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3,326,819 United States Patent Office Patented June 20, 1967 2 3,326,819 antimony tetroxide and stannic oxide themselves, it is (CATALYTIC COMPOSTIONS COMPRISING ANTE still preferred to subject the mixture to a prior heat-treat MONY OXDE, TN OXDE AND A PROMOTER ment With or without oxygen for instance at a temperature Frank Christopher Newman, Great Bookham, England, between 550° and 1100° C. assignor to The Distiers Company Limited, Edinburgh, A particularly preferred method of preparing the anti Scotland, a British company mony oxide/tin oxide catalytic composition comprises No Drawing. Filed Nov. 19, 1965, Ser. No. 508,831 intimately mixing stannic oxide or the hydrated oxide ob 4 Claims. (C. 252-461) . tained by the action of aqueous nitric acid on tin metal, with antimony pentoxide, antimony tetroxide or the hy This invention relates to the hardening of catalytic 10 drated oxide formed by the action of aqueous nitric acid compositions, and in particular to the hardening of catalyst on antimony metal, and heat-treating the resulting mix compositions containing antimony and tin for use in ture at 550° to 1100° C. in the presence of an oxygen organic Oxidation and dehydrogenation reactions, and is containing gas such as air. a continuation-in-part of application Ser. No. 174,688 Another preferred method of preparing the antimony filed Feb. 21, 1962, now abandoned. 5 oxide/tin oxide catalytic composition comprises hy Processes for the production of acrolein and metha drolysing with water cationic salts of the metals, such as crolein by the vapour phase catalytic oxidation of propyl the chlorides, and recovering and heating the resulting ene and isobutene and processes for the production of precipitate. To obtain complete hydrolysis it may be acrylonitrile and methacrylonitrile by the catalytic vapour necessary to add a volatile base such as ammonia. Either phase reactions of propylene or acrolein, or isobutene or 20 or both of the metal oxide components of the composi methacrolein, in the presence of a catalyst selected from tion may be prepared in this way. Particularly useful the group consisting of (i) a mixture of the oxides of catalytic compositions can be prepared by this method antimony and tin (ii) a compound containing antimony, from stannic chloride and antimony pentachloride by tin and oxygen are described in U.S. Patents 3,152,170; mixing them together in aqueous media and adding am 3,094,565, and 3,094.552. A particularly preferred catalyts 25 monia until the pH is greater than 5.0, recovering the for those reactions comprises antimony tetroxide in combi precipitate and heating it at a temperature between 550 nation or in admixture with stannic oxide. and 1100° C. In carrying out reactions of the above type on an When the tin and antimony compounds in the mixture industrial scale with pelleted catalysts particularly in a are present in the lower valency state, i.e., as divalent tin fluidised bed system it is essential that the pellets should 30 or trivalent antimony compounds, it is particularly pre be physically robust. If the granules are soft and easily ferred to subject the mixture to a preliminary heat-treat reduced to dusts and fines, this causes blockages and ment in an atmosphere comprising oxygen and an inert unequal flow of the gaseous reactants through the reactor gas such as nitrogen, carbon dioxide or steam, the tem tubes or beds. Rapid attrition is particularly noticeable perature being controlled so that no part of the catalyst with catalysts which have been subjected to a preheat treat during this preliminary heat-treatment exceeds a tem ment above 900 C, which renders them soft. perature of about 650° C.; in this way loss of the lower It has now been found that the catalytic properties of valent metallic compounds by volatilisation is avoided. Such catalysts are promoted by the incorporation of a A convenient way of doing this is to heat pellets of the compound additive of calcium or barium or a metal hav catalyst in a furnace, the temperature of which is raised ing an atomic number in the range 22 to 28 inclusive in 40 from about 300 to about 650° C., over a period of not amount up to 25% on a molar basis of the total mixture. less than about 8 hours, while passing a stream of air The metallic compound additives promoted are thus over the catalyst. After this preliminary heat-treatment, those of calcium, barium, tritanium, vanadium, chromium, the mixture is then subjected to a final heat-treatment in iron, manganese, cobalt or nickel, either singly or in air at a temperature in the range 550 to 1100° C. admixture. The use of oxides, sulphates, or compounds 45 The atomic ratio of tin or antimony in the catalytic forming oxides at the reaction temperatures employed, composition may vary