A way of preparing separation layers by the pyrolysis of fluorinated polyimide obtained from 2,4,6-trimethyl-m-phenylenediamine (2,4,6-TMmPDA) and 2,2-bis(3′,4′-dicarboxyphenyl)hexafluoropropane (6FDA) applied onto a diatomite carrier is described. Thermogravimetry, elemental analysis, low-temperature nitrogen adsorption, high-resolution electron microscopy, and gas chromatography are used to study changes in the texture and chromatographic characteristics of these layers. It is found that changes in the structure and the effectivity of separation characteristic of the layers depend on the temperature of pyrolysis, which ranges from 250 to 1100°C. It is established that a layer of separation is formed at 250–350°C, and the order of elution of hydrocarbons is similar to their chromatographic behavior on such stationary phases as OV-101. Layers of amorphous carbon formed on the surfaces of individual particles on a diatomite surface at 500–700°C. These layers ensure highly stable and selective separation of permanent gases and hydrocarbons when they are present together.