JPH0386791A - Manufacture of low boiling-point hydrocarbon oil - Google Patents

Abstract

PURPOSE: To effectively obtain a hydrocarbon oil with a high yield a high quality, low boiling point, and low pour point by recycling the mist in the thermally decomposed vapor product of a polyolefin melt in a thermal decomposition vessel and catalytically converting the other vapor product.

CONSTITUTION: A polyolefin plastic is melt and blended in a melting and blending vessel, and the melt is transferred to a thermal decomposition vessel to decompose. Then, the generating vapor product is transferred outside the vessel and at least a part of the mist coexisting in the vapor product is separated as liquid and recycled to the thermal decomposition vessel. The other vapor product is introduced to a zeolite catalyst layer and catalytically converted. The plastics used are usually polymers of 2-4C olefin, preferably polyethylene. These are usually supplied in a form of waste. The heating temp. for decomposition is usually about 350-450°C, and pressure usually around atmospheric pressure is preferable.

COPYRIGHT: (C)1991,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a low-boiling hydrocarbon oil useful as a raw material for gasoline and other raw materials from polyolefin plastics.

(Prior Art) It is well known that in recent years, as the production of plastics has increased, the disposal of plastic waste has become a social problem. Depending on the type of plastic, there are many that have reached the practical stage of reusing technology.

However, the technology for recycling polyolefin plastics, which is said to account for about half of the total production of thermoplastic plastics in Japan, has not achieved sufficient practical effects except for small-scale reuse such as reuse as molding materials. has not yet been reached.

Some studies have been made to convert polyolefin plastics into low molecular weight hydrocarbons and reuse them as fuel oil, etc., but there are some practical issues that need to be resolved, such as the properties of the product and continuous operability. ing.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for efficiently obtaining high-quality hydrocarbon oil having a low boiling point and low pour point from polyolefin plastics in a high yield and stably for a long period of time. There is a particular thing.

(Means for Solving the Problems) The present invention melts and mixes polyolefin plastics in a melt mixing tank, transfers the molten material to a pyrolysis tank and decomposes it, and guides the generated vaporized product to the outside of the pyrolysis tank. At least a part of the mist coexisting in the vaporized product is liquefied, separated, and circulated to a thermal decomposition tank, and the remaining vaporized product is led to a zeolite catalyst bed for catalytic conversion. It is characterized by a method for producing low boiling point hydrocarbon oil.

The plastic used in the method of the present invention may essentially be any polyolefin plastic, including olefinic polymers such as polyethylene, polypropylene, polybutylene, and even polystyrene (including copolymers and mixtures containing these as essential components). Hydrocarbon polymers having multiple bonds are exemplified, and C2 to C4 olefin polymers, particularly polyethylene, are preferably used. These are normally provided to the present invention in the form of waste (industrial waste, household waste, rejected products from factories, etc.).The shape may be any film, sheet, molded product, etc. Films and sheets used for other purposes are particularly preferred.

The present invention will be explained below based on the drawings.

FIG. 1 is a schematic process diagram suitable for carrying out the method of the present invention.

Polyolefin plastics are usually pulverized by an appropriate means and then heated using an extruder 1 or the like, or introduced in a molten state into a melt mixing tank 2. The mixing tank mixes the raw materials uniformly into a melt 11. Any type of extruder may be used as long as it has the function of producing a melted product. If an extruder with such a function can be used, it is also included in the melt mixing tank referred to in the present invention. The melt is then introduced into the pyrolysis tank 3. In the pyrolysis tank, the melt is decomposed (cracking) by heat; in the pyrolysis tank, it is preferable to feed the melt so that the level of the molten liquid phase is kept approximately constant;
This (first) thermal decomposition may be carried out with stirring or in the presence of a filler such as inorganic porous particles. However, it is preferable to carry out the process in the absence of a filler. The heating temperature varies depending on the temperature of the thermal decomposition tank of the material to be treated, but is usually about 350 to 450°C. Although pressure conditions are not particularly limited, it is usually preferred to be near normal pressure. Heating can be done by heating the plain wood in the pyrolysis tank, but an outside heating method is preferred.

That is, the molten material in the pyrolysis tank is introduced into the heating furnace 5, heated to a desired temperature, and then circulated to the pyrolysis tank 3. The vaporous products generated by thermal decomposition in the thermal decomposition tank come out from the upper part of the thermal decomposition tank, and are separated in a separator 6 where the mist portion with relatively large liquid particle size present in the vaporous products is liquefied. After that, the plate portions are sequentially introduced into the zeolite catalyst layer 4 and catalytically converted. The separated liquid valve is circulated to the pyrolysis tank.

