US3902989A - Method for producing hydrocracked lube oil products - Google Patents

Abstract

The production of lube oil product by hydrocracking is made more selective and commercially attractive by blending charge components to achieve viscosity levels suitable for temperature selective conversion to lube oil product commensurate with the relationships established by the curves of FIGS. 1 and 2.

Description

United States Patent Smith Sept. 2, 1975 [54] METHOD FOR PRODUCING 2,960,458 11/1960 Beuther et a1. 208/19 HYDROCRACKED LUBE OIL PRODUCTS 3,046,218 7/1962 Henke ct a1. 3,142,634 7/1964 Ireland et a1... Inventor: Fritz A. Smith, Haddonfield, NJ. 3, ,055 3 1967 white er a]. 3,493,493 2/1970 Henke et a1. [73] Assignee. Mobil Oll Corporation, New York, 3.506565 4/1970 white et aL 3,579,435 5/1971 Olenzak et a1. 208/59 [22] Filed: Sept. 5, 1974 Primary Examiner-Delbert E. Gantz 1211 Appl' 5031239 Assistant Examiner-G. E. Schmitkons Rdated U Appncation Data Attorney, Agent, or F irm-Charles A. Huggett; Carl D. [63] Continuation-impart of Scr. No. 2,764, Jan. 14, Famsworth 1970, abandoned.

[57] ABSTRACT [52] US. Cl. 208/; 208/19; 208/1 1 l The production of lube oil product by hydrocracking [51] Int. Cl... C01g 37/02; ClOg 13/02; ClOg 31/14 is made more selective and commercially attractive by [58] Field of Search 208/110, 111, 18, 19 blending charge components to achieve viscosity levels suitable for temperature selective conversion to [56] References Cited lube oil product commensurate with the relationships UNITED STATES PATENTS established by the curves of FIGS. 1 and 2. 2,917,448 12/1959 Beuther ct a1. 208/57 5 Claims, 3 Drawing Figures LUBE OIL HYDROCRACKING EFFECT OF CHARGE STOCK VISCOSITY ON LUBE OIL VISCOSITY VISCOSITY OF CHARGE STOCK, SSUQ 210' F. (:1 o o Conditions 2500psiq,O.4LHSV, aoooscru 1B CHARGE STOCK VISCOSITY,SS O 210 F.

9 W-TEXAS HVGO 64 WTHVGO/WTPDR 92 Q WTHVGO/WTPDR 20 POUR LUBE VISCOSITY, SS U(0 IOOF.

PATENTEU SEP 2 5 SHIN 3 OF 70 so 90 I00' FIGURE 5 Age/1f 1 METHOD FOR PRODUCING I-IYDROCRACKED LUBE OIL PRODUCTS This is a continuation-in-part of application Ser. No. 2.764 filed Jan. 14, 1970. now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the preparation of lubricating oils. A number of processing arrangements have been proposed in the prior art for producing lubricating oils from less suitable hydrocarbon charge stocks by catalytic conversion. hydrogenation processes. clay treating, solvent extraction and combinations thereof. Catalytic conversion processes and particularly catalytic hydrocraeking or hydrogenolysis can be defined as catalytic cracking in the presence ofa hydrogen atmosphere to accomplish significant reductions in the molecular weight of the charge stock. Hydrocracking is distinguishable from hydrotreating and hydrofinishing by the amoutn of molecular weight reduction and hydrogen consumption-Generally, a hydrofinishing operation consumes less hydrogen than hydrotreating and hydrotreating consumes less hydrogen than hydrocraeking.

To produce a refined lubricating oil by conventional solvent extraction techniques of desired viscosity index, it has been necessary to employ as a feed. an oil which already has a higher viscosity and lower VI than that desired. Thus high quality crude oils were segregated on a large mass basis for use in preparing lower viscosity but higher viscosity index lube oil products whether by hydrofining operations or by chemical treatment such as by extraction with solvents. The prior art processes are generally less than satisfactory since each was designed to operate for the production of a particular type of lubricating oil product and offering little versatility in operation. Thus numerous economic restrictions are imposed by such processes. Catalytic processes operating at elevated temperatures and pres sures are quite expensive and difficult to justify economically except when based on processing large quantities of charge material or unless a tremendous upgrading in the value of the products produced is obtained. Thus in a severe hydrogenation process such as obtained by destructive hydrogenation or hydrocraeking where distillate fuels of high value are produced, it was necessary to control the operation of the process under prior art practices so as to obtain a major amount of a general range of lube oil products produceable from the charge. Thus the quality and quantity of the lube 'oil product comes by happenstance rather than by design and specific control.

