Study On Zeolite Catalysts For Removal Of Trace Olefins From Aromatic Hydrocarbon

Aromatic hydrocarbons are important chemical raw materials. The olefin impurities are very harmful to the followed technological processes and applications of aromitcs. Therefore, these impurities must be removed with the suitable treatment technologies. There are two processes having been discovered for removing trace olefins from aromatics, i.e., particulated clay treating and catalytic hydrogenation treating. However, these two processes have some drawbacks. Therefore, a new process with zeolite as the catalyst appeared.The zeolite catalysts, in which HY zeolite was used as active component and alumina gel, silica-alumina gel and titania-alumina gel as binders, were prepared by mechanically mixing. The physico-chemical properties of these catalysts were characterized by means of BET, NH₃-TPD, XRD, TGA and activity evaluation. The effect of the kinds and contents of binders, calcinations temperature and different oxides modificator on activity of zeolite catalysts were studied. The catalyst deactivation reasons and the performances of regenerated catalyst were studied as well.It was found HY zeolite catalyst showed much better catalytic performance for olefin removal than NC-01 particulated clay due to its higher amount of acid sites. Among the catalysts containg different binders, the activity of the zeolite catalyst with silica-alumina gel as binder was best, which was owing to its more acidic sites. As the contents of binder increased, the activity of catalyst decreased. The proper content of the binder was between 20 wt.% and 30 wt.%. With the calcination temperature increased, the acidic sites of zeolite decreased and therefore its activity droped. However, the stability of catalyst is better originating from the decrease of strong acidic sites. The activity of modified catalysts by oxides dropped very quickly. In this study, among the catalysts concerned, the 20SiY823 containing 20 wt.% silica-alumina gel and calcined at 823 K showed better catalytic performance. Under the conditions of 453～463K, 1.1～1.2MPa and 65 h^-1, the Bromine Index of product was still lower than 90mgBr/100g over 20SiY823 after 12 h treating on the feed with Bromine Index of 667mgBr/100g,The deactivation of zeolite catalysts was due to coking. After high temperature...