Catalyst and method thereof

 

(57) Abstract:

The catalyst with a porous substrate on the basis of aluminum oxide on the surface layer of which the thickness of 300-400 microns uniformly applied cerium concentration of 4.7-9.4 per cent by weight of the substrate, and the concentration of cerium in the substrate outside of the surface layer is about zero or equal to zero. The thickness of the surface layer containing cerium, DC. The method of producing catalyst consists in impregnating the surface layer of the substrate of aluminum oxide colloidal solution hydroxynitrile cerium with a pH of 0.5 to 1, with the concentration of cerium oxide in solution 52-78,3 g/l, followed by drying and heat treatment. The average size of the colloidal particles of the solution is 5 nm, the average diameter of micropores of the aluminum oxide is . 2 S. p. and 2 C.p. f-crystals, 1 table.

The invention relates to the field of catalysts used, for example petroleum fractions, and waste streams, in particular of exhaust gases of internal combustion engines.

In particular, the invention relates to a catalyst containing a carrier formed of a porous material, the surface of which is coated with active elements, in particular cerium.

Known Kato as aluminum oxide, which give a different shape, for example the form of balls or cylinders, with multi-leaf cross-section or cross-section of a wheel type truck.

Known to the receiving media catalyst from mineral oxides that are in suspension in aqueous solution, with the formation of active surface sites.

Since most of the material oxides atterny, so reactive surface can equally well to react with electronegative compounds (anions) and electrophoretically compounds (cations).

These carriers have a high specific surface area, for example, above 20 m2/, But their catalytically active surface may be increased by applying active elements, selected, for example, from groups:

the actual catalytically active elements, which are usually represented by a platinum-group elements, such as palladium, rhodium;

elements-activators that favor the catalytic activity of the above elements.

Currently, the various elements, with the exception of platinum-group elements and the platinum, is usually applied by impregnation of the entire surface novtel is Tracey this item in any part of the surface.

In this study the rate of diffusion of reactants to the catalyst showed that only the surface areas of the catalyst are effective. Consequently, only a fraction of the marked items will be really effective.

Since the active elements are usually very expensive and significantly affect the cost of the catalyst and method of its production, it was assumed various methods of reducing the number of active elements in the catalyst, while maintaining a high or at least an equivalent level of catalytic activity.

For the most part of the catalyst was in contact with the reagents proposed in the known patent to give the carrier or the catalyst in this form, so thick it would not be more than twice the thickness of the diffusion of reagents.

However, the disadvantage of this solution lies in the need to resort to complex forms, leading to a fragile catalysts and expensive in manufacturing.

Another solution is to carry out the impregnation of the platinum group metals only on the surface layer of the carrier. However, this method, which uses the solution of salt of platinum elements.

The purpose of this decision is to reduce the cost of catalyst and method of its production by reducing the quantity of the applied active elements different from the platinum-group elements, without reducing the catalytic activity of the catalyst.

This goal is achieved by the proposed method of producing a catalyst, comprising impregnating a porous substrate of aluminum oxide with a solution of hydroxynitrile cerium, drying the impregnated substrate and activating heat treatment, whereby the impregnation with cerium surface layer of the substrate carry out a colloidal solution of hydroxynitrile cerium with pH=0.5 to 1 with the concentration of cerium oxide in solution 52-78,3 g/l

It is advisable that the thickness of the surface layer was equal to the depth of diffusion of the reactants in the catalyst.

The objective is achieved also provide the catalyst with a porous substrate on the basis of aluminum oxide, which is applied to the cerium with as an active ingredient, according to which the cerium is uniformly deposited on the surface layer of a thickness of 300-400 microns with a concentration of cerium is 4.7-9.4% of the total mass of the substrate, and the concentration of cerium in the substrate outside of the surface layer is about zero or racemose catalyst is at least equivalent to the classic activity of the catalyst, but with a much smaller mass of the active element.

In a preferred variant of the invention, the thickness of the surface layer is maintained constant.

The catalyst according to the invention is obtained by impregnation of the carrier with the help of a colloidal solution (Sol) connection of the applied element.

Since the diffusion rate constant at any point in the media, as well as the concentration of the homogeneous reactive sites in the media, neutralization Zola is on the profile, parallel and identical to the profile of the external surface of the media.

However, in order to obtain penetration of the elements in the pores of the carrier, it is necessary that the sizes of the colloidal particles forming the Sol was less than the diameter of the pores of the support and especially the micropores, which form a large part of the surface.

Thus, for media formed by alumina, the average diameter of micropores is 200 , and the average size of the colloidal particles of the solution is 5 nm.

