DE2112705B2 - Stabilization of isoprene in solvents - Google Patents

Description

R ₁ I
O

R ₂ -O-P = O

I.
R ₃

added to the isoprene-containing solvent as an inhibitor, where R ₁ , R ₂ and R _{3 are} phenyl groups or alkyl, phenyl or halogen-substituted phenyl groups, alkyl groups or halogen-substituted alkyl groups, the alkyl groups having 1 to 8 carbon atoms, or allyl groups being

I. Stabilization according to claim 1, characterized in that that a known polymerization inhibitor or antioxidant for unsaturated compounds from the group: sodium nitrite, potassium nitrite, Sodium sulfide, methylene blue, mercaptobenthiazole, phenolic compound and aromatic Amine compound as a second polymerization inhibitor is used.

diene or isoprene is accelerated in the solvent and the polymerisation product is deposited. This Knomen can easily be observed that the uro ^ ninolirh clear solution discolors over time,

^ ["ÄL is translucent and has deposits of the to this one: aurcu «,

Polymer zap. _{an polymer} ^. ^ ^

· U "difficulties For example, a thin one

Polvmeram over the inner wall of the equipment

to trained, the outlets become clogged, and the

Extiaktionsffekt is reduced and thus becomes

difficult to do continuously for several hours

^wi £

iuider DT-AS 18 16 826 the stabilization of butadiene is known, with the addition of an aromatic nitro compound to the butadiene-containing solution he ^f ° Another method of stabilizing butadiene

_{dien is known from} DT-OS15 43 061. Be here

»Furfural, benzaldehyde or aromatic N.troverb.n-

^ f ^ SrW conjugated diene is from the The ^^^ J ^ gb-PS 11 82 157 to de-

^FI >'^{Pi> 1} ^ "Ultimately, GB-PS 11 46 195 gives a take ^« WJeBg ^ bt d

> 5 procedures

zolL ^

Of the

merb.ldur, « 3 ° A decision will be made

The !! ^ ^

^ 7 | _ε ^^ 2 phosphoric acid esters, which can be used advantageously according to the invention, include such compounds as triphenyl phosphate or nucleus-substituted derivatives thereof where the substituents are alkyl groups, phenyl

_On top of that, the poly _{that is in the} main

did

The invention relates to the stabilization of isoprene groups in solvents at elevated temperatures against *> phate ^P tr _d ^S process for extractive distillation or absorption by solvents for separation and

Refining of butadiene or isoprene in high yield

prey became known, with these two products 45 Suitable J

represent valuable materials or products from Q-carbon Hydrogen fractions of cracked heavy oil, the

Butadiene, butane, butylene and isobutylene as the main and others

Compounds containing phenyl groups or allyl groups.

- ■ ■ "" phate or nuclear substitute

same are triohenyl phosphate, -> <? hat, tri- (m-cresyl) -phosphate, tri- :, Trixylenyl phosphate, tris- (4-t

(DMAC) and furfural applied

will.

It is usually known of the conjugated dienes given above that they are easily oxidizable and tend to be oxidized at normal temperature by means of oxygen or the like, which is present in the solvents. Forming polymers on prolonged standing. In the separation or refining by means of conventional extractive distillation or absorption processes, a solvent-containing butadiene or isoprene inevitably temperatures above the boiling point of the C ₄ or C _fi hydrocarbon fractions, e.g. B. over 70 ⁰ C, subjected. The result of this is the polymerization of buta-triheptyl phosphate, trioctyl phosphate and other organic phosphoric acid esters, the alkyl groups having 1 to 8 carbon atoms; and tri- (2-chloroethyl) phosphate, tri- (2-bromoethyl) phosphate, tri- (3-chloropropyl) phosphate, tri- (3-bromopropyl phosphate, tri- (3-iodopropyl) - phosphate, tri- (2,3-dichloropropyl) phosphate, tri- (2,3-dibromopropyl) phosphate, tri- (2,3-diiodopropyl) phosphate, tri- (4-chlorobutyl) phosphate, tri- (4-bromobutyl) phosphate, tri- (4-iodobutyl) phosphate and other organic phosphoric acid esters that contain halogen atom-substituted alkyl groups.

and allyl group ⁶¹¹ contain diallyl phenyl phosphate and allyl biphenyl phosphate.

The known polymerization inhibitors or antioxidants for unsaturated compounds in combination with the inhibitors according to the invention are applied are:

(1) NaNOg, KNO ₂ , Na ₂ S, methylene blue and mercaptobenzothiazole;

(2) phenolic compounds, e.g. B. hydroquinone, such as 2,5-di-tert-butylhydroquinone and 2,5-di-tert-amylhydroquinone, Phenols, such as o-phenyl-phenol, 2,6-di-tert-butyl-p-phenylphenol, butylated hydroxytoluene and p-methoxyphenol; Cresols, such as 2,6-di-tert-butyl-p-cresol, catechins, such as di-tert-butylcatechol and p-tert-butylcatechol, bisphenols such as 2,2'-methylenebis (4-methyl-6-tert-butylphenol) and 4,4'-methylenebis (2,6-di-tert-butylphenol); Naphthols, like «-naphthol, / Ϊ-naphthol, l, l'-methylenebis-2-naphthol; and Aminophenols such as p-aminophenol and 2,6-di-tert-butyl-ix-dimethyleneamine-p-cresol and

(3) aromatic amine compounds, e.g. B. p, p'-diaminodiphenylmethane, N-phenyl-a-naphthylamine, N-phenyl - /? - naphthylamine, p-isopropoxydiphenylamine, 4,4'-dimethoxydiphenylamine, N, N'-diphenyl-p-phenylenediamine, Ν, Ν'-diphenylethylenediamine, Ν, Ν'-di-o-tolylethylenediamine,

Table I.

