US2273263A - Sweetening petroleum oils - Google Patents

Description

Patest d Fe -17.1542 t Y R I 2373 263 i -UNITED sTArssa 2,213.20: 1 swas'rsmno PETltOLEUM ours I John Hapmh Jr-{Brooklym and Robertson; Queens Village. N. 1., amignors to sooonyevacnum Oil Company, New York, N. Y.', a corporation of York No Drawing- Application November 18 1939, e 'h Ni 3,5 4 chinaipl. lilo-89)] This invention has to do with processes for the q of the diiilculties'arising irom'the use of aqueous treatment of straight ru'n'and cracked gasolines, alkalinesolutions but still are at a common disnaphthas; kerosenes and similar light petroleum advsntag'ewith the conventional processes in that products tor the purposes of rendering those they involve costlyhandiing of considerable quanproducts sweet to thedoctor test." These products 5 titles oi reesehts 1 i g as originally produced usually contain a suilicient jRelated-"we'tg processes employing copper and amount or the so-called sour sulphur com- I similar-reage tshaveiikewise been proposed, but pounds usually or the nature-oi mercaptans v either inapplicable to related compounds to cause the products to be many oi-rthe which must be sweetened objectionable for the Moses oi commeree.-.- The .way of control of products are consequently treated in som'e man higli ren' them less attractive her either to remove the sour sulphur compounds uanq the operation; 7 I or to alter them to forms such as disulphides Since thediiliculties oi the usual syswhich are not objectionable in a finished product. teml oi the. carrying of The most widely used sweetening process is '15 the reagent. yolumesoi aqueous that which is commonly known as doctor" treatsolution, there-have processes V ment, in which gasoline, naphtha or kerosene is -wherein. oilJohiblefreagentsqhave {utilized contacted with an excess of aqueous alkaline solund a "oi'aqueous treating solutions tion of sodium plumbite and with a measured I ade. For example. copper naphthenate is'highamount of sulphur. The reactions of sweetening ly' oil solubleiand double decomposition are believed to take place substantialLv in 110- with memaptidesin (all solution inform copper cordance with the following equations: mercgztides welaich oil, soluble and which may remov readily" romtheoil, after which gfi zg fir 'jgfig f a light caustic wash will serve topiree the oil of the naphthenic acid without encountering the Whil quite generally utilized. this doctor pro usual emulsion dimculties and without requiring ess is not entirely satisfactory for a number of the utilization of large volumes of aqueous a1- reasons and considerable activity in research is k ime treating reagent. This method, however, directed towards search for improvement of the i n t highly applicable since-some oi the naphprocess, or to other processes capable of accomthenates most convenient ifoisuch use are those .p s ns t e so e eneral objects- O e 0! t e in which the metal radical does not form mercapdrawbacks of the doctor process isthe formation tides which are sumciently insoluble in oil to bring or emulsions with the aqueous reagents w i h r about their ready and complete removal.

suit in product losses and necessitate increased I This invention has for its object the provision e tl n q pmen This tendency to emulsiiy 'of a method for the sweetening of oils under conis more pronounced in cracked stocks than in trolled conditions in th'e absence of aqueousalstraight run products and at low temperatures kaline sweetening reagents capable of effecting a more than at elevated temperatures. complete quantitative ready removal of the ob- Another drawback of the doctor process arises jectionable products or reaction from the oil from the necessity of having anexcess of al- 40 treated. It has as'a further object the provision kalinity in the treating reagent giving rise to a of a method of sweetening utilizing as main retreated product sometimes having relatively hi h agents products which are entirely oil soluble and alkalinity. If the free alkali is not thoroughly rewhich consequently maybe added to the reaction moved from the treated product,it seriously interin precisely controlled propor'tions as solutions in ieres with the action of the inhibitors commonly anoil oi the same nature as the oil to be treated. added to asolines for improving their storage A further object-is the provision of a process stability. i capable oi'utilizing a lesser amount oi certain of Among th processes that have been proposed these reagents than any process heretofore iorraccomplishing this object 0! sweetening, there taught. These, and tur'ther'objects, such as will are such processes as the dry sweetening processes be made apparent by consideration of this speciwhich employ solid reagents, such as lead sulfide ncation may be attained by practice of the process and cupric chloride, deposited on granular inert herein described. carriers, the oil being percolated through a bed 4 The present invention accomplishes the several of the contactmass in the presence of dissolved objects outlined by carrying out the usual sweetoxygen or sulphur. These processes obviate many ening reaction, that is, the conversion of" merv a break.

