JPH0327541B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field] The present invention uses a new alkaline earth metal-containing crystalline aluminosilicate zeolite as a catalyst,
The present invention relates to a method for producing lower olefins from methanol and/or dimethyl ether. The alkaline earth metal-containing crystalline aluminosilicate zeolite (hereinafter sometimes simply referred to as zeolite or crystalline aluminosilicate) used in the present invention has a high catalyst content compared to conventionally known zeolite catalysts.
SiO ₂ /Al ₂ O ₂ ratio and high alkaline earth metal content, at least a portion of which can be easily exchanged to other ions by ion exchange methods. and this high alkaline earth metal content cannot be introduced by conventional ion exchange methods. A feature of the aluminosilicate production method of the present invention is that an alkaline earth metal salt is preliminarily present as part of the raw material for aluminosilicate production during the production of aluminosilicate crystals. In conventionally known crystalline aluminosilicates, a+b is 1 or less than 1, but in the crystalline aluminosilicate of the present invention, a
It is characteristic that +b is greater than 1. The method for producing lower olefins of the present invention comprises bringing methanol and/or dimethyl ether into contact with the above zeolite catalyst under heating in the gas phase.
This relates to the manufacturing method of _C2 - _C4 lower olefins, which produces lower olefins with high selectivity with less decomposition into CO and _CO2 , has less paraffin and aromatic side effects, and suppresses carbon deposition on the catalyst. Even at high temperatures, there is no reduction in catalyst activity or deterioration of the catalyst. [Prior art] In recent years, there has been concern about the supply of petroleum resources, and in particular, as Japan's dependence on foreign sources exceeds 99%, the effective use of coal, natural gas, etc. has become an important issue. There is a need to establish an industrial synthesis method for organic compounds such as olefins, paraffins, and aromatics from methanol obtained from , methane, CO, etc. Various types of crystalline aluminosilicate have been known so far, and among them, crystalline aluminosilicate zeolite is the most representative one. Crystalline aluminosilicate zeolites exist in abundance in nature and can also be obtained by synthesis, and have a certain crystal structure, with many holes and tunnels within the structure, which allows molecules up to a certain size to be adsorbed. However, it has the function of excluding anything larger than that, and is also sieved by molecular sieves. The pores caused by voids and tunnels are determined by the form in which SiO ₂ and Al ₂ O ₃ bond by sharing oxygen in the crystal structure. The electronegativity of the aluminum-containing tetrahedra is usually kept electroneutral by alkali metal ions, especially sodium and/or potassium. Normally, to produce crystalline aluminosilicate zeolite, a method is used in which SiO ₂ , Al ₂ O ₃ , alkali metal ion sources, and water are mixed in desired proportions, and then hydrothermal treatment is performed under normal pressure or increased pressure. It has been taken. There is also a method of using an organic nitrogen compound or an organic phosphoric acid compound as a base, and various zeolites with various adsorption properties and catalytic activities are synthesized using this method, and the synthesis of this type of zeolite has become very popular in recent years. Especially by Mobil Oil Co.
ZSM zeolites are tetraalkylammonium compounds, tetraalkylphosphonium compounds,
It is synthesized using pyrrolidine, ethylenediamine, choline, etc., and its unique adsorption ability and catalytic action are attracting attention. Among them, ZSM-5 is 5-6 Å
Because of its medium pore size, it has the property of adsorbing linear hydrocarbons and slightly branched hydrocarbons, but not highly branched hydrocarbons. This ZSM-5 is usually made of SiO ₂ , Al ₂ O ₃ ,
It is synthesized by hydrothermally treating a mixture consisting of each source of alkali metal, water, and a tetra-n-propylammonium compound. In recent years, much research has been conducted to obtain hydrocarbons by reacting methanol and/or dimethyl ether. The catalyst used in this reaction is generally called a solid acid, and many patents have been filed regarding various zeolites, heteropolyacids, etc. In particular, the aforementioned ZSM-5 by Mobil Oil uses methanol as a raw material and has a carbon number of
It is excellent for synthesizing hydrocarbons mainly composed of gasoline fractions up to 10, and has a relatively long life as a catalyst and exhibits stable activity.
