US2011954A - Method of sweetening hydrocarbon oil - Google Patents

Description

V Patented Aug. 20, 1935 HYDROCARBON OIL poration'of'Delaware Charles F; Teichnia'nn, New York, Ncligassignon any, New York, N. Y., a' cor-i r wing Application January 27;"19325 i i 1 g Serial No. 589,320

I invention relatesgtothe refiningof hydro;

carbomoils and particularly to a process of in+ creasing the reactivity of suspensions of lead compounds in alkaline solutions used for sweetenu5 m hydrocarbon oils; 7 k I Most light mineral oildistillatessuch asigasoline orkerosene contain sulfur compounds which impartdisagreeable odors to theoil. It has been common practice to remove these sulfur comm pounds "from the oils by agitating them with an alkaline solution of an alkali metalplumbite such as sodium plumbite, prepared by I dissolving lead oxidellinan excess of sodium hydroxide. This treatment pauses :a reaction between the sulfur compounds such as mercaptans and the plumbite solution with the formation of colored lead com pounds such 'as lead mercaptidesr In orderpto decompose these lead compounds, it is necessary to add free sulfur, jwhereuponthe lead-is pre- '2 cipitated as the insoluble lead sulfide which-perity of they product resulting from its use, the ex-.

1 ceptionally high cost 'introducesa 'serious' disadvantage. It is known that in the. case. offhigh sulfur naphth'as} asmuch as one pound of litharge per barrel of gasoline. mayfb'e consumed in the V operation 'i I e r r Several new methods of sweetening have been proposed in order tocircumventthe difiic-ulties ofanj alkali plumbite-sulfur method of treating; Mostj'of these methods feature a vigorous. direct 40 oxidation of the sulfur compounds by means of oxidizing agents. It has been ioundby the inventor that in the case of certain light hydrocarbons these Vmethods 'offdesulfurizingi may result inundesirable reductions in color stability and decreases theantikncckvalues or the i finished products" due to the factthat the oxidae I 'tion'ca'nnot be limited to the sulfurfcomp'ounds alonebut extendstoa vigorous actionon' those unstable hydrocarbon compounds" which 'by their very nature contribute desirable characteristics to the hydrocarbon products in which they are present. f g It has-also been proposed" to agitatelight by drocarbon oil distillates'with a suspension of lead lfide in. a solution: oijicaustic 'alkali." In

"or stable highe'molecular' weight {mercar'it order to activate: thesuspension itis; subjected to the actiontof 'air." It maybe"neeessaiy iiua process when treating light hydrocarbon foils on; tai'nin'g extremely stablesul'fu'r com oundsto bleed in 'quantities'ofoxygen or oxygeh containing gases while the hydrocarbon oils'are being agitated with the treating solution, The. reaction' which occurs: is" considered by some to' 'be' a -u a process is ofvalu'e; and fin'dsrea'd cation in thetreatment of straight runfdistillates n and"' sonie cracked petroleum produc f-With some of the 'naphth'as obtained bici'alnihnidif ficulties have arisen inits application whieh'dif ficulties are directly-traceable toijthepresence quiring disproportionately (long, agi tat ion the treating solutioni Thesta v v these mercaptans is such th'atftl'ieyj remain changed even when contacted with 'thetiati'ng solution and oxygen or oxygen-containing-lgases'.

Such naphthas require at teretreatment'awith a1- kali plumbite and sulfur to make them satis 25 factory for commercial purposes; 'Ili'e use'of" r, indirect contact with the 'oil is extremelyfune desirable since it reduces the stability of the oil,

' increases substantially the fire hazard "and brings about high evaporationlosses whichin tur'nflini- 30 crease the load onthe-gasolineabsorption plant.

By the applicationof my inventionifIar'nien 'abled to share inthe advantagesof 'all' of the above mentioned pr cesses 'while avoiding their respectivedisadvantages.' A 3 I have discovered'thatwhen" small quantities of organic or inorganic peroxides are added tof'a suspension of lead sulfide in an alkaline solution; thehigh-molecular weight mercaptans which" are 'not 'acted upon'by the ordinary lead sulfid'e'jsusj- 40 pensions in caustic solutions; are readilyfattackejd and removed; I h'avelikewise found tha'tthe life of my treating solution is longer than; any otherpropos'ed to date. The naphthas treatedtherewith are stablefto lightfai' d storage and 45 the'time necessarydo'r reaction-{is greatlyi q e creasedf' v v n i To explain thextradrdinarir {results' obtained with this treatingsolution, ,I advancethefollow ing theoretical explanationtothe'correctness of 50 which; I do not 'intend-toilimit "myself; q 1 .When an unsweetened naphtha is treated with a suspension of lead sulfide in sodiumzhydroxide, said treating solution having rbeenactivated prej via'usl'y by the introduction} of oxygen oroxygen containing gas, it is observed that the lowmolecular weight mercaptans are readily oxidized to disulfides. .There is also usually a slight discoloration of the naphtha which can be removed by the introduction of a small quantity of elementary sulfur. An analysis of the. peroxide content 30f the naphtha before and after treatment indicates that'the peroxide content has been materially decreased. It is believed that the or: ganic peroxides react with the lead sulfides sus-' pended in the sodium hydroxide according to the.

