AU580780B2

AU580780B2 - Titanium-silicate compositions

Info

Publication number: AU580780B2
Application number: AU42931/85A
Authority: AU
Inventors: Edith Marie Flanigen; Brent Mei-Tak Lok; Bonita Kristoffersen Marcus
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1984-04-26
Filing date: 1985-04-26
Publication date: 1989-02-02
Anticipated expiration: 2005-04-26
Also published as: CA1254189A; BR8506684A; JPS61501981A; EP0179875A1; WO1985004853A1; AU4293185A

Description

TITANIUM-SILICATE COMPOSITIONS

FIELD OF THE INVENTION

The present invention relates to a new class of molecular sieve compositions containing titanium and silicon in the form of framework tetrahedral oxide units. These compositions are prepared hydrothermally from reaction mixtures containing reactive sources of titanium, silicon and oxygen and preferably at least one organic templating agent.

DISCUSSION OF MOLECULAR SIEVES

Molecular sieves having crystalline structures and of the aluminosilicate type are well known to those familiar with molecular sieve technology. Both naturally occurring and synthetic aluminosilicates are known to exist and literally hundreds of such have been reported in the literature.

Although hundreds of aluminosilicates (binary molecular sieves) are known, the reports relating to other binary and ternary molecular sieves have been relatively few. Further, the reported ternary molecular sieves having titanium as a component have been even fewer and in those instances where titanium has been reported the amount contained in the molecular sieve has been relatively small or present as a deposition or surface modifying agent.

One early report of crystalline titano-silicate zeolites (Of course, these compositions are not zeolites as the term "zeolite" is commonly employed today.) is found in U.S. Patent No. 3,329,481. The crystalline titano-silicates are described in U.S. Patent No. 3,329.481 by the formula: (D_2/n)_x:TiO₂(SiO₂)_y wherein D is a monovalent metal, divalent metal, ammonuim ion or hydrogen ion, "n" is the valence of D, "x" is a number from 0.5 to 3 and y is a number from about 1.0 to 3.5. The crystalline titano-silicate zeolites are characterized by X-ray powder diffraction patterns including all the d-spacings of one of the patterns selected from the group:

Pattern A: Pat.tern B: Pattern C:

7.6 - 7.9Å 4.92 ± 0.04Å 2.82 ± 0.03Å

3.2 ± 0.05Å 3.10 ± 0.04Å 1.84 ± 0.03Å The titano-silicates of U.S. Patent No. 3,329,481 are prepared using as a "critical reagent" (column 3, line 17 et. seq.) an alkali metal peroxo-Groups IV-B metallate (M₄XO₆) or hydraded forms thereof. The difficulty in obtaining compositions containing titanuim is evidenced by the disclosure of U.S. Patent No. 4,358,397 which discloses modified aluminosilicates. The aluminosilicates are modified by treating an aluminosilicate with a compound derived from one or more elements of titanium, zirconuim or hafnium. The resulting compositions are said to contain a minor proportion of an oxide of such elements. It is clear that in the disclosed compositions that the oxides of titanuim, zirconium and hafnium are present as deposited oxides and are present in a minor proportion. As above mentioned, although there has been an extensive treatment in the patent art and in the published literature of aluminosilicates and, recently, aluminophosphates there has been little information available on other than such materials. This is particularly true in the area of titanium containing compositions. Molecular sieve compositions wherein titanium is present in the framework of the molecular sieve or is so intimately related as to change the physical and/or chemical characteristics of the molecular sieve have not been extensively reported. This is understandable in the question of aluminosilicates, as indicated by the article, "Can Ti⁴⁺ replace Si⁴⁺ in silicates?".

Mineralogical Magazine. September vol 37, No. 287, pages 366-369 (1969). In this article it is concluded that substitution of framework silicon by titanium does not usually occur in aluminosilicates owing to the preference of titanium to be octahedrally bound rather than tetrahedrally bound.

Even the formation of crystalline "titanosilicate zeolites", as disclosed in U.S. Patent No. 3,329,481 and discussed above, wherein a metallo-silicate complex is formed and treated to give the titano silicate product. The evidence for the claimed titanosilicate is based on the X-ray powder diffraction pattern data which are somewhat suspect as to whether such show substitution of titanium into the silicate framework inasmuch as the same claimed X-ray patterns are also observed for the zirconium silicates. Further, similar X-ray patterns showing similar interplanar distances for the two values in patterns B) have been reported for silicalite. (see: GB 2.071.071A).

The incorporation of titanium in a silicalite type structure is disclosed in GB 2.071.071A. published December 21. 1979. The amount of titanium claimed to be substituted into the silicalite-type structure is very small, being no more than 0.04 mole percent, based on the number of moles of silica, and may be as low as 0.0005. The titanium content was determined by chemical analysis and was not determined to be greater than 0.023 in any of the reported examples. As indicated by a comparison of Fig. la and Fig. lb of GB 2.071.071 A. the amount of titanium present is so small that no significant change in the X-ray diffraction pattern of silicalite was observed and the minor changes observed may simply be due to occluded titanium dioxide. Thus, absent other, analytical data the results of GB 2.071.071A are not well defined. No comparison data for titanium dioxide are disclosed.

The difficulty which is met in preparing titanium-containing molecular sieve compositions is further demonstrated by the failure of European Patent Application No. 82109451.3 (Publication No. 77.522) published April 27. 1983. entitled "Titanium-containing zeolites and method for their production as well as use of said zeolites.", to actually prepare titanium-containing molecular sieve compositions. Although the applicants claim the preparation of titano-aluminosilicates having the pentasil structure, it is evident from an analysis of the products of the examples that titanium was not present in the form of a framework tetrahederal oxide in a molecular sieve having the pentasil structure. The products of the examples of European patent Application No. 82109451.3 will be discussed in detail in a comparative example hereinafter.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1: SEM (Scanning Electron Micrograph of the product of European Application No. 82109451.3.

