US 3816296 A
Description (OCR text may contain errors)
United States Patent [191 Hass et al.
[ HYDROCRACKING PROCESS  Inventors: Robert H. Hass; Cloyd P.'Reeg, both of Fullerton; Edward C. Attane, Jr., Orange, all of Calif.
 Assignee: Union Oil Company of California,
Los Angeles, Calif.
 June 11, 1974 3,644,200 2/l972 Young 208/120 Primary ExaminerDelbert E. Gantz Assistant Examiner-G. E. Schmitkons Attorney, Agent, or Firm-Richard C. Hartman; Lannas S. Henderson; Michael H. Laird  ABSTRACT Midbarrel fuels boiling primarily between about 300 and about 700F are selectively produced from higher boiling feeds containing less than 10 ppm nitrogen by hydrocracking in the presence of controlled amounts of added nitrogen compounds including ammonia or hydrocarbon amines in amounts corresponding to about 5 to about 100 ppm nitrogen. Furthermore, the relative distribution of midbarrel and lower boiling products can be controlled by controlling the amount of nitrogen compounds added to the hydrocracking zone.
8 Claims, 1 Drawing Figure  Filed: Nov. 13, 1972  App]. No.: 305,783
 US. Cl. 208/111, 208/59  Int. Cl Cl0g 37/02  Field of Search 208/111, 59
[5 6] References Cited UNITED STATES PATENTS 3,437,587 4/1969 Ellert et al. 208/l20 3,523,887 8/l970 Hanson et al 2023/] ll 3,554,898 l/l97l Wood et al. 208/59 PATENTEDJUN 1 1 Ian slalslzss 1 HYDROCRACKING PROCESS BACKGROUND Hydrocracking of hydrocarbons boiling above about 700F can be controlled to produce'both midbarrel fuels boiling between about 300.and 700F and lower boiling products such as gasoline or naphtha fractions. However, depending upon market factors or other considerations it is sometimes desirable to maximize conversion or at least increase the conversion to either midbarrel products or gasoline boiling range products. The ability of a process to produce greater relative amounts of one or the other of these products is determined by selectivity.
l have now discovered that the selectivity of hydrocracking feedstocks containing less than about ppm nitrogen to midbarrel fuels can be increased by hydrocracking in the presence of controlled amounts of added nitrogen compounds. I have also discovered that the yield of either midbarrel or lower boiling products for any given conversion can be controlled and changed as desired during a protracted run period by controlling the amount of additional nitrogen compounds added to the hydrocracking zone.
It is therefore one object of this invention to provide an improved hydrocracking process. Another object is the provision of an improved midbarrel hydrocracking process. Another object is the provision of a method for controlling the relative distribution of midbarrel and lower boiling products in hydrocracking reactions. Another object is the control of hydrocracking selectivity in hydrocracking reactions employing relatively, nitrogen free feeds.
In accordance with one embodiment of this invention, feedstocks containing substantial amounts of hydrocarbons boiling above about 700F and containing less than about 10 ppm nitrogen are hydrocracked to midbarrel products boiling between about 300 and about 700F in the presence of added hydrogen and nitrogen added in the form of nitrogen containing compounds in concentrations corresponding to about 5 to about 100 ppm nitrogen. In accordance with another embodiment the selectivity of hydrocracking conversion to midbarrel or lower boiling products is controlled by controlling the amount of nitrogen compounds added to the hydrocracking zone.
The feedstocks employed in these processes boil primarily above about 700F and contain less than about 10 ppm nitrogen as either ammonia or organonitrogen compounds. As a general rule, at least about 90 volume percent of the feed will boil over 700F. Feedstocks of this nature include hydrofined or partially hydrocracked gas oils, cycle stocks, and the like. The organonitrogen content of the feed is generally less than 10 ppm and is preferably below about 5 ppm.
The nitrogen compounds added to the hydrocracking zone to control selectivity include ammonia and other nitrogen containing compounds convertible to ammonia in the hydrocracking zone. These include hydrocarbon amines containing less than 15 carbon atoms per molecule, preferably alkyl amines containing less than about 12 carbon units per molecule. These components can be added directly to the reactor, to the hydrocarbon feed upstream of the reactor, to the hydrogen recycle stream as hereinafter detailed, or by any other convenient procedure. The amount of nitrogen compounds thus added should correspond to between about 5 to about ppm added nitrogen based on the hydrocarbon feed.
