Lan-Lan Lou

Degradation of polycyclic aromatic hydrocarbons in crumb tyre rubber catalysed by rutile TiO2 under UV irradiation

The polycyclic aromatic hydrocarbons (PAHs) in crumb tyre rubber were firstly degraded under UV irradiation in the presence of rutile TiO2 and hydrogen peroxide. The effects of light intensity, catalyst amount, oxidant amount, initial pH value, co-solvent content, and reaction time on degradation efficiency of typical PAHs in crumb tyre rubber were studied. The results indicated that UV irradiation, rutile TiO2, and hydrogen peroxide were beneficial to the degradation of PAHs and co-solvent could accelerate the desorption of PAHs from crumb tyre rubber. Up to 90% degradation efficiency of total 16 PAHs could be obtained in the presence of rutile TiO2 (1 wt%) and hydrogen peroxide (1.0 mL) under 1800 µW cm−2 UV irradiation for 48 h. The high molecular weight PAHs (such as benz(a)pyrene) were more difficult to be degraded than low molecular weight PAHs (such as phenanthrene, chrysene). Moreover, through the characterization of reaction solution and degradation products via GC–MS, it was proved that the PAHs in crumb tyre rubber were successfully degraded. GRAPHICAL ABSTRACT

Polyoxometalate Supported Cinchona-Derived Chiral Amine for Asymmetric Organocatalysed Aldol Reaction

A heterogeneous polyoxometalate-based organocatalyst of cinchona-derived chiral amine that is supported on polyoxometalate was synthesized by a simple acid–base strategy for the asymmetric Aldol reaction. The organic–inorganic polyoxometalate catalyst could be easily recycled by filtration and reused four-times with only a slight change of enantioselectivity.

Pt nanoparticles stabilized by thermosensitive polymer as effective and recyclable catalysts for the asymmetric hydrogenation of ethyl pyruvate

Thermosensitive and thiol-terminated poly(N-isopropylacrylamide)s (PNIPAM-SHs) were synthesized and used to stabilize Pt nanoparticles. After chiral modification with cinchonidine, these nanocatalysts were firstly applied in the asymmetric hydrogenation of ethyl pyruvate. The influences of reaction solvent, chiral modifier concentration, hydrogen pressure, mean molecular weight and amount of polymer on the catalytic performance were investigated. These colloidal Pt catalysts exhibited remarkably high catalytic activity and enantioselectivity. Especially, high turnover frequencies up to 17820 h−1 were achieved, which is the best result for this reaction with regard to the colloidal Pt catalysts. The high catalytic activity was associated with the high hydrophobicity of isopropyl groups in polymer moieties in the catalyst. Moreover, recycling experiments showed that the thermosensitivity of PNIPAM-SH made these colloidal Pt catalysts easier to recover and reuse. Excellent stability and reusability were presented over these catalysts, and no obvious decrease in catalytic activity and enantioselectivity was observed for eleven runs.

3 D Ordered Macroporous Alumina–Carbon Nanocomposite Supported Platinum Nanoparticles as Effective and Reusable Catalysts for Asymmetric Hydrogenation

The three‐dimensionally ordered macroporous alumina‐carbon composite materials were firstly prepared through a surfactant‐assisted colloidal crystal template method and applied to support Pt nanoparticles. The results of SEM, XRD, TEM, and N2 sorption analyses revealed that these composite materials possessed highly ordered macroporous structures with meso‐ and micropores within the skeletons of macropores and that the Pt nanoparticles were well dispersed on these materials with a very narrow size distribution. These prepared Pt nanocatalysts were evaluated in the asymmetric hydrogenation of ethyl pyruvate after chiral modification with cinchonidine. Excellent catalytic activity and enantioselectivity were achieved. More importantly, these catalysts exhibited extraordinary stability and reusability during the reaction and could be reused at least 26 times without significant loss in catalytic activity and enantioselectivity.

Short‐Mesochannel SBA‐15‐Supported Chiral 9‐Amino Epicinchonine for Asymmetric Transfer Hydrogenation of Aromatic Ketones

A short‐mesochannel SBA‐15 material functionalized with propylthiol groups was prepared by co‐condensation and applied to the immobilization of chiral 9‐amino epicinchonine. After complexing with [Ir(cod)Cl]2 (cod=1,5‐cyclooctadiene), these mesoporous materials were evaluated as catalysts for the asymmetric transfer hydrogenation of aromatic ketones. Higher enantioselectivities and comparable, or even higher, catalytic activities were achieved compared with the free catalyst. Both the short mesochannel and co‐condensation approach for short‐mesochannel SBA‐15 materials functionalized with propylthiol groups, [SSBA‐SH(x)] materials were demonstrated to contribute to the excellent catalytic performance. In addition, the catalyst SSBA‐AEC(5)/Ir (AEC=9‐amino epicinchonine), with low 3‐mercaptopropyltrimethoxysilane (MPTMS) content, showed the best catalytic performance; a high enantiomeric excess of 84 % (homogeneous ee=60 %) along with a conversion of 97 % was achieved within 1 h for asymmetric transfer hydrogenation of acetophenone. Moreover, these immobilized catalysts showed high stability during the reaction and could be recovered for reuse.

Highly efficient and durable platinum nanocatalysts stabilized by thiol-terminated poly(N-isopropyl acrylomide) for selective hydrogenation of halonitrobenzene to haloaniline

In this paper, the selective hydrogenation of halonitrobenzenes (HNBs) to haloanilines (HANs) under mild conditions catalyzed by well-dispersed Pt nanoparticles protected by thiol-terminated poly(N-isopropyl acrylomide) (PNIPAM-SH) was firstly investigated. The polymer not only protected the Pt nanoparticles, but also inhibited the highly active Pt catalyst from producing undesired hydrodehalogenation products through anchoring the thiol groups to the surface of Pt nanoparticles. Thus high selectivities to HANs were achieved over this modified Pt catalyst for a variety of HNBs with satisfactory catalytic activities. Especially, the selectivity to HANs showed no obvious loss with the prolonging of the reaction time. Moreover, the recycling experiment showed that this Pt nanocatalyst was easier to recover and reuse based on the cononsolvency of PNIPAM-SH. Excellent stability and reusability were presented over this catalyst, and both the catalytic activity and selectivity were well maintained after fourteen runs.