CH136365A - Process for catalytically oxidizing sulfur dioxide to sulfur trioxide. - Google Patents

Description

Process for catalytically oxidizing sulfur dioxide to sulfur dioxide. The present invention relates to a process for the catalytic oxidation of sulfur dioxide to sulfur trioxide, ie to a so-called "contact" sulfur dioxide process.

According to the process which is the subject of the invention, a gaseous mixture containing sulfur dioxide and oxygen is passed at a high temperature over a catalyst containing at least one siliceous exchanger body. of bare, called zeolite compound, of the kind resulting from the reaction of a silicate with at least one metallate and at least one metal salt.

The components giving rise to the formation of said zeolitic compound can be divided into three classes: 1 Silicates with or without Partial substitution of other suitable acid oxides; 2 metalates (metal containing anion salts), such as alkali metal metalates; and 3 metal salts (non-metalate salts), which when reacted with Silicates under conditions suitable for the production of zeolites form base-exchanging bodies. Ordinary commercial zeolites are prepared by the reaction of a soluble silicate either with alkali metal mallates or with metal salts. On the other hand, the zeolite compounds contained in the catalysts employed in the process according to the invention are products of the reaction of a silicate with at least one metallate and at least one metal salt, and Ast precisely the use of zeolite compounds of this kind (so-called three-component or multi-component zeolite compounds) which constitutes the essential character of the new process. Both dilute and neat zeolites can be employed as multicomponent zeolite catalysts, but in most cases it is preferred to employ dilute multicomponent zeolites. In the dilute zeolite contact masses employed in the present invention, the catalytic power may reside either in the zeolite or in the bodies in combination with the zeolite, or partly in the zeolite and partly in diluents combined with the zeolite. to form mixtures or structures which are preferably chemically homogeneous.

All bare exchange bodies used in the present invention, both diluted and undiluted, possess a remarkably porous honeycomb structure and are in many cases opalescent. When suitable catalytically active components are present, they form catalysts or contact masses of remarkable efficiency, their efficiency being probably due, at least in part, to the extremely high surface energy of the microscopically porous structures and probably also, in many cases, to the presence of unsaturated valences and to the asymmetry of the molecules.

It is understood that the products employed in the present invention are chemically quite distinct from zeolites formed by the reaction of a silicate with either metallates or metal salts.

The products employed in the present invention can be classified into three main types, according to the relative proportions of the three classes of components: If the silicate and the metalate predominate over the metal salt, the resulting products resemble zeolites of the type aluminosilicate; if the metal salt and silicate predominate over the metalate, the resulting products bear some resemblance to zeolites of the double aluminum silicate or polysilicate type; in the case where the metallate and metal salt predominate over the silicate, the products resemble non-siliceous bare exchange bodies. It goes without saying that there is no clear line of demarcation between the different types, and that they encroach on each other when the relative proportions of the components are changed.

The zeolites employed in the process according to the present invention can be prepared under reaction conditions particularly suitable for the formation of bare exchange bodies, that is to say in reaction mixtures which are finally alkaline with sunflower. The best bare exchange power is obtained when the products are prepared in solutions which are neutral or preferably alkaline with phenolphthalein, but products of lower base exchange powers but frequently having the same efficiency for the manufacturing process. contact sulfuric acid can be obtained under reaction conditions ranging from red with phenolphthalein to blue with sunflower. It is not possible to determine whether the zeolites formed under these conditions are homogeneous chemical compounds; it is possible that in such cases you will obtain a mixture of zeolites and non-bar-exchanging polysilicates. However, the physical structure remains analogous and, for the manufacture of sulfuric acid by contact, the products are equivalent to zeolites produced under conditions producing higher bar exchange capacities. However, it is to be understood that the term "zeolite" as used in this description is limited to products having at least some base exchange capacity when freshly prepared.

The products used in this invention may be prepared by name. many ways. Applicant has found that it is usually desirable to add the metallic salts to the metallates and silicates so that the alkali of these latter components is at all times present in excess, so that the reaction remains automatically alkaline, at least with sunflower.

Some of the catalysts used in the present invention can be prepared by adding the silicate and the metalate to the metal salt, taking care to ensure that when the. reaction is complete, the reaction mixture is alkaline with toursalt and preferably neutral or alkaline with phenolphthalein.

