A method for synthesizing a mordenite-sAPO-34 zeolite core-shell structure composite zeolite

Abstract

The application discloses a synthesis method of a mordenite- SAPO-34 zeolite core-shell structure composite zeolite. The synthesis method comprises the following steps: (1) mixing mordenite, nano iron oxide particles, water and a saccharide, evaporating water, and then carrying out heat treatment under inert conditions; after acid treatment, separation and drying, a carbon-mordenite composite is prepared; (2) uniformly mixing water and an aluminum salt, and then adding the carbon-mordenite composite, a template agent, phosphoric acid and sodium silicate in sequence, uniformly mixing, crystallizing, and then carrying out separation, drying and calcination to obtain the composite zeolite. The composite zeolite has a stable core-shell structure and is particularly suitable for use as a catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a composite structure zeolite, and belongs to the field of inorganic porous material synthesis, in particular to a synthesis method of a mordenite-SAPO-34 zeolite core-shell structure composite zeolite. BACKGROUND

[0002] Single zeolite molecular sieve catalysts are widely used in industry. In order to improve the catalytic performance, a plurality of zeolite molecular sieves are mechanically mixed together to prepare a catalyst with better performance. With more stringent catalytic reactions and environmental protection requirements, composite structure zeolite molecular sieves are developed.

[0003] The main problem of the existing synthesis technology of the mordenite-SAPO-34 zeolite core-shell structure composite zeolite is that, in the case of maintaining the integrity of the mordenite and SAPO-34 zeolite framework structure, either the core-shell structure cannot be formed, most of which are eutectic composite molecular sieves, or unstable core-shell structure is formed, and the core zeolite and the shell zeolite are easily separated to form two independent states.

[0004] CN102974392B discloses a mordenite / SAPO-34 zeolite composite molecular sieve amine catalyst and a preparation method. In the mordenite / SAPO-34 zeolite composite molecular sieve, the SiO2 / Al2O3 of the mordenite is 20-80, the mordenite accounts for 50%-80% of the total weight of the composite molecular sieve, and the SAPO-34 zeolite accounts for 20%-60% of the total weight of the composite molecular sieve. The preparation method is as follows: an aluminum source and deionized water are mixed, then orthophosphoric acid is added and stirred uniformly, then silica sol is added and stirred uniformly, then a template agent is added dropwise and the pH value of the mixture is adjusted to 5-6, the mordenite zeolite is added to the obtained mixture, mixed uniformly, aged, and crystallized to obtain the mordenite / SAPO-34 zeolite composite molecular sieve. SUMMARY

[0005] The present application provides a synthesis method of a mordenite-SAPO-34 zeolite core-shell structure composite zeolite. The mordenite-SAPO-34 zeolite composite structure zeolite synthesized by the method can maintain the integrity and crystallinity of the mordenite and SAPO-34 zeolite framework structure, and the core-shell is tightly combined and the structure is stable.

[0006] The first aspect of the present application provides a synthesis method of a mordenite-SAPO-34 zeolite core-shell structure composite zeolite, comprising the following steps:

[0007] (1) mixing mordenite, nano iron oxide particles, water and sugar, evaporating the water, then heating under an inert atmosphere, then acid treatment, and then separating and drying to prepare a carbon-mordenite composite;

[0008] (2) First, mix water and aluminum salt uniformly, then add carbon-mordenite composite, template agent, phosphoric acid and sodium silicate in turn, mix uniformly, crystallize, then separate, dry, and calcine to obtain the composite zeolite.

[0009] In the method, the sugar in step (1) is at least one of sucrose, glucose, fructose, maltose, and lactose, and preferably at least one of sucrose and glucose.

[0010] In the method, the mordenite in step (1) has a size ranging from 500 nm to 3500 nm, and preferably ranging from 600 nm to 3000 nm. The nano iron oxide particles have a particle size ranging from 2 nm to 15 nm, and preferably ranging from 5 nm to 10 nm.

[0011] In the method, the mass ratio of the mordenite to the sugar in step (1) is 1:0.8-6.0, and preferably 1:1.0-5.0. The mass ratio of the mordenite to water is 1:80-210, and preferably 1:100-200.

[0012] In the method, the mass ratio of the mordenite to the iron oxide in step (1) is 1:0.08-0.60, and preferably 1:0.10-0.50.

[0013] In the method, the temperature for evaporating the water in step (1) is 80-160 ℃, and preferably 100-150 ℃. The reaction time is not limited, until the water is evaporated.

[0014] In the method, the temperature for heating treatment in step (1) is 200-400 ℃, and preferably 300-350 ℃. The treatment time is 1-12 h, and preferably 2-10 h. The high-temperature treatment is performed in an inert atmosphere, such as at least one of nitrogen, argon, and helium, and preferably in nitrogen. The high-temperature treatment can convert the sugar into carbon material through dehydration and dehydrogenation, and can wrap the zeolite therein. Compared with the calcination temperature for converting the sugar into carbon material with stable physical and chemical properties in the conventional method, the relatively low treatment temperature in the method can retain a part of the chemical groups of the sugar in the carbon material, so that the carbon material has certain chemical activity, which is beneficial to participating in adsorption and chemical reaction in the subsequent synthesis reaction process, promotes the synthesis of the shell material, and can improve the catalytic performance and adsorption performance of the final material.

