EP0000669A1

EP0000669A1 - Zeolite ZSM-11, a method for preparing it, and a process of catalytic conversion using a catalyst comprising it

Info

Publication number: EP0000669A1
Application number: EP78300219A
Authority: EP
Inventors: Louis Dean Rollmann; Ernest William Valyocsik
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1977-08-01
Filing date: 1978-08-01
Publication date: 1979-02-07
Also published as: EP0000669B1; NZ188025A; JPS6215488B2; AU515825B2; CA1119146A; DE2860140D1; ZA784360B; AU3848978A; IT7826376A0; JPS5452699A; IT1097569B; US4108881A

Abstract

A new as-synthesised form of zeolite ZSM-₁1, and a method of preparing it, which contrast with the conventional in provision of low sodium content. Synthesis is conducted in the presence of one or more 7-12 carbon alkylenediamines instead of the previously employed Group VA quaternary. The product has the lattice structure of ZSM-11 and similar catalytic effectiveness.

Description

The present invention relates to a new form of ZSM-11 to a process for preparing it and to a method for using it in organic compound conversion reactions.
Zeolite ZSM-11 is a relatively new zeolite which when conventionally synthesized frequently has the composition, expressed in terms of mole ratios of oxides in the anhydrous state:
wherein M is a mixture of at least one of the quaternary cations of Group VA of the Periodic Table, such as tetrabutylammonium or tetrabutylphosphonium, and alkali metal cations, especially sodium, n is the valence of M and x is from 10 to 150. It has a distinctive X-ray diffraction pattern which establishes its individuality. The original alkali metal cations of ZSM-11 have been exchanged with " other cations to form species of the zeolite which have catalytic properties. Zeolite ZSM-11 and its conventional preparation are the subject of U.S. Specification 3,709,979.
The known method of synthesising ZSM-11 has been to form a mixture of alumina, silica, alkali metal oxide, water and a quaternary compound of a Group VA element such that the mixturs has a composition, in terms of mole ratios of oxides, falling within the following range:
wherein M is an alkali metal ion and R' is a quaternary cation of a Group VA element. The reaction mixture is maintained at a temperature of from about 100°C to about 200°C until crystals of ZSM-11 are formed.
Zeolite ZSM-11 is characterised by a crystalline structure whose X-ray diffraction pattern shows the following significant lines:
The parenthesis around lines 3.07 and 3.00 indicate that they are separate and distinct lines, but are often superimposed. These values are determined by standard techniques. The radiation is the K-alpha doublet of copper, and a Geiger counter spectrometer with a strip chart pen recorder is used. The peak heights, I, and the positions as a function of 2 times theta, where theta is the Bragg angle, are read from the spectrometer chart. From these, the relative intensities, 100 I/I_o, where I is the intensity of the strongest line or peak, and d (obs.), the interplanar spacing in Angstrom units, corresponding to the recorded lines, are calculated.
This X-ray diffraction pattern is characteristic of all species of ZSM-11. Ion exchanged forms of the zeolite reveal substantially the same pattern possibly with some minor shifts in interplanar spacing and variation in relative intensity. Other minor variations can occur depending on the silicon to aluminum ratio of the particular sample and its thermal history.
According to the present invention zeolite ZSM-11 possesses, as synthesised, the formula, in terms of mole ratios of oxides:

(0.5-10.0)R:(0-0.5)M₂O:Al₂O₃:xSiO₂ wherein M is an alkali metal ion, R is an alkylenediamine having from 7 to 12 carbon atoms or an organic cation derived therefrom, and x is at least 10, for instance up to 1000, often falling within the range 10 to 150 or 20 to 200. The alkali metal is usually sodium and a pref.erred alkylenediamine is a polymethylenediamine of the formula H2N-(CH2)m NH₂ where m is from 7 to 12, preferably from 7 to 10. The zeolite may also exist in the exchanged form, suitable ions replacing those of the as-synthesised form being hydrogen, hydrogen precursors, rare earth, aluminum and/or other metals of groups IIA, IIIA, IVA, IB, IIB, IIIB, IVB and/or VIII.

