Hydrogenation of nitric oxide on platinum black in acidic solution

By comparison of the catalytic hydrogenation and electrochemical reduction of NO on platinum black catalysts it has been shown that the hydrogenation of NO to ammonia and to hydroxylamine occurs in the diffusion controlled region only.

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NO , NO .

     

Effect of pretreatment of graphite oxide on activity of platinum supported catalysts in liquid-phase hydrogenation

The effect of the reduction procedure of graphite oxide (GO) on activity of platinum supported catalysts in liquid-phase hydrogenation of nitrobenzene and dec-1-ene was studied. The following methods were applied to prepare the catalysts: simultaneous reduction of graphite oxide and H₂PtCl₆; deposition of platinum on graphite oxide which was preliminary subjected to reduction with sodium tetrahydroborate or hydrazine hydrate, or to thermal reduction at 1000 and 1050 °С. It was shown that at equal Pt particles size of ca. 2 nm the catalyst supported on thermally reduced graphite oxide is more active in the model reactions than the catalysts supported on chemically reduced graphite oxide. The catalyst prepared by simultaneous reduction was the least active.     

Mixed ligand platinum complexes as hydrogenation catalysts

PtLL′Cl₂ (L = PPh₃, L′ = sulphides, amines) are more effective catalysts for the hydrogenation of styrene to ethylbenzene, in the presence of SnCl₂·2H₂O than PtL₂Cl₂ or PtL′₂Cl₂; this effect is attributed to the ability of the weaker ligand L′ to function as a leaving group in the catalytic hydrogenation cycle.     

Thermal reduction of graphite oxide derivatives for preparation of supports for platinum hydrogenation catalysts

Thermal reduction of graphite oxide and its derivatives under argon atmosphere has been studied by means of thermogravimetric analysis. Carbon materials prepared via thermal reduction of graphite oxide derivatives in argon at 900°С during 3 h have been used for deposition of platinum from H₂PtCl₆ solutions. Pt particles supported on the support catalyze liquid-phase hydrogenation of nitrobenzene and dec-1-ene under atmospheric pressure of H₂. Thermal reduction of the supports based on graphite oxide results in the formation of the structural defects significantly enhancing the catalytic activity.     

Partial hydrogenation of benzene over platinum supported catalysts

Partial hydrogenation of benzene to cyclohexene has been studied on Pt/Nylon 66, Pt/MgO and Pt/TiO₂. An effect of the support on the selectivity to cyclohexene was observed, Pt/Nylon showing the highest selectivity, followed by Pt/MgO and Pt/TiO₂. An interaction of platinum with the more basic supports (Nylon, MgO) and a pretreatment under oxidizing conditions, results in a higher selectivity to cyclohexene.

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Pt/ 66, Pt/MgO PtTiO₂. , Pt/, Pt/MgO Pt/T,O₂. (, MgO) .

     

Preparing hydrogenation catalysts via the simultaneous reduction of graphite oxide and platinum(IV)

The simultaneous reduction of Pt(IV) and graphite oxide is performed for the preparation of hydrogenation catalysts. It is shown that of the four studied reducing agents (formate ion, ethylene glycol, sodium borohydride, and hydrazine), only NaBH₄ and hydrazine can be used in the preparation of catalysts. It is assumed that Pt particles (≥2 nm) are fixed to the defects, vacancies, and functional groups that are formed as a result of reduction. The prepared compositions catalyze the hydrogenation of decene-1 and nitrobenzene (45°C, 1 atm H₂) with specific activities comparable to those in the literature.     

Polymer-supported palladium and platinum species as hydrogenation catalysts

The synthesis of new hydrogel copolymers and their use for anchoring Pd and Pt species is described. The supported catalysts are effective for the reduction of alkenes, dienes, alkynes, and nitroaromatics under mild conditions. The catalysts have been characterized by chemical analysis, particle size measurement, IR, TGA, and x-ray photoelectron spectra. Relative reactivities and the effects of substrate structure, solvents, catalyst loading, particle size of the catalysts, and partial pressure of hydrogen have been determined. The kinetics of hydrogenation have been analyzed using concepts useful under slurry reaction conditions. The recycling efficiencies of the catalysts and product analysis to establish selectivities have been assessed. © 1992 John Wiley & Sons, Inc.     

Preparation of hydrogenation catalysts based on platinum nanoparticles supported on carbon nanomaterials

Hydrogenation catalysts as platinum nanoparticles supported on carbon nanomaterials (singleand multi-walled nanotubes, nanofibers, and fullerene black) have been obtained by modifying the platinum precursor with an organic base. A support pretreatment procedure for producing carboxyl groups on the nanotube and nanofiber surface is suggested.     

Mechanism of electroreduction of allyl alcohol at platinized platinum electrode in acidic aqueous solution.

