CN115990506A - Catalyst for co-cracking of carbon-four mixed hydrocarbon, and preparation method and application thereof - Google Patents
Catalyst for co-cracking of carbon-four mixed hydrocarbon, and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a catalyst for co-cracking of carbon-four mixed hydrocarbon, a preparation method and application thereof. The catalyst comprises the following components by taking the total weight of the catalyst as a reference: i) 58 to 84 percent of ZSM-5 molecular sieve; II) 10% -41% of a binder component; III) 0.5 to 6 percent of alkaline earth metal element; the acid quantity ratio of the B acid to the L acid of the catalyst is 0.5-2:1, and the apparent skeleton density is 1.0-2.3 g/ml. The catalyst is used in propylene ethylene production reaction by co-cracking of carbon-four mixed hydrocarbon, and the carbon-four olefin and the carbon-four alkane in the carbon-four mixed hydrocarbon can be subjected to co-cracking to produce propylene ethylene, and has the characteristics of high conversion rate of cracking raw materials, high propylene ethylene yield of products and good catalyst stability.
Description
Technical Field
The invention relates to the field of catalytic cracking, in particular to a catalyst for co-cracking of carbon-four mixed hydrocarbon, and a preparation method and application thereof.
Background
Propylene ethylene is an important base stock for the petrochemical industry, driven by the rapidly growing demand for polyolefins and derivatives thereof, and has been continuously and rapidly growing in recent years, and is thus considered a product having great market potential. With the annual improvement of oil refining capability, the yield of byproduct mixed C4 hydrocarbon increases, and the C4 hydrocarbon produced by a refinery mainly concentrates on the etherification of isobutene to produce methyl tertiary butyl ether as a fuel additive or for preparing products such as isobutene, and the rest takes liquefied petroleum gas as fuel. At present, the comprehensive utilization rate of the mixed C4 hydrocarbon in the refinery is very low, and an effective utilization way is required to be found for a large amount of byproduct mixed C4 hydrocarbon, so that petrochemical researchers in various countries pay great attention to the comprehensive utilization rate. In order to realize the high value-added utilization of light hydrocarbons with four or more carbon atoms of an FCC device or a cracking device, a global oil company and an Atofina company (Atofina) jointly develop an Olefin Cracking (OCP) process, a Lumms (Lumms) process develops an Olefin Conversion Technology (OCT), a Mobil company (Mobil) process develops an olefin interconversion (MOI) process, a Lu Ji company (Lurgi) and a southern chemical company (Schume) process develop a Propylur process, an Xudi chemical company develops an Omega olefin conversion process, a Shanghai petrochemical institute develops a catalytic cracking Olefin (OCC) process, and the processes can produce propylene and ethylene from the light hydrocarbons with four or more carbon atoms through a catalytic cracking or olefin disproportionation process. However, a large amount of alkane exists in the mixed C4, the chemical property of the C4 alkane is very stable, the research work on the mixed C4 hydrocarbon is focused on the utilization of the alkene in the C4 hydrocarbon, and a learner also specially performs the research on preparing propylene and ethylene by butane cracking, and further research on a catalyst for co-cracking the alkene alkane in the C4 mixed hydrocarbon is still yet to be explored.
The active components of the catalyst for olefin cracking are typically hydrogen-type ZSM-5, ZSM-11 or SAPO-34 molecular sieves, and inert gas is used as a heat carrier and a diluent to greatly improve various indexes of olefin cracking reaction. In general, under the high-temperature hydrothermal condition, the acid molecular sieve catalyst can generate serious framework dealumination, so that the acid density of the catalyst is rapidly reduced, and the activity of the catalyst is irreversibly lost. Meanwhile, because the molecular sieve has stronger acidity, when propylene and ethylene are generated by olefin pyrolysis, side reactions such as olefin superposition chain growth, hydrogen transfer, aromatization and the like can occur, even the molecular sieve is coked in a pore canal of the molecular sieve catalyst, and the reactive center is covered, so that the catalyst is quickly deactivated.
CN200410029871.2 discloses a catalyst for producing propylene by cracking C4-C7 olefins, comprising 1-20 mass% of group VIB metal oxide and zirconia carrier, wherein the average grain size of the zirconia is 10-100 nm. The catalyst is used for the reaction of propylene production by olefin pyrolysis, and the raw material volume space velocity is 3.0h at 440-470 ℃ and 0.3MPa -1 Under the condition of (1) the conversion rate of the carbon tetraolefin is 79-91%, and the single pass yield of propylene is 48-50%. US6307117 discloses a process for the production of propylene and ethylene by cracking C4-C12 olefins, wherein the active component of the catalyst used is an aprotic acid, group IB containing ZSM-5 molecular sieve.
In the olefin cracking process, the defects of poor product selectivity, low yield, low conversion rate of olefin raw materials, poor catalyst stability and the like exist in different degrees. The olefin cracking catalyst in the prior art is applied to the reaction of producing propylene and ethylene by co-cracking mixed hydrocarbon, and the catalytic performance needs to be further improved.
Disclosure of Invention
Aiming at the problems of complex cracking process of mixed hydrocarbon, low conversion rate of mixed hydrocarbon and low selectivity of products in the prior art, the invention provides a catalyst for producing propylene and ethylene by co-cracking carbon four mixed hydrocarbon, and a preparation method and application thereof. The catalyst is used in propylene ethylene production reaction by co-cracking of carbon-four mixed hydrocarbon, and the carbon-four olefin and the carbon-four alkane in the carbon-four mixed hydrocarbon can be subjected to co-cracking to produce propylene ethylene, and has the characteristics of high conversion rate of cracking raw materials of the carbon-four olefin and the carbon-four alkane, high propylene ethylene yield of the product and good catalyst stability.
