Technical Background Corresponding aldehydes or ketones obtained by oxidizing olefins with molecular oxygen are industrially useful compounds, and their synthesis by catalytic reactions have been carried out for a long time.

Particularly useful method among them is a reaction generally known as Wacker reaction. That is, a method in which acetaldehyde is produced from ethylene, and acetone from propylene, by molecular oxygen using an aqueous solution containing PdCl2 and CuCl2 as the catalyst has been employed industrially. However, in this conventional Wacker reaction, the aqueous solution is under a strongly acidic condition and highly corrosive hydrochloric acid is present, so that this is not always an industrially advantageous process from the viewpoint that high-grade materials are required for the reactors and peripheral devices and the reactive substrates are limited to lower hydrocarbons such as ethylene and propylene.

As a reaction analogous to the conventional Wacker reaction, a ketone-forming reaction of olefin by a hydroperoxide complex of Pd (Pd-OOH species) has also been examined (JP-A-57-156428 (corresponds to U. S. Patent 4, 400, 544), JP-A-60-92236, JP-A-61-60621 ; the term"JP-A" as used herein means an"unexamined published Japanese patent application"). In this reaction, a monohydric alcohol such as methanol or ethanol is used as the reaction medium instead of water which is used in the conventional Wacker reaction, and metal salts of Pd and Cu and/or Fe are used as the catalyst, but as a industrial process, this reaction has fatal disadvantages such as low selectivity of ketone or aldehyde as the product and precipitation of Pd metal when the reaction condition is shifted to high temperature side. These documents describe that the co-catalysts Cu and Fe have equivalent effect.

Also, J. Org. Chem., vol. 34, 3949 (1969) discloses that 1, 4-dioxospiro [4, 5] decane is obtained from cyclohexene with a high yield by the use of PdCl2 and CuCl2 as the catalyst and a polyhydric alcohol such as ethylene glycol or glycerol as the reaction solvent, but it does not describe details such as illustrative yield. This document does not describe about the use of iron salt as a catalyst component and also does not disclose about a method for solving the Pd precipitation which is a fatal disadvantage as a industrial process.

As described above, it is the present situation that an industrially effective method for the synthesis of corresponding aldehydes or ketones from olefins has not been found yet.

Particularly, cyclohexanone useful as a precursor of caprolactam is produced by a method in which cyclohexane is oxidized in the presence, as occasion demands, of a catalyst and the cyclohexanone-cyclohexanol mixture is dehydrogenated or a method in which cyclohexanol obtained by hydrating cyclohexene is subjected to dehydrogenation reaction. However, since the formed products in the former method are apt to undergo oxidation successively during the oxidation of cyclohexane, it is necessary to control the conversion to a considerably low level and to circulate large excess of unreacted cyclohexane, so that this method becomes a process having low energy efficiency as a result. Also, the latter method has problems in that yield of the hydration reaction is not sufficient and a large quantity of energy is consumed when cyclohexene is extracted and separated from a benzene-cyclohexane mixture having markedly close boiling point or when cyclohexanone alone is separated from an approximately equimolar cyclohexanone-cyclohexanol mixture having high boiling point.

Consequently, if there is a method for the selective and efficient synthesis of an aldehyde or ketone, particularly cyclohexanone, from corresponding olefin such as cyclohexene, its meaning is considerably large.

With the aim of solving such problems involved in the oxidation reaction of olefins, the present inventors have conducted intensive studies and found that the industrially fatal phenomenon of Pd precipitation can be prevented and reduction of the catalytic activity can be inhibited when (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table is used in addition to (a) palladium and (c) a halogen as the catalyst, in producing a ketal and/or acetal by allowing olefins to react with oxygen and a polyhydric alcohol, thus resulting in the accomplishment of the invention.

Disclosure of the Invention Accordingly, the gist of the invention resides in n the following aspects.

(1) A method for producing a ketal and/or acetal by allowing olefins having at least one ethylenic double bond to react with oxygen and a polyhydric alcohol in the presence of a catalyst, which comprises carrying out the reaction in the presence of (a) palladium, (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table and (c) a halogen as the catalyst.

(2) The method for producing a ketal and/or acetal as described in (1), wherein the reaction is carried out in a catalyst-dissolved liquid phase.

(3) The method for producing a ketal and/or acetal as described in (1) or (2), wherein copper is further included as the catalyst.

(4) The method for producing a ketal and/or acetal as described in (3), wherein the catalyst compound to be used as the copper source is at least one of copper (I) chloride and copper (II) chloride.

(5) The method for producing a ketal and/or acetal as described in (3) or (4), wherein copper is used in an amount of from 0. 1 to 100 mole times, based on the (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table.

