Study On Conversion Of Cellulose Into Organics By Degradation

As we know, non-renewable fossil resources such as oil, coal, natural gas will be exhausted one day. The solar energy, hydro energy and wind energy can produce power but not manufacturing chemicals. Therefore, renewable biomass resources have been used to create new compounds for human beings. Cellulose, as the main constituent of plant cell wall, is regenerated in large quantity by natural photosynthesis and is the most abundant biomass in nature. Glucose, which is the basic structural unit of cellulose, is the important raw material for producing alcohols, organic acids and furan compounds which have wide application in food, medicine, daily chemicals and chemical engineering fields. The research for the conversion of cellulose into various high value-added chemicals has strategic significance. This work refers to the fields including the polymer science, agricultural chemistry, environmental chemistry, organic chemistry and analytic chemistry. The main text of this article is about the catalytic degradation and products of cellulose by the ruthenium-based homogenous catalyst and the degradation of cellulose in homogeneous and alkaline aqueous solution. A lot of work have been made to study the degradation conditions for the selective conversion of cellulose, analysis for the degradation products and the establishment of the methods for the product separation. The results were compared with the related literature reports which have been referred to. This work has made creative contribution for the degradation of cellulose into platform compounds.The main innovation points of this paper include the following:(1) The Ru-based compound has been synthesized and employed as the catalyst for the hydrogenation of glucose to sorbitol in H2O/i-PrOH solvent system. And the reaction mechanism was proposed. The catalyst performed high activity and high selectivity with low catalyst loading; (2) The Ru-based homogenous catalyst has been firstly used for the catalytic conversion of cellobiose. The high yield of sorbitol has been successfully produced in the reaction. It had high selectivity in the catalytic reaction. The products system was simple to separate and analyze; (3) In NaOH/ZnO solvent system, it was the first example for the highly efficient conversion of cellulose solution into small molecular organic acids without adding heterogeneous catalyst. The high selectivity and yield for products were confirmed.In this paper the main research contents and conclusions briefly as follows.To solve the basic science issues in biomass conversion, the system in relation to the hydrogenation of glucose into alcohols was studied. A novelty ruthenium complex was designed and synthesized. As well as its single-crystal structure was obtained. Glucose was firstly catalyzed by Ru-based homogenous catalyst and the hydrogenation reaction was successfully accomplished. As the main product, sorbitol with the yield of 95.2% was produced in mild conditions which reflected the high reactivity for the Ru catalyst. The experimental results indicated that the reaction mechanism could be explained by the reduction of aldehyde group in glucose to hydroxy group and sorbitol was produced. The products were separated though physical and chemical methods. High performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS) were employed to analyze the products. The results demonstrated that the main product was sorbitol accompanied with a little 1,4-sorbitan which was dehydrated product from sorbitol. When the catalyst loading of Ru1 was 0.1 mol%, the conversion of glucose reached up to 97% and the yield of hexitol was 95.8% (reaction condition:100?,50 atm H2,24h). Compared with the heterogeneous catalyst, the ruthenium catalysts has the following advantages:it was synthesized using cheap and available raw materials and the synthetic procedures are simple; less product components; low catalyst loading, high efficiency; it avoided recycling and environmental pollution relating to heterogeneous catalyst; mild reaction conditions, lower reaction temperature. This work opened up new idea and method in the homogeneous catalysis of glucose.The transformation of cellulose into platform organic compounds with high efficiency and high selectivity is one of the important subject in the current resource utilization. Here the catalytic degradation of cellulose into organic compounds opens up new methods for the conversion of cellulose. The ruthenium homogeneous compound was firstly used to catalyse the conversion of cellobiose and cellulose into hexitols under acid condition with high selectivity. The viscosity molecular weight of cellulose was evaluated by viscosity. At the same time, further improvement was made for the separation of the degradation products. The results of HPLC and ESI-MS confirmed that the hydrogenation product of cellobiose and cellulose was sorbitol. The results proved that ball milling could obviously improve the conversion of substrates.The optimum reaction temperature was 100? and the catalyst loading of Rul was 0.1 mol%. Studies have shown that the yield of hexitol can reach up to 94.5% from cellobiose and 56.4% from cellulose which was one of highest values in the literature reported. About 50% of cellulose was subjected to carbonization. As a result, the catalytic system performed high conversion efficiency, mild reaction conditions and low catalyst loading which was 1/20 of Ru/C. The reaction mechanism was described that the glycosidic bond between glucose units was broken in acidic conditions. The transition state of Ru-H inserted into C=O in glucose. With the proton transferred to the oxygen atom, sorbitol was generated. The Ru-based homogeneous catalyst opened up a new avenue for the conversion of cellulose into sugar alcohol. And it has great significance and prospect in the research and application of biomass conversion.Cellulose was dissolved in NaOH/ZnO aqueous solution and transparent solution was obtained. The oxidative degradation of cellulose solution was conducted by hydrothermal method without catalysts. The viscosity molecular weight of cellulose was evaluated by viscosity. In this system, a small amount of ZnO was used which acted as cosolvent and homogeneous catalyst. The solvent, temperature, O2 pressure and reaction time had effect on the oxidative degradation of cellulose. The cellulose solution was degraded into various small molecular organic acids such as formic acid, oxalic acid, acetic acid, lactic acid and glycollic acid (reaction condition:150?,1.3MPa O2, 2h). When the reaction conducted at 150?,2.5MPa O2 for 2h, the yield of total organic acid was 97% and the yield of formic acid reached up to 68.3% which was the highest in the literature reported. The major advantages for this system includes:(1) Cellulose was degraded in the form of solution. (2) The NaOH/ZnO solvent had no pollution for environment. (3) Mild condition and high selectivity. (4) There was no heterogeneous catalyst. And the synthesis and recycle of catalyst were avoided. This work opened up a new way to degrade cellulose in green solvent. In the biomass conversion, this degradation system has great potential in the industrial production.The above results in relation to the conversion of glucose, cellobiose and cellulose by Ru-based homogeneous catalyst and the oxidative degradation of cellulose solution in NaOH/ZnO green solvent systems clearly illustrated the new ideas and new methods about the conversion of cellulose into organic compounds. The separation and analysis methods for biomass degradation to small molecular products is established. The degradation products of cellulose under different reaction conditions was separated and analyzed. A variety of valuable platform compounds such as sorbitol,1,4-sorbitan and small molecule acids were obtained. The effects of catalyst loading, reaction time, reaction temperature, O2 pressure and many other factors on the reaction of cellulose degradation were systematic studied. This work illustrated the degradation mechanisms about the catalytic conversion of cellulose by Ru-based homogeneous catalyst and about the alkaline degradation of cellulose solution. It provided valuable theoretical basis for the conversion research of cellulose, lignin, chitin and other important biomass under mild conditions. And it opened new approach to produce various platform chemicals through the biomass conversion. It has important academic significance and application prospects in the field of biomass conversion.