1520-21-4Relevant academic research and scientific papers
Origin and Abatement of Heterogeneity at the Support Granule Scale of Silver on Silica Catalysts
Plessers, Eva,van den Reijen, Jeroen E.,de Jongh, Petra E.,de Jong, Krijn P.,Roeffaers, Maarten B. J.
, p. 4562 - 4569 (2017)
Incipient wetness impregnation is used commonly to form supported metal nanoparticle catalysts. Recently, it has been revealed that this approach may induce severe heterogeneity between catalyst granules of the same batch. At least a 10-fold variation in metal loading was observed, which affect the catalytic performance of individual catalyst granules severely. However, the origin of this heterogeneity is still unclear. Here we show that every elementary step in the preparation procedure of a Ag on silica catalyst has an effect on the resulting interparticle heterogeneity, but the influence of the drying step is the most important. This is because drying by capillary force results in a heterogeneous sample. Specifically, the position of a granule in the stagnant drying bed influences the resulting color and, thus, Ag loading significantly. This is further demonstrated by varying the drying conditions: freeze-drying and fluidized-bed drying led to a more homogeneous Ag loading. An investigation of the fluidized-bed-dried sample by using optical microscopy revealed a large fraction of transparent granules (94 %), which indicates that almost all the Ag nanoparticles in this sample are confined within the 6 nm pores. The optimized supported Ag on silica catalyst shows a good catalytic performance. This adaptation of the drying step can be implemented easily on a laboratory scale, is scalable, and does not require the use of expensive solvents or metal precursors.
Room-Temperature Chemoselective Reduction of 3-Nitrostyrene to 3-Vinylaniline by Ammonia Borane over Cu Nanoparticles
Shen, Mengqi,Liu, Hu,Yu, Chao,Yin, Zhouyang,Muzzio, Michelle,Li, Junrui,Xi, Zheng,Yu, Yongsheng,Sun, Shouheng
, p. 16460 - 16463 (2018)
We report a new strategy of controlling catalytic activity and selectivity of Cu nanoparticles (NPs) for the ammonia borane initiated hydrogenation reaction. Cu NPs are active and selective for chemoselective reduction of nitrostyrene to vinylaniline under ambient conditions. Their activity, selectivity, and more importantly, stability are greatly enhanced by their anchoring on WO2.72 nanorods, providing a room-temperature full conversion of nitrostyrene selectively to vinylaniline (>99% yield). Compared with all other catalysts developed thus far, our new Cu/WO2.72 catalyst shows much enhanced hydrogenation selectivity and stability without the use of pressured hydrogen. The synthetic approach demonstrated here can be extended to prepare various M/WO2.72 catalysts (M = Fe, Co, Ni), with M being stabilized for many chemical reactions.
Robust Synthesis of Gold-Based Multishell Structures as Plasmonic Catalysts for Selective Hydrogenation of 4-Nitrostyrene
Li, Jian,Long, Yan,Liu, Yu,Zhang, Lingling,Wang, Qishun,Wang, Xiao,Song, Shuyan,Zhang, Hongjie
, p. 1103 - 1107 (2020)
A robust self-template strategy is used for facile and large-scale synthesis of porous multishell gold with controllable shell number, sphere size, and in situ surface modification. The process involved the rapid reduction of novel Au-melamine colloidal templates with a great amount of NaBH4 in presence of poly(sodium-p-styrenesulfonate) (PSS). After soaking the templates in other metal salt solution, the obtained bimetallic templates could also be generally converted into bimetallic multishell structures by same reduction process. In the hydrogenation of 4-nitrostyrene using NH3BH3 as a reducing agent, the porous triple-shell Au with surface modification (S-PTSAu) exhibited excellent selectivity (97 %) for 4-aminostyrene in contrast with unmodified triple-shell Au. Furthermore, it also showed higher enhancement of catalytic activity under irradiation of visible light as compared to similar catalysts with fewer shells.
