CATALYTIC DEWAXING OF LUBRICATING OILS

Abstract: Hydrocarbon lubricating oil feedstocks are dewaxed by passing the waxy feedstock over a catalyst of a mixture of medium pore zeolite and large zeolite catalysts having a Constraint Index less than 2 and having hydroisomerization activity in the presence of a hydrogenation component.

Description: This invention relates to the manufacture of high quality lubricating oil derived particularly from the catalytic dewaxing of petroleum distillate fractions. It is especially directed to the preparation of lubricating oils having a high viscosity index with high yield and reduced overnight cloud problems. Refining suitable petroleum crude oils to obtain a variety of lubricating oils which function effectively in diverse environments has become a highly developed and complex art. Although the broad principles involved in refining are qualitatively understood, the art is encumbered by quantitative uncertainties which require a considerable resort to empiricism in practical refining. Underlying these quantitative uncertainties is the complexity of the molecular constitution of lubricating oils. 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. 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 step provides one or more raw stocks within the desired boiling range. After preparation of a raw stock of suitable boiling range, it is extracted with a solvent, e.g., furfural, phenol, Sulfolane, or chlorex, which is selective for aromatic hydrocarbons, and which removes undesirable components. The raffinate from solvent refining is then dewaxed, for example, by admixing with a solvent, such as a blend of methyl ethyl ketone and toluene. The mixture is chilled to induce crystallization of the paraffins waxes, which are then separated from the raffinate. Sufficient quantities of wax are removed to provide the desired pour point for the raffinate. Other processes, such as hydrofinishing or clay percolation, may be used if needed to reduce the nitrogen and sulfur content or improve the color of the lubricating oil stock. Viscosity index (V.I.) is a quality parameter of considerable importance for distillate lubrication oils to be used in automotive engines and aircraft engines subject to wide variations in temperature. A high V.I. of 100 indicates an oil that does not tend to become viscous at low temperature ore become thin at high temperatures. The dewaxing mechanism of catalytic hydrodewaxing is different from that of solvent dewaxing, resulting in some differences in chemical composition. Some catalytically dewaxed products produce a haze on stands at 6°C (10°F) above specification pour point for more than twelve hours - known as the Overnight Cloud (ONC) formation. The extent of this ONC formation is less severe with solvent dewaxed oils. Although such an ONC formation does not affect the product quality of catalytically dewaxed oils, it is beneficial to reduce the Overnight Cloud (ONC) formation, since some areas of the marketplace any increase in ONC is considered undesirable. EP-A-101,177 discloses a dual bed hydrotreating/hydrocracking process in which the hydrocracking catalyst, comprising ultrastable zeolite Y (USY) and zeolite ZSM-5, is shown to be more active and stable than a similar catalyst containing REY instead of USY. Catalytic techniques for dewaxing of petroleum stocks are described in The Oil and Gas Journal, dated January 6, 1975, pages 69-73. See also U.S. Patent No. 3,668,113. U.S. Patent No. Re. 28,398 describes a process for catalytic dewaxing with a catalyst comprising zeolite ZSM-5. Such a process combined with catalytic hydrofinishing is described in U.S. Patent No. 3,894,938. U.S. Patent No. 3,755,138 describes a process for mild solvent dewaxing to remove high quality from a lube stock, which is then catalytically dewaxed to specification pour point. U.S. Patent No. 4,053,532 is directed towards a hydrodewaxing operation involving a Fischer-Tropsch synthesis product utilizing ZSM-5 type zeolites. US Patent No. 3,956,102 is connected with a process involving the hydrodewaxing of petroleum distillates utilizing a ZSM-5 type zeolite catalyst. US Patent No. 4,247,388 describes dewaxing operations utilizing ZSM-5 type zeolites of specific activity. US Patent No. 4,222,855 describes dewaxing operations to product lubricating oils of low pour point and of high V.I. utilizing zeolites including ZSM-23 and ZSM-35. US Patent No. 4,372,839 describes a method for dewaxing crude oils of high wax content by contacting the oils with two different zeolites, e.g., ZSM-5 and ZSM-35. US Patent No. 4,419,220 describes a dewaxing process utilizing a Zeolite Beta catalyst. The catalysts of the prior art often produce undesirable results. For example, when ZSM-5 is used to dewax a lube stock, unwanted high molecular-weight branched paraffins and naphthenic components with long alkyl branched chains are left behind due to their inability to freely diffuse into the pores of ZSM-5. Further, it will be