Facile preparation of efficient oil-soluble MoS_2 hydrogenation nanocatalysts

Oil-soluble MoS2 nanoparticles with narrow size distribution have been synthesized by a facile composite-surfactants-aided-solvothermal process.The as-prepared nanoparticles can be directly used as hydrogenation nanocatalysts or as precursors to achieve efficient supported nanocatalysts.The surfaces of these nanoparticles are proposed to be encapsulated within a layer of organic modifiers,which are responsible for the enhancement of their solubility in organic solvents.The activated-carbon supported MoS2 nanocatalysts exhibit higher activity than the unsupported ones towards hydrogenation reactions of naphthalene,owing to the synergistic effects between nanoparticles and supports.The advantages of the present nanocatalysts,such as removal of conventional presulfiding requirements and reduction of nanoparticle aggregations,make them become promising applications in related petroleum chemical industry.     

Selective catalytic activity of ball-shaped Pd@MCM-48 nanocatalysts

Remarkable selectivity is achieved in the cleavage of benzyl ethers using ball-shaped palladium nanocatalysts, Pd@MCM-48, in an MCM-48 matrix. The unique nanocatalysts not only feature unprecedented complete hydrogenolysis selectivity of a benzyl ether over hydrogenation of a double bond, but also demonstrate selective cleavage of unsubstituted benzyl ether over substituted benzyl ethers.     

Selective catalytic hydrogenation of acetylenes

The products of the stepwise catalytic hydrogenation of undeca-1,7-diyne (I) have been examined and the sequence of the reduction established. The ethynyl group may be protected during catalytic hydrogenation by conversion into the corresponding 1-bromoacetylene.

Certain palladium catalysts have been shown to produce substantial amounts of trans-ethylene in the catalytic partial reduction of several acetylenic hydrocarbons. Catalytic stereomutation of cis- to trans-ethylene has been observed, the extent of which depends on the relative proportions of catalyst and unsaturated hydrocarbon.     

Non-contact biomimetic mechanism for selective hydrogenation of nitroaromatics on heterogeneous metal nanocatalysts

While the enzymatic reduction of unsaturated compounds usually has high specificity, highly selective reduction processes are hardly realized by heterogeneous industrial catalysts, which is critical for the green production of many fine chemicals. Here, we report an unexpected discovery of a biomimetic behavior of dicyandiamide(DICY)-modified Pt nanocatalysts for the green hydrogenation of a wide range of nitroaromatics. We demonstrate that the surface modification by DICY not only prevents the ...     

SMFs-supported Pd nanocatalysts in selective acetylene hydrogenation:Pore structure-dependent deactivation mechanism

In the present study,CNFs,ZnO and Al2O3 were deposited on the SMFs panels to investigate the deactivation mechanism of Pd-based catalysts in selective acetylene hydrogenation reaction.The examined supports were characterized by SEM,NH3-TPD and N2adsorption-desorption isotherms to indicate their intrinsic characteristics.Furthermore,in order to understand the mechanism of deactivation,the resulted green oil was characterized using FTIR and SIM DIS.FTIR results confirmed the presence of more unsaturated constituents and then,more branched hydrocarbons formed upon the reaction over alumina-supported catalyst in comparison with the ones supported on CNFs and ZnO,which in turn,could block the pores mouths.Besides the limited hydrogen transfer,N2 adsorption-desorption isotherms results supported that the lowest pore diameters of Al2O3/SMFs close to the surface led to fast deactivation,compared with the other catalysts,especially at higher temperatures.     

SMFs-supported Pd nanocatalysts in selective acetylene hydrogenation: Pore structure-dependent deactivation mechanism

In the present study, CNFs, ZnO and Al₂O₃ were deposited on the SMFs panels to investigate the deactivation mechanism of Pd-based catalysts in selective acetylene hydrogenation reaction. The examined supports were characterized by SEM, NH₃-TPD and N₂ adsorption-desorption isotherms to indicate their intrinsic characteristics. Furthermore, in order to understand the mechanism of deactivation, the resulted green oil was characterized using FTIR and SIM DIS. FTIR results confirmed the presence of more unsaturated constituents and then, more branched hydrocarbons formed upon the reaction over alumina-supported catalyst in comparison with the ones supported on CNFs and ZnO, which in turn, could block the pores mouths. Besides the limited hydrogen transfer, N₂ adsorption-desorption isotherms results supported that the lowest pore diameters of Al₂O₃/SMFs close to the surface led to fast deactivation, compared with the other catalysts, especially at higher temperatures.     

