A process for producing hydrocarbons, especially C8 or larger alkenes, from lactones, hydroxy-carboxylic acids, alkene-carboxylic acids, alcohols, or mixtures thereof, or an aqueous solution of lactones, hydroxy-carboxylic acids, alkene-carboxylic acids, alcohols, or mixtures thereof is described. The process includes reacting the starting materials with a first acid catalyst to yield a first product mixture. The first product mixture is then reacted with a second acid catalyst (which can be the same or different from the first acid catalyst) to yield a second product mixture comprising hydrocarbons, for example alkenes having a chain length of C8+. The process is suitable for producing hydrocarbons that can be used in or as liquid transportation fuels.