SUMMARY OF THE INVENTION

The instant invention relates to new molecular sieve compositions having three- dimensional microporous crystalline framework structures of TiO₂ and SiO₂ tetrahedral oxide units. These new molecular sieves have a unit empirical formula on an anhydrous basis of: mR: (Ti_xSi_y)O₂ where "R" denominates an organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of

(Ti_xSi_y)O₂ and has a value of from zero to about 0.3; and "x". and "y" represent the mole fractions of titanium and silicon, respectively, present as framework tetrahedral oxide units. The values of "x" and "y" are generally greater than 0.01 and less than 0.99. x+y= 1 and are such that: (1) "y" is less than 0.9615 and "x" is greater than 0.0385 when characterized by the x-ray pattern of Table III; (2) "x" and "y" are greater than 0.01 and less than 0.99 when characterized by the x-ray pattern of Table VII; or (3) "y"' is greater than 0.7776 and less than 0.9615 or less than 0.05 and "x" is greater than 0.0385 and less than 0.2224 and greater than 0.5. The instant titanium silicate compositions will be generally referred to herein by the acronym "TiSO" to designate the instant molecular sieves having a framework structure of TiO₂ and SiO₂ tetrahedral oxide units. The individual class members or species will be identified by denominating the various structural species which make up the TiSO family by assigning a number to the species and. accordingly, are identified as "TiSO-i" where the number "i" is an integer. This designation is an arbitrary one and is not intented to denote structural relations to another material(s) which may also be characterized by a numbering system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to titanium silicate molecular sieves having three-dimensional microporous crystal framework structures of TiO₂ and SiO₂ tetrahedral units which have a unit empirical formula on an anhydrous basis of: mR : (Ti_χSi_y)O₂ (1) wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of (Ti_xSi_y)O₂ and has a value of between zero and about 0.3. , the maximum value in each case depending upon the molecular dimensions of the templating agent and the available void volume of pore system of the particular TiSO molecular sieve; and the values of "x" and "y" are generally greater than 0.01 and less than 0.99. x+y= 1 and are such that: (1) "y" is less than 0.9615 and "x" is greater than 0.0385 when characterized by the x-ray pattern of Table III; (2) "x" and "y" are greater

.than 0.01 and less than 0.99 when characterized by the x-ray pattern of Table VII; or (3) "y" is greater than 0.7776 and less than 0.9615 or less than 0.05 and "x" is greater than 0.0385 and less than 0.2224 and greater than 0.5.

The term "unit empirical formula" is used herein according to its common meaning to designate the simplest formula which gives the relative number of moles of titanium and silicon which form TiO₂ and SiO₂ tetrahedral units of the titanium silicate molecular sieves of the instant invention and which form the molecular framework of the TiSO composition(s). The unit empirical formula is given in terms of titanium and silicon and oxygen as shown in Formula (1). above, and does not include other compounds, cations or anions which may be present as a result of the preparation or the existence of other impurities or materials in the bulk composition not containing the aforementioned tetrahedral unit. The amount of template R is reported as part of the composition when the as-synthesized unit empirical formula is given, and water may also be reported unless such is defined as the anhydrous form. For convenience, coefficient "m" for template "R" is reported as a value that is normalized by dividing the number of moles of organic by the total moles of titanium and silicon.

The unit empirical formula for a given TiSO can be calculated using the chemical analysis data for that TiSO. Thus, for example, in the preparation of TiSOs disclosed hereinafter the over all composition of the as-synthesized TiSO is calculated using the chemical analysis data and expressed in terms of molar oxide ratios on an anhydrous basis.

The unit empirical formula for a TiSO may be given on an "as-synthesized" basis or may be given after an "as-synthesized" TiSO composition has been subjected to some post treatment process, e.g., calcination. A preferred subclass of the TiSO compositions of formula 1 is when "m" has a value of 0.01 to about 0.3. The term "as-synthesized" herein shall be used to refer to the TiSO composition(s) formed as a result of the hydrothermal crystallization but before the TiSO composition has been subjected to post treatment to remove any volatile components present therein. The actual value of "m" for a post-treated TiSO will depend on several factors (including: the particular TiSO, template, severity of the post-treatment in terms of its ability to remove the template from the TiSO. the proposed application of the TiSO composition, and etc.) and the value for "m" can be within the range of values as defined for the as-synthesized TiSO compositions although such is generally less than the as-synthesized TiSO unless such post-treatment process adds template to the TiSO so treated. A TiSO composition which is in the calcined or other post-treatment form generally has an empirical formula represented by Formula (1), except that the value of "m" is generally less than about 0.02 and preferably less than 0.01. Under sufficiently severe post-treatment conditions, e.g. roasting in air at high temperature for long periods (over 1 hr.), the value of "m" may be zero (0) or, in any event, the template, R, is undetectable by normal analytical procedures.

