US1998648A - Dewaxing lubricating oils - Google Patents

Description

April 1935. .1. A. ANDERSON 1,998,648

' DEWAXING LUBRICATING 61Ls Filed July 9, 1932 3 Sheets-Sheet 1 Chamber INVENTOR Q, kbmflfirzder on ATTORNEY Dz'lacnt ska/y April 23, 1935. -J. A. ANDERSON DEW AXIN G LUBRICATING guys 5 Sheets-Sheet 2 4 Filed July 9, 1932 N KQ ENGN w N 50 INVENTOR Jo/mfiflrzdersorz ATI'ORNE April 1935- J. A. ANDERSON 1,998,648

DEWAXING LUBRICATING OILS Filed July 9, 1952 s Shts-Sheet s Uent \sdr'ap vwzg a ma f m I INVENTOR .zlulndaraon ATTORNEY Patented Apr. 23, 1935 UNITED STATES PATENT OFFICE DEWAXIN G LUBRIOATIN G OILS tion of Indiana Application July 9, 1932, Serial N0. 621,692

6 Claims.

This invention relates to the separation of wax from mineral oils and pertains more specifically to a method of crystallizing wax in a particular manner so that it may be readily separated from oil by cold settling or by centrifuge.

Most petroleum oils, particularly paraflin and mixed base oils, contain substantial quantities of paraflin wax which accumulate in lubricating oil' fractions obtained by distillation. Mid-Continent lubricating distillates may contain 10% of paraflin wax; Salt Creek distillates as much as wax. For most lubricating purposes, it is necessary to remove this wax so that the oil will not solidify at low temperatures. A very small amount of wax will greatly increase the pour point or the temperature at which the oil congeals. The object of my invention is to remove all of the waxy bodies from lubricating oil which are responsible for unduly high pour points.

Heretofore, it has been the custom to dilute oils with naphtha or other light hydrocarbons, to chill the diluted oil, to crystallize out the wax and to mechanically separate the wax by filtration, centrifuging or settling. Filtration is expensive, and is difiicult because of the tendency to clog the filters'and because of the low temperatures at which the separation must be effected. Cold settling is the simplest method of wax separation, but it is open to the objection that many waxes will not settle at all and many other waxes will not settle sufliciently to make this process commercially feasible. Paraflin wax crystallizes in the form of plates or needles which are rather irregular in outline and which interlockor interlace and set up a skeleton framework throughout the entire body of the oil, to all intents and purposes causing the body of oil to solidify. In mariy oils the amount or nature of the wax is such that that the oil is not solid, but even in these cases 40 the interlacing of the wax crystals causes entrainment of so much oil that the oil and wax cannot be readily separated by cold settling. If such chilled diluted waxy oil is settled in a tank 100, units deep, the 'wax crystals may only settle a few units from the top; if they settle 10 units, it is said that the oil is settled to 90% bottoms. The object of my invention is to provide a method and means for separating waxy oil byja cold settling process wherein the diluted oil and wax mixture 50 may be settled to about 10% or 15% bottoms. In other words, I want to minimize the amount of oil which is entrained by wax and which is either carried down with it or which prevents it from settling.

A further object of my invention is to provide a process of dewaxing which will require a minimum initial cost, a minimum amount of space and a minmium operating expense, which will at the same time give maximum yield of Wax-free low cold testoil. Other objects will be apparent as the detailed description of my invention proceeds.

In practicing my invention I utilize certain condensation products to bring about the crystallization of wax in a readily settleable form. I add the condensation product before the dewaxing step and make use of it specifically to cause, the crystallization of wax in a form which can be readily settled or centrifuged. My theory is that these condensation products cause wax to solidify in compact particles instead of in elongated plates or crystals and I reason from this hypothesis that diluted oil can be chilled and settled to low bottoms because the interlacing of wax crystals will be prevented. Microscopic examinations confirm this theory and actual tests have demonstrated that diluted oil which is 100% solid at 10 F. can be settled to 8% to 15% bottoms by these condensation products. I have further discovered that the clear supernatant oil is characterized by a very low pour point, that the settling rate is much higher than can be otherwise obtained, and that markedly increased yields may be obtained.

