JPS62261803A - Contact burning method - Google Patents

Abstract

PURPOSE:To provide a stable and economical contact method by using a catalyst mainly composed of zirconia and/or zircon in a contact burning of a gas containing hydrogen. CONSTITUTION:As a raw material for zirconia which is a principal component of a catalyst used in the contact burning method, any of zirconium oxide, baddeleyite, zirconium oxychloride, zirconyl sulfate, and zirconyl nitrate can be used. As a raw material for zircon, any of natural zircon, zirconium silicate, sodium silicozirconate and potassium silicozirconate can be used. The contact burning method can be employed for gases in such a wide range where the hydrogen concentration in the gas is approximately 10ppm or more and up to 100%. It is desirable that the temperature of starting a combustion reaction is 100 deg.C or more in a case where no precious metal is added, and 200 deg.C or more particularly in a case where a catalyst consisting only of zirconia and/or zircon is used. In a case where it is necessary to set the combustion reaction temperature at 100 deg.C or less, a catalyst added with an extremely minute amount of a precious metal, particularly palladium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for catalytic combustion of gas containing hydrogen.

[Conventional technology]

Hydrogen, which is a clean energy source, has long been attracting attention as a next-generation fuel to replace hydrocarbons, but if hydrogen is used in large quantities as a fuel in the future, hydrogen alone or methane and other Catalytic combustion methods for gases containing relatively large amounts of hydrogen as well as hydrocarbons will become increasingly important.

Combustion using catalysts has traditionally been carried out at low temperatures and without flames, and there are many examples that have already been put into practical use, such as in acrylonitrile exhaust gas treatment and automobile afterburners. , these are all alumina, silica, silica-alumina, magnesia,
A heat-resistant zirconia anato catalyst carrier supported with noble metals such as platinum, palladium, ruthenylum, and rhodium, or metal oxides such as nickel oxide, cobalt oxide, iron oxide, copper oxide, and manganese oxide as an oxidation-active catalyst component. It was commonly used as an oxidation catalyst.

[Problem that the invention seeks to solve]

However, catalytic combustion using these oxidation catalysts has had various problems. In other words, high temperatures exceeding 1000℃, especially 1300℃ due to heat generated by combustion or oxidation reactions.
When a catalyst is placed in a high temperature condition of ~1600℃, ■ a rapid decrease in surface area due to sintering of the carrier; ■ sintering and/or volatilization of noble metals such as platinum and ruthenium; and ■ metal oxides such as nickel oxide and cobalt oxide. There has been a problem in that the activity of the catalyst is significantly reduced due to inactivation due to reaction with the carrier. In addition to such problems, another problem that cannot be ignored is that metals, particularly noble metals, which are catalyst components are expensive.

The present invention provides a stable and economical catalytic combustion method that can solve the above problems.

[Means for solving problems]

The present invention relates to a method for catalytic combustion of gas containing hydrogen, which is characterized by using a catalyst containing zirconia and/or zircon as a main component.

The present inventors have discovered that in catalytic combustion of hydrogen-containing gas, the combustion activity is high even at relatively low temperatures, and
In order to establish an excellent catalytic combustion method by developing a stable catalyst that retains its activity even at high temperatures exceeding 1500 to 1600 °C, we are working hard on oxidation catalysts based on various metal oxides. As a result of repeated studies, it was surprisingly discovered that zirconia and/or zircon not only have excellent heat resistance, but also have excellent combustion activity. Catalysts containing one or more metal oxides selected from the group consisting of yttrium oxide and aluminum oxide are superior catalysts that exhibit activity even at temperatures of about 100°C or lower. They discovered this and arrived at the catalytic combustion method of the present invention. The present inventors further investigated the case where noble metals were added to these catalysts of the present invention, and found that the catalysts of the present invention could be improved by adding a small amount of palladium, for example, about 0.02% by weight. We discovered that the low-temperature activity was significantly improved, hydrogen combustion reaction occurred even at room temperature, and that it was effective in preventing the decrease in catalytic activity due to sintering of young shell metals with trace amounts of precious metals added. We succeeded in further expanding the scope of application of the catalytic combustion method of the present invention.

