US3329593A

US3329593A - Process for anodically oxidizing olefins to ketones

Info

Publication number: US3329593A
Authority: US
Publication date: 1967-07-04
Anticipated expiration: 1984-07-04

Description

u y 1967 L- I. GRIFFIN. JR., ETAL 3,

PROCESS FOR ANODICALLY OXIDiZiNG OLEFINS TO KETONES Filed July 5, 1961 2 Sheets-Sheet 2 RECYCLE CONDENSATE DRUM so 7 l 1 SETTLER 35: 2 ,;DISTILLATION 1AGITATOR 25 9 J-156 Q TO l'l-BUTENE gflg ,Z T EXTRAOTOR 0R ACID 2o RECONCENTRATION UNIT FIGURE 2 To MEK EFFLUENT FROM ELECTROCHEMICAL FINISHING REACTOR l9,'FlG.-l

I n-BUTENE EXTRAOTOR SETTLER 4"|o J" 22 DISTILLATION l8 lol 4 Y H o a H so 'ro MEK f j 4 FINISHING F m ELECTROCHEMICAL REACTOR LINDSAY I. GRIFFIN, JR.

PATENT ATTORNEY United States Patent pany, a corporation of Delaware Filed July 3, 1961, Ser. No. 121,490 13 Claims. (Cl. 204-80) This invention relates to a process for converting an olefin to the corresponding ketone utilizing electrochemical oxidation. In particular, this invention relates to a process for separating normal olefins, hereinafter referred to as n-olefins, from a hydrocarbon mixture with sulfuric acid, converting the absorbed n-olefins and/ or acid hydration products thereof to the corresponding ketones while in contact with such acid by anodic oxidation and separating such ketones from such acid by liquid extraction. In one embodiment, this invention relates to a continuous process which comprises contacting a hydrocarbon mixture of parafiins, isoolefins and n-olefins with a first aqueous solution of sulfuric acid under conditions adapted to cause selective absorption of isoolefins by such solution, separating from such mixture an isoolefin-acid extract leaving a first residual hydrocarbon mixture comprising par-aflins and n-olefins, contacting such first residual hydrocarbon mixture with a second sulfuric acid solution under conditions adapted to cause absorption of n-olefins by .such solution, separating from such first residual hydrocarbon mixture a second olefin extract comprising nolefins and sulfuric acid leaving a paratfin comprising hydrocarbon mixture, employing the acid component of such second extract as an electrolyte in an electrochemical cell, converting the absorbed n-olefin therein to the corresponding ketone and employing said paraffin comprising-mixture in liquid phase in separating such ketone from such electrolyte. Hydrocarbon streams containing both n-olefins and aromatics, e.g., a C hydrocarbon mixture, are preferably pretreated, e.g., with a selective solvent such as phenol, to remove the aromatics before carrying out the instant process. Certain feedstocks, such as those obtained from wax cracking processes, may be essentially free of isoolefins, rendering the isoolefin separation step unnecessary.

With normal modifications in accordance with molecular weight, solubility characteristics, etc., the process of this invention may be effectively carried out to produce a wide variety of ketones, e.g., C to C or higher. This process is particularly applicable to production of C to C aliphatic ketones. The most preferred feedstock olefins are those for which the corresponding secondary alcohol is appreciably soluble in the olefin-containing electrolyte without the aid of mutual solvents, etc. Various operational techniques are available, however, to maintain the effectiveness of the process where the alcohol intermediate has a tendency to separate from the electrolyte. These include operation at elevated temperatures and pressures, control of acid concentration so that the rate of hydrolysis is essentially equal to the electrochemical oxidation rate, thorough mixing of reactants and electrolytes via recycling, etc., and cell design. However, to avoid unnecessary repetition this process will be primarily described with reference to the production of methylethyl ketone, sometimes referred to hereinafter as MEK, from a predominantly C hydrocarbon mixture containing nbutylenes.

Electrochemical conversion of chemical energy of hydrogen or an organic compound having a lower state of oxidation than carbon dioxide to electrical energy is known in the art and a device wherein such conversion is accomplished has become commonly known as a fuel "ice cell. The fuel cell can be operated solely to produce power, or, by removing from the cell partial oxidation products, it can be utilized to simultaneously produce useful electrical energy and valuable organic chemical products.

