Lube Oils By Solvent Dewaxing And Hydrodewaxing With A Zsm-5 Catalyst

Abstract

A two-step or combination process for preparing low pour point lube oils is set forth. The process involves subjecting a lube stock to a mild solvent dewaxing step, so as to obtain high quality waxes and a lube stock having an intermediate pour point; recovering the waxes and subjecting said intermediate pour point lube stock to a hydrowaxing step over a crystalline aluminosilicate of the ZSM-5 type to obtain a product having a pour point of 0.degree. F and lower.

Parent Case Text

CROSS REFERENCE TO RELATED CASES

This application is a continuation of U.S. Pat. Ser. No. 56,652 filed July 20, 1970, now abandoned and which is a continuation-in-part of U.S. Pat. Ser. No. 865,470 filed Oct. 10, 1969 now U.S. Pat. No. 3,700,585, issued Oct. 24, 1972.

Description

DESCRIPTION OF THE INVENTION

This invention relates to a process for dewaxing petroleum oils and fractions thereof by selectively removing normal paraffinic and other undesirable hydrocarbons from petroleum oils in which they are present in admixture with other hydrocarbons, in order to lower the pour point of such oils. More particularly, the invention relates to an improved process for selectively removing normal paraffinic and other undesirable hydrocarbons from petroleum oils by a two-step process involving solvent dewaxing followed by contact of such oils with specific types of crystalline aluminosilicate zeolites identified as those of the ZSM-5 type.

It is well known in the art to form various lubricating oils, commonly referred to as lubes, from hydrocarbon fractions derived from petroleum crudes. A heretofore practiced common procedure known in the art is to extract these hydrocarbon fractions with various solvents so as to give a raffinate of a desired high viscosity index, such material being resistant to changes in viscosity with changes in temperature and thus being useful under varying operating conditions. Moreover, it is particularly desired that the lube oil have a low pour point so that it can be effectively used at low temperature conditions, since excessive thickening at low temperatures is often unacceptable. It is also known in the art to carry out dewaxing operations by contacting hydrocarbon fractions with crystalline aluminosilicate zeolites having pore sizes of about 5 Angstrom units so as to selectively remove normal paraffins.

The present invention is concerned with an improved process for dewaxing normal paraffin-containing oils which is more economical than conventional solvent dewaxing procedures or catalytic dewaxing procedures involving 5 Angstrom unit zeolites and which, with certain feedstocks, produces a higher product yield with equivalent or higher pour point reduction.

Briefly, the present process employs the use of a conventional solvent dewaxing step but only to slightly reduce the pour point of the treated stock and obtain a product having an intermediate pour point. Quite obviously, the product of intermediate pour point is unsuitable for use as a low temperature lubricant at this stage. In accordance with the invention, this intermediate product is then subjected to hydrodewaxing with a crystalline aluminosilicate of the ZSM-5 type to yield a product having excellent low temperature properties.

It is to be immediately noted that the sequence of steps of the instant combination process is critical. In order to achieve the maximum economic advantage the solvent dewaxing must come first followed by the catalytic hydrodewaxing step. This is so because the highest quality wax which is obtained from a given feed is that obtained in the initial stages of the solvent dewaxing. If the feed stock were first subject to catalytic hydrodewaxing, the highest quality wax would be destroyed.

Additionally, it has been found that catalytic hydrodewaxing with a ZSM-5 type catalyst is more effectively carried out with intermediate pour point product than with a conventional lube stock. Thus, the unique processing scheme of this invention provides a maximization of desirable products from a given feed stock.

The feedstocks adapted for treatment in accordance with the present invention may be generally defined as hydrocarbon oils boiling above about 650.degree. F and particularly between about 650.degree. and about 1,100.degree. F.

As has heretofore been stated, the first step of the novel process of this invention involves subjecting a feed stock of the type above-described to a mild solvent dewaxing.

By mild solvent dewaxing is meant that the lube stock feed material is treated until it has a pour point of 10.degree. to 50.degree. F and preferably from 20.degree.-30.degree. F.