As the zeolite catalyst, a zeolite having a constraint coefficient in the range of 1 to 12 is preferably used. Constraint coefficient (con
strain 1ndex), for example, as described in U.S. Patent No. 4
016218.

Specific examples of such types of zeolites include ZSM-5, Z
SM-11, ZSM-12, ZS14-23, ZSM-
35, ZSM-38, ZSM-48, etc., especially ZS
M-5 is preferably used.

ZSM-5 is a crystalline zeolite that has the following lines in its X-ray diffraction pattern in the synthesized state.

Lattice spacing 11.2±0.2 10.1±0.2 3.86±0108 3.72±0.08 Relative strength S 3.66±0.05
M Such zeolites are usually used in the acid form (in which the original alkali metal is replaced with H), but zeolites containing platinum or other metals may also be used if necessary. Such zeolite is usually used by itself or together with a carrier such as alumina and molded into any shape having a particle size of about 0.1 to 10 am.

This catalytic conversion reaction in the zeolite catalyst bed is normally carried out at a temperature of 300 to 420°C, preferably 350 to 480°C. By passing the thermal decomposition products through such a zeolite catalyst layer, not only the decomposition reaction but also the isomerization reaction,
The aromatization reaction occurs, which has a remarkable effect on improving the quality and yield of the product, and also has effects such as lowering temperature conditions and making stable continuous operation possible. Moreover, this catalyst maintains its effectiveness even if it is reused.

One of the features of the present invention is the thermal decomposition tank 3 and the zeolite catalyst layer 4.
A separator 6 is interposed between the two. This separator has the function of bringing the mist components in the vaporized product into contact with each other or contact surfaces such as walls, and separating at least a portion of the mist components, especially the mist components with relatively large liquid particle sizes, into a liquid form. Although any appropriate type of separator such as a baffle plate or cyclone may be used as long as it has a cylindrical separator, a cylindrical separator as shown in A in FIG. 2 is particularly preferred.

This device has a cylindrical body partially shaped like a double tube. This internal tube 9 is open both upwardly and downwardly. The vaporous product is introduced along the inner wall surface from an oblique inlet 10 facing the inner wall of the cylinder, exits from an oblique outlet 11, and is guided to the zeolite catalyst bed. During this time, the mist component in the vaporized product comes into contact with the inner wall surface, the support plate 12 at the upper part of the diagonal population 10, etc., and by contacting each other, a part of it grows as liquid particles and reaches the liquid outlet 1313 at the bottom. ′
from there to the pyrolysis tank. 14 is a pressure gauge nozzle 15
indicates a thermometer nozzle.

B of FIG. 2 is a cross-sectional view taken along line a-a of A, and shows a state in which the upper support plate 12 of the double tube is partially in communication with the upper part. As a result of selectively separating components that have an adverse effect on the zeolite catalyst through such a device, the reaction in the catalyst bed becomes more controllable and uniform, improving the quality of the product and extending the life of the catalyst. It becomes long in width. The products transferred to the catalyst in the catalyst bed are cooled and separated into gaseous products and liquid products. The liquid product is the desired product. Although the gaseous product itself has uses as a gaseous fuel, it can also be effectively utilized in the method of the present invention by, for example, being used to heat the heating furnace 5.

In addition, in the present invention, it is preferable to circulate a part of the melt in the pyrolysis tank to the melt mixing tank 26.The amount of circulation varies depending on the properties such as the viscosity of the raw material, but it is per 1 part by weight of the polyolefin plastic normally supplied. 0.1 to 1.5 parts by weight,
Particularly preferred is about 0.5 to 1.2 parts by weight.

In the present invention, by circulating a portion of the melt to the melt mixing tank in this manner, the raw materials are more effectively mixed uniformly, and the quality of the product is also significantly improved.

It is preferable to supply the wax 8 to the melt mixing tank at the initial stage of operation when there is substantially no melt to be circulated. In this case, the amount of wax is usually 0.00% per part by weight of the supplied polyolefin plastic. About 5 to 5 parts by weight is preferable.

