CS251016B1 - Process for processing liquid pyrolysis fractions - Google Patents

Abstract

The method of processing liquid pyrolysis fractions boiling in the range of 58 to 205 °C consists in heating this pyrolysis fraction for 10 minutes to 5 hours to a temperature of 100 to 150 °C at the vapor pressure of the system and in the following stage, separating the residual fraction boiling above 150 °C, enriched with dicyclopentadiene, which is processed as a petrochemical raw material, and the fraction up to 150 °C, free from palm components, from which the C-fraction is removed and which is further processed by hydrogenation and/or for aromatics.

Description

The invention relates to the processing of liquid pyrolysis products boiling in the range of 36*205 C by thermal dimerization of cyclopentadiene present in these fractions. In this case, the quality of the produced, so-called non-hydrogenated C^-fraction, which mainly contains isopentane, cyclopentadiene, dicyclopentadiene, n-pentane, pentenes, isoprene, pentadienes, cyclopentane and cyclopentene and where cyclopentadiene and dicyclopentadiene are undesirable, is increased and the hydrogen consumption in the subsequent hydrogenation processing of these fractions is further reduced.

In the petrochemical industry, the pyrolysis of hydrocarbons produces a large number of fractions of 36 to 205°C, which contain various unsaturated hydrocarbons. Some of them are advantageously obtained before the subsequent hydrogenation of these fractions, which is aimed at their further treatment, e.g. for the production of gasoline components. These are mainly isoprene, cyclopentadiene (hereinafter referred to as CPD) and dicyclopentadiene (hereinafter referred to as DCPD), which are used for other petrochemical production.

The disadvantage of obtaining CPD and DCPD from these pyrolysis fractions is usually the low concentration of individual substances in the starting hydrocarbon fractions, usually not exceeding 10% by weight. The disadvantage of subsequent hydrogenation treatment of light pyrolysis fractions with a b.p. of 36 to 2O5°C, which are not sufficiently freed from CPD and DCPD, is also the relatively large consumption of hydrogen required for the hydrogenation of the dienes present, which is aimed at their removal as undesirable substances that make further processing difficult.

In the industrial production of DCPD from these fractions, the procedure is to first prepare a narrow distillation cut - the so-called C^-fraction - containing most of the hydrocarbons and five carbon atoms and not containing % - 2

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DGPD, which passes into the boiling products. The C^ fraction thus obtained usually contains 10 to 30 wt. % GPD under pyrolysis and distillation conditions. After thermal treatment in a reactor at temperatures of 100 to 150°C and reaction times of 1 to j hours, when dimerization of cyclopentadiene to DCPD takes place, and subsequent distillation of light components, about 85 % DGPD is obtained as a distillation residue. In this procedure, the use of primarily formed DCPD from the initial pyrolysis fraction is excluded. This DCPD passes together with other unsaturated hydrocarbons to the hydrogenation stage, where hydrogen consumption increases and the demands on the catalytic system increase. In the case where CPD and DCPD are not obtained, these hydrocarbons represent undesirable components in the so-called C^ fraction. It has also been proposed to subject the cyclopentadiene contained in the entire fraction to dimerization with the so-called light pyrolysis gasoline including the C^ fraction. However, this procedure, which performs dimerization and rectification at the same time, does not allow for a good course of the dimerization reaction, which under the conditions in the depentanizer does not proceed to the desired degree, part of the cyclopentadiene passes into the C^-fraction with all the consequences for further processing, and the yields of dicyclopentadiene are low.

The above-mentioned shortcomings are eliminated by the method of processing liquid pyrolysis fractions boiling in the range of 38 to 205°C, especially light pyrolysis gasoline boiling in the range of 38 to 180°C, thermal dimerization of cyclopentadiene present in these fractions to dicyclopentadiene and subsequent distillation treatment, which consists in the fact that the said pyrolysis fraction is heated to a temperature of 100 to 150 ^° C without prior distillation of the C^-fraction, left to react at the vapor pressure of the system to form dicyclopentadiene for 10 minutes to 3 hours, preferably 1 hour, and in the following stage, the distillation residue boiling above 150°C, which is enriched with dicyclopentadiene and is further processed as a petrochemical raw material, and the portions boiling up to 150°C, free from diene components, which are removed from the G^ fraction by rectification and further processed by hydrogenation or/and to BTX aromatics. The distillation residue enriched with dicyclopentadiene is processed according to specific requirements. One option is the production of DCPD concentrate by a combination of atmospheric and vacuum distillation without exceeding the maximum temperatures in the apparatus of 110°C.

Another way to utilize fractions with enriched DCPD content is to produce transparent petrochemical resins for other purposes.

