FeAPO-5分子筛的合成及其催化氧化水溶液中苯酚的性能

以水热晶化法合成了铁磷铝分子筛FeAPO-5,并用XRD、SEM、FT-IR和 UV-vis等对分子筛样品进行了表征。结果表明,所合成的FeAPO-5分子筛样品结晶度高,晶粒大小均匀,FeAPO-5样品中存在骨架Fe和骨架外Fe物种,并以骨架Fe物种为主。FeAPO-5作为一种非均相催化剂能有效催化氧化水溶液中苯酚,在苯酚初始浓度200 mg•L-1 、H2O2初始含量1200 mg•L-1、pH 5.0及溶液温度80℃的条件下,处理240 min后苯酚去除率达99.0％,TOC去除率可达77.8％。ICP分析结果表明,催化剂上析出到溶液中的铁离子浓度很低,催化剂性能稳定。     

Low temperature,efficient synthesis of new As(V)-silicate molecular sieves with MFI topology and their catalytic properties in oxidation reactions

New MFI type arseno-silicate molecular sieves (As(V)-MFI), synthesized for the first time, can be crystallized at lower temperature (70–90C) in 1–3 days under hydrothermal conditions. Interestingly, these As(V)-MFI molecular sieves can be synthesized even faster than the As-free silicalite-1 under identical conditions. Further, the crystallization becomes faster with the increase in As content of the reaction mixture, contrary to the observations made on all the other high silica molecular sieves, so far. These microporous As(V)-silicates exhibit significant catalytic activity in (i) phenol hydroxylation using 30% aq. H₂O₂ (ca. 55% H₂O₂ efficiency) and (ii) oxidative dehydrogenation of 2-butanol and benzyl alcohol using air under fixed bed vapor phase reaction conditions exhibiting ca. 75–85% selectivity towards 2-butanone and benzaldehyde+benzoic acid, respectively.     

Preparation, characterization and catalytic properties of carbon nanofiber-supported Pt, Pd, Ru monometallic particles in aqueous-phase reactions

Carbon nanofibers (CNF) synthesized by catalytic chemical vapor deposition (CVD) method were used to prepare supported platinum, palladium and ruthenium monometallic (2.0 wt.%) catalysts by means of incipient-wetness impregnation method. The CNF support and catalysts were characterized by X-ray powder diffraction (XRD), nitrogen adsorption/desorption isotherms, volumetric chemisorption of hydrogen, temperature-programmed reduction (H₂-TPR) and scanning electron microscopy (SEM). Solids were tested in catalytic wet-air oxidation (CWAO) of phenol aqueous solution (180–240 °C and 10.0 bar of oxygen partial pressure) carried out in a continuous-flow trickle-bed reactor. Trends of phenol and total organic carbon (TOC) conversion demonstrate that the CNF support and CNF-Pt catalyst did not exhibit constant activity for CWAO of phenol. A decrease of catalyst activity, detection of carbon dioxide in the off-gas stream while examining catalyst stability and significant textural changes observed, provide an evidence that under net oxidizing reaction conditions gasification of the CNF support occurs. The prepared catalysts were also tested in liquid-phase thermal decarboxylation of formic acid in inert atmosphere (60–220 °C). Among solids examined, the CNF-Pd exhibited the highest activity. At the employed conditions, no decomposition of the CNF support was observed during the thermal decarboxylation of formic acid.     

The synthesis and characterization of the molecular sieve SAPO-16 as well as other SAPO and CoAPO phases using bis(cyclopentadienyl) cobalt(III) hydroxide as a structure directing agent

The clathrate type molecular sieve SAPO-16 was prepared via a hydrothermal synthesis using bis(cyclopentadienyl)cobalt(III) hydroxide, Cp₂CoOH, as a template and characterized by XRD, FT-IR, UV-Vis and SEM. Additionally, the preparation and characterization of possibly new isostructural SAPO-UTD-3 and CoAPO-UTD-3 materials is reported.NSF Presidential Young Investigator 1991–1996.     

Chromium substituted A1PO-11: synthesis,characterisation and its application in oxidation reactions

Isomorphous substitution of Cr³⁺ for A1³⁺ in A1PO₄-11 framework followed by calcination converts Cr³⁺ to dioxochromium (VI) by incorporating extra framework O^2– ligands, generating Brønsted acidity. CrAPO-11 catalyses oxidation of phenol to dihydroxybenzenes to the extent of 28%.     

