阅读说明：本技术 一种具有短轴形貌的mtt沸石分子筛的合成方法 (Synthesis method of MTT zeolite molecular sieve with short shaft morphology ) 是由 谢彬 付凯妹 王嘉祎 张志华 张瑀健 余颖龙 王燕 王新苗 王延飞 张占全 张雅 于 2018-07-06 设计创作，主要内容包括：本发明涉及一种具有短轴形貌MTT沸石分子筛的合成方法,包含以下步骤：将氧化硅源、氧化铝源、碱金属源MeOH、有机模板剂R和去离子水混合均匀,然后加入MTT分子筛晶种,形成合成凝胶,MTT晶种加入量占凝胶总质量的1-5％,所述有机模板剂R为二甲胺和异丙胺中的一种或两种；密封条件下,将所述合成凝胶在搅拌速率200-300rpm,升温速率5-20℃/min下,达到140-180℃,恒温24-48小时,然后经冷却,过滤,烘干,即可得到轴径长度比小于10的MTT沸石分子筛。与现有合成具有短轴形貌的MTT分子筛方法相比,不需要使用辅助模板剂,并缩短了反应时间,降低了合成成本。(The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short shaft morphology, which comprises the following steps: uniformly mixing a silicon oxide source, an alumina source, an alkali metal source MeOH, an organic template agent R and deionized water, and then adding MTT molecular sieve seed crystals to form a synthetic gel, wherein the addition amount of the MTT seed crystals accounts for 1-5% of the total mass of the gel, and the organic template agent R is one or two of dimethylamine and isopropylamine; under the sealing condition, the synthetic gel is kept at the constant temperature of 24-48 hours at the stirring speed of 200-300rpm and the heating rate of 5-20 ℃/min to reach 140-180 ℃, and then the MTT zeolite molecular sieve with the axial-diameter length ratio of less than 10 can be obtained through cooling, filtering and drying. Compared with the existing method for synthesizing the MTT molecular sieve with the short shaft morphology, the method does not need to use an auxiliary template agent, shortens the reaction time and reduces the synthesis cost.)

1. A method for synthesizing an MTT zeolite molecular sieve with a short-axis morphology is characterized by comprising the following steps:

s1, uniformly mixing a silicon oxide source, an aluminum oxide source, an alkali metal source MeOH, an organic template agent R and deionized water, adding MTT molecular sieve seed crystal to form synthetic gel, and synthesizing SiO in the gel₂/Al₂O₃＝30～150，R/SiO₂＝0.3～0.9；MeOH/SiO₂＝0.3～0.9，H₂O/SiO₂30-50 percent of MTT crystal seed, wherein the addition amount of the MTT crystal seed accounts for 1-5 percent of the total mass of the gel, and the organic template R is one or more of dimethylamine or isopropylamine;

s2, under the sealing condition, keeping the temperature of the synthesized gel at 140-180 ℃ at the stirring speed of 200-300rpm and the heating speed of 5-20 ℃/min for 24-48 hours, and then cooling, filtering and drying the gel to obtain the MTT zeolite molecular sieve with the axial-diameter length ratio of less than 10.

2. The method for synthesizing the MTT zeolite molecular sieve with the short-axis morphology as claimed in claim 1, wherein the synthesized MTT zeolite molecular sieve has a silica-alumina ratio of 30-60, a crystallization temperature of 160-170 ℃, and an axial-diameter length ratio of less than 5.

3. The method for synthesizing the MTT zeolite molecular sieve with the short-axis morphology as claimed in claim 1, wherein the silica source is one or more of silica sol, silica gel, white carbon black, coarse silica gel and esters containing silica.

4. The method for synthesizing the MTT zeolite molecular sieve with short axis morphology as claimed in claim 1, wherein the alumina source is one or more of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum hydroxide and pseudo-boehmite.

5. The method of synthesizing the MTT zeolite molecular sieve with short axis morphology according to claim 1, wherein the alkali metal source MeOH is NaOH and/or KOH.