THE INVENTION The present invention is concerned with the preparation of particular lube oil products by a selective hydrocraeking operation designed to satisfy predetermined viscosity requirements Such'as required for high performance motor oils known as automotive gear oils. circulation oils. industrial hydraulic oilsrand other specialty lubricating oil products.

One'of the important specifications of a lubricating oil is its viscosity, that is. the resistance to deformation of the liquid when subjected to a shear stress. The present invention isparticularly concerned with the preparation of lube oil products having particularly desired viscosity rating by exercising a particular control over the viscosity of the'chargc stock converted by the process and over the temperature at which particular conversion occurs. A very effective method for exercising control on the viscosity of the charge stock is by a selective blending of charge stocks of different viscosities. An effective method for exercising selective control on the conversion temperature is to use the viscosity of the 650F waxy lube oil product as a basis to relate and regulate particularly the inlet temperature to the hydrocracker.

DESCRIPTION OF THE DRAWINGS FIG. 1 presents a family of VI (viscosity index) curves which show a relationship found to exist between the charge stock viscosity and a 20F. pour point lube oil product viscosity measured as SSU at l()()F.

FIG. 2 presents a family of V] (viscosity index) curves which show a relationship found to exist between the charge stock viscosity and a 20F. pour point lube oil product viscosity measured as SSU at 210F.

FIG. 3 identifies a blending chart showing the relationship existing between high and low viscosity oils for blending to produce a particular viscosity product.

DESCRIPTION OF SPECIFIC EMBODIMENTS In a particular aspect. the method and technique of the present invention has been demonstrated by blending low viscosity West Texas Sour Heavy Vacuum Gas Oil (WTSHVGO) with high viscosity West Texas Sour PD Raffinate (WTSPDR). For instance, West Texas Sour Heavy Vacuum Gas Oil (64 SSU at 2l()F) results in a dewaxed 65()"F pool viscosity of 43 SSU at 2 l 0F. after hydrocraeking to l25 V.I. However. the desired pool viscosity for this product, on the other hand, is 48 SSU at 210F. rather than 43 for V.I. material. This desired pool viscosity of 48 can be attained, it has been found, by blending a West Texas Sour PD Raffinate I60 SSU at 210F.) with the West Texas Sour Heavy Vacuum Gas Oil until the charge blend viscosity is about 116 SSU at 210F. This blend is then hydrocracked to 125 VI. to produce the desired 48 SSU product. Thus the concept of the present invention is concerned with selecting particular charge stock materials of suitable viscosity so that through selective blending thereof and/or control of a vacuum tower or other distillation means a particular charge stock viscosity can be obtained which upon hydrocraeking will provide a product of desired viscosity. This selective method of operation reduces losses attributed to overcracking and processing large excesses of charge material to obtain a particular viscosity-VI product.

In general, most charge stocks suitable for use in a lube oil hydrocraeking process are heavy materials such as vacuum gas oils and propane deasphalted raffinates. However other charge materials may be employed such as slack wax, petrolatum and even cracked gas oils can also be employed to advantage depending on the product desired. Charge stocks high in asphaltene content are less desirable because of their effect on catalyst aging and suspected adverse effect on product quality.

The type of compounds or components required in lube oil base stocks to attain a high viscosity index are known and discussed in the literature. In general, paraffin's, ring compounds (especially monoand dicycliccompounds) in which the rings are fully saturated, alkylbenzencs. alkyltetralins and some alkyl naphthalenes are desirable components. Unsaturated condensed ring compounds are less desirable since they have very low viscosity indexes. Normal paraffins, on the other hand, have high V.l.s but also have a high pour point which is an undesirable factor.

The method of the present invention is concerned with convening as many of the undesirable types of compounds or complex molecular structures found in lube oil charge stock into molecular structures having desired viscosity index and viscosity. This type of conversion can be done, it has been found, with good selectivity by use of a proper catalyst in combination with a proper charge material at selective operating conditions.

It has been observed further that the path of reaction during such conversion by which the undesirable components in, for example, a Kuwait PD Raffmate, may be converted into desired quality lube oil base stocks can be predicted. Thus it was found that the composition of the charge changes the space velocity is decreased when the hydrogen partial pressure is 2,500 psig and the temperature is 775F. For example, paraffms are found to increase monotonically; monoand di-nuclear naphthenes increase gradually, reach a maximum at a space velocity of about 0.9 and then decrease rapidly as space velocity decreases. Monoand di-nuclear aromatics increase rapidly, reach a maximum at a space velocity of three, and then decrease as space velocity decreases. Polynuclear naphthenes increase gradually, reach a maximum at a space velocity of about 2.5. and then gradually decrease as space velocity decreases. Polynuclear aromatics decrease monotonically and so do the resins and asphaltenes. The extent of all these chemical reactions is reflected in the viscosity of the product as shown on the attached figures.

