Methanol oxidative dehydrogenation and dehydration on carbon nanotubes: active sites and basic reaction kinetics

Abstract

In situ active site titration, carbonyl group containing model catalysts, and kinetic analysis have been applied to reveal the nature of oxidized carbon nanotubes catalyzed methanol dehydration and oxidative dehydrogenation reactions.

Supported metal and metal oxide particles with proximity effect for catalysis

“…Yan et al reported the oxidative dehydrogenation and dehydration of methanol over oxidized carbon nanotube catalyst (oCNT). 44 The catalytic efficiency of oCNT is comparable to that of industrial metal catalysts.…”

The High‐Temperature Acidity Paradox of Oxidized Carbon: An in situ DRIFTS Study

“…In this context, high specific surface areas, tunable pore structure and surface chemistry, chemical inertness in a wide range of conditions as well as high thermal and electrical conductivities render carbon the material-of-choice for a variety of catalytic applications. Transformations involving carbon materials reach from energy conversion processes (e. g. fuel cell, [1] electrochemical water splitting [2] ) over hydrogenation (e. g. catalyst supports for Fischer-Tropsch-Synthesis [3] ) and dehydrogenation reactions (e. g. catalysts for the dehydrogenation of ethyl benzene [4,5] and alcohols [6][7][8] ), all the way to acid-base catalysis. Concerning acid catalysis, extensive work has been carried out focusing on metal-free, solid acid catalysts obtained by functionalization of carbon materials with heteroatoms such as O, S or P. [9] From a technical point of view, especially O functionalized carbons represent appealing solid acids, since established oxidation processes allow functionalization to be carried out on an industrial scale, achieving high densities of surface groups.…”

“…[8] Strikingly, dimethyl ether (DME) was indeed observed as the main product of the conversion of methanol (MeOH) over MWCNTs in presence of oxygen at 320 °C. [7] Since especially DME is a promising candidate for the application as a sustainable, synthetic diesel fuel and represents an important intermediate in a hypothetical methanolbased circular economy for the production of various hydrocarbons, exploring high-temperature-acidic carbon materials as catalysts for DME production is of high interest. However, in order to enable a targeted catalyst design, identification of the responsible acidic centers as well as comprehension of the underlying mechanism of their formation are a prerequisite.…”

“…In this context, in situ analysis of carbon surface oxides appears to be the strategy-of-choice, but has so far only been applied sporadically in form of in situ titration and near ambient pressure XPS. [4,7,11] While in situ titration (selective poisoning of active centers) is a powerful strategy to quantify active sites and deduce reaction pathways, it is based on chemical modification of the carbon surface and simultaneously critically dependent on the selectivity of the chosen catalyst poison. Near ambient pressure XPS can provide a large amount of useful information, whereas it is limited to reactant pressures of a few millibars, and the differentiation of chemically similar surface oxide species provides a challenge.…”

Intrinsic kinetics of the methanol dehydration to dimethyl ether over laboratory and commercial γ‐alumina: a comparative study

“…15 Even carbon nanotubes were found to exhibit catalytic activity in the methanol conversion to DME. 16 For the direct route, bifunctional catalysts containing Cu, Zn, and Al are typically used. [17][18][19] Metal oxides modified with heteropolyacids 20 and mixed metal oxide-zeolite 21,22 catalysts for CO 2 hydrogenation to DME have been also reported recently.…”