Factorial design evaluation of the Suzuki cross-coupling reaction using a magnetically recoverable palladium catalyst

A magnetically recoverable catalyst [Fe₃O₄@SiO₂-AEAPTMS-Pd(II)] was prepared, fully characterized and had its catalytic activity evaluated on the Suzuki cross-coupling reaction under microwave irradiation. The reaction conditions for the synthesis of biaryl compounds was optimized in two stages - an initial fractional design 2⁴, in which the parameters reaction time, temperature, solvent and catalyst loading were evaluated, followed by a Doehlert design. The factorial design proved to be a viable approach for obtaining the optimal reaction conditions based on a relatively small number of experiments. Additionally, the biaryl derivatives synthesized by this method were obtained with good to excellent yields (71–96%) and the recovery and reuse of the palladium catalyst was also evaluated.     

Evaluation of Fe and Ru Pincer‐Type Complexes as Catalysts for the Racemization of Secondary Benzylic Alcohols

Fe and Ru pincer‐type catalysts are used for the racemization of benzylic alcohols. Racemization with the Fe catalyst was achieved within 30 minutes under mild reaction conditions, with a catalyst loading as low as 2 mol %. This reaction constitutes the first example of an iron‐catalyzed racemization of an alcohol. The efficiency for racemization of the Fe catalyst and its Ru analogue was evaluated for a wide range of sec‐benzylic alcohols. The commercially available Ru complex proved to be highly robust and even tolerated the presence of water in the reaction mixture.     

Reaction kinetics of carbon dioxide with glycidyl methacrylate using immobilized trioctylamine supported on poly(styrene-CO-vinylbenzyl chloride) as a catalyst

A soluble polymer-supprted catalyst containing pendant trioctylammonium chloride was synthesized by the radical copolymerization of p-chloromethylated styrene with styrene followed by the addition reaction of the resulting copolymer with trioctylamine. Absorption rate of carbon dioxide into glycidyl methacrylate (GMA) solutions containing the catalyst was measured using a semi-batch stirred tank with a plane gas-liquid interface at 101.3 kPa. The reaction kinetics of the reaction between carbon dioxide and GMA was evaluated using the absorption rate and the mass transfer mechanism of carbon dioxide. Solvents such as toluene, N-methyl-2-pyrrolidinone, and dimethyl sulfoxide influenced the reaction rate constants. Furthermore, this catalyst was compared to the monomeric tetraoctylammonium chloride under the same reaction conditions.     

Piperidine‐functionalized silica: an efficient and environmentally benign catalyst for Claisen–Schmidt condensation

Piperidine‐functionalized silica as a basic heterogeneous catalyst was synthesized via a simple protocol by condensing silica chloride with piperidine. The catalyst was characterized with various techniques (FT‐IR, solid state NMR, scanning electron microscopy, energy‐dispersive X‐ray, thermogravimetric, elemental, and NH₃ and CO₂ temperature‐programmed desorption analyses). Surface area was also evaluated through Brunauer–Emmett–Teller analysis. Its catalytic activity was evaluated for Claisen–Schmidt condensation under solvent‐free conditions. The catalyst was easily recovered and reused up to five cycles without considerable loss of activity and was not deactivated due to amide formation. Also, this method has attractive advantages such as short reaction time, mild reaction conditions, good to excellent yield of products, easy handling of the catalyst and simple operational procedure. Copyright © 2014 John Wiley & Sons, Ltd.     

Cu/ZnO@H-β-P催化剂在合成气制备液化石油气反应中的性能研究

采用共沉淀法制备Cu/ZnO催化剂、水热合成法制备H-β分子筛、通过物理包膜法制备了具有核壳结构的Cu/ZnO@H-β-P催化剂,并用于合成气制备液化石油气(LPG)反应。通过XRD、NH3-TPD、BET和SEM-EDS等手段对催化剂进行了表征,利用固定床连续反应装置对催化剂进行了活性评价。结果表明,Cu/ZnO@H-β-P催化剂是具有中孔的核壳结构材料,其协同作用打破了原有的热力学平衡,促进了甲醇→DME→LPG串联反应的连续进行。与物理混合的Mix-Cu/ZnO-H-β催化剂相比,Cu/ZnO@H-β-P催化剂的CO转化率和LPG选择性更高,空速和反应温度对催化剂活性影响明显,最佳空速和反应温度分别为2 400 h~(-1)和350℃。使用Cu/ZnO@H-β-P催化剂在最佳条件下进行合成气制备LPG反应,CO转化率达到了57.22%,LPG选择性达到了60.52%。     

