US1902221A - Process of purifying naphtha stocks - Google Patents

Description

Patented Mar. 21, 1933 "DAVID E. DAY, DE LOS PATENI. F -mg:

CALIFORNIA rnocnss orrunrrvme narnm s'rocxs Application filed December 5,1931.v s ria1@iw6.f 579,as7,.

This application is a'continuation in art of my application Serial No. 370,325, led June 12, 1929, for method of purifymg petroleum oils. j

a This invention relates to an improved method for purifying hydrocarbon oils derived by distillation or cracking ofgmineral oils or mineraloil products, such as lubrieating oil stodks, lamp oil distillates, gaso- 1o line or naphtha stocks, or any other distill,-

ates produced in generalrefinery practice, and more specifically refers to the treatment of gasoline or naphtha'stocks produced by cracking petroleum oils or distillates derived from relatively high sulphur bearing crude petroleum oils, in which hydrogen sulphide, mercaptans and other sulphur bearing conipounds, as well as varying percentages; of phenols and unsaturated hydrocarbons (such ,,-.29 as Idiolefines and 'acetylenes) may be present or formedduring a distillation or cracking operation. v ,1 For the purpose, of simplifying the. description-oftheinvention, reference will be 5 made to gasoline or naphtha stocks mainly.

By well known methods, gasoline stocks derived from cracking petroleum oils or from distilling high sulphur bearing crude petroleum oils are usually purified by varying .39 treatments with sulphuric acid, followed by neutralization with a water solution of-analkali, a sweetening operation and a final distillation. In the sweetening operation hypochlorite of soda or sodium plumbite in a 5 water solution of caustic soda may be employed to convert corrosive sulphur'compounds into noncorrosive bodies, so'that the treated gasoline stock will be sweet to the doctor test.

In these treatments, particularly where hypochlorite of soda is employed, chlorinated hydrocarbons may be formed to a small extent, which may be converted into corro sive compounds during a subsequent distillation. Also all the sulphur bearing hydrocarbons remaining in the gasoline stock after the purification operation form corrosive acid compounds during combustion, and if in appreciable amounts, may attackthe metal parts of anengine, Therefore, it is advantageous in the Jpurificationbfgasoline or naphtha stocks "to" use a purif in agent which in it's'elfwillnot'formchlorinated oils, and one'which reinove certain percentage of "the sulphur compoundsffiom a ga e: line qrnaphthaistok and 'pelymefiz the nus'cable hydrocarbons sothat magma-may be p te t erafiem ye l bse en i i l m- Y1. i 9 Y I .,my' pe din .aprl et s l N 370,325, filedfl June 12, 1929, forfmethod'of Pi i i e pe -c am s 1s," .h e closed that hydrocarbon oils, such as gasoline or naphtha stocks, maybe purified by passing the same, commingled with a substantially concentrated: water solution of caustic soda, caustic potash sodiumfcarbonate or potassium carbonate," 'throu'gh a heating coil Leade 5 P e sur l fii int o- P nt ,0 'stant vaporizatiom ata temperature be tween 350 and fioO-ldegrees F.,thenreleas- *ing the pressure andseparating by distillation and fractionation 'ap'urified gasoline or naphthafrom the excess'caustic alkali, the 7 extracted impurities and the products of polymerization or condensation. Water is continuously or intermittently introduced into the lower section of the distillation and fractionating apparatus in quantities sufii- 30 'cient toreplace the vaporized water-from the caustic alkali solution, so as to maintain the used caustic alkali or carbonate and products of reaction in a fluid state.

