DE1294366B - Process for the thermal cracking of hydrocarbons - Google Patents

Description

withdrawn product vapors directly with 30 to 70 weight percent of i ₀ can be related to this product by simple distillation well separated. Up until now it had to be assumed that the vapors were in contact with a waxy distillate
brings these product vapors in 0.2 to

2 seconds to be quenched below 538 ° C

Separate olefins with 10 to 16 carbon atoms by simple distillation, with only one low polymer contamination occurs.

It has been found that the polymeric products formed during the cracking of light petroleum are which are in the same range as the straight-chain olefins with Ciobis formed during wax cracking Ci (j-carbon atoms are boiling, in terms of quantity

in the usual cleavage process with a high degree of conversion polymers formed in the Straight-chain olefins formed by wax cleavage

and would contaminate a greater part of the waxy distillate at i _5. The boiling range and the about 593 ° C is split, and that one from the extent of polymer formation allow this resulting mixture of Cg to Cig olefins
rich fraction and a to C ₂ - to C5 olefins
and -diolefins-rich fraction cuts out.

The invention therefore relates to a method for steam cracking petrolatum (Paraffinum liquidum) at a low degree of conversion, in which straight-chain olefins with 5 to 18 carbon atoms can be obtained. These are olefins

according to the invention as an additional product at a 25 less than 20%, normally less than 10% Steam cracking of the known type (with a high degree of the amount of straight-chain olefins with the same degree of conversion) obtained from light petroleum, with boiling range. Since also the one after the well-known mainly unsaturated C2 to Cs hydrocarbons, steam cracking processes with a low conversion as Butadiene, isoprene and propylene are formed. degree of olefins formed by petrolatum

According to the invention, the liquid petrolatum, 30 branched chain olefins, some diolefins and some which are contaminated with a low degree of aromatics conversion, is a certain Reithermisch to be split, the one from the oil extraction of these olefins, for example by solution splitting plant with a temperature of 760 to 816 ° C medium extraction or selective hydrogenation in need, not quenched electricity supplied. manoeuvrable so that it can be used as a starting product for an-thereby you can reach both the fast racks for the production of detergents or for Scare the from the steam cracking plant with high use in the Oxo process. A mixture Temperature coming stream as well as only with about 10% polymer products, the largest parts associated with a low degree of conversion are olefinic in nature, makes only a slight one Cleavage of the petrolatum. Intensification of the necessary cleaning

The thermal cleavage of waxes or Pe- 40 processes is necessary and increases the costs for this trolatum is known e.g. B. from the German patent - not significant.

font 753 849. The same is true of the steam rack.

of petroleum known, with about 45 to 80 weight, according to which no significant changes are converted to dop percent in Gj hydrocarbons power, namely for additional production and predominantly olefins and diolefins with 2 to 45 large amounts of linear olefins with Cs- to Cm -5 carbon atoms are obtained. Temperatures and residence times must be controlled very carefully to prevent further cleavage
also to prevent polymerization.

Carbon atoms can be exploited, it is clear that the new process is economically extraordinary Offers advantages. In practice, the only major in-

The utilization of the waste heat from a first 50 investment item, the fractionation device for the reaction stage in a second reaction stage, is a measure that is frequently used _{to obtain the C 0 to C w fraction.} from one from the steam cracking deterrent tower

It has now surprisingly been found that the steam cracking of a light petroleum successfully with

emerging bypass flow is necessary and necessary for the purpose of removing the diolefins and aromatics

the steam rake of wax or petrolatum 55 devices for treating the current.

can be combined. Since you have so far been a very rapid quenching of the low molecular weight olefins and diolefins considered essential (U.S. Patent 2,951,029), and the thermal cleavage of

waxy distillates at relatively low temperatures are required, which is not economically advantageous. temperatures carried out (Sachanen, "The Chemi- (The attack on C3 during wax cracking with a cal Constituents of Petroleum" [1945], p. 288;
U.S. Patent 2,172,228; French patent specification 1,136,012), it is surprising that it is under
the combination of the two splitting processes 65
prevailing conditions (small amount of quenchant, relatively high temperature and long
Residence time in the 2nd stage) is possible, a noteworthy

So the following are the advantages of the present new process:

1. If the wax cracking is carried out separately, there is a special system for the light ends

the low conversion rate is 8% or less, and the product is also not particularly good olefinic.)

