BUSCA G.

The different types ofindustrial heterogeneous catalysis heterogeneous catalyst currently applied in the chemical industry are described. The catalytic activity is correlated to their main surface properties, which are the object of investigation based on surface science and theoretical calculations. Acidic, basic, oxidation, hydrogenation, and...

The applications of silica-aluminas in industrial catalytic processes are briefly reviewed. The literature data on the surface chemistry and structural chemistry of silica-aluminas are summarized. The Al-stuffed amorphous silica model is proposed for fully amorphous materials, and described. The reasons for the versatility of these materials as...

The structural, surface chemical and catalytic properties of the materials belonging to the SiO2-Al2O3 system are reviewed critically. In particular, amorphous silicas, transitional aluminas, different silica-aluminas (silica-rich and alumina-rich) and protonic zeolites are taken into consideration. The nature of the acid sites, of the Lewis...

The F.t.i.r. spectra of isobutene adsorbed at 170-300 K on the pure oxides silica, alumina, magnesia and titania, as well as on the phosphated samples prepared by impregnation of these pure oxides and of silica-alumina with phosphoric acid have been recorded. At low temperatures (170-220 K), molecularly adsorbed species are observed on pure...

BACKGROUND: γ-Al2O3 and silica-doped aluminas are largely used supports for industrial catalysts. The addition of silica to alumina modifies its acid–base properties, also affecting its dispersion ability of supported species. In this paper, investigations on the silica doping effect in alumina-supported MoO3 catalysts, developed for the...

The present work reports the feasibility of valorizing waste glass and aluminum scraps into zeotype materials. The raw materials were reacted hydrothermally at 60 °C using alkaline fusion prior to hydrothermal treatment. The obtained powders were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared...

Background: Acetaldehyde is a main organic intermediate for manifold chemical products. In the near future, its production using renewable raw materials is rapidly becoming highly desirable. In this paper, investigations on pure and silica-supported molybdenum oxide (MoO3) as catalysts for the ethanol oxidative dehydrogenation process to...

Two 20 wt.% Co/SiO2 catalysts have been prepared using silica gel as a support and cobalt acetate or nitrate as precursors. They were characterized before and after reaction using XRD, skeletal IR and DR-UV–vis-NIR spectroscopies and FE-SEM microscopy. Fresh catalysts are active in CO2 methanation at atmospheric pressure but rapidly deactivate...

Two 20 wt.% Co/SiO2 catalysts were prepared using silica gel as a support and cobalt acetate and nitrate as precursors, respectively. As a comparison unsupported amorphous cobalt nanoparticles (10–80 nm) were synthesized by decomposing cobalt carbonyl. They were characterized before and after reaction using XRD, IR spectroscopy in the range of...

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The adsorption of nitric oxide, nitrogen dioxide and ammonia and their coadsorption on vanadia-titania have been studied by FT-IR spectroscopy. Upon nitric oxide adsorption, a surface nitrosyl species is formed rapidly and nitrates are formed slowly by oxidation. Nitrogen dioxide adsorption forms nitrate species by oxidation and nitric oxide....

A detailed critical analysis of the scientific literature data concerning catalysts for CO2 methanation based on nickel supported over oxides was performed. According to the obtained information, it seems that an ionic support is necessary to allow a good nickel dispersion to produce very small nickel metal particles. Such small metal particles...

20 wt.% cobalt catalysts supported on pure and 5 wt.% silica-containing alumina have been prepared and characterized by X-Ray Diffraction, IR and DR-UV-vis-NIR spectroscopies and Field-Emission Scanning Electron Microscopy (FE-SEM). The presence of a cobalt-containing surface spinel phase Co3-xAlxO4 and, for the silica-containing sample, of a...

This review begins with the historical development of the theories of acidity and of the preparation of acids. The historical aspects of acid catalysis and catalysts are also briefly surveyed. The fundamentals concerning acidity and acid catalysis in liquid phases and at the solid-liquid interfaces are discussed. The factors determining acidity...

Commercial pure γ-Al2O3 and SiO2 (1−30 wt.%) doped γ-Al2O3 were characterized as acid catalysts in ethanol conversion and used as supports for NiO and MoO3. Supported catalysts were prepared by incipient wetness impregnation. All catalytic materials were characterized by BET, XRD, FE-SEM microscopy, UV–vis and IR spectroscopies. Pure and...

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The waste materials available as sources of silicon and aluminum for producing porous materials like amorphous silicas, aluminas, amorphous silica-aluminas, and zeolites, to be used as catalyst and adsorbents, are briefly summarized. The procedures for preparing these materials from wastes are also taken into account. The limits of this...

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To support the interpretation of the experimental results obtained from two laboratory-scale reactors, one working in the steam methane reforming (SMR) mode, and the other in the CO2 hydrogenation (MCO2) mode, a steady-state pseudo-homogeneous 1D non-isothermal packed-bed reactor model is developed, embedding the classical Xu and Froment local...

Three Ni-based natural gas steam reforming catalysts, i.e., commercial JM25-4Q and JM57-4Q, and a laboratory-made catalyst (26% Ni on a 5% SiO2-95% Al2O3), are tested in a laboratory reactor, under carbon dioxide methanation and methane steam reforming operating conditions. The laboratory catalyst is more active in both CO2 methanation...

BACKGROUND: Catalysts based on alumina-supported metal oxides are of crucial importance in the field of heterogeneous catalysis for several applications requiring tuning of surface acidity. RESULTS: In this work, the effects of K+, Ca2+ and La3+ cation doping have been evaluated on a well-characterized commercial gamma-Al2O3 through...

Copper based catalysts are central for carrying dehydrogenation reactions. However, these materials are prone to deactivation by sintering and coke deposition. Irreversible sintering occurring during reaction (under the effect of temperature) is known to decrease both activity and selectivity, where the unwanted dehydration activity of the...