US3309310A - Process for the removal of deposit formers - Google Patents

Description

United States l atetit 3,309,310 PROCESS FOR THE REMOVAL OF DEPOSIT FORMERS Blanchard L. Mickel, Munster, Ind., assignor to Standard Oil Company, Chicago, 11]., a corporation of Indiana No Drawing. Filed Apr. 30, 1964, Ser. No. 364,015 8 Claims. (Cl. 208255) This invention relates to a process for the removal of certain deposit formers from reformate.

The results from tests have consistently indicated that when the gasoline endpoint is increased, some undesirable eifects occur in the internal combusion engines in which these gasolines are being burned. These undesirable effects include increased deposits, increased octane requirement, surface ignition, and dilution of the crankcase lubricant.

The tendency of hydrocarbons to form deposits in engines is related to both the boiling point and type of the involved hydrocarbons. There are two types of deposits that occur in an internal combustion engine: those deposits which are found in the induction system and those which exist in the combustion chamber. Recent evidence suggests that the polycyclic aromatics apparently are associated with the harmful constituents of the hydrocarbons. In fact, it has been suggested that the compounds which form deposits in the induction system of an internal combustion engine are polycyclic aromatics which have incorporated polar groupings. These polar groupings cause the particular compound to separate from the bulk of the reformate at the conditions which exist in the induction system. In no way is this suggested theory presented here to limit the utility of my invention. The compounds which cause these deposits, whatever they may be, will hereinafter be referred to as deposit formers.

The inclusion of heavy aromatics from the various reforming processes in gasolines has been economically attractive. The consumer of these gasolines, which contain the so-called deposit formers, must be protected from the effects of such compounds. There are several ways to achieve this protection, and in one of them the harmful compounds are removed completely by physical separation processes; in the other, special gasoline additives are used to partially counteract the harmful effects of the deposit formers. Deposit formers may be removed by conventional re-running of the reformate. Re-running is the process of removing a small percentage of the heaviest portion of reformate by distillation. This is a sound method for removal, but its cost is high and the accompanying loss in gasoline volume is appreciable. be subjected to the re-running treatment, but in such a case, the feed endpoints might be more restricted than they would be if conventional re-running were used. Furthermore, the re-running process is not selective of the materials being removed with regard to performance in engines. Consequently, the removal of a greater percentage of the reformate bottoms might be necessitated to provide adequate protection from the most harmful portion of the deposit formers. The special gasoline additives which are used to counteract the harmful effects of the deposit formers would not completely prevent further build-up of the deposits.

My invention provides a relatively inexpensive method of selectively removing the deleterious deposit formers A portion of the total reformate couldthat exist in high-severity r'efo rmate. High-severity reformate is the product that is obtained from a reforming process that is being operated at a high temperature and a low pressure to furnish very high octane material. The process of my invention comprises the passing of the high-severity reformate, hereinafter called reformate, through a bed of material such as glass beads, sand, gravel, slag and coke at conditions which permit at least 98-99% of the hydrocarbons to remain in the vapor phase as they pass through the bed of small inert particles. The material making up the bed of small inert particles should be chemically inert with respect to hydrocarbons. The temperature of the surface of the inert particles is less than the condensation temperature of the heavy deposit-forming compounds, but greater than the vaporization temperatures of the, other constituents of the reformate. The pressure of this system should be maintained at a fairly low value since more heat is required to vaporize the hydrocarbons as the pressure is increased. As the hydrocarbon vapors move through the bed of particles, the undesirable heavy deposit formers condense and the liquid so formed adheres to the surface of the packing. The effluent reformate vapor, from which the deposit formers have been removed, passes on through and out of the column, is condensed and stabilized, and may be blended directly into motor gasoline without any further processing be ing required to reduce the deposit-forming tendencies of the product.

The reformate may be introduced into the packed column at the top of the column and pass downward through the bed of small inert particles, or it may be introduced into the column near the bottom of the column and pass upward through the bed of particles. In this latter case, the heavy material, which will tend to collect at the bottom of the bed, may be removed from the column periodically.

