Sulfur content naphtha

Naphtha desulfurization is conducted in the vapor phase as described for natural gas. Raw naphtha is preheated and vaporized in a separate furnace. If the sulfur content of the naphtha is very high, after Co—Mo hydrotreating, the naphtha is condensed, H2S is stripped out, and the residual H2S is adsorbed on ZnO. The primary reformer operates at conditions similar to those used with natural gas feed. The nickel catalyst, however, requires a promoter such as potassium in order to avoid carbon deposition at the practical levels of steam-to-carbon ratios of 3.5—5.0. Deposition of carbon from hydrocarbons cracking on the particles of the catalyst reduces the activity of the catalyst for the reforming and results in local uneven heating of the reformer tubes because the firing heat is not removed by the reforming reaction. 

Mercaptans are the main sulfur compounds in LCN, thiophenes and substituted-thiophenes are present in MCN and benzothiophene (BT) and substituted-BT in the heavy naphthas. A caustic treatment would work for the removal of mercaptans from LCN, and take the total sulfur content below 20 ppm. However, MCN and HCN have to be treated in a more severe way. 

Sulfur compounds are most commonly removed or converted to a harmless form by chemical treatment with lye. Doctor solution, copper chloride, or similar treating agents (Speight, 1999). Hydrorefining processes (Speight, 1999) are also often used in place of chemical treatments. When used as a solvent, naphtha is selected for its low sulfur content and the usual treatment processes remove only sulfur compounds. Naphtha, with its small aromatic content, has a slight odor, but the aromatics increase the solvent power of the naphtha and there is no need to remove aromatics unless odor-free naphtha is specified. 

Merox. A proprietary catalytic process for extracting and converting mercaptans in naphtha and kerosene range hydrocarbons to reduce the sulfur content. 

A similar study reports the results of adding 100 ppm thiophene to As in the Palm et al. study,the catalyst is not described rather, it is identified only as a commercial naphtha reforming catalyst, presumably Pt-based. In their reactor, the reformate from the ATR step passes through separate high and low temperature shift reactors before being analyzed. Thus, it was not possible to determine the effect of sulfur on the reforming step alone, nor was any post-reaction characterization of the catalyst reported, for example to determine coke or sulfur content. Figure 16 shows the observed deactivation, as measured by a decrease in H2 and CO concentrations. 

Of the North American total, about 1,100,000 barrels per day came from Texas, 420,000 from California, 170,000 from Mexico, and the remainder largely from Arkansas, Mississippi, and New Mexico. The sulfurous Venezuelan crudes come from the Lake Maracaibo area and these, like the Mexican crudes, give relatively low yields of naphtha and middle distillates, thus differing from the Middle East crudes. Only small amounts of crude oil with sulfur contents greater than 1% by weight exist in U.S.S.R., Europe, and the Far East. 

In Table X the properties of the syncrude prepared from in situ crude shale oil are compared with the properties of a syncrude listed by the NPC. Relative amounts and properties of the naphthas, light oils, and heavy oils are also compared. These data show that the nitrogen content, sulfur content, pour point, viscosity, and API gravity of syncrude prepared from in situ crude shale oil are lower than those suggested in... 

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. 

Partial oxidation has practically no restrictions regarding the nature of the hydrocarbon and the sulfur content. Natural gas, refinery gases, LPG, naphtha, heavy fuel, vacuum residue, visbreaker oil, asphalt, and tar can be used as feedstock. As the investment costs for partial oxidation are higher than for steam reforming, mainly because of the cyrogenic air separation, it is usually not a choice for the lighter hydrocarbons, but heavy feedstocks from fuel oil to asphalt, when favorably priced, can be a competitive option for various locations and circumstances. In some special cases, where the primary reformer is a bottleneck for a capacity increase, a small parallel partial oxidation unit based on natural gas could be installed, if a surplus of... 

Two stages of hydrotreatment were used to reduce further oxygen and especially nitrogen and sulfur contents in the naphtha from hydrocracking LGO. A catalyst of Ni/Mo on A1203 (Table II) was used in a 1-in. diameter trickle bed reactor at 400°C, 1500 psig, 5 M scf H2/bbl, and 4.8 LHSV in the first pass and at 450°C and 1.5 LHSV for recycle of the naphtha successively distilled off. 

The processing scheme just discussed uses atmospheric and vacuum residues as its raw material. Recently, consideration has been given to a fuels reflnery concept in which whole crude oil is processed to yield only utility fuels. The processing sequence discussed in this paper would flt quite well into such a processing sequence. A block flow diagram of a fuels reflnery is shown in Figure 9. Such a complex would produce low sulfur-content fuel oil, turbine fuel, and naphtha. The naphtha product could be a raw material for the production of either SNG or petrochemicals. 

Determination of Mercaptan Sulfur Content of Gasolines and Naphthas. 

Table VI presents the over-all material balance on the H-Oil unit used in this case. Conversion is achieved, of all but 9 vol % of the feed, into material boiling below 650°F. The sulfur contents of the distillate fractions produced are quite low, and should it be desirable to control the sulfur content of all of the steam cracker charge, the virgin naphtha and distillate could also be processed in the H-Oil unit to achieve an over-all purification of steam cracker charge.

Among the main processes marketed arc those developed by BP (British Pen-oleum), Engelhard, Esso, IFF, Shell, Standard Oil, UOP, etc., which reduce the sulfur content of 70-18Q°C naphtha from 200 to 1000 ppm to between 1 and 0.5 ppm. 

Catalyst pellets, x 3 in., with molybdena content from 6 to 15 % were used to reform a heavy virgin mixed naphtha with a research clear octane number of 39, a 240-430° F boiling range (ASTM), and a sulfur content near 0.1%. Pilot-plant studies were made at 488 to 530° and 250 psi. The feed rate was 1.0 volume of oil per volume of catalyst per hour and the hydrogen addition rate, 2500 SCF/Bbl. Activity and yield studies were made with the cogelled catalysts whereas activity determinations only were made on the impregnated catalysts. 

In all cases, the high sulfur content of the charges has been reduced to neghgible values in the naphthas and acceptable values for the diesel fuel. Furthermore, nitrogen compounds are almost completely eliminated from the products. Two very serious catalyst poisons, arsenic and lead, are shown to have been decreased to practical concentrations. Finally, the burning quality of the diesel fuel, as shown by the cetane number has been improved very considerably. 

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