Hydrogenation of sunflower oil over different palladium supported catalysts: Activity and selectivity (original) (raw)
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Palladium supported catalysts for the selective hydrogenation of sunflower oil
Journal of Molecular Catalysis A: Chemical, 2005
Selective hydrogenation of ethyl esters of traditional sunflower oil (SOEE) was carried out at low temperature (40 • C) in ethanol as solvent in the presence of supported palladium catalysts. In the range of studied dispersions (12-55%), the SOEE hydrogenation reaction is insensitive to the size of the palladium particles deposited on silica, but the largest metallic particles enhance the C18:1 cis-trans isomerization. The use of various oxide supports () to deposit palladium does not allow to improve the selectivity of the reaction toward the cis C18:1 compared to Pd/SiO 2 catalysts. On the other hand, the modification of palladium by lead, introduced by surface redox reaction (catalytic reduction), promotes the selectivity in cis C18:1. In addition, this technique of preparation involves a moderate decrease of the palladium activity compared to a traditional method of successive impregnations. The introduction of amines in the reaction medium modifies the hydrogenating properties of the Pd/SiO 2 catalyst. According to the quantity and the nature of the added amine (aliphatic with linear or ramified chain and cyclic compounds), the catalytic activity can either be unchanged or inhibited. These evolutions result from a promoter electronic effect generated by the presence of the amine and from a poison geometric effect related to the adsorption of this nitrogencontaining compound on the palladium surface. Whatever the nature of the amine, it induces an increase of the selectivity toward the cis C18:1.
Kinetics of the Hydrogenation of Sunflower Oil over Alumina Supported Palladium Catalyst
International Journal of Chemical Reactor Engineering, 2000
The present work studies the sunflower oil hydrogenation on supported palladium catalysts, by analyzing the surface kinetics and the mass transfer limitations of products and reactants. Initially, a simplified model was studied. This model took into account only the consecutive hydrogenation of linoleic acid (diene), to reach the production of oleic (monoene) and stearic (saturated) acids. Using the adjusted values of the kinetic constants and the activation energies of the hydrogenation obtained with this model, a new scheme was investigated considering the geometric isomerization reactions (cis-trans). The diene hydrogenation constant was larger than that of the monoene. This fact confirms the higher reaction rate of the diene hydrogenation in comparison with that of the monoene. With respect to the isomerization rates, these have an activation energy superior to that of the monoene hydrogenation, and slightly superior to the diene hydrogenation activation energy. This fact verifies the influence of temperature on the formation of trans-isomers.
Comparison of two palladium catalysts on different supports during hydrogenation
Journal of the American Oil Chemists' Society, 2006
Soybean oil was hydrogenated using two different palladium-based catalysts, 5% palladium on carbon (Pd/C) and 10% palladium on alumina (Pd/A), at various ratios in a 4-L reactor under constant conditions (165°C, 2 bar H 2 , and 500 rpm stirring rate). Reaction rate, trans isomer formation, selectivity ratios, and melting behaviors of the samples were monitored. Activity of Pd/C was about 10 times higher than that of Pd/A, and the reaction rate showed a strong dependency on the support material. Increases in the concentrations of both Pd catalysts did not have considerable effect on trans formation, which is slightly dependent on support material. Oleate selectivity (S 21) for all runs varied between 2.48 and 30.34, and type of support material did not have an effect on selectivity. Melting behaviors of the samples were mainly dependent on reaction rates.
International Journal of Chemical Reactor Engineering, 2005
Hydrogenation of sunflower oil over novel structured catalysts with pore size ranging from 3 to 20 nm, BET-specific surface of 710-1200 m 2 /g, and catalyst metal loadings ranging from 0.7 to 5.0 % w/w, was investigated and compared to a commercial Ni-catalyst. The activity and selectivity of the catalysts as well as profiles of the reaction products such as trans fatty acids (TFA) of the hydrogenated oils were investigated. Surface characteristics of the support and the metal loading significantly affected the activity and selectivity of the Pdcatalysts. Catalyst supports with the pore diameter between 7-8 nm were more active than supports with lower pore diameters. The activity and selectivity of hydrogenation depended on Pd content, with maxima in the concentration range of 0.8 to 1.2 % w/w.