Homogeneous and supported copper(II) acetate as catalyst for CO coupling reactions

The reactivity of copper(II) acetate as catalyst in a standard CO coupling reaction has been systematically evaluated. Optimization of the reaction conditions resulted in a protocol involving stoichiometric amounts of reagents, a substoichiometric amount of base and 20 mol% catalyst, at 50 °C in 1,2-dichloroethane and under 1 atm O₂. Next, the reactivity of polymer-supported copper(II) acetate was evaluated. Although it is found that, in contrast to previous results obtained in related CN coupling reactions, the polymer-supported catalyst is in this case less efficient than the corresponding homogeneous one, the catalyst turns out to be conveniently recovered from the reaction mixture by simple filtration.     

Efficient catalyst turnover in the phosphitylation of alcohols with phosphoramidites

We report a method for catalytic phosphitylation utilizing phosphoramidites. Traditionally, this reaction is inefficient unless an excess of catalyst is present due to catalyst deactivation by an amine by-product. Isocyanate additives have been evaluated for scavenging the amine to facilitate catalyst turnover. A variety of alcohols and phosphoramidites were screened with 5 mol % catalyst. In the presence of additive, 83-97% conversion was achieved in contrast to 7-31% conversion without additive.     

Silica–acetylacetone‐supported palladium nanoparticles as an efficient and reusable catalyst in the Heck–Mizoroki C–C cross‐coupling reaction

The preparation of palladium nanoparticles supported on acetylacetone‐modified silica gel and their catalytic application for Heck olefination of aryl halides were investigated. The catalyst was characterized using X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission and scanning electron microscopies. The supported palladium nanoparticles are demonstrated to be a highly active and reusable catalyst for the Heck reaction. Several reaction parameters, including type and amount of solvent and base, were evaluated. The heterogeneity of the catalytic system was investigated with results indicating that there is a slight palladium leaching into the reaction solution under the applied reaction conditions. Despite this metal leaching, the catalyst can be reused nine times without significant loss of catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Cure kinetics of biphenyl epoxy‐phenol novolac resin system using triphenylphosphine as catalyst

The effects of the concentration of triphenylphosphine as a catalyst on the cure reaction of the biphenyl epoxy/phenol novolac resin system were studied. The kinetic study was carried out by means of the analysis of isothermal experiments using a differential scanning calorimeter. All kinetic parameters including the reaction orders, activation energy and kinetic rate constants were evaluated. To describe the cure reaction with the catalyst concentration, the normalized kinetic model was developed. The suggested kinetic model with a diffusion term was successfully able to describe and predict the cure reaction of epoxy resin compositions as functions of the catalyst content and temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 713–720, 1999     

Efficient cenosphere supported catalyst for the esterification of n-octanol with acetic acid

An efficient heterogeneous acid catalyst was developed using cenospheres, a byproduct of coal-fired thermal power plants by the method of wet impregnation. Catalyst characterization was carried out using various analytical techniques, namely, Fourier transform infrared, X-ray diffraction, field emission gun scanning electron microscopy and Brunauer–Emmett–Teller surface area and surface acidity analysis. The characterization revealed the excellent catalytic activity of the catalyst for the esterification reaction of n-octanol and acetic acid. Various reaction parameters, namely, catalyst loading, a molar ratio of alcohol/acid and reaction temperature were evaluated and optimized by response surface methodology using the Box–Behnken model. The response surface methodology model equations corresponding to the conversion of acid and % yield of ester were developed. The model well predicted the optimal reaction conditions, which were validated experimentally with good agreement. The excellent catalytic performance was observed in the esterification reaction with high conversion of acid (95.34%) and high yield of n-octyl acetate (94.81%). Reusability study of the catalyst showed that the catalyst could be used efficiently up to three reaction cycles. This study explores the use of cenospheres to prepare a solid acid catalyst for the industrially important esterification reactions.     

