DE1249244B - Process for the production of terphenylene by pyrolysis of benzene-diphenyl vapors above 700 ° C - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07c

German class: 12 ο -1/01

Number: 1 249 244

File number: P 28364 IV b / 12 ο

Filing date: December 5, 1961

Opened on: September 7, 1967

The production of diphenyl by the pyrolysis of benzene has been carefully studied. One has carefully determined the conditions by which the formation of by-products to the minimum is reduced; these by-products are in particular coke, tars and higher polyphenyls. These last products include the terphenyls (also called triphenyls) mixed with Tetraphenylene and other polyphenylene, in such proportions that their separation does not occur is economical.

On the other hand, it is known that the cracking of diphenyl after the reaction indicated below leads to the formation of three isomers of terphenyl:

2 Cj ₂ H ₁₀ ^ C ₆ H ₆

(X)

However, such a production method is uneconomical, since one is from an expensive starting product goes out and the yields are not good.

Those promulgated filed the Italian Patent No. 602,707 describe the preparation of terphenyls by pyrolysis of benzene containing 5 to 30% of diphenyl at a temperature of 750 to 85O ⁰ C and heating times in the pyrolysis zone, which as below 5 seconds lying calculated. The examples of this patent show that the process disclosed there does not succeed in keeping the amount of diphenyl at the inlet and outlet of the pyrolysis tube approximately constant because either additional diphenyl is always formed or the originally added diphenyl is consumed.

The German Auslegeschrift 1 012 595 describes the production of diphenyl by pyrolysis of Benzene and also teaches how the yield of higher homologues of diphenyl can be suppressed can.

The process according to the invention for the production of terphenylene is independent of the production from diphenyl or another compound; it enables the terphenyls to be obtained in good quality Yield, in any desired amount and with little formation of by-products.

According to the new process, the pyrolysis of a mixture of benzene and diphenyl is carried out under conditions which favor the formation of a high content of terphenylene; the pyrolysis is preferably conducted in such a manner that the Ter-process for the preparation of terphenyls by pyrolysis of benzene-diphenyl-vapors above 700 ⁰ C.

Applicant:

Societe Progil, Paris

Representative:

Dr. D. Morf, patent attorney,

Munich 27, Pienzenauer Str. 28

Named as inventor:

Maurice Jaymond, Lyon (France)

Claimed priority:

France of December 10, 1960 (846 580) - -

phenyls only from the benzene present in the mixture according to the equation

3C ₆ H ₆ = C ₁₈ H ₁₄ + 2H ₂ (2)

can be obtained.

The process according to the invention for the preparation of terphenylene by pyrolysis of benzene-diphenyl vapors which contain up to 30 percent by weight of diphenyl above 700 ^° C. is characterized in that a gaseous mixture of 80 to 70 percent by weight of benzene and 20 to 30 percent by weight of diphenyl is carried out a pyrolysis zone passes, the mean temperature of which is 700 to 750 ° C., the residence time of the mixture in this zone being 10 to 50 seconds, the gaseous mixture emerging from the pyrolysis zone liquefies and the terphenyls separated from the liquid obtained.

The F i g. 1 and 2 indicate how the content of terphenyls formed depends on the amounts of diphenyl in depends on the pyrolysis mixture at different temperatures and heating times.

These figures explain part of the experiments which led to the method according to the invention.

In Fig. 1 on the ordinate are the percentages by weight of the constituents of the mixture after the reaction and on the abscissa the heating times (i) of the pyrolysis vapors in seconds, which are the residence times the pyrolysis vapors in the pyrolysis tube.

709 640/556

3 4

The curves labeled D, T and L show that the inlet temperature is preferably 600 to 700 ° C

respective percentages by weight of diphenyl (D), and the outlet temperature 750 to 820 ° C.

Terphenylenes (T) and heavy compounds (L), as shown above, is an important characteristic

special tetra and other polyphenyls !!, according to the invention in that a mixture of

pyrolysis. 5 Benzene and Diphenyl used, but among such

Dl, Tl and Ll relate to the pyrolysis under conditions that only the benzene of the pyrolysis

850 ° C, £ »2, Tl and Ll is subjected to pyrolysis at 785 ° C and gives terphenyls,

and D 3, T3 and L3 on the pyrolysis at 750 ° C. According to the invention, mixtures of 70 to

The curves of FIG. 1 enable 80% benzene and 30 to 20% diphenyl for medium

the best temperatures of 700 to 750 ^° C. and heating times to be used in each individual case

Diphenyl content, that is the content that is used from 10 to 50 seconds,

does not fluctuate during pyrolysis. This is precisely the importance of careful steering of the

that content which gives the best degree of diphenyl formation in the vapors to be pyrolyzed

of terphenylene only from that in the mixture is explained by the fact that outside the

existing benzene leads. 15 cheapest proportions the above implementation (2)

