JPH0452314B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for aromatizing hydrocarbon fractions,
More specifically, the present invention relates to a method for aromatizing a relatively low-boiling hydrocarbon fraction containing paraffins and/or olefins. Aromatic hydrocarbons occupy an important position in the petroleum industry as raw materials for gasoline or BTX. Such aromatic hydrocarbons are mainly obtained from reformed oil obtained by catalytic reforming of naphtha and from cracked gasoline produced separately through thermal decomposition of naphtha. As the demand composition ratio for products has changed significantly, problems are beginning to surface in aromatic production using existing technologies, such as a shortage of heavy naphtha for reforming reactions and a decline in the operating rate of ethylene cracking equipment. The development of new aromatization technology is strongly desired. Against this background, a technology to aromatize relatively light hydrocarbon fractions such as light naphtha, raffinate, and catalytic cracking off-gas, which are surplus to oil refineries or petrochemical plants, is attracting attention. Several methods have been proposed. As an example of this,
56-42639, JP 58-23368, JP 50-4029,
Examples include JP-A-50-82023. These methods use a new ZSM-5 type zeolite obtained by crystallizing a solution containing alkylammonium cations as a catalyst component, do not supply hydrogen, which is disadvantageous in equilibrium theory in the aromatization reaction, The aim is to obtain aromatics in high yield using paraffins or olefins. However, these conventional techniques suffer from significant deterioration of catalyst activity over time.
It is still insufficient to produce aromatics in an industrially stable manner, and zeolite, which is a catalyst component, is expensive. In view of this situation, the present inventors have conducted intensive research on a method for aromatizing hydrocarbon fractions, and as a result, the present inventors have developed a method in which a silica source, an alumina source, an alkali source, and an organic compound containing a carboxyl group are reacted in a predetermined composition. We have discovered that this reaction can proceed efficiently by bringing a hydrocarbon fraction into contact with a catalyst containing crystalline aluminosilicate obtained in the presence of hydrogen, and have arrived at the present invention. In the catalyst used in the present invention, the aromatic yield hardly decreases due to the presence of hydrogen, and the deterioration of activity over time is greatly suppressed.In fact, slightly pressurizing hydrogen allows aromatic yield to continue for a long time. This behavior shows that the rate can be increased. In addition, the catalyst of the present invention has a low decomposition activity into C ₁ and C ₂ hydrocarbon gases and a high aromatization activity for C ₃ or higher hydrocarbons, so it is possible to increase the aromatic yield by increasing the amount of the catalyst. is possible and can be obtained
It is characterized by a relatively high xylene content in the BTX fraction. The crystalline aluminosilicate used in the present invention can be synthesized as follows. That is, an aqueous reaction mixture consisting of a silica source, an alumina source, an alkali source, and an organic compound containing a carboxyl group (represented by SiO ₂ , Al ₂ O ₃ , OH ^- , and A, respectively) is expressed in molar ratio as follows: Preferred range) SiO ₂ /Al ₂ O ₃ 10-200 20-100 H ₂ O/SiO ₂ 5-100 5-100 OH ^- /SiO ₂ 0.01-1.0 0.05-0.40 A/Al ₂ O ₃ 0.05 or more 0.10-200 It can be produced by adjusting it so that it enters the crystals and allowing the reaction to occur until crystals form. As the silica source, for example, silica sol, silica gel, silica airgel, silica hydrogel, silicic acid, silicate ester, sodium silicate, etc. are used. As the alumina source, sodium aluminate, aluminum sulfate, aluminum nitrate, alumina sol, alumina gel, activated alumina, gamma alumina, alpha alumina, etc. are used. As the alkali source, caustic soda, caustic potash, etc. are used, and caustic soda is preferred. These alkaline sources are added so that OH ^- is present in the system preferably in the above composition. As the organic compound containing a carboxyl group, various types of carboxylic acids such as aromatic, aliphatic, and alicyclic acids are used. It is thought that these become alkali metal salts within the reaction system, but it goes without saying that they can be used as alkali metal salts in advance. Preferably, the alkali metal salt of the organic compound having a carboxyl group is soluble in water. The organic compound having a carboxyl group may contain a functional group other than the carboxyl group, such as a hydroxyl group or an amino group. As the organic compound having a carboxyl group, an aliphatic carboxylic acid having 3 to 6 carbon atoms is preferably used as long as it does not contain an aromatic ring. The number of carboxyl groups contained in one molecule is usually 1 to 3. Specific examples of such aliphatic carboxylic acids include monobasic oxycarboxylic acids such as glycolic acid, lactic acid, hydroacrylic acid, oxybutyric acid and derivatives thereof, dibasic and polybasic oxycarboxylic acids such as tartronic acid, malic acid, tartaric acid, citric acid or derivatives thereof, monobasic carboxylic acids such as propionic acid, butyric acid, valeric acid, caproic acid, acrylic acid, crotonic acid, methacrylic acid or derivatives thereof, dibasic and polybasic carboxylic acids such as malonic acid, Mention may be made of succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid or derivatives thereof. On the other hand, as the one having an aromatic ring, an aromatic carboxylic acid having 7 to 8 carbon atoms is used. Specific examples of such compounds include benzoic acid, phthalic acid, terephthalic acid, salicylic acid, parahydroxybenzoic acid, toluic acid, and derivatives thereof.
