DE2416753C3 - Support catalyst for exhaust gas purification, process for its manufacture and use - Google Patents

Description

The invention relates to improved supported catalysts based on systems as proposed in DE-PS 23 06 395. These systems contain ruthenium. Rhodium, palladium, platinum and aluminum. Titanium, chromium, manganese. Cobalt, nickel with at least J metals and are impregnated a carrier with an aqueous. Halides, especially chlorides, containing solution of the platinum group metals and base metals in an atomic ratio of I: 4 to 1: t. Drying and then Treat at temperatures above 450 ° C in a hydrogen stream obtain. They are suitable for cleaning collapsible and / or reducible pollutants Exhaust gases from internal combustion engines and industrial plants and are characterized by low Start-up and conversion temperatures, high conversion performance as well as favorable aging behavior

The invention also extends to a method of manufacturing the improved catalysts as well as their use.

It has now been found that the properties proposed in the cited patent

ίο Catalysts with regard to improved thermal shock fatigue strength and a considerably improved aging behavior without deterioration of the advantageous low start and conversion temperatures can be supplemented advantageously.

π The invention relates to a ruthenium, rhodium, palladium, platinum and aluminum, titanium, Chromium, manganese, cobalt, nickel-containing supported catalyst with at least 3 metals, obtained by Impregnation of a support with an aqueous solution containing halides, in particular chlorides the platinum group metals and the base metals in an atomic ratio of 1: 4 to 1: 1, drying and subsequent treatment at temperatures above 450 ° C in a hydrogen stream. The catalyst is

r> characterized in that the solution is halides of platinum and rhodium and at least one of the elements aluminum, chromium, manganese, cobalt, in one Contains atomic ratio between platinum group metal and base metal within 1: 4.0 to 1: 2.40.

jo With the element combinations to be used according to the invention there is thus compared to the teaching of DE-PS 23 06 395 that the minimum proportion of one or several of the elements aluminum, cobalt, chromium and manganese in the active phase of the catalyst

j) according to the ratio of the atoms of the two platinum group metals platinum and rhodium opposite the atoms of the base metal component must be increased to 1: 2.4 in order to achieve the additional advantages the increased thermal shock endurance strength wedge

4 (i and the improved aging behavior.

The catalyst according to the invention can correspondingly with regard to the materials of the carrier and support the catalyst of DE-PS 23 06 395 be designed (under a support is in the context of the registration

■ π a structural amplifier, ie a largely inert one Understood carriers with high temperature and abrasion resistance - see Ullmann's encyclopedia of technical chemistry, 1957, vol. 9, page 263).

The process for the production of the

-, o ßen supported catalyst is that one Carrier with an aqueous, halides, especially chlorides of platinum and rhodium and at least one of the elements aluminum, chromium, manganese, cobalt in an atomic ratio between platinum group metals

>-> and Uncdclmctall within 1: 4.0 to 1: 2.40 impregnated, dried and then at 450 ⁰ C in about Temperaluren Wasscrstoffslrom treated, preferably being, the dried Metallhalogenidimprägniemng in a hydrogen stream at temperatures of 450 to

wi 1000 ⁰ C, especially 700-850 ° C, treat.

It has also proven to be expedient to provide one with a film made of metal oxide which promotes catalysis shock-resistant, weakly porous, predominantly crystal-IiinTi ceramic support before impregnation with

hi the Metallhakigenidlösung with the solvent of the Impregnation solution before /.

When using an impregnation solution containing water it is advantageous to load with 5 to 95.

preferably 40 to 80, in particular 50 to 70 wt .-% water, based on the difference between the weight of the support plus the carrier film in a saturated, moist and resulting dry state Total water uptake, before.

The preloading yeast has the great advantage that the penetration depth of the impregnation solution is at an optimum Degree can be reduced, whereby an enrichment of the for the formation of the catalytically active System critical substances in the outer area of the Kataiysatorkörpers is enabled. This enrichment has a particularly favorable effect on the aceration behavior.

A combination of a support and a carrier film arranged on it, which is particularly suitable for practical purposes, consists of γ-aluminum oxide as carrier and cordierite or mullite with a specific surface area of at least 0.3 m ² / g, a macropore volume determined by mercury porosimetry of over 20% and with macropores over 10,000 Å in diameter, in the form of a monolithic skeleton structure with numerous, unobstructed gas channels as support.

In addition to the y-aluminum oxide carrier and the cordierite support, all of the catalysis-promoting metal oxides and support materials ^{already listed in DE-PS 2 r i 23 06 395 can be used.}

The invention also relates to the use of the improved catalysts for purification oxidizable and / or reducible pollutants containing exhaust gases from internal combustion engines and Industrial plants.

