Search results for: L. Ronchin

Items from 1 to 20 out of 21 results

article

Effectiveness of crystalline admixtures and lime/cement coated granules in engineered self-healing capacity of lime mortars

C. Nardi, S. Bullo, L. Ferrara, L. Ronchin, more

Materials and Structures > 2017 > 50 > 4 > 1-12

Recently, the use of lime mortars in the restoration of historic buildings has found a renewed interest because they can guarantee the required mechanical, chemical and physical compatibility with the existing substrate. Spontaneous occurrence of self-healing phenomena in lime-based mortars is well known; the possibility of engineering the self-healing capacity, through tailored additions, is therefore...

article

Inhibitive action of gramine towards corrosion of mild steel in deaerated 1.0M hydrochloric acid solutions

G. Quartarone, L. Ronchin, A. Vavasori, C. Tortato, more

Corrosion Science > 2012 > 64 > Complete > 82-89

The effect of addition of gramine on mild steel dissolution in deaerated 1.0M hydrochloric acid was studied through potentiodynamic polarisation curves, electrochemical impedance spectroscopy and gravimetric measurements in the temperature range from 25°C to 55°C. Gramine was found to shift the corrosion potentials towards less noble values and decrease both dissolution of mild steel and hydrogen...

article

Acid catalyzed alkylation of phenols with cyclohexene: Comparison between homogeneous and heterogeneous catalysis, influence of cyclohexyl phenyl ether equilibrium and of the substituent on reaction rate and selectivity

L. Ronchin, A. Vavasori, L. Toniolo

Journal of Molecular Catalysis. A, Chemical > 2012 > 355 > Complete > 134-141

The reactivity of several phenols toward liquid phase alkylation with cyclohexene in the presence of heterogeneous and homogeneous acid catalyst at 358K is studied. The comparison between Amberlyst 15 and CH ₃ SO ₃ H, as examples of heterogeneous and homogeneous systems, shows a higher activity of the former with different behavior of selectivity between the two systems, anyway, in...

article

Kinetics and mechanism of acid catalyzed alkylation of phenol with cyclohexene in the presence of styrene divinylbenzene sulfonic resins

L. Ronchin, G. Quartarone, A. Vavasori

Journal of Molecular Catalysis. A, Chemical > 2012 > 353-354 > Complete > 192-203

The kinetics of phenol cyclohexylation catalyzed by sulfonic resins is studied taking into account equilibria and side reactions observed in the reaction media. The influence of different sulfonic resins has been tested and only small variation of the catalyst activity, referred to the acid amount, has been observed. Besides, the selectivity is unaffected by varying the type of the catalyst. The effect...

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On the mechanism of the organocatalyzed Beckmann rearrangement of cyclohexanone oxime by trifluoroacetic acid in aprotic solvent

L. Ronchin, A. Vavasori

Journal of Molecular Catalysis. A, Chemical > 2009 > 313 > 1-2 > 22-30

The Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam in high yield catalyzed by trifluoroacetic acid in aprotic solvents is described. The influence of the concentration of reagents, intermediates, solvents on reaction rate and selectivity in ɛ-caprolactam is studied. The identification of the key intermediate and its role in the catalysis are reported together with the influence of...

article

Selective hydrogenation of ethyl-benzoylacetate to 3-hydroxy-3-phenyl-propionate catalyzed by Pd/C in EtOH as a solvent in the presence of KOH: The role of the enolate ion on the reaction mechanism

L. Ronchin, A. Vavasori, D. Bernardi, G. Cavinato, more

Applied Catalysis A, General > 2009 > 355 > 1-2 > 50-60

The selective hydrogenation of ethyl-benzoylacetate to 3-hydroxy-3-phenyl-propionate catalyzed by Pd/C in EtOH in a solution of KOH has been investigated. Mass transfers as well as adsorption and desorption stages do not influence reaction kinetics. A kinetic model is proposed based on the best fitting of the experimental data with Langmuir–Hinshelwood type kinetics equation. The mechanism implies...

