DE1543195A1 - Process for the production of high purity benzene - Google Patents

Description

W. 12182/65 9 / Hir

Mitsubishi Petrochemical Co., Ltd. lokyo (Japan)

Process for the production of high purity benzene.

The invention is directed to a method for the production of large quantities of high purity benzene from cracked oils, which is a by-product of its manufacture of gaseous olefins by steam cracking arise from petroleum hydrocarbons.

Such cracked oils, which are obtained as a by-product of the steam cracking of petroleum fuels to produce gaseous olefins such as ethylene and propylene, normally contain not less than 30 qevi, - and sometimes even not less than 60% by weight , of aromatic Hydrocarbons; the by-product cracked oils are therefore excellent

ORIGINAL INSPECTED

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aromatic materials.

Since such cracked oils have large amounts of very reactive unsaturated components, especially diolefins, However, they tend to form resinous or coke-like polymerizate when they are in a heat exchanger and a tubular preheater} this polymer is heated up when heated the heat exchange surfaces and pipe walls deposited, which worsens their thermal conductivity and continues to clog the pipelines within a short period of time. Also included these cracked oils contain sulfur compounds in the region of 0.01-0.1% by weight, with the majority being made up of it There is thiophene, which is extremely thermally stable and the most difficult compound to separate from benzene is. For these reasons, the efforts to produce high-purity aromatic hydrocarbons from the cracked oils to win the technically flawless and economical Elimination of diolefins and thiophene is a very difficult and serious problem,

Conventionally, therefore, are for extraction aromatic hydrocarbons of high purity from the cracked oils have been used very cumbersome and intricate procedures, e.g., in succession one

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First stage hydrogenation, a second stage hydrogenation, solvent extraction and distillation. The hydrogenation The first stage is to convert the diolefins contained in the cracked oils to monoolefins and / or paraffinic hydrocarbons carried out by means of hydrogenation and the second stage hydrogenation is used to convert the Monoolefins to paraffinic hydrocarbons and for conversion the sulfur compounds contained in the cracked oils to hydrogen sulphide by means of hydrocracking, in order to separate and remove them. With the conventional Methods will continue after the two-stage hydrogenation aromatic component extracted with a solvent and thereby from. separated from aliphatic hydrocarbons; furthermore the aromatic component is ent! tending solvent distilled to make such aromatic To extract hydrocarbons such as benzene, toluene and xylene

Among these aromatic hydrocarbons, benzene in particular is in greatest need and accordingly If it is desired to produce large quantities of benzene, the conventional methods are those described in US Pat alkyl-substituted aromatic hydrocarbons such as toluene and xylene obtained above Hydrodealkylation converted to benzene.

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However, these conventional methods require extremely intricate and cumbersome operations and they can, in particular because of the additional separation step of the aromatic hydrocarbons of aliphatic hydrocarbons by solvent extraction, hardly considered economically satisfactory Working procedures are addressed.

The solvent extraction step indicated above is necessary because some of the hydrocarbons formed by the previous hydrogenation form an azeotropic Forms mixture with benzene or toluene; since this has a boiling point close to that of benzene or toluene an attempt to separate non-aromatic hydrocarbons by distillation has not turned out to be a satisfactory one Result even when using a multi-tray distillation tower.

Accordingly, the main purpose of the invention is to provide a process for the production of benzene at a higher level Purity obtained from the cracked oils, which are a by-product of the production of gaseous olefins such as ethylene and propylene, from the steam cracking of petroleum hydrocarbons incurred, using relatively fewer work measures.

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Another purpose of the invention is to provide a process for producing high purity benzene from the cracked oils in a straightforward manner in high yield without the solvent extraction step.

Yet another purpose of the invention is to provide a technically and economically advantageous one Process for the recovery of high-unit benzene from the cracked oils at low cost.

Other purposes and advantages of the invention will appear from the description below.

