Replication of SMSI via ALD: TiO<Subscript>2</Subscript> Overcoats Increase Pt-Catalyzed Acrolein Hydrogenation Selectivity

The effects of sub-nanometer atomic layer deposition films of titania and alumina are compared for the acrolein hydrogenation selectivity of Pt/SrTiO₃ catalysts. The titania-overcoated catalyst is similar to strong metal-support interaction catalysts formed by high temperature reduction, with a thin titania film on top of the supported Pt nanoparticles and an increase in allyl alcohol selectivity, neither of which are observed for the alumina-overcoated catalyst.

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β-Cyclodextrin Based Nanosponge as a Biodegradable Porous Three-Dimensional Nanocatalyst in the One-Pot Synthesis of N- Containing Organic Scaffolds

The motivation behind the present study was to develop an application of β-cyclodextrin-based nanosponges with the tiny mesh-like structure as porous three-dimensional nanocatalyst in the one-pot three component condensations of various aromatic aldehydes with activated methylene compounds such as dimedone, thiobarbituric acid, 4-hydroxycoumarin, 4-hydroxy-6-methyl-2-pyrone and nucleophiles including indole and amines. This nanosponge catalyst afforded the privileged N- containing organic scaffolds as key intermediates in pharmaceutical chemistry in very short reaction times.

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Preparation of Polydopamine Sulfamic Acid-Functionalized Silica Gel as Heterogeneous and Recyclable Nanocatalyst for Acetylation of Alcohols and Amines Under Solvent-Free Conditions

To fabricate SiO₂/PDA–SO₃H nanocatalyst, a suitable method is designed for the loading of sulfonic acid groups on the surface of polydopamine (PDA)-encapsulated SiO₂ nanoparticles. To bridge the gap between heterogeneous and homogeneous catalysis, surface functionalization of silica gel is an elegant procedure. The morphology, structure, and physicochemical features were specified using different analytical techniques including field emission scanning electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FT-IR), high resolution-transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDS), wavelength-dispersive X-ray spectroscopy (WDX), X-ray photoelectron spectroscopy (XPS), and back titration. The SiO₂/PDA–SO₃H nanoparticles are efficient nanocatalysts for the acetylation of many alcohols, phenols, and amines with acetic anhydride under solvent-free conditions in good to excellent yields. Moreover, the reuse and recovery of the catalyst was shown seven times without detectible loss in activity.

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Impact of Support Oxide Acidity in Pt-Catalyzed HMF Hydrogenation in Alcoholic Medium

Abstract

Silica and three mixed silica oxides (silica–alumina, silica–niobia, and silica–zirconia) with nominally 5 wt% of the added element (Al, Nb and Zr) were prepared and used as supports for dispersing monometallic Pt-nanoparticles. The presence of the second oxide component on the silica surface influenced some properties of the final samples, like surface area and acidity. The samples acidity was measured in a recirculation adsorption line with 2-phenylethylamine probe, by performing the titrations both in cyclohexane and in methanol to gather the intrinsic and effective acidity, respectively. The acid site density of silica–alumina was the highest compared with the other oxides; in general, an important decrease of acid sites density was determined in methanol. The order of the effective acidity in methanol was different from that determined in cyclohexane only for silica–zirconia and silica–niobia, confirming the peculiar acidity of Nb-oxide compounds in polar liquids: Colloidal spherical platinum nanoparticles were synthesized and then deposited (1 wt%) on the oxide supports. The obtained metallic nanophases were studied in the reduction of 5-hydroxymethylfurfural (HMF) to valuable chemicals such as dimethylfuran, dimethyltetrahydro-furan, 2-hexanol. In particular, this study focused on the impact of the acidity of the oxide supports on reaction selectivity when 2-butanol is used as solvent. When Pt is not present, Nb-doped silica is the most effective catalyst to di-hydroxymethyl furan diether (DHMFDE) derived from Meerwein–Ponndorf–Verley reaction, maintaining its Lewis character also in protic medium. In the presence of Pt, Nb-doped silica, however, presents the higher selectivity to hydrogenolysis products, 5-methyl furan (5-MF).

