Dehydrogenation of Propane over Silica‐Supported Platinum–Tin Catalysts Prepared by Direct Reduction: Effects of Tin/Platinum Ratio and Reduction Temperature

Abstract

A series of Pt‐Sn/SiO2 catalysts with different Sn/Pt atomic ratios (1/3–3) were prepared by a direct reduction method and tested for the dehydrogenation of propane to propylene. Structural characterization by XRD, TEM, CO adsorption, X‐ray photoelectron spectroscopy, and X‐ray absorption fine structure analysis revealed that the Pt‐Sn/SiO2 catalysts possessed a highly dispersed Pt‐Sn alloy core with a Sn‐rich surface regardless of the Sn/Pt ratio or reduction temperature. Highly dispersed SnO2 coexisted with the Pt‐Sn alloy particles, and part of the Pt‐Sn alloy surface was covered with SnO2. Among the catalysts prepared, 1Pt1Sn/SiO2_1073 K (Sn/Pt ratio=1, reduced at 1073 K), composed of Pt3Sn alloy with a small fraction of Pt‐Sn alloy, exhibited the highest activity. In contrast, if the Sn/Pt ratio was larger than 1 and/or the reduction temperature was 1273 K, Pt‐Sn alloy was observed mainly and the Pt‐Sn/SiO2 catalysts showed low activity.

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

“…The catalyst synthesized with a bulk In:Pt atomic ratio of 0.7 formed the Pt 3 In phase with a Cu 3 Au structure. Pt 3 In has the same structure as the Pt 3 Sn alloy which has been reported for Pt-Sn bimetallic catalysts [14][15][16][17]. The Pt-In and Pt-Pt bond distances of 2.79 Å seen by EXAFS is in agreement with the bond distances in the ideal Pt 3 In structure of 2.82 Å.…”

“…The Pt 3 Sn, PtSn, and PtSn 2 alloy phases have been identified in model Pt-Sn catalysts. However, because of the very small particles and low metal loadings the crystal phase of commercial catalysts has not been reported [13][14][15][16][17]. For the electronic case the formation of Pt-Sn bonds is thought to transfer electron density from Sn to Pt resulting in enhanced olefin desorption and improved selectivity [17][18][19][20].…”

Effect of Direct Reduction Treatment on Pt–Sn/Al2O3 Catalyst for Propane Dehydrogenation

“…Figure 3 shows the XRD patterns of the five SR catalysts (SR450, SR500, SR550, SR600, and SR800) and the Cal600 catalyst. As shown in Figure 3, [10,21]. It has been reported that the Pt 3 Sn alloy is only formed when precursor's molar ratios of Pt/Sn is higher than 1 [21].…”

“…Similar to the trends in Figure 1, the selectivity values of SR500 and SR550 were similarly high until 180 min, after which SR550 showed slightly superior selectivity to SR500 until 5 h reaction time. As mentioned, the direct reduction method was first reported by Deng and coworkers [10,21]. They prepared Pt-Sn/SiO 2 catalysts and evaluated the effects of the direct reduction method.…”

“…Deng and coworkers [10,21,22] used a direct reduction method to prepare PDH catalysts, which did not include a calcination step, unlike the conventional protocol for catalyst preparation involving drying, calcination, and reduction. They applied a hydrogen reduction stage at high temperature (800 • C) immediately after drying the catalyst without a calcination step.…”