯酸酯(TMPTA).考察了原料配比、催化剂用量等因素对产品酯化率的影响.结果表明:以对苯二酚和吩噻嗪做混合阻聚剂,n(AA)∶n(TMP)=3.40,硫酸钙晶须的质量分数(以三羟甲基丙烷用量为基准)为2.0%,、环己烷用量20%、甲苯用量30%;酯化反应温度为98 ℃,反应时间为5 h,在此条件下合成的三羟甲基丙烷三丙烯酸酯酯化率大于96.8%,纯度达到97.6%. 相似文献
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咪唑阴离子型碱性离子液体的合成及其催化Knoevenagel缩合反应 总被引:13,自引:0,他引:13
设计合成了由1-丁基-3-甲基咪唑阳离子与咪唑阴离子搭配的[bmim]Im新型碱性离子液体并对其碱性进行研究.[bmim]Im离子液体的碱性与[bmim]OH的碱性接近且强于[bmim]OAc.在水溶液及室温条件下,2%的[bmim]Im离子液体对系列芳香醛与活泼的亚甲基化合物之间的Knoevenagel缩合反应具有较好的催化性能,目标产物的收率达到86%~95%,选择性为100%.同时,该催化剂体系具有良好的循环性能. 相似文献
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丙二醇醚类化合物是性能优良的精细化学品,也是环保型高级溶剂.该类化合物具有两个强溶解性功能基团—醚键和羟基,前者具有亲油性,可溶解疏水性物质,后者具有亲水性,可溶解亲水性物质,因而丙二醇醚具有很强的溶解能力,素有"万能溶剂"之称,可广泛应用于涂料、油墨、油漆、印刷、电子化学品、染料、净洗和纺织等行业.丙二醇醚类化合物目前主要由环氧丙烷和低级脂肪醇反应合成,然而,由于环氧丙烷的位阻效应,使其在酸或碱的条件下开环的位置会不同,从而得到不同的醇醚产物.由于碱催化的醇醚产物更加环境友好,因而越来越被人们所关注.工业上丙二醇醚合成多采用传统的强碱性催化剂醇钠以及氢氧化钠,腐蚀性强,产生的废液量大.本文采用环境友好的非卤素离子液体作为催化剂,研究了其催化环氧丙烷醚化合成丙二醇醚的反应特性.本文采用两步法合成了一系列环境友好的醋酸类碱性功能化离子液体,并在温和的条件下将其用于催化环氧丙烷与醇反应合成丙二醇醚.结果表明,该类离子液体可以高效催化该反应的进行.利用紫外-可见光谱测定Hammett指数来表征实验中所用离子液体的碱强度,并构建了离子液体碱性与催化活性之间的关系.结果表明,离子液体的催化性能和其碱性密切相关,随着离子液体碱性的增加,催化活性增强,其中咪唑醋酸类离子液体碱性强于季胺类,表现出优异的催化性能.离子液体的碱性明显弱于NaOH,但却呈现出更优异的催化性能.相同反应条件下,EmimOAc离子液体作为催化剂,PO的转化率分别较NaOH高出20%–30%,选择性略高于NaOH,这可能是由于二者催化机理不同造成的.传统NaOH催化机理的关键步骤是醇在碱性催化剂的作用下去质子化形成电子供体烷氧根离子,促进环氧丙烷的开环加成.而本文提出了离子液体亲电亲核双活化作用机理,即离子液体在阴阳离子之间的氢键和电荷相互作用的共同作用下,促进环氧丙烷开环和醇的去质子化,形成相应的反应中间体.通过电喷雾质谱分析手段检测到了阴阳离子通过协同作用亲电亲核催化过程中的反应中间体,证明了该假设机理的可行性.此外,还考察了催化剂浓度、醇比、反应温度以及醇的空间位阻效应对反应的影响.以EmimOAc催化合成丙二醇丁醚为例,反应的转化率随催化剂浓度的增加而增大,在催化剂添加量1%(催化剂与PO的摩尔比)时,PO转化率达到最大值为98.2%,1-丁氧基-2-丙醇的选择性为86.4%.当正丁醇与环氧丙烷的摩尔比为3时,转化率最高为88.6%,选择性高达94%.该反应为放热反应,最适反应温度约为140 oC,此时转化率高达96.5%.在环氧丙烷和不同的低碳醇合成丙二醇醚的反应中,反应物醇的碳链越短,支链越少,催化反应效率越高. 相似文献
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《催化学报》2017,(5)
丙二醇醚类化合物是性能优良的精细化学品,也是环保型高级溶剂.该类化合物具有两个强溶解性功能基团—醚键和羟基,前者具有亲油性,可溶解疏水性物质,后者具有亲水性,可溶解亲水性物质,因而丙二醇醚具有很强的溶解能力,素有"万能溶剂"之称,可广泛应用于涂料、油墨、油漆、印刷、电子化学品、染料、净洗和纺织等行业.丙二醇醚类化合物目前主要由环氧丙烷和低级脂肪醇反应合成,然而,由于环氧丙烷的位阻效应,使其在酸或碱的条件下开环的位置会不同,从而得到不同的醇醚产物.由于碱催化的醇醚产物更加环境友好,因而越来越被人们所关注.工业上丙二醇醚合成多采用传统的强碱性催化剂醇钠以及氢氧化钠,腐蚀性强,产生的废液量大.本文采用环境友好的非卤素离子液体作为催化剂,研究了其催化环氧丙烷醚化合成丙二醇醚的反应特性.本文采用两步法合成了一系列环境友好的醋酸类碱性功能化离子液体,并在温和的条件下将其用于催化环氧丙烷与醇反应合成丙二醇醚.结果表明,该类离子液体可以高效催化该反应的进行.利用紫外-可见光谱测定Hammett指数来表征实验中所用离子液体的碱强度,并构建了离子液体碱性与催化活性之间的关系.结果表明,离子液体的催化性能和其碱性密切相关,随着离子液体碱性的增加,催化活性增强,其中咪唑醋酸类离子液体碱性强于季胺类,表现出优异的催化性能.离子液体的碱性明显弱于NaOH,但却呈现出更优异的催化性能.相同反应条件下,EmimOAc离子液体作为催化剂,PO的转化率分别较NaOH高出20%–30%,选择性略高于NaOH,这可能是由于二者催化机理不同造成的.传统NaOH催化机理的关键步骤是醇在碱性催化剂的作用下去质子化形成电子供体烷氧根离子,促进环氧丙烷的开环加成.而本文提出了离子液体亲电亲核双活化作用机理,即离子液体在阴阳离子之间的氢键和电荷相互作用的共同作用下,促进环氧丙烷开环和醇的去质子化,形成相应的反应中间体.通过电喷雾质谱分析手段检测到了阴阳离子通过协同作用亲电亲核催化过程中的反应中间体,证明了该假设机理的可行性.此外,还考察了催化剂浓度、醇比、反应温度以及醇的空间位阻效应对反应的影响.以EmimOAc催化合成丙二醇丁醚为例,反应的转化率随催化剂浓度的增加而增大,在催化剂添加量1%(催化剂与PO的摩尔比)时,PO转化率达到最大值为98.2%,1-丁氧基-2-丙醇的选择性为86.4%.当正丁醇与环氧丙烷的摩尔比为3时,转化率最高为88.6%,选择性高达94%.该反应为放热反应,最适反应温度约为140 oC,此时转化率高达96.5%.在环氧丙烷和不同的低碳醇合成丙二醇醚的反应中,反应物醇的碳链越短,支链越少,催化反应效率越高 相似文献