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Preparation and Characterization of an Efficient Nano-Inorganic Composite of CuO/ZnO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for the Catalytic Amination of Aryl Halides in Aqueous Conditions

In this research, an efficient recyclable nano-inorganic composite of CuO/ZnO/Al₂O₃ (CuO/ZnO/Al₂O₃ nanocatalyst) is prepared, characterized and used for the amination of aryl halides with aqueous ammonia in water. The catalyst was prepared by co-precipitation method and characterized by various techniques such as the X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, and brunauer–Emmett–Teller surface area analysis. Various aryl halides reacted with aqueous ammonia and corresponding products were obtained in high yields. CuO/ZnO/Al₂O₃ nanocatalyst as an efficient stable catalyst is recyclable up to five consecutive runs by simple filtration.

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An efficient recyclable nano-inorganic composite of CuO/ZnO/Al₂O₃ (CuO/ZnO-Al₂O₃ nanocatalyst) is prepared, characterized and used for the amination of aryl halides with aqueous ammonia in water.

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Reaction Profiles of High Silica MOR Zeolite Catalyzed Friedel–Crafts Acylation of Anisole Using Acetic Anhydride in Acetic Acid

Friedel–Crafts reaction of anisole over high silica mordenite zeolite was investigated. Detailed reaction profiles were obtained using various reaction conditions. In particular, the behavior of acetic anhydride during the reaction and the effect on the hydrophilicity of the mordenite zeolite catalyst were investigated.

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Effect of Potassium on the Physiochemical and Catalytic Characteristics of V<Subscript>2</Subscript>O<Subscript>5</Subscript>/TiO<Subscript>2</Subscript> Catalysts in <Emphasis Type="Italic">o</Emphasis>-Xylene Partial Oxidation to Phthalic Anhydride

Abstract

Vanadia species formed on the surface depend on the K/V atomic ratio. At small K/V ratios, Raman spectra show the formation of the K-doped and K-perturbed monomeric species. At K/V?=?1, kristalline KVO₃ is mainly present on the surface. In situ high temperature XRD-results exhibit a promoting effect on the anatase to rutile phase transformation in the presence of 0.03 and 0.21 wt% potassium. Large amount of K (3 wt%) provides thermal stability of V/Ti/O catalyst and no transformation is found up to 600?°C. Reduction of vanadia K-doped vanadia catalysts is moved to higher temperatures than for the catalyst without potassium. The catalyst having 0.21 wt% K possesses the highest activity in o-xylene oxidation. Furthermore, the K-doped monomeric vanadia species in this catalyst leads to a promoted adsorption or a prevented desorption of phthalide, resulting in a decreased selectivity towards phthalide and CO_x and a increased PA selecticity.

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Early Transition Metal Doped Tungstite as an Effective Catalyst for Glucose Upgrading to 5-Hydroxymethylfurfural

Glucose valorization to 5-hydroxymethylfurfural (HMF) remains challenging in the transition towards renewable chemistry. Lewis acidic tungstite is a viable, moderately active catalyst for glucose dehydration to HMF. Literature reports a multistep mechanism involving Lewis acid catalyzed isomerization to fructose, which is then dehydrated to HMF by Brønsted acid sites. Doping tungstite with titanium and niobium improves activity by optimizing the ratio between Lewis and Brønsted acid sites.

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Highly Active Pd Nanocatalysts Regulated by Biothiols for Suzuki Coupling Reaction

A series of biothiols involving N-acetyl-l-cysteine (NAC), penicillamine (PEN), homocysteine (Hcys) and cysteine (Cys), were employed as nucleation templates to synthesize Pd nanocatalysts for Suzuki coupling reaction. It is the first report to comparatively study the physicochemical properties of Pd nanoparticles synthesized by biothiols with different chemical structures. Through the characterizations of UV–Vis, FT-IR, TEM, XPS and HPLC, it is demonstrated that Pd(II) precursors can coordinate with biothiols mainly through thiol, amino/amido and carboxyl groups. NAC molecules are capable of generating uniform Pd nanoparticles with the size distribution from 2.2 to 3.3 nm. At the [PdCl₄^2?]/[biothiol] of 6, NAC- and Hcys-stabilized Pd displays spherical particles with the average size of 3.3 and 3.6 nm respectively, whereas Cys- and PEN-capped Pd exhibit worm-like morphology with poor dispersion. NAC-capped Pd nanoparticles with the mean diameter of 3.3 nm and the Pd⁰ proportion of 63%, show highly active in Suzuki cross-coupling between iodobenzene and phenylboronic acid, with the turn over frequency (TOF) of 38625 mol biphenyl (mol Pd?×?h)^?1 in EtOH/water?=?1:2 at 60 °C. This work paves a promising way to construct highly active Pd nanocatalysts, with a facile modulation of the morphology, the particle size and the charge property via different biothiols.

