Mesoporous TiO2-rutile supported MnxOy-Na2WO4: Preparation, characterization and catalytic performance in the oxidative coupling of methane

Oxidative Coupling of Methane: Perspective for High-Value C2 Chemicals

“…Mn-NaWO 4 /SiO 2 catalyst is widely accepted as the most applicable catalyst, with a higher C 2 yield (~27%) in OCM [33,[52][53][54][55][56][57][58][59][60] However, the addition of La exhibited a higher C 2 yield even at lower temperatures of 750 • C. The Na 2 WO 4 -Mn/SiO 2 catalyst was stable and showed a higher C 2 yield (25%) in OCM, which is one of the best results in the literature. Wang et al [57] carefully explored the effect of Na 2 WO 4 -Mn/SiO 2 catalysts prepared by different methods such as incipient wetness impregnation (IWI), mixture slurry and the sol-gel method for OCM reaction.…”

“…This is mainly due to the similar ionic radii of Ca 2+ and Ce 4+ ions and the higher ratio of the oxygen species O2 − and O2 2− to lattice oxygen and a high amount of surface basic sites. Yıldız et al [33] proved that mesoporous TiO2-rutile This review presents three types of catalysts for OCM reaction and highlights the features that play key roles in the OCM reactions, such as active oxygen species, the mobility of the lattice oxygen, and the surface alkalinity of the catalysts. The catalyst compositions and their catalytic functions are also discussed.…”

“…Pristine or unmodified metal oxide catalysts generally exhibit low C 2 selectivity/yield and rapid deactivation in OCM reaction. Modified systems are considered to achieve higher yield at lower temperature regions due to the altered either basicity or oxygen vacancies and/or other defects, which are crucial for CH 4 activation [31][32][33][34][35][36]. Ferreira et al [32] developed CeO 2 catalysts modified with earth alkaline metals (M = Mg, Ca, and Sr) and demonstrated that among these three dopants, Ca-doped CeO 2 catalyst showed the best performance in the OCM reaction.…”

“…This is mainly due to the similar ionic radii of Ca 2+ and Ce 4+ ions and the higher ratio of the oxygen species O 2 − and O 2 2− to lattice oxygen and a high amount of surface basic sites. Yıldız et al [33] proved that mesoporous TiO 2 -rutile supported Mn x O y -Na 2 WO 4 catalysts' better performance than commercial TiO 2 -rutileand TiO 2 -anatase-supported catalysts. In addition, this catalyst is stable during 16 h on stream in OCM.…”

Effect of TiO2 on the Performance of Mn/Na2WO4 Catalysts in Oxidative Coupling of Methane

“…Today, TiO 2 is widely used as a support of selective catalytic reduction (SCR) due to its low cost, high surface area, reducibility properties, abundance, and nontoxicity . Most recently, the possibility of TiO 2 as a support of OCM catalysts has been investigated using mesoporous TiO 2 , WO 3 /TiO 2 , and Ce–Na 2 WO 4 /TiO 2 . For the Li–Mn/WO 3 /TiO 2 catalyst, it was reported that the highest C 2 yield of 16.3% was achieved at 750 °C.…”