US3122510A

US3122510A - Method of removing nickel and vanadium from synthetic gel silica-based catalysts

Info

Publication number: US3122510A
Application number: US54405A
Authority: US
Inventors: Jr Emmett H Burk; Erickson Henry; Arvin D Anderson
Original assignee: Sinclair Research Inc
Current assignee: Sinclair Research Inc
Priority date: 1960-09-07
Filing date: 1960-09-07
Publication date: 1964-02-25
Anticipated expiration: 1981-02-25

Description

E. H. BURK, JR., METHOD OF REMOVING NICKEL A SYNTHETIC G Feb. 25, 1964 ETAL ND VANADI UM FROM EL. SILICA-BASED CATALYSTS Filed Sept. 7, 1960 mwT INVENIORS HENRY ERICKSON EMMETT H. BURK JRv ARVIN D. ANDERSON BY @4144 ATTORNEYS United States Patent METHOD OF REMOVDIG NICKEL AND VANADI- UM FROM SYNTHE'HO GEL SElCA-BASED CATALYSTS Emmett H. Burk, Jr., Hazel Crest, and Henry Erickson, Park Forest, 111., and Arvin D. Anderson, Anaheim, Calif, assignors, by mesne assignments, to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware ra a Sept. 7, i969, Ser. No. 54,495 16 Claims. or. 252-413 This invention concerns a process for the removal from solid oxide hydrocarbon conversion catalysts of metals, e.g. Ni, V and Fe, which poison the catalytic activity of the catalysts. The method includes vapor phase chlorination of the catalyst to provide or remove the poisoning metals in the chloride form, and a wash with a liquid aqueous medium to remove poisoning metal constituents. This application is a continuation-in-part of our copending application Serial No. 849,199, filed October 28, 1959, and now abandoned.

Catalytically promoted methods for the chemical conversion of hydrocarbons include cracking, hydrocracking, reforming, hydroforming, coking, deasphalting, etc. Such reactions generally are performed at elevated temperatures, for example, about 300 to 1200 F., more often 600 to 1000 F. Peedstocks to these processes comprise normally liquid and solid hydrocarbons which at the temperature of the conversion reaction are generally in the fluid, i.e. liquid or vapor, state and the products of the conversion frequently are lower boiling materials.

In particular, cracking of heavier hydrocarbon feedstocks to produce hydrocarbons of preferred octane rating boiling in the gasoline range is widely practiced and uses a variety of solid oxide catalysts to give end products of fairly uniform composition. Cracking is ordinarily efiected to produce gasoline as the most valuable product and is generally conducted at temperatures of about 750 to 1100 F., preferably about 850 to 950 *1, at pressures up to about 2000 p.s.i.g., preferably about atmospheric to 100 p.s.i.g., and without substantial addition of free hydrogen to the system. In cracking, the feedstock is usually a mineral oil or petroleum hydrocarbon fraction such as straight run or recycle gas oils or other normally liquid hydrocarbons boiling above the gasoline range.

In this invention, the hydrocarbon petroleum oils utilized as feedstock for a conversion process may be of any desired type normally utilized in catalytic conversion operations. This feedstock contains one or both of vanadium and nickel metal contaminants and usually iron and the catalyst may be used as a fixed, moving or fluidized bed or may be in a more dispersed state. In the conversion system, the catalyst may be regenerated by contact with oxygen-containing gas intermittently or continuously as desired in order to restore or maintain the activity of the catalyst by removing carbon. F or typical operations, the catalytic cracking of the hydrocarbon feed would normally result in a conversion of about 50-6O percent of the fedstock into a product boiling in the gasoline boiling range.

One of the most important phases of study in the improvement of catalyst performance in hydrocarbon con 3,lZZ,5lfi Ce Patented Feb. 25, 1964 version is in the area of metals poisoning. Various petroleurn stocks have been known to contain at least traces of many metals. In addition to metals naturally present, including some iron, petroleum stocks have a tendency to pick up tramp iron from transportation, storage and processing equipment. Most of these metals, when present in a stock, deposit as a non-volatile compound on the catalyst during the conversion processes so that regeneration of the catalyst to remove coke does not remove these contaminants. Although referred to as metals, the contaminants may be in the form of free metals or non-volatile metal compounds. It is to be understood that the term metal used herein refers to either form.

Of the various metals which are to be found in representative hydrocarbon feedstocks some, like the alkali metals, only deactivate the catalyst without changing the product distribution; therefore they might be considered true poisons. Others such as iron, nickel, vanadium, and copper markedly alter the character and pattern of cracking reactions, generally producing a higher yield of coke and hydrogen at the expense of desired products, such as gasoline and butanes. For instance, it has been shown that the yield of gasoline, based on cracking feed disappearance to lighter materials dropped from 93 to 82% when the laboratory-measured coke factor of a catalyst rose from 1.0 to 3.0 in commercial cracking of a feedstock containing some highly contaminated marginal stocks. This decreased gasoline yield was matched by an increase in gas as well as coke. If a poison is broadly defined as anything that deactivates or alters the reactions promoted by a catalyst then all of the four metals mentioned above can be considered poisons. It is bypothesized that when deposited on the surface of a catalysts, Fe, Ni, V and Cu superimpose their dehydrogenation activity on the desired reactions and convert into carbonaceous residue and gas some of the material that would ordinarily go into more valuable products. The relatively high content of hydrogen in the gases formed by metals-contaminated catalysts is evidence that dehydrogenation is being favored. This unwanted activity is especially great when nickel and vanadium are present in the feedstocks. 1

Metal poisoning of cracking catalysts is a major cost item in present day refining and is a bottleneck in upgrading residual stocks. Current methods of combatting metal poisoning are careful preparation of feedstocks to keep the metals content low and catalyst replacement to control metals levels on the catalyst. An alternate solution, demetallizing the catalyst, which would avoid discarding of expensive catalyst, and enable much lower grade, highly metals-contaminated feedstocks to be used, is now made possible by the present invention.

