Study On Catalyst For Selective Hydrogenation Of 2-butyne-1,4-diol

Fine chemicals which possess high economic value have attracted widespread attention with the rapid development of the chemical industry,especially in the fields of medicine,textile,batterie,and military industries.The 2-butylene-1,4-diol（BED）is an important basic organic raw material in the synthesis process,and its demand at domestic and abroad has been increasing in recent years.The domestic production of BED mainly uses the Reppe process to semi-hydrogenate 2-butyne-1,4-diol（BYD）into BED by a heterogeneous hydrogenation catalyst（Lindlar catalyst）.However,the Lindlar catalyst has problems such as low product selectivity,short catalyst life,and poor stability during the catalytic reaction process,and it also causes environmental pollution.Therefore,studying the effects of hydrogen adsorption activation,product adsorption,carrier properties,and active component structure on selectivity.These key issues have important guiding significance for the design of hydrogenation catalysts with high selectivity and high stability.This thesis starts with the properties of the carrier and the structure of the active component and studies the influence of the properties of the carrier and the structure of the active component on the hydrogen adsorption activation and product adsorption.At the same time,it focuses on the electronic effects and structure in the heterogeneous catalytic system.Therefore,the control mechanism of the selectivity and activity of catalytic hydrogenation and the mechanism of catalytic hydrogenation are derived.The main research contents and conclusions are as follows:（1）The Pd/MgTiO₃ catalyst is prepared by using the gel-sol method to synthesize MgTiO₃ as support to support metal Pd.The activity test results show that the Pd/MgTiO₃catalyst has good catalytic activity and selectivity for BYD catalytic hydrogenation.The selectivity of BED at low temperature that the performance can be as high as 100%.The CO-TPD test found that catalysts with different structures support different CO adsorption strengths.This is mainly since when MgTiO₃ is used as a support,the Ti^x+in its structure can interact strongly with metal Pd.Charge transfer occurs between Pd and the surface electron state of Pd.Further XPS analysis shows that the active metal of the Pd/MgTiO₃ catalyst exhibits an electron-rich state.This electron-rich state inhibits the adsorption and activation of the active metal Pd on hydrogen,and at the same time weakens it.For the adsorption of olefin BED,the high selectivity of BED can be realized.And after the stability test of the Pd/MgTiO₃ catalyst,it is found that the catalyst has better stability and carbon deposition resistance.（2）The bimetallic NiBix/SiO₂ catalyst is prepared by impregnating and reducing Ni and Bi metals on mesoporous SiO₂.The analysis results show that the second metal Bi can increase the distance between Ni atoms and affect the adsorption mode of BYD on Ni active sites to avoid the formation of secondary intermediates during the hydrogenation reaction.The effect of Bi on Ni structure increases with the increase of reduction temperature.At the same time,there is an electron effect between Bi and the Ni because of the abundant outer unpaired electrons of Bi,which weakened by increasing the density of electron cloud of Ni hydrogen adsorption activation.This electrical effect can impact intermediate BED on the adsorption of the active site,make BED easy to desorption from the Ni active site to improve the selectivity of BED.The studies have shown that the selectivity of NiBi bimetallic catalyst for BED can reach more than 90%.Therefore,the structural and electronic effects of the second metal Bi on Ni significantly enhance the selectivity of the active Ni for BED,and the stability and carbon deposition resistance of the Ni and Bi bimetallic catalysts are also significantly better than that of the catalysts with only Ni as the active component.In summary,the research results can provide basic theoretical guidance for the preparation of high stability and high selectivity hydrogenation catalysts and have important practical significance.