JPS5814948A - Catalyst for low temperature combustion - Google Patents

Abstract

PURPOSE:To obtain the catalyst for low temp. combustion capable of extremely reducing effect of an S component contained in a fuel gas, by supporting Rh by an inorg. fiber laminate having micropores in a predetermined wt. ratio on the basis of said laminate. CONSTITUTION:As an inorg. fiber, a fiber comprising a polycrystalline metal oxide, for example, alumina or zirconia pref. having such properties that a specific surface area is 5-200m<2>/g, a mocropore volume is 0.005-0.3cm<2>/g and a diameter is about 3-10mum is prepared. In the next stage, 0.1-3wt%, especially about 0.3-1wt% of Rh is supported by this inorg. fiber to obtain an objective catalyst for low temp. combustion. In this case, about 1/3 of Rh may be replaced with one kind or more or Pt, Pd and Iv. By using this catalyst, combustion property of a low temp. catalytic burner is extremely enhanced as well as CO generating amount during combustion is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst body for use in a low temperature catalytic combustion burner.

A low-temperature catalytic burner is a catalytic body O with complete oxidation activity.
The trick is to send flammable gas or a gas mixed with air, and cause the oxygen diffused from the front cylinder side to react with the scum on the catalyst, at such a low temperature that a flame is generated. This is a burner configured to self-heat the gas. This type of burner has less risk of fire and contains no harmful gases such as Co, O, etc. It has the advantages of extremely low heat generation, high radiation heat (heat input), uniform combustion surface temperature, and stable combustion at low loads.
, useful for household and commercial and industrial purposes.

However, the conventional low temperature catalytic combustion burner
One LD for TG fee? %O, which shows a somewhat satisfactory effect in IC'')-, but uses fuel containing methane such as ordinary city gas, which has various effects in terms of combustion performance, catalyst durability, economic efficiency, etc. There was a problem, and a practically satisfactory %O was not obtained.The inventor, III Company,
A catalyst body used in a low-temperature catalytic combustion burner that uses methane-containing gas as fuel (hereinafter referred to as a catalyst body for low II fuel hooks)
], and some of the results have already been published (No. 4111111851-83088, $8
11 Showa 52-147590, Kawara 11I54-157
No. 409, Japanese Patent Application No. 159678-1978, Japanese Patent Application No. 1154
-159679 etc.). Through further research based on these O results, the present inventor discovered that K11L, which forms a catalyst for low-temperature combustion, and 0, which is a type of ghost metal O as a catalytically active metal, can be used as a catalyst for other platinum group metals. They discovered that it exhibits a behavior significantly different from that of urn, vanadium, etc., and conducted further experiments and research, leading to the completion of the present invention. That is, the present invention provides a laminate of inorganic fibers having micropores with a laminate weight of 00.1-'! The present invention provides a catalyst for low-temperature combustion in which 0-dium is supported.

Catalysts for low-temperature combustion have excellent retention of catalytically active metals, give shape and strength to the catalyst, have low specific heat, excellent sludge dispersibility, and high heat resistance. A carrier or support (hereinafter referred to as catalyst support) is required. In the present invention, an inorganic fiber O laminate or a low-density mat-like material □ having micropores is used as a catalyst support. Inorganic fibers include polycrystalline metal oxide fibers, more specifically alumina, zirconia, titania, thoria, and reed! A fiber made of Narsilica or Zirconia-Silica, with a specific surface area of 5 to 200♂/1. Pore capacity 0.005~0-5d/f, diameter 3~10μs1
Those having the properties of 1 degree are preferable. Such fiber Ia0
−For example, British Imperial Chemical Industries Re! Commercially available from Ted is the standard clade of %fh:h alumina fibers ``Safil''. This is a transition system of 95- or more □, 0
3 and 51! The following is a long fiber containing O5to2 and a small amount of recrystallization inhibitor, with a diameter of 5 μm and a specific surface area of 1 μOw.
? /l, pore volume 0.2 d/f, tensile strength 10
It has properties of 0Kg/J11 degrees and has sufficient heat resistance of 1000111: no change in pore structure occurs when heated. Hey Al! Depending on its own properties, the fibers are usually 0.02 to
0.1? In the low-temperature combustion catalyst body of the present invention having a bulk density of about /-, it is essential to use 0dium as the catalytically active metal.

