Italo Ferino

Microcalorimetric characterisation of acid–basic catalysts

Abstract Fundamentals of microcalorimetry are briefly reviewed. A heat-flow microcalorimeter of the Tian–Calvet type has been used to obtain information on the differential molar enthalpy of adsorption. Ammonia, pyridine, n-butylamine or CO2 and SO2 have been used to characterize the acid–base properties of several catalysts such as zeolites and oxides.

Liquid-phase alkylation of naphthalene by isopropanol over zeolites. Part II : Beta zeolites

The title reaction has been studied on various HY-based catalysts. Surface acidity has been evaluated by adsorption microcalorimetry and FTIR analysis, using pyridine as probe molecule. Catalytic tests were carried out at 623 K and 40 bar in liquid phase, with decalin as solvent, in flow reactor. Isopropylation is accompanied by oligomerisation/cracking of the reactant alcohol, cracking of the solvent, isomerization of the products of the main reaction. Pore filling by coke is fast for non-dealuminated HY, where naphthalene conversion remains high due to the occurrence of transalkylation between polyisopropylnaphthalenes trapped in the pores and naphthalene; this does not occur on dealuminated HY, owing to the low density of the acid sites and the presence of a secondary mesoporous system which allows easy diffusion of the reaction products in the zeolite pores.

Acid–base properties and catalytic activity of nanophase ceria–zirconia catalysts for 4-methylpentan-2-ol dehydration

The room-temperature high energy ball-milling technique was used to prepare nanophase Ce1-xZrxO2 (x=0; 0.2; 0.5; 0.8; 1) catalysts. The acid–base properties of these catalysts were investigated by means of adsorption microcalorimetry, using NH3 and CO2 as probe molecules. The catalytic activity for 4-methylpentan-2-ol dehydration was tested at atmospheric pressure in a fixed-bed flow microreactor. The inclusion of increasingly high contents of zirconium into the ceria lattice has a complex influence on the acidity and basicity of the pure parent oxide, in terms of both number and strength of the sites. A maximum in 1-alkene selectivity is observed for the ceria-rich catalyst and a minimum for the zirconia-rich sample. Catalytic results are correlated with the acid–base properties and can be interpreted in the light of the mechanism formerly proposed for zirconia, ceria and lanthania. Surface conditioning of the zirconia-rich catalyst occurs during the run, resulting in a remarkable variation of selectivity.

Thermodynamic properties of aqueous non-electrolyte mixtures. Alkanols + + water systems.

Abstract The molar excess enthalpies, H E , at 298.15 K, and the liquid-liquid equilibrium, LLE, of aqueous mixtures of alkanols have been measured. The results are interpreted qualitatively in terms of intercomponent molecular interactions and hydrophobic stabilization of the water structure by the alkanol molecules. The results obtained indicate that the geometry, the number of alkyl groups in the aliphatic chain and the relative position of the functional group -OH have an important action on these two effects.

4-Methylpentan-2-ol dehydration over zirconia catalysts prepared by sol-gel

Zirconia samples have been prepared from xerogels and aerogels obtained using zirconium n-propoxide as precursor. Structure and texture have been investigated by X-ray diffraction, thermal analysis, transmission electron microscopy, nitrogen adsorption/desorption. Surface acidity and basicity have been assessed by adsorption microcalorimetry, using ammonia and carbon dioxide as probe molecules. 4-Methylpentan-2-ol dehydration has been tested at atmospheric pressure in a fixed-bed flow microreactor. The xerogel gives tetragonal zirconia upon calcination, during which a mesoporous system is formed. The crystal phase depends on the presence of oxygen during the cooling step in the case of the aerogel, whose texture is partially retained upon calcination. Both kinds of catalysts have well-balanced concentrations of acid and base sites, but the acid sites are weaker in comparison with the basic ones. At 603 K the initial conversion of 4-methylpentan-2-ol over the calcined xerogel and aerogel is 45 and 63%, respectively; the selectivity to 4-methylpent-1-ene is 77% for both. The occurrence of an E2-like mechanism with the activated complex having a marked carbanionic character seems probable. The aerogel catalyst is quite stable during operation, whereas changes in activity and selectivity are observed for the xerogel catalyst.

CeO2–La2O3 catalytic system Part I. Preparation and characterisation of catalysts

The CeO2–La2O3 catalytic system was prepared by a sol–gel technique from inorganic precursors in the presence or absence of H2O2 . Samples were characterised by means of nitrogen physisorption, TG-DTA, XRD, IR, XPS and TEM. Preparation ia sol–gel in the presence of H2O2 produces certain interesting modifications in CeO2–La2O3, both structurally and morphologically. Higher surface areas have been found for the CeO2–La2O3 system prepared in the presence of H2O2. On the other hand, for La2O3 the structure obtained upon calcination at 873 K corresponds to La(OH)3, and for the system prepared with hydrogen peroxide, to a mixture of La(OH)3, and La2O3 which was detected by XRD. Interesting morphological differences were observed for both systems.

