WO1999032581A1

WO1999032581A1 - Raffinate dewaxing process

Info

Publication number: WO1999032581A1
Application number: PCT/US1998/026120
Authority: WO
Inventors: Donald S. Santilli
Original assignee: Chevron U.S.A., Inc.
Priority date: 1997-12-22
Filing date: 1998-12-09
Publication date: 1999-07-01
Also published as: AU1810599A

Abstract

A dewaxing process for reducing the cloud point of a hydrocarbon oil feed comprising contacting a raffinate under dewaxing conditions with a layered catalyst system including a first catalyst layer containing SSZ-32 and a hydrogenation component and a second catalyst layer containing ZSM-5.

Description

RAFFINATE DEWAXING PROCESS

I. FIELD OF THE INVENTION

The present invention relates to a process for catalytically dewaxing lube oils. In particular, the invention relates to a process for producing lube oil having an increased viscosity index by contacting a solvent extracted hydrocarbonaceous oil feedstock with a layered catalyst system.

II. BACKGROUND OF THE INVENTION

In general, the basic premise in lubricant refining is that a suitable crude oil, as shown by experience or by assay, contains a quantity of lubricant stock. The lubricant stock should have a predetermined set of properties, for example, appropriate viscosity, oxidation stability, and maintenance of fluidity at low temperatures. Current trends in the design of automotive engines are associated with higher operating temperatures as the efficiency of the engines increases. These higher operating temperatures require successively higher quality lubricants.

Viscosity index indicates the degree of change of viscosity with temperature. A high viscosity index of 100 indicates an oil that does not tend to become viscous at low temperature or become thin at high temperatures. For purposes of the present invention, whenever V.I. is referred to, it is meant the V.I. as determined by ASTM D-2270.

Mineral oil based lubricants are conventionally produced by a set of subtractive unit operations to isolate the lubricant stock and to remove unwanted components from the oil. For the preparation of a high-grade distillate lubricating oil stock, the current practice is to vacuum distill an atmospheric tower residuum from an appropriate crude oil as the first step. This provides one or more raw stocks having a boiling range of about 350°F to about 1050°F. This is then further separated, under vacuum processes, into suitable boiling range distillate fractions (gas oils) and a residual fraction which, after deasphalting and severe solvent treatment, may also be used as a lubricant base stock usually referred to as a bright stock. The gas oils undergo solvent extraction, also known as solvent refining, to remove low viscosity index components to produce oils known as neutral oils. These solvent extracted neutral oils are also known as raffinates.

Certain processes for dewaxing petroleum distillates are well known. Dewaxing is required when highly paraffinic oils are to be used in products which must be mobile at low temperatures, e.g., lubricating oils, heating oils, and jet fuels. The higher molecular weight straight chain normal, substituted and slightly branched paraffins present in such oils are waxes that cause high pour points and high cloud points in the oils. If adequately low pour points are to be obtained, the waxes must be wholly or partially removed.

In the past, various solvent removal techniques were employed to remove such waxes. In solvent dewaxing, the raffinates are solvent dewaxed by cooling oil-solvent admixtures under controlled conditions for crystallization of the paraffinic wax present in the admixtures. In such processes, the raffinates, or mixtures of raffinates and dewaxing solvent, are heated to a temperature at which the wax is dissolved.

The heated charge is then passed into a cooling zone wherein cooling is undertaken at a uniform slow rate in the range of about 1°F to 8°F/min. (0.56°F to 4.4°F/min.) until a temperature is reached at which a substantial portion of the wax is crystallized and at which dewaxed oil product has a selected pour point temperature. Upon achieving the desired dewaxing temperature, the mixture of wax crystals, oil and solvent is subjected to solid-liquid separation for recovery of a wax free oil-solvent solution and a solid wax containing a minor proportion of oil. This solid wax/oil composition is known as slack-wax.

The separated oil-solvent solution is subjected to distillation for recovery of a solvent fraction and a dewaxed oil product fraction. A refined lubricant stock may be used by itself, or it may be blended with another refined lubricant stock having different properties. Or the refined lubricant stock, prior to use as a lubricant, may be compounded with one or more additives which function, for example, as antioxidants, extreme pressure additives, and V.I. improvers.

