TWI593722B - Granular rutile titanium dioxide catalyst and the decomposition of plastic methods - Google Patents

Description

Granular rutile titanium oxide catalyst and decomposition method of plastic

The invention relates to a method for decomposing granular rutile-type titanium oxide catalyst and plastic.

The decomposition catalyst means a catalyst for decomposing organic substances, and examples thereof include a thermal decomposition catalyst, an oxidative decomposition catalyst, and a photocatalyst. Among them, it is known that a decomposition catalyst using titanium oxide is inexpensive, has excellent chemical stability, has high catalytic activity, is harmless to the human body, and is used for decomposing a catalyst (see, for example, Patent Documents 1 and 2). As a specific method of use, a method of vaporizing the waste plastic by irradiating the waste plastic with ultraviolet rays in the presence of a decomposition catalyst of titanium oxide is known (for example, see Patent Document 3). The method of thermally decomposing the waste plastic by using titanium oxide as a decomposition catalyst is to promote vaporization by thermal decomposition of the waste plastic. Usually, the titanium oxide is heated under stirring while the carrier gas is passed through the container. The plastic sheet is scraped, and the waste plastic is thermally decomposed, and the decomposition gas of the thermal decomposition product is discharged to the outside of the container. Therefore, the titanium oxide particles used as a catalyst are abraded and micronized, and are lost to the outside of the container together with the thermal decomposition gas of the waste plastic, so that it is difficult to reuse, and in order to have repeated catalyst performance, it has to be added because The problem of the amount of catalyst lost by wear. Further, with the micronization of the titanium oxide particles, the particle size distribution changes, and there is a problem that the decomposition efficiency of the waste plastic is lowered.

Further, as a decomposition catalyst having a high decomposition efficiency, there is a proposal that a decomposition catalyst having a particle size distribution of 1.2 to 120% by weight is 0.5 to 1.2% by weight, 0.5 to 1.2 mm is 40 to 90% by weight, and 0.5 mm or less is 1 to 20% by weight. Etc. (refer to Patent Document 4).

[Previous Technical Literature] [Patent Document]

[Patent Document 1] JP-A-2007-51263

[Patent Document 2] JP-A-2006-346651

[Patent Document 3] JP-A-2002-363337

[Patent Document 4] JP-A-2005-205312

However, when the decomposition catalyst described in Patent Document 4 is used, in particular, when the waste plastic is thermally decomposed using a titanium oxide catalyst, the decomposition catalyst is lost by abrasion, and the decomposition efficiency decreases with time, so that it is industrially implemented. There is still room for further improvement.

Accordingly, an object of the present invention is to provide a titanium oxide catalyst having a high decomposition efficiency and a small catalyst loss by abrasion in a decomposition reaction, and a decomposition method of a plastic using the titanium oxide catalyst.

As a result of various reviews in order to achieve the above object, the present inventors have found that a titanium oxide catalyst having a specific particle size distribution and holding a certain amount of crushing strength particles has high decomposition efficiency and wear by decomposition reaction. The catalyst has less loss. The present invention has been completed based on the above findings.

That is, the present invention provides the following [1] to [8].

[1] A particulate rutile-type titanium oxide catalyst having a particle diameter of 1.2 to 1.5 mm of 80% by mass or more and a BET specific surface area of 0.1 to 0.4 m ² /g.

[2] The particulate rutile-type titanium oxide catalyst according to the above [1], wherein the bulk density is 1.1 to 1.7 g/mL, and the average crushing strength is 10 to 70 N.

[3] The particulate rutile-type titanium oxide catalyst according to the above [1] or [2], wherein the titanium oxide powder is granulated and then fired at 900 to 1,200 °C.

[4] The particulate rutile-type titanium oxide catalyst according to any one of the above [1] to [3], wherein the rutile-type crystal form contains 78% by mass or more.

[5] The particulate rutile-type titanium oxide catalyst according to any one of the above [1] to [4], wherein the particulate rutile-type titanium oxide catalyst is supported by a copper oxide.

[6] The particulate rutile-type titanium oxide catalyst according to the above [5], for the particulate rutile-type titanium oxide catalyst 100 other than copper oxide The amount of copper oxide supported by the copper element is 1 to 15 parts by mass.

