CA1090097A

CA1090097A - Catalyst for converting nitrogen oxides and method for converting nitrogen oxides in exhaust gases by using said catalyst

Info

Publication number: CA1090097A
Application number: CA258,141A
Authority: CA
Inventors: Kazuya Soga; Kei Utsunomiya; Yutaka Mito; Katsunori Shimasaki; Mamoru Aoki; Shigeru Haseba; Hiroetu Miki; Michiko Masaki
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1975-09-05
Filing date: 1976-07-30
Publication date: 1980-11-25
Also published as: GB1557044A; JPS5231971A; JPS6052856B2; DE2634279C2; DE2634279A1; FR2322651A1; IT1064688B; FR2322651B1

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates to a catalyst to be used for catalytically reducing nitrogen oxides contained in a com-bustion exhaust gas discharged from a calcination furnace, a coking furnace or a boiler or an exhaust gas from a nitric acid-preparing plant in the presence of a reducing gas such as ammonia to convert the nitrogen oxides to harmless substances, and to a method for converting these nitrogen oxides by using this catalyst. According to the present invention, in the presence of a catalyst consisting essentially of oxides or organic or inorganic compounds of V and Nb or V, Nb and at least one element selected from the group consisting of Cu, Ti, Fe, Cr, W, Mo and Ni, which are supported on a carrier, a reducing gas such as ammonia is incorporated in an exhaust gas, and nitrogen oxides in the exhaust gas are catalytically reduced and converted to harmless substances. The catalyst of the present invention is not deactivated by other components contained in the exhaust gas, such as sulfurous acid gas, water and the like, and a very high conversion of nitrogen oxides can be attained not only in the high temperature range but also in the low temperature range.

Description

-`` 1~19C~9~7 ___________________________ (1) Field o~_the Invention The present invention relates to a catalyst ~or con-verting nitrogen oxides contained in exhaust gases to harmless substances by catalytic reduction in the presence of a reducing gas such as ammonia, and to a method for converting these nitrogen oxides to harmless substances by catalytic reduction using this catalyst.

(2) Description of the Prior Art ~ ith recent rapid progress of heavy chemical industries, air pollution by nitrogen oxides is accelerated, and solution of this problem is eagerly desired especially in large cities and in vicinities of industrial areas.
Under such circumstances, various methods for removing nitrogen oxides or reducing the contents of nitrogen oxides have heretofore been proposed in the art. Among these proposals, the so-called dry-type selective catalytic reduction method comprising selectively reducing nitrogen oxides to harmless nitrogen in the presence of a reducing gas such as ammonia is advantageous in various points. For example, a high conversion o~ nitrogen oxides can be obtained and the cost is much lower than in the we~-type method. Further, this method is advantageous over the wet-type method in the point that post treatments of waste water and the like need not be conducted. Moreover, the process maintenance can be conducted very easily. By virtue of these advantages, this method is going to be practically worked in -the art. This method, however, is still defective in that the reaction tempera-ture must be as high as about 400C and when this method is applied to the treatment of a low-temperature exhaust gas discharged from 09(~09~7 1 a coking furnace, a calcination furnace or the like, it is necessary to heat the exhaust gas or there is brought about such a disadvantage that an excessive portion of the reducing gas such as ammonia is discharged in the non-decomposed state.
Therefore, also this method involves problems to be solved.

SUMMARY OF THE INVENTION
________________________ The present invention has been completed as a result of our research works made with a view to overcoming the foregoing 1~ disadvantages and problems involved in the conventional methods.
It is therefore a primary object of the present inven- ;~
tion to provide a method for catalytically reducing nitrogen oxides contained in an exhaust gas in the presence of a reducing gas and converting them to harmless substances and a catalyst for use in practising this method.
A secondary object of the present invention is to provide a catalyst for conversion of nitrogen oxides which is not degraded by other components contained in an exha~st gas such as sulfurous acid gas and water and has an excellent durability.
A th~d object of t~e present invention is to provide a catalyst for conversion of nitrogen oxides which can be applied to exhaust gases in a broad temperature range.
A fourth object of the present invention i8 to provide a catalyst for conversion of nitrogen oxides which can be applied to exhaust gases containing large quantities of dusts.
In accordance with the first aspect of the present inven-tion attaining the foregoing objects, there is provided a method . .
comprising contacting an exhaust gas containing nitrogen oxides with a catalyst consisting essentially of the oxides of V and Nb or the oxides of V, Nb and at least one element selected from the ~' .

