MXPA01008891A - Process for preparing a modified zeolite - Google Patents

Abstract

A hydrophobic zeolite is prepared having high Hydrophobicity Index number by calcining a zeolite with steam under turbulent condition with respect to flow pattern of the zeolite and at a temperature within the range of 650-1000°C.

Description

PROCEDURE FOR PREPARING A MODIFIED ZEOLITE This application claims the benefit of the provisional application of E.U.A. No. 60 / 122,697, filed March 3, 1999, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION This invention relates to zeolites which are useful as adsorbents or catalyst supports. In particular, it relates to the production of a hydrophobic zeolite.

BACKGROUND OF THE INVENTION Most zeolites are hydrophilic (which attract water), and thus have a greater preference for the sorption of water than organic materials. However, highly siliceous zeolites tend to be hydrophobic (which attract organic materials). Hydrophobic zeolites are useful in selected applications such as removal of volatile organic compounds from environments containing water. Hydrophobic zeolites tend to have a relatively small number of catalytically active acid sites. These low acidity zeolites are sometimes useful in catalytic processes where the cracking reactions must be minimal. To measure the hydrophobic character of a zeolite, the inventors have developed a selection test by hydrophobic character index. An index of hydrophobic character (H) is calculated from the mass sorption ratio of organic compounds: sorption of water mass at specific partial pressures for the two adsorbates; in this way, we have Hc = Sc Sw for cyclohexane on water and Hn = Sn / Sw for n-hexane on water. Highly hydrophilic zeolites will have H values less than 1.0. Highly hydrophobic zeolites will have H values substantially greater than 1.0. The selection of the adsorbent depends on the pore opening of the structure of the zeolite of interest. It is well known that zeolites with ring openings of metal atoms of 10 members or less will not adsorb substantial amounts of cyclohexane. For these zeolites, for example, ZSM-5, ZSM-11, etc., n-hexane is a much more effective choice for the organic adsorbent. In addition, the partial pressure at which the adsorption is measured can have an effect on the absolute amount of adsorption of any component and also the value of the hydrophobic character index. For the purpose of defining the conditions to which the index is measured (adsorbate and partial pressures), the inventors have adopted the following convention: h / os refers to an index where the adsorption of cyclohexane to 7 torr (1 torr = 133.32 pascals) is with respect to water adsorption at 5 torr. Similarly, H / os refers to an index where the adsorption of n-hexane at 7 torr is with respect to water adsorption at 5 torr.

BRIEF DESCRIPTION OF THE INVENTION A hydrophobic zeolite can be prepared by calcining a precursor zeolite with a molar ratio of silica: alumina of at least 20 under high temperature and the presence of steam and under turbulent conditions with respect to the flow pattern of the zeolite. In particular, a novel hydrophobic Y zeolite is provided by this method, which has a hydrophobic character index (HC0705) greater than 20.

