chemical engineering research and design 1 0 0 ( 2 0 1 5 ) 72–80 Contents lists available at ScienceDirect Chemical Engineering Research and Design journal h om epage: www.elsevier.com/locate/cherd Influence of Ni/SiO 2 activity on the reaction pathway in sunflower oil hydrogenation J. Krsti´ c a,* , M. Gabrovska b , D. Lonˇ carevi´ c a , D. Nikolova b , V. Radonji´ c a , N. Vukeli´ c c , D.M. Jovanovi´ c a a University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Department of Catalysis and Chemical Engineering, Njegoˇ seva 12, Belgrade, 11000, Serbia b Institute of Catalysis, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria c University of Belgrade, Faculty of Physical Chemistry, Belgrade 11000, Serbia a r t i c l e i n f o Article history: Received 22 December 2014 Received in revised form 7 April 2015 Accepted 2 May 2015 Available online 11 May 2015 Keywords: Hydrogenation Nickel catalyst Silica Sunflower oil Reaction pathways a b s t r a c t 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/SiO 2 cata- lyst precursors. After precursors’ reduction and paraffin oil impregnation, obtained catalysts were used in sunflower oil hydrogenation reaction. For catalytic test, a new type of cat- alyst feeder was constructed and presented. The hydrogenation activity of catalysts was monitored through the decrease of refractive index and hydrogen consumption. A corre- lation between iodine value, refractive index and hydrogen consumption was established. The reaction rate constants were obtained from fatty acid composition of partially hydro- genated 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. © 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction The partial hydrogenation of the vegetable oils is an important hardening technology in the food industry aiming to decrease the unsaturation of high fatty acids to modify the melt- ing characteristics and plasticity of oils to achieve desirable techno-functional properties and to enhance the oxidative and thermal stability, as well as the utility of hydrogenated products. The process is still widely used in manufacture of margarines, cooking, frying and salad oils, spreads and frying fats, chocolates, ice creams, shortenings and baking prod- ucts. Conventional batch hydrogenation uses slurry reactors, ∗ Corresponding author. Tel.: +381 0 11 2630213; fax: +381 0 11 2637977. E-mail addresses: jkrstic@nanosys.ihtm.bg.ac.rs, jugoslav.krstic@gmail.com (J. Krsti ´ c), margo@ic.bas.bg (M. Gabrovska), dloncarevic@nanosys.ihtm.bg.ac.rs (D. Lonˇ carevi ´ c), dimi@ic.bas.bg (D. Nikolova), vradonjic@nanosys.ihtm.bg.ac.rs (V. Radonji ´ c), nikolav@ffh.bg.ac.rs (N. Vukeli´ c), dusanmj@nanosys.ihtm.bg.ac.rs (D.M. Jovanovi ´ c). hydrogen gas, high temperatures (140–230 ◦ C), low pressures, moderate to long reaction times and metal nickel catalysts supported on different silica sources. The metallic nickel (21–25 wt% Ni) represents a commonly applied commercial catalyst for the process because of its high activity, inert nature of metal relative to oil, its availability and low cost (Balakos and Hernandez, 1997; Fernández et al., 2007; Grau et al., 1988; Veldsink et al., 1997). In batch or semi-batch reactors, reaction of hydrogenation with the use of slurry catalysts, the general problem, even in scientific research, presents the initiation of the reac- tion process in the moment when the reaction conditions http://dx.doi.org/10.1016/j.cherd.2015.05.001 0263-8762/© 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.