Reforming hydrotreated naphthas

Hydrocracking of the mid-distillate and gas oil to produce naphtha and LPGs (3) hydrotreating of the straight run naphtha and hydro-crackate naphtha to remove heteroatoms and (4) reforming of the hydrotreated naphthas to maximize aromatics. 

Reforming. The hydrotreated naphthas were reformed over a conventional platinum reforming catalyst in an attempt to maximize aromatics. The catalyst was Cyanamid AERO PHF-4 (0.3% Pt, 0.6% Cl). The intent was to operate the reformer at constant conditions in order to better compare naphthas. By operating at severe conditions, the expected hydrocracking activity of the catalyst would tend to purify the aromatics by selectively cracking away the paraffins. If the resultant reformate had a suitably high aromatic content, it could be fed directly to a hydrodealkylator. 

The next cut gasoline stream from the crude distillation column is the naphtha cut. This stream has a boiling range of 200-365°F and contains a significant portion of naphthenes, aromatics, and paraffins. Thus, the naphtha cut is hydrotreated and reformed to upgrade this stream into a gasoline blending stock.9... 

Hydrotreated naphthas (combined) were then reformed over a 0.6% Pt on A1203 catalyst at 500°C, 500 psig, 3 LHSV, and 5 M scf H2/bbl. This simple catalyst was chosen in preference to the more advanced bi- and trimetallic catalysts because of its probably lower sensitivity to heteroatom poisoning. The reformates were analyzed by gas chromatography... 

After hydrotreating naphtha ex hydrocracking Reformate (from naptha ex hydrocracking LGO)... 

Capital costs which foUow the same trend as energy consumption, can be about 1.5 to 2.0 times for partial oxidation and coal gasification, respectively, that for natural gas reformiag (41). A naphtha reforming plant would cost about 15—20% more than one based on natural gas because of the requirement for hydrotreating faciHties and a larger front-end needed for carbon dioxide removal. 

A stripper column in a naphtha hydrotreating process unit needs to remove H2S, which is corrosive and could poison the catalyst in a downstream naphtha reforming unit. Another objective is to remove as much C5 as possible from the stripper bottom, as C5 does not contribute to the naphtha reforming reaction. 

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. 

The feed to a catalytic reformer is normally a heavy naphtha fraction produced from atmospheric distillation units. Naphtha from other sources such as those produced from cracking and delayed coking may also be used. Before using naphtha as feed for a catalytic reforming unit, it must be hydrotreated to saturate the olefins and to hydrodesulfurize... 

Yields Typical yields for severe Naphtha Feed reforming Hydrotreated Hydrocracked... 

The bulk of the naphtha was hydrotreated and catalytically reformed over a chlorided Pt/Al203-based catalyst to produce an aromatic motor gasoline. However, the hydrotreated Fischer-Tropsch naphtha is a poor feed for standard catalytic reforming on account of its high linear hydrocarbon content (>75%).37 In order to limit liquid yield loss, typical operation resulted in a reformate with quite low octane value (Table 18.10). Higher octane reformate could be produced, but at the expense of significant liquid yield loss. 

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