The invention provides a catalyst for co-cracking of carbon four-mixed hydrocarbon, which comprises the following components by taking the total weight of the catalyst as a reference:
i) 58 to 84 percent of ZSM-5 molecular sieve;
II) 10% -41% of a binder component;
III) 0.5 to 6 percent of alkaline earth metal element;
the acid quantity ratio of the B acid to the L acid of the catalyst is 0.5-2:1, and the apparent skeleton density is 1.0-2.3 g/ml.
In the above technical scheme, preferably, the acid amount ratio of the B acid and the L acid of the catalyst is 0.8-1.5:1.
In the above technical scheme, preferably, the apparent skeleton density of the catalyst is 1.0-1.8 g/ml.
In the technical scheme, siO of ZSM-5 molecular sieve in the catalyst component I) 2 /Al 2 O 3 The molar ratio is 50 to 1000, preferably 100 to 1000.
In the above technical scheme, the alkaline earth metal element in the catalyst component III) is at least one selected from Mg, ca, sr, ba.
The second aspect of the present invention provides a method for preparing the above catalyst, comprising the steps of:
a) Preparing ZSM-5 molecular sieve raw powder;
b) Kneading the raw powder obtained in the step a) and a binder for molding, drying, and performing first roasting to obtain a molded product;
c) Performing ammonium exchange on the formed product obtained in the step b), and performing second roasting to obtain an ammonium exchange product;
d) And c) treating the ammonium exchange product obtained in the step c) in acid liquor, and carrying out third roasting, alkaline earth metal loading and fourth roasting to obtain the catalyst.
In the technical scheme, the process for preparing ZSM-5 molecular sieve raw powder in the step a) comprises the following steps: uniformly mixing a template agent, an aluminum source, a silicon source, an alkali source and water, carrying out hydrothermal crystallization, and drying to obtain ZSM-5 molecular sieve raw powder.
In the above technical solution, in the step of preparing the raw powder in the step a), the template agent includes at least one of tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide and tetrapropyl ammonium hydroxide. The aluminum source includes at least one of aluminum nitrate, aluminum sulfate, aluminum phosphate, and sodium aluminate. The silicon source comprises at least one of water glass, silica sol and tetraethoxysilane. The alkali source comprises at least one of sodium hydroxide and potassium hydroxide.
In the technical proposal, in the raw materials used for preparing the raw powder in the step a), the template agent adopts NH 4 + Metering Al as Al source 2 O 3 Meter, silicon source with SiO 2 Counting the alkali source by OH - The mole ratio of the calculated water to the water is as follows: NH (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。
In the above technical scheme, in the step of preparing raw powder in the step a), the device is preferably an autoclave. The pressure is autogenous pressure, and is generally less than or equal to 2MPa. The hydrothermal crystallization conditions are as follows: crystallizing at 120-180 deg.c for 10-60 hr. The product obtained after hydrothermal crystallization can be washed and dried. The drying conditions are as follows: drying at 80-120 deg.c for 10-30 hr.
In the above technical solution, in step b), the binder is one or more selected from alumina, alumina sol, and silica sol. When an aluminum sol is used as the binder, the binder component is Al 2 O 3 The method comprises the steps of carrying out a first treatment on the surface of the When silica sol is used as the binder, the binder component is SiO 2 。
In the above technical solution, the drying conditions in step b) are: drying at 80-120 deg.c for 5-10 hr. The first roasting conditions are as follows: roasting for 4-8 hours at 500-600 ℃.
In the above technical scheme, the conditions of the ammonium exchange in step c) are: the temperature is 80-90 ℃ and the time is 1-3 h. The number of times of ammonium exchange is 2-5 times. The concentration of the ammonium salt aqueous solution in the ammonium exchange is 5-10 wt%. The ammonium salt is at least one selected from ammonium chloride, ammonium nitrate and ammonium sulfate. The ammonium exchange may be followed by washing and drying. The drying conditions are as follows: the drying temperature is 80-120 ℃ and the drying time is 6-20 hours. The second roasting condition is that roasting is carried out for 4-8 hours at 500-600 ℃.
In the technical scheme, the acid content in the acid liquor in the step d) is 2-5 wt%; the acid is an organic acid; the organic acid comprises at least one selected from citric acid, oxalic acid, acetic acid and oxalic acid. The treatment may be soaking, and the treatment conditions are as follows: the volume ratio of the acid liquor to the ammonium exchange product is 2:1 to 5:1, the treatment temperature is 70-80 ℃ and the treatment time is 4-8 hours. The treatment is carried out under stirring. Washing and drying may be performed after the treatment in the acid solution. The drying conditions are as follows: the temperature is 80-120 ℃ and the time is 6-20 hours. The third roasting condition is that roasting is carried out for 4-8 hours at 500-600 ℃.
In the above technical solution, the alkaline earth metal supported in step d) is an isovolumetric impregnation method. The impregnating solution is alkaline earth metal salt solution. The alkaline earth metal salt is a soluble salt of an alkaline earth metal, preferably a nitrate. The mass concentration of the alkaline earth metal salt solution is 0.5-5 percent based on metal ions. The soaking time is 5-15 hours. The impregnation may be followed by drying. The drying is carried out for 6-20 hours at the temperature of 80-120 ℃. The fourth roasting condition is that roasting is carried out for 4-8 hours at 500-600 ℃.