. - , , .
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1 group oonsisting of Cu, Ti, Fe, Cr, W, Mo and Ni in the presence of a reducing gas such as ammonia at a temperature of 200 to 500 C and a space velocity of 2000 to 100,000 hr In accordance with the second aspect of the present invention, there is provided a method as set forth in the first aspect, characterized in that the catalyst consists essentially of V, Nb and Ti wherein the atomic ratio of Nb to v is from 0.01 to 0.14 and the atomic ratio of Ti to V is from 0.4 to 0.8.
In accordance with the third aspect of the present lnvention, there is provided a method as set forth in the first aspect wherein the ratio of the atom number of Nb to he atom number of V, and the ratio of the total atom number of Nb and other element to the atom number of V are respectively in the range of from 0.1 to 5 and the ratio of the atom number of the ~-element other than V and Nb to the atom number of Nb is in the range of from 0.25 to 99.
In accordance with the fourth aspect of the present invention, there is provided a method as set ~orth in the first aspect wherein said catalyst components are supported on a carrier in the form of a bead, column, Raschig ring or plate or a multi-chambered carrier in an amount of 0.1 to 20% by weight, preferably l to 10~ by weight, based on the carrier.

BRIEF DESCRIPTION OF THE DRAWINGS
_________________________________ Fig. l is a diagram illustrating the shape of a pellet type catalyst of the present invention;
Fig. 2 is a diagram illustrating the shape of a multi-chambered catalyst of the present invention;
Fig. 3 illustrates data of the conversion o~ NOX obtained

3 when the catalytic xeduction was conducted at 220, 250, 300 and ~.~19V~)9'7 1 400C in the presence of a catalyst of the 30V-XNb-25Ti series according to the present invention while changing the Nb content;
Fig. 4 illustrates the relation between the NOX con-version and the temperature observed when the catalytic conversion was conducted in the presence of the catalyst of the present in-vention and the con~entional catalyst;
Fig. 5 illustrates the relation between the reaction temperature and the NOX conversion observed when the catalytic reduction was conducted in the presence of a multichambered catalyst and a pellet type catal~-st of the presen-t invention;
Fig. 6 illustrates data of the NOX conversion obtained when the catalytic reduction was conducted in the presence of a multichambered catalyst of the present invention at various space velocities and reaction temperatures; and ~ -Fig. 7 illustrates the relation between the NOX conver-sion and the reaction time observed when the catalytic reduction was conducted in the presence of a pellet type catalyst o~ the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
_ - _ ________~_______________ -As the catalyst active component for use in the method comprising contacting an exhaust gas containing nitrogen oxides wlth a catalyst in the presence of a reducing gas such as ammonia to catalytically reduce the nitrogen oxides and convert them to harmless substances, there can be mentioned various elements belonging to the groups V, VI and VIII of the Periodic Table. We made research works with a view to finding out effective catalyst components capable of exerting a high activity in a broad temper-ature range and maintaining the decomposing activity of a reduc-30 ing agent such as ammonia at a high level in a broad temperature `

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1 range, and as a result, we found that a catalyst consisting essentially of the oxides of V and Nb or the oxides of V, Nb and at least one element selected from the group consisting of Cu, Cr, W, ~o, Ti, Fe and Ni meets the above re~uirements suffiCiently. We have now completed the denitration technique utilizing the catalytic reduction using this catalyst based on this finding.
The present invention will now be described in detail by reference to the above catalyst and the method for conversion of nitrogen oxides using the above catalyst.
Starting substances of the respective catalyst components are first described. As the vanadium source, there can be used vanadium compounds such as ammonium metavanadate, vanadyl oxalate, vanadium oxychloride and vanadium oxides. As the niobium and titanium sources, there can be used niobium and titanium compounds such as pentachlorides and tetrachlorides of niobium and titanium, niobic acid, titanic acid, niobates, titanate~, titanium sulfate and oxides of niobium and titanium. As the starting substances of copper, iron, nickel and chromium, there can be effectively used various compounds of these metals such as oxides, nitrates, ~-sulfates, chlorides and organic acid salts. ~s the starting subs~ances of molybdenum and tungsten, there can be used acid salts such as ammonium molybdate and ammonium tungstate, and oxides of molybdenum and tungsten.
Catalysts may be prepared from the foregoing starting substances without using a carrier, but it is preferred that catalysts be prepared by supporting catalyst components on a porous carrier such as active alumina, titania, zirconia, thoria, silica-alumina, magnesia, silica, silicon carbide, clay or a mixture of two or more of them or by mixing catalyst active components with powder of such porous carrier and molding the , ~ 9(~)9'~
.

