DE1235490B - Process for the catalytic reforming of hydrocarbon mixtures - Google Patents

Description

GERMAN ■ tMWSSSP PATENT OFFICE

DeutscheKI .: 23 b -1/04

EDITORIAL . _Number : I ₂₃₅₄₉₀

File number: S 90219IV d / 23 b J 235490 Filing date: March 25, 1964

Open date: March 2, 1967

From British patent specification 717 725 a method is known in which a part of a hydrocarbon mixture, which has been obtained from a reforming process is extracted with a selective solvent for aromatics. One Fraction with a relatively low aromatic content is separated from the extract phase and partly in recycled the selective extraction stage.

In such processes, inter alia, some of the non-aromatic components of the starting material are converted, inter alia, by the reforming treatment into aromatic hydrocarbons, which are then enriched in the extract phase obtained so that a highly aromatic extract can be obtained therefrom. By separating the fraction with a relatively low aromatic content, the aromatic content of the extract to be obtained is further increased. The highly aromatic extract is z. B. used as a component for motor fuels with a high octane number λο or as a starting material in the chemical industry.

Furthermore, the Austrian patent specification 203 609 describes a method for catalytic reforming of petroleum, in which the initial reformate is subjected to solvent extraction. It an extract phase with a high aromatic content is obtained, the resulting Raffmatphase is in the Reforming stage returned. This makes the reforming stage very much paraffinic Contaminated material that can only be converted to a small extent into aromatics. By a After washing the aromatic extract, an aromatic content of 95% can be achieved. the The resulting naphthenic raffinate phase is partly in the washing zone and partly in the Extraction zone reused. A return to the reforming zone and thus transformation the naphthenes in aromatics do not occur.

It has now been found that the yield of aromatics obtained in such processes and as a result, the value of the products obtained can be increased even further by taking from the Extract phase separates a fraction with a relatively low aromatic content and one Part of this separated fraction subjected to a catalytic reforming or together with the catalytically reformed original hydrocarbon mixture.

It has been found that by re-reforming treatment of this fraction, a substantial portion of it is still converted into aromatics by catalytic reforming processes
Hydrocarbon mixtures

Applicant:

Shell International Research
Maatschappij NV, The Hague

Representative:

Dr. E. Jung, patent attorney,
Munich 23, Siegesstr. 26th

Named as inventor:

Hendricus Marinus Penning,

Walter Cornells Gerard Kosters, The Hague;

Heinz Voetter, Amsterdam (Netherlands)

Claimed priority:

Netherlands of March 27, 1963 C290 71 Z \

can be converted. As a result, this procedure gives a particularly high yield of others Aromatics, which is not achieved with the known processes.

The invention accordingly relates to a method for the catalytic reforming of hydrocarbon mixtures, in which at least part of the reformate obtained is subjected to selective extraction is subjected to a selective solvent for aromatics, whereupon a fraction with a relatively low aromatic content separated from the extract phase obtained in this way and a part of said fraction is recycled to the selective extraction step, which thereby is characterized in that a further part of said fraction again undergoes catalytic reforming is subjected.

By distillation or some other means, one or more, of course, can be made Fractions are removed from the reformate first obtained before the reformate is transferred to the extraction stage.

The said fraction, which has a relatively low aromatic content, can be of the Extract phase can be separated completely in one stage or in different stages.

If desired, said fraction or part thereof can be subjected to further reforming separately be subjected. In this case, the additional reformate obtained therefrom can also be converted into be extracted in a suitable manner. This is done before

709 517/484

partly in the same extraction stage in which the original reformate is worked up.

However, this fraction is preferably used together with the original hydrocarbon mixture subjected to catalytic reforming. On the one hand, so is the use a special reforming plant superfluous, on the other hand in this case the additional Amount of aromatics formed according to the invention in the highly aromatic extract product of the Process recovered.

It has been found that by recycling part of the said fraction, the one proportionately has a low aromatic content and is obtained from the extract phase into the selective Extraction stage the final composition of this fraction is changed so that the conversion of the portion subjected to re-reforming is further improved, so that the overall yield of aromatics is further increased in the process according to the invention.

The fraction with a relatively low aromatic content can be used together with the starting material for this stage (this is the reformate or part of it) or recycled to the extraction stage as a countercurrent solvent. in the In the latter case, the return can expediently at the end of the (multi-stage) extraction system from which the extract phase is withdrawn, and preferably in the first or second theoretical stage the same take place.

