VOx/AlPO4催化剂合成及其催化苯羟基化反应性能

以异丙醇铝与磷酸为原料,离子液体1-丁基-3-甲基咪唑溴盐([Bmim]Br)与二正丙胺为共模板剂合成了Al PO₄,进而采用水热法将V₂O₅负载于Al PO₄载体制备了VO_x/Al PO₄催化剂。采用XRD、SEM、TEM、Mapping、FTIR、N₂吸附-脱附、XPS对催化剂进行了表征,考察了其在苯羟基化反应中的催化性能。结果表明,钒氧化物负载量为16%(以V₂O₅和Al PO₄的总质量为基准,下同)的催化剂具有最多且分布均匀的V⁴⁺活性中心、契合反应的酸性微环境,在催化剂用量为0.2 g,苯用量4 mL,质量分数30%的H₂O₂用量12.5 mL,乙腈用量15 mL,反应温度70℃,反应时间7 h的条件下,苯转化率为53.4%,苯酚选择性为98.4%。基于催化剂表征分析及性能评估,推测催化反应机理...     

Characterization of silica supported Ni and Mg basic carbonate catalyst precursors

In Mg-doped Ni-silica catalyst precursors, magnesium preferentially precipitates as basic carbonate species by isomorphous substitution of nickel in basic nickel carbonate network. This has been confirmed by thermal and infrared studies. Presence of magnesium decreases the reducibility of neighbouring nickel atoms due to electronic effects and also acts as spacer/barrier thus minimizing sintering via nickel particle migration. As a consequence, the nickel dispersion in Mg/Ni-silica samples is higher than in Ni-silica samples at all SiO₂/Ni ratios.     

模板固相合成磷酸铝及其吸附性能应用研究

固相方法或固相模板方法在150℃、2h合成磷酸铝或纳米磷酸铝，通过XRD、IR、ICP和化学分析进行了表征。TG研究表明纳米磷酸铝从室温到1000℃范围热稳定性好。并对磷酸铝和3纳米磷酸铝对Cr(VI)的吸附性能进行了研究。结果表明它们对Cr(VI)具有良好的吸附性能。     

Al2O3对AlPO4催化剂的结构及其缩醛化反应活性的影响

采用溶胶-凝胶法制备了系列AlPO₄-Al₂O₃催化剂,利用XRD、TG-DTA、NH₃-TPD和催化剂评价等方法,研究了制备条件对催化剂结构和缩醛化反应催化性能的影响,结果表明,Al₂O₃的存在不仅能提高AlPO4的热稳定性,而且可以调节催化剂的表面酸性性能。在适宜的缩醛化反应条件下,400 ℃焙烧和Al₂O₃质量分数为15%的AlPO₄-Al₂O₃催化剂样品具有较好的催化活性,1,2-丙二醇转化率达28.1%,AlPO₄-Al₂O₃催化剂的缩醛化反应活性与表面弱酸中心的酸量成顺变关系。     

固相或固相模板法合成纳米磷酸铝及其对铬、镍离子吸附性能研究

用固相或固相模板方法于 1 5 0℃ ,2 h合成了 T-磷酸铝或纳米磷酸铝 ,并就它们对 Cr( )、Ni( )的吸附性能进行了研究 ,结果表明这类化合物对 Cr( )、Ni( )离子具有较好的吸附性能 ,且这类化合物对 Ni( )的吸附性能比对 Cr( )离子的吸附性能好     

Catalytic decomposition of ethanol on ­V2O5/AlPO4 catalysts

Different ratios of vanadium pentoxide supported on aluminum phosphate (1–30 mol%) have been prepared by an impregnation method. The original and calcined samples were characterized by TG, DTG, DSC, X‐ray diffraction, IR spectra, N₂ adsorption and electrical conductivity measurements. The catalytic decomposition of ethanol has been carried out at 210 °C in a flow system at 1 atm using air as a carrier gas. The results indicate that the catalysts calcined at 400 °C were active and selective towards ethene formation whereas the samples calcined at 600 °C showed a drastic reduction in both activity and selectivity. © 2000 Society of Chemical Industry     

