JPH0354717B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention selectively converts LPG (i.e., propane, butane-based hydrocarbons) by catalytically cracking pentane-containing hydrocarbon oil in the presence of a specific crystalline aluminosilicate catalyst. The present invention provides a method for manufacturing. In particular, the silica to alumina molar ratio is 12 or more and 200 or less,
The solid acid properties of acid-type crystalline aluminosilicate with a reduced sodium content of 0.5 wt% or less were measured by the temperature-programmed desorption method using pyridine, and the desorption peak temperature was
This is a method for converting a pentane fraction, which is characterized by using a crystalline aluminosilicate having a temperature of 650°C or higher as a catalyst. LPG, which is in high demand as household fuel and LPG automobile fuel, has been highly evaluated as a clean fuel that does not contain impurities such as sulfur and nitrogen. Normally, most of the supply of LPG comes from those accompanying the production of crude oil and those recovered during the distillation of crude oil, and therefore, the production amount depends on the crude oil production plans of the oil producing countries and other factors. There are factors that depend on demand trends for products. On the other hand, LPG is also produced through the conversion reaction of petroleum fractions; for example, 5 to 10 wt. with a yield of %
LPG is obtained. Several processes have been clarified so far to selectively produce LPG from petroleum fractions. This is a method of hydrogenolysis using an acid catalyst, for example, using a platinum silica/alumina catalyst, a Nickel HY zeolite catalyst, or a palladium H mordenite catalyst at a temperature of 400-450°C.
LPG under hydrogenation conditions at a pressure of about 100Kg/cm ² G
A typical example is the method of hydrogenolysis. Recent hydrocracking catalysts tend to use proton-type (hereinafter H-type) zeolite carriers, which have stronger solid acidity than amorphous silica and alumina, due to their activity. Although temperatures are gradually decreasing, current technology still requires temperatures of over 350 degrees Celsius. Also
For the purpose of selectively producing LPG, it is necessary to select and use hydrocarbons having 6 to 8 carbon atoms as feedstock oil. This means that for _C6 hydrocarbons, propane is selectively converted under hydrocracking conditions by the reaction of _C6 → _C3 + _C3 , for _C7 hydrocarbons, _C7 → _C3 + _C4 , and for _C8 hydrocarbons, C This is because propane or butane can be selectively produced by the reaction of ₈ → C ₄ + C ₄ . but
For pentane, a _C5 hydrocarbon, _C5 → _C2
The same amount of ethane is produced at the same time as propane through the +C ₃ reaction, and the ethane produced as a by-product at this time has a lower value than LPG, so when processing hydrocarbons containing pentane, pentane is actively hydrogenated. Treatment is carried out to the extent that n-pentane is isomerized to i-pentane while avoiding decomposition. In addition, even if pentane is to be hydrolyzed at a high decomposition rate, a high reaction temperature of 40°C or higher is usually required because the reactivity of pentane is significantly inferior to that of _C6 or higher hydrocarbons. Among petroleum products, naphtha, a hydrocarbon with a boiling point of 25°C to 180°C, undergoes conversion treatment to increase its octane number and is used as automobile gasoline, but hydrocarbons with carbon numbers of 6 or more are It can be easily converted to aromatics with the corresponding carbon number by catalytic reforming treatment using a platinum alumina catalyst,
Also, conversion to aromatics is the most effective way to increase the octane number. However, in pentane, there is no aromatic group with a corresponding number of carbon atoms, so it is not very likely that the octane number will be improved by the reforming treatment. Therefore, the raw materials for obtaining LPG are _C6 to _C3.
It would be of great industrial value if pentane could be used instead of using hydrocarbons. Therefore, the inventors conducted intensive research on a method for decomposing pentane into LPG, and found that a specific aluminosilicate with a silica to alumina molar ratio of 12 or more and a strong acid site specified by the pyridine temperature-programmed desorption method was found. By using methane as a catalyst, the production of methane and ethane can be kept extremely low.
The present invention was completed based on the discovery that it is possible to selectively produce LPG in high yield. Furthermore, the breakthrough result was that pentane is almost completely decomposed into LPG at temperatures below 300°C. Additionally, since this catalyst does not require supporting metals, the consumption of hydrogen during decomposition is low, and it exhibits high activity and selectivity even in the absence of hydrogen, in which case the main products are similar to those obtained in the presence of hydrogen. With propane and butane, almost no olefin was produced, and hydrogen was not consumed at all, but rather hydrogen was produced, an impressive result. Normally, when a paraffin hydrocarbon is brought into contact with a solid acid catalyst such as silica alumina or zeolite that does not support a metal capable of hydrogenation, such as group metals, at an elevated temperature, the paraffin hydrocarbon removes protons from the catalyst. The carbon-carbon bond located at the center of the hydrocarbon molecular structure is cleaved (usually referred to as β-cleavage), and one becomes paraffin and the other becomes olefin. Even in the presence of hydrogen in the reaction atmosphere, hydrogenation of olefin to paraffin hardly occurs. However, as mentioned above, the conversion reaction using the catalyst of the present invention does not produce olefins. Although it is not clear what causes the above-mentioned characteristics of the present invention, it is thought that the solid acid of the crystalline aluminosilicate used in the present invention has stronger acid sites than have been found so far. It will be done. Therefore, the reaction mechanism can be considered as follows. 2CH ₃ CH ₂ CH ₂ CH ₂ CH ₃ →2CH ₂ = CH ₂ +2CH ₃ CH ₂ CH ₃ or 2CH ₃ CH ₃ +2CH ₂ = CHCH ₃ First, according to the above equation, pentane produces ethylene, propylene, ethane, and propane. It is thought that ethylene immediately doubles and becomes butylene, which then undergoes a hydrogen transfer reaction to produce butane. Conventionally, it is known that cyclization of paraffins and olefins occurs on solid acid catalysts, but in the reaction of the present invention, the solid acidity is stronger than that of conventional catalysts, so cyclization occurs to a considerable extent, and in this case, The advantage is that the olefin is hydrogenated with the active hydrogen generated. Therefore, the crystalline alumina silicate used in the present invention has stronger solid acidity and strong acid points than Y-type zeolite or mordenite zeolite, which are often used in industrially used hydrocracking and catalytic cracking. It must be something that you have a lot of. The general method used to measure the solid acid properties of solid acids such as zeolites has been to titrate the solid acid point with a basic substance using an indicator in an organic solvent or water. ,
Since it is time consuming and requires a lot of skill to measure, there are many problems, so recently Temperature Programmed Desorption has been used as a simple but relatively accurate method to measure solid acidity.
In other words, the TPD method is adopted. Pyridine is usually used as the basic substance to be adsorbed, and the amount of acid is measured from the amount of pyridine that desorbs as the sample is heated, and the acid strength is measured from the temperature at which it desorbs. Solid acids with strong acidity have a high desorption temperature, while solid acids with only weak acidity have a low desorption peak temperature.
As an example, Figure 1 shows the TPD curve for pyridine.
Table 1 also shows the effects of pyridine on various solid acids.
The results of TPD were shown. In the present invention, we decided to measure the solid acid properties of crystalline alumina silicate that can be used using pyridine TPD. That is, a catalyst having a pyridine desorption peak temperature of 650° C. or higher and an acid amount of 0.1 milliequivalent/g of catalyst or higher can be used in the present invention.