6. The method for synthesizing the MTT zeolite molecular sieve with short shaft morphology according to claim 1, wherein the MTT molecular sieve seed crystal is one or more of ZSM-23, SSZ-32, KZ-1, EU-13 and ISI-6.

7. The method for synthesizing the MTT zeolite molecular sieve with short shaft morphology according to claim 1, wherein the MTT seed crystal is added in an amount of 1.5-4.5% of the total mass of the gel.

8. The method for synthesizing the MTT zeolite molecular sieve with short axis morphology according to claim 1, wherein the temperature rise rate of the synthesized gel is 10-20 ℃/min.

Technical Field

The invention belongs to the field of catalysts, and particularly relates to a synthesis method of an MTT zeolite molecular sieve with a short-axis morphology.

Background

MTT zeolite molecular sieves with one-dimensional 10-ring oval mesopore structures were first reported in 1978 by Mobil corporation patent publication US4076842 with pore sizes of about 0.45 x 0.52 nm. The catalyst has good selectivity in olefin oligomerization, olefin disproportionation, aromatic alkylation and other aspects due to the particularity of the pore structure and the adjustable modification of the framework calculation strength, so that the catalyst is used as an important hydrocarbon selective isomerization catalyst carrier and widely applied to reaction processes of petroleum refining, fine chemical engineering and the like.

Of zeolites, usually MTTDuring the synthesis process, SiO₂、Al₂O₃Mixing NaOH, an organic template agent and water, and carrying out hydrothermal reaction in a high-pressure reaction kettle at 90-200 ℃ for 3-7 days. For example, in US4076842, US4490342 and US5405596, different templates, such as pyrrolidine, N-trimethyl heptamine and N, N-trimethyl dodecylamine, are used as templates to synthesize the MTT structure zeolite molecular sieve, but the above patents do not make special requirements on the crystal morphology of the MTT molecular sieve. Chinese patent CN101214971A describes a method for synthesizing a molecular sieve with a nano MTT structure. However, it is only specified that the size range of the radial dimension of the molecular sieve is below 100nm, and no limitation is made on the axial dimension.

The MTT zeolite molecular sieve is a needle-rod-shaped crystal with a one-dimensional pore channel structure. The channels run in their axial direction and the array of orifices runs in the crystal interface or radial direction. It is well known that hydrocarbon isomerization reactivity is primarily affected by pore restriction and diffusion. Longer pore path trend can increase the diffusion resistance of the product and reduce the catalytic performance of the product. Therefore, the axial length ratio and the radial length ratio of the MTT zeolite molecular sieve crystal are effectively reduced, and the catalytic activity of the MTT zeolite molecular sieve crystal is improved. By using (CH) in CN102256704A and US7390763 respectively₃)₂N⁺CH₂CH₂CH₂N⁺(CH₃)₂CH₂CH₂CH₂N⁺(CH₃)₃Triquat-7 and N-lower alkyl-N' -isopropyl imidazolium cation are used as auxiliary template agents for short, and form co-template agents with isobutylamine, neopentylamine, monoethylamine and the like, and the nano MTT zeolite molecular sieve with the short-axis structure is synthesized through long-time (more than 72 hours) hydrothermal crystallization at a certain temperature. In the synthesis process, an auxiliary template agent is required to be used, and the nano MTT zeolite molecular sieve with the short-axis structure is synthesized through long-time (more than 72 hours) hydrothermal crystallization at a certain temperature. The auxiliary template agent is expensive and not easy to obtain, and reduces the value of the molecular sieve with special morphology in wide application.

Disclosure of Invention

The invention aims to provide a synthesis method of an MTT zeolite molecular sieve with a short-axis morphology, which aims to overcome the defect that an expensive auxiliary template agent is required to be used when the MTT zeolite molecular sieve with the short-axis morphology is prepared in the prior art.

