Study On Separation And Functionalization Of Cellulose From Pueraria Lobata Residue

Biomass is a kind of renewable resource,it possesses significant advantages such as abundant,easily available and low cost,which is generally taken from agroforestry waste,economic plant processing waste,domestic waste and so on.Cellulose is one of the most abundant components in biomass and an important chemical feedstock,it can be developed as a series of highly valuable materials or chemicals and is widely used in fields of food,medicine,textile and construction.The Pueraria lobata residue is produced during the production of Pueraria lobata starch.The value of Pueraria lobata residue implication is not exploited due to it is directly discarded.Cellulose was determined to be the most abundant components of Pueraria lobata residue.Therefore,in this paper,the study was carried out by isolating cellulose from Pueraria lobata residue,preparing nanocellulose and cellulose based solid acid catalyst,in order to provide reference for the utilization of Pueraria lobata residue.The details are shown in the following:(1)Cellulose in Pueraria lobata residue was isolated using sodium chlorite and sodium hydroxide as treatment reagents.The contents of lignin,hemicellulose,and cellulose in Pueraria lobata residue,Pueraria lobata residue after chlorite treatment,and Pueraria lobata cellulose were determined by Van Soest method,respectively.Various factors including concentrations of sodium chlorite and sodium hydroxide,reaction temperature and reaction time were optimized.In addition,the morphology,crystal structure,chemical structure,and thermal stability of Pueraria lobata residue,Pueraria lobata residue after chlorite treatment,and Pueraria lobata cellulose were characterized by scanning electron microscopy(SEM),X-powder diffraction(XRD),infrared spectroscopy(FT-IR)and differential thermal gravimetric analysises,respectively.The obtained results demonstrated that the content of cellulose in Pueraria lobata residue was59%.Moreover,the purity of cellulose isolated from Pueraria lobata residue was about94%after treatment with sodium chlorite and sodium hydroxide.Furthermore,the crystal texture of Pueraria lobata cellulose was ascribed to cellulose I with a 71.5%of crystallinity.The maximum pyrolysis temperature of Pueraria lobata cellulose was determined as 356°C,strongly demonstrating its good thermal stability.(2)The nanocellulose was prepared by phosphoric acid/oxalic acid mixed acid method from Pueraria lobata cellulose.The yield of nanocellulose was determined by gravimetric analysis,and the effect of the ratio of phosphoric acid/oxalic acid/water on the yield of the nanocellulose was investigated.The nanocellulose was characterized by atomic force microscopy,X-powder diffraction,zeta potential analysis,infrared spectroscopy,elemental analyzer,differential thermal thermogravimetric analysis.The results showed that the highest nanocellulose yield(67%)was obtained when the ratio of mixed acids was 30/45/15.The nanocellulose is rod shaped structure with a diameter of5.7-23.9 nm and crystallinity of 82.5%.The maximum pyrolysis temperature of nanocellulose was 369°C,demonstrating high thermal stability of nanocellulose.The excellent dispersion stability of the nanocellulose in different polar solvents was attributed to the nanocellulose size homogeneity and the introduction of bifunctional groups on the surface.(3)The Pueraria lobata cellulose based solid acid was prepared throughout one-step procedure by sulfuric acid with Pueraria lobata cellulose reaction directly.The Pueraria lobata cellulose based solid acid was characterized by SEM,X-powder diffraction,infrared spectroscopy,differential thermal and thermogravimetric measurements and its catalytic properties were tested in fructose-to-5-hydroxymethylfurfural(HMF)conversion and HMF-to-levulinic acid(LA)conversion,respectively.The results showed that the Pueraria lobata cellulose based solid acid is consisted of a non-porous amorphous carbon layer structure with a rough surface and contained-SO₃H groups.With tetrahydrofuran as solvent,HMF could be obtained in 65%yield from fructose under the optimal conditions(120?,40min,0.075g of catalyst,4m L of reaction of volume,tetrahydrofuran as solvent).With?-valerolactone as solvent,LA could be obtained in50.6%yield from HMF under optimal conditions(180?,16h,0.1g of catalyst,4m L of reaction of volume,?-valerolactone/water ratio was 3.6/0.4).