CN102241405A - Reduced mesoporous aluminosilicate molecular sieve, preparation method and application thereof, and diesel oil desulfurization method - Google Patents

Abstract

The invention relates to the field of molecular sieves. Specifically, the invention relates to a reduced mesoporous aluminosilicate molecular sieve, its preparation method, application, and diesel oil desulfurization method. The molecular sieves are prepared by the following methods: 1) preparing mesoporous aluminosilicate molecular sieves; 2) transition metal modification; 3) reducing the mesoporous aluminosilicate molecular sieves modified by the transition metal ions with a reducing gas, and the reduction temperature is It is 200°C to 700°C. The mesoporous aluminosilicate (MAS) salt adsorbent of the present invention is a molecular sieve compounded by micropores and mesoporuses. Density and acid strength, but also has the larger pore size of mesoporous molecular sieves and good thermal stability and hydrothermal stability. The adsorption capacity and adsorption selectivity of the adsorbent for sulfide can be further improved. By adjusting the reduction temperature, the morphology and properties of multivalent transition metals on the adsorbent can be changed to obtain the most suitable adsorption desulfurization effect.

Description

A reduced mesoporous aluminosilicate molecular sieve, its preparation method, application, and diesel desulfurization method

technical field

The invention relates to the field of molecular sieves. Specifically, the invention relates to a reduced mesoporous aluminosilicate molecular sieve, its preparation method, application, and diesel oil desulfurization method.

Background technique

The adsorbent can absorb and remove sulfur-containing compounds such as dibenzothiophene and tetrahexadimethyldibenzothiophene in hydrotreated diesel oil and gasoline under normal temperature and pressure, so as to achieve the purpose of ultra-deep desulfurization.

The adsorbent of existing adsorptive desulfurization can be metal oxide (USP6,184,176,2001-2-6; USP6,338,794,2002-2-15), molecular sieve (USP5,935,422,1999-8-10; USP5454933,1995 -10-3;), activated carbon (USP6,565,741, 2003-5-20) and metal alloys (6,558,533, 2003-5-6). Loading alkali metals or alkaline earth metals on these adsorbents can improve the sulfide adsorption selectivity of the adsorbent (USP5,935,422, 1999-8-10); loading transition metal oxides can increase the adsorption capacity of sulfide and improve the adsorption capacity of the adsorbent. Adsorption performance (4,085,195, 1978-4-18); supporting noble metal ions or oxides can improve the regeneration performance of the adsorbent (USP5,843,300; 1998-12-1). However, these adsorbents are all microporous adsorbents, and their pores are easily blocked by macromolecular substances in diesel oil, resulting in loss of adsorption performance.

Research on adsorption desulfurization of mesoporous molecular sieves such as modified MCM-41 and SBA-15 has also been paid attention to. Compared with microporous molecular sieves, mesoporous molecular sieves have better adsorption and desulfurization performance in hydrogenated diesel systems (Chem Eng Sci, 2008, 63: 356-365; Energy Fuels, 2007, 21, 250-255). However, the mesoporous pore wall has an amorphous structure, which will result in poor thermal and hydrothermal stability of the mesoporous molecular sieve, and the pore structure of the adsorbent is easily destroyed; compared with the microporous molecular sieve (such as Y-type molecular sieve), the ion exchange performance is relatively poor, The modified performance of the adsorbent is poor, the surface acid density is low, and the saturated adsorption capacity of sulfide is small. The main way to increase the saturated adsorption capacity of adsorbents is to increase the surface acid site density, and the specific methods include transition metal modification and so on. The modification methods of transition metal ions are mainly ion exchange methods, including gas phase ion exchange (VPIE), liquid phase ion exchange (LPIE) and solid phase ion exchange (SSIE). Compared with the liquid phase ion exchange method, the gas phase ion exchange method and the solid phase ion exchange method have more complete ion exchange, and the adsorption capacity of the adsorbent is larger. However, the liquid phase ion exchange method has the advantage of simple operation.

