Method for preparing isobutene by dehydrating tert-butyl alcohol

Abstract

The invention relates to the field of preparation of isobutene, and discloses a method for preparing isobutene by dehydrating tert-butyl alcohol. The method comprises the following steps: carrying out contact reaction on tert-butyl alcohol and a WO3-SiO2 composite oxide catalyst; in the WO3-SiO2 composite oxide catalyst, on the basis of the total weight of the WO3-SiO2 composite oxide catalyst, the content of WO3 is 5 to 40 weight percent; and the content of SiO2 is 60-95% by weight. The method has high tertiary butanol conversion rate and isobutene selectivity.

Description

Technical Field

[0001] The invention relates to the field of isobutylene preparation, and in particular to a method for preparing isobutylene by dehydrating tert-butyl alcohol. Background Art

[0002] Isobutylene is an important basic organic chemical raw material, widely used in the preparation of butyl rubber, polyisobutylene, methacrylate and other organic chemical raw materials and fine chemicals. The world's isobutylene production has reached nearly 30 million tons / year.

[0003] Industrially, isobutylene is usually produced by MTBE cracking or tert-butyl alcohol dehydration. Compared with MTBE cracking, tert-butyl alcohol dehydration has low raw material cost (a large amount of tert-butyl alcohol is produced as a by-product during the co-oxidation process to produce propylene oxide), simpler process, safer and more environmentally friendly. With the rapid growth of co-oxidation propylene oxide units, tert-butyl alcohol dehydration process has become an increasingly competitive production route for isobutylene.

[0004] The catalysts used in the prior art for dehydration of tert-butyl alcohol to prepare isobutylene include ion exchange resins, alumina, solid phosphoric acid and other supported acidic catalyst systems.

[0005] The catalysts used in the tert-butyl alcohol technology disclosed in CN103506158A, CN107457001A, CN1609082A, US4423271A, etc. are all polystyrene sulfonic acid resin catalysts. The resin is highly acidic and therefore has a high low-temperature activity (80-150°C), but has a serious defect that the resin has poor heat resistance and thermal conductivity, especially in the presence of a large amount of free water generated by dehydration of tert-butyl alcohol. The sulfonic acid group of the catalyst falls off at a fast rate, so the catalyst life is short, and the resin catalyst easily catalyzes the dimerization of isobutylene to form polyolefins, affecting the reaction selectivity.

[0006] CN102516030A discloses a method for dehydrating tert-butyl alcohol to prepare isobutylene, using a sodium hydroxide solution with a mass fraction of less than 0.4% and a specific surface area of ​​200-600 m 2 / g of alumina catalyst, the temperature of the dehydration reaction is 200-450°C, and tert-butyl alcohol is used to produce isobutylene in high yield, high selectivity and long-term stability.

[0007] US3665048A discloses a process for producing isobutylene by gas phase dehydration of tert-butyl alcohol in a fixed bed using alumina as a catalyst.

[0008] CN113926475A discloses a dehydration catalyst, a preparation method and its application in the production of isobutylene by dehydration of tert-butyl alcohol. The catalyst comprises the following components by mass fraction: a) 85.0% to 99.5% of aluminum oxide, b) 0.5% to 10.0% of rare earth elements, and c) 0 to 5.0% of phosphorus. When the catalyst is used for the production of isobutylene by dehydration of tert-butyl alcohol, a simple process flow is adopted, which can not only dehydrate tert-butyl alcohol to high-purity isobutylene, but also has the characteristics of high catalyst stability, high tert-butyl alcohol conversion rate and high isobutylene selectivity.

