US3796653A - Solvent deasphalting and non-catalytic hydrogenation - Google Patents

Abstract

AN ASPHALTENE-CONTAINING HYDROCARBONACEOUS CHARGE STOCK IS PRETREATED VIA A COMBINATION PROCESS TO PREPARE A SUITABLE HYDRODESULFURIZATION FEED STOCK. THE COMBINATION PROCESS INVOLVES THE INTEGRATION OF (I) NON-CATALYTIC HYDROGENATIVE CONVERSION (HYDROCRACKING) AT CONDITIONS WHICH MINIMIZE COKE-FORMING THERMAL CRACKING REACTINS AND (2) SOLVENT EXTRACTION OF THE RESULTING PRODUCT EFFLUENT WITH RECOVERY OF A SUBSTANTIALLY ASPHALTENE-FREE FEED STOCK

Description

United States Patent 3,796,653 SOLVENT DEASPHALTING AND NON- CATALYTIC HYDROGENATION John G. Gatsis, Des Plaines, Ill., assignor to Universal Oil Products Company, Des Plaines, Ill. No Drawing. Filed July 3, 1972, Ser. No. 268,277

Int. Cl. C10g 31/14 US. Cl. 20895 7 Claims ABSTRACT OF THE DISCLOSURE An asphaltene-containing hydrocarbonaceous charge stock is pretreated via a combination process to prepare a suitable hydrodesulfurization feed stock. The combination process involves the integration of (1) non-catalytic hydrogenative conversion (hydrocracking) at conditions which minimize coke-forming thermal cracking reactions and (2) solvent extraction of the resulting product eflluent with recovery of a substantially asphaltene-free feed stock.

APPLICABILITY OF INVENTION The invention herein described is adaptable to a process for the pretreatment of an asphaltene-containing hydrocarbonaceous charge stock in order to prepare a suitable hydrodesulfurization feed stock. More specifically, the present invention is directed toward a combination process for pretreating heavy carbonaceous material such as atmospheric tower bottoms products, vacuum tower bottoms products (vacuum residuum), crude oil residuum, topped crude oils, coal oil extract, crude oils extracted from tar sands, etc., all of which are commonly referred to in the petroleum refining art as black oils. These black oils contain high molecular weight sulfurous compounds in exceedingly large quantities and, in addition, excessive amounts of nitrogenous compounds, high molecular weight organometallic complexes principally comprising nickel and vanadium, and pentane-insoluble asphaltic material. Asphaltic material is generally found to be complexed, or linked with sulfur and, to a certain extent, with the or-ganometallic compounds. An abundant supply of such hydrocarbonaceous material exists, most of which has a gravity less than about 20.0 API; a significant quantity of this hydrocarbonaceous material has a gravity less than about 100 API. Furthermore, black oils are generally characterized by a boiling range which indicates that 10.0% by volume, and generally more, has a normal boiling point above a temperature of about 1050 F.

As hereinafter indicated, in a brief discussion of the applicable prior art, the virgin charge stocks to which the present combination process is particularly directed have, in the past, been subjected to deasphalting to eliminate asphaltic material and organometallic compounds. In and of itself, solvent deasphalting results in about 75.0% metal removal accompanied by approximately a 30.0% yield loss, based upon charge stock. The utilization of the present invention results in greater than 95.0% metal removal accompanied by only 10.0% yield loss. Specific examples of the black oil charge stocks, illustrative of those to which the present invention is especially applicable, include a vacuum tower bottoms product having a gravity of 7.1 API, and containing 4.05% by weight of sulfur and about 23.7% by weight of asphaltenes; and, a vacuum residuum having a gravity of about 8.8 API, containing 3.0% by weight of sulfur, 4,300 ppm. of nitrogen and having a 20.0% volumetric distillation temperature of about 1055 F. The utilization of the present invention affords the recovery of, higher yields of a substantially asphalteneand metal-free charge stock which is extremely well suited for subsequent use as ice the feed stock to a fixed-bed, catalytic hydrodesulfurization, or hydrotreating process.

OBJECTS AND EMBODIMENTS One object of this invention is to provide a more efficient process for the preparation of a hydrodesulfurization feed stock. A corollary objective is to increase the effective life of the solid, catalytic composite utilized in the subsequent hydrodesulfurization process, by eliminating asphaltics and metals.

Another objective is to convert hydrocarbon-insoluble asphaltenes into hydrocarbon-soluble, lower-boiling liquid hydrocarbon products.

