A method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves

Abstract

This invention discloses a method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves, belonging to the field of molecular sieve preparation technology. This method uses waste Y molecular sieves as a direct silica-alumina source, adds suitable template agents and alkali sources, strictly controls the pH of the reaction solution, and manages the reaction conditions to successfully convert waste Y molecular sieves into mordenite zeolite molecular sieves with a hierarchical porous structure. This achieves the resource utilization of waste Y molecular sieves, reduces production costs, and minimizes environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve catalyst preparation technology, specifically relating to a method for preparing mordenite molecular sieves using waste Y molecular sieves as raw materials through a specific conversion process. Background Technology

[0002] Y-type molecular sieves and mordenite zeolite molecular sieves are two types of molecular sieves widely used in the oil refining and petrochemical industries. Y-type molecular sieves consist of octahedral zeolite cages formed by β-cages and hexagonal prism cages. Their basic framework structure is composed of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra. They possess large supercage cavities and a three-dimensional twelve-ring channel system, and are widely used in hydrogenation catalysis, oil cracking, FCC catalysts, high-efficiency adsorption and separation, and environmental protection. However, with prolonged use, Y-type molecular sieves may deactivate due to carbon buildup, poisoning, and other reasons, resulting in a large amount of waste Y-type molecular sieves.

[0003] Mordenite zeolite possesses excellent thermal and hydrothermal stability, and its unique pore structure endows it with superior catalytic and adsorption properties. Mordenite zeolite is mainly used in heterogeneous catalysis, such as in toluene disproportionation, catalytic cracking, hydrocracking, alkylation of olefins, alcohol amination, and aromatic alkylation. It is also commonly used as an adsorbent for separating gas or liquid mixtures. Therefore, converting waste Y-molecule sieves into mordenite zeolite not only solves the problem of industrial waste catalyst disposal but also enables resource reuse, possessing significant economic and social value.

[0004] CN104276586B discloses a method for preparing mordenite zeolite, but the synthesis is too heavy and requires additional natural aluminosilicate minerals, which also need to be activated. CN109485064B discloses a method for preparing mordenite zeolite from spent MTP catalyst and the application of spent MTP catalyst. It uses spent MTP molecular sieve catalyst (SiO2 / Al2O3=4-14) as raw material, and removes carbon deposits from the catalyst before calcination for the preparation of mordenite zeolite. The MTP catalyst used in the MTP process is mainly the ZSM-5 molecular sieve active component containing silicon and aluminum species. ZSM-5 molecular sieve is composed of straight channels composed of ten-membered rings and helical channels composed of eight-membered rings. Y-zeolite molecular sieve (also known as FAU-type zeolite) is a zeolite with a three-dimensional twelve-membered ring channel structure, widely used in the petrochemical field, such as as a catalyst and catalyst support in cracking, isomerization, and hydrogenation reactions. The industrial use of Y-zeolite molecular sieve catalysts is enormous, generating a large amount of spent Y-zeolite molecular sieve catalysts annually. The treatment and reuse of waste Y-type zeolite molecular sieves is an important environmental issue. Currently, there are no publicly reported methods for converting waste Y-type molecular sieve catalysts into mordenite zeolite. Therefore, developing a method to directly prepare mordenite molecular sieves from waste Y-type molecular sieves would not only help realize the resource utilization of waste but also reduce production costs and environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing mordenite molecular sieves from waste Y molecular sieves. This method uses waste Y molecular sieves as raw materials and prepares mordenite molecular sieves with multi-level porous structures through a specific conversion process.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves, comprising the following steps:

[0008] a) Pretreatment of waste Y molecular sieves;

[0009] b) The pretreated waste Y molecular sieve was mixed with an alkali source and deionized water and stirred; then a template agent was added, and the mixture was stirred at a specific temperature to obtain a gel solution.

[0010] c) The above gel solution was placed in a sealed container for hydrothermal crystallization reaction to obtain Na-type mordenite molecular sieve.

[0011] d) The Na-type mordenite molecular sieve is washed, dried, ion-exchanged, and calcined to obtain the final product, mordenite molecular sieve.

[0012] Preferably, the method for pretreating the waste Y molecular sieve in step a) is as follows: grinding the waste Y molecular sieve to make the crystal particle size <10μm, and the silicon-to-aluminum ratio (SiO2 / Al2O3) of the waste Y molecular sieve is 5~100.

[0013] Preferably, the template agent in step (b) is one or a combination of piperazine, tetraethylammonium hydroxide, glycerol, ethylene glycol and polyethylene glycol.

[0014] Preferably, the alkali source in step (b) is sodium hydroxide or potassium hydroxide.

[0015] Preferably, in step (b), the pH of the gel solution is 13-14, and the reaction temperature is 40-60 °C with stirring for 1-4 h.

[0016] Preferably, in step (b), the molar ratio of template agent to waste Y molecular sieve is 1:2~20, and the molar ratio of waste Y molecular sieve to deionized water is 1:20~40.

[0017] Preferably, the hydrothermal crystallization reaction temperature is 140-220 °C, and the crystallization time is 12-72 h.

[0018] Preferably, the calcination temperature in step d) is 500-550 ℃ and the calcination time is 3-6 h.

[0019] The beneficial effects of this invention are:

[0020] (1) This invention realizes the reuse of waste Y molecular sieves without the need to add new silicon and aluminum sources, reduces the preparation cost of mordenite zeolite molecular sieves and the treatment cost of waste Y molecular sieves, realizes the resource utilization of waste, and reduces environmental pollution.

