US3438887A - Production of lubricating oils - Google Patents

Description

United States Patent US. Cl. 208-87 9 Claims ABSTRACT OF THE DISCLOSURE Improved lubricating oils are prepared from waxy distillates by the processing sequence of solvent refining, catalytic dewaxing and hydrorefining.

The present invention is directed to improvements in the manufacture of lubricating oils. More particularly, it is concerned with a process comprising the three-stage treatment of a wax distillate, namely, solvent refining, catalytic dewaxing and catalytic hydrorefining.

The quality of a lubricating oil is measured by certain characteristics such as oxidation stability, pour point, viscosity index and color. The requirements for various lubricating applications differ to a considerable extent and to obtain a satisfactory lubricating oil, a balance of the various characteristics is necessary depending on the requirements of the intended use.

Lubricating oils intended primarily for use in internal combustion engines should have among other properties a high viscosity index, a relatively low viscosity and a low pour point. Various processes are available for the production of lubricating oils, for example, solvent dewaxing to remove paraffins and reduce the pour point, deasphalting to remove asphaltic bodies, clay contacting to further improve color and remove traces of acid, and solvent refining to remove aromatics and improve the viscosity index. Ordinarily to produce a high quality motor oil recourse is bad in varying degrees to each of the processes mentioned above.

In the process of the present invention a lubricating oil of high quality is produced by a simplified process which reduces the number of operational steps and also eliminates the necessity of treating the oil with large amounts of solvents, acids and clay and the attendant problems of recovery and regeneration or disposal. In our process the lubricating oil stock is subjected to a particular sequence of steps involving solvent refining, catalytic de- Waxing and hydrorefining.

In the solvent refining operation, the oil undergoing treatment is subjected to liquid-liquid contact with a selective solvent which preferentially dissolves the more aromatic constituents from the oil undergoing treatment. It is a characteristic of the selective solvent employed that it is partially miscible with the oil undergoing treatment so that during the solvent refining operatlon there are formed two phases, a raffinate phase containing substantially only a solvent refined oil having a reduced amount or proportion of aromatic hydrocarbons as compared to the oil charged to the solvent refining operation, and an extract phase or mix comprising selective solvent and dissolved therein extract or extracted oil having a relatively increased proportion or amount of more aromatic hydrocarbons as compared with the charge oil. The aforesaid solvent refining operation may be carried out stagewise (combinations of mixer-settler) or con tinuously in a suitable contacting apparatus, e.g. packed or plate tower, rotating disc contactor, either concurrently or countercurrently. Selective solvents which are suitably employed include furfural, phenols, liquid sulfur dioxide, nitrobenzene, B,;3'-dichloroethylether, dimethylice formamide, diethylene glycol, N-methyl pyrrolidone and the like.

The solvent refined oil is then subjected to catalytic dewaxing. In this stage the oil is contacted with a catalyst in the pressence of hydrogen at elevated temperatures and pressures. The temperature will range from 450850 F2, preferably 550-7 50 F. Pressures of from atmospheric to 5000 psig and higher may be used although a preferred range is from 300 to 2000 p.s.i.g. A suitable liquid hourly space velocity (LHSV) is from 0.5 to 3.0 volumes of oil per hour per volume of catalyst although space velocities of from 01-10 may be used. Advantageously, hydrogen in an amount ranging up to 20,000 s.c.f.b. (standard cubic feet per barrel) of charge may be present, preferred rates being 500l0,000 s.c.f.b. The hydrogen need not be pure and gases containing more than about volume percent hydrogen may be used. In this connection, the

term hydrogen is also intended to include dilute hydrogen. Reformer by-product hydrogen, hydrogen produced by the partial oxidation of hydrocarbon materials followed by shift conversion and electrolytic hydrogen are satisfactory.

The catalyst used in the dewaxing stage of our process comprises a hydrogenating component supported on a low sodium mordenite. Synthetic mordenite is usually prepared as the alkali metal alumino silicate which for the purpose of the present invention is an inactive form. To convert the synthetic mordenite to a form active for the cracking of hydrocracking of the waxy components of the oil, it is converted to the hydrogen form by removal of the alkali metal ion, usually sodium. The removal of the sodium ion is accomplished by contacting the synthetic mordenite with ammonia or a compound thereof usually in the form of a water solution to incorporate the ammonium ion in the mordenite. Subsequent calcination converts the mordenite to the active or acid form. The mordenite may also be converted to the low sodium or acid form by contact with a dilute acid such as3Nor6NHCl.