It can be seen from the curves Dl and Tl that one is accompanied by secondary reactions. If for example

excess diphenyl is present at a temperature of 785 ^° C. when heated, so

duration (t) of 2 seconds a concentration of becomes part of the diphenyl after the reaction (1)

20.5% diphenyl pyrolysed to terphenylene to obtain 3.5% terphenyl. This consumption at

phenylene needed; if heated for 10 seconds, 20 expensive diphenyl is not economical,

you need a concentration of 26.5% di- If, on the other hand, there is not enough diphenyl available

phenyl, the content of terphenylene formed being present, is disadvantageous as a result of the pyrolysis

9% achieved. the yield of terphenylene produces this compound.

From the results that can be derived from the figure, this shows how advantageous the use of

the inclination of curves D is pointed out, lines 25 are mixtures whose diphenyl content is as close as possible

merge parallel to the abscissa; mitandereiiwords, the salary that is paid during the

the most favorable diphenyl content in the pyrolysis mixture does not change pyrolysis. If you lead the inventive

tends, for a given temperature, to be constantly following proper procedures in this way

will. Furthermore, the degree of formation of terphenyls increases only from benzene, while di-

phenylene fairly quickly with the heating time, 30 phenyl is neither formed nor consumed,

while the divergence between the levels of Another important factor of the method is the

terphenyls formed and those of the heavier duration of the pyrolysis, their influence on the yield

Connections, at least below 850 ⁰ C increases. can be seen from the figures described above.

In Fig. 2 are again percent on the ordinate. The heating times are in the range from 10 to

levels applied in weight while on the 35 50 seconds. This factor is, as shown above, with

The abscissa shows the pyrolysis temperatures. other factors, namely temperature

Two sets of curves are shown; D5, T5 and the diphenyl content. If for one

and L 5 give the diphenyl contents, terphenylene given diphenyl contents the temperature too low

and heavier compounds in percent by weight or the heating time is too short, the

as a function of the temperature for a constant 40 present diphenyl, which is thus consumed

Heating time of 5 seconds again; the series is formed, terphenyls. On the other hand, if for

Dl, Tl and Ll correspond to a heating time of a given diphenyl content the temperature

of 7 seconds. high or the heating time is too long, a

Here, too, it is shown again that the most favorable part of the benzene is converted into diphenyl and so on

Levels of diphenyl - curves D5 and Dl - on 45 not for the formation of terphenyls, but for others

run towards a constant value. A comparison is used up for purposes.

between curves TS and L 5 or Tl and Ll. With the process according to the invention, one can conclude that the degree of formation of the terphenyls, degrees of conversion of benzene into terphenyls, increases with the temperature, which is more favorable. 5 to 18% with the corresponding yields of 75 to at a temperature below 85O ° C, preferably 50 60% can be achieved, depending on duration of the heating and sequentially lower half 800 ⁰ C, to work to the lowest overall properly depending diphenyl content in Pyrolysedampf, hold on to heavier compounds in the reaction. The preferred embodiment of the process to obtain product. Thus, particularly if the is that the mixture of benzene-temperature passing a value of 75O ⁰ C does not exceed 55 oxidizable or heat-resisting steel at a heating time of more than and Diphenyldämpfen by a tube of not exceed 10 seconds proceeds, the weight ratio of polyphenylene produced inside a chamber to terphenylene to fall below 0.25 which is heated electrically or by hot gas. After leaving the pipe, the steam is

The conclusions from the figures allow a condensed form. After that the ingredients are through

the determination of the best process conditions 60 distillation separately. Be benzene and diphenyl

for the large-scale production of terphenyls after separation of the terphenyls and the heavy ones

according to the method according to the invention. Connections returned to pyrolysis. The disconnection

Very satisfactory results can also be obtained by fractional condensation of the

if you made the mixture of benzene and diphenyl steam leaving the pyrolysis tube

vapor through an area, generally a pipe 65.

conducts, which at the inlet end to a temperature of The invention is illustrated using ten examples,

450 to 750 ° C and at the outlet end to a temperature. Numerical results are shown in tabular form.

temperature of 750 to 900 ⁰ C has been heated. Can be specified.

The temperature of the steam is used for entry (A) into the pyrolysis tube and exit (B) indicated from the pyrolysis pipe. The arithmetic mean (C) of these two temperatures also becomes cited.

The residence time (R) is the time it takes for the vapors to pass through the pyrolysis zone need, this time is the heating time.

The composition of the steam treated, i.e. the pyrolysis mixture, is expressed in Weight percent benzene (E) and diphenyl (F) in the mixture.

The consumption of benzene (G) and diphenyl (H) are shown separately. This enables the knowledge under what conditions only benzene is the starting material for the formation of terphenyls represents. These consumption figures are in percent by weight of the amount originally imported Connection specified.

