One pot synthesis using supported reagents system KSCN/SiO2-RNH3OAc/Al2O3: synthesis of 2-aminothiazoles and N-allylthioureas

A simple and efficient method has been developed for the synthesis of 2-aminothiazoles and N-allylthioureas from commercially available materials in one pot by using a supported reagents system, KSCN/SiO₂-RNH₃OAc/Al₂O₃, in which α-halo ketone reacts first KSCN/SiO₂ and the product, α-thiocyanatoketone, reacts with RNH₃OAc/Al₂O₃ to give the final product, 2-aminothiazoles, in good yield and allyl bromide reacts with KSCN/SiO₂ and the product, allyl isothiocyanate, reacts with RNH₃OAc/Al₂O₃ to give N-allylthiourea.     

不同硅铝比Al-ITQ-13分子筛的甲醇制丙烯反应催化性能

采用晶种法直接合成了硅铝比(SiO_2/Al_2O_3物质的量比)为137、224和309的三种Al-ITQ-13分子筛,并采用粉末X射线衍射(XRD)、扫描电镜(SEM)、N_2吸附-脱附、固体核磁共振(MAS NMR)和NH_3-程序升温脱附(NH_3-TPD)等分析方法对不同硅铝比分子筛进行了表征,并在固定床微型反应评价装置上,考察了硅铝比对甲醇转化制丙烯反应性能的影响。结果表明,不同硅铝比Al-ITQ-13分子筛呈现出相似的织构性质,酸量及酸强度随着硅铝比的升高逐渐下降。硅铝比对甲醇转化反应的产物分布存在较大的影响;随着硅铝比的升高,氢转移反应和芳构化反应活性降低,使得乙烯选择性下降,而丙烯和丁烯的选择性升高。硅铝比由137提高到309,丙烯的选择性(质量分数)由46.04%增加到55.52%,而丙烯/乙烯比由3.39提高到6.57。     

Formation of organopalladium complexes on SiO2 and Al2O3 as a result of the reaction of allyl alcohol with supported PdCl2; thermal decomposition of these complexes

It was established by electronic spectroscopy in the UV and visible regions and mass spectrometry that when allyl alcohol reacts from the gas phase with palladium chloride supported on SiO₂ and Al₂O₃ a complex similar in characteristics to a bis--allylpalladium chloride complex that is fixed on the surface of the support is formed. Decomposition of this complex in vacuo occurs at 135°C with the formation of allyl chloride and zero-valence supported palladium.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1536–1539, July, 1992.     

One-pot synthesis of α-bromoesters and ketones from β-ketoesters and diketones using supported reagents system

A simple and efficient method has been developed for the synthesis of α-bromoesters and ketones from β-ketoesters and diketones in one pot using a supported reagents system, CuBr₂/Al₂O₃-Na₂CO₃/Al₂O₃, in which β-ketoester reacts first with CuBr₂/Al₂O₃ and the product, α-bromo-β-ketoester, reacts with Na₂CO₃/Al₂O₃ to give the final product, α-bromoesters in good yields.     

SiO2和Al2O3负载的Ni基催化剂在甲烷干重整中的催化性能差异

CH₄与CO₂干重整反应对于环境保护和天然气资源的合理利用具有重要意义。SiO₂和Al₂O₃是适用于甲烷干重整反应的两种典型的催化剂载体。为了阐明这两种载体对催化剂性能的影响,本研究采用等体积浸渍法制备了Ni/Al₂O₃和Ni/SiO₂催化剂,并利用BET、TEM、H₂-TPR、XRD、TG和Raman等技术对还原和反应后的催化剂进行了表征。结果表明,由于载体的性质不同,Ni基催化剂在甲烷干重整中的催化性能也不同。Ni/SiO₂催化剂的初始活性较高,但由于其金属-载体相互作用较弱,催化稳定性较差,在800℃下反应15h其催化活性急剧下降;较弱的金属-载体相互作用使得Ni/SiO₂催化剂上的Ni颗粒较大,有利于积炭前驱物种的生成,导致催化剂快速失活。而对于Ni/Al₂O₃催化剂,金属-载体相互作用较强,Ni颗粒较小,但由于Ni与Al₂O₃生成了NiAl_xO_y物种,有效活性位减少,其催化活性相对较低,但催化稳定性较好,干重整反应进行50h其活性保持稳定;Ni与Al₂O₃之间较强的相互作用有利于形成小且稳定的Ni粒子,能减少积炭,因而具有优异的催化稳定性。     

