A process for preparing at least one target product P by partial oxidation and/or ammoxidation of propylene, by a) subjecting prepurified propane, in a first reaction step in the presence of and/or with exclusion of molecular oxygen, to at least one dehydrogenation from the group comprising homogeneous dehydrogenation, heterogeneously catalyzed dehydrogenation, homogeneous oxydehydrogenation and heterogeneously catalyzed oxydehydrogenation to obtain a gas mixture 1 comprising unconverted propane and formed propylene, and b) optionally removing a portion or the entirety of the constituents other than propane and propylene present in the entirety or in a portion of gas mixture 1 therefrom and/or converting them to other compounds to obtain a gas mixture 1' comprising propane and propylene, and, in at least one further reaction step, c) subjecting gas mixture 1 or gas mixture 1' or a mixture of formed gas mixture 1' and remaining gas mixture 1, as a constituent of a gas mixture 2, to a heterogeneously catalyzed gas phase partial oxidation and/or partial gas phase ammoxidation of propylene present in gas mixture 1 and/or gas mixture 1' to obtain a gas mixture 3 comprising at least one target product P, d) removing target product from gas mixture 3 in at least one removal step and, of the remaining residual gas, recycling at least propane into the first reaction step, wherein the prepurified propane is obtained from crude propane which comprises ≥ 90% by weight of propane, ≤ 99% by weight of propane and propylene, ≥ 100 ppm by weight of C 2 hydrocarbons and ≥ 100 ppm by weight of C 4 hydrocarbons, with the proviso that the crude propane is conducted into a rectification column and the purified propane is removed above the feed point with the proviso that the content of C 2 hydrocarbons based on propane present in % by weight in the purified propane is not less than 80% and not more than 110% by weight of the corresponding content in the crude propane, and the content of C 4 hydrocarbons based on propane present in % by weight in the purified propane is at most 50% by weight of the corresponding content in the crude propane. a) subjecting prepurified propane, in a first reaction step in the presence of and/or with exclusion of molecular oxygen, to at least one dehydrogenation from the group comprising homogeneous dehydrogenation, heterogeneously catalyzed dehydrogenation, homogeneous oxydehydrogenation and heterogeneously catalyzed oxydehydrogenation to obtain a gas mixture 1 comprising unconverted propane and formed propylene, and b) optionally removing a portion or the entirety of the constituents other than propane and propylene present in the entirety or in a portion of gas mixture 1 therefrom and/or converting them to other compounds to obtain a gas mixture 1' comprising propane and propylene, and, in at least one further reaction step, c) subjecting gas mixture 1 or gas mixture 1' or a mixture of formed gas mixture 1' and remaining gas mixture 1, as a constituent of a gas mixture 2, to a heterogeneously catalyzed gas phase partial oxidation and/or partial gas phase ammoxidation of propylene present in gas mixture 1 and/or gas mixture 1' to obtain a gas mixture 3 comprising at least one target product P, d) removing target product from gas mixture 3 in at least one removal step and, of the remaining residual gas, recycling at least propane into the first reaction step, wherein the prepurified propane is obtained from crude propane which comprises ≥ 90% by weight of propane, ≤ 99% by weight of propane and propylene, ≥ 100 ppm by weight of C 2 hydrocarbons and ≥ 100 ppm by weight of C 4 hydrocarbons, with the proviso that the crude propane is conducted into a rectification column and the purified propane is removed above the feed point with the proviso that the content of C 2 hydrocarbons based on propane present in % by weight in the purified propane is not less than 80% and not more than 110% by weight of the corresponding content in the crude propane, and the content of C 4 hydrocarbons based on propane present in % by weight in the purified propane is at most 50% by weight of the corresponding content in the crude propane.