Study On Furfural Production From Lignocellulose Catalyzed By Low-cost Solid Acid

Furfural is not only an important solvent,but also a key precursor for the production of fuel additives and furan derivatives.The traditional furfural production process uses homogeneous inorganic acid as the main catalyst,which has some problems,such as corrosion,high energy consumption,difficult recovery and environmental pollution.Heterogeneous acid catalysts are widely used in the catalytic study of furfural because of their easy separation and regeneration.Among them,carbon-based catalysts have low cost and wide application,but so far most carbon-based catalysts have small specific surface area and few catalytic sites.In addition,the catalytic effect of solid acid on the preparation of furfural in water,the greenest solvent,is poor.Based on these,two kinds of solid acids supported by natural porous materials were prepared in this paper:carbon-based catalyst supported by rape pollen and diatomite based catalyst with hydrophobic carbon layer and core-shell structure,to achieve efficient,low-cost and green conversion of lignocellulose to furfural.Firstly,the carbon-based solid acid with rape pollen as carrier was studied.The pretreatment methods of ethanol-method and calcination at 400℃ for 2 h(heating rate of 2℃/min)could keep the original rape pollen with good morphology and carbon skeleton.The carbon-based solid acid(SO42-/Sn-TRP)was prepared by using carbonized pollen(TRP)as carrier,tin ion and sulfonic group as Lewis acid and Br(?)nsted acid.The structure of SO42-/Sn-TRP catalyst was characterized by SEM,EDS,FT-IR,ICP-OES,XRD,BET and Py-IR.The performance of SO42-/Sn-TRP for the preparation of furfural and the effects of different reaction conditions were investigated.Using only 10 wt%of SO42-/Sn-TRP catalyst loading,the furfural yield from xylose was 82.91%at 170℃ for 3 h,and the furfural yield from corn stover was 77.82%at 190℃ for 3 h.The catalyst still showed good recovery and stability after 5 batches.Then the solid acid with hydrophobic carbon layer and core-shell structure supported by diatomite was prepared.Sn was grafted onto diatomite as Lewis acid to prepare DM-Sn intermediate,then xylose was used as carbon source to wrap carbon layer on DMSn,and finally sulfonic acid group was grafted on carbon layer as Br(?)nsted acid to prepare SO42-/CX-DMSn catalyst.The SO42-/CX-DMSn catalyst was characterized by SEM,EDS,XPS,XRD,NH3-TPD and Py-IR.The catalytic performance of SO42-/CX-DMSn in pure water was studied:the furfural yields from xylose and corncob were 65.94%and 65.74%respectively under the optimum reaction condition of 180℃ for 5 h.Compared with the similar reported literatures,furfural yield from xylose and corncob both increased by about 15%.The relationship between the catalytic effect and the structure of the catalyst was deeply studied.The results show that:1)different solvents did not affect the active sites of the SO42-/CX-DMSn catalyst;2)the catalysts with hydrophobic carbon layer had higher initial reaction rate and higher catalytic performance;3)the appropriate amount of medium-strong acid site in SO42-/CX-DMSn catalyst is the effective catalytic active center.SO42-/CX-DMSn catalyst showed good water resistance and stability in high temperature water,and the catalyst could be renatured by water-ethanol washing method.This study provides an effective theoretical guidance for the preparation of furfural in pure water by efficient green catalysis.