C4 Mixed Hydrocarbons Co-Pyrolysis Catalyst and Its Preparation Method and Application

Abstract

The present invention discloses a catalyst for co-cracking of C4 mixed hydrocarbons, a preparation method thereof, and an application thereof. The catalyst, based on the total weight of the catalyst, comprises the following components: I) 58% to 84% of ZSM-5 molecular sieve; II) 10% to 41% of binder component; III) 0.5% to 6% of alkaline earth metal element; the acid amount ratio of B acid and L acid of the catalyst is 0.5 to 2:1, and the apparent framework density is 1.0 to 2.3 g / mL. This catalyst is used in the reaction of co-cracking C4 mixed hydrocarbons to produce propylene and ethylene. In the co-cracking of C4 olefins and C4 paraffins in the C4 mixed hydrocarbons, propylene and ethylene can be produced, and it has the characteristics of high conversion rate of cracking raw materials, high yield of product propylene and ethylene, and good catalyst stability.

Description

Technical Field

[0001] The present invention relates to the field of catalytic cracking, and particularly relates to a catalyst for co-cracking of C4 mixed hydrocarbons, a preparation method thereof, and an application thereof. Background Art

[0002] Propylene and ethylene are important basic raw materials in the petrochemical industry. Driven by the rapid growth in the demand for polyolefins and their derivatives, the demand for propylene and ethylene has been continuously strong and growing at a relatively fast rate in recent years. Therefore, they are considered products with great market potential. With the annual increase in refining capacity, the output of by-product mixed C4 hydrocarbons has increased accordingly. The utilization of C4 hydrocarbons produced by refineries mainly focuses on the production of methyl tert-butyl ether by isobutene etherification as a fuel additive or for the production of products such as isobutene, and the rest are mostly used as fuel in the form of liquefied petroleum gas. At present, the comprehensive utilization rate of refinery mixed C4 hydrocarbons is very low, and there is an urgent need to find effective utilization ways for a large amount of by-product mixed C4 hydrocarbons. Petrochemical researchers in various countries have paid great attention to this. In order to achieve the high-value utilization of C4 and higher light hydrocarbons in FCC units or cracking units, UOP and Atofina jointly developed the Oleflex (OCP) process, Lummus developed the Olefin Conversion Technology (OCT), Mobil developed the Methanol to Olefins (MTO) process, Lurgi and Süd-Chemie developed the Propylur process, Asahi Kasei developed the Omega olefin conversion process, and Shanghai Research Institute of Petrochemical Technology developed the Olefins by Catalytic Cracking (OCC) process. The above processes can all produce propylene and ethylene from olefins in C4 and higher light hydrocarbons through catalytic cracking or olefin disproportionation processes. However, in addition to olefins, there are a large number of alkanes in mixed C4. The chemical properties of C4 alkanes are very stable. The research work on mixed C4 hydrocarbons focuses on the utilization of olefins in C4 hydrocarbons. Some scholars have also specifically studied the cracking of butane to produce propylene and ethylene. Further research on catalysts for the co-cracking of olefins and alkanes in C4 mixed hydrocarbons remains to be explored.

[0003] The active components of catalysts for olefin cracking are generally molecular sieves such as hydrogen-type ZSM-5, ZSM-11, or SAPO-34. Inert gases, as heat carriers and diluents, are very beneficial to improving various indicators of olefin cracking reactions. Usually, under high-temperature hydrothermal conditions, acidic molecular sieve catalysts will undergo serious framework dealumination, resulting in a rapid decrease in the acid density of the catalyst, causing irreversible loss of catalyst activity. At the same time, due to the strong acidity of molecular sieves, during the olefin cracking to produce propylene and ethylene, side reactions such as olefin polymerization chain growth, hydrogen transfer, and aromatization will occur, and even coke will form in the pores of the molecular sieve catalyst, covering the reaction active centers, causing the catalyst to quickly deactivate.

[0004] CN200410029871.2 discloses a catalyst for cracking C4-C7 olefins to produce propylene, which comprises 1-20% by mass of a Group VIB metal oxide and a zirconia support, and the average grain size of the zirconia is 10-100 nm. This catalyst is used in the reaction of cracking olefins to produce propylene. Under the conditions of 440-470 °C, 0.3 MPa, and a raw material volume space velocity of 3.0 h -1 under the conditions of, the conversion rate of C4 olefins is 79-91%, and the single-pass yield of propylene is 48-50%. US6307117 discloses a method for cracking C4-C12 olefins to produce propylene and ethylene, wherein the active component of the catalyst used is a proton-free, ZSM-5 molecular sieve containing Group IB.

[0005] In the above-reported olefin cracking processes, there are defects such as poor product selectivity, low yield, low conversion rate of olefin raw materials, and poor catalyst stability to varying degrees. The olefin cracking catalysts in the prior art are applied to the reaction of co-cracking mixed hydrocarbons to produce propylene and ethylene, and their catalytic performance needs to be further improved. SUMMARY OF THE INVENTION

[0006] Aiming at the problems of complex mixed hydrocarbon cracking process, low conversion rate of mixed hydrocarbons, and low product selectivity existing in the prior art, the present invention provides a catalyst for co-cracking C4 mixed hydrocarbons to produce propylene and ethylene, and its preparation method and application. This catalyst is used in the reaction of co-cracking C4 mixed hydrocarbons to produce propylene and ethylene. The C4 olefins and C4 alkanes in the C4 mixed hydrocarbons can undergo co-cracking to produce propylene and ethylene, and it has the characteristics of high conversion rates of the cracking raw materials C4 olefins and C4 alkanes, high yields of the products propylene and ethylene, and good catalyst stability.

