Preparation Of Zirconium Catalysts Using Lignite Derivatives By NaOH Depolymerizaiton And Catalytic Property In The Conversion Of Ethyl Levulinate

Coal resource is an important fossil fuel,which has provided a lot of energy for the survival and development of human society for a long time.The low-rank coal represented by lignite has high moisture content and ash content,low calorific value,and has high pollution and low efficiency when directly used as fuel.Therefore,it is of great significance to fulfill the efficient and clean use of lignite and increase the added value of the products.In this paper,based on the high content of humic acid and oxygen-containing acidic groups in lignite,lignite was depolymerized via NaOH treatment and the derivatives were used to prepare zirconium based catalysts through the interaction between Zr⁴⁺and acidic functional groups in the derivatives.The effects of different depolymerization product components,catalyst preparation conditions and reaction conditions on the catalyst performance were investigated in detail.Based on the structure and composition property of lignite,the free humic acid?HAf?and total humic acid?HAt?in the lignite were extracted and used to prepare zirconium-based catalysts,respectively.The catalyst was used in the catalytic conversion of ethyl levulinate?EL?to produce?-valerolactone?GVL?.The reaction conditions were optimized and good catalytic effects were obtained.When using Zr-HAf catalyst,the conversion rate of EL is 92.7%,and the yield of?-valerolactone?GVL?is 90.1%.When using Zr-HAt catalyst,the conversion rate is 92.8%,and the yield is 92.6%.In order to make rational use of lignite components,it was also attempted to prepare zirconium catalysts using the solid residues after the humic acid extraction.Under the optimized reaction conditions,the conversion rate of EL is 92.4%,and the yield of?-valerolactone is 92.0%for Zr-SRf catalyst.The conversion rate of EL is 95.4%,and the yield of?-valerolactone is 92%for the Zr-SRt catalyst.The catalysts can be reused for more than 11 times and the catalytic activity is almost unchanged.Heterogeneity experiments show that they are heterogeneous reactions.Based on the fact that both humic acids and solid residues in lignite were efficient in preparing zirconium catalysts,the mixtures after NaOH treatment were directly used to prepare the catalysts without separation to improve the utilization efficiency of lignite and simply the preparation process of the catalysts.The effect of NaOH treatment conditions on the performances of the obtained catalysts,and the structures of the catalysts were characterized in detail.Under the optimized conditons,the conversion rate of EL is 92.2%,and the yield is 92%.The catalyst can be reused at least 11 times without obvious deactivation,and experimental resulted indicated that it was heterogeneous catalytic reaction.The performances of the catalysts were influenced by various factors,mainly including the Zr content,surface area,and the amounts of the acidic sites of the catalysts.The catalyst could also be used in the catalytic conversion of other carbonyl compounds,such as furfural to furfuryl,hexaldehyde to hexanol,2-hexanone to prepare 2-hexanol,etc.All the conversion rate for these substrates were over 93%.,indicationg the excellent substrate universality of the catalyst.