These carboxyl group-containing organic compounds or derivatives thereof may be used alone or in combination of two or more. The aqueous reaction mixture thus prepared is made into a slurry as uniform as possible and crystallized in a closed container, such as an autoclave made of iron, stainless steel, or lined with Teflon. The reaction conditions for crystallization are a reaction temperature of 80~
The temperature is 250°C, preferably 100-200°C, and the reaction time is 5 hours to 30 days, preferably 10 hours to 10 days. The reaction mixture is preferably kept in a homogeneous state by stirring continuously or periodically during crystallization. After cooling, the crystallized reaction product is taken out from the closed container, washed with water, filtered, and dried if necessary. Typical X-ray diffraction patterns of the crystalline aluminosilicate thus synthesized are shown in Table 1. Measurement of the X-ray diffraction pattern was carried out according to a conventional method. That is, X-ray irradiation is performed using a Geiger counter spectrometer equipped with a recording device using copper k-α rays to obtain a diffraction pattern. From this diffraction pattern, the relative intensity is 100I/MAX (MAX is the strongest line)
and lattice spacing d (unit angstrom Å)
seek. Table 1 X-ray diffraction pattern d (Å) 100I/Io 11.2±0.2 S 10.1±0.2 S 9.8±0.2 M 6.37±0.1 W 6.00±0.1 W 5.71±0.1 W 5.58±0.1 W 4.37±0.08 W 4.27±0.08 W 3. 86 ±0.08 VS 3.82±0.08 VS 3.75±0.08 S 3.72±0.08 S 3.66±0.05 M 3.00±0.05 M 2.00±0.05 W However, the relative strength (100I/Io) is as follows: VS=very strong, S=strong, M= Intermediate strength, expressed as W=weak. The crystalline aluminosilicate synthesized in this way does not have solid acidity as it is. When used in the reaction of the present invention, it is necessary to impart solid acidity to the crystalline aluminosilicate to make it into an acid form. As is well known, acid type crystalline aluminosilicate has polyvalent cations of divalent or higher valence, such as hydrogen ions, ammonium ions, or rare earth ions, as cations in crystalline aluminosilicate, and these are usually sodium ions. It can be obtained by ion-exchanging at least a part of the alkali metal ions of a crystalline aluminosilicate having a monovalent alkali metal ion, such as, with hydrogen ions, ammonium cations, or polyvalent cations. Such ion exchange treatments are often referred to as dealkalization treatments. In the present invention, ion exchange treatment is preferred in which hydrogen ions and/or hydrogen ion precursors are introduced into the crystalline aluminosilicate by treatment with a solution containing an acid and/or an ammonium salt compound. Ion exchange treatment is generally performed in an aqueous solution. Inorganic acids or organic acids can be used, with inorganic acids being more common. Examples of the inorganic acid include hydrochloric acid, nitric acid, phosphoric acid, carbonic acid, etc., but of course other acids may be used as long as they contain hydrogen ions. When using inorganic acids,
Treatment with a solution of too high concentration is not preferable because it causes structural changes. Since the concentration of the acid preferably used varies greatly depending on the type of acid, it is difficult to determine it unambiguously, and during use, sufficient care must be taken to avoid major structural changes. As ammonium salt compounds, inorganic ammonium salts such as ammonium nitrate, ammonium chloride, ammonium sulfate, ammonium carbonate, aqueous ammonia, etc., or ammonium salts of organic acids such as ammonium formate, ammonium acetate, ammonium citrate, etc. can be used, but more Inorganic ammonium salts are preferred. The ammonium salt used is preferably used as a 0.05 to 4N solution, more preferably about 0.1 to 2N solution. As a method for ion exchange treatment of crystalline aluminosilicate with an acid and/or ammonium hydrochloric acid solution, either a batch method or a flow method is preferably used. In the case of batch treatment, the solid-liquid ratio is preferably at least an amount that allows the crystalline aluminosilicate to come into sufficient contact with the liquid, specifically at least about 1/Kg. A treatment time of about 0.1 to 72 hours is sufficient, preferably about 0.5 to 24 hours. The treatment temperature may be below the boiling point, but it is preferable to heat it to promote the ion exchange rate. In the case of flow treatment, a fixed bed method, a fluidized bed method, etc. can be used, but it is necessary to take measures to prevent uneven flow of the fluid or non-uniform ion exchange treatment. The ion exchange treated crystalline aluminosilicate is then washed with water. Distilled water is preferably used as the washing liquid, and the washing may be carried out in batches or in a flow manner. In this way, hydrogen ions and/or ammonium ions, which are hydrogen ion precursors, are introduced into the crystalline aluminosilicate to impart solid acidity. Hydrogen ions and/or cations other than their precursors may be present in the crystalline aluminosilicate, and the type and amount thereof are not particularly limited. The apparatus that can be used for the reaction according to the present invention may be either a fixed bed or a fluidized bed, but a fixed bed type is preferably used because the apparatus is simpler and the operation is easier. In the case of a fixed bed system, the smaller the catalyst particle size is, the more preferable it is from the point of view of the catalyst effectiveness coefficient, but if the particle size becomes too small, pressure loss increases, which is not preferable. Therefore, there is a preferable range for the catalyst particle size. The particle size preferably used is 0.05 to 10 mm, more preferably 0.1 to 10 mm.
It is 3mm. The synthesized crystalline aluminosilicate is usually in a powder state. Therefore, in order to obtain a catalyst having such a preferable range,
It will be necessary to mold it. Examples of the molding method include compression molding and extrusion molding. Particularly in the case of extrusion molding, it is preferable to use a binder in order to improve the moldability or to impart strength to the molded product. Of course, it goes without saying that there is no need to use a binder if it can be sufficiently molded without a binder. Examples of binders include natural clays such as carrion, bentonite, and montmorillonite, or silica sol;