In a third aspect, the invention provides the use of the catalyst described above in a co-cracking reaction of a carbon-four mixed hydrocarbon to produce propylene and ethylene.
In the technical scheme, the carbon-four mixed hydrocarbon is derived from refinery carbon-four mixed hydrocarbon; the carbon-four mixed hydrocarbon comprises at least one of isobutane, n-butane, 1-butene, isobutene, trans-2-butene and 1, 3-butadiene; preferably, the carbon-four mixed hydrocarbon is at least one alkane and at least one alkene. Further preferably, in the carbon four mixed hydrocarbon, the mass ratio of alkane to alkene is 0.1 to 10, and examples are but not limited to: 0.3, 0.4, 0.5, 0.8, 1.0, 1.5, 2.0, 3.0, etc.
In the technical scheme, a fixed bed reactor can be adopted in the reaction of cracking and co-cracking the carbon four-mixed hydrocarbon to produce propylene ethylene.
In the technical scheme, the reaction conditions are as follows: the reaction temperature is 500-700 ℃, the reaction pressure is 0-1.0 MPa, and the weight airspeed of the mixed hydrocarbon raw material is 1-40 h -1 。
At present, in the reaction of preparing propylene and ethylene by catalytic cracking of mixed carbon four-hydrocarbon, the problems of low raw material conversion rate and low propylene and ethylene yield exist. This is mainly because the stability of butene and butane varies, the cracking mechanism varies, butene cracking occurs at a lower temperature, and butane cracking requires a higher reaction temperature, so that butane hardly reacts under the reaction conditions of butene catalytic cracking. And under the conditions of a butane cracking catalyst and a reaction, the yield of propylene ethylene which is a product is lower than that of single raw material cracking due to excessive byproducts of butene cracking.
Compared with the prior art, the invention has remarkable advantages and outstanding effects, and is concretely as follows:
(1) In the invention, the catalyst for co-cracking the carbon-four mixed hydrocarbon comprises the following components by taking the total weight of the catalyst as a reference: i) 58 to 84 percent of ZSM-5 molecular sieve; II) 10% -41% of a binder component; III) 0.5 to 6 percent of alkaline earth metal element; the acid quantity ratio of the B acid to the L acid of the catalyst is 0.5-2:1, and the apparent skeleton density is 1.0-2.3 g/ml. The catalyst has specific acid B/L ratio and special apparent skeleton density, and can convert the carbon tetraolefin and the carbon tetraalkane in the carbon tetramixed hydrocarbon into propylene and ethylene simultaneously under common process conditions by optimizing the reaction process conditions. The catalyst is used in the reaction of producing propylene and ethylene by co-cracking carbon four mixed hydrocarbon, and has the characteristics of high conversion rate of cracking raw materials, high propylene and ethylene yield of the product and good catalyst stability.
(2) In the preparation method of the catalyst, ZSM-5 molecular sieve raw powder is prepared firstly, and then the raw powder is molded, ammonium exchanged and acid modified to obtain the catalyst. According to the preparation method, the synthesized ZSM-5 molecular sieve raw powder is modified, so that the prepared catalyst has a specific acid B/L ratio and a special apparent skeleton density, a richer pore structure is generated, and the diffusion of reaction intermediates and products is accelerated. The catalyst prepared by the method can simultaneously convert the carbon tetraolefin and the carbon tetraalkane in the carbon tetramixed hydrocarbon into propylene and ethylene under the common process condition under the optimized reaction process condition, and has the characteristics of high conversion rate of cracking raw materials, high propylene and ethylene yield of products and good catalyst stability.
(3) In the application of the catalyst in the reaction of propylene and ethylene production by co-cracking of the carbon-four mixed hydrocarbon, the carbon-four olefin and the carbon-four alkane in the carbon-four mixed hydrocarbon can be simultaneously converted into propylene and ethylene under the common process condition under the optimized reaction process condition, and the catalyst has the characteristics of high conversion rate of cracking raw materials, high propylene and ethylene yield of products and good stability and feasibility of the catalyst. The reaction is carried out for 2 hours, the conversion rate of the carbon tetraolefin in the raw material mixed hydrocarbon can reach more than 75%, the conversion rate of the carbon tetraolefin can reach more than 41%, and the yield of the propylene ethylene of the product can reach more than 66%. The reaction runs for 75 hours for a long time, the catalyst has better stability, the catalytic activity is not obviously changed, and better technical effect is obtained.
Drawings
FIG. 1 is a pyridine adsorption infrared spectrum of the catalyst obtained in example 1;
FIG. 2 is an XRD pattern of the molecular sieve raw powder obtained in example 1;
FIG. 3 is an XRD pattern of the molecular sieve raw powder obtained in comparative example 1;
FIG. 4 is a pyridine adsorption infrared spectrum of the catalyst obtained in comparative example 1.
Detailed Description
The invention is further illustrated by the following examples.
In the context of the present specification, XRD analysis is described in RigakuThe process is carried out on a D/MAX-1400X type polycrystalline X-ray diffractometer, a graphite monochromator, cu K alpha rays, a tube voltage of 40kV, a tube current of 40mA and a scanning speed of 15 DEG min -1 The scanning range 2 theta is 5-50 deg.