[0009] CN105712831A discloses a method for preparing isobutylene from a mixture of methyl tert-butyl ether and tert-butyl alcohol. The method comprises contacting a mixture of MTBE and TBA with a catalyst A and a catalyst B in sequence to react and prepare isobutylene, wherein the catalyst A and the catalyst B used are novel catalysts with different core-shell ratios, the core is amorphous silicon aluminum, and the shell is aluminum oxide modified by silicon and tin. The method of the present invention realizes the simultaneous generation of isobutylene by the two reactions of MTBE cracking and TBA dehydration, so that the conversion rate of TBA and the conversion rate of MTBE are both high, and the selectivity of generating isobutylene is also high.

[0010] In summary, although a number of solid acid catalyst technical solutions for dehydration of tert-butyl alcohol to isobutylene have been disclosed, they all have certain defects: (1) the reaction conversion rate needs to be further improved, and overlapping components will be produced in the process, affecting the reaction selectivity; (2) the catalyst has poor heat resistance and a short service life, which cannot meet the maintenance requirements of more than 4 years for current petrochemical production equipment; (3) the catalyst cannot be recycled, and the waste catalyst produced is hazardous waste, which does not conform to the current world's environmental protection concept. Summary of the invention

[0011] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for preparing isobutylene by dehydrating tert-butyl alcohol. The method has high tert-butyl alcohol conversion rate and isobutylene selectivity.

[0012] In order to achieve the above object, the present invention provides a method for dehydrating tert-butyl alcohol to prepare isobutylene, the method comprising: contacting tert-butyl alcohol with a WO3-SiO2 composite oxide catalyst;

[0013] In the WO3-SiO2 composite oxide catalyst, based on the total weight of the WO3-SiO2 composite oxide catalyst, the content of WO3 is 5-40% by weight, and the content of SiO2 is 60-95% by weight.

[0014] Through the above technical solution, the beneficial effects of the present invention include:

[0015] The method provided by the invention has high tert-butyl alcohol conversion rate and isobutylene selectivity, and almost no side reaction occurs.

[0016] The WO3-SiO2 composite oxide catalyst used in the method of the present invention has high thermal stability, can operate stably for a long time without almost any decrease in activity, and the single-pass life of the catalyst can reach more than 4 years. DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] The first aspect of the present invention provides a method for preparing isobutylene by dehydrating tert-butyl alcohol, the method comprising: contacting tert-butyl alcohol with a WO3-SiO2 composite oxide catalyst;

[0019] In the WO3-SiO2 composite oxide catalyst, based on the total weight of the WO3-SiO2 composite oxide catalyst, the content of WO3 is 5-40% by weight, and the content of SiO2 is 60-95% by weight.

[0020] The inventors of the present invention have found in the course of research that the use of a WO3-SiO2 composite oxide catalyst of a specific composition in the process of dehydrating tert-butanol to produce isobutylene is beneficial to improving the conversion rate of tert-butanol and the selectivity of isobutylene.

[0021] In the present invention, in the WO3-SiO2 composite oxide catalyst, based on the total weight of the WO3-SiO2 composite oxide catalyst, the content of WO3 is 5-40% by weight, preferably 10-30% by weight, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% by weight, and any value in the range formed by any two of these values; the content of SiO2 is 60-95% by weight, preferably 70-90% by weight, such as 60%, 65%, 70%, 75%, 80%, 85%, 90% by weight, and any value in the range formed by any two of these values. By adopting this preferred embodiment, the catalyst has higher activity, thereby obtaining a higher decomposition rate of tert-butyl alcohol.

[0022] The WO3-SiO2 composite oxide catalyst of the present invention may further contain Na2O. The inventors have found that Na2O in the catalyst will seriously affect the selectivity of the reaction, especially the life of the catalyst, so the mass fraction of Na2O is preferably as low as 0.1wt% or less. Preferably, the WO3-SiO2 composite oxide catalyst further contains Na2O, and the content of Na2O is less than 0.1wt% based on the total weight of the WO3-SiO2 composite oxide catalyst.

