A Robust and Efficient Propane Dehydrogenation Catalyst from Unexpectedly Segregated Pt₂Mn Nanoparticles

Abstract

The increasing demand for short chain olefins like propene for plastics production and the availability of shale gas make the development of highly performing propane dehydrogenation (PDH) catalysts, robust toward industrially applied harsh regeneration conditions, a highly important field of research. A combination of surface organometallic chemistry and thermolytic molecular precursor approach was used to prepare a nanometric, bimetallic Pt−Mn material (3 wt % Pt, 1.3 wt % Mn) supported on silica via consecutive grafting of a Mn and Pt precursor on surface OH groups present on the support surface, followed by a treatment under a H 2 flow at high temperature. The material exhibits a 70% fraction of the overall Mn as Mn II single sites on the support surface; the remaining Mn is incorporated in segregated Pt 2 Mn nanoparticles. The material shows great performance in PDH reaction with a low deactivation rate. In particular, it shows outstanding robustness during repeated regeneration cycles, with conversion and selectivity stabilizing at ca. 37 and 98%, respectively. Notably, a material with a lower Pt loading of only 0.05 wt % shows an outstanding catalytic performance�initial productivity of 4523 g Cd 3 Hd 6 /g Pt h and an extremely low k d of 0.003 h −1 under a partial pressure of H 2 , which are among the highest reported productivities. A combined in situ X-ray absorption spectroscopy, scanning transmission electron microscopy, electron paramagnetic resonance, and metadynamics at the density functional theory level study could show that the strong interaction between the Mn II -decorated support and the unexpectedly segregated Pt 2 Mn particles is most likely responsible for the outstanding performance of the investigated materials.

Isolated Pt Species Anchored by Hierarchical-like Heteroatomic Fe-Silicalite-1 Catalyze Propane Dehydrogenation near the Thermodynamic Limit

“…Subsequently, in situ DRIFTS with CO adsorption was carried out to further acquire information on surface Pt ensembles in different catalyst samples (Figure i). For Pt/Fe-1, a prominent peak at 2077 cm –1 accompanied by a sharp peak at 2088 cm –1 was observed, which could be attributed to the CO adsorption on single Pt δ+ atoms and well-coordinated Pt metal nanoparticles. − Comparatively, Pt/Fe-3, Pt/Fe-4, and Pt/Fe-3-C1 showed only the CO adsorption peaks of single Pt δ+ atoms and Pt nanoparticles. Moreover, CO adsorption peaks detected only at 2077 cm –1 in Pt/Fe-3 after regeneration tests further supported the presence and stability of the isolated Pt δ+ atoms.…”

Recent Progress in Metal-Molecular Sieve Catalysts for Propane Dehydrogenation

“…Revealing the actual active site locations, the metal/oxide-molecular sieve interfaces, and the reaction mechanisms under reaction conditions requires advanced characterizations including iDPC-STEM images, in situ spectroscopy with well-designed atmosphere, and two-dimensional soild-state NMR microscopy. ,,,,,, In addition to experimental efforts, DFT calculation is another powerful technique for identifying the active site evolution and reaction network. In particular, the ab initio metadynamics simulations can screen the potential reactions between active center and given reactants, which is different from the conventional transition state calculations that typically predefined a reaction pathway. , Therefore, it is expected that the advanced metadynamics simulations may help explore the potential active centers and the reaction mechanisms.…”

“…In particular, the ab initio metadynamics simulations can screen the potential reactions between active center and given reactants, which is different from the conventional transition state calculations that typically predefined a reaction pathway. 152,153 Therefore, it is expected that the advanced metadynamics simulations may help explore the potential active centers and the reaction mechanisms.…”

Ti-Doping in Silica-Supported PtZn Propane Dehydrogenation Catalysts: From Improved Stability to the Nature of the Pt–Ti Interaction

“…The Oleflex process, developed in the 1990s, was the first industrial process for PDH based on a bimetallic catalyst, namely, PtSn supported on Al 2 O 3 . Much more recently, another bimetallic, PtGa-based catalyst was implemented in industrial settings. ,− Several recent reviews furthermore highlight the high relevance of this process. ,− Overall, many different metal promoters have been utilized to improve the catalytic performances of Pt-based systems for light alkane dehydrogenation; most of them being post-transition (Zn, − Ga, , In, and Sn ,, ) and transition metals (Mn − or Cu − ). Besides these promoters, alkali metals and different supports have been used to improve catalyst performances, with the goal to minimize cracking and improve the regeneration process …”