Basf Aktiengesellschaft

Albrecht Aicher

Hans Diem

Gunter Lehmann

Hans Haas

Guenther Matthias

Christian Dudeck

Fritz Brunnmueller

Norbert Petri

Rainer Diercks

Walter Pitteroff

Bernhard Knuth

Heinrich Sperber

Robert Sebastian

Fritz Finkbeiner

Gunter Reuss

Oskar Hussey, Deceased

Hans Schreiber

Packed silver-catalyst bed doped with phosphorus

Formaldehyde is prepared by (a) passing a mixture of methanol and water with a concentration of between 50 and 90% by weight, based on the total weight of the two substances, of methanol into a packed column which possesses a packing having a total layer thickness of not less than 50 cm and a total surface area of not less than 0.5 cm.sup.2 per cm.sup.3 of packing, a liquid circulation of from 15 to 90 g/min per g/min of methanol fed to the column, and a concentration of from 10 to 45% by weight of methanol in the recycle liquid, the temperature at the point of entry of the recycle liquid in the column being from 50.degree. to 86.degree. C. and the bottom temperature being 10.degree.-25.degree. C. lower than this, i.e. from 40.degree. to 70.degree. C., (b) separating off methanol and water from the column by stripping with air, an inert gas and/or exit gas, the throughput being from 0.5 to 3 tonnes of methanol and water per hour per m.sup.2 of column cross-section, (c) converting the gaseous mixture of methanol, water, air, inert gas and/or exit gas at a space velocity of from 0.5 to 3 tonnes of methanol per m.sup.2 of catalyst bed cross-section per hour, in the presence of a silver catalyst at from 550.degree. to 750.degree. C. and (d) finally, cooling and absorbing the hot reaction gases, and using the resulting heat of absorption and, if desired, the heat of reaction and/or the heat of condensation partially or completely for heating the recycle liquid, methanol containing impurities being used if desired and, after the stages (a) and (b) and before the stages (c) and (d), the measures of a stage (e) being carried out, wherein the gaseous mixture formed is passed through two layers of wire filter having a wire diameter of from 0.1 to 0.5 mm and a free layer volume of from 90 to 99.5 vol. %, based on the total volume of one wire layer, at a flow rate of from 7 to 13 m/sec in the first layer, and from 1 to 4 m/sec in the second layer. The formaldehyde obtainable by the process of the invention is a disinfectant, tanning agent, reducing agent and a useful starting material for the preparation of synthetic resins, adhesives and plastics.

Preparation of formaldehyde

Sulfur-free combustion gases of low soot content are produced by mixing oxygen and an off-gas of a defined composition in a defined weight ratio, passing the final mixture thus obtained through a defined number of slit channels of gas burners into a combustion chamber and combusting it at a defined temperature. Compared to the prior art, the process of the invention gives sulfur-free combustion gases, containing little or no soot (in general containing no detectable soot), more simply and more economically. These gases are used for heating, in particular for raising steam.

Production of sulfur-free combustion gases of low soot content

Formaldehyde is manufactured by oxidative dehydrogenation of methanol in the presence of a silver catalyst and of certain amounts of steam and formaldehyde, some formaldehyde and a part of the water being withdrawn from the reaction mixture and recycled. The formaldehyde manufactured by the process may be used as a disinfectant, tanning agent, reducing agent and starting material for the manufacture of synthetic resin, adhesives and plastics.

Manufacture of concentrated aqueous solutions of formaldehyde

The production of formaldehyde by oxidizing dehydrogenation of methanol in the presence of a silver catalyst which consists of three or more layers each of specific weight and particles of specific particle size and having a specific total layer thickness. Formaldehyde prepared according to the process of the invention is a disinfectant, tanning agent, reducing agent and valuable starting material for the production of synthetic resins, adhesives and plastics.

Production of formaldehyde

Manufacture of formaldehyde by oxidative dehydrogenation of methanol in the presence of a silver catalyst, wherein methanol and water are evaporated in the presence of air in a plate column containing a number of double plates each consisting of a sieve plate and a lower plate having the form of a shallow bowl and inclined at a specific angle to the horizontal, the resulting vaporous mixture then being reacted. The formaldehyde which may be produced by the process of the invention is a disinfectant, tanning agent, reducing agent and a valuable starting material for the manufacture of synthetic resins, adhesives and plastics.

Manufacture of formaldehyde

Growing community of inventors

Frankenthal, Germany

Albrecht Aicher