JPH02290251A - Gold-containing catalyst for contact combustion - Google Patents

Abstract

PURPOSE:To enhance catalyst activity and durability for water by carrying 1-5wt.% gold fine particles on the surfaces of a particle of titanium oxide, magnesium oxide, zirconium oxide, silicon oxide, aluminum oxide, tin oxide, cobalt oxide or lanthanum oxide. CONSTITUTION:1-5wt.% gold fine particles are carried on the surface of a particle of titanium oxide, magnesium oxide, zirconium oxide, silicon oxide, aluminum oxide, tin oxide, cobalt oxide or lanthanum oxide. Said catalyst, although the gold content is small, carries high catalyst activity, high durability for water content and is of a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Icheon Field] The present invention relates to a catalyst for the catalytic combustion of combustible gases, particularly carbon monoxide, at low temperatures. This catalyst is suitable for CO for mine mines.
It can be used to purify incomplete combustion gas generated from combustion appliances such as masks, gas sensors, oil fan heaters, and water heaters.

[Prior Art] Catalytic combustion using a catalyst, that is, catalytic combustion, is flameless, has high combustion efficiency, and has the characteristics of complete combustion at low temperatures.

They are classified into low temperature (room temperature to 300°C), medium temperature (300 to 800°C), and high temperature (800°C and above) depending on the degree of ignition. The present invention provides a catalyst for low temperature combustion of combustible gases, particularly carbon monoxide.

Conventionally, as a low-temperature carbon monoxide oxidation catalyst, manganese oxide copper monoxide-based Hovkarai I- (M.I.B-ri
ttan, II. Old iss, C. 8 lalke
r, AIChl mi. J. , 16305 (19
7.0) ”), Pt, Pt/SnOz, activated carbon (G.C. Rond, L.R. Molloy,
M. J,Fuller, J,Chem,Soc.
．． , CI+em. Comm. , l'975, 796
, Masahiro Kobayashi, Susumu Oikawa, Shimizu Construction Research Institute Report, 25. 77
(1975), Hiro Kamino, Tokuko Sho 54-22791 (19
79)), CuC1z-PdCI2/alumina based (M.N. Desai, J.B. Routt, J.
S. IJranoff, J. Cat-al. , 79
．． 95 (1983)), cobalt vorphyrin/titanium oxide type (1. Mochida, Y. rwai
, T. Kamo, 11. Fujitsu, J. Ph
ys. Chem. , 89. 5439 (1985)
), 8g-Co, 8g-Mn, 8g-11n-
Co-based ones (M. llaruta, 11. sano,
”Preparation of Catalyst
sll! ', G. PonceleL, P. Gra
nge+P. Eight. Jacobs eds. ，
Elsevier, 225-234 (1983)
) etc. are known. these? Lahobcalite is used in Minekawa CO masks and can oxidize CO at room temperature. I'd, I't/SnO■, activated carbon-based metals and platinum-based metals are often used in catalytic combustion because they generally have high oxidation activity.

Cobalt vorphyrin/titanium oxide type is -79
``C also has oxidation activity, and Ag-Go, 8g-
Mn, A8-Mn-Go series are room'/! It has one special feature such as having oxidation [1] in A.

On the other hand, it has recently been reported that gold, which has been generally thought to have almost no catalytic activity, can be used as a catalyst if it becomes fine particles. For gold-containing catalysts, 8u (5a
t$)/ (r-FC+2031 +1u(5atχ)
/CO. ,a,8u (10a tχ)/NiO type (Masaki Haruta, Hiroshi Sano, Nikka 52nd Spring Annual Meeting IC44
(1986), M. Ilaruta, T. Ko-
bayashi. Il. Sano, N. Ya
mada, Chem Lett. ．． 1987
．． 405-408, Japanese Unexamined Patent Publication No. 60-238148)
, 5-10 wL% static-Be oxide type (Haruta, Toriya, Kobayashi, Tsubota, Nakahara, 60th Catalyst Symposium (A) Lecture Preliminary Construction 31E25), 10-t% Au/Mg (Oil)
The Z series (Tsubota, Yama III, Haruta, Kobayashi, Nakahara, 62nd Catalyst Symposium (A) Lecture Proceedings 30221) has been reported. Behind these, ＾u(5atχ)/
a −FezOt+ Au(5atχ)/CosOa
The lAu(10a t!) /N to type catalyst is prepared by adding an alkali to a mixed solution of nitrate and chloroauric acid, co-precipitating it, and calcining it, and this catalyst has lνol% CO / It has the ability to completely oxidize air and is resistant to moisture. Although the reaction rate decreases with time, it has the characteristic of being able to be regenerated by heat treatment at 200"C.Also, it has the characteristics of a cap that can be regenerated by heat treatment at 200"C. , -70''C also provides long-term stable activity. On the other hand, 10wt%Au/Mg
(DIυ2-based products are made by adding 1 (hrt%) chloroauric acid solution to a suspension of MgO, and adding dropwise a saturated magnesium citrate solution to reduce the chloroauric acid with magnesium citrate to produce gold oxide. After precipitation and filtration, dry 250'
It is made of Mnl by firing with C.

