利用固体催化剂制备丙酮缩甘油的工艺研究

以固体酸作为催化剂,以甘油和丙酮为原料合成丙酮缩甘油,考察了反应温度、反应时间、反应物配比、催化剂用量对反应的影响。实验结果表明,甲苯为带水剂,催化剂用量为甘油质量的6%,原料n(甘油)∶n(丙酮)为1∶3,反应时间为6 h,反应的温度为80℃,丙酮缩甘油的产率可达80%。本文采用固体酸作为催化剂,产品易分离且无需除酸,后处理简单。     

β-环糊精/KI催化二氧化碳与环氧化合物偶联反应研究

发展高效、绿色、可降解、无毒的催化剂一直是研究二氧化碳与环氧化合物偶联反应的一个热点。研究了β-环糊精(β-CD)/无机盐体系催化二氧化碳与末端环氧化合物的偶联反应,考察了反应温度、催化剂用量和不同金属盐的影响以及催化剂的循环使用性能。结果表明,在150℃、0.9MPa和催化剂用量4 mol%条件下,以KI为催化剂,β-CD为共催化剂,无需任何溶剂就可以使二氧化碳和环氧化合物发生偶联反应,并以很高的收率得到环碳酸酯。     

对甲苯磺酸铜催化合成邻苯二甲酸二丁酯

以对甲苯磺酸铜作为合成邻苯二甲酸二丁酯的催化剂，考察醇酸物质的量比、催化剂用量和反应时间对酯化率的影响。实验结果表明，其较优条件为邻苯二甲酸酐0.05 mol，醇酸物质的量比=2.0∶1,催化剂用量为原料邻苯二甲酸酐物质的量的1.5%，回流温度下反应2.5 h，在此条件下酯化率可达98.5%。反应后对甲苯磺酸铜经过简单的相分离就可重复使用，无需再生，兼有均相和多相催化剂的优点。     

负载型HSiW/SBA-15催化丙烯酸与环己烯加成酯化的研究

文章采用SBA-15负载硅钨酸作为催化剂,以丙烯酸和环己烯为原料合成丙烯酸环己酯。考察硅钨酸负载量、催化剂用量、反应温度、酸烯摩尔比、阻聚剂用量对酯化的影响。最佳条件为:硅钨酸负载量30%,酸烯摩尔比为3,催化剂用量为酸烯总质量的7%,无需阻聚剂,反应温度95℃,反应时间9 h。在此条件下,环己烯转化率为83.3%,丙烯酸环己烯选择性为96.2%。     

对苯型不饱和聚酯树脂的工业生产

以钛系化合物为催化剂，采用二步法合成对苯型不饱和聚酯树脂。工艺简单，生产周期短，催化剂无需除去且对产品的性能、外观及储存等没有影响。生产成本与邻苯型树脂的生产成本相当，而产品性能优于间苯型和邻苯型不饱和聚酯树脂。     

无毒增塑剂乙酰柠檬酸三丁酯的合成研究

以自制固体酸为催化剂进行酯化反应,通过正交实验得出酯化反应最佳工艺条件为酸醇物质的量比1:4,催化剂用量3%,固载量1:10,反应时间4 h.酰化反应采用廉价易得且后处理简单的催化剂NaHSO4并用正交实验法优选酰化工艺.优化后的工艺条件不仅简单实现了催化剂的重复利用,而且解决了产品的色泽问题,测得乙酰柠檬酸三丁酯折光率为1.442 9,无需脱色即得到了合格产品.     

铂/碳催化剂无溶剂催化加氢制备3,4-二氯苯胺

以3,4-二氯硝基苯为原料,采用铂/碳催化剂进行催化加氢制备3,4-二氯苯胺,过程中无需添加水或有机溶剂,分别考察催化剂种类、反应时间、反应温度和反应压力对加氢反应的影响。结果表明,1%铂/碳催化剂具有较好的催化活性和选择性,最优反应条件为:反应温度80℃、反应压力1.0 MPa,反应时间180 min,在此条件下,加氢转化率达100%,产品收率超过95%,产品纯度大于99.5%,且催化剂重复使用15次后活性稳定。     

