A soluble HF/TaF.sub.5 catalyst is prepared in the absence of an organic solvent according to the steps of:(1) contacting tantalum metal with substantially anhydrous liquid HF to form soluble TaF.sub.5, the amount of HF being sufficient to maintain the TaF.sub.5 thus formed as a homogeneous substantially liquid phase catalyst at a temperature ranging from about 0.degree. to 150.degree. C.,(2) contacting the catalyst thus formed with a hydrocarbon feedstock in a hydrocarbon conversion process to form an acid catalyst phase and a hydrocarbon product phase,(3) stripping HF from said catalyst phase with a gas containing molecular hydrogen thereby reducing the mole ratio of HF to TaF.sub.5, and(4) passing the stripped acid catalyst phase from step (3) to the hydrocarbon conversion process, thereby maintaining the mole ratio of HF to TaF.sub.5 within said process at a level between that obtained in step (1) and step (3).