[The invention is not going to solve the problem.] [Issues to be solved]

Hopcalite, cobalt vorphyrin/titanium oxide, A
The catalyst of the B-Go-Mn example has poor resistance to moisture. Pd, Pt/SnOz, activated carbon, CIICl2
The temperature at which the PdCIz/alumina catalyst becomes active is 1.
The temperature is 50°C or higher, and the activity is poor at room temperature.

8u/α-FezO1, Co, Boa, Nio.
Bed, Mg(ol1), is a highly active catalyst, but in order to develop its activity it requires 5-10aL%, to
It is necessary to have a mouse hold 13 wt% and expensive gold. HIl again! (Oil) Other catalysts except for z are prepared by the coprecipitation method, but this method requires a solution of oxides other than gold, which make up the majority of the catalyst, and requires a large amount of water to precipitate it. A precipitation R agent is required. The coprecipitation method also has the disadvantage that the active gold is embedded in the transition metal Iu body, which is a carrier component, and does not come out on the surface. On the other hand, ＾u／｝i
The g(Oll)z catalyst also has the disadvantage of requiring expensive magnesium citrate as a gold precipitant.

[Means to solve the problem]

The present invention provides a catalyst for catalytic combustion that solves these problems, and includes titanium oxide, magnesium oxide, zirconium oxide, silicon oxide, aluminum oxide,
Is it because there is 1 to 5% gold on the surface of soot oxide, cobal oxide, or lanthanum oxide particles? It is characterized by having a gold-containing catalyst for catalytic combustion supported on JLI.

Support particles that hold gold on JH are TiOz, MgO, and Zr.
Ot, Sint, 8l20,, Snut, Co:+O
n, Laz01. Among these, T
i02 is also preferably Iυ, and gO is next most preferred.

The inventors of the present invention have found that 8 hllh, SiOz, 7, no, S
nOz, TiOz, MgO, Zr02, COsOa, F
e. O. , Laz02, a catalyst containing 2 wt % gold was prepared by a deposition method, and the CO oxidation activity of each was investigated. As a result, CO can be reduced by 50% even at temperatures as low as -78°C.
The catalyst carriers for the above conversion were Tie2 and MgO, and TiO2 in particular had the highest CO conversion rate of 95%. At room temperature, TiO1, ZrOz, SnOt, CO304, L
azO, has 100% conversion activity, 'gL Si0
2. AIzOi was the next highest. On the other hand, FetO. ,Z
nO■ had low activity. Therefore, TiOz is the best gold support, followed by Mgo, Zr02, Si02
,Eight! 20, SnOz, Co304, and La203 were excellent carriers.

The particle size of these carrier particles is suitably about 0.01 μm to 0.5 μm. This world particle may have a larger diameter. It is also possible to use a mixture of two or more types of JEI body particles.

Gold has an average particle size of 50 particles or less, preferably about 15 to 50 particles. Gold particles are supported on the surface of the carrier particles uniformly in 11k portions. has been done.

Such a catalyst forms a suspension of the carrier particles in an aqueous solution in which the carrier particles, chloroauric acid and a weakly alkaline substance coexist, so that gold hydroxide is precipitated under the growth-inhibiting strips 1'i; It can be obtained by solid-liquid separation and reduction of the gold hydroxide in the gas phase.

