Separation method for dinitrotoluene and mixed acid in a toluene to dinitrotoluene process

Patent metadata

Field	Value
Publication number	US-9284257-B2
Application number	US-201314653687-A
Country	US
Kind code	B2
Filing date	Dec 10, 2013
Priority date	Dec 20, 2012
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

Proposed is a separation method in a toluene to dinitrotoluene process, wherein said method with a first process step comprising feeding a toluene comprising first stream ( 1 ) and a nitric acid comprising second stream ( 2 ) into a first reactor (R 1 ), reacting of the toluene comprising first stream ( 1 ) and the nitric acid comprising second stream ( 2 ) within the first reactor (R 1 ) to a first reaction mixture ( 3 ), said first reaction mixture ( 3 ) comprising a first liquid/liquid mixed phase of an acid phase and an organic phase comprising mononitrotoluene, feeding the first reaction mixture ( 3 ) into a first separation device (S 1 ), separating the first reaction mixture ( 3 ) within the first separation device (S 1 ) into a first forward stream ( 4 ) having a flow direction to a second process step and a first backward stream ( 5 ) having a flow direction back to the first reactor (R 1 ), said method having a second process step comprising feeding the first forward stream ( 4 ) into a second reactor (R 2 ), feeding a nitric acid comprising third stream ( 6 ) and a sulfuric acid comprising fourth stream ( 7 ) into the second reactor (R 2 ), reacting of the first forward stream ( 4 ), the nitric acid comprising third stream ( 6 ) and the sulfuric acid comprising fourth stream ( 7 ) within the second reactor (R 2 ) to a second reaction mixture ( 8 ), said second reaction mixture ( 8 ) comprising a second liquid/liquid mixed acid phase and an organic phase comprising mononitrotoluene and dinitrotoluene, feeding the second reaction mixture ( 8 ) into a second separation device (S 2 ), separating the second reaction mixture ( 8 ) within the second separation device (S 2 ) into a second forward stream ( 9 ) having a flow direction to a process output and a second backward stream ( 10 ) having a flow direction back to the first reactor (R 1 ), wherein fine separating of at least one of the streams ( 4, 5, 9, 10 ) after the first separation step (S 1 ) and/or the second separation step (S 2 ) in a coalescer is carried out.

First claim

The invention claimed is:

1. A separation method in a toluene to dinitrotoluene process, said method comprising:
i) feeding a toluene comprising first stream ( 1 ) and a nitric acid comprising second stream ( 2 ) into a first reactor (R 1 ),
ii) reacting the toluene comprising first stream ( 1 ) with the nitric acid comprising second stream ( 2 ) within the first reactor (R 1 ) to obtain a first reaction mixture ( 3 ), which comprises a first liquid/liquid mixed phase of an acid phase and an organic phase comprising mononitrotoluene,
iii) feeding the first reaction mixture ( 3 ) into a first separation device (S 1 ),
iv) separating the first reaction mixture ( 3 ) within the first separation device (S 1 ) into a first forward stream ( 4 ) and a first backward stream ( 5 ) flowing back to the first reactor (R 1 ),
v) feeding the first forward stream ( 4 ) into a second reactor (R 2 ),
vi) feeding a nitric acid comprising third stream ( 6 ) and a sulfuric acid comprising fourth stream ( 7 ) into the second reactor (R 2 ),
vii) reacting the first forward stream ( 4 ), the nitric acid comprising third stream ( 6 ) and the sulfuric acid comprising fourth stream ( 7 ) within the second reactor (R 2 ) to a second reaction mixture ( 8 ), which comprises a second liquid/liquid mixed acid phase and an organic phase comprising mononitrotoluene and dinitrotoluene,
viii) feeding the second reaction mixture ( 8 ) into a second separation device (S 2 ), and
ix) separating the second reaction mixture ( 8 ) within the second separation device (S 2 ) into a second forward stream ( 9 ) flowing to a process output and a second backward stream ( 10 ) flowing back to the first reactor (R 1 ),
wherein
a fine separation of at least one of the streams ( 4 , 5 , 9 , 10 ) after said separating iv) and/or after said separating ix) is carried out in a coalescer.

2. The separation method of claim 1 , wherein a fine separation of the second backward stream ( 10 ) is carried out in a coalescer.

3. The separation method of claim 1 , wherein a fine separation of the second forward stream ( 9 ) is carried out in a coalescer.

4. The separation of claim 1 , wherein a fine separation of the first forward stream ( 4 ) is carried out in a coalescer.

5. The separation method of claim 1 , wherein a fine separation of the first backward stream ( 5 ) is carried out in a coalescer.

6. The separation method of claim 1 , wherein the second backward stream ( 10 ) comprises a liquid/liquid mixed acid phase comprising sulfuric acid of from about 70 wt % to about 95 wt % and nitric acid of from about 0.1 wt % to about 5 wt %, and an organic phase comprising mononitrotoluene and dinitrotoluene.

7. The separation method of claim 1 , wherein a fine separation of the second forward stream ( 9 ) comprises a liquid/liquid mixed acid phase comprising sulfuric acid of from about 0.1 wt % to about 20 wt % and nitric acid of from about 0.1 wt % to about 10 wt %, and an organic phase comprising mononitrotoluene and dinitrotoluene.

8. The separation of claim 1 , wherein a fine separation of the first forward stream ( 4 ) comprises a liquid/liquid mixed acid phase comprising sulfuric acid of from about 0.1 wt % to about 20 wt % and nitric acid of from about 0.1 wt % to about 15 wt %, and an organic phase comprising mononitrotoluene and dinitrotoluene.

9. The separation method of claim 1 , wherein a fine separation of the first backward stream ( 5 ) comprises a liquid/liquid mixed acid phase comprising sulfuric acid of from about 60 wt % to about 80 wt % and nitric acid of from about 0.1 wt % to about 5 wt %, and an organic phase comprising mononitrotoluene and dinitrotoluene.

10. The separation method of claim 1 , wherein a toluene concentration in the first reactor (R 1 ) ranges from about 0 wt % to about 10 wt %.

11. The separation method of claim 1 , wherein the coalescer is a predominantly cylindrical device having a longitudinal axis, which differs from a horizontal line with a gradient ranging from about 0.2° to about 5°.

12. The separation method of claim 1 , wherein at least one of the streams ( 4 , 5 , 9 , 10 ) feeding the coalescer has a dynamic viscosity ranging from about 0.1 mPas to about 20 mPas.

13. The separation method of claim 1 , wherein at least one of the streams ( 4 , 5 , 9 , 10 ) feeding the coalescer has a interfacial tension ranging from about 40 mN/m to about 80 mN/m.

14. The separation method of claim 1 , wherein at least one of the streams ( 4 , 5 , 9 , 10 ) feeding the coalescer has a flow rate per surface area through the coalsecer ranging from about 2 m 3 /h/m 2 to about 10 m 3 /h/m 2 .

15. The separation method of claim 1 , wherein at least one of the streams ( 4 , 5 , 9 , 10 ) feeding the coalescer has a residence time in the coalsecer ranging from about 1 min to about 30 min.

Assignees

• Basf Se
• Shanghai Basf Polyurethane Company Ltd

Inventors

• Dai Yuanshen
• Li Da Peng
• Jia Pei Shi
• Cai zhan
• Neto Samuel

Classifications

• C07C201/08 Primary

  by substitution of hydrogen atoms by nitro groups · CPC title

• B01D17/0217

  by centrifugal force · CPC title

• C07C201/16

  Separation; Purification; Stabilisation; Use of additives · CPC title