Jianglin Hu

Highly Dispersed Pd Catalyst Locked in Knitting Aryl Network Polymers for Suzuki–Miyaura Coupling Reactions of Aryl Chlorides in Aqueous Media

Highly dispersed palladium chloride catalysts locked in triphenylphosphine-functionalized knitting aryl network polymers (KAPs) are developed and exhibit excellent activity under mild conditions in the Suzuki-Miyaura cross-coupling reactions of aryl chlorides in aqueous media. This work highlights that the microporous polymers not only play the role of support materials, but also protect the Pd species from aggregation and precipitation, hence, positively effect the catalysis activity.

PdCl2(py)2 encaged in monodispersed zeolitic hollow spheres: a highly efficient and reusable catalyst for Suzuki–Miyaura cross-coupling reaction in aqueous media

By encaging the PdCl2(py)2 complex (py = pyridine) in the interior space of silicalite-1 hollow spheres (SHS), a novel solid palladium catalyst, PdCl2(py)2@SHS, was successfully prepared. The structure and composition of the solid catalyst was characterized by SEM, TEM, XRD, N2 sorption, FT-IR and XPS. This catalyst afforded fast conversions for the Suzuki–Miyaura cross-coupling reactions of various aryl halides and arylboronic acids even at Pd loadings of 0.0188 mol% in aqueous media. The turnover frequency (TOF) could be up to 63 210 h−1 under mild conditions in air. In particular, because of the antileaching effect of the surrounding zeolitic shell toward the entrapped Pd species, PdCl2(py)2@SHS showed outstanding stability and reusability, which could be reused at least 10 times without appreciable loss of its activity. The developed solid catalyst combined with the mild conditions represented one of the most efficient heterogeneous systems for the Suzuki–Miyaura cross-coupling reactions of aryl halides.

Preparation of hierarchical mesoporous Zn/HZSM-5 catalyst and its application in MTG reaction

Abstract The hierarchical mesoporous Zn/ZSM-5 zeolite catalyst was prepared by NaOH treatment and Zn impregnation, and its application in the conversion of methanol to gasoline (MTG) was studied. N2 adsorption-desorption results showed that the mesopores with sizes of 2-20 nm in HZ5/0.3AT was formed by 0.3 M NaOH alkali treatment. The zeolite samples after modification were also characterized by XRF, AAS, XRD, SEM and NH3-TPD methods. Zn impregnated catalyst Zn/HZ5/0.3AT exhibited dramatic improvements in catalytic lifetime and liquid hydrocarbons yield. The selectivity of aromatic hydrocarbons was also improved after Zn impregnation. It is suggested that the mesopores of Zn/HZ5/0.3AT enhanced the synergetic effect of Zn species and acid sites and the capability to coke tolerance, which were confirmed by the results of catalytic test and TGA analysis, respectively.

Facile synthesis of hierarchical nanocrystalline ZSM-5 zeolite under mild conditions and its catalytic performance

Hierarchical nanocrystalline ZSM-5 zeolite (NZ5) was synthesized at 100 °C under atmospheric pressure using methylamine as a mineralizing agent. The crystallization process of NZ5 was characterized by dynamic light scattering (DLS), X-ray diffraction (XRD), and infrared spectroscopy (FTIR). The results of contrastive experiments showed that evaporation of the solvent promoted the aggregation of primary particles, and the addition of methylamine accelerated the crystallization process. The NZ5 aggregate consisted of 20 nm individual particles, as shown in scanning electron microscope (SEM). The lattice fringes in the transmission electron microscope (TEM) images and the XRD results indicated that individual particles of NZ5 were highly crystalline. N(2) adsorption-desorption isotherms showed that NZ5 had high BET surface areas with mesopores having a mean diameter of about 9 nm. NZ5 exhibited a long lifetime, a stable and high yield of liquid hydrocarbons, and a high anti-coking performance in methanol-to-hydrocarbons reaction. Catalytic testing and TGA results showed that the lifetime of NZ5 was about ten times longer than that of micro-sized ZSM-5 zeolite (MZ5), and the average coking rate with NZ5 was one fifth over that of MZ5.

Palladium‐Catalyzed Carbonylation of Chloroacetates to Afford Malonates: Controlling the Selectivity of the Product in a Buffer

We report an efficient process for the synthesis of diethyl malonate (DEM) and other malonates through the palladium‐catalyzed carbonylation of chloroacetates. Excellent selectivity (96 %) and yield (94 %) were obtained without the formation of Pd black. For the first time, a weakly alkaline buffer was used to control the selectivity for DEM in the reaction and we discuss the relationship between the buffer medium and selectivity in the reaction. The combination of anisole as the solvent and a Na2HPO4/NaH2PO4 buffer was beneficial for completely restraining the phase‐transfer‐catalyzed substitution of DEM with ethyl chloroacetate, as well as accommodating the proposed [(PPh3)2PdI]−[Bu4N]+ intermediate, by providing a suitable environment for its stable existence. We achieved the highest efficiency in the catalytic cycle by fine‐tuning the balance between the rates of oxidative addition and reductive elimination; moreover, we synthesized a recoverable heterogeneous polymer‐bound Pd catalyst in 85 % yield that could be reused without an appreciable loss in activity over four cycles.