Nanocrystalline TiO_2 as an efficient and reusable catalyst for the chemoselective trimethylsilylation of primary and secondary alcohols and phenols

Nanocrystalline TiO₂ was used as an efficient and recyclable catalyst for the chemoselective trimethylsilylation of primary and less hindered secondary alcohols and phenols with hexamethyldisilazane（HMDS）.All reactions were performed under mild and completely heterogeneous conditions in good to excellent yields.     

One-pot synthesis of 1, 3-thiazolidin-4-one using Bi(SCH2COOH)3 as catalyst

A catalytic multi-component reaction involving aromatic amine,aromatic aldehydes,mercapto acid as substrates and Bi（SCH₂COOH）₃ as catalyst under solvent free conditions,afforded thiazolidin-4-one in good yields.The efficiency of the catalyst was proved with a variety of substrates,ranging from electrondeficient to electron-rich aldehydes.     

Characterization and photocatalytic properties of silver and silver chloride doped TiO2 hollow nanoparticles

Using polystyrene（PSt） particles as template,PSt/TiO₂ composite particles with AgCl incorporation were prepared through hydrolysis of tetrabutyl titanate in the presence of AgNO₃ and NaCl.AgCl doped TiO₂ hollow particles were successfully prepared with the PSt/TiO₂ composite microspheres pretreated at 180℃followed by calcination.The morphology of PSt/TiO₂ particles and the crystal structures of the AgCl doped TiO₂ hollow particles were characterized.The photocatalytic activity of the doped TiO₂ hollow particles in degradation of Rhodamine B was tested under UV and visible lights and compared to that with Ag doped TiO₂ particles.The results showed that TiO₂ hollow particles,either doped with Ag or AgCl,demonstrated higher photocatalytic activity than the pure TiO₂ particles.This enhancement in photocatalytic activity was more significant with AgCl doped TiO₂ than that with Ag doped,and more distinct when the degradation was done under visible light than that under LTV light.     

氧化铝负载的银纳米颗粒高选择性催化合成亚胺(英)

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al₂O₃ was studied.The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines.The reactions were performed under mild conditions and afforded the imines in high yield（up to 99%） without any byproducts other than H₂O.The highest activity was obtained over 5 wt%Ag/Al₂O₃ in toluene with air as oxidant.The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H₂ in the gas phase.The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis.     

A copper- and amine-free Sonogashira reaction employing chlorophosphine as new and efficient ligand

An efficient palladium-catalyzed copper- and amine-free Sonogashira coupling reaction of aryl bromides and chlorides was studied using a sterically hindered monooxychlorophosphine as new ligand.The use of 2 mol%Pd（OAc）₂ in the presence of K₂CO₃ allows the coupling reaction to proceed at mild condition with good to excellent yields.     

The amount effect of catalyst on the urethane reaction of o-hydroxybenzyl alcohol

The urethane reaction of o-hydroxybenzyl alcohol with phenyl isocyanate was monitored with in situ FT-IR.Dibutyltin dilaurate was used as catalyst and its amount effect was investigated.It was found that there was an obvious induction period before reaction began.It was interesting that the time of induction period climbed up and then declined with the increase of dibutyltin dilaurate. When the concentration of dibutyltin dilaurate reached 9.58×10^-5 mol/L,the induction period disappeared completely and hereafter did not appear any more.Furthermore,the urethane reaction kinetics was studied.When the concentration of dibutyltin dilaurate increased,the reaction rate of phenolic group（k₁） increased sharply,but the reaction rate of alcoholic group（k₂） appeared of little change on the whole.k₁ increased about 20-fold,yet k₂ increased about 2-fold when the concentration of dibutyltin dilaurate varied from 9.58×10^-6 mol/L to 1.92×10⁴ mol/L,which made the value of k₁/k₂ enlarge.     