My invention will be more clearly understood from the following detailed description and from the accompanying drawings which form a part of this specification and in which:

Figure 1 represents diagrammatically an elevation of my improved batch settler.

Figure 2 represents diagrammatically an elevation of my continuous settler.

Figure 3 represents diagrammatically an elevation of a centrifuge system, and

Figure 4 illustrates the microscopic appearance of wax crystal structure in the absence of a condensation product;

Figure 5 illustrates the microscopic appearance of wax crystals formed in the presence of a condensation product; and

Figure 6 illustrates the microscopic appearance of another form of wax crystalstructure in the presence of a condensation product.

My invention will be described in connection with the dewaxing of Mid-Continent treated distillate oil having a viscosity of about '74 seconds Saybolt at 210 F. I do not limit myself, however, to any particular type of wax-bearing oil,-the invention is applicable'to oils with viscosities of seconds at 210 F. and seconds at 100 F., all distillates, untreated as well as treated,

light as well as heavy, Pennsylvania, Coastal, etc. as well as Mid-Continent, etc.,any oil containing diflicultly settleable wax.

My condensation products may be described as a resinous material formed by condensation of halogenated hydrocarbons, with aromatic compounds in the presence of a catalyst such as aluminum chloride, the condensation preferably being effected in a suitable solvent. Asa halo-. genated hydrocarbon I-prefer to use chlorinated parafiin wax having a melting point of about 130 F. before chlorination and being chlorinated to about 15%. I may use other hydrocarbons, however, such as petrolatum, Montan wax, viscous oils, etc., and I may vary the amount of chlorination over a relatively wide range, although I prefer to use a hydrocarbon with about 10% to 20% of added chlorine. The aromatic compound is preferably naphthalene or diphenyl, although other compounds, such as benzene and toluene, may also be used. I prefer to effect the condensation in the presence of a chlorinated liquid, such as carbon tetrachloride, chloroform, tetrachlorethane, etc., although other liquid, such as naphtha, may be 'used if desired. Aluminum chloride or its equivalent has'been found to be the best catalyst. I

One specific example of my condensation prod-' uct may be made up as follows:

About 15 parts by weight of aluminum chloride is slowly added with stirring to a solution of parts by weight of chlorinated wax F. melting point with 15% chlorine) and 15 parts of naphthalene in enough carbon tetrachloride to maintain all of the ingredients in solution. The

- of naphthalene and 100 parts of chlorinated wax in a' chloroform solution. Here again the optimum temperature is about 130 to F. The reaction is usually complete in from one to ten hours.

As above stated, I may use a wide variation of chlorinated or halogenated waxes or hydrocarbons and I may vary the aromatic compound and the conditions of condensation throughout a relatively wide range. The expression condensation product as used in the following specification and claims is hereby defined to include that class of substances prepared in the manner hereinabove set forth.

Referring to Figure 1, the treated ,(or un- I treated) waxy lubricating oil distillate is introduced by pipe I0 and mixed with about 0.1% of my condensation product, which is transferred from storage tank I I through pipe I 2 by means of pump l3. The waxy oil with the condensation product mixed therewith is introduced by pipe I4 to mixer I5 where it is mixed with a diluent such as propane from storage tank l6 and pipe I'I, about five parts of propane being added to one part of waxy oil. This mixture is then selectively introduced by pipes l8 and I9 or 20 into cooling or chill chambers 2| and 22. These chambers may be refrigerated in any suitable manner by the use of brine coils or by direct expansion of ammonia. I prefer, however, to reing valves 23 and pipes 24 to low pressure gas main 25. Propane from main 25 is compressed by pump 26, condensed in coils 21, cooled in chamber 28 and finally returned to storage tank IS.

