A catalyst for low carbon alkane cracking to produce propane, and a preparation method and application thereof

Abstract

The application provides a catalyst for cracking low-carbon alkanes to produce propane as well as a preparation method and application thereof, and belongs to the technical field of cracking catalyst preparation. The catalyst comprises a molecular sieve, alumina, a first active component, a second active component and a modified component. The first active component is one or more selected from ZnO, NiO, CoO and CaO. The second active component is P2O5. The modified component is one or both of La2O3 and MgO. The catalyst for cracking low-carbon alkanes to produce propane provided by the application can obtain a higher propane yield at a lower reaction temperature and has high reactivity.

Description

Technical Field

[0001] This invention relates to the field of cracking catalyst preparation technology, and in particular to a catalyst for the cracking of low-carbon alkanes to propane, its preparation method, and its application. Background Technology

[0002] Propylene is an important chemical raw material, widely used in the production of chemical products such as polypropylene, acrylic acid, propylene oxide, and acrylonitrile. In my country, traditional propylene is mainly produced as a co-production or by-product of processes such as naphtha cracking and catalytic cracking. With the increasing consumption of propylene year by year, traditional propylene production can no longer meet the demand. Therefore, propane dehydrogenation to propylene technology has developed rapidly. Propylene, as a raw material for its production, can be obtained through petroleum refining and coal chemical processes, or it can be produced by cracking butane and naphtha topping oil, which have lower added value.

[0003] Since the 1960s, molecular sieves have been used as catalysts for catalytic cracking. Due to their good thermal stability, high catalytic activity and selectivity, they have been widely used in catalytic cracking reactions. Commonly used zeolite molecular sieves include single-structure zeolite molecular sieves such as Y-type, M-type and ZSM-type.

[0004] The cracking reaction of low-carbon alkanes occurs at temperatures between 300 and 500°C and is a strongly endothermic reaction. In addition to the main product propane, the cracking products include byproducts such as hydrogen, methane, ethane, and oligomer oils. During the reaction, the catalyst is easily clogged by the generated polycyclic aromatic hydrocarbons, leading to reduced activity or deactivation. Therefore, the catalyst needs to be treated to improve its resistance to carbon buildup and extend its service life. Currently, catalytic cracking catalysts suffer from problems such as short service life. Summary of the Invention

[0005] One of the objectives of this invention is to provide a catalyst for the cracking of low-carbon alkanes to produce propane. By modifying the catalyst, it is applied to the fixed-bed reaction of cracking low-carbon alkanes to produce propane, and has the advantages of high propane yield, low dry gas yield, simple catalyst preparation method, long service life and easy regeneration.

[0006] A second objective of this invention is to provide a method for preparing the catalyst.

[0007] A third objective of this invention is to provide an application of the catalyst.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] In a first aspect, the present invention provides a catalyst for the cracking of low-carbon alkane to propane, the catalyst comprising a molecular sieve, alumina, a first co-active component, a second co-active component, and a modifying component;

[0010] The first auxiliary active component is one or more selected from ZnO, NiO, CoO and CaO;

[0011] The second co-active component is P2O5;

[0012] The modifying component is selected from one or two of La2O3 and MgO;

[0013] Based on the mass of the catalyst, the mass percentage of molecular sieve is 65-75%, the mass percentage of alumina is 16-29.5%, the mass percentage of the first co-active component is 2-3%, the mass percentage of the second co-active component is 3-5%, and the mass percentage of the modifying component is 0.5-1%.

[0014] The following is a detailed description of each component:

[0015] Molecular sieves:

[0016] The molecular sieve can be a single HZSM-5, HUSY, or a mixture of both, preferably HZSM-5. More preferably, the HZSM-5 molecular sieve has a silica-alumina ratio of 20 to 40, a relative crystallinity of >80%, a grain size of <1 μm, and a Na2O content of <0.05%.

[0017] The molecular sieve accounts for a percentage of the catalyst by mass, for example, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, but is not limited thereto.

[0018] Alumina:

[0019] The alumina is derived from small-pore or macroporous boehmite, preferably small-pore boehmite. More preferably, the small-pore boehmite has a pore volume of 0.4–0.45 mL / g and a specific surface area ≥270 μm. 2 / g, Na2O content <0.1%, colloidal index >95%, dry basis content ≥67%.

[0020] The mass percentage of alumina in the catalyst is, for example, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, but is not limited thereto.

[0021] First active ingredient:

[0022] The first auxiliary active component is one or more selected from ZnO, NiO, CoO and CaO, and may be derived from the corresponding metal element salt, such as nitrate, sulfate and acetate, preferably nitrate and acetate.