The invention also comprehends a method of preparing zeolite ZSM-11 which comprises forming a mixture containing sources of an alkali metal, an oxide of aluminum, an oxide of silicon, water, and an alkylenediamine having from 7 to 12 carbon atoms, the mixture having the composition, in terms of mole ratios of oxides, within the following ranges: ^<
wherein R is the alkylenediamine and M is alkali metal ion; and maintaining the mixture at at least 50°C until crystals of the zeolite form. Preferably the mixture is maintained between 50 and 250°C, still more preferably between 80 and 200°C for a period of 3 hours to 180, advantageously 30, days.
A still further aspect of the invention is the conversion of an organic compound feedstock employing a catalyst comprising zeolite ZSM-11 constituted or synthesised as hereinabove described.
In addition to providing a low-sodium ZSM-11 which can be used as a catalyst without intermediate exchange, the method of preparation of ZSM-11 according to this invention also provides the benefit of being lower in cost than the conventional since the organic materials used herein are substantially lower in cost than the conventional. The zeolite product, therefore, is also of lower cost than conventionally prepared ZSM-11.
In calculating the mole ratio of hydroxide ions/ silica, it is conventional to calculate hydroxide by summing moles of OH^-, whether added as NaOH, as quaternary Group VA element hydroxide (in the case of a conventional preparation), as sodium silicate (NaOH + SiO₂), as sodium aluminate (NaOH + A1₂0₃), or the like and to subtract from that sum any moles of acid added. Acid may be added simply as HC1, HN03, H₂SO₄, acetic acid, and the like or it may be added as an aluminum sulfate (A1₂0₃ + HN0₃), etc. Each mole of A1₂0₃ is itself equivalent to 2 moles of acid in this calculation, since A1₂0₃ consumes 2 moles of hydroxide in its conversion to framework aluminate ion. In particular, no contribution is assigned to organic bases such as amines in this calculation. Amines present in reaction mixtures having an OH-/SiO₂ ratio of 0.01 are protonated when further acid is added. Until said additional acid exceeds the amine present, the pH remains above 7.
In a conventional calculation, which does not consider amines, the total moles of acid could thereby exceed the moles of hydroxide initially present in said reaction mixture and subtraction would thereby lead to apparent "negative" OH-/Si0₂ ratios. A negative ratio is, of course, not possible since the true moles of hydroxide (per liter) in an aqueous mixture are always positive and equal to 10-¹⁴ divided by the moles per liter of acid. Calculated from the true moles of hydroxide, the present invention would include an OH-/Si0₂ range of about 10^-10 to about 1.0.
For convenience, and to maintain the conventions established in describing reaction mixture compositions, we define a ratio of H⁺(additional)/Si0₂, which is equal to the moles of H+ added in excess of the moles OH- added in preparing the reaction mixture.
In the above reaction mixture composition, an optimum range in the OH-/SiO₂ and R/Si0₂ ratios exists which is specific to each individual diamine. When larger amounts of diamine are effective, higher OH-/Si0₂ ratios can.be used; when the diamine is effective at low R/Si0₂ ratio, the optimum OH-/SiO₂ ratio will generally
lower. These trends suggest that it is the protonated diamine which directs crystallization to ZSM-11.
The digestion of the gel particles is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, filtering and water washing.
The reaction mixture for the synthesis of ZSM-11 can be prepared utilizing materials which can supply the appropriate oxide. Such materials include aluminates, alumina, silicates, silica hydrosol, silica gel, silicic acid and hydroxides. It will be understood that each oxide component utilized in the reaction mixture for preparing ZSM-11 can be supplied by one or more essential reactants and they can be mixed together in any order. For example, any oxide can be supplied by an aqueous solution, sodium hydroxide or by an aqueous solution of a suitable silicate; the alkylenediamine cation can be supplied by a compound of that cation, such as, for example, a salt as well as by the indicated diamine. The reaction mixture can be prepared either batchwise or continuously. Crystal size and crystallization time of the ZSM-11 composition will vary with the nature of the reaction mixture employed.
