RU2525396C1 - Composition of charge for high-porosity ceramic material with latticed-cellular structure - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: composition of a charge for high-porosity ceramic material with latticed-cellular structure for catalyst carriers comprises an inert filler - electrically molten corundum and disperse phase with a strengthening additive. At the same time to increase material strength, they use a high-aluminous porcelain mass as a disperse phase, and the strengthening additive is a composition MgO+SiC, providing for formation of the phase of eutectic composition in the system MgO-SiO₂ when baked in the temperature range of 1250-1300°C with the following ratio of components: electrically molten corundum - 5-20 wt %, high-aluminous porcelain mass - 76.5-90 wt %, strengthening additive MgO+SiC - 3.5-5 wt %.

EFFECT: usage of the specified composition makes it possible to manufacture high-porosity strong ceramic materials with latticed-cellular structure with higher mechanical compression strength with preservation of total volume open porosity.

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Description

The present invention relates to the chemical technology of highly porous ceramic materials with a mesh-cellular structure, which can be used as stationary carriers of catalysts for the conversion of natural gas, neutralization of carbon oxides, nitrogen and hydrocarbons in products of the combustion of motor fuels, catalytic liquid-phase heterogeneous processes for the recovery of unsaturated hydrocarbons, aromatic compounds , aldehydes, ketones, carboxylic acids, etc., filters for filtering contaminated liquid gases and nozzles for mass and heat transfer processes, high-temperature heat-insulating materials and for other purposes.

For the manufacture of products from highly porous ceramic materials with a mesh-cellular structure, it is known to use aluminosilicate materials, the slip of which is applied to reticulated polyurethane foam, the products are squeezed from the excess slip, dried and fired at temperatures up to 1350 ° C (see, for example, V.N. Antsiferov , S.E. Porozova. // Highly porous permeable materials based on aluminosilicates. // Perm, 1996, 207 pp.).

The disadvantages of these materials are the lack of open porosity of the jumper cells, low specific surface area, large shrinkage in the range of 10-20%, which leads to the formation of tapering, deformation and the lack of preservation of the accuracy of the geometric shape and size of the products.

The properties of products based on aluminosilicates differ little and are, for example, for highly porous porcelain values: apparent density - 0.2-0.3 g / cm ³ ; total open volume porosity - 80-88%; mechanical compressive strength - 0.1-0.5 MPa (see V.N. Antsiferov, V.N. Ovchinnikova, S.E. Porozova, I.V. Fedorova. // Highly porous cellular ceramic materials. // Glass and ceramics, 1996, No. 9, pp. 19-20).

The disadvantage of highly porous porcelain is the low values of mechanical compressive strength (such materials are not suitable for use as catalyst supports).

The closest in technical essence and the achieved result to the claimed one is the composition of the mixture for the manufacture of highly porous material with a mesh-cellular structure for catalyst supports, selected as a prototype (see RF patent No. 2233700, priority dated June 11, 2002, August 10, 2004. Bull No. 22. The composition of the charge for highly porous material with a mesh-cellular structure for catalyst supports. / A.I. Kozlov, E.S. Lukin).

A highly porous material with a mesh-cellular structure for catalyst carriers is obtained by reproducing the structure of foamed reticulated polyurethane foam by applying a slip on a polymer matrix containing a mixture of an inert filler in the form of electrofused corundum, silicon carbide, quartz sand, and dispersed aluminum oxide powder with additives of group II and IV metal oxides D.I.Mendeleev's tables in any quantity with the addition of a binder followed by drying of the products, burning of the organic base and firing became the ceramic skeleton in the temperature range 1350-1500 ° C. After firing, the highly porous material with a mesh-cellular structure for catalyst supports has a total open volume porosity of 88-92%, and mechanical compressive strength from 0.5 to 1.8-2.0 MPa.

The ceramic suspension used to impregnate the polymer matrix has a low viscosity and high fluidity, which allows it to be applied uniformly to the polymer matrix.

The disadvantages of the manufactured highly porous material with a mesh-cellular structure include a relatively low mechanical compressive strength (not exceeding 2.0 MPa).

A number of technological processes require a significantly higher strength of the catalyst carrier due to the very high feed rate of the reaction mixture in the reactor and the occurrence of high pressures exerted by the catalyst carrier during reactor startup.

The technical result, to which the claimed invention is directed, is the manufacture of highly porous durable ceramic materials with a mesh-cellular structure with increased mechanical compressive strength while maintaining the same total open volume porosity.

This technical result is achieved by reproducing the structure of the foamed reticulated polyurethane foam of any geometric shape by impregnation with a slip prepared from a mixture of the following composition: inert filler in the form of electrocorundum (particle size 10-14 μm) - 5-20 wt.%, High-alumina porcelain mass in the form of powder ( with a content of A1 ₂ O ₃ 38-45 wt.%) - 76.5-90 wt.% and a hardening additive with a total content of MgO + SIC (particle size 0.3-1.0 μm) - 3.5-5 wt. .%, providing increased strength of ceramic materials with mesh mesh This structure due to the formation of a phase of the eutectic composition in the MgO-SiO _{2 system} , which structures the continuous phase of glass in porcelain during firing in the temperature range 1250–1300 ° С.

