A method for phosphating the surface of a zsm-5 zeolite molecular sieve

Abstract

The application provides a surface phosphating method of ZSM-5 zeolite molecular sieve, and relates to the technical field of catalytic materials.The surface phosphating method of ZSM-5 zeolite molecular sieve provided by the application comprises the following steps: subjecting ZSM-5 zeolite molecular sieve to alkali treatment to obtain alkali-treated ZSM-5 zeolite molecular sieve; mixing the alkali-treated ZSM-5 zeolite molecular sieve and a phosphorus source solution to perform hydrothermal reaction, and obtaining surface-phosphated ZSM-5 zeolite molecular sieve.The surface-phosphated ZSM-5 zeolite molecular sieve prepared by the application has the advantages of high relative crystallinity, large specific surface area and pore volume, good hydrothermal stability, simple process flow, low energy consumption and the like, and is suitable for popularization and application.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, specifically to a surface phosphating method for ZSM-5 zeolite molecular sieves. Background Technology

[0002] ZSM-5 zeolite molecular sieve is an inorganic porous crystalline material developed by Mobil. Due to its unique pore structure and ion exchange characteristics, it has been widely used in petrochemical and fine chemical industries. In silica-alumina zeolite molecular sieves, silicon-oxygen tetrahedra are connected to silicon (aluminum)-oxygen tetrahedra through shared oxygen atoms, forming structural units with specific geometric shapes. These structural units are then connected in a certain way to form the zeolite molecular sieve framework structure. Because the pore size of zeolite molecular sieves is similar to that of petroleum hydrocarbon molecules, the channels of zeolite molecular sieves have a strong sieving effect on hydrocarbon molecules. In addition, because aluminum atoms participate in the construction of the zeolite molecular sieve framework structure, silica-alumina molecular sieves also exhibit excellent catalytic activity. Although the silica-alumina ratio of ZSM-5 zeolite molecular sieves is significantly higher than that of industrial Y-type molecular sieves (SiO2 / Al2O3 approximately 5.0 mol / mol), in high-temperature hydrothermal environments, the aluminum atoms in the ZSM-5 zeolite molecular sieve framework remain very reactive, and the Si-OH-Al bonds are easily broken, leading to catalyst acidity and rapid decline in activity.

[0003] Studies have found that phosphorus modification of ZSM-5 zeolite molecular sieves can significantly improve their hydrothermal stability. It is generally believed that phosphorus modification improves the hydrothermal stability of zeolite molecular sieves because phosphorus species bond with aluminum species in the molecular sieve, inhibiting dealuminization of the zeolite molecular sieve framework in a high-temperature hydrothermal environment. Simultaneously, the phosphorus hydroxyl groups provide additional protic acids, thus preserving the acid centers of the molecular sieve. Currently, the main method for phosphorus modification of ZSM-5 zeolite molecular sieves is the impregnation method. The main problem with loading phosphorus using the impregnation method is that phosphorus species are difficult to bond with aluminum species in the zeolite molecular sieve framework at room temperature. Although phosphorus species easily bond with aluminum species in the framework at high temperatures, phosphorus species are prone to polymerization, clogging the pores of the zeolite molecular sieve and greatly reducing the catalytic activity of ZSM-5 zeolite molecular sieves. In industry, metal ion exchange modification is also commonly used to improve the stability of ZSM-5 zeolite molecular sieves. Common modifying elements include +2 and +3 valence metal ions, such as zinc and rare earth elements.

