Study On The Structure-performance Relationships Of Cu-based Alkynylation Catalyst Based On Hollow SiO₂ Microspheres

1,4-butynediol（BYD）is a fundamental material for the production of1,4-butanediol（BDO）.With the booming development of the new energy vehicle industry in recent years,the supply and demand gap of BDO and its downstream products has increased year by year.Therefore,the development of efficient BYD synthesis technology has become one of the important research contents in the BDO industry chain.At present,BYD is mainly synthesized from formaldehyde and acetylene under the action of Cu-based catalysts.However,the Cu species of traditional catalysts are easy to lose in the formaldehyde-acetylene reaction.Therefore,how to improve the stability of Cu species while ensuring high catalytic activity has become one of the key issues to be solved urgently for the development of Cu-based catalysts in the alkyne-aldehyde process.Based on the encapsulation and dispersion effect of hollow microspheres on catalytic active species,CuO/SiO₂ composite material was prepared by the impregnation-calcination process using hollow SiO₂ as support.On the basis of characterizing the morphology and structure of the composite material,the relationship between CuO loading,shell thickness,shell texture,and catalytic performance was discussed,and the influence mechanism was explored.The research results of the thesis provide a theoretical reference for the development of a highly stable formaldehyde-acetylene Cu-based catalyst.The main research contents of the thesis are as follows:（1）The effect of CuO loading on the catalytic performance of hollow CuO/SiO₂composite microspheres.PMMA@SiO₂ core-shell microsphere was synthesized using polymethyl methacrylate（PMMA）microspheres as template and TEOS as silicon source,and hollow SiO₂ microspheres were obtained by calcination.CuO/SiO₂composite microspheres with different CuO loading were prepared by impregnation-calcination process using Cu（NO₃）₂·3H₂O as percursor.The catalytic activity of CuO/SiO₂ composites increased gradually as the CuO loading increased.Compared with the typical peacock catalyst,CuO/SiO₂ composites showed better stability and catalytic activity.After 5 cycles,the conversion rate of formaldehyde for peacock catalyst decreased from 19.14%to 9.76%,and the selectivity of BYD changed from 99.78%to 95.84%.The conversion rate of formaldehyde for CuO/SiO₂changed from 22.84%to 22.56%,and the selectivity for BYD changed from 96.98%to 96.87%after 5 cycles.（2）The effect of SiO₂ shell thickness on the catalytic performance of hollow CuO/SiO₂ composite microspheres.Hollow SiO₂ microspheres with different shell thickness were prepared by changing the amount of TEOS during the synthesis of PMMA@SiO₂ process,followed by impregnation-calcination process to obtain CuO/SiO₂ composits with different shell thicknesses.The thickness of hollow SiO₂are 60 nm,110 nm,and 170 nm,the formaldehyde conversion of CuO/SiO₂composites are 30.20%,22.84%,and 18.55%,respectively,and the selectivities of BYD are 97.67%,96.98%,and 93.06%,respectively.The catalytic activity showed a decreasing trend with the increase of shell thickness.The catalyst recycling evaluation results showed that the catalyst was more prone to deactivation as the shell thickness decreased.（3）The effect of SiO₂ shell texture on the catalytic performance of hollow CuO/SiO₂ composite microspheres.Hollow SiO₂ microspheres with different shell texture were prepared by changing the amount of CTAB during the synthesis of PMMA@SiO₂ process,followed by impregnation-calcination process to obtain CuO/SiO₂ composite microspheres.As the amount of CTAB added increased,the catalytic activity of CuO/SiO₂ composites increased.When the specific surface area of CuO/SiO₂ composites was 401 m²/g,526 m²/g and 582 m²/g,the corresponding formaldehyde conversion rate are 17.57%,22.84%,and 30.55%,respectively,and the selectivity of BYD are 97.13%,96.98%,and 97.29%,respectively.The catalyst recycling evaluation results showed that the dense shell caused the Cu precursor to be prone to aggregation on the surface of hollow SiO₂ microspheres,resulting in the catalyst tending to deactivation.