US2039239A - Treating hydrocarbon oils - Google Patents

Description

Apwfil] 28, @36. c. W. WATSQN TREATING HYDROCARBON OILS m zs 2 Sheets-Sheet 1 Filed June 22, 1952 INVENTOR BY 3/5 ATTORNEY c W ON TREATING HYDROCARBON OILS zmww 2 Shets-Sheet 2 Filed June zz, 1932 m. ma Y mm W mm m A M w m- V fin s L a Y H Patented Apr. 28, 1936 UNITED STATES TREATING HYDROCARBON OILS Claude W. Watson,

Port Arthur, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application June 22, 1932, Serial No. 618,657

2 Claims.

This invention relates to the refining of hydrocarbons and more particularly to the refining of distillates obtained by cracking petroleum or other hydrocarbons.

The invention broadly contemplates a process of producing a color and gum stable hydrocarbon motor fuel which comprises cracking higher boiling petroleum or other hydrocarbons to form vapors of lower boiling hydrocarbons, subjecting these lower boiling vapors while in the freshly formed or nascent condition to fractionation to obtain a vapor fraction having a definite desired boiling range, then immediately contacting this fraction continuously with a suitable adsorbent catalyst by bringing the vapors into intimate contact and in countercurrent with a moving stream of liquid hydrocarbons, in which such finely divided adsorbent catalyst is suspended.

When hydrocarbon oils are subjected to cracking conditions, the products of the reaction include hydrocarbon compounds of varying degrees of unsaturation. The more unsaturated compounds are unstable in that they tend to combine among themselves to form gums or colored compounds. This formation of new compounds of substantially higher molecular Weight from unsaturated compounds of lower molecular weight is termed polymerization. While the products of the cracking operation are in the nascent state, that is, immediately upon or after their formation in the cracking reaction, the highly unsaturated and undesirable compounds may quite readily be removed by contacting them with a suitable catalytic adsorbent which selectively polymerizes these compounds. However, if the products of the cracking reaction are exposed to the atmosphere or are allowed to remain in storage for any length of time before they are contacted with such catalytic adsorbent, the accelerated polymerization may not only remove the undesirable highly unsaturated compounds but may also react with those unsaturated hydrocarbons whose presence in the final product is desirable.

Therefore, in order to effect the production of color stable cracked hydrocarbon products, it is desirable that the hydrocarbons be treated while in the nascent state, that is to say, immediately upon their formation by the cracking reaction. Practically, this is effected by carrying out the treating operation in direct conjunction with the cracking process.

This invention is directed in part to the continuous and simultaneous treatment of a specific hydrocarbon fraction which may be produced as the result of either a liquid or a vapor phase cracking operation. The invention may also be used in conjunction with any of the pyrolytic operations, sometimes termed reformations, which are directed to increasing the anti-deto- 5 hating qualities of hydrocarbon fractions, such as naphtha, kerosene and the like. The inven tion also finds application in connection with processes in which gaseous hydrocarbons are submitted to controlled pyrolytic conditions whereby there are produced liquid and gaseous hydrocarbons having unsaturated characteristics.

One of the advantages accruing to the operation of the herein disclosed invention resides in the fact that, by treating the nascent hydrocar- Icon vapors produced by a pyrolytic cracking process with catalytic adsorbents, the accelerated polymerization which takes place is limited to the undesirable highly unsaturated compounds. In this way, the efiiciency of the adsorbent is raised and a greater yield of treated product is obtainable with a unit amount of a catalyst material.

In accordance with the invention, a hydrocarbon material is submitted to a pyrolytic process and the vapor products are partially fractionated to produce a broad fraction having definite boiling limits. The purpose of this partial fractionation is to effect as far as possible the elimination of compounds having a boiling point higher than the end point of the final treated hydrocarbon fractions and return them to the pyrolytic cracking conditions. The partially fractionated vapor is then transported to a fractionating tower which also serves as the treating tower. This tower may be of the conventional type having bell-cap plates or similar liquid contact means which may or may not be altered to permit of their dual function. In this fractionating tower the vapors are contacted with a countercurrently moving suspension of clay in hydrocarbon oil which is introduced at an upper point in the tower and which forms pools on each plate of the fractionating tower. The vapors in their upward passage through the tower contact with the clay by passing through these pools of liquid hydrocarbon and clay suspension and are both treated and fractionated. The treated vapor fraction is drawn ofi at the top of the tower while the mixture of partly spent or completely spent clay and heavy hydrocarbons is drawn off at the bottom of the tower.

