CN101549874A

CN101549874A - Synthesizing process for improving generation rate of nano Y-shaped molecular sieve

Info

Publication number: CN101549874A
Application number: CNA200910011450XA
Authority: CN
Inventors: 徐龙伢; 胡林彦; 谢素娟; 刘盛林
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2009-05-08
Filing date: 2009-05-08
Publication date: 2009-10-07

Abstract

一种提高纳米Y型分子筛产率的合成工艺，将有机模板剂、铝源在搅拌条件下依次加入去离子水中，搅拌至溶解后加入硅源、钠源；然后将此合成体系转移至反应釜中，密闭后升温至90～130℃下水热晶化60～110小时；得到的固液混合物进行分离，其中母液保留，固体即为纳米Y型分子筛；对上述得到的母液补充适量反应原料，然后继续晶化、固液分离，再次得到纳米Y型分子筛和反应母液；反复补充反应原料、晶化、固液分离提高纳米Y型分子筛的产率；本发明有效地利用合成体系中未反应的硅、铝以及有机模板剂等原料，使纳米Y型分子筛的产率提高至40％以上；同时，产物的粒径在100nm以下，且每次晶化需要的时间较短。A synthesis process for improving the yield of nanometer Y-type molecular sieves, adding organic templates and aluminum sources to deionized water in turn under stirring conditions, stirring until dissolved, then adding silicon sources and sodium sources; then transferring the synthesis system to a reaction kettle After being airtight, heat up to 90-130°C for hydrothermal crystallization for 60-110 hours; the obtained solid-liquid mixture is separated, and the mother liquor is retained, and the solid is nano-Y type molecular sieve; the mother liquor obtained above is supplemented with appropriate amount of reaction raw materials, and then Continue crystallization and solid-liquid separation to obtain nano Y-type molecular sieve and reaction mother liquor again; repeatedly replenish reaction raw materials, crystallization, and solid-liquid separation to improve the yield of nano-Y-type molecular sieve; the present invention effectively utilizes unreacted silicon in the synthesis system Raw materials such as aluminum and organic templates increase the yield of nano Y-type molecular sieves to more than 40%. At the same time, the particle size of the product is below 100nm, and the time required for each crystallization is relatively short.

Description

A kind of synthesis technique that improves generation rate of nano Y-shaped molecular sieve

Technical field

The present invention relates to a kind of synthesis technique that improves generation rate of nano Y-shaped molecular sieve, specifically a kind ofly utilize raw materials such as unreacted silicon, aluminium and organic formwork agent in the mother liquor, significantly improve the synthesis technique of generation rate of nano Y-shaped molecular sieve by the repeatedly crystallization method of replenishing raw material.

Background technology

The zeolite crystal size of industrial use is generally micron order, the duct of this molecular sieve analog is longer, and reactant and product molecule are bigger at the diffusional resistance of molecular sieve intracrystalline in catalyzed reaction, cause deep reaction easily, produce carbon distribution, so the deactivation rate of catalyzer is very fast.The grain-size that reduces molecular sieve then can effectively address this problem.Along with reducing of grain-size, the surface atom number of crystal grain and the body ratio of atomicity mutually increase rapidly, can demonstrate stronger volume effect, surface effects and quantum size effect, can produce the physicochemical property that some are different from the uniqueness of macroparticle.Studies show that, with the catalyzer of superfine molecular sieves preparation in the utilization ratio that improves catalyzer, strengthen the macromole conversion capability, reduce reaction depth, improve selectivity and reduce aspects such as coking and deactivation and all show superiority.