[7] The particulate rutile-type titanium oxide catalyst according to any one of the above [1] to [6], which is used for thermal decomposition of an organic substance.

[8] A method for decomposing a plastic, characterized in that the particulate rutile-type titanium oxide catalyst of any one of the above [1] to [6] is mixed with a plastic and then heated.

According to the present invention, it is possible to provide a particulate rutile-type titanium oxide catalyst having high decomposition efficiency and little catalyst loss due to abrasion in the decomposition reaction. Further, in the case of a particulate rutile-type titanium oxide catalyst carrying copper oxide, the decomposition efficiency is further enhanced.

[Particulate rutile titanium oxide catalyst]

The titanium oxide catalyst of the present invention has a particle diameter of 1.2 to 1.5 mm and a content of particles of 80% by mass or more, and a granulated rutile-type titanium oxide catalyst having a BET specific surface area of 0.1 to 0.4 m ² /g (hereinafter referred to as abbreviated as The case of gold red stone type titanium oxide catalyst). Here, the particles mean granulated particles, and those obtained after firing. Further, the granular shape means having the shape of the aforementioned particles.

The rutile-type titanium oxide catalyst system of the present invention may also contain other crystal forms, such as an anatase type or a brookite type crystal form, and a crystal form mainly requiring a gold-red type. Specifically, the rutile crystal form It is preferably 78% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably a titanium oxide catalyst containing substantially 100% by mass.

The rutile-type titanium oxide catalyst of the present invention is superior in decomposition efficiency to the rutile-type titanium oxide catalyst other than the anatase-type titanium oxide and the brookite-type titanium oxide and the range of the present invention. Although the reason is not clear, it is presumed that in the presence of rutile-type titanium oxide, the reaction of obtaining oxygen from the air and supplying the obtained oxygen to the organic substance can be performed more efficiently.

The rutile-type titanium oxide catalyst of the present invention preferably has a content of particles having a particle diameter of 1.2 to 1.5 mm of 85% by mass or more, preferably 88% by mass or more, and more preferably 90% by mass or more. When the content of the particles having a particle diameter of 1.2 to 1.5 mm is less than 80% by mass, the decomposition efficiency is deteriorated, and the abrasion resistance is not necessarily high. The upper limit of the content of the particles having a particle diameter of 1.2 to 1.5 mm is not particularly limited, and is usually 98% by mass, and in many cases, it tends to be 96% by mass.

Further, the BET specific surface area is preferably 0.1 to 0.4 m ² /g as described above. When the BET specific surface area is in this range, grain growth of particles and flaking between particles are remarkably generated, and the decomposition efficiency is high and the abrasion resistance is high. From the same viewpoint, the BET specific surface area is preferably from 0.12 to 0.40 m ² /g, more preferably from 0.14 to 0.40 m ² /g.

The rutile-type titanium oxide catalyst of the present invention preferably has a bulk density of 1.1 to 1.7 g/mL, preferably 1.3 to 1.7 g/mL, more preferably 1.3 to 1.6 g/mL. When it is in this range, the contact frequency with an organic substance becomes high, decomposition efficiency becomes high, and abrasion resistance also becomes high. Further rutile of the present invention The average crushing strength of the titanium oxide catalyst is preferably from 10 to 70 N, preferably from 13 to 70 N, and in this range, the abrasion resistance is excellent.

The method for producing a titanium oxide catalyst is not particularly limited. For example, titanium tetrachloride is used as a raw material, and a gas phase method (a method of obtaining titanium oxide by a gas phase reaction between titanium tetrachloride and oxygen) is preferred. The titanium oxide catalyst obtained by the vapor phase method has a uniform particle diameter and a high crystallinity during production through a high-temperature process.

As the rutile-type titanium oxide catalyst, a commercially available titanium oxide catalyst can also be used. A commercially available product obtained by a vapor phase method (such as rutile-type titanium oxide "F-10" manufactured by SDK.Co.jp) may be used, and the BET specific surface area may be 0.1 to 0.4 m ² / g, and the content of the particles having a particle diameter of 1.2 to 1.5 mm is 80% by mass or more of the titanium oxide catalyst.