1 mixture. In this case, the e~fective surface area is increasea in the catalys-t and the mechanical strength is improved.
The carrier may have a form of a bead, column, Raschig ring or plate as shown in Fig. 1. When an exhaust gas containing large quantities of dusts, such as an exhaust gas discharged from a coking furnace or calcination furnace, is directly treated without performing preliminary dust precipitation, dusts are deposited on the catalyst layer to cause degradation of the catalyst and clogging in the catalyst layer, resulting in increase of the pressure loss. In this case, use of a multi-chambered carrier as shown in Fig. 2 is recommended. When a multichambered catalyst is employed, the pressure loss is very small and therefore, the exhaust gas can be treated at a very high space velocity. The cross section of the multichambered carrier shows a multitude of hollows of shapes including a number of hexagons, squar~s, triangles or other polygons or circles, or a sine wave shape, spidery shape or spiral shape. The carrier of such multichambered type includes voids or pores at a porosity of about 50 to about 70~.
A multichambered carrier may be prepared by coating and sintering a powder of silica, alumina, titania, zirconia,thoria or the like on a metal substrate. The so prepared carrier~
however, is defective in that because of insufficient adhesion between the coating and substrate the coating is readily peeled and because of a great difference of the thermal expansion co-efficient between the coating and substrate the resistance to the heat history is inferior. In view of the foregoing, it is preferred to use a multichambered carrier prepared by coating a mixture of a powder of silica, alumina, titania, zirconia, thoria or silica-alumina with a suitable binder on a ceramic substrate : ' " , ', ' ' ' ' ~

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such as cordierite and sintering the coating. In order to obtain a large surface area required of a carrier, a coating composed mainly of alumina is especially preferred. It is possible to coat titania, thoria, silica or zirconia on such coating composed mainly of alumina or a mixture of alumina with at least one member selected from silica, titania, zirconia and thoria or such coatin~ composed mainly of alumina.
The method of supporting the catalyst components on a support such as mentioned above will now be described by reference to a catalyst of the V-Nb-Ti-Cu series.
Prescribed amounts of aqueous solutions of ammonium metavanadate, niobium penta chloride and titanium tetrachloride are dissol~ed in an aqueous solution of an organic acid such as oxalic acid, tartaric acid, citric acid or the like, and a carrier such as mentioned above is dipped in the resulting solu-tion, taken out from the solution, dehydrated, dried and then calcined. Then, the calcined carrier is dipped in an aqueous solution of copper nitrate and the above post treatments are conducted. Thus, a supported catalyst can easily be prepared and the catalyst components are supported on the carrier in the form of the oxides. In this case, if suitable starting substances are chosen, the four components can be deposited simultaneously on the carrler. Components other than mentioned above can be deposited on the carrier according to similar methods. In order to obtain a sufficient activity, it is most preferred that the calcination be carried out at 200 to 600C. It also is prefer~ed that the catalyst active components be supported in an amount of 0.1 to 20% by weight, especially 1 to 15% by weight, based on the carrier.

The composition of the respective catalyst components in the catalyst of the present invention will now be described by reference to the ratio of the atom numbers.