In the operation of the herein disclosed process, it is preferable to use those adsorbent catalysts which have the property of exhibiting their greatest activities in decolorizing oils at elevated temperatures. Preferably the adsorbent decolorizing material may be a clay of the montmorillonite type, which has been subjected to a treatment with acid and which exhibits its greatest efficiency at temperatures in excess of 250 F.

The invention will be fully understood from the following description taken in connection with the accompanying drawings which represent in diagrammatic sectional elevation two modifications of an apparatus which may be employed for carrying out the process. The apparatus il-' lustrated in the drawings is shown and. described merely for the purpose of aiding in understanding the process and it is to be understood that any other suitable apparatus may be substituted for that shown.

In Figure 1, the numeral i0 designates a. charge pump which connects a source of charging stock, not shown, with reflux exchanger 12 through the line: I I. This reflux exchanger is situated in the upper part of a fractionating. tower to be hereinafter described, and its outlet communicates through. the line I3, controlled by the valve l4, with the coil [5 of the preheater H5. The outlet end of the preheater I6 is connected by the line I! controlled by thevalve l8, to an upper point of the reaction chamber IS. A tar draw-ofi line Zlllis providedin the lower end of the reaction chamber; in which line there is interposed a control valve 2|. The uppermost point of the reaction chamber is equipped with a vapor line 22 which connects through the expansion valve 23 witha lower point of'the fractionating tower 24,

which tower may be of the conventional tray type and which is fitted, at its lowest point, with a draw-01f line 21, which communicates with the Suction side of the hot oil pump 28'. This pump discharges into the charge li'ne 3| fitted with valve 32, which. line enters. the. coil l5 of preheater' l6 atfa point'intermediate its inlet and.

outlet.

The uppermost point of the fractionating tower 24 is provided with a vapor line 33 which conneots this point of the tower with a lower point of. the fractionating tower 35. A valve 34 is placed in this line for purposes of control. In an upper part of this fractionating tower there is situated a reflux cooling coil 36 while in a lower part of the structure the steam spray 31 is provided.

The lowest point of the fractionating tower 35' is fitted with a liquid draw-off line 38 controlled by the automatic valve 39. This line discharges into the separatory tank 48. The bottom of this tank discharges into the pump 42' through the line H and the pump in turn discharges into the manifold line 43. A plurality of branch lines 44,

46' and 48 controlled respectively by the valves 45, 41 and 49 connect the manifold line with various levels of thefractionating tower 35.

An upper point of the sep'aratory'tank' 4B is provided with a draw -off line 5| controlled by the valve 52 which communicates with the suction side of the pump 53. This pump discharges into a. pressurefilter 55' of suitable type, through the line 54. In order to permit of the removal of separated material from this filter; a solids discharge line 58 controlled by the valve 51 is provided. The outletof the filter is connected by means of the line 58 controlled by the valve 59 with the mixing chamber-15". In order to permit of the optional recirculation of some or all of the filtrate from the'pressure'filtertothe outlet of the preheater E5, the line 60 controlled. by the valve (H is used to connect the line 58 with the line H.

The top of the tower 35 is equipped with a vapor draw-off line 62 which communicates through the valve 63 with the condenser coils 64 of the condenser 55. The discharge side of these coils is connected by the line 66 through the valve 6? with the receiving drum E8. The top of the tank is fitted with a vapor ofi-take line 53 controlled by the valve 10 which leads to a gas compression plant or suitable storage.