shown in the examples to follow, see particularly Example 12, that Zeolite Beta requires increased temperatures in order to product adequate yields of dewaxed lube stock. Thus, Zeolite Beta alone in some cases is not the ideal dewaxing catalyst. According to the present invention a process for dewaxing a hydrocarbon lubricating oil feedstock, comprising contacting said feedstock under dewaxing conditions with a catalyst comprising a medium pore zeolite and a hydrogenation component, is characterised in that the catalyst further comprises zeolite beta, each zeolite constituting from 5 to 60% wt of the catalyst. Fig. 1 shows a comparison of viscosity index and pour point for Pt-ZSM-5/Zeolite Beta, Ni-ZSM-5/Zeolite Beta or Ni-ZSM-5 on a light neutral chargestock; Fig. 2 shows a comparison of tube yield and pour point for Pt-ZSM-5/Zeolite Beta, Ni-ZSM-5/Zeolite Beta or Ni-ZSM-5 on a light neutral chargestock; Fig. 3 shows a comparison of lube yield and reactor temperature for Pt-ZSM-5, Pt-ZSM-5/Zeolite Beta and Pt-Zeolite Beta on a light neutral chargestock; Fig. 4 shows a comparison of lube yield and pour point for steamed Ni-ZSM-5, Pt-ZSM-11, Pt-ZSM-11/Zeolite Beta and Pt-ZSM-5/Zeolite Beta; Fig. 5 shows a comparison of viscosity index and pour point for steamed Ni-ZSM-5, Pt-ZSM-11, Pt-ZSM-11/Zeolite Beta and Pt-ZSM-5/Zeolite Beta; Fig. 6 shows a comparison of lube yield and pour point for Pt-ZSM-11/Zeolite Beta, Pt-ZSM-5/Zeolite Beta, Pt-ZSM-23/ Zeolite Beta and Ni-ZSM-5; Fig. 7 shows a comparison of viscosity index and pour point for Pt-ZSM-11/Zeolite Beta, Pt-ZSM-5/Zeolite Beta, Pt-ZSM-23/Zeolite Beta and Ni-ZSM-5; Fig. 8 shows a comparison of viscosity index and pour point for steamed Ni-ZSM-5 and Pt-ZSM-5/Zeolite Beta on wary bright lube stock raffinate; and Fig. 9 shows a comparison of lube yield and pour point for steamed Ni-ZSM-5 and Pt-ZSM-5/Zeolite Beta on wary bright lube stock raffinate. The present process may be used to dewax a variety of feedstocks ranging from relatively light distillate fractions up to high boiling stocks, such as whole crude petroleum, reduced crudes, vacuum tower residua, propane deasphalted residua, e.g., brightstock, cycle oils, FCC tower bottoms, gas oils, vacuum gas oils, deasphalted residua and other heavy oils. The feedstock will normally be a C₁₀+ feedstock since lighter oils will usually be free of significant quantities of waxy components. However, the process is also particularly useful with waxy distillate stocks, such as gas oils, kerosenes, jet fuels, lubricating oil stocks, heating oils, hydrotreated oil stock, furfural-extracted lubricating oil stock, and other distillate fractions whose pour point and viscosity need to be maintained within certain specification limits. Lubricating oil stocks, for example, will generally boil above 230°C (450°F), more easily above 315°C (600°F). For purposes of this invention, lubricating or lube oil is that part of a hydrocarbon feedstock having a boiling point of 315°C (600°F) or higher, as determined by ASTM D-1160 test method. In general, hydrodewaxing conditions include a temperature between 230°C (450°F) and 400°C (750°F), a pressure between 100 and 21,000 kPa (0 and 3000 psig) and preferably between 800 and 7000 kPa (100 and 1000 psig). The liquid hourly space velocity (LHSV), i.e., the volume of feedstock per volume of catalyst per hour, is generally between 0.1 and 10 and preferably between 0.2 and 4 and the hydrogen-to-feedstock ratio is generally between 90 and 1400 of H₂ at standard conditions, per volume of liquid, at standard conditions VIV (500 and 8000 SCFB) and preferably between 140 and 700 V/V (800 and 4000 SCFB). The catalytic dewaxing process of this invention may be conducted by contacting the feed to be dewaxed with a fixed stationary bed of the defined crystalline silicate zeolite catalysts, a slurry bed or with a transport bed, as desired. The catalyst used in this process comprises a medium pore zeolite and Zeolite Beta and a hydrogenating component. Without wishing to be restricted to a certain theory, it is believed that a combination of a medium pore zeolite and a large pore zeolite, in the right proportion will offer superior dewaxing activities and yield lube oils of higher quality than the tube dewaxing catalysts of the prior art. zeolites termed medium or intermediate pore zeolites have an effective pore size of generally less than 0.7 nm (7 angstroms), such as to freely sorb normal hexane. By "effective pore size" it is meant that the pores of the medium pore zeolite behave in the same fashion as perfectly cylindrical pores, generally less than 0.7 nm (7 angstroms) in size. Thus, a medium pore zeolite may have pores in excess of 0.7 nm (7 angstroms) in size as long as the shape of the pores renders an effective pore size no greater than 0.7 nm (7 angstroms) in size. In addition, the structure must provide constrained access to larger molecules. It is sometimes possible to judge from a known crystal structure whether such constrained