Preparation of spherical silicon-aluminum compound for preparing acetoneketal by catalyzing glycerol-acetone

Abstract

The invention provides a preparation method of a spherical silicon-aluminum compound and application of the spherical silicon-aluminum compound in catalyzing glycerol acetone to prepare acetoneketal. On the basis of aluminum alkoxide hydrolysate and silicate ester, silicon-aluminum compound sol suitable for ball dropping is prepared through adjustment in a silicon adding mode, and the millimeter-level spherical silicon-aluminum compound is obtained through an oil ammonia column. The catalyst is used for catalyzing the ketalation reaction of glycerol acetone, and has high conversion rate and selectivity. In the preparation process of the method, only silicon and alcohol are introduced, other impurities are not introduced, the obtained spherical silicon-aluminum compound has proper acid content and high specific surface area, and is used for catalyzing preparation of acetoneketal, the glycerol conversion rate reaches 95%, and the acetoneketal selectivity is 97%. And the catalyst can be repeatedly used.

Description

Technical Field

[0001] The present invention belongs to the field of chemical production processes, and particularly relates to a method for preparing a spherical silica-alumina composite for catalyzing glycerol acetalization Background Art

[0002] In today's era, the demand for new energy has become one of the key issues faced by countries around the world. It is estimated that by 2030, the production of bioethanol and biodiesel will both increase steadily. However, it is worth noting that in the production process of biodiesel, up to 10wt% of glycerol is produced as a by-product. This clearly reveals that glycerol, as a renewable chemical raw material, has a rather large reserve globally. Therefore, converting glycerol into chemicals with higher added value undoubtedly becomes the best way to explore new markets for glycerol and enhance the sustainability of biodiesel production. Among various conversion methods of glycerol, the method of converting glycerol into acetone ketal by acetalization reaction has attracted much attention. Like other acetalization products, acetone ketal can be directly used as a fuel additive, thereby effectively reducing the formation of soot and gum. In addition, acetone ketal can also be applied in fields such as solvents, inks, drugs, and paints

[0003] The glycerol acetalization reaction is a typical acid-catalyzed reaction. In traditional production processes, inorganic acids such as HCl and H3PO4 are often used as catalysts. Such catalysts are usually liquids, with a large acid content per unit mass and strong acidity. However, these catalysts have many drawbacks, such as causing serious environmental pollution, being relatively dangerous during use, and being extremely troublesome to handle after the reaction. Therefore, it has become an urgent task to develop new green and highly efficient solid acid catalysts

[0004] Compared with traditional liquid acid catalysts, solid acid catalysts have obvious advantages. Feliczak-Guzik et al. added ammonium niobium oxalate during the synthesis of SBA-16, and synthesized Nb-SBA-16 under the condition of controlling the Si / Nb ratio to be 64. After reacting for 40 minutes, the glycerol conversion rate reached 86%, and the yield of acetone glycerol was 79%. The stability of the catalyst was relatively good, and the glycerol conversion rate remained at about 84% after the 4th cycle of use. Although the catalysts prepared in existing studies have good effects, due to the complex synthesis steps and high cost, they are not conducive to large-scale industrial production. Therefore, we are committed to finding a catalyst with simple synthesis, low cost, and high catalytic efficiency

[0005] Pseudoboehmite has the advantages of narrow pore size distribution, good mechanical strength, appropriate isoelectric point and high physicochemical stability, etc., and is the most commonly used catalyst support in the catalytic field. However, it only contains L acid itself and is difficult to catalyze the ketalization of glycerol and acetone, so it needs to be modified to improve its performance. Doping with silica can change the pore structure of alumina and form a material with both B and L acids, which is beneficial to the preparation of acetone glycerol ketal. Our research found that spherical low-silica modified pseudoboehmite has certain catalytic activity, but when the silicon content increases, the sol required for dropping balls cannot be formed. Therefore, a new method needs to be developed to prepare spherical silica-alumina composites for catalyzing acetone glycerol ketalization. Summary of the Invention

[0006] The object of the present invention is to prepare a spherical silica-alumina composite for catalyzing the production of acetone glycerol ketal from glycerol and acetone. Only silicon and alcohol are introduced during its preparation process, no other impurities are introduced, and there is no waste discharge. The obtained spherical silica-alumina composite has a high specific surface area and a macroporous structure, and contains B acid and L acid. It is used for catalyzing the ketalization reaction of glycerol and acetone and has high conversion rate and selectivity. The technical solution of the present invention is to prepare a silica-alumina composite sol suitable for dropping balls by adjusting the silicon addition method, and obtain a spherical silica-alumina composite by using an oil-ammonia column. The method adopted is to add an acid decomposing agent after the hydrolysis of alcohol aluminum, then add silicon ester for deposition, and the obtained sol is dropped into balls and heat-treated, and is used for catalyzing the acetone glycerol condensation reaction.

