Hydrocrackate naphtha

Gasoline, coal solvent extn, hydrocracked naphtha... 

In catalytic reforming, a low octane naphtha cut (typically a straight run or hydrocracked naphtha) is converted into high-octane aromatics, including benzene, toluene, and mixed xylenes. Aromatics are separated from the reformate by using a solvent such as diethylene glycol or sulfolane and then stripped from the solvent. Distillation is then used to separate the benzene-toluene-xylene into its components. 

Owing to the limited availability of the feedstocks, it was not possible to do parametric studies and then operate at a single set of conditions to provide a hydrocrackate naphtha. All of the hydrocrackate material from a given feedstock was combined, the naphtha distilled, and resultant unconverted mid-distillate subjected to second-pass hydrocracking. 

Heteroatom levels in the hydrocrackate naphthas could be reduced... 

Catalytic reformer feeds are saturated (i.e., not olefinic) materials in the majority of cases that feed may be a straight-run naphtha but in others by-product low-octane naphtha (e.g., coker naphtha) can be processed after treatment to remove olefins and other contaminants. Hydrocracker naphtha that contains substantial quantities of naphthenes is also a suitable feed. 

It should be emphasized that In actual practice It Is the maximum finished product rather than the quantity of C5+ hydrocrackate that Is the most critical yield affecting economic evaluations of hydrocracking catalysts. A portion of the hydrocracked naphtha Is usually catalytlcally reformed to produce high octane gasoline. Klttrell, Scott, and Lsinglols presented... 

The feedstocks (straight-mn naphtha (SRN) and a blend of SRN and hydrocracked naphtha) and hydrotreated products were analysed by ASTM methods for density, carbon, hydrogen, hydrocarbon and boiling point distribution. Total sulfur was determined by ASTM D-4045 method, mercaptan sulfur by the potentiometric method (ASTM D-3227 and UOP-212), disulfides by the UOP-202 method, polysulfides by polarography [1], and elemental sulfur by the UOP-286 method. The Perkin-Elmer gas chromatograph (Model 8700), equipped with a flame photometric detector (GC/FPD) and a DB-1 fused silica capillary column (30 m x 0.53 mm), was used for identification of individual sulfur compounds [2-6]. The sensitivity of the GC/FPD technique was maximized by optimizing the gas flow rates and temperature programming as presented elsewhere [1]. 

Nitrogen Content. The bulk of the shale oil nitrogen was removed in the hydrocracking step. All four products from fractionation of the hydrocrackate—naphtha, jet, diesel and heavy oil— contained substantial amounts of nitrogen, however. The data in Table I indicate that the lighter products had less total nitrogen. 

If not removed, mercaptans in hydrocracker naphtha may cause problems for downstream catalytic reforming units. Often, they are removed with a post-treat bed - a small layer of hydrotreating catalyst imdemeath the last... 

---