following reaction:

PbS+4 C +4Naon- 0 +4H2O NflzPbOrl- Thesodiuxn plumbite formed mthis way is then available for reacting with the high-molecular weightmercaptans in the usual manner.

By increasing the concentration of the organic peroxides to such a value as to make the available oxygen content equivalent to the sulfur content. of the high-molecular weight mercaptans,

it possible to. completely sweeten the naphtha bymea'nsof a suspension'of lead sulfide insodium {The sodium plumbite formed in this manner is "available for reaction withthestable mercaptans,

reacting with them according to the equation set down heretofore. It is of interest to note that when usingmyprooess, sulfuris necessary in order to decompose the'lead mercaptides that are formed. v a V .II have noted that mercaptans react very slowly with peroxides. This explains why naphthas containing both these compounds do not become fsweet on storage due-ftothe decomposition of the niercaptans. However, in the presence of lead sulfide an alkaline solution the reaction fgoesl very readily and is almost" quantitive.- I have also. observed that the surface of the gran ular lead sulfide used asa starting material in my processgradually becomes eroded, eventually losing its solidcharacter and becoming fiocculent. As' a specific exampleof the practice of my invention I give below the constitution of a treating solution whichmay be usedfor sweetening a. cracked naphtha containing approximately 0.20%

of high-molecular weight mercaptanswhich do While l 'have shown sodium hydroxide in'the above composition, it is understood that solutions substances which decompose to yield found that inorganic peroxides when.

of alkaline or caustic compounds or mixtures of these may be used in its stead. Among these may be identified solutions of ammonium hydroxide, potassium carbonate, calcium hydroxide, sodium carbonate, potassium hydroxide, trisodium phosphate and similar compounds of alkaline reaction.

;'I'he sodium peroxidemay be replaced by equivalent amounts of hydrogen peroxide, barium peroxide, sodium perborate or any such inorganic hydrogen peroxide in aqueous solutions.

I Organic peroxides, such as acetic peroxide, benzoyl peroxide, methyl-ethyl ketone peroxide 1 or any organic compound that is a potential source of hydrogen peroxide or nascent oxygen may be substituted for or used in conjunction with the inorganic peroxides.

My invention readily lends itself to continuous operation, in which case the hydrocarbon oil to be sweetened is intimately mixed with the suspension of leadsulfide in alkaline solution to which has been added'the correct quantity of the suitable peroxide. After thorough agitation the mixture is conductedthrough'one or more settling chambers, where the velocity of flow is reduced to such a rate as to allow the separation of the oil from the treating solution. The separated oil is then contacted with the proper amount of sulfur to bring aboutthe'decomposition of the lead mercaptidesinto-the corresponding organic disulfides and lead sulfide. j,

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be .madewithout departing from the spirit and scope method of sweetening hydrocarbon'oils which comprises reacting the oil with a suspension of lead sulfide in an alkaline solution containing inorganic peroxides.

2. A method of sweetening hydrocarbon oils which comprises reacting the oil with a suspension of lead sulfide in an alkaline solutioncontaining dissolved inorganic peroxides and thenrreacting said oil with elementary sulfur. 3. A method of sweetening hydrocarbon oils which comprises reacting the oil with a treating suspension consisting of lead sulfide, an aqueous arating the treated oil from the resulting suspensionand then reacting the treated oil with elementary sulfur. i

5. A method of sweetening hydrocarbonoils which comprises reacting'the oil witha treating suspension consisting of lead sulfide, an aqueous alkaline solution and an" inorganic eroxide, se

arating the treatedoil from thetreating suspension and then reacting the treate'doil with ele: mentary, sulfur, r w

6. A method of'sweetening hydrocarbon oils whichcomprises reacting the oil with a-treating suspensionconsisting of lead sulfide, an aqueous solutionof sodiumhydroxide and sodium peroxide, separating the treated oil from the treating suspension and'then reacting the treated oil with elementary sulfur.v p L I CHARLES F. TEICHMANN.