1,721,068 research outputs found
Catalytic transformation of renewables (Olefin, bio‐sourced, et al.)
Full text linkThe objective of this Special Issue is to provide new diverse contributions that can
demonstrate recent applications in biomass transformation using heterogeneous catalysts.
In recent decades, a wide variety of biomass-derived chemicals have emerged as key platform chemicals for the production of fine chemicals and liquid fuels using heterogeneous
catalysts as the preferred option for most of the developed and proposed catalytic processes.
A range of heterogeneous catalysts have been evaluated for effective biomass conversion,
such as supported metal nanoparticles, mixed metal oxides and zeolites, where the control
of particle size, porosity, acid-basic and redox properties is crucial for providing active,
stable and selective heterogeneous catalysts. Moreover, the crucial role of the solvent,
choice of reactor design and final chemical processes for controlling activity, selectivity and
deactivation phenomena has been demonstrate
A Career in Catalysis: Laura Prati
Full text linkThis account celebrates the long and successful scientific career of Laura Prati, recalling her most important scientific achievements since the beginning of her work as a researcher in inorganic chemistry. Laura went through many aspects of liquid-phase heterogeneous catalysis, taking her first steps in the field of catalysts
synthesis, where she pursued the development of innovative strategies for preparing catalysts until laying the foundations of the colloidal synthesis of metal nanoparticles, with particular interest in gold. Her investigations in colloids for catalysis had a natural outcome on catalysts synthesis and optimization. In her career, she dealt with liquidphase oxidation reactions, with particular attention to biomass valorization processes. According to this, she could not help to deal
also with hydrogenation and hydrogenolysis reactions, to which she dedicated herself, especially in the more recent years. Her discoveries have influenced many researchers in the area of heterogeneous catalysis and design of materials
Optimization of the Zr-loading on siliceous support catalysts leads to a suitable Lewis/Bronsted acid sites ratio to produce high yields to gamma-valerolactone from furfural in one-pot
Full text linkThe study for the production of gamma-valerolactone from furfural in one-pot has been carried out using ZrO2 supported on silica spheres. The catalysts synthesized were characterized by XRD, UV-vis, HR-TEM, N-2 adsorption, IR, pyridine adsorption-IR and NH3-TPD in order to determine their physicochemical characteristics. Both, Lewis and Bronsted acid sites are necessary to produce gamma-valerolactone from furfural, because they are involved in different steps of the reaction. Accordingly, a reaction mechanism has been proposed. Lewis acid sites of ZrO2 interacting with the -OH surface groups of the siliceous spheres can generate Bronsted acid sites in the supported Zr catalysts, which are absent in both pure ZrO2 and the silica spheres. Then, by controlling the amount of Zr in the supported catalysts, the relative amount of Lewis and Bronsted acid sites can be optimized to obtain the highest yields to gamma-valerolactone. The Zr-loading of the optimal supported catalyst was ca. 7 wt% Zr, which reached a gamma-valerolactone yield of 72.4 % after 8 h at 180 C using 2-propanol as a solvent and hydrogen donor
Mechanistic study of hydrazine decomposition on Ir(111)
Full text linkHydrogen transport and storage technology remain one of the critical challenges of the hydrogen economy. Hydrazine (N2H4) is a carbon-free hydrogen carrier which has been widely used as fuel in the field of space exploration. We have combined experiments and computer simulations in order to gain a better understanding of the N2H4 decomposition on Ir catalyst, the most efficient catalyst for hydrazine decomposition up to date. We have identified metallic Ir rather than IrO2 as the active phase for hydrazine decomposition and carried out density functional theory (DFT) calculations to systematically investigate the changes in the electronic structure along with the catalytic decomposition mechanisms. Three catalytic mechanisms to hydrazine decomposition over Ir(111) have been found: (i) intramolecular reaction between hydrazine molecules, (ii) intramolecular reaction between co-adsorbed amino groups, and (iii) hydrazine dehydrogenation assisted by co-adsorbed amino groups. These mechanisms follow five different pathways for which transition states and intermediates have been identified. The results show that hydrazine decomposition on Ir(111) starts preferentially with an initial N-N bond scission followed by hydrazine dehydrogenation assisted by the amino group produced, eventually leading to ammonia and nitrogen production. The preference for N-N scission mechanisms was rationalized by analyzing the electronic structure. This analysis showed that upon hydrazine adsorption, the π bond between nitrogen atoms becomes weaker
