Waste plastic treatment process

Abstract

Provided is a waste plastic treatment process that can produce, at a high yield, a high-quality catalytically-cracked product of waste plastic in which generation of characteristic odors, thermally unstable fractions, and tar and char is suppressed. The waste plastic treatment process comprises: pre-cracking a waste plastic-containing material through catalytic cracking; and catalytically cracking a pre-cracked product oil obtained by the pre-cracking.

Description

Waste plastic treatment process

[0001] The present invention relates to a process for treating waste plastics.

[0002] Because waste plastics are poorly degradable, discarded waste plastics contribute to, for example, marine pollution. Therefore, reducing the amount of waste plastics discarded directly reduces the environmental impact. Therefore, recycling of waste plastics has been considered. Examples of waste plastic recycling methods include chemical recycling, thermal recycling, and material recycling. Chemical recycling involves supplying pyrolysis oil from waste plastics to atmospheric distillation columns, fluidized bed cracking contactors, and the like, and utilizing the oil (see, for example, Patent Document 1). Patent Document 2 also discloses a recycling method in which carbon components in raw materials such as waste plastics are selectively combusted, and the raw materials are pyrolyzed and gasified using the combustion heat from the combustion process as a heat source, and the resulting pyrolysis product is supplied to at least one of an oil refining process and a petrochemical process.

[0003] Japanese Patent Application Laid-Open No. 2023-136646

[0004] As described in Patent Documents 1 and 2, waste plastics can be converted into pyrolysis oil and pyrolysis gas, and recycling these pyrolysis oil and pyrolysis gas is an effective means of reducing the amount of waste plastics disposed of. However, when pyrolysis oil is supplied to an atmospheric distillation column, as in Patent Document 1, the pyrolysis oil is distributed among all fractions obtained by the atmospheric distillation column, which increases the tolerance for impurities such as metals in the pyrolysis oil properties, and may limit the types and amounts of waste plastics that can be processed. The same applies when the pyrolysis oil is supplied to a fluid cracking contactor or the like.

[0005] The present inventors have conducted research into the properties of pyrolysis products, such as pyrolysis oil and pyrolysis gas, obtained from waste plastics and have found that the pyrolysis products contain heavy impurities, such as tar and char, as well as impurities such as components that produce a distinctive odor and thermally unstable fractions. It has been found that when chemical recycling as disclosed in Patent Documents 1 and 2 is performed, the by-production of these impurities leads to a significant deterioration in product quality. It has also been found that the by-production of these impurities increases the viscosity of the pyrolysis product, significantly reducing its oil passing performance, and further leads to problems such as deactivation of catalytic cracking catalysts when the pyrolysis product is fed to a reactor such as a fluid cracking contactor.

[0006] However, Patent Documents 1 and 2 do not acknowledge the various problems caused by the above-mentioned impurities contained in the pyrolysis product, and therefore, do not fully consider the removal of these impurities contained in the pyrolysis gas.

[0007] Thus, although there are hopes for recycling pyrolysis products obtained from waste plastics to meet the demand for reducing the amount of waste plastics disposed of, the current situation is that this is not being met sufficiently. Therefore, it is an issue to make it possible to use pyrolysis products obtained from waste plastics for recycling, particularly chemical recycling, without any problems.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a waste plastic treatment process for producing, at a high yield, high-quality catalytic decomposition products of waste plastics that suppress the generation of characteristic odors, thermally unstable fractions, and tar and char.

[0009] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that the problems can be solved by the following invention. That is, the present invention provides a waste plastic treatment process having the following configuration.