Solid oxide catalysts, both naturally-occurring activated clays and synthetically prepared gel catalysts, as well as mixtures of the two types, have long been recognized as useful in catalytically promoting conversion of hydrocarbons. A popular natural catalyst is Filtrol which is acid-activated montmorillonite. Active synthetic catalysts are generally gels or gelatinous precipitates and include alumina-based as well as silica-based materials. For cracking processes, the catalysts which have received the widest acceptance today are usually activated or calcined predominantly silica or silica-based compositions in a state of very slight hydration and containing acidic oxide promoters in many instances. Such materials include silica-alumina, silica-zirconia, etc. as well as ternary combinations such as silica-alumina-zirconia, etc. Ordinarily, this type of catalyst contains silica and at least one other material, such as alumina, zirconia, etc. These oxides may also contain small amounts of other materials, but current practice in catalytic cracking leans more toward the exclusion of foreign materials from the silica hydrate materials. The presence of foreign materials, such as alkaline salts, in the catalyst may cause sintering of the catalyst surface on regeneration to remove coke, and a drop in catalytic activity. For this reason, the use of synthetic catalysts, which are more uniform and less damaged by high temperatures in treatment and regeneration, is often preferable. Popular synthetic gel cracking catalysts generally contain about to 30% alumina. Two such catalysts are Aerocat which contains about 13% A1 0 and High Alumina 'Nalcat which contains about 25% A1 0 with substantially the balance being silica. The catalyst may be a semi-synthetic material such as made by precipitation of silica-alumina on a kaolinite or halloysite or an activated clay. One example of such catalysts contains about equal amounts of silica-alumina and clay.

The production of synthetic catalyst-s can be performed, for instance, (1) by impregnating silica with alum num salts; (2) by direct combination of precipitated (or gelated) hydrated alumina and silica in appropriate proportions; or (3) by joint precipitation of alumina and silica from an aqueous solution of aluminum and silicon salts. Synthetic catalysts may be produced by the combination of hydrated silica with other hydrate bases, as, for in stance, zirconia, etc. These synthetic gel type catalysts are activated or calcined before use.

Commercially used cracking catalysts are the result of years of study and research into the nature of cracking catalysis, and the cost of these catalysts is not negligible. The cost frequently makes highly poisoned feedstocks less desirable to use in cracking operations, even though they may be in plentiful supply, because of their tend ency to damage the expensive catalysts. The expense of such catalysts, however, is justified because the composition, structure, porosity and other characteristics of such catalysts are rigidly controlled so that they may 'give optimum results in cracking. It is important therefore, that removing poisoning metals from the catalyst does not jeopardize the desired chemical and physical constitution of the catalyst. Although methods have been suggested in the past for removing poisoning metals from a catalyst which has been used for high temperature hydrocarbon conversions, for example, the processes Of US. Patents 2,481,253; 2,488,718; 2,488,744; 2,668,798; and 2,693,455; the process of this invention is effective to remove poisoning metals without endangering the expensive catalyst.

' This invention makes use of chlorination at a moderate temperature up to about 700 F. or even up to about 900 or 1000 F., wherein the catalyst composition and structure is not unduly harmed by the treatment and a substantial amount of the poisoning metal content is converted to chlorides. The process of this invention is amenable to several modifications to cope with several discrete problems in the demetallization of catalysts which have become poisoned by use in the high temperature conversion of metals-contaminated feedstocks. For example, the chlorination may be preceded by a high tem perature treatment of a regenerated catalyst with molecular oxygen-containing gas to improved vanadium removal, and/or by sulfiding the poisoning metals to improve the removal of nickel and perhaps other metal poisons in subsequent steps; the treatment with the chlorinating agent may be followed by treatment with an inert vapor to enhance volatilization of the iron and vanadium chlorides formed. The chlorination is followed by a liquid aqueous wash for the removal of poisoning metal-s especially nickel. When only nickel is to be removed chlorination at only a slightly elevated temperature followed by a water wash will generally be found satisfactory.

The amount of Ni, V or Fe removed by the process of the invention or the proportions of each which are removed may be varied by proper choice of treating conditions. It may prove necessary, in the case of very severely poisoned catalysts, to repeat one or more modifications of the treatment to reduce the metals to an acceptable level and to give the catalyst an activity profile more comparable to that of a virgin, unpoisoned catalyst. When the chlorination is to be repeated a thermal or steam-treating step may be performed on the catalyst to redistribute poisons in the matrix and thereby make further quantities of metals accessible to chlorination. A significant advantage of the process lies in the fact that the overall metals removal operation, even if repeated, does not unduly deleteriously affect the activity, selectivity, porosity, and other desirable characteristics of the catalyst. Ordinarily the catalysts are treated before the poisoning metals have reached an undesirably high level, for instance, about 2%, generally no more than about 1% maximum, content of one or both of nickel and vanadium calculated as their common oxides. Before treatment is usually warranted the catalyst will have at least about 25-50 p.p.m. of nickel oxide and/ or about 250-500 p.p.m. vanadia. Also, the catalyst may contain similar amounts of iron oxide as it does vanadia.

The process of this invention includes removing a metal poisoned silica-based catalyst from contact with a metalscontaminated hydrocarbon feedstock in a conversion zone at elevated temperatures and reactivating the catalyst by treating it at moderately elevated temperatures, so as not to unduly alter the catalyst structure, to convert the poisoning metals to volatile or water-soluble chlorides by contact with a chlorinating agent, removing poisoning metals as by volatilization of their chlorides and by an aqueous wash and conducting the catalyst, with or without further processing, to a conversion process.

As pointed out, the chlorination takes place at a temperature up to about 1000 F., usually at least about 300 F. and preferably about 550 to 650 F., with opti mum results being obtained close to about 600 F. If the temperature of the chlorination is increased materially beyond 1000 F., increasing attack on the catalyst base is observed, that is, the percent demetallization will be increased slightly at the expense of a loss of catalyst components such as alumina. The chlorination, particularly when conducted in the lower temperature ranges, e.g. below about 550 'F., is effective for conversion to chlorides of the metal poisons, being rather complete in the case of nickel, and may be followed by a purge with an inert gas such as nitrogen or flue gas for instance at about 550 F. to 700 or 1000" F. to further volatilize.- tion and removal of chlorides such as ferric chloride, vanadium oxychloride and/or vanadium tetrachloride formed in the chlorination step.