Optimization and statistical analysis of Au-ZnO/Al2O3 catalyst for CO oxidation

In our former work[Catal.Today 174（2011） 127],12 heterogeneous catalysts were screened for CO oxidation,and Au-ZnO/Al₂O₃ was chosen and optimized in terms of weight loadings of Au and ZnO.The present study follows on to consider the impact of process parameters （catalyst preparation and reaction conditions）,in conjunction with catalyst composition（weight loadings of Au and ZnO,and the total weight of the catalyst）,as the optimization of the process parameters simultaneously optimized the catalyst composition.The optimization target is the reactivity of this important reaction.These factors were first optimized using response surface methodology（RSM） with 25 experiments,to obtain the optimum:100 mg of 1.0%Au-4.1%ZnO/Al₂O₃ catalyst with 220℃calcination and 100℃reduction.After optimization,the main effects and interactions of these five factors were studied using statistical sensitivity analysis（SA）.Certain observations from S A were verified by reaction mechanism,reactivity test and/or characterization techniques,while others need further investigation.     

Simple route to indeno[1, 2-b]quinoline derivatives via a coupling reaction catalyzed by TiO2 nanoparticles

A simple,efficient and high yielding approach for the synthesis of indeno[1,2-b]quinolinediones has been developed by a one-pot,four-component,coupling reaction utilizing TiO₂ nanoparticles（TiO₂-NPs） as a heterogeneous catalyst at 80℃in aqueous media.     

Epoxy ether cleaving reactions catalyzed by supporting Lewis acidic ionic liquid

Lewis acidic ionic liquids were used to catalyze the reaction of epoxypropane with POCl₃.Considering the lower cost and catalytic activities,we concluded that[Et₃NH]Cl/AlCl₃ was the most attractive ionic liquid from an economical point of view.But it would be easily inactivated because of sensitive to water and air.Moreover,it could not be reused easily because of difficulty recovery in the reaction.However,supporting[Et₃NH]Cl/AlCl₃ catalyst could resolve above problems.Supporting[Et₃NH]Cl/ AlCl₃ catalyst could be separated by filter easily and reused 5 times in 98%yield.Furthermore,the catalyst was applicable to other epoxy ether cleaving reactions.     

NiSe2-CoSe2 with a Hybrid Nanorods and Nanoparticles Structure for Efficient Oxygen Evolution Reaction

Hetero-structure induced high performance catalyst for oxygen evolution reaction(OER)in the water splitting reaction has received increased attention.Herein,we demonstrated a novel catalyst system of NiSe₂-CoSe₂ consisting of nanorods and nanoparticles for the efficient OER in the alkaline electrolyte.This catalyst system can be easily fabricated via a low-temperature selenization of the solvothermal synthesized NiCo(OH)x precursor and the unique morphology of hybrid nanorods and nanoparticles was found by the electron microscopy analysis.The high valence state of the metal species was indicated by X-ray photoelectron spectroscopy study and a strong electronic effect was found in the NiSe₂-CoSe₂ catalyst system compared to their counterparts.As a result,NiSe₂-CoSe₂ exhibited high catalytic performance with a low overpotential of 250 mV to reach 10 mA·cm^-2 for OER in the alkaline solution.Furthermore,high catalytic stability and catalytic kinetics were also observed.The superior performance can be attributed to the high valence states of Ni and Co and their strong synergetic coupling effect between the nanorods and nanoparticles,which could accelerate the charge transfer and offer abundant electrocatalytic active sites.The current work offers an efficient hetero-structure catalyst system for OER,and the results are helpful for the catalysis understanding.     

Catalytic effect of lucunary heteropolyanion containing molybdenum and tungsten atoms on decolorization of direct blue 71

In this research,a lucunary Keggin structure,[PMo₂W₉O₃₉]^7- was selected as an efficient homogenous catalyst for degradation of an azo dye（direct blue 71） and a simple method was developed for degradation of DB71.The method is based on the oxidation of azo dye in the presence of a lucunary Keggin form of polyoxometalates,K₇[PMo₂W₉O₃₉]? 19H₂O,as a homogenous catalyst at room temperature.The reaction is monitored spectrophotometrically by measuring the absorbance of dye atλ=585 nm.Some parameters including concentration of catalyst,concentration of H₂O₂,pH and reaction time were investigated and optimized. Results show that K₇[PMo₂W₉O₃₉]? 19H₂O is more efficient in the presence of hydrogen peroxide.Degradation of dye in the presence of the catalyst and H₂O₂ could lead to the disappearance approximately 65%of dye after 60 min.But degradation for the same experiment performed in the absence of catalyst or in the absence of H₂O₂ was 22%or 5%respectively.Approximately 87% azo dyes has been eliminated after 90 min in the presence of catalyst,H₂O₂ and optimize conditions(0.6 g/L of K₇[PMo_2- W₉O₃₉H₉H₂O,0.08 mol/L hydrogen peroxide and room temperature).     

