DE869940C - Process for the catalytic splitting off of hydrogen or its compounds - Google Patents

Description

To ethylene PH des Zu Athylen Contacted contact grains washed converted Alumina contact, made from after (2nd washing process) with alcohol in Heat to percent of 550 applied lot buyable aged Al (OH) 3 ................... 4.0 H2O 20 (deformed with nitric acid) ......................... 5.4 NH3, H2O 35 (Reversible) unaged Al (OH) 3 .............. 1.5 Unwashed 70 (made from aluminum nitrate Q ammonia at pH = 5) 5) 5.3 N H5, H2 0, NH3 99 (Reversible) unaged ^ Al (OH) 3 5.9 HNO3, H2O, NH3, H2O 99 (made from aluminate + nitric acid at pH = 6) 8, o H20 25 Aluminum salts, such as can be obtained by dissolving aluminum powder in a deficiency of acid or aluminum salt solution or by electrolysis of an aluminum salt solution or by reacting an aluminum salt solution with alkylene oxides and removing the organic substances formed, e.g. B. by distillation, or by peptization of hydroxides with a deficit of acid or acidic or acidic salts. The solid or liquid starting materials mentioned can be processed further by precipitation or by thermal means. In the latter case, basic salts with a low content of volatile acid residues can be used particularly advantageously because the strength of the contact then suffers the least when heating and driving off the acid residues and the fine structure is best preserved.

In contrast, most commercial hydroxides are in Water insoluble and practically hardly peptizable. So is commercial alumina hydrate, that from sodium aluminate solution, i.e. a strongly alkaline solution in non-volatile Alkalis, produced by stirring with clay or carbonic acid felling. a heavily aged, poorly peptisable aluminum hydroxide, from which catalysts are made can be produced, although they are useful for many purposes, for the present Purposes but have little effectiveness.

The catalysts are expediently prepared in such a way that that the unaged hydroxide after deformation into coarser pieces through Treatment at higher temperatures largely dehydrated and insoluble in water Form transferred. Aged hydroxides can also be used as carriers Oxides of sufficient porosity superficially with a gel or basic salts coat or deposit unaged hydroxide on the support and the mass then bring it to the required PH, but the catalytic effectiveness is the better, the greater the proportion that has emerged from unaged hydroxide of a catalyst.

It has also been found that the catalytic conversion is the best proceeds when the hydroxide, especially the aluminum hydroxide, by simultaneous Allowing the components used for precipitation to flow together at a temperature between 2 and 10, better 4 and 7, preferably 5 and 6 lying PH is precipitated. It can from The advantage of this is that the precipitations are not completely affected by the precipitation, in particular at the pH between 41 and 7 to free the salts formed by washing and they then to heat to such temperatures that the grains by contact with washing liquids are not destroyed, whereby the salt residue serves as a binding agent. Be on it the hard grains depending on the nature of the contamination of the catalyst with acidic ones or alkaline substances washed so that the catalyst on after heating preferably 450 to 500 a p which is between 2 and 7.

Such oxides or basic salts come into consideration as catalysts, those in the elimination of hydrogen and its compounds are preferred organic substances are common; may be mentioned e.g. B. the compounds of thorium, Cerium, aluminum, iron and chromium as well as titanium, zirconium, manganese, tin, vanadium, Molybdenum, tungsten, uranium, nickel, cobalt or mixtures of these among themselves or with other substances, e.g. B. silica, boric acid, phosphoric acid, sulfuric acid, etc.

