WO2010011423A2

WO2010011423A2 - Synthesis of chabazite-containing molecular sieves and their use in the conversion of oxygenates to olefins

Info

Publication number: WO2010011423A2
Application number: PCT/US2009/046172
Authority: WO
Inventors: Machteld M. Mertens; Guang Cao
Original assignee: Exxonmobil Chemical Patents Inc.
Priority date: 2008-07-25
Filing date: 2009-06-03
Publication date: 2010-01-28
Also published as: WO2010011423A8; WO2010011423A3

Abstract

In a method of synthesizing a mostly CHA-type silicoaluminophosphate sieve, a reaction mixture comprises sources of water, silicon, aluminum, phosphorus, and a template. In one aspect, when the reaction mixture Si/A1₂ ratio is less than 0.33, crystallization is induced at at least 165°C. Advantageously, the sieve so crystallized exhibits a Si/A1₂ ratio less than 0.33 and/or at least 0.10 greater than the synthesis mixture Si/A1₂ ratio. In another aspect, the aluminum and phosphorus sources are first combined to form a primary mixture that is aged. The silicon source and template can then be added to form the synthesis mixture. After inducing crystallization, in this aspect, both the synthesis mixture and crystallized sieve exhibit a Si/A1₂ ratio less than 0.33 and/or the crystallized sieve has an average crystal size not more than 3.0μm. The molecular sieve from both aspects can be used in a hydrocarbon (oxygenates-to-olefins) conversion process.

Description

SYNTHESIS OF CHABAZITE-CONTAINING MOLECULAR SIEVES AND THEIR USE IN THE CONVERSION OF OXYGENATES TO OLEFINS

FIELD OF THE INVENTION [0001] This invention relates to the synthesis of chabazite-type containing molecular sieves and their use in the conversion of oxygenates, particularly methanol, to olefins, particularly ethylene and/or propylene.

BACKGROUND OF THE INVENTION [0002] The conversion of oxygenates to olefins (OTO) is currently the subject of intense research because it has the potential for replacing the long-standing steam cracking technology that is today the industry-standard for producing world scale quantities of ethylene and propylene. The very large volumes involved suggest that substantial economic incentives exist for alternate technologies that can deliver high throughputs of light olefins in a cost efficient manner. Whereas steam cracking relies on non-selective thermal reactions of naphtha range hydrocarbons at very high temperatures, OTO exploits catalytic and micro- architectural properties of acidic molecular sieves under milder temperature conditions to produce high yields of ethylene and propylene from methanol. [0003] Current understanding of the OTO reactions suggests a complex sequence in which three major steps can be identified: (1) an induction period leading to the formation of an active carbon pool (alkyl-aromatics), (2) alkylation-dealkylation reactions of these active intermediates leading to products, and (3) a gradual build-up of condensed ring aromatics. OTO is therefore an inherently transient chemical transformation in which the catalyst is in a continuous state of change. The ability of the catalyst to maintain high olefin yields for prolonged periods of time relies on a delicate balance between the relative rates at which the above processes take place. The formation of coke-like molecules is of singular importance because their accumulation interferes with the desired reaction sequence in a number of ways. In particular, coke renders the carbon pool inactive, lowers the rates of diffusion of reactants and products, increases the potential for undesired secondary reactions and limits catalyst life. [0004] Over the last two decades, many catalytic materials have been identified as being useful for carrying out the OTO reactions. Crystalline molecular sieves are the preferred catalysts today because they simultaneously address the acidity and morphological requirements for the reactions. Particularly preferred materials are eight-membered ring aluminosilicates, such as those having the chabazite (CHA) framework type, as well as aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs) of the CHA framework type, such as SAPO-34.

[0005] Chabazite is a naturally occurring zeolite with the approximate formula CaeAli₂Si₂₄θ7₂. Three synthetic forms of chabazite are described in "Zeolite Molecular Sieves", by D. W. Breck, published in 1973 by John Wiley & Sons. The three synthetic forms reported by Breck are Zeolite "K-G", described in J. Chem. Soc, p. 2822 (1956), Barrer et al; Zeolite D, described in British Patent No. 868,846 (1961); and Zeolite R, described in U.S. Patent No. 3,030,181 (1962). Zeolite K-G zeolite has a silica : alumina mole ratio of 2.3: 1 to 4.15: 1, whereas zeolites D and R have silica : alumina mole ratios of 4.5: 1 to 4.9: 1 and 3.45: 1 to 3.65: 1, respectively.

[0006] In U.S. Pat. No. 4,440,871, the synthesis of a wide variety of SAPO materials of various framework types is described with a number of specific examples. Also disclosed are a large number of possible organic templates, with some specific examples. In the specific examples a number of CHA framework type materials are described. The preparation of SAPO-34 is reported, using tetraethylammonium hydroxide (TEAOH), or isopropylamine, or mixtures of TEAOH and dipropylamine (DPA) as templates. Also disclosed is a specific example that utilizes cyclohexylamine in the preparation of SAPO-44. Although other template materials are described, there are no other templates indicated as being suitable for preparing SAPO's of the CHA framework type.

[0007] U.S. Patent No. 6,162,415 discloses the synthesis of a silicoaluminophosphate molecular sieve, SAPO-44, which has a CHA framework type in the presence of a directing agent comprising cyclohexylamine or a cyclohexylammonium salt, such as cyclohexyl- ammonium chloride or cyclohexylammonium bromide. [0008] Silicoaluminophosphates of the CHA framework type with low silicon contents are particularly desirable for use in the methanol-to-olefins process. Thus, Wilson, et al., Microporous and Mesoporous Materials, 29, 117-126, 1999 report that it is beneficial to have lower Si content for methanol-to-olefins reaction, in particular because low Si content has the effect of reducing propane formation and decreasing catalyst deactivation. [0009] U.S. Patent No. 6,620,983 discloses a method for preparing silicoaluminophosphate molecular sieves, and in particular low silica silicoaluminophosphate molecular sieve having a Si/Al atomic ratio of less than 0.5, which process comprises forming a reaction mixture comprising a source of aluminum, a source of silicon, a source of phosphorus, at least one organic template, at least one compound which comprises two or more fluorine substituents and capable of providing fluoride ions, and inducing crystallization of the silicoaluminophosphate molecular sieve from the reaction mixture. Suitable organic templates are said to include one or more of tetraethyl ammonium hydroxide, tetraethyl ammonium phosphate, tetraethyl ammonium fluoride, tetraethyl ammonium bromide, tetraethyl ammonium chloride, tetraethyl ammonium acetate, dipropylamine, isopropylamine, cyclohexylamine, morpholine, methylbutylamine, morpholine, diethanolamine, and triethylamine. In the Examples, crystallization is conducted by heating the reaction mixture to 170⁰C over 18 hours and then holding the mixture at this temperature for 18 hours to 4days.

[0010] U.S. Patent No. 6,793,901 discloses a method for preparing a microporous silicoaluminophosphate molecular sieve having the CHA framework type, which process comprises (a) forming a reaction mixture comprising a source of aluminum, a source of silicon, a source of phosphorus, optionally at least one source of fluoride ions and at least one template containing one or more N,N-dimethylamino moieties, (b) inducing crystallization of the silicoaluminophosphate molecular sieve from the reaction mixture, and (c) recovering silicoaluminophosphate molecular sieve from the reaction mixture. Suitable templates are said to include one or more of N,N-dimethylethanolamine, N,N-dimethylbutanolamine, N,N- dimethylheptanolamine, N,N-dimethylhexanolamine, N,N-dimethylethylenediamine, N,N- dimethylpropylenediamine, N,N-dimethylbutylene-diamine, N,N-dimethylheptylenediamine, N,N-dimethylhexylenediamine, or dimethyl-ethylamine, dimethylpropylamine, dimethyl- heptylamine, and dimethylhexylamine. When conducted in the presence of fluoride ions, the synthesis is effective in producing low silica silicoaluminophosphate molecular sieves having a Si/Al atomic ratio of from 0.01 to 0.1. In the Examples, crystallization is conducted by heating the reaction mixture to 170 to 180⁰C for 1 to 5 days.

