Intrinsic promotion mechanism of calcium oxide on ketone production during catalytic fast pyrolysis of biomass via experiment and density functional theory simulation

[Display omitted] •Relationship between CaO intrinsic properties and bio-oil components was explored.•Adsorption energy of RS pyrolysis products on CaO was calculated by DFT simulation.•Modification with acid enhanced the length of Ca-O bond and strong basic sites.•Longer Ca-O bond promoted the conversion of cellulose/hemicellulose into ketones. CaO modified with acetic acid solution or sodium hydroxide (H-CaO/OH-CaO) was used to explore the relationship between the physical and chemical properties of CaO and the components of bio-oil during the pyrolysis of rice straw (RS) and model compounds via experiment and density functional theory(DFT) simulation. The results showed that the modification changed the properties of CaO, and thus the catalytic performance on production of bio-oil components. H-CaO with the larger number of strong basic sites (1.10 ∼ 2 times than commercial CaO) and the longer Ca-O bond length showed the better selectivity and performance on formation of ketones (the maximum relative content in bio-oil reached 43 %). The conversion pathway of cellulose/hemicellulose was changed by H-CaO, which promoted the formation of ketones. The easier combining of H-CaO with the pyrolysis primary products due to the longer Ca-O bond was the key to its better performance.