Synthesis, characterization and catalytic properties of a LEV type silicoaluminophosphate molecular sieve, SAPO-35 from aqueous media using aluminium isopropoxide and hexamethyleneimine template

A small-pore silicoaluminophosphate molecular sieve, SAPO-35 was synthesized using hexamethyleneimine template and aluminium isopropoxide as aluminium source in aqueous media is reported for the first time. Pure, highly crystalline samples were obtained in short period (96 h). The samples crystallize at narrow silicon content (0.3 M SiO₂). Fourier transform Infrared spectroscopic studies reveal the presence of three different silanol groups. A comparison with multinuclear solid-state Magic angle spinning nuclear magnetic resonance spectroscopic studies with FT-IR studies shows that these groups are located at Double six member ring, near to D6R and near to single six member ring. Other characterizations and methanol to olefin reaction studies shows that the molecular sieves synthesized by aqueous and non-aqueous media are having comparable properties. It reveals a possible application of this catalyst for industrial process.     

Layered nanocomposites based on molybdenum disulfide and hydroxy-NiAl oligocations: characterization and catalytic activities in oxidation of sulfide

A series of layered nanocomposites constructed from MoS₂ and hydroxy-NiAl oligocations with various Ni/Al ratios were prepared. The interlayer expansions of 8.11–9.03 Å with Ni/Al ≤ 0.8 indicate that the intercalated species should mainly be [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂]⁷⁺ or substituted [Al_13?x Ni _x O₄(OH)₂₄(H₂O)₁₂]^(7?x)+ Keggin oligocations. In the presence of molecular oxygen, the composites exhibit good catalytic activities in the oxidization of sulfide ions into thiosulfate ions, and their catalytic activities have been enhanced upon irradiation with visible light.     

Thermal behaviour, redox properties, and catalytic performance of alkali-promoted V2O5 catalysts in the selective oxidation of p-methoxytoluene: a comparative study

Alkali-promoted V₂O₅ catalysts M–V₂O₅ (M=Li, K, Cs) were synthesised by impregnation of V₂O₅ with alkali sulphate solution. Pure V₂O₅ was used for comparison. X-ray diffraction, spectroscopic (FTIR), and thermoanalytical methods (STA/MS) have been used to characterise the phase composition, the adsorption properties, and the reducibility of the catalysts. The catalytic performance was proved using the oxidation of p-methoxytoluene (PMT) to p-methoxybenzaldehyde (PMBA) as test reaction. The surface acidity is lowered, but the reducibility is enhanced with increasing size and basic properties of the alkali cation. This leads to an increased adduct (PMT) adsorption and decreased product (PMBA) adsorption in the order V₂O₅2O₅K–V₂O₅2O₅. Consequently, the catalytic performance is improved in the same way. The formation of bronze phases at relative low temperatures in the case of K– and Cs–V₂O₅ stabilise V⁴⁺ oxidation state and improve the redox properties and consequently the catalytic results. The admixture of the non-reactive pyridine enhances the aldehyde selectivity by further lowering of the surface acidity. Additionally, pyridinium cations generated during catalytic reaction and incorporated into the formed alkali bronze phases stabilise these structures.     

Impact of surface mobility in selective oxidation. Isotopic exchange of O2 with O2 on various oxides: MoO3, SnO2 and Sb2O4. Effect of a reducer gas

Isotopic oxygen exchange experiments were carried out on simple oxides (Sb₂O₄, MoO₃ and SnO₂) and mechanical mixtures of MoO₃ or SnO₂(acceptor phase) with Rh//Al₂O₃ or Sb₂O₄ (donor phase). With Rh//Al₂O₃ a synergy effect is found: the amount of oxygen exchanged on the mixture is higher than the sum of oxygen exchanged on the two separate phases. This is a prove of oxygen mobility between donor and acceptor phases. With Sb₂O₄ this effect is less marked suggesting that the presence of a reducer gas is required. In presence of hydrocarbon, no isotopic exchange is observed: only total oxidation occurs. The presence of Sb₂O₄ decreases the rate of total oxidation by blocking, by oxygen spillover, the most active sites for oxidation.     