[0011] U.S. Patent No. 6,835,363 discloses a process for preparing microporous crystalline silicoaluminophosphate molecular sieves of CHA framework type, the process comprising: (a) providing a reaction mixture comprising a source of alumina, a source of phosphate, a source of silica, hydrogen fluoride and an organic template comprising one or more compounds of formula (I):

(CHs)₂N-R-N(CHs)₂ where R is an alkyl radical of from 1 to 12 carbon atoms; (b) inducing crystallization of silicoaluminophosphate from the reaction mixture,; and (c) recovering silico- aluminophosphate molecular sieve. Suitable templates are said to include one or more of the group consisting of: N,N,N',N'-tetramethyl-l,3-propane-diamine, N,N,N',N'-tetramethyl-l,4- butanediamine, N,N,N',N'-tetramethyl- 1 ,3 -butanediamine, N,N,N',N'-tetramethyl- 1,5- pentanediamine, N,N,N',N'-tetramethyl- 1 ,6-hexanediamine, N,N,N',N'-tetramethyl- 1,7- heptanediamine, N,N,N',N'-tetramethyl-l,8-octanediamine, N,N,N',N'-tetramethyl-l,9- nonanediamine N,N,N',N'-tetramethyl- 1 , 10-decanediamine, N,N,N',N'-tetramethyl- 1,11- undecanediamine and N,N,N',N'-tetramethyl-l,12-dodecanediamine. In the Examples, crystallization is conducted by heating the reaction mixture to 120 to 200⁰C for 4 to 48 hours. [0012] U.S. Patent No. 7,247,287 discloses the synthesis of silicoaluminophosphate molecular sieves having the CHA framework type employing a directing agent having the formula:

R¹R²N-R³ wherein R¹ and R² are independently selected from the group consisting of alkyl groups having from 1 to 3 carbon atoms and hydroxyalkyl groups having from 1 to 3 carbon atoms and R³ is selected from the group consisting of 4- to 8-membered cycloalkyl groups, optionally substituted by 1 to 3 alkyl groups having from 1 to 3 carbon atoms; and 4- to 8- membered heterocyclic groups having from 1 to 3 heteroatoms, said heterocyclic groups being optionally substituted by 1 to 3 alkyl groups having from 1 to 3 carbon atoms and the heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S. Preferably, the directing agent is selected from N,N-dimethylcyclohexylamine, N,N- dimethyl-methylcyclohexylamine, N,N-dimethyl-cyclopentylamine, N,N-dimethyl-methyl- cyclopentylamine, N,N-dimethylcycloheptyl-amine, N,N-dimethyl-methylcycloheptylamine, and most preferably is N,N-dimethyl-cyclohexylamine. The synthesis can be effected with or without the presence of fluoride ions and, in the Examples, crystallization is conducted by heating the reaction mixture to 180⁰C for 3 to 7 days.

[0013] When any molecular sieve is used as an oxygenate conversion catalyst, three of the main economic drivers in evaluating the efficiency and precision of the manufacturing process are the yield of the molecular sieve catalyst, the template efficiency, and the accuracy to which the acid site density of the molecular sieve product can be controlled from the component ingredients. In practice, even small changes in yield, template efficiency, and/or acid site density can have an enormous effect on the economics of a commercial process, and hence there is a continuing need to develop catalysts with improved yields, improved template efficiencies, and/or improved accuracy of acid site densities for use in oxygenate conversion.

[0014] The Si/Al₂ molar ratio is one key parameter to control the acid site density and therefore the catalytic activity. This is easily done at higher Si/Al₂ ratios, where the Si/Al₂ ratio of the product composition is adjustable by changing the Si/Al₂ ratio of the synthesis mixture. In order to obtain molecular sieve catalysts with a low bulk Si/Al₂ molar ratio (e.g., no more than 0.15, preferably no more than 0.10), it has typically not been sufficient merely to reduce the Si/Al₂ ratio of the components of the synthesis mixture. In previous cases, this has only led to formation of molecular sieve products exhibiting a relatively high Si/Al₂ but which are recovered in relatively low yield. According to a first aspect of the invention, it has been discovered that a crystallization temperature of at least 165°C can unexpectedly allow formation of molecular sieve materials with more controlled Si/Al₂ ratios (and thus more controlled acid site densities, i.e., with Si/Al₂ ratios and/or acid site densities in the recovered product that are closer to the relatively low Si/Al₂ ratios in the synthesis mixture). [0015] According to a second aspect of the invention, it has unexpectedly been found that the mixing procedure, or more accurately the order of addition and relative homogenization of the synthesis mixture components, in silicoaluminophosphate molecular sieve formulations can enhance certain desirable properties, such as reducing the crystal size of the product, while still maintaining an acceptable product yield. Surprisingly, the procedure of mixing the sources of aluminum and phosphorus first, and allowing this mixture to age to facilitate more intimate combination, prior to the addition of the source of silicon, is a robust way to make the synthesis mixture and can result in more desirable molecular sieve products.

SUMMARY OF THE INVENTION [0016] In a first aspect, the invention relates to a method of preparing a silicoaluminophosphate molecular sieve having a controlled acid site density, the method comprising: (a) providing a synthesis mixture comprising a source of aluminum, a source of phosphorus, a source of silicon, and at least one organic template containing (i) a 4- to 8- membered cycloalkyl group, optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, or (ii) a 4- to 8- membered heterocyclic group having from 1-3 heteroatoms, said heterocyclic group being optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, and said heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S, wherein the synthesis mixture exhibits a Si/Al₂ ratio less than 0.33; and (b) inducing crystallization of a silicoaluminophosphate molecular sieve, which exhibits 90% or greater CHA framework type character, from said synthesis mixture at a crystallization temperature of at least 165°C for a crystallization time from 5 minutes to 350 hours to form a crystallized silicoaluminophosphate molecular sieve having a crystal size distribution such that its average crystal size is not greater than 3.0 μm, wherein (i) the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.33, (ii) the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Ak ratio not more than 0.10 greater than the Si/Al₂ ratio of the synthesis mixture, or (iii) both (i) and (ii). [0017] In a second aspect, the invention relates to a method of preparing a silicoaluminophosphate molecular sieve having a desired crystal size, the method comprising: (a) combining a source of phosphorus and a source of aluminum, optionally with a liquid mixture medium, to form a primary mixture; (b) aging the primary mixture for an aging time and under aging conditions sufficient to allow homogenization of the primary mixture, physico-chemical interaction between the source of phosphorus and the source of aluminum, or both; (c) adding a source of silicon, at least one organic template, and optionally additional liquid mixture medium, to the aged primary mixture to form a synthesis mixture; and (d) inducing crystallization of a silicoaluminophosphate molecular sieve, which exhibits 90% or greater CHA framework type character, from said synthesis mixture at a crystallization temperature, wherein the at least one organic template contains (i) a 4- to 8- membered cycloalkyl group, optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, or (ii) a 4- to 8- membered heterocyclic group having from 1-3 heteroatoms, said heterocyclic group being optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, and said heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S, wherein the synthesis mixture and the crystallized silicoaluminophosphate molecular sieve both exhibit a Si/Al₂ ratio less than 0.33, and wherein the crystallized silicoaluminophosphate molecular sieve has a crystal size distribution such that its average crystal size is not greater than 3.0 μm.

[0018] In another aspect, the invention relates to a method of converting hydrocarbons into olefins comprising: (a) preparing a silicoaluminophosphate molecular sieve according to the method of the first two aspects of the invention; (b) formulating said silicoaluminophosphate molecular sieve, along with a binder and optionally a matrix material, into a silicoaluminophosphate molecular sieve catalyst composition comprising from at least 10% to 50% molecular sieve; and (c) contacting said catalyst composition with a hydrocarbon feed under conditions sufficient to convert said hydrocarbon feed into a product comprising predominantly one or more olefins.

[0019] In another aspect, the invention relates to a method of forming an olefin-based polymer product comprising: (a) preparing a silicoaluminophosphate molecular sieve according to the method of the first two aspects of the invention; (b) formulating said silicoaluminophosphate molecular sieve, along with a binder and optionally a matrix material, into a silicoaluminophosphate molecular sieve catalyst composition comprising from at least 10% to 50% molecular sieve; (c) contacting said catalyst composition with a hydrocarbon feed under conditions sufficient to convert said hydrocarbon feed into a product comprising predominantly one or more olefins; and (d) polymerizing at least one of the one or more olefins, optionally with one or more other comonomers and optionally in the presence of a polymerization catalyst, under conditions sufficient to form an olefin-based (co)polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 shows a graph comparing the Si/Al₂ ratios of the various molecular sieves of Examples 1-8 and Comparative Examples A-H.

