Study On Preparation Of Furfural By Directional Catalytic Pyrolysis Of Corncob

Biomass as the only renewable carbon source can be transformed into high value chemicals by fast pyrolysis.The bio-oil derived from biomass fast pyrolysis has many disadvantages,such as high oxygen content,high acidity and low caloric value.These drawbacks may impede the development of commercialization process.Notably,the bio-oil contained large amounts of high value-added compounds as important chemical materials.Furfural（FF）is one of the most important derivatives of furan ring system,which is also widely used in the filed of synthetic plastics,medicine,pesticide,petrochemical.Therefore,it is necessary to study the relevant upgrading techniques to prepare high value-added bio-oil to enhance the economics of pyrolysis of biomass.In this paper,the corncob catalytic pyrolysis reaction was carried out in a home-made horizontal fixed-bed reactor.Therein,ZnCl₂ was used as a catalytic active component.Through the regulation of different catalytic methods,the reaction temperature and catalyst types on the components of bio-oil were investigated.The variation of the relative content of furfural in bio-oil was obtained eventually.Prior to the pyrolysis,the corncob was pretreated with ZnCl₂.The effects of various concentrations of ZnCl₂ impregnation solution on the microstructure and pyrolysis behavior of corncob were investigated by ICP-AES,SEM and TGA,respectively.The results showed that the surface structure of the corncob become looser and created new sheet structure in the presence of ZnCl₂（1.69%and 2.71%and 5.89%）.With the increase of the content of ZnCl₂,the initial pyrolysis temperature and the maximum pyrolysis weight loss rate moved to the low temperature region,and the volatile release region shifted to the left obviously.Pyrolysis experiments was conducted at four temperature levels of 300℃,350℃,400℃and 450℃.It showed that the initial pyrolysis temperature and the maximum pyrolysis weight loss rate moved to low temperature with the increase of the amount of ZnCl₂ at the same temperature,and the bio-oil yield also decreased with the increase of ZnCl₂ impregnation at the same temperature.Notably,the relative peak area of furfural in bio-oil decreased with the increase of temperature at the same amount of ZnCl₂ impregnation.But higher relative peak area of furfural was obtained under higher impregnation amount of ZnCl₂ at the same temperature.Based on aforementioned study,the mesoporous molecular sieve SBA-15 was modified with ZnCl₂ as the active component.The mesoporous catalyst modified by ZnCl₂/SBA-15 was prepared by impregnation method.The physicochemical properties of the ZnCl₂/SBA-15 were characterized by SEM,TEM,BET and XRD,respectively.The catalytic effects of different catalysts were then investigated.The ZnCl₂/SBA-15 still keeps a good SBA-15 microstructure and a good distribution of ZnCl₂ on the surface of the pore.The results revealed ZnCl₂/SBA-15could improve the catalytic performance and the selectivity of furfural.The catalytic activity and selectivity to furfural of ZnCl₂/SBA-15 exhibited the highest performance at the amount of0.4 ZnCl₂,and the yield of furfural reached the maximum at 400℃.These results indicated that furfural was originated from hemicellulose and partial cellulose.The relative peak area and selectivity of furfural were improved.However,the relative content of bio-oil exhibited a minor increasing trend.It shows that the macromolecule generates more water and small molecules in the process of the catalytic process.