article

New carboalkoxybis(triphenylphosphine)palladium(II) cationic complexes: Synthesis, characterization, reactivity and role in the catalytic hydrocarboalkoxylation of ethene. X-ray structure of trans-[Pd(COOMe)(TsO)(PPh3)2]·2CHCl3

E. Amadio, G. Cavinato, A. Dolmella, L. Ronchin, more

Journal of Molecular Catalysis. A, Chemical > 2009 > 298 > 1-2 > 103-110

The cationic complexes trans-[Pd(COOR)(H ₂ O)(PPh ₃ ) ₂ ](TsO) have been synthesised by reacting cis-[Pd(H ₂ O) ₂ (PPh ₃ ) ₂ ](TsO) ₂ ·2H ₂ O with CO in ROH (R=Me and Et), practically under room conditions, or by methathetical exchange of trans-[Pd(COOMe)Cl(PPh ₃ ) ₂ ] with Ag(TsO) (R=n-Pr, iso-Pr, n-Bu, iso-Bu,...

article

Oxidative carbonylation of phenols catalyzed by homogeneous and heterogeneous Pd precursors

L. Ronchin, A. Vavasori, E. Amadio, G. Cavinato, more

Journal of Molecular Catalysis. A, Chemical > 2009 > 298 > 1-2 > 23-30

Homogeneous and heterogeneous Pd-based catalysts (in the presence of Co(acac) ₃ /ligand/BQ/TBAB and molecular sieve 4A), have been compared in the oxidative carbonylation of phenols. The best yields have been observed in the presence of bulky bidentate N-N ligands such as dmphen and triind. The comparison between homogeneous and heterogeneous systems shows similar behavior in terms of yield...

article

Organocatalyzed Beckmann rearrangement of cyclohexanone oxime by trifluoroacetic acid in aprotic solvent

L. Ronchin, A. Vavasori, M. Bortoluzzi

Catalysis Communications > 2008 > 10 > 2 > 251-256

The Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam catalyzed by trifluoroacetic acid in aprotic solvents such as toluene, 1,2-dichloroethane, acetonitrile, benzonitrile, nitromethane and their mixtures is described. High yield and selectivity in ε-caprolactam have been observed. Data relative to cyclohexanone oxime protonation equilibrium, interaction of ε-caprolactam with the acid,...

article

Part 2: Influence of acid catalysts and organic promoters

N.C. Marziano, L. Ronchin, C. Tortato, A. Vavasori, more

Journal of Molecular Catalysis. A, Chemical > 2008 > 290 > 1-2 > 79-87

The influence of some transition metal oxide promoters in the catalyzed Beckmann rearrangement of cyclohexanone oxime was studied by preparing several heterogeneous H ₂ SO ₄ /M/SiO ₂ catalysts using SiO ₂ as support and H ₂ SO ₄ as acid source. A definite effect of each metal has been observed and the best results have been obtained with Cr-, Zr- and...

article

A DFT study on secondary reaction pathways in the acid-catalysed Beckmann rearrangement of cyclohexanone oxime in aprotic solvent

L. Ronchin, M. Bortoluzzi, A. Vavasori

Journal of Molecular Structure: THEOCHEM > 2008 > 858 > 1-3 > 46-51

In recent studies regarding acid-catalysed Beckmann rearrangement of cyclohexanone oxime in aprotic solvents it has been observed that a quite surprising hydrolysis of the starting material, i.e., cyclohexanone oxime, occurs even if the experimental conditions and the water concentration in the reaction mixture can not justify such a side-reaction. Being this apparent hydrolysis critical for catalyst...

article

Part 1: Batch and continuous operation with supported acid catalysts

N.C. Marziano, L. Ronchin, C. Tortato, A. Vavasori, more

Journal of Molecular Catalysis. A, Chemical > 2007 > 277 > 1-2 > 221-232

Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam has been studied in heterogeneous liquid/solid system at room temperature and pressure. In this first part preparation, characterization and reactivity of impregnated strong acids on solid support have been investigated, with particular attention to H ₂ SO ₄ /SiO ₂ catalysts. The influence of many preparative variables...

