US2684894A - Alkali metal chromates as sludge inhibitors for blended fuel oil - Google Patents

Description

Patented July 27, 1954 UNITED STATES "PATENT OFFICE ALKALI METAL CHROMATES AS SLUDGE INHIBITORS FOR BLENDED FUEL OIL ration of Delaware No Drawing. Application December 12, 19.51, Serial No. 261,369

2 Claims.

The present invention is concerned with the production of stabilized fuel oils. These fuel oils, such as the No. 2 and No. 3 grades, produced for and used in uses such as domestic heating, light heating, and the like, are oils of boiling range similar to kerosene and light gas oil, usually derived at least in part from a catalytic cracking operation. They are not to be confused with the heavier fuel oils of residual nature, obtained as a residue from the distillation of crude oil, or as a residue from cracking. These light fuel oils, particularly those derived from catalytic cracking operations, are frequently prone to deterioration in storage, possibly due to the 'mildbut prolonged oxidizing conditions of such storage. The deterioration results in the formation of objectionable sludge or sediment, which,

if not removed, plugs filter screens, orifices, and

other parts of the equipment used in burning "such fuel. Even when, after some storage, all. visible sediment is removed from such oils, other sediment continues to form. The present application is a continuation-in-part of U. S. Serial No. 141,849, filed February 1, 1950, for James J.

'Trexel, entitled Stabilizin Hydrocarbons, and "now abandoned.

Thus, the present invention broadly concerns hydrocarbon mixtures known as fuel oils of the nature employed in various burner systems, asdiesel fuels, ,or as domestic andindustrial heat- :ing oils. Fuel oils may be derived from petroleum by a variety of methods including straight distillation from crude petroleum oil, and thermal or fluid catalytic crackin of petroleum oil fractions.

As pointed out, it has been found that fuel oils consisting completely or in part of catalytic cracked stocks are characterized by an undesirable instability giving rise to the formation of sediment. As a result, such fuel oils tend to cause clogging of filters, orifices, or conduits associated with the burning systems in which they are employed.

In accordance with this invention it hasbeen established that instability of catalytic cracked heating oils may be substantially overcome by incorporating in the heating oil an alkali metal chromate such as sodium or potassium chromate. These compounds, when employed in combination with the fuel oil, are effective in stabilizing the heating oil. Heatin oils which may be stabilized by these additives are particularly hydrocarbon mixtures of which more than about preferably more than about 20% consist of stocks derived from catalytic cracking operations.

More precisely still, the base stocks may be characterized as petroleum fractions containing a proportion of catalytic cracked stocks greater than 10%, preferably greater than 20% and falling within A. S. T. M. specification D-9'75-48T for diesel fuel oils (Grades No. 1D to 4-D inclusive) and A. S. T. M. specification D396-48T for fuel oils (Grades No. 1 :to 6 inclusive) This invention has for its object the provision of light catalytic cracked fuel oils containingalkali metal chromate inhibitive materials capable of preventing the formation of sludge and/orsediment in such fuel oils under the conditions of .use usually encountered.

To enable understanding of this invention, there is first defined the type of fuel oil with which it is concerned, by way of the following examaple, showing properties of a typical #3 fuel oil:

Untreated #3 fuel oil Gravity, A. P. I 34.0 Distillation, A. -S.T. M.:

1 B. P 'F 342 5 F 405 10 F '41? 20 F 434 -30 F 444 40 F 454 50 F 4'64 F 4'73 F 484 F 494 F "524 E. P F 580 Recovery percent "9-8 Residue percent 2 Loss percent 0 lPour point, 'F 30 Flash point P. M., "F 156 B. :S. '& W O Kinematic visc. F 1.98 Aniline cloud point, F 112.0 Kauri-butano-l No 43.5 Neutralization No '0l07 --Ash 0f 10% bottoms (percent wt.) 0

' the formation of sludge and sediment under nortity of catalytically cracked stock. catalytic operation may be a fixed-bed or a fluid 3 mal storage conditions may be prevented substantially by the addition to such an oil of a small amount of an aqueous solution of an alkali metal chromate, such as sodium or potassium chromate.

