US3431198A - Two-stage catalytic hydrogenation of a dewaxed raffinate - Google Patents

Description

United States Patent 3,431,198 TWO-STAGE CATALYTIC HYDROGENATION OF A DEWAXED RAFFINATE Maurice K. Rausch, South Holland, Ill., assignor to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 12, 1966, Ser. No. 600,785 US. Cl. 208--143 6 Claims Int. Cl. C10g 23/02, 23/04 ABSTRACT OF THE DISCLOSURE This invention relates to a process for the production of high quality mineral oils from defined mineral lubricating oil distillates. More particularly, this invention concerns a catalytic conversion process for the production of mineral oils which are essentially odorless and tasteless.

Conventional refining techniques, for example, solvent extraction or solvent dewaxing, have been employed in an attempt to produce mineral oils which are substantially odorless and tasteless. However, these methods have been inadequate in that the mineral oil products will contain a moderately strong odor and a moderately strong taste. Thus, there is a need for an improved process for treating raw, waxy lubricating oil distillates to produce mineral oils which are odorless and tasteless and thus can be used in such applications as food processing or packaging.

The present invention concerns a solvent extractionsolvent dewaxing-catalytic hydrogenation process wherein a raw, waxy lubricating oil distillate having a strong odor and taste is converted into a refined mineral oil which is susbtantially odorless and tasteless. According to the process of the present invention, a raw, waxy lubricating oil distillate is subjected to solvent extraction to yield a raflinate with a viscosity index of about 70' to 110 (on a dewaxed basis) and the rafiinate is dewaxed to yield a product having a pour point in the range of about to +20 F. Alternatively, the dewaxing can precede the solvent extraction. The product is then subjected to a two-stage catalytic hydrogenation process for the elimination of remaining odor and taste-causing components in the hydrocarbon oil. These two properties are very important in such applications as food processing or packaging where it is highly undesirable to have oil odors or tastes imparted to the food product.

The mineral lubricating oil distillates treated by the process of the present invention are raw, waxy lubricating oil distillates often boiling primarily in the range of about 550 to 1100 F. and generally having a viscosity in the range of about to 1 00 SUS at 210 F., and a pour point of at least about 60 F., and are derived from crude oils having a characterization factor of at least 11.5, e.g., mixed base or paraflinic crude oils as distinguished from naphthenic types of crude oil. Parafiinic crudes are found, for instance, in Pennsylvania and other areas of the Eastern United States. Generally, mixed base crude oils are found in the Mid-Continent area of the United States, and for example, include such crudes as Oklahoma City and East Texas crudes. The compositions of mixed 3,431,198 Patented Mar. 4, 1969 base crude oils is intermediate that of parafiinic and naphthenic crudes and the physical properties of a mixed base crude are usually intermediate those of paraflinic and naphthenic crudes. Thus, the fraction of a mixed base crude boiling between 428 F. and 527 F. at atmospheric pressure may have an API gravity between about 33 and 40 API while the fraction boiling between 527 F. and 572 F. at 40 mm. may have an API gravity between about 2 0 and 30 API and a cloud point above 50 F. The characterization factor of mixed base crude oils normally falls in the range of from 11.5 to 12.1 while the characterization factor of paraifinic stocks is usually greater than 12.1. Mixed base crude oils can be chemically classified as parafiinic-naphthenic crude oils according to the system set forth in The Science of Petroleum, volume V, part I, pages -77, Oxford University Press, New York, 1953, and A. N. Sachanen, The Chemical Constituents of Petroleum, pages 4l9427, Reinhold Publishing Corporation, New York, 1945. Representative of such crude oils are an Oklahoma City crude with the approximate composition by weight of 36% parafiins, 45% naphthenes, 14% aromatics and 5% resins and asphaltenes and a ring analysis showing 65% parafiin side chains, 25% naphthenic rings and 10%? aromatic rings; and an East Texas crude with the approximate composition of 33% parafiins, 41% naphthenes, 17% aromatics and 9% resins and asphaltenes and a ring analysis showing 60% parafiin side chains, 26% naphthenic rings and 14% aromatic rings. Usually Mid-Continent mixed base crude oils will contain from 60 to 70 percent by weight parafiinic side chains and at least 20 percent by weight naphthenic rings.

'Removal of aromatics is performed by solvent extraction to give an extract phase containing solvent and aromatic components and a rafiiniate useful in the process of the invention. The solvent used in the extraction process may be one of a group of solvents selective for the separation of aromatic fractions, such solvents including phenol, furfural, liquid sulfur dioxide, and the like. Extraction is generally conducted countercurrently in a tower.

