US3128243A - Hydrocracking process with an aluminanickel sulfide catalyst activated with bf3 - Google Patents

Description

United States Patent HYDROCRACKING PROCESS WITH AN ALUMINA- NICKEL SULFIDE CATALYST A C T I V A T E D WITH BF Sac'hio Yamamoto, Richmond, Calif., assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Filed June 29, 1960, Ser. No. 39,449

4 Claims. (Cl. 208112) This invention relates to a hydrocarbon conversion process and, more particularly, to a conversion process involving the hydrocracking of hydrocarbon fractions to products of lower molecular weight than the hydrocarbons fed.

More specifically, this invention is directed to a hydrocracking process which comprises contacting a hydrocarbon distillate feed, along with added hydrogen, in a hydrocracking zone under hydrocracking conditions with a catalyst comprising nickel sulfide disposed on a nonsiliceous, predominantly alumina support, the catalyst having been rendered active for hydrocracking purposes by contact, following deposition of the nickel component on the catalyst support, with boron trifiuoride. After Contact of'the feed and the activated catalyst, at least one product fraction of lower molecular weight than the initial feed is recovered from the hydrocracking zone.

A variety of feeds have been found suitable for conversion according to the process of the present invention. In general, they can all be considered distillates and include such petroleum fractions commonly defined as naphthas, kerosenes, gas oils, cycle oils, and the like. These can be of straight-run origin, as obtained from the distillation of crude petroleum, or they may be derived from the effluents of various petroleum processing operations such as thermal or catalytic cracking, reforming, hydrofining, and other well-known refining processes. It

is also within the scope of the present invention to employ feeds derived from such sources as shale, gilsonite,

and the like. When employing the feedstocks noted above, it is preferred that they boil within the range of from about 200 to 900 F., and, more preferably, in the range of from about 320 to 750 F.

In addition to the aforenoted distillates that are generally defined in terms of their boiling range, i.e., naphthas, gas oils, etc., feeds that are of relatively pure molecular species, or mixtures thereof, can be employed advantageously. Feeds predominantly composed of one or more aromatic, parafiinic or naphthenic type compounds are entirely satisfactory for use in the subject process. For example, a relatively pure aromatic compound or a mixture of aromatics, such as found in aromatic extracts,

:can beieifectively employed as the feed. Thus, the process can be adapted to the production of lower molecular weight chemical products from such feedstocks. In gen- ,eral, it is preferred that these molecular species-type ifeeds boil above about 300 F.

The feedstocks of the present invention are preferably free of compounds that are known to adversely alfect catalyst activity. Among those generally undesirable The adverse effect of nitrogen compounds on the catalyst is particularly pronounced at the lower hydrocracking reaction temperatures described below. Accordingly, the nitrogen level, expressed as total nitrogen, should be below about 100 parts per million (p.p.m.), although appre- 'ciably improved results are obtained if the nitrogen content is below the preferred level of 10, or even 2, p.p.m. If the initial feedstocks contain nitrogen compounds above the described levels, they can be first subjected to a pretreatment that is relatively selective for the removal of the nitrogen compounds. For example, the feed can be intimately contacted with various acidic media such as liquid acids (H etc.) and/or such solid acidic materials as acid ion exchange resins, and the like. However, when denitrification is deemed necessary, it is preferred to reduce the nitrogen content by catalytic hydrogenation (hydrofining) of the feed. This can be done by contacting the feed, along with added hydrogen, at elevated temperatures and pressures with a hydrogenating catalyst in any conventional manner.