[0023] The mass percentage of the first co-active component in the catalyst is, for example, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, or 2.9%, but is not limited thereto.

[0024] Second active ingredient:

[0025] The second active component is P2O5, which can be derived from phosphoric acid or diammonium hydrogen phosphate, preferably diammonium hydrogen phosphate.

[0026] The mass percentage of the second co-active component in the catalyst is, for example, 3%, 3.2%, 3.4%, 3.5%, 3.6%, 3.8%, 4%, 4.2%, 4.5%, 4.6%, or 4.8%, but is not limited thereto.

[0027] Modified components:

[0028] The modified component is selected from one or both of La2O3 and MgO, and may be derived from the corresponding metal element salt, such as nitrate or acetate, preferably nitrate.

[0029] The modified component accounts for a percentage of the catalyst by mass, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, but is not limited thereto.

[0030] In some embodiments, the catalyst is a cylindrical or clover-shaped piece with a diameter of 1.5–2.5 mm and a specific surface area > 290 m². 2 / g, Na2O content <0.1%.

[0031] Secondly, the present invention provides a method for preparing the above-mentioned catalyst for the cracking of low-carbon alkanes to propane, comprising the following steps:

[0032] 1) Molecular sieve, pseudoboehmite, and guar gum powder are mixed evenly at a mass ratio of 140:45-90:5-8, and kneaded with an aqueous solution containing the metal salt corresponding to the first co-active component, the metal salt corresponding to the modified component, and citric acid. The kneaded material is extruded, dried, and calcined to obtain a catalyst semi-finished product. The mass ratio of molecular sieve to the metal salt corresponding to the first co-active component, the metal salt corresponding to the modified component, citric acid, and water is 100:10-16:2-4:3-5:25-30.

[0033] 2) Determine the water absorption rate of the catalyst semi-finished product obtained in step 1), impregnate it with an aqueous solution of phosphoric acid or diammonium hydrogen phosphate in an equal volume impregnation manner, and after impregnation, dry and calcine to obtain a catalyst for the cracking of low-carbon alkanes to produce propane.

[0034] The following is a detailed explanation of each step:

[0035] Step 1):

[0036] The molecular sieve can be a single HZSM-5, HUSY, or a mixture of both, preferably HZSM-5;

[0037] The pseudoboehmite can be either small-pore pseudoboehmite or large-pore pseudoboehmite, with small-pore pseudoboehmite being preferred.

[0038] The metal salt corresponding to the first auxiliary active component can be zinc nitrate hexahydrate, zinc acetate dihydrate, nickel nitrate hexahydrate, nickel acetate tetrahydrate, cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, calcium nitrate tetrahydrate, or calcium acetate monohydrate.

[0039] The metal salts corresponding to the modified components can be lanthanum nitrate hexahydrate, lanthanum acetate tetrahydrate, magnesium nitrate hexahydrate, and magnesium acetate tetrahydrate.

[0040] In some embodiments, in step 1), the drying temperature is 150-160°C and the drying time is 4-5 hours.

[0041] In some embodiments, in step 1), the calcination temperature is 500-600°C and the calcination time is 4-5 hours.

[0042] Step 2):

[0043] In some embodiments, in step 2), the mass ratio of the catalyst semi-finished product to phosphoric acid or diammonium hydrogen phosphate (preferably diammonium hydrogen phosphate) is 1000:56-93.

[0044] In some implementations, the immersion time in step 2) is 30 to 60 minutes.

[0045] In some embodiments, in step 2), the drying temperature is 150-160°C and the drying time is 4-5 hours.

[0046] In some embodiments, in step 2), the calcination temperature is 400-500°C and the calcination time is 4-5 hours.

[0047] Thirdly, the present invention also provides an application of the above-mentioned catalyst in the catalytic cracking of low-carbon alkanes to propane.

[0048] In some embodiments, the reaction conditions are: reaction temperature 300–450°C, reaction pressure 0.5–1 MPa, and weight hourly space velocity 0.4–1 h⁻¹. -1 .

[0049] Low-carbon alkanes include, but are not limited to, butane, pentane, hexane, and mixed alkanes such as naphtha and hair oil.

[0050] The catalyst of this invention is used for the cracking of low-carbon alkanes to produce propane. The catalyst has high initial activity, with a conversion rate of butane ≥60%, a conversion rate of pentane ≥70%, and corresponding propane yields of ≥50% and ≥40%, respectively, and a dry gas yield of <1%.

