Processi di deidrogenazione/deossigenazione catalitici su oli vegetali per ottenere bioprodotti e green diesel

Two hydrothermal processes on the vegetable oils (rapeseed and sunflower) have been concerned in this research: - Selective catalytic hydrogenation in order to maximize the content of oleic acid, which is a monounsaturated carboxylic acid with eighteen carbon atoms. It has suitable characteristics (stable in the presence of oxygen, and it remains liquid even at low temperatures) for use as a biodegradable lubricant and is a building block in the production of polymers and plastics from renewable resources. - Selective catalytic deoxygenation to increase the green diesel range (C15-C18) hydrocarbons, it is a premium diesel-blending component, its boiling range is comparable to conventional diesel, and it has substantially higher cetane content and lower density than the conventional one. The development of green diesel could solve not only the problems of the continuous and inevitable fossil fuel exhaustion but also the gas emissions pollution from fossil fuels. Our research activities in this doctoral thesis concerned the following arguments: - The state of the art exposed briefly, environmental pollution, green chemistry, fossil fuels shortage, renewable feeding stocks, catalytical hydrothermal reactions mechanisms, and the hydrothermal catalysis (homogeneous vs. heterogeneous). - Studying the most updated techniques for both preparation and characterization of catalysts, 5 different synthesized heterogenous mono and bimetallic catalysts have been prepared by co-precipitation method (Pd/HT) and conventional wet impregnation one (Pd/FAC, CoMo/FAC, NiMo/FAC, and NiMo/zeolite X). The 5 synthesized catalysts and a commercial one (Pd Lindlar) were characterized by elemental analysis (ICP), H2-chemisorption, Thermogravimetric analysis (TGA), X-ray diffraction (XRD), N2 adsorption (BET), programmed temperature reduction (TPR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and NH3-TPD acidity analysis. - Carrying out the hydrogenation tests in a laboratory-scale plant reactor, the core of this system is a Parr Instrument 4560 (600 mL) reactor unit operated in semi-batch mode, feeding the hydrogen continuously. The tests were performed with rapeseed and sunflower oils using different palladium supported catalysts (Pd Lindlar, Pd/HT, and Pd/FAC) under different levels of conditions; temperature (60 ° C, 90 ° C, 120 ° C, 180 ° C, and 240 ° C), hydrogen pressure (4 bar, 8 bar, and 12 bar), and catalyst concentration (4 mgcatalyst/mLoil, 2 mgcatalyst/mLoil, 1 mgcatalyst/mLoil , 0.5 mgcatalyst/mLoil). The best results of monounsaturated C18:1 were obtained for Pd Lindlar catalyst at (180 ° C, 4 bar and 4 mg/ml) with 88.4 % of C18:1 after about 90 min of the reaction time, for Pd/HT at (180 ° C, 4 bar) but with half catalyst concentration (2 mg/ml) obtaining 89.9 % of C18:1 after 180 min, whereas for Pd/FAC the best result was gotten at a higher temperature, higher pressure, and less catalyst concentration (a quarter of Pd Lindlar) (240 ° C, 8 bar and 1 mg/ml) with 82.7 % of C18:1 oleic acid after 210 min reaction time. The results highlight how it is possible to obtain the same conversion of polyunsaturated vegetable oils about 100 % and monoene acid C18:1 over 82 % with higher best reaction time using less concentration from the synthesized catalyst. - Implementing the deoxygenation tests in a laboratory-scale plant reactor, the heart of this system is a Parr micro Instrument 4598 (100 mL) reactor unit operated in semi-batch mode, feeding the hydrogen continuously. The tests were performed with stearic acid and sunflower oils using different mono and bimetallic catalysts (Pd Lindlar, Pd/FAC, CoMo/FAC, NiMo/FAC, NiMo/zeolite X) under different levels of conditions; temperature (280 ° C, 300 ° C, 320 ° C), hydrogen pressure (20 bar, and 40 bar), and catalyst concentration (2.5 wt%, and 10 wt%).