A process to reduce acidity of hydrocarbon mixtures (1) is described, that includes sending a hydrocarbon stream to a Microwave Treatment Unit (MTU), with a fixed stream or mud bed of microwave absorbent materials, pure or in mixtures, such as coke fines, spent catalysts that have already been used in FCC units or hydrotreatment (HDT) in a refinery, or even new catalysts which may be sulfided or not, under processing conditions.