US2756185A

US2756185A - Process for preparing an odorless naphtha

Info

Publication number: US2756185A
Application number: US349892A
Authority: US
Inventors: Allen E Brehm; Theodore B Tom
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1953-04-20
Filing date: 1953-04-20
Publication date: 1956-07-24
Anticipated expiration: 1973-07-24

Description

w mu @manu mm &9: mn SGS: mmhm. m m ...In Rubs@ m M w rvr.. w mv( m w N 7 W E. e m 2 .mv I n W T e M. A A N e m. Nv :ikv A M m M Tl' W w E N. m m L] n m 1 1 l M m m InM (n, H 1 mm m QQKNGY R n. a m M Imm E wn e P n.. A R F Swann O mu F S S m NM. on Dl 6 5 l I F l l @mm .uq kvnmm, y 4 .QN 2 NN\ .w. ERS U .J mm\ mm\ PROCESS FOR PREPARING AN ODORLESS NAPHTHA Allen E. Brehm and Theodore B. Tom, Grliiith, Ind., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application April 20, 1953, Serial No. 349,892 12 Claims. (Cl. 196-38) This invention relates to odorless naphthas. More particularly the invention relates to solvent naphthas such as painters naphtha, which naphthas must have a minimum of the so-called naphtha odor.

Petroleum naphthas have been used for many years in the paint and varnish industry as solvents. More recently petroleum naphthas are being used in the synthetic resin industry as solvents. The primary objection to the use of petroleum naphthas in these elds has been the odor of the naphtha. It has been found that naphthas that are essentially free of sulfur compounds still possess a characteristic parain odor. Continuous efforts have been made by the petroleum industry toward the production of a .so-called odorless naphtha for use as a solvent in the paint, varnish and resin trades.

An object of the invention is the production of an essentially odorless naphtha suitable for use in the paint, varnish and resin trades. Another object is the preparation of an odorless naphtha derived from petroleum hydrocarbons. A particular object is an odorless naphtha derived from a synthetic mixture of paraiiinic hydrocarbons derived from petroleum conversion processes. A specific object is the production of an odorless naphtha by acid refining of a fraction boiling between about 325 and 425 F. that has been derived from the acidcatalyzed alkylation of butenes and isobutane. Other objects will become apparent in the course of the detailed description of the invention.

A naphtha having an odor-quality suitable for use as a solvent particularly in the paint, varnish and resin trades, has been produced by a process comprising (l) treating a feed naphtha boiling between about 325 and 425 F. that has been derived from hydrocarbons containing from 3 to 5 carbon atoms, which feed is characterized by being essentially free of olefms and aromatic hydrocarbons and elemental sulfur, with an effective amount of sulfuric acid having a concentration of between about 90 and 100 weight per cent, (2) separating acid sludge from treated naphtha, (3) rain-washing said treated naphtha with liquid water to remove substantially all of the occluded-acid sludge particles therefrom,

(4) separating rain-wash water from rain-Washed naphtha, (5) intimately contacting said naphtha from step (4) with liquid water, (6) separating water from washed naphtha, (7) contacting said washed naphtha with an aqueous alkaline solution to essentially neutralize said washed naphtha, (8) separating aqueous alkaline solution from an essentially neutral naphtha, (9) water washing said neutralized naphtha and (10) removing occluded aqueous alkaline solution from said neutralized naphtha.

The feed to the process of this invention is composed essentially of a mixture of paratnic and isoparaflinic hydrocarbons, i. e., is essentially free of olens and aromatic-hydrocarbons. Very small amounts of organic sulfur., compounds may be present. However, the feed must be essentially free of hydrogen sulfide and elemental sulfur.

,The most suitable feed to the process is derived from ICC hydrocarbons containing from 3 to 5 carbon atoms, which hydrocarbons have interacted to produce a mixture of essentially parainic and isoparafnic hydrocarbons of the proper boiling range for the desired solvent naphtha. In general the solvent naphtha should boil between about 325 and 425 F. and preferably between about 350 and 400 F. A lower boiling point may be acceptable for some uses.

The mixture of hydrocarbons that are a suitable source for the feed to the process may be derived by alkylation of an olefin containing from 3 to 5 carbon atoms with an isoparafn containing from 4 to 5 carbon atoms, i. e., the feed naphtha may be derived from the product of an alkylation reaction between an olefin selected from the class consisting of propene, butenes and pentenes and an isoparaflin selected from the class consisting of isobutane and isopentane.

