In this study,laboratory scale pyrolysis and steam gasification experiments with direct causticization using TiO2 for wheat straw alkaline black liquor were performed in a thermo gravimetric analyzer and a tube furnace,respectively.Effects of TiO2 on the pyrolysis and steam gasification characteristics were discussed based on the products analysis.Results showed that with addition of TiO2,thermo gravimetric behaviors along with releasing patterns of CO2 and CO of the black liquor were changed when the pyrolysis temperature was higher than 550 °C due to the direct causticization reactions.In the presence of TiO2,swelling and agglomeration were prevented during the pyrolysis process.Meanwhile,sodium emission was significantly decreased on account of adding TiO2.In addition,steam gasification rate of the black liquor char at 850 °C was obviously improved and melting phenomenon during the gasification process was suppressed with direct causticization.Moreover,constant H2 yield and increasing yields of CO2 and CO of the gaseous products derived from the steam gasification process were obtained with addition of TiO2.