In the method according to the invention are of the cracked oils which are produced as by-product in the production of gaseous olefins such as ethylene and propylene, by Wasserdampfkrackung of petroleum hydrocarbons, those having a boiling point in the range of 60-200 ⁰ C at atmospheric pressure as Einsatzmateriaiien used. Accordingly, such cracked oils are hereinafter referred to as the cracking oil materials. As the cracking oil materials according to the invention, particularly those composed mainly of hydrocarbons having 6 to 9 carbon atoms are preferred. The invention provides a process for directly obtaining high-unit benzene in high yields from such cracking oil materials, hereinafter also called cracking oils.

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According to the invention, such cracking oil materials of the type (1) described above are in the first stage with 0.2-2.0 moles of hydrogen per mole of cracking oil material (0.2-2.0 moles times the material cracked oils of hydrogen) in the presence of a hydrogenation catalyst brought at temperatures in the range of Eaumtemperatur to 25O ⁰ C and pressures of not less than 10 kg / cm into contact to the diolefins in the cracked oil materials to mono-olefins and / or Parafi'inkohlenwasserstoffen convert.

(2) In the second stage the oil obtained in the preceding first step, with 2-20 moles of hydrogen Ze mol oil (2-20 mol times the Oil of hydrogen) at temperatures in the range 500-800 ⁰ C and pressures of

ο
brought into contact with not less than 10 kg / cm in order to convert the monoolefin and / or paraffin hydrocarbons to lower saturated hydrocarbons, e.g. methane and ethane, by means of hydrocracking and to dealkylate the alkyl-substituted aromatic hydrocarbons contained in the cracked oils.

(3) Thereafter, as the third stage is heated, the product obtained in the second stage in the presence of a hydrodesulfurization catalyst at a temperature between 100 and 25O ⁰ C, to the information contained in this product sulfur compounds (mainly thiophene) to decompose and to separate in the form of hydrogen sulfide and to

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remove.

(4 ·) As a fourth stage, benzene is made from the product the third stage by suitable measures known per se nai-men, e.g. distillation, separated.

Each of the aforementioned work steps carried out in the method according to the invention is explained in more detail below.

The first stage

The hydrogenation treatment of the first stage can be carried out either in a fixed bed using a shaped catalyst or in a suspended or fluidized bed using powdery! Catalyst are carried out. Any known hydrogenation catalyst can be used as the catalyst. For example, oxides and sulfides of metals from groups YI and YIII of the periodic table can be used. Furthermore, any other compound which has catalytic activity in hydrogenation can be used either alone or in admixture with other catalysts. Suitable hydrogenation catalysts are, for example, Mi, Pd, Pt, cobalt molybdate, WSp> ITiS, MoSp, MoS ,, OoMoO ^ -AlgO ,, MoS ₂ -activated carbon, Co-Fe-Ni, WS ₂ -UiS-Al ₂ O ₇ and Cr -Mo-W-SuIfide, etc. For the hydrogenation, these metal compounds can be used with suitable carriers, for example activated aluminum oxide, artificial

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or natural silicon, oxides of magnesium, zirconium and titanium, and other similar substances · Particularly suitable catalysts are Pd and Co-Mo catalysts.

The suitable reaction conditions are not permanent and depend on the type of catalyst used, but in general the starting materials are ^{brought into contact with the catalyst at reaction pressures above 10 kg / cm 2} and temperatures in the range from room temperature to 250 ° C. in the presence of hydrogen. In this case, must always be ensured that a temperature rise is avoided over 250 ⁰ G, in order to prevent polymerization of diolefins.

When a Oo-Mo catalyst is used, particularly preferred reaction conditions for the selective hydrogenation of diolefins and a portion of the monoolefins without bringing about a polymerization of diolefins reaction temperatures in the range of 150 - 23O ⁰ C and Reaktiongdrücke of 10-80 kg / cm.

When using a Pd catalyst reaction temperatures are 20-60 ⁰ C and pressures of 10-80 kg / cm satisfactory; however, if the feed used contains catalyst poisons, such as carbon monoxide and hydrogen sulfide, it is desirable to remove such gases beforehand.