Of the various natural and synthetic zeolites now available in the industry only the low sodium or acid form of mordenite is satisfactory for the purposes of the present invention. Other crystalline zeoli'es such as zeoli e A, faujasite, zeolite X and zeolite Y are unsatisfactory whether or not they have a low alkali me al content. This is attributed to the combination of pore size and unusual catalytic activity of the mordenite. Whereas zeolite A and faujasite have pore openings of 5 A. and zeolites X and Y have uniform pore openings of 10-13 A., the catalyst support u ed in our process has sorption channels which are parallel to the C-axis of the crystal and are elliptical in cross-section. The dimensions of the sorntion channels of sodium mordenite based on crystallographic studies have been reported as a minor diameter of 5.8-5.9 A., a major diameter of 7.07.1 A. and an average diameter of 6.6 A. The hydrogen form of the mordeni e appears to have somewhat larger pore o enings with a minor diameter of not less than 5.8 A. and a major diameter less than 8 A. The effective working pore diameter of the hydrogen mordenite prepared by acid treating synthetic mordenite appears tobe in the range of 8 A. to 10 A. as indicated by the adsorption of aromatic hydrocarbons.

Supported on the hydrogen form of the mordenite is a hydrogenating component which comprises a Group VIII metal or compound thereof, for example the oxide or sulfide, which may be associated with a Group VI metal or compound thereof. Noble metals such as platinum, palladium and rhodium have been found especially useful and may be used in amounts of O.15% based on the total catalyst weight with a range of 0.5-2.5 being preferred. Other suitable hydrogenating components comprise nickel, cobalt and iron, particularly when used in conjunction with a Group VI metal such as molybdenum or tungsten. Suitable combinations include cobalt molybdenum, nickel molybdenum and nickel tungsten. The latter type of hydrogenating component may be present in an amount ranging from 540% by weight, preferably 25%. The hydrogenating component may be incorporated into the support by ion exchange or by impregnation, each of these methods being well known in the art.

In the catalytic dewaxing stage of the process, the waxy components are cracked to lighter components having a boiling point considerably lower than the desired lube oil fraction and therefore are easily separated therefrom. The principal byproducts of our catalytic dewaxing process are light hydrocarbons such as ethane, propane and butane.

The catalytically dewaxed oil is then introduced into the hydrorefining stage and brought into contact with the hydrogenating catalyst at elevated temperatures and pressures in the presence of hydrogen. Suitable catalysts cornprise the oxides and/or sulfides of metals such as cobalt, molybdenum, nickel, tungsten, chromium, iron, manganese, vanadium and mixtures thereof. The catalytic materials may be used alone or may be deposited on or mixed with a support such as alumina, magnesia, silica, zinc oxide, natural and synthetic zeolites or the like. Particularly suitable catalysts are nickel tungsten sulfide, molybdenum oxide on alumina, a mixture of cobalt oxide and molybdenum oxide generally referred to as cobalt molybdate on alumina, molybdenum oxide and nickel oxide on alumina, molybdenum oxide, nickel oxide and cobalt oxide on alumina, nickel sulfide on alumina, molybdenum sulfide, cobalt sulfide and nickel sulfide on alumina.

In the hydrorefining zone, pressures and temperatures may range broadly between 500-5000 p.s.i.g. and 500 900 F., preferred ranges being 8003000 p.s.i.g. and 600800 F., respectively. Space velocities of 0.253.0 may be used although a rate between 0.5 and 1.5 is preferred. The hydrogen rate may range between 200 and 10,000 s.c.f.b. although suitable results are obtained at hydrogen rates between 2000 and 6000 s.c.f.b. This hydrorefining treatment results in a hydrogenated product having substantially the same boiling range as the charge to the hydrorefining zone and is termed non-destructive hydrogenation as distinguished from destructive hydrogenation in which a substantial portion of the product boils at a temperature below that of the charge.

It is possible to carry out the second and third stages of the process, namely the catalytic dewaxing and catalytic hydrorefining stages in separate reactors with the catalytic dewaxing catalyst in one reactor and the catalytic hydrorefining catalyst in the other with each reactor having its own hydrogen system and its own recycle system or with the reactors having a common recycle system. It is also possible to have two catalyst beds in the same reactor, for example having a bed of dewaxing catalyst superimposed over a bed of hydrorefining catalyst and to pass the solvent refined wax distillate downwardly through the two beds in sequence. In this way the entire eflluent from the catalytic dewaxing stage is introduced into the catalytic hydrorefining stage.