Of course you can also use a part of the mentioned fraction (e.g. a share and / or a or several fractions) from the process. He can z. B. as a suitable starting material for the chemical industry.

The fraction with a relatively low aromatic content is preferred from the extract phase separated by distillation. The extract phase can e.g. B. broken down into two fractions by distillation one of which consists mainly of hydrocarbons. By distilling the Hydrocarbon fraction is one or more relatively high-boiling aromatic-rich extract fractions and one or more relatively low-boiling low-aromatic extract fractions won.

However, said fraction is preferably obtained by distilling in the presence of a solvent (i.e. essentially by means of extractive distillation) by e.g. B. the extract phase broken down into two fractions, one of which is both solvent and hydrocarbons contains, it depends on the nature of the solvent used, whether the hydrocarbons are rich or poor in aromatics and the other is made up of hydrocarbons. The former Fraction can then be broken down again into solvents and hydrocarbons. When performing In the first-mentioned breakdown, the extract phase is expediently divided into the upper part of the relevant one Distillation column introduced, while the latter separation can be carried out in a column, which is operated at superatmospheric pressure and / or with the introduction of steam. Both decompositions can also be carried out in a single column, as in the process of the above British patent specification is the case.

In the second embodiment of the process according to the invention, the aromatic content is Fraction that is poor in aromatics is lower than if the distillation in the absence of a solvent takes place, so that in this case the amount of aromatics, in turn - for these components unnecessarily - subject to reforming is lower.

Another, very suitable procedure for separating the said fraction and the extract phase consists in an extraction. For this purpose, a paraffinic, secondary solvent is preferably used which has a higher boiling point than the reformate or reformate portion to be subjected to the aromatic extraction, since this solvent is able to effectively dissolve a low-aromatic material from the extract phase and then easily recover from the said fraction, e.g. B. can be separated by distillation.
: o The highest-boiling fraction and, most appropriately, also the lowest-boiling fraction is preferably removed from the fraction to be reformed again, since the fraction that remains appears to be particularly suitable for further conversion into aromatics. In this mode of operation, the highest-boiling portion and / or the lowest-boiling portion can be returned, for example in the extraction stage, or withdrawn from the process.

Suitable starting materials for the process according to the invention include light, direct distilled hydrocarbon oils such as gasolines or fractions thereof, e.g. B. under about 180 to Boil 200 ° C. Hydrocarbon mixtures obtained by cracking processes, such as gasoline (Fractions) can also be used. Preferably, however, the ones contained therein are used first Olefins completely or partially saturated. Mixtures (which may contain one or may contain several of the substances mentioned above) can of course also be used. It can e.g. B. alkanes are also added to the feedstock for the catalytic reformer be e.g. B. η-butane, n-pentane, η-hexane. In many cases it will be advisable to use the starting material for the catalytic reforming plant beforehand completely or partially of sulfur and / or nitrogen free, z. B. by catalytic hydrogenation.

The inventive catalytic reforming or reforming can or can, for. More colorful Use of metals from Group VI and / or Group VIII of the Periodic Table as catalysts be carried out, these metals optionally being in a metallic state and are deposited on, for example, an acidic carrier, such as molybdenum oxide and / or chromium oxide on aluminum oxide or platinum on silicon dioxide — aluminum oxide or on aluminum oxide alone. The reaction temperature is e.g. B. about 400 to 700 ° C. The reformings are optional carried out at a hydrogen partial pressure of, for example, 1 to 50 atm. The reform can be carried out in one or more stages using one or more reaction vessels.

In the case of selective extraction, all types of solvents which act selectively for aromatics can be used be used. Preferably a selective

tives solvent used that boils higher than the aromatic extraction to be subjected to reformate or reformate portion, z. B. furfural, phenol, acetonitrile, diethylene and / or dipropylene glycol. A solvent of the sulfolane type is particularly suitable for this purpose, ie a solvent which consists essentially of sulfolane (cyclic tetramethylene sulphone) itself, sulfolene and / or one or more sulfolane and / or sulfolene derivatives. In addition, it is also very useful to use a selective solvent which has a lower boiling point than the reformate or reformate component to be subjected to the aromatic extraction, e.g. B. SO ₂ .

