CN102259886A

CN102259886A - Preparation method of MCM-48 mesoporous molecular sieve

Info

Publication number: CN102259886A
Application number: CN 201110145746
Authority: CN
Inventors: 张坤; 袁恩辉; 赵安琪; 侯琼玮; 罗琛; 蒋金刚
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2011-06-01
Filing date: 2011-06-01
Publication date: 2011-11-30
Anticipated expiration: 2031-06-01
Also published as: CN102259886B

Abstract

The invention discloses a preparation method of an MCM-48 mesoporous molecular sieve. In the preparation method, cetyl trimethyl p-toluenesulfonate salt (CTATos) is used as a cationic surfactant, and the molar ratio of raw materials is as follows: SiO2/CTATos/NaOH/H2O = 1:(0.05-0.07):(0.5-0.67):(80-200). The preparation method comprises the specific steps: firstly dissolving silicon sol in an aqueous solution containing sodium hydroxide and stirring at the constant temperature of 60 DEG C for 1 hour; then adding dropwise the solution to an aqueous solution containing the surfactant and then further stirring at the constant temperature of 60 DEG C for 2 hours; after cooling to room temperature, transferring to a sealed reactor, and crystallizing at the temperature of 80-130 DEG C for 15 to 28 hours; and finally filtering the crystallized product, washing, drying and then baking at the temperature of 550-900 DEG C for 3-6 hours to obtain the MCM-48 molecular sieve. Compared with the prior art, the preparation method disclosed by the invention has the most significant advantage that: CTATos is used as the cationic surfactant, thus greatly reducing the use amount of the surfactant in a synthesis system; in addition, the synthesis method provided by the invention has short synthesis period, low cost and good reproducibility; the synthesized product has extremely high hydrothermal stability; and the synthesis method is environmentally friendly.

Description

A kind of preparation method of MCM-48 mesopore molecular sieve

Technical field

The present invention relates to a kind of preparation method of molecular sieve, the preparation method of specifically a kind of high thermal stability silicon-based mesoporous molecular sieve MCM-48.

Background technology

M41S series meso-porous molecular sieve material comprises the MCM-41 of one dimension hexagonal hole road structure, the MCM-48 of three-dimensional cubic topological framework and the MCM-50 of laminate structure, is researched and developed successfully in 1992 by Mobil company the earliest.Because this material has regular pore passage structure, bigger specific surface area (~ 1000m ²/ g) and pore volume (1.0ml/g) and aperture size that can modulation (2.0 ~ 50nm) have caused extensive studies interest at catalysis, absorption and separation field.Because MCM-48 has three-dimensional successive pore passage structure, with respect to the MCM-41 mesoporous material of one-dimensional channels, has bigger advantage and application prospect aspect molecular diffusion.But because the synthetic phase region of MCM-48 is narrow relatively, synthesis condition is extremely harsh, poor reproducibility, and synthetic cost is higher, greatly limits the range of application of MCM-48.The main synthesis strategy of current synthetic MCM-48 comprises: use single cats product (Chem. Mater., 1994,6,2317.), as cetyl trimethylammonium bromide (CTABr), the mol ratio of tensio-active agent/silicon has a large amount of foams to produce in the high and last handling process of synthetic cost between 0.65-1.5, separates extremely complicated; The synthesis strategy of mixed templates can greatly reduce the consumption of cats product, but both molar ratios are difficult to control, to such an extent as to be difficult to synthetic high-quality MCM-48 mesopore molecular sieve (Chinese patent, CN1188689A; ); The tensio-active agent of synthesizing new can greatly reduce the consumption of tensio-active agent as the Gemimi tensio-active agent, but this tensio-active agent synthesis program complexity, productive rate are low, synthetic (the Chem. Mater. that is unfavorable for extensive mesopore molecular sieve, 1996,8,1147.); Chinese patent has been reported and has been utilized F recently ^-Can effectively synthesize MCM-48 mesoporous material (CN1775673A) as organic additive, but the existence of a large amount of fluorions is to environment right and wrong close friend's.In addition, cetyl trimethylammonium bromide (CTABr) synthesizes the shortcoming that the MCM-48 mesoporous material has the hydrothermally stable difference usually, 550 as template molecule ^o12 hours most of structures that reflux in C roasting 6 hours or the boiling water are subsided, and have further hindered it in industrial application.From above-mentioned report as seen, existing synthetic method condition is extremely harsh, cost is high, pollution is big and shortcoming such as the finished product hydrothermal stability difference.Therefore improving the existing synthetic technology of MCM-48 is the top priority of MCM-48 fundamental research.

Summary of the invention

The object of the present invention is to provide a kind of fast, low-cost, the preparation method that pollutes little MCM-48 mesopore molecular sieve.

The object of the present invention is achieved like this:

The preparation method of a kind of mesopore molecular sieve MCM-48, it is characterized in that this method is that CTATos is a cats product with cetyl trimethyl p-methyl benzenesulfonic acid salt, alkaline silica sol is the silicon source, sodium hydroxide or potassium hydroxide are alkali source, its concrete steps are: 60 ℃ of constant temperature stirred 1 hour in the middle of earlier alkaline silica sol being dissolved into the aqueous solution that contains sodium hydroxide, this solution is dropwise joined in the middle of the aqueous solution that contains tensio-active agent then, 60 ℃ of constant temperature continue to stir 2 hours, be cooled to and be transferred to after the room temperature in the closed reactor 80～130 ℃ of crystallization 15～28 hours, at last after filtration with crystallization product, washing, after the drying, 550～900 ℃ of following roastings 3～6 hours, obtain the MCM-48 molecular sieve; Wherein: the mol ratio of described raw material is: SiO ₂: CTATos:NaOH/KOH:H ₂O=1:0.05～0.07:0.5～0.67:80～200.