The chlorinating reagent is essentially anhydrous, that is, if changed to the liquid state no separate aqueous phase would be observed in the reagent. Preferably the reagent is a vapor which contains a chlorination promoting compound of chlorine with carbon or sulfur. Such reagents include molecular chlorine but preferably are the chlorinesubstituted light hydrocarbons, such as carbon tetrachloride, which may be used as such or formed in situ by the use of, for example, a vaporous mixture of chlorine 'gas with low molecular weight hydrocarbons such as methane, n-pentane, etc. Also it has been found that a mixture of the carbon or sulfur chlorinating reagent with a gas, such as molecular chlorine or HCl which can supply additional chlorine, may be effective in reducing the amount of chlorinating reagent required for efiective conversion of iron and vanadium to their volatile chlorides. Molecular chlorine is considerably less expensive than carbon tetrachloride so that a gaseous mixture of the two is the preferred chlorinating reagent. The presence of molecular chlorine also seems to have the advantageous effect of keeping the iron and vanadium in their higher, more volatile valence states; that is, the iron is kept in the ferric state and the vanadium is maintained as vanadium oxytrichloride or vanadium tetrachloride. Ferrous chloride and vanadium trichloride are relatively non-volatile. Since either molecular chlorine or HCl alone has a relatively less efiect in chlorinating the catalysts, it is theorized that the presence of these auxiliary gases serves mainly to regenerate the carbon or sulfur chlorinating reagent in situ.

Work using thionyl chloride carried by nitrogen gas as the chlorinating reagent has been done with comparable results to those using CCII, In addition, sulfur monochlc-ride, with or without elemental chlorine, appears to be advantageous for use as a chlorinating reagent, sulfur monochloride being considerably less expensive than CCl Sulfur dichloride also shows advantageous properties, since it may be supplied as a liquid to the chlorination procedure and upon vaporization will give a mixture of sulfur monochloride and chlorine. Other chiorinating agents may be used such as sulfuryl chloride, mixtures of hydrogen sulfide and chlorine, ferric chloride for vanadium removal, etc.

The stoichiometric amount of chlorine required to convert iron, nickel and vanadium to their most highly chlorinated compounds is the minimum amount of chlorine ordinarily used and may be free chlorine, combined chlorine or a mixture of chlorine with the chlorine compound promoters described above. However, since the stoichiometric amount of chlorine frequently is in a neighborhood of only 0.00 1 g./g. of catalyst, a much larger amount of chlorine, say about 1-40 percent active chlorinating agent based on the Weight of the catalyst is used in the practice of the invention. The amount of chlorinating agent required is generally increased if any significant amount of water is present on the catalyst so that substantially anhydrous conditions preferably are maintained as regards the catalyst as Well as the chlorinating agent. The promoter is generally used in the amount of about 1-5 or percent or more, preferably about 2-3 percent, based on the weight or" the catalyst for good metals removal; however, even if less than this amount is used, a considerable improvement in metals conversion is obtained over that which is possible at the same temperature using chlorine alone. The amount of promoter may vary depending upon the manipulative aspects of the chlorination step, for example, a batch treatment may sometimes require more promoter than in a continuous treatment for the same degree of efl ectiveness and results. The chlorine and promoter may be supplied individually or as a mixture to a poisoned catalyst. Such a mixture may contain about 0.1 to 50 parts chlorine per part of promoter, preferably about 1-10 parts per part of promoter. A chlorinating gas comprising about 1-30 weight percent chlorine, based on the catalyst, together with one percent or more S Cl gives good results. Preferably, such a gas provides l-lO percent C1 and about 1.5 percent S Cl based on the catalyst. A saturated" mixture of l and CCl can be made by bubbling chlorine gas at room temperature through a vessel containing cCl such a mixture generally contains about 1 part CCl :5-l0 parts C1 Conveniently, a pressure of about 0-100 or more p.s.i.g., preferably about 0-15 p.s.i.g. may be maintained in chlorination.

r orination reaction proceeds to convert catalyticaily active iron, vanadium and nickel to their chlorides and perhaps also to remove the volatile chlorides. Usually the vanadium oxychloride and tetrachloride is vaporized prior to ferric chloride. in some cases, particularly when the chlorination is performed at a temperature too low to volatilize sufiicient of the chlorides and it is desired to remove iron and vanadium, the chlorination treatment may be followed, or interrupted, by a purge or" the catalyst with an inert gas, e.g. nitrogen, at a temperature of up to about 1600" F. to volatilize residual chlorides. The chlorination agent can contact the catalyst until iron chloride is no longer evolved; this may take about 5 to minutes, more usually about 20-60 minutes but shorter or longer reaction periods may be possible or needed, for instance depending on the linear velocity of the chlorinating and purging vapors. A fluidized solids technique is recommended for these processes as a Way to shorten the time requirements. After the available catalytically active poisoning metal has been removed, further reaction time has relatively little efiect on the catalytic activity of the depoisoned catalyst, although further metals content may be removed by repeated or other treatments.

T 0 remove increased amounts of metal, especially nickel, from the catalyst, after chlorination and usually after vaporization of iron and vanadium chlorides the catalyst is washed in a liquid aqueous medium to remove metal, for instance nickel chloride, preferably after the catalyst is cooled to avoid the use of excessive pressures to maintain the liquid phase. The catalyst structure may be quite sensitive to EC} formed in the treatment, so that several precautions should be observed in the aqueous liquid Washing. A great excess of water can be used, for instance sufiicient to give a slurry containing only minor amounts of solids, say about 2-20%. Also, the catalyst should not be allowed to remain in this slurry for too long a time, ordinarily not more than 5 minutes; a residence time of 2-3 minutes in the original wash water is generally preferred.

The water used is generally distilled or deionized prior to contact with the chlorinated catalyst. However, the aqueous medium can contain extraneous ingredients in trace amounts, so long as the medium is essentially water and the extraneous ingredients do not interfere with dernetallization or adversely affect the properties of the catalyst. Temperatures of about F. to the boiling point of Water are helpful in increasing the solubility of the chloride. Temperatures above 212 F. and elevated pressures may be used but the results do not seem to justify the added equipment. Contact with the hot catalyst may be sufhcient to raise the temperature of the water from ambient temperature to around the boiling point. The aqueous liquid is preferably acid and a Weakly acid condition may be obtained by the chlorides generally present in a chlorinated catalyst which has not been purged too severely.