The selective extraction and the secondary extraction (if used) can be used in any In one or more stages, in cocurrent or countercurrent, with or without application of a counter-solvent. Both extractions can e.g. B. expedient be carried out with the help of one or more contact devices with rotating disks equipped and possibly combined into a unit, although of course others as well Extraction equipment can be used. If desired, the extraction is also carried out in the presence carried out by material that does not come from the reforming plant (s), but rather for example, has been obtained by direct distillation.

For the desired distillation, it is expedient to use a device which is equipped with contact means (such as packing material or bottoms, especially bubble caps or intermediate floors with preferred passage zones).

The invention will now be explained in more detail with reference to the drawing, in which auxiliary devices, such as control, cooling and heating devices, valves, pumps and the like, are not shown.

According to FIG. 1, a hydrocarbon mixture, which if desired has been completely or partially freed from olefins and / or sulfur, nitrogen, is fed through a line together with a hydrogen-containing gas from line 2 through a furnace 3 and a line 4 to a reforming reactor 5 which is equipped with a Catalyst bed is provided. As the mixture flows through this reactor, the temperature drops due to the endothermic nature of the process. The product withdrawn from the reactor 5 through a line 6 is therefore reheated to the desired reaction temperature in an oven 7 , then it is passed through a line 8 to a second reforming reactor 9 which is similarly provided with a catalyst bed. Here the temperature drops again, and therefore the product withdrawn from the reactor 9 through a line 10 is again passed through the furnace 7 (of course it would also be possible to heat this product in a special furnace). The reaction mixture is then passed through a line 11 into a third reforming reactor 12 , which is also provided with a catalyst bed. In this case all reforming reactors 5, 9 and 12 contain the same catalyst. Different catalysts can of course also be used. The number of reforming reactors used

can also be larger or smaller than shown in the drawing. The same applies to the number of the ovens used.

The reformate obtained from the reforming reactor 12 is passed through a line 13 into a separating device 14 , where it is broken down into a gaseous and a liquid component. The gaseous part, which consists mainly of hydrogen, is partly returned through line 2 , ίο Another part is withdrawn from the process through line 15 . He can z. B. can be used as a treatment gas in a hydrating refining treatment. If desired, the hydrogen-rich gas that has been withdrawn from the separation device 14 can first be subjected to a cleaning treatment in order to remove sulfur compounds and / or other undesirable components (not shown).

The liquid obtained from the separating device 14 is passed through a line 16 into a stabilizer 17 which is equipped with a reheater with trays (not shown). The vapors exiting at the top of this column, which consist essentially of butane and lighter components, are drawn off through a line 18 and, after cooling and condensation, are converted into a gas which is removed through a line 19 , e.g. B. in an exhaust gas treatment system, and decomposed a liquid which is partially returned through a line 20 to the column 17 and partially removed through a line 21 from the process.

The stabilized bottom product from the column 17 is fed through a line 22 into an extraction vessel 23 , in this case into a device which is equipped with rotating disks. It is of course also possible to use other types of extraction systems. It is also possible, for example, to subject the stabilized reformate to a further breakdown in line 22 and to lead only part of it into the extraction apparatus 23 . The starting material for this apparatus can be introduced through one or different inlet lines. A solvent which is selective for aromatics and in this case has a higher boiling point than the material in line 22 is introduced through a line 24 at the top of the extraction apparatus 23 . The raffinate formed in the apparatus 23 during the extraction process is discharged from the top of the extraction apparatus 23 through a conduit 25th It can be treated further to remove any solvent it may contain.

An extract phase rich in aromatics is withdrawn from the bottom of the extraction apparatus 23 through line 26 and then fed into a stripping zone 27 which is equipped with a reheater and in the present case also provided with intermediate floors (not shown), the extract phase entering at the upper end of this zone . In the column 27 there is a separation into a top product, which contains some solvent, some of the aromatic hydrocarbons and the greater part of the non-aromatic hydrocarbons that are present in the extract phase, as well as a bottom product, the solvent, aromatic hydrocarbons and a (small) Contains amount of non-aromatic hydrocarbons. This latter product is through line 28 in

a distillation column 29 out, which in this case is also provided with an intermediate tray and into which steam is introduced through line 30. A separation takes place in the column mentioned into an overhead product containing aromatic hydrocarbons which is essentially free of solvent, and into a bottoms product that is essentially free of aromatic hydrocarbons. After condensing, the

Way or in any other way. In this case, the stabilized reformate (or a part or a fraction thereof) likewise through the line 22 into the extraction apparatus 23 introduced, from which the low-aromatic raffinate is again withdrawn through line 25 and, if desired is passed into an apparatus for separating off solvent. The ones from the extraction device 23 through line 26