[0021] Figure 2 shows a graph comparing the yields of the various molecular sieves of

Examples 1-8 and Comparative Examples A-H. [0022] Figure 3 shows an SEM micrograph of a sample made according to the method in Comparative Example I.

[0023] Figure 4 shows an SEM micrograph of a sample made according to the method in Comparative Example J.

[0024] Figure 5 shows an SEM micrograph of a sample made according to the method in Example 9.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] Described herein is a method of synthesizing a crystalline aluminophosphate or silicoaluminophosphate containing a molecular sieve having 90% or greater CHA framework-type character and to the use of the resultant molecular sieve as a catalyst in organic conversion reactions, especially the conversion of oxygenates to light olefins. [0026] In a first aspect of the invention in particular, it has been found that, by crystallizing at a crystallization temperature of at least 165°C in the molecular sieve synthesis, it is possible to produce a CHA framework-type containing molecular sieve having a crystal size distribution such that its average crystal size is not greater than 3.0 μm, having a relatively low Si/Al₂ ratio (e.g., not more than 0.10) in the product, and/or having an increased accuracy (i.e., decreased difference) between the Si/Al₂ ratio in the initial mixture and the Si/Al₂ ratio in the product.

[0027] In a second aspect of the invention in particular, it has been found that, by employing a particular order of addition of components (i.e., phosphorus and aluminum sources being combined first) in the molecular sieve synthesis, it is possible to produce a CHA framework-type containing molecular sieve (particularly having a relatively low Si/Al₂ ratio, e.g., not more than 0.10, in the product and/or in the mixture) having a desirably reduced crystal size, e.g., no greater than 3.0 microns instead of over 4 microns. [0028] In the present method, a reaction mixture is prepared comprising a source of aluminum, a source of phosphorous, at least one organic directing agent, and, optionally, a source of silicon. Any organic directing agent capable of directing the synthesis of CHA framework type molecular sieves can be employed, but generally the directing agent is a compound having the formula (I):

R¹R²N-R³ (I) wherein R¹ and R² are independently selected from the group consisting of alkyl groups having from 1 to 3 carbon atoms and hydroxyalkyl groups having from 1 to 3 carbon atoms and R³ is selected from the group consisting of 4- to 8-membered cycloalkyl groups, optionally substituted by 1 to 3 alkyl groups having from 1 to 3 carbon atoms; and 4- to 8- membered heterocyclic groups having from 1 to 3 heteroatoms, said heterocyclic groups being optionally substituted by 1 to 3 alkyl groups having from 1 to 3 carbon atoms and the heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S.

[0029] More particularly, the organic directing agent is a compound having the formula

(II):

(CHs)₂N-R³ (II) wherein R is a 4- to 8-membered cycloalkyl group, especially a cyclohexyl group, optionally substituted by 1 to 3 methyl groups. Particular examples of suitable organic directing agents include, but are not limited to, at least one of N,N-dimethyl-cyclohexylamine, N,N- dimethylmethylcyclohexylamine, N,N-dimethyl-cyclopentylamine, N,N-dimethyl- methylcyclopentylamine, NjN-dimethyl-cycloheptylamine, and N,N-dimethyl-methyl- cycloheptylamine, especially NjN-dimethyl-cyclohexylamine.

[0030] The sources of aluminum, phosphorus, and silicon suitable for use in the present synthesis method are typically those known in the art or as described in the literature for the production of aluminophosphates and silicoaluminophosphates. For example, the aluminum source may be an aluminum oxide (alumina), optionally hydrated, an aluminum salt, especially a phosphate, an aluminate, or a mixture thereof. Other sources may include alumina sols or organic alumina sources, e.g., aluminum alkoxides such as aluminum isopropoxide. A preferred source is a hydrated alumina, most preferably pseudoboehmite, which contains 75% AI₂O3 and 25% H₂O by weight. Typically, the source of phosphorus is a phosphoric acid, especially orthophosphoric acid, although other phosphorus sources, for example, organophosphates (e.g., trialkylphosphates such as triethylphosphate) and aluminophosphates may be used. When organophosphates and/or aluminophosphates are used, typically they are present collectively in a minor amount (i.e., less than 50% by weight of the phosphorus source) in combination with a majority (i.e., at least 50% by weight of the phosphorus source) of an inorganic phosphorus source (such as phosphoric acid). Suitable sources of silicon include silica, for example colloidal silica and fumed silica, as well as organic silicon source, e.g., a tetraalkyl orthosilicate such as tetraethylorthosilicate (TEOS), tetramethylorthosilicate (TMOS), or the like, or a combination thereof. [0031] Although, in most embodiments, the sources of silicon, phosphorus, and aluminum are the only components that form the framework of a calcined silicoaluminophosphate molecular sieve according to the invention, it is possible for some small portion (e.g., typically no more than 10 wt%, preferably no more than 5 wt%) of the silicon source can be substituted with a source of one or more of magnesium, zinc, iron, cobalt, nickel, manganese, and chromium.

[0032] In some embodiments, the reaction mixture can have a molar composition within the following ranges:

P₂O₅ : Al₂O₃ from 0.75 to 1.25, SiO₂ : Al₂O₃ from 0.01 to 0.32, H₂O : Al₂O₃ from 25 to 50, and

SDA : Al₂O₃ from 1 to 3, where SDA designates the structure directing agent (template), and wherein the molar ratios for the aluminum, phosphorus, and silicon sources are calculated based on the oxide forms, regardless of the form of the source added to the reaction mixture (e.g., whether the phosphorus source is added to the reaction mixture as phosphoric acid, H₃PO₄, or as triethylphosphate, the molar ratio is normalized to P₂O5 molar equivalents). [0033] Although the reaction mixture may also contain a source of fluoride ions, it is found that the present synthesis will proceed in the absence of fluoride ions, and hence it is generally preferred to employ a reaction mixture which is substantially free of fluoride ions. [0034] Typically, the reaction mixture also contains seeds to facilitate the crystallization process. The amount of seeds employed can vary widely, but generally the reaction mixture comprises from 0.01 ppm by weight to 10,000 ppm by weight, such as from 100 ppm by weight to 5,000 by weight, of said seeds. Generally, the seeds can be homostructural with the desired product, that is are of a CHA framework type material, although heterostructural seeds of, for example, an AEI, LEV, ERI, AFX, or OFF framework-type molecular sieve, or a combination or intergrowth thereof, may be used. The seeds may be added to the reaction mixture as a suspension in a liquid medium, such as water; in some cases, particularly where the seeds are of relatively small size, the suspension can be colloidal. The production of colloidal seed suspensions and their use in the synthesis of molecular sieves are disclosed in, for example, International Publication Nos. WO 00/06493 and WO 00/06494, both published on February 10, 2000. [0035] Crystallization of the reaction mixture is carried out at either static or stirred conditions in a suitable reactor vessel, such as for example, polypropylene jars or Teflon- lined or stainless steel autoclaves. In one embodiment, the crystallization regime can involve heating the reaction mixture relatively quickly, at a rate of more than 10°C/hour, conveniently at least 15°C/hour or at least 20°C/hour, for example from 15°C/hour to 150°C/hour or from 20°C/hour to 100°C/hour, to the desired crystallization temperature, typically between 50⁰C and 250⁰C, for example from 150⁰C to 225°C or from 150⁰C to 200⁰C, such as from 160⁰C to 195°C (of course, in the first aspect of the invention, however, the desired crystallization temperature is additionally at least 165°C, for example at least 170⁰C, and can optionally also be not more than 190⁰C, for example not more than 185°C or not more than 180⁰C). In this embodiment, when the desired crystallization temperature is reached, the crystallization can be terminated immediately or from 5 minutes to 350 hours, and the reaction mixture can be allowed to cool; additionally or alternately, the crystallization can run for at least 12 hours, preferably at least 16 hours, for example at least 24 hours, at least 36 hours, at least 48 hours, at least 60 hours, at least 72 hours, at least 84 hours, at least 96 hours, at least 120 hours, or at least 144 hours before cooling. Additionally in this embodiment, on cooling, the crystalline product can be recovered by standard means, such as by centrifugation or filtration, then washed and dried.

