Study On Catalyst And Process Of 2,3-pentanedione Peaction Based On Lactic Acid Condensation

For the wide range of raw materials for producing lactic acid and low cost,its downstream products are abundant.Therefore,the use of bio-based lactic acid to synthesize a series of high value-added chemicals will be an ideal alternative to traditional fossil energy routes.The development and utilization of downstream products of lactic acid not only makes effective use of biological resources,but also has important academic significance and application value.Therefore,this thesis designed and developed a series of highly efficient and stable catalysts based on the catalyst and process of lactic acid condensation based 2,3-pentanedione reaction,based on the characteristics of lactic acid condensation reaction-acid-base synergistic catalysis.Firstly,a mesoporous-macroporous TiPO carrier supported alkali metal nitrate catalyst was prepared.By changing the specific surface area of the TiPO support and the crystal form of the support to change its loading effect,the supported catalyst is used to control the surface acidity and alkalinity by changing the alkali metal ions?Na,K,Rb,Cs?and the loading amount.It has been found through investigation that the active sites of surface acid bases for the condensation reaction of lactic acid are necessary.This base can be regulated by different loadings,and the Lewis acid center plays an important role.The catalyst has a good porous structure and is favorable for the rapid diffusion of lactic acid into the active center.The product can quickly leave the active site due to its relatively low mass transfer resistance.Therefore,the catalyst has good activity and high stability.Next,an AlPO carrier having a layered structure and a perovskite BaTiO carrier-supported alkali metal nitrate catalyst were prepared.The preparation method of the carrier and the supported materials were separately investigated,aiming to screen out an excellent catalyst for preparing 2,3-pentanedione with efficient and stable catalytic lactic acid condensation.Analysis of all catalytic catalytic reaction mechanisms revealed that the alkali metal nitrate will first react with lactic acid,remove NO₃^-and combine with alkali metal ions to form lactate,and then lactate and synergistic carrier react with lactic acid to condense it.2,3-pentanedione is formed.This is why the catalyst is less active during the first few hours.This is also why the catalyst has better stability due to the persistence of lactate?continuous reaction for about 100 h?.At the same time,the understanding of the reaction of alkali metal nitrate for the preparation of 2,3-pentanedione by lactic acid condensation has been deepened.Finally,the reaction conditions for the preparation of 2,3-pentanedione by lactic acid condensation were investigated.It was determined that the catalyst was able to achieve optimum activity at a lower reaction temperature?270 ^oC?than reported in the literature.Since the reaction of lactic acid conversion to 2,3-pentanedione is a secondary reaction,the selectivity of 2,3-pentanedione increases as the concentration of lactic acid increases.Increasing the lactic acid feed rate at 270 ^oC reaction temperature reduces the external diffusion resistance and thus increases the reaction rate.