III International Conference

PP-II-83SIGNIFICANT ENHANCEMENT OF PROPENE SELECTIVITY IN PROPANEDEHYDROGENATION ON Pt/γ-Al 2 O 3 BY ADDITION OF TINMoghimpour-Bijani Parisa 1, 2 , Khodadadi Abbas Ali 1 , Sahebdelfar Saeed 21 Catalysis and Nanostructured Materials Laboratory, School of Chemical Engineering,University of Tehran, Tehran, Iran2 Catalyst Research Group, Petrochemical Research and Technology Company, NationalPetrochemical Company, Tehran, IranE-mail: khodadad@ut.ac.irWe report propane dehydrogenation on Pt/γ-Al 2 O 3 catalyst containing various amounts oftin at different H 2 /propane ratios and temperatures. In all cases propene selectivity enhanceswith the tin content. A sharp increase in the selectivity at 0.25 and 0.70 wt% tin contents areobserved at H 2 /propane ratios of 0.8 and 1.5, respectively. In most cases the propanedehydrogenation activity decreases with the tin content, however, a maximum activity isobserved at tin content of 0.5 wt% for H 2 /prpane molar ratio of 0.4.IntroductionThe propene produced in steam crackers or FCC units alone does not satisfy the growingdemands for propene. Therefore, there is a great interest in catalytic dehydrogenation ofpropane to propene [1]. The dehydrogenation is carried out at high temperature and lowpressure to overcome thermodynamic limitation. At such conditions coke is producedextensively leading to deactivation of the catalyst [2]. Nobel metals, especially platinum, arekey ingredients in most dehydrogenation catalysts. Usually a second metal (Sn, Ag, Ge, Pb)and/or alkali metals are incorporated into the catalysts, to decrease the deactivation rate and/orenhance the propene selectivity. Supported Pt–Sn catalysts have shown lower deactivationrate and high selectivity for dehydrogenation reactions [3].Experimentalγ-Al 2 O 3 with 130 m 2 /g area (Axen) was sequentially impregnated with aqueous solutionsof H 2 PtCl 6 and SnCl 2 , and then dried and calcined at 550 o C for 3 h. The catalysts werecharacterized by ICP elemental analysis, BET area measurement, TPR and TPD. 1.0 g of thecatalyst was reduced in situ in a fixed-bed quartz tube reactor of ID = 12 mm. Propane and H 2flows adjusted by mass-flow controllers were mixed and passed over the catalyst bed atdifferent temperatures. The reactor effluents were analyzed on an online gas chromatograph(Agilent 6890N) for C 1 -C 5 saturated and unsaturated hydrocarbons.Results and DiscussionsFig. 1a and 1b, respectively, show the propane conversion and propene selectivity withrespect to tin contents of the Pt/γ-Al 2 O 3 catalysts at different H 2 /propane molar ratios. At314