[0007] The first aspect of the present invention provides a catalyst for co-cracking C4 mixed hydrocarbons. The catalyst, based on the total weight of the catalyst, comprises the following components:

[0008] I) 58% - 84% of ZSM-5 molecular sieve;

[0009] II) 10% - 41% of binder component;

[0010] III) 0.5% - 6% of alkaline earth metal element;

[0011] The acid amount ratio of B acid and L acid of the catalyst is 0.5 - 2:1, and the apparent framework density is 1.0 - 2.3 g / ml.

[0012] In the above technical solution, preferably, the acid amount ratio of B acid and L acid of the catalyst is 0.8 - 1.5:1.

[0013] In the above technical solution, preferably, the apparent framework density of the catalyst is 1.0 - 1.8 g / ml.

[0014] In the above technical solution, in catalyst component I), the SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve is 50 to 1000, preferably 100 to 1000. 2 / Al 2 O 3 In the above technical solution, in catalyst component III), the alkaline earth metal element is selected from at least one of Mg, Ca, Sr, and Ba.

[0015] In the second aspect of the present invention, a method for preparing the above catalyst is provided, including the following steps:

[0016] a) Prepare the ZSM-5 molecular sieve raw powder;

[0017] b) Knead and shape the raw powder obtained in step a) with a binder, dry it, and perform the first calcination to obtain a shaped product;

[0018] c) Perform ammonium exchange on the shaped product obtained in step b), and perform the second calcination to obtain an ammonium-exchanged product;

[0019] d) Treat the ammonium-exchanged product obtained in step c) in an acid solution, perform the third calcination, load the alkaline earth metal, and perform the fourth calcination to obtain the catalyst.

[0020] In the above technical solution, the process of preparing the ZSM-5 molecular sieve raw powder in step a) includes: mixing a template agent, an aluminum source, a silicon source, an alkali source, and water evenly, performing hydrothermal crystallization, and drying to obtain the ZSM-5 molecular sieve raw powder.

[0021] In the above technical solution, in the step of preparing the raw powder in step a), the template agent includes at least one of tetraethylammonium bromide, tetrapropylammonium bromide, and tetrapropylammonium hydroxide. The aluminum source includes at least one of aluminum nitrate, aluminum sulfate, aluminum phosphate, and sodium aluminate. The silicon source includes at least one of water glass, silica sol, and tetraethyl orthosilicate. The alkali source includes at least one of sodium hydroxide and potassium hydroxide.

[0022] In the above technical solution, in the raw materials used in step a) for preparing the raw powder, the molar ratio of the template agent based on NH4, the aluminum source based on Al2O3, the silicon source based on SiO2, the alkali source based on OH, and water is: NH4:Al2O3:SiO2:OH:H2O = 0.01-0.1:0.01-0.1:1:0.1-1:30-100.

[0023] In the above technical solution, in the raw materials used in step a) for preparing the raw powder, based on NH4, Al2O3, SiO2, OH, and H2O, the molar ratio is: NH4:Al2O3:SiO2:OH:H2O = 0.01-0.1:0.01-0.1:1:0.1-1:30-100. 4 + Based on Al 2 O 3 Based on SiO 2 Based on OH - The molar ratio of water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2O = 0.1 to 0.5: 0.001 to 0.02: 1: 0.1 to 0.4: 5 to 10.

[0024] In the above technical solution, in the step a) of preparing the raw powder, the device is preferably an autoclave. The pressure is the autogenous pressure, generally less than or equal to 2 MPa. The conditions for hydrothermal crystallization are: crystallization at 120 to 180 °C for 10 to 60 hours. The product obtained after hydrothermal crystallization can be washed and dried. The conditions for drying are: drying at 80 to 120 °C for 10 to 30 hours.

[0025] In the above technical solution, in step b), the binder is selected from one or more of alumina, aluminum sol, and silica sol. When aluminum sol is used as the binder, the binder component is Al 2 O 3 ; when silica sol is used as the binder, the binder component is SiO 2 .

[0026] In the above technical solution, the conditions for drying in step b) are: drying at 80 to 120 °C for 5 to 10 hours. The conditions for the first calcination are: calcination at 500 to 600 °C for 4 to 8 hours.

[0027] In the above technical solution, the conditions for ammonium exchange in step c) are: the temperature is 80 to 90 °C, and the time is 1 to 3 h. The number of ammonium exchange times is 2 to 5 times. The concentration of the ammonium salt aqueous solution in ammonium exchange is 5 wt% to 10 wt%. The ammonium salt is selected from at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate. After ammonium exchange, it can be washed and dried. The conditions for drying are: the drying temperature is 80 to 120 °C, and the drying time is 6 to 20 hours. The conditions for the second calcination are calcination at 500 to 600 °C for 4 to 8 hours.

[0028] In the above technical solution, the acid content in the acid solution in step d) is 2 wt% to 5 wt%; the acid is an organic acid; the organic acid includes at least one selected from citric acid, oxalic acid, acetic acid, and ethanedioic acid. The treatment can be soaking, and the treatment conditions are as follows: the volume ratio of the acid solution to the ammonium-exchanged product is 2:1 to 5:1, the treatment temperature is 70 to 80 °C, and the treatment time is 4 to 8 hours. The treatment is carried out under stirring conditions. After treatment in the acid solution, it can be washed and dried. The conditions for drying are: the temperature is 80 to 120 °C, and the time is 6 to 20 hours. The conditions for the third calcination are calcination at 500 to 600 °C for 4 to 8 hours.

