Effect of reaction temperature on Mo/Al2O3 catalytic hydrodeoxygenation of alkali lignin bio-oils
Alkali lignin,an important source of industrial lignin,can be used for producing aromatic com-ponents in biofuels while retaining its aromatic ring structure through hydrothermal liquefaction technology.The temperature during the reaction process significantly influences the bio-oil yield and composition.This study investigates the impact of reaction temperature on the oil yield and aromatics yield in the preparation of bio-oil through hydrothermal liquefaction of alkali lignin catalyzed by Mo/Al2O3.The study's findings re-vealed that the oil yield initially increased and then decreased with increasing temperature,reaching its highest value at 280 ℃.As the temperature increased,the O/C ratio of the bio-oil continuously decreased to a minimum of 0.22.In contrast,the H/C ratio steadily increased to a maximum of 1.14.Additionally,the high calorific value steadily increased to a maximum of 30.41 MJ/kg.These results indicated that higher temperatures contributed to improving the fuel properties of the bio-oil.However,increasing the temperature was not conducive to the enrichment of aromatic components in the bio-oil.The higher the temperature,the lower the relative content of aromatic compounds and the higher the content of phenolic compounds in the bio-oil.The study observed that the relative content of aromatics reached its peak value of 34.1％at 260 ℃ when 15％Mo/Al2O3 was added as a catalyst.At this temperature,the selectivity to toluene in the aromatics product was as high as 97.7％,indicating the optimal enrichment of aromatics.In summary,the study dem-onstrates that the temperature during the hydrothermal liquefaction process of alkali lignin affects both the bio-oil yield and composition.While higher temperatures enhance the oil yield and fuel properties of the bio-oil,they also reduce the relative content of aromatic compounds.The addition of Mo/Al2O3 as a catalyst at an appropriate temperature can promote the enrichment of aromatics,where toluene is the dominant product.
Alkali ligninHydrothermal liquefactionBio-oilAromatic hydrocarbonsHydrodeoxy-genationReaction temperature
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