The number of elements which can be included in the products employed in the present invention is very large. thus, for example, one may employ any one or more of the metallic elements which are capable of forming soluble alkali metal metalates and complex compounds of metals which possess a more or less amphoteric property. for certain applications in that they allow the production of soluble alkali metal metallates whereas the simple oxides of the metals may not be suitable because they do not form soluble alkali metal metalates . A few of the complex ionogens may be mentioned: ammonia, hydrocyanic acid, sulphocyanic acid, oxalic acid, formic acid, tartaric acid, eitric acid, glycerine and various types of sugars.

Certain compounds such as vanadates, molybdates, tungstates, tantalates and uranates, which are not ordinarily considered to be metallates but which are capable of forming bare exchange bodies with soluble silicates and metallic salts, will be understood in the term "metalate" used in the present description. This term therefore includes any metal salt whose anion contains a metal.

Alkali metallates are capable of forming bare exchange bodies with soluble silicates and metal salts or can be rendered capable of reacting in another way by a valence change which can be effected during the reaction.

In the process according to the present invention, catalysts prepared by employing one or more metalates in any desired ratio can be used. The following elements are included among those forming metallates which can be advantageously employed: aluminum, chromium, zinc, vanacium, beryllium, lead, palladium, platinum, titanium, lead, tungsten, boron, molybdenum, uranium and tantalum, copper, nickel, iron, cobalt, silver, cadmium, manganese, zirconium, thorium and cerium.

The metallic salts (and by this it is necessary to understand the salts of metals not constituting metallates) which can be used are also numerous and, in general, all salts or mixtures of salts soluble in water, whether acidic , neutral or basic, can be used. The following elements are included among those which form suitable salts: copper, silver, gold, beryllium, zinc, cadmium, aluminum, rare earths, titanium, zirconium, lead, lead, thorium, chromium, uranium, vanadium, manganese, iron, nickel and cobalt.

The silicate may be an alkali metal silicate or other alkali-soluble silicate, or it may substitute for part of the silicate alkaline salts of the acids of the following elements: sulfur, nitrogen, tin, arsenic and antimony. All of these compounds are capable of forming bar exchange bodies with the other components and should therefore be considered as equivalents of silicates.

The range of new products employed in the present invention is not limited to the elements present in the components which form the non-exchangeable core of the zeolite. On the contrary, it is possible to replace the alkali metal cathions by other metallic cathions by an exchange of bars. Thus, for example, an can introduce one or more of the following cathions: ammonium, copper, silver, gold, beryllium, magnesium, calcium, zinc, strontium, cadmium, barium, aluminum, titanium, zirconium, tin , thorium, vanadium, chromium, uranium, manganese. iron, cobalt, nickel, palladium and platinum. The elements or radicals can be introduced in the form of simple or complex ions in any desired proportions. The introduction can be effected simultaneously or sequentially. The number of possible combinations per exchange of bars is of course very high, as is easy to conceive for a chemist specializing in zeolites. The number of these new compounds is therefore considerably increased, and numerous catalysts or activators for the production of S0 can be produced by the introduction into a zeolite compound, by suitable exchange of bars, of cations which can increase the concentration of catalysts or activators in the product or which can determine a more precisely regulated catalytic activity; this is frequently possible because proper introduction of the desired cations by bar exchange frequently increases the allowable loading of the product in the manufacture of sulfuric acid by contact and can increase the temperature resistance, the the percent yield that can be obtained from it or the production or both.

Another series of catalysts can be obtained by treating the aforesaid bare exchange bodies with compounds containing suitable arid radicals which form with said bodies salt-like bodies. These products behave in many respects as if they were real salts, but their exact chemical constitution is not known.

Acids or salts of the following elements can be employed to produce salt-like bodies useful in the process according to the present invention: vanadium, tungsten, uranium, chromium, molybdenum, manganese, arsenic, sulfur and chlorine. Simple arids or their salts can be used in place of polyarids, peracids and complex ions when desired. Other complex anions such as ferro- or ferricyanogen, sulfocyanogen, other metallic cyanogens, ammonia compounds, etc. are useful whenever they form salt-like bodies with the bare exchange bodies with which they are to react. One or more acid radicals can be introduced in the manner described above either simultaneously or successively, and the quantity of acid radicals introduced can be modified quantitatively and, by this means, bare exchange bodies analogous to salts. and having the characteristics of arid, neutral or basic derivatives can be produced.