After the Wash the slurry can be filtered to give a filter cake which may be reslurried with more water or rinsed in other ways, such as, for example, by a Water wash on the filter, and the rinsing may be repeated, if desired, several times. The catalyst is then conducted to a conversion system, although it may be desirable first to dry the catalyst filter cake or filter cake slurry at say 250 to 50 F. and also prior to reusing the catalyst in the c onversion operation it can be calcined as in air, say at temperatures usually in the range of about 700 to 1300 F., conveniently by addition to the cracking unit catalyst regenerator. Prolonged treatment with an oxygen-containing gas at above about 1100" F. may sometimes be disadvantageous. Calcination removes free water, if any be present, and perhaps some but not all of the combined Water and leaves the catalyst in an active state Without undue sintering of its surface.

The silica-alumina conversion catalyst can be removed from contact with the hydrocarbon feedstock before the total nickel and vanadium content of the catalyst reaches about 10,000 ppm. Preferably, it is removed from the conversion system-that is, the stream of catalyst which in most conventional procedures is cycled between conversion and regenerating operationsbefore the poison content reaches about 5000 ppm, the poisoning metals being calculated as their common oxides. The catalys to be treated may be removed before, after, or during the conventional oxidation regeneration which serves to remove carbonaceous deposits. The demetallizing process of this invention is effective despite the presence of small amounts of carbon on the treated catalyst, but preferably the catalyst is drawn from the conversion system after at least partial regeneration, for instance when containing not more than about 5.0% carbon, advantageously not more than about 0.5%. After removing the catalyst from the conversion system, subjecting the poisoned catalyst sample to magnetic fiux may be found desirable to remove any tramp iron particles which may have become mixed with the catalyst.

The process of this invention produces significantly greater removal of vanadium when, upon removal of the vanadium-poisoned catalyst from the reactor, it is regenerated and given a treatment at elevated temperatures with molecular oxygen-containing gas before chlorination, see application Serial No. 19,313, filed April 1, 1960. This treatment serves for conversion of metals, especially vanadium, to higher Valence states. The contact with oxygen is performed at a temperature of about 1000 F. to 1600 F. or 1800 F. Little or no effect on vanadium removal is accomplished by treatment below about 1000 F., even for an extended time. The upper limit, to avoid catalyst damage, will usually be below about 1800" F. Preferably a temperature of about l1501350 F is used. The length of the treatment is long enough to convert a substantial amount of vanadium to a higher valence state as evidenced by a significant increase, say at least about 10%, preferably at least aboue 100% of the vanadium removed in subsequent stages of the process. If the catalyst contains any substantial amount of carbon at the beginning of the high temperature treatment with molecular oxygen-containing gas the essential contact time is reckoned from the point where the catalyst reaches a substantially carbon-free state. The oxygen-containing gas used in the treatment contains molecular oxygen as the essential active ingredient, and there is little significant consumption of oxygen in the treatment. The gas may be oxygen, or a mixture of oxygen with inert gas, such as air or oxygen-enriched air. The partial pressure of oxygen in the treating gas may range widely, for example, from about 0.1 to 30 atmospheres, but usually the total gas pressure will not exceed about 25 atmospheres. The factors of time, partial pressure and extent of vanadium conversion may be chosen with a view to the most economically feasible set of conditions. It is preferred to continue the oxygen treatment for at least about 15 to 30 minutes with a gas containing at least about 1%, preferably at least about 10% oxygen. The treatment is not prolonged to a point Where the catalyst will be damaged. The maximum practical time of treatment will vary from about 4 to 24 hours, depending on the type of equipment used.

As mentioned previously, a sulfiding treatment of the catalyst after removal from the cracking operation and before chlorination is quite advantageous especially to enhance nickel removal. For example, in many cases it has been found that only 5 to of the nickel oxide in the poisoned catalyst is removed without sulfiding. It is theorized that metals, especially Fe and Ni, present in poisoned catalysts may be largely in solid solution in the catalyst matrix. The metal ions being mobile in solution at elevated temperatures, it has been found possible to concentrate the metals at the catalyst surface by treatment With a sulfiding agent, such as hydrogen sulfide at elevated temperatures. The sulfiding agent converts the metal ions at the surface to metal sulfides which seem less soluble in the matrix. Diffusion of metal ions transports additional metal to the surface where it is in turn converted to the sulfide. Thus, a continuing process concentrates the metals as sulfides on the catalyst surface whence they are more readily susceptible to chlorination.

The sulfiding step can be performed by contacting the poisoned catalyst with elemental sulfur vapors, or more conveniently by contacting the poisoned catalyst with a volatile sulfide, such as H S, CS or a mercaptan. The contact with the sulfur-containing vapor can be performed at an elevated temperature generally in the range of about 500 to 1500 F., preferably about 800 to 1300 F. Other treating conditions can include a sulfur-containing vapor partial pressure of about 0.1 to 30 atmospheres or more, preferably about 05-25 atmospheres. Hydrogen sulfide is the preferred sulfiding agent. Pressures below atmospheric can be obtained either by using a partial vacuum or by diluting the vapor with gas such as nitrogen or hydrogen. The time of contact may vary on the basis of the temperature and pressure chosen and other factors such as the amount of metal to be removed. The sulfiding may run for instance, at least about 5 or 10 minutes up to about 20 hours or more depending on these conditions and the severity of the poisoning. Temperatures of about 900 to 1200" F. and pressures approximating 1 atmosphere or less seem near optimum for sulfiding and this treatment often continues for at least 1 or 2 hours but the time, of course, can depend upon the the manner of contacting the catalyst and sulfiding agent and the nature of the treating system, e.g. batch or continuous, as well as the rate of diffusion within the catalyst matrix.

If desired, after purging to remove volatile chlorides, the catalyst may be further reduced in poisoning metals content by exposing it to a further chlorination treatment. As before, when rechlorination is to be performed a preliminary sulfiding such as is described above, will again be found advantageous, apparently by obtaining surface concentration of metal sulfides through converting at least a substantial amount of one or more of the poisoning metals to sulfide form. Also, prior to rechlorination, with or without sulfiding, a heat treatment may be given the catalyst. Exemplary of such a treatment is contact of the catalyst with for instance an inert flue gas for about 6 hours at about 1150 F. The demetallization treatment apparently has a greater effect upon poisoning materials close to the surface of the catalyst, establishing a metals gradient across the radius of the catalyst particle, the matrix being relatively depleted of poisons near the surface and relatively unaffected near the center. The heat treatment apparently tends to eliminate this gradient by redistributing the poisons. Preferably the heat treatment is continued sufficiently long to approach a uniform concentration of the poisoning metals in the catalyst matrix.

