Mesoporous-Silica-Stabilized Cobalt(II) Oxide Nanoclusters for Propane Dehydrogenation

Abstract

Propane dehydrogenation is a highly efficient and selective route to produce propylene. The development of transition-metal-based catalysts, especially cobalt oxide−Co(II) for propane dehydrogenation reaction has gained momentum in the past few years. However, the formation of bulk metallic cobalt is a major drawback of cobalt oxide-based catalysts, which need to be circumvented to maintain the high propylene selectivity. In this study, a facile route is proposed to prepare stable Co(II) on a mesoporous silica matrix (Co-mSiO 2 ) via a simple synthesis procedure using the neutral templating method. The cobalt content in the silica is varied to optimize the activity and stability during the reaction. The physicochemical properties of the catalyst measured using X-ray diffraction, N 2 adsorption−desorption, and transmission electron microscopy revealed the high surface area and well-dispersed cobalt oxide present in the mesoporous silica matrix. The coordination geometry found from the UV−vis and extended X-ray absorption fine structure analysis showed that Co(II) is highly dispersed with tetrahedral coordination in the mesoporous silica. The Co-mSiO 2 catalyst with the lowest cobalt content of 2 wt % tested for the propane dehydrogenation reaction at the operating temperature of 600 °C showed 36% propane conversion with 94% propylene selectivity. 2Co-mSiO 2 showed the nonredox properties of Co(II) with negligible metallic cobalt formed and a lower coke deposition rate (4 mg carbon /g cat. •h) after the reaction supported by X-ray absorption near-edge structure and thermogravimetric analysis. The source for the side reaction (coke formation) can be assigned to the strong adsorption of propylene, which was unraveled using Fourier transform infrared analysis, and a nonredox mechanism is proposed for propane dehydrogenation reaction over the 2Co-mSiO 2 catalyst.

Atomically Dispersed Co2+ Sites Incorporated into a Silicalite-1 Zeolite Framework as a High-Performance and Coking-Resistant Catalyst for Propane Nonoxidative Dehydrogenation to Propylene

“…Catalytic stability evaluation of Co-Silicalite-1 over PDH (A) and the recently reported TOF of Co-based catalysts in the PDH reaction (B). Co-mSiO 2 , CoO x @NC/S-1, Co/SiO 2 , Co-Al 2 O 3 , and CoAl 2 O 4 according to references.…”

“…Due to its earth abundance and low toxicity, Co-based catalysts have been studied to activate C–H effectively. , Subsequently, Co/SiO 2 , ,, ,, CoAl 2 O 4 , and Co/ZSM-5 , have been investigated over PDH correspondingly. Tetrahedrally coordinated Co 2+ species on oxide supports acting as Lewis acidic sites are proposed as corresponding PDH active sites, while metallic Co 0 species could be responsible for the cracking of C 3 H 8 to C 2 H 4 , CH 4 , and coke.…”

Ethane dehydrogenation performance and high temperature stability of silica supported cobalt phosphide nanoparticles

“…Co was chosen because it is a non-noble metal that has shown promising light alkane dehydrogenation performance when isolated, in oxide form, or promoted with elements such as Zn. [22][23][24][25][26][27][28][29][30][31] Additionally, Co has geometric site isolation and electronic charge transfer effects upon P incorporation similar to Ni which can benefit dehydrogenation performance. 8 We synthesized SBA-15 supported Co-P materials (Co-P/SBA-15) and utilized experimental EDH performance measurements, detailed characterization, and high temperature EDH stability studies to interrogate the effects of varying P content.…”

Suppressing C–C Bond Dissociation for Efficient Ethane Dehydrogenation over the Isolated Co(II) Sites in SAPO-34

“…Constructing a support–metal–strong-interaction (SMSI) catalyst is a general guide with various top-down and down-top methods. Incorporation of metal ions or oxides into the framework or the matrix of supports can be realized under a one-pot synthesis condition, − where the precursors of the metal and the elements of the support (such as Si and Al) are placed together in a beaker or autoclave. For example, Yang et al reported an Fe-containing MFI siliceous zeolite and Bian synthesized a mesoporous-silica-stabilized Co- m SiO 2 catalyst, and these catalysts have −M δ+ –O δ− – structures that are not easily reduced and have been demonstrated to be active, selective, and stable for alkane dehydrogenation.…”

“…Incorporation of metal ions or oxides into the framework or the matrix of supports can be realized under a one-pot synthesis condition, − where the precursors of the metal and the elements of the support (such as Si and Al) are placed together in a beaker or autoclave. For example, Yang et al reported an Fe-containing MFI siliceous zeolite and Bian synthesized a mesoporous-silica-stabilized Co- m SiO 2 catalyst, and these catalysts have −M δ+ –O δ− – structures that are not easily reduced and have been demonstrated to be active, selective, and stable for alkane dehydrogenation. Also, post-treatment of a prepared metal or metal oxide/support catalyst, such as using a water-assisted method, could also enhance the interaction between the metal and the support .…”