The feedstock can be introduced to the hydrocracking zone as either a liquid, vapor, or mixed liquid-vapor phase, depending upon the temperature, pressure, proportions of hydrogen and boiling range of the charge stock utilized. The feed is introduced in admixture with at least 750 s.c.f. (standard cubic feet) of hydrogen per barrel of total feed (including both fresh as well as recycle feed, if the latter is employed). Preferably, from about 1000 to 3000 s.c.f. of hydrogen per barrel of feed is passed into the hydrocracking zone. With feedstock such as naphthas, gas oils and cycle oils, at least 500 s.c.f. of hydrogen are consumed in the hydrocracking zone per barrel of total feed converted to synthetic products, i.e., those lower molecular weight products boiling below the initial boiling point of the fresh feed. The hydrogen stream admixed with the incoming feed is conveniently made up of recycle gas recovered from the effluent from the hydrocracking zone, together with fresh make-up hydrogen. The hydrogen content of the recycle gas stream, in practice, generally ranges upwardly of 70 volume percent.

The hydrocracking conditions employed in the hydrocracking zone can be varied over relatively wide ranges of temperature, pressure, and feed space velocity, but certain more narrowly defined portions of these ranges are preferred.

In general, the hydrocracking reaction may be conducted at temperatures ranging from about 350 to 800 F. or even higher, but it is preferred that they be maintained within the range of from about 400 to 700 F. as it has been found that the product distribution is much more favorable when the reaction is conducted within the noted low temperature preferred range. When the reaction temperature is kept below about 700 F., the reaction produces (1) extremely low yields of normally undesirable C and lighter gases, (2) the C to 180 F. product is characterized by iso to normal paraflin ratios normally Well in excess of thermodynamic equilibrium, and (3) long catalyst onstream periods, extending over many hundreds of hours, can be attained, particularly if the feedstock nitrogen content is maintained at the preferred levels hereinbefore set forth.

The pressures employed in the hydrocracking zone are in excess of about p.s.i.g. and may range upwardly to 2500 or 3000 p.s.i.g., with a preferred range being a total pressure of from about 500 to 2000 p.s.i.g. when employing naphthas, gas oils and cycle oils as feedstocks. Somewhat lower pressures can be employed when single molecular species-type feedstocks are employed.

Generally, the hydrocracking zone feed may .be introduced into thereaction zone at a liquid hourly space velocity (LHSV) of from about 0.1 to 20.0 or more volumes of hydrocarbon (calculated as liquid) per superficial volume of catalyst per hour (v./v./hr.), with a preferred rate being from about 0.5 to 15.0 v./v./hr.

The process of the present invention is conducted under the noted conditions of temperature, pressure and feed space rate such that at least 20 volume percent of the initial feed to the hydrocracking zone is converted perpass to lower molecular weight products boiling below the initial boiling point of said feed. Preferably, the reaction conditions are adjusted such that the per-pass conversion to synthetic product is in the range of from about 40 to 80 volume percent in the case of naphtha, gas oil and cycle oil feeds and from 40 to 100 volume percent when employing feeds predominantly aromatics, paraffins or naphthenes. Additionally, it is preferred to operate the hydrocracking process by periodically increasing the reaction temperature so as to maintain the selected per-pass conversion at relatively constant levels.

The catalyst of the present invention comprises nickel sulfide disposed on a non-siliceous, predominantly alumina support which, following deposition of the nickel component upon the support, is activated for hydrocracking purposes by contact with BF Among the predominantly alumina supports suitable for use in the present invention, but which are not necessarily equivalent, are such solid substances as alumina, aiumina-zirconia, aluminamagnesia, alumina-boria, alumina-titania, chromia-alumina, and bauxite. Of the above-mentioned supports, alumina is preferred, and particularly preferred is synthetically-prepared alumina of high purity. The surface of the support should preferably fall within the area of from 50 to 400 or more square meters per gram.

The preferred synthetic alumina support can be prepared by a number of known methods, as by (l) reacting sodium aluminate with an acidic reagent to form an aluminum hydroxide gel which is then calcined to convert the gel to the oxide, or (2) by adding ammonium hydroxide or carbonate to an aluminum salt, such as aluminum chloride, to form aluminum hydroxide which is then converted to the oxide by calcining.

