Biohidrocarbonetos a partir de processo catalíticos utilizando catalisadores micro e mesoporosos com Co e Mo

Abstract

The search for new sources of renewable energy is growing all over the world, this growth is due to the environmental problems caused by the excessive use of fossil fuels that cause a series of damages to the environment. Faced with this problem, the present doctoral work aims to evaluate the use of microporous catalysts of the ZSM-5 type and mesoporous type MCM-41 catalysts impregnated with cobalt and molybdenum metals in the production of biohydrocarbons via rapid pyrolysis of sunflower oil. The studied catalytic materials were characterized by X-Ray Diffraction (XRD), X-Ray Fluorescence (FRX), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) coupled to Energy Spectroscopy. Dispersive (EDS). The referred analyzes indicated that the porous structures were formed with excellence, and were maintained after the impregnation of the metals. Sunflower oil was characterized by physical-chemical analysis, such as: acidity, peroxide, saponification, refraction, free fatty acids and density, and subsequently a thermal and kinetic study of the oil degradation reaction was carried out using catalysts synthesized micro and mesoporous, and based on the free kinetic models proposed by Ozawa Flynn Wall (OFW) and Kissinger Akahira Sunose (KAS). Thermogravimetric analyzes (TGA) of sunflower oil and sunflower oil with catalysts were performed at heating rates (β) of 10, 20, 30 and 40ºC/min, then the data were treated according to the proposed models, obtaining if so values like: activation energies (Ea) for conversion rates (α) 5, 10, 20, 30, 40, 50, 60, 70, 80 and 90%. The results indicated that all catalysts tested showed catalytic activity. For sunflower oil the Ea ranged from 149.9 to 201.6 KJ/mol, for the mesoporous catalysts MCM-41, Mo/MCM41, Co/MCM-41 and Co-Mo/MCM-41 the Ea were from 121.1 to 143.6, 72.7 to 112.1, 136.5 to 170.6 and 152.2 to 165.4 KJ/mol respectively, and for microporous catalysts HZSM-5, Mo/HZSM -5, Co/HZSM-5 and Co-Mo/HZSM-5 the Ea ranged from 119.5 to 153.6, 114.8 to 146.7, 142.9 to 166.4 and 101.5 to 158, 0 KJ/mol respectively, with emphasis on Mo/MCM-41 and Mo/HZSM-5, which showed the greatest reductions in activation energies (Ea). Both in the OFW model and in the KAS, the methodologies used proved to be adequate (R2 > 0.9). The thermodynamic parameters (A, ΔH, ΔG and ΔS) were also calculated in the reactions of thermal and thermocatalytic degradation of sunflower oil, in which we can highlight the ΔH>0, indicating that it is an endothermic reaction and the ΔG>0, corresponding to a non-spontaneous reaction. The results of the kinetic study were also used as a basis for thermal and catalytic pyrolysis reactions. In the pyrolysis process, the percentages of hydrocarbons formed were as follows: in thermal pyrolysis, 16% were obtained, in catalytic pyrolysis, the percentages of hydrocarbon formation were 28% (MCM-41), 16% (Mo/MCM-41), 21 % (Co/MCM-41) and 45% (Co-Mo/MCM-41). According to the percentages of formed hydrocarbons, in the thermal pyrolysis 53.2% are in the Aviation Biokerosene range and 46.8% in the Green Diesel range. In the catalytic pyrolysis, the presence of the catalysts favored the deoxygenation of the products by the decarbonylation reaction, thus the catalysts MCM-41, Mo/MCM41, Co/MCM-41 and Co-Mo/MCM-41 presented 8.6 , 0, 0 and 0% in the biogasoline range, 29.4, 24.5, 27.5 and 19.4% in the aviation biokerosene range and 62.0, 75.5, 72.5 and 80.6 % in the range of green diesel respectively.