JPH04260486A - Treatment of waste refuse containing liquid crystal substance - Google Patents

Abstract

PURPOSE:To separate a liquid crystal substance from a substrate to make the same harmless by decomposition. CONSTITUTION:Waste refuse containing a liquid crystal substance is put in an extraction tank 11 and heated in the presence of moisture in a hermetically closed state. The water containing the separated liquid crystal substance is bubbled to send the gas containing the liquid crystal substance to a preheating tank 13 and this gas is adjusted to decomposition reaction temp. to be sent to a catalyst tank 14 to decompose the liquid crystal substance by a catalyst. The decomposing catalyst contains a noble metal catalyst component and a base metal catalyst component. By heating the waste refuse in the presence of moisture, the liquid crystal substance is easily separated from the waste refuse and efficiently decomposed using said catalyst.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating waste containing liquid crystal materials such as liquid crystal displays used in image display devices and the like.

0003

2. Description of the Related Art In recent years, with the rapid spread of word processors, liquid crystal televisions, etc., the amount of waste containing liquid crystals such as liquid crystal displays is rapidly increasing. Currently, waste such as liquid crystal displays is disposed of in landfills or incinerated along with other waste, and as a result, organic compounds, which are the liquid crystal substances in displays, are being released into the environment. It is starting to be released and accumulated.

[0004] A liquid crystal display has a liquid crystal material sandwiched between substrates such as glass, and the liquid crystal material generally consists of:
By liquid crystal substances such as organic halogen compounds and organic nitrile compounds having a structure represented by the following chemical formula (wherein R represents a halogen, an alkyl group, or a halogenated alkyl group, and the halogen is fluorine or chlorine) It is configured. Therefore, when liquid crystal displays and the like are disposed of, these organic compounds are released into the environment.

[0005]

[Chemical formula 1]

[0006] Although the toxicity of the above-mentioned organic compounds is not as great as that of PCB or trichlene, it is recognized that they accumulate in the human body. Therefore, in the near future, as the amount of discarded liquid crystal materials increases, the danger to living things is expected to further increase. Furthermore, it has recently become clear that fluorine, which is a constituent element of liquid crystal compounds, destroys the ozone layer and worsens the global environment. For this reason, various methods of decomposing and rendering harmless liquid crystal substances have been studied.

Currently known methods for decomposing organic halogen compounds include the high-temperature combustion method, catalytic combustion method, hydrogenolysis method, electron beam decomposition method, which is currently being developed as a method for decomposing PCBs and trichlene, etc. Examples include decomposition methods, photocatalytic decomposition methods, and the like.

However, each of these decomposition methods has drawbacks that hinder their practical application. For example, in the high-temperature combustion method, the decomposition efficiency is low and a large amount of energy needs to be supplied, resulting in large equipment and high operating costs. The catalytic combustion method has higher decomposition efficiency and requires less energy than the high-temperature combustion method, so it is highly economical, but due to the halides generated during the decomposition reaction,
There is a problem that the catalyst deteriorates rapidly. Like the high-temperature combustion method, the hydrocracking method has low cracking efficiency and requires a large amount of energy. In addition, the risk of corrosion of the equipment due to generated halides is greater than with other methods. Electron beam decomposition is the method with the lowest decomposition efficiency, and it is difficult to completely decompose with this method alone. Although the sodium decomposition method has high decomposition efficiency, it has the disadvantage that the equipment becomes large due to safety measures in handling sodium.

[0009] Therefore, there is still no method for decomposing organic halogen compounds that can be used to treat wastes containing liquid crystal substances, and a practical method for decomposing and rendering harmless wastes containing liquid crystal substances has not yet been completed. do not have.

0010

SUMMARY OF THE INVENTION As mentioned above, a method for treating waste containing liquid crystal materials that satisfies economic efficiency and safety has not yet been completed.

[0011] An object of the present invention is to provide a method for treating waste containing liquid crystal substances that is excellent in economy and safety and can be put to practical use.

[Configuration of the invention]

[0013]

[Means and Effects for Solving the Problems] In order to achieve the above object, the present inventors have conducted intensive research and found that when waste containing liquid crystal material is heated in the presence of moisture, liquid crystal material is removed from the waste. have found that the separated liquid crystal substance can be easily separated, and that the separated liquid crystal substance can be efficiently decomposed by using a catalyst containing a noble metal catalyst component and a base metal catalyst component,
The present invention has now been completed.