In the context of this specification, the pyridine adsorption infrared spectrum is determined by IFS-88IR spectrometer analysis from Bruker. Specifically: after the sample is ground, the body tabletting is carried out, the diameter is 2cm, and the weight of the whole tablet is 11-14mg. Then put in a sample tube at 10 -2 Desorbing at 300 ℃ for 4 hours under Pa vacuum degree to remove impurities such as water in the sample, placing the cooled sample in pyridine saturated steam for adsorption, then respectively heating to 150 ℃, 200 ℃, 250 ℃,300 ℃ and 350 ℃ for balancing different temperatures for 10 minutes, then taking spectra, and stabilizing the spectra at 300 ℃. In the obtained map, the wave number is 1452cm -1 The nearby peak corresponds to the L-acid center of the catalyst and is located at 1542cm wavenumber -1 The nearby peak corresponds to the B acid center of the catalyst. Acid amount ratio of B acid and L acid (B acid/L acid) of 1542cm -1 Nearby and 1452cm -1 Near infrared absorption peak area ratio.
In the context of the present specification, the molar ratio of silicon to aluminum SiO 2 /Al 2 O 3 The element composition of the solid sample is analyzed by using a Magix X-type fluorescence spectrometer of Philips company in the Netherlands, and then the solid sample is calculated, the operating voltage is 40kV, and the operating current is 40mA.
In the context of this specification, apparent skeletal density is measured using an AutoPorEv 9600 full automatic mercury porosimeter from America microphone, inc., with a high pressure analysis maximum pressure of 60000psia (413685 kPa) and a high pressure pore diameter analysis diameter of minimum to 4nm.
In the context of this specification, the following formula is calculated:
carbon tetraolefin conversion (%) = (mass of carbon tetraolefin in 1-product/mass of carbon tetraolefin in feedstock) ×100%;
conversion of ctetraparaffin (%) = (ctetraparaffin mass in 1-product/ctetraparaffin mass of feedstock) ×100%;
propylene ethylene diene yield (%) = mass of propylene ethylene produced in product/mass of feed carbon four mixed hydrocarbon x 100%.
In the examples and comparative examples of this specification, the carbon-four mixed hydrocarbons used were derived from a refinery. The specific composition is shown in Table 1.
[ example 1 ]
a) Preparation of ZSM-5 molecular sieve raw powder
The method is characterized by taking tetramethyl ammonium bromide as a template agent, aluminum nitrate as an aluminum source, silica sol as a silicon source and sodium hydroxide as an alkali source, wherein the molar ratio of the tetramethyl ammonium bromide to the aluminum nitrate to the silica sol to the alkali to the water is as follows: NH (NH) 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.2:0.001:1:0.2:5, and after thoroughly mixing and stirring, transferred into an autoclave, crystallized at 180 ℃ under autogenous pressure for 10 hours, and cooled. And (3) carrying out suction filtration, water washing and drying at 80 ℃ on the synthesized product for 30 hours to obtain ZSM-5 molecular sieve raw powder.
b) The 70 g ZSM-5 molecular sieve raw powder, 40 g of binder alumina and 30 g of 5% dilute nitric acid are kneaded, extruded, molded, dried at 80 ℃ for 10 hours, and then baked at 500 ℃ for 8 hours to obtain a molded product.
c) The resulting molded article was subjected to ammonium exchange in a 5wt% aqueous ammonium nitrate solution at 90℃for 1 hour. The number of ammonium exchanges was 5. Washing, drying at 120 deg.C for 6 hr, and calcining at 500 deg.C for 8 hr.
d) The obtained ammonium exchange product is placed in a citric acid solution with the concentration of 2wt% at 70 ℃ and stirred for 4 hours, and the volume ratio of the acid solution to the ammonium exchange product is 3:1, washing, drying at 80 ℃ for 120 hours, and roasting at 500 ℃ for 8 hours. The catalyst is immersed in 2wt% magnesium nitrate solution for 5 hr, dried at 120 deg.c for 6 hr and roasted at 500 deg.c for 8 hr to obtain the catalyst for producing propylene and ethylene through catalytic cracking of four-carbon mixed hydrocarbon.
FIG. 1 is a pyridine adsorption infrared spectrum of the catalyst obtained in example 1. The acid amount ratio of the B acid to the L acid in the catalyst was 1.06:1, and the apparent skeleton density was 1.0 g/ml.
The composition of the catalyst is as follows: a) 60% ZSM-5 molecular sieve; b) 38% of a binder component; c) 2% of metal element Mg.
ZSM-5 molecular sieve in the catalyst componentSilicon to aluminum molar ratio SiO 2 /Al 2 O 3 1000.
The XRD pattern of the obtained ZSM-5 molecular sieve raw powder is shown in figure 2.
The method adopts a fixed bed catalytic reaction device, uses the residual mixed carbon four of an ethylene plant as a raw material, carries out the catalytic cracking reaction activity evaluation of the prepared catalyst for producing propylene and ethylene by using the carbon four mixed hydrocarbon, and examines the used process conditions as follows: the catalyst is filled with 0.6 g, the reaction temperature is 500 ℃, the reaction pressure is 0.2MPa, and the weight space velocity is 10h -1 。
The results of reactions 2h and 75h are shown in Table 2.
