US2985579A - Refining of petrolatum - Google Patents

Description

Patented May 23, 1961 REFINING OF PETROLATUM Heinz Heinemann, Swarthmore, and Thomas H. Millikan,

Jr., Rose Valley, Pa., assignors to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Filed Feb. 17, 1958, Ser. No. 715,520

6 Claims. (Cl. 20827) The present invention relates to refining of crude petrolatum and petroleum waxes and is particularly concerned with the provision of improved methods for the more economical production therefrom of products of required market quality and/ or the production of products of higher quality as to color, taste and odor, for specialized uses thereof.

Petrolatum is known in commerce as a product of salve-like consistency obtained from petroleum crudes. It is marketed in various grades as to quality or degree of refinement ranging, from the color standpoint alone, from light amber or yellowish to white, and meeting other evaluated grade characteristics as to odor, taste, viscosity, etc. It is a mixture of mineral oils and mineral waxes maintained in stable or permanent u'nctuous condition by the presence therein of a natural protosubstance which apparently serves, in a manner that has not been fully understood, somewhat in the nature of an emulsifying agent, preventing separation or sweating of the liquid oil or granulation of the wax inthe mixture. In the refining of crude petrolatum, accordingly, care must be taken to avoid methods effecting removal or modification in desired properties of the naturally contained protosubstance.

Petrolatum is obtained commercially from paraflinbase or mixed-base crude petroleum oils. While the methods of deriving the crude petrolatum from the oil may vary with individual manufacturers or in accordance with the characteristics of the starting oil or with the grade of desired petrolatum product, the procedure generally involves fractional distillation of the crude oil leaving a still residue of predetermined viscosity which is then dewaxed to yield the crude petrolatum and a lubricating oil. In refining the crude petrolatum which serves for the purpose of removing impurities affecting color, odor and taste, the choice of method is limited with particular regard to preserving the important content of protosubstance. The types of the color bodies present are many and varied. Those which give the greatest concern are resinous type materials with olefinic, oxygen, sulfur or nitrogen groupings, presumably conjugated with each other and/or with aromatics. Many attempted decolorization processes have been found effective in producing an initial refined product of acceptable color grade but unfortunately these products do not retain the desired color on standing or exposure to light, or are otherwise unsatisfactory from the standpoint of meeting requirements as to freedom from taste and odor. Other more severe decolorizing methods proposed have pro'ved unacceptable from the standpoint of their undesired e'flect on viscosity or ductility (fiber length) of the finished product.

The methods which have been generally followed in commercial practice involve filtration or contact adsorption of impurities such as by percolation through bauxite or other mineral type adsorbent. Such operation, particularly when used for the production of good grades of white petroleum jelly, necessitates the use of large amounts of adsorbent for treating relatively small quantities of the crude petrolatum and the throughput rate is quite low such that the treating facilities must be comparatively large for any given production capacity. The adsorbent can be utilized effectively for only a short time of continuous operation, after which it must be reactivated or regenerated. Other commercial petrolatum refining methods employ sulfuric acid treatment, which produces products of acceptable grade only at the expense of the high cost of the acid and entails considerable loss of unrecovered product.

Among the objects of the present invention are the provision of an improved and more economical process for the production of acceptable grades of white petrolatum meeting pharmacopeia and/or market standards.

Another object is to provide an economically feasible method of manufacturing white petrolatum of lighter color than ordinary commercial grades and meeting high standards of quality particularly as to color stability, odor and taste. Such high quality product is particularly desired for certain specialized uses, as in bases for cosmetic and pharmaceutical preparations or the like.

Other objects and advantages achieved in practice of the invention will be appreciated from the description below.

In copending application Serial No. 715,519, filed of even date herewith, there are described methods of refining of crude petrolatum which involve catalytic hydrogenation at elevated temperature and pressure. The hydrogenated petrolatum thus obtained is of enhanced light color and can be made up to products of commercially acceptable quality. That application discloses the use of pressures in the hydrogenation reaction of up to 3000 pounds.

It has now been found that by carrying out the hydrogenation reaction at pressures above 3500 pounds per square inch, as in the order of 4000 to 6000 pounds per square inch, longer periods of continuous operation over the same catalyst are possible with the production of a refined product of desired white color before it becomes necessary to regenerate or reactivate the catalyst. The treatment at the higher pressure, above 4000 pounds, moreover, obtains a product of better color stability than that produced at pressures of 3000 pounds or less. Thus a product obtained by hydrogenation at 4500 pounds and after-treated by washing in aqueous caustic is considerably lighter after 8 hours exposure to ultraviolet light than a similarly after-treated product from hydrogenation at 3000 pounds. At pressures above about 6000 pounds any incremental improvement obtained by the increased pressure may be largely outweighed by increased operating costs.