[0015] In the method, the acid used in the acid treatment in step (1) is at least one of hydrochloric acid, nitric acid, and sulfuric acid. The mass concentration of the acid is 0.5%-5.5%, and preferably 1.0%-5.0%.

[0016] In the method, the mass ratio of mordenite and acid solution in step (1) is 1:80-210, preferably 1:100-200.

[0017] In the method, the acid treatment in step (1) is mixing the solid substance after high-temperature calcination with acid solution and treating at 10-40℃ for 5-35min, preferably 10-30min. The purpose of acid treatment is to remove iron oxide in the solid substance, so as to leave mesoporous channels in the carbon material, which is beneficial to the raw materials passing through the carbon layer to participate in the chemical reaction in the subsequent reaction process.

[0018] In the method, the separation in step (1) can be carried out by filtration, which usually includes multiple filtrations, generally 1-10 times.

[0019] In the method, the drying temperature in step (1) is 100-150℃, and the drying time is 1-20h.

[0020] In the method, the feeding sequence in step (2) is as follows: first, mixing water and aluminum source, then adding the carbon-mordenite composite and mixing uniformly, then adding the template agent and mixing uniformly, then adding the phosphorus source and mixing uniformly, and then adding the silicon source and mixing uniformly. Such feeding sequence can ensure that all materials pass through the carbon material in the carbon-mordenite composite to be closely combined with the core zeolite to form a composite zeolite.

[0021] In the method, sodium silicate is used as the silicon source in step (2), for example, water glass.

[0022] In the method, the aluminum salt is used as the aluminum source in step (2), which can be at least one of aluminum nitrate, aluminum sulfate and aluminum chloride.

[0023] In the method, phosphoric acid is used as the phosphorus source in step (2).

[0024] In the method, the template agent in step (2) is at least one of diethylamine and tetraethylammonium hydroxide.

[0025] In the method, the molar ratio of each material in step (2) is 0.6-1.35P:0.045-0.35SiO2:Al2O3:500-1300H2O:0.5-5.5M, preferably 0.7-1.3P:0.05-0.30SiO2:Al2O3:600-1200H2O:1-5M. Wherein, M represents the template agent, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P.

[0026] In the method, the mass ratio of the aluminum source (calculated as Al2O3) to the carbon-zeolite composite in step (2) is 12-30:100, preferably 15-25:100.

[0027] In the method, the crystallization reaction conditions in step (2) are as follows: the crystallization reaction temperature is 170-230℃, preferably 180-220℃, and the reaction time is 20-110h, preferably 30-100h.

[0028] In the method, the separation in step (2) can be performed by filtration, which usually includes multiple filtrations, typically 1-10 times.

[0029] In the method, the drying temperature in step (2) is 100-150℃, and the drying time is 1-10h.

[0030] In the method, the calcination in step (2) is high-temperature calcination at 400-600℃ for 1-10h, and the calcination needs to be performed in an oxygen-containing atmosphere, such as air or oxygen. The calcination can burn the carbon material to remove it in the form of carbon dioxide, leaving only the composite zeolite.

[0031] The second aspect of the present application provides a mordenite-SAPO-34 zeolite core-shell composite zeolite synthesized by the above method.

[0032] In the present application, the shell thickness of the composite zeolite is 20-150nm.

[0033] In the present application, the specific surface area of the composite zeolite is 350-650m 2 / g.

[0034] In the composite structure zeolite of the present application, the mordenite is the core, located at the center of the entire structure, and the SAPO-34 zeolite is the shell, wrapped on the outer surface of the core zeolite. The core-shell structure is very stable and does not separate into two phases.

[0035] The composite zeolite of the present application is mainly used in the field of petroleum chemical industry, and can be used as a catalyst or a catalyst carrier, and also can be used for the adsorption and separation of gases and liquids.

[0036] The third aspect of the present application provides the application of the above composite structure zeolite in a catalyst for the disproportionation of mesitylene.

[0037] In the present application, the application is to prepare a hydrogen-type molecular sieve from the composite structure zeolite by conventional ammonium ion exchange, i.e., a catalyst for the disproportionation of mesitylene.

[0038] Compared with the prior art, the present application has the following advantages:

[0039] The inventors have found that, when using the traditional hydrothermal synthesis method to synthesize the mordenite-SAPO-34 zeolite composite zeolite with a core-shell structure, the mordenite and the SAPO-34 zeolite often exist in an independent state instead of a stable core-shell structure, and the crystallinity of the mordenite is low. It is considered that one of the main reasons is that, in the hydrothermal synthesis process, a large amount of liquid water exists in the synthesis system, and the water will continuously impact the synthesis product under the action of heat. When the structure of the synthesis product is not stable enough, the core-shell structure zeolite will separate, and the crystallinity of the mordenite will decrease. The inventors have further found that, by first preparing a carbon-mordenite composite and then controlling the materials and the feeding sequence of the materials, it can be ensured that all the materials pass through the carbon material in the carbon-mordenite composite, and the core-shell structure of the mordenite-SAPO-34 zeolite composite structure zeolite obtained after crystallization is tight and not easy to separate, and the framework structures of the mordenite and the SAPO-34 zeolite are complete. The possible mechanism analysis is as follows: first, a carbon material with a specific mesoporous structure is formed on the surface of the mordenite, and because a relatively low treatment temperature is used, various chemical groups of the sugar substances are retained in the carbon material to improve the chemical activity of the carbon material. The carbon-mordenite composite material is a solid composite material with a size of tens or even hundreds of microns, and the mordenite is wrapped by the carbon material. Because the properties of the carbon material and the core zeolite are completely different, the carbon material and the core zeolite in the carbon-mordenite composite are not in close contact, but have a space of tens to hundreds of nanometers. By controlling the raw materials and the feeding sequence, the materials pass through the carbon material to reach the core zeolite and fill the space. When the crystallization reaction occurs, the formed zeolite shell layer can only combine with the core zeolite due to the limitation of the space, thereby forming a tight core-shell structure, so as to avoid the phenomenon that the shell layer and the core zeolite are separated from each other due to the severe impact of water during the crystallization reaction. Moreover, the framework structures of the mordenite and the SAPO-34 zeolite are complete, and the various chemical groups on the carbon material are beneficial to improve the crystallinity and the catalytic performance of the SAPO-34 zeolite.

[0040] The composite structure zeolite obtained by using the above synthesis method has a core-shell structure, contains mordenite and SAPO-34 zeolite, has a porous structure mainly composed of micropores, and the main framework structure elements include silicon, aluminum, phosphorus and oxygen. Especially, the connection between the core zeolite and the shell layer zeolite is the contact surface of the two structure zeolites, has a special topological structure, and can exhibit excellent catalytic performance in the catalytic reaction of isomerization of tri-methylbenzene. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A scanning electron microscope photograph of the sample L1 obtained in Example 1;

[0042] Figure 2The XRD spectrum of sample L1 obtained in Example 1 is shown in Figure 1.

[0043] Figure 3 The XRD spectrum of sample DL1 obtained in Comparative Example 1 is shown in Figure 2.

[0044] Figure 4 The XRD spectrum of sample DL5 obtained in Comparative Example 5 is shown in Figure 3.

[0045] Figure 5 The scanning electron microscope photograph of sample DL1 obtained in Comparative Example 1 is shown in Figure 4. DETAILED DESCRIPTION

[0046] The technical solutions and effects of the present application are further illustrated below in combination with examples, but are not limited to the following examples.

[0047] The pore structure of the composite zeolite is characterized by N2 adsorption-desorption, which is tested by a physical adsorption instrument of Micromeritics Corporation of the United States. Before testing, the sample is treated in vacuum at 300℃ for more than 4h. The total specific surface area and other parameters are calculated according to the BET formula.

[0048] The microcrystal morphology structure of the composite zeolite is characterized by a scanning electron microscope, which is tested by a JSM-6301F scanning electron microscope (equipped with Oxford EDS) of Japan Electronics Corporation, with a working voltage of 20kV, a working distance of 15mm and a resolution of 1.5nm.

[0049] The crystal phase structure and crystallinity of the composite zeolite are characterized by X-ray diffraction, which is tested by a D / max2500 X-ray diffractometer of Japan Science, with a Cu target, a Kα radiation source, a graphite monochromator, a tube voltage of 40kV, a tube current of 80mA, a scanning range of 5°-40°, a step length of 0.1° and a scanning speed of 1° / min.

[0050] The thickness of the shell layer of the composite structure zeolite is characterized by high-resolution transmission electron microscopy, which is tested by a high-resolution transmission electron microscope of Japan JEOL Company, with a model of JEM-2200FS field emission ultra-high-resolution transmission electron microscope and an acceleration voltage of 200kV, and a point resolution of 0.19nm.

[0051] Example 1

[0052] 120g mordenite (average particle size of 1500nm), 17000g distilled water, 15g iron oxide (average particle size of 7nm) and 150g sucrose are uniformly mixed; then the water is evaporated at 100℃; then the sample is treated at 300℃ in nitrogen for 10h; then the sample is mixed with 15000g (2.3wt% concentration of hydrochloric acid) for 150min; then the obtained sample is filtered for multiple times, and then dried in an oven at 110℃ for 12h to obtain a carbon-zeolite composite.

[0053] 6.2g of aluminum nitrate nonahydrate and 230g of distilled water were mixed thoroughly; 15g of carbon-zeolite complex was added and mixed thoroughly; then 13g of tetraethylammonium hydroxide (30wt%) was added and mixed thoroughly; then 1.3g of phosphoric acid was added and mixed thoroughly; finally, 0.52g of water glass (20wt% silicon dioxide content) was added and mixed thoroughly. The mixture was then placed in a crystallization reactor and crystallized at 185℃ for 70h; the resulting sample was filtered multiple times, then dried in an oven at 110℃ for 12h, and finally calcined in air at 400℃ for 10h. The resulting sample was designated L1.