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1 In case of the catalyst of the V-Nb series, the ratio of the atom number of Nb to the atom number of V should be in the range of from 0.1 to 5, and in case of khe catalyst of the V-Nb-X series (X denotes at least one element selected from the group consisting of Ti, Cu, Cr, W, Mo, Fe and Ni), the ratio of the total atom number of Nb and other element X should be in the range of from 0.1 to 5 and the ratio of the atom number of the element X othe.r than V and Nb to the atom number of Nb should be in the range of from 0.25 to 99. If the above re~uirements are.
not satisfied, no sufficient activity can be obtained.
If the ratio of the atom number of Nb or the atom number of Nb and other element to the atom number of V is lower than 0.1, no particular effect can be attained by addition of Nb or Nb and other element and the low temperature activity or the effect of improving the decomposing activity of ammonia is hardly enhanced. If the above ratio is higher than 5, the effect of improving the decomposing activity of ammonia is increased but the activity~manifesting temperature range is narrowed and the activity in the high temperature range is reduced. If the .
ratio of the atom number of the element other than V and Nb to the atom number of Nb is less than 0.25 and greater than 99, dis-advantages as mentioned above are similarly brough.t about.
In case of that the catalyst consists essentially of the oxides of V, Nb and Ti, the atomic ratio of Nb to V may be from 0.01 to 0.14 and the atomic ratio of Ti to V may be from 0.4 to 0.8, resulting in obtaining high. ratio of NO conversion and good durabilit~
Fig. 3 illustrates data of conversion of NO obtained when the catalytic reduction was conducted at temperatures of 200 to 400C in the catalyst of the 3QV-XNb-25Ti (each figure B

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~efore each element symbol denotes the amoun-t, g per Q of the carrier, of the element~ series according to the present inven-tion in which the amount X of NB was changed. From the results shown in Fig. 3, it will readily be understood that even if very small amounts of Nb and the third element are added, sufficient effects can be obtained.
The so prepared catalyst is disposed on a flue of an exhaust gas discharged from a combustion apparatus, and the exhaust gas is mixed with a reducing gas such as ammonia and the yas 1~ mixture is contacted with the catalyst at a reaction temperature of 200 to 500C and a space velocity of 2000 to 100,000 hr 1, whereby nitrogen oxides are converted to harmless substances.
According to the method of the present invention, a very high NOX conversion can be attained even at such a low temperature (200 to 300C) or such a high space velocity (~,000 to 20,000 or higher) as cannot be practically adopted in the conventional methods.
As is seen from the foregoing illustration, according to the method of the present invention it is possible to convert NOX to harmless substances effectively at a low temperature and a high space velocity, and therefore, there can be attained various advantages such as reduction of consumption o~ the heat energy, reduction of the pressure loss and prevention of degra~
dation o~ the catalyst. Accordingly, the method o~ the present invention is very valuable as an industrial method for convert-ing NOX contained in exhaust gases.
The present invention will now be described in detail by reference to the following Examples that by no means limit the scope of the invention.

9~(~9'7 To 1 Q of dlstilled water was added 470 g of oxalic acid and the oxalic acid was dissolved under heating. Then, 170 g of ammonium metavanadate, 276 g of an aqueous solution of titanium tetrachloride (containing about 70 g of titanium) and 93 g of niobium pentachloride were added to the solution under agitation to dissolve them in the solution completely. Then, 500 mQ of bead-like active alumina was dipped in the resulting solution for 30 minutes. The alumina was taken out from the solution, dehydrated, dried at 110C for 1 hour and calcined at 400C for 1 hour in an electric furnace while blowing air there-into to thereby obtain a catalyst consisting essentially of the oxides of vanadium, niobium and titanium deposited on the alumina carrier. The so prepared catalyst was dipped in an aqueous solution of copper nitrate (containing 74 g of copper nitrate in 1 Q of water) for 30 minutes, and the post treatments were carried out in the same manner as described above to obtain a catalyst having such a composition that one atom of titanium, 0.3 atom of niobium and 0.2 atom of copper were contained per atom of vanadium.
This catalyst was used for the treatment of a gas syn~hesized in a laboratory and an exhaust gas discharged from a coking furnace (at a rate of S Nm3/hr). Reaction conditions and experimental results are shown in Table 1. Results of the analysis of the reaction product oktained at the experiment made on the synthetic gas are shown in Table 2.
Results of the activity test made on a vanadium-niobium catalyst prepared in the same manner as described above are also shown in Table 1.
3~ Further, compositions o~ 10 catalysts prepared in the same manner as described above and the conditions and results of the synthetic gas test made on these gases are shown in Table 3.