The over-all fuel cell reaction is the sum of two essentially independent half-cell reactions. At the anode, hydrogen, carbon monoxide or a carbon and hydrogen-comprising compound is oxidized with a release of electrons to the anode. At the cathode, oxygen is reduced upon accepting electrons and water is formed at the cathode in an acid system with hydrogen ions from the electrolyte. The internal portion of the electrical circuit is completed by ion transfer between'such electrodes while electron transfer from anode to cathode external to such electrolyte completes the electrical circuit.

Anodic oxidation of an organic compound in a powerconsuming, electrochemical cell is also known in the art. In this type of cell oxidation is effected by admission of an electron flow from an outside source to a cathode therein, ion transfer between cathode and anode via a liquid electrolyte, and electron flow from the cell by way of an anode to complete the electrical circuit with such outside power source. This latter cell is referred to as an electrolytic cell or electrolytic reactor.

It has now been discovered that ketones can be produced electrochemically in a fuel cell or electrolytic cell in a single stage process from n-olefins, i.e., without intermediate separation and purification of the corresponding secondary alcohol as in conventional practice, by absorbing such n-olefins in sulfuric acid and subjecting the resulting extract to anodic oxidation in accordance with the processes hereinafter described. Further, it has been discovered that other hydrocarbons with which such nolefins are normally associated in refinery streams can be utilized in accordance with the processes hereinafter described to facilitate the separation and recovery of such ketones.

In the production of ketones from n-olefins by electrochemical oxidation selectivity to the desired ketone is increased if the olefin is not allowed to contact the reaction sites in free or unabsorbed form. The olefin can be prevented from contacting the anode directly by dissolving the olefin in the sulfuric acid electrolyte before such contact or by maintaining a sufiiciently high sulfuric acid concentration at the point of such contact. The olefin may be dissolved in the acid before admission of the acid to the cell or the olefins and acid may first contact each other within the cell proper or a compartment thereof in such a manner that the undissolved olefin does not come in contact with the anode.

It is one object of this invention to provide a process wherein n-olefins are separated from a hydrocarbon mixture containing saturated hydrocarbons, electrochemically converted to the corresponding ketones in sulfuric acid and extracted from such acid utilizing such saturated hydrocarbons in liquid phase contact.

It is another object of this invention to provide a continuous electrochemical process for producing methylethyl ketone wherein n-butylenes are absorbed from a C hydrocarbon mixture in a mixer-settler extraction unit converted to such ketone in a power producing fuel cell by anodic oxidation and said extraction unit is utilized for the dual purpose of absorbing fresh butylene feedstock and to provide a mixing zone for the acid containing ketone eflluent of said fuel cell with unabsorbed butanes in such unit to facilitate ketone separation.

These and other advantages, objects, and features of the invention will become apparent from the following description and drawings.

FIGURE I is a fiowpan for processing a C hydrocarbon stream in the production of methylethyl ketone elec trochemically from n-butylenes.

FIGURE II is a flowpan showing One embodiment of the product recovery unit of FIGURE I in greater detail.

FIGURE III is a modification of flowpans of FIGURES I and II utilizing the n-butylene extraction unit in the recovery of ketone product from the electrochemical reactor.

