JPS5936624B2 - Alkylbenzene recovery method from polyolefin plastic waste and benzene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing polyolefin plastic waste from polyolefin plastic waste.
This invention relates to a method for efficiently recovering alkylbenzene, which is valuable as a petrochemical raw material.

After the oil crisis in 1973, the finite nature of resources was once again recognized, and there was a growing trend to reconsider plastic waste as a resource.

Therefore, the public and private sectors have been working together to develop processing technologies for effective use, including 1. recycling treatment (remolding), 2. incineration treatment (industrial waste recovery), and 3. pyrolysis treatment (material recovery). Considered. However, each method has its drawbacks, and although only some of the recycling methods have been put into practical use, in reality, the problem remains largely unresolved from a social scale. For example, as a technology that has become known as a thermal decomposition treatment method, there is a method for recovering useful components from vinyl chloride polymer waste (Japanese Patent Publication No. 51-1269). This technology requires a large amount of expensive hydrogen, and the hydrogen chloride gas generated from the vinyl chloride polymer causes severe corrosion of the equipment, making it difficult to use on a practical scale. Now, after the so-called second oil shock in 1978, recycling of plastic products has been proposed in response to demands for energy and resource conservation. The present invention heats polyolefin plastic waste such as polyethylene and polypropylene and benzene in the presence of a solid acid catalyst such as silica/alumina or zeolite, and simultaneously performs a decomposition reaction and an alkylation reaction in the same container. The purpose is to efficiently produce alkylbenzene.

Polyolefin plastic waste is said to account for about 40% of all plastic waste.

However, research on treatment methods that take into account their effective use has mainly focused on gasification and liquefaction through thermal decomposition.
Although the aim is to use it as a fuel, recycling of the resource has not been realized. In the present invention, a metal autoclave is preferably used as the reaction apparatus from the viewpoint of reaction efficiency and safety.

Furthermore, in order to avoid unnecessary oxidation of the polyolefin and improve the yield of alkylbenzene, it is desirable to carry out the reaction in the absence of oxygen. In this specification, polyolefin plastics include homopolymers of ethylene and homologous olefins, and copolymers thereof, and include polyethylene, polypropylene, polybutene, and ethylene/propylene copolymers.

The polyolefin plastic waste used in the present invention includes molded polyolefin plastics discarded from general households, factories, or specific industries, or waste products thereof. The present invention is carried out in the presence of benzene, and the molar ratio of benzene to the monomer units of the polyolefin plastic is preferably 1.0 or more, particularly preferably 3.0 or more. The catalyst used in the present invention is an oxide-based solid acid catalyst, and for example, silica-alumina, silica-magnesia, and zeolite can be preferably used.

The amount of catalyst used is 10 to 100 wt%, especially 20 to 5 wt%, based on the weight of the polyolefin plastic.
0 wt% is preferred. A specific method of the present invention is to put appropriately pulverized polyolefin plastic waste and benzene into an autoclave, add a solid acid catalyst thereto, replace the air in the autoclave with nitrogen, and then heat the reaction mixture. The reaction temperature in the present invention is generally 3
It can be carried out at a temperature of 00 to 500°C, but a temperature of 400 to 460°C can be particularly advantageously employed.

In the present invention, the reaction time is 1 to 10 hours, preferably 3 to 8 hours.

The product in the present invention is a gas, a greenish-brown liquid, and a black solid.For qualitative and quantitative analysis of the product, a gas mass (Shimadzu LKB-19000) and a gas chromatograph (Yanagimoto Seisakusho Co., Ltd.) are used. , G-80), a preparative high-performance liquid chromatograph (Japan Analytical Industry Co., Ltd., LC-08), an infrared absorption spectrum Shimadzu Corporation, IR-420), and an ultraviolet absorption spectrum (Shimadzu Corporation, UV-202) were used as appropriate. The produced gas in the present invention is a mixture of aliphatic saturated hydrocarbons such as methane, ethanepropane, isobutane, and isopentane, and small amounts of unsaturated hydrocarbons such as ethylene and propylene.

In addition, the product liquid contains alkylbenzenes such as toluene, ethylbenzene, isopropylbenzene, n-propylbenzene, and butylbenzene with four types of isomers, and a small amount of polycyclic aromatic compounds such as naphthalene, α-methylnaphthalene, and β-methylnaphthalene. Hydrocarbons are present.

