DE1272281B - Process for the preparation of mixtures containing o-, m- and p-terphenyl isomers - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CI .:

C07c

German class: 12 ο -1/01

Number: 1272 281

File number: P 12 72 281.5-42 (P 28625)

Filing date: January 17, 1962

Opening day: July 11, 1968

The invention relates to a new process for the production of terphenyl isomers; it concerns especially the preparation of mixtures containing the three terphenyl isomers in certain proportions contain.

In the German Auslegeschrift 1 012 595 is a process for the production of diphenyl by thermal conversion of benzene described, whereby the higher polyphenyls, which are formed in addition to diphenyl, all or some of the benzene to be reacted are added. This publication Like the B.I.O. S. Final Report No. 1787, Item No. 22, does not contain any indication that how an enrichment of one of the terphenyl isomers could be achieved.

According to the process of Italian Patent 602707 terphenyls be produced by pyrolysis of benzene at 750 to 850 ⁰ C, wherein the benzene to pyrolisierenden preferably 5 to 20% of diphenyl are added from the return line. The aim of the process described is to reduce carbon deposits and increase the yield of terphenyl. This patent gives no indication of how one can vary the content of individual terphenyls in the terphenyl mixtures.

Of the various uses of the terphenyl isomers, most important at present is for heat transfer. However, the application is often limited by the relatively high melting point (150 ⁰ C) of the most commercially available mixtures, which are obtained directly from benzene by pyrolysis and which consist of 10 to 15% o-terphenyl, 60 to 66% m-terphenyl and 20 to Compose 30% p-terphenyl.

The temperature of onset of crystallization of the Terphenylisomergemische depends primarily on the content of p-terphenyl, whose melting point is 213 ° C compared to 56 ° C for o-terphenyl and 87.5 ⁰ C. for m-terphenyl. For this reason the o-terphenyl-rich mixtures have very low melting points. With the eutectic mixture of o- and m-terphenyl you can even reach a melting temperature of 29 ^° C.

It is of course of great interest to work with a mixture whose melting point is below the The boiling point of the water. Mixtures have been produced that are poor in p-terphenyl. This could can be achieved by crystallizing the highest melting point isomer in a solvent. One also has p-Terphenyl removed from such mixtures by distillation.

Process for the production of o-, m- and
mixtures containing p-terphenyl isomers

Applicant:
Progil, Paris

Representative:

Dr. D. Morf, patent attorney,

8000 Munich 27, Pienzenauer Str. 28

Named as inventor:

Maurice Jaymond, Lyon, Rhone (France)

Claimed priority:

France of January 18, 1961 (849 972)

However, these known processes lead to by-products which are difficult to use and which arise from p-terphenyl or a large fraction rich in p-terphenyl.

One could also isomerize p-terphenyl in the presence of aluminum chloride. The cost of this however, additional treatment markedly increases the cost of the terphenyl production and treatment also leads to contamination of chlorine and aluminum in the end product.

In contrast to the known methods mentioned above, the invention enables, starting from Benzene, the production of terphenyl mixtures with certain proportions of each of the isomers. The inventive Process is for the preparation of mixtures of o- and m-terphenyl isomers, which are poor in p-terphenyl, are suitable. Thus, the method of the invention makes any post-treatment obtained directly from the benzene and z. B. for heat transfer in various devices usable certain mixtures unnecessary. The new process is therefore much less complex than the previously known methods and also allows a considerable simplification of the necessary Manufacturing facilities.

The process of the invention for the preparation of mixtures containing o-, m- and p-terphenyl isomers by pyrolysis of a mixture of benzene, diphenyl and higher polyphenylene at 550 to 900 ⁰ C in the vapor phase, the flow

809 569/561

3 4

speed in the pyrolysis zone on Reynolds compounds that are formed during pyrolysis, such as

Numbers from 10,000 to 500,000 is set as it is explained below.

characterized in that, for the preferred preparation, the reaction is carried out at a temperature or

certain terphenyl isomers a mixture of temperature sequence between 550 and 900 ° C preferably

70 to 80 parts by weight of benzene, 20 to 30 parts by weight 5 carried out between 700 and 850 ° C.

parts of diphenyl and 0.5 to 10 parts by weight of one. Preferably prevails in the one to be pyrolyzed

or two terphenyl isomers, the formation of which produces a turbulent flow with a Reynolds

prevents or is to be reduced, as a starting number from 10,000 to 500,000.