Referring to FIGURE I, a refinery stream comprising a mixture of C hydrocarbons is passed via conduit 1 to isobutylene extraction unit 2. This stream contains about 40-60, normally 45-55, volume percent mixed butylenes with about 25-40 volume percent of the total butylenes being isobutylene. A typical feedstock contains about 10 volume percent n-butane, about 40 volume percent isobutane, about 35 volume percent n-butylenes and about 15 volume percent isobutylene. When minor amounts of other hydrocarbons, e.g., propylene and pentenes, are present in the feedstock their concentration should be minimized so far as the economies of separation permit. The isobutylene extraction unit 2 comprises one or more reactors or mixers each followed by an emulsion settler, an emulsion circulation pump and coolers. Alternatively, the isobutylene may be extracted from the C stream in a countercurrent operation employing a packed tower. These subunits are not shown in the drawings as conventional equipment now employed for isobutylene separation in butanol plants can be used and the techniques employed for this extraction step are well known in the art. In this unit the C fraction is contacted in liquid phase with 60-70, preferably about 63-68 and most commonly about 65, wt. percent sulfuric acid to extract the isobutylene. This extraction is preferably carried out in two or more mixer-settler stages at about 70-100 F. to yield a rich extract containing about 1.3 to 1.4 moles of isobutylene per moles of H 80 Contact of the C streams with such acid includes countercurrent fiow and/ or jet mixing. The reaction of isobutylene with sulfuric acid is much faster than that of n-butylenes under these conditions. Holdup time in isobutylene extraction unit 2 can therefore be terminated before any appreciable quantity of n-butylenes is absorbed. The isobutylene-acid extract is removed from isobutylene extraction unit 2 via conduit 3 and passed to isobutylene regeneration and recovery unit 4, while the unabsorbed remainder of the C stream comprising butanes and n-butylenes is passed via conduit 5 to n-butylene extractor 11. This stream normally contains less than about 2 volume percent isobutylenes. Regeneration unit 4 comprises a degassing drum and a regenerator tower which are not individually shown in the drawing. The isobutylene-acid extract is first heated by the injection of steam and passed to the degassing drum to flash off dissolved butanes which take with them some olefins. The degassed extract is then pumped to the regenerator tower where water is injected into the top of such tower to control the top temperature while a steam spray is admitted at the bottom thereof to maintain a temperature of about 250 F. An overhead stream from regeneration unit 4 comprising isobutylene, tertiary butanol, polymer and water is passed via conduit 6 to an isobutylene finishing unit, not shown. The sulfuric acid in regeneration unit 4 is diluted in the recovery of isobutylene to about 45 wt. percent and this diluted acid is passed via conduit 7 to acid reconcentration unit 8 where it is reconcentrated by means well known in the art, e.g., distillation, to about 60-70 wt. percent. Reconcentrated acid is recycled via line 9 and valve 10 to isobutylene extraction unit 2.

The n-butylene extraction unit comprises one or more extractors or mixers, normally about 3, here represented by extractor 11, each followed by an emulsion settler, here represented by settler 16. Certain other conventional auxiliary equipment will be employed in the absorption of n-butylenes, e.g., circulation pumps, coolers, etc. Such auxiliary equipment is conventional in processes of this type and hence is not shown in the drawings. In extractor unit 11 the C streams from which essentially all of the isobutylene content has been removed is again contacted with sulfuric acid to extract the n-butylenes. In a preferred embodiment the concentration of the absorbing acid employed is within the same concentration range as that employed in isobutylene extraction unit 2, i.e., 60-70, preferably 63-68, wt. percent. This acid can be supplied to extractor 11 from acid reconcentration unit 8 via line 9, Valve 10, line 12, valve 13 and line 14. In extractor 11 intimate mixing is achieved by countercurrent contact of butylenes with acid so as to form a hydrocarbon acid emulsion. Jet or spray mixing is particularly advantageous at this stage. Absorption of n-butylenes in acid at this strength is effected by increasing the absorption temperature and/ or increasing the residence time over that employed for isobutylene extraction in unit 2, e.g., absorption temperatures in the range of about 70-135 F. The emulsion formed is removed from extractor 11 and passed via conduit 15 to settler 16 where the emulsion separates into a lower extract layer of acid and n-butylenes and an upper hydrocarbon layer comprising nand iso-butanes. The extract layer from settler 16 is passed via conduit 17 to electrochemical reactor 19. Conduit 18 provides means for supplying additional water to the system in those embodiments hereinafter discussed wherein dilution is required or desirable and in this embodiment to provide makeup water to replace any losses occurring in either the electrochemical reactor or in product recovery. Electrochemical reactor 19 comprises at least one and preferably a plurality of electrochemical cells in series and/0r parallel, which may include either power-producing fuel cells which employ an oxygen receiving cathode or a power-consuming electrolytic cell wherein electrical energy is admitted to the cathode from an external source. For this purpose the power-producing fuel cell is preferred.

Both fuel cells and electrolytic cells suitable for carrying out the process of this invention are known in the art.

