Rice husk pyrolysis polygeneration of levoglucosan-rich bio-oil and functional bio-char: roles of hydrothermal pretreatment and acidic hydrothermal pretreatment on products

Positive roles of hydrothermal pretreatment and acidic hydrothermal pretreatment were researched in this study. Results of pyrolysis indicated that hydrothermal pretreatment not only significantly enriched levoglucosan (LG) content in bio-oil, but also increased specific surface area of bio-char. When acid was introduced into hydrothermal pretreatment process, the top-quality liquid and solid products acquired at a relatively low pretreatment temperature. For bio-oil, the LG content increased from 0% in rice husk (RH) to 32.68% in the sample hydrothermal pretreated in deionized water at 170 celcius (TRH170). The highest LG content of 43.0% obtained from the sample hydrothermal pretreated in phosphoric acid solution at 115 celcius (PTRH115). The BET of bio-char after activation increased from 2135.6 m(2)/g in RH to 2508.3 m(2)/g in TRH170. And acid addition optimized the pore distribution of activated bio-char. Both of the average pore size and efficient pore volume in micro-pore section were noticeably increased.

Automated summary

The positive roles of hydrothermal pretreatment and acidic hydrothermal pretreatment were investigated in this study. The pyrolysis results showed that hydrothermal pretreatment greatly increased the content of levoglucosan (LG) in bio-oil and also enhanced the specific surface area of bio-char. Introduction of acid into the hydrothermal pretreatment process resulted in higher quality liquid and solid products obtained at lower pretreatment temperatures. Specifically, the LG content in the bio-oil increased from 0% in rice husk (RH) to 32.68% in the sample hydrothermal pretreated in deionized water at 170 degrees celcius (TRH170). Furthermore, the addition of acid optimized the pore distribution of activated bio-char, with noticeable increases in average pore size and efficient pore volume in the micro-pore section.