Now I have discovered an improvement thereto, in which I have determined that, it is an advantage to mix air with the gasoline or naphtha stock duringjthe treating operation, in quantities sufiicient to oxidize the corrosive sulphur compounds contained 9 therein into compounds that may be extracted to a certain extent with the caustic alkali or carbonate treating solution; also that the introduction of air into the gasoline or naphtha stock assists in the polymerization of the unstable hydrocarbons and thereby produces gasoline or naphtha which is lower in sulphur content, sweet to the doctor test,'and contains substantially no gums or gum forming constituents. The air may be mixed with the 7 9 sweet to the doctor test.

liminary treatment with sulphurio'acidpr' other agents to partlyipurif-y'the'isame,-=or may be first partly purif ed by my invention and the purification completed by-methods known in the art. In the case pf asoline or naphtha stocks produced by'cra'c mg high sulphur ;bea ring crude petroleum oils. or -residuums, it may be advantageous to treat such gasolineor naphtha stocks with sulphuric acid ;at. low temperatures, ranging froinap- PE QlM- Q to -3 d e ees ib rek treatment-with I the concentrated water, solu tio c cei tie lk l m sa benate s il eeedg ape s and pe t-e; we n e One of he princlpal objects of this invent is o a ompl sh p rti lde rhu i tio'n andfpurificationbf gasoline'or naphtha stocks produced by thermo-niolecular decomposition of'high boilingtpetrole im 'Qils, by--a treatment with ais bst ntianyconcentrated water solution .of [an alkali hydroxide ,or car.- bonate and air, underapressuresufiicient' to prevent substantial vaporiaatio n of; the gasoline or naphtha stock, and atja) temperaturefof approximately 350-501) degrees 'F. follQYifd 35 by a distillation and fractionat n operation to separate-"the products 'fo'f reaction higher, boiling polymerized product from purified gasoline or naphtha. so

- Another object of the invention is to wide a continuous, rapid and economieal proc- .ess for-purifying gasoline'o'r naphtha stocks by treating the same, under superatmospheric pressure sufficient to maintain the gasoline or naphtha stock in a liquid phase, with a substantially concentrated water solution of an alkali hydroxide or carbonate and air, at

temperatures of approximately 350-500 degrees F., to polymerize, substantially all the unstable hydrocarbons contained therein, and at the same time remove oxygenated hydrocarbons and render the gasoline or naphtha Another object of the invention is to provide a continuous and economical method for improving the color-and removing gums and gum forming hydrocarbons from gasoline or naphtha stocks, so that the same maybe kept in storage for relatively long periods of time without change in color or quality by the formation of polymerized bodies. y

Other objects and advantages will be apparent from' the preferred embodiment of this invention, which will now be more fully explained by reference to the accompanying drawing, which is a diagrammatical repre-' tha or other petroleum oil stocks to be processed. Pipe 1, controlled by valve 2, connects gasoline stockgtank 3 near the top to a source of'supply not shown. Pipe 4, controlled by valve 5, connects gasoline stock tank 3 to the inlet side of -pump'6. Pipe 7 connects pump 6 to jet mixer 8.

13represents generally a caustic soda tank for holding a concentrated solution of a caustic alkali' such' as" caustic soda or caustic potash. Pipe let, controlled by valve 15, connects caustic soda 'ta-nk.13 near thetop to a source of supply not ,shown.' Pipe 11, controlled by Valve 12, connects caustic soda tank 13 near the bottom to the inlet side of 85 pump-110.. Pipe9connects the dischargeside of pump 10to jet mi'xer' 8. Pipe 10,0011- trolled by yalveel, 'islc onnected to jet mixer sand leads to a source of'compressed air. f

Pipe 16 connects jet'inixer 8 to heater coil 38. Heatercoil 38 is stationed'in furnace 17. Furnace 17 is providedwith a burner 18, which leads to a supply of fuel oil not shown.

Pipe 39','.controlledby pressure release valve 19, connects'heater coil .38 to distillation. tower 20. Pipe42, controlled by valve 43, connects pipe 39 to a source of compressed air. Distillation tower '20 is provided with bubble trays 21.: Pipe 22, controlled by valve 23, connjects distillation tower 20 near the bbttQmi'iO a source'of water or steam supply not shown. Pipe 25, controlled by valve 24, connects distillation tower 20 at the bottom to tank 26. Pipe 28, controlled by valve 27, connects tank'26 to a storage not shown.

