VPO／SiO2催化2,4—二氯甲苯氨氧化反应研究

研究Ｐ／Ｖ＝１的ＳｉＯ２负载钒磷氧化物催化剂催化２,４－二氯甲苯氨氧化反应,考察了反应温度,氨气比,空气比和空间速度等工艺条件的影响,在６７３Ｋ,二氯甲苯：氨气：空气：７：１５,空间速度２５０ｈ＾－１的条件下,２,４－二氯甲苯的转化率为９７％,２,４－二氯苯腈的摩尔产率为７０．２％,远高于文献所报道的使用未负载ＶＰＯ催化剂的结果,且反应温度降低４０Ｋ。     

醇在钒基催化剂上的氧化

以过氧化叔丁醇作为氧化剂,研究了醇类(苯甲醇、1-苯基乙醇和环己醇)在钒基催化剂上的氧化反应.制备了含苯磷二酚配体或吡嗪-2-羧酸酯配体的钒配合物,并运用傅里叶变换红外光谱、核磁共振谱、紫外-可见光谱及元素分析对其进行了表征.考察了溶剂对该类反应的影响.发现在甲苯溶剂中进行氧化反应时,苯甲醇被氧化成苯甲醛而不会被深度氧化为苯甲酸;而在乙腈溶剂中,苯甲醛和苯甲酸均有生成.此外,对不同钒磷氧化物的催化活性进行了比较,结果表明,在乙腈溶剂中的产品收率比在甲苯溶剂中高.     

2,6-二氯甲苯氨氧化制备2,6-二氯苯腈实验

本实验属于化工基础实验 ,采用对环境友好的氨氧化催化法 ,在连续流动固定床反应器上 ,以 2 ,6 二氯甲苯为原料制备重要的有机合成中间体 2 ,6 二氯苯腈。采用正交设计法筛选到合适的反应条件。本实验可以培养学生处理较复杂问题和初步从事多相催化研究的能力     

4-氰基吡啶的合成

以4-甲基吡啶为原料,在固定床反应器中通过含氧化钒的催化剂发生气固相接触氨氧化反应制备雷米封中间体4-氰基吡啶,4-甲基吡啶的转化率为99％,4-氰基吡啶的选择性为88％,收率为87．12％。     

9-氯甲基蒽的实验室制备法

介绍一个在室温条件下反应制备9-氯甲基蒽——构造荧光分子探针的常用中间体的,方法。该实验以9-蒽甲醇和二氯亚砜为原料,苯为溶剂,在吡啶催化下反应,经水洗,干燥,旋转蒸发除去溶剂,最后得到固体产品。推荐该方法作为高校实验室自制9-氯甲基蒽的方法。     

V_2O_5/CeO_2催化剂上甲醇氧化一步法合成二甲氧基甲烷

采用溶胶-凝胶法制备了V2O5/CeO2催化剂,并用于甲醇氧化一步法合成二甲氧基甲烷(DMM)反应中.考察了V2O5含量对钒氧化物的存在状态、催化剂表面酸性、氧化-还原性及其催化甲醇氧化反应性能的影响.结果表明,V2O5含量为15%时钒氧化物呈单层分散,小于15%时以孤立或聚合态存在,大于20%时出现V2O5晶体,达到30%时出现CeVO4.当V2O5含量为15%时,较高的钒氧化物分散度使催化剂具有较强的氧化还原能力和较多的酸性中心,从而使催化剂具有较高的活性和DMM选择性.     

硅胶负载钒磷氧化物催化2 ,6-二氯甲苯氨氧化反应(英)

对硅胶负载钒磷氧化物（ＶＰＯ） 催化剂（ ｎ（Ｖ）／ ｎ（Ｐ） ＝ １） 催化２ ,６二氯甲苯（ＤＣＴ） 氨氧化反应进行了研究． 考察了反应温度、空气／ＤＣＴ 比和氨／ＤＣＴ 比等因素对反应的影响． 反应温度对氨氧化反应影响较大,空气／ＤＣＴ比和氨／ＤＣＴ 比对反应的影响不很大． 最佳反应条件为： Ｔ＝ ６７３ Ｋ, ｎ（ａｉｒ）／ｎ（ＤＣＴ） ＝ ３０ , ｎ（ＮＨ３）／ｎ（ＤＣＴ）＝ ６ ． 在此条件下,ＤＣＴ转化率为９０ ％ , 产率为５７ ％ ． 与使用（ＮＨ４）２［（ＶＯ）３（Ｐ２Ｏ７）２］ 催化剂的文献报道值相比,反应温度降低４０ Ｋ, 产率提高３４ ％ ．ＸＲＤ分析结果表明, ＶＰＯ／ＳｉＯ２ 催化剂中的活性组分以均匀分散的无定形状态存在,而未负载的ＶＰＯ催化剂中存在αＶＯＰＯ４ 和βＶＯＰＯ４ 晶相．     

