US3539495A

US3539495A - Catalytic dewaxing

Info

Publication number: US3539495A
Application number: US771880A
Authority: US
Inventors: Clark J Egan
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1968-10-30
Filing date: 1968-10-30
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10
Also published as: FR2022327B1; DE1954368B2; GB1231970A; DE1954368C3; FR2022327A1; JPS4823323B1; DE1954368A1

Description

New'. 19, 1970 C. J. EGAN CATALYTIC DEWAXING Filed ou. 3o, 1969 2 Sheets-Sheet l LIGHT GASES LIGHT GASES 55o' F. f

F' l G. 1

HEAVY FEED *INVENTOR CLARK J EGAN MToRNEYs NOV. 10, 1 970 C, J, EGAN 3,539,495

CATALYTIC DEWAXING Filed oct. 30, 1968 2 Sheets-Sheet 2 N S WT :OHM .Y MS TE .M m NJ. .R M M EK O UT 0 l 0 VR mm n m .m NAi ,T T ET, r. M HS M p m u A M MM N MT R UA T Us 0 T mC O S Y NY 0 S T O B HM 6 2 Al. 6 N N ALM o MN P o 3 PC UY R HA R u E. AT u l l w m l LA w m l 5 PC 5 0 0 l o o 4 44 i|.|Y O. 0 m w o 3 4 m.. .mwmu mmsmmazm u. #z on. MNH Sanoma ABSTRACT OF THE DISCLOSURE A waxy hydrocarbon oil feed is catalytically dewaxed in the presence of hydrogen at dewaxing conditions using a catalyst comprising 0.01 to 3 weight percent platinum and 0.01 tot 5 weight percent rhenium in association with a porous solid carrier.

BACKGROUND OF THE INVENTION Field This invention relates to catalytic dewaxing processes. More particularly the present invention relates to catalytically dewaxing a waxy hydrocarbon oil feed with a catalyst comprising platinum and rhenium in association with a porous solid carrier.

Prior art Dewaxing of hydrocarbon oils is well known in the art and refers to the treatment of waxy hydrocarbon feeds to reduce the waxy constituents therein. The waxy com ponents of hydrocarbon oils, particularly long-chain normal paraiiins, impart, for many purposes, undesirable characteristics to the oils and hence must generally be removed, e.g., by solvent dewaxing, or, alternately, converted to nonwaxy components, e.g., by catalytic dewaxing, in order to produce commercially useful products. In particular, hydrocarbon oils having high concentrations of waxy components generally have higher freeze points or pour points than oils having lower concentrations of waxy components. For many purposes it is desirable to have oils with low freeze points or pour points. Thus, for example, the lower the freeze point of a jet fuel, the more suitable it will be for operations under conditions of extreme cold. Thus, the fuel will remain liquid and flow freely without external heating even at very low temperatures. In the case of lubricating oils, it is desirable that the pour points be low, thereby enabling the oil to pour freely and adequately lubricate, even at low temperatures. While the freeze point is generally used in reference to jet fuels and the pour point used in reference to diesel fuels and lubricating oils, the process for lowering the freeze point or the pour point, as the case may be, is commonly referred to as dewaxing.

Several processes are available in the prior art for dewaxing hydrocarbon oils. A particularly well known process for dewaxing lubricating oils is solvent dewaxing wherein a solvent such as a mixture of methylethylketone and benzene is added to the waxy hydrocarbon oil. The mixture of methylethylketone and benzene preferentially dissolves the nonwaxy hydrocarbons, thereby permitting separation of the nonwaxy hydrocarbons from the waxy hydrocarbons by cooling and filtration. Another known process is catalytic dewaxing, wherein the waxy components, which are primarily long-chain para'ins, are converted in the presence of a catalyst, primarily by isomerization and cracking reactions, to smaller-chain and/or branchchain parains. Catalytic dewaxing, e.g., with a catalyst comprising platinum, possesses the advantage in that separation of waxy and nonwaxy components is not required.

