Hydrocracking raffinate

High yields of LFG or Isobutane and octane Improvement of the C5" fraction can be simultaneously obtained by hydrocracking raffinate over a palladium-Impregnated, nickel-substituted synthetic mlca-montmorlllonlte catalyst (0.7 wt % Pd-15 wt % Nl-SMM). A critical sulfur level of about 100 to 200 ppm In the feed Is essential to combine the features of desired product... 

Raffinate Hydrocracking with Palladium-Nickel— Containing Synthetic Mica-Montmorillonite Catalysts... 

Previous results(2) had shown that a Pd-Ni-SMM catalyst was effective for hydrocracking hexane as well as a raffinate feed. Conclusions showed that this catalyst system when containing two nickel atoms per unit cell (15 wt % nickel) was approximately 15 times more active than a Pd-rare earth-Y zeolite catalyst and 1.2 times more active than Pd-H-mordenite. This same catalyst system (0.7 wt % Pd-15 wt % Ni-SMM) was chosen for our raffinate processing studies. 

Figure 1. Effect of sulfur in Pd-Nir-SMM raffinate hydrocracking. 7000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. Feed—Q, raffinate , raffinate + 1500 ppm sulfur. Catalyst—Q, reduced 0.7 wt % — 15 wt % Ni—SMM , sulfided 0.7 wt% — 15 wt % Nir-SMM.

An alternate course, which was not pursued, would be to operate the reformer at less severe conditions where naphthene conversions are high but where isomerization and hydrocracking are less. The resultant reformate could be extracted with raffinate going to a naphtha cracker for olefin production while the extract is hydrodealkylated. 

One of Sun s objectives for the new plant was that the base stocks be at least of the same quality as those from solvent refining, therefore this hurdle had to be overcome. Their solution was to give the total dewaxed hydrocrackate product a light furfural extraction (about 97% raffinate) to remove the tri+ aromatics which appeared to be at the root of the problem.1516 Thus their process involved two solvent extraction steps, one before the hydrocracker and one afterwards. This route gave stable base stocks, but with some residual color. An example of the improvement obtained can be seen in Table 7.10, where 100, 200, and 500 SUS base stocks ( 1, 2, and 3 in Table 7.10) of approximately 110 VI from hydrocracking a distillate/DAO blend were tested for stability before and after furfural extraction. The results show that the extraction improves color relative to unextracted samples for the immediate hydrocracker products and that their performance in the stability test was improved as well by extraction. 

Type of feeds Waxy solvent refined raffinates, waxy hydrocrackates,... 

Pentylamine Petroleum distillates, acid-treated middle Petroleum distillates, alkylate Petroleum distillates, catalytic reformer fractionator residue, low boiling Petroleum distillates, heavy hydrotreated naphthenic Petroleum distillates, heavy thermal cracked Petroleum distillates, hydrotreated light, low-boiling Petroleum distillates, hydrotreated middle Petroleum distillates, light hydrocracked Petroleum raffinates, sorption process... 

The combination of extraction and hydroprocessing is a very efficient route to basestocks needed for GF-3 quality. Extraction alone is inappropriate because of an inability to selectively remove multiring naphthenes (these tend to be split evenly between the raffinate and extract phases). Yields by extraction to the same basestock property levels may be less than half of that achieved by RHC . Also, VGO hydrocracking, i.e. with no pre-extraction step, requires more severe conditions and has potentially lower yields than RHC because of the higher conversion needed to offset the highly negative VI characteristics of refiiactory multi-ring species present in the distillate feed. 

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