- Ionic-liquid-assisted synthesis of nanostructured and carbon-coated Li 3V2(PO4)3 for high-power electrochemical storage devices
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Carbon-coated Li3V2(PO4)3 (LVP) displaying nanostructured morphology can be easily prepared by using ionic-liquid-assisted sol-gel synthesis. The selection of highly viscous and thermally stable ionic liquids might promote the formation of nanostructures during the sol-gel synthesis. The presence of these structures shortens the diffusion paths and enlarges the contact area between the active material and the electrolyte; this leads to a significant improvement in lithium-ion diffusion. At the same time, the use of ionic liquids has a positive influence on the coating of the LVP particles, which improves the electronic conductivity of this material; this leads to enhanced charge-transfer properties. At a high current density of 40 C, the LVP/N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide material delivered a reversible capacity of approximately 100 mA h g-1, and approximately 99 % of the initial capacity value was retained even after 100 cycles at 50 C. The excellent high rate and cycling stability performance make Li3V2(PO 4)3 prepared by ionic-liquid-assisted sol-gel synthesis a very promising cathode material for high-power electrochemical storage devices. Storage solutions: Carbon-coated Li3V2(PO 4)3 displaying nanostructured morphology is easily prepared by using ionic-liquid-assisted sol-gel synthesis. This material displays improved lithium-ion diffusion and electronic conductivity and thus enhanced charge-transfer properties. Li3V2(PO 4)3 prepared by this sol-gel route is a very promising cathode material for high-power electrochemical storage devices.
- Zhang, Xiaofei,Boeckenfeld, Nils,Berkemeier, Frank,Balducci, Andrea
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- Template-free synthesis of hierarchical vanadium-glycolate hollow microspheres and their conversion to V2O5 with improved lithium storage capability
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Nanosheet-assembled hierarchical V2O5 hollow microspheres are successfully obtained from V-glycolate precursor hollow microspheres, which in turn are synthesized by a simple template-free solvothermal method. The structural evolution of the V-glycolate hollow microspheres has been studied and explained by the inside-out Ostwald-ripening mechanism. The surface morphologies of the hollow microspheres can be controlled by varying the mixture solution and the solvothermal reaction time. After calcination in air, hierarchical V2O5 hollow microspheres with a high surface area of 70 m2 g-1 can be obtained and the structure is well preserved. When evaluated as cathode materials for lithium-ion batteries, the as-prepared hierarchical V2O5 hollow spheres deliver a specific discharge capacity of 144 mA h g-1 at a current density of 100 mA g-1, which is very close to the theoretical capacity (147 mA h g-1) for one Li+ insertion per V2O5. In addition, excellent rate capability and cycling stability are observed, suggesting their promising use in lithium-ion batteries. Copyright
- Pan, Anqiang,Zhu, Ting,Wu, Hao Bin,Lou, Xiong Wen
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- Layered hybrid phase Li2NaV2(PO4)3/carbon dot nanocomposite cathodes for Li+/Na+ mixed-ion batteries
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Hybrid phase Li2NaV2(PO4)3 (H-LNVP) is one of the most promising cathode materials for Li+/Na+ mixed-ion batteries. Here we have successfully synthesized layered hybrid phase Li2NaV2(PO4)3/carbon dot (H-LNVP/CD) nanocomposites via a simple sol-gel and carbon thermal reduction method and its inserted-extracted mechanism is investigated. As a novel composite cathode, H-LNVP/CD nanocomposite cathode delivers 158 mA h g-1 of reversible capacity at 0.1C in a Li+/Na+ mixed-ion cell with the electrochemically active redox reactions of V3+/V4+ and V4+/V5+, which is far higher than single phase contrastive samples. The cell exhibits one main high voltage plateau with well-defined discharge voltage near 3.7 V, and a coulombic efficiency of approximate 100 percent at 10C. Because the carbon dots on the surface of layered H-LNVP nanoparticles can remarkably enhance their electronic conductivity, the cell still exhibits a higher specific capacity of about 89.4 mA h g-1 at 10C. These results are attributed to the nanocomposite structure of H-LNVP and CDs. This work will contribute to the development of Li+/Na+ mixed-ion batteries.
