Preparation method and application of binder-free hydrogen type Mordenite molecular sieve catalyst

Abstract

The invention relates to a preparation method and application of a binder-free hydrogen type Mordenite molecular sieve catalyst. The preparation method comprises the following steps: uniformly mixing a silicon source, an aluminum source, an organic template agent (R1), an inorganic template agent (R2) and water according to a certain proportion to obtain a solid precursor; the obtained solid precursor is subjected to kneading and extrusion molding and then is crystallized in a crystallization kettle, the crystallization temperature is 130-200 DEG C, and the crystallization time is 12-72 h; and after crystallization, washing, filtering and drying a product, and directly roasting for 1-24 hours at the temperature of 450-600 DEG C to obtain the binder-free hydrogen type Mordenite molecular sieve catalyst. The preparation process of the formed catalyst has the characteristics that no molecular sieve seed crystal is added, ion exchange is not needed, and the discharge amount of waste liquid is remarkably reduced. The catalyst prepared by the method provided by the invention can be used for a reaction for preparing ethylene by ethanol dehydration, and has excellent catalytic activity.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and in particular relates to a preparation method and application of a binder-free hydrogen-type Mordenite molecular sieve catalyst. Background Art

[0002] Mordenite is a microporous aluminosilicate molecular sieve with an MOR-type topological structure. Its structure contains a 12-membered ring main channel (0.65nm×0.70nm) along the c-axis and an 8-membered ring side pocket (0.26×0.57nm) connected to the main channel. This unique structure enables it to perform well in petroleum refining, and can efficiently catalyze the cracking of heavy hydrocarbons and increase the yield of light fuels. At the same time, in organic synthesis reactions, such as the selective oxidation of glycerol to prepare dihydroxyacetone, Mordenite also exhibits excellent catalytic activity and selectivity. In addition, it has also been used in the fields of catalytic conversion of methylanthracene, carbonylation reaction and preferential oxidation of carbon monoxide, and has achieved good catalytic effects.

[0003] Molecular sieves obtained through conventional synthesis typically exist in powder form. Direct use in industrial production in this form is not only difficult to handle but also prone to dust pollution. More importantly, the powder form limits its filling efficiency and stability in the reactor, which in turn affects the separation or catalytic effect. Therefore, in industrial applications, the molecular sieve needs to be mixed with a binder and other materials for molding. This molding process not only improves the mechanical strength of the molecular sieve, facilitating loading and replacement, but also optimizes its distribution and mass transfer performance in the reactor, thereby improving overall process efficiency. However, due to the nature of the inert matrix, traditional binders have significant drawbacks during use. On the one hand, they reduce the active site density per unit volume of the catalyst, resulting in fewer active sites available for effective catalytic action when the catalyst contacts the reactants, thereby weakening the efficiency of the catalytic reaction. On the other hand, traditional binders also lead to increased mass transfer resistance. During the reaction process, the diffusion of reactants into the catalyst and the diffusion of products out of the catalyst are more difficult, resulting in insufficient contact between the reactants and the catalyst and delayed product discharge. Ultimately, the overall performance of the catalyst is significantly reduced, limiting its application effectiveness and development potential in fields such as industrial catalysis. Therefore, the preparation research of binder-free molecular sieve catalysts has become a focus area that has attracted much attention.

[0004] CN102039152A discloses a method for preparing a binderless mordenite catalyst. No seed crystal directing agent is required during the preparation process. A compound containing 0.1 to 20% by weight of an alkaline substance, 0.5 to 40% by weight of an aluminum compound, and 40 to 80% by weight of silicon oxide are mixed, shaped, and dried. The mixture is then placed in a vapor containing at least one template selected from water, ammonia water, ethylenediamine, triethylamine, n-butylamine, hexamethylenediamine, tetrapropylammonium bromide, or tetrapropylammonium hydroxide. The binderless mordenite catalyst is obtained after crystallization.

[0005] CN103657705A discloses a method for preparing a high-strength binder-free multi-level porous composite mordenite (MOR) catalyst. The method is characterized in that mesoporous silica is used as a precursor, and after being treated with aluminum impregnation with an aluminum source, a high-strength binder-free multi-level porous composite MOR molecular sieve catalyst is obtained by a gas phase synthesis method in an atmosphere of mixed steam of water, water and organic amine. The silicon-aluminum ratio of the catalyst can be arbitrarily adjusted within a certain range.