The diluted oil-wax mixture may be chilled at the rate of about 3 F. per minute. The original mixture may be at a temperature of about 80 to 100 F. and the mixture in the chill chambers is reduced to a temperature of about 40 F. This cold slurry is then selectively introduced by pipes 29 or 30 and 3] or 32 to settling tanks 33 or 34. It should be understood that by using a plurality of these tanks one tank may be filled while another is being cooled, etc. Further cooling may be effected in settling tanks by removing of propane vapors through reducing valves 35 and 36 to low pressure gas line 25. In fact, I may use the settling tanks to effect the entire chilling by passing the diluted waxy oil mixture directly from mixer l5 through pipes I8, 31, and 3| or 32. If additional propane is required as diluent and/or refrigeration in chill chambers it may be introduced through line 38.

The rapidity with which the wax crystals settle out in settling tanks 33 and 34 will depend to a large extent upon the nature of the waxy oil, the

nature of the diluent and the amount and quality of the condensation product. If the Mid- Continent stock above described is chilled in the absence of the pour condensation product, the wax will crystallize in the form of interlacing needles 39, as shown in Figure 4. By using condensation product the wax assumes the form of tiny slightly star-shaped aggregate 40 or tiny rounded particles 4| (see Figure 4), which settle rapidly and to very low bottoms. In one series of experiments, for instance, it was shown that without the use of condensation products the wax did not settle at allit gave 100% bottoms; when 0.3% of the condensation product was added, the wax settled to 17% bottoms, and this settling from propane required less than an hour.

The clear oil may be decanted from either settling tank through pipe 42 through outlets 43, 44, 45, 46 and 41. Pet cocks (not shown) are provided adjacent these outlets for sampling the oil before it is decanted. By having a plurality of these tanks, one of them may be settling while another is being emptied and furthermore, the oil may be decanted from the upper part of the tank while the wax is settling still further in the lower part. When the clear wax-free oil has been decanted, I remove the remaining wax slurry from the base of the settlers through pipes 43 and 44, usually this wax is in the form of a slurry so that it may be readily handled as a liquid, but if .desired I may melt it by means of steam coils 45 heater coil 50, the finished oil being withdrawn.

through pipe 5| and propane being returned to the low pressure gas line through pipe 52.

In Figure 2 I have shown a similar embodiment except that instead of using a plurality of batch settling tanks I use a large continuous settler 53 which may be in the form of a hopper bottomed cylinder or a large horizontal tank. In this case, the wax slurry is continuously removed from the base of the settler by means of screw conveyor 54 and the clear oil is directly introduced by pipe 55 to the stripper 49. In all other respects this modification is the same as that described in connection with Figure 1.

Referring to Figure 3, it will be observed that the slurry from the chill chambers is introduced into the centrifuge 56 instead of into its cold settling tanks. This centrifuge may be of the type commonly used in the oil industry and may be driven by motor 51. The wax may be delivered by pipe 58 to collector 59 and it may be transferred therefrom through pipe 60 by pump 6! to stripping still 62, which is heated by steam coil 63, thewax being withdrawn through pipe 64 to suitable storage tank and the propane being returned through pipe 55 to low pressure gas line. The diluted wax-free oil is withdrawn from centrifuge through pipe 66 to collector 61, from which it is pumped through pipe 68 by pump 69 to stripping still 49 as hereinabove described.

When the Mid-Continent distillate was cold settled with four volumes of propane without the use of a condensation product and the chilled mixture was allowed to stand for over six hours, the yield of finished oil was 63% of the weight of the original charge, and the pour point of the finished oil was about +3 F.- When the condensation product of chlorinated paraffin wax and naphthalene was added prior to the settling, the settling rate was markedly increased, the yield was about 10% higher and the pour point of the finished oil was below F.