The TiSO molecular sieves of the instant invention are generally synthesized by hydrothermal crystallization from a reaction mixture comprising reactive sources of titanium, silicon, oxygen and preferably one or more organic templating agents. Optionally, alkali metal(s) may be present in the reaction mixture. The reaction mixture is generally placed in a pressure vessel, preferably lined .with an inert plastic material, such as polytetrafluoroethylene. and heated, preferably under the autogenous pressure, at an effective temperature between about 50°C and about 250°C, until crystals of the molecular sieve product are obtained, usually for an effective period of from several hours to several weeks and typically an effective period of from about 2 hours to about 2 weeks. While not essential to the synthesis of the instant molecular sieves, it has been found that in general stirring or other moderate agitation of the reaction mixture and/or seeding of the reaction mixture with seed crystals of either the TiSO to be produced, or a topologically similar composition, facilitates the crystallization procedure. The product is recovered by any convenient method such as centrifugation or filtration.

After crystallization the TiSO may be isolated and washed with water and dried in air. As a result of the hydrothermal crystallization, the as-synthesized TiSO generally contains within its intracrystalline pore system at least one form of any template employed in its formation. Generally, the template is an organic molecular species, but it is possible, steric considerations permitting, that at least some of the template is present as a charge-balancing cation. Generally the template is too large to move freely through the intracrystalline pore system of the formed TiSO and may be removed by a post-treatment process, such as by calcining the TiSO at temperatures of between about 200°C and to about 700ºC so as to thermally degrade the template or by employing some other post-treatment process for removal of at least part of the template from the TiSO. In some instances the pores of the TiSO are sufficiently large to permit transport of the template, and, accordingly, complete or partial removal thereof can be accomplished by conventional desorption procedures such as carried out in the case of zeolites.

The TiSO compositions are preferably formed from a reaction mixture containing reactive sources of TiO₂ and SiO₂ and an organic templating agent, said reaction mixture comprising a composition expressed in terms of molar oxide ratios of: aR₂O:(Ti_χSi_y)O₂:b H₂O wherein "R" is an organic templating agent; "a" is an effective amount of "R" said effective amount being that amount which form said TiSO compositions and preferably being from greater than zero to about 50 and more preferably between about 0.5 and about 10; "b" is an effective amount of water and has a value of from zero to about 400. more preferably from about 50 to about 100; and "x" and "y" represent the mole fractions, respectively of titanium and silicon in the (Ti_xSi_y)O₂ constituent and each have a value of at least 0.001 and are preferably at least 0.01.

The reaction mixture from which these TiSOs are formed generally contain one or more organic templating agents (templates) which can be most any of those heretofore proposed for use in the synthesis of aluminosilicates and aluminophosphates. The template preferably contains at least one element of Group VA of the Periodic Table, particularly nitrogen, phosphorus, arsenic and/or antimony, mote preferably nitrogen or phosphorus and most preferably nitrogen and are of the formula R₄X⁺ wherein X is selected from the group consisting of nitrogen, phosphorus, arsenic and/or antimony and R may be hydrogen, alkyl, aryl. araalkyl, or alkylaryl group and is preferably aryl or alkyl containing between 1 and 8 carbon atoms. although more than eight carbon atoms may be present in "R" of group of the template. Nitrogen-containing templates are preferred, including amines and quaternary ammonium compounds, the latter being represented generally by the formula R'₄N⁺ wherein each R' is an alkyl. aryl, alkylaryl. or araalkyl group; wherein R' preferably contains from 1 to 8 carbon atoms or higher when R' is alkyl and greater than 6 carbon atoms when R' is otherwise, as hereinbefore discussed. Polymeric quaternary ammonium salts such as [(C₁₄H₃₂N₂) (OH)₂]_x wherein "x" has a value of at least 2 may also be employed. The mono-, di- and tri-amines, including mixed amines, may also be employed as templates either alone or in combination with a quaternary ammonium compound, quarternary phosphonium compound or another template. The exact relationship of various templates when concurrently employed is not clearly understood. Mixtures of two or more templating agents can produce either mixtures of TiSOs or in the instance where one template is more strongly directing than another template the more strongly directing template may control the course of the hydrothermal crystallization with the other template serving primarily to establish the pH conditions of the reaction mixture. Representative templates include: tetramethylammonium; tetraethylammonium; tetrapropylammonium; tetrabutylammonium ions; di-n-propylamine; tripropylamine; triethylamine; triethanolamine; piperidine; cyclohexylamine; 2-methylpyridine; N,N-dimethylbenzylaraine; N,N-diethylethanolamine; dicyclohexylamine; N,N-dimethylethanolamine; 1,4-diazabicyclo (2,2,2) octane; N-methyldiethanolamine, N-raethylethanolamine; N-methylcyclohexylamine; 3-methylpyridine; 4-methylpyridine; quinuclidine; N,N'-dimethyl-1,4-diazabicyclo (2,2,2) octane ion; di-n-butylamine, neopentylamine; di-n-pentylamine; isopropylamine; t-butylamine; ethylenediamine; pyrrolidine; and 2-imidazolidone. As will be readily apparent to one skilled in the art, not every template will produce every TiSO composition although a single template can, with proper selection of the reaction conditions, provide for the formation of different TiSO compositions, and a given TiSO composition can be produced using different templates.

In those instances where an alkoxide is the reactive titanium and/or silicon source, the corresponding alcohol is necessarily present in the reaction mixture since it is a hydrolysis product of the alkoxide. It has not as yet been determined whether this alcohol participates in the synthesis process as a templating agent, or in some other function and, accordingly, is not reported as a template in the unit formula of the TiSOs, although such may be acting as templates.