The design of the cells to be employed in this invention and the electrodes and catalysts employed therein do not comprise a part of this invention. Certain requirements, however, must 'be adhered to if the process is to function effectively over protracted periods of time. For instance, all cell components coming into contact with the sulfuric acid electrolyte must be essentially chemically inert to such electrolyte and the anodic catalyst employed must provide sufficient catalyst activity under the conditions of temperature and pressure employed to assure conversion of the absorbed olefin and/or its intermediate reaction products to the desired ketone at a satisfactory rate. It is therefore preferred to employ one or more of the noble metals of Group VIII of the Periodic Table at the anode whether the cell he of the power-producing or power-consuming variety. Gold from Group I-b of the Periodic Table may be included as a minor component of such Group VIII catalysts. Certain acid resistant compounds of other metals such as cobalt molybdate or manganese molybdate on a carbon base material may also be used. Since the reactant feed is soluble in the electrolyte there is no necessity to employ a porous or diffusion type anode to bring the ketone yielding material into simultaneous contact with the anode and electrolyte. The anode structure may therefore be in its simplest form metal sheet or screen surfaces with the anodic catalyst thereon. A simple sheet of platinum may be employed, but more effective reaction rates are obtainable by superimposing upon a metal sheet a surface of platinum black, e.g., by electrodeposition. Porous carbon impregnated with catalyst in accordance with techniques well known in the art is also suitable for use as an anode base.

When a power-producing fuel cell is employed, the cathode or oxygen electrode will have the requirements aforedescribed for the anode and in addition must be designed to admit of diffusion of oxygen so as to form a three-phase interface of solid electrode, liquid electrolyte and gaseous oxygen. Porous carbon impregnated with a noble metal catalyst, e.g., Pt, Pt-Au, or Pt-Ir, etc., is particularly suitable for this purpose. Other electrodes that can be used include porous structures of acid resistant metals surfaced with an appropriate catalyst and porous, acid resistant organic membranes having one or two pposing sides surfaced with a continuousfilm of catalytic metal. Techniques are now available in the art for surfacing such membranes so as not to materially disturb their existing porosity.

The cathode of a cell-receiving power from an outside source of direct current or its equivalent, e.g., storage batteries, alternating current rectifiers, fuel cells, etc., need only be of an acid resistant material which is a good electron conductor and may take the form of a-metal sheet or grid. It may be coated with a suitable catalytic salt or metal to reduce the voltage required for the cathodic process in a manner well known in the art.

The electrolyte chamber must include means of ingress and egress for continuously introducing olefin-electrolyte extract and continuously removing ketone product. Product can be removed as an overhead vapor when such cell is operated at a temperature sufficient to give a significant vapor pressure of MEK above the mixture or at a temperature above the boiling point of MEK, but preferably is removed as a product containing electrolyte stream and sent to a product recovery unit from whence the electrolyte is recycled after separation. The cell or cells may be operated at temperatures as low as room temperature or below, e.g., about 35 F., at atmospheric pressure to temperatures in the range of 300-400 F. when superatmospheric pressures are employed. It is preferred, however, to operate at temperatures in the range of about 75-250 F., and more preferably in the range of l20l80 F. Operation at atmospheric pressure eliminates the complexities inherent in designing and controlling a pressure resistant reactor but certain reaction rate advantages are to be gained at elevated pressures, e.g., between 1 and 50 atmospheres.

The oxygen admitted to' the fuel cell cathode may be admitted as pure molecular oxygen, as air, or admixed with nitrogen or other inert gases.