(6) The method for producing a ketal and/or acetal as described in any one of (1) to (5), wherein the (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table is a metal selected from iron, cobalt, nickel and tin.

(7) The method for producing a ketal and/or acetal as described in (6), wherein the (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table is iron.

(8) The method for producing a ketal and/or acetal as described in any one of (1) to (7), wherein the (c) halogen is chlorine (Cl).

(9) The method for producing a ketal and/or acetal as described in any one of (1) to (8), wherein concentration of palladium in the reaction solution is from 0. 001 to 10% by weight.

(10) The method for producing a ketal and/or acetal as described in any one of (1) to (9), wherein molar ratio of the (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table to palladium in the reaction solution is from 0. 1 to 100.

(11) The method for producing a ketal and/or acetal as described in any one of (1) to (10), wherein molar ratio of the (c) halogen to palladium in the reaction solution is from 0. 1 to 100.

(12) The method for producing a ketal and/or acetal as described in any one of (1) to (11), wherein the catalyst compound to be used as the source of (a) palladium is palladium chloride.

(13) The method for producing a ketal and/or acetal as described in any one of (1) to (12), wherein the catalyst compound to be used as the source of (a) palladium is a compound of divalent palladium.

(14) The method for producing a ketal and/or acetal as described in any one of (1) to (13), wherein the catalyst compound to be used as the source of (a) palladium is a nitrile compound-coordinated compound.

(15) The method for producing a ketal and/or acetal as described in any one of (1) to (14), wherein the catalyst compound to be used as the source of (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table is a chloride.

(16) The method for producing a ketal and/or acetal as described in any one of (1) to (15), wherein chlorine as the (c) halogen is used as a chloride of (a) or (b).

(17) The method for producing a ketal and/or acetal as described in any one of (1) to (16), wherein the olefins are a cyclic olefin having from 4 to 10 carbon atoms.

(18) The method for producing a ketal and/or acetal as described in (17), wherein the olefins are cyclohexene.

(19) The method for producing a ketal and/or acetal as described in any one of (1) to (16), wherein the olefins are a terminal olefin having from 2 to 25 carbon atoms.

(20) The method for producing a ketal and/or acetal as described in any one of (1) to (16), wherein the olefins are an internal olefin having from 4 to 25 carbon atoms.

(21) The method for producing a ketal and/or acetal as described in any one of (1) to (20), wherein the polyhydric alcohols are aliphatic or alicyclic diols.

(22) The method for producing a ketal and/or acetal as described in any one of (1) to (21), wherein the polyhydric alcohol is used in an amount of from 1 to 100 mole times, based on the olefins.

(23) A method for producing a ketone and/or aldehyde by hydrolyzing the ketal and/or acetal obtained by the method as described in any one of (1) to (22), in the presence of an acid catalyst.

Best embodiment for implementing the Invention (Catalysts) The catalyst of the invention is composed of components comprising (a) palladium, (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table and (c) a halogen. In this case, the components of (a) to (c) may be present in the reaction system in any form such as dissociated ions, salts or molecules.

The (a) palladium may be in divalent to tetravalent form, and can be selected optionally from known and commercially available compounds. Its examples include palladium halides such as palladium chloride and palladium bromide, palladium salts of inorganic acid or organic acid, such as palladium nitrate, palladium sulfate, palladium acetate, palladium trifluoroacetate and palladium acetylacetonate and inorganic palladium such as palladium oxide and palladium hydroxide. Also useful are base- coordinated compounds derived from these metal salts, such as [Pd (en) 2] C12, [Pd (phen) 2] C12, [Pd (CH3CN) 2] C12, [Pd (C6H5CN) 2] C12, [Pd (C204) 2] 2, [PdCl2 (NH3) 2] and [Pd (N02) 2 (NH3) 2] though not limited thereto (wherein en represents ethylenediamine, and phen represents 1, 10- phenanthroline). Among these palladium sources, it is desirable to use a divalent palladium source, particularly as a chloride or a nitrile compound-coordinated compound.

The role of palladium in the catalyst system is expressed by its mutual action with iron ion and polyhydric alcohol, but the action condition is not always clear. Since the essence is that palladium expresses its activity by constituting an active species with other catalyst components, it is enough if a palladium source sufficient for inducing the essence is present in the system.

As the (b) at least one metal other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table, iron, cobalt, nickel, ruthenium and tin can be cited, of which iron is preferred.