Usually utilize the reaction system of adding organic formwork agent synthesize particle diameter less than the nano Y-shaped molecular sieve of 100nm (Stud Surf Sci Catal, 125, Elsevier, Amsterdam, 1999, P.141; Micropor Mesopor Mater 74 (2004) 189).Adopt microwave heating also can synthesize the nano Y-shaped molecular sieve (CN1730391A) of particle diameter less than 100nm.But, in adding the system of organic formwork agent, during the synthesis of nano Y molecular sieve, must adopt very low sodium content, otherwise will produce stray crystal.And sodium ion is the crucial species that generate Y zeolite, and extremely low sodium content has determined synthetic nanometer Y molecular sieve productive rate very low (less than 8%, with the silicon source that adds in the raw material and the SiO in the aluminium source ₂With Al ₂O ₃The quality sum is a benchmark), so still have a large amount of unreacted silicon, aluminium and organic formwork agent species in the mother liquor after the crystallization.Document (Micropor Mesopor Mater 96 (2006) 405) proposes additionally not introduce under the situation of sodium ion having, and improves the productive rate of nano Y-shaped molecular sieve by crystallization repeatedly.Yet the productive rate of nano Y-shaped molecular sieve is closely related with the amount of sodium ion, and they are not introducing under the situation of sodium ion once more, only makes productive rate improve about 0.4% by three crystallization.Document (Stud Surf SciCatal, 135, Elsevier, Amsterdam, 2001, P.151) significantly improved the productive rate of molecular sieve by the single crystallization method of repeatedly introducing sodium ion, but the Y zeolite crystal that this method will not generate is earlier in time separated, but be retained in the reaction system, cause these molecular sieve crystals that formed in follow-up crystallization process, excessively to be grown up, the particle diameter of product surpasses 100nm; always In addition, this method requires the timed interval of twice introducing sodium ion to reach 7 days stray crystals in the ability elimination product, causes synthesis cycle longer.

Summary of the invention

The purpose of this invention is to provide a kind of synthesis technique that improves generation rate of nano Y-shaped molecular sieve, this technology is by replenishing the repeatedly crystallization method of raw material, realized effectively utilizing raw materials such as unreacted silicon, aluminium and organic formwork agent in the synthetic system, the productive rate of nano Y-shaped molecular sieve is increased to more than 40%.

The invention provides a kind of synthesis technique that improves generation rate of nano Y-shaped molecular sieve, its synthesis step is as follows:

A) organic formwork agent, aluminium source are added under agitation condition in the deionized water successively, be stirred to the dissolving back and add the silicon source, fully stirring or heating make the transparent or semitransparent back of solution add the sodium source;

Wherein the mole proportioning of reaction raw materials is: SiO ₂/ Al ₂O ₃=3.5～4.5, Na ₂O/Al ₂O ₃=0.020～0.050, H ₂O/Al ₂O ₃=230～270, organic formwork agent/Al ₂O ₃=4.0～5.0;

B) synthetic system that step a is obtained is transferred in the reactor, is warming up to 90～130 ℃ of following hydrothermal crystallizings 60～110 hours after airtight;

C) solidliquid mixture that step b crystallization is obtained separates, and the mother liquor that wherein obtains keeps, and solid is nano Y-shaped molecular sieve through washing, drying;

It is characterized in that:

D) replenish an amount of sodium source according to the proportioning among the step a in the mother liquor that previous step is obtained, the condition according to step b continues crystallization then, carries out solid-liquid separation after the crystallization, obtains nano Y-shaped molecular sieve and reaction mother liquor once more;

E) repeating step d makes accumulative total productive rate 〉=40% (the quality sum with silicon-dioxide in silicon source and the aluminium source and aluminium sesquioxide is a benchmark) of nano Y-shaped molecular sieve.

The synthesis technique of raising generation rate of nano Y-shaped molecular sieve provided by the invention according to the mole proportioning of above-mentioned reaction raw materials, adopts the feed way of step a in the mother liquor that obtains after carrying out step e, supply various reaction raw materials, repeating step b～e.

The synthesis technique of raising generation rate of nano Y-shaped molecular sieve provided by the invention, described organic formwork agent are Tetramethylammonium hydroxide TMAOH; The aluminium source is an aluminum isopropylate; The silicon source is at least a in silicon sol, white carbon black, the tetraethoxy; The sodium source is at least a in the soluble sodium salts such as NaOH, NaCl.

The present invention has following technique effect:

In the synthesis technique of the present invention, by the method for crystallization, separating for several times repeatedly, the molecular sieve crystal of having avoided forming is excessively grown up, and the products therefrom particle diameter is lower than 100nm; The single crystallization time is short, and the mother liquor after the crystallization is clear solution, can directly carry out crystallization after replenishing raw material, and twice crystallization can closely be connected, and saves generated time; Can only replenish the sodium source, also can replenish all the other raw materials, realize making full use of the purpose of each raw material, the productive rate of nano Y-shaped molecular sieve is increased to more than 40%; This technology has not only significantly reduced the synthetic cost of nano Y-shaped molecular sieve, has also reduced the synthesis mother liquid pollution on the environment.