[Table] As can be seen from Table 1, No. 5 H mordenite has the highest amount of acid corresponding to the γ peak, which is a strong acid site, but its desorption peak temperature is 610°C, so
It does not serve as the catalyst of the present invention. In addition, No. 6 HY zeolite has a desorption peak at 450°C, and No. 7 amorphous silica/alumina has almost no strong acid sites and only a β peak indicating weak acid sites, so both of them are true. It is not a catalyst for invention. The crystalline aluminosilicate most suitable for the purpose of the present invention is acid type DGA zeolite (hereinafter referred to as HDGAZ).
The pyridine desorption peak temperature of this solid acid catalyst is extremely high at 740°C, and all acid sites are occupied by substances with a desorption temperature of 600°C or higher. then acid form
It is a high silica zeolite of the ZSM-5 (hereinafter referred to as HZSM-5) series. ZSM-5 preferably has a silica/alumina ratio of 200 or less and a pyridine desorption peak temperature of 680°C. HDGAZ is Tokkai Sho
It is a high silica zeolite disclosed in No. 56-92114, which contains a silica source, an alumina source, an alkali metal source,
Crystalline aluminosilicate containing diglycolamine ions in its crystal structure is produced by hydrothermally synthesizing a raw material mixture containing diglycolamine in addition to water at a temperature and under pressure conditions that produce crystalline aluminosilicate. It is obtained by protonation using a known method and then heating to a temperature sufficient to remove diglycolamine ions by calcination. ZSM-5 zeolite is a new crystalline aluminosilicate disclosed by Mobil Oil Co. in Japanese Patent Publication No. 10064/1983, and is hydrothermally synthesized in the presence of a tetrapropylammonium compound or its precursor. ZSM-5 zeolite as used herein also includes crystalline aluminosilicate that can be synthesized using an organic compound described below instead of a tetrapropylammonium compound and exhibits an X-ray diffraction pattern similar to ZSM-5. The source of silica, which is the starting material for hydrothermal synthesis of DGA zeolite or ZSM-5 zeolite, is
The source of silica can be any silica or compound of silica commonly used in zeolite synthesis, for example silica powder, colloidal silica, or silicates such as water glass. Sources of alumina include alumina gel, alumina sol, alumina, sodium aluminate,
Aluminum sulfate, aluminum nitrate, aluminum chloride, etc. can be used, but water-soluble sodium aluminate is suitable for handling. As the source of alkali, hydroxides of alkali metals such as sodium and potassium or alkaline earth metals such as calcium, or compounds with aluminic acid and silicic acid are used, and sodium aluminate is preferable because it serves as a source of alumina and alkali. It is a compound. Diglycolamine, an organic compound used in the hydrothermal synthesis of DGA zeolite, is formally known as 2-(2
-aminoethoxy)ethanol,
The first diagram showing the molecular formula of NH ₂ CH ₂ CH ₂ OCH ₂ CH ₂ OH
It is distinguished from alcohol amines because it has an ether structure. In addition, of course, precursors that produce diglycolamine can be used. The following organic compounds can be used when hydrothermally synthesizing ZSM-5 or a high silica zeolite that gives an X-ray diffraction pattern similar to ZSM-5. (1) Organic amines; primary amines such as n-propylamine and monoethanolamine, secondary amines such as dipropylamine and diethanolamine, tertiary amines such as tripropylamine and triethanolamine, or ethylenediamine. In addition, mixtures of the above compounds and halogenated hydrocarbons, quaternary ammonium salts such as tetrapropylammonium salts, etc. (2) Organic nitrogen compounds other than organic amines; pyridine, pyrazine, pyrazole, etc. (3) Organic sulfur compounds; Methyl mercaptan, dimethyl sulfide, etc. (4) Alcohols or ethers. These various organic compounds are merely examples, and the present invention is not limited thereto. Next, the composition ratio of these starting materials is prepared in the following ratio (molar ratio).

