Highly Active and Selective Sites for Propane Dehydrogenation in Zeolite Ga-BEA

Abstract

A highly selective Ga-modified zeolite BEA for propane dehydrogenation has been synthesized by grafting Ga on Zn-BEA followed by removal of Zn in the presence of H 2 . A propene selectivity of 82% at 19% propane conversion illustrates the high selectivity at 813 K. The kinetic model of the catalyzed dehydrogenation including the elementary steps of propane adsorption, first and second C−H bond cleavage, and propene and H 2 desorption demonstrates that the propane dehydrogenation rate is determined by the first C−H bond cleavage at low p C 3 H 8 , while at high p C 3 H 8 , the rate is limited by the desorption of H 2 . The active sites have been identified as dehydrated and tetrahedrally coordinated Ga 3+ in the *BEA lattice. The low selectivity toward aromatics is concluded to be associated with the high Lewis acid strength of lattice Ga 3+ and the low Brønsted acid strength of the hydrated Ga sites.

Zinc Speciation and Propane Dehydrogenation in Zn/H-ZSM-5 Catalysts

“…Propylene, an essential building block for producing polypropylene, acrylic acid, propylene oxide, and acrylonitrile, has been mainly obtained as a byproduct from naphtha steam crackers and fluidized catalytic cracking (FCC) units in refineries. , Due to the growing demand for propylene and the large supply of shale gas, on-purpose propane dehydrogenation (PDH) is increasingly important. − Two processes have been industrialized for this reaction: the Oleflex process (Pt-Sn based catalyst) and the Catofin process (CrO x /Al 2 O 3 catalyst); however, the high cost of Pt and the toxicity of Cr motivates the search for alternative low-cost and environmentally friendly catalysts. ,, Many catalysts, in fact, show promising PDH performance: Ga-, − V-, , Zn-, − Co-, − Fe-, − Zr-, − Sn-, In-based catalysts, , and nanocarbon materials . Metal cations exchanged with zeolite catalysts (Ga/H-ZSM-5, Zn/H-ZSM-5, Co/H-ZSM-5) are efficient for propane dehydrogenation with approximately 90% C 3 H 6 selectivity. − However, the elucidation of the structure of metal cation species on zeolites remains unresolved and essential for catalyst improvement. − …”

Photothermal catalytic CO2 oxidative dehydrogenation of propane to propylene over BiOX (X = Cl, Br, I) nanocatalysts

“…In addition, the C 4 products increased with the decrease of CO 2 concentration, while the C 2 species (main ethylene) decreased, suggesting that the C 4 species were mainly produced from ethylene oligomerization. 57…”

“…In addition, the C 4 products increased with the decrease of CO 2 concentration, while the C 2 species (main ethylene) decreased, suggesting that the C 4 species were mainly produced from ethylene oligomerization. 57 The evolution of the total yield of each product was studied by prolonging the reaction time and the results are presented in Fig. 8d.…”

Manipulating the Cobalt Species States to Break the Conversion–Selectivity Trade-Off Relationship for Stable Ethane Dehydrogenation over Ligand-Free-Synthesized Co@MFI Catalysts

“…Because Cr is very harmful to the environment, in spite of its relative cheapness Cr-based catalysts are being phased out in the industry. Therefore, a large amount of non-noble-metal-based and environment-friendly catalyst systems for nonoxidative dehydrogenation were variously investigated, mainly including the first-row 3d (like V , and Zn − ) and group IIIA (like B, , Al, , Ga, , and In , ) metal-oxide-based catalysts.…”