C5 mixed hydrocarbon co-cracking catalysts, their preparation methods and applications

Abstract

This invention discloses a co-cracking catalyst for C5 mixed hydrocarbons, its preparation method, and its applications. The catalyst has a core-shell structure, with the core being a ZSM-5 molecular sieve modified with rare earth elements, and the shell being alumina. This catalyst is suitable for the co-cracking of C5 mixed hydrocarbons to produce propylene and ethylene. The C5 olefins and C5 alkanes in the C5 mixed hydrocarbons can undergo co-cracking to produce propylene and ethylene, and it features high feed conversion rate, good catalyst stability, and high yield of propylene and ethylene products.

Description

Technical Field

[0001] This invention belongs to the field of catalytic cracking, specifically relating to a catalyst for increasing the production of propylene and ethylene through co-cracking of C5 mixed hydrocarbons, its preparation method, and its application. Background Technology

[0002] Propylene and ethylene are important basic organic chemical raw materials, mostly derived from steam cracking and catalytic cracking units. Driven by the rapid growth in demand for polyolefins and their derivatives, the demand for propylene and ethylene has remained strong and grown at a rapid pace in recent years, thus being considered products with great market potential. To increase propylene and ethylene production, various countries have developed other methods for producing low-carbon olefins, such as the butene disproportionation (OMT) process, which uses the reaction of ethylene and butene to increase propylene production; propane dehydrogenation (PDH) process, which directly utilizes shale gas byproducts in chemical processes; and methanol-to-olefins (MTP / MTO) technology, which uses coal-based methanol to produce propylene and ethylene. Furthermore, utilizing the large quantities of C4 and C5 hydrocarbons generated by ethylene plants, FCC units, and MTO units to increase propylene and ethylene production through catalytic cracking of olefins is also an important research and development direction for petrochemical companies worldwide.

[0003] Currently, the main industrialized olefin cracking processes for increasing propylene and ethylene production include Asahi Kasei's Omega process and UOP's OCP process. Both processes use ZSM-5 molecular sieves as catalysts and mixed C4 / C5 monoolefins as byproducts from FCC, ethylene plants, or MTO as feedstock. The OCP and Omega processes do not add any diluents during the reaction, and are characterized by high space velocity, small reactor size, and high propylene space-time yield. The catalyst regeneration cycle is 2-3 days, requiring frequent switching for regeneration. Asahi Kasei's Omega process was industrially applied in 2006. UOP combines methanol-to-olefins (MTO) with OCP, characterized by high propylene and ethylene yields and fewer byproducts. CN98813467.5 discloses a process using crystalline silicate with a silicon / aluminum ratio of 180-1000 as a catalyst at 500-600°C and a space velocity of 10-30 h⁻¹. -1 The following method describes a process for cracking a feedstock rich in C4 and / or other olefins into a feedstock rich in light olefins such as propylene, where the total amount of olefins remains essentially unchanged before and after the reaction. CN99801204.1 discloses a method for producing ethylene and propylene from hydrocarbon feedstocks via catalytic conversion. This method includes using a ZSM-5 molecular sieve containing at least one C4-C4 olefin, with a silicon-aluminum molar ratio of 200–5000 and essentially free of protic acids, as a catalyst to crack a feedstock containing at least one C4-C4 olefin. 12 Olefins are cracked and converted into ethylene and propylene.

[0004] The C5 components produced as byproducts from refineries and ethylene plants are complex, with high levels of impurities such as organic sulfur and nitrogen. In addition to C5 olefins, there are also large amounts of C5 alkanes. C5 olefins are highly reactive, making catalysts more prone to carbon deposition during cracking reactions, while alkanes are stable. These factors lead to low yields of propylene and ethylene products and short catalyst operating cycles, necessitating the development of high-performance catalysts for co-cracking of C5 mixed hydrocarbons to increase propylene and ethylene production. Summary of the Invention

