US2174174A - Process for treating gasoline distillates - Google Patents

Description

v Sept. 26, 1939. B. s. GREENSFELDER Er AL 2,174,174

PROCESS FOR TREATING -G ASOLIINE DISTILLATES Filed' Nov. 1, 1937 Heater or Rebo/'ler Bq their Attorneg Y Patented Sept. 26, 1,939

unirsel STATES! Paocnss Fon mame GAsoLINE DrsmLATEs Bernard Sutro Greensfelder, San Francisco, and Monroe Edward Spaght, Wilmington, Calif., assignors to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application November l, 1937, Serial No. 172,204

2 Claims. (Cl. 26o-624) This invention relates to a method for the treatment oi hydrocarbon distillates, such as gasoline distillates, and more particularly is concerned with an improved method for neutralg izing gasoline and kerosene distillates which are susceptible to improvements in their storage stabilities by the addition of small amounts of gum inhibitors, and which contain acids capable to being neutralized with alkali 'carbonates Our invention comprises effecting the neutralization with alkali carbonate-bicarbonate solutions obtained in the liberation of alkyl phenols from aqueous alkali metal alkyl phenolate solutions by means ofcarbon dioxide.

It is a purpose of this invention to improve storage stability of the neutralized distillates by utilizing a product which is normally wasted. Another purpose is to increase the yield of alkyl phenols recoverable from petroleum oils containw ing same by extraction with aqueous alkali metal hydroxide, and it is a further purpose to reduce the consumption of alkali metal hydroxide incidental to such extraction.

Other objects and advantages of our invention a5 will lie-fully understood from the'drawing representing a flow diagram of our process, in which a heated mineral oil distillate, such as a cracked gasoline distillate boiling between about 100 and 250 acontaining alkyl phenols, organic sulfur Eil compounds and possibly hydrogen sulfide, is

introduced through line l into iractionating unit,

comprising columns 2 andl 3 from a source not shown. The distillate is fractionated into two or more fractions, the now diagram indicating @5 three fractions, namely 1st, 2nd and 3rd out distillates. The lightest lst cut, which may contain hydrogen sulide, and which is preferably freev from alkyl phenols, may have an end boiling point of about 150 C. It leaves the fractioningl 4l@ column 2 through vapor line ll, is condensed in condenser 5 and stored in storage tank 5. The remaining fraction passes through heater or reboiler 5 in bottom line l to column 3, where it is further fractionated into a 2nd cut which 45 may boil from about 150 to 205 C., containing alkyl phenols and varying amounts of hydrogen sulde formed by thermal decomposition of organic sulfur compounds in the heater t; anda 3rd cut preferably boiling above 205 C., also 50 containing alkyl phenols but normally being free 55 introduced into mixer l, where it is contacted with aqueous carbonate-bicarbonate solution ,.oming from the alkyl phenol plant I2 through line We have found that aqueous alkali metal ca rbonate-bicarbonate solutions produced in the liberation of alkyl phenols from aqueous alkali metal phenolate solutions by means of carbon dioxide, retain appreciable amounts,` of alkyl phenols which cannot be recovered by settling or centrifuging. These amounts normally vary between about 0.5 to 5% more or less of the solution. However, by bringing the aqueous carbonate solution in contact with a naphtha or the like, a large percentage of the retained alkyl phenols can be washed out. Therefore, in mixer l alkyl phenols retained by the carbonate-bicarbonate solution are largely returned to the raw 2nd cut distillate. Upon mixing of the two liquids the hydrogen sulfide of the distillate is absorbed by the carbonate-bicarbonate solution forming hydrosuldewhile an equivalent amount of carbonate is converted to bicarbonate.A

The mixture of aqueous solution and distillate is transferred from mixer l0 through line it to settler l5, waste liquor normally containing a mixture of carbonate, bicarbonate and hydrosufnde being discarded through drain l5. The 2nd cut distillate containing the original plus recovered alkyl phenols being substantially free from hydrogen sulde, passes through line ll to mixer i8, where it is contacted with strong aqueous caustic alkali admitted through line la for the purpose of extracting the alkyl phenols from the distillate. An aqueous alkali metal hydroxide solution of about 30 to 50% concentration containing lan amount of alkali metal hydroxide slightly in excess of the equivalent of the alkyl phenols in the distillate is preferred for carrying out the extraction, in accordance with the disclosure of the co-pending application of Greensfelder et al., Serial No. 91,864, led July ing mixture .passes through lined@ tov settler 2l where it is allowed to separate, 2nd cut distillate substantially free from alkyl phenols ilowing through line 22 to be stored, blended or otherwise utilized, or through line '32 to be acid treated. Alkalo metal alkyl phenolate solution, containing some free hydroxide, is conveyed through line 28 to the alkyl phenol plant l2.

In the latter plant the phenolate solution is carbonated by introducing carbon dioxide, or a gas containing carbon dioxide, through line 24,

, 21, 1936, now Patent No. 2,134,390. The resultnormally in an amount suilllcient to produce an aqueous carbonate solution containing a portion of bicarbonate. Alkyl phenols which are thereby liberated are separated and withdrawn through line 25. The carbonate-bicarbonate solution is returned through line I3 to mixer l0, to remove hydrogen sulde from the raw 2nd out distillate as described before.

In order that the hydrogen sulfide be removed thoroughly from the distillate, the amount of carbonate in the aqueous solution should be somewhat in excess of the mol equivalent of hydrogen sulde to be removed. Since, however, normally the quantities of hydrogen suliide inthe 2nd cut distillate are quite small, the available volume of carbonate-bircarbonate solution is usually more than sumcient. Moreover, the alkalinity of the carbonate-bicarbonate solution may be varied within limits by regulating the carbon dioxide input in the carbonating step, without greatly aiecting the economy of the alkyl phenol recovery.

