US 3712861 A
Description (OCR text may contain errors)
United States Patent US. Cl. 208-416 3 Claims ABSTRACT OF THE DISCLOSURE Upgrading of hydrocarbons containing sulfur and metal contaminants is effected with a catalyst containing 0.5-20 wt. percent metal sulfides dispersed in an alumina. The metal sulfides may include one or more metals of Groups VI and V111, such as molybdenum sulfide. The catalyst is characterized with an average pore diameter of about 278 angstroms and a surface area of about 60-65 m. gm.
CROSS REFERENCE This is a continuation-in-part application of application Ser. No. 20,028, filed Mar. 16, 1970, now abandoned.
BACKGROUND OF THE INVENTION Hydrodesulfurization of hydrocarbon oil fractions has been long used and is a highly developed art insofar as the catalyst temperature, pressures and other process variables are concerned. Catalysts employed for the hydrodesulfurization of oils tend to become deactivated and fouled by hydrocarbonaceous deposits along with other impurities encountered in the charge stock and the extent and rapidity of fouling depends in large part upon the source and boiling range of the charge being treated.
Crude petroleum oils, topped crudes, heavy residuums, other heavy hydrocarbon fractions and/or distillates obtained therefrom, depending upon the source of the crude, contain varying amounts of non-metallic and metallic impurities. By non-metallic impurities it is intended to include nitrogen, sulfur and oxygen which exist in various compounds and are often in relatively large quantities. By metallic impurities we intend to include iron, nickel and vanadium as the most common metallic contaminant or impurity although other metals including copper, zinc and sodium are often found in the different hydrocarbon fractions in Widely varying amounts. The metals may occur in several different forms such as metal oxides or sulfides which are easily removed by single processing techniques such as by filtration and water washing. However, the metal contaminants occur as relatively thermally stable metallo-organic complexes such as metal porphyrins and derivatives thereof along with complexes which are not completely identifiable. It has been found, however, that most of the metallo-organic complexes are associated with the asphaltenes and, therefore, become concentrated in residual fractions. Some metallo-organic complexes are volatile and, therefore, will be carried over in distillate fractions rather than remain With the bottom product. The asphaltenes are generally considered to be non-distillable, high molecular weight coke precursors containing nitrogen, sulfur, oxygen and metal contaminants which, when subject to heat, will coagulate and/or polymerize and become difficult to handle for further treatments.
The presence of sulfur and metal contaminants in the higher boiling fractions of petroleum hydrocarbons as 3,712,861 Patented Jan. 23, 1973 mentioned above is known to result in undesirable effects such as corrosion, pollution or poisoning of conversion catalysts. Also metal contaminants found in, for example, coker charge stocks concentrate in the coke product therefrom. To obtain clean stocks that can be further treated without significantly affecting the life of subsequent catalysts in the processing and to decrease the effects of corrosion and pollution, efficient and economic removal of these undesired metallic and non-metallic contaminants from the hydrocarbon charge stocks is of significant importance.
In the past, high molecular weight stocks containing sulfur, nitrogen and metals have often been processed in a coker to effectively remove metals and also some of the sulfur and nitrogen. However, there are limits to the amount of metals and sulfur that. can be tolerated in the product coke if it is to be saleable. Hence, there is a considerable need to develop economical as well as efficient means for effecting the removal and recovery of metallic and non-metallic contaminants from various fractions of petroleum oils so that conversion of such contaminated charges to more desirable product may be effectively accomplished. The present application is particularly concerned with the removal of metal contaminants from hydrocarbon materials contaminated with the same.
THE INVENTION The present invention is directed to a method for removing metallic impurities encountered in hydrocarbon charge stocks to an acceptable and desired level before further treating the charge stocks to effect upgrading thereof to desired products. More particularly, the present invention is based on the concept that the removal of metallic impurities is enhanced under hydrogenating conditions and besteffected in the presence of particular porous solid contact materials having some initial hydrogenation activity and maintained at operating conditions most suitable for effecting the removal of metals as distinguished from those conditions most effective for hydrogenative removal of sulfur and nitrogen compounds also found in the hydrocarbon charge. The invention thus includes the concept that the removal of metals, sulfur and nitrogen contaminants is each most efficiently effected within particularly selected temperature and pressure conditions. Sulfur and nitrogen contaminates are more completely removed from the charge after it has been reduced in metals to a desired low level with a porous solid adsorbent which inherently contains or is provided with some initial hydrogenation activity in combination with some cracking activity.
