Cracking catalyst, its preparation method and application

Abstract

The present application relates to a kind of cracking catalyst and its preparation method and application, belong to the technical field of catalyst.Solve the problem in prior art, using the cracking catalyst sold in market to carry out methyl tert-amyl ether cracking reaction, the activity of cracking catalyst is relatively low, the content of 2-methyl-2-butene in product is relatively low, the yield of isoamylene is low, and increase the separation energy consumption problem.The cracking catalyst of the present application includes amorphous aluminum silicate and inert carrier, amorphous aluminum silicate is prepared by step-by-step precipitation, and the inert carrier is selected from one or more of Al2O3, SiO2, activated carbon material.The cracking catalyst has the advantages of high reactivity, long service life, and can be applied in catalytic methyl tert-amyl ether cracking to prepare isoamylene, the content of 2-methyl-2-butene in product is high, and the separation energy consumption can be saved.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a cracking catalyst, its preparation method and application, and particularly to the application of the cracking catalyst in the catalytic cracking of methyl tert-amyl ether to isopentenene. Background Technology

[0002] Isoprene is mainly used in the production of pinacolone and tert-amyl alcohol, and can also be used as an intermediate in the synthesis of rubber, resins, and organic compounds. Isoprene is usually a mixture of 2-methyl-1-butene (2MB-1) and 2-methyl-2-butene (2MB-2). Since 2-methyl-2-butene is the active component in most reactions, the content of 2-methyl-1-butene in the product isoprene is strictly limited.

[0003] Isoprene is mainly found in the C5 fraction of catalytically cracked gasoline or the C5 fraction of naphtha cracking for ethylene production. Because these C5 fractions have similar boiling points, it is difficult to obtain high-content isopentene through simple distillation. Currently, the most commonly used separation method is the methyl tert-amyl ether (MTA) cracking method. The C5 fraction reacts with methanol to produce MTA, which is then purified to obtain high-purity MTA. This MTA is then subjected to high-temperature cracking and methanol removal to obtain isopentene. The resulting isopentene typically has a 2-methyl-2-butene / 2-methyl-1-butene ratio of 1–5 / 1, with a relatively low 2-methyl-2-butene content. Therefore, the obtained isopentene usually undergoes a double-bond isomerization reaction to convert the 2-methyl-1-butene portion to 2-methyl-2-butene, thereby increasing the 2-methyl-2-butene content. However, during the isomerization reaction, isopentene undergoes polymerization, leading to a decrease in product yield and an increase in energy consumption during the refining process. On the other hand, the polymerization reaction releases a large amount of heat, making it difficult to control the temperature of the catalyst bed stably. This results in large fluctuations in the isomerization reaction results and also leads to a shortened catalyst lifespan.

[0004] Chinese patent CN101723776A reports a method for preparing isopentenene. This method involves the gas-phase etherification of methyl tert-amyl ether through a fixed-bed catalyst bed packed with HF-modified α-Al₂O₃. The crude isopentenene obtained by removing methanol from the etherification product is mixed with tert-butanol and water, and then isomerized through a fixed-bed catalyst bed composed of sulfonic acid-based cation exchange resin. The 2MB₂ / 2MB₁ ratio in the etherification product is 2.96, and the dimer content in the isomerization product is 0.29–0.77%. The introduction of tert-butanol and water during the isomerization process increases the difficulty of isopentenene separation.

[0005] Chinese patent CN102040452A discloses a method for preparing isopentenene from methyl tert-amyl ether. This method involves the ether undergoing etherolysis in the gas phase through a fixed-bed catalyst bed packed with HF-modified α-Al₂O₃. The etherolysis product, containing methanol, undergoes isomerization in a fixed-bed catalyst bed composed of sulfonic acid-based cation exchange resin. After removing methanol from the isomerization product, isopentenene is obtained. The dimer content in the isomerization product is <1%. However, methanol and isopentenene readily react to form methyl tert-amyl ether under the catalysis of sulfonic acid-based cation exchange resin, thus reducing the product yield.