[0023] Preferably, the reaction temperature of the reaction is 180-250°C, preferably 180-220°C, such as 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, and any value in the range formed by any two of these values. The present invention provides that the use of a specific type of catalyst in the method can allow the reaction to be carried out at a higher reaction temperature than the prior art (about 170-180°C), thereby obtaining a higher single-pass conversion rate, while maintaining a high reaction selectivity.

[0024] According to the present invention, preferably, the reaction conditions include: temperature of 180-250°C, preferably 180-220°C; pressure of 0.1-1MPa, preferably 0.4-0.6MPa; mass space velocity of 0.1-5h -1 , preferably 0.2-2h -1 The use of this preferred embodiment is beneficial to improving the reaction conversion rate and product selectivity.

[0025] The present invention has no particular limitation on the reactor used in the reaction, and can be any reactor conventionally used in the art. For example, one or more of a kettle reactor, a fixed bed reactor, and a catalytic distillation column reactor. The present invention preferably uses a fixed bed reactor. This type of reactor is the simplest and most economical.

[0026] The raw material of the present invention can be pure tert-butyl alcohol; or it can be water-containing tert-butyl alcohol, for example, industrial 85wt% tert-butyl alcohol. Preferably, the concentration of the tert-butyl alcohol is ≥ 85wt%. The tert-butyl alcohol raw material of the present invention can be obtained commercially.

[0027] The present invention has no particular limitation on the preparation method of the WO3-SiO2 composite oxide catalyst, as long as the WO3-SiO2 composite oxide catalyst of the above composition can be prepared. In order to further improve the catalytic performance of the WO3-SiO2 composite oxide catalyst, the present invention also provides a preparation method of the above WO3-SiO2 composite oxide catalyst.

[0028] Preferably, the WO3-SiO2 composite oxide catalyst is prepared by a co-precipitation method.

[0029] Further preferably, the preparation method of the WO3-SiO2 composite oxide catalyst comprises:

[0030] (1) mixing a tungsten source and a silicon source in the presence of a solvent to obtain a mixed solution;

[0031] (2) subjecting the acid solution and the mixed solution to a precipitation reaction to obtain a solid product;

[0032] (3) Drying and calcining the solid product.

[0033] According to the present invention, preferably, in the mixed solution, the concentration of the silicon source is 50-300 g / L.

[0034] According to the present invention, preferably, in the mixed solution, the concentration of the tungsten source is 50-200 g / L.

[0035] The present invention has no particular limitation on the type of the silicon source, which can be selected conventionally in the art. Preferably, the silicon source is a silicate, preferably at least one selected from sodium silicate, water glass and potassium silicate.

[0036] The present invention has no particular limitation on the type of the tungsten source, as long as it contains metallic tungsten. Preferably, the tungsten source is a soluble salt of tungsten, preferably sodium tungstate and / or ammonium metatungstate.

[0037] In the present invention, the "soluble" means that the compound can be dissolved in a solvent directly or with the help of a co-solvent.

[0038] The present invention has a wide range of selections for the type of the solvent, which may be various solvents conventionally used in the art, and the present invention will not be described in detail herein.

[0039] Preferably, the mass fraction of the acid solution in step (2) is 10-30%.

[0040] In the present invention, the acid in the acid solution in step (2) may be an inorganic acid or an organic acid. Further preferably, the acid in the acid solution is an inorganic acid, preferably at least one selected from sulfuric acid, hydrochloric acid and nitric acid.

[0041] According to the present invention, preferably, the precipitation conditions in step (2) include: a temperature of 20-60°C.

[0042] Preferably, the precipitation reaction is terminated when the pH value is 6-9, preferably 7-7.5. This preferred embodiment is beneficial to improving the catalytic performance of the catalyst.

[0043] The pH may be adjusted by the addition ratio of the mixed solution and the acid solution, or may be adjusted by additionally adding another acid or base.

[0044] The precipitation reaction in step (2) of the present invention can be carried out in any reactor that can realize the above precipitation reaction. Preferably, the precipitation reaction in step (2) is carried out in a precipitation kettle.

