JPS6224476B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for cracking hydrocarbon feedstocks under conditions of high conversion using a catalyst containing mordenite and faugiasite. Traditionally, natural and synthetic zeolites have been known to have catalytic abilities for various hydrocarbon conversion reactions. That is, crystalline aluminosilicates of the phaujasite type, such as zeolite Typical prior art describing such a method is
Plank and Rosinski, US Pat. Nos. 3,140,249 and 3,140,253. It was also previously known to use mordenite and other crystalline aluminosilicate zeolites, either in natural or synthetic form, as hydrocarbon conversion catalysts. The use of acidic mordenite as a catalyst for various hydrocarbon conversion reactions, including cracking, is described in Frilette and Rubin, US Pat.
Described in No. 3597493. Mixtures of various zeolites, including faugiasite type and mordenite, are noted to be useful for the conversion of petroleum hydrocarbons, especially when at least one of these zeolites is used as the hydrogen type. i.e. Schutt U.S. Patent No.
No. 3830724 discloses that a mixed zeolite support consisting of a zeolite with a channel pore structure and a three-dimensional pore structure with a low alkali metal content is hydrolyzed using a catalyst having a group metal and/or a group B metal of the periodic table. It describes how to king. A typical example of a zeolite with a channel pore structure is mordenite, and a typical example of a zeolite with a three-dimensional pore structure is faugiasite, which may be either natural or synthetic, ie zeolite X or zeolite Y. at least one of mixed zeolites
The species, preferably both, are in the hydrogen form, for example a typical mixed zeolite is one of hydrogen form mordenite and hydrogen form zeolite Y. Scherzer, US Pat. No. 3,925,195, describes a mixture of rare earth hydrogen Y-type zeolites and hydrogen or transition metal substituted mordenites as hydrocarbon conversion catalysts. U.S. Pat. No. 3,769,202 to Plank and Rosinski discloses a catalyst composition comprising a mixture of discrete particles of a crystalline aluminosilicate whose pore size is less than 7 angstroms and a crystalline aluminosilicate whose pore size is greater than 8 angstroms. A contact cracking method using Kimberlin & Voorhies U.S. Patent No. 3764520
The numbers are for different ranges of pore sizes (i.e. 6 to 6).
A hydrocarbon conversion process is described using as a catalyst a mixture of two different aluminosilicate zeolites, one having a diameter of less than 15 angstroms and the other having a diameter of less than 6 angstroms. Previously, "the Oil and Gas" by JRMurphy
Journal'' (November 23, 1970), zeolite catalysts rapidly crack naphthenes, paraffins, or these compounds with side chains and have excellent selectivity; It was known to be ineffective in selectively cracking group nuclear components. The authors note that the inability of zeolite catalysts to selectively crack aromatic nuclei means that the limit on optimal conversion is highly dependent on the aromatic content, especially the polynuclear aromatic content. It was pointed out by. Since the polynuclear aromatic content generally decreases with decreasing boiling range, the selectivity when cracking light feedstocks is better than the selectivity when cracking heavy feedstocks from the same crude oil. However, the ability of the zeolite catalyst to crack low-boiling substances extends to non-aromatics in the gasoline boiling range, and is not necessarily satisfactory. That is, the cracking conditions must be carefully selected to avoid re-cracking the gasoline. The literature indicates that overcracking of gasoline can be minimized by using mild conditions that only partially crack the naphthenes and paraffins during the initial contact with the catalyst. Thereafter, it is necessary to recycle the unconverted material in order to achieve complete cracking of naphthenes and paraffins. Unfortunately in these types of operations cracking of polynuclear aromatic compounds in the recycle material cannot be avoided. Substantially non-selective cracking of polynuclear aromatics not only results in poor yields, but also increases the rate of coke deposition on the catalyst, which adversely affects the zeolite and reduces the yield of cracking of naphthenes and paraffins. have a negative impact on In conclusion, from the above prior art documents, it is found that when cracking gas oil with a zeolite catalyst, it is necessary to maximize the cracking of paraffins and naphthenes and minimize the cracking of polynuclear aromatic compounds. When considering the composition of gas oil obtained by high conversion operation, it is undesirable to crack polynuclear aromatic components in a high concentration excessively. According to the present invention, a method has been discovered for selectively cracking hydrocarbon feedstocks containing aromatic and non-aromatic components at a higher conversion rate and lower coke production than ever before. The process of the present invention uses a cracking catalyst consisting of two crystalline aluminosilicate zeolite components. One of these zeolite components is of the faugiasite type, ie natural or synthetic faugiasite, such as zeolite X or zeolite Y. The other zeolite component is mordenite. The two zeolite components are present as a mixture with a weight ratio of faujasite/mordenite ranging from about 30/1 to 1/5. The zeolite is desirably present in an inorganic oxide matrix and the total zeolite content in the composite is from about 5 to about 60% by weight. The alkali metal content of the catalyst composition is approximately 1.5% by weight
smaller. Preferably, the catalyst is after-treated with a solution containing rare earth or ammonium ions, so that after calcination the cations of both zeolites are occupied by rare earth and/or hydrogen. The conditions under which cracking is carried out using the catalyst are important to the success of the process of the invention.
