CO2 utilization as a soft oxidant for the synthesis of styrene from ethylbenzene over Co3O4 supported on magnesium aluminate spinel: role of spinel activation temperature

Abstract

Magnesium aluminate spinel (MgAl2O4) supported Co3O4 catalysts are synthesized and tested for the oxidative dehydrogenation (ODH) of ethylbenzene using CO2 as a soft oxidant. The effect of spinel calcination temperature on the catalytic performance has been systematically investigated. With an increase in the activation temperature from 600 to 900 °C, the active presence of a single-phase MgAl2O4 spinel is observed. A catalyst series consisting of MgAl2O4 spinel with varying Co loadings (10–20 wt%) were prepared and systematically distinguished by ICP, XRD, BET, TPR, NH3-TPD, UV–Vis DRS, FT-IR, XPS, SEM, and TEM. Among the tested cobalt catalysts, 15Co/800MA sample derived by calcination of MgAl2O4 support at 800 °C exhibits the most excellent catalytic performance with the maximum ethylbenzene conversion (≥ 82%). Also, high yields of styrene (≥ 81%) could be consistently achieved on the same active catalyst. Further, the catalyst exhibited almost stable activity during 20 h time-on-stream with a slow decrease in the ethylbenzene conversion from 82 to 59%. However, the selectivity of styrene (98%) stayed almost constant during the reaction. Activation of the MgAl2O4 spinel at 800 °C facilitates a dramatic chemical homogeneity for the alignment of Co3O4 nanoparticles on the surface of the active catalyst. Moreover, the isolated Co3O4 clusters have a strong chemical/electronic interaction with the Mg2+ and Al3+ ions on the support perform a crucial role to achieve the maximum catalytic activity.

Co‐Ni/MOF‐74 catalyst packed‐bed DBD plasma for ammonia synthesis

“…[ 34 ] The band at 585 cm −1 was attributed to stretching vibrations of M–O. [ 35 ] The results indicated that the main structure of organic ligand H 4 DHTP remains unchanged after the synthesis reaction and further confirmed the successful coordination of metal ions and ligand H 4 DHTP.…”

Insights on Guerbet Reaction: Production of Biobutanol From Bioethanol Over a Mg–Al Spinel Catalyst

“…NH 3 -TPD was carried out to evaluate the strength of acid sites in the catalyst surface. We differentiate two zones associated with the acid strength, depending on the NH 3 temperatures desorption: moderate (200–400°C) and strong (400–800°C) ( Madduluri et al, 2020 ). The peak at a lower temperature, 256°C, is associated with reversible adsorption H-bonded ascribed to hydroxyl groups presence over the surface, considered as BrØnsted acid sites ( Song et al, 2021 ).…”

Porphyrin N-Pincer Pd(II)-Complexes in Water: A Base-Free and Nature-Inspired Protocol for the Oxidative Self-Coupling of Potassium Aryltrifluoroborates in Open-Air

“…Hence, the present N-pincer Pd(II)-porphyrin catalyzed process is advantageous over the reported aryltrifluoroborate self-couplings. In view of global sustainability, the elimination/decrease of the application of volatile organics, the use of benign/naturemimicking catalysts, and conducting the chemical reactions at ambient conditions can make a significant contribution [74][75][76][77][78]. A comparison of reported self-coupling procedures of aryltrifluoroborates [39][40][41][42][43] is shown in Table 3 and evidences the clear merits of the present nature-mimicking method over the reported protocols using Pd NPs/Te-Dps [39], Au nanoclusters:poly(N-vinyl-2-pyrrolidine) [40], Pd(OAc)2-electrolysis [41], Cu(OAc)2-ultra sound [42], and Pd NPs@Al(OH)3 [43] which require organic solvent [41], base/additive [39][40][41][42][43], heating [39][40][41][42][43], long process time [39,40,42,43] or suffer from low biaryl yield with some aryltrifluoroborates [39][40][41][42][43].…”

“…Hence, the present N-pincer Pd(II)-porphyrin catalyzed process is advantageous over the reported aryltrifluoroborate self-couplings. In view of global sustainability, the elimination/decrease of the application of volatile organics, the use of benign/nature-mimicking catalysts, and conducting the chemical reactions at ambient conditions can make a significant contribution [74][75][76][77][78].…”