A product stream comprising methyethyl ketone, secondary butyl alcohol and sulfuric acid is removed from reactor 19 via conduit 20 and passed to product recovery unit 21 to which is also passed the aforesaid upper butane comprising layer from settler 16 via line 22. In product recovery unit 21 a crude methylethyl ketone product is separated from a sulfuric acid electrolyte and passed to a finished unit, not shown, via conduit 101. A spent butane stream which may include traces of sulfuric acid in addition to nand iso-butanes is removed from product recovery unit 21 via line 102 and passed .to a butane rerun product recovery unit 21 will be described 'in greater detail hereinafter in the description of FIGURES II and III. Acid recovered from product recovery unit 21 is recycled via conduit 25, valve 26 and line 14 to extractor 11. A portion of this stream may be diverted from line 14 via valve 13 so as to pass through line 27 to reactor 19. If, however, a more concentrated acid is employed for the absorption of n-butylenes in extractor 11, as in a convention-a1 absorption step in the production of secondary butanol, e.g., about 7580 wt. percent H SO ,,water is added to dilute the extract to an acid concentration in the range of about 60-70 wt. percent or lower for use in electrochemical reactor 19. This water is added via line 18. In this embodiment the acid recovered from product recovery unit 21 could be passed via line 25, valve 26 and line 28 to acid reconcentration unit 8 which is designed to admit of blocked operation wherein acids of varying degrees of reconcentration can be alternately re leased for use in either isobutylene extraction unit 2 or n-butylene extractor 11. It is preferred, however, to minimize dilution wherever possible since the resulting reconcentration appreciably increases the cost of' production.

Referring to FIGURE II, the MEK-electrolyte eflluent from the electrochemical reactor 19 in FIGURE I is passed via

conduits

20 and 56 to pump 57 and mixed with the butane comprising upper layer from settler 16 of FIGURE I which is passed to pump 57 via

conduits

22 and 56. The resulting mixture is passed from pump 57 via line 58 to an agitator or mixer vessel 29 wherein sufficient agitation is created by jetting and/ or mechanical stirring means to effect a hydrocarbon-ketone-electrolyte emulsion. Portions of the contents of agitator 29 are continuously withdrawn via conduit 56 and recycled to this vessel via pump 57 and line 58. An overhead stream of such emulsion is removed from agitator 29 via line 30 and passed to settler 31 where the emulsion separates to form a lower acid comprising layer and an upper organic layer comprising methylethyl ketone and mixed butanes. This upper layer is continuously withdrawn and passed via line 32 to distillation column 33 for separation of the butanes from the crude MEK. Agitator 29 and settler 31 are also representative of a plurality of agitator-settler units which are preferably employed instead of the single units shown. A bottoms stream comprising MEK is removed from distillation column 33 via line 101 and passed to an MEK finishing or purification unit, not shown. An overhead stream from column 33 comprising butanes is divided at valve 34 with a portion thereof passed from the system via line 102 while the remainder is passed via conduit 35, compressor .36, condenser 37 and recycle condensate drum 38 to con- .duit 22 was to eventually return to agitator 29 and settler 31. The acid comprising lower layer formed in settler 31 is drawn off via con-duit 25 from whence it may be recycled to the n-butyle-ne extractor or, in part, to acid reconcentration unit.

I Referring now to FIGURE III which represents a modification of the flow-plans set forth in FIGURES I and II, the C stream from which isobutylene has been removed is passed via conduit 5, conduit 20, pump 41 and conduit 42 to n-butylene extractor 11 where the n-butanes are intimately contacted with 60-70 wt. percent sulfuric acid and therein form a hydrocarbon acid emulsion which passes overhead via line 15 to settler 16. A portion of the emulsion in extractor 11 is removed as bottoms via line 40 and recycled via conduit 20, pump 41 and conduit 42 back to extractor 11. The emulsion in settler 16 initially separates into an upper butane comprising layer and a lower extract layer comprising n-butylenes and sulfuric acid. As in the other drawings, extractor 11 and settler 16, although shown as single units, preferably represent a plurality of such units. The lower layer from settler 16 is passed via line 17 to electrochemical reactor 19. Line 18 provides means for admitting water or acid makeup to the system. An MEK-electrolyte efiluent from electrochemical reactor 19 is removed via line 20 and recycled via pump 41 and line 42 to extractor 11. After intimate mixing with the contents of extractor 11 the crude MEK product passes with the acid-hydrocarbon emulsion from extractor 11 through conduit 15 to settler 16 where upon separation it forms with the butanes an upper organic layer above the extract layer which is continuously withdrawn from the settler. This upper organic layer is removed from settler 16 via line 22 and passed to a distillation column 23 wherein the butanes are separated from the crude MEK product and passed from the system via conduit 102. The crude methylethyl ketone is removed from distillation tower 23 via conduit 101 and passed on to an MEK finishing or purification unit, not shown.