- Wang, Jichao,Zhang, Xudong,He, Wen,Yue, Yuanzheng,Wang, Yaoyao,Zhang, Chuanjiang
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- Synthesis and thermal stability of W-doped VO2 nanocrystals
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Pure and W-doped vanadium dioxide nanocrystals have been synthesized by using V2O5 and oxalic acid as precursors via a thermolysis method. The VO2 nanocrystals have a nearly spherical morphology with size ranging from 50 to 100 nm. The metal-insulator transition (MIT) temperature of the nanocrystals decreases with increasing W-doping content. The successive heat-induced fatigue character of the MIT in W-doped VO2 nanocrystals was investigated by DSC analysis together with structural study, and a high stability upon heating-cooling cycles was found with respect to MIT temperature, peak temperature and latent heat of the phase transition.
- Kong,Li,Pan,Zhang,Li
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- Structural dynamics of molybdenum vanadium oxide (MoVOx): Influence of activation condition
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Molybdenum and vanadium oxides were known to be an effective catalyst for light olefin (propane) activation for conversion to value-added chemicals. However, it is difficult to control the selectivity to desired product whereby subsequent reaction can lead to coking and rapid catalyst deactivation. One of the key ways to improve on the above limitation is to optimise and control the molybdenum phase structure, particularly during catalyst precursor activation stage. This paper demonstrates the combination of optimal in situ activation under different condition and thermal analysis for structural control that can help to guide and gain an insight into the structure–activity relationship of the nanostructured catalyst system. In situ XRD analysis reveals the crystallization of molybdenum vanadium oxide was highly influenced by the activation condition hence exhibiting different structural properties. Activation under Air at 300?°C forms highly crystalline hexagonal phase and transforms to thermodynamically stable orthorhombic (o-MoO3) phase at 450?°C. Activation under inert (helium) reveals the precursor remains amorphous until nanostructuring occurs at 450?°C. The precursor further transforms to the thermodynamically stable crystallized tetragonal phase (Mo5O14) at 500?°C. The obtained structural transition information is important in order to control and identify the catalytic active phase that is suitable for a particular reaction.
- Suppiah, Durga Devi,Komar, Anna,Hamid, Sharifah Bee Abd
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- Superstructure ZrV2O7 nanofibres: Thermal expansion, electronic and lithium storage properties
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ZrV2O7 has attracted much attention as a negative thermal expansion (NTE) material due to its isotropic negative structure. However, rarely has investigation of the lithium storage behaviors been carried out except our first report on it. Meanwhile, the electrochemical behaviors and energy storage characteristics have not been studied in depth and will be explored in this article. Herein, we report on the synthesis, characterization and lithium intercalation mechanism of superstructure ZrV2O7 nanofibres that were prepared through a facile solution-based method with a subsequent annealing process. The thermal in situ XRD technique combined with the Rietveld refinement method is adopted to analyze the change in the temperature-dependent crystal structure. Benefiting from the nanostructured morphology and relatively high electronic conductivity, it presents acceptable cyclic stability and rate capability. According to the operando evolution of the XRD patterns obtained from electrochemical in situ measurements, the Li intercalation mechanism of the solid solution process with a subsequent conversion reaction can be concluded. Finally, the amorphous state of the electrodes after the initial fully discharged state can effectively enhance the electrochemical performances.
- Li, Qidong,Zhao, Yanming,Kuang, Quan,Fan, Qinghua,Dong, Youzhong,Liu, Xudong
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- Synthesis of biocarbon coated Li3V2(PO4)3/C cathode material for lithium ion batteries using recycled tea
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A biocarbon coated Li3V2(PO4)3/C (LVP-C) cathode material was synthesized by a facile sol-gel method using recycled tea as both the structural template and biocarbon source. X-ray diffraction (XRD) patterns show that LVP has a monoclinic structure with space group P21/n. High-resolution transmission electron microscopy (HRTEM) images show that the LVP nanoparticles are surrounded by amorphous biocarbon, and the thickness of the biocarbon shell is about 10-20 nm. Electrochemical measurements demonstrate that the LVP-C nanocomposite shows a significantly better rate capability and cycling performance than pure LVP. In the potential range of 3.0-4.3 V, the LVP-C nanocomposite delivers a high initial discharge capacity of 132 mA h g-1 at 0.5 C, and maintains an initial discharge capacity of 110 mA h g-1 at 10 C. After 80 cycles at 10 C, it still retains a discharge capacity of 110 mA h g-1. Electrochemical impedance spectroscopy (EIS) measurements have disclosed that the LVP-C sample exhibits enhanced electrode reaction kinetics and improved electrochemical performance. The good electrochemical performance of the LVP-C nanocomposite is mainly related to the presence of the conductive biocarbon, thus leading to an improvement in the electron and lithium ion diffusivity. These results indicate that the biocarbon coated LVP-C material is a promising candidate for large capacity and high power cathode materials in next generation lithium-ion batteries for electric vehicles.
