CA1232855A - Hydroisomerization of catalytically dewaxed lubricating oils - Google Patents

Abstract

HYDROISOMERIZATION Of CATALYTICALLY DEWAXED
LUBRICATING OILS

ABSTRACT

The quality of catalytically hydrodewaxed oils is improved by hydroisomerizing the oil to remove residual waxy components which contribute to poor performance in the Overnight Cloud Point test.
Conversion during the hydroisomerization is minimized so as to obtain a product of high clarity in good yield.

Description

~Z32~355 HYDROISOMERIZATION OF CATALYTICALLY DOCKSIDE
LUBRICATING OILS

The present invention relates to a method of nydrofinishing catalytically hydrodewaxed lubricating oil stocks (lube oil) by the hydroiscmerizatlon of the residual wax content which has not been removed by the dew axing process.
Catalytic dew axing of hydrocarbon oils to reduce the temperature at which separation of waxy hydrocarbons occurs is a known process and is described, for example, in the Oil and Gas Journal, January 6, 1975, pages 69-73. A number of patents have also issued describing catalytic dew axing processes, for example, U.S. Reissue Patent No. 28,398 describes a process for catalytic dew axing with a catalyst comprising a zealot of the ZSM-5 type and a hydrogenation/dehydrogenation component. A process for hydra-dew axing a gas oil with a ZSM-5 type catalyst is also described in U.S. Patent No. 3,956,102. A mordant catalyst containing a Group VI
or a Group VIII metal may be used to Dixie a low V.I. distillate from a waxy crude as described in U.S. Patent No. 4,100,056. U.S. Patent No. 3,755,138 esquires a process for mild solvent dew axing to remove high quality wax from a lube stock, which is then catalytically dockside to specification pour point.
Catalytic dew axing processes may be followed by other processing steps such as hydrodesulfurization and denitrogenation in order to improve the qualities of the product. For example, U.S.
Patent No. 3,668,113 describes a catalytic dew axing process employing a mordant dew axing catalyst which is follower by a catalytic hydrodesulfurization step over an alumina-based catalyst. U.S. Patent No. 3,894,938 describes a hydrodewaxing process using a ZSM-5 type catalyst which is followed by conventional hydrodesulfurization of the dockside intermediate.

In catalytic dew axing processes using shape selective catalysts such as ZSM-5, the waxy components particularly the n-paraf~ins, are cracked by the zealot into light gases, such as C
and C3 and some heavier olefinic fragments which remain in the lube oil boiling range. These olefinic fragments are unstable to oxidation so that the hydrodewaxed oil is subsequently hydrogenated over catalyst to saturate the olefins and improve the oxidation stability of the oil. The hydrogenation catalysts generally used are mild hydrogenation catalysts such as Comic type. The color of the oil may also be improved in Tunis hydrofinishing.
Tune waxy components in heavy lube fractions, particularly bright stock, contain not only the normal paraffins, but also slightly branched paraffin's and cycloparaffins. In the bright stock, the normal paraffins comprise the so-called microcrystalline wax while the 15 slightly branched paraffins and cycloparaffins comprise so-called petrolatum wax. When a shape selective catalyst such as HZSM-5 is used, the microcrystalline wax cracks much faster than the petrolatum wax. As a result, when sufficient microcrystalline wax is cracked to meet the pour point requirement of, for example, -7C, there it still I some petrolatum wax left. This small amount of petrolatum wax does not impair pour point specification but it makes the oil fail an overnight cloud point (ON) test (ASTM D-2500-66).
The overnight cloud point test is conducted my placing the finished oil overnight in a refrigerator set at 5.5C (10F) above the 25 pour point specified, for example -7C (20F). An oil sample passes the test if it remains clear and bright, but some oils, particularly hydrodewaxed oil become dull due to growth of wax crystals, and fail the test. The oil fails the overnight cloud test as soon as the wax crystals nucleate and grow to sufficient sizes of 0.05 to 0.5 microns.
If the severity of the dew axing is increased significantly, the product can be made to meet the overnight cloud point (ON) test. for instance, decreasing the product pour point to -23C
(-10F) by increasing temperature or decreasing space velocity, can produce a product that passes the ON test at -1C (30F).