DETAILED DESCRIPTION OF THE INVENTION The inventors have found that by calcining zeolites under a turbulent condition, high temperature and in the presence of steam, a hydrophobic zeolite can be prepared. The turbulent condition arises from the intimate mixture of the solid and the gas phase, so that the characteristic flow pattern of the solid can be considered turbulent. These zeolites are more hydrophobic than the zeolites that can be prepared by steam roasting a zeolite under non-turbulent conditions. Examples of hydrophobic zeolites that can be prepared by this method include, for example, Y zeolite, as well as beta zeolite. It is considered that these zeolites have interconnecting pores of at least two dimensions, preferably two or three dimensional interconnecting pores, more preferably three dimensions. The precursor zeolites (starting material) useful for preparing the hydrophobic zeolites have a molar ratio of silica: alumina of at least 20, preferably from about 25 to about 150. The calcination temperature is on the scale of about 650 ° C, preferably from about 700 ° C to 1000 ° C, preferably up to 850 ° C in the presence of steam. Preferably, the vapor is present in an amount of at least 10% by volume. In particular, the inventors have found that by preparing the zeolite by calcining a zeolite having a ratio of silica: alumina greater than 20, particularly zeoiite Y stabilized under a turbulent condition, high temperature and in the presence of steam, a hydrophobic zeolite can be prepared, particularly a stabilized Y zeolite having a hydrophobic character index (Hco7 / os) greater than 20, preferably at least 25. The highly hydrophobic zeolite products of the invention are prepared from zeolites having the zeolite structure And that is stabilized. These highly hydrophobic zeolites have a hydrophobic character index (HCOz / os) greater than 25, preferably greater than 30. Ultrahydrophobic materials have a hydrophobic character index (HCOO) greater than 30, preferably equal to or greater than about 35. It has surprisingly been found that a highly hydrophobic zeolite Y material can be prepared from a precursor material with a moderate molar ratio of silica: alumina in the range of about 25, preferably from about 40 to about 150, of preferably up to about 120. It has also been surprisingly found that an ultrahydrophobic zeolite Y material can be prepared from a precursor having a molar ratio of silica: alumina greater than about 60, preferably greater than about 75, preferably higher of about 85. The hydrophobic Y zeolite material of the invention can be produced by calcining a zeo lita and stabilized having a unit cell size within the range of less than 24.40, preferably less than 24.35, more preferably less than 24.30, most preferably less than 24.27, preferably greater than 24.15, under turbulent conditions at a temperature within of the scale of about 650 ° C, preferably from about 700 ° C to 1000 ° C, preferably up to 850 ° C in the presence of steam. Preferably, the vapor is present in an amount of at least 10% by volume. The turbulent condition referred to in the present is a condition in which there is sufficient mixture between the solid phase and the gas phase in which the gas flows through the dispersed solid phase without a discernible interface. The condition is not turbulent if the gas phase flows over a stationary solid so that there is a discernible interface between the solid and the gas.