In order to solve the above problems, the present invention provides a method for synthesizing a MTT zeolite molecular sieve having a short-axis morphology, comprising the following steps:

s1, uniformly mixing a silicon oxide source, an aluminum oxide source, an alkali metal source MeOH, an organic template agent R and deionized water, adding MTT molecular sieve seed crystal to form synthetic gel, and synthesizing SiO in the gel₂/Al₂O₃＝30～150，R/SiO₂＝0.3～0.9；MeOH/SiO₂＝0.3～0.9，H₂O/SiO₂30-50 percent of MTT crystal seed, wherein the addition amount of the MTT crystal seed accounts for 1-5 percent of the total mass of the gel, and the organic template agent R is one or more of dimethylamine, isopropylamine and N, N-dimethyldiamide;

s2, under the sealing condition, keeping the temperature of the synthesized gel at 140-180 ℃ at the stirring speed of 300rpm and the heating speed of 5-20 ℃/min for 24-48 hours, and then cooling, filtering and drying to obtain the MTT zeolite molecular sieve with the axial-diameter length ratio of less than 10.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology, disclosed by the invention, has the advantages that the silicon-aluminum ratio of the synthesized MTT zeolite molecular sieve is 30-60, the crystallization temperature is 160-170 ℃, and the axial-diameter length ratio is less than 5.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short shaft morphology, wherein a silicon oxide source is one or more of silica sol, silica gel, white carbon black, coarse silica gel and esters containing silicon oxide components. The ester containing the silicon oxide component may be methyl orthosilicate or ethyl orthosilicate, but is not limited thereto.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short shaft shape, wherein an alumina source is one or more of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum hydroxide and pseudo-boehmite.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short-axis morphology, wherein an alkali metal source MeOH is NaOH and/or KOH.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short shaft morphology, wherein an MTT molecular sieve crystal seed is a crystal with an MTT molecular sieve framework structure, and specifically can be one or more of ZSM-23, SSZ-32, KZ-1, EU-13 and ISI-6, but not limited thereto, and the crystal seed can be a crystal seed without an organic template or a crystal seed containing the organic template.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology comprises the following step of adding MTT crystal seeds in an amount of 1.5-4.5% of the total mass of the gel, and preferably, adding the MTT crystal seeds in an amount of 2-3% of the total mass of the gel.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology, disclosed by the invention, is characterized in that the stirring speed of the synthesized gel is 200-300 rpm.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology, disclosed by the invention, is characterized in that the temperature rise rate of the synthesized gel is 10-20 ℃/min.

The invention realizes the purpose of synthesizing the MTT zeolite molecular sieve with the short-axis crystal morphology under the relatively economic condition by simultaneously controlling the stirring speed and the heating rate and selecting specific crystal seeds. In the process, the proper stirring speed is controlled, the exchange process of substances in a reaction system is increased, the local concentration difference is reduced, and the reaction is rapidly carried out; meanwhile, the reaction rate is accelerated by utilizing higher temperature rise rate, the crystallization process can be completed in a short time, and the grain size of the molecular sieve is reduced; and proper seed crystal is selected as nucleating agent, which can provide crystal nucleus for the system, so that the reaction can be directly carried out; if no seed crystal exists, the growth of the molecular sieve needs a nucleation induction period of 1-2 days, and the nucleation amount is low, so that the crystal grows.

The invention has the beneficial effects that:

the method of the invention adopts a single cheap template agent, seed crystal auxiliary nucleation and rapid temperature rise method to complete the crystallization process in a short time. The MTT zeolite molecular sieve with the short-axis crystal morphology with the axial-to-diameter ratio of less than 10 and even less than 5 is formed.

Drawings

FIG. 1 is an X-ray diffraction (hereinafter, referred to as XRD) spectrum of the MTT zeolite molecular sieve synthesized in example 1 of the present invention and having an axial-to-diameter ratio of less than 10.

