DE2805720A1 - METHOD FOR SPLITING HEAVY HYDROCARBONS - Google Patents

Description

The invention relates to a method for splitting heavy hydrocarbons, the hydrocarbons first subjected to a hydrogenating pretreatment in the presence of hydrogen and a catalyst and then thermally be split.

For the production of olefins, light hydrocarbons such as for example fithane or propane or hydrocarbon mixtures with a boiling point below 200 °, such as Naphtha, particularly suitable. They lead to a high olefin

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'^ H U b V 2 0

yield and produce few undesirable by-products.

However, since there is a great need for olefins, which leads to a shortage or price increase of these cheap For some time now, attempts have been made to develop procedures that are also favorable Allow utilization of a higher-boiling feedstock.

The use of higher-boiling feeds basically entails the problem that the olefin yield decreases and a hydrocarbon fraction that boils over 200 ° C and is difficult to utilize is obtained, the proportion of which increases with the boiling range the use increases sharply. In addition, further difficulties arise because higher-boiling inserts lead to increased coke and tar formation. These products are deposited on the walls of the line elements, for example Pipelines and heat exchangers cause a deterioration in the heat transfer and also lead to Cross-sectional constrictions that have to be eliminated by regularly removing the deposits.

To solve this problem, DE-OS 21 64 describes a method in which the use before his thermal cleavage is catalytically hydrogenated. This pretreatment increases the proportion of polyaromatic compounds in the feedstock, which essentially lead to the undesired fission products. To make the procedure cost

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To be able to carry out cheap, however, it is necessary to carry out the hydrogenation under conditions in which practically no hydrocracking reactions take place. These reactions namely result in an increased consumption of hydrogen and also lead to the increased formation of undesirable, slight cleavage products, while the proportion of the desired olefinic products decreases. The one for hydrogenation The hydrogen required for use must also be carried out in an independent manner when proceeding according to the known process Process stage are generated.

The invention is based on the object of developing a method of the type mentioned at the beginning in which the cleavage products have a high proportion of olefins and an economically viable operation of a process Facility enables.

This object is achieved in that the hydrogen required for the hydrogenating pretreatment is at least partially dirch a Bamp reforming from at the cleavage produced light hydrocarbons is obtained.

The invention thus proposes an integrated method for splitting heavy hydrocarbons which the hydrogen required for the hydrogenation is obtained directly from a cleavage product. This allows separate Ancillary systems for the provision of hydrogen and a

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separate supply of these plants with special input material omitted. In the production of olefins, the light can be produced with the aid of the process according to the invention Hydrocarbons can be used in a particularly favorable manner, since no major measures for interim storage or are required for transport to a remote consumer.

In an advantageous embodiment of the invention, the energy for the steam reforming process is generated by the combustion recovered some of the light hydrocarbons produced during the cracking. This measure also allows it to be inexpensive Recovery and also makes steam reforming independent of other energy sources.

In the thermal cracking of the hydrogenated feedstock, hydrogen is also produced in addition to the other waste products. For the entire process, it is advantageous to feed this hydrogen directly to the hydrogenating pretreatment, since then only a small proportion of the cleavage products need to be converted into hydrogen in the steam reforming stage to cover the hydrogen requirement. The hydrogen generated in the thermal cracking can cover about 10-30% of the hydrogen requirement for the hydrogenation, the proportion depending on the selected reaction conditions and the feedstock.

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Jnachger eioht) LINDE AKTIENGESELLSCHAFT

The entire procedure essentially fails the process stages hydrogenation, thermal cracking and steam reforming together. By influencing the reaction conditions in the individual stages, the entire Adjust the process sequence so that the in the hydrogenation required hydrogen is generated in the other two stages in an amount sufficient to cover the entire hydrogen requirement sufficient. In such a procedure it is advantageous to control the reaction conditions in the hydrogenation stage so that just the amount of light needed to produce hydrogen Hydrocarbons is generated. Then you can go for the thermal Cleavage and steam reforming the .in view of the desired Reactions are chosen in each case the most favorable reaction conditions.

A particular advantage of the process according to the invention is that the formation of light gaseous Fission products, especially methane, does not represent an undesirable effect. The formation of these products depends in strong Manner of the extent of the hydrocracking reactions in the hydrogenation stage away. In a method according to the prior art, in which the products of the thermal cleavage only outside the plant can be recycled, is therefore through the choice of reaction conditions and catalysts in the Aimed for hydrogenation, such products in as little as possible

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Extent. However, since they are used in the process according to the invention for the production of hydrogen, leave choose reaction conditions which exclusively focus on a favorable, that is to say as large as possible, olefin yield of the cleavage process are aligned.