Contents of the invention

The purpose of the present invention is to provide a reduced mesoporous aluminosilicate molecular sieve with significantly improved adsorption performance.

Another object of the present invention is to provide a method for preparing the above-mentioned reduced mesoporous aluminosilicate molecular sieve.

Another object of the present invention is to provide the application of the above reduced mesoporous aluminosilicate molecular sieve.

Another object of the present invention is to provide a method for desulfurizing diesel oil using the above-mentioned reduced mesoporous aluminosilicate molecular sieve.

The inventors of the present invention are different from the existing research angles and found that the reduction of transition metal-modified mesoporous aluminosilicate molecular sieves with hydrogen can improve the adsorption capacity and selectivity of the adsorbent.

According to the reduced mesoporous aluminosilicate molecular sieve of the present invention, the molecular sieve is prepared by a method comprising the following steps:

1) preparing mesoporous aluminosilicate molecular sieves;

2) Transition metal modification;

3) Reducing the transition metal ion-modified mesoporous aluminosilicate molecular sieve with a reducing gas, the hydrogen-TPR result of the transition metal modified mesoporous aluminosilicate molecular sieve is required when the transition metal is fully reduced The temperature is preferably reduced by hydrogen to the transition metal ion modified mesoporous aluminosilicate molecular sieve. Multivalent metal ions are in different valence states with different reduction temperatures. The inventors of the present invention have found through research that the adsorption and desulfurization effect of fully reduced transition metals is the best.

According to the reduced mesoporous aluminosilicate molecular sieve of the present invention, the transition metal modification of the adsorbent can be by ion exchange method, impregnation method, or directly adding transition metal salt in the preparation process of the adsorbent. Transition metal salts may be sulfates, nitrates, chlorides, acetates or carbonates of iron, cobalt, nickel, zinc, copper, silver, lanthanum.

According to the reduced mesoporous aluminosilicate molecular sieve of the present invention, in step 2), the transition metal content in the molecular sieve loaded with transition metal ions is 3-30 wt%.

According to the reduced mesoporous aluminosilicate molecular sieve of the present invention, the mesoporous diameter of the mesoporous aluminosilicate molecular sieve is 2-4 nm.

Therefore, the method for preparing reduced mesoporous aluminosilicate molecular sieve according to the present invention comprises the following steps:

1) preparing mesoporous aluminosilicate molecular sieves;

2) Transition metal modification;

3) Reducing the mesoporous aluminosilicate molecular sieve modified by the transition metal ions with a reducing gas.

The present invention also provides the application of the reduced mesoporous aluminosilicate molecular sieve, for example, as a desulfurization adsorbent to adsorb sulfur-containing compounds in diesel oil.

Therefore, the method for desulfurizing diesel oil according to the present invention includes the step of contacting sulfur-containing diesel oil with the above-mentioned reduced mesoporous aluminosilicate molecular sieve. Preferably, in the desulfurization method according to the present invention, the sulfur content of diesel oil is 50-500mL/g; the ratio of diesel oil to the reduced mesoporous aluminosilicate molecular sieve is 10-60mL/g, and the temperature of diesel oil during adsorption is Room temperature ~ 150°C.

The mesoporous aluminosilicate (MAS) salt adsorbent of the present invention is a molecular sieve compounded by micropores and mesoporous pores, and the mesoporous pore wall contains primary and secondary structural units of microporous Y-type molecular sieves, which not only maintains the microporous molecular It has higher acid density and acid strength, and has the larger pore size of mesoporous molecular sieves and good thermal stability and hydrothermal stability. The reduced adsorbent obtained through modification of transition metal ions and hydrogen reduction treatment can further improve the adsorption capacity and adsorption selectivity of the adsorbent for sulfide. By adjusting the reduction temperature, the morphology and properties of multivalent transition metals on the adsorbent can be changed to obtain the most suitable adsorption desulfurization effect.

