Design Of Catalysts For Selectivity Hydrogenation Of 1,4-butynediol

As an important chemical intermediate of fine chemical industry,1,4-butenediol?BED?has been widely concerned about its green synthesis path.Among all of the synthetic methods for BED,selective hydrogenation of 2-butyne-1,4-diol?BYD?is an effective strategy.The commercial Lindlar catalyst presents a high selectivity to BED in the liquid phase hydrogenation of BYD to BED.However,lead acetate and organic bases such as quinoline are necessary to obtain a high selectivity,and thus the toxicity of lead acetate limits its application in fine chemical synthesis.Therefore,it is vital to develop a high efficient catalyst achieving the chemoselective hydrogenation of BYD to BED under alkali free conditions.In this paper,the geometric and electronic properties of the active components were modified by introducing nitrogen species on the surface of silica carrier,so as to change the hydrogenation selectivity of BYD.Some significant conclusions were obtained:1.The Schiff functional group was directly modified on the surface of SiO₂ by amine aldehyde condensation,and then Pd catalysts were prepared by liquid-phase reduction of sodium borohydride.The catalyst showed excellent catalytic performance in the selective hydrogenation of BYD to BED,even without adding basic additives.The results showed that95.2%BYD conversion has been achieved with ca.100%BED selectivity over the Pd/SiO₂-Schiff catalyst,at hydrogen pressure of 2 MPa and 50 ^oC for 4 h in aqueous solution.After six cycles of reaction,the catalyst can still maintain good activity?97.3%?and selectivity?96.4%?,with high stability.The results of FT-IR,XRD and XPS showed that the presence of the Schiff base functional groups on the surface of the support not only provided the alkaline environment for the reaction,but also improved the dispersion and stability of Pd,which makes the catalyst have good catalytic performance.2.The-NH₂ functional group was modified onto the surface of SiO₂ by sol-gel method.The Pd/SiO₂-NH₂ catalyst was prepared by liquid phase reduction of sodium borohydride.The catalytic hydrogenation of BYD under alkali free condition also showed excellent catalytic performance and good stability.In Pd_1.0/SiO₂-NH₂ catalyst,the conversion of BYD was 88.6%,and the selectivity of BED was nearly 100%at hydrogen pressure of 1 MPa and50 ^oC for 4 h.The conversion of BYD was 88.3%after six cycles of reaction,and the selectivity of BED was 97.4%.The results of FT-IR,XRD and XPS showed that Pd nanoparticles was uniformly and highly dispersed,and the strong interaction between amino modified carriers and nanoparticles improves the stability of the catalyst.