In practice the process could be applied in a refinery by removing a portion of catalyst from the regenerator of the cracking system after a standard regeneration treatment to remove a good part of the carbon, heating this portion of the catalyst inventory in hydrogen sulfide or a hydrogen sulfide-inert gas mixture for one to three hours at temperatures approximating 900 F., displacing the hydrogen sulfide with a somewhat cooler inert gas and then chlorinating the catalyst. The frequency of treatment and the fraction of catalyst inventory treated will be dependent on the severity of the metal problem at the unit in question. The treated catalyst usually after calcination, can be returned to the unit as make-up catalyst, reducing greatly the new catalyst requirement. Any given step in the demetallization treatment is usually continued for a time sufiicient to efiect a substantial conversion or removal of poisoning metal and ultimately results in a substantial increase in metals removal compared with that which would have been removed if the particular step had not been performed. The actual time or extent of treating depends on various factors and is controlled by the operator according to the situation he faces, e.g. the extent of metals content in the feed, the level of conversion unit tolerance for poison, the sensitivity of the particular catalyst toward a particular phase of the demetallization procedure, etc.

9 DESCRIPTION OF APPARATUS The invention can be better understood by reference to the accompanying drawing which represents schematically a preferred system for performing this invention on a semi-continuous or batch basis.

In the drawing 19 represents the catalyst regenerator associated with a conventional hydrocarbon catalytic conversion system. The regenerator 10 is provided with a line 12, having a valve 13, for drawing ofl continuously or intermittently a fraction of poisoned catalyst from the regenerator. The catalyst is permitted to flow to the junction 14 and through the line 15 to the junction 16 where it may be conducted by a fluid, preferably air from the compressor 18 and pipe 2t), through the pipe 22, having the valve 24-, to the conduit 26. Conduit 26 allows the catalyst to fall by gravity into the cooler where the temperature of the catalyst is allowed to fall from the 900 to 1175" F. temperature of regeneration to the chlorination temperature of about 350 to 1000 F. After the catalyst has cooled sufficiently it is withdrawn from the cooler 28 by the pipe 313. A conveying fluid, once more preferably air from the compressor 18 and the line 32 conveys the catalyst through line 34 to the chicrinator 36.

The chlorinator is generally an elongated chamber made of Monel or other chlorine resistant material and may be provided with one or a plurality of internal grids 33, 4t 42 for gas distribution and break up of catalyst particle agglomerates. The chlorinating agent is brought to the chlorinator from the conduit 44 and heater 46. The heater is provided to give the agent the required temperature of chlorination. The chlorinating agent enters the heater 46 from the mixing conduit 43, having been pumped into this conduit by one or both of the

pumps

56 and 52 which lead from suitable sources of the components which make up the chlorinating agent; for example, pump 5% may be connected with a source of chlorine gas while pump 52 is connected to a source of carbon tetrachloride by line 53.

The drawing shows apparatus for recovering excess chlorinating agent from the chlorinator 36. In the recovery apparatus shown, which is exemplary of various systems which can be adopted for recovery of the various chlorinating agents mentioned above, the excess chlorination vapor is withdrawn from the chlorinator by the line 54 to the tank bottom 56 of recovery vessel 53. This vessel, which may be supplied with

beds

60 and 62 of inert solid contact material, may be supplied at the top with a reagent such as a strong caustic soda solution from the storage vessel 64, pump 66 and line 68. The vessel may also have a line '79 for water from the line 72 and pump 74, and for recycle fluid from the tank bottom 56 through pump 76 and line 78. This particular system, of course, is designed to neutraL'ze the waste chlorine and flush out the metallic chlorides resulting from the chlon'nation. The aqueous mixture of chlorides is drawn from the tank bottom through the line 30 to the settling tank 82. Carbon tetrachloride settles to the bottom of this tank from which it may be drawn by the line 34 and adsorptive dryers 86 and 83 to storage by the line 9% or to reuse in the chlorination by line 92 and pump 52. The aqueous part of the mixture from tank bottom 56 goes to the top of the settling tank 82 where it may be withdrawn by line 94 to Waste.

The chlorinated catalyst leaves the chlorinator 36 by conduit 96. The catalyst particles, freed of accessible iron and vanadium, pass through valve 98 to slurry tank 180 which is advantageously provided with stirrer 1&2. In the slurry tank the chlorinated catalyst is quickly stirred into a large volume of distilled or deionized water from the line 1&4 and pump 1%. This very dilute slurry is quickly removed from the slurry tank 106 by the line 1&8 and pump 11S and conveyed through line 112. Valve 114 may be adjusted to direct the catalyst slurry through line 116 whence it may be conveyed through the line 113, by a fluid, e.g. air, from the compressor 120 and line 122. The conduit 118 has the valve 124. The catalyst slurry passes to the conduit 126, junction 14 and conduit 128, which has the valve 135?, back to the regenerator It When demetallizing is to be conducted on a continuous basis, the junction 14 is arranged to conduct the streams of poisoned and treated catalyst free from contact with each other. Alternatively the valve may be closed, allowing the catalyst to flow from junction 14 through line 15 and back into any or all parts of the demetallizing system.

Alternatively, valve 114 may be adjusted to direct the catalyst slurry through line 132 to the filter 134 which may advantageously be a rotary vacuum drum filter. The cake of catalyst particles on the filter may be rinsed by distilled or deionized water from line 135 and pump 136, scraped from the filter by doctor blade 138 and fall through the path or conduit 140 into the reslurry tank 142 which advantageously is provided with a stirrer 144 and a line for distilled or deionized water 146. This catalyst slurry is drawn by line 14-8 and slurry pump 159 to the conduit 152 provided with the valve 154 from which the catalyst slurry may be returned to the regenerator by the line 118 as previously described. Alternatively, valve 154 may be closed, directing flow from slurry pump 15% into the conduit 156 and the dryer section 158 of the dryer-calciner 160.

In the dryer, the free water contained in the catalyst slurry is evaporated preferably by contact with fiue gases leaving the calcination section 162, and the water vapors are exhausted through line 164. The dryer may also be equipped with the cyclone separator arrangement 166 for removal of catalyst fines from the exhaust vapors. The catalyst particles flow out of dryer section 158 through the pipe 163 to the calcination section 162.. In the calcination section the catalyst may be raised to calcination temperature of about 900 to 1200 F. or more, advantageously by burning a fuel in the catalyst bed. Pump 179 and line 172 are provided to convey fuel or a fuelcombustion supporting gas mixture into the bed. Calcined catalyst from the bed is allowed to fall through the screen 174- to the line 176 whence it may be conducted to other parts of the apparatus previously described.