A 5% solution of polyvinyl alcohol is used as the liquid phase of the slip.

After impregnation of the workpieces with a slip, its excess is squeezed. Then the preforms are subjected to heat treatment for burning the organic base and firing the ceramic frame in the temperature range 1250-1300 ° C. The total open volume porosity of the obtained ceramic product with a mesh-cellular structure is 85-92%. Samples from the obtained highly porous ceramics have increased mechanical compressive strength from 4.0 to 7.5 MPa.

Example No. 1. A sample of polyurethane is impregnated at room temperature with a slip prepared from a mixture of the following composition:

inert filler in the form of dispersed corundum (particle size 10-14 μm) - 5 wt.%, porcelain mass in the form of a powder (with a content of A1 ₂ O ₃ 38-45 wt.%) - 90 wt.%, hardening additives with particle size 0.3-1.0 μm - 5 wt.% And a 5% solution of polyvinyl alcohol, squeeze out the excess of slip, dried at a temperature of 100-110 ° C for 2.0-2.5 hours, and then fired at a temperature 1250 ° C. The dried and fired ceramic sample with a mesh-cellular structure has an apparent density of 0.33 g / cm ³ and a mechanical compressive strength of 7.5 MPa.

Example No. 2. A sample of polyurethane is impregnated at room temperature with a slip prepared from a mixture of the following composition:

inert filler in the form of dispersed corundum (particle size 10-14 μm) - 12.5 wt.%, porcelain mass in the form of a powder (with a content of A1 ₂ O ₃ 38-45 wt.%) - 83.4 wt.%, hardening additives with a particle size of 0.3-1.0 μm - 4.1 wt.% and a 5% solution of polyvinyl alcohol, squeeze out the excess of slip, dried at a temperature of 100-110 ° C for 2.0-2.5 hours and then fired at a temperature of 1280 ° C. The dried and calcined ceramic sample with a mesh-cellular structure has an apparent density of 0.40 g / cm ³ and a mechanical compressive strength of 5.3 MPa.

Example No. 3. A sample of polyurethane is impregnated at room temperature with a slip prepared from a mixture of the following composition:

inert filler in the form of dispersed corundum (particle size 10-14 μm) - 20 wt.%, porcelain mass in the form of powder (with a content of A1 ₂ O ₃ 38-45 wt.%) - 76.5 wt.%, hardening additives with a particle size of 0.3-1.0 microns - 3.5 wt.% and a 5% solution of polyvinyl alcohol, squeeze the excess of slip, dried at a temperature of 100-110 ° C for 2.0-2.5 hours, and then fired at a temperature of 1300 ° C. The dried and fired ceramic sample with a mesh-cellular structure has an apparent density of 0.43 g / cm ³ and a mechanical compressive strength of 4.0 MPa.

The manufacture of a carrier with a developed surface for the catalyst from highly porous durable ceramic materials with a mesh-cellular structure with the developed composition of the charge consists in applying aluminosol to them by impregnation followed by calcination at a temperature of 900 ° C. In the pores and on the surface of the lintels of highly porous durable ceramic materials with a mesh-cellular structure, porous particles of γ-A1 ₂ O _{3 are formed} . Aluminosol is applied in such an amount that the specific surface of the carrier increases several times in comparison with the original specific surface of the ceramic material. Particles γ-A ₁ O ₃ firmly bake to the surface of the lintels containing the glass phase of a given composition.

The obtained ceramic catalyst support with a mesh-cellular structure is characterized by high mechanical compressive strength from 4.0 to 7.5 MPa.

The application of the invention allows to obtain a highly porous durable ceramic product with a mesh-cellular structure of multifunctional purpose.

The obtained highly porous durable ceramic product with a mesh-cellular structure can be widely used as a carrier for catalysts for gas-phase and liquid-phase processes, in filter designs for filtering contaminated liquids and gases, nozzles for mass and heat transfer processes, high-temperature heat-insulating materials, and for other purposes .

After applying a catalytically active component to the surface of a prepared highly porous durable ceramic product with a mesh-cellular structure, the obtained catalyst can be used in various catalytic heterogeneous gas-phase and liquid-phase chemical processes: natural gas conversion, CO and CH oxidation, NO _x reduction, unsaturated hydrocarbons, aromatic compounds , aldehydes, ketones, carboxylic acids, etc.

Claims (1)

The composition of the charge for a highly porous ceramic material with a mesh-cellular structure for catalyst carriers, consisting of an inert filler - electrofused corundum and a dispersed phase with a reinforcing additive, characterized in that to increase the strength of the material, a high-alumina porcelain mass is used as a reinforcing additive - composition of MgO + SiC, providing the formation of the eutectic phase composition in the MgO-SiO ₂ system during firing in the temperature range 1250-1300 ° C follows from the soot Ocean components:
electrofused corundum - 5-20 wt.%;
high alumina porcelain mass - 76.5-90 wt.%;
hardening additive MgO + SiC - 3.5-5 wt.%