SYNTHETIC, CRYSTALLINE, POROUS MATERIAL CONTAINING SILICON OXIDE, TITANIUM OXIDE AND ALUMINIUM OXIDE

Abstract: A crystalline, porous, synthetic material is dis­ closed, together with its related preparation process. Such a material of zeolitic character, containing silicon, titanium and aluminum oxides, corresponds, in its calcined and anhydrous state, to the following empi­ rical formula: HAlO₂ . q TiO₂ . SiO₂ wherein p has a value greater than zero and lower than or equal to 0.050, q has a value greater than zero and lower than or equal to 0.025, and the H⁺ of HAlO₂ can be at least partly replaceable or replaced by cations.

Description: This invention relates to a synthetic, crystalline and porous material of zeolite character, containing silicon oxide, titanium oxide and aluminium oxide, and to the process for its preparation. The material in question is similar to the ZSM-5, an embodiment of US-A-3 702 886, and essentially consisting, in its anhydrous and calcined form, of M 2/n , SiO₂ and Al₂O₃, wherein M is an n -valent cation. Other like materials are known, such as the zeolite disclosed in US-A-4 061 724, which essentially consists, in its anhydrous and calcined form, of SiO2, the zeolite disclosed in FR-A-2 471 950, which is a titanium-containing silica, and the zeolite disclosed in EP-A-0 077 522, which is titanium-containing aluminosilicate. A novel synthetic zeolite has now been found, that can be defined as a "titanium-aluminium silicalite, which can be employed as a molecular sieve, or an ion-exchanger, or a catalyst in a number of reactions, such as: cracking, selectoforming, hydrogenation, dehydrogenation, oligomerization, alkylation, isomerization, dehydration of oxygen-containing organic compounds, selective hydroxylation by H₂O₂ of organic substrates, oxidation of olefins and hydroxylation of aromatics. The invention, therefore, provides a synthetic, crystalline and porous material of zeolite character, containing silicon oxide, titanium oxide and aluminium oxide, and having the powder X-ray diffraction spectrum exhibiting the following lines: Interplanar distances nm Rel.Intensities 1,114 ± 0,010 very strong 0,999 ± 0,010 strong 0,974 ± 0,010 medium 0,636 ± 0,007 medium-weak 0,599 ± 0,007 medium-weak 0,426 ± 0,005 medium-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-weak 0,299 ± 0,002 medium-weak, the I.R. spectrum of said material exhibiting at least the following bands: Wave number cm⁻¹ Rel.Intensities 1220 to 1230 weak 1080 to 1110 strong 965 to 975 medium-weak 795 to 805 medium-weak 550 to 560 medium 450 to 470 medium-strong said material being characterized in that its empirical formula, in its calcined and anhydrous state is: pHAlO₂ .qTiO₂ .SiO₂ wherein p is greater than zero and does not exceed 0,050, and q is greater than zero and does not exceed 0,025, the H+ of HAlO₂ being at least partially replaceable or replaced by cations. The passage from any cationic form to any other cationic form can be carried out by any conventional exchange procedure. As outlined above, the material in question is X-ray crystalline. The X-ray diffraction test has been effected on the powdered material on a diffractometer equipped with an electronic impulse-counting system, with a CuK-alpha radiation: to calculate the intensities, the peaks have been measured and their percentage heights relative to the height of the most intense peak have been calculated. The X-ray diffraction spectral characteristics are as reported above, and show that the X-ray diffraction is closely akin to that of a ZSM-5 zeolite and like zeolites. The InfraRed spectrum is as reported above, and is shown in Fig.1 of the accompanying drawings, wherein the wave numbers are plotted on the abscissae, whereas the percentage transmittance values are plotted on the ordinates. Such an InfraRed spectrum is very closely similar to that of the zeolite as disclosed in FR-A-2 471 950, patent whilst it is considerably different from that of ZSM-5 (or from similar structures), as shown in Figure 2. It can be observed that in this latter spectrum the band at 965-975 cm⁻¹, which is characteristic of titanium silicalite of FR-A-2 471 950 and of titanium-aluminum-silicalite, does not appear. Summarizing, the material as disclosed by ourselves is different from ZSM-5 of US-A-3,702,886, as for both its empirical formula and its I.R. spectrum; relatively to the zeolite of FR-A-2 471 950 as to its empirical formula; and relatively to the zeolite of EP-A-0 077 522 as to its I.R. spectrum. Furthermore, the use of the subject material of the present invention as a catalyst in the above listed reactions is a further