[0036] In an alternate embodiment, the crystallization regime can involve heating the reaction mixture slowly, at a rate of less than 8°C/hour, conveniently at least l°C/hour, such as from 2°C/hour to 6°C/hour, to the desired crystallization temperature, typically between 50⁰C and 250⁰C, for example from 150⁰C to 225°C or from 150⁰C to 200⁰C, such as from 160⁰C to 195°C (of course, in the first aspect of the invention, however, the desired crystallization temperature is additionally at least 165°C, for example at least 170⁰C, and can optionally also be not more than 190⁰C, for example not more than 185°C or not more than 180⁰C). In this embodiment, when the desired crystallization temperature is reached, the crystallization can be terminated immediately or at least within less than 10 hours, such as less than 5 hours, and the reaction mixture can be allowed to cool. Additionally in this embodiment, on cooling, the crystalline product can be recovered by standard means, such as by centrifugation or filtration, then washed and dried.

[0037] Optionally, the step of inducing crystallization can be done while stirring.

[0038] In one embodiment of the first aspect of the invention, the crystallized silicoaluminophosphate molecular sieve has a crystal size distribution such that its average crystal size is less than 1.5 μm, preferably no more than 1.2 μm, for example no more than 1.1 μm, no more than 1.0 μm, or no more than 0.9 μm.

[0039] As used herein, the term "average crystal size," in reference to a crystal size distribution, should be understood to refer to a measurement on a representative sample or an average of multiple samples that together form a representative sample. Average crystal size can be measured by SEM, in which case the crystal size of at least 30 crystals must be measured in order to obtain an average crystal size, and/or average crystal size can be measured by a laser light scattering particle size analyzer instrument, in which case the measured dso of the sample(s) can represent the average crystal size. It should also be understood that, while many of the crystals dealt with herein are relatively uniform (for instance, very close to cubic, thus having little difference between diameter measured along length, height, or width, e.g., when viewed in an SEM), the "average crystal size," when measured visually by SEM, represents the longest distance along one of the three- dimensional orthogonal axes (e.g., longest of length, width/diameter, and height, but not diagonal, in a cube, rectangle, parallelogram, ellipse, cylinder, frusto-cone, platelet, spheroid, or rhombus, or the like). However, the dso, when measured by light scattering in a particle size analyzer, is reported as a spherical equivalent diameter, regardless of the shape and/or relative uniformity of shape of the crystals in each sample. In certain circumstances, the dso values measured by the particle size analyzer may not correspond, even roughly, to the average crystal size measured visually by a representative SEM micrograph. Often in these cases, the discrepancy relates to an agglomeration of relatively small crystals that the particle size analyzer interprets as a single particle. In such circumstances, where the dso values from the particle size analyzer and the average crystal size from a representative SEM are significantly different, the representative SEM micrograph should be the more accurate measure of "average crystal size."

[0040] In a preferred embodiment, the order of addition of the components in the mixture (i.e., in step (a)) can be important and can advantageously be tailored, e.g., to provide better homogeneity. For instance, step (a) can preferably comprise: (i) combining the source of phosphorus and the source of aluminum, optionally with a liquid mixture medium, to form a primary mixture; (ii) aging the primary mixture for an aging time and under aging conditions (e.g., at an aging temperature), preferably sufficient to allow homogenization of the primary mixture, physico-chemical interaction between the source of phosphorus and the source of aluminum, or both; and (iii) adding the source of silicon, the at least one organic template, and optionally additional liquid mixture medium, to the aged primary mixture to form the synthesis mixture. In certain cases of this embodiment, within step (iii), said source of silicon is combined with said primary mixture prior to adding said at least one organic template (structure directing agent, or SDA). Advantageously, said primary mixture and said source of silicon can be combined to form a secondary mixture for a time and under conditions (e.g., temperature), preferably sufficient to allow homogenization of the secondary mixture, physico-chemical interaction between said source of silicon and said primary mixture, or both, after which said at least one organic template is combined therewith. [0041] When a component is added to a mixture to allow homogenization and/or physico-chemical interaction, the aging time and temperature are two of the primary conditions. Although a variety of conditions can exist to allow sufficient contact for homogenization and/or interaction, in one embodiment, when the aging temperature is somewhere between 0⁰C and 50⁰C, the aging time can advantageously be at least 5 minutes, for example at least 10 minutes, at least 15 minutes, at least 20 minutes, at least 25 minutes, at least 30 minutes, at least 45 minutes, at least 1 hour, or at least 2 hours. Again, when the aging temperature is somewhere between O⁰C and 50⁰C, the aging time does not really have a maximum, but can be up to 350 hours, for example up to 300 hours, up to 250 hours, up to 200 hours, up to 168 hours, up to 96 hours, up to 48 hours, up to 24 hours, up to 16 hours, up to 12 hours, up to 8 hours, up to 6 hours, or up to 4 hours, depending on practical concerns relating to synthesis timing, cost efficiency, manufacture schedules, or the like.

[0042] Preferably, the Si/Al₂ ratio added to the synthesis mixture can be as close as possible to the Si/Ak ratio of the crystallized silicoaluminophosphate molecular sieve (e.g., difference between the Si/Al₂ ratio in the synthesis mixture and in the crystallized silicoaluminophosphate molecular sieve can be no more than 0.10, preferably no more than 0.08, for example no more than 0.07) and/or the synthesis mixture and the crystallized silicoaluminophosphate molecular sieve can both exhibit a relatively low Si/Al₂ ratio (e.g., both can be less than 0.33, preferably less than 0.30, for example no more than 0.25, no more than 0.20, no more than 0.15, or no more than 0.10). [0043] In a preferred embodiment according to the first aspect of the invention, the crystallized silicoaluminophosphate molecular sieve is recovered from step (b) in a yield that is at least 2.0% (e.g., at least 2.5% or at least 3.0%) greater than a yield obtained by recovering a silicoaluminophosphate molecular sieve crystallized from an identical synthesis mixture at a crystallization temperature of 160⁰C or less for a crystallization time from 5 minutes to 350 hours. [0044] In a preferred embodiment of the invention, one or more of the following are satisfied: the source of aluminum comprises alumina; the source of phosphorus comprises phosphoric acid; the source of silicon can include an organosilicate comprising a tetra- alkylorthosilicate; and the at least one organic template comprises N,N-dime- thylcyclohexylamine. [0045] In a preferred embodiment according to the first aspect of the invention, the synthesis mixture exhibits a Si/Al₂ ratio less than 0.11, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.17, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 0.08 greater than the Si/Ak ratio of the synthesis mixture, said crystallization temperature is from 165°C to 180⁰C, and the crystallized silicoaluminophosphate molecular sieve from step (c) has a crystal size distribution such that its average crystal size is not greater than 1.2 μm. [0046] In a preferred embodiment according to the second aspect of the invention, the synthesis mixture exhibits a Si/Al₂ ratio less than 0.11, the crystallized silico- aluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.17, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 0.08 greater than the Si/Al₂ ratio of the synthesis mixture, and the crystallization temperature is between 150⁰C and 200⁰C.

[0047] The product of the crystallization is an aluminophosphate or silicoaluminophosphate containing a CHA framework-type molecular sieve having an X-ray diffraction pattern including at least the d-spacings shown in Table 1 below:

[0048] Although the crystallization product is normally a single phase CHA framework-type molecular sieve, in some cases the product may contain an intergrowth of a

CHA framework-type molecular sieve with, for example an AEI framework-type molecular sieve or small amounts of other crystalline phases, such as APC and/or AFI framework-type molecular sieves. In one embodiment, it is preferable for the crystallization product to have as high an amount of CHA framework type as possible, e.g., at least 95% CHA framework- type character, or even 100% CHA framework-type character (or as close as possible to single phase CHA framework-type character as can currently be measured). Without being bound by theory, it is believed that silicoaluminophosphate molecular sieves having increased

CHA framework-type character (and/or increased uniformity of distribution of silicon within the molecular sieve framework structure, i.e., decreased amounts of silicon islanding) can advantageously exhibit better performance (e.g., increased POS and optionally also POR, which means prime olefin, or ethylene-to-propylene, ratio) in oxygenates-to-olefins conversion reactions, particularly in methanol-to-olefins conversion reactions. [0049] As a result of the crystallization process, the recovered crystalline product contains within its pores at least a portion of the organic directing agent used in the synthesis. In a preferred embodiment, activation is performed in such a manner that the organic directing agent is removed from the molecular sieve, leaving active catalytic sites within the microporous channels of the molecular sieve open for contact with a feedstock. The activation process is typically accomplished by calcining, or essentially heating the molecular sieve comprising the template at a temperature of from 200⁰C to 800⁰C in the presence of an oxygen-containing gas. In some cases, it may be desirable to heat the molecular sieve in an environment having a low or zero oxygen concentration. This type of process can be used for partial or complete removal of the organic directing agent from the intracrystalline pore system.

