Selective Hydrogenation Of O-chloronitrobenzene Research Articles

Regulation of sulfur doping on carbon-supported Pd particles and abnormal relationship between Pd particle size and catalytic performance in selective hydrogenation of o-chloronitrobenzene

S was successfully doped into carbon via calcination and Pd size was modulated by adjusting the S content. Sulfur species were considered to be anchor sites, contributing to the highly dispersion of Pd nanoparticles. In addition, Pd/CS4 achieved 99.9% sel. With complete conversion in hydrogenation of o-chloronitrobenzene compared to Pd/AC (99.9% con., 61.6% sel.). Interestingly, catalysts with smaller metal size exhibited higher selectivity and lower activity, which was contrary to previous studies. It was suggested that electronic effects between S and Pd played an important role in this reaction, contributing to the excellent performance of the catalysts.

Biomass-Derived Carbon Nanospheres with Turbostratic Structure as Metal-Free Catalysts for Selective Hydrogenation of o-Chloronitrobenzene

Nowadays, metal-free catalysts are sought after for synthesis of fine chemicals. Herein, we utilized the natural biomass xylose as the precursor to fabricate carbon nanospheres with turbostratic carbon structure via hydrothermal treating and high-temperature calcinating. These green and sustainable carbon materials were used as metal-free catalysts in selective hydrogenation of o-chloronitrobenzene (o-CNB), exhibiting a significantly enhanced catalytic activity with the increasing calcination temperature, as well as 100% selectivity to o-chloroanilines (o-CAN). In terms of the systematic characterization and simulated calculation, it is found turbostratic carbon formed in the calcination process might act as the catalytic active center in this reaction, and its selective reaction with −NO2 in o-CNB results in the enhanced catalytic activity and fully selectivity to o-CAN.

Microemulsion-controlled synthesis of one-dimensional Ir nanowires and their catalytic activity in selective hydrogenation of o-chloronitrobenzene.

Ultrathin iridium nanowires have been synthesized using a convenient method mediated by microemulsion via oriented attachment growth for the first time. The interconnected polycrystalline Ir nanowires possess high aspect ratio, small average diameter of 2 nm, and length up to several hundred nanometers. The 1D growth of surfactant-encapsulated primary nanoparticles, which is determined by the inherent crystal growth habit and the specific interactions of nanocrystals with surfactant molecules, accounts for the formation of Ir nanowires. The as-prepared Ir nanowires show high activity and selectivity toward the hydrogenation production of industrially valuable chloroaniline from o-chloronitrobenzene. Theoretical evidence based on DFT calculation indicates that H2 could be dissociated more easily and quickly on Ir(100) surface than on Ir(111), accounting for the higher hydrogenation rate over Ir nanowires exposing both (200) and (111) crystal facets rather than only (111) facet for Ir nanoparticles.

Selective hydrogenation of o-chloronitrobenzene over anatase-ferric oxides supported Ir nanocomposite catalyst

The catalytic performance of Ir/TiO2–FeOx, an Ir/TiO2 catalyst modified with FeOx, was investigated for the hydrogenation of o-chloronitrobenzene, FeOx was found to promote both the activity and selectivity significantly. The initial reaction rate of Ir/TiO2–FeOx(10) nanocomposite catalyst was four times as high as that of Ir/TiO2 catalyst. Especially, the accumulation of intermediates was prohibited and finally 100% selectivity to o-chloroaniline was obtained at 100% conversion. Herein, we mainly discussed the promoting effect of FeOx with using the results of powder X-ray diffraction, transmission electron microscopy, element analysis mapping, hydrogen-temperature programmed reduction, hydrogen-temperature programmed desorption, diffuse reflectance infrared fourier transform spectra and X-ray photoelectron spectroscopy analysis. The FeOx was highly dispersed and a portion of FeO species existed in the Ir/TiO2–FeOx nanocomposite catalyst. Moreover, the FeOx was certified to have a strong interaction with Ir species, which should contribute to the excellent performance of the Ir/TiO2–FeOx nanocomposite catalyst.

Polyurea-supported metal nanocatalysts: Synthesis, characterization and application in selective hydrogenation of o-chloronitrobenzene

Polyurea (PU) spheres with size of 2–10μm were derived through the polymerization of CO2 with 1,4-butanediamine, and characterized by FTIR spectroscopy, scanning electron microscopy and TG analysis. It was demonstrated that the PU spheres displayed flower-like morphology with the betel thickness around 30nm, and they had high thermal stability. The resultant PU spheres were used to immobilize metal particles, and a series of PU-supported metal nanocatalysts including Pt/PU, Au/PU, Pd/PU were prepared via just mixing the metal precursors with the PU spheres in water, followed by the reduction of metal ions by NaBH4. Transmission electron microscopy examination indicated that the metal nanoparticles were distributed uniformly on the surface of the PU spheres with mean particle size less than 3.0nm, and the Pt particles existed mainly in the form of metallic state as confirmed by the X-ray photoelectron spectroscopy analysis. The performance of the Pt/PU catalyst was tested in the catalytic hydrogenation of o-chloronitrobenzene, and a high selectivity of 99.5% toward o-chloroaniline at complete conversion of o-chloronitrobenzene was obtained at room temperature.