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- 9 - The reaction pressure of the first stage should be at least

10 kg / cm, since at lower pressures the catalytically * Activity is decreased and accordingly the hydrogenation of diolefins is insufficient. However, there is no rigid upper limit for pressure. In general, pressures increase

above 80 kg / cm not the catalytic one in any noteworthy way Activity and consequently the use of such high pressures is not justified, as far as the with structural and operational problems associated with high pressures.

In performing the first step described above, the highly active component, e.g. The diolefins present in the cracked oils, stabilized and so treated feeds can now do that Form feed for dealkylation.

The cracked oils that are hydrogenated in this way have been subjected to the first stage, are accordingly directed to the location of the second stage treatment, in which the Excess hydrogen gas of the hydrogenation stage in the resulting 3? form than that required for the second stage reaction Gas is used.

The second stage

The purpose of the second stage is to add the alkyl substituted aromatic hydrocarbons dealkylate and the non-aromatic carbon

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ORlGfNAL INSPECTED

- ίο -

To completely decompose hydrocarbons so that they can be easily separated from the aromatic hydrocarbons in the form of gaseous hydrocarbons such as methane and ithane. Reaction conditions which are suitable for fulfilling this purpose are reaction temperatures of 500-800 ⁰ O _1, ^{preferably 650-730 0} O, tree velocities of the liquid of 1-6, preferably 2-4, and molar ratios of hydrogen to the oil of 2- 10. The head pressure should not be lower than 10 kg / cm, since too low a reaction pressure leads to the fact that small amounts of non-aromatic hydrocarbons, such as olefins, remain with the aromatic hydrocarbons. Although there is no particular upper limit on the reaction pressure, the application continues to lead

as high a bridge as above 60 kg / cm, not too special Advantages and is therefore inexpedient if one considers the structural and operational aspects associated with such high pressures Difficulties taken into account.

In carrying out the second stage, the addition of catalyst is unnecessary and rather it is preferred worked in the absence of catalyst. Since a catalytic procedure using This is often catalyzed by the small amount of sulfur compounds and other impurities that are present in the load is present, is poisoned,

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its activity is impaired. In general, of course, the second working stage of the method according to the invention either thermally (in the absence of a catalyst) or catalytically.

The second stage of the process according to the invention is very advantageous in terms of construction material compared to the conventional thermal dealkylation process in which pure toluene, xylene or catalytic reformate etc. is used as the feedstock. If, in fact, a steel reactor is used in the conventional thermal dealkylation process, core decomposition of carbon rings and thus the deposition of large amounts of carbonaceous substances is brought about by contact catalysis of the steel surface. This greatly reduces the yield of aromatic hydrocarbons and makes continuous operation over long periods of time impossible.In contrast, the process according to the invention has the advantage that even when conventional steel reactors are used, no deposits of carbonaceous materials are observed, because of the Trace amounts of sulfur compounds always present in the cracked oils and the small amount of hydrogen sulfide that was formed in the first stage hydrogenation and is present in the hydrogen gas that remains in the first stage product.

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The third stage

The desulfurization treatment of the third stage is similar to the first stage, but it is the material fed to this stage to the product of the second stage, which consists of hydrogen, methane, ithan and aromatic hydrocarbons (mainly benzene); the sulfur compounds remaining therein consist mainly of hydrogen sulfide and thiophene. The catalyst and the reaction conditions the third stage must therefore be chosen so that the thiophene is decomposed and removed and not more than 0.0001 g / 100 cnr of the same in aromatic hydrocarbons remain while nuclear hydrogenation of benzene rings is avoided.

Conventionally known hydrodesulfurization catalysts can be used as the catalyst of metals of groups VI and VIII of the periodic table in a manner similar to that of The stepping stage can be used, using Co-Mo catalyst particular is preferred. Nickel-containing catalysts are undesirable because they show a strong activity for nuclear hydrogenation of benzene rings.