Propane combustion over supported Pd catalysts

We prepared Pd catalysts supported on various metal oxides, viz. γ-Al₂O₃, α-Al₂O₃, SiO₂–Al₂O₃, SiO₂, CeO₂ and TiO₂ by an incipient wetness method and applied them to propane combustion. Several techniques: N₂ physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), CO chemisorption, temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPO) were employed to characterize the catalysts. Pd/SiO₂–Al₂O₃ showed the least catalytic activity at high temperatures among Pd catalysts supported on irreducible metal oxides, viz. SiO₂, Al₂O₃ and SiO₂–Al₂O₃. Pd/γ-Al₂O₃ was much superior for this reaction to Pd/α-Al₂O₃. The Pd catalyst supported on reducible metal oxides (CeO₂ and TiO₂) with a less specific surface area showed the higher catalytic activity compared with that supported on reducible metal oxides with a higher specific surface area, even though the former had a less Pd dispersion than the latter. In the case of Pd/SiO₂–Al₂O₃, the initially reduced Pd catalyst was superior to the fully oxidized one. The oxidation of metallic Pd occurred in the presence of O₂ with increasing reaction temperature, which resulted in the change in the catalytic activity.     

晶种协同廉价有机模板导向合成高纯度MCM-49沸石

采用廉价低毒性的环己胺（CHA）作为有机模板剂,并合理添加少量MCM-49沸石晶种,在静态水热条件下成功合成了高纯度MCM-49沸石.研究了起始凝胶组成（如Al₂O₃/SiO₂,H₂O/SiO₂,CHA/SiO₂,晶种/SiO₂,Na₂O/SiO₂）、晶化温度和时间等因素对合成MCM-49沸石的影响.通过XRD、SEM、N₂吸附、固体²⁷Al和²⁹Si MAS NMR等手段表征产物,结果表明合成的MCM-49沸石具有良好的结晶度、均匀的晶体尺寸、高比表面积和纯的四配位Al³⁺物种.热重差热分析（TG-DTA）和固体¹³C MAS NMR表征结果证实CHA是作为模板剂填充在沸石产物的孔道内.这种合成MCM-49的方法具有廉价和低毒性的特点,对其产业应用有潜在的重要价值.     

Ethoxyacetylene: A useful building block for the organocopper(I) mediated synthesis of 1,4-diketones

Ethoxyacetylene (I) has been converted by organocopper(I) species into (E)-2-ethoxy-1-alkenylcopper(I) compounds (II). The adducts II have been shown to be useful intermediates for preparation of 1,4-diketones (VI). Two routes to VI were used: (i) sequential treatment of II with allyl bromide, 3.0 N HCl, and PdCl₂/CuCl in DMF/H₂O, and (ii) sequential treatment of II with 2,3-dibromopropene and Hg(OAc)₂. A dienone was formed from the first procedure when after the reaction of II with allyl bromide the product was treated first with the PdCl₂/CuCl.     

