Effects Of Additives On The Performance Of Shaped ZSM-5 In Toluene Alkylation With Methanol To Para-xylene

para-Xylene is an important organic chemical feedstock.Due to the rapid development of the polyester industry,the demand for para-xylene is increasing.The high demand for para-xylene created incentives for researchers to develop processes for on-purpose para-xylene production.Toluene alkylation with methanol is an efficient path to increase the production of p-xylene,which can not only reduce cost of separation,but also combine petroleum chemical industry and coal chemical industry.It's beneficial to the development of polyester industry.The scale-up of catalyst from powder to certain shape and size is indispensable for industrial catalyst application.Accordingly,understanding the effects of additives on the performance of shaped catalysts is one of the prominent features in toluene methylation.This research studies the effects of shaping with attapulgite,alumina and attapulgite-alumina mixture on the properties and performance of ZSM-5 extrudates in toluene alkylation with methanol.Moreover,the adhesive solvent effect on the performance of ZSM-5 is discussed.The main results are listed below:(1)Attapulgite-bound ZSM-5 extrudates showed higher para-selectivity and better stability than alumina-bound ZSM-5 extrudates.Initial p-xylene selectivity of attapulgite extrudate was 11.5% higher than alumina extrudate.After 100 h,the toluene conversion deterioration of attapulgite extrudate is smaller than alumina extrudate.After regeneration,initial p-xylene selectivity of attapulgite extrudate was 66.2%,the same as the final para-selectivity of first cycle.Additionally,it is noted that the para-selectivity of attapulgite extrudate increase with time on stream.These results showed that attapulgite can modify the zeolite in situ.When the modified catalyst was extruded with attapulgite,p-xylene selectivity increased 20%.It shows that the attapulgite effect is universal.(2)Two-component binder was obtained by mixing attapulgite and alumina with different ratios.As the attapulgite content decreased,initial p-xylene selectivity of extrudate declined gradually.Increasing the attapulgite content,the catalyst's lifespan firstly increases and then decreases.The catalysts' mechanical strength increased gradually with the alumina contents.(3)In the absence of a binder,the effect of the adhesive solvent on the catalyst was studied by adding water or dilute nitric acid.Compared with the untreated catalyst,para-selectivity increased after adding water or dilute nitric acid.After combined modification,para-selectivity of dilute nitric treated catalyst increased about 17%,and the toluene conversion did not decrease.