! The suitable temperature is in the case of using a Co-Mo catalyst 100-230 ⁰ O, and preferably 150-200 ⁰ O. temperatures above 25O ⁰ O should be avoided, as these hydrogenation of benzene rings

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cause · The reaction may occur in. atmospheric pressure run, but pressures of 10-40 kg / cm are preferred. Pressures above 40 kg / cm are not particularly disadvantageous for the heating, but they do not lead either for some advantage »

The fourth stage

The liquid product obtained by removing gaseous substances, such as methane and ithan, from the product the third stage is obtained mainly from benzene and contains minor amounts of toluene and a tarry substance.

In the process according to the invention, benzene is used separated from the liquid product of the third stage by suitable measures such as distillation. Furthermore, this can Benzene obtained in this way by a simple treatment, such as with activated clay, turns into the product very much high purity can be processed.

Thus, according to the invention, benzene becomes high in purity obtained by simple work measures in a very high yield, while at the same time still a small amount of By-product, such as toluene, is obtained. If desired, this toluene can be further converted to benzene by it is introduced into the second stage, along with the feed to that stage.

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As hydrogen, "in the method according to According to the invention, not only purified hydrogen but also any hydrogen-containing gas can be used, e.g. Catalytic reforming by-product gas the dehydrogenation of ethylbenzene, from the production of ethylene or methane reforming gas and the circulating gas of the process according to the invention.

An embodiment of the method according to the invention is described below with reference to the accompanying drawings further illustrated, however, the invention is not limited to this particular mode of operation. The drawing shows in the form of a block diagram only the main facilities required to explain the method, while Associated devices, such as pumps, heat exchangers and compressors, are not shown.

The cracking oils, which are produced as a by-product in the production of gaseous olefins, such as ethylene and propylene, are produced by clay thermal cracking τοη oil hydrocarbons accumulate, are introduced into a pre-distillation tower 2 through a drilling pipe 1. The head of the tower 2 is light oil with not more than 5 carbon atoms removed and the distillate collected at the bottom of the tower 2 is through a ! Pipeline 3 into a further pre-distillation tower 4 introduced. Heavy oils are from the floor of the tower 4

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not less than 9 carbon atoms removed and the ° 6 " ^C 8 ^r3p ek * i ^{oniMl of the} distillate, which boil in the range of 65". 145 ⁰ O, are drawn off from the top of the tower 4 through a pipe 5, with hydrogen aue one Drilling line 6 mixed and fed through a drilling line 7 into a hydrogenation reactor 8 in which the first stage is carried out.

The amount of hydrogen introduced from the well 6 and the reaction conditions in the hydrogenation reactor 8 depend on the type of catalyst used. When a JPd catalyst is used, 0.2-0.5 mol of hydrogen is preferably introduced per mol of the oil material. In this case, the circulating gas should be off. a drilling pipe 19 cannot be used because it contains hydrogen sulfide. Suitable Beaktionsbedingungen temperatures are 20-60 ⁰ O and pressures above 10 kg / cm, preferably below 80 kg / cm. 2.0 moles of hydrogen per mole of oil materials and temperatures of 150 - - ^ Oo hand, if a Mo catalyst is used, 0.5 to 200 ⁰ C vorsugeweise applied, it should be noted wherein in the choice of temperature at the inlet of the reactor! that the temperature of the outlet does not exceed 230 ⁰ O, and it was because of the temperature rise in the reactor as a result of the reaction.

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The hydrogen-oil mixture that the hydrogenation reactor 8 leaves through a pipe 9, is mixed with the hydrogen from a pipe 10 and through a pipe introduced into a preheater 12

The hydrogen from the pipe 10 should be introduced to such an extent that the molar ratio of hydrogen to oil in the pipe 11 has a value of 2-10. Normally, a furnace is used as the preheater. The hydrogen-oil mixture is in the preheater 12 at 600 - 700 ⁰ O heated and then passed through a conduit 15 to a hydrocracking reactor fourteenth

Since the reaction in the reactor 14 is considerably exothermic, when using an adiabatic reactor it may sometimes be necessary to introduce hydrogenated oil, hydrocracked oil or chilled hydrogen from a suitable portion of the reactor 14 to prevent an abnormal increase in temperature. The reaction product is withdrawn from the reactor 14 through a pipeline 15, to 100-200 ⁰ O cooled and a desulfurization reactor 16 is supplied, in the third stage is carried out. In the reactor 16, thiophene is decomposed and the reaction material is passed through a pipe 17 in a gas / liquid separating device 18, where the gaseous components, such as hydrogen, methane and ithane, are led out of the system through a pipe 19, with a part of that

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via the pipes 6 and / or 10 through the device is circulated.

