Two-Dimensional Photocatalytic Materials And Their Application In The Preparation Of Xylonic Acid By Highly Selective Oxidation Of Xylose

Lignocellulose is a very important part of renewable energy and has a wide range of applications.It can be chemically or biologically converted into small molecule compounds such as ethanol,ethylene glycol and furfural,or converted into high-value gasoline,diesel,and aviation fuel.Fuels play an important role in the sustainable development of energy in human society.In nature,the content of xylose is the second most abundant sugar substance after the content of grapes,and it accounts for a large proportion of lignocellulose.Realizing the highefficiency utilization of xylose is the key factor and prerequisite for realizing the high-value utilization of lignocellulose.Xylonic acid is a five-carbon organic acid with a wide range of applications,including chelating agents,dispersants,clarifying agents,pH adjusters,antibiotics and health promoters.It is listed as the 30 most valuable chemicals by the US Department of Energy One of the products.Therefore,the demand continues to expand,showing a broad market prospect.Current research shows that there are two main methods for synthesizing xylonic acid,namely chemical method and biological method.However,chemical synthesis usually requires high temperature and high pressure,and the catalyst usually contains precious metals.However,the biological method has problems such as slow reaction process,high production cost and difficult purification of the product.By photocatalytic manner,xylonic acid has the advantages of green environmental protection,universal and equal beneficial.In recent years,metal oxides,sulfides,precious metal semiconductor materials and non-metal semiconductor materials have been favored by researchers in the field of photocatalysis,and the use of photocatalysis for high-value utilization of biomass has attracted much attention.This article has done research from the exploration of new and high-efficiency photocatalysts and high-efficiency catalysis of xylose to xylonic acid.The specific contents are as follows:1.Using zinc sulfate and bismuth sulfate as Zn source and Bi source,Zn-doped Bi2S3 nanosheet photocatalyst(2D ZnS@Bi2S3)was prepared by hydrothermal method and applied to photocatalytic oxidation of xylose to synthesize xylonic acid.The research results show that the thickness of 2D ZnS@Bi2S3 is about 3 nm.Compared with pure bismuth sulfide photocatalyst,2D ZnS@Bi2S3 photocatalyst has a wider visible light range and can better catalyze xylose synthesis under alkaline conditions.Xylonic acid.After 10 cycles of tests,the catalytic performance of 2D ZnS@Bi2S3 has not significantly decreased.Compared with traditional sulfides,it has improved its anti-corrosion performance,providing a new type of photocatalyst for traditional sulfides.Ways to improve the stability of photocatalysis.In this study,the conversion rate of xylose and the yield of xylonic acid can reach 91.67%and 74.24%.The catalyst used in the catalytic process has the advantages of simpler preparation,good stability,low energy consumption,and repeated use.The process of catalyzing the preparation of xylonic acid has certain potential in industrial production.2.Using titanium tetrachloride and nickel nitrate as the Ti source and Ni source,a selfassembled NiTi hydrotalcite nano-flower-like photocatalyst(NiTi-LDH)was prepared by hydrothermal method and applied to catalyze the oxidation of xylose to synthesize xylonic acid.The flowering NiTi-LDH is formed by Niti-LDH nano sheets,and there is a hole structure on NiTi-LDH nanosheets and there is Ti defects..Compared with the bulk NiTi-LDH photocatalyst,the flower-like NiTi-LDH photocatalyst with Ti defects and pore structure on the nanosheet has improved photocatalytic performance.The synthesized NiTi hydrotalcite nanoflower-like photocatalyst under normal temperature visible light has xylose conversion rate and xylonic acid yield of 78.75%and 66.46%,and it has good selectivity.In addition,the catalyst still maintains good stability in terms of catalytic performance after being recycled 10 times.Combining the preparation characteristics and catalytic reaction characteristics of the above catalysts,it shows that the process of preparing xylonic acid is relatively simple,economical and environmentally friendly,with good selectivity and low energy consumption,and has the potential for industrial production.