Isoprene purification

Isoprene can form ftve-membered hydrocarbon rings (8). A ftve-membered, sulfur-containing ring is an intermediate in an isoprene purification reaction ... 

Figure 5.18 Scheme of isoprene purification from acetylene hydrocarbons using a tubular prereactor. 1 - flow reactor of hydrogenation 2 - tubular turbulent prereactor 3- convergent-divergent turbulisers and 4 - connection pipes. Flows I - liquid monomer, and II - hydrogen... 

Table 5.9 Comparative analysis of technological processes of isoprene purification from acetylene hydrocarbons...

Table 3 provides typical specifications for isoprene that are suitable for Al—Ti polymerization (89). Traditional purification techniques including superfractionation and extractive distillation are used to provide an isoprene that is practically free of catalyst poisons. Acetylenes and 1,3-cyclopentadiene are the most difficult to remove, and distillation can be supplemented with chemical removal or partial hydrogenation. Generally speaking distillation is the preferred approach. Purity is not the main consideration because high quaUty polymer can be produced from monomer with relatively high levels of olefins and / -pentane. On the other hand, there must be less than 1 ppm of 1,3-cyclopentadiene. 

Monomers for manufacture of butyl mbber are 2-methylpropene [115-11-7] (isobutylene) and 2-methyl-l.3-butadiene [78-79-5] (isoprene) (see Olefins). Polybutenes are copolymers of isobutylene and / -butenes from mixed-C olefin-containing streams. For the production of high mol wt butyl mbber, isobutylene must be of >99.5 wt % purity, and isoprene of >98 wt % purity is used. Water and oxygenated organic compounds iaterfere with the cationic polymerization mechanism, and are minimized by feed purification systems. 

Isoprene (99 + %, Aldrich) and styrene (99%, Aldrich) were purified by initial stirring and degassing over freshly crushed Cal on a high vacuum line followed by distillation onto dibutyl-magnesium (Alpha Inorganics). Final purification involved distillation from this solution directly into calibrated ampoules and sealing with a flame. Benzene (Fisher, Certified ACS) was stored over cone. 

The reversibility of the diene-S02 cycloaddition makes it useful in the purification of reactive dienes. 2-Methyl-1,3-butadiene (isoprene) is purified commercially in this manner prior to being polymerized to rubber (Section 13-4) ... 

Isoprene (melting point -146°C, boiling point 34°C, density 0.6810) may be produced by the dehydrogenation of iso-pentane in the same plant used for the production of butadiene. However, the presence of 1,3-pentadiene (for which there is very little market) requires a purification step. One method produces isoprene from propylene. Thus, dimerization of propylene to 2-methyl-1-pentene is followed by isomerization of the 2-methyl-1-pentene to 2-methyl-2-pentene, which upon pyrolysis gives isoprene and methane. 

The checkers consistently obtained a slightly higher melting point (uncor.) in the range 64.4-65.4°. The purified cyclic sulfone serves as an ideal intermediate for the preparation of extremely pure isoprene, since the latter can be regenerated nearly quantitatively at 135-140°. Other sulfones that can be prepared by this method and that are uscfid in the purification of dienes are those of butadiene, m.p. 65.5°, and 2,3-dimethyl-butadiene, m.p. 135°. The sulfone of piperylene is a liquid. ... 

Purification of Individual Molecular Species. The chemical process industries use large amounts of hydrocarbons, which can be individually recovered and purified from petroleum refinery fractions. Examples would include ethane, propene, butadiene, isoprene, benzene, toluene, and xylenes. Sometimes distillation must be supplemented with liquid-liquid extraction, as well as extractive and azeotropic distillation, to purify these materials. The technology of recovering individual chemical species will be dealt with in other parts of this encyclopedia. 

HMG-CoA reductase. Some are analogs of the isoprene precursor while others are NADP(H) analogs. Analogs such as mevinolin have been extremely useful in evaluating the role of the enzyme and in manipulating the concentration of the enzyme in vivo and finally in stabilizing HMG-CoA reductase during purification (for example, see ref. 32). Several effective competitive inhibitors and their structural similarities are shown in Fig. 5. 

Materials. Cyclohexane, benzene, tetrahydrofiiran, ethylene oxide, styrene, isoprene and 1,3-butadiene were purified as described previously (27-30). Protected hydroxyl-functionalized initiators (see Scheme 2) (FMC, Lithium Div.) were used without further purification after double titration analyses (31). All chemicals for deprotection were used as received. 

Peroxides, removal from isoprene, 29,59 removal from isopropyl ether, 22,3 removal from o-tetrabne, 20, 95 Pexphthauc acid, mono-, 20, 70 Petroleum ether, 23,102, 104 Phenacyl chloride, 24, 25, 26 Phenanthrene, 28, 19 purification of, 28, 19 Phenanthrene-9-ai.dehvde, 28, S3 Phenanthrene, 9-bromo-, 28,19 9-Phenanthrenecarboniteile, 28, 7, 34... 

Wellburn et al. (1967) have described the isolation and purification of a mixture of ci s-frans-polyprenols from the leaves of the horse chestnut tree. Results of studies involving mass, NMR, and infrared spectroscopy and various chemical reactions showed that each of the prenols contains three trans internal isoprene residues and a cis OH-terminal isoprene residue. They differ from each other only in the number of cis internal isoprene residues. The names castaprenol-11, -12, and -13 were given to these compounds. 

A wide variety of products can be produced by fermentation. In some cases the microorganism itself is the product, for example, in the manufacturing of active dry yeast (ADY). Well-known pharmaceutical fermentation products are insulin and penicillin G. Fermentation processes are also used to produce various commodity bioproducts like organic and amino acids, polysaccharides, lipids, chemical compounds like isoprene (Whited et al., 2010), 1,3-propanediol (Nakamura and Whited, 2003), RNA, DNA, enzymes, and other proteins. The large variety of commodity bioproducts produced by fermentation requires an equally large variety of different methods to separate and purify them. Compared to fermentation processes, where usually one unit, the fermenter vessel, is used, several different steps and unit operations are necessary to achieve purification and formulation of bioproducts. 

Light D, Dennis M (1989) Purification of a prenyl transferase that elongates cis isoprene rubber from latex of Hevea brasiliensis. J Biol Chem 269 9278-9283... 

Furfural is a solvent that is widely used to extract raw lubricating feed stock to give a refined grade of lubricating oil. The solvency of furfural allows separation of undesirable aromatic and olefinic components from the desirable paraffinic and naphthenic fractions. A countercurrent extraction column gives the furfural extract which contains the undesirable fractions. A distillation step recovers the furfural for reuse in the process [4]. Furfural is used as an extractive distillation solvent in the purification of butadiene and isoprene. The presence of furfural in the process alters the relative volatility of the hydrocarbons enough so that a distillation separation is possible [5]. 

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