While not wishing it to be limited by theory, it is thought that the superior contact of the solid involved with the reactive gas atmosphere leads directly to the high hydrophobic characteristic of the present invention. It is thought that this condition is satisfied when a substantial portion of the solid particles is continuously and completely surrounded by the reactive gas mixture. This condition can be described as a flow velocity such that a significant fraction of the solid particles has reached the point where they have at least been suspended and are set in motion by the action of the gas. Said speed has often been described as the minimum fluidization velocity. This occurs frequently at Reynolds numbers (NRe!) Less than about 10 (DpGmf / μ). This phenomenon has been described by the following relationship (see Cam, "Fluidization," page 63, McGraw-Hill, New York 1959): where: Gmf = fluid surface mass velocity for minimum fluidization (x 4.88243 Kg-sec / m2) Dp = particle diameter (x .305 m) Gc = dimensional constant, 32.17 (x 1.48 Kg / m) / (. 454 Kg) (sec2) Pf = fluid density (x 16.01 g / l) ps = density of solids (x 16.01 g / l) Fs = particle shape factor, without dimension emf = minimum fluidity void, no dimension μ = viscosity of the fluid (x 1.35 joules / sec) Alternatively, this has been described by an equation similar (see Perry, "Chemical Engineers' Handbook," 4th edition, pp. 4-25, McGraw-Hill, New York): . 23xlQ5Dp2Pf "(Ps - Pf) Gmf = μ where: Gmf = fluid surface mass velocity for minimum fluidization (x 17576. 7 Kg-sec / m2) Dp = particle diameter (x .305 m) Pf = fluid density (x 16.01 g / l) ps = density of solids (x 16.01 g / l) μ = viscosity of the fluid (x 1.35 joules / sec) For the process of the invention, it is preferred to calcinate under a minimum fluidization rate through at least a substantial portion of the zeolite particles in contact with the gas phase, wherein the flow rate has a Reynolds number of at least 5, preferably at least 10. A substantial portion of the zeolite particles is in contact with the gas phase when at least 50%, preferably 85%, more preferably 95%, most preferably 100% the zeolite particles are in contact with the gas phase. To produce a turbulent condition, for example, a fluidized bed calciner or ebullient bed calciner may be used, such as those available from companies such as Procedyne (New Brunswick, N.J.) and A. J. Sackett & Sons (Baltimore, Maryland), and others. This does not mean that it is an exhaustive list of equipment, but only to provide a description of the types of equipment that are suitable for the procedures described herein. The equipment must be operated with sufficient gas phase flow to produce turbulence in the solid and at a temperature and partial pressure of steam effective to produce a hydrophobic zeolite of the invention. The starting stabilized Y zeolite can be prepared from NaY zeolite. NaY zeolite can be produced by any conventional form from water, a source of alumina, a source of silica, and sodium hydroxide. The resulting NaY zeolite has a molar ratio of silica: alumina on the scale of 4.0 to 6.0. The stabilization of this material is achieved by combining ion exchange and steam calcination with at least one step of each. One way of preparing said zeolite is described in the patent of E.U.A. No. 5,059,567, the disclosure of which is incorporated herein by reference, and another in the US patent. No. 4,477,336, the disclosure of which is also incorporated herein by reference. In a method for preparing the starting material, NaY zeolite can be ion exchanged with ammonium solution, such as ammonium sulfate one or more times, and can be washed and dried. The zeolite subjected to ion exchange of ammonium can be calcined at a temperature in the range of 550 ° C to 800 ° C in the presence of steam. This zeolite is then subjected to further ion exchange with an ammonium solution, and then recalculated at a similar temperature scale. After this calcination, the resulting zeolite is dealuminated by contact with mineral acid under conditions such that the desired molar ratio of silica: alumina is achieved. The novel hydrophobic Y zeolite of the invention has a unit cell size in the range of about 24.15, preferably from 24.20 to 24.35, preferably up to 24.28 angstroms. The surface area of these novel hydrophobic zeolite Y materials is preferably at least 500, more preferably at least 600 square meters per gram. The molar ratio (chemical ratio) of silica: alumina remains substantially unchanged from the stabilized precursor zeolite. The adsorption of organic materials is at least 10% by weight at a pressure of 7 torr. Without wishing to be bound by any particular theory, it is speculated that the exceptionally high degree of hydrophobic character obtained in the zeolite materials by the process of this invention, may be due to the modified nature of the interaction between the zeolite solids and the solids. the atmosphere of reactive gas. In the turbulent fluid bed, the degree of intimate contact between all the solid particles and the hydrothermally reactive gas phase is much greater than can be achieved in a static bed or in the bed of moderately cloudy dust present in a rotary kiln. The typical rotary kiln is operated as a continuous process with a constant feed of powder entering one end of a heated pipe, and a constant flow of processed material discharged from the other end. The vapor or air / vapor mixtures that are used in the countercurrent flow to treat the zeolite powder, in accordance with the teachings of the prior art, pass mainly on the solids bed, making its most effective contact only with the solids. solids exposed on the surface of the bed by slow turnover with rotation of the calciner tube. In such equipment, excessive turbulence should normally be prevented to prevent the capture of solids in the gas phase and the loss of kiln material. It is known that the combination of water and high temperature promotes the hydrolysis of structure A1 outside the structure of the zeolite, thereby eliminating load centers from the structure according to the following reaction: (1) [AI04"], H + + 3H20 = [(OH) 4] + Al (OH) 3 where [AI04"] indicates the anionic charge center in the network of the tetrahedral structure, and [(OH) 4] indicates the void of the structure of "Hydroxy nest" created by hydrolysis to generate AI (OH) 3 without structure and related species. The -OH groups in the vacuum bind to Si atoms in the network.