Hydrocracking conditions generally include reaction temperatures above about 500F, preferably above about 600F and usually between about 600 and 900F. Hydrogen addition rates should correspond to at least about 400 standard cubic feet per barrel of hydrocarbon feed, usually about 2000 to about 15,000 standard cubic feet. Reaction pressures mustexceed about 200 psig and are usually within the range of about 500 to about 3,000 psig. Contact times generally correspond to liquid hourly space velocities in fixed bed catalytic systems below about 15, preferably be tween about 0.2 and about 10.
Overall conversion rate is primarily controlled by reaction temperature and liquid hourly space velocity. However, selectivity to midbarrel fuels is generally inversely proportional to reaction temperature. It is not as severely affected by reduced space velocity at otherwise constant conversion. Conversely, selectivity is usually improved at higher pressures and hydrogen addition rates. Thus, the conditions required to obtain the desired distribution between midbarrel and lower boiling products for a given feedstock and catalyst can be determined by converting the feed over that catalyst at several different combinations of temperature, pressure, space velocity and hydrogen addition rate, correlating the efiect of each of these variables and selecting the best compromise of overall conversion and selectivity. g
These conditions should usually be chosen so that the overall conversion to products boiling below 700F will correspond to at least about 40 percent and preferably to at least about 50 percent per pass. ln midbarrel hydrocracking processes it is usually preferred that selectivity to midbarrel'products be in excess of about 50 percent, preferably in excess of about 60 percent. Of course, the product end boiling point (E.B.P.) need not be exactly 700F. For instance, a process might be controlled to produce only turbine fuel having an E.B.P. of 550F. Higher boiling material might be recycled to extinction. The conversion to products boiling below 550F would, of course, be less than the percentage conversion to 700F E.B.P. material. Thus, conversions based on a predetermined product end point, e.g., 550F, will be somewhat lower but will usually exceed 30 percent per pass.
Although midbarrel fuels are generally characterized as hydrocarbons boiling between about 300 and about 700F, the cut point between midbarrel fuels and lower boiling gasoline range products can vary substantially. For example, in a given process, midbarrel fuels might be characterized as products boiling between about 400 and 685F whereas the gasoline boiling range products might be characterized as those boiling between about 50 and 400F. Nevertheless, the methods of this invention can be employed to control selectively between midbarrel and gasoline range hydrocarbons even though the cut point between the product fractions may be arbitrarily set at any one of many different temperature levels.
The catalyst comprises a combination of a foraminous refractory oxide support and a hydrogenation active component. A wide variety of supports can be employed including alumina, silica, magnesia, zirconia, beryllia, titania, and crystalline or amorphous combinations of these such as crystalline aluminosilicate zeolites, silica-magnesia, silica-alumina, and the like. However, the amorphous, less acidic supports are preferred for high midbarrel selectivity. Thus, catalysts designed to maximize midbarrel production should contain less than 30, usually less than about 20, and preferably about 0.5 to about weight percent of a crystalline zeolite. The refractory oxide should comprise at least about 50 weight percent amorphous alumina. Never theless, zeolite concentrations above about 50 percent can be used if higher activity is required without de parting from the scope of these processes.
The hydrogenation components include the Group VI and VIII metal oxides and sulfides. Preferred components include the oxides and sulfides of molybdenum, tungsten, iron, nickel and cobalt. Compositions which exhibit relatively high selectivity to midbarrel fuels usually contain in excess of about 5 and preferably between about 5 to about 40 weight percent molybdenum and/or tungsten and at least about 0.5 and generally about 1 to about weight percent nickel and/or cobalt determined as their corresponding oxides. The sulfide form of these metals is most preferred for midbarre] hydrocracking.
These components can be added to the refractory oxide support by any one of numerous procedures generally well known in the art. These include comulling, impregnation, ion exchange, coprecipitation, and the like.
Although the hydrogenation components can be combined with the catalyst support in the sulfide form, that procedure is not usually followed. They are usually incorporated in the form of a metal salt which can be thermally converted to the corresponding oxide in an oxidizing atmosphere or which can be reduced to the metal with hydrogen or other reducing agents. The composition can then be sulfided by reaction with a sulfur donor such as carbon bisulfide, hydrogen sulfide, mercaptans, elemental sulfur, and the like.
-A particularly preferred midbarrel hydrocracking catalyst can be prepared by impregnating a foraminous support containing at least 50 weight percent amorphous alumina with an aqueous mixture or solution of a water soluble compound of molybdenum or tungsten such as ammonium heptamolybdate or ammonium tungstate, a water soluble compound of nickel or cobalt such as the nitrates, sulfates or chlorides and an acid of phosphorus such as orthophosphoric acid. The phosphorus concentration in the solution is preferably suffi cient to incorporate at least about 0.5 and even more preferably at least about 1 weight percent phosphorus in the final catalyst.
