US3112258A - Process for the recovery of minor amounts of solvent from solventextracted hydrocarbons - Google Patents

Description

United States Patent O the public This invention relates to a process for the removal of minor amounts of certain organic contaminants from liquid hydrocarbons. More particularly, the invention relates to a process for removing minor quantities of solvents firom the products of a solvent extraction process conducted .on certain petroleum stocks.

Solvent extraction processes are widely employed today in the petroleum and chemical industries. In the petroleum industry, solvent extraction is employed, for example, for the production of relatively pure aromatic hydrocarbons which may be employed as chemical intermediates or for increasing the aromatic content of gasoline stocks so as to raise their octane number.

The most common source of aromatic-containing stocks in the petroleum industry is the product of a catalytic reforming operation. Catalytic reforming refers to a process wherein a naphtha cut from crude oil boiling in the range of about ZOO-450 R, and often 225 to 400 F., is contacted with a platinum-ccntaimng or other catalyst under conditions of elevated temperature and pressure. The products of this opertion is rich in aromatic hydrocarbons but also contains significant amounts of parafiinic hydrocarbons.

Various processes have been developed for extracting the valuable aromatic hydrocarbons from the product of a catalytic reforming operation. One of these processes involves the use of a selective solvent which preferentially dissolves the aromatic hydrocarbons. One of the drawbacks of such process has been that the hydrocarbons become contaminated with minor amounts of the solvent. Accordingly, this invention is concerned with the removal of such minor amounts of solvent from the product of a solvent extraction process. The removal of the solvent not only enhances the value of the products but it may also permit the re-use of the solvent, which offers obvious economic advantage.

In the solvent extraction of catalytic reformate, the reformate is contacted in an extraction zone with a selective solvent, resulting in the yield :of two separate phases. The various solvents for use in this extraction process are well known in the art. One class of solvents known to the art which finds particular utility for solvent extracting catalytic reformate are polar organic solvents. Of this class, hydroxy amines and their derivatives, which selectively dissolve aromatic hydrocarbons from paraffinic hydrocarbons, are illustrative. These include phenylethanolamine, phenyldiethanolarnine, triethalolamine, diethylaminoethanol, dioctylaminoethanol, ethylphenylethanolamine, monoethanolamine, diethanolalmine, monoisopropanolamine, triisopropanolamine, diisopropanolamine, N- morpholinethanol, hydroxvethylethanoldiamine, triethanolamine abietate, triethanolamine naphthenate, butyl diethanolamine, N-dibutylaminoethanol, p-tertiary-amyl phenyldiethanolamine, p-tertiaryamyl phenylmonoethanolamine, diethylamino-2,3 propanediol, etc. In particular, phenylethanolamine has been found a very effective selective solvent for this extraction process, and the invention will be described in connection with this solvent.

The extract phase from the extraction operation con- 2 Claims.

3,112,258 Patented Nov. 26., 1963 tains the bulk of the solvent employed. The major amount of this solvent is removed trom the extract by conventional means. For example, the solvent may be separated from the extract phase by simple distillation. Regardless of the method employed, it is quite diflicult to obtain a complete removal of solvent from the extract phase, and minor amounts of the selective solvent usually remain in the aromatic product. Similarly, small amounts of solvent are included in the raflinate phase obtained from the extraction operation. The amount of solvent remaining in these products will vary depending upon the solvent and process conditions selected for the extraction process, and it may vary widely in the range of 0.01% up to about 5% by weight of the total hydrocarbon stock.

It is therefore the object of this invention to remove such minor amounts of solvent from the products of a solvent extraction process. The process of this invention is broadly applicable to removing minor amounts of any polar organic solvent for aromatic hydrocarbons remaining in either the extract or raflinate phases but has particular utility in connection with the solvents selected from that class of hydroxy amine compounds mentioned above.

Briefly stated, this invention is a process which comprises the step of contacting the products of a solvent extraction with a bed of adsorbent material.

The nature of the adsorbent materials is not critical in the process, and any solid particles having adsorbent characteristics may be employed, such as, for example, various types of commercially available charcoals, clays, bone chars, bauxitels, spent catalytic cracking catalysts, and natural or synthetic zeolites. The particle size of the solid adsorbent and the size of the bed are not critical and will depend in large part on the volume of the product stream that must be treated. In general, the particle size of the adsorbent may vary between 10 and Q00 mesh. Flow rate of the product stream need only be suflicient to insure good contact within the adsorption bed, and normally the flow rate may range from space velocities of approximately 1 to 10 volumes of product stream feed per hour per volume of bed.

The process may be conducted at atmospheric temperature and pressure. It is preferred, however, that the process be conducted at temperatures of approximately 60 F. to 220 F. but below 250" F. so as to avoid polymerization of any olefinic compounds which may be present in the products treated. These olefins are not objectionable when the stock is to be used as a gasoline component. The pressure may be super-atmospheric but there is no advantage to this unless the temperature is close to or above the boiling point of any component of the stock.

