Some Aspects of Particuology in Heterogeneous Catalysts

2014 ◽  
Vol 69 (5) ◽  
Author(s):  
Rasidah Razali ◽  
Ho Chin Siong ◽  
Lai Sin Yuan ◽  
Sheela Chandren ◽  
Hadi Nur
Keyword(s):  
Heterogeneous Catalysts ◽  
Sol Gel ◽  
Bifunctional Catalyst ◽  
Catalytic Systems ◽  
Particulate Materials ◽  
Design And Synthesis ◽  
Heterogeneous Catalytic ◽  
Catalyst Systems ◽  
First Time ◽  
High Length

The design and synthesis of particulate materials for new catalyst systems with novel properties remain a big challenge today. Here an attempt has been made to synthesize particulate materials for several heterogeneous catalytic systems, which contain examples from our recent research projects in this area. The particulate catalysts have been designed for single centre catalyst, phase-boundary catalyst, bifunctional catalyst, photocatalyst and chiral catalyst. In our current research, the synthesis of well-aligned titanium dioxide catalyst with very high length to the diameter ratio has also been demonstrated for the first time by sol-gel method under magnetic field with surfactant as the structure aligning agent. 

Design and Preparation of Heterogeneous Catalysts by Controlled Chemical Reactions with Oxygen and Hydrogen

1994 ◽  
Vol 368 ◽  
Author(s):  
David L. Cocke ◽  
Donald G. Naugle ◽  
Thomas R. Hess
Keyword(s):  
Chemical Reactions ◽  
Heterogeneous Catalysts ◽  
Formation Processes ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Reduction Processes ◽  
Alloy Oxidation ◽  
Reaction Models ◽  
Catalyst Systems ◽  
Insight Into

ABSTRACTChemical reactions of metals and strongly interacting alloys such as Cu-Mn, Ni-Ti, Ni-Hf and Ni-Zr with oxygen and hydrogen play important roles in the preparation, activation, and regeneration of many important heterogeneous catalytic systems involving supported and unsupported metals and alloys. Recent advances in the understanding of metal and alloy oxidation is bringing new insight into the reactive design and activation of bi- and multi-metallic catalysts. By surface studies of oxidation, thermal annealing and reduction of selected alloys and their thin films and reaction layers and products we have been able to delineate the factors which are most important to the oxide formation processes and the oxide reduction processes. Reaction models developed from these results are permitting the design of new catalyst systems and providing long sought understanding to explain specific aspects of well established metallic catalysts.

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.

scholarly journals Recent Progresses in the Multicomponent Synthesis of Dihydropyridines by Applying Sustainable Catalysts Under Green Conditions

2021 ◽  
Vol 9 ◽  
Author(s):  
Immandhi Sai Sonali Anantha ◽  
Nagaraju Kerru ◽  
Suresh Maddila ◽  
Sreekantha B. Jonnalagadda
Keyword(s):  
Heterogeneous Catalysts ◽  
Reaction Times ◽  
Cost Effective ◽  
Multicomponent Synthesis ◽  
One Pot ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Significant Efficacy ◽  
Magnetic Silica ◽  
Active Methylene

The synthesis of dihydropyridines, valuable molecules with diverse therapeutic properties, using eco-friendly heterogeneous catalysts as a green alternative received significant consideration. By selecting appropriate precursors, these compounds can be readily modified to induce the desired properties in the target product. This review focused on synthesising diverse dihydropyridine derivatives in single-pot reactions using magnetic, silica, and zirconium-based heterogeneous catalytic systems. The monograph describes preparation techniques for various catalyst materials in detail. It covers facile and benign magnetic, silica, zirconium-based, and ionic liquid catalysts, exhibiting significant efficacy and consistently facilitating excellent yields in short reaction times and in a cost-effective way. Most of the designated protocols employ Hantzsch reactions involving substituted aldehydes, active methylene compounds, and ammonium acetate. These reactions presumably follow Knoevenagel condensation followed by Michael addition and intra-molecular cyclisation. The multicomponent one-pot protocols using green catalysts and solvents have admirably increased the product selectivity and yields while minimising the reaction time. These sustainable catalyst materials retain their viability for several cycles reducing the expenditure are eco-friendly.