Even if it is the same platinum group metal, when using platinum,
Oxidizes the sulfur content contained in the fuel residue to K sulfuric acid,
Since it promotes erosion and embrittlement of the catalyst support, it becomes unusable as a catalyst within a short period of time.

When palladium is used, the catalyst activity quickly decreases due to carbon precipitation and direct poisoning of palladium itself by sulfur. On the other hand, when using 0 dium, the ζam problem does not substantially occur, which is necessary as a catalyst for low-temperature combustion. ; The amount carried by the ram is about 0.1-5 weight-1 weight, or about 0.3-1 weight-1 weight. If the supported amount of 0.0 dium is less than 0.1 weight, the catalytic activity will not be sufficiently exhibited, while if it exceeds 3 weight, no further improvement in the effect will be observed, and this will be economically disadvantageous. In addition, in the present invention, 0. ; Up to 96,011 degrees Celsius can be replaced with one or more of platinum, palladium, and iridium; in this case, the price can be reduced without substantially impairing the catalyst performance.

The low-temperature combustion catalyst of the present invention can be produced by various methods, but in order to uniformly knead KOdium in the catalyst support, it is preferable to produce it by the method exemplified below.

(-) Preferably 3000F/11? The inorganic woven laminate as a catalyst support adjusted to the following thickness,
A solution of a 0-dium compound containing 0-dium having a liquid volume 20 times or more the weight of the laminate and having a laminate weight of 60.1-'$1 GK is brought into contact with the 0-dium compound while being circulated, and then exposed to air. , preferably at a temperature below 20 G° C. under air circulation.

Not only in this manufacturing method, but also in each manufacturing method described below, it is preferable to contact the catalyst support and the 04I compound solution by the above-mentioned 04I standard method, and it is preferable to simply contact the catalyst support with the 04I standard method. ; Only immersion in the rum compound solution will not reach the desired O
The effect was obtained at 1% A. According to the immersion method, which is generally used as a method for producing conventional catalysts, the bulk density of the catalyst support of the present invention is small, that is, it has a shape with a large volume in terms of weight ratio. Therefore, most of the O-dium compound is adsorbed before the O-dium compound solution penetrates into the inner layer of the catalyst support, and the O-dium compound is non-uniform between the inner layer and the outer layer of the catalyst support. It is inevitable that a loading distribution will occur.

The zero-dium compound used in the production of the low-temperature combustion catalyst of the present invention includes reed chloride! Sci0dium Cu05ide [R
(Ml, )5C1) Cl2, chloride 0dium acid acid (NH,)3R Ct6, III[]dium λ
5(NO3)3, 0 sulfate RA2(S04)3, sulfite o, ; & 1As03, chloride 0 '':;')
MuRhC15, acetic acid ot! Ium JtA (CI, Co
o),,3''0';'y L Rh1s 1
Among the exemplified and weak forces, chloride ow! Ium, 0@5 um acetate and 0@5 um nitrate are particularly preferably used. The 4IOdium compound is usually brought into contact with the catalyst support in the form of 1 inch of water. The aqueous solution Kti,
(Improving the seismic intensity of 3fI um compounds, accelerating the decomposition of 00 dium compounds during drying, and improving the support of 0 dium compounds, etc.) by adding small amounts of inorganic and organic acids such as hydrochloric acid and quenchic acid, and organic solvents such as alcohol. It may be added.Obara which can replace a part of 0dium!: Oba5w as a lium source! Ba5dic acid chloride (jr2
Pact4), Tet5900A5'';') ammonium acid c <xi,)2pttct, 3, etc., are exemplified,
Examples of platinum compounds as a platinum source include platinic acid (jr2?tCt6), platinum platinum ((Jff4)2PtC16), and examples of iridium compounds as an iridium source. , iridium chloride (IrCl-25), and iridium chloride (lI21rC16 or &ix, zrct6).