It is unsuitable for producing lower olefins such as ethylene and propylene. Also, ZSM−34
Although it has high selectivity to ethylene and propylene as a catalyst for producing lower olefins in the same reaction, the activity decreases extremely quickly and is not practical. [Objective] The object of the present invention is to provide a catalyst that selectively produces hydrocarbons, particularly lower olefins such as ethylene and propylene, using methanol and/or dimethyl ether as a raw material, and has stable activity. [Structure] As a result of extensive research to achieve the above object, the present inventors have developed a composition formula aM ₂ O bM produced by pre-existing an alkaline earth metal salt in the production raw material during production of aluminosilicate crystals. 'O・Al ₂ O ₃・cSiO ₂・nH ₂ O (where M is an alkali metal and/or hydrogen atom,
M' is an alkaline earth metal, a is 0-1.5, b is 0.2-
40, but a+b>1, c is 12~3000 and n is 0~
It has been found that a crystalline aluminosilicate represented by 40) and exhibiting a specific X-ray diffraction pattern described below is suitable for this purpose. The above-mentioned alkaline earth metal-containing crystalline aluminosilicate zeolite has an X-ray diffraction pattern similar to that of a conventionally known zeolite catalyst having a pore diameter of 5 to 6 Å, but compared to it, the SiO ₂ /Al ₂ O ₃ ratio and It has a high alkaline earth metal/Al ratio and is a novel substance that is distinguished by its catalytic activity. Furthermore, the method for producing aluminosilicate of the present invention is distinguished from conventional methods in that an alkaline earth metal salt is present in the raw material during crystal production, and the catalytic performance of the obtained product is also different from conventionally known methods. It has been widely known that crystalline aluminosilicate is modified with alkaline earth metal ions, and the usual method is to support alkaline earth metal ions on proton (H ⁺ ) crystalline aluminosilicate by ion exchange. used. However, with this ion exchange method, it is difficult to support a large amount of alkaline earth metal ions, and it requires a lot of labor and is not economical.
For example, the limit is to introduce up to about 80% of the theoretical amount, and normally only about 50% can be introduced. Surprisingly, however, the present inventors were able to very easily incorporate a desired amount of alkaline earth metal salt by adding an alkaline earth metal salt during the synthesis of crystalline aluminosilicate. Furthermore, in the conversion reaction of methanol and/or dimethyl ether, the catalyst containing alkaline earth metal ions according to the present invention can be used for C ₂ -C ₄ such as ethylene and propylene. The present inventors have discovered that the present invention is excellent in the selective production of lower olefins, the suppression of carbon production, and the sustainability of catalytic activity. Conventionally, when producing crystalline aluminosilicate, coexisting alkaline earth metal salts in the production raw materials has been avoided because it disrupts the arrangement of the crystal lattice, prevents crystal growth, and tends to produce amorphous products. Ta. However, according to the research of the present inventors,
By using a tetrapropylammonium compound as a crystallization modifier and adopting a higher SiO ₂ /Al ₂ O ₃ than conventionally used when producing ZSM-5 type crystalline aluminosilicate, aluminosilicate Crystalline aluminosilicate can be obtained without any problems even if a large amount of alkaline earth metal salt is previously present in the raw material for crystal production,
It was discovered that it exhibits unexpectedly excellent catalytic activity. Next, the method for producing crystalline aluminosilicate containing an alkaline earth metal according to the present invention will be described in more detail. As the silica source, water glass, silica sol, silica gel, and silica are used, and water glass and silica sol are preferably used. As the alumina source, aluminum nitrate, aluminum sulfate, sodium aluminate, alumina, etc. can be used, and aluminum nitrate, aluminum sulfate, and sodium aluminate are preferred. As the alkali metal ion, for example, sodium oxide, sodium aluminate, sodium hydroxide, potassium hydroxide, sodium chloride, potassium oxide, etc. in water glass are used. As the alkaline earth metal ion, organic salts such as acetate and propionate, and inorganic salts such as chloride and nitrate are used. As the alkaline earth metal, calcium is particularly preferred, followed by magnesium, and strontium and barium tend to require high temperatures to develop their catalytic activity. A tetrapropylammonium compound is used as the crystallization modifier. The composition of the reaction mixture used to obtain the crystalline aluminosilicate by hydrothermal synthesis according to the method of the present invention is prepared in the following proportions. That is, SiO ₂ /Al ₂ O ₃ (molar ratio)
is 12-3000, more preferably 50-500; OH ^- /
SiO ₂ (molar ratio) is 0.02 to 10, more preferably 0.1 to
0.5; _H2BO / _SiO2 (molar ratio) is 1 to 1000, more preferably 30 to 80; tetrapropylammonium compound/ _SiO2 (molar ratio) is 0.02 to 2, more preferably 0.05 to 0.5, and alkaline earth The metal/Al (atomic ratio) is preferably 0.03 to 300, more preferably 0.5 to 8. In order to obtain a mixture having a composition within this range, add an acid such as hydrochloric acid, sulfuric acid, nitric acid, or an alkali metal hydroxide as necessary to bring the pH of the system to 11.
