Research progress of CO2 oxidative dehydrogenation of propane to propylene over Cr-free metal catalysts

Abstract

CO 2 -assisted oxidative dehydrogenation of propane (CO 2 -ODHP) is an attractive strategy to offset the demand gap of propylene due to its potentiality of reducing CO 2 emissions, especially under the demands of peaking CO 2 emissions and carbon neutrality. The introduction of CO 2 as a soft oxidant into the reaction not only averts the over-oxidation of products, but also maintains the high oxidation state of the redox-active sites. Furthermore, the presence of CO 2 increases the conversion of propane by coupling the dehydrogenation of propane (DHP) with the reverse water gas reaction (RWGS) and inhibits the coking formation to prolong the lifetime of catalysts via the reverse Boudouard reaction. An effective catalyst should selectively activate the C-H bond but suppress the C-C cleavage. However, to prepare such a catalyst remains challenging. Chromium-based catalysts are always applied in industrial application of DHP; however, their toxic properties are harmful to the environment. In this aspect, exploring environment-friendly and sustainable catalytic systems with Cr-free is an important issue. In this review, we outline the development of the CO 2 -ODHP especially in the last ten years, including the structural information, catalytic performances, and mechanisms of chromium-free metal-based catalyst systems, and the role of CO 2 in the reaction. We also present perspectives for future progress in the CO 2 -ODHP.

CO2-Assisted Oxidative Dehydrogenation of Propane over VOx/In2O3 Catalysts: Interplay between Redox Property and Acid–Base Interactions

“…1,11,30 However, due to the toxic and carcinogenic properties of Cr(VI) oxides, it is vital to find alternatives. 30 Group IIIA mixed oxides such as Ga 2 O 3 −Al 2 O 3 31,32 and In 2 O 3 −Al 2 O 3 33 and supported In 2 O 3 catalyst 25,34 show comparable catalytic performance as well. On Ga 2 O 3 , ODHP is proposed to proceed via the heterolytic propane dissociation on acid−base pairs, namely, Ga δ+ −O 2− pairs.…”

“…Therefore, designing catalysts that can selectively break the C–H bond to produce alkenes while suppressing PDR is of great interest. Similar to the O 2 -ODHP route, redox-active metal oxides (Cr and V) are promising candidates for CO 2 -ODHP. ,, However, due to the toxic and carcinogenic properties of Cr­(VI) oxides, it is vital to find alternatives . Group IIIA mixed oxides such as Ga 2 O 3 –Al 2 O 3 , and In 2 O 3 –Al 2 O 3 and supported In 2 O 3 catalyst , show comparable catalytic performance as well.…”

Metallic Catalysts for Oxidative Dehydrogenation of Propane Using CO2

“…To better address this challenge, Wang et al [111] reported PtSn/SiO 2 catalysts with the addition of CeO 2 as a promoter, which could improve the catalytic activity and selectivity. As in previous studies, [15,112] CeO 2 with high oxygen storage capacity and abundant oxygen defects was chosen to activate CO 2 . However, in this study, the order of the catalytic activity (PtSn/SiO 2 < PtCe/SiO 2 < PtSnCe/SiO 2 ) could be explained simply by the grain size and metal dispersion.…”

“…Furthermore, the development of metal-catalyzed CO 2 À ODP is just in its infancy. Although several review papers have summarized CO 2 À ODP reactions in recent years, they have mainly focused on the role of CO 2 [12,15] and the mechanistic differences among various metal oxides [13,[16][17][18][19][20] but rarely on the catalytic performance and design concept of metallic catalysts. Therefore, we summarized and compared the trends in the catalytic performance of the reported metal oxide-and metalbased catalysts in terms of CO 2 versus C 3 H 8 conversion (Figure 1b).…”

Mechanistic Interpretations and Insights for the Oxidative Dehydrogenation of Propane via CO2 over Cr2O3/Al2O3 Catalysts

“…High CO 2 partial pressures tend to mitigate coke formation, which is believed to result from the reverse Boudouard reaction (C + CO 2 → 2CO). ,,, Excess CO 2 is believed to enable the MvK reaction pathway by providing sufficient oxygen through CO 2 . Laboratory-scale experiments typically use 0.1 ≤ C 3 H 8 /CO 2 ≤ 0.5. , However, high CO 2 fractions up to C 3 H 8 /CO 2 = 1/20 were also studied .…”