The solvent dewaxing step is carried out in a conventional manner according to well known techniques. Suitable solvent mixtures include methyl ethyl ketone-toluene, methyl ethyl ketone-methyl isobutyl ketone etc.

The products from the solvent dewaxing step are high quality waxes which are recovered and an intermediate pour point stock which is then subjected to hydrodewaxing over a catalyst comprising a crystalline zeolite of the ZSM-5 type.

While not wishing to be bound by any theory of operation, nevertheless, it appears that the crystalline zeolitic materials employed in the instant invention cannot simply be characterized by the recitation of a pore size or a range of pore sizes. It would appear that the uniform pore openings of this new type of zeolite are not circular in nature, as is usually the case in the heretofore employed zeolites, but rather, are elliptical in nature. Thus, the pore openings of the instant zeolitic materials have both a major and a minor axis, and it is for this reason that the unusual and novel molecular sieving effects are achieved. This elliptical shape can be referred to as a "keyhole." From their dynamic molecular sieving properties it would appear that the major and minor axes of the elliptical pore in this family of zeolites have effective sizes of about 7.0 .+-. 0.7A and 5.0 .+-. 0.5A, respectively.

The family of ZSM-5 type compositions has the characteristic X-ray diffraction pattern set forth in Table 1, hereinbelow. ZSM-5 compositions can also be identified, in terms of mole ratios of oxides, as follows:

0.9 .+-. 0.2 (M.sub.2 O/n) : W.sub.2 O.sub.3 : 5-100 YO.sub.2 : 2 H.sub.2 O

wherein M is a cation, n is the valence of said cation, W is selected from the group consisting of aluminum and gallium, Y is selected from the group consisting of silicon and germanium, and Z is from 0 to 40. In a preferred synthesized form, the zeolite has a formula, in terms of mole ratios of oxides, as follows:

0.9 .+-. 0.2 (M.sub.2 O/n) : Al.sub.2 O.sub.3 : 5-100 SiO.sub.2 : z H.sub.2 O

and M is selected from the group consisting of a mixture of alkali metal cations, especially sodium, and tetraalkylammonium cations, the alkyl groups of which preferably contain 2-5 carbon atoms.

In a preferred embodiment of ZSM-5, W is aluminum, Y is silicon and the silica/alumina mole ratio is at least 10 and ranges up to about 60.

Members of the family of ZSM-5 zeolites possess a definite distinguishing crystalline structure whose X-ray diffraction pattern shows the following significant lines:

TABLE I

Interplanar Spacing d(A) Relative Intensity 11.1 .+-. 0.2 S 10.0 .+-. 0.2 S 7.4 .+-. 0.15 W 7.1 .+-. 0.15 W 6.3 .+-. 0.1 W 6.04 .+-. 0.1 W 5.97 .+-. 0.1 W 5.56 .+-. 0.1 W 5.01 .+-. 0.1 W 4.60 .+-. 0.08 W 4.25 .+-. 0.08 W 3.85 .+-. 0.07 VS 3.71 .+-. 0.05 S 3.64 .+-. 0.05 M 3.04 .+-. 0.03 W 2.99 .+-. 0.02 W 2.94 .+-. 0.02 W

these values as well as all other X-ray data were determined by standard techniques. The radiation was the K-alpha doublet of copper, and a scintillation counter spectrometer with a strip chart pen recorder was used. The peak heights, I, and the positions as a function of two times theta, where theta is the Bragg angle, were read from the spectrometer chart. From these, the relative intensities, 100 I/I, where I is the intensity of positions as a function of two times theta, where theta is the Bragg angle, were read from the spectrometer chart. From these, the relative intensities, 100 I/I, where I is the intensity of the strongest line or peak, and d (obs.), the interplanar spacing in A, corresponding to the recorded lines, were calculated. In Table I the relative intensities are given in terms of the symbols S = strong, M = medium, MS = medium strong, MW = medium weak and VS = very strong. It should be understood that this X-ray diffraction pattern is characteristic of all the species of ZSM-5 compositions. Ion exchange of the sodium ion with cations reveals substantially the same pattern with some minor shifts in interplanar spacing and variation in relative intensity. Other minor variations can occur depending on the silicon to aluminum ratio of the particular sample, as well as if it has been subjected to thermal treatment. Various cation exchanged forms of ZSM-5 have been prepared. X-ray powder diffraction patterns of several of these forms are set forth below. The ZSM-5 forms set forth below are all aluminosilicates.