[ example 2 ]
a) Preparation of ZSM-5 molecular sieve raw powder
The method is characterized by taking tetrapropylammonium bromide as a template agent, aluminum sulfate as an aluminum source, water glass as a silicon source and potassium hydroxide as an alkali source, wherein the mole ratio of the tetrapropylammonium bromide to the aluminum sulfate to the water glass to the alkali to the water is as follows: NH (NH) 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.5:0.01:1:0.4:10, and after thoroughly mixing and stirring, transferred into an autoclave, crystallized at 120 ℃ under autogenous pressure for 60 hours, and cooled. And (3) carrying out suction filtration, water washing and drying at 120 ℃ on the synthesized product for 10 hours to obtain ZSM-5 molecular sieve raw powder.
b) 70 g of ZSM-5 molecular sieve raw powder and 75 g of binder silica sol (SiO 2 40% by weight), kneading, extruding, drying at 120 ℃ for 5 hours, and roasting at 600 ℃ for 4 hours to obtain a molded product.
c) The resulting molded article was subjected to ammonium exchange at 80℃in a 10% by weight aqueous solution of ammonium sulfate for 2 hours, followed by washing, drying at 80℃for 20 hours, and then baking at 600℃for 4 hours.
d) The obtained ammonium exchange product is placed in 5wt% oxalic acid solution at 80 ℃ to be stirred for 8 hours, and the volume ratio of acid liquor to ammonium exchange product is 5:1, washing, drying at 120 ℃ for 6 hours, and roasting at 600 ℃ for 4 hours. The catalyst is immersed in 5% calcium nitrate solution for 15 hours by adopting an equal volume immersion method, dried at 80 ℃ for 20 hours and then baked at 600 ℃ for 4 hours, and the catalyst for producing propylene ethylene by catalytic pyrolysis of the required carbon four mixed hydrocarbon is obtained.
The acid amount ratio of the B acid to the L acid in the catalyst was 0.8:1, and the apparent skeleton density was 1.2 g/ml.
The composition of the catalyst is as follows: a) 64% ZSM-5 molecular sieve; b) 31% of a binder component; c) 5% of metal element Ca.
Silicon-aluminum molar ratio SiO of ZSM-5 molecular sieve in the catalyst component 2 /Al 2 O 3 100. The XRD pattern of the resulting ZSM-5 molecular sieve raw powder was similar to that of FIG. 2.
The method adopts a fixed bed catalytic reaction device, uses the residual mixed carbon four of an ethylene plant as a raw material, carries out the catalytic cracking reaction activity evaluation of the prepared catalyst for producing propylene and ethylene by using the carbon four mixed hydrocarbon, and examines the used process conditions as follows: the catalyst is filled with 0.6 g, the reaction temperature is 600 ℃, the reaction pressure is 0.5MPa, and the weight space velocity of the olefin raw material is 20h -1 。
The results of reactions 2h and 75h are shown in Table 2.
[ example 3 ]
a) Preparation of ZSM-5 molecular sieve raw powder
The method takes tetrapropylammonium hydroxide as a template agent, sodium aluminate as an aluminum source, ethyl orthosilicate as a silicon source and sodium hydroxide as an alkali source, wherein the mole ratio of tetrapropylammonium hydroxide, sodium aluminate, ethyl orthosilicate, alkali and water is as follows: NH (NH) 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.1:0.00125:1:0.1:8, and after thoroughly mixing and stirring, transferred into an autoclave, crystallized at 150 ℃ under autogenous pressure for 30 hours, and cooled. And (3) carrying out suction filtration, water washing and drying at 100 ℃ on the synthesized product for 20 hours to obtain ZSM-5 molecular sieve raw powder.
b) 80 g of ZSM-5 molecular sieve raw powder and 80 g of binder aluminum sol (Al 2 O 3 25% by weight), kneading, extruding, drying at 100deg.C for 8 hr, and calcining at 550deg.C for 6 hr to obtain the final product.
c) The resulting molded article was subjected to ammonium exchange at 85℃in a 10% by weight aqueous solution of ammonium chloride for 1.5 hours, followed by washing, drying at 120℃for 6 hours, and then calcination at 550℃for 6 hours.
d) The obtained ammonium exchange product is placed in an oxalic acid solution with the weight percentage of 3 percent at the temperature of 75 ℃ and stirred for 6 hours, and the volume ratio of the acid liquor to the ammonium exchange product is 2:1. washing, drying at 120 deg.C for 6 hr, and calcining at 550 deg.C for 7 hr. The catalyst is immersed in 3% strontium nitrate solution for 10 hours by adopting an isovolumetric immersion method, dried at 100 ℃ for 10 hours and then baked at 550 ℃ for 6 hours, and the catalyst for producing propylene ethylene by catalytic pyrolysis of the required carbon four mixed hydrocarbon is obtained.
The acid amount ratio of the B acid to the L acid in the catalyst was 1.5:1, and the apparent skeleton density was 2.02 g/ml.
The composition of the catalyst is as follows: a) 77.6% ZSM-5 molecular sieve; b) 19.4% of a binder component; c) 3% of metallic element Sr.
Silicon-aluminum molar ratio SiO of ZSM-5 molecular sieve in the catalyst component 2 /Al 2 O 3 800. The XRD pattern of the resulting ZSM-5 molecular sieve raw powder was similar to that of FIG. 2.