The process according to the invention thus also makes it possible, in particular, to carry out the hydrogenating pretreatment under conditions in which hydrocracking reactions take place to a considerable extent. Part of the feed is converted into gaseous and low-boiling hydrocarbons, which essentially contain 1-7 carbon atoms and consist for the most part of C-- and (^ -hydrocarbons. These reaction products lead to high olefin yields in thermal cracking and result in only one . low condensate addition contains the fission gas and about 15 - 25 wt -.% methane, which can be used for hydrogen production.

Suitable catalysts for the hydrogenation contain a hydrogenation component composed of one or more of the metals the VI. - VIII. Subgroup of the periodic table or their oxides or sulfides. Preference is given to catalysts with a Hydrogenation component, the at least one of the metals cobalt, nickel, molybdenum or tungsten in elemental, oxidic or contain sulfidic form. The hydrogenation component is conveniently applied to a carrier made of acidic silicates, alumino-

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LINDE AKTIENGESELLSCHAFT

Silicates, clays, sands, oxides or oxide mixtures of elements the II. - VI. Main group and the III. - IV. Subgroup des Periodic table, made of zeolitic material or mixtures of these carrier substances. Natural are particularly suitable or synthetic acidic zeolites, in particular zeolites of types X and Y in alkaline earth or rare earth exchanged Form or in their hydrogen form.

The hydrogenating pretreatment is in a favorable manner in a pressure range between 20 and 300, preferably between 30 and 120 bar, at temperatures between 200 and 500 ° C, preferably between 550 and 4-8O ⁰ C, and at a hourly space velocity of the liquid between 0.2 and 10 1 / 1h, preferably between 0.5 and 5 1 / lh.

The subsequent thermal cleavage of the hydrogenated product takes place favorably in a pressure range between 1.5 and 5 bar, preferably between 2 and 3 bar, with an outlet temperature of the cracked gases between 700 and 1000 C, preferably between 800 and 86o ° C and with a dwell time of the material in the crevice zone between 0.05 and 2 seconds, preferably between 0.2 and 0.7 seconds. D? R pre-treated Use is advantageously diluted with steam in an amount between 0.3 and 0.8 kg / kg of feed material.

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The steam reforming of the methane takes place favorably in a temperature range between 750 and 1000 ^° C., preferably between 800 and 900 ^° C., at a pressure between 5 and 40 bar, preferably between 20 and 30 bar and at a space velocity between 1500 and 2500 1/1 .H.

The method according to the invention is illustrated below the figure, which schematically illustrates the process sequence of an exemplary embodiment.

The heavy feedstock made from gas oil or vacuum gas oil can exist, passes through line 1 into the hydrogenation stage 2, in which the hydrogen required for the hydrogenation is supplied via line 3. The hydrogenation takes place in the presence of catalysts containing nickel, cobalt, molybdenum or tungsten or mixtures thereof on zeolitic supports. The hydrogenated product then reaches the thermal cleavage stage 5 via line 4 Most of the products emerging in gaseous form from the hydrogenation stage 2 on a recycle basis via the lines 6, 7 and 3 fed back to the hydrogenation stage 2. In addition to the hydrogenated use, the thermal cleavage stage 5 is supplied via line 8 Steam supplied to dilute the fissile material. The cleavage products cooled in a quench cooler (not shown) then pass through a line 9 into a separation stage There the olefins are isolated as desired process products

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and withdrawn via line 11, in addition is hydrogen separated and fed back to the hydrogenation stage 2 via lines 12, 7 and 3. Furthermore, the result of the split will be Methane is separated off and removed from separating stage 10 via line 13. Eventually, more by-products are over line 14 withdrawn.

The separated methane arrives via line 13 in a system 15 for steam reforming. The plant 15 is continues to be supplied with steam via line 16. The energy for steam reforming is obtained by burning a Part of the methane obtained, which is branched off from line 13 via line 17. If more in the case of thermal cleavage Methane was formed than is required for the steam reforming, the excess methane is withdrawn via line 17 and recycled elsewhere.

During the steam reforming 15, a gas consisting essentially of hydrogen and carbon oxides is formed is fed via line 18 to a separation stage 19 in which the carbon oxides are separated off and drawn off via line 20 will. The hydrogen stream produced is returned to the hydrogenation stage 2 via lines 7 and 3.

The hydrogenation stage 2 can finally also be connected to an external hydrogen supply via lines 21 and 3

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can be connected, which is only required in exceptional cases. This can be the case, for example, when the light hydrocarbons formed in the thermal cracking occur in such a small amount that they do not meet the hydrogen requirement after their steam reforming, or if operational disruptions occur.

Some embodiments of the process according to the invention, in which both the feedstock and the reaction conditions were changed, gave results which are described in FIGS the following examples are given.

