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1.
A simple and efficient method for liquid-phase catalytic nitration of 1-nitronaphthalene with NO2 to 1,5-dinitronaphthalene under mild conditions has been developed. The results indicated that the sulfated zirconia (SO42?/ZrO2) as solid superacid catalyst exhibits superior catalytic performance with dioxygen and acetic anhydride. 93.8% conversion of 1-nitronaphthalene and 52.8% 1,5-dinitronaphthalene selectivity were achieved. Furthermore, the physicochemical properties of SO42?/ZrO2 were determined by XRD, Py-FT-IR, BET, FT-IR, Raman spectroscopy and ICP-OES technologies. The possible nitration reaction mechanism over SO42?/ZrO2 catalyst was proposed. The present work provides an easy-to-implement, mild and eco-friendly approach for the efficient preparation of valuable 1,5-dinitronaphthalene, which has extensive industrial application prospects. 相似文献
2.
通过向SO 2-4 /ZrO 2催化剂中同时引入适量的Pt和Al 2O 3, 制备出了具有较高催化性能和稳定性的Pt-SO 2-4 /ZrO 2-Al 2O 3型固体超强酸催化剂. 以正戊烷异构化反应为探针, 考察了Al含量对催化剂性能的影响; 并采用X射线衍射(XRD)、比表面积测定(BET)、红外(IR)光谱、程序升温还原(TPR)、热重-差热分析(TG-DTA)和氨-程序升温脱附(NH 3-TPD)手段对催化剂进行了表征. 结果表明, Al能够提高ZrO 2的晶化温度, 抑制硫的分解, 增加催化剂的比表面积, 增强硫氧键的结合, 提高催化剂的还原性能, 增加催化剂的酸强度和酸总量. 当Al 2O 3含量(质量分数, w)为5.0%时, Pt-SO 2-4 /ZrO 2-Al 2O 3固体超强酸催化剂的催化活性最好, 在100 h内异戊烷收率可稳定在52.0%以上, 选择性在98.2%以上. 相似文献
4.
A series of ZrO 2-SiO 2 catalysts with various molar ratios of ZrO 2/SiO 2 were prepared by a coprecipitation method. The characterization of catalyst unmodified or modified with H 2SO 4 was performed using XRD, IR and XPS methods, and by the measurement of surface area. Mixing with amorphous SiO 2 or modifying with H 2SO 4 shifted the transition of ZrO 2 from the amorphous to tetragonal phase to a higher temperature. The catalytic activities for 2-propanol dehydration and cumene dealkylation were correlated with both acidity and acid strength of the catalyst, and the modification of catalyst with H 2SO 4 enhanced the catalytic activities remarkably. The difference in catalytic activities between modified and unmodified catalysts increased with increasing ZrO 2 content. 相似文献
5.
Superacid ZrO_2:H_2SO_4 showed high activity in Friedel-Crafts benzoylation of benzeneand substituted benzenes such an chlorobenzene,toluene and 1,3,5-trimethylbenzene.Benzophenonesin 90-100% yields were obtained with catalytic amount of superacid ZrO_2:H_2SO_4.The calcinationtemperature greatly influenced the acid strength and activity of the superacid ZrO_2:H_2SO_4.Thesuperacid has both Lewis and Bronsted acid sites.The reversibility of Friedel-Crafts benzoylation andtransacylation were observed over the superacid.The used superacid could be readily regenerated andshowed identical benzoylation activity to toluene. 相似文献
6.
Summary FT-IR and 29Si-NMR studies suggested the interaction of H 2SO 4 with the SiO 2 support in the material synthesized by the sol-gel method. 1H-NMR results showed that the acid strength of solid sulfuric acid was almost the same as that of liquid sulfuric acid. The catalyst showed higher catalytic activity and stability than that prepared by impregnation method. 相似文献
7.
This study aims to develop highly efficient, recyclable solid catalysts for the epoxidation of vegetable oils. An Al 2O 3–ZrO 2–TiO 2 solid acid catalyst was prepared by a co‐precipitation/impregnation method and characterised through scanning electron microscopy, energy‐dispersive spectroscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, Fourier‐transform infrared and nitrogen adsorption–desorption analyses. The solid acid catalyst with a high surface area and typical slit pore adsorption was successfully synthesised. Al 2O 3–ZrO 2–TiO 2 also exhibits high stability and improved catalytic efficiency in the epoxidation of soybean oil. An oil conversion rate of 86.6%, which is higher than that of conventional catalysts, was obtained with a catalyst loading of 0.8 wt% and was maintained at 76.6% even after recycling the catalyst three times. The performance of the solid catalyst was slightly superior to that of H 2SO 4. Therefore, this novel catalyst may potentially be applicable in catalysing soybean oil epoxidation. 相似文献
8.
