Catalyst for preparing isobutene by converting acetone as well as preparation method and application of catalyst

Abstract

The invention belongs to the technical field of molecular sieve catalysts, and discloses a catalyst for preparing isobutene through acetone conversion and a preparation method and application thereof.The preparation method comprises the steps that firstly, an HBeta molecular sieve is treated with concentrated nitric acid to prepare a dealuminated Beta molecular sieve; then loading the hafnium oxychloride octahydrate in the dealuminated Beta molecular sieve by an impregnation method; putting the obtained sample into a tetraethylammonium hydroxide solution, and fully stirring; and drying, centrifuging, washing to be neutral, drying, and roasting to obtain the Hf / Beta catalyst. The catalyst shows excellent catalytic activity and selectivity in the reaction of preparing isobutene through acetone conversion, is good in stability, and can obtain high-efficiency isobutene yield; the catalyst carrier and the metal precursor salt are cheap and easy to obtain, and the preparation process is simple; therefore, a new effective way is provided for production of isobutene, and the situation that isobutene mainly depends on traditional energy at present is effectively relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieve catalysts, and in particular relates to a catalyst for converting acetone into isobutylene, and a preparation method and application thereof. Background Art

[0002] Isobutylene is a very important chemical in the field of organic chemical industry. It is mainly used to produce a series of high value-added chemicals such as methyl tert-butyl ether, methyl tert-butyl ether, methyl methacrylate, polyisobutylene, butyl rubber and alkylphenol antioxidants.

[0003] At present, there are many processes for producing isobutylene, mainly sulfuric acid extraction, tert-butyl alcohol dehydration, methyl tert-butyl ether cracking, isobutane co-oxidation and co-production, isobutane dehydrogenation, ethanol to isobutylene and acetic acid to isobutylene. Among the above-mentioned methods, ethanol to isobutylene and acetic acid to isobutylene have received widespread attention in recent years. Patent CN108097300A applied by the inventor discloses a molecular sieve catalyst, which introduces rare earth active centers into the molecular sieve by impregnation method and is applied to the reaction of acetic acid conversion to isobutylene, with excellent catalytic activity and selectivity. Liu Tian et al. of Fudan University (patent CN104707591B) obtained a ZrO2-ZnO-Sc2O3 mixed oxide catalyst by hydrothermal method, which has a high isobutylene yield and reaction stability. Men Yong et al. of Shanghai University of Engineering Science (patent CN105056957A) prepared a ternary composite oxide A x B y Zr z O n , A is a transition metal, B is an alkaline metal, and the types and compositions of the three elements are regulated to obtain high-yield isobutylene. Therefore, the current production pathways for isobutylene are mainly focused on the conversion of small molecules such as acetic acid. However, finding other biomass platform molecules to convert isobutylene and further expanding the isobutylene production pathway is of great significance for the expansion of isobutylene production.

[0004] It is worth noting that acetone is also an important biomass platform molecule, which is mainly obtained through further fermentation of starch raw materials. Therefore, the conversion of acetone into isobutylene is of great significance for the efficient utilization of biomass and the dual-carbon strategy. At present, there are no reports on the catalyst design technology for the conversion of acetone to isobutylene. Summary of the invention

[0005] The present invention aims to solve the technical problem of lack of relevant high-efficiency catalysts in the current acetone conversion reaction to prepare isobutylene. A new method for preparing a catalyst for the acetone to isobutylene reaction is proposed. The catalyst is prepared by a tetraethylammonium hydroxide solution dissolution-recrystallization process, and the Lewis acid content of the catalyst is significantly increased. The catalyst is innovatively applied to the acetone to isobutylene reaction for the first time, and the isobutylene yield is increased while the isobutylene selectivity is also high.

[0006] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

[0007] According to a first aspect of the present invention, there is provided a catalyst for converting acetone to isobutylene, which is obtained by the following preparation method:

[0008] S1. Treating HBeta molecular sieve with concentrated nitric acid to prepare dealuminated Beta molecular sieve;

[0009] S2, loading hafnium oxychloride octahydrate into the sample obtained in S1 by an impregnation method;

[0010] S3. The sample obtained in S2 is placed in a 0.1-1 mol / L tetraethylammonium hydroxide solution and stirred thoroughly; then crystallized at 120-160°C, centrifuged after completion, washed to neutrality, and then dried at 80-120°C; finally calcined at 400-600°C to obtain Hf / Beta catalyst.

