GB820925A - Improvements in or relating to the regeneration of molecular sieves in separating hydrocarbons - Google Patents

Abstract

In the separation of normal paraffins from hydrocarbon mixtures by adsorption at 200-400 DEG C. on a molecular sieve wherein the adsorbed hydrocarbons are desorbed by a desorbing agent at the same temperature as the adsorption is performed, the desorbing agent itself being adsorbed on the sieve and in turn desorbed by the normal paraffins in a subsequent adsorption step, the sieve is periodically regenerated by heating to 650-850 DEG F. under conditions effecting a reduction in the partial pressure of the p adsorbed material. The feed to be separated is preferably first dried and purified by passage through a 4 or 5 molecular sieve, preferably at a lower temperature than the separation step, or silica gel. Separation is then carried out using a 5 molecular sieve at 0.25-2 wt./wt./hr. and 0.5 atmosphere-100 p.s.i.g. The desorbing agent may be an olefine such as propylene or butylene, butanol or ethylene oxide. Reduction of the partial pressure of adsorbed material is effected by reducing the pressure, preferably below 100 mm. Hg, or by using a purge gas, such as nitrogen or methane, or a combination of these two methods. In either case the sieve may be heated by passing a heated inert gas through the sieve. Regeneration in the manner is preferably effected every 100-300 cycles.