Search

This work is aimed at evaluating the performance of several catalysts in the partial hydrogenation of sunflower oil. The catalysts are composed of noble (Pd and Pt) and base metals (Ni, Co and Cu), supported on both silica and alumina. The following order can be proposed for the effect of the metal on the hydrogenation activity: Pd > Pt > Ni > Co > Cu. At a target iodine value of 70 (a typical value for oleomargarine), the production of trans isomers is minimum for supported nickel catalysts (25.7–32.4 %, depending on the operating conditions). Regarding the effect of the support, Al2O3 allows for more active catalysts based on noble metals (Pd and Pt) and Co, the effect being much more pronounced for Pt. Binary mixtures of catalysts have been studied, in order to strike a balance between catalyst activity and product distribution. The results evidence that Pd/Al2O3–Co/SiO2 mixture has a good balance between activity and selectivity, and leads to a very low production of trans isomers (11.8 %) and a moderate amount of saturated stearic acid (13.5 %). Consequently, the utilization of cobalt-based catalysts (or the addition of cobalt to other metallic catalysts) could be considered a promising alternative for the hydrogenation of edible oil.

This work focuses on the influence of the support and the preparation method on the activity and selectivity of nickel catalysts in the hydrogenation of sunflower oil. Catalysts were prepared over silica and alumina supports following the incipient wetness impregnation and deposition-precipitation techniques. The activation process was followed by temperature-programmed reduction (TPR). Precipitation-deposition method allowed a stronger metal-support interaction than incipient wetness impregnation. A precipitation-deposition time of 14 h (which allowed a Ni loading of about 20wt%) was deemed as the most adequate from the standpoint of high specific surface area and strong Ni-support interaction. The selectivity to oleic acid was not affected by the preparation method, but it was significantly influenced by the type of support. In this regard, the catalysts prepared on silica are more active and produce less saturated fatty acids.

Bone is an inorganic template containing organic material inside which can be converted into hydroxyapatite-rich material by pyrolysis. Nowadays, there is a growing research interest in the use of hydroxyapatite, the chemical formula of which is Ca10(PO4)6(OH)2. In the present work, pork bone, an abundant biomass source and food waste, has been converted into structured porous hydroxyapatite by a three-step process including precharring under mild conditions, chemical activation, and thermal activation. The investigated activating agents were NaOH, KOH, K2CO3, H2SO4, and H3PO4. A thorough investigation of the influence of different activating protocols on the chemical and textural properties of the produced material was carried out by nitrogen adsorption–desorption at 77 K, potentiometric titrations, Fourier transform infrared, and X-ray diffraction techniques. Chemical activation with NaOH, K2CO3, and H2SO4 increased the specific surface area up to 53%. H3PO4 reduced both surface area and pore volume, and KOH showed little influence on the pore structure. The produced materials were evaluated by methylene blue adsorption tests and showed significant improvement as a result of chemical activation. As a main effect, acid treatment increased methylene blue adsorption kinetics, probably owing to an increase in micropororosity, whereas alkali activation enhanced the adsorption capacity of the resultant biochar.

The solubilities of the fatty acids, tetradecanoic (myristic), hexadecanoic (palmitic), and octadecanoic (stearic), and of the triglycerides, glyceryl tridodecanoate (trilaurate), glyceryl trimyristate, glyceryl tripalmitate, and glyceryl tristearate, in 1-bromopropane were measured by the dynamic method from (280 to 350) K. The solubility of fatty acids decreased with the increase of molecular weight and was lower than ideal solubility. The systems triglycerides-1-bromopropane presented negative deviations of Raoult's law. The experimental data were correlated with Van Laar, Wilson, nonrandom two-liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC) equations.

