DE1568204C - Process for the production of un substituted aromatics of high purity - Google Patents

Description

will. Today's requirements; to the purity The space velocity in the case of the

of industrially produced benzene, which is a refining equivalent to benzene, is generally 2 to 10 kg with, a solidification point of 'above 5.50 ° C., a reaction product of the dealkylation stage per liter with a content of more than 0.05 per liter - catalyst and hour; as a technically particularly vorzent in other compounds in benzene. It consisted of 5 space velocities of 3 therefore the task of following the reaction zone of up to 6 kg / l / hour. proven.- · ν ^ _; i *: -., · dealkylation ■ still ■ · existing low levels in the individual leads to hydrogenate Verungesättigter compounds of the invention selectively to ^one such drive. B. in such a way that the aromatics present in the dealkylation without the gaseous reaction products leaving the reactor leaving the dealkylation are attacked. This io by heat exchange on a task for refining can according to the invention; cools down by the -special suitable temperature and directs a downstream second reactor directly via a combination of a dealkylation stage with a downstream, ¹ in the downstream mild, hydrogenating refining- the refining reaction takes place; After - further stage to be solved. Such a solution can neither be inferred from the cooling by means of a heat exchanger and cooler. Neither are gas and liquid separated from one another; even with knowledge of this state of the art for the gas is completely or partially, if necessary, been obvious to a person skilled in the art. '' after hydrogen enrichment through low temperature

Furthermore, it could not be foreseen that there would be temperature decomposition as cycle gas in the entalkylie would be returned to today's high-purity reactor. You liberate the liquid Changes regarding the non-aromatic content in ao reaction product after expansion to a Zwi-Benzene to be fulfilled by the hydrogenation of the pressure in a stabilizing column of dissolved, Benzene to cyclohexane even in the ppm range under gaseous constituents and works the reduction could be. In addition, through action product after further relaxation the inventive combination of entalkyly fractional distillation on pure aromatics. ration stages with downstream mild refining as The procedure according to the invention, according to which the the previously obligatory bleaching earth hand refining in the cooling route of the Hydroentalkylielung not required after the dealkylation stage. execution does not require any additional

The invention relates to a process for heating and evaporation processes and not a high additional hydrogen source for the production of unsubstituted aromatics. As a result of the very low purity due to dealkylation of alkyl-substituted amounts of unsaturated compounds in the reaction aromatic in the presence of hydrogen with increased "product of dealkylation, the hydrogen conversion temperatures and pressures and post-refining the need for their hydrogenation is very low, so that reaction products of dealkylation, characterized that the composition of the recycle gas is characterized by, that the reaction products refining undergoes no substantial ^change:; "the. Dealkylation together with the cycle gas 35 The space velocity for the refinement of dealkylation and without prior separation of the reaction can be selected to be very high and in this way gaseous and liquid fractions below the level of the catalyst volume required for the refraction pressure of dealkylation at temperatures can be kept very small, for example from 50 to 350 ° C. and space velocities of tenths of the reaction volume of the dealkylation. 2 to 10 kg of reaction product per liter of catalyst 40 It is therefore also possible to use the catalyst for and hour dealkylation over metals, oxides and / or sulfides and for refining spatially in metals of VI. and VIII. Group of the Pen to combine a reactor, if, for example, by Abodic system as catalysts, hydrogenating refined cooling with cold gas or liquid product or ned, after separation of the dealkylated by installing a heat exchanger for this. Pure aroma materials which are not converted and which ensure that the dealkylated reaction product, secondary reactions, is partially cooled or is cooled to the refining temperature, which is lower than the dealkylation temperature ... completely returned to the dealkylation stage. ^:. '''In the hydrorefining of Entalkylie-.