[0004] Chinese patent CN106140265A discloses a catalyst using phosphorus-modified ZSM-5 zeolite molecular sieve as a support and its preparation method. The phosphorus-modified ZSM-5 zeolite molecular sieve is obtained by impregnating hydrogen-form ZSM-5 zeolite molecular sieve with a phosphorus-containing solution (impregnation method). Chinese patent CN200810102241.1 discloses a method for efficiently improving the hydrothermal stability of zeolite molecular sieves in FCC catalysts. The zeolite molecular sieve is added to a phosphorus-containing aqueous solution and reacted for a period of time under certain pH, reaction temperature, and reaction pressure conditions. After filtration, drying, and calcination, modified phosphorus-modified ZSM-5 molecular sieve is obtained. The model catalyst prepared using this modified zeolite molecular sieve exhibits high hydrothermal stability and micro-reaction activity (without alkali treatment, and the filter cake is not washed; the effect is equivalent to the impregnation method). Chinese patent CN200910237006.X discloses a modified zeolite molecular sieve with improved sodium contamination resistance and its preparation method. The method involves adding the zeolite molecular sieve to a phosphorus-containing organic solution and reacting it for 10–200 min at a reaction temperature of 70–200℃ and a reaction pressure of 0.2–1.2 MPa. The resulting modified zeolite molecular sieve is then obtained through filtration, drying, and calcination. This method effectively improves the sodium contamination resistance of the molecular sieve (without alkali treatment and without washing the filter cake; the effect is equivalent to the impregnation method). Chinese patent CN200910237007.4 discloses a bicomponent modified zeolite molecular sieve for improving hydrothermal stability and its preparation method. The method involves adding the zeolite molecular sieve to a phosphorus-containing aqueous solution, reacting it under certain conditions, and then filtering, drying, and calcining it to obtain a phosphorus-modified zeolite molecular sieve. The phosphorus-modified zeolite molecular sieve is then added to an aqueous solution containing silver ions to obtain a bicomponent modified zeolite molecular sieve. The model catalyst prepared using this bicomponent modified zeolite molecular sieve exhibits high hydrothermal stability and low activity (no alkali treatment, no filter cake washing, the effect is equivalent to impregnation, multi-element composite). Chinese patent CN201810288536.6 discloses a method for preparing phosphorus-modified hierarchical porous ZSM-5 zeolite molecular sieve. The method involves placing HZSM-5 zeolite molecular sieve powder and piperidine compounds in an alkaline solution of inorganic alkali, treating at 50–80°C for 20–60 min, cooling to room temperature, adding an organic phosphorus compound, mixing and stirring for 0.5–4 h, filtering, washing to a pH of 7–8, drying at 100–130°C for 12–48 h, and then steam treating at 400–800°C for 0.5–24 h to obtain phosphorus-modified hierarchical porous ZSM-5 molecular sieve (HZSM-5 zeolite molecular sieve powder and piperidine compounds were mixed and alkali-treated, organic phosphorus was loaded at room temperature, and then dried and calcined).Chinese patent CN202110008846.X discloses a phosphorus- and metal-containing hierarchical porous ZSM-5 zeolite molecular sieve. The preparation method involves contacting a phosphorus-containing compound solution and a metal compound solution with a hydrogen-type hierarchical porous ZSM-5 zeolite molecular sieve, followed by drying and hydrothermal calcination under external pressure and water conditions (the hierarchical porous ZSM-5 zeolite molecular sieve is impregnated with phosphorus and then subjected to high-temperature hydrothermal calcination). Chinese patent CN201610048874.3 discloses a phosphorus modification method for a high-alkali metal ion content ZSM-5 zeolite molecular sieve. The method involves mixing a phosphorus-containing compound with a high-alkali metal ion content ZSM-5 zeolite molecular sieve, followed by drying, calcination, ammonium exchange, and water washing. The mixture is then dried and hydrothermally aged at 400–1000℃ under 100% steam conditions. The resulting phosphorus-containing ZSM-5 zeolite molecular sieve exhibits good hydrothermal and activity stability. Chinese patent CN201610175647.7 discloses a nano-ZSM-5 zeolite molecular sieve and a method for preparing its phosphorus-modified ZSM-5 zeolite molecular sieve. The preparation of the phosphorus-modified zeolite molecular sieve involves directly adding ammonium dihydrogen phosphate as a modifier to the product sol, utilizing the salting-out effect and the strong adsorption effect of the nano-molecular sieve to achieve aggregation. After centrifugation and drying, the product yields phosphorus-modified ZSM-5 zeolite molecular sieve powder (direct synthesis method). Chinese patent CN202010283413.0 discloses a phosphorus-modified ZSM-5 zeolite molecular sieve, which involves impregnating a phosphorus-containing compound solution onto a hydrogen-form ZSM-5 zeolite molecular sieve using a phosphorus-modifying method; followed by hydrothermal calcination under external pressure and with added water. This phosphorus-modified ZSM-5 zeolite molecular sieve exhibits good hydrothermal and activity stability. Chinese patent CN202010656386.7 discloses a modified ZSM-5 zeolite molecular sieve and its preparation method. The method involves mixing and slurrying ZSM-5 zeolite molecular sieve, a phosphorus-containing cationic compound, and deionized water, heating to 60–90°C, and continuously stirring for 0.5–3 hours. The mixture is then filtered, dried, and calcined at 400–700°C for 1–4 hours to obtain a phosphorus-modified ZSM-5 zeolite molecular sieve with high crystallinity and high cracking activity (untreated with alkali, organic phosphorus, with effects equivalent to the impregnation method). Chinese patent CN115594195A discloses a solid-phase method for preparing phosphorus-modified H-ZSM-5 zeolite molecular sieve. The method involves thoroughly grinding a silicon source, aluminum source, phosphorus source, organic template agent, and alkalinity regulator, then transferring the mixture to a reaction vessel for crystallization. The crystallized product is recovered, calcined to remove the template agent, immersed in an ammonium salt solution for ion exchange, and finally calcined at high temperature to obtain a phosphorus-modified HZSM-5 zeolite molecular sieve (direct synthesis method).US Patent 5171921A discloses a method for modifying ZSM-5 zeolite molecular sieves. The method involves synthesizing ZSM-5 zeolite molecular sieves using conventional methods, modifying the ZSM-5 zeolite molecular sieves with phosphoric acid, and then obtaining phosphorus-modified HZSM-5 zeolite molecular sieves (impregnation method) through drying, calcination and other steps.

