Isomerization reforming

Synthesis and catalytic properties of tungsten carbide for isomerization, reforming and hydrogenation... 

The increase of 1 unit of the RON corresponds to about 900.000 US per year for a 300.000 tpa hydroisomerization unit (1). In Figure 7.1, several major refinery processes to improve RON are shown these include isomerization, reforming, addition of FCC-Naphtha, alkylation, addition of oxygenates or polygas or butanes. The effect of these options with respect to the new specifications is different for each particular process. Keeping in mind the Californian ban on MTBE and also the fact... 

Source of feedstock Solvent extract Solvent extract and isomerate Reformate... 

The preceding information indicates the paths to follow in order to obtain stocks of high octane number by refining. The orientation must be towards streams rich in aromatics (reformate) and in isoparaffins (isomerization, alkylation). The olefins present essentially in cracked gasolines can be used only with moderation, considering their low MONs, even if their RONs are attractive. 

Typical feedstock composition, yields and characteristics of effluents fron reforming and isomerization processes. j... 

As a complementary process to reforming, isomerization converts normal paraffins to iso-paraffins, either to prepare streams for other conversions nCi —> /C4 destined for alkylation or to increase the motor and research octane numbers of iight components in the gasoiine pooi, i.e., the C5 or Cs-Ce fractions from primary distillation of the crude, or light gasoline from conversion processes, having low octane numbers. 

Figure 10.2 shows the locations of reforming and isomerization units in refinery configurations. 

We cite isomerization of Cs-Ce paraffinic cuts, aliphatic alkylation making isoparaffinic gasoline from C3-C5 olefins and isobutane, and etherification of C4-C5 olefins with the C1-C2 alcohols. This type of refinery can need more hydrogen than is available from naphtha reforming. Flexibility is greatly improved over the simple conventional refinery. Nonetheless some products are not eliminated, for example, the heavy fuel of marginal quality, and the conversion product qualities may not be adequate, even after severe treatment, to meet certain specifications such as the gasoline octane number, diesel cetane number, and allowable levels of certain components. 

Xylenes. The main appHcation of xylene isomers, primarily p- and 0-xylenes, is in the manufacture of plasticizers and polyester fibers and resins. Demands for xylene isomers and other aromatics such as benzene have steadily been increasing over the last two decades. The major source of xylenes is the catalytic reforming of naphtha and the pyrolysis of naphtha and gas oils. A significant amount of toluene and Cg aromatics, which have lower petrochemical value, is also produced by these processes. More valuable p- or 0-xylene isomers can be manufactured from these low value aromatics in a process complex consisting of transalkylation, eg, the Tatoray process and Mobil s toluene disproportionation (M lDP) and selective toluene disproportionation (MSTDP) processes isomerization, eg, the UOP Isomar process (88) and Mobil s high temperature isomerization (MHTI), low pressure isomerization (MLPI), and vapor-phase isomerization (MVPI) processes (89) and xylene isomer separation, eg, the UOP Parex process (90). 

Powerforming is one tecnique used for aromatics chemical production. Powerforming uses a platinum catalyst to reform virgin naphthas. The principal reaction is the conversion of naphthenes in virgin naphthas to aromatics e.g., isomerization and dehydrocyclization reactions also occur in catalytic reforming. 

In order to produce more paraxylene than is available in catalytic reformate, a xylenes-isomerization plant is sometimes included in the processing scheme. The isomerization step uses the effluent (filtrate) from the paraxylene crystallization step as feed. The filtrate contains about 7-9 percent of paraxylene. The isomerization unit brings the concentration back to its equilibrium value of about 20 percent. 

A dramatic discovery in this area was made in 1996 when a dicopper-dioxygen adduct was found to have two isomeric forms which featured either a side-on bridging unit Cu(/r ), ) -02)-Cu) " or a cyclic (Cu(/r-0)2Cu) " core depending on whether it was crystallized from CH2CI2 or thf, respectively. The two forms could be readily interconverted by reversible 0-0 bond cleavage and reformation, the 0-0 distance being 141 pm and 229 pm in the two isomers.The... 

Catalytic processes frequently require more than a single chemical function, and these bifunctional or polyfunctional materials innst be prepared in away to assure effective communication among the various constitnents. For example, naphtha reforming requires both an acidic function for isomerization and alkylation and a hydrogenation function for aromati-zation and saturation. The acidic function is often a promoted porous metal oxide (e.g., alumina) with a noble metal (e.g., platinum) deposited on its surface to provide the hydrogenation sites. To avoid separation problems, it is not unusual to attach homogeneous catalysts and even enzymes to solid surfaces for use in flow reactors. Although this technique works well in some environmental catalytic systems, such attachment sometimes modifies the catalytic specifici-... 

These various fractions are processed further into additional products. These value-added operations generally involve chemical transformations often using catalysts. They include cracking, hydrogenation, reforming, isomerization, and polymerization. The main output from these processes is fuels and petrochemicals. 

Catalytic conversion processes include naphtha catalytic reforming, catalytic cracking, hydrocracking, hydrodealkylation, isomerization, alkylation, and polymerization. In these processes, one or more catalyst is used. A common factor among these processes is that most of the reactions are initiated hy an acid-type catalyst that promotes carhonium ion formation. 

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