[0029] In the above technical solution, the alkaline earth metal supported in step d) is impregnated by the equal-volume impregnation method. The impregnating solution is an alkaline earth metal salt solution. The alkaline earth metal salt is a soluble salt of an alkaline earth metal, preferably a nitrate. Calculated as metal ions, the mass concentration of the alkaline earth metal salt solution is 0.5% to 5%. The impregnation time is 5 to 15 hours. Drying can be carried out after impregnation. The drying is carried out at 80 to 120 °C for 6 to 20 hours. The conditions for the fourth calcination are calcination at 500 to 600 °C for 4 to 8 hours.

[0030] The third aspect of the present invention provides the application of the above catalyst in the reaction of co-cracking of C4 mixed hydrocarbons to produce propylene and ethylene.

[0031] In the above technical solution, the C4 mixed hydrocarbons are derived from refinery C4 mixed hydrocarbons; the C4 mixed hydrocarbons include at least one of isobutane, n-butane, 1-butene, isobutene, trans-2-butene, 1,3-butadiene; preferably, the C4 mixed hydrocarbons are at least one alkane and at least one alkene. Further preferably, in the C4 mixed hydrocarbons, the mass ratio of alkane to alkene is 0.1 to 10, for example, but not limited to: 0.3, 0.4, 0.5, 0.8, 1.0, 1.5, 2.0, 3.0, etc.

[0032] In the above technical solution, the reaction of co-cracking C4 mixed hydrocarbons to produce propylene and ethylene can use a fixed-bed reactor.

[0033] In the above technical solution, the conditions for the reaction are: the reaction temperature is 500 to 700 °C, the reaction pressure is 0 to 1.0 MPa, and the weight hourly space velocity of the mixed hydrocarbon raw material is 1 to 40 h -1 .

[0034] At present, in the reaction of catalytic cracking of mixed C4 hydrocarbons to produce propylene and ethylene, there are problems of low raw material conversion rate and low propylene and ethylene yields. This is mainly because there are differences in the stability of butene and butane, and the cracking mechanisms are different. Butene cracking can occur at a lower temperature, while butane cracking requires a higher reaction temperature. Therefore, under the reaction conditions of butene catalytic cracking, butane hardly reacts. And under the catalyst and reaction conditions of butane cracking, there are too many by-products of butene cracking, and the yields of the products propylene and ethylene are lower than those of single raw material cracking.

[0035] Compared with the prior art, the present invention has significant advantages and outstanding effects, as follows:

[0036] (1) In the present invention, the catalyst for the co-cracking of C4 mixed hydrocarbons, based on the total weight of the catalyst, comprises the following components: I) 58% - 84% of ZSM-5 molecular sieve; II) 10% - 41% of binder component; III) 0.5% - 6% of alkaline earth metal element; the acid amount ratio of B acid and L acid of the catalyst is 0.5 - 2:1, and the apparent framework density is 1.0 - 2.3 g / ml. The catalyst of the present invention has a specific acid amount B / L ratio and a special apparent framework density. By optimizing the reaction process conditions, the C4 olefins and C4 paraffins in the C4 mixed hydrocarbons can be simultaneously converted into propylene and ethylene under the same process conditions. The catalyst of the present invention is used in the reaction of co-cracking C4 mixed hydrocarbons to produce propylene and ethylene, and has the characteristics of high conversion rate of cracking raw materials, high yield of product propylene and ethylene, and good catalyst stability.

[0037] (2) In the present invention, in the preparation method of the catalyst, the ZSM-5 molecular sieve raw powder is first prepared, and then the raw powder is formed, ammonium-exchanged, and acid-modified to obtain the catalyst. The preparation method of the present invention modifies the synthesized ZSM-5 molecular sieve raw powder, and the prepared catalyst has a specific acid amount B / L ratio and a special apparent framework density, generating a more abundant pore structure and accelerating the diffusion of reaction intermediates and products. The catalyst prepared by this method, under the optimized reaction process conditions, can simultaneously convert the C4 olefins and C4 paraffins in the C4 mixed hydrocarbons into propylene and ethylene under the same process conditions, and has the characteristics of high conversion rate of cracking raw materials, high yield of product propylene and ethylene, and good catalyst stability.

[0038] (3) In the application of the catalyst in the reaction of co-cracking C4 mixed hydrocarbons to produce propylene and ethylene in the present invention, under the optimized reaction process conditions, the C4 olefins and C4 paraffins in the C4 mixed hydrocarbons can be simultaneously converted into propylene and ethylene under the same process conditions, and have the characteristics of high conversion rate of cracking raw materials, high yield of product propylene and ethylene, and good catalyst stability. After reacting for 2 h, the conversion rate of C4 olefins in the raw material mixed hydrocarbons can reach more than 75%, the conversion rate of C4 paraffins can reach more than 41%, and the yield of product propylene and ethylene can reach more than 66%. The catalyst has good stability after running for 75 h in the long term, and the catalytic activity has no obvious change, achieving good technical effects. Description of the Drawings

[0039] Figure 1 It is the pyridine adsorption infrared spectrum of the catalyst obtained in Example 1;

[0040] Figure 2 It is the XRD spectrum of the molecular sieve raw powder obtained in Example 1;

[0041] Figure 3 It is the XRD spectrum of the molecular sieve raw powder obtained in Comparative Example 1;

[0042] Figure 4 It is the pyridine adsorption infrared spectrum of the catalyst obtained in Comparative Example 1. Detailed implementation manners

[0043] The present invention will be further described below by way of examples.

[0044] In the context of this specification, XRD analysis is carried out on a Rigaku D / MAX-1400X type polycrystalline X-ray diffractometer, with a graphite monochromator, Cu Kα radiation, a tube voltage of 40 kV, a tube current of 40 mA, and a scanning speed of 15°·min -1 , and the scanning range 2θ is 5 to 50°.

