CH144568A - A process for the catalytic synthesis of ammonia. - Google Patents

Description

  

  Process of catalytic synthesis of ammonia. The present invention relates to the synthesis of ammonia by the catalytic combination of hydrogen and nitrogen at high pressure and high temperature.



  According to the invention, the hydrogen and nitrogen are reacted in the presence of a catalytically active contact mass containing a body of a mieroporous structure (resulting from the formation of an exchanging body; basics.



  Such a body can be either a base exchange body, or a derivative of such a body, obtained for example by leaching the latter with an acid.



  The expression "base exchange body" encompasses all bodies, natural or artificial; which have the property of exchanging their bases for other bases of saline solutions. The base exchange products which are used in the formation of catalyst compositions which are employed in the process according to the present invention, or as starting material for derivatives to be used thus, can possess a high base exchange power. its or, in many cases, may have a lower base exchange power, then that the catalytic value of the final compositions does not mainly depend (read willingly on the base exchange power present.

         Generally speaking. the base exchange bodies can be grouped as follows: zeolites with two or multiple constituents. that is, base exchange bodies containing chemically combined silicon in their core, and non-siliceous base exchange bodies in which all of the silicon is replaced by other suitable acidic or amphoteric metal oxides.

    Two-component zeolites are the reaction products of two types of initial components, i.e. metallates and silicates (using the term metallate in a broad sense which will be defined later. in this brief), or metal salts and silicates. It frequently happens that more than one member of a type can react, that is, such a licate can react with more than one metallate or more than one metal salt.

   Multi-constant zeolites are the reaction products of at least three types of constituents, i.e. at least one silicate, at least one metallate and at least one metal salt. (By metallate is meant any salt the anion of which contains a metal; under metallic salt is meant a salt in which the anion does not contain any metal.) Base exchange bodies, both zeolite and base exchange bodies bases not sili those, can be associated with diluents. preferably in the form of a physically homogeneous structure, as will be described below.

   Base exchange bodies, either diluted or undiluted, may be present in the contact masses used in the present invention, or their derivatives may be present; but it goes without saying that, wherever it is a question here of hash exchange bodies, this expression includes both diluted and undiluted products.



  As already stated, base exchange bodies, both zeolites and non-siliceous base exchange bodies, can also be transformed into derivatives, which can be used for the formation of the catalytic mass and which have many chemical characteristics and most of the physical characteristics of the substances. base exchange bodies from which they derive.

    These derivatives can be salt-like bodies, that is to say the reaction products of base exchange bodies with compounds containing anions capable of reacting with the base exchange bodies to form products which; do have properties of salts. Another class of these derivatives is that of acid-leached base exchange bodies. When subjecting a base exchange body to leaching by acids, especially dilute mineral acids, the exchangeable bases are first removed gradually.

   The resulting products contain both the more basic and the more acidic constituents of the non-exchangeable core of the base exchange body, with or without a portion of the exchangeable bases. As the leaching is carried out further, more and more of the relatively positive constituents of the non-exchangeable core are removed, and if the leaching is carried to completion, the leach contains only the relatively acidic constituents of the core. non-exchangeable core.

    In the case of zeolites, the end product of long-lasting leaching is a complex silicone acid which has many physical properties of the original ba ses exchange body. In the remainder of the present description, for simplicity, the base exchange bodies and their derivatives will be designated. both by acid leaching and by the formation of salt-like bodies, under the generic term "periuutogenic" products.



  Catalytically active constituents can be found in the catalyst mass employed in four main forms: 1. They can have been physically mixed with or impregnated with the permutogenes. 2.

   They may have been incorporated physically, in a homogeneous manner, in the permutogenetic products. before the latter have been completely formed, in the form of catalytically active diluents or in the form of diluents which have been impregnated with the substance; catalytically active. 3.

   They can be chemically combined in the per mutogenetic products in a non-exchangeable form, i.e. they can form part of the non-exchangeable core of the base exchange body present in the final contact mass, or which is transformed into the derivatives; or they can be combined chemically with the base exchange bodies in the form of catalytically active anions which together with the base exchange body form salt-like bodies. 4.

   They can be chemically combined in exchangeable form either during formation of the base exchange body, or by base exchange after formation. Naturally,

   the same catalytically active constituents or catalytically active constituents (different may be present in more than one of the above-described forms and an advantage of the invention is that catalytically active substances can be introduced in a wide variety of forms, this which offers a wide choice to the catalyst chemist.