Isobaric vapor−liquid equilibrium (VLE) data were determined for the binary systems 3-methylbutan-1-ol (3-methyl-1-butanol) + ethyl (2S)-2-hydroxypropanoate (ethyl lactate) and pentan-1-ol (1-pentanol) + ethyl lactate at two pressures (13.0 and 101.3 kPa). The data were obtained using a vapor recirculating-type equilibrium device. Calculations of the nonideality of the vapor phase were made with the second virial coefficients evaluated from the Hayden−O’Connell method. VLE experimental data were tested by Herrington and a modified DECHEMA test, which proved their thermodynamic consistency. The activity coefficients and boiling points of the solutions were well correlated with the mole fraction using Wilson, NRTL, and UNIQUAC equations. The mixtures do not present azeotropes.

Isobaric vapor−liquid equilibrium data at 101.325 kPa have been determined for the binary systems 3-methyl-1-butanol + 3-methyl-1-butyl ethanoate and 1-pentanol + pentyl ethanoate. The data were obtained using a vapor recirculating-type equilibrium still. Vapor pressures of 3-methyl-1-butanol and 3-methyl-1-butyl ethanoate were measured in a Swiestoslawski apparatus. Calculations of the nonideality of the vapor phase were made with the second virial coefficients evaluated from the Hayden−O’Connell method. The activity coefficients and boiling points of the solutions were well-correlated with the mole fraction using the Wilson, nonrandom two-liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC) equations. The mixtures do not present an azeotrope.

Density, refractive index and speed of sound at 298.15 K, together with isobaric vapor−liquid equilibria data (VLE) at 101.3 kPa are reported for two binary mixtures, methanol + ethyl lactate and 1-propanol + ethyl lactate. Excess molar volumes on mixing were determined from the experimental data and consequently fitted with Redlich−Kister polynomials. VLE experimental data were tested by Dechema test, which proved their thermodynamic consistency. The activity coefficients were correlated with the Margules, van Laar, UNIQUAC, NRTL, and Wilson equations. The Analytical Solutions of Groups and Universal quasichemical Functional group Activity Coefficients models were also used for the prediction. Investigated binary systems did not show any azeotrope.

The solubilities of lauric acid in n-hexane, acetone, 2-propanol, propanol, 1-bromopropane, and trichloroethylene have been measured using a dynamic equilibrium method from (279.0 to 315.3) K. All systems present positive deviations of the ideal behavior. The solvent that presented the lowest average deviation, concerning the ideality of the system, was trichloroethylene, and the highest value of deviation was found in acetone. The experimental solubility data were correlated with the NRTL, Wilson, and UNIQUAC models. In the n-hexane case, the correction for the existence of dimers was applied. The best results were obtained using UNIQUAC with 0.26 K average root-mean-square deviation of temperature. The solubility in pure solvents decreased in the order: trichloroethylene > 1-bromopropane > 2-propanol > propanol > acetone > n-hexane.

The solubility of palmitic acid has been measured in ethanol, 2-propanol, acetone, heptane, hexane, and trichloroethylene and in the azeotropic mixtures of the solvents (ethanol−heptane; hexane−ethanol; ethanol−trichloroethylene; acetone−heptane; heptane−2-propanol; acetone−hexane; hexane−2-propanol; 2-propanol−trichloroethylene), by a dynamic method, from (290 to 325) K. Solubility data in pure solvents were fitted by the Wilson, NRTL, and UNIQUAC equations and the solubility of palmitic acid in azeotropic mixtures with the NIBS/Redlich−Kister equation. For all calculated results, the root-mean-square deviations of solubility temperatures vary from (0.2 to 0.82) K, depending on the equation used. The solubility in pure solvents decreased in the order: trichloroethylene > 2-propanol > hexane > heptane > acetone > ethanol. The solubility of the palmitic acid increased in azeotropic mixtures compared to the pure solvents, except for the ethanol−trichloroethylene mixture where the solubility was similar to t...