scholarly journals HOMOGENEOUS VINYLATION OF 2-HYDROXY-2 PHENYLETHANICAL ACID

2018 ◽  
Vol 6 (11) ◽  
pp. 350-354
Author(s):  
Parmanov A.B. ◽  
Nurmanov S.E. ◽  
Tomash Maniecki ◽  
Ziyadullayev O.E. ◽  
Abdullayev J.U.
Keyword(s):  
Carboxylic Acids ◽  
Vinyl Ester ◽  
Mandelic Acid ◽  
Heterogeneous Catalysts ◽  
Raw Materials ◽  
Zinc Salt ◽  
Vinyl Esters ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Ethylene Series

Homogeneous-catalytical vinylation of 2-hydroxy-2-phenylethanical acid was carried out. Influence of catalylists nature, temperature and duration reaction on yield of synthesized vinyl ester has been investigated. basis of natural raw materials. Based on vinyl esters of carboxylic acids, their polymers and copolymers with unsaturated compounds of the ethylene series, emulsifiers for emulsion paints have been obtained; compounds that improve the viscosity of lubricating oils and are used as crosslinking agents in the rubber industry. Synthesis of vinyl esters based on monobasic aliphatic acids has been studied by the example of acetic acid by many researchers. In this respect, the aromatic carboxylic acids remain unexplored. Goal: Synthesis of vinyl ester of mandelic acid by it’s reaction with acetylene in the presence of heterogeneous catalysts, investigation of the influence of the nature of catalysts and the reaction temperature on the yield of obtained product. Methodology: Catalytic systems based on AlCl3∙6H2O or zinc salt of mandelic acid with dimethylsulfoxide were prepared and heterogeneous catalytic vinylation of mandelic acid with acetylene was carried out and it’s vinyl ether was obtained. Scientific Novelty. The synthesis of vinyl ester of mandelic acid with it’s reactions with acetylene using the catalytic systems AlCl3∙6H2O-DMSO and (C6H5CH(OH)COO)2Zn-DMSO was carried out. Obtained Data: The vinyl ester of mandelic acid was synthesized by it’s vinylation in stationary heterogeneous conditions. The influence of the nature of the catalyst (AlCl3∙6H2O, (C6H5CH(OH)COO)2Zn), temperature and duration of the reaction on the yield of the product was investigated. Features: vinylation of hydroxy carboxylic acid was investigated; the catalytic systems AlCl3∙6H2O-DMSO and (C6H5CH(OH)COO)2Zn-DMSO are used; factors influencing the yield of vinyl ester of mindalic acid and optimal conditions of it’s synthesis were found.

In Situ Nanoscale Studies of Liquid Polymerization Reactions in the Manufacture of Polyamides and.Combinatorial Catalysis

2001 ◽  
Vol 7 (S2) ◽  
pp. 1060-1061
Author(s):  
Pratibha L. Gai ◽  
K. Kourtakis ◽  
S. Ziemecki
Keyword(s):  
Low Temperature ◽  
Heterogeneous Catalysts ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Single Step ◽  
Heterogeneous Catalytic ◽  
Rutile Titania ◽  
Real Time Information

Low temperature heterogeneous catalytic routes for polymers are of considerable interest in the chemical sciences and technology because they are economical and environmentally beneficial. However such routes have been difficult because of an incomplete understanding of process control and low yields. Currently, hydrogenation of aliphatic dintriles in solvents is used in the chemical industry to manufacture the corresponding diamenes which are subsequently reacted with adipic acid solutions and polymerized to produce the polyamide, nylon (6,6).Here we report an alternative, low temperature heterogeneous catalytic process for the polymerization reactions using novel environmental-HRTEM (EHREM) in liquid environments. EHREM under simulated reaction conditions provides direct, in situ real-time information on the dynamic structural and chemical changes and reaction modes of operation. We prepared high surface area heterogeneous catalysts including cobalt-ruthenium nanoclusters supported on rutile titania using a single step sol-gel technique, (shown in Fig. 1).