  Although the different permutogenes can vary widely in their chemical characteristics, they all have a similar physical structure (characterized by greater or lesser microporosity, and high resistance to high temperatures and, in the case of base exchange bodies containing catalytic constituents and which have not been leached with acids to the point of removing catalytically active constituents,

   these are distributed throughout the carcass of the products in atomic or molecular dispersion, as will be described in more detail below, and this chemical homogeneity is one of the most important advantages of some of the contact masses used. in the process of the invention.

      Although the combination of catalytically active substances can be effected with undiluted permutogenetics as well as with diluted permutogenetics, it has been found that masses (contact formed of dilute permutogenetics of a homogeneously are advantageous, in particular when the diluents are of a physical nature such that they exert a desired influence on the catalytic activity of the contact masses., as when, for example, the diluents are rich in silica,

   that it has been found to have a <B> -you </B> power due to, or when the diluents, (a great porosity, a great capillary or a great surface energy, can be considered to be physical catalysts or activators.



  The base exchange bodies behave as if they were extremely high molecular weight products, since catalytically active constituents can be introduced either into the non-exchangeable core. either in the form of bases exchangeable in virtually any desired proportions and the ordinary law of chemical combination proportions, which in low molecular weight compounds restricts the proportions in which constituents can be chemically incorporated, appears to be weak , which makes it reasonable to assume that the molecular weight is so high that it completely masks the effect of the law.

   It is, of course, possible that the base exchange bodies, or some of them, then smell to be solid solutions of several compounds of lower molecular weights. relating to each other. It has not been possible, until now, to settle this question definitively, because base exchange bodies are not easy to analyze chemically as to their structure.

    The invention is, of course, not limited to any theory; but, whatever the fundamental reasons, the fact that catalytically active constituents can be chemically introduced in any desired proportion is of enormous importance to the catalyst chemist and enables him to produce an almost unlimited number of catalysts. or finely and gradually dosed contact masses for the synthesis of ammonia, and in all cases the contact masses produced are highly efficient.

    due to the physical structure of the permutogenetic products contained therein and the wide limits of homogeneous dilution of catalytically active molecules or atoms, with resulting uniformity and smoothness of action.



  In addition to the important characteristics with which the permutogenetic products endow the contact masses used in the process according to the invention, it has been found frequently desirable to control the action of these contact masses and this can be done by associating with permutogenetic products. or by incorporating therein, or forming therein, compounds of the alkali metals, of the alkaline earth metals and of the strongly basic earth metals. These compounds appear to slow or soften the catalytic reaction and will be referred to throughout this specification as regulators.

   The regulators can be non-alkaline, weakly alkaline, or strongly alkaline, depending on the nature of the catalytically active constituents used. A great advantage is that in the normal formation of base exchange bodies, oxides of alkali-forming metals are present as exchangeable bases and, when used without acid treatment or acid treatment,

   they form key regulators which are combined or associated with the resulting permutogenes in an extremely fine dividing state in which these regulators are particularly active. Thus, basic key exchange bodies containing alkali metals can be regarded as complex regulators.



  In addition to the use of regulators, it has been found that it is possible, in many cases, to increase the action of these and the total efficiency of the contact masses by associating with them, or by chemically combining therein, elements or radicals or groups which are catalytically active but do not possess any specific catalytic activity for the synthesis of ammonia. <B> Of </B> such catalysts, or catalytic constituents which are not-catalysts specific for the reaction in which it is used, under the reaction conditions at which one has.

   matter, will be referred to throughout this brief as auxiliary catalyst bodies, as they appear to enhance the dosing effect which can be accomplished by regulators. Such auxiliary catalysts can be present where there are no regulators.



  The enormous range of chemical groups which can be combined in, or with, or incorporated into permutogenetics allows a wide choice of auxiliary catalyst bodies as well as specific catalysts - and allows their association with the masses of. contact in an extremely homogeneous and catalytic form. is lying. effective. Thus, many base exchange bodies - or their derivatives can constitute at the same time catalysts, regulators and complex auxiliary catalysts :.

    because all the elements playing these different roles can be present in the same chemical compound and participate in the advantages deriving from its physical structure and its desirable chemical properties. Of course, both regulatory bodies and auxiliary catalyst bodies may be mixed partially or completely with permutogenetics and a single regulatory body or a single auxiliary catalyst may be present part in physical mixture and part in chemical combination, as will be understood. clearly the informed base exchange chemist.



