固体超强酸催化合成富马酸二甲酯的研究

研究了以ZrO2／SO42-固体超强酸催化富马酸和甲醇合成富马酸二甲酯的反应，表征了催化剂的物化性质，探讨了催化剂制备条件、原料配比、反应时间、催化剂用量等工艺参数对收率的影响。催化剂的重复使用实验表明：ZrO2／SO42-是富马酸二甲酯合成的较适宜的催化剂。     

多元醇修饰Pd-氮杂环卡宾复合物的制备及其对Suzuki-Miyaura反应的催化行为

提高催化剂在反应体系中的分散性,是有效提高催化剂活性的重要手段。本文利用Ullmann反应在大位阻氮杂环卡宾配体(NHC配体)上修饰丙三醇基团,以此来提高催化剂的分散性,进而促进其催化效率的提升。并通过这种大位阻NHC配体与乙酰丙酮钯的络合反应,制备高活性的钯复合物催化剂,进一步以Suzuki-Miyaura偶联反应为模型反应,评价该催化剂的活性与稳定性。结果表明,该催化剂在多种溶剂中表现出较好的分散性,针对溴苯甲醚和苯硼酸的偶联反应,在不同催化条件下,均表现出良好的催化活性,其中转化数(TON)值最高可达到99000。而且该催化剂针对溴苯与苯硼酸的反应体系中,具有广泛的反应底物适用性。与传统的四-(三苯基膦)钯相比较,该催化剂在空气气氛中仍可保持高效的催化行为,表现出较好的稳定性。     

A Dynamic Kinetic Model for Methanol to Light Olefins Reactions over a Nanohierarchical SAPO‐34 Catalyst: Catalyst Synthesis,Model Presentation,and Validation at the Bench Scale

This study includes three main parts: synthesizing the hierarchical silicoaluminophosphate (SAPO‐34) catalyst, evaluating the performance of this modified catalyst in the methanol to light olefins (MTO) process, and providing a new dynamic kinetic model for the modified catalyst. At first, a carbon nanotube (CNT) was used as a mesopore template in the sonochemical synthesis of SAPO‐34 hierarchical catalyst. By comparing the performance of this hierarchical catalyst and the common catalyst in the MTO process, it is observed that better performance is obtained on a modified catalysts for a longer period of time. Then, nine process tests were performed in differential fixed bed reactors at different temperatures and space velocities to obtain the kinetic model of the desired catalyst in the MTO process. Finally, the dynamic kinetic model of the modified SAPO‐34 catalyst was considered for main reactions in the MTO process. In this model, the rate equations were assumed elementary and lumped, and the decreasing of the catalyst activity over time on stream was also considered. The reactions constant and catalyst activity coefficient for different reactions were obtained by simultaneous connection of the code related to the reactor model and the genetic algorithm and genetic programming codes. The results obtained from the kinetic model were consistent with the experimental results.     

Dry Reforming of Methane Over Cobalt Catalysts: A Literature Review of Catalyst Development

Dry reforming of methane produces syngas with desirable H₂/CO ratio. Besides noble metal catalysts, the cobalt catalyst performs good activity in this reaction. However, carbon deposition and catalyst deactivation are becoming the main problems inhibiting the scale up of this process into industrial application. Recently, many scientists were trying to increase the activity as well as the stability toward coking by using variants of support, promoter, and combination of metal series catalyst. This paper presents a recent technology of methane dry reforming over cobalt metal-base catalyst, covering the catalyst activity and their resistance of catalyst deactivation.     

Current understanding of catalyst/ionomer interfacial structure and phenomena affecting the oxygen reduction reaction in cathode catalyst layers of proton exchange membrane fuel cells