Alkali metal cations when present in the reaction mixture may facilitate the crystallization of certain TiSOs although the exact function of such cations in crystallization, if any, is not presently known. Alkali cations present in the reaction mixture generally appear in the formed TiSO compositions, either as occluded (extraneous) cations and/or as structural cations balancing net negative charges at various sites in the crystal lattice. It should be understood that although the unit formula for the TiSOs does not specifically recite the presence of alkali cations they are not excluded in the same sense that hydrogen cations and/or hydroxyl groups are not specifically provided for in the traditional formulae for zeolitic aluminosilicates. Most any reactive titanium source may be employed herein. The preferred reactive titanium sources include titanium alkoxides, water-soluble titanates. titanium chelates, titanate esters and titanium salts and the like.

Most any reactive source of silicon can be employed herein. The preferred reactive, sources of silicon are silica, either as a silica sol or as fumed silica, a reactive solid amorphous precipitated silica, silica gel, alkoxides of silicon, silicic acid or alkali metal silicate and mixtures thereof.

The X-ray patterns carried out herein and all other X-ray patterns appearing herein were obtained using either: (1) standard x-ray powder diffraction techniques; or (2) by use of using copper K-alpha radiation with computer based techniques using Siemens D-500 X-ray powder diffractometers, Siemens Type K-805 X-ray sources, available from Siemens Corporation, Cherry Hill. New Jersey, with appropriate computer interface. When employing the standard X-ray technique the radiation source is a high-intensity, copper target. X-ray tube operated at 50 Kv and 40 ma. The diffraction pattern from the copper K-alpha radiation and graphite monochromator is suitably recorded by an X-ray spectrometer scintillation counter, pulse height analyzer and strip chart recorder. Flat compressed powder samples are scanned at 2°(2θ) per minute, using a two second time constant. Interplanar spacings (d) in Angstrom units are obtained from the position of the diffraction peaks expressed as 2θ (theta) where theta is the Bragg angle as observed on the strip chart. Intensities are determined from the heights of diffraction peaks after subtracting background. "I_o" being the intensity of the strongest line or peak, and "I" being the intensity of each of the other peaks. When Relative Intensities are reported herein the following abbreviations mean: vs = very strong; s = strong; m a medium, w = weak; and vw = very weak. Other abbreviations include: sh = shoulder; and br a broad.

As will be understood by those skilled in the art, the determination of the parameter 2 theta is subject to both human and mechanical error, which in combination, can impose an uncertainty of about ±0.4° on each reported value of 2 theta. This uncertainty is, of course, also manifested in the reported values of the d-spacings, which are calculated from the 2 theta values. This imprecision is general throughout the art and is not sufficient to preclude the differentiation of the present crystalline materials from each other and from the compositions of the prior art.

The following examples are provided to exemplify the invention and are not meant to be limiting thereof in any way.

EXAMPLES 1-18 (a) Examples 1 to 18 were carried out to demonstrate the preparation of the TiSO compositions of this invention. The TiSO compositions were carried out by the hydrothermal crystallization procedure discussed supra. Reaction mixtures were prepared for each example using one or more of the following preparative reagents:

(a) Tipro: Titanium isopropoxide;

(b) LUDOX-LS: Trademark of DuPont for a low soda aqueous solution of 30 weight percent SiO₂ and 0.1 weight percent Na₂O;

(c) LUDOX-AS: Trademark of DuPont for an ammonium stabilized aqueous solution of 40 weight percent SiO₂ and 0.08 weight percent Na₂O.

(d) Ammonium hydroxide;

(e) Sodium hydroxide;

(f) TBAOH: tetrabutylammonium hydroxide;

(g) TEAOH: tetraethylammonium hydroxide; (h) TPAOH: tetrapropylammonium hydroxide.

The method of addition of the above mentioned components to the reaction mixture was done according to three methods (A. B and C). Methods A. B and C are as follows:

METHOD A

LUDOX-LS and one-third of the water were blended to form a homogeneous mixture. The sodium hydroxide was dissolved in two-thirds of the water and mixed with the above mixture to form a homogeneous mixture. Titanium isopropoxide was blended into this mixture followed by the addition of the organic templating agent (tetrapropylammonium hydroxide). This mixture was then blended until a homogeneous mixture was observed.

METHOD B

Method B is similar to Method A except that LUDOX-LS was blended with eighty percent of the water and the sodium hydroxide was blended with 20 percent of the water.

METHOD C

LUDOX-AS, ammonium hydroxide and water are blended to form a homogeneous mixture. Titanium isopropoxide is added to this mixture and blended to form a homogeneous mixture. Tetrabutylammonium hydroxide was added and the mixture again blended until a homogeneous mixture was observed.

(b) Table I sets forth the preparation of TiSO-45 and TiSO-48 wherein the various reagents are set forth by denominating the moles of each as follows: cR: dTiO₂ : eSiO₂: fNaOH: gH₂O where c, d, e. f and g represent the number of moles of organic templating agent R, TiO₂ , SiO₂, NaOH and H₂O, respectively.

EXAMPLE 19 The TiSO-45 product from example 10 was calcined in air at 600ºC for 1 hour and its .adsorption capacity determined. The adsorption capacities were measured using a standard McBain-Bakr gravimetric adsorption apparatus on samples activated in a vacuum at 350°C. The data for TiSO-45 were as follows:

(Example 10) TiSO-45:

Kinetic Pressure Temp. wt % Diameter, A° (Torr) (ºC) Adsorbed

O₂ 3.46 105 -183 11.8

O₂ 3.46 741 -183 13.4

Cyclohexane 6.0 65 23.6 2.5

Neopentane 6.2 739 23.5 1.3 H₂O 2.65 4.6 23.8 2.7 H₂O 2.65 20 24.0 6.1

A portion of the above calcined TiSO-45 was acid washed with 1 Normal hydrochloric acid and the adsorption capacities measured. The data were as follows:

Kinetic Pressure Temp. wt % Diameter, Aº (Torr) (ºC) Adsorbed

O₂ 3.46 105 -183 14.1 O₂ 3.46 741 -183 15.8

Cyclohexane 6.0 65 23.6 3.0

Neopentane 6.2 739 23.5 1.4

H₂O 2.65 4.6 23.8 2.8

H₂O 2.65 20 24.0 6.6 EXAMPLE 20

(a) The as-synthesized products of examples 10 and 18 were analyzed (chemical analysis) to determine the weight percent SiO₂, Na₂O,

TiO₂ , LOI (Loss on Ignition), carbon (C) and nitrogen (N) present as a result of the template. The results of these analyses were as follows:

(b) (Example 10) TiSO-45: Component Weight Percent SiO₂ 68.3 TiO₂ 13.7

Na₂O 3.7

C 5.8

N 0.6

LOI 12.5

The above chemical analysis gives an anhydrous formula of:

0.040 R (Si_0.869Ti_0.132)

(c) (Example 18) TiSO-48: Component Weight Percent SiO₂ 82.8

TiO₂ 3.8

Na₂O 0.05*

C 7.3

N 0.71

LOI 13.2

*less than 0.05 The above chemical analysis gives an anhydrous formula of:

0.038 R (Si_0.967Ti_0.033)

(c) EDAX (energy dispersive analysis by X-ray) microprobe analysis was carried out on clean crystals (polished with diamond powder and carbon coated) on the TiSO product prepared in example 10. The EDAX microprobe analysis showed titanium present as an integral part of the crystal particle of the TiSO compositions. The relative amounts of SiO₂, TiO₂ and Na₂O expressed as a weight percent was as follows:

Example 10

Spot Probe

Ti 3.4

Si 10.0

Al 1.2

EXAMPLE 21 a) TiSO-45. as prepared in example 10, was subjected to x-ray analysis. TiSO-45 was determined to have a characteristic x-ray powder diffraction pattern which contains the d-spacings set forth in Table II below:

b) All of the as-synthesized TiSO-45 compositions for which X-ray powder diffraction data have been obtained to date have patterns which are characterized by the data of Table III. below:

(c) A portion of the as-synthesized TiSO-45 of part (a) was calcined in air at 600ºC for about one hour. The calcined product was characterized by the X-ray powder diffraction pattern of Table IV below: (d) The TiSO-45 compositions for which X-ray powder diffraction data have been obtained to date have patterns which are characterized by the X-ray powder diffraction pattern shown in Table V below:

EXAMPLE 22 a) TiSO-48, as prepared to in example 18, was subjected to X-ray analysis and was determined to have a characteristic X-ray powder diffraction pattern which contains at least the d-spacing set forth in Table VI. below:

b) All of the TiSO-48 compositions for which X-ray powder diffraction data have been obtained to date have patterns which are characterized by the data of Table VII. below:

(c) A portion of the as-synthesized TiSO-48 of part (a) was calcined in air at 500ºC for 1.5 hours. The calcined product was characterizedby the X-ray powder diffraction pattern of Table VIII below:

(d) The TiSO-48 compositions for which X-ray powder diffraction data have been obtained to date have patterns which are characterized by the X-ray powder diffraction pattern shown in Table IX below:

EXAMPLE 23

In order to demonstrate the catalytic activity of the TiSO compositions a calcined (air, 600ºC. 1 hour) sample of the product of Example 10 and an calcined and acid washed (air, 600°C. 1 hour. IN HCl) were tested for catalytic cracking. The test procedure employed was the catalytic cracking of premixed two (2) mole % n-butane in helium stream in a 1/2" O.D. quartz tube reactor over up to about 5 grams (20-40 mesh) of the TiSO samples to be tested. The sample was activated in situ for 60 minutes at 500°C under 200 cm³/min dry helium purge. Then the two (2) mole (percent) n-butane in helium at a flow rate of 50 cm³/min was passed over the sample for 40 minutes with product stream analysis being carried out at 10 minute intervals. The pseudo-first-order rate constant (k_A) was then calculated to determine the catalytic activity of the TiSO composition. The k_A value (cm³/g min) obtained for the TiSO compositions are set forth below:

Sample Ex. No. Rate Constant (k_A)

10 0.3

10* 0.3

* acid washed sample EXAMPLE 24 (COMPARATIVE EXAMPLE) This is a comparative example wherein example 1 of European Patent Application No. 82109451.3 was repeated and the product evaluated by several techniques as hereinafter discussed:

(a) Example 1 of European Patent Application No. 82109451.3 was repeated with the starting reaction mixture having a composition based on molar ratios of:

1 Al₂O₃:47 SiO₂ :1.32 TiO₂:11.7 NaOH:28 TPAOH:1498 H₂O The reaction mixture was divided and placed in two digestion vessels. At the end of the procedure set forth in example 1 of the European Application a sample of the product from each digestion vessel was analyzed and gave the following chemical analyses: Weight Percent

Sample 1 Sample 2 siO₂ 75.3 75 .9

Al₂O₃ 3.02 2 .58

TiO₂ 3.91 4 .16

Na₂O 3.66 3 .46

Carbon 6.3 6.7

Nitrogen 0.62 0. 65

LOI* 14.0 14. 0

*Loss on Ignition

The two samples were then analyzed by SEM (scanning electron microscope) and EDAX (energy dispersive analysis by X-ray) microprobe. The SEM probe of the two samples showed four morphologies to be present and such are shown in FIG. 1. The four morphologies of the two samples prepared in accordance with the European application and the EDAX microprobe analysis for each morphology was as follows:

