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Dec. 29, 1936.. G. J. sTREzYNsKl PRocEss .oF PURIFYING AND DEWAXING MINERAL oILs V’ Filed June 27, 1935 Apo/r/a/VAL Pl/MPJ 26,066,165 2,066,165 Patented Dec. 29, 1936 UNITED STATES PATENT OFFICE 2,066,165 PROCESS OF PURIFYING AND DEWAXING MINERAL OILS George J. Strezynski, Poughkeepsie, N. Y., as signor to The De Laval Separator Company, New York, N. Y., a corporation of New Jersey Application June 27, 1935, Serial No. 28,656 i) 2 Claims. (Cl. 196-21) In an application ñled by me June 27, 1935, step of the process and particularly to the tem Serial No. 28,655, I describe a process for purify perature of the acid added in its relation to the ing and dewaxing mineral oil containing both temperature to which the oil ischilled. The tem amorphous and crystalline waxes and producing perature of chilling, dependent Aon the desired , therefrom a dewaxed lubricating oil having a pour point of the finished oil, may vary from high pour test. In this process, which is prefer about 0° F. to _50° F. Since the freezing point ably applied to crude oil from which no or feW of sulfuric acid of the high concentrations that light fractions have been distilled, but which is give the best results may vary from about _8° F. also applicable to any heavy fraction of the to not much above 30° F. (usually in the upper . crude, such as the long residuum containing all part of such range), it is `obvious that, if there or most of the lubricating fractions, the crude is blended with any suitable light diluent, such as naphtha or other light hydrocarbon, and the blend is subjected to chilling, preferably shock chilling with pronounced agitation, to reduce its temperature to approximately 35° F. below the desired pour point of the finished oil. The dil uent is added in such proportion that the treated blend, after addition of acid, will, when centri 20 fuged with a force 6000 times gravity, gives a heavy layer of waxy acid sludge not less than 15% or more than 30% of the mass of the chilled and treated blend. After the chilling step, wherein all the wax, amorphous and crystalline, is precipitated (that is, all the wax is precipi tated down to the temperature of the pour point desired), a continuous stream of acid is added to the continuous stream of the mixture of oil and wax ñowing from the chiller and the two streams are subjected to a mixing action, the acid combining with undesirable compounds (im purities) in the oil and wax to form a waxy acid sludge. The treated mixture then flows contin uously to a centrifuge wherein a purified com pletely dewaxed oil is separated from the sludge. In the process set forth in said application, the oil is chilled, for example, to a temperature of approximately _16° F. if it is desired to produce a finished lubricating oil having a pour point of 40 20° F., or to approximately _35° F. if the ñn ished lubricating oil is desired to have a pour point of 0° F. In the specific example of the process therein given, there is treated a typical east Texas paraffin base (more accurately mixed 45 base) crude containing gasoline about 29%, kero sene about 14%, gas oil about 21%, wax and asphaltic material about 12% (wax about 8%) and lubricating oil constituents 1'7-18%, which, when separated, give a lubricating oil having a 50 pour point of 20° F., viscosity index 86 and viscosity 67. The present process is not concerned with the centrifugal separating step of the process where by there is secured a maximum yield of the qual 55 ity of oil desired, but relates to the acid. addition were no chemical reaction, the acid would freeze almost immediately upon >coming into contact with the cold oil. The chemical reaction, how ever, produces a certain amount of heat and this prevents the immediate freezing of the acid. It has heretofore been deemed necessary to add the acid at a reasonably low temperature in order to avoid too great a rise in the temperature of the mixture of cold oil and wax. 'I‘he reaction con- Y sequently proceeds so slowly that eventually a 20 certain amount of acid freezes into hard crystals and causes clogging and overflow. The use of fuming acid has been suggested, but the freezing point of fuming acid is higher than that of 98% acid. ~ I have found, however, that if the oil is chilled to a temperature more than 30% below that of the desired pour point of the finished oil, that> is, below what has been deemed necessary, and if the added acid is at a substantially higher tem 30 perature than that hitherto employed, the chemical reaction is so far expedited and the heat generation so far accelerated that the re action will be completed before the acid is suf ñciently reduced in temperature to freeze, there 35 by eliminating the clogging elfect of acid crys tals. While the temperature of the oil and Wax mixture is thereby raised more than it otherwise would be, it Will not be raised above the permis sible maximum if, in the initial chilling, it is 40 chilled to only a very few degrees below the temperature required if the acid were