壳聚糖负载L-脯氨酸对水中不对称Aldol反应的催化性能

以壳聚糖为载体制备了负载型L-脯氨酸不对称催化剂;将合成产物用于催化丙酮与取代苯甲醛在水中的直接不对称Aldol反应,考察了其催化性能.结果表明,与在有机溶剂中的L-脯氨酸催化剂相比,在水相中的壳聚糖负载L-脯氨酸催化剂表现出更好的催化活性;就间硝基苯甲醛与丙酮在水中的不对称Aldol反应而言,壳聚糖负载L-脯氨酸催化下的产率和ee值分别达95%和48%.此外,壳聚糖负载L-脯氨酸催化剂在水中具有很好的重复使用性能,重复使用10次后相应的产率和ee值分别为88%和68%.     

Synthesis of melamine-formaldehyde resin functionalised with sulphonic groups and its catalytic activities

Spherical melamine-formaldehyde resin (MFR) particles were synthesised using the condensation reaction of melamine and formaldehyde with PEG-2000 as an additive. After thermal treatment at 200°C and then sulphonation by chlorosulphuric acid, an MFR-supported strong acid catalyst (SMFR) was prepared with an acidity of 3.23 mmol g^?1. This new acid catalyst was evaluated in the reactions of esterification and acetalisation, with the results indicating that this novel acid catalyst was highly efficient in the traditional acid-catalysed reaction. Its high activity, stability and reusability give it great potential for “green” chemical processes.     

PC/EAA共混体系在加工过程中的反应

采用差示扫描量热法(DSC)和核磁共振氢谱法(1H-NMR)研究了不同聚碳酸酯(PC)/乙烯-丙烯酸共聚物(EAA)共混体系在加工过程中的大分子反应,考察了有机金属催化剂二丁基锡DBTO)含量和反应时间对体系的影响.采用哈克(Haake)转矩流变仪的混合器作反应釜,索氏抽提器分离产物.结果表明,PC和EAA在加工中反应剧烈,在共混体系的界面原位形成接枝或交联的PC-EAA共聚物,随催化剂用量增大、反应时间延长易生成共交联的PC-EAA共聚物.但混合时间过长,体系的断链反应会加剧,生成产物不稳定.     

Esterification reaction kinetics of acetic acid and n-pentanol catalyzed by sulfated zirconia

This study reports experimental data and kinetic modeling of acetic acid esterification with n-pentanol using sulfated zirconia as a catalyst. Reactions were carried out in an isothermal well-mixed batch reactor at different temperatures (50-80°C), n-pentanol to acid molar ratios (1:1-3:1), and catalyst loadings (5-10 wt% in relation to the total amount of acetic acid). The reaction mechanism regarding the heterogeneous catalysis was evaluated considering pseudo-homogeneous, Eley–Rideal, and Langmuir–Hinshelwood model approaches. The reaction mixture was considered a nonideal solution and the UNIQUAC thermodynamic model was used to take into account the nonidealities in the liquid phase. The results obtained indicated that increases in the temperature and catalyst loading increased the product formation, while changes in the n-pentanol to acetic acid molar ratio showed no significant effect. The estimated enthalpy of the reaction was −8.49 kJ mol⁻¹, suggesting a slightly exothermic reaction. The Eley–Rideal model, with acetic acid adsorbed on the catalyst as the limiting step, was found to be the most significant reaction mechanism.     

Silica-supported vanadium oxide nanoparticles as efficient heterogeneous catalyst for hydrolysis of sucrose

The reaction kinetics of the hydrolysis of sucrose by solid catalysts was investigated using polarimetry. In this research work the V₂O₅/SiO₂ was selected as appropriate catalyst. This catalyst was prepared by impregnation method. At the optimizing conditions the activation parameters have been evaluated using the Arrhenius and Eyring plots. The structure and particle size of catalyst has been studied with the use of XRD.     

Palladium tetrazole–supported complex as an efficient catalyst for the Heck reaction

Abstract  

A tetrazole-supported polymeric ligand has been synthesized. The palladium complex derived from the polymeric material has been evaluated as a catalyst for the Heck reaction of aryl iodides and bromides with styrene to provide the corresponding products in high yields. The reaction proceeded smoothly in the presence of 1 mol% with respect to Pd of catalyst in DMF at 125 or 140 °C within 1–3 h. Recycling studies showed that the catalyst can be readily recovered and reused for several times without significant loss of catalytic activity.     

