JP3207577B2 - Hydrocarbon adsorbent and adsorption purification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorbent for purifying hydrocarbons (hereinafter abbreviated as HC) discharged from an internal combustion engine or the like and a method for adsorbing and removing HC.

[0002]

2. Description of the Related Art In recent years, with the development of catalytic converters, exhaust gas from gasoline vehicles has been increasingly purified. However, the temperature at which the catalyst acts is as high as 200 ° C. or more, and at a low temperature such as when starting, there still remains a problem that unburned HC and the like generated from the internal combustion engine are directly discharged into the atmosphere.

[0003]

In view of the above-mentioned situation, attempts to adsorb and remove HC and the like generated at low temperatures by using an adsorbent have been carried out by many research institutions. For example, when activated carbon is used as an adsorbent, a large amount of unburned HC is adsorbed in a low-temperature region, but the activated carbon itself has no oxidizing action in a high-temperature region, so the adsorbed HC is desorbed and released to the atmosphere. There is a problem. Furthermore, since activated carbon is an organic adsorbent, there is a danger that the activated carbon itself will burn and ignite at high temperatures. On the other hand, examples of the inorganic adsorbent include alumina and silica, but there is a problem that a large amount of adsorbent is required due to a small capacity of adsorbing HC. Therefore, application of an adsorbent capable of adsorbing a large amount of HC at a low temperature and burning and removing the HC adsorbed at a high temperature to self-regenerate has been desired.

The present invention has been made in view of the above-mentioned state of the art,
Provided is an adsorbent capable of adsorbing a large amount of C and burning and removing the adsorbed HC at a high temperature to be able to self-regenerate, and a method capable of adsorbing and removing HC generated from an internal combustion engine or the like using the adsorbent. What you want to do.

[0005]

Means for Solving the Problems The inventors of the present invention have studied the development of an adsorbent suitable for this purpose, and found that a crystalline silicate having a molecular sieve structure carrying copper is a preferable adsorbent. They have found something and have completed the present invention.

[0006] The present invention is expressed in terms of mole ratios of oxides in (1) Copper Ri name from the crystalline silicate having a molecular sieve structure formed by carrying a state where the crystalline silicate is dehydrated, (1 ± 0 .6) R ₂
O. [aM ₂ O ₃ .bAl ₂ O ₃ .cMeO] .ySi
O ₂ (wherein R is an alkali metal ion and / or a hydrogen ion, M is at least one metal selected from the group consisting of group VIII metals, rare earth metals, titanium, vanadium, chromium, niobium, antimony, and gallium) , Me is an alkaline earth metal, a ≧ 0, b ≧ 0, c ≧ 0, a + b = 1, y / c>
12, y> 12) of has the formula, and adsorbent charcoal hydrogen you being a crystalline silicate having an X-ray diffraction pattern shown in Table A to Shoki in the body, (2) A crystalline silicate of the above (1), which is a crystalline silicate having a molecular sieve structure previously synthesized, is used as a mother crystal, and a crystalline silicate made of Si and O having the same crystal structure as the mother crystal is grown on the outer surface thereof. and adsorbent charcoal hydrogen you being a layered composite crystalline silicate having an X-ray diffraction pattern shown in Table a to Shoki in the body, a molecular sieve structure formed by carrying (3) copper Crystalline silique
And the crystalline silicate is an L- type zeolite;
Clinoptilolite, A-type zeolite, ferrierite, adsorbent charcoal <br/> hydrogen you being a ZSM-5 type zeolite. (4) The crystalline silicate having a molecular sieve structure carrying any one of the above (1) to (3) is further added with cobalt, nickel, chromium, iron, manganese, silver, gold, platinum,
A hydrocarbon adsorbent, which carries one or more metals selected from the group consisting of palladium, ruthenium, rhodium, and vanadium; (5) hydrocarbons in exhaust gas when starting an internal combustion engine or the like In removing the waste gas, the exhaust gas at low temperature is removed from the above (1) to
(4) Contacting any of the hydrocarbon adsorbents to adsorb and remove the hydrocarbons in the exhaust gas, and then burning the adsorbed hydrocarbons under the high temperature condition of the adsorbent and regenerating the adsorbent. (6) cutting out the inside of the hydrocarbon adsorbent, installing a switching valve at the cut-out point, and adsorbing the hydrocarbons in the exhaust gas at low temperature to the adsorbent. Close the switching valve and contact the exhaust gas with the adsorbent to allow the adsorbent to adsorb hydrocarbons,
(5) The method for adsorbing and removing hydrocarbons according to the above (5) , wherein when the adsorbed hydrocarbons are burned and removed, the switching valve is opened and the high-temperature exhaust gas is purged through the cut-out portion to bring the adsorbent to high-temperature conditions.