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A series of biothiols were employed as nucleation templates to synthesize Pd nanocatalysts for Suzuki coupling reaction. This work paves a promising way to construct highly active Pd nanocatalysts, with a facile modulation of the morphology, the particle size and the charge property via different biothiols.

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Higher Alcohol Synthesis Over Rh Catalysts: Conditioning of Rh/N-CNTs by Co and Mn Entrapped in the Support

Abstract

Rh nanoparticles supported on commercial non-purified N-doped CNTs (NCNTs) containing residual CNT growth catalyst have been studied in hydrogenation of CO to higher alcohols. It has been found that Co and Mn residues in NCNTs are not inert, but change the catalyst under reaction conditions and efficiently promote the catalyst resulting in both increasing activity and selectivity to C₂₊ alcohols with time on stream.

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Increased Dispersion of Nickel Particles Supported on Activated Carbon by Treating with Methyl Iodide

A novel method dispersing nickel in fine particles on activated carbon (AC) was proposed in this study. The nickel particles with 2.2 nm average diameter supported on AC were obtained through re-dispersing the nickel particles by treating with methyl iodide under atmospheric pressure. High dispersion of nickel particles promoted the activity for methanol vapor-phase carbonylation over Ni/AC catalyst.

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Hen Egg White Lysozyme Catalyzed Efficient Synthesis of 3-Indolyl-3-hydroxy Oxindole in Aqueous Ethanol

A green synthesis of 3-indolyl-3-hydroxy oxindoles was reported using hen egg white lysozyme (HEWL) in an aqueous ethanol. The HEWL promotes this reaction efficiently from various isatins and indoles under mild reaction conditions with yields up to 98% bearing good adaptability to varied substrates in the reaction. This conversion has provided a new strategy to synthesize 3-indolyl-3-hydroxy oxindole derivatives employing biocatalytic promiscuity of less explored lysozyme. Based on the experimental studies, the plausible reaction mechanism is proposed.

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Gold Nanoparticles-Decorated Dithiocarbamate Nanocomposite: An Efficient Heterogeneous Catalyst for the Green A<Superscript>3</Superscript>-Coupling Synthesis of Propargylamines

Gold nanoparticles decorated magnetic dithiocarbamate nanocomposite (Au@CS₂–AP@Fe₃O₄) led to a suitable catalyst for the propargylamines synthesis via A³-coupling reaction in water. The prepared catalyst was characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, atomic absorption spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy measurements.

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Palladium-Catalyzed Direct Ortho C–O bond construction of Azobenzenes with Iodobenzene diacetate via C–H Activation

Abstract

A method of direct synthesis of ortho-acyloxylated azoarenes via palladium-catalyzed C–H bond activation was developed. The reaction proceeded was smoothly at room temprature and have better yield in shorter times. The obtained ortho-acyloxylated azoarenes could be efficiently converted into 2-hydroxyazobenzenes in good yields through a hydrolysis process.

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Many various ortho-acyloxylated azoarenes were obtained in moderate to high yields by palladium-catalyzed direct C(sp²)-H acyloxylation of aromatic azo compounds with PhI(OAc)₂

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Strontium Doped MCM-41: A Highly Efficient,Recyclable and Heterogeneous Catalyst for the Synthesis of Phenoxy Pyrazolyl Pyrazolines

Strontium doped MCM-41 (Sr-MCM-41) has been synthesized as an efficient, heterogeneous and recyclable catalyst. The catalyst, Sr-MCM-41 is characterized by various techniques such as FTIR, SEM, EDX, elemental Mapping, TEM, TGA, BET, XRD, XPS and ICP-AES analyses. The catalytic activity of the catalyst (Sr-MCM-41) has been explored by synthesizing a library of phenoxy pyrazolyl pyrazoline derivatives in excellent yield (96–98%) under microwave irradiation (3–5 min) using ethanol as solvent. The catalyst could be recycled upto five cycles.