Adjust to the appropriate value below. This mixture is heated to 80-200℃, preferably 150-180℃.
C. for about 1 to 200 hours, preferably 5 to 50 hours, under normal pressure or increased pressure, generally heated and stirred. The reaction product is separated by filtration or centrifugation, washed with water to remove excess ionic substances, and then dried and calcined. In this way, a crystalline aluminosilicate containing an alkaline earth metal is obtained, and this crystalline aluminosilicate contains an alkali metal oxide and an alkaline earth metal oxide, and is prepared by a conventional method.
For example, protons ( ^H It can be converted to crystalline aluminosilicates in the substituted hydrogen form. In this case, a part or all of the alkali metal is easily replaced by protons (H ⁺ ), but only part of the alkaline earth metal is replaced by protons (H ⁺ ). Conventionally known aluminosilicates modified with alkaline earth metals are hydrogen type or alkali metal type aluminosilicate into which alkaline earth metal ions are introduced by an ion exchange method, and in this case, the introduced alkaline earth metal The ions can be converted back into hydrogen form etc. by an ion exchange method and can be distinguished from the aluminosilicate obtained in the present invention. In other words, at least a portion of the alkaline earth metal in the aluminosilicate obtained in the present invention is more strongly bound than in conventionally known alkaline earth metal-containing aluminosilicate. As mentioned above, the crystalline aluminosilicate produced in this way is aM ₂ O・bM′O・Al ₂ O ₃・cSiO ₂・nH ₂ O (where a, b, c, M, and M′ are as above). It has the same composition) and a pore diameter of 5 to 6 Å, and the fired product shows the following typical X-ray diffraction pattern.

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As shown in Figure 1, in proton-type crystalline aluminosilicate that does not carry alkaline earth metal ions such as calcium, an almost complete decrease in activity is observed at 510°C (). When this proton-type crystalline aluminosilicate is loaded with calcium by an ion exchange method, the yield of ethylene and propylene is improved;
Above this, a tendency for catalyst deterioration is observed (). On the other hand, the crystalline aluminosilicate according to the present invention exhibits activity at around 350°C, and at 500°C.
At these high temperatures, the yields of ethylene and propylene exceed those of the former two, and there is almost no deterioration even at 600°C (). The synthesis reaction of olefin from methanol and/or dimethyl ether, which is the method of the present invention, is an exothermic reaction, and the temperature of the reaction system naturally rises.
There is no particular problem in energy consumption when the reaction is carried out at a high temperature; on the contrary, it is easier to control the temperature of the reaction system than keeping it at a low temperature, and the reaction rate is increased, so there is an advantage that a small reactor can be used. However, there are problems with the use of high temperatures of 600℃ or higher due to the material of the reactor, such as stainless steel.