The dilute zeolites which the applicant has found to be the most effective as catalysts or contact masses for the manufacture according to the invention of sulfuric acid by contact can be prepared in very diverse ways by the incorporation of a Brand number of thinners such as highly porous thinners such as kieselguhr, glaucosil, celite brick waste, silicates, inactive zeolites, pumice powder and other products, or can coat massive Support fragments, natural or artificial. Diluents can be incorporated. one or more of the components of the zeolites before the reaction; in addition to certain diluents, this gives the most homogeneous products. Valuable catalysts can also be produced by incorporating into the zeolite, after its formation and while still in a gelatinous state, suitable finely divided diluents, which is obtained by kneading or any other suitable process. . The zeolite can also be formed in the interstices of porous diluents such as, for example, pumice chips, by any suitable method of impregnation, preferably by reacting the zeolite components in the diluents.

The important property of porosity of bar exchange products prepared as described can, in many cases, be rendered more pronounced by incorporating into the bodies, during formation, products which are easily removed (by volatilization, combustion or leaching) and which leave additional pores, which further increases the permeability of the framework of the bar-exchanging products. The eliminable products to be employed can be inorganic or organic and are very numerous, but their choice will of course depend on the characteristics of the bare exchange body.

The production of bare exchange bodies usually results in a considerable percentage of soluble salts in the reaction mixture, and it is generally desirable to remove these salts by washing and drying the products, preferably at moderate temperatures which may advantageously be below 100° C. Some products may be very weak mechanically and they may advantageously be washed or impregnated with a dilute solution of water glass instead of water, this determines a superficial silicification which considerably increases the mechanical resistance of the product.

The applicant has found it advantageous to subject the catalysts and contact masses used in the present invention to a preliminary treatment consisting, in the first place, of calcination carried out in the presence of air or other gases. This preliminary treatment and the catalysis itself, which take place at a high temperature, produce in the catalyst or contact mass certain chemical changes which are not well defined, and when it is a question of a catalyst in what follows by which is meant the freshly prepared catalyst, as is usual in the nomenclature of catalytic chemistry.

Contact masses not containing metals of the platinum group, in particular those - which the applicant has found the most effective - whose main catalytically active element is vanadium, have, in addition to brande resistance to temperatures high and desirable mechanical strength which characterizes multicomponent zeolite catalysts and contact masses, the very important advantage being that they are not substantially influenced by substances which corrupt platinum catalysts (,, It is therefore possible to carry out the manufacture of sulfuric anhydride by contact without eliminating the poisons of platinum from the reaction gases, and it is possible, in most crs, to eliminate mechanically entrained dust Expensive purification installations - essential when using platinum catalysts - can therefore be eliminated, which translates into savings in equipment and maintenance costs. Despite the marked advantages of catalysts which do not contain platinum group metals and which the applicant prefers, it is understood that, as regards its general characteristics, the invention is not limited to the application of these catalysts or contact masses not containing platinum group metals. On the contrary, one can make use of contact masses con- A@@t, platinum or platinum group metals in combination with multicomponent zeolites, the compounds thus obtained constituting excellent catalysts with regard to the 'efficiency. These compounds are, of course, subject to a greater or lesser degree to the disadvantages inherent in the use of platinum contact masses.

It has been found that certain catalytically active elements or groups, although not selectively active for the formation of SO on contact, appear to enhance or regulate the action of the selectively active catalysts present. Thus, many heavy metal compounds, which may for example be present in diluents, or which may be introduced into the zeolite by bar exchange, appear to have catalytic activity but are not selective catalysts for the process. manufacture of sulfuric acid by contact.

It should be described, to make it better understood. nature of the zeolitic compounds to be employed, several examples of the preparation of compounds of this kind.