[0021] (2) The preparation method of the present invention is simple, low cost and high conversion efficiency, and the prepared mordenite molecular sieve has good catalytic performance, realizing the conversion of low-value waste catalyst into high-value mordenite molecular sieve, with significant social and economic benefits. Attached Figure Description

[0022] Figure 1 The XRD pattern of the mordenite molecular sieve prepared in Example 1 is shown.

[0023] Figure 2 The image shows a SEM image of the mordenite molecular sieve prepared in Example 1. Detailed Implementation

[0024] The following embodiments are intended only to illustrate preferred technical solutions of the present invention and are not intended to limit the scope of the invention in any way. For those skilled in the art, the present invention possesses a high degree of flexibility and variability, allowing for various adjustments and modifications. The relevant content of the present invention will be further illustrated below through specific implementation examples.

[0025] Example 1

[0026] A method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves, comprising the following steps:

[0027] a) Grind the waste Y molecular sieve to make the crystal particle size <10μm, wherein the silicon-to-aluminum ratio (SiO2 / Al2O3) of the waste Y molecular sieve is 5;

[0028] b) Weigh 0.40 g of NaOH and 12 g of H2O, stir to dissolve; add 2 g of ground waste Y molecular sieve and stir to mix, then add 3.56 g of template agent tetraethylammonium hydroxide, age at 60 ℃ for 4 h and adjust the pH of the mixture to about 13;

[0029] c) The above gel solution was transferred to an autoclave and crystallized at 160 °C for 48 h to obtain Na-type mordenite;

[0030] d) The above product was washed, dried, calcined at 550 °C for 5 h and subjected to ammonium ion exchange (80 °C-5 h) to obtain the product H-type mordenite zeolite.

[0031] Example 2

[0032] A method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves, comprising the following steps:

[0033] a) Grind the waste Y molecular sieve to make the crystal particle size <10μm, wherein the silicon-to-aluminum ratio (SiO2 / Al2O3) of the waste Y molecular sieve is 40;

[0034] b) Weigh 2 g of ground waste Y molecular sieve, 0.50 g of NaOH and 13 g of H2O, and stir for 30 min; then add 2 g of ethylene glycol and 1.56 g of tetraethylammonium hydroxide; use sodium hydroxide to adjust the pH of the gel system to about 14 to obtain the gel solution.

[0035] c) The gel solution was placed in a high-pressure reactor and crystallized at 180 °C for 36 h to obtain Na-type mordenite;

[0036] d) The above product was washed, dried, calcined (550 ℃-5 h) and subjected to ammonium ion exchange (80 ℃-5 h) to obtain the product H-type mordenite zeolite.

[0037] Example 3

[0038] A method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves, comprising the following steps:

[0039] a) Grind the waste Y molecular sieve to make the crystal particle size <10μm, wherein the silicon-to-aluminum ratio (SiO2 / Al2O3) of the waste Y molecular sieve is 100;

[0040] b) Weigh 2.42 g of the ground waste Y molecular sieve and add it to an alkaline aqueous solution composed of 0.24 g KOH and 12 g water. Stir vigorously for 30 min. Then add 2.55 g tetraethylammonium hydroxide and 1.25 g polyethylene glycol. Stir at 60 °C for 4 h and adjust the pH of the mixture solution to about 13.

[0041] c) The reaction mixture was then transferred to a reaction vessel and crystallized at 210 °C for 72 h;

[0042] d) Filter the obtained solid, wash it until the pH is between 7 and 8, and dry it overnight; calcine the obtained powder at 550 °C for 5 h to exchange ammonium ions, and H-type mordenite zeolite molecular sieve can be obtained.

[0043] After testing, the crystal phase of the sample prepared by the method of this invention is consistent with that of the mordenite molecular sieve obtained by hydrothermal synthesis in the prior art (e.g., Figure 1 (As shown).

[0044] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves, characterized in that, It includes the following steps: a) Pretreatment of waste Y molecular sieve: Grind the waste Y molecular sieve to make the crystal particle size <10 μm, and the silicon-to-aluminum ratio (SiO2 / Al2O3) of the waste Y molecular sieve is 5~100; b) The pretreated waste Y molecular sieve is mixed with an alkaline source and deionized water and stirred; then the template agent is added, and the mixture is stirred at 40-60℃ for 1-4 h to obtain a gel solution; the pH of the gel solution is 13-14; the molar ratio of the template agent to the waste Y molecular sieve is 1:2~20, and the molar ratio of the waste Y molecular sieve to the deionized water is 1:20~40; c) The above gel solution is placed in a sealed container for hydrothermal crystallization reaction to obtain Na or K type mordenite molecular sieve; d) The Na or K type mordenite molecular sieve is washed, dried, ion-exchanged and calcined to obtain the final product, mordenite molecular sieve. The template agent is one or a combination of piperazine, tetraethylammonium hydroxide, glycerin, ethylene glycol, and polyethylene glycol; In step b), the alkali source is sodium hydroxide or potassium hydroxide.

2. The method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves according to claim 1, characterized in that, The hydrothermal crystallization reaction temperature is 140-220 ℃, and the crystallization time is 12-72 h.

3. The method for preparing mordenite zeolite molecular sieves from waste Y molecular sieves according to claim 1, characterized in that, In step d), the calcination temperature is 500-550 ℃ and the calcination time is 3-6 h.

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