[0045] The present invention has no particular limitation on the type of the precipitation tank, which can be any conventional type in the art.

[0046] In step (2), the present invention has no particular limitation on the manner of adding the acid solution and the mixed solution. The acid solution can be added to the mixed solution (positive addition method), and then the mixed solution can be added to the acid solution (reverse addition method), or the acid solution and the mixed solution can be added to the precipitation kettle at the same time (parallel flow method). Preferably, step (2) comprises: adding the acid solution and the mixed solution to the precipitation kettle at the same time for precipitation reaction to obtain a solid product. The inventors have found that the performance of the catalyst obtained by the parallel flow method is significantly better than that of the catalyst obtained by the positive addition method or the reverse addition method.

[0047] When the acid solution and the mixed solution are added to the precipitation tank at the same time, preferably, the addition time of the acid solution and the mixed solution is independently 1-2 hours.

[0048] The present invention has no particular limitation on the adding rate of the acid solution and the mixed solution, and can be appropriately adjusted according to the size of the reaction device to meet the above-mentioned adding time.

[0049] In order to allow the acid solution to react completely with the tungsten source and the silicon source in the mixed solution, preferably, the amounts of the acid solution and the mixed solution satisfy the following reaction stoichiometry:

[0050] WO4 2- +2H + →WO3↓H2OSiO3 2- +2H + →SiO2↓+H2O

[0051] According to the present invention, preferably, the preparation method of the WO3-SiO2 composite oxide catalyst further comprises: aging the product of the precipitation reaction, wherein the aging conditions include: an aging temperature of 60-80°C and an aging time of 2-5h. By adopting this preferred embodiment, a higher preparation yield can be obtained, and the precipitate can be separated more easily.

[0052] Preferably, the method for preparing the WO3-SiO2 composite oxide catalyst further comprises: separating the aging product to obtain a solid product.

[0053] The present invention has no particular limitation on the separation method, and the separation can be carried out by conventional technical means in the art, for example, centrifugation, filtration, suction filtration and other methods.

[0054] According to a specific embodiment of the present invention, the aged product is filtered and washed to obtain a solid product.

[0055] Specifically, the washing includes washing with a dilute acid solution having a mass fraction of less than 0.1 wt% and washing with desalted water. The present invention has no particular limitation on the number of washings, which is based on the fact that the mass fraction of Na2O is reduced to less than 0.1 wt%.

[0056] The present invention has no particular limitation on the drying conditions of step (3), which can be selected conventionally in the art. Preferably, the drying conditions of step (3) include: a temperature of 100-150° C. and a time of 6-24 hours.

[0057] According to the present invention, preferably, the calcination conditions in step (3) include: a calcination temperature of 500-700° C. and a calcination time of 6-24 h.

[0058] According to the present invention, preferably, the method for preparing the WO3-SiO2 composite oxide catalyst further comprises a molding step, and the molding is performed before or after the calcination in step (3).

[0059] The molding method of the present invention can be a conventional molding method in the art, such as one or more of tablet molding, extrusion molding and ball molding.

[0060] When tableting is adopted, the forming is carried out after the calcination in step (3).

[0061] When extrusion molding or ball molding is adopted, the molding is carried out after the drying in step (3) and before roasting.

[0062] The WO3-SiO2 composite oxide catalyst provided by the present invention can fully restore its activity through regeneration. Preferably, the WO3-SiO2 composite oxide catalyst can be regenerated for use.

[0063] The WO3-SiO2 composite oxide catalyst of the present invention can be regenerated by a conventional method. Preferably, the regeneration conditions include: in air, at a temperature of 450-500°C, and a regeneration time of 24-48h.

[0064] The present invention has no particular limitation on the air introduction rate, and the air introduction rate can be carried out according to a conventional method. In order to prevent the charcoal burning from being too intense and damaging the catalyst, the air introduction rate is generally increased from low to high.