TABLE 2

X-Ray Diffraction

ZSM-5 Powder in Cation Exchanged Forms

d Spacings Observed

As Made HCl NaCl CaCl.sub.2 ReCl.sub.3 AgNO.sub.3 11.15 11.16 11.19 11.19 11.19 11.19 10.01 10.03 10.05 10.01 10.06 10.01 9.74 9.78 9.80 9.74 9.79 9.77 9.01 9.02 8.99 8.06 7.44 7.46 7.46 7.46 7.40 4.46 7.08 7.07 7.09 7.11 7.09 6.70 6.72 6.73 6.70 6.73 6.73 6.36 6.38 6.38 6.37 6.39 6.37 5.99 6.00 6.01 5.99 6.02 6.01 5.70 5.71 5.73 5.70 5.72 5.72 5.56 5.58 5.58 5.57 5.59 5.58 5.37 5.38 5.37 5.38 5.37 5.13 5.11 5.14 5.12 5.14 4.99 5.01 5.01 5.01 5.01 5.01 4.74 4.61 4.62 4.62 4.61 4.63 4.62 4.46 4.46 4.46 4.36 4.37 4.37 4.36 4.37 4.37 4.26 4.27 4.27 4.26 4.27 4.27 4.08 4.09 4.09 4.09 4.09 4.00 4.01 4.01 4.00 4.01 4.01 3.84 3.85 3.85 3.85 3.86 3.86 3.82 3.82 3.82 3.82 3.83 3.82 3.75 3.75 3.75 3.76 3.76 3.75 3.72 3.72 3.72 3.72 3.72 3.72 3.64 3.65 3.65 3.65 3.65 3.65 3.60 3.60 3.60 3.61 3.60 3.48 3.49 3.49 3.48 3.49 3.49 3.44 3.45 3.45 3.44 3.45 3.45 3.34 3.35 3.36 3.35 3.35 3.35 3.31 3.31 3.32 3.31 3.32 3.32 3.25 3.25 3.26 3.25 3.25 3.26 3.17 3.17 3.18 3.13 3.14 3.14 3.14 3.15 3.14 3.05 3.05 3.05 3.04 3.06 3.05 2.98 2.98 2.99 2.98 2.99 2.99 2.97 2.95 2.95 2.94 2.95 2.95 2.86 2.87 2.87 2.87 2.87 2.87 2.80 2.78 2.78 2.78 2.73 2.74 2.74 2.73 2.74 2.74 2.67 2.68 2.66 2.65 2.60 2.61 2.61 2.61 2.61 2.61 2.59 2.59 2.57 2.57 2.56 2.57 2.50 2.52 2.52 2.52 2.52 2.49 2.49 2.49 2.49 2.49 2.49 2.45 2.41 2.42 2.42 2.42 2.42 2.39 2.40 2.40 2.39 2.40 2.40 2.38 2.35 2.38 2.33 2.33 2.32 2.33 2.30 2.24 2.23 2.23 2.20 2.21 2.20 2.20 2.18 2.18 2.17 2.17 2.13 2.13 2.11 2.11 2.11 2.10 2.10 2.08 2.08 2.08 2.08 2.07 2.07 2.04 2.01 2.01 2.01 2.01 2.01 2.01 1.99 2.00 1.99 1.99 1.99 1.99 1.97 1.96 1.95 1.95 1.95 1.95 1.95 1.94 1.92 1.92 1.92 1.92 1.92 1.91 1.91 1.88 1.87 1.87 1.87 1.87 1.87 1.87 1.86 1.84 1.84 1.84 1.84 1.83 1.83 1.83 1.83 1.83 1.82 1.81 1.82 1.77 1.77 1.79 1.78 1.77 1.76 1.76 1.76 1.76 1.76 1.76 1.75 1.75 1.74 1.74 1.73 1.71 1.72 1.72 1.71 1.70 1.67 1.67 1.67 1.67 1.67 1.66 1.66 1.66 1.66 1.66 1.65 1.65 1.64 1.64 1.63 1.63 1.63 1.63 1.62 1.61 1.61 1.61 1.61 1.58 1.57 1.57 1.57 1.57 1.56 1.56 1.56

