Moving bed pellet catalyst for preparing propylene from refinery dry gas as well as preparation method and application thereof

Abstract

The invention discloses a moving bed pellet catalyst for preparing propylene from refinery dry gas as well as a preparation method and application of the moving bed pellet catalyst. The catalyst comprises: (1) a transition metal oxide-silicon oxide solid solution; (2) preparing an alkaline metal oxide-aluminum oxide solid solution; (3) kaolin; wherein the mass ratio of the transition metal oxide-silicon oxide solid solution to the alkaline metal oxide-aluminum oxide solid solution to the kaolin is (15-30): (60-80): (5-10). The catalyst provided by the invention is applied to the field of refinery dry gas chemical engineering utilization, and has the advantages of high conversion rate, good selectivity and excellent regeneration performance.

Description

Technical Field

[0001] The invention relates to the field of chemical utilization of refinery dry gas, and in particular to a moving bed pellet catalyst for preparing propylene from refinery dry gas, and a preparation method and application thereof. Background Art

[0002] Refinery dry gas mainly refers to tail gas from catalytic cracking, catalytic cracking, delayed coking and other units, which contains hydrogen, nitrogen, methane, ethylene, ethane, etc. At present, these dry gases are mainly used as low-grade fuels, which is particularly regrettable from the perspective of resource utilization. On the other hand, with the popularization of new energy vehicles and the commissioning of multiple large-scale refining and chemical integration projects in recent years, refining capacity has become oversupplied, and new refining units tend to choose deep catalytic cracking processes (such as DCC-plus, RTC, etc.) that produce more olefins and have higher ethylene content in dry gas. In addition, fuel-type refineries that have been put into production have also proposed new goals of transforming into chemical-type refineries. In the context of the above-mentioned "oil conversion", whether for refining and chemical units that have been built or are to be built, the recovery and utilization of ethylene in dry gas and high-value conversion have become the focus of attention of enterprises.

[0003] At present, there are two main ways to utilize ethylene in dry gas. One is to concentrate ethylene through methods such as cryogenic separation, membrane separation, pressure swing adsorption separation, and oil absorption separation, and then send it to the ethylene unit; the other way is to use the ethylene in the dry gas as a raw material directly through chemical conversion, such as dry gas superposition to produce isooctene, dry gas to produce ethylbenzene, etc. Among the above two types of technologies, ethylene separation and concentration technology is more suitable for large refineries due to investment and other reasons, and is not suitable for the oil conversion and upgrading needs of small and medium-sized refineries; and the existing dry gas direct chemical utilization technology is not smoothly promoted in small and medium-sized refineries due to constraints such as downstream product outlets and public utility supporting facilities. In this context, new technologies for the chemical utilization of dry gas with low development investment, simple operation, and flexible and rich downstream product lines are particularly attractive.

[0004] Olefin disproportionation is a process in which the C=C bonds of olefins are broken up, reorganized, and new molecules are formed under the action of a catalyst. In the field of basic organic chemical raw materials, a typical reaction is as follows: C4, mainly n-butene, reacts with excess polymerization-grade ethylene to generate propylene through double bond replacement and reorganization. CN200580045983.X proposes a method for producing propylene from a C4 feed containing 2-butene, the method comprising contacting the feed with ethylene in a metathesis reaction zone containing a metathesis catalyst of an oxide of a VIB or VIIB group metal under metathesis reaction conditions to provide an effluent containing propylene. CN202011126304.4 discloses a catalyst particle for olefin disproportionation reaction and a preparation method thereof, wherein a disproportionation catalyst and an isomerization catalyst are layered and integrated into a catalyst particle, which has good catalytic activity and stability when used for olefin disproportionation reaction. Although the above methods involve the reaction and catalyst of butene and ethylene disproportionation to produce propylene, pure ethylene or even polymerization grade ethylene is used as the source of ethylene raw material, and the refinery dry gas raw material is not involved. The main reason is that the refinery dry gas components are complex and the impurities are more, which will pose a major challenge to the stability of the catalyst. CN201510685645.8 pre-treats the refinery gas through pressure swing adsorption, dry gas concentration, dry gas refining and other steps and passes it into a fixed bed reactor at the same time with a C4 raw material containing butene. The ethylene and butene in the refinery gas are converted into propylene on the surface of the olefin double bond metathesis catalyst. After separation, the mixed material obtains ethane-rich C2 hydrocarbons, which can be directly used as a raw material for the cracking furnace of the ethylene device. Although the method proposes to convert ethylene in the refinery gas into propylene by olefin disproportionation reaction, the main purpose is to obtain ethane-rich material. Therefore, in order to improve the single-pass conversion rate of ethylene, the method adopts a feeding scheme with a large amount of excess butene (the molar ratio of butene to ethylene is (8:1) to (2:1)), which is not conducive to the improvement of propylene selectivity in the product. Furthermore, this method does not address the stability of the catalyst in dry gas application scenarios. Summary of the invention