One embodiment of this invention is illustrated in the drawing which is a schematic representation of a two stage hydrocracking system. A gas oil feed boiling between about 650 and 980F and containing 4000 ppm total nitrogen and 6000 ppm sulfur is passed to hydrofining zone 3 by way of lines 1 and 2. The hydrofining zone contains a conventional desulfurizationdenitrogenation catalyst comprising about 5 to about 40 weight percent molybdenum or tungsten sulfides and about one to about 15 weight percent nickel or cobalt sulfides determined as the respective oxides deposited on an amorphous support such as gamma alumina. The catalyst may also contain a minor amount of phosphorus, e.g., about 0.5 to about 6 weight percent.
Hydrofining conditions include hydrogen addition rates of 2000 to 15,000 standard cubic feet per barrel of hydrocarbon feed, temperatures of about 600 to about 900F, liquid hourly space velocities of about 0.5 to about 10, and reaction pressures of about 500 to about 3000 psig. These conditions should be sufficient to reduce the organonitrogen and organosulfur levels in the feed to less than about 200 and about 500 ppm respectively, the nitrogen and sulfur compounds being converted to ammonia and hydrogen sulfide.
As a general rule, very little, if any, hydrocracking occurs in hydrofining zone 3. The total effluent for the hydrofining zone is passed through initial hydrocrackemployed in this zone are also sufficient to essentially complete the conversion of organonitrogen and/or organosulfur components that may be carried over into reactor 4 from hydrofining zone 3. Thus, the concentrations of organonitrogen compounds in the efiluent from hydrocracking zone 4 will correspond to less than about 20 ppm nitrogen. This product is then passed to high pressure scrubber-separator 5 in which the effluent is scrubbed with water entering by line 23 to remove ammonia and hydrogen sulfide. The water phase containing these impurities is withdrawn through line 24.
Hydrogen is taken overhead and recycled to the reactor through line 6. Makeup hydrogen is added via line 7. The hydrocarbon phase is passed to fractionator 9 via line 8 where it is separated into gasoline range hydrocarbons boiling below 400 or below about 200F which are recovered via line 10. Midbarrel fuels boiling between the gasoline cut point and about 700F are recovered via line 11. Unconverted hydrocarbons boiling above the midbarrel fuels cut point, e.g., above about 700F, and containing less than about 5 ppm total nitrogen are passed to second hydrocracking stage 13 via line 12.
In this stage the hydrocarbon feed is reacted with hydrogen over the catalyst of this invention in the presence of nitrogen compounds added via line 19. However, as previously mentioned, these nitrogen compounds may be added to the fresh hydrocarbon feed or at some intermediate point in the reactor. Reaction conditions are similar to those described for hydrocracking zone 4 and should be sufficient to convert at least 30 percent of the feed per pass to hydrocarbons boiling below the midbarrel range cut point. The total effluent is then recovered via line 14 and separated in separator 15 preferably without water scrubbing and recycled to fractionation zone 9 via line 16. Hydrogen recovered from separator 15 is recycled to hydrocracker 13 via line 17. Makeup hydrogen is added via v line 18.
It is presently preferred that the second hydrocracker be operated with a closed hydrogen system. Thus if separator 15 is operated under anhydrous conditions there will be very little or no water in hydrocracker 13. It is also preferred that the desulfurization conversion in reactors 3 and 4 be sufficient to reduce the organic sulfur level, if any, to less than 100 and preferably less than 50 ppm. The feed to reactor 13 will have a correspondingly low sulfur level which results in better conversions under otherwise identical conditions.
EXAMPLE 1 A vacuum distillate was hydrotreated and hydro cracked in a two-stage operation with extinction recycle in the second stage hydrocracker. The raw feedstock boiled between 572 and 1007F, had an API gravity of 18.8, a sulfur content of 1.34 weight percent determined by 'X-ray fluorescence and a total nitrogen content of 0.378 weight percent determined by Kjeldahl analysis.
This feed was hydrotreated in the presence of a sulfided catalyst having an equivalent concentration of 19.0 weight percent M00 3.2 weight percent NiO, and 2.8 weight percent phosphorus deposited on gamma alumina. Reaction conditions included a space velocity of 0.167 LHSV, a temperature of 688 to 698F, reaction pressure of 2500 psig and a hydrogen recycle gas rate of 8000 standard cubic feet per barrel of feed. These conditions were sufficient to reduce the organonitrogen content to less than 1 ppm. Reaction temperature in this zone was gradually adjusted throughout the run to maintain 9.2 percent conversion per pass to products boiling below 550F.