Sending used. An important application of the invention is that

According to another embodiment of the invention, the preparation of mixtures with variable p-terms Process, it is advantageous to the phenyl content of the pyrolysis. You can actually see the proportion of the The mixture to be subjected also to polyphenyl compound p-terphenyl in the feed to the reactor add fertilizers which change in the course of the pyrolysis, so that the immediate production of all Isobilden, Mixtures of mers with 5 to 20% o-, 55 to 95% m- and

The process of the invention arises from the 15 0 to 40% p-terphenyl, especially of mixtures with

surprising finding that the content of an 8 to 16% 0-, 75 to 90% m- and 0 to 4% p-ter-

given isomers in the pyrolysed vapor phase phenyl becomes possible. Such mixtures melt

changes very little if this isomer is already below 8O ⁰ C.

the vapor phase to be subjected to pyrolysis. According to the method of the invention,

is present. The presence of an isomer does not constitute a mixture rich in o-terphenyl

Hindrance to the formation of the other isomers. and their melting points are therefore the lowest

So if you are out of the way with the feed to the reactor. For this it is necessary to use the whole or

Benzene and diphenyl make up a percentage of a portion of the p- and m-terphenyl isomers

Terphenyl isomers fed in and the pyrolysis withdrawn under the same pyrolysis tube, again

If known conditions are carried out, the 25 can be added to the mixture to be pyrolyzed.

Prevent the formation of this isomer. Mixtures of the following composition are obtained:

This shows the advantage of the method of

Invention, especially when using 40 to 90% o-terphenyl,

p-terphenyl was applied; namely, it allows 10 to 50% m-terphenyl,

an almost exclusively composed of m- and o-terphenyl 30 0 to 5% p-terphenyl

standing product without significant content of,

p-Terphenyl to prepare in a simple manner. ^{and in advance}

It goes without saying that the process of 60 to 80% o-terphenyl,

Invention to each or even to two of the 20 to 35 ⁰ I m-terphenyl

three isomers can be used. Will m-ter- 35 qy _s 3 0 / p-terphenyl. '
phenyl introduced into the mixture to be pyrolyzed,

so the formation of this isomer is quantitatively Such mixtures begin below 50 ⁰ C.

reduced or practically prevented. The formation of crystallize.

o-Terphenyl is reduced if this connection is made, although different embodiments are used added to the initial mixture. On the other hand, turn 40 and put it in the pyrolysis tube earlier the formation of o-terphenyl is increased when it is diphenyl and terphenyl, especially p-terzu pyrolysing mixture at the same time m- and p-terphenyl, which from processes other than that of the contains phenyl. present invention originates, can introduce,

The in the starting mixture of benzene and is the device by recycling the Diphenyl amount of a terphenyliso- 45 all or part of that to be introduced in the course of the Hermeren depends on the position to be formed by the reaction isolated diphenyls and p-terphenyls and desired amount of this isomer. It's easy.

Formation of this isomer is undesirable, so the one in the drawing is a diagram of a fabrication amount to be supplied approximately equal to the amount of this plant according to the method of the invention is shown. Isomers which a Kozogenen Terphenylisomerengemisch is present in the off from the reaction zone 50 Here, A represents the pyrolysis tube, B. lonne for the separation of benzene and diphenyl,

In commercial operation C is of course a column for separation of the o- and m-ter-

the addition of the selected isomer (s) to the phenyl isomer and D a column for separation

The pyrolysis tube is charged by adding the heavy components again, with p-terphenyl am

or return an appropriate frac- 55 head escapes while the residue is below

tion causes which are deducted from the separation of the by the.

Reaction products formed by pyrolysis originate. When the plant is in operation, benzene passes through 1 to

In the method of the invention, the pyrolysis tube A contains this. At the same time, line 2

Mixture to be subjected to pyrolysis 70 to 80 Ge is a mixture of benzene and diphenyl, which from the

by weight of benzene, 20 to 30 parts by weight of diphenyl 60 originates from the upper part of the separating column B, into the

and 0.5 to 10 parts by weight of a selected ter pyrolysis tube introduced. Furthermore, a certain

phenyl isomers or a mixture of two from the amount of the from the upper part of the separating column D

selected terphenyl isomers. When the introduced p-terphenyl escaping through line 3 into the

Terphenyl is the p-isomer, the feed pyrolysis tube is initiated.

mixture preferably from about 75 parts by weight 65 The pyrolysis tube consists of a reaction benzene, 25 parts by weight of diphenyl and 1 to 5 parts by weight of suitable materials, be it from pipe parts by weight p-terphenyl and, if appropriate, bundles or from a single pipe. The second all or part of the higher polyphenyl solution is preferable because it enables the achievement of a

high flow rates of the gases corresponding to Reynolds' numbers is essential to achieve the best performance conditions.

A particularly advantageous form of the pyrolysis vessel A consists of a single pyrolysis tube which is provided with a number of hairpin-shaped angle tubes which are cylindrical and are heated with electrical resistors or in some other way. In a particularly practical way, the heating takes place from the outside of the cylinder formed by the angled tube in order to achieve an even distribution of the heat. A very specific temperature gradient is maintained from the entrance to the exit of the above-mentioned pyrolysis tube.

The converted or unconverted products leave the reactor through line 4 and enter the distillation column B, from the upper part of which benzene and diphenyl escape to flow back through line 2 into the pyrolysis tube. At the bottom of column B , the terphenyl isomers and the heavier products are drawn off, which are then passed through line 5 to column C, where the m- and o-terphenyl isomers are separated off.

