The Origin of the Special Surface and Catalytic Chemistry of Ga-Rich Ni₃Ga in the Direct Dehydrogenation of Ethane

Abstract

Synthesis of kinetically trapped, alumina-supported Ni3Ga nanoparticles with particle surface composition partially controlled by off-stoichiometric Ni:Ga loading ratios enabled active, highly selective, and stable catalysts to be developed for the direct dehydrogenation of ethane to ethylene. Experimental studies indicated a direct correlation between superstoichiometric Ga loading and ethylene selectivity yet an inverse correlation with ethane conversion. A catalyst with a 1:1 Ni:Ga loading ratio exhibited a good balance between activity (TOF 5.0 × 10–2 s–1), selectivity (94%), and stability (94 to 90% over the 32-h test). The catalyst could also be easily regenerated using an oxidation and reduction cycle. DFT calculations and in situ DRIFTS CO adsorption confirm that surface reactivity is attenuated as Ga concentration at the particle surface increased.

High-loading Ga-exchanged MFI zeolites as selective and coke-resistant catalysts for nonoxidative ethane dehydrogenation

“…This formation rate is the highest among the reported Pt-free catalysts (Table S1 in the ESI†). 55,66–75 After the reaction, Ga-MFI-1.0(800) could be regenerated by oxidation treatment (a 5% O 2 /He flow at 600 °C for 1.5 h) followed by H 2 treatment at 800 °C. The regenerated catalyst exhibited similar initial conversion and selectivity values to the original values (see Fig.…”

Propane dehydrogenation over extra-framework In(i) in chabazite zeolites

“…10). With the increase of the In/Al ratio to 1.7 on the In-CHA (Si/Al ¼ 12) catalyst, several interesting trends were observed: (1) the initial activity including C 3 H 8 dehydrogenation and C 3 H 8 cracking decreases; (2) the ratio between the C 3 H 8 dehydrogenation and C 3 H 8 cracking increases monotonically; (3) the catalyst exhibits better stability over 10 hours of testing (Fig. S32 †).…”

“…1 PDH technologies, i.e., the Catofin process using CrO x /Al 2 O 3 catalyst, and the Oleflex process using supported Pt-Sn catalyst have drawbacks, such as the high cost and rapid deactivation of Pt and the potential environmental impact caused by Cr. Many other catalysts for PDH have been investigated including Ga-, [2][3][4][5][6][7][8][9][10] Zn-, 11,12 Co-, [13][14][15] Fe-, [16][17][18] V-, [19][20][21][22] Zr-based materials, [23][24][25] and nanocarbon catalysts. 26,27 Metal cations (Ga + , Zn 2+ , Co 2+ , etc.)…”

Near 100% ethene selectivity achieved by tailoring dual active sites to isolate dehydrogenation and oxidation

“…The oxidative dehydrogenation of light alkanes to olefins (ODH) which are important building blocks for a handful of industrial processes is a well-known example of such a challenging reaction that is a promising alternative to the current industrial practice of steam cracking with no thermodynamic limitation, coke formation, and large CO 2 emission but difficult to realize commercialized utilization impeded by the liable deep oxidation [6][7][8][9] . This was because alkene is facile to be further oxidized before its desorption or re-adsorbed on the active sites of dehydrogenation (usually oxygen species) according to the Mars-van Krevelen mechanism 1,10,11 which resulted from its higher affinity and reactivity than alkane to most surfaces particularly for those of V-and Ni-based catalysts which have been studied most for ODH [12][13][14][15][16][17] . Extensive studies have contributed to manipulating the chemical environment of active oxygen species to decrease its insertion as large extent as possible concurrently with activation for C−H bond in alkane.…”