The liquid product is introduced into a distillation tower 21 through a pipe 20. A high-boiling fraction of the distillate with a boiling range above 160 ⁰ G is discharged from the bottom of the tower from the plant and the remainder is led from the top of the tower 21 through a pipe 22 into another distillation tower 23. From the bottom of the tower 23, toluene and xylene (in fact, xylene is essentially absent) are withdrawn through a pipe 24 and, if necessary, returned through the pipe 1. The remaining benzene is passed from the top of the distillation tower 23 through a pipe 25 to a tower 26 where it is treated with clay to remove the trace amount of olefin present therein; after that it is through a pipe 2? withdrawn from the system.

The invention is further illustrated in connection with the following exemplary embodiments.

example 1

The Og - Og fraction of the distillate, which by Removal of the light oil fraction of Oc and less and the Heavy oil fraction from Oq and above from the as a by-product in olefin production by steam cracking of naphtha

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resulting cracking oils had been received, the Operating equipment for the first stage is supplied as cracking oil feedstock of the process according to the invention. In Tables I-III below are the properties of the cracking oil material, the composition of its aromatics and the results of the fractional distillation investigation are given.

Table I.

Properties of cracking oil material, bromine number 34.0

Service number 19 »?

Sulfur content 0.047% by weight

Tabel II

Composition of aromatics in the cracking oil material (by gas chromatography)

Benaol 25.8 wt .- #

Toluene 23.0 "ethylbenzene 7.1"

m-p-xylene 9.3 "

o-xylene 3.5

Og Aroaaten 5.6 "

Total amount of aromatics 74.3 "

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INSPECTED

Table III 67, O ⁰ O Investigation by fractional distillation of the 77, O ⁰ O Cracking oil materialβ 81.5 ° 0 Initial boiling point 89.2 ⁰ O 5% 98.0 ⁰ O 10 % 108.0 ⁰ O 30 % 15O.5 ° E 50% 137 # O ° E 70 % 144 O ⁰ C 90 % 95 % Dry point

In the first stage, a Go-Mo catalyst was used and the feedstock was treated under the following conditions, namely a flow rate of the liquid of 2.3, a molar ratio of hydrogen to oil of 1.0, a reaction pressure of 50 kg / cm, an inlet temperature of 200 ⁰ O and a Auetrittstemperatur of 223 ⁰ O. The product had an oil Bromeahl of 16.7, a diene value of 1.7 and a flohwefelgehalt of 0,034- Öew .- #.

Then, hydrogen cffg as containing 20 mol% methane in an amount became the first stage product added that the molar ratio of pure hydrogen

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to oil was about 4-5, and the mixture underwent hydrocracking subject} this is the second stage. The following reaction conditions were used:

Pressure 20 kg / cm

Inlet temperature 665 ⁰ C 695 ⁰ O JLustrittsremperatur iäfenthaltszeit about 28 seconds

(calculated assuming that the number of moles does not change as a result of the reaction); it became a reaction product obtained according to Table IV.

Table IY

Composition and characteristics of the product of the second stage

18.0 wt% / cracking oil material

methane 18.0 JLthan 18.5 propane 0.6 benzene 51.5 toluene 8.1 Og aromatics 0.8 Heavy fuel oil 5.1

Bromine number des

liquid product. 0.073 % sulfur content of the liquid product 450 parts of a milion (ppm)

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ORIGINAL INSPECTED

The product of the second stage was fed to the desulphurisation in the form it was obtained, which forms the third stage of the process. An Oo-Mo catalyst was used in the desulphurization stage and the treatment was carried out at a reaction temperature of about 180 ^° C. and a pressure of 20 kg / cm. The liquid product obtained from the third stage was then subjected to the fourth stage treatment, that is, it was distilled in a distillation tower of about 40 plates and the benzene fraction of the distillate was separated and treated with clay. The resulting benzene yield was 50.3 % y based on the weight of the oil material. The properties of the product benzene were excellent as shown in Table V below.