Therefore, in one embodiment, the present invention involves a process for pretreating an asphaltene-containing hydrocarbonaceous black oil which comprises the steps of: (a) reacting said black oil with hydrogen, in a noncatalytic reaction zone, at hydrocracking conditions including a temperature in the range of about 300 C. to about 500 C.; (b) deasphalting at least a portion of the resulting reaction zone efiluent with a selective solvent in a solvent extraction zone to provide (i) a solvent-rich liquid phase and (ii) a solvent-lean asphaltene concentrate; and, (c) recovering the pretreated black oil from said liquid phase.

Other embodiments of my invention relate primarily to operating conditions and the solvent used within the solvent extraction zone. In one such other embodiment, the non-catalytic hydrocracking conditions also include a pressure from about 1,000 to about 3,000 p.s.i.g. and a hydrogen concentration of about 1,000 to about 30,000 s.c.f./bbl.- In another embodiment, the selective solvent is a naphtha fraction having an end boiling point below about 200 F.

PRIOR ART Candor compels recognition of the fact that the appropriate prior art is replete with a myriad of techniques designed to effect solvent deasphalting of asphaltene-containing hydrocarbonaceous charge stocks. In the interest of brevity, no attempt will be made herein to exhaustively delineate such solvent deasphalting art.

U.S. Pat. No. 2,002,004 (Class 208-14) involves -a 2- stage deasphalting process wherein the second stage completes the precipitation of asphalts which was only partially effected within the first stage. Suitable solvents are indicated as including naphtha, gasoline, casinghead gasoline and liquefied normally gaseous hydrocarbons such as ethane, propane, butane and mixtures thereof.

US. Pat. No. 2,914,457 (Class 20879) describes a multiple combination process involving fractionation, vacuum distillation, solvent deasphalting, hydrogenation and catalytic reforming. Again, the suitable liquid deasphalting-solvents include liquefied normally gaseous hydrocarbons such as propane, n-butane, isobutane, or mixtures thereof, as well as ethane, ethylene, propane, propylene, n-butylene, isobutylene, pentane, isopentane, and mixtures thereof.

While the foregoing examples of the deasphalting'art serve to indicate the now ancient use of a wide variety of deasphalting solvents, it must necessarily be noted that there is no awareness of the present combination process wherein the black oil charge stock is initially reacted with hydrogen in a non-catalytic reaction zone.

Mention should-also be made of US. Pat. No. 2,975,121 (Class 208251) wherein the charge stock is initially subjected to hydrogenative cracking, followed by solvent deasphalting of the hydrogen-treated oil to remove suspended solid metal constituents. This reference indicates that the hydrogenation operation, for the initial treatment of the metal-containing charge stock, is carried out in the presence of a suitable hydrogenation catalyst, and preferably one which is sulfur-resistant.

Although non-catalytic, hydrogenative conversion processes have been recognized for some time, relatively recent United States patents indicate the integration of this technique in combination with other technology. For example, US. Pat. No. 3,494,855 (Class 20897) describes a process involving the integration of hydrogenative cracking and catalytic desulfurization. In the described combination process, the heavier portion of the cracked eflluent is subjected to a series of separations, including the use of a standard vacuum column, in order to separate an asphaltic residuum prior to effecting the fixed-bed catalytic desulfurization.

US. Pat. No. 2,989,459 (Class 208102) discloses a hydroconversion process wherein the liquid portion of the efiluent is quenched to precipitate solid particulate asphalts. Similar processes are described in US. Pat. No. 2,989,460 (Class 208107) and No. 2,989,461 (Class 208--107). US. Pat. No. 3,017,345 (Class 208-210) involves a combination process in which hydroconversion at highly turbulent fiow is coupled with catalytic desulfurization of at least a portion of the liquid product. Similar processes form the subject matter of US. Pats. No. 3,089,843 (Class 20858) and No. 3,228,871 (Class 20858).

SUMMARY OF INVENTION The inventive concept herein described encompasses a combination process in which non-catalytic hydrocracking of a hydrocarbonaceous black oil is integrated with a solvent deasphalting system in order to prepare a suitable feed stock for a subsequent hydrodesulfurization process. An essential feature of this combination process resides in the temperature at which the hydrogenative cracking is effected; since it is intended to avoid thermal cracking reactions, the temperature will be maintained below a level of about 510 C., preferably being in the range of about 300 C. to about 500 C. A particularly preferred temperature range is about 350 C. to about 450 C. Other hydrocracking conditions, for utilization in the non-catalytic reaction zone, include a pressure from about 1,000 to about 3,000 p.s.i.g. and a hydrogen concentration of about 1,000 to about 30,000 s.c.f./bbl. At these conditions, the thermal cracking of the hydrocarbonaceous charge stock is minimized to the extent that it is virtually non-existent and, therefore, those reactions which ultimately foster coking are significantly reduced. Simultaneously, oil-soluble, metal-containing compounds are subject to hydrocracking to produce a lower-boiling, metalfree hydrocarbon and an oil-insoluble metal-containing substance. Furthermore, a significant degree of asphaltene conversion is effected.