Synthesis of high-surface-area micro/mesoporous ZnAl2O4 catalyst support and application in selective hydrogenation of o-chloronitrobenzene

High-surface-area ZnAl 2 O 4 with micro/mesoporous frameworks was synthesized via a facile one-pot solvothermal approach without using any surfactants or post-treatment. The results revealed that the textural properties of micro/mesoporous ZnAl 2 O 4 were tuned by changing alcohol/water mixture solvents used in solvothermal synthesis and Ag nanoparticles were dispersed uniformly on the surface of ZnAl 2 O 4 supports. Especially, the supported Ag catalyst on the microporous ZnAl 2 O 4 synthesized in methanol/water solvent exhibited good catalytic performance for liquid phase selective hydrogenation of o -chloronitrobenzene to o -chloroaniline, owing to the high dispersion of Ag nanoparticles and the strong metal-support interaction. ► Micro/mesoporous ZnAl 2 O 4 was fabricated via one-pot solvothermal approach. ► The textural properties of ZnAl 2 O 4 were tuned by changing alcohol/water solvents. ► Ag nanoparticles could be dispersed uniformly and stably on the ZnAl 2 O 4 supports. ► Supported catalysts exhibited good catalytic performance in selective hydrogenation.

Selective hydrogenation of o-chloronitrobenzene ( o-CNB) over supported Pt and Pd catalysts obtained by laser vaporization deposition of bulk metals

Carbon nanotubes (CNTs), γ-alumina (γ-Al 2O 3) and silica (SiO 2) supported Pt and Pd catalysts were produced by laser vaporization deposition of respective bulk metals. The catalysts were characterized by inductive coupled plasma emission spectrometer (ICP), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic properties of the catalysts were investigated in the liquid phase hydrogenation of o-chloronitrobenzene ( o-CNB) to o-chloroaniline ( o-CAN) under 333 K and 1.0 MPa hydrogen pressure. The results show that the catalytic properties are greatly affected by the supports. Pt/CNTs catalyst exhibits the best catalytic performance among the Pt-based catalysts, producing o-CAN with 99.6% selectivity at complete conversion. Pd/CNTs catalyst exhibits the best catalytic performance among the Pd-based catalysts, giving o-CAN with 95.2% selectivity at complete conversion. For Pt-based catalysts, geometric effect and the textures and properties of the supports play important roles on catalytic properties. On the other hand, geometric effect, electronic effect and the textures and properties of the supports simultaneously influence the catalytic properties of the Pd-based catalysts. In addition, hydrogenolysis of the C–Cl bond can be well inhibited over all catalysts prepared by laser vaporization deposition.

Selective hydrogenation of o-chloronitrobenzene over palladium supported nanotubular titanium dioxide derived catalysts

Abstract Titania derived nanotubes were synthesized by treating P-25 Degussa TiO2 with a concentrated (18 M) KOH solution. Ageing the material in KOH solution for 2 days resulted in formation of tubular titania and Raman analysis revealed that the material has a titanate structure. The synthesized material was used as a catalyst support for the hydrogenation of ortho-chloronitrobenzene (o-CNB) with Pd as the active phase. The vapour-phase hydrogenation of o-CNB was carried out in ethanol at 523 K and atmospheric pressure over a Pd/TiO2 derived nanotube catalyst (Pd/TiO2-M). Pd/TiO2-M gave complete conversion (100%) of o-CNB with the selectivity to ortho-chloroaniline (o-CAN) of 86%. The stability of the Pd/TiO2-M catalyst was tested over 5 h during which time the conversion slowly dropped to 80% (selectivity 93%) due to catalyst poisoning. TPR analysis revealed the existence of a strong palladium-support interaction and this was found to be crucial to the overall activity of the catalyst.

Role of boron species in the hydrogenation of o-chloronitrobenzene over polymer-stabilized ruthenium colloidal catalysts

The role of boron species in selective hydrogenation of o-chloronitrobenzene ( o-CNB) over polymer-stabilized ruthenium colloids has been studied. Of the two kinds of boron species (boride and borate) present in ruthenium colloids prepared by NaBH 4 reduction, it was verified that only borate had a significant effect on the hydrogenation of o-CNB, while boride performed as a spectator. When metal cations were added into ruthenium colloidal catalyst system as modifiers, respectively, we observed that the synergetic effect between borate and metal cations occurred in these systems. It is suggested that metal complex ions were formed between the metal cations and borate ions.

Selective hydrogenation of o-chloronitrobenzene over polymer-stabilized ruthenium colloidal catalysts

The selective hydrogenation of ortho-chloronitrobenzene ( o-CNB) to ortho-chloroaniline ( o-CAN) was accomplished without dehalogenation over finely dispersed polyvinylpyrrolidone-stabilized ruthenium colloids (PVP–Ru). The influence of experimental parameters on reaction was also investigated. It was observed that some metal cations added to the system increased the activity while the selectivity remained constant.