FI89012C - Katalytbärare - Google Patents

Description

89012

Catalyst support

The invention relates to a silica-based catalyst support material with a versatile structure, thanks to which it is possible to increase the efficiency of the catalysts and to lower the reaction temperature, especially in various combustion and oxidation reactions.

In the current technology, mainly ceramic granules or ceramic and, more recently, metallic so-called monoliths coated with a high specific surface area oxide layer, most commonly alumina, so-called Wash coatilla. For the most part, both industrial process catalysts and exhaust gas converters are based on this technology.

The literature also presents the use of various fibrous materials as catalyst supports, especially the so-called in the area of flameless combustion. There are still few practical applications. Perhaps the best known is the catalyst curler.

The fibrous materials used or proposed are quartz fibers, glass fibers, ceramic fibers, asbestos, etc. which are made of wool, felt, yarn, fabric or knit for use as a carrier. These materials have a few weaknesses that have limited their deployment. The specific surface area is small, most often less than 10 m2 / g (BET), compared to normal carriers. For this reason, the actual catalytic material, usually an expensive precious metal, cannot be dispersed into small effective particles in the absence of surface area. In all applications, the poor mechanical strength of fibers for their usability.

If the duration is improved, the performance of the catalyst is negatively affected: the surface area is further reduced or harmful foreign elements have to be added to the product. Due to the fragility and stiffness of the fibers, it is very difficult to make them from fabric, knit or felt and to further develop them. more advanced structures as catalyst supports. Thus, it is often necessary to limit oneself to small applications to which wool or felt is applied. The best known material is quartz felt.

The silica-based catalyst structure EPO Patent No. 377290 (CA 113: 196927b) is disclosed in the literature.

The main difficulties in the prior art are: - the difficulty of the quartz fiber in the structure processing - the small specific surface area obtained in the processing of the quartz fiber - the large amount of precious metal required for the catalysis

In the present invention, these problems have been solved in a new way. By making an entirely new catalyst supported on a ceramic textile, which can be constructed not only of needle felt, but also of any textile structure, knit, nonwoven, woven fabric, wadding or rope. Such a support can be prepared if a silica-containing viscose fiber known, e.g. GB-pat, is used as a precursor. 1064271. The silica-containing viscose fiber can be made into a suitably shaped structure, after which the viscose can be removed from the structure by pyrolysis, which means that the structure and shape of the fiber product can be freely selected according to the end use. Thus, prior to firing, the silicic acid-containing fiber can be made like a woven fabric woven from ordinary viscose fiber or, like cotton fiber, various textile structures. Thus, a new way has been found to prepare a catalyst using a silica-containing viscose textile as a carrier precursor and combining a noble metal-based catalytic mixture with it. It should also be noted that any viscose process equipment can be used to make the fabric and knit.

The combustion conditions themselves can control both the specific surface area of the fiber (Figure 1) and the sintering of the structure. If the combustion temperature is kept below 1000 degrees, the SiO2 fiber remains amorphous, so that the dust which may be released from it is not as dangerous as, for example, the dust released from quartz felt. Thus, the firing temperature may be 400 to 1500 degrees (preferably 750 to 1050 degrees).

When the silica according to the invention is used, a wide variety of fabrics and knits can be produced due to the viscose step, and these can still be fired after combustion, e.g. The shape of the structure may be based on a cylinder or nested cylinders through which the gas passes in the axial direction, different shaped packing structures, cylinders rolled together with a support structure, etc. The structure and necessary supports are selected , delay times, etc. The invention allows a considerably greater freedom in this respect.

Such a catalyst is excellently suitable e.g. flameless combustion for both large and small applications. Examples include a catalyst brush, cookers for domestic and large households, hot air generators, etc. Other items include e.g. cleaning of flue gases and solvent vapor emissions by oxidation. Special mention should be made of the cleaning of the exhaust gases of a diesel engine, in which the use of a silica support is an absolute prerequisite for obtaining a good cleaning result also for sulfur-containing gases. The fabrics and knits produced by the process according to the invention offer new versatile possibilities for the production of a diesel catalyst.

The addition of the catalytic material, most usually the metal, to the surface of the support can be done by conventional means by chemical misorption, impregnation, evaporation from an alcoholic or aqueous solution, etc. The product is then normally dried, calcined and / or reduced.

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It can be seen from the attached figure, Figure 2, that such a catalyst works effectively. Highly successful samples 1 and 2 achieved good conversion with small amounts of Pt. The same efficiency is achieved by using a traditional quartz felt catalyst if the amount of precious metal is three times.

This is because the specific surface area of the fiber is quite high compared to quartz fiber. The proportion of precious metal can thus be considerably reduced and cobalt can be used as an auxiliary metal, which lowers the cost of the catalyst structure and still achieves as good combustion results as if pure platinum had been used.

The support structure of the combustion catalyst according to the present invention can be prepared e.g. as follows:

The silica viscose material fiber is prepared by pressing a homogeneous solution containing silica monomer and viscose through a spinning nozzle into a polymerization and regeneration solution. The fiber or filament of silicic acid viscose material is thus prepared by polymerizing monomeric silica in a cellulose matrix. This is preferably done using a viscose process.

