US2759873A - Sweetening of hydrocarbon oils with raw clay followed by copper sweetening - Google Patents

Description

United States Patent Ofiiice 2,759,873 Patented Aug. 21, 1956 SWEETENING OF HYDROCARBON. OILS WITH. lAW (gLAY FOLLOWED BY COPPER SWEET- Eric McNeil] and Russell Ignatius Boyle, Sunbury-on- Thames, England, assignors to The British Petroleum Company Limited No Drawing. Application June 20, 1952,. SerialNo. 294,716-

Claims priority, application Great Britain July 5, 1951 6 Claims. (Cl..1 96--29) This invention relates to the sweetening of hydrocarbon oils, that is to say to the treatment of hydrocarbon oils for the elimination of mercaptans contained therein.

Among the processes commonly used for sweetening hydrocarbon oils is the so-called copper sweetening process wherein the oils are contacted with a copper salt, preferably cupric chloride,, in the presence of oxygen. This process has found wide application inthe sweetening of the light petroleum distillates in the boiling range below 150 C. Where this temperature is exceeded ithas been found that the traces of oil-soluble copper compounds which remain in the sweetened distillate after copper sweetening and water washing adversely affect stability both with regard to colour and gum formation instorage. Furthermore, traces of copper in a single component of a blend can give rise to. instability in other components and is therefore. to be avoided. It is known that, prolonged treatment with water followed by addition of a compound known as copper deactivator can do much to mitigate the effects ofcopper contamination.

There has for this reason. been a tendency to avoid using the copper sweetening process for the higher boiling petroleum distillates and particularly forv those boiling in the range 150 C. to 350 C. such as kerosines, lamp oils, burning oils, tractor and diesel fuels, aviation turbine fuels and solvent and white spirits unless these have first been subjected to a preliminary treatment of the distillates with strong acid or liquid sulphur dioxide. Unless such treatments are given, difficulties can arise such as increase in colour, decrease in colour stability, the presence of oil-soluble compounds of copper, corrosive effects which may prevent the oil meeting the copper strip corrosion test I. P. 64/51 C or A, reappearance of mercaptans, deposit of known precipitates in storage and ill effects on the gum stabilities of such cracked this does in some cases reduce the copper contaminatiom toa sutliciently small amount so that it can be rendered, This is by no means.

harmless by addition of deactivator. a certain method and very exhaustive water treatment at elevated temperatures may not be sufficient to reduce thecopper contamination to reasonable limits for distillatesfrom certain crude oils.

The principal object of the present invention is to enable distillates. boiling in the range. 150? to 350 C. to be satisfactorily coppen sweetened. although it may also, be applied, to light distillates. which may, through,

temporary operating. difiiculties with. regeneration of the reagent, have become contaminated. In both cases, use of the relatively expensive deactivator may be avoided.

According to the invention, a process for the sweetening of a petroleum distillate, comprises contacting the distillate, either before or after subjecting the distillate to a known copper sweetening process, with a clay having a montmorillonite type structure.

The clay treatment may be carried out at temperatures ranging from atmospheric to 250 F., and preferably at a temperature within the range ISO-220 F.

The clay treatment is preferably carried out after copper sweetening since the amount of oil-soluble copper complex in the sweetened distillate can thereby be reduced to a lower figure.

It is preferred to use clay belonging to the group known as fullers earth, a particularly suitable clay be-.

ing known by the trade name of Surrey powder. This material is readily and cheaply available from natural deposits and is not activated. It so happens that the same material is commonly used. as a carrier for cupric chloride in the so-called slurry form of copper chloride sweetening so that the use of the same material without copper for the clay treatment is convenient.

It has. been established that there is attached to the used; clay a coloured compound having an odour characteristic of certain nitrogen bases, as well as other irnpurities. It has further been established that the quantities of clay required are small, being in the region of 0:050.5 lb. per gallon of oil. The clay is easily removed from the treated oil by filtration or settling and can be freed from adsorbed compounds by a variety of methods such as extraction, steaming and treatment with chemicals.

It has been found that a separate treatment with clay enables'any conventional form of copper chloride sweetening to be carried out without difiiculty to yield a productof excellent colour, colour stability, permanently free from mercaptans and oil-soluble copper compounds, and passing both the I. P. 64/51 A and C tests for copper strip corrosion.

