Activity and Selectivity of Nanostructured Sulfur-Doped Pd/SBA-15 Catalyst for Vegetable Oil Hardening

Abstract

Sunflower and canola oils were hardened over a novel sulfur-promoted Pd catalyst. The formulated catalyst comprised of 0.7 wt % palladium nanoparticles promoted with 0.3 wt % sulfur highly dispersed on mesoporous silica SBA-15 (0.7% Pd-0.3% S/SBA-15). The effect of temperature (80-130 °C) and H 2 pressure (3.6-9.3 atm) on the activity, selectivity, and trans (TFA) and saturated (SFA) fatty acids formation were studied for both oils. Under similar temperature and H 2 -pressure conditions, sunflower and canola oils exhibited different reactivities toward hydrogenation. For both oils, the activity of the catalyst increased with the temperature and with the pressure. However, increasing the temperature raised the levels of trans C18:1 especially at low hydrogen pressure. Partial hydrogenation of both oils from initial iodine (IV o ) values of 120-130 to a final value of 90 with the sulfur-doped Pd catalyst yielded modified oils with a low TFA level (6%) and also controlled the formation of SFA (∼7%) under mild temperature conditions (80 °C) and relatively moderate hydrogen pressure (9 atm). The sulfur-doped Pd catalyst proved to be versatile and more active than the Pd catalyst using similar Pd loading and reaction conditions but slightly less selective toward monoene formation. It was found that the intraparticle diffusion limitation for triglycerides does not occur during the hydrogenation of vegetable oils, but the hydrogen transfer limitation cannot be neglected and could partially explain the formation of trans-fatty acids. Modulating the Weisz-Prater modulus used to demonstrate the presence of H 2 intraparticle gradients could be a criterion to control the hydrogenation and cis-trans isomerization activities.

Conjugated linoleic acid formation by hydrogenation/isomerisation of safflower oil over bifunctional structured catalyst Rh/SBA‐15

“…It appears that the agitation rate and the reaction temperature have a synergetic effect in the enhancement of total CLA production. This may be attributed to better mass transfer features of oil triglycerides at the catalyst active sites owing to the reduced level in the oil viscosity and enhanced triglyceride diffusion in the catalyst pores at more elevated temperature and agitation rate (Kemache et al, 2010).…”

Hydrogenation of soybean oil over various platinum catalysts: Effects of support materials on trans fatty acid levels

“…Lower temperatures and higher pressures result in lower TFA levels [7]; however, it has not been possible to produce partially hydrogenated oils with low TFA levels. There have been numerous studies for hydrogenation of vegetable oils over supported metal catalysts, with many reports on the various modifications of nickel, palladium, and platinum catalysts to reduce TFA levels during hydrogenation [8][9][10][11][12][13][14][15][16][17][18]. For example, Li et al reported that a nickel-boron alloy catalyst has a lower TFA selectivity for the hydrogenation of soybean oil [8].…”

Influence of Ni/SiO2 activity on the reaction pathway in sunflower oil hydrogenation

“…Kemache et al showed that different chemical composition of initial oil leads to the different catalyst activities under same reaction conditions (Kemache et al, 2009). It is well known that even the oils that originate from the same herbal species can have significantly different fatty acids composition (Fernández et al, 2009;Naglič et al, 1998;Rudan-Tasic and Klofutar, 1999).…”

“…Although, amount of trans fatty acids produced during the process of oil hydrogenation, depends of the activity of used catalysts (McArdle et al, 2014) optimization parameter which increases activity also leads to the increased trans content (Kemache et al, 2009;Plourde et al, 2004;Rylander, 1970).…”