12~2855 However, this decrease in pour point leads to increased cost because of reaction severity and, particularly, to decreased yield.
It would therefore be desirable to find some way of improving the quality of the catalytically de-waxed product so that it is capable of passing the ON
test without incurring the disadvantages of a higher severity dew axing and, in particular, to avoid the losses in yield concomitant upon such a treatment.
We have now found that much of the petrolatum wax can be converted to more soluble isomers by hydra-isomerization under mild conditions with little loss in yield. This treatment results in a product which has a markedly improved overnight cloud point (a lower cloud point temperature). The hydrofinished products are also characterized by improved oxidation stability and rota-live freedom from color bodies. These improvements are obtained, moreover, with only minimal losses in the yield of the finished oil.
According to the present invention, there is therefore provided a process for improving the overnight cloud point of a catalytically dockside lubricating oil stock containing petrolatum wax which is relatively in-soluble comprising contacting said oil with a catalyst having both an acidic function and a hydrogenation-dehydrogenation function in the presence of hydrogen at hydroisomerization conditions to produce a product containing branched chain isoparaffins which are more soluble at low temperatures, and wherein the conversion of said oil to lower boiling components is less than about 10 weight percent.
The isomerization is carried out in the presence of hydrogen under isomerization conditions of elevated temperature and pressure, typically from 200C to 450C
(392F to 842F), 400 to 25,000 spa (58 to 3626 prig) with space velocities of 0.1 to 10 ho LHSV.