[0010] [1] A process for treating waste plastics, comprising pre-cracking a waste plastic-containing material by catalytic cracking and catalytically cracking the pre-cracked product oil obtained by the pre-cracking. [2] The process for treating waste plastics as described in [1] above, wherein the pre-cracking is carried out using a catalytic cracking catalyst. [3] The process for treating waste plastics as described in [2] above, wherein the catalytic cracking catalyst is a spent catalyst. [4] The process for treating waste plastics as described in [2] or [3] above, wherein the activity of the catalytic cracking catalyst measured in accordance with the microactivity test specified in ASTM D5154 is 58% by mass or more and 68% by mass or less. [5] The process for treating waste plastics as described in any of [1] to [4] above, wherein the temperature in the pre-cracking is 10°C or more lower than the temperature in the catalytic cracking. [6] The process for treating waste plastics as described in any of [1] to [5] above, wherein the amounts of oxygen, nitrogen, sulfur, and chlorine of the waste plastics contained in the waste plastic-containing material are adjusted so that the effective H / C ratio of the pre-cracked product oil, calculated by the following formula, is 1.9 or more. Effective H / C (mol / mol) = ((M Ｈ - (2 x M Ｏ ) - (3 x M Ｎ ) - (2 x M Ｓ )-M Ｃｌ )) / M Ｃ (In the above formula, M Ｈ , M Ｏ , M Ｎ , M Ｓ , M Ｃｌ and M Ｃindicates the contents (mol %) of hydrogen, oxygen, nitrogen, sulfur, chlorine, and carbon contained in the pre-cracked product oil, respectively. [7] The process for treating waste plastics according to any one of [1] to [6] above, wherein the content of aromatics contained in the pre-cracked product oil is 1 mol % or more and 15 mol % or less. [8] The process for treating waste plastics according to any one of [1] to [7] above, wherein a catalyst is used in catalytic cracking the pre-cracked product oil, and the catalyst contains ZSM-5 zeolite. [9] The process for treating waste plastics according to any one of [1] to [8] above, wherein the catalytic cracking of the pre-cracked product oil involves catalytic cracking of an inclusion containing the pre-cracked product oil and a feed oil derived from a fossil feedstock.

[10] The process for treating waste plastics according to [9] above, wherein the content of the pre-cracked product oil contained in the inclusion is 1 vol % or more and 20 vol % or less.

[0011] According to the present invention, a waste plastic treatment process can be provided for producing, at a high yield, high-quality catalytic decomposition products of waste plastics that suppress the generation of characteristic odors, thermally unstable fractions, and tar and char.

[0012] Below, we will specifically explain the waste plastic treatment process according to an embodiment of the present invention (hereinafter sometimes simply referred to as the "present embodiment"). In this specification, the values ​​"less than," "greater than," and "to" used in describing a numerical range are values ​​that can be arbitrarily combined. For example, when a certain numerical range is described as "A to B" and "C to D," the ranges also include "A to D" and "C to B." Furthermore, the numerical values ​​in the examples are values ​​that can be used as upper or lower limits.

[0013] [Waste Plastic Treatment Process] The waste plastic treatment process of this embodiment includes pre-cracking a waste plastic-containing material by catalytic cracking, and catalytically cracking the pre-cracked product oil obtained by the pre-cracking.

[0014] As described above, the inventors of the present invention have noticed that pyrolysis products obtained from waste plastics contain impurities such as heavy fractions, such as tar and char, as well as components that produce a distinctive odor and thermally unstable fractions. These impurities pose a bottleneck when attempting to recycle waste plastics, particularly chemical recycling. Further research led to a solution by performing two-stage catalytic cracking. Two-stage catalytic cracking can suppress the generation of thermally unstable fractions and heavy impurities, such as tar and char. This improves the yield of useful catalytic cracking products, such as light olefins, naphtha, kerosene, and diesel fuel, and also improves the content of useful catalytic cracking products in the pyrolysis product of waste plastics. Furthermore, two-stage catalytic cracking can adjust the reaction severity of the catalytic cracking reaction to adjust the balance, thereby improving the yield of the useful catalytic cracking products.

[0015] [Pre-cracking] The waste plastic treatment process of this embodiment includes pre-cracking a material containing waste plastics by catalytic cracking, which produces a pre-cracked product oil that is to be subjected to the subsequent catalytic cracking.

