JPS6215487B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to crystalline aluminosilicate zeolite ZSM-5, which is larger than about 1 micron;
That is, it relates to a process for making the above-described zeolite which crystallizes a high purity crystalline aluminosilicate into large particles with a final crystal size of about 1 to 2 microns or more. ZSM with the above crystal dimensions
The 5 catalyst is highly useful in selective toluene disproportionation reactions and methanol conversion processes and other aromatic selective conversion processes. ZSM-5 crystalline aluminosilicate zeolite is well known in the industry and is available in U.S. Patent No. 3,702,886.
This is specifically stated in the specification of the No. Large particle ZSM
Although -5 zeolite has been produced in the past, such methods have generally not been commercially viable operations. It was previously thought that the final zeolite crystal size depended primarily on the nature of the reaction mixture used. However, it has been found that the crystal size is significantly influenced by the rate of addition of the organic compound, ie its effective concentration in the crystallization medium, the temperature of the crystallization medium, the PH conditions and the degree of stirring. Accordingly, the present invention relates to a large-crystal ZSM-5 crystalline aluminosilicate zeolite catalyst, and to preparing aluminosilicate gels in a convenient manner.
It is heated to at least about 104°C (about 220°C) and an organic component (e.g., tetrapropylammonium bromide) is added to the gel such that the organic component is only present in low concentrations while the gel crystallizes; at least 1 micron, preferably 1 micron, including rapidly heating the mixture to a temperature of about 149°C (about 300°C).
The present invention also relates to a method for making a ZSM-5 crystalline aluminosilicate zeolite catalyst characterized by having at least one crystalline size of ~2 microns or more. Large crystals are 1 micron or more, for example about 1 to 2
A related term used to define crystals with a diameter of microns or more. Such crystal sizes are useful in hydrocarbon conversion processes.
This has proven to be advantageous in the case of ZSM-5 catalysts. For example, ZSM-5 catalysts containing crystals of such size as described above are highly useful in selective toluene disproportionation reactions and methanol conversion processes. The manufacturing method of the present invention relates to ZSM-5, but ZSM-5 has a similar crystal structure to ZSM-5.
11, ZSM-12, ZSM-35, ZSM-38 and similar materials may also be applied. As mentioned above, US Pat. No. 3,702,886 describes and claims ZSM-5. ZSM-11 is specifically described in US Pat. No. 3,709,979, the entire contents of which are incorporated herein by reference. ZSM-12 is further described in US Pat. No. 3,832,449, the entire contents of which are incorporated herein by reference. ZSM-35 is described in further detail in US Pat. No. 4,016,245, the entire contents of which are incorporated herein by reference. ZSM-38 is described in United States Patent Application Serial No. 560,412, filed March 30, 1975, the entire contents of which are incorporated herein by reference. The organic components used to produce large sized zeolite crystals according to the invention are usually selected from alkylammonium compounds, especially quaternary compounds such as tetramethylammonium bromide or tetrapropylammonium bromide. However, other suitable organic compounds known to those skilled in the art can be used. Furthermore, instead of the organic compounds themselves, their precursors can also be used with advantage. In the case of tetra-n-propylammonium bromide, tri-n-propylamine and n-propylbromide can be used. The method for preparing large crystal ZSM-5 catalysts of the present invention employs techniques that suppress crystal nucleation of ZSM-5 from the crystallization reaction mixture while promoting crystal growth. In particular, this technique takes advantage of the fact that crystal growth is promoted at high temperatures and crystal nucleation is promoted by high concentrations of quaternary organic compounds or other organic compounds essential for zeolite crystal formation.
One way to successfully make ZSM-5 large crystals is (a)
An aluminosilicate gel consisting of water, an alkali metal oxide source, a silica source, and an alumina source was prepared at an elevated temperature, i.e., approximately 126°C ± 34°C.