issue The feed stock for the present isomerization process is a catalytically dockside oil which typically has a boiling point above the distillate range (above about 343C (650F)). Products of this kind are lubricating (lube) oil stocks which possess a 5 characteristically low content of n-paraffins but containing residual small quantities of slightly branched chain paraffins and cycloparaffins which are responsible for unacceptable results in the ON test. The content of these petrolatum waxes is typically in the range 0.5 to 5 percent by weight of the oil but slightly higher or lower contents my be encountered, depending upon the nature of the feed stock to the dew axing step and the conditions (catalyst severity) used in the dew axing. Typical boiling ranges for lube stocks will be over 345C depending upon the grades.
The present process is applicable to stocks other than lube 5 stocks when a low wax content is desired in the final product and, in particular, when a product passing a test similar to ON is desired.
Thus, the process may also be applied to catalytically dockside distillate range materials such as heating oils, jet fuels and diesel fuels.
'The catalytically dockside oil may be produced by any kind of catalytic dew axing process, for example, processes of the kind described in U.S. Patents Nos. 3,668,113 and 4,110,056 but is especially useful with oils produced by dew axing processes using shape selective catalysts such as ZSM-5 or ZSM-ll, ZSM-23, ZSM-35, or 25 ZSM-38. Dew axing processes using catalysts of this kind are described, for example, in U.S. Patents Nos. Rev 28,398, 3,956,102, 3,755,138 and 3,894,938 to which reference is made for details of such processes. Since dew axing processes of this kind are invariably operated in the presence of hydrogen they are frequently referred to 30 as hydrodewaxing processes and, for this reason, the dockside oil may be obtained from a process which may be described either as catalytic dew axing or catalytic hydrodewaxing. For convenience, the term - 1232~55 "catalytic dew axing" will be used in this specification to cover both designations. When used in combination with the present hydrofinishing process, the catalytic dew axing step need not be operated at such severe conditions as would formerly have been necessary in order to meet all product specifications - especially the pour point and the ON specification - because the present process will improve the quality of the product and in particular, will improve its pour point and ON performance and stability. However, if desired, the catalytically dockside oil may be hydrodesulfurized or denitrogenated prior to the present hydrofinishing step in order to remove heterocyclic contaminants which might otherwise adversely affect catalyst performance. Hydrotreating steps of this kind are described, for example, in U.S. Patents Nos. 3,668,113 and 3,894,938 to which reference is made for details of these steps.
The catalysts used in the present hydrofinishing process are hydroisomerization catalysts which comprise an acidic component and a hydrogenation-dehydrogenation component (referred to, for convenience, as a hydrogenation component) which is generally a metal or metals of Groups IBM JIB, VA, VIA or VOW of the Periodic Table (I'M C and U.S.
National bureau of Standards approved Table as shown, for example, in the Chart of the Fisher Scientific Company, Catalog No. 5-702-10).
The preferred hydrogenation components are the noble metals of Group VOW, especially platinum but other noble metals such as palladium, gold, sliver, rhenium or rhodium may also be used. Combination of 25 noble metals such as platinum-rhenium, platinum-palladium, platinum-iridium or platinum-iridium-rhenium together with combinations with non-noble metals, particularly of Groups VIA and VOW are of interest, particularly with metals such as cobalt;
nickel, vanadium, tungsten, titanium and molybdenum, for example, 30 platinum-tungsten, platinum-nickel or platinum-nickel-tungsten. Base metal hydrogenation components may also be used, especially nickel, cobalt, molybdenum, tungsten, copper or zinc. Combinations of base metals such as cobalt-nickel, cobalt-molybdenum, nickel-tungsten, issue cobalt-nickel-tungsten or cobalt-nickel-titanium may also be used.
because the isomerization which is desired is favored by strong hydrogenation activity in the catalyst, the more active noble metals such as platinum and palladium will normally be preferred over the less active base metals.
The metal may be incorporated into the catalyst by any suitable method such as impregnation or exchange onto the zealot.
The metal may be incorporated in the form of a cat ionic, anionic or neutral complex, such as Pt(NH3)4+, and cat ionic complexes of 0 this type will be found convenient for exchanging metals onto the zealot. Anionic complexes are also useful for impregnating metals into the zealots.
The amount of the hydrogenation-dehydrogenation component is suitably from 0.01 to 10 percent by weight, normally 0.1 to 5 percent by weight, although this will, of course, vary with the nature of the component, less of the highly active noble metals, particularly platinum, being required than of the less active metals.
The acidic component of the zealot may be porous amorphous material such as an acidic clay, alumina, or silica-alumina but the porous, crystalline zealots are preferred. The crystalline zealot catalysts used in the catalyst comprise a three dimensional lattice of Sue tetrahedral cross linked by the sharing of oxygen atoms and which may optionally contain other atoms in the lattice, especially aluminum in the form of Aye tetrahedral the zealot will also include a 25 sufficient cat ionic complement to balance the negative charge on the lattice. Zealots have a crystal structure which is capable of regulating the access to an egress from the intracrystalline free space. This control, which is effected by the crystal structure itself, is dependent both upon the molecular configuration of the 30 material which is or, alternatively, is not, to have access to the internal structure of the zealot and also upon the structure of the zealot itself. The pores of the zealot are in the form of rings which are formed by the regular disposition of the tetrahedral making up the anionic framework of the crystalline aluminosilicate, the 35 oxygen atoms themselves being bonded to the silicon or aluminum atoms i232~355 at the centers of the tetrahedral A convenient measure of the extent to which a zealot provides this control for molecules of varying sizes to its internal structure is provided by the Constraint Index of the zealot: zealots which provide but highly restricted access to and egress from the internal structure have a high value for the Constraint Index and zealots of this kind usually have pores of small size. Contrariwise, zealots which provide relatively free access to the internal zealot structure have a low value for the Constraint Index. The method by which Constraint Index is determined is I described fully in U.S. Patent 4,016,218 to which reference is made for details of the method together with examples of Constraint Index for some typical zealots. because Constraint Index is related to the crystalline structure of the zealot but is nevertheless determined by means of a test which exploits the capacity of the zealot to engage 15 in a cracking reaction, that is, a reaction dependent upon the possession of acidic sites and functionality in the zealot, the sample of zealot used in the test should be representative of zeolitic structure whose Constraint Index is to be determined and should also possess requisite acidic functionality for the test.
I Acidic functionality may, of course, be varied by artifices including base exchange, steaming or control of sil1ca:aluminai~atio.
A wide variety of æ idle zealots may be used in tune present including large pore zealots such as natural faujasite, mordant, zealot X, zealot Y, ZSM-2û and zealot beta, small pore zealots 25 such as zealot A and zealots which are characterized by a Constraint Index from 1 to 12 and a silica alumina ratio of at least 12:1.
Specific zealots having a Constraint index of 1 to 12 and silica alumina ratio include ZSM-5, ZSM-ll, ZSM-12, ZSM-35 and ZSM-38 which are disclosed, respectively, in U.S. Patent Nos. 3,702,886;
30 3,709,979; 3,832,449; 4,016,245 and 4,046,859. Of them, ZSM-5 is preferred. Highly siliceous forms of ZSM-ll are described in European Patent Publication No. 14059 and of ZSM-12 in European Patent Publication No. 13630. Reference is made to these patents and applications for details of these zealots and their preparation.