2. Take over the waxes, petrolatums or paraffins used as quenching oil an important function in the main steam cracking process.

3. Wax and petrolatum are preferred feed materials for wax crackers and also of the highest value. A raw paraffin stream for refining (untreated Gas oil, the raffinate from a catalytic circulation system) is cheaper, but the possible degree of Conversion into linear olefins of good quality is lower here than with wax. The cracking plant will thus more expensive, since more load has to be processed than with pure wax or petrolatum. In which The method according to the invention is the quenching oil (after which the greatest economic advantages showing method) is only cracked up to a few percent (3 to 5) anyway, and that's why you can the low conversion ratios and those for cracking in the mild gas oil cracking process largely tolerate the large quantities of oil required from an economic point of view.

4. The pour point and cloud point of the quench product is increased by 2.78 to 5.56 ° C. Therefore, if gas oil or a raffinate from a recirculation system is used for this deterrent, so becomes:

a) quenching the light petroleum steam cracking stream;

b) straight chain olefins made from the cheapest starting material;

c) the pouring point and the cloud point of the middle distillation products arising from the quenching oil lowered.

In the drawings, an explanation is given of a steam cracking furnace and a quenching plant.

F i g. 1: A light crude oil with a boiling range between 38 and 149 ^° C., preferably between 38 and 104 ^° C., best between 71 and 104 ^° C., is fed into the cracking plant 3 via line 1 together with steam supplied via line 2 . This plant will be at 704 and 816 ° C, preferably operated at 749-788 ⁰ C, for example at 76o ⁰ C, under a pressure from 0 to 3.5 atm, preferably 0.35 to 1.75 atm, for example, 0 , 7 atü, with residence times of 0.1 to 5, preferably from 0.5 to 2, for example 1 second, the amounts of steam supplied from 0.1 to 1, preferably 0.2 to 0.5, e.g. B. 0.25 kg of steam per kg of oil. These conditions are set so that the conversion into C3 hydrocarbons is more than 40 percent by weight, preferably 45 to 80 percent by weight. A waxy distillate serving as quenching oil is fed in via line 6 in order to quench the stream coming from the cracking plant, which is brought into the quenching zone 5 via line 4. This quenching zone consists of an elongated tube, which has devices for multiple or alternating injections of the waxy distillate oil via lines 7, 8, 9, 10, 11, 12 and 13 in addition to line 6, if this occurs while the vapors are flowing through the Pipe is required. The quenched products coming from the cracking of the light petroleum and from the cracking of the wax distillate with a low degree of conversion are fed from the quenching zone 5 via line 15 to further quenching systems and, for the purpose of separating the products, fractionation systems.

Suitable for quenching waxy distillate oils are highly paraffinic crude oils which contain less than 50 weight percent aromatics and naphthenes, and from 260 to 65O ⁰ C, preferably 316-593 ° C, for example 343-427 ° C, boil. These paraffin oils can come from Lirik, Bahia or San Joaquin crude oils, for example. Furthermore, a petrolatum with a boiling range between 343 and 593 ⁰ C and a wax content of about 10 to 60% is suitable. Other suitable products are heavy gas oil fractions from less paraffinic crude oils, for example crude oils from the Middle East, but the resulting straight-chain olefins are not as good in quality. Other starting products are extracted gas oils (from which some of the aromatics and naphthenes have been removed) as well as the raffinate from the extraction of catalytic cyclic cracking plants with a boiling range of 343 to 482 ° C. All of these products result in linear olefins with Cs to Cis hydrocarbons in good yield.

