US3511772A - Hydrocracking - Google Patents

Description

United States Patent Office Patented May 12,1970

3,511,772 HYDROCRACKING Sheldon L. Thompson, Glen Mills, and Albert T. Olenzak, Media, Pa., assignors to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Filed Nov. 19, 1968, Ser. No. 777,154

I Int. Cl. Cg 13/02 US. Cl. 208-112 8 Claims ABSTRACT OF THE DISCLOSURE A lube oil hydrocracking process wherein the lube oil charge stock is mixed with a low viscosity material as diluent prior to charging to a hydrocracking reaction carried out at a temperature in the range of about 650 to 875 F. and a pressure of at least about 500 p.s.i. over? hydrocracking catalyst.

This invention broadly relates, to an improved lube oil hydrocracking process wherein the normally viscous hydrocracking charge stocks are first diluted with a light material whereby catalyst beneficiation is obtained as to both activity and longevity and the V.I. profile of the hydrocracked product appears to be enhanced in som cases.

BACKGROUND OF THE INVENTION In recent times, the demand for high V.I. lube oil products has increased at a tremendous pace, and the natural sources of these materials continues to diminish up to the present time. Because it increases the supply of such materials, one process is very important because it provides for synthetically preparing high V.I. lubes by hydrocracking certain natural crudes with a low V.I. In hydrocracking, the V.I. of a lube fraction is upgraded by molecular transformation. Accordingly, any significant improvement ina lube oil hydrocracking process for upgrading the V.I.

of lube fractions is tobe commended, and the present process constitutes a significant advance as will become apparent from a reading of this. disclosure in entirety.

SUMMARY OF THE INVENTION DETAILED DISCUSSION Lube oil hydrocracking is now well known in the art. Among the more advantageous processes, however, is the one which will be briefly described hereinafter.

While the precise reason or mechanism'involved in the beneficial elfect of the diluent isnot known for certain, we propose the following theory with the understanding that we are not in any way bound by such mechanism since it may not be correct. In final analysis we propose an improved technique of hydrocracking which comprises positive process features which, if practiced, will provide one or more advantages regardless, of whatever mechanism or mechanisms may be involved-To the extent, however, that the mechanism we' propose may be of some additional benefit to those skilled in the art, we now set same forth.

The catalyst is very heat sensitive and so are some of the reactions which occur in hydrocracking operations. The hydrocracking reaction,"or more properly the overall the likelihood of some hot spots and/or'great heat release near the surface of the catalyst. In addition to promoting less desired reactions which normally occur in hydrocracking, the reaction temperatures involved, especially when increased in localized areas by the release of heat by the reaction, can cause coke formation on the catalyst. Coke deposition causes catalyst deactivation by occlusion of the surface. Temperature itself, however, accelerates catalyst change with decreased activity. The temperature and catalyst deactivation relationship is especially important because at the elevated temperatures required for th reaction the deactivation rate becomes progressive in a geometric fashion. In short, the diluent probably operates as a heat sink although it may function also to continuously wash the catalyst in some fashion to keep its surface cleaner and therefore more active. It is also possible that the diluent provides for better contact of the lube with the catalyst because 'of the reduction in the viscosity in the reactor.

The hydrocracking feed for lube oil production-comprises waxy and dewaxed vacuum distillates, a deasphalted or Duo-Sol extracted residuum, waxy and de waxed deasphalted residuum boiling above about 650 F., or blends thereof. Preferably, the lube oil charge boils above about 700 F., and most preferably above about 735 F.