The nickel component of the catalyst is first disposed upon the support in any desired manner, as by impregnation, coprecipitation, or the like. For example, the support can be impregnated with a nickel solution, such as nickel nitrate, and the resulting impregnated catalyst dried and calcined, or the nickel can be coprecipitated along with aluminum hydroxide gel and thereafter dried and calcined. These methods are well known in the art and need no further explanation here. The total amount of nickel disposed on the support may be varied within relatively wide limits of from about 0.1 to 35 percent (as the metal) based upon the weight of the entire finished catalyst composition. Preferably, the nickel content will lie in the range of from about 1.0 to 25 percent by Weight.

Following deposition of the nickel upon the catalyst support, the resulting composite is contacted with boron trifluoride to render the catalyst active for the hydrocracking reaction. However, the treatment with BF can be done at various stages of the catalyst preparation once the nickel is composited with the support. As noted, the finished catalyst has, as the hydrogenating component, nickel sulfide, but the actual order of sulfid ing and treating with BF is not critical. Thus, after the nickel is composited with the support, as by impregnation, the catalyst can be dried and calcined to convert the nickel to the oxide and then sulfided directly, or, following calcining, the nickel can be reduced and then sulfided. The B1 treatment can be done at any stage in this preparation once the nickel is upon the support. Thus, for example, the catalyst can be contacted with BF after drying and calcining, after reduction, or after the nickel is converted to the sulfide. Preferably, the BF treatment is done after a major proportion of the nickel component has been converted to the sulfide.

Exemplary methods of accomplishing drying, calcining, reduction and sulfiding of the catalyst following the compositing of the nickel with the alumina-containing support are as follows. Drying and calcining can be done by drying the composite at a temperature of from about 200 to about 500 F., and thereafter calcining by heating the catalyst at a temperature of from about 800 to 1200 F. for a period of an hour or more. Reduction of the nickel oxide can be accomplished by contacting the catalyst with hydrogen at atmospheric pressure while heating from room temperature to about 600-900 F., at a rate of about F. per hour, and thereafter contacting the catalyst with hydrogen at elevated pressures (1500 p.s.i.g., for example) and temperatures (550-900 P.) for an hour. Sulfiding of the nickel oxide or, preferably, metallic nickel, can be done by contacting the catalyst with hydrogen sulfide or with hydrogen and a low molecular weight mereaptan or organic sulfide, or with hydrogen and a hydrocarbon containing a dissolved sulfur compound, at temperatures below about 750 F., and preferably below about 700 F.

Activation of the alumina-nickel composite with BF can be done (during the stages of catalyst manufacture outlined above) by passing normally gaseous B1 over the catalyst, under pressure if desired, such that from about 2 to 30 or more weight percent of the final catalyst is fluoride. Preferably, the final catalyst has a fluoride content of from about 5 to 25 weight percent. The contact between the BF and the catalyst can be done with the BF alone or in the presence of diluents, for example, hydrogen and/ or paraffin hydrocarbons, all in the gaseous phase. If desired, contact in the liquid phase can also be accomplished by dissolving 8P in paraflinic compounds under pressure. However, the most preferable manner of activating the catalyst is by including the BE; in the feed and/or hydrogen entering the hydrocracking zone itself. This in situ activation can be done by inserting the nickel-alumina composite, preferably with the nickel in the form of the sulfide, in the reaction zone and then passing the necessary amount of BF along with the feed, into said zone. Activation of the catalyst is generally very rapid (within a few hours) and the eflluent from the reaction zone during the activation period can be recycled to that zone.

The hydrocracking zone of the present invention is Well adapted to any type feed catalyst contacting method. Thus, such methods as fixed-bed, moving-bed, slurry, or fluid catalyst systems can be employed by procedures well known in the art. The preferred method is that employing at least one fixed catalyst bed. Since reaction onstream periods are extensive with low nitrogen feeds, generally it is more economic to merely replace the deactivated catalyst with fresh catalyst. However, catalyst regeneration can be performed, for example, by contacting the deactivated catalyst with an oxygen-containing gas at temperatures of from about 700 to 1000 F., and then continuing the reduction, sulfiding and BF activation steps as outlined above in the description of the method of manufacturing the catalyst.