In addition, in the titanium oxide catalyst of the commercially available product, when the specific surface area is large and the rutile-type crystallinity is low, the oxidation is performed to have a predetermined specific surface area and particle size distribution. Titanium can be used. The firing temperature is preferably 900 to 1,200 ° C, preferably 900 to 1,100 ° C. The firing time is not particularly limited, and usually, it is preferably 10 minutes to 5 hours, preferably 30 minutes to 3 hours, more preferably 45 minutes to 2 hours.

[Particulate rutile-type titanium oxide catalyst carrying copper oxide]

By allowing the rutile-type titanium oxide catalyst of the present invention to carry copper oxide, the decomposition efficiency can be improved. Moreover, the copper oxide is mainly carried on the surface of the catalyst. Although copper oxide is not particularly limited, it is preferably copper oxide, preferably divalent copper oxide.

Thus, in order to carry copper oxide, the copper compound used will be described below.

(copper compound)

The copper compound used for supporting the copper oxide in the rutile-type titanium oxide catalyst of the present invention may be a monovalent copper compound or a divalent copper compound. Further, a monovalent copper compound and a divalent copper compound may be used in combination.

The monovalent copper compound is not particularly limited, and may be at least 1 selected from the group consisting of copper (I) oxide, copper (I) sulfide, copper (I) iodide, copper (I) chloride, and copper (I) hydroxide. Kind is better. Among them, copper (I) oxide is more preferable.

The divalent copper compound is not particularly limited, and examples thereof include copper (II) hydroxide, copper (II) oxide, copper (II) chloride, copper (II) citrate, copper (II) sulfate, and copper nitrate ( II), at least one of copper (II) fluoride, copper (II) iodide and copper (II) bromide is preferred. Among them, copper (II) nitrate (Cu(NO ₃ ) ₂ ) is more preferable.

As the copper compound, a divalent copper compound is preferred, and copper (II) nitrate is more preferred.

The average particle diameter of the copper compound used is preferably from 0.5 to 100 nm. When it is 0.5 nm or more, the crystallinity becomes good, and the decomposition efficiency is improved. When the thickness is 100 nm or less, the (i) specific surface area is increased, the decomposition efficiency is excellent, and (ii) the effect of being supported on titanium oxide is good. From this point of view, the average particle diameter of the copper compound is preferably from 0.5 to 80 nm, more preferably from 1 to 70 nm, particularly preferably from 2 to 50 nm. Further, the particle diameter can be confirmed by observation with an electron microscope. Here, the average particle diameter means an average value obtained from the size of 50 particles.

The amount of the copper compound of the rutile-type titanium oxide is 1 to 15 by mass in terms of the amount of the copper oxide in terms of copper element, based on 100 parts by mass of the particulate rutile-type titanium oxide catalyst other than the copper oxide. The method of adjustment can be. When it is 1 part by mass or more, the effect of enhancing the decomposition efficiency is exhibited by the bearing of the copper oxide. In addition, when it is 15 parts by mass or less, the surface of the titanium oxide cannot be largely coated with copper oxide, and the organic matter decomposition function of the red sapphire type titanium oxide is favorably exhibited. From the same viewpoint, the carrying amount of the copper oxide in terms of copper element is preferably from 1 to 12 parts by mass, more preferably 100 parts by mass of the particulate rutile-type titanium oxide catalyst other than the copper oxide. It is 1 to 10 parts by mass.

(Method of carrying copper oxide)

The method for supporting the copper oxide of the particulate rutile-type titanium oxide catalyst of the present invention is not particularly limited, and examples thereof include a method in which the particulate rutile-type titanium oxide is brought into contact with a copper compound and then fired.

As a method of contacting the particulate rutile-type titanium oxide with the copper compound, a method of immersing the particulate rutile-type titanium oxide in the copper compound solution is preferred. Here, as the copper compound solution, an aqueous copper compound solution is preferred. The temperature at the time of contact is preferably 0 to 40 ° C, and the point at which the temperature is normal temperature is preferable for the simplification of the operation.

After immersing the granular rutile-type titanium oxide in the copper compound solution, the solution was evaporated and then fired. Therefore, the copper compound in the solution is incorporated into the titanium oxide once it becomes a full amount. The content of copper in titanium oxide is measured by ICP (Inductively Coupled Plasma) emission spectroscopy to measure copper and titanium. The composition can be quantified.

