CN100473461C - Catalyst for C4 liquefied petroleum gas aromatization and preparing method thereof - Google Patents

Abstract

The invention belongs to the field of petrochemical catalyst preparation, and relates to a catalyst suitable for the aromatization of C4 liquefied petroleum gas in a fixed-bed reactor and a preparation method thereof. Its technical feature is that the precursor of the catalyst is a high-silica zeolite with a grain size of 10-500 nanometers. The zeolite precursor is formed by alumina and prepared into a hydrogen-type catalyst by a conventional method, and then the hydrogen-type catalyst is treated with water vapor to adjust its acidity. , and then use acid reaming to restore the smoothness of the catalyst pores. The effect and benefit of the invention are that when the prepared catalyst is used to catalyze the aromatization of C4 liquefied petroleum gas, the reaction temperature is low, the olefin conversion rate is high, and the anti-coking ability is strong.

Description

Catalyst for aromatization of C4 liquefied petroleum gas and preparation method thereof

technical field

The invention belongs to the technical field of petrochemical catalyst preparation. It relates to a catalyst suitable for the aromatization of C4 liquefied petroleum gas in a fixed-bed reactor and a preparation method thereof.

Background technique

A large amount of C4 liquefied petroleum gas is produced by steam cracking units and various catalytic cracking units in refineries. C4 liquefied petroleum gas contains a large amount of various butenes, and converting butenes into fuel gasoline is a very meaningful way of resource utilization.

Patent document US3960978 (1976) discloses a catalyst capable of converting low-carbon olefins (C ₂ -C ₅ ) into olefin gasoline through oligomerization or superimposition. The catalyst is modified with Ni, Zn or Cr metal ions The ZSM-5/ZSM-11. After this patent, many patents at home and abroad related to oligomerization or superposition catalysts of low-carbon olefins. The conversion of light olefins into olefinic gasoline through oligomerization or superposition has certain application limitations. This is because the content of olefins in gasoline has been strictly limited, so olefin gasoline must be hydrogenated and saturated before it can be accepted. Hydrogenation requires increased investment in equipment, especially the consumption of very scarce hydrogen resources.

On the other hand, aromatized gasoline can be obtained through the aromatization reaction of light olefins (C ₂ -C ₅ ). The aromatization reaction of low-carbon olefins contains the following main elementary reaction steps: first, low-carbon olefins generate long-chain olefins by oligomerization or superposition on weaker proton acid centers, and then the above-mentioned long-chain olefins are formed on stronger proton acid centers. Isomerization and cyclization on the acid center generate aromatic hydrocarbon precursors. Finally, the aromatic hydrocarbon precursor removes hydrogen atoms on the medium-strength Lewis acid center (ie L-acid) to generate aromatic hydrocarbons, and the removed hydrogen atoms are combined with the alkene The double bond undergoes an addition reaction to saturate the double bond of olefins (including low-carbon olefins and long-chain olefins generated by oligomerization or superposition). Due to the above-mentioned hydrogen transfer reaction in the aromatization process, the content of olefins in aromatized gasoline (refers to liquid hydrocarbons with carbon five or more) is very small, and there is no need to consume hydrogen for saturation. In addition to a large number of high-octane aromatic components, aromatized gasoline also contains many saturated alkanes, of which quite a lot are high-octane isoparaffins, so the cost of aromatized gasoline obtained from low-carbon olefins Low, high octane number, low olefin and sulfur content, it is a good clean gasoline blending component. As mentioned above, the aromatization process is a co-catalyzed process of protonic acid centers and Lewis acid centers. Since the transfer of each hydrogen atom needs to be completed through the breaking of a carbon-hydrogen bond and the formation of a carbon-hydrogen bond, and the formation of an aromatic hydrocarbon molecule requires the transfer of multiple hydrogen atoms, the hydrogen transfer step is the aromatization reaction. The rate-controlling step, increasing the ratio of the number of Lewis acid sites to protonic acid sites on the catalyst is beneficial to the aromatization reaction. Generally, the ratio of the number of Lewis acid sites to protic acid sites on the aromatization catalyst must be adjusted in catalyst modification. In addition, since the aromatization process is always accompanied by carbon deposition, the problem of carbon deposition and deactivation of aromatization catalysts is very prominent. One of the reasons leading to the deactivation of aromatization catalyst carbon deposition is the presence of strong acid centers (including protonic acid centers and Lewis acid centers) on the catalyst. Strong acid sites will cause strong adsorption of reactants and products, thereby accelerating the deactivation rate of the catalyst. Therefore, eliminating the strong acid center of the catalyst is beneficial to improve the reaction stability of the catalyst. Generally, elimination of strong acid sites on the aromatization catalyst must also be accomplished in catalyst modification.

Some low-carbon olefin aromatization catalysts and preparation methods thereof are disclosed in the following patent documents:

US4150062 (1979) discloses a zeolite catalyst capable of producing high-octane aromatic gasoline with C ₂ -carbon tetraolefins, which is metal ion modified ZSM-5, ZSM-11, ZSM-12, ZSM-35 or ZSM-38 zeolite. The examples describe in detail the aromatization effect of a potassium-modified ZSM-5 in a fixed-bed reactor. Among them, in order to reduce the deactivation rate of the catalyst by carbon deposition, the patent uses water as a co-feed (the water/olefin molar ratio is 0.5-15).

The low carbon olefin aromatization catalyst disclosed in CN1057476 (1992) is a zinc-containing ZSM zeolite catalyst. The examples describe in detail the reaction effect of a Zn-Ti(SO ₄ ) ₂ -ZSM-5 zeolite catalyst in a fixed bed reactor: when the feed space velocity of the liquefied petroleum gas raw material is WHSV, it is 1 to 2h ^-1 , under the condition that the reaction temperature was 500-550° C., the catalyst was evaluated for 1000 hours in total. However, a total of 6 regenerations are required in a reaction time of 1000 hours. In a one-way reaction evaluation of a continuous reaction of 168 hours, the yield of benzene, toluene and xylene (BTX) in the product decreased from 42.0% at the beginning to 32% at the end.

