This study systematically investigates the pyrolysis process of wheat straw in a ternary carbonate molten salt system (Li2CO3-Na2CO3-K2CO3) with the addition of different metal oxides (CaO, Al2O3, Fe2O3, TiO2). The effects of the ratio of molten salt, type of metal oxide, and pyrolysis temperature on the pyrolysis products were examined. As the temperature increased, in the MS15 (wheat straw: molten salt = 1:15) system, the yield of gasphase products rose from 21.21 wt% to 82.57 wt%, while the yields of solid products and bio-oil rapidly decreased to 23.76 wt% and 37.60 wt%, respectively. Additionally, the system exhibited the highest lower heating value (LHV) within the temperature range of 450-750 degrees C. Therefore, the optimal ratio of wheat straw to carbonate molten salt is 1:15. Furthermore, when adding four metal oxides (Al2O3, CaO, Fe2O3, TiO2) to the MS15 system, it was found that the addition of CaO (CaO-MS15) resulted in the highest LHV across all pyrolysis temperatures. Notably, at 550 degrees C, the maximum LHV was 21.89 MJ/Nm3, an increase of 5 MJ/Nm3 compared to MS15. Analysis of the solid phase using XRD, XPS, and SEM indicated that the active sites on the surface of CaO facilitated the cleavage and deoxygenation of bio-oil on the biochar during the pyrolysis process, breaking it down into small molecular gases.