草酸处理对丙烷氨氧化催化剂Sb-V-O结构和催化性能的影响

以不同量的草酸处理钒的起始原料,采用共沉淀法制备了VSb3混合氧化物催化剂,运用N2低温吸附、X射线衍射、X射线光电子能谱和H2程序升温还原等方法对催化剂进行了表征,并考察了其在丙烷氨氧化反应中的催化性能.结果表明,草酸的处理可使所得样品中V处于较低的价态,从而有利于活性相SbVO4的生成.当草酸/V(摩尔比)为3时,所制VSb3混合氧化物中存在较多的活性相SbVO4,且其表面具有适量Sb和V的分布,使催化剂具有良好的氧化/还原性能平衡,因而在丙烷氨氧化反应中表现出更高的活性和丙烯腈选择性.     

硅胶负载钒磷氧化物催化2,6-二氯甲苯氨氧化反应

对硅胶负载钒磷氧化物（ＶＰＯ）催化剂（ｎ（Ｖ）／ｎ（Ｐ）＝１）催化２,６－二氯甲苯（ＤＣＴ）氯氧化反应进行了研究。考察了反应温度、空气／ＤＣＴ比和氨／ＤＣＴ比等因素对反应的影响。反应温度对氨氧化反应影响较大,空气／ＤＣＴ比和氨／ＤＣＴ比对反应的影响很大。最佳反应条件为：Ｔ＝６７３Ｋ,ｎ（ａｉｒ）／ｎ（ＤＣＴ）＝３０,ｎ（ＮＨ３）／ｎ（ＤＣＴ）＝６．在此条件下,ＤＣＴ转化率为９０％,产率为５７％。与     

交联聚苯乙烯微球固载的双齿席夫碱型氧钒(Ⅳ)配合物催化分子氧氧化苯甲醇

利用水杨醛(SA)和氨甲基(MA)交联聚苯乙烯(CPS)微球反应,制得键合有双齿席夫碱配体SAAM的交联聚苯乙烯SAAM-CPS微球,再与硫酸氧钒发生螯合配位反应,制备了固载有席夫碱型氧钒(Ⅳ)配合物催化剂,采用红外光谱、扫描电镜及热失重等手段对催化剂进行了表征,并用于催化分子氧氧化苯甲醇反应,考察了催化剂用量、反应温...     

XRD and TPR Studies of Cu-Al Hydrotalcite Derived Highly Dispersed Mixed Metal Oxides

A series of Cu/Al catalysts, containing different proportions of copper and aluminium, have been prepared by coprecipitation using metal nitrate precursors and Na₂CO₃. The dried precipitate catalyst precursors were characterized by X-ray diffraction (XRD) to show the presence of Cu-Al binary hydrotalcite-like phase. The dried precipitates were calcined at 873 K for 3 h. The calcined catalysts were characterized by XRD and temperature-programmed reduction (TPR) methods to show the presence of unidentified mixed oxides. The results showed that the extent of metal-support interaction increased with copper loading due to the mixed oxides formed from the hydrotalcite-type phase during calcination. High dispersion of the mixed metal oxides was indicated by comparison with similar studies on Cu-Al catalysts, prepared by similar methods, whose precursors showed no hydrotalcite formation.     

Sol-gel processing and characterization of potassium niobate nano-powders by an EDTA/citrate complexing method

The present research describes a modified sol-gel technique used to obtain nano-crystalline potassium niobate (KNbO₃) powders by using ethylene diamine tetraacetic acid (EDTA)/citrate as a complexing agent. The metal ions chemically interact with EDTA in the precursor sol. The aging treatments lead to the formation of a precursor-polymeric gel network. The effects of the amounts of citric acid and EDTA on the stability of the precursor sol are investigated. The influence of excess K on the formation of pure-phase KNbO₃ powders is also studied. The obtained gels and powders are characterized by thermogravimetric-differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that a stable precursor sol is formed when n(CA):n(Mⁿ⁺) = 3:1 and n(EDTA) :n(NH₄OH) = 1:3.5. The xerogel is calcined at 700–850 °C to prepare the KNbO₃ nano-powder. The smallest grain size of the sample obtained at 850 °C is about 60 nm when the K/Nb molar ratio equals 1.2.     