Example <I>1:</I> 0n forms a slurry with 16 Parts of vanadic acid and 300 Parts of water and an <B>,</B> aü ,idifies this slurry ,ä. the aid of sulfuric acid. The mixture is then brought to a boil and a vigorous stream of sulfur dioxide is passed through the hot solution. A blue solution of vanadyl sulphate is formed in a short time. After the excess sulfur dioxide has been boiled off, the blue solution can be divided into two fractions in the ratio of 2 to 3. solution of caustic potash is mixed until a light brown solution of potassium vanadite is formed. 140 Parts of Potassium Silicate at 39 Bé are diluted with 500 Parts of water and the potassium vanadite is added thereto while stirring vigorously. The mixture is then moderately heated and the remaining 2/5 of the Vanadyl Sulfate added in a thin stream while stirring vigorously. The mass then begins to solidify into a greyish-green gel and, with continued stirring, becomes granular aggregates which are easy to filter.

The amount of aloali used in the solutions should be chosen such that, at the end of the reaction, the mixture remains weakly alkaline or neutral with the phenolphthalein. If the alkalinity of the reaction mixture is much higher, the precipitation is retarded, but it can be accelerated by adding about 50 parts of a saturated solution of Potassium Sulfate which, by its salt elimination effect , increases yield.

Another method of accelerating precipitation is to lower the alkalinity of the reaction mixture by carefully adding arids or dilute solutions of arid salts such as, for example, hydrochloric acid, sulfuric acid, potassium bisulfate, etc. By this means, any desired degree of alkalinity or neutralization of the resulting reaction product can be easily achieved.

The reaction mixture is allowed to stand, then decanted, pressed and washed with water. The press product is hoisted, preferably below 100 C, and the base exchange body, which body contains SiO and V'204, is then broken into fragments or hydrated with water. , at which aas it also breaks into granules. The final product is a Blair Gray Hard Body having a conchoidal fracture and possessing base exchange properties.

The base exchange body can be heated for a considerable time at 400-500 C in a stream of diluted burner gases: it then becomes a good contact mass for the manufacture of sulfuric acid by contact.

If you wish to dilute the bare exchange body, mix one or more of the three initial solutions constituting the components, and preferably either the water glass solution or the potassium vanadite solution, with a total volume of 60 to 80 Parts of cellite brick waste, the resulting product being a dilute bare-exchanging body which can be dehydrated in a current of hot air and carbon dioxide and which, after being of acids such as hydrochloric acid, nitric acid and sulfuric acid, constitutes an excellent contact mass for the catalytic oxidation of S0 to SO. Burner gases containing 5-9% SO 2 are passed over the contact mass at temperatures of 400-550 C and thus a high conversion of SO to SO 2 is achieved.

The bare exchange body - concentrated or dilute - can be treated by trickling 3 to 5% solutions of heavy metal salts such as sulphates of copper, nickel, aluminum and titanium, used alone or in a mixed state, on the said body, with the aim of effecting an exchange of kisses, so that the resulting products are made more suitable for resisting the high temperatures which often prevail. wind in the process for the manufacture of sulfuric acid by contact. Example 2: Three mixtures are prepared as follows: 1 0n mixture 42 ä. 50 parts of SiO2 in the form of a solution of potassium or sodium silicate diluted with 20 parts of water with kieselguhr or other materials rich in SiO2, such as glaucosil (the residue of green sand treats by acid) until a slurry is obtained which can just be stirred further.

2 18 Parts of VO' are dissolved in just enough 10-20% potash or caustic soda solution to obtain potassium or sodium vanadate.

3 Eighteen parts of V2O are reduced with sulfur dioxide in aqueous solution in the usual manner to form blue vanadyl sulphate, approximately 200 to 300 parts of water being required. Excess SO is removed by boiling.

Pour mixtures (1) and (2) into each other and then pour solution (3) while stirring vigorously, taking care that the reaction mixture remains at least alkaline with litmus. The alkalinity can be adjusted by slight additions of potassium hydrate solution, if necessary. A dirty greyish-blue gel is obtained which is filtered under a vacuum, washed with a little water, then searched. The product obtained is a three-component bare exchange body which contains tetravalent and pentavalent vanadium in a non-exchangeable form and in the framework of which SiO-rich materials are finely distributed in all parts.

After a short time treatment at 400-500 C with burner gases at about 3, the product becomes an excellent contact mass for the contact sulfuric acid manufacturing process. When burner gases pass at 5-9% of this mass, a high conversion of SO2 to S03 takes place at temperatures between 400 and 550 C.

A still finer control of the contact mass for the manufacture of sulfuric acid can be effected by replacing part of the exchangeable alkali with other cations such as, for example, sulfuric acid. copper, silver, iron, cobalt, aluminum, titanium, calcium, manganese, cerium, strontium and nickel, using 3 to 6% solutions of the salts of these metals or their mixtures.