The process of the invention may be carried out either batchwise or continuously.

According to one embodiment of batchwise operation, the oil to be treated is heated in a vessel, warmed by a jacket or coil through which. steam or hot water is circulated, to give an oil temperature in the range ISO-220 F. Agitation is effected by a dry air jet, paddle, centrifugal pump or liquid jet. After agitation for a: period. of one. hour, the. oil is allowed to stand, the clay settled, and the clear oil decanted from the settled clay. If desired a filter can also be used. When cool, the oil is sweetened by means of an excess of cupric chloride solution in accordance with the well-known process.

A continuous process may be operated by means of a pre-heater and a clay mixer followed by a thickener and filter. The spent clay is then subjected to a succession of steps in order to de-oil and then remove the contaminant bodies from the clay by solvent action. The subsequent copper chloride treatment can be by any of the well-known processes, in which the copper chloride is either in solution, carried on a slurry or attached to a fixed'bed of mineral.

The process of the invention will now be described with. reference to the following examples.

EXAMPLE 1 8 litres of raw kerosine distilled from Iranian crude oil were heated to 200 F. in a: glassflask by means of a hot water bath. To the kerosine, which was agitated by means of a small air jet, was added grams of Surrey powder supplied by the Pullers Earth Union, and the stirring was continued for one hour. The greater part of the clear kerosine was decanted from the dark brown powder, the remainder being filtered free from powder. The clear kerosine, after cooling to 70 F. still contained mercaptans and was agitated for 15 minutes with twice the volume of an aqueous solution containing copper sulphate pentahydrate 176 grams per litre and common salt 160 grams per litre. This served to convert the mercaptans to disulphides.

The resulting product was of much improved colour and the pretreatment enabled sweetening to take place without difiiculty, using the copper-containing solution. The results obtained are set out in the following table,

Table I Pretreated with Surrey No No Yes Powder at 200 F.

Sweetened with copper No Yes Yes chloride solution.

ColourSaybolt Dark Green Minus13 Plus 25. Cop/perCStrip Test I. P. No Change No Change" No Change.

Doctor TestforMercaptans. Pos Neg Neg.

EXAMPLE 2 A kerosine distilled from Iranian crude oil and washed at once with lime water was charged, 700 ml. at a time, to a cone-bottomed air jet circulated glass vessel. This was placed in a boiling water bath. When the contents reached 200 F. 7 grams of Surrey powder from the Fullers Earth Union were added and circulation of a slurry from the bottom of the cone back to the centre of the vessel promoted by an air jet entering an external pipe sealed to the base of the cone. This was continued for 30 minutes, after which the contents of the vessel were cooled and filtered. Sweetening was completed by means of a solution containing 176 grams per litre of CuSO4.5H2O and 160 grams per litre of sodium chloride using the necessary precautions to prevent contamination of the sweetened oil with copper compounds.

The results obtained are set out in the following table, No.2.

Table 2 of this blend were charged to a flask immersed in a steam-heated water bath, and when the temperature of the contents reached 195 F., grams of Surrey powder were added and agitation, by means of an air jet, continued for one hour. The contents of the flask were allowed to cool and were decanted from the clay, the remaining oil being recovered by filtration. The resulting product, which was of improved colour, was sweetened using a solution containing:

Grams per litre CuSO4.SH2O 176 NaCl 160 This was used in such excess as to minimise the presence of cuprous copper, and consequent contamination of the sweetened oil with traces of copper compounds. Sweetening took place without difficulty. The results obtained are set out in the following table No. 3.

Table 3 Pretreated Raw with Surrey Powder and Sweetened Oolour6" Lovibond 2.1Y l.2R 0.1Y 0.113.

C0lour-0 Lovibond after 4 hours in 3.0Y 0.6R 0.5Y.

bomb at C., 10 p. s. i. g. Oxygen. Copper Strip Test 1. P. 64/51A Slight Discol- No Change.

are 1011.

Dithizone Test for traces of Copper Negative. Doctor Test for Mercaptans Positive Do.

The product so treated will meet the proposed modified specification for aero turbine fuels.

