NOVELTY - A method for separating gaseous reaction products (A) from the steam dealkylation of at least 6C and/or at least 7C hydrocarbon (HC) fractions, in a plant for generating HC's from HC-containing starting materials, involves liquid-gas extraction with a liquid consisting of or containing ionic liquid(s) (I), the liquid being loaded with extracted components and subsequently regenerated by release of these components.    USE - The steam dealkylation process is useful for producing aromatic hydrocarbons (specifically toluene, xylene or especially benzene, which is a starting material for plastics and an antiknock additive for gasoline) as main valuable products.    ADVANTAGE - A simple, inexpensive method is provided for separation of the individual components of (A). The components can be recovered in sufficiently high purity for particular application, so that the whole of (A) can be utilized economically. Typically hydrogen is reused in the dealkylation or recovered as a product of the plant; carbon monoxide is reused in the dealkylation or shift reactions; and methane is used as fuel for heating the dealkylation reactor. The ionic liquid extractants (I) are 'designer solvents', which have properties (e.g. density and melting point) controllable by choice of the contained ions and have no measurable vapor pressure (thus being easy to regenerate without loss and in high purity by temperature increase and/or pressure reduction).    DETAILED DESCRIPTION - A method is claimed for separating gaseous reaction products (A) (mainly hydrogen, carbon monoxide, carbon dioxide and methane) from the steam dealkylation of at least 6C and/or at least 7C hydrocarbon (HC) fractions in a plant for generating HC's from HC-containing starting materials, the dealkylation products comprising aromatic HC's, alkanes and (A). The method involves liquid-gas extraction with a liquid consisting of or containing ionic liquid(s) (I), the liquid being loaded with extracted components and subsequently regenerated by release of these components.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of one form of the process for separating gaseous reaction products from steam dealkylation of hydrocarbons.    At least 6C or at least 7C hydrocarbon fraction (1)    Heat exchanger (2)    Steam dealkylation reactor (3)    Product stream (4)    3-Phase separator (5)    Gaseous reaction products (6)    Hydrocarbons (7)    Water (8)    Benzene, as desired product (9)    Residual hydrocarbons (10)    Charging of ionic liquid with carbon dioxide (11)    Regeneration of ionic liquid (12)    Carbon dioxide outlet (13)    Regenerated fluid recycling line (14)    Gaseous product outlet (15)