[0005] In order to solve the problem of poor stability and selectivity of olefin disproportionation catalysts when applied to refinery dry gas chemical utilization scenarios, the present invention provides a moving bed pellet catalyst for preparing propylene from refinery dry gas and its preparation method and application. The catalyst of the present invention has extremely high strength and good fluidity, and can be used for the moving bed catalytic reaction of preparing propylene from refinery dry gas disproportionation to achieve stable production of propylene.

[0006] The first aspect of the present invention provides a moving bed pellet catalyst for preparing propylene by disproportionation of refinery dry gas, comprising: (1) a transition metal oxide-silicon oxide solid solution; (2) an alkaline metal oxide-aluminum oxide solid solution; and (3) kaolin. The mass ratio of the transition metal oxide-silicon oxide solid solution: the alkaline metal oxide-aluminum oxide solid solution: the kaolin is 15-30: 60-80: 5-10.

[0007] In the above technical solution, the mass ratio of transition metal oxide to silicon oxide is 0.05-0.18, and the mass ratio of basic metal oxide to aluminum oxide is 0.05-0.25.

[0008] In the above technical solution, the alkaline metal oxide-alumina solid solution is an alkali metal oxide-alumina solid solution, an alkaline earth metal oxide-alumina solid solution, or an alkali metal oxide and an alkaline earth metal oxide-alumina solid solution.

[0009] In the above technical solution, in the catalyst, based on the weight of the catalyst, the total content of transition metal oxides and silicon oxide is 15% to 30%, the total content of basic metal oxides and aluminum oxide is 60% to 80%, and the content of kaolin is 5% to 10%.

[0010] In the above technical solution, the transition metal element is selected from at least one of the VIB group elements or the VIIB group elements, preferably at least one of the VIB group elements Mo and W, and more preferably W; the alkaline metal is selected from at least one of the alkali metals and alkaline earth metals, the alkali metal element is selected from Na or K, preferably K, and the alkaline earth metal element is selected from Mg or Ca, preferably Mg.

[0011] In the above technical solution, the average size of the pellet catalyst is 2 to 5 mm, and the crushing strength of the catalyst particles is ≥80N / particle.

[0012] The present invention provides a method for preparing the above-mentioned refinery dry gas to propylene moving bed pellet catalyst, comprising:

[0013] (1) preparing a transition metal oxide-silicon oxide solid solution;

[0014] (2) preparing a basic metal oxide-alumina solid solution;

[0015] (3) The solid solution of step (1), the solid solution of step (2) and kaolin are mixed, and the mixture is subjected to ball rolling, curing, drying and calcining to obtain the catalyst.

[0016] In the above technical solution, in step (1), the solid solution is prepared by equal volume impregnation or mechanical mixing. Specifically, the silicon oxide carrier is impregnated with an equal volume of a transition metal salt solution or the silicon oxide carrier and the transition metal salt are mechanically mixed and ground to obtain a precursor, which is dried and calcined to obtain a transition metal oxide-silicon oxide solid solution, which is then powdered and sieved for later use.

[0017] In the above technical solution, in step (1), when an equal volume impregnation method is adopted, the transition metal salt is dissolved in deionized water, and the mass ratio of salt to water is 1:1 to 1:100, preferably 1:3 to 1:30. The mass ratio of the transition metal salt to silicon oxide is 0.05 to 0.18. The transition metal salt is selected from at least one of the nitrate or ammonium salt of the transition metal, preferably ammonium metatungstate.

[0018] In the above technical solution, in step (1), the drying conditions are: temperature of 60-150°C, preferably 80-120°C, time of 8-48h, preferably 10-18h. The roasting conditions are: temperature of 400-650°C, preferably 450-560°C, time of 0.5-6h, preferably 1-6h.

[0019] In the above technical solution, in step (1), the particle size of the solid solution after powdering and sieving is 400-800 mesh.