[0005] The existing methods for phosphorus modification of ZSM-5 zeolite molecular sieves mainly involve solution impregnation combined with high-temperature calcination. Phosphorus species are prone to polymerization to generate pyrophosphate and polyphosphate, which can block the molecular sieve channels, reduce the reactivity of the zeolite molecular sieve, and the preparation process is also relatively complex. Summary of the Invention

[0006] The purpose of this invention is to provide a surface phosphating method for ZSM-5 zeolite molecular sieves. The surface-phosphated ZSM-5 zeolite molecular sieves prepared by this invention have advantages such as high relative crystallinity, large specific surface area and pore volume, good hydrothermal stability, simple process flow, and low energy consumption, and are suitable for widespread application.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a surface phosphating method for ZSM-5 zeolite molecular sieves, comprising the following steps:

[0009] ZSM-5 zeolite molecular sieve was alkali-treated to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0010] The alkali-treated ZSM-5 zeolite molecular sieve and the phosphorus source solution are mixed and subjected to a hydrothermal reaction to obtain a surface-phosphorized ZSM-5 zeolite molecular sieve; the pH value of the hydrothermal reaction is 0.5 to 6.5.

[0011] Preferably, the ZSM-5 zeolite molecular sieve includes one or both of NaZSM-5 zeolite molecular sieve and HZSM-5 zeolite molecular sieve.

[0012] Preferably, the silicon-aluminum ratio (SiO2 / Al2O3) of the ZSM-5 zeolite molecular sieve is 20-300 mol / mol.

[0013] Preferably, the temperature of the alkali treatment is 25–200°C, and the time of the alkali treatment is 0.5–24 h.

[0014] Preferably, the alkaline solution used in the alkaline treatment includes an aqueous solution of one or more of alkali metal hydroxides, alkali metal carbonates, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0015] Preferably, the concentration of the alkaline solution is 0.01–5.0 mol / L.

[0016] Preferably, the phosphorus source in the phosphorus source solution includes one or more of phosphoric acid, ammonium salt of phosphoric acid, trimethyl phosphate, metaphosphoric acid, ammonium salt of metaphosphoric acid, hypophosphoric acid, and ammonium salt of hypophosphoric acid.

[0017] Preferably, the concentration of the phosphorus source solution, calculated as P2O5, is 0.1–5.0 mol / L.

[0018] Preferably, the temperature of the hydrothermal reaction is 50–200°C, and the time of the hydrothermal reaction is 0.5–24 h.

[0019] Preferably, the P2O5 content of the surface-phosphated ZSM-5 zeolite molecular sieve is 0.5–5.0 wt%.

[0020] This invention provides a surface phosphating method for ZSM-5 zeolite molecular sieves. The method first involves alkali treatment of the ZSM-5 zeolite molecular sieve, causing desilication and generating numerous defect sites. Then, phosphorus loading is achieved through a hydrothermal reaction, significantly increasing the loading of the modifying element. Alkali treatment, while increasing the phosphorus loading, also creates numerous mesopores and macropores within the molecular sieve. The formation of hierarchical pores also facilitates the diffusion of reactant and product molecules onto the catalyst. Furthermore, compared to the impregnation method, the hydrothermal method for loading phosphorus not only does not reduce the relative crystallinity of the alkali-treated ZSM-5 molecular sieve but also increases it. Additionally, because high-temperature calcination is avoided, no bonding occurs between phosphorus species, resulting in a more open pore structure in the phosphorus-modified ZSM-5 zeolite molecular sieve prepared by this method. The surface-phosphated ZSM-5 zeolite molecular sieve prepared by this invention has advantages such as high relative crystallinity, large specific surface area and pore volume, good hydrothermal stability, simple process flow, and low energy consumption, making it suitable for widespread application. Attached Figure Description

[0021] Figure 1 The X-ray diffraction patterns of HZSM-5 zeolite molecular sieve, HZSM-5 / OH and HZSM-5 / P-1 in Example 1 are shown below.

[0022] Figure 2 This is a transmission electron microscope image of the HZSM-5 zeolite molecular sieve in Example 1;

[0023] Figure 3 This is a transmission electron microscope image of HZSM-5 / OH in Example 1;

[0024] Figure 4 This is a transmission electron microscope image of the HZSM-5 / P-1 sample in Example 1;

[0025] Figure 5The X-ray diffraction patterns of HZSM-5 / OH and HZSM-5 / P-5 zeolite molecular sieves in Example 5 are shown (* indicates diffraction peaks of aluminum phosphate).

[0026] Figure 6 X-ray diffraction patterns of HZSM-5 and HZSM-5 / PR-1 zeolite molecular sieves in Comparative Example 1;

[0027] Figure 7 The X-ray diffraction patterns of HZSM-5 and HZSM-5 / PR-2 zeolite molecular sieves in Comparative Example 2 are shown. Detailed Implementation

[0028] This invention provides a surface phosphating method for ZSM-5 zeolite molecular sieves, comprising the following steps:

[0029] ZSM-5 zeolite molecular sieve was alkali-treated to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0030] The alkali-treated ZSM-5 zeolite molecular sieve and the phosphorus source solution are mixed and subjected to a hydrothermal reaction to obtain a surface-phosphorized ZSM-5 zeolite molecular sieve; the pH value of the hydrothermal reaction is 0.5 to 6.5.

