JPH0747987B2 - Inflatable gas seal member - Google Patents

Description

The present invention relates to a catalyst body to which a high concentration of hydrocarbon is supplied and to retain the same when using a catalyst body that catalytically burns an unburned mixture of gas and petroleum. The present invention relates to a gas seal member used when a particularly sufficient sealability is required for a gap with a frame.

2. Description of the Related Art Conventionally, there are two types of general gas seal members. One is a method in which the heat-resistant inorganic fiber is processed into a sheet or felt, and these are used while being compressed in a place where they are desired to be used. Also another 1
One is a method of performing gas sealing by treating a gas seal member containing unexpanded vermiculite commercially available as Interam (3M, trade name) mat to about 400 to 600 ° C. to expand the member. However, it has been difficult for these conventional gas seal members to provide sufficient gas sealability when used in a catalytic combustion device.

More specifically, in the catalytic combustion device, a very high concentration of unburned air-fuel mixture is supplied to the ceramic honeycomb-shaped catalyst body for catalytic combustion. At that time, even if a slight gas leak occurs from the seal part in the gap between the catalyst body and the frame body holding the catalyst body, the unburned gas causes a significant odor.

Therefore, it is necessary to pay sufficient attention to the gap between the catalyst body and the frame body that holds it. With the conventional inorganic fiber seal member,
In order to improve the sealing property, it is necessary to increase the bulk density of the gas sealing member to make it dense.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional inorganic fiber seal member, the cushioning property of the gas seal member is lost when the bulk density is increased and made dense, and the catalyst body and the frame body having a high temperature in the catalytic combustion state Expand together, but if there is a difference in thermal expansion (generally, the frame body has a larger coefficient of thermal expansion than the catalyst body), a gap is created in the seal member that has lost cushioning properties, and unburned gas It was easy to slip and it was difficult to prevent this.

In addition, the conventional gas seal member containing another unexpanded vermiculite maintains the sealing property for the above problems. However, even this seal member could not be put to practical use as a catalytic combustion device.

Therefore, the present invention has been devised as a gas seal member that can be put to practical use in a catalytic combustion device based on the conventional problems.

Means for Solving the Problems In the present invention, (1) a sheet or felt made of unexpanded vermiculite, heat-resistant inorganic fibers, ceramic powder having a high specific surface area, and an inorganic binder is loaded with a platinum group metal. An inflatable gas seal member,
(2) Sheet or felt composed of 2.7 to 18 wt% ceramic powder having a high specific surface area of 20 to 77 wt% unexpanded vermiculite, 20 to 77 wt% heat-resistant inorganic fiber, and 0.3 to 3 wt% inorganic binder. An expansive gas sealing member, characterized in that it carries a platinum group metal, (3) the sheet or felt has a specific surface area of 3 m ² / g or more, and a bulk of 0.30 to 0.70 g / cc. An inflatable gas seal member having a density.

Effect The present invention can provide a member having excellent gas sealing properties due to the above configuration.

Specifically, when the unburned air-fuel mixture is ignited in the catalytic combustion device, the honeycomb-shaped catalyst body is heated to a temperature at which sufficient activity is exhibited, and at the same time, the gas seal member according to the present invention is also heated. Therefore, the platinum group metal carried on the seal member also reaches a temperature at which sufficient catalytic activity can be exhibited, and the unburned fuel gas that has entered the seal member is burned and purified here. Therefore, unlike the conventional case, unburned fuel gas does not pass through the seal member and leak.

If the conventional gas seal member directly supports the platinum group metal, the carried platinum group metal particles have poor dispersibility, and heat deterioration occurs immediately. However, as in the present invention, if the gas seal member uniformly contains a ceramic powder having a high specific surface area (for example, activated alumina or the like) and carries a platinum group metal therein, there is almost no concern.

The unexpanded vermiculite used in the present invention is a mica mineral, and has a property of expanding and dehydrating about 10 times in a direction perpendicular to the mica-like cleavage when heat-treated (for example, 500 ° C.).

The heat-resistant inorganic fiber used in the present invention may be any inorganic fiber having heat resistance such as alumina silica fiber, silicon carbide fiber, silicon nitride fiber, etc., but from the viewpoint of cost, alumina silica fiber is most preferable. . The composition is 40 to 95 wt% alumina and 5 to 60 wt% silica.
% Is preferable. The reason is that if the heat resistance is taken into consideration, it is better to increase the alumina content, but if the alumina content is too high, the fiber becomes brittle. Further, considering the cushioning property and mechanical strength of the gas seal member, it is preferable to use fibers having a fiber length of 10 mm or more and a fiber diameter of 5 μm or less.

The ceramic powder having a high specific surface area used in the present invention may be any ceramic powder having a specific surface area of 50 m ² / g or more that can exhibit sufficient performance as a platinum group metal catalyst carrier. Specifically, activated alumina, activated alumina added with an alkaline earth metal, activated alumina added with a rare earth metal oxide, and the like can be used. Since this ceramic powder is preferably attached to the inorganic fibers with an inorganic binder, it is preferable to use one having an average particle size of 5 μm or less.

Alumina sol, silica sol, aluminum nitrate aqueous solution, etc. are used as the inorganic binder, and the solid content (alumina, silica) is 10 to 50 wt% with respect to the ceramic powder.
% Must be added. However, it should be noted that if the amount is more than 3 wt% with respect to the entire gas seal member, the member will become extremely hard.