[0050] Once the crystalline product has been activated, it can be formulated into a catalyst composition by combination with other materials, such as binders and/or matrix materials, which provide additional hardness or catalytic activity to the finished catalyst. [0051] Materials which can be blended with the present molecular sieve material include a large variety of inert and catalytically active materials. These materials include compositions such as kaolin and other clays, various forms of rare earth metals, other non- zeolite catalyst components, zeolite catalyst components, alumina or alumina sol, titania, zirconia, quartz, silica or silica sol, and mixtures thereof. These components are also effective in reducing overall catalyst cost, acting as a thermal sink to assist in heat shielding the catalyst during regeneration, densifying the catalyst and increasing catalyst strength. When blended with such components, the amount of present CHA-containing crystalline material contained in the final catalyst product ranges from 10 to 90 weight percent of the total catalyst, preferably 20 to 80 weight percent of the total catalyst.

[0052] The CHA framework type crystalline material produced by the present process can be used to dry gases and liquids; for selective molecular separation based on size and polar properties; as an ion-exchanger; as a chemical carrier; in gas chromatography; and as a catalyst in organic conversion reactions. Examples of suitable catalytic uses of the CHA framework type crystalline material described herein include (a) hydrocracking of heavy petroleum residual feedstocks, cyclic stocks and other hydrocrackate charge stocks, normally in the presence of a hydrogenation component selected from Groups 6 and 8-10 of the Periodic Table of Elements; (b) dewaxing, including isomerization dewaxing, to selectively remove straight chain paraffins from hydrocarbon feedstocks typically boiling above 177°C, including raffinates and lubricating oil basestocks; (c) catalytic cracking of hydrocarbon feedstocks, such as naphthas, gas oils, and residual oils, normally in the presence of a large pore cracking catalyst, such as zeolite Y; (d) oligomerization of straight and branched chain olefins having from 2-21, preferably 2-5, carbon atoms, to produce medium to heavy olefins which are useful for both fuels, e.g., gasoline or a gasoline blending stock, and chemicals; (e) isomerization of olefins, particularly olefins having 4-6 carbon atoms, and especially normal butene to produce iso-olefins; (f) upgrading of lower alkanes, such as methane, to higher hydrocarbons, such as ethylene and benzene; (g) disproportionation of alkylaromatic hydrocarbons, such as toluene, to produce dialkylaromatic hydrocarbons, such as xylenes; (h) alkylation of aromatic hydrocarbons, such as benzene, with olefins, such as ethylene and propylene, to produce alkylated aromatics, such as ethylbenzene and cumene; (i) isomerization of dialkylaromatic hydrocarbons, such as xylenes; (j) catalytic reduction of nitrogen oxides; and (k) synthesis of monoalkylamines and dialkylamines.

[0053] In particular, the CHA framework type crystalline material produced by the present process is useful as a catalyst in the conversion of oxygenates to one or more olefins, particularly ethylene and propylene. As used herein, the term "oxygenates" is defined to include, but is not necessarily limited to, aliphatic alcohols, ethers, carbonyl compounds (aldehydes, ketones, carboxylic acids, carbonates, and the like), and also compounds containing hetero-atoms, such as, halides, mercaptans, sulfides, amines, and mixtures thereof. The aliphatic moiety will normally contain from 1-10 carbon atoms, such as from 1-4 carbon atoms. [0054] Representative oxygenates include lower straight chain or branched aliphatic alcohols, their unsaturated counterparts, and their nitrogen, halogen, and sulfur analogues. Examples of suitable oxygenate compounds can include, but are not necessarily limited to: methanol; ethanol; n-propanol; isopropanol; C₄ to C₁₀ alcohols; methyl ethyl ether; dimethyl ether; diethyl ether; di-isopropyl ether; methyl mercaptan; methyl sulfide; methyl amine; ethyl mercaptan; di-ethyl sulfide; di-ethyl amine; ethyl chloride; formaldehyde; di-methyl carbonate; di-methyl ketone; acetic acid; n-alkyl amines; n-alkyl halides; n-alkyl sulfides having n-alkyl groups comprising from 3-10 carbon atoms; and the like; and mixtures thereof. Particularly suitable oxygenate compounds are methanol, dimethyl ether, and mixtures thereof, and most preferably comprise methanol. As used herein, the term "oxygenate" designates only the organic material used as the feed. The total charge of feed to the reaction zone may contain additional compounds, such as diluents. [0055] In one embodiment of the oxygenate conversion process, a feedstock comprising an organic oxygenate, optionally with one or more diluents, is contacted in the vapor phase in a reaction zone with a catalyst comprising the present molecular sieve at effective process conditions so as to produce the desired olefins. Alternatively, the process may be carried out in a liquid or a mixed vapor/liquid phase. When the process is carried out in the liquid phase or a mixed vapor/liquid phase, different conversion rates and selectivities of feedstock-to- product may result depending upon the catalyst and the reaction conditions. [0056] When present, the diluent(s) is(are) generally non-reactive to the feedstock or molecular sieve catalyst composition and is typically used to reduce the concentration of the oxygenate in the feedstock. Non-limiting examples of suitable diluents include helium, argon, nitrogen, carbon monoxide, carbon dioxide, water, essentially non-reactive paraffins (especially alkanes such as methane, ethane, and propane), essentially non-reactive aromatic compounds, and mixtures thereof. The most preferred diluents include water and nitrogen, with water being particularly preferred. Diluent(s) may comprise from 1 mol% to 99 mol% of the total feed mixture.

[0057] The temperature employed in the oxygenate conversion process may vary over a wide range, such as from 200⁰C to 1000⁰C, for example from 250⁰C to 800⁰C, including from 250⁰C to 750 ⁰C, conveniently from 300⁰C to 650⁰C, typically from 350⁰C to 600⁰C and particularly from 400⁰C to 600⁰C.

[0058] Light olefin products will form, although not necessarily in optimum amounts, at a wide range of pressures, including but not limited to autogenous pressures and pressures in the range from 0.1 kPa to 10 MPa. Conveniently, the pressure can be in the range from 7 kPa to 5 MPa, such as from 50 kPa to 1 MPa. The foregoing pressures are exclusive of diluents, if any are present, and refer to the partial pressure of the feedstock as it relates to oxygenate compounds and/or mixtures thereof. Lower and upper extremes of pressure may adversely affect selectivity, conversion, coking rate, and/or reaction rate; however, light olefins such as ethylene and/or propylene still may form. [0059] In a preferred embodiment, the method of converting hydrocarbons into olefins according to the invention comprises: (a) preparing a silicoaluminophosphate molecular sieve according to the methods disclosed hereinabove; (b) formulating said silicoaluminophosphate molecular sieve, along with a binder and optionally a matrix material, into a silicoaluminophosphate molecular sieve catalyst composition, typically comprising from at least 10% to 50% molecular sieve; and (c) contacting said catalyst composition with a hydrocarbon feed under conditions sufficient to convert said hydrocarbon feed into a product comprising predominantly one or more olefins, preferably to attain a prime olefin selectivity of at least 70 wt% (as measured at 500⁰C). Preferably, the hydrocarbon feed is an oxygenate- containing feed comprising methanol, dimethylether, or a combination thereof, and the one or more olefins typically comprises ethylene, propylene, or a combination thereof. [0060] A wide range of weight hourly space velocities (WHSV) for the feedstock will function in the oxygenate conversion process. WHSV is defined as weight of feed (excluding diluents) per hour per weight of a total reaction volume of molecular sieve catalyst (excluding inert and/or fillers). The WHSV generally should be in the range from 0.01 hr^"1 to 500 hr^"1, such from 0.5 hr^"1 to 300 hr^"1, for example from 0.1 hr^"1 to 200 hr^"1.

[0061] A practical embodiment of a reactor system for the oxygenate conversion process is a circulating fluid bed reactor with continuous regeneration. Fixed beds are generally not preferred for the process, because oxygenate-to-olefin conversion is a highly exothermic process that requires several stages with intercoolers or other cooling devices. The reaction also results in a high pressure drop, due to the production of low pressure, low density gas. [0062] Because the catalyst typically needs to be regenerated frequently, the reactor should preferably allow easy removal of at least a portion of the catalyst to a regenerator, where the catalyst can be subjected to a regeneration medium, such as a gas comprising oxygen, for example air, to burn off coke from the catalyst, which should restore at least some of the catalyst activity. The conditions of temperature, oxygen partial pressure, and residence time in the regenerator can typically be selected to achieve a coke content on regenerated catalyst of less than 1 wt%, for example less than 0.5 wt%. At least a portion of the regenerated catalyst should be returned to the reactor.