Another suitable source of feed naphtha to the process is a mixture of hydrocarbons obtained by the polymerization of oleiins containing from 3 to 5 carbon atoms and the hydrogenation of the polymeric materials to form a mixture of essentially parainic and isoparaflnic hydrocarbons, i. e., the feed naphtha may be derived from the hydrogenated product of the polymerization of an olefin selected from the class consisting of propenes, butenes and pentenes.

Many processes are known for the preparation of materials of the type described above. For example, a suit-` able source of feed naphtha is the total alkylate derived from the acid-catalyzed alkylation of butenes and isobutane, which reactants have been obtained from petroleum refining operations. Typical acid catalysts are liquid hydrogen fluoride and sulfuric acid. Another example of a process for the preparation of a suitable feed is the hydrocodimer derived from the polymerization of a refinery propene and butene stream over a supported phosphoric acid catalyst to form a broad boiling range unsaturated liquid product; this unsaturated product is hydrogenated in the presence of a catalyst to produce an essentially saturated broad boiling product commonly known as hydrocodimer.

The preferred feed to the process of this invention is derived from the heavy alkylate fraction of a cold-acid alkylation process utilizing petroleum refinery butenes and isobutane as the feed to the alkylation reaction. This material is essentially free of olens and contains only a very minor amount of organic sulfur compounds.

The detailed description of the process of this invention is made in conjunction with the annexed drawing, which drawing forms a part of this specification. The drawing shows in schematic and figurative form a preferred method of carrying out the process. Many details of equipment have been omitted as these may be readily supplied by those skilled in this art. 4

In the drawing a heavy alkylate derived from the sulfuric acid alkylation of refinery butenes and isobutane which boils between about 325 and 600 F. is passed from source 11 by way of line 12 into fractionator 13. Fractionator 13 is provided with an internal heat exchanger 14 and with a stripping medium distributor 16. In this embodiment fractionator 13 is operated with the use of steam stripping; steam from source 17 is passed by way of line 18 into distributor means 16, which means 16 is positioned near the bottom of fractionator 13. Instead of using a stripping medium such as steam, comparable results can be obtained by operating fractionator 13 under vacuum. A high boiling bottoms fraction is withdrawn from fractionator 13 and is passed to storage not shown by way of line 19.

An overhead fraction having a maximum ASTM boiling point of about 400 F. is withdrawn along with steam by way of line 21. The overhead naphtha and steam are condensed by means of heat exchanger 22 and the condensate is passed into line 23.

It has been found that the presence of elemental sulfur in the naphtha feed to the acid treating step of the process has an extremely deleterious effect` on the quality of the solvent uaphtha. Solvent naphtha. is required to be substantially non-corrosive to the copper strip test. The organic sulfur compounds normally present inl thealkylate` decompose to some extent in the distillation step to produce hydrogen sulfide. This hydrogen sulfide is oxidized Aby free-oxygen on exposure to the atmosphere, e. gf, in a storage tank, t o form elemental sulfur. In general the H23 containing naphtha may be exposed to freefoiiygen for as much as four hours before deleterious amountsof elemental sulfur are formed. In order to eliminate the formation of elemental sulfur the H28 present in the naphtha in line 23. is neutralized by the injection of aqueous caustic solution from source 26 and line 27. Herein a l weight precent aqueous NaOH solution is used.

The combined stream of naphtha, condensed steam and aqueous caustic solution is passed into mixer 28 wherein intimate contacting takes place. Mixer 2S may be any form of apparatus provided for intimate contacting such as knothole mixer or a tank provided with a stirrer. From mixer 23 the mixture is passed by way of line 29 into separator 31. From separator 31 the lower aqueous phase is passed by way of line 32 to waste caustic disposal.

Feed naphtha essentially free of HzS and elemental sulfur is withdrawn by separator 31e. and is passed by way of line 33 into agitator 34. Agitator 34 .is` a conebottomedV contacting vessel, provided `with a roof, of the. type Widely used in the petroleum industry. Agitator 34 is provided with various lines for introducing liquid and gaseous materials into the vessel and also means for withdrawing materials from the tip of the cone. In this particular agitator a distributor means36 and valved line 37 are provided near the top of the vessel. i

For clarity of presentationthe process is depicted in` the drawing as taking place in a

pluralityof agitators

34a, 3417, 34e and 34d. Thesealphabetically designated agitators are shown by means of broken lines.` Thiso h as been done in order to indicate thatagitators` 34m-34d do notactually exist in the process. The entire processing ofthe feed naphtha from line 33 actually occurs in a singlegagitator 34. For clarity each distinctly different individual operation has been presented as though .it occurred in a different agitator. i i