Thermodynamic properties of binary mixtures containing aldehydes. I. Excess enthalpies of some n-alkanal + n-alkane mixtures: Measurement and analysis in terms of a quasi-chemical group-contribution model and estimation of excess Gibbs Energies

Abstract A Tian—Calvet-type calorimeter has been used to determine molar excess enthalpies at 298.15 K as a function of concentration for the following binary mixtures: ethanal, propanal, butanal or pentanal + hexane, heptane, dodecane or hexadecane. These and the few data available in the literature for liquid—vapor equilibria are examined on the basis of a quasi-chemical theory using group-surface interactions. With two group-interaction parameters and three alkyl-group increments, the model provides a fairly consistent description of the excess enthalpies as functions of composition and n -alkane chain length. Molar excess Gibbs energies are estimated for the n -alkanal + n -alkane mixtures and the results discussed in comparison with the properties of n -alkanone + n -alkane mixtures.

Thermodynamics of binary mixtures containing tertiary amines. I. Excess enthalpies of some N,N-dialkylmethylamine+normal alkane mixtures. Measurement and analysis in terms of group contributions. Estimation of excess gibbs energies

Abstract A Tian-Calvet type calorimeter was used to determine molar excess enthalpies, HE, at 298.15 K, as a function of concentration, for the twelve mixtures: N,N-dimethylethylamine, N,N-dimethylbutylamine, N,N-diethylmethylamine, and N,N-dipropylmethylamine+n-hexane, +n-heptane, +n-dodecane, or + n-hexadecane. This data and the data available in the literature on the liquid-vapour equilibria of trimethylamine + n-hexane are examined based on the quasi-lattice theory, in the random-mixing approximation, using group surface interactions. With two adjusted group interaction parameters and three alkyl-group increments, the model provides a fairly consistent description of HE of the investigated mixtures and an estimate of the molar excess Gibbs energies, GE. The results are discussed in terms of steric and Patterson effects.

Thermodynamics of binary mixtures containing tertiary amines. III. Excess enthalpies of N,N,N′,N′-tetramethylalkanediamine + normal alkane mixtures: A group contribution study of the NN proximity effect

Abstract Ferino, I., Marongiu, B., Solinas, V., Torrazza, S. and Kehiaian, H.V., 1983. Thermodynamics of binary mixtures containing tertiary amines. III. Excess enthalpies of N,N,N′,N′-tetramethylalkanediamine+normal alkane mixtures: a group contribution study of the NN proximity effect. Fluid Phase Equilibria, 11: 1–12. A Tian—Calvet-type calorimeter has been used to determine molar excess enthalpies HE at 298.15 K as a function of concentration for seventeen binary mixtures containing N,N,N′,N′-tetramethylalkanediamine, (CH3)2N(CH2)uN(CH3)2 (u = 0–4), with n-alkanes, CH3(CH2)m-2CH3 (m = 6, 7, 12, 16). The experimental data are interpreted quantitatively on the basis of the same group contribution model which was applied to N,N-dialkylmethylamine+n-alkane mixtures. Comparison of the interchange parameters for diamines, containing two > N- groups, with the corresponding values for monoamines, containing a single > N- group, reveals a significant decrease of intermolecular interactions with decreasing intramolecular > N-...-N

Dehydration of 4-methylpentan-2-ol over lanthanum and cerium oxides

Lanthanum and cerium oxides have been tested for the title reaction at 623 K and atmospheric pressure in a flow reactor. Lanthanum oxide (prepared from the corresponding nitrate) gives mainly 4-methylpent-1-ene (80% of the products). Similar results are observed with cerium oxide obtained from the corresponding hydroxide, whereas cerium oxide prepared from nitrate is less selective towards alk-1-enes. In addition to dehydration, dehydrogenation to 4-methylpentan-2-one is also observed to a limited extent for all the catalysts. Information on the acid–base properties of the samples was obtained by adsorption microcalorimetry of ammonia and carbon dioxide and correlated to reaction selectivities. Possible changes in the oxidation state of cerium ions due to the reaction atmosphere are considered. The present results are compared with former data for zirconia catalysts. Modification of cerium oxide via immersion in NaOH solution does not appear to be useful for improving alk-1-ene selectivity.