[0016] (Waste Plastics) The waste plastics contained in the waste plastic-containing material can be any that are called waste plastics, and representative examples include materials that make up various materials such as containers such as food and drink bottles; packaging supplies such as shopping bags, food trays, and packaging films; interior and exterior parts for housing construction materials, interior parts for automobiles, and exterior parts for electrical appliances; construction materials such as PVC pipes; etc. Representative examples of materials that make up these various materials include various resins such as acrylic resin, styrene resin, polyester resin, polyamide resin, PVC resin, polyolefin resin such as polyethylene and polypropylene, and mixtures of these resins.

[0017] From the viewpoint of improving the efficiency of catalytic cracking, it is preferable that these waste plastics have been processed into the shape of beads, flakes, chips, granules, pellets, etc. Furthermore, in consideration of improving the efficiency of catalytic cracking and the efficiency of sorting, it is preferable that the waste plastics have been processed, for example, by pulverization, so that the longest diameter is preferably 5 mm or more and 50 mm or less, more preferably 10 mm or more and 40 mm or less, and even more preferably 15 mm or more and 25 mm or less.

[0018] In the waste plastic treatment process of this embodiment, the waste plastic contained in the waste plastic-containing material may also be pyrolysis oil obtained by thermally decomposing the waste plastic. The waste plastic-containing material may contain one or more types of waste plastics, may contain pyrolysis oil of one or more types of waste plastics, or may contain one or more types of waste plastics and pyrolysis oil.

[0019] When using pyrolysis oil from waste plastics, the method for pyrolysis of the waste plastics is not particularly limited as long as pyrolysis oil can be obtained, and may be carried out according to a conventionally known method, for example, by pyrolysis treatment in a pyrolysis furnace. The pyrolysis temperature in the pyrolysis furnace is preferably 550°C or higher, more preferably 565°C or higher, and even more preferably 580°C or higher, with the upper limit being preferably 700°C or lower, more preferably 690°C or lower, and even more preferably 680°C or lower.

[0020] The amounts of oxygen, nitrogen, sulfur, and chlorine in the waste plastic (or thermal cracking oil) contained in the waste plastic-containing material are preferably adjusted so that the effective H / C ratio of the pre-cracked product oil obtained by pre-cracking, calculated by the following formula, is 1.9 or more. By setting the effective H / C ratio within the above range, the generation of thermally unstable fractions and heavy impurities such as tar and char is more easily suppressed, thereby improving the yield of useful catalytic cracking products. Among the above useful catalytic cracking products, the yield of light olefins, i.e., the content of light olefins contained in the thermal cracking product of waste plastic, is more easily improved. Furthermore, the generation of a characteristic odor is also more easily suppressed. From the same perspective, the effective H / C ratio is preferably 2.0 or more, more preferably 2.3 or more, with no particular upper limit, and is usually 4.0 or less.

[0021] Effective H / C (mol / mol) = ((M Ｈ - (2 x M Ｏ ) - (3 x M Ｎ ) - (2 x M Ｓ )-M Ｃｌ )) / M Ｃ (In the above formula, M Ｈ , M Ｏ , M Ｎ , M Ｓ , M Ｃｌ and M Ｃ indicates the contents (mol%) of hydrogen, oxygen, nitrogen, sulfur, chlorine and carbon contained in the preliminary cracking product oil.)

[0022] The effective H / C ratio of the pre-cracked product oil can be adjusted by, for example, the type, material and blending ratio of the waste plastics.