[0020] In the above technical solution, in step (2), the solid solution is prepared by equal volume impregnation or mechanical mixing. Specifically, the alumina carrier is impregnated with an alkaline metal salt solution in equal volume or the alumina carrier and the alkaline metal salt are mechanically mixed and ground to obtain a precursor, which is dried and calcined to obtain an alkaline metal oxide-alumina solid solution, which is then powdered and sieved for later use.

[0021] In the above technical solution, in step (2), when the equal volume impregnation method is adopted, the alkaline metal salt is dissolved in deionized water, and the mass ratio of salt to water is 1:1 to 1:100, preferably 1:3 to 1:30. The mass ratio of the alkaline metal in terms of oxide to silicon oxide is 0.05 to 0.25. The alkaline metal salt is selected from at least one of nitrate and acetate.

[0022] In the above technical solution, in step (2), the drying conditions are: temperature of 60-150°C, preferably 80-120°C, time of 8-48h, preferably 10-18h. The roasting conditions are: temperature of 400-650°C, preferably 450-560°C, time of 0.5-6h, preferably 1-6h.

[0023] In the above technical solution, in step (2), the particle size of the solid solution after powdering and sieving is 400-800 mesh.

[0024] In the above technical solution, in step (3), the rolling ball is made of a mixture of the solid solution obtained in step (1) and step (2) and kaolin, and is rolled in a rolling ball machine to obtain small balls. The mass ratio of the solid solution in step (1): the solid solution in step (2): kaolin is 15-30: 60-80: 5-10.

[0025] In the above technical scheme, in step (3), the curing conditions are: temperature of 25-40°C, time of 8-48h. The drying conditions are: temperature of 60-150°C, preferably 80-120°C, time of 8-48h, preferably 10-18h. The roasting conditions are: temperature of 400-650°C, preferably 450-560°C, time of 0.5-6h, preferably 1-6h.

[0026] The third aspect of the present invention provides a method for preparing propylene by disproportionation of dry gas and C4, comprising mixing a dry gas feedstock containing ethylene with a C4 feedstock containing butene, and then contacting the mixture with the above-mentioned moving bed pellet catalyst to react to obtain propylene.

[0027] In the above technical scheme, the hydrogen content in the dry gas raw material containing ethylene is controlled below 1 vol%, the isobutylene content in the C4 raw material containing butene is controlled below 5 wt%, and the butadiene content is controlled below 1 wt%.

[0028] In the above technical scheme, the ethylene content in the dry gas raw material containing ethylene is above 20 vol%, and the total content of 1-butene and 2-butene in the C4 raw material containing butene is above 30 wt%.

[0029] In the above technical scheme, the reaction temperature is 250-350°C; the reaction pressure is 1.0-3.0MPa; the total weight space velocity of the dry gas raw material and the C4 raw material is 1.0-4.0h -1 ; The molar ratio of ethylene:butene at the reactor inlet is 0.5 to 1.5.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The catalyst of the present invention is a moving bed olefin disproportionation pellet catalyst containing dual active sites, that is, it contains two types of active sites, namely, disproportionation and isomerization, wherein the disproportionation active site catalyzes the reaction of ethylene and 2-butene to generate propylene, and the isomerization active site converts 1-butene into 2-butene. The two active sites work together to enable the catalyst to fully convert ethylene and butene in the raw materials. In order to avoid the loss and mutual coverage of the two types of active sites of the moving bed catalyst during continuous regeneration, the present invention uses a step-by-step preparation method to place the disproportionation and isomerization dual active sites on different carriers, and then the two types of powders containing different active sites are fully mixed with kaolin, and high-strength spherical olefin disproportionation catalyst particles are formed by rolling. The coexistence of the two types of active sites at the micrometer scale in the same catalyst particle enables the catalyst to have higher activity, selectivity, and excellent regeneration performance.

[0032] 2. The catalyst of the present invention is applied to the field of dry gas chemical utilization in refineries. After pre-treated dry gas that meets the standards is mixed with C4, it is efficiently converted into propylene through a moving bed reactor loaded with the catalyst, and a high-purity propylene product can be further obtained by separation. The catalyst has high conversion rate, good selectivity, and good regeneration performance. Among them, the selectivity of propylene obtained by the reaction is above 90%, and the single-pass conversion rate of ethylene in dry gas is above 50%. The moving bed catalyst can better solve the problem that the olefin disproportionation catalyst is sensitive to impurities in the dry gas of refineries and is easily poisoned and deactivated, providing a new alternative for the chemical utilization of dry gas. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0034] The raw materials used in the examples of the present invention are all conventional commercially available raw materials.