Table Y

Properties of the product ^{benzene Specific gravity (15A 0} O) 0.8835 Freezing point, ⁰ O 5

Thiophene, g / 100cm ⁵ below 0.0001

Carbon disulfide, g / 100 cnr ⁵ below 0.0001 copper corrosion no discoloration recognizable sulfuric acid color Kr. 1 or weaker with

Relation to the standard color comparison liquid

Reaction neutral

Color satisfactory

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(Continued Table V)

Testing by fractional distillation

IBP 79.7 ⁰ C

50 % 8O ₁ I ⁰ O

Endpoint 80.1 ⁰ C

Total distillate (volume #) 98.0

Example 2

The same starting material as used in Example 1 was used in the first stage of a Pd catalyst at reaction temperatures of 25 - 4-5 ° C> a pressure of 40 kg / cm and a molar ratio of hydrogen to oil of 0.25. That I The resulting product oil had a diene number of 1.3, a bromine number of 23.2 and a sulfur content of 0.044% by weight.

The above first-stage product was with a hydrogen gas containing 5 mol # methane in one Amount added so that the molar ratio of pure hydrogen to oil was about 3, and fed to the second stage.

The reaction in the second stage was carried out at a reaction pressure of 35 kg / cm, an inlet temperature of 613 ° C and an outlet temperature of 645 ⁰ C; a reaction product having the composition and properties shown in Table VI was obtained.

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! Table VI Wt .- # / cracked oil composition II second stage *
and properties of the product Il methane Il A'than 15.4 dd PiX) ρ 19.4 Il benzene 0.8 Il ioluene 50.5 Cg aromatics 9.4 Heavy fuel oil 1.1

Bromine number of the liquid product 0.054

Sulfur content of the liquid product 520! Eile-je-lflillion

(ppm)

The gaseous components contained therein were removed from the product of the second stage, and hydrogen was added to the resulting liquid product in an amount such that the molar ratio of pure hydrogen to oil was 0.5 a reaction temperature of about 150 ⁰ G and a pressure of 40 kg / cm was carried out using a co-catalyst.

The third stage liquid product was distilled in an approximately 40 tray distillation tower, this represents the fourth stage and the benzene fraction of the distillate has been separated and with activated clay

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treated. Benzene with excellent properties, which was similar to the product of Example 1, was obtained in one yield from about 4-9.8% by weight of the oil material.

Example g

In the range 67-190 ⁰ C boiling fraction of distillate obtained as a by-product of olefin production by cracking of naphtha Wasserdampfkrackung oil was used as oil cracking material of this example.

In the first stage, the above oil material became in the presence of a Ni-Mo catalyst under conditions

with a reaction pressure of 60 kg / cm, a molar ratio from hydrogen to oil of 1.8, an inlet temperature of 185 ° C and an outlet temperature of 222 0 treated. The resulting product was a hydrogen gas containing 15 mol% methane in added in an amount such that the molar ratio of pure hydrogen to oil was 6.4; the mixture was fed to the second stage,

The second stage was under conditions with | one

Reaction pressure of 15 kg / cm, an inlet ^{temperature of 680 0} O and an outlet temperature of 74-6 ⁰ C carried out; the product obtained in this way was cooled to 200 ⁰ C.

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In the third stage, the above product of the second stage was brought into contact with a Co-Mo catalyst at a reaction pressure of 11.4 kg / cm and the resulting product was sent to the fourth stage to be in a distillation tower at about 40 Soils to be distilled. The benzene fraction of the distillate was thus separated and ^{treated with activated r} Don to give a purified benzene yield of about 45.8% by weight of the oil material. The quality of the product benzene was excellent and similar to that of the product according to Example 1.