[0045] In the context of this specification, the pyridine adsorption infrared spectrum is analyzed and measured by an IFS-88IR type infrared spectrometer of Bruker Corporation. Specifically: after the sample is ground fine, it is pressed into a tablet in bulk, with a diameter of 2 cm and the whole tablet weighing 11 - 14 mg. Then it is placed in a sample tube and desorbed at 300 °C for 4 hours under a vacuum of 10 -2 Pa to remove moisture and other impurities in the sample. After cooling, the sample is placed in pyridine saturated vapor for adsorption, and then the temperature is raised to 150 °C, 200 °C, 250 °C, 300 °C, 350 °C respectively, and spectra are taken after equilibration for 10 minutes at different temperatures. The spectrum tends to be stable after 300 °C. In the obtained spectrum, the peak near the wave number of 1452 cm -1 corresponds to the L acid center of the catalyst, and the peak near the wave number of 1542 cm -1 corresponds to the B acid center of the catalyst. The acid amount ratio of B acid to L acid (B acid / L acid) is the ratio of the infrared absorption peak areas near 1542 cm -1 and near 1452 cm -1 .

[0046] In the context of this specification, the silicon-aluminum molar ratio SiO 2 / Al 2 O 3 is calculated by analyzing the elemental composition of the solid sample using a Magix X type fluorescence spectrometer of Philips Company of the Netherlands, with an operating voltage of 40 kV and an operating current of 40 mA.

[0047] In the context of this specification, the apparent framework density is measured using an AutoPore V 9600 type full-automatic mercury intrusion porosimeter of Micromeritics Instrument Corporation of the United States. The maximum pressure for high-pressure analysis is 60000 psia (413685 kPa), and the minimum diameter for high-pressure pore size analysis is 4 nm.

[0048] In the context of this specification, it is calculated according to the following formula:

[0049] Conversion rate of C4 olefins (%) = (1 - mass of C4 olefins in product / mass of C4 olefins in feedstock) × 100%;

[0050] Conversion rate of C4 alkanes (%) = (1 - mass of C4 alkanes in product / mass of C4 alkanes in feedstock) × 100%;

[0051] Yield of propylene and ethylene (%) = mass of propylene and ethylene produced in product / mass of C4 hydrocarbon mixture in feedstock × 100%.

[0052] In the examples and comparative examples of this specification, the C4 hydrocarbon mixture used is from a refinery. The specific composition is shown in Table 1.

[0053]

Example 1

[0054] a) Preparation of ZSM-5 molecular sieve raw powder

[0055] Using tetraethylammonium bromide as the template agent, aluminum nitrate as the aluminum source, silica sol as the silicon source, and sodium hydroxide as the base source, the molar ratio of tetraethylammonium bromide, aluminum nitrate, silica sol, base, and water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O = 0.2:0.001:1:0.2:5. After thorough mixing and stirring, it is transferred to an autoclave and crystallized at 180 °C for 10 hours under autogenous pressure and then cooled. The synthesized product is filtered by suction, washed with water, and dried at 80 °C for 30 hours to obtain the ZSM-5 molecular sieve raw powder.

[0056] b) Knead 70 g of the above ZSM-5 molecular sieve raw powder, 40 g of binder alumina, and 30 g of 5% dilute nitric acid, extrude into pellets, dry at 80 °C for 10 hours, and then calcine at 500 °C for 8 hours to obtain the formed product.

[0057] c) Exchange the ammonium of the obtained formed product in a 5 wt% ammonium nitrate aqueous solution at 90 °C for 1 hour. The number of ammonium exchange times is 5 times. After washing and drying at 120 °C for 6 hours, it is calcined at 500 °C for 8 hours.

[0058] d) Place the obtained ammonium-exchanged product in a 2 wt% citric acid solution at 70 °C and stir for 4 hours. The volume ratio of the acid solution to the ammonium-exchanged product is 3:1. After washing and drying at 80 °C for 120 hours, it is calcined at 500 °C for 8 hours. Using the equal-volume impregnation method, impregnate the above catalyst in a 2 wt% magnesium nitrate solution for 5 hours, dry at 120 °C for 6 hours, and then calcine at 500 °C for 8 hours to obtain the catalyst required for catalytic cracking of C4 hydrocarbon mixture to produce propylene and ethylene.

[0059] Figure 1This is the pyridine adsorption infrared spectrum of the catalyst obtained in Example 1. The acid ratio of B acid to L acid in the catalyst is 1.06:1, and the apparent skeleton density is 1.0 g / ml.

[0060] The catalyst comprises: a) 60% of ZSM-5 molecular sieve; b) 38% of binder component; and c) 2% of metal element Mg.

[0061] The silicon-aluminum molar ratio of the ZSM-5 molecular sieve in the catalyst component is SiO 2 / Al 2 O 3 is 1000.

[0062] The XRD pattern of the obtained ZSM-5 molecular sieve raw powder is shown in Figure 2 .

[0063] The fixed bed catalytic reaction device was used to evaluate the catalytic cracking activity of the prepared catalyst to produce propylene and ethylene using mixed C4 residues extracted from ethylene plants as raw materials. The process conditions used were: 0.6 g catalyst, 500 °C reaction temperature, 0.2 MPa reaction pressure, and 10 h-1 weight space velocity. -1 .

[0064] The results of the reaction at 2 h and 75 h are listed in Table 2.

