锌离子液体系高效催化合成环状碳酸酯

研究了离子液体助催化的各种无机盐催化剂体系用于二氧化碳和环氧化合物通过环加成反应制备环状碳酸酯 ,结果表明锌盐催化剂体系能够非常高效地催化该反应 ,最高得到了 5 472h- 1的催化转化频率 (TOF)和 10 0 %的选择性 ,催化剂使用六次以后没有发现催化活性和选择性的下降 ,并且该催化剂体系能够适用于各种结构的环氧化合物。

锌离子液体系高效催化合成环状碳酸酯

研究了离子液体助催化的各种无机盐催化剂体系用于二氧化碳和环氧化合物通过环加成反应制备环状碳酸酯.结果表明,锌盐催化剂体系能够高效地催化该反应,最高得到了5580h-1的催化转化频率(TOF)和100%的选择性,催化剂使用6次以后没有发现催化活性和选择性下降,并且该催化剂体系能够适用于各种结构的豢养化合物.

几种杂多酸在环己烯合成中的催化作用

通过几种杂多酸在环己醇脱水合成环己烯反应中的催化作用研究,考察了几种不同的杂多酸催化剂的作用效果,及其用量对环己烯产率的影响;进一步探究了各种催化剂可重复使用的次数。实验结果表明,磷钨酸为最佳催化剂,用量为反应物质量的4%时,反应可在0.5 h内结束,环己烯的产率可达到53.5%,产物纯度达99.21%,可重复使用3次。

高分子负载催化剂的设计、合成及其在有机合成反应中的应用

发展可回收和可重复利用的催化剂是过去几十年研究的一个热点,在这篇综述中,我们简要介绍了高分子负载催化剂的设计和合成策略以及这些催化剂在各种不同有机反应中的深入应用。在很多情况下,这一策略显示了在产物分离以及昂贵催化剂回收和再利用上的显著优点。与没有负载的同类催化剂相比,高分子负载催化剂可以保持同样的催化活性。另外,发展可控结构、尺寸、外观以及可溶性的线型聚合或树枝状的手性催化剂对于它们在有机合成中的应用都具有非常重要的意义。通过有机、高分子以及材料化学家的共同努力,这一方法在跨学科间取得了很大的进展,这一发展对于决定载体的选择起到了很大的作用。因此,进一步发展高活性和高对映选择性的催化剂仍将是这一领域的重要目标和挑战。

Immobilized nickel(Ⅱ) on organic-inorganic hybrid materials: The effective and reusable catalysts for Biginelli reaction

The immobilized nickel(II) on the organic-inorganic hybrid material was prepared and used as an effective catalyst for the Biginelli reaction.In the presence of the immobilized nickel catalyst,aromatic aldehydes reacted with ethyl acetoacetate and urea (or thiourea) smoothly to generate the corresponding Biginelli products in good to excellent yields without using any additive.The work-up procedure is very simple and practical.Furthermore,the silica-supported nickel(II) could be recovered and recycled for six consecutive trials without significant loss of its catalytic activity.

Ni/Pd core/shell nanoparticles supported on graphene as a highly active and reusable catalyst for Suzuki- Miyaura cross-coupling reaction

Monodisperse Ni/Pd core/shell nanoparticles （NPs） have been synthesized by sequential reduction of nickel（II） acetate and palladium（II） bromide in oleylamine （OAm） and trioctylphosphine （TOP）. The Ni/Pd NPs have a narrow size distribution with a mean particle size of 10 nm and a standard deviation of 5% with respect to the particle diameter. Mechanistic studies showed that the presence of TOP was essential to control the reductive decomposition of Ni-TOP and Pd-TOP, and the formation of Ni/Pd core/shell NPs. Using the current synthetic protocol, the composition of the Ni/Pd within the core/shell structure can be readily tuned by simply controlling the initial molar ratio of the Ni and Pd salts. The as-synthesized Ni/Pd core/shell NPs were supported on graphene （G） and used as catalyst in Suzuki-Miyaura cross-coupling reactions. Among three different kinds of Ni/Pd NPs tested, the Ni/Pd （Ni/Pd = 3/2） NPs were found to be the most active catalyst for the Suzuki-Miyaura cross-coupling of arylboronic acids with aryl iodides, bromides and even chlorides in a dimethylformamide/water mixture by using K2CO3 as a base at 110 ℃. The G-Ni/Pd was also stable and reusable, providing 98% conversion after the 5th catalytic run without showing any noticeable Ni/Pd composition change. The G-Ni/Pd structure reported in this paper combines both the efficiency of a homogeneous catalyst and the durability of a heterogeneous catalyst, and is promising catalyst candidate for various Pd-based catalytic applications.

Pd single-atom monolithic catalyst: Functional 3D structure and unique chemical selectivity in hydrogenation reaction

Regulating the selectivity of catalysts in selective hydrogenation reactions at the atomic level is highly desirable but remains a grand challenge. Here we report a simple and practical strategy to synthesize a monolithic single-atom catalyst(SAC) with isolated Pd atoms supported on bulk nitrogen-doped carbon foams(Pd-SAs/CNF). Moreover, we demonstrate that the single-atom Pd sites with unique electronic structure endow Pd-SAs/CNF with an isolated site effect, leading to excellent activity and selectivity in 4-nitrophenylacetylene semi-hydrogenation reaction. In addition, benefiting from the great integrity and excellent mechanical strength, monolithic Pd-SAs/CNF catalyst is easy to separate from the reaction system for conducting the subsequent recycling. The cyclic test demonstrates the excellent reusability and stability of monolithic Pd-SAs/CNF catalyst.The discovery of isolated site effect provides a new approach to design highly selective catalysts. And the development of monolithic SACs provides new opportunities to advance the practical applications of single-atom catalysts.

Epoxidation of olefins with hydrogen peroxide catalyzed by a reusable lacunary-type phosphotungstate catalyst

Olefins and allylic alcohols have been epoxidized with commercially available hydrogen peroxide (30% H2O2) using a phase transfer catalyst,composed of cetyltrimethylammonium cations and a lacunary-type phosphotungstate anion [PW11O39]7-or the complete Keggin-type heteropolyanion [PW12O40]3-,under two-phase conditions using ethyl acetate as the solvent. It was found that the lacunary-type catalyst showed higher activity and better recyclability than the complete Keggin-type catalyst under the same reaction conditions. 31P NMR spectroscopy and solubility measurements for the two catalysts revealed that the [PW11O39]7-anion had a much faster degradation rate than the [PW12O40]3-anion in an excess of H2O2,which resulted in the formation of more catalytically active species. As a result,the lacunary-type phosphotungstate anion-based catalyst gave a better catalytic performance than the complete Keggin-type anion in ethyl acetate.