℃ (approximately 260〓±60〓), usually above 104℃, then (b) adding an alkyl ammonium compound or its precursor to said gel, and (c) reducing the nitrogen atom content of said gel to Gel from 104℃ to 216℃ (approximately 220〓 to (420〓) while maintaining less than 0.003% by weight of
, preferably at a temperature of 149°C (300°C) or higher. If the alkyl ammonium compound is crystallized at a temperature below e.g.
If introduced at 93°C to 160°C (200° to 320°C), the temperature must be raised to the final crystallization temperature without delay. The reaction mixture obtained in step (b) above usually contains silica,
It consists of an aqueous or gel phase containing alumina and alkali metal oxides, an organic phase containing alkylammonium compound precursors (usually tripropylamine and propyl bromide), and a solvent for the organic phase. The mixture is then stirred to disperse the precursor and inhibit the reaction that produces the alkyl ammonium compound. This alkylammonium compound is insoluble in the organic phase but soluble in the gel phase. No analysis is performed during crystallization, or is more practical, but analysis of the mother liquor (organic phase and
The mixture (with residual gel phase in which ZSM-5 crystals have formed) is flashed (this removes unconverted amines) and analyzed for nitrogen atoms. The desired large crystal ZSM-5 has a mother liquor of 0.003
It has been found that this is obtained only when the nitrogen analysis shows that it contains % by weight of nitrogen atoms.
Since alkylammonium compounds are inherently insoluble in the organic phase, it is reasonable to assume that the above analysis will give the nitrogen atomic content of the gel remaining after crystallization and thus the nitrogen atomic content of the gel during crystallization. . Another method of controlling organic compound concentration that is a preferred embodiment of this invention is to transfer organic compounds, such as tetrapropylammonium bromide, to a mixture of precursors, such as tri-n-propylamine and n-propyl bromide, in an aluminosilicate gel. The mixture is introduced at an elevated temperature, with moderately high agitation and a controlled crystallization temperature. The high stirring (approximately 90 to 140 rpm) is applied uniformly throughout the reaction mixture so that the reaction producing the quaternary organic compound is suppressed and a uniformly low concentration of the quaternary organic compound is maintained during the crystal formation reaction. The organic precursor is dispersed in the organic precursor. Quaternary compounds (i.e. organic components or precursors)
is introduced during or before crystal formation. The organic material is also introduced at the crystallization temperature and/or at a controlled slow rate. The high temperature preparation methods in the Table 3 below show the effect of the concentration of essential organic components. Concentrations of tetra-n-propylammonium bromide and its precursor tri-n-
The change was made by substituting propylamine with n-propyl bromide and limiting the extent of reaction by stirring. Tables 1, 2, and 4 list the crystal dimensions for each crystal, and Table 3 lists the major and minor dimensions of the crystals. Examples 1 to 4 described later are comparative examples, Examples 5 to 12 are working examples, and Examples 13 to 14 are comparative examples. In each example, an aqueous gel containing a source of silica, a source of alumina, and a source of alkali metal is created, mixed with an organic phase containing an alkyl ammonium precursor, and the resulting mixture is then stirred. to disperse the precursors and suppress reactions between the precursors to maintain the required low concentration of alkylammonium compound. Of course, the same effect can also be achieved by directly adding alkyl ammonium compounds at low concentrations. All examples listed below are ZSM−
5. Table 1 - High Concentration of Organic Species and Variable Stirring Examples 1, 2 and 3 are from the conventional preparation of ZSM-5 using the quaternary salt tetra-n-propylammonium bromide. There is no difference in the size of the crystals even if the stirring is changed. This is because the concentrations of crystal nucleus species are the same. Example 4 shows that quaternary precursors can be reacted in the presence of methyl ethyl ketone to create significant concentrations of crystal nucleating species. A resting period is required for the precursor reaction. "Nitrogen atom content (wt%) in the aqueous phase remaining after crystallization" in the table below refers to the nitrogen atom content (wt%) in the aqueous phase remaining after crystallization (i.e., in the gel), This is equal to the nitrogen content (wt%) of the gel in the crystals.