The following examples illustrate a few specific applications of the present invention.

EXAMPLE 1 The hydrocracking reaction employed in this example and Example 2 was made in a continuous flow, fixed bed, high pressure microcatalytic unit. The 3 ml. of catalyst was supported inside "of a 0.79 cm. LD. stainless steel tube which was surrounded by a heavy-walled steel block inside an electrically heated oven. Catalyst temperatures were measured by a chromel-alumel thermocouple located on the reactor wall at the central portion of the catalyst bed. Hydrocarbon rates were measured by a Microfeeder pump and the hydrogen rate was measured by oil displacement in a reservoir. Liquid products were analyzed by gas chromatography and the accuracy of the method confirmed by analysis of known mixtures of similar bydrocarbons. The gaseous portion of the product was analyzed by mass spectrometry.

A catalyst preferred for use in the subject process was prepared by impregnating A -inch essentially pure alumina extrudate with a nickel nitrate solution. The nickel on the non-siliceous alumina support amounted to 6.66

weight percent of the entire weight of the catalyst. The latter was dried for 20 hours at 400 F. and atmospheric pressure and then calcined by heating for 4 hours at 900 F. and atmospheric pressure. The surface area of the catalyst was 220 mF/gm. The nickel oxide was then reduced by contacting the composite with about 0.1 sci/hour of hydrogen at 900 F. under a pressure of about 1100 p.s.i.g. The catalyst was then sulfided in situ (in the hydrocracking reaction zone) by passing feed (normal decane) and dimethyl disulfide into the reaction zone. After 4 hours, the disulfide was out 01f. Normal decane feed was then passed, along with hydrogen (hydrogen to feed ratio of 9.8), at an LHSV of 2 into the reaction zone maintained at a temperature of 570 F. and a pressure of 1185 p.s.i.g. At the end of an hour and a half, no hydrocracking or conversion of n-decane to lower molecular weight products had occurred. B F at a ratioof BF to n-decane of 0.1, was then simultaneouslypassed with the feed and hydrogen (B1 partial pressure 12 p.s.i. a.) into the hydrocracking zone at the same temperature (570 F.) and pressure (1185 p.'s.i.g.). After only 5 hours of BF addition, the conversion of n-decane to lower molecular weight products went from zero to 95 volume percent The addition of BF to the feed was then halted and only feed and hydrogen were passed into the reactor. After 4 hours on-stream time without the addition or" BF the n-decane conversion had leveled off to a relatively constant conversion of 90 volume percent. The catalyst employed in this run was analyzed and found to contain about 17 weight percent fluoride (based on the total weight of the catalyst).

A sample of the hydrocraoking zone efi uent was taken after a total on-stream period 'of about 4 /2 hours (3 hours after the first addition of BF At that time, the total cracking conversion of n-decane to hydrocarbons containing less than 10 carbon atoms per molecule was 78 volume percent. The hydrocarbon products were analyzed and the results are shown on Table I below.

Table 1 Product, =mols/100 mols of feed:

Methane 0.08 Ethane 0.2 Propane 12.2 Isobutane 47.5 n-Butane 9.9 Isopentane 46.0 n-Pentane 6.2 lsohexane 31.4 n-Hex-ane 4.0 I'soheptaue 6.7 n-Heptane 0.5 Total C paraflins 0.9 Total C paraffins Isodecane 0.5 n-Decane (feed) 21.6 iso/normal paraffin ratios:

C 4.8 C 7.4 C 7.9 C 7.4

From the data presented above, it can be seen that, until the catalyst was contacted with BF no conversion of the normal decane feed occurred and, almost immediately upon contact of the catalyst with B1 cracking began and shortly reached a cracking conversion of 95 volume percent. Further, after discontinuance of the BF addition to the catalyst, conversion to lower boiling products was maintained at about 90 volume percent.