access exists. For example, if the only pore windows in a crystal are formed by 8-membered rings of silicon and aluminum atoms, then access by molecules of larger cross-section than normal hexane is excluded and the zeolite is not of the desired type. Windows of 10-membered rings are preferred, although, in some instances, excessive puckering of the rings or pore blockage may render these zeolites ineffective. Although 12-membered rings in theory would not offer sufficient constraint to produce advantageous conversions, it is noted that the puckered 12-ring structure of TMA offretite does show some contrained access. Other 12-ring structures may exist which may be operative for other reasons, and therefore, it is not the present intention to entirely judge the usefulness of a particular zeolite solely from theoretical structural considerations. A convenient measure of the extent to which a zeolite provides control to molecules of varying sizes to its internal structure is the CI of the zeolite. The method by which CI is determined is described fully in U.S. Patent No. 4,016,218, to which reference is made for details of the method. CI values for some typical materials are: CI ZSM-4 0.5 ZSM-5 6-8 ZSM-11 6-8 ZSM-12 2 ZSM-20 0.5 ZSM-23 9.1 ZSM-34 30-50 ZSM-35 4.5 ZSM-38 2 ZSM-48 3.5 TMA Offretite 3.7 TEA Mordenite 0.4 Clinoptilolite 3.4 Mordenite 0.5 REY 0.4 Amorphous Silica-Alumina 0.6 Dealuminized Y (Deal Y) 0.5 Chlorinated Alumina 1 Erionite 38 Zeolite Beta 0.6-1+ CI seems to vary somewhat with severity of operation (conversion) and the presence or absence of binders. Likewise, other variables, such as crystal size of the zeolite, the presence of occluded contaminants, etc., may affect the CI. Therefore, it will be appreciated that it may be possible to so select test conditions as to establish more than one value for the CI of a particular zeolite. This explains the range of Constraint Indices for zeolites, such as ZSM-5, ZSM-12, ZSM-34 and Zeolite Beta. Zeolite ZSM-4 is taught by U.S. Patent No. 3,923,639. Zeolite ZSM-5 is taught by U.S. Patent No. 3,702,886, and Re. No. 29,949. Zeolite ZSM-11 is taught by U.S. Patent No. 3,709,979. Zeolite ZSM-12 is taught by U.S. Patent No. 3,832,449. Zeolite ZSM-20 is taught by U.S. Patent No. 3,972,983. Zeolite ZSM-23 is taught by U.S. Patent No. 4,076,342. Zeolite ZSM-34 is described in U.S. Patent No. 4,086,186. Zeolite ZSM-35 is described by U.S. Patent No. 4,016,245. Zeolite ZSM-38 is described in U.S. Patent No. 4,046,859. Zeolite ZSM-48 is described in U.S. Patent No. 4,397,827. Zeolite Beta is described in U.S. Patent Nos. 3,308,069 and Re. 28,341. The medium or intermediate pore zeolites useful in this invention are also described in U.S. Patent No. 4,401,572. The large pore hydroisomerization catalysts 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 IB, IIB, VA, VIA or VIIIA of the Periodic Table (IUPAC 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 VIIIA, expecially platinum, but other noble metals, such as palladium, gold, silver, rhenium, rhodium, may also be used. Combinations of noble metals, such as platinum-rhenium, platinum-palladium, platinum-iridium or platinum-iridium-rhedium, together with combinations with non-noble metals, particularly of Groups VIA and VIIIA are of interest, particularly with metals such as cobalt, nickel, vanadium, tungsten, titanium and molybdenum, for example, 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, cobalt-nickel-tungsten or cobalt-nickel-titanium, may also be used. The metal may be incorporated into the catalyst by any suitable method, such as impregnation or exchange, onto the zeolite. The metal may be incorporated in the form of a cationic, anionic or neutral complex, such as Pt(NH₃) +2 / 4 , and cationic complexes of this type will be found convenient for exchanging metals onto the zeolite. Anionic complexes are also useful for impregnating metals into the zeolites. The acidic component of the zeolite is preferably a porous, crystalline zeolite. The crystalline zeolite catalysts used in the catalyst comprise a three-dimensional lattice of SiO4 tetrahedra, cross-linked by the sharing of oxygen atoms and which may optionally contain other atoms in the lattice, especially aluminum in the form of A104 tetrahedra; the zeolite will also include a sufficient cationic complement to balance the negative charge on the lattice. Acidic functionality may, of course, be varied by artifices including base exchange, steaming or control of silica:alumina ratio. The isomerization reaction is one which requires a relatively small degree of acidic functionality in the catalyst. Because of this, the zeolite 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 zeolites 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 contemplated. The original cations associated with each of the crystalline silicate zeolites utilized herein may be replaced by a wide variety of other cations according to techniques well known in the art. Typical replacing