CN-117582967-B - Modified alumina and preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a modified alumina, a preparation method and application thereof, a supported catalyst and application thereof. The modified alumina comprises silicon and alumina, wherein the silicon is connected to the surface of the alumina through Si-O-Al chemical bonds, adjacent silicon on the surface of the alumina is connected through Si-O-Si chemical bonds, the silicon-aluminum ratio of the modified alumina is less than 1, and the acid density of B of the modified alumina is less than or equal to 2 mu mol/g. The invention effectively reduces the acid density B of the modified alumina on the premise of ensuring that the modified alumina has low wear index, high crushing strength, high specific surface area and low average pore diameter, and simultaneously, the modified alumina is used for a catalyst carrier, and the prepared supported catalyst has higher catalytic activity.

Inventors

• LIU KANGYU
• LI XUEFENG
• ZHANG YI
• ZONG BAONING
• LIU WEI
• ZHENG BO

Assignees

• 中国石油化工股份有限公司
• 中石化石油化工科学研究院有限公司

Dates

Publication Date

20260505

Application Date

20220808

Claims (15)

1. 1. The modified alumina is characterized by comprising silicon and alumina, wherein the silicon is connected to the surface of the alumina through Si-O-Al chemical bonds, and adjacent silicon on the surface of the alumina is connected through Si-O-Si chemical bonds, wherein the silicon-aluminum ratio of the modified alumina is <1; Wherein the acid density of the modified alumina B is 0-1.4 mu mol/g, the specific surface area is 100-220m 2 /g, the average pore diameter is 10-30nm, the abrasion index is 1-20%, and the crushing strength is 50-150N/cm; Wherein the content of the aluminum oxide is 50-90wt% based on the total weight of the modified aluminum oxide, and the content of the silicon calculated by SiO x is 10-50wt%, wherein x is more than or equal to 1 and less than or equal to 2; The modified alumina is prepared by the following steps of (1) carrying out first mixing on an aluminum source, an acidic compound and water to obtain a first mixture, (2) sequentially carrying out molding, first drying and first roasting on the first mixture to obtain molded alumina, (3) dissolving the molded alumina in water, firstly adding an alkaline compound to adjust the pH value to 7-12, then adding a silicon source to carry out second mixing to obtain a second mixture, and (4) carrying out solid-liquid separation on the second mixture, and sequentially carrying out second drying and second roasting on the obtained modified alumina precursor to obtain the modified alumina.
2. 2. The modified alumina of claim 1, wherein the modified alumina has a B acid density of 0-0.5 μmol/g.
3. 3. The modified alumina according to claim 1, wherein the modified alumina has a specific surface area of 120-200m 2 /g, an average pore size of 15-25nm, a wear index of 1-15%, and a crush strength of 70-130N/cm.
4. 4. The modified alumina according to claim 1, wherein the content of the alumina is 70 to 80wt% and the content of the silicon calculated as SiO x is 20 to 30wt%, wherein 1≤x≤2, based on the total weight of the modified alumina; Wherein the alumina is gamma-alumina.
5. 5. A method for preparing the modified alumina according to any one of claims 1 to 4, comprising the steps of: (1) Firstly mixing an aluminum source, an acidic compound and water to obtain a first mixture; (2) Sequentially molding, first drying and first roasting the first mixture to obtain molded alumina; (3) Dissolving the formed alumina in water, adding an alkaline compound to adjust the pH to 7-12, and then adding a silicon source to perform second mixing to obtain a second mixture; (4) And carrying out solid-liquid separation on the second mixture, and sequentially carrying out second drying and second roasting on the obtained modified alumina precursor to obtain the modified alumina.
6. 6. The method of claim 5, wherein in step (1), the amount of the aluminum source in the first mixture is 0.01 to 10wt%, and the amount of the acidic compound is 0.01 to 3wt%; Wherein the first mixing condition comprises a temperature of 15-40 ℃, a rotating speed of 100-1000rpm and a time of 0.1-5h.
7. 7. The method of claim 6, wherein in step (1), the amount of the aluminum source in the first mixture is 0.05 to 5wt%, and the amount of the acidic compound is 0.05 to 1wt%; Wherein the first mixing condition comprises a temperature of 20-30 ℃, a rotating speed of 300-1000rpm and a time of 0.1-2h.
8. 8. The method according to claim 5, wherein in the step (2), the molding mode is selected from the group consisting of oil ammonia drop molding, spray drying molding, extrusion molding; In the step (2), the first roasting condition comprises the temperature of 700-1200 ℃ and the time of 1-10h.
9. 9. The method of claim 8, wherein in the step (2), the first firing conditions include a temperature of 800 to 1000 ℃ and a time of 1 to 5 hours.
10. 10. The method according to claim 5, wherein in the step (3), the pH is adjusted to 8 to 12; wherein the weight ratio of the formed aluminum oxide calculated by Al 2 O 3 to the silicon source calculated by SiO x is 5-9:1-5, wherein x is more than or equal to 1 and less than or equal to 2; Wherein the second mixing condition comprises 20-70 ℃, 100-1000rpm and 1-20h.
11. 11. The method according to claim 10, wherein in step (3), the pH is adjusted to 10.5 to 11.5; Wherein the weight ratio of the formed aluminum oxide calculated by Al 2 O 3 to the silicon source calculated by SiO x is 7-8:2-3, wherein x is more than or equal to 1 and less than or equal to 2; wherein the second mixing condition comprises a temperature of 25-60 ℃, a rotating speed of 300-1000rpm and a time of 6-12h.
12. 12. The method according to claim 5, wherein in the step (4), the condition of the second firing includes a temperature of 400-1000 ℃ and a time of 1-10 hours.
13. 13. The method of claim 12, wherein in step (4), the conditions of the second firing include a temperature of 500-900 ℃ and a time of 1-5 hours.
14. 14. A supported catalyst, characterized in that the supported catalyst comprises a carrier and an active component supported on the carrier; Wherein the support is selected from the group consisting of modified aluminas according to any one of claims 1 to 4.
15. 15. Use of the supported catalyst of claim 14 in the hydrocephalus reaction of aminocaprolactam and paraformaldehyde to prepare dimethylaminocaprolactam.