Any lube oil hydrocracking catalyst suitable for the manufacture of high V.I. lubes can be employed. As is well known, such catalysts are materials having a high activity for saturation of aromatics and high activity and selectivity for ring-scission. Generally preferred catalysts are sulfides of a Group VI metal, left-hand column, of the periodic system, mixed with an iron group metal. Most preferably, the catalyst is a mixture of nickel sulfide and tungsten sulfide in a 1:1 to 4:1 metal ion ratio on an alumina carrier. Other advantageous catalyst: metals are cobait and molybdenum. The catalyst may be in two or more beds, and the feed can be fractionated and charged at different points with the heavier fractions generally charged to provide for a greater exposure to hydrocracking conditions. This is so whether the beds are in a serial or parallel arrangement or if the reaction is carried out in a blocked-out operation. Also, the catalyst composition may be the same or different in the several beds or zones of a single bed, with the composition selected dependent upon the properties of the charge stock to be passed over same (i.e., refractory content which correlates directly with polycyclic content and boiling point) and the known performance characteristics of the particular catalyst composition.

The temperatures employed throughout the beds can be the same or different but, in general, will be in therange of about 650 to 875 F., more usually and preferably it the range of about 735 to 825 F. The partial pressure of hydrogen (i.e., refinery hydrogen streams can beemployed preferably containing at least about- 70% of hydrogen) can be as low as about 500 p.s.i. but should be a1 least about 1500 p.s.i., and preferably is above abou1 2500 to about 4000 p.s.i. Theoretically, hydrogen partiaf pressures as high as about 10,000 p.s.i., or higher can be employed. For most applications, the first-mentioned pressures suflice and are more economical. If adequate provisions are taken in constructing the equipment-in 2 multiple catalyst bed and feed charge arrangement; the pressure can then be varied in the various catalyst beds tc optimize the hydrogen pressure for each treating stage.

The space velocity will be slightly affected by the ust of the diluent of the present invention; however, itgen erally will be found still suitable to employ conventiona' lube oil hydrocracking space velocities of" about'0.1"t(

lent has a viscosity of about 0.4 cs. to about 2 '05. at

i F. Illustrative but nonlimiting examples are hexane, vtase, naphthas, spirits, fuel oil, and 60 SUS Neutral, ich has a viscosity .in centistokes of about 10.3. The cunt of diluent required will, of course, vary dependupon the viscosity of the particular charge material l of the diluent itself employed. Accordingly, in some es an amount of diluent that can be employed is as low about 5% by volume based on the. total charge with sfactory results. In other cases the amount of diluent irably employed will run as high as about 80% by time based on the total charge. In the typical case, amount of diluent inthe range of about to 50% normally be adequate, especially when the diluent is taphtha. Following the hydrocracking operation, the tent is readily separated and recovered from the lube fraction-by any conventional means. By some of these ventional, techniques, of course, some light materials It the hydrocracking will be recovered with the diluent; vever, if further purification is required or desired, this be readily accomplished. For the most part, a portion this slightly adulterated" diluent can be reused for .ation purposes without further purification. he present invention can be used in combination with other compatible refining procedures, particularly 1 pre-treatments and post-treatments of the hydro- :king operation. Examples of these, in addition to ie already briefly referred to hereinabove such as demalting and dewaxin-g, are subsequent hydrogenating mprove color and UVstability of same, furfural or :r solvent extraction, or rehydrocracking to further uple the V.I. of the product or improve its stability.

4 We claim:

1. In a process wherein a lubricating oil fraction which boils above about 700 F. is hydrocracked under hydro cracking conditions, the improvement comprising mixing the lubricating oil fraction with from about 5 to percent by volume of a hydrocarbon diluent having a kinematic viscosity in the range of about 0.15 to 17 centistokes at F. prior to charging same to the hydrocracking reaction.

2. A process according to claim 1 wherein said hydrocracking is carried out at a temperature in the range of about 700 to 825 F. and a hydrogen partial pressure of at least about 1500 p.s.i. 1

3. A process according to claim 2 wherein about 10 to 50% by volume of diluent is employed. 7

4. A process according to claim 3 wherein thevhydro- I cracking temperature is at least about 735 F.

5. A process according to claim 4 wherein the partial References Cited UNITED STATES PATENTS DELBERT E. GANTZ, Primary Examiner A. RIMENS, Assistant Examiner US. Cl. X.R.

3/1967 Kozlowski 208 112,