Slack wax may be recovered as is, or may be subjected to additional processing, such as repulp filtration for the removal of additional oil. Solid- liquid separation techniques which may be employed for separation of wax crystals from the oil-solvent solutions include known solid-liquid separation processes, such as gravity settling, centrifugation, and filtration. Most commonly, in commercial processes, filtration in a rotary vacuum filter, followed by solvent wash of the wax cake, is employed.

Solvents known to be useful as dewaxing solvents are the ketones containing 3 to 6 carbon atoms, for example, acetone, methylethylketone (MEK) and methylisobutylketone (MIBK); mixtures of ketones; and mixtures of ketones with aromatic hydrocarbons including benzene and toluene. Halogenated low molecular weight hydrocarbons, including dichloromethane and dichloroethane, and their mixtures, are also known dewaxing solvents.

Solvent dilution of waxy oil stocks maintains fluidity of the oil for facilitating easy handling, for obtaining optimum wax-oil separation, and for obtaining optimum dewaxed oil yields. The extent of solvent dilution depends upon the particular oil stocks and solvents used, the approach to filtration temperature in the cooling zone, and the desired final ratio of solvent to oil in the separation zone. Solvent dewaxing processes, however, will give a low yield with very waxy feeds, have high operating costs, significant environmental impacts, and produce oils which are inferior to catalytically-dewaxed oils. Thus, catalytic dewaxing processes are preferred. Catalytic dewaxing processes are more economical and remove the waxes by selectively isomerizing and cracking paraffinic components to produce lower molecular weight products, some of which may be removed by distillation.

Because of their selectivity, known dewaxing catalysts generally comprise an aluminosilicate zeolite having a pore size which admits the straight chain n-paraffins either alone or with only slightly branched chain paraffins, but which excludes more highly branched materials, larger cycloaliphatics and aromatics. Zeolites such as ZSM-5, ZSM-11 , ZSM-12, ZSM-23, ZSM-35 and ZSM-38 have been proposed for this purpose in dewaxing processes. Their use is described in U.S. Pat. Nos. 3,700,585; 3,894,938; 4,176,050; 4,181 ,598; 4,222,855; 4,229,282 and 4,247,388, the disclosures of which are incorporated herein by reference. Catalytic processes are more economical and lower the pour point of the waxy feedstock by selectively cracking the longer chain n-paraffins. A disadvantage associated with catalytically dewaxing a raffinate is that a number of useful products become degraded to lower molecular weight materials.

For example, waxy paraffins may be cracked down to butane, propane, ethane and methane, and so may the lighter n-paraffins which do not contribute to the waxy nature of the oil. Because these lighter products are generally of lower value than the higher molecular weight materials, it is desirable to limit the degree of cracking which takes place during a catalytic dewaxing process. Since lube oil is valuable, maximization of the yield is commercially important. The catalysts used in the process of this invention are very selective. Therefore, the gas yield is reduced, thereby preserving the economic value of the feedstock. U.S. Pat. No. 4,734,539 discloses a method for isomerizing a naphtha feed using an intermediate pore size zeolite catalyst, such as an H-offretite catalyst. U.S. Pat. No. 4,518,485 discloses a process for dewaxing a hydrocarbon feedstock containing paraffins by a hydrotreating and isomerization process.

U.S. Pat. No. 4,689,138 discloses an isomerization process for reducing the normal paraffin content of a hydrocarbon oil feedstock using a catalyst comprising an intermediate pore size silicoaluminophosphate molecular sieve containing a Group VIII metal component which is occluded in the crystals during growth.

U.S. Pat. No. 5,135,638 issued on August 4, 1992 to Miller discloses a process for producing lube oil from a feedstock having greater than 50% wax. The feedstock is isomerized over a catalyst comprising a molecular sieve having generally oval 1-D pores having a minor axis between about 4.2 Angstroms and about 4.8 Angstroms and a minor axis between about 5.4 Angstroms and about 7.0 Angstroms and at least one Group VIII metal at a pressure of from about 15 psig to about 2000 psig.

U.S. Pat. No. 4,960,504 issued on October 2, 1990 to Pellet et al. discloses a process for producing an oil having a reduced pour point by catalytically dewaxing the hydrocarbon feedstock using a catalyst comprising a silicoaluminophosphate and an inorganic oxide matrix. The patent does not indicate that it would be possible to produce a lube oil having an extra high V.I. from a solvent extracted feedstock.

