Influence of preparation conditions on physicochemical properties and catalytic activity of stabilized zeolites

1980 ◽  
Vol 45 (7) ◽  
pp. 2042-2048
Author(s):  
Jana Nováková ◽  
Ludmila Kubelková ◽  
Blanka Wichterlová
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Structural Changes ◽  
Oh Groups ◽  
Stabilization Process ◽  
Preparation Conditions ◽  
Catalytically Active ◽  
Active Electron ◽  
Acid Centers ◽  
Stabilization Temperature

Highly decationized zeolite NH4NaY, stabilized by water vapour under steaming conditions at 1030 K, was characterized by its lattice constant, sorption capacity, quantity of extralattice Al, number and character of OH groups present after dehydration in vacuum at 670 K. The catalytic activity and the effect of Lewis and Broensted type acid centers were tested by oligomeration of ethylene and propylene at 310 K and isotopic exchanges of ethylene-d4 + OH and propylene-d6 + OH at 570 K. The properties of this zeolite were compared with zeolites stabilized under selfsteaming conditions at 1040 and 820 K. Structural changes caused by the stabilization process are more pronounced with the steamed zeolite than with the selfsteamed one; in the latter case they diminish with stabilization temperature. Accordingly, the results of catalytic measurements reveal the effect of strong Broensted acid centers in the case of low-temperature selfsteamed zeolite; these centers apparently originate from remainders of the original decationized zeolite. The high-temperature self-steamed zeolite is essentially inactive, whereas the activity of the high-temperature steamed zeolite suggest the presence of catalytically active electron-acceptor centers.

From Ru nanoparticle-encapsulated metal–organic frameworks to highly catalytically active Cu/Ru nanoparticle-embedded porous carbon

2017 ◽  
Vol 5 (10) ◽  
pp. 4835-4841 ◽  
Author(s):  
Pradip Pachfule ◽  
Xinchun Yang ◽  
Qi-Long Zhu ◽  
Nobuko Tsumori ◽  
Takeyuki Uchida ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Porous Carbon ◽  
Metal Organic Frameworks ◽  
Ammonia Borane ◽  
Carbon Composites ◽  
High Catalytic Activity ◽  
Catalytically Active ◽  
Metal Organic

High-temperature pyrolysis of Ru nanoparticle-encapsulated MOF (Ru@HKUST-1) afforded ultrafine Cu/Ru nanoparticle-embedded porous carbon composites (Cu/Ru@C), which show high catalytic activity for ammonia borane hydrolysis.

scholarly journals A pyrolysis-free path toward superiorly catalytic nitrogen-coordinated single atom

2019 ◽  
Vol 5 (8) ◽  
pp. eaaw2322 ◽  
Author(s):  
Peng Peng ◽  
Lei Shi ◽  
Feng Huo ◽  
Chunxia Mi ◽  
Xiaohong Wu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Oxygen Reduction ◽  
Structural Changes ◽  
Carbon Matrix ◽  
Single Atom ◽  
Synthetic Approach ◽  
Iron Phthalocyanine ◽  
Practical Applications ◽  
Single Atoms

Nitrogen-coordinated single-atom catalysts (SACs) have emerged as a frontier for electrocatalysis (such as oxygen reduction) with maximized atom utilization and highly catalytic activity. The precise design and operable synthesis of SACs are vital for practical applications but remain challenging because the commonly used high-temperature treatments always result in unpredictable structural changes and randomly created single atoms. Here, we develop a pyrolysis-free synthetic approach to prepare SACs with a high electrocatalytic activity using a fully π-conjugated iron phthalocyanine (FePc)–rich covalent organic framework (COF). Instead of randomly creating Fe-nitrogen moieties on a carbon matrix (Fe-N-C) through pyrolysis, we rivet the atomically well-designed Fe-N-C centers via intermolecular interactions between the COF network and the graphene matrix. The as-synthesized catalysts demonstrate exceptional kinetic current density in oxygen reduction catalysis (four times higher than the benchmark Pt/C) and superior power density and cycling stability in Zn-air batteries compared with Pt/C as air electrodes.

Synthesis of Cerium Phosphate White Pigments from Cerium Oxalate

2019 ◽  
Vol 814 ◽  
pp. 445-450
Author(s):  
Hiroaki Onoda ◽  
Rie Tanaka
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Cerium Dioxide ◽  
Cerium Phosphate ◽  
Cerium Oxalate ◽  
High Smoothness ◽  
Catalytically Active ◽  
Long Time ◽  
Powder Properties ◽  
Xrd Patterns

