44ª Reunião Anual Virtual da SBQ

Two biochars were obtained from centrifuged sewage sludge (CLC) and non-centrifuged sludge (CLETE) by pyrolisis at 380ºC (yield of 68% for both materials). The thermogravimetric characterizations showed ash contents of 58% and 65% due to the inorganic fraction in these materials.1 Atomic Emission Spectroscopy confirmed the presence of several metals in the biochars, highlighting Al and Fe that were found in higher concentrations (8.0% and 4.8% for CLETE and 4.3% and 4.5% for CLC, respectively). The samples also were evaluated by X-Ray Diffraction analysis, which indicated that these metals were mostly present as oxides. The organic portion was characterized by infrared spectroscopy and the characteristic bands for hydroxyl groups (3200 cm-1), Aromatic C=C stretch (1510 cm-1) and C-O stretch (1020 cm-1) were found, confirming the sludge pyrolysis. Scanning electron microscopy coupled with X-ray dispersive analysis (Figure 1) exhibited similar wrinkled and porous structures for both materials, however, the surface compositions were different, as expected. For the CLC sample, higher concentrations of aluminum (11%) and silicon (15%) were observed, while CLETE presented higher iron content (45%). Table 1 shows the acidity (by Pyridine-infrared and thermogravimetric analysis) and catalytic results (by Gas chromatography-Mass spectrometry). The CLETE biochar exhibited higher Brønsted and Lewis acidities and also presented higher furfural conversion. However, CLC presented a higher selectivity for furfuryl alcohol (FA) although its lower acidity. Other products, such as isopropyl furfuryl ether (PMF), furfuryl ether (DFE), and isopropyl furfuryl ester (IPF) were also formed, especially for CLETE, which explains the lower FA selectivity.2,3 Thus, these materials were suitable for furfural conversion to obtain not only furfuryl alcohol but also other valuable-added products.