GB1581513A - Preparation of zeolites in the absence of alkali metal - Google Patents

Description

(54) PREPARATION OF ZEOLITES IN THE ABSENCE OF ALKALI METAL (71) We, MOBIL OIL CORPORATION, a Corporation organised under the laws of the State of New York, United States of America, of 150 East 42nd Street, New York, New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to the preparation of certain zeolites in the absence of alkali and alkaline earth cations.

Zeolitic materials, both natural and synthetic, have been known in the past to have catalytic capability for various types of hydrocarbon conversion reactions.

Certain of these zeolitic materials comprising ordered porous crystalline aluminosilicates have a definite crystalline structure, as determined by X-ray diffraction, within which there are a number of small cavities which are interconnected by a number of still smaller channels. These cavities and channels are precisely uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption purposes molecules of certain dimensions while rejecting those of larger dimensions, these materials' have commonly been known to be "molecular sieves" and are utilized in a variety of ways to take advantage of the adsorptive properties of these compositions.

Crystalline aluminosilicates have been characterized by the presence of aluminum and silicon, the total of such atoms to oxygen being 1:2. The amount of aluminum present in conventional aluminosilicates appears directly related to acidity characteristics of the resulting product. Low aluminum content is advantageous in attaining low acid density, desirable for low coking, for low aging rates, and for high stability.

Crystallization of catalytically useful zeolites in the absence of alkali and alkaline earth metal cations has not been previously possible, although the desirability of such a crystallization in eliminating a costly and time-consuming exchange to remove metal cations is well recognized. D. W. Breck, in his book, Zeolite Molecular Sieves, published by J. Wiley, New York, in 1974, stated on page 304 that zeolite crystallization from "systems involving alkylammonium ions require two bases. The alkylammonium base is used together with alkali hydroxide in nearly every case".

In U.S. 3,306,922 it was found that, when zeolites such as A, X and Y, were prepared from reaction mixtures to which only tetramethylammonium (herein called TMA) cations had been added, the products contained sodium, probably leached from the glass container, in substantial quantity, typically in a Na2O/AI203 mole ratio of about 0.4. D. W. Breck, after referencing this patent, states on page 308 of his book that: "Traces of sodium help to nucleate crystallization of zeolite N A and N-Y. The rate of crystallization seems to depend on the amount of sodium present". (N-A and N-Y simply designate an A and a Y zeolite, respectively, prepared with TMA cation.) Only the dense, small pore zeolite structures have been prepared to date in the careful exclusion of alkali and alkaline earth cations. C. Baerlocher and W. M.

Meir in their two articles in Helvetica Chimica Acta, volume 52, page 1853 (1969) and volume 53, page 1285 (1970), reported synthesis of TMA-sodalite and of TMAgismondine, respectively.

In U.S. 3,702,886 is disclosed the preparation of zeolite ZSM-5. Just as had been common to the N-A, N-X and N-Y preparations, it is only disclosed that crystallization can occur from reaction mixtures containing alkali and alkaline earth cations. Where specifically sodium is involved, a range of compositions is disclosed wherein sodium comprises at least 5 and as much as 80 /" of the monovalent cations present, tetrapropylammonium (herein called TPA) ion comprising the remainder. Preferred is a range in which sodium comprises at least 10% of the cations.

In U.S. 3,709,979, the preparation of zeolite ZSM-ll is described, wherein it is disclosed that sodium should comprise at least 20% of the monovalent cations present. In preferred reaction mixtures sodium comprises at least 25 /n of these cations.

In U.S. 3,941,871, a method is described for synthesizing a crystalline metal organosilicate having an X-ray pattern similar to that of the ZSM-5 type aluminosilicates. It was recognized in the above patent that very minor amounts of alumina may be found in these organosilicates. Such aluminum impurities were sufficiently low that the SiO2/AI203 mole ratio in the silicates would exceed 200. In spite of the essential absence of alumina, sodium was again preferred in the reaction mixtures, preferably comprising at least 20% of the monovalent cations.