  The base exchange bodies which form the important constituents, or the starting material for derivatives, in the contact forms used in the process according to the invention, can be prepared by any of the well known methods.

   Thus, for example, two-component zeolites can be prepared by wet methods, in which the metallate components or the metal salt components, some or all of which may be catalytically active, are reacted with silicates. soluble for forming zeolites of the aluminosilicate or double aluminum silicate types; or the constituents can be melted, preferably in the presence of fluxes.

   It goes without saying that the expression metallate encompasses not only alkaline solutions of amphoteric metal oxides or hydroxides but also salts of metals, forming the alkalis, of metal acids, such as the oxacids of metals of the fifth and sixth groups. , which in at least one of the oxidation stages are not strictly speaking amphoteric, but which are capable of reacting with so licates to form zeolites, or with. other constituents to form non-siliceous base exchange bodies.

   Throughout the brief, we will adhere strictly to this somewhat more general definition of metals. In wet bicomponent zeolite formation, the final reaction product should be alkaline with respect to sunflower-lr. @, Where having a strong base exchange power, it should be neutral or alkaline to with respect to phenolphthalein. In order to produce base exchange bodies to be used in the preparation of contact masses for carrying out the process according to the invention, it is sometimes unnecessary to provide a high base exchange power and, for many purposes,

   Zeolites formed under conditions resulting in a final product which is <<void with respect to phenolphatlein, but alkdin with respect to sunflower, have an advantage. We don't really know if. products obtained under these circumstances range from homogeneous chemical compounds, although they behave in many ways as if they were. However, there is reason to believe that in some cases at least. mixtures of Rase exchanger and non-base exchanger polysilicates can occur.

   For the purpose of this specification, a product will be considered to be a base changer product if it has base exchange power, however low.



  It is desirable for many purposes, and in particular when two-component zeolites having a high base exchange capacity are required, to add the relatively acidic components, for example the metal salts in the case of zeolites of double aluminum silicate type, with relatively more alkaline constituents such as soluble silicates for example. By this means a continuous alkalinity is ensured and this way of proceeding can be regarded as that which is preferable to adopt in most airlocks;

   but the way of proceeding in reverse is advantageous for certain contact masses which can be used in the process according to the invention.



  Multi-component zeolites can be prepared by any of the above methods making use of at least three types of components, i.e. at least one metallate. at least one metal salt and at least one soluble silicate.

         In the case of multiple constituent zeolites, as in the case of bicomponent zeolites, the alkalinity conditions must be observed, and for many purposes it is advantageous to add them. Relatively acidic constituents to relative constituents ensure alkaline in order to ensure a continuous alkaline reaction.

   The multi-component zeolites produced vary in nature with respect to the proportion of the different reactive components. Thus, when metallates and silicates predominate over metal salts. the resulting products resemble the alumino-silicate bicomponent zeolites. If the metallic salts and silicates predominate over the metallates, the products resemble two-component zeolites of the double aluminum silicate type and, finally,

   if the metallates and metal salts outweigh the silicates, the resulting products more or less resemble non-siliceous base exchange bodies.

   It is clear that there is no sharp dividing line between the three types of multicomponent zeolites and that one merges into the other as the proportions of the different constituents vary. . An advantage of multi-component zeolites over two-component zeolites is that, if desired, the catalytically active component is greater.

   for certain catalytically active elements or groups can only be incorporated in the form of metallates and others only: in the form of metal salts. In a multi-component zeolite, each catalytically active group can be included in the form in which it is most beneficial.



  Basic exchanger bodies: not if those are produced by the general methods described above; but, instead of determining reactions between silicates and other metal oxide constituents, two or more oxymetallic compounds are reacted of which, in general at least one will be a metallate, and at least one at least one. metal salt;

   or, in certain cases, it is possible to produce a reaction between two different metallates in lG @ - which one negative radical is more acidic than the other. It is possible to produce non-siliceous base exchange bodies in which several metal oxides are. present. It is also possible to produce non-siliceous base exchange bodies in which only one metal is present.

    Thus, for example, certain metals may be of a sufficiently amphoteric nature to form both metallates and metal salts which are capable of reacting with each other to produce base exchange bodies.



  A special method of producing non-siliceous base exchange bodies is the gradual neutralization of strongly alkaline salts of the oxacids of metal elements of the fifth and sixth group in oxidation stages in which they are sufficiently amphoteric. Neutralization of other strongly alkaline metallates can also lead to the formation of non-siliceous base exchange bodies. The reverse method, whereby non-alkaline salts of suitable metals are gradually treated with an alkali until the reaction is sufficiently alkaline to allow the formation of base exchange bodies can also be employed.

