Abstract
The pyrolysis of pine sawdust was carried out in a fixed bed reactor heated from 30 °C to a maximum of 700 °C in atmospheric nitrogen and pressurized hydrogen (5 MPa). The yield, elemental composition, thermal stability, and composition of the two pyrolysis bio-oils were analyzed and compared. The result shows that the oxygen content of the bio-oil (17.16%) obtained under the hydrogen atmosphere was lower while the heating value (31.40 MJ/kg) was higher than those of bio-oil produced under nitrogen atmosphere. Compounds with a boiling point of less than 200 °C account for 63.21% in the bio-oil at pressurized hydrogen atmosphere, with a proportion 14.69% higher than that of bio-oil at nitrogen atmosphere. Furthermore, the hydrogenation promoted the formation of ethyl hexadecanoate (peak area percentage 19.1%) and ethyl octadecanoate (peak area percentage 15.42%) in the bio-oil. Overall, high pressure of hydrogen improved the bio-oil quality derived from the pyrolysis of pine biomass.
Highlights
Biomass is one of the most potential renewable resources [1], which can replace fossil feedstocks to produce chemicals [2]
Considering that the volatile free radicals and molecular fragments produced by the thermal decomposition of biomass in a hydrogen atmosphere are stabilized in combination with hydrogen, it escapes from the inside of the particles, remarkably improving the yield of pyrolysis bio-oil
The results show that the content of compounds with a boiling point of 0–200 ◦ C in the pyrolysis bio-oil obtained in a hydrogenation atmosphere is 63.21%, while the content of compounds with a boiling point of 0–200 ◦ C of pyrolysis bio-oil in a nitrogen atmosphere is 55.11%
Summary
Biomass is one of the most potential renewable resources [1], which can replace fossil feedstocks to produce chemicals [2]. The pyrolysis under different atmospheres and pressures can regulate the thermochemical conversion process of biomass, promote some reactions, and inhibit other reactions to realize the high enrichment of high value-added chemicals in pyrolysis bio-oil [9]. Compared with ordinary pyrolysis, hydropyrolysis has the advantages of high carbon content, hydrocarbon yield, and bio-oil quality [15]. Zheng et al [18] studied the hydrogasification of biomass and found that hydrogenolysis can directly generate high-quality and high-yield pyrolysis bio-oil and gaseous hydrocarbons without catalysts. The study on pyrolysis mostly concentrated in the nitrogen atmosphere, and limited studies have focused on the pyrolysis of biomass for bio-oil production in the hydrogen atmosphere. This work improves the bio-oil quality of pine biomass pyrolysis in pressurized hydrogen gas and is an interesting experimental scheme for wood pyrolysis
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