Description

Modified alumina and preparation method and application thereof Technical Field The invention relates to the technical field of catalysts, in particular to modified alumina, a preparation method and application thereof, a supported catalyst containing the modified alumina and application thereof. Background The catalyst carrier is an important basic stone for synthesizing the supported catalyst, and the structure and physical and chemical properties of the catalyst carrier have great influence on the properties and application range of the supported catalyst. Alumina is an important and common industrial catalyst carrier, and the properties of reactivity, hydrothermal stability, wear resistance and the like are important indexes for evaluating the catalyst carrier. Modification of the surface of alumina can enhance certain properties of alumina, which is of great significance for extending and expanding the application range of alumina. CN101448565A discloses an alumina with high hydrothermal stability, which is improved by treating the transition alumina used as adsorbent and catalyst carrier with soluble silicon inorganic compound. CN107774248a discloses a silicon modified fischer-tropsch synthesis catalyst and its application, and the alumina catalyst carrier synthesized by the silicon modification method has excellent stability and wear resistance in fischer-tropsch reaction. CN106582597a discloses a silicon modified alumina, its preparation method and application, by adjusting the pH value of the mixed system of alumina sol and silica sol, flexible conversion between improving pore volume with emphasis and improving B acid content with emphasis can be achieved, the B/L of the material surface is 40-95%, and the pore volume is 0.8-1.2cm 3/g. CN113562751a discloses a modified pseudo-boehmite and a preparation method thereof, and when preparing the modified pseudo-boehmite, the modified pseudo-boehmite has specific surface hydroxyl distribution after calcination by adding a phosphorus-containing compound, a non-metal auxiliary compound, a grain growth regulator and the sectional control of the pH in the preparation process, so that the catalyst has excellent heavy oil hydrogenation activity and high stability. The prior art does not relate to how to regulate complex acid sites on the surface of the alumina, and the application of the alumina in the field of fine chemical engineering is limited by the acid sites with different types and different intensities. Thus, there is a need for a modified alumina having low acidity. Disclosure of Invention The invention aims to overcome the problems that the existing modified alumina has complex acid sites, cannot have wear resistance, high stability, adjustable acid quantity and the like, and has low activity, short service life and the like in the field of fine chemical industry, and provides a modified alumina, a preparation method and application thereof, a supported catalyst containing the modified alumina, and application thereof. In order to achieve the above object, a first aspect of the present invention provides a modified alumina comprising silicon and alumina, wherein the silicon is connected to the surface of the alumina by a Si-O-Al chemical bond, and adjacent silicon on the surface of the alumina is connected by a Si-O-Si chemical bond; Wherein the acid density of B of the modified alumina is less than or equal to 2 mu mol/g. Preferably, the modified alumina has a B acid density of 0 to 2. Mu. Mol/g, preferably 0 to 1.4. Mu. Mol/g, more preferably 0 to 0.5. Mu. Mol/g. Preferably, the content of the aluminum oxide is 50-90wt% based on the total weight of the modified aluminum oxide, and the content of the silicon calculated as SiO x is 10-50wt%, wherein x is 1-2; preferably, the alumina is gamma-alumina. The second aspect of the present invention provides a method for producing a modified alumina, comprising the steps of: (1) Firstly mixing an aluminum source, an acidic compound and water to obtain a first mixture; (2) Sequentially molding, first drying and first roasting the first mixture to obtain molded alumina; (3) Dissolving the formed alumina in water, adding an alkaline compound to adjust the pH to 7-12, and then adding a silicon source to perform second mixing to obtain a second mixture; (4) And carrying out solid-liquid separation on the second mixture, and sequentially carrying out second drying and second roasting on the obtained modified alumina precursor to obtain the modified alumina. The third aspect of the invention provides a modified alumina provided in the first aspect or the modified alumina prepared by the method provided in the second aspect, and the application of the modified alumina in a catalyst carrier, gas-liquid adsorption and solid-phase filling agent. A fourth aspect of the present invention provides a supported catalyst comprising a carrier and an active component supported on the carrier; wherein the support is selected