These conditions are of such severity that a conversion rate that exceeds the conversion of the non-aromatic components of the feedstock is obtained. The conversion conditions used in the method of the invention are 482-649°C
(900~1200〓) temperature, 7Kg/ from almost atmospheric pressure
^cm2 instrument pressure (100 psig), the oil contact time with the catalyst was about 0.5 minutes to about 15 minutes, and the catalyst/
Oil conversion is about 1 to about 20. Within the range, the conversion conditions are adjusted to obtain the severity, taking into account the activity of the catalyst. According to the present invention, when using mordenite and faugiasite low alkali metal cracking catalysts under specific cracking conditions, a process with high conversion and improved selectivity, i.e. with low coke formation, is achieved. It was discovered that. By using the cracking mordenite-phaujasite catalyst of the present invention, coke is produced at much higher conversion than currently practiced processes and at the same conversion than with similar catalysts that do not contain mordenite. It was discovered that the amount decreased. The coke formed during the cracking reaction is of importance in modern catalytic cracking equipment. Air oxidation of the coke during the regeneration process provides the heat required for endothermic cracking of the feedstock. However, excess coke production is undesirable since coke is produced at the expense of valuable liquid products. Additionally, many cracking devices are constrained by the composition of the feedstock to operate at lower temperatures than those allowed by the feedstock. If excess coke is produced,
During the regeneration process, the temperature may rise above the limits and damage the device. In such a case,
To lower the regeneration temperature, either conversion or production must be reduced, which reduces the desired yield of product. In such cases, the use of a catalyst that produces less coke during cracking will result in a higher yield of the desired product. The opposite case can also occur. That is, for some cracking feedstocks, the amount of coke produced is too low to provide sufficient heat during the regeneration process to drive the cracking reaction. In such cases, heat must be added, usually by burning valuable fuel to heat the feedstock. Alternatively, additional coke must be produced by increasing the conversion (eg, by increasing the reaction temperature). This additional coke is generally not accompanied by additional liquid products that crack into both gas and coke. At such conversions, a more selective catalyst would therefore provide the required additional coke as well as additional liquid product. Typical catalytic cracking feedstocks, such as synthetic oils derived from gas oils, residual oils, shale oils and coal, with boiling ranges of 204-593°C (400-1100°C) contain various hydrocarbons, e.g. It is composed of a component characterized by the presence of a ring) and a non-aromatic component (including a straight-chain aliphatic compound, a branched aliphatic compound, and a naphthenic hydrocarbon). All feedstocks contain polynuclear aromatic components to some extent, and these components cannot be cracked directly by either conventional amorphous or zeolite-containing catalysts. Therefore, at high conversion rates,
The maximum yield of gasoline relative to conversion depends primarily on the recracking of the gasoline product and the ability of the catalyst to selectively convert the aromatic residues of the feedstock. The maximum yield of gasoline is thus generally limited by the phenomenon of overcracking. In commercial practice, maximum yield of gasoline is determined by appropriate adjustment of operating factors such that overall conversion is maximized and production of coke and gas is increased at the expense of gasoline. This is achieved by avoiding high conversion rates. The amount of aromatic component is expressed as C _A , and this term is expressed as a percentage of the number of carbon atoms in the aromatic ring structure as follows. C _A (%) = Number of carbon atoms in the aromatic ring / Number of carbon atoms in the entire raw material x 100 The value of C _A is generally determined by the so-called "nd-M method", which has a correlation with refractive index, density, and molecular weight. be led out. Regarding the “n-d-M” method, see K.
“Aspects” by van Ness and HA van Westen
of the Constitution of Mineral Oils”
Published by Elsevier Publishing Co., Inc. in 1951, see especially pages 335-347). The value of C _A is MEFitzgerald, JL
Applied by Moiraso, H. Morgan & VACirillo
“Characterization of Gas Oil Stock: An
It can also be determined by a combination of mass spectrometry and other standard methods, such as those described by ``Integrated Analysis''. This method allows for a more detailed analysis of aromatic ring types. It is generally believed that the coke formed on the catalyst during catalytic cracking has an _aromatic character. is converted only after C A is converted. Substantial conversion of the C _A portion does not occur until the value of conversion, expressed in volume percent, exceeds about 100 - C _A. For conventional catalysts, C _A
The fraction is almost completely converted to coke. According to the present invention, by combining a faugiasite-type cracking component and mordenite as a catalyst, it is possible to selectively crack cracks at a much higher conversion rate than when either faugiasite or mordenite is used alone. It is possible. The faugiasite component may be either natural or synthetic faugiasite, such as zeolite X or zeolite Y.
There is. Preferred faugiasites are rare earth-exchanged and calcined zeolites X or Y, but may also be hydrogen-type zeolites, such as HY. The mordenite component is generally of the synthetic hydrogen type, such as Norton H-Zeolon (Norton H-Zeolon).
