BONDED ZEOLITES AND PROCESS FOR PREPARING THEM

Abstract: Zeolites having a pore diameter comprised within the range of from 5 to 12 Å are bonded with amorphous oligomeric silica, by dispersing them in an aqueous solution of silica and alkylammonium hydroxide, and submitting the obtained suspension to a quick drying.

Description: This invention relates to a process for preparing bonded zeolites, and, more particularly, zeolites bonded with oligomeric silica. Bonded zeolites are known to have an improved mechanical resistance, which is useful for exploitation in various industrial processes. The production methods of the prior art, however, are impaired by the defect that the zeolite cavities are partially occluded, whereby their activity is compromised. EP-A-0 200 260 discloses a process for preparing a titanium silicalite bonded with oligomeric silica, in which the molar ratio of oligomeric silica to titanium silicalite is from 0,05 to 0,11: said bonded zeolite is prepared by hydrolyzing a tetraalkyl-orthosilicate in an aqueous solution of a tetraalkylammonium hydroxide at a temperature from ambient to 200°C and for a time of from 0,2 hour to 10 hours, whereupon titanium silicalite crystals are slurried in the liquid phase thus obtained, and the resultant slurry is rapidly dried. With a view to overcoming the defects of the prior art approaches referred to above, the present invention provides a process for preparing zeolites bonded with oligomeric silica, comprising the steps of: (a) mixing an aqueous slurry of: a zeolite selected from: calcined and anhydrous zeolites, facultatively exchanged with ammonium ions; non-calcined damp zeolites prepared hydrothermally and containing ammonium-or alkylammonium counter-cations, in the facultative presence of ammonium- or alkylammonium hydroxides, and having a pore diameter of from 0,5 nm to 1,3 nm, with an aqueous solution of oligomeric silica and an alkylammonium hydroxide, the percentage by weight of the zeolite in said slurry being from 20% to 50%, the molar ratio of oligomeric silica to alkylammonium hydroxide in said solution being from 0,05 to 0,2, and the molar ratio of the oligomeric silica to water being from 0,025 to 0,0125, and (b) rapidly drying the resultant mixture, characterized in that a zeolite based on: 1) Si, Al and B; 2) Si, Al and Ti; 3) Si, Ti and Fe; 4) Si and Ti; 5) Si and B; 6) Zeolite ZSM-5; 7) Zeolite ZSM-11, and 8) Zeolite T, is used, in which the weight ratio of the oligomeric silica to the zeolite in the mixture resultant from stage (a) is from 5:95 to 20:80, the 5:95 to 10:90 range being excluded in the case of a Si- and Ti-based zeolite. The alkylammonium hydroxide is selected among those having a C1-C5 alkyl: preferred is tetrapropylammonium hydroxide, and among the tetraalkyl orthosilicates tetraethylorthosilicate is preferred. The aqueous solution of silica and alkylammonium hydroxide is prepared by hydrolyzing a tetraalkyl orthosilicate in an aqueous solution of an alkylammonium hydroxide at a temperature of from 2°C to 120°C for a time of from 0,2 hour to 24 hours. Zeolites having a pore size of from 0,5 nm to 1,3 nm have proven particularly suitable for the process as outlined above. The zeolite crystals, under the process conditions specified in the foregoing, are encaged with each other by Si-O-Si bridges and are in the form of micropsheres having a diameter of from 5 µm to 1 mm. According to a particular embodiment of the process defined hereinabove, a zeolite, based on Si, Al and B is used, which has, in its anhydrous and calcined state, the following molar composition: pHAlO₂ . qB₂O₃ . SiO₂ (1) in which p is from 0,034 to 0,0050, and q is from 0,1 to 0,005, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HAlO₂ being at least partially replaceable by cations, said zeolite (1) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,112 ± 0,01 very strong 0,998 ± 0,01 strong 0,974 ± 0,01 medium 0,634 ± 0,007 medium to weak 0,597 ± 0,007 medium to weak 0,424 ± 0,005 medium to weak 0,384 ± 0,004 strong 0,381 ± 0,004 strong 0,373 ± 0,004 strong 0,371 ± 0,004 strong 0,363 ± 0,004 medium 0,304 ± 0,002 medium to weak 0,297 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 890 to 920 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. According to another embodiment of the process defined hereinabove, a zeolite, based on Si, Al and Ti is used, which has, in its anhydrous and calcined state, the following molar composition: pHAlO₂ . qTiO₂ . SiO₂ (2) in which p is up to 0,050, and q is up to 0,025, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HAlO₂ being at least partially replaceable by cations, said zeolite (2) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,114 ± 0,01 very strong 0,999 ± 0,01 strong 0,974 ± 0,01 medium 0,636 ± 0,007 medium to weak 0,599 ± 0,007 medium to weak 0,426 ± 0,005 medium to weak 0,386 ± 0,004 strong 0,382 ± 0,004 strong 0,375 ± 0,004 strong 0,372 ± 0,004 strong 0,365 ± 0,004 medium 0,305 ± 0,002 medium to weak 0,299 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 960 to 975 