CA1075682A - Control of chemical reaction - Google Patents
Control of chemical reactionInfo
- Publication number
- CA1075682A CA1075682A CA258,829A CA258829A CA1075682A CA 1075682 A CA1075682 A CA 1075682A CA 258829 A CA258829 A CA 258829A CA 1075682 A CA1075682 A CA 1075682A
- Authority
- CA
- Canada
- Prior art keywords
- nitrite
- reaction
- controlled
- reactor
- valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000006243 chemical reaction Methods 0.000 title claims description 29
- 238000000034 method Methods 0.000 claims abstract description 27
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 claims abstract description 20
- 238000010924 continuous production Methods 0.000 claims abstract description 4
- 150000004982 aromatic amines Chemical class 0.000 claims abstract description 3
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical group [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 claims description 32
- 150000001412 amines Chemical class 0.000 claims description 20
- 235000010288 sodium nitrite Nutrition 0.000 claims description 16
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 14
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 8
- 229910052697 platinum Inorganic materials 0.000 claims description 4
- GVBHRNIWBGTNQA-UHFFFAOYSA-N 2-methoxy-4-nitroaniline Chemical compound COC1=CC([N+]([O-])=O)=CC=C1N GVBHRNIWBGTNQA-UHFFFAOYSA-N 0.000 claims description 3
- DLURHXYXQYMPLT-UHFFFAOYSA-N 2-nitro-p-toluidine Chemical compound CC1=CC=C(N)C([N+]([O-])=O)=C1 DLURHXYXQYMPLT-UHFFFAOYSA-N 0.000 claims description 3
- HUWXDEQWWKGHRV-UHFFFAOYSA-N 3,3'-Dichlorobenzidine Chemical compound C1=C(Cl)C(N)=CC=C1C1=CC=C(N)C(Cl)=C1 HUWXDEQWWKGHRV-UHFFFAOYSA-N 0.000 claims description 3
- 239000011260 aqueous acid Substances 0.000 claims description 3
- LTPSRQRIPCVMKQ-UHFFFAOYSA-N 2-amino-5-methylbenzenesulfonic acid Chemical compound CC1=CC=C(N)C(S(O)(=O)=O)=C1 LTPSRQRIPCVMKQ-UHFFFAOYSA-N 0.000 claims description 2
- PBGKNXWGYQPUJK-UHFFFAOYSA-N 4-chloro-2-nitroaniline Chemical compound NC1=CC=C(Cl)C=C1[N+]([O-])=O PBGKNXWGYQPUJK-UHFFFAOYSA-N 0.000 claims description 2
- 239000003795 chemical substances by application Substances 0.000 claims description 2
- 230000001105 regulatory effect Effects 0.000 claims description 2
- 239000000243 solution Substances 0.000 description 23
- 238000003860 storage Methods 0.000 description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 239000012267 brine Substances 0.000 description 8
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 8
- -1 aromatic primary amine Chemical class 0.000 description 7
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 6
- 238000001816 cooling Methods 0.000 description 6
- 229960000443 hydrochloric acid Drugs 0.000 description 6
- 235000011167 hydrochloric acid Nutrition 0.000 description 6
- 239000002002 slurry Substances 0.000 description 6
- 125000000664 diazo group Chemical group [N-]=[N+]=[*] 0.000 description 5
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- 239000012429 reaction media Substances 0.000 description 4
- 239000011541 reaction mixture Substances 0.000 description 4
- 238000005057 refrigeration Methods 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 230000009850 completed effect Effects 0.000 description 3
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 description 3
- 238000010517 secondary reaction Methods 0.000 description 3
- CXNVOWPRHWWCQR-UHFFFAOYSA-N 4-Chloro-ortho-toluidine Chemical compound CC1=CC(Cl)=CC=C1N CXNVOWPRHWWCQR-UHFFFAOYSA-N 0.000 description 2
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 description 2
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 125000004442 acylamino group Chemical group 0.000 description 2
- 125000003545 alkoxy group Chemical group 0.000 description 2
- 125000000217 alkyl group Chemical group 0.000 description 2
- MWPLVEDNUUSJAV-UHFFFAOYSA-N anthracene Chemical compound C1=CC=CC2=CC3=CC=CC=C3C=C21 MWPLVEDNUUSJAV-UHFFFAOYSA-N 0.000 description 2
- 229940075397 calomel Drugs 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 150000001989 diazonium salts Chemical class 0.000 description 2
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000000049 pigment Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- LPDSNGAFAJYVKH-UHFFFAOYSA-N 4-(4-aminophenyl)-2,3-dichloroaniline Chemical compound C1=CC(N)=CC=C1C1=CC=C(N)C(Cl)=C1Cl LPDSNGAFAJYVKH-UHFFFAOYSA-N 0.000 description 1
- QSNSCYSYFYORTR-UHFFFAOYSA-N 4-chloroaniline Chemical compound NC1=CC=C(Cl)C=C1 QSNSCYSYFYORTR-UHFFFAOYSA-N 0.000 description 1
- QFMJFXFXQAFGBO-UHFFFAOYSA-N 4-methoxy-2-nitroaniline Chemical compound COC1=CC=C(N)C([N+]([O-])=O)=C1 QFMJFXFXQAFGBO-UHFFFAOYSA-N 0.000 description 1
- LXTWQCCQOZDVPB-UHFFFAOYSA-N 7-amino-6-chloro-4-methyl-1h-quinolin-2-one Chemical compound NC1=C(Cl)C=C2C(C)=CC(=O)NC2=C1 LXTWQCCQOZDVPB-UHFFFAOYSA-N 0.000 description 1
- 101100037762 Caenorhabditis elegans rnh-2 gene Proteins 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 125000006615 aromatic heterocyclic group Chemical group 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 238000006149 azo coupling reaction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 235000010290 biphenyl Nutrition 0.000 description 1