U.S. Pat. No. 4,859,311 issued on August 22, 1989 to Miller, the disclosure of which is incorporated herein by reference in its entirety, discloses a process for dewaxing a hydrocarbonaceous feedstock containing straight and slightly branched chain hydrocarbons by contacting the feedstock with a catalyst comprising SAPO-11 and a Group VIII metal. Since dewaxing processes of this kind function by means of cracking reactions, a number of useful products become degraded to lower molecular weight materials. For example, waxy paraffins may be cracked down to butane, propane, ethane and methane and so may the lighter n-paraffins which do not contribute to the waxy nature of the oil. Because these lighter products are generally of lower value than the higher molecular weight materials, it is desirable to limit the degree of cracking which takes place during a catalytic dewaxing process.

European Patent Application No. 225,053 discloses a process for producing lubricant oils by partially dewaxing a lubricant base stock by isomerization dewaxing followed by a selective dewaxing step. The isomerization dewaxing step is carried out using a large pore, high silica zeolite dewaxing catalyst such as high silica Y or zeolite beta which isomerizes the waxy components of the base stock to less waxy branched chain isoparaffins. The selective dewaxing step may be either a solvent, e.g., MEK dewaxing operation or a catalytic dewaxing, preferably using a highly shape zeolite such as ZSM-22 or ZSM-23.

U.S. Pat. No. 4,437,976 discloses a two-stage hydrocarbon dewaxing hydrotreating process wherein the pour point of a hydrocarbon charge stock boiling from 400°F to 1050°F is reduced by catalytically dewaxing the charge stock in the presence of a zeolite catalyst and subsequently subjecting at least the liquid portion thereof to hydrogenation in the presence of a hydrotreating catalyst comprising a hydrogenating component and a siliceous porous crystalline material from the class of ZSM-5, ZSM-11 , ZSM-23 and ZSM-35 zeolites.

U.S. Pat. No. 4,575,416 to Chester et al. discloses a hydrodewaxing process with a first zeolitic catalyst having a Constraint Index not less than 1 , a second catalytic component of specified characteristics and a hydrogenation component.

U.S. Pat. No. 5,149,421 teaches a dewaxing catalyst which provides superior selectivity with respect to the nature of the products obtained in a dewaxing process. By using an intermediate pore size silicoaluminophosphate molecular sieve catalyst in the dewaxing process, hydrocarbon oil feedstocks are effectively dewaxed and the products obtained are of higher molecular weight than those obtained using the other aluminosilicate zeolites. The products obtained from the dewaxing process have better viscosities and viscosity indexes at a given pour point as compared to the above-described prior art process using aluminosilicate zeolites.

Raffinate, especially heavy raffinate, a lubricating oil base stock with a high boiling point, is difficult to dewax; a wax haze tends to remain while dewaxing a raffinate to the target pour point. This residual haze is indicated by a large spread between the cloud point and the pour point of the dewaxed oil. A cloud-pour point spread of less than 5-10°C is generally observed for most lube oils (with the cloud point being higher than the pour point). It is desirable to have the cloud point be less than 10°F higher than the pour point.

When dewaxing raffinate, pour-cloud spreads of greater than 20°C are often encountered, at least in pilot plant work. Increasing dewaxing severity to reduce the cloud-pour spread results in reduced yields, and often the cloud point cannot be reduced enough, regardless of how low the pour point is dropped. It is desirable to identify a catalyst system which removes the wax haze during dewaxing to the target pour point (less than -9°C usually).

It would be advantageous to have an improved process for dewaxing and reducing the cloud point of raffinates without unduly reducing yield. The present invention provides such a process. SUMMARY OF THE INVENTION

The present invention overcomes the problems and disadvantages of the prior art by providing a process for catalytically dewaxing a hydrocarbon oil feedstock which produces a superior lube oil having excellent viscosity and viscosity index properties and a low pour point, low cloud point, and high yield. It has now been found that it is possible to catalytically produce a lubricating oil having a high viscosity index from a solvent refined gas oil feedstock (also denoted herein as a solvent extracted oil, a raffinate oil, or a neutral oil).

