US2379228A - Diesel fuel - Google Patents

Description

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. DESELFUM;

George h. Gilbert, hiaytown, 'lem, assig'nor to Standard @ii Development Company,

ration of Delaware Ne Drawing. Application February 27,1942,

Serial No; 432,629

1 Claim. (oi. 44- 57) This'invention isconcerned with improving combustion characteristics of high boiling fuel oils, more particularly with improving the ignition quality of Diesel fuel oils by a reaction of an inorganic hypochlorite.

It has the object of providing a method for,

efiectively increasing the ignition quality of Diesel fuels with some elimination of objectionable mercaptans from the fuel oils.

Other objects and advantages of the invention tvivill be made apparent by the following descrippolysulfide compounds were found to be fairly efiective ignition accelerators in Diesel fuels and that it has been proposed to use a doctor sweetening treatment on sour Diesel fuels having a high mercaptan content with an excess of added It is known that elementary sulfur and certain clearly understood; but it is believed that the active ingredients of the solution (oxygen and chlorine) react with mercaptans and possibly other components of the fuel to form a product insitu which contributes to the superior ignition qualities observed. However, it is to be clearly understood that nay-invention is not to be limited to any theory advanced in explanation thereof.

In the presentinvention, an inorganic hypochlorite ostensibly reacts' with mercaptans and forms ignition accelerating com-pounds which are more potent than organic di-. and polysulfides. The reaction, of the hypochlorite agent gave results far superior to those obtained by treating mercaptan-enriched Diesel fuels with a doctor solution (sodium plumbite) or its modifications.

' It does, not require addition of free sulfur. It

sulfur to convert the mercaptans into ignition accelerating organic polysulfldes. Howeventhe practical use-of thesetreatments is hampered by (1) common fuel specifications limiting the total sulfur content of the fuels, and (2) the corrosive action of the sulfur incorporated into the fuel. It has also been Mom to subject certain mineral oil fractions, primarilystraight run gasoline and similar light non-cracked products, to the treating action of an aqueous alkaline hypochlorite solution. In sweetening such petroleum oil fractions with hypochlorite solutions, particularly solutions of sodium and calcium hypochlorite,

'forbcst results it was considered necessary to became regarded as entirely unjustifiable.

Now I have found that if a Diesel fuel oil is treated with an aqueous alkaline hypochlorite solution at elevated temperatures,.a product havhas given satisfactory results when applied to fuels containing very low concentrations of mer-' captans. It has been found to work wellon fu'els of low sulfur content. If desired, the hypochlo rite may be reacted with a. mercaptan to form an ignitionaccelerator compound soluble in Diesel fuel and the reaction product incorporated in a Diesel fuel.

As a specific embodiment, the process of the present invention is suitably applied to petroleum gas oil which meets requirements of'Diesel fuel specifications and with very little mercaptan sulfur present before the treatment with the hypochlorite solution. The hypochlorite treating solution may be prepared by chlorination of a causticalkali solution, but other convenient methods may be used. In a satisfactory treatment, the treating solution is maintained alkaline, the hypochlorite solution is intimately mixed in a minor proportion with the fuel at a suitably elevated temperature until the desired improvement of iging aremarkably improved cetane rating is obtallied. Furthermore, I have chemical analysis of the product treated in accordance with .my invention that very-little, if am, chlorination of the fuel takes place but that aoertain change in chemical properties is effected.

The reason forthls unexpected result is not 36- determined by nition quality is obtained, and thereafter, the treated fuel is water-washed.

The process is illustrated by the followinggspecific examples: v A

'The hypochlorite, solution .was prepared by bubbling chlorine gas thru approximately 20 B. aqueous NaOH solution which was cooled in an ice bath to prevent an excessive rise in temperature. 'The anlysis of the. prepared solution showed about 4.66 weight per cent available chlorine, 7.40 weight per cent NaOH, and 8.88 weight per cent total sodium content. Teri liters of gas oil hydrocarbons containing about 3 mg. of mercaptan sulfur per ml. of oil and having a total sulphur content of 0.22% by weight by bomb analysis were agitated with two liters of the hypochlorite solutionfor30min.atabout200'-1".to 210 F.in a closed iron agitator. (turbo-miner). After separating the oil from the partially spent hypochlorite solution by settling, the oil product was washed with two 10 liter batches of hot water and wasthen nltered thru paper.

Inspections of the oil before and after the treat ment are summarized in the following table:

, Table 1 W Hypochlorite I on treate t l gas ' Octane n -J. 66.4 (60 62.6 64

0rsvity,A.P T 81 37.3. I. B. P "I All 446. was}. 'r m m. I. 2.. 630 636. Via. 100' l". (B. U. 8.) 1, 871 88.0. Glen .4. B. 'i.-M., '1 14. Pour, I 10 10. M, PM, F m 218. Bomb sultunpccent 0.22 0.20.

. Cu strip corrosion, 8 hrs. 0 212 '11..-. Barely pass. Pass.

Chlorine content per cen 0 0. Odor Mercaptaus. Sweet. Doctor test N. G Essa.

Msrosptsn sultur, mg./10o ml 3.0- 0. s.

Thefuel oil was memcauy analysed before and after thetreatment to determine the action of the hypoohlorite agent on the composition.