The non-catalytic hydrogenative cracking may be effected in a suitable elongated reaction vessel in either countercurrent flow, or co-current flow; the latter may be effected either upflow, or downfiow. The utilization of an upflow system is somewhat more advantageous in view of the fact that the extremely heavy portion of the charge stock will have an appreciably longer residence time within the reaction zone, with the result that a greater degree of conversion is readily attainable.

The product eflluent, from the hydrogenation zone, is introduced into a suitable separation system from which a hydrogen-rich gaseous phase is recovered for the purpose of recycle to combine with the fresh feed charge stock. The hydrogen separtion system is not considered an essential feature of the present combination process. It may consist of one or more suitably operated vessels from which the hydrogen is recovered; other normally gaseous streams may be separately recovered including, for example, a methane/ethane concentrate and a butane/propane concentrate.

The normally liquid portion of the product efiluent is introduced into the upper portion of a solvent deasphalting zone, wherein it countercurrently contacts a suitable selective solvent which is introduced into the lower portion thereof. The solvent deasphalting zone will function at a temperature generally in the range of about 50 F. to about 500 F., and preferably from about F. to about 350 F.; the deasphalting zone will be maintained under a pressure within the range of about 100 to about 1,000 p.s.i.g., and preferably from about 200 to about 600 p.s.i.g. The precise operating conditions will generally depend upon the characteristics of the normally liquid product effluent, emanating from the non-catalytic, hydrogenative cracking zone, as well as the selected solvent. In general, the temperature and pressure are selected to maintain the operation in the liquid phase, and to insure that all the asphaltics are removed within the solvent-lean heavy phase. Suitable solvents include those hereinbefore described with respect to the discussion of the applicable prior art. Thus, it is contemplated that the selective solvent will be selected from the group of light hydrocarbons such as methane, ethane, propane, butane, isobutane, pentane, isopentane, neo-pentane, hexane, isohexane, heptane, etc. Likewise, the solvent may be a normally liquid naphtha fraction containing hydrocarbons having from about 5 to about 14 carbon atoms per molecule, and preferably a naphtha fraction having an end boiling point below about 200 F. The solvent-rich, normally liquid phase is introduced into a suitable solvent recovery system, the design and operating techniques of which have been thoroughly described in the prior art.

In another operating embodiment of the present combination process, the intended results of the hydrogenative cracking reactions appear to be beneficially enhanced when effected in the presence of hydrogen sulfide. Therefore, it is within the scope of the present invention that from about 5.0 to about 30.0 mol percent hydrogen sulfide be present in the hydrogen being admixed with the fresh feed charge stock.

As previously stated, whereas deasphalting in and of itself results in about 75.0% metal removal accompanied by an approximate 30.0% yield loss, the present combination process achieves greater than 95.0% metal removal with an accompanying yield loss of only 10.0%.

EXAMPLES The examples which follow are presented to further illustrate the benefits afforded through the utilization of the present combination process. It is understood that it is not intended to limit unduly the scope of the appended claims to the charge stock, operating conditions, selective solvents, etc.

The charge stock employed was a Boscan crude oil having a gravity of 16.9 API and containing 6.39% by weight of sulfur and 1,305 ppm. by weight of metals; 28.0% by weight of the charge stock consisted of pentane-insoluble asphaltenic material. These experiments were effected in an 1,800-ml. rocker-type autoclave. The autoclave treatment was conducted by charging the indicated quantities of charge stock and pressuring the same to 100 atmospheres with either hydrogen or nitrogen as indicated. The autoclave was heated to a temperature of 400 C. for about two hours, after which the same was cooled to room temperature and depressured. The autoclave was flushed three times with nitrogen and the contents removed. These were stripped with nitrogen on a steam bath and deasphalted as hereinafter described.