[0065] [Example 2]

[0066] a) Preparation of ZSM-5 molecular sieve raw powder

[0067] Tetrapropylammonium bromide is used as template, aluminum sulfate is used as aluminum source, water glass is used as silicon source, potassium hydroxide is used as alkali source, and the molar ratio of tetrapropylammonium bromide, aluminum sulfate, water glass, alkali and water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.5:0.01:1:0.4:10, transfer to an autoclave after sufficient mixing and stirring, crystallize at 120°C for 60 hours under autogenous pressure, and then cool. Filter the synthesized product, wash with water, and dry at 120°C for 10 hours to obtain ZSM-5 molecular sieve raw powder.

[0068] b) 70 g of the ZSM-5 molecular sieve raw powder and 75 g of the binder silica sol (SiO 2 The mixture was kneaded with a weight content of 40%, extruded into strips, dried at 120° C. for 5 hours, and then calcined at 600° C. for 4 hours to obtain a molded product.

[0069] c) The obtained formed product is subjected to ammonium exchange in an aqueous solution of ammonium sulfate at 10% by weight at 80 °C for 2 hours. The ammonium exchange is carried out twice in total. After washing and drying at 80 °C for 20 hours, it is calcined at 600 °C for 4 hours.

[0070] d) The obtained ammonium-exchanged product is placed in a 5% oxalic acid solution at 80 °C and stirred for 8 hours. The volume ratio of the acid solution to the ammonium-exchanged product is 5:1. After washing and drying at 120 °C for 6 hours, it is calcined at 600 °C for 4 hours. By using the equal-volume impregnation method, the above catalyst is impregnated in a 5% calcium nitrate solution for 15 hours, dried at 80 °C for 20 hours, and then calcined at 600 °C for 4 hours to obtain the catalyst for catalytic cracking of C4 mixed hydrocarbons to produce propylene and ethylene.

[0071] The acid amount ratio of Brønsted acid to Lewis acid in the catalyst is 0.8:1, and the apparent skeletal density is 1.2 g / mL.

[0072] The composition of the catalyst is as follows: a) 64% ZSM-5 molecular sieve; b) 31% binder component; c) 5% metal element Ca.

[0073] In the catalyst component, the silicon-aluminum molar ratio of the ZSM-5 molecular sieve SiO 2 / Al 2 O 3 is 100. The XRD pattern of the obtained ZSM-5 molecular sieve raw powder is similar Figure 2 .

[0074] Using a fixed-bed catalytic reaction device, with the raffinate C4 mixture from an ethylene plant as the raw material, the prepared catalyst was evaluated for the catalytic cracking reaction activity of C4 mixed hydrocarbons to produce propylene and ethylene. The process conditions investigated were as follows: 0.6 g of the catalyst was loaded, the reaction temperature was 600 °C, the reaction pressure was 0.5 MPa, and the weight hourly space velocity of the olefin raw material was 20 h -1 .

[0075] The results of the reaction for 2 h and 75 h are listed in Table 2.

[0076]

Example 3

[0077] a) Preparation of ZSM-5 molecular sieve raw powder

[0078] Using tetrapropylammonium hydroxide as the template agent, sodium aluminate as the aluminum source, tetraethyl orthosilicate as the silicon source, and sodium hydroxide as the base source, the molar ratio of tetrapropylammonium hydroxide, sodium aluminate, tetraethyl orthosilicate, base, and water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2O = 0.1:0.00125:1:0.1:8. After sufficient mixing and stirring, it was transferred into an autoclave and crystallized at 150 °C for 30 hours under autogenous pressure and then cooled. The synthesized product was filtered by suction, washed with water, and dried at 100 °C for 20 hours to obtain the ZSM-5 molecular sieve raw powder.

[0079] b) 80 g of the above-mentioned ZSM-5 molecular sieve raw powder and 80 g of binder aluminum sol (Al 2 O 3 with a weight content of 25%) were kneaded, extruded into shapes, dried at 100 °C for 8 hours, and then calcined at 550 °C for 6 hours to obtain the shaped product.

[0080] c) The obtained shaped product was subjected to ammonium exchange in a 10 wt% aqueous ammonium chloride solution at 85 °C for 1.5 hours, and the ammonium exchange was carried out 4 times in total. After washing and drying at 120 °C for 6 hours, it was calcined at 550 °C for 6 hours.

[0081] d) The obtained ammonium-exchanged product was placed in a 3 wt% oxalic acid solution at 75 °C and stirred for 6 hours, and the volume ratio of the acid solution to the ammonium-exchanged product was 2:1. After washing and drying at 120 °C for 6 hours, it was calcined at 550 °C for 7 hours. By the equal-volume impregnation method, the above catalyst was impregnated in a 3% strontium nitrate solution for 10 hours, dried at 100 °C for 10 hours, and then calcined at 550 °C for 6 hours to obtain the catalyst for catalytic cracking of C4 mixed hydrocarbons to produce propylene and ethylene.

[0082] The acid amount ratio of B acid and L acid in the catalyst is 1.5:1, and the apparent framework density is 2.02 g / mL.

[0083] The composition of the catalyst is: a) 77.6% of ZSM-5 molecular sieve; b) 19.4% of binder component; c) 3% of metal element Sr.

[0084] In the catalyst component, the silica-alumina molar ratio of ZSM-5 molecular sieve SiO 2 / Al 2 O 3 is 800. The XRD pattern of the obtained ZSM-5 molecular sieve raw powder is similar Figure 2 .

[0085] Using a fixed-bed catalytic reaction device, with the raffinate C4 mixture from an ethylene plant as the raw material, the catalytic cracking reaction activity of the prepared catalyst for C4 mixed hydrocarbons to produce propylene and ethylene was evaluated. The process conditions investigated were: 0.6 g of catalyst was loaded, the reaction temperature was 700 °C, the reaction pressure was 0.1 MPa, and the weight hourly space velocity of the olefin raw material was 1 h -1 .