(1) Smooth, intergrown hexagonal particles (at B in FIG. 1) which are associated with a ZSM-5 morphology had an EDAX microprobe of:

Average of Spot Probes Ti 0

Si 1.0

Al 0.05

(2) Flat, smooth plates (at A in FIG. 1) had an EDAX microprobe of:

Average of Spot Probes

Ti 0.13

Si 1.0

Al 0.05

(3) Spheres and elongated bundles (at C in FIG. 1) had an EDAX microprobe of:

Average of Spot Probes Ti 0.22

Si 1.0

Al 0.05

Na 0.10

(4) Needles or fine rods (at D in FIG. 1) had an EDAX microprobe of: Average of Spot Probes Ti 0.05

Si 0.8

Al 0.13

Na 0.05

Cl 0.10

The above SEM and EDAX data demonstrate that although ZSM-5 type crystals were formed that these crystals contained no detectable titanium. The only detectable titanium was present as impurity phases and not in a crystal having the ZSM-5 structure.

The X-ray diffraction patterns of the as-synthesized materials were obtained and the following X-ray patterns were observed:

Tables X and XI shows an X-ray pattern typical of a ZSM-5 type product and can be attributed to the smooth, integrown hexagonal particles which contained no titanium. The X-ray patterns of Tables X and XI show three peaks (2θ = 5.6-5.8, 12.45-12.54 and 24.5-24.72) which could not be explained. Two samples were calcined with a separate portion of each sample being calcined in air 540ºC for sixteen hours. These calcination conditions correspond to those employed in European Application No. 82109451.3. The X-ray patterns of the calcined products were as follows:

The X-ray diffraction patterns of the calcined samples show a ZSM-5 type pattern with only slight differences from the as-synthesized. When chemical analysis (bulk) of a portion of the calcined samples 1 and 2 are carried out the following is obtained:

Weight Percent

Sample 1 Sample 2

SiO₂ 79.6 81.2 Al₂O₃ 3.5 2.9 Na₂O 4.4 4.1

TiO₂ 4.4 4.6

C 0.1 0.10 LOI 8.1 7.6

When the molar ratio of oxides is computed for the above bulk analysis the following is obtained:

1 SiO₂: 0.043 TiO₂: 0.021 Al₂O₃.: 0.049 Na₂O This compares quite well with the bulk chemical analysis reported in the European application which is:

1 SiO₂: 0.047 TiO₂: 0.023 Al₂O₃ : 0.051 Na₂O Although it is clear that the product crystals which gave the product an X-ray pattern characteristic of ZSM-5 contained no titanium, the bulk analysis of the product showed titanium to be present as a result of impurity crystals not having an X-ray pattern characteristic of ZSM-5.

PROCESS APPLICATIONS The TiSO compositions of this invention have unique surface characteristics making them useful as molecular sieves and as catalyst or as bases for catalysts in a variety of separation, hydrocarbon conversion and oxidative combustionprocesses. The TiSO composition can be impregnated or otherwise associated with catalytically active metals by the numerous methods known in the art and used, for example, in fabricating catalysts compositions containing alumina or aluminosilicate materials.

TiSO's may be employed for separating molecular species in admixture with molecular species of a different degree of polarity or having different kinetic diameters by contacting such mixtures with a TiSO(s) having pore diameters large enough to adsorb at least one but not all molecular species of the mixture based on the polarity of the adsorbed molecular species and/or its kinetic diameter. When TiSOs are employed for such separation processes the TiSOs are at least partially activated whereby some molecular species selectively enter the intracrystalline pore system thereof.

The hydrocarbon conversion reactions catalyzed by TiSO compositions include; cracking, hydrocracking; alkylation of both the aromatic and isoparaffin types; isomerization (including xylene isomerization); polymerization; reforming; hydrogenation; dehydrogenation; transalkylation; dealkylation; and hydration.

When a TiSO containing catalyst compositions contains a hydrogenation promoter, such promoter may be platinum, palladium, tungsten, nickel or molybdenum and may be used to treat various petroleum stocks including heavy petroleum residual stocks, cyclic stocks and other hydrocrackable charge stocks. These stocks can be hydrocracked at temperatures in the range of between about 400°F and about 825°F using molar ratios of hydrogen to hydrocarbon in the range of between about 2 and about 80. pressures between about 10 and about 3500 p.s.i.g., and a liquid hourly space velocity (LHSV) of between about 0.1 and about 20. preferably between about 1.0 and about 10.

TiSO containing catalyst compositions may also be employed in reforming processes in which the hydrocarbon feedstocks contact the catalyst at temperatures between about 700ºF and about 1000°F. hydrogen pressures of between about 100 and about 500 p.s.i.g., LHSV values in the range between about 0.1 and about 10 and hydrogen to hydrocarbon molar ratios in the range between about 1 and about 20, preferably between about 4 and about 12.

Further. TiSO containing catalysts which contain hydrogenation promoters, are also useful in hydroisomerization processes wherein the feedstock(s). such as normal paraffins, is converted to saturated branched-chain isomers. Hydroisomerization processes are typically carried out at a temperature between about 200°F and about 600°F. preferably between about 300°F and about 550ºF with an LHSV value between about 0.2 and about 1.0. Hydrogen is typically supplied to the reactor in admixture with the hydrocarbon feedstock in molar proportions of hydrogen to the feedstock of between about 1 and about 5. TiSO-containing compositions similar to those employed for hydrocracking and hydroisomerization may also be employed at between about 650°F and about 1000ºF. preferably between about 850ºF and about 950°F and usually at somewhat lower pressures within the range between about 15 and about 50 p.s.i.g. for the hydroisomerization of normal paraffins. Preferably the paraffin feedstock comprises normal paraffins having a. carbon number range of C₇-C₂₀. The contact time between the feedstock and the TiSO containing catalyst is generally relatively short to avoid undersirable side reactions such as olefin polymerization and paraffin cracking. LHSV values in the range between about 0.1 and about 10, preferably between about 1.0 and about 6.0 are suitable.