The deposits which adhere to the finely divided packing must, from time to time, be removed from the packing. This removal may be brought about by oxidative regeneration. As an alternate method of providing clean packing, the spent packing may be removed periodically from the column and replaced with fresh packing.

In another embodiment of my invention, reformate is contacted with air prior to its introduction into a column which is packed with material such as glass beads, sand, gravel, slag and coke. This contacting with air may be performed by permitting the reformate to stand in a tank and be exposed to air, or it may be accomplished by bubbling air through reformate in a tank. It is possible that the air might be injected into a stream of hydrocarbon as it passes through a line or pipe. In any event, it should be pointed out that such contacting and the subsequent handling of the air-contacted hydrocarbons should be done with the aid of techniques which are consistent with current safe practices known to those skilled in the art.

The deposit formations, which are caused by polycyclic aromatics having incorporated polar groupings and their associated compounds and which can be prevented by the use of my invention, occur in the induction system of internal combustion engines. Such deposit formations, hereinafter called deposits, may be studied conveniently in a laboratory bench apparatus which is referred to as the Rotogurn. This apparatus is discussed in detail in US. Patent 3,108,468. In the carrying out of the test Patented Mar. 14, 1967 wherein this apparatus is used, 100 ml. of fuel is slowly injected onto the walls of a rotating, inclined, heated glass tub during a 40-minute test period. The glass tube is heated to a temperature in the range between about 350 and 400 F. Light ends are carried out of the tube in a stream of air and gasoline bottoms remain in the tube and form varying quantities of adherent deposits. These deposits are removed and weighed at the end of each test. Deposits found in the Rotogum test may be conveniently expressed as milligrams of deposit per 100 milliliters of fuel tested. The deposit-forming performance of gasolines in the Rotogum test have been correlated with their behavior in the intake manifolds of laboratory test engines. This Rotogum test is very sensitive to changes in reformate tail-end composition.

The polycyclics found in Rotogum deposits are more dependent upon hydrocarbon type than upon their original concentration in gasoline. Aromatics such as anthracenes and pyrenes are predominant in Rotogum deposits even though their concentration in gasoline is very low. The following table illustrates an example of the distribution of the polycyclics from a reformate in the hydrocarbon portion of the Rotogum deposits.

Approximate percent Hydrocarbon: in deposit Pyrenes 30 Anth rac enes 2 1 Naphthalenes 4.5 Diphenyls 4 Acenaphthenes l a-Phenyl-naphthalenes 12.5 Chrysenes 13 Others Pyrenes comprise about 30% of the hydrocarbons found, and are the predominant aromatic. The next most prevalent aromatic, anthracenes, comprise about 20% of the hydrocarbons. Hydrocarbons that boil higher than anthracenes or pyrenes were found in smaller quantities in these deposits. The relative contributions of these aromatics to the formation of intake-system deposits in engines have not been established.

Example I This example illustrates the effectiveness of my invention in removing the deposit formers from a reformate, whether the reformate is treated immediately after it has been produced in the reformer or whether it has been permitted to stand for a period of time in a storage tank. For convenience in the laboratory, the liquid reformate was introduced into the column at its top and the initial portion of the heated packed bed was used to preheat the reformate. This column, which had a volume of approximately 100 ml., was filled with 3 mm.-diameter glass beads. The column was heated along its entire length and was maintained at a maximum temperature of 650 R, which was the temperature of the treated reformate as it exited from the column. The vapors of the treated reformate were condensed and collected at a rate of about 200 mil. per hour. Three dilferent reformates were treated in this manner. The first, referred to as reformate A, was purged with nitrogen prior to its passage through the packed column. The second and third were made up of reformate B. The second reformate was purged with nitrogen prior to its passage into the packed column while the third was contacted with air prior to its passage into the packed column. For each of these reformates, 100- ml. samples were periodically withdrawn from the material as it exited from the packed column and were tested in the Rotogum apparatus. Prior to treatment in the packed column, reformate A was found to yield a Rotogum deposit of 5.5 mg. per 100 ml.; reformate B, a Rotogum deposit of 11.0 mg. per 100 ml.; and air-contacted reformate B, a Rotogum deposit of" 11.0 mg. per 100 m1.

