Patent GB-593837-A (GB)
Title: Improvements in and relating to the production of formaldehyde
IPC: B01J27/19
Filed: 1945-06-15
Abstract: Catalysts for use in the oxidation of methanol to formaldehyde contain molybdenum and another metal selected from manganese, magnesium, cadmium and the alkaline earth metals, the total gram atoms of said other metal or metals not being more than four times the number of gram atoms of molybdenum present.  They may be promoted with phosphorus, sulphur or alkali metal and are prepared as follows: (1) manganese nitrate and ammonium molybdate are kneaded with water, dried and crushed; (2) manganese molybdate is precipitated by adding ammonia to a solution containing manganese sulphate and ammonium molybdate.  The precipitate is washed, dried and crushed and may be kneaded with phosphoric or sulphuric acid or sodium hydrogenphosphate; (3) magnesium nitrate, ammonium molybdate, phosphoric and nitric acids are kneaded together, ignited and pelleted; (4) cadmium-manganese molybdate is precipitated by adding ammonia to a solution containing manganese and cadmium nitrates and ammonium molybdate, and the precipitate, after washing and drying kneaded with sulphuric acid; (5) calcium molybdate is precipitated by adding ammonia to a solution containing calcium nitrate, ammonium molybdate and molybdic acid; (6) magnesium nitrate is kneaded with aqueous ammonia, ammonium molybdate and nitric acid, dried and crushed.ALSO:Formaldehyde is prepared by oxidizing methanol in the vapour phase with an oxygen containing gas in the presence of an oxidation catalyst containing molybdenum and another metal selected from the group: manganese, magnesium, cadmium and the alkaline earth metals, the total gram atoms of said other metal or metals not being more than four times the number of gram atoms of molybdenum present. The use of catalysts containing molybdenum, calcium and nickel is excluded.  The catalyst may be promoted with phosphorus, sulphur or an alkali metal, but when phosphorus is used, the ratio of phosphorus to molybdenum must be less than 2 : 1.  Carriers such as pumice, silica gel or infusorial earth may be used.  Catalysts may be prepared as follows: (1) manganese nitrate or ammonium molybdate are kneaded with water, dried and crushed; (2) manganese molybdate is precipitated by adding ammonia to a solution containing manganese sulphate and ammonium molybdate. The precipitate is washed, dried and crushed, and may be kneaded with phosphoric acid, sodium hydrogenphosphate or sulphuric acid; (3) magnesium nitrate, ammonium molybdate, phosphoric and nitric acid are kneaded together, ignited and pelleted; (4) cadmium-manganese molybdate is precipitated by adding ammonia to a solution containing manganese and cadmium nitrates, and ammonium molybdate and the precipitate after washing and drying is kneaded with sulphuric acid; (5) calcium molybdate is precipitated by adding ammonia to a solution containing calcium nitrate, ammonium molybdate and molybdic acid; (6) magnesium nitrate is kneaded with aqueous ammonia, ammonium molybdate and nitric acid, dried and crushed.  In a detailed example, the catalyst (5) is employed. Specifications 280,712, 286,212, 296,071, 298,142, 313,575, [all in Class 2 (iii)], 381,570 and 547,743 are referred to.