Examples include synthetic products such as alumina sol and alumina gel. The amount of binder added is 70% by weight or less, preferably 30% by weight or less. Such molding may be performed before ion exchange treatment of the crystalline aluminosilicate, or ion exchange may be performed after molding. The catalyst of the present invention has activity, selectivity,
Group B according to the periodic table, to improve lifespan
Metal components such as group a, group b, group b, group a, group a, group or rare earth metals may be added. Methods for adding these metal components include an ion exchange method, a kneading method, an impregnating method, a method of physically mixing powders together, but are not necessarily limited to these methods. However, a more uniform distribution of these components throughout the catalyst is more desirable for activity and selectivity. The catalyst prepared as described above is dried prior to use and subsequently calcined. Drying at 50-250℃ for 0.1 hour or more.
Preferably it is carried out for 0.5 to 48 hours. Firing in air,
At 300-700℃ in an atmosphere such as nitrogen or helium
It is carried out for 0.1 hour or more, preferably 0.5 to 24 hours at 400 to 600°C. The calcined catalyst is preferably further heat-treated in a steam atmosphere in order to suppress deterioration of activity over time. The conditions for steam treatment are:
Water vapor partial pressure 50mmHg to 5 atm, temperature 400 to 700℃
Approximately 0.5 to 24 hours is appropriate. Water vapor partial pressure 50mm
If the temperature is below Hg or 400°C, the stabilizing effect on the activity is not sufficient, and if the water vapor partial pressure is 5 atm or above or the temperature is 700°C or above, the catalyst activity is greatly reduced and is not practical. Particularly preferable steam treatment conditions are a steam partial pressure of 100 mmHg to 760 mmHg and a temperature of 500 to 600°C. Steam treatment may be performed at the same time as firing,
Alternatively, it may be carried out after firing. The catalyst prepared as described above is used under the following reaction conditions. That is, the reaction operation temperature is 200 to 700°C, preferably 300 to 600°C.
It is. Reaction operating pressure is atmospheric pressure ~ 50Kg/cm ²・G,
Preferably it is 1Kg/cm ² ·G to 30Kg/cm ² ·G.
The weight hourly space velocity (WHSV), which refers to the catalytic time of the reaction, is between 0.1 and 10 hr ^-1 , preferably between 0.5 and 10 hr -1
It is 4.0hr ^-1 . Hydrogen to hydrocarbon ratio is 0.1~
It is 10 mol/mol, preferably 0.5-4 mol/mol. In the reaction of the present invention, hydrogen is generated as aromatics are produced, but in order to suppress deterioration of catalyst activity over time, it is necessary to mix hydrogen into the raw material hydrocarbon in advance and bring it into contact with the catalyst. . If the ratio of supplied hydrogen to supplied hydrocarbon is less than 0.1 mol/mol, the stability of catalyst activity over time is insufficient, and if it is more than 10 mol/mol, the effect of stabilizing catalyst activity over time has already been sufficiently achieved. This is not desirable as it will lead to an unnecessary increase in utility costs. Feedstocks include light naphtha, raffinate after BTX extraction and separation, catalytic cracking product gas, catalytic or pyrolysis gasoline, and various carbonized materials with relatively low boiling points, including paraffinic and/or olefinic hydrocarbons with a boiling point of C ₃ to 250°C. Hydrogen fraction can be used. The present invention will be explained in detail below using examples. Example 1 11.5 grams of solid caustic soda and 12.7 grams of tartaric acid were dissolved in 343.4 grams of water. 10.5 grams of sodium aluminate solution was added to this solution to make a homogeneous solution. 68.3 grams of silicic acid was gradually added to this mixture with stirring to prepare a homogeneous slurry-like aqueous reaction mixture. The composition ratio (molar ratio) of this reaction mixture was as follows. SiO ₂ /Al ₂ O ₃ 50 H ₂ O/SiO ₂ 20 OH ⁻ /SiO ₂ 0.17 A/Al ₂ O ₃ 4.2 This mixture was placed in a 500 ml autoclave and sealed. Thereafter, the mixture was heated to 160° C. with stirring and crystallized for 72 hours. Cool after crystallization,
Then, remove the product from the autoclave and
Wash with distilled water until the pH is almost neutral, filter,
It was dried at 110°C overnight. The resulting product was a zeolite having the X-ray diffraction pattern shown in Table 1. The zeolite powder obtained in this way is
Solid-liquid ratio of 5 with 0.75 normal ammonium chloride aqueous solution
(/Kg), heated to 80 to 90°C, and subjected to ion exchange treatment in batches for 30 minutes. Thereafter, it was thoroughly washed with distilled water and dried at 110°C overnight. To this dealkalized zeolite powder, alumina sol was added as a binder in an amount of 15% by weight in terms of alumina (Al ₂ O ₃ ), and thoroughly kneaded. After kneading, the particles were formed into particles having a size of 10 to 24 meshes (JIS sieve), dried at 110°C overnight, and then calcined at 550°C for 2 hours in air containing 200 mmHg of water vapor. The catalytic performance of the catalyst thus obtained was evaluated by aromatization reaction of light naphtha using a fixed bed flow reactor. The reaction has a weight hourly space velocity (WHSV) of 2.0hr ^-1 ,
The reaction temperature was 470°C, the H ₂ /raw material ratio was 300 N-ml/ml, and the reaction pressure was 2.0 Kg/cm ² G. Table 2 shows the composition of light naphtha and the changes in gas components over time according to the present invention. Indicated. Note that the aromatic yield A described in the examples indicates the actual conversion ratio obtained by subtracting the aromatic content in the raw material from the aromatic content in the product, and the aromatic yield B indicates the aromatic content in the product. It shows the percentage.

