公开(公告)号：DE2220905A1

公开(公告)日：1973-11-08

申请号：DE2220905

申请日：1972-04-28

Applicant: BASF AG

Inventor： SCHWARZMANN MATTHIAS DR ,  FROMM DIETER DR ,  WIDMANN ALFRED DIPL-ING DR ,  VOGEL LUDWIG DIPL-ING

IPC: C07D251/60 ,  C07D20060101 ,  C07D55/28

Abstract: Catalytic manufacture of melamine from urea by thermal cracking of urea and converting the resulting cracked gases to melamine in the presence of catalysts. The thermal decomposition is carried out in a fluidized bed, the necessary heat being applied by heat exchangers located in the fluidized bed. Conversion of the cracked gases to melamine is effected either in the same fluidized bed, in which case the fluidized solid consists of conventional catalysts, or in a reaction zone remote from said fluidized bed. In the latter case, the solids fluidized consist of catalytically inactive particles, the conversion being carried out in the presence of catalysts in said reaction zone remote from the fluidized bed. In both cases, the urea is fed to the fluidized bed at a point above the heat exchangers.

公开(公告)号：DE3162170D1

公开(公告)日：1984-03-15

申请号：DE3162170

申请日：1981-07-13

Applicant: BASF AG

Inventor： BORHO KLAUS DR ,  FROMM DIETER DR ,  SCHIER ERNST-JUERGEN DR ,  SCHNEEHAGE HANS HENNING DR ,  WIDMANN ALFRED DR

IPC: C07C273/10 ,  C07C67/00 ,  C07C239/00 ,  C07C273/12 ,  C07C273/16 ,  C07D251/62 ,  C07C126/08

Abstract: A process for isolating liquid urea and its thermal decomposition products from the off-gas of melamine synthesis, which gas has been freed from melamine by fractional condensation and then been washed with molten urea, wherein the off-gas, containing 2-10 kg of melt per kg of pure gas, is passed at 8-30 m/sec tangentially into the upper part of an axially symmetrical separation zone. As a result of the rotation imparted to the gas/liquid mixture, the two phases are separated from one another, and both pass downward through the separation zone. The gas and liquid are separately taken off at the bottom end of the separation zone. The residence time of the gas mixture in the separation zone is not less than 0.5 second.

公开(公告)号：DE3302833A1

公开(公告)日：1984-08-02

申请号：DE3302833

申请日：1983-01-28

Applicant: BASF AG

Inventor： FROMM DIETER DR ,  WIDMANN ALFRED DR ,  SCHNEEHAGE HANS-HENNING DR ,  SCHIER ERNST-JUERGEN DR ,  GRUBE HELMUTH DR ,  MOLZAHN MARTIN DR ,  AUER HEINZ ING GRAD

IPC: C07D251/60 ,  C07D251/56

Abstract: In a process for the preparation of melamine by catalytic rearrangement of urea, the synthesis gases from which the melamine has already been deposited are treated with urea melts. The treatment is carried out in a scrubber which is provided with cooling elements, the urea melt being introduced both above and below the cooling elements. From the gas mixture, which still contains ammonia and carbon dioxide, treated in this way, the ammonia is preferably absorbed in a solvent with contact times of at most 0.1 seconds and the solvent is regenerated again in two following desorption zones with the recovery of pure ammonia. The bottom temperature in the last desorption step is 105 to 120 DEG C. This temperature is maintained by heating a part of the ammonia to 115 to 135 DEG C in the cooling elements of the scrubber and recycling it to the bottom. The virtually ammonia-free solution drawn off from the bottom is initially used for the scrubbing of the carbon dioxide drawn off from the absorption zone before it is employed therein as a solvent.

公开(公告)号：DE3274858D1

公开(公告)日：1987-02-05

申请号：DE3274858

申请日：1982-09-18

Applicant: BASF AG

Inventor： FROMM DIETER DR ,  SCHIER ERNST-JUERGEN DR ,  SCHNEEHAGE HANS HENNING DR ,  VODRAZKA WOLFGANG DR

IPC: B01J21/20 ,  B01J38/06 ,  C07B61/00 ,  C07D251/60

Abstract: In the synthesis of melamine by conversion of urea in a fluidized catalyst bed, the melamine quality is improved by reactivating the catalyst by treating it, in the fluidized bed, with gases containing steam, in the absence of oxygen, at from 250 DEG to 450 DEG C.