AirCoutacted Reformate B Reformate A Reformate B No bottoms other than those which adhered to the glass-bead packing were removed from the reformate. These results show a substantial reduction in the depositforming tendencies of the reformate after it has been passed through a bed of samll inert particles and a further reduction if the reformate has been contacted with air prior to its passage through the packed column.

Example 11 This example illustrates the effectiveness of removing deposit formers from a reformate by passing the reformate through a bed of gravel. The particle size of the gravel varied from about A3" to about A" in diameter. Testing was performed as above and the value of the Rotogum deposit obtained with reformate prior to its treatment was 11.0 mg. per 100 ml.

Total volume passed Rotogum deposits,

through column, liters: mg./ 100 ml. 1 3.0 2 2.7 3 3.6 4 5.0

These results show that the deposits were appreciably reduced when the reformate was passed through a bed of gravel.

Example III This example illustrates the elfectiveness of removing, deposit formers from a reformate by introducing the reformate at a point on the column containing the packingwhich is somewhere between the middle of the colu't'n'rr and the bottom of the column. In this case, the inlet to the column, a glass tube which was about two feet long and had a diameter of 18 mm., was located so that 18 inches of the packing, glass beads, were above the inlet and 4 inches of glass beads were below the inlet. At the bottom of the column was a stopcock, an outlet through which the heavy liquid which contained deposits could be removed periodically from the column. At the top of the column was a side arm through which the vapor was discharged into a condenser. A collection vessel was placed below the outlet of the condenser and received the condensed, treated reformate'. T reformate to be treated was charged into the colum at the inlet at a rate of one liter per hour. The coitlm temperature was maintained at 650 F. by means of an electrical tape heater wound over its entire length. A thermometer was placed at the top of the column so that the vapors rising out of the packed bed would sweep past the thermometer into the condenser. The temperatures of these vapors ranged from about 450 F. to 500 F., values which were above the endpoint of the reformate. With this method, almost gallons of reformate were treated. Only 0.34% of the charged reformate was withdrawn through the stopcock as hottoms. This removal was done on a semi-continuous basis. The following data were obtained from samples taken from the first 25 gallons charged to the system. The Rotogum deposit resulting from the untreated reformate was 11.0 mg. per ml.

The results of this example clearly demonstrate the efieetiveness of removing deposit formers by introducing the reformate at a point near the bottom of the packed column and permitting the treated reformate to pass up through the packing while removing, from time to time, the heavy deposits from the bottom of the column. A very clean reformate is obtained. Furthermore, a larger quantity of reformate can be treated before the packing in the column must be regenerated or replaced.

A further understanding of my process may be gained from the following proposed installation. Reformate, obtained from either the high-pressure separator of a reformer or from a storage tank, passes through a line into a furnace Where it is heated to a temperature that is above the endpoint of the reformate as determined by ASTM distillation method D-86. The heated reformate then passes from the furnace into one of two parallel packed columns at a point near the bottom of that particular column. The appropriate piping and valves connect the furnace to the column so that the heated reformate will be introduced into only one of the columns at any given time. The other column is maintained as a spare. Each of the columns is packed with one of the following materials: glass beads, coke, sand, gravel and slag. The heated reformate passes up through the packing of the column being used. The heavy deposit formers in the reformate adhere to and-are retained on the surface of the packing. Some of this heavy liquid descends through the head to the bottom of the column where it is collected and removed periodically from the system through a line and a valve. The remainder of the reformate, still in the vapor phase, continues onup through the bed and out of the column into a condenser. An appropriate system of piping and valves connects the column to the other column and the condenser. Operation of the proper valves above and below the column restricts the flow of the reformate through only one of the packed columns at a time. The reformate is condensed in the condenser and passes therefrom through a line into a stabilizer where the light ends are separated from the rest of the reformate and sent from the top of the stabilizer through a line, perhaps back to the reformer. The stabilized liquid product is removed from the bottom of the stabilizer through a line to gasoline-blending facilities.