[0011] According to a second aspect of the present invention, there is provided a method for preparing a catalyst for converting acetone to isobutylene, comprising:

[0012] S1. Treating HBeta molecular sieve with concentrated nitric acid to prepare dealuminated Beta molecular sieve;

[0013] S2, loading hafnium oxychloride octahydrate into the sample obtained in S1 by an impregnation method;

[0014] S3. The sample obtained in S2 is placed in a 0.1-1 mol / L tetraethylammonium hydroxide solution and stirred thoroughly; then crystallized at 120-160°C, centrifuged after completion, washed to neutrality, and then dried at 80-120°C; finally calcined at 400-600°C to obtain Hf / Beta catalyst.

[0015] For the above-mentioned catalyst for converting acetone to isobutylene and its preparation method:

[0016] Furthermore, S1 includes: mixing HBeta molecular sieve with concentrated nitric acid and heating to react; after the reaction is completed, filtering and washing the product to neutrality, and then drying it for later use.

[0017] Preferably, in S1: the reaction temperature is 80-120° C., the reaction time is 20-30 hours; the feed ratio of HBeta molecular sieve to concentrated nitric acid is 1 g: 10-30 ml; the drying temperature is 80-120° C., and the drying time is 6-10 hours.

[0018] Furthermore, S2 comprises: after mixing hafnium dichloride octahydrate with water and stirring, adding the sample obtained in step (1), stirring sufficiently, and then heating and stirring to evaporate to dryness; after drying, the sample obtained by evaporation is calcined to obtain a Hf / Beta catalyst.

[0019] Preferably, in S2: the stirring time is 3-6 hours; the evaporation temperature is 50-90°C; the drying temperature is 80-120°C, and the drying time is 12-24 hours; the calcination temperature is 400-600°C, and the calcination time is 4-8 hours; and the Hf loading in the Hf / Beta catalyst is 5-15wt%.

[0020] Furthermore, in S3, the usage ratio of the sample obtained in S2 to the tetraethylammonium hydroxide solution is 1 g: 1-20 ml.

[0021] Preferably, in S3: the crystallization time is 12-24 hours, and the calcination time is 4-8 hours.

[0022] According to a third aspect of the present invention, there is provided an application of the above-mentioned catalyst for converting acetone to isobutylene, which is used for the reaction of acetone to isobutylene, and the reaction temperature is 300-500°C.

[0023] Furthermore, the obtained catalyst is first pressed into tablets, and then placed in a reaction bed, and pretreated at a temperature of 400-500° C. for 0.5-2 hours with a carrier gas flow rate of 20-40 ml / min; after the pretreatment, the reaction temperature is set, and acetone is fed into the reaction bed with an acetone flow rate of 0.1-1 ml / min.

[0024] The beneficial effects of the present invention are:

[0025] The invention provides a catalyst for preparing isobutylene through conversion of acetone, and a preparation method and application thereof. The Lewis acid content of the prepared catalyst is significantly increased through a dissolution-recrystallization process of a tetraethylammonium hydroxide solution. The catalyst exhibits excellent catalytic activity and selectivity in the reaction of preparing isobutylene through conversion of acetone, has good stability, and can obtain a high isobutylene yield. Moreover, the catalyst carrier and the metal precursor salt are both cheap and readily available, and the preparation process is simple. Therefore, a new and effective way is provided for the production of isobutylene, and the current situation in which isobutylene mainly relies on traditional energy sources is effectively alleviated. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1The results of catalyst activity treated with templates of different concentrations obtained in Example 1 of the present invention are shown in FIG.