Table I clearly shows the low production of C and lighter gases and the extremely high iso to normal parafiin ratios in the product. These iso to normal paraflin ratios are well above thermodynamic equilibrium.

Comparable product distribution was attained under essentially identical conditions except that the space velocity was increased to 8.0 v./v./hr. The conversion to products contalning less than 10 carbon atoms per molecule was 40.9 volume percent.

EXAMPLE 2 Following the 10 /2 hour run-described in Example 1, hydrogen and BF were passed through the same reaction zone for about one hour at a temperature of about 565 F. and a pressure of 1185 psig Essentially puretetramethylcyclohexane was then passed, at an LHSV of 2, into the reactor with the hydrogen and BP The reaction temperature was 565 'F.; the pressure was 1185 p.s.i.g.; the hydrogen to feed ratio was 8.9 and the BF to feed ratio was 0.1. After about one hour of on-stream time, a product sample was taken and analyzed. It was found that 81.9 percent of the tetramethylcyclohexane feed was converted to compounds containing less than 10 carbon atoms per molecule. An analysis of the products is given in Table H, below.

Table 11 Product, mols/ mols of feed:

Methane 0.01 Ethane 3.2 Propane 3.2 Isobutane 1 42.6 n-Butane 3.0 Isopentane 14.2 n-Pentane 0.8 Is'ohexane 13.9 n-Hexane 0.6 Total heptanes 0.6 Total octanes 0.5 Methylcyclopentane 45 .3 Cyclohexane 5.8 Dimethylcyclopentane 4.6 Methylcyclohexane 6.0 Ethylcyclopentane 0.7 Trimethylcyclopent ane 0.9 Dimethylcyclohexane 3.0 Other C naphthenes 0.7 Total C naphthenes 2.2 Total C naphthenes 18.1

Iso to normal paraflin ratios:

C 14 C 18 C 23 1 Some C4 parafiins lost during sampling.

From the above data it can be seen that, with a naphthene feed, high conversions can be readily attained by the process of the present invention and that the hydrocarbon product tlS characterized by low C and lighter gases and extremely high iso to normal paratiin ratios.

EXAMPLE 3 In the manner identical to that described in Example 1, a catalyst containing 6.66 weight percent nickel (as the metal) oxide on alumina was prepared by nickel nitrate impregnation of alumina followed by drying and calcining. Seventy grams of the resulting composite were then heated to 450 F. for 2 hours during which the catalyst was purged with nitrogen. The catalyst was then contacted with BF 3 at 450 F. and one atmosphere for 2 hours and then purged with nitrogen for 2 more hours. The catalyst contained 9.6 weight percent (of the entire catalyst) fluoride. Sixty-five cubic centimeters of catalyst were then placed in a hydrocracking reaction zone and the latter heated to 600 F. at 1200 psig in the presence of oncethrough hydrogen. The reactor was maintained at this temperature and pressure for one-half hour. The nickel component of the catalyst was then substantially sulfided by introducing into the reaction zone, at a rate of cc. per hour, a 10 volume percent solution of dimethyl disulfide in mixed hexanes and flowing hydrogen for a period of one hour. The hydrogen and sulfide solution was equivalent to about a 2% H 8 concentration.

The feed employed in the present run was a light catalytic cracking unit cycle oil and had the following inspections.

Distillation, ASTM D-158, a;

The feed was introduced into the reaction zone, along with 12,000 s.c.f. of hydrogen per barrel of feed, at a space velocity of about 2 v./v./hr., and kept on-stream for 14 hours with the zone being maintained at a pressure of 1200 p.s.i.g., an initial catalyst temperature of 600 F. and a maximum catalyst temperature of 660 F. Samples of the reaction zone eifiuent Were taken every tWo hours and the conversion, gravity and aniline point determined. The average values of these samples under the conditions after 8 hours on-stream are as follows. It Was found that about 65 volume percent of the feed was converted to products boiling below 400 F. and that over 60 volume percent of the feed was converted to products boiling below the initial boiling point of the feed (384 F.). The aniline point was 88.5 R, which shows that saturation of compounds, such as aromatics, was extremely small. The gravity was 18 API.

