4. Catalysts for the cracking and conversion of hydrocarbons as follows: a. Single metal (platinum group) on alumina type or on zeolite, specially designed for catalytic reforming process; b. Mixed metal species (platinum in combination with other noble metals) on alumina type or on zeolite, specially designed for catalytic reforming process; c. Cobalt and nickel catalysts doped with molybdenum on alumina type or on zeolite, specially designed for catalytic desulphurisation process; d. Palladium, nickel, chromium and tungsten catalysts on alumina type or on zeolite, specially designed for catalytic hydrocracking process.