As catalysts for the hydrogenating refining products, in addition to the desired occurrence of metals, oxides and / or sulphides from hydrogenation of the unsaturated compounds, one of the 6th and 8th groups of the Periodic Table must be desired (under the reaction conditions: the catalytically active compodynamically favored) hydrogenation of aromatic substances on carriers such as active clay, materials that are applied during distillation or similar substances, are advantageously avoided. Catalysts have proven to be particularly suitable for working up the dealkylation products to one of these, which lower the solidification point of the Reiriaro sulfides and / or oxides of cobalt and molybdenum and / or lead to yield losses. Sp ver _r included. '..'- .. causes, for example, a cyclohexane content of 0.1 weight

In many cases it is also possible for the refining percentage in benzene to already have a Gefrieφunktserniedriden same catalyst as for dealkylation,, supply around 0.066 ° C. With the invention z. B. a catalyst, the chromium oxide and potassium 60 working method surprisingly succeeds containing oxide on alumina. with complete saturation of the sulfur

The hydrogenating refining according to the invention is acid-resistant and harmful olefinic compounds follows, depending on the choice of catalyst, in a hydrogenation of the pure aromatics to be produced to keep the correct range within the temperature limits low, that neither yield nor melting of 50 to 350 ° C. If sulfidic or oxy-point 65 of the pure aromatics are mechanically influenced, If the catalysts are used, the hydrogenation is expediently carried out by hydrogenating the unsaturated mixture at temperatures between 150 and 350 ° C, bonds are formed preferably between 200 and 300 ° C., on the other hand, when producing pure aromatics by distillation

not noticeable because they are present in very small amounts; : " _: .. · .; - v.-.-. V .-"; .-: ■ ". ■; ■. '." ...

On the other hand, undesirable higher aromatics, which are formed as by-products during dealkylation, for example, are hydrogenated. In the dealkylation of z. B. toluene is formed by side reactions in an amount of about 1 to 2 percent by weight, based on benzene produced, higher boiling hydrocarbons than toluene, the majority of D> phenyl, alkyldiphenylene and fluorene, but also from ring-condensed polynuclear aromatics, such as Naphthalene, anthracene, phenanthrene, pyrene, benzperylene »fluoranthrene and others exist. When this high-boiling residue is recycled together with the unreacted toluene, diphenyls and fluorene are split up again with an increase in the benzene yield; In this case, however die.mehrfach condensed aromatics accumulate, so ^that: Part of the residue needs to be removed from the system, to keep stationary the composition of the residue. As a result of the hydrogenating aftertreatment, the amount of high-boiling polynuclear aromatics is reduced considerably, sometimes by more than one pot. In this way, depending on the dealkylation conditions, it is possible to reduce the residue boiling over toluene without causing a Teflstront; must be removed from the system j. or the amount of this substream is significantly reduced compared to a procedure without additional aftertreatment, so that overall there is an increase in the yield of benzolate.

Feraer wkd the amount of the high molecular weight carbonaceous compound fertilizers deposited on the Ental & yKerungskatalysator when using the h-ydneiende; Itaehbehaadruag noticeably less than dme this, because with the hydrating; Nachrefinatiort prefers the highest level. zu, further cond ^ n! - = sation ^ gfffiiea mehEkerattgea aromatics, hydrogenated werderi ... ; ..: '. _{;! :} -: '\ _i: '_iP;. ". ■:. · ... .-. ■ * ;. '. ■ ·.: ■■ -: _-. · ,. ·' - ■ '■'^■; - ^';.;' * '! example' ■■ '■;' ■ '':

Ia efetfif adjtab ^ tischßri VersuehsappaEatur with Ga & - circuit and with a Katelysatoi volume of $ Μ \ '; an insert tojuoi with the following properties

Teiuoi ^. ".; ^". ;; "_; 99.45 ° / » Dimethylcyctohexatt and i

Ethylpyciohcxane. "". " (^ 43 ¹ Ve

Benzene "._._:". % O6 «/ o

Metylhcptart "...". OiOd ⁰ / * -

Specific weight / 15 ° e: O, 86 &

Bromzabl ... "..". "". ' Bmg / 10Qmli

under the following operating conditions; Catalytically dealkylated over a catalyst which contained 10 percent by weight Cr ^ Oj, and O ^ weight percent K ₂ O - on clay, catalytically dealkylated: total pressure 60 at, hydrogen partial pressure 30 at, increasing temperature 570; up to 630? Q space velocity over the catalyst. O ^ kg of toluene per liter of catalyst and hour. The fresh gas used was 99 ° / (tiger hydrogen, the partial pressure of hydrogen was set by means of a corresponding expansion of the circulating gas.

A sample of the taken from the pressure separator The reaction product contained 70 percent by weight benzene and 29 percent by weight unreacted toluene and 1 percent by weight of a residue boiling over toluene.