The present invention creates a number of technically very advantageous new ways of increasing effectiveness and durability of catalysts whose ii active component generally platinum group metal and base metal containing at least three metals represent comprehensive, intermetallic systems, to increase further.

DE-PS 8 52 989 already describes a catalytic process for the dehydrogenation of naphthenic hydrocarbons and optionally cyclization, cleavage and / or isomerization of paraffinic hydrocarbons by the action of hydrogen under excess pressure above 400 ^° C. on a supported catalyst which contains ruthenium or its compounds and optionally compounds of the 5 to 7th group of the periodic table. In the only exemplary embodiment, only a single Ru-on-AhCh catalyst is listed. However, the patent specification discloses neither a discrete production process nor conditions for the quantitative composition for the intended metal combinations. DE-PS 17 68 181 relates to a catalytic process for the production of aromatic isocyanates from nitroaromatics and CO. Combinations of platinum metals with base metals as well as three-part systems of these components are mentioned here, which can be applied to carriers. However, it is not required NEN supported catalyst according to the invention in contrast to the beschriebe- hereinafter _W), that at least 3 metals must be present in certain ways, in particular a final hydrogen treatment produced intermetallic system as. ηϊ

In addition, the special suitability of the The two last-mentioned known catalytic converters for purposes that are remote from the exhaust gas purification, by no means usefulness in that area can be inferred.

Finally, in DE-PS 22 14 604.9-41, the production of an exhaust gas purification catalyst has already been proposed, which can contain the platinum group metals ruthenium, rhodium, palladium, platinum and the base metals titanium, chromium, manganese, cobalt, nickel as active elements, and also contain at least 3 metals are present. However, this is not a supported catalyst, but a mixed or interspersant catalyst, which is a system of oxides of the base metals statistically distributed in the binder γ- and 77-Al2O3, which is still coated on the surface with platinum group metal. While the production of the coating can also be used to reduce the platinum group metal salt to the metal using hydrogen, this treatment only affects the components of the coating, but not the mixed catalyst carrying them, which leads to the formation of intermetallic phases between noble and base metals, which in the The scope of the invention described below are essential, excludes.

The invention is explained further with the aid of the following exemplary embodiments.

example 1

(Application of a calcium ion containing

Active alumina as a catalyst that promotes catalysis

Metal oxide intermediate layer on a shock-resistant,

weakly porous, predominantly crystalline

ceramic support)

It became the EX 20 support measuring 4 inches in diameter and 3 inches in length, as follows described, covered with an active intermediate layer. The specifications of this commercially available support body are the following:

Specific surface area of at least 0.3 m ² / g,
Macropore volume of over 20%, determined by mercury porosimetry,
Macropores over 10,000 Å in diameter,
monolithic skeleton with numerous gas channels that run through it without any obstacles.

It became a solution which

3.5 kg AI (NOj) ₁ -9 H ₂ O and
58 g Ca (NOJ ₂ ■ 4 H ₂ O

contains dissolved in 31.5 liters of water (solution I) and 15 liters of a 5% ammonia solution (solution 2). The two solutions were mixed in separate storage vessels in a special precipitation apparatus at room temperature with vigorous stirring, the pH in the precipitation chamber being kept constant at 9.0 ± 0.1. The precipitate flowed continuously via an overflow into a collecting vessel. After about two hours of standing was suction filtered and the slurry in 6 IH ₂ O, the

30 g Methyiccllulose as well
3.5 kg AI (NOi)) - 9 H ₂ O and
58 g Ca (NOi) ₂ -4 H ₂ O

had been added '. intimately stirred. After intense Stirring for about 3 hours was the

Slurry ready to use. The solid sound. based on AbO ₃ , is approx. 22% by weight. To determine the solids content, the slurry was evaporated, dried and then calcined at 1100 ° C. to constant weight.

The monolithic support was immersed in the suspension described above, blown out with compressed air to clean the channels, dried at 120 ° C. and calcined at 500 ° C. for 2 hours. This immersion, cleaning and calcination were carried out three times. The composite body obtained in this way then had a specific surface area of 28 m ² / g, measured according to BET.

activation

The following aqueous impregnation solution was then prepared:

38.02 g H ₂ PtCl ₆ (20% by weight Pt)
10.65 g RhCI ₃ - XH ₂ O (37.7% Rh)
56.74 g of AlCl ₃ - 5 H ₂ O
in 1000 ml of solution.

The carrier body coated with the calcium-containing active alumina was dipped into the impregnation solution, blown out with compressed air, dried at 200 ° C. and ^{reduced for 30 min at 400 ° C. in a stream of H2 (volume velocity 35 h "1} ). This activation process was carried out a total of twice, after the second impregnation, the reduction took place at a temperature of 500 ° C. The noble metal content of the catalyst was 0.3% by weight, the atomic ratio P1 to Rh to Al was 1: 1: 6. The catalyst is designated below Number 1.