[0031] This invention involves alkali treatment of ZSM-5 zeolite molecular sieves to obtain alkali-treated ZSM-5 zeolite molecular sieves. In this invention, the ZSM-5 zeolite molecular sieve preferably comprises one or both of NaZSM-5 zeolite molecular sieves and HZSM-5 zeolite molecular sieves. In a specific embodiment of this invention, the NaZSM-5 zeolite molecular sieve has a silica-to-alumina ratio (SiO2 / Al2O3) of 30 mol / mol, a relative crystallinity of 89%, a Na2O content of 4.52 wt%, and a water content of 15.4 wt%. In a specific embodiment of this invention, the HZSM-5 zeolite molecular sieve has a silica-to-alumina ratio of 30–110 mol / mol, a relative crystallinity of 88–92%, a Na2O content of 0.04–0.08 wt%, and a water content of 5.3–9.1 wt%. In this invention, ZSM-5 zeolite molecular sieves are widely available. Not only can HZSM-5 zeolite molecular sieves be used to achieve phosphorus loading, but NaZSM-5 zeolite molecular sieves can also be used, reducing the exchange and calcination steps of NaZSM-5 zeolite molecular sieves.

[0032] In this invention, the silicon-aluminum ratio (SiO2 / Al2O3) of the ZSM-5 zeolite molecular sieve is preferably 20-300 mol / mol, more preferably 30-100 mol / mol.

[0033] In this invention, the temperature of the alkali treatment is preferably 25–200°C, more preferably 50–170°C; the time of the alkali treatment is preferably 0.5–24 h, more preferably 2–12 h. In this invention, the alkali treatment is preferably carried out under water bath stirring conditions or in a hydrothermal reactor.

[0034] In this invention, the alkaline solution used for the alkaline treatment preferably comprises an aqueous solution of one or more of alkali metal hydroxides, alkali metal carbonates, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. In a specific embodiment of this invention, the alkaline solution used for the alkaline treatment is an aqueous solution of sodium hydroxide, sodium carbonate, or potassium hydroxide.

[0035] In this invention, the concentration of the alkaline solution is preferably 0.01–5.0 mol / L, more preferably 0.1–2.0 mol / L. In this invention, the mass ratio of the ZSM-5 zeolite molecular sieve to the alkaline solution is preferably 1:5–12, more preferably 1:5–8.

[0036] In this invention, after the alkali treatment, the resulting molecular sieve slurry is preferably filtered, washed, and dried sequentially to obtain alkali-treated ZSM-5 zeolite molecular sieve. Preferably, the filtered solid material is washed with deionized water. In this invention, the drying temperature is preferably 100–120°C; the drying time is preferably 12–24 hours.

[0037] This invention involves alkali treatment of ZSM-5 zeolite molecular sieve, which generates numerous defects and large and medium-sized pores on the surface of the molecular sieve, facilitating the diffusion of raw material molecules and product molecules.

[0038] After obtaining the alkali-treated ZSM-5 zeolite molecular sieve, the present invention mixes the alkali-treated ZSM-5 zeolite molecular sieve with a phosphorus source solution and carries out a hydrothermal reaction to obtain a surface-phosphorized ZSM-5 zeolite molecular sieve.

[0039] In this invention, the phosphorus source in the phosphorus source solution preferably includes one or more of phosphoric acid, an ammonium salt of phosphoric acid, trimethyl phosphate, metaphosphoric acid, an ammonium salt of metaphosphoric acid, hypophosphoric acid, and an ammonium salt of hypophosphoric acid. Specifically, the ammonium salt of phosphoric acid includes one or more of ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate; the ammonium salt of metaphosphoric acid specifically includes ammonium metaphosphoric acid; and the ammonium salt of hypophosphoric acid specifically includes ammonium hypophosphoric acid.

[0040] In this invention, the concentration of the phosphorus source solution, calculated as P2O5, is preferably 0.1 to 5.0 mol / L, more preferably 0.5 to 4.0 mol / L.

[0041] In this invention, the mass ratio of the alkali-treated ZSM-5 zeolite molecular sieve to the phosphorus source solution is preferably 1:5 to 12, more preferably 1:5 to 8.

[0042] In this invention, the temperature of the hydrothermal reaction is preferably 50–200°C, more preferably 60–180°C; the time of the hydrothermal reaction is preferably 0.5–24 h, more preferably 2–12 h. This invention achieves phosphorus loading in a low-temperature solution, avoiding the polymerization of phosphorus species under high-temperature conditions and preventing phosphorus species from clogging the molecular sieve channels.

[0043] In this invention, the pH value of the hydrothermal reaction is 0.5–6.5, preferably 1.2–2.0. In this invention, the reagents used to adjust the pH value of the hydrothermal reaction preferably include one or more of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, metaphosphoric acid, and hypophosphoric acid.

[0044] Preferably, after the hydrothermal reaction, the resulting hydrothermal reaction system is sequentially filtered, washed, and dried to obtain a surface-phosphated ZSM-5 zeolite molecular sieve. Preferably, the filtered solid material is washed with deionized water. In this invention, the drying temperature is preferably 100–120°C; the drying time is preferably 12–24 hours.

[0045] In this invention, the P2O5 content of the surface-phosphated ZSM-5 zeolite molecular sieve is preferably 0.5 to 5.0 wt%, more preferably 1 to 3 wt%.

[0046] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] The raw materials used in the examples and comparative examples are all commercially available industrial products, with no other special requirements.

