Abstract
The aim of this work was to prepare activated carbon (AC) from sugarcane bagasse by the physical activation process (CO2) and subsequently evaluate the physicochemical characteristics of the AC and of the bio oil produced. In a physical activation process, the biomass is pyrolysed, under an inert atmosphere (N2), and the resulting char with small adsorption capacity is subjected to a partial and controlled gasification at high temperature with carbon dioxide to afford adsorbents with high specific areas. Furthermore, in the pyrolysis step there is the production of bio oil, which is a liquid with a high energy density and it is able to substitute conventional fuels in different applications. During the pyrolysis were evaluated the effect of different temperatures (400, 500, 700 and 800 °C) on the physicochemical characteristics of the AC. The activation step was realized under flow of 150 ml min-1 of carbon dioxide (CO2), at 800 °C for 2 hours, using a heating ramp of 10 °C min-1. The activated carbons were characterized by nitrogen adsorption isotherms (77 K), FTIR and point of zero charge (PZC). It was possible to obtain microporous adsorbents with specific area ranging between 300 and 410 m2.g-1. The materials proved hydrophobic and basic superficial character (PZC~9). It was observed that pyrolysis temperature does not significantly affect the characteristics of activated carbons obtained. The total yield for the activated carbon production ranged between 24 and 54%, decreasing with the increase of the pyrolysis temperature. In this way, the process can be conducted at 400 °C, achieving, thus, energy saving and higher total yields (54%). It was noted that an increase of the temperatures increases the liquid and gaseous yields and decreases the solid residue yield. The pyrolysis liquid showed an acidic character (pH = 1.0). The chemical composition of the bio-oil was analyzed by gas chromatography coupled to a mass spectrometer and were identified a great variety of compounds. Such composition suggests that the bio-oil from sugarcane bagasse pyrolysis is a promising source of components for chemical, nutritional and pharmaceutical use.