[0027] Figure 2 The XRD spectra of the catalysts treated with templates of different concentrations obtained in Example 1 of the present invention;

[0028] Figure 3 NH3-TPD diagram of the catalyst treated with templates of different concentrations obtained in Example 1 of the present invention;

[0029] Figure 4 This is a graph showing the catalyst activity results for different Hf contents obtained in Example 2 of the present invention;

[0030] Figure 5 This is a graph showing the reaction activity of Hf / Beta and Hf / Beta-0.5 changing with time in Example 3 of the present invention. DETAILED DESCRIPTION

[0031] In some preferred embodiments of the present invention, a catalyst for converting acetone to isobutylene and a preparation method thereof are provided, which are carried out according to the following steps:

[0032] S1. Treating HBeta molecular sieve with concentrated nitric acid: mixing HBeta molecular sieve and concentrated nitric acid in proportion, the feeding ratio of HBeta molecular sieve to concentrated nitric acid is 1g:10-30ml; stirring at 80-120°C for 20-30 hours, and the stirring rate is 700-1000 rpm; after the reaction is completed, washing it by suction filtration until it is neutral, and then drying it in an oven at 80-120°C for 6-10 hours for standby use, to obtain a dealuminated Beta molecular sieve;

[0033] S2. Weigh a certain amount of hafnium dichloride octahydrate and add it into a beaker containing 20-60 ml of water. Then add 1-2 g of the sample obtained in S1, stir thoroughly for 3-6 hours, and then heat and stir at 50-90°C to evaporate to dryness. Put the evaporated sample into an oven at 80-120°C to dry for 12-24 hours, and then place it in a muffle furnace and roast it for 4-8 hours at a roasting temperature of 400-600°C to obtain Hf / Beta catalysts with different contents.

[0034] S3. The sample obtained in S2 is placed in 10 ml of 0.1-1 mol / L tetraethylammonium hydroxide solution, stirred for 30-60 minutes, then placed in a hydrothermal kettle, placed in an oven at 120-160° C. for 12-24 hours, centrifuged after crystallization, washed to neutrality, dried in an oven at 80-120° C., and finally calcined in an oven at 400-600° C. for 4-8 hours to obtain a Hf / Beta-X catalyst, where X represents the concentration of tetraethylammonium hydroxide.

[0035] The Hf / Beta-X catalyst of the present invention is used for the reaction of preparing isobutylene from acetone: firstly, the obtained catalyst is tableted, 0.1-0.3 g of the catalyst with a mesh size of 20-40 is sieved out with a sieve, and then the catalyst is placed in a fixed bed for pretreatment for 0.5-2 hours, the pretreatment temperature is 400-500° C., and the carrier gas flow rate is 20-40 ml / min; after the pretreatment is completed, the temperature is set to a specified temperature, and acetone is sent into the fixed bed with an injection pump, the acetone flow rate is 0.2 ml / min, and the reaction temperature is 300-500° C.

[0036] The following is a more detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings and embodiments, so as to better understand the scheme of the present invention and its advantages in various aspects. It should be noted that the specific implementation methods and embodiments described below are only for the purpose of illustration, and are not intended to limit the present invention.

[0037] Example 1

[0038] In this embodiment, HBeta catalyst is used as raw powder, and the silicon-to-aluminum ratio used is 28.

[0039] Preparation of dealuminated Beta molecular sieve: Concentrated nitric acid and HBeta raw powder with a molar ratio of 28 are placed in a three-necked flask and mixed, and placed in a 100°C oil bath for heating and reflux for 20 hours, wherein the feed ratio of HBeta to concentrated nitric acid solution is 1:20 (g / ml); after completion, filter, wash to neutrality, and dry in an 80°C oven for 24 hours.

[0040] Weigh 0.1379 g of HfOCl2·8H2O into a beaker, add 40 ml of water, stir for ten minutes, then add 1 g of the dealuminated Beta molecular sieve powder treated with concentrated nitric acid, stir for 3 hours, heat in an 80°C water bath and stir until evaporated, put into an 80°C oven to dry for 24 hours, and then put into a muffle furnace and calcine at 550°C for 6 hours to obtain Hf / Beta (the Hf loading in the Hf / Beta catalyst is 5 wt%).

[0041] 1 g of Hf / Beta powder obtained above was dissolved in tetraethylammonium hydroxide solution of different concentrations. After stirring for 10 minutes, the concentrations of the tetraethylammonium hydroxide solution were 0.1 mol / L, 0.3 mol / L, 0.5 mol / L and 0.7 mol / L, respectively. Then, the powder was put into a hydrothermal kettle and placed in an oven at 140°C for 24 hours. After the powder was taken out and centrifuged to neutrality, it was dried in an oven at 80°C for 24 hours and calcined in a muffle furnace at 550°C for 6 hours. The obtained sample was Hf / Beta-X, where X represented the concentration of the tetraethylammonium hydroxide solution.