added while comparatively cold. To prevent freezing, the temperature of the acid sho-uld be above 110° F. More desirably it should be added at a 45 temperature within about 10° F. of 150° F. It will be understood that the hotter the acid, the greater must be the degree of refrigeration. It is permissive to add the acid at a temperature substantially higher than 150° F., but it is un 50 economical to do do so, since it involves the ex pense of refrigeration to a lower temperature with no corresponding gain. The amount of acid added may be varied With in limits at the discretion of the operator. The 55 2 2,066,165 desirable amount will vary with the desired pour test of the finished oil. Thus, in producing 20° F. pour test oil, a preferable addition of acid is patents granted to me December 3, 1935, No. 2,022,814, No. 2,022,815, No. 2,022,816, and No. about 12 to 14 pounds per barrel of oil, or about 21/2%; While in producing 0° F. pour test oil, It will be understood that I do not herein claim, separate and apart from the above described a preferable addition of acid is about 24 to 28 pounds, or about 5%. The amount of acid in these examples is about 20% moreL than is used in conventional methods and is distinctly above 10 the amount required to produce the necessary reaction. The addition of acid in such substan- 5 tial excess is of advantage invse’veral respects. It insures a sufficient gravity> differential be tween the oil and sludge. It speeds the reac 15 tion. It results in the production of a lubricat-` ing oil having a higher viscosity index number than is obtainable by the addition of a smaller quantity. It decreases the temperature spread between the operation temperature and the pour I 20 point of the finished oil. , Referringto the drawing, which is a diagram or flow sheet of an apparatus for practicing the above described process: Separate streams of the oil tor be dewaxed and purifiedV (which may be 2,022,817. ' process, certain novel features thereof, such as the regulation of the percentage of the diluent, which form the subject matter of an application filed by Strezynski and Pfau >July 25,1935, Serial No. 33,073. n n mineral oil to obtain therefrom high test pour oil, which comprises chilling the oil to a tem 15 perature below 0° F. to precipitate the wax, mix ing concentrated sulfuric acid with the mixture of oil and precipitated wax and centrifuging the resultant mixture of waxy acid sludge and puri fied dewaxed oil and thereby effecting their sepa ration; the improvement which comprises,ìin the chilling operation, sub-cooling the oil below the temperature that would be required, if cold acid Yand a diluent, such as naphtha, are delivered'to a were added, to subsequently produce purified de waxed oil of the desired pour point, and, in the acid treating operation, adding the acid While at blending tank I0, whence the oil is pumped a temperature above 110° F. to thereby, by ac through a chiller II and therein sub-cooled to a temperature. of . about l35° `F. below the desired pour test of the finished oil. The chilling opera celerating the generation of heat by the reaction, prevent freezing of the acid before completion of tion will precipitate all the wax which precipi pitates at the temperature of chilling. By means 2. In the process of purifying and dewaxing mineral oil to obtain therefrom high testV pour oil, whichfcomprises chilling the oil to a tem perature below 0° F. to precipitate the wax, mix crude oilV of the character hereinbefore described) of a pump I2 the mixture of oil and wax is con veyed to a mixer I4, which may be a centrifugal 35 pump. YInto the oil line leading to the mixer I4 is conveyed, through a pump I3, a stream of con centrated sulfuric acid (preferably about 98% H2804) at a temperature of about 150° F. The mixing may be completed in the pump I4, or it 40 may berun through an additional mixer I5, which maybe a series of centrifugal pumps. The acid reacts with the oil and forms a mixture of waxy acid sludge and oil, the latter usually contain ing'wax in ñne suspension but otherwise purified. 45 The mixture is then conveyed to a centrifuge I6, which is specially designed to act upon the mix ture so as to enable the recovery of completely dewaxed oil. Suitable centrifuges are shown in 10 What I claim and desire to protect by Letters Patent is: 1. In the process of purifying and dewaxing the raction. , ing concentrated sulfuric acid with the mixture of oil and precipitated wax and centrifuging the resultant mixture of waxy acid sludge and puri fied dewaxed oil and thereby effecting their sepa ration; the 'improvement which comprises, in the chilling operation, sub-cooling the oil below the 40 temperature that would be required, if cold acid were added, to subsequently produce purified de waxed oil of the desired pour point, and, in the acid treating operation, adding the acid while at a temperature Within 10° F. of 150° F. to thereby 45 speed the reaction and prevent freezing of the acid before the completion of the reaction. ' GEORGE J. STREZYNSKI.