-Zeolon) or tetraethylammonium (TEA) The hydrogen form is derived by heating mordenite, but other cationic forms or natural mordenite are also possible. Generally, crystalline aluminosilicate zeolites are ion-exchanged, either separately or as a final catalyst, to exchange the alkali metals present in the zeolite from the beginning of nature or incorporated into the zeolite during synthesis. Due to ion exchange, the alkali metal content in the final catalyst is less than about 1.5% by weight;
Preferably it will be less than about 0.5% by weight. The purpose of ion exchange is to substantially remove alkali metal cations, which are known to adversely affect cracking, and to introduce various cations in the ion exchange medium to enhance the desired catalytic activity. For the cracking operation of the invention, preferred cations are hydrogen, ammonium, rare earths and mixtures thereof, particularly preferred are rare earths. Ion exchange is suitably accomplished by contacting the zeolite or catalyst with a solution of the desired cation, such as a sulfate, chloride or nitrate. The zeolites, ie faugiasite and mordenite, can be synthesized in situ in a matrix of inorganic oxides, raw or calcined clays or mixtures thereof. The faugiasite and mordenite components are each used as a mixture of separate particles or as a mixture of combined particles in a suitable inorganic oxide matrix. Generally, the latter type of catalyst is preferred in terms of wear resistance, high activity, and flow stability. Such a catalyst can be easily produced by dispersing the two types of zeolites in a suitable siliceous sol and gelling the sol using various methods. Examples of inorganic oxides used as a matrix for dispersing the zeolite include silica gel or cogels of silica and a suitable metal oxide. Typical examples of cogels include silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryria, silica-titania, and the ternary systems silica-alumina-magnesia, silica-alumina-zirconia and silica. −
There is magnesia-zirconia. Examples of preferred cogels are silica-alumina, silica-zirconia or silica-alumina-zirconia. The gels and cogels are generally mostly silica, with the remainder being other oxides. That is, the silica content of the siliceous gel or cogel matrix is generally 55 to 100% by weight, preferably 60 to 95% by weight, and the content of other metal oxides is generally 0 to 45% by weight, preferably 5 to 40% by weight. Weight%. In addition to the above materials, the matrix may also contain natural or synthetic clays such as kaolin type clays, montmorillonite, bentonite or halloysite. These clays may be used alone or in combination with silica or any of the cogels described above. When a matrix is used, the content of crystalline aluminosilicate zeolite, i.e., the amount of faujasite component, generally ranges from about 5 to about 30% of the total catalyst composition.
% by weight, preferably from about 10 to about 25%, and the amount of mordenite component generally ranges from about 1 to about 30% by weight,
Preferably from about 5 to about 25% by weight. The ion exchange of the zeolite to replace the alkali metal present from the beginning may be performed either before or after the zeolite is mixed into the matrix. When a mixture of zeolites is used without a matrix, the two types of zeolites are suitably ground together and then granulated or pelletized for use. Or 2 above
Seed zeolites may be pelletized or granulated separately and the pellets or granules then mixed. The catalyst composition can easily be made suitable for a fluidized cracking catalyst by spray drying the composite to form microspherical particles of appropriate size. Alternatively, the composition can be adjusted to appropriate concentrations and temperatures to form bead-like catalyst particles suitable for use in moving bed type cracking systems. The catalyst can be formed into various forms by tabletting, spheronizing or extrusion. Along with the activity of the catalyst, the catalytic cracking conditions, especially the temperature of 482-649°C (900-1200〓),
Oil contact time from 0.5 seconds to 15 minutes and catalyst from 1 to 20/
By properly adjusting the oil ratio, the severity is such that the overall conversion level exceeds the conversion of the non-aromatic core components of the feedstock. Severity can be increased within the above ranges by increasing temperature, contact time and/or catalyst/oil ratio. The activity of the catalyst can be increased by increasing the fresh catalyst replenishment rate and/or the crystalline aluminosilicate content. In the present invention, the catalytic cracking conditions and catalyst activity are adjusted such that the severity results in a level of conversion that exceeds that of the non-aromatic core components of the feedstock alone. Preferably, the catalyst is used in combination with a CO oxidizing component such as a platinum group metal (ie, platinum, palladium, rhenium, osmium, iridium or thenium) in an amount of 0.1 to 100 ppm. The present invention will be described in the following embodiments (hereinafter simply referred to as examples).
However, the present invention is not limited thereto. Examples 1 to 6 (Example 1, Example 2 and Example 6 are comparative reference examples,
Others are reference examples) A series of catalysts in which a combination of rare earth-exchanged zeolite Y (REY) and mordenite were mixed into a silica-alumina-clay matrix were prepared as follows. REY in the examples is sodium type zeolite Y
was ion-exchanged and 68% of the sodium cations were converted into Sm, Nd, Pr, Ce and La with the following distribution composition:
It is ion-exchanged with rare earth cations such as. After ion exchange, the REY product at 1200〓
Bake for 10 minutes. The compositions of REY and other used zeolites, namely mordenite and tetraethylammonium (TEA) mordenite, are shown in the table below.