- Wei, Chuanliang,He, Wen,Zhang, Xudong,Liu, Shujiang,Jin, Chao,Liu, Shikun,Huang, Zhen
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- The influence of support on ammoxidation of 3-picoline over vanadia catalyst
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The influence of high content of MoO3 (32 mol%) in V 2O5-MoO3-P2O5 catalyst system supported on alumina, silica, HZSM-5 and modified clay was investigated for ammoxidation of 3-picoline. Un
- Roy, Shyam Kishore,Dutta,Nandi,Yadav,Mondal,Ray,Mitra, Swapan,Samuel
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- The synthesis and structure of a single-phase, nanocrystalline MoVW mixed-oxide catalyst of the Mo5O14 type
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The different preparation steps are characterized for the single-phase, crystalline, ternary oxide (MoVW)5O14, which is important for catalytic, mild selective oxidation reactions. For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and vanadyl oxalate were spray-dried followed by different thermal treatments. The structures of the materials formed at each preparation step, starting from the precursor to the final product, were studied using scanning and transmission electron microscopy, X-ray powder diffraction, thermal analysis, and Raman spectroscopy. Raman spectroscopy was also applied to shed some light into the aqueous chemistry of the mixed precursor solutions. Raman data indicate that a molecular structure which seems to be closely related to that of the final crystalline Mo5O14-type oxide is already formed in solution. X-ray diffraction revealed that the thermal treatment steps strongly affect the degree of crystallinity of the ternary Mo5O14 oxide. Transmission electron microscopy with energy-dispersive microanalysis confirmed the presence of V and W in the molybdenum oxide particles and gave evidence for the (010) plane as the most developed face of the crystals of this phase. Details of the structural transformation of this system at the different preparation and calcination steps are discussed in relation to their performance in the selective partial oxidation of acrolein to acrylic acid.
- Knobl,Zenkovets,Kryukova,Ovsitser,Niemeyer,Schloegl,Mestl
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- Designing a facile low cost synthesis strategy for the Na-V-S-O systems, NaV(SO4)2, Na3V(SO4)3 and Na2VO(SO4)2
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Alkali metal transition metal sulfates have attracted considerable interest as potential electrodes for Na ion battery materials. While there has been significant research on Fe based systems, research on V based systems has been lacking, apart from a recent report on Na2VO(SO4)2. This can be related to the complex synthetic routes previously reported to make sodium vanadium sulfate systems. In this paper, we report a simple route towards the synthesis of three such sodium vanadium sulfate systems, NaV(SO4)2, Na2VO(SO4)2, and Na3V(SO4)3. We analyse the resulting products through X-ray diffraction and Raman spectroscopy to highlight the formation of high quality samples via this simple solution route, with subsequent low temperature (400 °C) heat treatment. This facile new route will allow these materials to be considered for future applications rather than as simply chemical curiosities.
- Driscoll,Wright,Slater
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- Structural and electrochemical properties of Al3+ doped V 2O5 nanoparticles prepared by an oxalic acid assisted soft-chemical method
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V2O5 and Al0.2V2O5 nanoparticles were prepared by an oxalic acid assisted soft-chemical method. X-ray photoelectron spectroscopy confirmed the V5+ oxidation state of V2O5, whereas an intermediate state between V 5+ and V4+ of Al0.2V2O5. Raman scattering showed that the Al3+ ions existed in an [AlO 6] octahedral environment. The doping of Al3+ increased the cohesion between the V2O5 slabs, which enhanced the structural stability of the material. The chemical diffusion coefficients of the Al0.2V2O5 nanoparticles were a little bit smaller than those of V2O5. Charge-discharge cycling showed that the Al0.2V2O5 nanoparticles exhibited much better capacity retention than the un-doped V2O 5, which was attributed to the enhanced structural stability of the material.