zeolite ZSM-5 can be suitably prepared by preparing a solution containing tetrapropyl ammonium hydroxide, sodium oxide, an oxide of aluminum or gallium, an oxide of silica or germanium, and water and having a composition, in terms of mole ratios of oxides, falling within the following ranges:

TABLE 3

Particularly Broad Preferred Preferred OH.sup.-/SiO 0.07-1.0 0.1-0.8 0.2-0.75 R.sub.4 N+/(R.sub.4 N .sup.++Na.sup.+) 0.2-0.95 0.3-0.9 0.4-0.9 H.sub.2 O/OH.sup.- 10-300 10-300 10-300 YO.sub.2 /W.sub.2 O.sub.3 5-100 10-60 10-40

wherein R is propyl, W is aluminum or gallium and Y is silicon or germanium maintaining the mixture until crystals of the zeolite are formed. Thereafter, the crystals are separated from the liquid and recovered. Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature of from about 150.degree. C to 175.degree. C for a period of time of from about 6 hours to 60 days. A more preferred temperature range is from about 160.degree. to 175.degree. C with the amount of time at a temperature in such range being from about 12 hours to 8 days.

The digestion of the gel particles is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, filtering, and water washing.

The foregoing product is dried, e.g., at 230.degree. F, for from about 8 to 24 hours. Of course, milder conditions may be employed if desired, e.g., room temperature under vacuum.

ZSM-5 is preferably formed as an aluminosilicate. The composition can be prepared utilizing materials which supply the appropriate oxide. Such compositions include for an alumino-silicate, sodium aluminate, alumina, sodium silicate, silica hydrosol, silica gel, silicic acid, sodium hydroxide and tetrapropylammonium hydroxide. It will be understood that each oxide component utilized in the reaction mixture for preparing a member of the ZSM-5 family can be supplied by one or more initial reactants and they can be mixed together in any order. For example, sodium oxide can be supplied by an aqueous solution of sodium hydroxide, or by an aqueous solution of sodium silicate; tetrapropylammonium cation can be supplied by the bromide salt. The reaction mixture can be prepared either batchwise or continuously. Crystal size and crystallization time of the ZSM-5 composition will vary with the nature of the reaction mixture employed. ZSM-5 is disclosed and claimed in copending U.S. Pat. application Ser. No. 865,472, filed Oct. 10, 1969.

Another operable zeolite falling within the above class is zeolite ZSM-8 which is described and claimed in U.S. Pat. Ser. No. 865,418, filed Oct. 10, 1969 now abandoned.

ZSM-8 can also be identified, in terms of mole ratios of oxides, as follows:

0.9 .+-. 0.2 (M.sub.2 O/n) : Al.sub.2 O.sub.3 : 5-100 SiO.sub.2 : z H.sub.2 O

wherein M is at least one cation, n is the valence thereof and z is from 0 to 40. In a preferred synthesized form, the zeolite has a formula, in terms of mole ratios of oxides, as follows:

0.9 .+-. 0.2 (M.sub.2 O/n) : Al.sub.2 O.sub.3 : 10-60 SiO.sub.2 : z H.sub.2 O

and M is selected from the group consisting of a mixture of alkali metal cations, especially sodium, and tetraethylammonium cations.