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. According to a further embodiment of the process defined hereinabove, a zeolite, based on Si and Ti is used, which has, in its anhydrous and calcined state, the following molar composition: xTiO₂ . (1-x) SiO₂ (3) wherein x is from 0,0005 to 0,004, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%. According to yet another embodiment of the process defined hereinabove, a zeolite, based on Si, Ti and Fe is used, which has, in its anhydrous and calcined state, the following molar composition: pHFeO₂ . qTiO₂ . SiO₂ (4) in which p is up to 0,050, and q is up to 0,025, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite (4) is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HFeO₂ being at least partially replaceable by cations, said zeolite (1) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,114 ± 0,01 very strong 0,999 ± 0,01 strong 0,974 ± 0,01 medium 0,636 ± 0,007 medium to weak 0,599 ± 0,007 medium to weak 0,426 ± 0,005 medium to weak 0,386 ± 0,004 strong 0,382 ± 0,004 strong 0,375 ± 0,004 strong 0,372 ± 0,004 strong 0,365 ± 0,004 medium 0,305 ± 0,002 medium to weak 0,299 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 960 to 975 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. In summation, a distinctive feature of the zeolites bonded with oligomeric silica, prepared by the process of the present invention, is that the crystals of a zeolite based on: 1) Si, Al and B; 2) Si, Al and Ti; 3) Si, Ti and Fe; 4) Si and Ti; 5) Si and B; 6) Zeolite ZSM-5; 7) Zeolite ZSM-11, and 8) Zeolite T, are encaged with each other by Si-O-Si bridges and are in the form of microspheres having a diameter of from 5 µm to 1 mm, the weight ratio of the oligomeric silica to the zeolite concerned in the mixture of an aqueous slurry of said zeolite with an aqueous solution of oligomeric silica and alkylammonium hydroxide used for their preparation being from 5:95 to 20:80, the 5:95 to 10:90 range being excluded in the case of an Si- and Ti-based zeolite. Zeolites 1, 2, 3, 4, 5, 6, 7 and 8 are prepared by means of the following procedures: Zeolite 1 : Under hydrothermal conditions a silicon derivative, a boron derivative, an aluminum derivative and a nitrogenous organic base are reacted, with an SiO₂/Al₂O₃ molar ratio of the reactants larger than 100, preferably comprised within the range of from 300 to 400, an SiO₂/B₂O₃ molar ratio of the reactants comprised within the range of from 5 to 50, an H₂O/SiO₂ molar ratio of the reactants preferably comprised within the range of from 20 to 40, possibly in the presence of one or more alkali- and or alkali-earth-metal salts and/or hydroxides, with a molar M/SiO₂ ratio (wherein M is the alkali- and/or alkali-earth-metal cation) of the reactants smaller than 0.1, preferably smaller than 0.01, or equal to zero. In the empirical formula of the material, aluminum has been shown in HAlO₂ form, to underline that the material is in the H⁺ form. When the ratios between the various reactants are discussed, for aluminum the Al₂O₃ form is used, in that it is the most usual. The silicon derivative is selected from silica gel, silica sol and alkyl-silicates, among which tetraethyl-silicate is the most preferred; the boron derivative is selected from boric acid and the organic derivatives of boron, such as, e.g., alkyl-borates, preferably triethyl-borate; the aluminum derivative is selected from its salts, such as, e.g., the halides and the hydroxides, and its organic derivatives, such as, e.g., the alkyl aluminates, preferably isopropyl-aluminate. The nitrogenous organic base can be an alkyl-ammonium hydroxide, preferably tetrapropyl-ammonium hydroxide. In case tetrapropyl-ammonium hydroxide is used, the TPA⁺/SiO₂ ratio (wherein TPA = tetrapropyl-ammonium) of the reactants is comprised within the range of from 0.1 to 1, preferably of from 0.2 to 0.4. The reactants are reacted by operating at a temperature comprised within the range of from 100 to 200°C, preferably comprised within the range of from 160 to 180°C, at a pH comprised within the range of from 9 to 14, preferably of from 10 to 12, and for a time ranging from 1 hour to 5 days, preferably of from 3 hours to 10 hours. Zeolite 2 : Under hydrothermal conditions a silicon derivative, a titanium derivative, an aluminum derivative and a nitrogenous organic base are reacted, with an SiO₂/Al₂O₃ molar ratio of the reactants larger than 100, preferably comprised within the range of from 300 to 400, an SiO₂/TiO₂ molar ratio of the reactants larger than 5, preferably comprised within the range of from 15 to 25, an H₂O/SiO₂ molar ratio of the reactants preferably comprised within the range of from 10 to 100, more preferably within the range of from 30 to 50, possibly in the presence of one or more alkali- and or alkali-earth-metal salts and/or hydroxides, with a molar M/SiO₂ ratio (wherein M is the alkali- and/or alkali-earth-metal cation) of the reactants smaller than 0.1, preferably smaller than 0.01, or equal to zero. In the empirical formula of the material, aluminum has been shown in the HAlO₂ form, to