Effects of potassium salt on the pyrolysis products characteristics of alkali lignin from furfural residue

•Potassium salt has an interactive effect on the organic components of pyrolysis products.•Both potassium ions and acid ions can affect the pyrolysis products.•K2CO3 has the strongest catalytic effect and its demethylation ability reaches about 57.00%.•KCl produces the highest proportion of guaiacol.•CH3COOK promoted the formation of acids in the product and had better fusion effect with bio-chars.