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PhI-Catalyzed Intramolecular Oxidative Coupling Toward Synthesis of 2-Amino-1,3,4-Thiadizoles

A highly efficient method for the synthesis of thiadiazole derivatives via intramolecular oxidative coupling of thiosemicarbazide, using the in situ generated hypervalent iodine(III) reagents is developed. The protocol can be carried out smoothly and provides a variety of thiadiazole derivatives in moderate to excellent yields.

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A highly efficient method for the synthesis of thiadiazole derivatives via PhI-catalyzed intramolecular oxidative coupling of thiosemicarbazide has been developed.

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[Zn(<Emphasis Type="SmallCaps">l</Emphasis>-proline)<Subscript>2</Subscript>] Catalyzed One-Pot Synthesis of Propargylamines Under Solvent-Free Conditions

A simple, one-pot, three-component, green synthesis of a wide range of propargylamines is reported by A³-coupling (aldehyde, alkyne and amine) via C–H activation of alkynes using [Zn(l-proline)₂] as an efficient and reusable heterogeneous catalyst. High catalytic activity was achieved in comparatively low temperature under solvent-free conditions. All reactions were carried out in an open atmosphere without the use of any co-catalyst/additive.

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Impact of Chain Length on the Catalytic Performance in Hydroisomerization of <Emphasis Type="Italic">n</Emphasis>-Alkanes Over Commercial and Alkaline Treated *BEA Zeolites

The present paper highlights the influence of desilication of nanocrystal *BEA zeolites (CP811 and CP814E) by different alkaline treatments in presence of NaOH alone, NaOH?+?TPABr and NaOH?+?TBAOH, on the catalytic performance in the hydroisomerization reactions of n-alkanes (n-C₁₀, n-C₁₂ and n-C₁₄). The well-balanced catalyst was reached after impregnation of 1.5 wt% of Pt, where the activity and isomers selectivity was seen to be the maximum, knowing that the Pt content effect was studied on the CP811 zeolite catalyst. All the other catalysts were after impregnated by approximately 1.5 wt% of Pt. The improvement of the textural properties by means of desilication was not always accounting for the influence of the catalytic performance of the catalysts, but rather it may be the bifunctional characteristics in charge. The impact of chain length was investigated on the catalysts to study if the presence of the inter- and intracrystalline mesopores would account for better diffusion of larger molecules as, n-C₁₂ and n-C₁₄. It was found on the majority of the catalysts that the activity was high whether the chain length was, but the isomers selectivity was decreasing with chain length except on one catalyst that possesses high textural and bifunctional characteristics. Among the three n-alkanes studied, n-C₁₂ have marked the highest TOF values and lowest selectivity to isomers, a phenomenon attributed to the confinement effect that seems to increase the interaction of n-C₁₂ molecules with the acidic sites of the zeolites, apparently causing their strength to be higher. This effect was pronounced more with n-C₁₂ than the other two n-alkanes.

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Self-Oscillations During Ethylene Oxidation Over a Ni foil

Oscillatory behavior during ethylene oxidation over a Ni foil has been discovered in the temperature range of 600–800 °C. The oscillatory behavior occurred in C₂H₄ excess in contrast to the well-known oscillations during C₂H₄ oxidation over Pt and Rh. The periodic variation in oxygen imbalance together with in situ TGA measurements and the variation in color during the oscillations indicate that the oscillations are closely connected with reversible oxidation of Ni to NiO. The observation of oscillations in pulse supply mode prove also important role of periodic carbon deposition/removal. A characteristic feature of the oscillations during ethylene oxidation is high sensitivity of the oscillation waveform to the catalyst temperature. The oscillations were accompanied by propagation of the oxidation and reduction fronts which could be observed with the naked eye.

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Highly Efficient Dehydration of Glycerol to Acrolein Over Isomorphously Substituted Fe-MFI Zeolites

Gas phase dehydration of glycerol formerly in aqueous solution to acrolein was studied over iron MFI zeolites prepared by post-synthesis isomorphous substitution with different iron contents, Si/Al and substitution ratios. High Si/Al (60) ratios led to high conversion in presence of air and the insertion of iron in the zeolite framework greatly improved the catalytic performances by altering the amount and the nature of the coke components reducing dramatically the deactivation. Over the most efficient sample, acrolein yield reached a stabilized value of 68% with an excellent selectivity (80%), which ranked this catalyst among the best for the selective conversion of crude glycerol.

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