HYDROCARBONPROCESSING TOLUENE

DIISOCYANATE (TDI)

Toluene diisocyanate (TDI) CH3C6H3 (NCO)2 is an organic compound where two of the six possible isomers - 2,4-TDI and 2,6-TDI - are used in the commercial production of an extensive range of materials. These include flexible polyurethane foams (the largest market for TDI products); rigid foams, which use polymeric MDI as the isocyanate component; and in adhesives, sealants, surface coatings and elastomers.

TDI synthesis is a complex, three-stage process which first requires the

production of toluene diamine (TDA) and phosgene which are then combined and distilled to create TDI, with hydrochloric acid as a by-product. The process, which involves combining a range of toxic materials including hydrogen, chlorine and carbon monoxide, requires high levels of gas analysis for both process control and product purity throughout all three processes.

Servomex is an expert in the supply of analyzers and systems designed to meet all requirements of the TDI process.

With an industry-leading range of analyzer technologies, we offer a turnkey solution for TDI gas analysis that overcomes common process problems including gas cross sensitivity, the highly toxic nature of the process and detecting low levels of chlorine within the TDI product.

Supported by a global network of Service and Support, our expertise in TDI analysis enables us to consult, design and build systems that are safe, reliable, highly efficient and highly productive.

• Proven experience in solving complex TDI analysis issues with full, independently verified SIL reports available

• Servomex analyzers deliver safe surrogate calibrations, eliminating requirement to use highly toxic 100% phosgene

• More than twenty TDI systems installed and supported to a global customer base

CUSTOMER PROCESS BROCHURE

TOLUENE DIISOCYANATE PROCESS APPLICATION MAP

TDA PRODUCTIONHydrogen (H2)from the HyCO process is used for the Hydrogenation of dinitrotoluene (DNT) and the next step is the catalytic reduction of dinitrotoluene under H2 pressure which is subsequently undertaken to produce toluene diamine (TDA). There are a number of measurements to ensure the quality of the Carbon Monoxide (CO) using the SERVOPRO MultiExact 5400 (1), SERVOPRO 4210 (2), SERVOTOUGH OxyExact 2200 (3) and SERVOTOUGH LaserSP 2900 (4), which measure H2, methane (NH4), oxygen (O2) and water (H2O) impurities respectively. The purity of the hydrogen is also measured, with the MultiExact (5) measuring percent H2 and 4210 (6) measuring ppm CO. H2 is also measured as an offgas (7).

PHOSGENE MANUFACTUREPhosgene is made using the CO from the HyCO process and chlorine (Cl2) from the electrolysis of brine. The SERVOTOUGH SpectraExact 2500 (8) provides a critical purity measurement for the supplied CO while the SERVOTOUGH LaserSP (9) monitors for ppm moisture levels in the Cl2 feed.

KEY:APPLICATION TYPES: PROCESS CONTROL QUALITY SAFETY COMBUSTIONEMISSIONS

SpectraExact 0-500 ppm ODCB in HCl

SpectraExact 0-500 ppm COCI2 in HCI

SOLVENTOrthodichlorobenzene

RECYCLE

HCIBy Product

CH4 + H2OCO + 3H2

HYCO

HYDROGENH2

TOLUENEDIAMINE

TDA

CARBONMONOXIDE

CO

CHLORINECI2

PHOSGENECOCI2

PHOSGENECOCI2

DISTILLATION

PHOSGENATION 1

PHOSGENATION 2

REDUCER

DINITROTOLUENEDNT

ELECTROLYSISOF BRINE

1 3

2

MultiExact TCD 0-1% H2 in CO

4210 0-0.1% CH4 in CO

OxyExact/Oxy 0-0.5% O2 in CO

SpectraExact 0-1000 ppm H2O in CO

MultiExact TCD 90-100% H2 in Hydrogen

4210 0-10ppm CO in H2

MultiExact TCD 50-100%H2 in Hydrogen off gas

SpectraExact 90-100% CO in CO LaserSP 0-500 ppm H2O in Cl2

SpectraExact 0-200 ppm Cl2 in COCl2

SpectraExact (2510) 0-15% CO in COCl2

SpectraExact 0-100% COCl2in reaction gas (COC12 + HCI)

SpectraExact 0-100% HCIin reaction gas (COC12 + HCI)

SpectraExact 0-3% CO2

in reaction gas (COC12 + HCI)

SpectraExact/LaserSP 0-500 ppm H20in reaction gas (COC12 + HCI)