Description of drawings

Fig. 1 is the XRD spectra of embodiment 1 synthesis of nano Y zeolite;

Fig. 2 is the laser particle size analysis result of embodiment 1 synthesis of nano Y zeolite;

Fig. 3 is the TEM photo of embodiment 1 synthesis of nano Y zeolite;

Fig. 4 is the XRD spectra of the former powder of embodiment 2 synthesis of nano Y zeolites;

Fig. 5 is the SEM photo of embodiment 2 synthesis of nano Y zeolites;

Fig. 6 is the XRD spectra of the former powder of embodiment 3 synthesis of nano Y zeolites.

Embodiment

Following examples will give further instruction to the present invention, but not thereby limiting the invention.

Embodiment 1

With 100 gram tetramethyl ammonium hydroxide solutions (25%) and 26.5 gram aluminum isopropylate (〉=24.7%Al ₂O ₃), add successively in the 216 gram deionized waters, be stirred to solution clarification back and add 50 gram tetraethoxy (〉=28.0%SiO ₂), 0.2 gram sodium hydroxide.Make the mole proportioning that obtains reaction mixture be: SiO ₂/ Al ₂O ₃=3.65, Na ₂O/Al ₂O ₃=0.032, H ₂O/Al ₂O ₃=249, TMAOH/Al ₂O ₃=4.30.Then this mixture is transferred in the reactor airtight back crystallization 85 hours under 100 ℃, dynamic condition.System after the crystallization is carried out centrifugation, and the solid product that obtains (S-A1) washing back keeps the mother liquor (M-A1) that obtains in 120 ℃ of oven dry 24 hours, and this is synthetic for the first time.In M-A1, add 0.2 gram sodium hydroxide, continued under 100 ℃, dynamic condition crystallization then 85 hours, the system after the crystallization is carried out centrifugation, the solid product that obtains (S-A2) washing back was in 120 ℃ of oven dry 24 hours, keep the mother liquor (M-A2) that obtains, this is synthetic for the second time.Identical process repeats (gained solid product remember successively make S-A1, S-A2, S-A3, S-A4, S-A5, S-A6, S-A7 and S-A8) eight times, and the XRD spectrum (Fig. 1) of products therefrom shows that eight times the synthetic sample is Y zeolite; Adopt the dynamic light scattering particle size instrument that these samples are carried out testing graininess, result (Fig. 2) shows that the particle diameter of the first five time synthetic product is about 40nm, and the particle diameter of back three synthetic products is at 40～60nm.Fig. 3 is the TEM photo of the 4th synthetic nano Y-shaped molecular sieve (S-A4).Through eight times synthetic after, the productive rate of molecular sieve (is benchmark with the silicon source that adds and the quality sum of silicon-dioxide in the aluminium source and aluminium sesquioxide) is 53%.

Embodiment 2

With 186 gram tetramethyl ammonium hydroxide solutions (25%) and 44 gram aluminum isopropylate (〉=24.7%Al ₂O ₃), add successively in the 328 gram deionized waters, be stirred to dissolving back and add 28 gram white carbon blacks, heat and be stirred to the transparent back of solution and add 0.2 gram sodium hydroxide.Make the mole proportioning that obtains reaction mixture be: SiO ₂/ Al ₂O ₃=4.36, Na ₂O/Al ₂O ₃=0.024, H ₂O/Al ₂O ₃=240, TMAOH/Al ₂O ₃=4.78.Then this mixture is transferred in the reactor airtight back crystallization 100 hours under 100 ℃, dynamic condition.System after the crystallization is carried out centrifugation, and the solid product that obtains (S-B1) washing back keeps the mother liquor (M-B1) that obtains in 120 ℃ of oven dry 24 hours, and this is synthetic for the first time.In M-B1, add 0.20 gram sodium hydroxide, continued under 100 ℃, dynamic condition crystallization then 100 hours.System after the crystallization is carried out centrifugation, and the solid product that obtains (S-B2) washing back keeps the mother liquor (M-B2) that obtains in 120 ℃ of oven dry 24 hours, and this is synthetic for the second time.Repeat said process ten times (gained solid product remember successively make S-B1, S-B2, S-B3, S-B4, S-B5, S-B6, S-B7, S-B8, S-B9 and S-B10), the spectrum (Fig. 4) that obtains product X RD shows that ten times the synthetic sample is Y zeolite.The SEM characterization result shows that the particle diameter of institute's synthetic product is all less than 90nm, and particle size distribution is narrow.The SEM photo of the 4th synthetic product (S-B4) as shown in Figure 5.Through ten times synthetic after, the productive rate of nano Y-shaped molecular sieve is 44%.

