Enhancing the quality of bio-oil and selectivity of phenols compounds from pyrolysis of anaerobic digested rice straw

• Anaerobic digested substrate was high value-added utilized by pyrolysis.
• The thermal decomposition characteristics of ADRS changed significantly.
• The pyrolysis selectivity of ADRS for 4-Vinylphenol was improved.
• The yield of phenols increased after anaerobic digestion treatment.

This study investigated the thermal decomposition characteristics and pyrolytic products of anaerobic digested rice straw (ADRS) by thermogravimetric (TG) and pyrolysis–gas chromatograph/mass spectrometry (Py-GC/MS) analysis. Compared with the raw rice straw (RS), the thermal decomposition temperature of ADRS was shifted to higher temperature zone and the second decomposition zone of cellulose (Toffset(c) − Tpeak) became narrower (14 °C less), which indicated that the composition of rice straw were changed significantly by the anaerobic digestion pretreatment. Py-GC/MS analysis showed that the quality of the bio-oil and the selectivity of pyrolytic products could be obviously improved by anaerobic digestion. The total yields of alcohols, acids, aldehydes, furans, anhydrosugars, and ketones pyrolysis substances decreased, while the yield of phenols increased. The yield of 4-Vinylphenol (4-VP) increased from 29.33%, 8.21% and 5.76% to 34.93%, 12.46% and 7.68% at 330, 450 and 650 °C, respectively, after anaerobic digestion.