[0007]

The crystalline silicate having a molecular sieve structure according to the present invention has an X-ray diffraction pattern as shown in Table A below, and is expressed as a molar ratio of oxide in a dehydrated state (1 ± 1).
0.6) R ₂ O · _{[aM 2 O 3 · bAl 2 O} 3 · cMe
O] · ySiO ₂ (where R is an alkali metal ion and / or hydrogen ion, M is a group VIII element, a rare earth element,
At least one metal selected from the group consisting of titanium, vanadium, chromium, niobium, antimony, and gallium; Me is an alkaline earth metal of magnesium, calcium, strontium, barium, a ≧ 0, b ≧ 0, c
≧ 0, a + b = 1, y / c> 12, y> 12).

[0008]

[Table 1] W: weak M: intermediate S: strong VS: very strong (irradiation and copper Kα ray) (I ₀ is the strongest peak intensity and I / I ₀ is the relative intensity)

Further, the crystalline silicate is obtained by using the previously synthesized crystalline silicate as a mother crystal, and growing a crystalline silicate made of Si and O having the same crystal structure as the mother crystal on the outer surface of the mother crystal. It is a layered composite crystalline silicate, and may be a crystalline silicate having improved heat resistance and steam resistance, and the crystalline silicate may be an L- type zeolite,
Clinoptilolite, A-type zeolite, ferrierite and ZSM-5-type zeolite are also sufficiently effective as adsorbents.

Further, the metal supported on the crystalline silicate is copper alone or a metal selected from the group consisting of copper and cobalt, nickel, chromium, iron, manganese, silver, gold, platinum, palladium, ruthenium, rhodium and vanadium.
HC adsorbing power and oxidizing power can be controlled by using an adsorbent in which at least one kind of metal is supported and coexisted.

As a method for incorporating copper into a crystalline silicate having a molecular sieve structure, the crystalline silicate is supported by an ion exchange method or an impregnation method using an aqueous solution of a metal copper salt of copper nitrate, copper acetate, copper chloride or copper sulfate. The method is preferred.

Incidentally, copper and cobalt, nickel, chromium,
Iron, manganese, silver, gold, platinum, palladium, ruthenium, rhodium, vanadium supported on the crystalline silicate, nitrate, acetate, chloride of each metal,
Examples of the method include a coion exchange method or a co-impregnation method using an aqueous solution such as a sulfate.

The HC adsorbent of the present invention is downstream of a three-way catalyst for a gasoline engine (usually a catalyst containing a Pt, Rh-based noble metal and capable of simultaneously removing NOx, CO, and HC near the stoichiometric air-fuel ratio). When installed, the temperature of the exhaust gas at the time of startup is usually from room temperature to about 100 ° C., and a large amount of HC can be adsorbed in this temperature range. The temperature at which the three-way catalyst acts is about 200 ° C. or more, and when the exhaust gas temperature is 250 ° C. or more, HC can be removed by the three-way catalyst. Therefore, the HC catalyst of the present invention is installed downstream of the three-way catalyst, and adsorbs HC at a temperature of 200 ° C. or lower where the three-way catalyst does not act, thereby making the HC outside the system.
Prevent emissions. Warm air advances and the temperature of the adsorbent is about 150 ° C
Above this, the adsorbed HC is burned and H ₂ O, CO ₂
Then, the HC adsorbent is desorbed and regenerated, and unburned HC is adsorbed again in a low temperature range.

