Octane number products

In its work, the Development Co. has been impressed by the flexibility of the process. As no functional process limitations such as maximum carbon or restrictive high temperatures in regeneration exist in the Fluid system, units can be designed for any octane number product or any type of feed. Moreover, the merits of improved catalysts can be exploited to maximum advantage. 

The additive used In the commercial test Is being used In nearly all of Exxon s alkylation units. No operating problems have been encountered and It generally has been found to reduce acid consumption by 15 to 20 percent and to generate slightly higher octane number product. The cost of the additive Is small relative to the acid savings alone and It Is available for license. 

In commercial practice a reformer is operated to produce a constant octane number product. As the catalyst deactivates, the temperature of the system may be increased to compensate for the lower activity. In this way the octane number of the product can be maintained at the desired level. Illustrative data for alumina-supported platinum, platinum-rhenium, and platinum-iridium catalysts in this type of operation are given in Figure 5.4 (7). 

Figure 5.4 Data on the reforming of a 99-17fC boiling range naphtha showing the temperature required to produce 100 octane number product as a function of time on stream for alumina-supported platinum, platinum-rhenium, and platinum-iridium catalysts at 14.6 atm pressure (2,7).

As shown in Figure 5.4, the temperature required to maintain 100 research clear octane number product varies with the catalyst and is also a function of time on stream (the higher the catalytic activity, the lower the temperature required to produce the desired octane number reformate). 

The space velocity required to produce a given octane number product is a clear measure of catalytic activity (the higher the space velocity that can be used to obtain the desired octane number, the higher the catalytic activity). In devising the activity scale used in these studies, a value of 100 was assigned to the activity of a reference catalyst that produced a certain octane number product at a standard set of conditions (space velocity, temperature, hydrogen partial pressure, naphtha partial pressure). 

The activity of a test catalyst, either in the fresh state or after a substantial time on stream, is obtained simply by determining the space velocity required to produce the same octane number product at the standard conditions. Empirical relations between reformate octane number and naphtha space velocity as a function of temperature, hydrogen partial pressure, and other process variables for the reference catalyst make it possible to determine the activity of a test catalyst from data at a variety of conditions. For our purposes here, the absolute values shown for the activities are not important, since we will be concerned strictly with ratios of catalytic activities. 

In Figures 5.5 and 5.6, data on the platinum-iridium and platinum-rhenium catalysts are shown for the reforming of a 70-190 C boiling range Persian Gulf naphtha to produce 98 research octane number product at a pressure of 28.2 atm and a temperature of 490 C (33). The naphtha contained (on a liquid volume percentage basis) 69.7% alkanes, 18.5% cycloalkanes, and 11.8% aromatic hydrocarbons. The density of the naphtha was 0.7414 g/cm3. The data in Figure 5.5 show that the platinum-iridium catalyst is almost twice as active as the platinum-rhenium catalyst. 

For early polymerization units, the catalyst was phosphoric acid on a quartz or kieselguhr support. Many of these units were shut down when the demand for gasoline with increased octane numbers prompted the diversion of the olefin feeds to alkylation units that gave higher octane number products. Yet some refinery balances have more propylene than alkylation can handle, so a newer version of polymerization was introduced.It is the Dimersol process of the Institut Frangais du Petrole, for which the flow diagram is shown in Fig. 15.18. 

Figure 5.5 can be used to place the different product streams with respect to the objectives required for commercial octane numbers for Eurosuper and Superplus. It is clearly evident that the preparation of Superplus (RON 98, MON 88) will require careful screening of its components. 

Formulation consists of mixing the effluent streams coming from the different refining units in order to obtain products conforming to the specifications. It is also at this point that additives are added, the reasons for which and whose action will be described later. One can easily see that as far as octane numbers are concerned, or for that matter any other parameter, the... 

