Efficient UV-vis-IR photothermocatalytic selective ethanol oxidation on MnOx/TiO2 nanocomposites significantly enhanced by a novel photoactivation

2020 ◽  
Vol 8 (3) ◽  
pp. 1254-1264 ◽  
Author(s):  
Yi Yang ◽  
Shaowen Wu ◽  
Yuanzhi Li ◽  
Qian Zhang ◽  
Xiujian Zhao
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Ethanol Oxidation ◽  
Good Catalytic Activity

MnOx/TiO2 nanocomposites exhibit good catalytic activity and excellent durability for photothermocatalytic selective ethanol oxidation under UV-vis-IR and IR irradiation. A novel photoactivation is found to significantly enhance catalytic activity due to activation energy being reduced upon irradiation.

scholarly journals The Determing Activation Energy of Total Oxidation Reaction of m-xylene over La0,7Sr0,3BO3 (B = Mn, Fe, Ni) Perovskite Catalysts

2017 ◽  
Vol 33 (4) ◽  
Author(s):  
Tran Thi Thu Huyen ◽  
Tran Thi Luyen ◽  
Nguyen Thi Tuyet Mai
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Oxidation Reaction ◽  
Mixed Oxides ◽  
Catalytic Properties ◽  
Rare Earth Ions ◽  
Exhaust Emission ◽  
Total Oxidation ◽  
Low Reaction Temperature ◽  
Good Catalytic Activity

Perovskite-type oxides containing rare earth ions and transition metals are of interest for catalytic oxidation and reduction reactions associated with automotive exhaust emission control. They are known to exhibit a good catalytic activity in the total oxidation reaction of carbon monoxide or hydrocarbon and removal of nitrogen oxides. By partially substitution of A and B ions of the perovskite with others, a wide variety of mixed oxides A1-xA’xB1-yB’yO3 can be obtained, allowing the systematic modification of the catalytic properties. We presented the preparation and the catalytic properties of and La0.7Sr0.3BO3 (B = Mn, Fe, Ni) perovskites in total oxidation of m-xylene in previous report. Obtained results showed that they exhibit a good catalytic activity in total oxidation of  m-xylene at relatively low reaction temperature. In present work, the activation energy of total oxidation reaction of m-xylene over these catalysts are determined. The results show that the activation energy of studied catalyst is ranging about from 11.5 to 13.4 kcal/mol. The replacement of Mn by Fe and Ni in La0.7Sr0.3MnO3  perovskite catalyst reduces the catalytic property of  La0.7Sr0.3MnO3 catalyst and increases the activation energy of the total oxidation reaction of m-xylene. 

High resolution electron microscopy of lanthanum phosphate crystals

1978 ◽  
Vol 36 (1) ◽  
pp. 274-275
Author(s):  
J. C. Wheatley ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
High Resolution ◽  
Petroleum Industry ◽  
High Resolution Electron Microscopy ◽  
Lanthanum Phosphate ◽  
Good Catalyst ◽  
Resolution Electron ◽  
Good Catalytic Activity ◽  
Physical And Chemical

Rare-earth phosphates are of particular interest because of their catalytic properties associated with the hydrolysis of many aromatic chlorides in the petroleum industry. Lanthanum phosphates (LaPO4) which have been doped with small amounts of copper have shown increased catalytic activity (1). However the physical and chemical characteristics of the samples leading to good catalytic activity are not known.Many catalysts are amorphous and thus do not easily lend themselves to methods of investigation which would include electron microscopy. However, the LaPO4, crystals are quite suitable samples for high resolution techniques.The samples used were obtained from William L. Kehl of Gulf Research and Development Company. The electron microscopy was carried out on a JEOL JEM-100B which had been modified for high resolution microscopy (2). Standard high resolution techniques were employed. Three different sample types were observed: 669A-1-5-7 (poor catalyst), H-L-2 (good catalyst) and 27-011 (good catalyst).

scholarly journals CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131 ◽  
Author(s):  
Rola Mohammad Al Soubaihi ◽  
Khaled Mohammad Saoud ◽  
Myo Tay Zar Myint ◽  
Mats A. Göthelid ◽  
Joydeep Dutta
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Active Sites ◽  
Bond Activation ◽  
Dissociative Adsorption ◽  
High Catalytic Activity ◽  
Good Catalytic Activity ◽  
Pretreatment Conditions ◽  
Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

