The high molecular weight and size of triglycerides molecules, which comprise vegetable oils and animal fats, prevent their direct use as transport fuels, and hence, they must be upgraded. Hydrotreatment of triglyceride-based feedstocks (vegetable oils and animal fats) for automotive fuels has been studied in detail (Bezergianni et al., 2009; Huber et al., 2007; Lappas et al., 2009; Petri and Marker, 2006). Hydrocracking of these renewable raw materials has been also studied by several authors (Bezergianni et al, 2009; da Rocha Filho et al., 1993; Gusmao et al., 1989; Kubickova et al., 2005). However, high amounts of hydrogen are required to enhance hydrodeoxygenation processes. Such reaction pathway implies the conversion of the oxygen present in the triglyceride in form of water (Gusmao et al, 1989; Huber et al., 2007). The formed water, as well as the initial content in the feedstocks of metals (such as sodium, potassium, calcium or phosphorous), and other impurities (solid particles, water or detergents) are associated with problems related to the durability of the sensitive hydrogenation catalyst (Petri and Marker, 2006). Furthermore, there is always a problem with the operating costs related to the high hydrogen consumed along the reactions, which advise against the co-processing of renewable raw materials in refining units that work with high-pressured hydrogen.

On the other hand, there is the possibility of cracking triglyceride-based feedstocks in refining units without the presence of hydrogen. These possible units are thermal cracking units such as visbreaker or coker and the FCC unit. Thermal cracking units are used for the breakdown of heavy crude oil into smaller molecules in the absence of catalyst and hydrogen. Several vegetable oils have been thermally cracked and the results reported in literature: tung oil (Chang and Wan, 1947), soybean oil (Demirbas and Kara, 2006; Lima et al., 2004; Schwab et al., 1988), high-oleic safflower oil (Schwab et al, 1988), palm oil (PO) (Chew and Bhatia, 2008; Lima et al., 2004), castor oil (Lima et al., 2004), canola oil (Idem et al., 1996; Sadrameli and Green, 2007), several tropical vegetable oils (Alencar et al., 1983) and oleaginous waste feedstocks such as waste cooking oil (Dandik and Aksoy, 1998), oils from non-edible fruits (such as Macauba fruit; Fortes and Baugh, 1999, 2004) and non-edible animal fats (Adebanjo et al., 2005; Demirbas, 2009). Moreover, Padmaja et al. (2009) have recently reported the thermal cracking of a biocrude extracted from Calotropis procera (laticiferous arid plant from India) under conditions similar to those found in visbreaking and delayed coking. All of the above-mentioned reactions have been usually performed in batch reactors, although fixed bed reactors (usually under the presence of inert materials) and fluidized bed have been also reported. Temperature ranges usually between 300°C and 500°C and the operating pressure is always close to the atmospheric. From this work, a high amount of oxygenated hydrocarbons is found in the final reaction products independently of reaction temperature. Although the thermal decomposition of triglyceride molecules and their associated heavy oxygenated hydrocarbons is always initiated at temperatures of 240-300°C (without the presence of oxygen) (Adebanjo et al, 2005; Crossley et al, 1962), the presence of a catalyst is necessary to remove oxygen from oxygenated hydrocarbons such as carboxylic acids, esters, aldehydes or ketenes and to obtain an organic liquid fraction suitable for gasoline and diesel formulation. Thus, the co-feeding of this renewable feedstock to an FCC unit would be more feasible. This unit is the most widely used process for the conversion of heavy fraction of

crude oil into high-value products (e. g. diesel, gasoline). This unit operates under high temperatures (> 500°C) and pressure close to the atmospheric in the absence of hydrogen and the presence of an acid catalyst.

In this section, we will discuss the chemistry involved in the catalytic cracking of triglyceride molecules as well as the work dealing with the processing of this biomass feedstock under FCC realistic conditions.