      Many metals are only able to enter into the formation of base exchange bodies in certain stages of oxidation and. It is sometimes necessary to introduce these metals in a different oxidation stage from that which is desired in the final base exchange body, the change of oxidation stage preferably being carried out during the formation of the exchange body basics. Certain other elements can be incorporated in the form of complex compounds of the most diverse types, such; for example, that ammoniacal groups, etc.

      In addition to the artificial base exchange bodies briefly described above, use can be made of natural base exchange bodies such as nepheline, leucite, feldspar, etc.



  - The most important mkaeVb do oo-ta.ot-es for many reactions contain permutogenetic products in which, preferably, the diluents are incorporated in a homogeneous manner in the base exchange bodies before formation of the latter, or at least before the base exchanger body has set after formation. Many diluents, both inert and regulating activators, catalytically active or having auxiliary catalyst effects, can be employed.

   Here are some of them: kieselguhrs, of all kinds, in particular cellulose earth, natural or treated; silica powders of various types; pulverized pei7nutogenetics; natural or artificial powders of rocks, stones, tuffs, trass, lava and similar volcanic products which are frequently very porous; green sand; glauconite or its acid-leached derivative; glaucosilL; pulverized slag wool; cements; sand;

         silica gel; pulverized pottery; fuller's earth; talc; glass powder; pumice stone powder. meerschaum, magnesia; asbestos; graphite; activated charcoal; quartz powder; various powdered minerals rich in quartz; metal powders and powders of metal alloys or spongy metals;

   salts of oxymethyl acids such as tungstates, vanadates, chromates, uranates, manganates, cerates, molybdates, etc., in particular, salts of the above elements; silicates such as copper silicate. iron silicate, nickel silicate, cobalt silicate, aluminum silicate, titanium silicate; minerals and ores, especially those rich in copper, etc.

   Thinly divided diluents are of great advantage, especially when the average particle size is less than 60 microns, in which case the diluents have a high surface energy, which increases the adsorptive and absorptive capacity of the mass. contact, diffusion speed and porosity. These finely divided diluents can be considered as physical catalysts or activators.

   Diluted permutogenetic bodies can also be finely divided and used as part or all of the diluents from other base exchange bodies.



  The nine. The following methods are the most effective for the introduction of diluents; but any other suitable method may be used: 1. The diluents may be mixed with one or more liquid constituents of the bodies. base exchangers to be formed, when the latter are prepared by the wet process.



  2. Constituents, either catalytically active, regulators or auxiliary catalysts or others, can be precipitated in diluents, or impregnated with these bodies, which are then incorporated into the base exchange bodies by any method of incorporation. suitable poration.



  3. Diluents can be mixed with base exchange bodies, by kneading or kneading, while the latter are still in jelly form, in which case the base scaler jelly behaves like an adhesive. The homogeneity and uniformity of the distribution of diluents is, of course, not quite as great by this method as by Method 1, but for the synthesis of ammonia, extreme uniformity is not. essential.



  4. We can. To form diluents during the formation of base exchange bodies by mixing suitable compounds with the constituents of the base exchange bodies so that the particles of diluents are precipitated during formation. Protective colloids can be added to prevent coagulation of the thinner particles before the base exchange bodies have set sufficiently.



  5. Compounds may be added which react with some of the constituents forming the base exchange bodies to produce diluents; for example, salts of the metals of the fifth and sixth groups may be added in sufficient excess. so that they react with constituents of the base exchange body, such as, for example, heavy metal oxides, to form insoluble diluents.



  6. Already formed base exchange bodies, diluted or undiluted, artificial or natural, can be impregnated with true or colloidal solutions of effectively efficient constituents and then dried.



  7. A base exchange body, already formed, diluted or undiluted, can be impregnated with several solutions which react therein to precipitate any desired diluents.



  8. Soluble diluent compounds may be added to the constituents forming a base exchange body which, after formation, hold the compounds in solution and which are dried without washing, or treated to precipitate the compounds. compounds. 9. Natural base exchangers or artificial base exchangers, diluted or undiluted, or their derivatives, can be impregnated with solutions of the desired compounds which are then precipitated by means of reactive gases.