CN1154687 (1997) discloses a ZSM-5 zeolite catalyst modified by water vapor passivation. In a fixed-bed single-stage adiabatic reactor with double reaction towers, carbon-four mixtures are used as raw materials, under the conditions of feed space velocity WHSV of 2.8h ^-1 , pressure of 0.5Mpa, and reaction temperature of 530°C, when the reaction proceeds to The yield of C ₆ -C ₉ aromatics reached 52.3wt% in 10 hours, and the yield of C ₆ -C ₉ aromatics dropped to 49wt% when the reaction continued for 120 hours.

CN1232071 (1999) discloses an aromatization catalyst, which uses ZSM-5 zeolite and γ-Al ₂ O ₃ as the carrier, and is modified by Zn and mixed rare earth and then modified by water vapor treatment. When using mixed C4 as raw material, in a fixed bed reactor, under the conditions of reaction temperature 530°C, reaction pressure 0.2MPa, feed space velocity WHSV 0.65h ^-1 , continuous reaction for 450 hours, yield of aromatics The initial value of 50wt% was finally reduced to 43wt%.

A catalyst disclosed in CN1321728 (2001) is obtained by using ZSM-5 zeolite and γ-Al ₂ O ₃ as the carrier, Zn and mixed rare earth modified and then modified by water vapor treatment. When the feed is liquefied petroleum gas, the reaction is carried out continuously for 16 days under the conditions of normal pressure, 530-540 ° C, and WHSV of 0.6 ± 0.1 h ^-1 . % and 40%, the final values are 68% and 38%, respectively.

A kind of aromatization catalyst disclosed by CN1340601 (2002), it is characterized in that, take ZSM-5 zeolite as precursor, impregnate metal ion (Zn) earlier, then introduce the second modification component VA or VIB group metal to prevent Zn The loss of the catalyst is molded with a binder and then modified by water vapor passivation. When mixed C4 is used as raw material, the reaction is carried out at 530°C, 0.2MPa, and WHSV of 0.65h ^-1 , the initial value of aromatics yield is 50wt%, and the result after continuous reaction for 450 hours is 43wt%.

An aromatization catalyst disclosed in CN1341699 (2002) is Zn-Ni-ZSM-5 zeolite. When the mixed carbon four reacts in a fixed-bed reactor with a temperature of 500°C, a pressure of 0.5-1MPa, and a WHSV of 1.0-1.5h ^-1 , the liquid yield is 60.37wt% in 40 hours of reaction, and the total aromatics yield It was 57.30wt%; when reacting for 120 hours, the liquid yield dropped to 47.80wt%, and the total aromatics yield dropped to 45.34wt%.

As mentioned above, the preparation and modification of existing aromatization catalysts are completed by modification with metal oxides, modification with steam treatment, or a combination of the above two methods. Both metal oxide modification and steam treatment modification can eliminate strong acid sites on the catalyst and increase the ratio of Lewis acid sites to protonic acid sites. Among them, the modification of metal oxides to eliminate the strong acid centers on the catalyst is achieved through surface coverage. Since metal oxides themselves belong to Lewis acids, the ratio of Lewis acid centers to protonic acid centers can be simultaneously increased by metal oxide modification. The removal of strong acid centers on the catalyst by water vapor treatment modification is mainly achieved by dealuminating the zeolite framework. Since the aluminum of the zeolite framework corresponds to the protonic acid center, and the aluminum species detached from the zeolite framework are retained in the micropores of the zeolite, New Lewis acid centers are generated in the form of non-framework aluminum, so the modification by steam treatment can also increase the ratio of Lewis acid centers to protic acid centers.

However, although the aromatization catalyst prepared by the existing method has good aromatization catalytic performance, the coking deactivation speed of the catalyst is fast, the single-pass operation period is short, and the operating temperature must generally be higher than 500°C.

After analysis, the inventor believes that the problem of the existing preparation method of aromatization catalyst is that it reduces the ratio of strong acid centers on the catalyst and increases the ratio of Lewis acid centers to protonic acid centers on the catalyst, and reduces the density of zeolite micropores. The effective size, results in a corresponding increase in the diffusion resistance in the micropores. This is because whether the metal oxide used for modification exists in the micropores of the zeolite in a highly dispersed state or in an aggregated state, it will become an obstacle in the micropores of the zeolite. Likewise, non-framework aluminum species generated due to water vapor treatment and trapped within the pores of zeolites are also obstacles within the pores of zeolites. These micropore obstacles due to modification increase the resistance of carbon deposition precursors (product aromatic molecules belong to carbon deposition precursors) from the zeolite micropores to the outside, thus increasing the carbon deposition precursors in the catalyst. Opportunities for deep reaction to generate carbon deposits.

Contents of the invention

The object of the present invention is to provide a method for preparing an aromatization catalyst capable of overcoming the above disadvantages.

The object of the present invention can be achieved through the following two aspects: on the one hand, the catalyst modification is carried out as follows: first adopt water vapor treatment to eliminate the strong acid center on the catalyst surface and improve the ratio of Lewis acid center and protonic acid center, then treat with dilute acid solution The catalyst after water vapor passivation (i.e. acid pore expansion), so that the non-skeleton aluminum detached from the zeolite framework and retained in the zeolite micropores is dissolved and removed, and the smoothness of the zeolite micropores is restored. On the other hand, using high-silica zeolite with a grain size of less than 500 nanometers as the catalyst matrix, the inherent advantages of small-grain zeolite with short pores are used to further improve the diffusivity of the aromatization catalyst.

