Macroporous high-purity silica-alumina gel and preparation method thereof

Abstract

The invention relates to the field of silica-alumina gel preparation, and discloses macroporous high-purity silica-alumina gel and a preparation method thereof. According to the macroporous high-purity silica-alumina gel produced by the invention, the mass fraction of Al2O3 can reach 9%, the mass fraction of SiO2 can reach 95%, the pore volume can reach 1.2 ml / g, the mass fraction of Na2O is lessthan or equal to 0.1%, the mass fraction of CaO is less than or equal to 0.05%, and the mass fraction of MgO is less than or equal to 0.03%. The preparation method of the macroporous high-purity silica-alumina gel comprises the following eleven production steps: preparing an acid solution of aluminum salt, preparing an aqueous solution of sodium silicate, carrying out sol-gel reaction, soaking with an auxiliary agent for the first time, soaking with an acidic material, washing with water for the first time, soaking with an auxiliary agent for the second time, drying for the first time, soakingwith an auxiliary agent for the third time, washing with water for the second time and drying. The macroporous high-purity silica-alumina gel disclosed by the invention is large in pore volume and specific surface area, high in content of coordination aluminum and bonding aluminum, low in metal impurity content, high in purity, stable in skeleton structure, good in product quality and wide in application field.

Description

technical field [0001] The invention relates to the field of silica-alumina gel preparation, in particular to a macroporous high-purity silica-alumina gel and a preparation method thereof. Background technique [0002] Silica-alumina glue is a kind of silica gel containing alumina, chemical formula mSiO 2 ·nAl 2 o 3 ·xH 2 O, which is chemically stable, non-combustible, and insoluble in any solvent, is mainly used as a catalyst and catalyst carrier in the petrochemical industry, and is also used in industry as a desiccant, liquid adsorbent, and gas separation. [0003] There are three main methods for preparing silica-alumina gels in the prior art: (1) sol-gel method adding aluminum salts. The silica-alumina chemical bonds in the silica-alumina gels obtained by this method are stable, the skeleton structure is stable, and the product strength is stable. A high and stable skeleton structure is beneficial to the adjustment of the pore structure and the loading of the cataly...

AI Technical Summary

Problems solved by technology

[0003] There are three main methods for preparing silica-alumina gels in the prior art: (1) sol-gel method adding aluminum salts. The silica-alumina chemical bonds in the silica-alumina gels obtained by this method are stable, the skeleton structure is stable, and the product strength is stable. A high and stable skeleton structure is beneficial to the adjustment of the pore structure and the loading of the catalyst, but in this method, the solution control is not uniform in the process of sol and gel, and a uniform solution cannot be formed, most of which are suspensions or emulsions. As a result, the activity of silica-alumina coordination is affected, resulting in poor product uniformity; (2) the template agent method is used to prepare silica-alumina gel, which needs to increase the template agent removal process, which is complicated. During the high-temperature calcination process for template agent removal Problems affecting the skeleton strength, pore structure, coordination bond breakage and impurity content, and the template method also has the problems of difficult environmental protection and high cost; (3) the carbonization method uses aluminum salts and silicon-containing compounds to react with carbon dioxide. The gel process adopts the pH swing method, and the silicon source is introduced during the swing process. The pore volume and pore size of the silica-alumina gel obtained by this method are small, and the pores need to be enlarged. After the expansion, the skeleton strength and specific surface area will decrease, and the silica-alumina coordination bond is destroyed, causing it to be limited in the field of application

[0004] Chinese patent CN106587085A discloses a preparation method of macroporous silica-alumina gel, adding silica sol after beating boehmite, controlling the pH value at 3-5 and adding alkali to adjust the pH value of the slurry at 9-10 to obtain silica-alumina Gel, after drying, macroporous silica-alumina gel is obtained; the reaction process of this method is limited by the uniformity of stirring, the beating of raw material boehmite, and the uniformity of pH value, and the reaction process cannot obtain uniform silica-alumina gel, silica-alumina The content of chemical coordination bonds is low, and the strength of the obtained macroporous silica-alumina gel is low, which is limited in the field of use

Chinese patent CN1765742A discloses a method for preparing amorphous silica-alumina gel by carbonization. Sodium aluminate solution and silicon-containing compound solution are mixed, and carbon dioxide gas is introduced to form a gel by controlling the pH value, and the product is obtained after filtering, washing and drying; The preparation cost is low, and the obtained amorphous silica-alumina sol has a large specific surface area and pore volume, which can be used as a catalyst carrier for catalytic cracking and hydrocracking. The uniformity of the product decreases, the coordination bonds are complex and uncontrollable, and the strength of the obtained product is low, and the application field is limited

Chinese patent CN108046280A discloses a preparation method of silica-alumina colloid, which uses aluminum salt and acid-base joint sol-gel reaction, the reaction is uniform and the skeleton structure is stable, and the pore structure and aluminum content of the obtained silica-alumina colloid are controllable, but the produced by this method The content of high-reactivity coordination aluminum and bonded aluminum in silica-alumina gel is low, and the high content of impurities such as metal ions in silica-alumina gel is not conducive to high-end applications