Electron Donating, Acid-Base and Catalytic Properties of Perovskite-Type Mixed Oxides of Rare Earths

1995 ◽  
Vol 60 (6) ◽  
pp. 977-982
Author(s):  
S. Sugunan ◽  
V. Meera
Keyword(s):  
Catalytic Activity ◽  
Electron Donor ◽  
Rare Earths ◽  
Electron Affinity ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Surface Acidity ◽  
Electron Acceptors ◽  
Acid Base ◽  
Perovskite Type

The electron donor properties of perovskite-type mixed oxides (LaFeO3, PrFeO3, SmFeO3, LaCoO3, PrCoO3, SmCoO3, LaNiO3, PrNiO3 and SmNiO3) were studied based on the adsorption of electron acceptors exhibiting different electron affinity viz. 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro-1,4-benzoquinone, p-dinitrobenzene, and m-dinitrobenzene. The surface acidity/basicity of the oxides was determined using a set of Hammett indicators. The data were correlated with the catalytic activity of the oxides for the reduction of cyclohexanone with 2-propanol.

Electron Donating and Acid-Base Properties of Cerium Oxide and Its Mixed Oxides with Alumina

1994 ◽  
Vol 59 (12) ◽  
pp. 2604-2610
Author(s):  
Sankaran Sugunan ◽  
Jacob M. Jalaja
Keyword(s):  
Electron Transfer ◽  
Cerium Oxide ◽  
Electron Acceptor ◽  
Electron Affinity ◽  
Mixed Oxides ◽  
Surface Acidity ◽  
Electron Acceptors ◽  
Oxide Surface ◽  
Acid Base ◽  
Titration Method

The electron donating properties of ceria activated at 300, 500 and 800 °C and its mixed oxides with alumina are reported from the studies on adsorption of electron acceptors of various electron affinity. The surface acidity/basicity of the oxides have been determined by titration method and H0,max values are reported. The limit of electron transfer from oxide surface is between 1.77 and 2.40 eV in terms of the electron affinity of the electron acceptor. Ceria promotes the electron donating of alumina without changing the limit of electron transfer.

scholarly journals The Study on the Reaction Order and Kinetics of Total Oxidation Reaction of m-xylene over LaMnO3 Perovskite Catalyst

2018 ◽  
Vol 34 (3) ◽  
Author(s):  
Tran Thi Thu Huyen ◽  
Dang Thi Minh Hue ◽  
Nguyen Thi Tuyet Mai ◽  
Tran Thi Luyen ◽  
Nguyen Thi Lan
Keyword(s):  
Catalytic Activity ◽  
Reaction Order ◽  
Catalytic Properties ◽  
Sol Gel ◽  
Deep Oxidation ◽  
Perovskite Oxide ◽  
Mixed Metal Oxide ◽  
Total Oxidation ◽  
Kinetics Of ◽  
Perovskite Type

