Renzo Ganzerla

Catalytic behavior of chromia and chromium-doped alumina pillared clay materials for the vapor phase deep oxidation of chlorinated hydrocarbons

Abstract The catalytic behavior of a chromium-doped alumina pillared clay (ACrPA) and a series of chromia-pillared clay materials (XSCr) for the deep oxidation of methylene chloride has been studied. Both types of catalysts showed a high activity (conversion > 80%) at T > 350°C. The ACrPA sample showed a virtually constant catalytic activity (conversion > 99%) in the 300–400°C temperature range while the activity of the XSCr samples markedly increased with the temperature reaching an almost total conversion at 400°C. XPS (X-ray photoelectron spectroscopy) and temperature programmed reduction (TPR) studies demonstrated that ACrPA is a Cr(VI) Cr(III) mixed valence catalyst, whereas XSCr samples contain only chromium(III) ion. The high activity shown by ACrPA at low temperatures was attributed to the presence of highly dispersed Cr(VI) species, which exhibited an unusually high stability. The metal oxidation state of the two chromium based systems seemed to be important in determining the catalytic activity. The increase of the activity with the Cr content in XSCr samples suggested that the acid sites in these catalysts were located on the chromia pillars.

Hexagonal close packed nickel powder: Synthesis, structural characterization and thermal behavior

Abstract Hexagonal close packed nickel powder has been prepared upon reduction of Ni(II) with a K/B liquid alloy. This structural habit is stable at low temperature, undergoing a transition to a face centered cubic phase above 380°C.

Solid acid catalysts from clays: Evaluation of surface acidity of mono- and bi-pillared smectites by FT-IR spectroscopy measurements, NH3-TPD and catalytic tests

Alumina-pillared and double-pillared montmorillonite and saponite samples have been prepared and characterised from the point of view of their thermal stability, porosity and structure. Surface acidity was studied by ammonia TPD, iso-propanol conversion and n-butene skeletal isomerisation catalysis, and by FT-IR spectroscopy of the surface hydroxy-groups, and of adsorbed acetonitrile and pivalonitrile. The data show that the alumina pillars of pillared montmorillonite carry stronger Lewis sites than those of pillared saponite. Additionally, stronger Bronsted sites are carried by the montmorillonite layers with respect to those of saponite. Finally, pillared montmorillonite is more active in converting iso-propanol. However, it is also too active in converting n-butene, so giving rise to faster coking and more extensive cracking. So, pillared saponite has a more selective behavior in converting n-butene into iso-butene. ©2000 Elsevier Science B.V. All rights reserved.

Hydroformylation of simple olefins catalyzed by metals and clusters supported on unfunctionalized inorganic carriers

The results, published in the open literature up to the end of 1995 on the hydroformylation of simple olefins in vapor and liquid phase catalyzed by metals or metal complexes adsorbed on inorganic oxides, clays, active carbons and zeolites, are reviewed.

Highly selective Friedel–Crafts acylation of 2-methoxynaphthlene catalyzed by H-BEA zeolite

Abstract The Friedel–Crafts acylation of 2-methoxynaphthalene with acetic and propionic anhydrides is actively catalyzed by H-BEA zeolite in batch conditions. Zeolite pre-treatment at increasing temperature leads to increasing selectivity of the less bulky 6-acyl-2-methoxy isomer. The selectivity toward the 6-isomer also increases if the catalyst/substrate ratio is increased. Catalyst activity and selectivity are correlated with the extra framework aluminum formation during thermal pretreatments of the zeolite.

Post-synthetic thermal and chemical treatments of H-BEA zeolite: effects on the catalytic activity

Abstract A beta zeolite sample (SiO 2 /Al 2 O 3 =25) was dealuminated by thermal treatment in the 773–1023 K temperature range. One sample, after the treatment at 923 K, was further washed with diluted HCl solution and rinsed with water, in order to remove the extraframework aluminum debris from its surface. Structural and morphological changes were monitored by powder X-ray diffraction, nitrogen adsorption–desorption and FT-IR spectroscopy, the surface acidity was evaluated by temperature programmed desorption of ammonia, FT-IR of adsorbed pyridine and potentiometric titration. The influence of the thermal treatments on the catalytic activity of the zeolite samples was tested in the anisole acylation and the Baeyer–Villiger oxidation of cyclohexanone. The catalytic performances were correlated with the physico-chemical and structural changes induced on the catalyst by the thermal and/or chemical pretreatments.

