Shaped carrier, preparation method and application thereof, and dehydrogenation shaped catalyst

Abstract

The present invention relates to the technical field of catalyst molding, and discloses a molding carrier, a preparation method and application thereof, and a dehydrogenation molding catalyst. The molding carrier comprises an all-silicon molecular sieve and SiO2, and the content of Al2O3 in the molding carrier is less than 1% by weight. No aluminum-containing molding aid or mineralizer is introduced in the preparation process of the molding catalyst provided by the present invention, which can effectively avoid the problems of accelerated carbon deposition rate of the molding catalyst, shortened service life, decreased catalytic effect, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst molding, and in particular to a molding carrier, a preparation method and application thereof, and a dehydrogenation molding catalyst. Background Art

[0002] In order to meet the equipment needs of industrial production, industrial catalysts are often formed catalysts with a certain strength. The common method of preparing formed catalysts is to first form the carrier and then load the active components on the formed carrier. Common carrier forming processes include extrusion forming, ball forming, spray forming, etc. All-silicon molecular sieves are often used as catalyst carriers due to their high specific surface area and weak acidity. However, due to their own crystallization and crystal structure characteristics, all-silicon molecular sieves are difficult to extrude into products of ideal strength in ordinary extrusion equipment like other materials. Therefore, during the forming process of all-silicon molecular sieves, mineralizers such as alumina are often added as forming aids to increase the strength of the forming carrier.

[0003] However, the reaction stability of the all-silicon molecular sieve shaped carrier with aluminum oxide is poorer than that of the all-silicon molecular sieve (original powder), and the one-way stable reaction time is greatly reduced, thereby increasing the use cost of industrial catalysts (for example, the reduction in the one-way stable reaction time leads to the need for frequent catalyst regeneration or replacement). Therefore, how to ensure the strength of the all-silicon molecular sieve carrier without affecting the catalyst performance as much as possible is a very important issue for the research of dehydrogenation catalysts, especially industrial dehydrogenation catalysts. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems in the prior art such as insufficient strength of the all-silicon molecular sieve during molding, or the influence on the activity and life of the catalyst due to the addition of a mineralizer, and to provide a molding carrier and its preparation method and application, as well as a dehydrogenation molding catalyst. The molding carrier does not introduce strong acidic sites on the surface on the basis of achieving a certain molding strength, thereby reducing the influence of the carrier molding on the catalyst performance, especially the influence on the propane dehydrogenation catalytic reaction performance.

[0005] The inventors of the present invention have found that the addition of alumina can easily weaken the weak acidity advantage of silicon oxide molecular sieves. At the same time, for some dehydrogenation reactions, such as propane dehydrogenation to propylene, the introduction of alumina can also cause problems such as accelerated carbon deposition rate and corresponding shortened catalyst life, which affects the performance of the catalyst. Therefore, in order to achieve the above-mentioned purpose, the present invention provides a shaped carrier, the shaped carrier comprises an all-silicon molecular sieve and SiO2 in an amorphous state, and the content of Al2O3 in the shaped carrier is less than 1% by weight.

[0006] The second aspect of the present invention provides a method for preparing a shaped carrier, the method comprising mixing an all-silicon molecular sieve, amorphous SiO2 and a molding aid, and then molding the obtained mixture, wherein the content of Al2O3 in the molding aid is less than 1 weight%.

[0007] The third aspect of the present invention provides a shaped carrier prepared by the method as described above.

[0008] The fourth aspect of the present invention provides the use of the shaped carrier as described above in the preparation of industrial catalysts.

[0009] A fifth aspect of the present invention provides a dehydrogenation shaped catalyst, which comprises a shaped carrier and an active component loaded on the shaped carrier, wherein the shaped carrier is the shaped carrier as described above.