  The nucleus or non-exchangeable part of the molecules of the base exchange bodies is ordinarily considered to consist of these types of oxides namely: relatively basic, usually amphoteric, metallic oxides, and relatively acidic oxides, such as SiO2, some. amphoteric metal oxides and certain metal oxides which have a markedly acidic character.

   The nucleus behaves like a single anion; it is advantageous to regard the two portions of the nucleus as the basic and acidic portions, without losing sight, naturally, that the nucleus behaves as a single group. The metal compounds which are capable of forming the basic portion of the core are those of the following metals copper, silver, gold, bismuth, beryllium, zinc, cadmium, boron, aluminum, some rare earths, titanium, zirconium, tin. lead, thorium, niobium, antimony, tantalum, chromo.

        molybdenum, tungsten, uranium, vanadium, manganese, iron, nickel, cobalt, platinum, paitadium. Compounds of these elements can be introduced singly or in mixtures, in any desired proportions, and can be in the form of simple or complex ions.

    It goes without saying that some of the elements in certain oxidation stages can be introduced either as metallates or as metal salts. Others._ne-Feuvent - etrf, - introduced only in one of the forms and others still can be introduced in an oxidation stage other than that which is desired in the base exchange body final, or in the form of complex compounds. Among the complex ionogens are ammonia, hydrocyanic acid, oxalic acid, formic acid, tartaric acid, citric acid, glycerin, etc.



  Many metals are specific catalysts; others are Nt regulators and still others are auxiliary catalysts.



  Examples of constituents forming the relatively acidic portion of the base exchange core are alkali metal silicates, which are soluble in alkali, and alkali metal salts of acids such as boron, nitrogen, .titanium, vanadium, tungsten, chromium, niobium, tantalum, uranium, antimony, manganese, etc.



  The exchangeable bases of the base exchange bodies can be replaced by base exchange and the elements which can be introduced individually or as a mixture, by base exchange, are as follows: copper, silver, gold, ammonium, beryllium, cal cium, manganese, cesium, potassium, sodium zinc, strontium, cadmium, barium, lead; aluminum, scandium, titanium, zirconium, tin, antimony, thorium, vanadium, li thium, rubidium, thallium, bismuth, chromium, uranium, manganese, iron, cobalt, nickel, ru thenium, palladium, platinum and cerium.



  The exchangeable bases introduced can be specific catalysts; they can be regulators or they can be auxiliary catalyst bodies. They can be introduced as single ions or as complex ions and can increase the catalytic activity of the final contact mass, improve its physical strength, or act in both ways.



  As has been described above, base exchange bodies can be reacted with acid radical compounds to form salt-like bodies with them. The radicals can be present in the form of simple acid radiocals, polyacid radicals or complex acid radicals, and include radicals containing the following elements: chromium, vanadium, tungsten, uranium, molgbdenum, manganese , tantalum, niobium, antimony, bismuth, chlorine, platinum, boron.

   Among the complex radicals are the ferro- and ferricyanogen, certain ammoniacal groups, etc. The amount of acid radicals caused to unite with the base exchange bodies to form salt-like bodies can be varied so that the resulting products may have the character of acidic, neutral or basic salts. Most of these aci radicals are regulators or auxiliary catalysts for the catalytic synthesis of ammonia.



  Dilute or undiluted base exchange bodies, or certain derivatives thereof constituting salt-like bodies, can be treated with acids such as mineral acids, for example sul acids. 2-10% furic, hydrofluoric or nitrogenous, to remove part or all of the exchangeable bases or, also, part or all of the basic portion of the nucleus.

      In the case of zeolites, partial leaching with acids, which leaves some or all of the basic portion of the nucleus, or even some of the exchangeable bases, does not affect the function. zeolites as catalysts when they contain. elements catalytically active in the basic portion of the nucleus, or in some cases even -exchangeable bases, and these partially leached catalysts are of great importance.

   When the leaching is carried to completion, the desirable physical structure remains to a considerable extent the same, but the remainder is, of course, a form of silica or, in the case of zeolites in which a part of it is replaced by other acidic compounds, a mixture of the two. It can serve as an advantageous physical carrier of specific catalysts for the synthesis of ammonia and, in the case of partially substituted zeolites, can also contain auxiliary catalysts.



  Non-silicate exchange bodies & bases, either partially or completely leached, may contain catalytically active constituents and behave as (catalysts or auxiliary catalysts, or both. This is particularly the case when a A relatively alkali-free contact mass is required for best results and when the alkali content of a contact mass containing a base exchange body may be too strong for optimum results.