Returning yto the rst step in the process proper, feed naphtha from line33V is introducedL into agitatora34 until the desired amount of naphtha is present. Sulfuric acid from source 4l is passed by way of line 42 into agitator 34. The sulfuric `acid must have a concentration" be@ tween about 90 and l0() weight percent and` must be` used in at least an effective amount to produce the desired odorless naphtha product. Excessive. usage of sulfuric acid should be avoided. In general between` about and 25 lbs. of sulfuric acid should be `used per barrel of feed naphtha. In order to produce `the highest odorquality solvent naphtha, the sulfuric acid should be either white acid derived from SO2 or the so-called blacleacid derived from the processing 0f refinery waste acids and acid sludges. It is preferred to use sulfuric acid having a concentration between about 96 and 100 weight percent. The amount of acid used will vary with the type of feed naphtha charged to the process..

In this embodiment l2 lbs. of 96.5% black acid are used per barrel of feed naphtha (herein 42-gallonbarrels are meant). The acid and naphtha in agitator 34 are thoroughly agitated by means of compressed air intros duced from source d6 by way of valved` line 47 `into a lower portion of agitator 34. The agitation is continued until it is believed the reaction has been completed.

After `the completion of the air agitation the contents of agitator are permitted to settle into an acid sludge phase and a treated naphtha phase. The lower layer of acid sludge is withdrawn by way of valved line 49 and is sent to acid recovery means not shown.

It may be desirable to carry out the acid treating in more than one stage. Thus a portion of the acid may be placed in the agitator with the naphtha, the contacting carried out and acid sludge separated. Then the remainder of the acid may be used to treat the once-treated naphtha. This multiple dump procedure is particularly useful when quite large amounts of acid are being used.

The treated naphtha contains entrained sludge particles as well as dissolved acidic materials. It has been found that the entrained sludge particles, i. e., pepper sludge, readily hydrolyze on contact with water to produce naphtha-soluble materials which impart an undesirable odor to the product naphtha.' The pepper sludge is removed from the treated naphtha by means of a rain-wash procedure. lnthis procedure a gentle drizzle of` liquid water, from source 51 and line 37,` is provided by distributor 36. This rain causes droplets of water to flow through the pool of treated naphtha without agitating the body of treated naphtha. rl`he droplets wash out of the treated naphtha, the pepper sludge and also wash from the wall of agitator 34 adhering sludge particles. The pool of treated naphtha in the agitator is maintained in a relatively static position except for the gentle rise in level as a lower layer of rain-wash water is formed in the bottom of the agitator. (No agitation air is introduced into agitator 34` during the rain-washing procedure.)

Sutiicient rain-wash water must be introduced into the agitator to remove substantially all the occluded-acid sludge particles from the treated naphtha. In the case of a well settled treatednaphtha, the amount of water may be between aboutS and volume percent based on treated naphtha. Better results are obtained by the use of two rain washes, i. e., the treated naphtha is rain washed once and the rain-wash water withdrawn from the agitator and the rain-washed naphtha is then given a second rain wash followedby withdrawall of rain-wash Water from the` agitator. When operating with a p1urality of rain washes a relatively. small amount of water can be used in each wash. The waste water from the rainwashing procedure is Withdrawn from the agitator by way of valved line 49.

The rain-washednaphtha which is now substantially free of pepper sludge is given a conventional water wash. Liquid water from source 51 is introduced by way of valved line 37 and distributor 36 into the agitator. When the, desired amount of water has been introduced into the agitator` the naphtha and water are intimately contacted by agitating the contents of the agitator with compressed `air from source 46 and valvedline 47. The amount of water used in this conventional water-washing operation should be enough to remove essentially all the pepper sludge and water-soluble acidic materials remaining in the rain-Washedv naphtha. The amount of water may be between about 5 and 100 volume percent based on naphtha. At the endof the contacting time thecontents of the agitator are settled and theflower water layer is withdrawnto waste water disposal by v/ay of line 491 The washed naphtha contains dissolved acidic materials` which must be removed to produce a satisfactory product naphtha. Aqueous caustic solution from source 53 is passed into the agitator` by Way of line 37 andA distributor 36. In this example a 5 weight percent aqueous NaOH solution is used in an amount, of about livolumes percent based onnaphtha. Thenaphtha and aqueous caustic solution are thoroughly intermingled by means of air from source 46 and line 47. When thenaphtha is essentially neutralized the contents of the agitator are `settled and the lower aqueous layer is withdrawn to waste caustic disposal by way of valvedline 49.