Chemical Characterization of Si-Al-C-O Precursor and Its Pyrolysis

Polycarbosilane was modified by reaction with an aluminum alkoxide to get a precursor for Si-Al-C-O ceramics. The precursor was essentially characterized by magic-angle spinning nuclear magnetic resonance (²⁹Si, ²⁷Al, and ¹³C) and appeared as a dispersion of Al(OH)₃-based particles in a polycarbosilane chain matrix. After the material was heat-treated under argon at 1500°C, X-ray diffraction showed that it crystallized mainly as SiC 2H. The presence of this rather unusual polytype for polycarbosilane-derived ceramics seemed to be related to the presence of aluminum atoms.     

Low-temperature preparation of novel stabilized aluminum titanate ceramic fibers via nonhydrolytic sol-gel method through linear self-assembly of precursors

Stabilized aluminum titanate fibers were prepared via nonhydrolytic sol-gel (NHSG) method through linear self-assembly of precursors. The results show that NHSG method generates the heterogeneous condensation with the formation of Al–O–Ti, Mg–O–Ti, Fe–O–Ti, Mg–O–Al, Fe–O–Ti bonds, which ensures that magnesium ions and iron ions can enter aluminium titanate lattice and stabilize it at 750 °C. Bimolecular associated structure of chlorotitanium ethoxide titanium precursor promotes the self-linear-assemble of all precursors, which enables the excellent spinnability of sol. Stabilized aluminum titanate fibers have excellent corrosion resistance. The thermal expansion coefficient of stabilized aluminum titanate ceramic is −0.142 × 10⁻⁶°C⁻¹.     

Reactions of metal chlorides with hexamethyldisilazane: Novel precursors to aluminum nitride and beyond

Metal nitrides are intensely investigated because they can offer high melting points, excellent corrosion resistance, high hardness, electronic and magnetic properties superior to the corresponding metals/metal oxides. Thus, they are used in diverse applications including refractory materials, semiconductors, electronic devices, and energy storage/conversion systems. Here, we present a simple, novel, scalable and general route to metal nitride precursors by reactions of metal chlorides with hexamethyldisilazane [HMDS, (Me₃Si)₂NH] in tetrahydrofuran or acetonitrile at low temperatures (ambient to 60°C/N₂). Such reactions have received scant attention in the literature. The work reported here focuses primarily on the Al-HMDS precursor produced from the reaction of AlCl₃ with HMDS (mole ratio = 1:3) characterized by matrix-assisted laser desorption/ionization-time of flight, Fourier-transform infrared spectroscopy, thermogravimetric analysis-differential thermal analysis, and multinuclear nuclear magnetic resonance spectroscopy (NMRs) for chemical and structural analyses. The Al-HMDS precursor heated to 1600°C/4 h/N₂ produces aluminum nitride, characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and magic-angle spinning NMR. On heating to 800–1200°C/4 h/N₂, the precursor transforms to an amorphous, oxygen-sensitive powder with very high surface areas (>200 m²/g) indicating nanosized particles, which can be used as additives to polymer matrices to modify their thermal stabilities. Al₂O₃ is also presented in the final product after heating, due to its high susceptibility to oxidation. This approach was extended via proof-of-concept studies to other metal chloride systems, including Zn-HMDS, Cu-HMDS, Fe-HMDS, and Bi-HMDS. The formed precursors are volatile, offering the potential utility as gas-phase deposition precursors for their corresponding metal nitrides.     

