Naphtha olefins content

Naphthas boiling up to 185°C can be reformed at pressures up to 600 psig. Naphthas with final boiling point up to 240 C may be reformed at lower pressures. Higher olefin contents may be accepted provided that sufficient hydrogen is available in the recycle gas to saturate the feed in the desulfurization section. Higher aromatic contents may be accepted but tile catalyst life will be reduced. 

The fraction of diesel-oil-like hydrocarbons had also a triple sequence and the main aliphatic componnds may be characterized with carbon numbers 12, 15, 18, 21, 24, 27. In contrast with the experimental results of naphtha diesel oil had considerably lower concentration of aromatics. In the case of each MPW sample its concentration was not more than 1%, because aromatics with lower boiling point stayed in the naphtha-like fraction. Similarly, as mentioned above, the diesel-oil-like fraction also had favourable properties for further fuel-like application. The olefin content was a bit smaller than in case of naphtha-like fractions, because cracking reaction resulting olefins (e.g. P-scission) produced hydrocarbons with a shorter length of carbon chain. Both cetane numbers and diesel indexes of products were high enough, while the CFPP was rather low. 

Naphtha feed is treated as a single pseudo species. Naphthas, used as pyrolysis feedstocks, are mainly composed of paraffins and naphthenes, with lesser amounts of aromatics. Olefin content is usually very small. Consistent with observed pyrolytic behavior of paraffins and naphthenes (15,16,26,27,28), feed decomposition is assumed to follow first-order kinetics. Equation 3 of the reactor model can be simplified as follows. 

Selective hydrogenation is of importance industrially. It is used in the manufacture and in the purification of ethylene, in removing substituted acetylenes from butadiene, in lowering the olefin content of cracked naphthas while leaving the aromatics unchanged, and in various other petroleum-processing reactions such as hydrodesulfurization. 

Catalytic reforming Catalytic cracking Naphtha b.p. 30-190°C H, (6 1) Fractions b.p. 220-540°C 0.3-0.5% Pt on y-AI2O3 promoted by 1% chlorine. Zeolite or + SiO 500-525°C 23.3 atm 500-550°C 1 atm Dehydrogenation Isomerization (Hydrocracking) Carbonium ion reactions (acidic sites) Aromatics Alkanes Gasoline (high olefin content)... 

The feed can be obtained from cat naphtha, coker naphtha, and steam cracker s C4 s and pyrolysis gasoline. The largest source of olefinic feedstock molecules is cat naphtha, which contain 20-60% olefins. Most of linear cat naphtha olefins are converted to light olefins, and at the same time, an increased octane and reduced olefin content naphtha is produced by the concentration of higher octane aromatics, plus isomerization and some additional aromatics formation. 

For desulfurization of naphtha, a more complicated process is required. Hydrodesulfurization quite often is used. About 0.5 mole of H2 is mixed with 1 mole of vaporized naphtha or 250 scf (Standard Cubic Feet) per barrel, depending upon the sulfur and olefin content. The mixture is preheated to 320 "C and passed over a cobalt-molybdenum catalyst, where the olefins are hydrogenated to paraffin hydrocarbons and the sulfur compounds are reduced to H2S. The gas then is passed over a sulfur adsorbent such as iron or zinc oxide. It may or may not be necessary to condense the naphtha, depending upon the amount of hydrogen used and the need to remove it from the naphtha. 

This test method is applicable to olefln-free (<2 % olefins by liquid volume) liquid hydrocarbon mixtures including virgin naphthas, reformates, and alkylates. Olefin content can be determined by Test Method D 1319. The hydrocarbon mixture must have a 98 % point of 250 C or less as determined by Test Method D 3710. 

All of the liquid products require further processing due to their high olefins content, which makes them unstable and poorly suited for direct blending into finished products (gasoline and diesel). The coker naphtha and LCGO are hydrotreated. The HCGO can go either to an FCC unit or a hydrocracker unit, and the hot residue keeps flowing into the coke drum until it is filled with solid coke. 

When simple Hquids like naphtha are cracked, it may be possible to determine the feed components by gas chromatography combined with mass spectrometry (gc/ms) (30). However, when gas oil is cracked, complete analysis of the feed may not be possible. Therefore, some simple definitions are used to characterize the feed. When available, paraffins, olefins, naphthenes, and aromatics (PONA) content serves as a key property. When PONA is not available, the Bureau of Mines Correlation Index (BMCI) is used. Other properties like specific gravity, ASTM distillation, viscosity, refractive index. Conradson Carbon, and Bromine Number are also used to characterize the feed. In recent years even nuclear magnetic resonance spectroscopy has been... 

Naphtha is also a major feedstock to steam cracking units for the production of olefins. This route to olefins is especially important in places such as Europe, where ethane is not readily available as a feedstock because most gas reservoirs produce non-associated gas with a low ethane content. 

The amount of benzene produced in a reformer will depend on the composition of the feed. Every crude oil has naphtha with different PNA (paraffin, naphthene, aromatics) content. In commercial naphtha trading, the PNA content is often an important specification. High naphthene and aromatic content would indicate a good reformer feed. High paraffin content would indicate a good olefin plant feed. 

SCANfining A selective catalytic hydrotreating process for reducing the sulfur content of naphtha. Developed by ExxonMobil and Albemarle. The catalyst, developed by ExxonMobil and Akzo Nobel, contains cobalt and molybdenum. The key feature is its prevention of the mercaptans reversion reaction — the formation of mercaptans from olefins and hydrogen sulfide. The process also minimizes olefin saturation and hydrogen loss. To be used at the Bazan Oil Refinery, Israel, from 2001, and at the Statoil refinery at Mongstad, Norway. Also planned for use in the Williams refinery in Memphis, TN. 

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