Cr-Substituted Mesoporous Aluminophosphate Molecular Sieve: Synthesis, Characterization, Crystallization Kinetics and Catalytic Activity

2013 ◽  
Vol 316-317 ◽  
pp. 1018-1023
Author(s):  
Xin Zhu Li ◽  
Ji Shi Zhang
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Crystal Growth ◽  
Crystallization Kinetics ◽  
Molecular Sieve ◽  
Arrhenius Equation ◽  
Degree Of Crystallinity ◽  
Tert Butylhydroperoxide ◽  
Growth Activation ◽  
Cr Map

Cr-substituted mesoporous aluminophosphate molecular sieve (Cr-MAP) was synthesized and characterized. Crystallization kinetics curves measured as an index to the relative degree of crystallinity, according to the Arrhenius equation to calculate the apparent nucleation activation energy and crystal growth activation energy of Cr-MAP, which was 63.7 and 14.7 kJ• mol-1, respectively. Cr-MAP had highly catalytic activity for fabricating acetophenone by selectively oxizing ethylbenzene. Using tert-butylhydroperoxide as oxidant and chlorobenzene as solvent at 100 °C for 8 h, acetophenone selectivity, acetophenone yield and ethylbenzene conversion reaches 85.4, 62.2 and 72.8 %, respectively.

Molecularly imprinted nanozymes with faster catalytic activity and better specificity

Nanoscale ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 4854-4863 ◽  
Author(s):  
Zijie Zhang ◽  
Yuqing Li ◽  
Xiaohan Zhang ◽  
Juewen Liu
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Molecular Imprinting ◽  
Selective Adsorption ◽  
Molecularly Imprinted ◽  
Product Release

Molecular imprinting accelerates nanozyme catalysis and improves specificity attributable to selective adsorption of imprinted substrate, decreasing activation energy and facilitating product release.

scholarly journals Palladium-Supported Zirconia-Based Catalytic Degradation of Rhodamine-B Dye from Wastewater

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1522
Author(s):  
Salma Jabeen ◽  
Muhammad Sufaid Khan ◽  
Rozina Khattak ◽  
Ivar Zekker ◽  
Juris Burlakovs ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Rhodamine B ◽  
Dye Degradation ◽  
Freundlich Isotherm ◽  
Impregnation Method ◽  
K Value ◽  
First Order Kinetics ◽  
Good Catalytic Activity ◽  
Rhodamine B Dye ◽  
Best Fit

The catalytic activity of Pd/ZrO2 was studied in terms of the degradation of rhodamine-B dye in the presence of hydrogen peroxide. Pd/ZrO2 was prepared by impregnation method, calcined at 750 °C and characterized by XRD, SEM and EDX. The catalyst showed good catalytic activity for dye degradation at 333 K, using 0.05 g of the catalyst during 5 h. The reaction kinetics followed the pseudo-first order kinetics. The Freundlich, Langmuir and Temkin isotherms were applied to the data and the best fit was obtained with Freundlich isotherm. Thermodynamic parameters, like ΔH, ΔG and ΔS were also calculated. The negative values of ΔH (−291.406 KJ/mol) and Gibbs free energy (ΔG) showed the exothermic and spontaneous nature of the process. The positive ΔS (0.04832 KJ/mol K) value showed suitable affinity of catalyst for dye degradation. The catalyst was very stable, active and was easily separated from the reaction mixture by filtration. It can be concluded from the results that the prepared catalyst could be effectively used in dyes degradation/removal from water subjected to further validation and use for various dyes.

scholarly journals Transformation of 2-Butene into Propene on WO3/MCM-48: Metathesis and Isomerization of n-Butene

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 585 ◽  
Author(s):  
Derun Hua ◽  
Zheng Zhou ◽  
Qianqian Hua ◽  
Jian Li ◽  
Xinning Lu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Temperatures ◽  
Thermodynamic Analysis ◽  
Reaction Temperature ◽  
Thermodynamic Calculations ◽  
Metathesis Reaction ◽  
Good Catalytic Activity

