Patent GB-1282307-A (GB)
Title: Method of preparation of homogeneous oxides of two or more elements in a fineley divided form and products obtained
Inventor: COURTY PHILIPPE
IPC: H01F1/11
Filed: 1969-07-01
Abstract: 1282307 Oxidation catalysts COMMISSARIAT A L'ENERGIE ATOMIQUE INSTITUT FRANCAIS DU PETROLE DES CARBURANTS ET LIBRIFIANTS 1 July 1969 [2 July 1968 9 June 1969] 33222/69 Heading B1E [Also in Divisions C1 C2 and H1] Homogeneous oxides of two or more elements are made in a finely-divided state by (1) forming a solution containing salts of the elements to be combined and an organic complexing agent; (2) concentrating the solution in less than 30 mins to a viscosity greater than 200 centipoises at 20‹C; (3) further concentrating the viscous solution to an amorphous product and (4) thermally decomposing the precursor thus passed at temperatures above 200‹C in an atmosphere which is inert or contains O 2  in about the same proportions as in air. The complexing agent is a polybasic acid, amino-acid, keto-acid or ammonium or organic base salts thereof. Citric, glycollic, malic, tartaric, lactic and pyruric acids, and alanine are used in the Examples. The solvent may be aqueous (neutral, acidic or basic) or non-aqueous e.g. DMF, DMS n-methylpyrrolidone, nitro-compounds, alcohols, ketones or nitrites. An additional acid and/or base may be used to aid e.g. Fe 1À72  Co 0À28  (MoO 3 ) 2À7  (WO 3 ) 0 . 3 . Solid solutions: 20 mole % MoO 3  in V 2 O 5 ; 0.5In 2 O 3 -0.5Y 2 O 3 ; 10 wt% ThO 2  in Y.O,; 10 wt% ZrO 2  in Y 2 O 3  and MoO 3 , WO 3  and P 2 O 5  in V 2 O 5 . Examples describe the preparation of:- Chromites: CuCr 2 O 4 ; ZnCr 2 O 4 . Ferrites: CuFe 2 O 4 ; NiFe 2 O 4 ; CoFe 2 O 4 ; BaFe 12 O 19 ; Ni 0À8 Zn 0À2 Fe 2 O 4 ; Li 0À5 Al 0À95  Fe 1À55 O 4 ; Mn 0À6 Zn 0À4 Fe 2 O 4 . Aluminates: MgAl 2 O 4 . Zirconates and titanates: MgTi 2 O 4 ; PbTiO 3 ; BaTiO 3  PbZrO 3 ; BaZrO 3 ; Pb(Zr x Ti 1-x-y Sn y )O 3  where X=0-0.9; 1-X-Y=0.1-0.6, Y=0- 0.65; Pb 1-a M a (Zr x Ti 1-x-y Sn y )O 3  where M=Ca, Sr or Ba, a =0-0.25; also the above compounds doped with less than 0.5% MnO or .less than 0.3% IrO 2 . Manganites: CoMnO 3 . Molybdates: CoMaO 4 ; Cr-Fe molybdate (MoO 3 /Fe 2 O 3  + Cr 2 O 3 =24.7; Cr/Fe+Cr= 0.08). Pyrochlore: La 2 Sn 2 O 7 . Garnets: Y 3 Fe 5 O 12 ; Y 3 Al 5 O 12 ; Nd 0À1 Y 2À9 Fe 5 O 12 ; Gd 0À68 Y 2À32 Fe 4À58 Al 0À42 O 12 . Perooskites: YFeO 3 ; TbFeO 3 ; TmFeO 3 ; SmAlO 3 ; LaDyO 3 ; YCrO 3 ; TbAl 0À5 Co 0À5 O 3 . Mixed phases: AO-BO 3  and Fe 2 O 3 -3(BO 3 ) where A=Co, Ni or Mn and B=Mo or W The solution may also be made by mechanical trituration, using little or no solvent other than the water of crystallisation of the salts. The solution may be concentrated at atmospheric pressure or in vacuo at temperatures of -50 to 200‹C, in 2 stages or in a single stage. The single stage process may comprise spray-drying or freeze-drying, or trituration and dehydration of the resulting solution, in the same apparatus. The dehydrated precursor is a vitreous lacquer or foam, which may be in the form of flakes or spherules 10-750 microns diam. Thermal decomposition may be carried out in a fixed or fluidised bed at temperatures approaching 600‹C. Dehydration and thermal decomposition may be effected simultaneously by spray atomising the solution in a hot atmosphere. The oxides always appear as a light ash of fine particles or particle aggregates. The oxides may have specific gravity 0.01-0.5, particle size 10-10,000Š and specific surface area more than 0.1m<SP>2</SP>/g. The oxides are used as oxidation catalysts e.g. methanol to formaldehyde.