The method and concept of the present invention relates to contacting a metals contaminated hydrocarbon charge material with a relatively large pore adsorbent material having an average pore diameter of at least about and preferably greater than about angstroms having from about 0.5 up to about 20 wt. percent of one or more metal components selected from Groups VI and VIII of the Periodic Table providing hydrogenating activity therein. The adsorbent materials employed in the method of this invention preferably will have an average pore diameter greater than 100 angstroms. Thus the surface area of the demetallizing particulate material preferably will be less than about 100 mF/g. so that the pore diameter will be at least :80 angstroms and more preferably less than about 65 mF/g. so that the pore diameter will be at least about 123 angstroms. The porous support material may be one having little acid activity such as provided by an alumina base calcined at high temperature and containing up to about 10 percent weight silica. On the other hand, the porous support material used, as above discussed, may have cracking activity based on CAT-A activity which is at least about to or higher. In any event the support material is preferably a large pore composition comprising alumina in an amount of at least about by weight which is provided with hydrogenation activity by one or more sulfided elements and combinations thereof selected from Group VI-B and Group VII of the Periodic Table. The alumina containing porous particulate material will be provided with an initial hydrogenation activity amounting up to about 10 but more usually it will initially be in the range of from about 0.2 up to about 8.
One method of measuring hydrogenation activity of a catalyst is described by Myers et al., Journal of Chemical and Engineering Data, volume 7, page 258, 1962. It may be defined as the weight percent conversion of benzene to hydrogenated products over the catalyst at 1050 p.s.i.g., using a space velocity of 2 vol./hr./vol. at a temperature of 700 F. and 4000 s.c.f. of hydrogen charge per barrel of hydrocarbon charge.
It was also found that a relationship exists between pressure and hydrogenation activity; the lower the hydrogenation activity, the higher the pressure one must use to effect desired metals removal. On the other hand, since the demetallizing catalyst is expendable due to metals accumulation, it is also desirable for economic reasons to keep the cost and therefore, the hydrogenation component level as low as possible consistent with maintaining reasonable pressure operating conditions. Reasonable pressure operating conditions are those falling below about 3000 p.s.i.g. and preferably those falling below about 2500 p.s.i.g.
The hydrocarbon charge reduced in metal contaminates to an acceptable level by the hydrogenation operation herein described may thereafter be subjected to further treatment such as catalytic conversion reactions and/or desulfurization and denitrogenation reactions in the presence of catalyst compositions particularly suitable for that purpose. Thus the hydrocarbon charge may be subjected to one or more stages of hydrogenation for effecting desulfurization and denitrogenation. Desulfurized and denitrogenated hydrocarbon charge may then be upgraded by catalytic or hydrocracking reactions effected in the presence of crystalline alumino-silicate containing catalyst compositions.
The method of the present invention preferably includes at least a two stage hydrogenation operation wherein the predominate reaction of metals removal is effected in an initial catalyst contact zone under substantially liquid phase processing conditions employing relatively mild hydrogenation conditions but sufficiently severe to remove and detach metals bound in the metallo-organic complexes. The detached metals are deposited upon and within the pores of the catalytic adsorbent selected for that purpose. In a second or subsequent hydrogenation stage, the reactions are predominantly those of desulfurization and/or denitrogenation. These reactions may be effected at the same or more severe hydrogenating reaction conditions than those employed in the metals removal step. The separate hydrogenation steps may be accompanied by some cracking of the hydrocarbon charge so as to produce lower boiling products including gasoline, kerosine and other lighter fuel oil products.
The method of the present invention is suitable for treating many different hydrocarbon fractions varying considerably in composition as well as boiling range. For example, full boiling range crudes, topped crude oils and distillates therefrom, atmospheric distillates, cycle oils, light and heaw vacuum gas oil, coker gas oils and heavy residuums. Thus the processing combination of this invention is particularly suitable for processing substantially any hydrocarbon charge stock containing undesirable concentrations of metallic and non-metallic impurities.
The hydrogenation operations herein contemplated are often effected in the liquid phase and at least in a partially liquid phase condition. In such operations, the catalyst particles are dispersed in the liquid in relatively large amounts so that it resembles a dense fluid mass of solid particulate material suspended in the liquid material. The technique of causing random movement of the particles by the upward flow of liquid has been identified with the prior art as ebullation. Although it is preferred in this embodiment to effect the demetallizing of the hydrocarbon feed in a liquid phase operation, demetallizing of the feed may also be accomplished in a dense fluid bed of catalyst particles, a moving bed operation or other convenient means for effecting the hydrogenation reactions desired and permit replacement of the solid particulate material essentially as required.
