Selective hydrogenation of sunflower oil over supported precious metals (original) (raw)
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Supported Nickel-Based Catalysts for Partial Hydrogenation of Edible Oils
New Advances in Hydrogenation Processes - Fundamentals and Applications, 2017
Nickel-based catalysts, supported on diatomite, silica gel and perlite, with high nickel loadings, have been prepared by precipitation-deposition method. Various nickel precursor salts were used for the preparation of catalyst precursors. In the precursor state, the catalysts were characterized using nitrogen physisorption, mercury porosimetry, infrared, and X-ray diffraction spectroscopy. The reducibility of catalyst precursors was evaluated using hydrogen temperature programmed reduction. Hydrogen chemisorption and X-ray photoelectron spectroscopy measurements were performed with the aim of characterizing the chemical state of the catalyst precursors. This research was focused on the study of some major factors on the state, dispersion and reducibility of a deposited Ni 2+ phase by the combined use of mentioned experimental techniques. We have examined the influence of the nature of support and the use of modifiers on activity of nickel-based catalysts in the partial hydrogenation of sunflower and soybean oils. Nitrogen physisorption and mercury porosimetry data showed that synthesis operating conditions and pore structure of supports have a profound effect on the textural properties of catalyst precursors. The analysis of infrared and X-ray diffraction spectra showed the existence of chemical species and phases which indicate the different extent of interaction between the support and the active metal. Temperature programmed reduction study revealed that the reduction features depend on the identity of the nickel precursor salt and its interaction with the support. A stronger interaction of the supported Ni 2+ phase with support hinders the reduction of catalyst precursors. Hydrogen chemisorption results showed the presence of nickel crystallites varying from 5 to 47 nm in size. The X-ray photoelectron spectroscopy data confirmed the formation surface species with different strength of interaction and different nickel crystallite sizes. The hydrogenation results showed significant differences, depending on the support and the modifier, as well as structural characteristics of reduced catalyst precursors. The results show the importance of modifiers in the control of the activity and selectivity of the partial hydrogenation
2017 Chapter 8 Supported Nickel-Based Catalysts for Partial Hydrogenation of Edible.pdf
Nickel-based catalysts, supported on diatomite, silica gel and perlite, with high nickel loadings, have been prepared by precipitation-deposition method. Various nickel precursor salts were used for the preparation of catalyst precursors. In the precursor state, the catalysts were characterized using nitrogen physisorption, mercury porosimetry, infrared, and X-ray diffraction spectroscopy. The reducibility of catalyst precursors was evaluated using hydrogen temperature programmed reduction. Hydrogen chemisorption and X-ray photoelectron spectroscopy measurements were performed with the aim of characterizing the chemical state of the catalyst precursors. This research was focused on the study of some major factors on the state, dispersion and reducibility of a deposited Ni 2+ phase by the combined use of mentioned experimental techniques. We have examined the influence of the nature of support and the use of modifiers on activity of nickel-based catalysts in the partial hydrogenation of sunflower and soybean oils. Nitrogen physisorption and mercury porosimetry data showed that synthesis operating conditions and pore structure of supports have a profound effect on the textural properties of catalyst precursors. The analysis of infrared and X-ray diffraction spectra showed the existence of chemical species and phases which indicate the different extent of interaction between the support and the active metal. Temperature programmed reduction study revealed that the reduction features depend on the identity of the nickel precursor salt and its interaction with the support. A stronger interaction of the supported Ni 2+ phase with support hinders the reduction of catalyst precursors. Hydrogen chemisorption results showed the presence of nickel crystallites varying from 5 to 47 nm in size. The X-ray photoelectron spectroscopy data confirmed the formation surface species with different strength of interaction and different nickel crystallite sizes. The hydrogenation results showed significant differences, depending on the support and the modifier, as well as structural characteristics of reduced catalyst precursors. The results show the importance of modifiers in the control of the activity and selectivity of the partial hydrogenation process. The developed kinetic models of the hydrogenation of soybean and sunflower oils over studied catalytic systems were found useful in the prediction of the rate of reactions, product selectivity and catalytic activity.
The influence of the support on the properties of nickel catalysts for edible oil hydrogenation
Applied Catalysis A-general, 2006
Two silica-containing materials, diatomite and waterglass, have been used as supports of nickel catalysts for edible oil hydrogenation. The active phase has been deposited following the precipitation-deposition method. The textural and structural characteristics of the supports and precursors have been studied by nitrogen sorption, scanning electron microscopy (SEM), infrared (IR) spectroscopy and X-ray powder diffraction (XRD). The thermogravimetric (TG) analyses have been carried out under hydrogen flow at different heating rates. Chemisorption of hydrogen has also been applied for precursor characterization and the metal particle size has been calculated from hydrogen adsorption isotherms at 25 8C. The catalysts have been tested in the soybean oil hydrogenation reaction. The differences in the textural and structural properties of the catalysts under study have not been found to reflect on their activity and selectivity. However, the use of water glass as the support is considered to be preferable, because of the lower economic cost of the catalyst, related to the elimination of the mechanical, chemical and thermal treatment of the crude diatomite. # (M. Gabrovska), jkrstic@nanosys.ihtm.bg.ac.yu (J. Krstić), rumedkar@ic.bas.bg (R. Edreva-Kardjieva), mstankov@nanosys.ihtm.bg.ac.yu (M. Stanković), dusanmj@nanosys.ihtm.bg.ac.yu (D. Jovanović). 0926-860X/$ -see front matter #
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.