A more complete understanding of the invention may be gained from the following working examples, which are offered to illustrate and not to limit this invention.

Example I 80 bbl. of heptane per hour, containing 0.3 Weight percent of phenylethanolamine, corresponding to a raffinate phase, was passed over an adsorption bed having a volume of ft. containing 2800 lbs. charcoal having a particle size in the range of 10 to 200 mesh. The operation was carried out at atmospheric pressure and at a temperature of F. The effluent contained substantially no phenylethanolamine and the operation was continued until an analysis of the product showed a phenylethanol amine content exceeding 10 ppm. During this period, 800 bbl. of heptane was treated.

Example II A hydrocarbon stream comprising a 70% toluene and 30% heptane mixture containing 2 weight percent of (B phenylethanolamine, corresponding to an extract phase, was passed at a rate of 100 bbl./hr. over an adsorption bed having a volume of 75 ft. containing 2800 lbs. charcoal having a particle size in the range of to 200 mesh. The operation was carried out at atmospheric pressure and at a temperature of 130 F. The efiluent contained substantially no phenylethanolamine and the operation was continued until an analysis of the effluent showed a phenylethanolamine content exceeding 40 p.p.m. During this period, 55 bbl. of the hydrocarbon stream was treated.

It is contemplated that when the concentration of the solvent in the product exceeds a predetermined amount, the flow of hydrocarbon to the bed is discontinued and the adsorbent particles in the bed may be discarded and replaced with fresh particles. Alternatively, the spent bed may be regenerated by any suitable means known to the art and the adsorbent re-used. Regeneration of the bed may be accomplished, for example, by steam stripping. A preferred means of regenerating the spent bed is disclosed in my co-pending application Serial No. 773,155, filed November 12, 1958.

Although the process of this invention may be readily adapted to remove any amount of contaminating solvent within the concentration range stated heretofore as 0.01% to 5% by weight, it may be desirable when the concentration of the solvent is 2% or above to first water-wash the products by methods well described in the prior art to reduce the solvent content to below approximately 1% before treating the products with the process of this invention for the substantially complete removal of solvent.

It will be obvious to those skilled in the art that various modifications of the process described herein may be readily made without departing from the spirit and intent of this invention, and hence it is desired that application for Letters Patent cover all such modifications of the invention as would reasonably fall Within the scope of the appended claims.

I claim:

1. A process for removing phenylethanolamine from a hydrocarbon liquid stream obtained in the selective solvent extraction of catalytic reformate with phenylethanolamine, said stream containing tfrom about 0.001 to about 5% phenylethanolamine, comprising the steps of introducing said liquid hydrocarbon stream into a closed vessel containing a bed of adsorbent material, contacting said hydrocarbon stream with said bed at a temperature under 250 F., and recovering the hydrocarbon stream substantially free from said phenylethanolamine from said vessel.

2. The process of claim 1 in which the adsorbent material is charcoal.

References Cited in the file of this patent UNITED STATES PATENTS 1,882,002 Dietrich Oct. 11, 1932 2,398,101 Lipkin Apr. 9, 1946 2,651,594 Blatz Sept. 8, 1953 2,711,433 Pofienberger June 21, 1955 2,744,942 Wankat May 8, 1956 2,856,442 Munk Oct. 14, 1958 2,858,902 Cottle Nov. 4, 1958 OTHER REFERENCES Nevens: Petroleum Engineer, June 1954, vol. 26, Number 6, pages D3334.

Perry: Chemical Engineers Handbook, 1950, 3rd ed., pp. ass-901.

Sachanen: Chemical Constituents of Petroleum," Reinhold Pub. Co., 1945, page 219.

Claims (1)

1. A PROCESS FOR REMOVING PHENYLETHANOLAMINE FROM A HYDROCARBON LIQUID STREAM OBTAINED IN THE SELECTIVE SOLVENT EXTRACTION OF CATALYTIC REFORMATE WITH PHENYLETHANOLAMINE, SAID STREAM CONTAINING FROM ABOUT 0.001 TO ABOUT 5% PHENYLETHANOLAMINE, COMPRISING THE STEPS OF INTRODUCING SAID LIQUID HYDROCARBON STREAM INTO A CLOSED VESSEL CONTAINING A BED OF ADSORBENT MATERIAL, CONTACTING SAID HYDROCARBON STREAM WITH SAID BED AT A TEMPERATURE UNDER 250*F., AND RECOVERING THE HYDROCARBON STREAM SUBSTANTIALLY FREE FROM SAID PHENYLETHANOLAMINE FROM SAID VESSEL.