Catalyst, forming method and application thereof

Abstract

The present invention discloses a catalyst, a molding method, and an application thereof. The catalyst has a core-shell structure, wherein the shell layer of the catalyst is a silicon dioxide layer. The catalyst molding method comprises the following steps: mixing molecular sieve raw powder, a silicon source, and an alkaline solution and performing a first drying process; extruding the dried catalyst with deionized water into strips; and performing a second drying and calcining process on the molded molecular sieve. The catalyst of the present invention has a more uniform secondary pore size distribution, good mechanical strength, and catalytic performance. The method of the present invention does not require the use of an adhesive during the preparation process, and the prepared catalyst has excellent performance.

Description

Technical Field

[0001] The present invention relates to a method for forming molecular sieves without using an adhesive. Specifically, a method is provided in which a silicon source, a raw material used to synthesize molecular sieves, is added during catalyst kneading, and then the silicon source is hydrolyzed into viscous silica gel to bond the catalyst, thereby improving the secondary pore distribution of the molecular sieve. Specifically, the present invention relates to a catalyst, a forming method thereof, and applications thereof. Background Art

[0002] Typically, the synthesized molecular sieve raw powder is in the form of an extremely fine powder, only a few microns. However, for a catalyst to be used in industrial applications, it is required to have a certain shape and mechanical strength. Otherwise, the pressure of the load during application will cause many adverse consequences and even force the plant to stop. In order to meet the requirements of actual applications, the fine molecular sieve powder often needs to be formed into catalysts of different shapes together with inorganic binders such as clay or alumina. In order to ensure that catalysts of different shapes have the corresponding mechanical strength, binders are indispensable molding aids. The distribution of binders and active components in granular, strip-shaped, and other catalysts prepared by this method is random, resulting in the molecular sieve powder being diluted by the binder. Moreover, the addition of the binder will hinder the utilization of the active sites of the catalyst, block the pores of the zeolite, affect the diffusion of the reaction molecules, and reduce the utilization rate of the catalyst. Therefore, the many adverse effects of the binder on the catalyst are a common problem encountered in the current application of catalysts.

[0003] To reduce the adverse effects of binders on catalysts and improve the catalytic performance of molecular sieve particle catalysts in applications, two main areas of research have been explored. One approach involves adjusting the structure of the catalyst particles through possible means, altering the relative amounts of various species within the particles and thereby changing the distribution of macroscopic rates of relevant reactions, thereby reducing the adverse effects of binders on the catalyst. Another approach involves adjusting the active components of zeolite catalysts, modifying their pore structure and physical and chemical properties to reduce the adverse effects of binders on the zeolite catalyst. However, these methods still require the use of binders for molding, which can still occupy active sites and dilute the active components of the catalyst. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for forming a catalyst without using an adhesive. The method adopts the addition of a silicon source and an alkaline solution used for synthesizing molecular sieves during the kneading stage of molecular sieve forming, and the alkaline solution is used to alkaline hydrolyze the silicon source to generate a silica gel mesh with a sticky structure. The molecular sieves are bonded to each other using the silica gel mesh. After forming, these silica gel meshes are transformed into a silica film with the same structure as the outer wall of the molecular sieve under high-temperature calcination conditions, further strengthening the mechanical strength of the molecular sieve. At the same time, a protective film is provided for the structure of the molecular sieve itself. This protective film is similar to the silica structure of the molecular sieve skeleton structure, so it does not affect the activity and diffusion performance of the molecular sieve itself. At the same time, the silica film is attached to the outer surface of each molecular sieve particle. Due to the action of the silica film on the outer surface, the secondary pores formed when the molecular sieve particles are stacked on each other become ordered, thereby completing the process of forming while improving the distribution of the secondary pores of the molecular sieve without the need for any pore expander, and can improve the selectivity of the catalyst.

[0005] A first aspect of the present invention provides a catalyst having a core-shell structure, wherein the shell layer of the catalyst is a silicon dioxide layer.

[0006] In the present invention, by but not limited to Figure 2 It can be seen that the catalyst of the present invention has a core-shell structure. The molecular sieve powders of MCM-41, SBA-15 and SBA-16 are amorphous and cannot be observed by scanning electron microscopy. MCM-22, ZSM-5 and Silicalite-1 are not round when observed by scanning electron microscopy. Therefore, Figure 2 It can be proved that the catalyst of the present application has a core-shell structure.

[0007] In the present invention, the shell layer of the catalyst is a silicon dioxide layer, that is, the outer surface of the catalyst of the present invention has a silicon dioxide protective film layer.