" aired States Patent O ice' 3,539,495 Patented Nov. 10, 1970 SUMMARY OF THE INVENTION It has now been discovered that catalytic dewaxing can be accomplished using a catalyst comprising a porous solid support in association with platinum and rhenium. The presence of rhenium with the platinum-supported catalyst permits a significant improvement in the fouling rate of the catalyst as well as in the reduction in waxy components. Thus in the case of catalytic dewaxing of a jet fuel with a platinum-rhenium catalyst, a significant improvement in freeze point lowering is obtained com pared to catalytic dewaxing at similar conditions with a platinum catalyst. Furthermore the length of useful life of the platinum-rhenium catalyst is significantly greater than that of a platinum catalyst without rhenium.

Thus the process of the present invention comprises catalytically dewaxing a waxy hydrocarbon oil feed by contacting the feed and hydrogen at dewaxing conditions in the presence of a catalyst comprising 0.01 to 3 weight percent platinum and 0.01 to 5 weight percent rhenium in association with a porous solid carrier. Preferably the catalyst contains a halide.

As a preferred embodiment the waxy hydrocarbon feed is contacted with a platinum-rhenium catalyst in a dewaxing zone to significantly dewax the feed and then the dewaxed product is contacted in a dehydrogenation Zone with a dehydrogenation catalyst having essentially no cracking activity to reduce the naphthenic hydrocarbon content.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention may be better understood and will be further explained hereinafter with reference to FIGS. l, 2 and 3.

FIG. 1 is a schematic drawing of a particular embodiment of the process of the present invention.

FIGS. 2 and 3 illustrate the improved stability and product quality of the dewaxing process of the present invention. FIG. 2 shows for comparison purposes the increase in catalyst temperature as a function of on-stream time for a dewaxing process using a platinum catalyst and a process using a platinum-rhenium catalyst. FIG. 3 sho-ws for comparison purposes the freeze point as a function of hours on-stream for the product from a catalytic dewaxing process using a platinum catalyst and a process using a platinum-rhenium catalyst. It is evident from FIGS. 2 and 3 that the platinum-rhenium catalyst is markedly superior to the platinum catalyst without rhenium in the catalytic dewaxing of waxy hydrocarbon oils.

DESCRIPTION OF THE INVENTION The catalyst useful for the catalytic dewaxing process of the present invention comprises platinum and rhenium in association with a porous solid carrier. The porous solid carrier or support can include a large number of materials upon which the catalytically active amounts of platinum and rhenium can be disposed. The porous solid carrier can be, for example, silicon carbide, charcoal or carbon. Preferably the porous solid carrier is an inorganic oxide. A high surface area inorganic carrier is particularly preferred, for example, an inorganic oxide having a surface area of from 50 to at least 700 m.2/gm. The carrier can be a natural or a synthetically-produced inorganic oxide or combination of inorganic oxides. Typical acidic inorganic oxide supports which can be used are the naturally occuring aluminum silicates, particularly when acid treated to increase the activity, and the syntheticallyproduced cracking supports, such as silica-alumina, silicazirconia, silica-alumina-zirconia, silica-magnesia, silicaalumina-magnesia, and crystalline zeolitic aluminosili- Cates. Generally, however, it is preferred to use catalysts having low cracking activity, i.e., catalysts of limited acidity. Hence, preferred carriers are inorganic oxides such as magnesia and alumina, particularly high purity alumina.

A particularly preferred catalytic carrier for purposes of this invention is alumina. Alumina which is satisfactory for the purpose of this invention can be prepared by a variety of methods. The preparation of alumina is well known in the prior art. Thus the alumina may be prepared as alumina hydrosol, alumina hydrogel, alumina xerogel, alumina monohydrate, sintered alumina and the like.

The catalyst proposed for use in the present invention preferably comprises platinum in an amount from about 0.01 to 3 weight percent and more preferably from about 0.2 to 1 weight percent based on the finished catalyst. Concentrations of rhenium in the finished catalyst composite are preferably from 0.01 to 5 weight percent and more preferably from y0.1 to 2 weight percent. It may be desirable to have other metals present with the platinum and rhenium. However, in general, metals which effectively poison or limit the catalytic dewaxing properties of the platinum and rhenium should not be used. Metals which may be used to advantage in the process of the present invention include iridium. Thus iridium in an amount from about 0.001 to 1 weight percent based on the finished catalyst can be used. However, it is understood that the metals which must be present as part of the catalyst, in addition to the support, are platinum and rhenium.

