阅读说明：本技术 一种丝光沸石的制备方法及其制备的高硅铝比丝光沸石 (Preparation method of mordenite and mordenite with high silica-alumina ratio prepared by preparation method ) 是由 黄小东 李青山 彭卫平 于 2021-08-05 设计创作，主要内容包括：本申请公开了一种丝光沸石的制备方法及其制备的高硅铝比丝光沸石,涉及沸石材料技术领域。一种丝光沸石的制备方法,包括以下步骤：S1凝胶制备：取氢氧化钠,加水配制成氢氧化钠水溶液,搅拌,加入硅源和四乙基季铵盐,搅拌不少于120min,加入铝源,继续搅拌不少于60min,加入氢氧化钙,继续搅拌10-50min,制得凝胶；S2晶化：密封状态下将凝胶加热至170-200℃晶化不少于20hr,降温,回收晶化产物,制得高硅铝比丝光沸石。高硅铝比丝光沸石的制备方法具有可改善高硅铝比丝光沸石的结晶度的优点。(The application discloses a preparation method of mordenite and mordenite with a high silica-alumina ratio prepared by the same, and relates to the technical field of zeolite materials. A method for preparing mordenite, which comprises the following steps: s1 gel preparation: preparing sodium hydroxide aqueous solution with water, stirring, adding silicon source and tetraethyl quaternary ammonium salt, stirring for not less than 120min, adding aluminum source, stirring for not less than 60min, adding calcium hydroxide, and stirring for 10-50min to obtain gel; s2 crystallization: heating the gel to 170-200 ℃ under a sealed state for crystallization for not less than 20 hours, cooling, and recovering a crystallization product to prepare the mordenite with the high silica-alumina ratio. The preparation method of the mordenite with the high silica alumina ratio has the advantage of improving the crystallinity of the mordenite with the high silica alumina ratio.)

1. A method for preparing mordenite is characterized by comprising the following steps:

s1 gel preparation: preparing sodium hydroxide aqueous solution with water, stirring, adding silicon source and tetraethyl quaternary ammonium salt, stirring for not less than 120min, adding aluminum source, stirring for not less than 60min, adding calcium hydroxide, and stirring for 10-50min to obtain gel;

s2 crystallization: heating the gel to 170-200 ℃ under a sealed state, crystallizing for not less than 20 hours, cooling, and recovering crystallized products to obtain the mordenite with the high silica-alumina ratio;

silicon source of SiO₂Calculated by Na, calculated by R, calculated by tetraethyl quaternary ammonium salt, calculated by Ca, calculated by Al and calculated by aluminum source₂O₃The gel comprises the following components in parts by weight: SiO 2₂：Na：R：Ca：Al₂O₃: water = 1: (0.35-0.45): (0.05-0.5): (0.02-0.04): (0-0.03): (25-40).

2. A method for preparing mordenite according to claim 1, wherein the ratio of the amounts of each component in said gel is: SiO 2₂：Na：R：Ca：Al₂O₃: water = 1: (0.35-0.45): (0.25-0.3): (0.02-0.04): (0.005-0.02): (30-35).

3. A process for the preparation of mordenite as claimed in claim 1, wherein: the specific surface area of the calcium hydroxide is not less than 20 square meters per gram, and the particle size of the calcium hydroxide is not more than 25 mu m.

4. A process for the preparation of mordenite as claimed in claim 1, wherein: the silicon source is silica sol, water glass, solid silica gel or white carbon black.

5. A process for the preparation of mordenite as claimed in claim 1, wherein: the aluminum source is aluminum sulfate, aluminum nitrate, aluminum oxide or pseudo-boehmite.

6. A process for the preparation of mordenite as claimed in claim 1, wherein: the tetraethyl quaternary ammonium salt is tetraethyl ammonium bromide, tetraethyl ammonium chloride or tetraethyl ammonium iodide.