SpectraExact 0-500 ppm H2O in ODCB

SpectraExact 0-0.1% NCO in ODCB

SCRUBBERSpectraExact 0-1000 ppm COCI2 in stack

4210 0-100 ppm CO in air

CH3

NO 2

NO2

CH3

NH 2

NH2

O

Cl Cl

C

CH3

NCO

NCO

TOLUENEDIISOCYANATE

TDI

TOLUENEDIAMINE

TDA

1

1 2

5

7

8 9

6 2 3 4

TDI MANUFACTUREThe TDA is then treated with the phosgene under controlled temperature and pressure conditions, with quality ppm measurements of Cl2 (10) and CO (11). This results in a TDI isomer mixture in solution, together with traces of phosgene and HCl. These traces are subsequently separated and recycled. During the phosgenation stages the orthodichlorobenzene solvent is monitored for moisture (12) and NCO (cyanate groups) (13). The phosgene quality is also measured by the SpectraExact for purity (14) and also for impurities including HCl (15), CO2 (16) and moisture (17).

The TDI isomer mixture is then purified by distillation. There is no change to the 80:20 isomer composition during this step. During the distillation process the HCl by-product is monitored for impurities such as phosgene and solvents by the SpectraExact (18), (19). Phosgene emission in the stack and CO emissions are measured by the SpectraExact (20) and 4210 (21) respectively.

KEY:APPLICATION TYPES: PROCESS CONTROL QUALITY SAFETY COMBUSTIONEMISSIONS

TOLUENE DIISOCYANATE PROCESS APPLICATION MAP

SpectraExact 0-500 ppm ODCB in HCl

SpectraExact 0-500 ppm COCI2 in HCI

SOLVENTOrthodichlorobenzene

RECYCLE

HCIBy Product

CH4 + H2OCO + 3H2

HYCO

HYDROGENH2

TOLUENEDIAMINE

TDA

CARBONMONOXIDE

CO

CHLORINECI2

PHOSGENECOCI2

PHOSGENECOCI2

DISTILLATION

PHOSGENATION 1

PHOSGENATION 2

REDUCER

DINITROTOLUENEDNT

ELECTROLYSISOF BRINE

1 3

2

MultiExact TCD 0-1% H2 in CO

4210 0-0.1% CH4 in CO

OxyExact/Oxy 0-0.5% O2 in CO

SpectraExact 0-1000 ppm H2O in CO

MultiExact TCD 90-100% H2 in Hydrogen

4210 0-10ppm CO in H2

MultiExact TCD 50-100%H2 in Hydrogen off gas

SpectraExact 90-100% CO in CO LaserSP 0-500 ppm H2O in Cl2

SpectraExact 0-200 ppm Cl2 in COCl2

SpectraExact (2510) 0-15% CO in COCl2

SpectraExact 0-100% COCl2in reaction gas (COC12 + HCI)

SpectraExact 0-100% HCIin reaction gas (COC12 + HCI)

SpectraExact 0-3% CO2

in reaction gas (COC12 + HCI)

SpectraExact/LaserSP 0-500 ppm H20in reaction gas (COC12 + HCI)

SpectraExact 0-500 ppm H2O in ODCB

SpectraExact 0-0.1% NCO in ODCB

SCRUBBERSpectraExact 0-1000 ppm COCI2 in stack

4210 0-100 ppm CO in air

CH3

NO 2

NO2

CH3

NH 2

NH2

O

Cl Cl

C

CH3

NCO

NCO

TOLUENEDIISOCYANATE

TDI

TOLUENEDIAMINE

TDA

10

12

14

16

18

20

11

13

15

17

19

21

3

SERVICE SYSTEMS

RUGGED PHOTOMETRIC GAS ANALYZER FOR DEMANDING PROCESS APPLICATIONS

Oxy 2200

SE

RV

OT

OU

GH

SpectraExact 2500

MonoExact TCD

SE

RV

OT

OU

GH

SE

RV

OP

RO

AWARD-WINNING DIGITAL O2 ANALYZER

HIGH SPECIFICATION PROCESS O2 ANALYZER

Oxy 1900

SE

RV

OT

OU

GH

DIGITAL SINGLE GAS ANALYZER WITH NEW TCD MEASUREMENTS

HIGH-SENSITIVITY CROSS-STACK TDL ANALYZER

LaserSP 2900

SE

RV

OT

OU

GH

Servomex has a policy of constant product improvement and reserves the right to change specifications without notice. © Servomex Group Limited. 2014. A Spectris company. All rights reserved.

S E R V O M E X . C O M

TDI ANALYSIS SOLUTIONS

EXPERT

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