Study of a new combined method for pre-extraction of essential oils and catalytic fast pyrolysis of pine sawdust

A new combined method for the pre-extraction of essential oils (EOs) and the uniformly dispersion of alkaline earth metal oxide (AEMO) on pine sawdust (PS) was investigated. EOs were firstly extracted from PS after mixing with a certain amount of AEMO through steam distillation (SD), and then the pretreated PS was utilized in the process of fast pyrolysis to produce the upgraded bio-oil. A maximum extraction yield of EOs was 1.61 wt% from PS mixed with 5 wt% CaO within 300 min, compared with 1.21 wt% from the control (raw PS). The proportion of alcohols in EOs increased significantly when using PS mixed with AEMO. When PS was pretreated by the combined AEMO mixing and SD, the content of hydrocarbons in organic phase of the bio-oil increased significantly while that of acids and CnHmOx decreased. The analysis of physicochemical properties for the bio-oil further demonstrated that the quality of bio-oil was improved based on the new pretreatment method. Furthermore, the maximum bio-oil yield was obtained at pyrolysis temperature of 500 °C in almost all cases.