Further, the HC adsorbent of the present invention is used to
When considering a system that adsorbs and removes gas, it is necessary to take into account the pressure loss due to the magnitude of the gas amount. Normally, when starting at low temperature, the amount of gas is small, so that the entire amount of exhaust gas containing HC may be circulated to the HC adsorbent. However, at high temperatures, the amount of gas increases, so that the entire amount of gas is flowed through the adsorbent and adsorbed. H
Regeneration of the HC adsorbent by burning and removing C may affect pressure loss and adsorbent life. In this case, HC
Cut out the inside of the adsorbent, install a valve at this cutout location, close the valve when adsorbing HC at low temperature, flow HC-containing gas to the HC adsorbent to adsorb HC, while at high temperature because when the amount of gas is large to reduce the pressure loss, taking a method of directly purging exhaust gas opened valve, in this case, adsorbed HC but is burned off by the oxidation action of the HC adsorbent, the resulting CO _2, It is preferable to adopt a method in which H ₂ O is purged by self-diffusion and discharged out of the system to regenerate the HC adsorbent.

[0015]

【Example】

(Example 1) Water glass No. 1 (SiO ₂ : 30%): 56
16 g was dissolved in 5429 g of water, and this solution was designated as solution A. On the other hand, water: 4175 g and aluminum sulfate: 71
8.9 g, ferric chloride: 110 g, calcium acetate: 4
7.2 g, sodium chloride: 262 g, concentrated hydrochloric acid: 202
0 g is dissolved, and this solution is referred to as solution B. The solution A and the solution B are supplied at a constant rate to form a precipitate, and the mixture is sufficiently stirred to obtain a slurry having a pH of 8.0. This slurry was charged into a 20-liter autoclave, and 500 g of tetrapropylammonium bromide was further added. Hydrothermal synthesis was performed at 160 ° C. for 72 hours. After the synthesis, the resultant was washed with water and dried. Obtain silicate 1. This crystalline silicate is represented by the following composition formula in terms of the molar ratio of the oxide (omitting the crystallization water), and the crystal structure is represented by X-ray diffraction in Table A above. 0.5Na ₂ O.0.5H ₂ O. [0.8Al ₂ O _3.
0.2Fe ₂ O ₃ .0.25CaO] .25SiO ₂

Using the above crystalline silicate 1, 0.0
It was immersed in a 4M copper acetate aqueous solution and stirred for 24 hours to perform Cu ion exchange. After washing and drying, powder adsorbent 1 was obtained.

Next, 3 parts of alumina sol as a binder and 200 parts of water were added to 55 parts of silica sol (SiO ₂ : 20%) with respect to 100 parts of the powder adsorbent 1 and sufficiently stirred to obtain a slurry for wash coating. . Next, a cordierite monolith substrate (400-cell grid) is immersed in the slurry, taken out, and then sprayed with excess slurry.
Dried at 00 ° C. The coated amount is 200 g per liter of the base material.

Example 2 In the synthesis of the crystalline silicate of Example 1, cobalt chloride was used instead of ferric chloride.
Crystallinity except that ruthenium chloride, rhodium chloride, lanthanum chloride, cerium chloride, titanium chloride, vanadium chloride, chromium chloride, antimony chloride, gallium chloride and niobium chloride are each added in the same mole number as Fe ₂ O _{3 in} terms of oxide. The same operation as in silicate 1 was repeated to prepare crystalline silicates 2 to 12. The crystal structures of these crystalline silicates are shown in Table A above by X-ray diffraction, and their compositions are represented by the molar ratio of oxides (dehydrated form) of 0.5Na ₂ O · 0.5H ₂ O ・ [0.2M ₂ O
₃ · 0.8Al ₂ O ₃ · 0.25CaO] · 25SiO
₂ Where M is Co, Ru, Rh, La, Ce,
It is a crystalline silicate of Ti, V, Cr, Sb, Ga, Nb.