The removal of hydrogen sulde from the 2nd cut distillate prior to extraction of alkyl phenols with aqueous caustic alkali has a considerable eiect on the consumption of caustic alkali, savings varying anywhere from about to 25% being commonly achieved.

The 3rd cut produced in column 3 is withdrawn through bottom line 26 to storage tank 21, and at a time when the 2nd cut runs into storage il, 3rd cut distillate may be processed in the alkyl phenol recovery system, the stored 3rd cut being transferred from tank 21 through line 28 to mixer l0.

If desired, a portion or .all of the carbonatebicarbonate solution from plant I2 may be conductedl through line 29 to mixer 30 where it is brought in contact with acid treated substantially sludge free 1st or 2nd cut, normally containing SOz, sulfuric acid esters, sulfonic acids and traces of sulfuric acid. In order to acid treat these cuts they are transferred from tanks A5' and 2l through lines 3l and 32, respectively, simultaneously or at dlerent times, to agitator 33. Sulfurlc acid is admitted to the agitator through line 34, sludge is withdrawn through sludge line 35 and the desludged acid reacting distillates are moved to treater 30 to be contacted and neutralized with the carbonate-bicarbonate solution containing small amounts of alkyl pheany source which are susceptible to improvement q in gum and/or color stability by means of gum inhibitors, and containing small amounts of mineral or organic acids capable of being neutralized with alkali carbonate solutions, may bel neutralized to great mivantage with the carbonate-bi-- carbonate solution produced in the liberation of alkyl phenol, in accordance with our invention.'

As has been shown, our process has many ad- I vantages and is capable of considerable flexibility depending upon the desired result. Thus if the.`

distillate, and the amount of carbon dioxide used for springing the alkyl phenolate solution is preferably suilicient to eiect substantially complete liberation of the alkyl phenols. On the other hand if the primary purpose is to neutralize hyrogen sulfide or other acids contained in distillate oils and simultaneously to improve the gum and color stabilities of `the latter, a portion or all of the carbonate-bicarbonate solution may be diverted to contact these'olls, and the amount of carbon dioxide for springing may be less than that required for complete liberation of alkyl phenols, in order to raise both the alkalinity of the aqueous solution and the amount of retained alkyl phenols which Will be transferred into the distillates to be stabilized.

The following examples serve to illustrate the advantages of our method:n V

A cracked gasoline distillate boiling between 150 to 250 C. containing .2% hydrogen suliicle and .7% alkyl phenols was extracted with an amount of an aqueous 40 B. caustic sodeJ solution slightly in excess over the equivalent corresponding to the acid oils plus hydrogen suliide in the distillate. After steaming and carbonating the alkaline extract the yield of acid Aoils was 76% of the theoretical. When the aqueous solution produced in the carbonating step was used to effect neutralization of the hydrogen sulde in the raw distillate prior to extraction with the caustic soda solution, the yield of acid oil was increased to 78% and the consumption of caustic soda in the extraction wasreduced by about 10%.

In another test a cracked gasoline distillate boiling between 150 and 250 C. was extracted with an aqueous 40 B. caustic soda solution under conditions to reduce its alkyl phenol content to less than 0.07%. The treated distillate, which was doctor sour, was then treated with 8 pounds o 81% sulfuric acid per barrel of distillate, reducing its alkyl phenol content to less than 0.02%. Sludge was separated and the acidreacting distillate was divided into two portions, one of which was neutralized with ammonia and the other with carbonate-bicarbonate solution from the alkyl phenol plant. Both neutralized portions were sweetened. Colors were equally good. However, the gum contents diiered considerably, that of the distillate neutralized with carbonate-bicarbonate solution being very much lower as shown by the data below:

Series l Series 2 Neutralized witho bo te C bo war na ar nu NH' bicarbonate NH' bicarbonate Normal glass dish gum 30 17 11 9 Accelerated glam Idish gum 1, 152 472 150 a2 lr let gum 343 Z39 Copper dish gum- 33 We claim as our invention:

1. In the continuous process of neutralizing a cracked hydrocarbon distillate containing a suliur acid and alkyl phenols, the improvement comprising treating said distillate with an excess over the equivalent to said sulfur acid of an aqueous alkali metal carbonate-bicarbonate solution containing small amounts of alkyl phenols under conditions to form two layers,n an aqueous layer containing an alkali metal salt of said sulfur acid, and a distillate layer substantially free from said sulfur acid containing alkyl phenols, separating the layers and treating said disarranca tic alkali in an ramount suicient to remove the tillate layer with an amount of aqueous alkali metal hydromde of 30 to 50% concentration slightly in excess of the equivalent of said alkyl phenols to produce an extract comprising an aqueous alkali metal alkyl phenolate solution and a residual distillate, separating the extract from the distillate, carbonating the extract to liberate alkyl phenols and to produce an alkyl phenol phase and an aqueous carbonate-bicarbonate solargest portion of said alkyl phenols from the distillate under conditions to form two liquid layers, one comprising an aqueous solution of alkyl phenolates and caustic alkali, and the other consisting essentially of treated hydrocarbon distillate, separating the layers, adding an amount of CO2 to the aqueous layer sumcient to convert same to a carbonate-bicarbonate solution to liberate alkyl phenols and form an alkyl phenol phase and an aqueous carbonate-bicarbonate s0- lution phase containing a part, of the liberated alkyl phenols, separating said phases, and passing the aqueous carbonate-bicarbonate solution phase through the first of said treaters in contact with said distillate, whereby the hydrogen sulilde is removed from the distillate and alkyl phenols in the aqueous solution are dissolved in the distillate.

BERNARD SU'I'RO GREENSFEIDER. MONROE EDWARD SPAGHT.

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