We have discovered that, by layering SSZ-32 with ZSM-5, the cloud point of the heavy raffinates are reduced to acceptable levels while yields remain high. Furthermore, there appears to be a synergy between the particular molecules converted by SSZ-32 and those converted by ZSM-5, as the yield from the layered system is higher than we would expect, or have found, from either catalyst alone.

The invention is, in one embodiment, a dewaxing process which comprises contacting a raffinate with a catalyst comprising a first catalyst layer comprising SSZ-32 and a hydrogenation component and a second catalyst layer comprising ZSM-5. The ratio of the liquid hourly space velocity of the contacting with said first catalyst to the contacting with said second catalyst is from about 1 :10 to about 1 :2.

The invention is, in another embodiment, a process for dewaxing a hydrocarbon feed comprising contacting a heavy raffinate, under dewaxing conditions, with a first catalyst comprising SSZ-32, and recovering a first effluent therefrom, contacting at least a portion of said effluent, under dewaxing conditions, with a second catalyst comprising ZSM-5, wherein at least a portion of said feedstock is converted. The invention is, in another embodiment, is a process for dewaxing a hydrocarbon feed comprising contacting a raffinate with a first catalyst comprising SSZ-32, and recovering a first effluent therefrom, contacting at least a portion of said effluent with a second catalyst comprising ZSM-5, wherein at least a portion of said raffinate is converted, wherein said contacting with said first catalyst and said second catalyst is at a temperature of from about 200°C to 475°C, a pressure of from about 15 psig to about 3000 psig, a liquid hourly space velocity of from about 0.1 hr to about 20 hr^" ¹, and a hydrogen circulation rate of from 500 to about 30,000 SCF/bbl, and wherein said raffinate contains less than 50 ppmw organic nitrogen, in the presence of added hydrogen gas.

IV. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A. Steps of the Process

The steps of the process are contacting a hydrocarbon feedstock under dewaxing conditions with a catalyst system comprising a first catalyst layer comprising SSZ-32 and a hydrogenation component and a second catalyst layer comprising ZSM-5.

The catalyst system optionally further includes a catalyst selected from the group consisting of an intermediate pore size silicoaluminophosphate molecular sieve, an amorphous catalyst, and mixtures thereof. For pre-treatments, the feed may be hydrocracked or solvent extracted and hydrotreated. This type of two-stage process and typical hydrocracking conditions are described in U.S. Patent No. 4,921 ,594, issued May 1 , 1990 to Miller, which is incorporated herein by reference in its entirety. Post-treatments can include hydrofinishing, discussed below.

Without being limited by theory, in one embodiment, the dewaxing mechanism is isomerization and/or cracking of waxy compounds. Typically, catalytic dewaxing, e.g., Chevron's ISODEWAXING catalytic dewaxing process, operates to improve the pour point and viscosity index of a feedstock, compared to solvent dewaxing.

B. Feedstock

The process of the invention is for dewaxing is a lube oil range hydrocarbon oil having a major portion that is a solvent extraction raffinate. The raffinate includes a light raffinate, medium raffinate, and heavy raffinate. The term "major portion" means at least 50 weight percent. Typically, the boiling points of light raffinates, medium raffinates, and heavy raffinates are from about 650°F to about 850°F, from about 750°F to about 950°F, and from about 850°F to about 1050°F, respectively.

The feedstock, optionally, can include a minor portion of a variety of hydrocarbon oil feedstocks classified generally as any waxy hydrocarbon feed, lube oil feedstock, or middle distillate oil. The term "minor portion" means less than 50 weight percent. The minor portion of the feedstocks include distillate fractions, e.g., hydrocrackates, up to high boiling stocks such as deasphalted and solvent extracted oils. The minor portion of the feedstock will normally be a C₁₀+ feedstock generally boiling above about 350°F since lighter oils will usually be free of significant quantities of waxy components. However, the process is particularly useful with waxy distillate stocks such as middle distillate stocks including gas oils, kerosenes, and jet fuels, lubricating oil stocks, heating oils and other distillate fractions whose pour point and viscosity need to be maintained within certain specification limits. Lubricating oil stocks will generally boil above 230°C (450°F), more usually above 315°C (600°F).