At high temperatures above .degree. C., there is a possibility that the catalyst crystals may collapse due to the water vapor present in the reaction system, so the upper limit of the reaction temperature that can be practically adopted is limited to about 600.degree. In the olefin production reaction in which the catalyst of the present invention is used, methanol and dimethyl ether are both starting materials, so when calculating selectivity, dimethyl ether produced from methanol may be regarded as an unreacted material. It should be noted that the alkaline earth metal-containing crystalline aluminosilicate zeolite catalyst of the present invention has a higher selectivity to lower olefins than other comparative example catalysts, produces less paraffin and BTX, and has a higher catalyst resistance at high temperatures. The point is that no decrease in activity is observed. An aluminosilicate containing an alkaline earth metal in a higher amount than specified in the present invention is prepared, and then a part of the alkaline earth metal is removed by an ion exchange method to reduce the alkaline earth metal content according to the present invention. The catalyst reduced within the specified range surprisingly has a low selectivity to olefins, promotes decomposition to CO and CO ₂ , and shows a significant difference in catalytic performance. [Example] Next, the present invention will be specifically explained using Examples and Comparative Examples, but the present invention is not limited thereto unless the gist thereof is exceeded. Reference example 1 Dissolve 0.75 g of aluminum nitrate nonahydrate and 0.91 g of calcium acetate monohydrate in 90 g of water to make solution A, and prepare Cataloid SI-30 water glass (Catalyst Kasei Co., Ltd., SiO ₂
30.5%, Na ₂ O 0.42%) dissolved in 40 g of water,
This was designated as liquid B. Add liquid B to liquid A while stirring vigorously, then add 1.14 g of sodium hydroxide to 20 g of water.
Add the dissolved g. Furthermore, a solution of 8.11 g of tetrapropylammonium bromide in 30 g of water was added, and stirring was continued for about 10 minutes to obtain an aqueous gel mixture. This charging molar ratio SiO ₂ /Al ₂ O ₃ =
It is 300. This aqueous gel mixture was charged into an autoclave with an internal volume of 300 ml, and hydrothermally treated at 160°C under autogenous pressure for 18 hours with stirring (500 rpm). The reaction product is separated into a solid component and a solution part using a centrifuge.
Thoroughly wash the solid components with water and heat them at 120℃ for 5 minutes.
Dry for an hour. Next, it was treated in air at 520°C for 5 to 10 hours. Next, 15 ml of a 0.6N aqueous hydrogen chloride solution was mixed with 1 g of this calcined crystalline aluminosilicate, and the mixture was stirred at room temperature for 24 hours. After that, it was thoroughly washed with water at room temperature, dried at 120℃, and then heated to 520℃.
Calcination was performed in air at ℃ for 5 hours to convert it to hydrogen form. Table 2 shows the raw material charging ratio. Reference Examples 2 to 13 Various alkaline earth metal-containing crystalline aluminosilicate zeolites were produced using the same method as described in Reference Example 1, except that the blending composition of the production raw materials was changed. Table 2 shows the raw material charging ratio, and Tables 3A and 3B show the analysis results of the crystalline aluminosilicate obtained in Reference Examples 4 and 7 and those converted into hydrogen form. Moreover, the X-ray diffraction pattern of the product (fired product) obtained in Reference Example 4 is shown in FIG. Note that this diffraction data was obtained by standard X-ray techniques using K-alpha irradiation of copper, and the peak height I was recorded on a recorder as a function of 2θ, which is twice the Black angle θ. be done. I/Io is the relative intensity, and the strongest peak is 2θ = 23.1°.
This is a relative value when set to 100. Comparative Reference Examples 1 to 3 Three types of crystalline aluminosilicates were synthesized in the same manner as in Reference Example 1, except that no alkaline earth metal salt was added. Comparative Reference Example 1 corresponds to Reference Examples 1 to 3, Comparative Reference Example 2 corresponds to Reference Examples 4 and 5, and Comparative Reference Example 3 corresponds to Reference Examples 6 and 7.