Description of drawings

Figure 1 shows the adsorption breakthrough curves of Ni(II)-MAS and Zn(II)-MAS.

Figure 2 is the H2-TPR spectrum of Ni-MAS.

Figure 3 shows the breakthrough curves of adsorption and desulfurization of DBT by Ni-MAS at different reduction temperatures.

Figure 4 is the determination of the adsorption saturation capacity of Ni(II)-MAS at different adsorption temperatures.

Figure 5 is a comparison of the adsorption curves of Ni-MAS adsorbents on DBT and toluene before and after reduction, Figure 5A: no reduction; Figure 5B: reduction at 450 °C.

Detailed ways

The preparation of embodiment 1Ni(II)-MCM-41 and Ni(II)-Y

1. Preparation of mesoporous molecular sieve MCM-41: choose water glass as the silicon source, sodium aluminate as the aluminum source, and prepare it in a 100mL polytetrafluoroethylene reactor. Surfactant concentration CTAB/SiO ₂ molar ratio was 0.15, Si/Al ratio was 40, pH was adjusted to 10.0, crystallized at 120°C for 24 hours. The product was washed with deionized water, dried, and calcined at 400°C to obtain MCM-41.

2. Transition metal modified mesoporous molecular sieve (Ni(II)-MCM-41)

Using the method of ion exchange, the above-mentioned mesoporous molecular sieve MCM-41 was added to 0.5mol/L Ni(NO ₃ ) ₂ aqueous solution, stirred at room temperature for 24 hours, then washed with deionized water and suction filtered, dried, and calcined at 400°C for 4 hours. Ni(II)-MCM-41 is obtained.

3. Transition metal modified Y-type molecular sieve (Ni(II)-Y)

Using the method of ion exchange, Y-type molecular sieve (purchased from Qilu Petrochemical Company Catalyst Factory) was added to 0.5mol/L Ni(NO ₃ ) ₂ aqueous solution, stirred at room temperature for 24 hours, then washed with deionized water and suction filtered, dried, 400 ℃ calcined for 4 hours to obtain Ni(II)-Y.

Example 2 Preparation of reduced mesoporous aluminosilicate molecular sieves

1. Preparation of mesoporous aluminosilicate molecular sieves

Synthesis of Y-type molecular sieve precursor: Heat and stir 0.446g NaAlO ₂ , 1.619g NaOH and 4.0mL H ₂ O until dissolved, add 7.1mL water glass solution and stir until the solution is clear, transfer the solution to a plastic container and age at room temperature for 24h , to obtain the Y-type zeolite precursor.

Synthesis of mesoporous aluminosilicate MAS: Dissolve different doses of CTAB in 50 mL of water with heating and stirring, add 12 mL of ammonia water to the CTAB solution, then add 5 mL of aged Y-type zeolite precursor solution, adjust the pH with 10% sulfuric acid solution To 9-10, after stirring for 3 hours, put it into a reaction kettle and crystallize at 100°C for 24 hours, 48 hours, and 72 hours. The product is suction filtered, dried and then calcined to obtain MAS with a pore size of 3nm.

2. Transition metal modified mesoporous aluminosilicate molecular sieves (Ni(II)-MAS and Zn(II)-MAS)

Using the method of ion exchange, the above-mentioned mesoporous aluminosilicate MAS was added to 0.5mol/L Ni(NO ₃ ) ₂ and Zn(NO ₃ ) ₂ aqueous solution, stirred at room temperature for 24 hours, and then washed with deionized water and suction filtered. Dry to obtain Ni(II)-MAS and Zn(II)-MAS, wherein the content of transition metal Ni is 4.2wt%, and Zn is 5.6wt%. Multiple ion exchanges can increase the content of loaded metals. After three ion exchanges, the Ni content in Ni(II)-MAS can be increased to 11.6%.