Catalytically active cerium dioxide is used as light reflection materials for cosmetic applications. Therefore, cosmetics containing this pigment too much cause oxidation of the skin. Therefore, the substitute for cerium dioxide is required to prepare the cosmetics without catalytic activity. Herein, as novel white pigments for use in cosmetics, cerium phosphates were prepared from cerium oxalate under various conditions. The chemical composition, powder properties, catalytic activity, color phase, and smoothness of the cerium phosphates were evaluated. All samples had weak unknown peaks in XRD patterns. Samples prepared at high temperature and for long time indicated the peaks of phosphate in IR spectra. Samples prepared in this work had no photo and oxidation catalytic activities. Samples prepared at high temperature and for long time indicated enough high whiteness and high smoothness.

scholarly journals Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

2016 ◽  
Vol 17 (4) ◽  
pp. 309 ◽  
Author(s):  
D.A. Kazakov ◽  
V.V. Vol’khin ◽  
K. Kaczmarski ◽  
Yu.O. Gulenova ◽  
M.N. Obirina ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Fine Particles ◽  
Aqueous Media ◽  
Composite Catalyst ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Catalytically Active ◽  
Magnetite Particles ◽  
Magnetically Separable

<p>This paper deals with determining catalytic activities of titania (TiO<sub>2</sub>) with various crystalline structures and magnetite (Fe<sub>3</sub>O<sub>4</sub>) during mineralization of 4-nitrophenol in aqueous media by ozonation. Among the titania samples under study, amorphized TiO<sub>2</sub> was shown to have the highest catalytic activity, while magnetite was characterized by the lowest catalytic activity. A procedure is proposed to synthesize a magnetically separable composite (TiO<sub>2</sub>/Fe<sub>3</sub>O<sub>4</sub>) including amorphized titania and magnetite phases, which involves deposition of a catalytically active titania phase on preformed magnetite particles. We also studied the effect of mass ratio of titania and magnetite phases in the composite on its catalytic activity during 4-nitrophenol mineralization by ozonation. It was found that catalytic activity of composite increased as the amorphized titania phase was doped with magnetite phase up to 30% wt but as the magnetite portion in the composite catalyst was further increased, its activity decreased. According to Fourier transform infrared (FTIR) spectroscopy, content of catalytically active sites (hydroxyl groups of titania) in the composite catalyst decreases as compared to the pure phase of amorphized titania. Increase in catalytic activity of the composite as its magnetite content increases to 30% wt can be attributed to increase of accessibility of catalytically active sites (OH groups) for ozone, because specific surface area and total pore volume of the composite catalyst as determined by BET increase as compared to amorphized TiO<sub>2</sub> and catalytically active titania phase is located mostly on surface of magnetite particles which is indicated by scanning electron microscopy (SEM) results and electrophoretic light scattering (ELS) data. It was shown that the obtained composite catalyst of optimized composition, in spite of its fine particles, can be easily recovered from aqueous phase by magnetic field and used repeatedly in ozonation in order to promote water purification process.</p>

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.

scholarly journals Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

2021 ◽  
Author(s):  
Petar Djinović ◽  
Janez Zavašnik ◽  
Janvit Teržan ◽  
Ivan Jerman
Keyword(s):  
Catalytic Activity ◽  
Activated Carbon ◽  
Oxidative Dehydrogenation ◽  
Active Phase ◽  
Lattice Oxygen ◽  
Chemisorbed Oxygen ◽  
Catalytically Active ◽  
Temperature Programmed ◽  
Propane Cracking

AbstractCeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. Graphic Abstract

Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions

2011 ◽  
Vol 89 (8) ◽  
pp. 939-947 ◽  
Author(s):  
Irena Mihailova ◽  
Dimitar Mehandjiev
Keyword(s):  
Catalytic Activity ◽  
Solid Phase ◽  
Sol Gel ◽  
Cobalt Content ◽  
Octahedral Coordination ◽  
Tetrahedral Coordination ◽  
Oxidation Reactions ◽  
Oxidation Of Co ◽  
Phase Synthesis ◽  
Catalytically Active

Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.

Application of S2O82-/FexOy Solid Super Acid as a Heterogeneous Fenton-Like Catalyst for the Degradation of Orange IV in Water

2010 ◽  
Vol 150-151 ◽  
pp. 1710-1713
Author(s):  
Ying Jie Zhang ◽  
Yue Xiao Tian ◽  
Da Peng Li ◽  
Guo Rui Liu ◽  
Li Zhang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Iron Oxides ◽  
Catalytic Decomposition ◽  
Optimal Conditions ◽  
Heterogeneous Fenton ◽  
Effective Catalyst ◽  
Preparation Conditions ◽  
Super Acid ◽  
Decomposition Of H2o2

A new Fenton-like catalyst was prepared to degrade Orange IV in water by catalytic decomposition of H2O2. The optimal preparation conditions were discussed. The catalytic activity of catalyst was evaluated by the degradation of Orange IV and the decomposition of H2O2. The results show that solid super acid (S2O82-/FexOy) soaked in (NH4)2S2O8 is the most effective catalyst among the synthesized iron oxides soaked in other oxidants. The optimal conditions for solid super acid preparation are calcined at 500 for 2 h in the air.

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