JPH0689341B2 - Aromatic hydrocarbon manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention decomposes petroleum hydrocarbons to obtain olefins and aromatic hydrocarbons [hereinafter, BTX (B represents benzene, T represents toluene, X represents xylene). Abbreviated as)], etc., for producing a useful petrochemical product with high yield and high selectivity.

(Prior Art) Conventionally, as a method for converting light gaseous hydrocarbons such as ethane and propane and liquid hydrocarbons such as naphtha and kerosene into olefins and BTX, the first method is steam cracking. It is a method of using a tube type pyrolysis furnace called as (for example, described in "The Oil and Gas Journal" P220-222. MAY12,1969).

The thermal decomposition temperature in this method is usually in the range of 750 to 850 ° C. In the present method, the reaction proceeds by a radical reaction mechanism, so when the decomposition temperature is raised, the yields of ethylene and BTX increase, the yields of propylene and C ₄ fractions decrease, and conversely the decomposition temperature increases. If it is lowered, the yield of propylene is increased, but the yields of ethylene and BTX are greatly reduced.

The second method is to use a ZSM-5 type zeolite catalyst as a method for producing a hydrocarbon rich in BTX components. As this method, for example, (1) a liquid hydrocarbon having 5 or more carbon atoms and having an aromatic content of 15% by weight or less is ZS
Method of converting to aromatic compound by contacting with M-5 type zeolite (Japanese Patent Publication No. 56-426239), or (2) C _{2 to} C ₄
Method of converting paraffin and olefin into aromatic compounds by contacting with ZSM-5 type zeolite (Japanese Patent Publication No. 58-23368).
No.) is known.

(Problems to be Solved by the Invention) However, in the first method, since the reaction proceeds by the radical reaction mechanism as described above, in order to obtain BTX in a high yield,
Extremely harsh reaction conditions are required, and as a result, the so-called coking progress in the tube heating furnace is accelerated, resulting in an increase in pressure loss in the reaction tube and a decrease in reaction selectivity, and the decoking interval is increased. I have to squeeze. Further, there is a problem that it is difficult to obtain a propylene and a C ₄ fraction at a high yield at the same time because the yield composition in the thermal decomposition is biased to ethylene and BTX.

In the second method, in addition to aromatic compounds, hydrogen and light hydrocarbons having 1 to 3 carbon atoms are by-produced in the catalytic reaction, so a separation and purification device is required to recover the target BTX. It is inevitable that the capital investment and energy involved in separation and refining will impose an excessive economic burden. Therefore, in order to produce useful petrochemicals, aromatic hydrocarbons are selectively produced stably and inexpensively while maintaining a flexible yield composition according to demand, and are raw materials. Ethylene, propylene, butadiene, BTX from petroleum hydrocarbons
The total yield (hereinafter abbreviated as the effective product yield) of
There is a strong demand for a production method capable of achieving a yield higher than that obtained by any conventional method.

(Means for Solving Problems) The present inventors have solved the above-mentioned drawbacks of the conventional technology and made it possible to obtain an effective product yield from a petroleum hydrocarbon as a raw material that is higher than that of the conventional method. As a result of intensive studies on a selective aromatic hydrocarbon production method that requires less capital investment and energy, the ethylene production process has a carbon number of 4 to 5 obtained when the petroleum hydrocarbon is pyrolyzed. Hydrocarbons at temperatures of 300-600 ° C and 0-60kg
It is fed to a catalytic cyclization reactor which is brought into contact with crystalline aluminosilicate under the condition of a pressure of / cm ³ G to be converted into an aromatic compound, and the reaction product obtained there is again pyrolyzed in the ethylene production process. Recycle it into a gasoline separator,
This could be achieved by recovering the aromatic compounds as pyrolysis gasoline.

The present invention will be described in detail with reference to the drawings showing one embodiment in which the method of the present invention is applied in engineering.

In the drawings, 1 is a tubular heating furnace for the pyrolysis step, and 2 is a reactor for the catalytic cyclization step. First, the tubular heating furnace 1 is supplied with liquid hydrocarbons such as naphtha and kerosene, preferably naphtha 3, temperature of 750 to 850 ° C, pressure of normal pressure to 15 kg / cm ³ G, 0.1 to 0.8 seconds. Is pyrolyzed with a residence time of ethylene,
The reaction fluid 4 mainly containing propylene and BTX is produced. The reaction fluid 4 enters the heat exchanger 5 to recover heat, and the reaction fluid 6 exiting the heat exchanger 5 enters the pyrolysis gasoline separator 7 to separate the pyrolysis gasoline 8.