In accordance with the present invention a method of preparing a crystalline zeolite having a SiO2 to Al203 molar ratio of 10 to 3000, and having at 550 to 9500F a constraint index, as herein defined, in the range 1 to 12, comprises synthesising the zeolite from a reaction mixture having, in terms of mole ratios, the composition: R/SiO2: 0.01-1.5 SiO2/Al2O3: 11000 H2O/SiO2: 5-100 OHlSiO2: 0.01--1.5 wherein R represents one or more organic nitrogen and/or organic phosphorus cations, said reaction mixture being free of alkali or alkaline earth cations.

The organic nitrogen cation may advantageously be tetramethylammonium (TMA) or tetrapropylammonium (TPA), and we have found that when both are present many syntheses yield a product of unusually large crystal size. The zeolite obtained will often possess a silica/alumina ratio in the range 10 to 200, and it will frequently be preferred to obtain by the exercise of the invention zeolites having the same structure as ZSM-5, ZSM- 11 or ZSM-12, which have been shown to have remarkable catalytic properties.

The present invention is applicable to the preparation of zeolites having the same structure as e.g. ZSM-5, which retain their crystallinity for long periods in spite of the pesence of steam at high temperature, which induces irreversible collapse of the framework of other zeolites, e.g. of the X and A types. Furthermore, carbonaceous deposits, when formed, may be removed by burning at higher than usual temperatures to restore activity. In many environments, the zeolites of this class exhibit very low coke forming capability, conducive to very long times on stream between burning regenerations.

An important characteristic of the crystal structure of the ZSM-5 type of zeolites is that they provide constrained access to, and egress from, the intracrystalline free space by virtue of having a pore dimension greater than about 5 Angstroms and pore windows of about a size such as would be provided by 10membered rings of oxygen atoms. It is to be understood, of course, that these rings are those formed by the regular disposition of the tetrahedra making up the anionic framework of the crystalline zeolite. Briefly, preferred crystalline zeolites for preparation by the method of this invention possess, in combination: a silica to alumina ratio of 10 to 1000, and a structure providing constrained access to the crystalline free space.

The silica to alumina ratio referred to may be determined by conventional analysis. This ratio is meant to represent, as closely as possible, the ratio in the rigid anionic framework of the zeolite crystal. Such zeolite crystals, after activation, acquire an intracrystalline sorption capacity for normal hexane which is greater than that for water, i.e., they exhibit "hydrophobic" properties. It is believed that this hydrophobic character is an advantageous feature of zeolites prepared by the method of the present invention.

Crystalline zeolites can be prepared by the method of this invention which freely sorb normal hexane and have a pore dimension greater than 5 Angstrom. In addition, the structure must provide constrained access to larger molecules. It is sometimes possible to judge from a known crystal structure whether such constrained access exists. For example, if the only pore windows in a crystal are formed by 8-membered rings of oxygen atoms, then access by molecules of larger cross-section than normal hexane is excluded and the zeolite is not of the desired type. Windows of 10-membered rings are preferred, although, in some instances, excessive puckering or pore blockage may render these catalysts ineffective.

Twelve-membered rings do not generally appear to offer sufficient constraint to produce the advantageous conversions, although puckered structures exist such as TMA offretite which is a known effective zeolite. Also, structures can be conceived, due to pore blockage or other cause, that may be operative.

Rather than attempt to judge from crystal structure whether or not a zeolite possesses the necessary constrained access, a simple determination of the "constraint index" may be made by passing continuously a mixture of an equal weight of normal hexane and 3-methylpentane over a small sample, approximately 1 gram or less, of zeolite at atmospheric pressure according to the following procedure. A sample of the zeolite, in the form of pellets or extrudate, is crushed to a particle size about that of coarse sand and mounted in a glass tube. Prior to testing, the zeolite is treated with a stream of air at 10000F for at least 15 minutes.

The zeolite is then flushed with helium and the temperature adjusted between 550OF and 950OF to give an overall conversion between 10% and 60 /,,. The mixture of hydrocarbons is passed at 1 liquid hourly space velocity (i.e., 1 volume of liquid hydrocarbon per volume of catalyst per hour) over the zeolite with a helium dilution to give a helium to total hydrocarbon mole ratio of 4:1. After 20 minutes on stream, a sample of the effluent is taken and analyzed, most conveniently by gas chromatography, to determine the fraction remaining unchanged for each of the two hydrocarbons.