ZSM-8 has an exceptionally high degree of thermal stability thereby rendering it particularly effective for use in processes involving elevated temperatures. In this connection, ZSM-8 appears to be one of the most stable zeolites known to date.

ZSM-8 possesses a definite distinguishing crystalline structure having the following X-ray diffraction pattern.

TABLE 4

dA.degree. I/I.sub.o I/I.sub.o dA.degree. 11.1 46 4 2.97 10.0 42 3 2.94 9.7 10 2 2.86 9.0 6 1 2.78 7.42 10 4 2.73 7.06 7 1 2.68 6.69 5 3 2.61 6.35 12 1 2.57 6.04 6 1 2.55 5.97 12 1 2.51 5.69 9 6 2.49 5.56 13 1 2.45 5.36 3 2 2.47 5.12 4 3 2.39 5.01 7 1 2.35 4.60 7 1 2.32 4.45 3 1 2.28 4.35 7 1 2.23 4.25 18 1 2.20 4.07 20 1 2.17 4.00 10 1 2.12 3.85 100 1 2.11 3.82 57 1 2.08 3.75 25 1 2.06 3.71 30 6 2.01 3.64 26 6 1.99 3.59 2 2 1.95 3.47 6 2 1.91 3.43 9 3 1.87 3.39 5 1 1.84 3.34 18 2 1.82 3.31 8 3.24 4 3.13 3 3.04 10 2.99 6

zeolite ZSM-8 can be suitably prepared by reacting a solution containing either tetraethylammonium hydroxide or tetraethylammonium bromide together with sodium oxide, aluminum oxide, and an oxide of silica and water.

The relative operable proportions of the various ingredients have not been fully determined and it is to be immediately understood that not any and all proportions of reactants will operate to produce the desired zeolite. In fact, completely different zeolites can be prepared utilizing the same starting materials depending upon their relative concentration and reaction conditions as is set forth in U.S. Pat. No. 3,308,069. In general, however, it has been found that when tetraethylammonium hydroxide is employed, ZSM-8 can be prepared from said hydroxide, sodium oxide, aluminum oxide, silica and water by reacting said materials in such proportions that the forming solution has a composition in terms of mole ratios of oxides falling within the following range

SiO.sub.2 /Al.sub.2 O.sub.3 -- from about 10 to about 200

Na.sub.2 O/tetraethylammonium hydroxide -- from about 0.05 to 0.20

Tetraethylammonium hydroxide/SiO.sub.2 -- from about 0.08 to 1.0

H.sub.2 o/tetraethylammonium hydroxide -- from about 80 to about 200

Thereafter, the crystals are separated from the liquid and recovered. Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature of from about 100.degree. to 175.degree. C for a period of time of from about 6 hours to 60 days. A more preferred temperature range is from about 150.degree. to 175.degree. C with the amount of time at a temperature in such range being from about 12 hours to 8 days.

The digestion of the gel particles is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, filtering, and water washing.

The foregoing product is dried, e.g., at 230.degree. F for from about 8 to 24 hours. Of course, milder conditions may be employed if desired, e.g., room temperature under vacuum.

ZSM-8 is prepared utilizing materials which supply the appropriate oxide. Such compositions include sodium aluminate, alumina, sodium silicate, silica hydrosol, silica gel, silicic acid, sodium hydroxide and tetraethylammonium hydroxide. It will be understood that each oxide component utilized in the reaction mixture can be supplied by one or more initial reactants and they can be mixed together in any order. For example, sodium oxide can be supplied by an aqueous solution of sodium hydroxide, or by an aqueous solution of sodium silicate, tetraethylammonium cation can be supplied by the bromide salt. The reaction mixture can be prepared either batchwise or continuously.

The zeolites used in the instant invention can have the original cations associated therewith replaced by a wide variety of other cations according to techniques well known in the art. Typical replacing cations would include acidic cations such as hydrogen, ammonium and metal cations including mixtures of the same. Of the replacing metallic cations, particular preference is given to cations of metals such as rare earth metals, manganese, calcium, as well as metals of Group II of the Periodic Table, e.g. zinc, and Group VIII of the Periodic Table, e.g., nickel.