The carrier particles are preferably suspended in an aqueous liquid such as water in advance, and the chloroauric acid and the weak alkaline substance are also dissolved in the aqueous liquid such as water. Examples of weakly alkaline substances include ammonium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like. The amount of the weakly alkaline substance added is suitably at least three times the equivalent of gold. The gold hydroxide and the weakly alkaline substance may be added in any order and both may be added at the same time. Gold hydroxide is precipitated by bringing a weakly alkaline substance into contact with chloroauric acid. This gold hydroxide grows
Precipitate under R++I conditions. Growth-inhibiting conditions are conditions such that the average particle size of gold particles in the obtained catalyst is 50 or less. These conditions include, for example, suspending carrier particles in a solution of a weakly alkaline substance, or combining a suspension of carrier particles with a solution of a weakly alkaline substance to prepare a suspension of particles in the presence of a weakly alkaline substance, and stirring. It is formed by adding a chloroauric acid solution below. Conversely, by suspending carrier particles in a chloroauric acid solution or combining a suspension of Iu particles with a chloroauric acid solution, 1u particles in which chloroauric acid exists! You can also prepare a suspension and add a weakly alkaline substance to it. In this case, add the gold hydroxide quickly so that it does not grow, and stir it to make it uniform by stirring 1↑ or the like. Either method can be carried out under cooling in order to suppress the growth of gold hydroxide.

After charging, if necessary, leave it alone or continue stirring 1↑ to reach a supersaturated state before solid-liquid separation. Solid-liquid disturbance may be performed by a known method, such as filtration, centrifugation, decantation, etc. After solid-liquid separation, the obtained particles are washed with water and dried if necessary.

Dry particles are reduced in the gas phase to convert gold hydroxide to gold. The gas phase is a reducing atmosphere in which gases such as hydrogen and carbon monoxide are present. At that time, an inert gas may be present if necessary. In addition, reduction is performed under force (1 heat).

[Function] In the catalyst of the present invention, in addition to the fine gold particles, the surface of the oxide particles, which are the Sekyu particles, is thought to be involved in the catalytic action, and the catalytic activity is determined by the part of the fine gold particles to which the Sekyu particles are attached. It seems to be nearby.

To create this catalyst, first add a chloroauric acid solution, stir thoroughly, and then slowly add a weak alkaline substance solution.The gold precipitate particles that are formed will grow into large particles, which will cause oxidation. Activity decreases.

Also, is there a chloroauric acid solution at the end of the oxide particles, which are carrier particles? Even with the usual impregnation method in which the solvent is evaporated, the gold particles grow and high activity cannot be obtained. Furthermore, the coprecipitation method cannot achieve reproducibility depending on the combination of oxides. [Example] Example I Titanium oxide powder (TtJ) 2 (1
The mixture was placed in a 0 cc beaker, and about 100 ml of water was added and stirred. Add 4. 067x 10-Smo
l/mf of chloroauric acid (llALIc14.411■O)
Add 5 g of aqueous solution (0.04 g as gold) and immediately add 2N ammonium hydrogen carbonate (N!I s1) as a precipitant.
5 ml of the 1Coff) solution was quickly injected to give a sufficient processing time of 132 1't'L. Chloroauric acid can be converted into gold(III) hydroxide Au(O
ll)s and deposited on the titanium oxide surface. This was filtered, thoroughly washed with water, and then dried on IIO'C. Next, while passing hydrogen gas through the reaction tube, the mixture was heated at 400'C for 6 hours for reduction. After reduction, the mixture was allowed to cool down to room temperature under nitrogen flow, and a small amount of air was added in pulses until no heat was generated, and then the mixture was taken out from the reaction tube.

The catalyst was 2wt% Au/Ti02. When the catalyst surface was observed using a transmission electron microscope and the diameter of the supported gold particles was measured, it was found that an average of 32 well-aligned particles were evenly separated and supported.

0.1 g of the catalyst prepared in this way was placed in a glass reaction tube.
It was filled and set in a closed circulation reactor.