Shape-selective synthesis of Sn(MoO4)2 nanomaterials for catalysis and supercapacitor applications
Sakthikumar,Ede, Sivasankara Rao,Mishra, Soumyaranjan,Kundu, Subrata
, p. 8897 - 8915 (2016)
Size and shape-selective Sn(MoO4)2 nanomaterials have been synthesized for the first time using a simple hydrothermal route by the reaction of Sn(ii) chloride salt with sodium molybdate in CTAB micellar media under stirring at 60 °C temperature for about three hours. Needle-like and flake-like Sn(MoO4)2 nanomaterials were synthesized by optimizing the CTAB to metal salt molar ratio and by controlling other reaction parameters. The eventual diameter and length of the nanoneedles are ～100 ± 10 nm and ～850 ± 100 nm respectively. The average diameter of the flakes is ～250 ± 50 nm. The synthesized Sn(MoO4)2 nanomaterials can be used in two potential applications, namely, catalytic reduction of nitroarenes and as an anodic material in electrochemical supercapacitors. From the catalysis study, it was observed that the Sn(MoO4)2 nanomaterials could act as a potential catalyst for the successful photochemical reduction of nitroarenes into their respective aminoarenes within a short reaction time. From the supercapacitor study, it was observed that the Sn(MoO4)2 nanomaterials of different shapes show different specific capacitance (Cs) values and the highest Cs value was observed for Sn(MoO4)2 nanomaterials having a flake-like morphology. The highest Cs value observed was 109 F g-1 at a scan rate of 5 mV s-1 for the flake-like Sn(MoO4)2 nanomaterials. The capacitor shows an excellent long cycle life along with 70% retention of the Cs value, even after 4000 consecutive cycles at a current density of 8 mA cm-2. Other than the applications in catalysis and supercapacitors, the synthesized nanomaterials can find further applications in photoluminescence, sensor and other energy-related devices.
Base-free chemoselective transfer hydrogenation of nitroarenes to anilines with formic acid as hydrogen source by a reusable heterogeneous Pd/ZrP catalyst
Tuteja, Jaya,Nishimura, Shun,Ebitani, Kohki
, p. 38241 - 38249 (2014)
A highly efficient, chemoselective, environmentally-benign method is developed for the catalytic transfer hydrogenation (CTH) of nitroarenes using FA as a hydrogen source. Various supported Pd catalysts were examined for this transformation, and Pd supported ZrP (Pd/ZrP) proved to be the best catalyst for CTH of nitrobenzene. Applicability of the Pd/ZrP catalyst is also explored for hydrogenation of various substituted nitroarenes. The Pd/ZrP catalyst showed high specificity for hydrogenation of nitro groups even in the presence of other reducible functional groups such as -CC, -COOCH3, and -CN. To investigate the reaction mechanism, a Hammett plot was obtained for CTH of p-substituted nitroarenes. The active site is thought to be in situ generated Pd(0) species as seen from XRD and TEM data. The Pd/ZrP catalyst is reusable at least up to 4 times while maintaining the same activity and selectivity. To the best of our knowledge, this is one of the best methodologies for CTH of nitroarenes under base-free conditions with high activity and chemoselectivity over heterogeneous Pd-based catalysts. the Partner Organisations 2014.
Co based N, S co-doped carbon hybrids for catalytic hydrogenation: Role of cobalt salt and doped S
Gao, Ruixiao,Guo, Haotian,Wang, Bowei,Qiu, Pengzhi,Sun, Mingming,Chen, Ligong
, p. 99 - 105 (2019)
A series of Co-based N, S dual-doped carbon catalysts were prepared successfully via the pyrolysis of porous organic polymers (POPs)impregnated with cobalt salt and characterized by TEM, XRD, XPS, etc. The successful construction of cobalt-nitrogen (Co-Nx)sites is confirmed by XPS spectra. It was found that the content of Co-Nx sites is markedly affected by the type of cobalt salt, and the catalyst derived by the pyrolysis of the complex of POPs with Co(NO3)2·6H2O displays the best activity and outstanding selectivity for catalytic hydrogenation of various aromatic nitro compounds, it also demonstrates good recyclability. According to the results of control experiments, the activity for catalytic hydrogenation is mainly attributed to the Co-Nx sites. In addition, the doped S species in carbon shells can promote the formation of the active sites, which can effectively improve the performance of catalysts. Thus, this work can provide an effective and green approach for design highly effective transition metal-based multi-doped carbon catalysts with abundant metal-Nx sites.
Selective Liquid-Phase Hydrogenation of a Nitro Group in Substituted Nitrobenzenes over Au/Al2O3 Catalyst in a Packed-Bed Flow Reactor
Nuzhdin, Alexey L.,Moroz, Boris L.,Bukhtiyarova, Galina A.,Reshetnikov, Sergey I.,Pyrjaev, Pavel A.,Aleksandrov, Pavel V.,Bukhtiyarov, Valerii I.