[0048] Example 1

[0049] At room temperature, 100.0 g of deionized water and 2.4 g of NaOH were added sequentially to a plastic beaker and the NaOH was dissolved. Then, 11.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; then place the plastic beaker in a 65℃ water bath and react for 2 hours under stirring; after the reaction, filter the resulting molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve, denoted as HZSM-5 / OH (the relative crystallinity of this molecular sieve is 77%). The X-ray diffraction patterns and transmission electron microscope images of HZSM-5 and HZSM-5 / OH are shown in [reference needed]. Figures 1-3 .

[0050] At room temperature, 100.0 g of deionized water and 3.2 g of H3PO4 solution (85 wt% phosphoric acid) were added sequentially to a glass beaker and mixed thoroughly. Then, 10.0 g of the above HZSM-5 / OH (on a dry basis) was added to the glass beaker and mixed thoroughly. The resulting molecular sieve slurry (pH 1.2) was then transferred to a Parr hydrothermal reactor and reacted at 120 °C for 4 h. After the reaction, the hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. The mixture was then dried at 100 °C for 24 h to obtain a surface-phosphated ZSM-5 zeolite molecular sieve, denoted as HZSM-5 / P-1. The X-ray diffraction pattern and transmission electron microscope image of HZSM-5 / P-1 are shown below. Figure 1 and Figure 4 .

[0051] Example 2

[0052] At room temperature, 75.0 g of deionized water and 1.0 g of NaOH were added sequentially to a plastic beaker and the NaOH was dissolved. Then, 9.0 g of NaZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 89%, Na2O content 4.52 wt%, water content 15.4 wt%, specific surface area 336 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in a 65℃ water bath and react for 4 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry it at 120℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve, denoted as NaZSM-5 / OH.

[0053] At room temperature, 100.0 g of deionized water and 5.0 g of H3PO4 solution (phosphoric acid content of 85 wt%) were added to a glass beaker and mixed thoroughly. Then, 10.0 g of the above NaZSM-5 / OH (on a dry basis) was added to the glass beaker and mixed thoroughly. The resulting molecular sieve slurry (pH value of the molecular sieve slurry was 1.0) was transferred to a Parr hydrothermal reactor and reacted at 80 °C for 8 h. After the reaction, the resulting hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. The mixture was then dried at 100 °C for 24 h to obtain a surface-phosphated ZSM-5 zeolite molecular sieve, denoted as NaZSM-5 / P-2.

[0054] Example 3

[0055] At room temperature, 100.0 g of deionized water and 9.6 g of Na2CO3 were added sequentially to a plastic beaker, allowing the Na2CO3 to dissolve completely. Then, 11.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in an 80℃ water bath and react for 4 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0056] At room temperature, 100.0 g of deionized water and 8.2 g of H3PO4 solution (phosphoric acid content of 85 wt%) were added to a glass beaker and mixed thoroughly. Then, 10.0 g of the above-mentioned alkali-treated ZSM-5 zeolite molecular sieve (on a dry basis) was added to the glass beaker and mixed thoroughly. The resulting molecular sieve slurry (pH value of the molecular sieve slurry was 0.8) was transferred to a Parr hydrothermal reactor and reacted at 100 °C for 4 h. After the reaction, the resulting hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. The mixture was then dried at 100 °C for 24 h to obtain a surface-phosphated ZSM-5 zeolite molecular sieve, denoted as HZSM-5 / P-3.

[0057] Example 4

[0058] At room temperature, 80.0 g of deionized water and 1.8 g of KOH were added sequentially to a plastic beaker to dissolve the KOH. Then, 11.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in a 65℃ water bath and react for 4 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry at 120℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0059] At room temperature, 100.0 g of deionized water and 6.7 g of H3PO4 solution (phosphoric acid content of 85 wt%) were added to a glass beaker and mixed thoroughly. Then, 10.0 g of the above-mentioned alkali-treated ZSM-5 zeolite molecular sieve (on a dry basis) was added to the glass beaker and mixed thoroughly. The resulting molecular sieve slurry (pH value of the molecular sieve slurry was 0.6) was transferred to a Parr hydrothermal reactor and reacted at 110 °C for 4 h. After the reaction, the resulting hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. The mixture was then dried at 110 °C for 24 h to obtain the surface-phosphated ZSM-5 zeolite molecular sieve, denoted as HZSM-5 / P-4.

[0060] Example 5

[0061] At room temperature, 120.0 g of deionized water and 1.2 g of NaOH were added sequentially to a plastic beaker to dissolve the NaOH. Then, 11.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in a 65℃ water bath and react for 8 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry it at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve, denoted as HZSM-5 / OH.

[0062] At room temperature, 100.0 g of deionized water and 5.0 g of NH4H2PO4 were added sequentially to a glass beaker, and the NH4H2PO4 was dissolved. Then, 10.0 g of the above-mentioned HZSM-5 / OH (on a dry basis) was added to the glass beaker and mixed thoroughly. The pH of the slurry was then adjusted to 1.3 with 2.0% hydrochloric acid and mixed thoroughly. The resulting molecular sieve slurry was then transferred to a Parr hydrothermal reactor and reacted at 175 °C for 24 h. After the reaction, the resulting hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. It was then dried at 100 °C for 24 h to obtain a surface-phosphated ZSM-5 zeolite molecular sieve, denoted as HZSM-5 / P-5. The X-ray diffraction patterns of HZSM-5 / OH and HZSM-5 / P-5 are shown below. Figure 5 .

