US2756181A - Process for improving engine cleanliness characteristics of cracked gasolines by treating with phosphorus pentoxide - Google Patents

Description

July 24. 1 5 G. P. HAMNER PROCESS FOR IMPROVING ENGINE CLEANLINESS CHARACTERISTICS OF Filed May 21. 1952 Glen QHamrzer zvnvcrztor :1: H I13. HHH QEQJJFQ WWW FZMEFlMWP N HHH w P I II I. I. z HUM we MWm NI HUN 3 A 13 HHl N HHH H HHH N Ill mzON. ill A Ill QCQJJFQ PM .rzuih g I p I1 I L Nlw IL QCZJJF DM Al l-1.1 in i Clttor'oeg United States Patent PROCESS FOR IMPROVING ENGINE CLEANLI- NESS CHARACTERISTICS OF CRACKED GASOLINES BY TREATING 'WITH PHOS- PHORUS PENTOXIDE Glen P. Hamner, Baton Rouge, La., assignor to Esso Research and Engineering Company, a corporation of Delaware Application May 21, 1952, Serial No. 289,036

3 Claims. (Cl. 196-43) This invention concerns a novel refining process for cracked gasolines. The process of this invention serves to remove sulfur compounds, increase octane number, reduce gum content and to eliminate compounds responsible for poor engine cleanliness characteristics. The process of this invention requires the debutanization of a cracked naphtha fractionation followed by fractionation of the naphtha into at least two fractions. Each of these fractions is then treated with P205 under critical conditions to selectively polymerize and/or condense undesired constituents of the naphtha. The treated fractions are again subjected to fractionation and are finally combined to provide the naphtha product.

It is now appreciated that cracked gasolines are characterized by undesired deposition of deposits causing fouling of engines. The precise mechanism causing cracked gasolines to have inferior engine cleanliness characteristics is not understood. However, it is believed that certain reactive components of cracked gasolines produced by the cracking process are responsible. Thus, it is particularly thought that highly reactive diolefinic compounds, which are capable of reaction at ambient temperatures, probably react with oxygen to form high molecular weight compounds depositing varnish or sludge in an engine during use. It is known that C5 diolefins such as isoprene, piperylene and cyclopentadiene are present in cracked gasoline. Cs diolefins such as methyl cyclopentadiene and hexadienes are also present and certain diolefins having more thanG carbon atoms such as di-methyl cyclopentadiene and heptadienes are also to be found. Thermally cracked gasolines contain about 0.5 to l% of these constituents while catalytically cracked gasoline generally contain higher proportions ranging from about 1% to 2 /2 The present invention is particularly adapted for the polymerization or condensation of diolefinic compounds of this character in a manner permitting removal from the gasoline of the polymerized product. Thereby, engine cleanliness characteristics of a gasoline are substantially improved. I The process of this invention not only serves to improve the engine cleanliness of a gasoline but also provides an octane number improvement. At the same time the process causes a reduction of sulfur and improves other of the critical properties of cracked gasoline.

A great many refining processes are now known for treating and improving gasolines. For example, gasolines are commonly treated with sulfuric acid, clay or other re by substantial losses of the gasoline treated. It may be observed therefore-that the refining proc'ess of this inven- 2,756,181 Patented July 24, 1956 tion is particularly desirable in providing a highly selec-- tive manner of removing undesired constituents, permitting a high yield of treated gasoline without any loss in octane number.

In accordance with this invention, diolefinic compounds are removed from a gasoline by a particular combination of fractionation and P205 treating steps. In a first step of the process any portion of the'gasoline boiling below about 86 F. is removed. This fractionation serves to eliminate butadiene which under the P205 treatment would otherwise polymerize to constituents boiling in the gasoline boiling range. gasoline is divided into at least two fractions. A first fraction is segregated boiling from about 86 to 248 F., while a second fraction is segregated boiling from about 248 to 430 F. Each of these two fractions is then separately treated with P205 under carefully controlled conditions. The temperature of P205 treatment must be in the range of about 0 to 250 F., and preferably in the range of to F. The catalyst concentration and the residence time in the reaction zone is also carefully controlled to provide about 0.2 to 2 volumes of feed per volume of catalyst per hour (v./v.hr.). The reaction is to be carried out under liquid phase conditions at pressures of about 0 to 100 lbs. p. s. i. The P205 employed may be used in pure form, or if desired, may be deposited on a suitable carrier.

Reaction of the two naphtha fractions with P205 under these conditions causes a highly selective polymerization of diolefinic compounds present in the two fractions. The polymer produce predominantly boil outside the boiling range of the fractions treated so that the polymer products may then be removed by distillation after the P205 treatment. Thus, the first naphtha fraction, boiling up to 248 'F., after treatment is fractionated to eliminate all compounds boiling above 248 P. so as to eliminate the polymer products. Similarly the second naphtha fraction boiling from 248 to 430 F. is fractionated to eliminate all polymer products boiling above 430 F. These fractionated naphtha fractions may then be combined to provide the final naphtha product. This naphtha product may be blended with alkyl lead compounds, lead scavengers, dyes and other conventional gasoline additives, in order to provide a superior gasoline. In this connection, it is notable that the process of this invention is not detrimental to the lead susceptibility of the gasoline.

