Anhydrous halides of pentavalent antimony are prepared by contacting SbF5- nCln.xH2O where n is 0-4 with SOX2, COX2, or CSX2, where X is F, Cl, or Br, e.g. SOF2, SOCl2, CSCl2, COCl2 or COBr2. The COCl2 may be formed in situ by using Cl2 and CO in a molar ratio of at least 1.2, to give an excess of free Cl2. The reaction may be effected at 75-150 DEG C. under 5-100 kg/cm.2 pressure, using 0.8-5 moles of the halogen compound per mole of hydrate water. The reaction may be used in the regeneration of antimonic acid catalysts of formula RSbF6- nCln, where n is 0-4 and R is H or a hydrocarbon radical, preferably saturated cyclic 4-10 C, e.g. methyl cyclopentane. The spent catalyst is first stripped of any diluent, e.g. anhydrous HF or SO2, e.g. by heating at 50-90 DEG C., then hydrolysed at below 100 DEG C., e.g. 25-50 DEG C., with 5-50 moles, per mole of Sb compound, of water or an aqueous acid, e.g. HCl. The aqueous and organic phases are separated; the aqueous phase may be washed with CH2Cl2, and the organic phase may be washed with water, wash water being added to the aqueous phase. The aqueous phase may be passed through an ion-exchanger, and water is then evaporated, e.g. by stripping with N2 or the off-gases from the reaction, preferably in the presence of HCl (said to form SbF3Cl2) at 75-150 DEG C. The hydrated Sb halide residue is then reacted with the halogen compound, and the product treated with excess HF, e.g. at 15-150 DEG C. at superatmospheric pressure under N2, to reform the acid catalyst. The acid may initially be obtained by reacting HF with SbF5 or SbCl5 to give HSbF6(sB Cl) which may be reacted with hydrocarbon to give RSbF6. It is used as catalyst in the isomerization and alkylation of hydrocarbons, and becomes in-activated owing to the formation of organic complexes with the acid.ALSO:Spent catalysts of formula RSbF6- nCln, where n is 0-4 and R is hydrocarbon, preferably saturated cyclic 4-10C, e.g. methylcyclopentane, are regenerated by hydrolysing the spent catalyst, separating the organic and aqueous phases, evaporating water from the aqueous phase to obtain SbF5-nCln.xH2O, contacting this with SOX2, COX2, or CSX2, where X is F, Cl, or Br (e.g. SOF2, SOCl2, CSCl2, COCl2, COBr2) to give an anhydrous Sb halide, and reacting with excess HF to form the acid catalyst (where R is H) which converts to the R form on reaction with hydrocarbon. The spent catalyst may first be stripped of any diluent, e.g. anhydrous HF or SO2, e.g. by heating at 50-90 DEG C. Hydrolysis may be effected at below 100 DEG C., e.g. 25-50 DEG C., with 5-50 moles, per mole of residue, of water or an aqueous acid, e.g. HCl. The separated aqueous and organic phases may be washed with CH2Cl2 and water resp., wash water being added to the aqueous phase. The aqueous phase may be passed through an ion-exchanger, and the water may then be evaporated by stripping with N2 or the off gases from the next stage, preferably in the presence of HCl at 75-150 DEG C. The reaction with the halogen compound may be effected at 75-150 DEG C. under 5-100 kg./cm.2 pressure, using 0.8-5 moles of the compound per mole of hydrate water. The COCl2 may be formed in situ by using Cl2 and CO in a molar ratio of at least 1.2, to give an excess of free Cl2. The reaction with HF may be effected at 15-150 DEG C. at superatmospheric pressure under N2. The catalyst may initially be obtained by reacting HF with SbF5 or SbCl5 to give HSbF6 (sBCl) and then reacting with hydrocarbon. It is used in the isomerization and alkylation of hydrocarbons, and becomes inactivated owing to the formation of organic complexes.
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