[0010] Through the above technical scheme, the shaped carrier prepared by the method provided by the present invention uses all-silicon molecular sieve as the main raw material, adopts the all-silicon extrusion molding method, and does not add aluminum-containing molding aids such as alumina during the process. While achieving the ideal strength, the impact on the catalyst performance is reduced, especially when used as a dehydrogenation catalyst carrier, avoiding the problems of accelerated carbon deposition rate and corresponding shortened life, reduced catalytic effect, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a photo of the all-silicon molecular sieve formed carrier sample 1# obtained in Example 1;

[0012] Figure 2 is a cross-sectional SEM image of the all-silicon molecular sieve formed carrier sample 1# obtained in Example 1;

[0013] Figure 3 and Figure 4 This is a schematic diagram of the changes in propane conversion and propylene selectivity with reaction time when the catalytic performance of the molded dehydrogenation catalyst made of molded carrier samples 1# and 8# in Test Example 2 was tested. DETAILED DESCRIPTION

[0014] 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.

[0015] The inventor of the present invention cleverly discovered during the research process that by mixing natural plant gum (such as sesbania powder, etc.), amorphous SiO2 (powder) and all-silicon molecular sieve in dilute acid (such as dilute nitric acid, etc.), and then molding, drying and roasting the obtained mixture, not only can the strength of the molded carrier be improved, but also the introduction of strong acid sites in the molded carrier, which would affect the performance of the catalyst, can be avoided.

[0016] On one hand, the present invention provides a shaped carrier, which includes an all-silicon molecular sieve and SiO2 in an amorphous state, and the content of Al2O3 in the shaped carrier is less than 1% by weight (that is, the shaped carrier does not contain intentionally added Al2O3).

[0017] According to a preferred embodiment of the present invention, the shaped carrier does not contain Al2O3.

[0018] Any type of all-silicon molecular sieve can be formed by the method provided by the present invention. Preferably, the all-silicon molecular sieve is selected from MFI type all-silicon molecular sieve or silicalite-2, preferably silicalite-1.

[0019] The inventors of the present invention found in the process of research that after being formed by the method provided by the present invention, the pore size characteristics of the formed carrier will change to a certain extent (for example, the specific surface area of ​​the micropore part is reduced, the surface area is increased, etc.) compared with the all-silicon molecular sieve (original powder) before forming. By adjusting the content ratio of each component in the mixture used for forming, the pore size change of the formed carrier can be controlled within a certain range, so that the performance of the formed carrier is not affected as much as possible.

[0020] Preferably, based on the unformed all-silicon molecular sieve, the specific surface area of ​​the pore characteristics of the formed carrier decreases by no more than 20%, and the external surface area increases by 30-60%.

[0021] More preferably, based on the unformed all-silicon molecular sieve, the pore size characteristic micropore specific surface area of ​​the formed carrier decreases by 1-15%, and the external surface area increases by 40-60%.

[0022] The second aspect of the present invention provides a method for preparing a molding carrier, which comprises mixing an all-silicon molecular sieve, an amorphous SiO2 (powder) and a molding aid, and then molding the obtained mixture, wherein the Al2O3 content in the molding aid is less than 1 wt.%, that is, the molding aid does not contain intentionally added Al2O3).

[0023] According to a preferred embodiment of the present invention, the all-silicon molecular sieve is selected from MFI-type all-silicon molecular sieve or silicalite-2, preferably silicalite-1.

[0024] The inventors of the present invention discovered during the course of their research that the particle size characteristics of amorphous SiO2 (powder) used for preparing a shaped carrier have a certain influence on the strength of the shaped carrier and the performance of the catalyst prepared using the shaped carrier.

[0025] In order to obtain a shaped carrier with higher strength and better performance, according to a preferred embodiment of the present invention, the amorphous SiO2 (powder) is selected from SiO2 (powder) with a particle size of 1-5 μm.

[0026] According to a preferred embodiment of the present invention, the molding aid is selected from sesbania powder and / or dilute nitric acid.

[0027] Preferably, the molding aid is selected from sesbania powder and 2-8 wt% nitric acid aqueous solution.

[0028] In the present invention, there is no particular restriction on the specific usage ratio of the all-silicon molecular sieve, the amorphous SiO2 and the molding aid, as long as a molding carrier with sufficient strength and satisfactory performance can be obtained. According to a preferred embodiment of the present invention, the weight ratio of the all-silicon molecular sieve to the molding aid is 1:0.1-1.2, preferably 1:0.5-0.9.