The low alkali metal content (often not measurable by current analytical techniques) of the instant TiSO compositions make them particularly well suited for use in the conversion of alkylaromatic compounds, particularly for use in the catalytic disproportionation of toluene, xylene. trimethylbenzenes. tetramethylbenzenes and the like. In such disproportionation processes it has been observed that isomerization and transalkylation can also occur. The TiSO-containing catalysts for such processes will typically include Group VIII noble metal adjuvants alone or in conjunction with Group VI-B metals such as tungsten, molybdenum and chromium which are preferably included in such, catalyst compositions in amounts between about 3 and about 15 weight-% of the overall catalyst composition. Extraneous hydrogen can, but need not be present in the reaction zone which is maintained at a temperature between about 400 and about 750°F, pressures in the range between about 100 and about 2000 p.s.i.g. and LHSV values in the range between about 0.1 and about 15.

TiSO containing catalysts may be employed in catalytic cracking processes wherein such are preferably employed with feedstocks such as gas oils, heavy naphthas, deasphalted crude oil residues etc. with gasoline being the principal desired product. Temperature conditions are typically between about 850 and about 1100ºF. LHSV values between about 0.5 and about 10 pressure conditions are between about 0 p.s.i.g. and about 50 p.s.i.g.

TiSO containing catalysts may be employed for dehydrocyclization. reactions which employ paraffinic hydrocarbon feedstocks, preferably normal paraffins having more than 6 carbon atoms, to form benzene, xylenes, toluene and the like. Dehydrocyclization processes are typically carried out using reaction conditions similar to those employed for catalytic cracking. For such processes it is preferred to use a Group VIII non-noble metal cation such as cobalt and nickel in conjunction with the TiSO composition.

TiSO containing catalysts may be employed in catalytic dealkylation where paraffinic side chains are cleaved from aromatic nuclei without substantially hydrogenating the ring structure at relatively high temperatures in the range between about 800°F and about 1000°F at moderate hydrogen pressures between about 300 and about 1000 p.s.i.g. with other conditions being similar to those described above for catalytic hydrocracking. TiSO containing catalysts for catalytic dealkylation are of the same type described above in connection with catalytic dehydrocyclization. Particularly desirable dealkylation reactions contemplated herein include the conversion of methylnaphthalene to naphthalene and toluene and/or xylenes to benzene.

TiSO containing catalysts may be used in catalytic hydrofining wherein the primary objective is to provide for the selective hydrodecomposition of organic sulfur and/or nitrogen compounds without substantially affecting hydrocarbon molecules present therewith. For this purpose it is preferred to employ the same general conditions described above for catalytic hydrocracking. The catalysts are the same typically of the same general nature as described in connection with dehydrocyclization operations. Feedstocks commonly employed for catalytic hydroforming include: gasoline fractions; kerosenes; jet fuel fractions; diesel fractions; light and heavy gas oils; deasphalted crude oil residua; and the like. -The feedstock may contain up to about 5 weight-percent of sulfur and up to about 3 weight-percent of nitrogen.

TiSO containing catalysts may be employed for isomerization processes under conditions similar to those described above for reforming although isomerization processes tend to require somewhat more acidic catalysts than those employed in reforming processes. Olefins are preferably isomerized at temperatures between about 500°F and about 900°F. while paraffins, naphthenes and alkyl aromatics are isomerized at temperatures between about 700°F and about 1000°F. Particularly desirable isomerization reactions contemplated herein include the conversion of n-heptane and/or n-octane to isoheptanes, iso-octanes, butane to iso-butane, methylcyclopentane to cylcohexane, meta-xylene and/or ortho-xylene to para-xylene. 1-butene to 2-butene and/or isobutene. n-hexene to isohexane. cyclohexane to methylcyclopentene etc. The preferred cation form is a combination of a TiSO with polyvalent metal compounds (such as sulfides) of metals of Group II-A. Group II-B and rare earth metals. For alkylation and dealkylation processes TiSO compositions having pores of at least 5A are preferred. When employed for dealkylation of alkyl aromatics. the temperature is usually at least 350°F and ranges up to a temperature at which substantial cracking of the feedstock or conversion products occurs, generally up to about 700°F. The temperature is preferably at least 450°F and not greater than the critical temperature of the compound undergoing dealkylation. Pressure conditions are applied to retain at least the aromatic feed in the liquid state. For alkylation the temperature can be as low as 250°F but is preferably at least 350°F. In alkylation of benzene, toluene and xylene. the preferred alkylation agents are olefins such as ethylene and propylene. The TiSO compositions of this invention may be employed in conventional molecular sieving processes as heretofore have been carried out usingaluminosilicate, aluminophosphate or other commonly employed molecular sieves. TiSO compositions are preferably activated prior to their use in a molecular sieve process to remove any molecular species which may be present in the intracrystalline pore system as a result of synthesis or otherwise. For the TiSO compositions this is sometimes accomplished by thermally destroying the organic species present in an as-synthesized TiSO since such organic species may be too large to be desorbed by conventional means.