The aforementioned mixing chamber is connected with a source 18 of adsorbent catalyst by means of the line F9 and with the receiving drum 68 by means of the line (6 controlled by the valve l'l'. A line 88 controlled by the valve 8! which is connected to a trap tray located immediately below the reflux coil 36 in fractionating tower 31 leads into the mixing chamber 15. In order to permit of the agitation of the contents of the mixing chamber 15, both the mixing device 53 as well as the gas spray 13 are provided. The latter is connected with the vapor off-take line 59 by means of the line ll controlled by the valve "E2. The bottom of the mixing chamber is fitted with a line 84 which in turn is connected to the inlet side of the pump 85. This pump discharges into an upper point of the fractionating tower 35 through the line controlled by the valve 87.

Figure 2 represents a modification of the apparatus shown in Figure 1. It differs from the described apparatus in that two treating and fractionating towers are used in series instead of a single. tower. Reference to the figure and the following description will assist in an understanding of the structure of the apparatus and its operation.

The top of the tower 35 is fitted with the vapor line 62 which connects through the valve 63 with the fractionating tower 64. In an upper point of the structure of the fractionating tower there is incorporated a reflux exchanger 65 while a lower point of the structure is equipped with the steam spray 66. The bottom of the tower is connected by the line 6'! controlled by the automatic valve 68, with a circulating pump 69 which discharges through the line 10 into an upper part of the fractionating tower 35. The top of the tower 64 is equipped with a vapor line 72 which discharges through the valve 13 into the coils M of the condenser 15. The outlet of the condenser coils communicate with the receiving drum 18 through the line 16 controlled by valve 77. The tank is fitted at an upper point of its structure with a vent line 19 controlled by valve 88.

The numeral 86 designates a mixing chamber preferably provided with a conical bottom. This chamber is connected with the receiving drum 78 by means of the line 82 controlled by valve 83 and by means of line 85 with the storage vessel 84 which serves as a source of adsorbent catalyst. The line 8'! controlled by the valve 88 connects a trap tray located immediately below the reflux coil 65 in the fractionating tower 64 with the mixing chamber 86. In order to permit of the agitation of the contents of the mixing chamber 86, both the mixing device 89 as well as the gas spray 92 are provided. The latter is connected with the vapor offtake line 19 by means of the line SO-controlled by the valve 9|. The bottom of the mixing chamber is fitted with a line which in turn is connected'to the inlet side of the pump 96. This pump discharges into an upper point of the fractionating tower 64 through the line 9'! controlled by the valve 98. The top of the mixing chamber is provided with a line 93 controlled by the valve 94 which connects the vapor space of the mixing chamber with the vapor off-take line 19.

In the operation of the process in connection with an apparatus such as that illustrated in Figure 1, a higher boiling hydrocarbon oil is charged by the pump l0 through the coils of the reflux exchanger l2 where the temperature may be raised to a temperature of 250 F. by heat interchange with hot oil vapors. The oil is then circulated through the tubes l5 of the'preheater I 6 where the oil is raised to a temperature at which substantial cracking takes place. This temperature may, with advantage, be in the neighborhood of 900 F. The heated oil is discharged from the preheater under a pressure of 400 lbs. per sq. in. into the reaction chamber H! where a large portion of the oil is vaporized. The residual non-vaporized oil settles to the bottom of this chamber and may be drawn off through the line 20 to a suitable storage tank. The vapors in the reaction chamber which may have a temperature of 860 F. under the existing conditions of operation, escape through the vapor line 22 and pass into the fractionating tower 24 which may be maintained under a pressure of approximately 350-400 lbs. per sq. in. In this tower a hydrocarbon fraction of widely varying boiling points may be produced. The primary object of the fractionation is to remove those fractions of heavy hydrocarbons which are not desired in the 'final treated product and which may with advantage be recirculated to the preheater so that they may again be subjected to conditions favoring pyrolytic decomposition. These heavy hydrocarbons collect as a liquid at the bottom of the tower and can be drawn oil through the draw-oil? line 21 which is in communication with the inlet side of the recirculating pump 28. They are then charged by this pump through line 3| and valve 32 into the tubes of the preheater at a point which is situated intermediate the inlet and outlet of the preheater. Under the existing conditions of operation, the temperature of this oil may be about 790 F.