[0023] In the above formula, the contents (mol%) of oxygen, nitrogen, sulfur, and chlorine contained in the preliminary cracking product oil cannot be generalized because they may vary depending on the type, material, and compounding ratio of the waste plastic contained in the waste plastic-containing material. Ｏ is usually 9.0 x 10 －３ ~6.0 x 10 －１ mol%, nitrogen content M Ｎ is usually 1.0 x 10 －３ ~5.0 x 10 －１ mol%, sulfur content MＳ is usually 5.0 x 10 －４ ~2.0 x 10 －１ mol%, chlorine content M Ｃｌ is usually 1.0 x 10 －５ ~2.0 x 10 －２ In addition, the effective H / C ratio of the preliminary cracking product oil is adjusted to be within the above range, the yield of useful catalytic cracking products is improved, and in particular, the content of light olefins is increased, and from the viewpoint of easily suppressing the generation of a specific odor, the oxygen content M Ｏ 9.9 x 10 －３ ~5.4 x 10 －１ mol%, nitrogen content M Ｎ to 1.4 x 10 －３ ~4.4 x 10 －１ mol%, sulfur content M Ｓ 5.5 x 10 －４ ~1.2 × 10 －１ mol%, chlorine content M Ｃｌ to 1.5 x 10 －５ ~1.8 x 10 －２ It is preferable to adjust the content to mol %.

[0024] The hydrogen and carbon contents (mol%) contained in the preliminary cracking product oil cannot be generalized because they may vary depending on the type, material, and compounding ratio of the waste plastic contained in the waste plastic-containing material. For example, the hydrogen content M Ｈ is usually 50.0 to 75.0 mol %, preferably 57.0 to 71.0 mol %, and the carbon content M Ｃ is usually 24.0 to 49.0 mol %, preferably 28.0 to 42.0 mol %. Ｈ , M Ｏ , M Ｎ , M Ｓ , M Ｃｌ and M Ｃ is a content that can be measured using an organic elemental analyzer (for example, a CHN coder, etc.).

[0025] The preliminary catalytic cracking of waste plastic-containing materials is preferably carried out using a catalyst, and among other catalysts, a catalytic cracking catalyst is preferably used. The use of a catalyst, particularly a catalytic cracking catalyst, promotes preliminary catalytic cracking, making it easier to suppress the generation of thermally unstable fractions and heavy impurities such as tar and char, and improving the yield of useful catalytic cracked products. In addition, the generation of components that are the source of a distinctive odor can be suppressed, making it easier to suppress the generation of the distinctive odor.

[0026] As the catalytic cracking catalyst used in the preliminary cracking, it is preferable to use waste catalysts discarded from oil refineries, and it is particularly preferable to use waste catalysts used in fluid catalytic cracking units, i.e., catalysts generally referred to as fluid catalytic cracking catalysts. By using waste catalysts, it is possible to promote effective use of the catalyst and reduce the initial investment required for the catalyst. Furthermore, by suppressing the generation of impurities, it is possible to improve the yield of the above-mentioned useful catalytic cracking products and suppress the characteristic odor.

[0027] Preferred examples of waste catalysts include waste solid acid catalysts, which are catalytic cracking catalysts used in fluid catalytic cracking units, and among these, waste synthetic zeolite solid acid catalysts are preferred. Preferred examples of synthetic zeolite solid acid catalysts include Y-type zeolites, such as Y-type zeolites and ultrastable Y-type zeolites; pentasil-type zeolites, such as MFI-structure zeolites and MEL-structure zeolites; and zeolites such as β-type zeolites and L-type zeolites, with Y-type zeolites and pentasil-type zeolites being preferred. These solid acid catalysts can be used alone or in combination as the catalytic cracking catalyst.

[0028] As the pentasil type zeolite, that is, the zeolite composed of a combination of five-membered oxygen rings, from the viewpoint of ease of production, MFI structure zeolite and MEL structure zeolite are preferably mentioned as already mentioned.

[0029] Examples of MFI structure zeolites include ZSM-5 type zeolites and ZSM-8 type zeolites having a structure similar to that of ZSM-5 (these zeolites are also referred to as "ZSM-5 type zeolites" in this specification). Examples of MEL structure zeolites include ZSM-11 type zeolites and those having a structure similar to that of ZSM-11 type zeolites. Among these pentasil type zeolites, ZSM-5 type zeolites are preferred.