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通过γ-氯丙基三甲氧基硅烷将磺基功能化离子液体-N-磺丙基咪唑盐化学键合到微球硅胶上,制得微球硅胶固定化离子液体(IL3). 用FTIR、TG、~(13)C NMR、SEM、BET及酸度测定等测试技术对IL3进行了表征,并考察其在果糖脱水合成5-羟甲基糠醛(HMF)过程中的催化性能. 研究结果表明,氯丙基三甲氧基硅烷可以将磺基功能化咪唑型离子液体化学键合到微球硅胶上. 微球硅胶固定化磺基咪唑离子液体能有效催化果糖脱水生成HMF. 果糖在固载率45.4%的IL3催化下、乙二醇甲醚(EGME)溶剂中、115 ℃反应5 h,HMF收率可达82.1%. 催化剂循环使用4次后,HMF的收率下降为53.0%. 相似文献
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制备了一种以三乙烯二胺(DABCO)为基础的离子液体;在水溶剂中,以该离子液体为催化剂催化三组分一锅法制备四氢苯并吡喃的反应,得到2-氨基-3-氰基-4-芳基-7,7-二甲基-5-氧代-4H-5,6,7,8-四氢苯并[b]吡喃;考察了反应时间、催化剂用量、催化剂加入时间、反应温度对反应收率的影响,确定了最优反应条件;由不同的芳香醛和活性亚甲基化合物制备了一系列四氢苯并吡喃衍生物,并讨论了可能的反应机理.结果表明,所选用的合成反应条件温和、时间短、收率高、后处理简单,且催化剂重复使用4次催化效果变化不大;就反应机理而言,所用催化剂具有双重催化活性. 相似文献
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筛选高效、高选择性多相催化剂异构化亚油酸是共轭亚油酸(CLA)研究的重点。 本文采用溶剂挥发自组装改进的溶胶-凝胶法,合成有序介孔Ru掺杂的MgO-ZrO2固体碱催化剂。 考察了催化剂中不同Mg物质的量对催化剂孔径、比表面积和表面碱性以及Ru等的结构和性能对催化性能的影响。 对比了催化剂的形貌、表面碱性及Ru组分对催化性能的影响程度。 结果表明,n(Zr)∶n(Mg)=3∶1时,Ru掺杂的MgO-ZrO2固体碱催化剂具有高度有序的介孔结构和高的比表面积。 而n(Zr)∶n(Mg)=1∶1时, MgO-ZrO2固体碱催化剂合成CLA产率较高,反应时间4 h,产率达到85%,催化效率为0.099 g(CLA)·L-1(solvent)·min-1,并且催化产物主要为具有生物活性的3种共轭亚油酸异构体。 催化剂的强碱性位点和晶格Ru是催化异构化反应的两个活性位点,强碱性位点是提高催化性能的关键。 固体碱复合氧化物催化效率高、制备方法简单、反应产物生物活性高等优点,具有较好的应用前景。 相似文献
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Influence of alkali metal doping on surface properties and catalytic activity/selectivity of CaO catalysts in oxidative coupling of methane 下载免费PDF全文
Surface properties (viz. surface area, basicity/base strength distribution, and crystal phases) of alkali metal doped CaO (alkali metal/Ca= 0.1 and 0.4) catalysts and their catalytic activity/selectivity in oxidative coupling of methane (OCM) to higher hydrocarbons at different reaction conditions (viz. temperature, 700 and 750 ℃; CH4/O2 ratio, 4.0 and 8.0 and space velocity, 5140-20550 cm^3 ·g^-1·h^-1) have been investigated. The influence of catalyst calcination temperature on the activity/selectivity has also been investigated. The surface properties (viz. surface area, basicity/base strength distribution) and catalytic activity/selectivity of the alkali metal doped CaO catalysts are strongly influenced by the alkali metal promoter and its concentration in the alkali metal doped CaO catalysts. An addition of alkali metal promoter to CaO results in a large decrease in the surface area but a large increase in the surface basicity (strong basic sites) and the C2+ selectivity and yield of the catalysts in the OCM process. The activity and selectivity are strongly influenced by the catalyst calcination temperature. No direct relationship between surface basicity and catalytic activity/selectivity has been observed. Among the alkali metal doped CaO catalysts, Na-CaO (Na/Ca = 0.1, before calcination) catalyst (calcined at 750 ℃), showed best performance (C2+ selectivity of 68.8% with 24.7% methane conversion), whereas the poorest performance was shown by the Rb-CaO catalyst in the OCM process. 相似文献