Although platinum and rhenium can be intimately associated with the porous solid carrier by suitable techniques such as by ion-exchange, coprecipitation, etc., the metals are usually associated with the porous solid carrier by impregnation. Furthermore, one of the metals can be associated with the carrier by one procedure, e.g., ionexchange, and the other metal associated with the carrier by another procedure, e.g., impregnation. As indicated,`

however, the metals are preferably associated with the carrier by impregnation. The catalyst can lbe prepared either by coimpregnation of the two metals or by sequential impregnation. In general, the carrier material is impregnated with an aqueous solution of a decomposable compound of the metal in sufcient concentration to provide the desired quantity of metal in the finished catalyst; the resulting mixture is then heated to remove water. Chloroplatinic acid is generally the preferred source of platinum. Other feasible platinum-containing compounds, e.g., arnmonium chloroplatinates and polyammineplatinum salts, can also be used. Rhenium compounds suitable for incorporation onto the carrier include, among others, perrhenic acid and ammonium or potassium perrhenates. It is contemplated in the present invention that incorporation of the metals with the carrier can be accomplished at any particular stage of the catalyst preparation. For example, if the metals are to be incorporated onto an alumina support, the incorporation may take place while the alumina is in the sol or gel form followed by precipitation of the alumina. Alternatively, a previously prepared alumina carrier can be impregnated with a water solution of the metal compounds. Regardless of the method of preparation of the supported platinum-rhenium catalyst it is desired that the platinum and rhenium be in intimate association with each other.

Following incorporation of the carrier material with platinum and rhenium, the composite is dried by heating, for example, at a temperature no greater than 500 and preferably from 200 to 400 F. and then calcined at an elevated temperature of up to 1200o F., if desired. Calcination temperatures are preferably from 600 to l200 F. and more preferably from 600 to 1000 F.

The catalyst comprising platinum and rhenium is preferably subjected to a reducing atmosphere at an elevated temperature prior to use in the catalytic dewaxing process. The prereduction is preferably performed in the presence of hydrogen and more preferably in the presence of dry hydrogen. It is preferred that the prereduction be accomplished at a temperature in the range of from 600 to 1300 F., preferably 600 to 1000 F.

The catalyst can be promoted for catalytic dewaxing by the addition of halides, particularly fluoride or chloride. Bromides are also useful for promoting the catalyst for dewaxing. The halides apparently provide a limited amount of acidity to the catalyst which is beneficial to most dewaxing operations. A catalyst promoted with halide preferably contains from 0.1 to 5 weight percent total halide content and more preferably from 0.1 to 1 weight percent total halide. The halides can be incorporated onto the catalyst carrier at any suitable stage of catalyst manufacture, e.g., prior to or following incorporation of the platinum and rhenium. Some halide is often incorporated onto the carrier when impregnating with the platinum or the rhenium; for example, impregnation with chloroplatinic acid normally results in chloride addition to the carrier. Additional halide may be incorporated onto the support simultaneously with incorporation of the metals if so desired. In general, the halides are combined with the catalyst carrier by contacting suitable compounds such as hydrogen liuoride, ammonium iiuoride, hydrogen chloride, or ammonium chloride, either in a gaseaus form or in a water soluble form, with the carrier. Preferably, the halide is incorporated onto the carrier from an aqueous solution containing the halide.

The catalytic dewaxing conditions are dependent in large measure on the feed used and upon the desired extent of lowering of the freeze point, or pour point, as the case may be. Generally the temperature will be within the range of from 700 to 950 F. and preferably from 750 to 900 F. The pressure preferably will be within the range from 500 to 5000 p.s.i.g. and more preferably 500 to 2500 p.s.i.g. The liquid hourly space velocity (LHSV) preferably will be from 0.1 to l0 and more preferably from 0.3 to 3.

Hydrogen must be present in the reaction zone during the catalytic dewaxing process. Thus hydrogen from an extraneous source may be introduced into the reaction Zone. For example, hydrogen produced from a naphtha reforming process may be purified and passed to the dewaxing Zone. |The hydrogen to feed ratio should be from 500 to 20,000 sci/bbl. of oil, preferably 1,0001 to 20,000 s.c.f./bbl. and more preferably 2,000 to 10,000 s.c.f./bbl. Generally, hydrogen will be separated from the product and be recycled to the reaction zone.

