CN1052452C - Method for preparing vanadium-silicon molecular sieve (VS-2) - Google Patents

Abstract

A method for preparing vanadium-silicon molecular sieve (VS-2) with MEL structure, which is to dissolve vanadium source and a small amount of auxiliary agent ethylenediamine (if necessary) in tetrabutylammonium hydroxide aqueous solution, and mix with 60-220 mesh solid silica gel The balls are mixed evenly to obtain a reaction mixture, which is crystallized in an autoclave at 110-180°C for 1-8 days, then filtered, washed, dried, and roasted according to conventional methods, wherein the molar composition of the reaction mixture is :

SiO ₂ /VO ₂ 10～600,

Ethylenediamine/VO ₂ 0～20

TBAOH/SiO ₂ 0.03～0.40

H ₂ O/SiO ₂ 1-40.

Description

A kind of preparation method of vanadium silicon molecular sieve (VS-2)

The invention relates to a preparation method of a vanadium-silicon molecular sieve, in particular to a preparation method of a vanadium-silicon molecular sieve (VS-2) with an MEL structure.

The introduction of transition element vanadium with coordination and valence characteristics into molecular sieves can combine the performance of molecular sieves with the catalytic performance of transition metals to produce unique catalytic effects. Experiments have shown that vanadium-silicon zeolites have good catalytic performance in xylene isomerization, alkane oxidation and many organic oxidation reactions involving H ₂ O ₂ , especially their high selectivity, such as in saturated alkane/H ₂ In the _O2 oxidation reaction, vanadium-silicon molecular sieves can be used as catalysts to oxidize carbon atoms at different positions, even carbon atoms at primary positions to generate corresponding aldehydes or ketones. more and more attention from the catalysis community.

As early as 1974, the East German patent DD110645 reported the preparation method of vanadium-containing Y-type molecular sieve. The method is to exchange VOSO ₄ solution with Y-type molecular sieve under the condition of maintaining pH=4-5.3. Literature CatalysisToday, 3 (1988) 519 also reports the method that vanadium is introduced into ZSM-11 molecular sieve by impregnation method and ion exchange method, and this vanadium-containing molecular sieve becomes furan and maleic anhydride in xylene ammoxidation, butadiene oxidation exhibited good catalytic performance in such reactions. However, due to the large charge-to-diameter ratio of vanadium ions, it is difficult to enter the molecular sieve framework. So far, the truly effective vanadium-silicon molecular sieves are vanadium-silicon molecular sieves synthesized by hydrothermal crystallization. In 1991, Rigutto. M S. et al. (Appl.Catal.68, L1 (1991)) and Fejes P. et al. (Stud.Surf Sci.Catal.69, 173 (1991)) reported vanadium silicon molecular sieve (VS -1) hydrothermal synthesis.

The synthesis method of the vanadium silicon molecular sieve (VS-2) with MEL structure was first reported by P.R.Hari Prasad Rao et al. in India in 1992 (J.Catalysis137, 225-231 (1992)). Its synthesis method is: slowly add an aqueous solution of tetrabutylammonium hydroxide (TBAOH) to a mixture of tetraethylsilicate and isopropanol at room temperature, and then add sulfuric acid oxygen very slowly to the resulting mixture under vigorous stirring. Vanadium aqueous solution, the mixture was stirred at 40-50°C for about 30 minutes, then an appropriate amount of TBAOH aqueous solution was added, and stirred at 50°C for 6 hours, and then the clear reaction mixture was transferred to an autoclave at Crystallization at 170°C for four days. A characteristic absorption peak of 960-970 cm-1 appears in the infrared absorption spectrum (IR) of the obtained sample. This is due to the antisymmetric stretching vibration of the Si-O bond caused by V entering the framework of the zeolite, which is considered to be the evidence of V entering the framework of the zeolite. The disadvantage of this method is that the raw material price of ethyl silicate used is high, and the amount of expensive organic base is large, so that the cost of the obtained VS-2 molecular sieve is high, and the synthesis steps are strict and complicated.

The purpose of the present invention is to provide a method for preparing VS-2 molecular sieve, which makes the prepared VS-2 molecular sieve cost lower and the preparation steps relatively simple.