The hydrocracking reaction of the present invention is particularly useful in the conversion of naphthas, light and heavy gas oils and cycle oils to high octane gasolines, reformer feedstocks, kerosenes and various fuels such as jet and diesel. For example, naphthas and light gas oils and cycle oils can be employed to produce synthetic gasolines and reformer feeds with the heavier portions of the hydro cracking zone efiiuent either recycled to the reaction zone or employed directly as fuels. Heavy gas oils and cycle oils can produce excellent synthetic jet and diesel fuels in addition to gasolines and/ or reformer feedstocks. Also, as hereinbefore indicated, the hydrocracking process of the present invention can be employed to produce various low molecular Weight products from relatively pure molecular species feedstocks.

I claim:

1. A hydrocracking process which comprises contacting a hydrocarbon distillate feed, along With added hydrogen, in a hydrocracking zone under hydrocracking conditions with a catalyst comprising nickel sulfide disposed on a non-siliceous, predominantly alumina support, said catalyst having been activated after deposition of the nickel component on said support by contact with BF and recovering from said zone products of lower molecular Weight than said feed.

2. The process of claim 1, wherein the BF is employed in an amount such that from 2 to 30 Weight percent of the final catalyst is fluoride.

3. The process of claim 1, wherein the catalyst is activated in situ by BB, passed into the hydrocracking zone simultaneously with said distillate feed for at least a portion of the total on-stream period.

4. A hydrocracking process for converting a hydrocarbon distillate feed to products boiling below the initial boiling point of said feed in a yield of at least 20% per-pass, which comprises contacting said feed, along with at least 750' s.c.f. of hydrogen per barrel of said feed, in a hydrocracking zone at a temperature below about 700 F., a pressure in the range of from about 500 to 2000 p.s.i.g., and an LHSV of from about 0.5 to 15.0 v./v./hr. with a catalyst comprising nickel sulfide disposed on a non-siliceous, predominantly alumina support, said catalyst having been activated after deposition of the nickel component on said support by contact with BF and recovering from said zone products boiling below the initial boiling point of said feed.

References Cited in the file of this patent UNITED STATES PATENTS 2,428,692 Voorhies Oct. 7, 1947 2,859,174 Adams et al. Nov. 4, 1958 2,878,180 Watkins Mar. 17, 1959 2,935,545 Block et al. May 3, 1960

Claims (1)

1. 4. A HYDROCRACKING PROCESS FOR CONVERTING A HYDROCARBON DISTILLATE FEED TO PRODUCTS BOILING BELOW THE INITIAL BOILING POINT OF SAID FEED IN A YIELD OF AT LEAST 20% PER-PASS, WHICH COMPRISES CONTACTING SAID FEED, ALONG WITH AT LEAST 750 S.C.F. OF HYDROGEN PER BARREL OF SAID FEED, IN A HYDROCRACKING ZONE AT A TEMPERATURE BELOW ABOUT 700*F., A PRESSURE IN THE RANGE OF FROM ABOUT 500 TO 2000 P.S.I.G., AND AN LHSV OF FROM ABOUT 0.5 TO 15.0 V./V./HR. WITH A CATALYST COMPRISING NICKEL SULFIDE DISPOSED ON A NON-SILCEOUS, PREDOMINANTLY ALUMINA SUPPORT, SAID CATALYST HAVING BEEN ACTIVATED AFTER DEPOSITION OF THE NICKEL COMPONENT ON SAID SUPPORT BY CONTACT WITH BF3, AND RECOVERING FROM SAID ZONE PRODUCTS BOILING BELOW THE INTIAL BOILING POINT OF SAID FEED.