Structural properties and reactivity variations of wheat straw char catalysts in volatile reforming

Abstract

Abstract In this study, wheat straw char was prepared at 500°C and used as a catalyst (at 500–700°C) to reform the wheat straw volatiles. The char samples before and after reforming were characterized in terms of N2 adsorption (BET area), Raman spectroscopy, Fourier transform infrared spectroscopy, proximate analysis, ultimate analysis, and inductively coupled plasma measurements. The surface morphology of the used char was analyzed by a scanning electron microscope. The results have revealed that following the reforming process, the carbon content increased from 69.2% to 71.7% (at 500°C), 73.9% (at 600°C), and 74.3% (at 700°C) and the fixed carbon content increased from 64.6% to 68.7% (at 500°C), 71.4% (at 600°C), and 72.4% (at 700°C). In contrast, the higher heating value of the used char remained unchanged. We observed a decrease in specific surface area (from 112.67 to 7.93 m2·g−1), but an increase in char defects and functional groups following the reforming process (at 600°C) served to maintain catalytic activity, as shown in a second reforming test. Our results suggest that surface defects and functional groups are the main factors contributing to char reactivity.