7. A process for the preparation of mordenite as claimed in claim 1, wherein: and S2, transferring the gel into a reaction kettle, sealing, vacuumizing to-0.095 MPa to-0.09 MPa, heating to 190-.

8. A method for preparing mordenite as claimed in claim 7, wherein said step S2 further comprises the steps of: filtering the crystallized product, washing the filter cake with water until the pH value is 6-8, and drying to obtain crystallized zeolite; roasting the crystallized zeolite at the temperature of 450-650 ℃ for not less than 180min to prepare the demoulded zeolite; adding 4-10 times of the weight of the demould zeolite into 5-15% ammonium exchange reagent aqueous solution, heating to 50-90 ℃, keeping the temperature and stirring for not less than 4h, filtering, drying, and roasting at 400-500 ℃ for not less than 120min to prepare the mordenite with high silica-alumina ratio.

9. A mordenite zeolite with high silica-alumina ratio, which is characterized in that: prepared by the process for the preparation of mordenite of any of claims 1 to 8.

Technical Field

The application relates to the technical field of zeolite materials, in particular to a preparation method of mordenite and mordenite with a high silica-alumina ratio prepared by the same.

Background

The mordenite is in an orthorhombic system, the crystals are needle-shaped or fibrous, and the aggregates are in a bundle shape or a radial shape. Mordenite has excellent heat resistance, acid resistance and steam resistance, is widely used as an adsorbent for separating gas or liquid mixtures, a catalyst for cracking hydrocarbon, hydrocracking, dewaxing, synthesizing dimethylamine, isomerizing alkane, alkylating polycyclic aromatic compounds and the like in industry, and can also be used as a drying agent and an adsorbent.

Mordenite has been widely used in the catalytic field, however, natural mordenite has a low silica-alumina ratio, and mordenite with a high silica-alumina ratio is required in the fields of toluene disproportionation catalysis and the like. The present commonly used mordenite synthesis process with high silica-alumina ratio uses organic ammonium as template agent, raises the silica-alumina ratio of the material, and synthesizes the mordenite with high silica-alumina ratio under the action of the template agent.

In view of the above-mentioned related art, the inventors thought that, due to the high silicon-aluminum ratio of the charge, especially when the silicon-aluminum ratio exceeds 25 (SiO)₂/Al₂O₃Mole ratio), the crystallization rate is slower, which affects the crystallinity of the mordenite with high silica-alumina ratio and affects the catalytic performance of the mordenite with high silica-alumina ratio.

Disclosure of Invention

In order to improve the crystallinity of the mordenite with the high silica-alumina ratio, the application provides a preparation method of the mordenite and the mordenite with the high silica-alumina ratio prepared by the preparation method.

In a first aspect, the present application provides a method for preparing mordenite, which adopts the following technical scheme:

a method for preparing mordenite, which comprises the following steps:

s1 gel preparation: preparing sodium hydroxide aqueous solution with water, stirring, adding silicon source and tetraethyl quaternary ammonium salt, stirring for not less than 120min, adding aluminum source, stirring for not less than 60min, adding calcium hydroxide, and stirring for 10-50min to obtain gel;

s2 crystallization: heating the gel to 170-200 ℃ under a sealed state, crystallizing for not less than 20 hours, cooling, and recovering crystallized products to obtain the mordenite with the high silica-alumina ratio;

silicon source of SiO₂Calculated by Na, calculated by R, calculated by tetraethyl quaternary ammonium salt, calculated by Ca, calculated by Al and calculated by aluminum source₂O₃The gel comprises the following components in parts by weight: SiO 2₂：Na：R：Ca：Al₂O₃: water 1: (0.35-0.45): (0.05-0.5): (0.02-0.04): (0-0.03): (25-40).

