Preparation Of MOFs And Employed In Catalytic Conversion Mechanism Of Cellulose To Produce Organic Acids

Cellulose is one of the important components of biomass,which is an inexhaustible natural renewable resource and considered to be one of the most promising precursors to high value-added chemicals.Among the products obtained from cellulose,organic acids have received extensive attention as important chemical raw materials.However,there are still some challenges in the process of converting cellulose into organic acids.On a molecular level,the conversion of a typical cellulose to organic acids follows a complicated reaction pathway,resulting in a very complicated final products.So,there is an urgent need to develop an efficient conversion pathway from cellulose to organic acids.Due to its unique pore structure,large specific surface area and multiple active sites,metal organic framework materials have been used in the catalytic conversion of small molecules such as glucose.However,there have been few reports on the use of framework materials as catalysts for the catalytic conversion of cellulose in aqueous media.Based on this,a series of metal-modified metal framed materials catalysts were prepared and used for the catalytic conversion of cellulose in aqueous media.The distribution,selectivity and conversion mechanism of metal-modified metal framed material acidity and supported metal components on cellulose conversion were studied,which laid a foundation for efficient conversion and resource utilization of cellulose.The main research contents are as follows:?1?A series of metal-modified MOFs catalysts were prepared by loading Ce,Ga and Co into UiO-66 and UiO-66NH2 by ion exchange method and equal volume impregnation method.The structural parameters of the catalyst were characterized by XRD,TEM,BET,XPS and NH₃-TPD.The results show that the metal can be well dispersed on the support without changing its basic skeleton and pore structure,and increase the total acidity of the material.?2?The product distribution and catalytic performance of cellulose in aqueous media were investigated by using M-UiO-66 and HM-UiO-66 as catalysts.The reaction time,catalyst acidity and supported metal components were analyzed for the distribution of cellulose conversion products.And the effect of product yield.The results show that the main product of cellulose conversion in aqueous medium is organic acid,and the selectivity and yield of each product are significantly improved after the catalyst is used.The HGa-UiO-66catalyst with the highest Br?nsted acid content promoted the formation of levulinic acid,and obtained 53%selectivity and 32%yield,while HCo-UiO-66 with the highest Lewis acid content was lactic acid.It has a 45%selectivity and a 30%yield.?3?The M/UiO-66-NH₂ and HM/UiO-66-NH₂ with basic groups were used as catalysts to investigate the product distribution and catalytic activity of cellulose in aqueous medium.The effects of acidity and alkalinity of the catalyst and the type of supported metal on the distribution of cellulose conversion products were investigated.The results show that the production of levulinic acid is affected by Br?nsted acid content.The formation of lactic acid is not only related to the content of Lewis acid,but also closely related to the strength of alkali.The metal oxide was capable of exerting catalytic oxidation performance when the basicity of the catalytic system was increased,resulting in an increase in the yield of glyceric acid.When Co/UiO-66-NH2 was used as the catalyst,72%glyceric acid selectivity and 30% yield were obtained.