Due to the drying operation after being impregnated with the 0.0-dium compound solution, the bulk density of the catalyst is 0.02-0, which is the bulk density of the initial catalyst support.
．． Recover to 1F/-K. The O catalyst body was adjusted to 200 to 6001/♂ based on the weight of OjO, and 940 was useful as a catalyst body for low-temperature combustion, and OjPh for LPG.
It is used in burners for gases containing 0 metals, such as energized city gas.

(-) The obtained nine catalysts are further heat-treated in air at 550 to 650°C for 50 minutes to 2 hours in the same manner as in the method (:) above. The catalyst obtained in this way further improves the combustibility of low-temperature catalytic combustion burners and reduces CO during firing.
Reduce the amount generated. K if the heating temperature is less than 550℃
a, 0dium compound or 0! ; Because the O decomposition activation of rum compounds and platinum compounds is insufficient, the amount of CO generated during combustion can be reduced by [at], but it is OK, but 65
Above 0℃, crystal growth of catalyst particles is promoted,
However, Dco generation cannot be sufficiently suppressed.

(■) The nine catalysts obtained in the same manner as in the method (1) above were further heated under an oxygen-free steam atmosphere, preferably in an oxygen-free state and in the presence of at least 1 volume of steam.
Heat treatment at ~650°C for 30 minutes to 2 hours. Oxygen bar?
In order to carry out this process, it is preferable to use at least one of N2, CO2, helium, alcon, etc. in combination with the steam. The catalyst body thus obtained is as described above (iris).
Similar to the previous catalyst body obtained by the method described above, the combustibility of a low-temperature catalytic combustion burner is greatly improved.

When the heating temperature is lower than 350°C or higher than 6-50°C, there is a tendency for Ti and combustibility to decrease and CO generation to increase.

θVΣ The catalyst body obtained in the same manner as in the method (1) above is further treated in a reducing gas atmosphere, preferably with hydrogen, -carbon oxide,
Reduction such as annealing at 200°C to 600°C for 30 minutes to 4 hours in the presence of 1 volume or more of at least one type of reactive gas.
Heat treatment for an hour. To create an anoxic state, use N2, C
It is preferable to use at least one of O2, helium, and Alj:J together with a reducing gas. The catalyst body obtained by this method has the same excellent combustibility as the catalyst body obtained by the above methods (II) and ON), and also has a uniform black-gray color over the entire surface. 41 colors appear on the ink dots.

The catalyst body obtained from Kamiayu (1) Noka@O direction is almost white, similar to the color of the catalyst support 0. However, when such a white catalyst is deposited in a burner and used for combustion, the color gradually changes to blackish gray starting from a high temperature.

However, even in the steady combustion condition 11, the color of the catalyst is not uniform over the entire surface, and the peripheral part is bright white.
It is t. This kind of uneven coloring, especially when using a low-temperature catalytic combustion burner as a household heater,
O gives a feeling of anxiety or discomfort to the user, so it is preferable or not. The catalyst body obtained by this method exhibits a uniform black-gray color on the entire surface regardless of whether it is used before or after use.
If the temperature is less than 60°C, if the flammability of the catalyst is not sufficiently improved and the color becomes a uniform black-gray, then the temperature is 60°C.
If the temperature exceeds 0°C, the flammability tends to decrease on the contrary.

(V) In the same manner as in method (1) 0 above, the obtained catalyst body is further heated in an atmosphere of steam and reducing gas, preferably in the presence of 1 volume or more of steam and 1 volume or more of reducing gas. Heat treatment at ~600°C for 50 minutes to 2 hours. As for the reducing gas, hydrogen, carbon oxide, acacia, etc. are used, and in order to create an oxygen-free state, phoneme, carbon dioxide gas, helium, alcone, etc. are used in combination, as described in (IV) above.
This is the same as in the case of the 0 method. The black-gray catalyst body obtained by this method not only has the same excellent combustibility as the catalyst body obtained by the above methods (■) to (IV), but also has the following It has color. That is, when each of the catalyst bodies described above starts combustion for the first time, it is necessary to perform steady combustion and 'Ik
It takes about 20 minutes and 1 degree. However, the precatalyst obtained by the present production method reaches steady combustion within 10 minutes even in the first combustion. Note that the heat treatment temperature was set at 200 to 600°C for the same reason as in the case of the method (-) above.