This treatment removes sites in which polar water molecules can be retained by dipole ion interaction. Water can also be bound to the solid by interaction with residual hydroxyl groups (-OH) through the formation of hydrogen bonds. The heat treatment only removes most of the hydroxyl groups in the zeolite materials at temperatures between 500-650 ° C, as indicated by TGA analysis. The hydroxy elimination reaction can be written in its simplest form as: (2) = Si-OH + HO-Si = = = Si-O-Sfe + H20 However, the inventors have discovered that this reaction is not sufficient to substantially conclude the removal of the hydrophilic centers for the zeolites. The inventors have surprisingly discovered that contacting the zeolite with steam under turbulent conditions, at temperatures greater than 650 ° C with steam, produces zeolites that are highly hydrophobic. The inventors now speculate that the forced removal of the hydroxyl groups at high temperature can generate significant stress on the siloxane bonds formed in this way. The structural gaps are especially susceptible to the formation of tension centers. Such deformed bonds possess varying degrees of partial polarization, and this residual polarity provides water sorption sites and reaction inversion (2) when the zeolite material is exposed to aqueous vapor again under more moderate thermal conditions.

In order to minimize such polarized stress sites within the structure of the zeolite, it is necessary to promote the release of tension to a substantial degree by a time-dependent retraction procedure. The mechanism of annealing can involve a continuous and reversible breaking, and the formation of bonds that allow the complete crystalline structure to suffer a progressive relaxation towards minimized residual tension. This mechanism is most effectively catalyzed by the well-known "mineralization action" of water vapor. The hydrothermal treatment of the zeolite materials in a turbulent fluidized bed without tangibly identifiable phase boundaries, seems to lead the hydrophobicization process in zeolite materials to a degree that has not been previously recognized, and which is not achievable by the treatment of non-fluidized material for comparable times under equivalent hydrothermal conditions. Since the inventors think that the optimal annealing procedure involves a uniform minimization of the residual stress energy along the structure of each crystal, there is reason to assume that the mechanism will be more effective for treatments that expose the zeolite particles. and particularly to the crystals at uniform conditions of heat transfer and contact with water vapor that is independent of any direction in space due to equipment or powder bed configuration. Although it would not be surprising to find differences in the response of different crystal structures to this isotropic environmental condition, the inventors think that the treatment given to the zeolites by the process of this invention is expected to move the material in the hydrophobic direction in any case. improved. These novel zeolites can be useful as absorbers for organic materials.

EXAMPLES The following examples illustrate certain embodiments of the invention. These examples are not given to establish the scope of the invention, which is described in the description and claimed in the claims. The proportions are given in parts by weight (pbw), weight percent, moles or equivalents.

X-ray diffraction The X-ray diffraction patterns of the Y zeolites prepared in the examples were determined. Relative crystallinity was determined by the test method of ASTM D3906-97, standard test method for the determination of the relative intensities of X-ray diffraction of materials containing faujasite-type zeolite. The network constants were determined by the method of ASTM D3942-97, standard test method for the determination of the unit cell dimension of a faujasite-type zeolite. The sharp peaks of the XRD spectra of the Y zeolite prepared by the present method also indicate its good crystallinity and lack of defects or amorphous material.

Surface area The surface areas of the zeolite samples were determined by the ASTM test method (D3663-92). This method uses a modification of the surface area measurement technique by gas adsorption described by Brunauer, Emmett and Teller (BET). Zeolite was calcined in air at 500 ° C for a period of 4 hours, and then degassed by heating under vacuum at 350 ° C to remove the sorbed vapors. The samples were then cooled to the temperature of the liquid nitrogen. The amount of nitrogen adsorbed at low pressure is determined by measuring the pressure difference after introducing a fixed volume of nitrogen into the sample. Under these conditions, nitrogen is sucked into the micropores of the zeolite. The measurement of volumetric sorption is measured at P / Po pressure levels between 0.02 and 0.05. The magnitude of the sorbed nitrogen is calculated using the BET equation.

Mass sorption Sorption of water mass and organic materials was measured (cyclohexane or n-hexane) using a RXM-100 multifunctional catalyst characterization and testing machine from Advanced Scientific Design, Inc. For the water sorption test, approximately 20 milligrams of zeolite samples were used. The zeolites dried perfectly before measuring. The samples were pretreated by heating the sample from 20 ° C to 500 ° C at 20 ° C / min under uneven vacuum, and kept at 500 ° C for 1 hour under high vacuum. The reactor containing the sample is maintained at 25 ° C using a water bath. Total water adsorption is measured by first introducing water vapor at an initial pressure, resulting in the desired final pressure after 5 minutes of adsorption. To obtain a complete isotherm from 10 to 12, final pressure points were measured at final pressures between 0.5 and 12 torr, with the last point being approximately 12 torr. To correct the condensation of water vapor in the walls, an empty reactor was operated in a similar way, and subtracted from the test results to obtain the net adsorption. For sorption tests of organic materials, approximately 100 mg of zeolite samples were used. The zeolites dried perfectly before measuring. The samples were pretreated by heating the sample from 20 ° C to 500 ° C at 20 ° C / min under uneven vacuum, and kept at 500 ° C for 1 hour under high vacuum. The reactor containing the sample is maintained at 25 ° C using a water bath. The total adsorption of the organic material is measured by first introducing steam from the organic material at an initial pressure, resulting in the desired final pressure after 3 minutes of adsorption. To obtain a complete isotherm from 6 to 8, final pressure points were measured at final pressures between 0.5 and 45 torr, the last point being approximately 45 torr.