[0005] The technical problem this invention aims to solve is that existing technologies can only catalytically crack olefins or alkanes in C5 mixed hydrocarbons to propylene and ethylene, but cannot achieve the co-cracking of olefins and alkanes in C5 mixed hydrocarbons under the same catalyst and process conditions. This results in low conversion rates and low yields of propylene and ethylene from the catalytic cracking of C5 mixed hydrocarbons. This invention provides a catalyst for increasing the production of ethylene and propylene through co-cracking of C5 mixed hydrocarbons, its preparation method, and its application. This catalyst is suitable for the reaction of producing propylene and ethylene from the co-cracking of C5 mixed hydrocarbons. C5 olefins and C5 alkanes in the C5 mixed hydrocarbons can undergo co-cracking to produce propylene and ethylene, and it features high feed conversion rate, good catalyst stability, and high yield of propylene and ethylene products.

[0006] The first aspect of this invention provides a C5 mixed hydrocarbon co-cracking catalyst, wherein the catalyst has a core-shell structure, the core being a ZSM-5 molecular sieve modified with rare earth elements, and the shell being alumina. Preferably, the mass ratio of the core to the shell is 0.1 to 5:1.

[0007] According to the present invention, the modifying elements in the catalyst preferably include rare earth elements and alkaline earth metal elements. Further, the mass ratio of rare earth elements to alkaline earth metal elements is 0.05–300, preferably 0.05–2. The rare earth elements and alkaline earth metal elements synergistically improve the catalytic performance of the catalyst, particularly increasing the conversion rate of the feedstock and the yield of the product.

[0008] According to the present invention, the content of the modifying element in the catalyst is 0.01% to 4%, preferably 0.05% to 3%, based on the weight of the core layer of the catalyst.

[0009] According to the present invention, based on the weight of the core layer of the catalyst, the content of rare earth elements is preferably 0.05% to 3%, more preferably 0.05% to 2%.

[0010] According to the present invention, the content of alkaline earth metals is 0.01% to 1%, preferably 0.1% to 1%, based on the weight of the core layer of the catalyst.

[0011] According to the present invention, the rare earth elements include one or more of La, Ce, Pr and Nd.

[0012] According to the present invention, the alkaline earth metal element includes one or more of Mg, Ca, Sr and Ba.

[0013] According to the present invention, the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 50 to 1000.

[0014] According to the present invention, the ZSM-5 molecular sieve is a hydrogen-form molecular sieve.

[0015] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, the method comprising the following steps:

[0016] (1) Disperse boehmite in a dispersant to form an aluminum hydroxide slurry;

[0017] (2) The aluminum hydroxide slurry obtained in step (1) is mixed with the ZSM-5 molecular sieve modified by the modifying element, dried, and calcined to obtain the catalyst.

[0018] According to the present invention, the dispersant in step (1) is a mixture of dilute nitric acid solution and ethanol. And / or preferably, the concentration of nitric acid in the dilute nitric acid solution is 1 wt% to 10 wt%. And / or preferably, the volume ratio of dilute nitric acid to ethanol is 1 to 8:1. And / or preferably, the dispersion temperature is 30 to 80°C. And / or preferably, the mass ratio of boehmite to dispersant is 1:2 to 5.

[0019] According to the present invention, the molecular sieve in step (2) is preferably a ZSM-5 molecular sieve modified with rare earth elements and alkaline earth metal elements.

[0020] According to the present invention, the drying and calcination in step (2) are performed under conventional operating conditions. For example, but not limited to, a drying temperature of 80–120°C; and / or a drying time of 5–20 hours. For example, a calcination temperature of 450–600°C; and / or a drying time of 4–12 hours.

[0021] According to the present invention, the method for modifying ZSM-5 molecular sieves with modifying elements in step (2) can be prepared by conventional methods, preferably by impregnation. The impregnation method is preferably equal-volume impregnation.

[0022] A third aspect of the present invention provides the application of the above-mentioned catalyst in the co-cracking reaction of C5 mixed hydrocarbons to produce propylene and ethylene.

[0023] According to the present invention, the C5 mixture is derived from refinery C5 mixtures. And / or preferably, the C5 mixture comprises at least one pentane and at least one pentene. And / or preferably, the pentane comprises one or more of n-pentane, isopentane, and neopentane. And / or preferably, the pentene refers to a mono-olefin, including one or more of 1-pentene, cis-2-pentene, trans-2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene. Preferably, the weight ratio of pentene to pentane is 0.5 to 2:1.