These alkylbenzenes are extremely important substances as raw materials for the chemical industry, and can be recovered as pure products through distillation. At the same time, unreacted benzene is also collected.
Can be reused. Further, the catalyst recovered from the autoclave together with the solid residue (residual carbon) is calcined at 450 to 500° C. in an air stream, and can be reused after reactivation.

In the present invention, in the absence of both benzene and solid acid catalyst for polyolefin plastics,
No alkylbenzene is produced.

Furthermore, when polyolefin plastics are thermally decomposed in benzene without a catalyst, the decomposition reaction proceeds more favorably than in the absence of benzene. Based on these facts, the reaction mechanism of the present invention is that polyolefin plastic is reacted in benzene, with the addition of the solvent effect, and a solid acid catalyst.
It decomposes very efficiently, producing low-molecular unsaturated hydrocarbons. Furthermore, it is considered that the action of the solid acid catalyst causes an alkylation reaction of low-molecular unsaturated hydrocarbons to benzene, producing alkylbenzene. The produced gas and produced oil other than alkylbenzene in the present invention are suitable for use as fuel, and have the advantage that polyolefin plastic waste can be used almost completely effectively in terms of resource and energy conservation.

The present invention will be explained below with reference to Examples.

Example 1 In a stainless steel autoclave with an internal volume of 100 m1, 2
V polyethylene (degree of polymerization 2300), benzene 28y
) and 1.5V of silica-alumina catalyst (8wt% alumina) activated in an air stream at 500°C for 2 hours, and nitrogen gas at 40ml/Wu! It is circulated for 2' time at t to purge the air inside.

After heating started, the temperature reached 430℃ in about 1 hour, and the gauge pressure was 7.
Indicates 0 kg/1. At that time, the reaction was started, and after reacting for 5 hours, it was allowed to cool to room temperature.

After the produced gas is collected into a gas reservoir by water displacement, the contents of the reaction vessel are quickly evacuated in a refrigerator set at -5°C to separate the liquid product, catalyst, and solid residue. The yield of the liquid product after removing unreacted benzene is 3.2V, and the liquid yield relative to the polyolefin plastic is 160 wt%. The alkylbenzene present in it is isopropylbenzene (20%)
, Sec- and IsO-butylbenzene (13%),
Ethylbenzene (12%), toluene (10%), n-
propylbenzene (5%), and valuable alkylbenzenes account for 60 wt% in the product liquid. Also, the produced gas was recovered at 6.2 wt% based on the weight of the polyolefin plastic, and was composed of isobutane (59%).
, isopentane (16%), n-butane (4%), methane (3.6%), ethane (3%) and 90% paraffin.
This gas accounts for the majority of Furthermore, the carbon in the solid residue is 12
wt% is obtained. Example 2 A reaction was carried out in the same manner as in Example 1 using proton type Y zeolite (degree of proton exchange: 55%) as a catalyst. As a result, a liquid product of 83 wt % was produced based on the polyolefin plastic. The composition was: toluene (27%), ethylbenzene (21%), isopropylbenzene (9%), n-propylbenzene (6.5%).
), Sec- and IsO-butylbenzene (4%),
n-butylbenzene (1%).

Also, the generated gas is 3.6wt%, and the residual carbon is 46wt%.
% respectively. Example 3 Polyethylene film as polyolefin plastic waste was exposed to a carbon arc ultraviolet weather meter (Suga Test Instruments, WEL-2) for 900 hours.
Example 1 above using artificially accelerated degraded raw materials
As a result of carrying out the reaction in the same manner as above, a liquid product having a weight of 110% by weight based on the polyolefin plastic was obtained.

Its composition is toluene (12.3%), isopropylbenzene (9.4%), ethylbenzene (7.3%), S
ec- and IsO-butylbenzene (6.2%), n
Propylbenzene (3%) n-butylbenzene (1%)
It is becoming. Additionally, 21% residual carbon is obtained.
Furthermore, the calorific value of the resulting oil from which alkylbenzenes have been removed is 8800 cal/7. As described above, according to the present invention, alkylbenzene useful as a petrochemical raw material can be obtained in high yield by reacting polyolefin plastic waste and benzene in the presence of a solid acid catalyst.

Claims (1)

[Claims] 1 Polyolefin plastic waste characterized by heating polyethylene waste or (and) polypropylene waste and benzene in the presence of a solid acid catalyst to simultaneously cause a decomposition reaction and an alkylation reaction in the same container. Method for recovering alkylbenzene from