A further improvement can be brought to these contact masses intended for the manufacture of sulfuric acid by contact by forming a salt-like body by the reaction of the three-element bare exchange body with acids of the elements. fifth and sixth groups of the Periodic System, especially vanadium and tungsten, this formation increasing the resistance of said masses to high temperatures.

Silica-rich diluents, such as kieselguhr, which are introduced by mixing them into the N 1 waterglass solution, can also advantageously be used. eire impregnated with 3-5% of the salts of the oxy-acids of iron, nickel, silver, copper, cobalt and aluminum, or else an can precipitate their oxides in the diluents using dilute alkali solutions, in the usual manner. The diluents can also be impregnated with metallic vanadates, molybdates, tungstates, chromates, tantalates, especially heavy metals, 3-5% of these metalates being sufficient. This treatment of the diluents increases the catalytic efficiency of the contact masses for the manufacture of sulfuric acid by contact, acting partly as catalyst components and partly as reaction promoters.

Example 3: A mixture of 10 parts of V20" and 4 parts of W03 is dissolved in 300 parts of a dilute KOH solution containing 10.5 parts of 90% gOF1. 5 is added to this solution. While stirring vigorously - ly, about 90 parts of waste celite brick or an equal volume of a mixture of ground quartz and diatomaceous earth Other diluents such as those described in Example 2 are also applicable.

The slurry is heated to 80 to 90 C and gradually made weakly acidic to congo, using sulfuric acid to precipitate V205 and WO3 in this diluent or in the mixture of diluents. The mixture obtained is then dried and ground.

40 parts of a solution of potassium silicate are weighed out. 33 Be. 2 parts of Al 2 O are converted in the usual manner with the aid of a caustic potash solution into the corresponding potassium aluminate. The two solutions are then mixed and, immediately afterwards, they are perfectly kneaded with the V20 and the W03 precipitated in the cellite brick waste, and the product is then formed into pieces of suitable shape. These pieces are then dried at temperatures below 100 C, preferably using gas containing C02, so that a diluted three-component bare exchange body is obtained which contains VȎ5, WO , AlȎ and SiO in the non-exchangeable part, the W03 then playing the same role as tungsten in a metallic salt.

The contact mass thus obtained is calcined with SO 2 gases which are strongly diluted by air and, after having subsequently treated the mass with 7-9% gases, a very efficient production of sulfuric acid by contact begins.

Instead of PO5 and WO , an can employ in the same way, for the preparation of the contast mass, other catalytically active components, such as VȎ4 and Mo03.

Instead of employing potassium aluminate, one can employ other metalates of amphoteric elements such as Cd, Be and Zn. In order to increase the resistance of these contact masses to the high temperatures which often prevail in the manufacture of sulfuric acid by contact, one can embed in the contact mass, during its formation, agents promoting the reaction, for example 5 % FeȎ and TiO.

Example 4: 1 6.6 parts of freshly precipitated AlȎ are dissolved in a KOH solution to form the corresponding potassium aluminate. Diluents rich in SiO are added to this solution, such as: silicates, quartz, rocks, tuffs, lava of volcanic or eruptive origin, artificial and natural zeolite, kieselguhr, waste celite brick, etc. materials being reduced to a suitable degree of Fineness. When using waste celite brick or kieselguhr, 80 to 100 parts is the proper proportion for the preparation of the dilute three-component zeolite.

Very advantageous diluents can also be specially prepared, such as colloidal SiO2 or SiO obtained starting from base-exchanging silicates - natural or artificial - which are treated with diluted mineral arids in order to eliminate the alkali. in the exchangeable part of the bare exchange bodies and the amphoteric metal oxide, so that a compound of SiO having a high absorbency is obtained. SiO2 thus prepared and mixed with waste celite brick or kieselguhr is an excellent diluent for the preparation of zeolitic contact masses in the manufacture of sulfuric acid by contact.

