| With the continuous development of society and economy,the demand of the hydrogenation products of 2-butyne-1,4-diol(BYD),such as 1,4-butenediol(BED),butane-1,4-diol(BDO),2-hydroxytetrahydrofuran(2-HTHF),are dramatically increasing.However,the reaction conditions required in most studies as well as the industrial process at present require high temperature and pressure,which will cause the catalyst to be easily deactivated due to carbon deposition,and many side reactions will occur thus decline the selectivity of the target product.Furthermore,it is difficult to obtain BED and 2-HTHF.In this work,the catalysts were accordingly developed to achieve high selectivities for different target products of BYD hydrogenation under the mild temperature and pressure.In this thesis,the performance of Pd-based catalysts supported on different acid and alkaline carriers,such as WO3,WO3 modified γ-Al2O3,γ-Al2O3,α-Al2O3,MgO modified γ-Al2O3,and MgO,were firstly studied in BYD hydrogenation reaction.The active component Pd was supported on different acid-base oxide supports by using the excessive impregnation method.The catalytic performance of the hydrogenation reaction of BYD was evaluated under mild conditions(30℃,0.15 MPa),and XRD,HRTEM,ICP,BET,NH3-TPD,CO2-TPD,and H2-TPR were used to characterize the catalysts.The investigations shown that as the acidity of the catalyst increases,the enhanced adsorption of BED facilitates the isomerization reaction.For the most acidic catalysts in this stidy,Pd/WO3,the conversion of BYD is 100%,and the selectivity to 2-HTHF reaches 31.3%.With the increase of the basic strength of the catalyst,the decrease in the adsorption of BED is beneficial to the inhibition of the isomerization and hydrogenolysis reactions.For the strongest basicity catalyst Pd/MgO,the selectivity to the semi-hydrogenated product BED can be acheived around 96.1%when BYD is nearly completely converted.Further increasing the reaction time,the complete hdrgenation becomes domination as the selectivity of the deep hydrogenated product BDO reaches 96.3%.In order to exclude the effect of carrier acidity and basicity on the selectivities of hydrogenation products of BYD,Pd supported on neutral carrier SiC were prepared by using excess impregnation method and hydrazine hydration reduction method,respectively.XRD,HRTEM,BET,CO2-TPD and H2-TPR were applied to characterize and evaluate these two Pd/SiC catalysts.Compared with the catalyst prepared by the excessive impregnation method,the Pd particles on the surface of the Pd/SiC catalyst prepared by the hydrazine reduction method will agglomerate and grow,making the catalyst has relatively low hydrogenation activity.It needs to be noted that the strong base NaOH was actually added to make the catalyst have strong basic sites when the hydrazine reduction method is used in the preparation process.The catalysts can reach the selectivity to BED to 96%when the BYD conversion was 99.7%.Based on this,experiments were carried out using Pd/SiC prepared by the hydrazine hydration reduction method,and with different Pd loadings(0.1%,0.5%,1%and 5%).The results showed that the higher the loading,the more hydrogenation active sites,the stronger its hydrogenation activity.Finally,in order to improve the dispersion of Pd particles and reduce the loading of precious metals,the metal additive Ni was introduced and a 0.5%Pd4%Ni/SiC catalyst was prepared by hydrazine hydration reduction.The results show that the introduction of Ni may change the electronic state of Pd,and the deep hydrogenation activity of bimetallic 0.5%Pd4%Ni/SiC catalyst is much lower than that of 0.5%Pd/SiC catalyst,thus obtaining high selectivity(96.6%)for BED. |
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