US3434963A - Solvent demetalation of a hydrocarbon oil - Google Patents

Description

United States Patent US. Cl. 208-252 Claims ABSTRACT OF THE DISCLOSURE A process for removal of metal contaminants, such as nickel and vanadium, from hydrocarbon oils by contacting the oils simultaneously with a parafiinic solvent, an aromatic solvent and an acid. The preferred solvents are C C paraflins and C C aromatics. Preferred acids are sulfuric, hydrochloric and hydrofluoric. Operating conditions described are those required to keep the entire system in the liquid phase during contacting. Volumetric amounts of the various components are specified.

BACKGROUND OF THE INVENTION This invention relates to processes for removing metal contaminants from hydrocarbon oils. More particularly, it relates to a process wherein a novel combination of treating agents is used to remove the metal contaminants while minimizing the oil loss.

Petroleum crude oils, and the heavier hydrocarbon fractions and/or distillates obtained therefrom, particularly heavy vacuum gas oils, oils extracted from tar sands and topped or reduced crudes, contain excessive quantities of organometallic contaminants causing detrimental effects with respect to various catalytic composites utilized in a multitude of processes to which the heavy hydrocarbon fraction may be subjected. Of the metallic contaminants, those containing nickel and vanadium are most common although other metals, including iron, copper, lead, zinc, etc., are often present. These metallic contaminants, as Well as others, may be present within the hydrocarbonaceous material in a variety of forms. They may exist therein as metal oxides or sulfides, introduced as metallic scale or particles, or they may exist in the form of soluble salts of such metals. Usually, however, the naturally occurring metallic contaminants are found to exist as organo-metallic compounds of relatively high molecular weight, such as metallic porphyrins and the various derivatives thereof. Where the metallic contaminants are present as oxide or sulfide scale, they may be removed, at least in part, by a relatively simple filtering technique, the water-soluble salt being removed by washing and subsequent dehydration of the crude oil. A considerable quantity of the organo -metallic complexes, however, are linked with asphaltenic material and become concentrated in the residual fractions; other organo-metallic complexes are volatile, oil-soluble and are, therefore, carried over in the distillate fraction in high vacuum distillation. A considerable reduction in the concentration of the organo-metallic complexes is not easily achieved to the extent that the crude oil, reduced crude oil or other heavy hydrocarbon charge stock becomes suitable for further processing. Notwithstanding that the concentration of these organo-metallic compounds may be relatively small, for example often less than about 10 ppm. (calculated as if the metallic complex existed as the elemental metal), subsequent processing techniques are adversely affected thereby. For example, when a hydrocarbon charge stock containing or- 3,434,963 Patented Mar. 25, 1969 gano-metallic compounds, such as metal porphyrins, in amounts above about 1-10 p.p.m. (calcaulated as elemental metal), is subjected to catalytic cracking for the purpose of producing lower boiling hydrocarbon prod ucts, the metals become deposited upon the catalyst, steadily increasing in concentration as the process continues. The composition of cracking catalyst is closely controlled with respect to the nature of the charge stock being processed and to the desired product quality and quantity. Such composition is changed drastically as a result of the deposition of the metallic contaminants thereupon, the changed composite resulting, therefore, in changed catalytic characteristics. Such an effect is undesirable since the deposition of the metallic contaminants usually results in a lesser quantity of normally liquid hydrocarbon products and produces large quantities of hydrogen and coke, the latter also promoting relatively rapid catalyst deactivation.

Eventually the catalyst must be subjected to elaborate regenerative techniques or, more often, be replaced with fresh catalyst. The presence of excessive quantities of organo-metallic complexes adversely affects other processes, including catalytic reforming, isomerization, hydrodealkylation, etc. With respect to a process for hydrorefining or treating of hydrocarbon fractions and/or distillates, the presence of exceedingly large quantities of asphaltenic material and organo-metallic compounds interferes considerably with the activity of the catalyst with respect to the destructive removal of the nitrogenous, sulfurous and oxygenated compounds, which function is normally the easiest for the catalytic composite to perform to an acceptable degree. Therefore, it is highly desirable to produce a hydrocarbon mixture substantially free from asphaltenic material and organo metallic compounds.

It has been suggested that substantial removal of asphaltenic materials and organo-metallic compounds from oils might be accomplished by simultaneous contacting of the oils with a parafiinic solvent and an acid immiscible in the solvent. Combinations which have been suggested or tried include HF-propane, HF-isopentane and propane-sulfuric acid. In processes of this type, there would be a phase separation to produce a demetallized, deasphalted oil phase and a metals-containing asphalt phase. The oil phase may be processed further into products, such as gasoline and lubricating oil. The asphalt phase may be demetallized if subsequent processing of the asphalt so requires or if the amount of metals present is sufiiciently high to make metals recovery economically attractive.

Processes of this type have not been considered especially successful, however, since in order for demetalation to be relatively complete the yield of the desired product, demetallizecl and deasphalted oil, had to be unsuitably low. In many cases the major portion of the original hydrocarbon material is removed with the asphalt phase, leaving a product oil yield of less than 50 liquid volume percent. Attempts to overcome this problem by using higher molecular weight parafiins (e.g., isooctane) have not resulted in significant improvement. Consequently, it would be most desirable to have a process which would give equivalent dernetalation while at the same time providing for significant increases in oil yields over previously known processes.