[0063] Example 6

[0064] At room temperature, 80.0 g of deionized water and 3.5 g of NaOH were added sequentially to a plastic beaker to dissolve the NaOH. Then, 8.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in an 80℃ water bath and react for 2 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry it at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0065] At room temperature, 100.0 g of deionized water and 6.6 g of trimethyl phosphate were added to a glass beaker and mixed thoroughly. Then, 10.0 g of the above-mentioned alkali-treated ZSM-5 zeolite molecular sieve (on a dry basis) was added to the glass beaker and mixed thoroughly. The resulting molecular sieve slurry (pH 6.1) was then transferred to a Parr hydrothermal reactor and reacted at 180 °C for 2 h. After the reaction, the resulting hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. The mixture was then dried at 100 °C for 24 h to obtain a surface-phosphated ZSM-5 zeolite molecular sieve, denoted as HZSM-5 / P-6.

[0066] Example 7

[0067] At room temperature, 100.0 g of deionized water and 1.2 g of NaOH were added sequentially to a plastic beaker, allowing the NaOH to dissolve completely. Then, 10.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio of 110 mol / mol, relative crystallinity of 88%, Na2O content of 0.04 wt%, water content of 5.3 wt%, specific surface area of ​​376 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in a 65℃ water bath and react for 4 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0068] At room temperature, 100.0 g of deionized water and 14.3 g of (NH4)2HPO4 were added sequentially to a glass beaker to fully dissolve the (NH4)2HPO4. Then, 10.0 g of the aforementioned alkali-treated ZSM-5 zeolite molecular sieve (on a dry basis) was added to the glass beaker and mixed thoroughly. The pH of the slurry was then adjusted to 1.1 using 2.0% dilute hydrochloric acid and mixed thoroughly. The resulting molecular sieve slurry was then transferred to a Parr hydrothermal reactor and reacted at 165°C for 12 h. After the reaction, the resulting hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. The filtered cake was then dried at 100°C for 24 h to obtain a surface-phosphated ZSM-5 zeolite molecular sieve, designated HZSM-5 / P-7.

[0069] Comparative Example 1

[0070] Phosphorus-modified ZSM-5 zeolite molecular sieves were prepared by the equal-volume impregnation method.

[0071] First, 20g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30mol / mol, relative crystallinity 92%, Na2O content 0.08wt%, water content 9.1wt%, specific surface area 340m²) was tested. 2 Add 9g of NH4H2PO4 solution (6.5% by mass) to a beaker, and then add 9g of NH4H2PO4 solution under stirring. After stirring evenly, dry the molecular sieve in an oven at 120℃ for 24h, and then calcine it in a muffle furnace at 550℃ for 2h to obtain the modified zeolite molecular sieve HZSM-5 / PR-1. The X-ray diffraction patterns of HZSM-5 and HZSM-5 / PR-1 are shown in the figure. Figure 6 .

[0072] Comparative Example 2

[0073] At room temperature, 100.0 g of deionized water and 10.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio of 30 mol / mol, relative crystallinity of 92%, Na2O content of 0.08 wt%, water content of 9.1 wt%, specific surface area of ​​340 m²) were added sequentially to a glass beaker. 2 The molecular sieve slurry (pH 1.0) was prepared by mixing 3.7 g of H3PO4 solution (85 wt% phosphoric acid) with 3.7 g of phosphoric acid and thoroughly mixing. The resulting slurry was then transferred to a Parr hydrothermal reactor and reacted at 120 °C for 8 h. After the reaction, the hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. The cake was then dried at 110 °C for 24 h to obtain the modified molecular sieve HZSM-5 / PR-2. The X-ray diffraction patterns of HZSM-5 and HZSM-5 / PR-2 are shown below. Figure 7 .

[0074] Comparative Example 3

[0075] At room temperature, 80.0 g of deionized water and 2.1 g of NaOH were added sequentially to a plastic beaker, allowing the NaOH to dissolve completely. Then, 8.1 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in an 80℃ water bath and react for 4 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0076] Phosphorus-modified ZSM-5 zeolite molecular sieve was prepared by the equal volume impregnation method: 20.0 g (dry basis) of the above-mentioned alkali-treated HZSM-5 zeolite molecular sieve was weighed and placed in a beaker. Under stirring conditions, 10 g of NH4H2PO4 solution with a mass percentage of 6.5% was added. After stirring evenly, the beaker was placed in an oven at 120℃ to dry, and then the molecular sieve was placed in a muffle furnace and calcined at 550℃ for 2 h to obtain the modified molecular sieve HZSM-5 / PR-3.