It has been found that with substantially any hydrocarbon charge stock the V.l. (viscosity index) increases but yield decreases as the hydrocracking reaction se verity is increased, thus resulting in an undesired in creased conversion to, for example. lower boiling products. In the present discussion, conversion is based primarily as a matter of convenience on a 650F. cut point but other cut points, such as 600F. or up to 700F. would be suitable in some instances with appropriate adjustments. The yield of 650F waxy conversion product was correlated to the V.l. of the 650F dewaxed oil. It was observed from the results obtained that the V.l. increases as conversion increases, reaches a maximum and then decreases as conversion continues to increase. The region of decreasing V.l. is construed as over-cracking" although this may be viewed as a misnomer by some.

As severity of the hydrocracking reaction or conversion is increased by either increasing temperature or decreasing space velocity, the viscosity index increases as yields of (60F product material decrease and the viscosity also decreases. On the other hand, as the conversion increases and the 650F yields decrease, the change in viscosity of the 650F waxy or dewaxed oil becomes less and appears to approach an equilibrium value which is found quite unexpectedly to be charge stock dependent.

Thus temperature has a significant effect on 650F lube yields, viscosity and viscosity index (V.l. If the space velocity is increased, however, then the temperature must also be increased to maintain the V.l. level. Temperatures should be maintained within the range of 700 to 850F. and preferably should be from about 720F. to about 800F. Thus, in order to maximize yield of the waxy 650F product material it is desirable to employ as low a space velocity as possible commensurate with acceptable temperature operating conditions in the range of from about 700F. to about 850F. A space velocity in the range of0.25 up to about 3.0 may be employed. However, it is preferred that the space velocity be maintained in the range of 0.4 to about I .5. Pressure has also been found to have a significant effect on the yield structure at constant V.l. For example, decreasing the hydrogen pressure by 500 psig decreases the waxy 650F product yield as much as 5 or more volume percent. At the lower pressure, hydrogen consumption is slightly lower and so is the viscosity. Thus the hydrogen partial pressure should be retained within the range of from about L800 to about 3,000 psig and more preferably should be within the range of 2,200 to about 2,800 psig.

FIGS. 1 and 2 presented herewith are essentially selfexplanatory. They differ from one another in that FIG. 1 applies when the 20F. pour point lube oil viscosity is measured as SSU at I00F. whereas FIG. 2 applies when the viscosity is measured as SSU at 210F. It will be observed upon examination of the figures that for a given V.l. material, the viscosity of the product varies as the viscosity of the charge varies.

FIG. 3 provides a blending relationship between low and high viscosity materials and identifies the amount of each of these materials to be blended with one another to produce a blended charge material of predetermined desired viscosity requirement which will provide upon selected hydrocracking severity conditions, a product of desired V.l. and viscosity. From FIG. 3, it will be observed by way of example identified by the dotted lines that blending a 40 viscosity material with a 200 viscosity material (Universal Saybolt Scale) requires about 64 percent of the high viscosity oil in the blend to produce a blended material having a viscosity of about 83 or 84. Hydroeraeking such a blended product-charge under severity conditions selected to produce a I25 V.I. product is shown by FIG. 1 to produce a product of I50 viscosity as measured on the SSU scale at I00F. However, when measured at 210F. FIG. 2 shows that the product will have a viscosity of only about 44.40.

The specific embodiments herein discussed have established that a relationship exists between specific charge stocks and product obtained when using a CMZS (cobalt-molybdenum-zirconium-silica) catalyst composition for hydrocracking which clearly demonstrates the concept of the present invention. It is to be noted, however, that different hydrocracking catalyst compositions will effect the severity of a hydrocracking operation for any given pressure, temperature and space velocity condition selected. Allowance for this difference must be made when employing a different catalyst. Also. the family of curves and representationpresented in FIGS, I and 2 will vary to some extent depending upon the charge stocks employed as well as the catalyst composition used to effect the hydrocracking operation. However, a relationship or correlation remains and substantially any known hydrocracking composition may be employed in practising the concept of the present invention. A suitable hydrocracking catalyst will include one or more hydrogenation components selected from the group comprising the sulfides and oxides. or mixtures thereof, of the metals of Groups VI and VII dispersed on a suitable carrier material. The carrier material may be a silicious cracking component or it may be an alumina base which is active under the conditions employed. The carrier material may include composites such as silica-alumina. silicatitania. silica-zirconia, silica-magnesia or other silicious base carrier compositions.

