Octane improvement

Propjiene [115-07-17, CH2CH=CH2, is perhaps the oldest petrochemical feedstock and is one of the principal light olefins (1) (see Feedstocks). It is used widely as an alkylation (qv) or polymer—ga soline feedstock for octane improvement (see Gasoline and other motor fuels). In addition, large quantities of propylene are used ia plastics as polypropylene, and ia chemicals, eg, acrylonitrile (qv), propylene oxide (qv), 2-propanol, and cumene (qv) (see Olefin POLYMERS,polypropylene Propyl ALCOHOLS). Propylene is produced primarily as a by-product of petroleum (qv) refining and of ethylene (qv) production by steam pyrolysis. 

Di- and Triisobutylcncs. Diisobutylene [18923-87-0] and tnisobutylenes are prepared by heating the sulfuric acid extract of isobutylene from a separation process to about 90°C. A 90% yield containing 80% dimers and 20% trimers results. Use centers on the dimer, CgH, a mixture of 2,4,4-trimethylpentene-1 and -2. Most of the dimer-trimer mixture is added to the gasoline pool as an octane improver. The balance is used for alkylation of phenols to yield octylphenol, which in turn is ethoxylated or condensed with formaldehyde. The water-soluble ethoxylated phenols are used as surface-active agents in textiles, paints, caulks, and sealants (see Alkylphenols). 

SiHcone residue introduced to gasoline with toluene plugged catalysts on vehicles (83). Also a manganese-based octane improver known as MMT has been shown to clog catalyst surfaces (84). 

Mixed xylenes are used as an octane improver in gasoline and for commercial solvents, particularly in industrial cleaning operations. By far, most of the commercial activity is with the individual isomers. Para-xylene, the most important, is principally used in the manufacture of terephthalic acid and dimethyl terephthalate en route to polyester plastics and fibers (Dacron, films such as Mylar, and fabricated products such as PET plastic bottles). Ortho-xylene is used to make phthalic anhydride, which in turn is used to make polyester, alkyd resins, and PVC plasticizers. Meta-xylene is used to a limited extent to make isophthahc acid, a monomer used in making thermally stable polyimide, polyester, and alkyd resins. 

Before an in-depth discussion of mass transfer models and coefficients we need to be explicitly clear that all mass transfer models are approximations that allow us to solve the partial differential equations (pde) describing an adsorption problem. There are a great many sources that derive and present the partial differential equations that describe adsorption of gases appropriate for column separations. The Design Manual For Octane Improvement, Book I [7] was among the earlier works to show them. The forms as presented by Ruthven [2] are shown here owing to the consistent and compact nomenclature that he has employed. There are a wider array of forms to choose from in the literature including [6, 7]... 

The carbonylation-homologation reaction may also be carried out on a mixture of alcohols and their formates. For instance, at a very high conversion of the reagents, methanol-methyl formate and i-butaiol -i-butyl formate produce a mixture of oxygenates particularly rich in acetates that are useful as octane improvers for gasoline (Fig. 3). 

Finally, the product slate (e.g. olefin production, petrochemical feedstock production), or the product quality (e.g. gasoline octane improvement) may dictate a reduction in rare earth usage. 

Additive A chemical substance added to a product to impart or improve certain properties. Typical fuel additives include antioxidants, cetane improvers, corrosion inhibitors, demulsifiers, detergents, dyes, metal deactivators, octane improvers, and wax crystal modifiers. 

To produce the maximum yield of finished gasoline in a hydrocracker-reformer combination, the hydrocracker should be operated to give maximum liquid yields, followed by a modem low pressure catalytic reformer to give the desired octane improvement (6). More severe hydrocracker operation produces higher octane naphtha but leads to an increase in the production of butanes with reduced yields of finished... 

For instance, methyl tert-butyl ether (MTBE) used worldwide as an octane improver in gasoline is produced at a still growing global capacity of approx. 8 million mt/yr using sulfonated resins as catalysts (ref. 1). 

The desire to improve the octane rating of fuels after the refining process without the use of lead has intensified a search for other "antiknock compounds. For example, compounds of Mn (5) and Ce (9) have been explored for this purpose. Methylcyclopentadienyl manganese tricarbonyl, in particular, is already being marketed for octane improvement. At a recommended level of 0.125 g Mn/gal, 200-500 g of Mn can be expected to pass the exhaust system within 50,000 miles. The main criteria in accepting such fuel additives are their compatibility with catalytic systems, and, of course, health-safety considerations. 

Our study was undertaken specifically to investigate the processing of a typical raffinate to produce either high yields of LPG or isobutane as well as to determine the octane improvement in the C5+ fraction due to hydroisomerization. A 0.7 wt % Pd-15 wt % Ni-SMM catalyst was used for all the experimentation. 

Looking at what happens within each carbon number group, one finds that for 40 S/A, the main contributor to octane enhancement in the C5 s is increased olefinicity. While the olefinicity also increases with 525 S/A, nearly half the C5 octane increase with that additive comes from a higher iso/normal paraffin ratio. The olefinicity enhancement is of a lesser degree in the C6 s and essentially nil in the C7 s. Nevertheless, higher iso/normal ratios contribute to octane improvement in both carbon number fractions. 

Evaluation of the octane-improving characteristics of methanol ded with several gasoline base stocks. 

High yields of LFG or Isobutane and octane Improvement of the C5" fraction can be simultaneously obtained by hydrocracking raffinate over a palladium-Impregnated, nickel-substituted synthetic mlca-montmorlllonlte catalyst (0.7 wt % Pd-15 wt % Nl-SMM). A critical sulfur level of about 100 to 200 ppm In the feed Is essential to combine the features of desired product... 

S.R. Newman, K.L. Dille, R.Y. Heisler and M.F. Fontaine, Tertiary Butyl Acetate - An Octane Improver for Leaded Gasoline, SAE Technical Paper 127U (1959). 

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