The accompanying drawing diagrammatically illustrates a suitable flow plan embodying the process of this invention. Referring to the drawing, a cracked naphtha obtained from either a thermal or catalytic cracking zone is passed through line 1 for introduction to distillation zone 2. As thermal and catalytic cracking processes are well known to the art and no part of this invention, a description of the cracking process is not included herein. It should be emphasized however, that the process of this invention is particularly adapted for the treatment of a catalytically cracked gasoline so that the fraction passed through line 1 preferably will constitute a catalytically cracked gasoline fraction boiling up to 430 F.

In distillation zone 2, an overhead stream is removed through line 3 constituting all constituents boiling below about86 F. Thus, line 3 will include C4 hydrocarbons and lighter constituents of the cracked naptha. Distillation zone 2 is operatd to permit removal of a bottoms product through line 4 constituting all portions of the cracked naphtha boiling above about 430 F. Finally,

Thereafter, the remaining debutanizeddistillation zone 2 is operated to permit removal of two side stream products through lines 5 and 6 boiling respectively in the ranges of about 86 to 248 F, and 248 to 430 F. The stream of line 5 is then conducted to a reactor 7 in which this stream is treated with P205. Similarly the higher boiling fraction of line 6 is conducted to reactor 8 for treatment with P205. Reactor 7 and 8 may constitute any desired form of contactor permitting contact of the naphtha fractions with the P205.

The P205 treatment is conducted at temperatures of 100to 150 F., 50 to 100 lbs. p. s. i. g., and preferably at about /2 to 1 v./v./hr.

The P205 treated fractions are removed from zones 7 and 8 through lines 9 and 10 respectively. Each of these fractions is then introduced to separate distillation zones 11 and 12, operated to permit removal of all constituents from each fraction boiling above the final boiling point of the initial fractions. A bottoms stream 13 is removed from still 11 constituting all constituents boiling above 248 F. A bottoms stream 14 is removed from still 12 boiling above 430 F. The remaining portion of each fraction is removed as an overhead stream from stills 11 and 12 through lines 15 and 16. These streams are combined as by means of the orifice mixer 17 to provide the final naphtha product.

As described, the process of this invention concerns the fractionation of a cracked naphtha into at least two fractions which are separately treated with P205, subsequently fractionated and then reblended. The combination of fractionation and P205 treatment is employed to permit elimination from the final product of polymers formed by the P205 treatment. Thus C5 to C7 diolefins present in the fraction boiling below about 248 F. are

polymerized to constituents boiling above 248 F., al-

though within the motor gasoline boiling range. These constituents are removed by the fractionation of the treated fraction. Similarly diolefins having more than 7 carbon atoms boiling above 248 F. and below 430 F. are removed by polymerization and fractionation.

It may be observed that while the preferred process of this invention requires treatment of the two fractions identified with P205, the benefits of this invention can at least in part be obtained by treating either one of the two fractions with P205. Particularly, the invention contemplates the treatment of only the higher boiling fraction boiling in the range of 248 to 430 F. with P205. Thus, referring to the drawing, the stream of line 5 from distillation zone 2 maybe blended directly with the treated naphtha obtained as an overhead from still 12 through line 16.

The nature and advantages of this invention may be better understood by reference to the following examples, whicl1 provide typical data concerning the process of this invention.

EXAMPLE I A thermally cracked distillate was fractionated into four fractions. A first fraction boiling below 86 F. amounting to 9.6 weight percent of the original distillate was obtained. A second fraction boiling in the range of 86 to 248 F., amounting to 23.2 weight percent of the original distillate was obtained. A third fraction boiling in the range of 248 to 428 F., amounting to 47.7 weight percent of the distillate was obtained, and a bottoms product boiling above 428 F. amounting to 19.5 weight percent of the original distillate was segregated. Each of the intermediate fractions was separately treated with P205 and for control purposes a blend of the two intermediate fractions was also treated with P205. The P205 treatments were conducted at 150 F., atmospheric pressure, and 0.5 v./v./hr. Each of the treated fractions was fractionated after P205 treatment to remove constituents boiling above the initial endpoint of each fraction. In the case of the separately treated intermediate fractions the treated and fractionated fractions were 4 then combined to provide the final naphtha product boiling in the range of 86 to 428 F.

The data obtained by these procedures is presented in Table I:

Galculated from polymer yield obtained on treat; of each fraction. 8.6 wt. percent from 86248 F. fraction (31.7%); 4.3 wt. percent from 248-428" F. fraction (68.3%).

