Intrinsic Activity of MnOx-CeO2 Catalysts in Ethanol Oxidation

Abstract

MnO x -CeO 2 mixed oxides are considered efficient oxidation catalysts superior to the corresponding single oxides. Although these oxides have been the subject of numerous studies, their fundamental performance indicators, such as turnover frequency (TOF) or specific activity, are scarcely reported. The purpose of the present work is to investigate the effect of catalyst composition on the concentration of active sites and intrinsic activity in ethanol oxidation by the employment of temperature-programmed desorption and oxidation of isotopically-labelled ethanol, 12 CH 3 13 CH 2 OH.The transformation pathways of preadsorbed ethanol in the absence of gaseous oxygen refer to dehydrogenation to acetaldehyde followed by its dissociation combined with oxidation by lattice oxygen. In the presence of gaseous oxygen, lattice oxygen is rapidly restored and the main products are acetaldehyde, CO 2 , and water. CO 2 forms less easily on mixed oxides than on pure MnO x . The TOF of ethanol oxidation has been calculated assuming that the amount of adsorbed ethanol and CO 2 produced during temperature-programmed oxidation (TPO) is a reliable indicator of the concentration of the active sites.

Metaphors and allusions to ancient writers and the Bible in Ioannis Apocaukos’ epistles relevant to medical and paramedical issues

“…me from my bed of illness 29 . This is an allusion to the Psalm 41.3: "The Lord sustains them on their sickbed and restores them from their bed of illness".…”

Catalytic Ketonization over Oxide Catalysts (Part XIV): The Ketonization and Cross-Ketonization of Anhydrides, Substituted Acids and Esters

“…The oxides of manganese, cerium, zirconium and thorium deposited onto the surface of the supports (Al 2 O 3 , SiO 2 , TiO 2 , active carbon or pumice) are active catalysts [18]. Manganese and cerium oxides, due to the possibility of changing the oxidation states of manganese and cerium, have been commonly applied as catalysts [19][20][21][22] and catalyst supports [23,24], even in combination [25]. ZrO 2 has also been applied in catalysis for decades [26,27].…”

The Formation of Mn-Ce Oxide Catalysts for CO Oxidation by Oxalate Route: The Role of Manganese Content

“…The Mn-Ce oxides show excellent catalytic performance in the oxidation of hydrocarbons, volatile organic compounds, CO [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] and selective catalytic oxidation of NO x with NH 3 [ 5 , 21 ]. Recently, the number of works devoted to Mn-Ce oxide catalysts has sharply increased [ 12 , 15 , 16 , 17 , 22 , 23 , 24 , 25 , 26 , 27 ]; special attention is paid to improving the synthesis methods leading to the formation of active, highly dispersed and nanostructured compounds. For the preparation of MnO x -CeO 2 catalysts, methods such as combustion [ 11 ], coprecipitation [ 19 , 28 , 29 ], sol–gel [ 19 , 25 ], and template synthesis [ 14 ] are used.…”