3. Mesoporous aluminosilicate molecular sieves modified by reducing transition metals

Put the transition metal-modified mesoporous aluminosilicate molecular sieve Ni(II)-MAS or Zn(II)-MAS under nitrogen protection, raise the temperature to 450°C for activation for 2 hours, and then use hydrogen gas to reduce at high temperature for 2 hours. That is, the reduction adsorbent Ni(II)-MAS or Zn(II)-MAS is obtained.

The desulfurization performance comparison of embodiment 3 different molecular sieve carriers

Adopt the reduced Ni(II)-Y that embodiment 1-2 prepares, Ni(II)-MAS, Ni(II)-MCM-41 adsorbent removes the sulfur-containing compound in diesel oil, the ratio of diesel oil and adsorbent is 30mL/g. The performance of diesel oil is shown in Table 1. The adsorption desulfurization effects of three different types of diesel oil (marked as A, B, and C) were compared. Table 1 shows the performance of three kinds of hydrogenated diesel oil.

Table 1 Physicochemical properties of three kinds of hydrogenated diesel oil

Note: nd20 is the refractive index of the diesel sample

The results after desulfurization are shown in Table 2:

Table 2 Diesel adsorption desulfurization results, μg/g (oil ratio: 30mL/g)

Change the ratio of diesel oil and adsorbent to be 10mL/g and 60mL/g, use the Ni(II)-Y prepared in Example 1-2, Ni(II)-MAS, Ni(II)-MCM-41 adsorbent to remove The results of sulfur compounds in diesel (A, B, C) after desulfurization are shown in Tables 3 and 4:

Table 3 Results of diesel adsorption desulfurization, μg/g (oil ratio: 10mL/g)

Table 4 Results of diesel adsorption desulfurization, μg/g (oil ratio: 60mL/g)

It can be seen from the above table 2-4 that the adsorption capacity for diesel oil is in the order of Ni(II)-MAS>Ni(II)-MCM-41>Ni(II)-Y. Under the same conditions of loading transition metals, Mesoporous aluminosilicate adsorbent (MAS) containing microporous molecular sieve structural units in the pore wall has a larger adsorption capacity than microporous molecular sieve (Y-type molecular sieve) and mesoporous molecular sieve (MCM-41).

The desulfurization performance comparison of embodiment 4 different metal ions

Two reduced mesoporous aluminosilicate adsorbents, Ni(II)-MAS or Zn(II)-MAS, were used to compare the adsorption desulfurization effects of simulated oil systems on a fixed bed. The reduction temperature of the adsorbent is 450°C. The simulated oil is n-octane solution of 2mmol/LDBT, the adsorption temperature is 50°C, and the flow rate during adsorption is 0.2mL/min. As shown in Figure 1. The modification effect of Ni metal is better than that of Zn metal. Under the same conditions, the saturated adsorption capacity of Ni-MAS adsorbent is larger than that of Zn-MAS adsorbent.

Example 5

Selection of reduction temperature and comparison of desulfurization effect of reduced mesoporous aluminosilicate Ni(II)-MAS. According to the hydrogen-TPR characterization results of Ni(II)-MAS, as shown in Figure 2, the selected reduction temperatures were no reduction, 400 °C reduction and 450 °C reduction, so that the Ni element in the adsorbent was in three different forms. Then compare the adsorption and desulfurization effects. As shown in Figure 3, the adsorbent obtained by reduction at 450°C has the best desulfurization effect. However, the adsorption performance of the adsorbent obtained by reducing at 390°C is not as good as that of the unreduced adsorbent, which shows that although the reduction treatment can improve the adsorption capacity of the adsorbent, the selection of the reduction temperature is a critical step. It will inhibit the desulfurization effect of the adsorbent.