Embodiment 3

In embodiment 2, in through the mother liquor after 10 crystallization, add 15 gram tetramethyl ammonium hydroxide solutions (25%), 22 gram aluminum isopropylate (〉=24.7%Al ₂O ₃), 42 gram silicon sol (30.4%SiO ₂, 0.1%Al ₂O ₃, 0.1%Na ₂O, 69.4%H ₂O) and 0.29 the gram sodium-chlor.Make the mole proportioning of synthetic system be: SiO ₂/ Al ₂O ₃=4.36, Na ₂O/Al ₂O ₃=0.030, H ₂O/Al ₂O ₃=260, TMAOH/Al ₂O ₃=4.78.Crystallization 100 hours under 115 ℃, dynamic condition then.System after the crystallization is carried out centrifugation, and the solid product that obtains (S-C1) washing back keeps the mother liquor (M-C1) that obtains in 120 ℃ of oven dry 24 hours, and this is synthetic for the first time.In M-C1, add 0.29g sodium-chlor, continued under 115 ℃ of whipped states crystallization then 100 hours, the system after the crystallization is carried out centrifugation, the solid product that obtains (S-C2) washing back was in 120 ℃ of oven dry 24 hours, keep the mother liquor (M-C2) that obtains, this is synthetic for the second time.Repeat said process six times (gained solid product remember successively make S-C1, S-C2, S-C3, S-C4, S-C5 and S-C6), the XRD spectrum (Fig. 6) that obtains product shows that six times the synthetic sample is Y zeolite.The SEM characterization result shows that the particle diameter of institute's synthetic product is all less than 90nm.Through six times synthetic after, the productive rate of molecular sieve is 66%.

Claims

1, a kind of synthetic technique that improves nanometer Y type molecular sieve productive rate, its synthetic steps are as follows:

a) Add the organic template agent and the aluminum source to deionized water sequentially under stirring conditions, add the silicon source after stirring until dissolved, fully stir or heat to make the solution transparent or translucent, and then add the sodium source;

The molar ratio of the reaction raw materials is: SiO ₂ /Al ₂ O ₃ =3.5-4.5, Na ₂ O/Al ₂ O ₃ =0.020-0.050, H ₂ O/Al ₂ O ₃ =230-270, organic template _{/Al2O3＝4.0～5.0} _;

b) Transfer the synthesis system obtained in step a to a reaction kettle, heat up to 90-130° C. for hydrothermal crystallization for 60-110 hours after airtight;

c) separating the solid-liquid mixture obtained by the crystallization in step b, wherein the obtained mother liquor is retained, and the solid is washed with water and dried to obtain a nano Y-type molecular sieve;

It is characterized by:

d) supplement the sodium source according to the proportioning in step a to the mother liquor obtained in the previous step, then continue crystallization according to the conditions of step b, carry out solid-liquid separation after crystallization, and obtain nanometer Y-type molecular sieve and reaction mother liquor again;

e) Repeat step d to make the cumulative yield of the nano Y-type molecular sieve ≥ 40%.

2, according to claim 1, improve the synthetic technique of nanometer Y type molecular sieve productive rate, it is characterized in that: in the mother liquor that obtains after carrying out step e, according to the molar proportion of above-mentioned reaction raw material, adopt the charging mode of step a, make up each A reaction raw material, repeat steps b ~ e.

3. The synthesis process for increasing the yield of nano Y-type molecular sieve according to claim 1, characterized in that: the organic template is tetramethylammonium hydroxide TMAOH.

4. The synthesis process for increasing the yield of nano Y-type molecular sieve according to claim 1, characterized in that: the aluminum source is aluminum isopropoxide.

5. The synthesis process for increasing the yield of nano Y-type molecular sieve according to claim 1, characterized in that: the silicon source is at least one of silica sol, white carbon black, and ethyl orthosilicate.

6. According to claim 1, the synthesis process for improving the yield of nanometer Y-type molecular sieves is characterized in that: the sodium source is at least one of some soluble sodium salts of NaOH and NaCl.

7. According to claim 1, the synthesis process for improving the yield of nanometer Y-type molecular sieve is characterized in that: the calculation of the cumulative yield of said nanometer Y-type molecular sieve is based on silicon dioxide and trioxide in silicon source and aluminum source The sum of the mass of two aluminum is used as the benchmark.

8. According to claim 1, the synthesis process for improving the yield of nanometer Y-type molecular sieve is characterized in that: the crystal grain size of the synthesized nanometer Y-type molecular sieve is below 100nm.