It has been further found that major improvement in color stability of the refined product is obtained by lowering the feed rate of the crude petrolatum charged to hydrogenation. Such major improvement in color stability is evidenced at a critical space rate below 0.5 volume of petrolatum per hour per volume of catalyst.

In carrying out the improved process at the higher pressure and/or at the low space rate, the conditions as to temperature, hydrogen ratio, etc. may be the same as those heretofore described. Under these conditions there is no excess hydrocracking of the charge despite the increased severity of treatment. The hydroge'native refining according to the present invention utilizes temperatures of 400 to 700 F., and hydrogen to petrolatum mol ratios of 0.2/1 to 2/1, in most instances of about 1/1.

As previously described hydrogenation over the same catalyst is continued until the colorof the efiluent falls below that desired, for instance to meet specification color standards, after which the feed of petrolatum is stopped and the catalyst subjected to regeneration or reactivation.

In previous operations at the lower pressures, as up to about 3000 pounds per square inch, it was found that the activity of the catalyst was prolonged by the presence of H S in the hydrogenation zone. This effect of added sulfur compounds is less pronounced in operations at the higher pressures advocated in accordance with the present invention, since even without such addition of sulfur compounds refined products of desired light color are obtained in continued operation for several hundred hours or more. On the other hand, no detrimental effect has been observed and it is possible that such addition of sulfur compounds might be found desirable in the higher pressure operation, at least in some instances. For this purpose, there may be added with the petrolatum charge H 8 as such; mercaptans, carbon disul'fide, thiophenes, or other readily decomposable sulfur compounds, converted to H 8 under reaction conditions, in an amount furnishing 0.1 to 0.5 percent S by weight of the petrolatum charged. Residual sulfur compounds which remain dissolved in the liquid condensate from the hydrogenation effiuent must, of course, be removed therefrom, otherwise the product will have poor color stability.

Several difierent standardized tests have been used for color grading of refined petrolatum. While these have been found generally adequate for setting up color specifications for marketed products, these permit a fairly wide range of perceptible color differences within a specified numerical grade. Thus, the National Petroleum Association color numbers which are essentially similar to the proposed ASTM color designations (Dl55-45T), run from 1 for the best grades of white petrolatum to 8 for the reddish, half numbers being used for in-between shades up to Color is determined by the ASTM method by use of the union colorimeter wherein the sample is matched against a numbered glass color standard. Because the more common numerical color grading standards do not provide for sufliciently narrow differentiation between numerical grades, various manufacturers of refined petrolatum and laboratories handling these materials have adopted wider numerical scales based on color comparison with control samples. The color numbers referred to in the description which follows is based on a numerical color scale which runs from 1 to 40 for refined marketable grades of pharmaceutical petrolatum wherein Color Index'No. 4 aboutrcorresponds to U.S.P. Petrolatum Album and Color Index numbers between 30 and 40 correspond to commercial grades of yellow petroleum jelly; the palest grades of green-yellow petrolatum corresponding to about 15 color. On this scale numbers running in the range of about 300 identify crude (unrefined) petrolatum which appears almost black in color, and fractional numbers between Zero and one designate highly refined colorless to water white or pure white products of above common marketed quality for white petrolatum.

The crude petrolatum subjected to refining in the examples below had the following characteristics:

Crude petrolatum charge, above-described, was passed over sulfided cobalt-molybdena-alumina catalyst at 600 F., under pressure of 4500 p.s.i.g. and at a liquid hourly charge rate of 1 volume petrolatum per volume of catalyst, together with 1 mol hydrogen per mol of the hydrocarbon. The product obtained during the 4 hour run was of about 0.25 color. After removal of sulfide and mercaptans and exposing the product to ultraviolet light for eight hours the color darkened to acceptable extent only (color about 15).

EXAMPLE II The above run was repeated over the described catalyst and under the same operating conditions to determine catalyst life. After 203 hours continuous operation over the same catalyst the product color was still running better than 1. There was no indication of significant catalyst deactivation wherefore it was predicted that several times this length of continuous operation was possible, without necessitating change or reactivation of the catalyst, if a product of up to 4 color is to be made (accetable Petrolatum Album, U.S.P.).

The addition of t-butyl mercaptan in a concentration of 0.2 of S toward the end of the described run showed some immediate improvement in product color; indicating that the beneficial effect of adding sulfur compounds in the feed heretofore found in operations at pressures of 3000 and lower may also be present in the high pressure operations.

