Fast pyrolysis product distribution of biopretreated corn stalk by methanogen

•Methanogen pretreatment changed remarkably pyrolysis product distribution in bio-oil.•After biopretreatment, the phenols content increased from 42.25% to 79.32%.•Methanogen pretreatment improved the pyrolysis selectivity of CS for 4-VP.•Biopretreatment increased the 4-VP content from 28.6% to 60.9% in bio-oil.•Effects of biopretreated time on pyrolysis product distribution were insignificant. After pretreated by methanogen for 5, 15 and 25days, corn stalk (CS) were pyrolyzed at 250, 300, 350, 400, 450 and 500°C by Py–GC/MS and product distribution in bio-oil was analyzed. Results indicated that methanogen pretreatment changed considerably the product distribution: the contents of sugar and phenols increased; the contents of linear carbonyls and furans decreased; the contents of linear ketones and linear acids changed slightly. Methanogen pretreatment improved significantly the pyrolysis selectivity of CS to phenols especially 4-VP. At 250°C, the phenols content increased from 42.25% for untreated CS to 79.32% for biopretreated CS for 5days; the 4-VP content increased from 28.6% to 60.9%. Increasing temperature was contributed to convert more lignin into 4-VP, but decreased its content in bio-oil due to more other chemicals formed. The effects of biopretreatment time on the chemicals contents were insignificant.