Catalytic cracking of toluene over hematite derived from thermally treated natural limonite

摘要

The catalytic performance of hematite derived from thermally treated natural limonite on catalytic cracking of biomass tar using toluene as a model compound was investigated. The catalysts before and after catalytic reaction were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Magnetic Susceptibility meter (MS). The effect of reaction temperature and gas hourly space velocity (GHSV) on the catalytic performance of the newly formed hematite was studied in a laboratory scale fixed bed reactor. Furthermore, the composition of gas product was measured by gas chromatograph (GC) and the lifetime as well as the regeneration times was also evaluated. The results showed that the newly formed hematite had a high catalytic activity for the decomposition of toluene compared with that of quartz at the designed experimental temperature between 500 and 800 degrees C. The toluene conversion of 90% was obtained as the GHSV was not more than 5662 h(-1) at the reaction temperature of 700 degrees C. Meanwhile, the toluene was mainly decomposed into H-2, CO2, CO and hematite was transformed into magnetite after catalytic cracking. What is more important, the spent catalysts can be reclaimed easily by a magnet, which benefited the recycle and regeneration of the catalyst. In addition, the strong resistance of this hematite to carbon deposit in lifetime test due to the existence of active lattice oxygen in hematite was documented. Therefore, this kind of low cost and high activity hematite derived from natural limonite is considered to be an advantageous catalyst for catalytic cracking of toluene. (C) 2016 Elsevier Ltd. All rights reserved.