The pyrolysis gasoline 8 is supplied to a carbon number 5 fraction separator 9 that separates the carbon number 5 fraction, and the carbon number 5 fraction 13 and BT are supplied.
It is separated into a fluid 10 which is rich in X component and is generally called a heart cut. For the purpose of producing benzene, for example, the fluid 10 is supplied to a dealkylation device 11 to produce benzene 12 by a hydrodealkylation reaction. On the other hand, carbon number 5
The carbon number 5 fraction 13 separated by the fraction separator is fed to the catalytic cyclization reactor 2, but preferably isoprene contained in the carbon number 5 fraction 13 is used as a useful synthetic rubber. It is preferable to provide a device for separating cyclopentadiene as a raw material and for the purpose of suppressing deterioration of the catalyst of the catalytic cyclization reactor 2 with time.

The reaction conditions of the catalytic cyclization reactor 2 are atmospheric pressure to 60 kg / cm ³ G, preferably atmospheric pressure to 10 kg / cm ³ G, temperature 300 to 600 ° C.
It is preferably 450 to 600 ° C. Weight space velocity (WHSV) is
It is 0.1-10 Hr ^-1 , preferably 0.1-2.0 Hr ^-1 , and more preferably 0.1-0.8 Hr ^-1 .

As the catalyst used in the above-mentioned catalytic cyclization, aluminosilicate zeolite having a function as a solid acid catalyst can be widely used. Desirably, a ZSM-5 type zeolite, for example, (1) a method of converting a liquid hydrocarbon having 5 or more carbon atoms and having an aromatic content of 15% by weight or less into an aromatic compound (Japanese Patent Publication No. 56-42639), or ( 2) Ethylene ~
It is preferable to use a zeolite catalyst used in a method for converting a hydrocarbon having a boiling point of 204 ° C. or less to an aromatic compound (Japanese Patent Laid-Open No. 40-4029). The ZSM-5 type zeolite referred to here has the same X-ray diffraction pattern as ZSM-5,
Or it may be similar, but instead of aluminum as metal, it may be replaced by another,
It may contain aluminum and other elements.

As the catalyst used in the present invention, more preferably, in ZSM-5 type zeolite containing zinc, the ZSM-
Type 5 zeolite satisfies the following (i) to (iii).

(I) has an atomic ratio of silicon / aluminum of 10 to 75, preferably 12 to 50 (ii) has an atomic ratio of zinc / silicon of 0.008 to 0.03, preferably 0.01 to 0.02 (iii) using pyridine, The ZSM-5 at 500 to 900 ° C by the thermal desorption method when the temperature rising rate is 15 ° C / min.
Desorption of pyridine is 40-120μmol per 1g of zeolite
In addition, the range of pyridine desorption amount in the above (iii) is ZSM-
Type 5 zeolite is heat-treated in the presence of water vapor under the conditions of a temperature of 600 to 800 ° C, a water pressure of 0.1 to 1 atm, and a treatment time of 0.2 to 20 hours in order to suppress the activity of the catalyst and stabilize it. Can be obtained.

Further, in the above catalyst, it is desirable that the ZSM-5 type zeolite is a ZSM-5 type zeolite hydrothermally synthesized in the coexistence of one or more compounds selected from lower alkylurea compounds and lower alkylthiourea compounds. .

In the present invention, as the model of the catalytic cyclization reactor,
It has the advantage that not only a fluidized bed but a fixed bed reactor can be used.

In this catalytic cyclization reactor 2, the supplied carbon number 5 fraction 13
And, a C 4 fraction 19 described later is converted into a BTX component in a high yield with high selectivity by the action of a catalyst, and a reaction fluid 14 rich in the BTX component is produced.

The reaction fluid 14 that has left the catalytic cyclization reactor 2 enters the heat exchanger 15 where heat is recovered and then merges with the reaction fluid 6 again and is supplied to the pyrolysis gasoline separator 7.

As a result, the BTX component contained in the reaction fluid 16 is separated as pyrolysis gasoline 8, and hydrogen and hydrocarbons having 1 to 4 carbon atoms are separated as cracked gas 17. That is, the BTX separation from the reaction fluid 16 is carried out by using the same pyrolysis gasoline separator 7 as the reaction fluid 6 containing the BTX fraction produced from the fresh fed raw hydrocarbons 3, so that the contact ring is separated. Since there is no need to provide an independent separation and recovery device for the reaction fluid 14 that has left the chemical reaction reactor 2, capital investment and energy use for separation and recovery can be greatly reduced.