1~ 09'7 , ~ r--l ~) Sl ~ rl S-l U~ -~ ~H .~:: r ~H ~ O IH ~H ~
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O ~
r~ ~0 O O O O O O
O ~ Otl') IYl o t~) ~r ~1 N ~ `1 N

~ o o o o o o rl~ o o o o o o o o o o o o r~ c~ o l td r~ ~ O O O O O O
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U~ ~ Z ~ ~~ 10 ~ co ~ o ~1 ~ ~1 :

~ 0 1 EX~MPLE 2 An active alumina carrier was dipped in an oxalic acid solution containing active components such as V, Nb, Cu and the -like for 30 minutes, dried and calcined for 1 hour at 400C.
Then, the carrier was dipped in the above solution again, and dried and calcined. A synthetic gas comprising 240 ppm of NO, 338 ppm of NH3, 7.2% of 2~ 10.5% of H2O and 43 ppm of SO2 with the balance being N2 was contacted with the so obtained catalyst at a space velocity of 10,000 hr 1. The relation between the conversion of NO and the reaction temperature which was observed at this experiment is shown in Fig. 4. Each number before each catalyst element symbol denotes the amount of the element (g per Q of the catalyst)~
From results shown in Fig. 4, it will readily be under-stood that the catalyst of the present invention (samples Nos.
1 and 2) were superior to the conventional catalysts (samples Nos.
3 and 4) with respect to the reducing activity in the total temperature range, especially in the low temperature range.
~ .
EX~LE 3 ~0 In distilled water were dissolved 470 g of oxalic acidt170 g of ammonium metavanadate, 93 g of niobium pentachloride and 276 g of a solution of titanic acid to form 1 Q of a solu~ion.
A mixture of alumina and a binder was coated in an amount of about 30~ on a multichambered ceramic substrate, and the coated substrate was dipped in the above aqueous solution for 30 minutes. Then, the ceramic substrate was taken out from the aqueous solution, dehydrated, dried at 110C for 1 hour and calcined at 500C for 1 hour in an electric furnace while blowing air into the furnace, to obtain a multichambered catalyst having vanadium, niobium and titanium oxides supported thereon.

..

la~s(,~ 7 1 A mixed gas comprising 250 ppm of NO, 375 ppm of NH3, 4~ f 2 and 7% of H2O with the balance being N2 was catalytically reduced at a space velocity of 10,000 hr 1 in the presence of the so prepared catalyst while changing the reaction temperature, and the NO conversion was examined to obtain results shown in Fig. 5.
Separately, in the same manner as described above, 500 mQ of a bead-like porous alumina carrier was dipped in the aqueous solution and subjected to the post treatments to obtain a pellet type catalyst having vanadium, niobium and titanium 1~ oxides supported thereon. (The amount of each catalyst component supported was twice as large as the amount in the above multi-chambered catalyst.) By using the so prepared catalyst, the mixed gas was treated in the same manner as described above, and the NO conversion was examined to obtain results shown in Fig. 5.
As will readily be understood from the results shown in Fig. 5, when the multichambered catalyst was used, a much higher NOX conversion could be obtained than in case o the pellet type catalyst, if compared at the same space velocity, and the difference was greater in the low temperature range.
The pressure loss in case of the multichambered catal~st was about 1/10 of the pressure loss in case o~ the pelIet type catalyst.

EXAMPLE 4 ~;
By using a multichambered catalyst prepared in the same manner as described in Example 3, a synthetic mixed gas having the same compositio~ as described in Example 3 was treated at a space velocity of 10,000, 20,000 or 30,000 hr 1 while changing the reaction temperature, and the NOX conversion was e~amined to obtain results shown in Fig. 6.

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, . .

1 As will be apparent from these results, when the multi-chambered catalyst of the present invention was employed, NOX
conversion of at least 90% could be obtained at a space velocity o~ 30,000 hr 1 if the reaction temperature was 300C or higher.
The pressure loss in case of this multichambered catalyst was about 1/15 of the pressure loss in case of a pellet type catalyst prepared in the same manner as described above.

EXAMP~E 5 By using a multichambered catalyst prepared in the same manner as described in Example 3, a coking furnace exhaust gas comprising up to 350 ppm of NO, 2 to 8~ of 2 and up to 200 ppm f S2 with the balance being CO2, H2O and N2 was catalytically-reduced at a space velocity of 10,000 hr 1 and an NO/NH3 ratio of 1.5 while changing the reaction temperature, and the NOX
conversion was examined to obtain results shown in Fig. 6.
The coking furnace exhaust gas was similarly treated at 250C for 500 hours to evaluate the durability of the catalyst.
The increase of the pressure loss was not caused at all.

