(JP7308580-A)       A catalyst comprising silica and an acid phase contg. H2 SO4 and HB(SO4 )4 is claimed. The silica is impregnated with the acid phase and consists essentially of particles of mean dia. 0.1-30 m. The silica (before impregnation) has a total porous vol. of 0.1-0.6 cm3 /g and the acid phase comprises 0.4-68.8% of HB(HSO4 )4 and 31.2-99.6% of H2 SO4 . It contains neither SO3 nor H3 BO3.    Also claimed is the prepn. and use of the catalyst.    USE -   The catalyst is used in the alkylation of iso-paraffins (isobutane and/or isopentane) by at least one 3-6C olefin. The reaction requires a strongly acidic catalyst to suppress side reactions such as H abstraction from the olefin, polymerisation, cracking etc. The alkylate prod. is mainly used for high octane fuel compsns. for high compression internal combustion engines.    ADVANTAGE -    Catalysts contg. HB(HSO4 )4 as additive have been found to give improved performance compared with those contg. other cpds. such as H3 PO4 , B(OH)3 , SO3 etc. The cpd. HB(HSO4 )4 is easily obtainable by the reaction of 1 mole of B(OH)3 with 3 moles of SO3 and 1 mole of H2 SO4.    (US5489728-A)       A catalyst contg. silica and an acid phase comprising sulphuric acid and HB(HSO4 )4 , the silica having been impregnated with the acid phase and the catalyst being such that it consists essentially of particles with an average dia. of 0.1-150 m, such that the silica, prior to its impregnation with the acid phase, has a total porous vol. of 0.1-0.6 cm3 /g, the acid phase contg. (in % by wt.) 0.4-68.8% of HB(HSO4 )4 and 31.2-99.6% of H2 SO4, and the acid phase not contg. sulphuric anhydride or boric acid.    (EP645184-B1)      Catalyst containing silica and an acid phase consisting of sulphuric acid and the compound HB(HSO4)4, the silica having been impregnated with said acid phase and said catalyst being such that it is composed substantially of particles with an average diameter of between 0.1 and 30 micron, such that the silica, prior to its impregnation with said acid phase, has a total porous volume of between 0.1 and 6 cm(3) per gram, in that said acid phase contains (in% by weight) between 0.4% and 68.8% of the compound HB(HSO4)4 and between 31.2% and 99.6% of the compound H2SO4, said acid phase being characterised by the fact that it does not contain sulphuric anhydride or boric acid.