[0006] Chinese patent CN103846098A reports a catalyst, preparation method, and application for the cracking of methyl tert-amyl ether to prepare isopentene. A multi-component X / Z₂O₃ / POMs / Al₂O₃ catalyst is used for the cracking reaction of methyl tert-amyl ether. The reaction is carried out at 140–160 °C, and the liquid hourly space velocity is 2–5 times higher than that of similar industrial catalysts. The content of 2-methyl-1-butene in isopentene in the reaction product is 21–29%. However, the preparation of this catalyst involves multiple impregnation and calcination processes, making the preparation process complex. Summary of the Invention

[0007] The purpose of this invention is to solve the problems that when commercially available cracking catalysts are used for the cracking reaction of methyl tert-amyl ether, the catalyst activity is low, the content of 2-methyl-2-butene in the product is relatively low, the isomerization reaction of 2-methyl-1-butene produces more polymers, which reduces the yield of isopentene and increases the energy consumption for separation.

[0008] To address the aforementioned problems, this invention provides a catalyst for the cracking of methyl tert-amyl ether to produce isopentenene, its preparation method, and its application. This catalyst has the advantages of high reactivity and long service life. When used in the cracking of methyl tert-amyl ether to produce isopentenene, it can reduce energy consumption and increase the yield of the product (high content of 2-methyl-2-butene) without changing the existing reaction equipment.

[0009] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows.

[0010] The cracking catalyst of the present invention comprises amorphous aluminum silicate and an inert support. The amorphous aluminum silicate is prepared by stepwise precipitation, and the inert support is selected from one or more of Al2O3, SiO2, and activated carbon materials.

[0011] Preferably, the mass ratio of the amorphous aluminum silicate to the inert carrier is 10 to 15:2.

[0012] Preferably, the content of Al2O3 in the amorphous aluminum silicate is 3-10 wt%, more preferably 4-6 wt%.

[0013] Preferably, in the amorphous aluminum silicate, Al2O3 is derived from one or more of AlCl3, Al(NO)3·9H2O, and Al2(SO4)3·18H2O.

[0014] Preferably, the SiO2 content in the amorphous aluminum silicate is 90-97 wt%, more preferably 94-96 wt%.

[0015] Preferably, in the amorphous aluminum silicate, SiO2 is derived from Na2SiO3·9H2O.

[0016] Preferably, the method for preparing amorphous aluminum silicate by stepwise precipitation comprises the following steps:

[0017] Step 1: Dissolve the Al2O3 raw material in deionized water to prepare an aluminum-containing solution;

[0018] Step 2: Dissolve the SiO2 raw material in deionized water to prepare a silicon-containing solution. While stirring, adjust the pH value to 2.5-5 to obtain silica gel.

[0019] Step 3: After heating to 50-65℃, add the aluminum-containing solution from Step 1 to the silica gel from Step 2, and adjust the pH value to 7.5-10 while stirring to generate aluminum silicate gel.

[0020] Step 4: Aging, filtering, washing, and drying the aluminum silicate gel prepared in Step 3 to obtain amorphous aluminum silicate.

[0021] Preferably, in step one, the raw material for Al2O3 is one or more of AlCl3, Al(NO)3·9H2O, and Al2(SO4)3·18H2O, and more preferably Al2(SO4)3·18H2O.

[0022] Preferably, in step one, the temperature of the deionized water is 60-65°C, and the content of Al2O3 in the aluminum-containing solution is 10-18 wt%, more preferably 13-15 wt%.

[0023] Preferably, in step two, the raw material for SiO2 is Na2SiO3·9H2O.

[0024] Preferably, in step two, the content of SiO2 raw material in the silicon-containing solution is 20-30 wt%, more preferably 22-25 wt%.

[0025] Preferably, in step two, dilute sulfuric acid is used to adjust the pH value; more preferably, the pH value is controlled between 3 and 4.

[0026] Preferably, in step two, the stirring speed is 200–300 r / min.

[0027] Preferably, in step three, ammonia is used to adjust the pH value, and the pH value is controlled between 8 and 9.

[0028] Preferably, in step three, the stirring speed is 200–300 r / min.

[0029] Preferably, in step three, the aluminum-containing solution is added to the silica gel at a uniform rate over a period of 15–25 minutes.

[0030] Preferably, in step four, the aging temperature is 50–65°C and the aging time is 1–4 hours; more preferably, the aging time is 1.5–2 hours.

[0031] Preferably, in step four, deionized water at 50–55°C is used for washing.

[0032] Preferably, in step four, the drying temperature is 120–160°C and the drying time is 4–6 hours.

[0033] Preferably, in step four, after drying, grinding is also included, grinding to a mesh size of 200 or higher.

[0034] Preferably, the pyrolysis catalyst is cylindrical or clover-shaped.