According to the hydrogen catalytic combustion method of the present invention, for example, 100°C
From the relatively low temperature range below to 160℃ when exceeding 1300℃
Very stable catalytic combustion is possible over a wide temperature range, even as high as 0°C. Furthermore, the catalytic combustion method of the present invention is extremely economical since no or very small amounts of precious metals are used.

The present invention is a successful solution to the above-mentioned problems that it seeks to solve.

The raw materials for zirconia, which is the main component of the catalyst used in the catalytic combustion method of the present invention, include zirconium oxide, natural baddeleyte, zirconium oxychloride, zirconyl sulfate, zirconyl nitrate, zirconyl carbonate, zirconyl hydroxide, zirconyl acetate, and stearin. Any of zirconyl acid, zirconyl octylate, etc. can be used. Natural zircon, zirconium silicate, sodium zirconate, and potassium zirconate can be used as raw materials for zircon, and each of the above-mentioned zirconium raw materials, colloidal silica, water glasses, silica gel, silicon, silicon tetrachloride, and silicic acid can be used as raw materials for zircon. It is also possible to use various silica raw materials such as ethyl as 5102 in combination in an amount equal to or less than the molt relative to ZrO2.

As raw materials for the subcomponents cerium oxide, calcium oxide, yttrium oxide, and aluminum oxide, any of their oxides, hydroxides, various mineral acid salts, and various organic acid salts can be used. The content of these subcomponent oxides in the catalyst is preferably in the range of 0.5 to 50% by weight, and 1 to 40% by weight.
A weight percent range is more preferred. When adding a small amount of noble metal such as palladium, the addition ratio is preferably in the range of 0.02 to 0.2% by weight. The effect of adding a noble metal is not significant below this range, and above this range, the noble metal causes sintering, resulting in a decrease in activity and destabilizing the catalyst, which is rather undesirable. As raw materials for adding noble metals, halides, various mineral acid salts such as nitric acid, sulfuric acid, etc. can be used.

As a method for producing the catalyst used in the method of the present invention, any of the methods normally used for producing catalysts, such as precipitation, kneading, and impregnation, and combinations thereof, can be used. The catalyst may be molded by any method such as extrusion molding, rolling granulation, or tableting. Furthermore, it is also possible to cover a support such as corallite resin, ceramic foam, metal foam, etc. with the catalyst component using a wash coat or the like.

The molded product produced in this way is usually heated to a temperature of 120 to 200°C.
After drying, the catalyst is fired at a temperature of about 400°C or higher and 1,600°C or lower to obtain a finished catalyst. In this case, the specific surface area of the catalyst is 10
Although the value is extremely small, such as m2/g to 0.01 mar, there is no problem with its activity as a catalyst for the method of the present invention.Increasing the specific surface area of the catalyst increases the activity. However, since this is disadvantageous in terms of thermal stability, the specific surface area of the catalyst for the present invention is 207
It is desirable to perform firing so that rL7 is as follows.

The catalytic combustion method of the present invention can be applied to a wide range of gases having a hydrogen concentration of about 10% or more up to 100%. In this case, the temperature at which the combustion reaction starts is desirably 100° C. or higher when no noble metal is added, and particularly preferably 200° C. or higher when using a catalyst consisting only of zirconia and l or zircon. If the combustion reaction temperature needs to be lower than 100° C., a catalyst to which a very small amount of a noble metal, particularly palladium, is added must be used. Although the catalyst using the method of the present invention has particularly excellent heat resistance, in order to maintain its performance over a long period of time, it is desirable to keep the maximum temperature in the catalyst layer as low as possible. It should be avoided that the temperature exceeds 1600°C, and it is especially desirable to keep the maximum temperature always below about 1300-1400°C. To this end, designs such as multi-stage combustion with cooling midway may be considered.

In the case of catalytic combustion of a gas containing relatively little hydrogen and other combustible gases such as hydrocarbons, a relatively high temperature range such as 600°C is used to increase the combustion rate of the combustible gases other than hydrogen. It is necessary to proceed with the combustion reaction.