In the viscose process thus modified, the silica base solution and the viscose are first mixed together into a multicomponent solution. The silica base solution is added to the viscose at the stage when the viscose is dissolved and preferably when it has been post-ripened and filtered. In this case, care must be taken to ensure that the co-solution contains enough sodium so that the silicic acid does not regenerate the cellulose too early in its sodium xanthate form.

After solution formation, a solution of silica, base and viscose is pressed through a spinneret or other die and directly into an acidic bath solution which polymerizes the silica and regenerates the cellulose. This produces a precursor of the carrier fiber product, i.e. a silica viscose material fiber, which can be washed and dried in the same way as in a conventional viscose process.

The carrier obtained in the following examples is called VISIL.

Examples: l.a VISIL fabric burning.

VISIL fiber was used to make 2 x 25 tex yarn and 2 x double knit yarn with a basis weight of 540 g / m2. The fabric was washed with an alcohol solution and rinsed with water to remove any contaminants that had adhered during the process. The fabric was then placed in an oven below 300 ° C, allowed to rise to 900 ° C, and the sample kept at 900 ° C for one hour. The analysis showed that the specific surface area of the fiber was about 80 m 2 / g and the structure of the double knit had remained exactly as original, with a shrinkage of 20%.

l.b The fiber is made into a nonwoven fabric (needle felt) of 80 g / m2. Using the carding and needling technique, proceed as in Example l.a.

1. c As Example l.a. except the combustion temperature is 750 ° C.

2. a Example A fabric according to l.a was cut into a piece 6 cm in diameter and impregnated with a solution of alcohol (20 ml) and the cobalt salt Co (NO 3) 2 6H 2 O. The impregnated fabric was dried at room temperature for 12 hours, after which the sample was heated at 550 ° C for one hour. The sample was then soaked in a solution of alcohol and platinum salt (H 2 Pt-Cl 6 XH 2 O) and dried for 12 hours at room temperature and heated at 550 ° C for 1 hour. The amount of cobalt in the sample became 0.17 g and the amount of platinum was 11 mg.

The catalyst was tested and an efficiency of 99.3% was achieved with a fuel flow of 0.1 and an air flow of 2.64 l / min.

6 89012 2.b As 2.a except the amount of platinum was 9 mg. The result is the same as in Example 2.a.

2.c As in Example 2.b except platinum was 7 mg.

2. d As in Example 2.a except for the textile structure according to l.b so that the weight of the carrier was equal to that in Example 2 .a.

3. a, b and c As in Examples 2.a, b and c, except that the amount of cobalt was 0.08 g. The efficiency achieved by these was 99%.

4. a, b and c As in Examples 3.a, b and c, except for the amount of cobalt in the catalyst 0.05 g, power 96.8%.

The results of Examples 2-4 show that the prepared catalysts work excellently.

5. Three catalysts were prepared: 1. 0.18 g cobalt + 10 mg platinum 2. 10 mg platinum 3. 0.18 g cobalt

It can be seen from the results (Figure 2) that when the amount of platinum is only one third compared to a commercial platinum catalyst, the catalyst according to the invention gives completely satisfactory results. Table 2 shows that the same catalysts also work well in the so-called as oxidizing exhaust catalysts.

6. 3 catalysts were prepared from different VISIL materials: sparse and dense fabric, yarn. The materials were washed from the impurities remaining during spinning with ammonia solution and clean water. They were then dried and the cellulose was burned off by raising the temperature to 900 degrees in a controlled manner.

The obtained silica samples were impregnated with palladium from the amine solution, dried and calcined. The resulting samples were aged for 7 h at 900 ° C and then tested with a gas mixture describing the composition of the diesel exhaust gas with the following analysis: propylene 500 ppm, carbon monoxide 500 ppm, NO 1000 ppm, carbon dioxide 10%, oxygen 5% , water vapor 7% and the remainder nitrogen.

The sample size was about 3 ml and the gas turnover was 50,000 l / h. Results in the table below.

Sample Pd amount Ignition temperature Conversion

Dense fabric 135 mg 225 ° C 90-95%

Rare fabric 105 mg 230 ° C 75%

Langat 190 mg 215 ° C 90%

Ignition temperatures and conversions are averages of CO and hydrocarbon estimates that were very close to each other.

Claims (5)

A combustion catalyst having a silica-based support for hydrocarbon-containing gases, characterized in that the support material is a silica structure prepared using silicic acid-containing viscose fiber as a raw material, to which the catalytic agents are attached. Catalyst according to Claim 1, characterized in that a ceramic textile structure, e.g. a needle felt, rope, knit, fabric or nonwoven fabric, is used as support. Catalyst according to Claim 1, characterized in that the support is combusted before attaching the catalysts to a substantially amorphous SiO 2 fiber. Catalyst according to Claims 1 and 3, characterized in that the firing temperature is between 400 and 1500 ° C, preferably between 750 and 1050 ° C. Catalyst according to Claims 1, 3 and 4, characterized in that the catalyst substances are absorbed as solutions into the structure, followed by calcination. 9 89012