scholarly journals Rh-induced Support Transformation and Rh Incorporation in Titanate Structures and Their Influence on Catalytic Activity

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 212 ◽  
Author(s):  
János Kiss ◽  
András Sápi ◽  
Mariann Tóth ◽  
Ákos Kukovecz ◽  
Zoltán Kónya
Keyword(s):  
Catalytic Activity ◽  
Specific Activity ◽  
Atomic Scale ◽  
Ionic Form ◽  
Electronic Interaction ◽  
Decomposition Reactions ◽  
Heterogeneous Catalytic ◽  
Ethanol Decomposition ◽  
Titanate Nanowires ◽  
Degussa P25

Rh is one of the most effective metals in several technologically important heterogeneous catalytic reactions, like the hydrogenation of CO2, and CO, the CO+H2O reaction, and methane and ethanol transformations. Titania and titanates are among the most frequently studied supports for Rh nanoparticles. The present study demonstrates that the nature of the support has a marked influence on the specific activity. For comparison, the catalytic activity of TiO2 P25 is also presented. It is pointed out that a certain amount of Rh can be stabilized as cation (Rh+) in ion-exchange positions (i.e., in atomic scale distribution) of the titanate framework. This ionic form does not exists on TiO2. We pay distinguished attention not only to the electronic interaction between Rh metal and the titania/titanate support, but also to the Rh-induced phase transitions of one-dimensional titanate nanowires (TiONW) and nanotubes (TiONT). Support transformation phenomena can be observed in Rh-loaded titanates. Rh decorated nanowires transform into the TiO2(B) phase, whereas their pristine counterparts recrystallize into anatase. The formation of anatase is dominant during the thermal annealing process in both acid-treated and Rh-decorated nanotubes; Rh catalysis this transformation. We demonstrate that the phase transformations and the formation of Rh nanoclusters and incorporated Rh ions affect the conversion and the selectivity of the reactions. The following initial activity order was found in the CO2 + H2, CO + H2O and C2H5OH decomposition reactions: Rh/TiO2 (Degussa P25) ≥ Rh/TiONW > Rh/TiONT. On the other hand it is remarkable that the hydrogen selectivity in ethanol decomposition was two times higher on Rh/TiONW and Rh/TiO(NT) catalysts than on Rh/TiO2 due to the presence of Rh+ cations incorporated into the framework of the titanate structures.

Ordered Intermetallic Nanoparticles with High Catalytic Activity Prepared by an Electrochemically Induced Phase Transformation

2019 ◽  
Author(s):  
Du Sun ◽  
yunfei wang ◽  
Kenneth Livi ◽  
chuhong wang ◽  
ruichun luo ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Diffusion Mechanism ◽  
Reduction Reaction ◽  
Atomic Scale ◽  
High Catalytic Activity ◽  
Ambient Conditions ◽  
Magnetic Devices ◽  
Disordered Alloys ◽  
Ordered Intermetallic ◽  
Intermetallic Nanoparticles

<div> <p>The synthesis of alloys with long range atomic scale ordering (ordered intermetallics) is an emerging field of nanochemistry. Ordered intermetallic nanoparticles are useful for a wide variety of applications such as catalysis, superconductors, and magnetic devices. However, the preparation of nanostructured ordered intermetallics is challenging in comparison to disordered alloys, hindering progress in materials development. We report a process for converting colloidally synthesized ordered intermetallic PdBi<sub>2</sub> to ordered intermetallic Pd<sub>3</sub>Bi nanoparticles under ambient conditions by an electrochemically induced phase transition. The low melting point of PdBi<sub>2</sub> corresponds to low vacancy formation energies which enables the facile removal of the Bi from the surface, while simultaneously enabling interdiffusion of the constituent atoms via a vacancy diffusion mechanism under ambient conditions. The resulting phase-converted ordered intermetallic Pd<sub>3</sub>Bi exhibits 11x and 3.5x higher mass activty and high methanol tolerance for the oxygen reduction reaction compared to Pt/C and Pd/C, respectively,which is the highest reported for a Pd-based catalyst, to the best of our knowledge. These results establish a key development in the synthesis of noble metal rich ordered intermetallic phases with high catalytic activity, and sets forth guidelines for the design of ordered intermetallic compounds under ambient conditions.</p> </div>

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.

Construction of solvent-dependent self-assembled porous Ni(ii)-coordinated frameworks as effective catalysts for chemical transformation of CO2

RSC Advances ◽  
2016 ◽  
Vol 6 (109) ◽  
pp. 108010-108016 ◽  
Author(s):  
Zhen Zhou ◽  
Lu Yang ◽  
Yefei Wang ◽  
Cheng He ◽  
Tao Liu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Chemical Transformation ◽  
Self Assembly ◽  
Ambient Conditions ◽  
Heterogeneous Catalytic ◽  
Self Assembled

Two types of Ni(ii)-based coordinated frameworks have been solvothermally synthesized via solvent driven self-assembly, showing efficient heterogeneous catalytic activity toward cycloaddition of CO2 with epoxides under ambient conditions.