within moderately wide limits, for e.g., nitrates are preferred. instance between 0.1:1 and 20:1, although compositions The catalytic composition itself may be regarded either containing proportions of tin to antimony outside this as a mixture of antimony tetroxide with stannic oxide or 50 range may be useful for some purposes. as a compound of antimony, tin and oxygen; under the By whichever method the oxides or hydrated oxides reaction conditions either or both forms may be present have been prepared the mechanical stability of the finished in the catalyst. The catalytic composition may be pre catalyst is enhanced by washing, preferably with Water pared from any of the oxides of antimony and tin, or before drying. from compounds of tin or antimony which on heating 55 The metal compound additive may be added in any in the presence of an oxygen-containing gas, such as air, suitable manner to the catalyst composition and at any are converted to the oxides provided the final composi time but preferably during the preparation of the catalyst, tion contains antimony tetroxide and stannic oxide. Oxides and before the final drying thereof. Preferahly the addi of antimony and tin, or substances yielding these oxides, tion is made by slurrying the filter cake, produced after which may be used in the manufacture of the catalytic 60 filtering and washing the catalyst mixture, with a solution composition include antimony trioxide, antimony tetroX or slurry of the metal compound additive and subsequent ide, antimony pentoxide or mixtures of such oxides; stannic ly drying, and if desired, pelleting the resultant mixture. oxide, stannous oxide, or mixtures of such oxides. Hy The addition of metal compound additives to the catalyst drated forms of these oxides may also be used, for instance composition in the form of slurries of insoluble salts, e.g., Such as are formed by the action of aqueous nitric acid 65 calcium sulphate, or in the form of gels, e.g., that of ti on antimony or tin metals or on mixtures of the metals. tanium oxide, is particularly useful. The catalyst may be prepared for instance by mixing to The proportions of promoter incorporated in the cat gether any of the oxides of antimony and tin, or sub alyst composition may vary up to about 25% on a molar stances yielding these oxides, and subjecting the mixture basis according to the catalytic properties of the catalyst to a heat-treatment in the presence of an oxygen-contain 70 desired. Generally, incorporation of about 2% to about ing gas such as air, for instance at a temperature between 10% on a molar basis of the promoter is sufficient. 550 and 1100° C. Where the initial components are Further it has been found that the incorporation of 3,326,819 3 4. metallic compound additives in accordance with the in the filter cake and the resulting mixture dried. The mix vention exhibits particular advantage in catalyst compo ture was sieved to give granules of less than 30 mesh sitions which are to be preheated to temperatures above B.S.S., pelleted and heated in air at 725 C., for 16 hours about 900 C. and then at 950-1,000 C. for 16 hours. In operation the catalyst may be employed in a fixed 5 The catalyst was placed in a reactor and maintained at bed in the form of granules or pellets or in a fluidised or the various temperatures indicated below whilst being con moving bed. tacted with a gaseous feed stream consisting of, by vol Reactions in which tin/antimony catalyst promoter ume, 10% propylene, 40% water vapour and 50% air. composition is of particular value include the oxidation As the basis for comparison the process of the above of propylene to acrolein and/or acrylic acid, the oxidation O examples was repeated using a tin/antimony catalyst pre of acrolein to acrylic acid, the oxidation of isobutene to pared as described above but without the addition of the methacroiein and/or methacrylic acid, the oxidation of metal compound additive as promoter. TABLE Temperature Yield of Yield of of final heat Attrition Reaction acrolein based acrolein based Example treatment, Additive Fate, tempera- on propylene on propylene o C. percent ture, C. fed (Efficiency)consumed 1-------------- 950 2%sulphate. molar calcium 3.2 486 37.6 68 2-------------- 1,000 --- 0------------ 4.9 484 36.8 72 8-------------- 950 2% molar ferric 3.3 488 37.0 68 nitrate. Comparison l,000 -------------------- 63 527 35.7 66 test. methacrolein to acrylic acid, the oxidative dehydrogena In the above table the “attrition rate percent' relates tion of butene to butadiene in the presence of molecular to the percentage weight of the original pellets, which as oxygen, the oxidative dehydrogenation of methylbutene fines will pass a 16 mesh B.S.S., after a crushing and to isoprene in the presence of molecular oxygen, the con 30 grinding test in which a 10 gm.