[0006] CN112551546A discloses a method for preparing a binder-free macroporous high-silicon Na-type MOR zeolite molecular sieve, which comprises hydrothermally synthesizing macroporous high-silicon Na-type MOR zeolite powder having a silicon-aluminum ratio greater than 15 in a pressure-resistant reactor; mixing the macroporous high-silicon Na-type MOR zeolite powder with a binder to form a granular precursor; and subjecting the granular precursor to a hydrothermal crystallization reaction in a pressure-resistant reactor to prepare a binder-free macroporous high-silicon Na-type MOR zeolite having a silicon-aluminum ratio greater than 15.

[0007] CN119118146A discloses a method for preparing a binder-free self-forming MOR molecular sieve. The method comprises mixing sodium hydroxide, alkaline silica sol, and an aluminum source, stirring and aging the mixture to form a gel, which is then transferred to a hydrothermal kettle. The mixture is sealed and crystallized at 170°C for 5 days. After the crystallization, a centimeter-scale MOR molecular sieve can be obtained.

[0008] In the process of preparing binderless MOR molecular sieve catalysts, some of the above methods require the use of seed crystals, some require the use of a sodium source followed by ion exchange, and some require hydrothermal crystallization. As a result, these methods make the catalyst preparation process cumbersome, the production cost expensive, and generate a large amount of waste liquid. Summary of the Invention

[0009] The present invention aims to provide a method for preparing a binderless hydrogen-type Mordenite molecular sieve catalyst and the use of the catalyst prepared by the method in an ethanol dehydration reaction, thereby resolving the problems of the prior art, such as the cumbersome steps in the catalyst preparation process, high production costs, and the generation of large amounts of waste liquid. The method for preparing the binderless hydrogen-type Mordenite molecular sieve catalyst of the present invention comprises the following steps:

[0010] (a) mixing a silicon source, an aluminum source, an organic template (R1), an inorganic template (R2), and water in a certain proportion to obtain a solid precursor;

[0011] (b) kneading and extruding the obtained solid precursor into strips, and then crystallizing it in a crystallization kettle at a crystallization temperature of 130 to 200° C. for a crystallization time of 12 to 72 hours;

[0012] (c) After crystallization, the product is washed, filtered, dried, and then directly calcined at 450° C. to 600° C. for 1 h to 24 h to obtain a binder-free hydrogen-type Mordenite molecular sieve catalyst.

[0013] The preparation process of the binder-free hydrogen-type Mordenite molecular sieve catalyst of the present invention does not require the addition of seed crystals, ion exchange, or the generation of waste liquid. Therefore, the preparation method effectively simplifies the preparation process, reduces production costs, and reduces waste liquid discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the XRD spectrum of the binderless hydrogen-type Mordenite molecular sieve catalyst prepared in Example 1.

[0015] Figure 2 This is a SEM photograph of the binderless hydrogen-type Mordenite molecular sieve catalyst prepared in Example 1.

[0016] Figure 3 The catalytic reaction performance of the binderless hydrogen-type Mordenite molecular sieve prepared in Example 1 for the dehydration of ethanol to ethylene. DETAILED DESCRIPTION

[0017] The present invention provides a method for preparing a binder-free hydrogen-type Mordenite molecular sieve catalyst, comprising the following steps:

[0018] (a) mixing a silicon source, an aluminum source, an organic template (R1), an inorganic template (R2), and water in a certain proportion to obtain a solid precursor;

[0019] (b) kneading and extruding the obtained solid precursor into strips, and then crystallizing it in a crystallization kettle at a crystallization temperature of 130 to 200° C. for a crystallization time of 12 to 72 hours;

[0020] (c) After crystallization, the product is washed, filtered, dried, and then directly calcined at 450° C. to 600° C. for 1 h to 24 h to obtain a binder-free hydrogen-type Mordenite molecular sieve catalyst.

[0021] According to the method of the present invention, in step (a), the silicon source is at least one of silica sol, powdered silica gel, white carbon black, diatomaceous earth, kaolin, and bentonite; the aluminum source is at least one of pseudo-boehmite, aluminum hydroxide, aluminum chloride, and aluminum sulfate; the organic template is at least one of tetraethylammonium hydroxide, tetraethylammonium fluoride, tetraethylammonium bromide, and tetraethylammonium chloride; the inorganic template is at least one of ammonium chloride, ammonium fluoride, ammonium bromide, and ammonia water; the total mass of SiO2 in the silicon source is equal to the mass of A in the aluminum source. l2O3, i.e., n(SiO2) / n(Al2O3), is greater than or equal to 20; the ratio of the total mass of SiO2 in the silicon source to the mass of the organic template, i.e., n(SiO2) / n(R1), is between 0.1 and 1.0; the ratio of the total mass of SiO2 in the silicon source to the mass of the inorganic template, i.e., n(SiO2) / n(R2), is between 0.1 and 1.0; the weight percentage of water in the solid precursor is between 10% and 40%.