- ` ~2321~55 The silica alumina ratios referred to in this specification are the structural or framework ratios, that is, the ratio for the Sue to the Aye tetrahedral which together constitute the structure of which the zealot is composed. This ratio may vary from the silica alumina ratio determined by various physical and chemical methods. For example, a gross chemical analysis may include aluminum which is present in the form of cations associated with the acidic sites on the zealot, thereby giving a low silica alumina ratio.
Similarly, if the ratio is determined by thermogravimetric analysis lo (TOGA) of ammonia resorption, a low ammonia titration may be obtained if cat ionic aluminum prevents exchange of the ammonium ions onto the acidic sites. These disparities are particularly troublesome when certain treatments such as the dealuminization methods described below which result in the presence of ionic aluminum free of the zealot structure are employed. Due care should therefore be taken to ensure that the framework 6ilica:alumina ratio is correctly determined.
Large pore zealots such as zealots Y, ZSM-20 and beta are useful in the present process. Zealots of this kind will normally have a Constraint Index of less than l. They may be used on their own or in combination with a zealot having a Constraint Index of l to 12 and such combinations may produce particularly desirable results. A
combination of zealots Y and ZSM-5 has been found to be especially good.
Zealot beta is disclosed in U.S. Patent No. 3,308,069 to 25 which reference is made for details of this zealot and its preparation.
When the zealots have been prepared in the presence of organic cations they are catalytically inactive, possibly because the int~acrystalline free space is occupied by organic cations from the forming solution. They may be activated by heating in an inert atmosphere at 540C for one hour, for example, followed by base exchange with ammonium salts followed by calcination at 540C in air.
The presence of organic cations in the forming solution may not be absolutely essential to the formation of the zealot; but it does 35 appear to favor the formation of this special type of zealot.
, .,.

issue Some natural zealots may sometimes be converted to zealots of the desired type by various activation procedures and other treatments such as base exchange, steaming, alumina extraction and calcination.
When synthesized in the alkali metal form, the zealot is conveniently converted to the hydrogen form generally by intermediate formation of the ammonium form as a result of ammcnium ion exchange and calcinat$on of the ammonium form to yield the hydrogen form. It has been found that although the hydrogen form of the zealot catalyzes the reaction successfully, the zealot may also be partly in the alkali metal form although the selectivity to alpha-picoline is lower with the zealot in this form.
It may be desirable to incorporate the zealot in another material resistant to the temperature and other conditions employed in the process. Such matrix materials include synthetic or naturally occurring or in the form ox gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays can be composite with the zealot and they may be used in the raw state as originally mined or initially subjected to calcination, acid treatment I or chemical modification. Alternatively the zealot may be composite with a porous matrix material, such as alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-berylia, silica-titania as well as ternary compositions, such as silica-alumina-thoria, silica-alumina-zirconia, 25 silica-alumina-magnesia or silica-magnesia-zirconia. The matrix may be in the Norm of a Vogel. The relative proportions of zealot component and inorganic oxide gel matrix may vary widely with the zealot content typically ranging from l to 99 percent by weight and more usually in the range of 5 to 80 percent weight of the composite.
30 The matrix itself may have catalytic properties of an acidic nature which may contribute to the functionality of the catalyst. Zealots may also be combined with amorphous catalysts and other porous materials such as alumina. The combination of zealots Y and ZSM-5 with alumina has been found to be particularly desirable.