[Table] This mixture is usually heated at a temperature of 80 to 300℃, preferably 120 to 300℃.
Heat in a closed container at a temperature of 200°C for approximately 0.5 to 30 days. Although the pressure is not particularly limited, it is preferable to carry out the test under its own pressure. The hydrothermal synthesis reaction is continued by heating the raw material mixture at the desired temperature, with stirring if necessary, until crystalline aluminosilicate is formed. After crystals have formed, the reaction mixture is fractionated. Furthermore, drying is usually performed at 100°C or higher for about 5 to 24 hours. The crystalline aluminosilicate produced by the method described above is calcined at a temperature of 400°C or higher, or made into an acid form by a well-known technique such as proton treatment described below, and then used as it is or conventionally used for catalyst formation. It is used as a catalyst by mixing it with a binder such as alumina, silica, natural clay minerals, or their sol or gel, and molding it into an appropriate size. The mixing ratio of binder is usually 5 to 60 wt%, preferably 10
~50wt% range. The ZSM series of zeolites disclosed by Mobil Oil Co. has shown up to ZSM-34 by changing the types of organic compounds during hydrothermal synthesis. Among these, crystalline aluminosilicates having pores capable of adsorbing hydrocarbons having one or more methyl groups are preferably used in the present invention. Crystalline aluminosilicates are _SiO4 and _AlO4
and share oxygen to form a network structure, and the pore structure is determined by this bond. The crystalline aluminosilicates known so far include about 50% of crystalline aluminosilicates such as erionite, offretite, and A zeolite.
an 8-membered oxygen ring type zeolite having pores of Å;
10-member oxygen ring zeolites with pore diameters of approximately 6 to 9 Å such as DGA zeolite, ZSM-4, and ZSM-5, and approximately 10 Å pores such as X zeolite and Y zeolite.
It is a 12-membered oxygen ring type zeolite with pores.
The crystalline alumina silicate preferably used in the present invention has a pore size capable of adsorbing i-pentane. In crystalline aluminosilicate, the negative electricity of the SiO ₄ tetrahedron is due to the fact that when it is hydrothermally synthesized in the presence of alkali metal cations such as sodium or potassium or organic compounds, the cations are included in the structure and the electrical balance is maintained. There is. The acid-type crystalline aluminosilicate with strong solid acidity used in the present invention is produced by treating hydrogen ions generated by firing organic cations or alkali metal ions with ammonium salts such as ammonium nitrate and ammonium chloride. Hydrogen ion type obtained by directly exchanging hydrogen ions with hydrogen ions or mineral acids such as hydrochloric acid or nitric acid, which are produced by exchanging the hydrogen ions with ions and then firing them. In addition to hydrogen ions, cations that provide acid-type crystalline aluminosilicate include ions of rare earth elements such as lanthanum and cerium, which can be easily exchanged using chlorides, nitrates, etc. of rare earth elements. In addition, other cations such as calcium, magnesium, zinc, and potassium can also be used as exchange ions as long as they do not damage the solid acid of the crystalline aluminosilicate. The pentane fraction, which is the raw material hydrocarbon used in the present invention, is a light hydrocarbon fraction containing a total of n-pentane and i-pentane of 30 wt% or more, preferably 50 wt% or more, and has an aromatic group hydrocarbons
It is a hydrocarbon mixture with a carbon number of up to 4-8 and less than 50wt%. Sulfur content is 0.2wt%, nitrogen content is 100ppm
Hydrocarbon oils with a boiling point of 20-100℃ obtained by distilling ordinary crude oil, as well as those obtained by desulfurization treatment, and treatments such as hydrocracking, catalytic cracking, and thermal cracking of heavy hydrocarbons. A pentane-containing hydrocarbon mixture obtained by is used. It is known that ZSM-5 type crystalline aluminosilicate exhibits excellent performance in catalytic dewaxing or selective cracking of catalytic reformed oil, but the raw material oil for catalytic dewaxing has a carbon number of 11- 30. It is a hydrocarbon with a boiling point range of 220 to 440℃ and a wax content of 5 to 15 wt%, and in selective cracking, n-paraffin and monomethyl paraffin with a low octane number in the reformed naphtha containing a large amount of aromatics are selected. Since the purpose is to increase the octane number of the reformed naphtha by decomposing it, the aromatic content in the raw material must be 30wt% or more. Therefore, the feedstock oils used in these known techniques are different from the feedstock oils used in the present invention, and the intended products are different. Next, the reaction conditions will be described. The temperature is not particularly limited, and the range varies depending on the contact time between the catalyst and feedstock oil, but it is usually between 200 and 350 degrees Celsius. In particular, using the temperature in the low temperature range of 200 to 300 degrees Celsius will improve catalyst performance over a long period of time. This is preferable because it can be stably maintained. The pressure is not particularly limited, but 100
Kg/cm ² G or less pressure, usually 1-30Kg/cm ² G
This is the pressure of The LHSV is 0.01-100 h ^-1 , preferably 0.1-10 h ^-1 , and the gas supply amount is 0-500, preferably 0-100 in molar ratio of gas to feedstock oil. The gas mixed with the raw material oil and supplied to the reactor is not particularly limited, and includes, for example, hydrogen, carbon monoxide, carbon dioxide,
In addition to nitrogen, the gas after removing the liquid fraction from the product flowing out from the reactor outlet can be recycled and used. Next, the present invention will be specifically explained using experimental examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded. Zeolite Synthesis Example 1 DGA zeolite was synthesized as follows.
Colloidal silica (silica content 20.36wt%) 325
ml, 188 ml of water and 72 g of diglycolamine were added and stirred. Add a solution of 5.1 g of sodium aluminate and 7.5 g of sodium hydroxide dissolved in 100 ml of water and stir for 30 minutes. Put this raw material mixture into the stainless steel autoclave No. 2 and heat it to 160°C.
The mixture was heated under autogenous pressure for 3 days, and the obtained white fine crystals were washed with pure water from Step 2 and dried at 130°C. This crystalline material contains 0.2wt% Na ₂ O 5.8wt% Al ₂ O ₃ ,
It contained 11.1 wt% organic matter, which gave a nitrogen to carbon ratio comparable to diglycolamine.
The molar ratio of silica to alumina was 26. According to X-ray diffraction analysis, the diffraction pattern was as shown in Table 2, and there was no other foreign crystalline aluminosilicate, and the zeolite was 100% pure and contained diglycolamino cations.