By adopting the technical scheme, the tetraethyl quaternary ammonium salt is used as the template agent, the composite inorganic alkali consisting of the sodium hydroxide and the calcium hydroxide is used as the alkali source, the sodium hydroxide can provide an alkaline environment and accelerate the crystallization rate on one hand, and on the other hand, sodium ions have a certain template effect, so that the dosage of the template agent can be properly reduced, and the cost is favorably reduced. The specific surface area of the calcium hydroxide is large, in the crystallization process, along with the increase of crystallization temperature, a silicon source is hydrolyzed and dissolved in water, the calcium hydroxide is slightly soluble in water, a small amount of calcium ions and silicic acid are combined to form calcium silicate with a large specific surface area, tetraethylammonium cations serving as a template agent are adsorbed on the surfaces of the calcium silicate and the calcium hydroxide with the large specific surface area, the decomposition of the template agent can be obviously reduced, the crystallization temperature is increased, and the crystallization rate is obviously accelerated. With the crystallization, a large amount of mordenite crystals with high specific surface area appear in the system, the mordenite crystals contain a large amount of microporous pore channels, calcium ions can be dissociated into the microporous pore channels of the mordenite crystals to promote the dissolution of calcium hydroxide and calcium silicate, and with the completion of the crystallization, the calcium ions are stored in the microporous pore channels of the mordenite crystals. The method uses tetraethyl quaternary ammonium salt as a template agent, uses composite inorganic base consisting of sodium hydroxide and calcium hydroxide as an alkali source, and is matched with higher crystallization temperature, so that the method can keep lower decomposition rate of the template agent while crystallizing at high temperature, can improve crystallization rate, improves product crystallinity, improves specific surface area of the product, and improves product performance.

Preferably, the ratio of the amount of each component in the gel is as follows: SiO 2₂：Na：R：Ca：Al₂O₃: water 1: (0.35-0.45): (0.25-0.3): (0.02-0.04): (0.005-0.02): (30-35).

By adopting the technical scheme, the better raw material feeding proportion is used, the generation of impurities is favorably reduced, and the catalytic performance of the product is favorably improved.

Preferably, the specific surface area of the calcium hydroxide is not less than 20 square meters per gram, and the particle size of the calcium hydroxide is not more than 25 μm.

By adopting the technical scheme, the calcium hydroxide with small particle size and high specific surface area is used, so that tetraethyl quaternary ammonium cations can be adsorbed on the surface of the calcium hydroxide in the temperature rising stage, calcium ions can be dissolved and dissociated into microporous pore channels of mordenite crystals in the crystal nucleus growth stage, the impurity content can be reduced, and the catalytic performance of the mordenite can be improved.

Preferably, the silicon source is silica sol, water glass, solid silica gel or white carbon black. Preferably, the silicon source is solid silica gel.

By adopting the technical scheme, a proper silicon source is selected, so that the nucleation rate is favorably controlled, and the product performance is favorably improved.

Preferably, the aluminum source is aluminum sulfate, aluminum nitrate, aluminum oxide or pseudo-boehmite. More preferably, the aluminum source is aluminum sulfate.

By adopting the technical scheme, a proper aluminum source is used to interact with the template agent, so that the crystallization is promoted, and the product crystallinity is improved.

Preferably, the tetraethyl quaternary ammonium salt is tetraethylammonium bromide, tetraethylammonium chloride or tetraethylammonium iodide. Preferably, the tetraethyl quaternary ammonium salt is tetraethylammonium chloride.

By adopting the technical scheme, the proper template agent is dissolved in the system in the crystallization process and interacts with aluminum ions to crystallize and form crystal nuclei, which is beneficial to improving the catalytic performance of zeolite products.

Preferably, the step S2 is to transfer the gel into a reaction kettle, seal, vacuumize to-0.095 MPa to-0.09 MPa, heat to 190-.

By adopting the technical scheme, the temperature is raised and the crystallization is started under the condition that the initial pressure is in a vacuum state, so that the nucleation rate is favorably adjusted, and the impurity generation under the high-temperature crystallization condition is favorably avoided by matching with the higher crystallization temperature, the product purity is favorably improved, and the product catalytic performance is favorably improved.