[0029] According to a preferred embodiment of the present invention, the weight ratio of the all-silicon molecular sieve to the amorphous SiO2 is 1:0.1-0.5, preferably 1:0.15-0.3.

[0030] According to a preferred embodiment of the present invention, the weight ratio of the all-silicon molecular sieve to the sesbania powder is 1:0.001-0.1, preferably 1:0.005-0.05.

[0031] According to a preferred embodiment of the present invention, the amount of the dilute nitric acid is 0.1-1 mL, preferably 0.5-0.8 mL, relative to 1 g of the all-silicon molecular sieve. The concentration of HNO3 in the dilute nitric acid is 2-8% by weight.

[0032] In the present invention, any existing molding method in the art can be used, as long as the strength of the molding carrier can be ensured to meet the requirements.

[0033] According to a preferred embodiment of the present invention, the molding method is extrusion molding.

[0034] Preferably, the extrusion molding conditions include room temperature (eg, 20-30° C.) and 100-150 rpm.

[0035] According to a preferred embodiment of the present invention, the method further comprises the steps of sequentially performing low temperature drying and calcining on the formed product. The low temperature drying refers to performing drying at a temperature not exceeding 150°C.

[0036] The inventors of the present invention also found during the research process that, compared with a one-step heating method, a molded carrier with higher strength can be obtained by roasting the dried molded product in a segmented and gradual heating method.

[0037] In order to obtain a shaped carrier with higher strength, preferably, the calcination process is performed in a step-by-step manner.

[0038] More preferably, the stepwise roasting method comprises:

[0039] (1) Low temperature calcination: temperature 200-300°C, time 0.2-2h;

[0040] (2) Medium temperature roasting: temperature 350-450°C, time 0.2-2h;

[0041] (3) High temperature calcination: temperature 550-650℃, time 5-10h.

[0042] In order to further improve the strength of the shaped carrier, according to a preferred embodiment of the present invention, the temperature of the medium-temperature calcination is 100-200° C. higher than the temperature of the low-temperature calcination.

[0043] In order to further improve the strength of the shaped carrier, according to a preferred embodiment of the present invention, the temperature of the high-temperature calcination is 150-200° C. higher than the temperature of the medium-temperature calcination.

[0044] Preferably, the temperature difference between high temperature roasting and medium temperature roasting is 20-50° C. higher than the temperature difference between medium temperature roasting and low temperature roasting.

[0045] Preferably, during the calcination process, the heating rate is 1-5°C / min, preferably 1-3°C / min;

[0046] In the present invention, during the stepwise calcination, the heating rates used in each stage may be the same or different. Preferably, the heating rates of the low temperature calcination and the medium temperature calcination are the same.

[0047] More preferably, the heating rate of the high temperature calcination is slightly lower than the heating rate of the low temperature calcination and / or the medium temperature calcination.

[0048] According to a preferred embodiment of the present invention, the step-by-step roasting method comprises:

[0049] (1) Low temperature calcination: heating to 230-280°C at a heating rate of 2-3°C / min, and calcining at this temperature for 0.5-2h;

[0050] (2) Medium temperature roasting: heating to 380-420°C at a heating rate of 2-3°C / min, and roasting at this temperature for 0.5-2h;

[0051] (3) High temperature calcination: Raise the temperature to 550-600°C at a heating rate of 1.5-2.5°C / min and calcine at this temperature for 5-7h.

[0052] Preferably, the medium-temperature roasting temperature is 130-170° C. higher than the low-temperature roasting temperature.

[0053] Preferably, the temperature of the high temperature calcination is 160-190° C. higher than that of the medium temperature calcination.

[0054] More preferably, the temperature difference between high temperature roasting and medium temperature roasting is 25-35° C. higher than the temperature difference between medium temperature roasting and low temperature roasting.