[0063] In a preferred embodiment, the method of forming an olefin-based polymer product comprises: (a) preparing a silicoaluminophosphate molecular sieve according to the methods described hereinabove; (b) formulating said silicoaluminophosphate molecular sieve, along with a binder and optionally a matrix material, into a silicoaluminophosphate molecular sieve catalyst composition comprising from at least 10% to 50% molecular sieve; (c) contacting said catalyst composition with a hydrocarbon feed under conditions sufficient to convert said hydrocarbon feed into a product comprising predominantly one or more olefins; and (d) polymerizing at least one of the one or more olefins, optionally with one or more other comonomers and optionally (but preferably) in the presence of a polymerization catalyst, under conditions sufficient to form an olefin-based (co)polymer. Preferably, in this preferred embodiment, the hydrocarbon feed is an oxygenate-containing feed comprising methanol, dimethylether, or a combination thereof, the one or more olefins typically comprises ethylene, propylene, or a combination thereof, and the olefin-based (co)polymer is an ethylene-containing (co)polymer, a propylene-containing (co)polymer, or a copolymer, mixture, or blend thereof. [0064] Additionally or alternately, the invention can be described by the following embodiments.

[0065] Embodiment 1. A method of preparing a silicoaluminophosphate molecular sieve having a controlled acid site density, the method comprising: (a) providing a synthesis mixture comprising a source of aluminum, a source of phosphorus, a source of silicon, and at least one organic template containing (i) a 4- to 8- membered cycloalkyl group, optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, or (ii) a 4- to 8- membered heterocyclic group having from 1-3 heteroatoms, said heterocyclic group being optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, and said heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S, wherein the synthesis mixture exhibits a Si/Al₂ ratio less than 0.33; and (b) inducing crystallization of a silicoaluminophosphate molecular sieve, which exhibits 90% or greater CHA framework type character, from said synthesis mixture at a crystallization temperature of at least 165°C for a crystallization time from 5 minutes to 350 hours, wherein (i) the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.33, (ii) the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 0.10 greater than the Si/Al₂ ratio of the synthesis mixture, or (iii) both (i) and (ii).

[0066] Embodiment 2. A method of preparing a silicoaluminophosphate molecular sieve having a desired crystal size, the method comprising: (a) combining a source of phosphorus and a source of aluminum, optionally with a liquid mixture medium, to form a primary mixture; (b) aging the primary mixture for an aging time and under aging conditions sufficient to allow homogenization of the primary mixture, physico-chemical interaction between the source of phosphorus and the source of aluminum, or both; (c) adding a source of silicon, at least one organic template, and optionally additional liquid mixture medium, to the aged primary mixture to form a synthesis mixture; and (d) inducing crystallization of a silicoaluminophosphate molecular sieve, which exhibits 90% or greater CHA framework type character, from said synthesis mixture at a crystallization temperature, wherein the at least one organic template contains (i) a 4- to 8- membered cycloalkyl group, optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, or (ii) a 4- to 8- membered heterocyclic group having from 1-3 heteroatoms, said heterocyclic group being optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, and said heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S, wherein the synthesis mixture and the crystallized silicoaluminophosphate molecular sieve both exhibit a Si/Al₂ ratio less than 0.33, and wherein the crystallized silicoaluminophosphate molecular sieve has a crystal size distribution such that its average crystal size is not greater than 3.0 μm.

[0067] Embodiment 3. The method of embodiment 1 or embodiment 2, wherein the synthesis mixture exhibits a Si/Al₂ ratio less than 0.17, and wherein the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.25. [0068] Embodiment 4. The method of any of the previous embodiments, wherein step

(b) is done while stirring.

[0069] Embodiment 5. The method of any of the previous embodiments, wherein the at least one organic template contains a cyclohexyl group, optionally substituted by 1 to 3 methyl groups. [0070] Embodiment 6. The method of embodiment 5, wherein the at least one organic template comprises N,N-dimethylcyclohexylamine.

[0071] Embodiment 7. The method any of embodiments 1-5, wherein one or more of the following are satisfied: the source of aluminum comprises alumina; the source of phosphorus comprises phosphoric acid; the source of silicon comprises a tetraalkylorthosilicate; and the at least one organic template comprises N,N-dimethylcyclohexylamine.

[0072] Embodiment 8. The method of any of the previous embodiments, wherein step

(b) was accomplished using seeds having a framework type of CHA, AEI, AFX, LEV, an intergrowth thereof, or a combination thereof. [0073] Embodiment 9. The method of any of the previous embodiments, wherein the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 100% greater than the Si/ Al₂ ratio of the synthesis mixture. [0074] Embodiment 10. The method of any of the previous embodiments, wherein said crystallization temperature is from 170⁰C to 200⁰C.

[0075] Embodiment 11. The method of any of embodiments 1 and 3-10, wherein the crystallized silicoaluminophosphate molecular sieve from step (b) has a crystal size distribution such that its average crystal size is not greater than 1.2 μm.

[0076] Embodiment 12. The method of any of embodiments 1 and 3-11, wherein the crystallized and treated silicoaluminophosphate molecular sieve is recovered from step (b) in a yield that is at least 2.0% greater than a yield obtained by recovering a silicoaluminophosphate molecular sieve crystallized from an identical synthesis mixture at a crystallization temperature of 160⁰C or less for a crystallization time from 5 minutes to 350 hours.

[0077] Embodiment 13. The method of any of embodiments 1 and 3-12, wherein: the synthesis mixture exhibits a Si/Al₂ ratio less than 0.11, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.17, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 0.08 greater than the Si/Al₂ ratio of the synthesis mixture, the crystallization temperature is between 165°C and 180⁰C, and the crystallized silicoaluminophosphate molecular sieve from step (b) has a crystal size distribution such that its average crystal size is not greater than 1.2 μm. [0078] Embodiment 14. The method of any of embodiments 1-12, wherein the crystallized silicoaluminophosphate molecular sieve exhibits a Si/ Al₂ ratio not more than 0.10 greater than the Si/Al₂ ratio of the synthesis mixture.

[0079] Embodiment 15. The method of any of embodiments 2-9, 11, and 14, wherein the crystallization temperature is between 150⁰C and 200⁰C. [0080] Embodiment 16. The method of any of embodiments 2-15, wherein, within step (c), said source of silicon is combined with said primary mixture prior to adding said at least one organic template.

[0081] Embodiment 17. The method of embodiment 16, wherein said primary mixture and said source of silicon are combined to form a secondary mixture for a time and under conditions sufficient to allow homogenization of the secondary mixture, physico-chemical interaction between said source of silicon and said primary mixture, or both, after which said at least one organic template is combined therewith.

[0082] Embodiment 18. The method of any of embodiments 2-17, wherein the aging time is at least 15 minutes at aging temperatures between 0⁰C and 50⁰C. [0083] Embodiment 19. The method of any of embodiments 2-9, 14, and 16-18, wherein: the synthesis mixture exhibits a Si/Al₂ ratio less than 0.11, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.17, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 0.08 greater than the Si/Al₂ ratio of the synthesis mixture, and the crystallization temperature is between 150⁰C and 200⁰C.

[0084] Embodiment 20. A method of converting hydrocarbons into olefins comprising:

(a) preparing a silicoaluminophosphate molecular sieve according to the method of any of the previous embodiments; (b) formulating said silicoaluminophosphate molecular sieve, along with a binder and optionally a matrix material, into a silicoaluminophosphate molecular sieve catalyst composition comprising from at least 10% to 50% molecular sieve; and (c) contacting said catalyst composition with a hydrocarbon feed under conditions sufficient to convert said hydrocarbon feed into a product comprising predominantly one or more olefins. [0085] Embodiment 21. The method of embodiment 20, wherein the hydrocarbon feed is an oxygenate-containing feed comprising methanol, dimethylether, or a combination thereof, and wherein the one or more olefins comprises ethylene, propylene, or a combination thereof.