[Table] Zeolite synthesis example 2 ZSM-5 zeolite was synthesized as follows. Water glass (SiO ₂ 37wt%, Na ₂ O 17.5wt%,
Add 220 g of water to 240 g of H ₂ O (45wt%) and mix well. Add a solution consisting of 11.2 g of sodium chloride, 46 g of sulfuric acid, 24.0 g of aluminum sulfate, and 178 g of water and mix and stir thoroughly. Next, here are 33.2 g of tri-normal propylamine, 28.4 g of normal propyl bromide, and methyl ethyl ketone.
53.8g was added, and these raw material mixtures were placed in two stainless steel autoclaves and heated at 100℃ for 1 day.
Heated at 170°C for 2 days under autogenous pressure. The obtained white fine crystals were washed with pure water from step 2 and dried at 130°C.
The crystalline material contained 2.1 wt% _Na2O , had a silica to alumina ratio of 32, and had a diffraction pattern consistent with Mobil ZSM-5 zeolite according to X-ray diffraction analysis. In Synthesis Example 2, when the amount of aluminum sulfate added was 4.8 g, ZSM-5 was obtained with a silica to alumina ratio of 120, and when no aluminum sulfate was added, a silica to alumina ratio of 450 was obtained. Example 1 An acid type crystalline aluminosilicate catalyst was prepared as follows. After calcining the DGA zeolite synthesized in Synthesis Example 1 at 550℃ for 3 hours, 50g of it was mixed with 1N
It was placed in a glass flask equipped with a stirrer together with 300 ml of an aqueous hydrochloric acid solution and treated at 80°C for 48 hours. The treatment with a 1N hydrochloric acid aqueous solution was performed three times with a fresh solution, then washed with filtered pure water until almost no chlorine ions were detected in the solution, and then dried at 130°C for 4 hours. The acid properties of the acid type crystalline aluminosilicate thus obtained are as shown in No. 1 of Table 1. This product was compression molded, the particle size was made uniform to 12-20 mesh, and it was subjected to the reaction of n-pentane and i-pentane. The reaction was carried out under a hydrogen pressure of 24 kg/cm ² G or under a nitrogen stream at normal pressure, and the results are shown in Table 3.