The low-temperature combustion catalyst of the present invention exhibits remarkable electrodynamics as described below.

(1) Since Orium itself is difficult to be poisoned by sulfur and has a low ability to oxidize sulfur with Kt sulfuric acid, the influence of sulfur contained in fuel gas can be significantly reduced.

(2) There is very little carposi precipitation.

(4) As a result of the above (1) to (ml O), the durability is extremely excellent.

(Container) O exhibits high catalytic activity with low rhodium loading, and is highly economical.

+6) Applicable not only to ZPG but also to all fuel gases such as natural gas, manufactured gas, and other gases containing methane.

Example 1 Including At2039591 or higher and 5=o25 or lower,
Specific area area 150w? yt, a laminate with a bulk density of 0.06 F/- consisting of fibers with a fiber diameter of 311 and 0 is 500 mm in width,
The length was adjusted to 300 mm and the weight was 300 mm.
hct3) Spray 6t of aqueous solution and cycle for 11 hours.
11 Let them touch. The amount of the aqueous solution is 020 times the weight of the stack. After contacting, the laminate was dried for 5 hours under 120' CO air flow and then steamed 85 vol - 1 hydrogen 0.7
in an atmosphere consisting of 5 volumes and 14.5 volumes of nitrogen.
The catalyst was heat-treated at 00°C for 1 hour.

5 each from the upper layer, middle layer, and lower layer of the obtained precatalyst
Scrape each f and use the fluorescent X-ray method! Table 1 shows the results of measuring P(3/um) and chlorine content.

111th! Next, the pre-catalyst body obtained as described above was heated to 400few?
The catalyst body 11) is adjusted to have a thickness of 0, is attached to a low-temperature catalytic combustion burner having the structure shown in No. 111, and a combustion test is performed. Installed 9, electric heated (not shown) from 250K
Since the catalyst body (1) is preheated to ℃, there is a supply channel (
7), natural gas having the composition shown in Table 2 is supplied. The heat load is 1.5kea+l/d·static. The combustion exhaust is sent from the 7-door (9) through the tact ← 1) to the gas tank 0 matograph (not shown), and the exhaust components are analyzed.
Find the combustion efficiency according to the formula below. As shown in Table 5 below, the initial combustion efficiency was 99.0 degrees, and no CO was detected.

However, the value in brackets indicates the loss value.

Table 2 CH488 Capacity CH C, H66# C3lIs 4 # C, H□. 2# Sulfur content 5q-5/Nd Calorific value 11000 heal/Nd A continuous combustion test was conducted for 5000 hours under the above combustion conditions, and the combustion efficiency and CO/CO2 after the specified time had passed.
The changes in the ratio are as shown in Table 3.

Table 3 The combustion efficiency decreased to 98.0- after too many hours, but remained constant after that, and the CO/CO2 ratio was
It is always below the regulation value of 5 for stoves, and no large disturbances are allowed. Furthermore, no change was observed in the appearance, mechanical strength, burner surface temperature, etc. of the catalyst itself, and it was found that the catalyst had extremely satisfactory performance in practical terms.

Example 2 Using an O catalyst as in Example i, city gas with a calorific value of 4500 keaL/Nttl, a methane content of approximately 2L, and a sulfur content of 40q-5IN- was subjected to a heat load in the same manner as in Example 1. It was continuously burned for 5000 hours at 1.5 hcal/ai・kr. The result is number 41! ! This is the circular shown in .