In the previous patent application hereinabove referred to, certain methods of after-treatment are described for removal of volatile sulfur compounds and other volatile contaminants from the hydrogenated product. Among the methods therein described are steaming, filtration through absorptive minerals such as alumina, bauxite or charcoal or chemical treatments effective in removal of simpler mercaptans. While these methods are applicable in the treatment of the product obtained by hydrogenation at the now advocated higher pressures, it has been found that tasteless and odorless products of excellent color stability are obtained without resort to special aftertreatment. The residual sulfur compounds and other deleterious contaminants are readily removed from the high pressure hydrogenation product by a simple vacuum flashing, which can be carried out at a temperature of 425 F. or higher, short of that which may cause overheating and accompanying cracking, thereby obtaining products of superior quality. No particular advantage has been found in raising the temperature as high as 600 F., and in general, temperatures of 450'550 F. have 0.5% of a very light lower boiling product condensible in Dry Ice. The residum can be combined with the water (or air) condensible distillate to give the desired product of high color stability and acceptable taste and odor characteristics.

In practical operation it is generally unnecessary to prolong the distillation for as much as an hour. Distillation can be stopped short of the time that the air or water condensible material begins to come over in significant quantity. The initial lowest boiling material comprising up to about 1% or even less of the distilland can be fully driven off in about ten minutes. This initial distillate contains practically all of the volatilizable deleterious contaminants, so that further distillation has no observed advantage. i

' EXAMPLE I11 I A series of hydrogenation runs were car ried outsuccessfully over the described sulfided cobalt-molybdena- L. t. m

alumina catalyst at 600 F., 4500 p.s.i.g. hydrogen pres sure at 1 molar ratio to petrolatum charge, and at various space rates indicated below; 0.2% S being added to the charge as t-butyl mercaptan. The results of these runs are shown in the following table:

These results show that desired very light products having excellent color stability are best obtained at space rates below about 0.5 (v./v./hr.), and that removal of the H 8 in the hydrogenated product is readily accomplished by simple vacuum flashing. With higher space rate color stability drops sharply. Lowering the hourly charge rate to 0.2 volume or below did not seem to give any significant further improvement.

The catalyst employed in the foregoing examples was prepared by soaking porous alumina pellets for one hour in a solution prepared by mixing: 137.4 parts aqueous ammonia (33.4% NH 126 parts aqueous ethylene diamine solution (93% EDA), approximately 194 parts of molybdenum oxide (M and 266.5 parts of an aqueous solution of cobalt nitrate hexahydrate [71% Co(NO -6H O] with about 350 parts water, employing sufiicient solution to keep the alumina pellets covered throughout the soaking period. The pellets were then drained, dried in air at 200300 F. and heat treated by being passed first through a steaming zone during approximately 2 hours at a maximum bed temperature of 550 F., then during approximately 6 hours through an air heating zone having a maximum bed temperature of 950 F., thus efiecting conversion of the salts to the oxides of molybdenum and cobalt, respectively. The treated pellets contained approximately 1.75% 000 and 7.75% M00 These pellets were then treated at 800 F. for 3 hours in a mixture of 25% H S75% N (mol) and purged and cooled in nitrogen to a sulfur content of 4.46%.

Molybdenum sulfide catalyst should contain about 7 to 20% by weight Mo on a suitable support such as activated alumina. Such catalysts are prepared by impregnating the support with a solution of a molybdenum compound which is converted to the oxide and then sulfided with H S or similar sulfiding gas as described above.

In practice of the invention no particular handling problems are encountered. The petrolatum crude is heated to desired reaction temperature and pumped in liquid state into the top of a downflow catalytic reactor, the hydrogenrich gas and added sulfur compound being introduced into the feed line or directly into the reactor. The total reactor efiluent is cooled to about ZOO-300 F., for instance by passage through a water-cooled condenser, from which the products flow through a pressure control valve into a low pressure receiver by means of which gas is flashed from the refined liquid petrolatum. The low pressure receiver may operate at temperatures of 120-300 F. and at atmospheric pressure or higher if desired. The petrolatum is maintained in desired liquid state by steam jacketing the vessel or other known means. Hydrogenated molten petrolatum is drained from the bottom of the vessel.

The preferred sulfided cobalt-molybdena on alumina catalysts should contain 1 to cobalt and 3 to 5 times as much molybdena (as M00 prior to sulfidation. If desired, sulfidation of the catalyst can be efiected in the hydrogenation reactor prior to introduction of the petrolatum charge or a higher quantity of sulfur compound can be initially added with the charge for a short period until the catalyst has been sulfided, at which time sulfur addition is reduced to 0.5% or less as above described.