The neutralized naphtha contains occluded aqueous caustie solution.` This occluded` aqueouscaustic solution is removed by a conventional waterwash. Water froml source 5l is passed into the agitator by way of line 37 and'di'stributor 36.. Sufficient water must be usedto remove the occluded caustic. The water and naphtha are intimately contacted by agitation with air from source 46 and valved line 47. The contents of the agitator are settled and the lower water layer is passedv to waste water disposal by way of valved line 49. v

Product naphtha is Withdrawn from the agitator and passed to storage for further treatment by Way of valved line 49d.

Normally the slight haze present in the product naphtha disappears in storage. However, this haze can be removed by passing the hazy naphtha through a coalescer filled with fiberglass packing or rock salt granules.

All the various steps described in the above embodiment are normally carried out at the temperature of the water available for the washing operations. Although normally the acid treating is so mind that excessive temperature rise does not occur, with some types of feed and veryl heavy acid usages, it may be desirable to cool the contents of agitator 34 by means'of an internal heat eX- `changer not shown.

The odor quality of product solvent naphtha is determined by a standardized odor evaluation procedure. In

this procedure a solvent naphtha of about-ordinary com mercial odor quality has been assigned an arbitrary odor value of 100. Other naphthas are compared to this standard naphtha by the following' procedure. The unknown naptha is smelled by each of twelve sensitive and experienced individuals; each member of this odor panel assigns the unknown naphtha a point value as compared to the standard naphtha. The odorquality of the unknown naphtha is determined as the arithmetical average ofthe numerical value assigned to the naphtha by the individual members of the panel. It has been found that quite accurate reproducibility is obtainable in this panel odor evaluation and the odor panel can check an unknown naphtha within il unit.

The results obtainable by the process of this invention and by conventional procedures are illustrated below.

In all the experimental runs the feed naphtha was derived from a heavy alkylate that had been produced by the sulfuric acid-catalyzed alkylation of a refinery butenebutane stream. The heavy alkylate was steam distilled, taking overhead about 70% of the charge. The overhead fraction contained H28 and was treated with 5% aqueous NaOH solution to neutralize the HzS. Tests indicated that this feed naphtha contained on detectable amounts' of elemental sulfur.

The ASTM distillation, API gravity and sulfur content of the heavy alkylate charged to the steam distillation, the feed naphtha which corresponds to about 70% of the heavy alkylate and a product naphtha obtained by the treatment of this feed naphtha according to the process of this invention are presented in Table I below:

sludge withdrawn.

6 Run I For comparison purposes a portion of the feed naphtha was acid treated with 10 lbs/bbl. of naphtha using 98%'.

refinery black acid. The acid sludge was withdrawn from the small agitator used for the processing. Two successive conventional water washes were then given the treated naphtha. Each wash amounted to 50 volume percent based on naphtha. using 5 volume percent of a 5 weight percent aqueous NaOH solution. Finally the neutralized naphtha was given a final water wash using about 5 volume percent of water. All these washes were carried out at about room temperature.

. Run 2 ln this run the feed naphtha was treated in one dump with 10 lbs./ bbl. of 98% refinery black acid and the acid The treated naphtha was given two rain washes using 50 volume percent of water in each rain wash. The rain-washed naphtha was given a conventional water wash using 5 volume percent of water.`

The washed naphtha was then neutralized byv contacting it with 5 volume percent of an aqueous solution containing 5 weight percent of NaOH. The neutral naphtha was given a final water wash using 5 volume percent of water.

Run 3 In order to determine the effect of using waste acid available in the refinery spent sulfuric acid catalyst from the alkylation of a refinery butene-butane stream, normally known as spent alkylation acid, having an effective sulfuric acid content of about 86% was used in this run. The spent alkylation acid was fortified with new acid to an effective concentration of about 98%. The procedure in this run was essentially identical with that of Run 2 except that 20 lbs/bbl. of the fortified spent alkylation acid was used in the acid treating step.

The panel odor-intensity evaluation of the product naphthas of Runs l-3 and of two odorless naphthas widely used in the paint industry are listed in Table II below:`

The odor panel indicates that the product of Run 2 is a very superior product for use as an odorless solvent naphtha. The results of Run 3 indicate that the presence of dissolved carbonaceous materials in the spent alkylation acid has an adverse effect on the odor-intensity of the product naphtha even though double the amount of acid was used as compared with Run 2. The results of Run l indicate that the rain-washing procedure is an essential step in the production of a satisfactory odorless naphtha from the feed naphtha of this invention.