The Chemis Analysis v 5.04 program was used to generate the isotherm. The data used to calculate the index of hydrophobic character were chosen at 5 torr for water and 7 torr for cyclohexane, to ensure values found in the monomolecular cover. An alternative method was used to measure some of the samples using a Landolt type sorption apparatus (see Landolt, George R., Analytical Chemistry, 43, 613 (1971)). Samples were pretreated by heating the sample in a ventilated muffle furnace with a 3 ° C / min jump, and maintained at 520 ° C for 4 hours. Cyclohexane sorption measurements were carried out at a pressure of 40 mm (torr) at room temperature (21-25 ° C). Sorption was measured as mass difference after equilibrium was reached (typically, after about 20 minutes). The water sorption measurements were carried out at a pressure of 11 torr at room temperature, or in a constant humidity desiccator containing a saturated solution of magnesium nitrate. A correlation to convert the data generated by the alternative method to the pressure points used for the RXM-100 method, was derived empirically from the data generated from the RXM method at multiple pressure points.

Methanol Adsorption Methanol adsorption measurements were made using a RXM-100 multifunctional catalyst characterization and testing machine from Advanced Scientific Design, Inc. 80 to 100 mg of zeolite samples were used. The zeolites dried perfectly before measuring. Samples were pretreated by heating the sample for 20 ° C to 500 ° C at 20 ° C / min under uneven vacuum, and kept at 500 ° C for 1 hour under high vacuum in a BET reactor. The reactor containing the sample is maintained at 25 ° C using a water bath. Methanol vapor is introduced at about 40 torr, and the pressure is recorded initially and after a stabilization reading interval of 3 to 5 minutes. This step is repeated until the desired final pressure is reached. The Chemis Analysis v 5.04 program was used to generate the isotherm.

Base titration Approximately 10 grams of zeolite (100 ml of H20) was titrated using aqueous solution of 1 M NH 4 OH to a final pH of about 9 ± 0.01.

PH treatment An NH 4 OH solution was used to treat the zeolite to an appropriate pH level for a sufficient time to reach a stable pH.

Calcination method 1 This is the process of the invention. Zeolite was introduced into a conical-shaped fluid bed design (BCF) calciner, and heated to a temperature of 750-770 ° C under fluidizing conditions using a vapor / air mixture, and maintained at temperature at typical intervals specified from 30 minutes to 4 hours. The vaporizing / air fluidizing mixture is on the approximate scale of 60/40 to 80/20. The steam flow is then discontinued, and the fluidization medium is changed to air alone. The product is then transferred to a chiller with air only for about 30 minutes.

Calcination method 2 This is a comparative procedure using a rotating calciner where calcination occurred without turbulence. 6.81 kg of zeolite are loaded into a cylinder with a diameter of 139.7 cm in length and 38.1 cm in length, which has two deflectors of 2.54 cm located opposite each other. The calciner with the cylinder is heated to approximately 398.8 ° C, while the cylinder is rotated at 6 RPM. The typical heating time is 3 Vz hours. Steam is maintained at 100% by injecting 18 ml per minute of H2O, and without air in the rotating cylinder. The contact time with the steam is 1 to 2 hours. Steam and / or air was injected above the bed of the zeolite powder, so that there would be a discernible interface between the gas phase and the solid phase.

Calcination method 3 This is a comparative procedure under fixed bed condition. The system consists of an alloy vessel (sample chamber) contained within a muffle furnace with superior ventilation, to which air and steam are supplied. The oven is heated from 110 ° C to 760 ° C. The vessel is supplied with steam that varies in water content (air / water), made from a steam generator with temperatures ranging from 400 ° C-450 ° C. Steam is added to the sample chamber at approximately 250 ° C. The air flow is 500 ml / min. The volume percent of steam is regulated by the flow of liquid water to the steam generator. The oven is heated to the desired calcination temperature. Steam is forced through the sample by camera design and sample support. The sample holder is an open steel cylinder 10 cm in diameter with 1.4 cm in height that can hold approximately 15 to 25 grams of zeolite. The zeolite is supported on a bed of quartz mats fiber over the top of the perforated steel bottom sample holder that allows steam to flow uniformly through the sample.

Zeolite Material A and Stabilized Starting A procedure similar to Example 1 of the US Pat.

E.U.A. No. 5,059,567, except that ammonium chloride was used in place of ammonium sulfate. The Hco7 / os of this zeolite material A is from about 6 to 8. The properties of the precursor zeolites are given in Table 1 below. The network constant of A was 24.24.

B Material of Zeolite Y Stabilized Starting A procedure similar to the starting material A was used, except that the exchange step of aluminum sulfate was removed. The Hco7 / o5 of this zeolite material B is from about 7 to 9. The properties of the precursor zeolites are given in Table 1 below. The constant of the network of B was 24.25-24.26.

