Produção do biodiesel de óleo de soja utilizando catalisador heterogêneo da cinza da casca da tangerina ‘Ponkan’ (Citrus reticulata Blanco)

Abstract

The advance of global energy demand has intensified environmental problems caused by the use of fossil fuels and has been driving the search for and development of greener matrices, which are being used to minimize environmental impacts and human health. This work proposed a sustainable process for the production of biodiesel, an alternative fuel to diesel, with the use of a heterogeneous, green catalyst, called CT, derived from residual biomass, from the peel of 'Ponkan' mandarin (Citrus reticulata Blanco). Through D-optimal experimental planning to obtain soybean biodiesel, process parameters such as methanol/oil molar ratio, catalyst concentration, temperature, and reaction time were optimized. Initially, three catalyst samples were prepared by calcination of the ashes of the tangerine peels at a time of 4h, CT7 (700 ° C), CT8 (800 ° C), and CT9 (900 ° C), and after preliminary tests, the yields (m/m) in biodiesel were 79.77, 77.58 and 77.40 %, respectively. The mass catalyst yield obtained for each temperature (700, 800, and 900 °C) from 50 g of residue was 3.76, 1.54, and 0.98%, respectively. The catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM-FEG), X-ray dispersive energy (EDS), CO2 desorption at programmed temperature (TPD-CO2), thermal analysis (TG/DTG), and Hammett's basicity test. The quality of biodiesel was evaluated according to the standard procedures established by ASTM (American Society for Testing and Materials) for the properties of kinematic viscosity and density. The DRX patterns of the CT catalyst showed the peaks associated with the characteristic phases of K2CO3, K2O, K2Ca(CO3)2, SiO2, Na2O confirmed by FRX which identified large proportions of these oxides and carbonates. Good thermal stability was observed through the TG/ DTG curves and the TPD-CO2 analysis demonstrated the presence of weak and moderate base sites in the CT catalyst. The optimized conditions generated by the response surface were: 3 h reaction time, catalyst concentration of 3.5% m/m, the molar ratio of 15: 1 (methanol: oil), and temperature of 64 ° C. For these optimized conditions, the conversion of the reaction quantified by 1H NMR was greater than 87%, and the catalyst presented a reuse capacity of up to 5 times. The catalyst proved to be effective for soybean biodiesel production, making the process more environmentally friendly and economical by using a low-cost residue from the agroindustry, being synthesized simply and quickly.