Typical ion exchange techniques would be to contact the particular zeolite with a salt of the desired replacing cation or cations. 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. Pat. No. 3,140,249; U.S. Pat No. 3,140,251; and U.S. Pat. No. 3,140,253.

Following contact with the salt solution of the desired replacing cation, the zeolites are then preferably washed with water and dried at a temperature ranging from 150.degree. F to about 600.degree. F and thereafter calcined in air or other inert gas at temperatures ranging from about 500.degree. F to 1,500.degree. F for periods of time ranging from 1 to 48 hours or more. It has been further found in accordance with the invention that catalysts of improved selectivity and having other beneficial properties in some hydrocarbon conversion processes such as catalytic cracking are obtained by subjecting the zeolite to treatment with steam at elevated temperatures ranging from 800.degree. to 1,500.degree. F and preferably 1,000.degree. F and 1,400.degree. F. The treatment may be accomplished in atmospheres of 100 percent steam of 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 pressures, e.g., 350.degree.-700.degree. F at 10 to about 200 atmospheres.

The ZSM-5 type zeolites must be used in intimate combination with a hydrogenating component such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, zinc, or a noble metal such as platinum or palladium since a hydrogenation/dehydrogenation function is to be performed. Such component can be exchanged into the composition, impregnated therein or physically intimately admixed therewith. Such component can be impregnated in or onto zeolite such as, for example, by, in the case of platinum, treating the zeolite with a platinum metal-containing ion. Thus, suitable platinum compounds include chloroplatinic acid, platinous chloride and various compounds containing the platinum ammine complex.

The compounds of 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(NH.sub.3).sub. 4 Cl.sub.2 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.degree. to 600.degree. C 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 a sufficient amount of dehydration.

Operating conditions include temperatures between 650.degree. F and 1,000.degree. F, a pressure between 100 and 3,000 psig but preferably between 200 and 1,500 psig. The liquid hourly space velocity is generally between 0.1 and 100, preferably between 0.5 and 20 and the hydrogen to hydrocarbon mole ratio is generally between 1 and 80 preferably between 4 and 40.

The following examples will illustrate the best mode now contemplated for carrying out this invention.

EXAMPLES 1 - 2

Examples 1 and 2 are directed towards conventional solvent dewaxing and in each case the charge stock was a furfural raffinate having the following properties:

Gravity, .degree.API 32.1 Pour Point, .degree.F. +105 K.V. at 210.degree.F, cs. 5.45

In both examples, conventional solvent ratios were employed which were as follows on a volume to volume basis:

Solvent --*MEK/Toluene 60/40 Dilution, Solvent/Oil 3/1 Wash, Solvent/Oil 1/1 * methylethylketone

In Example 1 the dewaxing was carried out at 0.degree. F whereas in Example 2 the temperature employed was -20.degree. F.

Typical results of dewaxing at 0.degree. F and -20.degree. F are as follows:

Example 1 2 Dewaxing Temperature, .degree.F. 0 -20 Yield of Oil, Wt. % 83 80.5 Gravity, .degree.API 29.5 29.1 Pour Point, .degree.F. +20 0 K.V. at 100.degree.F, cs. 43.0 45.0 K.V. at 210.degree.F, cs. 6.11 6.23 Viscosity Index 95 92 Yield of Wax, Wt. % 17 19.5 Melting Point, .degree.F. +132 +127 Oil Content 1.9 3.85

The small incremental wax from dewaxing to 0.degree. F pour (Example 2) over +20.degree. F pour (Example 1) hurts the quality of the wax, i.e., melting point goes down and oil content goes up. For highest quality wax it is therefore desirable to first dewax to about +20.degree. F, and then further process to reduce the pour to 0.degree. F. When this is done by solvent dewaxing, the material removed is commonly combined with "foot's oil" and sent to catalytic cracking.

