Oxidation of methanol to formaldehyde over a series of Fe(1-x)Al(x)-V-oxide catalysts

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Oxidation of methanol to formaldehyde over a series of Fe(1-x)Al(x)-V-oxide catalysts. / Häggblad, Robert; Wagner, Jakob; Hansen, Staffan; Andersson, Arne.

I: Journal of Catalysis, Vol. 258, Nr. 2, 2008, s. 345-355.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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Häggblad, Robert ; Wagner, Jakob ; Hansen, Staffan ; Andersson, Arne. / Oxidation of methanol to formaldehyde over a series of Fe(1-x)Al(x)-V-oxide catalysts. I: Journal of Catalysis. 2008 ; Vol. 258, Nr. 2. s. 345-355.

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TY - JOUR

T1 - Oxidation of methanol to formaldehyde over a series of Fe(1-x)Al(x)-V-oxide catalysts

AU - Häggblad, Robert

AU - Wagner, Jakob

AU - Hansen, Staffan

AU - Andersson, Arne

N1 - The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Polymer and Materials Chemistry (LTH) (011001041), Chemical Engineering (011001014)

PY - 2008

Y1 - 2008

N2 - A series of triclinic Fe1−xAlxVO4 phases with 0 <= x <= 1 were prepared and used in the oxidation of methanol to formaldehyde. The activity measurements revealed that both the activity and especially the selectivity to formaldehyde increased with time of operation for at least 16 h, indicating restructuring of the catalysts. Characterisation of the catalysts with XRD, XANES, and electron microscopy after use in methanol oxidation showed that the stability of the bulk phases improved when Al was substituted for Fe in the structure. XRD and XANES of the used FeVO4 showed that it partly transformed into a cation-vacant spinel-type Fe1.5V1.5O4 phase, whereas the AlVO4 phase showed no change in the bulk structure. HRTEM imaging of used catalysts confirmed that structural changes,including in the surface, occurred during catalysis. Quantitative surface analysis by XPS of the catalysts before and after use in methanol oxidation revealed no significant change in the metal composition, in good agreement with the corresponding bulk values, except for a lower Fe value. Steady-state activity data showed a modest increase in specific activity with the Al content, whereas the selectivity to formaldehyde was about 90% for all samples at high methanol conversion. The similar catalytic behaviour of the vanadates irrespective of the differences in the bulk structure indicates that the surface structure differed from the bulk structure. Compared with pure vanadia, the vanadates had lower activity per V atom and slightly greater selectivity to formaldehyde. Consequently, for methanol oxidation, the role of Al and Fe on the catalyst surface can be described as that of a spacer, decreasing the surface concentration of active V sites and the number of less selective V–O–V ensembles.

AB - A series of triclinic Fe1−xAlxVO4 phases with 0 <= x <= 1 were prepared and used in the oxidation of methanol to formaldehyde. The activity measurements revealed that both the activity and especially the selectivity to formaldehyde increased with time of operation for at least 16 h, indicating restructuring of the catalysts. Characterisation of the catalysts with XRD, XANES, and electron microscopy after use in methanol oxidation showed that the stability of the bulk phases improved when Al was substituted for Fe in the structure. XRD and XANES of the used FeVO4 showed that it partly transformed into a cation-vacant spinel-type Fe1.5V1.5O4 phase, whereas the AlVO4 phase showed no change in the bulk structure. HRTEM imaging of used catalysts confirmed that structural changes,including in the surface, occurred during catalysis. Quantitative surface analysis by XPS of the catalysts before and after use in methanol oxidation revealed no significant change in the metal composition, in good agreement with the corresponding bulk values, except for a lower Fe value. Steady-state activity data showed a modest increase in specific activity with the Al content, whereas the selectivity to formaldehyde was about 90% for all samples at high methanol conversion. The similar catalytic behaviour of the vanadates irrespective of the differences in the bulk structure indicates that the surface structure differed from the bulk structure. Compared with pure vanadia, the vanadates had lower activity per V atom and slightly greater selectivity to formaldehyde. Consequently, for methanol oxidation, the role of Al and Fe on the catalyst surface can be described as that of a spacer, decreasing the surface concentration of active V sites and the number of less selective V–O–V ensembles.

KW - SEM¨

KW - XPS

KW - Formaldehyde

KW - Methanol

KW - Fe1−xAlxVO4 catalysts Fe–V–O spinel-type phases

KW - Selective oxidation

KW - XRD

KW - XANES

KW - HRTEM

U2 - 10.1016/j.jcat.2008.06.029

DO - 10.1016/j.jcat.2008.06.029

M3 - Article

VL - 258

SP - 345

EP - 355

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 1090-2694

IS - 2

ER -