Study On The Properties Of Kaolinite In Catalytic Hydrolysis From Cellulose To Reducing Sugars

At present,due to the depletion of fossil fuels and the continuous deterioration of the global environment,the development and utilization of renewable resources have received more and more attention.Among various renewable energy sources,nuclear energy and large-scale hydropower have potential ecological and environmental risks,and there are regional resource constraints such as wind energy and geothermal energy,which are not conducive to vigorous development and use.Features such as good reproducibility are recognized.As the most abundant biomass resource on the planet,cellulose is often used as a suitable research target for biomass conversion.Therefore,the efficient use of cellulose can effectively alleviate huge energy needs and environmental problems to a certain extent.The key to efficient use of cellulose is to hydrolyze it into glucose.As an important platform compound,glucose can be further converted to obtain a variety of high value-added chemical products such as furfural,polyols,and organic acids.For the cellulose hydrolysis reaction,the solid acid catalyst has become a research hotspot due to its light corrosion of equipment and simple catalyst separation in recent years.Choosing an inexpensive and efficient solid acid catalyst for cellulose hydrolysis can effectively reduce the cost of the reaction.Therefore,this subject selected the clay mineral kaolinite rich in nature as a solid acid catalyst to catalyze the hydrolysis of cellulose,and modified kaolinite to improve its catalytic performance,and successfully achieved the efficient hydrolysis of cellulose.Firstly,in this experiment,natural kaolinite was used as a catalyst for cellulose hydrolysis.X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),thermogravimetric-differential thermogravimetry(TG-DTG),scanning electron microscopy(SEM)and other methods were used to characterize and analyze the catalyst structure.In addition,the effects of hydrolysis temperature,hydrolysis time,amount of catalyst,and amount of water on the total reducing sugars(TRS)yield and cellulose conversion in cellulose hydrolysis were explored.The optimal hydrolysis conditions for cellulose were finally determined as: the temperature was 200 °C,the hydrolysis time was 3 hours,the mass ratio of catalyst to cellulose was 0.2,and the ratio of the amount of water to the mass of cellulose was 12.Under optimal conditions,the cellulose conversion and TRS yield were 56% and 38.8%,respectively.And further research was made on the regeneration performance of the kaolinite catalyst,and it was found that the kaolinite catalyst had good stability and regeneration performance.The catalyst still had good catalytic performance after 4 times of recycling.The catalyst still has good catalytic performance after 4 times of recycling.After the fourth regeneration,it still has a TRS yield of 38.1% for cellulose hydrolysis.Finally,the reaction mechanism of kaolinite-catalyzed cellulose hydrolysis was proposed.In addition,in order to further improve the yield of TRS in the reaction,a variety of methods were used to modify the kaolinite in this subject.In this experiment,the kaolinite was acidified by the impregnation method,the kaolinite was thermally modified by the calcination method,and the metal ion-doped kaolinite composite catalyst was prepared by the hydrothermal method.Comparing the results of catalysts catalyzed by cellulose hydrolysis obtained by various modification methods,the metal ion-doped kaolinite catalyst prepared by hydrothermal method has good catalytic activity for cellulose hydrolysis.The Cu2+-Zn2+-Al3+/Kaol catalyst prepared in the experiment hydrolyzed cellulose at a hydrolysis temperature of 200 ?,a hydrolysis time of 3 h,a catalyst to cellulose mass ratio of 0.2,and a water to cellulose mass ratio of 12.A TRS yield of 47.5% was obtained.In short,the natural kaolinite clay and metal ion-doped kaolinite composite catalyst prepared by hydrothermal method were used as low-cost and high-efficiency solid acid catalysts,and distilled water was used as the reaction solvent to successfully achieve green and efficient conversion of cellulose.The development and research of cost,high stability and high activity catalyst provided new ideas.