confirmation of the difference of our product relatively to those of the prior art. In fact, both ZSM-5 of US-A-3,702,886, and the zeolite of EP-A-0 077 522 are used as catalysts in such reactions as dehydrations of oxygenated organic compounds, cracking, selectoforming, hydrogenations and dehydrogenations, oligomerizations, alkylations, isomerizations, but they result inactive in the reactions between organic substrates and H₂O₂ (hydroxylation of phenol to diphenols, oxidation of olefins), whilst the zeolite of FR-A-2 471 950 results inactive for the first reactions and active for the last ones; to the contrary, our zeolite is active for all of the above mentioned reactions. A second object of the present invention is the preparation process for the obtainment of the crystalline, porous, synthetic material as defined above. The invention, therefore, provides also a process for preparing the synthetic, crystalline and porous material as defined in the foregoing, said process comprising the step of reacting, at a temperature of from 120°C to 200°C, at a pH of from 9 to 14 and for a time from 1 h to 5 days a silicon compound, a titanium compound, an aluminium compound and an organic nitrogenous base, in the facultative presence of one or more salts and/or hydroxides of an alkali or alkaline earth metal , the SiO₂/Al₂O₃ molar ratio of the reactants being greater than 100, the SiO₂ molar ratio of the reactants being greater than 5, and the M/SiO₂ molar ratio (wherein M is an alkali metal or an alkaline earth metal) of the reactants being from less than 0,1 to zero. In the empirical formula of the material, the aluminium has been indicated in the HAlO₂ form, to underline that the material is in the H⁺ form. When speaking of the ratios between the various reactants, we use, for aluminum, the Al₂O₃ form, which is the most usual. The silicon compound is selected from silica gel, silica sol and alkyl silicates, among which, preferably, tetraethyl silicate; the titanium compound is selected from titanium salts, such as, e.g., its halides, and organic titanium derivatives, such as, e.g., alkyltitanates, preferably tetraethyl titanate; the aluminium compound is selected from aluminum salts, such as, e.g., its halides and hydroxides, and its organic derivatives, such as, e.g., alkyl aluminates, preferably isopropyl aluminate. The nitrogenous organic base can be an alkylammonium hydroxide, preferably tetrapropyl-ammonium hydroxide. In case tetrapropylammonium hydroxide is used, the TPA⁺/SiO₂ ratio (wherein TPA = tetrapropylammonium) of the reactants is comprised within the range of from 0.1 to 1, preferably from 0.2 to 0.4. The reactants are reacted with each other by operating at a temperature of from 100° to 200°C, preferably 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 period ranging from 1 hour to 5 days, preferably from 3 hours to 10 hours. For the purpose of better illustrating the meaning of the present invention, some preparation and use examples are given, which in no way are to be considered as being limitative of the invention. Example 1 This example shows the preparation of titanium-aluminum-silicalite. 0.3 g of aluminum isopropoxide is dissolved in 54 g of solution at 18.7% by weight of tetrapropyl-ammonium hydroxide. In a separate vessel, 2.3 g of tetraethyl-orthotitanate is dissolved in 41.6 g of tetraethyl-silicate and this solution is added to the previously prepared one, with stirring. The whole mass is heated at 50-60°C, always with stirring, until a single-phase solution is obtained, then 100 cc of water is added. The obtained solution is charged to an autoclave and is heated, under its autogenous pressure, at 170°c over 4 hours. The discharged product is centrifuged and washed twice by re-dispersion and centrifuging; it is then dried 1 hour at 120°C, and is then calcined 4 hours at 550°C in the air The obtained product has an SiO₂/Al₂O₃ molar ratio of 98, and an SiO₂/TiO₂ molar ratio of 99, and is already in the H⁺ form. Examples 2-6 In Table 1 other titanium-aluminum-silicalites are shown, which have been prepared by the same modalities as disclosed in Example 1, by varying the composition of the reactants, and the crystallization times. The products obtained from Examples 2-5 are in the H⁺ form, whilst the product obtained from Example 6 is in the Na⁺ form; it can be turned, by the known processes, into its H⁺ form. From the above-reported preparation examples, one can observe that the maximum amounts of titanium and aluminum which can be obtained in the end product are not independent from each other. The minimum SiO₂/TiO₂ ratio which can be obtained in the