Vapors from the top of the column 29 by a io solid extract phase is passed in this case, in a line 31 to a settler 32, performed in a secondary extraction apparatus 40, which takes place here, the separation into two layers, is also equipped with rotating disks namely a Bottom layer which is drawn off by a line (in the case shown in the figure a separate 33 and is rich in water (from the apparatus, but possibly with the apparatus, this layer is combined, if desired, completely or 15 23) in which said Phase formed with a partial vapor, which is to be introduced through line 30, paraffinic secondary solvent treated), and in an upper layer, which is introduced through line 41, which consists essentially of hydrocarbons. A first secondary phase, the selective dissolving-this last-mentioned layer is partly returned to the medium aromatic hydrocarbons and a distillation column 29 and partly ao (small) amount of non-aromatic hydrocarbons

discharged through a line 34 as an aromatic extract from the process. The soil product from the Distillation column 29 is returned through line 24 to extraction unit 23, if desired after cooling (not shown). If necessary, part of this soil product can are discharged through a line 35 for cleaning or removal from the system, while fresh or purified solvent

Contains substances is discharged from the secondary extraction apparatus 40 through a line 42. This first secondary phase is then freed from the selective solvent in which Neten in the figure Drawn s5 case in a single stage in an evaporator 43, but possibly also in other ways. In this case, the recovered solvent is removed from the upper part of the evaporator 43 and can be fed through a line 36 after cooling and condensing. It 30 through a line 24 into the extraction apparatus

would also be possible, the separation operations that are carried out in columns 27 and 29, in a single column (analogous to the procedure described in the above-mentioned British patent carried out) or carried out in more than two columns.

According to the invention, the top vapors from the stripping zone 27 are in the present case in part, if desired after water separation, through a line 37 into the line 1 and the furnace 3 returned to be subjected to reforming treatment again, d. H. in the present In the case of the same treatment as the hydrocarbon mixture flowing through line 1

23 returned. The aromatic-rich extract product obtained by the process is withdrawn from the evaporator 43 as the bottom product.

Addition and removal of solvents through lines 35 and 36 are in this case also possible.

The secondary extractor 40 becomes a second secondary phase through a line 44 withdrawn, in addition to the secondary solvent, a part of the withdrawn from the extraction apparatus 23 and relatively contains low-aromatic extract phase. This second

secondary phase is fed into a distillation column. The introduction of this material is broken down into 45 45, which, however, can also be done separately with a reheater and like the furnace 3. It is in turn provided with intermediate floors. The bottom is also possible to first decompose the material in the product consists at least mainly of line 37, before it is again partially secondary solvent, which is subjected to the secondary reforming treatment. Extraction apparatus 40 through line 41 - if desired, part of the top product 50 can be recycled. Removal and replenishment of the secondary solvent from column 27 through line 38 can be removed through lines 46 process. and 47 are of course always possible.

In addition, some of the vapors from the upper After cooling and condensation, part of the end of the washing column 27 after cooling, condensation of the vapors with a low aromatic content from the and, if desired, water separation as 55 the upper part of the column 45 through a line 48

Counter-solvent returned to extractor 23 through line 39 and one or more inlets.

F i g. 2 shows an embodiment of the method according to the invention, in which the to be reformed again Proportion of the parliamentary group concerned is obtained in another way. The part of the plant used which includes the reforming stage (including stabilizer and possibly another

returned to the column by reflux, while another portion as a counter-solvent by a line 49 is led to the extraction apparatus 23. Another part of the fumes from the upper part of the column 45 is passed through a line 50 into a fractionation column 51, which is also is provided with reheater, intermediate floors and reflux facilities. In this column 51 becomes this part of the top product from the column

fractionating device, corresponding to the 65 45 into a number of fractions, in the present

Elements 2 through 21 in FIG. 1) is designated as a block A in this figure. It is clear that this reforming stage is either in the form shown in FIG. 1 shown

Case three, but possibly more or less, disassembled. The top and bottom fractions the column 51 are in the present case