超增溶自组装法合成纳米AlPO_4-5分子筛

采用超增溶自组装法合成纳米级AlPO4-5分子筛,考察了焙烧温度、乳化剂质量分数对分子筛粒径及其分布的影响,结果表明在超增溶纳米自组装的条件下能够合成出类球形的纳米磷铝分子筛,并且通过调节乳化剂的质量分数可以控制纳米分子筛的粒径大小,纳米磷铝分子筛直径为10~80 nm,长度为0.1~0.2μm。     

Thermal Conversion of Preceramic Polyiminoalane Precursors to Aluminum Nitride: Characterization of Pyrolysis Products

This study introduces a new method for the synthesis of aluminum nitride by pyrolysis of a polymeric precursor. Metallic aluminum is electrolytically dissolved in an electrolyte containing a primary amine. Subsequent drying and heating enables the formation of a polymeric, gellike intermediate polyiminoalane compound. Calcining in ammonia atmosphere at 850°C results in aluminum nitride powder with a mean crystallite size of about 30 nm.     

Observation of [Al(OH) n (H2O)6-n ] n (MoO4) in hydrotreating catalyst precursors by solid-state27 Al NMR

A previously unobserved octahedral²⁷Al MAS NMR resonance has been detected in rehydrated calcined Mo/Al₂O₃ hydrotreating catalyst precursors. This resonance is attributed to the presence of hydrated forms of aluminum molybdate such as [Al(OH) _n (H₂O)_6-n ] _n (MoO₄) (n = 1 or 2). The cross-polarization relaxation parameters, obtained from variable contact time experiments, yielded information on the relative sizes of the [Al(OH) _n (H₂O)_6-n ] _n (MoO₄) domains in the catalysts with different molybdenum loadings. Analysis of the²⁷A1 MAS NMR spectra of P-Mo(8)/Al₂O₃ and P-Mo(12)/Al₂O₃ (wt%P = 0.0–12.0) shows that a function of the phosphate in the 12 wt% Mo catalyst is to prevent the re-hydration of the molybdate phases on the calcined catalysts.     

用DSC研究选择聚丙烯腈原丝的共聚单体

本文主要利用差示扫描量热分析(DSC)研究了聚丙烯腈的共聚物及其原丝的热性能，研究结果发现国产原丝具有相似的放热单峰，而日本某公司的原丝具有两个峰，分峰使聚丙烯腈原丝放热峰宽化，避免了在预氧化、碳化时放热集中产生熔化、断丝现象．聚丙烯腈原丝的纺丝、溶解、氨改性等加工过程不能明显改变其放热峰的形状，而共聚单体的种类和组成配比才是最重要的因素，通过适当的共聚单体选择、配比设计可以制得具有与日本原丝放热峰相似的聚丙烯腈聚合物或原丝。     

Influence of zirconium salt precursors on the crystal structures of zirconia

Procedures have been developed for preparing zirconia to yield either tetragonal or monoclinic phases following low (400–600 °C) temperature calcination. The data in this note emphasize the need for paying attention to the precursor zirconium salt in preparing the monoclinic or tetragonal phases. A salt precursor obtained from a supplier at different times may produce different results. Generally, it is more difficult to obtain a precursor that will produce the monoclinic phase than the one that will produce the tetragonal form.     

Characterization of the Free-Carbon Phase in Precursor-Derived Si-C-N Ceramics: I, Spectroscopic Methods

Polyvinylsilazane, as a precursor for Si-C-N ceramics, was prepared by ammonolysis of functionalized chlorosilanes. Pyrolysis under inert atmospheres at T _p= 1000°C led to an amorphous Si-C-N-(H) ceramic. Further heat treatment caused the transformation to the thermodynamically stable crystalline phase assemblage. The structural changes, especially those of the excess carbon, were studied by characterizing the solid intermediates via solid-state magic angle spinning nuclear magnetic resonance spectroscopy. Moreover, Raman spectroscopy, electron spin resonance spectroscopy, and chemical analysis were used. Based on these methods, a comprehensive picture of the formation and behavior of the free-carbon phase present in polymer-derived ceramics was obtained.     