The firing temperature is preferably from 250 to 600 ° C, preferably from 250 to 550 ° C, more preferably from 300 to 550 ° C, and particularly preferably from 300 to 500, from the viewpoint of the decomposition efficiency of the rutile-type titanium oxide catalyst. °C. Although the firing time is not particularly limited, it is usually from 30 minutes to 10 hours, preferably from 1 to 8 hours, more preferably from 3 to 8 hours.

By doing so, the copper compound in the particulate rutile-type titanium oxide catalyst is converted into copper oxide, and a particulate rutile-type titanium oxide catalyst carrying a copper oxide can be obtained. The supported copper oxide system is usually 80% by mass or more, preferably 90% by mass or more, preferably 95% by mass or more, and in many cases, it accounts for 100% by mass. Further, the analysis of monovalent copper and divalent copper is carried out using a measurement method such as X-ray absorption fine structure analysis (XAFS) or electron spin resonance (ESR), and is quantified using a calibration curve method.

The particulate rutile-type titanium oxide of the present invention may also contain other metal elements than copper. Examples of the other metal element include tungsten, gallium, germanium, zirconium, aluminum, molybdenum, manganese, chromium, and the like. Others may also contain an alkali metal or an alkaline earth metal.

In the case where the metal element is contained, the content is preferably 3% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, based on the total amount of the catalyst. The metal element acts as a reactive site, and the content is preferably 0.1% by mass or less from the viewpoint of suppressing the deactivation of the reactive site present in the titanium oxide.

Especially as a catalyst for decomposition of organic matter, for example, as The catalyst for thermal decomposition of waste plastics, rubber, plants, and the like is excellent in the particulate rutile-type titanium oxide of the present invention. That is, the present invention also provides a method for decomposing a plastic by heating the granular rutile-type titanium oxide catalyst and plastic of the present invention.

Further, the thermal decomposition here means a decomposition reaction caused by heating to a temperature of 50 ° C or more, and the case of oxidative decomposition (oxidative decomposition) as a whole or a part of oxidative decomposition is also included in the "thermal decomposition". .

The temperature at the time of thermal decomposition differs depending on the object to be decomposed, and may be appropriately selected. For example, the case where the object is a plastic is preferably 200 to 600 ° C, preferably 300 to 600 ° C, more preferably 300 to 500 ° C.

[Examples]

Hereinafter, the present invention will be specifically described based on the reference examples, examples, and comparative examples, but the present invention is not limited to the examples.

In addition, the physical properties and performance of the catalyst obtained in each example were evaluated by the following methods.

[1. Rutile content (rutile content)]

The rutile content (% by mass) is measured by X-ray diffraction, from the peak height of the corresponding anatase crystal (abbreviated Ha.), to the peak height of the brookite crystal (abbreviated Hb.), and the corresponding rutile. The peak height of the type crystal (Hr is abbreviated) is a value obtained based on the following formula.

[Number 1] Rutile content (% by mass) = {Hr / (Ha + Hb + Hr)} × 100

[2.BET specific surface area]

The BET specific surface area (m ² /g) was measured using a fully automatic BET specific surface area measuring device "Macsorb, HM model-1208" manufactured by Mountech Co., Ltd.

[3. Content of particles with a particle size of 1.2 to 1.5 mm]

The sieve was divided into fine particles or coarse particles by a sieve having a mesh size of 1.14 and 1.45 mm, and the content (% by mass) of particles having a particle diameter of 1.2 to 1.5 mm was measured by examining the weight.

[4. Minimum diameter, center diameter, maximum diameter]

The minimum diameter, the center diameter, and the maximum diameter (mm) of each particle diameter were measured by a sieve using a standard sieve.

[5. Average crush strength]

The average crushing strength (N) was determined from a value obtained by measuring 10 times using a wooden house type hardness tester "WPF 1600-B" manufactured by a wooden house.

It can be judged that the average crushing strength is strong, and it is hard and excellent in abrasion resistance.

[6. Bulk density]

The pellets were placed in a 200 mL graduated cylinder and the bulk density was measured by examining the weight.