[Table] The zeolite was incorporated into a gel matrix consisting of 60.45% SiO ₂ , 4.55% Al ₂ O ₃ and 35% clay. The matrix was prepared by slurrying 407.5 parts by weight of kaolin clay and 2101.4 parts by weight of sodium silicate (28.8% by weight SiO ₂ and 8.8% by weight Na ₂ O) with 10,000 parts by weight of water, and adding the slurry to concentrated sulfuric acid at 49°C (120°C). PH of about 10.7 at
It was prepared by acidifying to The gel thus prepared was aged by heating to 49°C (120°C) for 30 minutes and then cooled to ambient temperature. Thereafter, 1328 parts by weight of a 20% by weight aqueous solution of aluminum sulfate (17.7% Al ₂ O ₃ ) was gradually added to mix alumina. After adding aluminum sulfate, the PH was about 4.5. A suitable zeolite was added to the clay-gel mixture thus prepared. The resulting zeolite and host composite was homogenized, then the inlet temperature was 371°C (700°) and the outlet temperature was 177°C (350°).
〓) and spray-dried. The resulting spray dried product was ion exchanged with a 5% aqueous solution of ammonium sulfate and then washed with water until substantially free of sulfate. The water-washed product was then further ion-exchanged with a 1% aqueous solution of rare earth chloride to obtain a catalyst composition whose RE ₂ O ₃ content and composition distribution were as shown in the table below. The ion exchanged product was then washed with water until substantially free of chloride. In the case of the catalysts of Example 2, Example 3 and Example 4, the washing with a solution containing sufficient Pt(NH ₃ ) ₄ Cl ₂ to deposit 1.5 ppm of platinum on the catalyst was carried out at this stage. The prooxidant was incorporated by slurrying the wet mass of the product. After passing through
The wet mass was dried at 121°C (250°C) for about 40 hours. Regarding the catalyst prepared as described above, its composition,
The chemical and physical properties are shown in the table below.