The method provided by the present invention is characterized in that it adopts cheap solid silica gel pellets as a silicon source, soaks the _SiO pellets with vanadium-dissolved tetrabutylammonium hydroxide (TBAOH) aqueous solution, and crystallizes on the surface of the silica gel pellets from outside to inside. Carry out layer by layer until the crystallization is complete, so that as little water as possible can be added to the synthesis system, so that a small amount of organic base (TBAOH) can be used to meet the basicity and template dosage required for the synthesis of molecular sieves, thereby reducing costs and simplify operations.

The method for preparing VS-2 molecular sieve provided by the present invention is to dissolve the vanadium source and a small amount of auxiliary agent ethylenediamine (if necessary) in tetrabutylammonium hydroxide (TBAOH) aqueous solution, and mix with solid silica gel beads to obtain a reaction mixture , crystallize the reaction mixture in an autoclave at 110-180°C for 1-8 days, then filter, wash, dry and roast according to conventional methods, wherein the molar composition of the reaction mixture is:

Scope Scope Preferred

SiO ₂ /VO ₂ 10～600 30～300

Ethylenediamine/VO ₂ 0～20 1～10

TBAOH/ _SiO2 0.03～0.40 0.05～020

H ₂ O/SiO ₂ 1～30 1～20

Said vanadium source in the method provided by the present invention can be vanadium pentoxide, metavanadate (MVO ₃ ), vanadium salt (for example VCl ₃ , V(C ₂ O ₄ ) ₂ ), vanadium oxycompound (for example VOSO ₄ , VOCl ₃ ) or organovanadium complexes (eg vanadium acetylacetonate V(C ₅ H ₇ O ₂ ) ₃ ).

The particle size of the solid silica gel beads in the method provided by the present invention is 60-220 mesh, and the preferred particle size is 80-180 mesh.

The crystallization conditions in the method provided by the present invention are that the temperature is 110-180°C and the time is 1-8 days, and the preferred conditions are that the temperature is 120-170°C and the time is 2-6 days.

Compared with the prior art, the method for preparing VS-2 molecular sieve provided by the present invention has cheap and easy-to-obtain raw materials, low consumption of organic ammonium templating agent, low product cost, and less strict condition control in the preparation process It is complex, the preparation process is relatively simple, and it is easy to be applied in industry, and because the amount of water in the reaction system is less, the output of a single tank is increased.

Fig. 1 is an X-ray diffraction (XRD) crystal phase diagram, and the instrument used is Japanese Rigaku D/Max-IIIA type, CuKα. Wherein a represents the pure silicon molecular sieve (Silicalite-2) sample with NEL structure prepared according to the method described in document Stud. .

Fig. 2 is the infrared absorption spectrum (IR) figure of four kinds of samples, and instrument used is Perkin-Elmer 580 double-beam infrared spectrometers, and wherein a represents the Silicalite-2 sample described above, and b, c, d, e are embodiments respectively Samples prepared in 2, 1, 3, 4.

The following examples will further illustrate the present invention. In each of the following examples, the solid silica gel beads used are products of Qingdao Silica Gel Factory, TBAOH is a product of Beijing Daxing Xingfu Chemical Reagent Research Institute (containing a small amount of Na ⁺ , K ⁺ ), and all other reagents are commercially available chemically pure reagents .

Instance 1

Dissolve _{0.116g of V2O5} in 9.07g of 40wt% TBAOH aqueous solution, add 6.27g of 80-120 mesh _SiO2 pellets (95.7% on a dry basis) and 1.46g _{of H2O} under stirring, and mix the obtained reaction mixture into Crystallization was carried out at 140° C. for 4 days in a stainless steel reactor with a Teflon liner. After the crystallized product is washed and dried, it is calcined at 530° C. for 4 hours. Wherein the molar composition of the reaction mixture is:

SiO ₂ : 0.013VO ₂ : 0.14TBAOH : 4H ₂ O, (SiO ₂ /VO ₂ =77)

The XRD spectrogram of the obtained sample is shown in b in Fig. 1, its crystal phase is similar to Silicalite-2, and is a typical MEL structure, and its relative crystallinity is 88.6% (relative to Silicalite-2, according to the document Stud.Surf .Sci.Catal., Vol.18, 1984, P159 synthesized). Its IR spectrum shows an obvious characteristic absorption peak at 960cm ^-1 .