The present invention can specifically be implemented according to the following steps:

Firstly, a high silica zeolite precursor with a grain size of less than 500 nanometers is prepared by a hydrothermal synthesis method. Silica zeolites specifically include ZSM-5, ZSM-11, and ZSM-8. The method for preparing high-silica zeolite with a grain size of less than 500 nanometers by hydrothermal synthesis has been described in many patent documents and published documents, such as the method disclosed in the following patent documents and published documents: U.S.Pat.No.3702886, U.S.Pat. .No.3709979, U.S.Pat.No.3781226, U.S.Pat.No.3926782, U.S.Pat.No.4205053, U.S.Pat.No.4289607, U.S.Pat.No.5405596, U.S.Pat.No.1334243, EP173901, EP130809 , Danish Patent PR 173,486, GB1334243A, Chem.Mater 5(1993)452, Zeolites 14(1994)557, Zeolites 14(1994)643, J.Catal.145(1994)243, Mater.Res.Soc.Symp.Proc .371(1995)21, Aangew.Chem.Int.Ed.Engl.34(1995)73, Chem.Mater.7(1995)920, Colloid Interface Sci.170(1995)449, Micropor.Mater.5(1996 )381, Zeolites 18(1997)97, J.Phys.Chem.B101(1997)10094, Micropor.Mesopor.Mater.22(1998)9, Micropor.Mesopor.Mater.25(1998)434, Chem.Comm. 673(1999), Micropor.Mesopor.Mater.31(1999)141, Micropor.Mesopor.Mater.31(1999)241, Micropor.Mesopor.Mater.39(2000)393, Inorg.Chem.39(2000)2279 , Micropor. Mesopor. Mater. 50 (2001) 121-128, Micropor. Mesopor. Mater. 43 (2001) 51-59, Mater. Sci. Eng. C 19 (2002) 111-114. Therefore, any engineer familiar with the field can hydrothermally synthesize the silicalite with a grain size of less than 500 nanometers as mentioned in the present invention according to the existing method. According to common practices in the art, the zeolite structure and zeolite grain size were confirmed by X-ray polycrystalline powder diffraction method and scanning (transmission) electron microscope method, respectively.

The zeolite powder obtained from hydrothermal synthesis belongs to the inactive sodium form raw powder. The former powder of sodium type zeolite is prepared into the said catalyst of the present invention, it should be made into hydrogen type catalyst at first according to the following steps:

Firstly, the raw sodium zeolite powder is dried and calcined at programmed temperature. The suitable temperature range for drying is that the drying atmosphere is an air atmosphere, and the drying time is 3 to 12 hours. The suitable temperature range for the temperature-programmed roasting is 300-600° C., the roasting atmosphere is air atmosphere, and the roasting time is 3-24 hours. The purpose of calcination is to remove the organic template agent occupied in the zeolite channel. The method of temperature programming can prevent the organic matter from burning too violently, thereby avoiding local overheating inside the zeolite crystal and destroying the zeolite crystal structure. As a special example, the drying is carried out at 110°C, and the drying time is 3 hours; the temperature-programmed roasting is carried out in a muffle furnace, and the heating method is: from room temperature to 300°C at a rate of 1°C/min. ℃, keep the temperature at 300℃ for 1 hour; then raise the temperature to 400℃ at the same heating rate, and keep the temperature at 400℃ for 1 hour; then raise the temperature to 500℃ at the same heating rate, and keep the temperature at 500℃ for 1 hour; The temperature was raised to 550° C. at the same heating rate, and the temperature was kept at 550° C. for 12 hours.

Secondly, mix the sodium zeolite powder that has taken off the organic template with a certain amount of alumina, and mix it with an appropriate amount of 10% dilute nitric acid (percentage by weight), and then press or extrude or spray or roll the ball according to the conventional method. forming. Wherein, the dry basis weight ratio of the small-crystalline zeolite to the alumina is preferably in the range of 1:9-9:1. If the content of zeolite is below this range, the activity and stability of the catalyst will be poor. On the contrary, if the content of zeolite is higher than this range, the catalyst particles are easily broken. After shaping, the granular sodium zeolite is dried and calcined. Suitable conditions for drying are as described above. The suitable conditions for firing are: air atmosphere, 500-600°C, 3-8 hours. The purpose of calcination here is to enhance the mechanical strength of the particles. As a special case, said zeolite molding is carried out on a twin-screw extruder, the rod diameter size is selected as 1 mm, and the dry basis weight ratio of zeolite to alumina is selected as 8:2, wherein the alumina is provided by boehmite . Drying was carried out at 110°C, and the drying time was 3 hours; roasting was carried out in a muffle furnace, and the heating method was as follows: directly increase the temperature from room temperature to 550°C at a rate of 3°C/min, and then keep the temperature for 3 hours.

Secondly, the formed small crystal grain zeolite particles are exchanged with ammonium salt to make a hydrogen catalyst. The ammonium salt exchange is carried out at room temperature, the appropriate range of the ammonium ion concentration of the exchange liquid used is 0.1-1.0 mol/liter, the appropriate range of the liquid-solid volume ratio of the exchange liquid to the zeolite particle solid is 1-100, and the number of exchanges is 1-5 times , each exchange time is 0.5 to 10 hours. After each exchange, discard the residual solution and add fresh exchange solution. Ammonium ions in the exchange liquid are provided by ammonium nitrate, ammonium chloride, ammonium acetate or ammonium carbonate and other ammonium salts. After all the ammonium exchange work was completed, the residual liquid was poured off, and the zeolite particles were washed once with deionized water. Then, the exchanged zeolite particles are dried and calcined. Suitable conditions for drying are as described above. The suitable conditions for firing are: air atmosphere, 500-600°C, 3-8 hours. The purpose of roasting here is to release ammonia and make the zeolite acidic. As a special example, said ammonium salt exchange uses 0.6M ammonium nitrate solution, the liquid-solid volume ratio of the exchange liquid and the zeolite particle solid is selected as 10, the number of exchanges is 4 times, and each exchange time is 1 hour. Drying was carried out at 110°C, and the drying time was 3 hours; roasting was carried out in a muffle furnace, and the heating method was as follows: directly increase the temperature from room temperature to 550°C at a rate of 3°C/min, and then keep the temperature for 3 hours.