- 239000004305 biphenyl Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 125000002837 carbocyclic group Chemical group 0.000 description 1
- GEKUQANHMMHUDO-UHFFFAOYSA-N carboxy azanylidynemethanesulfonate Chemical group OC(=O)OS(=O)(=O)C#N GEKUQANHMMHUDO-UHFFFAOYSA-N 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000005352 clarification Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 125000004093 cyano group Chemical group *C#N 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 150000008049 diazo compounds Chemical class 0.000 description 1
- GHQCIALFYKYZGS-UHFFFAOYSA-N dibenzofuran-3-amine Chemical compound C1=CC=C2C3=CC=C(N)C=C3OC2=C1 GHQCIALFYKYZGS-UHFFFAOYSA-N 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 125000005843 halogen group Chemical group 0.000 description 1
- 150000002367 halogens Chemical group 0.000 description 1
- 125000000623 heterocyclic group Chemical group 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 229910001959 inorganic nitrate Inorganic materials 0.000 description 1
- 238000012432 intermediate storage Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- VBEGHXKAFSLLGE-UHFFFAOYSA-N n-phenylnitramide Chemical compound [O-][N+](=O)NC1=CC=CC=C1 VBEGHXKAFSLLGE-UHFFFAOYSA-N 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 150000003142 primary aromatic amines Chemical class 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- BDHFUVZGWQCTTF-UHFFFAOYSA-N sulfonic acid Chemical compound OS(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-N 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C245/00—Compounds containing chains of at least two nitrogen atoms with at least one nitrogen-to-nitrogen multiple bond
- C07C245/20—Diazonium compounds
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D11/00—Control of flow ratio
- G05D11/02—Controlling ratio of two or more flows of fluid or fluent material
- G05D11/13—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D21/00—Control of chemical or physico-chemical variables, e.g. pH value
- G05D21/02—Control of chemical or physico-chemical variables, e.g. pH value characterised by the use of electric means
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Automatically controlled continuous process for the diazotisation or tetrazotisation of aromatic amines in which the rate of addition of the inorganic nitrite is controlled by a polarovoltric method.
Automatically controlled continuous process for the diazotisation or tetrazotisation of aromatic amines in which the rate of addition of the inorganic nitrite is controlled by a polarovoltric method.
Description
~75~
The present invention relates to the preparation of diazo compounds and more particularly to a method of automatic control of the diazotisation of arvmatic amines on a continuous basisO
The diazotisation of aromatic amines is a fundamental step in the production of azo pigmentsc In the most cvmmon diazotisation process an aromatic primary amine is reacted with an inorganic nitrate usually sodium nitri~e under aqueous acid conditions to give a diazonium compound which is usually obtained in solution for~ The reaction may be represented by the following equation.
RNH2 + 2HCl ~ NaN02 R~N Cl ~ NaCl ~ H20 .
in which R is an aromatic nucleus which may be substituted by groups such as alkyl, halogen, alkoxy, nitro, acylamino, carboxy, cyano, sulphonic acid or sulphonamido.
' Diazotisation in a~ueous acidic media may be carried out batch-wise or continuouslyO In a batch-wise process the amine is mixed to a smooth paste with water and hydrochloric acid in a mechanically stirred vessel and a aqueous solu~ion of sodium nitrite is addedO ~te reaction is practically quantitative~
There are two main parameters which vary using manual control on a batch-wise process. These are:
1) ~
.
With amines which gi~e a fast reaction e.g. 3~3~dichloro-benzidine~ a ve~y large amount of heat is released very qulckly and since diazonium compounds are sensitive to heat~ the heat evolved must be absorbed and this is usually done by having flake or crushed ice present in the reaction mixture to keep the temperature arotmtl 0C. Although this method is very effective it entails the making and
The present invention relates to the preparation of diazo compounds and more particularly to a method of automatic control of the diazotisation of arvmatic amines on a continuous basisO
The diazotisation of aromatic amines is a fundamental step in the production of azo pigmentsc In the most cvmmon diazotisation process an aromatic primary amine is reacted with an inorganic nitrate usually sodium nitri~e under aqueous acid conditions to give a diazonium compound which is usually obtained in solution for~ The reaction may be represented by the following equation.
RNH2 + 2HCl ~ NaN02 R~N Cl ~ NaCl ~ H20 .
in which R is an aromatic nucleus which may be substituted by groups such as alkyl, halogen, alkoxy, nitro, acylamino, carboxy, cyano, sulphonic acid or sulphonamido.