The catalysts described are suitable, for example, for production of isobutylene from isobutanol or isobutane, ethylene from alcohol, propylene from isopropanol, Tetrahydrofuran from I, 4-) butylene glycol, phenylpyrrolidine from tetrahydrofuran and Aniline and methylpyrrolidine from tetrahydrofuran and methylamine. The pyrrolidines mentioned is also obtained from 1,4-butylene glycol and aniline or methylamine. N-alkyl derivatives aromatic amines are obtained from these amines with alcohols or ethers, e.g. B. Dimethylaniline from aniline and dimethyl ether. Furthermore, from carbon oxide and Ammonia or from formamide hydrogen cyanide and from alcohols and ammonia Alkylamines. Dliphenylamine can be obtained by cleaving amino acids from aniline. In the mentioned Cases has particularly proven active alumina as a catalyst, while for the Production of unsaturated hydrocarbons from polyhydric alcohols, including those containing phosphoric acid Alumina contacts come into question. Silica-alumina contacts are particularly useful for Sick of hydrocarbons suitable. The favorable PH of the catalyst can the less the starting or end products tend to become resinous, the more acidic they are and the higher the temperatures, the catalyst at work or at exposed to resuscitation provided the E-catalyst is non-volatile alkalis contains. In the absence of these or in the presence of ammonium salts as impurities the PH area in question is the largest, as it is even prone to resinification Substances, e.g. B. aniline or isobutanol, and 'the unsaturated ones obtainable therefrom Hydrocarbons in the course of the catalytic process or during resuscitation the catalyst gradually a substantial removal of the ammonium salts or their Decomposition products takes place thermally. With regard to the fact that both acids and bases the finest pores of the oxides, z. B. the clay, as a result easily destroyed by chemical action, and the faster the higher the temperature and the duration of action is, the PH must not exceed the claimed limits.

Example I By boiling 240 parts by weight of 50% sodium hydroxide solution with 160 parts by weight of commercial alumina hydrate powder containing about 64 0 / aluminum oxide while stirring and making up the solution with condensed water, a sodium aluminate solution becomes which contains about 200 g of aluminum oxide per liter. For the precipitation of the aluminum hydroxide is left in a stirred tank made of corrosion-resistant material, in which an antimony electrode immerses the aluminate solution cooled to 200 at the same time with a 40: to 450 / siegen Pour in nitric acid while stirring well. The feed rate of the solutions is adjusted so that the mixture has a pH of 6 at the beginning of the precipitation at 200 to 7 and when the precipitation is complete after about 1 hour has a pH of 5 to 61. As a result of the heat of reaction, the temperature rises to about 550. The contents the kettle is passed through a filter press and the precipitate with cold Water under the control of the draining wash water washed only so long that a noticeable amount of sodium nitrate still remains in the precipitate, which is about after t / 2 hours of washing is the case. The precipitate is then spread into metal sheets and cut into cubes. After drying at 3000 it remains due to the content hard moldings of small amounts of nitrate. These will be with you for a few hours 50% nitric acid, then with ammonia water, then with water and finally treated again with ammonia water. If a sample after drying and three hours Heating to 5000 at zo0 has a pn of 5 to 6, the main amount of catalyst is heated to 500 to 5500 for a few hours while passing gases through, otherwise the treatment of the main amount must be with acid or with ammonia, depending on the pH of the sample be continued. A catalyst obtained in this way with a pH of 5.8 results in the manufacture of ethylene from alcohol under the conditions already given, conversions of 980 / o.

Example 2 Aluminum hydroxide becomes with constant PH = 6, but otherwise as described in Example I. When the precipitation is complete, the mixture is under Addition of 2o.0% ammonia water brought to a pH of Z to g. The content the kettle is passed through a filter press and the precipitate with hot Water thoroughly, d. H. as salt-free as possible, washed and dried at 100 to 1200, it disintegrates into a white, soft powder, containing about 68 to 70 per cent. aluminum oxide contains. Gravel reactive aluminum hydroxide is in an iI (net machine under Addition of about 0.07 to 0.15 moles of nitric acid to 1 mole of aluminum oxide with that much Water added, so that a homogeneous one that is easily kneadable and malleable in the extruder Dough is made. The strands obtained after thorough kneading and molding become cut into small cylinders and gradually increasing the temperature to 300 ° heated. At this temperature the content of the mass of sodium nitrate is sufficient in the presence the peptizing acid is not enough to make the mass alkaline.

Remained hard, water-resistant, consisting mainly of aluminum oxide Pieces are first washed thoroughly with 5 ° ammonia water and then with hot water washed and finally treated again with ammonia. If a sample after three hours Heating to 5000 has a pH of 5 to 6, the bulk of the catalyst becomes heated for a few hours to 500 to 5500 while passing gases through. Otherwise the treatment of the major part with acids or ammonia must be continued. A A catalyst obtained in this way with a pH of 5.9 results in the processing of aniline with a large excess of dimethyl ether at 2200 under ordinary pressure a complete Conversion of the aniline into dimethvlaniline.

