Lewis Acids: From Conventional Homogeneous to Green Homogeneous and Heterogeneous Catalysis

Nanostructures have attracted huge interest as a rapidly growing class of materials for many applications. Several techniques have been used to characterize the size, crystal structure, elemental composition and a variety of other physical properties of nanoparticles. In several cases, there are physical properties that can be evaluated by more than one technique. Different strengths and limitations of each technique complicate the choice of the most suitable method, while often a combinatorial characterization approach is needed. In addition, given that the significance of nanoparticles in basic research and applications is constantly increasing, it is necessary that researchers from separate fields overcome the challenges in the reproducible and reliable characterization of nanomaterials, after their synthesis and further process (e.g. annealing) stages. The principal objective of this review is to summarize the present knowledge on the use, advances, advantages and weaknesses of a large number of experimental techniques that are available for the characterization of nanoparticles. Different characterization techniques are classified according to the concept/group of the technique used, the information they can provide, or the materials that they are destined for. We describe the main characteristics of the techniques and their operation principles and we give various examples of their use, presenting them in a comparative mode, when possible, in relation to the property studied in each case.

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Characterization techniques for nanoparticles: comparison and complementarity upon studying nanoparticle properties

The replacement of fossil resources that currently provide more than 90% of our energy needs and feedstocks of the chemical industry in combination with reduced emission of carbon dioxide is one of the most pressing challenges of mankind. Biomass as a globally available resource has been proposed as an alternative feedstock for production of basic building blocks, which could partially or even fully replace the currently utilized fossil-based ones in well-established chemical processes. The destruction of lignocellulosic feed followed by oxygen removal from its cellulose and hemicellulose content by catalytic processes results in the formation of initial platform chemicals (IPCs). However, their sustainable production strongly depends on the availability of resources, their efficient or even industrially viable conversion processes, and replenishment time of feedstocks. Herein, we overview recent advances and developments in catalytic transformations of the carbohydrate content of lignocellulosic biomass ...

Catalytic Conversion of Carbohydrates to Initial Platform Chemicals: Chemistry and Sustainability

Recent developments in the stereoselective synthesis of α-aminoacids

Metal nanoparticles have attracted much attention over the last decade owing to their unique properties as compared to their bulk metal equivalents, including a large surface-to-volume ratio and tunable shapes. To control the properties of nanoparticles with particular respect to shape, size and dispersity is imperative, as these will determine the activity in the desired application. Supported metal nanoparticles are widely employed in catalysis. Recent advances in controlling the shape and size of nanoparticles have opened the possibility to optimise the particle geometry for enhanced catalytic activity, providing the optimum size and surface properties for specific applications. This Review describes the state of the art with respect to the preparation and use of supported metal nanoparticles in catalysis. The main groups of such nanoparticles (noble and transition metal nanoparticles) are highlighted and future prospects are discussed.

Sustainable Preparation of Supported Metal Nanoparticles and Their Applications in Catalysis

Knoevenagel condensation in the heterogeneous phase using aluminum phosphate-aluminum oxide as a new catalyst

Etude de la condensation de Knoevenagel entre des aldehydes ou des cetones et des dinitriles ou cyanoesters. Obtention de dinitriles et cyanoesters vinyliques

Knoevenagel condensation in the heterogeneous phase using AlPO4-Al2O3 as a new catalyst

Alkali-promoted AlPO4 catalysis

A series of metal phosphates (Al, Fe, Ni, Ca and Mn) and stoichiometric (Al/Fe=Al/Ca=1) mixed systems: FeAl(PO 4 ) 2 and Ca 3 Al 3 (PO 4 ) 5 , were prepared by an ammonia gelation method. Their amorphous character was determined through several physical methods: nitrogen adsorption, DRIFT and XRD patterns. Gas-phase competitive dehydration/dehydrogenation reaction of cyclohexanol was carried out as a probe reaction and cyclohexene was usually the main reaction product, but different amounts of 1- and 3-methylcyclopentenes as well as cyclohexanone were always obtained. These results were compared to those obtained with 17 commercial inorganic solids (several metal oxides, sulfates and phosphates). A main unexpected conclusion was that cyclohexanol dehydration is obtained not only in acid sites but also in basic sites.

Influence of acid–base properties of catalysts in the gas-phase dehydration–dehydrogenation of cyclohexanol on amorphous AlPO4 and several inorganic solids

The skeletal isomerization of cyclohexene, in a microcatalytic pulse reactor, was investigated by using aluminium orthophosphates (Al/P = 1) as catalysts. An attempt has been made to correlate the ...

Angel Garcia

Papers

Knoevenagel condensation in the heterogeneous phase using aluminum phosphate-aluminum oxide as a new catalyst

Knoevenagel condensation in the heterogeneous phase using AlPO4-Al2O3 as a new catalyst

Alkali-promoted AlPO4 catalysis

Influence of acid–base properties of catalysts in the gas-phase dehydration–dehydrogenation of cyclohexanol on amorphous AlPO4 and several inorganic solids

Skeletal isomerization of cyclohexene on AlPO4 catalysts