US2281892A - Method of producing oxidation inhibitors - Google Patents

Description

May 5, 1942.

WASHER.

FQJEAcr'IQM CHAMBER FEE/ EATIN J. A. TlLTON METHOD OF PRODUCING OXIDATION INHIBITORS Filed March 4, 1939 A c /.D

7122.4 TING CHAMBER cHAMBaz 12 H 1 5 gig-2 0 0071- 71 625 .25 5.. H

CHARGE OIL IIVLE 7' generate the catalyst.

Fatented May 5, 142

' METHOD (PF PRQDUCING Q ACTION ETORS Joshua A. Tilton, Baton Rouge, La., asslgnor to Standard Oil Development Company, a corpo-.

ration of Delaware Application March 4, 1939, Serial No. 259,781

4 Claims.

It has heretofore been proposed to, form gasoline by cracking higher-boiling hydrocarbons in the presence of a catalyst such as naturally active or activated clays or the like. According to one of the methods employed, the oil to be cracked is passed in vapor form through a reaction zone containing said catalyst maintained at the required cracking temperature.v When operating in this manner, the catalyst gradually becomes fouled with carbonaceous deposits requiring periodic interruption of the cracking operation to re- The regeneration is accomplished by passing an oxidizing gas through the catalyst to burn the deposits.

I have found that gasoline and other light distillate formed as a result of such a process contains substantial quantities of constituents which are capable of inhibiting the formation of oxygenated bodies and that the amount of such constituents formed as a result of the process is substantially in excess to that necessary to stabilize the gasoline or other light distillate formed as a result of the process.

While the exact nature of the oxidation inhibitor constituents formed as a result of the catalytic cracking operation has not been definitely established, it has been found .that the excess of such inhibitors can be removed from the gasoline or other light distillate by treatment with a basic solution which leads to the conclusion that they are essentially acidic in nature, such as phenolic compounds or other hydroxy aromatic materials.

It has been further found that the amount of oxidation inhibitor formed as a result of the catalytic cracking process, before outlined, is substantially in excess of that which is normally .formed as the result of a conventional thermal cracking process. While the reason for this is not definitely known, it may be due to the fact that in the catalytic cracking process the catalyst is periodically subjected to oxidizing treatment during regeneration and that traces of oxygen remaining on the catalyst at the start of the cracking operation may react with the oil being cracked to form hydroxy compounds or other acidic constituents capable of inhibiting formation of oxygenated compounds. Whatever the explanation uents than similar constituents formed as a result of conyentional cracking processes.

Having described the general nature and objects, the invention will be better understood by the more detailed description hereinafter in which reference will be.made to the accompanymay be, it has been found that products produced from the catalytic'cracking process are definitely richer in oxidation inhibiting constiting drawing which is a diagrammatic illustration of an apparatus suitable for carrying out the present invention.

Referring to the drawing, the numeral I0 designates a charge line through which the oil to be cracked is introduced into the system. This charge oil is preferably a clean condensate stock such as a virgin gas oil. The oil introduced through line II] is forced by means of pump ll through a preheating coil l2 located in furnace l3 wherein the oil is vaporized and heated to the desired reaction temperature. The preheated vapors from the heating coil l2 pass through line It to a manifold line i5 having branched lines It and I1 leading to reaction chambers l8 and i9 respectively. Two reaction chambers are shown so that one reaction chamber may be on the cracking cycle while the other is undergoing regeneration.

Cracked products from the reaction chambers [8 or 19 as the case may be, are removed through lines 20 and 21 respectively and passed through line 22 to a fractionating tower 23.

Each reaction chamber l8 and I9 contains a mass of catalytic material such as naturally active or activated clays or similar adsorptive synthetic compounds of silica and alumina. Regeneration of the catalyst is accomplished by means of an oxidizing gas such as air diluted with an inert gas introduced through line 24. The regenerating gas introduced through line it is forced by means of blower 25 to either of the two reaction chambers 18 and is through branch lines 25 and 27 respectively. Products of regeneration are removed from reaction chambers 58 and I9 through lines 28 and 29 and may be rejected from the system through line 30. Ifdesired a portion of the spent regenerating gases after sufficient cooling may be recycled to the inlet as a diluent for the air. As before-mentioned, in the apparatus illustrated one of the reaction chambers is adapted to be on the cracking cycle while the other is undergoing regeneration and the cracking and regenerating cycles will be shifted from one reaction chamber to the other as desired.