实验条件对活性炭基固体酸催化剂制备的影响

以煤基商品活性炭为载体,通过苯磺酸重氮盐还原反应制备活性炭基固体酸催化剂。系统考察了重氮盐制备方法,无水乙醇、蒸馏水、次磷酸的用量等实验条件对炭基固体酸催化剂磺酸密度以及催化活性的影响。研究得到的最优实验条件是,苯磺酸重氮盐无需抽滤处理,重氮盐制备反应时间为45 min、无水乙醇用量为50 mL、不加蒸馏水、次磷酸用量300 mL,该条件下得到的炭催化剂磺酸密度达到1.46 mmol/g,超过目前催化剂磺酸密度的2倍,其对乙酸酯化反应的催化性能比未优化时提高了38%。     

香料1,5-二硫杂螺[5,5]十一烷的合成

以环己酮和1,3-丙二硫醇为原料,TiSiW12O40/TiO2作催化剂,合成了一种新型香料化合物1,5-二硫杂螺[5,5]十一烷,并用元素分析、IR、1HNMR对其结构进行表征。结果表明,n(环己酮)∶n(1,3-丙二硫醇)=1.0∶1.2,催化剂用量约为环己酮质量的4%,反应3 h,目标产物的收率为86.5%。催化剂无需处理可直接重复使用8次以上。     

固体超强酸S2O2-8/TiO2的溶胶-凝胶法制备与表征

以钛酸四丁酯、无水乙醇、冰醋酸和过硫酸铵等为原料,采用溶胶-凝胶法制得前驱体,再经500℃焙烧得到固体超强酸S2O2-8/TiO2催化剂,采用XRD、IR和Hammett指示剂法对其进行表征,结果显示催化剂样品为超强酸,酸强度Ho<-14.52.以乙酸乙酯合成反应为模型反应考察其催化活性和稳定性.结果表明,催化剂有较高的活性,当反应条件为醇酸体积比1.5:1、催化剂0.6 g和反应时间3.0 h时,乙酸转化率可达73.09%(不加分水器).催化剂稳定性较好,活性下降缓慢,可在无需任何再生的条件下重复使用.重复使用5次后,乙酸转化率仍然达55.13%.     

A highly efficient polymer‐anchored palladium(II) complex catalyst for hydrogenation,Heck cross‐coupling and cyanation reactions

BACKGROUND: Precise architectures of steric and electronic properties of palladium species play a crucial role in designing highly functionalized catalyst systems responsible for target organic transformations. Pd catalysts supported on polymer materials have been employed extensively as catalysts not only for hydrogenation but also for coupling reactions in the production of fine chemicals. RESULTS: A new polymer‐anchored Pd(II) complex has been synthesized and characterized. The catalyst shows high catalytic activity in the hydrogenation of styrene oxide, Heck cross‐coupling and cyanation reactions of aryl halides. The effect of various reaction parameters were investigated to optimize reaction conditions. The catalytic system shows good activity in the hydrogenation of styrene oxide (conversion 98%) with a selectivity to 2‐phenylethanol (93%) which is higher than its homogeneous analogues. The catalyst also exhibits excellent catalytic activity for the Heck cross‐coupling and cyanation reactions of various substituted and non‐substituted aryl halides. CONCLUSIONS: Results demonstrate that the catalyst is robust and stable and can be recovered quantitatively by simple filtration and reused several times without loss of activity. Copyright © 2010 Society of Chemical Industry     

CATALYST PRODUCT SEPARATION TECHNIQUES IN HECK REACTION

The Heck reaction finds several applications in industry because it is one of the effective tools for the formation of a new C─C bond. In addition to the catalytic activity and selectivity, catalyst-product separation strategies are very important for the industrial application. There are various methods of interest ranging from conventional heterogeneous catalysts to heterogenization of homogeneous catalysts. The heterogeneous catalysts are classified into supported metal catalysts, zeolite-encapsulated catalysts, colloids-nanoparticles, and intercalated metal compounds. The homogeneous metal complexes catalysts are heterogenized using modified silica catalysts, polymer-supported catalysts, biphasic catalysts, supported liquid-phase catalysts, nonionic liquids solvents, perfluorinated solvents, and reusable homogeneous complexes. In general, heterogeneous catalysts are effective and stable at higher temperatures, which may be important for the activation of less reactive but less expensive chloroaryls substrates. However, the heterogeneous catalysts have a major drawback of poor selectivity toward Heck coupling products. The heterogenized metal complexes catalysts operate under relatively mild conditions as compared with heterogeneous catalysts, and so they can be applied to the production of pharmaceuticals and fine chemicals. Catalysis using supercritical solvents with catalyst separation techniques is promising for the development of green chemistry processes. Although the concepts described in this article have been reviewed mainly for Heck reactions, they should be applicable to a wide range of other chemical transformations (hydrogenation, carbonylation, hydroformylation, and so on) that, currently, are homogeneously catalyzed reactions.     