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Oxidative coupling of methane over La-promoted CaO catalysts: Influence of precursors and catalyst preparation method 下载免费PDF全文
The oxidative coupling of methane to C2 hydrocarbons has been studied over a series of La-promoted CaO (La/Ca = 0.05) catalysts, prepared using different precursor salts for CaO and La2O3 (viz. acetates, carbonates, nitrates and hydroxides) and catalyst preparation methods (viz. physical mixing of precursors, co-precipitation using ammonium carbonate/sodium carbonate as a precipitating agent), under different reaction conditions (temperature: 700-850℃, CH4/O2 ratio: 4.0 and 8.0, and GHSV: 51360 cm3 g-1 h-1)... 相似文献
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Hydroxyl ionic liquid (HIL) has been explored as a novel support for Baylis-Hillman catalyst. The HIL-supported catalyst showed a better catalytic activity compared to other IL-immobilized catalyst that has no hydroxyl group attached to the IL scaffold. The hydroxyl group linked on IL played an important role in facilitating efficient catalysis under solvent-free conditions. The corresponding Baylis-Hillman and aza-Baylis-Hillman adducts were obtained in good to excellent yields in all cases examined. The HIL-supported quinuclidine can be readily recovered and reused for six times without significant loss of catalytic activity. 相似文献
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Herbert M Montilla F Galindo A Moyano R Pastor A Álvarez E 《Dalton transactions (Cambridge, England : 2003)》2011,40(19):5210-5219
Biphasic catalytic olefin epoxidation systems consisting of oxodiperoxomolybdenum catalysts in 1-n-alkyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) media with aqueous hydrogen peroxide oxidant were optimised by tuning the molecular structure of the IL and employing N-heterocyclic donor base additives to inhibit hydrolysis and enhance the activity of the catalyst. The latter study was only made possible by the solubilising properties of the IL media. Of the bases investigated, pyrazoles were identified as the most efficient additive species and the best results were obtained using 3,5-dimethylpyrazole. Immobilisation of the catalyst in the IL allowed for very efficient catalyst recycling. Finally, the compound [MoO(O(2))(2)(3-Mepz)(2)] (3-Mepz = 3-methylpyrazole) was characterised and its structure determined by X-ray crystallography. 相似文献
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用于NH3选择性催化还原NOx的钒基催化剂 总被引:1,自引:0,他引:1