The waxy hydrocarbon oil feed which can be catalytically dewaxed by the present process includes jet fuel, middle distillate, and lubricating oil boiling range hydrocarbons. Thus the feed should boil above at least 300 F. For purposes of the present invention, the feed preferably should substantially boil within the range from 400 through 750 F. This range includes the middle distillate, jet fuel, and diesel fuel boiling range materials. Heavier hydrocarbon oils can be used, for example7 lubricating oils which boil above 650 F. and generally substantially above 750 F.

When treating high boiling feedstock, particularly lubrieating oils which boil above 750 F., it may be desirable to hydrotreat the feed With a hydrocracking-denitrification-type catalyst in a hydrocracking-denitriiication zone to convert-organic nitrogen compounds and organic sulfur compounds in the feed to ammonia and hyrogen sulfide. The ammonia and hydrogen sulfide can then be removed from the reaction Zone etiiuent, and the substantially nitrogen and sulfur-free product contacted with a catalyst comprising platinum and rhenium in a catalytic dewaxing zone. As a further modification, the nitrogen and sulfur free feed from the hydrocracking-denitrifcation zone can be hydrogenated with an active hydrogenation catalyst in the presence of hydrogen at a temperature in the range of, eg., from 200 to 650 F. and a pressure in the range of, eg., 1000 to 5000 p.s.i.g., to substantially convert aromatics to naphthenic products before catalytic dewaxing.

The waxy hydrocarbon feedstock desirably contains at least weight percent of waxy hydrocarbons, more preferably at least weight percent, and most preferably at least 20 percent by weight of waxy hydrocarbons. Waxy hydrocarbons mean any normally solid paraffinic hydrocarbons, and include paraffin wax and microcrystalline wax. Preferably the feed contains at least 5 weight percent of `C-lnormal parans, that is, at least 5 weight percent of normal pentadecane plus higher boiling range normal paraflins. It has been realized that the C154- normal parains are the most troublesome waxy components; thus lowering the C15-{- normal parafn concentration produces significant changes in the freezing point and/ or pour point.

The feed to be catalytically dewaxed may contain nitrogen, as organic nitrogen, and sulfur, as organic sulfur. Thus, the feed may be a straight-run distillate which has not been reduced in sulfur, i.e., which contains at least l0 p.p.m. sulfur by weight. Generally, however, it is preferred that the feed contain less than about 50 p.p.rn. nitrogen by weight, more preferably7 less than about 40 p.p.m., and less than about 1.0 percent sulfur by weight, more preferably, less than about 0.5 percent. Feeds which are not already low in nitrogen and sulfur impurities may be reduced in nitrogen and sulfur by hydrofining and/or hydrocracking the hydrocarbon feeds. As one embodiment of the present process the feed used in the present invention is a hydroned waxy hydrocarbon oil or a hydrocracked waxy hydrocarbon oil.

Hydroning operations for lowering the nitrogen and/ or sulfur content of petroleum fractions are generally conducted at a temperature of from 500` to 850 F., a pressure within the range of from 400 to 4000 p.s.i.g., a liquid hourly space velocity (LHSV), i.e., the ow of hydrocarbon feed to catalyst, of from 0.2 to l0 volume of feed/ volume of catalyst/ hour (v./v./ hr.) and a hydrogen flow rate of above about 500 s.c.f./ bbl. of feed. Catalysts useful in hydroning operations include, among others, alumina-containing supports having molybdenum and/ or chromium oxide together with iron, cobalt and/ or nickel oxides thereon.

Hydrocarbon oils to be catalytically dewaxed can also be prepared by hydrocracking heavy virgin crudes, vacuum distillate residues, catalytic cycle oils, etc., followed by fractionation to obtain the desired boiling range material for dewaxing. Hydrocracking is generally accomplished at a temperature of from 450 to 900 F. and a pressure between about 500 to 10,000 p.s.i.g. Preferably, presures of 1200 and 6000 p.s.i.g. are used. The hydrogen ow rate into the reactor is preferably maintained between l,000 and 20,000 s.c.f./bbl. of feed, more preferably in the range of 4,000 to 10,000 s.c.f./bbl. Suitable hydrocracking catalysts include silica-containing supports, eg., silica-alumina, silica-zirconia, silica-alumina-zirconia, crystalline zeolitic aluminosilicates, etc., in association with metals of Groups VI through VIII aswell as the oxides and suldes thereof, eg., nickel.