3 The optical density test is a measure of the engine cleanliness of a gasoline utilizing the coupling reaction between diazotized p-nitro aniline and unsaturated compounds of the gasoline causing engine fouling. This reaction results in formation of a colored compound and the intensity of color as determined by optical density measurements is used as an index of the engine cleanliness of the gasolinc. The test is conducted by free tionatiug the sample and treating the fraction boiling over 275 i with dilute acid and alkali followed by steam distillation to 3% bottoms. A fixed amount of this fraction is added to a solution of n-nitro aniline diazonium fluoborate in acetone and the optical density measured at different time intervals. The optical density is plotted against time and the value after 20 minutes is read from the curve.

Comparing the first and third columns of Table I, in which column 3 exemplifies this invention, it will be observed that the process of this invention resulted in substantial improvement in the engine cleanliness of the naphtha as determined by the optical density test. The oxidation stability of the gasoline was also greatly improved. Comparing columns 2 and 3 of Table I, it will be observed that a significantly greater improvement in the naphtha was obtained by the separate treatment of the intermediate fractions than in the case in whichthe intermediate fractions were both treated together with P205. This is borne out by the fact thata greater amount of polymer was obtained by employing the process of this invention as compared to the case in which the fractions were not separately treated.

EXAMPLE II A thermally cracked distillate was fractionated to obtain a naphtha fraction boiling in the range of 250 to 430 F. This fraction was treated in liquid phase with P205 at 150 F., 100 lbs. pressure and 1 v./v./hr. The inspections of the original and treated fraction are given in Table II:

T able II THERMAL CRACKED DISTILLATE Original Treated Boiling Range, F 250-430 250430 Diazoninm tluoboratc deposit factor Y 5 Research Octane Number:

1 Sulfur analysis on polymer formed showed 2.4 wt. percent.

Referring to the data in Table II it will be observed that the engine cleanliness properties of the naphtha fraction were greatly improved by the P205 treatment as indicated by the fluoborate test. This is accompanied by a substantial increase in the octane number of the fraction, both clear and with tetraethyl lead. The sulfur content of the gasoline as indicated by the Cu Number and the actual sulfur analysis was greatly improved. The

treatment resulted in formation of 2.8 weight percent of polymer as indicated in the table. It may be observed that in a polymerization proce of this character employing an activated clay as the catalyst, some to of polymer formation would be required to provide an equivalent improvement in engine cleanliness. As shown by the data of Table II therefore, the P205 treatment of this invention serves to substantially improve a cracked naphtha to provide a high yield of treated product.

EXAMPLE III In still another embodiment of the invention, a thermally cracked naphtha was fractionated to obtain the fraction boiling in the range of 250 to 430 F. This fraction was then treated with P205 at about 150 F., atmospheric pressure, and l v./v./hr., and then redistilled. The following blends were then made:

(1) 70% of a premium gasoline with of this untreated fraction.

(2) of a premium gasoline with 30% of the treated fraction.

obtainable by treating at least the higher boiling fraction of a naphtha boiling above 250 F. with P205 as described.

What is claimed is:

l. A process for improving the engine cleanliness of a catalytically cracked naphtha in which the cracked naphtha is segregated into at least two fractions, a first fraction boiling in the range of about 86 to 250 F., and a second fraction boiling in the range of about 250 to 430 F., thereafter treating each of said fractions in liquid phase with P205 at a temperature in the range of about 0 to 250 F, and at about 0.2 to 1 v./v./hr., thereafter separately fractionating said treated fractions to segregate higher boiling constituents formed by the P205 treatment, and combining said fractions.

2. The process defined by claim 1 in which the said temperature of P205 treatment is in the temperature range of to F.

3. The process defined by claim 1 in which the reaction is conducted at 1 v./v./h1'.

References Cited in the file of this patent UNITED STATES PATENTS 1,827,537 Morrell Oct. 13, 1931 1,914,953 Malishev June 20, 1933 2,002,902 Martin et a1. May 28, 1935 2,191,043 Sachs Feb. 20, 1940 2,342,630 Forney Feb. 29, 1944

Claims (1)

1. A PROCESS FOR IMPROVING THE ENGINE CLEANLINESS OF A CATALYTICALLY CRACKED NAPHTHA IN WHICH THE CRACKED NAPHTHA IS SEGREGATED INTO AT LEAST TWO FRACTIONS, A FIRST FRACTION BOILING IN THE RANGE OF ABOUT 86* TO 250* F., AND A SECOND FRACTION BOILING IN THE RANGE OF ABOUT 250* TO 430* F., THEREAFTER TREATING EACH OF SAID FRACTIONS IN LIQUID PHASE WITH P2O5 AT A TEMPERATURE IN THE RANGE OF ABOUT 0* TO 250* F., AND AT ABOUT 0.2 TO 1 V./V./HR., THEREAFTER SEPARATELY FRACTIONATING SAID TREATED FRACTIONS TO

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