在富氧且有催化剂存在条件下以NH3或尿素为还原剂选择性地还原NOx为N2的技术,即NH3/Urea-SCR技术,是去除固定源和移动源NOx最为有效且应用最广的技术之一,其中最重要的催化剂体系是钒基催化剂。本文从钒基催化剂的组成及其NH3-SCR反应性能、钒基催化剂的活性改进以及钒基催化剂上的NH3-SCR反应机理三个方面对该领域的研究进展做了较为全面的综述,并对NH3-SCR领域可能的发展方向做了展望。传统的V2O5-WO3(MoO3)/TiO2催化剂以及改性后的钒基催化剂在中温段具有优异的NOx净化效率和抗SO2中毒性能,其中高分散的V5+物种以及多聚的钒酸盐物种为NH3-SCR反应的活性中心。针对采用不同方法制备的或具有不同组成的钒基催化剂体系,多数学者认为NH3-SCR反应按照Eley-Rideal(E-R)机理进行,部分学者认为按照Langmuir-Hinshelwood(L-H)机理进行,这可能与催化剂的钒负载量以及反应温度区间相关。在后续工作中研究者应结合多种测试手段,具体问题具体分析,综合考虑温度的动态影响以及表面酸碱性对反应物的吸附活化,以得出更为全面、真实的反应机理。系统了解前人在钒基NH3-SCR催化剂领域的研究进展有助于现阶段开发高效稳定、可适应复杂工作条件的钒基SCR催化转化器,同时也对设计合成新型高效、环境友好且抗中毒的非钒基SCR催化剂体系具有一定的参考价值。 相似文献
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Ahmed Sadeq Al‐Fatesh Muhammad Awais Naeem Wasim Ullah Khan Ahmed Elhag Abasaeed Anis Hamza Fakeeha 《中国化学会会志》2014,61(4):461-470
Two series of Co and Ni based catalysts supported over commercial (ZrO2, CeO2, and Al2O3) nano supports were investigated for dry reforming of methane. The catalytic activity of both Co and Ni based catalysts were assessed at different reaction temperatures ranging from 500—800 °C; however, for stability the time on stream experiments were conducted at 700 °C for 6 h. Various techniques such as N2 adsorption‐desorption isotherm, temperature‐programmed reduction (H2‐TPR), temperature‐programmed desorption (CO2‐TPD), temperature‐programmed oxidation (TPO), X‐ray diffraction (XRD), thermogravimetric analysis (TGA) were applied for characterization of fresh and spent catalysts. The catalytic activity and stability tests clearly showed that the performance of catalyst is strongly dependent on type of active metal and support. Furthermore, active metal particle size and Lewis basicity are key factors which have significant influence on catalytic performance. The results indicated that Ni supported over nano ZrO2 exhibited highest activity among all tested catalysts due to its unique properties including thermal stability and reducibility. The minimum carbon deposition and thus relatively stable performance was observed in case of Co‐Al catalyst, since this catalyst has shown highest Lewis basicity. 相似文献
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<正>In this article,an efficient,simple and environmentally friendly approach to the synthesis of diacetals(diketals) pentaerythritol using SO_3H-functionalized ionic liquids(ILs) as catalysts was reported.The ILs show high catalytic activity and reusability with good to excellent yields of the desired products.Hammett method has been used to determine the acidity order of these ionic liquids and the results are consistent with the catalytic activities observed in acetalization reaction.Maximum product yield of 93%was observed on using[PSPy][OTf]as catalyst and it can be reused at least 8 times without obvious activity loss. 相似文献