The Clicked Pyridyl‐Triazole Ligand: From Homogeneous to Robust,Recyclable Heterogeneous Mono‐ and Polymetallic Palladium Catalysts for Efficient Suzuki–Miyaura,Sonogashira, and Heck Reactions

Various mono‐ and polymetallic palladium complexes containing a 2‐pyridyl‐1,2,3‐triazole (pyta) ligand or a nonabranch‐derived (nonapyta) ligand have been synthesized by reaction of palladium acetate with these ligands according to a 1:1 metal‐ligand stoichiometry and used as catalysts for carbon‐carbon cross‐coupling including the Suzuki–Miyaura, Sonogashira and Heck reactions. The unsubstituted monopalladium and nonapalladium complexes were insoluble in all the reaction media, whereas tri‐ and tetranuclar palladium complexes were soluble, which allowed conducting catalysis under either homogeneous or heterogeneous conditions. The organopalladium complexes were characterized by standard analytical and spectroscopic methods and by thermogravimetry showing decomposition above 110 °C. Both types of catalysts showed excellent activity for these cross carbon‐carbon bond formations involving aryl halides including activated aryl chlorides or acyl chloride. Besides the comparison between homogeneous and heterogeneous catalysis, the key feature of these catalysts is their remarkable robustness that allowed recycling at least ten times in the example of the Heck reaction with excellent yields and without significant reduction of the conversion.     

Carbon dioxide pressure induced heterogeneous and homogeneous Heck and Sonogashira coupling reactions using fluorinated palladium complex catalysts

The Heck reaction of iodobenzene and methyl acrylate was investigated with CO₂-philic Pd complex catalysts having fluorous ponytails and the organic base triethylamine (Et₃N) in the presence of CO₂ under solventless conditions at 80 °C. The catalysts are not soluble in the organic phase in the absence of CO₂ and the reaction occurs in a solid-liquid biphasic system. When the organic liquid mixture is pressurized by CO₂, CO₂ is dissolved into the organic phase and this promotes the dissolution of the Pd complex catalysts. As a result, the Heck reaction occurs homogeneously in the organic phase, which enhances the rate of reaction. This positive effect of CO₂ pressurization competes with the negative effect that the reacting species are diluted by an increasing amount of CO₂ molecules dissolved. Thus, the maximum conversion appears at a CO₂ pressure of around 4 MPa under the present reaction conditions. The catalysts are separated in the solid granules by depressurization and are recyclable without loss of activity after washing with n-hexane and/or water. When the washing is made with hexane alone, the catalytic activity tends to increase on the repeated Heck reactions, probably due to the accumulation of such a base adduct as Et₃NHI on the catalysts. When the washing is further made with water, however, the base adduct is taken off from the catalysts and they show similar activity levels in the repeated runs. The potential of CO₂ pressure tunable heterogeneous/homogeneous reaction system has also been investigated for Sonogashira reactions of iodobenzene and phenylacetylene under similar conditions.     

Suzuki‐ and Heck‐Type Cross‐Coupling with Palladium Nanoparticles Immobilized on Spherical Polyelectrolyte Brushes

We report on a systematic study of the use of palladium nanoparticles immobilized on spherical polyelectrolyte brushes – Pd@SPB – for Heck‐ and Suzuki‐type coupling reactions. The spherical polyelectrolyte brush particles serving as carriers for the palladium nanoparticles consist of a solid polystyrene core with a radius of 46 nm onto which long chains of cationic polyelectrolytes are grafted. The palladium nanoparticles have directly been generated within this brush layer and the stabilization of the nanoparticles is effected by the colloidal carriers, no further surface stabilization is necessary. We demonstrate that these composite particles present robust catalysts for the Heck‐ and Suzuki‐type coupling reactions. This was shown by carrying out the Suzuki‐ and Heck‐type coupling reactions at relatively low temperatures (Suzuki reaction: 50 °C, Heck reaction: 70 °C). We demonstrate that the catalytic composite particles are not changed by these reaction conditions and retain their full activity for at least four runs. The yields obtained for both reactions are good to excellent. The mild operation conditions of the palladium nanoparticles are traced back to the absence of surface stabilization. Further mechanistic implications are discussed.     