The catalytic decomposition of dichlorodifluoromethane (CFC‐12) in the presence of water vapor on a series of SO 42?‐promoted solid adds was investigated. CFC‐12 was decomposed completely on SO 42?/ZrO 2, SO 42?/TiO 2, SO 42?/SnO 2, SO 42?/ Fe 2O 3 and SO 42–/Al 2O 3 at 265°C, 270°C, 325°C, 350°C and 325°C, respectively, and the selectivity to by‐products was neglectable. Obvious deactivation was found on SO 42?/ZrO 2 and SO 42?/Al 2O 3, during several hours on stream, while the catalytic activity was maintained on SO 42?/TiO 2, SO 42?/SnO 2 and SO 42?/Fe 2O 3 for 240 h on stream. 相似文献
9.
The catalytic activity of superacidic systems based on SO 4/ZrO 2 and modified by IV Period metals in isomerization of n-butane was studied. At low temperatures of the reaction, the introduction of Fe 3+, Sc 3+, Co 2+, or Zn 2+ ions (1%) increases the yield of isobutane by 1.5 times due to the activation of n-butane on the sites created by the promoting ions. The addition of Cr 3+, V 4+, or Mn 2+ (1%) decreases the catalytic activity because of a decrease in the catalyst acidity, most likely, due to the reduction of
surface sulfur species. The influence of the nature of the support and surface additives of SiO 2, TiO 2, and ZrO 2 on the activity and selectivity of the catalytic system in n-butane isomerization was studied.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7 pp. 1276–1280, July, 1999 相似文献
10.
Solid-acid catalytic materials such as ZrO 2-Al 2O 3 containing 80?mol% of ZrO 2 were prepared by the solution combustion method (SCM) using different fuels such as urea, hexamethylene tetramine, glycine, and sucrose. All the prepared solid acid catalytic materials were characterized for their physico-chemical properties like crystalinity, acidity, functionality and morphology. These materials were evaluated for their catalytic activity in the synthesis of a series of novel substituted benzimidazoles. The reaction conditions were optimized by varying the solvents, reaction temperature, weight of solid acid catalyst, molar ratio of the reactants, and reaction time. The ZrO 2-Al 2O 3 solid acid catalytic material prepared by urea as a fuel was found to be highly active, recyclable, and reusable in the synthesis of benzimidazoles. A possible reaction mechanism for the synthesis of benzimidazoles is also proposed. 相似文献
11.
A signal‐enhanced label‐free electrochemical immunosensor was constructed by the employment of Prussian blue doped silica dioxide (PB‐SiO 2) nanocomposite. At first, PB‐SiO 2 nanocomposite which was produced by using a microemulsion method was used to obtain a nanostructural monolayer on a glassy carbon electrode (GCE) surface. Next amino‐functionalized interface were prepared by self‐assembling 3‐aminopropyltriethoxy silane (APTES) on the PB‐SiO 2 nanoparticle surface. Then chitosan stabled gold nanoparticle (CS‐nanoAu) was subsequently attached, while the entire surface was finally loaded with neuron‐specific enolase antibody (anti‐NSE) via the adsorption of gold nanoparticle. The sensitivity of the proposed immunosensor has greatly improved as the PB‐SiO 2 nanostructural sensing film provides plenty of active sites which might catalyze the reduction of H 2O 2. The immunosensor exhibited good linear behavior in the concentration range from 0.25–5.0 and 5.0–75 ng/mL for the quantitative analysis of neuron‐specific enolase (NSE), a putative serum marker of small‐cell lung carcinoma (SCLC), with a limit of detection of 0.08 ng/mL. The resulting NSE immunosensor showed high sensitivity and long‐term lifetime which can be attributed to the extremely high catalytic activity and biocompatibility of CS‐nanoAu/APTES/PB‐SiO 2 nanostructural multilayers. 相似文献
12.
The aromatic aldehydes underwent cross aldol condensation with cycloalkanones in the presence of a catalytic amount of nanoporous silica-based sulfonic acid (SiO2-Pr-SO3H) under solvent-free conditions to afford the corresponding α,α’-bis(substituted benzylidene)cycloalkanones in excellent yields with short reaction time without any side reactions. This method is very general, simple and environmentally friendly in contrast with other existing methods. SiO2-Pr-SO3H was proved to be an efficient heterogeneous solid acid catalyst, which could be easily handled and removed from the reaction mixture by simple filtration, and also recovered and reused without loss of reactivity. 相似文献
13.
