Effect of the Method of Synthesis, Forming, and Activation on the Catalytic Activity of Vanadium-Phosphorus Catalysts

1993 ◽  
Vol 58 (5) ◽  
pp. 1007-1012 ◽  
Author(s):  
Milan Brutovský ◽  
Lucia Ferdinandyová ◽  
Štefan Gerej ◽  
Ján Novák
Keyword(s):  
Catalytic Activity ◽  
Phase Composition ◽  
Maleic Anhydride ◽  
Partial Oxidation ◽  
Temperature Regime ◽  
Catalytic Properties ◽  
Active Catalyst ◽  
Catalyst Activity ◽  
Gas Atmosphere ◽  
Condensed Phosphates

Methods where vanadium in the precursor is reduced to V4+ in solution are well suited to the synthesis of vanadium-phosphorus catalyst because the high temperatures (500 to 800 °C) required to transform the precursor to the active catalyst are thus avoid, which is desirable from the chemical as well as structuro-physical aspects. The way of forming and activating the catalyst, i.e. the temperature regime of the treatment and the kind of the gas atmosphere, were found to affect appreciably the catalyst activity in the partial oxidation of butane to maleic anhydride.. Forming procedures resulting in sufficiently fine crystals and optimized lattice defects are suitable. The application of synthesis, forming and activation procedures exhibiting a low tendency to form, in the catalyst phase composition, condensed phosphates such as VO(PO3)2 or even V(PO3)3 is also beneficial to the catalyst activity. The catalytic properties of the vanadium-phosphorus catalyst which was prepared in concentrated HCl were improved considerably by doping the lattice with modifying metal cations.

Study of Structural and Catalytic Properties of Pt/WOх/ZrO₂, Modified by Lanthanum Cations

2020 ◽  
pp. 133-141
Author(s):  
Svetlana A. Naumova ◽  
Anastasia V. Obukhova ◽  
Ludmila I. Kuznetsova
Keyword(s):  
Solid Solution ◽  
Catalytic Activity ◽  
Phase Composition ◽  
Structural Properties ◽  
Catalytic Properties ◽  
Surface Layers ◽  
Tetragonal Modification ◽  
Nanocrystalline Zirconia ◽  
Positive Effect

The effect of the addition of La3+ cations on the structural properties of Pt/WOх/ZrO₂ catalysts and the characteristics of catalytic activity in the process of hydroisomerization of n-heptane and benzene mixture was studied. The phase composition of the catalysts is represented by a solid solution of lanthanum cations in nanocrystalline zirconia of tetragonal modification with localization of lanthanum in the surface layers predominantly. The positive effect of La3+ additives on the selectivity and yield of isomerized products was shown

Phase Composition and Catalytic Activity of Nanostructured Materials Based on Solid Component of Welding Aerosol

2015 ◽  
Vol 230 ◽  
pp. 279-284 ◽  
Author(s):  
Tatyana L. Rakitskaya ◽  
Alla S. Truba ◽  
A.A. Ennan ◽  
S.A. Kiro ◽  
V.Ya. Volkova
Keyword(s):  
Catalytic Activity ◽  
Phase Composition ◽  
Maximum Permissible Concentration ◽  
Catalytic Properties ◽  
Ozone Decomposition ◽  
Temperature Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Welding ◽  
Ph Metry

The comparison of the phase compositions and catalytic properties of the solid components of welding aerosol (SCWAs) obtained as a result of metal welding by two types of electrodes, ANO-4 and TsL‑11 was made. Their phase compositions were investigated by X-ray diffraction phase analysis, IR spectroscopy, and pH-metry. The catalytic properties of SCWAs were studied in the low-temperature reaction of ozone decomposition. Both SCWA samples were found to purify the ozone-air mixtures (OAM) from ozone at its concentration of 1 mg/m3 to the levels below the maximum permissible concentration (MPCO3) however the protective time of SCWA-ANO-4 (50 h) was higher than that of SCWA-TsL-11 (3 h) because of the differences in their compositions

scholarly journals MECHANOCHEMICAL SYNTHESIS OF CHROMIUM (III) MOLYBDATES ON THE BASIS OF VARIOUS PRECURSORS

2020 ◽  
pp. 96-109
Author(s):  
Александр Александрович Батанов ◽  
Руслан Николаевич Румянцев ◽  
Виктория Алексеевна Горянская ◽  
Александр Александрович Ильин ◽  
Александр Павлович Ильин
Keyword(s):  
Gas Chromatography ◽  
Catalytic Activity ◽  
Phase Composition ◽  
Specific Surface ◽  
Mechanochemical Synthesis ◽  
Catalytic Properties ◽  
Ammonium Paramolybdate ◽  
X Ray Diffraction ◽  
X Ray ◽  
By Products