Diffusion Processes Affecting the Performance of Heterogeneous Catalysts: Part 1

2011 ◽  
Vol 319-320 ◽  
pp. 107-115
Author(s):  
Mohammad Ebrahim Zeynali ◽  
S. Hakim
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Heterogeneous Catalysts ◽  
Molecular Diffusion ◽  
Diffusion Processes ◽  
Knudsen Diffusion ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic

The diffusion processes taking place in heterogeneous catalytic systems have been discussed. Various diffusion mechanisms such as Knudsen diffusion, molecular diffusion, configurational diffusion and surface diffusion sensitivity in catalytic systems were investigated. The concentration gradients inside the catalyst pellet were obtained for various Thiele modulus. The Knudsen number was calculated and discussed for large and small pores. The transitional diffusion coefficient was determined for diethylbenzene. The experimental pore size distribution carves for an industrial and synthesized catalyst was obtained and the effect of pore size distribution on diffusion coefficient was discussed.

Dissolution and Performing Homogeneous Photocatalysis of Polymeric Carbon Nitride

2018 ◽  
Author(s):  
Chaofeng Huang ◽  
Jing Wen ◽  
Yanfei Shen ◽  
Fei He ◽  
Li Mi ◽  
...  
Keyword(s):  
Conjugated Polymer ◽  
Carbon Nitride ◽  
Heterogeneous Catalysts ◽  
Methane Sulfonic Acid ◽  
Environment Friendly ◽  
The Poor ◽  
Catalytic Sites ◽  
Homogeneous Photocatalysis ◽  
Polymeric Carbon ◽  
First Time

<a></a><a>As a metal-free conjugated polymer, carbon nitride (CN) has attracted tremendous attention as heterogeneous (photo)catalysts. </a><a></a><a>By following prototype of enzymes, making all catalytic sites of accessible via homogeneous reactions is a promising approach toward maximizing CN activity, but hindered due to </a><a></a><a>the poor insolubility of CN</a>. Herein, we report the dissolution of CN in environment-friendly methane sulfonic acid and the homogeneous photocatalysis driven by CN for the first time with the activity boosted up to 10-times, comparing to the heterogeneous counterparts. Moreover, facile recycling and reusability, the <a>hallmark</a> of heterogeneous catalysts, were kept for the homogeneous CN photocatalyst via reversible precipitation using poor solvents. It opens new vista of CN in homogeneous catalysis and offers a successful example of polymeric catalysts in bridging gaps of homo/heterogeneous catalysis.

Nickel (II) and oxovanadium (IV) complexes supported on MCM-41 mesoporous and their application in catalytic selective sulfide and thiol oxidation

2020 ◽  
Vol 23 ◽  
Author(s):  
Mohsen Nikoorazm ◽  
Maryam Khanmoradi ◽  
Masoumeh Sayadian
Keyword(s):  
Catalytic Activity ◽  
Room Temperature ◽  
Sol Gel ◽  
Reaction Times ◽  
Significant Loss ◽  
Spectral Studies ◽  
High Catalytic Activity ◽  
Catalytic Systems ◽  
Solvent Free Conditions ◽  
Mcm 41

Introduction:: MCM-41 was synthesized using the sol-gel method. Then two new transition metal complexes of Nickel (II) and Vanadium (IV), were synthesized by immobilization of adenine (6-aminopurine) into MCM-41 mesoporous. The compounds have been characterized by XRD, TGA, SEM, AAS and FT-IR spectral studies. Using these catalysts provided an efficient and enantioselective procedure for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using hydrogen peroxide at room temperature. Materials and Methods:: To a solution of sulfide or thiol (1 mmol) and H2O2 (5 mmol), a determined amount of the catalyst was added. The reaction mixture was stirred at room temperature for the specific time under solvent free conditions. The progress of the reaction was monitored by TLC using n-hexane: acetone (8:2). Afterwards, the catalyst was removed from the reaction mixture by centrifugation and, then, washed with dichloromethane in order to give the pure products. Results:: All the products were obtained in excellent yields and short reaction times indicating the high activity of the synthesized catalysts. Besides, the catalysts can be recovered and reused for several runs without significant loss in their catalytic activity. Conclusion:: These catalytic systems furnish the products very quickly with excellent yields and VO-6AP-MCM-41 shows high catalytic activity compared to Ni-6AP-MCM-41.

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.

Sign in / Sign up

Export Citation Format

Share Document