Removal of trace olefins from aromatics with modified USY zeolite and clays

Abstract

Naphtha reforming is an important raw material for aromatic hydrocarbon products in petrochemical processes. However, aromatic hydrocarbon streams obtained from refinery contain unavoidable trace amounts of olefins as an impurity. The trace olefins must be removed because these undesirable olefins are harmful to the following separation processes. Alkylation reaction has been used to remove olefins with acid catalysts. In this study, clays and zeolites were screened for further modification in order to enhance the catalytic activity of olefins removal. The catalytic activity testing was studied in a batch reactor at 195 ℃ for 6 h under 12 barg. USY was modified by dealumination with 0.075 – 0.3 M citric acid, and bentonite was modified by acid activation with 1–6 M hydrochloric acid. The properties of catalysts were determined by XRD, XRF, N₂ adsorption, TPD-NH₃, and STA. The results showed that the modification of USY with 0.15 M citric acid increased the surface area and proportion of strong acid sites to total acid sites resulting in the increase in the initial and final olefins removal from 76 to 87% and 84 to 90%, respectively. Likewise, the modification of bentonite with 1 M hydrochloric acid increased the acidity leading to the increase in the initial and final olefins removal from 74 to 81% and 86 to 90%, respectively.