product is of about 40, and it can be only obtained if SiO₂/Al₂O₃ ratio in the product is higher than about 120 In order to obtain SiO₂/Al₂O₃ ratios lower than about 120, an increase in SiO₂/TiO₂ ratio must be accepted. At SiO₂/Al₂O₃ molar ratios higher than 150 in the reaction mixture (Examples 1-5), the crystallization occurs, and with increasing SiO₂/Al₂O₃ ratios in the reactant mixture a decrease in SiO₂/TiO₂ ratio and an increase in SiO₂/Al₂O₃ ratio occurs in the obtained product. SiO₂/TiO₂ ratio in the obtained product continues to decrease until it reaches its minimum value around 40, which is reached when SiO₂/Al₂O₃ in the reaction mixture is of from 300 to 400; further increases of SiO₂/Al₂O₃ ratio in the reactant mixture cause only SiO₂/Al₂O₃ to increase in the product, whilst SiO₂/TiO₂ remains nearly constant. When the SiO₂/Al₂O₃ ratio in the reactant mixture is lower than or equal to 150, adding to the reaction mixture, to the purpose of obtaining the crystallization, salts and/or hydroxides of such cations as tetramethylammonium, ammonium alkali metals or alkali-earth metals (Example 6) is necessary. These variations cause also an increase in SiO₂/TiO₂ ratio in the obtained product. Examples 7-10 Referring to Table 1, products are shown, which do not have the same characteristics as of the preceding product. It can be observed from Examples 7, 8 and 9 that, when the molar composition of the reactant mixture is the following: SiO₂/AL₂O₃ = 100-150; SiO₂/TiO₂ = 20; TPA⁺/SiO₂ = 0.25; H₂O/SiO₂ = 40; at a temperature of from 160° to 180°C and under its autogenous pressure, the mixture does not crystallize. It can be observed from Example 10 that, even if an alkali metal is added (Na⁺/SiO₂ = 0.04), after 5 hours, the mixture does not crystallized, because the SiO₂/Al₂O₃ ratio in the reaction mixture is lower than or equal to 100. Example 11 Referring to Table 1, the product of Example 11 is shown, which is obtained by starting from the same composition of the reactants of Example 10. It can be observed that after a crystallization time of 96 hours the mixture is crystallized. The I.R. spectrum of this product, shown in Figure 3, is not essentially equal to that shown in Figure 1. From the spectrum of Fig. 3, it can be observed, in fact, that the band at 965-975 cm⁻¹ is present, but it has a much lower intensity than that represented in the spectrum of Fig. 1, although the product of Example 11 has a higher titanium contents. All of the above allows us to state that the addition of large amounts of alkali metals (M⁺/SiO₂ ≧ 0.04) in the reaction mass can cause an increase in titanium amount, which can be detected from the chemical analysis of the obtained product, an SiO₂/TiO₂ ratio lower than 40 being obtained, but is such case TiO₂ is at least partly in a form different from the form it has in the titanium-aluminum-silicalite according to the invention, and such as not to yield the spectrum of Fig. 1, but that of Fig. 3. In Fig. 4, a chart is shown, which sets forth the dependence of the maximum amounts of titanium (shown in the ordinates as SiO₂/TiO₂ molar ratio) and of aluminum (shown in the abscissae as SiO₂/Al₂O₃ molar ratio) which can be obtained in the end product. Example 12 To a tubular steel reactor, 1.04 g is charged of catalyst of 1mm - 420 mm particle size (18-40 mesh), prepared according to Example 2. The reactor is placed inside and electrical oven and is gradually heated up to the reaction temperature, with a stream of dimethyl ether being flowed through it. The gaseous reaction products are analyzed by in-line chromatography after the liquid products being condensed in a bath kept at 0-5°C. These latter are separately weighed and analyzed, always by chromatographic way. The conversion and selectivity are computed according to the hereunder shown equations: (DME = dimethyl ether; in = incoming; out = outgoing). The reaction conditions and the results obtained are gathered in Table 2. Example 13 To a small, 250-cc glass flask, there are charged, in the order as shown: phenol, 56.7 g; water, 8.4 g; acetone, 13.5 g; catalyst, prepared as in Example 2, 3 g. The mixture is heated at 100°C with stirring and under reflux, then, under the same conditions, within a 45 minutes time, 10.5 g of 35% (weight/volume) H₂O₂ is added dropwise. After 55 minutes from the beginning of the addition, all of H₂O₂ has been converted and the products are analyzed by gas-chromatography. A yields of diphenols of obtained diphenol mols = 0.08019 charged H₂O₂ mol = 0.099 is obtained. The residual amount of H₂O₂ is converted into pitches and O₂. On formed diphenols, ortho/para ratio is 1.18.