[0086] Embodiment 22. A method of forming an olefin-based polymer product comprising: (a) preparing a silicoaluminophosphate molecular sieve according to the method of any of embodiments 1-19; (b) formulating said silicoaluminophosphate molecular sieve, along with a binder and optionally a matrix material, into a silicoaluminophosphate molecular sieve catalyst composition comprising from at least 10% to 50% molecular sieve; (c) contacting said catalyst composition with a hydrocarbon feed under conditions sufficient to convert said hydrocarbon feed into a product comprising predominantly one or more olefins; (d) polymerizing at least one of the one or more olefins, optionally with one or more other comonomers and optionally in the presence of a polymerization catalyst, under conditions sufficient to form an olefin-based (co)polymer.

[0087] Embodiment 23. The method of embodiment 22, wherein the hydrocarbon feed is an oxygenate-containing feed comprising methanol, dimethylether, or a combination thereof, wherein the one or more olefins comprises ethylene, propylene, or a combination thereof, and wherein the olefin-based (co)polymer is an ethylene-containing (co)polymer, a propylene-containing (co)polymer, or a copolymer, mixture, or blend thereof. [0088] The invention will now be more particularly described with reference to the following Examples and the accompanying drawings.

EXAMPLES [0089] The analysis techniques described below were among those used in characterizing various samples from the Examples. ICP-OES

[0090] Elemental analysis has been done using ICP-OES (Inductively Coupled Plasma

- Optical Emission Spectrometry). Samples were dissolved in a mixture of acids and diluted in deionized water. The instrument (Simultaneous VISTA-MPX from Varian) was calibrated using commercial available standards (typically at least 3 standards and a blank). The power used was 1.2 kW, plasma flow 13.5 L/min, and nebulizer pressure 200 kPa for all lines. Results are expressed in wt% or ppm by weight (wppm), and the values are recalculated to Si/Al₂ molar ratios. XRD

[0091] Either of two X-ray diffractometers was used: a STOE Stadi-P Combi

Transmission XRD and a Scintag X2 Reflection XRD with optional sample rotation. Cu-K_α radiation was used. Typically, a step size of 0.2° 2Θ and a measurement time of 1 hour were used. SEM

[0092] A JEOL JSM-6340F Field-Emission-Gun scanning electron microscope (SEM) was used, operating at 2 kV and 12 μA. Prior to measurement, samples were dispersed in ethanol, subjected to ultrasonic treatment for 5 to 30 minutes, deposited on SEM sample holders, and dried at room temperature and pressure (20-25⁰C and 101 kPa). If an average particle size was determined based on the SEM micrographs, typically the measurement was performed on at least 30 crystals. In case of the near cubic crystals, the average was based on the sizes of one of the edges of each crystal. PSA [0093] Particle size analysis was performed using a Mastersizer APA2000 from Malvern Instruments Limited, equipped with a 4mW laser beam, based on laser scattering by randomly moving particles in a liquid medium. The samples to be measured were dispersed in water under continuous ultrasonic treatment to ensure proper dispersion. The pump speed applied was 2000 RPM, and the stirrer speed was 800 RPM. The parameters used in the operation procedure were: Refractive Index = 1.544, Absorption = 0.1. The results were calculated using the "general purpose-enhanced sensitivity" model. The results were expressed as dso, meaning that 50 vol% of the particles were smaller than the value. The average of at least 2 measurements, with a delay of at least 10 seconds, was reported. Comparative Examples A-H

[0094] For Comparative Example A, a synthesis mixture having a molar composition of 0.02 SiO₂ : P₂O₅ : Al₂O₃ : 2 DMCHA : 40 H₂O, as well as 100 wt ppm seeds, was prepared according to the following procedure. A solution of phosphoric acid was prepared by combining phosphoric acid [Acros 85%] and water. To this solution was added the appropriate amount of Condea Pural SB [Sasol, 75.6 wt% Al₂O₃] and the slurry was stirred for 1 hour at 10⁰C. To this mixture was added the appropriate amount of TEOS [tetraethyorthosilicate from Aldrich, 98%]. This mixture was then aged at 10⁰C while stirring for another one hour. Then the appropriate amount of dimethylcyclohexylamine [DMCHA from Purum Fluka] was added. This mixture was stirred for 10 minutes before the seeds (SAPO-34 seeds) were added. The final mixture was transferred to an autoclave which was stirred and heated to 160⁰C with a heat-up rate of 40°C/hr, while stirring, and was kept under these conditions for 144 hours. After this time, the autoclave was cooled to approximately room temperature (20-25⁰C), and the solids were washed with demineralized water and dried at 120⁰C. The phase purity of the sample was determined by X-ray diffraction and was characterized substantially by the d-spacings shown in Table 1 above. The yield was determined by weighing the dried solids and dividing this weight by the weight of the initial synthesis mixture. The so-calculated yield was 2.8 wt%. SEM micrographs were recorded, and the crystal size was determined to be, on average, approximately 1.0 μm. The Si/Al₂ ratio in the recovered product was determined to be 0.13. [0095] A series of samples was made according to the same procedure, only changing the Si/Al₂ ratio of the synthesis mixture (Comparative Examples B-H). All of these remaining product samples were determined to be characterized substantially by the d-spacings shown in Table 1 above, with an average crystal size, dso, smaller than 1 μm. The various Si/Al₂ ratios in the recovered product and the yields are summarized in Table 2 below. Table 2. Yield, dso, and Si/Al₂ ratio in products crystallized at 160⁰C, based on various Si/Al₂ ratios in the synthesis mixture.

Examples 1-8

[0096] A similar series of synthesis mixtures as in Comparative Examples A-H was subjected to crystallization at 170 ⁰C under stirred conditions for 24 hours, with all other parameters of the Comparative Examples remaining the same. The results are summarized in Table 3 below.

Table 3. Yield, dso, and Si/Al₂ ratio in products crystallized at 170⁰C, based on various Si/Al₂ ratios in the synthesis mixture.

[0097] The graphical results of the Examples and the Comparative Examples from Tables 2 and 3, with some additional data that are either repeats of the same Si/Al ratio as shown in the examples or an extension of Si/Al ration into higher values, are shown in attached Figures 1 and 2.

[0098] From these results it can be concluded that, in order to obtain molecular sieve catalyst materials (e.g., such as characterized substantially by the d-spacings shown in Table 1 above) with relatively low Si/Al₂ molar ratios (e.g., below 0.10) in the product, a hydrothermal treatment at a temperature above the crystallization temperature can preferably be undertaken and/or the crystallization temperature can preferably be greater than 160⁰C. The yields of the products made using such higher temperatures have also been shown to be higher, even despite relatively shorter crystallization/treatment times. Comparative Example I [0099] A synthesis mixture having a molar composition of 0.03 Siθ₂ : P₂O5 : AI₂O3 : 2

DMCHA : 40 H₂O, as well as 100 wt ppm seeds (SAPO-34 seeds), was prepared according to the following procedure. The appropriate amount of the silicon source, TEOS [tetraethyorthosilicate from Aldrich, 98%], was added to a dilute solution of phosphoric acid [prepared from a mixture of water and 85% phosphoric acid from Acros], in order to sufficiently disperse the silicon source in the liquid. To this solution was added the appropriate amount of Condea Pural SB [Sasol, 74.2 wt% AI₂O3] as the alumina source. The resulting mixture was stirred for 10 minutes before the appropriate amount of dimethylcyclohexylamine [DMCHA from Purum Fluka] template was added. This resulting slurry/mixture was stirred for another 10 minutes before the seeds (SAPO-34 seeds) were added, after which the final mixture was homogenized for another 10 minutes before being loaded into a reactor vessel. The final mixture was stirred and heated to 170⁰C with a heat-up rate of 5°C/hr, and was kept under these conditions for 120 hours. After this time, the reaction mixture was cooled to approximately room temperature, and the solids were separated from the mother liquor, washed with demineralized water, and dried at 120⁰C. The yield was determined by weighing the dried solids and dividing this weight by the weight of the initial synthesis mixture. The so-calculated yield was 9.7 wt%. The phase purity of the sample was determined by X-ray diffraction and was characterized substantially by the d- spacings shown in Table 1 above. The dso, as determined by PSA, was approximately 4.9 μm. The Si/Al₂ ratio of the product, as determined by ICP after dissolution of the crystals, was 0.14. The SEM of the product is shown in Figure 3.

