Construction Of Active Sites For Cu-catalyzed Dehydrogenation Of 2,3-butanediol And Study On Its Reaction Properties

Selective dehydrogenation of alcohols to corresponding ketones or aldehydes is important in chemical industry.3-Hydroxybutanone,a high value-added chemical,has been widely used in food,daily chemical and pharmaceutical.In this work,the selective dehydrogenation of 2,3-butanediol,a crucial biomass-based molecule,to produce 3hydroxybutanone,is considered to be an environmentally friendly and high atomutilization route.Cu-based catalysts show high activity for-O-H bond breaking of monohydric alcohol,but there are few studies on Cu-catalyzed dehydrogenation of diols.Meanwhile,the catalysts surfer the serious deactivation resulting from the sintering of the copper particles and irreversible adsorption of by-products on the copper surface,which limits the practical application.Therefore,it is very crucial to prepare highly efficient and stable copper-based catalysts for the dehydrogenation of 2,3-butanediol and employed in the dehydrogenation of 2,3-butanediol.The physicochemical properties of copper catalysts were systematically investigated to establish the relationship between the catalytic structure and performance.1.One-step hydrothermal preparation of Cu-SiO2 catalysts and dehydrogenation performance study of 2,3-butanediolMesoporous Cu-SiO2 catalysts were synthesized by a one-step hydrothermal method which the structural properties of Cu-SiO2 catalysts were analyzed by various characterization methods.It was found that the copper particles entered into the support mesopores and were highly dispersed,and the dispersion of copper increased and then decreased with the increase of copper loading.In addition,the pH of the synthesis solution affected the reactivity of the catalysts,and the proper alkalinity of the synthesis solution helped to strengthen the metal-support interaction and improve the catalytic activity.When the copper loading was 20 wt.%and the pH of the synthesis solution was 10,the best performance of the catalyst was produced with 63.0%conversion of 2,3-butanediol and 95.5%selectivity of 3-hydroxybutanone.2.Stepped-pore Cu/Silicalite-1 catalysts for ammonia evaporation and dehydrogenation performance of 2,3-butanediolStepped-pore Cu/Silicalite-1 catalysts were synthesized by the evaporation ammonia method,and the influence law of ammonia dosage on the catalysts structure and reaction performance were investigated.It was found that ammonia destroyed the microporous structure of silicalite-1 allowing the generation of mesoporous structures while the metal-support interaction gradually increased in strength.However,excessive ammonia treatment resulted in a complete collapse of the skeletal structure of silicalite1 and a significant reduction in the mesoporous structure and metal-support interaction.Cu/Silicalite-1-x catalytic performance showed an increasing and then decreasing trend,with the best reaction effect at the ammonia dosage of 25 mL.In addition,excessive reduction temperature would weaken the metal-support interaction and agglomerate the active component copper.The reaction activity showed a trend of increasing and then decreasing with the reduction temperature,and the best catalytic performance was achieved at the reduction temperature of 300℃,the conversion of 2,3-butanediol was 77.9%and the selectivity of 3-hydroxybutanone was 91.5%.3.Preparation of core-shell S-1@Cu/SiO2 catalysts and study on the dehydrogenation of 2,3-butanediolCore-shell structure S-1@Cu/SiO2 catalysts synthesized by hydrothermal method catalyzed the dehydrogenation of 2,3-butanediol.The influence of NaOH etching dosage and pH of the synthesis solution on the catalyst structure and reaction performance was investigated by various characterization methods.It was found that NaOH could etch the microporous structure of silicalite-1,accompanied by the generation of mesoporous structures.However,excessive NaOH treatment severely damaged the skeletal structure of silicalite-1 and affected the formation of S1@Cu/SiO2.Meanwhile,too strong alkalinity of the synthesis solution would destroy the catalysts mesoporous structure,weaken the metal-support interaction and reduce the dispersion of copper.The catalytic activity of S-1@Cu/SiO2-y-z tended to increase and then decreased with NaOH etching dosage and the alkalinity of the synthesis solution.The highest conversion of 2,3-butanediol was 54.7%and the selectivity of 3hydroxybutanone was 96.9%with high stability when NaOH etching dosage was 0.7 g and the pH of the synthesis solution was 10.The Cu-SiO2 and Cu/Silicalite-1 catalysts prepared in this paper showed excellent activity and selectivity for selective catalytic dehydrogenation of 2,3-butanediol,but the stability was poor.By improving the preparation method of copper catalysts,coreshell structure S-1@Cu/SiO2 was prepared,which significantly improved the stability of catalytic 2,3-butanediol dehydrogenation.In addition,the copper species form,copper-support interactions and their effects on catalytic performance were investigated in this paper,which laid the foundation for revealing the mechanism of 2,3-butanediol dehydrogenation.