Experimental Study On Catalytic Hydropyrolysis Of Biomass For The Production Of Advanced Biofuel

The efficient use of biomass energy can improve the national energy structure,alleviate the energy crisis,and reduce the pressure of environmental pollution.Biomass fast pyrolysis can efficiently produce liquid products.However,the products have high oxygen content due to the low carbon hydrogen ratio of biomass and need to be upgraded.Catalytic fast pyrolysis of biomass can deoxygenate pyrolysis vapor during the process and improve the quality of liquid products.However,there are problems such as low liquid product yield and rapid catalyst deactivation.Biomass catalytic hydropyrolysis,introducing an external hydrogen source and hdyrodeoxygenation catalysts in the catalytic fast pyrolysis process,can increase hydrocarbon production and reduce coke.It also can efficiently convert biomass into high-quality liquid fuels.This study thoroughly explored the catalytic effect of the bifunctional catalyst of the zeolites loaded with transition metal oxides in the catalytic hydropyrolysis of biomass,studied the influence of various factors on the regulation of the product.Experimental exploration of the mechanism of oxygen compound hydrodeoxygenation and the principle of catalyst deactivation were also conducted.Firstly,the experiments of biomass pine catalytic fast pyrolysis was carried out on a micro pyrolysis reactor.The effects of pyrolysis atmosphere,supported metal type,metal loading and catalytic temperature on the distribution of pyrolysis products and catalyst coke were deeply explored.The experimental results showed that the hydrogen increases the production of hydrocarbons and reduces the coke of the catalyst.Compared with pure HZSM-5,HZSM-5 loaded with metal oxides increased aliphatics by 60%and reduced coke by 52%.Among them,molybdenum oxide obtained the highest hydrocarbon product among metal oxides.In this study,acetone and m-cresol,the two main products of hydropyrolysis of cellulose and lignin,were selected as model compounds.Experiments of hydrodeoxygenation of model coupounds were carried out for the catalytic reaction mechanism.Experimental results show that the addition of molybdenum oxide enhance the direct hydrodeoxygenation reaction activity of acetone,making it more prone to generate propylene,butene and corresponding alkanes.The m-cresol was also enhanced in the direct hydrodeoxygenation reaction activity,and the toluene in the BTX product reached an average product selectivity of 98%.The experimental results of different hydrogen pressure conditions show that the increase of hydrogen pressure enhances the hydrodeoxygenation and hydrogenation reaction of MoO₃,which increases the yield of aliphatic hydrocarbons in the acetone experiment by 72%relative to normal pressure.The monocyclic ring in the meta-cresol experiment Aromatic products increased the yield by 22.7%.Finally,under different hydrogen pressures(0.1bar,10bar,20bar,30bar),the actual biomass was subjected to PY-GCMS catalytic hydropyrolysis experiments.The experimental results prove that the increase of hydrogen pressure can increase the yield of target hydrocarbon products.Compared with the normal pressure,the 30bar hydrogen pressure experiment results increase the yield of monocyclic aromatic hydrocarbons by 11.2%and gaseous alkanes by 30.9%.At the same time,continuous biomass sampling experiments were carried out under normal pressure and high-pressure hydrogen conditions.The results show that the loading of molybdenum oxide can effectively extend the catalyst activity time,and the use of high hydrogen pressure(30bar)greatly enhances this improvement effect.In this paper,transition metal oxides are loaded on molecular sieves to form a dual-functional catalytic system for biomass hydrocatalytic pyrolysis.The mechanism of the hydrodeoxygenation reaction and the regulation of biomass hydrocatalytic pyrolysis products under the action of various factors are deeply explored.The efficient generation of target hydrocarbon products is realized,and the coking and deactivation of the catalyst is greatly reduced,which lays the theoretical foundation and technical support for the large-scale application and promotion of the biomass pyrolysis conversion process.