As one embodiment of the present invention the waxy hydrocarbon feed is catalytically dewaxed at dewaxing conditions and in the presence of hydrogen with a catalyst comprising 0.01 to 3 weight percent platinum and 0.01 to 5 weight percent rhenium associated with a porous solid carrier to lower the waxy hydrocarbon concentration, then dehydrogenating the catalytically dewaxed product at dehydrogenation conditions and in the presence of hydrogen with a catalyst having substantially no cracking activity comprising 0.01 to 3 weight percent platinum and 0.1 to 10 weight percent alkali metal or alkaline earth metal in association with a porous solid carrier. The dehydrogenation catalyst substantially dehydrogenates naphthenic hydrocarbons, particularly cyclohexane and alkylcyclohexane compounds, present in the feed. Thus, preferably at least volume percent of the naphthenes are dehydrogenated. Hydrogen which is produced in the dehydrogenation step is preferably recycled to the catalytic dewaxing zone. The hydrogen-containing gas which is recycled to the catalytic dewaxing zone can desirably have HZS removed, e.g., by scrubbing. Also water can be removed as, e.g., by passing the gas through a molecular sieve. The combined catalytic dewaxing and dehydrogenation process is preferably operated with no net consumption of hydrogen. Thus sucient hydrogen is produced in both zones to satisfy the requirements for the catalytic dewaxing.

The `waxy hydrocarbon oil feed containing naphthenic hydrocarbons which is subject to catalytic dewaxing followed by dehydrogenation preferably boils within the middle distillate range, for example, in the range from 400 to 750 F. Generally at least 30 volume percent naphthenes should be present in the waxy hydrocarbon oil feed in order to operate with no net consumption of hydrogen.

The dehydrogenation catalyst will contain platinum and an alkali or alkaline earth metal in association with a. porous solid carrier. The carriers suitable for the dehydrogenation catalyst should be nonacidic porous solid carriers. The term nonacidic is intended to preclude the use of halogen components and those inorganic oxides which possess .the acidic function characteristic of materials which actively promote cracking reactions. Preferably the porous nonacidic solid carrier is an inorganic oxide. The carrier material can be a natural or a synthetically-produced inorganic oxide or combinations of inorganic oxides. Supports which inherently have acidic sites which promote cracking reactions must have their acidic sites completely neutralized in order to produce the desirable nonacidic carrier. Alumina is a particularly preferred carrier for the dehydogenation catalyst.

The dehydrogenation catalyst preferably has disposed thereon an alkali or alkaline earth metal, for example, lithium, sodium, potassium, rubidium, cesium, calcium, magnesium, etc. Preferably, the carrier has associated therewith an alkali metal, particularly lithium. Su'lcient alkali or alkaline earth metal or other neutralizing material should be present to completely neutralize the acidic sites of the carrier plus ony other inherent acidity possessed by the dehydrogenating metal, for example, platinum. Generally, the alkali and alkaline earth metals are present in an amount, calculated as the metal, of from 0.1 to 20 weight percent based on the finished catalyst and preferably from 0.1 to 10 weight percent. The carrier should remain effectively neutralized throughout the dehydrogenation process. Neutralization of acidic sites is preferred even in the case of the relatively nonacidic carriers, for example, alumina. Such carriers, although considered to be nonacidic, possess a limited amount of acidity which is not desirable for purposes of the present invention. Furthermore, platinum possesses a certain inherent acid function which it is desirable to counteract.

The dehydrogenation reaction conditions are generally at a temperature of from 700 to 950 F., a pressure from 500 to 5000 p.s.i.g. and a liquid hourly space velocity of from 0.1 to l0. In the combination process of catalytic dewaxing followed by dehydrogenation, the temperature in the dehydrogenation zone is preferably 25 to 200 higher than the temperature in the catalytic dewaxing zone. The higher temperature permits more effective dehydrogenation of naphthenes. Since the support is nonacidic or has essentially no cracking activity, the increase in temperature does not result in an appreciable increase in cracking.