The impregnation of the carrier exercised by any known methods. However, the preferred method of dry impregnation, as it allows you to better adjust the thickness of the impregnated layer.

Then impregnated in this way the carrier is dried, then subjected to heat treatment for activating the catalyst.

The pH of the colloidal solution is chosen depending, firstly, on the stability of the used Zola, and, secondly, from the acidic or basic nature of the impregnated carrier.

The following examples illustrate the invention.

P R I m e R 1. Prepare 100 g of beads of alumina of gamma structure with a specific surface area of 100 m2/g and total pore volume of 0.90 cm3/the Volume of micropores with a diameter above 1000 is 0.20 cm3/g, average diameter of micropores is 200 .

Prepared as a colloidal suspension of hydroxide as follows.

In a three-neck flask with a capacity of 2 l, equipped with a thermometer, a stirrer, a feed system reagents, reflux with heating device is injected at room temperature:

942 g of distilled water;

558 cm3solution of cerium nitrate containing a 1.25 mol/l of cerium III, and having a free acidity of 0.5 N.

Stirred reaction medium with reflux for 4 h, then filtered through ritterband glass (porosity No. 3). Dry the scientists of the product in distilled water in an amount sufficient for a volume of 200 cm3.

The concentration of CeO2in the resulting suspension of 300 g/l (the average size of the colloidal particles is 5 nm).

This colloidal suspension was diluted to obtain a solution containing 52 g/l CeO2with pH=1.

Sprinkle 90 cm3this solution per 100 g balls of aluminum oxide, rotating, for example, a rotary drum.

After 30 min of contact balls are dried at 150aboutC, then calcined in air at 400aboutC for 3 h

This media contains 4.7 wt.% cerium, in relation to the total mass of the carrier.

This cerium is contained entirely in the surface layer of a thickness of 400 μm. In this layer the concentration of cerium is 10 wt.%.

P R I m m e R 2. Repeat example 1. However, the solution of the cerium has a pH=0.5, and its concentration is to 78.3 g/L.

Balls of aluminum oxide have a specific surface area of 100 m2g, total pore volume of 1.20 cm3g, of which 0,45 cm3/g correspond to the volume of micropores with a size above 1000 . The average diameter of micropores, the appropriate volume of 0.75 cm3/g is approximately 200 .

The volume of the spray solution of cerium is 120 cm3.

Bulbs sum cerium deposited entirely on the surface layer with a thickness of 300 μm.

P R I m e R 3 (comparative).

Impregnate 100 g balls of aluminum oxide having the characteristics of the beads of example 1, an aqueous solution (90 cm3) of cerium nitrate with 52 g/l according to the operating conditions specified in example 1.

Thus obtained carrier contains 4.7 wt.% cerium by weight of the entire carrier. However, as indicated in the table, cerium distributed over the entire surface of the media.

Various media were analyzed by x-ray fluorescence to determine the concentration profile of cerium on its thickness.

To do this, select the balls of aluminum oxide with a diameter of 3.2 mm Beads, forming a statistically typical sample, divided into two equal parts and determine the concentration of cerium from the surface of the ball to the centre of the x-ray fluorescence using the apparatus "EDAX".

The results are expressed in medium mass% of cerium for each section or layer of the media. These results are summarized in the following table.

These results clearly show the advantage of the media according to the invention and the method of impregnation, which allows you to apply the cerium only on the surface layer of the device.

Of course, other active ele is if after applying the above item on the entire surface of the substrate or only on the surface layer.

CATALYST AND PROCESS FOR ITS PRODUCTION.

1. The catalyst with a porous substrate on the basis of aluminum oxide, which is applied to the cerium as the active element, characterized in that the cerium uniformly applied on the surface layer of a thickness of 300 to 400 microns with a concentration of cerium is 4.7 - 9.4% of the total mass of the substrate, and the concentration of cerium in the substrate outside of the surface layer is about 0 or equal to 0.

2. The catalyst p. 1, characterized in that the thickness of the surface layer of the substrate containing cerium, DC.

3. The method of producing the catalyst by impregnation of a porous substrate of aluminum oxide with a solution of hydroxynitrile cerium, drying the impregnated substrate and activating heat treatment, characterized in that the impregnation with cerium surface layer of the substrate carry out a colloidal solution of hydroxynitrile cerium with a pH of 0.5 to 1, with a concentration of cerium oxide in a solution of 52 - to 78.3 g/L.

4. The method according to p. 3, characterized in that the average size of the colloidal particles of the solution is 5 nm and the average diameter of micropores of the aluminum oxide is

 

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