The same operation as that of the crystalline silicate 1 was carried out except that magnesium acetate, strontium acetate and barium acetate were added in the same manner as in the case of CaO in terms of oxide in place of calcium acetate in the method for synthesizing the crystalline silicate 1. Was repeated to prepare crystalline silicates 13 to 15. The crystal structures of these mother crystals are shown in Table A by X-ray diffraction, and the composition is represented by a molar ratio of oxide (dehydrated form) of 0.5Na ₂ O.O.
5H ₂ O · _{[0.2Fe 2 O 3 · 0.8Al 2 O} 3 ·
0.25MeO] is a · 25SiO _2. Here, Me is Mg, Sr, and Ba.

The above crystalline silicates 2 to 15 were used in Example 1.
Cu ion exchange was performed in the same manner as in Example 1 to obtain powder adsorbents 2 to 15, and the powder adsorbent was formed into a honeycomb in the same manner as in Example 1 to obtain honeycomb adsorbents 2 to 15.

(Example 3) 1000 g of the crystalline silicate 1 obtained in Example 1 was used as a mother crystal, and this was mixed with water: 2160
g of colloidal silica (SiO ₂ : 20)
%): 4590 g was added, and the mixture was sufficiently stirred, and this solution was designated as solution a. On the other hand, 105.8 g of sodium hydroxide is dissolved in 2008 g of water to obtain a solution b. While stirring the solution a, the solution b is gradually added dropwise to form a precipitate to obtain a slurry. The slurry was placed in an autoclave, and 568 g of tetrapropylammonium bromide was added to water:
The solution dissolved in 2106 g is added to the autoclave. Hydrothermal synthesis is performed in this autoclave at 160 ° C. for 72 hours (stirring at 200 rpm), and after stirring, washing and drying, baking is performed at 500 ° C. for 3 hours to obtain a layered composite crystalline silicate 1. This surface layered silicate is called silicalite.

The layered composite crystalline silicate 1 was subjected to Cu ion exchange and honeycomb formation in the same manner as in Example 1 to obtain a powder adsorbent 16 and a honeycomb adsorbent 16.

Example 4 Na-type Y-type zeolite (SiO ₂ / Al ₂ O ₃ ratio:
5), mordenite (SiO ₂ / Al ₂ O ₃ ratio: 1)
5), L-type zeolite (SiO ₂ / Al ₂ O ₃ ratio:
6), clinoptilolite (ratio of SiO ₂ / Al ₂ O ₃ :
5), A-type zeolite (SiO ₂ / Al ₂ O ₃ ratio:
1), ferrierite (SiO ₂ / Al ₂ O ₃ ratio:
5), ZSM-5 type zeolite (SiO ₂ / Al ₂ O ₃₎
The zeolite having a ratio of 30) was subjected to Cu ion exchange and honeycomb formation in the same manner as the crystalline silicate 1 of Example 1 to obtain powder adsorbents 17 to 23 and honeycomb adsorbents 17 to 23. What
The honeycomb adsorbents 17 and 18 are reference examples.

(Example 5) The crystalline silicate 1 obtained in Example 1 was treated with an aqueous solution of (0.04 M cupric chloride + 0.04 M cobalt chloride) and an aqueous solution of (0.04 M cupric chloride + 0.04 M nickel chloride). , (0.04M cupric chloride + 0.0
4M ferric chloride aqueous solution, (0.04M cupric chloride +
0.04 M manganese chloride) aqueous solution and (0.04 M cupric chloride + 0.01 M vanadium trichloride) aqueous solution and stirred, and co-ion exchange was carried out in the same manner as in Example 1 to obtain powder adsorbents 24-28. And honeycomb adsorbents 24-2
8 was obtained.