The illustration also shows a suitable arrangement for sulfiding the catalyst when this is to be performed before chlorination. When sulfiding is to be performed, valve 24 is closed so that the catalyst particles flowing to junction 16 are conveyed by the fluid from line 20 through the line having the valve 186 to an outer chamber 188 of sulfider 190.

The catalyst particles and the sulfider itself are raised to the sulfiding temperature of say about 1150 F. advantageously by burning a fuel in the bed of particles in this chamber. The fuel, with or without the addition of combustion supporting gas, may be supplied by line 192 and pump 1%, and the exhaust gas may be vented through line 1%. The heated catalyst particles may flow into the sulfiding chamber as through the opening 198. A sulfiding gas, e.g. H 8 or CS is passed to the bottom of the sulfider 19% by the line 200 from the pump 292. When the sulfiding gas is wet, passage to the line 200 may be through the adsorptive dryers 204 and 206. Exhaust sulfiding gas is passed out of the sulfider 198 through the line 203, advantageously to a burner 210. This burner may be provided with a line 212 and pump 214 for supplying combustion-supporting gas, and with a vent 216 to the atmosphere.

The apparatus used to perform the process of the invention may contain other valves, pressure control mechanisms, meters, etc., besides those shown, and the flow controllers may be automatically actuated in response to time, amount of flow, pressure, etc. The equipment illustrated is suitable for conducting the process of the invention and some of its auxiliary treatments by using fluidized beds of the catalyst in various operations. When fluidized manipulations are to be used, the various .1 1 gas or vapor treating systems shown may be provided with additional inlets and pumps for inert fluidizing gases, such as nitrogen, where the flow of gases described above is not sufficient for fluidization.

EXAMPLES The following examples are illustrative of the invention but should not be considered limiting. Analyses used were obtained by X-ray fluorescence.

Example I A Nalcat synthetic gel silicaalumina fluid-type cracking catalyst composed of about 22% A1 substantially the rest SiO was used in a commercial catalytic cracking conversion unit, using conventional fluidized catalyst techniques, including cracking and air regeneration to convert a feedstock (A) comprising a blend of Wyoming and Mid-Continent gas oils containing 1.0 ppm. Fe, 0.3 ppm. NiO, 1.2 ppm. V 0 and about 2 weight percent sulfur. This gas oil blend had a gravity (API) of 24, a carbon residue of about 0.3 weight percent and a boiling range of about 500 to 1000 F. When this catalyst had the poisoning metals content of 332 ppm. NiO, 4366 ppm. V 0 and 0.398% Fe, a sample (61) of the catalyst was removed from the cracking system after regeneration. A 42.9 gram batch of this catalyst sample, treated with steam to simulate the condition of a catalyst which is at equilibrium in the cracking system, was used to test-crack a petroleum hydrocarbon East Texas gas oil fraction (feedstock B) having the following approximate characteristics:

The results of this cracking are given in Table I below.

An eight pound batch of this catalyst was treated with an equimolar mixture of CCL; and C1 gases at about 600 F. for about one hour, after which it was slurried in deionized water, quickly filtered, dried and calcined. After the treatment this catalyst sample (29) had a NiO content of 336 p.p.m., a V 0 content of 3710 ppm. and contained 0.351% Fe, no chlorine, 21.5% A1 0 and 77.5% S with a surface area of about 144 square meters per gram, for a removal of of the vanadium and 12% of the iron. This sample (29) after steam ng was conducted to the test-cracking process on feedstock B with the results reported in Table I. In the following tables R.A. stands for relative activity, D.+L. for distillate plus loss, a measure of conversion to lower-boiling components, GP. for gas factor, GP. for coke factor and HPF for hydrogen producing factor.

These results show the effectiveness of the moderate temperature chlorination in removing vanadium and iron poisons from a catalyst with the subsequent improvement in conversion results thereby obtained.

12 Examples II-V An eight pound regenerated sample of High Alumina Nalcat the synthetic gel catalyst described above, had been poisoned by use in cracking feedstock A described above to a N10 content of 325 p.p.m., a V 0 content of 4075 ppm. and 0.328% Fe. The catalyst contained 25.7% A1 0 and 71.7% SiO and had an area of 147 m. gm. A 42.9 gram sample or" this catalyst gave the cracking results on feedstock B reported in Table II, which also gives the poisoning metals content of this sample. The remaining portion of this material was charged to a reactor where it was held overnight in air at about 1000" F. to oxidize coke which still remained on the catalyst. The mass of catalyst was then subjected to the action of H 8 at about 1025 F. for 3 hours and cooled in a fiuidizing flow of nitrogen gas to about 600 F. It was then chlorinated in a fluidized bed. The chlorine flow was introduced, and when there was evidence that chlorine was present in the reactor eflluent, an equimolar amount of CCl; was mixed with the chlorine vapors. This chlorination was continued for an hour after which the catalyst sample was slurried with deionized water and quickly filtered. The catalyst was washed on the filter until all signs of chloride ion were gone from the wash water. The washed catalyst was then pan dried at 300 C. overnight. A 42.9 gram sample (31) of this catalyst mass had the poisoning metals content reported in Table II. This sample was sent to a catalytic cracking activity test unit and had the activity reported in Table II in cracking feedstock B.

The remaining portion of this material was retreated with H 8 and a Cl /CCl mixture as described above. A 42.9 gram sample (32) of this doubly-treated catalyst had the metals content and cracking activity on feedstock B reported in Table II. The remaining portion of I this material was again sulfided, chlorinated and Washed as described above to give a 42.9 gram sample (33) which had the characteristics reported in Table II and the final portion of this material which was again sulfided and chlorinated as above to give sample 36. The percent metals removal figure given in Table II is a comparison with the poisoning meta s content of untreated sample 35. Each of the samples reported on in Table II was steamed before the cracking conversion operation.

TABLE II These results show the beneficial effect on the removal of metals, especially Ni, of a sulfiding treatment prior to the chlorination.

