Catalyzing Reed To Furoic Acid By Chemical-biological Method

Lignocellulosic biomass is one of the most important renewable energy sources after fossil energy sources such as coal,natural gas and petroleum,with low price and abundant reserves.Among them,the xylan in hemicellulose is acid-hydrolyzed to produce xylose,and then dehydrated into furfural(FAL).FAL is an organic reagent widely used in industry and is known as one of the top 12 value-added products.Furoic acid(FA)is one of FAL derivatives,mainly produced by oxidation of FAL.In the process of preparing FA through catalytic oxidation of catalysts,high temperature and high pressure reaction conditions and environmental unfriendliness make it unfavorable for industrial production,so a green and environmentally friendly catalysis method has been developed.In this study,lignocellulosic biomass reed was tandemly catalyzed into FA by sequential conversion with solid acids and and biocatalysts in the aqueous phase and in the deep eutectic solvent(DES)-water system.The results were as follows:Firstly,using vermiculite as carrier,solid acid Sn-vermiculite loaded with SnCl4 was prepared.The raw materials of vermiculite and Sn-vermiculite were characterized by FT-IR,XRD,SEM and BET.The results showed that the surface morphology and structure of Sn-vermiculite changed to a certain extent.Compared with fresh vermiculite,the specific surface area of modified Sn-vermiculite increased to 170 m2/g,and the pore volume increased to 0.11 m3/g.The average pore diameter decreased from 7.6 nm to 2.5 nm.Probably,the intercalation of Sn4+and SO42-blocked the pore structure of vermiculite,thereby increasing the contact opportunity of catalyst and substrate.Thus,the catalytic effieciency was enhanced.Secondly,the catalytic processfor the production of FAL from reed in the water and DES-water system were investigated,and the following conclusions were obtained:(1)In the aqueous system,the reed was pretreated with 1 wt%NaOH,and then Sn-vermiculite(4.0 wt%)catalyzed the reaction of 3 g AP-reed for 20 min.The reed-derived FAL could reach 55.0 mM,and the yield of FAL was 38.4%.(2)In the DES ChCl:LA-water system,3 g AP-reed was catalyzed at 180℃ for 30 min to obtain FAL 75.5 mM,and the yield of FAL was 58.4%.(3)The FT-IR and SEM spectra showed that the characteristic peaks of hemicellulose and lignin were weakened,and the hemicellulose and lignin in the reeds were almost completely removed.XRD patterns showed that the treatment with dilute NaOH increased the crystallinity of the reeds,and the crystallinity of the reed pretreated in the ChCl:LA-water system was obviously higher than that in the aqueous system.In addition,using solid acid Sn-vermiculite(4.0 wt%)as catalyst,the optimum catalytic temperature and catalytic time were obtained as follows:170℃ and 20 min in the aqueous water;180℃ and 30 min in 20 wt%ChCl:LA-water system.Thirdly,in order to synthesize FA in the aqueous system,the chemical-biological method by sequential catalysis with Sn-vermiculite and recombinant E.coli HMFOMUT was used for FA production using AP-reed as feedstock.The optimum catalytic temperature,catalytic pH,NAD+dose,surfactant loading,and metal ion addtive dosage were 30℃,pH 6.5,0.25 mol NAD+/mol FAL,6.0 mM PEG-4000 and 1.5 mM Sn4+,respectively.Under the conditions of 30℃ and pH 6.5,the reed-derived FAL(52.0 mM,adjusted pH)was subjected to E.coli HMFOMUT whole cell biotransformation for 72 h,and FAL was almost completely converted.The FA yield was obtained at 0.077 g FA/g AP-reed(0.269 g FA/g xylan in AP-reed).This verified the feasibility of synthesizing FA from reed via chemical-biological approach in water system.Finally,in order to synthesize FA in ChCl:LA-water system,various parameters affecting the biocatalytic processes were investigated.The optimal reaction temperature,pH,Tw-80 dosage and Co2+ dose were 30℃,7.0,8.0 mM and 2.0 mM,respectively.The reed-derived FAL(66.7 mM)was subjected to E.coli HMFOMUT whole cell biotransformation for 56 h,and FAL was almost completely converted.The FA yield was obtained at 0.116 g FA/g AP-reed(0.404 g FA/g xylan in AP-reed),which had better catalytic efficiency than that in the aqueous system.In ChCl:LA-water system,one effective synthesis route for synthesizing FA from AP-reed was successfully demonstrated.In summary,effective tandem catalysis of AP-reed into FA was established by sequential conversion with solid acid Sn-vermiculite and recombinant E.coli HMFOMUT cells in two kinds of reaction media.Compated to the aqueous system,the DES ChCl:LA-water system was better as reation media for catalyzing AP-reed into FA.This study provided a new idea for synthesis of furan-based compounds from lignocellulosic materials.