Udex process

UOP s Parex Process UOP Sulfolane process UOP Udex Process Upilex UpilexR... 

Gycloaliphatics and Aromatics. Cychc compounds (cyclohexane and benzene) are also important sources of petrochemical products (Fig. 14). Aromatics are ia high concentration ia the product streams from a catalytic reformer. When aromatics are needed for petrochemical manufacture, they are extracted from the reformer s product usiag solvents such as glycols (eg, the Udex process) and sulfolane. 

Sulfolane A process for removing aromatic hydrocarbons from petroleum fractions by liquid-liquid extraction using sulfolane (tetramethylene sulfone tetrahydrothiophene-1,1-dioxide) at approximately 190°C. Developed by Shell Development Company in 1959 and first commercialized in 1962 now licensed through UOP. It replaced the Udex process. Sulfolane is used for another purpose in the Sulfinol process. 

The Platforming-Udex process for catalytic reforming of naphtha is also used for toluene. The feedstock should be rich in seven carbon naphthenes such as dimethylcyclopentanes, methylcyclohexane, and ethylcyclopentane... 

The most common form of extraction involves two immiscible liquids and a solute that is soluble in both and will be recovered. Liquid-liquid extraction requires (1) extraction, (2) medium recovery, and (3) raffinate desolventizing. The Udex process is a cost-effective liquid-liquid fractionation process for the separation of aromatics from aliphatics. The extraction solvent (diethylene or triethylene glycol) is recovered by steam distillation, and the raffinate and extract streams are desol-ventized by water extraction. 

The first economic version of aromatics extraction, available industrially, was the Udex process, developed by Daw and licensed by UOP since 195Z Due to competition from new techniques, it has been practically abandoned since 1965, or its facilities altered and their production capacities increased. 

Solvent Extraction. Diethylene glycol extraction of benzene, toluene, and xylene from Platformates is one commercial method for the recovery of these materials. The process has been named the Udex process and has been described by Read (70). 

FIGURE 7.8-9 Udex process flowsheet for aromatics extraction. From Ref. 22 with perarission.)... 

Diethylene glycol (DEG) was the first solvent employed in the Udex process. The structural formula of DEG, as well as those of the other presently used glycols, are shown in Table I. Diethylene glycol is ethylene glycol with an extra ethylene oxide group. Triethylene and tetraethylene glycols merely have additional ethylene oxide groups. 

Figure 8. Schematic flow diagram of Udex process...

Removal of Aromatic Compounds. Because of the demand for high-purity aromatic compounds for petrochemical feedstocks, several processes have been developed for BTX (benzene, toluene, and xylenes) recovery from distillate streams. In these processes, aromatic compounds are separated from nonaromatic compounds by liquid—liquid extraction using polar solvents. The three major processes in use are the UOP—Dow UDEX process (di- or triethylene glycol solvent), the UOP sulfolane process (tetrahydrothiophene 1,1-dioxide), and the Union Carbide TETRA process (tetraethylene glycol). 

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