[7. Catalyst performance evaluation]

In a reaction tube made of heat-resistant glass (registered trademark) having an internal volume of 10 L, 200 g of a titanium oxide particle catalyst and 0.02 g of a polypropylene resin pellet were mixed in a synthesis air (a ratio of nitrogen to oxygen of 8:2) to raise the temperature to After 400 minutes at 400 ° C, it was cooled at room temperature. The gas type and gas concentration generated were measured by a gas analyzer "PG-240" (manufactured by Horiba Co., Ltd.) to evaluate the decomposition ability.

It can be judged that carbon monoxide (CO) is small, and those with more carbon dioxide (CO ₂ ) have high decomposition efficiency.

[8. Method for calculating the wear rate of the catalyst in the reaction]

In the evaluation of the catalyst performance, a sieve having a mesh size of 1.14 mm was used, and the ratio of the weight of the catalyst passing through the sieve at the time of screening the catalyst after the reaction, and the ratio of the amount of the catalyst before the reaction, was determined. The catalyst wear rate in the reaction was calculated.

[Number 2] Wear rate = {(activator weight before reaction - catalyst weight on the sieve after the above sieve) / catalyst weight before reaction} × 100

[9. Measurement of copper bearing capacity]

The sample obtained by heating in a hydrofluoric acid solution was completely dissolved, and the extract was quantitatively analyzed by ICP emission spectrometry.

<Example 1>

The anatase-type titanium oxide powder having a primary particle diameter of about 30 nm was granulated by a granulator, and calcined at 1,000 ° C for 90 minutes to obtain a particulate rutile-type titanium oxide catalyst. A particulate rutile-type titanium oxide catalyst having a predetermined particle size is obtained by a catalyst obtained by a sieve sieve having a mesh size of 1.14 and 1.45 mm. By sieving the sieve, particles having a weight of from 1.2 to 1.5 mm of 90% were obtained.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Example 2>

A particulate rutile-type titanium oxide catalyst was obtained in the same manner as in Example 1 except that an anatase-type titanium oxide powder having a primary particle diameter of about 60 nm was used.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Example 3>

The pelletized rutile-type titanium oxide catalyst was obtained in the same manner as in Example 1 except that the firing temperature was changed to 900 °C.

Calculate the rutile content, BET specific surface area, and particle size of the catalyst. The cloth, the particle size, the average crushing strength, the bulk density, and the wear rate of the catalyst in the reaction, and the results thereof are shown in Table 1 together with the results of the catalyst performance evaluation.

<Example 4>

The pelletized rutile-type titanium oxide catalyst was obtained in the same manner as in Example 1 except that the firing temperature was changed to 1,100 °C.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Example 5>

100 g of the particulate rutile-type titanium oxide catalyst obtained in Example 1 was immersed in 0.5 L of a 0.094 mol/L copper nitrate aqueous solution, and after evaporating and drying at 100 ° C, it was baked at 400 ° C for 5 hours. The amount of copper (II) oxide (100% by mass) of the particulate rutile-type titanium oxide catalyst in addition to the copper oxide is 3 parts by mass of the particulate rutile-type titanium oxide catalyst.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Example 6>

A granular rutile-type titanium oxide other than copper oxide was obtained in the same manner as in Example 5 except that 0.313 mol/L of copper nitrate was used. The amount of copper (II) oxide (100% by mass) of the catalyst is 10 parts by mass of the particulate rutile-type titanium oxide catalyst.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Comparative Example 1>

In the same manner as in Example 1, except that the sieving was carried out, a particulate rutile-type titanium oxide catalyst was obtained.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Comparative Example 2>

The anatase-type titanium oxide powder having a primary particle diameter of about 30 nm was granulated by a granulator, and calcined at 800 ° C for 90 minutes to obtain a particulate rutile-type titanium oxide catalyst, but the sieve was not sieved.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Comparative Example 3>

The anatase-type titanium oxide powder having a primary particle diameter of about 30 nm was granulated by a granulator, and calcined at 700 ° C for 90 minutes to obtain a granular gold red. Stone type titanium oxide catalyst. A particulate rutile-type titanium oxide catalyst having a predetermined particle diameter was obtained by obtaining a catalyst by a sieve sieve having a mesh size of 1.14 and 1.45 mm. By sieving the sieve, particles having a weight of 91% to 1.5 mm were obtained.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Comparative Example 4>