The conditions under which the extraction tower may be operated can be those conventional in the art, as for example, temperatures generally in the range of from about to 300 F. with a temperature gradient through the tower of about 0 to 50 F., and solvent-to-oil ratios of from about 0.5 to 6:1, preferably about 1 to 3:1. Normal operating pressures should be higher than the vapor pressure of the solvent system used at the temperature of operation. For example, in a solvent system comprising phenol, pressures Within the range of about to 300 p.s.i.g. may be used. The extract phase may be conducted to a zone where, for example, by a pressure and/or temperature change the solvent is vaporized leaving higher boiling aromatics which may be used as a raw material for various petrochemical processes. Traces of be carried out, by using a solvent or a mixture of solvents which dissolve the material and which, upon cooling, precipitate the waxy components as a separate solid phase. Suitable solvents include toluene, benzene, acetone, methylethyl ketone, etc., and especially specific mixtures of these solvents such as a mixture of toluene and methylethyl ketone. The mixture of lubricating oil and solvent, after the wax has been precipitated and different temperature, generally example, toluene and benzene boil at a temperature of about 200 F. while the initial boiling point of the lubricating oil fraction is often at a temperature of about 600 F. Generally, about 100 to 600 percent of solvent based on the oil is suificient but this can vary with the characteristics of the extract. Generally, filter temperatures of about to F. are employed. The dewaxing can precede the solvent extracting, however, for the proper control of pour point it is preferred to extract the lubricating oil distillate first and then dewax. The solvent dewaxed hydrocarbon raffinate is characterized by a substantially reduced pour point and a moderately strong odor and taste.

The dewaxed raifinate is subjected to catalytic hydrogenation wherein the raffinate is contacted in a first stage with hydrogen in the presence of a desulfurizationdenitrogenation type catalyst under hydrorefining conditions, and further contacted in a second stage with hydrogen in the presence of an aromatic hydrogenation catalyst.

The desulfurization-denitrogenation type catalysts used in the first stage can be any of the sulfur-resistant, nonprecious metal hydrogenation catalysts conventionally employ in the hydrogenation of heavy petroleum oils. Examples of suitable catalytic ingredients are tin, vanadium, members of Group VI-B in the Periodic Table, i.e., chromium, molybdenum and tungsten and metals of the iron group, i.e., iron, cobalt and nickel. These metals are present in catalytically effective amounts, for instance about 2 to 30 weight percent, and may be present in the form of oxides and sulfides. Mixtures of these materials or compounds of two or more of the oxides or sulfides can be employed, for example, mixtures or compounds of the iron group, metal oxides or sulfides with the oxides or sulfides of Group VI-B constitute very satisfactory catalysts. Examples of such mixtures or compounds are nickel molybdate, tungstate or chromate (or thiomolybdate, thiotungstate or thiochromate) or mixtures of nickel or cobalt oxides with molybdenum, tungsten or chromium oxides. As the art is aware and as the specific examples below illustrate, these catalytic ingredients are generally employed while disposed upon a suitable carrier of the solid oxide refractory type, e.g., a predominantly calcined or activated alumina. Commonly employed catalysts have about 1 to 10% of an iron group metal and S to of a Group VIB metal (calculated as the oxide). The catalyst may be nickel molybdate or cobalt molybdate supported on alumina. Such catalysts can be prepared by the method described in US. Patent 2,938,002.

The aromatic hydrogenation catalyst used in the second stage has a platinum group metal on a suitable support. This catalyst is to be distinguished from the catalyst of the first stage in that the former is not normally sulfur-resistant. The latinum group catalysts include such Group VIII metals as, for example, platinum, palladium, rhodium or iridium, and are present in catalytically effective amounts, generally in the range of about 0.01 to 2 weight percent, preferably about 0.1 to 1 weight percent. The platinum group metal may be present in the metallic form or as a sulfide, oxide or other combined form. The metal may interact with other constituents of the catalysts, but if during use the platinum group metal is present in the metallic form, then it is preferred that it be so finely divided that it is not detectable by X-ray diffraction means, i.e., that it exists as crystallites of less than 50 A. in size. Of the platinum group metals, platinum is preferred.

The preferred catalyst support used in the second stage of the present process is composed predominantly of alumina of the activated or calcined type. The alumina base generally constitutes at least about 75 weight percent of a catalyst and preferably at least about 85 to 99.8 percent. The alumina catalyst base can be an activated or gamma alumina such as those derived by calcination of amorphous hydrous alumina, alumina monohydrate, alumina trihydrate or their mixtures. The alumina portion of the catalyst base may contain a major portion of, for example, about 65 to 95 weight percent, one or more of the alumina trihydrates bayerite, nordstrandite or gibbsite, and about 5 to 35 weight percent of alumina monohydrate (boehmite), amorphous hydrous alumina or their mixture.

The process conditions employed in the first stage of the catalytic hydrogenation step generally include temperatures of about 625 to 775 F., preferably about 650 to 725 F., pressures of about 1500 to 4000 p.s.i.g., preferably about 2000 to 3000 p.s.i.g., weight hourly space velocities (WHSV) of about 0.1 to 2, preferably about 0.15 to l, and hydrogen rates of about 1000 to 5000 s.c.f./b. of feed, preferably about 1200 to 3000 s.c.f./b.