Examples VI-XII Regenerated catalyst sample had been poisoned to the levels indicated in Table III by use in cracking feedstock A. Sample 40 contained 0.24% carbon and had the cracking results on feedstock B also reported in Table Ill. Sample of Table III was a portion of sam- 1? pic 40 which had been chlorinated by a mixture of Cl /CCl for an hour at about 600 F. without prior sulfiding, Washed, dried and calcined. Sample 57 of Table III was a portion of sample 40 which had been chlorinated by contact with a mixture of elemental chlo- 5 rine and methane for about an hour at about 600 F. in a fluidized bed, washed, dried and calcined.

Sample 5 9 was a portion of sample 40 which was treated with air overnight at about 1000 F., and sulfided by contact with carbon disulfide vapors at about 1025 F. for 10 for one hour at a chlorine flow rate of 0.014 ft./sec. and

then purged with nitrogen at 600 F. for 10 minutes. Sample 12 was contacted with a mixture of C1 and n- A portion of the regenerated catalyst was contacted with air for 16 hours at 1000 F. and then was contacted with H S gas for 3 hours at 1050" F. Chlorination was performed on the sulfided catalyst by contacting it with a flowing mixture of C1 and CCl for an hour at about 600 F. After a quick wash the catalyst was dried and analyzed as 306 p.p.m. N10, 709 p.p.m. V 0 and 0.318% Fe, a reduction of 6% nickel, 6.5% in vanadium and 12% in iron. This sample was passed to test cracking of feedstock B with the following results:

Example Xi V A semi-synthetic catalyst, such as described above had been poisoned to a level of 322 ppm. NiO, 2972 ppm. V 0 and 0.432% Fe. When regenerated and used to test crack feedstock B the results were:

pentane for an hour at 600 F. and was not given a 1 purge with rutrogen after the chlorination. -T 290 Sample 73 was a portion of sample 40 which was sulfided with H 5 at 1025* F. for six hours and chlorinated 109 with flowing S Cl mixed with N for one hour at 600 F. Grav' The cracking results reported in Table III were 010- tained from test conversions on feedstock B, after each A portion of the regenerated catalyst was contacted catalyst was water Washed, dried and calcined. 30 'ith air for 10 hours at 1000 F. and then sulfided,

TABLE III Smple N0 40 57 59 63 C0 12 73 Treatment:

OTc-ontaining gas air air air air Sultiding agent CS2 .1 H23 HES H28 Chlorinating agcnt CIZICCI; 012/0011 C12 Clz/CrHm S 012 Results:

N10, ppm 327 292 V205, .m 4, 240 s, 740 Percent Fe 0. 270 0. 272 Percent 01 O. 03 Percent A1203. 25. 8 25. 3 Percent $102-"- 70. 5 70.8 Area m gm 151 Percent Metal Removal:

Ni 10. 7 4. 9 33. 9 s3. 9 20. 2 5s 44 11. s 10. 2 15.6 14. 9 9. 3 12 1s 0 10. 7 17. 4 20. 7 o 20 14. 5

a .6 42. 5 47. 9 40.8 47. 42. 2 3x1 37.0 29.2 36.1 39. 36.8 1. 62 1. 34 1. 34 1. 43 1. 1. 34 or 1. 30 1. 21 0. 97 1. 16 1. 1. 18 Gas Grav 1. 0s 1. 21 1. 2G 1. 21 1. 1. 25

These examples show that the process of this invention d es not harm the alumina content or surface area of 5 the catalyst even when some residual carbon is present, and also show CS to be a satisfactory sulfiding agent. Sulfur monochloride and mixtures of chlorine with low molecular weight paraffns are shown to be satisfactory chlorinating agents, while molecular chlorine used as the sole reagent does not produce results as good as chlorine compounds.

Example XIII A natural Filtrol catalyst such as described above was poisoned by its use in the cracking conversion of a feedstock containing large amounts of iron, vanadium and nickel to a poison content of 325 ppm. N10, 758 p.p.m. V 0 and 0.362% Fe. When regenerated and used to test crack feedstock B the results were:

D.{L. 27.0 GB. 1.41

CF. 1.16 Gas Grav. 1.22

chlorinated and washed as in Example Xill. The treated sample contained 176 ppm. F00, 2663 ppm. V 0 and 0.418% Fe :1 reduction of 48% in niche-1, 3% in iron and 10% in vanadium. The sample was passed to test cracking of feedstock B with the following results:

D.+L. 30.7 G.F. r 1.37

C.F. 1.02 Gas Grav. 1.32

HPF 94 Example XV to XXI rination treatment for 13 minutes; the other samples were treated for one hour.

After the chlorination treatment, each catalyst sample was quickly washed with water and dried and calcined. Table IV below gives the composition of the chlorinating agent and its amount, as well as the metals removal by each treatment and the results obtained when each treated catalyst sample was used in a test cracking procedure on feedstock B.

TABLE IV Sample 14 17 24 ll 5 Chlorine/ting Agent:

Wt. percent Cl: on catalyst 2G l3 l3 9 7, 3 Wt. percent CH4 on catalyst l 5 Wt. percent H28 on catalyst. 1 2 W t. percent C014 on catalyst -8 Wt. percent $5012 on cata lyst 1.2 Percent Metals Removal:

Ni 6G 65 6O 80 10 8 12 28 11 12 1(3 16 We claim:

1. In a method for treating a synthetic gel, silica-based catalyst which has been poisoned by contamination with a metal selected from the group consisting of nickel and vanadium due to use of said catalyst in converting at elevated temperature a hydrocarbon feedstock containing said poisoning metal, the steps which comprise bleeding a portion of the catalyst containing poisoning metal from the hydrocarbon conversion system, said bled catalyst being out of contact with the hydrocarbon feedstock, sulfiding poisoning metal containing component on bled catalyst by contact with a sulfiding agent at a temperature of about 500 to 1500 F., chlorinating poisoning metal containing component on the sulfided catalyst by contact with an essentially anhydrous chlorinating agent at a temperature up to about 1000 F., removing poisoning metal from the chlorinating agenttreated catalyst by washing the catalyst with a liquid aqueous medium and conducting the demetallized catalyst to a hydrocarbon conversion system.

2. The method of claim 1 in which the catalyst is a synthetic gel, silica-alumina catalyst.

3. The method of claim 1 in which the chlorination is at a temperature of about 550 to 650 F.

4. The method of claim 1 in which the chlorinating agent consists essentially of a compound of chlorine and said compound contains a member selected from the group consisting of carbon and sulfur.