[0077] Comparative Example 4

[0078] At room temperature, 100.0 g of deionized water and 2.4 g of NaOH were added sequentially to a plastic beaker, allowing the NaOH to dissolve completely. Then, 11.0 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in a 65℃ water bath and react for 4 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0079] At room temperature, 100.0 g of deionized water and 9.0 g of (NH4)2HPO4 were added to a glass beaker to dissolve the (NH4)2HPO4 completely. 10.0 g of the above-mentioned alkali-treated ZSM-5 zeolite molecular sieve (on a dry basis) was added to the glass beaker and mixed thoroughly. The resulting molecular sieve slurry (pH 7.6) was transferred to a Parr hydrothermal reactor and reacted at 120 °C for 4 h. After the reaction, the resulting hydrothermal reaction system was filtered, and the filter cake was thoroughly washed with deionized water. Then, it was dried at 100 °C for 24 h to obtain the modified molecular sieve HZSM-5 / PR-4.

[0080] Comparative Example 5

[0081] At room temperature, 90.0 g of deionized water and 1.8 g of NaOH were added sequentially to a plastic beaker, allowing the NaOH to dissolve completely. Then, 9.2 g of HZSM-5 zeolite molecular sieve (SiO2 / Al2O3 ratio 30 mol / mol, relative crystallinity 92%, Na2O content 0.08 wt%, water content 9.1 wt%, specific surface area 340 m²) was added to the plastic beaker. 2 / g), and mix thoroughly; place the plastic beaker in an 80℃ water bath and react for 2 hours under stirring; after the reaction is complete, filter the obtained molecular sieve slurry, wash the filter cake thoroughly with deionized water, and then dry at 100℃ for 24 hours to obtain alkali-treated ZSM-5 zeolite molecular sieve.

[0082] At room temperature, 100.0 g of deionized water and 6 g of H3PO4 solution (phosphoric acid content of 85 wt%) were added to a beaker and mixed thoroughly. 10.0 g of the above-mentioned alkali-treated ZSM-5 zeolite molecular sieve was added to the beaker and mixed thoroughly (the pH of the slurry was 0.8). The beaker was reacted at room temperature for 12 h. After the reaction was completed, the resulting molecular sieve slurry was filtered, and the filter cake was thoroughly washed with deionized water. Then, it was dried at 100 °C for 24 h to obtain the modified zeolite molecular sieve HZSM-5 / PR-5.

[0083] The physicochemical properties of the surface-phosphated ZSM-5 zeolite molecular sieve prepared in the examples and the modified ZSM-5 zeolite molecular sieve prepared in the comparative examples are shown in Table 1. The relative crystallinity was tested using X-ray diffraction, with characteristic diffraction peaks selected in the range of 22.5°–25.0°. The relative crystallinity of the sample was the ratio of the peak area integral of the characteristic diffraction peak of the sample to the peak area integral of the standard sample. The P2O5 content was tested using X-ray fluorescence. Specific surface area and pore volume were tested using a Mack 2460N2 physical adsorption instrument, and the specific surface area was obtained using the BET method. The micro-reaction activity index (MAT) test conditions were: reaction temperature 500℃, reaction feedstock straight-run diesel, molecular sieve particle loading 5.00 g, and oil feed rate 1.56 g, specifically referring to the National Energy Administration's method for determining the micro-reaction activity index of catalytic cracking catalysts (NB / SH / T 0952-2017). Before the MAT test, the molecular sieve was treated at 800℃ and 100% water vapor for 4 hours.

[0084] Table 1. Performance Comparison of Phosphorus-Modified ZSM-5 Zeolite Molecular Sieves

[0085] Example 1 85 1.6 392 0.39 41 Example 2 84 2.5 389 0.38 38 Example 3 83 2.9 374 0.41 39 Example 4 84 2.6 379 0.38 39 Example 5 83 2.4 393 0.39 40 Example 6 84 2.3 387 0.38 39 Example 7 83 3.8 382 0.35 34 Comparative Example 1 79 2.0 311 0.19 34 Comparative Example 2 85 0.2 338 0.21 23 Comparative Example 3 81 2.2 331 0.34 34 Comparative Example 4 77 0.1 369 0.37 24 Comparative Example 5 76 0.3 371 0.39 27

[0086] Table 1 shows that after alkali treatment of ZSM-5 zeolite molecular sieves and different phosphorus sources in a hydrothermal environment of 50–200℃ within a pH range of 0.5–6.5 for 0.5–24 h, the ZSM-5 molecular sieves were loaded with a certain amount of phosphorus. The relative crystallinity, specific surface area, and diesel micro-reaction activity were all improved compared to Comparative Examples 1 and 3, demonstrating excellent hydrothermal stability. Comparative Examples 1 and 3 prepared phosphorus-modified ZSM-5 molecular sieves using an impregnation method. Although the phosphorus loading was high, the crystallinity and specific surface area of ​​the molecular sieves were significantly reduced compared to the untreated samples. Compared to the alkali-treated ZSM-5 molecular sieves, the HZSM-5 molecular sieve in Comparative Example 2 was not alkali-treated. Although it reacted for a certain time in an acidic, high-temperature hydrothermal environment, after thorough washing of the filter cake with deionized water, a large amount of residual phosphorus source on the molecular sieve filter cake entered the filtrate, indicating that under these reaction conditions, the untreated HZSM-5 molecular sieve did not react significantly with the phosphorus source. In Comparative Example 4, although the HZSM-5 molecular sieve was treated with alkali, the phosphorus loading on the ZSM-5 molecular sieve was low under the high-temperature hydrothermal reaction conditions between the molecular sieve and the phosphorus source due to the high pH value of the solution. In Comparative Example 5, the alkali-treated HZSM-5 molecular sieve did not react significantly with the phosphorus source at room temperature.