underline that the material is in the H⁺ form. When the ratios between the various reactants are discussed, for aluminum the Al₂O₃ form is used, in that it is the most usual. The silicon derivative is selected from silica gel, silica sol and alkyl-silicates, among which tetraethyl-silicate is the most preferred; the titanium derivative is selected from the salts, such as, e.g., the halides, and the organic derivatives of titanium, such as, e.g., alkyl-titanates, preferably triethyl-titanate; the aluminum derivative is selected from its salts, such as, e.g., the halides and the hydroxides, and its organic derivatives, such as, e.g., the alkyl aluminates, preferably isopropyl-aluminate. The nitrogenous organic base can be an alkyl-ammonium hydroxide, preferably tetrapropyl-ammonium hydroxide. In case tetrapropyl-ammonium hydroxide is used, the TPA⁺/SiO₂ ratio (wherein TPA = tetrapropyl-ammonium) of the reactants is comprised within the range of from 0.1 to 1, preferably of from 0.2 to 0.4. The reactants are reacted by operating at a temperature comprised within the range of from 100 to 200°C, preferably comprised within the range of from 160 to 180°C, at a pH comprised within the range of from 9 to 14, preferably of from 10 to 12, and for a time ranging from 1 hour to 5 days, preferably of from 3 hours to 10 hours. Zeolite 3 : Under hydrothermal conditions a silicon derivative, a titanium derivative, an iron derivative and a nitrogenous organic base are reacted, with an SiO₂/Fe₂O₃ molar ratio of the reactants larger than 50, preferably comprised within the range of from 150 to 600, an SiO₂/TiO₂ molar ratio of the reactants larger than 5, preferably comprised within the range of from 15 to 25, an H₂O/SiO₂ molar ratio of the reactants preferably comprised within the range of from 10 to 100, more preferably within the range of from 30 to 50, possibly in the presence of one or more alkali- and or alkali-earth-metal salts and/or hydroxides, with a molar M/SiO₂ ratio (wherein M is the alkali- and/or alkali-earth-metal cation) of the reactants smaller than 0.1, preferably smaller than 0.08, or equal to zero. In the empirical formula of the material, iron has been shown in HFeO₂ form, to underline that the material is in H⁺ form. When the ratios between the various reactants are discussed, for iron the Fe₂O₃ form is used, in that it is the most usual. The silicon derivative is selected from silica gel, silica sol and alkyl-silicates, among which tetraethyl-silicate is the most preferred; the titanium derivative is selected from the salts, such as, e.g., the halides, and the organic derivatives of titanium, such as, e.g., alkyl-titanates, preferably tetraethyl-titanate; the aluminum derivative is selected from its salts, such as, e.g., the halides or the nitrates, the hydroxides, and the organic derivatives, such as, e.g., the alkoxides. The nitrogenous organic base can be an alkyl-ammonium hydroxide, preferably tetrapropyl-ammonium hydroxide. In case tetrapropyl-ammonium hydroxide is used, the TPA⁺/SiO₂ ratio (wherein TPA = tetrapropyl-ammonium) of the reactants is comprised within the range of from 0.1 to 1, preferably of from 0.2 to 0.4. The reactants are reacted by operating at a temperature comprised within the range of from 100 to 200°C, preferably comprised within the range of from 160 to 180°C, at a pH comprised within the range of from 9 to 14, preferably of from 10 to 12, and for a time ranging from 1 hour to 5 days, preferably of from 3 hours to 10 hours. Zeolite 4 : Preparation according to US-A-4,410,501. Zeolites 5 : Zeolites based on Si and B of A, B, C and D type; preparations according to FR-A-2,429,182; and of the types disclosed in FR-A-2,526,414; and in EP-A-98,641: for their preparation, reference is made to the above cited patent literature. Zeolite 6 : ZSM-5; preparation as disclosed by US-A-3,702,886 and Reissue US-A-29,948. Zeolite 7 : ZSM-11; preparation according to US-A-3,709,979. Zeolite 8 : T Zeolite; preparation according to DE-A-3,139,355. The following Examples illustrate the specific preparations of some of the zeolites used, and some specific preparations of the zeolites with bonding agent. Example 1: Zeolite 1 67.8 g of Al(NO₃)₃.9H₂O is dissolved in 1,275 g of ethyl alcohol and to the so-obtained solution 2,819 g of tetraethyl-silicate is added, with stirring until a homogeneous and clear solution is obtained. To a stainless-steel vessel 1,036 g of deionized water, 8,878 g of an aqueous solution at 15.5% by weight of tetrapropyl-ammonium (TPA⁺) hydroxide and 167.5 g of boric acid powder are charged in the order shown, with stirring. When all the acid has gone into solution, to this latter solution the previously obtained solution is added, and the mixture is stirred, while being heated at 60°C for approximately 4 hours, and anyway until the hydrolysis of the silicate is complete and the ethyl alcohol present is nearly completely removed. The molar composition of the reaction mixture is the following: SiO₂/Al₂O₃ = 150; SiO₂/B₂O₃ = 10; TPA⁺/SiO₂ = 0.5; H₂O/SiO₂ = 35. The so-obtained solution is charged