US2017730A - Process of refining hydrocarbons, their derivatives, and the like - Google Patents

Description

J. W. POOLE Oct. 15, 1935.

PROCESS OF REFINING HYDROCARBONS, THEIR DERIVATIVES AND THE.- LIKE 2 Sheets-Sheet 1 Filed March 24, 1933 .v w mmm \venTor. John W. Poole Oct. 15, 1935. J, w POOLE 2,017,730

PROCESS OF REFINING HYDROCARBONS, THEIR DERIVATIVES AND THE LIKE Filed March 24, 1933 2 Sheets-Sheet 2 Q mg InvenTof. Uohn W. Poole b www AT Tys.

Patented Get. 15, 1935 ENT orrle PROCESS OF REFINING HYDROCARBONS,

THEIR DERIVATIVES, AND THE LIKE John W. Poole, Jaffrcy, N. H.

Application March 24, 1933, Serial No. 662,500

5 Claims.

This invention relates to improvements in methods of refining mixtures of hydrocarbons for the purpose of producing other mixtures of greater purity and greater utility.

More particularly the invention relates to the refining of petroleum or synthetic oils by a solvent or extraction method for the purpose of obtaining oils and/or waxes of commercial utility.

Still more specifically the invention relates to improvements in steps in the method of separation or refinement of hydrocarbons, and particularly crude petroleum or distillation cuts thereof. The term hydrocarbons is used herein as descriptive of hydrocarbons, and/or hydrocarbon derivatives.

In the refinement of hydrocarbons and their derivatives in the petroleum industry, which is an especially important industry, it is customary to remove difierent types of undesirable components by separate steps, and in fact by entirely dissimilar means. If, for example, the object of processing is to produce a lubricating oil of the type known as a parafiin base neutral, it has been universally found that to produce the highest grade lubricant for general use, two types of materials occurring in petroleum .must be removed. These are both constituents which either cannot be removed by distillation or cannot be economically removed by such distillation processes as are in use.

Crude petroleum or crude oil, as commercially encountered, varies in composition from two different standpoints. First, it varies in the matter of boiling points of its component parts. In general, it will contain compounds which in their pure state may not be liquefied under normal conditions of temperature and pressure. From these extremely low boiling members the substance will contain others progressively decreasing in volatility to members impossible to vaporize at atmospheric pressure with temperatures below the point where thermal decomposition takes place. As is well known, these facts are made use of to separate crude petroleum into fractions or cuts of narrower boiling range than was the raw material. All of these cuts may be expected to possess constituents, such as hydrocarbons of comparatively low hydrogen-carbon ratio or hydrocarbon derivatives of sulphur, oxygen, nitrogen, etc., which render the material less desirable than a material containing smaller quantities of such constituents. Although the term may not be completely descriptive, for brevity, this group will be hereinafter referred to as gummy materials.

Second, in certain of the less volatile fractions of petroleum, notably those from which lubricants will eventually be produced, certain undesirable constituents quite diiferent from the gummy materials may be found. These substances are 5 either members of the parafiin series, or of closely allied series, and freeze or harden at temperatures much higher than the remainder of the fraction, so that frequently by their action the entire mass will be rendered non-fluid at atmosl0 1 pheric temperatures. If such high melting material is not removed, the oil, due to non-fluidity, will not be a satisfactory lubricant.

At the present time there are several methods in use for removing gummy constituents. The 15 more common are treatment with concentrated sulfuric acid and/ or treatment with fullers earth. Solvent extraction is becoming more and more important having certain desirable features which the first two methods lack. 20

Paraffin substances are removed quite differently. With distilled or neutral oil, the procedure is to chill the wax distillate, as the fraction is then called, and force the mixture of liquid and suspended solids through a filter press. This process can be made to produce good results, but is slow, costly and requires bulky apparatus.- Solvent separation, which is used to a minor degree, has not become satisfactorily developed.

