Process for preparing alkenes by dehydrogenation of alkanes having the following steps: a) providing a liquid feedstock mixture at a pressure between 0.1 ∗ 10 5 Pa and 6.0 ∗ 10 5 Pa, wherein the feedstock mixture comprises alkanes having two to five carbon atoms and alkenes having two to five carbon atoms, and wherein the part by mass of alkenes in the feedstock mixture based on the total mass thereof is 1% by weight to 10% by weight; b) evaporating the feedstock mixture by increasing the temperature; c) adding hydrogen to the evaporated feedstock mixture such that the molar ratio of hydrogen to the alkenes present in the feedstock mixture is between 0.8: 1 and 1.2: 1; d1) contacting the evaporated, hydrogen-containing feedstock mixture with a solid catalyst at a temperature between 450°C and 760°C and a pressure of 0.1 ∗ 10 5 Pa to 6.0 ∗ 10 5 Pa to obtain a product mixture, wherein the part by mass of the alkenes having two to five carbon atoms in the product mixture based on the total mass thereof is 30% by weight to 70% by weight; d2) contacting the evaporated, hydrogen-containing feedstock mixture with a first solid catalyst and a pressure between 0.1 ∗ 10 5 Pa and 6 ∗ 10 5 Pa to obtain an intermediate, wherein the part by mass of the alkenes in the intermediate based on the total mass thereof is 0% by weight to 1% by weight and wherein the temperature of the evaporated, hydrogen-containing feedstock mixture and/or of the intermediate is increased; and e) contacting the intermediate with a second solid catalyst at a temperature between 450°C and 760°C and a pressure of 0.1 ∗ 10 5 Pa to 6.0 ∗ 10 5 Pa to obtain a product mixture, wherein the part by mass of the alkenes having two to five carbon atoms in the product mixture based on the total mass thereof is 30% by weight to 70% by weight. a) providing a liquid feedstock mixture at a pressure between 0.1 ∗ 10 5 Pa and 6.0 ∗ 10 5 Pa, wherein the feedstock mixture comprises alkanes having two to five carbon atoms and alkenes having two to five carbon atoms, and wherein the part by mass of alkenes in the feedstock mixture based on the total mass thereof is 1% by weight to 10% by weight; b) evaporating the feedstock mixture by increasing the temperature; c) adding hydrogen to the evaporated feedstock mixture such that the molar ratio of hydrogen to the alkenes present in the feedstock mixture is between 0.8: 1 and 1.2: 1; d1) contacting the evaporated, hydrogen-containing feedstock mixture with a solid catalyst at a temperature between 450°C and 760°C and a pressure of 0.1 ∗ 10 5 Pa to 6.0 ∗ 10 5 Pa to obtain a product mixture, wherein the part by mass of the alkenes having two to five carbon atoms in the product mixture based on the total mass thereof is 30% by weight to 70% by weight; d2) contacting the evaporated, hydrogen-containing feedstock mixture with a first solid catalyst and a pressure between 0.1 ∗ 10 5 Pa and 6 ∗ 10 5 Pa to obtain an intermediate, wherein the part by mass of the alkenes in the intermediate based on the total mass thereof is 0% by weight to 1% by weight and wherein the temperature of the evaporated, hydrogen-containing feedstock mixture and/or of the intermediate is increased; and e) contacting the intermediate with a second solid catalyst at a temperature between 450°C and 760°C and a pressure of 0.1 ∗ 10 5 Pa to 6.0 ∗ 10 5 Pa to obtain a product mixture, wherein the part by mass of the alkenes having two to five carbon atoms in the product mixture based on the total mass thereof is 30% by weight to 70% by weight.