An insight into the effect of calcination conditions on catalytic cracking of toluene over 3Fe8Ni/palygorskite: Catalysts characterization and performance

In this paper, the effect of calcination conditions on catalytic cracking of toluene over 3Fe8Ni/PG (PG: palygorskite) was investigated. The experimental parameters including the calcination temperature, time and atmosphere and reaction temperature were evaluated. The catalysts were characterized using X-ray diffraction (XRD), H-2 temperature-programmed reduction (TPR), transmission electron microcopy (TEM) and Raman spectroscopy. The gas composition was analyzed by a gas chromatograph (GC). The results showed that 3Fe8Ni/PG catalyst exhibited a higher catalytic reactivity for catalytic cracking of toluene than that of thermal cracking over quartz. In consideration of the thermal stability and catalytic reactivity of catalyst, a proper calcination temperature and time should be employed in the preparation of 3Fe8Ni/PG catalyst. The 3Fe8Ni/PG reduced in hydrogen at 700 degrees C for 2 h showed the highest catalytic reactivity as evidenced by the toluene conversion of 100% at the reaction temperature of 550 degrees C. The catalytic reactivity of 3Fe8Ni/PG reduced in hydrogen for toluene conversion was superior to that of 3Fe8Ni/PG calcinated in air, 3Fe/PG, and 8Ni/PG, which revealed that the awaruite (Ni-Fe) was the active component for the decomposition of toluene. Moreover, steam reforming of toluene over 3Fe8Ni/PG catalysts suggested that 80% toluene conversion can be achieved and most of toluene was converted into H-2 and CO. Both amorphous carbon and graphitic carbon species were formed on 3Fe8Ni/PG catalysts after the catalytic reaction. The D/G ratio (the relative intensity of D-band to G-band ratio) was positively correlated to the catalytic reactivity of 3Fe8Ni/PG catalysts. (C) 2016 Elsevier Ltd. All rights reserved.