US2981678A - Basic nitrogen removal from hydrocarbons with an alkaline bisulfate - Google Patents

Description

April 25, 1961 W. C. BUNINGH ETA]- BASIC NITROGEN REMOVAL FROM HYDROCARBONS WITH AN ALKALINE BISULFATE Filed Sept. 15

INVENTORSI WEIGERT C. BUNINGH WILLEM J. PIETERS BY: J. WQWMJ THEIR ATTORNEY BASIC NITROGEN REMOVAL FROM HY DROCAR- BONS WITH AN ALKALINE BISULFATE 'Weigert C. Buningh, Amsterdam, and Willem J. Pieters,

The Hague, Netherlands, assignors to Shell Oil Company, a corporation 'of Delaware Filed Sept. 15, 1958, Ser. No. 761,229 Claims priority, application Netherlands Dec. 20, 1957 4 Claims. (Cl. 208254) This invention relates to an improved process for re-' with a small amount of the bisulfate solution dispersed throughout it. The presence of the water particles imparts a hazy appearance to the hydrocarbon and this condition often requires after-treatment of the product.

A second approach for basic nitrogen compound removal involves the use of solid bisu-lfate compounds. In this latter method the hydrocarbon in vapor form, at a temperature in the range of say 110 to 250 C. is passed into contact with the solid anhydrous bisulfate material. This process, in addition to its obvious high cost, has a further disadvantage of converting any unsaturated hydrocarbons that may be present into unde sirable resinous components, thus making this vaporsolid approach unsuitable for the treatment of olefin containing streams.

An apparent method would seemingly involve the use of the bisulfate compounds as solid contacting agents for the treatment of liquid hydrocarbons; however, experience has shown this method to be unfeasible since the solid bisulfate bed clogs in an unreasonably short time. For this reason, the treatment of liquid hydrocarbons by means of a solid bisulfate bed has not been adopted on wide spread industrial scale.

It is an object of this invention to provide a suitable process facilitating the use of solid bisulfate compounds for the removal of nitrogen bases from hydrocarbon streams. Other objects and advantages of the process of the invention will become more apparent from the following description and single figure of the accompany drawing which is a schematic representation of a preferred embodiment of an apparatus suitable for the practice of the process.

It has now been found that basic nitrogen compounds may be etficiently removed from a liquid hydrocarbon through treatment with a solid bisulfate material. In a preferred embodiment of the process of the invention, the liquid hydrocarbon containing a small amount of added water is passed into contact with a solid bisulfate bed and there there occurs a reaction of at least a substantial portion of the basic nitrogen compounds with the bisulfate material to form a water-soluble, oil-insoluble reaction product. The reaction product preferentially dissolves in the water and thereafter the treated hydrocarbon and its associated water are phase separated to States Patent obtain a hydrocarbon product with a reduced nitrogen content. It is postulated that in the previous attempts to utilize a solid bisulfate bed the reaction products of the bisulfate and nitrogen bases deposited on the bed, causing the aforesaid clogging. The aqueous solution leaving the bed and separating from the treated hydrocarbon as a bottom layer in the separation zone is substantially non-corrosive, because virtually only the reaction products formed from the bisulfate and the nitrogen compounds are dissolved therein.

Since the liquid to be treated will generally contain a small quantity of basic nitrogen compounds, say for example 0.0050.05% by weight in cracked gasoline, only a small quantity of water need be used compared to the amount of hydrocarbon undergoing treatment. No more than 6 kg. of water need be supplied to the bed per mol of basic nitrogen compounds (calculated as nitrogen) present in the liquid to be treated. Larger quantities of water may be employed although generally this is unnecessary as satisfactory extraction may be had with much smaller quantities of water. Generally speaking, the amount of water employed on a weight basis is in the range of 25 to 400 times the amount of nitrogen present. The process may be carried on at room temperature and is preferably practiced at a temperature no more than 40 -C., although higher temperatures may be applied. The process is adaptable to the treatment of various petroleum fractions, including straight run fractions and products obtained through thermal or catalytic cracking. The process may also be used for the treatment of reformed hydrocarbons. As mentioned before the process is particularly useful for the treatment of hydrocarbon streams which contain appreciable amounts of olefinic materials since these unsaturated hydrocarbons are not converted by the solid bisulfate into undesirable resinous components as does occur in the vapor solid bisulfate process. The process is suitable for removal of basic nitrogen compounds from oil products derived from various sources including shale and tar sands.