The method adopts a fixed bed catalytic reaction device, uses the residual mixed carbon four of an ethylene plant as a raw material, carries out the catalytic cracking reaction activity evaluation of the prepared catalyst for producing propylene and ethylene by using the carbon four mixed hydrocarbon, and examines the used process conditions as follows: the catalyst is filled with 0.6 g, the reaction temperature is 700 ℃, the reaction pressure is 0.1MPa, and the weight space velocity of the olefin raw material is 1h -1 。
The results of reactions 2h and 75h are shown in Table 2.
[ example 4 ]
a) Preparation of ZSM-5 molecular sieve raw powder
The method is characterized by taking tetraethyl ammonium bromide as a template agent, aluminum phosphate as an aluminum source, water glass as a silicon source and potassium hydroxide as an alkali source, wherein the molar ratio of the tetraethyl ammonium bromide to the aluminum phosphate to the water glass to the alkali to the water is as follows: NH (NH) 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.2:0.002:1:0.2:10, and after thoroughly mixing and stirring, transferred into an autoclave, crystallized at 160 ℃ under autogenous pressure for 15 hours, and cooled. And (3) carrying out suction filtration, water washing and drying at 90 ℃ on the synthesized product for 25 hours to obtain ZSM-5 molecular sieve raw powder.
b) 80 g of ZSM-5 molecular sieve raw powder and 50 g of binder silica sol are mixed(SiO 2 40% by weight), kneading, extruding, drying at 80 ℃ for 10 hours, and roasting at 500 ℃ for 8 hours to obtain a molded product.
c) The resulting molded article was subjected to ammonium exchange at 80℃in a 5wt% aqueous ammonium nitrate solution for 2 hours, followed by washing and drying at 100℃for 10 hours, and then roasting at 600℃for 4 hours.
d) The resulting ammonium exchange product was stirred in a 5wt% citric acid solution at 70 ℃ for 4 hours at a volume ratio of acid to ammonium exchange product of 2:1. washing, drying at 100deg.C for 10 hr, and calcining at 500deg.C for 6 hr. The catalyst is immersed in 2% magnesium nitrate solution for 10 hours by adopting an equal volume immersion method, dried at 100 ℃ for 10 hours and then baked at 550 ℃ for 6 hours, and the catalyst for producing propylene ethylene by catalytic pyrolysis of the required carbon four mixed hydrocarbon is obtained.
The acid amount ratio of the B acid to the L acid in the catalyst was 0.8:1, and the apparent skeleton density was 2.3 g/ml.
The composition of the catalyst is as follows: a) 76.9% ZSM-5 molecular sieve; b) 21.1% of a binder component. c) 2% of metal element Mg.
Silicon-aluminum molar ratio SiO of ZSM-5 molecular sieve in the catalyst component 2 /Al 2 O 3 500. The XRD pattern of the resulting ZSM-5 molecular sieve raw powder was similar to that of FIG. 2.
The method adopts a fixed bed catalytic reaction device, uses the residual mixed carbon four of an ethylene plant as a raw material, carries out the catalytic cracking reaction activity evaluation of the prepared catalyst for producing propylene and ethylene by using the carbon four mixed hydrocarbon, and examines the used process conditions as follows: the catalyst is filled with 0.6 g, the reaction temperature is 550 ℃, the reaction pressure is 1.0MPa, and the weight space velocity of the olefin raw material is 40h -1 。
The results of reactions 2h and 75h are shown in Table 2.
[ example 5 ]
a) Preparation of ZSM-5 molecular sieve raw powder
The preparation method comprises the steps of taking tetrapropylammonium hydroxide as a template agent, aluminum nitrate as an aluminum source, silica sol as a silicon source and sodium hydroxide as an alkali source, wherein the mole ratio of tetrapropylammonium hydroxide, aluminum nitrate, silica sol, alkali and water is as follows: NH (NH) 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.1:0.005:1:0.2:6, and after thoroughly mixing and stirring, transferred into an autoclave, crystallized at 180 ℃ under autogenous pressure for 10 hours, and cooled. And (3) carrying out suction filtration, water washing and drying at 120 ℃ on the synthesized product for 10 hours to obtain ZSM-5 molecular sieve raw powder.
b) The 85 g ZSM-5 molecular sieve raw powder, 25 g of binder alumina and 32 g of 5% dilute nitric acid are kneaded, extruded, molded, dried at 80 ℃ for 10 hours, and then baked at 600 ℃ for 4 hours to obtain a molded product.
c) The resulting molded article was subjected to ammonium exchange at 90℃in a 10% by weight aqueous solution of ammonium sulfate for 1.5 hours, followed by washing, drying at 120℃for 6 hours, and then baking at 500℃for 8 hours.
d) The resulting ammonium exchange product was stirred in a 5wt% acetic acid solution at 70 ℃ for 6 hours, the volume ratio of acid solution to ammonium exchange product being 5:1. washing, drying at 120 deg.C for 6 hr, and calcining at 500 deg.C for 8 hr. And (3) soaking the catalyst in a 2% calcium nitrate solution for 8 hours by adopting an isovolumetric soaking method, drying at 120 ℃ for 6 hours, and roasting at 550 ℃ for 8 hours to obtain the catalyst for producing propylene ethylene by catalytic pyrolysis of the required carbon four mixed hydrocarbon.
The acid amount ratio of the B acid to the L acid in the catalyst is 1:1, and the apparent skeleton density is 1.5 g/ml.
The composition of the catalyst is as follows: a) 74% ZSM-5 molecular sieve; b) 24% of a binder component; c) 2% of metal element Ca.