SUMMARY OF THE INVENTION This invention provides such a process. It has now been discovered that if a light, aromatic solvent is added to an acid and parafiinic solvent combination there is a significant increase in the yield of product oil without adverse etfect on the degree of demetalation achieved.

More particularly stated, this invention comprises demetallizing a metalsand asphaltene-containing hydrocarbon oil by contacting it with a combination of treating agents comprising an aromatic solvent, a parafiinic solvent and an acidic component.

Still more particularly, this invention comprises demetallizing a metalsand asphaltene-containing hydrocarbon oil by contacting it with a combination of treating agents which comprises contacting said oil with a combination of treating agents consisting essentially of 0.l2.0 volumes of an acidic component, 0.025.0 volumes of an aromatic solvent and 0.1l0.0 volumes of a parafifinie solvent per volume of said oil.

Still more particularly, this invention comprises demetallizing a metalsand asphaltene-containing hydrocarbon oil by contacting it with a solvent which comprises a combination of treating agents consisting essentially of 0.1-2.0 volumes of an acidic component, 0.02- 5.0 volumes of an aromatic solvent and O.1-l0.0 volumes of a paraffinic solvent per volume of oil, followed by separation into a lighter phase and a heavier phase and recovering from said lighter phase a substantially metaland asphaltene-free hydrocarbon oil.

DESCRIPTION OF PREFERRED EMBODIMENTS Within the definition of combination of treating agents are intended to be included all processes wherein residua is subjected to simultaneous acid treating and paraffinic solvent deasphalting in the presence of an added aromatic solvent, whether concurrently, countercurrently or batchwise, and whether the aromatic solvent is added to the oil, acid or paraflinic solvent. However, outside the scope of this definition are those processes in which one of the essential components of the combination contacts the oil individually in a separate step with separation of that component of the combination from the oil before contacting the oil with another of the essential components. In a preferred embodiment of the invention, the paraffinic solvent and the aromatic solvent are mixed with the oil before the acidic component is added to the system.

The following discussion, although not meant to be limiting to any extent, is offered as a possible explanation of the efficacy of this invention. It is known that the feed oil contains a certain amount of condensed ring structure compounds in addition to the organo-metallic compounds which are to be removed. These condensed ring structure compounds are, in general, relatively insoluble in paraffins and relatively more soluble in acids. Consequently, when only parafiinic solvents and acid It is believed that the maximum oil yield which can be recovered for a given parafiinic solvent at a given temperature is a function of the solubility of the condensed ring structure compounds in the solvent and is independent of the amount of solvent present once a suflicient amount of solvent has been contacted with the oil to cause a phase separation. Consequently, if a paraffinic solvent alone is used, a maximum limit of oil yield is rapidly reached which cannot be increased (at constant temperature) by addition of more solvent. Additional oil yield can, however, be obtained without increasing treating temperature, in accordance with the invention, by the addition of an aromatic solvent to the system. While different types of paraffinic solvents may give different oil yields, the oil yield of each will be significantly increased by the addition of an aromatic solvent.

The paraflinic solvent used in this invention may be any of those paraflinic solvents which have heretofore been found suitable for demetalation and deasphalting. In general, suitable solvents are those iso-, normal and cyclic paraffins containing from 31() carbon atoms per molecule. A single paralfinic solvent or mixtures of two or more solvents may be used. Among those paraflins commonly used are propane, n-butane, isopentane, isooctane, cyclohexane and methylcyclopentane.

The acidic component used in this invention may be one or more of those acids which have heretofore been found suitable for demetalation. Among these are sulfuric, hydrofluoric and hydrochloric acids. Particularly good results have been obtained with essentially anhydrous HF.

The aromatic solvent may be one or more light, liquid, aromatic hydrocarbons containing from 6l0 carbon atoms per molecule, such as benzene, toluene or one or more of the xylenes. The principal requirement for a suitable aromatic solvent is that it be miscible with the parafiin-oil base after phase separation so that the condensed ring structure compounds that it dissolves will be retained in that phase rather than being removed with the acid phase. Particularly good results have been obtained with the mixed xylenes.

The following example illustrates that the maximum oil yield obtainable with combinations of acid and paralfinic solvent can be significantly increased by the process of this inventioni.e., addition of an aromatic solvent to the system. The data for this example were obtained by mixing one volume of the oil with six volumes of the combination of treating agents in an enclosed steel vessel, separating the phases and measuring the yield and metals content of the solvent free oil phase.

Solvent Components Acl Run

A B C D HF Isooctane 1 Xylene HF HF Isopentane Isooctane HF Isooctane l Xylene Composition of treating agent comblnatlon, LV percent:

A id

Aromatic solvent- Temperatur e, Total Metals (Ni+V), p

Feed Product 0! Oil Yield, LV percent 1 Mixed isomers. 1 Maximum.

