Gasoline polymerization

The application of the design methods developed in the previous sections has been demonstrated on a CSTR, a distillation column, fluid catalytic cracking units and a gasoline polymerization plant (20). Here, we will discuss optimizing control of the fluid catalytic cracker. 

A RON value of 96 is claimed for the alkylate obtained through the Allqr-Clean process. AlkyClean has been presented as a very versatile option to retrofit liquid acid processes, having up to 20% lower inside-battery-limits cost than for a H2SO4 unit and comparable to that for a HF plant. The process is also shown as attractive to revamp gasoline polymerization units, offering a short time for payback (252). 

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. 

Polymerization. In the petroleum iadustry, polymerization is the process by which olefin gases are converted to higher molecular weight Hquid products which may be suitable for gasoline (polymer gasoline) or other Hquid fuels. 

This combination of monomers is unique in that the two are very different chemically, and in thek character in a polymer. Polybutadiene homopolymer has a low glass-transition temperature, remaining mbbery as low as —85° C, and is a very nonpolar substance with Htde resistance to hydrocarbon fluids such as oil or gasoline. Polyacrylonitrile, on the other hand, has a glass temperature of about 110°C, and is very polar and resistant to hydrocarbon fluids (see Acrylonitrile polymers). As a result, copolymerization of the two monomers at different ratios provides a wide choice of combinations of properties. In addition to providing the mbbery nature to the copolymer, butadiene also provides residual unsaturation, both in the main chain in the case of 1,4, or in a side chain in the case of 1,2 polymerization. This residual unsaturation is useful as a cure site for vulcanization by sulfur or by peroxides, but is also a weak point for chemical attack, such as oxidation, especially at elevated temperatures. As a result, all commercial NBR products contain small amounts ( 0.5-2.5%) of antioxidant to protect the polymer during its manufacture, storage, and use. 

A modem petroleum refinery is a complex system of chemical and physical operations. The cmde oil is first separated by distillahon into fractions such as gasoline, kerosene, and fuel oil. Some of the distillate fractions are converted to more valuable products by cracking, polymerization, or reforming. The products are treated to remove undesirable components, such as sulfur, and then blended to meet the final product specifications. A detailed analysis of the entire petroleum production process, including emissions and controls, is obviously well beyond the scope of this text. 

Polymerization - Polymerization is occasionally used to convert propene and butene to high octane gasoline blending components. The process is similar to alkylation in its feed and products, but is often used as a less expensive... 

Polymerization is a reaction in which several molecules of the same or similar material combine to form a larger molecule. We will only discuss the polymerization of C3, C4, and C5 olefins to products in the gasoline boiling range (C5 - Cl2). A typical reaction which occurs in polymerization is illustrated in Figure 24. 

To obtain light ends conversion, alkylation and polymerization are used to increase the relative amounts of liquid fuel products manufactured. Alkylation converts olefins, (propylene, butylenes, amylenes, etc.), into high octane gasoline by reacting them with isobutane. Polymerization involves reaction of propylene and/or butylenes to produce an unsamrated hydrocarbon mixture in the motor gasoline boiling range. 

The catalyst must also be selective to valuable products. Gasoline is desirable, so a lot must be produced, but it must be high octane gasoline. Cj s and C s are sometimes required for polymerization, alkylation and chemical production. Certain catalysts give high yields of these compounds, especially the imsaturated components. Gases, such as methane and hydrogen, are undesirable so the yield of these products must be suppressed. 

Most of the propylene polymerized by this process is used in motor gasoline ("Polymer Gasoline"). However, an appreciable portion of the C7, C, and C,2 olefins find use as feedstocks for production of Oxo alcohols. 

Chemical additives first entered the industry in the first decade of the centuiy. These additives sewed a number of uses. For example, they lessened the capacity of gasoline to vaporize out of the gas tank or to polymerize (i.e., produce gummy residues) in the engine. In the early 1920s, the most important application for these substances was to eliminate knocking. Tetraethylead (TEL) was the first major gasoline additive to be commercialized for this purpose. 

Through the 19.30s, Ipatieff led UOP in its effort to develop two catalytic processes for the production of high-octane fuel alkylation and polymerization— the first, a reaction of a hydrocarbon with an olefin (double-bonded compound) the second, the formation of long molecules from smaller ones. Both processes produce high-octane blending compounds that increase the quality of cracked gasoline. 

An alternative method for separating the hutenes is hy extracting isobutene (due to its higher reactivity) in cold sulfuric acid, which polymerizes it to di- and triisohutylene. The dimer and trimer of isobutene have high octane ratings and are added to the gasoline pool. 

The final step in the methanol-to-gasoline process can be carried out in an adiabatic, fixed-bed reactor using a zeolite catalyst. A product mixture similar to ordinary gasoline is obtained. As is typical of polymerizations, a pure reactant is converted to a complex mixture of products. 

Uses Used in the petroleum industry to make so-called alkylate for improved octane gasoline. Large quantities are polymerized to polypropylene for carpeting, upholstery, ropes, and other uses. Used in the chemical industry as a starting material for many large-volume chemicals such as acetone, acrylonitrile, and propylene oxide. 

The coverage on liquid fuels must include an account of the processes for synthesis of gasoline. The synthesis process is carried out by any one of the following (i) polymerization, (ii) Fischer-Tropsch method and (iii) Bergius process. The following description relates only to the first of these methods. 

Thermal polymerization, in which polymerization of cracked gases is implemented at specified temperature and pressure the product is a mixture of gasoline and gas oil. A subsequent fractionation process accomplishes separation between the two. 

Catalytic polymerization, which is implemented in presence of a catalyst such as phosphoric acid in this case, lower temperatures are used and the products are gasoline and unpolymerized gases. The unpolymerized portion is separated and recycled for polymerization. 

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