article

Part 2: Oxidations of alcohols and ketones over solid acid catalysts

N.C. Marziano, L. Ronchin, C. Tortato, S. Ronchin, more

Journal of Molecular Catalysis. A, Chemical > 2005 > 235 > 1-2 > 26-34

The reactivity of a nitrosating agent (N ₂ O ₃ ) on oxidations of alcohols and the methyl group of acetophenone were tested. Active electrophylic surface nitrosonium ions (NO ⁺ ) was detected on H ₂ SO ₄ /SiO ₂ catalysts by Raman spectroscopy, suggesting a surface ionic mechanism of oxidation in agreement with the one proposed in acid aqueous solutions...

article

Part 1: Oxidations of ketones in concentrated sulfuric acid

N.C. Marziano, L. Ronchin, C. Tortato, A. Zingales, more

Journal of Molecular Catalysis. A, Chemical > 2005 > 235 > 1-2 > 17-25

Selective oxidations by nitrous acid in aqueous sulfuric acid towards alkyl side chains of enolizable ketones are reported. The conversion reagents–products in different experimental conditions is explored and the reaction path of the compounds involved as intermediates is tested. Side-chain oxidations are particularly successful for substrates with one site or with equivalent sites of oxidation....

article

Selective oxidations by nitrosating agents in liquid and solid acid catalysts

N.C. Marziano, L. Ronchin, C. Tortato

Catalysis Today > 2004 > 91-92 > Complete > 225-229

The oxidative properties of N ₂ O ₃ and NO ⁺ ion towards methyl or methylene groups of enolizable ketones are tested at 25 ^o C in homogeneous and heterogeneous acid systems. The results in concentrated aqueous sulphuric acid show that reasonable good yields (~95%) of benzoylformic acid from acetophenone are obtained at selected acidity ranges. A kinetic study for the...

article

Selective hydrogenation of benzene to cyclohexene catalyzed by Ru supported catalysts - Influence of the alkali promoters on kinetics, selectivity and yield

L. Ronchin, L. Toniolo

Catalysis Today > 2001 > 66 > 2-4 > 363-369

The selective hydrogenation of benzene to cyclohexene in the presence of Ru supported catalysts has been investigated in a tetraphase slurry reactor at 423K, at 5MPa of pressure, in the presence of two liquid phases: benzene and an aqueous solution of ZnSO ₄ (0.6moll ^- ¹ ). A study of the influence of the transport phenomena on the reactivity of the catalyst has been carried out...

article

Selective hydrogenation of benzene to cyclohexene using a Ru catalyst suspended in an aqueous solution in a mechanically agitated tetraphase reactor: a study of the influence of the catalyst preparation on the hydrogenation kinetics of benzene and of cyclohexene

L. Ronchin, L. Toniolo

Applied Catalysis A, General > 2001 > 208 > 1-2 > 77-89

The reactivity of Ru based catalysts in the benzene selective hydrogenation to cyclohexene has been studied. The reaction has been carried out in a tetraphase slurry reactor at 423K, at 5MPa of pressure, in the presence of two liquid phases: benzene and an aqueous solution of 0.6moll ^- ¹ ZnSO ₄ . A detailed kinetic measurement has been carried out in order to study the influence...

article

Hydrogenation of mandelic acid derivatives to the corresponding phenyl acetic acid derivative catalysed by Pd/C. A kinetic study

L. Ronchin, L. Toniolo, G. Cavinato

Applied Catalysis A, General > 1997 > 165 > 1-2 > 133-145

The hydrogenolysis of the α-C—O bond of mandelic acid derivatives catalysed by 5% Pd/C, in the presence of hydrochloric or sulphuric acids as cocatalysts, was carried out in water or ethanol as solvent, under 35–150 kPa of hydrogen pressure, at 343 K. Typically, the substrate/catalyst/cocatalyst ratio was 200 : 1 : 10. The hydrogenation of the ethyl ester of mandelic acid in ethanol as solvent is...

article

Palladium catalyzed hydrodechlorination of α-chloroacetophenones by hydrogen transfer from the H ₂ O-CO system