Example 2

Commercially available catalyst supports (type EX 20) were coated, as in Example 1, with an active alumina intermediate layer containing calcium ions. The dimensions were 4 inches in diameter and 3 inches in length, and the specific surface area after application of the active intermediate layer was 30 m ² / g.

These supports coated with carrier material were immersed in deionized water for one minute submerged. The water still remaining in the channels was passed through a double slot nozzle (Arrangement 1 cm above and below the monolith 10 cm, offset in the direction of passage) blown out and the weight of the wet monolith is determined.

The weight difference between the wet and dry monolith represents the water absorption. By passing air over it were

a) 10%

b) 40%

c) 60%

d) 90%

the water absorption defined away.

These partially dried monoliths were impregnated according to Example 1 with noble metal osteos. blown out, dried and reduced in hydrogen. The catalysts are designated below 2a. 2b, 2c, 2d.

The noble metal content of the catalysts was 0.3% by weight. The atomic ratio of Pt to Rh to Al was for all catalysts 1: 1: 6.

Example 3

A commercially available support "Alsimag 795" with an outer diameter of 4 inches and a thickness of 3 inches was used with the slurry of aluminum nitrate, methyl cellulose and calcium nitrate described in Example 1 impregnated. The specific surface area of the support / carrier combination was then 20 m - '/ g. the The catalyst support body was activated as described in Example 2. The precious metal content was 0.48 wt%. The pre-allocation with water was set to 60%. The catalyst is in denoted below by 3.

At game eI 4

An oval WI carrier body coated with an active alumina in Example 1 with dimensions 85 × 130 × 150 mm and a specific surface area of 50.8 m ² / g was produced analogously to method 2 (i of Example 2 with a Pt - Rh - Co-AI activation provided using the following impregnation solution:

36.5 g H ₂ PtCIb (25% Pt)

12.6 g RhCl ₃ · X H ₂ O (38.3% Rh)
18.4 g CoCl ₂ -5 H ₂ O

in 2000 ml of solution.

The water supply was set to 55%. The body had one after activating it three times 3d precious metal content of 0.3% by weight. The catalyst will hereinafter referred to as 4.

Example 5

300 g of a monolithic carrier body, type j ") Alsimag 795 HSA (= high suface area), were with 60 ml of an aqueous solution that

6.66 g of H ₂ PtCl6 solution with a Pt content of

15% by weight and

1,319 g RhClj AH ₂ O solution (37.84% Rh),
4.726 g of AICIj-6H ₂ O

and with the catalysts

5.1 1.35 g

5.2 2.02 g

CoCl ₂ · _{6H 2} O
CoCl ₂ -OH ₂ O

contained, impregnated, dried at 120 ° C in a circulating air drying oven for 1 hour and for 30 min at 500 ° C in the hydrogen stream (volume velocity 35h- ') reduced. The catalysts contain 0.5 w% by weight precious metals. The atomic ratios of the active phase are as follows:

Pt

Rh: Co: Al

Catalyst 5.1
Catalyst 5.2

1.05: 1.00
1.05: 1.00

1.17: 4.00 1.77: 4.00

Example 6

The Pt / Rh / Cr / Al and Pt / Rh / Mn / Al catalysts were produced analogously to Example 5. The precious metal or non-precious metal impregnation was carried out from aqueous solutions of the corresponding chlorine compounds, z. B.

H ₂ PtCIb,

RhCl ₃ - A ^- H ₂ O.

AICIj · 6H ₂ O.

MnCl ₂ -4 H ₂ O.

The atomic ratios of these catalysts are as follows:

Catalyst 6.1:

Pt / Rh / Cr / Al 1: 0.94: 1.86: 2.86
Catalyst 6.2:

Pt / Rh / Mn / Al 1: 0.94: 1.77: 2.86

Example 7

The catalytic converters are checking their Thermal shock fatigue strength re-educated a test that proceeds as follows:

On a 1.9-1 in-line engine with electric fuel injection two monolith catalysts are alternately heated and cooled. The heating up takes place with engine exhaust. Compressed air is blown in for cooling. The temperature profile on the catalyst Is as follows:

constant

Driving conditions:

Cooling down:

Duration of the test cycle:

Heating:

150 ° C to 750 ° C - 2 min
max.heating rate = 2.225 ⁰ CmIn- ¹

750 ⁰ C = 14 min 750 ⁰ C to 150 ⁰ C = 14 min max. Cooling rate = 455 ° C min ^ ¹ 30 min

The cycle is run through 200 times, this corresponds to a total test time per monolith of 50 hours.