There are two parallel packed columns in this installation so that when packing of the column in use has become spent, that is, the heavy deposit formers adhering to the packing surface have reduced its effectiveness in the removal of the deposit formers, the alternate parallel column can be placed in service While the spent packing in the original column is either regenerated or removed and replaced with fresh packing. Another reason for the dual columns is that if the temperature differential between the surface of the packing in the column in service and the hydrocarbon vapors passing therethrough becomes so small that the column will not effectively perform its function, the alternate column can be used while the temperatures in the first column are being reduced.

If the reformate is obtained from a storage tank, it will have been contacted with air through exposure as a result of not being hermetically sealed in the tank. Of course, air can be bubbled through the reformate being stored in the tank prior to its subjection to the process for removal of the deposit formers.

The above examples are presented solely to illustrate my invention and they are intended in no way to limit the scope of my invention.

What I claim is:

l. A process for the removal of deposit formers from a reformate which comprises the passing of said reformate through a bed of small inert particles at conditions which permit at least 9899% of said reformate to exist in the vapor phase as it passes through said bed, the temperature of the surface of said particles being less than the condensation temperature of said deposit formers and greater than the vaporization temperatures of the other constituents in said reformate.

2. Process of claim 1 wherein saidbed is made up of a material which is a member of the group which consists of glass beads, coke, gravel, sand and slag.

3. Process of claim 1 wherein said reformate is introduced into the top of a vertical column containing said bed and is passed down through said bed.

4. Process of claim 1 wherein said reformate is charged near the base of a vertical column containing said bed and is passed up through said bed, the heavy deposits which collect at the base of said bed being removed therefrom periodically.

5. A process for the removal of deposit formers from a reformate which comprises contacting said reformate with a molecular-oXygen-containing gas and subsequently passing said reformate through a bed of small inert particles at conditions which permit at least 9899% of said reformate to exist in the vapor phase as it passes through said bed, the temperature of the surface of said particles being less than the condensation temperature of said deposit formers and greater than the vaporization temperatures of the other constituents in said reformate.

6. Process of claim 5 wherein said bed is made up of a material which is a member of the group which consists of glass beads, coke, gravel, sand and slag.

7. Process of claim 5 wherein said reformate is introduced into the top of a vertical column containing said bed and is passed down through said bed.

3. Process of claim 5 wherein said reformate is charged near the base of a vertical column containing said bed and is passed up through said bed, the heavy deposits which collect at the base of said bed being removed therefrom periodically.

References Cited by the Examiner UNITED STATES PATENTS 1,780,977 11/1930 Leslie et al. 208364 2,848,379 8/1959 Rehner et al. 20899 3,085,972 4/1963 Krane et al 208-99 DELBERT E. GANTZ, Primary Examiner.

SAMUEL P. JONES, Examiner.

Claims (1)

1. A PROCESS FOR THE REMOVAL OF DEPOSIT FORMERS FROM A REFORMATE WHICH COMPRISES THE PASSING OF SAID REFORMATE THROUGH A BED OF SMALL INERT PARTICLES AT CONDITIONS WHICH PERMIT AT LEAST 98-99% OF SAID REFORMATE TO EXIST IN THE VAPOR PHASE AS IT PASSES THROUGH SAID BED, THE TEMPERATURE OF THE SURFACE OF SAID PARTICLES BEING LESS THAN THE CONDENSATION TEMPERATURE OF SAID DEPOSIT FORMERS AND GREATER THAN THE VAPORIZATION TEMPERATURE OF THE OTHER CONSTITUENTS IN SAID REFORMATE.