Hydrocracking process

#The field of art to which this invention pertains is the hydrocracking of a hydrocarbonaceous feedstock. Petroleum refiners often produce desirable products such as turbine fuel, diesel fuel and other products known as middle distillates as well as lower boiling hydrocarbonaceous liquids such as naphtha and gasoline by hydrocracking a hydrocarbon feedstock derived from crude oil or heavy fractions thereof, for example. Feedstocks most often subjected to hydrocracking are gas oils and heavy gas oils recovered from crude oil by distillation. A typical heavy gas oil comprises a substantial portion of hydrocarbon components boiling above about 371° C. (700° F.), usually at least about 50 percent by weight boiling above 371° C. (700° F.). A typical vacuum gas oil normally has a boiling point range between about 315° C. (600° F.) and about 565° C. (1050° F.).

#Hydrocracking is generally accomplished by contacting in a hydrocracking reaction vessel or zone the gas oil or other feedstock to be treated with a suitable hydrocracking catalyst under conditions of elevated temperature and pressure in the presence of hydrogen so as to yield a product containing a distribution of hydrocarbon products desired by the refiner. The operating conditions and the hydrocracking catalysts within a hydrocracking reactor influence the yield of the hydrocracked products.

#Traditionally, the fresh feedstock for a hydrocracking process is first introduced into a denitrification and desulfurization zone particularly suited for the removal of sulfur and nitrogen contaminants and subsequently introduced into a hydrocracking zone containing hydrocracking catalyst. Another method of hydrocracking a fresh feedstock is to introduce the fresh feedstock and the effluent from the hydrocracking zone into the denitrification and desulfurization zone. The resulting effluent from the hydrocracking zone is separated to produce desired hydrocracked products and unconverted feedstock which is then introduced into the hydrocracking zone.

#The drawing is a simplified process flow diagram of a preferred embodiment of the present invention. The drawing is intended to be schematically illustrative of the present invention and not be a limitation thereof.

#The process of the present invention is particularly useful for hydrocracking a hydrocarbon oil containing hydrocarbons and/or other organic materials to produce a product containing hydrocarbons and/or other organic materials of lower average boiling point and lower average molecular weight. The hydrocarbon feedstocks that may be subjected to hydrocracking by the method of the invention include all mineral oils and synthetic oils (e.g., shale oil, tar sand products, etc.) and fractions thereof. Illustrative hydrocarbon feedstocks include those containing components boiling above 288° C. (550° F.), such as atmospheric gas oils, vacuum gas oils, deasphalted, vacuum, and atmospheric residua, hydrotreated or mildly hydrocracked residual oils, coker distillates, straight run distillates, solvent-deasphalted oils, pyrolysis-derived oils, high boiling synthetic oils, cycle oils and cat cracker distillates. A preferred hydrocracking feedstock is a gas oil or other hydrocarbon fraction having at least 50% by weight, and most usually at least 75% by weight, of its components boiling at temperatures above the end point of the desired product, which end point, in the case of heavy gasoline, is generally in the range from about 193° C. (380° F.) to about 215° C. (420° F.). One of the most preferred gas oil feedstocks will contain hydrocarbon components which boil above 288° C. (550° F.) with best results being achieved with feeds containing at least 25 percent by volume of the components boiling between 315° C. (600° F.) and 538° C. (1000° F.).

#Also included are petroleum distillates wherein at least 90 percent of the components boil in the range from about 149° C. (300° F.) to about 426° C. (800° F.). The petroleum distillates may be treated to produce both light gasoline fractions (boiling range, for example, from about 10° C. (50° F.) to about 85° C. (185° F.)) and heavy gasoline fractions (boiling range, for example, from about 85° C. (185° F.) to about 204° C. (400° F.)). The present invention is particularly suited for maximizing the yield of liquid products including middle distillate products.

#In the drawing, the process of the present invention is illustrated by means of a simplified schematic flow diagram in which such details as pumps, instrumentation, heat-exchange and heat-recovery circuits, compressors and similar hardware have been deleted as being non-essential to an understanding of the techniques involved. The use of such miscellaneous equipment is well within the purview of one skilled in the art.

#With reference now to the drawing, a feed stream comprising vacuum gas oil is introduced into the process via line 1 and admixed with a hereinafter-described liquid recycle stream transported via line 30. The resulting admixture is transported via line 2 and is admixed with a hydrogen-rich gaseous stream provided via line 22 and the resulting admixture is carried via line 3 and introduced into denitrification and desulfurization zone 4. The resulting effluent from the denitrification and desulfurization zone 4 is carried via line 5 and is admixed with a hereinafter-described effluent from hydrocracking zone 10 carried via line 11 and the resulting admixture is transported via line 6 and introduced into stripping zone 7. A liquid hydrocarbonaceous stream is removed from the bottom of stripping zone 7 via line 8 and is admixed with a hydrogen-rich gaseous stream provided via line 24 and the resulting admixture is carried via line 9 and introduced into hydrocracking zone 10. A resulting hydrocracking effluent is removed from hydrocracking zone 10 via line 11 as hereinabove described. A vaporous stream is stripped and carried upwards in stripping zone 7 and is contacted with hydrogenation zone 31 and a resulting effluent is removed from stripping zone 7 via line 12. The resulting vapor stream contained in line 12 is introduced into heat-exchanger 13 and a partially condensed effluent stream is removed from heat-exchanger 13, carried via line 14 and introduced into high pressure separator 15. A gaseous stream containing hydrogen and hydrogen sulfide is removed from high pressure separator 15 via line 16 and introduced into acid gas recovery zone 17. A lean solvent is introduced via line 18 into acid gas recovery zone 17 and contacts the hydrogen-rich gaseous stream in order to dissolve an acid gas. A rich solvent containing acid gas is removed from acid gas recovery zone 17 via line 19 and recovered. A hydrogen-rich gaseous stream containing a reduced concentration of acid gas is removed from acid gas recovery zone 17 via line 20 and is admixed with fresh make-up hydrogen which is introduced via line 21. The resulting admixture is transported via line 22 and a portion thereof is carried via line 23 to serve as stripping gas in stripping zone 7. Another portion of the hydrogen-rich gaseous stream carried in line 22 is transported via line 24 and is introduced into hydrocracking zone 10 as hereinabove described. The third and remaining portion of the hydrogen-rich gaseous stream carried via line 22 is introduced into denitrification and desulfurization reaction zone 4 as hereinabove described. A liquid stream is removed from high pressure separator 15 via line 25 and is introduced into fractionation zone 26. Light gaseous hydrocarbons and naphtha boiling range compounds are removed from fractionation zone 26 via line 27 and recovered. A liquid stream containing kerosene boiling range compounds is removed from fractionation zone 26 via line 28 and recovered. A liquid hydrocarbon stream containing diesel boiling range compounds is removed from fractionation zone 26 via line 29 and recovered. A heavy liquid hydrocarbon steam containing compounds boiling in the range greater than diesel boiling range compounds is removed from fractionation zone 26 via line 30 and admixed with the fresh hydrocarbonaceous feed as described hereinabove.

#The process of the present invention is further demonstrated by the following illustrative embodiment. This illustrative embodiment is, however, not presented to unduly limit the process of this invention, but to illustrate the advantage of the hereinabove-described embodiment. All of the following data were not obtained by the actual performance of the present invention but are considered prospective and reasonably illustrative of the expected performance of the invention.