系列硅铝比纳米薄层ZSM-5分子筛的合成和表征

以自制不对称双子季铵盐表面活性剂为模板, 在水热合成体系中控制合成系列硅铝比纳米薄层ZSM-5分子筛.采用X射线衍射(XRD)、N₂吸附-脱附、X射线荧光光谱(XRF)、扫描电镜(SEM)和²⁷Al魔角旋转核磁共振(²⁷Al MAS-NMR)对合成的样品进行了表征. 详细研究了晶化温度、晶化时间、结构导向剂(SDA)用量、碱度等对合成的影响和纳米薄层ZSM-5分子筛的形成过程. 结果表明: 分子筛硅铝比越高, 结构导向剂用量越大, 所需的晶化时间越短; 晶化温度越高, 晶化时间越短; 且不同硅铝比纳米薄层ZSM-5分子筛的形貌规整度、比表面积和介孔/微孔孔容比例随着硅铝比而变化.     

Synthesis and properties of PdSn/Al2O3 and PdSn/SiO2 prepared by solvated metal atom dispersed method

A series of solvated metal atom dispersion (SMAD) catalysts: Pd/SiO₂, Pd/Al₂O₃, Sn/SiO₂, Sn/Al₂O₃, Pd_xSn_y/SiO₂ and Pd_xSn_y/Al₂O₃. It was prepared by simultaneous evaporation of Pd and Sn. The metals were co-deposited at 77 K using acetone, 2-propanol and THF to produce colloids “in situ” all the supported catalyst were characterized by chemisorption, transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and TPR. This series of catalyst were tested for crotonaldehyde hydrogenation in gas phase to obtain crotyl alcohol.     

Resonance Raman spectroscopy and DFT calculations of the protonation of 4-(2-pyridylazo)-N,N-dimethylaniline in solution and adsorbed on oxide surfaces

The protonation of 4-(2-pyridylazo)-N,N-dimethylaniline (PYAD) in aqueous solution and its adsorption on oxide surfaces has been studied by resonance Raman (RR) spectroscopy. The gas phase structures of neutral, protonated and diprotonated forms of PYAD were modelled by SCF-DFT calculations at the B3-LYP/DZ level, enabling determination of the simulated vibrational spectra of these species, together with vibrational assignments, and providing confirmation that protonation occurs initially at the pyridyl nitrogen atom. Electronic absorption spectra were interpreted using time-dependent DFT calculations. Adsorption of PYAD on SiO₂ or Al₂O₃ surfaces is mainly via the neutral species, hydrogen bonded to surface OH groups, although a small proportion of adsorbed molecules are protonated. By contrast, adsorption on SiO₂–Al₂O₃ results in complete protonation, indicating the presence of Brønsted acidic sites with pK_a values ? 4.5, whereas adsorption on H-mordenite results in diprotonation, indicating the presence of Brønsted acidic sites with pK_a values ? 2.     

Glycerol catalytic cyclocondensation with ethanediamine to pyrazinyl compounds over the modified SiO2‐Al2O3

The Fe, Zn, and Mn‐modified SiO₂‐Al₂O₃ catalysts for the glycerol vapor‐phase cyclocondensation with ethanediamine (ED) to 2‐pyrazinemethanol (2‐PMol) and 2‐methylpyrazine (2‐MP) in a fixed‐bed system were prepared by coprecipitation and characterized by N₂ adsorption–desorption, X‐ray powder diffraction, and NH₃ temperature‐programmed desorption (NH₃‐TPD) in the present work. The results showed that the Mn‐modified SiO₂‐Al₂O₃ catalyst with a SiO₂/Al₂O₃ molar ratio 15.84 and 6% Mn gave the highest catalytic activity for formation of 2‐PMol (53.1%) and 2‐MP (42.9%). Mn species could cause the modulation of the acidic species of catalysts, improving the glycerol cyclocondensation with ED to 2‐PMol, and also acted as the catalytic centers for the hydrodehydration of 2‐PMol to 2‐MP. However, too many strong acidic sites could lead to ED self‐cyclocondensation to form a by‐product pyrazine. The optimum temperature was tested to be 380°C for the cyclocondensation over a 6%Mn‐SiO₂‐Al₂O₃ catalyst. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:377–382, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21026     

Catalytic reduction of nitrogen dioxide with propene in the presence and absence of oxygen over various metal oxides

Over metal oxides (SiO₂, ZrO₂, Al₂O₃, MgO, La₂O₃, and CaO) with-H values of metal oxide formation higher than 700 kJ/mol, C₃H₆ reacts with NO₂ in preference to O₂.     

