Fractionators typical applications

Aliphatic C-5—C-6. Aliphatic feedstreams are typically composed of C-5 and C-6 paraffins, olefins, and diolefins, the main reactive components being piperylenes cis-[1574-41 -0] and /n j -l,3-pentadiene [2004-70-8f). Other main compounds iaclude substituted C-5 and C-6 olefins such as cyclopentene [142-29-OJ, 2-methyl-2-butene [513-35-9] and 2-methyl-2-pentene [625-27-4J. Isoprene and cyclopentadiene maybe present ia small to moderate quaatities (2—10%). Most steam cracking operatioas are desigaed to remove and purify isoprene from the C-5—C-6 fraction for applications ia mbbers and thermoplastic elastomers. Cyclopentadiene is typically dimerized to dicyclopentadiene (DCPD) and removed from C-5 olefin—diolefin feedstreams duriag fractionation (19). 

Sephadex. Other carbohydrate matrices such as Sephadex (based on dextran) have more uniform particle sizes. Their advantages over the celluloses include faster and more reproducible flow rates and they can be used directly without removal of fines . Sephadex, which can also be obtained in a variety of ion-exchange forms (see Table 15) consists of beads of a cross-linked dextran gel which swells in water and aqueous salt solutions. The smaller the bead size, the higher the resolution that is possible but the slower the flow rate. Typical applications of Sephadex gels are the fractionation of mixtures of polypeptides, proteins, nucleic acids, polysaccharides and for desalting solutions. 

As a typical application, the separation of an octylphenoxy-terminated PEO with respect to the terminal groups by LCCC is presented in Fig. 17.6. Similar to previous investigations on RP-18 stationary phases (Gorshkov et al., 1990 Pasch and Zammert, 1994), the critical eluent composition was achieved with methanol-water 86 14% by volume. Five well-separated peaks appeared in the chromatogram, which could be identified by MALDI-TOF mass spectrometry as being different functionality fractions. Accordingly, separation took place strictly with respect to the chemical structure of the end groups. 

Fixed-bed reactors Trickle-flow reactor (TFR) This is a tubular flow reactor with a concurrent down-flow of gas and liquid over a fixed-bed of catalyst (Figure 3.10). Liquid trickles down whereas the gas phase is continuous. This reactor is mainly used in catalytic applications. Typical application examples of this reactor type are the following HDS of heavy oil fractions and catalytic hydrogenation of aqueous nitrate solutions. 

Due to a cancellation of errors, the equation (without modification) is applicable for aqueous ethylene glycol concentrations to about 0.40 mole fraction (typically for system operation to 233 K). A comparison of results from Hammerschmidt s equation, as well as the prediction by the freezing point depression of water for methanol inhibition is summarized in Table 4.6. 

The GPC/DRI/FTIR instrument is complementary to the UV detector for compositional distribution. It runs at 135°C in TCB and can be used for EP analysis. Typical applications include ethylene content as a function of molecular weight, maleic anhydride content in maleated EP, or PCL content in caprolactone-g-EP copolymers. The FTIR detector is off-line so that 5-10 fractions of the eluant are collected on KBr plates and analyzed. This procedure gives calibration of IR absorption bands. This method is much more labor intensive than the other techniques and should be used with discretion. 

The individual steps of the method are shown in the flow chart of Figure 1. Hydrocarbons are extracted from ocean water and measured by IR spectroscopy. Then the sample is placed on a silica gel column and hydrocarbons are eluted as a fraction(s) which is examined by IR and UV spectrometry, gas chromatography, and mass spectrometry. Each of the principal steps is described in the following sections. Some aspects of this method and typical applications were briefly described by Brown etal. (6). 

Solution NMR is widely used in polymer processing for the qualitative and quantitative analyses of tacti-city, end-groups, degradation products, chain defects, and monomer sequence distribution.A typical application is in the characterization of monomer sequence distribution by quantitative NMR spec-troscopy. For example. Fig. 7 shows a typical NMR spectrum of ethylene-co-l-butene. From the relative peak areas, it is possible to determine the fractions of the two monomers, their reactivity ratios, the triad distribution, and the blockiness or randomness of the monomer distributions. All of these structure factors play an important role in the polymer s physical and mechanical properties. 

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