Claims (3)

withdrawn from the process through lines 52 and 53, while the middle fraction that is obtained from this column represents the reformate portion, which according to the invention is at least partially returned through a line 37 to the reforming stage ^ l 5 (although a treatment in a separate reforming stage in would also be possible in this case). It is also possible to remove part of this reformate component through line 38. A smaller part of this can, if desired, be introduced into the extraction apparatus 23 as counter-solvent instead of the material in the line 49 (not shown). Furthermore, it is also possible to carry out this separation between reformate and secondary solvent as well as the breakdown of the reformate into fractions in one and the same column or, in another embodiment, each of these breakdowns in more than one fractionation column. The invention will now be explained in more detail by the following comparative example. Example A gasoline fraction was treated in a plant essentially similar to that shown in FIG. 1, with the modification that four were used instead of three reconstruction reactors and that a fraction of the reformate from line 22 and additionally directly distilled material was treated in the extraction apparatus 23. 100% of the gasoline fraction consisting of 0.8 percent by weight of benzene, 2.1 percent by weight of toluene and the remainder non-aromatics were introduced through line 1. The reforming reactors were equipped with a platinum-on-alumina catalyst containing chlorine and fluorine. The average temperature in the reactors was 490 ° C., the outlet pressure from the last reactor was about 25.5 at abs. Hydrogen-containing gas was introduced through line 2 in such an amount that the molar ratio between hydrogen and gasoline fraction was about 4. In this case, in addition to the liquid material from the boiler 14, a light, directly distilled hydrocarbon fraction was passed through the line 16 into the column 17, which (partly) occurred in the bottom product of this column. This bottom product was broken down into three fractions, of which the middle fraction (which in addition to reformed material also contained material from the above-mentioned directly distilled fraction) was passed through line 22 into the extraction apparatus 23 in an amount of 830 t per day. This middle fraction contained 16.8 percent by weight benzene, 17.5 percent by weight toluene, while the remainder consisted of non-aromatics. In the extraction apparatus 23, said middle fraction was treated at a temperature of 150 ° C. with 52001 diethylene glycol per day, which had a water content of 0.8 percent by weight. An amount of 550 liters of raffinate was withdrawn daily through line 25, which consisted of 0.2 percent by weight of toluene, the remainder containing non-aromatics. The top product of the column 27 (630 t per day; benzene or toluene content 31.8 and 18.3 percent by weight) was returned to the extraction apparatus 23 through the line 39. The bottom temperature and the pressure in column 27 were 175 ° C. and 1 at abs., While these values in column 29 were 180 ° C. and 0.35 at abs. cheat. A quantity of 280 t of extract was obtained daily through the line 34. This extract consisted of 49.2 percent by weight benzene and 50.8 percent by weight toluene, in this case 138 tons of benzene and 1421 toluene, which were recovered daily. According to the invention, not the entire top product of the column 27, but rather only 57 percent by weight thereof, was then returned to the extraction apparatus 23. The remainder was recycled through line 37 into line 1 in order to be re-subjected there to reforming. In this procedure, an amount of 10801 per day of the reformate-containing middle fraction was passed through line 22 into the extraction apparatus 23 and treated there with 69001 diethylene glycol per day. The amount of raffinate which was then withdrawn through line 25 was 5201 per day, 0.2 percent by weight of the raffinate consisting of toluene and the remainder of non-aromatics. A quantity of 310 t per day of extract was withdrawn through line 34, of which 52.3 percent by weight, i.e. H. 1621 per day, from benzene and 47.7 percent by weight, i.e. H. 481 per day, composed of toluene. By using the method according to the invention, 301 more aromatic extract were obtained per day. This means an increase of almost 11 percent by weight. The yield of benzene was even increased by 17 percent by weight. Patent claims: 1. A method for the catalytic reforming of hydrocarbon mixtures, in which at least part of the reformate obtained from a selective extraction with a selective Solvent for aromatics is subjected, whereupon a fraction with a proportionate separated from the extract phase obtained in this way and a low aromatic content Part of this said fraction is returned to the selective extraction stage, thereby characterized in that a further part of said fraction is again a catalytic Is subjected to reforming or optionally together with the original hydrocarbon mixture is catalytically reformed. 2. The method according to claim 1, characterized in that the highest boiling portion and preferably also the lowest-boiling fraction from said fraction or said fraction Part of the same is removed before this part is again subjected to catalytic reforming or reformed together with the original mixture. 3. The method according to claim 1, characterized in that the hydrocarbon mixture has been at least partially freed from sulfur and / or nitrogen. Considered publications:
Austrian patent specification No. 203 609. 1 sheet of drawings 709 517/484 2.67 © Bundesdruckerei Berlin