The quenching can be carried out either by adding quenching oil at many points in stages along the quenching zone or by adding all of the quenching oil once at the beginning. In some circumstances it can be advantageous to add the largest amount of the quenching oil at the beginning so that the temperature can quickly rise to about 650 to 705 ° C, e.g. B. to 677 ⁰ C, so as to avoid further cracking and polymerizing of the high temperature, coming from the cracking of the light petroleum product and to achieve that the cracking of the waxy distillate for the most part at the preferred temperatures about 593 ⁰ C takes place. It is also possible to supply water via lines 6 to 14 for additional temperature regulation and, if necessary, to introduce steam at the beginning of the zone via line 6 to regulate the ratio of steam to hydrocarbon in the quenching zone. The waxy distillate oil can at temperatures from 205 to 427 ⁰ C, preferably from 260 to 37o ° C, for example at 316 ° C and calculated according to the exiting gaseous stream (including H2O), in an amount of 30 to 70 weight percent, preferably 40 up to 60 percent by weight, e.g. B. 55 percent by weight, are supplied. Quench times are between 0.2 and 2 seconds, preferably 0.2 to 1 second, for example 0.5 seconds (the time required to reduce the temperature to less than about 538 ° C).

After quenching, the separation is effected of the cracked total product in the following manner: The exit 538 ⁰ C product is passed in one of the usual Dampfcrackabschrecktürme in which by known fractionating the original, coming from the steam cracker product from the auxiliary, derived from the wax cracking treatment product is separated. The light products (C5 and lighter) are drawn off overhead as a gas, which is further processed in one of the usual plants for light fractions. Steam-cracked petroleum (final boiling point around 149 ° C) is also

5 6

if drawn off overhead as liquid and measured in the quenching zone. As for the former,

the same system for light fractions was used in a laboratory

and / or a known petroleum fractionation treatment steam cracking operation

ment and at the end of a charcoal treatment used to determine the reaction rate constant

subject. 5 for crack treatment at a specific

The straight-chain olefins are used as a temperature and a certain pressure.

average several side streams from the quenching tower:

withdrawn and can be tempered by steam distillation of the wax

for removing lighter materials and with Destil SL wax loading

lation for the separation of finer fractions _{further- ϊ0} T _em , JLt, \ i · 'kV;™' δ ', 7 ^ · «

are processed. Before these processing stages dTschlanee 593 ° C

or afterwards an extraction and / or v> ™ p'iw't 1 <? ν Λ

"" ■ * «Ä« Äe :: I StTf

and aromatics to clean. 15 P ^ze

In the following examples and tables, the cracking

explained: speed constant, K, as follows

1. that there is enough heat available,

the proposed cracking treatment by dx ν, mn

respectively; ²⁰ "dö" ^{= K} ' ⁽¹⁰ ° ~ ^x) '

2. that the kinetic conditions are favorable for the reaction; χ = conversion into C ₃ products in weight

3. that only small amounts of contaminating substances ■ P ^r ? ^ze " ¹ '

(10 to 25 percent by weight) in the form of poly- 25 ^{β = time} 'customers.

meren of the same boiling range from the

Petroleum vapor crackers in the cracked wax- With an equal variation of K ₁ versus the

product occur; Temperature (t ° C) as with other constants of the

4. That with the wax distillate the rate of conversion of gas oil resulted in the ^{relationship of up to 10 and 20 percent by weight per passage 3 °}

can be achieved ( _{unconverted, 47 gno N}

Product can of course be replaced by Destil- (K ₁ = K ₁₂₀₀ P, 18 ■ 10 ¹² ] - ) ·

lation separated and recycled); ^ i + 4oü /

5. that in this way under extremely favorable economic 35 A whole elevation of such Variierungen of K-scientific conditions large amounts of straight versus temperature was calculated and is made in-chain olefins having Qo 'to the Cu F i g. II shown.

can be (e.g. 14 515t olefins with regard to the temperature gradient along the

CiQ to Cn per year in a petroleum vapor cracking quenching zone, a heat equalization (under

system with a daily output of 954 m ³ ), 40 taking into account the endothermic heat of reaction)

and created by ten identical

A technical steam cracking plant with a high degree of conversion is under the similar conditions operated. Instead of the usual catalytic cycle product, it is used as a quenchant a wax distillate preheated to 316 ° C. in one of the drawings (FIG. 1) corresponding Plant used. So much of the wax distillate gets into what comes out of the cracking plant Product injected so that it is cooled from 760 to 538 C. In the quenching zone, a Dwell time of, for example, 0.5 seconds is observed, with the entire length of the zone quenchant is evenly added to the flowing gas stream. It will obtained similar results as with a known quenching treatment in which a single injection point is present at the feed opening.

