(57c) Production of Metaxylene within the Aromatic Complex

Although the metaxylene (MX) market is much smaller than the paraxylene one, there is however an interest in the production of pure metaxylene within the aromatic complex.

Different options for MX production within the C8-aromatics loop were developed and analyzed. More particularly, two interesting options can be further detailed :

- The first option is the adsorption based ELUXYL-MX^TM metaxylene production process, new process available at Axens in the ParamaX portfolio. This process relies on both a high performance adsorbent-desorbent system and the industrially proven ELUXYL^TM simulated moving bed (SMB) technology for PX world-scale capacities. When coproduction of pure PX and pure MX is wanted, an excellent synergy can be found putting the two SMB processes in series, the ELUXYL^TM raffinate is sent to the ELUXYL-MX^TM SMB unit dedicated to the production of MX with high purity (99.5+%) and high recovery.

- The second option relies on the ELUXYL^TM Twin Raffinate technology [1], a modified version of the ELUXYL^TM PX production process. In ELUXYL^TM Twin Raffinate process, in addition to the conventional inlets and outlets (desorbent and feed injections, extract and raffinate withdrawals) of the simulated moving bed, a second raffinate is used allowing the recovery of a pure MX/OX mixture. This raffinate 2 is sent to an MX/OX splitter, which allows to get an MX enriched stream at the column head and an OX concentrated stream at the bottom. Then, either the head or the bottom stream may be sent to a crystallizer for production of MX or OX respectively. An interesting point of this process scheme is the flexibility offered for either producing MX or OX.

ELUXYL^TM Twin Raffinate and ELUXYL-MX^TM technologies can also be associated.

We propose to detail how the ELUXYL-MX^TM was developed in terms of adsorbent intrinsic performances and process design and how benefits can be taken from particular arrangements involving ELUXYL^TM Twin Raffinate technology for pure PX and MX coproduction.

[1] L. Wolff, Ph. Leflaive, "ELUXYL^TM Twin Raffinate Technology", AIChE National Meeting 2004