Preferably, the step S2 further includes the steps of: filtering the crystallized product, washing the filter cake with water until the pH value is 6-8, and drying to obtain crystallized zeolite; roasting the crystallized zeolite at the temperature of 450-650 ℃ for not less than 180min to prepare the demoulded zeolite; adding 4-10 times of the weight of the demould zeolite into 5-15% ammonium exchange reagent aqueous solution, heating to 50-90 ℃, keeping the temperature and stirring for not less than 4h, filtering, drying, and roasting at 400-500 ℃ for not less than 120min to prepare the mordenite with high silica-alumina ratio. Preferably, the ammonium exchange reagent is ammonium chloride, ammonium nitrate or ammonium sulfate.

By adopting the technical scheme, a proper zeolite crystallization product recovery process is selected, the template agent is removed by roasting, sodium ions in zeolite pore channels are exchanged into ammonium ions by ammonium exchange, and the ammonium ions are decomposed to form hydrogen type zeolite by secondary roasting, so that the method is favorable for improving the hydrophobicity of the mordenite and improving the purification efficiency of the mordenite for the purification treatment of the coke oven gas.

In a second aspect, the present application provides a mordenite with a high silica-alumina ratio, which adopts the following technical scheme:

a mordenite with high silica-alumina ratio is prepared by the preparation method of the mordenite.

By adopting the technical scheme, the method disclosed by the application is used for preparing the mordenite with the high silica-alumina ratio, so that the silica-alumina ratio of the mordenite is improved, the higher specific surface area and the higher crystallinity are kept, the crystallinity of the mordenite with the high silica-alumina ratio is improved, and the catalytic performance of the mordenite with the high silica-alumina ratio is improved.

In summary, the present application includes at least one of the following beneficial technical effects:

1. the method takes tetraethyl quaternary ammonium salt as a template agent, takes a composite inorganic base of calcium hydroxide and sodium hydroxide as an alkali source, and carries out crystallization under the vacuum condition of high temperature and initial pressure, so that the crystallization temperature is increased, the decomposition of the template agent is reduced while the high-temperature crystallization is carried out, the crystallization rate is increased, the crystallinity of the mordenite with high silica-alumina ratio is increased, the specific surface area of the mordenite with high silica-alumina ratio is increased, and the improvement of the catalytic performance of the mordenite with high silica-alumina ratio is facilitated;

2. the method helps to improve the crystallinity of the mordenite with the high silica-alumina ratio by controlling the specific surface area and the particle size of the calcium hydroxide.

Drawings

Figure 1 is an XRD pattern of a sample of high silica to alumina ratio mordenite prepared in example 1.

Detailed Description

The inventor finds that in the long-term research and development process, in order to improve the silicon-aluminum ratio in the process of synthesizing the mordenite with the high silicon-aluminum ratio, the charging silicon-aluminum ratio needs to be increased, namely the dosage of a silicon source is increased, and when the dosage of the silicon source is increased, OH is added^-/SiO₂The reduction and the reduction of the crystallization speed affect the crystallinity of the mordenite with high silica-alumina ratio and reduce the specific surface area. Methods for increasing the crystallinity of the mordenite product are: the alkali dosage is increased and the crystallization temperature is increased; but increasing the amount of alkali reduces the silicon-aluminum ratio of the product; after the crystallization temperature is increased, the tetraethyl quaternary ammonium salt template agent is easily decomposed, so that mixed crystals appear in the product, and the specific surface area is reduced. Therefore, the crystallinity of the mordenite with high silica-alumina ratio prepared by the conventional mordenite with high silica-alumina ratio synthesis process is lower. Based on the above technical background, the present application provides a technical solution for improving the crystallinity of mordenite with high silica-alumina ratio, which is specifically described in the following detailed description.