To improve the performance of membrane electrode assemblies used in proton exchange membrane fuel cells, a better understanding is necessitated regarding the nano/microstructure of the catalyst layer and the physicochemical phenomena responsible for the oxygen reduction reaction (ORR) occurring on this layer. In particular, it is very important to understand catalyst/ionomer interfaces in the cathode catalyst layer to apply the advanced ORR catalysts to the cathode catalyst layer in membrane electrode assemblies, which have solid-phase electrolytes; these catalysts are primarily developed under liquid electrolyte conditions. A closer observation of the catalyst/ionomer interfacial structure shows that all the transport processes required for ORR are controlled by the ionomer thin film covering the catalyst. Therefore, this review addresses this issue and introduces recent studies on catalyst/ionomer interfaces. We discuss the current understanding of the structure of the catalyst/ionomer interface, which depends on the surface characteristics of the catalyst and the ionomer, as well as transport of water, ions, and gas; these factors are in turn dependent on the structure of the interface. In addition, we introduce research efforts for improving the properties of catalyst inks, which form the basis for controlling the catalyst/ionomer interfacial structure. Based on the findings of these studies, we propose further opportunities and challenges in the study of catalyst/ionomer interfaces.     

In situ Generated Ruthenium Catalyst Systems Bearing Diverse N‐Heterocyclic Carbene Precursors for Atom‐Economic Amide Synthesis from Alcohols and Amines

The transition‐metal‐catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom‐economic process. Among various catalyst systems, in situ generated N‐heterocyclic carbene (NHC)‐based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron‐deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR‐scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=?7.8 ppm in the ¹H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system.     

Zirconyl chloride: an efficient recyclable catalyst for synthesis of 5-aryl-2-oxazolidinones from aziridines and CO2 under solvent-free conditions

Zirconyl chloride was found to be an efficient catalyst for the cycloaddition reaction of aziridines with CO₂, thus leading to the preferential formation of 5-aryl-2-oxazolidinones under solvent-free conditions. The methodology could be extended to various substituted aziridines with high conversion and chemo-, regio-, and stereoselectivity. Furthermore, the catalyst could be reused over five times without significant loss in activity. Interestingly, the recovered catalyst showed higher activity in comparison with the fresh catalyst, presumably due to its morphological variation. The use of this cheap and moisture stable catalyst make this protocol practical, environmentally benign, and economically attractive.     

Chitosan‐Silica Sulfate Nano Hybrid as a Novel and Highly Proficient Heterogeneous Nano Catalyst for Regioselective Ring Opening of Epoxides via Carboxylic Acids

The synthesis and characterization of chitosan‐silica sulfate nano hybrid (CSSNH ) as a novel and efficient heterogeneous nano catalyst involving acid‐base bifunctional activity is described. The catalytic potency and activity of this eco‐friendly catalyst was investigated in regioselective ring opening of epoxides with carboxylic acids to access structurally diverse 1,2‐diol mono‐esters in good to excellent yields. CSSNH catalyst was characterized using different microscopic and spectroscopic techniques encompassing scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption isotherm, and Fourier transform infrared spectroscopy. The green nature, cheapness, efficiency, ease of preparation, handling and reusability of this new catalyst makes this catalyst to be useful for green industrial processes.     

Lacunary Keggin Polyoxotungstate as Reaction-controlled Phase-transfer Catalyst for Catalytic Epoxidation of Olefins

A new reaction-controlled phase-transfer catalyst system, lacunary Keggin polyoxotungstate [C7H7N(CH3)3]9PW9O34 has been synthesized and used for catalytic epoxidation of olefins with H2O2 as the oxidant. Infrared spectra were used to analyze the behavior of the phase transfer of catalyst. In this system, the catalyst not only can act as homogeneous catalyst but also as heterogeneous catalyst to be easily filtered and reused. The epoxidarion reaction is clean and exhibits high conversion and selectivity as well as excellent catalyst stability.     

燃料电池中氢电极催化剂的研究

燃料电池是借助于电池内的燃烧反应，将化学能直接转为电能的装置，是一种新型的高效化学电源，是除火力、水力、核能之外的第四种发电方式。对燃料电池，性能良好的催化剂至关重要，它决定着大电流密度放电时的电池性能、运行寿命和成本。燃料电池的催化剂应该满足以下条...     