2 3~35 5 F-175~ -10-The isomerization-reaction is one which requires a relatively small degree of acidic functionality in the catalyst. ekes this the zealot may have a very high silica alumina ratio since this ratio is inversely related to the acid site density of the catalyst.
Thus, structural silica alumina ratios of 50:1 or higher are preferred and in fact the ratio may be much higher e.g. 100:1, 200:1, 500:1, 1000:1 or even higher. Since zealots are known to retain their acidic functionality even at very high silica alumina ratios of the order of 25,000:1, ratios of this magnitude or even higher are 0 contemplated.
If the zeolite`selected may be produced in the desired highly siliceous form by direct synthesis, this will often be the most convenient method for obtaining it. Zealot beta, for example, is known to be capable of being synthesized directly in forms having 15 silica alumina ratios up to 100:1, as described in U.S. Patents Nos.

3,308,069 and Rye 28,341 which describe zealot beta, its preparation and properties in detail. Reference is made-to these patents for these details. Zealot Y, on the other hand, can be synthesized only in forms which have silica alumina ratios up to about Sol and in order 20 to achieve higher ratios, resort may be made to various techniques to remove structural aluminum so as to obtain a more highly siliceous zealot. The same is true of mordant which, in its natural or directly synthesized form has a silica alumina ratio of about 10:1.
Zealot ZSM-20 may be directly synthesized with silica alumina ratios 25 of 7:1 or higher, typically in the range of 7:1 to 10:1, as described in U.S. Patents Nos. 3,972,983 and 4,021,331 to which reference is made for details of this zealot, its preparation and properties.
Zealot ZSM-20 also may be treated by various methods to increase its silica alumina ratio.
Control of the silica alumina ratio of the zealot in its as-synthesized form may be exercised by an appropriate selection of the relative proportions of the starting materials, especially the silica and alumina precursors, a relatively smaller quantity of the alumina precursor resulting in a higher silica alumina ratio in the 35 product zbolite, up to the limit of the synthetic procedure. If 1~23Z~SS

higher ratios are desired and alternative syntheses affording the desired high silica alumina ratios are not available, other techniques such as those described below may be used in order to prepare the desired highly siliceous zealots.
A number of different methods are known for increasing the structural silica alumina ratio of various zealots. Many of these methods rely upon the removal of alumni w from the structural framework of the zealot by chemical agents appropriate to this end.
A considerable amount of work on the preparation of aluminum deficient 10 faujasites has been performed and is reviewed in Advances in Chemistry Series No. 121, Molecular Sieves, GUT. Kerr, American Chemical Society, 1973. Specific methods for preparing dealuminized zealots are described in the following, and reference is made to them for details of the method: Catalysis by Zealots (International Symposium 15 on Zealots, Lyon, September 9-11, 1980), Elsevier Scientific Publishing Co., Amsterdam, 1980 (dealuminization of zealot Y with silicon tetrachloride); U.S. 3,442,795 and GOB. 1,058,188 (hydrolysis and removal of aluminum by chelation); GOB. 1,061,847 (acid extraction of aluminum); U.S. 3,493,519 (aluminum removal by steaming and 20 chelation); U.S. 3,591,488 (aluminum removal by steaming); U.S.