Influence of hydro-soluble polymeric stabilizers in nano-catalysis: molecular weight effect
No full textThe effect of carbon nanofibers surface properties in hydrogenation and dehydrogenation reactions
No full textIn this study, carbon nanofiber-supported Pd nanoparticles were used in the hydrogenation of cinnamaldehyde and in the dehydrogenation of cinnamyl alcohol. The different graphitisation of the surface of the nanofibers and the amount of oxygen functionalisation significantly affected both activity and selectivity to the various reaction products. In particular, a decrease in nanoparticle dimensions and oxygen content resulted in an increase in overall activity for both of the studied reactions. Moreover, the selectivity to hydrocinnamaldehyde enhanced with increasing surface oxygen content in the cinnamaldehyde hydrogenation, while the selectivity to cinnamaldehyde was higher with low-functionalised nanofibers in the cinnamyl alcohol dehydrogenation. Finally, the most active catalyst proved also to be stable in consecutive runs
Plasmonic Oxidation of Glycerol Using Au/TiO2 Catalysts Prepared by Sol-Immobilisation
Full text linkAu nanoparticles supported on P25 TiO2 (Au/TiO2) were prepared by a facile sol-immobilisation method and investigated for the surface plasmon-assisted glycerol oxidation under base-free conditions. The Au/TiO2 samples were characterized by UV–vis spectroscopy and transmission electron microscopy. Catalysts were prepared using polyvinyl alcohol as stabiliser as well as in the absence of polymer stabiliser. Both the conversion and the reaction selectivity are affected by the plasmon-assisted oxidation and there is an interplay between the presence of the stabiliser and the Au nanoparticle size
A Career in Catalysis: Graham J. Hutchings
Full text linkThis Account is to commemorate the 70th birthday of Graham Hutchings and his diverse and distinguished career in catalysis, working in industry and academia. The scope of his work is wide ranging, and he has contributed to many areas of catalysis and has been a pioneer in several of them. Notable contributions to the discipline include novel methods of catalyst preparation for both metal oxides and supported nanoparticles, selective oxidation, acetylene hydrochlorination, and direct hydrogen peroxide synthesis, and he has played a central role in the discovery, application, and understanding of gold-based catalysts. The aim of this article is to provide an outline of his career and highlight some of the contributions he has made to the field of catalysis. Successfully supervising over 190 Ph.D. students, working directly with more than 90 postdoctoral researchers, and collaborating widely nationally and internationally, his work has influenced many in the discipline of heterogeneous catalysis
Optimization of sol-immobilized bimetallic Au–Pd/TiO2 catalysts: reduction of 4-nitrophenol to 4-aminophenol for wastewater remediation
Full text linkA sol-immobilization method is used to synthesize a series of highly active and stable AuxPd1−x/TiO2 catalysts (where x = 0, 0.13, 0.25, 0.5, 0.75, 0.87 and 1) for wastewater remediation. The catalytic performance of the materials was evaluated for the catalytic reduction of 4-nitrophenol, a model wastewater contaminant, using NaBH4 as the reducing agent under mild reaction conditions. Reaction parameters such as substrate/metal and substrate/reducing agent molar ratios, reaction temperature and stirring rate were investigated. Structure-activity correlations were studied using a number of complementary techniques including X-ray powder diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. The sol-immobilization route provides very small Au–Pd alloyed nanoparticles, with the highest catalytic performance shown by the Au0.5Pd0.5/TiO2 catalyst.This article is part of a discussion meeting issue ‘Science to enable the circular economy’
Hydrous hydrazine decomposition for hydrogen production using of ir/ceo2: Effect of reaction parameters on the activity
Full text linkIn the present work, an Ir/CeO2 catalyst was prepared by the deposition–precipitation method and tested in the decomposition of hydrazine hydrate to hydrogen, which is very important in the development of hydrogen storage materials for fuel cells. The catalyst was characterised using different techniques, i.e., X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with X‐ray detector (EDX) and inductively coupled plasma—mass spectroscopy (ICP‐MS). The effect of reaction conditions on the activity and selectivity of the material was evaluated in this study, modifying parameters such as temperature, the mass of the catalyst, stirring speed and concentration of base in order to find the optimal conditions of reaction, which allow performing the test in a kinetically limited regime
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