[0035] The present invention also provides a method for preparing the above-mentioned cracking catalyst, wherein amorphous aluminum silicate and inert support raw materials are kneaded evenly, extruded into strips, dried, and calcined to obtain the cracking catalyst.

[0036] Preferably, after the amorphous aluminum silicate and guar gum powder are mixed evenly, an inert carrier material is added and kneaded evenly. The amount of guar gum powder added is 3 to 5% of the mass of the amorphous aluminum silicate.

[0037] Preferably, the inert carrier material is silica sol, and more preferably, the inert carrier material is 29-31 wt% silica sol.

[0038] Preferably, the mass ratio of the amorphous aluminum silicate to the inert carrier raw material is 10 to 15:6.

[0039] Preferably, the drying temperature is 120–160°C and the drying time is 4–6 hours.

[0040] Preferably, the calcination temperature is 400–500°C and the calcination time is 4–6 hours.

[0041] The present invention also provides the application of the above-mentioned cracking catalyst in the catalytic cracking of methyl tert-amyl ether to isopentenene, or in the catalytic cracking of methyl tert-butyl ether to isobutylene, or in the catalytic cracking of tert-butanol to isobutylene.

[0042] Preferably, the pyrolysis reaction temperature is 150–250°C, the reaction pressure is atmospheric pressure to 1 MPa, and the liquid hourly space velocity is 0.2–1.5 h⁻¹. -1 .

[0043] More preferably, the pyrolysis reaction temperature is 170–220°C, the reaction pressure is atmospheric pressure to 0.5 MPa, and the liquid hourly space velocity is 0.5–1 h⁻¹. -1 .

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] Firstly, in the cracking catalyst provided by this invention, amorphous aluminum silicate is prepared by stepwise precipitation, which is a simple preparation method.

[0046] Secondly, the cracking catalyst provided by this invention has high catalytic activity, long service life, high operational flexibility, and strong applicability.

[0047] Thirdly, the cracking catalyst provided by this invention, when used in the cracking reaction of methyl tert-amyl ether to produce isopentenene, can reduce energy consumption and increase the yield of the product (high content of 2-methyl-2-butene) without changing the existing reaction equipment.

[0048] Fourth, the cracking catalyst provided by this invention can be used not only for the cracking reaction of methyl tert-amyl ether, but also for the cracking of methyl tert-butyl ether to produce isobutylene, the cracking of tert-butanol to produce isobutylene, and other reactions. Detailed Implementation

[0049] To further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0050] The cracking catalyst of the present invention includes amorphous aluminum silicate and an inert support, or may consist only of amorphous aluminum silicate and an inert support.

[0051] In this invention, the inert support is selected from one or more of Al2O3, SiO2, and activated carbon materials, preferably SiO2.

[0052] In this invention, amorphous silica is prepared by stepwise precipitation; in amorphous aluminum silicate, the Al2O3 content is 3-10 wt%, more preferably 4-6 wt%; in amorphous aluminum silicate, the Al2O3 is derived from one or more of AlCl3, Al(NO)3·9H2O, and Al2(SO4)3·18H2O; the SiO2 content is 90-97 wt%, more preferably 94-96 wt%; and the SiO2 is derived from Na2SiO3·9H2O.

[0053] A method for preparing amorphous aluminum silicate by stepwise precipitation includes the following steps: Step 1: Dissolve Al2O3 raw material in deionized water to prepare an aluminum-containing solution; Step 2: Dissolve SiO2 raw material in deionized water to prepare a silicon-containing solution, and adjust the pH value to 2.5-5 with stirring to obtain silica gel (first step precipitation); Step 3: After heating to 50-65℃, add the aluminum-containing solution from Step 1 to the silica gel from Step 2, and adjust the pH value to 7.5-10 with stirring to generate aluminum silicate gel (second step precipitation); Step 4: Age the aluminum silicate gel prepared in Step 3, filter (usually by vacuum filtration), wash, and dry to obtain amorphous aluminum silicate.