Table 2 - Low Concentration of Organic Species and Low Agitation Examples 5, 6 and 7 produced larger crystals than those obtained by the preparation method shown in Table 1. This large crystal was obtained from the low concentration of organic species required for crystal nucleation. The low concentration produced by limiting the reaction of the precursor by stirring the mixture is evidenced by the low nitrogen content of the mother liquor. Although this stirring does not serve sufficiently to disperse the organic precursor throughout the mixture, its effect on the reaction of the precursor is evident when comparing Example 7 with Example 4.
Example 7 produced crystals larger than about 1 micron, but
Example 4 produced crystals with a size of only about 0.1 micron. This is due to the low effective concentration of organic species in Example 7, as evidenced by the low nitrogen content of the mother liquor after crystallization. Table 3 - Low Concentration Organic Species and High Agitation Rates Higher degrees of agitation than those used in Examples 5-7 were used during the manufacturing operations of Examples 8, 9, 10, 11, and 12. did. This degree of agitation increases the dispersion of the precursor and generally produces larger crystals than those obtained with lower degrees of agitation. The data in Table 3 clearly show that large crystals are easily obtained with high agitation and low concentrations of organic material.

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[Table] Table 4 shows the effect of temperature on the growth rate of crystals. Both products used tetra-n-propylammonium bromide. Example 14 is 99℃
(210〓), it took 192 hours and the diameter
Crystals less than 0.05 microns were produced. The crystallization process of Example 13, carried out at 158°C (317°) from essentially the same reaction mixture, produced crystals at least twice the size of Example 15 (~
0.1 micron). The invention is not limited to the specific examples described above. Equivalents that can be deduced by those skilled in the art are within the scope of this invention.

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Claims (1)

[Claims] 1. A method for producing ZSM-5 crystalline aluminosilicate zeolite having at least one crystal size of 1 micron or larger, comprising: (a) water, and an alkali metal oxide source and a silica source; (b) adding an alkyl ammonium compound or its precursor to said gel; (c) adjusting the nitrogen atom content of the gel in the crystals to the weight of the gel;
Gel at 104°C while maintaining below 0.003% by weight
A process for producing ZSM-5 crystalline aluminosilicate zeolite with at least one crystal size of 1 micron or more, characterized in that it is crystallized at a temperature of 216°C. 2. The method according to claim 1, wherein the alkylammonium is a C1 _{- C10} alkylammonium compound or an ion thereof. 3. The production method according to claim 2, wherein the alkylammonium compound is a tetraalkyl ammonium halide compound. 4. The production method according to claim 3, wherein the alkylammonium compound is tetrapropylammonium bromide. 5 Claim 4 using tri-n-propylamine and n-propyl bromide as precursors of tetraalpropylammonium bromide
Manufacturing method described in section. 6. The method according to claim 1, wherein the aluminosilicate gel is heated to an elevated temperature of 126°C ± 34°C before adding the alkylammonium compound. 7. The method of claim 3, wherein the elevated temperature is at least 104°C. 8. The method according to claim 1, wherein the crystallization temperature is at least 149°C. 9. The method of claim 1, wherein the zeolite has a crystalline size greater than about 2 microns. 10. The method of claim 9, wherein the crystal size is about 3 to 5 microns in the larger dimension of the zeolite. 11. The method of claim 1, wherein the concentration of the organic component is controlled by introducing a mixture of precursors of the organic component into the aluminosilicate gel at elevated temperature and under high agitation conditions of about 90 to about 150 rpm. Manufacturing method. 12. The method according to claim 1, wherein the alkylammonium compound or its precursor is introduced into the crystallization medium under highly agitated conditions before crystallization. 13. The method of claim 12, wherein the stirring speed is at least about 90 rpm. 14. The process according to claim 1, wherein the organic component or precursor is introduced during crystallization under high stirring.