Sodium tungstate-promoted CaMnO3 as an effective, phase-transition redox catalyst for redox oxidative cracking of cyclohexane

Cracking and Dehydrogenation of Cyclohexane by [(phen)M(X)]+ (M = Ni, Pd, Pt; X = H, CH3) in the Gas Phase

“…While a large percentage of naphtha consists of linear hydrocarbons, a portion is made up of cyclic hydrocarbons called naphthenes, which consist of saturated cyclic hydrocarbons like cyclohexane. The transformation of these cyclic hydrocarbons into high-commodity chemicals like hydrogen, ethylene, and propylene constitutes a large economic portion of the petroleum-refining industry Thermal cracking of cyclohexane has been studied and employed for several decades. − In essence, it can be visualized by scission of two C–C bonds of the ring structure leading to the formation of ethylene and 2-butene (eq ) or two molecules of propylene (eq 2). The cracking process requires high temperatures (>700 °C) and pressures (>70 atm), and even the use of catalysts does not afford significantly lower temperatures .…”

“…The cracking process requires high temperatures (>700 °C) and pressures (>70 atm), and even the use of catalysts does not afford significantly lower temperatures. 5 Normally, the ethylene production channel (eq 1) dominates. However, given the rising demand for propylene and the fact that eq 2 produces it as the only product, efforts to improve propylene yield have intensified.…”

Zeolite–Perovskite Composites as Effective Redox Catalysts for Autothermal Cracking of n-Hexane

“…23,24 Hao et al further illustrated that Na 2 WO 4 -promoted CaMnO 3 has a core−shell structure, where a Na 2 WO 4 shell covers the bulk CaMnO 3 particle and undergoes dynamic phase transition during the ROC reaction cycles. 25 However, these reported redox catalysts still need operating temperatures higher than 700 °C in order to achieve satisfactory olefin yield. Moreover, the propylene/ethylene product ratio (P/E ratio) is limited to 0.6 (carbon mole basis), resulting in poor propylene yields (<16%).…”

“…Despite high naphtha conversions (>86%) under a typical operating temperature of 750 °C, high CO x yields (≥15%) were reported with light olefin yields limited to 44%. − Unlike conventional oxidative cracking, redox oxidative cracking (ROC) utilizes lattice oxygen from a metal oxide redox catalyst to facilitate naphtha conversion and hydrogen combustion in a so-called chemical looping approach. − Dudek et al and Tian et al reported Na 2 WO 4 -promoted CaMnO 3 , SrMnO 3 and BaFe x Al 12‑x O 19 and obtained up to 58% of olefin yield at 750 °C with CO x yield as low as 1.7%. Na 2 WO 4 is essential for obtaining high olefin selectivities. , Hao et al further illustrated that Na 2 WO 4 -promoted CaMnO 3 has a core–shell structure, where a Na 2 WO 4 shell covers the bulk CaMnO 3 particle and undergoes dynamic phase transition during the ROC reaction cycles . However, these reported redox catalysts still need operating temperatures higher than 700 °C in order to achieve satisfactory olefin yield.…”

Chemical Looping Combustion over a Lanthanum Nickel Perovskite-Type Oxygen Carrier with Facilitated O2– Transport

“…In recent decades, perovskite-type oxides are investigated for the performance of oxygen transfer and carbon resistance. 27 Li et al 28 comprehensively discussed the advance of using perovskites as OCs for methane CLC processes and indicated that doping A or B sites on perovskite-type materials can improve the oxygen transportation capacity. Imanieh et al 29 have tested the calcium manganese (CM) perovskites for CLC as well as the A-site-doping materials.…”