A particularly preferred embodiment of the present process is illustrated in FIG. 1. A heavy feed, eg., a crude petroleum oil boiling within the range of from about 500 to 1000o F., is fed to hydrocracking unit 1 via line 2. Hydrogen is added to the hydrocracking unit via line 3. Any of a number of conventional hydrocracking catalysts could be used in the hydrocracking unit 1, as, for example, a Group VIII metal-containing silicaalumina catalyst. The heavy feed is converted in the hydrocracking unit to a number of lighter materials. These materials are removed from hydrocracking unit 1 and passed to fractionation zone 4 through line 5 and are there separated into a plurality of streams. Light hydrocarbon gases, particularly C1s to C4s and hydrogen are removed from the fractionator through line 6. A gasoline fraction boiling in the range of, e.g., 180 to 300 F. is removed from line 7. The gasoline fraction may desirably be further treated in a naphtha reforming zone where the fraction is contacted with a platinum-alumina catalyst to produce a high octane gasoline product. A jet fuel cut boiling Within the range f, e.g., 300 to 500 F. is removed from the fractionator through line 8. High boiling products, particularly products boiling above about 700 F., are removed from the fractionator through line 9. These may desirably be recycled to the hydrocracking unit 1 or can be further fractionated to recover a lubricating oil cut, the lubricating oil cut being separately treated to increase its usefulness. A waxy distillate boiling within the range from about 500 to 700 F. is removed from fractionator unit 4 through line 10. It is understood that fewer or additional streams could be withdrawn from the fractionator 4, depending on the particular needs of the renery.

The waxy distillate is passed into a reaction vessel 11 which contains in dewaxing zone 12 a bed of platinumrhenium catalyst described above. The waxy distillate is catalytically dewaxed in zone 12 at dewaxing conditions including, e.g., a temperature of 700-950 F., a pressure of 500 to 2500 p.s.i.g., and hydrogen to feed ratio of 500 to 20,000 s.c.f./bbl. The product emerging from zone 12 has a significantly lower freeze point than the feed to zone 12. The low freeze point product from zone 12 is then passed in contact with a dehydrogenation catalyst in dehydrogenation zone 13. The dehydrogenation catalyst possesses essentially no cracking activity. A suitable catalyst as described above is platinum and alumina, having lithium in association therewith. Rhenum may also be present on the catalyst. The dehydrogenated product is recovered from reactor 11 and sent to separator 14 through line 1S. Hydrogen recovered in separator 14 is recycled to reactor 11 by means of line 16. As an alternate to having the dewaxing catalyst and the dehydrogenation catalyst in the same reactor, two reactors may be used, the dewaxing catalyst in one reactor and dehydrogenation catalyst in the other reactor.

The product recovered from separator 14 is passed to zone 18 via line 17 wherein the oil is separated into a plurality of products including a low freeze point, 300 to 550 F. jet fuel which is withdrawn from zone 18 through line 19. Other products which can be withdrawn from separator zone 18 include light gases and hydrogen from line 20, a gasoline cut boiling within the range from 180 to 300 F. from line 21, and a 550 F.{ material from line 22. The gasoline and 550 F.-|- product may be separately treated.

In a preferred embodiment of the process, the jet fuel fraction withdrawn from separation zone 18 through line 19 is combined with the jet fuel fraction withdrawn from fractionator 4 through line 8. Alternately, the dewaxed product from zone 12 may be recovered directly from zone 12 via line 23 without being subjected to dehydrogenation in zone 13, and then fractionated to obtain a jet fuel cut. The resulting jet fuel cut may then be blended with the jet fuel from line 8 to obtain an improved low freeze point product. Alternately, the dewaxed jet fuel from

line

19 or 23 could be combined with a straightrun jet fuel; this combination has a synergistic effect on the freeze point, giving the resulting blended jet fuel product an unexpectedly low freeze point.