Hydroprocessed stocks are a convenient source of stocks of this kind and also of other distillate fractions since they have a higher hydrogen content over solvent-processed stocks and are usually relatively free of heteroatoms (e.g., sulfur and nitrogen compounds) which can impair the performance of the dewaxing and hydrofinishing catalysts. The minor portion of the feedstock of the present process will normally be a C₁₀+ feedstock containing paraffins, olefins, naphthenes, aromatics and heterocyclic compounds and a substantial proportion of higher molecular weight n-paraffins and slightly branched and substituted paraffins which contribute to the waxy nature of the feedstock.

During processing, feed molecules undergo some cracking or hydrocracking to form liquid range materials which contribute to a low viscosity product. The degree of cracking which occurs is, however, limited to preserve the yield of the valuable liquids.

During processing, the n-paraffins and slightly branched paraffins undergo some cracking or hydrocracking to form liquid range materials which contribute to a low viscosity product. The degree of cracking which occurs is, however, limited so that the gas yield is reduced, thus preserving the economic value of the feedstock. Typical feedstocks include light gas oils, heavy gas oils and reduced crudes boiling above 350°F. In one embodiment, the feedstock contains a major portion of a hydrocarbon oil feedstock boiling above about 350°F and contains straight chain and slightly branched chain hydrocarbons. In one embodiment, the hydrocarbon oil feedstock includes a C₂₀+ olefin feed and the process is a process for producing a C₂₀+ lube oil from said C₂₀+ olefin feed including isomerizing the olefin feed under isomerization conditions over the catalyst.

While the process of the invention can be practiced with utility when the feed contains organic nitrogen (nitrogen-containing impurities), it is preferred that the organic nitrogen content of the feed be less than 50 ppmw, more preferably less than 10 ppmw. Particularly good results, in terms of activity and length of catalyst cycle (period between successive regenerations or startup and first regeneration), are experienced when the feed contains less than 10 ppmw of organic nitrogen.

C. Zeolite

Suitable aluminosilicate zeolite catalysts for use in the process of the invention include SSZ-32 and ZSM-5. ZSM-5 is taught in R. Szostak, Handbook of Molecular Sieves (Van Norstrand Reinhold 1992), at pages 518-528, which is incorporated herein by reference. U.S. Pat. No. 5,053,373 describing and claiming SSZ-32 is incorporated herein by reference. U.S. Pat. No. 3,702,886 describing and claiming ZSM-5 is incorporated herein by reference. Where two or more zeolite catalysts are employed, they are mixed in an effective weight ratio to enhance dewaxing. Preferred ratios for two zeolites are from about 1 :5 to about 20: 1.

Any zeolite used in the process may optionally contain a hydrogenation component of the type commonly employed in dewaxing catalysts. See the aforementioned U.S. Patent No. 4,910,006 and U.S. Patent No. 5,316,753 for examples of these hydrogenation components, the disclosures of which are incorporated herein by reference.

The hydrogenation component is present in an effective amount to provide an effective hydrodewaxing and hydroisomerization catalyst preferably in the range of from about 0.01 to 10% by weight, more preferably from about 0.05 to 5% by weight. The catalyst may be run in such a mode to increase isodewaxing at the expense of cracking reactions.

The aluminosilicate zeolite catalyst preferably contains a Group VIII metal, such as platinum, palladium, molybdenum, nickel, vanadium, cobalt, tungsten, zinc, and mixtures thereof. More preferably, the intermediate pore size aluminosilicate zeolite catalyst contains at least one Group VIII metal selected from the group consisting of platinum and palladium. Most preferably, the intermediate pore size aluminosilicate zeolite catalyst contains platinum.

The amount of metal ranges from about 0.01 % to about 10% by weight of the molecular sieve, preferably from about 0.2% to about 5%, based on the weight of the molecular sieve. The techniques of introducing catalytically active metals to a molecular sieve are disclosed in the literature, and pre-existing metal incorporation techniques and treatment of the molecular sieve to form an active catalyst such as ion exchange, impregnation or occlusion during sieve preparation are suitable for use in the present process. Such techniques are disclosed in U.S. Pat. Nos. 3,236,761 ; 3,226,339; 3,236,762; 3,620,960; 3,373,109; 4,202,996; 4,440,781 and 4,710,485, the disclosures of which are incorporated herein by reference.