The reaction product is then in a Column separated into gaseous fractions, a benzene fraction and a toluene residue. The properties column 1 of table 1 gives the benzene fraction

'5 Again .. ■■. · - ■■: · ■; ■. · ■.: ■■■■ ·; ■■']: ■ ... '■■. ■> - ■ ·: .-: ; ::. · ■>-;;;;. · :: C- \

In the same apparatus, but in the dealkylation reactor. Intercooler wad \ a second reactor with a; Catalyst volume yaa. 1 liter using a catalyst that

If it contained 4 percent by weight CoO and 10 percent by weight MoO ₃ , the same toluene was dealkylated under the conditions specified above. The gas-vapors mixture leaving the first reactor was in general fed to the intercooler

iS a temperature of 260 ° C and cooled over the second reactor passed. The reaction products; were then processed as indicated above destölattV, the benzene fraction was obtained in practically the same yield. Your properties, there

sea column 2 of the table below.

Tabular - - '/

Bromzabl, mg / ΙΘΟ ml ...
Sulphuric acid test (ASTM
D 84 & 42). accordingly
Color distance no ..

Weight percent

- Cyclopenta ».........

Methyleyclopentart ....

Gyelohexaa ..........

Toluene .......

Beazolfraktipa .. '. ■ aas EntalkylieningspFodokt

Without next t With Naqfc -.;. rafßnatioQ {refining

40

4 to 5

0.03
0.02, '
99.8 »

Öbkl

0.03

0.05

It can be seen that there is the catalytic, hydrating post-treatment of the EntalkyEeiungspiiOr d »ktes the unsaturated: compounds: largely aBffeyd celebrates wewfert and thus also won benzene will; can, the aueb MosichtEcit de & Scawefefsäuretestes de »AafoEdeEungen · for a NiteieEbenzoI is equivalent to; (Better from. Color Standard No. ^ X Likewise Measures Table I to see that the proportion of non-aromatic compounds that

5 «resulting inadequate inconsistencies: is increased. The Qlefin saturation takes place very selectively without = noticeable dissolution of aromatics. ,!

Example 2

a, an isothermal ¥ ersuehsapparat jnifc gas circuit and a reaction volume of 200; mt using the same catalyst as in Example 1 at 50at total pressure (30at H _t -

6o. Pressure), a space velocity over the catalyst: from 0> 5 kg. Toluene per liter of catalyst and: hour and at a temperature of 590 ° C toluene dealkylated. The pale greenish colored reaction product contained 55% benzene, 44 ^β / α toluene and 1% a residue, the combined capillary gas chromatographic and UV spectrometric analysis of which is shown in the left column of Table 2 below.

1 568 204 7th Table 2 The

Alkylbenzenes

Naphthalenes + alkyl-

naphthalenes

Diphenyls + alkyl-

diphenyls

Fluorene

Anthracene

Phenanthrene

Fluoranthrene

Pyrene

Benzperylene

Hydroaromatics

without refining

12.1 5.0

61.6 15.6 0.46 3.75 0.58 0.84 0.02

with post-refining

12.2 4.5

61.5

15.3 0.02 1.60 0.03 0.003 0.004 4.8

entire reaction product (including residue) was then via a second isothermal experimental reactor, which was charged with 20 ml of the catalyst from Example 2, at 30 at Hydrogen pressure, a space velocity over the catalyst of 5 kg per liter of catalyst per hour and a temperature of 300 ° C. The reaction product was clear as water; the composition of the above The residue boiling in toluene is shown in column 2 of table 2.

The comparison of the residue analyzes with and with post-refining of the dealkylation products shows that the polynuclear aromatics, despite the relatively mild refining conditions, to a large extent are hydrogenated to hydroaromatics. When they are returned to the dealkylation reactor, these under the severe reaction conditions of dealkylation to compounds of lower molecular weight or degraded to benzene.