Gases of m-xylene is one of the popurlar toxic pollutants in the exhaust gases, it is emitted into the environment from factories and engines because the fuel in the engine does not burn completely. The best solution in order to remove this toxic gases of m-xylene to protect the environment is transforming them completely into CO2 and H2O by catalysts. Perovskite of LaMnO3 is one of the catalysts that was synthesized and studied the catalytic properties in total oxidation of m-xylene in our previous report. Obtained results showed that the LaMnO3 perovskite has good catalytic characterizations such as large surface area and the amount of α-oxygen adsorbed on the catalyst is large too. So, it exhibits a good catalytic activity in total oxidation of m-xylene at relatively low reaction temperature. In present work, the reaction order  and kinetics of this reaction are determined. The obtained results demonstrated that the reaction order value with respect to m-xylene is equal to about 1, to oxygene is proximately equal to 0 and the order of reaction is equal to about 1. Based on reaction order data, it was thought that the pathway of m-xylene oxidation by air oxygen  over LaMnO3 may be followed through which the Langmuir - Hinshelwood mechanism. Keywords Catalyst, perovskite, oxidation, m-xylene, kinetics References [1] Penã M.A and Fierro J.L.G (2001), << Chemical Stuctures and Performance of Perovskite Oxide>>, Chem. Rev, 101, pp 1981-2018. [2] Seiyama T., Yamazoe N. and Eguchi K. (1985), <<Characterization and Activity of some Mixed Metal Oxide Catalysts>>, Ind. Eng. Chem. Prod. Res. Dev., 24, pp. 19-27.[3] [3] Van Santen R. A., Neurock M. (2006), Molecular Heterogeneous catalysis, Wiley – VCH, pp.62-244. [4] Petrovics, Terlecki - Baricevic A., Karanovic Lj., Kirilov - Stefanov P. , Zdujic M., Dondur V., Paneva D., Mitov I., Rakic V. (2008), <<LaMO3 (M = Mg, Ti, Fe) perovskite type oxides : Preparation, Characterization and Catalytic Properties in Methane deep Oxidation>>, Appl. Catal. B, Env., 79, pp. 186-198. [5] Spinicci R., Tofanari A., Faticanti M., Pettiti I. and Porta P. (2001), <<Hexane Total Oxidation on LaMO3 (M = Mn, Co, Fe) perovskite-type oxides>>, J. Mole. Catal., 176, pp. 247-252. [6] Trần Thị Thu Huyền, Nguyễn Thị Minh Hiền, Nguyễn Hữu Phú (2006), <<Study on the preparation of perovskite oxides La1-xSrxMnO3 (x = 0; 0,3; 0,5) by sol - gel citrate method and their catalytic activity for m-xylene toltal oxidation>>, Hội nghị xúc tác và hấp phụ toàn quốc lần thứ IV, Tp. Hồ Chí Minh, Tr. 477-482.[7] Trần Thị Thu Huyền, Nguyễn Thị Minh Hiền, Nguyễn Hữu Phú (2009), <<Nghiên cứu động học của phản ứng oxi hóa hoàn toàn m-xylen trên các xúc tác perovskit LaMnO3 và La0,7A0,3MnO3 (A = Sr, Ca, Mg)>>, Tạp chí Hóa học, T.47 (6A), Tr 132-136.[8] Geoffrey C. Bond, Catherine Louis, David T. Thompson (2006), <<Catalysis by Gold>>, Catalytic Science Series-Vol.6.

scholarly journals Catalytic Properties of Perovskite-type Mixed Oxides, La1−xSrxCoO3

1982 ◽  
Vol 55 (2) ◽  
pp. 394-399 ◽  
Author(s):  
Teiji Nakamura ◽  
Makoto Misono ◽  
Yukio Yoneda
Keyword(s):  
Mixed Oxides ◽  
Catalytic Properties ◽  
Perovskite Type

scholarly journals Synthesis of Chalcone Using LDH/Graphene Nanocatalysts of Different Compositions

2019 ◽  
Vol 3 (1) ◽  
pp. 29 ◽  
Author(s):  
Mayra Álvarez ◽  
Dana Crivoi ◽  
Francesc Medina ◽  
Didier Tichit
Keyword(s):  
Active Sites ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Condensation Reaction ◽  
Nanocomposite Materials ◽  
Acid Base ◽  
Basic Sites ◽  
Base Catalysts ◽  
Reduced Graphene ◽  
Double Hydroxides

Layered double hydroxides (LDH) or their derived mixed oxides present marked acid-base properties useful in catalysis, but they are generally agglomerated, inducing weak accessibility to the active sites. In the search for improving dispersion and accessibility of the active sites and for controlling the hydrophilic/hydrophobic balance in the catalysts, nanocomposite materials appear among the most attractive. In this study, a series of nanocomposites composed of LDH and reduced graphene oxide (rGO), were successfully obtained by direct coprecipitation and investigated as base catalysts for the Claisen–Schmidt condensation reaction between acetophenone and benzaldehyde. After activation, the LDH-rGO nanocomposites exhibited improved catalytic properties compared to bare LDH. Moreover, they reveal great versatility to tune the selectivity through their composition and the nature or the absence of solvent. This is due to the enhanced basicity of the nanocomposites as the LDH content increases which is assigned to the higher dispersion of the nanoplatelets in comparison to bulk LDH. Lewis-type basic sites of higher strength and accessibility are thus created. The nature of the solvent mainly acts through its acidity able to poison the basic sites of the nanocatalysts.

scholarly journals Tracing The Acid-Base Catalytic Properties Of MON2O Mixed Oxides (M=Be, Mg, Ca; N=Li, Na, K) By Theoretical Calculations