[0087] Figure 1 The images show the X-ray diffraction patterns of the HZSM-5 zeolite molecular sieve, HZSM-5 / OH, and HZSM-5 / P-1 samples from Example 1. Figure 1 It can be seen that the intensity of the diffraction peaks of HZSM-5 zeolite molecular sieve decreased slightly after alkali treatment, and the crystallinity of the zeolite molecular sieve was partially restored after hydrothermal loading of phosphorus element. Meanwhile, compared with HZSM-5 and HZSM-5 / OH zeolite molecular sieves, the diffraction peaks of HZSM-5 / P-1 zeolite molecular sieve showed a significant shift towards higher diffraction angles due to the participation of framework aluminum atoms in the reaction.

[0088] Figure 2 , Figure 3 and Figure 4 The images show transmission electron microscopy (TEM) images of the HZSM-5 zeolite molecular sieve, HZSM-5 / OH, and HZSM-5 / P-1 samples from Example 1. As can be seen from the figures, compared to the HZSM-5 molecular sieve, the HZSM-5 / OH sample exhibits a large number of alkaline etching marks. After alkaline etching and hydrothermal reaction with a phosphorus source, the alkaline etching marks are reduced.

[0089] Figure 5 The images show the X-ray diffraction patterns of the HZSM-5 / OH and HZSM-5 / P-5 zeolite molecular sieves from Example 5. Figure 5It can be seen that after phosphating, the characteristic diffraction peaks of HZSM-5 / P-5 zeolite molecular sieve are the same as those of HZSM-5 / OH zeolite molecular sieve, but the characteristic diffraction peaks of aluminum phosphate appear in the X-ray diffraction pattern of HZSM-5 / P-5 zeolite molecular sieve.

[0090] Figure 6 The X-ray diffraction patterns are shown for HZSM-5 and HZSM-5 / PR-1 zeolite molecular sieves in Comparative Example 1. Figure 6 It can be seen that the intensity of the diffraction peaks of HZSM-5 / PR-1 zeolite molecular sieve is significantly reduced. Meanwhile, compared with HZSM-5 zeolite molecular sieve, the diffraction peaks of HZSM-5 / PR-1 zeolite molecular sieve show a significant shift due to the reaction of framework aluminum atoms with phosphorus species under high-temperature calcination conditions.

[0091] Figure 7 The X-ray diffraction patterns are shown for HZSM-5 and HZSM-5 / PR-2 zeolite molecular sieves in Comparative Example 2. Figure 7 It can be seen that the diffraction peak intensity and position of HZSM-5 / PR-2 zeolite molecular sieve did not change significantly compared with HZSM-5 zeolite molecular sieve, indicating that under these conditions, the aluminum framework of HZSM-5 zeolite molecular sieve did not react significantly with phosphorus species.

[0092] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for surface phosphating of ZSM-5 zeolite molecular sieve, comprising the following steps: ZSM-5 zeolite molecular sieve is subjected to alkali treatment to obtain alkali-treated ZSM-5 zeolite molecular sieve; the ZSM-5 zeolite molecular sieve includes one or two of NaZSM-5 zeolite molecular sieve and HZSM-5 zeolite molecular sieve. The alkali-treated ZSM-5 zeolite molecular sieve and phosphorus source solution are mixed and subjected to a hydrothermal reaction to obtain a surface-phosphorylated ZSM-5 zeolite molecular sieve. The phosphorus source solution includes one or more of phosphoric acid, ammonium salt of phosphoric acid, metaphosphoric acid, ammonium salt of metaphosphoric acid, hypophosphoric acid, and ammonium salt of hypophosphoric acid. The pH value of the hydrothermal reaction is 0.5~2. The temperature of the hydrothermal reaction is 50~200℃. The time of the hydrothermal reaction is 0.5~24 h.

2. The surface phosphating method according to claim 1, characterized in that, The silicon-aluminum ratio of the ZSM-5 zeolite molecular sieve is 20~300 mol / mol.

3. The surface phosphating method according to claim 1, characterized in that, The alkali treatment temperature is 25~200℃; the alkali treatment time is 0.5~24 h.

4. The surface phosphating method according to claim 1 or 3, characterized in that, The alkaline solution used in the alkaline treatment includes one or more aqueous solutions of alkali metal hydroxides, alkali metal carbonates, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

5. The surface phosphating method according to claim 4, characterized in that, The concentration of the alkaline solution is 0.01~5.0 mol / L.

6. The surface phosphating method according to claim 1, characterized in that, The concentration of the phosphorus source solution, calculated as P2O5, is 0.1~5.0 mol / L.

7. The surface phosphating method according to claim 1, characterized in that, The P2O5 content of the surface-phosphated ZSM-5 zeolite molecular sieve is 0.5~5.0 wt%.

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