M. Pasqualetto, L. Ronchin, L. Toniolo, G. Cavinato

Journal of Molecular Catalysis. A, Chemical > 1997 > 125 > 1 > 15-22

PdCl ₂ (PPh ₃ ) ₂ , in combination with an extra amount of PPh ₃ , is an excellent catalyst precursor for the hydrodechlorination of α-chloroacetophenone to acetophenone by hydrogen transfer from the H ₂ O-CO system. The reaction occurs with concomitant evolution of CO ₂ . Under typical reaction conditions (50-70°C, 40-80 atm, substrate/Pd/P = 2000/1/50,...

article

Synthesis of arylacetic acid derivatives from mandelic acid derivatives by hydrogen transfer from H ₂ O-CO catalyzed by a Pd/C-HCl system

G. Cavinato, L. Toniolo, L. Ronchin

Journal of Molecular Catalysis. A, Chemical > 1995 > 102 > 3 > 129-134

A Pd/C-HCl catalytic system is highly active and selective in the hydrogen transfer from H ₂ O-CO to ArCHOHCOOH for the synthesis of ArCH ₂ COOH (Ar is para substituted with a OH group). Typical reaction conditions are: temperature 50-70°C; P _C _O 20-80 atm; solvent: acetonitrile; substrate/Pd/HCl/H ₂ O = 200-400/1/25-100/500-2000; [Pd] = 0.6-1.2 mmol l ^- ...

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Search results for: L. Ronchin

Effectiveness of crystalline admixtures and lime/cement coated granules in engineered self-healing capacity of lime mortars

Inhibitive action of gramine towards corrosion of mild steel in deaerated 1.0M hydrochloric acid solutions

Acid catalyzed alkylation of phenols with cyclohexene: Comparison between homogeneous and heterogeneous catalysis, influence of cyclohexyl phenyl ether equilibrium and of the substituent on reaction rate and selectivity

Kinetics and mechanism of acid catalyzed alkylation of phenol with cyclohexene in the presence of styrene divinylbenzene sulfonic resins

On the mechanism of the organocatalyzed Beckmann rearrangement of cyclohexanone oxime by trifluoroacetic acid in aprotic solvent

Selective hydrogenation of ethyl-benzoylacetate to 3-hydroxy-3-phenyl-propionate catalyzed by Pd/C in EtOH as a solvent in the presence of KOH: The role of the enolate ion on the reaction mechanism

New carboalkoxybis(triphenylphosphine)palladium(II) cationic complexes: Synthesis, characterization, reactivity and role in the catalytic hydrocarboalkoxylation of ethene. X-ray structure of trans-[Pd(COOMe)(TsO)(PPh3)2]·2CHCl3

Oxidative carbonylation of phenols catalyzed by homogeneous and heterogeneous Pd precursors

Organocatalyzed Beckmann rearrangement of cyclohexanone oxime by trifluoroacetic acid in aprotic solvent

Part 2: Influence of acid catalysts and organic promoters

A DFT study on secondary reaction pathways in the acid-catalysed Beckmann rearrangement of cyclohexanone oxime in aprotic solvent

Part 1: Batch and continuous operation with supported acid catalysts

Part 2: Oxidations of alcohols and ketones over solid acid catalysts

Part 1: Oxidations of ketones in concentrated sulfuric acid

Selective oxidations by nitrosating agents in liquid and solid acid catalysts

Selective hydrogenation of benzene to cyclohexene catalyzed by Ru supported catalysts - Influence of the alkali promoters on kinetics, selectivity and yield

Selective hydrogenation of benzene to cyclohexene using a Ru catalyst suspended in an aqueous solution in a mechanically agitated tetraphase reactor: a study of the influence of the catalyst preparation on the hydrogenation kinetics of benzene and of cyclohexene

Hydrogenation of mandelic acid derivatives to the corresponding phenyl acetic acid derivative catalysed by Pd/C. A kinetic study

Palladium catalyzed hydrodechlorination of α-chloroacetophenones by hydrogen transfer from the H ₂ O-CO system

Synthesis of arylacetic acid derivatives from mandelic acid derivatives by hydrogen transfer from H ₂ O-CO catalyzed by a Pd/C-HCl system

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