Solid acid catalysts from clays: Acid leached metakaolin as isopropanol dehydration and 1-butene isomerization catalyst

Abstract Some samples of acid leached kaolin were prepared by calcination of the natural clay at 873 K to obtain metakaolin followed by treatment at 353 K for 4 h with HCl or H 2 SO 4 solutions of various concentrations. Some samples were washed with distilled water after the treatment. The modified clays were studied by chemical analysis, differential thermal analysis (DTA), and X-ray diffraction. The nature and strength of the acid sites was evaluated by FT-IR spectroscopy of adsorbed pyridine. All samples were tested as catalyst for the 1-butene isomerization and isopropanol dehydration. The sulfuric acid treated and washed MKH 2 SO 4 1 Mw sample resulted in a very active isopropanol dehydration catalyst. The MKH 2 SO 4 1 Mw sample and the two unwashed HCl treated samples MKHCl 2 M and MKHCl 6 M were found very active in the conversion of 1-butene to iso -products, which requires strong Bronsted acid sites. The well known K10 catalyst is less active in both reactions and the MKH 2 SO 4 1 Mw catalyst could be proposed as its suitable substitute.

Bifunctional catalysts from pillared clays: Vapour phase conversion of propene to acetone catalyzed by iron and ruthenium containing aluminum pillared bentonites

Abstract A natural bentonite was pillared with aluminum, aluminum—iron and aluminum—ruthenium polyoxocations. The alkali cations of some clays were successively exchanged with iron. The prepared pillared clays were characterized by X-ray diffraction, DTA, TGA, ESCA and N 2 adsorption. The relative amount of Lewis and Bronsted acid sites was estimated from FT-IR spectra of adsorbed pyridine. All the clays resulted active catalysts for the vapour phase conversion of propene to acetone in the 150–350°C temperature range. The reaction appeared to occur via acid catalyzed propene hydration to isopropanol and successive oxidative dehydrogenation of the alcohol to acetone. The reactivity of all the prepared samples was correlated to the nature and number of the redox and acid sites.

Solid acid catalysts from clays: Cumene synthesis by benzene alkylation with propene catalyzed by cation exchanged aluminum pillared clays

The alkylation of benzene with propene to produce cumene was carried out in batch (benzene/propene=20/1) at T=353 K and P=0.55 MPa over aluminum pillared bentonite (APB) exchanged with K+, La3+ and Al3+ cations. Both Al3+ and La3+ exchanged pillared clays were more active than APB. As expected a complete deactivation was observed for the K+ exchanged pillared clay. The large modifications of the catalytic activity cannot be explained by the observed slight textural differences. Cation exchange appeared to strongly modify the amount and nature of the clays acid sites. The relative amount of Lewis and Bronsted acid sites was evaluated by IR spectroscopy of adsorbed pyridine and analyzing the product distribution of the catalytic 1-butene isomerization. An apparent dependence of the reactivity from the amount of strong Lewis acid centers was clearly evident while a relationship with the amount of strong Bronsted acid sites was not found.

Solid acid catalysts from clays: Part 3: benzene alkylation with ethylene catalyzed by aluminum and aluminum gallium pillared bentonites

Abstract A montmorillonite pillared with aluminum (APM) or aluminum/gallium polyoxycations (AGPM) and their respective repillared derivatives (AP2M and AGP2M) were prepared. The materials were characterized by chemical analysis, X-ray diffraction, N 2 adsorption–desorption. The surface acidity was evaluated by FT-IR spectroscopy of adsorbed pyridine and from the analysis of the product distribution of the 1-butene gas phase isomerization. The catalytic activity for the alkylation of benzene with ethylene to produce ethyl benzene was determined and correlated with the samples acidity. The derivatives pillared with Al 12 Ga mixed pillars resulted to be the more active catalysts.