Example 1 ;

A gas oil with the properties given in Table I, column (l) was used as the feed. It was hydrogenated at a pressure of 80 bar and at a temperature of 450 ° C. in the presence of a nickel-molybdenum catalyst on a magnesium-exchanged zeolite Y support at a space velocity of 2.6 l of feed material per liter of catalyst material per hour. The hydrogen consumption was 570 Nl / kg input. The hydrogenating pretreatment carried out in this way led to a product which was ^{completely gaseous at 0} ° C. and at normal pressure. The composition of the hydrocarbons was determined by gas chromatographic analysis and led to the result given in Table II, column (1). The hydrogenated gas oil was then with 0.4o kg

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Steam per kg of gas oil diluted and thermally split. The Brexit The temperature of the cleavage products was 840 ° C. The distribution of the cleavage products is given in Table III, column (l).

The hydrogen balance in this process is given in Table IV, column (l). The hydrogen requirement listed in the first line is offset by the amounts of hydrogen and methane generated during thermal cracking. In order to cover the hydrogen requirement, it is necessary to feed about 55% of the methane produced into the steam reforming process, taking into account that part of this methane is burned to provide the energy required for the steam reforming process.

Example 2 ;

The same feed as in Example 1 was used. Was hydrogenated in this case, at a pressure of 50 bar and a temperature of 45O ⁰ C. over a cobalt-molybdenum catalyst on decationized Y zeolite was passed, the feedstock with a Raurageschwindigkeit of 1.7 per 1 liter catalyst material per hour. The hydrogen consumption was 510 Nl per kg of feed material.

In the hydrogenation, a product was obtained which at 0 ⁰ C and at normal pressure to 21 wt .- $ of liquid and 79 wt -% consisted from gaseous components.. The overall composition of the liquid and gaseous products was determined by

-A

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a gas chromatographic analysis determined. The result is given in Table II, column (2).

The hydrogenated product was then thermally cracked at a steam dilution of 0.6 kg per kg of feedstock, whereby the cleavage products again emerged from the cleavage stage at a temperature of 840 ° C. The distribution of the fission products is given in Table III, column (2).

In this case, around 68% of the methane produced had to be converted to cover the hydrogen requirement. The hydrogen balance is given in Table IV, column (2).

Example 3 :

A vacuum gas oil, the composition of which is given in Table I, column (2), was at a pressure of 50 bar and a temperature hydrogenated at 450 ° C. The feedstock was with a nickel-tungsten catalyst on decationized zeolite Y with a space velocity of 0.85 liters per liter of catalyst material and hour led. The hydrogen consumption was 590 Nl per kg of feedstock.

In this hydrogenating pretreatment created products that were present in gaseous form liquid at 0 ⁰ C and under atmospheric pressure to 38.2 wt .- ^ and 6l, 8 wt .- ^. The result of the gas

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chromatographic analysis of the gaseous and liquid products is given in Table II, column (3).

Each part by weight of this product was diluted with 0.65 parts by weight of steam and thermally cracked, the outlet temperature was again 840 ° C. The distribution the cleavage products obtained in this way is given in Table III, column (3).

Around 92% of the methane produced was converted to cover the hydrogen requirement. The hydrogen balance for this example is given in Table IV, column (3).

Example 4 ;

The same feed as in Example 2 was used. The hydrogenation was carried out at a pressure of 100 bar and a temperature of 45O ⁰ C. The feedstock was passed over a Kolbalt molybdenum catalyst on decationized Y zeolite at a space velocity of 0.58 liters per liter of catalyst material per hour. The hydrogen consumption was 790 Nl per kg of feedstock.

The hydrogenated products were ^{completely gaseous at 0} ° C. and at normal pressure. The gas chromatographic analysis gave the composition given in Table II, column (4).

One part by weight of this pretreated material was each diluted with 0.4 parts by weight of steam and thermally

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split, with the outlet temperature again at 84o ° C lay. The distribution of the cleavage products is given in Table III, column (4).

Around 93% of the methane produced was converted to cover the hydrogen requirement. The hydrogen balance is given in table IV, column (4).