The powder adsorbent 1 obtained in Example 1 was impregnated with aqueous solutions of silver nitrate, chloroauric acid, chloroplatinic acid, palladium chloride, ruthenium chloride and rhodium chloride, and Ag, Au per powder adsorbent was used. , Pt, Pd, Ru, and Rh are supported by about 1%, and evaporated to dryness to obtain a powder adsorbent 29-3.
4 was obtained. Further, these powder adsorbents were wash-coated to obtain honeycomb adsorbents 29 to 34.

Example 6 The layered composite crystalline silicate 1 obtained in Example 3 was prepared in the same manner as in Example 5 (0.04M
Aqueous solution of cupric chloride + 0.04 M cobalt chloride), (0.
04M cupric chloride + 0.04M nickel chloride) aqueous solution,
(0.04M cupric chloride + 0.04M ferric chloride) aqueous solution, (0.04M cupric chloride + 0.04M manganese chloride) aqueous solution, (0.04M cupric chloride + 0.01M vanadium trichloride) aqueous solution The powder adsorbent 35-39 and the honeycomb adsorbent 35
~ 39 was obtained.

The powder adsorbent 17 (Cu
/ Y type zeolite) is impregnated with aqueous solutions of silver nitrate, chloroauric acid, chloroplatinic acid, palladium chloride, ruthenium chloride, and rhodium chloride, and Ag, Au,
After loading 0.6 wt% of Pt, Pd, Ru, and Rh, and evaporating to dryness, powder adsorbents 40 to 45 were obtained, and further, honeycombs 40 to 45 were obtained.

(Comparative Example 1) Powdered activated carbon and copper-carrying γ-Al ₂ O ₃ (CuO: 10 wt%) were coated on a honeycomb substrate by a wash coat method, and a comparative honeycomb was prepared in the same manner as in Example 1. Adsorbents 46 and 47 were obtained.

Honeycomb adsorbents 1 to 47 described in Examples 1 to 6 and Comparative Example 1 (Honeycomb adsorbents 17 and 18 are reference
Examples) are summarized in Table B below.

(Experimental Example 1) One liter of honeycomb adsorbents 1 to 47 were set in an adsorption tower, and a hydrocarbon adsorption test was carried out. The test conditions are as follows. ○ Gas composition C ₂ H ₄ : 2000 ppm C ₃ H ₆ : 2000 ppm (THC = 10,000 ppm) O ₂ : 5% CO ₂ : 10% H ₂ O: 10% NO: 50 ppm N ₂ : balance ○ GHSV: 30, 000h ^-1 ○ Adsorption temperature: 50 ℃ ○ Desorption temperature: 150 ℃

FIG. 1 shows the test apparatus, and FIG. 2 shows the temperature patterns of the exhaust gas and the adsorbent. The adsorbed HC is detected by the FID meter. When the desorption temperature is set to 150 ° C., HC
Other gases, except for, were supplied as they were. The amount of HC adsorbed and desorbed when equilibrium is reached while alternately repeating the adsorption temperature and desorption temperature with the above gas composition is shown in Table C below.

From these results, it can be seen that the present metal honeycomb adsorbent 1
By using ~ 45, a considerable amount of H
It was found that C was adsorbed and the adsorbed HC was burned and removed at 150 ° C., so that HC was not exhausted.

On the other hand, activated carbon (honeycomb adsorbent 46) is adsorbed to some extent at 50 ° C., but at 150 ° C., the adsorbed HC is desorbed as it is and Cu-loaded γ-Al ₂
It was found that O ₃ (honeycomb adsorbent 47) hardly adsorbs hydrocarbons even at 50 ° C.

(Experimental Example 2) As a test similar to Experimental Example 1, a metal honeycomb catalyst 1 was installed as shown in FIG. 3, an intermediate portion was cut out, and a switching valve was provided behind the cutout portion. The gas composition was the same as in Experimental Example 1, but the adsorption temperature was 5
0 ° C. is GHSV: 30,000 h ⁻¹ , desorption temperature is 150 ° C.
Was carried out at GHSV: 100,000 h ^-1 .

