Air-stable,storable, and highly selective chiral Lewis acid catalyst

An air-stable, storable, and highly selective chiral Lewis acid catalyst for asymmetric Mannich-type reactions has been developed. The catalyst can be stored for more than three months in air at room temperature without loss of activity. Moreover, it has also been demonstrated that the catalyst can be recovered and reused. [structure: see text]     

A silica-supported, switchable, and recyclable hydroformylation-hydrogenation catalyst

A homogeneous hydroformylation catalyst, designed to produce selectively linear aldehydes, was covalently tethered to a polysilicate support. The immobilized transition-metal complex [Rh(A)CO]+(1+)), in which A is N-(3-trimethoxysilane-n-propyl)-4,5-bis(diphenylphosphino)phenoxazine, was prepared both via the sol-gel process and by covalent anchoring to silica. 1+ was characterized by means of (31)P and (29)Si MAS NMR, FT-IR, and X-ray photoelectron spectroscopy. Polysilicate immobilized Rh(A) performed as a selective hydroformylation catalyst showing an overall selectivity for the linear aldehyde of 94.6% (linear to branched aldehyde ratio of 65). In addition 1-nonanol, obtained via the hydrogenation of the corresponding aldehyde, was formed as an unexpected secondary product (3.6% at 20% conversion). Under standard hydroformylation conditions, 1+ and HRh(A)(CO)(2)(1) coexist on the support. This dual catalyst system performed as a hydroformylation/hydrogenation sequence catalyst (Z), giving selectively 1-nonanol from 1-octene; ultimately, 98% of 1-octene was converted to mainly 1-nonanal and 97% of the nonanal was hydrogenated to 1-nonanol. The addition of 1-propanol completely changes Z in a hydroformylation catalyst (X), which produces 1-nonanal with an overall selectivity of 93%, and completely suppresses the reduction reaction. If the atmosphere is changed from CO/H(2) to H(2) the catalyst system is switched to the hydrogenation mode (Y), which shows a clean and complete hydrogenation of 1-octene and 1-nonanal within 24 h. The immobilized catalyst can be recycled and the system can be switched reversibly between the three "catalyst modes" X, Y, and Z, completely retaining the catalyst performance in each mode.     

A Manganese Pre‐Catalyst: Mild Reduction of Amides,Ketones, Aldehydes,and Esters

A new (N ‐phosphinoamidinate)manganese complex is shown to be a useful pre‐catalyst for the hydrosilative reduction of carbonyl compounds, and in most cases at room temperature. The Mn‐catalyzed reduction of tertiary amides to tertiary amines, with a useful scope, is demonstrated for the first time by use of this catalyst, and is competitive with the most effective transition‐metal catalysts known for such transformations. Ketones, aldehydes, and esters were also successfully reduced under mild conditions by using this new Mn catalyst.     

A Manganese Pre‐Catalyst: Mild Reduction of Amides,Ketones, Aldehydes,and Esters

A new (N ‐phosphinoamidinate)manganese complex is shown to be a useful pre‐catalyst for the hydrosilative reduction of carbonyl compounds, and in most cases at room temperature. The Mn‐catalyzed reduction of tertiary amides to tertiary amines, with a useful scope, is demonstrated for the first time by use of this catalyst, and is competitive with the most effective transition‐metal catalysts known for such transformations. Ketones, aldehydes, and esters were also successfully reduced under mild conditions by using this new Mn catalyst.     

Hydrolysis of cellulose by amorphous carbon bearing SO3H, COOH, and OH groups

The hydrolysis of cellulose into saccharides using a range of solid catalysts is investigated for potential application in the environmentally benign saccharification of cellulose. Crystalline pure cellulose is not hydrolyzed by conventional strong solid Br?nsted acid catalysts such as niobic acid, H-mordenite, Nafion and Amberlyst-15, whereas amorphous carbon bearing SO 3H, COOH, and OH function as an efficient catalyst for the reaction. The apparent activation energy for the hydrolysis of cellulose into glucose using the carbon catalyst is estimated to be 110 kJ mol (-1), smaller than that for sulfuric acid under optimal conditions (170 kJ mol (-1)). The carbon catalyst can be readily separated from the saccharide solution after reaction for reuse in the reaction without loss of activity. The catalytic performance of the carbon catalyst is attributed to the ability of the material to adsorb beta-1,4 glucan, which does not adsorb to other solid acids.     