EX~LE 6 .
By using a pellet type catalyst of the 40V-1.7Nb-20Ti series prepared according to the method described in Example 1, a coking furnace exhaust gas comprising up to 350 ppm of NO, up to 200 ppm of SO2 and 2 to 8~ f 2 with the balance being N2 was catalytically reduced in the presence of NH3 incorporated at an NH3/NO ratio of 1.5 at a space velocity of 5000 hr 1 and a temperature of 220 or 250C The relation between the NO con-version and the reaction time obtained in this experiment is shown in Fig. 7.

, .
' '' ' . ' ' , .

9~ 9'7 1 From Fig. 7, it will readily be understood that in the catalyst of the present invention, the activity was not reduced even if it was used for a long time and a high NO conversion could be maintained if the reaction was continued for a long time.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for converting nitrogen oxides present in exhaust gases to harmless substances, which comprises:
contacting an exhaust containing nitrogen oxides in the presence of a reducing agent at a temperature of 200° to 500°C, and a space velocity of 2,000 to 100,000 hr1 with a catalyst consisting essentially of the oxides of V and Nb.

2. The method of claim 1, wherein said reducing agent is ammonia.

3. The method of claim 2, wherein the ratio of the atom number of Nb to the atom number of V is in the range of from 0.1 to 5Ø

4. A method for converting nitrogen oxides present in exhaust gases to harmless substances, which comprises:
contacting an exhaust gas containing nitrogen oxides in the presence of a reducing agent at temperature of 200° to 500°C and a space velocity of 2,000 to 100,000 hr-1 with a catalyst consisting essentially of the oxides of V, Nb and at least one element selected from the group consisting of Cu, Ti, Fe, Cr, W, Mo and Ni.

5. The method of claim 4, wherein said reducing agent is ammonia.

6. The method of claim 5, wherein the ratio of the total atom number of Nb and said element to the atom of V is in the range of from 0.1 to 5Ø

7. A method for converting nitrogen oxides present in exhaust gases to harmless substances, which comprises:
contacting an exhaust gas containing nitrogen oxides in the presence of a reducing agent at a temperature of 200° to 500°C and a space velocity of 2,000 to 100,000 hr-1 with a catalyst consisting essentially of the oxides of V, Nb and Ti.

8. The method of claim 7, wherein said reducing agent is ammonia.

9. The method of claim 5, wherein the ratio of the atom number of said element to the atom number of Nb is in the range of from 0.25 to 99.

10. The method of claim 8, wherein the atomic ratio of Nb to V is from 0.01 to 0.14 and the atomic ratio of Ti to V is from 0.4 to 0.8.

11. The method of claim 2, wherein said catalyst is supported on a carrier.

12. The method of claim 5, wherein said catalyst is supported on a carrier.

13. The method of claim 8, wherein said catalyst is supported on a carrier.

14. The method of claim 11, wherein said carrier is formed in a shape of beads, columns, Rashing rings, plates or of a honeycomb structure.

15. The method of claim 12, wherein said carrier is formed in a shape of beads, columns, Rashing rings, plates or of a honeycomb structure.

16. The method of claim 13, wherein said carrier is formed in a shape of beads, columns, Rashing rings, plates or of a honeycomb structure.

17. The method of claim 14, wherein said catalyst com-ponents are supported in an amount of 0.1 to 20% by weight based on said carrier.

18. The method of claim 15, wherein said catalyst com-ponents are supported in an amount of 0.1 to 20% by weight based on said carrier.

19. The method of claim 16, wherein said catalyst com-ponents are supported in an amount of 0.1 to 20% by weight based on said carrier.

20. The method of claim 17, wherein the catalyst compon-ents are supported in an amount of 1 to 10% by weight based on the carrier.

21. The method of claim 18, wherein the catalyst compon-ents are supported in an amount of 1 to 10% by weight based on the carrier.

22. The method of claim 19, wherein the catalyst compon-ents are supported in an amount of 1 to 10% by weight based on the carrier.