Probability of chain growth in coke formation on metals and on supports during catalytic reforming over Pt, Pt-Sn and Pt-Sn-K catalysts mixed physically with Al2O3

Abstract

The main goal of this contribution was to study the probability of chain growth of coke on metal sites and on support sites for hexane dehydrogenation. The coke structure of the catalysts examined by IR was found to have the aromatic structure. Soxhlet extraction coupled with GC-14B (DB1 column) analysis was mainly employed for coke composition analysis and determination of the probability of chain growth (alpha value). It was found that the soluble coke was mainly composed of C8–C12 on both sites. Interestingly, the probabilities of chain growth on both sites were identical. However, the extracted coke on the metal site was more easily removable and had lower carbon numbers than that on the support site. Moreover, the addition of promoter, especially of K promoter, was sensitive to inhibit the probability of chain growth, resulting in the reduction of the amount of coke.