On the basis of the above-mentioned hydrogen-type catalyst, further modification according to the following steps can obtain the said aromatization catalyst of the present invention:

First, the above-mentioned hydrogen-type zeolite catalyst is subjected to water vapor passivation treatment: water vapor treatment can be conveniently carried out in a well-known fixed-bed reactor, and water vapor treatment can use pure water vapor, or water vapor carried by air or nitrogen . It has been confirmed through research that when performing steam treatment, the appropriate volume percentage of water vapor in the atmosphere is 1% to 100%, and the balance gas is air or nitrogen; the suitable temperature range for steam treatment is 400-800°C; The suitable pressure range is from normal pressure to 5.0MPa; the suitable range of the water feed amount converted into pure water vapor (the weight of water passing through the cross-sectional area of the fixed bed reactor per unit time) is 0.1 to 1000 grams × hour ^-1 × square centimeter ^-1 . The suitable range of steam treatment time under the above conditions is 5 minutes to 200 hours.

Secondly, acid pore expansion treatment is carried out on the catalyst modified by steam treatment: acid pore expansion treatment can be conveniently carried out in an acid-resistant container. It has been confirmed by research that acid pore expansion treatment can choose the aqueous solution of any acid in hydrochloric acid, nitric acid or sulfuric acid, or the mixed acid solution of the above inorganic acids; you can also choose the aqueous solution of any acid in formic acid, acetic acid or citric acid, or Select the mixed acid solution of the above organic acids; in the case of selecting the above inorganic acids, the suitable range of hydrogen proton concentration in the acid solution is 0.001 mol/liter to 5.0 mol/liter; in the case of selecting the above organic acids, the solute in the acid solution The suitable range of weight percent concentration is 0.1%-20%; the acid hole expansion treatment is carried out under normal pressure, and the suitable temperature range is 1°C-80°C. Acid pore-enlarging treatment can be carried out under static conditions, or under the condition of circulating acid solution. Under the above conditions, the suitable time range for acid pore expansion is 0.5-200 hours. After acid pore expansion, the catalyst is washed to neutral with deionized water, then dried and calcined to obtain a finished catalyst. Drying was carried out at 110°C, and the drying time was 3 hours; roasting was carried out in a muffle furnace, and the heating method was as follows: directly increase the temperature from room temperature to 550°C at a rate of 3°C/min, and then keep the temperature for 3 hours.

Effect of the present invention can be evaluated with following method:

The acidity of the catalyst was evaluated by pyridine adsorption-infrared spectroscopy. Pyridine adsorption-infrared spectroscopy is a routine method in the art for distinguishing protic acid sites from Lewis acid sites. This method can simultaneously provide information on the acid strength of the catalyst. Any engineer familiar with the art can measure the acidity of the catalyst of the present invention according to the experimental procedure of the pyridine adsorption-infrared spectroscopy method recorded in the literature.

The smoothness of catalyst micropore diffusion was evaluated by the adsorption method of n-hexane and cyclohexane. Measuring the adsorption amount of hydrocarbon molecular probes such as n-hexane and cyclohexane is a conventional method used in this field to characterize the effective size of zeolite molecular sieve channels. The smoothness of micropores of zeolite catalysts can be characterized by the effective size of pores. When obstacles appear in the micropores of the zeolite catalyst during the modification process, the effective size of the pores will decrease. The more obstacles appear in the micropores, the greater the degree of reduction in the effective size of the zeolite pores. Conversely, when the obstacles in the zeolite micropores are removed, the effective size of the zeolite channels will be restored. Under the same adsorption conditions, for the same hydrocarbon molecular probe, the greater the adsorption amount measured in the same adsorption time, the faster the adsorption rate of the hydrocarbon molecular probe in the zeolite micropores, that is to say, the The larger the effective micropore size of the measured zeolite sample, the fewer obstacles in the channel; on the contrary, the smaller the adsorption amount measured in the same adsorption time, the slower the adsorption rate of the hydrocarbon molecular probe in the zeolite micropore , that is to say, the smaller the effective micropore size of the tested zeolite sample, the more obstacles in the channel. Any engineer familiar with the field can characterize the micropore diffusion smoothness of the catalyst of the present invention according to the experimental steps of the n-hexane and cyclohexane adsorption method recorded in the literature.

To evaluate the aromatization activity of the catalyst of the present invention and its anti-coking deactivation stability, a conventional fixed-bed pressurized reaction method is used. The raw material of the fixed bed reaction is C4 liquefied gas, and no carrier gas is used in the reaction process. As a special case, the raw material for the fixed bed reaction is the C4 liquefied gas by-product of the catalytic cracking unit, in which the content of various C4 olefins is not less than 50%. The range of suitable conditions for the reaction is: the reaction temperature is 300-500°C, the reaction pressure range is 0.1-5 MPa, and the feed space velocity (WHSV) of the C4 liquefied gas is 0.05-20h ^-1 . If the reaction temperature is too low or the feed space velocity is too high, it is not conducive to the olefin aromatization reaction. On the contrary, if the reaction temperature is too high or the feed space velocity is too small, the coking and deactivation of the catalyst will be severe.