The conditions of temperature and pressure under which the process of this invention may be operated are dependent on the nature of the paraflinic and aromatic solvents used. The temperature for a given run may be any convenient temperature at which phase separation will occur, usually 60-350 F. The pressure is dependent on the temperature and must be sufficient to maintain all portions of the solvent in the liquid state. Determination of suitable temperature and pressure ranges for each solvent Volumes per volume of feed oil Acidic component 0.1-2.0 Aromatic solvent 0.02-5.0 Paraffinic solvent 0.1-l0.0

These limitations have been developed based on the considerations that there must be substantial demetalation, good phase separation and high oil yield. It is considered within the ability of one skilled in the art to determine the optimum composition for any particular combination of components.

There must be sufficient acid present in the system to draw the metals into the asphalt phase upon phase separation. However, there is a certain acid-feed ratio above which the addition of more acid will not increase the amount of demetalation. In general, acid-free volumetric ratios of 1:10 to 2:1 satisfactorily meet these two criteria. In the above example, the acid-free ratio was approximately 1:4 in each run.

The total hydrocarbon solvent content of the system is determined by reference to the volume of feed to be treated. Phase separation and oil yield considerations indicate that best results are obtained when the hydrocarbon solvents are present in the system in an amount equal to 0.5-10.0 volumes per volume of feed. In the example above, the hydrocarbon solvent content of the system was six volumes of solvent per volume of feed.

The range of proportions of aromatic to parafiinic solvents in the system is determined by the factors illustrated by Runs B, C and D of the example above. The minimum limit on the operative range represents the point below which there is too little aromatic solvent in the system to produce a significant improvement in oil yield over systems containing no aromatic material (e.g., if the aromatic solvent content of the system in Run C were decreased, oil yield would also decrease until, as the aromatic solvent content approached insignificant amounts, the oil yield would become approximately that of the nonaromatic solvent-containing system of Run B). The maximum limit on the operative range represents the point above which the benefit of the increased oil yield gained by increased aromatic content is offset by a significant decrease in the amount of demetalation achieved. (Comparison of Runs C and D in the above example illustrates that demetalation achieved decreased with increasing aromatic content.) It has been found in practice that best results are obtained when the proportion of aromatic solvent to paraflinic solvent is from about 1:25 to about 1:2. The more preferred range is from 1:20 to 1:4. Runs C and D in the above example show, respectively, proportions of approximately 1:10 and 1:4.

The data of the above example were derived from batchtype laboratory experiments. In actual commercial practice, however, the process of the invention would preferably be operated as a continuous flow system. In a typical operation, the parafiinic and aromatic solvents would be mixed in a mixing zone with the oil. The acid would then be added to the system. The eflluent of the mixing zone would be separated by conventional separation means into two phases, a lighter phase containing oil and the paraffinic and aromatic components of the solvent and a heavier phase containing metal compounds, asphalt and the acidic component of the solvent. Because of lack of complete immiscibility of solvent components in one or the other of the separated phases, some small amount of the paraflinic and aromatic components of the solvent will appear in the asphalt phase and some amount of the acid component will appear in the oil phase. Each phase would then be treated by conventional separation means to remove all significant amounts of solvent from the phase. The solvent would be recovered and recycled to contact fresh feedstock. Make-up solvent could be added to the recycle stream if needed. The final products would be a metalscontaining asphalt and deasphalted, demetallized oil suitable for further processing, such as catalytic conversion. In a particularly preferred embodiment, demetallized oil is hydrocracked while the asphalt is converted to hydrogen in a partial oxidation process. The degree of phase separation is controlled to provide only that amount of asphalt which *will, upon conversion by partial oxidation, produce the amount of hydrogen required to hydrocrack the demetallized oil, thus maintaining the process in overall hydrogen balance.

The above described examples and operating conditions are given for illustrative purposes only. It is apparent that many widely dilferent embodiments of this invention may be made without departing from the scope and spirit thereof, and therefore it is not'intended to be limited except as indicated in the appended claims.

We claim:

1. A process for the demetalation of a metal-parafiinand aromatic-containing hydrocarbon oil which comprises contacting said oil in a reaction zone with a combination of treating agents consisting essentially of 0.1-10.0 volumes of a paraflinic solvent comprising at least one C C paraifinic hydrocarbon, 0.02-5.0 volumes of an aromatic solvent comprising at least one C -C aromatic hydrocarbon, and 0.1-2.0 volumes of an acidic component.

2. The process of claim 1 wherein said acidic component is selected from the group consisting of sulfuric acid, hydrofluoric acid, hydrochloric acid, and essentially anhydrous HP.

3. The process of claim 2 wherein said acidic component comprises essentially anhydrous HF.

4. The process of claim 1 wherein said metals are separated from said hydrocarbon oil and are recovered as insoluble compounds.

5. The process of claim 1 wherein said aromatic solvent comprises a plurality of xylene compounds.

References Cited UNITED STATES PATENTS 3,245,902 4/ 1966 Adams et al 208-252 FOREIGN PATENTS 1,212,662 3/1966 Germany.

DELBERT E. GANTZ, Primary Examiner. J. D. MYERS, Assistant Examiner.