[0055] The third aspect of the present invention provides a shaped carrier prepared by the method as described above. The characteristics of the shaped carrier are as described above and will not be repeated here.

[0056] The fourth aspect of the present invention provides the use of the above-mentioned shaped carrier in the preparation of industrial catalysts, especially in the preparation of dehydrogenation (especially propane dehydrogenation to propylene) catalysts.

[0057] A fifth aspect of the present invention provides a dehydrogenation shaped catalyst, which comprises a shaped carrier and an active component loaded on the shaped carrier, wherein the shaped carrier is the shaped carrier as described above.

[0058] In the present invention, there is no particular limitation on the active components in the dehydrogenation shaped catalyst, which can be any active component used in any existing supported dehydrogenation shaped catalyst, such as precious metals, alkaline earth metals, alkali metals, transition metals, etc. In order to improve the performance of the dehydrogenation shaped catalyst, the dehydrogenation shaped catalyst may also include components such as additives supported on the shaped carrier.

[0059] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0060] In the following examples, the all-silicon molecular sieve used is silicalite-1 all-silicon molecular sieve, with an average particle size of 200-500 nm. The particle size of SiO2 powder is 2-4 μm.

[0061] In the following examples, a twin-screw extruder (South China University of Technology Science and Technology General Factory, F-26 model) was used to form the carrier at room temperature and 120±10 rpm.

[0062] Example 1

[0063] The following method is used to prepare the all-silicon molecular sieve forming carrier:

[0064] Molding: Weigh 60 g of all-silicon molecular sieve, 10 g of SiO2 powder, and 0.5 g of sesbania powder and mix them evenly, then add 33 mL of a 5 wt% dilute nitric acid solution, continue mixing evenly, and then extrude the obtained mixture using a twin-screw extruder.

[0065] The extruded product was dried at 120°C and then calcined in the following manner.

[0066] Calcination: (1) Low temperature calcination: heating to 250 °C at a heating rate of 2.5 °C / min and calcining at this temperature for 2 h;

[0067] (2) Medium temperature calcination: heating to 400 °C at a heating rate of 2.5 °C / min and calcining at this temperature for 2 h;

[0068] (3) High temperature calcination: The temperature was raised to 580°C at a heating rate of 2°C / min and calcined at this temperature for 6 h. The all-silicon molecular sieve molded carrier No. 1 sample (appearance: Figure 1 The cross section was scanned by SEM, and the results were as follows Figure 2 shown).

[0069] Example 2

[0070] The method in Example 1 was used to prepare the all-silicon molecular sieve shaped carrier, except that the amount of raw materials was adjusted to: 60 g of all-silicon molecular sieve, 15 g of SiO2 powder, 1 g of sesbania powder, and 35 mL of a 5 wt% dilute nitric acid solution. A 2# sample of the all-silicon molecular sieve shaped carrier was obtained.

[0071] Example 3

[0072] The method in Example 1 was used to prepare the all-silicon molecular sieve shaped carrier, except that the amount of raw materials was adjusted to: 60 g of all-silicon molecular sieve, 15 g of SiO2 powder, 1.5 g of sesbania powder, and 35 mL of a 5 wt% dilute nitric acid solution. A 3# sample of the all-silicon molecular sieve shaped carrier was obtained.

[0073] Example 4

[0074] The method in Example 1 was used to prepare the all-silicon molecular sieve shaped carrier, except that the amount of raw materials was adjusted to: 60 g of all-silicon molecular sieve, 18 g of SiO2 powder, 1.5 g of sesbania powder, and 38 mL of 5 wt% dilute nitric acid solution. Sample 4# of the all-silicon molecular sieve shaped carrier was obtained.

[0075] Example 5

[0076] The method in Example 1 was used to prepare the all-silicon molecular sieve shaped carrier, except that the amount of raw materials was adjusted to: 60 g of all-silicon molecular sieve, 18 g of SiO2 powder, 2 g of sesbania powder, and 40 mL of a 5 wt % dilute nitric acid solution. A 5# sample of the all-silicon molecular sieve shaped carrier was obtained.