EXAMPLE 4 Pretreated with Surrey Powder at 200 F Sweetened with a copper chloride solution Colour-Lovibond 6 cell a.

Colour Stability Test Lovibond 6 after heating in a bomb at 100C. and 10 p. s. i. ga. Oxygen for 4 hours.

Copper Strip Test I. P. /64/51 C No change Spectroscopic Determination of Copper parts per 0.2

million.

Doctor Test for Mercaptans Pos No change 1.1

Neg.

Yes

Yes

No change. s1. disc. 0.2 0.2.

The resulting product was suitable for inclusion as a component of an aero turbine fuel under the British Specification DERD.2482.

colour, contained very little copper contamination and had a better colour stability than the unrefined kerosine EXAMPLE 3 A long cut aero turbine fuel of boiling range 100 to 250 C. by A. S. T. M. distillation was made by blending the following distillates from Iranian crude oil:

Heavy gasoline White spirit I Kerosine in the proportions in which they were produced. 9 litres About 40 gallons of Kuwait kerosine containing mercaptans equivalent to 0.018% wt. sulphur was sweetened in a continuous mixer with 176 grams/litre of CuSO4.5H2O grams/litre of NaCl All precautions were taken to prevent any concentration of cuprous ions in the mixing zone and the conditions chosen were such as would give a product free from copper contamination in fractions lighter than 150 C. boiling point. Using this method for this kerosine re- 6 2. A process according to claim 1, wherein the clay is a fullers earth.

3. A process according to claim 1, wherein said temperature is in the range 180-220 F.

sulted in formation of an oil soluble copper complex 5 4. Aprocess according to claim 1, wherein the amount and resulted in poor colour stability. A number of exof clay used is between 0.05 and 0.5 lb. per gallon of periments were made in which the copper contaminated distillate. sweetened kerosine was mixed at room temperature with 5. A process according to claim 1, wherein the disvarious amounts of Surrey powder. The results are set ti'llate is a kerosine. out in the following table, No. 5, and it will be seen that 10 6. A process according to claim 1, wherein the disan improvement in colour stability took place with intillate is an aero turbine fuel of boiling range 100 to 250 creased treatment. C. A. S. T. M.

Table 5 Fuller's Earth Treatment, lb./gallon None 0.001 0.005 0.02 0.05 0.1

Colouriufi Lovtbond cell 0. 5Y+0. 2R 0. 4Y+0.1R 0.3Y+0.1R 0.3Y+0.1R 0.2Y+0.1R 0.1Y+0.1R Colour in 6" Lovlbond cell after 16 hours inthe A. s. 'r. M. bomb at 100 0, and

100p. s. i. g. oxy en 9. 7Y+2. 5R 5Y+1. 7R 2i9Y+1.2R 3.6Y-l-L2R 2. 4Y+0.8R 0. 4Y-l-0. 3R Copper cont., mg. itre (UOP method) 0.89 0. 62 0. 84 0. 43 0.22 0.24 Copper cont., 1). p. m. (Spectr0sc0plc) 0.7 0.7 0.7 0.6 0. 4 0. 3

We claim:

1. A process for the sweetening of a petroleum dis- 25 References cued m the file of thls patent tillate comprising contacting the distillate with an agent UNITED STATES PATENTS consisting of a raw clay having montmorillonite type 2,204,234 Schulze June 11, 1940 structure at an elevated temperature in the range of be- 2,227,089 Hopper Dec. 31, 1940 tween atmospheric to about 250 F., and subjecting the 2,329,930 Nebeck Sept. 21, 1943 contacted distillate to a copper sweetening process. 30 2,503,627 McBride et a1. Apr. 11, 1950

Claims (1)

1. A PROCESS FOR THE SWEETENING OF A PETROLEUM DISTILLATE COMPRISING CONTACTING THE DISTILLATE WITH AN AGENT CONSISTING OF A RAW CLAY HAVING MONTMORILLONITE TYPE STRUCTURE AT AN ELEVATED TEMPERATURE IN THE RANGE OF BETWEEN ATMOSPHERIC TO ABOUT 250* F., AND SUBJECTING THE CONTACT DISTILLATE TO A COPPER SWEETENING PROCESS.