Effect of initial precursor concentration on TiO2 thin film nanostructures prepared by PCVD system

TiO₂ thin film was prepared on Si substrate by plasma chemical vapor deposition（PCVD） system and the morphologies of TiO₂ thin film were controlled by adjusting the initial precursor concentration.As the initial titanium tetra-isopropoxide（TTIP） concentration increases in PCVD reactor,the shapes of TiO₂ particles generated in PCVD reactor change from the spherical small-sized particles around 20 nm and spherical large-sized particles around 60 nm to aggregate particles around 100 nm.The TiO₂ particles with different shapes deposit on the substrate and become the main building blocks of resulting TiO₂ thin film.We observed the TiO₂ thin film with smooth morphology at low initial TTIP concentration,granular morphology at medium initial TTIP concentration,and columnar morphology at high initial TTIP concentration.It is proposed that we can prepare the TiO₂ thin film with controlled morphologies in one-step process just by adjusting the initial precursor concentration in PCVD.     

Amorphous Cu0 on Carbon Nanofiber as Recyclable Heterogeneous Catalyst for N-Arylation Reactions

A novel heterogeneous catalyst,amorphous Cu^0 on the carbon nanofibers was developed and characte-rized by means of several characterization techniques.The prepared Cu^0 was investigated as a heterogeneous catalyst for N-arylation reaction.The results show it is an excellent catalyst with recyclability,high consistency and catalytic activity.After the catalyst was used for 5 cycles in the N-arylation reaction,amorphous Cu^0 reunited into crystalline copper nanoparticles with different particle sizes and its good heterogeneity in the catalytic system was confirmed after the catalyst recovery.     

PEG-OSO3H as an efficient and recyclable catalyst for the synthesis of β-amino carbonyl compounds via the Mannich reaction in PEG-H2O

Sulfuric acid-modified polyethylene glycol 6000（PEG-OSO₃H） was applied as an efficient and recyclable catalyst for the synthesis ofβ-amino carbonyl compounds via the Mannich reaction between aldehydes,aromatic ketones and aromatic amines at room temperature using PEG400-H₂O（1:1） as environment-friendly solvents.The reactions were completed in short times and mild reaction conditions with good to excellent yields.     

Preparation of polypropylene/clay nanocomposites by <Emphasis Type="Italic">in situ</Emphasis> polymerization with TiCl<Subscript>4</Subscript>/MgCl<Subscript>2</Subscript>/clay compound catalyst

TiCl₄/MgCl₂/clay compound catalyst was prepared by chemical reaction.Exfoliated polypropylene（PP）/clay nanocomposites were synthesized by in situ polymerization with this compound catalyst.Effects of polymerization temperature,polymerization time,propylene pressure,solvent consumption and pre-treat time of catalyst on catalyst activity and catalytic stereospecificity were studied.Under optimal conditions,activity of the nano-compound catalyst is about 88.3 kg/（mol Ti·h）.Isotacticity of PP obtained in the nanocomposites is in the range of 89%-99%,and its melting temperature is about 159℃.The weight-average molecular weight of PP can reach 6.7×10⁵ - 7.8×10⁵,and the molecular weight distribution is between 7.7 and 7.9.     

Synergistic catalysis of isolated Fe~(3+) and Fe_2O_3 on FeO_x/HZSM-5 catalysts for Friedel-Crafts benzylation of benzene

FeO_x/HZSM-5 catalyst with 8 wt.%Fe-loading（8-FeZ） exhibited significantly higher reactivity in the benzylation of benzene with benzyl chloride than FeO_x/HZSM-5 catalyst with 2.5 wt.%Fe-loading（2.5-FeZ） because the synergistic catalysis between isolated Fe³⁺ and superfine Fe₂O₃ occurred on 8-FeZ in the reaction.     