【table】

[Table] In experiment numbers 1 to 3, the reaction of n-pentane was carried out under hydrogen pressure at a molar ratio of hydrogen to raw oil of 5. At 260°C, n-pentane had already decomposed 48.6%, and at 300°C, it decomposed by 48.6%.
Most of it is decomposed at 89.1%. The decomposition products are dominated by propane and butane, including undesirable methane,
Very little ethane is produced, and no olefin is produced at all. Another advantage is that the hydrogen consumption associated with the reaction is low; even at 89.1% cracking, the hydrogen consumption is 40% of that of conventional hydrocracking. Experiment No. 4 shows a reaction example of i-pentane, which shows a high decomposition rate of 43.1% at 260° C. like n-pentane, and also has high selectivity for C ₃ and C ₄ . Experiment No. 5 is the result of the reaction of n-pentane under the conditions of a nitrogen to raw material molar ratio of 3 under normal pressure nitrogen flow, and although the decomposition rate is lower than under hydrogen pressure, it still achieved a reaction rate of 58.5% at 320°C. It shows the decomposition rate and also LPG
The selectivity is as high as under hydrogen pressure. The advantage of this catalyst is that even in the absence of hydrogen, it can be operated under much lower conditions than conventional cracking conditions, and hydrogen is generated without being consumed. In addition, even though this reaction was continued for 10 hours, stable activity and selectivity were obtained without any deterioration of activity. Examples 2 and 3 Silica to alumina ratio synthesized in Synthesis Example 2 of 32 and
ZSM-5 zeolite No. 120 was made into an acid form in the same manner as in Example 1. The acid properties of the zeolite thus obtained are as shown in Nos. 2 and 3 of Table 1. This product was molded in the same manner and subjected to the reaction with n-pentane. The results are shown in Table 4.