The electroreduction of allyl alcohol to form propene at the platinized platinum electrode in acidic aqueous solution has been studied using CV plots, IR, ESR, and MS spectra, and a semiempricial MO method (MOPAC7/AM1, PM3). From the determinations of charge-transfer coefficients, reaction orders and apparent activation energy for the given reaction, the detection of the intermediates such as C(3)H(5)(+), C(3)H(5)(*), and C(3)H(5)(-) species, and PM3 calculations of charge distribution and frontier orbital energies of the reaction species C(3)H(5)OH and C(3)H(5)(+), the authors suggest that in acidic aqueous solution the production of propene via reductive splitting of the C-OH bond situated in the allyl position of allyl alcohol obeys a carbonium ion-carbanion mechanism.     

Deamination of butylamines on the surface of acidic oxide catalysts

Studies of the deamination of tert-, sec- and n-butylamines on several silicate and phosphate catalysts at 543–704 K have revealed that the reaction proceeds only with the participation of protonic cneters, its rate is independent of the strength of acidic centers and affected only by the amine structure. Butylammonium ion conversion is suggested to be the rate-determining step.

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-, - - 543–703 . , . , . , .

     

Catalytic transfer hydrogenation of 2-butanone over oxide catalysts

Catalytic transfer hydrogenation of 2-butanone with 2-propanol was studied in gas phase over a series of oxides of different acid-base properties. Although the basic oxides (MgO, La₂O₃) gave high initial conversions, these oxides underwent deactivation during the reaction. This deactivation could be partially prevented by a previous treatment with chloroform of the oxide. The amphoteric oxides (TiO₂, ZrO₂, Al₂O₃) were also active in this reaction. Increasing the acidic character of the catalyst (Nb₂O₅, WO₃) led to a pronounced dehydration of 2-propanol. The results obtained over a series of rare earth oxides (La₂O₃, Sm₂O₃, Gd₂O₃, Dy₂O₃, Er₂O₃) revealed that beside the role of basic and acid sites a correlation seems to exist between the number of unpaired electrons of the metal ion and the catalytic activity, indicating the role of one electron donor sites.     

Metal organic frameworks as nitric oxide catalysts

The use of metal organic frameworks (MOFs) for the catalytic production of nitric oxide (NO) is reported. In this account we demonstrate the use of Cu(3)(BTC)(2) as a catalyst for the generation of NO from the biologically occurring substrate, S-nitrosocysteine (CysNO). The MOF catalyst was evaluated as an NO generator by monitoring the evolution of NO in real time via chemiluminescence. The addition of 2, 10, and 15-fold excess CysNO to MOF-Cu(II) sites and cysteine (CysH) resulted in catalytic turnover of the active sites and nearly 100% theoretical yield of the NO product. Control experiments without the MOF present did not yield appreciable NO generation. In separate studies the MOF was found to be reusable over successive iterations of CysNO additions without loss of activity. Subsequently, the MOF catalyst was confirmed to remain structurally intact by pXRD and ATR-IR following reaction with CysNO and CysH.     

Oxidation of ethanol on platinum/alumina and copper oxide catalysts

The oxidation of ethanol on CuO, CuO/Al₂O₃ and Pt/Al₂O₃ catalysts has been studied at various concentrations of alcohol, oxygen and water vapor in the reaction mixture. The reaction order and activation energies have been determined for both complete and partial oxidation processes. A consecutive oxidation scheme is suggested.

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CuO, CuO/Al₂O₃ Pt/Al₂O₃ , . . .

     

NiO增强Pt/C催化剂催化氧化甲醇活性的研究

本文基于NiO作为Pt催化甲醇助催化剂的思路,通过Pt纳米颗粒担载在NiO修饰的碳材料载体上制备了Pt/NiO-C催化剂,系统地研究了不同的NiO/C热处理温度对Pt粒径的影响,并重点探讨了Pt对NiO的质量比对催化氧化甲醇的影响。X射线衍射分析结果显示NiO和Pt均为立方晶系,且NiO的加入有利于主催化剂Pt形成较小的粒径,且经400℃热处理NiO修饰的C材料作为载体有利于Pt的有效分散。所获得的Pt/NiO-C催化剂的电化学活性在甲醇酸性溶液中通过循环伏安法(CV)和计时电流法(CA)进行性能测试。CV测试结果显示以Pt/NiO重量比为4∶1的催化剂其电氧化甲醇活性最大,其峰值氧化电流密度达806 mA/mgPt,是Pt/C催化剂的1.64倍。CA测试结果显示Pt/NiO-C比Pt/C具有更好的抗CO中毒性能和稳定性。     

Chemoselective hydrogenation of phenol to cyclohexanol using heterogenized cobalt oxide catalysts

Cobalt oxide nanoparticles (NPs) supported on porous carbon (CoO_x@CN) were fabricated by one-pot method and the hybrids could efficiently and selectively hydrogenate phenol to cyclohexanol with a high yield of 98%.