The catalysts are subjected to a function test to check their activity. Hierzi the conversions for CO, HC and NO, be gradually changed A value in the range A = 0.95 bi < 1.01 and 3000 revolutions per minute measured at an engine load of 27 kW. The spatial speed is 75,000 h '(NTP). For the ready before A is greater than 1, the mean conversion rates are de of CO and HC, for area A less than 1, the mean conversion rate for NO is calculated.

The degrees of conversion of various types of catalyst, which according to the aforementioned Examples 1 to e are shown on the fresh unc aged catalyst as follows:

Example no.

Catalyst pattern
Activity: fresh
(Conversion,%)
CO HC

Activity: aged nc NO ₍ (Conversion,%) 77.6 72.8 CO 79.1 75.3 94.8 82.7 84.2 94.9 82.4 83.8 96.8 79.0 75.3 96.2 82.9 85.0 95.0 85.7 94.5 96.7 83.0 84.9 100.0 82.8 83.4 96.2 75.6 71.2 95.1 92.4

Comparison
example 10
(DE 23 06 395)

97.9
97.2
98.4
98.1
96.8
98.9
100.0
98.2
97.3

96.9

84.4
84.3
87.1
86.9
83.7
88.0
88.5
88.2
87.9

83.4

81.7 82.5 91.2 90.9 82.5 92.0 100.0 91.8 90.2

From the table it can be seen that the catalyst samples produced according to the invention have significantly better activities in the fresh and aged state than a catalytic converter DE-PS 23 06 395. This was produced according to Example 10 of the aforementioned patent application. It's falling furthermore that the Kataiysatormuster produced according to the invention an improved aging behavior

- less drop in CO, HC and NO, conversion

- demonstrate.

Example 8

The catalytic converter described in more detail under Example 2b with the dimensions 85 χ 130 χ 225 mm was connected in a suitable muffler to the exhaust pipe of a series-produced motor vehicle with regulated fuel injection and subjected to a road test in accordance with the regulations of the Federal Register Volume 37, No. 221 (November 15 1972), checked. The results are summarized in the table below: Mileage
(mi)

HC

(g / mi)

CO

(g / mi)

NO, (g / mi)

0 0.16 2.25 0.15 4,000 0.22 2.56 0.30 8,000 0.27 2.72 0.35 12,000 0.25 3.19 0.25 16000 0.35 2.10 0.33 20000 0.31 3.20 0.38 24,000 0.30 3.00 0.40 28,000 0.32 3.12 0.39

From the table it can be seen that with the help of the catalyst according to the invention the originally fü b5 1976 in the USA required limit values (HC = 0.40 CO = 3.50; NO, = 0.41 g / ml) over 25,000 ml. This is so far not from any other system known.

Claims (6)

Patent claims: 1. Ruthenium, rhodium, palladium, platinum and aluminum, titanium, Cl.rom. Manganese, cobalt, nickel-containing supported catalyst with at least 3 metals, obtained by impregnating a support with an aqueous one. Halides, especially chlorides, containing solution of platinum group metals and base metals in an atomic ratio of 1: 4 to 1: 1, drying and subsequent treatment at temperatures above 450 ⁰ C in a hydrogen stream, characterized in that the solution halides of platinum and rhodium and at least one of the Contains elements aluminum, chromium, manganese, cobalt, in an atomic ratio between platinum group metal and base metal within 1: 4.0 to 1: 2.40. 2. A method for producing the supported catalyst according to claim 1, characterized in that one a carrier with an aqueous, halides, especially chlorides, of platinum and rhodium and at least one of the elements aluminum, chromium, manganese, cobalt in an atomic ratio within 1: 4.0 to 1: 2.40 impregnated, dried and then at temperatures above 450 ° C in a stream of hydrogen treated. 3. The method according to claim 2, characterized in that the dried metal halide impregnation in a hydrogen stream at temperatures of 450 to 1000 ⁰ C, in particular 700-850 ⁰ C, treated. 4. The method according to claim 2, characterized in that one with a film one Carrier made of catalysis-promoting metal oxide provided ceramic support before impregnation with the metal halide solution is preloaded with the solvent of the impregnation solution. 5. The method according to claim 4, characterized in that that when using the aqueous Imprägnicrlösung with 5 to 95, preferably 40 to 80, in particular 50 to 70 wt .-% water, based on the difference between the weight of Support plus carrier film in saturated moist and total water absorption resulting in dry state, preloaded. 6. Use of the catalysts according to the preceding claims for cleaning oxidizable and / or redu / .icrbarc pollutant-containing exhaust gases from internal combustion engines and industrial plants.