[Table] Comparative example 1 Synthesis of zeolite ZSM-5
The procedure was carried out according to the method described in No. The synthesis conditions are shown in the table below. Starting components (g) A: Hydrous silicic acid 68.3 B: Sodium aluminate solution 10.5 C: Tetrapropylammonium hydroxide aqueous solution (25% aqueous solution) 439.4 Reaction mixture composition ratio (molar ratio) SiO ₂ 1.00 Al ₂ O ₃ 0.02 Na ₂ O 0.034 [(CH ₃ HC ₃ CH ₂ ) ₄ N] ₂ O 0.31 H ₂ O 20 B was added to starting component C to form a homogeneous solution. Starting component A was gradually added to this mixed solution and stirred to prepare a homogeneous slurry-like reaction mixture. This reaction mixture was charged into an autoclave and heated to 160° C. with stirring, and crystallization was performed for 72 hours. After crystallization, wash with water until neutral, then heat at 120℃
and dried for 15 hours. The obtained zeolite was ZSM-5 according to the X-ray diffraction pattern. The thus obtained ZSM-5 zeolite was molded, calcined, ammonium ion exchanged, and calcined in the same manner as in Example 1, and was used as a catalyst to perform an aromatization reaction of light naphtha. The results are shown in Table 3.

[Table] Example 2 In Example 1, zeolite was synthesized by changing the composition ratio (molar ratio) of the aqueous reaction mixture as follows. SiO ₂ /Al ₂ O ₃ 95 H ₂ O/SiO ₂ 25 OH ^- /SiO ₂ 0.32 A/Al ₂ O ₃ 7.0 The product obtained is a zeolite with an X-ray diffraction pattern basically the same as in Table 1. Ta. The zeolite thus obtained was acidified, shaped, and calcined in the same manner as in Example 1 to be used as a catalyst.
Aromatization reaction of n-hexane at WHSV=5.0hr ^-1
I went there. The results are shown in Table 4. Comparative Example 2 In Example 2, the catalyst was calcined at 550°C for 2 hours in air without substantially adding water vapor, and the reaction was carried out using only n-hexane under atmospheric pressure without adding hydrogen. The results are shown in Table 4. Comparative Example 3 In Comparative Example 1, zeolite was synthesized by changing the composition ratio (molar ratio) of the aqueous reaction mixture as follows. SiO ₂ 1.00 Al ₂ O ₃ 0.010 Na ₂ O 0.017 [(CH ₃ HC ₃ CH ₂ ) ₄ N] ₂ O 0.309 H ₂ O 20 The obtained product was determined by ZSM from the X-ray diffraction pattern.
It was -5. The ZSM-5 zeolite obtained in this way was molded, calcined, and ammonium ion exchanged in the same manner as in Example 1, and was then heated in air without substantially adding water vapor.
The mixture was calcined at 550°C for 2 hours to form a catalyst, and only n-hexane was reacted at atmospheric pressure without adding hydrogen. The results are shown in Table 4.