209 530/55

Claims (1)

'' Containers that are operated alternately are Claim: ν will see. A regeneration and reuse dung of fuller's earth is; not worthwhile, so that Process for the production of unsubstituted additionally the problem of waste disposal occurs. High-purity aromatics through dealkylation 5 The bleaching earth treatment must be carried out at an increased temperature of alkyl-substituted aromatics in the presence of temperature and in the liquid phase, so that relatively hydrogen at elevated temperatures and expensive pressure vessels including expensive filling pressures and refining of the reaction preparation and discharge facilities are required. Füldukte the dealkylation, characterized by identification and emptying, in contrast to the one characterized in that the reaction products of the petrochemical plants usual fully automatic dealkylation together with the cycle gas operating mode, essentially by hand and in relader dealkylation and without prior separation ^;! tiv utristian way. Despite this, open from gaseous and liquid components with the obvious disadvantages, this process is currently the reaction pressure of dealkylation \ at; Temper technically only applied
doors from 50 to 350 ⁰ C and space velocity 15 It is already from the French patent. dities of 2 to 10 kg of reaction product per 1346 467 known, the color fastness of earth liters of catalyst and hour over metals,, oil hydrocarbons through hydrogenation with sulfur oxides and / or sulfides of metals of the VL solid catalysts in relation to a special and VIII. Group of the Periodic Table as a test, the so-called sulfuric acid test, refined to verbes catalysts hydrogenating, with ao acids. If concentrated sulfuric acid is added to separate off the dealkylated pure aromatics, the petroleum hydrocarbons, in the presence of unreacted compounds and those compounds that have been saturated by mel) reactions in these hydrocarbons, some or all of the substances become discolored. To improve the dealkylation are recycled. Color stability is therefore a hydrogenation of un- 35 saturated compounds in petroleum hydrocarbons . suggested. It is also known to refine crude benzene under pressure. It is this a process to make crude benzenes It is known that one can by hydrentalkyly with largely preservation of the aromatics of anrung alkyl-substituted aromatics, such as toluene or subsequent further processing Alky! Naphthalenes, make the corresponding unsubstituted (see. German Patent 841587 and can convert ated aromatics. - '.. U.S. Patent 2,705,733). The hydrodealkylation is both catalytic. In British Patent 886 710, the as well as thermally at temperatures from 550 to a person skilled in the art taught how pure benzene is carried out by 700 ⁰ C and pressures of 35 to 70 atm in the presence of catalytic reforming and subsequent aroof hydrogen, which can be obtained in an added material extraction. It is necessary to remove fresh gas and / or a recycle gas contained in the separation of the low olefin content in the extract by a reaction product contained in the separation of the sulfuric acid treatment. In the USA.-is. Patent Specification 3 081259 and in British Patent Hydroentalkylation allows the production of 40 script 916 597, processes are described with very high purity of aromatics, since with the relatively high purity coke oven light oils in the presence of severe water reaction conditions, none of the substances contained in the raw material and catalysts under dealkylation conditions or that arise as intermediates, ie between 600 and 630 ° C treats matic compounds that are close to those to be won. The aromatic compounds selected in these patents boil and their distillative start-up parameters make it difficult at the same time to break down easily separable, raw material-containing non-aromatics from the boiling range which are broken down by hydrieine gaseous compounds. In this way, aromatic compounds can be removed by a simple distillation. The reaction of the reaction product of the hydroentalkylation of products from this purification stage contain toluene, a benzene with a purity of over 50 traces of unsaturated compounds, such as. B. olefins, 99.95% and thus a melting point "of about 5.4 ° C to remove the reaction product still obtained. 'Ν ώ: ^v must be post-treated Under the severe reaction conditions column 15, lines 33 and 34 of the USA patent) are formed. However, in very small amounts unsaturated compounds. Due to their low concentration, borrowed absorbents were carried out (see column 3, flow, although they yield and melting point of lines 59 and 60, column 5 from line 62, column 9 from Pure aromatics are practically non-existent, but line 39). In British Patent 916,597 it is in another purity test. the so-called post-treatment of the reaction product Sulfuric acid test, noticeable disturbing; not mentioned in addition, but must be taken from the comparison with concentrated sulfuric acid, discoloration occurs 60 of the aforementioned U.S.A. patent closed on. that the reaction products are still unsaturated These unsaturated compounds will more commonly contain compounds. wisely removed by a treatment with fuller's earth. None of these references is a Although the consumption of fuller's earth can be seen in the small drive, in which the unsaturated ver-olefin concentrations in the reaction products of the 65 bonds are practically completely removed without Dealkylation is relatively low, this process has that, however, z. B. in the dealkylation of significant disadvantages. Benzene produced in order to operate without lower alkyl-substituted aromatics To be able to maintain refraction, two have to be hydrogenated to cyclohexane in only ppm amounts