The method for treating waste containing a liquid crystal substance according to the present invention includes a first step of heating waste containing a liquid crystal substance in the presence of water to separate the liquid crystal substance from the waste, and a noble metal catalyst component and a base metal catalyst. and a second step of thermally decomposing the separated liquid crystal material using a catalyst having the components.

The present invention will be explained in more detail below.

The waste containing the liquid crystal material passes through a first step of separating the liquid crystal material from the waste, and the separated liquid crystal material is decomposed using a catalyst in the second step.

In the first step, the liquid crystal material is easily separated and extracted from the waste material by adding moisture to the waste material and heating it. The liquid crystal material adheres to the substrate in a viscous state, but when moisture is added to the waste and heated, the liquid crystal material partially decomposes and becomes easily separated from the substrate. Moisture may be added in the form of an atmosphere containing water vapor, liquid water, or an aqueous solution containing acid or alkali components. It is more preferable to use an aqueous solution in which an alkaline component such as an amine compound is dissolved, since this accelerates the decomposition of the liquid crystal substance. Liquid crystal materials are effectively separated from waste when heated above 200°C. Separation occurs even at temperatures below 200°C, but higher heating temperatures are preferred. However, in consideration of separation from things other than the liquid crystal material such as the substrate, the temperature is preferably below the melting point of the substrate material. Therefore, it is better to separate the liquid crystal at a temperature below the melting point of glass, which is commonly used as a substrate material. Note that since the amount of liquid crystal material remaining on the substrate after separation of the liquid crystal material is very small, it is considered that the substrate after liquid crystal separation can be relatively safely subjected to incineration treatment.

In the second step, the liquid crystal substance separated in the first step is thermally decomposed and rendered harmless using a catalyst. As the decomposition catalyst in this step, a catalyst in which a noble metal catalyst component and a base metal catalyst component are supported on a porous carrier layer is used. Examples of the noble metal catalyst component include gold, silver, and platinum group elements, and among these, platinum and palladium are particularly preferred, and one or more of these are used. Base metal catalyst components include nickel, cobalt, rare earth elements, alkaline earth elements, magnesium, silicon, and oxides thereof, and one or more of these may be used.

In the decomposition catalyst, the noble metal catalyst component is considered to be mainly responsible for the decomposition reaction as an oxidation catalyst, and the base metal catalyst component is considered to act as a hydrogenation catalyst. Therefore, by combining both catalyst components, both oxidation and hydrogenation reactions are carried out, and furthermore, the base metal catalyst is considered to improve the poisoning resistance of the noble metal catalyst component to halides and support the reaction. The noble metal catalyst component and the base metal catalyst component may be supported individually and used in combination, and a state where both components are mixed is preferable. A catalyst in which a noble metal catalyst component and a base metal catalyst component are supported on oxide particles such as titania and zirconia so that both catalyst components are present on the same particle (hereinafter, these supported catalysts are referred to as composite particle catalysts). This will further improve performance. In these cases, the performance of the catalyst is thought to vary depending on the supported positional relationship between the noble metal catalyst component and the base metal catalyst component in the composite particle catalyst.

[0020] The composition ratio of the above-mentioned noble metal catalyst component and base metal catalyst component is preferably 0.1 to 10. Although the reason for this is not clear, it is thought that a synergistic effect between the two components can be expected within this range.

[0021] The decomposition catalyst efficiently decomposes the liquid crystal substance at a temperature of 100°C or higher, more preferably 200°C or higher.

In the second step, the presence of water improves the decomposition efficiency of the catalyst. The amount of water supplied during the decomposition reaction varies depending on the type of liquid crystal material and processing temperature, but in the gas phase, it is necessary to completely hydrogenoly decompose the liquid crystal material into methane, etc. The amount of water is preferably 0.1 to 1 times the amount of water corresponding to the amount of hydrogen. More preferably 0.2~
The amount is 0.7 times, and about 0.6 times the amount is most preferred. The moisture source may be of any type as long as it contains moisture, but one with as few impurities as possible is preferred. A common method for supplying moisture is to transport moisture using a carrier gas, but in the present invention, since moisture is supplied in the first step, there is no need to supply it again. It is preferable that the amount of water can be controlled in order to control the catalyst activity. It is also possible to add a catalyst to the water containing the liquid crystal substance separated in the first step to carry out the reaction in a liquid phase.