[0024] According to the present invention, the preferred reaction temperature is 500–700°C, more preferably 550–650°C.

[0025] According to the present invention, the reaction pressure is preferably 0 to 1.0 MPa, more preferably 0.03 to 0.8 MPa.

[0026] According to the present invention, the preferred weight hourly space velocity (WHSV) of the C5 mixed hydrocarbons is 1–30 h⁻¹. -1 More preferably 2-20h -1 .

[0027] According to the present invention, the reaction for producing propylene and ethylene by co-cracking of C5 mixed hydrocarbons can be carried out using a moving bed reactor or a fluidized bed reactor, preferably a fixed bed reactor.

[0028] Currently, in the catalytic cracking of mixed C5 hydrocarbons to propylene and ethylene, simultaneous cracking of pentene and pentane under the same reaction conditions is not possible, resulting in low feedstock conversion rates and low propylene and ethylene yields. This is mainly because pentene and pentane have different stability and cracking mechanisms. Pentene is highly reactive and cracking can occur at lower temperatures, while pentane is relatively stable and requires higher reaction temperatures for cracking. Therefore, under the reaction conditions for pentene catalytic cracking, pentane hardly reacts. Furthermore, under the catalyst and reaction conditions for pentane cracking, there are too many byproducts from pentene cracking, resulting in lower yields of propylene and ethylene compared to cracking with a single feedstock.

[0029] Compared with the prior art, the present invention has significant advantages and outstanding effects, as follows:

[0030] (1) In this invention, a core-shell catalyst is used, with the core being a ZSM-5 molecular sieve modified by a modifying element and the shell being alumina, with a core-to-shell mass ratio of 0.1 to 5:1. Preferably, the core is a ZSM-5 molecular sieve jointly modified by rare earth and alkaline earth metal elements. During the cracking process of mixed C5 hydrocarbons, side reactions such as polymerization and hydrogen transfer are easily occurring. Alumina has a rich macroporous structure and strong acidity, which is conducive to the diffusion and further cracking of macromolecular intermediates. The core layer ZSM-5 molecular sieve has excellent shape selectivity, which is conducive to the generation of the target products propylene and ethylene. In particular, the modification by rare earth and alkaline earth metal elements is conducive to the cracking of C5 hydrocarbons. Under the action of this core-shell catalyst, mixed C5 hydrocarbons undergo simultaneous and efficient conversion of pentene and pentane to generate propylene and ethylene products.

[0031] (2) In this invention, the catalyst is prepared by dispersing boehmite in a dispersant to form an aluminum hydroxide slurry; then, the aluminum hydroxide slurry is sprayed onto a ZSM-5 molecular sieve modified with core-layer modification elements, followed by drying and calcination to obtain a core-shell catalyst. This method prevents the ZSM-5 molecular sieve crystals in the core layer from agglomerating, maximizing the protection of the core layer's pyrolysis performance, while the shell layer provides a good pathway for the pyrolysis and diffusion of macromolecular intermediates. The core-shell molecular sieve catalyst of this invention, especially the combined modification with rare earth and alkaline earth metal elements, synergistically enables the simultaneous and efficient conversion of pentene and pentane, resulting in high yields of propylene and ethylene products and good catalyst stability.

[0032] (3) In this invention, the application method of pentene-pentane co-cracking to increase the production of propylene and ethylene overcomes the shortcomings of the existing mixed C5 hydrocarbon cracking to propylene and ethylene technology, which has low mixed hydrocarbon conversion rate and low product propylene and ethylene yield. By optimizing the reaction process conditions, the conversion rate of raw material mixed C5 hydrocarbons can reach more than 72%, and the product propylene and ethylene yield can exceed 46%, achieving better technical results. Detailed Implementation

[0033] The present invention will be further illustrated by the following embodiments, but the scope of protection of the present invention is not limited by the embodiments.