With residual stocks, (the portion of the raw 30 material remaining undistilled), the stock is generally diluted with solvent naphtha to reduce iscosity, the solution is chilled, in some cases to as low as minus forty degrees F., when the waxy material, known as petrolatum, is removed by 35 centrifuging, or settling. Insofar as I know, there is no other method used commercially to dewax residual stocks.

The present invention comprises the process of refining a mixture of hydrocarbons and/or 40 hydrocarbon derivatives, such as petroleum, or fractional distillates thereof, or synthetic oils, such as are produced by hydrogenation of coal and the like, by adding to and thoroughly diffusing throughout said mixture a solvent capable of selectively dissolving certain types of the constituents of said mixture, thereby to cause the material to resolve itself into a greater number of phases than previously existed, such as phases herein defined as an oil phase, a solvent 50 phase, and/or a solid or semi-solid phase, and separating said phases by centrifugal force of such intensity as separately to deliver said oil phase and said solvent phase each substantially 1 free from finely divided droplets of the other. 55

I have discovered that the rate of diffusion of solvent into the oil phase and the movement of such diffused solvent back into the solvent phase, together with the replacement of more solvent from the solvent phase and so on until essential equilibrium, which is equivalent to maximum efficiency, can be a very slow process if viscous or waxy oil is being treated and the oil globules are of fairly good size. For example, it is found that by vigorous hand-shaking of the solvent containing mixture for periods of five minutes repeated every half hour, several hours may be required to develop a reasonable solvent efficiency. Upon the other hand, if the solvent containing mixture is agitated vigorously as by the use of a mechanical mixing device, the globules will be finely sub-divided almost to colloidal sizes, so that the thickness of the oil through which the diffusion of solvent must take place will be so reduced that essential equilibrium may be obtained within one or two minutes.

I have also discovered that in order to break up this semi-emulsion within a reasonable time into the two phases, requires the use of centrifugal forces.

The present invention, therefore, may be defined as the process of refining a mixture of hydrocarbons and/or hydrocarbon derivatives which comprises adding to and thoroughly diffusing throughout said mixture a solvent capable of selectively dissolving certain types of the con stituents to produce a greater number of phases in said mixture than originally existed including an oil phase and a solvent phase, separating said phases by centrifugal force of such intensity as to deliver said oil phase and said solvent phase separately each substantially free from finely divided droplets of the other.

In the preferred performance of my method I have employed as a selected solvent an unsaturated aldehyde selected from the group of unsaturated aldehydes and their isomers, which includes crotonaldehyde and acrolein, and which are characterized in that a multiple bond of unsaturated compound occurs in an aliphatic chain and which are selectively absorptive by solvent action of hydrocarbons of relatively low hydrogen-carbon ratio and such hydrocarbons as are soluble therein,

By reason of this method I am able to secure greatly improved results over the preceding methods above described.

First, the time required is greatly reduced. Second, it appears to be universally true that one secures more efficient use of solvent. Both phases when separated solely by gravity usually .are cloudy, each containing minute globules of the other. ities of the two phases are close together settling tends to become extremely slow and even after once being accomplished, the turbulence caused by drawing from the settling tanks will cause material quantities of the other phase to be drawn off with the one which it is designed to remove.

In addition, it is often found that the phase usually called the oil phase, is not a homogeneous phase, but consists of a solution of solvent in oil plus a solid or semi-solid phase which is held in complete or partial suspension. By the action of gravity alone this suspension will rarely be broken, but by the increased action of centrifugal force the mixture of solvent and original oil may be divided into three distinct and separate phases. With a centrifuge running at high speed and expelling two streams, working with low Furthermore, when the specific gravgrade mid-continent residual stock, I have found that from the inside port of the centrifuge the solvent phase was discharged and from the outside port a moderately fluid solution of solvent in oil was expelled. This continued for some time until the oil phase was found to be issuing in a somewhat irregular manner. Upon examination this was found to be caused by pieces of petrolatum issuing from the same port as did the oil phase. Upon stopping the machine it was found to be approximately one-third. filled with a circumferential layer of petrolatum.