铂负载AlPO-5催化剂的制备及其甘油催化氧化性能研究

采用水热合成法制备磷酸铝分子筛AlPO-5,并通过焙烧处理得到AlPO-5分子筛多孔材料,以浸渍法和沉淀法分别制备了Pt负载型AlPO-5催化剂,通过粉末XRD、TEM、氮气吸附-脱附等手段对制备的催化剂进行了对比表征,研究了负载方法对Pt团簇分散度以及粒径尺寸的影响。以Pt/AlPO-5作为催化剂,研究了其对甘油的催化氧化性能,系统考察了Pt负载量、还原方法和反应时间对甘油转化率和产物选择性的影响。实验结果表明,由浸渍法制备的催化剂对甘油的转化率和甘油醛的选择性较高,甘油醛的选择性最高可达到63.46%。甘油醛作为起始反应产物,其高选择性与较大尺寸的Pt纳米团簇有关。     

Al2O3对AIPO4催化剂的结构及其缩醛化反应活性的影响

采用溶胶-凝胶法制备了系列AlPO4-Al2O3催化剂,利用XRD、TG-DTA、NH3-TPD和催化剂评价等方法,研究了制备条件对催化剂结构和缩醛化反应催化性能的影响,结果表明,Al2O3的存在不仅能提高AlPO4的热稳定性,而且可以调节催化剂的表面酸性性能.在适宜的缩醛化反应条件下,400℃焙烧和Al2O3质量分数为15%的AlPO4-Al2O3催化剂样品具有较好的催化活性,1,2-丙二醇转化率达28.1%,AlPO4-Al2O3催化剂的缩醛化反应活性与表面弱酸中心的酸量成顺变关系.     

Characterization and Dehydration Behavior of a Natural,Ammonium Hydroxide,and Thermally Treated Zeolitic Tuff

Aqueous NH₄OH-treated and subsequently calcined forms of local natural zeolitic tuff were characterized by different techniques including scanning electron microscopy (SEM), X-ray powder diffraction, inductively coupled plasma–atomic emission spectroscopy (ICP-AES), volumetric N₂ adsorption at ?196°C, thermogravimetry (TG), differential scanning calorimetry (DSC), and transmittance infrared spectroscopy. The dehydration behavior of the samples was investigated using an in situ temperature-programmed diffuse reflectance Fourier transform infrared spectroscopy (TP-DRIFTS) method under vacuum. The DRIFTS spectra recorded yielded information about the effect of the NH₄OH treatment and subsequent calcination on the dehydration behavior of the natural zeolite. Changes in the infrared bands corresponding to vibrations of the O–H and N–H bonds upon in situ heating under vacuum were analyzed.     

The dilution of vanadyl pyrophosphate, catalyst for n-butane oxidation to maleic anhydride, with aluminum phosphate: unexpected reactivity due to the contribution of the diluting agent

This paper describes the preparation, characterization and reactivity in n-butane oxidation of catalysts made of vanadyl pyrophosphate (VPP) diluted in aluminum phosphate. Catalysts were prepared by synthesizing at the same time the VPP precursor and AlPO₄, in order to develop mixed systems, suitable for the conglomeration into fluidizable particles by spray-drying. Al phosphate was chosen due to its presumed chemical inertness towards the active phase and towards n-butane. No evidence was obtained for the formation of mixed V/Al phosphates; an homogeneous reciprocal dispersion of the two compounds developed. However, Al phosphate showed an unexpected activity in n-butane oxidation; specifically, in the temperature range comprised between 340 and 400 °C, the hydrocarbon was converted to formaldehyde and carbon monoxide by radical-like reactions. The activity of Al phosphate became negligible above 400 °C, in the temperature range where instead VPP was active in hydrocarbon oxidation and selective to maleic anhydride. Moreover, Al phosphate was also responsible for the consecutive oxidative degradation of maleic anhydride, at high temperature.     

含金属锌磷酸铝的固相合成及表征

用固相合成方法,在模板剂存在下,以结晶氯化铝、磷酸二氢铵和适量的醋酸锌为原料,合成了含金属元素锌的磷酸铝类化合物,合成的化合物通过元素的化学分析和ICPS测定、XRD和IR图谱,确定其元素的组成,并对产物进行了表征。