Silicon-aluminum molar ratio SiO of ZSM-5 molecular sieve in the catalyst component 2 /Al 2 O 3 200. The XRD pattern of the resulting ZSM-5 molecular sieve raw powder was similar to that of FIG. 2.
The method adopts a fixed bed catalytic reaction device, uses the residual mixed carbon four of an ethylene plant as a raw material, carries out the catalytic cracking reaction activity evaluation of the prepared catalyst for producing propylene and ethylene by using the carbon four mixed hydrocarbon, and examines the used process conditions as follows: the catalyst is filled with 0.6 g, the reaction temperature is 650 ℃, the reaction pressure is 0.05MPa, and the weight space velocity of the olefin raw material is 30h -1 。
The results of reactions 2h and 75h are shown in Table 2.
Comparative example 1
a) Preparation of ZSM-5 molecular sieve raw powder
The method takes tetrapropylammonium hydroxide as a template agent, sodium aluminate as an aluminum source, ethyl orthosilicate as a silicon source and sodium hydroxide as an alkali source, wherein the mole ratio of tetrapropylammonium hydroxide, sodium aluminate, ethyl orthosilicate, alkali and water is as follows: NH (NH) 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.1:0.00125:1:0.1:8, and after thoroughly mixing and stirring, transferred into an autoclave, crystallized at 150 ℃ under autogenous pressure for 30 hours, and cooled. And (3) carrying out suction filtration, water washing and drying at 100 ℃ on the synthesized product for 20 hours to obtain ZSM-5 molecular sieve raw powder.
b) 80 g of ZSM-5 molecular sieve raw powder and 80 g of binder aluminum sol (Al 2 O 3 25% by weight), kneading, extruding, drying at 100deg.C for 8 hr, and calcining at 550deg.C for 6 hr to obtain the final product.
c) The resulting molded article was subjected to ammonium exchange at 85℃in a 10% by weight aqueous solution of ammonium chloride for 1.5 hours, followed by washing, drying at 120℃for 6 hours, and then calcination at 550℃for 6 hours.
d) And (3) immersing the obtained ammonium exchange product in a 3% strontium nitrate solution for 10 hours by adopting an isovolumetric immersion method, drying at 100 ℃ for 10 hours, and roasting at 550 ℃ for 6 hours to obtain the catalyst for producing propylene ethylene by catalytic pyrolysis of the required carbon four-mixed hydrocarbon.
FIG. 4 is a pyridine adsorption infrared spectrum of the catalyst obtained in comparative example 1, wherein 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.
The composition of the catalyst is as follows: a) 77.6% ZSM-5 molecular sieve; b) 19.4% of a binder component; c) 3% of metallic element Sr.
Silicon-aluminum molar ratio SiO of ZSM-5 molecular sieve in the catalyst component 2 /Al 2 O 3 800.
XRD patterns of the obtained ZSM-5 molecular sieve raw powder are shown in figure 3.
The catalyst evaluation method was the same as in example 3, and the reaction results are shown in Table 2.
Comparative example 2
a) Preparation of ZSM-5 molecular sieve raw powder
The method takes tetrapropylammonium hydroxide as a template agent, sodium aluminate as an aluminum source, ethyl orthosilicate as a silicon source and sodium hydroxide as an alkali source, wherein the mole ratio of tetrapropylammonium hydroxide, sodium aluminate, ethyl orthosilicate, alkali and water is as follows: NH (NH) 4 + :Al 2 O 3 :SiO 2 :OH - :H 2 O=0.1:0.00125:1:0.1:8, and after thoroughly mixing and stirring, transferred into an autoclave, crystallized at 150 ℃ under autogenous pressure for 30 hours, and cooled. And (3) carrying out suction filtration, water washing and drying at 100 ℃ on the synthesized product for 20 hours to obtain ZSM-5 molecular sieve raw powder.
b) 80 g of ZSM-5 molecular sieve raw powder and 80 g of binder aluminum sol (Al 2 O 3 25% by weight), kneading, extruding, drying at 100deg.C for 8 hr, and calcining at 550deg.C for 6 hr to obtain the final product.
c) The resulting molded article was subjected to ammonium exchange at 85℃in a 10% by weight aqueous solution of ammonium chloride for 1.5 hours, followed by washing, drying at 120℃for 6 hours, and then calcination at 550℃for 6 hours.
d) The obtained ammonium exchange product is placed in an oxalic acid solution with the weight percentage of 3 percent at the temperature of 75 ℃ and stirred for 6 hours, and the volume ratio of the acid liquor to the ammonium exchange product is 2:1. washing, drying at 120 deg.C for 6 hr, and calcining at 550 deg.C for 7 hr. The catalyst for producing propylene and ethylene by catalytic cracking of the required carbon four mixed hydrocarbon is obtained.
The acid amount ratio of the B acid to the L acid in the catalyst was 2.1:1, and the apparent skeleton density was 2.0 g/ml.
The composition of the catalyst is as follows: a) 78.3% ZSM-5 molecular sieve; b) 21.7% of a binder component.
Silicon-aluminum molar ratio SiO of ZSM-5 molecular sieve in the catalyst component 2 /Al 2 O 3 800. The catalyst evaluation method was the same as in example 3, and the reaction results are shown in Table 2.