To determine the level of conversion of the quenching oil occurring in the quenching zone Both the reaction rate constant and the temperature gradient along the

pfSf €

the quench zone shows F1 g. III. In this, the coordinates of each curve are indicated by the arrows drawn in, the x-coordinate having a double graduation, which applies to both curves. Likewise, the level of quenching oil conversion, which results along the quenching zone, was calculated from the temperature gradient and from the plot of the reaction constants with respect to temperature and is shown in FIG. III. It can be seen from this figure that after 0.1 seconds the temperature has dropped to 649 ° C. and the conversion is almost two thirds complete, while only 20% of the quenching oil has been introduced. After 0.25 seconds, the temperature has dropped below 593 ⁰ C, and 90% of the final conversion has been reached. If necessary, one of the usual (possibly cheaper) quenching oils can be used as the remaining half of the quenching oil to be fed to the quenching zone, since 90% of the total conversion has already been achieved halfway through the quenching zone.

The yields of linear olefins with Cn to C _{] 3} from various gas oil feeds were shown in

I 294366

in a laboratory system and, together with the conversion into Cg products, are in listed in the following table. The table shows that with a strongly paraffinic loading the amount of olefins with Cn to ds about 40 to 50% of the conversion to Cg.

Steam cracking yields Bulge
at Cn to C ₁₃
Weight percent C ₁₁ to C ₁₃ IC ₃ Olefins in C ₁₁ to C ₁₃
Weight percent feed Conversion to C ₃
Weight percent 3.5
3.6
5.8
4.1
3.3
5.0
5.3 0.46
0.49
0.42
0.43
0.74
0.57
0.39 95.6
94.6
84.3
86.3
66.9
67.2
77.5 Eicosan
Cetane
Lirik (Sumatra)
Bahia (Brazilian) ....
Tia Juana (Venezuela) ...
Middle East
Catalytic raffinate
Crack circuit oil after
Phenol extraction .... 7.6
7.3
13.7
9.6
4.5
8.8
13.6

To differentiate the numbers for Cm to Cu of those for Cn to C13 became the latter multiplied by 5/3 which is the molecular weight range. This factor is right by the way very well with the corresponding yields of these fractions in the petrolatum cracking treatment match.

As far as the yield of steam cracking polymers in the Cio to Cu range is concerned, they come from Information from a technical steam cracking plant. The plant processes at a high degree of conversion for G) a mixed petroleum.

Feed:

60 percent by volume 16/71 C

40 percent by volume 138/182 C

Conversion: 55 percent by weight

Oil yield:

Beginning to 16 C.

19.1 percent by weight, calculated on the charge

16/221 C ■., -, ..: ...

23.3 percent by weight calculated on the charge

221/254 C · ■■, ■ ·

0.6 percent by weight, calculated on the charge

254 C + 1.9 percent by weight, calculated on the clothing

These data indicate that the polymer build-up at 204 to 260 C is about 0.1 weight percent of the 5.56 C boiling range feed. However, taking into account that in other plants, feeds with a final boiling point of 104 C are used and that the

35

40

45 conversion is 45 percent by weight, the polymer accumulation in these systems is in the C10 to Cu range probably only at 0.05 percent by weight 5.56 C boiling range. Based on these numbers it can be assumed that the polymer yield in the Cio to Cu boiling range is at most 1 percent by weight, calculated on the charge fed to the camp cracking plant. ,

To lower the pour point after this quenching process: An Aramco gas oil, boiling range 316 to 427 ° C, was cracked in such a way that a conversion to Cs products of 8.3 to 9.2 ¹¹ liters was achieved. The following results were obtained:

Pour point of the starting material

(316 to 427 C) 18.33 C

Pour point of the product 321 C + .. 12.78 C The pour point of the product 316

'up to 427 C must be ....,' .. <12.78 C

The product 321 C + accounted for 63 to 66% of the starting material.