Device C can be a distillation column in which the m- and o-terphenyl isomers are obtained at the top. But it can also be a crystallization vessel for fractional crystallization. In any case, p-terphenyl, the higher polyphenyls and the tars leave this column through line 7 and are separated from one another in separating column D.

This last column can be adjusted so that the higher polyphenyls and tars, and the p-terphenyl at the top, are separated off in outlet 8. The regulation can also be such that only the tars are separated in the process and p-terphenyl escapes at the top together with higher polyphenyl compounds (four to five phenyl rings), which are then returned together through line 3 to the pyrolysis tube A.

The recycling of the higher polyphenyl compounds has two advantages: The recycled Mixture has a lower melting point than p-terphenyl alone. In addition, the yield will increase the desired reaction products are significantly increased, since the heavy constituents are thermally decompose and produce significant proportions of substances of lower molecular weight.

If you do not want to return the entire amount of the substances escaping at the top of columns B and D , 2 and 3 taps are attached to the pipes for discharging the compounds in question.

If the main interest of the process is directed to the production of p-terphenyl, the tube 6 carrying the o- and m-terphenyl isomers is connected to the feed tube of the pyrolysis tube A and the p-terphenyl is removed at the top of the separating column D.

example 1

A mixture is obtained through a knee tube reactor, which is heated to 785 ° C. and described above Benzene, diphenyl and p-terphenyl vapor passed. The diphenyl content is regulated so that this Compound is not consumed by the pyrolysis. The residence time of the vapors in the heated pipe is 5 seconds.

The following table gives the compositions of the starting steam mixtures and the Terphenyl mixtures and the yields from four experiments:

Attempt no. benzene [C t]
p-terphenyl 0 Preserved Terphei
[Weight percent
I ^m lyle
t] P. yield
I ⁰ Io] I. 75
76
73 O
0.68
1.5 11.6
10
15th 28
25th
8th 80
79
77 π 73.5 2.7 13th 1 75 III feed
weight percent
Diphenyl 60
60.5
77.7 IV 25th
23.3
25th 86 24

Example 2

In the same device as in Example 1, ^{an experiment according to Example 1 is carried out at 785 °} C. and a residence time of 7 seconds, but in which the higher polyphenyl compounds (such as tetra-, penta- etc. polyphenyls) are returned to the starting charge. This gives yields of 85 to 90 ° / _0th

Example 3

There are attempts I carried out in accordance with Example 1 to IV, however, at 75O ⁰ C and a residence time of 10 seconds. The following results are obtained:

attempt
No.

C ₈ H ₆ (C ₆ H ₅ ),

Charge, weight percent

Heaviness
Components

p-terphenyl

Terphenyl isomers
in the reaction product

Heavy products
in the reaction product

0 / / 0

Exploit

78

76.5

76

74

22nd 22nd 22nd 22nd

1.5
0

0 0

2 2

(25 ° / ₀ para-containing)
5.5 (with less than 2% para-)
5.8 (containing 25% para)
6.1 (with less than 2% para-)

1.5
2.2
0.5

1.5

77
71.5
92
80

The content of p-terphenyl and heavy components in the product formed is in each case expressed after deducting the content of these substances in the feed mixture.

Example 4

As in Example 3, experiments V to VII are carried out at 830 ° C. and a residence time of 3 seconds executed. The results are as follows:

attempt
No.

C ₀ H ₆

Charge, weight percent

Heaviness
Components

(C ₆ H ₅ ),

p-terphenyl

Terphenyl isomers
in the reaction product

Heavy products
in the reaction product

Exploit

72
68
63.5

28
28
28

4th
3.5

0 0

(Containing 30% para)

(5 ° / ₀ para-containing)

(Containing 5% para)

10

Claims (4)

Patent claims: 1. Process for the preparation of mixtures containing o-, m- and p-terphenyl isomers by pyrolysis of a mixture of benzene, diphenyl and higher polyphenylene at 550 to 900 ° C in the vapor phase, with the flow velocity in the pyrolysis zone based on Reynolds numbers is set from 10,000 to 500,000, characterized in that for the preferred preparation of certain terphenyl isomers, a mixture of 70 to 80 parts by weight Benzene, 20 to 30 parts by weight of diphenyl and 0.5 to 10 parts by weight of one or two Terphenyl isomers, the formation of which is to be prevented or reduced, as a starting charge used. 2. The method according to claim 1, characterized in that the mixture to be pyrolyzed also contains all or part of the polyphenyls which normally occur in the course the pyrolysis form. 3. The method according to claim 1 or 2, characterized in that the mixture to be pyrolyzed about 75 parts by weight benzene, about 25 parts by weight diphenyl, and 1 to 5 parts by weight Contains p-terphenyl. 4. The method according to any one of claims 1 to 3, characterized in that the pyrolysis in a single tube, which is a series of consecutive, cylindrically arranged Has knees, makes. Considered publications:
German Auslegeschrift No. 1 012 595;
Italian patent specification No. 602 707;
BIOS, Final Report No. 1787, Item No. 22. 1 sheet of drawings 809 569/561 7.68 © Bundesdruckerei Berlin