Catalytic Upgrading Of Biomass Pyrolysis Volatile Over Medical Stone

Biomass is a potential energy with variety of advantages,such as abundant reserves,low-cost,renewable,low pollution and so on.Due to the shortage of fossil feedstock and environmental pollution,the use of biomass as a substitute for fossil fuels has been gaining an increased attention recently.Fast pyrolysis is considered a promising technology to convert biomass into liquid products and high value-added chemicals.However,crude bio-oil has many disadvantages,such as abundant oxygenic compounds,low heating value,high corrosion and high viscosity,and so on.How to improve the quality of bio-oil is one of the key technologies for industrialization.In this paper,pine sawdust was used as raw material.The effect of medical stone on biomass fast pyrolysis volatile was studied.To improve catalytic performance of medical stone,Mg and Ni modified medical stone was prepared.The specific work and results are as follows:（1）The catalytic upgrading experiment of biomass pyrolysis volatile over medical stone was carried out in a dual loop reaction system.The effects of upgrading bed material,catalytic upgrading temperature and circulating rate of medical stone were investigated.The results showed that upgrading by medical stone decreased both the yields of light tar and heavy tar while increased the content of light tar compared to quartz sand.Medical stone can promote the removal of oxygen in bio-oil in the form of H₂O and CO_x,especially in the form of H₂O and CO.After catalytic upgrading by medical stone,the content of hydrocarbons and phenols in the tar increased significantly,while the content of acids and ketones decreased.Increasing catalytic upgrading temperature is more favorable to remove oxygen of tar in the form of H₂O and CO.And the content of hydrocarbons in the tar increased while the content of acids,esters and ketones decreased with the increasing of catalytic upgrading temperature.When increasing the circulating rate of medical stone bed material,the light tar content increased while the content of hydrocarbons and phenols in the tar decreased.When the catalytic upgrading temperature was 520^oC,the circulating rate was 5.5 kg/h,tar quality was in a good state,high content of light tar and the content of phenols reached 46.37%.（2）Mg and Ni modified medical stone catalysts were prepared by impregnation method.The catalytic upgrading experiment of biomass pyrolysis volatile over modified medical stone catalysts was carried out in a fixed bed reactor.The pyrolysis temperature was 500 ^oC,and the catalytic upgrading temperature was 500 ^oC.After modification,the catalytic activity of the catalysts performed much better than unmodified catalysts,the tar yield decreased significantly,the gas yield increased,and the water yield increased.The catalytic cracking activity of Ni/MS was significantly higher than that of Mg/MS.Compared to unmodified medical stone,Ni/MS promoted the decarboxylation and dehydroxylation reactions,which resulted in the removal of oxygen from bio-oil in the form of CO₂ and water.After catalyzed by Ni/MS,the tar yield was 35.17 wt.%,the water yield was 25.01 wt.%,the CO yield was5.43 wt.%,the CO₂ yield was11.29 wt.%,and the carbon deposition yield was only 0.13 wt.%.The main components of tar were phenols.Mg and Ni modified medical stone catalysts had poor effect on tar upgrading,and could not enrich certain compounds in the tar.Modified medical stone catalysts could reduce the acids content,and lowered the content of high oxygenated compounds in tar.Compared to Ni/MS,the quality of Mg/MS catalytic upgrading oil was better.