It can be seen from this that the new cracking process is a method for lowering the pouring point of the Represents quenching oil. The actual Senkyng betfü > 5.56 C.

At s ρ i el

In a system, as shown schematically in Fig. I, A light petroleum (boiling range 71 to 104 CJ.) was cracked.

In order to demonstrate that in the process according to the invention far lower amounts of Abschre'ckOi used and yet 'good conversions' are achieved, comparative tests were carried out under the conditions of 'USA.-Pätepts 2-951Ό29 carried out; the results 'are' listed in the second column.

Present invention

U.S. Patent 2,951,029

a) At the outlet of the furnace:

Hydrocarbon

steam

temperature

28 412 kg / h

7,961 kg / h

760 C

28,412 kg / h 7,961 kg / h 760 C

909 519/543

continuation

10

Present invention U.S. Patent 2,951,029 b) In the case of quenching (even feeding): Supplied wax quenching oil 19 868 kg / h 113,000 kg / h Temperature at the exit of the quenching zone ... 524 ° C Quenching oil temperature at feed 316 ° C • 288 to 316 ° C Total deterrent time 0.5 seconds 0.005 seconds c) Results: Implementation of quenching oil in C3 product / Throughput (weight percent) 12.5 0.19 Yield from Cio to Cw (percent by weight of Wax) 8.7 0 13 1,728 kg / h 179 14 424 t / year Poly formed in the petroleum steam cracking plant meres in the range C ₁₀ to Cn (weight percent, calculated on the basis of the steam cracking plant led loading) 1 285 kg / h 285 kg / h 2,359 t / year 464 Total yield of Cio to Cm 16,783 t / year

In these tables, the% C3 conversion refers to the amount of C3 gas recovered in weight percent compared to the weight of the cracked petroleum.

Claims (7)

Patent claims: 1. Process for the thermal cracking of hydrocarbons using the Heat from hot fission gases to break down further hydrocarbons, characterized in that that a light petroleum in a crevice zone in the presence of water vapor at temperatures from 704 to 816 ° C with conversion into Cs products of over 40 percent by weight splits, withdraws the product vapors from this cleavage zone, the withdrawn product vapors immediately with 30 to 70 percent by weight, based on these product vapors, of a waxy Brings distillate into contact, causing these product vapors to drop in 0.2 to 2 seconds 538 ° C and a larger part of the waxy distillate at about 593 ° C is split, and that one rich in Cs to Ci8 olefins from the resulting mixture Fraction and one at CV to Cs-olefins and -Cuts out diolefins rich fraction. 2. The method according to claim 1, characterized in that a waxy distillate untreated gas oil with a boiling range of 260 to 649 ° C is used. 3. The method according to claim 1, characterized in that that as a waxy distillate a petrolatum with a boiling range of 343 to 593 ° C is used. 4. The method according to claim 1, characterized in that the light petroleum is a petroleum with a boiling range of 38 to 149 ° C is used. 5. The method according to claim 1, characterized in that the quenching in the Manner occurs that the quenching oil at a plurality of points along a stepped Quenching zone is fed. 6. The method according to claim 1, characterized in that the quenching oil in its Total amount is fed to the quenching zone at a single point. 7. The method according to claim 1, characterized in that that in the first cracking zone steam in an amount of 0.2 to 0.5 kg / kg of oil supplied and residence times of 0.5 to 2 seconds are observed and that also the Vapors emerging from the first cracking zone immediately with a boiling point between 343 and 593 ° C Petrolatum in an amount of 40 to 60 percent by weight, calculated on these product vapors, quenched and maintained in the quench zone temperatures of 760 to 528 ° C will. 1 sheet of drawings