[0051] Beneficial effects

[0052] (1) The catalyst for producing propane from low-carbon alkane cracking provided by the present invention can obtain a high propane yield at a lower reaction temperature, has high reaction activity, and can use multiple raw materials at the same time (such as a mixture of butane and butene, naphtha top oil, etc.).

[0053] (2) The catalyst for producing propane from low-carbon alkane cracking provided by the present invention has a simple preparation method, a long single-pass operation cycle, and is easy to regenerate.

[0054] (3) The catalyst for producing propane from low-carbon alkane cracking provided by the present invention has low dry gas yield and high atom utilization rate in the reaction of producing propane from low-carbon alkane cracking.

[0055] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Detailed Implementation

[0056] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0057] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0058] The raw materials involved in the examples are as follows:

[0059] HZSM-5 molecular sieve is from Zhongchumei New Materials Co., Ltd., with a silicon-to-aluminum ratio of 25.2, relative crystallinity of 98.5%, grain size of 200-600nm, and Na2O content of 0.03%.

[0060] HZSM-5 molecular sieve is from Zhongchumei New Materials Co., Ltd., with a silicon-to-aluminum ratio of 39.7, relative crystallinity of 91.4%, grain size of 200-600nm, and Na2O content of 0.04%.

[0061] The small-pore pseudoboehmite, sourced from Zibo Hengyi Chemical Technology Co., Ltd., has a pore volume of 0.41 mL / g and a specific surface area of ​​278.4 μm. 2 / g, Na2O content 0.09%, colloidal index 96.54%, dry basis content 68.5%.

[0062] Example 1

[0063] The catalyst preparation steps are as follows.

[0064] 1) Place 70Kg HZSM-5 molecular sieve (silicon-to-alumina ratio 25.2), 30Kg small-pore boehmite, and 3Kg guar gum powder into a kneader and turn on the stirrer to mix the materials for 5 minutes.

[0065] 2) Dissolve 9.1 kg of zinc nitrate hexahydrate, 2.1 kg of lanthanum nitrate hexahydrate, and 2.8 kg of citric acid in 20 kg of deionized water and stir until completely dissolved;

[0066] 3) Spray the solution prepared in step 2) evenly onto the powder in the kneader for 20-30 minutes, and continue kneading for 10-15 minutes.

[0067] 4) Extrude the kneaded material into 2mm round strips using an extruder, dry at 150℃ for 4 hours, and calcine at 550℃ for 4 hours;

[0068] 5) The water absorption rate of the catalyst semi-finished product obtained in step 4) was 42.75%. 10 kg of the catalyst semi-finished product was weighed and modified by impregnation with equal amounts.

[0069] 6) Weigh 0.75 kg of diammonium hydrogen phosphate into a 50 L plastic container, add 4.27 kg of deionized water, and stir until completely dissolved;

[0070] 7) Pour 10 kg of catalyst semi-finished product into the prepared solution, shake to allow the diammonium hydrogen phosphate solution to be completely adsorbed onto the catalyst, and let stand for 20 min.

[0071] 8) The impregnated catalyst was dried at 150°C for 4 hours and calcined at 450°C for 4 hours to obtain the catalyst, denoted as CatA.

[0072] Example 2

[0073] The steps are the same as in Example 1, except that the silica-alumina ratio of the molecular sieve is changed to 39.7, and the prepared catalyst is denoted as CatB.

[0074] Example 1

[0075] 50g of CatA and CatB were respectively packed into an adiabatic fixed-bed reactor, and butane containing some butene was used as raw material for cracking reaction. The reaction pressure was 1MPa, the reaction temperature was 320℃, and the feed rate was 25g / h. Samples were taken for analysis 4 hours after feeding. The experimental results are shown in the table below (dry gas in the table refers to hydrogen, methane, ethane, and ethylene).

[0076]

[0077]

[0078] Example 2

[0079] Following the evaluation method in Example 1, naphtha topsoil was used as raw material for pyrolysis reaction. The reaction pressure was 1 MPa, the reaction temperature was 340℃, and the feed rate was 25 g / h. Samples were taken for analysis 4 hours after feeding. The test results are shown in the table below (dry gas in the table refers to hydrogen, methane, ethane, and ethylene).

[0080]

[0081]

[0082] Example 3

[0083] The stability test of CatB was carried out according to the evaluation method of Example 1. The propane yield was maintained at ≥45% by continuously increasing the reaction temperature. After running for 950 hours, the propane yield was 42.56% and the dry gas yield was 1.76% after the heating temperature was increased to 440℃. The catalyst was removed and dried at 200℃ for 4 hours, and then regenerated at 500℃ for 4 hours under air flow. The carbon deposition was 15.27%. The regenerated catalyst was evaluated at a reaction temperature of 320℃ and its performance was basically the same as that of the fresh catalyst.