Spectral and chemical monitoring of cyclo-addition reaction of CO2 with poly(MMA-co-GMA) copolymers

This paper deals with the monitoring cyclo-addition of CO₂ to methyl methacrylate（MMA）-glycidyl methacrylate （GMA） copolymers using spectral（¹H-NMR and FTIR） and chemical（elemental analysis and titration） methods.Thus, poly（MMA-co-GMA）,was first prepared via solution polymerization.The copolymer was then treated with CO₂ gas flow in the presence of cetyltrimethyl ammoniumbromide as a catalyst.In terms of the carbonation reaction time,the terpolymer poly（MMA-co-GMA-co-2-oxo-l,3-dioxolane-4-yl-methyl methacrylate） was prepared in various yield of CO₂ fixation （>90%）.The peak intensity changes in the ¹H-NMR and FTIR spectra provided excellent demonstrative techniques to monitor the carbonation reaction progression.In a comparative analytical viewpoint,the NMR and elemental analysis were recognized to be the most accurate ways to follow the cyclo-addition reaction progression.However,titration was recognized to be the most preferred method,because it is a very inexpensive,facile and available method with a reasonable costaccuracy balance.     

Tuned selectivity and enhanced activity of CO2 methanation over Ru catalysts by modified metal-carbonate interfaces

Carbonate-modified metal-support interfaces allow Ru/MnCO₃ catalyst to exhibit over 99% selectivity,great specific activity and long-term anti-CO poisoning stability in atmospheric CO₂ methanation.As a contrast,Ru/MnO catalyst with metal-oxide interfaces prefers reverse water-gas shift rather than methanation route,along with a remarkably lower activity and a less than 15% CH₄ selectivity.The carbonatemodified interfaces are found to stabilize the Ru species and activate CO₂ and H₂ molecules.Ru-CO⁴ species are identified as the reaction intermediates steadily formed from CO₂ dissociation,which show moderate adsorption strength and high reactivity in further hydrogenation to CH₄,Furthermore,carbonates of Ru/MnCO₃ are found to be consumed by hydrogenation to form CH₄ and replenished by exchange with CO₂,which are in a dynamic equilibrium during the reaction.Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique catalytic functions for selective CO₂ hydrogenation.     

Zn(NO_3)_2·6H_2O/2,4,6-trichloro-1,3,5-triazine(TCT) a mild and selective system for nitration of phenols

<正>Certain phenols and naphthols were nitrated regioselectively with Zn(NO_3)_2·6H_2O/TCT in acetonitrile as solvent at room temperature and short reaction time in good yields.The reaction condition was mild.TCT is a cheap and commercially available reagent.It performed as an acid catalyst in this transformation.     

Insight into the hydrogen oxidation electrocatalytic performance enhancement on Ni via oxophilic regulation of MoO_2

Exploring platinum-group-metal(PGM)free electrocatalysts for hydrogen oxidation reaction(HOR)in alkaline media is essential to the progress of anion exchange membrane fuel cells(AEMFCs).In this work,a Ni/MoO₂ heterostructure catalyst with comparable HOR activity in alkaline electrolyte with PGM catalyst was prepared by a simple hydrothermal-reduction method.Remarkably,the Ni/MoO₂ presents a mass kinetic current density of 38.5 mA mgNi^-1 at the overpotential of 50 mV,which is higher than that of the best PGM free HOR catalyst reported by far.Moreover,the HOR performance of Ni/MoO₂ under 100 ppm CO shows negligible fading,together with the superior durability,render it significant potential for application in AEMFCs.A particular mechanistic study indicates that the excellent HOR performance is ascribed to the accelerated Volmer step by the incorporation of MoO₂.The function of MoO₂ was further confirmed by CO striping experiment on Pt/C-MoO₂ that MoO₂ can facilitated OH adsorption thus accelerate the HOR process.On account of the high performance and low cost,the Ni/MoO₂ electrocatalyst encourages the establishment of high performance PGM free catalyst and shows significant potential for application in AEMFCs.