Our process also permits the use of starting materials which are more viscous than those used in conventional processing. For example, the catalytic dewaxing and hydrorefining of a furfural refined wax distillate results in a product having a lower viscosity at the viscosity index level of a sovent refined-solvent dewaxed oil. (231 SU/vis./ 100 F. vs. 250 SUS for furfural refined and solvent dewaxed wax distillate 15.) The corresponding viscosities for wax distillate when treated according to our process are 330 vs. 350 when treated by conventional solvent refining and solvent dewaxing. This indicates that our process results in a greater reduction in viscosity than conventional treatment and therefore can handle more viscous charge stocks than can the conventional solvent refining-solvent dewaxing treatment.

The following examples are given for illustrative purposes only and should not be construed as limiting the invention in any manner.

EXAMPLE I Below are set forth the data for a run in which the charge stock, a furfural refined distillate wax 20, having a viscosity SUS at 100 F. of 271, a viscosity index of 103 and a pour point of 95 F. is catalytically dewaxed in one reactor and the product catalytically refined in a second reactor under the various conditions set out in Runs 11-14. The catalyst in the first reactor is 2% palladium on decationized or acid mordenite and the catalyst in the second reactor is sulfided nickel tungsten.

TABLE I First Stage Second Stage Run No 10 11 12 13 14 Pressure, p.s.i.g 850 1, 500 1, 400 850 850 Temperature, F- 625-650 650 675 675 700 LHSV, v./v./hr 0 5 0. 5 0.5 0.5 0.5 Hydrogen rate, S.c.f.b 8, 0O016, 000 6, 800 8, 600 8, 400 7, 800 Product Viscosity, SUS at It will be noted that the hydrorefining recovered to a large extent the viscosity index lost in catalytic dewaxing.

EXAMPLE II In this example a furfural refined waxy distillate having an SUS viscosity at 100 F. of 264, a viscosity index of 105 and a pour point of 100 F. is passed downwardly through a reactor containing two catalyst beds, an upper bed of 0.5% palladium on decationized mordenite and a bed of equal size comprising 3% nickel and 9.5% tungsten on decationized mordenite. The results are set forth in Table II.

TABLE II Run N o Pressure, p.s.i.g. Temperature, F LHSV, v./v./hr

Hydrogen rate, 8.0 7, 800 1, 200 Product Viscosity, SUS at 100 F. 184 181 Viscosity Index 92 Pour, F 5 15 EXAMPLE III TABLE III Hydro- Catalytic Solvent refining Dewaxing Refining Temperature, F 750 650 187 Pressure, p.s.i.g 1, 500 850 LHSV, v./v./hr 1.0 0. 51 Hydrogen rate, S.c.f.b 2, 500 8, 400 Batch dosage, v01. percent 1X 200%+1X 300% Product Viscosity, SUS at These results compare unfavorably with those obtained in Example I in which the sequence is solvent refining catalytic dewaxing and hydrorefining.

invention as hereinbefore set forth may be made with out departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for the production of lubricating oils of improved properties which comprises subjecting a wax distillate to a solvent refining treatment to remove aromatics therefrom, contacting the solvent refined product with a catalyst comprising a hydrogenating component on low sodium mordenite under dewaxing conditions and then subjecting the solvent refined dewaxed oil to catalytic non-destructive hydrogenation.

2. The process of claim 1 in which the solvent defining step comprises contacting the wax distillate with furfural.

3. The process of claim 1 in which the solvent refining step comprises contacting the wax distillate with N- methyl pyrrolidone.

4. The process of claim 1 in which the dewaxing catalyst comprises palladium.

5. The process of claim 1 in which the low sodium mordenite is prepared by ion exchanging a synthetic mordenite with ammonia or a compound thereof and then calcining.

6. The process of claim 1 in which the low sodium mordenite is prepared by contacting a synthetic mordenite with dilute acid.

7. The process of claim 6 in which the dilute acid is 3-6 N HCl.

8. The process of claim 1 in which the non-destructive hydrogenation catalyst comprises nickel and tungsten.

9. The process of claim 1 in which the entire effluent from the dewaxing zone is introduced into the non-destructive hydrogenation zone.

References Cited UNITED STATES PATENTS 3,242,068 3/1966 Paterson 208-18 3,243,366 3/1966 Kimberlin et al. 208-28 3,256,175 6/1966 Kozlowski et al. 208-87 3,365,390 .1/ 1968 Egan et al. 208-18 HERBERT LEVINE, Primary Examiner.

11.8. C1. X.R.