[0054] The XRD pattern of sample L1 is shown below. Figure 2 As shown in the figure, the composite material contains two types of crystals, namely mordenite and SAPO-34 zeolite. According to Table 1, both crystals have high crystallinity and high specific surface area.

[0055] Scanning electron microscope image of sample L1 is shown below. Figure 1 ,Depend on Figure 1 It is evident that the sample has a core-shell structure. The composite material has a particle size of approximately 1200 nm and consists of irregular particles. The outer shell is rough, consisting of a coarse SAPO-34 zeolite shell with a thickness of approximately 80 nm.

[0056] Example 2

[0057] 100g of mordenite zeolite (average particle size 2000nm), 10000g of distilled water, 10g of iron oxide (average particle size 8nm), and 100g of sucrose were mixed evenly; then the water was evaporated at 100℃; then the mixture was treated at 300℃ in nitrogen for 10h; then it was mixed with 10000g (1wt% hydrochloric acid) and treated for 10min; the resulting sample was filtered several times and then dried in an oven at 110℃ for 12h to obtain the carbon-zeolite composite.

[0058] 6.2g of aluminum nitrate nonahydrate and 151g of distilled water were mixed thoroughly; 20g of carbon-zeolite complex was added and mixed thoroughly; then 7.5g of tetraethylammonium hydroxide (30wt%) was added and mixed thoroughly; then 1g of phosphoric acid was added and mixed thoroughly; finally, 0.22g of water glass (20wt% silicon dioxide content) was added and mixed thoroughly. The mixture was then placed in a crystallization reactor and crystallized at 180℃ for 100h. The resulting sample was filtered multiple times, then dried in an oven at 110℃ for 12h, and finally calcined in air at 400℃ for 10h. The resulting sample was designated L2.

[0059] Sample L2 has a core-shell structure and contains two types of crystals: mordenite and SAPO-34 zeolite. Both types of crystals have high crystallinity and high specific surface area.

[0060] Example 3

[0061] Mix 100 g of mordenite (average particle size of 1200 nm), 20000 g of distilled water, 50 g of iron oxide (average particle size of 8 nm), 500 g of glucose uniformly; then evaporate the water at 150 ℃; then treat at 350 ℃ for 2 h in nitrogen; then mix with 20000 g of (5 wt% concentration of hydrochloric acid) for 30 min; then filter the obtained sample multiple times, and then place it in an oven at 110 ℃ for drying for 12 h to obtain a carbon-mordenite composite.

[0062] Mix 6.2 g of aluminum nitrate nonahydrate, 277 g of distilled water uniformly; add 12.5 g of carbon-mordenite composite uniformly; then add 35 g of tetraethylammonium hydroxide (concentration of 30 wt%) uniformly; then add 1.85 g of phosphoric acid uniformly; then add 1.3 g of water glass (silicon oxide content of 20 wt%) uniformly. Then load into a crystallization reaction kettle and treat at 220 ℃ for 30 h; then filter the obtained sample multiple times, and then place it in an oven at 110 ℃ for drying for 12 h, and finally calcine at 600 ℃ in air for 1 h, and the obtained sample is numbered as L3.

[0063] The sample L3 belongs to a core-shell structure, and contains two crystals, mordenite and SAPO-34 zeolite, both of which have high crystallinity and high specific surface area.

[0064] Example 4

[0065] Mix 125 g of mordenite (average particle size of 1500 nm), 17500 g of distilled water, 22 g of iron oxide (average particle size of 6 nm), 170 g of glucose uniformly; then evaporate the water at 110 ℃; then treat at 325 ℃ for 4 h in nitrogen; then mix with 15000 g of (2.6 wt% concentration of hydrochloric acid) for 20 min; then filter the obtained sample multiple times, and then place it in an oven at 110 ℃ for drying for 12 h to obtain a carbon-mordenite composite.

[0066] Mix 6.2 g of aluminum nitrate nonahydrate, 277 g of distilled water uniformly; add 12.5 g of carbon-mordenite composite uniformly; then add 35 g of tetraethylammonium hydroxide (concentration of 30 wt%) uniformly; then add 1.85 g of phosphoric acid uniformly; then add 1.3 g of water glass (silicon oxide content of 20 wt%) uniformly. Then load into a crystallization reaction kettle and treat at 220 ℃ for 30 h; then filter the obtained sample multiple times, and then place it in an oven at 110 ℃ for drying for 12 h, and finally calcine at 600 ℃ in air for 1 h, and the obtained sample is numbered as L3.

[0067] Sample L4 belongs to core-shell structure, containing two crystals, mordenite and SAPO-34 zeolite, both of which have high crystallinity and high specific surface area.

[0068] Example 5

[0069] Mix 110 g of mordenite (average particle size of 1600 nm), 18000 g of distilled water, 17.9 g of iron oxide (average particle size of 7 nm), and 155 g of glucose uniformly; then evaporate the water at 115°C; then treat in nitrogen at 325°C for 6.5 h; then mix with 13000 g of hydrochloric acid (3.5 wt% concentration) for 23 min; then filter the obtained sample multiple times, and then dry in an oven at 110°C for 12 h to obtain a carbon-zeolite composite.