' Diazotisation in a~ueous acidic media may be carried out batch-wise or continuouslyO In a batch-wise process the amine is mixed to a smooth paste with water and hydrochloric acid in a mechanically stirred vessel and a aqueous solu~ion of sodium nitrite is addedO ~te reaction is practically quantitative~
There are two main parameters which vary using manual control on a batch-wise process. These are:
1) ~
.
With amines which gi~e a fast reaction e.g. 3~3~dichloro-benzidine~ a ve~y large amount of heat is released very qulckly and since diazonium compounds are sensitive to heat~ the heat evolved must be absorbed and this is usually done by having flake or crushed ice present in the reaction mixture to keep the temperature arotmtl 0C. Although this method is very effective it entails the making and
- 2 ~O~S~2 handling of large quantities of ice. In addition the process operator has to judge the amount of ice which should be added and if too little is added the temperature rises too high causing the quality of the diazo solution to suffer due to formation of unwanted by-products.
2) Rate of Addition of Sodium Nitrite The sodium nitrite solution is addPd to the mixture of amine and acid at such a rate that a fairly heavy excess of sodium nitrite is maintained. This is controlled by a spot test method using Eilter- -paper impregnated with a mixture of starch and potassium iodide, When excess of sodium nltrite is present in the reaction the test paper gives a blue spot and the rate of addition of sodium nitrite solution is controlled so that the reaction mixture gives a very dark blue spot on the test paper. Close control of the rea~tion manually requlres a great degree of skill in order to reproduce conditions correctly in every batch because a) if the sodium nitrite is not added fast enough an e~cess of nitrite is not maintained and a secondary reaction can take place wi~h certain amines in which diazotised amine reacts with undiazotised amine to orm a diazoamino compound and . - ' :~ .
;~ b) if the sodium nitrite is added too fast so that a gross excess of nitrite is present other secondary reactions involving ' oxidatlon rather than diazotisation may take place.
'1 ,., `' These secondary reaction products cause difficulties when the diazo solution is being clarified and they also result in variations in the quali~y of the azo pigment produced from the diazo solution.
~ ... .
- Continuous diazotisation processes have been developed in which ~he temperature and rate of addition of sodium nitrite are controtled autGmatically rahter than manually and such processes are described in British Patent Specifications 812,368 and 844,0620 These processes use a potentiometric technique using oxidation-reducti~n ~075682 electrodes such as a platinum-calomel electrode system arld a gold-calomel electrode system respectively to control the rate of addition of sodium nitrite. We have found that by using a polarovoltric method to control the rate of addition of the nitrite we can obtain greatly increased sensitivity compared with the redox systems described in these patents.
According to the present invention there is provided an automatically controlled continuous process for the diazotisation or tetrazotisationof ~romatic amines, in which the rate of addition of the inorganic nitrite is controlled by a pair or platinum electrodes which are polarised by connecting a suitable constant current across them, such that the pre-sence of excess nitrite depolarises the electrodes and causes the voltage to drop sharply7 the voltage variation being used to control the valve used for adding the nitrite solution to the reaction vessel.
A suitable constant current is obtained, for example, by means of a 6-volt battery in combination with a series of resistors. The polarisation voltage is indica~ed by a milliYolt meter. The presence of excess nitrite depolarises the electrod~s and the voltage drops very sharply. This voltage variation can be used to control the valve used for adding nitrite solution to the reaction vessel either by a simple on/off switch or by continuously regulating the degree of opening of the valve The millivolt meter/controller can be set at an~-point along the sharp variation in voltage so that the nitrite supply is decreased or switched off when the voltage falls below the set-poiDt and increased or switched on when the voltage rises above theset-point. ~
In ~rder to obtain ~reater sensitivity at the end-point of the reac ion it is desirable to use at least two reaction vessels in series with the contents of one overflowing to the next in the serîes.
Each vessel is fitted with a polarovoltric control mechanism In the case o fast-reacting amines lil~e 3,3'-dichiorbenzidine two vessels are s~f~icient since the main part of the reaction occurs in the ~ ' ' '' ' ' ' ' ~756~ -, , first vessel and the second vessel can be used for fine adjustment of ~he reaction e~d-point by selecting a suitable setting on the controller. With weakly-basic amines like 3-nitro-4-aminotoluene which react fairly slowly it is best to use a series o three or perhaps even four vessels again with the fine adjustment taking place in the last vessel.
If desired an automatic cooling system may be used to control the temperature of the reaction mixture. For example, the reaction mixture may be circulated through an external heat exchanger using brine supplied from a refrigeration system as a coolant. If two or more reaction vessels are used the amount of heat generated in the second and subsequent reaction vessels is small and sufficient cooling can be obtained either b~ inser~ing a cooling coil in the reaction vessels and passing brine through or by usingjacketed reaction vessels and passing brine through the jacket.