Even though the presently prepared ZSM-11 has an extremely low amount of alkali metal, e.g. sodium, ions, as synthesized, and therefore can be utilized as catalytic material for a number of hydrocarbon conversion reactions substantially as synthesized, the original cations of the as synthesized ZSM-11 can be replaced in accordance with techniques well known in the art, at least in part, by ion exchange with other cations. Preferred replacing cations include metal ions, ammonium ions, hydrogen ions and mixtures thereof. Particularly preferred cations are those which render the zeolite catalytically active especially for hydrocarbon conversion. These include hydrogen, rare earth metals, aluminum, metals of Groups IIA, IIIB, IVB, VIB, VIII, IB, IIB, IIIA, IVA. Of the replacing metallic cations, particular preference is given to cations of metals such as rare earth, Mn, Ca, Mg, Zn, Cd, Pd, Ni, Ti, Al, Sn, Fe and Co.
A typical ion exchange technique is to contact the ZSM-11 zeolite with a salt of the desired replacing cation or cations. Although a wide variety of salts can be employed, particular preference is given to chlorides, nitrates and sulfates. Representative ion exchange techniques are disclosed in a wide variety of patents including United States Patents 3,140,249; 3,140,251; and 3,140,253.
Following contact with the salt solution of the desired replacing cation, the zeolite is then preferably washed with water and dried at a temperature ranging from 150^oF to about 600°F and thereafter may be calcined in air-or other inert gas at temperatures ranging from about 500°F to 1500°F for periods of time ranging from 1 to 48 hours or more to produce a catalytically-active thermal decomposition product thereof.
The hereby prepared zeolite ZSM-11 may be used in a wide variety of organic compound, e.g. hydrocarbon compounds and oxygenates such as methanol, conversion processes. Such processes include, for example, alkylation of aromatics with olefins, aromatization of normally gaseous olefins and paraffins, aromatization of normally liquid low molecular weight paraffins and ole'fins, isomerization of aromatics, paraffins and olefins, disproportionation of aromatics, transalkylation of aromatics, oligomerization of olefins and cracking and hydrocracking. All of the foregoing catalytic processes are of value since they result in upgrading of the organic charge being processed.
Synthetic ZSM-11 zeolites prepared in accordance hereto can be used either in the organic cation or alkali metal form and hydrogen form or another univalent or multivalent cationic form. They can also be used in intimate combination with a hydrogenating component such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a noble metal such as platinum or palladium where a hydrogenation-dehydrogenation function is to be performed. Such components can be exchanged into the composition, impregnated therein or physically intimately admixed therewith. Such components can be impregnated in or on to ZSM-11 such as, for example, by, in the case of platinum, treating the zeolite with a platinum metal-containing ion. Thus, suitable platinum compounds for this purpose include chloroplatinic acid, platinous chloride and various compounds containing the platinum amine complex: Combinations of metals and methods for their introduction can also be used.
The aluminosilicate prepared by the instant invention is formed in a wide variety of particle sizes. Generally speaking, the particles can be in the form of a powder, a granule, or a molded product, such as extrudate having particle size sufficient to pass through a 2 mesh (Tyler) screen and be retained on a 400 mesh (Tyler) screen. In cases where the catalyst is molded, such as by extrusion, the aluminosilicate can be extruded before drying or dried or partially and then extruded.
In the case of many catalysts, it is desired to incorporate the ZSM-11 hereby prepared with another material resistant to the temperatures and other conditions employed in organic conversion processes. Such matrix materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and/or metal oxides. The latter may be either naturally occurring or in the form of gelatinous precipitates, sols or gels including mixtures of silica and metal oxides. Use of a material in conjunction with the ZSM-11 i.e. combined therewith, which is active, tends to improve the conversion and/or selectivity of the catalyst in certain organic conversion processes._' Inactive materials suitably serve as diluents to control the amount of conversion in a given process so that products can be obtained economically and orderly without employing other means for controlling the rate of reaction. Frequently, zeolite materials have been incorporated into naturally occurring clays, e:g. bentonite and kaolin. These materials, i.e. clays, oxides, etc., function, in part, as binders for the catalyst. It is desirable to provide a catalyst having good crush strength, because in a petroleum refinery the catalyst is often subjected to rough handling, which tends to break the catalyst down into powder-like materials which cause problems in processing.