Influence of Ni/SiO2 activity on the reaction pathway in sunflower oil hydrogenation
2015
Sunflower oil hydrogenation process was studied on silica supported nickel catalysts. Three texturally different silica gel materials were used as supports for synthesis of Ni/SiO2 catalyst precursors. After precursors’ reduction and paraffin oil impregnation, obtained catalysts were used in sunflower oil hydrogenation reaction. For catalytic test, a new type of catalyst feeder was constructed and presented. The hydrogenation activity of catalysts was monitored through the decrease of refractive index and hydrogen consumption. A correlation between iodine value, refractive index and hydrogen consumption was established. The reaction rate constants were obtained from fatty acid composition of partially hydrogenated oil and further studied for the investigation of possible reaction pathways. Kinetics and mechanisms were evaluated and tested with the aim to reduce the number of reactions participating in the reaction scheme. A set of ordinary differential equations, corresponding to the investigated model, was solved numerically by Gear's algorithm. It was shown that a number of significant reactions in a model depend on the activity of catalysts. More active catalyst results in more reaction pathways and more side chemical reactions.
Russian Journal of Physical Chemistry A, 2011
Ni/SiO 2 materials with identical composition (SiO 2 /Ni = 1.0) have been synthesized by precipi tation of Ni(NO 3 ) 2 · 6H 2 O solution with Na 2 CO 3 solution on the silica gel, obtained at three different pH values. The present investigation was undertaken in an endeavor to study the effects of the silica gel support type and the reduction temperature on the formation and dispersion of the metallic nickel phase in the reduced Ni/SiO 2 precursors of the vegetable oil hydrogenation catalyst. The physicochemical characteriza tion of the unreduced and reduced precursors has been accomplished appropriately by powder X ray diffrac tion, infrared spectroscopy, temperature programmed reduction and H 2 chemisorption techniques. It can be stated that the texture peculiarities of the silica gels used as supports influence on the crystalline state and dis tribution of the deposited Ni containing phases during the preparation of the precursors, on the reduction temperature of the investigated solids as well as on the bulk size and surface dispersion of the arising metallic nickel particles. It was shown that two types of Ni 2+ species are formed during the synthesis procedure, namely basic nickel carbonate like and Ni phyllosilicate with different extent of presence, location and strength of interaction. The different location of these species is supposed to result in various strength of Ni-O and Ni-O-Si interaction, thus determining the overall reducibility of the precursors. It was specified that the Ni 2+ species are strongly bonded to the surface of the silica gel obtained at neutral pH value and weakly bonded to the surface of those prepared in acidic and alkaline conditions. It was established that the precur sor, derivates from the silica gel obtained at alkaline conditions, demonstrates both significant reduction of the Ni 2+ ions at 430°C and finely dispersed metallic nickel particles on its surface. High dispersion of the metallic nickel might be the crucial reason for achieving of high activity in the vegetable oil hydrogenation.
Chemical Engineering Journal, 2009
Six palladium catalysts were prepared using different precursors (palladium acetylacetonate, palladium nitrate and tetraamminepalladium nitrate) and supports (␣-Al 2 O 3 , ␥-Al 2 O 3 , ZSM-5, and MCM-22). The samples were characterized by atomic absorption spectroscopy, N 2 adsorption isotherms, XRD, H 2 chemisorption, transmission electron microscopy and temperature programmed reduction. The activity and selectivity of the catalysts were investigated in the hydrogenation of sunflower oil and compared to a commercial Ni catalyst.
Sunflower oil hydrogenation: Study using response surface methodology
Journal of Food Engineering, 2008
The hydrogenation of sunflower oil to oleomargarine (70 iodine index) was studied from data obtained using a central composite experimental design. The nickel on silica catalyst was made by precipitation-deposition. The reaction was performed in a semi-batch reactor at temperatures between 120°C and 180°C, hydrogen pressures from 2.5 to 4.5 bar and catalysts loadings of 0.012-0.039% (Ni/oil). Response surface methodology was used to predict the effect of reaction temperature, hydrogen pressure and catalyst loading on the overall rate constant of hydrogenation, total trans-isomers and stearic acid triglycerides production. Statistical assessment showed a good agreement between predicted and observed values.
Perlite As a Potential Support for Nickel Catalyst in the Process of Sunflower Oil Hydrogenation 1
—Investigation was conducted in order to elucidate the possibility of using perlite as support for preparation of nickel based precursor catalyst, potentially applicable in vegetable oil hydrogenation process. On three differently prepared expanded perlite, nickel catalyst precursors with identical Ni/SiO 2 = 1.1 and Ni/Mg = 10/1 ratios were synthesized by precipitation-deposition method. Different techniques, SEM micrography, He-pycnometry, calcimetry, Hg-porosimetry, N 2-physisorption, H 2-chemisorption and temperature programmed reduction, were used for characterization of obtained samples. Determining the precursor texture, morphology and reducibility shows a successfully deposited nickel phase on perlite support with promising properties for vegetable oil hydrogenation. Chosen precursor was reduced and passivated in paraffin oil and the obtained catalyst showed significant catalytic activity in the test of sunflower oil hydro-genation.
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.