The coke oven gas contains substances such as sulfide, nitrogen-containing compounds, naphthalene and the like, and causes certain corrosion to equipment, and the coke oven gas is generally required to be subjected to purification pretreatment to remove impurities such as sulfide, nitrogen-containing compounds, naphthalene and the like. The mordenite with the high silica-alumina ratio prepared by the method has excellent performance in the purification pretreatment of the coke oven gas and has a relatively high application prospect.

The silicon source may be solid silica or solid silica gel, or may be liquid silica sol (for example, a 40% silica sol aqueous solution may be used) or water glass. The water in the gel component proportion comprises the sum of the water for dissolving the sodium hydroxide and the water contained in the silicon source; such as SiO₂/H₂O ═ 1:35 means that the molar ratio of silica contained in the silicon source to the total of water used to dissolve sodium hydroxide and water contained in the silicon source was 1: 35.

The calcium hydroxide used in the following examples had a specific surface area of 27.6 square meters per gram, and was sieved through a sieve having 25 μm pore size, using calcium hydroxide powder having a particle size of less than 25 μm.

The present application is described in further detail below with reference to the attached drawings.

Examples

Example 1: the synthesis process of mordenite with high silica-alumina ratio comprises the following steps:

s1 gel preparation: preparing 21g of sodium hydroxide (analytically pure), adding 945g of water to prepare a sodium hydroxide aqueous solution, stirring at the rotating speed of 200 revolutions per minute, adding 225g of a liquid silica sol aqueous solution (the mass concentration of silicon dioxide is 40%, LS50C40, Shandong Baite new material), adding 124.3g of tetraethylammonium chloride (industrial pure, Kent catalysis), continuing stirring for 120min, adding 30g of aluminum sulfate (aluminum sulfate octadecahydrate, analytically pure, molecular weight of 666.4), continuing stirring for 60min, adding 2.22g of calcium hydroxide powder, continuing stirring for 30min, and preparing the gel.

S2 crystallization: transferring the gel into a 2L high-temperature high-pressure reaction kettle, sealing, stirring at a rotating speed of 80 r/min, heating to 180 ℃ at a heating rate of 30 ℃/h for crystallization for 40h, and cooling to room temperature to obtain a crystallized product.

And (3) recovering a crystallization product: filtering the crystallized product, washing the filter cake with water to pH 7, drying at 100 deg.C for 240min to obtain crystalline zeolite, and sending the crystalline zeolite to sample for XRD detection to obtain mordenite crystal phase structure shown in figure 1; roasting the crystallized zeolite at 550 ℃ for 240min to obtain demoulded zeolite; adding 6 times of the weight of the demoulded zeolite into 10 mass percent of ammonium chloride aqueous solution, heating to 70 ℃, keeping the temperature and stirring for 4 hours, filtering, drying at 100 ℃ for 100 minutes, and roasting at 500 ℃ for 120 minutes to obtain the mordenite with the high silica-alumina ratio.

Example 2

Example 2 differs from example 1 in that example 2 used a solid chromatographic silica gel (90.5% silica solids, CT-199, changtai micro nano chemical plant, shou, shandong) in place of the liquid aqueous silica sol solution, the amount of chromatographic silica gel was 99.4g, and the amount of water used to dissolve the sodium hydroxide was increased from 945g to 1070.5g, all of which remained the same as example 1.

Example 3

Example 3 differs from example 2 in that example 3 replaces aluminum sulfate with an equivalent amount of aluminum nitrate (aluminum nitrate nonahydrate, analytically pure) and otherwise remains the same as example 2.

Example 4

Example 4 differs from example 2 in that example 4 increased the crystallization temperature to 195 deg.c, otherwise consistent with example 2.

Example 5

Example 5 is different from example 2 in that the gel in step S2 of example 5 is transferred to a reaction kettle, vacuum is applied to-0.092 MPa, sealing is applied, and crystallization is performed by heating, all the other steps being the same as example 2.

Example 6

Example 6 differs from example 5 in that example 6 increased the crystallization temperature to 195 deg.c, otherwise consistent with example 5.