[0034] In the context of this specification, the following formula shall be used for calculation:

[0035] C5 olefin conversion rate (%) = (1 - mass of C5 olefin in product / mass of C5 olefin in feedstock) × 100%;

[0036] C5 alkane conversion rate (%) = (1 - mass of C5 alkane in product / mass of C5 alkane in feedstock) × 100%;

[0037] Conversion rate of mixed C5 in raw materials (%) = (1 - mass of mixed C5 in product / mass of mixed C5 in raw materials) × 100%;

[0038] Propylene-ethylene diene yield (%) = Mass of propylene and ethylene produced in the product / Mass of the C5 mixed hydrocarbon feedstock × 100%.

[0039] Example 1

[0040] NaZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 500 was exchanged with 5wt% ammonium nitrate, dried in an oven at 80℃ for 20 hours, and then calcined in a muffle furnace at 500℃ for 5 hours to obtain hydrogen-form ZSM-5 molecular sieve, i.e., HZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of lanthanum nitrate solution containing 1% La, dried in an oven at 120℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain La-modified ZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of magnesium nitrate solution containing 0.5% Mg, dried in an oven at 100℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain La and Mg co-modified ZSM-5 molecular sieve, for later use. The modified molecular sieve had a La content of 1% and a Mg content of 0.5%.

[0041] 28.6 g of boehmite was added to a mixed solution of 100 g of 5 wt% dilute nitric acid aqueous solution and ethanol, wherein the volume ratio of dilute nitric acid aqueous solution to ethanol was 2:1. The mixing temperature was controlled at 60 °C, and the mixture was stirred vigorously to form an aluminum hydroxide slurry. 60 g of La and Mg co-modified ZSM-5 molecular sieve was obtained by spray impregnation with the above slurry, dried in an oven at 80 °C for 20 hours, and then calcined in a muffle furnace at 550 °C for 4 hours to obtain a core-shell material. This core-shell material was pressed, ground, and sieved to obtain a catalyst for co-cracking of C5 mixed hydrocarbons to increase the production of propylene and ethylene. In the catalyst, the mass ratio of the core to the shell was 3:1.

[0042] A fixed-bed catalytic reactor was used, with 5 grams of the above-mentioned catalyst loaded. A mixed hydrocarbon mixture of 67% 1-pentene and 33% n-pentane was used as feedstock. The reaction was carried out at a temperature of 550°C, a pressure of 0.03 MPa, and a mixed hydrocarbon weight hourly space velocity of 15 h⁻¹. -1 Under the given reaction conditions, the activity of the pentene-pentane co-cracking reaction was evaluated, and the results are shown in Table 1.

[0043] Example 2

[0044] NaZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 200 was exchanged with 5wt% ammonium nitrate, dried in an oven at 80℃ for 20 hours, and then calcined in a muffle furnace at 500℃ for 5 hours to obtain hydrogen-form ZSM-5 molecular sieve, i.e., HZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of cerium nitrate solution containing 0.5% Ce, dried in an oven at 120℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain Ce-modified ZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of barium nitrate solution containing 0.1% Ba, dried in an oven at 100℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain Ce and Ba co-modified ZSM-5 molecular sieve, for later use. The Ce content of the modified molecular sieve was 0.5%, and the Ba content was 0.1%.

[0045] 50 g of pseudoboehmite was added to a mixed solution of 100 g of 5 wt% dilute nitric acid aqueous solution and ethanol, wherein the volume ratio of dilute nitric acid aqueous solution to ethanol was 1:1. The mixing temperature was controlled at 30°C, and the mixture was stirred vigorously to form an aluminum hydroxide slurry. 50 g of Ce and Ba co-modified HZSM-5 molecular sieve was obtained by spray impregnation with the above slurry, dried in an oven at 80°C for 20 hours, and then calcined in a muffle furnace at 550°C for 4 hours to obtain a core-shell material. The core-shell material was pressed, ground, and sieved to obtain a catalyst for increasing the production of propylene and ethylene through co-cracking of C5 mixed hydrocarbons. In the catalyst, the mass ratio of the core to the shell was 1.4:1.

