Prodn. of isobutane from 4C hydrocarbon mixt - comprising distillation, adsorption-desorption and isomerisation steps

摘要

Process for producing isoparaffins from a mix. of 4C hydrocarbons comprises: 1) deisobutanisation by distillation of mixture of 4C mix and effluent from step 3) below with part condensation of distillate for recycle as reflux liquid; 2) adsorption of the other part of the distillate by upward flow through a bed of molecular sieve whilst in vapour phase to give essentially pure isobutane product; 3) desorption, alternating with step 2), by lowering pressure in the adsorber and passing through a portion of the isobutane product from step 2), with desorption effluent being passed to the column in step 1); 4) isomerisation of residue from step 1) in the vapour phase; and 5) separation of isomerisation product into recycled vapour phase and liquid crude effluent. ADVANTAGE - High purity isobutane (suitable for MTBE manufacture) is produced with minimised energy use. The process allows use of high-activity halogenated catalysts without effecting molecular sieves used in the adsorptive separation.