We studied on the function of the metal in the sulfated zirconia(SO 42–/ZrO 2) catalyst for the isomerization reaction of light paraffins. The addition of Pt to the SO 42–/ZrO 2 carrier could keep the high catalytic activity. The improvement in this isomerization activity is because Pt promotes removal of the coke precursor deposited on the catalyst surface. Though this catalytic function was observed in other transition metals, such as Pd, Ru, Ni, Rh and W, Pt exhibited the highest effect among them. It was further found that the Pd/SO 42–/ZrO 2–Al 2O 3 catalyst possessed a catalytic function for desulfurization of sulfur-containing light naphtha in addition to the skeletal isomerization. The sulfur tolerance of catalyst depended on the method of adding Pd, and the catalyst prepared by impregnation of the SO 42–/ZrO 2–Al 2O 3 with an aqueous solution of Pd exhibited the highest sulfur tolerance.Further, we investigated the improvement in sulfur tolerance of the Pt/SO 42–/ZrO 2–Al 2O 3 catalyst by impregnation of Pd. The results of EPMA analysis indicated that this catalyst was a hybrid-type one (Pt/SO 42–/ZrO 2–Pd/Al 2O 3) in which Pt/SO 42–/ZrO 2 particles and Pd/Al 2O 3 particles adjoined closely. This hybrid catalyst possessed a very high sulfur tolerance to the raw light naphtha that was obtained from the atmospheric distillation apparatus, although this light naphtha contained much sulfur. We assume that such a high sulfur tolerance in the hybrid catalyst is brought about by the isomerization function of Pt/SO 42–/ZrO 2 particles and the hydrodesulfurization function of Pd/Al 2O 3 particles. Besides, since the hybrid catalyst also provides high catalytic activity in the isomerization of HDS light naphtha, we suggest that the Pd/Al 2O 3 particles supply atomic hydrogen to the Pt/SO 42–/ZrO 2 particles by homolytic dissociation of gaseous hydrogen and also enhance the sulfur tolerance of Pt/SO 42–/ZrO 2 particles. Finally, we also propose the most suitable location of Pd and Pt in the metal-supported SO 42–/ZrO 2–Al 2O 3 catalyst. 相似文献
14.
Catalysis and deactivation of SO 42−/ZrO 2 solid acid on the alkylation of benzene and 1-dodecene were studied by the characterization of XRD, BET, IR, TG/DTA, and
NH 3-TPD techniques and the determination of the 1-dodecene conversion, the yield of dodecylbenzene and the selectivity of linear
alkylbenzene respectively. In addition, some treatment methods, such as the extraction with benzene or THF as solvent, and
the calcinations with or without the dipping of H 2SO 4 in air, were respectively used to recover the activity of deactivated catalyst. The results indicate that SO 42−/ZrO 2 solid acid shows higher catalytic activity for the alkylation of benzene and 1-dodecene with nearly 100% of 1-dodecene conversion
and more than 80% of dodecylbenzene yield, and higher selectivity of 2-LAB. The activity of catalyst for the alkylation of
benzene is in proportion to the content and the strength of medium acid site. However, the distinct deactivation of catalyst
was also obversed in the alkylation. According to the characterization of deactivated catalyst, the accumulation of hydrocarbon
fragment and the removal of are mainly reasons of SO 42−/ZrO 2 deactivation. The SO 42−/ZrO 2 calcinated at higher temperature is apt to deactivate. The treatment by extraction with solvent or calcinations can recover
the catalytic activity of spent catalyst at a certain extent, especially calcination with the dipping of H 2SO 4.
Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 3, pp. 455–463.
The article is published in the original. 相似文献
15.
Catalytic direct dehydrogenation of methanol to formaldehyde was carried out over Ag‐SiO 2‐MgO‐Al 2O 3 catalysts prepared by sol‐gel method. The optimal preparation mass fractions were determined as 8.3% MgO, 16.5% Al 2O 3 and 20% silver loading. Using this optimum catalyst, excellent activity and selectivity were obtained. The conversion of methanol and the selectivity to formaldehyde both reached 100%, which were much higher than other previously reported silver supported catalysts. Based on combined characterizations, such as X‐ray diffraction (XRD), scanning electronic microscopy (SEM), diffuse reflectance ultraviolet‐visible spectroscopy (UV‐Vis, DRS), nitrogen adsorption at low temperature, temperature programmed desorption of ammonia (NH 3‐TPD), desorption of CO 2 (CO 2‐TPD), etc., the correlation of the catalytic performance to the structural properties of the Ag‐SiO 2‐ MgO‐Al 2O 3 catalyst was discussed in detail. This perfect catalytic performance in the direct dehydrogenation of methanol to formaldehyde without any side‐products is attributed to its unique flower‐like structure with a surface area less than 1 m 2/g, and the strong interactions between neutralized support and the nano‐sized Ag particles as active centers. 相似文献
16.