cations include hydrogen, ammonium, alkyl ammonium and metal cations, including mixtures of the same. Of the replacing metallic cations, particular reference is given to cations of metals such as rare earth metals, manganese, as well as metals of Group II A and B of the Periodic Table, e.g., zinc, and Group VIII of the Periodic Table, e.g., nickel, platinum and palladium. Typical ion exchange techniques are to contact the particular zeolite with a salt of the desired replacing cation. Although a wide variety of salts can be employed, particular preference is given to chlorides, nitrates and sulfates. Representative ion exchange techniques are disclosed in a wide variety of patents, including U.S. Patent Nos. 3,140,249; 3,140,251; and 3,140,253. Following contact with a solution of the desired replacing cation, the zeolite is then preferably washed with water and dried at a temperature ranging from 60°C to 320°C (150°F to 600°F) and thereafter calcined in air, or other inert gas at temperatures ranging from 260°C to 800°C (500°F to 1500°F) for periods of time ranging from 1 to 48 hours or more. It has been further found that catalysts of improved selectivity and other beneficial properties may be obtained by subjecting the zeolite to treatment with steam at elevated temperatures ranging from 260°C to 649°C (500°F to 1200°F) and preferably 399°C to 538°C (750°F to 1000°F). The treatment may be accomplished in an atmosphere of 100% steam or an atmosphere consisting of steam and a gas which is substantially inert to the zeolites. A similar treatment can be accomplished at lower temperatures and elevated pressure, e.g., 177°C to 371°C (350-700°F) at 10 to 200 atmospheres. The crystalline silicate zeolite utilized in the process of this invention is desirably employed in intimate combination with one or more hydrogenation components, such as tungsten, vanadium, zinc, molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a nobel metal such as platinum or palladium, in an amount between 0.1 and 25% by weight, normally 0.1 to 5% by weight especially for noble metals, and preferably .3 to 1% by weight. Such component can be exchanged into the composition, impregnated thereon or physically intimately admixed therewith. Such component can be impregnated into or onto the zeolite, such as, for example, in the case of platinum, by treating the zeolite with a platinum metal-containing ion. Thus, suitable platinum compounds include chloroplatinic acid, platinous chloride and various compounds containing the platinum amine complex. The compounds of the useful platinum or other metals can be divided into compounds in which the metal is present in the cation of the compound and compounds in which it is present in the anion of the compound. Both types of compounds which contain the metal in the ionic state can be used. A solution in which platinum metals are in the form of a cation or cationic complex, e.g., Pt(NH₃)₄C₁2, is particularly useful. Prior to use, the zeolites should be dehydrated at least partially. This can be done by heating to a temperature in the range of 200°C to 600°C (392°F to 1112°F) in an inert atmosphere, such as air, nitrogen, etc., and at atmospheric or subatmospheric pressures for between 1 and 48 hours. Dehydration can also be performed at lower temperatures merely by using a vacuum, but a longer time is required to obtain sufficient amount of dehydration. A preferred method for preparing the catalyst is to blend the zeolite with an inorganic oxide, such as alumina hydrates, form the composite into extrudates, dry the extrudate and calcine in an atmosphere such as nitrogen or air. The extrudate may then be exchanged with cations, such as ammonium, and recalcined, prior to adding a hydrogenation component, such as metals of Groups VI, VII, and VIII of the Periodic Table, e.g., platinum, molybdenum, nickel and cobalt. The addition of the hydrogenation component may be accomplished by impregnation and ion exchange. Drying and calcining subsequent to the addition of the hydrogenation component is then used to complete the preparation. The catalysts of this invention are typically prepared by mulling together from 5 to 60% by weight, preferably 20 to 40% by weight medium pore zeolite (SiO₂/Al₂0₃ mole ratio of 70), from 5 to 60% by weight, preferably 20 to 40% by weight large pore zeolite, e.g., NH₄ Zeolite Beta (SiO₂/Al₂0₃ mole ratio of 30), and from 0 to 50% by weight, preferably 0 to 40% by weight binder alpha alumina monohydrate. During the mulling process, a sufficient amount of water containing H₂PtCl₆ or Pt(NH₃)₄(NO₃)₂ added slowly to the dry mulling mixture. The mulling process is continued for 20 minutes or until the mixture is uniform. The mixture is then extruded and dried at 110°C (230°F) for approximately 3 hours. The extrudates are crushed and sized to 0.595 to 0.25mm diameter (30.60 mesh) material and calcined in air at 540°C (1000°F) for 3 hours. The catalyst thus produced contains from .1 to 2% by weight, preferably .3 to 1% by