to an autoclave equipped with stirring means, and is heated, under its autogenous pressure, at 170°C, for 4 hours. The discharged product is centrifuged, and the centrifuge cake is carefully dispersed in 70 litres of deionized water; the obtained suspension is centrifuged again, yielding a washed cake. A portion of the obtained product is calcined in air for 5 hours at 550°C, and at the end it shows to be a zeolite having, in the anhydrous form, the following composition: 0.0098 Al₂O₃; 0.0108 B₂O₃; SiO₂. Example 2: Zeolite 1 with Bonding Agent The zeolite is prepared as disclosed in Example 1, then 219 g of tetraethyl-silicate is added, with vigorous stirring, to 234 g of aqueous solution of tetrapropyl-ammonium hydroxide at 12% by weight, and the reaction mixture is stirred for 1 hour at 60°C; then, 958 g of demineralized water is added to it, and stirring is continued for a further hour. A clear solution is thus obtained, inside which 875 g of the centrifuging cake of zeolites of Example 1, prepared as above said, containing 9% by weight of TPA⁺, 26% by weight of water and 65% by weight of zeolite 1 is added. The milky suspension resulting from the dispersion is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomized product is charged to a muffle under a N₂ atmosphere, and is heated up to 550°C. After a 2-hour stay at that temperature under N₂, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air. The obtained product has the following molar composition: 0.0088 Al₂O₃; 0.0097 B₂O₃; SiO₂. Example 3: Zeolite 2 27 g of aluminum isopropoxide is dissolved in 5,400 g of solution at 18.7% by weight of tetrapropyl-ammonium hydroxide. Separately, 230 g of tetraethyl-orthotitanate is dissolved in 4,160 g of tetraethyl-silicate, and this solution is added to the previous one, with stirring. The resulting mixture is heated up to 50-60°C, always with stirring, until a single-phase solution is obtained; then, 10,000 cc of water is added. The so-obtained solution is charged to ah autoclave and is heated, under its autogenous pressure, at 170°C, for 4 hours. The product discharged from the autoclave is centrifuged and washed twice by re-dispersion and centrifugation. A portion of the washed centrifuge cake is calcined in air for 5 hours at 550°C, and at the end it shows to be a zeolite having, in the anhydrous form, the following composition: 0.0081 Al₂O₃; 0.0250 TiO₂ ; SiO₂. Example 4: Zeolite 2 with Bonding Agent The zeolite is prepared as in Example 3, then 320 g of of tetraethyl-silicate is added with vigorous stirring to 340 g of an aqueous solution of tetrapropyl-ammonium hydroxide at 12% by weight, and the resulting mixture is stirred 1 hour at 60°C; then, 1,400g of demineralized water is added, and the solution is kept stirred a further hour. A clear solution is so obtained, into which 1,280 g is carefully dispersed of the washed centrifugation cake of zeolite 2, prepared as disclosed above, containing 9% by weight of TPA⁺ and 26% by weight of water, and 65% of zeolite 2. The milky suspension resulting from the dispersion is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomized product is charged to a muffle under a N₂ atmosphere and is heated up to 550°C. After a 2-hour stay at that temperature, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air. The obtained product has the following molar composition: 0.0073 Al₂O₃; 0.0225 TiO₂; SiO₂. Example 5: Zeolite 3 This Example illustrates the preparation of titanium-ferrosilicalite. 20.2 g of Fe(NO₃)₃.9H₂O is dissolved in water, and from the solution the hydroxide is precipitated by means of the addition of ammonium hydroxide. The precipitate is filtered off, and is washed by being re-dispersed in cold water and filtered until the filtrate turns to neutral. The damp hydroxide is then dissolved in 2,700 g of solution of tetrapropyl-ammonium hydroxide at 18.7% by weight. Separately, 114 g of tetraethyl-orthotitanate is dissolved in 2,080 g of tetraethyl-orthosilicate, and this solution is added to the previous one, with stirring. The resulting mixture is heated up to 50-60°C, always with stirring, until a single-phase solution is obtained; then, 5,000 cc of water is added. The so-obtained solution is charged to an autoclave and is heated, under its autogenous pressure, at 170°C, for 4 hours. The product discharged from the autoclave is centrifuged and washed twice by re-dispersion and centrifugation. A portion of the washed centrifuge cake is calcined in air 4 hours at 550°C, and at the end it shows to be a zeolite having, in the anhydrous form, the following composition: 0.0025 Fe₂O₃; 0.0208 TiO₂; SiO₂. Example 6: Zeolite 3 with Bonding Agent The zeolite is prepared as in Example 5, then 162 g of tetraethyl-silicate is added with vigorous stirring to 173 g of a solution of tetrapropyl-ammonium hydroxide at 12% by weight, and the resulting mixture is stirred 1 hour at 60°C; then, 709 g of demineralized water is added, and the solution is kept stirred a further hour. A clear solution is so obtained, into which 720 g is carefully dispersed of the centrifugation cake