A process for the gas phase isomerisation of an alkane to an isomerised product comprises: (a) continuously introducing, under conditions effective to isomerise the alkane to the isomerised product, the alkane and a desorbent into a simulated moving bed of a mixture of solids where the mixture of solids contains a catalyst effective to isomerise the alkane and an adsorbent effective to selectively adsorb the alkane relative to the isomerised product; (b) isomerising at least a portion of the alkane to at least one isomerised product in a zone of the simulated moving bed with concurrent separation of the isomerised products formed using the adsorbent; (c) desorbing the alkane from the adsorbent using the desorbent in a subsequent zone of the simulated moving bed; and (d) removing and collecting the isomerised products from the simulated moving bed.    The alkane is n-butane and the isomerised product is 2-methylpropane. Alternatively, the alkane is n-pentane and the isomerised product is 2-methylbutane or 2,2-dimethyl propane. Alternatively, the alkane has 6-8 carbon atoms with no more than one methyl branch and the isomerised product has at least two methyl branches.    USE -   The process is used to convert normal 4 and 5C alkanes and normal and mono-methyl branched 6C alkanes into more valuable branched alkanes. Multi-methyl branched 6C alkanes have a higher octane number and are used as gasoline blending components to boost the octane number of the gasoline. Mono-methyl branched 4 and 5C alkanes may also be used as intermediates, after dehydrogenation, for such oxygenate products as methyl tertiary butyl ether, ethyl tertiary butyl ether and tertiary amyl methyl ether. The process can also produce isomerised 7 and 8C products which can be used as octane number boosters in gasoline blending instead of conventional benzene and other aromatics.    ADVANTAGE -   The process makes use of both simulated moving bed technology and reactive chromatography to perform isomerisation of hydrocarbons containing 4-8C atoms. Reactive chromatography allows for concurrent isomerisation and separation of the unconsumed reactants from the products, thereby extending product yields beyond thermodynamic equilibrium limitations.