[0022] The binderless hydrogen-type Mordenite molecular sieve catalyst prepared by the method of the present invention can be used for the dehydration of ethanol to ethylene. The reaction is carried out in a fixed reaction bed. The catalyst is 0.15g. During the reaction, the raw material ethanol is brought to the reactor at 30°C by N2 bubbling. The weight hourly space velocity of ethanol is 1h -1 The reaction pressure was normal pressure, the reaction temperature was 300°C, and the products were analyzed online by gas chromatography (SHIMADZU GC-2014) equipped with a hydrogen ion flame detector (FID) and a PoraPLOTQ capillary column.

[0023] 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.

[0024] Example 1

[0025] 80g of powdered silica gel, 8g of pseudo-boehmite, 7g of ammonium chloride, and 78.4g of tetraethylammonium hydroxide (25 wt%) were stirred thoroughly until uniformly mixed to obtain a solid precursor. The solid precursor was then kneaded and extruded into strips with a diameter of 1.5mm. The strips were placed in a stainless steel sealed reactor lined with polytetrafluoroethylene and crystallized at 180°C for 48h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550°C in an air atmosphere for 6h to obtain a binder-free hydrogen-type Mordenite molecular sieve catalyst. The catalyst was used in the dehydration of ethanol to ethylene reaction, with a weight hourly space velocity of ethanol of 1h. -1 The reaction temperature is 300℃, the ethanol conversion rate reaches 99.9%, and the ethylene selectivity reaches 98.3%. The XRD spectrum, SEM image and reaction performance of the catalyst for ethanol dehydration to ethylene are shown in the figure below. Figure 1 、 Figure 2 and Figure 3 shown.

[0026] Example 2

[0027] 80 g of powdered silica gel, 4 g of pseudo-boehmite, 7 g of ammonium chloride and 78.4 g of tetraethylammonium hydroxide (25 wt %) were fully stirred until uniformly mixed to obtain a solid precursor. The solid precursor was then kneaded and extruded into strips to form strip particles with a diameter of 1.5 mm. The strip particles were placed in a stainless steel closed reactor containing a polytetrafluoroethylene liner and crystallized at 180° C. for 48 h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550° C. in an air atmosphere for 6 h to obtain a binderless hydrogen-type Mordenite molecular sieve shaped catalyst.

[0028] Example 3

[0029] 80 g of powdered silica gel, 8 g of pseudo-boehmite, 14 g of ammonium chloride and 78.4 g of tetraethylammonium hydroxide (25 wt %) were fully stirred until uniformly mixed to obtain a solid precursor. The solid precursor was then kneaded and extruded into strips to form strip particles with a diameter of 1.5 mm. The strip particles were placed in a stainless steel closed reactor lined with polytetrafluoroethylene and crystallized at 180° C. for 48 h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550° C. in an air atmosphere for 6 h to obtain a binderless hydrogen-type Mordenite molecular sieve shaped catalyst.

[0030] Example 4

[0031] 80 g of powdered silica gel, 8 g of pseudo-boehmite, 7 g of ammonium chloride and 78.4 g of tetraethylammonium hydroxide (50 wt %) were fully stirred until uniformly mixed to obtain a solid precursor. The solid precursor was then kneaded and extruded into strips to form strip particles with a diameter of 1.5 mm. The strip particles were placed in a stainless steel closed reactor lined with polytetrafluoroethylene and crystallized at 180° C. for 48 h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550° C. in an air atmosphere for 6 h to obtain a binder-free hydrogen-type Mordenite molecular sieve shaped catalyst.

[0032] Example 5

[0033] 80 g of silica sol (50 wt %), 40 g of powdered silica gel, 8 g of pseudo-boehmite, 7 g of ammonium chloride and 39.2 g of tetraethylammonium hydroxide (50 wt %) were fully stirred until uniformly mixed to obtain a solid precursor, which was then kneaded and extruded into strips to form strip-shaped particles with a diameter of 1.5 mm. The strips were placed in a stainless steel closed reactor lined with polytetrafluoroethylene and crystallized at 180° C. for 48 h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550° C. in an air atmosphere for 6 h to obtain a binderless hydrogen-type Mordenite molecular sieve shaped catalyst.