of zeolite 3, prepared as disclosed above, containing 9% by weight of TPA⁺, 26% by weight of water, and 65% by weight of zeolite 3. The milky suspension resulting from the dispersion is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomized product is charged to a muffle under an N₂ atmosphere and is heated up to 550°C. After a 2-hour stay at that temperature, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air. The obtained product has the following composition: 0.0025 Fe₂O₃; 0.0188 TiO₂; SiO₂. Example 7: Zeolite 4 A Titanium-Silicalite zeolite is prepared according to Example 1 of US patent No. 4,410,501: 4,160 g of tetraethyl-silicate is charged to a pyrex-glass beaker, and to it, 137 g of tetraethyl-titanate firstly, and then 7,310 g of an aqueous solution at 25% by weight of tetrapropyl-ammonium hydroxide are added with stirring. The reaction mixture is kept stirred approximately 5 hours at 80°C, and then demineralized water is added, up to the volume of approximately 14 litres. The obtained mixture is charged to an autoclave, and is left standing 10 days at 175°C under its autogenous pressure. The crystalline solid discharged from the autoclave is washed, dried and calcined at 550°C. The X-ray and I.R. analyses show that it is titanium-silicalite. Example 8: Zeolite 4 with Bonding Agent The zeolite is prepared as in Example 7; then, 370 g of tetraethyl-silicate is added, with vigorous stirring, to 395 g of aqueous solution of tetrapropyl-ammonium hydroxide at 12% by weight, and the resulting mixture is stirred 1 hour at 60°C; then, 1,620 g of demineralized water is added, and stirring is continued a further hour. A clear solution is so obtained, into which 1,000 g is carefully dispersed of the zeolite 4, obtained as disclosed in Example 7. The milky suspension resulting from the dispersion is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomized product is charged to a muffle under an N₂ atmosphere and is heated up to 550°C. After a 2-hour stay at that temperature, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air. The obtained product has the following chemical molar composition: 0.02 TiO₂; SiO₂. Example 9: Zeolite 5 (Boralite C with Bonding Agent) Boralite-C zeolite is prepared as in Example 14 of FR patent No. 2,429,182; then, 562 g of tetraethyl-silicate is added with vigorous stirring to 600 g of solution of tetrapropyl-ammonium hydroxide at 12% by weight, and the resulting mixture is stirred 1 hour at 60°C; then, 2,460 g of demineralized water is added, and stirring is continued a further hour. A clear solution is so obtained, into which 1,450 g is carefully dispersed of the previously prepared Boralite-C zeolite. The milky suspension resulting from the dispersion is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomized product is charged to a muffle under an N₂ atmosphere and is heated up to 550°C. After a 2-hour stay at that temperature under N₂, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air. The obtained product has the following composition: SiO₂/B₂O₃ = 4.5. Example 10: Zeolite 6 To 6,090 g of an aqueous solution of tetrapropyl-ammonium hydroxide at 20%, 40 g of aluminum isopropoxide is added with stirring, and the obtained mixture is kept stirred, if necessary with a slight heating, up to complete dissolving. To the obtained solution, 4,160 g of tetraethyl-silicate is added with stirring and possibly heating, until hydrolysis is complete, and a single-phase solution is obtained. Then, 9,500 g of demineralized water is added, and stirring is continued a further hour. The so-obtained solution, which has the following molar composition: SiO₂/Al₂O₃ = 200; TPA⁺/SiO₂ = 0.3; H₂O/SiO₂ = 40 is charged to a stainless-steel autoclave, and is heated, with stirring, to the temperature of 170°C, under its autogenous pressure, and is allowed to remain under these conditions for 4 hours; the autoclave is then cooled and discharged. The obtained solution is centrifuged, and the solid is washed by re-dispersion and centrifugation. At the X-ray diffraction analysis of the powders, a portion of the calcined solid shows to be a ZSM-5-type zeolite. Example 11: Zeolite 6 with Bonding Agent 550 g of tetraethyl-silicate is added with stirring to 590 g of aqueous solution of tetrapropyl-ammonium hydroxide at 12%, and the resulting mixture is stirred 1 hour at 60°C; then, 2,400 g of demineralized water is added, and stirring is continued a further hour, while the solution is allowed to cool to approximately 25°C. Into the so-obtained clear solution, 2,050 g is carefully dispersed of the washed centrifuge panel, prepared as disclosed in Example 10. The panel contains approximately 70% by weight of zeolite. The resulting milky suspension is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomizer is put under an N₂ atmosphere, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air. The obtained product has, in its calcined and anhydrous form, the following composition, expressed as molar ratio: SiO₂/Al₂O₃ = 145. Example 12: Zeolite 7 To 4,050 g of an aqueous solution of tetrabutyl-ammonium hydroxide