P. Amorphous Catalysts

These materials can be used alone or in conjunction (for example, as a layer after a conventional dewaxing catalyst) to produce raffinate with satisfactorily low cloud points. The amorphous catalysts useful in the invention are any amorphous catalysts having hydrogenation and/or isomerization effects on the feedstock. Such amorphous catalysts are taught, e.g., in U.S. Patent No. 4,383,913, the disclosure of which is incorporated herein by reference.

These include, e.g., amorphous catalytic inorganic oxides, e.g., catalytically active silica-aluminas, clays, synthetic or acid activated clays, silicas, aluminas, silica-aluminas, silica-zirconias, silica-magnesias, alumina-borias, alumina-titanias, pillared or cross-linked clays, and the like and mixtures thereof.

E. Process Conditions

The process is conducted at catalytic dewaxing conditions. Such conditions are known and are taught for example in U.S. Patent Nos. 5,591 ,322; 5,149,421 ; and 4,181 ,598, the disclosures of which are incorporated herein by reference. The catalytic dewaxing conditions are dependent in large measure on the feed used and upon the desired pour point. Hydrogen is preferably present in the reaction zone during the catalytic dewaxing process. The hydrogen to feed ratio, i.e., hydrogen circulation rate, is typically between about 500 and about 30,000 SCF/bbl (standard cubic feet per barrel), preferably about 1000 to about 20,000 SCF/bbl. Generally, hydrogen will be separated from the product and recycled to the reaction zone. Catalyst bed arrangements suitable for use in the process of the invention are any conventional catalyst bed configuration.

The catalytic dewaxing conditions employed depend on the feed used and the desired pour point. For dewaxing, generally, the temperature is from about 200°C and about 475°C, preferably between about 250°C and about 450°C. The pressure is typically from about 15 psig and about 3000 psig, preferably between about 200 psig and 3000 psig. The liquid hourly space velocity (LHSV) preferably will be from 0.1 to 20, preferably between about 0.2 and 10. Preferably, the ratio of the liquid hourly space velocity of the contacting with said first catalyst, SSZ-32, to the contacting with said second catalyst, ZSM-5, is from about 1 :10 to about 1 :2. Hydrogen is preferably present in the reaction zone during the catalytic isomerization process. The hydrogen to feed ratio is typically between about 500 and about 30,000 SCF/bbl (standard cubic feet per barrel), preferably from about 1000 to about 20,000 SCF/bbl. Generally, hydrogen will be separated from the product and recycled to the reaction zone.

F. Post-Treatments

It is often desirable to use mild hydrogenation (sometimes referred to as hydrofinishing). The hydrofinishing step is beneficial in preparing an acceptably stable product (e.g., a lubricating oil) since unsaturated products tend to be unstable to air and light and tend to degrade. The hydrofinishing step can be performed after the isomerization step. Hydrofinishing is typically conducted at temperatures ranging from about 190°C to about 340°C, at pressures of from about 400 psig to about 3000 psig, at space velocities (LHSV) of from about 0.1 to about 20, and hydrogen recycle rates of from about 400 to about 1500 SCF/bbl.

The hydrogenation catalyst employed must be active enough not only to hydrogenate the olefins and diolefins within the lube oil fractions, but also to reduce the content of any aromatics present.

Suitable hydrogenation catalysts include conventional, metallic hydrogenation catalysts, particularly the Group VIII metals such as cobalt, nickel, palladium and platinum. The metals are typically associated with carriers such as bauxite, alumina, silica gel, silica-alumina composites, and crystalline aluminosilicate zeolites and other molecular sieves. Palladium is a particularly preferred hydrogenation metal. If desired, non-noble Group VIM metals can be used with molybdates. Metal oxides or sulfides can be used. Suitable catalysts are disclosed in U.S. Pat. Nos. 3,852,207; 4,157,294; 4,921 ,594; 3,904,513 and 4,673,487, the disclosures of which are incorporated herein by reference.