[0035] Example 1

[0036] WO3 / SiO2 solid solution (WO3:SiO2 (mass ratio) = 0.054). Weigh 100kg of 99.5% pure silicon dioxide powder and 6kg of ammonium metatungstate (WO3≥90%). Dissolve the above tungsten salt in 20kg of deionized water, and soak the silicon dioxide powder in equal volume for 6h. Then put the impregnated silicon dioxide into an oven, dry it at 120℃ for 12h, and calcine it at 450℃ for 4h to obtain WO3 / SiO2 solid solution. After powdering, pass through a 400-800 mesh sieve for use.

[0037] Example 2

[0038] WO3 / SiO2 solid solution (WO3:SiO2 (mass ratio) = 0.144). Weigh 100kg of 99.5% pure silicon dioxide powder and 16kg of ammonium metatungstate (WO3≥90%). Mix the above tungsten salt and silicon dioxide powder, grind them evenly, and calcine them at 550℃ for 4h to obtain WO3 / SiO2 solid solution. After powdering, pass through a 400-800 mesh sieve for use.

[0039] Example 3

[0040] MgO / Al2O3 solid solution (MgO:Al2O3 (mass ratio) = 0.093). Weigh 100kg of γ-Al2O3 and 50kg of magnesium acetate tetrahydrate. Dissolve the above magnesium salt in 150kg of deionized water, and soak the alumina powder in equal volume for 6h. Then put the impregnated alumina into an oven, dry it at 80℃ for 12h, and calcine it at 520℃ for 4h to obtain the MgO / Al2O3 solid solution. After powdering, pass through a 400-800 mesh sieve for use.

[0041] Example 4

[0042] K2O / Al2O3 solid solution (K2O:Al2O3 (mass ratio) = 0.204). Weigh 100kg of γ-Al2O3 and 30kg of potassium carbonate, then mix the above potassium carbonate and alumina powder, grind them evenly, and calcine them at 550°C for 4h to obtain K2O / Al2O3 solid solution. After powdering, sieve through 400-800 mesh for later use.

[0043] Example 5

[0044] Weigh 20kg of the solid solution of Example 1, 70kg of the solid solution of Example 3 and 10kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled at 2-3mm. In order to make the powders stick to each other, water is sprayed appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24h, they are sent to a 120℃ oven for drying for 12h, and the finished ball catalyst A is obtained after being roasted at 550℃ for 4h.

[0045] Example 6

[0046] Weigh 30kg of the solid solution of Example 1, 60kg of the solid solution of Example 4 and 10kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled at 3-4mm. In order to make the powders stick to each other, water is sprayed appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24h, they are sent to a 120℃ oven for drying for 18h, and the finished ball catalyst B is obtained after being roasted at 550℃ for 4h.

[0047] Example 7

[0048] Weigh 15kg of the solid solution of Example 2, 80kg of the solid solution of Example 3 and 5kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled at 2-3mm. In order to make the powders stick to each other, water is sprayed appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24h, they are sent to a 120℃ oven for drying for 10h, and the finished ball catalyst C is obtained after being roasted at 550℃ for 3h.

[0049] Example 8

[0050] Weigh 25kg of the solid solution of Example 2, 65kg of the solid solution of Example 4 and 10kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled at 4-5mm. In order to make the powders stick to each other, water is sprayed appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24h, they are sent to a 120℃ oven for drying for 24h, and then calcined at 500℃ for 6h to obtain the finished ball catalyst D.

[0051] Comparative Example 1

[0052] Weigh 5 kg of the solid solution of Example 1, 90 kg of the solid solution of Example 3 and 5 kg of kaolin, and mix them in a kneader in the form of dry powder for 2 hours. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled at 2 to 3 mm. In order to make the powders stick to each other, water is sprayed appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24 hours, they are sent to a 120°C oven for drying for 12 hours, and the finished ball catalyst E is obtained after being calcined at 550°C for 4 hours.

[0053] Comparative Example 2

[0054] Weigh 75kg of the solid solution of Example 1, 20kg of the solid solution of Example 3 and 5kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled at 2-3mm. In order to make the powders stick to each other, water is sprayed appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24h, they are sent to a 120℃ oven for drying for 12h, and the finished ball catalyst F is obtained after being roasted at 550℃ for 4h.