Pd/C embedded crosslinked polystyrene fibers as an efficient catalyst for Heck reactions

Pd/C embedded polystyrene fibers were successfully prepared by electrospinning. The polystyrene molecules were then cross-linked by paraformaldehyde in sulfuric acid to improve the solvent resistance of composite fibers. SEM images conformed the preparation of uniform and smooth composite fibers. FT-IR spectra demonstrated that the polystyrene molecules inside fibers have been sulphonated and crosslinked. Heck reactions were used to evaluate the catalytic performance of these novel composite fibers. The catalysis results show that this composite fiber mat catalyzed Heck reactions could be evidently promoted by using preferred reducing alcohol agent and solvent. Under the optimized reaction conditions, this composite fiber mat could effectively catalyze the Heck reactions of aromatic iodides with n-butyl acrylate to afford the products with satisfied yields. Especially, compared with the particulate Pd/C catalyst, the separation and recycling of this fibrous catalyst from the reaction mixture were significantly improved due to the larger fibrous structure. At last, this fiber catalyst was successfully reused for eight times with little loss of initial catalytic activity, which was even better than the pristine Pd/C catalyst. Hence, embedment of particulate supported metal catalysts inside the crosslinked polystyrene fibers can effectively improve their catalytic performance and handiness.     

Oxidative Heck Coupling Using Pd(II) Supported on Organosilane-Functionalized Silica Mesocellular Foam

Oxidative Heck couplings of arylboronic acids and olefins are carried out under air to facilitate reoxidation of palladium without the need for an added co-oxidant using Pd(II) supported on silica surface-tethered bipyridyl, iminopyridine, or 3-aminopropyl ligands. Use of silica-supported iminopyridine or bipyridine ligands gives active catalysts, with the bipyridine-based catalyst being most efficient. The Heck products are formed with high yields and selectivities over the 1,4-addition product, and the silica supported bipyridine-based catalyst is easily recovered via simple filtration. Unlike similar supported catalysts in traditional Heck reactions involving aryl halides and olefins, the catalysts presented here can be used for multiple catalytic cycles without activity or selectivity loss.     

氯代芳烃偶联反应中钯催化剂的研究进展

在合适的钯催化作用下,可将廉价易得、低活性的氯代芳烃应用于C—C键和C杂键形成的偶联反应。对偶联反应用钯催化剂的研究进行了综述。通过选择合适的配体,钯催化剂可有效地催化带有多种体取代基的氯代芳烃或氯代杂芳烃,发生Suzuki、Negishi、Stille和Heck等多种偶联反应,获得较高的收率和很高的选择性。     

Development of Efficient and Reusable Diarylphosphinopolystyrene‐Supported Palladium Catalysts for C?C Bond Forming Cross‐Coupling Reactions

Short and versatile syntheses of reusable diarylphosphinopolystyrene‐supported palladium catalysts 3a – j are described. The bis(o‐tolyl)phosphino catalyst 3b is particularly efficient for the Suzuki and Sonogashira cross‐couplings, whereas the bis(m‐tolyl)phosphino catalyst 3c is the most active catalyst for Heck reactions. The couplings are performed under non‐anhydrous reaction conditions and require only low amounts of supported palladium (0.5 mequivs. for Suzuki–Miyaura, 1.0 mequiv. for Sonogashira and 0.5 mequivs. for Heck reactions could be sufficient). Catalysts 3a–j are recovered by filtration and can be reused more than four times with no loss of efficiency.     

Heck Cross‐Coupling of Aryldiazonium Tetrafluoroborate with Acrylates Catalyzed by Palladium on Charcoal

A property‐activity relationship study of various palladium supported on charcoal (Pd/C) catalysts has been undertaken for the Heck reaction of aryldiazonium tetrafluoroborate with acrylates. The optimized protocol enables the cross‐coupling with a low loading of palladium at room temperature in technical grade methanol. Although the catalyst could not be recycled at this time, measurement of the palladium content by inductively coupled plasma mass spectrometry (ICP‐MS) shows low palladium contamination of the solvent and product, rendering this method safer for the environment compared to homogeneous conditions.