In the second step, it is preferable that oxygen be present in order for the catalyst to function efficiently. The amount of oxygen varies depending on the type of liquid crystal material, processing temperature, etc., but the amount of oxygen is 0.95% of the amount required to completely oxidize the liquid crystal material.
It is preferably about 2 to 0.7 times. As the oxygen source, a gas containing oxygen is preferred, and air is practically used. If it is necessary to control the amount of oxygen to control the catalyst activity, it is desirable to use a gas containing a high concentration of oxygen.

The decomposition catalyst described above decomposes liquid crystal substances efficiently in the presence of moisture and has good poisoning resistance to halides. The catalytic decomposition produces small amounts of harmless oxides such as carbon dioxide and water, as well as hydrogen halides and nitrogen dioxide, which are relatively easy to treat.

[0025]

EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples conducted using an apparatus embodying the method for treating waste containing a liquid crystal substance of the present invention.

FIG. 1 schematically shows an apparatus 10 for treating waste containing liquid crystal materials according to the treatment method of the present invention. This processing device 10 includes an extraction tank 11, a gas flow path 12, a preheating tank 13, and a catalyst tank 14. The waste containing the liquid crystal material is placed in an extraction tank 11 and heated in a closed state in the presence of moisture to separate the liquid crystal material from the substrates and the like. By bubbling the water containing the separated liquid crystal substance, the gas containing the liquid crystal substance flows into the gas flow path 12.
The gas is adjusted to the decomposition reaction temperature in a preheating tank 13 and sent to a catalyst tank 14. The liquid crystal substance in the gas is decomposed in the catalyst tank 14, and the gas whose liquid crystal concentration has been measured is discharged from the chimney 16 through an activated carbon adsorption tower 15 provided for safety.

FIG. 2 shows an apparatus 20 for treating waste according to another treatment method of the present invention. In this processing device 20, similarly to the processing device 10, waste containing a liquid crystal substance and water are placed in an extraction tank 21 and heated in a sealed state to separate the liquid crystal substance, and then the obtained liquid crystal substance-containing water is Decomposition processing is performed on. That is, the water containing the liquid crystal substance is sent through the liquid channel 22 to a decomposition tank 24 equipped with a decomposition catalyst, and a decomposition reaction is performed in the decomposition tank 24 in a closed system.

Using the above apparatus, a liquid crystal display processing test was conducted as follows. The liquid crystal displays used in the test were A (ZLI-1132, manufactured by MERCK) and B (ZLI-1132, manufactured by MERCK).
LI-1370, manufactured by MERCK), C (ZLI-17
38, MERCK), D (DOX-1083, RO
DIK), E (DOX-1082, RODIK), F (E-90, BDH), G (E-100, B
(manufactured by DH) and H (E-110, manufactured by BDH).

Example 1 The following experiment was conducted using the processing apparatus shown in FIG.

As waste containing liquid crystal substances, 10 pieces of liquid crystal display A taken out from a word processor were soaked in 2 parts of water.
0 g (30 wt% based on the liquid crystal material) was placed in the extraction tank 1 and heated at 200° C. for 1 hour in a closed state. after that,
A gas containing a liquid crystal substance was obtained by bubbling water in which a liquid crystal substance was dissolved with carrier air. This gas (flow rate 6l/
min. , liquid crystal material concentration 1.0%) in preheating tank 3.
It was heated to 0°C and supplied to the catalyst tank 4. In the catalyst tank 4,
Palladium catalyst and nickel oxide catalyst (composition ratio 1:1)
filled with. The size of the catalyst tank is 3 cm in diameter and 5 cm in length.
It is m. The concentration of liquid crystal substance in the gas discharged from the catalyst tank 4 was measured, and the gas was discharged to the outside air from the chimney 6 through the activated carbon adsorption tower 5.

The amount (weight ratio) of the remaining liquid crystal substance in the treated substrate residue in the extraction tank 1 was measured. The results are shown in Table 1.

Examples 2 to 22 Using the same apparatus as in Example 1, the type of liquid crystal sample, the amount and nature of the water supplied in the first step, the amount of water in the second step, and the type of catalyst were changed. The same test as in Example 1 was conducted to measure the amount of liquid crystal material in the treated residue and the concentration of liquid crystal material in the gas discharged from the catalyst tank. In the examples, the composite particle catalyst contained palladium and nickel oxide (composition ratio 1
:1) was supported on titania particles by a commonly used method. These results are shown in Table 1.