On the other hand, "formed diphenyl (J)" means the degree of conversion of benzene into diphenyl, when the latter compound is formed alongside terphenylene.

The term »formed terphenyls (K)« refers to the percentage of terphenyls obtained, related the weight of the material from which they are formed, d. H. based only on diphenyl (examples 1 and 2), only to benzene (Examples 4 to 10) or based on both compounds (Example 3). These Of course, the data only relate to a single passage of the steam through the heated tube without repatriation.

The yield of terphenylene (Y) is calculated from the amount of starting compounds actually consumed. This value is therefore equal to the quotient from the amount of terphenylene formed (K) and the consumption of benzene (G), diphenyl (H) or both compounds, multiplied by 100.

example

3 4th 5 6th 7th 8th 9 700 700 750 660 680 680 800 790 790 850 755 790 790 820 745 745 800 707 735 735 810 10 15th 15th 50 20th 40 3 65 80 80 78 73 72 100 35 20th 20th 22nd 27 28 . 3.5 12.6 27.5 9.3 11.5 21 15.3 14th - - - - - - - 4.4 8.7 - - - 12th 5.4 5.75 11.3 6.5 7.5 12.6 1.8 75 70 60 70 65 60 12th

Reaction conditions:

Temperature ( ⁰ C)

at entry (A)

at the exit (B)

mean temperature (C)

Dwell time in the zone (seconds) .. (R)

Composition of the pyrolysis mixture

Weight percent

Benzene (E)

Diphenyl (F)

Results:
Consumption (%)

Benzene (G)

Diphenyl (H)

Formed D iph enyl

__. _{ιυυ (J)}

Formed terphenyls

(E) and / or (F) ' ^1W

Yield of terphenylene based on

Consumption - ^ - Φ-ϊ — does ^-10 ° ■
(G) and / or (H)

650
750
700

700

760

730

12th

- 100

12th

14th

50, 800

820

810

Example 1 in the table relates to the production of terphenylene only from diphenyl, that is to say in its absence of benzene. This example is given for comparison with Examples 2 to 8, which relate to embodiments in which one starts from mixtures Runs out of benzene and diphenyl.

The comparison shows that the results are much better when using mixtures of benzene and Diphenyl used instead of diphenyl alone.

In Examples 1 and 2, the terphenyls are prepared from diphenyl, in Example 1, in which absolutely no benzene is used to obtain 6% terphenyl, with a yield of 50 ° / _0, based on diphenyl; in example 2, these values are 14 and 70%, respectively, because of the high benzene content in the pyrolysis mixture.

In Example 3 it is interesting that 35 ° / ₀ diphenyl (F) in the starting mixture is too much for the temperature and time used there. In fact, 14% of diphenyl (H) is converted to terphenyls under these conditions, compared to only 3.5% converted benzene (G).

In contrast, the amount of 20 ° / ₀ diphenyl (F) in Examples 4 and 5 is too small, since the pyrolysis is 4.4 or 8.7% undesired Diphenyl (J).

Examples 6, 7 and 8 show embodiments according to the invention. Here it becomes clear that indeed a constancy of the diphenyl content (F) - 22, 27 and 28% - exists, which during pyrolysis neither increased is still consumed. The terphenyls are only made from benzene, an inexpensive starting material, educated. The content of terphenylene (K) produced is 6.5 to 12.6%. The yields are 70 to 60%. Incidentally, the contents can be 18% and the yields 75% under such conditions reach.

In contrast to the preceding examples according to the invention, Examples 9 and 10 relate to production processes at very high temperatures (towards 820 ^° C.) with very short pyrolysis times of 3 and 5 seconds, respectively. In Example 9, only benzene vapor without diphenyl is used. The yield of terphenylene (Y) is therefore very low and is 11.9%. In Example 10, due to the presence of 20% diphenyl in the starting mixture, the yield of terphenylene (Y) is very much better (42.5%) than in Example 9, but lower than the yields of the
play 6 to

procedure
8th.

the case of the invention

Claims (1)

Claim: Process for the production of terphenyls by pyrolysis of benzene-diphenyl vapors which contain up to 30 percent by weight of diphenyl above 700 ^° C., characterized in that a gaseous mixture of 80 to 70 percent by weight of benzene and 20 to 30 percent by weight of diphenyl is passed through a pyrolysis zone conducts, the mean temperature of which is 700 to 750 ^° C., the residence time of the mixture in this zone being 10 to 50 seconds, the gaseous mixture emerging from the pyrolysis zone liquefied and the terphenyls separated from the liquid obtained. Considered publications:
German Auslegeschrift No. 1 012 595;
announced documents of the Italian
tents No. 602 707. 1 sheet of drawings 709 640/556 8. 67 © Bundesdruckerei Berlin