The "constraint index" referred to in the present description and claims is to be understood to be that calculated from these fractions by use of the following formula: log10 (fraction of n-hexane remaining) Constraint Index= log1O (fraction of 3-methylpentane remaining) The constraint index approximates the ratio of the cracking rate constants for the two hydrocarbons. Zeolites prepared by the method of the present invention are those having a constraint index, as herein defined, in the range of 1 to 12.

Constraint Index (CI) values for some typical zeolites are: Zeolite C.I.

ZSM-5 8.3 ZSM-11 8.7 ZSM-12 2 Beta 0.6 ZSM-4 0.5 H-Zeolon 0.5 Rare-earth exchanged zeolite Y 0.4 Amorphous Silica-Alumina 0.6 Erionite 38 It is to be realized that the above constraint index values typically characterize the specified zeolites but that such are the cumulative result of several variables used in determination and calculation thereof. Thus, for a given zeolite depending on the temperature employed within the aforenoted range of 550OF to 9500 F, with accompanying conversion between 10% and 60%, the constraint index may vary within the indicated range of 1 to 12. Likewise, other variables such as the crystal size of the zeolite, the presence of possibly occluded contaminants and binders intimately combined with the zeolite may affect the constraint index.It will accordingly be understood by those skilled in the art that the constraint index, as utilized herein, while affording a highly useful means for characterizing the zeolites of interest, is approximate, taking into consideration the manner of its determination, with the probability, in some instances, of compounding variable extremes. However, in all instances at a temperature within the above-specified range of 550" F to 9500 F, the constraint index will have a value for any given zeolite prepared by the present method within the range of-l to 12.

From the above list, it is apparent that zeolites having the same structures as ZSM-5, ZSM-l 1 and ZSM-12 can be prepared by the method of the invention.

There is no need to present a full disclosure of these zeolites in this Application since they are fully described elsewhere. Thus ZSM-5 is the subject of U.S.

3,702,886, ZSM-II of U.S. 3,709,979 and ZSM-12 of U.S. 3,832,449.

The specific zeolites described, when prepared in the presence of organic cations, are catalytically inactive, possibly because the intracrystalline free space is occupied by organic cations from the forming solution. They may, however, be activated by simple calcination, e.g. to at least 3000 C, preferably in air.

The zeolites can be used in various cation forms, e.g., the ammonium form, the hydrogen form, or another univalent or multivalent cationic form. Preferably, one or the other of the last two forms is employed. They can also be used in intimate combination with a hydrogenating component such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a noble metal such as platinum or palladium where a hydrogenation-dehydrogenation function is to be performed. Such components can be exchanged into the composition, impregnated onto it or physically intimately admixed therewith. Such component can be impregnated in or onto the present zeolite by, for example, treating the zeolite with a platinum metal-containing ion.Suitable platinum compounds that may be used include chloroplatinic acid, platinous chloride and various compounds containing the platinum amine complex.

The compounds of platinum or other useful metals can be divided into compounds in which the metal is present in the cation of the compound and compounds which it is present in the anion of the compound. Both types which contain the metal in the ionic state can be used. A solution in which platinum metals are in the form of a cation or cationic complex, e.g., Pt(NH3)6C14 is particularly useful. For some hydrocarbon conversion processes, this noble metal form of the catalyst is unnecessary, such as in low temperature, liquid phase ortho xylene isomerization.

The zeolite, when employed either as an adsorbent or as a catalyst in one of the aforementioned processes, should be dehydrated at least partially. This can be done by heating to a temperature in the range of 200 to 6000C in an atmosphere such as air, nitrogen, etc., and at atmospheric or subatmospheric pressures for between 1 and 48 hours. Dehydration can also be performed at lower temperatures merely by placing the zeolite in a vacuum, but a longer time is required to obtain a sufficient amount of dehydration.

It has been found that zeolites which satisfy the mentioned criteria act on a variety of feedstocks to maximize the production of gasoline boiling range hydrocarbon products.