The process of the presen~ invention may be used for all amines ~hich are diazotisable under aqueous acid conditions: Such dia-zotisa~eamines are, for example, primary aromatic amines or poly-amines derived from benzene, or from biphenyl, or from condensed benzenoid s~ructures such as naphthalene or anthracene, or from structures in which benzene is condensed wi~h a heterocyclic ring, in which the carbocyclic or heterocyclic aromatic nucIeus can be unsubsti-tuted or substituted with one or more of the following groups: Alkyl, alkoxy, halogeno, nitro, cyano, acylamino, sulphonamido, carboxylic acid, and sulphonic acid. Examples of diazotisable amines are 2:5 di-cbloraniline, 3,3'-dichlorbenzidine7 5-nitro-2-aminoanisole~, 3 nitro-4-aminotoluene, 4-chloro-2-nitroaniline, 4-aminotoluene-3-sulphonic acid, 4-chloraniline 2-4-dichloraniline ~^~nitroaniline
2) Rate of Addition of Sodium Nitrite The sodium nitrite solution is addPd to the mixture of amine and acid at such a rate that a fairly heavy excess of sodium nitrite is maintained. This is controlled by a spot test method using Eilter- -paper impregnated with a mixture of starch and potassium iodide, When excess of sodium nltrite is present in the reaction the test paper gives a blue spot and the rate of addition of sodium nitrite solution is controlled so that the reaction mixture gives a very dark blue spot on the test paper. Close control of the rea~tion manually requlres a great degree of skill in order to reproduce conditions correctly in every batch because a) if the sodium nitrite is not added fast enough an e~cess of nitrite is not maintained and a secondary reaction can take place wi~h certain amines in which diazotised amine reacts with undiazotised amine to orm a diazoamino compound and . - ' :~ .
;~ b) if the sodium nitrite is added too fast so that a gross excess of nitrite is present other secondary reactions involving ' oxidatlon rather than diazotisation may take place.
'1 ,., `' These secondary reaction products cause difficulties when the diazo solution is being clarified and they also result in variations in the quali~y of the azo pigment produced from the diazo solution.
~ ... .
- Continuous diazotisation processes have been developed in which ~he temperature and rate of addition of sodium nitrite are controtled autGmatically rahter than manually and such processes are described in British Patent Specifications 812,368 and 844,0620 These processes use a potentiometric technique using oxidation-reducti~n ~075682 electrodes such as a platinum-calomel electrode system arld a gold-calomel electrode system respectively to control the rate of addition of sodium nitrite. We have found that by using a polarovoltric method to control the rate of addition of the nitrite we can obtain greatly increased sensitivity compared with the redox systems described in these patents.
According to the present invention there is provided an automatically controlled continuous process for the diazotisation or tetrazotisationof ~romatic amines, in which the rate of addition of the inorganic nitrite is controlled by a pair or platinum electrodes which are polarised by connecting a suitable constant current across them, such that the pre-sence of excess nitrite depolarises the electrodes and causes the voltage to drop sharply7 the voltage variation being used to control the valve used for adding the nitrite solution to the reaction vessel.
A suitable constant current is obtained, for example, by means of a 6-volt battery in combination with a series of resistors. The polarisation voltage is indica~ed by a milliYolt meter. The presence of excess nitrite depolarises the electrod~s and the voltage drops very sharply. This voltage variation can be used to control the valve used for adding nitrite solution to the reaction vessel either by a simple on/off switch or by continuously regulating the degree of opening of the valve The millivolt meter/controller can be set at an~-point along the sharp variation in voltage so that the nitrite supply is decreased or switched off when the voltage falls below the set-poiDt and increased or switched on when the voltage rises above theset-point. ~
In ~rder to obtain ~reater sensitivity at the end-point of the reac ion it is desirable to use at least two reaction vessels in series with the contents of one overflowing to the next in the serîes.
Each vessel is fitted with a polarovoltric control mechanism In the case o fast-reacting amines lil~e 3,3'-dichiorbenzidine two vessels are s~f~icient since the main part of the reaction occurs in the ~ ' ' '' ' ' ' ' ~756~ -, , first vessel and the second vessel can be used for fine adjustment of ~he reaction e~d-point by selecting a suitable setting on the controller. With weakly-basic amines like 3-nitro-4-aminotoluene which react fairly slowly it is best to use a series o three or perhaps even four vessels again with the fine adjustment taking place in the last vessel.
If desired an automatic cooling system may be used to control the temperature of the reaction mixture. For example, the reaction mixture may be circulated through an external heat exchanger using brine supplied from a refrigeration system as a coolant. If two or more reaction vessels are used the amount of heat generated in the second and subsequent reaction vessels is small and sufficient cooling can be obtained either b~ inser~ing a cooling coil in the reaction vessels and passing brine through or by usingjacketed reaction vessels and passing brine through the jacket.
The process of the presen~ invention may be used for all amines ~hich are diazotisable under aqueous acid conditions: Such dia-zotisa~eamines are, for example, primary aromatic amines or poly-amines derived from benzene, or from biphenyl, or from condensed benzenoid s~ructures such as naphthalene or anthracene, or from structures in which benzene is condensed wi~h a heterocyclic ring, in which the carbocyclic or heterocyclic aromatic nucIeus can be unsubsti-tuted or substituted with one or more of the following groups: Alkyl, alkoxy, halogeno, nitro, cyano, acylamino, sulphonamido, carboxylic acid, and sulphonic acid. Examples of diazotisable amines are 2:5 di-cbloraniline, 3,3'-dichlorbenzidine7 5-nitro-2-aminoanisole~, 3 nitro-4-aminotoluene, 4-chloro-2-nitroaniline, 4-aminotoluene-3-sulphonic acid, 4-chloraniline 2-4-dichloraniline ~^~nitroaniline
3-nitro-4-aminoanisole : .
