Homogeneous Catalysis

The structure-activity properties of MnOx/CeO2nanorods and MnOx/CeO2nanoparticles, with the impor-tance of CeO2morphology have been investigated for the solvent-free oxidation of amines using oxygenas a green oxidant. The physicochemical properties of the samples have been investigated using HRTEM,XRD, Raman, BET, XPS, and FT-IR techniques. HRTEM studies reveal that CeO2nanorods preferentiallyexpose {1 1 0} and {1 0 0} crystal planes, while CeO2nanoparticles expose {1 1 1} planes. The additionof manganese to CeO2supports leads to an enhancement in the concentration of Ce3+ions and oxy-gen vacancies, which are more pronounced for the MnOx/CeO2nanorods as evidenced by Raman andXPS studies. Another striking observation noticed from XPS studies is that MnOx/CeO2nanorods cata-lyst exhibits Mn4+, Mn3+, and Mn2+species, whereas only Mn4+and Mn3+are presented in MnOx/CeO2nanoparticles catalyst. It was found that MnOx/CeO2nanorods catalyst exhibit a two-fold higher activityfor the oxidation of benzylamine with superior selectivity to dibenzylimine (∼99%) compared with thatof MnOx/CeO2nanoparticles catalyst. The MnOx/CeO2nanorods catalyst was also found to be effectivefor the oxidation of various amines, and moderate to good product yields were obtained. Novel probablereaction pathways are proposed for solvent-free oxidation of primary and secondary benzylamines overMnOx/CeO2nanorods catalyst. The presence of surface-active Mn4+/Mn2+couple and the enhanced defectstructure of CeO2nanorods (i.e., higher numbers of Ce3+ions and abundant O vacancies) are found to bekey factors for the high catalytic efficiency of the MnOx/CeO2nanorods

Styrene polymerization was carried out with Ni(acac)2/MAO and Ni(acac)2/SiO2/MAO. The influence of reaction parameters (Al/Ni mole ratio, catalyst concentration, temperature and time polymerization) on styrene polymerization was evaluated. It was observed that both catalytic systems were affected by reaction parameters and that the heterogeneous catalyst presented higher activity than the homogeneous one. Polystyrenes with different molecular weight, stereoregularity and polydispersity were obtained. These results suggest that different active catalyst species could have been present. In addition, two types of methylaluminoxane (MAO) with different molecular weights were also evaluated as cocatalyst. As a result, the catalyst activity and stereospecificity were strongly affected by the MAO type.

The kinetics of the high-temperature (1070–1134 K), low- and high-pressure gas-phase forward water–gas shift reaction (fWGSR) were evaluated in an empty quartz reactor and a quartz reactor packed with quartz particles. The power-law expression for the reaction rate was consistent with the Bradford mechanism and was invariant with respect to pressure. The experimental rate constant was lower than that published by Graven and Long, and slightly higher than estimates obtained using the reaction rate expression derived from the Bradford mechanism in conjunction with values of reaction rate constants obtained from the GRI database. Similar experiments conducted using a reactor composed of Inconel® 600, a representative reactor shell material, exhibited substantially enhanced rates of reaction. A simple power-law rate expression was incorporated into a surface-catalyzed plug flow reactor (PFR) model to correlate the results between 600 and 900 K. Palladium and palladium–copper alloy surfaces, representative of hydrogen membranes, were also shown to enhance the fWGSR rate, but not as much as the Inconel® 600 surfaces. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Exploiting the reactivity of one functional group within a molecule to generate a reaction at a different position is an ongoing challenge in organic synthesis. Effective remote functionalization protocols have the potential to provide access to almost any derivatives but are difficult to achieve. The difficulty is more pronounced for acyclic systems where flexible alkyl chains are present between the initiating functional group and the desired reactive centres. In this Review, we discuss the concept of remote functionalization of alkenes using metal complexes, leading to a selective reaction at a position distal to the initial double bond. We aim to show the vast opportunity provided by this growing field through selected and representative examples. Our aim is to demonstrate that using a double bond as a chemical handle, metal-assisted long-distance activation could be used as a powerful synthetic strategy.

"This guide sets out the key steps in the design of gas or liquid phase homogeneous reactors and suggests appropriate types of reactor according to the required residence time, flow pattern and heat transfer duty.

A liquid phase reactor with a vapor product is covered only if the vapor removal rate does not affect the overall rate. If it does, consider thin-film reactors.
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#Fundamentals; #New Preparations and New Active Materials; #Synthesis and Characterization of Catalysts; #Characterization of Catalyst in its Working State; #Catalyst Deactivation; #Reaction Kinetics; #Reactor Modeling; #Reactor Design, Control and Optimization; #Novel Reactors and Process Developments;

Biodiesel is one of the potential alternative energy sources that can be derived from renewable and low-grade origin through different processes. One of the processes is alcoholysis or transesterification in the presence of a suitable catalyst. The catalyst can be either homogeneous or heterogeneous. This article reviews various catalysts used for biodiesel production to date, presents the state of the art of types of catalysts, and compares their suitability and associated challenges in the transesterification process. Biodiesel production using homogeneous and heterogeneous catalysis has been studied extensively, and novel heterogeneous catalysts are being continuously investigated. Homogeneous catalysts are generally efficient in converting biodiesel with low free fatty acid (FFA) and water containing single-origin feedstock. Heterogeneous catalysts, on the other hand, provide superior activity, range of selectivity, good FFA, and water adaptability. The quantity and strengths of active acid or basic sites control these properties. Some of the heterogeneous catalysts such as zirconia and zeolite-based catalysts can be used as both basic and acidic catalyst by suitable alteration. Heterogeneous catalysts from waste and biocatalysts play an essential role in attaining a sustainable alternative to traditional homogeneous catalysts for biodiesel production. Recently, high catalytic efficiency at mild operating conditions has drawn attention to nanocatalysts. This review evaluates state of the art and perspectives for catalytic biodiesel production and assesses the critical operational variables that influence biodiesel production along with the technological solutions for sustainable implementation of the process.

The importance of ethyl levulinate (EL) as a fuel additive and a potential biomass-derived platform molecule is noteworthy. EL is obtained from the esterification of levulinic acid (LA) in the presence of ethanol. Besides LA, the acid-catalyzed ethanolysis reaction to produce EL can be carried out on a variety of biomass-derived substrates including furfuryl alcohol (FAL), chloromethyl furfural, monosaccharides, polysaccharides and lignocellulosic biomass. The acid catalysts employed for such conversions cover a wide range of structure and properties. The nature of the acid catalysts and the key intermediates formed during the reaction dictate the overall yield of the desired product. For example, in the ethanolysis reaction of FAL to produce EL, diethyl ether (DEE) and ethoxymethylfuran (EMF) produced as side products are suggested to influence the selectivity of EL. Similarly, in the ethanolysis of glucose, formation of ethyl-D-glucopyranoside (EDGP) results in a slow conversion to product EL. The review, therefore, focuses on highlighting the importance of catalyst structure, acidity and reaction mechanism and the role of key intermediates in the production of EL from biorenewable resources.