Synthesis of nanostructured perovskite powders via simple carbonate co-precipitation

A very simple, cost-effective, chloride- and alkali-free, carbonate co-precipitation synthesis in aqueous medium was applied in the preparation of perovskite-type lanthanum manganese oxide-based powders, i.e. La_0.70Sr_0.30MnO_3?δ (LSM) and La_0.75Sr_0.25Cr_0.5Mn_0.5O_3?δ (LSCrM). The precursors so obtained yielded nano-structured perovskite oxides when treated at 900°C and 800°C, respectively. The measured BET surface areas were in the low-end range for high temperature oxides (4 m² g^?1 and 10 m² g^?1) but the X-ray crystallite size was as low as 50 nm for LSCrM and 90 nm for LSM.     

Effect of fuel content on formation of zinc aluminate nano and micro-particles synthesised by high rate sol–gel autoignition of glycine-nitrates

The autoignition technique using glycine as fuel and related nitrate salts as an oxidiser is able to produce zinc aluminate spinel. The precursors were synthesised with lean and rich fuel at pH of 7.0 and the materials so obtained were calcined at various temperatures ranging from 600–1200°C. The autoignition process of precursors was studied by the simultaneous thermo-gravimetric and differential thermal analyses to determine the ignition mechanism. The calcined powders were characterised by X-ray diffraction, Brunauer–Emmett–Teller technique and transmission electron microscopy. The product contains nano-sized particles with an average size of approximately 20 nm. The XRD patterns showed the formation of ZnO in the powder obtained by the fuel-rich precursor and calcined at 600 C which disappears at 800 C due to solid-state reaction and proper crystallisation after heat treatment. The results presented here can be useful in manufacturing nano and micro-sized ZnAl₂O₄ on an industrial scale using the combustion technique.     

Synthesis of strontium substituted hydroxyapatite by solution combustion route

Hydroxyapatite is a versatile compound resembling natural bone mineral. HAP insinuates feasibility with substitution ensuing in its application in various fields. The properties of calcium and strontium are cognate and pose as a bone-seeking trace-element that accumulates in new trabecular bone. Strontium substituted hydroxyapatite, Ca₉.₅Sr_0.5(OH)₂(PO₄)₆, was synthesized using citric acid as fuel and calcined 900 ​°C. The as-prepared product notably was characterized by powder X-ray diffraction, Fourier - Transform Infrared spectroscopy and Scanning Electron Microscope along with Energy Dispersive Spectroscopy. FT-IR analysis exhibited stretching and bending vibrations of (PO₄)^3- and OH⁻ groups along without any signal of carbonate group. Studies showed that product formed is strontium substituted hydroxyapatite, and calcination temperature plays an essential role in the formation of hydroxyapatite phase. The precursors when calcined resulted in 46–50 ​nm of Sr substituted hydroxyapatite.     

Synthesis of tin oxide nanoparticles by sol–gel process: effect of solvents on the optical properties

Tin oxide (SnO₂) nanoparticles were synthesized by the reaction of SnCl₄·5H₂O in methanol, ethanol and water via sol–gel method. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared, Scanning electron microscopy and Transmission electron microscopy. The optical properties of the as-prepared samples were investigated. The XRD analysis showed well crystallized tetragonal SnO₂ can be obtained and the crystal sizes were 3.9, 4.5 and 5 nm for the sample calcined at 400 °C for 2 h. It was found that solvents played important roles in the particle size effect of nanocrystalline SnO₂.     

Hydrotalcite-derived Co-containing mixed metal oxide catalysts for methanol incineration

The Co–Mg–Al mixed metal oxides were prepared by calcination of co-precipitated hydrotalcite-like precursors at various temperatures (600–800 °C), characterised with respect to chemical (AAS) and phase (XRD) composition, textural parameters (BET), form and aggregation of cobalt species (UV–vis-DRS) and their redox properties (H₂-TPR, cyclic voltammetry). Moreover, the process of thermal decomposition of hydrotalcite-like materials to mixed metal oxide systems was studied by thermogravimetric method combined with the analysis of gaseous decomposition products by mass spectrometry. Calcined hydrotalcite-like materials were tested as catalysts for methanol incineration. Catalytic performance of the oxides depended on cobalt content, Mg/Al ratio and calcination temperature. The catalysts with lower cobalt content, higher Mg/Al ratio and calcined at lower temperatures (600 or 700 °C) were less effective in the process of methanol incineration. In a series of the studied catalysts, the best results, with respect to high catalytic activity and selectivity to CO₂, were obtained for the mixed oxide with Co:Mg:Al molar ratio of 10:57:33 calcined at 800 °C. High activity of this catalyst was likely connected with the presence of a Co–Mg–Al spinel-type phases, containing easy reducible Co³⁺ cations, formed during high-temperature treatment of the hydrotalcite-like precursor.     