【table】

[Table] Example 3 Zeolite was synthesized in the same manner as in Example 1 using the following carboxylic acid instead of tartaric acid. The composition ratio (molar ratio) of the reaction mixture was as follows.

[Table] The product obtained was a zeolite having essentially the same X-ray diffraction pattern as in Table 1. The zeolite thus obtained was acidified, shaped, and calcined in the same manner as shown in Example 1 to be used as a catalyst, and the aromatization reaction of light naphtha was carried out.
The results are shown in Table 5.

【table】

[Table] Example 4 The zeolite powder obtained in Example 1 was mixed with a 0.75N ammonium chloride aqueous solution at a solid-liquid ratio of 5 (/Kg).
The mixture was heated to 80 to 90°C and ion exchanged four times in batches for 30 minutes. After that, wash thoroughly with distilled water, and
Solid-liquid ratio 3 (/Kg) with molar zinc nitrate aqueous solution
The mixture was heated to 80 to 90°C, ion exchanged in batches for 2 hours, and thoroughly washed with distilled water. Thereafter, it was molded in the same manner as in Example 1, and calcined at 550°C for 2 hours in air containing 500 mmHg of water vapor to form a catalyst.
Aromatization reaction of propane/propylene mixed gas
I did it with WHSV2.0hr ^-1 . The composition of the raw material gas is propane 22.4, propylene 74.4, isobutane 3.2, each
The results are shown in Table 6 in mol%. Example 5 In Example 4, the catalyst was adjusted by replacing zinc nitrate with copper nitrate, and the aromatization reaction of catalytic cracking gasoline was carried out.
I did it with WHSV1.0hr ^-1 . Table 6 shows the raw material composition and reaction results.

【table】

【table】

Claims (1)

[Scope of Claims] 1. A mole of an aqueous reaction mixture consisting of a silica source, an alumina source, an alkali source, and an aliphatic carboxylic acid having 3 to 6 carbon atoms and/or an aromatic carboxylic acid having 7 to 8 carbon atoms. Expressed as a ratio, SiO ₂ /Al ₂ O ₃ 10-200 H ₂ O/SiO ₂ 5-100 OH ^- /SiO ₂ 0.0-1.0 A/Al ₂ O ₃ 0.05 or more (However, A has the above carbon number of 3-6 In the presence of hydrogen, C. A method for aromatizing hydrocarbon fractions, characterized by contacting hydrocarbon fractions with a boiling point of ₃ to 250°C.