[0042] The obtained Hf / Beta, Hf / Beta-0.1, Hf / Beta-0.3, Hf / Beta-0.5 and Hf / Beta-0.7 were used for the evaluation of the acetone to isobutylene reaction. First, the tablets were pressed and sieved with a 20-40 mesh sieve. 0.16 g of the sample was weighed and then placed in a fixed bed quartz reaction tube and pretreated with nitrogen at 450°C for 1 hour with a nitrogen flow rate of 20 ml / min. After the pretreatment, acetone was introduced through a syringe pump with a mass space velocity of 1 / h for 0.5 hours. The product was introduced into a gas chromatograph for online analysis.

[0043] The catalyst performance evaluation of the above five catalysts is as follows: Figure 1 As shown in the figure, compared with the untreated Hf / Beta catalyst, the activity of the catalyst was significantly improved after being treated with the template agent. When the concentration of the tetraethylammonium hydroxide solution was 0.1-0.5 mol / L, the isobutylene yield gradually increased. When the concentration of the tetraethylammonium hydroxide solution increased to 0.7 mol / L, the isobutylene yield decreased. Therefore, the activity of Hf / Beta after being treated with 0.5 mol / L tetraethylammonium hydroxide solution was the best. In addition, Figure 2 As shown in Figure 2, it is found that the structure of the molecular sieve does not change after the template treatment. Moreover, it is worth noting that the template treatment can significantly increase the acid content, such as Figure 3 shown.

[0044] Example 2

[0045] Weigh 0.1379 g of HfOCl2·8H2O into a beaker, add 40 ml of water, stir for ten minutes, then add 1 g of dealuminated Beta prepared in Example 1, stir for 3 hours, heat in an 80°C water bath and stir until evaporated, put into an 80°C oven to dry for 24 hours, and then put into a muffle furnace and calcine at 550°C for 6 hours to obtain Hf / Beta (the Hf loading in the Hf / Beta catalyst is 5 wt%).

[0046] Weigh 0.2758 g of HfOCl2·8H2O into a beaker, add 40 ml of water, stir for ten minutes, then add 1 g of the dealuminated Beta molecular sieve powder prepared in Example 1, stir for 3 hours, heat in an 80°C water bath and stir until evaporated, put into an 80°C oven to dry for 24 hours, and then put into a muffle furnace and calcine at 550°C for 6 hours to obtain Hf / Beta (the Hf loading in the Hf / Beta catalyst is 10 wt%).

[0047] Weigh 0.4137 g of HfOCl2·8H2O into a beaker, add 40 ml of water, stir for ten minutes, then add 1 g of the dealuminated Beta molecular sieve powder prepared in Example 1, stir for 3 hours, heat in an 80°C water bath and stir until evaporated, put into an 80°C oven to dry for 24 hours, and then put into a muffle furnace and calcine at 550°C for 6 hours to obtain Hf / Beta (the Hf loading in the Hf / Beta catalyst is 15 wt%).

[0048] The obtained Hf / Beta (5wt%), Hf / Beta (10wt%) and Hf / Beta (15wt%) were used for the evaluation of the acetone to isobutylene reaction. First, the tablets were pressed and sieved with a 20-40 mesh sieve. 0.16 g of the sample was weighed and then placed in a fixed bed quartz reaction tube and pretreated with nitrogen at 450°C for 1 hour with a nitrogen flow rate of 20 ml / min. After the pretreatment, acetone was introduced through a syringe pump with a mass space velocity of 1 / h and an introduction time of 0.5 hours. The product was introduced into a gas chromatograph for online analysis.

[0049] Activity evaluation tests were carried out on the above three catalysts. Figure 4 As shown in Figure 2, it is found that the yield of isobutylene increases with the increase of metal loading, but the increase is small. Figure 1 In comparison, the catalytic activity of Hf / Beta (15wt%) is still lower than that of Hf / Beta-0.5, indicating that after being treated with the template, the acid amount and acid site type change, which is more conducive to the conversion of acetone to isobutylene.