[0086] The results of the reaction for 2 h and 75 h are listed in Table 2.

[0087]

Example 4

[0088] a) Preparation of ZSM-5 molecular sieve raw powder

[0089] Using tetraethylammonium bromide as the template agent, aluminum phosphate as the aluminum source, sodium silicate as the silicon source, and potassium hydroxide as the base source, the molar ratio of tetraethylammonium bromide, aluminum phosphate, sodium silicate, base, and water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O = 0.2:0.002:1:0.2:10. After thorough mixing and stirring, it is transferred to an autoclave and crystallized at 160 °C for 15 hours under autogenous pressure and then cooled. The synthesized product is filtered by suction, washed with water, and dried at 90 °C for 25 hours to obtain ZSM-5 molecular sieve raw powder.

[0090] b) Knead 80 g of the above ZSM-5 molecular sieve raw powder and 50 g of binder silica sol (SiO 2 weight content 40%), extrude into pellets, dry at 80 °C for 10 hours, and then calcine at 500 °C for 8 hours to obtain the shaped product.

[0091] c) The obtained shaped product is subjected to ammonium exchange in a 5 wt% ammonium nitrate aqueous solution at 80 °C for 2 hours, and the ammonium exchange is carried out 3 times in total. After washing and drying at 100 °C for 10 hours, it is calcined at 600 °C for 4 hours.

[0092] d) Place the obtained ammonium-exchanged product in a 5 wt% citric acid solution at 70 °C and stir for 4 hours. The volume ratio of the acid solution to the ammonium-exchanged product is 2:1. After washing and drying at 100 °C for 10 hours, it is calcined at 500 °C for 6 hours. Using the equal-volume impregnation method, the above catalyst is impregnated in a 2% magnesium nitrate solution for 10 hours, dried at 100 °C for 10 hours, and then calcined at 550 °C for 6 hours to obtain the catalyst for catalytic cracking of C4 mixed hydrocarbons to produce propylene and ethylene.

[0093] The acid amount ratio of B acid and L acid in the catalyst is 0.8:1, and the apparent framework density is 2.3 g / mL.

[0094] The composition of the catalyst is: a) 76.9% ZSM-5 molecular sieve; b) 21.1% binder component. c) 2% metal element Mg.

[0095] The silicon-aluminum molar ratio SiO 2 / Al 2 O 3 in the ZSM-5 molecular sieve in the catalyst components is 500. The XRD pattern of the obtained ZSM-5 molecular sieve raw powder is similar Figure 2 .

[0096] Using a fixed-bed catalytic reaction device, with the raffinate mixed C4 from an ethylene plant as the raw material, the prepared catalyst was evaluated for the catalytic cracking reaction activity of C4 mixed hydrocarbons to produce propylene and ethylene. The process conditions investigated were as follows: 0.6 grams of the catalyst was loaded, the reaction temperature was 550 °C, the reaction pressure was 1.0 MPa, and the weight hourly space velocity of the olefin raw material was 40 h -1 .

[0097] The results of the reaction for 2 h and 75 h are listed in Table 2.

[0098]

Example 5

[0099] a) Preparation of ZSM-5 zeolite powder

[0100] Using tetrapropylammonium hydroxide as the template agent, aluminum nitrate as the aluminum source, silica sol as the silicon source, and sodium hydroxide as the base source, the molar ratio of tetrapropylammonium hydroxide, aluminum nitrate, silica sol, base, and water was: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O = 0.1:0.005:1:0.2:6. After thorough mixing and stirring, it was transferred to an autoclave and crystallized at 180 °C for 10 hours under autogenous pressure and then cooled. The synthesized product was filtered, washed with water, and dried at 120 °C for 10 hours to obtain ZSM-5 zeolite powder.

[0101] b) Knead 85 grams of the above ZSM-5 zeolite powder, 25 grams of binder alumina, and 32 grams of 5% dilute nitric acid, extrude into pellets, dry at 80 °C for 10 hours, and then calcine at 600 °C for 4 hours to obtain the formed product.

[0102] c) The obtained formed product was subjected to ammonium exchange in a 10 wt% ammonium sulfate aqueous solution at 90 °C for 1.5 hours, and the ammonium exchange was carried out 3 times in total. After washing and drying at 120 °C for 6 hours, it was calcined at 500 °C for 8 hours.

[0103] d) The obtained ammonium-exchanged product was stirred in a 5 wt% acetic acid solution at 70 °C for 6 hours, and the volume ratio of the acid solution to the ammonium-exchanged product was 5:1. After washing and drying at 120 °C for 6 hours, it was calcined at 500 °C for 8 hours. Using the equal-volume impregnation method, the above catalyst was impregnated in a 2% calcium nitrate solution for 8 hours, dried at 120 °C for 6 hours, and then calcined at 550 °C for 8 hours to obtain the catalyst for catalytic cracking of C4 mixed hydrocarbons to produce propylene and ethylene.

[0104] The acid amount ratio of B acid and L acid in the catalyst is 1:1, and the apparent framework density is 1.5 g / mL.

[0105] The catalyst comprises: a) 74% of ZSM-5 molecular sieve; b) 24% of binder component; and c) 2% of metal element Ca.

[0106] The silicon-aluminum molar ratio of the ZSM-5 molecular sieve in the catalyst component is SiO 2 / Al 2 O 3 The XRD pattern of the obtained ZSM-5 molecular sieve raw powder is similar to Figure 2 .