[Table] Both of these catalysts selectively produce LPG, and the production of undesirable methane and ethane is extremely low. The product also contains no olefins and is high in paraffins. Silica to alumina ratio of 32
The decomposition rate of n-pentane by HZSM-5 was determined by the HDGA shown in Example 1, as shown in Experiment No. 6.
Although it is lower than zeolite, it still provides sufficient performance at temperatures below 300℃. As the silica to alumina ratio increases, the decomposition rate of n-pentane decreases as shown in Experiment Nos. 7 and 8, so it is considered preferable that the silica to alumina ratio is usually 12 or more and 200 or less. Comparative Examples 1 and 2 Table 5 shows the results of comparative examples under the following conditions. Comparative Example 1 is ammonia-type Y zeolite obtained by repeating the operation of treating NaY zeolite (UCC SK-40), which is a large-pore zeolite, with a 4N ammonium chloride aqueous solution at 95°C for 3 hours three times, and a paldium amount of 0.6 wt. % of palladium chloride ammonia aqueous solution was replaced, the catalyst calcined at 530° C. was brought into contact with n-pentane, and a reaction was carried out. The decomposition of n-pentane does not occur sufficiently unless the reaction temperature is raised above 400℃, and the product is
Not only LPG but also methane and ethane are produced. Hydrogen consumption is also large, and n-
The equivalent number of moles of pentane is consumed. Comparative example 2
The amount of palladium in Norton H Zeolon is
After ion-exchanging palladium using an aqueous palladium chloride ammonia solution to make it 0.6wt%,
This shows the results of the reaction of n-pentane using a catalyst containing mordenite zeolite calcined at 550°C.The decomposition rate of n-pentane at 310°C is as low as 14.4%, and it is the same as propane and butane. Almost the same number of moles of methane and ethane are produced, and the selectivity of LPG is poor.

[Table] Example 4 Straight-run light naphtha obtained by distilling crude oil was used as the feedstock, and the acid type crystalline aluminosilicate (HDGA zeolite) obtained in Example 1 was used as the catalyst.
After wet mixing 60 parts of boehmite alumina and 40 parts of boehmite alumina, the mixture was molded into a 1.5 mm diameter and approximately 5 mm length using an extruder, and a conversion reaction was carried out. As shown in Table 6, the properties of the feedstock oils are two types of straight-run naphtha with different pentane contents, and contain sulfur of 210 ppm and 250 ppm, respectively.

【table】

[Table] The conversion reaction was carried out using a flow-type high-pressure reactor, reaction temperature 300℃, pressure 24Kg/cm ² G LHSV, 1.5h ^-1 ,
It was carried out at a molar ratio of hydrogen to feedstock oil of 5, and the results obtained are shown in Table 7.

[Table] Pentane at 300℃ for all feedstock oils is
It is converted to LPG with a high decomposition rate of over 70%, with only a small amount of undesirable methane and ethane produced.
Moreover, the activity was not decreased due to poisoning by the sulfur contained in the feedstock oil, and no decrease in activity over time was observed even after 50 hours of continuous operation.
Raw material oils A and B with different pentane contents,
There was little difference in the yield of LPG, indicating that this catalyst is particularly capable of selectively decomposing pentane. Furthermore, since feed oil A with a high pentane content consumes less hydrogen, expensive hydrogen can be saved and it is economical. As can be seen from the above, the method of the present invention can be applied to C ₆ , which was conventionally considered preferable for LPG production.
A feature is that superior effects can be obtained by using the _C5 fraction rather than the _C7 fraction as the feedstock oil. Furthermore, it is produced as a by-product along with LPG.
The _C5 ⁺ fraction has a higher octane number than the feedstock oil, and its value is 81-82 according to the research method, and can be preferably used as a feedstock for gasoline production.

[Brief explanation of drawings]

FIG. 1 is a graph showing the solid acid properties of pyridine TPD.

Claims (1)

[Claims] 1. When selectively producing LPG from a hydrocarbon oil containing bentane, the hydrocarbon is converted into an acid form that exhibits solid acidity with a silica to alumina molar ratio of 12 or higher and a temperature-programmed desorption temperature peak of pyridine of 650°C or higher. A method for catalytic cracking of a pentane fraction, characterized by bringing it into contact with a crystalline aluminosilicate.