[0046] A fixed-bed catalytic reactor was used, with 5 grams of the above-mentioned catalyst loaded. A mixed hydrocarbon mixture of 67% 1-pentene and 33% n-pentane was used as feedstock. The reaction was carried out at a temperature of 550°C, a pressure of 0.03 MPa, and a mixed hydrocarbon weight hourly space velocity of 15 h⁻¹. -1 Under the given reaction conditions, the activity of the pentene-pentane co-cracking reaction was evaluated, and the results are shown in Table 1.

[0047] Example 3

[0048] NaZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 500 was exchanged with 5wt% ammonium nitrate, dried in an oven at 80℃ for 20 hours, and then calcined in a muffle furnace at 500℃ for 5 hours to obtain hydrogen-form ZSM-5 molecular sieve, i.e., HZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of lanthanum nitrate solution containing 0.05% La, dried in an oven at 120℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain La-modified ZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of magnesium nitrate solution containing 1% Mg, dried in an oven at 100℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain La and Mg co-modified ZSM-5 molecular sieve, for later use. The La content of the modified molecular sieve was 0.05%, and the Mg content was 1%.

[0049] 28.6 g of boehmite was added to a mixed solution of 100 g of 5 wt% dilute nitric acid aqueous solution and ethanol, wherein the volume ratio of dilute nitric acid aqueous solution to ethanol was 2:1. The mixing temperature was controlled at 60 °C, and the mixture was stirred vigorously to form an aluminum hydroxide slurry. 60 g of La and Mg co-modified HZSM-5 molecular sieve was obtained by spray impregnation with the above slurry, dried in an oven at 80 °C for 20 hours, and then calcined in a muffle furnace at 550 °C for 4 hours to obtain a core-shell material. This core-shell material was pressed, ground, and sieved to obtain a catalyst for co-cracking of C5 mixed hydrocarbons to increase the production of propylene and ethylene. In the catalyst, the mass ratio of the core to the shell was 3:1.

[0050] A fixed-bed catalytic reactor was used, with 5 grams of the above-mentioned catalyst loaded. A mixed hydrocarbon mixture of 67% 1-pentene and 33% n-pentane was used as feedstock. The reaction was carried out at a temperature of 550°C, a pressure of 0.03 MPa, and a mixed hydrocarbon weight hourly space velocity of 15 h⁻¹. -1 Under the given reaction conditions, the activity of the pentene-pentane co-cracking reaction was evaluated, and the results are shown in Table 1.

[0051] Example 4

[0052] NaZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 200 was exchanged with 5wt% ammonium nitrate, dried in an oven at 80℃ for 20 hours, and then calcined in a muffle furnace at 500℃ for 5 hours to obtain hydrogen-form ZSM-5 molecular sieve, i.e., HZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of cerium nitrate solution containing 3% Ce, dried in an oven at 120℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain Ce-modified ZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of barium nitrate solution containing 0.01% Ba, dried in an oven at 100℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain Ce and Ba co-modified ZSM-5 molecular sieve, for later use. The Ce content of the modified molecular sieve was 3%, and the Ba content was 0.01%.

[0053] 50 g of pseudoboehmite was added to a mixed solution of 100 g of 5 wt% dilute nitric acid aqueous solution and ethanol, wherein the volume ratio of dilute nitric acid aqueous solution to ethanol was 1:1. The mixing temperature was controlled at 30°C, and the mixture was stirred vigorously to form an aluminum hydroxide slurry. 50 g of Ce and Ba co-modified HZSM-5 molecular sieve was obtained by spray impregnation with the above slurry, dried in an oven at 80°C for 20 hours, and then calcined in a muffle furnace at 550°C for 4 hours to obtain a core-shell material. The core-shell material was pressed, ground, and sieved to obtain a catalyst for increasing the production of propylene and ethylene through co-cracking of C5 mixed hydrocarbons. In the catalyst, the mass ratio of the core to the shell was 1.4:1.

[0054] A fixed-bed catalytic reactor was used, with 5 grams of the above-mentioned catalyst loaded. A mixed hydrocarbon mixture of 67% 1-pentene and 33% n-pentane was used as feedstock. The reaction was carried out at a temperature of 550°C, a pressure of 0.03 MPa, and a mixed hydrocarbon weight hourly space velocity of 15 h⁻¹. -1 Under the given reaction conditions, the activity of the pentene-pentane co-cracking reaction was evaluated, and the results are shown in Table 1.