Проведен анализ влияния прекурсоров (оксид молибдена (VI) и парамолибдат аммония) на физико-химические и каталитические свойства синтезированных образцов молибдатов хрома (III). Исследован фазовый состав и удельная поверхность данных образцов. Методами рентгенофазового, рентгеноструктурного, синхронного термического анализов, газовой хроматографии изучен процесс механохимического синтеза молибдатов хрома. Установлено, что в зависимости от источника молибдена, образуется молибдат хрома (III) различной структуры. Показана каталитическая активность и селективность молибдатов хрома (III) в реакции окислительного дегидрирования метанола. Установлены побочные продукты, образующиеся в ходе данной реакции. Степень конверсии для всех образцов составила более 80 %. Показано, что селективность молибдата хрома (III), полученного с использованием парамолибдата аммония значительно превосходит данный показатель у образца, полученного из оксида молибдена (VI), и достигает ~80%. The influence of precursors (molybdenum (VI) oxide and ammonium paramolybdate) on the physicochemical and catalytic properties of the synthesized samples of chromium (III) molybdates is analyzed. The phase composition and specific surface of these samples were studied. The process of mechanochemical synthesis of chromium molybdates. studied by methods of X-ray phase, X-ray diffraction, thermal synchronous analysis, gas chromatography. It was demonstrated that depending on the source of molybdenum, chromium (III) molybdate of various structures is formed. The catalytic activity and selectivity of chromium (III) molybdates in the oxidative dehydrogenation of methanol is shown. The by-products formed during this reaction have been identified. The degree of conversion for all samples was more than 80%. It was shown that the selectivity of chromium (III) molybdate obtained using ammonium paramolybdate significantly exceeds that of a sample obtained from molybdenum (VI) oxide and reaches ~ 80%.

Catalytic Properties of a Heated Ammonium-Saturated Dioctahedral Smectite

2000 ◽  
Vol 65 (9) ◽  
pp. 1527-1536 ◽  
Author(s):  
Ľuboš Jankovič ◽  
Peter Komadel
Keyword(s):  
Catalytic Activity ◽  
Acetic Anhydride ◽  
Catalytic Properties ◽  
Active Catalyst ◽  
Acid Catalysts ◽  
Test Reaction ◽  
Dioctahedral Smectite

A series of acid catalysts was prepared by heating of NH4-saturated montmorillonite at 200-600 °C for 24 h. Their catalytic activity was tested in acetylation of 3,4,5-trimethoxybenzaldehyde with acetic anhydride. This reaction is sufficiently sensitive to modification of the catalyst and thus suitable for testing catalytic activity of modified montmorillonites. Most of the prepared catalysts were able to catalyse the test reaction and produce diacetate in higher than 50% yields. The most active catalyst was obtained after heating at 300 °C. It was slightly less effective than commercially available acid-activated K10 catalyst.

Decomposition of hydrogen peroxide on a two-component NiO-CdO catalyst and the effect of ionizing radiation on its catalytic properties

1979 ◽  
Vol 44 (4) ◽  
pp. 1015-1022 ◽  
Author(s):  
Viliam Múčka
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Nickel Oxide ◽  
Catalytic Properties ◽  
Cadmium Oxide ◽  
Chemisorb Oxygen ◽  
Composition Region ◽  
Chemisorbed Oxygen ◽  
Two Component

The catalytic properties of two-component catalyst nickel oxide-cadmium oxide with the proportions of the components covering the whole composition region 0-100% were examined by studying the decomposition of hydrogen peroxide in aqueous solution on it. In the range 0-25 mol.% CdO, cadmium oxide is found to affect infavourably the ability of nickel oxide to chemisorb oxygen. The amount of the chemisorbed oxygen increases several times on gamma irradiation of the samples. The effect of cadmium oxide on the catalytic activity of the system shows up in fresh samples only indirectly via the changed amount of the oxygen chemisorbed. In older samples the initial catalytic activity of the system is changed, which can be explained based on the concept of bivalent catalytic centres in terms of the co-action of the catalytic centres of the two oxides, which are in equilibrium. The irradiation of the system under study speeds up the processes leading to the establishing of this equilibrium which is thermally very stable, and results in a substantial increase of the catalytic activity of the samples investigated.