IR structural evidence of hydrotalcites derived oxidic forms

Ni–Al hydrotalcite-like compounds with the general formula [Ni_1−xAl_x(OH)₂](CO₃)_x/2⋅mH₂O, where 0.25≤x≤0.66, were synthesised using coprecipitation at a constant pH, and were treated hydrothermally. The structures of the oxidic forms obtained by calcination of the hydrotalcites at 450°C and 900°C, respectively, were investigated using X-ray diffraction and, mainly, IR and UV–VIS spectroscopy. A NiO phase was identified by XRD in all calcined samples; an additional oxidic phase — the nickel spinel, NiAl₂O₄ — developed at 900°C. IR spectroscopy results gave supplementary information about the incipient, local organisation of cations in the interstices of the oxygen atoms lattice. IR spectra were different, depending on the samples' composition. In case of the HT precursors calcined at 450°C a structure like a transition alumina (γ-Al₂O₃) was found as a main oxidic phase in samples with a high Al-content; IR spectra of the samples with a high Ni content evidenced NiO as the main oxidic phase; in case of these latter samples, the formation of an oxidic structure with a spinel-type local order was identified at this temperature. This structure developed to an inverse nickel spinel oxidic phase at 900°C, as shown by the IR absorption bands. The NiO structure in the samples with a high Ni content at 450°C was found also in the oxides obtained by calcination at 900°C. The spinel-type local order was also observed by UV–VIS spectroscopy in case of the HT precursors calcined at 450°C, by the presence of both absorption bands of the tetrahedral and octahedral Ni(II) ions in the Al₂O₃ lattice and of octahedral Ni(II) ions in the NiO lattice. The same absorption bands were found also in the samples calcined at 900°C, proving that the NiAl₂O₄ spinel identified has a partial inverse structure, with the Ni(II) ions both in tetrahedral and octahedral crystalline fields. Our found structural data were in accord with the models proposed in the literature.     

Preparation and characterization of nanocrystalline ZnO by direct precipitation method

Nanocrystalline ZnO was prepared with ZnCl₂·2H₂O and (NH₄)₂CO₃ as raw materials by direct precipitation method. The precursor was proved to be [Zn₅(OH)₆(CO₃)₂] by TG-DTG-DTA and IR analysis. This precursor was calcined at 300°C for 1, 2 and 3 hours respectively, and then the nanocrystalline ZnO of different grain size were obtained. The nanocrystalline ZnO was characterized using X-ray diffraction (XRD), TEM and Brunner-Emmett-Teller method (BET). Experimental results for nanocrystalline ZnO showed that the minimum size was about 8nm, the maximum was about 15 nm and the mean grain size was 12 nm, the surface area was 80.56 m²/g and the purity was 99.9% when the precursor was calcined at 300°C for 2 h. __________ Translated from Journal of Inner Mongolia Normal University (Natural Science Edition), 2006, 35(1) (in Chinese)     

Ammoxidation of 3-picoline to nicotinonitrile using silica-supported VCrO catalysts

A series of vanadium–chromium oxide (VCrO) catalysts supported on silica was prepared by wetness impregnation method with different Cr/V molar ratios from 0.2 to 1.0. These catalysts were characterized by XRD, TG, temperature-programmed desorption of ammonia (NH₃-TPD), X-ray photoelectron spectra (XPS), and Raman spectroscopy, and their catalytic activity was evaluated in the ammoxidation of 3-picoline (3-PIC) to nicotinonitrile (NN). The results of XRD, TG, Raman, and XPS confirmed that the active components on the silica surface were mainly amorphous V₂O₅ and CrVO₄. The results of NH₃-TPD showed that acidity of the catalysts decreased with the increase of Cr/V ratio. Catalytic results revealed that acidity of the catalysts was closely related to the catalytic performance. Low acidity gave low conversion of 3-PIC and high NN selectivity. Furthermore, the conversion of 3-PIC increased with rise in reaction temperature, and the selectivity of NN was slightly influenced by the 3-PIC conversion. Therefore, among the catalysts (Cr/V ratio was 0.2, 0.4, 0.6) tested, Cr/V-0.6 catalyst retained the lowest acidity and exhibited the highest selectivity and yield of NN in the ammoxidation of 3-PIC.