[0077] Example 6

[0078] The method in Example 1 was used to prepare the all-silicon molecular sieve shaped carrier, except that the calcination was performed by heating to 580°C at a heating rate of 2.5°C / min and calcining at this temperature for 10 hours to obtain the all-silicon molecular sieve shaped carrier sample 6#.

[0079] Example 7

[0080] The method in Example 1 was used to prepare the all-silicon molecular sieve shaped carrier, except that the heating rates of low-temperature calcination, medium-temperature calcination and high-temperature calcination were all 2.5° C. / min. The all-silicon molecular sieve shaped carrier 7# sample was obtained.

[0081] Comparative Example 1

[0082] The method in Example 1 was used to prepare the all-silicon molecular sieve forming carrier, except that the amount of raw materials was adjusted to: 50 g of all-silicon molecular sieve, 15.5 g of pseudo-boehmite, 2.1 g of SiO2 powder, 1.5 g of sesbania powder, and 33 mL of 5 wt% dilute nitric acid solution. Sample 8# of the all-silicon molecular sieve forming carrier was obtained.

[0083] Test Example 1

[0084] The crushing strength test of the molded carrier obtained in the above examples and comparative examples was carried out using a KC-2A digital particle strength instrument from Jiangsu Jiangyan Analytical Instrument Factory. The specific surface area and external surface area of ​​the original molecular sieve powder and the molded carrier obtained in the above examples and comparative examples were detected using a Quantachrome physical adsorption instrument to calculate the specific surface area reduction and external surface area increase of the molded carrier. The results are shown in Table 1.

[0085] Specific surface area reduction = (specific surface area of ​​molecular sieve raw powder - specific surface area of ​​molded carrier) / specific surface area of ​​molecular sieve raw powder × 100%

[0086] Increased surface area = (surface area of ​​the molded carrier - surface area of ​​the original molecular sieve powder) / surface area of ​​the original molecular sieve powder × 100%

[0087] Table 1

[0088]

[0089]

[0090] Test Example 2

[0091] The catalytic performance of the shaped dehydrogenation catalyst prepared by the shaped carrier obtained by the above examples and comparative examples was tested. The test results are shown in Table 2 ( Figure 3 and Figure 4 2 and 3 show the changes in propane conversion and propylene selectivity of the shaped dehydrogenation catalyst prepared by using the shaped carrier obtained in Example 1 and Comparative Example 1 as a function of reaction time, respectively).

[0092] The specific detection methods are as follows:

[0093] Preparation of shaped dehydrogenation catalyst: The active component (Pt) precursor and the auxiliary agent (Zn) precursor are loaded on the shaped carrier by impregnation method, and then dried and calcined in sequence to obtain a shaped dehydrogenation catalyst. The active component loading is 0.5% by weight, and the auxiliary loading is 1% by weight. The drying temperature is 120°C and the time is 2h. The calcination method is: heating to 600°C at a heating rate of 2°C / min, and then calcining at this temperature for 2h.

[0094] The performance of the formed dehydrogenation catalyst for propane dehydrogenation to propylene was evaluated using a fixed bed microreactor. The specific conditions included: catalyst loading 0.5 g, reaction tube diameter 10 mm, hydrogen as diluent gas with a volume ratio of 1:3 to propane, and propane mass space velocity 3 h -1 , reaction temperature 600℃, normal pressure.

[0095] The reaction products were detected by gas chromatograph (Agilent 6890B model), and the propane conversion was calculated according to the following formula.

[0096] Propane conversion rate = moles of propane converted / moles of feed propane × 100%

[0097] Propylene selectivity = molar amount of propane converted to propylene / molar amount of propane converted × 100%

[0098] Table 2

[0099] Molding carrier Propane conversion Propylene selectivity One-way stability / h 1# 35-40％ 92-95％ 280 2# 35-40％ 92-95％ 240 3# 35-40％ 92-95％ 250 4# 35-40％ 92-95％ 200 5# 35-40％ 92-95％ 180 6# 35-40％ 92-95％ 260 7# 35-40％ 92-95％ 250 8# 35-40％ 92-95％ 80

[0100] * In Table 2, propylene conversion and propylene selectivity are the ranges of conversion and selectivity within the single-pass stable reaction time. Single-pass stability refers to the time during the reaction when the propylene yield can be maintained at 90% or more of the initial yield.