Regarding product characteristics, European specifications were established in 1992. They concern mainly the motor octane number (MON) that limits the olefin content and which should be higher than 89, and the vapor pressure, tied to the C3/C4 ratio which should be less than 1550 mbar at 40°C (ISO 4256). On the other hand, to ensure easy vehicle start-ups, a minimum vapor pressure for winter has been set which is different for each country and depends on climatic conditions. Four classes. A, B, C, and D, are thus defined in Europe with a minimum vapor pressure of 250 mbar, respectively, at -10°C (A), -5 C (B), 0°C (C) and -t-10°C (Z)). France has chosen class A. 

Their production in a refinery begins with base stocks having narrow boiling ranges and high octane numbers iso C5 cuts (used in small concentrations because of their high volatility) or alkylates are sought for such formulations. 

If one talks henceforth about the necessity of matching an engine and its fuel, the demand for quality in motor fuels has, however, never ceased to be a preoccupation for refiners ever since gasoline became a commodity item. Two main classes of products are added to gasoline coming from refining octane number improvers and detergents. 

The trend in d and has also been accompanied by improvements in product quality illustratisd by the increases in gasoline octane numbers and diesel oil cetane numbers. 

A key process in the production of gasoline, catalytic reforming is used to increase the octane number of light crude fractions having high paraffin and naphthene contents (C7-C8-C9) by converting them to aromatics. 

One can react methanol with the tertiary olefins having five c irbon atoms (isoamylenes). This process increases the octane number of FCC olefinic C5 fractions, in order to reduce the concentration of olefins and to increase gasoline production. 

The products could be classified as a function of various criteria physical properties (in particular, volatility), the way they are created (primary distillation or conversion). Nevertheless, the classification most relevant to this discussion is linked to the end product use LPG, premium gasoline, kerosene and diesel oil, medium and heavy fuels, specialty products like solvents, lubricants, and asphalts. Indeed, the product specifications are generally related to the end use. Traditionally, they have to do with specific properties octane number for premium gasoline, cetane number for diesel oil as well as overall physical properties such as density, distillation curves and viscosity. 

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. 

Product characterization aims at defining their end-use properties by means of conventional standard measurements related as well as possible — and in any case, being the object of a large consensus— to end-use properties. We cite for example that octane numbers are supposed to represent the resistance of gasoline to knocking in ignition engines. 

Benzene, toluene, and xylene are made mosdy from catalytic reforming of naphthas with units similar to those already discussed. As a gross mixture, these aromatics are the backbone of gasoline blending for high octane numbers. However, there are many chemicals derived from these same aromatics thus many aromatic petrochemicals have their beginning by selective extraction from naphtha or gas—oil reformate. Benzene and cyclohexane are responsible for products such as nylon and polyester fibers, polystyrene, epoxy resins (qv), phenolic resins (qv), and polyurethanes (see Fibers Styrene plastics Urethane POLYiffiRs). 

Butylenes. Butylenes are the primary olefin feedstock to alkylation and produce a product high in trimethylpentanes. The research octane number, which is typically in the range of 94—98, depends on isomer distribution, catalyst, and operating conditions. 

The cumene product is 99.9 wt % pure, and the heavy aromatics, which have a research octane number (RON) of 109, can either be used as high octane gasoline-blending components or combiaed with additional benzene and sent to a transalkylation section of the plant where DIPB is converted to cumene. The overall yields of cumene for this process are typically 97—98 wt % with transalkylation and 94—96 wt % without transalkylation. 

Polymer Gasoline. Refinery trends tend to favor alkylation over polymerisation. Unlike the alkylation process, polymerisation does not require isobutane. The catalyst is usually phosphoric acid impregnated on kieselghur pellets. Polymerisation of butylenes is not an attractive alternative to alkylation unless isobutane is unavailable. The motor octane number of polymer gasoline is also low, and there is considerable shrinkage ia product volume. The only commercial unit to be built ia recent years is at Sasol ia South Africa. The commercial process was developed by UOP ia the 1940s (104). 

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