Patent ID: 9145343
Filing Date: 2015-09-29
Classification: B01D,C07C

Abstract:
1. A process for separating xylenes by simulated counter-current (SCC) using two adsorbers, the process containing a bed wherein the total number of beds Nt is at most 22, and having a line for introducing feed (F), a line for introducing eluent (D), a line for withdrawing extract (E) and a line for withdrawing raffinate (R) and being divided into 4 chromatographic zones defined as follows: zone 1: para-xylene desorption zone, included between the injection of desorbant D and the removal of extract E; zone 2: isomers of para-xylene desorption zone, included between the removal of the extract E and the injection of the feed to be fractionated F; zone 3: para-xylene adsorption zone, included between the injection of the feed and the withdrawal of the raffinate R; zone 4: zone located between the withdrawal of the raffinate and the injection of the desorbant; the two adsorbers functioning in series wherein the last bed of the first adsorber is connected to the first bed of the second adsorber via a line containing a recirculation pump, and the last bed of the second adsorber is connected to the first bed of the first adsorber via a line containing a recirculation pump which is distinct from the preceding pump, and said process operating under the following operating conditions: a temperature of 100° C. to 250° C.; a pressure in the range between the bubble pressure of the xylenes at the process temperature and 30×10 a ratio of desorbent to feed flow rates of 0.7 to 2.5; a recycle ratio of 2.5 to 12, wherein the recycle ratio is defined as the ratio between the mean flow rate in the various beds of the adsorber to the flow rate of injection of feed into this adsorber; a cycle time for the adsorbers in the range 14 to 30 minutes; a mean linear velocity with respect to the empty reactor in the range 0.7 cm/s to 1.4 cm/s; a water content in the liquid phase maintained at an amount in the range 70 to 140 ppm by weight.