The following are results of working methods under conditions outside the scope of the Invention are given as control experiments for comparison with the invention.

Control attempt 1

The distillate fraction boiling in the range from 65.2 to 153 ° G from the cracking oils obtained as a by-product in the production of olefins, which had a bromine number of 36-2, an oil number of 20.4% and a total sulfur content of 0.036% by weight, was used as cracking oil material »This oil was produced under conditions with a reaction ^{temperature of 3Bu 0} C, ie a temperature beyond the upper temperature t: retis.e of the first stage according to the invention, a pressure of

BATH ORIGINAL

60 kg / cm ^ and a molar ratio of hydrogen too oil of 1.2 hydrogenated. The resulting hydrogenated oil had a diene number of 0, a bromine number of 0.2, and a sulfur content of 13 parts-per-million (ppm). Wake up some In hours of operation, however, the pressure drop in the reaction zone became excessive and continued operation was impossible.

After the operation was stopped, the reactor was opened and it was found that there was some carbonaceous Polymer had built up in the upper part of the reaction zone in an amount of 0.55% by weight of the oil material.

Control attempt 2

The same starting material, v / ie it at. the control experiment 1 was used in the presence of the same Catalyst as in Control 1 in accordance with those for the first stage of the process according to the invention required conditions, i.e. at a reaction temperature of 185 ° C, a pressure of 60 kg / cm and a molar ratio of hydrogen to oil of 1.2 «· There was no pressure drop in the reaction zone over several

JMß ^ -JnAahfLah ± Rii ^ iir) n fl1e__Re.action was continued smoothly .

Thereafter, the resulting hydrogenated oil was subjected to hydrocracking in accordance with the conditions of subjected to the second stage of the method according to the invention,

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BATH ORIGINAL

ie at an average reaction temperature of 690 ⁰ O, an average reaction pressure of 20 kg / cm and a molar ratio of hydrogen to the hydrogenated oil of 4.5 over a residence time of about 28 seconds. (It was assumed that the number of moles did not change with the reaction). In this control experiment, the third stage, which was intended to follow in accordance with the invention, was omitted and the liquid product of the above hydrocracking was fed directly into a distillation tower with about 40 plates to separate benzene. The benzene obtained in this way had a freezing point of 5 »40 ⁰ O and was of good quality, but it contained about 150 parts-per-million (ppm) thiophene.

Control attempt 3

The hydrogenated oil obtained in the first stage of Vorstenenderi control experiment 2 was alc second stage hydrocracking among the following i3edinp.mgen subject to:

Average reaction temperature 690 ⁰ O

Jt-f'ition pressure '4 k ^ / cm' "

{- ■ in pressure outside of the specified ^ vreichß for the second stage ί oaiäß the invention)

Ratio of hydrogen to (U .-. M hydrogenated oil about 4.5

L ■ .. '<i nt ij al ^; ■: ζ for about 28 seconds

C '% v, ν ~; χ ·' λ <"· assumed that the U) I are not affected by the reaction

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The product obtained in this way by the above hydrocracking was introduced directly into a distillation tower of about 40 plates without the preceding third stage of the process according to the invention, and benzene was separated therefrom. The resulting benzene had an initial point of 4, 85 ⁰ C and a thiophene content of about 1? 0 parts-per-million (ppm); accordingly it was of even poorer quality than the product of control experiment 2.

Control attempt 4-

The starting material obtained by adding 250 parts million (ppm) thiophene had been made to pure benzene, desulfurization tests were carried out under three sets each of different conditions, as given in Table VII below, in the presence of one Oo-Ivio catalyst subjected.

In these experiments, the source of hydrogen was a gaseous genic that uses 15 V0I.-7 & methane and contained 10% by volume of Itban.

