<PICT:0731075/IV (b)/1> The aromaticity of a naphthene-containing naphtha feed is improved by providing a fluidized bed of powdered hydroforming catalyst in a conversion zone, simultaneously feeding thereto the naphtha feed in a preheated vapour phase condition and a free hydrogen-containing gas, causing the hydrocarbon vapours and hydrogen-containing gas to flow upwardly through the catalyst bed at a rate sufficient to maintain the catalyst in a fluidized state, restricting back-mixing of the upper portion of the fluidized catalyst bed with the lower portion thereof so as to permit of the existence of an appreciable temperature differential between the upper and lower portions of the catalyst bed, maintaining in the conversion zone hydroforming conditions of temperature, pressure and contact time of reactants while maintaining the upper portion of the bed at a temperature appreciably exceeding that of the lower portion and recovering from the conversion zone a hydroformed product. The back-mixing of the catalyst may be effected by a grid or packing. The appreciable temperature differential permits isomerization to occur in the lower portion of the catalyst bed at temperatures below average hydroforming temperature while dehydrogenation occurs in the upper portion at higher than average hydroforming temperature without excessive gas formation. Thus, a feed comprising 47.5 per cent paraffins and 44 per cent naphthenes, B.R. 227-333 DEG F. is fed via a furnace 4 to a reactor 1 containing fluidized catalyst. A hydrogen-containing gas is also fed to the reactor via line 6, a furnace F, a coil 10 serving to heat the upper portion of the catalyst bed, a second furnace F1 and lines 13 and 14. A grid 12 prevents back-mixing in the reactor. The hydroformed products pass through a cyclone separator 15 and cooler 19 to a separator 21 from which liquid products are removed via line 23 and gas containing hydrogen via line 6 for recycling or line 22 for purging. Suitable hydroforming conditions include upper bed temperatures of 875-1000 DEG F. and lower bed temperatures of 850-950 DEG F., providing temperature differentials of 25 DEG to 50 DEG F. or higher, pressures of 100-500 p.s.i. and superficial velocities of 0.3 to 1 foot per second. As catalysts there may be used the oxides or sulphides of metals of Groups IV to VIII of the Periodic Table, e.g. molybdenum or chromium oxide or nickel or tungsten sulphide; these may be supported on, e.g., alumina, especially heat-stabilized alumina containing silica, zirconia or chromia or combined in a spinel-type form such as zinc aluminate. Regeneration of the catalyst in the above process is effected by withdrawing catalyst through line 24, treating the catalyst in a stripper 25 by means of a stripping agent such as steam and then regenerating in the regenerator 28 by incomplete combustion with air introduced via lines 271 and 30. Fluidized conditions are maintained and the regenerated catalyst is then returned in suspension via lines 36 and 38 to the hydroforming zone.ALSO:<PICT:0731075/III/1> The aromaticity of a naphthene-containing naphtha feed is improved by providing a fluidized bed of powdered hydroforming catalyst in a conversion zone, simultaneously feeding thereto the naphtha feed in a preheated vapour phase condition and a free hydrogen-containing gas, causing the hydrocarbon vapours and hydrogen-containing gas to flow upwardly through the catalyst bed at a rate sufficient to maintain the catalyst in a fluidized state, restricting back-mixing of the upper portion of the fluidized catalyst bed with the lower portion thereof so as to permit of the existence of an appreciable temperature differential between the upper and lower portions of the catalyst bed, maintaining in the conversion zone hydroforming conditions of temperature, pressure and contact time of reactants while maintaining the upper portion of the bed at a temperature appreciably exceeding that of the lower portion and recovering from the conversion zone a hydroformed product. The back-mixing of the catalyst may be effected by a grid or packing. The appreciable temperature differential permits isomerization to occur in the lower portion of the catalyst bed at temperatures below average hydroforming temperature while dehydrogenation occurs in the upper portion at higher than average hydroforming temperature without excessive gas formation. Thus, a feed comprising 47.5 per cent paraffins and 44 per cent naphthenes, B.R. 227-333 DEG F. is fed via a furnace 4 to a reactor 1 containing fluidized catalyst. A hydrogen-containing gas is also fed to the reactor via line 6, a furnace F, a coil 10 serving to heat the upper portion of the catalyst bed, a second furnace F1 and lines 13 and 14. A grid 12 prevents back-mixing in the reactor. The hydroformed products pass through a cyclone separator 15 and cooler 19 to a separator 21 from which liquid products are removed via line 23 and gas containing hydrogen via line 6 for recycling or line 22 for purging. Suitable hydroforming conditions include upper bed temperatures of 875-1000 DEG F. and lower bed temperatures of 850-950 DEG F., providing temperature differentials of 25 DEG to 50 DEG F. or higher, pressures of 100-500 p.s.i. and superficial velocities of 0.3 to 1 ft. per sec. As catalysts there may be used the oxides or sulphides of metals of Groups IV to VIII of the Periodic Table, e.g. molybdenum or chromium oxide or nickel or tungsten sulphide; these may be supported on e.g. alumina, especially heat-stabilized alumina containing silica, zirconia or chromia or combined in a spinel-type form such as zinc aluminate. Regeneration of the catalyst in the above process is effected by withdrawing catalyst through line 24, treating the catalyst in a stripper 25 by means of a stripping agent such as steam and then regenerating in the regenerator 28 by incomplete combustion with air introduced via lines 271 and 30. Fluidized conditions are maintained and the regenerated catalyst is then returned in suspension via lines 36 and 38 to the hydroforming zone.