[For production]

The catalytic combustion method of the present invention uses a catalyst particularly excellent in heat resistance, and is suitable for a catalytic combustion method in which the maximum temperature reaches 700 to 1600°C. The catalyst is also inexpensive and has excellent activity. Therefore, the present invention can be applied to the catalytic combustion area, which has been restricted due to lack of heat resistance and high cost of conventional catalysts.

〔Example〕

The invention will be explained in more detail by the following examples.

Example 1゜Commercially available zirconium oxide 3.2 m x p x 3.2
ms, and then in an air atmosphere for 130 ms.
Catalyst A was produced by firing at 0°C for 10 hours. This catalyst was crushed into 12 to 24 meshes, packed into a quartz reactor with an inner diameter of 6H at 5CC, and heated to 5V20,000 using a mixed gas consisting of 6.0% N2, 0.3.5% N2, and the remainder at a reaction temperature. A hydrogen combustion test was conducted at 0-1200°C. The results are shown in Table 1.

The specific surface area of this catalyst was 0.2 m''/l.

Example 2゜32 hours after thermally decomposing zirconium nitrate at 400℃
Catalyst B was produced by compressing into tablets of 3.2 mm x 3.2 mm and then calcining in an air atmosphere at 1300° C. for 10 hours. This was subjected to a hydrogen combustion test under the same conditions as in Example 1. The results are shown in Table 1.

Example 3 Zirconium carbonate was dissolved in nitric acid and co-precipitated with calcium nitrate and ammonia. This was calcined at 1300°C for 5 hours to form an oxide of CaO/Zr02=11/89.
(weight ratio) Catalyst C was manufactured. Table 1 shows the results of a hydrogen combustion test conducted under the same conditions as in Example 1.

Examples 4 to 6 Examples E and F were produced using cerium nitrate, yttrium nitrate, and aluminum nitrate as catalysts in place of calcium nitrate. The contents of cerium, yttrium, and aluminum were each 11 wt% as oxides. Table 1 shows the results of a hydrogen combustion test conducted under the same conditions as in the examples.

November - February 2nd - A commercially available zircon carrier was used as catalyst G. To this, power hsium,
The catalysts were impregnated and supported with nitrates of cerium, yttrium, and aluminum, and then calcined at 1300°C to support 19 wt% of the above elements as oxides, respectively.
, to. Table 1 shows the results of a hydrogen combustion test conducted using the same sweeping method as in Example 1.

Example 12.13° Catalyst G was impregnated and supported with palladium chloride, and then 1000
0.02 wt% and 0.2 w of Pd by firing at °C.
Each of the catalysts retained at t% is designated as M.

Table 1 After heat treating catalysts A-M at 1200° C. for 500 hours in a Matsufuru furnace, a hydrogen combustion test was conducted under the same conditions as Examples 1 to 13. The hydrogen combustion rate at each temperature was almost the same as in Examples 1-13.

〔Effect of the invention〕

The catalytic combustion method of the present invention is characterized by the use of a catalytic combustion catalyst that is inexpensive, has excellent durability (heat resistance), and hydrogen oxidation activity, and therefore requires inexpensive equipment and equipment that can operate at relatively high temperatures. Patent applicant: Toyo CCI Co., Ltd., which is characterized by providing a catalytic combustion method using equipment with low maintenance costs.

Procedural amendment (voluntary) May 21, 1981

Claims (6)

[Claims] (1) A catalytic combustion method for a gas containing hydrogen, characterized in that a catalyst containing zirconia and/or zircon as a main component is used. (2) The method according to claim 1, wherein the catalyst contains one or more oxides selected from the group consisting of cerium oxide, calcium oxide, yttrium oxide, and aluminum oxide as a subcomponent. (3) The method according to claim 1 or 2, wherein the specific surface area of the catalyst is in the range of 0.01 to 20 m^2/g. (4) The method according to any one of claims 1 to 3, wherein the catalyst contains a trace amount of noble metal. (5) The method according to claim 4, wherein the noble metal is palladium. (6) The catalytic combustion method according to any one of claims 1 to 5, wherein the maximum temperature of the catalyst layer is 1600°C or less.