The liquid product thus obtained is a high-quality hydrocarbon oil with high fluidity at low temperatures and can be used as a high value-added product such as gasoline. Example 1 A recovered polyethylene bottle was crushed using a crusher, placed in a screw feeder 1, heated to 230 to 300°C, and extruded into a melt mixing tank 2. Approximately 5 parts by weight of wax per 1 part by weight of polyethylene was placed in the melting mixing tank in advance and heated. Heating was performed by heating the outside of the cypress with heat transfer oil, and the heating temperature was approximately 280 to 300°C. The molten material from the melt mixing tank was led to the thermal decomposition tank 3 via a pump according to FIG. 1, and the temperature was raised to 380-400°C to carry out a thermal decomposition reaction. This heating is done in heating furnace 5.
carried out by heating the melt to 0-420°C,
There was no filler in the pyrolysis tank.The generated vaporous product was guided into the cylindrical body (knockout pot) shown in Figure 2, and the mist with large droplet size was liquefied and circulated to the pyrolysis tank. At the same time, it was guided to the catalyst layer 4 filled with ZS14-5 catalyst. For ZS14-5, a hydrogen type (H-ZSM-5) was used, and the temperature condition was 300 to 380°C. The product from below the catalyst layer was cooled with a condenser, and the gas was collected with a gas holder and a liquid valve. It was obtained in an oil storage tank (not shown). From the stage when the operation became steady, the decomposed melt was circulated from the pyrolysis tank 3 to the melt mixing tank in a proportion roughly equivalent to the amount of raw polyethylene supplied. Mixing in the tank is done by using a gear pump instead of using an agitator (disassembly)
This was done by feeding the melt. The amount of circulation was adjusted while checking the flow state within the system. The liquid yield was 64%, the gas yield was 23%, and the residue was 13%.

Table 1 shows the property test results of the pyrolysis oil and the final product after leaving the pyrolysis tank.

Density@15℃ 0.7814 RON Roasted 1 Saturated sand volX 62.9 Olefin II 31.4 Aromatic Horn 5.7 ASTM Dist IBP ``C325%℃85 10%℃117 20X''Cl67 30%℃215 40%℃ 249 50%"C273,5 60% ℃290 70%"C303 1i1ntY'Q11''; 0, 8093 98, 8 39, 4 1, 2 59, 4 7 6 6 02 22 33 44 58 79 1A 90X ℃334236 ( 85 Tsuta) 95 Tsuta ℃ 355 EP ℃ Cracking 267 TDvolX 90.0Res vo
lX -1,0 Loss volX -9,0 70@CD1st volX 98.5 11.
Note) RON Research Octane Number The above operation was continued for one month, but there was no change in the quality of the product or the catalyst performance.

[Brief explanation of drawings]

FIG. 1 is a schematic process diagram suitable for implementing the method of the present invention, and FIG. 2 is a sectional view showing an example of a separator.

Claims (10)

[Claims] (1) Polyopine plastics are melted and mixed in a melt mixing tank, the molten material is transferred to a pyrolysis tank, where it is thermally decomposed, and the generated vaporous product is guided outside the pyrolysis tank and coexists in the vaporous product. Production of a low-boiling hydrocarbon oil, characterized in that at least a part of the mist is liquefied, separated, and circulated to a thermal decomposition tank, and the remaining vaporized product is led to a zeolite catalyst bed for catalytic conversion. Method. (2) A cylindrical separator is installed between the thermal decomposition tank and the zeolite catalyst bed, and by introducing a vaporous product into the separator, at least a portion of the coexisting mist is liquefied and separated using the difference in specific gravity. 2. The method according to claim 1, wherein the pyrolyzate is circulated through a pyrolysis tank. (3) The method according to claim 1 or 2, wherein a part of the melt in the pyrolysis tank is circulated to the melt mixing tank. (4) The method according to claim 1 or 3, wherein the polyolefin plastic is melt-mixed in a melt-mixing tank in the presence of wax at the start of the operation. (5) The method according to any one of claims 1 to 4, wherein the zeolite is a zeolite having a constraint number in the range of 1 to 12. (6) The method according to any one of claims 1 to 4, wherein the zeolite is ZSM-5. (7) Claim 1, wherein the temperature of the melt in the pyrolysis tank is 350 to 450°C, and the temperature of the catalyst layer is 300 to 420°C.
6. The method according to any one of 6 to 6. (8) The method according to any one of claims 1 to 7, wherein the polyolefin plastic comprises polyolefin plastic waste. (9) Polyolefin plastics are C_2 to C_4
Claim 1 is a homopolymer or copolymer of an olefin.
9. The method according to any one of 8 to 8. (10) The method according to any one of claims 1 to 9, wherein the polyolefin plastic is ethylene.