[0055] Example 5

[0056] NaZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 500 was exchanged with 5wt% ammonium nitrate, dried in an oven at 80℃ for 20 hours, and then calcined in a muffle furnace at 500℃ for 5 hours to obtain hydrogen-form ZSM-5 molecular sieve, i.e., HZSM-5 molecular sieve. This molecular sieve was then impregnated with an equal volume of lanthanum nitrate solution with a La content of 1.5%, dried in an oven at 120℃ for 10 hours, and then calcined in a muffle furnace at 550℃ for 5 hours to obtain La-modified ZSM-5 molecular sieve. The La content of the modified molecular sieve was 1.5%.

[0057] 28.6 g of boehmite was added to a mixed solution of 100 g of 5 wt% dilute nitric acid aqueous solution and ethanol, wherein the volume ratio of dilute nitric acid aqueous solution to ethanol was 2:1. The mixing temperature was controlled at 60 °C, and the mixture was stirred vigorously to form an aluminum hydroxide slurry. 60 g of La-modified ZSM-5 molecular sieve prepared by spray impregnation with the above slurry was dried in an oven at 80 °C for 20 hours, and then calcined in a muffle furnace at 550 °C for 4 hours to obtain a core-shell material. This core-shell material was pressed, ground, and sieved to obtain a catalyst for co-cracking of C5 mixed hydrocarbons to increase the production of propylene and ethylene. In the catalyst, the mass ratio of the core to the shell was 3:1.

[0058] A fixed-bed catalytic reactor was used, with 5 grams of the above-mentioned catalyst loaded. A mixed hydrocarbon mixture of 67% 1-pentene and 33% n-pentane was used as feedstock. The reaction was carried out at a temperature of 550°C, a pressure of 0.03 MPa, and a mixed hydrocarbon weight hourly space velocity of 15 h⁻¹. -1 Under the given reaction conditions, the activity of the pentene-pentane co-cracking reaction was evaluated, and the results are shown in Table 1.

[0059] Comparative Example 1

[0060] NaZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 500 was exchanged with 5wt% ammonium nitrate, dried in an oven at 80℃ for 20 hours, and then calcined in a muffle furnace at 500℃ for 5 hours to obtain hydrogen-form ZSM-5 molecular sieve. This molecular sieve was then pressed, ground, and sieved as a catalyst for increasing the production of propylene and ethylene through co-cracking of C5 mixed hydrocarbons.

[0061] A fixed-bed catalytic reactor was used, with 5 grams of the above-mentioned catalyst loaded. A mixed hydrocarbon mixture of 67% 1-pentene and 33% n-pentane was used as feedstock. The reaction was carried out at a temperature of 550°C, a pressure of 0.03 MPa, and a mixed hydrocarbon weight hourly space velocity of 15 h⁻¹. -1 Under the given reaction conditions, the activity of the pentene-pentane co-cracking reaction was evaluated, and the results are shown in Table 1.

[0062] Comparative Example 2

[0063] NaZSM-5 molecular sieve with a SiO2 / Al2O3 molar ratio of 500 was exchanged with 5wt% ammonium nitrate, dried in an oven at 80℃ for 20 hours, and then calcined in a muffle furnace at 500℃ for 5 hours to obtain hydrogen-form ZSM-5 molecular sieve, namely HZSM-5 molecular sieve, for later use.

[0064] 28.6 g of pseudoboehmite was added to a mixed solution of 100 g of 5 wt% dilute nitric acid aqueous solution and ethanol, wherein the volume ratio of dilute nitric acid aqueous solution to ethanol was 2:1. The mixing temperature was controlled at 60°C, and the mixture was stirred vigorously to form an aluminum hydroxide slurry. 60 g of HZSM-5 molecular sieve prepared by spray impregnation with the above slurry was dried in an oven at 80°C for 20 hours, and then calcined in a muffle furnace at 550°C for 4 hours to obtain a core-shell type ZSM-5 / Al2O3 material. This core-shell material was pressed, ground, and sieved to obtain a catalyst for co-cracking of C5 mixed hydrocarbons to increase the production of propylene and ethylene. In the catalyst, the mass ratio of the core to the shell was 3:1.