5. The method of claim 1 in which poisoning metal chloride is also removed from the catalyst by volatilization during chlorination.

- 6. The method of claim 3 in which the chlorinating agent consists essentially of carbon tetrachloride.

7. The method of claim 3 in which the chlorinating agent consists essentially of sulfur monochloride.

8. The method of claim 3 in which the chlorinating agent is made in situ from molecular chlorine and a low-boiling hydrocarbon.

9. In a method for treating a synthetic gel, silica based catalyst which has been poisoned by contamination with a metal selected from the group consisting of nickel and vanadium due to use of said catalyst in converting :at elevated temperature a hydrocarbon feedstock containing said poisoning metal, the steps which comprise bleeding a portion of the catalyst containing poisoning metal from the hydrocarbon conversion system, said bled catalyst being out of contact with the hydrocarbon feedstock, sulfiding poisoning metal containing component on bled catalyst by contact with a sulfiding agent at a temperature of about to 13 F., chlorinating poisoning metal containing component on the sulfided catalyst by contact with an essentially anhydrous chlorinating agent at a temperature of about 300 to 700 F., removing poisoning metal from the chlorinating agent-treated catalyst by Washing the catalyst with a weakly acidic, liquid aqueous medium and conducting the demetallized catalyst to a hydrocarbon conversion system.

10. The method of claim 9 in which the sulfiding is erformed by contact with H S.

11. The method or" claim 9 in which poisoning metal chloride is also removed from the catalyst by volatilizetion during chlorination.

12. The method of claim 10 in Which the catalyst is a synthetic gel silica-alumina catalyst.

13. The method of claim 10 in which poisoning metal chloride is also removed from the catalyst by volatilation during chlorination.

14. In a method for treating a synthetic gel, silicaalumina catalyst which has been poisoned by contamination with a metal selected from the group consisting of nickel and vanadium due to use of said catalyst in converting at elevated temperature a hydrocarbon feedstock containing said poisoning metal, the steps which comprise bleeding a portion of the catalyst containing poisoning metal from the hydrocarbon conversion system, said bled catalyst being out of contact with the hydrocarbon feed stock, sulfiding poisoning metal of the bled catalyst by contact with H 5 at a temperature of about 800 to 1300 F., chlorinating the poisoning metal sulfide by contact with an anhydrous chlorinating agent which consists essentially of a compound of chlorine and said compound contains a member selected from the group consisting of carbon and sulfur at a temperature of about 550 to 650 F. While removing poisoning metal chloride from the catalyst, washing the chlorinating agent-treated catalyst in a weakly-acidic environment with an essentially aqueous liquid, calcining the catalyst and conducting the demetallized catalyst to a hydrocarbon conversion system.

15. The method of claim 14 in which some poisoning metal chloride is removed from the catalyst by volatilizetion during chlorination and some is removed by the washing in a weakly acidic environment with an aqueous liquid.

16. In a method for treating a synthetic gel silicaalurnina catalyst which has been poisoned by contamination with a metal selected from the group consisting of nickel and vanadium due to use of said catalyst in converting at elevated temperature a hydrocarbon feedstock containing said poisoning metal, the steps which comprise blceding a portion of the catalyst containing poisoning metal from the hydrocarbon conversion system, said bled catalyst being out of contact with the hydrocarbon feedstock, sulfiding poisoning metal containing component on bled catalyst by contact with a sulfiding agent at a temperature of about 860 to 1500 F. for up to about 1200 minutes, chlorinating poisoning metal containing component on the sulfided catalyst by contact with an essentially anhydrous chlorinating agent at a temperature of about 300 to 700 F. for about 5420 minutes, and removing poisoning metal from the chlorinating agenttreated catalyst by washing the catalyst with a weakly acidic, liquid aqueous medium and conducting the demetallized catalyst to a hydrocarbon conversion system.

References Cited in the tile of this patent UNITED STATES PATENTS 2,129,693 Houdry Sept. 13, 1938. 2,414,736 Gray Ian. 21, 1947 2,481,253 Snyder Sept. 6, 1949 2,488,744 Snyder Nov. 22, 1949 2,668,798 Plank Feb. 9, 1954 2,977,323 Johnson et al Mar. 28, 1961 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N06 3 122510 February 25 1964 Emmett H, Burk, Jr. et a1.

It is hereby certified that error appears in the above numbered patent req'liring correction and that the said Letters Patent should read as corrected below.

Column 1, line 62 for fedstoclfl' read.v feedstock column 7 line 29 for "aboue" read. about column 14, line 56, for "nichel" read nickel column 16, line l for so to 13 F2," read ..80.0.. .to 13,00 P,

Signed and sealed this 13th day of April 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attcsting Officer Commissioner of Patents

Claims

1. IN A METHOD FOR TREATING A SYNTHETIC GEL, SILICA-BASED CATLAYST WHICH HAS BEEN POISONED BY CONTAMINATION WITH A METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL AND VANADIUM DUE TO USE OF SAID CATALYST IN CONVERTING AT ELEVATED TEMPERATURE A HYDROCARBON FEEDSTOCK CONTAININT SAID POISONING METAL, THE STEPS WHICH COMPRISE BLEEDING A PORTION OF THE CATALYST CONTAINING POISONING METAL FROM THE HYDROCARBON CONVERSION SYSTEM, SAID BLED CATALYST BEING OUT OF CONTACT WITH THE HYDROCARBON FEEDSTOCK, SULFIDING POISONING METAL CONTAINING COMPONENT ON BLED CATALYST BY CONTACT WITH A SULFIDING AGENT AT A TEMPERATURE OF ABOUT 500 TO 1500*F., CHLORINATING POISONING METAL CONTAINING COMPONENT ON THE SULFIDED CATALYST BY CONTACT WITH AN ESSENTIALLY ANHYDROUS CHLORINATING AGENT AT A TEMPERATURE UP TO ABOUT 1000*F., REMOVING POISONING METAL FROM THE CHLORINATING AGENTTREATED CATALYST BY WASHING THE CATALYST WITH A LIQUID AQUEOUS MEDIUM AND CONDUCTING THE DEMETALLIZED CATALYST TO A HYDROCARBON CONVERSION SYSTEM.