When the instant process is employed to produce acetone from propylene, acetone should be removed from the electrochemical cell as soon as possible after its formation since appreciable quantities of acetone in the electrolyte adversely affect the reaction rate. With higher molecular weight ketones no particular problem is presented by product accumulation and relatively high product concentrations in the electrolyte exhibit little, if any, effect on reaction rates.

This invention will be more fully understood from the following examples which are for purposes of illustration and should not be construed as limitations on the true scope of the invention.

Example I Ketones were produced electrochemically from a variety of olefin feedstocks in the following manner. Aqueous sulfuric acid electrolytes ranging in concentration from 0.5 to 12 moles H SO /liter were employed in a power driven electrolytic cell. The anode employed in such cell was a platinum sheet upon which platinum black had been elect-rodeposited while the cathode was a platinum wire screen. The source of power was rectified alternating current at an average potential of about 1 volt. In one embodiment electrolyte was placed in the cell and the olefin was admitted thereto as a gas. In another embodiment the olefin was preadsorbed in the electrolyte and admitted to the cell with the electrolyte. The gaseous efiluent from the cell was continuously collected and after several hours operation this and the electrolyte were analyzed.

The following table sets forth the conditions and resulting product distribution obtained from the conversion of three representative olefins to the corresponding ketones. In these runs the olefin was admitted to the cell as a gas.

TABLE I.ELECTROCHEMICAL PRODUCTION OF KE- TONES FROM OLEFINS IN SINGLE STAGE PROCESS Reaction Temp., F 180 Cone. of Electrolyte, Moles 8 10 10. HQSOJ/IitQr.

Olefin Feedstock Propylene" Butene-2 Pe2netene- Ketone Product Acetone Methyl Methyl ethyl propyl ketone. ketone.

Product Selectivity:

To Ketone, mole percent 50... To mole percent 22-30..

TION AND GAS FEED INTO ELECTROLYTE OF OPE RAT- ING CELL Reaction Temp, F 180 Cone. of Electrolyte, Moles HzSO4/liter 6 Efiect of Method of Feeding of Olefin on Product Dist.:

Preadsorption at 75 F.:

Selectivity to MEK, mole percent 60 75 Selectivity to CO mole percent a. 6-15 9-20 Gas Feed to Electrolyte:

Selectivity to MEK, mole percent 70 75 Selectivity to C02, mole percent 23-25 8-20 A separate oxidation was made with butene-Z and 10 molar H 80 to determine the effect of temperature on product selectivity. The reaction temperature employed was 120 F. The selectivity to MEK was slightly in creased with a corresponding decrease in selectivity to CO Example II Employing a processing unit in accordance with FIG- URES I and II of the drawings, methylethyl ketone is produced from n-butylenes from a mixed C hydrocarbon as hereinbefore described utilizing a 65 wt. percent sulfuric acid electrolyte in both the n-butylene extractor and the electrochemical reactor. The olefin is absorbed step-wise in 3 extraction stages, each employing a mixing chamber, an emulsion settler, emulsion circulator pump and emulsion cooler. Each mixer is equipped with jet orifices for intimate mixing of butane and extract phases. Pressure on the system is controlled by a pressure control valve in the spent butane line to the product recovery unit. The reaction temperature for each stage is controlled by the water rate to the emulsion coolers. The operating conditions are set forth in the following table.

TABLE III.ABSORPTION CONDITIONS OF n-BUTYLENES WITH 65% H2804 Rich Middle Lean Stage Stage Stage 1 2 3 Absorption Temp, F 115-125 115125 110 Settler Pressure, p.s.i.g 102 91 WITH 65 WT. PERCENT H2804 IN CLOSED ELECTROLYTE CIRCUIT Wt. Percent H 804, SBOH Free Basis 65' RecycleRatio, Moles of Reclaimed Acid to Electrochemical Reactor/Mole oi Reclaimed Acid to Extractor Total Feed to Electrochemical Reactor, Mole Percent:

H2804 H2O Sec. Butanol (absorbed olefin equivalent) MEK Moles Sec. Butanol/Mole HzSOt MEK Recovery by ExtractionMinimurn Partition Ceefiicient, Wt. Ratio of MEK in Hydrocarbon Extractant Divided by Wt. Ratio of MEK in Acid Phase NbPlO ren wowzmooc N w r umhzowoo Example Ill The process of Example II is repeated but modified so as to be conformed to the fiowplan of FIGURE III with direct recycle from electrochemical reactor to butylene absorber and the employment of an extraneous organic extractant.