Naturally occurring clays which can be composited with the hereby synthesized ZSM-11 catalyst include the montmorillonite and kaolin family,which families include the sub-bentonites,and the kaolins commonly known as Dixie, McNammee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite, or anauxite. Such clays can be u3ed in the raw state or initially subjected to calcination, acid treatment or chemical modification.
In addition to the foregoing material, the ZSM-11 catalyst hereby synthesized can be composited with a porous matrix material such as silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. The matrix can be in the form of a cogel.
A mixture of these components could also be used. The relative proportions of finely divided crystalline aluminosilicate ZSM-11 and inorganic oxide gel matrix vary widely with the crystalline aluminosilicate content ranging from about 1 to about 90 percent by weight and more usually in the range of about 2 to about 50 percent by weight of the composite.
For conversion of organic compounds in general, the organic compound or feedstock containing same may be contacted with a catalyst containing the hereby prepared zeolite ZSM-11, commonly with a silica/alumina mole ratio in the range of from about 20 to about 200, at a temperature between about 100°F and about 14000F, a pressure between about atmospheric and about 200 atmospheres, a hydrogen/organic compound mole ratio of between 0 and about 80, and a weight hourly space velocity (WHSV) of from about 0.1 hr-¹ to about 1000 h_r-1_.
More specifically, when said conversion involves polymerization of olefin-containing liquid or gaseous feedstocks the temperature will be between about 500°F and about 900°F, the pressure will be from about atmospheric to about 50 atmospheres and the WHSV will be from about 0.5 hr-¹ to about 50 hr-¹. When said conversion is aromatization of gaseous or liquid feedstocks which may be olefinic or paraffinic with or without aromatics present, the temperature will be from about 800°F to about 1200°F, the pressure will be from about atmospheric to about 10 atmospheres and the WHSV will be from about 0.1 hr-¹ to about 10 hr-¹. When said conversion is the alkylation of aromatics, such as benzene or toluene, with an alkyla ting agent of an olefin or alcohol, reaction conditions will include a temperature of from about 400°F to about 1000^oF, a pressure of from about atmospheric to about 60 atmospheres, a WHSV of from about 0.5 hr^-1 to about 50 hr-¹ and an aromatic compound/alkylating agent mole ratio of from about 2 to about^-200. When said conversion is isomerization of aromatics such as xylenes, reaction conditions will include a temperature of from about 300-900°F, a pressure of from about 1-60 atmospheres, and a WHS of from about 0.2 hr-¹ to about 100 hr-¹. When said conversion is isomerization of paraffins or olefins, reaction conditions will include a temperature of from about 100-700°F, a pressure of from about 1-60 atmospheres, and a WHSV of from about 0.1 hr-¹ to about 2 hr-¹. When said conversion is disproportionation of aromatics, such as toluene, reaction conditions will include a temperature of from about 600-1100⁰F, a pressure of from about 1-50 atmospheres, and a WHSV of from about 0.5 hr-¹ to about 20 hr-¹. When said conversion is transalkylation of aromatics, such as benezene, with alkylaromatics, such as trimethylbenzenes, reaction conditions will include a temperature of from about 500-1100°F, a pressure of from about 1-50 atmospheres, and a WHSV of from about 0.5 hr-¹ to about 20 hr-¹. When said conversion is oligomerization of olefins, such as propylene, reaction conditions will include a temperature of from about 500-1100°F, a pressure of from about 1-50 atmospheres, and a WHSV of from about 0.1 hr-¹ to about 1000 hr-¹. When said conversion is cracking of a gas oil or a residual oil, reaction conditions will include a temperature of from about 600-1400°F, a pressure of from about 1-10 atmospheres, and a WHSV of from about 0.5 hr-¹ to about 50 hr-¹. When said conversion is hydrocracking of hydrocarbon-containing feedstocks, such as resids or heavy petroleum stocks, reaction conditions will include a temperature of from about 400-850°F, a pressure of from about 10-200 atmospheres, a WHSV of from about 0.1 hr-¹ to about 10 hr-¹ and a H₂/hydrocarbon mole ratio of from 2-80.
The following Examples more fully illustrate the nature of the invention and the manner of practising it.

