GB280712A - Improvements in the regeneration of catalysts - Google Patents

Abstract

280,712. Fairweather, H. G. C., (Selden Co.). Nov. 26, 1926. Formaldehyde ; benzaldehyde ; acetic acid; maleic acid ; benzoic acid ; phthalic anhydride; naphthalic anhydride ; benzoquinone; a-naphthaquinone ; anthraquinone phenanthraquinone ; acenaphthaquinone. - Catalysts which have deteriorated through use in the catalytic oxidation of organic compounds are regenerated by treatment with one or more of the following reagents, viz., a halogen, a non-metallic halogen compound, a non-metallic acid or its anhydride, ozone, or hydrogen peroxide, the regenerating agent being such that it is volatile below about 550‹ C., and does not decompose and leave a residue which, when treated with oxygen at an elevated temperature, is not volatile; the regenerating agents may be used in admixture with steam. Generally, the catalyst is treated simultaneously or subsequently with oxygen-containing gases at an elevated temperature, but this treatment may be omitted when the regenerating agent is such that it decomposes with the production of oxygen. The catalyst may be treated in situ and the treatment may be performed at any desired pressure. In one example, a contact mass comprising silver vanadate, potassium sulphate, and kieselguhr is used at 340-420‹ C. in the production of phthalic anhydride from a mixture of naphthalene and air, and is regenerated by mixing sulphur dioxide with the naphthalene-air mixture. Alternatively the spent contact mass may be treated first with air and then with a mixture of sulphur dioxide and air, with or without steam at 350-500‹ C., or it may be treated in turn with air and sulphur trioxide at a temperature below 200‹ C. and then with air alone at 350-500‹ C. A further alternative consists in substituting for the sulphur dioxide, wholly or in part, nitric acid vapours or gases containing nitrogen oxides, which may be used at any temperature up to 500‹ C. and with or without air or steam. In another example, a contact mass comprising iron vanadate, iron molybdates, and pumice, after use in the oxidation of acenaphthene 'to naphthalic anhydride, is treated first with chlorine at ordinary temperature and then with air, with or without steam, at 200-500‹ C. Alternatively, the regeneration may be effected with a mixture of chlorine and air, or ethylene chloride and air, at 300-500‹ C., or the reagents of the preceding example may be employed. In a further example, a contact mass comprising nickel molybdate, calcium chloride, and pumice, after use in the production of formaldehyde from methyl alcohol, is treated first with a current of air containing nitrosyl chloride and then with air alone. The treatment mav be effected at ordinary temperature or, if the contact mass is contaminated with carbon, at 300-500‹ C. Alternatively, the mass may be regenerated by treating it first with phosgene at 200‹ C. and then with air at 400- 500‹ C. This treatment with phosgene and air is used, according to another example, in the regeneration of a contact mass, prepared by treating granules of ferrosilicon with an aqueous solution of ammonium vanadate, evaporating the mixture, and heating it to 400-450‹ C., the mass having become spent in the oxidation of naphthalene to phthalic anhydride. A further example describes the regeneration of a contact mass comprising iron vanadate, cobalt molybdate, potassium sulphate, and pumice after use in the oxidation of anthracene to anthraquinone. The mass is heated in air or oxygen at 300-450‹ C. and is then cooled and treated at ordinary temperature with an aqueous solution of hydrogen peroxide, whereafter the water is evaporated. In another example, a contact mass comprising silver vanadate and aluminium, after use in the oxidation of benzene to maleic acid or of methyl alcohol to formaldehyde, is treated with ozonized air at a temperature gradually @ising to 300‹ C. In the final example, a contact mass for use in the oxidation of naphthalene to phthalic anhydride is prepared by the interaction of a sodiumsilicate solution containing cellite and solutions of potassium vanadate and potassium aluminate, the zeolitic product being treated with sulphuric acid and than calcined in air at 300-400‹ C. The mass is regenerated after use by treatment with a mixture of sulphur dioxide and/or chlorine and air at 200-500‹ C. The regeneration of other polysilicate catalysts and of catalysts comprising the oxides or other compounds of the elements of the fifth, sixth, and seventh groups of the periodic system is referred to, and, as further instances of reactions in which the ' catalysts may have become spent, reference is made 'to the oxidation of naphthalene to a-naphthaquinone or maleic acid, of toluene or phenol to maleic acid, of benzene or phenol to benzoquinone, of toluene and its substitution products and derivatives to the corresponding aldehydes and acids, of acenaphthene to acenaphthaquinone. of phenanthrene to phenanthraquinone, and of ethyl alcohol to acetic acid. Mention is made also, as additional regenerating agents, of hydrogen halides, ammonium halides, sulphur chloride, sulphuryl chloride, thionyl chloride, chlorinated aromatic hydrocarbons, acyl halides, and ethylene bromide.