Example IV v The process of Example 11 is repeated except for the modification wherein the extract is diluted prior to entry into a fuel cell type, power producing, electrochemical reactor in an amount corresponding to the amount of water loss in the air exhaust stream over water formation in the cell.

The term anodic oxidation employed herein shall be understood to include anodic dehydrogenation.

The term electrochemical reactor employed herein shall be understood to include both fuel cells which generate electrical energy and electrolytic cells driven by an external source of electrical energy.

What is claimed is:

1. A continuous process for converting a n-olefin to the corresponding ketone which comprises contacting a hydrocarbon mixture containing said olefin and a saturated hydrocarbon in an absorption zone with aqueous sulfuric acid, absorbing said olefin in said acid, separating the resulting olefin-acid extract from said mixture leaving an unabsorbed residue containing said saturated hydrocarbon, passing said olefin-acid extract to an electrochemical cell and utilizing the acid component of said extract as an electrolyte in said cell, electrochemically converting the absorbed olefin in said extract to the corresponding ketone by anodic oxidation of said absorbed olefin, continuously removing ketone-containing electrolyte from said cell, intimately contacting said ketone-containing electrolyte with said saturated hydrocarbon in liquid phase, separating a saturated hydrocarbon-ketone containing extract from said electrolyte and recovering said ketone therefrom.

2. A process in accordance with claim 1 wherein said ketone-containing electrolyte is continuously recycled to said absorption zone.

3. A process in accordance with claim 1 wherein said sulfuric acid contains about 60 wt. percent H 80 4. A process in accordance with claim 1 wherein the H 80 concentration of the aqueous sulfuric acid in said absorption zone and in said electrochemical reactor are essentially the same.

5. A process in accordance with claim 1 wherein the acid employed in said absorption zone is diluted with water before entering said electrochemical reactor.

6. A process in accordance with claim 1 wherein said n-olefin is a C n-olefin, said aqueous sulfuric acid has an H 50 concentration in the range of about 60 to 70 wt. percent, and said saturated hydrocarbon is butane.

7. A continuous process for producing methylethyl ketone which comprises contacting a C hydrocarbon mixture containing isobutylene, n-butylenes and butanes with a first aqueous sulfuric acid solution in an absorption zone, absorbing isobutylenes in said acid, separating the resulting isobutylene-acid extrace from said mixture leaving a first residual mixture comprising butanes and n-butylenes, contacting said first residual mixture with a second aqueous sulfuric acid solution having an acid concentration of above about 60 wt. percent absorbing n-butylenes in said acid, separating the resulting n-butylene-acid extract from said first residual mixture leaving a second residual mixture comprising butanes, passing said extract into an electrochemical cell utilizing the acid therein as the electrolyte for said cell, electrochemically converting absorbed n-butylenes in said extract to methylethyl ketone by anodic oxidation of the absorbed form of said n-butylenes, continuously removing a product stream from said cell comp-rising methylethyl ketone and sulfuric acid, passing said product stream to a product recovery unit, contacting said product stream with said butanes in liquid phase, separating from said product stream a methylethyl ketone-butane extract leaving an acid-comprising residue, recovering said methylethyl ketone from said butanes and recycling said residue to said absorption zone.

8. A process in accordance with claim 7 wherein said electrochemical react-or is operated at a temperature in the range of about 75250 F.

9. A process in accordance with claim 7 wherein said electrochemical reactor is operated at a temperature in the range of about 120-180* F.