热处理及反应介质对Cu-Zn-Al催化剂的结构及CO加氢催化性能的影响

催化剂的形成和使用环境对催化剂的结构和性能会产生重要的影响。本文采用完全液相法,以PEG-400和液体石蜡分别作为热处理介质制备Cu-Zn-Al催化剂,用X射线粉末衍射、H2程序升温还原、N2吸附、X射线光电子能谱对其进行表征,考察热处理介质对催化剂结构的影响;以相应的热处理介质作为浆态床反应介质,考察介质对CO加氢催化反应性能的影响。结果表明,PEG-400作为热处理介质有助于提高催化剂的比表面积、ZnO的分散度和表面铜含量,催化剂中存在难还原的Cu ,有利于形成Cu -Cu0之间的协同作用;在反应过程中,PEG-400作为反应介质可以抑制铜晶粒的长大,有利于乙醇的生成及C5烃选择性的提高,但催化剂的结构和表面组成会发生较大的变化。     

Synthesis of hexamethylene-1,6-dicarbamate by methoxycarbonylation of 1,6-hexamethylene diamine with dimethyl carbonate over bulk and hybrid heteropoly acid catalyst

Synthesis of HDC by methoxycarbonylation of HDA with DMC was carried out over the bulk and hybrid heteropoly acid (HPA) catalyst. The catalysts were systematically characterized by XRD, FTIR, SEM and NH₃-TPD techniques. The by-products produced in the reaction were identified and a possible reaction pathway was proposed based on the by-products analysis. The performances of bulk and hybrid HPA catalysts were evaluated. The H₄[SiW₁₂O₄₀] catalyst revealed high performance compared with other catalysts and its high performance was attributed to its acidic properties. Effects of reaction parameters and reusability of the H₄[SiW₁₂O₄₀] catalyst were also investigated. Under the optimized reaction conditions, HDA conversion reached 93.2% with 64.8% HDC selectivity and only 3.8% by-product selectivity. Moreover, a possible reaction mechanism was proposed for the synthesis of HDC over H₄[SiW₁₂O₄₀] catalyst.     

Immobilized Pd nanoparticles on Tris-modified SiO2：Synthesis,characterization, and catalytic activity in Heck cross-coupling reactions

The preparation of supported Pd nanoparticles on Tris (tris(hydroxymethyl)aminomethane)- modified SiO₂ gel and their catalytic application in Heck coupling are investigated. The catalyst was characterized using a combination of X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy. The supported Pd nanoparticles were found to be a highly active and reusable catalyst for the Heck reaction at a low Pd loading (0.02 mol%) because of stabilization by the Tris moieties. Several reaction parameters, including the type and amount of solvent, base, and temperature, were evaluated. The heterogeneity of the catalytic system was investigated using different approaches, and showed that slight Pd leaching into the reaction solution occurred under the reaction conditions. Despite this metal leaching, the catalyst can be reused seven times without significant loss of its activity.     

Bi2O3/FAp,a sustainable catalyst for synthesis of dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives through green strategy

The bismuth loaded on fluorapatite (Bi₂O₃/FAp) proved to be an excellent catalyst for the synthesis of novel dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives via a three-component reaction involving the mixture of 1H-1,2,4-triazol-5-amine, ethyl cyanoacetate or ethyl acetoacetate, and different benzaldehydes in ethanol at room temperature. The catalyst material was characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The efficacy of Bi₂O₃/FAp as a heterogeneous catalyst was evaluated with the loading of different wt% of bismuth on FAp. The 2.5% bismuth on FAp performed extremely well as a catalyst with a high yield of products (92%–96%) in a short reaction time (25–35 min). The catalyst was recovered by simple filtration. It showed undiminished activity up to five runs. Simple work-up, room temperature reaction, short reaction time, high yields, no column chromatography, and good reusability of catalyst are the merits of the proposed protocol. In addition, this process offers 100% carbon efficiency and 98% atom economy with noteworthy fiscal and environmental benefits.