The hydrocarbon vapors which are formed in the fractionating tower 24 are fractionated by passing upwardly through the tower and in countercurrent to the descending reflux liquid which is formed by the heat interchange between the cold charging oil in the reflux exchanger and the vapors which contact the coils of the exchanger. The broad fraction of hydrocarbon vapors which is drawn oiT from the top of the tower through the vapor line 33 may have a tempera.- ture of 650 F. These vapors are transported through the line 33 through the expansion valve 34 where a reduction in pressure may be brought about. Upon leaving this valve, the vapors enter the fractionating tower 35 at a lower point in its structure.

The fractionating tower 35 serves a dual function in that it not only is used for preparing a vapor fraction having definite boiling point limits but is also used as an apparatus for treating with catalytic adsorbents the hydrocarbons introduced thereinto. The catalytic adsorbents are introduced into an upper point of the tower in the form of a suspension which may be prepared by admixing with the finely divided adsorbent a quantity of treated hydrocarbons which may or may not have been prepared by this process or by suspending the adsorbents in an oil having a gravity higher than the treated hydrocarbon product, which oil may be produced as one of the by-products of the process, and, for example, may be taken on from the trap tray situated immediately below the reflux coils 36. So, for example, adsorbent catalytic material stored in storage chamber 18 may be introduced into the mixing chamber 15 where it is agitated with treated oil from the receiving drum 68, with oil taken oif from the trap tray in an upper point of the fractionating tower 35, or with a heavier oil obtained by filtering the residual oil from this tower in the pressure filter 55. The operations incidental to the production of this heavier filtered oil will be described hereinafter.

The formation of adsorbent is advantageously brought about by agitating the mixture by means of an agitating device such as that indicated by the numeral 30 in the drawings.

In certain operations of the process the contents of the mixing chamber may be efliciently agitated by introducing into the bottom of the chamber hydrocarbon gases such as those produced in the process and which are separated from the final treated condensate which accumulates in the receiving drum 68. The gases are bubbled upwardly through the mixture of adsorbent catalyst and oil and are drawn ofi from the top of the chamber through a line which connects with the vapor line connecting the vapor 1 space of the receiving drum with the gas compression plant or the storage for non-condensable gases.

The suspension of catalytic adsorbent in treated oil is then charged by means of the pump into an upper point of the iractionating tower 35 through the line 86 controlled by the valve 81. The catalytic adsorbent and liquid oil then pass downwardly through the tower whereby the ascending hydrocarbon vapors are brought into intimate contact with the adsorbent.

In the operation of the tower, the temperature is maintained sufiiciently high to permit of the vaporization of all those hydrocarbon constituents which are desired in the finished product. Hydrocarbons having higher boiling points are separated and collect at the bottom of the tower in admixture with the partly or completely spent catalytic adsorbent. In order to free this mixture of any low boiling hydrocarbons contained therein, it may be desirable to inject steam into the mixture through the steam spray 31.

The mixture of adsorbent and heavy oil which has been denuded of light hydrocarbons is then drawn oif through the line 38 controlled by the automatic valve 39 into the separator chamber 40 where some separation of the adsorbent from the oil may take place. The temperature 01 this mixture in this operation of the process may be about 580 F. In those operations of the tower where the adsorbent is not completely spent, th slurry of adsorbent and oil collecting at the bot. tom of the separator chamber 40 may be recirculated through the line 43 and the branch lines 44, 46 and 48 to one or more levels of the fractionating tower. In other operations of this process it may be desirable to draw off some or all of the mixture of residual oil and adsorbent which has been introduced into the separator chamber 40.

This may be accomplished by placing this chamher in communication with the suction side of the pump 53, which pump is used for charging the mixture to a pressure filter 55. In the filter, substantial separation of the adsorbent from the residual oil is brought about and the adsorbent the suspension of catalytic so separated is drawn off through the. solids dismunicate with the discharge line 58 so that if it is found desirable, the separated oil may be recirculated to the outlet of the preheater 16 of the cracking unit into the line H.