The zeolites prepared by the method of the present invention are preferably prepared from a reaction mixture having the following composition, in terms of mole ratios: Particularly Broad Preferred Preferred R*/SiO2 0.01-1.5 0.05-0.8 0.1-0.4 SiO2/Al2O3 10--20d 2150 30--100 H2O/SiO2 5-100 170 2-50 OH-/SiO2 0.01-1.5 0.05-0.8 0.1-0.4 *R is the sum of the organic cations.

Typical reaction conditions include heating the above mixture at a temperature of from 80"C to 2000C for a period of time from 4 hours to 30 days. As in the case of ZSM-5 aluminosilicate synthesis, the digestion of the gel particles is carried out until the crystalline zeolite forms completely. The product crystals are then separated, as by cooling and filtering, and are water washed and dried at from 80"C to 1500C.

Zeolites prepared by a method according to the invention can have a wide variety of other cations associated therewith according to ion exchange techniques well known in the art. Typical cations would include hydrogen, ammonium and metal cations including mixtures of the same. Of the metallic cations, particular preference is given to cations of metals such as rare earth metals, manganese and calcium, as well as metals of Group II of the Periodic Table, e.g., zinc and Group VIII of the Periodic Table, e.g., nickel.

As in the case of many zeolitic catalysts, it may be desired to incorporate a zeolite prepared by the method of this invention with another material resistant to the temperatures and other conditions employed in organic conversion processes.

Such materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and/or metal oxides. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Use of an additional material in conjunction with the present zeolite tends to improve the conversion and/or selectivity of the product when employed as a catalyst in certain organic conversion processes. Inactive materials suitably serve as diluents to control the amount of conversion in a given process so that products can be obtained economically and in orderly manner without employing other means for controlling the rate of reaction.Normally, zeolite materials have been incorporated into naturally occurring clays, e.g., bentonite and kaolin, to improve the crush strength of the product under commercial operating conditions. These materials, i.e., clays, oxides, etc. function as binders for the zeolite. It is desirable to provide a zeolitic catalyst having good crush strength, because in a petroleum refinery the catalyst is often subjected to rough handling, which tends to break the catalyst down into powder-like materials which cause problems in processing. The clay binders have been employed for the purpose of improving the crush strength of the catalyst.

Naturally occurring clays which can be composited with the zeolite include the montmorillonite and kaolin family, which families include the sub-bentonites, and the kaolins commonly known as Dixie, McNamee-Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite, or anauxite. Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification.

In addition to the foregoing materials, the zeolite can be composited with a porous matrix material such as alumina, silica, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-aluminamagnesia and silica-magnesia-zirconia. The matrix can be in the form of a cogel.

The relative proportions of the finely divided crystalline aluminosilicate containing the aluminum-free outer shell and inorganic oxide gel matrix can vary widely, with the crystalline aluminosilicate content ranging from 1 to 90 percent by weight and more usually, particularly when the composite is prepared in the form of beads in the range of about 2 to 50 percent by weight of the composite.

Employing a zeolite prepared by the method of this invention containing a hydrogenation component, heavy petroleum residual stocks, cycle stocks and other hydrocrackable charge stocks can be hydrocracked at temperatures between 400OF and 850OF using molar ratios of hydrogen to hydrocarbon charge in the range between 2 and 80. The pressure employed will vary between 10 and 2,500 psig and the liquid hourly space velocity between 0.1 and 10.

Employing a zeolite prepared by the method of this invention for catalytic cracking, hyrocarbon cracking stocks can be cracked at a liquid hourly space velocity between about 0.5 and 50, a temperature between about 550OF and 1300OF, a pressure between about atmospheric and a hundred atmospheres.

Employing a catalytically active form of a zeolite prepared by the method of this invention containing a hydrogenation component, reforming stocks can be reformed employing a temperature between 700OF and 1000OF. The pressure can be between 100 and 1000 psig, but is preferably between 200 and 700 psig. The liquid hourly space velocity is generally between 0.1 and 10, preferably between 0.5 and 4 and the hydrogen to hydrocarbon mole ratio is generally between 1 and 20 preferably between 4 and 12.

