Effects of different low temperature pretreatments on properties of corn stover biochar for precursors of sulfonated solid acid catalysts

In this study, the effects of different pretreatment methods including phosphoric acid (PA), freeze drying (FD) and phosphoric acid-freeze drying combined (PA-FD) pretreatment on corn stover characteristics and pyrolysis of corn stover samples was investigated. The results demonstrated that the physiochemical properties of biochars varied significantly. In comparison, PA pretreatment could effectively remove a large portion of inorganics and improve the fuel characteristics. PA-CSB-600 had a greater HHV, lower O/C and H/C ratios, and a lower biochar energy yield (Ye), indicating the possibility for an attractive fuel source. PA-FD pretreatment would significantly affected cell volume and caused mechanical damage to corn stover structure. As a sulfonated solid acid catalyst precursor, the results of cellulose catalytic hydrolysis indicated that the density of -SO3H in FD-CSA was much higher than PA-FD-CSA, but lower surface special area. Specifically, PA-FD-CSB prepared at 600 °C resulted in the maximum increase of cellulose conversion by 34.7-81.3%.