[0034] Example 6

[0035] 80 g of powdered silica gel, 28.4 g of aluminum nitrate, 7 g of ammonium chloride and 78.4 g of tetraethylammonium hydroxide (25 wt %) were fully stirred until uniformly mixed to obtain a solid precursor, which was then kneaded and extruded into strips to form strip-shaped particles with a diameter of 1.5 mm. The strips were placed in a stainless steel closed reactor lined with polytetrafluoroethylene and crystallized at 180° C. for 48 h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550° C. in an air atmosphere for 6 h to obtain a binder-free hydrogen-type Mordenite molecular sieve shaped catalyst.

[0036] Example 7

[0037] 80 g of powdered silica gel, 10.4 g of aluminum hydroxide, 7 g of ammonium chloride and 78.4 g of tetraethylammonium hydroxide (25 wt %) were fully stirred until uniformly mixed to obtain a solid precursor, which was then kneaded and extruded into strips to form strip-shaped particles with a diameter of 1.5 mm. The strips were placed in a stainless steel closed reactor lined with polytetrafluoroethylene and crystallized at 180° C. for 48 h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550° C. in an air atmosphere for 6 h to obtain a binder-free hydrogen-type Mordenite molecular sieve shaped catalyst.

[0038] Example 8

[0039] 80 g of powdered silica gel, 8 g of pseudo-boehmite, 13 g of ammonium bromide and 78.4 g of tetraethylammonium hydroxide (25 wt %) were fully stirred until uniformly mixed to obtain a solid precursor, which was then kneaded and extruded into strips to form strip-shaped particles with a diameter of 1.5 mm. The strips were placed in a stainless steel closed reactor lined with polytetrafluoroethylene and crystallized at 180° C. for 48 h. The product was then washed, filtered, dried, and calcined in a muffle furnace at 550° C. in an air atmosphere for 6 h to obtain a binder-free hydrogen-type Mordenite molecular sieve shaped catalyst.

Claims

1. A method for preparing a binderless hydrogen-type Mordenite molecular sieve catalyst, comprising the following steps: (a) mixing a silicon source, an aluminum source, an organic template (R1), an inorganic template (R2), and water in a certain proportion to obtain a solid precursor; (b) kneading and extruding the obtained solid precursor into strips, and then crystallizing it in a crystallization kettle at a crystallization temperature of 130 to 200° C. for a crystallization time of 12 to 72 hours; (c) After crystallization, the product is washed, filtered, dried, and then directly calcined at 450° C. to 600° C. for 1 h to 24 h to obtain a binder-free hydrogen-type Mordenite molecular sieve catalyst.

2. The method according to claim 1, characterized in that In step (a), the silicon source is at least one of silica sol, powdered silica gel, white carbon black, diatomaceous earth, kaolin, and bentonite.

3. The method according to claim 1, characterized in that In step (a), the aluminum source is at least one of pseudo-boehmite, aluminum hydroxide, aluminum nitrate, aluminum chloride, and aluminum sulfate.

4. The method according to claim 1, characterized in that In step (a), the organic template is at least one of tetraethylammonium hydroxide, tetraethylammonium fluoride, tetraethylammonium bromide and tetraethylammonium chloride.

5. The method according to claim 1, characterized in that In step (a), the inorganic template is at least one of ammonium chloride, ammonium fluoride, ammonium bromide and ammonia water.

6. The method according to claim 1, characterized in that In step (a), the ratio of the total mass of SiO2 in the silicon source to the mass of Al2O3 in the aluminum source, i.e., n(SiO2) / n(Al2O3), is greater than or equal to 20.

7. The method according to claim 1, characterized in that In step (a), the ratio of the total amount of SiO2 in the silicon source to the amount of the organic template, i.e., n(SiO2) / n(R1), is between 0.1 and 1.

0.

8. The method according to claim 1, characterized in that In step (a), the ratio of the total amount of SiO2 in the silicon source to the amount of the inorganic template, i.e., n(SiO2) / n(R2), is between 0.1 and 1.

0.

9. The method according to claim 1, characterized in that In step (a), the weight percentage of water in the solid precursor is between 10% and 40%.

10. Use of the binderless hydrogen-type Mordenite molecular sieve catalyst prepared according to the method according to any one of claims 1 to 9 in the dehydration of ethanol to ethylene reaction.

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