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, GR, LI, LU, NL, SE A synthetic, crystalline and porous material of zeolite character, containing silicon oxide, titanium oxide and aluminium oxide and having the powder X-ray diffraction spectrum exhibiting the following lines: Interplanar distances nm Rel.Intensities 1,114 ± 0,010 very strong 0,999 ± 0,010 strong 0,974 ± 0,010 medium 0,636 ± 0,007 medium-weak 0,599 ± 0,007 medium-weak 0,426 ± 0,005 medium-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-weak 0,299 ± 0,002 medium-weak, the I.R. spectrum of said material exhibiting at least the following bands: Wave number cm⁻¹ Rel.Intensities 1220 to 1230 weak 1080 to 1110 strong 965 to 975 medium-weak 795 to 805 medium-weak 550 to 560 medium 450 to 470 medium-strong said material being characterized in that its empirical formula, in its calcined and anhydrous state is: pHAlO₂ .qTiO₂ .SiO₂ wherein p is greater than zero and does not exceed 0,050, and q is greater than zero and does not exceed 0,025, the H+ of HAlO₂ being at least partially replaceable or replaced by cations. Process for preparing the synthetic, crystalline and porous material as defined in Claim 1, comprising the step of reacting, at a temperature of from 120°C to 200°C, at a pH of from 9 to 14 and for a time of from 1 h to 5 days a silicon compound, a titanium compound, an aluminium compound and an organic nitrogenous base, in the facultative presence of one or more salts and/or hydroxides of an alkali or alkaline earth metal, the SiO₂/Al₂O₃ molar ratio of the reactants being greater than 100, the SiO₂/TiO₂ molar ratio of the reactants being greater than 5, and the M/SiO₂ molar ratio (wherein M is an alkali metal or an alkaline earth metal) of the reactants being from less than 0,1 to zero. Process according to Claim 2, wherein the H₂O/SiO₂ molar ratio of the reactants is from 10 to 100. Process according to Claim 2, wherein the SiO₂/Al₂O₃ molar ratio is from 300 to 400, the SiO₂/TiO₂ molar ratio of the reactants is from 15 to 25, the H₂O/SiO₂ molar ratio of the reactants is from 30 to 50, and the M/SiO₂ molar ratio of the reactants is zero. Process according to Claim 2, wherein the silicon compound is selected from silica gel, silica sol and the alkyl silicates, the titanium compound is selected from the salts of organic titanium compounds, and the aluminium compound is selected from the aluminium salts and the organic aluminium compounds. Process according to to Claim 5, wherein the alkyl silicate is tetraethyl silicate. Process according to Claim 5, wherein the titanium salts is a titanium halide. Process according to Claim 5, wherein the organic titanium compound is an alkyl titanate. Process according to Claim 8, wherein the alkyl titanate is tetraethyltitanate. Process according to Claim 5, wherein the aluminium salt is an aluminium halide or an aluminium hydroxide. Process according to Claim 5, wherein the organic aluminium compound is an alkyl aluminate. Process according to Claim 11, wherein the alkyl aluminate is isopropyl aluminate. Process according to Claim 2, wherein the nitrogenous base is an alkylammonium hydroxide. Process according to Claim 13, wherein the alkylammonium hydroxide is tetrapropylammonium hydroxide. Process according to Claim 2, wherein the reaction is carried out at a temperature of from 160°C to 180°C, at a pH of from 10 to 12, and for a time of from 3 h to 10 h. Process according to Claim 14, wherein the TPA⁺/SiO₂ molar ratio of the reactants, where TPA⁺ is the tetrapropylammonium ion, is from 0,1 to 1. Process according to Claim 14, wherein the TPA⁺/SiO₂ ratio of the reactants is from 0,2 to 0,4. Claims for the following Contracting States : AT, ES Process for preparing a synthetic, crystalline and porous material of