EXAMPLES 1 TO 14 These examples illustrate the preparation of the hydrophobic Y zeolite of the invention. The zeolites A or B used as starting material described above were calcined under various conditions as indicated in Table 1 below. The calcination method 1 was used to calcine this material to obtain the products of this invention. The properties of the products are given in Tables 1-2, 4-5 below.

COMPARATIVE EXAMPLE A This is a comparative example where the starting material B was calcined using the calcination method 2. The properties of the starting material, the process conditions and the properties of the products are given in the following tables 3, 4 and 5 .

COMPARATIVE EXAMPLE B This is a comparative example where the starting materials A or B were calcined using the calcination method 3. The properties of the starting material, the process conditions and the properties of the products are given in tables 3, 4 and 5 following COMPARATIVE EXAMPLE C This is a comparative example where the hydrophobic character index of a commercially available Y zeolite having a molar ratio of silica: alumina of 200, HSZ-390HUA, from Tosoh Corporation was measured. The result is given in table 3.

EXAMPLE 15 Adsorption of methanol on the hydrophobic Y zeolite of the invention The physical sorption of methanol (MetOH) on the hydrophobic Y zeolite of the invention of Example 3, resulted in unusual adsorption isotherms at temperatures of 0 to 60 ° C. These type 5 or type 6 isotherms showed an acute adsorption step close to p / p0 ~ 0.2, which is markedly different from the type 1 adsorption isotherms that are usually observed in microporous materials and also from the isotherms of typical type 3 for the adsorption of alcohols or water on most hydrophobic surfaces. Except for an article, U. Müller, KK Unger, Characterization of Porous Solids (Ed. By KK Unger et al., Elsevier, Amsterdam) 101 (1988), which describes the adsorption of N2 on ZSM5 to about 77K, the inventors they have not found any report in the open literature that describes an acute adsorption step near p / p0 ~ 0.2 for some adsorbate on microporous silicates or aluminosilicates (zeolites). As table 6 indicates, the adsorption of MetOH gives a type 1 adsorption isotherm on the material A of stabilized starting zeolite Y, which is a source compound of hydrophobic Y zeolite. Acetone, H2O and cyclohexane also have type 1 isotherms on the hydrophobic Y zeolite of the invention. The adsorption isotherms are grouped into classes originally proposed by Brunauer, Deming, Deming and Teller (BDDT), (1) S. Brunauer, L. S. Deming, W. S. Deming, E. Teller, Journal of American Chemical Societv. 62, p. 1723 (1940), citation sometimes referred to as Brunauer, Emmett and Teller (BET), (2) S. Brunauer, P. H. Emmett, E. Teller, Journal of American Chemical Societv, 60, p. 309 (1938), or Brunauer, (3) S. Brunauer, The Adsorption of Gases and Vapors, Oxford University Press (1945), and further described by Gregg and Sing (4) SJ Gregg, KSW Sing, Adsorption, Surface Area and Porosity, 2a. edition, Academic Press, Inc. (1982), chapter 1. The results of the development of molecular models indicate that the singular form of the MetOH adsorption isotherms on the hydrophobic Y zeolite of the invention, can be directly related to the structure specific for the dealuminated Y zeolite. The visualization of the adsorption process on the alumina-free zeolite Y suggests that only a small number of MetOH molecules can accumulate in the curved corners of the supeoils at vapor pressures of MetOH p / po <; 0.1. This is understandable when one considers that the forces of attraction between the sorbate and the surface are weak, but the force field around the methanol molecules is strongest in the curved corners of the supertouches near the entrance of the cuboctahedral units. Apparently, the MetOH concentration is sufficient for there to be a substantial sorbato-sorbate interaction at p / p0 ~ 0.1, where condensation-like processes occur within the micropores, which results in the saturation of the zeolite pores by methanol Once this happens, only a small part of the crystal network remains unfilled; in this way, the adsorbed amount of methanol will only increase slightly when the vapor pressure increases to p / p0 > 0.1. These hydrophobic Y zeolites of the invention are useful as adsorbents for polar hydrocarbon materials, particularly alcohol.

TABLE 1 TABLE 2 Methanol adsorption data TABLE 3 (1) Empirical number generated from measured values of Hc4o / n- IS) (2) Measured as values of Hc07 / o5- TABLE 4 Baseline titling data * Due to light over titration (pH of about 9.08) not counted on average.

