Avaliação de catalisadores à base de zircônia e ferro na decomposição de defeito PVA de café em condições hidrotérmicas

Abstract

Coffee is one of the main agricultural commodities in the world, along with sugarcane, wheat, beef and cotton. Many coffee residues and byproducts are generated during production and processing. During harvest, the presence of black, green and sour grain, or PVA defect, in addition to implying productivity loss, can aggravate product quality. These factors can contribute to the importance of the residue. One way to completely use this residue would be to study its transformation by decomposition or conversion. In this context, the process of hydrothermal conversion presents great advantages, such as drying or separation treatment being unnecessary; the availability of water with no toxicity, used as solvent and presents singular chemical properties, used as a catalyst with redox properties in a subcritical condition. The thermo-chemical characteristics of the water, with characterize it as hydrothermal (subcritical), are understood as any temperature above 100oC, with which we have enough pressure to maintain it in a liquid state. In a hydrothermal process, the catalysts can decrease the energetic need of the process and direct reactional means to obtain the interest products. With the need of taking advantage of the PVA defect, and of understanding the reactional potential of the water under subcritical conditions with the presence of catalysts, this work aimed at evaluating catalyst materials under subcritical water conditions in the decomposition of the PVA defect. We prepared four iron and zircon based catalysts, placed separately in a high-pressure reactor with 10 g of PVA defect, under the temperatures of 150oC, 200oC and 250oC, and initial pressures of 1 bar, 30 bar and 60 bar. With the results of the concentration of trigonelina and caffeine, obtained by high performance liquid chromatography – HPLC, and temperature and pressure variation along the reaction at the end of each treatment, we verified that none of the catalysts increased the pressure of the system. The tested materials showed distinct behaviors for each reaction, according to the results obtain with the HPLC. The goethite and goethite/boron catalysts were more influential over the concentration of trigonelina and caffeine in hydrothermal mediums.