It was thus found that by stopping the machine at this point in its operation three distinct products could be recovered from the original material. Consequently, there must exist three phases each differing in specific gravity from the other two. In practice, either of the two first liquid phases may in various instances be lighter than the other or occasionally may be essentially identical; If the latter is the case, no separation can be eifected by gravity or centrifugal action and conditions must be imposed which will cause the phases to diifer in specific gravity. This may be effected by decreasing the solvent power of the solvent to force the lightest of the dissolved material back into the undissolved or oil phase, thereby causing the solvent phase to become heavier.

Again, the specific gravity of the solid or semisolid phase must be different from both of the liquid phases. This will be generally so. In fact, in my experience this phase has usually proved to be the heaviest of all. Whereas, it might be expected that material of such high hydrogencarbon ratio, would be light compared with the oil present, there are certain facts that explain why it is often of actually greater density than the oil phase. First, from my own researches and from published data of other investigators, I have established a useful rule of miscibility: The molecular weights remaining essentially constant; as the hydrogen carbon ratio of hydrocarbons increases the solubility of said hydrocarbons in the solvent decreases, and conversely the solubility of the solvent in said hydrocarbons decreases. To the best of my knowledge there are no exceptions to this rule. From the second half of this rule, that as hydrocarbons increase in hydrogen-carbon ratio, organic solvents will dissolve less readily in said hydrocarbons, there is established a reason why the solid or semi-solid phase should increase in density, relative to the undissolved oil phase. Consequently, since the solid or semi-solid materials are in general close to the highest possible hydrogen-carbon ratio, such material will contain less dissolved solvent than will the liquid oil phase which consists mainly in hydrocarbons of somewhat lower hydrogen-carbon ratio. This difference in dissolved material will influence the relative specific gravities of these two phases. If the solvent is of low specific gravity, like crotonaldehyde or acrolein, the result will be to make the oil phase relatively low in specific gravity. Second, since paraffins contract upon passing from the liquid to the solid state, and solid paraifins constitute the major portion of the solid or semi-solid phase, solidification will also tend to make this phase the heavier.

It is, to be sure, possible to conceive of conditions under which two or possibly all of the phases'will be identical in specific density, or so nearly so as to make effective separation impossible. 0n the other hand, since the respective (if) i densities are influenced in different ways and to different degrees by several controllable factors, such as, temperature, solvent power, oil solvent ratio, or the type of solvent used, it is very unlikely that conditions will ever arise under which it is impossible to force the desired differences in density.

In view of these facts separation of the phases above described can be commercially accomplished.

Any centrifuge possessing sufficient space for collection of non-fluid material, such as parafiin wax and petrolatum, may be employed to accomplish the three-phase separation. In the handling of large quantities of material to secure more economical procedure, it was found that by rotating the bowl of the centrifuge at a lower rate continuous processing could be effected, the lessened centrifugal force resulting from the lower speed being insuficient to deposit the solid or semi-solid material upon the walls of the bowl. There were consequently expelled two streams, one consisting of an essentially clear and homogeneous liquid phase, the other of a heterogeneous phase containing both liquid and particles of solid or semi-solid material. This heterogeneous phase was then passed to a second centrifuge in which it was subjected to centrifugal force of sufficiently greater intensity to separate the solid from the liquid material. These separated constituents were then expelled continuously and concurrently from the two ports, the liquid phase issuing from the inner port, the solid or semisolid phase from the outer port. By such processing it is possible to eliminate certain iuidesirable features which accompany such intermittent procedure as previously described.

Similar results were obtained by the treatment of mid-continent neutral oil by each of the processes above described.

I have found that in certain cases where the viscosity of the oil phase was comparatively high, a small quantity of non-viscous liquid, such as petroleum ether, which is of relatively light specific gravity, or a mixture of petroleum ether with ethyldichloride, which is of relatively heavy specific gravity, miscible with the oil phase, was found to facilitate the dewaxing operation.

Suitable apparatuses for performing the process above described are illustrated in the accompanying drawings, in which,

Fig. l is a view, partially in vertical section, of a centrifuge; and,

Fig. 2 is a graphic illustration of a system illustrating an intermittent three-phase separation in a single centrifuge; and,

Fig. 3 is a graphic illustration of a system illustrating continuous separation by the use of two centrifuges.