The anatase-type titanium oxide powder having a primary particle diameter of about 30 nm was granulated by a granulator, and calcined at 750 ° C for 90 minutes to obtain a particulate rutile-type titanium oxide catalyst. A particulate rutile-type titanium oxide catalyst having a predetermined particle diameter was obtained by obtaining a catalyst by a sieve sieve having a mesh size of 1.14 and 1.45 mm. By sieving the sieve, particles having a weight of 91% to 1.5 mm were obtained.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

<Comparative Example 5>

The anatase-type titanium oxide powder having a primary particle diameter of about 30 nm was granulated by a granulator, and calcined at 1,300 ° C for 90 minutes to obtain a particulate rutile-type titanium oxide catalyst. By obtaining a catalyst by a sieve sieve having a mesh size of 1.14 and 1.45 mm, a granular rutile oxidation of a predetermined particle size is obtained. Titanium catalyst. By sieving the sieve, particles having a weight of 93% of particles of 1.2 to 1.5 mm were obtained.

The rutile content, BET specific surface area, particle size distribution, particle diameter, average crushing strength, bulk density, and the wear rate of the catalyst in the reaction were determined, and the results were compared with the results of the catalyst performance evaluation. Shown in Table 1.

According to Examples 1 to 4 of Table 1, the particulate rutile-type titanium oxide catalyst of the present invention has high decomposition efficiency and excellent abrasion resistance. Further, according to Examples 5 and 6, it is understood that the particulate rutile-type titanium oxide catalyst carrying the copper oxide maintains the wear resistance at a high level, and the decomposition efficiency can be further improved.

On the other hand, in the case of the catalysts of Comparative Examples 1 and 2 having a small particle diameter of 1.2 to 1.5 mm, it was found that there was room for further improvement of the decomposition efficiency. In the case of the catalysts of Comparative Examples 3 and 4 which were fired at a low temperature, the wear of the catalyst was remarkable, and when the catalyst reaction was again performed, the addition of a new catalyst was required, which was economically disadvantageous.

On the other hand, in the case of the catalyst of Comparative Example 5 which was fired at a high temperature, the specific surface area of the catalyst became too small, the wear rate became low, and the decomposition efficiency was also lowered.

Further, as a gas generating gas, carbon monoxide and carbon dioxide are monitored, and carbon monoxide is a toxic gas, and it is desirable to discharge less, but it is preferable to discharge more carbon dioxide in the complete oxidant. Therefore, for practical use, the ratio of carbon monoxide is small, and the ratio of carbon dioxide is preferably high. From this point of view, the catalysts of Comparative Examples 1 to 5 can be judged, and the catalysts of Examples 1 to 6 are more excellent catalysts.

Claims (8)

A particulate rutile-type titanium oxide catalyst having a particle diameter of 1.2 to 1.5 mm of 80% by mass or more and a BET specific surface area of 0.1 to 0.4 m ² /g. For example, the granular rutile-type titanium oxide catalyst of the first aspect of the patent application has a bulk density of 1.1 to 1.7 g/ml and an average crushing strength of 10 to 70 N. A granular rutile-type titanium oxide catalyst according to claim 1 or 2, wherein the titanium oxide powder is granulated and then fired at 900 to 1,200 °C. The particulate rutile-type titanium oxide catalyst according to claim 1 or 2, wherein the rutile-type crystal form is 78% by mass or more. A particulate rutile-type titanium oxide catalyst according to claim 1 or 2, wherein the particulate rutile-type titanium oxide catalyst is loaded with a copper oxide. In the particulate rutile-type titanium oxide catalyst of the fifth aspect of the invention, the amount of copper oxide in terms of copper element is 1 for 100 parts by mass of the particulate rutile-type titanium oxide catalyst other than the copper oxide. ~15 parts by mass. The particulate rutile-type titanium oxide catalyst according to claim 1 or 2, wherein the particulate rutile-type titanium oxide catalyst is used for thermal decomposition of an organic substance. A method for decomposing a plastic, characterized in that the granular rutile-type titanium oxide catalyst of any one of the first to sixth aspects of the patent application is mixed with a plastic and then heated.