The metathesis of 2-butene (Trans and Cis) to propene was investigated over W-based catalysts. Thermodynamic calculations for metathesis and isomerization were carried out at various temperatures to test the reactions. The results showed that the WO3/MCM-48 catalyst had good catalytic activity. The metathesis activity depended on the acidity of the catalyst and the dispersity of the WO3 on the supports. High temperatures promoted the isomerization of 2-butene to 1-butene. According to thermodynamic analysis, however, this is adverse to the metathesis reaction, making it important to determine an appropriate reaction temperature.

scholarly journals Apparent Activation Energy in Electrochemical Multistep Reactions: A Description via Degrees of Rate Control

2020 ◽  
Author(s):  
Alfredo Calderón-Cárdenas ◽  
Enrique A. Paredes-Salazar ◽  
Hamilton Varela
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Apparent Activation Energy ◽  
Chemical Kinetics ◽  
Rate Control ◽  
Rate Coefficients ◽  
Intrinsic Activity ◽  
Empirical Parameter ◽  
Heterogenous Catalysis ◽  
Multistep Reactions

<div> <div> <div> <p>Activation energy is a well-known empirical parameter in chemical kinetics that characterises the dependence of the chemical rate coefficients on the temperature and provides information to compare the intrinsic activity of the catalysts. However, the determination and interpretation of the apparent activation energy in multistep reactions is not an easy task. For this purpose, the concept of degree of rate control is convenient, which comprises a mathematical approach for analyzing reaction mechanisms and chemical kinetics. Although this concept has been used in catalysis, it has not yet been applied in electrocatalytic systems, whose ability to control the potential across the solid/liquid interface is the main difference with heterogenous catalysis, and the electrical current is commonly used as a measure of the reaction rate. Herein we use the definition of ‘degree of rate control for elementary step’ to address some of the drawbacks that frequently arise with interpreting apparent activation energy as a measure of intrinsic electrocatalytic activity of electrode. For this, an electrokinetic model Langmuir-Hinshelwood-like is used for making numerical experiments and verifying the proposed ideas. The results show that to improve the catalytic activity of an electrode material, it must act upon the reaction steps with the highest normalised absolute values of degree of rate control. On the other hand, experiments at different applied voltages showed that if the electroactive surface poisoning process take place, changes in 𝐸𝑎𝑝𝑝 can not be used to compare the catalytic activity of the electrodes. Finally, the importance of making measurements at steady-state to avoid large errors in the calculations of apparent activation energy is also discussed. </p> </div> </div> </div>

Synthesis, Characterization, and Crystal Structure of Several Novel Acidic Ionic Liquids: 1-ethyl-2-alkyl-benzimidazolium Tetra-Fluoroborate

2013 ◽  
Vol 457-458 ◽  
pp. 139-143 ◽  
Author(s):  
Ming Tian Wang ◽  
Chang Ping Pan ◽  
Wei Peng Gai ◽  
Xiao Xia Lv ◽  
Min Gang Zhai ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ionic Liquid ◽  
Acetic Acid ◽  
Catalytic Activity ◽  
Lamellar Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acidic Ionic Liquid ◽  
Acidic Ionic Liquids ◽  
Good Catalytic Activity

A series of novel acidic ionic liquid: 1-ethyl-2-alkyl-benzimidazolium tetra-fluoroborate (alkyl= Et, Pr-n, Bu-n) were prepared by simple acid-based neutralization of 1-ethyl-2-alkyl-benzimidazole and tetrafluoroboric acid. The compounds were characterized by FTIR spectra, elemental analysis,1HNMR spectra and thermogravimetric analysis. These novel tetra-fluoroborate salts show good catalytic activity to esterification of benzyl alcohol and acetic acid. Furthermore, a crystal of ([H-ebBiBF4) was prepared with the crystal structure and determined by X-ray diffraction analysis. The molecular is of lamellar structure as mainly π electron ring is stacked interleaving between two layers. The results of cation and anion arranged orderly in pair indicate that the coulombic attraction is more dominant. Simultaneously, the weak local hydrogen bonds C-H···F exist in the molecules.

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