zeolite character, containing silicon oxide, titanium oxide and aluminium oxide and having the powder X-ray diffraction spectrum exhibiting the following lines: Interplanar distance nm Rel.Intensities 1,114 ± 0,010 very strong 0,999 ± 0,010 strong 0,974 ± 0,010 medium 0,636 ± 0,007 medium-weak 0,599 ± 0,007 medium-weak 0,426 ± 0,005 medium-weak 0,386 ± 0,004 strong 0,382 ± 0,004 strong 0,375 ± 0,004 strong 0,372 ± 0,004 strong 0,369 ± 0,004 medium 0,305 ± 0,002 medium-weak 0,299 ± 0,002 medium-weak, the I.R. spectrum of said material exhibiting at least the following bands: Wave number cm⁻¹ Rel.Intensities 1220 to 1230 weak 1080 to 1110 strong 965 to 975 medium-weak 795 to 805 medium-weak 550 to 560 medium 450 to 470 medium-strong said material having, in its calcined and anhydrous state, the empirical formula: pHAlO₂ .qTiO₂ SiO₂ wherein p is greater than zero and does not exceed 0,050, and q is greater than zero and does not exceed 0,025, the H+ of HAlO₂ being at least partially replaceable or replaced by cations, comprising the step of reacting, at a temperature of from 120°C to 200°C, at a pH of from 9 to 14 and for a time of from 1 h to 5 days a silicon compound, a titanium compound, an aluminium compound and an organic nitrogenous base, in the facultative presence of one or more salts and/or hydroxides of an alkali or alkaline earth metal, the SiO₂/Al₂O₃ molar ratio of the reactants being greater than 100, the SiO₂/TiO₂ molar ratio of the reactants being greater than 5, and the M/SiO₂ molar ratio (wherein M is an alkali metal or an alkaline earth metal) of the reactants being from less than 0,1 to zero. Process according to Claim 1, wherein the H₂O/SiO₂ molar ratio of the reactants is from 10 to 100. Process according to Claim 1, wherein the SiO₂/Al₂O₃ molar ratio is from 300 to 400, the SiO₂/TiO₂ molar ratio of the reactants is from 15 to 25, the H₂O/SiO₂ molar ratio of the reactants is from 30 to 50, and the M/SiO₂ molar ratio of the reactants is zero. Process according to Claim 1, wherein the silicon compound is selected from silica gel , silica sol and the alkyl silicates , the titanium compound is selcted from the salts of organic titanium compounds, and the aluminium compound is selected from the aluminium salts and the organic aluminium compounds. Process according to to Claim 4, wherein the alkyl silicate is tetraethyl silicate. Process according to Claim 4, wherein the titanium salts is a titanium halide. Process according to Claim 4, wherein the organic titanium compound is an alkyl titanate. Process according to Claim 7, wherein the alkyl titanate is tetraethyltitanate. Process according to Claim 4, wherein the aluminium salt is an aluminium halide or an aluminium hydroxide. Process according to Claim 4, wherein the organic aluminium compound is an alkyl aluminate. Process according to Claim 10, wherein the alkyl aluminate is isopropyl aluminate. Process according to Claim 1, wherein the nitrogenous base is an alkylammonium hydroxide. Process according to Claim 12, wherein the alkylammonium hydroxide is tetrapropylammonium hydroxide. Process according to Claim 1, wherein the reaction is carried out at a temperature of from 160°C to 180°C, at a pH of from 10 to 12, and for a time of from 3 h to 10 h. Process according to Claim 13, wherein the TPA⁺/SiO₂ molar ratio of the reactants, where TPA⁺ is the tetrapropylammonium ion, is from 0,1 to 1. Process according to Claim 15, wherein the TPA⁺/SiO₂ ratio of the reactants is from 0,2 to 0,4.

Inventors: BELLUSSI, GIUSEPPE, BUONOMO, FRANCO, ESPOSITO, ANTONIO, GIUSTI, ALDO
Applicants: ENICHEM SYNTHESIS S.P.A., ENIRICERCHE S.P.A., SNAMPROGETTI S.P.A.
Application year: 1986
Main classification: C01B33
IPC codes: C10G3, C07C1, C07C27, C07C67, B01J29, C01B39, C01B37, C07C37, C07C39