4,273,753 (dealuminization by silicon halides and oxyhalides); U.S.
3,691,099 (aluminum extraction with acid); U.S. 4,û93,560 (dealuminization by treatment with salts); U.S. 3,9 *,791 (aluminum removal with Cry) solutions); U.S. 3,506,400 (steaming followed by 25 chelation); U.S. 3,640,681 (extraction of aluminum with acetylacetonate followed by dehydroxylation); U.S. 3,836,561 (removal of aluminum with acid); DEMOS 2,51û,740 (treatment of zealot with chlorine or chlorine-contrary gases at high temperatures), NO
7,604,264 (acid extraction), JAY 53,101,003 (treatment with ETA or 30 other materials to remove aluminum) and J. Catalysis 54 295 (1978) (hydrothermal treatment followed by acid extraction).
Because of their convenience and practicality the preferred dealuminization methods for preparing the present highly siliceous zealots are those which rely upon acid extraction of the aluminum 3sfrom the zealot by contacting the zealot with an acid, preferably a ` lZ~2855 mineral acid such as hydrochloric acid. With zealot beta the dealuminization proceeds readily at ambient and mildly elevated temperatures and occurs with minimal losses in crystallinity, to form high silica forms of zealot beta with silica alumina ratios of at least 100:1, with ratios of 200:1 or even higher being readily attainable.
Highly siliceous forms of zealot Y may be prepared steaming - or by acid extraction of structural aluminum (or both) but because zealot Y in its normal, as-synthesized condition, is unstable to acid, it must first be converted to an acid-stable form. Methods for doing this are known and one of the most common forms of acid-resistant zealot Y is known as "Ultra stable Y" (US) which is described in U.S. Patent Nos. 3,293,192 and 3,402,996 and the publication, Society of Chemical Engineering (London) Monograph 15 Molecular Sieves, page 186 (1968) by TV McDaniel and PI Maker.
Reference is made to these for details of the zealot and its preparation. In general, "ultra stable" refers to Y-type zealot which is highly resistant to degradation of crystallinity by high temperature and steam treatment and is characterized by a R
20 content therein R is Nay K or any other alkali metal ion) ox less than 4 weight percent, preferably less than 1 weight percent, and a unit cell size less than 24.5 Angstroms and a silica to alumina mole ratio in the range of 3.5 to 7 or higher. The ultra stable form of Y-type zealot is obtained primarily by a substantial reduction of the alkali 25 metal ions and the unit cell size reduction of the alkali metal ions and the unit cell size reduction. The ultra stable zealot is identified both by the smaller unit cell and the low alkali metal content in the crystal structure.
The ultra stable form of the Y-type zealot can be prepared by 30 successively base exchanging a Y-type zealot with an aqueous solution of an ammonium salt, such as ammonium nitrate, until the alkali metal content of the Y-type zealot is reduced to less than 4 weight percent. The base exchanged zealot is then calcined at a temperature of 540C to 300C for up to several hours, cooled and successively 35 base exchanged with an aqueous solution of an ammonium salt until the ,, .

12~2855 alkali metal content is reduced to less than 1 weight percent, followed by washing and calcination again at a temperature of 540C to 800C to produce an ultra stable zealot Y. The sequence onion exchange and heat treatment results in the substantial reduction of the alkali metal content of the original zealot and results in a unit cell shrinkage which is believed to lead to the ultra high stability of the resulting Y-type zealot.
The ultra stable zealot Y may then be extracted with acid to produce a highly siliceous Norm of the zealot. The acid extraction 10 may be made in the same way as described above for zealot beta.
Methods for increasing the silica alumina ratio of zealot Y
by acid extraction are described in U.S. Patents 4,218,307, 3,591,488 and 3,691,099, to which reference is made for details of these methods.
Zealot ZSM-20 may be converted to more highly siliceous 15 forms by a process similar to that used for zealot Y. First, the zealot is converted to an "ultra stable" form which is then dealuminized by acid extraction. The conversion to the ultra stable form may suitably be carried out by the same sequence of steps used or preparing ultra stable Y. The zealot is successively 20 base-exchanged to the ammonium form and calcined, normally at temperatures above 700C. The calcination should be carried out in a deep bed in order to impede removal of gaseous products, as recommended in Advances in Chemistry Series, No. 121, ox cit. Acid extraction of the "ultra stable" ZSM-2~ may be effected in the same way 25 as described above for zealot beta.
Highly siliceous forms of mordant may be made by acid extraction procedures of the kind described, for example, in U.S.
Patent Nos. 3,691,099, 3,591,488 and other dealuminization techniques which may be used for mordant are disclosed, for example, in U.S.
30 Patent Nos. 4,273,753, 3,493,519 and 3,442,795. Reference is made to these patents for a full description of these processes.
Another property which charæterizes the zealots which may be used in the present catalysts is their hydrocarbon sorption capacity. The zealot used in the present catalysts should have a 35 hydrocarbon sorption capacity for Nixon of greater than 5 .