After the color of the hydrogenated effluent becomes darker than desired in continuous operation over the hydrogenation catalyst, such catalyst can be regenerated by conventional oxidative combustion. In the preferred practice, however, activity of the catalyst is restored by hydrogenative treatment for at least an hour at a temperature above that employed in hydrogenation of the petrolatum and generally at the same pressure as described in copending application Serial No. 715,521, filed of even date herewith. To maintain continuity of operation the unit can be provided with two catalytic reactors operating in parallel so that petrolatum flow can be switched periodically to permit reactivation of the used catalyst.

The hydrogen employed in the process need not be of high purity grade. Ordinary refinery hydrogen of about purity has been found satisfactory.

Appropriate means for vacuum flashing of the hydrogenation efiluent can be readily provided as part of the hydrogenation unit, so that the hot hydrogenated petrolatum as withdrawn from hydrogenation is subjected directly to appropriate evacuation, furnishing refined product of superior quality.

Obviously many modifications nad variations of the present invention as hereinbefore set forth may be made without 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. The method of refining crude petrolatum and petroleum waxes which comprises subjecting the same essentially in liquid phase to hydrogenation over solid sulfur-resistant hydrogenation catalyst at a temperature in the range of 400 to 700 F. and at a pressure above 3500 pounds per square inch and vacuum-flashing the hydrogenated product at a temperature of at least 425 F. and for a time at least sufiicient to distill off a fraction including substantially all materials which are condensible at Dry Ice temperature under vacuum, thereby removing practically all of the volatilizable deleterious contaminants.

2. The method according to claim 1 wherein said hydrogenation is eifected at liquid hourly space rate of not greater than 0.5 volume of petrolatum per volume of catalyst.

3. The method according to claim 1 wherein said vacuum-flashing is effected at a pressure of below 10 mm. Hg.

4. The method according to claim 1 wherein said vacuum-flashing is effected at a temperature in the range of 450550 F. and at a pressure below 5 mm. Hg.

5. The method according to claim 1 wherein said vacuum-flashing is elfected at a temperature in the range of 450550 F. and at a pressure below 5 mm. Hg.

6. The method according to claim 1 wherein the vaporized overhead from vacuum flashing is condensed at ambient temperatures, lower boiling materials not so condensed being separated from such condensate and the thus purified condensate admixed with the unvaporized petrolatum distilland.

References Cited in the file of this patent UNITED STATES PATENTS 1,930,468 Mueller-Cunradi et al Oct. 17, 1933 1,973,833 Wietzel Sept. 18, 1934 2,574,331 Knox Nov. 6, 1951 2,651,655 Loughran Sept. 8, 1953 2,734,365 Ferris et al. Feb. 14, 1956 2,756,180 Perry et al. July 24, 1956 2,794,766 Offutt June 4, 1957 2,834,718 Stanford et a1 May 13, 1958 2,846,356 Mills et al Aug. 5, 1958 ewc i" V UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 2,985,579 May 23,, 196i Heinz Heinemann et a1.

, It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 26, for "nad" read and lines 48 and 51, for the claim reference numeral "1" each occurrence, reaC 2 r Signed and sealed thisi IQ-th day of December 1961,,

(SEAL) Attest:

DAVID L. LADD Commissioner of Patent:

U$COMM-D( ERNEST W. SWIDER Attesting Officer

Claims (1)

1. THE METHOD OF REFINING CRUDE PETROLATUM AND PETROLEUM WAXES WHICH COMPRISES SUBJECTING THE SAME ESSENTIALLY IN LIQUID PHASE TO HYDROGENATION OVER SOLID SULFUR-RESISTANT HYDOGNEATION CATALYST AT A TEMPERATURE IN THE RANGE OF 400 TO 700*F. AND AT A PRESSURE ABOVE 3500 POUNDS PER SQUARE INCH AND VACUM-FLASHING THE HYDROGENATED PRODUCT AT A TEMPERATURE OF AT LEAST 425* F. AND FOR A TIME AT LEAST SUFFICIENT TO DISTILL OFF A FRACTION INCLUDING SUBSTANTIALLY ALL MATERIALS WHICH ARE CONDENSIBLE AT DRY ICE TEMPERATURE UNDER VACUUM, THEREBY REMOVING PRACTICALLY ALL OF THE VOLATILIZABLE DELETERIOUS CONTAMINANTS.