The benefit of the effect of the present invention is: the catalyst is carried out aiming at adjusting its acid strength and the modification of Lewis acid and protonic acid ratio, can keep the diffusion unimpeded property of zeolite micropore in the catalyst; High-silica zeolite is used as the catalyst matrix, making the zeolite micropores in the catalyst more conducive to molecular diffusion. Therefore, the aromatization catalyst prepared by the invention has low reaction temperature, high aromatization activity and strong anti-coking deactivation ability. In addition, because the present invention has few modification steps for the catalyst and does not use metals, especially metals lacking in resources such as gallium, the cost of the catalyst prepared by the present invention is low.

Detailed ways

Specific embodiments of the present invention will be described in detail below in conjunction with technical solutions.

Catalyst Preparation Example 1: A hydrogen-type zeolite catalyst was prepared by using sodium-type ZSM-5 zeolite with a grain size of 20-50 nanometers.

(1) Removal of organic amine template agent treatment: take sodium ZSM-5 zeolite raw powder (SiO ₂ /Al ₂ O ₃ molar ratio 26) with a grain size of 20-50 nm, dry it at 110° C. for 3 hours, and then Carry out temperature-programmed roasting in a muffle furnace. The heating method is as follows: from room temperature to 300°C at a heating rate of 1°C/min, and keep the temperature at 300°C for 1 hour; Keep the temperature at ℃ for 1 hour; then raise the temperature to 500℃ at the same heating rate, and keep the temperature at 500℃ for 1 hour; then raise the temperature to 550℃ at the same heating rate, and keep the temperature at 550℃ for 12 hours.

(2) Molding: According to the weight ratio of zeolite to alumina on a dry basis of 8:2, take 80 grams of sodium zeolite (dry basis) and 20 grams of boehmite (dry basis) that have been burned with organic amine templates, and manually After mixing evenly, use 10% dilute nitric acid as a binder for kneading, and then use a twin-screw extruder for extrusion molding, and the diameter of the strip is selected as 1 mm. The extruded zeolite particles were dried at 110°C for 3 hours, and finally roasted in a muffle furnace. The heating method was as follows: from room temperature to 550°C at a rate of 3°C/min, and then kept at a constant temperature for 3 hours.

(3) Ammonium exchange to prepare a hydrogen-type catalyst: Ammonium exchange uses 0.6 mol/liter ammonium nitrate solution, the liquid-solid volume ratio of the exchange liquid to the zeolite particle solid is 10, exchange 4 times, each exchange time is 1 hour, and the middle exchange liquid. After the exchange, the zeolite particles were washed with deionized water and dried at 110° C. for 3 hours. Then, the deammonization gas was roasted in a muffle furnace, and the heating method was as follows: from room temperature to 550° C. at a rate of 3° C./min, and then kept at a constant temperature for 3 hours. So far, the hydrogen-type catalyst HZSM-5(A) was obtained.

Catalyst Preparation Example 2: A hydrogen-type zeolite catalyst with low molecular sieve content was prepared by using sodium-type ZSM-5 zeolite with a grain size of 20-50 nanometers.

Example 1 was repeated, but the weight ratio of 20-50 nm ZSM-5 zeolite (SiO ₂ /Al ₂ O ₃ molar ratio 26) to alumina was 50:50 on a dry basis. Accordingly, the obtained hydrogen-form catalyst was designated as HZSM-5(B).

Catalyst Preparation Example 3: A hydrogen-type zeolite catalyst was prepared by using sodium-type ZSM-5 zeolite with a grain size of 300-500 nm.

Repeat Example 1, but the grain size of the sodium ZSM-5 zeolite raw powder used is 300-500 nm (SiO ₂ /Al ₂ O ₃ molar ratio 26). Accordingly, the obtained hydrogen-form catalyst was designated as HZSM-5(C).

Catalyst Preparation Example 4: A hydrogen-type zeolite catalyst was prepared by using sodium-type ZSM-11 zeolite with a grain size of 100-500 nm.

Example 1 was repeated, but the raw sodium zeolite powder used was ZSM-11 (SiO ₂ /Al ₂ O ₃ molar ratio 26) with a grain size in the range of 100-500 nm. Accordingly, the obtained hydrogen-type catalyst was designated as HZSM-11.

Catalyst Preparation Example 5: A hydrogen-type zeolite catalyst was prepared by using sodium-type ZSM-8 zeolite with a grain size of 90-300 nm.

Example 1 was repeated, but the raw sodium zeolite powder used was ZSM-8 (SiO ₂ /Al ₂ O ₃ molar ratio 20) with a grain size in the range of 90-300 nm. Accordingly, the obtained hydrogen-form catalyst was designated as HZSM-8.

Catalyst Preparation Example 6: Preparation of the modified catalyst of the present invention from a hydrogen-type zeolite catalyst

Get each 3 grams of hydrogen-type zeolite catalysts HZSM-5 (A), HZSM-5 (B), HZSM-5 (C), HZSM-11 and HZSM-8 prepared by Catalyst Preparation Examples 1～Example 5 and mix them Process it into columnar particles of φ1×(2-3), and then sequentially install them in the constant temperature zone of a fixed-bed reactor with an inner diameter of φ7 for steam treatment. Steam treatment is carried out in 100% steam atmosphere, and the temperature of steam treatment is 550 ℃, and the pressure of steam treatment is normal pressure, and the water feeding amount of reactor (unit fixed-bed reactor cross-sectional area in unit time The weight of passing water) was 7.8 g×hour ⁻¹ ×square centimeter ⁻¹ , and the steam treatment time was 3 hours. Prepare 0.6 mol/L HNO ₃ aqueous solution (that is, the concentration of hydrogen protons in the acid solution is 0.6 mol/L) to carry out acid pore expansion treatment on the above-mentioned steam treatment catalyst. The conditions of the acid pore expansion treatment are: the liquid-solid mass ratio of the HNO ₃ solution to the catalyst is 5:1, the acid pore expansion treatment is carried out by static immersion under normal pressure and 25°C, and the immersion time is 24 hours. After acid pore expansion, the catalyst is washed to neutral with deionized water, then dried and calcined to obtain a finished catalyst. Drying was carried out at 110°C, and the drying time was 3 hours; roasting was carried out in a muffle furnace, and the heating method was as follows: directly increase the temperature from room temperature to 550°C at a rate of 3°C/min, and then keep the temperature for 3 hours. The catalysts modified through the above steps are successively recorded as SIHZSM-5(A), SIHZSM-5(B), SIHZSM-5(C), SIHZSM-11 and SIHZSM-8.