captans to disulfides, by treating the sour oil with controlled amounts of oil solutions of lead soaps and sulphur, followed by settling and removal of the lead sulfide and by removal of the acid as for example by use of lead naphthenate. In this manner the usual sweetening reaction is carried out entirely in the oil p'hase, thus eliminating any possibility of emulsion losses and greatly minimizing the possibility of residual alkalinity in the treating stocks. Very small amounts of lead naphthenate and sulphur are required, and since these may be added to the process in the form of solutions in oil, having easily determinable and easily controlled concentrations, extremely precise control of the amount of reagents utilized can be had when conducting the plant operations in any conventional continuous sweetening apparatus, merely by the establishment of proper proportions between the flowing streams of oil to be treated and of the oil solutions of the two reagents. There is no necessity for utilizing complicated systems for preparing reagents, since the reagents indicated are quite readily soluble in oils of the nature of those to be treated, at least to an extent entirely sufficient for the purposes of the present reaction. The process may, in fact, be substantially self contained in that the oil used as a carrier for the reagents conveniently and indeed preferably, may be a portion of the oil which has already been through the sweetening operation. The process is entirely acceptable in results since the sweetened product in addition to being sweet to the doctor test (U. S. Gov. Test 520.31), is also non-corrosive (ASTM Method D 130-30), and does not require r'e-run'ning.

While the exact mechanism of the reaction taking place is not entirely clear, it is quite evident that the overall result obtained conforms substantially to the usual doctor sweetening reaction, except that an organic acid, e. g., naphthenic acid, takes the place of the usual as maybe seen fron'i'the following equations:

sweetening in that upon the addition of the lead na hthenate solution to the oil, there is not produc d a precipitate which may be removed from the oil and that the reaction i not completed except in the presence of or until the addition of free sulphur. Just as in the usual doctor sweetening process, it is necessary to add sulphur to-g'et case of sour oils, an immediate break is gotten upon the addition of free sulphur, whereas, in the absence of such sulphur, the reaction which has at that time proceeded only so far as the production of a lead mercaptide, has not resulted in the formation of any reaction product which can be "removed from the oil by any process conveniently and commercially available or which may be allowed to remain in the oil, if the oil is to be marketed.

Experience has shown that in the tion as shown below. The sulphur solution-was.

thing more than the plain steps indicated by the above equations, in that lead compounds in the presence of sulphur appear to exhibit a catalytic effect on a conversion of mercaptans into disulfides. Furthermore, it has been found that within these limits, that is, with amounts of lead less than the theoretical, according to the above equations, it is quite necessary that th amount of lead which is added in theform of a lead soap solution, in order to give a break or precipitation of lead sulfide, should be controlled within quite close limits. These limits can readily be determined for each lot of sour oil by simple laboratory tests. The amount of sulphur which is utilized, while it should be controlled so that no excess of sulphur remains in the oil to cause a positive copper strip corrosion test, need not be given such close attention as should the amount of lead.

Among the usual refinery stocks, the cracked products and particularly those containing the higher mercaptans, are more diflicult to sweeten. In demonstrating the capability of ,t'he novel sweetening process herein disclosed, tests were conducted upon that heavy part of cracked gasoline boiling between 200 F. and 400 known to the industry as debutanizer bottomsfl'that stock being known as one of the normally more difficult stocks usual in refinery practice.

The sweetening operations were conducted by mixing the sour oil with sulphur solution and then with various amounts of lead naphthenate soluprepared by dissolving 0.4% of sulphur in a portion of the sour oil, and the theoretical amount of sulphur, one part for every two parts of mercaptan sulphur in the sour oil, was added. The lead naphthenate was prepared in naphtha solution (300 F. to 400 F. boiling range) containsodium hydroxide,

A further diiference over processes presently proposed exists in the fact that instead of requiring the utilization of the amount of lead naphthenate normally equivalent to the mercaptan present in the oil to be treated, it has been established that only from 30% to 50% of the calcu; lated amount of lead is necessary. It consequently appearsthat there is in this reaction someing 39 grams of Pb per liter.