[0065] According to a specific embodiment of the present invention, the reaction system is first purged with an inert gas, and then the catalyst regeneration process is performed. With this preferred embodiment, impurities remaining from the previous reaction in the reaction system can be effectively removed.

[0066] Preferably, the regeneration process further comprises: raising the temperature to 450-500° C. under the action of an inert gas. With this preferred embodiment, impurities remaining from the reaction can be completely eliminated.

[0067] The above-mentioned inert gas can be selected conventionally. Based on cost considerations, the present invention preferably uses nitrogen.

[0068] According to a particularly preferred embodiment of the present invention, a method for preparing isobutylene by dehydrating tert-butyl alcohol comprises: contacting tert-butyl alcohol with a WO3-SiO2 composite oxide catalyst;

[0069] In the WO3-SiO2 composite oxide catalyst, based on the total weight of the WO3-SiO2 composite oxide catalyst, the content of WO3 is 10-30 weight %; the content of SiO2 is 70-90 weight %;

[0070] The WO3-SiO2 composite oxide catalyst is prepared by a coprecipitation method;

[0071] The reaction temperature is 180-220°C.

[0072] The above preferred embodiment is further beneficial to improve the conversion rate of tert-butyl alcohol and the selectivity of isobutylene.

[0073] The present invention will be described in detail below through examples.

[0074] In the following examples, the catalyst composition was analyzed using an X-ray fluorescence analyzer (XRF);

[0075] The compositions of raw materials and reaction products in the following examples were measured by an Agilent 7890A gas chromatograph, and the specific test conditions were as follows: injector temperature 250°C; detector: TCD, detector temperature 250°C; analytical column: INNOVAX weak polar column, 50m×0.25mm×1μm; column box program: 40°C for 2 minutes, then heated to 240°C at a rate of 5°C / min, and stayed for 60min.

[0076] The preparation example described in the present invention is used to prepare WO3-SiO2 composite oxide catalyst.

[0077] Preparation Example 1

[0078] In a 2L beaker, add 284.2g of sodium silicate nonahydrate and 33g of sodium tungstate (dihydrate) to 700g of desalted water to fully dissolve, transfer to a 1000mL measuring cylinder, add water to make up to 1000mL, and obtain a mixed solution. Add 700g of desalted water to a 2L beaker, then add 220g of concentrated sulfuric acid (98wt%) to the desalted water, stir evenly and cool to below 40°C, transfer to a 1000mL measuring cylinder, add water to make up to 1000mL, and obtain an acid solution.

[0079] Add about 200mL of desalted water to a 3L three-necked flask precipitation reactor, start electric stirring, adjust the stirring rate to 300rpm, and then heat to about 50°C. Maintain the reaction temperature at about 50°C, use a peristaltic pump to add the mixed solution and acid solution to the precipitation reactor at a rate of 15-20mL / min, respectively, and add them in about 1h to make the final pH 7.2. Then heat to 65°C and age for 2h to obtain an aged product. Filter the aged product with a Buchner funnel. Wash the precipitate 5 times with 1500mL of a dilute sulfuric acid solution with a mass fraction of 0.1wt%, and pulp and filter each time. Finally, wash once with 1500mL of desalted water, filter, and obtain a solid product.

[0080] The solid product was dried in an oven at 120°C for 8 hours, and then calcined in a muffle furnace at 600°C for 8 hours. The calcined product was pressed into tablets using a tablet press. Finally, 83 g of catalyst A sample was obtained. The catalyst composition is shown in Table 1.

[0081] Preparation Example 2

[0082] In a 2L beaker, add 284.2g of sodium silicate nonahydrate and 26.4g of sodium tungstate (dihydrate) to 700g of desalted water to fully dissolve, transfer to a 1000mL measuring cylinder, add water to make up to 1000mL, and obtain a mixed solution. Add 700g of desalted water to a 2L beaker, then add 216g of concentrated sulfuric acid (98wt%) to the desalted water, stir evenly and cool to below 40°C, transfer to a 1000mL measuring cylinder, add water to make up to 1000mL, and obtain an acid solution.

