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A series of Cr-SiO2-Al2O3(abbreviated as Cr-Si-Al) catalysts were synthesized using an evaporation induced self-assembled (EISA) method and applied to the N2O-assisted dehydrogenation of ethylbenzene (EB), offering a versatile solution for greenhouse gas recycling and a novel pathway for styrene (ST) production. Notably, the Cr-5Si-Al catalyst calcinated at 850 °C exhibited remarkable performance with a high EB conversion of 71% and a good ST selectivity of 62%, resulting in an optimal ST yield of nearly 44%. To elucidate the impact of calcination temperature and reveal the underlying promoting mechanism, numerous types of characterization particularly in-situ DRIFTS were used. Results indicated that the Cr-5Si-Al-850 catalyst possessed a distinctively ordered mesoporous structure, which improved the specific surface area and facilitated the dispersion of active species. The interaction among the multiple species in the catalyst was enhanced under the high calcination temperatures, leading to an increased ratio of Cr6+and Oα, and thus promoting the dehydrogenation of EB. Furthermore, in situ DRIFTS revealed two favorable reaction pathways: one involving the reaction between adsorbed N2O and EB, and the other involving the reaction between adsorbed EB and N2O. These pathways led to the formation of a similar intermediate, observed at a wavenumber of 1285 cm−1. The improved adsorption of EB played a pivotal role in the excellent catalytic performance of the Cr-5Si-Al-850 catalyst.

The mesoporous Cr-mAl2O3and Ce-Cr-mAl2O3catalysts were prepared via a one-pot hydrothermal process for the N2O-assisted ethylbenzene (EB) selective oxidation to styrene, which was viewed as both a greenhouse recycling method and a new process for styrene (ST) production. It was found that 7Cr-mAl2O3provided superior catalytic performance with respect to ST among Cr oxide-doped catalysts and that the Ce modification could further increase the ST yield to 54%. To clarify the promoting effect and mechanism of Ce-Cr species on catalytic performance, numerous types of characterization, particularly in-situ DRIFTS, were used. Results indicated that the favorable reducibility of catalyst was crucial for N2O activation. Carbon deposition was unavoidable during the reaction process, but adding Ce-Cr could reduce the stability of the deposited carbon and relief its detrimental effect on catalytic performance. The suitable surface acidity and high relative content of Cr6+and Oαcould be responsible for the excellent catalytic performance of Ce-7Cr-mAl2O3. In-situ DRIFTS not only identified the coupling effect between EB dehydrogenation and N2O decomposition but also proposed the possible reaction pathway that the adsorbed N2O reacted with the EB molecule, thereby providing a good explanation for the promoting effects of high content of N2O on the activity of Ce-7Cr-mAl2O3.