[0008] According to some embodiments of the catalyst of the present invention, preferably, the shell size of the catalyst measured by SEM is 40 to 150 nm, preferably 50 to 140 nm.

[0009] According to some embodiments of the catalyst of the present invention, preferably, the secondary pore size distribution of the catalyst is 2 to 5 nm. In the present invention, the secondary pore size distribution can be measured using, but is not limited to, a Micromeritics ASAP2020 fully automatic surface area and pore size analyzer.

[0010] According to some embodiments of the catalyst of the present invention, preferably, the strength of the catalyst is ≥ 100 N, preferably 100 to 120 N. In the present invention, the strength of the catalyst can be measured by, but is not limited to, a ZQJ-II intelligent particle strength tester from Dalian Intelligent Testing Machine Factory.

[0011] The second aspect of the present invention provides a catalyst molding method, which includes the following steps: mixing molecular sieve raw powder, silicon source and alkaline solution and performing a first drying, extruding the dried catalyst with deionized water, and performing a second drying and calcining on the molded molecular sieve.

[0012] According to some embodiments of the molding method of the present invention, preferably, the molecular sieve raw powder includes one or more of MCM-41, SBA-15, SBA-16, MCM-22, ZSM-5 and Silicalite-1.

[0013] According to some embodiments of the molding method of the present invention, preferably, the silicon source includes one or more of tetraethyl orthosilicate (TEOS), silica sol or water glass.

[0014] According to some embodiments of the molding method of the present invention, preferably, the weight ratio of the silicon source to the molecular sieve raw powder is 1:5 to 2:5.

[0015] According to some embodiments of the forming method of the present invention, preferably, the alkaline solution is a NaOH solution.

[0016] According to some embodiments of the molding method of the present invention, preferably, the amount of the alkaline solution added is 20% to 50% of the weight of the silicon source, wherein the concentration of the alkaline solution is 0.1 mol / L.

[0017] According to some embodiments of the molding method of the present invention, preferably, the amount of deionized water used is 10% to 30% of the weight of the dried catalyst, preferably 15% to 25%.

[0018] According to some embodiments of the molding method of the present invention, preferably, the conditions for the first drying and the second drying each independently include: a temperature of 100-150° C., preferably 120-130° C.; and a time of 2-12 hours, preferably 4-6 hours.

[0019] According to some embodiments of the molding method of the present invention, preferably, the calcination conditions include: a temperature of 400 to 600° C. and a time of 2 to 10 hours.

[0020] In the method provided by the present invention, the silicon source is hydrolyzed under the action of an alkaline solution to generate a silica gel mesh with a sticky structure. The sticky silica gel mesh bonds the molecular sieve particles to each other. After extrusion, these silica gel meshes are transformed into silica films under high-temperature calcination conditions, covering the silanol structure on the outer surface of the molecular sieve. Due to the silicon-oxygen structure type of the molecular sieve's own skeleton structure, the outer surface of the molecular sieve will not be covered and blocked. In actual applications, the reactants will enter the outer surface of the molecular sieve from the silica film in the form of diffusion. These silica films are attached to the outer surface of each molecular sieve particle. Due to the action of the silica film on the outer surface, the secondary pores formed when the molecular sieve particles are stacked on each other become ordered, thereby achieving the purpose of improving the secondary pore distribution of the molecular sieve.

[0021] The third aspect of the present invention provides a catalyst prepared according to the above-mentioned molding method, wherein the catalyst has a core-shell structure, and the shell layer of the catalyst is a silicon dioxide layer.

[0022] According to some embodiments of the catalyst of the present invention, preferably, the shell size of the catalyst measured by SEM is 40 to 150 nm, preferably 50 to 140 nm.

[0023] According to some embodiments of the catalyst of the present invention, preferably, the secondary pore size distribution of the catalyst is 2 to 5 nm. In the present invention, the secondary pore size distribution can be measured using, but is not limited to, a Micromeritics ASAP2020 fully automatic surface area and pore size analyzer.

[0024] According to some embodiments of the catalyst of the present invention, the strength of the catalyst is ≥100 N, preferably 100-120 N. In the present invention, the strength of the catalyst can be measured by, but is not limited to, a ZQJ-II intelligent particle strength tester from Dalian Intelligent Testing Machine Factory.

[0025] In the present invention, by but not limited to Figure 2 It can be seen that the catalyst of the present invention has a core-shell structure. The molecular sieve powders of MCM-41, SBA-15 and SBA-16 are amorphous and cannot be observed by scanning electron microscopy. MCM-22, ZSM-5 and Silicalite-1 are not round when observed by scanning electron microscopy. Therefore, Figure 2 It can be proved that the catalyst of the present application has a core-shell structure.

