Catalytic properties of chromium-molybdenum oxide catalysts in methanol oxidation

Popov, T.; Popov, B. I.; Bibin, V. N.; Bliznakov, G.; Боресков, Г. К.

doi:10.1007/bf02187510

Cited by 23 publications

(30 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The fraction from the outlet consisted of the MoO 3 and Fe 2 (MoO 4 ) 3 phases, however, the Mo/Fe ratio was higher than in the unused catalyst and needle-like MoO 3 crystals were observed on the catalyst rings. As previously has been explained, Mo in the upper part of the catalyst forms volatile species with methanol [9,10], which species decompose and condense as needles in the lower part of the bed [9,11]. Thus, the activity data in Fig.…”

Section: Influence Of the Phase Composition On The Catalytic Performancementioning

confidence: 76%

“…The durability of the catalyst depends on several factors including the methanol and oxygen concentrations, the temperature and the pellet diameter [10]. In practice it varies between 8 and 18 months depending on the operating conditions and tolerances.…”

Section: Introductionmentioning

confidence: 99%

“…In practice it varies between 8 and 18 months depending on the operating conditions and tolerances. By now, it is well established that the catalyst deactivates because it looses Mo during operation due to the formation of volatile species [9][10][11][12][13], causing lower activity and selectivity as well as increased pressure drop as molybdena needles condense in the lower part of the reactor. Another deactivation cause is sintering of the catalyst in the hot spot [11,14,15].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

On the Synergy Effect in MoO3–Fe2(MoO4)3 Catalysts for Methanol Oxidation to Formaldehyde

et al. 2008

View full text Add to dashboard Cite

Methanol oxidation to formaldehyde was studied over a series of Fe-Mo-O catalysts with various Mo/Fe atomic ratio and the end compositions Fe 2 O 3 and MoO 3 . The activity data show that the specific activity passes through a maximum with increase of the Mo content and is the highest for Fe 2 (MoO 4 ) 3 . The selectivity to formaldehyde, on the other hand, increases with the Mo content in the catalyst. A synergy effect is observed in that a catalyst with the Mo/Fe ratio 2.2 is almost as active as Fe 2 (MoO 4 ) 3 and as selective as MoO 3 . Imaging of a MoO 3 / Fe 2 (MoO 4 ) 3 catalyst by SEM and TEM shows that the two phases form separate crystals, and HRTEM reveals the presence of an amorphous overlayer on the Fe 2 (MoO 4 ) 3 crystals. EDS line-scan analysis in STEM mode demonstrates that the Mo/Fe ratio in the amorphous layer is *2.

show abstract

Section: Influence Of the Phase Composition On The Catalytic Performancementioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the Synergy Effect in MoO3–Fe2(MoO4)3 Catalysts for Methanol Oxidation to Formaldehyde

et al. 2008

View full text Add to dashboard Cite

show abstract

“…and Fe 3? industry there is an interest to increase the productivity by increasing the methanol concentration [40]. Since increase of the partial pressure of methanol increases the volatilization rate and thus shortens the life-time of the catalyst [9], there is a general interest to explore alternative less volatile catalysts.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, the catalyst in the first part of the reactor becomes poor in molybdenum, which lowers both the activity and the selectivity, and moreover the formation of needles increases the backpressure, giving higher electricity cost [8]. Besides increasing with the methanol pressure, the volatility also increases with lowering of the oxygen pressure [9]. Therefore, the fact that operation with high methanol content requires lower oxygen concentration to avoid the flammability region further accelerates the ageing of the catalyst.…”

Section: Introductionmentioning

confidence: 97%

Cation Vacant Fe3−x−y V x □ y O4 Spinel-Type Catalysts for the Oxidation of Methanol to Formaldehyde

2011

View full text Add to dashboard Cite

The potential of Fe-V-oxide catalysts for use in methanol oxidation is explored. Our results show that although FeVO 4 is active and selective for formaldehyde (FA) formation, it is not completely stable towards volatilization under reaction conditions. Attempts to stabilize Fe-V-oxide were made using titania, alumina and silica supports. However, we observe that although some stabilization is achieved using titania and alumina, the supported catalysts are sensitive to volatilization considering the relatively low content of active oxide. Compared with supported V-oxide, the results show that iron causes stabilization of vanadium decreasing its volatility. Considering the observation that the neat FeVO 4 restructures to form a spinel-type phase under influence of the catalysis, we prepared a series of cation vacant spinel-type Fe 3-x-y V x h y O 4 catalysts with various V/Fe ratio and consequent number of cation vacancies h. Opposed to the activity, which is rather constant irrespectively of the vanadium content, the selectivity to FA passes through a maximum of about 90% for Fe/V = 14. A spinel-type phase with the composition Fe 2.62 V 0.19 h 0.20 O 4 was prepared and subsequently preoxidized to different degree. It is observed that the spinel-type structure is stable and that the oxidation of vanadium and iron is balanced by an increasing number of cation vacancies. Moreover, irrespectively of the original degree of preoxidation, it is found that in methanol oxidation a steady state is reached where all samples are equally active and selective and have the same composition both in the bulk and at the surface. The results clearly demonstrate that the spinel-type catalysts are phase-stable, nonvolatile and flexible in that the cations can change oxidation state retaining the same basic structure type and Fe/V ratio.

show abstract

Operando XAS/XRD and Raman Spectroscopic Study of Structural Changes of the Iron Molybdate Catalyst during Selective Oxidation of Methanol

et al. 2019

View full text Add to dashboard Cite

The structural changes of an iron molybdate/molybdenum oxide (Mo/Fe = 2.0) catalyst for the selective oxidation of methanol to formaldehyde were studied using combined operando X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) as well as operando Raman spectroscopy. Under operating conditions, the Mo K-edge XANES spectra showed a transition from a mixture of α-MoO 3 and Fe 2 (MoO 4 ) 3 towards only Fe 2 (MoO 4 ) 3 . XRD and Raman spectroscopy also showed disappearance of the α-MoO 3 phase with time on stream. The results evidenced that the α-MoO 3 component evaporated completely, while the Fe 2 (MoO 4 ) 3 component remained stable. This was linked to a decrease in catalytic activity. Further studies unraveled that the rate of α-MoO 3 evaporation increased with increasing MeOH concentration, decreasing O 2 concentration and increasing temperature. The simultaneous measurements of catalytic activity and spectroscopy allowed to derive a structure-activity relationship showing that α-MoO 3 evaporation needs to be prevented to optimize MoO 3 -based catalysts for selective oxidation of methanol.

show abstract

Catalytic properties of chromium-molybdenum oxide catalysts in methanol oxidation

Cited by 23 publications

References 0 publications

On the Synergy Effect in MoO3–Fe2(MoO4)3 Catalysts for Methanol Oxidation to Formaldehyde

On the Synergy Effect in MoO3–Fe2(MoO4)3 Catalysts for Methanol Oxidation to Formaldehyde

Cation Vacant Fe3−x−y V x □ y O4 Spinel-Type Catalysts for the Oxidation of Methanol to Formaldehyde

Operando XAS/XRD and Raman Spectroscopic Study of Structural Changes of the Iron Molybdate Catalyst during Selective Oxidation of Methanol

Contact Info

Product

Resources

About