G. Product Properties

As a result of the contacting between the feed and the catalysts at dewaxing conditions, the dewaxed product, preferably, has the following properties: viscosity index is >95 and preferably >100. The pour point is <-5°C and preferably <-10°C. The cloud point is <0°C, preferably <-2°C, more preferably <-5°C, and most preferably <-9°C. The yield is >68 wt. % of feed, preferably >70 wt. % of feed, and more preferably >72 wt. % of feed. V. ILLUSTRATIVE EMBODIMENTS

The invention will be further clarified by the following examples, which are intended to be purely exemplary of the invention.

A. Introduction

In the tests discussed below on dewaxing raffinates, Pt/SSZ-32 gave superior performance, and the degree of superiority increased as the feeds got heavier. The results for Pt/SSZ-32 are given in Tables 1-3 for light, medium and heavy raffinates. The target pours were -12°C for the raffinates (and - 21 °C for the waxes). The target cloud point was at least below 0°C.

B. Results

It was found that the product Vl's for Pt/SSZ-32 all met specs for the raffinates (>100 for the 150 raffinates, >95 for the rest), and the viscosities either met targets or were close. The Pt/SSZ-32 yield for the light raffinate feed was high and the vis@100 of 4.8 met target specs (-4.7 min). The yield of the medium raffinate/300R mixed raffinate was also high. These values were obtained at the lower (0.45 WHSV) space velocity.

The catalyst struggled getting the cloud point down, probably because of all of the S in the feed (almost 1 wt. %). This hurt the metal activity. It is known that without a metal SSZ-32 has trouble dewaxing medium neutral oils. At the lower SV, the catalyst (such as ZSM-5) may be useful for these extremely tough feeds. Also, the S and N were reduced from 8355 and 109 ppm, respectively, in the feed to 2000 and 50 ppm, respectively, in the products (from yield periods 5 and 6).

We went on to test the heavy raffinate (Table 3), and at 780°F at the higher SV, the cloud point dropped only to 2°C. At 770°F at the lower SV, the cloud dropped below 0°C, but the pour dropped all the way to -36°C, and the yield dropped over 10%. We then tested whether using ZSM-5 after the Pt SSZ-32 could help out. We ran the Pt/SSZ-32 at the higher SV at 760°F, giving a +1 °C-pour/+15°C cloud product at -78% 750⁺ yield. This product was fed directly into a second reactor containing a bound ZSM-5 catalyst (1/5 the weight of the Pt/SSZ-32 catalyst). The ZSM-5 was run at 680°F and 700°F. The results are given in Table 4, and the synergism between the two catalysts was evident. Good product was obtained at higher yields than when using Pt/SSZ-32 alone (~72wt% was collected vs. 66% for 9), and the product VI met specs (95 minimum) even though it dropped from 109 (seel 1 ) after reaction over ZSM-5. The viscosity increased, but is still a little low for hn specs.

C. Conclusion

Obtaining high product yield from such a heavy raffinate is surprising. Compared to the product obtained using Pt/SSZ-32 alone at 760°F-780°F, the product obtained after using the ZSM-5 as a second catalyst at 680°F-700°F actually looks better. That is, it is lighter and clearer in appearance. This occurs even though there is no metal on the ZSM-5 and the pressure is only 580 psig. Second, runs with lighter lube oil base stock (non raffinate) at 2300 psig before and after the raffinate runs showed no catalyst deactivation (at least not any which is irreversible at high pressures).

Claims

VI. CLAIMSWHAT IS CLAIMED IS:

1. A process for producing lube oil stock comprising:

(a) contacting a raffinate with a first catalyst comprising SSZ-32 under dewaxing conditions, thereby producing a dewaxed product, and

(b) contacting, under dewaxing conditions, at least a portion of said dewaxed product with a second catalyst comprising ZSM-5.

2. The process of claim 1 wherein said first catalyst consists essentially of SSZ-32.

3. The process of claim 1 wherein said second catalyst consists essentially of ZSM-5.

4. The process of claim 1 wherein said dewaxed product has a viscosity index greater than about 100.

5. The process of claim 1 wherein said raffinate is a light raffinate.

6. The process of claim 1 wherein said raffinate is a medium raffinate.

7. The process of claim 1 wherein said raffinate is a heavy raffinate.

8. The process of claim 1 wherein said first catalyst further comprises a hydrogenation component.

9. The process of claim 8 wherein said hydrogenation component comprises a Group VIII metal.

10. The process of claim 9 wherein said Group VIII metal is selected from the group consisting of platinum, palladium, and mixtures thereof.

