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

Jose P Ruelas-Leyva,Luis F Maldonado-Garcia,Alfonso Talavera-Lopez,Carlos E Santolalla-Vargas,Sergio A Gómez Torres,Gustavo A Fuentes,Lorenzo A Picos-Corrales,Iván A Santos-López

doi:10.3390/catal11010128

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.

Highlights

Propylene, relatively non-toxic to humans, is a widely used raw material in the production of several important chemicals like polypropylene, acrolein and isopropyl alcohol, among others [1,2]
The textural properties and the hysteresis loops depend strongly on the hydrothermal temperature used during the synthesis of SBA-16
Catalysts containing Pt were barely active, while the bimetallic Pt-Sn catalysts were highly active

Summary

Introduction

Relatively non-toxic to humans, is a widely used raw material in the production of several important chemicals like polypropylene, acrolein and isopropyl alcohol, among others [1,2]. For propane production via catalytic routes, some of the most effective catalytic systems are the ones containing Pt or CrOx. Pt catalysts are preferred due the higher toxicity of Cr species. Despite the great potential of Pt catalysts, they suffer from deactivation [4] due to coke deposition [5]. Several reports in the technical literature shed some light in the current understanding of ways of dealing with catalyst deactivation, for example, by adding a second metal to the Pt catalyst [6], using other supports rather than the typically employed

Methods

Results

Conclusion