In the construction illustrated in Fig. l, the centrifuge comprises a stand I having an upwardly tapered hollow casing 2 to contain the bowl of the centrifuge. The bowl is a cylinder 3 which is mounted axially in the casing 2 and provided at its lower end with a head 4 which is rotatably mounted in suitable bearings in a preferably removable support 5 at the lower end of the casing. The liquid to be separated is introduced through a suitable pipe 6 and passageway l communicating with the lower end of the bowl. The bowl is connected at its upper end to a head 8 to which a vertical driving shaft 9 is coupled, preferably by a screw threaded connection. The shaft 9 is preferably supported by an overhead thrust bearing it and is actuated by a worm ll and gear l2 driven by a suitable belt l3 from a motor I4, or the motor maybe mounted directly upon the upper end of the stand. Suitable means may be provided such as a rheostat Mar, for controlling the speed of the motor, so that the desired speed of rotation may be imparted to the bowl of the centrifuge to accomplish the purposes herein described.

Suitable ports IS in the head 8 are provided to deliver the heavier phase, which is thrown outwardly by centrifugal force, into a receiver it from which it is delivered through a suitable conduit H. The lighter phase is delivered through ports [8 located more nearly to the axis of the bowl into a receiver I 9 from which it is delivered through a suitable conduitiii.

The steps in the process of the separation by a single centrifuge'into three phases are graphically illustrated in Fig. 2 of the drawings. In the performance of this process the raw material is delivered through a suitable pipe 2i and the solvent is delivered through another pipe 22 into a mixer 23 containing a suitable agitator 24. The mixture is delivered through the pipe 6, (see Fig. 1) into the lower end of the bowl 3. When the centrifuge is run at a high speed, the solid or semi-solid material A, such as paraffin and petrolatum, is forced and mainly held against the wall of the centrifuge. The heavier solvent phase B is forced and maintained within the solid phase and gradually escapes through the port l5 into the receptacle l6 and is discharged through the conduit ll into a suitable container 25. The lightest phase C is discharged upwardly through the inner port It to the receptacle i9 and from it through the conduit 26 into a suitable receptacle 26.

This three-phase separation by a single centrifuge, as above described, requires intermittent operation of the centrifuge in order that the solids and semi-solids maybe removed from the centrifuge after the machine has been stopped, and this, of course, is accomplished by the removal of the head and preferably also the removal of the bowl.

The apparatus for performing the continuous operation of the process is illustrated in Fig. 3. In this apparatus the base material the solvent are respectively introduced through the pipes 2! and 22 into the mixer 23 and are delivered therefrom through the pipe 6 into the lower end of the centrifuge, as above described. The centrifuge, however, is rotated at a lesser speed, so that a heterogeneous phase B is forced and maintained by centrifugal force against the wall of the bowl 3. The lighter phase C is delivered through the port l9 and a conduit 2! to a receptacle 25. The heterogeneous phase is delivered from the bowl through the port it: into the receptacle Hi from which it passes through the conduit I! to a pipe 6 leading to the lower end of the bowl 3 of a second centrifuge. The bowl of this centrifuge is run at a higher speed and the heterogeneous phase is thereupon separated into the solid phase A and the heavier liquid phase B, the solid and semi-solid phase being delivered through the port IE to a pipe 21 leading to a suitable receptacle 28. The heavier liquid phase B is delivered through ports I9 and 20' to a suitable receptacle 25. 7

In either process the oil phase and solvent phase are so completely separated that each is substantially free from finely divided droplets of the other.

In the production of lubricating oil the solvent may be recovered from the oil phase by distillation. The solvent may also be recovered from the solvent phase by distillation leaving an extract containing impurities which, while detrimental to lubricating oil and other commercial oil products, is itself valuable as a fuel oil and which may contain certain ingredients which when recovered therefrom are of considerable value.

