Patented Jan. 30, 1934 ,< 1,945,262 UNITED STATES PATENT OFFICE 1,945,267 CONTACT SULPHURIC ACID PROCESS Franz P. Fiecller, Pittsburgh, and Alphons 0. Jaeger, Mount Lebanon, Pa., assig?nors- to The Selden Company, Pittsburgh, Pa.,_ a corporation of Delaware No Drawing. Application Junev 1, 1931 Serial No. 541,488 5 Claims. (01. 23-475) This invention relates to the catalytic oxida are prepared by spraying or otherwise coatingor tion of sulphur’ dioxide to sulphur trioxide, the impregnating the catalysts upon the carrier ma contact sulphuric acid process, by means of a new terial, the various components being‘ applied class of catalysts. either simultaneously or successively. The prod According to the invention catalysts are used ucts so obtained are preferably given a pretreat which contain vanadium or other metal element ment at elevated temperatures with air, S02 or of the 5th and 6th groups of the periodic system S03 gases or mixtures of these and during this in chemical combination together with thallium treatment, as well as during the ?rst stages of in chemical combination, the thallium being use, secondary changes occur in the catalyst such present either as an oxide or salt and the vana as the neutralization of basic components by- the 65. dium in the form of a metallate, an oxide, or in acid gases, driving o? of volatile components, and the form of a vanadyl salt. The presence of thal the like. It is to be understood- that- catalysts lium compounds in vanadium catalysts for use which have undergone such secondary changes in the contact sulphuric acid process has been are included within the scope of the invention found to exert a decided improvement on the as well as those which are freshly prepared. yield both at low and high loadings, and the re The invention will be further described in sults obtained are much superior to those pro connection with the following examples which duced when vanadium oxides are used alone. are for illustrative purposes and to which it is Although ef?cient catalysts may be obtained not limited. by the use of thallium and vanadium compounds Ewample 1 alone, we have further found that the addition of compounds of aluminum or silver to the cata 8 parts by weight of T1203 are dissolved in aqua lyst results in further improvements in the re regia, diluted to about 200 volumes, and sprayed sults obtained. The silver or aluminum may be onto 250 parts by volume of “Silocel 0-22” of ' present in chemical combination with the vana 6-10 mesh. 16 parts by weight of NH4VO3 are 3.0 dium or in the form of an oxide admixed there dissolved in about 250 parts of water and also with or, in the case of aluminum, it may be pres sprayed onto the carrier, which is preferably ent in the form of a metallate. heated and agitated in such a manner as to pro In order to increase the activity and effective duce a uniform coating. The catalyst is calcined for 11/2 to 2 hours at 30 life of the catalysts of the present invention sta bilizers are preferably added, which are com temperatures of BOO-400° C. using air or dilute pounds of the alkali forming metals. The alka S02 gases, after which it is ?lled into a converter line earth metals appear to produce a more fa and 7% burner gases passed over it. Yields up vorable effect on the catalysts containing thal to 97-98% are obtained and the catalyst retains lium and vanadium than do the alkali metal com its activity over long periods of time. pounds, and compounds of calcium, particularly Example 2 calcium oxide, appear to be the most desirable. The invention is not limited however to the use A catalyst containing thallium, silver and vana of any de?nite class of stabilizer and in fact sat dium in the ratio T1203 : Ag2O 2V2O5= 1/4 : 1: 1 is pre 40 isfactory results may be obtained in some cases pared as follows: 9,5 when no stabilizer is used at all. 8 parts by weight of T1203 are dissolved in aqua ' The catalysts of the present invention are pref regia and heated with H2SO4 until the HCl and erably supported upon carriers, of which those HNO: are mostly expelled. The suspension is containing silicon are the most satisfactory. Such diluted to 250 parts by weight and boiled to bring carrier materials as kieselguhr, diatomaceous the compound into solution. This solution is -.1.00 earth, and “Celite” brick fragments are suitable sprayed upon 250 parts by volume of “Silocel ‘ for this purpose, as are the synthetic pellets pre C-3”. pared from silicious material with metallates or A solution of 24 parts by weight of silver ni metal oxides as a binder. We do not here claim trate in 50 parts diluted water is poured into broadly the use of the last two forms of carriers 220 parts of water containing 16 parts ammonium . 195 ' as these form the subject matter of the co-pend vanadate and the precipitate dissolved by the ing applications of Alphons O. J aeger Serial No. addition of ammonium hydroxide. This solution 541,118 ?led May 29, 1931 and Serial No. 526,133 is then sprayed upon the prepared carrier, which ?led March 28, 1931. is heated to evaporate the water and produce ‘a The catalysts for use in the present invention uniform coating. The catalyst, when tested in the usual manner, taining thallium oxide and vanadium in chemical gives the following results: combination. 2. A process of oxidizing sulphur dioxide to Loadings, liters/hr ___________________________ _ sulphur trioxide, which comprises bringing about % convar inn _ , reaction between sulphur dioxide and oxygen con taining gases in the presence of a catalyst con Ewainple 3 taining thallium oxide and vanadium oxide. A stabilized catalyst containing thallium ‘and 3. A process of oxidizing sulphur dioxide to vanadium is prepared in the following manner: sulphur trioxide, which comprises bringing about A slurry of 4.5 parts by weight CaCOa' in 100 reaction between sulphur dioxide and oxygen con 85 parts water is neutralized with nitric acid and taining gases in the presence of a catalyst con added to a solution prepared by dissolving 8 parts taining a carrier with which is associated an T1203 in aqua regia and the solution, made up to oxide of thallium and an oxide of vanadium. 250 parts by volume, is sprayed'onto 250 parts by 4. A process of oxidizing sulphur dioxide to 15 volume of “Silocel 0-22” or other suitable car sulphur trioxide, which comprises bringing about 90 rier material. A second coating consisting of 16 reaction between sulphur dioxide and, oxygen parts NI-I4VO3, suitably dissolved in water, is then containing gases in the presence of a catalyst con applied and the catalyst calcined as in previous taining diatomite brick fragments with which is examples. With this catalyst, under the usual associated an oxide of thallium and an oxide of 20 conditions, yields of 98%,and better can be ob vanadium. I 95 tained. - 5. A process of oxidizing sulphur dioxide to ; “The term “metallate” is used in the speci?ca sulphur trioxide, which comprises bringing about tion to cover salts ‘of metal acids such as, for ex reaction between sulphur dioxide and oxygen ample, potassium aluminate, potassium vanadate, containing gases in the presence of a catalyst 25 etc., as opposed to salts of the acids of the non containing a carrier with which is associated 100 . thallium oxide, silver oxide and vanadium pen metals. , ' -What is claimed as new is: toxide in proportions not materially‘ diiferent 1., A process of oxidizing sulphur dioxide to from the ratio 14111 respectively. ~ ~ _ ' ' sulphur trioxide, which comprises bringing about FRANZ P. FIEDLER. ~ in reaction between sulphur dioxide and oxygen con ALPHONS 0-. JAEGER. 105 .taining gases in the presence of a catalyst con 85. 110 115 it 120 86 125 130 it 135 146 145 .