The effluent from the hydrotreating zone was flashed and water washed to remove hydrogen, ammonia, hydrogen sulfide and C and lighter hydrocarbons. The hydrogen was recycled to the hydrotreater. The C and heavier hydrocarbons were then fractionated to recover products boiling below 550F. The higher boiling cycle oil containing less than 1 ppm nitrogen was passed to the hydrocracking zone containing the catalyst described above. Reaction conditions included a reactor pressure of 2500 psig, a fresh hydrogen addition rate of 8000 standard cubic feet per barrel, and a liquid hourly space velocity of 0.50. Reactor temperature was adjusted throughout the run to maintain 36.3 percent conversion per pass to products boiling below 550F in the second stage.'The hydrocarbon effluent from the second stage was passed to the fractionation zone and recycled to extinction so that ultimately 100 percent of the raw feed was converted to products boiling below 550F.
During the first period of operation when the second stage was operated in the absence of added nitrogen compounds and water vapor, a temperature of 690F was required to maintain 36.3 percent conversion per pass in the second stage. This corresponded to 40 percent conversion per pass overall. Selectivity to turbine fuel boiling between 300 and 550F was 75.7 volume percent of fresh feed.
EXAMPLE 2 The operation of Example 1 was continued with the exception that the recycle hydrogen added to the second stage hydrocracker was humidified by saturation with water vapor at 2500 psig and 125F. Reactor temperature was increased to 699F to maintain an overall conversion of 40 percent per pass. Part of this temperature increase was due to the temperature increase requirement accompanying gradual catalyst deactivation during the run length. Selectivity to turbine fuel boiling between 300 and 550F was 81.8 volume percent of fresh feed.
151.13 3 The operation of Example 1 was continued using the same catalyst in both stages. The recycle hydrogen to EXAMPLE 4 A midbarrel cracking operation similar to that described in Examples l-3 was conducted using heavy gas-oil boiling between 700 and 1000F, having an AP! gravity of 22.3 and containing 2.91 weight percent sulfur and 820 ppm total nitrogen. This feed was hydrotreated over a catalyst prepared from a support containing 95 percent alumina and 5 percent nickel backexchanged hydrogen zeolite Y. The catalyst contained 2.8 weight percent phosphorus, an amount of molybdenum corresponding to 19.0 weight percent M00 and an amount of nickel corresponding to 3.2 weight percent NiO (including that contained in the zeolite). This material was sulfided prior to use. Operating conditions in both stages were 2250 psig, 0.75 Ll-lSV, and a recycle hydrogen gas rate of 8000 standard cubic feet per barrel of total feed. Reaction temperatures were adjusted to obtain 40 and percent conversion per pass respectively in the first and second stages. Separate hydrogen recycle systems were used for each stage.
The first hydrotreating-hydrocracking stage product was flashed and scrubbed to recover a hydrogen recycle stream and to remove ammonia and hydrogen sulfide. The liquid hydrocarbon phase was then fractionated to recover products boiling below 550F. Higher boiling hydrocarbons were passed to the second stage wherein they were hydrocracked over the above described catalyst.
The second stage product was flashed to recover a hydrogen recycle stream. The liquid hydrocarbon phase was recycled to the fractionation zone to recover products boiling below 550F. Thus the higher boiling products were recycled to extinction.
Under these conditions the feed to the second stage contained less than 1 ppm nitrogen and approximately 1 ppm sulfur. Temperatures of 738F firststage and 604F second stage were required to maintain the designated conversion rates. The yield of turbine fuel products fraction boiling between 300 and 550F was 65.5 percent based on fresh feed.