[0084]

[0085]

[0086] Comparative Example 1

[0087] The catalyst was prepared according to the method in Example 1, without adding lanthanum nitrate hexahydrate in step 2), and the resulting catalyst was labeled CatC.

[0088] Comparative Example 2

[0089] The catalyst semi-finished product was prepared according to the method in Example 1, without adding lanthanum nitrate hexahydrate in step 2) and without performing the impregnation step of the semi-finished catalyst, and the resulting catalyst semi-finished product was labeled CatD.

[0090] Comparison of effects Example 3

[0091] The two catalysts, CatC and CatD, were evaluated according to the method in Example 2. The test results are shown in the table below (dry gas in the table refers to hydrogen, methane, ethane, and ethylene).

[0092]

[0093]

[0094] The above experimental results show that adding diammonium hydrogen phosphate reduces the catalyst activity but is beneficial to the propane yield. Adding lanthanum nitrate hexahydrate reduces the dry gas yield. When the catalyst prepared in this invention is used for the cracking reaction of low-carbon alkanes to produce propane, in the initial stage of the reaction, when the conversion rate of butane is >60% and the conversion rate of pentane is >70%, the corresponding propane yields are >50% and >40%, respectively. When butane is used as a raw material, the propane yield is high, and n-alkanes are more conducive to cracking to produce propane.

[0095] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. The application of a catalyst in the catalytic cracking of low-carbon alkanes to propane, characterized in that, The catalyst comprises molecular sieve, alumina, a first co-activating component, a second co-activating component, and a modifying component; The first auxiliary active component is one or more selected from ZnO, NiO, CoO and CaO; The second co-active component is P2O5; The modified component is La2O3; Based on the mass of the catalyst, the mass percentage of molecular sieve is 65-75%, the mass percentage of alumina is 16-29.5%, the mass percentage of the first co-active component is 2-3%, the mass percentage of the second co-active component is 3-5%, and the mass percentage of the modifying component is 0.5-1%. The method for preparing the catalyst includes the following steps: 1) Molecular sieve, pseudoboehmite, and guar gum powder are mixed evenly at a mass ratio of 140:45~90:5~8, and kneaded with an aqueous solution containing the metal salt corresponding to the first co-active component, the metal salt corresponding to the modified component, and citric acid. The kneaded material is extruded, dried, and calcined to obtain a catalyst semi-finished product; wherein the mass ratio of molecular sieve to the metal salt corresponding to the first co-active component, the metal salt corresponding to the modified component, citric acid, and water is 100:10~16:2~4:3~5:25~30. 2) Determine the water absorption rate of the catalyst semi-finished product obtained in step 1), impregnate it with an aqueous solution of diammonium hydrogen phosphate in an equal volume impregnation manner, and after impregnation, dry and calcine to obtain a catalyst for the cracking of low-carbon alkanes to produce propane.

2. The application according to claim 1, characterized in that, The molecular sieve is selected from one or both of HZSM-5 and HUSY.

3. The application according to claim 2, characterized in that, The molecular sieve is HZSM-5; the HZSM-5 molecular sieve has a silica-alumina ratio of 20~40, a relative crystallinity of >80%, a grain size of <1μm, and a Na2O content of <0.05%.

4. The application according to claim 1, characterized in that, The alumina is derived from either small-pore or large-pore boehmite.

5. The application according to claim 1, characterized in that, The alumina is derived from small-pore boehmite; the pore volume of the small-pore boehmite is 0.4~0.45 mL / g, and the specific surface area is ≥270 μm. 2 / g, Na2O content <0.1%, colloidal index >95%, dry basis content ≥67%.

6. The application according to claim 1, characterized in that, In step 1) of the preparation method, the drying temperature is 150~160℃, and the drying time is 4-5h; and / or In step 1), the roasting temperature is 500~600℃ and the roasting time is 4-5h.

7. The application according to claim 1, characterized in that, In step 2) of the preparation method, the mass ratio of the catalyst semi-finished product to diammonium hydrogen phosphate is 1000:56~93; and / or In step 2), the soaking time is 30-60 minutes; and / or In step 2), the drying temperature is 150~160℃, and the drying time is 4-5 hours; and / or In step 2), the roasting temperature is 400~500℃ and the roasting time is 4-5h.

8. The application according to claim 1, characterized in that, The reaction conditions described in the application are: reaction temperature 300~450℃, reaction pressure 0.5~1MPa, and weight hourly space velocity 0.4~1h. -1 .

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