【table】

[Table] Examples 7 to 12 (Examples 7 to 12 are all comparative examples) Each of the freshly prepared catalysts of Examples 1 to 6 was heated to atmospheric pressure (0 psig) in 100% steam in a fixed fluidized bed.
Steam treatment was performed at 760°C (1400°C) for 4 hours. In each case, the catalyst was preheated to 732° C. (1350°) in steam before starting the 4 hour steam treatment and then heated to 1400° under nitrogen. The steam-treated catalyst was then tested for cracking activity by cracking wide cut mid-continent gas oil (WCMCGO) having the properties shown in the table below in a fixed fluidized bed test apparatus. Selectivity was tested.

【table】

【table】

[Table] A series of cracking tests were conducted at a severity level to reach high conversions typical of commercially available equipment, but not sufficiently severe to cause cracking of polycyclic aromatics. Ivy. Conversion conditions and representative data obtained are shown in the table below.

[Table] Examples 13 to 18 (Examples 13, 14 and 18 are comparative examples) Another series of cracking tests were carried out under conditions where the conversion exceeded the conversion of non-aromatic components, i.e.
In the case of WCMCGO, the severity was such that 100-C _A = 85% conversion by volume was achieved. Conversion conditions and representative data obtained are shown in the table below.

【table】

TABLES The tables and tables show the selectivity factors for gasoline and coke yield versus conversion. Under the conversion conditions of the table, where no aromatic component conversion occurs, the selectivity factors for Examples 7-12 are very similar, indicating that the added zeolite has little effect on selectivity. However, under high severity conditions where aromatic component conversion occurs, mordenite-containing catalysts exhibit much improved selectivity over mordenite-free catalysts. For example, the mordenite-containing catalyst of Example 16 has a 4% higher gasoline/conversion ratio and a 24% higher coke selectivity (conversion/coke) than its corresponding mordenite-free catalyst of Example 14. Similarly, the TEA mordenite-containing catalyst of Example 17 has a lower gasoline volume/
Conversion ratio increased by 5% and coke selectivity increased by 22%
increased. The presence of mordenite in the catalyst thus improves product selectivity when aromatic components are converted. The data in Tables and Tables Examples 12 and 18 indicate that mordenite alone does not provide sufficient activity to convert the non-aromatic components of the feedstock at high conversion rates even under high severity conditions. . It should be understood that the foregoing description merely indicates preferred embodiments of the invention, and that those skilled in the art can make various modifications within the scope of the following claims without departing from the spirit of the invention. be.

Claims (1)

[Claims] 1. A method for cracking a hydrocarbon feedstock containing aromatic components and non-aromatic components, comprising: (a) an alkali metal content of less than 1.5% by weight; and (b) faugiasite/mordenite. The raw material is contacted with a catalyst composition characterized in that it contains a mixture of faugiasite and mordenite in a weight ratio of 30/1 to 1/5, and the contact is carried out at a temperature of 482°C to 649°C; ^The catalyst/
Conducted under catalytic cracking conditions with an oil ratio of 1 to 20,
Similar catalysts that do not contain mordenite at the same conversion level, with the activity of the catalyst and the catalytic cracking conditions adjusted to a severity that results in a conversion level that exceeds the conversion level based on the conversion of non-aromatic components of the feedstock. 1. A method for cracking hydrocarbon feedstocks containing aromatic and non-aromatic components, the method comprising producing less coke than when using. 2. The method according to claim 1, wherein the faugiasite and mordenite are rare earth type, hydrogen type, or ammonium type. 3. The method according to claim 1, wherein the faugiasite is a synthetic faugiasite. 4. The method according to claim 3, wherein the synthetic phaujasite is zeolite X. 5. The method according to claim 3, wherein the synthetic phaujasite is zeolite Y. 6. The method according to claim 1, wherein a mixture of faugiasite and mordenite is contained in the inorganic oxide matrix. 7. The method of claim 1, wherein the faugiasite and mordenite are contained in separate flowable particles. 8. The method of claim 1, wherein the mixture of faujasite and mordenite is in the form of a fluid cracking catalyst. 9. The method of claim 1, wherein the mixture of faugiasite and mordenite is in the form of particles for a moving bed cracking system. 10. The method according to claim 1, wherein the raw material is light oil. 11. The method according to claim 1, wherein the alkali metal content is less than 0.5% by weight. 12. The method according to claim 1, wherein the faugiasite is a rare earth type and the mordenite is a hydrogen type. 13. The method of claim 1, wherein the catalyst contains a platinum group metal as CO oxidizing component in an amount of 0.1 to 100 ppm. 14. The method of claim 6, wherein the faugiasite is present in an amount of 5 to 30% by weight of the catalyst composition and the mordenite is present in an amount of 1 to 30% by weight of the catalyst composition. 15. The method of claim 6, wherein the faujasite is present in an amount of 10 to 25% by weight of the catalyst composition and the mordenite is present in an amount of 5 to 25% by weight of the catalyst composition.