N.N'-naphthylenediamine, octyldiphenylamines (mono- and di-) and 2,4-diaminotoluene.
The amounts of the polymerization inhibitors to be added can be changed in accordance with the nature of the water content of the solvent and the operating conditions used. Usually, however, the purpose is achieved by adding the inhibitors first, e.g. B. organic phosphoric acid ester, in an amount of 0.01 to 10%, preferably 0.05 to 5% by weight based on the weight basis of the solvent, and then adding the second inhibitors, e.g. B. sodium nitrite, phenolic compounds, aromatic amine compounds, etc. in an amount of 0.001 to 5%, voi preferably 0.005 to »5 1%, on the basis of the weight of the solvent. These inhibitors classified according to the above two groups can be added individually or in combination in order to achieve the desired effect. It goes without saying, of course, that the amounts of these such additives are not limited by the scope of the invention.

example

There are 70 parts by weight of water containing 30 parts of acetonitrile and isoprene mixed with one or more of the inhibitors set forth below, and the resulting mixtures are allowed to react at 120 ⁰ C in the presence of Eisenox d. The properties of the products are tested and the results are summarized in Table I.

No. Polymerization inhibitor Weight 2. Inhibitors ppm State after heating 80 h 1. Inhibitors percent no 24 hours 1 no 100 Polymer stores polymer Sodium nitrite himself off deposit 2 no 100 becomes minor - p-tert-butyl catechol 100 White - 3 no Phenyl - /? - naphthyl- Polymer deposition 4th no amine Polymer deposition polymer
deposit
clear 0.5 no ICO slightly
tiipi [\ 5 Triphenyl phosphate 0.5 Sodium nitrite 50 slightly white WCIlJ
slightly
IVAl ti 6th Triphenyl phosphate 0.5 Sodium nitrite 100 clear WClU
slightly 7th Triphenyl phosphate 0.5 p-tert-butyl catechol 100 clear White 8th Triphenyl phosphate 1.0 Phenyl- / S-naphthyl- clear clear 9 Triphenyl phosphate amine 100 clear clear 0.5 Sodium nitrite 100 clear 10 Tricresyl phosphate 0.5 Sodium nitrite 100 clear clear 11 Tris (4-tert-butylphenyl) -
phosphate
Tri (n) butyl phosphate 0.5 Sodium nitrite 100 clear clear 12th Tris (o-biphenyl) phosphate 0.5 Sodium nitrite 100 clear 13th Dialvlphenvlohosühat 0.5 Sodium nitrite clear 14th clear

Example 2

In an extraction-distillation column with 100-stage plates, a CV hydrocarbon fraction containing Tsonren is fed using an extraction solvent which has been added by adding 0.5% by weight of triphenylphosphate and 100 ppm of sodium nitrite to acetonitrile containing 5% by weight of water at a value (molar ratio ) of 7: 1 of the CV hydrocarbon fraction has been produced. The mixture is continuously introduced into the tenth stage of KolonnensDitze, and the column is operated at a reflux ratio of 5.0, a Kolonnensoitzen temperature of 47 ° C and a column Bodentemoeratur of 100 ⁰ C. The extraction solution containing isoprene

is continuously reacted at the next stripping zone, and the extraction solvent recovered is returned directly to the extraction distillation column.

The operation is continued for a week, but the extraction solvent shows no changes and remains clear. When the same process is repeated, but without the addition of triphenyl phosphate and sodium nitrite to the solvent, the solution begins to turn white and becomes ^cloudy: n 10 hours and leads to a polymer deposit that turns a light orange color in 20 hours.

Example 3

Test solutions are used under the same conditions as described in Example 1 with the

assumed that N-methylpyrrolidone are used as the solvent and the various inhibitors given below. The respective solutions are reacted in the presence of iron oxide by heating to 140 ⁰ C. the

ίο properties of the solutions are examined and the Results are given in Table II below.

Table II

Kr. Polymerization Inhibitor
1. Inhibitors

Weight percent

2. Inhibitors

Properties after heating
24 h 72 h

1
2 no
no 0.5 no
Sodium nitrate 3 Triphenyl phosphate 0.5
0.5 no 4th
5 Triphenyl phosphate
Tri (n) butyl phosphate 0.5 Sodium nitrite
no 6th Triinibutvlnhosnhat Sodium nitrite

Similar experiments are carried out under the same conditions given above, however using dimethylformamide or dimethylacetamide in place of N-methylpyrrolidone as Solvent. In either case, the application of only sodium nitrite (100 ppm) to deposit the polymer in 72 hours, but if sodium nitrite (100 ppm) and tri-n-butyl phosphate 0.5 percent by weight are added, the test solutions remain clear 72 hours afterwards.