The zeolite can also be used for hydroisomerization of normal paraffins, when provided with a hydrogenation component, e.g., platinum. Hydroisomerization is carried out at a temperature between 200 and 700OF, preferably 300 to 550OF, with a liquid hourly space velocity between 0.1 and 2, preferably between 0.25 and 0.50 employing hydrogen, in such a manner that the hydrogen to hydrocarbon mole ratio is between 1:1 and 5:1. Additionally, the catalyst can be used for olefin isomerization employing temperatures between 30"F and 500OF.

Other reactions can be accomplished employing a zeolite prepared by the method of this invention and containing a metal, e.g., platinum, including hydrogenation-dehydrogenation reactions and desulfurization reactions.

In the illustrative Examples which follow, all gels were prepared from silica gel containing 99.6% SiO2, 0.03 /O Al2O3 and 0.04 /O Na2O. TPA . OH was prepared from TPA . Br and Ag2O. Aluminum was added as Al2(SO4)3. 161120, as aluminum granules or as A12O3. 31120.

EXAMPLE 1 To a mixture of 7.1 g silica gel, 34.7 g of 25% TPA . OH and 17.7 g H2O in a "Teflon" (registered Trade Mark) bottle was added a solution of 1.5 g Al2(SO4)3. 16 H2O and 11.4 g. TPA Br in 49g H2O. The bottle was placed in an autoclave and maintained at 160 C for 4 days. The resulting crystals were filtered, washed and dried to vield 6.1 g of a material identified as zeolite ZSM-5 of 100% crystallinity.

The characteristics of reaction mixture and product are set forth in the following Table.

EXAMPLES 2-4 The procedure of Example 1 was three times repeated, with the inclusion of TMA (added as hydroxide, chloride or bromide) in the reaction mixtures of Examples 2 and 3. The characteristics of the reaction mixtures and products are set forth in the Table.

TABLE Reaction Mixture Composition, Mole Ratios Product, Mole Ratios Other Other SiO2 H2O OH TPA SiO2 TPA Cations Example Cation Al2O3 SiO2 SiO2 SiO2 Al2O3 SiO2 SiO2 I(a) None 50 44 0.20 0.72 175 0.05 0 2(b) TMA 175 46 0.23 0.08 159 0.04 0.003 3(c) TMA 90 45 0.10 0.67 86 0.03 0.025 4(d) None 50 44 0.20 0.40 185 0.05 0 (a) Crystallized at 160 C for 4 days, 100% ZSM-5 (b) Crystallized at 1600C for 6 days, 70% ZSM-5 (c) Crystallized at 1600C for 7 days, 50% ZSM-5 (d) Crystallized at 1600C for 6 days, 100% ZSM-5 Conventional procedures for the synthesis of zeolite ZSM-5, in particular those in which alkali metal cation is present in the reaction mixture, usually yield crystals about 0.2 microns in size.The products of Examples 1 and 4, by contrast, had crystals about 0.5x 1.0 microns in size, whilst those of Examples 2 and 3 were about 4x20 microns in size. The invention is thus of considerable use in the synthesis of zeolites for use as catalysts in those processes known to proceed more effectively when the zeolite is of relatively large crystal size; this applies particularly to zeolites prepared by a method according to the invention in which more than one organic cation is present.

WHAT WE CLAIM IS: 1. A method of preparing a crystalline zeolite having a SiO2 to Al2O3 ratio of 10 to 3000, and having at 550 to 9500F a constraint index, as herein defined, of 1 to 12, comprising synthesising the zeolite from a reaction mixture having, in terms of mole ratios, the composition: R/SiO2: 0.01-1.5 SiO2/AI203: 11000 H2O/SiO2: 5-100 OH-/SiO2: 0.01--1.5 wherein R represents one or more organic nitrogen and/or organic phosphorus cations, said reaction mixture being free of alkali or alkaline earth cations.