After applying a vacuum of Jl+2 at room temperature, add 4 x 10-
'mol was added, and the temperature was raised to 300°C for 30 minutes. After pick-up, the same tank was vacuum degassed at 300°C for 30 minutes, and then cooled to the reaction temperature of 100"C1 room temperature - 78°C.

In the reaction, carbon monoxide and oxygen were added in an amount of 3 x 10-' mol each at a predetermined reaction temperature, and the mixture was circulated for 30 minutes. After 2, 5, 10, 20, and 30 minutes, COt was analyzed by gas chromatography to determine the reaction rate. The results are shown in Table 1 along with other catalysts. The CO addition rate 2 minutes after the reaction reached 100% when the reaction temperature was 100°C, and 95% even at -78°C.

Example 2 2wt% magnesium oxide powder (MgO)
An Au/MgO catalyst was prepared. εI! ]Production method and reaction? The method was the same as in Example 1.

The results are shown in Table 1. This catalyst has a temperature of 2 after the reaction at -78°C.
The conversion was 60% in 1 minute, 68% in 5 minutes, and there was no change thereafter.

At room temperature, the conversion rate at 2 minutes after reaction was 18 (3 I), but it gradually increased and reached 85% after 30 minutes.At 100°C, the activity decreased to 6% at 2 minutes after reaction. After 30 minutes, the conversion rate was 33%.

Example 3 2w with 11 pieces of zirconium oxide powder (ZrO■)
L%flu/ZrQ! A catalyst was prepared. The preparation method and reaction procedure were the same as in Example 1.

The results are shown in Table 1. At -78°C, this catalyst
Even at 0 minutes, only 2% conversion was achieved, but at room temperature and 100″
C had 100% conversion after 2 minutes.

Example 4 2wt%A using tin oxide j5} powder (SnO■) as a carrier
A u/SnO■ catalyst was prepared. The preparation method and reaction method were the same as in Example 1.

The results are shown in Table 1. At -78"C, this catalyst
Even at 0 minutes, only 1% conversion occurred, but at room temperature and 100°C.
After two minutes, the conversion was already 100%.

Example 5 Cohart oxide powder (COJa) was used as a worldly product (%A
A u/Co304 catalyst was prepared. The preparation method and reaction method were the same as in Example I.

The results are shown in Table 1.

2 minutes after reaction at reaction temperature -78°C? :I29<, 3[
} minutes later, the conversion was 49%. On the other hand, room temperature and 100” (
: After 2 minutes, 100% conversion was already achieved.

Example 6 Lanthanum oxide powder (LazO*) 2wL%
An Au/Laz'Jt catalyst was prepared. The preparation method and reaction method were the same as in Example 1.

The results are shown in Table 1. The conversion was 3.3% two minutes after the reaction and 17.9% after 30 minutes. On the other hand, at room temperature and 100°C, 2
After minutes there was already 100% conversion.

Example 7 Catalysts with different gold content were prepared from the TiOzlLj gold-bearing catalyst that had the highest activity. Both the preparation method and the experimental method were the same as in Example 1.

? The content of is 0.5, ■, 2 (Example I), and 5-(?A).

The results are shown in Table 2.

With a gold content of 0.5 L%, there was no conversion at all at -78°C. 3.3 after 2 minutes at room temperature and I00'C, respectively.
%, 3.7%, and 20.7% and 21.30 minutes after 30 minutes, respectively.
Although the conversion was 5%, the activity was low.

When the gold content was 5 hL%, the reaction results were exactly the same as those shown in Example 1, indicating high activity.

Example 8 The sustainability of the activity of the 2wt% Au/TiO2 catalyst, which showed the highest activity, was investigated. Catalyst 0. A reaction tube filled with 1 g was set in a normal pressure flow reactor. After vacuum degassing at room temperature, hydrogen was passed through the reactor at 300°C for 30 minutes to purify the reactor, and the reactor was cooled to room temperature while purging with a sieve. After reaching room temperature, a standard gas in which lvol% CO was balanced with air was flowed at 33.5 me/min for reaction. The conversion rate was determined by dividing 1 kg of CO in the outlet gas by gas chromatography.

The treatment activity is 100%, and 30 hours have passed since the start of the reaction? However, the activity remained more than 94%.