The raw material composition and the analysis results of the aluminosilicate obtained in Comparative Reference Examples 2 and 3 are shown in Tables 2 and 3, respectively. Comparative Reference Example 4 After converting the crystalline aluminosilicate synthesized in Comparative Reference Example 1 at a charging molar ratio (SiO ₂ /Al ₂ O ₃ = 300) into a hydrogen form, ion exchange with calcium ions was performed using a conventional method. Ta. Initially, 40 ml of 1N CaCl ₂ solution was added to 5 g of the sample, and stirring was performed in an oil bath equipped with a reflux condenser and adjusted to 80°C. Approximately every 3 hours, the exchange solution was removed by decantation and 30 ml of new exchange solution was added. This operation
After repeating this process 20 times, the mixture was thoroughly washed and filtered with water until no Cl ^- ions were observed, dried, and then calcined at 500°C for 3 hours to obtain a calcium-supported type. The amount of calcium supported was 45% of the isoelectric amount.

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[Table] *Analysis was performed using atomic absorption spectrometry.
Examples 1 to 12, Comparative Examples 1 to 3 Reference Examples 1 to 9 and 11 to 13, and the crystalline aluminosilicate powder obtained in the hydrogen form of Comparative Reference Examples 1, 2, and 4 were heated at a pressure of 400 Kg/cm ² Compressed into tablets and then crushed into 10 to 20 mesh pieces 2
ml was filled into a reaction tube with an inner diameter of 10 mm. Liquid methanol is sent to the vaporizer at a rate of 4 ml/hr (the reaction is a gas phase reaction, but if the raw material supply amount is expressed in liquid phase, LHSV = 2 hr ^-1 ), and here it is sent at 10 ml/min. The mixture was mixed with argon gas and sent to a reaction tube at approximately normal pressure, and the reaction was carried out at 300 to 600°C. The reaction was carried out by starting at 300°C and increasing the temperature by 20°C every 2 hours up to 600°C. Further, the product was analyzed using a gas chromatograph. A summary of the results is shown in Table 4. Furthermore, details of the results obtained in Examples 2, 4, 7, and 11 and Comparative Examples 1, 2, and 3 are shown in FIGS. 9 to 11, respectively. In addition, C″ ₂ and C″ ₃ shown in the table below mean ethylene and propylene, respectively.

[Table] Effective conversion rate

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[Table] FIG. 1 shows the relationship between the total yield of ethylene and propylene obtained in Example 2 and Comparative Examples 1 and 3 and the reaction temperature. It is understood that the catalyst of the present invention provides a high ethylene + propylene yield and maintains high catalytic activity without deterioration even in a high temperature range. In the figure, the line shows the results of Example 2, the line shows the results of Comparative Example, and the line shows the results of Comparative Example 3. Similarly, the relationship between the ethylene+propylene yield and reaction temperature obtained in Examples 4, 8, and 9 and Comparative Example 2 is also shown in FIG. In the figure, the line is Example 4, the line is Example 8, the line is Example 9, and the line is Comparative Example 2.
The results are shown below. As is clear from the figure, Ca
Example 4 containing Mg shows excellent results, and Example 8 containing Mg shows better results than the one containing Ca in the low temperature range, but is inferior to the one containing Ca in terms of maximum yield. Comparative example 2 of alkaline earth metal addition
The results are similar to those of Example 8 containing Mg in the low temperature range, but the additive-free one maintains its activity even in the high temperature range. In Example 9 containing Sr, expression of activity in a high temperature range is observed.

Claims (1)

[Claims] 1 Methanol and/or dimethyl ether in a gas phase, aM ₂ O・bM′O・Al ₂ O ₃・cSiO ₂・nH ₂ O (wherein M is an alkali metal and/or a hydrogen atom,
M' is an alkaline earth metal, a is 0-1.5, b is 0.2-
40, but a+b>1, c is 12-3000 and n is 0
~40) and has a composition of X shown in Table 1
An alkaline earth metal-containing crystalline aluminosilicate zeolite catalyst that has a line diffraction pattern and is produced by allowing an alkaline earth metal salt to be present in the crystal production raw material during crystal production, and a weight hourly space velocity of 0.1 to
20 hr ^-1 , a reaction temperature of 300 to 600°C and a total pressure of 0.1 to 100 atm. 2. The manufacturing method according to claim 1, wherein the alkaline earth metal is calcium. 3. The manufacturing method according to claim 1 or 2, wherein c is 50 to 500 and b is 1 to 7.