Moving into Nanotechnology Roles to Mimic and Boost Enzyme Activity

2018 ◽  
pp. 421-440
Author(s):  
Maria Laura Soriano
Keyword(s):  
Enzyme Activity ◽  
Catalytic Activity ◽  
Enzyme Immobilization ◽  
Mesoporous Materials ◽  
Specific Activity ◽  
Artificial Enzymes ◽  
Catalytic Nanoparticles ◽  
Solid Liquid ◽  
By Products ◽  
Insight Into

A new tendency toward the design of artificial enzymes based on nanostructures (nanodots, nanofibers, mesoporous materials) has emerged. On one hand, nanotechnology bestows self-catalytic nanoparticles with a specific activity to achieve efficient reactions with low number of by-products. On other hand, the nanoparticles may behave as nanometric scaffolds for hosting enzymes, promoting their catalytic activity and stability. In this case, enzyme immobilization requires the preservation of the catalytic activity by preventing enzyme unfolding and avoiding its aggregation. These approaches render many other advantages like hosting/storing enzymes in nanotechnological solid, liquid, and gel-like media. This chapter focuses on the most up-to-date approaches to manipulate or mimic enzyme activity based on nanotechnology, and offers examples of their applications in the most promising fields. It also gives new insight into the creation of reusable nanotechnological tools for enzyme storage.

scholarly journals Fabrication of Core-Shell Structural SiO2@H3[PM12O40] Material and Its Catalytic Activity

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Xin Yang ◽  
Junhai Wang ◽  
Qi Zhang ◽  
Xu Wang ◽  
Linlin Xu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Heterogeneous Catalysts ◽  
Sol Gel ◽  
Operating Conditions ◽  
Core Shell ◽  
Catalytic Wet Air Oxidation ◽  
Air Oxidation ◽  
Wet Air Oxidation ◽  
Heterogeneous Catalytic ◽  
Room Condition

Through a natural tree grain template and sol-gel technology, the heterogeneous catalytic materials based on polyoxometalate compounds H3[PM12O40] encapsulating SiO2: SiO2@H3[PM12O40] (SiO2@PM12, M = W, Mo) with core-shell structure had been prepared. The structure and morphology of the core-shell microspheres were characterized by the XRD, IR spectroscopy, UV-Vis absorbance, and SEM. These microsphere materials can be used as heterogeneous catalysts with high activity and stability for catalytic wet air oxidation of pollutant dyes safranine T (ST) at room condition. The results show that the catalysts have excellent catalytic activity in treatment of wastewater containing 10 mg/L ST, and 94% of color can be removed within 60 min. Under different cycling runs, it is shown that the catalysts are stable under such operating conditions and the leaching tests show negligible leaching effect owing to the lesser dissolution.

A polyhedral oligomeric silsesquioxane (POSS)-bridged oxo-molybdenum Schiff base complex with enhanced heterogeneous catalytic activity in epoxidation

2014 ◽  
Vol 4 (4) ◽  
pp. 997-1004 ◽  
Author(s):  
Yan Leng ◽  
Jian Liu ◽  
Chenjun Zhang ◽  
Pingping Jiang
Keyword(s):  
Schiff Base ◽  
Catalytic Activity ◽  
Polyhedral Oligomeric Silsesquioxane ◽  
Schiff Base Complex ◽  
Efficient Catalyst ◽  
Butyl Hydroperoxide ◽  
Base Complex ◽  
Heterogeneous Catalytic ◽  
Oligomeric Silsesquioxane ◽  
Epoxidation Of Alkenes

A novel POSS-bridged oxo-molybdenum Schiff base complex was demonstrated to be a highly efficient catalyst for epoxidation of alkenes with aqueous tert-butyl hydroperoxide.

Nanoporous twinned PtPd with highly catalytic activity and stability

2015 ◽  
Vol 3 (5) ◽  
pp. 2050-2056 ◽  
Author(s):  
Xuefeng Zhang ◽  
Pengfei Guan ◽  
Lidija Malic ◽  
Michel Trudeau ◽  
Federico Rosei ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Catalytic Activity ◽  
Electrochemical Oxidation ◽  
High Density ◽  
Atomic Scale ◽  
High Catalytic Activity ◽  
Twin Boundaries ◽  
Oxidation Of Methanol ◽  
Overall Performance

Nanoporous composition-tunable PtPd catalysts, combining with a high density of twin boundaries and atomic-scale Pt–Pd interfaces, can be synthesized by a simple thermal-decomposition strategy. The most optimized PtPd represents the superior overall performance high catalytic activity and stability in the electrochemical oxidation of methanol.

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