[0007] The technical solution of the present invention is as follows: A method for preparing a spherical silica-alumina composite for catalyzing the production of acetone glycerol ketal from glycerol and acetone, using alcohol aluminum as a raw material, adding silicon ester after hydrolysis, and the content of added SiO2 is 60% by weight, including the following steps: In the first step, hydrolyze alcohol aluminum to prepare pseudoboehmite, add acid and then add silicon ester to obtain a silica-alumina composite sol, and use the oil-ammonia column method to prepare millimeter-scale spherical composites.

[0008] In the second step, calcine the heat-treated spherical silica-alumina composite and use it for the catalytic reaction of acetone and glycerol. The reaction temperature is 30-90 °C, the reaction time is 0.5-4 h, and the molar ratio of glycerol to acetone is 1:1-10.

[0009] According to the above method, when hydrolyzing alcohol aluminum, the used alcohol aluminum is C2-C6 alcohol aluminum, the water is high-purity water, and the hydrolysis is carried out during stirring.

[0010] According to the above method, the hydrolysis time is 0.5-4 h.

[0011] According to the above method, the pseudoboehmite obtained after hydrolysis is acid peptized, and the peptization temperature is 70-110 °C.

[0012] According to the above method, it is characterized in that a silicate ester is added, and the silicate ester and alcohol are mixed and then added.

[0013] According to the above method, the oil-ammonia column method is used for dropping the ball. The oil used is one or a mixed oil of paraffin oil and kerosene, and the ammonia used is ammonia water or organic amine.

[0014] According to the above method, the treatment temperature of the obtained spherical object is 90 - 120 °C, the time is 6 - 8 h, the calcination temperature is 550 - 600 °C, and the calcination time is 4 - 7 h.

[0015] Compared with the existing acetone glycerol acetal catalyst, the composite prepared by the present invention does not need to load other components, the catalyst composition is simple, the specific surface area is high, the pore volume and pore diameter are large, the acid amount is high, it can directly catalyze the preparation of acetone glycerol acetal, the conversion rate and selectivity are high, and the spherical particles have the advantages of good wear resistance, can be reused, and are easy to separate from the product. Description of the Drawings

[0016] Figure 1 It is the XRD diffraction pattern of the spherical silicon-aluminum composite before calcination in Example 1 Figure 2 It is the EDX diagram of the spherical silicon-aluminum composite after calcination in Example 1 Figure 3 It is the TG-DTG diagram of the spherical silicon-aluminum composite before calcination in Example 1 Figure 4 It is the conversion rate and selectivity of acetone glycerol acetal of the spherical silicon-aluminum composite catalyst in Example 1 repeated 5 times Detailed Description of the Invention

[0017] Example 1: First, 10 grams of aluminum isopropoxide is added to a four-necked flask and dissolved in isopropanol, then 22 milliliters of deionized water is added for hydrolysis at 85 °C, and then 5 milliliters of HNO3 (0.1 mol / L) is added. After peptization at 95 °C to prepare an aluminum sol, a mixed solution of 13.33 g of TEOS in isopropanol is added to the above sol and reacted for 3 h. The alcohol is evaporated at 110 °C to obtain a silicon-aluminum sol. Spherification and solidification are carried out in a graduated cylinder with paraffin oil on the upper layer and ammonia water (concentration about 10%) on the lower layer. The obtained spherical particles are naturally dried in a fume hood overnight and then placed in an oven at 110 °C for 7 h, and calcined in a muffle furnace at 550 °C to obtain a sample.

[0018] Example 2: First, 12 g of aluminum sec-butoxide was added to a four-necked flask and dissolved in sec-butanol. Then, 22 mL of deionized water was added and hydrolyzed at 85 °C. Next, 5 mL of HNO3 (0.1 mol / L) was added, and peptization was carried out at 95 °C to prepare an aluminum sol. After that, a mixture of 13.33 g of TEOS and isopropanol was added to the above sol and reacted for 3 h. The alcohol was evaporated at 110 °C to obtain a silica-alumina sol. Spheroidization and curing were carried out in a graduated cylinder with paraffin oil on the upper layer and ammonia water (concentration about 10%) on the lower layer. The obtained spherical particles were naturally dried in a fume hood overnight and then placed in an oven at 110 °C for 7 h, and calcined in a muffle furnace at 550 °C to obtain the sample.

