초록 ▼

Normal paraffins are separated from a hydrocarbon vapor feedstream having 10 to 25 carbon atoms per molecule in a constant pressure process employing a molecular sieve adsorbent and n-hexane for purging and for dilution of gas oil - containing feedstocks. A portion of the countercurrent, desorption

Normal paraffins are separated from a hydrocarbon vapor feedstream having 10 to 25 carbon atoms per molecule in a constant pressure process employing a molecular sieve adsorbent and n-hexane for purging and for dilution of gas oil - containing feedstocks. A portion of the countercurrent, desorption purge effluent is employed as a hexane - containing cocurrent purge stream, thereby significantly reducing the required amount of n-hexane purge recycle material, and the size of the equipment and the energy consumed in the processing of said recycle stream. A portion of said countercurrent purge effluent can also be used to provide a source of n-hexane diluent for the gas oil - containing feedstocks, as can the cocurrent purge effluent, resulting in further reduction in required equipment and energy costs, and increasing adsorption efficiency and adsorbent utilization.

대표청구항 ▼

In an isobaric process for separating normal paraffins from non-normal hydrocarbons in a feed stream containing between 10 and 40 mol percent normal paraffins having 10 to 25 carbon atoms and non-normal hydrocarbons by (1) the selective adsorption of normal paraffins by passage of said feed stream t

In an isobaric process for separating normal paraffins from non-normal hydrocarbons in a feed stream containing between 10 and 40 mol percent normal paraffins having 10 to 25 carbon atoms and non-normal hydrocarbons by (1) the selective adsorption of normal paraffins by passage of said feed stream through a molecular sieve adsorbent bed, (2) cocurrent purge with n-hexane to sweep out void space vapor containing a high concentration of non-normal hydrocarbons from the effluent end of the bed, (3) countercurrent purge with n-hexane to desorb normal paraffin adsorbate from the bed, (4) recovery of n-hexane from said separated normal paraffins and non-normal hydrocarbons, and (5) recycling of said n-hexane for purging of said bed, the improvement comprising diverting a portion of the desorption effluent from said countercurrent purge step as a source of said n-hexane used for cocurrent purge, the quantity of said countercurrent purge effluent diverted as cocurrent purge being that necessary to achieve a desired degree of separation of said normal paraffins and non-normal hydrocarbons and comprising from about 2.5 to about 5 bed volume voids, whereby the equipment size and energy consumption for the processing of said recycle n-hexane is reduced, without need to increase the adsorbent bed size to adsorb the additional normal paraffins introduced to the bed with the desorption effluent used as cocurrent purge gas.