EXAMPLE 5 The operation of Example 4 was repeated under identical conditions with the exception that an amount of tertiary butylamine corresponding to 42 ppm nitrogen was added to the second stage recycle stream. During this operation a first stage temperature of 738F and a second stage temperature of 693F were required to maintain the respective conversion levels. The yield of turbine fuel products increased to 68.7 percent based on fresh feed. 7
We claim: 1
l. The method of producing midbarrel fuels boiling above about 300F and below a predetermined product end point below about 700F from hydrocarbons boiling above said end point wherein said hydrocarbons contain less than about 20 ppm nitrogen including the steps of reacting said hydrocarbons with hydrogen in the presence of added nitrogen compounds introduced as ammonia or hydrocarbon amines having less than 15 carbon atoms per molecule in amounts corresponding to about to about 1.00 ppm total nitrogenbased on said hydrocarbons under hydrocracking conditions including a temperature of at least about 500F, a pressure of at least about 200 psig and a hydrogen addition rate of at least about 400 standard cubic feet per barrel of said hydrocarbons sufficient to convert at least about 30 volume percent of said hydrocarbons per pass to products boiling below said end point with at least about 50 percent selectivityto said midbarrel fuels in the presence of a hydrocracking catalyst comprising a refractory inorganic oxide and a catalytic amount of molybdenum, tungsten, iron, nickel or cobalt metals, oxides or sulfides.
2. The method of claim 1 wherein said hydrocarbons boil above about 700F and are reacted in the presence of said hydrogen added at a rate of about 2000 to about 15,000 standard cubic feet per barrel of said hydrocarbons at a temperature between about 600 and about 900F, a pressure of about 500 to about 3,000 psig and a liquid hourly space velocity less than about 15 sufficient to convert at least about 50 percent of said hydrocarbons per pass to products-boiling below about 700F with a selectivity of at least about 60 percent to products boiling between about 300 and about 700F.
-3. The method of claim 2 wherein said catalyst comprises at least about 5 weight percent of at least one of molybdenum and tungsten sulfides, said refractory oxide comprises a catalytic amount below about 30 weight percent of a crystalline aluminosilicate zeolite, said feed contains less than ppm organonitrogen and is reacted with said hydrogen in the presence of said catalyst under conditions sufficient to convert said hydrocarbons with at least about 60 percent selectivity to midbarrel fuels boiling between about 400 and about 700F.
4. The method of claim 1 wherein said refractory oxide contains less than about 10 weight percent of a crystalline zeolite and comprises at least about 50 weight percent amorphous alumina, said hydrogenation component comprises the sulfides of molybdenum, tungsten, nickel or cobalt, and said hydrocarbons reacted with said hydrogen in the presence of said added nitrogen compound contain less than about 100 ppm sulfur as organic sulfur compounds.
5. The method of claim 1 wherein said hydrocarbons are obtained by reacting a hydrocarbon feed containing hydrocarbons boiling above said end point and more than about ppm nitrogen with added hydrogen under denitrogenation and hydrocracking conditions to convert a portion of said feed to products boiling below said end point and reduce the organonitrogen content of said feed to a level below about 10 ppm, and separating the anunonia produced in the hydroconversion of said organonitrogen compounds from saidhydrocarbons thereby producing said hydrocarbons boiling above said end point and containing less than about 10 ppm nitrogen.
6. The method of producing midbarrel fuels boiling above about 300F and below a predetermined product endpoint from hydrocarbons boiling above said end point and containing less than about 10 ppm organic nitrogen including the steps of reacting said hydrocarbons with hydrogen added in amounts of at least about 400 standard cubic feet per barrel of said hydrocarbons under hydrocracking conditions including a temperature of at least about 500F, a pressure of at least about 200 psig and a liquid hourly space velocity below about 15 sufficient to convert at least about 30 volume percent of said hydrocarbons per pass to products boiling below said end point with at least about 50 percent selectivity to said midbarrel fuels, the improvement comprising controlling the selectivity of conversion to said midbarrel fuels and/or said lower boiling hydrocarbons by adding to said hydrocracking zone an amount of a nitrogen containing compound selected from ammonia and hydrocarbon amines containing less than about 15 carbon atoms corresponding to about 5 to about 100 ppm nitrogen based on reactor feed.
7. The method of claim 6 wherein said nitrogen containing compound is selected from ammonia and alkyl amines containing less. than 12 carbon atoms, said hydrocarbons are reacted with said hydrogen added at a rate of about 2000 to about 15,000 standard cubic feet per barrel of said hydrocarbons at a temperature between about 600 and about 900F and a pressure of about 500 to about 3000 psig, and said catalyst com- 4 prises a hydrogenation active amount of at least one of molybdenum, tungsten, nickel and cobalt sulfides combined with a forarninous refractory oxide support.
8. The method of claim 7 wherein said catalyst comprises at least about 1 weight percent nickel or cobalt sulfide and at least about 5 weight percent molybdenum or tungsten sulfide, said refractory oxide comprises at least about 50 weight percent amorphous alumina, and said hydrocarbons contain less than about 100 ppm organic sulfur.