In Table 1, the amount of remaining liquid crystal material in the residue after separating the liquid crystal material in the presence of water in the first step is:
The weight ratio was 0.3 ppm or less. Further, in the second step, when a catalyst containing a combination of a noble metal catalyst component and a non-metal catalyst component was used in the presence of moisture, the concentration of liquid crystal substance in the exhaust gas was 0.3 ppm or less.

[0034]

[Table 1]

Example 23 The following experiment was conducted using the processing apparatus shown in FIG.

Liquid crystal display A as waste containing liquid crystal material
The 10 sheets were placed in an extraction tank 1 together with 20 g of water and heated at 200° C. for 1 hour in a closed state to obtain water containing a liquid crystal substance. Water containing liquid crystal substance (water volume 10 l, liquid crystal substance concentration 2.0
wt%) was placed in a decomposition tank 24 containing a catalyst and heated to 200° C. for 30 minutes in a closed system. The catalyst used was a composite particle catalyst (50 g) in which palladium and nickel oxide (composition ratio 1:1) were supported on titania particles by a conventional method.

The amount (weight ratio) of the remaining liquid crystal substance in the treated residue in the extraction tank 1 and the concentration of the liquid crystal substance in the aqueous solution in the decomposition tank 24 were measured. The results are shown in Table 2.

Examples 24 to 35 Using the same apparatus as in Example 23, the type of liquid crystal sample, the nature of the aqueous solution in the first step, the reaction temperature in the second step, and the type of catalyst were changed.
A test similar to that in Example 23 was conducted, and the amount of liquid crystal material in the treated residue and the concentration of liquid crystal material in the aqueous solution in the decomposition tank 24 were measured. The results are shown in Table 2.

In Table 2, the concentration of liquid crystal in the aqueous solution after heat-treating the aqueous solution containing the liquid crystal substance using a decomposition catalyst was 0.1 ppm or less.

[0040]

[Table 2]

Comparative Examples 1 to 20 Using the same equipment as in Example 1, Example 1 was prepared with different types of catalyst, no catalyst, and no water in the first or second step. The test was conducted in the same manner as in 22. The amount (weight ratio) of the remaining liquid crystal substance in the treated residue in the extraction tank 1 and the concentration of the liquid crystal substance in the gas discharged from the catalyst tank 4 were measured. The results are shown in Table 3.

In Table 3, when no water is used in the first step, the amount of residual liquid crystal material in the treated residue is 2000p.
It was pm. In addition, in the second step, the concentration of liquid crystal substance in the exhaust gas from the catalyst tank exceeded 10 ppm in each case where no moisture was used and when a noble metal catalyst or a base metal catalyst was used alone.

[0043]

[Table 3]

Comparative Examples 21 to 30 Using the same equipment as in Example 23, the nature of the aqueous solution in the first step and the reaction temperature in the second step were changed for cases where the type of catalyst was changed or when no catalyst was used. ,
A similar test was conducted. The amount of remaining liquid crystal substance in the treated residue in extraction tank 1 and the concentration of liquid crystal substance in the aqueous solution in decomposition tank 24 were measured. The results are shown in Table 4.

In Table 4, when a noble metal catalyst or a base metal catalyst was used alone, the concentration of the liquid crystal substance in the aqueous solution after treatment was 50 ppm or more. When no catalyst was used, it was 300 ppm or more.

[0046]

[Table 4]

[0047]

[Effects of the Invention] As is clear from the above explanation, the method for treating waste containing liquid crystal substances of the present invention allows liquid crystal substances to be easily separated and extracted and efficiently decomposed, resulting in economic efficiency. It is excellent and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the processing method of the present invention.

FIG. 2 is a schematic diagram showing an apparatus for carrying out another treatment method of the present invention.

[Explanation of symbols]

10 Processing equipment 11 Extraction tank 12 Gas flow path 13 Preheating tank 14 Catalyst tank 15 Activated carbon adsorption tower 16 Chimney 20 Processing equipment 21 Extraction tank 22 Liquid flow path 24 Decomposition tank

Claims (1)

[Claims] Claim 1: A first step of heating waste containing a liquid crystal substance in the presence of water to separate the liquid crystal substance from the waste; and separating the liquid crystal substance using a catalyst having a noble metal catalyst component and a base metal catalyst component. A method for treating waste containing a liquid crystal substance, comprising a second step of thermal decomposition.