MEA with double-layered catalyst cathode to mitigate methanol crossover in DMFC

Methanol permeation is one of the key problems for direct methanol fuel cell (DMFC) applications. It is necessary to change the structure of the cathode of membrane electrode assembly (MEA). Therefore, a novel MEA with double-layered catalyst cathode was prepared in this paper. The double-layered catalyst consists of PtRu black as inner catalyst layer and Pt black as outer catalyst layer. The inner catalyst layer is prepared for oxidation of the methanol permeated from anode. The results indicate that this double-layered catalyst reduced the effects of methanol crossover and assimilated mixed potential losses. The performance of MEA with double-layered catalyst cathode was 52.2 mW cm⁻², which was a remarkable improvement compared with the performance of MEA with traditional cathode. The key factor responsible for the improved performance is the optimization of the electrode structure.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-hydroxy-imidamide-functionalized graphene: an efficient metal-free electrocatalyst for oxygen reduction

Metal-free electrocatalysts for oxygen reduction reaction (ORR) are key to the development of efficient, durable, and low-cost alternatives to noble-metal-based electrocatalysts in fuel cell cathodes. In recent years, many efforts are directed to the metal-free catalyst based on heteroatom-doped graphene. In this work, we demonstrate that the graphene surface can be converted into the catalyst for the oxygen reduction by chemical functionalization. In this context, we first synthesized malononitrile-functionalized graphene oxide. Amidoximation of nitrile group and reduction in graphene oxide were then carried out by hydroxylamine in one step. The electrochemical behavior of functionalized graphene-modified electrode for the reduction in oxygen was studied. The results showed that the electrocatalyst fabricated by this method exhibited striking catalytic activities in alkaline solution. In alkaline solution, this catalyst showed a competitive activity to the commercial Pt catalyst via four-electron transfer pathway with better ORR selectivity and stability. In addition, this metal-free electrocatalyst exhibited tolerance to methanol crossover effect. Based on its outstanding performance, this functionalized graphene electrocatalyst showed the promising prospect of a metal-free catalyst for fuel cell with much lower cost than currently used Pt/C catalyst.     

丙烯、氧气和环氧丙烷在Cu-NaCl/SiO2催化剂上吸附的红外光谱研究

 用红外光谱法研究了丙烯、丙烯/氧气混合气以及环氧丙烷(PO)在Cu-NaCl/SiO2催化剂上的吸附. 结果表明,丙烯在载体和催化剂上的吸附是完全可逆的. 丙烯和氧气在催化剂上共吸附后生成了丙烯醛,未观察到环氧丙烷(PO)生成. PO在载体和未还原催化剂上的吸附行为表明,PO与载体的硅羟基有强相互作用,PO发生开环反应生成开环物种. 而PO在还原态催化剂上的吸附行为较复杂,可能生成了酮类化合物.     

Impact of ageing on the distribution of platinum group elements and catalyst poisoning elements in automobile catalysts

The distribution of platinum group elements (PGEs) and catalyst poisoning elements (Pb, Zn, P and S) on the surface of gasoline and diesel automobile catalysts was investigated within this study. Laser ablation–inductively coupled plasma mass spectrometry (LA–ICPMS) provides both the sensitivity and the spatial resolution required for the surface analysis of sectioned automobile catalysts, and scanning along channels reveals the distribution of longitudinal changes in PGE and catalyst poisoning elements. Changes in catalyst surface features were studied for fresh catalysts and after ageing of the catalyst up to 80 000 km for both types of catalysts studied. The PGEs in the gasoline catalyst were found to decrease at the front of the catalyst after ageing, whereas the diesel catalyst presented a more constant loss along the catalyst. The fraction of poisoning elements (Pb, P and Zn for the gasoline catalyst and P and Zn for the diesel catalyst) retained by the catalyst is distributed non‐uniformly over the length of the catalyst. This could indicate different ageing mechanisms for gasoline and diesel catalysts. Copyright © 2003 John Wiley & Sons, Ltd.     

甲醇羰基化制醋酸铱基催化剂的研究

摘要 醋酸是一种重要的化工原料，甲醇羰基化是目前生产醋酸的主要方法， 铱基催化剂是最有发展前景的甲醇羰基化反应制备醋酸的催化剂。介绍了铱基催化 剂体系的催化机理、速度影响因素，并与铑基催化剂进行了比较．     

