The Research On Cu-based Catalysts For Selective Dehydrogenation Of 2,3-butanediol

The selective dehydrogenation of alcohols to aldehydes or ketones is an important chemical reaction.3-hydroxybutanone has high added value and is widely used in food,medicine,organic synthesis and other fields.Catalytic dehydrogenation of the bio-platform compound 2,3-butanediol to 3-hydroxybutanone is in line with the green reaction concept.Cu-based catalysts exhibit high activity for catalyzing the cleavage of the O-H bond,but the higher reaction temperatures tends to cause the sintering of metal particles and the formed by-products facilely adsorbs on the metal surface resulting in the severe deactivation.Therefore,it is particularly important to prepare a highly efficient and stable catalyst.In the paper work,the design and preparation of the supported Cu-based catalysts were conducted.The catalytic performance of Cu-based catalysts for 2,3-butanediol dehydrogenation was studied to have a deep understanding of the mechanism of 2,3-butanediol dehydrogenation and structure-activity relationship of the catalysts.1.The research on Cu/SiO₂ catalysts prepared by co-precipitatin methodCu/SiO₂ catalysts were prepared by co-precipitation method.It was found that Cu dispersion decreased with increasing the loading of Cu,and the catalytic performance was best when the Cu loading was 20 wt%,with a conversion of 35.5%,and selectivity to 3-hydroxybutanone of 97.0%.In addition,the effects of the reaction temperature and flow of the carrier gas were investigated and the optimal process conditions were determined.2.The research on Cu-MCM-41 catalysts prepared by hydrothermal methodIn order to investigate the effect of the support structure on the copper properties and catalytic dehydrogenation performance,a series of Cu-MCM-41 catalysts were synthesized by hydrothermal method.It was found that the Cu was highly dispersed.The structure of MCM-41 was destroyed in some extent and Cu dispersion decreased slightly at the Cu content of 30 wt%.The alkaline of the synthetic solution has the significant effects on the catalyst structure and states of copper species.It was found that the ordered structure of MCM-41 gradually disappeared with increasing the alkaline,while Cu-O-Si structures were formed under the alkaline condition,leading to a strong interaction between Cu and SiO₂.The Cu-MCM-41 catalyst with the Cu content of 20 wt%and synthesized at the pH of 10.5 shows the best catalytic performance with the conversion of 53.0%and selectivity of 98.9%.3.The research on catalytic dehydrogenation of 2,3-butanediol by metal-support interaction in Cu/SBA-15 catalystsIn order to further enhance the interaction Cu-support,the Cu/SBA-15 catalyst was prepared via the ammonia-evaporation?AE?method.The properties of Cu-SiO₂ were controlled by adjusting the pH of the precursor solution and reduction temperature to investigate the relationship between Cu-SiO₂ interaction and catalytic performance.It was found that the effects of the alkaline of the precursor solution?pH=8.8-12.0?and reduction temperature?200-400??on the Cu dispersion and catalyst structures are negligible.On the other hand,the properties of Cu²⁺,Cu+and Cu⁰ remaining in the reduced catalyst are depended on the pH of the precursor solution and reduction temperature.It is because that the strong interaction of Cu-SiO₂ inhibits the complete reduction of Cu²⁺and Cu+to Cu⁰.After reduction in H₂ at 300?,the Cu/SBA-15 catalyst synthesized at pH=10,0 achieves the highest catalytic activity with the conversion of 84.0%as well as the selectivity 88.8%,which can be attributed to the synergistic effect of the Cu²⁺-Cu⁰ structure.Cu/SiO₂ catalyst exhibits good catalytic performance for dehydrogenation of 2,3-butanediol,and has broad industrial application prospects.At the same time,Cu-MCM-41 and Cu/SBA-15 catalysts which prepared by improved support and method show better activity.The theoretical study of Cu-SiO₂ interaction provides reference and basis for further analysis of dehydrogenation mechanism.