Table 4 From the results shown in Table 4, it is clear that the catalyst properties, combustion efficiency, and carbonization of the CO/COa ratio of the present invention are very small, and that it is stable even after combustion for a long time and exhibits precatalytic activity. or,
Since no changes were observed in the appearance and mechanical strength of the catalyst, as well as in the bartOII temperature, the catalyst body of the present invention
It was confirmed that the present invention has satisfactory performance as a low-temperature catalytic combustion burner for city gas with relatively high sulfur content.

Comparative Example 1 Al! used in Example 1 and similar to 9! A laminate of glass fibers was adjusted to have a length of 300w, a width of 500mm, and a weight of 300fK, and platinum was added to the laminate to reduce the weight of the laminate. , 5 weight - to include +
Spray 6 L of an aqueous solution of Zaku 00 platinic acid <H2ptct6> and keep in circulation contact for 1 hour from the surface. After the contact is complete, the laminate is dried under air flow at 120°C for 5 hours, and then heated with 85 volumes of steam - 0.7 volumes of hydrogen and 14 volumes of nitrogen.
A catalyst body is obtained by heat treatment at 500° C. for 1 hour in an atmosphere consisting of 3 volumes.

5 each from the upper layer, middle layer and lower layer of the obtained catalyst body.
Table 5 shows the results of measuring the self-gold and chlorine contents by linking each sample using a fluorescent X-ray method.

Table 5 The catalyst body obtained in the above 04l) K was adjusted to a thickness of 60017♂O, and city gas was combusted in the same manner as in Example 1 and in the same manner as in Example 2. The results are shown in Table 6.

Table 6 From the results shown in Table 6 and various tests, it is clear that low-temperature combustion catalysts using platinum as the catalytically active metal have the following problems, and should not be used for gas combustion with a large sulfur content. It turned out that it couldn't be done.

(α) Although the CO/CO2 ratio fluctuates, the combustion efficiency significantly decreases over time, reaching 90% after 5000 hours.
Below vomit.

The surrounding area was easily destroyed (due to the OIR edge of the cocatalyst being hardened and brittle, and due to vibration). During most of the hardening, the sulfur content in the gas is oxidized to SO3, which reacts with At203 in the carrier and j! 2 (,504)
It was found that the weight was 3.8 Jr.20. This is thought to be the main cause of embrittlement and decreased catalyst activity.

Comparative Example 2 A catalyst body obtained in the same manner as in Comparative Example 1 was adjusted to a thickness of 400 f//, and treated in the same manner as in Example 1 using natural gas (however, the sulfur content was 1081-5/N-: &AIII' C) was continuously burned for 2000 hours. The results are shown in Table 7.

Table 7 The CO/CO2 ratio hardly changes, and the decrease in combustion efficiency is relatively small, and - as in Comparative Example 1, the peripheral part of the catalyst body is hardened and brittle. The sulfur content in natural gas is due to the sulfur compounds currently added as odorants, and is usually 3 to 10q-5/N-.
It fluctuates within a range of . Therefore, a catalyst body containing platinum as a catalytically active component is not practical because it deteriorates over a long period of time.

Comparative Example 3 The same Al! as used in Example 1! The laminate of fibers was adjusted to a length of 300m, a width of 500wa+, and a weight of 5oot.
While spraying 6 tons of a dilute hydrochloric acid aqueous solution of palladium chloride containing 1.0 weight of the weight of the mosquito stack as palladium, the mixture was brought into cyclic contact for 1 hour. After the contact is completed, the laminate is
It was dried at 20° C. for 5 hours under air circulation, and then heat-treated at 500° C. for 1 hour in an atmosphere consisting of 85 volumes of steam, 0.7 volumes of hydrogen, and 14.5 volumes of nitrogen.

The laminate was once again brought into circulation contact with a dilute aqueous solution of palladium chloride in hydrochloric acid in exactly the same manner as above, dried, and heat-treated.

The cibaradium and chlorine contents of the obtained catalyst were measured by the fluorescent X-ray method in the same manner as in Example 1, and the results were 81st! As shown.