  Diluted or undiluted base exchange bodies, or their derivatives, can also be applied as a film to massive carrier granules or can be impregnated therein. The massive carriers can be inert, activating, or themselves be catalysts. For example, certain catalytic metal alloys and catalytic minerals fall into this class.

   Aluminum or copper alloy granules play an additional advantageous role in that their relatively high thermal conductivity tends to prevent local overheating, which is of considerable importance for obtaining good yields. because the reaction is an equilibrium reaction.



  It is desirable in many cases to subject the contact masses to preliminary treatment at elevated temperatures with air, nitrogen, hydrogen, or mixtures of nitrogen and gas. 'hydrogen. It is also advantageous in certain cases. to introduce ammonium as an exchangeable base which is then released during the catalysis and which increases the efficiency of many of the contact masses to be used in the process according to the invention.



  The preparation of contact masses and their use in the ammonia synthesis process according to the invention will be described in more detail in the following examples. However, the latter is by no means limited to the details of the examples, which are only representative illustrations. Example <I> 1: </I> 15 parts of aluminum oxide, 11.5 parts of zirconium oxide and 18 parts of anhydrous potassium carbonate are ground together and mixed thoroughly with 1 ( 10 parts of iron oxide, preferably magnetic iron oxide, or with a corresponding amount of pulverized iron The mixture is melted and the molten material is broken into pieces and treated with water. .

   The product is a nonsensitive base exchange substance which, after drying, can be used as a contact mass for the catalytic ammonia synthesis.



  Instead of proceeding with the melting as described, an intimate mixture of iron oxide, aluminum oxide, zirconium oxide and anhydrous potassium carbonate is introduced into a tower and passed over the metal. mixes a gas mixture. hot, air and a combustible organic substance such as mothballs. The gases should have a temperature of 450-550 C. Catalytic oxidation occurs and the organic material is completely burnt, the heat given off causing the catalyst components to sinter together or completely melt. The sintered or melted material is broken into suitable pieces and hydrated with water.



  A converter is filled with a contact inasso such as that described in one or the other of the preceding paragraphs and this mass is subjected to a short preliminary treatment, at 400-600 C, with gases containing ammonia. After that, a mixture of hydrogen and nitrogen in the proportion of 3: 1 is passed over the contact mass, at a temperature of 400-600 C and under a pressure of 50-250 atmospheres. being a circulatory process. Good yields of ammonia are obtained which are removed by washing from the gas stream after which the gases which have not undergone have been put into circulation after adjustment of their composition by the addition of fresh gas. the reaction.

     Instead of treating the contact mass beforehand with gases containing ammonia, a 10% solution of ammonium chloride can be run on the contact mass, after hydration, which results in the replacement. of a part of the al cali exchangeable by ammonia. A high pressure converter can be filled directly with the contact mass as follows: a high pressure converter and a catalytic synthesis of ammonia <B> at </B> 350-500 C under a pressure of 100-250 atmospheres can be carried out.



  Another modification is to treat the contact material compositions described above with a 2-3% nitrogenous acid solution to leach out some of the exchangeable alkali. The les- # siv6- product should be washed with water to remove the last traces of acid. - Example <I> 2: </I> Is suspended in 300 parts of water, 1000 parts of iron oxide, freshly precipitated, to form a slurry.

   15 parts of freshly precipitated aluminum oxide are dissolved in potassium hydroxide of twice the normal strength to form potassium aluminate containing 20% excess of the alumina. cali. The iron oxide is stirred in this solution, and, finally, it is added to da. aluminate-iron oxide suspension a 5% solution containing zirconium nitrate, zinc nitrate and cadmium nitrate in the ratio of 2: 1:

   1, until the final reaction mixture remains just alkaline with respect to the. phenolphthalein. The product is removed by suction, then dried at temperatures below. 100 C, after which it is broken into fragments. The resulting mass contains a non-siliceous base exchange body impregnated with iron oxide.

   The uniform distribution of the base exchange body which acts as a regulator and auxiliary catalyst increases the catalytic activity of iron oxide in an excellent manner. The physical structure of the base exchange body is very favorable and. increases the absorptive and adsorptive power of the contact mass for the nitrogen-hydrogen mixture at high temperatures.



  The contact mass is subjected to a short preliminary treatment, at 400-600 <B> C </B>, with a mixture of hydrogen and nitrogen, then a mixture of these two gases is passed through the proportion of 3: 1, on the mass of .contact at 400-550 C and at a pressure of 80 to 250 atmospheres.