[0026] In the present invention, the shell layer of the catalyst is a silicon dioxide layer, that is, the outer surface of the catalyst of the present invention has a silicon dioxide protective film layer.

[0027] A fourth aspect of the present invention provides applications of the above catalyst or the above catalyst molding method, such as but not limited to applications in the preparation of p-tert-octylphenol.

[0028] Beneficial effects of the present invention:

[0029] (1) In the method provided by the present invention, the silicon source is hydrolyzed under the action of an alkaline solution to generate a silica gel mesh with a sticky structure. The sticky silica gel mesh bonds the molecular sieve particles to each other. After extrusion, these silica gel meshes are transformed into silica films under high-temperature calcination conditions, covering the silicon hydroxyl structure on the outer surface of the molecular sieve. Due to the silicon-oxygen structure type of the molecular sieve's own skeleton structure, the outer surface of the molecular sieve will not be covered and blocked. In actual applications, the reactants will enter the outer surface of the molecular sieve from the silica film in the form of diffusion. These silica films are attached to the outer surface of each molecular sieve particle. Due to the action of the silica film on the outer surface, the secondary pores formed when the molecular sieve particles are stacked on each other become ordered, thereby achieving the purpose of improving the distribution of the secondary pores of the molecular sieve.

[0030] (2) The secondary pores of the molecular sieve obtained by the method of the present invention are concentrated at about 4 nm (2 to 5 nm). These uniformly sized and concentrated secondary pores effectively solve the diffusion problem of reactants and products between the molecular sieves, thereby improving the selectivity of the catalyst. Conventional molecular sieves, on the other hand, have two problems: first, the secondary pores are too small, making it difficult for reactants to diffuse into the pores of the molecular sieve for reaction, and second, the generated products are difficult to diffuse out of the molecular sieve, thereby reducing the catalytic performance of the catalyst; second, the secondary pores are not concentrated, resulting in disordered stacking pores between the molecular sieves, which is not conducive to the diffusion of reactants and products; third, the secondary pores are too large. Although larger secondary pores are conducive to the diffusion of reactants and products between the molecular sieves, the larger secondary pores will cause the strength of the molecular sieve itself to decrease, and it cannot meet the requirements of industrial use. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the pore size distribution diagram of the MCM-41 molecular sieve catalyst (finished product) obtained in Example 3 of the present invention.

[0032] Figure 2 This is a scanning electron microscope image of the MCM-41 molecular sieve catalyst (finished product) obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are only for illustration and do not limit the scope of application of the present invention.

[0034] The test method of the present invention and the equipment used in the test are as follows:

[0035] (1) The pore size distribution (secondary pore size distribution) was measured using a Micromeritics ASAP2020 fully automatic surface area and pore size analyzer.

[0036] (2) The strength was measured using the ZQJ-II intelligent particle strength testing machine from Dalian Intelligent Testing Machine Factory.

[0037] (3) The scanning electron microscope used was a Hitachi S-4700 scanning electron microscope.

[0038] [Example 1]

[0039] 40g of MCM-41 molecular sieve powder, 8g of TEOS, and 1.6g of 0.1mol / L NaOH solution were added to a mortar and mixed. After uniform mixing, the mixture was dried at 100°C for 3h. 30g of the dried sample was then placed in an extruder, and 3g of deionized water was added and stirred uniformly before forming. The formed molecular sieve was dried at 100°C for 3h and then calcined at 400°C for 3h to obtain the catalyst (finished product). The obtained sample was subjected to BET analysis. The secondary pore size distribution and strength of the obtained product are shown in Table 1.

[0040] [Example 2]

[0041] The difference from Example 1 is that the molecular sieve powder is replaced with SBA-15 molecular sieve, the amount used is 40 g, the silicon source is replaced with silica sol, the amount used is 12 g, the amount of alkaline solution is changed to 3.6 g, the amount of deionized water is changed to 6 g, the drying temperature is changed to 110°C, the drying time is changed to 5 h, the calcination temperature is changed to 450°C, and the calcination time is changed to 4 h. The other components and conditions remain unchanged. The obtained sample was subjected to BET analysis. The secondary pore size distribution and strength of the obtained product are shown in Table 1.

[0042] [Example 3]

[0043] The difference from Example 1 is that the amount of TEOS is changed to 12g, the amount of alkaline solution is changed to 4.8g, the amount of deionized water is changed to 7.5g, the drying temperature is changed to 120℃, the drying time is changed to 6h, the roasting temperature is changed to 500℃, the roasting time is changed to 5h, and the other components and conditions remain unchanged. The obtained sample was subjected to BET analysis. The secondary pore size distribution and intensity of the obtained product are shown in Table 1. The pore size distribution diagram of the sample is shown in Figure 1 , SEM images are shown in Figure 2 .