EXAMPLE 3

This example illustrates further pour point reduction by conventional solvent dewaxing. This example is carried out at -35.degree. F which represents the lower limit at which solvent dewaxing is practical. The solvents were those used in Example 1 and the charge stock is the solvent dewaxed oil of Example 1 having a pour point of +20.degree. F.

The results are as follows:

Dewaxing Temp., .degree.F -35 Oil, Wt. % (of +20.degree.F chg.) 76.4 Gravity, .degree.API 28.8 Pour Point, .degree.F -15 K.V. at 100.degree.F, cs 49.16 K.V. at 210.degree.F, cs 6.63 V.I. 94 "Wax", wt.% 23.6

EXAMPLE 4

The +105.degree. F pour point raffinate used as feed material in Example 1 was subjected to catalytic hydrodewaxing with a ZSM-5 type catalyst which contained zinc and which had been base exchanged with ammonium ions (This catalyst was prepared by the same general procedure used to prepare the catalyst in Example 9 of parent U.S. Pat. application Ser. No. 865,470, filed Oct. 10, 1969). This hydrodewaxing took place without first carrying out solvent dewaxing. The operation conditions were 750 psig, 750.degree. F, 1 LHSV, and 8,000 SCF H.sub.2 /bbl. The results obtained were as follows:

Oil, Wt. % 54 Gravity, .degree.API 29.9 Pour Point, .degree.F. +25 K.V. at 100.degree.F, cs 36.28 K.V. at 210.degree.F, cs 5.64 V.I. 103 Cracked Products, Wt. % 46

Note that although the pour point was indeed lowered, the yield of oil was only 54 percent as compared to 83 percent for solvent dewaxing, i.e., see Example 1.

EXAMPLES 5-7

These examples will illustrate operations in accordance with this invention.

In each of these examples a charge stock was first subjected to solvent dewaxing in the same manner as Example 1. The oil resulting from the treatment of Example 1, i.e., the +20 pour point fraction, was then subjected to hydrodewaxing with a Zn/HZSM-5 catalyst (This catalyst was prepared according to the same procedure as that used in Example 9 of U.S. Pat. Ser. No. 865,470).

The results and operating conditions are set forth below:

Example 5 6 7 Yield of Oil, Wt. % 86 84 74 Gravity, .degree.API 27.8 28.5 27.7 Pour Point, .degree.F -20 -40 <-80 K.V. at 100.degree.F, cs 47.95 53.38 46.93 K.V. at 210.degree.F, cs 6.42 6.72 6.08 Viscosity Index 89 83 76 Cracked Products, Wt. % 14 16 26 Reaction Conditions Pressure, psig 500 750 750 Temperature, .degree.F 750 750 750 H.sub.2, SCF/bbl (H.sub.2 /HC mol ratio) 11,000 2,000 2,000 (30) (5.4) (5.4) LHSV 8 4 1

as can be seen from the above results, the process of this invention allows for greater yields of lower pour point material as well as taking advantage of producing and recovering high quality waxes from the conventional solvent extraction step.

Claims

What is claimed is:

1. A process for preparing low pour point lube oils which comprises subjecting a petroleum feed stock to solvent dewaxing so as to obtain a lube oil having an intermediate pour point of 10.degree. to 50.degree. F and thereafter subjecting said intermediate pour point product to catalytic hydrodewaxing by contacting the same in the presence of added hydrogen with a crystalline aluminosilicate of the ZSM-5 type containing a hydrogenation component and obtaining a product having a pour point no higher than 0.degree. F.

2. The process of claim 1 wherein the ZSM-5 type zeolite has X-ray diffraction patterns corresponding to that set forth in Table 1.

3. The process of claim 1 wherein the ZSM-5 type zeolite is ZSM-8.

4. The process of claim 1 wherein the ZSM-5 type zeolite has been base exchanged with hydrogen ions, ammonium ions, and mixtures thereof.

5. The process of claim 4 wherein the product obtained has a pour point no higher than -20.degree. F.