at 40%, 50 g of aluminum isopropoxide is added with stirring, and the obtained mixture is kept stirred, if necessary with a slight heating, up to complete dissolving; the obtained solution is then diluted with 4,050 g of demineralized water. To the obtained solution, 5,200 g of tetraethyl-silicate is added with stirring and possibly heating, until hydrolysis is complete, and a single-phase solution is obtained. Then, 11,900 g of demineralized water is added, and stirring is continued a further hour. The so-obtained solution, which has the following molar composition: SiO₂/Al₂O₃ = 203; TPA⁺/SiO₂ = 0.25; H₂O/SiO₂ = 41 is charged to a stainless-steel autoclave, and is heated, with stirring, to the temperature of 170°C, under its autogenous pressure, and is left under these conditions for 15 hours; the autoclave is then cooled and discharged. The obtained suspension is centrifuged, and the solid is washed by re-dispersion and centrifugation. At the X-ray diffraction analysis of the powders, a portion of the calcined solid shows to be a ZSM 11-type zeolite. Example 13: Zeolite 7 with Bonding Agent 690 g of tetraethyl-silicate is added with stirring to 740 g of an aqueous solution of tetrapropyl-ammonium hydroxide at 12%, and the resulting mixture is stirred 1 hour at 60°C; then, 3,000 g of demineralized water is added, and stirring is continued a further hour, while the solution is allowed to cool to approximately 25°C. Into the clear solution so obtained, 2,550 g of the washed centrifuge panel, prepared as disclosed in Example 12, is carefully dispersed. The panel contains approximately 70% by weight of zeolite. The resulting milky suspension is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomizer is put under an N₂ atmosphere, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air. The obtained solid has, in its calcined and anhydrous form, the following molar composition: SiO₂/Al₂O₃ = 145. Example 14: Zeolite 8 A T zeolite (D.W. Breck, Zeolite Molecular Sieves, J. Wiley & Sons Ed., 1974, 288 ) was synthetized according to the process as disclosed in DE patent No. 3,139,355, and was then agglomerated according to the process of the present invention. To 4,500 g of colloidal silica containing 40% of SiO₂, 360 g was added, with vigorous stirring, of aqueous solution of tetramethylammonium hydroxide (25% by weight). Separately, a solution was prepared by dissolving, in the order: 576 g of NaOH, 201 g of KOH and 474 g of NaAlO₂ (at 56% of Al₂O₃) in 8,300 g of demineralized water. This solution was added to the preceding one with vigorous stirring, and stirring was maintained for approximately 2 hours. The so-obtained reaction mixture, having the following composition, expressed as molar ratios: SiO₂/Al₂O₃ = 11.5; K⁺/SiO₂ = 0.12; Na⁺/SiO₂ = 0.48; TMA⁺/SiO₂ = 0.03; H₂O/SiO₂ = 20.8 was charged to a stainless-steel autoclave, was heated, to 190°C, and was left at this temperature, with stirring, under its autogenous pressure, for 2 hours; then, after cooling, the autoclave was discharged. The obtained product was centrifuged, and the solid was washed by re-dispersions in water and centrifugations. A portion of the washed solid was calcined at 550°C for three hours; when it was then analysed by X-ray diffraction of the powders, it showed to be a well-crystallized T zeolite. The washed, not calcined solid, was exchanged three times, according to the known techniques, so to exchange with NH₄⁺ all the exchangeable cations. At the end of the last centrifugation, a damp cake containing 85% of solids was obtained. Example 15: Zeolite 8 with Bonding Agent 550 g of tetraethyl-silicate is added with stirring to 590 g of an aqueous solution of tetrapropyl-ammonium hydroxide at 12% and the resulting mixture is stirred 1 hour at 60°C; then, 2,400 g of demineralized water is added, and stirring is continued a further hour, while the solution is allowed to cool to approximately 25°C. Into the clear solution so obtained, 1,250 g is carefully dispersed of the washed centrifuge panel, prepared as disclosed in Example 14. The resulting milky suspension is fed to a spray-dryer (NIRO-ATOMIZER disk-atomizer; inlet air temperature 300°C; outlet air temperature 120°C; chamber diameter 1.5 m), compact microspheres being obtained, which have an average diameter close to 20 µm. The atomizer is put under an N₂ atmosphere, the atmosphere is gradually turned from N₂ to air, and the product is left standing a further two hours at 550°C in air.