Air-promoted selective hydrogenation of phenol to cyclohexanone at low temperature over Pd-based nanocatalysts

Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy(E_a, 55–70 kJ/mol). Here we report a simple and efficient strategy for phenol hydrogenation catalyzed by Pd in aqueous phase at 30 °C by introducing air to promote the catalysis. With the assistance of air, 99% conversion and 99% selectivity were achieved over Pd(111)/Al_2O_3 with an overall turnover frequency(TOF) of621 h~(-1), ~80 times greater than that of the state-of-art Pd catalyst at 30 °C. Mechanism studies revealed that phenol was activated to generate phenoxyl radicals. The radicals were yielded from the reaction between phenol and hydroxyl radicals in the presence of hydrogen, oxygen and protic solvent on Pd. The phenoxyl pathway resulted in a low apparent E_a(8.2 kJ/mol) and thus high activity. More importantly, this strategy of activating substrate by air can be adapted to other Pd based catalysts, offering a new thinking for the rational design of cyclohexanone production in industry.     

Selective hydrogenation of nitro derivatives of hydroquinolines

By catalytic hydrogenation of p-nitrophenylhydroquinolines with 5-oxo- and 5-oxime functional groups in the presence of heterogeneous palladium complex catalysts, we have obtained the corresponding amino derivatives.Scientific-Research Institute of Chemistry at Saratov State University, Saratov 410026. Translated from Khimiya Geterotsildicheskikh Soedinenii, No. 8, pp. 1138–1140, August, 1995. Original article submitted June 8, 1995.     

Selective hydrogenation of the vinyl group of 1-vinylpyrroles

The hydrogenation of 1-vinylpyrroles over Raney nickel in ethanol at 50–90°C proceeds exclusively at the 1-vinyl group and leads to the formation of 1-ethylpyrroles in 80–90% yields. The IR and PMR spectra are presented.Translated from Khimiya Geterotsilicheskikh Soedinenii, No. 2, pp. 215–216, February, 1077.     

Selective iron-catalyzed transfer hydrogenation of terminal alkynes

A novel iron-catalyzed transfer hydrogenation of alkynes to the corresponding alkenes applying formic acid as a hydrogen donor is reported. An in situ combination of Fe(BF(4))(2)·6H(2)O and tetraphos allows for highly selective hydrogenation of a broad range of aromatic and aliphatic alkynes tolerating different functional groups.     

Selective hydrogenation of nitrobenzene in aprotic media

The kinetics of hydrogenation of nitrobenzene in aprotic media was studied, and a scheme of the mechanism and a kinetic equation, corresponding to it, for the initial reaction rate are proposed. High selectivity with respect to N-phenylhydroxylamine is apparently due to the aprotic nature and donor properties of the solvent and also to the functioning of the catalyst as a unique hydrogen electrode.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 45–48, January, 1991.The author thanks V. V. Strelets for useful discussion.     

水-有机两相体系中钌络合物催化肉桂醛选择性加氢瓜研究

对RuCl3·XH2O和TPPTS[P(m-C6H4SO3Na)3]原位合成的水溶性钌膦络合物在水-有机两相体系中对肉桂醛的选择性加氢反应,考察了反应温度时间、膦配体浓度、搅拌速度、底物和催化剂之比等条件对反应活性和选择性的影响.对比了单长工链阳离子表面活性剂CTAB和双长链阳离子表面活性剂DCMAB(dicetyldimethylammonium)的助催化作用,发现DCMAB化作用明显优于CTAB,在DCMAB助催化作用下,转化率98.3%,选择性96.9%.     

Selective hydrogenation of phenol in supercritical carbon dioxide

Liquid phase hydrogenation of phenol over Pt/C catalysts was investigated under conventional conditions and supercritical carbon dioxide (scCO2). The equivalent ration of hydrogen to phenol shows a significant effect on the product selectivity. Hydrogenation of phenol in different solvents was also studied, the experimental results show that polarity of solvents influences the yield of cyclohexanone remarkably, scCO2 has the highest one. Catalytic hydrogenation of phenol in scCO2 or sub-scCO2 was emphatically researched. The result is that near the critical point of CO2 phenol has higher reaction activity than that of normal organic solvents, cyclohexanone has 47% in yield and 87% in selectivity.     