Wherein: employed cetyl trimethyl p-methyl benzenesulfonic acid salt (CTATos) cats product comes from the Merck chemical reagents corporation of Germany; Said silicon source reaches no sodium type silicon sol that contains silicon-dioxide 30% or the Ludox of the E.I.Du Pont Company series silicon sol that company produces for the Zhejiang space; Alkali source is commercially available sodium hydroxide or potassium hydroxide.

The present invention compared with prior art has following advantage:

⑴, can reduce tensio-active agent (CTATos)/Si mol ratio to 0.05, reduce synthetic cost, reduce environmental pollution.In addition because the tensio-active agent in the system by 100% utilization, filters, in the middle of the washing process without any foam produce, greatly simplified the operation steps that sample reclaims.

⑵, the relatively inexpensive nontoxic silicon sol of use replace relatively costly organosilicon source (TEOS) as the silicon source, have further reduced synthetic cost.

, from the characterization result of product, the product regular shape that the present invention obtains, aperture homogeneous and hydrothermal stability height.Even sample is 900 ℃ of roastings 3 hours, and surface-area reaches 1095m ²/ g, pore volume are 0.87ml/g, and the aperture slightly is reduced to 2.4nm.

Description of drawings

Fig. 1 is the XRD figure spectrum of MCM-48 mesopore molecular sieve under different maturing temperatures of the present invention's preparation;

Fig. 2 is scanning electron microscope (SEM) figure of the MCM-48 mesopore molecular sieve of the present invention's preparation;

Fig. 3 is nitrogen adsorption-desorption curve and the BJH graph of pore diameter distribution of MCM-48 mesopore molecular sieve under different maturing temperatures of the present invention's preparation.

Embodiment

The invention will be further described below by embodiment, and its purpose only is better to understand research contents of the present invention and unrestricted protection scope of the present invention.

Embodiment 1

At first 2.104g NaOH is joined in the beaker that contains the 68ml deionized water, add 17.42g silicon sol (SiO then ₂=30%, Ludox-AM30), stirred 1 hour at 60 ℃ of constant temperature, obtain solution A; 2.705g cetyl trimethyl p-methyl benzenesulfonic acid salt (CTATos) is joined in the beaker that contains the 80ml deionized water, and 60 ℃ of constant temperature stir 1 hour to the solution becomes clarification, obtain solution B; Solution A is dropwise joined in the solution B, and 60 ℃ of constant temperature stirred 2 hours, obtained white precipitate, and the mole of this mixture consists of SiO ₂/ CTATos/NaOH/H ₂O=1:0.068:0.60:102; After this mixture is cooled to room temperature, be transferred in the reactor 130 ℃ of crystallization 20 hours, products therefrom suction filtration, washing, oven dry with 550 ℃ of roastings of the former powder of gained 6 hours, promptly get the MCM-48 mesopore molecular sieve, productive rate 50%.

Gained MCM-48 mesopore molecular sieve heat stability testing: with suction filtration, washing and oven dry obtain former powder respectively in 750 ℃ and 900 ℃ roasting 6 hours and 3 hours respectively, pore structure remains intact (Fig. 1 and Fig. 3).

Embodiment 2

Silicon sol (the Zhejiang space reaches chemical reagents corporation, no sodium type 30% silicon sol) prepares high-quality MCM-48 mesopore molecular sieve as the silicon source:

The Ludox-AM30 except that reach no sodium type silicon sol replacement embodiment 1 with the Zhejiang space in, other preparation condition is all identical with embodiment 1.

Embodiment 3

Potassium hydroxide prepares high-quality MCM-48 mesopore molecular sieve as alkali source:

Except that the sodium hydroxide that replaces with potassium hydroxide among the embodiment 1, other preparation condition is all identical with embodiment 1.

Embodiment 4

Reduce crystallization temperature and prolong crystallization time and prepare high-quality MCM-48 mesopore molecular sieve:

Keep the mole of mixture to form SiO ₂/ CTATos/NaOH/H ₂O=1:0.068:0.60:102 is constant, and crystallization temperature is 100 ℃, crystallization time 24 hours, and other preparation condition is all identical with embodiment 1 with process.

Claims

1. the preparation method of a mesopore molecular sieve MCM-48, it is characterized in that this method is a cats product with cetyl trimethyl p-methyl benzenesulfonic acid salt, alkaline silica sol is the silicon source, sodium hydroxide or potassium hydroxide are alkali source, its concrete steps are: 60 ℃ of constant temperature stirred 1 hour in the middle of earlier alkaline silica sol being dissolved into the aqueous solution that contains sodium hydroxide, this solution is dropwise joined in the middle of the aqueous solution that contains tensio-active agent then, 60 ℃ of constant temperature continue to stir 2 hours, be cooled to and be transferred to after the room temperature in the closed reactor 80～130 ℃ of crystallization 15～28 hours, at last after filtration with crystallization product, washing, after the drying, 550～900 ℃ of following roastings 3～6 hours, obtain the MCM-48 molecular sieve; Wherein: the mol ratio of described raw material is: SiO ₂: CTATos:NaOH/KOH:H ₂O=1:0.05～0.07:0.5～0.67:80～200.