[0054] In the above method, in step one, the temperature of the deionized water is preferably 60-65°C, and the content of Al2O3 in the aluminum-containing solution is 10-18 wt%, more preferably 13-15 wt%; in step two, the content of SiO2 in the silicon-containing solution is 20-30 wt%, more preferably 22-25 wt%; in step two, dilute sulfuric acid is preferably used to adjust the pH value, more preferably the pH value is controlled at 3-4, and the stirring speed is preferably 200-300 r / min; in step three, ammonia water is preferably used to adjust the pH value, more preferably the pH value is... The stirring speed is preferably 200-300 r / min, controlled at 8-9. In step three, the aluminum-containing solution is preferably added to the silica gel at a uniform rate within 15-25 min. In step four, the aging temperature is preferably 50-65℃, and the aging time is preferably 1-4 hours, more preferably 1.5-2 hours. In step four, washing with deionized water at 50-55℃ is preferred. In step four, the drying temperature is preferably 120-160℃, and the drying time is preferably 4-6 hours. After drying, grinding is also preferred, to a mesh size of 200 or higher. The raw material for Al2O3 is preferably one or more of AlCl3, Al(NO)3·9H2O, and Al2(SO4)3·18H2O, more preferably Al2(SO4)3·18H2O. The raw material for SiO2 is sodium silicate, such as Na2SiO3·9H2O.

[0055] The preparation method of the cracking catalyst of the present invention is as follows: take amorphous aluminum silicate and inert support raw materials, knead them evenly, extrude them into strips, dry them, and calcine them to obtain the cracking catalyst.

[0056] In the above preparation method, guar gum powder can be added to increase viscosity. Specifically, amorphous aluminum silicate and guar gum powder are first mixed evenly, and then an inert carrier material is added and kneaded until homogeneous. The preferred amount of guar gum powder added is 3-5% of the mass of the amorphous aluminum silicate.

[0057] In the above preparation method, the inert carrier raw material is preferably silica sol, more preferably 29-31 wt% silica sol.

[0058] In the above preparation method, the preferred mass ratio of inert carrier raw material to amorphous aluminum silicate is 10-15:6.

[0059] In the above preparation method, the preferred drying temperature is 120-160℃ and the drying time is 4-6 hours.

[0060] In the above preparation method, the preferred calcination temperature is 400-500℃ and the calcination time is 4-6 hours.

[0061] The cracking catalyst of the present invention can be used in the cracking of methyl tert-amyl ether to isopentenene, or in the cracking of methyl tert-butyl ether to isobutylene, or in the cracking of tert-butanol to isobutylene.

[0062] In the above applications, the pyrolysis reaction temperature is 150–250℃, preferably 170–220℃, the reaction pressure is atmospheric pressure to 1 MPa, preferably atmospheric pressure to 0.5 MPa, and the liquid hourly space velocity is 0.2–1.5 h⁻¹. -1 Preferably 0.5 to 1 hour -1 .

[0063] In the above applications, methyl tert-amyl ether is passed through a pyrolysis catalyst bed in the gas phase to undergo a pyrolysis reaction, generating isopentenene and methanol. At the same time, side reactions such as isopentenene polymerization and methanol dehydration to generate dimethyl ether also occur.

[0064] The terminology used in this invention generally has the meanings commonly understood by those skilled in the art, unless otherwise stated.

[0065] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0066] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0067] Example 1

[0068] Under a water bath at 60℃, 102.38g of aluminum sulfate octahydrate was dissolved in 248.29g of deionized water to prepare a solution with an aluminum sulfate content of 15wt%.

[0069] 1162.9 g of sodium silicate nonahydrate was dissolved in 837.1 g of deionized water at room temperature to prepare a sodium silicate content of 25 wt%. Under high-speed stirring (200-300 r / min), the pH value was adjusted to 3-5 with 5 mol / L sulfuric acid to form silica gel. After the silica gel was formed, the temperature was raised to 60℃, and the aluminum sulfate solution prepared above was added to the silica gel at a uniform rate over 15-25 min. Under stirring (200-300 r / min), the pH value was adjusted to 9-10 with 10% ammonia water to form aluminum silicate gel. After stirring and aging for 2 hours, the mixture was filtered and the filter cake was washed more than five times with 50℃ deionized water. The obtained filter cake was dried at 150℃ for 4-6 hours and then ground to a fineness of 200 mesh or higher to obtain amorphous aluminum silicate.

[0070] Take 200g of ground amorphous aluminum silicate, add 6g of guar gum powder, mix evenly, then add 120g of 30wt% silica sol, knead evenly, and then extrude it into a 3mm cylinder using an extruder. Dry at 150℃ for 2 hours and calcine at 450℃ for 4 hours to prepare cracking catalyst A.

[0071] 30g of cracking catalyst was loaded into a small fixed-bed reactor with an inner diameter of 29mm. Methyl tert-amyl ether was injected using a plunger pump. The cracking test results are shown in Table 1.