Gold supported on Mg, Al and Cu containing mixed oxides: Relation between surface properties and behavior in catalytic aerobic oxidation of 1-phenylethanol

Aerobic oxidation of 1-phenylethanol was investigated over Au deposited on flame-derived Mg–Al and Cu–Mg–Al mixed oxides with different metal ratios. A maximum in acetophenone (1-phenyl-ethanone) yield was observed for catalysts based on both Cu–Mg–Al and Mg–Al mixed oxides depending on their composition. Special attention was given to the elucidation of the role of surface basicity and the influence of the preparation route on the particle size of Au. Adsorption of CO₂ from the liquid phase combined with in situ ATR-IR and modulation excitation spectroscopy (MES) was applied to investigate differences in the surface properties of the mixed oxides as a function of the composition. Monodentate and bidentate carbonates were identified, the former being dominant on supports with high Cu contents. In order to obtain a rough quantification of the surface basicity, the retroaldolisation of 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol, DAA) was chosen as a probe reaction indicating that a ratio Mg/Al = 3 results in optimal surface basicity. Moreover, the addition of Cu only lead to a partial loss in retroaldolisation activity, indicating that also the copper sites form basic centers on the surface, however, slightly weaker ones than the corresponding Mg sites. The preparation routes applied (adsorption of colloid, deposition precipitation, and impregnation) lead to different gold particle sizes characterized by mean diameters of ≈2, ≈9 and ≈30 nm, respectively. Catalytic tests using Au/Cu₁Mg₂Al₁O_x catalysts with different mean gold particle size hint towards a particle size dependence of the aerobic oxidation of 1-phenylethanol, showing higher activity for the catalyst containing gold particles of ca. 9 nm compared to those with 2 and 30 nm particles, respectively.     

Nano-sized Cu/Zn-modified MCM-41 (Cu/Zn-MCM-41): preparation,characterization and catalytic application in a new more atom efficient synthesis of tetrasubstituted imidazoles

The nano-sized copper/zinc-modified MCM-41 (Cu/Zn-MCM-41) was successfully prepared, characterized and applied as a new heterogeneous mesoporous and reusable nano-catalyst in a more atom efficient and novel one-pot three component strategy for the synthesis of tetrasubstituted imidazoles from nitriles, amines and benzoins under microwave irradiation. Using this method, the major problem of previously reported method (application of toxic and non-recoverable trifluoroacetic acid (TFA) as a catalyst) have been solved and all obtained results were highly similar (reaction times and yields) to the application of TFA that proved the efficiency of prepared catalyst in titled reaction.     

Novel poly(phenylene ethynylene)‐type conjugated polymers containing diketopyrrolopyrrole or triphenylpyrazoline units in the main chain: synthesis,characterization and photophysical properties

BACKGROUND: Polymer‐based light emitting diodes (PLEDs) have received considerable attention as they combine the good mechanical and processing properties of polymers with semiconducting behavior, and can be easily fabricated as flexible devices. To obtain high‐performance PLED materials by balancing the carrier injection of poly(phenylene ethynylene)s (PPEs), polymers containing two aryl‐heterocyclic rings, namely diketopyrrolopyrrole (DPP) or triphenylpyrazoline (TPP), have been synthesized and investigated. RESULTS: PPE‐type polymers containing DPP or TPP units were synthesized using Heck–Sonogashira coupling methodology and characterized by ¹H NMR, Fourier transform infrared and UV‐visible spectroscopies, elemental analysis, gel permeation chromatography, photoluminescence (PL), X‐ray diffraction, thermogravimetic analysis and cyclic voltammetry. The polymers obtained are easily soluble in common solvents and form smooth and uniform films. They are yellow or red emitters as revealed by PL. In addition, they show large Stokes shifts, which is in agreement with their twisted molecular structures determined via quantum chemical calculations. CONCLUSION: PPE‐type polymers containing DPP or TPP units were successfully synthesized by coupling polymerization. They exhibit band gaps of 1.73 and 2.37 eV, respectively, and show potential as PLED materials. In addition, DPP‐containing polymers with a very low band gap could be applied as potential photovoltaic materials. Copyright © 2009 Society of Chemical Industry     

A new approach to artificial and modified proteins: theory-based design, synthesis in a cell-free system and fast testing of structural properties by radiolabels

A novel approach to the creation of artificial and modifiedproteins has been elaborated. The approach includes a sequencedesign based on the molecular theory of protein secondary structureand folding patterns, gene expression in a cell-free systemand testing of structural properties of the synthesized polypeptidesat a nanogram level using radiolabelled chains. The approachhas been applied to a new synthetic protein albebetin whichhas been designed to form a 3-D fold which does not contradictany structural rule but has been never observed up to now innatural proteins. Using size-exclusion chromatography, urea-gradientelectrophoresis and limited proteolysis of a radiolabelled chain,it has been shown that the artificial protein is nearly as compactas natural proteins, cooperatively unfolds at high urea concentrationsand has some structural features of a definite structure consistentwith the designed one. As albebetin has been designed as consistingof two structural repeats, a ‘halfalbebetin’ (oneof these repeats) has also been synthesized and studied. Itwas shown that ‘half-albebetin’ is also compact