DE1097961B - Process for the protection of hygroscopic shaped catalyst pieces against moisture by applying a coating to the shaped pieces - Google Patents

Description

Process for the protection of hygroscopic shaped catalyst pieces Moisture by applying a coating to the molded articles The invention relates to a process to insheson, dere on such catalysis moldings, the Kalitim in Form of a hygroscopic, alkaline reacting compound contain, l: Yberzüge to raise.

It is known that potassium is a very desirable one in many catalysts Promoter (a substance that increases the activity of the catalyst) that is used by many Types of catalytic conversions is useful. The following are examples Catalyst types mentioned: 1. Chromium oxide-aluminum oxide catalysts activated by cerium for the ring-forming dehydrogenation of n-paraffin hydrocarbons to aromatic ones Hydrocarbons; 2. Ammonia synthesis catalysts based on iron; 3. Fischer-Tropsch catalysts based on iron; 4. Washer gas stratified catalysts, mainly based on iron, chromium and manganese oxides or a mixture thereof; 5. Nicel and cobalt silicate catalysts for the amination of olefins; 6. nickel, Iron and / or cobalt catalysts for the dehydrogenation of olefins and / or alkylaryl hydrocarbons to the corresponding diolefins or hydrocarbons of the styrene type; 7. Molybdenum Oxide - Alumina catalysts for the selective desulfurization of olefinic Light petrol; 8. Special catalysts, the heavy metal chromites and molybdenites or tungstites for the hydrogenation of various organic compounds or inorganic sulfur compounds or for the reduction of nitrates.

These and many others suitable for the above and other reactions Catalysts are often made by incorporating potassium in the form of potassium carbonate, activated hydroxide or oxide in the catalyst.

The potassium compound is generally used as such during mixing the catalyst components and before the tabletting or shaping of the mixture introduced into lumpy fabric particles; however, it can also be introduced later.

These potassium compounds are hygroscopic.

Consequently, deformed catalysts tend to contain them Connections during packing, work, etc. to absorb water from the air, which generally reduces their mechanical strength considerably will. Furthermore, there is an end to sweating, the catalytic converter and therefore a bad one Distribution of the potassium promoter.

These difficulties have been recognized, but only partially resolved. by storing the catalyst in containers with expensive, proprietary closures and was transported, but this did not rule out that the catalyst was during came into contact with the air during packaging and loading.

The difficulties identified are due to the invention e procedure eliminated by the fact that the hygroscopic, alkaline reacting potassium compounds containing catalyst moldings by applying coatings to their surface be protected against the effects of moisture, whereby the moldings with vapors of such nitrogen-free aliphatic compounds treated by action polymerizes the alkaline reacting potassium compound to form a solid polymer will.

This treatment of the catalyst moldings, for. B.

Tablets, can be done after their drying, if the drying the a final stage in the production of the moldings. Should the catalyst moldings are subjected to calcination, then the treatment should follow the calcination connect. When the catalyst particles are made by pressing the dry mixture, then the treatment should follow the pressing.

According to the invention, the catalyst components can generally also include any organic compound can be treated which is easily evaporable and under the alkaline effect of the potassium compound, e.g. B. the carbonate, easily to one solid, resin-like or plastic material potym erisiert.

A group of preferred compounds includes the monomers of unsaturated aldehyde polymers, among which acrolein and methacrolein in particular are preferred. Another preferred class comprises the monomers of unsaturated Ketone polymers, of which methyl vinyl ketone is particularly preferred.

A third preferred group comprises the monomers of epoxy polymers, of which propylene oxide is particularly preferred. Propylene oxide is opposite to ethylene oxide preferred because the resulting polymer is more hydrophobic and much less in water is soluble.

The monomer and consequently also the resulting polymer should be preferred be essentially free of halogens.

During the treatment, the catalyst tablets are simply exposed to the vapors of the appropriate monomer or a mixture of the appropriate monomers. This can be done in any convenient way. One possible way is to that the catalyst moldings are introduced into a tubular reaction vessel and the vapors of the monomer passes through the reaction vessel up to the surface of the catalyst the desired amount of polymer was produced. If the vapors of the monomer without any diluent is bubbled through the reaction vessel, then the temperature in the reaction vessel should be at least close to the boiling point of the monomer under the prevailing pressure, preferably somewhat higher.

However, if the vapor of the monomer is mixed with air or other inert gases, e.g. natural gas, is diluted, then lower temperatures can be used, down to that at room temperature.