Synthesis, characterization, and catalytic application of PbS nanoparticles for the synthesis of amidoalkyl naphthols under solvent-free conditions

A simple one-pot synthesis has been developed for the synthesis of amidoalkyl naphthols using an efficient and recyclable nanocrystalline PbS catalyst under solvent-free condition. Using this nanocrystalline solid catalyst, the reactions could be carried out under mild reaction conditions with very good yield (85–95 %). This catalyst could be recycled very easily, which makes this methodology environmentally benign. The biologically active drug-like molecule 1-aminomethyl-2-naphthol derivatives can be easily obtained from 1-amidomethyl-2-naphthol by amide hydrolysis reaction in the presence of PbS nanoparticles. Characterization of the catalyst was performed by X-ray diffraction, transmission electron microscopy, and adsorption/desorption analysis (BET).     

Catalytic,theoretical, and biological investigation of an enzyme mimic model

Artificial catalyst studies were always stayed at the kinetics investigation level, in this work bioactivity of designed catalyst were shown by the induction of biomineralization of the cells, indicating the possible use of enzyme mimics for biological applications. The development of artificial enzymes is a continuous quest for the development of tailored catalysts with improved activity and stability. Understanding the catalytic mechanism is a replaceable step for catalytic studies and artificial enzyme mimics provide an alternative way for catalysis and a better understanding of catalytic pathways at the same time. Here we designed an artificial catalyst model by decorating peptide nanofibers with a covalently conjugated catalytic triad sequence. Owing to the self-assembling nature of the peptide amphiphiles, multiple action units can be presented on the surface for enhanced catalytic performance. The designed catalyst has shown an enzyme-like kinetics profile with a significant substrate affinity. The cooperative action in between catalytic triad amino acids has shown improved catalytic activity in comparison to only the histidine-containing control group. Histidine is an irreplaceable contributor to catalytic action and this is an additional reason for control group selection. This new method based on the self-assembly of covalently conjugated action units offers a new platform for enzyme investigations and their further applications. Artificial catalyst studies always stayed at the kinetics investigation level, in this work bioactivity of the designed catalyst was shown by the induction of biomineralization of the cells, indicating the possible use of enzyme mimics for biological applications.     

In an attempt to provide a user's guide to the galaxy of benzylidene, alkoxybenzylidene, and indenylidene ruthenium olefin metathesis catalysts

The data reported in this paper demonstrate that great care must be taken when choosing an appropriate catalyst for a given metathesis reaction. First-generation catalysts were found to be useful in the metathesis of sterically unhindered substrates. Second-generation catalysts (under optimised conditions) showed good to excellent activities toward sterically hindered and electron-withdrawing group (EWG)-substituted alkenes that do not react using the first-generation complexes. A strong temperature effect was noted on all of the reactions tested. Interestingly, attempts to force a reaction by increasing the catalyst loading were much less effective. Therefore, when possible, it is suggested that metathesis transformations should be carried out with a second-generation catalyst at 70 degrees C in toluene. However, different second-generation catalysts proved to be optimal for different applications and no single catalyst outperformed all others in all cases. Nevertheless, some empirical rules can be deduced from the model experiments, providing preliminary hints for the selection of the optimal catalysts.     

Non-Oxidative Reforming of Methane in a Mini-Gliding Arc Discharge Reactor: Effects of Feed Methane Concentration, Feed Flow Rate, Electrode Gap Distance, Residence Time, and Catalyst Distance

In this work, a mini-gliding arc discharge reactor was employed for the reforming of methane under ambient temperature and pressure operation. Acetylene and hydrogen were produced dominantly with high selectivities of ~70?C90 and ~75%, respectively. The results showed that both methane conversion and product selectivities depended strongly on various operating parameters, including feed methane concentration, feed flow rate, electrode gap distance, residence time, and the presence of a reforming catalyst (as a function of catalyst distance). The Ni catalyst-loaded porous alumina-silica plate was used to study the catalytic effect on the process performance at various residence times. A considerable enhancement of methane conversion and product yields was achieved in the combined plasma-catalytic system, particularly at a longer residence time. The catalyst distance, or packing position of catalyst plate, was also found to be an important factor affecting the process performance of the combined plasma-catalytic methane reforming. The closer catalyst distance led to the greater methane conversion because of the greater possibility of adsorption?Cdesorption interactions of excited gaseous species on the catalyst surface to enhance subsequent reactions.     