It is preferred to operate the dewaxing and dehydrogenation steps in FIG. 1 at conditions of no net consumption of hydrogen. Thus it is preferred that no excess hydrogen be added to reactor 11. The conversion of naphthenes to aromatics in

zones

12 and 13 results in the production of hydrogen which is recovered from the products in separator 14 and recycled to the dewaxing zone 12 through line 16. It is apparent that in order to operate the dewaxing and dehydrogenation zones at no net consumption of hydrogen the conditions in the dewaxing zone 12 and dehydrogenation zone 13 must be suitably controlled so that sufficient hydrogen is produced in

zones

12 and 13 to accommodate the needs of zone 12. Thus the dehydrogenation zone is preferably operated at the same pressure as the dewaxing zone 12 but at a temperature from 25 to 200 F. higher than the temperature maintained in the dewaxing or isomerization zone 12. The higher temperature permits greater conversion of naphthenes to aromatics; inasmuch as the dehydrogenation catalyst has essentially no cracking activity, the higher temperature does not result in significant cracking which consumes hydrogen.

The process of the present invention may be better understood by reference to the following example.

EXAMPLE A platinum catalyst was compared with a platinumrhenium catalyst for the catalytic dewaxing of a 415 to 575 F. waxy hydrocarbon distillate. The distillate had a sulfur content of 1100 ppm., a nitrogen content of l0 ppm., and a freeze point of -{-l8 F. The feed contained 46.9 volume percent parains, 44.4 volume percent naphthenes and 8.7 volume percent aromatics. The C15+ normal paraffin content was 21.1 Weight percent.

The platinum catalyst used was a conventional catalyst consisting of approximately 0.37 weight percent platinum, 0.27 weight percent chloride, 0.50 weight percent fluoride, all disposed on an alumina carrier. The platinum-rhenium catalyst comprised 0.37 weight percent platinum, 01.35 weight percent rhenium, 0.22 weight percent chloride, and 0.50 weight percent fluoride, disposed on alumina.

The results of catalytic dewaxing with the two catalysts over the 400 to 750 hour on-stream period are shown in FIGS. 2 and 3. During this period of time, the reaction conditions of pressure (900 p.s.i.g.), liquid hourly space velocity (1.0 v./v./hr.), and hydrogen to feed ratio (5000 scf/bbl.) were the same for the two runs. Once-through hydrogen was used in both cases FIG. 2 shows the temperature increase as a function of hours on-stream necessary to produce a product of the freeze point shown in FIG. 3. Thus, FIG. 3 shows the freeze point of the products produced in catalytic dewaxing processes as a function of hours on-stream.

The advantages of the catalytic dewaxing process of the present invention are clearly shown in the two figures. The lowest possible freeze point is the most desirable, and as can be seen in FIG. 3, the process using the platinumrhenium catalyst produces a product oil which has a freeze point considerably below that of the product oil produced under similar reaction conditions with a platinum catalyst without rhenium. Furthermore, the product stability is significantly better in the catalytic dewaxing process using the platinum-rhenium catalyst. The product produced by the process using the platinum-rhenium catalyst does not increase in freeze point with length of run as rapidly as the product produced in the catalytic dewaxing process with the platinum catalyst. This difference between the effects of the two catalysts is even more pronounced when one notes in FIG. 2 that the temperature necessary to maintain the conversion of the product to the particular freeze point shown in FIG. 3 using the platinum catalyst had to be significantly increased during the run. Thus the platinum catalyst fouled rapidly during the process. The temperature for the platinum catalyst was rapidly raised in an effort to keep the freeze point temperature down. Had the temperature not been raised, it is apparent that the product freeze point would have risen even faster and would have been much higher at the end of the time interval. On the other hand, the temperature used in the dewaxing process using the platinum-rhenium catalyst was maintained at a constant level during the period of the run; furthermost, the freeze point of the product remained uniformly low.

The foregoing description of this invention is not to be considered as limiting since many variations can be made by those skilled in the art without departing from the spirit or scope of the appended claims.

'I claim:

1. A process for catalytically dewaxing a waxy hydrocarbon oil feed which comprises contacting said feed at dewaxing conditions and in the presence of hydrogen with a catalyst comprising 0.0l to 3 weight percent platinum and 0.01 to 5 weight percent rhenium in association with a porous inorganic oxide.