, p. 1741 - 1749 (2015)
A series of substituted nitrobenzenes with the general formula XC6H4NO2 (X=Cl, CH=CH2, or C(O)CH3) dissolved in toluene were reduced with hydrogen over the 1.9 % Au/Al2O3 catalyst at 60-110 C and 10-20 bar in a three-phase packed-bed reactor operating in up-flow mode. Under these conditions, hydrogenation of isomeric ClC6H4NO2 gives exclusively chloroanilines. Hydrogenation of 3-CH2CHC6H4NO2 and 4-CH3C(O)C6H4NO2 leads to the formation of 3-CH2CHC6H4NH2 and 4-CH3C(O)C6H4NH2 with selectivities of up to 93 and 97 % at substrate conversions of 98 and 100 %, respectively. Smooth catalyst deactivation was observed regardless of which substituted nitrobenzene was taken for hydrogenation. According to the results obtained by temperature-programmed oxidation of the spent catalyst, a carbonaceous deposit formed that might block the catalyst surface. Almost complete regeneration of the supported gold catalyst with retention of its high selectivity to hydrogenation of a nitro group was achieved in a flow of air at temperatures up to 400 C to eliminate carbonaceous deposits.
Efficient and highly selective boron-doped carbon materials-catalyzed reduction of nitroarenes
Lin, Yangming,Wu, Shuchang,Shi, Wen,Zhang, Bingsen,Wang, Jia,Kim, Yoong Ahm,Endo, Morinobu,Su, Dang Sheng
, p. 13086 - 13089 (2015)
Exploring the potential catalytic applications of boron-doped carbon materials is a fascinating challenge. Here we describe that boron-doped onion-like carbon and carbon nanotubes as metal-free catalysts exhibit excellent catalytic activity and stability in nitroarene reduction under a stoichiometric amount of reductant.
Bimetallic Platinum-Tin Nanoparticles on Hydrogenated Molybdenum Oxide for the Selective Hydrogenation of Functionalized Nitroarenes
Shu, Yijin,Chan, Hang Cheong,Xie, Lifang,Shi, Zhangping,Tang, Yi,Gao, Qingsheng
, p. 4199 - 4205 (2017)
The hydrogenation of functionalized nitroarenes to the corresponding anilines is of great importance in the fine chemical industry and requires high-performance catalysts with a good activity and selectivity. Herein, hydrogenated MoOx (H-MoOx) supported bimetallic Pt-Sn (Pt-Sn/H-MoOx) was developed to accomplish selective and efficient hydrogenation. In the case of 4-nitrostyrene, an outstanding selectivity to 4-vinylaniline (≈93 %) with a high turnover frequency (0.094 s?1) was achieved under mild conditions (T=30 °C, PH2 =1 atm). The metal–support interactions contributed to the efficient turnover on the ultrafine nanoparticles, and the atom-rearranged bimetallic Pt-Sn surface promoted the selectivity because of the preferred adsorption of the nitro group. The good efficiency for various functionalized nitroarenes further verified the promise of Pt-Sn/H-MoOx in chemoselective hydrogenation.
Resolving Interparticle Heterogeneities in Composition and Hydrogenation Performance between Individual Supported Silver on Silica Catalysts
Plessers, Eva,Stassen, Ivo,Sree, Sreeprasanth Pulinthanathu,Janssen, Kris P. F.,Yuan, Haifeng,Martens, Johan,Hofkens, Johan,De Vos, Dirk,Roeffaers, Maarten B. J.
, p. 6690 - 6695 (2015)
Supported metal nanoparticle catalysts are commonly obtained through deposition of metal precursors onto the support using incipient wetness impregnation. Typically, empirical relations between metal nanoparticle structure and catalytic performance are inferred from ensemble averaged data in combination with high-resolution electron microscopy. This approach clearly underestimates the importance of heterogeneities present in a supported metal catalyst batch. Here we show for the first time how incipient wetness impregnation leads to 10-fold variations in silver loading between individual submillimeter-sized silica support granules. This heterogeneity has a profound impact on the catalytic performance, with 100-fold variations in hydrogenation performance at the same level. In a straightforward fashion, optical microscopy interlinks single support particle level catalytic measurements to structural and compositional information. These detailed correlations reveal the optimal silver loading. A thorough consideration of catalyst heterogeneity and the impact thereof on the catalytic performance is indispensable in the development of catalysts.