I :Pipe 29 connects distillation tower '20 at the top to condenser coil 31. Condenser coil '31 is stationed in condenser box 30, and .is provided with a water inlet pipe 32 and a water outlet pipe 37. Pipe 32 leads to a ,1

46' near the top to an absorber not shown. -115 Pipe 33' connects air separator 46 to treated gasoline tank 34. Pipe 36, controlled by valve 35, connects treated gasoline tank 34 near thebottom to a storage not shown.

The preferred process as carried out in the apparatus just described is as follows:

Petroleum oil distillate, such as gasoline orv naphtha stock, contained in tank 3, is permitted to flow through pipe 4 and into the inletside of pump 6, the rate of flow being.

governed by operation of valve 5. Pump 6 continuously discharges the gasoline stock through pipe 7 under a pressure of approximately 1501000 pounds gauge, into jet mixer 8, wherein the gasoline stock is continuously 'commingled' with the necessary quantity of air, and a substantially concentrated water solution of caustic alkali coming from the caustic soda supply tank 13.

The air introduced into jet mixer 8 comes from a source of compressed air through pipe 40, controlled by valve 41, and may range from approximately one-half volume to four volumes of air per volume of liquid gasoline under treatment.

The water solution of caustic alkali contamed in supply tank 13 is permitted to flow through pipe 11 and into the inlet side of pump 10, which discharges the same, under a pressure ranging from approximately 150- T000 pounds gauge, through pipe 9 and into jet mixer 8, the rate of flow being governed by operation of valve 12. The quantity of water solution of caustic alkali employed may range from as low as approximately 1 per cent to as high as 10 per cent by volume or more, depending upon the stock to be treated. For example, if a crude gasoline stock contains a high percentage of impurities to be extracted, or has had a preliminary treatment with sulphuric acid, as much as 10 per cent by volume or more of a concentrated water solution of caustic alkali may be employed.

The pressure maintained on the system by means of pumps 6 and 10 is regulated so that the commingled mixture of water solution of caustic alkali and gasoline or naphtha stock under treatment will be maintained in a substantially liquid phase, such pressure depending upon the boiling points of the gasoline or naphtha stock and the temperature employed.

From jet mixer 8 the gasoline stock, commingled with the water solution of caustic alkali and air, passes through pipe 16, heater coil 38, pipe 39, pressure release valve 19 where the pressure is reduced to atmospheric or approximately atmospheric, and into distillation tower 20. The c-ommingled mixture passing through heater coil 38 is heated to a temperature greater than 350 degrees F. Preferably, approximately 400 degrees F. is a suitable temperature to employ in treating ordinary gasoline or naphtha stocks. how ever, with some grades of petroleum distilla-tes as high as 500 degrees F. or a little higher may be employed.

In distill tion. tower 20 the purified. gasoline stock, at a temperature of approximately 400 degrees F., together with a portion of the water content of the alkali solution, is vaporized and separated from. the products of reaction and the caustic alkali employed. The purified gasoline stock. mixed with water vapor and air, passes out of distillation tower 20, through pipe 29, into condenser coil 31, which is stationed in condenser box 30, wherein the major portion of the purified gasoline stock and water vapor is condensed to a liquid 22d passed through pipe 47 into air separator FFrom -"separator 46 "the: tr ma. gasoline {passes througb pipe" ;33 into tank 34: i From treated gfaspli-netank 34 the purified gasoline stpck may i b'e conducted -to a storage" not shown throughj pipe'..36; controlled by valv'e -35. l he purified ga soline stoek sow'obtained may :bei therea'ftes treated; di -necessary, by othefi m'ethods known 'inj, the f art} or may: be slibjeeteil to a distillation operation to sepahate ffractions having anydesired 1 ange sof boilifig"p'0ints: w .ei-v' 'ra'g no l."-"""(i The caustic alkali-'and 'products of reaction,

