DE2112705C3 - Stabilization of isoprene in solvents - Google Patents

Description

R, - O - P = O

ι ό

the isoprene-containing solvent is added 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, where the alkyl groups have 1 to 8 carbon atoms, or are allyl groups.

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

The invention relates to the stabilization of isoprene tn solvents at elevated temperatures against polymerization.

Processes for extractive distillation or absorption by solvents for separating and refining butadiene or isoprene in high yield have become known, these two products being valuable materials or of C ₄ hydrocarbon fractions from split heavy oil, which is butadiene, butane, butylene and isobutylene Contains main constituents, or of Cs hydrocarbon fraction, which contains pentane, pentene, isoprene and piperylene ils main constituents.

It is also known that solvents such as acetonitrile (ACN), N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAC) and furfural are used 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. When separating 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 _r , carbon fractions, e.g. B. over 70 ^c C, subjected. As a result, the polymerization of butadiene or isoprene in the solvent is accelerated and the polymerization product is deposited. This phenomenon can easily be observed because the originally transparent solution discolors over time until it is translucent and shows deposits of the polymer.

Such polymer deposition creates numerous difficulties. For example, a thin one Polymer film is formed over the inner wall of the equipment ίο, the outlets become clogged, and the Extraction efficiency is lowered, and thus it becomes difficult to keep on for several hours work.

From DT-AS 18 16 826 the stabilization of is butadiene is known, with an addition of an aromatic Nitro compound to the butadiene-containing solution takes place.

Another method of stabilizing butadiene is known from DT-OS 15 43 061. Be here »O Furfural, benzene dehyde or aromatic nitro compounds added.

The stabilization of conjugated dienes can be found in FR-PS 15 75 149 and GB-PS 11 82 157, and finally, GB-PS 11 46 195 gives a method for stabilizing isoprene and / or Pentadiene, using m-dinitrobenzene for stabilization.

The invention is based on the object of further reducing polymer formation.

This problem is solved by the features specified in the main claim.

The subclaim represents a preferred design of the invention.

The organic phosphoric acid esters according to the invention Advantageously employed include such compounds as triphenyl phosphate or ring-substituted derivatives thereof, the substituents being alkyl groups, phenyl groups or represent halogen atoms, trialkyl phosphates with or without substitution of the hydrogen atom the alkyl group by means of halogen atom, AUvI-biphenyl phosphate, diallyl phenyl phosphate and others Compounds containing phenyl groups or allyl groups.

Suitable triphenyl phosphate or ring-substituted products thereof are triohenyl phosphate, Tri- (o-cresyl) phosphate, tri- (m-cresyl) phosphate. Tri- (p-cresyl) phosphate, trixylenyl phosphate, tris (4-tert.-butylphenyO-phosphate, Tris (o-biphenyl) phosphate etc., where the substituents are alkyl groups, phenyl groups or represent halogen atoms.

Suitable trialkyl phosphates and halogen-substituted derivatives thereof are trimethyl phosphate, Triethyl phosphate, thi-n-propyl phosphate, triisopropyl phosphate, Tri-n-butyl phosphate, tri-sck.-butyl phosphate, tri-n-amyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate and other organic Phosphoric acid esters, the alkyl groups having 1 to 8 carbon atoms: and tri- (2-chloroethyD-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) phosphnt, Tri - (2,3 - diiodopropyl) - phosphate, tri - (4 - chlorobutyl) phosphate, Tri- (4-bromobutyl) phosphate. Tri- (4-iodobutyl) phosphate and other organic phosphoric acid esters containing halogen atom-substituted alkyl groups. As organic phosphoric acid esters, the phenyl

and allyl groups, diallyl phenyl phosphate and allyl biphenyl phosphate are suitable.

The known polymerization inhibitors or antioxidants for unsaturated compounds that are found in Combination with the inhibitors according to the invention are used:

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

10

(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, like 2,6-di-tert-butyl-p-cresol, catechins, such as di-tert-butylcatechin and p-tert-butylcatechol, bisphenols such as 2,2'-methylenebis (4-mei! iyl-6-tert-butylphenol) and 4,4'-methylenebis (2,6-di-tert-butylphenol); Naphthols, such as \ -naphthol, / Ϊ-naphthol, l, l'-methylenebis-2-naphthol; and Aminophenols such as p-aminophenol and 2,6-di-tert-butyl-A-dimethylamine-p-cresol and

(3) aromatic amine compounds, e.g. B. p, p ^: -diaminodiphenylmethane, N-phenyl - \ - naplithylamine, N-phenyl - /? - naphthylamine, p-isopropoxydiphenylamine, 4,4'-dimethoxydiphenylamine, N, N'-diphenyl-p-phenylenediamine, N, N'-Diphen \ läthylenediamine, N.N'-Di-o-tolyläthylendianui,

Table I.

Ν, Ν'-naphthylenediamine, octyldiphenylamine (mono- üiid dl-) and 2,4-diainiiiüiüIüüi.

The amounts of the polymerization inhibitors to be added can be changed in accordance with the kind and water content of the solvent and the operating conditions used. Usually, however, the purpose is achieved by adding the inhibitors first, e.g. Organic phosphoric ester, in an amount from 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 ^{a /} ", preferably 0.005 to 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 to achieve the desired effect.