1232l355 preferably greater than 6 percent by weight at 50C. The hydrocarbon sorption capacity is determined by measuring the sorption at 50C, 20 mm Hug (2666 Pa) hydrocarbon pressure in an inert carrier such as helium.
Hydrocarbon sorption capacity (%) Wt. of z~r~be------~~ x 100 The sorption test is conveniently carried out by TOGA with helium as a carrier gas flowing over the zealot at 50C. The hydrocarbon of 10 interest e.g. Nixon is introduce into the gas stream adjusted to 20 mm Hug hydrocarbon pressure and the hydrocarbon uptake, measured as the increase in zealot weight is recorded. The sorption capacity may then be calculated as a percentage.
The zealot hydroisomerization catalysts are generally used in a 15 cat ionic form which gives the required degree of acidity and stability at the reaction conditions used. The zealot will be at least partly in the hydrogen form, such as HZSM-5, HO, in order to provide the acidic functionality necessary for the isomerization but cation exchange with other cations, especially alkaline earth cations such as calcium and 20 magnesium and rare earth cations such as lanthanum, curium, praseodymium and neodymium, may be used to control the proportion of protonated sites and, consequently, the acidity of the zealot. Rare earth forms of the large pore zealots X and Y, REX and RYE, are particularly useful as are the alkaline earth forms of the ZSM-5 type zealots, such as MgZSM-5, 25 provided that sufficient acidic activity is retained for the isomerization.
cause the isomerization reactions require both acidic and hydrogenation-dehydrogenation functions in the catalyst with a suitable balance between the two functions for the best performance, it may be 30 desirable to use more active hydrogenation components such as platinum with the more highly acidic components. Conversely, if the acidic component has but a low degree of acidic activity it may become possible to use a less active hydrogenation component, such as nickel or nickel-tungsten.

i232~355 - .

The feed stock is isomerized over the hydroisomerization catalyst in the presence of hydrogen under isomerization conditions of elevate temperature and pressure. The reaction temperature should be high enough to obtain sufficient isomerization activity but low enough to reduce cracking activity in order to avoid losses in product yield. The temperature will generally be in the range of 20ûC to 450C (392F to 842F) and preferably 250C to 375C (482F to 7û7F). With the more highly acidic catalysts lower temperatures within these ranges should normally be employed in order to minimize the conversion to lower boiling 10 range products. Reaction pressures (total) are usually from 400 to 25000 spa ~58 to 3626 prig), and more commonly in the range of 3500 to 12000 ha (507 to 1740 prig). Spa e velocities are normally held in the range 0.1 to 10, preferably 0.5 to 5, ho 1 LHSV. Hydrogen circulation rates of 30 to 700, usually 200 to 500, 15 null 1 (168 to 3932, usually 1123 to 281û SCF/Obl) are typical. The hydrogen partial pressure will normally be at least 50 percent of total system pressure, more usually 80 to 90 percent or-total system pressure.
The isomerization reaction is carried out so as to minimize conversion to lower boiling range products, especially to gas 20 (Cluck). Curing the isomerization, tune petrolatum wax (slightly branched paraffins and cyclupa~affins, generally of at least ten carbon atoms and usually C16-C40) are converted to branch chain iso-paraffins which are more soluble at low temperature. Conversion to lower boiling range products is normally not greater than 10 percent by 25 weight and in favorable cases is less than 5 percent by weight, for example, 3 percent by weight.
The invention is illustrated by the following Examples in which all parts, proportions and percentages are by weight unless stated to the contrary.