2. A method according to Claim 1 wherein the organic nitrogen cation is tetramethylammonium and/or tetrapropylammonium.

3. A method according to Claim 1 or Claim 2 wherein the zeolite has a silica/alumina ratio in the range 10 to 200.

4. A method according to any of Claims 1 to 3 wherein the zeolite has the same structure as ZSM-5, ZSM- 11 or ZSM-12.

5. A method according to any preceding claim wherein the reaction mixture has the composition:

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. containing 99.6% SiO2, 0.03 /O Al2O3 and 0.04 /O Na2O. TPA . OH was prepared from TPA . Br and Ag2O. Aluminum was added as Al2(SO4)3. 161120, as aluminum granules or as A12O3. 31120. EXAMPLE 1 To a mixture of 7.1 g silica gel, 34.7 g of 25% TPA . OH and 17.7 g H2O in a "Teflon" (registered Trade Mark) bottle was added a solution of 1.5 g Al2(SO4)3. 16 H2O and 11.4 g. TPA Br in 49g H2O. The bottle was placed in an autoclave and maintained at 160 C for 4 days. The resulting crystals were filtered, washed and dried to vield 6.1 g of a material identified as zeolite ZSM-5 of 100% crystallinity. The characteristics of reaction mixture and product are set forth in the following Table. EXAMPLES 2-4 The procedure of Example 1 was three times repeated, with the inclusion of TMA (added as hydroxide, chloride or bromide) in the reaction mixtures of Examples 2 and 3. The characteristics of the reaction mixtures and products are set forth in the Table. TABLE Reaction Mixture Composition, Mole Ratios Product, Mole Ratios Other Other SiO2 H2O OH TPA SiO2 TPA Cations Example Cation Al2O3 SiO2 SiO2 SiO2 Al2O3 SiO2 SiO2 I(a) None 50 44 0.20 0.72 175 0.05 0 2(b) TMA 175 46 0.23 0.08 159 0.04 0.003 3(c) TMA 90 45 0.10 0.67 86 0.03 0.025 4(d) None 50 44 0.20 0.40 185 0.05 0 (a) Crystallized at 160 C for 4 days, 100% ZSM-5 (b) Crystallized at 1600C for 6 days, 70% ZSM-5 (c) Crystallized at 1600C for 7 days, 50% ZSM-5 (d) Crystallized at 1600C for 6 days, 100% ZSM-5 Conventional procedures for the synthesis of zeolite ZSM-5, in particular those in which alkali metal cation is present in the reaction mixture, usually yield crystals about 0.2 microns in size.The products of Examples 1 and 4, by contrast, had crystals about 0.5x 1.0 microns in size, whilst those of Examples 2 and 3 were about 4x20 microns in size. The invention is thus of considerable use in the synthesis of zeolites for use as catalysts in those processes known to proceed more effectively when the zeolite is of relatively large crystal size; this applies particularly to zeolites prepared by a method according to the invention in which more than one organic cation is present. WHAT WE CLAIM IS:

1. A method of preparing a crystalline zeolite having a SiO2 to Al2O3 ratio of 10 to 3000, and having at 550 to 9500F a constraint index, as herein defined, of 1 to 12, comprising synthesising the zeolite from a reaction mixture having, in terms of mole ratios, the composition: R/SiO2: 0.01-1.5 SiO2/AI203: 11000 H2O/SiO2: 5-100 OH-/SiO2: 0.01--1.5 wherein R represents one or more organic nitrogen and/or organic phosphorus cations, said reaction mixture being free of alkali or alkaline earth cations.

2. A method according to Claim 1 wherein the organic nitrogen cation is tetramethylammonium and/or tetrapropylammonium.

3. A method according to Claim 1 or Claim 2 wherein the zeolite has a silica/alumina ratio in the range 10 to 200.

4. A method according to any of Claims 1 to 3 wherein the zeolite has the same structure as ZSM-5, ZSM- 11 or ZSM-12.

5. A method according to any preceding claim wherein the reaction mixture has the composition:

R/SiO2: 0.05-0.8 SiO2/Al2O3: 20-150 H2O/SiO2: 10-70 OH-/SiO2: 0.05-0.8

6. A method according to any preceding claim wherein the reaction mixture has the composition: R/SiO2: 0.1-0.4 SiO2/Al2O3: 30-100 H2SiO2: 20-50 OH-/SiO2: 0.1-0.4