Preparation of superhydrophobic PET fabric from Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> hybrid: geometrical approach to create high contact angle surface from low contact angle materials

In this work we prepare high contact Poly Ethylene Terephthalate (PET) fabric surface from low contact angle materials. Superhydrophobic PET fabric is prepared by coating the fabric with hybrid Al₂O₃–SiO₂ sol. In this case, the high contact angle Al₂O₃–SiO₂ hybrid is created from low contact angle Al₂O₃ and SiO₂ precursors. PET treated with hybrid Al₂O₃–SiO₂ exhibit Water Contact Angle (WCA) as 150°, while PET treated with individual Al₂O₃ sol or SiO₂ sol exhibits lower WCA, (Al₂O₃ WCA = 137°; SiO₂ WCA = 141°). FESEM and AFM investigations show that the hybrid Al₂O₃–SiO₂ sol and individual Al₂O₃ or SiO₂ sol imparted different roughness geometry on the PET fabric surface. We observe surface structure of fish fin-like, particle-like and hybrid fin-particle for treated PET fabric with; Al₂O₃, SiO₂ and hybrid Al₂O₃–SiO₂ sol, under FESEM and AFM observations.AFM observations show the evolution of roughness (Ra) dimension of different surface structures with the order of: SiO₂ < Al₂O₃ < Al₂O₃–SiO₂ (Ra = 31, 63 and 273 nm). We believe that the disparity of the surface geometries lead into different surface WCA. FTIR spectra of Hybrid Al₂O₃–SiO₂ shows additional peak at 902, 850, 557, and 408 cm⁻¹ which can be ascribed to the hybridization structure.     

Regioselective synthesis of trifluoromethyl group containing allylic amines by palladium-catalyzed allylic amination and sequential isomerization

The palladium-catalyzed regioselective allylic amination of the α-trifluoromethyl group-substituted allyl acetate has been accomplished using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/DPPF as catalysts. The selective formation of the γ-product was attained in the presence of Pd(OAc)₂/DPPE, while the α-product was obtained using [Pd(π-allyl)(cod)]BF₄/DPPF. We also succeeded in the regioselective synthesis of the enantiomerically enriched aminated product from chiral allyl acetate using Pd(OAc)₂/DPPE and [Pd(π-allyl)(cod)]BF₄/(S)-BINAP. Furthermore, we found that kinetic resolution had occurred during the isomerization step from the γ-type product to the α-type product by the [Pd(π-allyl)(cod)]BF₄/(S)-BINAP catalyst.     

An expedient synthesis of indolo[1,2-a]quinolines via Mn(OAc)3-mediated oxidative free radical cyclization and NaI/O2-assisted dealkoxycarbonylation/aerobic oxidation cascade

An expedient synthetic procedure of indolo[1,2-a]quinolines was developed using a sequential Cu-mediated N-arylation of indole, Mn(OAc)₃-mediated oxidative free radical cyclization, and NaI/O₂-assisted concomitant dealkoxycarbonylation/aerobic oxidation. The last step was replaced by a palladium-catalyzed decarboxylation/elimination protocol for the allyl ester derivatives.     

Reaktionen von Natronwasserglas mit Kaolin unter hydrothermalen Bedingungen

Reactions of Sodium Silicate with Kaolin under Various Hydrothermal Conditions The reactions of sodium silicate (molar ratio SiO₂/Na₂O 3.8) with kaolin were investigated under various conditions of hydrothermal treatment in saturated water vapours in an autoclave. The products of reaction were identified by X-ray, electron-microscopic, and infrared methods. The results have shown that, under autoclave conditions, sodium silicate reacts with kaolin to alumosilicagel or to a crystallized zeolite mineral analcime Na₂O · Al₂O₃ · 4 SiO₂ · 2 H₂O. At the reaction kaolin dissolves and α-quartz simultaneously appears in the product of reaction.     