[00100] The mixing procedure of Comparative Example I, though resulting in relatively well-dispersed silicon, did not result in small crystals and exhibited an unacceptably high silicon incorporation level, despite the low initial Si/Al₂ molar ratio of the initial synthesis mixture. Comparative Example J

[00101] A synthesis mixture having a molar composition of 0.03 SiO₂ : P₂O5 : AI₂O3 : 2 DMCHA : 40 H₂O, as well as 100 wt ppm seeds (SAPO-34 seeds), was prepared according to the following procedure. A solution of phosphoric acid was prepared by combining phosphoric acid [Acros 85%] and water. To this solution was added the appropriate amount of Condea Pural SB [Sasol, 74.2 wt% AI₂O3] and the slurry was stirred for 10 minutes. To this mixture was added the appropriate amount of TEOS [tetraethyorthosilicate from Aldrich, 98%]. Then the appropriate amount of dimethylcyclohexylamine [DMCHA from Purum Fluka] template was added. This mixture was stirred for 10 minutes before the seeds were added. The final mixture was transferred to an autoclave which was heated to 170⁰C with a heat-up rate of 5°C/hr, while stirring, and was kept under these conditions for 100 hours. After this time, the autoclave was cooled to approximately room temperature, and the solids were washed with demineralized water and dried at 120⁰C. The yield was determined by weighing the dried solids and dividing this weight by the weight of the initial synthesis mixture. The so-calculated yield was 15.1 wt%. The phase purity of the sample was determined by X-ray diffraction and was characterized substantially by the d-spacings shown in Table 1 above. The dso, as determined by PSA, was approximately 4.1 μm. The Si/Al₂ ratio of the product, as determined by ICP-OES after dissolution of the crystals, was 0.03. The SEM of the product is shown in Figure 4.

[00102] The mixing procedure of Comparative Example J, like Comparative Example I, resulted in relatively large crystals. Unlike Comparative Example I, Comparative Example J exhibited not only relatively high yield, but also an accurate (low) silicon incorporation level, in line with the low initial Si/Al₂ molar ratio of the initial synthesis mixture. Example 9

[00103] A synthesis mixture having a molar composition of 0.03 Siθ2 : P2O5 : AI2O3 : 2 DMCHA : 40 H₂O, as well as 100 wt ppm seeds, was prepared according to the following procedure. A solution of phosphoric acid was prepared by combining phosphoric acid [Acros 85%] and water. To this solution was added the appropriate amount of Condea Pural SB [Sasol, 74.2 wt% AI₂O3] and the slurry was stirred for 1 hour at 35°C. To this mixture was added the appropriate amount of TEOS [tetraethyorthosilicate from Aldrich]. Then the appropriate amount of dimethylcyclohexylamine [DMCHA from Purum Fluka] was added. This mixture was stirred for 10 minutes before the seeds (SAPO-34 seeds) were added. The final mixture was transferred to an autoclave which was stirred and heated to 170⁰C with a heat-up rate of 5°C/hr, while stirring, and was kept under these conditions for 120 hours. After this time, the autoclave was cooled to approximately room temperature, and the solids were washed with demineralized water and dried at 120⁰C. The yield was determined by weighing the dried solids and dividing this weight by the weight of the initial synthesis mixture. The so-calculated yield was 9.2 wt%. The phase purity of the sample was determined by X-ray diffraction and was characterized substantially by the d-spacings shown in Table 1 above. The dso, as determined by PSA, was approximately 2.7 μm. The Si/Al₂ ratio of the product, as determined by ICP-OES after dissolution of the crystals, was 0.08. The SEM of the product is shown in Figure 5.

[00104] In examining the aforementioned Comparative Examples I- J and Example 9, it can be seen that the preferred mixing procedure (e.g., the sequence of addition, as well as aging times) according to the invention can advantageously result in crystals of molecular sieve material having a smaller average crystal diameter (dso) and a lower Si/Al₂ ratio in the product sieve.

[00105] While the present invention has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the invention lends itself to variations not necessarily illustrated herein. For this reason, then, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.

Claims

CLAIMSWhat is claimed is:

1. A method of preparing a silicoaluminophosphate molecular sieve having a controlled acid site density, the method comprising: (a) providing a synthesis mixture comprising a source of aluminum, a source of phosphorus, a source of silicon, and at least one organic template containing (i) a 4- to 8- membered cycloalkyl group, optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, or (ii) a 4- to 8- membered heterocyclic group having from 1-3 heteroatoms, said heterocyclic group being optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, and said heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S, wherein the synthesis mixture exhibits a Si/Al₂ ratio less than 0.33; and (b) inducing crystallization of a silicoaluminophosphate molecular sieve, which exhibits 90% or greater CHA framework type character, from said synthesis mixture at a crystallization temperature of at least 165°C for a crystallization time from 5 minutes to 350 hours, wherein (i) the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.33, (ii) the crystallized silicoaluminophosphate molecular sieve exhibits a Si/ Al₂ ratio not more than 0.10 greater than the Si/Al₂ ratio of the synthesis mixture, or (iii) both (i) and (ii).

2. A method of preparing a silicoaluminophosphate molecular sieve having a desired crystal size, the method comprising: (a) combining a source of phosphorus and a source of aluminum, optionally with a liquid mixture medium, to form a primary mixture; (b) aging the primary mixture for an aging time and under aging conditions sufficient to allow homogenization of the primary mixture, physico-chemical interaction between the source of phosphorus and the source of aluminum, or both; (c) adding a source of silicon, at least one organic template, and optionally additional liquid mixture medium, to the aged primary mixture to form a synthesis mixture; and (d) inducing crystallization of a silicoaluminophosphate molecular sieve, which exhibits 90% or greater CHA framework type character, from said synthesis mixture at a crystallization temperature, wherein the at least one organic template contains (i) a 4- to 8- membered cycloalkyl group, optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, or (ii) a 4- to 8- membered heterocyclic group having from 1-3 heteroatoms, said heterocyclic group being optionally substituted by 1-3 alkyl groups having from 1-3 carbon atoms, and said heteroatoms in said heterocyclic groups being selected from the group consisting of O, N, and S, wherein the synthesis mixture and the crystallized silicoaluminophosphate molecular sieve both exhibit a Si/Al₂ ratio less than 0.33, and wherein the crystallized silicoaluminophosphate molecular sieve has a crystal size distribution such that its average crystal size is not greater than 3.0 μm.

3. The method of claim 1 or claim 2, wherein the synthesis mixture exhibits a Si/Al₂ ratio less than 0.17, and wherein the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.25.

4. The method of any of the previous claims, wherein step (b) is done while stirring.

5. The method of any of the previous claims, wherein the at least one organic template contains a cyclohexyl group, optionally substituted by 1 to 3 methyl groups.

6. The method of claim 5, wherein the at least one organic template comprises N,N-dimethylcyclohexylamine.

7. The method any of claims 1-5, wherein one or more of the following are satisfied: the source of aluminum comprises alumina; the source of phosphorus comprises phosphoric acid; the source of silicon comprises a tetraalkylorthosilicate; and the at least one organic template comprises N,N-dimethylcyclohexylamine.

8. The method of any of the previous claims, wherein step (b) was accomplished using seeds having a framework type of CHA, AEI, AFX, LEV, an intergrowth thereof, or a combination thereof.

9. The method of any of the previous claims, wherein the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 100% greater than the Si/Ak ratio of the synthesis mixture.

10. The method of any of the previous claims, wherein said crystallization temperature is from 170⁰C to 200⁰C.

11. The method of any of claims 1 and 3-10, wherein the crystallized silicoaluminophosphate molecular sieve from step (b) has a crystal size distribution such that its average crystal size is not greater than 1.2 μm.

12. The method of any of claims 1 and 3-11, wherein the crystallized and treated silicoaluminophosphate molecular sieve is recovered from step (b) in a yield that is at least 2.0% greater than a yield obtained by recovering a silicoaluminophosphate molecular sieve crystallized from an identical synthesis mixture at a crystallization temperature of 160⁰C or less for a crystallization time from 5 minutes to 350 hours.

13. The method of any of claims 1 and 3-12, wherein: the synthesis mixture exhibits a Si/Al₂ ratio less than 0.11, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio less than 0.17, the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 0.08 greater than the Si/Al₂ ratio of the synthesis mixture, the crystallization temperature is between 165°C and 180⁰C, and the crystallized silicoaluminophosphate molecular sieve from step (b) has a crystal size distribution such that its average crystal size is not greater than 1.2 μm.

14. The method of any of claims 1-12, wherein the crystallized silicoaluminophosphate molecular sieve exhibits a Si/Al₂ ratio not more than 0.10 greater than the Si/Al₂ ratio of the synthesis mixture.

15. The method of any of claims 2-9, 11, and 14, wherein the crystallization temperature is between 150⁰C and 200⁰C.