11. The process of claim 1 wherein said contacting in step (a) and step (b) is carried out at a temperature of from about 200┬░C to 475┬░C, a pressure of from about 15 psig to about 3000 psig, a liquid hourly space velocity of from about 0.1 hr¹ to about 20 hr¹, and a hydrogen circulation rate of from 500 to about 30,000 SCF/bbl.

12. The process of claim 1 wherein the ratio of the liquid hourly space velocity of the contacting in step (a) to the contacting in step (b) is from about 1 :10 to about 1 :2.

13. The process of claim 11 wherein said raffinate contains less than 50 ppmw organic nitrogen.

14. The process of claim 13 wherein said raffinate contains less than 10 ppmw organic nitrogen.

15. The process of claim 1 wherein said raffinate comprises a heavy raffinate and wherein the process is a process for isomerization dewaxing said heavy raffinate comprising contacting said heavy raffinate in the presence of added hydrogen under isomerization dewaxing conditions with said first and second catalyst.

16. The process of claim 1 wherein said raffinate comprises a heavy raffinate and wherein the process is a process for improving the viscosity index of a dewaxed product of said heavy raffinate comprising contacting said first and second catalysts with said heavy raffinate under isomerization dewaxing conditions.

17. The process of claim 1 wherein the process is a process for preparing a lubricating oil: (a) wherein said raffinate is the effluent of hydrocracking in a hydrocracking zone a hydrocarbonaceous feedstock to obtain an effluent comprising a hydrocracked oil; and

(b) wherein said contacting steps (a) and (b) comprise catalytically dewaxing said effluent at a temperature of at least about 400┬░F and at a pressure of from about 15 psig to about 3000 psig in the presence of added hydrogen gas.

18. A process for dewaxing a hydrocarbon feed comprising:

(a) contacting a raffinate, under dewaxing conditions, with a layered catalyst system comprising a first catalyst layer comprising SSZ-32 and a hydrogenation component and a second catalyst layer comprising ZSM-5;

(b) wherein the ratio of the liquid hourly space velocity of the contacting with the first catalyst layer to the second catalyst layer is from about 1:10 to about 1:2;

(c) wherein at least a portion of said raffinate is converted; and

(d) recovering a dewaxed product therefrom having a viscosity index of at least 95.

19. The process of claim 18 wherein said raffinate is a light raffinate.

20. The process of claim 18 wherein said raffinate is a medium raffinate.

21. The process of claim 18 wherein said raffinate is a heavy raffinate.

22. The process of claim 18 wherein said hydrogenation component comprises a Group VIII metal.

23. The process of claim 22 wherein said Group VIII metal is selected from the group consisting of platinum, palladium, and mixtures thereof.

24. The process of claim 18 wherein said hydrogenation component is present in an amount of from about 0.01 % to about 10% based on the weight of said first catalyst.

25. The process of claim 18 wherein said contacting in step (a) and step (b) is carried out at a temperature of from about 200┬░C to 475┬░C, a pressure of from about 15 psig to about 3000 psig, a liquid hourly space velocity through said first catalyst layer of from about 0.1 hr¹ to about 20 hr¹, and a hydrogen circulation rate of from 500 to about 30,000 SCF/bbl.

26. The process of claim 18 wherein said pressure is from about 400 psig to about 1200 psig.

27. The process of claim 18 wherein said first dewaxed product has a viscosity index of at least about 100.

28. A process for dewaxing a hydrocarbon feed comprising contacting a heavy raffinate with a first catalyst consisting essentially of SSZ-32, and recovering a first dewaxed product therefrom, contacting at least a portion of said dewaxed product with a second catalyst consisting essentially of ZSM-5, wherein at least a portion of said heavy raffinate is converted, wherein said contacting with said first catalyst and said second catalyst is at a temperature of from about 200┬░C to 475┬░C, a pressure of from about 15 psig to about 3000 psig, a liquid hourly space velocity of from about 0.1 hr¹ to about 20 hr¹, and a hydrogen circulation rate of from 500 to about 30,000 SCF/bbl, and wherein the ratio of the liquid hourly space velocity of the contacting with said first catalyst to the contacting with said second catalyst is from about 1 :10 to about 1 :2.