Hydrogen peroxide decomposition on a two-component CuO-Cr2O3 catalyst

1988 ◽  
Vol 53 (8) ◽  
pp. 1636-1646 ◽  
Author(s):  
Viliam Múčka ◽  
Kamil Lang
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Extreme Values ◽  
Catalytic Properties ◽  
Active Components ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Peroxide Decomposition ◽  
Two Component ◽  
Catalytically Active

Some physical and catalytic properties of the two-component copper(II)oxide-chromium(III)oxide catalyst with different content of both components were studied using the decomposition of the aqueous solution of hydrogen peroxide as a testing reaction. It has been found that along to both basic components, the system under study contains also the spinel structure CuCr2O4, chromate washable by water and hexavalent ions of chromium unwashable by water. The soluble chromate is catalytically active. During the first period of the reaction the equilibrium is being established in both homogeneous and heterogeneous catalytic systems. The catalytic activity as well as the specific surface area of the washed solid is a non-monotonous function of its composition. It seems highly probable that the extreme values of both these quantities are not connected with the detected admixtures in the catalytic system. The system under study is very insensitive with regard to the applied doses of gamma radiation. Its catalytic properties are changed rather significantly after the thermal treatment and particularly after the partial reduction to low degree by hydrogen. The observed changes of the catalytic activity of the system under study are very probably in connection with the changes of the valence state of the catalytically active components of the catalyst.

A Contribution to the Structure Characteristics and Phase Composition of Vanadium-Phosphorus Catalysts Prepared from the VOPO4.xH2O.yH3PO4 Precursor

1992 ◽  
Vol 57 (12) ◽  
pp. 2475-2480 ◽  
Author(s):  
Milan Brutovský ◽  
Štefan Gerej ◽  
Ján Novák ◽  
Lucia Ferdinandyová
Keyword(s):  
Heat Treatment ◽  
Phase Composition ◽  
Ir Spectra ◽  
Metal Cations ◽  
Preparation Procedure ◽  
Final Temperature ◽  
Structure Characteristics ◽  
Heat Treatment Regime ◽  
Condensed Phosphates ◽  
Defective Crystals

Catalysts were prepared from VOPO4.xH2O.yH3PO4 (x = 0.3-2, y = 0.2-0.85) by reduction with SO2 up to a final temperature of 750-800 °C, and activated in a reaction mixture of 1.0-1.4% butane in air up to 500 °C. The structure characteristics and phase composition of the catalysts were found to be affected by the preparation procedure and heat treatment regime. Their diffraction lines and IR spectra revealed that the catalysts from larger and less defective crystals than catalysts which were obtained from the VOHPO4.xH2O.yH3PO4 precursor and activated in the reaction mixture at temperatures up to 500 °C. In the catalysts prepared by the above procedure, the tendency to the formation of phases of higher-condensed phosphates, in particular VO(PO3)2 or even V(PO3)3, increases with increasing n(P):n(V) ratio and is then more pronounced than with vanadium-phosphorus catalysts prepared by other procedures. The tendency to the formation of the catalytically less active condensed phosphates is partly suppressed by the embedding of modifying metal cations (Fe or Cu in this case).

scholarly journals Oscillatory Behaviour of Ni Supported on ZrO2 in the Catalytic Partial Oxidation of Methane as Determined by Activation Procedure

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2495
Author(s):  
Daniela Pietrogiacomi ◽  
Maria Cristina Campa ◽  
Ida Pettiti ◽  
Simonetta Tuti ◽  
Giulia Luccisano ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Partial Oxidation ◽  
Active Sites ◽  
Direct Reduction ◽  
Partial Oxidation Of Methane ◽  
Catalytic Partial Oxidation ◽  
Oxidation Of Methane ◽  
Short Contact Time ◽  
Oxidation Reduction ◽  
Ni Species

