SnO₂Based Catalysts with Low‐Temperature Performance for Oxidative Coupling of Methane: Insight into the Promotional Effects of Alkali‐Metal Oxides

Abstract

To develop reactive catalysts for oxidative coupling of methane at low temperatures, different alkali-metal oxides are adopted in this study to modify the surface of SnO 2 . In comparison with the unmodified SnO 2 , the reaction performance of all of the modified catalysts can be significantly improved, among which lithium oxide shows the best promotional effects, and the optimal catalyst is achieved with a Sn/Li molar ratio of 5:5. With this catalyst, the highest C 2 product yield of 16 % is achieved at 750°C. The XPS and CO 2 -TPD results reveal that for those catalysts with evident enhanced OCM reaction performance, the coexistence of a suitable amount of surface alkaline and electrophilic oxygen sites is indispensable. Furthermore, with the catalysts modified by different amounts of lithium oxide, the C 2 yield at different temperatures is nearly [a

Nanosheet-Like Ho2O3 and Sr-Ho2O3 Catalysts for Oxidative Coupling of Methane

“…As evidenced in Figure 10, the C 2 -C 3 yield obtained at 700 • C correlates well with the number of moderate basic sites present on the Ho 2 O 3 -based catalysts. This finding is in accordance with some previous reports that the surface basic sites with moderate strength are more favorable for the C 2 product formation in the OCM process [25,26,44,55,[57][58][59][60].…”

Optimizing the Reaction Performance of La2Ce2O7‐Based Catalysts for Oxidative Coupling of Methane (OCM) at Lower Temperature by Lattice Doping with Ca Cations

“…The O1s spectra of the samples are deconvoluted and analyzed in detail by assuming that a single oxygen peak has a FWHM of 1.8–2.0 eV and with 80 % Gaussian plus 20 % Lorentzian peak shape . Considering the results in Figure S3, the contribution from carbonate has been excluded in the deconvolution and quantification.…”

“…Therefore, CO 2 ‐TPD experiments have been carried out to characterize the surface alkalinity of the catalysts (Figure a). It is reported that not only the overall alkalinity, but also the number of surface alkaline sites can affect significantly the C 2 product selectivity and yield , , , . While all the alkaline sites can play the role to activate CH 4 molecules, the intermediate strength alkaline sites are especially important to improve the coupling product selectivity , , , …”

Effect of Calcination Temperature on the Characteristics and Performance of Solid Acid WO3/TiO2‐Supported Lithium‐Manganese Catalysts for the Oxidative Coupling of Methane

“…Some transition metal containing catalysts, including Li/MgO, Mn/TiO 2 , and Mn/Na 2 WO 4 /SiO 2 , had been investigated and shown to be active for OCM. It is widely accepted that Li content is a promising chemical promoter for many kinds of OCM process catalysts . Extensive evaluations of the catalysts have identified that Mn content with different valence states are responsible for the catalysis in OCM…”