The state of surface Pt atoms in the Pt/SO 4/ZrO 2/Al 2O 3 catalyst and the effect of the state of platinum on its adsorption and catalytic properties in the reaction of n-hexane isomerization were studied. The Pt-X/Al 2O 3 alumina-platinum catalysts modified with various halogens (X = Br, Cl, and F) and their mechanical mixtures with the SO 4/ZrO 2/Al 2O 3 superacid catalyst were used in this study. With the use of IR spectroscopy (CO ads), oxygen chemisorption, and oxygen-hydrogen titration, it was found that ionic platinum species were present on the reduced
form of the catalysts. These species can adsorb to three hydrogen atoms per each surface platinum atom. The specific properties
of ionic platinum manifested themselves in the formation of a hydride form of adsorbed hydrogen. It is believed that the catalytic
activity and operational stability of the superacid system based on sulfated zirconium dioxide were due to the participation
of ionic and metallic platinum in the activation of hydrogen for the reaction of n-hexane isomerization. 相似文献
17.
The condensation reaction of 2-aminobenzamide and aldehydes or ketones was investigated in the presence of nanocrystalline sulfated zirconia (SO 4 2?/ZrO 2) as solid acid catalyst. SO 4 2?/ZrO 2 nanoparticles with different calcination temperatures were prepared and characterized by XRD, FT-IR and SEM techniques. The results confirm good stabilization of tetragonal phase of zirconia in the presence of sulfate. The reusability experiments show partial deactivation of the catalyst due to leaching of the sulfate and coke deposition on the catalyst. 相似文献
18.
A series of Zr(SO 4) 2/SiO 2 solid acid catalysts with different Zr(SO 4) 2 loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of N 2, and temperature-programmed desorption of NH 3. The results showed that the active component Zr(SO 4) 2 was successfully adhered to the mesoporous SiO 2, and the acid amount of Zr(SO 4) 2/SiO 2 increased with the increasing of the Zr(SO 4) 2 loadings. Finally, the wheat stalk was used as raw material and depolymerized over Zr(SO 4) 2/SiO 2 to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% Zr(SO 4) 2/SiO 2 exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO 4) 2 loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation. 相似文献
19.
CeO 2‐promoted Na‐Mn‐W/SiO 2 catalyst has been studied for catalytic oxidation of methane in a micro‐stainless‐steel reactor at elevated pressure. The effect of operating conditions, such as GHSV, pressure and CH 4/O 2 ratio, has been investigated. 22.0% CH 4 conversion with 73.8% C 2‐C 4 selectivity (C 2/C 3/C 4 = 3.8/1.0/3.6) was obtained at 1003 K, 1.5 × 10 5 h ?;1 GHSV and 1.0 MPa. The results show: Elevated pressure disadvantages the catalytic oxidation of methane to C 2‐C 4 hydrocarbons. Large amounts of C 3 and C 4 hydrocarbons are observed. The unfavorable effects of elevated pressure can be overcome by increasing GHSV; the reaction is strongly dependent on the operating conditions at elevated pressure, particularly dependent on GHSV and ratio of CH 4/O 2. Analyses by means of XRD, XPS and CO 2‐TPD show that CO 2 produced from the reaction makes a weakly poisoning capacity of the catalyst; information of changeful valence on Ce and Mn was detected over the near‐surface of the Ce‐Na‐W‐Mn/SiO 2 catalyst; the existence of Ce 3+/Ce 4+ and Mn 2+/Mn 3+ ion couple supported that the reaction over the catalyst followed the Redeal‐Redox mechanism. Oxidative re‐coupling of C 2H 6 and CH 4 in gas phase or over surface of catalyst produces C 3 or C 4 hydrocarbons. 相似文献
20.
Alumina doping and sulfation in hierarchically porous zirconia solid acids have been achieved simultaneously via one‐pot and bi‐surfactant‐assisted self‐assembly process, using aluminum sulfate as both Al and SO 42? sources. The prepared composite solid acids showed much enhanced acidity and recycling catalytic activity for an esterification reaction compared with sulfated zirconia without alumina doping and Al‐doped sulfated zirconia without hierarchically porous structure. 相似文献
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