Example 3 Nitric acid containing sodium aluminate solution and chromium nitrate are put together under the conditions mentioned in Ee Example I, so that the consisting of a finely divided mixture of the hydroxides of aluminum and chromium Precipitate to about 80 to 98 parts by weight of A1 (OH) 3, about 20 to 2 parts by weight Contains Cr (O H) 3. The mass is filtered off, washed and dried at 100 to 120 °. That very It is known that from non-aged aluminum hydroxides Manufactured catalysts can be particularly effective. It has already been established that the hydrogen ion concentration (PH) at which one falls the hydroxides for the effectiveness of the catalysts is important. illspecial one has the metal hydroxides obtained in the precipitation of metal salt solutions with alkaline solutions washed out with a solution whose p, with that present at the end of the precipitation essentially coincides. It is also known. that one made from aluminum nitrate solution precipitated with ammonia at a pH = 4 and washed out with ammonium nitrate solution at a pH = 4 and then dried aluminum hydroxide as a catalyst for the formation of hydrocyanic acid from ammonia and carbon dioxide is less useful than one precipitated at pH = 6.5 and aluminum hydroxide washed and dried with ammonium nitrate solution from the same pn, while a at PH = IO Process for the catalytic splitting off of hydrogen or its connections until ri fell and with a solution of the same Pn washed aluminum hydroxide is useless for the stated purpose. Aluminum hydroxide can only be completely freed from salts with great difficulty by washing. It contains, depending on whether it is, for example, from the nitrate and ammonia or caustic soda or is made from sodium aluminate and nitric acid, even larger or smaller Amounts of ammonium or sodium nitrate included. This is all the more the case if an ammonium nitrate solution is used for washing. .When heating the aluminum hydroxide -The ammonium nitrate then splits into ammonia and nitric acid. The former evaporates rapidly, while nitric acid becomes more tenacious in aluminum hydroxide or oxide is retained and only expelled completely at relatively high temperatures can be. The same applies to hydrochloric acid in the presence of ammonium chloride. Depending on the ammonium nitrate content of the washed precipitate and the duration and At the temperature of the heating, the end product reacts more or less acidic. It can have a PH below a even if the precipitate is, for example, at PH = 7 and higher. The opposite can occur if the Precipitation of sodium nitrate has arisen. The end product has an alkaline reaction, because during Heat the salt to relatively high temperatures in volatile nitric acid and breaking down sodium hydroxide, which reacts with the clay. Usually takes place an aging of the hydroxide or oxide and a destruction of the fine structure by Sintering instead. In the case of the known precipitation of a catalytically active aluminum hydroxide at pn = 4 to 6.5 by washing out with a solution of the same pn one can therefore do not expect the pn of the catalyst not to change after heating Has. The p-value can be determined by finely dividing the heated one Mass with hot, pure water extracts and the pK value in the aqueous extract certainly.

It has now been found that the catalytic elimination of hydrogen or its compounds with oxygen, nitrogen, sulfur or halogen under Use of porous oxides or basic salts of such metals as catalysts, which occur in at least trivalent, in particular trivalent and tetravalent, form can, at a relatively low temperature to achieve high conversions and Yields and a particularly long life of the catalysts can make, if one uses such catalysts, wholly or largely by heating or cases of non-aged hydroxides are made, and. the after Heating to at least the relevant working temperature of the catalyst, preferably to 450 to 6500, a pn between 2 and 7, better 4 and 7, preferably 5 and 6.

In order to meet this condition, the precipitation must either be very high washed for a long time and the pH of heated samples checked, or it must, which is more useful, results in better washability through pre-drying will.

You can also wash out the precipitate less thoroughly, then Heat to the appropriate temperature and then, if the dry products are too acidic, these with aqueous solutions of ammonia, ammonium carbonate and similar, preferably volatile alkaline agents or urea or ethylene oxide or, if they are too alkaline, with preferably volatile acidic agents, e.g. B. aqueous Solutions of hydrochloric, nitric or formic acid, treat or with basic metal salts, z. B. basic or highly basic aluminum chlorides or nitrates or salts of ammonium, since these split into ammonia and acid when heated, which the latter is more strongly retained by the catalyst than ammonia. Thereby finds a topochemical decomposition takes place. A washing process can then be carried out and the acid treatment can, if the product becomes too acidic, by a subsequent treatment with preferably volatile alkalis are removed. the acidic or alkaline agents can also be used in gas or vapor form reach. This treatment is usually followed by activation at a higher temperature which, like treatment with volatile acidic or alkaline agents, for example, be carried out in the furnace used for the catalytic reaction can.