separate in the bottom" of distillation twefi 20 are intermittently or =continuously withdrawnintogtaiik 26 through pipe 25; controlled; by yalye 24, water being: continuously or intermittentlyiintroduced into'the lower section of 'dist'illati'on tower 20 through pipe "22, 'controlledbytyalve 23', inquantities sufli- --cient to-replace the vaporizedwater from the caustie'alkali iwater solution, so asto maininthe used cau'stiwalkali and products of reactionin'a fiuid condition. Pf?

' From tank: 26-:the-excess ;water solution of 4 v 1 caustic alkali aind pr )'ducts of reaction iare "conducted to a": storage: not shown through "pipe 28f-controll'ed' by valve 27," and the canstic alkali may be separatedfrom the reaction products and recovered for reuse: I

Pi a The air in the treatment may be intro- ;duced'into the treating system through pipe 42, controlled by'rva'lve43, which is connected top'pe' 39, and'leads to a source of compressed ='air-not shown'w While *the'pro'cess' her ein 'de'scribed is well adapted for carryinggout the objectsof this "inventiong'various modifications'and':changes may: 1 be {'made', such= asthe employment of 'various" types of .fraction'ating equipment 3 known in: the;artto' effect any desired separationot "the treated gasoline I stockinto frac tionshaving a 'desired range-of boiling points, .and the "invention includes'all such changes and modifications as appear within the scope M of the appended claims.

I claim:

1. A process of purifying naphtha stocks, comprising, commingling a naphtha stock with a substantially concentrated water solution of a caustic alkali, passing the commingled mixture through a heating zone at temperatures of approximately 350500 degrees F., under a pressure suflicient to prevent substantial vaporization of the naphtha stock, releasing the pressure and introducing air into the oommingled :mixtame, and .a purified naphtha iby vaporization, fractionatiw (condensation from produots of reaction, excess caustic alkali and .aeriform products.

2. A.- process of removing gum forming emstituents from cracked gasolinestock, comprising, contacting the cracked gasoline stockwitha water-solution of aeanstiealkall, at temperatures-of approximately 3-50-5Q0degrees R, under a pressure sufiicient to prevent substantial vaporization thereof, while passing through a heating zone, for a period of time 'snfiicienttocause unstable hydrocarbons eontainedjin the gasoline stock-to polymerize with the formation of gums, then reducing the pressure to-approximately atmospheric, intnoduemg air,- and separating by vaporization, fractionation and condensation purified gasoline stookinom reaction and polymerization products, excess caustic a1- .kali and aeriformzpnodncts,

3.. A continuous pnooess for purifying gasoline stocks derived by thermo-molecular decomposition of higher boiling petroleum oils, comprising, continuously comm'ingling a gasoline stock with amater solution-of a caustic alkali; continuously passing the commingled mixture through a heatnlg zone to heat the eommingled gasoline stock and wafer solu tion of caustic alkali to a temperature of approximately 400 degrees'R, undera pressure sufiicient to prevent substantial vaporization therein; continuously releasing the prwsure after the commingled .mixtune. of gasoline stock and water solution of caustic alkali has passed'through the said heating zone and has been heated to a temperature of approximately 400 degrees F.;icontinuously introducing air into the heated mixture of gasolinestock and water solution of alkali; continuously passing the same into a vaporizing zone and vaporizing, fractionating, condensing and separating purified gasoline stock mixed with water from higher boiling products of reaction, excess caustic alkali and aeriform' products; continuously introducing water "into the said vaporizing zone in quantities suificient to replace water of vaporization; and continuously withdrawing products of reaction and introduced water containing caustic alkali, substantially as described.

In testimony whereof I afiix my signature.

DAVID E. DAY.

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