The solid or semi-solid phase may be treated by well known methods to obtain parafiins and waxes of a commercial value.

It will be understood that whereas crotonaldehyde and acrolein have been described herein as the solvents which preferably are employed in the performance of the process, any other selective solvent possessing sufiiciently high volatility as to enable it to be removed and/or reclaimed by distillation, may be employed within the scope of the invention defined by the claims.

Having thus described the invention, what is claimed as new, and desired to be secured by Letters Patent, is:

1. The process of refining petroleum substances containing fluid and non-fluid materials which comprises adding thereto and thoroughly diffusing therethrough a solvent selectively dissolving certain types of the constituents thereby forming three phases, an oil phase, a solvent phase, and a solid or semi-solid phase consisting of paraffin wax or petrolatum and concurrently separating said phases by centrifugal force of such intensity as to deliver said oil phase and said solvent phase separately, each substantially free from finely divided droplets of the other and also free of the non-fluid material, and finally recovering the non-fluid material.

2. The process of refining petroleum substances containing fluid and non-fluid material which comprises adding thereto a solvent, selectively dissolving certain types of constituents thereof thereby forming three phases, an oil phase, a

solvent phase, and a solid or semi-solid phase consisting of paraffin wax or petrolatum, separating said phases by centrifugal force of such intensity as to deliver one essentially homogeneous liquid phase and another heterogeneous phase consisting of liquids and solid or semi-solid materials including parafiin wax or petrolatum, subjecting the latter phase without addition of supplementary materials to greater centrifugal force of sufiicient intensity to effect separation of the liquid from the solid and semi-solid constituents.

3. The process of refining petroleum substances containing fluid and non-fluid material which comprises adding thereto a solvent, selectively dissolving certain types of constituents thereof thereby forming three phases, an oil phase, a solvent phase, and a solid or semi-solid phase consisting of parafiin wax or petrolatum, separating said phases by centrifugal force of such in- 3 tensity as to deliver one essentially homogeneous liquid phase and another heterogeneous phase consisting of liquids and solid or semi-solid materials including paraffin wax or petrolatum, subjecting the latter phase with the addition of a 10 further amount of solvent materials to centrifugal force of suificient intensity to effect separation of the liquid from the solid or semi-solid constituents.

4. The process of refining petroleum substances 15 containing fluid and non-fluid material at the temperatures of ope-ration, which comprises adding thereto and thoroughly difiusing therethrough an unsaturated aldehyde selected from the group of unsaturated aldehydes and their isomers which includes crotonaldehyde and acrolein and which are characterized in that a multiple bond of the unsaturated compound occurs in an aliphatic chain which are selectively absorptive by solvent action of hydrocarbons of relatively low hydrogen-carbon ratio and such other hydrocarbon derivatives as are soluble therein, in amount sufiicient to dissolve certain types of constituents thereof thereby forming three phases, an oil phase, a solvent phase, and a solid or semi-solid phase including paraffin wax or petrolatum and concurrently separating said phases by centrifugal force of such intensity as to deliver said' oil phase and said solvent phase separately.

5. The process of refining petroleum substances containing fluid and non-fluid material at the temperatures of operation, which comprises adding thereto and thoroughly diffusing therethrough an unsaturated aldehyde selected from 40 the group of unsaturated aldehydes and their isomers which includes crotonaldehyde and acrolein and which are characterized in that a multiple bond of the unsaturated compound occurs in an aliphatic chain which are selectively absorptive by solvent action of hydrocarbons of relatively low hydrogen-carbon ratio and such other hydrocarbon derivatives as are soluble therein, in amount sufiicient to dissolve hydrocarbon derivatives and hydrocarbon constituents 60 of low hydrogen carbon ratio to produce one substantially homogeneous liquid phase and another heterogeneous phase consisting of liquids and solid or semi-solid material including paraifin wax or petrolatum, separating by centrifugal force the homogeneous liquid phase and thereafter subjecting said heterogeneous phase to centrifugal force of sufficient intensity to separate the same intoa liquid phase and solid or semisolid phase.

JOHN W. POOLE.

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