Naphtha hydrocarbon types

J. J. Szakasits and R. E. Robinson, Hydrocarbon type determination of naphthas and catalytically reformed products hy automated multidimensional gas cliromatography . Anal. Chem. 63 114-120(1991). 

Hydrocarbon composition is also determined by mass spectrometry, a technique that has seen wide use for hydrocarbon-type analysis of naphtha and gasoline (ASTM D2789) as well as for the identification of hydrocarbon constituents in higher-boiling naphtha fractions (ASTM D2425). 

A comparison has been made of Platforming and of thermal reforming from the standpoint of yield-octane number relationships, product properties, hydrocarbon types, and with respect to the nature of chemical reactions responsible for improvement of octane number. Comparison is based on studies of thermal reforming in a commercial operation at a Pennsylvania refinery and in a pilot plant on a midcontinent naphtha and in pilot plants and laboratory Platforming on the same stocks. 

Hydrocarbon types were estimated using the substractive method of Poulson (15,16) for the fractions boiling above 175°F. The hydrocarbon compound composition of the C5-175°F naphtha was determined by gas chromatography. Paraffin and naphthene contents of the 175°-350°F naphtha and of the 350°-550°F light oil were calculated from mass spectra. Liquid displacement chromatography on Florisil was used to determine the amount of polar material in the 550°-850°F heavy oil. 

Hydrocarbon-type Characterization. Table I lists the four fractions, their wt % of the syncrude, and their hydrocarbon-type compositions. The values for polar material for the two naphthas and the light oil are estimates based on their nitrogen contents. The polar material value for the heavy oil is based on the recovered weights from the Florisil separa-... 

Figure 2. Hydrocarbon type distribution in naphthas from entrained-solids retort crudes (19)...

This chapter presents a close look at the standard silica gel analysis of a shale oil naphtha with an evaluation of its effectiveness, a description of the new method now used to quantify olefins in shale oil products, a summary of results of the hydrocarbon-type analysis using the new method for a series of three related shale oils, and a discussion of the information on olefin-type compounds which can be revealed by IR examination of whole shale oils. The paper concludes with a brief discussion of additional applications of the hydroboration of olefins to problems of interest to the petroleum analyst. 

The number of potential hydrocarbon isomers in the naphtha boiling range (Tables 4.1 and 4.2) renders complete speciation of individual hydrocarbons impossible for the naphtha distillation range, and methods are used that identify the hydrocarbon types as chemical groups rather than as individual constituents. 

Other test methods are available. Content of benzene and other aromatics may be estimated by spectrophotometric analysis (ASTM D-1017) and also by gas-liquid chromatography (ASTM D-2267, ASTM D-2600, IP 262). However, two test methods based on the adsorption concept (ASTM D-2007, ASTM D-2549) are used for classifying oil samples of initial boiling point of at least 200°C (392°F) into the hydrocarbon types of polar compounds, aromatics, and saturates and recovery of representative fractions of these types. Such methods are unsuitable for the majority of naphtha samples because of volatility constraints. 

Kosal, N. Bhairi, A. Ali, M.A., Determination of Hydrocarbon Types in Naphthas, Gasolines and Kerosenes a Review and Comparative Study of Different Analytical... 

With this type of burner, a wide variety of raw materials, ranging from propane to naphtha, and heavier hydrocarbons containing 10—15 carbon atoms, can be used. In addition, the pecuhar characteristics of the different raw materials that can be used enable the simultaneous production of acetylene and ethylene (and heavier olefins) ia proportioas which can be varied within wide limits without requiring basic modifications of the burner. 

Solvents for A-type inks are aUphatic hydrocarbons, for example, hexane, textile spidts, Apco Thinner, lactane, VM P (varnish makers and painters ) naphtha, and mineral spirits. Aromatic hydrocarbons such as toluene and xylene are solvents for B-type inks. Generally, a blend of aUphatic and aromatic hydrocarbons is commonly used for this type of ink. 

As the name implies, these stains are sprayed on and require Httie if any wiping. The solvent itself penetrates into the pore and allows the pigment and a small amount of binder to remain on the surface. These stains usually are composed of an oil-type vehicle and a combination of earth pigments reduced in a combination of aHphatic and aromatic hydrocarbons such as naphtha and toluene. The solvent system itself plays a big role in the appearance of the stain owing to the varying degrees to which solvents penetrate. Restrictions on the use of certain aromatic hydrocarbons have affected the manner in which these stains work. 

Saturated cyclic hydrocarbons, normally known as naphthenes, are also part of the hydrocarbon constituents of crude oils. Their ratio, however, depends on the crude type. The lower members of naphthenes are cyclopentane, cyclohexane, and their mono-substituted compounds. They are normally present in the light and the heavy naphtha fractions. Cyclohexanes, substituted cyclopentanes, and substituted cyclohexanes are important precursors for aromatic hydrocarbons. 

Products from coking processes vary considerably with feed type and process conditions. These products are hydrocarbon gases, cracked naphtha, middle distillates, and coke. The gas and liquid products are characterized by a high percentage of unsaturation. Hydrotreatment is usually required to saturate olefinic compounds and to desulfurize products from coking units. 

Most industrial hydrogen is manufactured by the following hydrocarbon-based oxidative processes steam reforming of light hydrocarbons (e.g., NG and naphtha), POx of heavy oil fractions, and ATR. Each of these technological approaches has numerous modifications depending on the type of feedstock, reactor design, heat input options, by-product treatment,... 

The linear response of sample chemistry across all hydrocarbons allows spectrum-property regressions to be performed on a wide range of samples in a given chemometric model. The modeling approach can literally include individual parameter models that span a single product type (e.g. aU diesels) or span several product types (e.g. naphtha, kerosene, diesel, gas oils). Thus, the modeling is far more robust and does not have to be continually updated and thoroughly localized as is often the case for NIR or mid-lR spectroscopy. 

The octane number improvement obtained by isomerization of paraffin hydrocarbons is not great since the amounts of the more highly branched paraffins formed at equilibrium are small at the temperatures employed in catalytic reforming (5). Naphthene isomerization, on the other hand, plays a more important role in reforming. In most naphthas about 50% of the naphthene hydrocarbons are of the cyclopentane type (4) so that in order to obtain the maximum aromatic formation, isomerization of these rings to cyclohexane rings must be promoted by the catalyst. 

Sulfur compounds contained in hydrocarbon feedstock vary, depending on the types of crudes and their boiling points. Naphtha, for example, contains mainly mereaptans. disulfides, and thiophenes. Such sulfur compounds deteriorate the activity of the low-temperature steam-reforming MRG catalyst. They should be removed to some degree before the feedstock enters the system. Major reactions of the hy diodesulfurization step are ... 

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