Study of Catalysts Deactivation in Isomerization Process to Produce High Octane Gasoline


In this study the isomerization of desulfuerized light iraqi petroleum naphtha (Al-Dura Refinery) with boiling point range of 37 to 124 °C , 80.5 API specific gravity and 68.2 octane number has been investigated. Two types of catalysts were prepared (Pt/HX and Pt/SrX) by impregnation of 0.8 wt% Pt on 13X-zeolite. The catalyst activity and selectivity toward isomerization, and catalyst deactivation were investigated.The isomerization unit consisted of a vertical tubular stainless steel reactor of 2 cm internal diameter, 3 cm external diameter and 6 height The operating pressure was atmospheric for all experimental runs. The l(quidflow of light naphtha was 0.4 Lih, and the catalyst weight was 50 gm, H2/H.C ratio used was 4 for all experimental runs. The isomerization process was studied at different temperatures of 250, 270, 275, 300, 325, and 350°C. It was found that, the optimum isomerization temperature is 270°C.The isomerization activities and selectivities as afunction of time showed high activity at the beginning of the reaction and were deactivated rapidly. This indicates that the deactivation of Pt/HX and Pt/SrX results from the blocking of pore mouth by the deposited carbon. The following deactivation decreasing order, Pt/HX> Pt/SrX was found. On the other hand, Pt/FIX catalyst shows higher activity and selectivity than that of Pt/ was concluded that, only an average of 90 wt% of the carbon atoms fled into the reactor (light naphtha) is detected in the product strewn due to formation of coke deposits which leads to catalyst deactivation. The results clearly showed that hydrogen is necessary for the hydrogenation of olefins in order to prevent oligomerization reaction that leads to coke formation and catalyst deactivation.