Journal of Molecular Catalysis A: Chemical 417 (2016) 126–134 Contents lists available at ScienceDirect Journal of Molecular Catalysis A: Chemical jou rnal h om epa ge: www.elsevier.com/locate/molcata Catalytic decarboxylation of non-edible oils over three-dimensional, mesoporous silica-supported Pd Ravindra Raut, Vikram V. Banakar, Srinivas Darbha ∗ Catalysis and Inorganic Chemistry Division, CSIR-National Chemical Laboratory, Pune 411 008, India a r t i c l e i n f o Article history: Received 11 February 2016 Received in revised form 8 March 2016 Accepted 9 March 2016 Available online 11 March 2016 Keywords: Biofuel Vegetable oil Deoxygenation Mesoporous silica Supported palladium Diesel-range hydrocarbons a b s t r a c t Deoxygenation of fatty acids (oleic and stearic acids) and non-edible oil (jatropha oil) over Pd(1–5 wt%) supported on two structurally different, three-dimensional, mesoporous silica (SBA-12 and SBA-16) cat- alysts was investigated. Pd/SBA-16 (cubic mesoporous structure with space group Im ¯ 3m) showed higher catalytic activity than Pd/SBA-12 (hexagonal mesoporous structure with space group p6 3 /mmc). The influ- ence of reaction parameters like temperature, H 2 pressure and Pd content as well as the nature of the feedstock on catalytic activity and product selectivity was studied. A temperature of above 320 ◦ C, reaction time of 5 h and Pd content (on silica surface) of 3 wt% enabled complete conversion of the fatty compounds into diesel-range hydrocarbons. Deoxygenation proceeded through hydrodeoxygenation and decarboxy- lation mechanisms when a saturated (stearic) acid was used as a feed while it advanced mainly through decarboxylation route when an unsaturated (oleic) acid was employed. Higher surface hydrophobicity and smaller size particles of Pd are the possible causes for the superior catalytic activity of Pd/SBA-16. © 2016 Elsevier B.V. All rights reserved. 1. Introduction According to the world energy council, about 82% of the energy is currently derived from fossil resources (petroleum, natural gas and coal). Usage of fossil fuels has been realized to cause adverse effects to the environment [1,2]. Moreover, at the projected rate of con- sumption, the availability of petroleum and natural gas is expected to run out in about 70 years and coal in 200 more years. Biofuels show the way to sustainable environment, energy independence, employment to rural population and savings in oil import bill. Vegetable oils such as soybean, rapeseed and palm oils comprise triglycerides (TGs) which can be converted into diesel-like fuels [3–5]. Use of non-edible oils instead of edible ones makes the bio- fuels production more attractive as the former are cheaper and do not lead to issues like food versus fuel controversy. Non-edible oils contain a significant amount of free fatty acids (FAs) in their com- position along with glycerides. One option exists in the form of hydroprocessing for removal of oxygen from the constituent TGs and FAs toward producing diesel-range hydrocarbons (HCs) [6–8]. Fatty acid methyl esters (FAMEs) represent the first generation biodiesel formed via methanolysis of vegetable oils. Unfortunately, ∗ Corresponding author. E-mail address: d.srinivas@ncl.res.in (S. Darbha). use of FAMEs can cause problems in vehicles due to their high oxygen content and viscosity rendering them a less than an ideal fuel for conventional engines. For example, the unburnt part of biodiesel, when mixed with the lubricating oil, can promote engine aging [9]. Further, FAMEs are associated with issues related to cold- flow and oxidation stability. The diesel-like HCs consisting of 15–18 carbon atoms (produced by the hydroprocessing route) provide good fuel properties [10]. Unlike FAMEs, the HC-based biofuels have the advantage of using them as they are or as a blend with the conventional diesel in any proportion. Two types of catalyst systems were reported for deoxygenation of vegetable oils: (i) Mo and W promoted hydrotreating cata- lysts (Ni-Mo/Al 2 O 3 , Ni-W/Al 2 O 3 , Co-Mo/Al 2 O 3 and Co-W/Al 2 O 3 ) [9,11–14] and (ii) supported noble metal catalysts [15–18]. While the mode of deoxygenation is mainly through dehydration (H 2 O removal) over the former type catalysts, it is through decar- bonylation/decarboxylation (CO/CO 2 removal) on the latter type catalysts. Relatively lesser amount of hydrogen is needed while using the noble metal catalysts (5–20 bar) as against Ni-Mo/W cata- lysts (50–70 bar). After screening several supported metal catalysts, Snåre et al. [19] found that carbon-supported Pd converts stearic acid completely with >98% selectivity toward heptadecane (C 17 ). The efficiency of deoxygenation of different metals decreased in the order: Pd > Pt > Ni > Rh > Ir > Ru > Os. They found that decarboxyla- tion was profound over Pd/C, while decarbonylation was prevalent http://dx.doi.org/10.1016/j.molcata.2016.03.023 1381-1169/© 2016 Elsevier B.V. All rights reserved.