-Retuming now to the cracking process, the cracked products introduced into the fractionating tower 23 are subjected to fractionation therein to condense insumciently converted products as reflux condensate. Condensate formed in the fractionating tower 23 may be withdrawn therefrom through line 3| and may be rejected from the system as shown or recycled to the inlet side of the heating coil l2 and subjected to further cracking treatment.

Products remaining uncondensed in the fracseparated in the receiver 34 are removed therefrom through line 35 having a suitable valve for imposing the desired back pressure on the cracking operation.

It will be understood that the present invention is not concerned with the details of carrying out the catalytic cracking process but is directed to the treatment of the motor fuel distillate resulting from such a process.

In accordance with the present invention, the. raw liquid distillate collected in the receiver 34 is withdrawn therefrom and treated with a mild alkaline solution such as a weak sodium hydroxide solution to partially neutralize acidic constituents contained in said raw distillate. As a result of the alkaline treatment, the. acidic constituents are converted into the corresponding salt. It is preferred not to completely neutralize the acidic constituents contained in the raw distillate but to retain therein sufllcient of said constituents to stabilize the distillate product against oxygen reactions.

The solution containing the salt of the inhibitor is then separated from the distillate and neutralized with a weak acid solution such as sulfuric acid, hydrochloric acid, carbon dioxide and the like to reconvert the inhibitor-salts into the inhibitor.

The inhibitor so liberated can be then separated from the neutral solution either by settling or centrifuging. The inhibitor being heavier than the neutral solution separates as the bottom layer.

. Referring specifically to the drawing, the raw distillate removed from the receiver 3 5 through line 36 is passed to an alkali treating chamber 3? wherein it is treated with a weak alkaline solution introduced through line 38. The alkali treating chamber may be of any conventional design and may be of a continuous or discontinuous type. The distillate and alkaline solution separates in two phases within the alkali treating chamber 37. The lighter distillate phase may be removed from the chamber through line 39 and the alkaline solution containing the inhibitor salt is removed through line db and passed to a neutralizing chamber 4i wherein it is neutralized with a weak acid solution such as sulphuric acid or hydrochloric acid introduced through line 62. The inhibitor liberated as a result of the neutralizing treatment may be allowed to separate in the bottom of the neutralizing chamber 4i and can be withdrawn through line 43.

The product so recovered has been found to be an exceptionally good inhibitor for suppressing the formation of oxygenated bodies in gasoline and other light hydrocarbon distillates.

The alkali washed distillate withdrawn from the alkali treating chamber 37 through line 39 is preferably passed to an acid treating chamber it more stable.

menses 8B where it is treated with sulphuric acid to remove highly unsaturated constituents and thereby reduce the acid heat of the product and make From theacld treating chamber 44 the product may be passed to a suitable washer 45 wherein the acid is removed. The resulting product may be subjected to sweetening or other *flm'shing treatment in accordance with the common practice. In case the acid and finishing treatment resultsin removal the natural inhibitors remaining in the gasoline after the controlled alkali treat,

additional material inhibitors recovered by the alkali treat may be added to the finished product. For example, a part or all of the natural inhibitors removed from the neutralizing chamber 4| through line 43 may be passed through line 46 and blended with the finished product of the process.

Theinitial alkali treatment of the raw dis tillate prior to the acid treatment has a further advantage in that it effects a more complete removal of sulphur impurities from the gasoline and thereby improves the leadsusceptibility of the product.

The following example may prove helpful for a fuller understanding of the invention, it being understood that the values'and conditions there given are illustrative rather than limitive.

A catalytically cracked gasoline was first prepared in the following manner. A virgin East Texas gas oil having an A. P. I. gravity of 33.4 was passed through a reaction zone containing activated clay of the type known as Superfiltrol. The rate of feed was 0.5 volume of liquid feed per volume of catalyst per hour and the length of the cracking cycle between regenerations was 30 minutes. The temperature within the reaction zone was maintained at 850 F. The products were fractionated to separate a gasoline distillate having a final boiling point of 418 F.