[0083] Add about 200mL of desalted water to a 3L three-necked flask precipitation reactor, start electric stirring, adjust the stirring rate to 300rpm, and then heat to about 60°C. Maintain the reaction temperature at about 60°C, use a peristaltic pump to add the mixed solution and acid solution to the precipitation reactor at a rate of 15-20mL / min, respectively, and add them in about 1h to make the final pH 7.5. Then heat to 65°C and age for 2h to obtain an aged product. Filter the aged product with a Buchner funnel. Wash the precipitate 5 times with 1500mL of a dilute sulfuric acid solution with a mass fraction of 0.1wt%, and pulp and filter each time. Finally, wash once with 1500mL of desalted water, filter, and obtain a solid product.

[0084] The solid product was dried in an oven at 120°C for 8 hours, and then calcined in a muffle furnace at 600°C for 8 hours. The calcined product was pressed into tablets using a tablet press. Finally, 78.5 g of catalyst B sample was obtained. The catalyst composition is shown in Table 1.

[0085] Preparation Example 3

[0086] In a 2L beaker, add 284.2g of sodium silicate nonahydrate and 19.8g of sodium tungstate (dihydrate) to 700g of desalted water to fully dissolve, transfer to a 1000mL measuring cylinder, add water to make up to 1000mL, and obtain a mixed solution. Add 700g of desalted water to a 2L beaker, then add 212g of concentrated sulfuric acid (98wt%) to the desalted water, stir evenly and cool to below 40°C, transfer to a 1000mL measuring cylinder, add water to make up to 1000mL, and obtain an acid solution.

[0087] Add about 200mL of desalted water to a 3L three-necked flask precipitation reactor, start electric stirring, adjust the stirring rate to 300rpm, and then heat to about 50°C. Maintain the reaction temperature at about 50°C, use a peristaltic pump to add the mixed solution and acid solution to the precipitation reactor at a rate of 10-12mL / min, and add them over 1.5h to make the final pH 7.1. Then heat to 75°C and age for 2.5h to obtain an aged product. Filter the aged product with a Buchner funnel. Wash the precipitate 5 times with 1500mL of a 0.1wt% dilute sulfuric acid solution each time, and pulp and filter each time. Finally, wash once with 1500mL of desalted water, filter, and obtain a solid product.

[0088] The solid product was dried in an oven at 120°C for 8 hours, and then calcined in a muffle furnace at 700°C for 6 hours. The calcined product was pressed into tablets using a tablet press. Finally, 73.6 g of catalyst C sample was obtained. The catalyst composition is shown in Table 1.

[0089] Preparation Example 4

[0090] The method of Preparation Example 1 was followed, except that the mass of sodium tungstate dihydrate and concentrated sulfuric acid were changed to 13.19 g and 208 g, respectively. Finally, about 69.2 g of Catalyst D sample was obtained. The catalyst composition is shown in Table 1.

[0091] Preparation Example 5

[0092] The method of Preparation Example 1 was followed, except that the mass of sodium tungstate dihydrate and concentrated sulfuric acid were changed to 8.25 g and 205 g, respectively. Finally, 65.6 g of Catalyst E sample was obtained. The catalyst composition is shown in Table 1.

[0093] Preparation Example 6

[0094] The method of Preparation Example 1 was followed, except that the mass of sodium tungstate dihydrate and concentrated sulfuric acid were changed to 41.2 g and 225 g, respectively. Finally, 88.6 g of Catalyst F sample was obtained. The catalyst composition is shown in Table 1.