weight of finely dispersed platinum. It is to be understood that metal cations other than platinum may be incorporated into the catalyst. The following examples will serve to illustrate the process of the invention without limiting the same. Examples 1 - 9 In Examples 1 - 9, the chargestock was a light neutral lubricating oil chargestock having the following properties: Examples 1-2 Examples 1 and 2 illustrate the effect of unsteamed Ni-ZSM-5 catalyst on the chargestock as it was passed over the catalyst. The catalyst was loaded into a fixed-bed reactor. After the reactor temperature was lowered to the desired setting, the chargestock was passed over the catalyst along with hydrogen under the controlled process conditions which are recited in Table 1. The product stream leaving the reactor was passed through a heated trap, a cold-water trap, and a gas-sampling bomb. The gas samples were analyzed by mass spectrometry for C₁-C₆ components. Liquid products were topped under less than 0.1 mm Hg pressure and maximum pot temperature of 204°C (400°F), to isolate the 343°C (650°F) fraction. Some of the topped samples were processed through a simulated distillator. The light liquid products, i.e., the condensate from the cold trap and the overhead from the topped samples, were analyzed by gas chromatography. Overall material balances were made based on total liquid feed charge plus hydrogen. The results are also recited in Table 1. Examples 3-4 Examples 3 and 4 illustrate the effect of steamed Ni-ZSM-5 catalyst on the chargestock. The procedure of Examples 1-2 was followed under conditions specified in Table 2, which also recites the results. Examples 5-6 Examples 5 and 6 illustrate the effect of a 0.5% Pt-ZSM-5 catalyst on the chargestock. The platinum catalyst was reduced in situ at 482°C (900°F) and 2900 kPa (400 psig) of hydrogen for one hour before introducing the feed into the reactor. The procedure of Examples 1-2 was followed under conditions specified in Table 3, which also recites the results. Examples 7-9 Examples 7-9 illustrate the effect of 0.44% Pt-ZSM-5/Zeolite Beta on the chargestock. The composition of the catalyst is as follows: Component Wt. % NH₄ ZSM-5 32.5 NH₄ Zeolite Beta 32.5 Alpha Alumina Monohydrate (binder) 35 Platinum .44 The procedure of Examples 5-6 was followed under conditions specified in Table 4, which also recites the results. The results of Examples 1-9 are summarized below in Table 5, based upon data at -15°C (5°F) pour point for unsteamed Ni-ZSM-5, Pt-ZSM-5, and Pt-ZSM-5/Zeolite Beta catalysts (Examples 1, 5 and 9) and -9°C (15°F) pour point for steamed Ni-ZSM-5 (Example 3). The results of Examples 1-9 demonstrate: (1) For the 343°C (650°F+) pour point yield, Pt-ZSM-5/Zeolite Beta yields approximately a 5 wt % improvement over Pt-ZSM-5, steamed Ni-ZSM-5 or unsteamed Ni-ZSM-5; (2) Pt-ZSM-5/Zeolite Beta improved viscosity index of the dewaxed product by approximately four numbers ; and (3) Compared to unsteamed Ni-ZSM-5, either Pt-ZSM-5/Zeolite Beta or Pt-ZSM-5 improved overnight cloud (ONC) performance substantially. The products from these platinum catalysts clearly passed the ONC test. Thus, the catalyst used in the present invention is superior to prior art dewaxing catalysts in viscosity index, lubricating oil yield and overnight cloud performance. Additionally, the catalyst used in the present invention is substantially more active than the currently-used dewaxing catalyst: steamed Ni-ZSM-5. Examples 10-20 In the following examples, the chargestock used was a light neutral lubricating oil chargestock having the following properties: Light Neutral Stock Specific Gravity 0.8774 API° 29.8 Pour Point, °F/°C 85/29 Cloud Point, °F/°C 120/49 Viscosity KV at 100°C 5.341 Sulfur, Wt. % 0.76 Basic Nitrogen, ppm 45 Hydrogen, Wt. % 13.7 ASTM Color L1.0 Examples 10-12 Examples 10-12 illustrate the effect of unsteamed 0.1% Pt-Zeolite Beta on the light neutral chargestock. The procedure of Examples 5-6 was followed under conditions specified in Table 6, which also recites the results. Examples 13-16 Examples 13-16 illustrate the effect of .5% Pt-Zeolite Beta on the light neutral chargestock. The procedure of Examples 5-6 was followed under conditions specified in Table 7, which also recites the results. Examples 17-20 Examples 17-20 illustrate the effect of unsteamed 1.1% Ni-ZSM-5/Zeolite Beta on the light neutral chargestock. The procedure of Examples 1-2 was followed under conditions specified in Table 8, which also recites the results. Examples 21-25 Examples 21-25 illustrate the effect of 0.5% Pt-ZSM-11/Zeolite Beta on the light neutral chargestock. For these examples, ZSM-11 was first calcined in a nitrogen atmosphere at 538°C (1000°F) for 3 hours to decompose tetrabutyl ammonium and other organics in its structure. The ZSM-11 was subsequently NH₄NO₃ exchanged to reduce its Na content to less than 0.02%. Zeolite Beta was pretreated in a similar procedure as ZSM-11. 