In another series of tests using filter naphtha as a diluent inthe ratio of three parts waxy oil to seven parts naphtha and using about 0.1 to 0.3% of the condensation product referred to above, I obtained 17% bottoms from a diluted oil-wax mixture which was absolutely solid under the same conditions without the small amount of condensation products.

Generally speaking, the effects of the condensation products in increasing settling rates and decreasing the bottoms, is more useful with larger amounts of diluent and with lighter diluents (higher A. P. I. gravityor lower specific gravity).

The microscopic examination of wax solidified from overhead cuts with and without the use of condensation products supports my theory of how and why I obtain my improved results.

Heretofore this wax crystallized out in the form of interlacing plates or needles throughout the entire mass of the liquid, thereby entraining the oil and supporting other wax crystals. It is obvious that in such a system settling is impossible. The condensation products prevent this type of crystallization and cause the formation of small aggregates of needles or tiny rounded particles which have no tendency to interlock and which may be readily settled or centrifuged.

Instead of using propane as a diluentI may use naphtha, normally gaseous light hydrocarbon diluents, such as butane, iso-butane, propylene, butylene, etc., antisolvents such as acetone,

methyl formate, nitrobenzene, etc. or mixturesthereof with miscibility agents, such as benzol and toluol. In other words, the invention is of greatest value in light diluents such as propane, but it is not limited thereto.

The apparatus will, of course, be suitably insulated and provided with valves, pumps, collector tanks, etc. All of these engineering details are commonly known in the art. They form no part of the present invention and they will therefore not be described in detail.

The amount of condensation products used may vary considerably. About 0.1 to 0.3% of the concentrated resins gives excellent results, but much larger quantities can be used if desired.

While I have described my invention in detail and have set forth a theory of operation, it should be understood that I do not limit myself to either the details nor the theory except as defined by the following claims, which,should be construed as broadly as the prior art will permit.

I claim:

1. The method of separating wax from waxbearing mineral oil which comprises adding to said oil a synthetic product formed by the addition of aluminum chloride to a mixture of naphthalene and chlorinated wax, diluting said oil with a diluent, chilling the diluted mixture to effect solidification of the wax, mechanically removing the wax from the diluted oil, and removing the diluent from the wax-free oil.

2. The method of separating wax from a waxbearing animal oil which comprises admixing with a waxy oil and a diluent a small amount of a synthetic product formed by the reaction of naphthalene with chlorinated wax by the addition of aluminum chloride, chilling the mixture to effect solidification of the wax in the form of small aggregates, separating the solidified wax from the diluted oil, and separating the diluent from the wax-free oil.

3. The method of accelerating the rate of settling and increasing the wax-free oil yield of a cold settling process which comprises diluting a wax-containing oil with a diluent, adding to said diluted oil a small amount of a condensation product formed by the reaction of naphthalene with a chlorinated wax by the addition of aluminum chloride thereto, chilling said diluted oilwax mixture in the presence of said condensation product to cause the solidification of wax without the formation of interlacing crystals, and allowing said cold mixture to settle.

4. The method of claim 1 wherein about .1% to about .3% of the synthetic product is added to the wax-bearing oil, based on the weight of the wax-bearing oil.

5. The method of claim 1 wherein the synthetic product is prepared by condensing the chlorinated wax with the naphthalene, both dissolved in a halogenated liquid, the aluminum chloride being added to said ingredients.

6. The method of separating wax from a waxbearing mineral oil, which comprises diluting said oil with a light diluent for reducing its viscosity, adding to said oil a small amount of a crystallization inhibitor formed by reacting a halogenated hydrocarbon with an aromatic compound by slowly adding aluminum chloride to a molten mixture of said halogenated hydrocarbon and aromatic compound at a temperature of about 130 to 140 F., cooling the diluted oil containing the crystallization inhibitor-to effect solidification of the wax in the form of small aggregates, separating the wax from the diluted oil by utilizing their difi'erence in specific gravity, and separating the diluent from the wax-free oil.

JOHN A. ANDERSON.

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