Thus having described the invention, what is claimed l. A process for the production of an odorless naphtha, which process comprises l) treating a feed naphtha boiling between about 325 and 425 -F. that has been derived from hydrocarbons containing from 3 to 5 carbon atoms, which feed is characterized by being essentially free of olefins and aromatic hydrocarbons and elemental sulfur, with an effective amount of sulfuric acid having a concentration of between about and 100 weight percent, (2) separating acid sludge from treated naphtha,

(3) rainewashing said treated naphtha with liquid water under conditions to maintain a substantially stationary pool of said treated naphtha to remove substantially The washed naphtha was neutralized znsetss' is derived from the product of an alkylation reaction between an olefin selectedfrorn the class consisting of propene, butenes and` pentenes and anisoparaffin selected from' the classsconsistingof isobutane and isopentane.

3. Thefprocess4 ofv claim 2k wherein said reactants are obtained' from petroleum refining operations.

4. The processof claiml `whereinlsaid feednaphtha is derivedfrom-vthe hydrogenated product of the polymerization` of an Volefin selected from the classvconsisting of propene,. butenes and` pentenes.

5. The process o` claim 4 wherein said reactants are obtained` frompetroleurn refining operations.

6. The process of claim 1 wherein the sulfuric acid usage is between about 5 and 25 lbs./bbl. of feed naphtha. 7. The process ofV claim l wherein said sulfuric acid concentration is between. about 96 and 100 Weight percent.`

8l The process of claim 1 wherein said rain-washing consists ofowing onto the surface of a pool of treated naphtha a gentle drizzle of liquid Water in an amount betweenabout 5 and 100 volume percent, based on said treatednaphtha. i

9'; A'iprocess for'producing an odorlessnaphtha, which process comprises (a) distilling an alkylate derived from the acid-catalyzed reaction of an olefin selected from the class consisting of propene, butene and pentene with isobutane to produce a feed naphtha distilling between about325 and 425 F., which' feed naphtha isessentially," free of): elemental sulfur', (b)` treating' said feedL naphtha.A withbetween about 5lV and 25f lbs. of sulfuric acid having'a concentration of between about 96 and weight percent and separating acid sludge from treated naphtha,` (c) removing substantially all of the occluded-acid sludge particles from said` treated naphtha by gently flowing drops of water through a relatively static poolof said treatednaphthaand separating rainwash water from washed naphtha, (d) intimately contacting said washed naphtha with liquid water and separating an aqueous phase from a naphtha containing essen# tially only dissolved acidic materials, (e) neutralizing the naphtha from step (d) by contacting said naphtha with an aqueous lalkaline `solution and separating an aqueous phase from a naphtha phase and (f) removing entrained aqueous alkaline solution from the naphtha phase of step (e). p

10. The process of claim 9 wherein said rain-washing consists of two consecutive washes wherein each wash uses between about 5 and 50 volume percent of liquid water, based on treated naphtha.

11. The process of claim 9'whcrein step (f) consists of washing said naphtha phase with liquid water to produce an aqueous phase'and a product naphtha essentially free of alkaline material.

12. Ther process of claim 9 wherein said feed naphtha is, freed of H25 before essentially any elemental sulfur had been formed by reaction of said HzS with freeoxygen.

References Cited in the tile of this patent UNITED'STATES PATENTS 1,310,164 Leslie Jan. 15, 1919 1,704,246 Halloran Mar. 5, 1929 1,751,862 Huff Mar. 25, 1930- 2,397,077 Alspaugh Mar. 26, 1946

Claims

1. A PROCESS FOR THE PRODUCTION OF AN ODORLESS NAPHTHA, WHICH PROCESS COMPRISES (1) TREATING A FEED NAPHTHA BOILING BETWEEN ABOUT 325* AND 425* F. THAT HAS BEEN DERIVED FROM HYROCARBONS CONTAINING FROM 3 TO 5 CARBON ATOMS, WHICH FEED IS CHARACTERIZED BY BEING ESSENTIALLY FREE OF OLEFINS AND AROMATIC HYDROCARBONS AND ELEMENTAL SULFUR, WITH AN EFFECTIVE AMOUNT OF SULFURIC ACID HAVING A CONCENTRATION OF BETWEEN ABOUT 90 AND 100 WEIGHT PERCENT, (2) SEPARATING ACID SLUDGE FROM TREATED NAPHTHA, (3) RAIN-WASHING SAID TREATED NAPHTHA WITH LIQUID WATER UNDER CONDITIONS TO MAINTAIN A SUBSTANTIALLY STATIONARY POOL OF SAID TREATED NAPHTHA TO REMOVE SUBSTANTIALLY