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, FR, GB, GR, IT, LI, LU, NL, SE A process for preparing zeolites bonded with oligomeric silica, comprising the steps of: (a) mixing an aqueous slurry of: a zeolite selected from: calcined and anhydrous zeolites, facultatively exchanged with ammonium ions; non-calcined damp zeolites prepared hydrothermally and containing ammonium-or alkylammonium counter-cations, in the facultative presence of ammonium- or alkylammonium hydroxides, and having a pore diameter of from 0,5 nm to 1,3 nm, with an aqueous solution of oligomeric silica and an alkylammonium hydroxide, the percentage by weight of the zeolite in said slurry being from 20% to 50%, the molar ratio of oligomeric silica to alkylammonium hydroxide in said solution being from 0,05 to 0,2, and the molar ratio of the oligomeric silica to water being from 0,025 to 0,0125, and (b) rapidly drying the resultant mixture, characterized in that a zeolite based on: 1) Si, Al and B; 2) Si, Al and Ti; 3) Si, Ti and Fe; 4) Si and Ti; 5) Si and B; 6) Zeolite ZSM-5; 7) Zeolite ZSM-11, and 8) Zeolite T, is used, in which the weight ratio of the oligomeric silica to the zeolite in the mixture resultant from stage (a) is from 5:95 to 20:80, the 5:95 to 10;90 range being excluded in the case of a Si- and Ti-based zeolite. Process according to Claim 1, wherein the zeolite based on Si, Al and B has, in its anhydrous and calcined state, the following molar composition: pHAlO₂ . qB₂O₃ . SiO₂ (1) in which p is from 0,034 to 0,0050, and q is from 0,1 to 0,005, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HAlO₂ being at least partially replaceable by cations, said zeolite (1) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,112 ± 0,01 very strong 0,998 ± 0,01 strong 0,974 ± 0,01 medium 0,634 ± 0,007 medium to weak 0,597 ± 0,007 medium to weak 0,424 ± 0,005 medium to weak 0,384 ± 0,004 strong 0,381 ± 0,004 strong 0,373 ± 0,004 strong 0,371 ± 0,004 strong 0,363 ± 0,004 medium 0,304 ± 0,002 medium to weak 0,297 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 890 to 920 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. Process according to Claim 1, wherein the zeolite based on Si, Al and Ti has, in its anhydrous and calcined state, the following molar composition: pHAlO₂ . qTiO₂ . SiO₂ (2) in which p is up to 0,050, and q is up to 0,025, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HAlO₂ being at least partially replaceable by cations, said zeolite (2) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,114 ± 0,01 very strong 0,999 ± 0,01 strong 0,974 ± 0,01 medium 0,636 ± 0,007 medium to weak 0,599 ± 0,007 medium to weak 0,426 ± 0,005 medium to weak 0,386 ± 0,004 strong 0,382 ± 0,004 strong 0,375 ± 0,004 strong 0,372 ± 0,004 strong 0,365 ± 0,004 medium 0,305 ± 0,002 medium to weak 0,299 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 960 to 975 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. Process according to Claim 1, wherein the zeolite based on Si and Ti has, in its anhydrous and calcined state, the following molar composition: xTiO₂ . (1-x) SiO₂ (3) wherein x is from 0,0005 to 0,004, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%. Process according to Claim 1, wherein the zeolite based on Si, Ti and Fe has, in its anhydrous and calcined state, the following molar composition: pHFeO₂ . qTiO₂ . SiO₂ (4) in which p is up to 0,050, and q is up to 0,025, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite (4) is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HFeO₂ being at least partially replaceable by cations, said zeolite (1) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,114 ± 0,01 very strong 0,999 ± 0,01 strong 0,974 ± 0,01 medium 0,636 ± 0,007 medium to weak 0,599 ± 0,007 medium to weak 0,426 ± 0,005 medium to weak 0,386 ± 0,004 strong 0,382 ± 0,004 strong 0,375 ± 0,004 strong 0,372 ± 0,004 strong 0,365 ± 0,004 medium 0,305 ± 0,002 medium to weak 0,299 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 960 to 975 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. Process according to Claim 1, wherein the aqueous solution of silica and alkylammonium hydroxide is prepared by hydrolyzing a tetraalkyl orthosilicate in an aqueous solution of an alkylamonium hydroxide at a temperature of from 2°C 120°C for a time of from 0,2 h to 24 h. Process according to Claim 6, wherein the tetraalkyl orthosilicate is tetraethyl orthosilicate. Process according to Claim 1, wherein the alkyl in the alkylammonium hydroxide is a C₁-C₅ alkyl. Process according to Claim 8, wherein the alkyl in the alkylammonium hydroxide is tetrapropyl. A zeolite bonded with oligomeric silica, characterized in that the crystals of a zeolite based on: 1) Si, Al and B; 2) Si, Al and Ti; 3) Si, Ti and Fe; 4) Si and Ti; 5) Si and B; 6) Zeolite ZSM-5; 7) Zeolite ZSM-11, and 8) Zeolite T, are encaged with each other by Si-O-Si bridges and are in the form of microspheres having a diameter of from 5 µm to 1 mm, the weight ratio of the oligomeric silica to the zeolite concerned in the mixture of an aqueous slurry of said zeolite with an aqueous solution of oligomeric silica and alkylammonium hydroxide used for their preparation being from 5:95 to 20:80, the 5:95 to 10:90 range being excluded in the case of an Si- and Ti-based zeolite. Claims for the following Contracting State : ES A process for preparing zeolites bonded with oligomeric silica, comprising the steps of: (a) mixing an aqueous slurry of: a zeolite selected from: calcined and anhydrous zeolites, facultatively exchanged with ammonium ions; non-calcined damp zeolites prepared hydrothermally and containing ammonium-or alkylammonium counter-cations, in the facultative