[0070] Mix 6.2 g of aluminum nitrate nonahydrate and 230 g of distilled water uniformly; add 14 g of the carbon-zeolite composite and mix uniformly; then add 11.5 g of tetraethylammonium hydroxide (30 wt% concentration) and mix uniformly; then add 1.36 g of phosphoric acid and mix uniformly; then add 0.52 g of water glass (20 wt% silicon oxide content) and mix uniformly. Then load into a crystallization reactor and treat at 185°C for 70 h; then filter the obtained sample multiple times, and then dry in an oven at 110°C for 12 h, and finally calcine in air at 400°C for 10 h, and the obtained sample is numbered as L5.

[0071] Sample L5 belongs to core-shell structure, containing two crystals, mordenite and SAPO-34 zeolite, both of which have high crystallinity and high specific surface area.

[0072] Comparative Example 1

[0073] Compared with Example 1, the only difference is that the carbon-mordenite material is not prepared.

[0074] Mix 6.2 g of aluminum nitrate nonahydrate and 230 g of distilled water uniformly; add 12 g of mordenite (average particle size of 1500 nm) and mix uniformly; then add 1.3 g of phosphoric acid and mix uniformly; then add 52 g of silica sol; then add tetraethylammonium hydroxide to adjust the pH value to 5-6. Then load into a reactor and treat at 185°C for 70 h; then filter the obtained sample multiple times, and then dry in an oven at 110°C for 12 h, and finally calcine in air at 400°C for 10 h, and the obtained sample is numbered as DL1.

[0075] The XRD spectrum of sample DL1 is shown in Figure 3 As can be seen from the figure, the composite material contains two crystals, mordenite and SAPO-34 zeolite. As can be seen from Table 2, the crystallinity of mordenite is too low, and the specific surface area is slightly low.

[0076] The scanning electron microscope photograph of sample DL1 is shown in Figure 1. Figure 5 As can be seen from Figure 1, the sample contains two kinds of zeolites, wherein the large-micron-sized round-pie-shaped crystals are mordenite, and the small particles scattered on the mordenite are SAPO-34 zeolite. The SAPO-34 zeolite is not tightly combined with the mordenite, and cannot form a shell layer on the surface of the mordenite, indicating that the synthesis product is in an independent state, rather than a core-shell structure. The occurrence of two kinds of zeolites in the comparative example 1 indicates that the method is not stable, and the synthesized core-shell structure may be dissociated into an independent state during the preparation process. Figure 5 As can be seen from Figure 1, the sample contains two kinds of zeolites, wherein the large-micron-sized round-pie-shaped crystals are mordenite, and the small particles scattered on the mordenite are SAPO-34 zeolite. The SAPO-34 zeolite is not tightly combined with the mordenite, and cannot form a shell layer on the surface of the mordenite, indicating that the synthesis product is in an independent state, rather than a core-shell structure. The occurrence of two kinds of zeolites in the comparative example 1 indicates that the method is not stable, and the synthesized core-shell structure may be dissociated into an independent state during the preparation process.

[0077] Comparative example 2

[0078] Compared with example 1, the only difference is that no iron oxide is added in the preparation of the carbon-zeolite composite, and silica gel is used as the silicon source in the preparation of the core-shell zeolite.

[0079] 120 g of mordenite (average particle size of 1500 nm), 17000 g of distilled water, and 150 g of sucrose were uniformly mixed; then the water was evaporated at 100°C; then the sample was treated at 300°C for 10 h under nitrogen; then 15000 g of 2.3 wt% hydrochloric acid was added and mixed for 150 min; then the obtained sample was filtered multiple times, and then dried in an oven at 110°C for 12 h to obtain a carbon-zeolite composite.

[0080] 6.2 g of aluminum nitrate nonahydrate, 230 g of distilled water were uniformly mixed; 15 g of the carbon-zeolite composite was added and uniformly mixed; 13 g of tetraethylammonium hydroxide (concentration of 30 wt%) was added and uniformly mixed; then 1.3 g of phosphoric acid was added and uniformly mixed; then 0.12 g of silica gel (silicon oxide content of 100 wt%) was added and uniformly mixed. Then it was loaded into a crystallization reactor and crystallized at 185°C for 70 h; then the obtained sample was filtered multiple times, and then dried in an oven at 110°C for 12 h, and finally calcined at 400°C in air for 10 h, and the obtained sample was numbered.

[0081] The sample DL2 is in an independent state, and contains two kinds of crystals, which are mordenite and SAPO-34 zeolite, respectively. The crystallinity of the two kinds of crystals is low, and the specific surface area is also low.

[0082] Comparative example 3

[0083] Compared with example 1, the only difference is that no iron oxide is added in the preparation of the carbon-zeolite composite, and aluminum hydroxide is used as the aluminum source in the preparation of the core-shell zeolite.