多相催化元素的有效性:新型催化剂的工业活性预测（英文）

人们对化学工业可持续性关注的不断提高推动了更加高效催化反应的开发.第一代评估催化剂活性的方法基于其地壳丰度,该方法存在严重不足.本文提出了第二代评估催化剂活性的办法,该方法可以在工业应用之前预测新型催化剂的活性,从而使全球化学工业受益.采用该评估法发现,对于11个有代表性的工业催化过程,催化剂消耗与催化剂元素的年度生产或价格之间存在着关联.基于该关联,我们引入了两个新概念来描述催化剂活性:每年催化剂消耗量与可用量的比值(CCA)和每年消耗催化剂成本与产品价值的比值(CCP).将CCA和CCP评估法用于选定的工业反应,进行实例分析并根据活性将催化剂分类,根据CCA和CCP值即可确定催化剂活性的普遍极限.计算CCA和CCP,并将其与催化剂活性的普遍极限进行比较,可以为研究者提供一个新的框架,用以评估一个新催化剂的成本或物理有效率是否会成为限制因素.我们还将该方法用于计算并预测新型催化剂的可行性生产及产品成本的经济极限.     

烷基化催化剂表面酸性及催化性能的动力学研究

在确定关联升温速率、脱附峰温和脱附峰覆盖率的程序升温脱附动力学模型的基础上，通过TPD实验和模型参数估值，建立了表征催化剂酸密度、酸强度及强度分布情况的方法。研究表明，随着活化温度的提高，固体酸催化剂表面酸中心强度分布先变宽后趋于均匀，350?℃活化催化剂的强度分布最宽；催化剂表面酸强度和酸密度随活化温度提高均呈先增大后降低、分别在350 ℃和250 ℃活化温度达到极大值的变化规律。催化剂酸性与催化性能关联的结果表明，随着活化温度的提高，烷基化反应速率常数与总脱附量的变化趋势相同，而催化剂失活速率常数与脱附活化能变化趋势相同；催化剂活性稳定性随其酸强度的增大而变差，催化剂活性与催化剂酸量和酸强度有关。     

Efficient aldol condensation by using modified CaO as solid-base catalysts

A new type of solid-base catalyst for aldol condensation reaction was prepared by modifying commercial CaO with benzyl bromide in a simple way. It was found that modified CaO can effectively catalyze the aldol condensation of acetophenone and benzaldehyde to produce chalcone with a high conversion and good selectivity. The catalyst gave a higher yield (90.5%) of chalcone than commercial CaO. The high catalytic activity and stability of this catalyst was related to the organic modifier with a hydrophilic functional group that improved the diffusion of grease to the catalyst surface and prevented its hydration. The influence of several reaction parameters, such as temperature, catalyst loading and the moisture absorption rate of modified CaO, was investigated. From the results, the basic centers of modified CaO are stable and hardly poisoned by CO₂ unlike commercial CaO. The catalyst was completely recyclable without significant loss in activity up to five reaction cycles. Moreover, this catalyst showed a promising future in providing an environmentally clean process for the industrial sector.     

Rational Optimization of Supramolecular Catalysts for the Rhodium‐Catalyzed Asymmetric Hydrogenation Reaction

Rational design of catalysts for asymmetric transformations is a longstanding challenge in the field of catalysis. In the current contribution we report a catalyst in which a hydrogen bond between the substrate and the catalyst plays a crucial role in determining the selectivity and the rate of the catalytic hydrogenation reaction, as is evident from a combination of experiments and DFT calculations. Detailed insight allowed in silico mutation of the catalyst such that only this hydrogen bond interaction is stronger, predicting that the new catalyst is faster. Indeed, we experimentally confirmed that optimization of the catalyst can be realized by increasing the hydrogen bond strength of this interaction by going from a urea to phosphine oxide H‐bond acceptor on the ligand.     

Recent advances in the development of Fischer-Tropsch catalysts at sasol

Sasol's experience of more than 50 years in the field of Fischer-Tropsch puts it in a unique position to exploit the renewed interest in the utilization of the Fischer-Tropsch process to convert natural gas to liquids. In order to capitalize on this position, Sasol has made significant improvements to its low temperature and high temperature Fischer-Tropsch catalysts. A review is given of the development of Sasol's Co-based catalyst for low temperature Fischer-Tropsch applications. Sasol has also developed a new Fe-based catalyst for the high temperature Fischer-Tropsch process. The advantages of this catalyst compared to the existing catalyst are discussed.