. ' .
' ~ . : .. : - " ' ' " ' ' ' ' . . .. ':, ' ' '. ' ' ' .', ' ' :: . ' -~7~ 3Z
2-chloro-4-nitroaniline 2-amino anisole-4-sulphodiethylamide 5-chloro-2-amino-toluene
. ' .
' ~ . : .. : - " ' ' " ' ' ' ' . . .. ':, ' ' '. ' ' ' .', ' ' :: . ' -~7~ 3Z
2-chloro-4-nitroaniline 2-amino anisole-4-sulphodiethylamide 5-chloro-2-amino-toluene
4-chloro-2-amino-toluene 4-nitro-2-amino-toluene
5-nitro-2-amino-toluene 4-nitro-2-amino-anisole 3,3'-dimethoxybenzidine 3,3'-dimethoxy-6,6'-dichlorbenzidine anthranilic acid methyl ester 2-chloro-4-aminotoluene-5-sulphonic acid 2-chloro-5-aminotoluene-4-sulphonic acid 4-chloroaniline-3-sulphonic acid aniline-2:5-disulphonic acid : 2-chloro-5-amino~ethylbenzene-4-sulphonic acid 5-amino-6-~ethyl-benzimidazolone 4-methyl-6-chloro-7-amino-quinolone 4C-2'-methoxy 4'-amino-5'-chlorophenylamino)-quinazoline 3-amino-dibenzofuran
6-methyl-7-amino-phenomorpholoneC3).
The diazotising agent is usually an inorganic nitrite such as sodium nitrite in combination with a mineral acid such as hydrochloric acid.
The diazotised amine solution may be passed to a storage vessel or it may be continuously analysed and afterwards be reacted with a suitable coupling component to form an azo pigment without intermediate storage.
The invention will be further described by way of example with reference to the drawings accompanying the provision~specification in which ~S -. ., .: . , ' .: ~ '' . - : ' ' .
,~ .
Figure 1 represents a diagrammatic view of the plant for a continuous process, Figure 2 repr~sents a diagrammatic view of the polarovoltric control system and Figure 3 is a graph representing - 6 a -' ' '' . . ,, ' ~ ' ' ': ' ' . '' ' : ' ~7~61~Z
the degree of voltage variation for a polarovoltric method and a redox method in a typical diazotisation process for aniline.
It can be seen from Figure 3 that the redox method is much less sensitive than the polarovoltric method of the present invention by the type of curve obtained (broken line) which shows that at the end-point the voltage rises from about 500mV to about 700mV, a much smaller step than is obtained by the polarovoltimetric method where the curve shows that at the end-point~ the voltage falls from about 700mV to about lOOmV. In ~he drawings the same numeral is used for similar parts of the system.
The system contains three storage vessels 10, 11 and 12.
Storage vessel 10 contains diazotisable amine mixed with water and sufficient hydrochloricacid forthe reaction, storagevessel 11 contains water, and storage vessel 12 contains sodium nitrite solution. The reaction is carried ou~ in two reactors 13 and 14 in series. The slurry of the diazotisable amine from storage vessel 10 and the water from s~orage vessel 11 are metered into reactor 13 using me~ering pumps 15 and 16 respectively at a rate noxmally set so that the average residence time in the reactor is 30 minutes but this can be varied as required. Sodium nitrite solution from storage vessel 12 i8 added simultaneously to reactor 13 by means of a valve 17 at such a rate that a slight excess of nitrite is present in the reaction.
This is controlled by a potentiometric syste~ in which the detector head is a platinum electrode pair 18 polarised by connecting a suit-able constant current across them by means of a 6~volt battery 19 in combination with a series of resistors 20. The polarisation voltage is indicated by a millivolt meter 21.
The tempexature in reactor 13 is con~rolled by circulating the contents by a pump 22 through an external heat e~changer 23 using brine from a refrigeration system as the cooling medium. The flow of brine is controlled by the temperature indira~or/controller 33 which operates the valve 24~ The reaction medium from reactor 13 ~ .
[)7561!3Z
overflows to reactor 14 through a coarse stra;ner 25 which holds back any large unreacted particles. I~e diazotisation reaction is completed in the jacketed reactor 14 where sodium ni,tri~e solution from storage vessel 12 is added by means of a valve 26 at such a rate that a slight excess of nitrite is present in the reaction. ~his is controlled in the same manner as described for the process in reactor 13 by a potentiometric system in which the detector head is a platinum electrode pair 18 polarised by connecting a suitable constant current across them. The polarisation voltage is indicated by a millivoltmeter 21. Cooling of reactor 14 is obtained by passing brine, supplied fro~
a refrigeration system through a valve 28 and controlled by a temper-ature indicator/controller 34, through the jacket.
The diazotised amine solution passes from reactor 14 by pump '' "
29 through clarification filters 30 and 31 arranged in parallel (this allows one to be cleaned while the other is operating) and then to a storage vessel 32. The level of the solution in vessel 14 is controlled by the level indica~or/controller 35. When the level is too low, the valve 36 is opened to allow the solution to recirculate to the vessel.
When ~he level rises above the set point, the controller closes valve 36 and the solution passes through the filter to the storage vessel.
The following Examples fllrther illustra~es the present invention. - .