[0030] The catalytic cracking catalyst is preferably a catalyst that uses the above-mentioned solid acid catalyst itself as a catalyst or a catalyst that contains the above-mentioned solid acid catalyst, and more preferably a catalyst that contains a solid acid catalyst. When the catalytic cracking catalyst contains a solid acid catalyst, preferred examples of the catalyst include a catalyst that contains the above-mentioned Y-type zeolite or ZSM-5-type zeolite, which is a solid acid catalyst.

[0031] The catalyst discarded from the above-mentioned oil refinery facilities, etc., may have coke attached thereto due to use, and its activity may be reduced. When using such a catalyst as a waste catalyst in pre-contact, it is preferable to use a regenerated catalyst by subjecting the catalyst to a treatment such as calcination to burn off and remove the coke attached to the catalyst.

[0032] For the catalytic cracking catalyst used for pre-cracking, the activity of the catalytic cracking catalyst, measured in accordance with the microactivity test specified in ASTM D5154, is preferably 58% by mass or more and 68% by mass or less. The use of a catalyst having such catalytic activity promotes pre-cracking by catalytic cracking, thereby suppressing the generation of the above-mentioned impurities and making it easier to improve the yield of the above-mentioned useful catalytic cracked products. Furthermore, the generation of components that are the source of the characteristic odor is suppressed, making it easier to suppress the generation of the characteristic odor. From the same perspective, a value of 60% by mass or more and 65% by mass or less is more preferable. The microactivity test specified in ASTM D5154 is a test for evaluating the relative performance of fluid catalytic cracking catalysts (FCC catalysts), and the activity of the catalyst is a numerical value expressed as the ratio (mass%) of vacuum gas oil to vacuum gas oil minus cracked gas oil and cracked residue.

[0033] The reaction temperature in the preliminary decomposition is not particularly limited as long as the catalytic decomposition of the waste plastic-containing material proceeds, but is, for example, preferably 350°C or higher, more preferably 375°C or higher, and even more preferably 400°C or higher, with the upper limit being preferably 500°C or lower, more preferably 475°C or lower, and even more preferably 450°C or lower.

[0034] Furthermore, in relation to the temperature in catalytic cracking of the pre-cracked product oil obtained by pre-cracking, which will be described later, the temperature in pre-cracking is preferably at least 10°C lower than the temperature in catalytic cracking, and more preferably at least 50°C lower. By setting such a temperature, pre-cracking by catalytic cracking can be promoted, and at the same time, catalytic cracking, which will be described later, can be promoted, thereby suppressing the generation of the above-mentioned impurities and making it easier to improve the yield of the above-mentioned useful catalytic cracked products, and suppressing the generation of components that are the source of the characteristic odor, making it easier to suppress the generation of the characteristic odor. Furthermore, it is possible to distribute the reaction severity of catalytic cracking and make it easier to adjust the balance, and it becomes possible to effectively utilize catalysts that are preferably used in pre-cracking and catalytic cracking, so that the yield of catalytic cracked products can be more efficiently improved.

[0035] The pre-cracked product oil obtained by pre-cracking contains useful catalytic cracking products such as light olefins, naphtha, kerosene, diesel, etc., and catalytic cracking, as described below, is carried out to increase the content of these catalytic cracking products and improve the yield. The content of these useful catalytic cracking products in the pre-cracked product oil is usually 70 mol % or more and 95 mol % or less, and preferably 90 mol % or more and 95 mol % or less.

[0036] Furthermore, the content of aromatic components contained in the pre-cracked product oil is preferably 1 mol% or more and 15 mol% or less. When the content of aromatic components contained in the pre-cracked product oil is within the above range, catalytic cracking, which will be described later, proceeds more efficiently, thereby suppressing the generation of the above-mentioned impurities and making it easier to improve the yield of the above-mentioned useful catalytic cracked products, and suppressing the generation of components that are the source of the characteristic odor, making it easier to suppress the generation of the characteristic odor. From the same perspective, it is more preferable that the content of aromatic components contained in the pre-cracked product oil is 10 mol% or less.

