Stable Preparation And Application Of Palladium Based Catalyst For The Semi-hydrogenation Of Alkynes

Selective hydrogenation of alkynes to olefin has been widely used in petrochemical and fine chemical fields,such as the purification of ethylene in the pyrolysis process of petroleum industry and the selective hydrogenation of 1,4-butynediol to 1,4-butynediol in fine chemical industry.Lindela catalyst is a classic catalyst for the semi-hydrogenation of alkynes and has been widely used for more than 40 years.However,the mechanism of improving the selectivity of Lindella catalyst is the poisoning of precious metal palladium by additives,which leads to the low yield of precious metal.In addition,lead and other additives used are more toxic and can not meet the needs of some specific application scenarios.To solve these problems,this paper aims to develop a high selectivity,low load of precious metals and low toxicity of alkynes half hydrogenation catalyst,mainly from the Pd4S base catalyst preparation,Pd4S kg stability of catalyst in the 1,4-butyl selective hydrogenation of acetylene glycol preparation of 1,4-butylene glycol PdxSy catalyst and application of novel preparation technology development and so on three aspects.The specific content is as follows:On the basis of summarizing the development of alkynes semi-hydrogenation catalysts,the characteristics and preparation methods of semi-hydrogenation catalysts were summarized systematically,and the advantages of using palladium as active component for catalytic hydrogenation were expounded.Based on the analysis of the key problems existing in the semi-hydrogenation of alkynes in industry,the basis of the topic selection and the main contents of the research were put forward.Supports of Pd/C and Pd/γ-Al2O3 were prepared using chloropalladium acid as the precursor system.Supports of Pd4S were prepared by sodium sulfide aqueous phase method.Modified mercaptan ligands were used to prepare alkynyl semi-hydrogenation catalyst.In addition,the effects of different sodium sulfide treatment processes on the crystal shape of the prepared catalyst,the types of modified ligands and the amount of ligands on the hydrogenation performance of the catalyst were also investigated.Furthermore,the semi-hydrogenation catalyst was applied to the actual reaction of selective hydrogenation of 1,4-butynediol to prepare 1,4-butynediol.The effects of different solvents and reaction conditions on the hydrogenation process were investigated.The conversion rate was 100%in methanol solvent,and the selectivity was more than 95%.Development instead of sodium sulfide and water phase of Pd4S prepared new method,respectively with thiourea and palladium chloride acid as S,Pd precursor,after reduction preparation PdxSy modified mercaptan preparation by the middle of acetylene hydrogenation catalyst,explores the thiourea modified quantity and affect the performance of hydrogenation reduction process,optimization of catalyst to achieve the 100%conversion of alkyne,olefin selectivity up to 96.5%.On the basis of summarizing the research results of this paper,the applications of new palladium sulfides in the semi-hydrogenation of alkynes are summarized and prospected.