  The iron oxide can be replaced by a magnet or other iron ore. E.Venaple <I> 3: </I> Fragments of iron of any desired size are exposed to moist air in order to cover them with a film of iron oxide. They are then placed in a crucible converter and passed over, to. 4-50-500 ° C, a hot mixture of air and an organic substance such as mothballs. Catalytic oxidation occurs and the organic substance is. completely burnt. the heat given off causing the iron to sinter or melt and at the same time remove unwanted impurities from the iron.

   The sintered or molten material, which consists of magnetic iron oxides, is then ground and added to a water glass solution containing 75-90 parts of SiO2 diluted with 20-25 volumes of water. Magnetic iron oxide should be added until the solution is just easy to stir. The water glass-iron suspension is heated and a saturated aqueous solution containing 11.6 parts of W03 as potassium tungstate, 7.2 parts of IVIO3 as potassium molybdate and 9 parts of potassium molybdate is stirred therein. V20 'in the form of potassium vanadate.

   To the mixture thus obtained is added, with vigorous stirring, a <B> 10% </B> solution containing 20 parts of zirconium nitrate with 5 molecules of water and: 3-1 parts of nitrate & thorium with 12 parts. water; then, the reaction mixture gelatinizes. We can. increase the rate of gelatinization by carefully adding a small amount of nitrogen acid, but care should be taken that the reaction mixture remains neutral or slightly alkaline to phenolphthalein. The jelly is pressed, dried and washed with ammonia water.

   the resulting product- being a body (-base exchanger containing tungsten, molybdenum, vanadium, zirconium -and thorium in non-exchangeable form (-t being diluted with a special mixture of iron oxides in a finely divided state, united formally distributed.

   After drying, the base exchange body can be treated with a 2-5% nitrogen solution in order to remove part of the exchangeable alkali and a partially leached permutogenetic body results; or, if desired, it is possible, after having hydrated it with water, to subject the base exchange body to an exchange of bases by running over it a dilute solution of cerium nitrate, in order to exchange a part of sodium for cerium.

   The product is dried, reduced with hydrogen at 300-400 ° C. and it is an excellent contact mass for the synthesis of ammonia under the reaction conditions described in the previous examples. can also introduce, by exchange of bases, other elements than cerium, such as aluminum, iron, manganese, strontium, oobalt, beryllium, rare earths other than cerium, zirconium, titanium, chromium, zinc, lead, cadmium, copper, silver, etc.

   The introduction, which may be of one or more of the above-mentioned elements, is preferably carried out by trickling dilute saline solutions of the elements onto the base exchange body.



  Another modification is to treat the base exchange body by spraying nitrogen acid on it to form the nitrate, a so-called salt-like body, of the base exchange body; or the treatment can be carried out by means of solutions of water-soluble salts of acids of metals of the fifth and sixth groups of the periodic system, such as ammonium varadate, ammonium molybdate or tungstate ammonium.

   It is also possible to treat the base exchange bodies. with ammoniacal or cyanogenous groups, to form complex salt-like bodies. We submit. preferably the salt-like bodies to a preliminary treatment with gases containing ammonia, hydrogen or a mixture of hydrogen and nitrogen.

           Example -4: 24 parts of 8iO2 are mixed in the form of a sodium or potassium soluble glass solution diluted with 4 to 5 volumes of water, with sufficient of a 10% solution. </B> salts of chromium, tetravalent vana dium, zinc, lead. cad mium, copper, iron, aluminum, beryllium, zirconium, titanium or cobalt. individually or as a mixture, for example: a solution of one or more of the ni trates.

   The addition of the saline solution should be sufficient to cause that: the reaction mixture remains alkaline with respect to sunflower and preferably neutral or alkaline with respect to phenolphthalein. A jelly is obtained consisting of a two-component zeolite. The jelly is separated from the mother liquor and dried at temperatures below 100 ° C.



  To the god of making use of salts, one can make use of the corresponding metallates such as beryllate, aluminate, chromite, vanadite, plumbite, cadmiate or zincate -de metal alkali. When using a metallate solution, it is desirable to accelerate the reaction by the addition of an amount of acid sufficient to neutralize the excess alkalinity. The resulting jelly is freed from the mother liquor, washed with water and then dried at temperatures up to 100 C.