- Zhan, Shiying,Wei, Yingjin,Bie, Xiaofei,Wang, Chunzhong,Du, Fei,Chen, Gang,Hu, Fang
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- Superior lithium storage performance of hierarchical porous vanadium pentoxide nanofibers for lithium ion battery cathodes
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The hierarchical V2O5 nanofibers cathode materials with diameter of 200-400 nm are successfully synthesized via an electrospinning followed by annealing. Powder X-ray diffraction (XRD) pattern confirms the formation of phase-pure product. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) obviously display the hierarchical porous nanofibers constructed by attached tiny vanadium oxide nanoplates. Electrochemical behavior of the as-prepared product is systematically studied using galvanostatic charge/discharge testing, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). It turns out that in comparison to the commercial V2O5 and other unique nanostructured materials in the literature, our V2O5 nanofibers show much enhanced lithium storage capacity, improved cyclic stability, and higher rate capability. After 100 cycles at a current density of 800 mA g-1, the specific capacity of the V2O5 nanofibers retain 133.9 mAh g-1, corresponding to high capacity retention of 96.05%. More importantly, the EIS at various discharge depths clearly reveal the kinetics process of the V2O5 cathode reaction with lithium. Based on our results, the possible approach to improve the specific capacity and rate capability of the V2O5 cathode material is proposed. It is expected that this study could accelerate the development of V2O5 cathode in rechargeable lithium ion batteries.
- Yan, Bo,Li, Xifei,Bai, Zhimin,Li, Minsi,Dong, Lei,Xiong, Dongbin,Li, Dejun
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- Electrochemical performances of Li3V2-(4/3)xTix(PO4)3/C as cathode material for Li-ion batteries synthesized by an ultrasound-assisted sol-gel method
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Cathode materials Li3V2-(4/3)xTix (PO4)3 (x = 0,0.03, 0.06, 0.09, 0.12) using Polyvinylidene Fluoride (PVDF) as carbon source are synthesized via an ultrasound-assisted sol-gel method. Ultrasound helps to a uniform dispersion of the water insoluble PVDF. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that samples exhibit pure monoclinic structure and have similar morphology. Electrochemical galvanostatic charging/discharging results show that the capacities at low current density (less than 2C) of all samples are not that different. However, the discharge capacities and cyclic performance are improved at higher current density by a proper amount of Ti4+ doping (x = 0.03-0.06). The electrochemical performances become a bit worse when x is higher than 0.06. This may be attributed to the uniform lattice distortion caused by the overmuch dopant.
- Li, Lingfang,Fan, Changling,Zeng, Taotao,Zhang, Xiang,Zhang, Weihua,Han, Shaochang
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- Vibrational spectra of disodium-oxidovanadium(IV) disulfate
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Disodium-oxidovanadium(IV) disulfate, a new and interesting battery electrode material, is prepared by a new very simple, and easy synthetic procedure. Its infrared and Raman spectra were recorded and discussed on the basis of their structural peculiarities with the aid of a factor group analysis of the internal vibrations of the sulfate groups of the compound. The spectra appear strongly dominated by correlation field effects.
- Barone, Vicente L.,González-Baró, Ana C.,Baran, Enrique J.
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p. 430 - 434
(2020/06/01)
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- Direct hydroxylation of benzene to phenol with molecular oxygen over vanadium oxide nanospheres and study of its mechanism
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Direct hydroxylation of benzene to phenol using molecular oxygen is a green route with high atom economy but still a great challenge when compared with the existing method of production. The activation of oxygen is necessary and reductive agents were used to activate dioxygen in a so-called reductive activation process. Here, nano vanadium oxides that consist mainly of low valence vanadium to activate dioxygen were prepared under different conditions via a hydrothermal method. Under the optimized conditions, an excellent phenol selectivity of 96.3% with benzene conversion of 4.2% was achieved over the VOC2O4-N-5 without reductive agents. Characterizations revealed that VOC2O4-N-5 was composed of a mesoporous nanosphere structure with medium strong acid sites and low valence vanadium species. A mechanism was proposed as follows: dioxygen was activated by low valence vanadium in VOC2O4-N-5 to produce the active oxygen species which oxidized acetic acid to peracetic acid. Then the active oxygen species was subsequently transferred from peracetic acid to benzene and inserted into the C-H bond to give phenol.
