Patent GB-1109890-A (GB)
Title: Preparation of finely divided metals
Inventor: BUCKLAND IVOR JOHN
IPC: C22B11/00
Filed: 1965-12-21
Abstract: Finely-divided iridium or ruthenium is produced by thermally decomposing, under non-oxidizing conditions and at a temperature not exceeding 400 DEG C., a halogen-free compound containing iridium or ruthenium in a complex in which the complexing groups comprise at least one of ammonia or oxalate groups, the balance of the compound consisting of groups that decompose and volatilize at the decomposition temperature to leave no residue.  Suitable compounds are:-  trisoxalato iridous-III acid ammonium trisoxalato iridite-III and ruthenate-III ammonium bis-oxalato bis-hydroxo ruthenate-III ammonium oxalato bis-carbonate ruthenate-III ammonium oxalato tetra-nitrito ruthenate-III hexammino ruthenium-III oxalate oxalato tetrammino ruthenium-III oxalate. tetrammino bis-aquo ruthenium-III oxalate.  Decomposition may be effected under hydrogen with or without nitrogen, or carbon monoxide. Supported catalysts may be produced by impregnating carbon or g -alumina with a solution of the complex, drying to deposit the complex and then heating to decompose the complex.  Mixed catalysts consisting of iridium-ruthenium or containing other platinum-group metals may be produced by thermally decomposing mixtures of complexes. Suitable ammonium compounds of palladium, platinum and rhodium containing oxalate groups are disclosed. The finely-divided iridium and ruthenium are also useful in the production of coatings and sintered compacts.ALSO:Organic Ru and Ir compounds which may be thermally decomposed to yield finely-divided metal are prepared as follows:-  (1) Ammonium trisoxalato ruthenate-III: (NH4)3[Ru(C2O4)3]. Ruthenium dioxide is dissolved in aqueous ammonium acid oxalate by heating, excess of the latter is precipitated by n-propanol after the solution has cooled, and acetone then added.  (2) Ammonium bis-oxalato bis-hydroxo ruthenate-III: (NH4)3[Ru(C2O4)2(OH2)]. As (1) except that n-propanol is added to hot solution.  (3) Ammonium oxalato bis-carbonato ruthenate-III: (NH4)3[Ru(C2O4)(CO3)2]. A solution of compound (1) is heated with lead carbonate and ethanol subsequently added.  (4) Ammonium oxalato tetra-nitrito ruthenate-III: (NH4)3[Ru(C2O4)(NO2)4]. A solution of compound (1) is heated with silver nitrite.  (5) Hexammino ruthenium-III oxalate: [Ru(NH3)6]2(C2O4)3. Ammonia gas is passed through a solution of compound (1).  (6) Oxalato tetrammino ruthenium-III oxalate: [Ru(NH3)4(C2O4)]2(C2O4). Ammonia gas is passed through an aqueous suspension of compound (5).  (7) Tetrammino bis-aquo ruthenium-III oxalate: <FORM:1109890/C2/1> Ethanol is added to an aqueous solution of compound (6).  (8) Trisoxolato iridous-III acid: H3[Ir(C2O4)3]. Iridium dioxide is heated with aqueous oxalic acid.  (9) Ammonium trisoxolato iridite-III: (NH4)3[Ir(C2O4)3] A solution of compound (8) is neutralized with potassium bicarbonate, shaken with a sulphonated polystyrene cation exchange resin in the calcium form to precipitate excess oxalate, passed through the same resin to remove potassium ions, and then passed through the resin in ammonium form.ALSO:Supported catalysts are produced by impregnating carbon or g -alumina with a solution of a halogen-free compound containing Ir or Ru in a complex in which the complexing groups comprise at least one of ammonia or oxalate groups, drying to deposit the complex, and then heating to decompose it and deposit the Ir or Ru.  Suitable compounds are:-  trisoxalato iridous-III acid  ammonium trisoxalato iridite-III and ruthenate-III  ammonium bis-oxalato bis-hydroxo ruthenate-III  ammonium oxalato bis-carbonato ruthenate-III  ammonium oxalato tetra-nitrito ruthenate-III hexammino ruthenium-III oxalate  oxalato tetrammino ruthenium-III oxalate  tetrammino bis-aquo ruthenium-III oxalate  Mixed catalysts consisting of Ir-Ru or containing other Pt-group metals may be produced by thermally decomposing mixtures of complexes.  Suitable ammonium compounds of Pd, Pt and Rh containing oxalate groups are also disclosed.