CuO nano-particles supported on silica,a new catalyst for facile synthesis of benzimidazoles,benzothiazoles and benzoxazoles

A facile synthetic route for benzimidazoles, benzothiazoles and benzoxazoles comprising the reaction of corresponding o-phenylenediamine, o-aminothiophenol and o-aminophenol with various aldehydes using silica supported nano-copper (II) oxide as a catalyst has been described. The catalyst exhibited a clean reaction profile with excellent yields in a short reaction time. The catalyst can be recycled effectively after use.     

Acrylonitrile from Propylene,Ammonia, and Atmospheric Oxygen

Acrylonitrile was produced in pilot plant from propylene, ammonia, and atmospheric oxygen in a fixed-bed reactor in the presence of Bi/Mo/Si oxide shell catalyst. The propylene conversion, which can amount to about 70% under optimal conditions, was studied as a function of structural properties and the chemical composition of the catalyst, and of the composition of the starting mixture. Acrylonitrile of adequate purity for use in polymerizations could be obtained by multi-stage processing of the crude product.     

Concise synthesis,preparative resolution,absolute configuration determination,and applications of an atropisomeric biaryl catalyst for asymmetric acylation

A new three-step synthesis and resolution of nucleophilic catalyst 1 suitable for large-scale preparation has been developed, and this catalyst has been shown to be effective for the kinetic resolution and asymmetric desymmetrization of a range of sec-alcohol substrates.     

Pt/CeO2-ZrO2变换催化剂的制备、表征与性能

 用共沉淀法制备了不同Ce/Zr比的CeO2-ZrO2复合氧化物,用浸渍法制备了Pt/CeO2-ZrO2水煤气变换催化剂,并对该催化剂进行了活性评价. 结果表明,与传统的Cu基低变催化剂相比,该催化剂具有操作温度范围宽和抗氧化冲击等优点,具有应用于车载重整制氢过程的潜力. 考察了温度、空速和汽/气比等条件对催化剂活性的影响,对催化剂的制备参数和工艺参数进行了研究. 结果表明,不同Ce/Zr比的Pt/CeO2-ZrO2催化剂的活性相差很大,其中Pt/Ce0.8Zr0.2O2变换催化剂活性最高. XRD结果表明,制备的Pt/Ce0.8Zr0.2O2形成了固溶体. 通过增加单位质量催化剂表面的Pt原子数可提高催化剂的活性.     

CuMoO4 Bimetallic Nanoparticles,An Efficient Catalyst for Room Temperature C−S Cross-Coupling of Thiols and Haloarenes

Cu^II catalyst is less efficient at room temperature for C−S cross-coupling. C−S cross-coupling by Cu^II catalyst at room temperature is not reported; however, doping of copper with molybdenum metal has been realized here to be more efficient for C−S cross-coupling in comparison to general Cu^II catalyst. The doped catalyst CuMoO₄ nanoparticle is found to be more efficient than copper. The catalyst works under mild conditions without any ligand at room temperature and is recyclable and effective for a wide range of thiols and haloarenes (ArI, ArBr, ArF) from milligram to gram scale. The copper-based bimetallic catalyst is developed and recognized for C−S cross-coupling of haloarenes with alkyl and aryl thiols.     

Synthesis,characterization, and application of hollow ceramic microsphere based Pd catalyst for hydrogenation of 2-ethylanthraquinone

Palladium metal has been used extensively in the hydrogenation reactions due to their great affinity towards hydrogen atoms. In the present study, the catalyst preparation attempted with Pd supported Hollow Ceramic Microspheres using wet impregnation method and its use as catalysts is explored in the hydrogenation of 2-ethylanthraquinone studing the effect of the reaction time, temperature, volume of working solution and the catalyst dosages on the conversion of 2-ethylanthraquinone and yield of hydrogen peroxide. The hydrogenation reaction of 2-ethylanthraquinone is the key step in the anthraquinone method for the industrial production of the hydrogen peroxide. The Pd supported catalyst was characterized by XRF, FTIR, and BET to confirm the composition of the prepared catalyst, Pd deposition, and the surface area. The highest catalyst activity was found to be 9.42 ​g/L with the maximum conversion of 96% at 70°C, 0.3 ​MPa. The kinetics of the heterogeneous hydrogenation reaction of 2-ethylanthraquinone with Pd supported on Hollow Ceramic Microspheres as catalyst was also investigated. This paper is in contribution of our earlier publication.     

