Method for simultaneously preparing iron oxide red pigment and aromatic amine

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.

Claims

1. 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 catalyst to the open reactor to obtain a first solution, wherein a mass of the catalyst is 0.1% to 1.0% of a mass of the iron oxide red pigment produced, heating the first solution to 85° C. to 90° C. and simultaneously adding a solution of a ferrous salt and a solution of an aromatic nitro compound dropwise to the first solution, wherein a dropping rate of the solution of the ferrous salt is larger than a dropping rate of the solution of the aromatic nitro compound so that the solution of the aromatic nitro compound is left when the solution of the ferrous salt is completely consumed; after finishing adding the solution of the ferrous salt, stopping adding the solution of the aromatic nitro compound to obtain a second solution, and using a caustic soda solution to tune a pH of the second solution to be 3.8-4.1, wherein the aromatic nitro compound is reduced by ferrous ions to produce an aromatic amine and an α-Fe.sub.2O.sub.3 crystal nucleus step (2): adding a first amount of an iron powder to the second solution when the pH of the second solution decreases to 3.5 to 3.8; after 10 min, adding dropwise the solution of the aromatic nitro compound left in the step (1) in a duration of 210 min to obtain a third solution, wherein a second amount of the iron powder is added at 70 minutes, and a third amount of the iron powder is added at 140 minutes; a temperature of the duration is kept from 85° C. to 88° C.; and after finishing adding the solution of the aromatic nitro compound keeping the third solution at the temperature for a period of time to produce a mixture of the iron oxide red pigment and the aromatic amine; step (3): filtering the mixture to obtain the iron oxide red pigment and a filtrate; and acidifying the filtrate to obtain the aromatic amine.

2. The method for simultaneously preparing the iron oxide red pigment and the aromatic amine according to claim 1, wherein the catalyst used in the step (1) is α-Fe.sub.2O.sub.3 with a particle size of less than 100 nm or in-situ amorphous δ-FeOOH.

3. The method for simultaneously preparing the iron oxide red pigment and the aromatic amine according to claim 1, wherein the ferrous salt is any one or a mixture of two from the group consisting of ferrous sulfate and ferrous chloride.

4. The method for simultaneously preparing the iron oxide red pigment and the aromatic amine according to claim 1, wherein in the step (2), the iron powder has a mesh size of 80 mesh to 100 mesh.

5. The method for simultaneously preparing the iron oxide red pigment and the aromatic amine according to claim 1, wherein in the step (2), the period of time is from 40 min to 50 min.

6. The method for simultaneously preparing the iron oxide red pigment and the aromatic amine according to claim 1, the first amount of the iron powder, the second amount of the iron powder, and the third amount of the iron powder are the same.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an electron micrograph for Example 1 of the method for simultaneously preparing an iron oxide red pigment and an aromatic amine.

(2) FIG. 2 is an electron micrograph for Example 2 of the method for simultaneously preparing an iron oxide red pigment and an aromatic amine.

(3) FIG. 3 is an electron micrograph for Example 3 of the method for simultaneously preparing an iron oxide red pigment and an aromatic amine.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) To make the objectives, technical solutions, and advantages of the present disclosure clearer, the present disclosure is further described in detail below with reference to specific implementations. However, it should be understood that the description is exemplary and is not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of conventional structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

Example 1

(5) 500 mm of bottom water was added to a stirrer-equipped reduction reactor with a diameter of 3,000 mm and a height of 3,600 mm, and then the reactor was heated to 80° C. to 85° C. 2,800 kg of solid FeSO.sub.4.7H.sub.2O was added to the water, and a resulting mixture was heated to about 70° C. until the solid was completely dissolved. A resulting solution was diluted to a volume of 3.76 m.sup.3. 842 Kg of 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNS) was added to water, a resulting mixture was heated to 95° C. to make the DNS completely dissolved, and a resulting solution was diluted to a volume of 3.1 m.sup.3. The DNS solution and a ferrous sulfate solution were simultaneously added to the reactor at a temperature controlled at 85° C. to 87° C. for a time controlled at about 50 min, and a pH of a reaction system was controlled at 4 to 4.1 using a liquid caustic soda. After the addition of the ferrous sulfate solution was completed, iron powder (80 mesh) was added for the first time; after the iron powder reacted for 10 min, the remaining DNS was added at a temperature controlled at 87° C. to 88° C. for a time controlled at 210 min, during which the remaining iron powder was added for a second time and a third time at 70 min and 140 min, respectively; and after the addition of the DNS was completed, the reactor was further kept at the temperature for 40 min, and then a reaction solution was discharged. The reaction solution was subjected to plate and frame filtration, and a resulting filter cake was washed and dried to obtain an iron oxide red powder, which was quasi-spherical particles with a particle size of 150 nm to 180 nm and had the following L*a*b* color standard compared with German BAYFERROX inorganic pigment iron oxide red 130 M: L*=45.48, a*=26.51, b*=17.1, and tinting strength: 95%. A filtrate was acidified to obtain a DSD acid, with a purity of 97.36%, an amino value of 43.18, a color strength of 5.0, and class I dying lines.