Examples 7 to 12

Examples 7 to 12 are different from example 6 in the addition amount of each raw material of examples 7 to 12 is different from example 6, and the addition amount of each raw material of examples 7 to 12 is shown in Table 1.

TABLE 1 addition amount of each raw material of examples 7 to 12

Examples 13 to 16

Examples 13-16 differ from example 11 in that the process parameters for each step of examples 13-16 are different and all of them are identical to example 11, and the process parameters for each step of examples 13-16 are shown in Table 2.

TABLE 2 parameters in the various steps of examples 13-16

Comparative example

Comparative example 1

Comparative example 1 differs from example 1 in that comparative example 1 does not have calcium hydroxide added, and otherwise remains the same as example 1.

Comparative example 2

Comparative example 2 differs from example 1 in that comparative example 2 has a crystallization temperature of 160 c, otherwise it is identical to example 1.

Comparative example 3

Comparative example 3 differs from comparative example 1 in that comparative example 3 has a crystallization temperature of 160 c, and otherwise remains the same as comparative example 1.

Performance detection

1. Specific surface area: the specific surface area detection is carried out by adopting a full-automatic specific surface and pore analyzer with the model Tristar II 3020, and the result is shown in Table 3;

2. high-temperature thermal stability: the product is aged at the high temperature of 900 ℃ for 6h, the specific surface area before and after the high-temperature aging treatment is tested, the specific surface area loss rate of the product after the high-temperature aging treatment is calculated, and the result is shown in table 3.

TABLE 3 comparison table of different product performance test results

Compared with example 1, the comparative example 3 does not add calcium hydroxide, and the crystallization is carried out at a lower temperature, so that the specific surface area of the prepared product is not high, and the high-temperature resistance and thermal stability are not good. Comparative example 2 is added with calcium hydroxide, but crystallization is carried out under low temperature condition, and the prepared product has low specific surface area and poor thermal stability; comparative example 1 was crystallized at high temperature, but the specific surface area of the product was still not high without the addition of calcium hydroxide. Comparing the experimental results of the example 1 and the comparative examples 1 to 3, in the example 1, a small amount of calcium hydroxide is added in the synthesis process of the mordenite with the high silica alumina ratio, the crystallization temperature is increased, and the calcium hydroxide and the crystallization temperature act together, so that the specific surface area of the prepared product is obviously increased, the crystallinity is higher, the thermal stability is better, and the popularization and the use of the mordenite with the high silica alumina ratio are facilitated.

Comparative example 1 and example 2 the product properties obtained with different silicon sources were not very different. In example 3, product properties were made with a different aluminum source than in example 1 with little difference. Example 4 further increases the crystallization temperature and produces a product with a reduced specific surface area. Example 5 crystallization was performed under vacuum at the initial pressure based on example 2, and the specific surface area of the obtained product was not greatly changed. Example 6 crystallization was carried out under vacuum conditions at the initial pressure, and the crystallization temperature was increased, and the combined action of both increased the specific surface area of the product, which was helpful to improve the catalytic performance of mordenite with high silica-alumina ratio.

Compared with example 6, examples 7-10 are different templating agent dosage comparison experiments, and the specific surface area of the prepared product is increased with the increase of the templating agent dosage, but certainly, the specific surface area of the prepared product is not changed greatly after the templating agent dosage is too large, and a proper templating agent dosage range is needed. Compared with example 6, examples 11-12 adopt better raw material feeding proportion, and the prepared product has better heat resistance stability.

Compared with example 11, the process parameters of the steps of examples 13-16 are changed, wherein the crystallization temperature of example 13 is lower, the specific surface area of the prepared product is lower, and the heat resistance stability is poor. The examples 14 to 16 select proper process parameters, and the prepared product has higher specific surface area and better heat-resistant stability, thereby being beneficial to the market popularization of the product.

The embodiments of the present invention are preferred embodiments of the present application, and the scope of protection of the present application is not limited by the embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.