Phosphorus-Doped Activated Coconut Shell Carbon-Anchored Highly Dispersed Pt for the Chemoselective Hydrogenation of Nitrobenzene to p-Aminophenol.

Highly dispersed Pt nanoparticles (∼2.5 nm) on phosphorus-doped activated coconut shell carbon (Pt/P-ACC) were synthesized by a two-step impregnation route. Pt/P-ACC showed a high activity, chemoselectivity, and reusability toward the hydrogenation of nitrobenzene to p-aminophenol, with hydrogen as the reducing agent in sulfuric acid. The effects of P species on the catalyst structure, surface properties, and catalytic performance were investigated. It was found that the Pt/P-ACC catalyst had an excellent catalytic activity due to its smaller Pt nanoparticles and higher content of surface-active metal compared with Pt/ACC. Besides, the experimental results and in situ infrared studies demonstrated that the interaction effect between the Pt and P species imbued the surface of Pt with an electron-rich feature, which decreased the adsorption of electron-rich substrates (that is, phenylhydroxylamine) and prevented their full hydrogenation, leading to enhanced selectivity during the hydrogenation of nitrobenzene to p-aminophenol.

One-Pot Synthesis of Al-P-O Catalysts and Their Catalytic Properties for O-Methylation of Catechol and Methanol.

A series of Al-P-O catalysts (Al-xP-O) were prepared using a P123-assisted one-pot method at different P/Al molar ratios and used for O-methylation of catechol and methanol. The influences of the P/Al molar ratio and P123 addition on catalyst structure and surface acid-base characteristics were investigated in detail. Increasing the P/Al molar ratio more favored crystalline aluminophosphate. The P123-assisted Al3+ and PO43- are known to be stabilized through weak steric force so that the formation of crystalline aluminophosphate could be inhibited at higher P/Al molar ratios. The results showed that the prepared Al-P-O catalysts possessed appropriate weak acid and weak base sites, which was beneficial to the reaction of catechol and methanol. The Al-1.1P-O catalyst synthesized with the assistance of P123 exhibited superior catalytic performances, with 52.5% catechol conversion and higher guaiacol selectivity of 97.6%.

Highly efficient oxidation of 2,2'-hydrazobis-isobutyronitrile to 2,2'-azobis-isobutyronitrile over a CrOx/TiO2 catalyst with hydrogen peroxide.

Green oxidation of 2,2'-hydrazobis-isobutyronitrile (HAIBN) to 2,2'-azobis-isobutyronitrile (AIBN) over a recyclable solid catalyst was a significant challenge. A titanium dioxide-supported chromium oxide (CrOx/TiO2) catalyst was, for the first time, developed for oxidation of HAIBN with hydrogen peroxide and achieved complete conversion of HAIBN with a high (94.8%) yield of AIBN.

Synthesis of Mesoporous γ-Alumina-Supported Co-Based Catalysts and Their Catalytic Performance for Chemoselective Reduction of Nitroarenes.

Mesoporous γ-alumina (γ-MA)-supported cobalt oxides (Co3O4) with large surface areas and narrow pore size distributions were first prepared through one-pot hydrolysis of metal nitrates. The obtained Co3O4/γ-MA materials were impregnated with a water-ethanol solution of 1,10-phenanthroline, followed by treatment at 700 °C in N2 atmosphere, generating Co-NC/γ-MA catalysts containing N-doped graphitic carbon (NC). The Co-NC/γ-MA catalysts maintained the mesoporous structure of γ-MA, and Co3O4 was reduced to metallic Co nanoparticles highly dispersed in the γ-MA frameworks. Metallic Co species had a strong interaction with NC in the matrices, avoiding the surface oxidation of Co particles. The Co-NC/γ-MA catalysts exhibited superior catalytic activity and quantitatively reduced a variety of functionalized nitroarenes to the corresponding arylamines with hydrazine hydrate in ethanol at near room temperature, affording yields of >99%. The recycling test of 2-chloronitrobenzene as a model reaction showed no detectable change in catalyst performance after 10 cycle reactions.

Nitrogen-doped graphene-activated metallic nanoparticle-incorporated ordered mesoporous carbon nanocomposites for the hydrogenation of nitroarenes.