2. The process of claim 1 wherein said porous inorganic oxide is alumina.

3. The process of claim 1 wherein said catalyst contains a halide.

4. The process of claim 3 wherein said halide is selected from the group consisting of fluoride and chloride.

5. The process of claim 3 wherein said halide is present in an amount from 0.1 to 5 weight percent.

6. The process of claim 5 wherein said halide is present in an amount less than l weight percent.

7. The process of claim 1 wherein said catalyst contains from 0.001 to l weight percent iridium.

8. The process of claim 1 wherein said catalyst comprises platinum in an amount from 0.2 to l weight percent and rhenium in an amount from 0.1 to 2 weight percent.

9. The process of claim 1 wherein said dewaxing conditions include a temperature of from 700 to 950 F., and a pressure of from 500 to 5000 p.s.i.g., and hydrogen to feed ratio of 500-20,000 s.c.f./bbl.

10. The process of claim 1 wherein said feed boils substantially within the range from 40G-750 F.

11. The process of claim 10 wherein said feed contains less than about 50 p.p.m. nitrogen.

12. The process of claim 1 wherein said feed is a straight-run distillate containing greater than l p.p.m. sulfur.

13. The process of claim 1 wherein said feed is a hydroned oil.

14. The process of claim 1 wherein said feed is a hydrocracked oil.

1S. The process of claim 1 wherein said feed contains at least volume percent of C15-|- normal parafns.

16. A process for the conversion of waxy hydrocarbons which comprises contacting a feed containing said hydrocarbons at a temperature of from 700-950 F., a pressure of from 500 to 2500 p.s.i.g., a liquid hourly space velocity of from 0.1 to and in the presence of 500-20,000 s.c.f. hydrogen/bbl. of feed with a catalyst comprising a porous inorganic oxide carrier in association with from 0.01 to 3 weight percent platinum, 0.0i to 5 weight percent rhenium and 0.1 to 3 weight percent halide.

17. A process for the conversion of a waxy hydrocarbon oil feed containing naphthenic hydrocarbons `which comprises contacting said feed at dewaxing conditions and in the presence of hydrogen with a catalyst comprising 0.01 to 3 weight percent platinum and 0.01 to 5 weight percent rhenium to substantially lower the freeze point, then contacting said low freeze point product at dehydrogenation conditions and in the presence of hydrogen with a catalyst having substantially no cracking activity comprising 0.01 to 3 weight percent platinum and 0.1 to 10 weight percent alkali metal or alkaline earth metal in association with a porous inorganic oxide carrier to substantially dehydrogenate said naphthenic hydrocarbons.

18. The process of claim 17 wherein said alkali metal on said dehydrogenation catalyst is lithium.

19. The process of claim 17 wherein there is no net consumption of hydrogen.

20. The process of claim 17 wherein the temperature in said dehydrogenation zone is between 25 to 200 higher than the temperature maintained in said dewaxing zone.

21. The process of claim 17 wherein the jet fuel component of the product: from said dehydrogenation zone is mixed with a straight-run jet fuel.

22. A process for producing a high quality jet fuel which comprises hydrocracking a heavy feed boiling within the range from 500 to l000 F. in a hydrocracking zone and in the presence of hydrogen with a hydrocracking catalyst, fractionating said product from said hydrocracking zone into at least two fractions, a jet fuel fraction boiling within the range from about 300 to 500 F. and a waxy distillate boiling within the range from about 500 to 700 F., catalytically dewaxing said waxy distillate in the presence of hydrogen at a temperature from 700 to 950 F. and a pressure of 500 to 2500 p.s.i.g. with a catalyst comprising 0.01 to 3 weight percent platinum and 0.01 to 5 weight percent rhenium in association with alumina, recovering a product from said catalytic dewaxing zone of lowered freeze point, recovering a jet fuel fraction boiling from about 300 to 550 F. from said lowered freeze point product, and mixing said last-mentioned jet fuel fraction with said first-mentioned jet fuel fraction.

References Cited UNITED STATES PATENTS 3,073,777 1/1963 Oettinger 208-112 3,132,087 5/1964 Kelley et al 208-60 3,268,439 8/1966 Tupman et al 208-112 DELBERT E. GANTZ, Primary Examiner A. RIMENS, Assistant Examiner U.s. C1. X.R.