[0095] Preparation Example 7

[0096] The method of Preparation Example 1 was followed, except that 98 wt% sulfuric acid was replaced with 36.5 wt% hydrochloric acid, and the mass of the hydrochloric acid was 220 g. Finally, 82.8 g of Catalyst G sample was obtained. The catalyst composition is shown in Table 1.

[0097] Preparation Example 8

[0098] The method of Preparation Example 1 was followed, except that the acid solution was first added to the mixed solution, and then added to the precipitation kettle at a rate of 20 mL / min using a peristaltic pump to obtain 82 g of catalyst H sample. The catalyst composition is shown in Table 1.

[0099] Preparation Example 9

[0100] The method of Preparation Example 1 was followed, except that the amount of acid solution added was reduced so that the final pH was 8.5.

[0101] 63 g of sample of catalyst I was obtained. The catalyst composition is shown in Table 1.

[0102] Table 1

[0103]

[0104] Example 1

[0105] The cracking reaction of tert-butyl alcohol was carried out in a jacketed fixed bed reactor built in the laboratory. 30 g of the catalyst prepared in the preparation example was loaded into a fixed bed reactor tube with a jacket. The reaction temperature was 200°C and the reaction pressure was 0.5 MPa. Tert-butyl alcohol (mass fraction 99.9%) was fed at a feed mass space velocity of 1 h -1 The reaction product was analyzed online by gas chromatography. The reaction results after 24 hours of reaction are listed in Table 2.

[0106] Table 2

[0107]

[0108] Embodiment 2-6

[0109] The cracking reaction of tert-butyl alcohol was carried out in a jacketed fixed-bed reactor built in the laboratory. 30 g of catalyst A was loaded into a jacketed fixed-bed reactor tube, and tert-butyl alcohol (mass fraction 99.9%) was fed at a feed mass space velocity of 1 h. -1The reaction pressure was 0.5 MPa and the reaction temperature was adjusted as shown in Table 3. The pyrolysis products were analyzed online by gas chromatograph. The reaction results after 24 hours of reaction are listed in Table 3.

[0110] Table 3

[0111]

[0112] Example 8

[0113] The cracking reaction of tert-butyl alcohol was carried out in a jacketed fixed bed reactor built in the laboratory. 30 g of catalyst A was loaded into a jacketed fixed bed reactor tube, the reaction temperature was controlled at 200 ° C, and the reaction pressure was controlled at 0.5 MPa. Tert-butyl alcohol (mass fraction 85%) was fed at a feed mass space velocity of 1 h -1 The reaction product was analyzed online by gas chromatography. The reaction results after 24 hours of reaction are shown in Table 4.

[0114] Table 4

[0115]

[0116] It can be seen from the results in Tables 2-4 that the method for preparing isobutylene by the present invention has a high conversion rate of tert-butyl alcohol and isobutylene selectivity, and almost no side reactions occur.

[0117] This example is used to illustrate the stability of the catalyst used in the present invention.

[0118] Example 9

[0119] The cracking reaction of tert-butyl alcohol was carried out in a jacketed fixed bed reactor built in the laboratory. 30 g of catalyst (A) was loaded into a jacketed fixed bed reactor tube, the reaction temperature was controlled at 220°C, and the reaction pressure was controlled at 0.5 MPa. Tert-butyl alcohol (mass fraction 99.9%) was fed at a feed mass space velocity of 1 h -1 The pyrolysis products were analyzed online by gas chromatography. The product composition and reaction results are shown in Table 5.

[0120] Table 5

[0121]

[0122] It can be seen from the results in Table 5 that the WO3-SiO2 composite oxide catalyst used in the method of the present invention has high thermal stability and can operate stably for a long time with almost no decrease in activity.

[0123] This example is used to illustrate the regeneration effect of the catalyst of the present invention.