[0107] The fixed-bed catalytic reaction device was used to evaluate the catalytic cracking activity of the prepared catalyst in the production of propylene and ethylene using mixed C4 residues from ethylene plants as raw materials. The process conditions used in the investigation were: 0.6 g catalyst, reaction temperature of 650 °C, reaction pressure of 0.05 MPa, and weight space velocity of olefin raw materials of 30 h -1 .

[0108] The results of reaction for 2 h and 75 h are listed in Table 2.

[0109] [Comparative Example 1]

[0110] a) Preparation of ZSM-5 molecular sieve raw powder

[0111] Tetrapropylammonium hydroxide is used as the template, sodium aluminate is used as the aluminum source, tetraethyl orthosilicate is used as the silicon source, and sodium hydroxide is used as the alkali source. The molar ratio of tetrapropylammonium hydroxide, sodium aluminate, tetraethyl orthosilicate, alkali, and water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.1:0.00125:1:0.1:8, transfer to an autoclave after sufficient mixing and stirring, crystallize at 150°C for 30 hours under autogenous pressure, and then cool. Filter the synthesized product, wash with water, and dry at 100°C for 20 hours to obtain ZSM-5 molecular sieve raw powder.

[0112] b) 80 g of the ZSM-5 molecular sieve raw powder and 80 g of the binder aluminum sol (Al 2 O 3 The mixture was kneaded with a weight content of 25%, extruded into strips, dried at 100°C for 8 hours, and then calcined at 550°C for 6 hours to obtain a molded product.

[0113] c) The obtained molded product was subjected to ammonium exchange in a 10 wt% aqueous solution of ammonium chloride at 85°C for 1.5 hours, for a total of 4 times, washed, dried at 120°C for 6 hours, and then calcined at 550°C for 6 hours.

[0114] d) The ammonium exchange product was immersed in a 3% strontium nitrate solution for 10 hours by an equal volume impregnation method, dried at 100°C for 10 hours, and then calcined at 550°C for 6 hours to obtain the desired catalyst for catalytic cracking of C4 mixed hydrocarbons to produce propylene and ethylene.

[0115] Figure 4 This is the pyridine adsorption infrared spectrum of the catalyst obtained in Comparative Example 1. The ratio of B acid to L acid in the catalyst is 0.13:1, and the apparent skeleton density is 2.4 g / ml.

[0116] The catalyst comprises: a) 77.6% of ZSM-5 molecular sieve; b) 19.4% of binder component; and c) 3% of metal element Sr.

[0117] The silicon-aluminum molar ratio of the ZSM-5 molecular sieve in the catalyst component is SiO 2 / Al 2 O 3 is 800.

[0118] The XRD pattern of the obtained ZSM-5 molecular sieve raw powder is shown in Figure 3 .

[0119] The catalyst evaluation method is the same as in Example 3, and the reaction results are listed in Table 2.

[0120] [Comparative Example 2]

[0121] a) Preparation of ZSM-5 molecular sieve raw powder

[0122] Tetrapropylammonium hydroxide is used as the template, sodium aluminate is used as the aluminum source, tetraethyl orthosilicate is used as the silicon source, and sodium hydroxide is used as the alkali source. The molar ratio of tetrapropylammonium hydroxide, sodium aluminate, tetraethyl orthosilicate, alkali, and water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.1:0.00125:1:0.1:8, transfer to an autoclave after sufficient mixing and stirring, crystallize at 150°C for 30 hours under autogenous pressure, and then cool. Filter the synthesized product, wash with water, and dry at 100°C for 20 hours to obtain ZSM-5 molecular sieve raw powder.

[0123] b) 80 g of the ZSM-5 molecular sieve raw powder and 80 g of the binder aluminum sol (Al 2 O 3 The mixture was kneaded with a weight content of 25%, extruded into strips, dried at 100°C for 8 hours, and then calcined at 550°C for 6 hours to obtain a molded product.

[0124] c) The obtained formed product is subjected to ammonium exchange in a 10 wt% aqueous ammonium chloride solution at 85 °C for 1.5 hours. The ammonium exchange is carried out 4 times in total. After washing and drying at 120 °C for 6 hours, it is calcined at 550 °C for 6 hours.

[0125] d) The obtained ammonium-exchanged product is placed in a 3 wt% oxalic acid solution at 75 °C and stirred for 6 hours. The volume ratio of the acid solution to the ammonium-exchanged product is 2:1. After washing and drying at 120 °C for 6 hours, it is calcined at 550 °C for 7 hours. Thus, the catalyst for catalytic cracking of C4 mixed hydrocarbons to produce propylene and ethylene is obtained.

[0126] The acid amount ratio of B acid to L acid in the catalyst is 2.1:1, and the apparent skeletal density is 2.0 g / mL.

[0127] The composition of the catalyst is as follows: a) 78.3% ZSM-5 molecular sieve; b) 21.7% binder component.

[0128] In the catalyst component, the silica-alumina molar ratio of the ZSM-5 molecular sieve is SiO 2 / Al 2 O 3 is 800. The catalyst evaluation method is the same as that in Example 3, and the reaction results are listed in Table 2.

[0129] Table 1 Composition of refinery C4 hydrocarbon raw materials

[0130] Component Composition (wt%) Isobutane 30.64 n-Butane 9.25 1-Butene 10.23 Isobutylene 24.76 trans-2-Butene 14.52 cis-2-Butene 10.54 1,3-Butadiene 0.06

[0131] Table 2 Catalyst evaluation results of each example

[0132]

Claims

1. A catalyst for co-cracking of C4 mixed hydrocarbons, which catalyst, based on the total weight of the catalyst, comprises the following components: I) 58% - 84% of ZSM-5 molecular sieve; II) 10% - 41% of binder component; III) 0.5% - 6% of alkaline earth metal element; The acid amount ratio of B acid and L acid of the catalyst is 0.5 - 2:1, and the apparent framework density is 1.0 - 2.3 g / mL.

