A Comprehensive Study of Coke Deposits on a Pt-Sn/SBA-16 Catalyst during the Dehydrogenation of Propane

Abstract

Catalytic propane dehydrogenation is an attractive method to produce propylene while avoiding the issues of its traditional synthesis via naphtha steam cracking of naphtha. In this contribution, a series of Pt-Sn/SBA-16 catalysts were synthesized and evaluated for this purpose. Bimetallic Pt-Sn catalysts were more active than catalysts containing only Pt. The catalyst with the best performance was assessed at different reaction times of 0, 60, 180, and 300 min. The evolution of coke deposits was also studied. Thermogravimetric analysis demonstrated the presence of two types of coke on the catalyst surface at low and high temperature, respectively. Raman results showed an increased coke’s crystal size from 60 to 180 min on stream, and from 180 to 300 min under reaction, Raman suggested a reduction in the crystal size of coke. Also transmission electron microscopy confirmed a more evident agglomeration of metallic particles with reaction times higher than 180 min. These results are consistent with the phenomena called “coke migration” and the cause is often explained by coke movement near the particle to the support; it can also be explained due to sintering of the metallic particle, which we propose as a more suitable explanation.

Keywords

• propane dehydrogenation
• propylene
• SBA-16
• Pt-Sn
• deactivation
• coke deposits