The solubility of stearic acid was measured in ethanol, 2-propanol, heptane, hexane, acetone, and trichloroethylene and in the azeotropic mixtures of the solvents (ethanol−heptane; hexane−ethanol; ethanol−trichloroethylene; acetone−heptane; heptane−2-propanol; acetone−hexane; hexane−2-propanol; 2-propanol−trichloroethylene), by the phase disappearance method, from (290 to 325) K. The stearic acid−pure solvent experimental data were correlated with the Van Laar, Wilson, NRTL, and UNIQUAC equations and the solubility of stearic acid in azeotropic mixtures with the NIBS/Redlich−Kister equation. The UNIFAC solubility prediction improved when the correction for the existence of stearic acid dimers was applied except for systems with trichloroethylene and 2-propanol. The solubility of stearic acid increased in azeotropic mixtures regarding pure solvents except for the heptane−acetone and hexane−acetone mixtures.

The effect upon kinetic behaviour (activity and selectivity) of the physical properties (pore volume distribution) and acidic characteristics (nature of acidic sites and acidic strength distribution) of acidic catalysts in the skeletal isomerization of n-butenes has been studied. The catalysts studied are the following: γ-alumina, alumina modified by introduction of F, Cl and Br, silica–alumina, HZSM-5 zeolite-based catalyst and SAPO-34-based catalyst. It has been proven that the selectivity of acidic catalysts towards the skeletal isomerization of n-butenes is the result of a compromise between pore shape selectivity and intrinsic selectivity of the acidic sites of different strength, this latter property being more significant. Strong acidic sites are needed for the skeletal isomerization, but sites which are too strong produce important amounts of byproducts. A chlorinated alumina is a highly active and selective catalyst for skeletal isomerization. © 1998 SCI.

The skeletal isomerization of n-butenes over a chlorinated alumina catalyst has been studied, by operating under reaction−regeneration cycles in an isothermal fixed-bed integral reactor. The limiting values of the reaction and regeneration temperatures for avoiding irreversible deactivation by loss of chlorine have been determined. Reversible deactivation by deposition of coke, which is completely removable by combustion, is unavoidable. The effect of the operating conditions upon the deposition of coke and the deterioration of the porous structure as a consequence of the deposition have been analyzed.

The selective deactivation by coke deposition in the skeletal isomerization of n-butenes over a chlorinated alumina catalyst has been studied. The methodology used is based on that described in previous work (Gayubo et al., 1993), where the selective deactivation of a silica-alumina catalyst used in the double bond isomerization of n-butenes was studied. For this reaction, the triangular kinetic scheme establishes the interconversion between 1-, cis- and trans-butene.

The solubilities of anthracene and anthraquinone in isopropyl alcohol, methyl ethyl ketone, acetonitrile and isopropyl alcohol-methyl ethyl ketone, isopropyl alcohol-acetonitrile mixtures, have been measured for temperatures ranging from 298 to 318 K. The solubility data have been correlated as functions of the temperature. Activity coefficients for anthracene have been estimated from the group contribution method UNIFAC and with them were calculated solubility data that were compared with the experimental ones.

Isobaric vapor-liquid equilibrium data are reported for the binary systems cumene + benzyl alcohol and phenol + benzyl alcohol at 10 kPa. The activity coefficient data were tested for thermodynamic consistency by the methods of Herington, Black, and Van Ness and correlated with the Wilson equation. None of the systems show an azeotrope.

are negative. In the case of aqueous solutions the B,,o) values as absolute values are larger than B,," values. From this it follows that the addition of acetamide to water reduces the difference between B,, and B,,,,,; however, the Bi,s(O) values increase only a lik. Moreover, it is noticed that the coefficient BI,so as absolute value increases with increasing ionic radii. The facts observed lead one to conclude that the Iion has the largest breaking effect on the structure of water-acetamide mixture. The effect of temperature on Bi,s (parameter a ) decreases with increasing ionic radii.

Les solubilites de l'anthracene et de l'anthraquinone dans le dioxanne-1,4, le N,N-dimethylformamide, l'ethylene glycol et des melanges dioxanne-ethylene glycol sont mesurees entre 303 et 323 K (de 338 et 433 K dans l'ethylene glycol)

Les coefficients d'activite sont testes avec les methodes de Herington, Black et van Ness et correles avec les equations de Norrish, Twigg et Wilson