EXAMPLES 1-29

Crystallizations were carried out at 160°C in both static and stirred systems and employed Q-brand sodium silicate (27.8% Si0₂, 8.42% Na₂0) as a source of silica and Al₂(SO₄)₃ 16H₂0 as a source of alumina. Reaction mixture compositions are described by the mole ratios SiO₂/Al₂O₃, H₂0/Si0₂, Na/Si02, and R/SiO₂, where R is moles of alkylenediamine, in each instance being of the formula H₂N-(CH₂)_m-NH₂ where m is from 4 to 12, and where each mole of A1₂0₃ is considered to consume two moles of OH- on conversion to framework A10₂-. Moles of OH- are defined as moles of OH- added less any moles of mineral acid (H⁺) added to the mixture. The pH of all reaction mixtures was above 7.
Table II records the results of crystallization experiments conducted at 1600C in a stirred system. From these data one observes that crystallization shifted from other zeolites to ZSM-11 as the diamine chain length increased from six carbon atoms to seven carbon atoms. Transition points were reached at C₅ and C₇. At C₅ alkylenediamine the product ZSM-35 cage appeared unable to accommodate the protonated (note low OH-/Si0₂) diamine so that crystallization was directed to ZSM-5. Similarly, in the interval C₇-C₁₂ alkylenediamines, ZSM-11 resulted. Crystallizationswith C₇-C₁₀ alkylenediamines were a particularly efficient route to ZSM-11.
In Table II are recorded detailed runs at 160°C and at 100⁰C showing that the same general trends pertain in static crystallizations. These runs tend to concentrate in the low OH-/Si0₂ range, compatible with the need to protonate an amine to render it both soluble and effective as a template. The results exhibit a scatter not found with the stirred crystallizations and suggestive of mixing problems, perhaps even partial phase separation, with the longer alkyl chains.
Analytical data for several of the ZSM-11 products relative to product composition is listed in Table IV.

EXAMPLE 30

A sample of zeolite ZSM-11 prepared as in Example 6 is calcined at 1000°F for 2 hours, contacted with ammonium chloride solution to effect ammonium exchange for residual sodium, dried at 200^oF for 4 hours and then calcined at 1000°F for 2 hours. After sizing to 60/80 mesh, the zeolite's catalytic activity is meaured by contact with a five-component feedstock comprising equal parts by weight of n-hexane, 3-methylpentane, 2,3-dimethylbutane, benzene and toluene at conditions of 800°F, 200 psig, a hydrogen/hydrocarbon mole ratio of 3 and a WHSV of 3 hr-¹. This test demonstrates simultaneously paraffin cracking, aromatization and aromatics alkylation and interconversion activity of the zeolite. The ratio of rate constants for n-hexane and 3-methylpentane conversion generated by this test is 2.3. Further demonstrated here is that 10% of the cracked paraffin fragments react with available aromatics in the feedstock to produce alkylaromatics with benzene, rather than toluene, being preferentially alkylated.

Claims

1. Zeolite ZSM-11 having as synthesised the formula, in terms of mole ratios of oxides in the anhydrous state:

(0.5-10.0)R : (0-0.5)M₂0 : A1₂0₃: xSi0₂ wherein M is an alkali metal ion, R is an alkylenediamine having from 7 to 12 carbon atoms or an organic cation derived therefrom, and x is at least 10.

2. Zeolite ZSM-11 as claimed in Claim 1 wherein x is from 10 to 1000.

3. Zeolite ZSM-11 as claimed in Claim 2 wherein x is from 10 to 150.

4. Zeolite ZSM-11 as claimed in Claim 2 wherein x is from 20 to 200.

5. A zeolite according to any preceding claim wherein said alkali metal is sodium and said alkylenediamine is a polymethylenediamine of the formula H₂N-(CH₂)_m-NH₂ wherein m is from 7 to 12.

6. A zeolite according to Claim 5 wherein m is from 7 to 10.

7. A zeolite according to any preceding claim the original cations of which have been replaced, at least; in part, by ion exchange with hydrogen and hydrogen precursors, rare earth metals, aluminum, and/or metals from Groups IIA, IIIA, IVA, IB, IIB, IIIB, IVB, VIB and/or VIII.

8. A method for preparing zeolite ZSM-11 which comprises forming a mixture containing sources of an alkali metal, an oxide of aluminum, an oxide of silicon, water and an alkylenediamine having from 7 to 12 carbon atoms and having a composition, in terms of mole ratios of oxides, within the following ranges:

wherein R is an alkylenediamine having 7 to 12 carbon atoms and M is an alkali metal ion, and maintaining the mixture at a temperature of at least 50⁰C until the crystals of said zeolite are formed.

9. A method according to Claim 8 wherein said mixture has the composition:

10. The method according to Claim 9 wherein the temperature is maintained between 50°C and 250°C., preferably between 80°C and 2000C.

11. A method according to any of claims 8 to 10 wherein said mixture is maintained at said temperature for from 3 hours to 180, preferably 30, days.

12. A process of catalytically converting an organic compound feedstock which comprises contacting said feedstock under conversion conditions with a catalyst comprising ZSM-11 according to any of claims 1 to 7 or a product of calcination thereof.