[0101] 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 a shaped carrier, characterized in that: The method comprises mixing all-silicon molecular sieve, SiO2 in an amorphous state and a molding aid, and then molding the obtained mixture, wherein the content of Al2O3 in the molding aid is less than 1% by weight; The molding aid is sesbania powder and 2-8 wt% nitric acid aqueous solution; relative to 1 g of the all-silicon molecular sieve, the amount of the nitric acid aqueous solution is 0.4-0.6 mL.

2. The method according to claim 1, wherein: The all-silicon molecular sieve is selected from MFI type all-silicon molecular sieve or silicalite-2; And / or, the SiO2 is selected from SiO2 powder in an amorphous state.

3. The method according to claim 2, wherein: The all-silicon molecular sieve is silicalite-1.

4. The method according to any one of claims 1 to 3, wherein: The weight ratio of the all-silicon molecular sieve to the amorphous SiO2 is 1:0.1-0.5; And / or, the weight ratio of the all-silicon molecular sieve to the molding aid is 1:0.1-1.2; And / or, the weight ratio of the all-silicon molecular sieve to the sesbania powder is 1:0.001-0.

1.

5. The method according to claim 4, wherein: The weight ratio of the all-silicon molecular sieve to the amorphous SiO2 is 1:0.15-0.3; And / or, the weight ratio of the all-silicon molecular sieve to the molding aid is 1:0.5-0.9; And / or, the weight ratio of the all-silicon molecular sieve to the sesbania powder is 1:0.005-0.

05.

6. The method according to claim 1, wherein: The method further comprises the steps of sequentially performing low temperature drying treatment and calcining treatment on the formed product.

7. The method according to claim 6, wherein: The calcination process is carried out in a step-by-step manner.

8. The method according to claim 7, wherein: The step-by-step roasting method comprises: (1) Low temperature roasting: temperature 200-300℃, time 0.2-2h; (2) Medium temperature roasting: temperature 350-450℃, time 0.2-2h; (3) High temperature calcination: temperature 550-650℃, time 5-10h.

9. The method according to claim 8, wherein: The temperature of the medium temperature roasting is 100-200°C higher than that of the low temperature roasting; And / or, the temperature of the high temperature calcination is 150-200° C. higher than the temperature of the medium temperature calcination.

10. The method according to claim 9, wherein: During the calcination process, the heating rate is 1-5°C / min; And / or, the temperature difference between high temperature roasting and medium temperature roasting is 20-50° C. higher than the temperature difference between medium temperature roasting and low temperature roasting.

11. The method according to claim 10, wherein: During the calcination process, the heating rate is 1-3°C / min.

12. A shaped carrier prepared according to the method according to any one of claims 1 to 11.

13. The forming carrier according to claim 12, wherein: The shaped carrier does not contain Al2O3.

14. The forming carrier according to claim 12, wherein: Taking the unformed all-silicon molecular sieve as a benchmark, the micropore specific surface area of ​​the formed carrier is reduced by no more than 20%, and the external surface area is increased by 30-60%.

15. The forming carrier according to claim 14, wherein: Taking the unformed all-silicon molecular sieve as a benchmark, the micropore specific surface area of ​​the pore size characteristic of the formed carrier is reduced by 1-15%, and the external surface area is increased by 40-60%.

16. Use of the shaped carrier according to any one of claims 12 to 15 in the preparation of industrial catalysts.

17. The use according to claim 16, wherein: The industrial catalyst is a dehydrogenation catalyst.

18. A dehydrogenation shaped catalyst, characterized in that: The shaped catalyst comprises a shaped carrier and an active component loaded on the shaped carrier, wherein the shaped carrier is the shaped carrier according to any one of claims 12 to 15.

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