32.5 parts of NH₄ ZSM-11, 32.5 parts of NH₄ Zeolite Beta and 35 parts of alpha alumina monohydrate were mulled together to form a uniform mixture which was then impregnated with H₂PtCl₆ in a stream of CO₂. The sample was finally sized to 0.25 to 0.60 mm (30/60 mesh) and activated with an air calcination for 3 hours at 538°C (1000°F). The sample was analyzed and found to contain 0.49 wt % and 0.01 wt % Na. The runs were made in a 1.16 mm (15/32 in.) ID fixed-bed reactor with a spiral preheater and a three-zone furnace for good temperature control. The platinum composite catalyst was reduced in situ at 482°C (900°F) and 2900 kPa (400 psig) of hydrogen for one hour before the reactor temperature was lowered to 260°C (500°F) and the feed was started pumping into the reactor. The product stream leaving the reactor was passed through a heated trap, a cold water trap, and a gas-sampling bomb. The gas samples were analyzed by mass spectrometry for C₁-C₆ components. Liquid products were topped under less than 0.1 mm Hg pressure, maximum pot temperature 204°C (400°F), to isolate the 343°C (650°F+) part. Light liquid products (the condensate in the cold trap and the overhead from topping) were sent for gas chromatography analysis. Overall material balances were made based on total liquid feed charge plus hydrogen. Fresh catalyst was used for each run. The run conditions and results are specified in Table 9. Examples 26-29 Examples 26-29 illustrate the effect of 0.5% Pt-ZSM-23/ Zeolite Beta on the light neutral chargestock. The composite catalyst of Zeolite Beta and ZSM-23 was prepared by combining 32.5 parts of Zeolite Beta, 32.5 parts of ZSM-23 and 35 parts of alpha alumina monohydrate. The mixture was mulled together with water added to 50% in solids content. After 30 minutes, the mix was dried, formed, and sized to 0.71 to 1.41 mm (14/25 mesh). The sample was then impregnated with H₂PtCl₆ solution in a stream of CO₂. The air calcined final sample (at 538°C [1000°F], 3 hours) was analyzed and found to contain 0.53% weight Pt and 0.02% weight Na. The samples were tested using the procedure outlined for Examples 21-25. The run conditions and results are specified in Table 10. The results indicate that Pt-ZSM-5/Zeolite Beta, Ni-ZSM-5/Zeolite Beta, Pt-ZSM-11/Zeolite Beta and Pt-ZSM-23/Zeolite Beta are catalysts superior in V.I. and lube yield to the steamed Ni-ZSM-5 catalyst, the catalyst currently commonly used in lube dewaxing. Figs. 1 and 2 depict the relationships of V.I. and lube yield versus pour point for Pt-ZSM-5/Zeolite Beta and Ni-ZSM-5/Zeolite Beta. Generally, Pt-ZSM-5/Zeolite Beta improved V.I. by 3-5 numbers and lube yields by 4-6 wt. % over steamed Ni-ZSM-5. Ni-ZSM-5/Zeolite Beta also improved V.I. and lube yield over steamed Ni-ZSM-5 by 1-2 numbers and 2-3 wt. % respectively. Pt-ZSM-5/Zeolite Beta had constant lube yields over a pour point range of -15 to 7°C (5-45°F). With regard to Ni-ZSM-5, lube yield generally declined with decreasing pour point. Pt-ZSM-5/Zeolite Beta also reduces overnight cloud (ONC) formation in the light neutral stock. At -15°C (5°F), the product processed over this catalyst passed the ONC test, while the products from the steamed Ni-ZSM-5 catalyst failed. Additionally, both Pt- and Ni-ZSM-5/Zeolite Beta catalysts produce a lube stock with higher sulfur and lower nitrogen contents than the standard steamed Ni-ZSM-5 catalyst. The quality of the lube stock is generally enhanced by higher sulfur and lower nitrogen contents. Further, Pt-ZSM-5/Zeolite Beta reduces the ASTM color of dewaxed products. At -15°C (5°F), the ASTM color of the lube stock is L1.0 for Pt-ZSM-5/Zeolite Beta and 3.0 for unsteamed Ni-ZSM-5. Pt-ZSM-5/Zeolite Beta also yields less C₃-C₅ gaseous products than steamed Ni-ZSM-5, indicating that the Pt composite catalyst has less undesired cracking activity. With respect to the Zeolite Beta catalysts tested (0.1 and 0.5 wt. % Pt), the figures in Tables 7 and 8 indicate that the higher platinum content, i.e., 0.5 wt. %, slightly increased catalytic cracking activity. This is shown by the lower lube yields when the lube stock is processed over .5 wt. % Pt-Zeloite Beta. At the same pour point, the lube yields, specific gravities and viscosity indexes were comparable for 0.1 and 0.5 wt. % Pt-Zeolite Beta catalysts. However, compared to either of the Pt-ZSM-5/Zeolite Beta catalysts, Pt-Zeolite Beta has a lube dewaxing activity disadvantage of at least 111°C (200°F). As indicated on Table 4, a reactor temperature of 304°C (580°F) is required to yield a -15°C (5°F) pour product, with unsteamed .45% Pt-ZSM-5/Zeolite Beta. However, a reactor temperature of 427°C (800°F) is needed for .44% Pt-Zeolite Beta (Table 7). Additionally, at 427°C (800°F), Pt-Zeolite Beta severely reduces the viscosities of the dewaxed product, resulting in a V.I. of only 80.5. The product lube stock from Pt-Zeolite Beta also has a darker ASTM color (4.0 - Table 7) than the lube stocks treated with either Pt-ZSM-5/Zeolite Beta (L1.0 - Table 9). Fig. 3, which plots the relationship of lube yield