2. The catalyst according to claim 1, wherein, the acid amount ratio of B acid and L acid of the catalyst is 0.8 - 1.5:1, and the apparent framework density is 1.0 - 1.8 g / mL.

3. The catalyst according to claim 1, wherein, The SiO of the ZSM-5 molecular sieve in Component I 2 / Al 2 O 3 has a molar ratio of 50 to 1000; and / or, the alkaline earth metal element in component III) is selected from at least one of Mg, Ca, Sr, Ba.

4. The catalyst according to claim 1, wherein, The SiO 2 / Al 2 O 3 molar ratio of the ZSM-5 molecular sieve in Component I) is 100 to 1000.

5. A preparation method of the catalyst according to any one of claims 1 - 4, wherein, it comprises the following steps: a) Prepare the ZSM-5 molecular sieve raw powder; b) Knead and shape the raw powder obtained in step a) with the binder, dry, and perform the first calcination to obtain a shaped product; c) Perform ammonium exchange on the shaped product obtained in step b), and perform the second calcination to obtain an ammonium-exchanged product; d) Treat the ammonium-exchanged product obtained in step c) in an acid solution, perform the third calcination, load the alkaline earth metal and perform the fourth calcination to obtain the catalyst.

6. The preparation method according to claim 5, wherein, the process of preparing the ZSM-5 molecular sieve raw powder in step a) includes: uniformly mixing a template agent, an aluminum source, a silicon source, an alkali source, and water, performing hydrothermal crystallization, and drying to obtain the ZSM-5 molecular sieve raw powder.

7. The preparation method according to claim 6, wherein, the template agent includes at least one of tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, and tetrapropylammonium hydroxide; and / or, the aluminum source includes at least one of aluminum nitrate, aluminum sulfate, aluminum phosphate, and sodium aluminate; and / or, the silicon source includes at least one of water glass, silica sol, and tetraethyl orthosilicate; and / or, the alkali source includes at least one of sodium hydroxide and potassium hydroxide.

8. The preparation method according to claim 6, wherein, In the raw materials used in step a) for preparing the ZSM-5 molecular sieve raw powder, the template agent is calculated as NH 4 + , the aluminum source is calculated as Al 2 O 3 ; the silicon source is calculated as SiO 2 ; the base source is calculated as OH - ; and the molar ratio of water is: NH 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O = 0.1 - 0.5:0.001 - 0.02:1:0.1 - 0.4:5 - 10; and / or, the conditions of the hydrothermal crystallization are: crystallizing at 120 - 180 °C for 10 - 60 hours.

9. The preparation method according to claim 5, wherein, in step b), the binder is selected from one or more of alumina, aluminum sol, and silica sol; and / or, the conditions of drying in step b) are: drying at 80 - 120 °C for 5 - 10 hours; and / or, the conditions of the first calcination are: calcining at 500 - 600 °C for 4 - 8 hours.

10. The preparation method according to claim 5, wherein, the conditions of the ammonium exchange in step c) are: the temperature is 80 - 90 °C, and the time is 1 - 3 h.

11. The preparation method according to claim 10, wherein, the number of times of ammonium exchange in step c) is 2 - 5 times.

12. The preparation method according to claim 10, wherein, In step c), the concentration of the ammonium salt aqueous solution in the ammonium ion exchange is 5 wt% to 10 wt%; the ammonium salt is at least one selected from ammonium chloride, ammonium nitrate, and ammonium sulfate; and / or, the conditions for the second calcination are calcination at 500 to 600 °C for 4 to 8 hours.

13. The preparation method according to claim 5, wherein, in step d), the acid content in the acid solution is 2 wt% to 5 wt%; the acid is an organic acid; the organic acid includes at least one selected from citric acid, oxalic acid, acetic acid, and ethanedioic acid; and / or, in step d), the treatment is soaking, and the treatment conditions are as follows: the volume ratio of the acid solution to the ammonium ion exchange product is 2:1 to 5:1, the treatment temperature is 70 to 80 °C, and the treatment time is 4 to 8 hours; and / or, the conditions for the third calcination in step d) are calcination at 500 to 600 °C for 4 to 8 hours.

14. The preparation method according to claim 5, wherein, in step d), the loading of the alkaline earth metal is by the incipient wetness impregnation method; and / or, the conditions for the fourth calcination are calcination at 500 to 600 °C for 4 to 8 hours.

15. Use of the catalyst according to any one of claims 1 to 4 or the catalyst prepared by the preparation method according to any one of claims 5 to 14 in the reaction of co-cracking of C4 mixed hydrocarbons to produce propylene and ethylene.

16. The use according to claim 15, wherein, the C4 mixed hydrocarbons are derived from refinery C4 mixed hydrocarbons.

17. The use according to claim 16, wherein, the C4 mixed hydrocarbons include at least one of isobutane, n-butane, 1-butene, isobutene, trans-2-butene, and 1,3-butadiene.

18. The use according to claim 17, wherein, the C4 mixed hydrocarbons are at least one alkane and at least one alkene.

19. The use according to claim 15, wherein, The conditions of the reaction are as follows: the reaction temperature is 500 to 700 °C, the reaction pressure is 0 to 1.0 MPa, and the weight hourly space velocity of the mixed hydrocarbon raw material is 1 to 40 h -1 .

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