Instances 2~5

Prepare according to the method described in example 1, but change _V O _consumption , be mixed with the reaction mixture of following molar composition:

(2) SiO ₂ : 0.026VO ₂ : 0.14TBAOH : 4H ₂ O. (SiO ₂ /VO2=38)

(3) SiO ₂ : 0.0065VO ₂ : 0.14TBAOH : 4H ₂ O. (SiO ₂ /VO2=153)

(4) SiO ₂ : 0.0038VO ₂ : 0.14TBAOH : 4H ₂ O. (SiO ₂ /VO2=263)

(5) SiO ₂ : 0.0025VO ₂ : 0.14TBAOH : 4H ₂ O. (SiO ₂ /VO2=400)

The above four reaction mixtures were crystallized at 140°C for 4 days, and the crystallized products were filtered, washed, and dried, and then calcined at 530°C for 4 hours. The relative crystallinity of the obtained samples were: (2) 86.9%, ( 3) 91.4%, (4) 93.2% (5) 97.3%. The characteristic absorption peak of 970cm ^-1 appears in its IR spectrum.

Example 6

Dissolve 0.116g _{of V2O5} and 0.16g of ethylenediamine in _9.07g of 40% TBAOH aqueous solution, add 6.27g of 80-120 mesh _SiO2 pellets and 3.05g _{of H2O} under stirring, and the molar composition of the resulting reaction mixture is: _SiO2 : 0.013VO ₂ : 0.14TBAOH: 4.8H ₂ O: 0.026 ethylenediamine, the reaction mixture was crystallized in a stainless steel reactor at 130°C for 5 days, filtered, washed and dried, then roasted at 540°C for 5 hours . The relative crystallinity of the obtained sample was 87.9%. There is a characteristic absorption peak at 970cm ^-1 in its IR spectrum.

Example 7

Dissolve 0.27g VOSO ₄ ·3H ₂ O and 1.2g of ethylenediamine in 6.48g of 40% TBAOH aqueous solution, stir at 20°C for 30min, add 6.27g of 80-120 mesh SiO ₂ pellets and 3.0g of H ₂ O, and mix well to obtain The molar composition of the reaction mixture is: SiO ₂ : 0.0125VO ₂ : 0.10TBAOH: 4H ₂ O : 0.20 ethylenediamine, the reaction mixture was crystallized in a stainless steel reactor at 150°C for 4 days, filtered, washed and dried Afterwards, bake at 500°C for 4 hours. The relative crystallinity of the obtained sample is 87.4%, and there is a characteristic absorption peak at 970cm ^-1 in its IR spectrum.

Example 8

Dissolve 0.45g of V(C ₅ H ₇ O ₂ ) ₃ in 5.18 g of 40% TBAOH aqueous solution and stir at 25°C for 20 min, add 627 g of 80-120 mesh SiO ₂ pellets and 2.0 g of H ₂ O, stir well, and the moles of the resulting reaction mixture The proportion is: SiO ₂ : 0.013VO ₂ : 0.08TBAOH : 3H ₂ O, the reaction mixture was crystallized in a stainless steel reactor at 160°C for 3 days, filtered, washed and dried, then roasted at 540°C for 5 hours , the relative crystallinity of the product obtained is 88.1%. There is a characteristic absorption peak at 970cm ^-1 in its IR spectrum.

Example 9

Dissolve 0.158g NaVO ₃ ·2H ₂ O in 10.36g 40% TBAOH aqueous solution, stir at 18°C for 40min, then add 6.27g 140-180 mesh SiO ₂ pellets (dry basis 95.7%) and 11.7g H ₂ O, stir well , the molar composition of the resulting reaction mixture is: SiO ₂ : 0.010VO ₂ : 0.16TBAOH: 10H ₂ O, the reaction mixture was crystallized in a stainless steel reactor at 140°C for 4 days, filtered, washed and dried, Baking at 540°C for 4 hours. The relative crystallinity of the obtained sample was 83.2%. There is a characteristic absorption peak at 970cm ^-1 in its IR spectrum.