[0055] Comparative Example 3

[0056] Weigh 20 kg of the solid solution of Example 2 and 80 kg of the solid solution of Example 3, and mix them in a kneader in the form of dry powder for 2 hours. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled to be 2-3 mm. After the formed balls are cured at room temperature for 24 hours, they are sent to a 120°C oven for drying for 10 hours, and calcined at 550°C for 3 hours to obtain the finished ball catalyst G.

[0057] Comparative Example 4

[0058] Weigh 15kg of the solid solution of Example 1, 60kg of the solid solution of Example 3 and 25kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained mixed powder is rolled into balls in a ball rolling machine, and the ball size is controlled at 2-3mm. In order to make the powders stick to each other, water is sprayed appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24h, they are sent to a 120℃ oven for drying for 12h, and the finished ball catalyst H is obtained after being calcined at 550℃ for 4h.

[0059] Comparative Example 5

[0060] Weigh 15kg of 99.5% pure silica powder and 60kg of γ-Al2O3 powder, mix them and mix them in a kneader in the form of dry powder for 2h. Dissolve 1.2kg of ammonium metatungstate and 5.6kg of magnesium acetate tetrahydrate in deionized water, and soak the mixed powder of silica and alumina in equal volumes for 6h. Put the impregnated powder into an oven and dry it at 120℃ overnight. After drying, beat the powder, pass it through a 400-800 mesh sieve, add 10kg of kaolin and mix evenly, and roll it into balls. In order to make the powders stick to each other, spray water appropriately during the rolling process according to the ball formation. After the formed balls are cured at room temperature for 24h, they are sent to a 120℃ oven for drying for 12h, and calcined at 550℃ for 4h to obtain the finished ball catalyst I.

[0061] Comparative Example 6

[0062] Weigh 15kg of the solid solution of Example 2 and 1.5kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained powder is rolled into balls in a ball rolling machine, and the sphere size is controlled at 2-3mm. Weigh 80kg of the solid solution of Example 3 and 3.5kg of kaolin, and mix them in a kneader in the form of dry powder for 2h. The obtained powder is rolled into balls in a ball rolling machine, and the sphere size is controlled at 2-3mm. In order to make the powders bond to each other, spray water appropriately during the rolling process according to the sphere formation. After the two kinds of small balls are formed, they are cured at room temperature for 24h, sent to a 120℃ oven for drying for 10h, and calcined at 550℃ for 3h. Thereafter, the two small balls are mechanically mixed evenly to obtain the finished small ball catalyst J.

[0063] Example 9

[0064] Catalyst strength determination. The crushing strength of the pellet catalysts prepared in Examples 5-8 (catalysts AD) and Comparative Examples 1-6 (catalysts EJ) was measured using a Dalian Penghui DL4 intelligent particle strength tester and the average value was taken. The results are shown in Table 2. From the test results, it can be seen that the crushing strength of the pellet catalyst G without kaolin is low and cannot fully meet the requirements of the moving bed catalyst.

[0065] Table 1 Composition of the pellet catalyst obtained in each example

[0066]

[0067]

[0068] Table 2 Crushing strength of the pellet catalyst obtained in each example

[0069]

[0070] Example 10

[0071] Catalyst performance evaluation. The catalysts prepared in Examples 5-8 (catalysts AD) and Comparative Examples 1-6 (catalysts EJ) were tableted, crushed, and sieved, and 20-40 mesh catalysts were loaded into a moving bed reactor with a diameter of 8 mm. The catalysts were activated with air and high-purity nitrogen at a high temperature of 550°C to fully expose the active sites. Thereafter, ethylene (20 vol%, the remainder being methane) and carbon tetrachloride (1-butene, 99.5 wt%) were introduced into the reaction tube and entered the catalyst bed for reaction. The reaction temperature was 290°C, the pressure of the reaction system was 2.0 MPa, and the raw material reaction space velocity was 1.0 h -1 The disproportionation reaction was carried out under the condition that the ethylene:butene (molar ratio) was 0.5. The reaction results are shown in Table 3.