[0019] Example 3: First, 7.94 g of aluminum ethoxide was added to a four-necked flask and dissolved in ethanol. Then, 22 mL of deionized water was added and hydrolyzed at 85 °C. Next, 5 mL of HNO3 (0.1 mol / L) was added, and peptization was carried out at 95 °C to prepare an aluminum sol. After that, a mixture of 13.33 g of TEOS and ethanol was added to the above sol and reacted for 3 h. The alcohol was evaporated at 110 °C to obtain a silica-alumina sol. Spheroidization and curing were carried out in a graduated cylinder with paraffin oil on the upper layer and ammonia water (concentration about 10%) on the lower layer. The obtained spherical particles were naturally dried in a fume hood overnight and then placed in an oven at 110 °C for 7 h, and calcined in a muffle furnace at 550 °C to obtain the sample.

[0020] Example 4: First, 12 g of aluminum n-butoxide was added to a four-necked flask and dissolved in n-butanol. Then, 22 mL of deionized water was added and hydrolyzed at 85 °C. Next, 5 mL of HNO3 (0.1 mol / L) was added, and peptization was carried out at 95 °C to prepare an aluminum sol. After that, a mixture of 13.33 g of TEOS and n-butanol was added to the above sol and reacted for 3 h. The alcohol was evaporated at 110 °C to obtain a silica-alumina sol. Spheroidization and curing were carried out in a graduated cylinder with paraffin oil on the upper layer and ammonia water (concentration about 10%) on the lower layer. The obtained spherical particles were naturally dried in a fume hood overnight and then placed in an oven at 110 °C for 7 h, and calcined in a muffle furnace at 550 °C to obtain the sample.

[0021] Example 5: First, 16.2 g of aluminum n-hexoxide was added to a four-necked flask and dissolved in n-hexanol. At 85 °C, 22 mL of deionized water was added for hydrolysis. Next, 5 mL of HNO3 (0.1 mol / L) was added, and peptization was carried out at 95 °C to prepare an aluminum sol. After that, a mixture of 13.33 g of TEOS and isopropanol was added to the above sol and reacted for 3 h. The alcohol was evaporated at 110 °C to obtain a silica-alumina sol. Spheroidization and curing were carried out in a graduated cylinder with paraffin oil on the upper layer and ammonia water (concentration about 10%) on the lower layer. The obtained spherical particles were naturally dried in a fume hood overnight and then placed in an oven at 110 °C for 7 h, and calcined in a muffle furnace at 550 °C to obtain the sample.

[0022] The spherical silica-alumina composite obtained by the present invention has a relatively high specific surface area, large pore volume and pore diameter, and an appropriate amount of acid. The catalyst with such a structure has practical significance for the preparation of acetone glycerol ketal and can promote the in-depth application of biomass resources.

[0023] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several improvements and modifications are made, and these all belong to the protection scope of the present invention.

Claims

1. A preparation method of a spherical silica-alumina composite for catalyzing glycerol acetone to form acetal glycerol, using alcohol aluminum as a raw material, hydrolyzing it and then adding silicate ester, with the SiO2 content added being 60% by weight, comprising the following steps: In the first step, hydrolyze alcohol aluminum to prepare pseudo-boehmite, add acid and then add silicate ester to obtain a silica-alumina composite sol, and use the oil-ammonia column method to prepare millimeter-scale spherical composites. In the second step, calcine the heat-treated spherical silica-alumina composite and use it for the catalytic reaction of acetone and glycerol. The reaction temperature is 30 - 90 °C, the reaction time is 0.5 - 4 h, and the molar ratio of glycerol to acetone is 1:1 - 10.

2. The method according to claim 1, characterized in that When hydrolyzing alcohol aluminum, the alcohol aluminum used is C2 - C6 alcohol aluminum, and the water used is high-purity water. The hydrolysis is carried out under stirring conditions.

3. The method according to claim 1, wherein When hydrolyzing alcohol aluminum, the hydrolysis time is 0.5 - 4 h.

4. The method according to claim 1, wherein Carry out acid peptization on the pseudo-boehmite obtained after hydrolysis, and the peptization temperature is 70 - 110 °C.

5. The method according to claim 1, wherein When adding silicate ester, mix the silicate ester and alcohol and then add them.

6. According to the method described in claim 1, using the oil-ammonia column method to drop balls, the oil used is one or a mixture of paraffin oil and kerosene, and the ammonia used is ammonia water or organic amine.

7. According to the method described in claim 1, the treatment temperature of the obtained millimeter-scale spherical silica-alumina composite is 90 - 120 °C, the time is 6 - 8 h, the calcination temperature is 550 - 600 °C, and the calcination time is 4 - 7 h.

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