On the other hand, the reaction fluid 17 discharged from the pyrolysis gasoline separator 7 is supplied to a C4 cut fraction separator 18 and is composed of a C4 cut fraction 19, hydrogen, and a light hydrocarbon having 1 to 3 carbon atoms. Divided into 20. The reaction fluid 20 is supplied to a separation and purification device 21, and is separated into hydrogen and a stun 22, a light olefin 23 such as ethylene and propylene, and a light parifine 24 such as ethane and propane.

The C4 cut 19 may be directly combined with the C5 cut 13 and supplied to the catalytic cyclization reactor 2, but is preferably useful as a raw material for petrochemical products contained in the C4 cut. It is advisable to provide a device for separating one or two kinds of butadiene and isobutylene. By supplying the C4 fraction 19 to the catalytic cyclization reactor 2, as in the C5 fraction 13, the BTX component produced through the same reaction and the same route is
It is recovered as pyrolysis gasoline 8.

In the figure above, the C4 fraction and the C5 fraction, which are usually evaluated only as a fuel and are produced by the thermal decomposition of the raw material hydrocarbons, are subjected to a catalytic cyclization reaction, where BTX is selectively and highly yielded. It was shown that the existing pyrolysis gasoline separator was shared and recovered as pyrolysis gasoline without using an independent separation / recovery device.

(Effects of the Invention) According to the present invention described in detail above, the following effects can be achieved.

(1) Equipment for separation, purification and recovery of light gas and BTX produced by catalytic cyclization reaction by organically combining conventional thermal decomposition of petroleum hydrocarbons and catalytic cyclization technology Investment and energy use can be significantly reduced.

(2) The yield of the effective product from the petroleum hydrocarbon as the raw material was about 60% by weight in the conventional pyrolysis, but the selective aromatics of the C ₄ and C ₅ fractions as the by-product. It can be increased up to about 65% by weight.

(3) The organic combination of the thermal decomposition process and the catalytic cyclization process makes it possible to maintain the effective product yield which is not achievable by each independent process or more,
It is possible to have a flexible yield structure according to the demand for petrochemical products. That is, for example, lowering the thermal decomposition temperature in order to increase the propylene yield, typically, ethylene, by reduced yield of BTX, it leads to a significant reduction in the effective product yield, C _4, C ₅ fraction Since it becomes possible to selectively convert benzene to BTX components, the total effective product yield, including catalytic cyclization process, is the same as or better than that of conventional pyrolysis. , BTX can be selectively increased.

(Example) Next, the present invention will be described in more detail with reference to Examples.

Examples 1 and 2 and Comparative Examples 1 and 2 (1) Preparation of catalyst (a) Sodium silicate (water glass No. 3) 290 g, distilled water 230 g
A solution dissolved in, separately aluminum sulfate 16-hydrate 11.4 g
A solution B prepared by dissolving 50 g of tetrapropylammonium bromide and 13 g of sulfuric acid in 300 g of distilled water was prepared. Then, using a homogenizer, solution B was added to solution A with vigorous stirring to form a homogeneous mixed gel. This gel was charged into one autoclave, and kept and crystallized for 35 hours under stirring at 160 ° C. and 1000 rpm. After the reaction, the solid matter was filtered, washed with water, dehydrated, dried, and then calcined in air at 550 ° C. for 3 hours. When the obtained white powder was confirmed by X-ray diffraction, it showed a ZSM-5 type diffraction pattern. When the Si / Al ratio was determined by fluorescent X-ray analysis, it was 23. This zeolite was ion-exchanged with a 10% ammonium chloride aqueous solution by a conventional method to obtain an H-type zeolite. Then, it was impregnated with a 5% aqueous solution of zinc nitrate, evaporated to dryness, dried and calcined (500 ° C., 3 hours) to obtain a zinc-containing zeolite. Next, this was compression-molded into 9 to 20 mesh, sized, then filled in a quartz reaction tube for the purpose of activity control, and treated in 80% by volume steam (diluted with nitrogen, atmospheric pressure) at 650 ° C. for 1 hour. . (Catalyst A).

(B) The steaming condition for activity control is 65
Prepared in the same manner as Catalyst A except that the temperature was 0 ° C. for 5 hours (Catalyst B).

(C) Instead of using tetrapropylammonium bromide in the preparation of catalyst A, 1,3-dimethylurea 23.
It was prepared in the same manner except that 4 g was used. However, the steaming for controlling the activity was performed at 650 ° C. for 5 hours, which is the same as that of the catalyst B (catalyst C).

