GB364586A - Improvements in catalysts for carrying out destructive hydrogenation and cracking processes - Google Patents

Abstract

The cracking or destructive hydrogenation of hydrocarbons such as tars, mineral oils or their distillation, extraction or cracking products or residues is effected in the presence of catalysts obtained by thermally decomposing the carbonyl compounds of chromium, molybdenum or tungsten alone or in admixture with each other or with the carbonyl compounds of iron, nickel or cobalt. The decomposition may be effected in the presence of carrier substances such as solid inorganic compounds containing oxygen and especially hydroxides, carbonates, borates, silicates, phosphates, and similar salts having a basic reaction of the metals of the first to the third groups of the periodic system which may be employed alone as carriers or precipitated on further carrier substances such as pumice, artificial zeolites, or silica gel and then used alone or in admixture with each other or with other substances. The vaporized carbonyl may be passed, with exclusion of oxygen, through a tube containing the carrier substance heated to slightly above the decomposition point of the carbonyl, the finely divided metal being precipitated on the carriers. Alternatively the carbonyls are dissolved in an inert solvent such as hexane or benzene and the carrier is impregnated with the solution. The activity of the metal catalyst is increased by the carrier which may also have catalytic activity. The activity and working life of the catalysts may be increased by converting them wholly or partly into oxides or sulphides by treatment with oxygen, or hydrogen sulphide at elevated temperatures, e.g. over 200 DEG C. The catalysts may also be prepared by decomposing the carbonyls within the hydrocarbons during the treatment, the carbonyls being first added in gas or vapour form, and carrier substances on which the metals deposit may also be present. The amount of carbonyl used may be 1-10 per cent of that of the hydrocarbons. In an example, a catalyst suitable for cracking paraffin wax at 520 DEG C. is obtained by heating pumice coated with magnesium oxide and impregnated with a solution of molybdenum hexacarbonyl in pure benzene, a current of nitrogen being passed through until the benzene has evaporated. In another example, aluminium hydroxide gel soaked in a hexane solution of molybdenum hexacarbonyl and nickel tetracarbonyl is heated in hydrogen to 60 DEG C. and then to 450 DEG C. in a current of hydrogen sulphide, the catalyst being finally treated with hydrogen at 450 DEG C.