The TiSO compositions of this invention are also useful as adsorbents and are capable of separating mixtures of molecular species both on the basis of molecular size (kinetic diameters) and based on the degree of polarity of the molecular species. When the separation of molecular species is based upon the selective adsorption based on molecular size, the TiSO is chosen in view of the dimensions of its pores such that at least the smallest molecular specie of the mixture can enter the intracrystalline void space while at least the largest specie is excluded. When the separation is based on degree of polarity it is generally the case that the more hydrophilic TiSO will preferentially adsorb the more polar molecular species of a mixture having different degrees of polarity even though. both molecular species can communicate with the pore system of the TiSO.

Claims

WHAT IS CLAIMED IS:

1. Crystalline titano-silicate molecular sieves having pores having nominal diameters of greater than about 3 Angstroms and whose chemical composition in the as-synthesized and anhydrous form is represented by the unit empirical formula: mR:(Ti_χSi_y)O₂

wherein "R" represents organic templating agent present in the intracrystalline pore system; "m" represents the moles of "R" present per mole of

(Ti_xSi_y)O₂ and has a value of from zero and about 0.3; and the values of "x" and "y" are generally greater than 0.01 and less than 0.99, x+y= 1 and are such that: (1) "y" is less than 0.9615 and "x" is greater than 0.0385 when characterized by the x-ray pattern of Table III; (2) "x" and "y" are greater than 0.01 and less tha 0.99 when characterized by the x-ray pattern of Table VII; or (3) "y" is greater than 0.7776 and less than 0.9615 or less than 0.05 and "x" is greater than 0.0385 and less than 0.2224 and greater than 0.5.

2. Molecular sieve according to claim 1 wherein "x" and "y" are as in (1) of claim 1.

3. Molecular sieve according to claim 2 wherein "x" and "y" are as in (2) of claim 1.

4. Crystalline titano-silicate molecular sieves wherein "x" and "y" are as in (3) of claim 1.

5. The titano-silicates of claim 1 having the characteristic X-ray powder diffraction pattern set forth in Table III.

6. The titano-silicates of claim 1 having the characteristic X-ray powder diffraction pattern set forth in Table VII.

7. The titano-silicates of claim 1 or claim 2 wherein "m" has a value of greater than 0.01 to about 0.3.

8. The crystalline molecular sieves of claim 1 or claim 4 wherein said molecular sieves have been calcined to remove at least some of any organic template present.

9.. Process for preparing the crystalline titano-silicate molecular sieves comprising providing at an effective temperature and for an effective time a reaction mixture composition expressed in terms of molar oxide ratios as follows: aR:(Ti_xSi_y):bH₂O wherein "R" is an organic templating agent; "a" is an effective amount of "R" from greater than zero to about 50; "b" has a value of from zero to about 400; and "x" and "y" represent the mole fractions of titanium and silicon, respectively, in the (Ti_xSi_y) constituent, and each has a value of at least 0.01. whereby the crystalline molecular sieves of claim 1 or claim 2 are prepared.

10. Process according to claim 9 wherein the source of silicon in the reaction mixture is silica.

11. Process according to claim 9 wherein the source of titanium is selected from the group consisting of titanium alkoxides. water soluble titanates. titanium chelates and titanate esters.

12. Process according to claim 8 where the organic templating agent is selected from the group consisting of quaternary ammonium or quaternary phosphonium compounds of the formula:

R ₄X⁺ wherein X is nitrogen or phosphorous and each R is alkyl containing between 1 and about 8 carbon atoms or aryl.

13. Process according to claim 9 wherein the templating agent is selected from the group consisting of tetrapropylammonium ion: tetraethylammonium ion; tripropylamine: triethylamine; triethanolamine; piperidine; cyclohexylamine; 2-methyl pyridine; N,N-dimethylbenzylamine; N,N-diethylethanolamine; dicyclohexylamine; N,N-dimethylethanolamine; choline; N,N-dimethylpiperazine; pyrrolidine; 1,4-diazabicyclo-(2.2.2) octane; N-methylpiperidine; 3-methylpiperidine; N-methylcyclohexylamine; 3-methylpyridine; 4-methylpyridine; quinuclidine; N,N-dimethyl-1.4-diazabicyclo (2.2.2) octane ion; tetramethylammonium ion; tetrabutylammonium ion. tetrapentylammonium ion; di-n-butylamine: neopentylamine; di-n-pentylamine; isopropylamine; t-butylamine; ethylenediamine and 2-imidazolidone; di-n-propylamine; and a polymeric quaternary ammonium salt [(C₁₄H₃₂N₂)(OH)₂]x wherein x is a value of at least 2.

14. Process for separating mixtures of molecular species wherein such mixtures contain molecular species having different degrees of polarity and/or kinetic diameters comprising contacting said mixture with a composition of claim 1 or Claim 2.

15. Process for converting a hydrocarbon which comprises contacting said hydrocarbon under hydrocarbon converting conditions with a crystalline molecular sieve as set forth in claim 1 or claim 2.

16. Process according to claim 15 wherein the hydrocarbon conversion process is cracking.

17. Process according to claim 15 wherein the hydrocarbon conversion process is hydrocracking.

18. Process according to claim 15 wherein the hydrocarbon conversion process is hydrogenation.

19. Process according to claim 15 wherein the hydrocarbon conversion process is polymerization.

20. Process according to claim 15 wherein the hydrocarbon conversion process is alkylation.

21. Process according to claim 15 wherein the hydrocarbon conversion process is reforming.

22. Process according to claim 15 wherein the hydrocarbon conversion process is hydrotreating.

23. Process according to claim 15 wherein the hydrocarbon conversion process is isomerization.

24. Process according to claim 15 wherein the hydrocarbon conversion process is dehydrocyclization.