A desulfurization catalyst suitable for use in the method of the present invention is broadly characterized as any hydrogenation catalyst which is tolerant of sulfur and nitrogen and which can be employed in an operating cycle or onstream life that is economically attractive. Thus the desulfurization and/or denitrogenation catalyst may be any one of those known and used for such purposes in the prior art. Prominent catalysts used for this purpose include cobalt molybdate on alumina with or without small amounts of silica, nickel molybdate on alumina with or without small amounts of silica, nickel sulfide, tungsten sulfide, nickel-tungsten sulfide alone or on a support material such as alumina which may or may not contain small amounts of combined silica. Other known desulfurization catalysts may also be employed.
The demetallizing compositions discussed below are considered commercially attractive for use in reducing the metal content of hydrocarbon materials such as, for example, heavy residuum to a level below about 50 p.p.m. and preferably to a residual metals level not exceeding about 20 or 30 p.p.m. of metals.
A particularly suitable particulate material for demetallizing is one which has pores sufiiciently large to permit relatively unrestricted movement of the metal complex molecule in and out of the pore as well as decomposition products thereof after deposition of released metal. Solid porous particulate materials which may be used with varying degrees of success for this purpose include relatively large pore silica alumina and silica-magnesia type compositions of little cracking activity, activated carbon, charcoal, petroleum coke, and particularly large pore aluminas or high alumina ores and clays.
Clay supports of particular interest are those known as dickite, halloysite and kaolinite. On the other hand, ores fitting the herein provided physical properties either as existing in their natural or original form or employed with alumina binders or after chemical treatment thereof may also be used as porous support materials in combination with the desired hydrogenation activity herein discussed. By chemical treatment we intend to include acid or caustic treatment as well as treatment with aqueous solutions like sodium aluminate and alumina sulfate containing alumina to increase the alumina content of the support. In addition to the above defined limits it is preferred that the support and/or final catalyst composition have certain minimum physical properties. In this regard it is preferred that the demetallizing porous compositions have a minimum surface area of about 10 m. /g. in combination with a minimum pore volume of about 0.2 cc./ g. and a minimum pore diameter of angstroms.
As mentioned hereinbefore the demetallizing solid adsorbent particulate material is required to have some initial hydrogenation activity and this hydrogenation activity is preferably supplied by one or more hydrogenation components dispersed throughout the large pore material. The hydrogenation metal component of the demetallizing catalyst is preferably selected from the class of metals comprising cobalt, nickel, copper, molybdenum, tungsten and iron and combinations thereof. The demetallizing catalyst eventually becomes contaminated by metal deposits of nickel, vanadium, iron and copper and thus will eventua ly be regenerated for reuse or discarded from the process when the metals level exceeds an undesired limit for economically effecting further metals removal.
The operating conditions of temperature, pressure and space velocity employed in the demetallizing zone are interrelated as a function of the catalyst hydrogenation activity and are thus selected so that the demetallizing conditions are most suitable for particularly effecting release of the combined metal from the metallo-organic complexes. The demetallizing pressure conditions are intfluenced by the hydrogenation activity of the demetallizing catalyst and can vary considerably depending upon the catalyst employed and feed treated. Thus there is an economic balance between cost of providing hydrogenation activity to the catalyst and operating pressure investment costs. Generally it is preferred to employ pressure operating conditions below 3000 p.s.i.g. and more usually below 2500 p.s.i.g. since such conditions are more attractive economically. However, it is contemplated and it may be particularly desirable to operate the demetallizing step at the higher pressures so that the hydrocarbon eflluent thereof can be cascaded therefrom to another lower pressure catalyst contacting step. The temperature conditions selected for use in the demetallizing zone and the desulfurization zone are also greatly influenced by the hydrogenation activity of the solid contact material or catalyst and will usually be selected from within the range of from about 600 to about 950 F. but preferably the temperature is maintained below about 900 F. for the demetallizing step. The space velocity conditions employed in the demetallizing contact zone will be selected from within the range of about 0.2 to about LHSV.
In a particularly preferred embodiment of the present invention, the operating conditions are selected to provide pressure conditions during demetallization which do not exceed desulfun'zation conditions by any significant magnitude. Generally the desulfurization conditions will be in excess of 500 p.s.i.g. and may be as high as 1000, 1500 or even 3000 p.s.i.g.
To demonstrate the method and concept of the present invention for effecting demetallization of a hydrocarbon charge material containing such impurities, the following specific examples are provided. However, it is to be understood that the invention is not to be unduly restricted by virtue of the specific examples hereinafter presented.
Reference is now had to the examples presented below.