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BATH ORIGINAL

- 29 Table VII

Conditions Conditions Conditions outside those inside those outside for the third for the third that for the stage of the stage of the third invention stage of the

invention

Reaction
temperature, 0 300 175 70 Reaction ~
pressure, kg / cm 30th 30th 30th Space velocity
diness of
liquid 3 3 3 Molar ratio
of hydrogen too
oil 3.3 3.2 3.2 Thiophene content of
Product, ppm 0 3 215 Cyclohexane im
Product, wt% 3.3 0 0 Benzene production,
Wt% 96.5 99.8 99.8

In the above experiment at 300 ° C, i.e. one The temperature was higher than the upper temperature limit for the third stage of the process according to the invention Thiophene completely decomposed but at the same time a nuclear hydrogenation of benzene occurred and cyclohexane was formed » At 175 0, i.e. a temperature within the conditions for the third stage of the method according to the invention,

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BATH ORIGINAL

again, thiophene was almost completely decomposed, but furthermore, no nuclear hydrogenation of benzene occurred. In the experiment, which was carried out at 70 ° 0, i.e. at a Temperature below the stated range according to the invention, however, did essentially no thiophene decomposition observed, but the thiophene remained in the benzene and no nuclear hydrogenation of benzene occurred.

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Claims (2)

Claims 1. A process for the production of benzene of high purity, characterized in that first a distillate fraction boiling in the range of 60-200 ° 0 is obtained from the cracking oils obtained as a by-product in the production of gaseous olefins, such as ethylene and propylene, by steam cracking of petroleum hydrocarbons ( Cracking oil material) with 0.2 to 2.0 moles of hydrogen per mole of the cracking oil material at temperatures in the range from room temperature to 25O ⁰ C and pressures of not less than 10 kg / cm in the presence of a hydrogenation catalyst in the first stage To convert diolefins in the cracking oil material to ivionoolefins and / or paraffinic hydrocarbons, in the second stage the resulting oil is brought into contact with 2-10 mol hydrogen ge mol oil at temperatures of % ^{0-800 0} O and pressures of not less than 10 kg / cm to hydrocrack the monoolefin and / or paraffin hydrocarbons and the alkyl substituted ones contained in the cracked oil to dealkylate aromatic hydrocarbons, in the third stage that itself 909831/1380 BAD ORiGiNAt ^{The resulting product is heated to 100 to 250 0} O in the presence of a hydrodesulfurization catalyst in order to decompose and remove the sulfur compounds contained in the product, and then, in the fourth stage, separates benzene from the resulting liquid product. 2. The method according to claim 1, characterized in that the cracking oil. '. Material which consists mainly of hydrocarbons with 6 to 9 carbon atoms composed distillate fraction of the cracking oils, which as a by-product in the production of gaseous olefins such as ethylene and propylene by steam cracking of petroleum hydrocarbons incurred ©, used. 3. The method according to claim 1 or 2, characterized in that the second stage is essentially in Absence of the catalyst used in the southernmost stage performs. 4. The method according to any one of claims 1-3 »characterized in that the third stage is carried out in the presence of 0.2 to 2 moles of hydrogen per mole of the product of the second stage. 5. The method according to any one of claims 1-4, characterized in that gaseous components contained therein are removed from the product of the second stage and the remaining liquid material with 0.2 to 2 moles of hydrogen per mole of the liquid material at temperatures from 100 to 250 C and pressures from atmospheric pressure to 60 kg / cm 909831/1380 _8A D in the presence of a hydrodesulfurization catalyst. 6. The method according to any one of claims 1-4, characterized in that the product of the second stage as it is to a temperature between 100 ° and 250 ⁰ O at a pressure between atmospheric pressure and 60 kg / cm in the presence of a hydrodesulfurization catalyst heated. 7. The method according to any one of claims 1-6, characterized in that the first stage under pressure in the range of 10 to 80 kg / cm. 8. The method according to any one of claims 1-7, characterized in that the second stage at Performs 2 pressures in the range of 10 to 60 kg / cm. 9 · The method according to any one of claims 1-8, characterized in that the third stage at Pressures in the range from atmospheric pressure to 60 kg / cm performs. 909831/1380 Blank page