Table 8 The pre-catalyst body obtained as described above was adjusted to a thickness of 40017-vm'', and continuous combustion of O natural gas was carried out in the same manner as in Example 1.The results were as follows: As shown in Table 9.

No. 91I Observation of the catalyst body after each combustion period revealed that carbon gradually precipitated from the lower layer of the catalyst body through the middle layer to the upper layer I1 as time progressed, and this rapidly and drastically reduced the catalyst activity. It was determined that there was.

Therefore, the catalyst body of this comparative example using palladium as the catalytically active metal cannot be practically used for natural gas combustion.

Comparative Example 4 City gas was combusted in the same manner as in Example 2 using the same catalyst as in Comparative Example 3.
After several hours, the combustion efficiency decreased by 701GK and it became unusable. The main cause is believed to be poisoning by sulfur contained in city gas at a concentration of 4011f-S/N-.

Example 5 A laminate of alumina fibers similar to those used in Example 1 was made into a laminate of 300 wr1. Adjusted to width 500m and weight 3001,
This contains 0.4 - of the weight of the laminated layer as rhodium! ; Contains ram (xhct3) and platinum toshite 0.11 + SakuO [1 white 1tWI CH2ptct6)
While spraying 6 t of mixed aqueous solution, the mixture is brought into contact with circulation for 1 hour. Contact completed @ 0 By activating the laminate using the O method as in Example 1, 0 dium 0.4-1 platinum 0.1
- and less than 0.1 s of chlorine were uniformly supported as a whole.

The thickness of the obtained catalyst body was adjusted to 400 f/ia'', and city gas was continuously operated for 5000 hours in the same manner as in Example 2. The results are shown in Table 10.

From the results shown in 10th to 1011th K, the catalyst body of this example had a
Even after 0 hours, there was no substantial decrease in catalyst activity, and no decrease in catalyst strength or change in appearance was observed, which was extremely satisfactory for practical use.

Example: 0.41G of current, 0.1% of palladium, and 0.41G of chlorine.
City gas was combusted in the same manner as in Example 3, except that a catalyst supporting less than 11 was used.

The results are as shown in Table 11, and a catalyst body having excellent performance similar to the catalyst body of Example 3 was obtained.

Table 11 Comparative Examples 5 to 6 0! :, um0.5*, platinum 0.3% and al
Catalyst supporting less than 1EO, 1S (Comparative Example 5) and 0
0.5-, 0.3% palladium and 0.1% chlorine
Continuous combustion of city gas was carried out in the same manner as in Example 3, except that a catalyst supporting less than - (Comparative Example 6) was used.

The catalyst body of Comparative Example 5 was found to be difficult to put into practical use because the peripheral portion became hardened and brittle after 2000 hours, and a portion was destroyed.

In the catalyst of Comparative Example 6, carposi was deposited near the upper layer after too many hours, and the combustion rate decreased to 85-9, making it impractical.

[Brief explanation of the drawing]

FIG. 1 shows the combustion test O1 using a low-temperature catalytic combustion burner equipped with the catalyst of the present invention! This is a drawing showing the main points (1)...
・Catalyst body, (3)...Protection wire mesh, (6)...Heat insulation material, (7)...Scrap supply path, (s)...Hood, (t')... ... Takt (above) Figure 1 Procedural Amendment (Own Ship August 27, 1981 1, Incident Indication 1981 III#P Application No. 106566 2
, Name of Nenmei Catalyst for Low Temperature Combustion 3, Relationship with the Amendment Case Patent Applicant 4, Agent, Heiwa Building, 2-10 Hirano-cho, Higashi-ku, Osaka Telephone: 06-203
-0941 (Main) Contents of the amendment as attached to the attached sheet ＠ - Book, page 6, line 15 to page 7, line 1, the phrase ``Price [can be lowered]'' has been replaced with ``can be used. ” he corrected. (that's all)

Claims (1)

[Claims] (2) A catalyst for low-temperature combustion, characterized in that a laminate of inorganic fibers having micropores supports 0 dium having a weight of O0.1 to 5-.