Promoting Propane Dehydrogenation with CO₂ over the PtFe Bimetallic Catalyst by Eliminating the Non-selective Fe(0) Phase

Abstract

Fine tuning the structure of bimetallic nanoparticles is critical toward understanding structure−activity relationships and further improving the catalytic performance in propane dehydrogenation (PDH). Excessive Fe species in the PtFe bimetallic catalysts promote carbon deposition leading to low propylene selectivity, and it remains challenging to synthesize welldefined PtFe catalysts while selectively eliminating the excessive Fe. Herein, we show that the formation of coke can be significantly inhibited by introducing CO 2 into the PDH over PtFe catalysts, where CO 2 effectively eliminates the active Fe(0) coking sites without changing the catalytic surface structure of the PtFe alloy. With a CO 2 /C 3 H 8 feeding ratio of 0.20, the Pt1Fe7/S-1 catalyst shows the highest propylene production rate and decreased amount of coke from 18.8 to 1.0 wt % compared with dehydrogenation without CO 2 . X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and 57 Fe Mossbauer results indicate that it is the oxidation of excessive unalloyed Fe species during the CO 2 -PDH reaction, instead of the reverse Boudouard reaction (CO 2 + C = 2CO), that significantly inhibits the carbon deposition. This work provides a promising strategy for tuning the structure of PtFe bimetallic catalysts under reaction conditions and improving the performance of the PDH reaction.

Design Strategies of Stable Catalysts for Propane Dehydrogenation to Propylene

“…Many other metals, including Fe, − Cu, , and Co, can also be promoters for Pt-based catalysts to adjust the electronic properties and improve the dispersion of Pt atoms for further stability enhancement. A catalyst with Pt–Fe nanoparticles supported on dendritic mesoporous silica was developed and exhibited high propylene selectivity and catalytic activity during a 60 h long-term test .…”

Reaction-Mediated Transformation of Working Catalysts

“…As a result, the performance of the propane dehydrogenation reaction has been greatly improved. 77 The goal for the planning of synthesis strategies and operation protocols should be to start from not only the characteristics of the desired active centers but also the possible transformation pathways of the active sites in reactors. Atomic engineering of catalyst design and a molecular-level understanding of transformation mechanisms will be applied to many new frontiers, including subsurface design 78,79 and liquid-phase catalysts.…”

“…By cofeeding CO 2 , which oxidized the Fe to Fe 3 O 4 , the amount of coke has therefore been reduced from 18 wt % to 1 wt %. As a result, the performance of the propane dehydrogenation reaction has been greatly improved …”

Promoting n-Butane Dehydrogenation over PtMn/SiO2 through Structural Evolution Induced by a Reverse Water-Gas Shift Reaction

“…19 Bian et al introduced CO 2 to PDH over PtFe catalysts to eliminate the unalloyed Fe(0) coking sites while maintaining the surface structure of the PtFe alloy, which minimized the coke deposition from ∼18 to 1 wt % and improved the stability and C 3 H 6 selectivity. 20 Therefore, a new oxidative PDH process on PtFe catalysts was achieved with better performances compared with direct dehydrogenation. In addition to eliminating the active sites for side reactions, knowledge of the structural evolution in CO 2 hydrogenation might also be used to tune the structure of the active sites/ surfaces for alkane dehydrogenation.…”

“…Liu et al reported that addition of CO 2 to propane dehydrogenation (PDH) accelerates the transformation of unfavorable Ga δ+ –H x species to Ga 3+ –O pairs, regenerating the active sites for the selective C–H bond activation of propane . Bian et al introduced CO 2 to PDH over PtFe catalysts to eliminate the unalloyed Fe(0) coking sites while maintaining the surface structure of the PtFe alloy, which minimized the coke deposition from ∼18 to 1 wt % and improved the stability and C 3 H 6 selectivity . Therefore, a new oxidative PDH process on PtFe catalysts was achieved with better performances compared with direct dehydrogenation.…”