In the test apparatus method shown in FIG.
V: 100,000h ^-1 desorption conditions cause a disadvantage that the pressure loss becomes large. However, by passing the intermediate portion as it is as shown in FIG. 3, no pressure loss is applied under the desorption conditions. Metal honeycomb adsorbent 1 under desorption conditions
Almost no gas flows into the tank, but the adsorbed HC
It has been found that since H ₂ O and CO ₂ produced by sufficiently burning and removing at 0 ° C. are purged by self-diffusion, regeneration can be stabilized.

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

[0041]

[Table 7]

[0042]

According to the present invention, there is provided an adsorbent for HC in which HC is adsorbed and removed in a low temperature range, and the adsorbed HC is quickly burned and removed in a high temperature range. HC can be effectively removed, and the effect is industrially remarkable.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an adsorption test apparatus using a honeycomb adsorbent of one experimental example of the present invention.

FIG. 2 is a chart showing a correlation between a temperature change of exhaust gas and a temperature change of a honeycomb adsorbent in one experimental example of the present invention.

FIG. 3 is an explanatory view of a usage mode of the honeycomb adsorbent of the present invention.

Continuation of the front page (56) References JP-A-6-63394 (JP, A) JP-A-5-345129 (JP, A) JP-A-5-317701 (JP, A) JP-A-5-293369 (JP) JP-A-5-285378 (JP, A) JP-A-64-34440 (JP, A) JP-B-46-10064 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B01J 20/00-20/34

Claims (6)

(57) [Claims] 1. A crystalline silicate having a molecular sieve structure supporting copper , wherein said crystalline silicate is dehydrated.
It was expressed in terms of mole ratios of oxides in the _{state, (1 ± 0.6) R 2} O · _{[aM 2 O 3 · bAl 2 O} 3 ·
cMeO] · ySiO ₂ (where R is an alkali metal
Ion and / or hydrogen ion, M is group VIII metal, rare earth
Metal, titanium, vanadium, chromium, niobium, antimo
One or more metals selected from the group consisting of
Me is an alkaline earth metal, a ≧ 0, b ≧ 0, c ≧ 0, a
+ B = 1, y / c> 12, y> 12) , and X shown in Table A described in detail in the text.
A hydrocarbon adsorbent, which is a crystalline silicate having a line diffraction pattern . 2. A crystalline silicate having a molecular sieve structure is preliminarily obtained.
2. The crystalline silicate according to claim 1 synthesized in a mother crystal.
Having an outer surface having the same crystal structure as that of the mother crystal.
growing a crystalline silicate consisting of i and O, and
Has the X-ray diffraction pattern shown in Table A detailed in the text
An adsorbent for hydrogen carbonate, which is a layered composite crystalline silicate . 3. A crystal having a molecular sieve structure carrying copper.
The crystalline silicate is an L-type zeolite.
Light, clinoptilolite, zeolite A, ferri
Characterized by being Elite, ZSM-5 type zeolite
Hydrocarbon adsorbent. 4. The method according to claim 1 wherein copper is supported.
Crystalline silicate with a molecular sieve structure
G, nickel, chromium, iron, manganese, silver, gold, platinum,
From palladium, ruthenium, rhodium and vanadium
That one or more metals selected from the group
Characterized hydrocarbon adsorbent. 5. In an exhaust gas at the time of starting an internal combustion engine or the like.
Low-temperature exhaust gas to remove hydrocarbons
Claims 1 to 4
Adsorb and remove hydrocarbons in the gas, then raise the adsorbent
Combustion and removal of adsorbed hydrocarbons under temperature conditions
Of adsorbing and removing hydrocarbons by regenerating sorbents
Law. 6. A method for cutting out the inside of a hydrocarbon adsorbent,
A switching valve is installed at the punching point,
When the hydrocarbon is adsorbed by the adsorbent, close the switching valve.
Contact the exhaust gas with the adsorbent to absorb hydrocarbons
Switching valve to burn and remove adsorbed hydrocarbons
Open and purge hot exhaust gas through the cutout
6. The method according to claim 5, wherein the adsorbent is heated to a high temperature.
Absorption and removal method for hydrocarbons mentioned.