The preferred temperature depends on the reactivity of the particular used monomer and the amount of potassium carbonate in the catalyst and can can be varied considerably. Generally temperatures are from room temperature up to about 2000 C most appropriate. At least in some cases it can be higher Temperatures are applied; however, the temperature should in no case be so high lie that the polymer is caused to decompose. A small amount of water vapor may be desirable to prevent alkaline catalysis of the polymerizations to promote.

The procedure can be carried out at any pressure. Push around however, around atmospheric pressure are appropriate and preferred.

The time required to treat the catalyst depends on the effectiveness of the particular monomer used, the temperature used, the Amount of potassium compound in the catalyst and the amount of polymer that is on the Surface of the catalyst is to be applied from. Treatment should preferably take until at least 1 percent by weight is on the surface of the particles (based on the weight of the catalyst) in the solid polymer of the above polymerizable Connection is provided. Very good results are obtained if you click on the Olierfläche of the particles 1 to 25 percent by weight (based on the weight of the Catalyst) of the solid polymer generated.

After the above-described treatment of the catalyst particles with the monomer, these no longer require any further treatment and can be used for transport be packed. In most cases, however, it is appropriate to use the catalyst moldings Post-treat with hot air or other gases to remove the remaining vapors of the monomer, as these are generally malodorous.

The catalysts of the invention can often simply be placed in the reaction vessel filled in and used for the intended purpose. In other cases it is appropriate to put the catalyst in the reaction vessel in which it is to be used should be pretreated. The last mentioned pretreatment can be any suitable method which decomposes and removes the polymer. So z. B. that containing the polymer The catalyst was poured into the reaction vessel and left in it for a few hours to be destroyed of the polymer can be heated to 500 to 6000 C, or it can be mixed with a mixture treated from steam and air. In other cases the reaction vessel can take place which are rinsed with a solvent for the polymer.

Example 1 The catalyst consisted of iron oxide, chromium oxide and potassium carbonate and was made by moistening the appropriate powder, extrusion into tablets of 4.8 mm, drying the tablets with the help of hot air and calcining about 6000 C. The potassium carbonate content of the catalyst was approximately 35 o / o. These calcined tablets had an average mechanical strength of about 5.6 kg. After taking these tablets for 28 hours at room temperature exposed to moist air, they became mushy and lacking firmness more on.

A portion of the calcined tablets was at 270 for 25 hours C and treated with acrolein vapors under atmospheric pressure, resulting in the The area of the catalyst formed by the acrolein polymer and the weight of the tablets increased by 150 per cent. After the tablets treated in this way for 28 hours exposed to humid air at room temperature as in the case of the control samples, the strength of the tablets was at least as great as that of the control samples such a measure.

When the catalyst tablets have been heated to about 7000 C in air, then the polymer burned, but the tablets did not soften.

Example 2 Commercially available tablets of 4.8 mm, similar to those of the example 1 were dried at 1200 C and then treated with acrolein vapors. In order to promote the uniformity of the treatment of the tablets, they were made periodic shaken. The treatment was carried out at atmospheric pressure and room temperature and continued for a little over 24 hours. After this treatment, it enlarged the weight of the tablets by about 5.3%. The tablets that have a strong smell after acrolein were then dried at 1200.degree. This caused weight loss of 0.6 0.6% and banished the odor.

The original dried but untreated tablets had a mechanical strength of about 6.1 kg. After they have been around for 6 hours the atmosphere the strength was about 0.9 kg.

On the other hand, the tablets treated with acrolein vapors after being exposed to the surrounding atmosphere for 6 hours, a mechanical one Strength to at least that of the control samples prior to any such action equaled.

When using methacrolein and methyl vinyl ketone, similar Results are achieved.

PATENTANsP (I1 1. Process for protecting hygroscopic, alkaline reacting catalyst moldings containing potassium compounds against the action of moisture by applying coatings to their surface, characterized in that the moldings with vapors of such nitrogen-free aliphatic compounds treated, which by the action of the alkaline reacting potassium compound to one solid polymer are polymerized.

Claims (1)

2. The method according to claim 1, characterized in that as polymerizable compound an unsaturated aldehyde, preferably acrolein or Methacrolein, is used. 3. The method according to claim 1 or 2, characterized in that the polymerizable compound is an unsaturated ketone, preferably methyl vinyl ketone, used. 4. The method according to claim 1 to 3, characterized in that one an epoxy, preferably propylene oxide, as the polymerizable compound. used. 5. The method according to claim 1 to 4, characterized in that one carries out the treatment of the catalyst particles under such conditions that on the surface of the particles 1 to 25 percent by weight (based on the weight of the catalyst) of the solid polymer. Considered publications: German Patent Specifications No. 300 225, 937 047; U.S. Patent No. 2,513,997.