The autoclave contents were treated with five volumes of n-pentane, being stirred for 15 minutes. Pentane which was lost through evaporation was replaced, and the samples stirred for about two minutes. After a period of about 30 minutes, standing at room temperature, the sample was centrifuged at 3,000 r.p.m. for 30 minutes. The supernatant liquid was decanted and filtered. Centrifugal solids were dried over nitrogen, evacuated in a vacuum oven at room temperature and stored under a blanket of nitrogen. Solvent was distilled from the filtrate using vacuum-flash distillation, while controlling the flask temperature at about 150 C.

EXAMPLE I In this instance, 200 grams of the Boscan crude oil charge stock was subjected only to solvent deasphalting using n-pentane. The deasphalted product, upon analysis, indicated a gravity of 14.8 API, a sulfur concentration of 6.12% by weight and a metals content of 390 p.p.m. The pentane-insoluble portion was 59 grams (29.5% by weight, based upon the quantity of the charge stock).

EXAMPLE -II In this instance, 205 grams of the charge stock within the autoclave was pressured to 100 atmospheres using a nitrogen stream. After two hours at a temperature of 400 C., the autoclave was cooled and depressured and the contents subjected to deasphalting and subsequent analysis. The deasphalted oil indicated a gravity of 16.8 API, and contained 4.47% by Weight of sulfur and 140 p.p.m. by weight of metals. The pentane-insoluble portion was 53 grams, or 25.9% by weight, based upon the quantity of charge stock.

EXAMPLE III 206 grams of the Boscan charge stock were pressured to 100 atmospheres utilizing a hydrogen stream. Following two hours at a temperature of 400 C., the autoclave was cooled and depressured, the contents being subjected to solvent extraction utilizing n-pentane. The deasphalted oil indicated a gravity of 17.5 API, and contained 4.29% by weight of sulfur and 352 p.p.m. by weight of metals. The pentane-insoluble portion was 39.4 grams, or approximately 19.1% by weight, based upon the quantity of charge stock.

EXAMPLE IV Hydrogen sulfide, in an amount of about 34 grams, was admixed with 203 grams of the Boscan crude oil and pressured to 100 atmospheres with hydrogen. Following a 2-hour period at 400 C., cooling and depressuring, the contents were again subjected to solvent deasphalting. The deasphalted product indicated a gravity of 17 .0 API, a sulfur content of 4.18% by weight and 40.6 p.p.m. by weight of metals. The pentane-insoluble portion was in an amount of 16.0 grams, or about 7.9% by weight, based upon the quantity of charge stock.

With respect to the foregoing Examples II and IV, the pentane-insoluble portion contained high molecular weight coke. In Examples III and V, the pentane-insolubles are soluble in benzene which indicates no coke formation.

The foregoing specification, and particularly the examples, indicate the method of eifecting the present invention and the benefits to be afforded through the utilization thereof.

I claim as my invention:

1. A process for pretreating an asphaltene-containing hydrocarbonaceous black oil which comprises the steps of:

(a) reacting said black oil with a hydrogen stream containing from 5.0 mol percent to about 30.0 mol percent hydrogen sulfide, in a non-catalytic reaction zone, at hydrocracking conditions including a temperature in the range of about 300 C. to about 500 C., a pressure from about 1,000 to about 3,000 p.s.i.g. and a hydrogen concentration of about 1,000 to about 30,000 s.c.f./bbl.;

(b) deasphaltiug at least a portion of the resulting reaction zone effluent with a selective solvent in a solvent extraction zone to provide (i) a solventrich liquid phase and (ii) a solvent-lean asphaltene concentrate; and

(c) recovering the pretreated black oil from said liquid phase.

2. The process of claim 1 further characterized in that said reaction zone effiuent is deasphalted at a temperature from 50 F. to about 500 F. and a pressure from to about 1,000 p.s.i.g.

3. The process of claim 1 further characterized in that said selective solvent is a light hydrocarbon containing from one to about seven carbon atoms per molecule.

4. The process of claim 1 further characterized in that said selective solvent is a normally liquid naphtha fraction containing hydrocarbons having from about five to about fourteen carbon atoms per molecule.

5. The process of claim 1 further characterized in that the volume ratio of said selective solvent to said reaction zone eifiuent is about 3:1 to about 15:1.

6. The process of claim 3 further characterized in that said selective solvent comprises n-butane.

7. The process of claim 4 further characterized in that said naphtha fraction has an end boiling point below about 200 F.

References Cited UNITED STATES PATENTS 2,943,047 6/1960 'Reeg et a1 208-251 H 2,975,121 3/ 1961 Whaley 208-251 R 3,338,818 8/1967 Paterson 20858 HERBERT LEVINE, Primary Examiner US. 01. X.R.