ChemInform Abstract: Characterization of Chromia‐Promoted γ‐Iron Oxide Catalysts and Their CO Conversion Efficiency.

Abstract

The nature of incorporation of Cr3+ ions and the evolution of phases in Cr2O3‐promoted γ‐Fe2O3 prepared under different conditions are studied by DTA, XRD, TEM, IR and Moessbauer spectroscopy.

Reaction and characterization studies of an industrial Cr-free iron-based catalyst for high-temperature water gas shift reaction

“…It has been realized that activity and thermo-stability of the iron catalyst is corrected with crystal structure of iron oxides such as a-Fe 2 O 3 and g-Fe 2 O 3 [6,17]. g-Fe 2 O 3 was found to be more active for the WGS reaction than a-Fe 2 O 3 , since the activation energy of the former phase is less than that of the latter [17].…”

“…On the other hand, the crystal of g-Fe 2 O 3 generally possesses an imperfect cubic spinel structure, which is different from that of a-Fe 2 O 3 , hexagonal structure. The imperfect spinel of g-Fe 2 O 3 allows promoters such as Cr or Ce to be incorporated into vacant sites in the g-Fe 2 O 3 , resulting in less sintering of active phase in the catalysts consisting of gFe 2 O 3 than those containing a-Fe 2 O 3 under identical operating conditions [6]. To this end, it is very important to form as much g-Fe 2 O 3 as possible during preparation of Cr-free iron-based WGS catalyst.…”

“…This type of catalyst has demonstrated high WGS activity and excellent thermostability, probably because the Cr promoter acts as a structural stabilizer and/or a structure promoter [1,2]. However, it has been found that commercial iron-based WGS catalysts with as high as 8-14 wt% Cr promoter generally contain about 2 wt% Cr 6+ compound, which is highly toxic to humans and environment during its manufacture and deposition [1,[3][4][5][6]. Thus, it has drawn considerable attention to study Cr-free iron-based WGS catalysts in past years.…”

In situ DRIFTS studies of high-temperature water-gas shift reaction on chromium-free iron oxide catalysts

“…CO 2 +H 2 )i s generally operated according to a two-step process, namely at high (HTS, 350-450 8C) and low (LTS, 250-300 8C) temperatures, over two main types of catalysts, Fe-Cr and Cu-Zn systems, respectively. Iron oxide based HTS catalysts, Fe 3 O 4 [1,2] or Fe 2 O 3 [3], are generally doped with Cr 2 O 3 [4][5][6][7]. The recognized role of chromium is preventing iron oxide from sintering as well as catalyzing the WGS reaction.…”

Preparation of Mesoporous Chromium Promoted Magnetite Based Catalysts for High Temperature Water Gas Shift Reaction

“…During the water gas shift, reaction the oxidation and reduction cycle can be improved by the electron hopping between Fe 2+ and Fe 3+ in the octahedral sites . Preparation of catalysts directly in Fe 3 O 4 phase significantly decreases the sintering of catalyst during pretreatment step compared to catalyst containing α-Fe 2 O 3 or γ-Fe 2 O 3 under the same operating conditions …”