Alkyne hydrogenation using Pd–Ag hybrid nanocatalysts in surface‐immobilized dendrimers

A series of Pd–Ag mixed‐metal nanocatalysts were prepared by reduction of Pd–Ag salts in the presence of poly(propylene imine) dendrimers, which were covalently bound to the surface of a silica polyamine composite, BP‐1 (polyallylamine covalently bound to a silanized amorphous silica gel). Three different Pd‐to‐Ag ratios were evaluated (50:50, catalyst 1 ; 40:60, catalyst 2 ; 60:40, catalyst 3 ) with the goal of determining how the amount of Ag effects selectivity, rate and conversion in the selective reduction of alkynes, such as phenylacetylene and 1‐ or 4‐octyne, to the corresponding alkenes. Conditions for the catalysis are reported where there is improved selectivity without a serious reduction in rate when compared with the analogous Pd‐only catalysts. Catalyst 2 worked best for phenylacetylene and catalyst 3 worked best for the octynes. The catalysts could be reused seven times without loss of activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Selective hydrogenation of tetrahydrofuryl acetylenic alcohols and acetates

Hydrogenation of tetrahydrofuryl acetylenic alcohols and acetates in the presence of a supported Pd-containing catalyst has been revealed to proceed at high rate and selectivity to compounds with internal triple bonds. Selectivity in olefin production is 98–99% at the complete conversion of the substrate, the activity of the catalyst varies from 1700 to 13,100 mol/g-at. Pd'h at 20°C and P_{H 2}=0.1 MPa.

---

. . , . 98–99% , 1700–13 100 /-. Pd' 20°C 0,1 .

     

Selective hydrogenation of ergosterol and its acetate.

Selective hydrogenation of ergosterol or its acetate in solution in different solvents over Raney nickel to give 5α-ergosta-7,22-dien-3β-ol or its acetate can be controlled by the addition of paraformaldehyde, acetaldehyde, benzaldehyde, 4-dimethylaminobenzaldehyde, and dimethylaniline, the latter 2 giving the best yield. When using pure solvents 5α-ergost-7-en-3β-ol or its acetate can be obtained in almost quantitative yield.     

Selective dehalogenation and hydrogenation of compounds in adsorption layers with tritium gas

Selective dehalogenation and hydrogenation were observed in treating the corresponding precursors supported on a heterogeneous carrier with tritium gas. This technique was used to obtain tritium-labeled 3′,3,5-triiodothyronine, dihydrofusicoccin terpenoid (DHF), and 3-(piperidine-4-yl)-1,4-dihydroquinazoline-2-on with a molar radioactivity of 0.76, 2.3, and 6.5 PBq/mol, respectively.     

Selective hydrogenation of crotonaldehyde over raney cobalt catalysts modified with heteropolyacid salts

RCo-based catalysts were modified with Keggin type heteropolyacid salts, including alkali, alkaline earth and transition metal salts. The selective hydrogenation of crotonaldehyde was investigated over these catalysts. The selectivities to crotyl alcohol can be improved on all modified catalysts. Among them, the catalyst modified with copper salts of 12-molybdophosphates shows the best performance in improving the selectivity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Unique hydrogenation activity of supported tin catalyst: Selective hydrogenation catalyst for unsaturated aldehydes

Selective hydrogenation of unsaturated aldehydes, crotonaldehyde (CH₃CH=CHCH=O) and cinnamaldehyde (C₆H₅CH=CHCH=O), has been studied over SiO₂-supported monometallic Sn and bimetallic Rh---Sn catalysts in the liquid phase. Over a silica-supported monometallic Rh catalyst, Rh/SiO₂, no unsaturated alcohol (crotyl alcohol or cinnamyl alcohol) was formed, whereas considerable amounts of the corresponding saturated aldehyde and saturated alcohol were obtained. The selectivity to the unsaturated alcohol was improved over the Rh---Sn bimetallic catalyst. The selectivity to the corresponding unsaturated alcohol attained ca. 65% over the Rh---Sn bimetallic catalysts. On the other hand, The supported Sn catalyst showed markedly high selectivity to the unsaturated alcohols. The selectivity of the Sn/SiO₂, attained 95% to crotyl alcohol and 100% to cinnamyl alcohol, respectively. Although the conversion of each unsaturated aldehyde over Rh---Sn/SiO₂ catalysts was greater than that over Sn/SiO₂ catalysts, the selectivity of Sn/SiO₂ catalysts to the corresponding unsaturated alcohols was superior to that over Rh---Sn/SiO₂. The selectivity of Sn/SiO₂ was also compared with that of Rh---Sn/SiO₂ at a similar conversion of the unsaturated aldehydes. The selectivity of Sn/SiO₂ was significantly greater than that of the Rh---Sn bimetallic catalyst. These results indicate that the high selectivity over Sn/SiO₂ was ascribed not to low conversion but to intrinsic selectivity of the Sn catalyst.