The results aresummarised as follows:

These analytical results indicate that the treatment can be carried out without appreciable chlorination of the fuel components and without making any substantial change of the sulphur content'in giving the fuel the remarkably good increase of about 7 oetane number units. The high order of ignition quality improvement thus obtained can be appreciated by comparison with aavaaas which is indicative of the formation of substances similar to peroxides in potent oxidising properties. The peroxide number is a well known test mmin parenthesis are results obtained at a diiimntlsbon- Y the eifectiveness ofvarious s tion accelerator additions, even' the outstanding alkyl nitrates.

Moreover, this extraordinary octane number increase doesnotentailanymaterialreductionin heating value, since the hydrogen and as in the use of previously contsntisnot-lowered known additives.

The active ignition promoting compound formed gave a much-higher octane number creasethan could be'acoounted foronabasis is also possible that other reactive components 0! the 11181, ll hydrocarbons. parti ipate in reactionto form the ignition promoting sub- Itisofmteresttonotethatthetreatmeptmade a significant increase in the peroxide number,

such as of the order of 0.01%, which does not show up in ordinary chemical analyses. Thus, it is possible that active oxygen or some other active oxidizing function is introduced into the fuel in extremely smallamounts. In gasoline motor fuels, low peroxide numbers of 1-3 are obtained when such fuels are very unstable and undergo rapid deterioration with gum formation, but high peroxide number Diesel fuel products prepared in accordance with the presmt invention, i. e., with peroxide numbers above 3, were found to be satisfactorily stable. The mercury number'increase may also be regarded as indicating the same change as shown by the peroxide number increase. Taking these changes into consideration it is evident that the amount of the active ignition acelerating'ingredient formed in'the fuel to make a cetane number increase of 6 to 7 is less than about 0.1%.

The hypochlorite solution described in Example I was employed to treat three separate portions of gas oil whose physical and chemical characteristics have also been described therein. Ten liter portions of gas oil were agitated with two liter portions of hypochlorite solution while maintaining all conditions, except temperature, exactly as hasbeen outlined in the preceding example. In this case, one 10 liter portion of oil was treated with hypochlorite at'80' 1'. The second 10 liters were treated at temperatures between about I". and 1". and the third 10 liter portion at temperatures of about 200 I. to 210' F. After separating the oil from the partially spent hypochlorite solution by settlins, each treated 10 liter portion was washed separately with 10 liter batches of hot water and then iiltered through paper.

Cetane numbers of the several portions of oil after treatment at the varying temperatures tures, as compared with usual pracflce for sw eningnaphtha, the cetane rating was raised approximately 7 units over that of the original oil.

' Whentreatingoilsatrelativeiy-low 'e.g.,80'i".,anincreaseofonly1unitwaseffected. Therefore, it is omchlded that treating Diesel fuel oils in accordance with'my invmtion 'IsresultsinamarkedbsuperlornoductirtnetegnJ- with an alkaline hypochlorite improvement in the Since with the present ment of ignition'quality is not essentialiy.ac-

elevated to above 80' E, and the range of about 125'1'.

peratures (80 F), a product the doctor test but with only a neglibile rise in cetane numher was obtained. when employing my invention, i. e., treatment lrvpochlorite and in sulfur, a sweet product results.

Diesel fuels treated in the at high temperatures with the presence of mercaptan of high octane ratin manner described solution may be used as such or may be blended with an untreated Diesel fuel stock to form a blend having improved ignition quality.

within the contemplation of this invention It is to treat gas oils which are practically sweet, or which have been partly desulfurized or sweetened, by any suitable refining method even though the hypochlorite is capable of eflecting some elimination of mercaptan sulfur when accomplishing the desired improvement in ignition quality. The present process was found to effect a substantial ignition quality of gas oils which contained practically no reactive sulfur (free sulfur or polysulfide sulfur), and also, it was found eflective for increasing the cetane numbers of sour and cracked gas oils having high sulfur contents without making any decided desulfurization.

procedure the improvecompanied by substantial desulfurization, it is preferred to apply the described treatment to Diesel fuel oils which do not have extremely-high sulfur contents. A preferred starting oil for the ignition quality improving treatment is a gas oil that while treating the or similar high boiling petroleum fractionboilin: mainly above 450 F. with an end point below 150' E. with a sulfur content within specification limits, such as below 1%, and with a mercaptan suigiglc zntent less than 0.05%, e. g., about 0.001% to Although caustic soda is preferred for use in the hypochlorite solution, being the most practical, other metals may be used in the reagent, e. g., aluminum, zinc, magnesium. iron, copper, potassium, or calcium. One of the additional modifications which may be carried out is to use with the hypochlorlte treating agent a small amount of an oxidizing agent or a chlorinating sc such as chlorine gas. hypwmorous acid,

hydrogen chloride, or other halogens. Also, the treating conditions may be influenced by exposure of the reaction mixture-to light, varying the intensity of agitation and varying the time of coming within the scope of be included therein.

I of a Diesel engine.

contact. The reaction may be purification treatments, such with adsorbents. or the, like. A While the invention has been described in terms of preferred embodiments thereof, the examples given are not intended to be taken as a limitation on the scope of the invention but only illustrative, and all modifications or variations as filtering, contact I claim:

The method ofimproving a Diesel fuel which comprises reacting a mercaptan with an inorganic hypochlorite to form an oil-soluble ignition accelerator possessing oxidizing potency of incorporating said accelerator fuel oil adapted for operation active oxygen and into a petroleum followed bxvariousthe invention are to GEORGE R. GILBERT.