...
.- . . . ~ . . , , : .
,' . ; ~: ' :
:
- ~0~56~Z
Example 1: In the plant described above one storage vessel contains 3,3'-dichlorobenzidine ~ixed with water and sufficient hydrochloric acid for the reac~ion. This is a smooth pumpable slurry containing approximately 20~ 3,3'-dichloroben~idine by weight. One storage vessel contains water and the other contains 40% by weight aqueous solution of sodium nitrite.
The slurry of 3,3'-dichlorobenzidine and water are metered into a first reactor using metering pumps at a rate so that the average residence time in the reactor is 30 minutes. Sodium nitri-te solution is added simultaneously at such a rate that a slight excess is present in the reaction this being controlled by the potentiometric system described above and illustrated in Figure 2. The degree of voltage variation is illustrated by the graph in Figure 3. When no unreacted nitrite is present the voltage stays constant at between 600 and 700 millivolts but the presence of excess nitrite depolarises the electrodes and the voltage drops sharply to around 100 millivolts.
A millivolt meter/controller is set at a point on the steep part of the curve i,e, between 700 and 300 millivolts to switch off the nitrite suppLy when the voltage fal~s below the set-point and switch it on when the voltage rises above the set-point.
The temperature in the first reactor is controlled by circul-ating the contents through an external heat exchanger using brine supplied from a refrigeration system. The reaction medium overflows into a second reactor ~hrough a coarse strainer which holds back ~ny large unreacted particles and the diazothisation reaction is com-pleted using exactly the same control mechanism as described for the first reactor. Cooling i5 carried out by using a jacketed reactor and pas~ing brine through this jacket. The dia~otised amine solution then passes through a clari~ication filter to a storage vessel.
Example Z: ~ferring to Figure 1 the storage vessel 10 contains ._ ' a smooth slurry of 100.0 parts 5-nitro-2-aminoanisole, 181.0 parts hydrochloric acid S.G, l.l8~ and 3.0 part ~ THOMEEN C25 ~ade ~o .' ., : .
, ~:. :: . , . : . - .
~7~ii6~
, --.
1.100 parts with water.
Storage vessel 12 contains a solution of 41.1 par~s sodium nitrite made to 100 parts with water.
The slurry is metered to the reactor 13 at such a rate that the average residence time in this reactor is 100 minutes. The addition of sodium nitrate solution from storage vessel 12 to reactor 13 is automatically controlled by the polarovoltric system as in Example 1 so that a slight excess is maintained throughout the reac~ion. The temperature in reactor 13 is automatically controlled at 0,2C by the cooling system. The reaction medium passes from reactor 13 to reactor 14 through the coarse strainer 25 and the reactio~ is completed during an average residence time of 15 minutes in reactor 14 again under the automatic control of the polarovoltric system after which the diazo solution is filtered and passes to storage or further reaction.
Example 3: A slurry consisting of 210 parts 2:5-dichloraniline and .. . . ~ .
460 parts hydrochloric acid made to 4.000 parts with water is metered from storage ~essel 10 to reactor 13 at such a rate that the average residence time in reactor 13 is 1 hour~ Sodium nitrite solution is added to reactor 13 simultaneously under the control of the polaro-voltric system which automatically maintains a slight excess of nitrite in the reaction. The reaction medium then passes to reactor 14 via an overflow and coarse screen and the reaction goes to com-pletion during a further 1 hour residence in this reactor again under the automatic control of the polarovoltric systemO The temRerature is automatically controlled between 0C and 2C. The diazo solution is ; filtered and then passed to storage or directly to further reaction e.g. an azo coupling reaction.
, :
~.
. :
' : . : ` .. ` "
.
`` ' ". ` ~' ''`'~'` '"'`. ` ~
The diazotising agent is usually an inorganic nitrite such as sodium nitrite in combination with a mineral acid such as hydrochloric acid.
The diazotised amine solution may be passed to a storage vessel or it may be continuously analysed and afterwards be reacted with a suitable coupling component to form an azo pigment without intermediate storage.
The invention will be further described by way of example with reference to the drawings accompanying the provision~specification in which ~S -. ., .: . , ' .: ~ '' . - : ' ' .
,~ .
Figure 1 represents a diagrammatic view of the plant for a continuous process, Figure 2 repr~sents a diagrammatic view of the polarovoltric control system and Figure 3 is a graph representing - 6 a -' ' '' . . ,, ' ~ ' ' ': ' ' . '' ' : ' ~7~61~Z
the degree of voltage variation for a polarovoltric method and a redox method in a typical diazotisation process for aniline.
It can be seen from Figure 3 that the redox method is much less sensitive than the polarovoltric method of the present invention by the type of curve obtained (broken line) which shows that at the end-point the voltage rises from about 500mV to about 700mV, a much smaller step than is obtained by the polarovoltimetric method where the curve shows that at the end-point~ the voltage falls from about 700mV to about lOOmV. In ~he drawings the same numeral is used for similar parts of the system.
The system contains three storage vessels 10, 11 and 12.