2021 ◽  
Author(s):  
Dawid Faron ◽  
Piotr Skurski ◽  
Iwona Anusiewicz
Keyword(s):  
Alkali Metal ◽  
Gas Phase ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Theoretical Calculations ◽  
Lewis Acidity ◽  
Free Energies ◽  
Acid Base ◽  
The Stability ◽  
Fragmentation Processes

Abstract The stability and acid-base properties of MON2O mixed oxides (where M = Be, Mg, Ca; N = Li, Na, K) are studied by using ab initio methods. It is demonstrated that (i) the basicity of such designed systems evaluated by estimation of electronic proton affinity and gas-phase basicity (defined as the electronic and Gibbs free energies of deprotonation processes for [MON2O]H+) were found significant (in the ranges of 272–333 kcal/mol and 260–322 kcal/mol, respectively); (ii) in each series of MOLi2O/MONa2O/MOK2O the basicity increases with an increase of the atomic number of alkali metal involved; (ii) the Lewis-acidity of the corresponding [MON2O]H+ determined with respect to hydride anion (assessed as the electronic and Gibbs free energies of H− detachment processes for [MON2O]H2) decreases as the basicity of the corresponding oxide increases. The thermodynamic stability of all [MON2O]H2 systems is confirmed by estimating the Gibbs free energies for the fragmentation processes yielding either H2 or H2O.

scholarly journals Tracing the acid-base catalytic properties of MON2O mixed oxides (M = Be, Mg, Ca; N = Li, Na, K) by theoretical calculations

2021 ◽  
Vol 27 (7) ◽  
Author(s):  
Dawid Faron ◽  
Piotr Skurski ◽  
Iwona Anusiewicz
Keyword(s):  
Gas Phase ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Theoretical Calculations ◽  
Lewis Acidity ◽  
Ab Initio Methods ◽  
Free Energies ◽  
Acid Base ◽  
The Stability ◽  
Fragmentation Processes

AbstractThe stability and acid-base properties of MON2O mixed oxides (where M = Be, Mg, Ca; N = Li, Na, K) are studied by using ab initio methods. It is demonstrated that (i) the basicity of such designed systems evaluated by estimation of electronic proton affinity and gas-phase basicity (defined as the electronic and Gibbs free energies of deprotonation processes for [MON2O]H+) were found significant (in the ranges of 272–333 and 260–322 kcal/mol, respectively); (ii) in each series of MOLi2O/MONa2O/MOK2O, the basicity increases with an increase of the atomic number of alkali metal involved; (ii) the Lewis acidity of the corresponding [MON2O]H+ determined with respect to hydride anion (assessed as the electronic and Gibbs free energies of H− detachment processes for [MON2O]H2) decreases as the basicity of the corresponding oxide increases. The thermodynamic stability of all [MON2O]H2 systems is confirmed by estimating the Gibbs free energies for the fragmentation processes yielding either H2 or H2O.

Structural and catalytic properties of MoO3-NiO mixed oxides system

1989 ◽  
Vol 54 (6) ◽  
pp. 1508-1513 ◽  
Author(s):  
Abd El Aziz A. Said ◽  
Ehsan A. Hassan ◽  
Ahmed M. El-Awad ◽  
Khalf-Alla M. Abd El-Salaam
Keyword(s):  
Electrical Conductivity ◽  
Catalytic Activity ◽  
Solid State ◽  
Surface Area ◽  
Solid State Reaction ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Xrd Analysis ◽  
Conductivity Measurements ◽  
Activity Measurements

The unsupported MoO3-NiO catalysts were investigated. The addition process of NiO was followed by electrical conductivity measurements, IR, XRD, surface area and finally catalytic activity measurements. The conductivity measurements revealed an increase in σ values when 2-propanol vapour was admitted in the gas feed. IR and XRD analysis detected a solid state reaction at about 500 °C and its maximum was shown around 70 mole % Ni2+ where NiMoO4 lattice diffraction type was detected. Parallel with these measurements, the catalytic activity was determined for the catalysts calcined at 500 °C using the decomposition of 2-propanol. The conversion and the selectivity increased as Ni2+ was added to a concentration of 70 mole % Ni2+ ions. The results were discussed in respect to the creation of holes associated to Ni2+ addition.

Sign in / Sign up

Export Citation Format

Share Document