Synthesis Of N-Hydroxyethylpyrrolidone And Dehydration Of N-Vinylpyrrolidone Over Supported Catalysts

N-hydroxyethylpyrrolidone（NHP）is an important raw material for the synthesis of N-vinylpyrrolidone（NVP）,and NVP is an important raw material for the synthesis of polyvinylpyrrolidone（PVP）.With the global demand for PVP increasing year by year,the market demand for NVP also increases.The synthesis of NVP by catalytic dehydration has the advantages of low equipment corrosion,high safety,high yield and continuous production,which is a promising process route.The core of this route is to develop dehydration catalyst with high performance and strong stability.In this paper,Sn O₂-Zr O₂catalyst with acid-base bifunctional active sites were prepared.The effects of preparation method,crystal structure,element composition and metal loading on the catalytic performance of Sn O₂-Zr O₂catalyst were investigated.The specific researchs are as follows:（1）NHP was prepared by tubular reaction withγ-butyralactone（GBL）and ethanolamine（MEA）as raw materials.The effects of reaction conditions and ratio of raw materials on the yield of NHP were investigated.The results showed that the optimal process conditions were n（GBL）:n（MEA）:n（H₂O）=1.08:1:11.4（mole ratio）,280℃,8.0MPa and 2.5 h.At this time,ethanolamine was almost completely transformed and the yield of NHP was up to 96.0%.（2）As for the preparation of NVP by NHP catalytic dehydration,the performance of Sn O₂-Zr O₂catalyst prepared by co-precipitation method and sol-gel method was compared,and it was found that the catalyst prepared by sol-gel method had higher catalytic activity.Three types of Sn O₂-Zr O₂catalysts were further prepared by sol-gel method.It was found that the different types of Sn O₂-Zr O₂catalysts had different catalytic activities,and the（m+t）-Zr O₂catalysts had the best catalytic performance.Finally,the effect of different Sn O₂loading on the catalytic performance of Sn O₂-Zr O₂catalyst was investigated.The results showed that the catalyst with 15%Sn O₂loading had the best catalytic performance,the conversion rate of NHP was 66.4%,and the selectivity of NVP was 74.6%.（3）A series of single-metal supported catalysts x Ce/Sn Zr and bimetallic supported catalysts x Cey La/Sn Zr were prepared by the equal volume impregnation method.The elemental composition,morphology,structure and surface acidity and basicity of the catalyst were characterized by XRD,FT-IR,SEM,NH₃-TPD,CO₂-TPD and N₂adsorption-desorption.The results show that the x Ce/Sn Zr catalyst has high specific surface area and pore size,and has medium-strong acid active sites and medium-strong base active sites with different strengths and concentrations.Among them,1Ce/Sn Zr catalyst has the best catalytic activity,the conversion rate of NHP was 69.2%and the selectivity of NVP was 77.5%.In addition,the specific surface area and pore volume of the bimetal supported catalyst x Cey La/Sn Zr are higher than those of the single metal supported catalyst x Ce/Sn Zr,and it has stronger and more concentrated active sites for moderately strong acids and active sites for moderately strong bases.Among them,0.5Ce0.5La/Sn Zr showed the best catalytic activity.Under the conditions of reaction temperature 180℃,reaction time 2.5 h and catalyst dosage 3.0 wt%,the conversion rate of NHP was 72.1%and the selectivity of NVP was 81.8%,and the activity has no obvious change after 8 cycles of use.The results show that it has excellent stability.