In some cases it is also advantageous to add 5 to 10% of specially prepared silicates which behave in this process as reaction control agents. Such silicates constitute an intermediate phase in the preparation of the Si0 complex starting from artificial and natural bar-exchange silicates. Such bare-exchanging silicates, such as leucite or the artificial zeolites usually prepared, are leached using dilute mineral acids, for example 5 to 10% sulfuric, hydrochloric or nitric acids. , for the purpose of removing the alkali from the. Exchangeable part of the bare exchange body, so that the amphoteric metal oxide remains in chemical combination with the SiO2 group. Silicates of this kind have a very high absorbing power and are an excellent means for regulating the action of catalysts.

2 80 parts of a solution of potassium silicate at about 33 Bé are dissolved in 100 parts of water.

3 Dissolve in 150 parts of water 24 parts of Al(SO4) plus 18 aq.

The aluminate suspension (1) is quickly mixed with the water glass solution by stirring vigorously and the aluminum sulphate solution is added in the form of a thin stream, so that a diluted bare exchange body is obtained. three-component which is gelatinous and contains Al20 and SiO in the non-exchangeable part. The mother liquor is removed from the bare exchange body in the usual way, the press product obtained is sought, preferably below 100° C., and then broken into suitable pieces. To increase the yield, one can use small quantities of very dilute SO4H (5%), taking care that the reaction product and the mother liquor remain substantially neutral or weakly alkaline with respect to phenolphia. - line.

In this bare exchange body, the silicate and metalate predominate over the metal salt, the resulting product therefore resembling an aluminosilicate-type zeolite.

By employing the same amount of components, a different type of three-component zeolite can be obtained when changing the order in which the three classes of components react with each other. In this case, the alkaline reacting components, i.e. the aluminate and water glass solutions, are poured into the aluminum sulphate solution, the diluents possibly being present in the mixture of the components. alkaline or in the metal salt component. 0n works and Seehe in the same way as previously the gelatinous mass obtained. Alternatively, the metal salt and the metalate can be reacted first, in which case the diluent would preferably form part of one of these two components and the SiO component would then be added.

These methods show the many possible embodiments of the preparation of certain types of bare exchange bodies. three components.

Instead of changing the order in which the three classes of components react with each other, one can change the proportions of the components and thus obtain other types of three-component zeolites.

In this way, the following proportions of the components can be obtained: 10n dissolves 3.4 parts of freshly precipitated Al2O in a KOH solution so as to form the potassium aluminate solution as a component. metallate.

2 120 to 150 Parts of 33 Bé potassium silicate are dissolved in approximately 200 Parts of water.

3 0n dissolves 44.5 Parts of Al2 (SO4) plus 18 aq. in about 200 parts of water. The diluent is added to either or both mixtures of the alkaline reacting components.

A special process for the preparation of this three-component zeolite consists in mixing together the aluminate and the SiO constituting two of the components and then adding the Aluminum Sulfate constituting the third component, or vice versa. The reaction product obtained is worked up in the usual way and, in this case, the metal salt and the silicate predominate over the metalate, so that the resulting three-component zeolite resembles from certain points of view a zeolite of the double aluminum silicate type.

The preparation of the three-component base exchange bodies in which the metallate and the metal salt predominate over the silicate, so that the product obtained resembles a non-siliceous base exchange body, is carried out as follows: dissolves 5 parts of freshly precipitated Al0 in a KOH solution to form the corresponding potassium aluminate.

2 0n dissolves 34 parts of Al (SO4) plus 18 aq. in 200 parts of water.

30n dissolves 50 parts of 33 Bé potassium silicate in 100-150 parts of water.

The proper proportion of the diluents described above may be added to one of the components or to the mixture of alkaline reacting components.

A base-exchanging body of this type possessing a well-developed base-exchanging power is obtained by mixing together the aluminate and the silicate and then adding the aluminum sulphate while stirring vigorously. The resulting reaction product is stripped of mother liquor and dried in the usual manner. Another embodiment can be obtained by reacting the components in reverse order.

Instead of using Al0 like the metallate, you can use other components of this class which contain vanadium, tungsten, molybdenum, lead, zinc, cadmium with or without aluminum, separately or together. state of mixing.

Instead of using aluminum sulphate, one can use other metal salts, with or without aluminum sulphate, separately or in the state of mixture, such as for example those which contain the vanadium (especially vanadyl sulphate), zinc, cadmium, titanium, zirconium, copper, nickel, cobalt, silver, beryllium, cerium, tin, thorium, manganese, chromium.