It is of course to be understood that the amounts of these diluents are outside the scope of the invention are limited.

example

There are 70 parts by weight percent water-containing acetonitrile and 30 parts isoprene with a or more of the inhibitors given below are mixed, and the mixtures obtained are Reacted at 120 "C in the presence of Eisenox d. Di, · Properties of the products are checked, 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 h 1 no 100 Polymer stores Polvmer Sodium nitrite himself off deposit 2 no 100 becomes minor - p-lcri-butyl catechol 100 White - 3 no Phenyl - /? - naphth \ l- Polymer storage 4th no amine Polymer deposition polymer 0.5 no deposit rr 5 Triphenyl phosphate 1Γ0 slightly white clear' 0.5 Sodium nitrite 50 slightly 6th Triphenyl phosphate 0.5 Sodium nitrite clear White 7th Triphenyl phosphate ! 00 clear slightly
White 0.5 p-tert-butyl catechol 100 slightly 8th Triphenyl phosphate 1.0 Phenyl - /? - naphthyl- clear White 9 Triphenyl phosphate aiiiin 100 clear clear 0.5 Sodium nitrite 100 clear 10 Tricresyl phosphate 0.5 Sodium nitrite clear 11th Tris (4-tert-butylphenyl) - 100 clear clear phosphate 0.5 Sodium nitrite 100 clear 12th Tri (n) butyl phosphate 0.5 Sodium nitrite 100 clear clear 13th Tris (o-biphenyl) phosphate 0.5 Sodium nitrite clear 14th Diallyl phenyl phosphate clear

Example 2

In an extraction / distillation column with 100-stage plates, a C-hydrogen hydrogen fraction is added. which contains isoprene, introduced using a fractionation solution. that by means of additions. \ on 0.5 weight percent triphenyl phosphate ίΐηΊ 100 ppm sodium nitrite to acetonitrile, which contains 5 weight percent water, at a value (molar ratio) of 7: 1 of the (. "'-, - hydrocarbon! fraction has been produced. The mixture is continuously in the tenth stage of Kolonnensnitze introduced, and the column is operated at a Riickflußverhältnis of 5.0, a column peak temperature of 47 C ^r and a column Bodentcmncratur of 100 "C ^1. the extraction solution containing isoprene

is continuously reacted at the next stripping zone, and the recovered extraction solvent becomes dircki to the F. extraction pestillation column returned.

The operation will continue for a week, but the extraction solvent center shows! no changes and remains clear. When repeating the same process, but without adding triphenyl phosphate and sodium nitrite to the solvent, the solution starts to turn white and will turn out in 10 hours cloudy and leads to a polymer deposit that turns a light orange color in 20 hours.

Example 3

There are test solutions under the same conditions as described in Example 1 with the exception made that N-methylpyrrolidone as a solvent as well as the various inhibitors indicated below can be used. The corresponding Solutions are reacted in the presence of iron oxide with heating to 140 ° C. the ίο properties of the solutions are examined and the Results are given in Table II below.

Table II

No. It Polymerization inhibitor Weight 2. Inhibitors ppm Properties after heating 72 h ]. Inhibitors percent no 100 24 hours Polymer- 1 no Sodium nitrate Polymer deposition uni deposits 2 no becomes minor Polyiner 0.5 no White Ablaiicrunnen 3 Triphenyl phosphate 100 becomes minor clear ~ 0.5 Sodium nitrite White polymer 4th Triphenyl phosphate 0.5 no clear deposits 5 Tri (n) butyl phosphate 100 becomes minor clear 0.5 Sodium nitrite White 6th Tri (n) butyl phosphate similar attempts are made among the same 30 clear Example 4

using \ on dimethylformamide or dimethylacetamide instead of N-methylpyrrolidone as Solvent. In either case, the use of sodium nitrite only (100 ppm) results in the separation of the polymer in 72 hours, but if nairium nitrite (100 ppm) and Tii-n-butyl phosphate 0.5 weight percent are added, the test solutions remain clear 72 hours afterwards.

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 converted against iron oxide at 120 C. and examined the properties of the products. The results are given in Table Hi below.

Table III

Polymerization inhibitor

1. Inhibitors 2. Inhibitors

ppm state after heating
24 hours

48 h

no
no

no

no
Sodium nitrite

p-tert-butyl kaleine

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-PS 1146 195 and the present invention

parameter

Htfindunj,

Citation
(Example 6)

solvent

Monomer

Inhibitor

pressure
temperature
Results according to lOStd.
Stand

DMF

Isoprene (iron rust)

Triphenyl phosphate (5000 ppm)

3.5 kgf / cm ²
120 C

completely transparent (polymer yield 0.03 percent by weight)

DMF

Isoprene (iron rust)

m-Dinitrobenzo

(5000 ppm)

3.5 kp / crn ²

120 C

completely transparent

(Polymer yield

0.06 percent by weight)

fourth is the superiority of the inhibitors according to the invention.

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

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. Quantitatively, however, these are unmistakable on the basis of the polymer yields determined; the difference is clearly expressed and documented in the 100% higher yield of polyra

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 Citation (Example 11, Sample 8) solvent DMF DMF Monomer Isoprene (iron rust) Isoprene (Iron rust) Inhibitor Tri-n-butyl Λ-nitroso- phosphate / J-naphthol (5000 ppm) (10,000 ppm) NaNO ₂ (IOO ppm) pressure 3.0 kg / cm ² 3.0 kg / cm ² temperature 150 ° C 150 ⁰ C Results after transparent "practical 18 hours standing transparent"

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-butylphosphate Isoprene (iron rust) N-methylpyrro- Inhibitor Tri-n-butyl phosphate (1.0%) N-methvlovrrolidone 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 kgf / cm ² pressure 3 kgf / cm ² 150 ⁰ C 2 kp / cm ^a 150 ° 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 used in the same amount as the inhibitor of the reference, findei there is a significantly lower polymer formation than in the case of the citation.

The above comparison tests show that the he

inventive inhibitors are superior to the previously known agents. Stabilized isoprene Solutions form less polymer, which means that more concentrated isopic solutions may be less Lends to be able to store less polymer formation

nen.

Claims (1)

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