[0084] A mixture of 120 g of mordenite (average particle size of 1500 nm), 17000 g of distilled water, 150 g of sucrose was mixed well; then the water was evaporated at 100°C; then treated at 300°C for 10 h under nitrogen; then mixed with 15000 g of hydrochloric acid (2.3 wt% concentration) for 150 min; then the obtained sample was filtered several times, and then dried in an oven at 110°C for 12 h to obtain a carbon-mordenite composite.

[0085] A mixture of 3.6 g of aluminum hydroxide, 230 g of distilled water was mixed well; then 15 g of the carbon-mordenite composite was added and mixed well; then 13 g of tetraethylammonium hydroxide (30 wt% concentration) was added and mixed well; then 1.3 g of phosphoric acid was added and mixed well; then 0.52 g of water glass (silicon oxide content of 20 wt%) was added and mixed well. Then it was put into a crystallization reactor and treated at 185°C for 70 h; then the obtained sample was filtered several times, and then dried in an oven at 110°C for 12 h, and finally calcined at 400°C in air for 10 h, and the obtained sample was numbered as DL3.

[0086] The sample DL3 belongs to an independent state, and contains two crystals, mordenite and SAPO-34 zeolite, and the crystallinity of the two crystals is low, and the specific surface area is low.

[0087] Comparative Example 4

[0088] Compared with Example 1, the only difference is that no iron oxide is added in the preparation of the carbon-mordenite composite, and the raw materials are not added according to the feeding sequence of the application.

[0089] A mixture of 120 g of mordenite (average particle size of 1500 nm), 17000 g of distilled water, 150 g of sucrose was mixed well; then the water was evaporated at 100°C; then treated at 300°C for 10 h under nitrogen; then mixed with 15000 g of hydrochloric acid (2.3 wt% concentration) for 150 min; then the obtained sample was filtered several times, and then dried in an oven at 110°C for 12 h to obtain a carbon-mordenite composite.

[0090] A mixture of 6.2 g of aluminum nitrate nonahydrate, 230 g of distilled water, 15 g of the carbon-mordenite composite, 13 g of tetraethylammonium hydroxide (30 wt%), 1.3 g of phosphoric acid, and 0.52 g of water glass (silicon oxide content of 20 wt%) was added at the same time and mixed well. Then it was put into a crystallization reactor and treated at 185°C for 70 h; then the obtained sample was filtered several times, and then dried in an oven at 110°C for 12 h, and finally calcined at 400°C in air for 10 h, and the obtained sample was numbered as DL4.

[0091] The sample DL4 belongs to an independent state, and contains two crystals, mordenite and SAPO-34 zeolite, and the crystallinity of the two crystals is low, and the specific surface area is low.

[0092] Comparative Example 5

[0093] Compared with Example 1, the only difference is that the carbon-zeolite composite was treated at a conventional high temperature during preparation.

[0094] 120g of mordenite zeolite (average particle size 1500nm), 17000g of distilled water, 15g of iron oxide (average particle size 7nm), and 150g of sucrose were mixed evenly; the water was then evaporated at 100℃; the mixture was then treated at 900℃ in nitrogen for 5h; the mixture was then mixed with 15000g of hydrochloric acid (2.3wt%) and treated for 150min; the resulting sample was filtered several times and then dried in an oven at 110℃ for 12h to obtain the carbon-zeolite composite.

[0095] 6.2 g of aluminum nitrate nonahydrate and 230 g of distilled water were mixed thoroughly; 15 g of carbon-zeolite complex was added and mixed thoroughly; then 13 g of tetraethylammonium hydroxide (30 wt%) was added and mixed thoroughly; then 1.3 g of phosphoric acid was added and mixed thoroughly; finally, 0.52 g of water glass (20% silica content) was added and mixed thoroughly. The mixture was then placed in a reaction vessel and treated at 185 °C for 70 h; the resulting sample was filtered multiple times, then dried in an oven at 110 °C for 12 h, and finally calcined in air at 400 °C for 10 h. The resulting sample was designated DL5. Sample DL5 exhibits a core-shell structure.

[0096] Depend on Figure 4 It can be seen that sample DL5 contains two types of crystals, namely mordenite and SAPO-34 zeolite. Both types of crystals have low crystallinity and low specific surface area.

[0097] Comparative Example 6

[0098] Compared with Example 1, the only difference is the order in which the raw materials are added.

[0099] 120g of mordenite zeolite (average particle size 1500nm), 17000g of distilled water, 15g of iron oxide (average particle size 7nm), and 150g of sucrose were mixed evenly; the water was then evaporated at 100℃; the mixture was then treated at 300℃ in nitrogen for 10h; the mixture was then mixed with 15000g of hydrochloric acid (2.3wt%) and treated for 150min; the resulting sample was filtered several times and then dried in an oven at 110℃ for 12h to obtain the carbon-zeolite composite.

[0100] Example 1 6.2 g of aluminum nitrate nonahydrate, 230 g of distilled water, 0.52 g of water glass (silica content 20 wt%), 15 g of carbon-zeolite composite, 13 g of tetraethylammonium hydroxide (concentration 30 wt%), and 1.3 g of phosphoric acid were simultaneously added and uniformly mixed. Subsequently, the mixture was loaded into a crystallization reactor and subjected to crystallization treatment at 185°C for 70 h. The obtained sample was filtered multiple times and then dried in an oven at 110°C for 12 h, and finally calcined in air at 400°C for 10 h. The obtained sample was numbered DL6.