10. A continuous process for converting a n-olefin of a hydrocarbon mixture to the corresponding ketone which process comprises contacting said mixture with aqueous sulfuric acid in an absorption zone, absorbing said olefin in said acid, separating an acid extract containing said olefin in absorbed form, utilizing the acid component of said extract as the electrolyte of an electrochemical cell, preparing said ketone by electrochemically converting said absorbed form of said olefin to said ketone by anodic oxidation, removing a ketone containing electrolyte from said cell, intimately contacting said ketone-containing electrolyte with a saturated hydrocarbon in liquid phase, separating from said ketonecontaining electrolyte a hydrocarbon-ketone comprising extract leaving an acid comprising aqueous residue, recovering said ketone from said hydrocarbon-ketone comprising extract and recycling said residue to said absorption zone.

11. A continuous process for converting a n-olefin of a hydrocarbon mixture to the corresponding ketone with simultaneous generation of electrical energy which process comprises contacting said mixture with aqueous sulfuric acid in an absorption zone, absorbing said olefin in said acid, separating an acid extract containing said olefin in absorbed form, utilizing the acid component of said extract as the electrolyte in an electrochemical cell having an anode and a cathode separated by said electrolyte and conduction means est-ablising electrical connection between said anode and cathode external to said electrolyte, maintaining said electrolyte at a temperature in the range of about to 250 F., passing oxygen gas into dual contact with said cathode and said electrolyte thereby initiating anodic oxidation of said absorbed form of said olefin at said anode to said ketone, removing a ketone-containing electrolyte from said cell, intimately contacting said ketone-containing electrolyte with a saturated hydrocarbon in liquid phase, separating from said ketone-containing electrolyte a hydrocarhon-ketone comprising extract leaving an acid comprising aqueous residue, recovering said ketone from said hydrocarbon-ketone comprising extract and recycling said residue to said absorption zone.

12. A process in accordance with claim 11 wherein said electrolyte temperature is maintained in the range of about 120 to 180 F.

13. A process in accordance with claim 11 wherein said electrolyte temperature is maintained in the range of about 180 to 250 F.

References Cited UNITED STATES PATENTS 1,365,053 1/1921 Ellis et al. 20480 2,384,463 9/1945 Gunn et al 13686 2,658,069 11/1953 Van der Waals 260-593 2,756,266 7/1956 Francis 260677 2,925,454 2/1960 Justi et al. 13686 2,981,767 4/1961 Gay et al 260677 2,992,284 7/1961 Sanford et a1. 260677 OTHER REFERENCES Proceedings Thirteenth Annual Power Sources Conference, April 1959, page 107.

JOHN H. MACK, Primary Examiner.

JOHN R. SPECK, MURRAY TILLMAN, WINSTON A. DOUGLAS, Examiners.

G. KAPLAN, H. FLOURNOY, Assistant Examiners.

Claims

1. A CONTINUOUS PROCESS FOR CONVERTING A N-OLEFIN TO THE CORRESPONDING KETONE WHICH COMPRISES CONTACTING A HYDROCARBON MIXTURE CONTAINING SAID OLEFIN AND A SATURATED HYDROCARBON IN AN ABSORPTION ZONE WITH AQEOUS SULFURIC ACID, ABSORBING SAID OLEFIN IN SAID ACID, SEPARATING THE RESULTING OLEFIN-ACID EXTRACT FROM SAID MIXTURE LEAVING AN UNABSORBED RESIDUE CONTAINING SAID SATURATED HYDROCARBON, PASSING SAID OLEFIN-ACID EXTRACT TO AN ELECTROCHEMICAL CELL AND ULITIZING THE ACID COMPONENT OF SAID EXTRACT AS AN ELECTROLYTE IN SAID CELL, ELECTROCHEMICALLY CONVERTING THE ABSORBED OLEFIN IN SAID EXTRACT TO THE CORRESPONDING KETONE BY ANODIC OXIDATION OF SAID ABSORBED OLEFIN, CONTINUOUSLY REMOVING KETONE-CONTAINING ELECTROLYTE FROM SAID CELL, INTIMATELY CONTACTING SAID KETONE-CONTAINING ELECTROLYTE WITH SAID SATURATED HYDROCARBON IN LIQUID PHASE, SEPARATING A SATURATED HYDROCARBON-KETON CONTAINING EXTRACT FROM SAID ELECTROLYTE AND RECOVING SAID KETONE THEREFROM.