Ni/ZrO2 catalysts, active and selective for the catalytic partial oxidation of methane to syngas (CH4-CPO), were prepared by the dry impregnation of zirconium oxyhydroxide (Zhy) or monoclinic ZrO2 (Zm), calcination at 1173 K and activation by different procedures: oxidation-reduction (ox-red) or direct reduction (red). The characterization included XRD, FESEM, in situ FTIR and Raman spectroscopies, TPR, and specific surface area measurements. Catalytic activity experiments were carried out in a flow apparatus with a mixture of CH4:O2 = 2:1 in a short contact time. Compared to Zm, Zhy favoured the formation of smaller NiO particles, implying a higher number of Ni sites strongly interacting with the support. In all the activated Ni/ZrO2 catalysts, the Ni–ZrO2 interaction was strong enough to limit Ni aggregation during the catalytic runs. The catalytic activity depended on the activation procedures; the ox-red treatment yielded very active and stable catalysts, whereas the red treatment yielded catalysts with oscillating activity, ascribed to the formation of Niδ+ carbide-like species. The results suggested that Ni dispersion was not the main factor affecting the activity, and that active sites for CH4-CPO could be Ni species at the boundary of the metal particles in a specific configuration and nuclearity.

scholarly journals Influence of the Reduction Temperature and the Nature of the Support on the Performance of Zirconia and Alumina-Supported Pt Catalysts for n-Dodecane Hydroisomerization

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 88
Author(s):  
Diana García-Pérez ◽  
Maria Consuelo Alvarez-Galvan ◽  
Jose M. Campos-Martin ◽  
Jose L. G. Fierro
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Catalytic Properties ◽  
Catalytic Performance ◽  
Major Influence ◽  
Pt Catalysts ◽  
Reduction Temperature ◽  
Metal Dispersion ◽  
Tungsten Oxides ◽  
Supported Pt Catalysts

Catalysts based on zirconia- and alumina-supported tungsten oxides (15 wt % W) with a small loading of platinum (0.3 wt % Pt) were selected to study the influence of the reduction temperature and the nature of the support on the hydroisomerization of n-dodecane. The reduction temperature has a major influence on metal dispersion, which impacts the catalytic activity. In addition, alumina and zirconia supports show different catalytic properties (mainly acid site strength and surface area), which play an important role in the conversion. The NH3-TPD profiles indicate that the acidity in alumina-based catalysts is clearly higher than that in their zirconia counterparts; this acidity can be attributed to a stronger interaction of the WOx species with alumina. The PtW/Al catalyst was found to exhibit the best catalytic performance for the hydroisomerization of n-dodecane based on its higher acidity, which was ascribed to its larger surface area relative to that of its zirconia counterparts. The selectivity for different hydrocarbons (C7–10, C11 and i-C12) was very similar for all the catalysts studied, with branched C12 hydrocarbons being the main products obtained (~80%). The temperature of 350 °C was clearly the best reduction temperature for all the catalysts studied in a trickled-bed-mode reactor.

scholarly journals Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4508
Author(s):  
Zeinab Mcheik ◽  
Ludovic Pinard ◽  
Joumana Toufaily ◽  
Tayssir Hamieh ◽  
T. Jean Daou
Keyword(s):  
Catalytic Activity ◽  
Amorphous Materials ◽  
Essential Role ◽  
Aluminum Content ◽  
Catalytic Properties ◽  
Hexadecyltrimethylammonium Bromide ◽  
Zeolite Framework ◽  
Ctab Concentration ◽  
Porous Volume ◽  
Synthesis Medium

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 mol·L−1, amorphous materials are observed. These hierarchical mordenite possess a higher porous volume compared to its counterpart conventional micrometer crystals. Nitrogen sorption showed the presence of mesoporosity for all mordenite samples synthesized in the presence of CTAB. The creation of mesopores due to the presence of CTAB in the synthesis medium does not occur at the expense of zeolite micropores. In addition, mesoporous volume and BET surface seem to increase upon the increase of CTAB concentration in the synthesis medium. The Si/Al ratio of the zeolite framework can be increased from 5.5 to 9.1 by halving the aluminum content present in the synthesis gel. These synthesized hierarchical MOR-type zeolites possess an improved catalytic activity for n-hexane cracking compared to large zeolite crystals obtained in the absence of CTAB.

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