vs. reactor temperature for Pt-ZSM-5, Pt-ZSM-5/Zeolite Beta, and Pt-Zeolite Beta, illustrates that at the reactor temperature below 343°C (650°F), lube yield is greater than 90% for Pt-Zeolite Beta. At temperatures above 343°C (650°F), lube yield decreases. With respect to Pt-ZSM-5, lube stock yield decreased with increasing reactor temperatures. The lube stock yield remained constant at 85 wt. % at increasing temperatures for Pt-ZSM-5/Zeolite Beta. Tests conducted with Pt-ZSM-11/Zeolite Beta and Pt-ZSM-23/Zeolite Beta are summarized as follows: (a) The Pt-ZSM-11/Zeolite Beta catalyst gave 3-5 numbers higher V.I.'s and 3-5 wt % higher lube yields than Ni-ZSM-5; (b) The Pt-ZSM-23/Zeolite Beta catalyst produced 3-4 wt % higher lube yield with V.I.'s 6-8 numbers higher than Ni-ZSM-5; and (c) Three Zeolite Beta based composite catalysts: ZSM-5/Zeolite Beta, ZSM-11/Zeolite Beta and ZSM-23/Zeolite Beta, produced almost equivalent lube yield, but the ZSM-23/Zeolite Beta catalyst gave the highest V.I. improvement. Referring now to ZSM-11, the following Table shows a comparison of a dewaxed lube oil processed with Pt-ZSM-11/Zeolite Beta and Pt-ZSM-11 at 0°C (15°F) pour point. Catalyst Pt-ZSM-11 Pt-ZSM-11/Zeolite Beta Pour Point, °F/°C 15/-9 15/-9 Reactor Temp., °F/°C 540/282 590/310 Days-on-Stream 3.5 6.5 Specific Gravity 0.880 0.880 Gravity, API° 29.0 28.9 Lube Yield, wt. % 81.9 84.1 KV at 40°C, cs 42.32 41.0 KV at 100°C, cs 6.31 6.294 VI 95.2 95.8 Sulfur, wt. % 0.84 0.88 Basic Nitrogen, ppm 43 37 Compared to Pt-ZSM-11, the Pt-ZSM-11/Zeolite Beta catalyst improved lube yield by 2% by weight, and offered a little V.I. improvement. Because of the relatively low cracking activity of Zeolite Beta, the Pt-ZSM-11/Zeolite Beta catalyst is 17°C (30°F) less active than Pt-ZSM-11 after the correction for catalyst aging. As to product gravity, kinematic viscosities, sulfur and nitrogen contents, little or no difference was observed between Pt-ZSM-11 and Pt-ZSM-11/Zeolite Beta. With the same feed charge at 1 LHSV, Pt/Zeolite Beta needed a processing temperature of 427°C (800°F) to reduce the pour point to -15°C (5°F). But Pt-ZSM-11/Zeolite Beta needed only 316°C (600°F) and, therefore, is at least 93°C (200°F) more active than Pt/Zeolite Beta. Apparently, Pt/Zeolite Beta by itself has very low dewaxing activity under normal lube oil dewaxing conditions. The comparisons are as follows: Catalyst Pt-ZSM-11/C-56 Pt/C-56 Pour Point, °F/°C 5/-15 5/-15 Reactor Temp., °F/°C 600/316 800/427 Days-on-Stream 7.5 6 Specific Gravity 0.88 0.88 Gravity, API° 28.8 29.0 Lube Yield, wt. % 83.0 52.5 KV at 40°C, cs 42.8 13.05 KV at 100°C, cs 6.339 3.035 VI 94.3 80.5 Sulfur, wt. % 0.85 0.22 Basic Nitrogen, ppm 40 5 At 427°C (800°F), the Pt/Zeolite Beta catalyst exhibited very high cracking activity and thus severely cracked lube molecules. As a result, the lube yield was only 53% with a V.I. of 81. Additionally, the sulfur and nitrogen contents were reduced substantially to 0.22% by weight and less than 5 ppm, respectively. Therefore, the addition of ZSM-11 to Zeolite Beta offers the necessary cracking activity for lube dewaxing under normal conditions. Figs. 4 and 5 compare lube yields and V.I.'s, respectively, for steamed Ni-ZSM-5, Pt-ZSM-11, Pt-ZSM-11/Zeolite Beta and Pt-ZSM-5/Zeolite Beta. Compared to steamed Ni-ZSM-5/, Pt-ZSM-5/Zeolite Beta had the highest improvement in lube yield and V.I., followed by Pt-ZSM-11/Zeolite Beta and Pt-ZSM-11. Referring now to ZSM-23, the following Table gives a comparison of the properties of a dewaxed product processed with Pt-ZSM-23/Zeolite Beta, Pt-ZSM-5/Zeolite Beta and Pt-ZSM-11/ Zeolite Beta: Catalyst Pt-ZSM-11/Zeolite Beta Pt-ZSM-5/Zeolite Beta Pt-ZSM-23 Zeolite Beta Pour Point, °F/°C 20/-7 20/-7 25/-4 Reactor Temp., °F/°C 580/304 565/296 680/360 Days-on-Stream 5.5 2 7 Specific Gravity 0.88 0.88 0.87 Gravity, API° 29.1 28.9 30.1 Lube Yield, wt. % 84.3 84.8 84.6 KV at 40°C, cs 41.06 42.44 38.83 KV at 100°C, cs 6.236 6.363 6.084 VI 97.5 97.0 100.9 Sulfur, wt. % 0.85 0.88 0.27 Basic Nitrogen, ppm 34 32 26 At -7 to -4°C (20 to 25°F) pour, the product from the ZSM-23/Zeolite Beta catalyst has the highest V.I. compared to either ZSM-11/ Zeolite Beta or ZSM-5/Zeolite Beta. The sulfur level in the product from ZSM-23/Zeolite Beta was only 30% of that present in the products from ZSM-11/Zeolite Beta and ZSM-5/Zeolite Beta. The degree of sulfur removal in the ZSM-23/Zeolite Beta product may substantially contribute to the increased V.I. observed. Shown in Figs. 6 and 7 are the relationship of lube yield and viscosity index versus pour point, respectively, for Pt-ZSM-11/Zeolite Beta, Pt-ZSM-5/Zeolite Beta, Pt-ZSM-23/Zeolite Beta, and Ni-ZSM-5. Compared to steamed Ni-ZSM-5, the ZSM-23/ Zeolite Beta catalyst gave 3-4% by weight yield and 6-8 numbers V.I. advantage for Paulsboro light neutral. The V.I. improvement with ZSM-23/Zeolite Beta is the highest among the tested catalysts, although the degree of desulfurization may contribute substantially to the