Table I. (1) (2) 0.82 0.93 density g / ml (25 ° C) 208-354 400-560 Boiling range ° C 1,820 1.631 H: C ratio (mol H / mol C) 0.42 3.2 S content Weight % 50 630 N content ppm 17.9 17.4 Mono aromatics Weight % 10.1 42.9 Poly aromatics Wt .- ^ 72.0 39.6 Paraffins + Weight # Naphthenes 0 0.07 Hexane-insoluble ver
ties Weight %

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Weight # Tabel D. II (2) (3) (4) Weight % ( , 0 0.8 1.6 2.33 CH4 Weight % 4th , 3 3.5 4.8 5.35 C2H6 Weight % 8th ,1 28.6 19.8 32.95 C3H8 Weight % 40 , 6 33.5 29.9 41.71 (i + n) -C4H10 Weight % 33 , 0 15.1 12.2 17.33 (i + n) -C5H12 Weight # 6th , 9 0.32 C5 + Weight % 7th 0.1 0.3 cykl. C5-KW Weight % 5.6 14.96 (C6 + CT) -KW Weight % 5.9 2.13 (C8 + C9) -KW Weight ^ 0.5 0.58 (C1O + C11) -KW Weight # - 0.07 CIl + -KW Weight % 0.5 2.18 benzene Weight % 2.2 5.90 toluene Weight % 2.3 3.73 Xylenes Weight % 0.3 0.63 Ethylbenzene Weight # 0.8 0.72 Trimethyl
benzenes 0.5 0.52 Methyl methyl
benzenes

unsaturated HC wt.

0.01

H2

CH4 C2H4 C3H6 c4h6 C4h8 05+

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% Tabel III 1.2 1.1 1.3 Weight % 1.4 19.4 17.6 23.1 Weight % 25.8 27.5 25.8 29.9 Weight % 28.4 15.0 14.1 16.8 Weight % 15.4 2.8 4.8 5.2 Weight % 2.6 4.9 2.8 3.4 Weight 4.8 19.4 24.8 8.6 Weight 8.4

LINDE AKTIENGESELLSCHAFT Table IV

Nl H2 / kg mission (D (2) (3) W. H2 demand of the
Hydrocracking Nl H2 / kg mission 570 510 590 790 H2 generation at
the thermal
cleavage l6o 130 125 l60

Methane production in thermal cleavage

Nl CH4 / kg input 380 280 250 340

Nl CHVkg insert 210 + 190+ 230+ 315+ 30

20 20 20 ~ ~

Methane demand for H2 generation through steam reforming

"ReI.Ji of methane attack 55 + 5 68 + 7 92 + 8 93 + 7

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Claims (10)

Claims 1. "Process for splitting heavy hydrocarbons, wherein the hydrocarbons are first subjected to a hydrogenating pretreatment in the presence of hydrogen and a catalyst subjected and then thermally cracked, characterized in that the for the hydrating pre-treatment required hydrogen at least partially by steam reforming of generated during the cleavage light hydrocarbons is obtained. 2. The method according to claim 1, characterized in that the energy required for the steam reforming process the combustion of some of the light hydrocarbons produced in the cracking is obtained. 3. The method according to claim 1 or 2, characterized in that the hydrogen generated in the thermal cracking is fed to the hydrogenating pretreatment. 9098 3 3/0208 ORIGINAL LINDE AKTIENGESELLSCHAFT 280S72Q 4. The method according to any one of claims 1 to 3, characterized in that that the reaction conditions for the hydrogenating Pretreatment and thermal cleavage of the hydrocarbons as well as the steam reforming of the light ones obtained Hydrocarbons are coordinated so that the amount of hydrogen produced or the light hydrocarbons to cover the hydrogen requirements of the hydrating Pretreatment is sufficient. 5- The method according to any one of claims 1 to 4, characterized in that that for the hydrogenating pretreatment catalysts with a hydrogenation component consisting of one or more of the Metals of the VI - VIII. Subgroup of the periodic table or their oxides or sulfides, on an acidic carrier be used. 6. The method according to any one of claims 1 to 5j, characterized in that that for the hydrogenating pretreatment catalysts with a hydrogenation component on a support consisting of acidic Silicates and / or aluminosilicates and / or clays and / or sands and / or oxides or oxide mixtures of elements of the II. - VI. Main group or III, - IV. Subgroup of the periodic table and / or consists of zeolitic material, be used. 909833/02 LINDE AKTIENGESELLSCHAFT 7. The method according to one of claims 1 to 6, characterized in that the hydrogenating pretreatment in a pressure range between 20 and 300 bar, at temperatures between 200 and 500 ⁰ C and at an hourly space velocity of the liquid between 0.2 and 10 l / l · h is carried out. 8. The method according to any one of claims 1 bis'7 »characterized in that the thermal cleavage in a pressure range between 1.5" and 5 bar, at an outlet temperature of the cracking gases between 700 and 1000 ⁰ C and a residence time between 0.05 and 2 seconds is carried out., 9. The method according to any one of claims 1 to 8, characterized in that that methane as a feedstock for steam reforming is used. 10.Verfahren according to any one of claims 1 to S, characterized in that the steam reforming is carried out at temperatures between 750 and 1000 ° C, a pressure between 5 and 40 bar and a space velocity between 15ΟΟ and 2500 l / l "h. 909833/0208