FIG. 2 is a scanning electron microscope (hereinafter referred to as SEM) picture of the MTT zeolite molecular sieve synthesized in example 1 of the present invention and having an axial-to-diameter ratio of less than 10.

FIG. 3 is an XRD spectrum of the molecular sieve of MTT zeolite with the axial-to-diameter ratio less than 5 synthesized in example 2 of the invention.

FIG. 4 is SEM picture of MTT zeolite molecular sieve synthesized in example 2 of the present invention and having an axial to diameter ratio of less than 5.

FIG. 5 is an XRD spectrum of the MTT zeolite molecular sieve of comparative example 1 of the present invention with the synthetic axial-to-diameter ratio of more than 20.

FIG. 6 is an SEM image of a synthesized MTT zeolite molecular sieve with an axial-to-diameter ratio of more than 20 in comparative example 1 of the invention.

FIG. 7 is an XRD spectrum of the MTT zeolite molecular sieve of comparative example 2 of the present invention with the synthetic axial-to-diameter ratio of more than 15.

FIG. 8 is an SEM image of a synthesized MTT zeolite molecular sieve of comparative example 2 of the present invention with an axial-to-diameter ratio of more than 15.

Detailed Description

The present invention is described in further detail below by way of examples, which should not be construed as limiting the invention thereto.

A method for synthesizing an MTT zeolite molecular sieve with short-axis morphology comprises the following steps:

s1, uniformly mixing a silicon oxide source, an aluminum oxide source, an alkali metal source MeOH, an organic template agent R and deionized water, adding MTT molecular sieve seed crystal to form synthetic gel, and synthesizing SiO in the gel₂/Al₂O₃＝30～150，R/SiO₂＝0.3～0.9；MeOH/SiO₂＝0.3～0.9，H₂O/SiO₂30-50 percent of MTT crystal seed, wherein the addition amount of the MTT crystal seed accounts for 1-5 percent of the total mass of the gel, and the organic template agent R is one or more of dimethylamine, isopropylamine and N, N-dimethyldiamide;

s2, under the sealing condition, keeping the temperature of the synthesized gel at 140-180 ℃ at the stirring speed of 300rpm and the heating speed of 5-20 ℃/min for 24-48 hours, and then cooling, filtering and drying to obtain the MTT zeolite molecular sieve with the axial-diameter length ratio of less than 10.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology, disclosed by the invention, has the advantages that the silicon-aluminum ratio of the synthesized MTT zeolite molecular sieve is 30-60, the crystallization temperature is 160-170 ℃, and the axial-diameter length ratio is less than 5.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short shaft morphology, wherein a silicon oxide source is one or more of silica sol, silica gel, white carbon black, coarse silica gel and esters containing silicon oxide components. The ester containing the silicon oxide component may be methyl orthosilicate or ethyl orthosilicate, but is not limited thereto.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short shaft shape, wherein an alumina source is one or more of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum hydroxide and pseudo-boehmite.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short-axis morphology, wherein an alkali metal source MeOH is NaOH and/or KOH.

The invention relates to a synthesis method of an MTT zeolite molecular sieve with a short shaft morphology, wherein an MTT molecular sieve crystal seed is a crystal with an MTT molecular sieve framework structure, and specifically can be one or more of ZSM-23, SSZ-32, KZ-1, EU-13 and ISI-6, but not limited thereto, and the crystal seed can be a crystal seed without an organic template or a crystal seed containing the organic template.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology comprises the following step of adding MTT crystal seeds in an amount of 1.5-4.5% of the total mass of the gel, and preferably, adding the MTT crystal seeds in an amount of 2-3% of the total mass of the gel.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology, disclosed by the invention, is characterized in that the stirring speed of the synthesized gel is 200-300 rpm.

The synthesis method of the MTT zeolite molecular sieve with the short-axis morphology, disclosed by the invention, is characterized in that the temperature rise rate of the synthesized gel is 10-20 ℃/min.