TABLE 5 Treatment data with pH TABLE 6

Claims (28)

NOVELTY OF THE INVENTION CLAIMS

1. - A process for preparing a hydrophobic zeolite, characterized in that it comprises calcining a zeolite having a molar ratio of silica: alumina of at least 20, at a temperature in the range of about 650 ° C to about 1000 ° C in the presence of steam and under a turbulent condition with respect to the flow pattern of the zeolite for at least 15 minutes, thereby producing the hydrophobic zeolite.

2. The process according to claim 1, further characterized in that the zeolite has a molar ratio of silica: alumina of at least 40.

3. The process according to claim 1, further characterized in that the partial pressure of steam is at least 10% by volume.

4. The method according to claim 1, further characterized in that the zeolite to be calcined is a two-dimensional or three-dimensional interconnected zeolite.

5. The process according to claim 4, further characterized in that the zeolite to be calcined is a three-dimensional interconnected zeolite.

6. The process according to claim 5, further characterized in that the zeolite to be calcined is zeolite Y having a unit cell size less than or equal to 24.40 angstroms.

7. The process according to claim 6, further characterized in that the zeolite to be calcined is zeolite Y having a unit cell size less than or equal to 24.30 angstroms.

8. The process according to claim 1, further characterized in that the zeolite is calcined under a minimum fluidization rate, although at least a substantial portion of the particles of the zeolite is in contact with a gas phase whose flow rate has a Reynolds number of at least 5.

9. The method according to claim 1, further characterized in that the turbulent condition is produced by calcining the zeolite in a fluidized calciner.

10. The process according to claim 9, further characterized in that the zeolite to be calcined is a three-dimensional interconnected zeolite.

11. The process according to claim 10, further characterized in that the zeolite to be calcined is zeolite Y having a unit cell size less than or equal to 24.40 angstroms.

12. The process according to claim 11, further characterized in that the Y zeolite is prepared by exchanging with ammonium a NaY zeolite, and dealuminating the Y zeolite exchanged with ammonium.

13.- A hydrophobic Y-zeolite having a unit cell size on the scale of 24.15 to 24.40, silica molar ratio: alumina greater than 20 and hydrophobic character index (Hco7 / os) greater than 30.

14.- The zeolite hydrophobic according to claim 13, further characterized in that the molar ratio of silica: alumina is greater than about 60.

15.- The hydrophobic Y zeolite according to claim 14, further characterized in that the index of hydrophobic character (Hco7 / os ) is greater than 35.

16.- The hydrophobic Y zeolite according to claim 15, further characterized in that the unit cell size is in the range of 24.15 to 24.35.

17.- Hydrophobic Y zeolite in accordance with the claim 15, further characterized in that the hydrophobic zeolite has a surface area of at least 500 m2 / g.

18.- Hydrophobic Y zeolite having a unit cell size in the range of 24.15 to 24.40, silica: alumina molar ratio greater than 30 to 150 and hydrophobic character index (Hco7 / os) greater than 25.

19.- The hydrophobic Y zeolite according to claim 18, further characterized in that the molar ratio of silica: alumina is in the range of 40 to 100.

20. - The hydrophobic Y zeolite according to claim 19, further characterized because the unit cell size is in the range of 24.15 to 24.35.

21. The hydrophobic Y zeolite according to claim 18, further characterized in that the hydrophobic character index (Hco7 / os) is greater than 30.

22. The hydrophobic Y zeolite according to claim 18, further characterized in that the hydrophobic character index (Hco7 / os) is greater than 35.

23.- Hydrophobic Y zeolite in accordance with the claim 18, further characterized in that the hydrophobic zeolite has a surface area of at least 500 m2 / g.

24. The hydrophobic Y zeolite according to claim 18, further characterized in that the molar ratio of silica: alumina is in the range of 40 to 100.

The hydrophobic Y zeolite according to claim 22, further characterized in that the molar ratio of silica: alumina is in the range of 40 to 100.

26.- A hydrophobic Y-zeolite having a unit cell size on the scale of 24.15 to 24.40, silica molar ratio: alumina greater than 20, and has an isotherm of type 5 or type 6 for physical sorption of methanol.

27. - The use of the hydrophobic Y zeolite as claimed in claim 26, as an adsorbent of polar hydrocarbon material.

28. The use as claimed in claim 27, wherein the polar hydrocarbon material is alcohol.