Hydrocarbon processes polymerization

Hydrocarbon emissions, polymerization-process, 20 231 Hydrocarbon film, 24 750 Hydrocarbon injectants, in oil recovery, 23 617... 

Because of the (chain-length dependent) restricted solubility of polymers in hydrocarbons, solution polymerization requires higher temperatures and / or higher pressures. Technologically, solution polymerization processes are similar to the high-pressure LDPE process, see chapter 3, and will not be discussed here. 

Polymerization of Styrene Solutions of Volatile Hydrocarbons. Addition of Hydrocarbon before Polymerization. Bulk Polymerization. Expandable polystyrene was prepared inadvertently in 1945 in an attempt to bulk copolymerize 10% isobutylene with styrene. The product formed a low density foam when heated (96). An early method (1950) for rendering polystyrene expandable by petroleum ether was to dissolve 6 parts of petroleum ether in a 40% solution of polystyrene in benzoyl peroxide-catalyzed styrene and to hold the mass for 28 days at 32 °C. (124). In a recent version of this process, the monomer (chlorostyrene) and blowing agent (trichlorofluoromethane) in a poly (vinyl fluoride) bag were irradiated with y-rays (105). 

Fig. 18.25. Alkylation (indirect)—UOP LLC. Process uses solid catalyst major processing steps include polymerization (1), hydrogenation reactor (2), hydrogen recovery (3), and product stabilization (4). (Source Hydrocarbon Processing, 2004 Refining Process Handbook. CD-ROM. September 2004 copyright 2004 by Gulf Publishing Co., all rights reserved.)...

Another important reaction involving certain unsaturated hydrocarbons is polymerization, a process in which many small molecules are joined together to form a large molecule. Polymerization will be discussed in Section 22.5. 

For suspension polymerization the initial system is obtained by dispersion of an aqueous monomer solution in an organic liquid by mechanical stirring in the presence of stabilizers [402]. The dispersion medium may be represented by aromatic and aliphatic saturated hydrocarbons. The polymerization is initiated by water-soluble initiators, UV or y-radiation. The process occurs in droplets of an aqueous monomer solution (diameters 0.1-5.0mm) that act as microreactors [419,420]. 

Kissin also explains that the silica-supported catalysts are not suitable for a high-temperature (80-90°C) hydrocarbon slurry polymerization process, as the zirconium catalyst component is not chemically fixed to the silica surface and the zirconium catalyst component is extracted from the silica due to its solubility in the hydrocarbon medium resulting in poor polymer particle morphology. However, the catalyst may be retained in the silica pores during a gas-phase polymerization process and, therefore, may provide good particle morphology necessary for a gas-phase process. Consequently, this unique cocatalyst activator may be able to provide a... 

Fig. 15.18. Polymerization (Dimersol)—Institute Franpaisdu P6trole. Includes a reactor (1) of several in series, catalyst removal using a caustic wash (2), water wash (3), and distillation (4). (Hydrocarbon Processing, 69, no. 11, p. 134, Nov. 1990 copyright 1990 by Gulf Publishing Co. and used by permission of the copyright owner.)...

In the solution process, polymerization takes place in solution, in a liquid hydrocarbon such as cyclohexane or iso-octane, in which both the monomer and polymer can dissolve. About 0.2-0.6 wt% of a Ziegler catalyst is normally suspended in the solvent, by stirring efficiently in a suitable reactor. The operating temperature must be above the melting point of the polymer but lower than the decomposition point of the catalyst Typical temperatures are in the range 125-175°C. 

Before we examine the polymerization process itself, it is essential to understand the behavior of the emulsifier molecules. This class of substances is characterized by molecules which possess a polar or ionic group or head and a hydrocarbon chain or tail. The latter is often in the 10-20 carbon atom size range. Dodecyl sulfate ions, from sodium dodecyl sulfate, are typical ionic emulsifiers. These molecules have the following properties which are pertinent to the present discussion ... 

The Fischer-Tropsch process can be considered as a one-carbon polymerization reaction of a monomer derived from CO. The polymerization affords a distribution of polymer molecular weights that foUows the Anderson-Shulz-Flory model. The distribution is described by a linear relationship between the logarithm of product yield vs carbon number. The objective of much of the development work on the FT synthesis has been to circumvent the theoretical distribution so as to increase the yields of gasoline range hydrocarbons. 

The polymerization of monomers to form hydrocarbon resins is typically carried out by either the direct addition of catalyst to a hydrocarbon fraction or by the addition of feed to a solvent—catalyst slurry or solution. Most commercial manufacturers use a continuous polymerization process as opposed to a batch process. Reactor temperatures are typically in the range of 0—120°C. 

The feedstocks used ia the production of petroleum resias are obtaiaed mainly from the low pressure vapor-phase cracking (steam cracking) and subsequent fractionation of petroleum distillates ranging from light naphthas to gas oil fractions, which typically boil ia the 20—450°C range (16). Obtaiaed from this process are feedstreams composed of atiphatic, aromatic, and cycloatiphatic olefins and diolefins, which are subsequently polymerized to yield resias of various compositioas and physical properties. Typically, feedstocks are divided iato atiphatic, cycloatiphatic, and aromatic streams. Table 2 illustrates the predominant olefinic hydrocarbons obtained from steam cracking processes for petroleum resia synthesis (18). 

Cycloaliphatic Diene CPD—DCPD. Cycloatiphatic diene-based hydrocarbon resias are typically produced from the thermal or catalytic polymerization of cyclopeatadieae (CPD) and dicyclopentadiene (DCPD). Upon controlled heating, CPD may be dimerized to DCPD or cracked back to the monomer. The heat of cracking for DCPD is 24.6 kJ / mol (5.88 kcal/mol). In steam cracking processes, CPD is removed from C-5 and... 

Other nonpolymeric radical-initiated processes include oxidation, autoxidation of hydrocarbons, chlorination, bromination, and other additions to double bonds. The same types of initiators are generally used for initiating polymerization and nonpolymerization reactions. Radical reactions are extensively discussed in the chemical Hterature (3—15). 

From the time that isoprene was isolated from the pyrolysis products of natural mbber (1), scientific researchers have been attempting to reverse the process. In 1879, Bouchardat prepared a synthetic mbbery product by treating isoprene with hydrochloric acid (2). It was not until 1954—1955 that methods were found to prepare a high i i -polyisoprene which dupHcates the stmcture of natural mbber. In one method (3,4) a Ziegler-type catalyst of tri alkyl aluminum and titanium tetrachloride was used to polymerize isoprene in an air-free, moisture-free hydrocarbon solvent to an all i7j -l,4-polyisoprene. A polyisoprene with 90% 1,4-units was synthesized with lithium catalysts as early as 1949 (5). 

Polymerization in Solution or Slurry. Many hydrocarbon solvents dissolve PE at elevated temperatures of 120—150°C. Polymerization reactions in solution requite, as theit last step, the stripping of solvent. A variety of catalysts can be used in these processes. 

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