Polymer deposition -
becomes slightly polymer

70 parts of acetonitrile, which contains 5 percent by weight of water, and 30 parts of isoprene are mixed with the addition of the various inhibitors shown below. The corresponding mixtures are reacted in the presence of iron oxide at 120 ° C and the properties of the products are investigated. The results are given in Table III below.

White slightly deposits will polymer White deposits clear slightly clear will polymer White deposits clear game 4 clear at

Table III

Polymerization inhibitor

1. Inhibitors 2. Inhibitors

ppm state after heating
H

48 h

no
no

no

no
Sodium nitrate

p-tert-butyl catechol

Polymer deposition
slightly white

Polymer deposition

Polymer deposition

The following is a comparison of the present invention and the aforementioned GB-PS 11 46 195.11 82 157 and FR-PS 15 75 149 for the purpose of explaining technical progress. Comparison of GB-PS 11 46 195 and the present invention

Comparison of GB-PS1146195 and the present invention

parameter

invention

Resignation
(Example 6)

solvent

Monomer

Inhibitor

pressure
temperature
Results after 10 hours
Stand

DMF

Isoprene (iron rust)

Triphenyl phosphate (5000 ppm)

3.5 kg / cm ^a
120 ⁰ C

completely transparent (polymer yield 0.03 percent by weight)

DMF

Isoprene (iron rust)

m-Dinitrobenzo

(5000 ppm)

3.5 kgf / cm ²

120 ° C

completely transparent

(Polymer yield

0.06 percent by weight)

The polymer yield was determined as follows:

After distilling off the solvent and isoprene under reduced pressure, the solid became Residue (including oily material) collected, dried and weighed. The polymer yield is given as a percentage of the solid residue, based on isoprene.

The above table gives the results of comparative tests, which among the same Conditions as in Example 6 of the reference when using the inhibitor according to the invention were carried out.

From a purely qualitative point of view, both materials turned out to be completely transparent, so that there are no clear differences were recognizable. In quantitative terms, however, these are unmistakable on the basis of the polymer yield determined; the difference is clearly expressed and documented in the 100% higher polymer yield the superiority of the inhibitors according to the invention.

Comparison of GB-PS 11 82 157 and the present invention

parameter

invention

Citation (example 11,
Sample 8)

solvent
Monomer

Inhibitor

pressure
temperature
Results after
18 sid. Stand

DMF

Isoprene (iron rust)

Tri-n-butyl phosphate
(5000 ppm)
NaNO ₈ (IOO ppm)
3.0 kp / crn *
150 ⁰ C
transparent

DMF

Isoprene

(Iron rust)

«-Nitroso-

/ 3-naphthol

(10,000 ppm)

3.0 kg / cm ^a
150 ° C
"practically
transparent"

The above results were obtained using the conditions of Example 11 of the reference carried out when using the inhibitors according to the invention, with different amounts of inhibitor were to be used.

Despite the higher concentration of inhibitor, the materials in the citation were less transparent than in the case of the invention.

Comparison of FR-PS 15 75 149 and the present invention

parameter invention 2 Citation Example 4 (3) 1 DMF Example 4 (1) DMF solvent DMF Isoprene (iron rust) DMF Isoprene (iron rust) Monomer Isoprene (iron rust) Tri-n-butyl phosphate Isoprene (iron rust) N-methylpyrro Inhibitor Tri-n-butyl phosphate (1.0%) N-methylpyrrolidone lidon (1%) (0.5%) NaNO ₂ (1000 ppm) (1%) NaNO ₂ (1000 ppm) NaNO ₂ (100 ppm) 3 kgf / cm ² S (1000 ppm) 2 kg / cm ⁸ pressure 3 kgf / cm ² 150 ° C 2 kp / cm * 150 ^c C temperature 150 ⁰ C transparent 150 ° C transparent Results after transparent transparent 120 hours standing transparent less than 0.1 0.3 Polymer yield 0.1 0.1

The experiments on which the table above is based were carried out under roughly the same conditions, however using different pressures, as in Example 4 of the reference and use of the carried out inhibitor according to the invention.

Even if one works according to the invention with higher pressure, i. H. with higher isoprene concentrations in the solvent, less polymer formation is observed (2 / invention), moreover results a significantly smaller amount of the inhibitor according to the invention produces approximately the same polymer yield. Will the inhibitor according to the invention is used in the same amount as the inhibitor of the citation there is a significantly lower polymer formation than in the case of the citation.

The above comparative experiments show that the inhibitors according to the invention compared to the previously known means are superior. Stabilized isoprene solutions form less polymer, which is synonymous is to be able to store more concentrated isopy solutions with as little polymer formation as possible.

509532/423

Claims (1)

Patent claims: 1. Stabilization of isoprene in solvents at elevated temperatures against polymerization, characterized in that at least one organic phosphoric acid ester compound the general formula