Method for simultaneously preparing iron oxide red pigment and aromatic amine
AssigneeHebei Caike Chemical Co., Ltd.
InventorsWeidong DUAN, Guofu ZHANG, Yu WEI
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Abstract
A method for simultaneously preparing an iron oxide red pigment and an aromatic amine is provided. In the method, an aromatic nitro compound and ferrous iron are first used to prepare an iron oxide red seed crystal under the action of a catalyst, and then iron powder is used to reduce the aromatic nitro compound and generate iron oxide in situ which grows into iron oxide red with pigment performance on the seed crystal. The method provides a clean and economical way for the reduction of an aromatic nitro compound (especially those in which there are other easily-reduced substituents on an aromatic ring) to prepare an aromatic amine.
Claims8
A method for simultaneously preparing an iron oxide red pigment and an aromatic amine, comprising the following steps:
- step (1):
- adding a specified amount of water to an open reactor provided with a stirrer, adding a small amount of a catalyst to obtain a first solution, and heating the first solution in the reactor to 85° C. to 90° C.;
- simultaneously adding a ferrous salt solution and an aromatic nitro compound solution dropwise to the reactor;
- and after the dropwise addition of the ferrous salt solution is completed, stopping the dropwise addition of the aromatic nitro compound solution to obtain a second solution, and using a liquid caustic soda to keep a pH of the second solution in the reactor constant, wherein the aromatic nitro compound is reduced by ferrous ions to produce an aromatic amine and a α-Fe2O3 crystal nucleus, and the pH of the second solution in step (1) is controlled to be 3.8-4.1;
- step (2):
- when the pH of the second solution in the reactor decreases to 3.5 to 4.0 with the progress of a reaction, adding iron powder to the reactor;
- after reacting for 10 min, adding dropwise the aromatic nitro compound solution left from the reaction in step (1), wherein a time of adding dropwise the aromatic nitro compound solution left from the reaction in step (1) is controlled to be 210 min;
- when the time of adding dropwise the aromatic nitro compound solution is 70 min and 140 min, the iron powder is added to the reaction for the second time and third time;
- a temperature of a solution in the reactor is kept at 85° C. to 88° C.;
- and after the dropwise addition of the aromatic nitro compound solution is completed, further keeping the reactor at the temperature for a time period to produce a mixture of iron oxide red and an aromatic amine;
- and
- separating and post-treating the iron oxide red and the aromatic amine obtained in step (2) by conventional methods to obtain the iron oxide red pigment and the aromatic amine.
6-8. (canceled)
Dependencies are inferred from the claim text.