Synthesis Of Hydroxybutyl Vinyl Ether Catalyzed By Solid Base Catalyst K/ZrO₂

The molecular structure of vinyl ether contains a double bond and an ether bond connected thereto,and it is an important kind of high polymer monomers and organic synthesis intermediate.As a polymer monomer,the vinyl ether is mainly used for the production of fluororesin,fluorine coating,reactive diluents and polycarboxylate water reducer etc.It can also be used as an organic synthesis intermediate to synthesize tetramethoxy propane,4-methyl pyridine and excellent bactericides such as glutaraldehyde.The huge market demand for downstream products has caused the synthesis of vinyl ethers to receive much attention.At present,there are four methods for synthesizing vinyl ether,such as acetylenemethod,dehydrohalogenationmethod,acetalthermal decomposition method and transesterification method.Compared with the other three methods,the liquid-phase acetylene process has a wide range of raw materials,which is relatively cheap and easy to obtain.In addition and the reaction has a low requirement on the pressure of the equipment,and it has a competitive advantage in industrial production for liquid-phase acetylene process.However,the process mainly uses liquid alkali as a catalyst,which possesses many problems such as many by-products,difficult separation of catalysts,non-reusable use,and equipment corrosion.It is an effective way to solve the above problems by preparing a solid base catalyst with good catalytic performance and developing a catalytic synthesis process that is suitable for it.However,few solid basic catalysts reported have the disadvantages of low catalytic activity and non-recyclability.Therefore,it is an urgent problem to improve the catalytic activity and recycling performance of the solid base catalyst,by the rational design of the structure of the catalyst and the optimization of the preparation method.In this paper,according to the specific technical requirements for hydroxyethyl vinyl ether（HBVE）in the industry,the K/Al₂O₃ and K/ZrO₂catalysts were prepared by the impregnation-grind method,combined with the above-metioned problems in the existing process.The K/Al₂O₃ and K/ZrO₂ catalysts were also investigated for their reactivity in the synthesis of hydroxybutyl vinyl ether from 1,4-butanediol and acetylene.The characterization of the catalyst’s composition structure,texture characteristics,and surface basicity were carried out by N₂-physisorption,XRD,and CO₂-TPD.The reasons for the differences in the structural properties of the catalysts prepared with the two supports were further investigated.On this basis,K/ZrO₂ with better catalytic performance was further studied.Firstly,the effect of KOH loading amount on the catalytic performance of the catalyst was explored.Secondly,the factors such as the amount of catalyst,reaction temperature,and reaction time were investigated,and the most suitable synthesis technological conditions were determined.Finally,the recycling performance of the K/ZrO₂ catalyst was also examined.The main results and conclusions are as follows:1.Under the same reaction conditions,neither carrier showes obvious catalytic activity.Relative to the carriers,the catalytic activity of the catalyst has been improved to varying degrees.Compared with the K/Al₂O₃ catalyst,the HBVE yield of the K/ZrO₂ catalyst is significantly increased.The characterization results show that although the K/Al₂O₃ catalyst has higher specific surface area,only weakly alkaline and moderately strong alkaline sites are formed due to its rich surface-OH.In the K/ZrO₂ catalyst,K⁺enters the octahedral vacancies of ZrO₂ to form a K-O-Zr structure,and a large number of strongly basic sites are formed on the surface,thus it exhibits much higher catalytic performance than K/Al₂O₃.2.The K/ZrO₂ catalyst showes higher catalytic activity when KOH loading amount is around 25%.Through single-factor experiments,the optimum conditions for the synthesis of hydroxybutyl vinyl ether by acetylene with K/ZrO₂ as catalyst were determined:m（K/ZrO₂）/m（BDO）=15%,T=150℃,t=9 h,the acetylene flow rate is 0.04 L/min and the stirring speed is 400 r/min.Under these technological conditions,the results of reusability experiments showes that the catalytic activity of the K/ZrO₂ catalyst decreases after the first use.However,during the next four consecutive uses for the catalytic reaction,the yield of HBVE tends to be stable and shows a high stability for repeated use.