Effect of Mg substitution on LaTi1-xMgxO3+delta catalysts for improving the C2 selectivity of the oxidative coupling of methane

Author(s)

Lopes, Larissa B. ^[1] ; Vieira, Luiz H. ^[1] ; Assaf, Jose M. ^[2] ; Assaf, Elisabete M. ^[1]

Affiliation

^[1] Univ Sao Paulo, Sao Carlos Inst Chem, Av Trabalhador Saocarlense 400, BR-13560970 Sao Carlos - Brazil

^[2] Univ Fed Sao Carlos, Rod W Luiz, Km 235, Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: CATALYSIS SCIENCE & TECHNOLOGY; v. 11, n. 1, p. 283-296, JAN 7 2021.
• Web of Science Citations: 0

Abstract

This study investigated the effect of the partial substitution of Ti by Mg on the La2Ti2O7 perovskite-type structure towards improvements in the selective results of OCM reactions. The LaTi1-xMgxO3+delta catalysts were prepared with x = 0, 0.25 and 0.50 according to a polymer complexing method. XPS analysis showed a surface reconstruction with Mg addition, increasing the formation of oxygen vacancies in the interface formed by La-O-Mg and with an Mg-enriched surface compared to bulk compositions. DRIFTS results presented spectra more restricted to mono- and bidentate carbonate bands with the Mg load increasing, which significantly influence the OCM reaction. Differences in the M-O bonding force were demonstrated by XPS, FTIR, and Raman analysis, which result in the change of the catalyst basicity with the Mg addition. The M-O bond force constants (k) were calculated and showed a linear correlation with C2 selectivity. The catalytic results showed that methane conversion and C2 selectivity increased as a function of the Mg amount. Changes in the reaction conditions confirmed that both CH4/O-2 feed ratio and reaction temperature are important parameters for the OCM reaction. The best catalytic reaction conditions were WHSV = 30 000 mL g(cat)(-1) h(-1), CH4/O-2 = 8 and T = 800 degrees C for LaTi0.5Mg0.5O3 (LTMO-50) catalyst, which achieved 51.4% C2 selectivity. The catalyst remained thermally stable under such conditions even after 24 h of reaction, which has proven the advantage of Mg substitution in this catalyst structure. (AU)

• FAPESP's process: 17/03623-0 - Perovskite applied to the oxidative coupling of methane generated in the treatment of wastewater
• Grantee: Larissa de Bessa Lopes
• Support type: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 15/06246-7 - Biorefinery concept applied to biological wastewater treatment plants: environmental pollution control coupled with material and energy recovery
• Grantee: Marcelo Zaiat
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 18/12021-6 - Partial oxidation of methane to methanol catalyzed by single-atom noble metal (Rh, Pd or Pt) supported on doped mesoporous CeO2 (Ce1-xMxO2, M = Zr, Sn or La)
• Grantee: Luiz Henrique Vieira
• Support type: Scholarships in Brazil - Post-Doctorate