Storage vessel 10 contains diazotisable amine mixed with water and sufficient hydrochloricacid forthe reaction, storagevessel 11 contains water, and storage vessel 12 contains sodium nitrite solution. The reaction is carried ou~ in two reactors 13 and 14 in series. The slurry of the diazotisable amine from storage vessel 10 and the water from s~orage vessel 11 are metered into reactor 13 using me~ering pumps 15 and 16 respectively at a rate noxmally set so that the average residence time in the reactor is 30 minutes but this can be varied as required. Sodium nitrite solution from storage vessel 12 i8 added simultaneously to reactor 13 by means of a valve 17 at such a rate that a slight excess of nitrite is present in the reaction.
This is controlled by a potentiometric syste~ in which the detector head is a platinum electrode pair 18 polarised by connecting a suit-able constant current across them by means of a 6~volt battery 19 in combination with a series of resistors 20. The polarisation voltage is indicated by a millivolt meter 21.
The tempexature in reactor 13 is con~rolled by circulating the contents by a pump 22 through an external heat e~changer 23 using brine from a refrigeration system as the cooling medium. The flow of brine is controlled by the temperature indira~or/controller 33 which operates the valve 24~ The reaction medium from reactor 13 ~ .
[)7561!3Z
overflows to reactor 14 through a coarse stra;ner 25 which holds back any large unreacted particles. I~e diazotisation reaction is completed in the jacketed reactor 14 where sodium ni,tri~e solution from storage vessel 12 is added by means of a valve 26 at such a rate that a slight excess of nitrite is present in the reaction. ~his is controlled in the same manner as described for the process in reactor 13 by a potentiometric system in which the detector head is a platinum electrode pair 18 polarised by connecting a suitable constant current across them. The polarisation voltage is indicated by a millivoltmeter 21. Cooling of reactor 14 is obtained by passing brine, supplied fro~
a refrigeration system through a valve 28 and controlled by a temper-ature indicator/controller 34, through the jacket.
The diazotised amine solution passes from reactor 14 by pump '' "
29 through clarification filters 30 and 31 arranged in parallel (this allows one to be cleaned while the other is operating) and then to a storage vessel 32. The level of the solution in vessel 14 is controlled by the level indica~or/controller 35. When the level is too low, the valve 36 is opened to allow the solution to recirculate to the vessel.
When ~he level rises above the set point, the controller closes valve 36 and the solution passes through the filter to the storage vessel.
The following Examples fllrther illustra~es the present invention. - .
...
.- . . . ~ . . , , : .
,' . ; ~: ' :
:
- ~0~56~Z
Example 1: In the plant described above one storage vessel contains 3,3'-dichlorobenzidine ~ixed with water and sufficient hydrochloric acid for the reac~ion. This is a smooth pumpable slurry containing approximately 20~ 3,3'-dichloroben~idine by weight. One storage vessel contains water and the other contains 40% by weight aqueous solution of sodium nitrite.
The slurry of 3,3'-dichlorobenzidine and water are metered into a first reactor using metering pumps at a rate so that the average residence time in the reactor is 30 minutes. Sodium nitri-te solution is added simultaneously at such a rate that a slight excess is present in the reaction this being controlled by the potentiometric system described above and illustrated in Figure 2. The degree of voltage variation is illustrated by the graph in Figure 3. When no unreacted nitrite is present the voltage stays constant at between 600 and 700 millivolts but the presence of excess nitrite depolarises the electrodes and the voltage drops sharply to around 100 millivolts.
A millivolt meter/controller is set at a point on the steep part of the curve i,e, between 700 and 300 millivolts to switch off the nitrite suppLy when the voltage fal~s below the set-point and switch it on when the voltage rises above the set-point.
The temperature in the first reactor is controlled by circul-ating the contents through an external heat exchanger using brine supplied from a refrigeration system. The reaction medium overflows into a second reactor ~hrough a coarse strainer which holds back ~ny large unreacted particles and the diazothisation reaction is com-pleted using exactly the same control mechanism as described for the first reactor. Cooling i5 carried out by using a jacketed reactor and pas~ing brine through this jacket. The dia~otised amine solution then passes through a clari~ication filter to a storage vessel.
Example Z: ~ferring to Figure 1 the storage vessel 10 contains ._ ' a smooth slurry of 100.0 parts 5-nitro-2-aminoanisole, 181.0 parts hydrochloric acid S.G, l.l8~ and 3.0 part ~ THOMEEN C25 ~ade ~o .' ., : .
, ~:. :: . , . : . - .
~7~ii6~
, --.
1.100 parts with water.
Storage vessel 12 contains a solution of 41.1 par~s sodium nitrite made to 100 parts with water.
The slurry is metered to the reactor 13 at such a rate that the average residence time in this reactor is 100 minutes. The addition of sodium nitrate solution from storage vessel 12 to reactor 13 is automatically controlled by the polarovoltric system as in Example 1 so that a slight excess is maintained throughout the reac~ion. The temperature in reactor 13 is automatically controlled at 0,2C by the cooling system. The reaction medium passes from reactor 13 to reactor 14 through the coarse strainer 25 and the reactio~ is completed during an average residence time of 15 minutes in reactor 14 again under the automatic control of the polarovoltric system after which the diazo solution is filtered and passes to storage or further reaction.
Example 3: A slurry consisting of 210 parts 2:5-dichloraniline and .. . . ~ .