The list on the right shows which sales in the dehydration of alcohol to ethylene at 3200 using catalysts of aged and non-aged aluminum hydroxide obtained after heating have different pH can be achieved.

It became more liquid every hour at I space part catalyst I space part Alcohol applied.

The catalysts obtained from aged aluminum hydroxide result So even with a suitable PH only moderate conversions, on the other hand, the Catalysts obtained from non-aged aluminum hydroxide at certain p, are unusable be; Catalysts with particularly good properties are obtained when both above conditions are met.

Unaged hydroxides are hydrous forms of oxides that with water without further ado or after treatment with a peptizer, such as hydrochloric or nitric acid, the amount of which is significantly below that for the transfer of the total oxide required in the chloride or nitrate lies, a colloidal one Ability to form a solution. They can be made from colloidal solutions and metal salts, preferably from basic, in particular hocir basic salts or containing salts produce colloidal hydroxides. It should be noted that during manufacture of the hydroxide in the presence of non-volatile alkalis causes a strongly alkaline reaction absolutely avoided. Suitable starting materials are, for example, basic responsive Hydroxide mixture is made using a little nitric or chromic acid as a peptizing agent thoroughly kneaded, pressed into hollow cylinders at the same time by means of an extruder and heated to 300 to 6000. The moldings are washed with water containing nitric acid washed from pH 3 to 5 and dried at I250. Will about the catalyst that a p, of 3.75, passed butane at 100O, so 15 to 15 are obtained in the end gas 250/0 butylene.

Example 4 One by introducing ethylene oxide into an aluminum chloride solution and distilling off the ethylenedlorohydrin formed solution of Al2 (OH) 5C1 is used while cooling and stirring at 500/0 to transfer all of the aluminum added amount of phosphoric acid required in aluminum phosphate. The received After standing for a short time, the sol solidifies to form a water-soluble jelly of the composition A12 ('O H) 2 Cl P 04.

The jelly pieces are broken and with as much ammonia water washed as necessary to remove the chlorine in the form of ammonium chloride. The now water-insoluble mass consisting of Alæ (OH) 3PO4 becomes at 150 to 2500 dried and the porous wide-pored carrier then with a solution of ammonium dichromate soaked and heated to 5oo °. A catalyst of p, = 6, og, which is obtained at the dehydrogenation of butane to butylene and of isobutane to isobutylene about 100% Yield there.

PATENT CLAIM I. Process for the catalytic splitting off of hydrogen or its compounds with oxygen, nitrogen, sulfur or halogen under Use of porous oxides or basic salts of such metals as catalysts, which occur in at least trivalent, in particular trivalent and tetravalent, form can, characterized in that the catalysts wholly or largely through Heating or precipitation of non-aged hydroxides are made and after that Heating to at least the relevant working temperature of the catalyst, preferably on X50 to 6; ohr, ap, between 2 and 7, better ß and 7, preferably 5 and 6.

Claims (1)

2. The method according to claim I, characterized in that the not aged hydroxides from basic, preferably highly basic salts or such containing colloidal hydroxides are prepared. 3. Process according to Claims I and 2, characterized in that the catalysts are prepared in such a way that the hydroxides, in particular the aluminum hydroxide, by simultaneous confluence of the for precipitation Serving components are precipitated, the precipitation from the majority of the resulting The salts are freed by washing and then heated to such temperatures that the grains are not destroyed by contact with washing liquid, whereupon the grains depending on the nature of the impurities of the catalyst with acidic or alkaline substances are washed out, so that the catalyst after heating to 450 to 6500 has a Pn which is between 2 and 7, more preferably 4 and 7, preferably 5 and 6, lies. 4. The method according to claims 1 to 3, characterized in that that one aluminum hydroxide or oxide, preferably in powder form, with a deficit of acid or acids or acidic salts in the presence of so much water added that a paste is formed, which after molding, drying and heating a PH between 2 and 7.