Modification Of Zeolite And Its Application In Catalytic Benzylation Of Arenes

Diphenylmethane and its derivatives has been considered as a sustainable alternative to replace petrochemical feedstocks in the synthesis of monobenzylation products,key industrial intermediates,via benzylation reactions.Zeolites with micro-pores are the most widely used catalysts in the benzylation of arenes,however,their performance suffers from diffusion limitations in converting large arenes.In this paper,mesoporous H-βzeolite and a series of modified HY catalysts were prepared.Their catalytic performance were investigated for the Friedel-Crafts benzylation of various arenes（benzene,toluene,p-xylene and mesitylene）with benzyl alcohol（Bz OH）.The influence of the pore structure and surface acidity on the catalyst activity of the catalysts was discussed.Research has shown that the mesoporous H-βzeolite,which can greatly improve the catalytic activity of diphenylmethane.Under the reaction conditions of 100°C,7 m L of toluene,0.01 m L of benzyl alcohol,and reaction time of 10 min,the Bz OH conversion was94%and the selectivity of diphenylmethane reached only 85%.HY zeolites were modified with Cu O,Zn O and Ni O and a series of catalysts with different loadings were prepared.But the unmodified HY zeolite catalyst for the reaction showed low catalytic activity.the modified HY zeolites catalysts can greatly improve the catalytic activity and renewable performance.Consistent with the reaction conditions of the H-βcatalyst,the order of the catalytic activity of the four catalysts is:Cu/HY>Zn/HY>Ni/HY>Mg/HY>HY.Among them,1%Zn/HY zeolite catalyst showed excellent catalytic performance.The conversion of Bz OH and the selectivity of diphenylmethane reached 100%.The local structure and acidity of modified HY zeolites were studied by XRD,N₂adsorption–desorption isotherms,FTIR spectroscopy,NH₃-TPD and ¹H MAS NMR spectroscopy and so on.¹H MAS NMR spectroscopy investigations determined the catalytically active Br?nsted acid sites,and the addition of metal can effectively adjust the acidity of HY zeolite.These modification HY zeolites are highly active catalyst to desired monobenzylation products depending on the synergistic effect of metallic ion with acidity.The catalytic performance of four kinds of aromatics is:benzene>toluene>p-xylene>mesitylene,typically for benzylation reaction.The benzylation studies have shown that synergistic effect of metallic ion with acidity can significantly increase the diffusion/access of arenes to surface sites,enhance their catalytic performance in modified HY zeolites.Therefore,the synergistic effect of metallic ion with acidity are keys in the tailoring of the catalytic performance of modified HY zeolite for target benzylation reactions.