Various solid bisulfate materials are available for use in the bed including the water-soluble alkali metal or ammonium bisulfates, for example, sodium bisulfate, potassium bisulfate, ammonium bisulfate, lithium bisulfate and mixtures of these materials. The bed may be made up in part of an inert filler uniformly distributed throughout. If such a filler is used the size of the filler particles best approximates the size of the bisulfate particles. It is recommended that the liquid be supplied to the bisulfate bed in aspace velocity in the range of 215- 5000 volumes of the liquid (water and hydrocarbon) per a volume of the bisulfate crystals on a hourly basis. The concentration of the nitrogen compounds is a primary factor in determining the desirable space velocity. Generally speaking, a hydrocarbon of low nitrogen content will be passed through the bed at a higher space velocity.

With reference to the drawing, there is shown a cylindrical upright vessel 10 which is provided with a conical shaped bottom 12. A bed of solid sodium bisulfate crystals (NaHSO H O) is supported by a grid 13 which expands the cross section of the vessel a short distance above the conical bottom. An inlet line 15 opens laterally into an upper section of the vessel at a level above the bisulfate bed. A second inlet line 17 extends through the top of the vessel terminating in a spray head 18. Preferably, the head is designed to supply spray to substantially all of the cross section of the vessel. The vessel is supplied with two removal lines, one which is an extension of the conical bottom through which the liquid layer collecting in the bottom may be removed. This latter removal line 19 has disposed in it a valve 21 for controlling the flow of liquid therethrough. The second exit line 23 extends laterally from the vessel and leaves at a level intermediate the conical bottom and the bed supporting grid.

In the practice of the process a nitrogen containing material such as cracked gasoline is continuously passed through the supply linelS into the column. Water is supplied to the spray head 18 through the line 17 in considerably less quantity than the entering gasoline. The water, if desired, may be premixed with the hydrocarbon, and the combined stream passed to the vessel 10 through the line 15. The water and gasoline trickle downwardly through the bed of sodium bisulfate exposing the basic nitrogen compounds to reaction with the material of the bed. As mentioned herein there is an oil-insoluble reaction product formed of the bis-ulfate and nitrogen compounds, which product preferentially dissolves in the water phase, thus avoiding the build-up of the reaction product on the bed as occurs in the absence of the water hase.

P The hydrocarbon and water phase separate below the bed into an underlying water layer which collects in the conical bottom 12 and into an overlying hydrocarbon layer which is continuously removed through the line 23 as the treated product. The water containing the nitrogen material may be intermittently or continuously removed through line 19 and valve 21, depending on the flow rate of that phase.

In practice it may be desirable to employ two bisulfate bed containing columns connected in parallel. When the bed of one of the columns is almost spent, the hydrocarbon stream may be switched over to the second column while the first column is being washed with water and refilled with the bisulfate.

Example I A catalytically cracked gasoline derived from a Middle East crude oil and having a nitrogen content of 0.05% by weight was passed at a rate of 150 volumes per hour through a bed consisting of 0.7 volume of solid sodium bisulfate monohydrate crystals (NaHSO H O) gravity packed. This represents a space velocity of about 215 volumes of liquid per volume of the crystals per hour. The treatment was undertaken in a system of the type illustrated in the drawing. The bed of crystals had a height four times its diameter. Water was supplied along with the gasoline to the bed at a rate of 5 volumes per hour. The amount of water used on a weight basis is somewhat in excess of 80 times the amount of nitrogen present. Treated gasoline substantially free of nitrogen was removed from the overlying layer, immediately below the bed as illustrated in the figure through the line 23. The aqueous solution containing the nitrogen compounds was removed as a bottom layer at a rate of 5 volumes per hour through the line 19. Approximately 1300 volumes of gasoline were passed through the bed before it had to be renewed. In a control test where the same cracked gasoline without water was passed through the bed, the bed became clogged after it had passed approximately 30 volumes of the gasoline.