The treated vapors which escape from the top of the tower 35 pass through the vapor line 62 and the valve 63 into the coils 64 of the condenser 55 where substantial condensation is brought about. The condensate which may have an end point of about 400 F. is drawn off through the line 66 and valve 61 into the receiving drum 68. If found desirable, the condensation may be carried out under pressure by the proper manipulations of the valves 63 and B1. The line 69 controlled by valve 10 which communicates with the vapor space of the receiving drum 68 may connect this drum with a gas compression plant or a suitable storage for the light hydrocarbons and non-condensable gases which may have been formed in the operation of the process.

In carrying out an operation with the apparatus shown in Figure 2, the heavy hydrocarbon oil may be subjected to pyrolytic reactions under conditions of pressure and temperature similar to those used in the apparatus shown in Figure l. The nascent hydrocarbon vapors produced by such a. cracking are subjected to a fractionation whereby hydrocarbons heavier than those desired in the final treated product, are substantially separated. The separated hydrocarbons may, with advantage, be returned to the preheater outlet for resubjection to pyrolytic conditions. In the operation of this modification of the apparatus, the vapor fraction is subjected to treatment in two fractionating towers connected in series. In the first of these towers designated by numeral 35 in Figure 2, the vapors are passed in countercurrent with partly spent absorbent catalyst which may consist either of that portion of the catalyst which has already been circulated through the tower 35 and which has accumulated in separatory chamber 40 or it may consist of partly spent adsorbent which has been discharged from the bottom of the second fractionating and treating tower, which is operated in series with tower 35. The second tower which is designated by the numeral 84 serves for the final fractionation and final treatment of the vapors which have been discharged from the tower 35. They are caused to travel countercurrently against a'fiowing stream of catalytic absorbent suspended in either a treated hydrocarbon oil produced by this process or a heavier hydrocarbon oil which may be produced as a by-product of the process. The

operations incidental to the production of the final treated condensate are similar to those described in the previous description of the apparatus shown in Figure 1.

Obviously many modifications and variations of the 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.

I claim:

1. The process of producing a color stable motor fuel from heavy hydrocarbons which comprises cracking a higher boiling hydrocarbon oil to produce vapors of lower boiling hydrocarbons, fractionating these vapors to produce a vapor fraction of a definite boiling range, passing this fraction while in a nascent condition into treating and rectifying apparatus where the vapors are simultaneously rectified and contacted with a countercurrently flowing suspension of a catalytic adsorbent and a treated liquid hydrocarbon, then withdrawing the treated and fractionated hydrocarbon vapors and condensing them to yield a color stable liquid suitable for use as a motor fuel while concurrently and simultaneously withdrawing from the rectifying and treating tower those hydrocarbons which remain unvaporized and which occur together with partly or completely spent catalytic adsorbent as a mixture, and recirculating this mixture to one or more different levels of the fractionating tower.

2. The process of producing a color stable motor fuel from heavy hydrocarbons which com- I prises cracking a higher boiling hydrocarbon oil to produce vapors of lower boiling hydrocarbons, fractionating these vapors to produce a vapor fraction of a definite boiling range, passing this fraction while in 'a nascent condition into treating and rectifying apparatus where the vapors are simultaneously rectified and contacted with a countercurrently flowing suspension of a catalytic adsorbent and a treated liquid hydrocarbon, then withdrawing the treated and fractioned hydrocarbon vapors and condensing them to yield a color stable liquid suitable for use as a motor fuel while concurrently and simultaneously withdrawing the unvaporized oil which occurs together with the partly or completely I.

spent adsorbent as a mixture, dividing this mixture into two portions, subjecting one portion to a filtration to effect the substantial separation of the oil and the suspended adsorbent, and

returning the separated oil to pyrolytic reactions, recirculating the other portion of the mixture to one or more difierent levels in the fractionating tower structure.

CLAUDE W. WATSON.

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