Example 9 The sustainability of activity of the 2wL% Au/ZrO catalyst was examined in the same manner as in Example 8.

The initial activity was 100%, and the activity remained at 95% or more even after 3 hours from the start of the reaction.

Example 1 () 1! ! The body was made of silica (SiO2) and 2 wt % of gold was supported in the same manner as in Example 1 of the actual can. These two packs (%Au/
The activity and sustainability of the Sift catalyst were examined in the same manner as in the example day. The initial [υ1 activity and the CO oxidation activity were maintained at 99% or more even after 2 hours after the reaction.

Example 1l JU body was used as alumina (Ah(h)) and 5 wL% of gold was supported in the same manner as in Example 1. To this 2-L%, 117
The activity and sustainability of the AI20:l catalyst were examined in the same manner as in Example 8. Initial activity and post-reaction 2
Over 99% of the CO oxidation activity was maintained over time.

Comparative example 1 1! ! Iron oxide (Fezes), zinc oxide (ZnO)
), 2 wt % gold was supported in the same manner as in Example 1.

The reaction method was also the same as in Example 1.

The results are shown in Table 1.

In all cases, high activity like the catalysts shown in Examples 1 to 6 was not obtained.

Comparative Example 2 Regarding 2 wt% Au/Tiet, after suspending TiOz as a support in water, a predetermined amount of chloroauric acid aqueous solution was added, and after stirring thoroughly for 1 hour, an ammonium hydrogen carbonate solution of 5 times the amount of gold and 4 times the amount of gold was added. was added dropwise to deposit gold hydroxide onto the carrier. The subsequent operations were the same as in Example 1.

A reaction was carried out using this catalyst in the same manner as in Example 1.

Even 30 minutes after the start of the reaction, the CO conversion rate was -78, and the room temperature was 10.
0″C are 10%, 34%, and 8%, respectively,
The catalyst shown in Example 1, which was prepared by adding a precipitant immediately after converting the aqueous chloroauric acid solution, did not have the same high activity as the catalyst. The average gold particle size determined from a transmission electron micrograph of this catalyst was 60 particles, and some particles with larger particle sizes were also observed. From this result, it was found that gold exhibits high activity when it is atomized to 50 particles or less and uniformly divided into 1 u particles.

Comparative Example 3 Regarding 2wt% 8u/TiOt, a catalyst was prepared by adding a predetermined amount of chloroauric acid aqueous solution to lj-form Ti02 and drying it in one shot using a normal impregnation method. The 01 treatment method and reaction method for the catalyst were the same as in Example 1.

At a reaction temperature of -78°C and a room temperature of 100°C, no total co was converted. When the gold particle size of this catalyst was measured by ζ-X-ray diffraction, it was found to be 160 particles on average.

Comparative Example 4 Co-precipitation method 2 which is said to have high activity in oxidizing CO
wt%Au/FezO. A catalyst was prepared. First, a mixed aqueous solution of chloroauric acid and nitric acid of a predetermined thickness was prepared, and 5 times as much ammonium hydrogen carbonate was added thereto for coprecipitation. Filtration, drying {
% (110°C), reduced in the same manner as in Example 1,
It was used for reaction. The reaction method was also the same as in Example 1. Even 30 minutes after the start of the reaction at a reaction temperature of -78°C, the CO conversion rate was IO%, and the reported high activity could not be reproduced. Table 1 Activity table of various oxide catalysts containing 2 wt% gold prepared by deposition method 2? Inclusion dependence of u/TiO■? Effects of the Invention The catalyst of the present invention has high catalytic activity despite its low gold content (1), and exhibits catalytic activity even at a low temperature of -78°C. It also has good stability, can withstand long-term reactions, and has high durability against moisture.

It is inexpensive because the amount of expensive gold used can be reduced. The catalyst of the present invention is an oxidation catalyst and is not limited to oxidizing CO! It can be used for various oxidation reactions such as the oxidation of 1.

Claims (1)

[Claims] A gold-containing catalyst for catalytic combustion in which 1 to 5% by weight of gold fine particles are supported on the surface of particles of titanium oxide, magnesium oxide, zirconium oxide, silicon oxide, aluminum oxide, tin oxide, cobalt oxide, or lanthanum oxide.