[0044] [Example 4]

[0045] The difference from Example 1 is that the molecular sieve powder is replaced with MCM-22 molecular sieve, the amount is 40g, the silicon source is changed to water glass, the amount is 16g, the amount of alkaline solution is changed to 8g, the amount of deionized water is changed to 9g, the drying temperature is changed to 130°C, the drying time is changed to 4h, the roasting temperature is changed to 550°C, and the roasting time is changed to 6h. The other components and conditions remain unchanged. The obtained sample was subjected to BET analysis. The secondary pore size concentration distribution and strength of the obtained product are shown in Table 1.

[0046] [Example 5]

[0047] The difference from Example 1 is that the molecular sieve powder is replaced with ZSM-5 molecular sieve, the amount used is 40 g, the amount of silicon source is changed to 10 g, the amount of alkaline solution is changed to 2.5 g, the amount of deionized water is changed to 4.5 g, the drying temperature is changed to 110°C, the drying time is changed to 7 h, the calcination temperature is changed to 600°C, and the calcination time is changed to 4 h. The other components and conditions remain unchanged. The obtained sample was subjected to BET analysis. The secondary pore size concentration distribution and strength of the obtained product are shown in Table 1.

[0048] [Comparative Example 1]

[0049] 40g of MCM-22 molecular sieve powder and 14.2g of pseudo-boehmite (Al2O3 content of 70%) were added to a mixer and mixed. After uniform mixing, 25.8g of dilute nitric acid (HNO3 content of 6.3% by weight) was added and kneaded. Subsequently, 15.5g of deionized water was added and kneaded again. The kneaded material was then placed in an extruder for molding. The molded molecular sieve was dried and calcined to obtain a finished catalyst. The resulting sample was subjected to BET analysis. The secondary pore size distribution and strength of the resulting product are shown in Table 1.

[0050] [Comparative Example 2]

[0051] 40g of MCM-22 molecular sieve powder was mixed with 16g of water glass and 11.2g of 0.1mol / L NaOH solution in a mortar. After uniform mixing, the mixture was dried at 130°C. 30g of the dried sample was then placed in an extruder, mixed with 9g of deionized water, and formed into a strip. The formed molecular sieve was dried at 130°C and then calcined at 550°C for 6h to obtain the finished catalyst. The resulting sample was subjected to BET analysis. The secondary pore size distribution and strength of the product are shown in Table 1.

[0052] [Comparative Example 3]

[0053] 40g of MCM-41 molecular sieve powder and 1.6g of 0.1mol / L NaOH solution were added to a mortar and mixed. After mixing, the mixture was dried at 100°C for 3h. 8g of TEOS was then added, mixed, and dried at 100°C for 3h. 30g of the dried sample was then placed in an extruder, and 3g of deionized water was added and stirred until uniform. Molding began. The molded molecular sieve was dried at 100°C and then calcined at 400°C for 3h to obtain the catalyst (finished product). The resulting sample was subjected to BET analysis. The secondary pore size distribution and strength of the resulting product are shown in Table 1.

[0054] Table 1

[0055] Secondary pore diameter distribution (nm) Strength (N) Shell size measured by SEM (nm) Example 1 2～5 100 50-140 Example 2 3～5 110 50-130 Example 3 4 118 50-120 Example 4 3～4 105 50-130 Example 5 3～4 108 50-130 Comparative Example 1 2～10 102 50-160 Comparative Example 2 2～50 50 none Comparative Example 3 2-30 70 none

[0056] Test Example

[0057] The catalysts of Examples 1-5 and Comparative Examples 1-3 were used in the alkylation of isooctene with phenol to prepare p-tert-octylphenol. The experimental process was as follows: 80 g of phenol was mixed with 24 g of isooctene and 2.0 g of catalyst and reacted at 90° C. for 6 h. The remaining material was then subjected to chromatographic analysis. The selectivity for p-tert-octylphenol and the conversion of isooctene are shown in Table 2.