Topics in Catalysis, 2006
Hydrogenation of sunflower and canola oils over a novel Pd-supported catalyst (pore size of 6.8 nm and BET specific surface area of 837 m 2 /g) was investigated and compared to commercial nickel catalyst. The formulated catalyst with Pd-loading of 1 wt%, supported on structured silica material was active and selective for the hydrogenation of sunflower and canola oils under mild process conditions. For both oils, the novel Pd supported catalyst exhibited a better selectivity than commercial Ni catalyst at a similar activity with a lower metal loading. For the same iodine value (IV) reduction, the Pd-catalyst produced less saturated fatty acids (SFA) and about the same level of trans fatty acids (TFA), but was more selective towards cis monoenes formation than Ni-catalyst. More importantly, this catalyst produced a reduced level of stearic acid, which at increased levels causes waxy mouth feel of the hydrogenated fat.
Optimization of Sunflower Oil Hydrogenation on Pd-B/-Al2O3 Catalyst
Oriental Journal of Chemistry, 2014
Hydrogenation of vegetable oils is a heterogeneous process where the process factors influence the conversion and selectivity. A Statistical study was performed on a sunflower oil (SFO) hydrogenation process using Pd-B/g-Al 2 O 3 catalyst to study the effect of the process factors, including temperature, hydrogen pressure, agitation, catalyst dose and reaction time on the iodine value and trans fatty acid content of hydrogenated SFO. It was found that each factor has a noticeable effect on the iodine value and trans fatty acid content of hydrogenated SFO. The study was also aimed to find out the optimum values for the hydrogenation factors which are capable to decline the IV to 70 (g iodine per 100 g oil) as well as produce a minimum trans fatty acid content of the hydrogenated SFO. The optimum values were found to be 431 K, 1000 kPa, 1000 kPa, 0.29 % and 42.2 min for the temperature, hydrogen pressure, agitation, catalyst dose and reaction time respectively.
Solid Fuel Chemistry, 2014
Studies on the synthesis of powdered Pd/C catalysts prepared by the supporting of Pd onto a mesoporous carbon material from the Sibunit family and the characterization of their properties in the pro cess of the partial hydrogenation of sunflower oil are reported. The comparative tests of a 1.0 wt % Pd/Sibunit catalyst and Pricat and Nysosel commercial nickel catalysts in the hydrogenation sunflower oil were per formed with the use of a Parr batch reactor. It was found that the Pd catalyst was superior to Ni analogs in activity, and it afforded sunflower oil partial hydrogenation products with reproducible characteristics.
Catalysis Today, 2001
The hydrogenation of 1,5-cyclo-octadiene has been studied on well-defined Pd catalysts. The reaction is affected by internal diffusion of hydrogen into the catalyst particles. Despite this limitation, the reaction orders of the reactants have been determined. All the performed kinetic runs have been simulated and the kinetic and mass-transfer parameters giving the best fit of experimental data have been evaluated. The reaction occurs in two steps, in the first, a conjugate diene (1,3-cyclo-octene) is formed via isomerization, then, hydrogenation occurs quickly forming the monoene. The hydrogenation of the obtained cyclo-octene is relatively slow and strongly inhibited by the presence of the cyclo-octadiene. This last reaction has, therefore, been used for comparing the activities of different palladium catalysts showing an exponential behaviour of the reaction rate with the metal dispersion.
Revisiting the hydrogenation of sunflower oil over a Ni catalyst
Journal of Food Engineering, 2007
In the present paper the performance of commercial Ni catalyst in edible oil hydrogenation is evaluated under different operating conditions. Particularly, the influence of mass transport resistance on the trans-isomers selectivity is analyzed. Initially a series of experiments aim to analyze the effect of four process variables (reaction temperature, hydrogen bubbling device, agitation rate and stirrer design) on catalyst activity and selectivity to trans-isomers. These experiments are conducted in diffusional regimes. A simpler set of experiments is carried out operating under conditions that allow the authors to neglect some diffusional resistances although those associated to the catalyst are still present. In the first case activity and selectivity appear to be independent of the hydrogen bubbling system and the catalyst loading. The whole set of data analyzed in terms of the C18:1/C18:2 0 ratio as a function of the C18:2/C18:2 0 ratio shows that the former, a sort of selectivity, depends on the agitation regime. The formation of trans-isomers however, appears to be a function of the reaction extent only.