[0050] Example 3

[0051] The Hf / Beta and Hf / Beta-0.5 catalysts prepared in Example 1 were used for reaction tests. First, the tablets were pressed and sieved with a 20-40 mesh sieve. 0.16 g of the sample was weighed and then placed in a fixed bed quartz reaction tube and pretreated with nitrogen at 450° C. for 1 hour with a nitrogen flow rate of 20 ml / min. After the pretreatment, acetone was introduced through a syringe pump at a mass space velocity of 1 / h for 8 hours. The product was introduced into a gas chromatograph for online analysis to obtain a graph of the catalytic activity changing over time.

[0052] pass Figure 5 It can be clearly seen that the conversion rates of the two products decrease significantly with time. After being treated with 0.5 mol / L template, the conversion rate decreases slowly, and the activity of Hf / Beta-0.5 is significantly increased compared to Hf / Beta, which can produce more isobutylene.

[0053] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms of specific changes without departing from the scope of protection of the invention and the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for converting acetone to isobutylene, characterized in that: include: S1. Treating HBeta molecular sieve with concentrated nitric acid to prepare dealuminated Beta molecular sieve; S2, loading hafnium oxychloride octahydrate into the sample obtained in S1 by an impregnation method; S3. The sample obtained in S2 is placed in a 0.1-1 mol / L tetraethylammonium hydroxide solution and stirred thoroughly; then crystallized at 120-160°C, centrifuged after completion, washed to neutrality, and then dried at 80-120°C; finally calcined at 400-600°C to obtain Hf / Beta catalyst.

2. The method for preparing a catalyst for converting acetone to isobutylene according to claim 1, characterized in that: S1 includes: The HBeta molecular sieve is mixed with concentrated nitric acid and heated to react; after the reaction is completed, the product is filtered and washed to neutrality, and then dried for later use.

3. The method for preparing a catalyst for converting acetone to isobutylene according to claim 2, characterized in that: In S1, the reaction temperature is 80-120°C, the reaction time is 20-30 hours; the feed ratio of HBeta molecular sieve to concentrated nitric acid is 1g:10-30ml; the drying temperature is 80-120°C, and the drying time is 6-10 hours.

4. The method for preparing a catalyst for converting acetone to isobutylene according to claim 1, characterized in that: S2 includes: After hafnium dichloride octahydrate is mixed and stirred with water, the sample obtained in step (1) is added, and after sufficient stirring, the mixture is heated and stirred and evaporated to dryness; The sample obtained by evaporation is dried and then calcined to obtain a Hf / Beta catalyst.

5. The method for preparing a catalyst for converting acetone to isobutylene according to claim 4, characterized in that: In S2: the stirring time is 3-6 hours; the evaporation temperature is 50-90°C; the drying temperature is 80-120°C, and the drying time is 12-24 hours; the calcination temperature is 400-600°C, and the calcination time is 4-8 hours; the Hf loading in the Hf / Beta catalyst is 5-15wt%.

6. The method for preparing a catalyst for converting acetone to isobutylene according to claim 1, characterized in that: In S3: the usage ratio of the sample obtained in S2 to the tetraethylammonium hydroxide solution is 1g:1-20ml.

7. The method for preparing a catalyst for converting acetone to isobutylene according to claim 1, characterized in that: In S3: the crystallization time is 12-24 hours, and the calcination time is 4-8 hours.

8. A catalyst for converting acetone to isobutylene, characterized in that: Obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the catalyst for converting acetone to isobutylene as claimed in claim 8, characterized in that: Used in the reaction of acetone to isobutylene, the reaction temperature is 300-500℃.

10. Use of the catalyst for converting acetone to isobutylene as claimed in claim 9, characterized in that: First, the obtained catalyst is pressed into tablets, and then placed in a reaction bed, and pretreated at a temperature of 400-500°C for 0.5-2 hours with a carrier gas flow rate of 20-40 ml / min; after the pretreatment, the reaction temperature is set, and acetone is fed into the reaction bed with an acetone flow rate of 0.1-1 ml / min.

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