(2) Conversion reaction In the example of the conversion reaction, the medium bundle naphtha (boiling point 40
~ 180 ℃), first, to the tube-type pyrolysis device, at atmospheric pressure, steam dilution ratio 0.5, at each predetermined temperature conditions, pyrolysis,
The C ₄ fraction and the C ₅ fraction thus obtained were separated by distillation to separate butadiene, isobutylene, isobrene and cyclopentadiene, respectively, and then fed to a fixed bed reactor filled with the above-mentioned catalyst for catalytic cyclization. The reaction fluid was supplied to the pyrolysis gasoline separation column for recycling.

Table 1 shows the yields only when the thermal decomposition is mild and when the thermal decomposition is severe under the practical thermal decomposition conditions as Comparative Examples, respectively, as Comparative Example 1 and Comparative Example 2. . As the catalyst for catalytic cyclization used in the examples in Table 1, the catalyst A prepared above was used.

As is clear from the examples and comparative examples in Table 1, according to the method of the present invention, the C ₄ fraction excluding butadiene and isobutylene, and the C ₅ fraction excluding isobrene and cyclopentadiene are subjected to catalytic cyclization. By recycling to the pyrolysis gasoline separation tower, it is clear that the C ₄ and C ₅ fractions that have been only evaluated as fuels are destroyed and selectively useful C _{6 to} C ₈ aromatics are produced. Also, the yield of effective product is increased by about 5 to 8% as compared with the case of only thermal decomposition, and the increase range is larger when the thermal decomposition is mild. Depending on the combination, it is impossible only by thermal decomposition,
It shows that it enables arbitrary pyrolysis operation conditions according to demand without reducing the effective product yield.

Examples 3 and 4 Table 2 shows reaction products obtained by one-pass conversion when the C ₄ fraction and the C ₅ fraction were each subjected to catalytic cyclization using the catalyst A.

From Table 2, it is shown that both fractions have high conversion and high C _{6 to} C ₈ aromatic selectivity, and that this reaction is useful for selective C _{6 to} C ₈ aromatic production.

Examples 5 to 7 In Table 3, WHSV was slightly changed so as to keep the conversion rate constant by using the catalysts A, B and C, and the C ₅ fraction obtained by distillation separation of isoprene and cyclopentadiene was continuously oiled. The catalyst activity half-life of each catalyst is shown from the deterioration of the catalyst over time. The catalyst activity half-life referred to here is the date from when the catalytic cyclization reaction is the first order and the tendency of deterioration of the activity of the catalyst over time due to continuous oil passage is grasped until it becomes half of the initial reaction rate constant.

If the catalysts A, B and C all have the same temperature and conversion, C ₆
It can be seen that the C ₈ aromatic yield is also almost constant.

However, it is clear that the deterioration resistance of the catalyst is excellent in the order of C, B, and A.

[Brief description of drawings]

 The drawings are flow sheets showing one embodiment of the present invention.

Claims (3)

[Claims] 1. A pyrolysis gasoline that is pyrolyzed by a pyrolysis gasoline separator after pyrolysis of petroleum hydrocarbons by a steam cracking device is fed to a 5-carbon fraction separator to produce a 5-carbon fraction. Is separated and one or two of cyclopentadiene and isoprene in the fraction are separated, and the crystalline alumino is obtained under the conditions of a temperature of 300 to 600 ° C. and a pressure of 0 to 60 kg / cm ³ G. A process for producing an aromatic hydrocarbon, which comprises supplying to a catalytic cyclization reactor which is brought into contact with a silicate, converting it into an aromatic compound, and recycling the obtained reaction product to the pyrolysis gasoline separator. 2. Pyrolysis by a steam cracking device is performed at a temperature of 750 to 850 ° C., a pressure of 0 to 15 kg / cm ³ G, and a residence time of 0.1.
The method of claim 1, wherein the method is ˜0.8 seconds. 3. A pyrolysis gasoline which is pyrolyzed by a pyrolysis gasoline separator after pyrolysis of petroleum hydrocarbons by a steam cracking device is supplied to a 5-carbon fraction separator to produce a 5-carbon fraction. Is separated, and the fraction or one or two of cyclopentadiene and isoprene in the fraction is separated, and the remaining pyrolysis product obtained by separating the pyrolysis gasoline is supplied to a carbon number 4 fraction separator. A fraction having 4 carbon atoms and separating the fraction or one or two of butadiene and isobutylene therein, at a temperature of 300 to 600 ° C. and a pressure of 0 to 60 kg / cm ³ G. An aromatic hydrocarbon characterized by being fed to a catalytic cyclization reactor which is brought into contact with a crystalline aluminosilicate under the conditions to be converted into an aromatic compound, and the resulting reaction product being recycled to the pyrolysis gasoline separator. Manufacturing method.