Characterization of Pt,Sn/Mg(Al)O Catalysts for Light Alkane Dehydrogenation by FT-IR Spectroscopy and Catalytic Measurements

Abstract

The Pt function in Pt,Sn/Mg(Al)O and in Pt/Mg(Al)O catalysts has been studied by a combination of catalytic testing for ethane dehydrogenation at 450−650 °C under a C2H6/H2/CO2/N2/Ar = 10:1.6:6.8:5.9:75.7 flow and Fourier transform infrared spectroscopy (FT-IR), using CO as a probe molecule. The acid−base properties of the support were also investigated by FT-IR, using CH3CN as a probe molecule. CO adsorption experiments revealed the presence of Pt terraces, as well as Pt sites with low coordination number (steps, edges, corners, or defects) on Pt/Mg(Al)O. The same experiments on Pt,Sn/Mg(Al)O revealed that Sn covers the steps, corners, edges, and defects of the Pt particles, thus developing simultaneously a geometric and a chemical effect on the surface properties of the exposed Pt atoms. Accordingly, the ethane dehydrogenation reaction proceeds with a lower activation energy over Pt,Sn/Mg(Al)O compared to Pt/Mg(Al)O. Further, Sn addition leads to more selective and more stable ethane dehydrogenation catalysts. The higher dehydrogenation selectivity of Pt,Sn catalysts was correlated to the masking of low-coordinated Pt sites. The Pt/Mg(Al)O and Pt,Sn/Mg(Al)O catalysts were subjected to an activation procedure consisting of several test−regeneration cycles. Good correlation was found between the number of accessible Pt sites and the catalytic activity after each cycle.

Selectivity in Propene Dehydrogenation on Pt and Pt3Sn Surfaces from First Principles

“…This can probably be achieved even with a small amount of Sn introduced on Pt catalysts because Sn atoms are known to decorate step sites. 16 The lack of reactive Pt steps on Pt 3 Sn(211) suppresses propene dehydrogenation, which explains in part the increased selectivity. In addition, the weaker propene adsorption identified here and in earlier studies 8,21 has a positive impact on the selectivity as propene desorption becomes easier.…”

Structure and reactivity of Pt–In intermetallic alloy nanoparticles: Highly selective catalysts for ethane dehydrogenation

“…Industrially, Pt is used for LAD due to its intrinsic nature of favoring C-H bond activation over C-C bond activation [2]. The addition of Sn as a promoter results in higher olefin selectivity and catalyst stability [3][4][5][6][7][8][9][10][11][12]. The promotional effects have been attributed to the formation of Pt-Sn alloys [3,[10][11][12].…”

The influences of Mg/Al molar ratio on the properties of PtIn/Mg(Al)O- x catalysts for propane dehydrogenation reaction

“…Previous studies showed that metal oxide supports including K-L zeolite, spinels, alkali-doped alumina, calcined hydrotalcite greatly suppressed coke formation due to the free of acid sites and low alkene adsorption [32][33][34][35][36][37]. Among these supports, the studies about the calcined hydrotalcite (Mg(Al)O) or hydrotalcite-like materials were especially attractive due to their moderate basic characteristics and high thermal stability.…”