Preparation of ZSM‐5 Coated on Monolithic Interconnected Macroporous Al2O3 Using Cheap n‐Butylamine as Template

Using cheap n‐butylamine as template, ZSM‐5 zeolites have been successfully synthesized and coated on monolithic interconnected macroporous Al₂O₃ by the secondary growth method. The use of cheap n‐butylamine could significantly reduce the synthesis cost. Hierarchical monolithic ZSM‐5 zeolites were prepared from synthetic mixtures with different H₂O/Na₂O or SiO₂/Al₂O₃ ratio. The synthesized samples were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR) and N₂ adsorption‐desorption. The results show that the hierarchical monolithic zeolites were obtained with cheap n‐butylamine template as template. During the hydrothermal reaction process, the morphology of the micrometer‐sized support was well maintained. The irregular crystals were formed in a wide range of the H₂O/Na₂O or SiO₂/Al₂O₃ ratio of synthetic mixtures and coated on monolithic Al₂O₃. The relative crystallinity of the zeolites was highest at H₂O/Na₂O=250 or SiO₂/Al₂O₃=160. This type of composites exhibited hierarchical porous structures and relatively high specific surface areas.     

Densification mechanisms of alumina,aluminosilicates and aluminoborosilicates gels,glasses and ceramics

The thermal evolution of gels, glasses and ceramics of various more or less refractory compositions (Al₂O₃, 3Al₂O₃2SiO₂, 7Al₂O₃3SiO₂, Al₂O₃2SiO₂, Al₂O₃2SiO₂0.7B₂O₃, Al₂O₃2SiO₂2B₂O₃, Al₂O₃2SiO₂6B₂ O₃) have been studied by dilatometry, DTA, and helium density measurements. Comparison is made for materials prepared by rapid (powder) or by very slow gelation (optically clear monoliths). The influence of atmosphere sintering (air, H₂, vacuum) is reported. Densification and kinetic laws are discussed.Also at LASIR, CNRS, 2 rue Henry Dunant, 94320 Thiais, France.     

Effect of substrate on phase formation and surface morphology of sol-gel lead-free KNbO3, NaNbO3, and K0.5Na0.5NbO3 thin films

Environmentally acceptable lead-free ferroelectric KNbO₃ (KN) or NaNbO₃ (NN) and K_0.5Na_0.5NbO₃ (KNN) thin films were prepared using a modified sol-gel method by mixing potassium acetate or sodium acetate or both with the Nb-tartrate complex, deposited on the Pt/Al₂O₃ and Pt/SiO₂/Si substrates by a spin-coating method and sintered at 650°C. X-ray diffraction (XRD) analysis indicated that the NN and KNN films on the Pt/SiO₂/Si substrate possessed a single perovskite phase, while NN and KNN films on the Pt/Al₂O₃ substrate contained a small amount of secondary pyrochlore phase, as did KN films on both substrates. Scanning electron microscopic (SEM) and atomic force microscopic (AFM) analyses confirmed that roughness R _q of the thin KNN/Pt/SiO₂/Si film (?? 7.4 nm) was significantly lower than that of the KNN/Pt/Al₂O₃ film (?? 15 nm). The heterogeneous microstructure composed of small spherical and larger needle-like or cuboidal particles were observed in the KN and NN films on both substrates. The homogeneous microstructure of the KNN thin film on the Pt/SiO₂/Si substrate was smoother and contained finer spherical particles (?? 50 nm) than on Pt/Al₂O₃ substrates (?? 100 nm). The effect of different substrates on the surface morphology of thin films was confirmed.