Example 6

Fixed-bed adsorption and desulfurization performance of hydrogenated diesel oil with reduced mesoporous aluminosilicate Ni(II)-MAS. Using 90ppm hydrogenated diesel as raw material, the effect of adsorption temperature on desulfurization performance was investigated at 30, 70 and 110°C , the flow rate is 0.2mL/min, as shown in Figure 4, the adsorption breakthrough points of the adsorbent are 7, 12 and 18mL/g adsorbent respectively. It can be seen that with the increase of temperature, the sulfur adsorption capacity of the adsorbent for diesel oil increases, and the desulfurization effect is enhanced.

Example 7

The effect test of the adsorption selectivity of reduced mesoporous aluminosilicate Ni(II)-MAS on DBT. There is competitive adsorption between aromatic compounds and sulfides in diesel oil, which will affect the adsorption effect of adsorbents on sulfides. Using toluene as a model compound, the adsorption selectivity of reduced adsorbent Ni(II)-MAS to DBT was investigated. Using n-octane solution of 3mmol/LDBT+20mmol/L toluene as raw material, the adsorbents reduced at 450°C were compared with those without reduction. The adsorption temperature was 50°C and the flow rate was 0.2mL/min. As shown in Figure 5, the saturated adsorption capacity of the adsorbent to DBT and toluene when not reduced is 8.2mL/g and 7.4mL/g respectively, and the relative adsorption ratio is 0.17, while the adsorption capacity of the adsorbent after reduction to DBT and toluene They are 12.6mL/g and 8.9mL/g respectively, and the relative adsorption ratio is 0.21. It can be seen that the reduction treatment can improve the adsorption selectivity of the adsorbent to sulfide.

Claims (10)

1. a reduced form mesoporous aluminoshilicate molecular sieve is characterized in that, the method preparation of described molecular sieve by may further comprise the steps:

1) preparation mesoporous aluminoshilicate molecular sieve;

2) transition metal modified;

3) reduce the mesoporous aluminoshilicate molecular sieve of above-mentioned transition metal modified mistake with reducing gas, reduction temperature is needed temperature when transition metal fully reduces among the hydrogen-TPR result of mesoporous aluminoshilicate molecular sieve of described transition metal modified mistake.

2. reduced form mesoporous aluminoshilicate molecular sieve according to claim 1 is characterized in that, in step 2) in, the content of transition metal is 3～30wt% in the transition metal modified molecular sieve.

3. reduced form mesoporous aluminoshilicate molecular sieve according to claim 1 is characterized in that described transition metal is iron, cobalt, nickel, zinc, copper, lanthanum.

4. reduced form mesoporous aluminoshilicate molecular sieve according to claim 1 is characterized in that the mesoporous aperture of described mesoporous aluminoshilicate molecular sieve is 2～4nm.

5. reduced form mesoporous aluminoshilicate molecular sieve according to claim 1 is characterized in that, in step 3), with the above-mentioned transition metal modified mesoporous aluminoshilicate molecular sieve of hydrogen reducing.

6. method for preparing reduced form mesoporous aluminoshilicate molecular sieve said method comprising the steps of:

1) preparation mesoporous aluminoshilicate molecular sieve;

2) transition metal modified;

3) reduce above-mentioned transition metal modified mesoporous aluminoshilicate molecular sieve with reducing gas, needed temperature when transition metal fully reduces among the hydrogen-TPR result of the mesoporous aluminoshilicate molecular sieve of described transition metal modified mistake.

7. the application of the described reduced form mesoporous aluminoshilicate of claim 1 molecular sieve.

8. the described reduced form mesoporous aluminoshilicate of claim 1 molecular sieve is as the application of desulfuration adsorbent.

9. a diesel fuel desulfurization method is characterized in that, described method comprises the step that the described reduced form mesoporous aluminoshilicate of sulfur-containing diesel and claim 1 molecular sieve is contacted.

10. sulfur method according to claim 9 is characterized in that, the sulphur content of diesel oil is 50～500mL/g; The ratio of diesel oil and described reduced form mesoporous aluminoshilicate molecular sieve is 10～60mL/g, and the temperature of diesel oil is room temperature～150 ℃ during absorption.

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