Table 1 refinery C4 hydrocarbon feedstock composition
| Component (A) | Composition (wt%) |
| Isobutane | 30.64 |
| N-butane | 9.25 |
| 1-butene | 10.23 |
| Isobutene (i-butene) | 24.76 |
| Trans-2-butene | 14.52 |
| Cis-2-butene | 10.54 |
| 1, 3-butadiene | 0.06 |
Table 2 results of evaluation of catalysts
Claims (14)
1. A catalyst for co-cracking of a carbon-four mixed hydrocarbon, which comprises the following components by taking the total weight of the catalyst as a reference:
i) 58 to 84 percent of ZSM-5 molecular sieve;
II) 10% -41% of a binder component;
III) 0.5 to 6 percent of alkaline earth metal element;
the acid quantity ratio of the B acid to the L acid of the catalyst is 0.5-2:1, and the apparent skeleton density is 1.0-2.3 g/ml.
2. The catalyst of claim 1, wherein the catalyst has an acid amount ratio of B acid to L acid of 0.8 to 1.5:1 and an apparent skeletal density of 1.0 to 1.8 g/ml.
3. Catalyst according to claim 1, characterized in that the ZSM-5 molecular sieve of component I) has SiO 2 /Al 2 O 3 The molar ratio is 50-1000, preferably 100-1000;
and/or, the alkaline earth metal element in component III) is selected from at least one of Mg, ca, sr, ba.
4. A process for preparing a catalyst according to any one of claims 1 to 3, comprising the steps of:
a) Preparing ZSM-5 molecular sieve raw powder;
b) Kneading the raw powder obtained in the step a) and a binder for molding, drying, and performing first roasting to obtain a molded product;
c) Performing ammonium exchange on the formed product obtained in the step b), and performing second roasting to obtain an ammonium exchange product;
d) And c) treating the ammonium exchange product obtained in the step c) in acid liquor, and carrying out third roasting, alkaline earth metal loading and fourth roasting to obtain the catalyst.
5. The method according to claim 4, wherein the process of preparing the ZSM-5 molecular sieve raw powder in the step a) comprises the following steps: uniformly mixing a template agent, an aluminum source, a silicon source, an alkali source and water, carrying out hydrothermal crystallization, and drying to obtain ZSM-5 molecular sieve raw powder.
6. The method of claim 5, wherein the templating agent comprises at least one of tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide, and tetrapropyl ammonium hydroxide;
and/or, the aluminum source comprises at least one of aluminum nitrate, aluminum sulfate, aluminum phosphate, and sodium aluminate;
and/or, the silicon source comprises at least one of water glass, silica sol and tetraethoxysilane;
and/or the alkali source comprises at least one of sodium hydroxide and potassium hydroxide.
7. The process according to claim 5, wherein in the raw materials used in the preparation of ZSM-5 molecular sieve raw powder in step a), the template agent is NH 4 + Metering Al as Al source 2 O 3 Meter, silicon source with SiO 2 Counting the alkali source by OH - The mole ratio of the calculated water to the water is as follows: NH (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 hydrothermal crystallization conditions are: crystallizing at 120-180 deg.c for 10-60 hr.
8. The preparation method according to claim 4, wherein in the step b), the binder is one or more selected from the group consisting of alumina, alumina sol and silica sol;
and/or, the drying conditions in step b) are: drying at 80-120 deg.c for 5-10 hr;
and/or, the conditions of the first roasting are as follows: roasting for 4-8 hours at 500-600 ℃.
9. The process according to claim 4, wherein the conditions for the ammonium exchange in step c) are: the temperature is 80-90 ℃ and the time is 1-3 h;
preferably, the number of ammonium exchanges is 2 to 5;
further preferably, the concentration of the ammonium salt aqueous solution in the ammonium exchange is 5wt% to 10wt%; the ammonium salt is at least one selected from ammonium chloride, ammonium nitrate and ammonium sulfate;
and/or the second roasting condition is that roasting is carried out for 4-8 hours at 500-600 ℃.
10. The method according to claim 4, wherein the acid content in the acid solution in step d) is 2 to 5wt%; the acid is an organic acid; the organic acid comprises at least one selected from citric acid, oxalic acid, acetic acid and oxalic acid;
and/or, the treatment in step d) is soaking, and the treatment conditions are as follows: the volume ratio of the acid liquor to the ammonium exchange product is 2:1 to 5:1, the treatment temperature is 70-80 ℃ and the treatment time is 4-8 hours;
and/or, the third roasting condition in the step d) is that roasting is carried out for 4-8 hours at 500-600 ℃.
11. The process according to claim 4, wherein the alkaline earth metal supported in step d) is an isovolumetric impregnation process; and/or the fourth roasting condition is that roasting is carried out for 4-8 hours at 500-600 ℃.
12. Use of a catalyst according to any one of claims 1 to 3 or a catalyst prepared by a process according to any one of claims 4 to 11 in a co-cracking of a carbon-four mixed hydrocarbon to produce propylene and ethylene.
13. The use according to claim 12, wherein the carbon-tetra mixed hydrocarbon is derived from a refinery carbon-tetra mixed hydrocarbon;
preferably, the carbon-four mixed hydrocarbon comprises at least one of isobutane, n-butane, 1-butene, isobutene, trans-2-butene and 1, 3-butadiene;
more preferably, the carbon-four mixed hydrocarbon is at least one alkane and at least one alkene.
14. The use according to claim 12, wherein the reaction conditions are: the reaction temperature is 500-700 ℃, the reaction pressure is 0-1.0 MPa, and the weight airspeed of the mixed hydrocarbon raw material is 1-40 h -1 。
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