Example 2

(6) 500 mm of bottom water was added to a stirrer-equipped reduction reactor with a diameter of 3,000 mm and a height of 3,600 mm, and then the reactor was heated to 80° C. to 85° C. 3.41 m.sup.3 of a ferrous chloride solution with a concentration of 2.8 mol/L was added. 842 Kg of DNS was added to water, a resulting mixture was heated to 95° C. to make the DNS completely dissolved, and a resulting solution was diluted to a volume of 3.1 m.sup.3. The DNS solution and a ferrous chloride solution were simultaneously added to the reactor at a temperature controlled at 85° C. to 87° C. for a time controlled at about 50 min, and a pH of a reaction system was controlled at 4 to 4.1 using a liquid caustic soda. After the addition of the ferrous chloride solution was completed, iron powder (80 mesh) was added for the first time; after the iron powder reacted for 10 min, the remaining DNS was added dropwise at a temperature controlled at 87° C. to 88° C. for a time controlled at 210 min, during which the remaining iron powder was added for a second time and a third time at 70 min and 140 min, respectively; and after the addition of the DNS was completed, the reactor was further kept at the temperature for 50 min, and then a reaction solution was discharged. The reaction solution was subjected to plate and frame filtration, and a resulting filter cake was washed and dried to obtain an iron oxide red powder, which was quasi-spherical particles with a particle size of 160 nm to 190 nm and had the following L*a*b* color standard compared with German BAYFERROX inorganic pigment iron oxide red 130 M: L*=46.23, a*=27.14, b*=16.2, and tinting strength: 99%. A filtrate was acidified to obtain a DSD acid, with a purity of 97.51%, an amino value of 42.21, a color strength of 5.0, and class I dying lines.

Example 3

(7) 500 mm of bottom water was added to a stirrer-equipped reduction reactor with a diameter of 3,000 mm and a height of 3,600 mm, and then the reactor was heated to 80° C. to 85° C. 2,800 kg of FeSO.sub.4.7H.sub.2O was added to the water, and a resulting mixture was heated to about 70° C. until the solid was completely dissolved. A resulting solution was diluted to a volume of 3.76 m.sup.3. 842 Kg of DNS was added to water, a resulting mixture was heated to 95° C. to make the DNS completely dissolved, and a resulting solution was diluted to a volume of 3.1 m.sup.3. The DNS solution and a ferrous sulfate solution were simultaneously added to the reactor at a temperature controlled at 85° C. to 87° C. for a time controlled at about 50 min, and a pH of a reaction system was controlled at 4 to 4.1 using a liquid caustic soda. After the addition of the ferrous sulfate solution was completed, iron powder (200 mesh) was added for the first time; after the iron powder reacted for 10 min, the remaining DNS was added at a temperature controlled at 87° C. to 88° C. for a time controlled at 210 min, during which the remaining iron powder was added for a second time and a third time at 70 min and 140 min, respectively; and after the addition of the DNS was completed, the reactor was further kept at the temperature for 30 min, and then a reaction solution was discharged. The reaction solution was subjected to plate and frame filtration, and a resulting filter cake was washed and dried to obtain an iron oxide red powder, which was quasi-spherical particles with a particle size of 170 nm to 200 nm and had the following L*a*b* color standard compared with German BAYFERROX inorganic pigment iron oxide red 130 M: L*=45.12, a*=26.34, b*=16.36, and tinting strength: 96%. A filtrate was acidified to obtain a DSD acid, with a purity of 97.53%, an amino value of 42.15, a color strength of 5.0, and class I dying lines.

(8) The preparation of the α-Fe.sub.2O.sub.3 crystal nucleus in Examples 1 to 3 of the present disclosure involves the following chemical reaction equations:
Fe(II)+Fe(III).fwdarw.Fe(III)+≡Fe(II)  (I)
Fe(III).fwdarw.δ-FeOOH+H.sup.+  (II)
δ-FeOOH+H.sub.2O.fwdarw.α-Fe.sub.2O.sub.3+H.sup.+  (III)
Ar—NO.sub.2+Fe(II).fwdarw.Ar—NH.sub.2+≡Fe(III)  (IV)
total reaction:
Fe(II)+Ar-NO.sub.2+OH.sup.−.fwdarw.α-Fe.sub.2O.sub.3+Ar-NH.sub.2  (V)

(9) Fe(III) and ≡Fe(III) involved in the present disclosure represent trivalent iron ion in a solution and trivalent iron in a surface structure of iron oxide, respectively;

(10) Fe(II) and ≡Fe(II) involved in the present disclosure represent divalent iron ion in a solution and divalent iron in a surface structure of iron oxide, respectively; and ArNO.sub.2 and ArNH.sub.2 represent an aromatic nitro compound and an aromatic amine, respectively.

(11) It should be understood that the above-mentioned specific implementations of the present disclosure are only used to exemplarily illustrate or explain the principle of the present disclosure, and do not constitute a limitation to the present disclosure. Any modifications, equivalent substitutions, and improvements made without departing from the spirit and scope of the present disclosure should be included in the protection scope of the present disclosure. In addition, the appended claims of the present disclosure are intended to cover all changes and modifications that fall within the scope and boundary of the appended claims or equivalent forms of such scope and boundary.