The gasoline so prepared was then treated with one-fifth its volume of a 2% solution of sodium hydroxide. The sodium hydroxide solution was then separated from the gasoline and neutralized by treatment with one-tenth normal sulfuric acid. The inhibitor was allowed to settie in the bottom or the neutral solution and was withdrawn therefrom. The following table.

illustrates the properties or the gasoline before and after the alkali treatment.

original camp Catalytically iytically fi g'g cracked gasone um moval of inhibitor sac 67.8 +4 +6 11 234 s. 2 a a so 50 91 91 7a a 19. o s1 89 Percent c. 158.. 26. 0 26. 5 Percent c. 212. 44. 0 43. 5 Final, F 418 420 The breakdown time listed in the above table was determined by the method described by Winning and Thomas in an article appearing in the Industrial 8: Engineering Chem. vol. 25 page 5111 (1933) and the copper dish gum test was Federal Specifications accuses treatment, it will be noticed that the only important change in the characteristics is the drop in the breakdown time from ll to 2 /4 hours. Inasmuch as the breakdown of 2%, is sumciently stable to meet all practical requirements and specifications, the inherent properties of the gasoline remain unimpaired by the alkali treatment. Not only is the gasoline unimpaired, but the odor thereof is materially improved by removal of the excess inhibitors contained therein.

The inhibitor prepared as above described when added to thermally cracked gasoline in 6.2% concentration increased the breakdown time from 1 /2 hours to 8 hours. It will thus be seen that the inhibitor recovered from the catalytically' cracked gasoline is extremely potent for suppressing reactions between oxygen and gasoline.

of removing the excess natural inhibitors from the cataiytically cracked gasoline by means of the alkali treatment previously de-.

scribed, such gasoline may be used directly as a blending agent in unstable motor fuels such as thermally cracked gasoline, gasoline ether blends and the like so that the excess natural inhibitors present in the catalytically cracked gasoline may be employed as an inhibitor for the unstable portion of the blend.

Having described the specific embodiment and given a specific example thereof, it will be understood that the invention covers such other variations and modifications as come within the spirit thereof. It will be further understood that it is not my intention to unnecessarily restrict the invention except as necessary to adequately distinguish from prior art.

I claim:

1. A method of producing inhibitors capable of suppressing the oxidation of hydrocarbon distillates which comprises subjecting a high-boiling hydrocarbon oil to cracking in vapor form in the absence of any substantial amount of free oxygen in the presence of an adsorptive cracking catalyst, periodically regenerating said catalyst with an oxidizing gas, fractionating the cracked products to separate a light distillate product therefrom, treating said light distillate product with a weak solution of sodium hydroxide, separating the sodium hydroxide solution distillate, and neutralizing the sodium hydroxide from the treated solution separated from said distillate to liberate inhibitors contained therein.

2. A method of preparing inhibitors capable of suppressing the oxidation of hydrocarbon diatillate which comprises cracking high-boiling hydrocarbon oils in the presence of a catalyst comprising activated clay, periodically regenerating said clay with an oxidizing gas, fractionating the cracked products to separate a light distillate product therefrom,'treating said distillate with an alkaline solution capable of neutralizing hydroxyaromatic constituents contained therein, separating the alkaline solution from the treated distillate and treating the alkaline solution so separated to liberate inhibitors contained therein.

3. A method of refining cracked distillates, obtained by cracking higher boiling oils in the presence of an adsorptive cracking catalyst and wherein the adsorptive cracking catalyst is subjected to periodic regenerations' by oxidation, to

improve the odor of said cracked distillates and to recover oxidation inhibitors therefrom which comprises treating said distillate with an alka line solution capable of neutralizing hydroxyaromatic constituents contained therein to form a salt, separating the alkaline solution containing said salt from the treated distillate and treating the alkaline solution so separated to liberate hydroxyaromatic constituents contained therein.

4. A method of producing a stable motor fuel of high anti-knock properties which comprises cracking higher boiling oil into motor fuel constituents in the presence of a solid catalyst, periodically regenerating said catalyst in situ with an oxidizing gas, treating the raw motor distillate from the process with an alkali solution capable of reacting with the hydroxyaromatic constituents contained therein to form a salt, separating the alkali solution containing the said salt from the distillate so treated, treating the alkali solution to decompose the salt to liberate oxidation inhibitors therefrom, further treating the alkalitreated distillate with acid to remove highly unsaturated constituents therefrom and. thereafter adding to the acid-treated product at least a portion of the oxidation inhibitors liberated from the alkali solution.

. JOSHUA A. TILTON.

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