V.I. All the composite catalysts give the similar improvement in lube yield. The lube yield and V.I. improvements relative to steamed Ni-ZSM-5 are summarized as follows: Process Improvement With Composite Catalysts Lube Yield, wt. % V.I. Pt-ZSM-5/Zeolite Beta + 3-5 + 4-7 Pt-ZSM-11/Zeolite Beta + 3-5 + 3-5 Pt-ZSM-23/Zeolite Beta + 3-4 + 6-8 Examples 30-39 In the following examples, the chargestock used was a heavy neutral lubricating oil chargestock having the following properties: Heavy Neutral Stock Specific Gravity 0.8945 API° 26.5 Pour Point, °F/°C 110/43 Cloud Point, °F/°C 120/49 Viscosity KV at 100°C 12.33 Sulfur, Wt. % 1.07 Basic Nitrogen, ppm 64 Hydrogen, Wt. % 13.57 ASTM Color 4.0 Examples 30-33 Examples 30-33 illustrate the effect of steamed Ni-ZSM-5 on the heavy neutral lube stock. The procedure of Examples 1-2 was followed under conditions specified in Table 11, which also recites the results. Examples 34-39 Examples 34-39 illustrate the effect of unsteamed Pt-ZSM-5/Zeolite Beta on the heavy neutral lube stock. The procedure of Examples 5-6 was followed under conditions specified in Table 12, which also recites the results. The results of Examples 30-39 indicate that V.I. and lube yield were improved by approximately 1-2 numbers and 2-3 wt. % respectively when processed with the Pt-ZSM-5/Zeolite Beta. Both catalysts produced lube stock products which are comparable in specific gravity, hydrogen, sulfur and nitrogen contents. Examples 40-50 In the following examples, the chargestock used was a waxy bright lubricating oil chargestock raffinate having the following properties: Waxy Bright Stock Raffinate Specific Gravity 0.9036 API° 25.1 Pour Point, °F/°C 120/49 Cloud Point, °F/°C 120/49 Viscosity KV at 100°C 29.06 Sulfur, Wt. % 1.13 Basic Nitrogen, ppm 130 Examples 40-45 Examples 40-45 illustrate the effect of steamed Ni-ZSM-5 on the waxy bright lube stock raffinate. The procedure of Examples 1-2 was followed under conditions specified in Table 13, which also recites the results. Examples 46-50 Examples 46-50 illustrate the effect of unsteamed Pt-ZSM-5/Zeolite Beta on waxy bright lube chargestock raffinate. The procedure of Examples 5-6 was followed under conditions specified in Table 14, which also recites the results. Figs. 8 and 9 show the comparison of V.I. or lube yield and pour point for steamed Ni-ZSM-5 and Pt-ZSM-5/Zeolite Beta when used on waxy bright lube stock raffinate. The results indicate that V.I. is slightly improved by the use of Pt-ZSM-5/ Zeolite Beta. Lube yields for the catalysts were comparable. Turning now to Tables 13 and 14, it can be seen that Pt-ZSM-5/Zeolite Beta reduced ONC formation. The ONC's of the product lube at -18°C (0°F) pour point were 7 and 25 for Pt-ZSM-5/Zeolite Beta respectively. In conclusion, the medium pore zeolite/large pore zeolite catalysts have been shown to be unexpectedly superior to prior art lube dewaxing catalysts, e.g., Ni-ZSM-5, and Zeolite Beta, especially in terms of V.I., lubricating oil yield and ONC with a variety of lube oil feedstocks.

Claims: A process for dewaxing a hydrocarbon lubricating oil feedstock, comprising contacting said feedstock under dewaxing conditions with a catalyst comprising a medium pore zeolite and a hydrogenation component, characterised in that the catalyst further comprises zeolite beta, each zeolite constituting from 5 to 60% wt of the catalyst. A process according to claim 1 wherein each zeolite constitutes from 20 to 40% wt of the catalyst. A process according to claim 1 or claim 2 wherein the catalyst further comprises a binder. A process according to claim 3 wherein the binder is alpha alumina monohydrate, silica, silica-alumina and/or naturally occurring clay. A process according to claim 3 or claim 4 wherein the binder constitutes up to 50% wt of the catalyst. A process according to any preceding claim wherein the medium pore zeolite is ZSM-5, -11, -12, -23, -35, -38 or -48, or TMA offretite. A process according to any preceding claim wherein the hydrogenation component comprises a metal of Group VI, VII and/or VIII of the Periodic Table. A process according to any preceding claim wherein the catalyst is prepared by blending the two zeolites and a binder to form an extrudable composite, extruding the composite, drying the extrudate and adding the hydrogenation component to the dry extrudate. A process according to claim 8 wherein the extrudate is calcined. A process according to any preceding claim which is carried out in the presence of hydrogen. A process according to claim 10 which is carried out at 0.5 to 4 LHSV, a temperature of 260 to 399°C (500 to 750°F), a pressure of 800 to 10,500 kPa (100 to 1500 psig) and a hydrogen/feedstock ratio of 90 to 1400 v/v (500 to 8000 SCFB). A process according to any previous claim wherein the hydrogenation component comprises platinum.

Inventors: CHU, POCHEN, YEN, JEFFREY HSING-GAN
Applicants: MOBIL OIL CORPORATION
Application year: 1985
Main classification: B01J29
IPC codes: B01J29, C10G73, C10G45