Stamicarbon B.v.

Stamicargon B. V.

Rudolf Van Hardeveld

Petrus F Hendriks

Franciscus T Van Den Brink

Marinus Alfenaar

Franciscus H Vandenbooren

Theodorus J Van De Mond

Pierre G Bruls

Dominique J Moreau

Andreas M Thomas

Johannes G Van Hinsberg

The invention relates to a process for the electrochemical oxidation of organic products at a lead-silver anode in acid medium, in which process the organic products used are alkyl-substituted heterocycles and in which process a lead-silver anode with 2-10% (wt) silver is used.

Process for the electrochemical oxidation of organic products

The invention relates to a process for the electrochemical oxidation of an alkylpyridine having the formula ##STR1## where R represents an alkyl group with 1-6 C atoms, and x is 1,2 or 3, in an acid medium at a lead-containing anode of an electrolytic cell with anode and cathode compartments separated by an ion-exchange membrane, this process being characterized in that as an ion-exchange membrane an anion-exchange membrane is used and as catholyte an aqueous solution of the same acid as used in the anolyte, which solution is dilute in respect of this anolyte, and subsequently the reaction product is recovered from the anolyte.

Process for the electrochemical oxidation of alkylpyridines

An improved process for the preparation of cyanamide or a cyanamide-containing gas mixture by passing urea and/or urea decomposition products over a catalyst at a temperature in the range of between about 200.degree. C. and 600.degree. C. A porous catalyst is utilized which has an intracrystalline pore diameter of at most 8 A, whereby a high conversion to cyanamide is obtained and the formation of melamine by-products is substantially reduced.

Process for preparing cyanamide

An improved process for the preparation of melamine from urea or thermal decomposition products thereof. A melamine containing reaction mixture is cooled with an aqueous medium to form an aqueous product stream containing melamine and reaction by-products. Product melamine is separated from the aqueous product stream leaving a residual aqueous stream which is recycled into the process. A portion of this residual aqueous stream still containing reaction by-product is treated to remove by-products therefrom prior to being recycled to the process.

Process of preparing melamine

An improved method for the preparation of melamine by the conversion of urea and/or thermal decomposition products thereof. The urea and/or thermal decomposition products are converted to melamine in the presence of a gas mixture containing ammonia and carbon dioxide in a reaction zone containing a fluidized bed of catalytically active material. Melamine is desublimated from the melamine containing gas mixture in a desublimation zone by a dry-capture method leaving a desublimator off-gas mixture of ammonia, carbon dioxide and gaseous impurities. A major portion of this desublimator off-gas mixture is compressed and recirculated to the reaction zone as fluidizing gas for the bed of catalytically active material, without intervening treatment to remove gaseous impurities from the desublimator off-gas.

Method for the preparation of melamine

A two phase sprayer and process are disclosed in which the sprayer has a liquid supply tube surrounded by a coaxial gas or gas mixture supply tube which extends beyond the length of the liquid supply tube where the gas flow surrounds and atomizes the expelled liquid. The sprayer has a unique structure in part characterized by a narrowed taper gas supply tube which converges towards the outlet at an angle of 70.degree.-90.degree. with respect to the sprayer axis. The internally-positioned, coaxial liquid supply tube is chamfered also at a similar 70.degree.-90.degree. angle, the gas and liquid tubes at their outlet being essentially parallel. The joint of the narrowing part of the gas tube and the outflow channel is rounded. These sprayers efficiently spray relatively large amounts of liquid at low gas velocities and are particularly adapted for spraying a mixture of urea and ammonia into a bed of reactive, fluidized particles to form melamine without destroying desirable features of the fluidized bed into which the urea/ammonia mixture is sprayed.

Process and device for spraying liquid

An improved process for the preparation of melamine from a feed of urea, thermal decomposition products of urea, or a mixture thereof, in the presence of a catalyst and an ammonia-containing gas. The reactor is divided into a lower and an upper reaction zone by a permeable grid or other restriction which reduces the catalyst flow between the two zones to 5 to 75% of what it would have been in the absence of such restriction. The feed is introduced into the lower reaction zone, which is maintained at a temperature of between 325.degree. and 425.degree. C., wherein substantially all of the urea is decomposed into thermal decomposition products, and a major portion of the thermal decomposition products are converted into melamine, which together with the remaining unreacted thermal decomposition products, is passed into the upper reaction zone. In the upper reaction zone, which is maintained at a temperature at least as high as the temperature of the lower reaction zone, substantially all of the remaining unconverted thermal decomposition products are converted into melamine.

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Geleen, Netherlands

Rudolf Van Hardeveld