Regeneration of Pt-Sn/Al2O3 Catalyst for Hydrogen Production through Propane Dehydrogenation Using Hydrochloric Acid

Abstract

Compared with dehydrogenation in conventional petroleum refinery processes, relatively pure hydrogen can be produced by propane dehydrogenation (PDH) without innate contaminants like sulfur and metals. Among the existing catalysts for PDH, Pt catalysts are popular and are often used in conjunction with Sn as a co-catalyst. Coke formation is a major concern in PDH, where catalyst regeneration is typically achieved by periodic coke burning to achieve sustainable operation. In this study, Pt-Sn/Al2O3 catalysts were regenerated after coke burning in three stages: mixing the catalyst with liquid hydrochloric acid, drying, and calcining under air atmosphere. In this process, the optimum concentration of hydrochloric acid was found to be 35% w/w. HCl treatment was effective for enhancing redispersion of the metal catalysts and aiding the formation of the Pt3Sn alloy, which is considered to be effective for PDH reaction. HCl treatment may provide oxychlorination-like conditions under the calcination atmosphere. The characteristics of the catalysts were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and CO chemisorption.

Self-adaptive structure and catalytic performance of the Pt–Sn/Al2O3 propane dehydrogenation catalyst regenerated by dichloroethane oxychlorination

“…Although the conversion decreased, the calculated TOF for propane conversion (shown in Table 1) on these catalysts actually increased. During the oxidation treatment, surface chlorine species and hydroxyl groups are partly removed from the support surface and the sites for anchoring Pt and/or Sn species also change 28 and, therefore, the structural properties and catalytic performance change as well. From the characterization results stated above, it's found that the multiple Pt–Pt sites and the Pt species with a weak interaction with the carrier diminish due to the mobility of the Pt and/or Sn species.…”

“…During the oxidation treatment, surface chlorine species and hydroxyl groups are partly removed from the support surface and the sites for anchoring Pt and/or Sn species also change 28 and, therefore, the structural properties and catalytic performance change as well. From the characterization results stated above, it's found that the multiple Pt-Pt sites and the Pt species with a weak…”

“…Arteaga et al 32 found that the presence of Sn reduced the formation of the oxychloroplatinum surface complex, Pt IV O x Cl y , during the regeneration process and the diffusion of SnO 2 on the support hindered the mobility of the complexes and the redispersion of Pt. Choi et al 28 found that hydrochloric acid treatment of the Pt–Sn/Al 2 O 3 catalyst (similar to oxychlorination) could promote the formation of a Pt 3 Sn alloy, which was beneficial to the propane dehydrogenation reaction.…”

Propylene Synthesis: Recent Advances in the Use of Pt-Based Catalysts for Propane Dehydrogenation Reaction

“…Coke burning may result in extensive active metal sintering, so alternative regeneration processes have also been proposed, which make use of ozone, hydrogen and oxychlorination. Optimal conversion recovery has been obtained by treatment of Pt-Sn/Al 2 O 3 catalysts, with 35% HCl, after coke burning [98]. HCl treatment seems to play a similar role as oxychlorination in redispersing the Pt particles and generating the Pt 3 Sn alloy.…”

Mesoporous Silica Encapsulated Platinum–Tin Intermetallic Nanoparticles Catalyze Hydrogenation with an Unprecedented 20% Pairwise Selectivity for Parahydrogen Enhanced Nuclear Magnetic Resonance

“…The measured values for the conversions, signal enhancement factors, and pairwise selectivities of three NPs after the oxidation–reduction cycling are summarized in Figure S6 and Table S7. The restoration in the performance of three NPs is likely due to the removal of surface carbon deposits during the catalyst regeneration process. − Thus, Pt 3 Sn@mSiO 2 and PtSn@mSiO 2 iNPs are robust and effective catalysts for achieving high NMR signal enhancement with excellent durability and recyclability in parahydrogen enhanced NMR. For these catalysts, the mSiO 2 shell effectively prevents the encapsulated iNPs from aggregation at high temperatures.…”