In addition to the above, the present invention contemplates controlling the hydrocracking reaction by mechanism commensurate with identification of particularly desired products. Thus in one embodiment it is contemplated employing the 600F. or 650W product viscosity before or after dewaxing as a control function to control the outlet temperature of the preheat furnace used in a hydrocracking process to raise the temperature of the hydrocarbon charge to a desired inlet reaction temperature. In addition, the above identified viscosity control function may be employed to control the exothermic hydrocracking reaction temperatures within desired limits by employing the control function to control the amount of quench fluid such as quench hydrogen or recycle gas introduced to the hydrocracking reactor between catalyst beds,

Having thus provided a general discussion of the present invention and provided specific examples in support thereof, it is to be understood that no undue restrictions are to be imposed by reasons thereof except as provided by the following claims.

I claim:

I. In a process for producing 650"F waxy lube oils of desired viscosity by hydrocracking a hydrocarbon charge stock in the presence of a hydrocracking catalyst at a temperature within the range of 700 to 850F., a space velocity within the range of 0.25 to 3.0 and a hydrogen partial pressure within the range of L800 to 3,000 psig, the improvement for reducing the volume of hydrocarbon charge to the process which comprises,

selecting from the relationship provided by FIG. 1

and 2 the viscosity of the charge stock required to produce a product of desired viscosity and viscosity index,

blending charge stocks of different viscosityin accordance with the relationship provided by FIG. 3 to form a charge stock of desired viscosity as determined from FIGS. 1 and 2,

hydrocracking the blended charge stock within the processing limits above identified and using the viscosity of the 650F waxy lube oil product as a basis for exercising a selective control on the conversion temperature.

2. The process of claim 1 wherein the hydrocracking temperature is maintained within the range of 720800F.

3. The process of claim I wherein the hydrocarbon space velocity is within the range of 0.4 to L5.

4. The process of claim 1 wherein the hydrogen partial pressure is maintained within the range of 2,200 to 2,800 psig.

5. The process of claim 1 wherein the hydrocracking catalyst comprises cobalt-molybdenum-zirconium and silica. I

Claims (5)

1. IN A PROCESS FOR PRODUCING 650*F+ WAXY LUBE OILS OF DESIRED VISCOSITY BY HYDROCACKING A HYDROCARBON CHARGE STOCK IN THE PRESENCE OF A HYDROCRACKING CATALYST AT A TEMPERATURE WITHIN THE RANGE OF 700* TO 850*F, A SPACE VELOCITY WITHIN THE RANGE OF 0.25 TO 3.0 AND A HYDROGEN PARTIAL PRESSURE WITHIN THE RANGE OF 1,800 TO 3,000 PSIG, THE IMPROVEMENT FOR REDUCING THE VOLUME OF HYDROCARBON CHARGE TO THE PROCESS WHICH COMPRISES, SELECTING FROM THE RELATIONSHIP PROVIDES BY FIG. 1 AND 2 THE VISCOSITY OF THE CHARGE STOCK REQUIRED TO PRODUCE A PRODUCT OF DESIRED VISCOSITY AND VISCOSITY INDEX, BLENDING CHARGE STOCKS OF DIFFERENT VISCOSITY IN ACCORDANCE WITH THE RELATIONSHIP PROVIDED BY FIG. 3 TO FORM A CHARGE STOCK OF DESIRED VISCOSITY AS DETERMINED FROM FIGS, 1 AND 2, HYDROCRACKING THE BLENDED CHARGE STOCK WITHIN THE PROCESSING LIMITS ABOVE IDENTIFIED AND USING THE VISCOSITY OF THE 650*F+ WAXY LUBE OIL PRODUCT AS A BASIS FOR EXCERCISING A SELECTIVE CONTROL ON THE CONVERSION TEMEPERATURE.

2. The process of claim 1 wherein the hydrocracking temperature is maintained within the range of 720*-800*F.

3. The process of claim 1 wherein the hydrocarbon space velocity is within the range of 0.4 to 1.5.

4. The process of claim 1 wherein the hydrogen partial pressure is maintained within the range of 2,200 to 2,800 psig.

5. The process of claim 1 wherein the hydrocracking catalyst comprises cobalt-molybdenum-zirconium and silica.

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