Instance 10

Dissolve _{0.116g of V2O5} in 9.07g of 40% TBAOH aqueous solution, add 6.27g of 80-120 mesh _SiO2 pellets (95.7% on a dry basis) and 30.28g _{of H2O} under stirring, and stir evenly. The composition is: SiO ₂ : 0.013VO ₂ : 0.14TBAOH: 20H ₂ O, and the reaction mixture was crystallized in a stainless steel reactor at 140°C for 5 days. After the samples were washed and dried, they were baked at 530°C for 4 hours. The relative crystallinity of the obtained sample was 81.3%. There is a characteristic absorption peak at 970cm ^-1 in its IR spectrum.

Instance 11

0.22g VOCl ₃ was dissolved in 15.53g 40% TBAOH aqueous solution, and 6.27g 80-120 mesh SiO ₂ pellets (dry basis 95.7%) were added under stirring state, and stirred evenly, the molar composition of the resulting reaction mixture was: SiO ₂ : 0.0125VO ₂ : 0.24TBAOH: 5.33H ₂ O, the reaction mixture was crystallized in a stainless steel reactor at 142°C for 6 days. After the samples were washed and dried, they were baked at 535°C for 5 hours. The relative crystallinity of the obtained sample was 93.8%. There is a characteristic absorption peak at 970cm ^-1 in its IR spectrum.

Instance 12

Dissolve 0.21g of _VCl3 in 9.07g of 40% TBAOH aqueous solution, add 6.27g of 80-120 mesh _SiO2 pellets (95.7% on a dry basis) and 1.46g of _H2O under stirring, and mix evenly. The molar composition of the resulting reaction mixture is: SiO ₂ : 0.013VO ₂ : 0.14TBAOH : 4H ₂ O, the mixture was put into a stainless steel reactor with polytetrafluoroethylene liner and crystallized at 138°C for 6 days. After the crystallized product is washed and dried, it is calcined at 540° C. for 6 hours. The relative crystallinity of the obtained product was 89.8%. A characteristic absorption peak at 970cm ^-1 appeared on its IR spectrum.

Example 13

Dissolve 0.31g of VOC ₂ O ₄ in 9.07g of 40% TBAOH aqueous solution, add 6.27g of 80-120 mesh SiO ₂ pellets (dry basis 95.7%) and 2.40g of H ₂ O under stirring state and mix evenly, the molar composition of the resulting reaction mixture SiO ₂ : O.02VO ₂ : 0.14TBAOH : 4.5H ₂ O, the mixture was put into a stainless steel reactor with polytetrafluoroethylene lining and crystallized at 144°C for 5 days. The crystallized product was washed, dried, and calcined at 540°C for 6 hours. The relative crystallinity of the obtained product was 86.6%. A characteristic absorption peak at 970cm ^-1 appeared on its IR spectrum.

Claims (9)

1. preparation method with V-Si molecular sieve of MEL structure, it is characterized in that this method comprises is dissolved in the vanadium source in the aqueous solution of TBAH (TBAOH), and mix with the solid silicone bead and to obtain reaction mixture, with this reaction mixture in autoclave in 110～180 ℃ of crystallization 1～8 day, filter according to a conventional method then, wash, drying and roasting, wherein the mole of said reaction mixture consists of:

SiO ₂/VO ₂＝10～600，

TBAOH/SiO ₂＝0.03～0.40

H ₂O/SiO ₂＝1～40。

2. according to the preparation method of claim 1, it is characterized in that when being dissolved in the vanadium source in the TBAH aqueous solution, can adding quadrol auxiliary agent, wherein quadrol/VO ₂Mol ratio be 0～20.

3. according to the preparation method of claim 2, quadrol/VO wherein ₂Mol ratio be 1～10.

4. according to the preparation method of claim 1, wherein said vanadium source is Vanadium Pentoxide in FLAKES, metavanadate, vanadic salts, oxyvanadium compound or organic vanadium complex compound.

5. according to the preparation method of claim 4, wherein said vanadium source is a Vanadium Pentoxide in FLAKES.

6. according to the preparation method of claim 1, the granularity of wherein said solid silicone bead is 60～220 orders.

7. according to the preparation method of claim 6, wherein said granularity is 80～180 orders.

8. according to the preparation method of claim 1, wherein the condition of said crystallization is that temperature is 120～170 ℃, the time can be 2～6 days.

9. according to the preparation method of claim 1, wherein the mole of said reaction mixture consists of:

SiO ₂/VO ₂＝30～300，

TBAOH/SiO ₂＝0.05～0.20

H ₂O/SiO ₂＝1～20。

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