Example An expansive gas seal member according to an example of the present invention will be described below.

(Example 1) Unexpanded vermiculite, alumina-silica fiber (70 wt% alumina, 30 wt% silica), activated alumina powder containing 5 wt% CeO ₂ (specific surface area: 180 m ² / g), alumina sol and water were used as a slurry. I was in a state. Next, by pouring an appropriate amount of this slurry on a screen, a felt having a thickness of 3 mm was processed by a usual papermaking method to obtain gas seal members having the compositions shown in Table 1. Then, this gas seal member was immersed in an aqueous solution of chloroplatinic acid, dried and heat-treated to carry 0.2 wt% of platinum.

The gas seal member 2 obtained in this example was expanded at 500 ° C., and the concentration of hydrocarbon (HC) gas at the seal portion was 2 mmφ at a distance of 1 cm from the seal portion using a catalytic combustion device as shown in the figure. Nozzle No. was provided and the measurement was performed.
The catalytic combustion apparatus applied a combustion load of 6 kcal · h / cm ² to the catalyst body 1, set the catalyst body 1 to about 800 ° C., and measured the gas concentration. In the figure, 3 is a frame for holding the catalyst 1, 4 is a fuel gas supply chamber, 5 is a blower, 6 is a premixed air chamber, and 7 is an exhaust chamber.

In addition, as a gas seal member life test, the above combustion state was set to 1
After continuing for a period of time, the process of extinguishing the fire and cooling for 30 minutes was defined as one cycle, and after 5000 cycles, the gas sealing property in the above combustion state was evaluated again.

Also, the tensile strength is 20 mm for members with a width of 30 mm and a length of 50 mm.
The value was obtained by pulling at a speed of mm / min and showing the maximum load.

The results are shown in Table 1.

(Comparative Example 1) 50 parts by weight of unexpanded vermiculite, 48 parts by weight of alumina-silica fiber (70% by weight of alumina, 30% by weight of silica), 2 parts by weight of alumina sol (as alumina content) and water were used to make a slurry state. Next, by injecting an appropriate amount of this slurry on the screen, a thickness of 3 mm can be obtained by a normal papermaking method.
The felt was processed into a gas seal member.

(Comparative Example 2) The gas sealing member of Comparative Example 1 was immersed in an aqueous solution of chloroplatinic acid, dried and heat-treated to carry 0.2 wt% of platinum.

The sealing properties of the gas sealing members obtained in Comparative Examples 1 and 2 were also measured under the same conditions as in Example 1.

The results are shown in Table 2.

From the results shown in Tables 1 and 2, it can be seen that the gas seal member obtained in this example has excellent performance.

Further, specifically, in Table 1, when the content of alumina-silica fiber is 20 wt% or less, the tensile strength of the gas seal member becomes too small, which is inconvenient for practical use. It was also found that when the unexpanded vermiculite is 20 wt% or less, the cushioning property of the member deteriorates, and as a result, the performance after the 5000 cycles of the life test deteriorates.

It was also found that the gas seal member exhibits excellent sealing properties when the specific surface area is 3 m ² / g or more. For that purpose, it was necessary to add at least 3 wt% or more of a ceramic powder having a high specific surface area (specific surface area 180 m ² / g) such as activated alumina containing 5 wt% of CeO ₂ . But,
When the amount of added ceramic powder was increased, the gas seal member became brittle and the cushioning property gradually deteriorated, and gas leakage was likely to occur after the life test.
Therefore, the addition amount of the ceramic powder is preferably 3 to 18 wt%. It has been found that 5 to 10 wt% is particularly preferable.

Was impregnated carrying platinum in gas sealing member of Example 1, felted, CeO ₂ 5 wt% impregnated carrying advance platinum
Even if a similar felt-shaped gas seal member was prepared using the contained active alumina, the same effect as in Example 1 was obtained.

Effect of the Invention According to the present invention, it is possible to completely prevent unburned components from leaking from the gas seal member in the gap between the catalyst body and the frame body holding the catalyst body. In particular, the effect of the present invention is remarkable in the catalytic combustion apparatus in which the gas contains a high concentration of unburned components.

Further, compared to the conventional case, the unburned component that has infiltrated the member is burned and purified by the action of the catalyst carried on the gas seal member without paying attention to the airtightness between the catalyst member and the frame holding it. To be done.

[Brief description of drawings]

FIG. 1 is a sectional view showing a catalytic combustion device for evaluating a gas seal member according to an embodiment of the present invention. 1 ... Catalyst body, 2 ... Gas seal member, 3 ... Frame body.

Claims (3)

[Claims] 1. An expansive gas seal comprising a platinum group metal supported on a sheet or felt comprising unexpanded vermiculite, heat resistant inorganic fibers, ceramic powder having a high specific surface area, and an inorganic binder. Element. 2. A sheet composed of 20-77 wt% unexpanded vermiculite, 20-77 wt% heat-resistant inorganic fibers, 2.7-18 wt% ceramic powder having a high specific surface area, and 0.3-3 wt% inorganic binder. Alternatively, an expansive gas seal member, characterized in that a felt carries a platinum group metal. 3. The expansive gas seal member according to claim 1, wherein the sheet or felt has a specific surface area of 3 m ² / g or more and a bulk density of 0.30 to 0.70 g / cc. .