Study On Modification Of Pd-based Catalysts For Anthraquinone Hydrogenation Reaction

Hydrogen peroxide is an important green chemical product in industry.With the continuous development of social economy and new green chemical processes,the global market demand for hydrogen peroxide is increasing.The supported palladium-based catalyst is the most widely used hydrogenation catalyst for the hydrogenation of anthraquinone.In order to improve the activity and selectivity of the hydrogenation,this article uses two different silane coupling agents for modifying commercial spherical alumina and improving the metal dispersion of the catalyst.In the first part,we studied the effect of the grafting of 3-aminopropyltriethoxysilane（APTES）on the catalytic performance of Pd-based catalysts.The theoretical addition amount is added according to the molar ratio of APTES and Pd（APTES/Pd）.Anthraquinone hydrogenation performance test shows that the catalyst has the highest hydrogenation performance when APTES/Pd is 2.Compared with unmodified catalyst,the hydrogenation efficiency increases from 7.69g/L to 12.84 g/L,the selectivity of active anthraquinone was also increased to 100%from 98.24%.The characterization results of the catalyst show that the addition of APTES greatly improves the dispersion of Pd and reduces the size of metal palladium nanoparticles.At the same time,the addition of APTES can increase the weak acid content on the surface of the catalyst and improve the hydrophobic properties of the catalyst,which is conducive to improving the activity and selectivity of anthraquinone hydrogenation.However,with the increase in the amount of APTES added,the activity and selectivity of catalytic hydrogenation have decreased.The reason may be the uneven grafting of APTES on the alumina surface,which leads to the decrease of metal dispersion.In the second part,we explored the effect of grafting of 3-mercaptopropyltriethoxysilane（MPTES）on the catalytic hydrogenation performance of Pd-based catalysts.The hydrogenation efficiency is the highest when MPTES/Pd is4,and the selectivity is the best when MPTES/Pd is 2.Through a series of characterization techniques,it is found that the addition of an appropriate amount of MPTES can improve the metal dispersion and hydrophobicity of the catalyst,but the addition of excessive MPTES will lead to a decrease in dispersion,an increase in surface acidity and Pd²⁺content,which is not conducive to anthraquinone hydrogenation activity and selectivity.