| Acetal（ketone）is a new type of perfume.It has the advantages of rich raw materials,unique and lasting aroma and stable chemical properties.It is widely used in food,cosmetics and pharmaceutical industries.With the growth of flavor and fragrance market,the synthesis of acetal（ketone）spices has attracted much attention.In the traditional production process of acetal（ketone）,protonic acids such as sulfuric acid,hydrochloric acid and phosphoric acid are often used to catalyze the condensation reaction between aldehydes（ketones）and alcohols.Proton acid catalysis has good catalytic activity,but the reaction process corrodes the equipment and post-treatment seriously pollutes the environment.Although the problems in the catalytic process of strong protic acid are solved to a certain extent when heteropoly acid,ionic liquid and molecular sieve are used to prepare acetals（ketones）,there are still some disadvantages such as easy loss of active sites,poor stability and high cost of preparation.Therefore,from the perspective of environmental protection and economic benefits,it is of great significance to carry out more efficient,green and low-cost catalyst research.In this paper,a variety of green,highly efficient and economical Fe based solid acid catalysts were prepared by ion exchange and sol-gel methods using Fe as the active center.SEM,EDS,BET,FT-IR,XRD,XPS,NH3-TPD,N-butyl amine titration and TGA-DTG were used to characterize the catalysts and explore their catalytic performance in the condensation reaction of benzaldehyde with ethylene glycol.The acetal preparation process was optimized by single factor experiment and response surface methodology,and the acetal reaction kinetic model under the optimal conditions was constructed,which provided a theoretical basis for the green and efficient preparation and large-scale production of other acetal（ketone）fragrances.In Chapter 2,a series of Fe modified heteropoly acid catalysts were prepared by ion exchange method,and their structures and catalytic acetal reaction performance were studied.The experimental results showed that Fe modified phosphotungstic acid catalyst had better catalytic performance in the preparation of benzaldehyde glycol acetal,among which Fe2/3HPW12O40 catalyst had the best catalytic performance.The strong acidity of the catalyst,the synergistic effect between Lewis acid center and Br（?）nsted acid center and more acidic active sites were the reasons for the high catalytic activity of the catalyst.Using Fe2/3HPW12O40 as catalyst,the optimum preparation conditions of benzaldehyde ethylene glycol acetal were optimized by response surface methodology:the amount of Fe2/3HPW12O40 was 2.6 wt%,the molar ratio of alcohol to aldehyde was 1.6:1,the reaction time was 3.3 h,and the amount of cyclohexane was 12.4 mL.Under these conditions,the acetal yield was 94.3%.The kinetic study showed that under the optimized conditions,the kinetic equation of Fe2/3HPW12O40 catalyst for the preparation of benzaldehyde glycol acetal was as follows:r=-（dcA）/（dt）=1.37exp（-18.02/（RT））cAcB.In Chapter 3,a series of metal organic framework materials were synthesized from metal acetate and pyromellitic acid,and their structures and catalytic acetal reaction properties were studied.The experimental results showed that Fe-MOFs catalyst had the best catalytic performance.The large specific surface area,suitable acidity and multiple acidic sites of metal frame materials were the reasons for their high catalytic activity.Using Fe-MOFs as catalyst,the optimum preparation conditions of benzaldehyde ethylene glycol acetal were optimized by response surface methodology:the amount of Fe-MOFs was 2.0 wt%,the molar ratio of alcohol to aldehyde was 1.65:1,the reaction time was 2.4 h,and the amount of cyclohexane was 13 mL.Under these conditions,the acetal yield was 91.9%.The kinetic study showed that under the optimized conditions,the kinetic equation of Fe MOFs catalyst for the preparation of benzaldehyde glycol acetal was as follows:r=-（dcA）/（dt）=2.73exp（-21.37/（RT））cAcB.In the Chapter 4,a series of metal modified carbon titanium solid acid catalysts were prepared by sol-gel method using fructose,N-butyl titanate and metal nitrate as raw materials,and their structures and catalytic acetal reactivity were studied.The experimental results showed that C-Fe-Ti solid acid catalyst had the best catalytic performance.Using C-Fe-Ti as catalyst,the optimum preparation conditions of acetal were optimized by response surface methodology:the amount of C-Fe-Ti was 1.0 wt%,the molar ratio of alcohol to aldehyde was1.67:1,the reaction time was 2.1 h,and the amount of cyclohexane as water carrying agent was 11.8 mL.Under these conditions,the acetal yield was 93.9%.The kinetic study showed that under the optimized conditions,the kinetic equation of C-Fe-Ti solid acid catalyst for the preparationofbenzaldehydeglycolacetalwasasfollows:r=-（dcA）/（dt）=2.18exp（-48.23/（RT））cAcB.In the Chapter 5,a series of metal modified carbon silicon solid acid catalysts were prepared by sol-gel method,and their structure and catalytic acetal reaction properties were studied.The experimental results showed that C-Fe-Si solid acid catalyst had the best catalytic performance.The high catalytic activity of the catalyst was related to its suitable acidity,more acidic sites and large specific surface area.Using C-Fe-Si as catalyst,the optimum preparation conditions of benzaldehyde ethylene glycol acetal were optimized by response surface methodology:the amount of C-Fe-Si was 1.85 wt%,the molar ratio of alcohol to aldehyde was 1.5:1,the reaction time was 2.2 h,and the amount of cyclohexane was 10.5 mL.Under these conditions,the acetal yield was 97.7%.The kinetic study showed that under the optimized conditions,the kinetic equation of C-Fe-Si solid acid catalyst for the preparationofbenzaldehydeglycolacetalwasasfollows:r=-（dcA）/（dt）=15.38exp（-64.66/（RT））cAcB.C-Fe-Si solid acid catalyst had a good industrial application prospect because of its low preparation cost,high catalytic activity and stability. |
PDF Full Text Request