Solvent-free,microwave-assisted highly efficient,rapid and simple synthesis of biphenyl compounds by using silica based Pd(II) catalyst

To maintain catalytic performance of any catalyst for a long time, the selection of support material is a very important parameter for heterogeneous catalytic systems, and this performance makes the catalyst valuable. In view of its low cost and availability, silica can be considered as a good support material for transition metal ions in the cross coupling reactions. Therefore, this study describes i) silica-gel based palladium catalyst with a long-term catalytic performance, ii) rapid, simple, economic, and green procedure which was developed for Suzuki reactions. The catalyst showed superior reusability (ten runs) and catalytic efficiency against coupling reactions under mild conditions (50°C, 5 min and air atmosphere). Moreover, the catalyst gave partially good reaction yields with aril chlorides which have poor activity in coupling reactions. In addition, an excellent turnover number (TON: 66000) and frequency (TOF: 825000) were obtained using very small catalyst loading (1.5 × 10^?3 mol %). This paper concludes that silica-gel based Pd(II) catalyst and the protocol of synthesis of biaryls were suitable for coupling reactions.     

Structured Catalysts Prepared by Electroless Plating Technique onto a Metal Substrate, for a Wall-Type Hydrogen Production System

This article reviews our works on the structured catalysts for a wall-type hydrogen production system including methanol steam reforming (MSR), CO shift reaction (CO SR) and methanol decomposition (MD). The structured catalysts were copper-based, palladium-based and nickel-based catalysts. Such a series of structured catalysts were prepared by the electroless plating technique that is a novel method for preparing a structured type catalyst onto a metal-substrate. The copper-based catalyst exhibited high performance for MSR and CO SR, the palladium-based catalyst high for MSR, and the nickel-based catalyst high for MD. The catalytic properties of these catalysts were affected by the difference of the plating condition and the pretreatment condition prior to the reaction. In the copper-based catalyst, the reforming and shift activities were enhanced by the oxidation treatment. One of the factors of such activity enhancement by the oxidation was thought to be in close proximity existence of copper and zinc atoms. A lot of monodentate-type formate species having high reactivity was formed on the oxidized catalyst, which would be correlated to the activity enhancement. In the palladium-based catalyst, the reforming activity was improved by the continuous reduction treatment followed by the oxidation. Such continuous pretreatment formed the PdZn alloy species thought to be a reforming site in the surface layer. The decomposition performance of the nickel-based catalyst depended on the ratio of the crystallite size of nickel particles to that of aluminum particles. The electronic influence of zinc and phosphorous components incorporated in the plated layer contributed to the improvement of the selectivity of product.     

A new advanced method for heterogeneous catalysed dechlorination of 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzenes in hydrocarbon solvent

A new advanced method for dechlorination of 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzenes in organic solvent catalysed by palladium on carbon support and solid hydrazine hydrochloride yields benzene in short reaction times. The catalyst system can be efficiently reused for several cycles. Ultrasound radiation of the heterogeneous catalyst reaction increases remarkably the rate of dechlorination.     

Pd-poly(N-vinyl-2-pyrrolidone)/KIT-6 nanocomposite: Preparation,structural study,and catalytic activity

The Pd-poly(N-vinyl-2-pyrrolidone)/KIT-6 nanocomposite was prepared by an in situ polymerization method and used as an efficient heterogeneous catalyst for C–C bond formation through the Heck coupling reaction of aryl iodides, bromides and chlorides with styrene. The physical and chemical properties of the catalyst were characterized by XRD, BET, FT-IR, TGA, UV-Vis and TEM techniques. The reactions were performed in methanol-water as solvent and the products were obtained in high yield and purity after a simple work-up. The stability of the nanocomposite catalyst was excellent and could be reused 8 times without much loss of activity in the Heck coupling reaction.     

Short synthesis of bis-NHC-Pd catalyst derived from caffeine and its applications to Suzuki, Heck, and Sonogashira reactions in aqueous solution

A short and efficient synthesis of a bis-NHC-palladium catalyst simply prepared from caffeine in two steps was reported. The air and moisture stable Pd catalyst can be used as a good catalyst in running Suzuki-Miyaura, Mizoroki-Heck, and Sonogashira reactions in aqueous solution.