[0072] Table 3 Catalytic performance of the pellet catalysts obtained in each example

[0073]

[0074]

[0075] Embodiment 11

[0076] Catalyst regeneration. The deactivated catalyst was selected for online regeneration, and the catalyst was charred and activated with air and high-purity nitrogen at a high temperature of 550°C, respectively, to expose the active sites again. The performance of the catalyst was evaluated immediately after regeneration. The above process was repeated multiple times to examine the catalyst regeneration performance, and the results are shown in Tables 4 and 5. It can be seen that Example 7 (catalyst C) has good regeneration performance for multiple times, and after regeneration of Comparative Example 6 (catalyst J), the disproportionation catalytic component and the isomerization catalytic component are gradually stratified due to the moving bed, and the catalytic activity shows a gradual downward trend with each regeneration.

[0077] Table 4 Regeneration performance of pellet catalyst C

[0078]

[0079] Table 5 Regeneration performance of pellet catalyst J

[0080]

[0081] The above describes the specific implementation of the present invention in detail, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features being combined in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A moving bed pellet catalyst for preparing propylene by disproportionation of refinery dry gas, comprising: (1) Transition metal oxide-silicon oxide solid solution; (2) basic metal oxide-alumina solid solution; (3) Kaolin; wherein the mass ratio of transition metal oxide-silicon oxide solid solution: basic metal oxide-aluminum oxide solid solution: kaolin is 15-30:60-80:5-10.

2. The catalyst according to claim 1, characterized in that: In the catalyst, based on the weight of the catalyst, the total content of transition metal oxide and silicon oxide is 15% to 30%, the total content of basic metal oxide and aluminum oxide is 60% to 80%, and the content of kaolin is 5% to 10%; And / or, the mass ratio of the basic metal oxide to aluminum oxide is 0.05 to 0.25, and the mass ratio of the transition metal oxide to silicon oxide is 0.05 to 0.

18.

3. The catalyst according to claim 1, characterized in that: The transition metal element is selected from at least one of the Group VIB elements or the Group VIIB elements, preferably at least one of the Group VIB elements Mo and W, and more preferably W; the alkaline metal is selected from at least one of an alkali metal and an alkaline earth metal, the alkali metal element is selected from Na or K, and preferably K; the alkaline earth metal element is selected from Mg or Ca, and preferably Mg.

4. The catalyst according to claim 1, characterized in that: The average size of the catalyst is 2 to 5 mm, and the crushing strength of the catalyst particles is ≥80N / particle.

5. A method for preparing the catalyst according to any one of claims 1 to 4, comprising: (1) preparing a transition metal oxide-silicon oxide solid solution; (2) preparing a basic metal oxide-alumina solid solution; (3) The solid solution of step (1), the solid solution of step (2) and kaolin are mixed, and the mixture is subjected to ball rolling, curing, drying and calcining to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that: In step (1) or step (2), the solid solution is prepared by equal volume impregnation or mechanical mixing.

7. The preparation method according to claim 6, characterized in that: In step (1), when an equal volume impregnation method is adopted, the transition metal salt is dissolved in deionized water, and the mass ratio of salt to water is 1:1 to 1:100, preferably 1:3 to 1:30; And / or, in step (2), when an equal volume impregnation method is adopted, the alkaline metal salt is dissolved in deionized water, and the mass ratio of salt to water is 1:1 to 1:100, preferably 1:3 to 1:

30.

8. The preparation method according to claim 5, characterized in that: In step (1) or step (2), the particle size of the solid solution after powdering and sieving is independently selected from 400 to 800 meshes.

9. The preparation method according to claim 5, characterized in that: In step (3), the curing conditions are: temperature of 25 to 40° C., and time of 8 to 48 hours; And / or, the drying conditions are: temperature of 60 to 150° C., preferably 80 to 120° C., time of 8 to 48 hours, preferably 10 to 18 hours; And / or, the calcination conditions are: temperature of 400-650° C., preferably 450-560° C., and time of 0.5-6 h, preferably 1-6 h.

10. A method for preparing propylene by disproportionation of dry gas and C4, comprising mixing a dry gas feedstock containing ethylene and a C4 feedstock containing butene, and then contacting the mixture with a moving bed pellet catalyst according to any one of claims 1 to 4 to react and obtain propylene.

11. The method according to claim 10, characterized in that: The hydrogen content in the dry gas containing ethylene is controlled below 1 vol%, the isobutylene content in the C4 raw material containing butene is controlled below 5 wt%, and the butadiene content is controlled below 1 wt%.

12. The method according to claim 10, characterized in that: The reaction temperature is 250-350°C; the reaction pressure is 1.0-3.0MPa; the total weight space velocity of the raw materials is 1.0-4.0h -1 ; The ethylene:butene (molar ratio) at the reactor inlet is 0.5 to 1.5.

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