Some variants of a specific solution are shown in the attached diagram (Fig. 1), where

- light pyrolysis gasoline (b.v. 38 to 180°C)

- dimerization reactor

- reaction product from dimerization reactor II - separation of the product into light and heavy fractions

- light fractions up to 150°C - according to the apparatus mode - DCPD must not pass into the distillate

- heavy fraction (DCPD enriched fraction)

III - depentanizer - separation of C^-fraction

- C^-fraction depleted in CPD and DCPD

- heavy pyrolysis gasoline option A: 6a - introduction of heavy pyrolysis gasoline into the depentanizer option B: 6b - introduction of heavy pyrolysis gasoline outside the depentanizer

- the residue from the depentanizer (fraction free of C^-hydrocarbons) or according to the variant

- mixture of pyrolysis gasolines (non-hydrogenated) variant C: 8c - injection of combined streams for hydrogenation IV - hydrogenation reactor

- hydrogenated pyrolysis gasoline for further standard processing variant D: 8d - injection into the BTX column (separation of Cg to Οθ aromatics from heavier fractions of pyrolysis gasoline)

V - BTX-column

- residue from the BTX column (so-called C^-unhydrogenated fraction)

- overhead product of the BTX-column for standard processing (for hydrogenation) variant E: 4e - injection into distillation column VI variant F: 4f - fraction enriched with DCPD for the production of petrochemical resins (injection into reactor VIII)

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variant G: 12 g - option H: 12 h - top product of distillation column VI (joint injection into depentanizer) processing by blending into pyrolysis gasoline VI - distillation column VII - distillation column

lj - overhead product of column VII (DCPD-concentrate - according to requirements) 14 - residue from column VII (mixing into heavy pyrolysis residues)

VIII- polymerization reactor for the production of petrochemical resins by thermal oligomerization

IX - distillation separation of unreacted fractions from the polymerization reactor

- unreacted products introduced into the pyrolysis gasoline mixture

Note: Streams lj and 10 can also be used for the production of petrochemical resins.

The basic effect of the process according to the invention is that it utilizes almost all of the cyclopentadiene in monomeric and dimeric form for the production of DCPD from the broad pyrolysis fraction 38 to 205°C. Another effect is to improve the quality of the unhydrogenated C^-fraction, where the content of these substances is undesirable. Another effect is to reduce the content of hydrogenable substances, and therefore the amount of hydrogen required for hydrogenation. It can also be expected that by reducing the content of polymerizable substances, the operating time of the hydrogenation catalyst will increase.

The method according to the invention is further described in more detail on several examples of obtaining DCPD from light pyrolysis gasoline. The syntheses were carried out in a laboratory autoclave with the possibility of temperature regulation. The distillation obtaining of DCPD concentrate was also confirmed in the laboratory. in a two-stage laboratory distillation device.

Example 1

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Light pyrolysis gasoline was thermally processed in the above equipment under the following conditions:

Temperature: 120°C

Reaction time: 2 hours

Table 1

Composition of the input raw material and the product of its heat treatment

input raw material label % tuaulb. product % hmp/. C^-hydrocarbons <C ₄ ) below 0.1 below 0.1 Ctj-carbon hydrogens (0 ₅ ) 52.2 43.8 Cg-Cg nonaromatics ⁽⁰ 6- ^C 8> 10.8 7.6 C^-hydrocarbons (C ₉ ⁺ ) 7.,7 15.9 Benzene (B) 25.9 28.1 Toluene (T) 3.4 3.9 Xylene (X) below 0.1 below 0.1 Ethylbenzene (EB) 0.2 0.2 Styrene (Wed) 0.1 0.1 Isoprene (I.Z.) 11.5J 10.08 Cyclopentadiene (CPD) 6.59 0.99 Dicyclopentadiene (DCPD) 5.96 11.25

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Claims (1)

SUBJECT OF THE INVENTION 251 016 Process for the treatment of liquid pyrolysis fractions boiling in the range of 38-250 ° C, in particular light pyrolysis gasoline boiling in the range of 38-180 ° C, by thermal dimerization of the cyclopentadiene present in these fractions to the dipentadiene and subsequent treatment, characterized in that the pyrolysis fraction is heated to a temperature of 100 to 150 ° C, is allowed to react at a vapor pressure of the system to form dicyclopentadiene for 10 minutes to 3 hours, preferably 1 hour, and in the next step the distillation residue boiling above 150 ° C, enriched with dicyclopentadiene, is rectified; further processed as a petrochemical feedstock, and fractions boiling up to 150 ° C, free of diene components, which are rectified by fraction C ^, and further processed by hydrogenation and / or to BTX aromatics.