EXAMPLE 1 Debutanz'zer bottoms-mercaptan S content 0.15 grm./Ziter, 8 added (in solution) 0.072 grm./lz'ter Debntanizer bottoms-mercaptan S content 0.17 grm./Ziter, Sadded in solution) 0.08 grm./Ziter Mere. S g% Pb added, content of I Solution percent of treated Doctor test ll real;

added theoretical product,

grms/llter 0 0 .17 Positive... None. 0.5 30 .05 do Quick 0.6 43 .03 d0 D0. 0.7 50 0 Negative Do. 0.8 57 0 .do None. 1.4 100 0 (lov Do.

All. sweetened products passed the copper strip corrosion test.

It will be noted that both the negative doctor testand the quick break were obtained simultaneously when the amount of lead added was properthe mercaptan present.

ly controlled. In Example-i this corref unded ing to the equations,'and in Exampl'e'2, to 50%.

Free sulphur and lead naphthenatedo not ieact in the absence of mercaptans, e. 3., no darkening or :brealr occurswhen lead naphthenate is added to a sweet naphtha containing anadequate lead sulfide.

It will also be noted that with larger amounts to 31% of the lead theoretically required accorde doctor test which comprises contacting the oil I v v to'be treated" with an oil soluble lead naphthenateamount of tree sulphur, but the subsequent addition of mercaptan produces the precipitate of of lead reagent. than the optimum, that no-break;

is gotten, although in many-such cases a break can be. obtained by the addition or with the assistance oi an absorbent, such as clay, which, however, introduces a new operating step which in itseltmay be objectionable.

While the most convenient and preferred form of lead soap to be used is lead naphthenate, any oil soluble lead soap may be used in this sweetening procedure. The lead naphthenate is .preferred, because of it's high solubility iii-petroleum fractions of the nature of those to be treated, because it is readily available and may be produced locally as a by-product of the usual operations of refining. The amount of lead utilized in the form of lead soap for the proper conduct 01- this sweetening processwill, of course, vary some--v what with thenature of the oil to be treated, but it will be found in the usual instanceto bebetween from about to about 65% of the theoretical amount of lead -required,',based upon the mercaptan sulphur content-of theoilbeing treated and willin' all casesbe substantially less than the theoretical amount required for double decomposition between the lead soap reagent and In many cases, the presence of organic acidic residues in the tratedproducts resulting from the sweetening reaction will not be objectionable.

, quantity of free sulphur sumcient to cause: the precipitation of lead sulfide and separating from remove from the oil the lead sulfide fox-medley v However, in case it is desired to remove them,

either ior the benefit of the product or to. permit their recovery for further utilization by .retumto the process, all that is necessaryis the subjection of the treated product to averylight alkaline'wash in which very little dimculty with emulsions and with residual alkalinity oi the treated oil will be experienced.

We claim:

1. The method of renderingoil fractions con-'' and with added reagent' sulphur. in the absence of water, and'at-normal atmospheric temperature, and removing from the oil the lead sulfide formed by the reaction. I

' 2: The process of rendering oil fractions containing sour sulphursweet to the doctor test without the use of aqueous solutions, which comprises admixingv with the oil a quantity of an oil soluble lead naphthenate substantially less than thattheoretlcally required to effect double decomposition with the sour sulphur compounds present and also introducing to the reaction a.

the-oil the lead sulfide so produced.

3. The method of rendering oil containing sour sulphur compounds such as mercaptans sweet to the doctor test without theusebf aqueous solutions, which comprises admixing with the oil to be treated acontrolledaniou'nt of an oil solution of an oil soluble lead naphthenate and a controlled amount; of free sulphur, the amount or lead. so utilized being irom about 20% to about of that theoreticallyrequired for double decomposition with themercaptans present, and

the reaction.

4.- The process of treating sour petrolemn dis- 'tillates "containing mercaptans to convert said mercaptans to disulfldes, thereby rendering the oil sweet to the doctor test without the fuse of aqueous solutions, which comprises admixing with the oil a quantity of an oil soluble lead naphthenatawhichfquantity of leadnaphthenate con tains' betweenabout'ail ltand about 65% ofthe lead theoretically necessary for double decomposition'with the mercaptans present and a quantity' otiree sulphur, the 'leadand sulphur so'introdueed-gbeingasoproportioned with respect to themercaptan sulphur present in the oil to be a gulch-break is obtained in the trea that lead sulfide may be precipitated and-removed without substantial increase in the. amountoi'sulphur in the oil treated.

, some. JR. I mm WARREN ROBERTSON.