Herein, nanoscale metallic nanoparticle-incorporated ordered mesoporous carbon catalysts activated by nitrogen-doped graphene (NGr) were fabricated via an efficient multi-component co-assembly of a phenolic resin, nitrate, acetylacetone, the nitrogen-containing compound 1,10-phenanthroline, and Pluronic F127, followed by carbonization. The obtained well-dispersed nitrogen-doped graphene-activated transition metal nanocatalysts possess a 2-D hexagonally arranged pore structure with a high surface area (∼500 m2 g-1) and uniform pore size (∼4.0 nm) and show excellent activity for the selective hydrogenation-reduction of substituted nitroarenes to anilines in an environmentally friendly aqueous solution. The high catalytic performance and durability is attributed to the synergistic effects among the components, the unique structure of the nitrogen-doped graphene layer-coated metallic nanoparticles, and electronic activation of the doped nitrogen.

Direct Synthesis and Catalytic Application of Ordered Mesoporous Ru/C Composites with Homogeneously Dispersed Ruthenium Nanoclusters.

Direct synthesis of metal/carbon nanocomposites with ordered mesoporous frameworks has attracted increasing interest in various applications including catalysis, optics, and electronics. Herein, we demonstrate a simple one-pot co-assembly route to synthesize Ru/carbon composites by using resol, ruthenium chloride, and Pluronic F127 as a template with the assistance of 8-hydroxyquinoline. 8-Hydroxyquinoline exerts a significant influence on the mesostructure ordering and specific surface area of the Ru/carbon composites. The obtained Ru/carbon materials show well-ordered hexagonal arrays of mesopores with homogeneously dispersed sub-2 nm Ru nanoclusters throughout the carbon frameworks, which can efficiently and quantitatively hydrogenated nitrobenzene to aniline with H2 in the absence of solvent for multiple recycling runs without loss of activity.

Preformed precursor of microporous aluminophosphate coating on mesoporous SBA-15: synthesis, characterization, and catalytic property for selective O-methylation of catechol.

The synthesis of mesoporous SBA-15 coated with the preformed precursor of microporous aluminophosphate (AlPO) has been reported. The physicochemical properties of the coated samples were investigated by using XRD, FT-IR, N(2)-adsorption, ICP, (29)Si MAS NMR, NH(3)-TPD and CO(2)-TPD. The characterization results suggest that the nanometer-scaled zeolite units are present on the wall surface of SBA-15, thus bringing the weak acid-base characteristics to the resulting mesoporous materials, and that the acid-base properties of these materials can be modified by the aging treatment in glycol. Moreover, vapor-phase O-methylation of catechol with methanol has been studied on these coated samples as catalysts. It is found that the coated sample bearing suitable weak acid-base sites exhibits the relatively high activity and selectivity to guaiacol.

Thermally stable amorphous mesoporous aluminophosphates with controllable P/Al ratio: synthesis, characterization, and catalytic performance for selective O-methylation of catechol.

Amorphous mesoporous aluminophosphates (AlPO) with P/Al molar ratio in the range 0.8-1.15 are synthesized by using the citric acid (CA) route and are systematically characterized using N(2)-adsorption, XRD, SEM, solid-state CP-MAS NMR, FT-IR, TG-DTA, CO(2)-TPD, and NH(3)-TPD. The characterization studies show that the change in P/Al ratio could affect the structure, texture, thermal stability, and surface acid-base properties of AlPO. Samples with a relatively low P/Al ratio (< or =1.0) exhibit uniform amorphous mesoporous character and high thermal stability (up to 1173 K). Partial crystallization of the AlPO framework easily occurred on the sample with higher P/Al ratio (> or =1.1), thus leading to significant decrease of surface area and formation of particle pile mesopores. Both weak acid and weak base sites are observed over AlPO materials, and the amounts of acid-base sites can be effectively controlled by adjusting the P/Al ratio. The presence of suitable interaction between citric acid and AlPO framework is critical for the formation of mesoporous structures. Both CA and PO(4) units are considered to be ligands to coordinate with aluminum ions, forming relative uniform complexes (such as CA-Al-PO(4)) in the as-synthesized AlPO materials. The mesoporous structure of AlPO materials is obtained after the rapid decomposition of citric acid. Vapor phase selective O-methylation of catechol with methanol reaction is carried out to investigate the catalytic performances of AlPO materials with different P/Al ratios. Among them, AlP(1.1)O shows the highest activity (88.4% conversion of catechol) and the highest yield of guaiacol (74.3%). The presence of suitable weak acid-base pairs may play an important role on the title reaction.