Study On Steam Pretreatment For Simultaneous Essential Oils Extraction Combined Pyrolysis Catalyst Loading And Its Influence On The Products Of Pyrolysis

Biomass resource has the advantages of large stock,environmental friendly and renewable;meanwhile,it can be converted into high quality liquid or gas fuel.Thus,bio-energy has a potential to be a supplement or a substitute for fossil fuels in the future.Fast pyrolysis technology is considered as one of the most promising technologies for converting renewable biomass resources into high-energy density liquid fuel called bio-oil.But there are some drawbacks for the application of bio-oil as fuel,including high water and oxygen content,high viscosity,chemical instability and poor ignition characteristics.A combined method for the pre-extraction of essential oils(EOs)and the uniformly dispersion of alkaline earth metal oxide(AEMO)catalyst on pine sawdust(PS)are studied in the present work.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).Results suggest that PS mixed with AEMO was greatly benefit for the extraction of EOs,AEMO could enhance the disruption of oil glands in PS,resulting in a higher extraction yield of EOs.The proportion of alcohols in EOs increased significantly but that of hydrocarbons decreased while PS mixed with CaO or MgO,which indicated that AEMO tended to favor for the extraction of alcohols.When PS was pretreated by AEMO loading and SD,the concentration of hydrocarbons in the organic phase of 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 ? in almost all cases,and the GC-MS peak area selective of hydrocarbons in the organic phase of bio-oil could reach to 37.19%for the pyrolysis of pine sawdust mixed with 5 wt.%CaO and then treated by steam distillation.It is found that when the PS was pretreated by SD,much more micro-channels appeared in the spent sawdust.These micro-channels in PS can prolong the residence time of pyrolysis vapor and increase the activity of secondary reactions,which is of benefit to the deoxygenation reaction in fast pyrolysis process.High pyrolysis temperature deserves to consider because it was helpful for improving bio-oil quality,the GC-MS peak area selective of hydrocarbons in the organic phase of bio-oil could reach to 62.48%when the pyrolysis temperature was 600 ?,however,when the pyrolysis temperature is higher than 600 ?,the yield of bio-oil started to decrease significantly.