[0058] Table 2

[0059] Isooctene conversion rate (%) Selectivity of p-tert-octylphenol (%) Strength (N) Example 1 99.3 96.7 100 Example 2 99.3 97.0 110 Example 3 99.4 98.5 118 Example 4 99.2 97.2 105 Example 5 99.4 97.5 108 Comparative Example 1 98.0 93.7 102 Comparative Example 2 11.6 25.9 50 Comparative Example 3 18.7 33.8 70

[0060] Depend on Figure 1 It can be seen that the secondary pores of the molecular sieve obtained by the method provided by the present invention are relatively uniformly distributed, and most of them are concentrated around 4nm. However, the secondary pores of the molecular sieves prepared by the prior art are either too large, resulting in the strength of the molecular sieve itself not meeting the industrial use standard, or too small, resulting in slow diffusion of reactants and products between the molecular sieves. Figure 2 It can be seen that the outer surface of the molecular sieve obtained by the method provided by the present invention has a layer of silicon dioxide protective film (the shell layer is a silicon dioxide layer). While strengthening the mechanical strength, this protective film makes the secondary pores formed by the molecular sieve particles when they are stacked on each other become orderly, thereby achieving the purpose of improving the secondary pore distribution of the molecular sieve.

[0061] From embodiment 4 and comparative example 1, table 2, can know that the molecular sieve forming process prepared according to the method provided by the present invention does not need to be formed by means of any adhesive, and compared with the forming method of conventional comparative example 1, mechanical strength is higher, and secondary pore distribution (secondary pore aperture concentrated distribution) is also more uniform, from the reaction performance point of view, in the catalyst of the same amount, because there is no adhesive in the catalyst obtained by this method, therefore active sites are more, catalytic activity is higher. In comparative example 2, due to the addition of too much alkali, the collapse of the molecular sieve skeleton can be caused while the silicon source is hydrolyzed, so catalytic activity is relatively low. In comparative example 3, due to the addition of NaOH first when not adding TEOS, alkali is caused to etch the molecular sieve structure itself first, thereby causing the destruction of the molecular sieve structure itself, so catalyst effect is relatively poor.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, under the technical enlightenment provided by the present invention, as common knowledge in the art, other equivalent variations and improvements can be made, which should also be considered as the scope of protection of the present invention.

Claims

1. A catalyst having a core-shell structure, wherein the shell layer of the catalyst is a silicon dioxide layer; The secondary pore diameter of the catalyst is concentrated in the range of 2 to 5 nm; The catalyst forming method comprises the following steps: The molecular sieve raw powder, silicon source and alkaline solution are mixed and dried for the first time, the dried catalyst is extruded with deionized water to form strips, and the formed molecular sieve is subjected to the second drying and calcination; The amount of the alkaline solution added is 20% to 50% of the weight of the silicon source, wherein the concentration of the alkaline solution is 0.1 mol / L.

2. The catalyst according to claim 1, characterized in that The shell size of the catalyst measured by SEM is 40-150 nm.

3. The catalyst according to claim 2, characterized in that The shell size of the catalyst measured by SEM is 50-140 nm.

4. The catalyst according to claim 1, characterized in that The strength of the catalyst is ≥100N.

5. The catalyst according to claim 4, characterized in that The catalyst has a strength of 100-120 N.

6. A method for forming the catalyst according to any one of claims 1 to 5, comprising the following steps: The molecular sieve raw powder, silicon source and alkaline solution are mixed and dried for the first time, the dried catalyst is extruded with deionized water to form strips, and the formed molecular sieve is subjected to the second drying and calcination; The amount of the alkaline solution added is 20% to 50% of the weight of the silicon source, wherein the concentration of the alkaline solution is 0.1 mol / L.

7. The molding method according to claim 6, characterized in that: The molecular sieve raw powder includes one or more of MCM-41, SBA-15, SBA-16, MCM-22, ZSM-5 and Silicalite-1; and / or, The silicon source includes one or more of ethyl orthosilicate, silica sol or water glass; and / or, The weight ratio of the silicon source to the molecular sieve raw powder is 1:5 to 2:

5.

8. The molding method according to claim 6, characterized in that: The alkaline solution is NaOH solution.

9. The molding method according to any one of claims 6 to 8, characterized in that: The amount of deionized water used is 10% to 30% of the weight of the dried catalyst.

10. The molding method according to claim 9, characterized in that: The amount of deionized water used is 15% to 25% of the weight of the dried catalyst.

11. The molding method according to any one of claims 6 to 8, characterized in that: The first drying and second drying conditions each independently include: The temperature is 100~150℃; the time is 2~12h.

12. The molding method according to claim 11, characterized in that: The conditions for the first drying and the second drying independently include: a temperature of 120-130° C.; and a time of 4-6 hours.

13. The molding method according to any one of claims 6 to 8, characterized in that: The calcination conditions include: a temperature of 400-600° C. and a time of 2-10 h.

14. Use of the catalyst according to any one of claims 1 to 5 or the catalyst obtained by the molding method according to any one of claims 6 to 13 in the preparation of p-tert-octylphenol.

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