30 examples 1-22 Apparatus: A laboratory continuous down-flow reactor was used.
It was equipped with feed reservoir and pump, reactor temperature controllers and monitoring devices, gas regulators, flow controller and pressure gauges. Products were discharged into a sample receiver through a grove loader which controlled the operating pressure. Light products were collected in a dry ice cold trap downstream of the sample receiver.
Uncondensed gases were first passed through a gas sampler and then Noah scrubber before passing through a gas meter.
Startup Procedure: The reactor was packed with 10 cc of catalyst. It was activated by passing hydrogen at 370C for I hours with the same Ho circulation rate and pressure as in the projected run. A line out period of 12 hours was followed after the reaction temperature had been set and feeding started.
Jo The operating conditions and catalysts used in the Examples are shown in Table 1 below.
sample Preparation and Testing procedures: The collected oil product was vacuum stripped at 125C/0.05 mm Hug I Pa) for two hours to remove moisture and volatile fractions. The yield was calculated based on the final stripped product. The products were filled in 5.7 cm No. 1 screw capped vials and placed in a refrigerator kept at -1C for 16 hours to develop haze.
. . _ To evaluate and quantify the degree of cloudiness of each oil product, a set of standards was prepared. These were binary mixtures of a catalytically hydrodewaxed then solvent dockside bright stock (this material passed the ON test) and a hydrodewaxeq bright stock (this material failed the ON test). The mixtures of one component in the other ranged from O to 100 percent. Such a set of standards furnished 25 the whole range of cloudiness from 0-100%. The slight dark coloration of the solvent dockside oil was removed by percolating it through basic alumina column to obtain the same hue as that of the hydrodewaxed bright stock before it was used in the preparation of the standards.
To grade the clarity-cloudiness of the product oil, both were 30 contained in the same size vial and kept side by side in a refrigerator at -1C for 16 hours. The clarity/cloudiness of the product was then matched against the standard. A quality number corresponding to the percent of content of solvent dockside oil component in a particular standard was assigned to the oil sample to express its degree of us clarity. For example, a number of 80 means that particular oil sample 12~2855 has the same degree of clarity as that ox a standard containing 80%
solvent dockside oil.
The conditions used in the hydroisomerization and the results obtained are shown in Table 1 below. All runs were conducted at a pressure of 403û spa (584.5 prig).

~Z32~SS

Example H2/Char~e No. Catalyst Temp. C null LHSV Yield % Quality 1 A 315 178 0.82 -- 20 3 A 345 178 0.82 97.4 20 4 B 260 356 0.53 83.6 20 B 288 178 1.2 90.3 30 6 9 345 178 1.2 96.1 20 7 B 290 178 1 99.4 10 8 C 293 178 1.1 99.1 20 9 C 315 178 0.86 97.1 10 C ~345 178 1.1 98.7 30 11 C 370 178 0.95 96.9 30 12 D 288 178 1.35 95.6 40 13 D 315 178 1.2 -- 70 14 D 275 356 0.65 20 D 260 356 0.61 -- 30 16 P 260 356 ,0~53 99 50 17 D 315 356 0.56 98 50 18 D 345 356 û.55 93.5 60 19 D 345 356 0.47 93.9 60 D 320 356 0.45 99.7 70 21 D 293 356 0.45 99.8 80 22 D 370 356 0.46 92.4 95 Catalysts:
A: Tao (0.3 % Pi) B: Pd/HY
C: Pt/Mg Betty (0.3% Pi; 50% My Beta/50% Aye ;
Beta Sue = 100:1~
D: Pd/REY/HZSM-5/A1203 (0.35% Pod; 50% ROY% HZSM-5, 35% Aye) These results show that a high degree of improvement in ON may be achieved by hydroisomerization with little loss in yield.

Claims (6)

Claims:

1. A process for improving the overnight cloud point of a catalytically dewaxed lubricating oil stock containing petrolatum wax which is relatively insoluble comprising contacting said oil with a catalyst having both an acidic function and a hydrogenation-dehydrogenation function in the presence of hydrogen at hydroisomerization conditions to produce a product containing branched chain isoparaffins which are more soluble at low temperatures, and wherein the conversion of said oil to lower boiling components is less than about 10 weight percent.

2. The process according to claim 1 in which the hydrogenation component comprises a metal component of Group VIA or VIIIA of the Periodic Table.

3. The process according to claim 1 in which the acidic component comprises a crystalline zeolite.

4. The process according to any of claims 1 to 3 in which the acidic component comprises a large pore zeolite having a Constraint Index of less than 1.

5. The process according to any of claims 1 to 3 in which the acidic component comprises a zeolite having a silica:alumina ratio of at least 12:1 and a Constraint Index of 1 to 12.

6. The process according to any of claims 1 to 3 in which the hydrodewaxed oil is hydroisomerized at a temperature of 200°C to 450°C, a pressure of 400 to 25,000 kPa and a space velocity of 0.1 to 10.