[0037] [Catalytic Cracking] The waste plastic treatment process of this embodiment includes catalytic cracking of the pre-cracked product oil obtained by the pre-cracked process. The catalytic cracking of the pre-cracked product oil produces a thermal cracking product of the waste plastic, preferably a thermal cracking oil of the waste plastic. By performing the pre-cracked process and catalytic cracking, the generation of the impurities can be suppressed, the yield of the useful catalytic cracked product can be improved, and the generation of components that are the source of the characteristic odor can be suppressed, thereby suppressing the generation of the characteristic odor. Furthermore, the severity of the catalytic cracking reaction can be dispersed and the balance can be easily adjusted, thereby improving the yield of the useful catalytic cracked product.

[0038] The catalytic cracking of the pre-cracked product oil is preferably carried out using a catalyst, and among catalysts, it is preferable to carry out the catalytic cracking using a catalytic cracking catalyst. The use of a catalyst, and in particular the use of a catalytic cracking catalyst as the catalyst, promotes pre-cracking by catalytic cracking, which makes it easier to suppress the generation of thermally unstable fractions and heavy impurities such as tar and char, thereby improving the yield of the above-mentioned useful catalytic cracked products. In addition, since the generation of components that are the source of the characteristic odor can be suppressed, the generation of the characteristic odor can be easily suppressed.

[0039] Examples of catalysts preferably used in the catalytic cracking of pre-cracked product oil include the same catalysts as those exemplified as the fluid catalytic cracking catalysts that can be used in the pre-cracked product oil, and an appropriate catalyst may be selected from these catalysts. Among the catalysts exemplified as the fluid catalytic cracking catalysts, catalysts preferably used in catalytic cracking are preferably pentasil-type zeolites, more preferably MFI-structure zeolites, and even more preferably ZSM-5-type zeolites. As with the catalysts that can be used in the pre-cracked product oil, catalysts containing these zeolites are also preferred, and in this case, catalysts supporting the metal compounds exemplified above as active metal species are also preferred.

[0040] The reaction temperature for catalytic cracking of the pre-cracked product oil is not particularly limited as long as the catalytic cracking of the waste plastic-containing material proceeds, but is, for example, preferably 350°C or higher, more preferably 375°C or higher, and even more preferably 400°C or higher, with the upper limit being preferably 500°C or lower, more preferably 475°C or lower, and even more preferably 450°C or lower.

[0041] Furthermore, as described above, in relation to the temperature in the pre-cracking, the temperature in the catalytic cracking is preferably at least 10°C higher than the temperature in the pre-cracking, and more preferably at least 50°C higher. By setting the temperature relationship between the pre-cracking and the catalytic cracking in the above range, the pre-cracking by catalytic cracking is promoted, which makes it easier to suppress the generation of thermally unstable fractions and heavy impurities such as tar and char, and improves the yield of the above-mentioned useful catalytic cracking products. Furthermore, since the generation of components that are the source of the characteristic odor can be suppressed, the generation of the characteristic odor can be easily suppressed.

[0042] In catalytically cracking the pre-cracked product oil, it is preferable to catalytically crack a mixture (pre-cracked product oil mixture) containing the pre-cracked product oil and a feed oil derived from a fossil feedstock. The use of a feed oil derived from a fossil feedstock makes it easier to suppress the generation of thermally unstable fractions and heavy impurities such as tar and char, thereby improving the yield of the useful catalytic cracked product. Furthermore, the generation of components that are the source of a distinctive odor can be suppressed, making it easier to suppress the generation of the distinctive odor.

[0043] Preferred examples of feedstock oils derived from fossil feedstocks that can be used in combination with the pre-cracked product oil include heavy cracked gas oil, cracked residual oil, atmospheric residual oil, desulfurized residual oil, desulfurized vacuum gas oil, undesulfurized vacuum gas oil, undesulfurized vacuum residual oil, light hydrocarbon oil, and heavy hydrocarbon oil.