The reaction conditions used in the second hydrogentreating stage, i.e., aromatic hydrogenation stage, generally include temperatures of about 500 to 600 F., preferably about 525 to 575 F. The other reaction conditions may include pressures of about 1000 to 4000 p.s.i.g., preferably about 1500 to 3000 p.s.i.g., weight hourly space velocities (WI-ISV) of about 0.1 to 2, preferably about 0.15 to 1, and hydrogen rates of about 1000 to 5000 s.c.f./b. of feed, preferably about 1200 to 3000 s.c.f./b.

The process of the present invention is illustrated in detail by the following example which is not to be considered limiting.

Example I A raw, waxy lubricating oil distillate fraction derived from a mixed base crude and exhibiting 82.4 SUS viscosity at 210 F., 120+ pour point, a 5 to percent boiling range of 859 to 1030 F. and containing a very strong odor and taste, was first subjected to solvent extraction using phenol as the solvent. The resulting waxy rafiinate yield was 62.8 percent and exhibited a viscosity of 64.3 SUS at 210 F., a pour point of 120+ and possessed a moderately strong odor and taste. This material was then solvent dewaxed using a 50/50 mixture of methylethyl ketone and toluene to yield a 67.3 percent dewaxed raffinate having a viscosity of 68.7 SUS at 210 F., a viscosity index of 96, a pour point of +15, with the ratfinate possessing a moderately strong odor and taste. The dewaxed raffinate was then subjected to a catalytic hydrogenation step using a commercial cobalt molybdate on alumina catalyst in the first stage and a commercial platinum on alumina catalyst in the second stage. Process conditions in the first stage included a temperature of about 700 F., a pressure of about 2,400 p.s.i.g., a weight hourly space velocity of about 0.25 and a hydrogen rate of about 1500 s.c.f./b. The second stage process conditions included a temperature of about 550 F., a pressure of about 2,400 p.s.i.g., a weight hourly space velocity of about 0.25 and a hydrogen rate of about 2500 s.c.f./ b. The final product was recovered in a yield of 95.5 percent, had a viscosity of 62.2. SUS at 210 F. and was substantially odorless and tasteless.

It is claimed:

1. A process for producing mineral oils which are substantially odorless and tasteless and possess a low pour point which comprises subjecting a dewaxed rafiinate produced by treatment with a solvent selective for aromatics, of a mineral lubricating oil distillate of lubricating viscosity, said distillate oil being derived from a crude oil having a characterization factor of at least 11.5, said raffinate having a viscosity index of about 70 to and a pour point of about 20 to +20 F., to a two stage catalytic hydrogenation process wherein the dewaxed raf'rlnate is contacted with a hydrogen rich gas and a catalytic amount of a sulfur-resistant hydrogenation catalyst at a temperature of about 625 to 775 F., a pressure of about 1500 to 4000 p.s.i.g., a weight hourly space velocity of about 0.1 to 2, and a hydrogen feed rate of about 1000 to 5000 s.c.f./b. of feed, and further contacted in a second stage with a hydrogen rich gas and a catalytic amount of a platinum group metal supported on alumina catalyst at a temperature of about 500 to 600 F., a pressure of about 1000 to 4000 p.s.i.g., a weight hourly space velocity of about 0.1 to 2, and a hydrogen feed rate of about 1000 to 5000 s.c.f./ b.

2. The process of claim 1 in is platinum.

3. The process of claim 2 wherein said sulfur-resistant catalyst is cobalt molybdate supported on alumina.

4. A process for producing mineral oils which are substantially odorless and tasteless and possess a low pour point which comprises, subjecting a dewaxed rafiinate produced by treatment with a solvent selective for aromatics of a mineral lubricating oil distillate derived from a crude oil having a characterization factor of at least 11.5, said distillate having a viscosity of about to 100 SUS at 210 F., a pour point of at least about F. and boiling primarily in the range of about 550 to 1100 F., said dewaxed raifinate having a viscosity index of about to and a pour point of about 20 to +20 F., to a two stage catalytic hydrogenation process wherein the dewaxed rafiinate is contacted with a hydrogen rich gas and a catalytic amount of a cobalt molybdate on alumina catalyst at a temperature of about 650 to 725 F., a pressure of about 2000 to 3000 p.s.i.g., a weight hourly space velocity of about 0.15 to 1 and a hydrogen feed rate of about 1200 to 3000 s.c.f./b. of feed, and further contacted in a second stage with a hydrogen rich gas and a catalytic amount of a platinum which the platinum metal group metal supported on alumina catalyst at a temperature of about 525 to 575 F., a pressure of about 1500 to 3000 p.s.i.g., a weight hourly space velocity of about 0.15 to l and a hydrogen feed rate of about 1200 to 3000 s.c.f./'b.

5. The process of claim 4 wherein the platinum group metal is platinum.

6. The process of claim 5 wherein said sulfur-resistant catalyst is cobalt molybdate supported on alumina.

References Cited UNITED STATES PATENTS 3,328,293 6/1967 Brenken 208143 2,915,452 12/1959 Fear 208-57 2,967,147 1/1961 Cole 208144 3,340,181 9/1967 Diringer et al. 208-143 DELBERT E. GANTZ, Primary Examiner. H. LEVINE, Assistant Examiner.

US. Cl. X.R. 208-87, 143, 264