Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

Abstract

It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II) as a precursor instead of Fe(III). This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III) oxide impurities which are detrimental for the process selectivity. The system containing Fe(II) and Mo(VI) species in aqueous solution was investigated using UV-Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II)-Mo(VI) system: (i) formation of complexes between Fe(II) and molybdate(VI) ions, (ii) inner sphere oxidation of coordinated Fe(II) by Mo(VI) and (iii) decomposition of the Fe-Mo complexes to form scarcely soluble Fe(III) molybdate, Mo(VI) hydrous trioxide and molybdenum blue. Solid molybdoferrate(II) prepared by interaction of Fe(II) and Mo(VI) in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II) precursor was tested in methanol-toformaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III).

A Review and Experimental Revisit of Alternative Catalysts for Selective Oxidation of Methanol to Formaldehyde

“…At higher temperatures, CO 2 was measured [243]. The E a on BiPO 4 (67.2 kJ/mol) [243] and on FePO 4 (56.6 kJ/mol) [242] were rather close to that reported on industrial FeMo catalysts (64 kJ/mol) [244].…”

Detoxifying SARS-CoV-2 antiviral drugs from model and real wastewaters by industrial waste-derived multiphase photocatalysts

“…Due to a low concentration of other elements, iron with a higher concentration is present in the form of Fe 2 (MoO 4 ) 3 ( Tian et al, 2011 ) . Thus, the high concentration of iron (FeOOH and Fe 2 O 3 ) leads to the formation of mixed-valence compounds [Fe III Mo VI O 2– 4 ] X =[Fe III (Mo VI O 2– 4 ) X –1 (Mo V O 3– 4 )] and ammonium molybdoferrate (NH 4 ) 3 H 6 [Fe III (Mo VI O 4 ) 6 ] ( Nikolenko et al, 2018 ). Additionally, the reflections of some natural minerals, including quartz (SiO 2 ), talc (Mg 3 Si 4 O 10 (OH) 2 ), and hydrotalcite (Mg 6 Al 2 (CO 3 )(OH) 16 ∙4H 2 O), are also observed.…”

Hydroxyapatite supported molybdenum oxide catalyst for selective oxidation of methanol to formaldehyde: studies of industrial sized catalyst pellets

“…We developed a compartmental model for an industrial fixed bed reactor to investigate the influence of pellet size and MoO3 content in the inlet part of the reactor on the development of the pressure drop 26 utilizing a previously made single pellet model for the loss of MoO3 from an industrial FeMo pellet 27 . Recent papers from other research groups dealing with understanding the industrial type catalyst includes preparation of Mo/Fe = 1.7 catalyst with γ-Al2O3 by co-precipitation to provide information of the structure sensitivity of the reaction 28 , modelling of the deactivation behavior for a multi-tube industrial reactor 29 , new methods of preparation 30,31 , DFT studies of methanol partial oxidation 32 and investigations of the active site 33,34 . A CFD study on the 4/29 influence of pellet shape (cylinders, spheres, rings and trilobes) on reactor performance found that rings gave the best overall performance, trilobes had the lowest pressure drop and a mixture of rings and trilobes may give a slight operational improvement 35 .…”