   The base exchange bodies obtained as has been described above are preferably treated with saline solutions such as manganese trate, thorium nitrate, copper trate, zirconium nitrate, - or titanium trate, solutions which are preferably 5 to 10% strength and which are trickled onto the base changer body to substitute some of the exchangeable alkali.



  Another modification consists in treating the obtained base exchange bodies with salts of the acids of metals of the fifth and sixth groups of the periodic system by making use, for example, of 1-solutions of ammonium vanadate, ammonium molybdate or ammonium tungstate, or a mixture of two or more thereof. What are called salt-like bodies are obtained and, if desired, the metallic acids can be replaced by nitrogen acid, in order to form the nitrate, by applying, of course, the nitrogen acid so as to avoid leaching.



  Other effective contact masses of the class described above can be prepared by leaching the base exchange bodies with dilute acids before or after base exchange, or before or after formation of the salt-like body. It will be appreciated that the catalytically effective elements can be present either in the complex nucleus as exchangeable bases, or as anions in salt-like bodies.



  Very desirable contact masses can also be obtained by diluting permutogenetic bodies, preferably during formation, with diluents which may be inert, auxiliary regulators or catalysts or even be products themselves. catalytically effective. Examples of such thinners are: asbestos, meerschaum, pumice, refractory brick, A1203, kieselguhr, activated carbon of various kinds, graphite, metals, alloys metals, quartz, magnesia, etc.

   Instead of incorporating diluents in the base exchange body in the permutogenetic body, the latter can be applied to the carrier fragments in the form of films or coated therewith. Examples of -these carrier fragments are roughened alloys, such as ferromolybdenum, ferrochrome, rail-nanadium, silico-ferromanganese, silico-alumino-ferromanganese, ferrotitanium. ferro-tungsten, ferronickel, etc.

   If necessary, adhesives can be used to adhere the film to the carrier fragments. Examples of these adhesives are. alkali metal or alkaline earth metal cyanides, or the corresponding ferro- or ferricyanides.



  Before using the con, tact suasses, it is preferable to -subject them to a preliminary treatment with -hydrogen, or hydrogen and ammonia, at 400-500 C. After the preliminary treatment However, a mixture of hydrogen and nitrogen in the proportion of about 3: 1 is passed over the contact masses at 400-600 ° C. and good yields of ammonia are obtained. being preferably practiced as a circulatory process, the ammonia being removed from the circulating current and the gases which have not undergone the reaction being, after suitable adjustment of their composition, recirculated on the contact mass.

 

Claims (1)

CLAIM <B> - </B> Process for the synthesis of ammonia starting from its elements, according to which a gas mixture containing hydrogen and nitrogen is passed, at high temperatures and pressures, over a A catalytically active contact mass containing at least one body of a microporous structure which results from the formation of a base exchange body. <B> SUB-CLAIMS </B> 1 The method of claim, wherein said body of microporous structure is a base exchange body. 2 A method according to claim, in which said body of microporous structure is a body resulting from at least partial leaching, by an acid, of a base exchange body. A method according to sub-claim 1. wherein said base exchange body is siliceous. 4 The method of sub-claim 1, wherein said base exchange body is non-siliceous. 5 The method of sub-claim 2, wherein said body results from the leaching of a base exchange body sili those. 6 The method of claim, wherein said body of microporous structure is a body similar to a salt, resulting from the combination of a base exchange body with an acidic compound. Method according to claim 1, in which a catalyst mass further containing at least one diluent is employed. 8 The method of claim, wherein at least one catalytically active constituent is present in said body of microporous structure. 9. A process according to sub-claim 1, wherein at least one catalytically active component is present as the exchangeable base. A process according to sub-claim 6, wherein the anion joined to the base exchanger to form a salt is catalytically active. 11. The method of sub-claim 7, wherein the diluent employed is catalytically active. 12 A method according to claim, in which a catalytic mass is employed which also contains a constituent regulating the reaction. 18. Process according to claim, in which a catalytic mass containing an auxiliary catalytic component is employed which, without being a specific catalyst for the formation of ammonia, activates the reaction. A method according to subclaim ï, wherein the diluent forms with said body of microporous structure a homogeneous mass. 15. A method according to claim, in which a mass containing at least iron as an active catalyst component is employed. 16 The method of sub-claim 15. in which the iron is part of the base exchange body. 17. The method of sub-claim 15. wherein an iron compound is physically mixed with said body of microporous structure. <B> 18 </B> Process according to claim, in which one operates according to a cycle by returning the unreacted gases to the catalyst.