[0065] A fixed-bed catalytic reactor was used, with 5 grams of the above-mentioned catalyst loaded. A mixed hydrocarbon mixture of 67% 1-pentene and 33% n-pentane was used as feedstock. The reaction was carried out at a temperature of 550°C, a pressure of 0.03 MPa, and a mixed hydrocarbon weight hourly space velocity of 15 h⁻¹. -1 Under the given reaction conditions, the activity of the pentene-pentane co-cracking reaction was evaluated, and the results are shown in Table 1.

[0066] Table 1. Evaluation results of each catalyst example.

[0067]

[0068]

[0069] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of a C5 mixed hydrocarbon co-cracking catalyst in the reaction of C5 mixed hydrocarbon co-cracking to produce propylene and ethylene, wherein the catalyst has a core-shell structure, the core is a ZSM-5 molecular sieve modified with a modifying element including rare earth elements, and the shell is alumina.

2. The application according to claim 1, characterized in that, The mass ratio of the core to the shell is 0.1 to 5:

1.

3. The application according to claim 1, characterized in that, In the catalyst, the modifying elements include rare earth elements and alkaline earth metals.

4. The application according to claim 3, characterized in that, The mass ratio of rare earth elements to alkaline earth metal elements is 0.05 to 300.

5. The application according to claim 4, characterized in that, The mass ratio of rare earth elements to alkaline earth metal elements is 0.05~2.

6. The application according to claim 1, characterized in that, In the catalyst, the content of the modifying element is 0.01% to 4% based on the weight of the catalyst core layer.

7. The application according to claim 6, characterized in that, In the catalyst, the content of the modifying element is 0.05% to 3% based on the weight of the catalyst core layer.

8. The application according to claim 3 or 4, characterized in that, Based on the core weight of the catalyst, the content of rare earth elements is 0.05% to 3%, and / or the content of alkaline earth metals is 0.01% to 1%.

9. The application according to claim 8, characterized in that, Based on the core weight of the catalyst, the content of rare earth elements is 0.05%~2%, and / or the content of alkaline earth metals is 0.1%~1%.

10. The application according to claim 1 or 3, characterized in that, The rare earth elements include one or more of La, Ce, Pr and Nd.

11. The application according to claim 3, characterized in that, The alkaline earth metal elements include one or more of Mg, Ca, Sr and Ba.

12. The application according to claim 1, characterized in that, The method for preparing the catalyst includes the following steps: (1) Disperse boehmite in a dispersant to form an aluminum hydroxide slurry; (2) The aluminum hydroxide slurry obtained in step (1) is mixed with the ZSM-5 molecular sieve modified by the modifying element, dried and calcined to obtain the catalyst.

13. The application according to claim 12, characterized in that, The dispersion temperature is 30~80℃, and / or the mass ratio of boehmite to dispersant is 1:2~5.

14. The application according to claim 1, characterized in that, The C5 mixture is derived from refinery C5 mixtures, which include at least one pentane and at least one pentene.

15. The application according to claim 14, characterized in that, The pentane hydrocarbons include one or more of n-pentane, isopentane, and neopentane; the pentenes include mono-olefins, including one or more of 1-pentene, cis-2-pentene, trans-2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene.

16. The application according to claim 14, characterized in that, The weight ratio of pentene to pentane is 0.5 to 2:

1.

17. The application according to claim 1, characterized in that, The reaction temperature is 500–700℃, and / or the reaction pressure is 0–1.0 MPa, and / or the weight hourly space velocity (WHSV) of the C5 mixture is 1–30 h⁻¹. -1 .

18. The application according to claim 17, characterized in that, The reaction temperature is 550~650℃, and / or the reaction pressure is 0.03~0.8MPa, and / or the weight hourly space velocity (WHSV) of the C5 mixed hydrocarbons is 2~20h. -1 .

Images