One-pot Degradation Of Cellulose/Chitin Into Fluorescent Carbon Dots And Organic Acids In Their Homogeneous Aqueous Solution

Biomass is the most important renewable resource in nature.In recent decades,with the over-consumption of non-renewable fossil energy,biomass materials play the role of the future alternative energy and chemicals,and how to convert biomass into valuable chemicals or cheap and clean fuels is the key problem,which most researchers pay attention to.Cellulose,as the main component of the cell wall of plants,is the product of the process of photosynthesis and the most abundant natural biomass macromolecular resource in nature.Compared with other sugars,the transformation and consumption of cellulose does not compete with the human food chain.As the second largest biomass resource in nature,chitin is naturally renewable and has excellent utilization value as well.At present,the main purpose of the study of the hydrothermal degradation of cellulose and chitin is to obtain valuable small molecular compounds or fluorescent carbon dots,respectively,and there is still no relevant research on the simultaneous investigation of these products.What's more,due to the poor solubility of cellulose and chitin,most of the studies on their hydrothermal transformation are carried out in the solid-liquid heterogeneous system,resulting in low yields of products and low utilization rates of raw materials.Therefore,based on the above problems,microcrystalline cellulose and chitin were selected as the main raw materials in the study.In this paper,investigating the hydrothermal degradation of the two biomass materials is the main task of us.First of all,the hydrothermal degradation of homogeneous cellulose solution was studied at high temperature.Formic acid,lactic acid,acetic acid and other small molecule organic acids were existed in the liquid by the analysis of high performance liquid chromatograph.In addition,the existence of the fluorescent substance carbon dots was also detected.The study was mainly focus on the influence of different reaction conditions(temperature,time and concentration)on the yields of all kinds of reaction products,in order to achieve the goal of optimization of experimental conditions and maximum utilization.Based on the former research,we regarded nitrogen-containing biomass material-chitin as raw material that substitutes the function of microcrystalline cellulose,which has the similar structure with cellulose.With the aid of potassium hydroxide and urea,chitin can dissolve in the alkaline aqueous solution,forming homogeneous solution.The degradation degree of homogeneous chitin solution was studied under different reaction conditions,as well as the yields of lactic acid,malonic acid,formic acid,malonic acid,acetic acid and famaric acid.In addition,besides the quantitative analysis of small molecule acids under different reaction conditions,the powder of fluorescent carbon dots was also obtained by the method of freeze drying.Furthermore,the structure,composition and optical properties of the obtained carbon dots were characterized by TEM,XPS,FT-IR,UV-Vis,FL and so on.Fluorescence studies reveal that the as-prepared CDs has efficient selectivity and sensitivity toward iron ions in acidic condition,indicating that it is a potential fluorescent sensor to the detection of Fe3+.In general,this paper provides a panorama to summary the degradation routes of cellulose in its homogeneous aqueous solution with both organic molecules and CDs as products,providing a good basis for better utilization of biomass energy.