[0124] Example 10

[0125] Since Catalyst A has stable performance and deactivated catalyst cannot be obtained under normal laboratory conditions, the reaction temperature was increased to 300 °C and the feed space velocity was increased by 5 h. -1 , to accelerate the deactivation of the catalyst. After 7 days of operation, the activity of the catalyst decreased and the TBA conversion rate was only 50% of the original. Stop feeding the reaction material and purge the reaction system with nitrogen. Then, gradually increase the reactor temperature from about 300°C to 500°C while maintaining nitrogen at 500mL / min, and introduce air from 5mL / min to 500mL / min. Finally, regenerate at 500°C for 8h while introducing air.

[0126] After the catalyst regeneration was completed, the air was stopped, and nitrogen was continued to be introduced to replace the oxygen in the system, the temperature was lowered to 200° C., and tert-butyl alcohol was introduced to react. The evaluation experimental conditions were the same as those in Example 1. The product composition and reaction results are shown in Table 6 below.

[0127] Table 6

[0128]

[0129] It can be seen from the results in Table 6 that the activity of the WO3-SiO2 composite oxide catalyst after regeneration used in the method of the present invention is close to the level of a fresh catalyst.

[0130] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing isobutylene by dehydrating tert-butyl alcohol, the method comprising: The tert-butyl alcohol is contacted with a WO3-SiO2 composite oxide catalyst for reaction; In the WO3-SiO2 composite oxide catalyst, based on the total weight of the WO3-SiO2 composite oxide catalyst, the content of WO3 is 5-40 weight %; the content of SiO2 is 60-95 weight %.

2. The method according to claim 1, wherein: In the WO3-SiO2 composite oxide catalyst, based on the total weight of the WO3-SiO2 composite oxide catalyst, the content of WO3 is 10-30 weight %; the content of SiO2 is 70-90 weight %.

3. The method according to claim 1, wherein: The WO3-SiO2 composite oxide catalyst further contains Na2O, and the content of Na2O is less than 0.1 wt% based on the total weight of the WO3-SiO2 composite oxide catalyst.

4. The method according to any one of claims 1 to 3, wherein: The reaction conditions include: temperature of 180-250°C, preferably 180-220°C; pressure of 0.1-1MPa, preferably 0.4-0.6MPa; mass space velocity of 0.1-5h -1 , preferably 0.2-2h -1 ; Preferably, the concentration of tert-butyl alcohol is ≥ 85 wt %.

5. The method according to any one of claims 1 to 4, wherein: The WO3-SiO2 composite oxide catalyst is prepared by a coprecipitation method; Preferably, the preparation method of the WO3-SiO2 composite oxide catalyst comprises: (1) mixing a tungsten source and a silicon source in the presence of a solvent to obtain a mixed solution; (2) subjecting the acid solution and the mixed solution to a precipitation reaction to obtain a solid product; (3) Drying and calcining the solid product.

6. The method according to claim 5, wherein: In the mixed solution, the concentration of the silicon source is 50-300 g / L; Preferably, in the mixed solution, the concentration of the tungsten source is 50-200 g / L; Preferably, the silicon source is selected from at least one of sodium silicate, water glass and potassium silicate; Preferably, the tungsten source is sodium tungstate and / or ammonium metatungstate.

7. The method according to claim 5, wherein: The precipitation conditions in step (2) include: a temperature of 20-60° C.; Preferably, the precipitation reaction is terminated when the pH is 6-9, preferably 7-7.

5.

8. The method according to claim 5, wherein: The preparation method of the WO3-SiO2 composite oxide catalyst further comprises: aging the product of the precipitation reaction, wherein the aging conditions include: an aging temperature of 60-80°C and an aging time of 2-5h.

9. The method according to any one of claims 5 to 8, wherein: The calcination conditions in step (3) include: a calcination temperature of 500-700° C. and a calcination time of 6-24 hours.

10. The method according to any one of claims 5 to 9, wherein: The preparation method of the WO3-SiO2 composite oxide catalyst also includes a molding step, and the molding is performed before or after the calcination in step (3).

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