[0072] Table 1. Experimental results of cleavage catalyst A for methyl tert-amyl ether.

[0073]

[0074] Example 2

[0075] Under a water bath at 60°C, 68.25g of aluminum sulfate octadechydrate was dissolved in 165.53g of deionized water to prepare a solution with an aluminum sulfate content of 15wt%. Subsequent steps were carried out according to Example 1 to obtain cracking catalyst B. The cracking test results are shown in Table 2.

[0076] Table 2. Test results of cleavage catalyst B for methyl tert-amyl ether.

[0077]

[0078]

[0079] As can be seen from Tables 1 and 2, the cracking catalyst of the present invention has high cracking activity at a relatively low reaction temperature, and is suitable for atmospheric pressure and pressurized operation. It is used for the cracking reaction of methyl tert-amyl ether, and the product has a high content of 2-methyl-2-butene, which facilitates subsequent separation.

[0080] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A catalyst for the catalytic cracking of methyl tert-amyl ether to isopentene, characterized in that The amorphous silicate aluminum and inert carrier are prepared by step-by-step precipitation, and the inert carrier is selected from one or more of Al2O3, SiO2, and activated carbon material; the content of Al2O3 in the amorphous silicate aluminum is 3-10 wt%, and the content of SiO2 is 90-97 wt%; The mass ratio of the amorphous silicate aluminum and the inert carrier is 10-15:

2. The method for preparing the amorphous silicate aluminum by step-by-step precipitation comprises the following steps: Step one: dissolving Al2O3 raw material in deionized water to prepare an aluminum-containing solution; Step two: dissolving SiO2 raw material in deionized water to prepare a silicon-containing solution, adjusting the pH value to 2.5-5 under stirring to obtain a silica gel; Step three: after being heated to 50-65℃, the aluminum-containing solution of step one is added to the silica gel of step two, and the pH value is adjusted to 7.5-10 under stirring to generate an aluminum silicate gel; Step four: the aluminum silicate gel prepared in step three is aged, filtered, washed, and dried to obtain the amorphous silicate aluminum; In step one, the Al2O3 raw material is one or more of AlCl3, Al(NO)3·9H2O, and Al2(SO4)3·18H2O, the temperature of the deionized water is 60-65℃, and the content of the Al2O3 raw material in the aluminum-containing solution is 10-18 wt%; In step two, the SiO2 raw material is Na2SiO3·9H2O, the content of the SiO2 raw material in the silicon-containing solution is 20-30 wt%, dilute sulfuric acid is used to adjust the pH value, and the pH value is controlled at 3-4; the stirring speed is 200-300 r / min; In step three, the aluminum-containing solution is added to the silica gel at a uniform speed within 15-25 min, ammonia water is used to adjust the pH value, and the pH value is controlled at 8-9; the stirring speed is 200-300 r / min; In step four, the aging temperature is 50-65℃, the aging time is 1-4 hours, the deionized water is washed at 50-55℃, the drying temperature is 120-160℃, and the drying time is 4-6 hours; After drying, it further comprises grinding to more than 200 mesh; The shape of the cracking catalyst is cylindrical or trilobal.

2. The method of claim 1, wherein the cracking catalyst is prepared by a method comprising: The amorphous silicate aluminum and the inert carrier raw material are kneaded uniformly, extruded into strips, dried, and calcined to obtain the cracking catalyst.

3. The preparation method of the cracking catalyst according to claim 2, characterized in that, The amorphous silicate aluminum and the inert carrier raw material are kneaded uniformly, extruded into strips, dried, and calcined to obtain the cracking catalyst. The mass ratio of the amorphous silicate aluminum and the inert carrier raw material is 10-15:6; The inert carrier raw material is 29-31 wt% of silica sol; The drying temperature is 120-160℃, and the drying time is 4-6 hours; The calcination temperature is 400-500℃, and the calcination time is 4-6 hours.

4. Use of a cracking catalyst according to claim 1 or a cracking catalyst produced according to the method of claim 2 in the catalytic cracking of methyl tert-amyl ether to produce isoamylene.

5. Use of a cracking catalyst according to claim 4 for the catalytic cracking of methyl tert-amyi ether to isopentene, characterized in that, The cleavage reaction temperature is 150-250℃, the reaction pressure is normal pressure-1 MPa, the liquid hourly space velocity is 0.2-1.5h -1 .

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