Example 1 A sample of aAl O .H O aluminais first pelleted into particles having inch diameters, and then is calcined. The calcination is done at a heat up rate l C. per minute in the presence of moist air at atmospheric pressure to a temperature of 1050 C. for 2 hours. During this thermal treatment the alumina phase is transformed to theta phase having a surface area of about 60 mP/g.
100 grams sample of the above treated alumina particles is then impregnated with 43 ml. (volume necessary to fill pores) of ammonium molybdate solution containing 12.5 g. of M00 Following the impregnation step the catalyst is air dried at 90-150" C. and recalcined in air at 500 C. prior to use. The catalyst thus prepared is sulfided to provide a catalyst composition comprising molybdenum sulfide dispersed in an alumina composition having the characteristics identified below.
Composition, wt. percent M00 11.1 Pore diameter, angstroms 2718 Pore volume, cc./g. 0.431 Density, particles 1.41 Surface area, m. /g. 62
Example 2 An alternate approach to the above catalyst is to start with a beta alumina trihydrate containing no alkali and heat to 800-1000 C. at 1 C. perminute in dryair at atmospheric pressure for about 2 hours. This treatment is sufficient to obtain the desired theta alumina phase having a surface area of about 60 m /g. Subsequent impregnation and calcination is the same as described above.
Sources of starting hydrated alumina used as above examples are many. These can be obtained either from commercial sources or through various synthesis schemes. An example of one of these methods is illustrated in Pat. No. 3,003,952.
The present invention contemplates the use of a solid particulate material provided with relatively low initial hydrogenation activity which will be suitable for promoting demetallization of the hydrocarbon charge. Thus the solid particulate material is preferably a material that will adsorb relatively large amounts of metal contaminants dislodged from the hydrocarbon feed. Thereafter, the hydrocarbon feed reduced in metals content to a desired lower level may be further converted such as by contact with a desulfurization catalyst.
The following data present the results obtained employing a molybdenum sulfide on alumina catalyst as defined in Example 1 above.
TABLE 1 Demetallization and Desulfurization of Kuwait Short Residuum 2500 p.s.i.g., 1 LHSV, 4-5000 s.c.f. of H charge/bbl. residuum Catalyst:
Composition, wt. percent: b
SiO Apparent density, gm./cc. 1.06 Surface area, m ./gm. 62
Pore volume, cc./gm. r 02431 colgaining 4.97 wt. percent S, 29 p.p.m. N1 and p.p.m.
b Balance of composition is A1203.
0 40,000Xpore volume/surface area.
Wt. percent conversion of benzene to hydrogenated products at 1050 p.s.i.g., 2 LHSV, 700 F. and 400 s.c.f. of hydrogen charge/bbl. of benzene.
The metallo-organic complexes decomposed in the presence of the porous particle-form material defined herein and having hydrogenation activity have a combination of constituents comprising nickel, vanadium, copper and sometimes iron depending upon the source of the crude deposited with the porous particle material. Thus it is important to employ a porous material that has an average pore. size suificiently large to accept relatively large amounts of metal deposits. The method of the present invention contemplates that metal deposit may be recovered from at least the support material employed in the demetallizing step. Such metals recovery is known in the prior art as metal winning and substantially any procedure may be adopted which will permit the eflicient and economical recovery of the metals as separate constituents. One advantage of using a porous carbonaceous material as adsorbent for metals released from the hydrocarbon charge is attributable to the ease of recovering the metals therefrom.
Having thus provided a general description of the invention and presented specific examples in support thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof except as defined by the claims.
1. In a process for upgrading a hydrocarbon fraction comprising sulfur and metal contaminants, the improvement which comprises hydrogenating said hydrocarbon fraction at a temperature in the range of 600 to 950 F. under elevated pressure condition by contact with a catalyst comprising from 0.5 to 20 wt. percent of one or more metal sulfides selected from Groups VI and VIII of the Periodic Table dispersed in an alumina, said catalyst providing an average pore diameter of about 278 angstroms and a surface area of about 60 to 65 mfi/gm.
2. The process of claim 1 wherein the catalyst comprises molybdenum sulfide dispersed in an alumina, said catalyst providing 62 rnfi/gm. surface area having a pore volume of 0.43 cc./gm.
3. The process of claim 2 wherein hydrogenation of the charge is effected at 800 F. using a pressure of 2500 p.s.i.g.
References Cited UNITED STATES PATENTS 2,902,429 9/1959 Scott 208-253 3,530,066 9/1970 Kuwata et a1. 208--216 3,393,148 7/1968 Bertolacini et a1. 208-216 DELBERT E. GANTZ, Primary Examiner G. J. CRASANAKIS, Assistant Examiner US. Cl. X.R.