Processes MX Sorbex

As documented in Chapter 5, zeolites are very powerful adsorbents used to separate many products from industrial process steams. In many cases, adsorption is the only separation tool when other conventional separation techniques such as distillation, extraction, membranes, crystallization and absorption are not applicable. For example, adsorption is the only process that can separate a mixture of C10-C14 olefins from a mixture of C10-C14 hydrocarbons. It has also been found that in certain processes, adsorption has many technological and economical advantages over conventional processes. This was seen, for example, when the separation of m-xylene from other Cg-aromatics by the HF-BF3 extraction process was replaced by adsorption using the UOP MX Sorbex process. Although zeolite separations have many advantages, there are some disadvantages such as complexity in the separation chemistry and the need to recover and recycle desorbents. 

Until late 1990s, purified m-xylene was produced predominantly by the HF/BF3 process developed by Mitsubishi Gas Chemical Co. The separation is based on the complex formation between m-xylene and solvent HF/BF3. However, concerns about the process operation, environment, metallurgy and safety render the process commercially unattractive due to its use of HF/BF3. These concerns led to many developments in the adsorptive separation process for m-xylene separation [3-8]. The UOP MX Sorbex process, developed by UOP and commercialized in 1998, already accounts for more than 70% of the world s m-xylene capacity. A 95% m-xylene recovery with 99.5% purity can be achieved by the MX Sorbex process. 

The Parex and MX Sorbex processes are quite similar with regard to the adsorbent section mechanics so all of the discussion about the functional zones in the section for the Parex process applies to the MX Sorbex process also. The MX Sorbex process produces m-xylene at 99.5-99.8% purity at a recovery in excess of 95%. The major differences between the two technologies are the choice of adsorbent and desorbent... 

Zeolite/Desorbent Combination A light desorbent, that is a desorbent that boils lighter than the mixed xylene feed, is used in the MX Sorbex process. This means that the energy demand of the distillation columns per unit feed for the MX Sorbex... 

The Parex, Toray Aromax and Axens Eluxyl processes are the three adsorptive liquid technologies for the separation and purification of p-xylene practiced on a large scale today. The MX Sorbex process is the only liquid adsorptive process for the separation and purification of m-xylene practiced on an industrial scale. We now consider a few other liquid adsorptive applications using Sorbex technology for aromatics separation that have commercial promise but have not found wide application. 

The Parex and MX-Sorbex processes are both members of UOP s family of Sorbex processes. The MX-Sorbex process for the separation of high-purity meta-xylene was introduced in 1998. Five MX-Sorbex units were commercialized between 1998 and 2001. The market for meta-xylene is expected to grow to 800,000 metric tons per year by 2009 (23). The Parex process was introduced in 1971 for the separation of para-xylene, and 71 units were commercialized by 2001. 

Application The MX Sorbex process recovers mefa-xylene (m-xylene) from mixed xylenes. UOP s innovative Sorbex technology uses adsorptive separation for highly efficient and selective recovery, at high purity, of molecular species that cannot be separated by conventional fractionation. 

Economics The MX Sorbex process has been developed to meet increased demand for purified isophthalic acid (PIA). The growth in demand for PIA is linked to the copolymer requirement for PET bottle resin applications, a market that continues to rapidly expand. The process has become the new industry standard due to its superior environmental safety and lower cost materials of construction. Estimated ISBL costs based on unit production of 50,000 mtpy of m-xylene (US Gulf Coast site in 2003). 

Liquid Phase Separation. UOP have pioneered several small-scale processes to fractionate mixtures of liquids. The Parex process was introduced in 1971 and by 2001 71 units were running conunercially. The MX-Sorbex process was introduced in 1998 and so far 5 units have been commerciahzed. Very recently, in 2001, UOP introduced a new Sorbex process, MaxEne, to increase the ethlene yield from Naphtha Crackers. Examples of these are listed in Table 30. 

MX Sorbex A process for extracting m-xylene from mixed xylene streams, using a variation of the Sorbex process. Five units were operating in 2005. 

MX Sorbex A version of the UOP Sorbex process for removing m-xylene from its isomers. First licensed in 1995. 

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