[0101] The sample DL6 belongs to the independent state and contains two crystals, mordenite and SAPO-34 zeolite, and the crystallinity of the two crystals is low, and the specific surface area is low.

[0102] Comparative Example 7

[0103] Compared with Example 1, the only difference is that iron oxide is not used.

[0104] 120 g of mordenite (average particle size 1500 nm), 17000 g of distilled water, and 150 g of sucrose were uniformly mixed. Subsequently, the water was evaporated at 100°C. Then, the mixture was treated in nitrogen at 300°C for 10 h to obtain a carbon-zeolite composite.

[0105] 6.2 g of aluminum nitrate nonahydrate and 230 g of distilled water were uniformly mixed. 15 g of carbon-zeolite composite was added and uniformly mixed. 13 g of tetraethylammonium hydroxide (concentration 30 wt%) was added and uniformly mixed. 1.3 g of phosphoric acid was added and uniformly mixed. Then, 0.52 g of water glass (silica content 20 wt%) was added and uniformly mixed. Subsequently, the mixture was loaded into a crystallization reactor and subjected to crystallization treatment at 185°C for 70 h. The obtained sample was filtered multiple times and then dried in an oven at 110°C for 12 h, and finally calcined in air at 400°C for 10 h. The obtained sample was numbered DL7.

[0106] The sample DL7 belongs to the independent state and contains two crystals, mordenite and SAPO-34 zeolite, and the crystallinity of the two crystals is low, and the specific surface area is low.

[0107] Comparative Example 8

[0108] Mordenite / SAPO-34 zeolite composite molecular sieve was prepared according to the method disclosed in CN102974392B.

[0109] The aluminum source and deionized water were mixed at 60℃ according to the mass ratio (template agent: silicon source: aluminum source: phosphorus source: water = 2: 1: 1: 1: 30), and 85wt% orthophosphoric acid was added dropwise, stirred for 1h, then silicon sol was added, stirred for 1h, then triethylamine was added dropwise, the pH of the mixture was adjusted to 6, and stirring was continued for 1h; mordenite molecular sieve was added to the obtained mixture, stirring was continued for 1h, the mixture was uniformly mixed, and aged for 1h. Hydrothermal crystallization was carried out at 130℃ for 10h, then the temperature was increased to 180℃, and hydrothermal crystallization was carried out at constant temperature for 24h, then the obtained sample was filtered multiple times, and then placed in an oven at 110℃ for drying for 12h, and calcined at 500℃ in an air atmosphere for 2h, and the obtained sample was numbered as DL8.

[0110] The sample DL8 belongs to an independent state, and contains two crystals, mordenite and SAPO-34 zeolite, and the crystallinity of the two crystals is low, and the specific surface area is low.

[0111] Table 1: Physicochemical properties of samples obtained in each example

[0112]

[0113]

[0114] Note: In the present application, the crystallinity of mordenite and SAPO-34 zeolite in the sample in Example 1 is 100%, the relative crystallinity of mordenite in all samples is obtained by comparing the crystallinity of mordenite in the sample with the crystallinity of mordenite in the sample in Example 1, and the relative crystallinity of SAPO-34 zeolite in all samples is obtained by comparing the crystallinity of SAPO-34 zeolite in the sample with the crystallinity of SAPO-34 zeolite in the sample in Example 1; the shell thickness given in Table 1 is about the thickness.

[0115] Table 2: Physicochemical properties of samples obtained in each comparative example

[0116]

[0117] Note: In the present application, the crystallinity of mordenite and SAPO-34 zeolite in the sample in Example 1 is 100%, the relative crystallinity of mordenite in all samples is obtained by comparing the crystallinity of mordenite in the sample with the crystallinity of mordenite in the sample in Example 1, and the relative crystallinity of SAPO-34 zeolite in all samples is obtained by comparing the crystallinity of SAPO-34 zeolite in the sample with the crystallinity of SAPO-34 zeolite in the sample in Example 1.

[0118] Application example

[0119] The catalytic performance of the material was investigated by using trimethylbenzene catalysis.

[0120] The materials of Example 1-5, Comparative Example 1, Comparative Example 5, Comparative Example 6, Comparative Example 7 and Comparative Example 8 were prepared into catalysts Cat1-Cat5, DCat1 and DCat5-DCat8 respectively according to conventional method, which included conventional ammonium ion exchange to prepare hydrogen type molecular sieve as catalyst.

[0121] The materials were respectively evaluated for performance on a micro fixed bed reactor, with nitrogen as carrier gas, reaction pressure of 0.1 MPa, reaction temperature of 320℃, mass space velocity of 0.2h -1 , and mesitylene as raw material. The catalytic performance index was the yield of tetramethylbenzene. The calculation method of the yield of tetramethylbenzene was the mass percentage of the yield of tetramethylbenzene in the reaction products. The evaluation results are shown in Table 2.