Regenerated catalyst is withdrawn from the regenerator and flows by gravity down a standpipe, wherein a suiiiciently high pressure head is built up on the catalyst to allow its injection into For example, the effectiveness of such addition 5 the fresh liquid oil stream. The resulting mixmay be shown by the following tabulation of data ture of oil and catalyst flows into the reaction obtained on an untreated light heating oil from vessel, in which gas velocity is intentionally low, the catalytic cracking of a vacuum flashed gas so that a high concentration of catalyst will result. The cracking that takes place results in Sefilmegt PH sample Mos tor- Condition of Strip as; G81 tion 1 tion 1 Heating Oil (N Catalytic Cracked)...-. 4.43 (l)+ ml. of distilled water 4. 23 6. 3 2. 7 (2) +steel strip 23 ry rusty. 6. 3 2. 7 (1) +5 ml. of tank water+steel strip. 4. 23 d 4. 3 2.7 (3)+0.1% Sodium Ohromate 4.09 1 9 3. 6 (3)+1.0% Sodium Ghromate 3. 95 1 9 6.7 (3)+l0.0% Sodium Chromate. 3. 68 1 9 7, 5 (3)+40.0% Sodium Chromate. 3. 61 I 9 7. 5 (4)+0.1% Sodium Chromate 3.95 6. 6 6. 9 (4)4-1 0% Sodium Ohromate 3. 74 7. 6 6. 7 0% Sodium Chromate... 3. 74 8. 2 7. 3 (4)+40 0% Sodium Ohromate. 3. 81 8. 5 7. 8 (3)+l0 0% Sodium Ohromate. 4. 23 Z 4 3, 8 (3)+10 0% Sodium chromate. 4.02 2 6 5.6 (3)+l0.0% Sodium Ghromate 3. 95 2 8 7. 1 (3)+10.0% Sodium Ohromate 3.74 5 10 7,1 Catalytic Heating Oil 0 (l7)+5 ml. of 10% aqueous solution of Sodium Ohromate (.005%)+steel strip 4.77 2 10 6.1

a 5 ml. of sodium chromate of indicated strength used per 100 ml. of 01].

While many methods have been devised to determine the stability of heating oils, actual storage for a period of time followed by measuring the sediment formed is most reliable.

; toward the production of a high quality fuel oil when the fuel oil contains an appreciable quan- While the type, it is particularly adapted for the stabilization of fluid catalytically crackedstocks which contain a relatively high proportion of unsaturates and aromatics. The fluid catalytic cracking plant is composed of three sections: cracking, regeneration and fractionation. The cracking reaction takes place continuously in one reactor, the spent catalyst being removed continuously for regeneration in a separate vessel, from which it is returned to the cracking vessel. Continuity of flow of catalyst as well as of oil is thus accomplished, and the characteristic features of fixedbed designs involving the intermittent shifting of reactors through cracking, purging, and regeneration cycles are eliminated.

carbon deposition on the catalyst, requiring regeneration of the catalyst. The cracked product oil vapors are withdrawn from the top of the reactor after passing through cyclone separators to free them of any entrained catalyst particles, while the spent catalyst is withdrawn from the bottom of the reactor and is injected into a stream of undiluted air which carries the catalyst into the regeneration vessel. The products of combustion resulting from the regeneration of the catalyst leave the top of this vessel and pass through a series of cyclones where the bulk of the entrained catalyst is recovered. The regenerated catalyst is withdrawn from the bottom of the vessel to complete its cycle.

What is claimed is: 1. A hydrocarbon fuel oil composition comprismg up to about of non-catalytically cracked fuel oil, at least 20% of a catalytically cracked fuel oil and having added thereto as a sludge inhibitor about 0.005 to 0.5% by weight of an al- 1l ls ali metal chromate in about 10% aqueous solu ion.

2. A composition as defined by claim 1 where the alkali metal chromate is sodium chromate.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,241,638 Ffield May 13, 1941 2,455,659 Duncan et a1. Dec. 7, 1948

Claims (1)

1. A HYDROCARBON FUEL OIL COMPOSITION COMPRISING UP TO ABOUT 80% A NON-CATALYTICALLY CRACKED FUEL OIL, AT LEAST 20% OF A CATALYTICALLY CRACKED FUEL OIL AND HAVING ADDED THERETO AS A SLUDGE INHIBITOR ABOUT 0.005 TO 0.5% BY WEIGHT OF AN ALKALI METAL CHROMATE IN ABOUT 10% AQUEOUS SOLUTION.