Example II A second catalytically cracked gasoline obtained from a Middle East crude oil and this time having a nitrogen content of 0.005% by weight was passed at a rate of 500 volumes per hour through a bed made. up of 0.12 volume of the solid sodium bisulfate crystals, again gravity packed. The space velocity of the liquid here approximates 4166 volumes of liquid per volume of crystals per hour. The height of the bed of this example was five times the diameter. Water. was supplied to the bed at a rate of 1.7 volumes per hour on a weight basis. Here again the amount of water employed is somewhat more than times the amount of nitrogen. The treated gasoline free from nitrogen was removed through the line 23 at a rate of 500 volumes per hour and the aqueous solution containing the extracted nitrogen material left the treating vessel through the bottom line 19 at a rate of 1.7 volumes per hour.

In this example approximately 2200 volumes of gasoline passed through the bed before it had to be re plenished. In the control test of the example when the gasoline containing the nitrogen compounds flowed through the bed without water, the bed became clogged after approximately 50 volumes of gasoline had passed therethrough.

We claim as our invention:

1. In a process for removing basic nitrogen compounds from a liquid hydrocarbon with an alkaline bisulfate material selected from the group consisting of ammonium bisulfate, sodium bisulfate, potassium bisulfate, lithium bisulfate, and mixtures thereof, the improvement comprising passing the liquid hydrocarbon containing from 0.005 to 0.05 percent by weight basic nitrogen and containing a small amount'of added Water into contact with a solid bed of said bisulfate and there reacting at least a substantial portion of the nitrogen bases with the bisulfate material to form a water-soluble, oil-insoluble reaction product, said added water being present in an amount effective to remove the water-soluble, oil-insoluble reaction product from the bed, removing the hydrocarbon and its associated water to a separation zone, and there phase separating the liquid hydrocarbon now characterized by a reduced nitrogen content from the added water which contains said reaction product dissolved therein.

2. A process in accordance with claim 1 wherein the bisulfate material is an alkali metal bisulfate.

p 3. A process in accordance with claim 1 wherein the bisulfate material is sodium bisulfate monohydrate.

4. A process in accordance with claim 1 wherein the References Cited in the file of this patent UNITED STATES PATENTS Baehr Mar. 28, 1939 McKinnis Aug. 8, 1950

Claims (1)

1. IN A PROCESS FOR REMOVING BASIC NITROGEN COMPOUNDS FROM A LIQUID HYDROCARBON WITH AN ALKALINE BISULFATE MATERIAL SELECTED FROM THE GROUP CONSISTING OF AMMONIUM BISULFATE, SODIUM BISULFATE, POTASSIUM BISULFATE, LITHIUM BISULFATE, AND MIXTURES THEREOF, THE IMPROVEMENT COMPRISING PASSING THE LIQUID HYDROCARBON CONTAINING FROM 0.005 TO 0.05 PERCENT BY WEIGHT BASIC NITROGEN AND CONTAINING A SMALL AMOUNT OF ADDED WATER INTO CONTACT WITH A SOLID BED OF SAID BISULFATE AND THERE REACTING AT LEAST A SUBSTANTIAL PORTION OF THE NITROGEN BASES WITH THE BISULFATE MATERIAL TO FORM A WATER-SOLUBLE, OIL-INSOLUBLE REACTION PRODUCT, SAID ADDED WATER BEING PRESENT IN AN AMOUNT EFFECTIVE TO REMOVE THE WATER-SOLUBLE, OIL-INSOLU-

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