Depending on the components chosen, it will be possible to obtain base exchange bodies which have a direct catalytic action in the production of sulfuric acid by contact, especially when vanadium is used as one of said components.

When using components which are not catalytically active in the base exchange body combination, the catalytically active component may be introduced by base exchange, by the formation of salt-like bodies, or by both. means at a time, in which case the catalytic power resides, especially in the case of the formation of salt-like bodies, in a chemical combination with the three-component zeolite.

A dilute three-component zeolite, which contains aluminum and SiO in the non-exchangeable part and has no catalytic capacity for the production of sulfuric acid by contact, can be transformed into a contact mass. effective in various ways. The alkali metal of the exchangeable part of the base-exchange body can be partially or mainly replaced by other metals, especially by heavy metals such as iron, copper, nickel, cobalt, manganese, silver, titanium, zirconium, aluminum, which is obtained by streaming over the body solutions of 5 to 10% of corresponding salts or their mixtures at regular temperatures or at temperatures a little high in order to speed up the exchange of bases. For this purpose, before applying the salt solution, it is advantageous in many cases to hydrate the body of base exchange by running water over this body. After this treatment, an reacts the base exchange bodies with ammonium vanadate or other soluble vanadates to form the base exchange body vanadate. The best way to carry out this reaction is to impregnate said Body with the vanadate solution and, after the reaction, to wash away the alkali. The base exchange body takes on the color of the corresponding vanadates. A 1 to 10% solution of vanadate may be employed for this purpose.

After drying, the resulting contact mass can first be calcined at 400-500°C. Clean and then with dilute burner gases containing approximately 3% SO`. After this treatment, an exhaust gas is passed at 7-8% over the contact mass, which initiates efficient manufacture of sulfuric acid by contact at temperatures of 420-550 C. the heat distribution at the various points of the catalyst is such that a high temperature of 500-550 C reigns in the part of the contact mass which comes into contact with the concentrated SO' gases and at the place where the maximum speed reaction is desired, while the latter portions of the contact mass are maintained at temperatures of 400 to 480° C., which promotes the best reaction equilibrium.

In many cases, it is desirable to introduce catalytically active components into the exchangeable portion of the three component zeolite molecule. A particularly effective product is obtained by treating the zeolite with a 3-5% vanadyl sulphate solution to remove as much of the exchangeable alkali metal as possible. The product thus obtained can also be treated with 3-5% solutions of vanadates, tungstates, molybdates or mixtures of these compounds to form salt-like bodies and thus further increase the concentration of the compounds. catalysts in chemical combination with the three-component zeolite. These contact masses are also excellent for the manufacture of sulfuric acid by contact.

Contact masses suitable for the manufacture of sulfuric acid by contact can also be produced by introducing catalytically active diluents into so-called three-component zeolites, these diluents possibly containing a certain amount, for example 5 to 10% of a metalate dopt the union contains a metal of the fifth and sixth groups of the periodic system, such as vanadate of silver, copper, manganese, etc., singly or together. state of mixing.

Claims (7)

CLAIM Process for catalytically oxidizing sulfur dioxide to sulfur dioxide, according to which a gaseous mixture containing sulfur dioxide and oxygen is passed at an elevated temperature over a catalyst containing at least one siliceous substance. bare exchanger, called zeolitic compound, of the kind resulting from the reaction of a silicate with at least one metallate and at least one metal salt. SUB-CLAIM S 1 Process according to claim, characterized in that the contact mass which is employed does not contain elements of the platinum group. 2 Process according to claim, characterized in that the reaction gases are freed from the chemically entrained dust before passing them over the catalyst, but that these gases still contain "poisons" for platinum catalysts. 3. Process according to claim, characterized in that a multicomponent zeolite containing vanadium is used as catalyst. 4. Process according to claim, characterized in that a body obtained by reacting the zeolite compound with a catalytically active acid radical to form a salt-like body is employed as catalyst. Process according to claim, characterized in that the aforementioned zeolite compound is used as catalyst in admixture with a diluent to form a contact mass of physically homogeneous structure. 6. Process according to claim, characterized in that the multicomponent zeolite body is applied in the form of a layer on solid support fragments. 7. Process according to claim, characterized in that the aforementioned zeolite compound is used as catalyst in a mixture with a diluent containing agents for regulating the catalytic action.