Catalyst Preparation Example 7: Using different steam treatment temperatures to prepare the modified catalyst of the present invention from a hydrogen-type zeolite catalyst

Get the hydrogen-type zeolite catalyst HZSM-5 (A) prepared by Catalyst Preparation Example 1, repeat Example 6, but the steam treatment temperature is respectively 450 ° C and 700 ° C, correspondingly, the steam treatment time is respectively 100 hours and After 0.5 hours, the obtained modified catalysts are SIHZSM-5(A)-01 and SIHZSM-5(A)-02 in turn.

Catalyst Preparation Example 8: Using different water vapor treatment atmospheres to prepare the modified catalyst of the present invention from a hydrogen-type zeolite catalyst

Get the hydrogen-type zeolite catalyst HZSM-5 (A) prepared by Catalyst Preparation Example 1, repeat Example 6, but feed air (through dedusting, carbon dioxide removal and drying treatment) and nitrogen (common steel cylinder) respectively in the steam treatment process Nitrogen, purity greater than 99%), in terms of ideal gas, the volume percentage of water vapor in the mixed gas is 15%, correspondingly, the water feed amount converted by pure water vapor (unit fixed bed reactor in unit time The weight of the water passing through the cross-sectional area) is 1.0 g × hour ^-1 × square centimeter ^-1 , the pressure of steam treatment is 2.0MPa, and the steam treatment time is 48 hours, then the obtained modified catalyst is SIHZSM -5(A)-03 and SIHZSM-5(A)-04.

Catalyst Preparation Example 9: The modified catalyst of the present invention is prepared by using different inorganic acid solutions to expand the pores of the water vapor treatment catalyst

Get the hydrogen-type zeolite catalyst HZSM-5 (A) prepared by Catalyst Preparation Example 1, repeat Example 6, but the acid solution used in the acid pore-enlarging step is respectively 0.01 mol/liter of nitric acid, 2 mol/liter of nitric acid, 0.6 mol/L hydrochloric acid, 0.6 mol/L sulfuric acid, mixed acid of 0.2 mol/L nitric acid and 0.2 mol/L sulfuric acid, then the obtained modified catalysts are SIHZSM-5(A)-05, SIHZSM-5(A) -06, SIHZSM-5(A)-07, SIHZSM-5(A)-08, SIHZSM-5(A)-09.

Catalyst Preparation Example 10: Using different organic acid solutions to expand the pores of the water vapor treatment catalyst to prepare the modified catalyst of the present invention

Get the hydrogen-type zeolite catalyst HZSM-5 (A) prepared by Catalyst Preparation Example 1, repeat Example 6, but the acid solution used in the acid pore expansion step is respectively 0.5% citric acid, 5% citric acid, 15% Citric acid, 5% formic acid, 5% acetic acid, a mixed acid composed of 2.5% formic acid and 2.5% acetic acid, the acid hole expansion treatment is carried out under normal pressure, but the temperature is 80 ° C, the acid solution circulates, and the time for acid hole expansion takes 120 hours. Then the modified catalyst obtained is successively SIHZSM-5(A)-10, SIHZSM-5(A)-11, SIHZSM-5(A)-12, SIHZSM-5(A)-13, SIHZSM-5(A) )-14, SIHZSM-5(A)-15.

Catalyst preparation example 11 (comparative example): the modification catalyst that only passes through steam treatment is prepared with the sodium type ZSM-5 zeolite that grain size is 20-50 nanometers

Get the hydrogen-type zeolite catalyst HZSM-5 (A) prepared by Catalyst Preparation Example 1, repeat Example 6, but the catalyst only carries out steam treatment, does not carry out acid pore expansion treatment, and the prepared modified catalyst is recorded as SHZSM -5(A).

Catalyst preparation example 12 (comparative example): the modified catalyst is prepared by using a large-grain sodium ZSM-5 zeolite with a grain size of 1000-2000 nanometers

Take the large-grain sodium ZSM-5 zeolite (SiO ₂ /Al ₂ O ₃ molar ratio 26) that the grain size is 1000-2000 nanometers, repeat the catalyst preparation example 1 and the catalyst preparation example 6, the obtained improved The active catalyst is recorded as SIHZSM-5 (LR).

Catalyst Characterization Example 1: Determination of Catalyst Acidity by Pyridine Adsorption Infrared Spectroscopy

Pyridine adsorption-infrared spectroscopy experiments were carried out according to conventional methods. Wherein, the sample purification temperature is 500° C., the vacuum degree is 0.07 Pa, the purification time is 1 hour, and the pyridine adsorption temperature is room temperature. After the adsorption of pyridine is saturated, the samples are degassed at 150°C and 350°C, respectively, and the infrared absorption spectrum is taken in the wave number range of 1000 cm ^-1 to 2000 cm ^-1 . According to generally accepted knowledge, the absorption peak of the sample at 1540 cm ^-1 was assigned to the protic acid center, while the absorption peak of the sample at 1450 cm ^-1 was assigned to the Lewis acid center. The present invention uses the relative peak height of the absorption peak corresponding to the protonic acid center and the Lewis acid center to represent the quantity of the protonic acid center and the Lewis acid center (expressed as the quantity of the acid center on the catalyst per unit weight, unit: mmol/g), with The ratio of the number of Lewis acid (L acid) centers and proton acid (B acid) centers of the sample at 150°C (ie: total L acid/total B acid) measures the adjustment effect of the modification on the catalyst Lewis acid center and proton acid center , using the sum of the number of Lewis acid sites and protonic acid sites (strong L acid + strong B acid) of the sample at 350°C to measure the effect of modification on the elimination of strong acid sites in the catalyst. The result is as follows:

Total L acid/total B acid strong L acid+strong B acid

HZSM-5(A): 1.39 0.36

HZSM-5(B): 1.42 0.21

HZSM-5(C): 1.25 0.43

HZSM-11: 1.30 0.31

HZSM-8: 1.20 0.25

SIHZSM-5(A): 2.43 0.20

SIHZSM-5(B): 2.50 0.11

SIHZSM-5(C): 2.20 0.23

SIHZSM-11: 2.50 0.18

SIHZSM-8: 2.29 0.12

SIHZSM-5(A)-01: 1.78 0.29

SIHZSM-5(A)-02: 3.56 0.08

SIHZSM-5(A)-03: 2.15 0.26

SIHZSM-5(A)-04: 2.11 0.25

SIHZSM-5(A)-05: 2.35 0.19

SIHZSM-5(A)-06: 2.50 0.20

SIHZSM-5(A)-07: 2.44 0.21

SIHZSM-5(A)-08: 2.39 0.19

SIHZSM-5(A)-09: 2.40 0.22

SIHZSM-5(A)-10: 2.08 0.18

SIHZSM-5(A)-11: 2.20 0.19

SIHZSM-5(A)-12: 2.50 0.15

SIHZSM-5(A)-13: 2.40 0.22

SIHZSM-5(A)-14: 2.42 0.20

SIHZSM-5(A)-15: 2.40 0.20

SHZSM-5(A) 2.00 0.18

SIHZSM-5(LR) 2.51 0.26

Catalyst Characterization Example 2: Evaluation of Catalyst Micropore Diffusion Smoothness by Adsorption of n-Hexane and Cyclohexane

The experiments for the determination of the adsorption capacity of n-hexane and cyclohexane were carried out according to the conventional practice. Among them, the sample was purified in a flowing nitrogen atmosphere for 30 minutes, the purification temperature was 350°C, the adsorption temperature was 25°C, the adsorbate partial pressure was 20 mmHg, the atmospheric pressure was 760 mmHg, and the adsorption time was 5 hours. In the present invention, the adsorption amount ratio of n-hexane and cyclohexane is defined as the constraint index of zeolite micropores in the catalyst. The present invention uses the constraint index of zeolite micropores to reflect the resistance of zeolite micropores to diffusion molecules: the larger the constraint index, the greater the resistance of zeolite micropores to diffusion molecules. The result is as follows:

Pore Constraint Index

HZSM-5(A): 1.12

HZSM-5(B): 1.10

HZSM-5(C): 1.16

HZSM-11: 1.13

HZSM-8: 1.11

SIHZSM-5(A): 1.14

SIHZSM-5(B): 1.13

SIHZSM-5(C): 1.16

SIHZSM-11: 1.14

SIHZSM-8: 1.15

SIHZSM-5(A)-01: 1.13

SIHZSM-5(A)-02: 1.15

SIHZSM-5(A)-03: 1.12

SIHZSM-5(A)-04: 1.13

SIHZSM-5(A)-05: 1.15

SIHZSM-5(A)-06: 1.11

SIHZSM-5(A)-07: 1.13

SIHZSM-5(A)-08: 1.13

SIHZSM-5(A)-09: 1.14

SIHZSM-5(A)-10: 1.16

SIHZSM-5(A)-11: 1.14

SIHZSM-5(A)-12: 1.10

SIHZSM-5(A)-13: 1.14

SIHZSM-5(A)-14: 1.14

SIHZSM-5(A)-15: 1.13

SHZSM-5(A) 1.25

SIHZSM-5(LR) 1.50

Aromatization reaction embodiment 1

Carry out aromatization reaction experiment in conventional fixed-bed pressurized reactor, reaction raw material is the C4 liquefied gas of catalytic cracking unit by-product, concrete composition is: isobutane (i ^C40 ): 26.24%, n-butane Alkane (n carbon four ⁰ ): 11.53%, normal isobutene (n, i carbon four ⁼ ): 29.54%, trans-butene (t carbon four ⁼ ): 18.60%, butene (c c four ⁼ ): 13.86% , carbon five (C ₅ ): 0.23%, do not use any carrier gas in the reaction process, catalyzer is SIHZSM-5 (A), and loading capacity is 2 grams, and reaction temperature is 400 ℃, and reaction pressure is 3MPa (reaction begins with Nitrogen pressurization), the feed space velocity (WHSV) of C4 liquefied gas is 0.8h ^-1 , sampling and analysis in the continuous reaction process, its C4 olefin conversion rate (X, %), C5 and above liquid yield (Y , weight %), aromatics content (Z, weight %) in gasoline and olefin content (W, weight %) in gasoline are respectively in reaction the 1st day, the 6th day and the 10th day:

SIHZSM-5(A) X, % Y, wt % Z, wt % W, wt %

Day 1 98 70 53 1.8

Day 6 98 73 49 2.1

Day 10 97 74 46 2.5

Aromatization reaction embodiment 2

Repeat aromatization reaction example 1, but the reaction temperature is 370 DEG C and 450 DEG C respectively, its C4 olefin conversion rate (X, %), the liquid recovery (Y, weight %) above carbon five, aromatics content in gasoline (Z , weight %) and olefin content (W, weight %) in the gasoline in the 6th day of reaction are:

SIHZSM-5(A) X, % Y, wt % Z, wt % W, wt %

370℃ 88 54 35 18.2

450℃ 99.5 77 64 1.5

Aromatization reaction embodiment 3

Repeat the aromatization reaction embodiment 1, but the reaction pressure is respectively 0.1MPa, 1.0MPa and 4MPa, its carbon four olefin conversion rate (X, %), the liquid recovery (Y, weight %) above carbon five, aromatic hydrocarbon content in gasoline (Z, weight %) and olefin content (W, weight %) in the gasoline in reaction the 6th day are:

SIHZSM-5(A) X, % Y, wt % Z, wt % W, wt %

0.1MPa 90 66 34 20

1.0Mpa 94 68 40 15

4.0Mpa 99 75 51 2.0

Aromatization reaction embodiment 4

Repeat the aromatization reaction example 1, but the feed space velocity (WHSV) of C4 liquefied gas is 0.1 ^-1 and 5h ^-1 respectively, the conversion rate of C4 olefins (X, %), and the liquid yield above C5 ( Y, weight %), aromatics content (Z, weight %) in gasoline and olefin content (W, weight %) in gasoline are at the 6th day of reaction:

SIHZSM-5(A) X, % Y, wt % Z, wt % W, wt %

WHSV＝0.1h ^-1 99 67 58 1.0

WHSV＝5h ^-1 75 48 29 26

Aromatization reaction embodiment 5

Repeat the aromatization reaction example 1, but the catalysts used are SIHZSM-5(B), SIHZSM-5(C), SIHZSM-11, SIHZSM-8, SIHZSM-5(A)-01, SIHZSM-5(A )-02, SIHZSM-5(A)-03, SIHZSM-5(A)-04, SIHZSM-5(A)-05, SIHZSM-5(A)-06, SIHZSM-5(A)-07, SIHZSM -5(A)-08, SIHZSM-5(A)-09, SIHZSM-5(A)-10, SIHZSM-5(A)-11, SIHZSM-5(A)-12, SIHZSM-5(A) -13, SIHZSM-5(A)-14, SIHZSM-5(A)-15, its carbon four olefins conversion rate (X, %), liquid yield (Y, weight %) above carbon five, aromatics content in gasoline ( Z, weight %) and olefin content (W, weight %) in gasoline are respectively on the 6th day of reaction:

X, % Y, wt % Z, wt % W, wt %

SIHZSM-5(B): 91 64 39 10.6

SIHZSM-5(C): 96 68 43 7.5

SIHZSM-11: 97 69 46 4.3

SIHZSM-8: 96 67 44 4.9

SIHZSM-5(A)-01: 86 53 34 18

SIHZSM-5(A)-02: 97 70 47 3.1

SIHZSM-5(A)-03: 93 65 43 5.2

SIHZSM-5(A)-04: 92 67 40 7.9

SIHZSM-5(A)-05: 95 64 41 8.3

SIHZSM-5(A)-06: 97 70 48 1.9

SIHZSM-5(A)-07: 97 69 47 2.2

SIHZSM-5(A)-08: 96 71 47 2.0

SIHZSM-5(A)-09: 95 63 42 4.7

SIHZSM-5(A)-10: 90 59 37 12.5

SIHZSM-5(A)-11: 93 61 40 8.0

SIHZSM-5(A)-12: 97 70 46 3.3

SIHZSM-5(A)-13: 94 62 42 7.0

SIHZSM-5(A)-14: 94 60 39 9.2

SIHZSM-5(A)-15: 93 58 37 11.4

Aromatization reaction embodiment 6 (comparative example)

Repeat the aromatization reaction example 1, but the catalysts used are SHZSM-5 (A), SIHZSM-5 (LR) successively, the conversion rate of carbon four olefins (X, %), and the liquid yield above carbon five (Y, weight % ), aromatics content (Z, weight %) in gasoline and olefin content (W, weight %) in gasoline are respectively at the 6th day of reaction:

X, % Y, % by weight Z, % by weight W, % by weight

SHZSM-5(A): 86 48 31 24

SIHZSM-5(LR): 80 42 24 29

Claims (4)

1. A preparation method of a catalyst for aromatizing C4 liquefied petroleum gas in a fixed-bed reactor, characterized in that the parent body of the catalyst is a high-silica zeolite with a grain size less than 500 nanometers, and the zeolite parent body and aluminum oxide After molding with a dry basis weight ratio of 1:9 to 9:1, use an ammonium ion solution with a concentration of 0.1 to 1.0 mol/liter to exchange it into a hydrogen-type catalyst according to a liquid-solid volume ratio of 1 to 100, and then heat it at 400 to 800°C Under high temperature, treat the above-mentioned hydrogen-type catalyst with water vapor for 5 minutes to 200 hours, and then use an acid solution at 1°C to 80°C to carry out acid pore expansion treatment on the above-mentioned steam-treated catalyst for 0.5 to 200 hours, and the obtained catalyst can be used at the reaction temperature. The temperature is 300℃～500℃, the reaction pressure is 0.1MPa～5MPa, the feeding space velocity of C4 liquefied petroleum gas is 0.05h ^-1 ～20h ^-1 and no carrier gas is used, in a fixed bed reactor Aromatization of C4 liquefied petroleum gas. 2. The preparation method according to claim 1, characterized in that the precursor of the catalyst refers to ZSM-5 zeolite, ZSM-8 zeolite or ZSM-11 zeolite with a grain size less than 500 nanometers. 3. preparation method according to claim 1 is characterized in that, the acid solution that is used for acid reaming process refers to hydrochloric acid solution, nitric acid solution, the mixed acid solution of sulfuric acid solution or above inorganic acid, requires the hydrogen proton in the acid solution The concentration satisfies 0.001 mol/liter to 5.0 mol/liter. 4. preparation method according to claim 1 is characterized in that, the acid solution that is used for acid reaming treatment is formic acid solution, acetic acid solution, the mixed acid solution of citric acid solution or above organic acid, requires the amount of solute in the acid solution The weight percent concentration satisfies 0.1%-20%.