[0122] Table 2 Evaluation results

[0123] Catalyst number Sample number Tetramethylbenzene content, % Cat1 L1 61 Cat2 L2 59 Cat3 L3 58 Cat4 L4 61 Cat5 L5 59 DCat1 DL1 30 DCat5 DL5 41 DCat6 DL6 32 DCat7 DL7 31 DCat8 DL8 29

Claims

1. A method for synthesizing a mordenite-SAPO-34 zeolite core-shell structure composite zeolite, comprising the following steps: (1) mixing mordenite, nano iron oxide particles, water and a saccharide, evaporating the water, then heating under inert conditions, followed by acid treatment, and then separating and drying to obtain a carbon-mordenite composite; (2) mixing water and an aluminum salt, then adding the carbon-mordenite composite, a template agent, phosphoric acid and sodium silicate in sequence, mixing uniformly, crystallizing, and then separating, drying and calcining to obtain the composite zeolite; the saccharide in step (1) is at least one of sucrose, glucose, fructose, maltose and lactose; the mass ratio of the mordenite to the saccharide in step (1) is 1:0.8-6.0, the mass ratio of the mordenite to water is 1:80-210, and the mass ratio of the mordenite to iron oxide is 1:0.08-0.60; the heating temperature under inert conditions in step (1) is 300-350°C, and the heating time is 2-10 h; the acid used in the acid treatment in step (1) is at least one of hydrochloric acid, nitric acid and sulfuric acid, and the mass concentration of the acid is 0.5%-5.5%; in step (1), the mass ratio of the mordenite to the acid solution is 1:80-210, and the acid treatment is mixing the heated solid with the acid solution and treating at 10-40°C for 5-35 min; in step (2), the sodium silicate is water glass, the aluminum salt is at least one of aluminum nitrate, aluminum sulfate and aluminum chloride, and the template agent is at least one of diethylamine and tetraethylammonium hydroxide; In step (2), the molar ratio of each material of the phosphorus source, the silicon source, the aluminum source, water and the template agent is 0.6-1.35P: 0.045-0.35SiO2: Al2O3: 500-1300H2O: 0.5-5.5M; wherein, M represents the template agent, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P; in step (2), the mass ratio of the aluminum source calculated as Al2O3 to the carbon-zeolite composite is 12-30:100; in step (2), the crystallization reaction conditions are as follows: the crystallization reaction temperature is 170-230°C, and the reaction time is 20-110 h; in step (2), the drying temperature is 100-150°C, and the drying time is 1-10 h; in step (2), the calcination is high-temperature calcination at 400-600°C for 1-10 h, and the calcination needs to be carried out in an oxygen-containing atmosphere.

2. The method of synthesis according to claim 1, wherein, the saccharide in step (1) is at least one of sucrose and glucose.

3. The method of synthesis according to claim 1, wherein, in step (1), the size of the mordenite ranges from 500 nm to 3500 nm; and / or, the particle size of the nano iron oxide particles is 2-15 nm.

4. The method of synthesis according to claim 3, wherein, in step (1), the size of the mordenite ranges from 600 nm to 3000 nm; and / or, the particle size of the nano iron oxide particles is 5-10 nm.

5. The method of synthesis according to claim 1, wherein, in step (1), the mass ratio of the mordenite to the saccharide is 1:1.0-5.0; and / or, the mass ratio of the mordenite to water is 1:100-200; and / or, the mass ratio of the mordenite to iron oxide is 1:0.10-0.

50.

6. The method of synthesis according to claim 1, wherein, the evaporation temperature in step (1) is 80-160°C.

7. The method of synthesis according to claim 6, wherein, the evaporation temperature in step (1) is 100-150°C.

8. The method of synthesis according to claim 1, wherein, The mass concentration of the acid in step (1) is 1.0% to 5.0%.

9. The method of synthesis according to claim 1, wherein, In step (1), the mass ratio of mordenite to acid solution is 1:100 to 200; and / or, the acid treatment time is 10 to 30 min.

10. The method of synthesis according to claim 1, wherein, The drying temperature in step (1) is 100 to 150℃, and the drying time is 1 to 20 h.

11. The method of synthesis according to claim 1, wherein, In step (2), the molar ratio of each material of the phosphorus source, the silicon source, the aluminum source, water and the template agent is 0.7 to 1.3 P: 0.05 to 0.30 SiO2: Al2O3: 600 to 1200 H2O: 1 to 5 M; wherein M represents the template agent, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P; and / or, the mass ratio of the aluminum source calculated as Al2O3 to the carbon-modenite composite in step (2) is 15 to 25:

100.

12. The method of synthesis according to claim 1, wherein, In step (2), the crystallization reaction conditions are as follows: the crystallization reaction temperature is 180 to 220℃, and the reaction time is 30 to 100 h.

13. The mordenite-SAPO-34 zeolite core-shell composite zeolite synthesized by the synthesis method of any one of claims 1 to 12.

14. The composite zeolite according to claim 13, characterized in that, In the composite zeolite, the thickness of the shell layer is 20 to 150 nm.

15. The composite zeolite of claim 13, wherein, The specific surface area of the composite zeolite is 350~650m 2 / g.

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