Hydrolysis Of Golden Grass And Preparation Of Xylose Derivatives

Golden grass as a new biomass feedstock,it is significant to develop its hydrolysis process and whole component utilization.In this paper,firstly,the process conditions for oxalic acid-catalyzed hydrolysis of golden grass hemicellulose to extract xylose were explored;secondly,the synthetic preparation method was developed to convert D-xylose into oligosaccharide(XOS)and gallate xylose ester(GX)polymers;and finally,biomass carbon from the hydrolysis residue of golden grass was prepared by the pyrolysis method,which basically realized the resource utilization of the whole component of goldenrod.The main contents and results of this thesis study are as follows.(1)Hydrolysis study of hemicellulose from golden grass.It has a high content of 25.52%pentosan,which is the preferred material for xylose extraction.By exploring the factors of xylose extraction from oxalic acid catalyzed hydrolysis of hemicellulose of golden grass,it was found that the optimal hydrolysis conditions were:1 wt%oxalic acid solution,hydrolysis temperature of140°C and holding time of 240 min.Under these conditions,the xylose extraction of golden grass could reach 154.8 mg/g.In addition,freeze-thawing,boiling water cooking or ultrasonic treatment of the samples before hydrolysis were all effective in enhancing xylose extraction by up to 46.5%～53.2%compared to the no pretreatment scheme.(2)Oxalic acid-catalyzed synthesis of Xylo-oligosaccharides(XOS)from D-xylose was investigated.The effects of reaction time and the initial mass ratio of oxalic acid and xylose on the yield of XOS were investigated using D-xylose as raw material,and the structure of XOS was characterized.The results showed that the XOS yield could reach 53.75±3.48%by regulating the mass ratio of oxalic acid and xylose as 1/3 and the reaction time as 40 min.The synthesized XOS was analyzed by FTIR,NMR,MS and GPC characterization,and it was found that XOS was mainly connected by theα1-β4 andβ1-α4 glycosidic bonds and contained both the D-xyloseα-configuration unit andβ-configuration unit.(3)Preparation of gallate xylose ester(GX)polymers and their antioxidant properties were studied.GX polymers was successfully synthesized from D-xylose and gallic acid(GA).The polymers are an off-white powder insoluble in water with a yield of 80.1%of gallic acid mass.The results of FTIR,NMR,MS,and TGA characterization showed that GX polymers are esterified products consisting of xylose and gallic acid units which contain a small amount of bound water in the molecule.When the concentration of GX polymers exceeded 0.2mg/m L,its scavenging activity of DPPH radicals could exceed 80%,which has the potential to become an antioxidant component in skin care products;In addition,the reaction mechanism of DPPH radical scavenging by GA and GX polymers was refined by MS analysis of the reaction solution of gallic acid and DPPH.(4)Study on the preparation of biomass char from the hydrolysis residue of golden grass.Biomass char was prepared from the hydrolysis residue of golden grass.The adsorption capacity of the biomass char prepared under different pyrolysis conditions for methylene blue(MB)was explored,and its structure was characterized.The results showed that the best adsorption capacity(196.96 mg/g)was prepared at a pyrolysis temperature of 450°C and a charring time of 90 min,while the specific surface area of the biomass char reached 361.116 m~2/g and the surface showed a thin lamellar structure with more pores.Therefore,this research provides theoretical support and technical reference to promote the development and utilization of grasses such as golden grass,and also contributes significant value to promote the research of xylose derivatives.