[0044] The content of the pre-cracked oil contained in the composition containing the pre-cracked oil and the feed oil derived from a fossil feedstock (pre-cracked oil composition) is preferably 1% by volume or more and 20% by volume or less, more preferably 3% by volume or more and 15% by volume or less, and even more preferably 5% by volume or more and 10% by volume or less. By setting the content to such a level, it becomes easier to more efficiently suppress the generation of thermally unstable fractions and heavy impurities such as tar and char, thereby improving the yield of the above-mentioned useful catalytic cracking products and suppressing the generation of a characteristic odor.

[0045] The catalytic cracker of waste plastics (catalytic cracker of pre-cracked oil) contains heavy components such as tar and char in an amount of 2 to 5% by mass. Thus, the catalytic cracker of waste plastics (catalytic cracker of pre-cracked oil) obtained by the waste plastic treatment process of this embodiment has a high content of useful catalytic crackers such as light olefins, naphtha, kerosene, heating oil, diesel, etc., and a low content of impurities such as heavy components such as tar and char.

[0046] In the waste plastic treatment process of this embodiment, the properties of the catalytic cracking products of the above-mentioned waste plastics (content of useful catalytic cracking products, content of aromatic components, and content of heavy components such as tar and char) can be adjusted by selecting the waste plastics to be treated, the treatment time and treatment temperature in the pre-cracking and catalytic cracking, etc.

[0047] According to the waste plastic treatment process of this embodiment, it is possible to produce, at a high yield, a high-quality catalytic decomposition product of waste plastic that is suppressed in terms of the generation of characteristic odors, thermally unstable fractions, and tar and char. Therefore, the thermal decomposition product of waste plastic obtained by the waste plastic treatment process of this embodiment is suitable for use as a petroleum product or as a raw material for various petroleum products.

Claims

1. A process for treating waste plastics, comprising: pre-crack- ing a material containing waste plastics by catalytic cracking; and catalytically cracking the pre-cracked product oil obtained by said pre-crack- ing.

2. The process for treating waste plastics according to claim 1, wherein the pre-cracking is carried out using a catalytic cracking catalyst.

3. The process for treating waste plastics according to claim 2, wherein the catalytic cracking catalyst is a spent catalyst.

4. A process for treating waste plastics according to claim 2 or 3, wherein the activity of the catalytic cracking catalyst measured in accordance with the microactivity test specified in ASTM D5154 is 58% by mass or more and 68% by mass or less.

5. A process for treating waste plastics according to any one of claims 1 to 4, wherein the temperature in the pre-decomposition is set to be at least 10°C lower than the temperature in the catalytic decomposition.

6. A process for treating waste plastics according to any one of claims 1 to 5, wherein the amounts of oxygen, nitrogen, sulfur, and chlorine in the waste plastics contained in the waste plastic-containing material are adjusted so that the effective H / C of the preliminary cracking product oil, calculated by the following formula, is 1.9 or more. Effective H / C (mol / mol) = ((M Ｈ - (2 x M Ｏ ) - (3 x M Ｎ ) - (2 x M Ｓ )-M Ｃｌ )) / M Ｃ (In the above formula, M Ｈ , M Ｏ , M Ｎ , M Ｓ , M Ｃｌ and M Ｃ indicates the contents (mol%) of hydrogen, oxygen, nitrogen, sulfur, chlorine and carbon contained in the preliminary cracking product oil.) 7. A process for treating waste plastics according to any one of claims 1 to 6, wherein the content of aromatic components contained in the pre-cracked product oil is 1 mol % or more and 15 mol % or less.

8. The process for treating waste plastics according to any one of claims 1 to 7, wherein a catalyst is used in catalytic cracking of the pre-cracked product oil, and the catalyst contains ZSM-5 type zeolite.

9. A process for treating waste plastics according to any one of claims 1 to 8, wherein the catalytic cracking of the pre-cracked product oil comprises catalytic cracking of a mixture containing the pre-cracked product oil and a feedstock oil derived from a fossil feedstock.

10. The process for treating waste plastics according to claim 9, wherein the content of the pre-cracked product oil contained in the inclusions is 1% by volume or more and 20% by volume or more.