460 parts hydrochloric acid made to 4.000 parts with water is metered from storage ~essel 10 to reactor 13 at such a rate that the average residence time in reactor 13 is 1 hour~ Sodium nitrite solution is added to reactor 13 simultaneously under the control of the polaro-voltric system which automatically maintains a slight excess of nitrite in the reaction. The reaction medium then passes to reactor 14 via an overflow and coarse screen and the reaction goes to com-pletion during a further 1 hour residence in this reactor again under the automatic control of the polarovoltric systemO The temRerature is automatically controlled between 0C and 2C. The diazo solution is ; filtered and then passed to storage or directly to further reaction e.g. an azo coupling reaction.
, :
~.
. :
' : . : ` .. ` "
.
`` ' ". ` ~' ''`'~'` '"'`. ` ~
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An automatically controlled continuous process for the diazotisa-tion or tetrazotisation of aromatic amines, in which the rate of addition of the inorganic nitrite is controlled by a pair of platinum electrodes which are polarised by connecting a suitable constant current across them, such that the presence of excess nitrite depolarises the electrodes and causes the voltage to drop sharply, the voltage variation being used to control the valve used for adding the nitrite solution to the reaction vessel.
2. A process as claimed in claim 1 in which the valve is controlled by an on/off switch.
3, A process as claimed in claim 1 in which the valve is controlled by continuously regulating the degree of opening.
4 A process as claimed in claim 1 in which there are used at least two reaction vessels in series with contents of one overflowing to the next in the series, each vessel being fitted with a polarovoltric control mechanism.
5. A process as claimed in claim 4 in which the last reaction vessel is used for fine adjustment of the reaction end-point by selecting a suitable setting on the controller.
6. A process as claimed in claim 1, 2 or 3 in which the amine used is one which is diazotisable under aqueous acid conditions.
7. A process as claimed in claim 1, 2 or 3 in which the amine used is 2:5-dichloraniline, 3,3'-dichlorbenzidine, 5-nitro-2-aminoanisole, 3-nitro-4-aminotoluene, 4-chloro-2-nitroaniline or 4-amino-toluene-3-sulphonic acid.
8. A process as claimed in claim 1, 2 or 3, in which the diazotising agent is sodium nitrite in combination with hydrochloric acid.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB33614/75A GB1547760A (en) | 1975-08-12 | 1975-08-12 | Control of continuos diazotisation of aromatic amines |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1075682A true CA1075682A (en) | 1980-04-15 |
Family
ID=10355210
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA258,829A Expired CA1075682A (en) | 1975-08-12 | 1976-08-10 | Control of chemical reaction |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5227725A (en) |
| CA (1) | CA1075682A (en) |
| CH (1) | CH623029A5 (en) |
| DE (1) | DE2635778A1 (en) |
| DK (1) | DK363176A (en) |
| FR (1) | FR2320937A1 (en) |
| GB (1) | GB1547760A (en) |
| IT (1) | IT1065121B (en) |
| SE (1) | SE7608970L (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2741925A1 (en) * | 1977-09-17 | 1979-03-29 | Bayer Ag | PROCESS FOR CONTINUOUS INDIRECT DIAZOTATION OF AROMATIC AMINES |
| EP0003656B1 (en) * | 1978-02-14 | 1981-07-15 | Imperial Chemical Industries Plc | Process for the diazotisation of amines |
| DE2825655A1 (en) * | 1978-06-12 | 1979-12-20 | Hoechst Ag | METHOD OF CONTINUOUS DIAZOTATION OF AMINES |
| DE3104375A1 (en) * | 1981-02-07 | 1982-08-19 | Hoechst Ag, 6000 Frankfurt | METHOD FOR CONTROLLING DIAZOTING REACTIONS |
| US4845638A (en) * | 1985-07-15 | 1989-07-04 | Ciba-Geigy Corporation | Method of eliminating excess nitrite in diazotisation solutions |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL211338A (en) * | 1954-08-26 |
-
1975
- 1975-08-12 GB GB33614/75A patent/GB1547760A/en not_active Expired
-
1976
- 1976-08-09 DE DE19762635778 patent/DE2635778A1/en active Granted
- 1976-08-09 CH CH1013176A patent/CH623029A5/en not_active IP Right Cessation
- 1976-08-10 CA CA258,829A patent/CA1075682A/en not_active Expired
- 1976-08-11 FR FR7624490A patent/FR2320937A1/en active Granted
- 1976-08-11 IT IT7626221A patent/IT1065121B/en active
- 1976-08-11 DK DK363176A patent/DK363176A/en not_active Application Discontinuation
- 1976-08-11 SE SE7608970A patent/SE7608970L/en unknown
- 1976-08-12 JP JP51096591A patent/JPS5227725A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6210222B2 (en) | 1987-03-05 |
| IT1065121B (en) | 1985-02-25 |
| DK363176A (en) | 1977-02-13 |
| FR2320937B1 (en) | 1978-05-05 |
| DE2635778A1 (en) | 1977-02-24 |
| SE7608970L (en) | 1977-02-13 |
| DE2635778C2 (en) | 1987-08-27 |
| CH623029A5 (en) | 1981-05-15 |
| FR2320937A1 (en) | 1977-03-11 |
| JPS5227725A (en) | 1977-03-02 |
| GB1547760A (en) | 1979-06-27 |
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