presence of ammonium- or alkylammonium hydroxides, and having a pore diameter of from 0,5 nm to 1,3 nm, with an aqueous solution of oligomeric silica and an alkylammonium hydroxide, the percentage by weight of the zeolite in said slurry being from 20% to 50%, the molar ratio of oligomeric silica to alkylammonium hydroxide in said solution being from 0,05 to 0,2, and the molar ratio of the oligomeric silica to water being from 0,025 to 0,0125, and (b) rapidly drying the resultant mixture, characterized in that a zeolite based on: 1) Si, Al and B; 2) Si, Al and Ti; 3) Si, Ti and Fe; 4) Si and Ti; 5) Si and B; 6) Zeolite ZSM-5; 7) Zeolite ZSM-11, and 8) Zeolite T, is used, in which the weight ratio of the oligomeric silica to the zeolite in the mixture resultant from stage (a) is from 5:95 to 20:80, the 5:95 to 10;90 range being excluded in the case of a Si- and Ti-based zeolite. Process according to Claim 1, characterized in that the zeolite based on Si, Al and B has, in its anhydrous and calcined state, the following molar composition: pHAlO₂ . qB₂O₃ . SiO₂ (1) in which p is from 0,034 to 0,0050, and q is from 0,1 to 0,005, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HAlO₂ being at least partially replaceable by cations, said zeolite (1) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,112 ± 0,01 very strong 0,998 ± 0,01 strong 0,974 ± 0,01 medium 0,634 ± 0,007 medium to weak 0,597 ± 0,007 medium to weak 0,424 ± 0,005 medium to weak 0,384 ± 0,004 strong 0,381 ± 0,004 strong 0,373 ± 0,004 strong 0,371 ± 0,004 strong 0,363 ± 0,004 medium 0,304 ± 0,002 medium to weak 0,297 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 890 to 920 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. Process according to Claim 1, characterized in that the zeolite based on Si, Al and Ti has, in its anhydrous and calcined state, the following molar composition: pHAlO₂ . qTiO₂ . SiO₂ (2) in which p is up to 0,050, and q is up to 0,025, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HAlO₂ being at least partially replaceable by cations, said zeolite (2) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,114 ± 0,01 very strong 0,999 ± 0,01 strong 0,974 ± 0,01 medium 0,636 ± 0,007 medium to weak 0,599 ± 0,007 medium to weak 0,426 ± 0,005 medium to weak 0,386 ± 0,004 strong 0,382 ± 0,004 strong 0,375 ± 0,004 strong 0,372 ± 0,004 strong 0,365 ± 0,004 medium 0,305 ± 0,002 medium to weak 0,299 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 960 to 975 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. Process according to Claim 1, characterized in that the zeolite based on Si and Ti has, in its anhydrous and calcined state, the following molar composition: xTiO₂ . (1-x) SiO₂ (3) characterized in that x is from 0,0005 to 0,004, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%. Process according to Claim 1, characterized in that the zeolite based on Si, Ti and Fe has, in its anhydrous and calcined state, the following molar composition: pHFeO₂ . qTiO₂ . SiO₂ (4) in which p is up to 0,050, and q is up to 0,025, with the proviso that, for an ammonium-base containing zeolite hydrate, the ratio of the weight of the water to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 23% to 28%, and the ratio of the weight of the ammonium ion or the alkylammonium base to the sum of the weights of the water, the ammonium ion or the alkylammonium base and the calcined and anhydrous zeolite is from 7% to 12%, the hydrogen ion of HFeO₂ being at least partially replaceable by cations, said zeolite (1) having, in its powdered state an X-ray diffraction spectrum with the following characteristics: Interplanar distance, nm Rel.Intensity 1,114 ± 0,01 very strong 0,999 ± 0,01 strong 0,974 ± 0,01 medium 0,636 ± 0,007 medium to weak 0,599 ± 0,007 medium to weak 0,426 ± 0,005 medium to weak 0,386 ± 0,004 strong 0,382 ± 0,004 strong 0,375 ± 0,004 strong 0,372 ± 0,004 strong 0,365 ± 0,004 medium 0,305 ± 0,002 medium to weak 0,299 ± 0,002 medium to weak and an Infra Red spectrum exhibiting all the following bands: Wave number, cm⁻¹ Rel.Intensity 1220 to 1230 weak 1080 to 1110 strong 960 to 975 medium to weak 795 to 805 medium to weak 550 to 560 medium 450 to 470 medium to strong. Process according to Claim 1, characterized in that the aqueous solution of silica and alkylammonium hydroxide is prepared by hydrolyzing a tetraalkyl orthosilicate in an aqueous solution of an alkylamonium hydroxide at a temperature of from 2°C 120°C for a time of from 0,2 h to 24 h. Process according to Claim 6, characterized in that the tetraalkyl orthosilicate is tetraethyl orthosilicate. Process according to Claim 1, characterized in that the alkyl in the alkylammonium hydroxide is a C₁-C₅ alkyl. Process according to Claim 8, characterized in that the alkyl in the alkylammonium hydroxide is tetrapropyl.

Inventors: BELLUSSI, GUISEPPE, BUONOMO, FRANCO, CLERICI, MARIOGABRIELE, ESPOSITO, ANTONIO, ROMANO, UGO
Applicants: ENICHEM SYNTHESIS S.P.A., ENIRICERCHE S.P.A., SNAMPROGETTI S.P.A.
Application year: 1987
Main classification: C01B35
IPC codes: C01B39, C01B35