- Luo, Guanhua,Lv, Xuechuan,Wang, Xingwang,Yan, Su,Gao, Xiaohan,Xu, Jie,Ma, Hong,Jiao, Yujuan,Li, Fayun,Chen, Jinzhu
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p. 94164 - 94170
(2015/11/17)
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- A Bi-doped Li3V2(PO4)3/C cathode material with an enhanced high-rate capacity and long cycle stability for lithium ion batteries
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Bi-doped compounds Li3V2-xBix(PO4)3/C (x = 0, 0.01, 0.03, 0.05, 0.07) are prepared by a sol-gel method. The effects of Bi doping on the physical and electrochemical properties of Li3V2(PO4)3 are investigated. X-ray diffraction (XRD) analysis indicates that Bi doping does not change the monoclinic structure of Li3V2(PO4)3. A detailed analysis of the XRD patterns suggests that Bi3+ ions partly enter into the crystal structure of Li3V2(PO4)3 and enlarge the lattice volume of Li3V2(PO4)3. According to the results of cycle and rate performance measurements, moderate Bi3+ doping is beneficial in improving the electrochemical properties of Li3V2(PO4)3. Among all the samples, Li3V1.97Bi0.03(PO4)3/C shows the best cycle and rate performance. At 3.0-4.3 V, the initial discharge capacity of Li3V1.97Bi0.03(PO4)3/C is as high as 130 mA h g-1, close to the theoretical specific capacity of 133 mA h g-1. The capacity retention of Li3V1.97Bi0.03(PO4)3/C is almost 100% after 100 cycles at 3.0-4.3 V. In addition, Li3V1.97Bi0.03(PO4)3/C exhibits excellent low-temperature and high-rate performance. Impedance spectroscopy (EIS) and cyclic voltammetry (CV) curves indicate lower charge transfer resistance and a larger Li ion diffusion rate of Li3V1.97Bi0.03(PO4)3/C than the primary Li3V2(PO4)3/C. The excellent electrochemical performance of Li3V1.97Bi0.03(PO4)3/C can be attributed to its larger Li ion diffusion channels, higher electronic conductivity, higher structural stability and smaller particle size.
- Cheng, Yi,Feng, Kai,Zhou, Wei,Zhang, Hongzhang,Li, Xianfeng,Zhang, Huamin
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p. 17579 - 17586
(2015/10/19)
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- AMMOXIDATION CATALYST AND METHOD FOR PRODUCING NITRILE COMPOUND USING THE SAME
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The present invention provides an ammoxidation catalyst containing vanadium oxide, titanium oxide and diamond.
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Page/Page column 7
(2012/06/18)
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- PROCESSES FOR PRODUCING 3-CYANOPYRIDINE FROM 2-METHYL-1,5-PENTANEDIAMINE
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A process for the production of 3-cyanopyridine by ammoxidation of 2-methyl-1,5-pentanediamine to form 3-cyanopyridine, optionally carried out as an oxidative ammonolysis process.
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Page/Page column 5
(2008/06/13)
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- Catalyst and process for producing nitrile compounds
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The present invention relates to a catalyst which comprises a molybdenum oxide and a phosphorus oxide prepared from phosphorus molybdic acid or phosphorousmolybdate, a vanadium oxide, a chromium oxide and a boron oxide supported on a silica carrier. This catalyst is suitable for use in the production of nitrile compound by catalytic reaction of a gas mixture containing (1) an alkyl-substituted compound selected from the group of alkyl-substituted aromatic compounds and alkyl-substituted heterocyclic compounds, (2) ammonia, and (3) oxygen or a gas containing molecular oxygen. The present invention further relates to a process for producing the nitrile compound using said catalyst.
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- Catalyst and process for producing aromatic nitriles
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The present invention relates to a catalyst which comprises a vanadium oxide, a chromium oxide, a molybdenum oxide and a boron oxide supported on a silica carrier. This catalyst is suitable for use in the production of aromatic nitriles from alkyl-substituted aromatic compound by the catalytic reaction of a gas mixture containing an alkyl-substituted aromatic compound, ammonia and oxygen or a gas containing molecular oxygen over a catalyst. The present invention further relates to a process for producing the aromatic nitriles using said catalyst.
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- Process for producing cyanopyridines
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A process for producing a cyanopyridine which comprises reacting the corresponding methylpyridine, ammonia and an oxygen-containing gas in the presence of a catalyst comprising a vanadium oxide, a chromium oxide, a boron oxide and optionally a phosphorus
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