The catalyst compound to be used as iron source may be in a divalent or trivalent form. For example, it can be used in the reaction as various salts including chlorides such as iron (II) chloride and iron (III) chloride, bromides such as iron (II) bromide and iron (III) bromide, inorganic acid salts such as iron (II) sulfate, iron (III) sulfate, iron (II) nitrate and iron (III) nitrate and salts such as iron (II) acetate, iron (III) acetate, iron (II) oxalate, iron (III) oxalate, iron formate and iron acetylacetone, or in the form of coordination compounds thereof. Similar to the case of palladium, the essence is that iron expresses its activity by constituting an active species with other catalyst components, so that it is enough if an iron source sufficient for inducing the essence is present in the system.

The catalyst compound to be used as the source of cobalt, nickel, ruthenium or tin may be in a divalent, trivalent or tetravalent form. Illustratively, various salts including their halides such as chloride and bromide, inorganic acid salts such as sulfate and nitrate and salts such as acetate, oxalate, formate and acetylacetonate salt, or coordination compounds thereof can be used. When the component (b) is cobalt, nickel, ruthenium or tin, it is desirable to further combine with copper.

The main effect of the invention is that the Pd precipitation is markedly inhibited by the addition of the component (b), but further addition of a copper compound such as CuCl or CuCl2 thereto exerts another advantageous result as an industrial process in which the reaction rate is improved and by-products such as halides are reduced.

The halogen (c) is chlorine (Cl) and/or bromine (Br), but chlorine (Cl) is particularly preferable. The halogen may be present in the reaction system as counter anions of Pd and/or Fe. Also, it is possible to supply it to the reaction system as a halide of other catalyst component or in a certain form such as HC1 or HBr, but it is necessary that such a compound is present in the reaction system in the form of ions in ether case.

According to the invention, a ketal and/or acetal is produced by allowing olefins to react with oxygen and a polyhydric alcohol in a liquid phase in which the catalyst described above is dissolved.

(Olefins) The olefins to be used in the invention are aliphatic or alicyclic organic compounds containing at least one ethylenic double bond. As chain olefins, olefins having generally 2 or more, preferably from 2 to 25, more preferably from 3 to 10 carbon atoms, such as ethylene, propylene, butene, pentene, hexene and octene, can be cited. In this case, the position of double bond may be either terminal or internal, and an acetal or ketal of methyl ketones is mainly formed in the case of terminal olefin, and a corresponding ketal is mainly obtained in the case of internal olefin.

Examples of cyclic olefins include compounds having from 4 to 10, preferably from 5 to 8 carbon atoms and containing at least one ethylenic double bond, such as cyclopentene, cyclohexene, cyclohexadiene, cycloheptene and cyclooctene, of which cyclopentene and cyclohexene are particularly useful compounds industrially. When cyclohexene is used as the olefins, 1, 4- dioxospiro [4, 5] decane (to be referred to as cyclohexanone ketal hereinafter) is formed as the product.

At least one substituent group such as alkyl group, alkoxy group, aryl group, phenyl group, carboxyl group, halogen atom or nitro group may be present on any position of the principal chain of these olefins. For example, olefins having a functional group such as acrylonitrile, acrolein, acrylic acid or vinyl chloride on the 2-position, or styrene or methylstyrenes undergo the reaction suitably.

In addition, a compound having condensed ring, such as 3, 4-dihydronaphthalene, can also be used if it has an ethylenic double bond.

(Polyhydric alcohol) The polyhydric alcohol is generally divalent to tetravalent, and diols are particularly desirable. In the case of a diol, it generally has 2 or more carbon atoms, but preferably from 2 to 10, more preferably from 3 to 8 carbon atoms when cost, stability and easy formation of acetal or ketal are taken into consideration, and preferred illustrative examples of these diols include ethylene glycol, 1, 3-propanediol, 1, 2-dihydroxybutane, 1, 2-dihydroxypropane, 1, 4-butanediol, 1, 4-cyclohexane- dimethanol, 1, 2-cyclohexanedimethanol, diethylene glycol, 1, 2-trans-cyclopentanediol, 2, 4-pentanediol, styrene glycol, 1, 5-dihydroxycyclooctane, 1, 4-dihydroxycyclooctane, 2, 5-dihydroxynorbornane, 2, 6-dihydroxynorbornane, 1, 4- dihydroxy-2, 3-dimethylbutane, 1, 5-dihydroxy-2, 4-dimethyl- pentane, cyclobutane-1, 2-dimethanol, cyclohexane-1, 3- dimethanol, 1, 4-dihydroxy-2, 3-dichlorobutane and 2, 5- dihydroxyhexane, with ethylene glycol, 1, 3-propanediol, 1, 2-dihydroxybutane, 1, 2-dihydroxypropane, 1, 4-butanediol, 1, 4-cyclohexanedimethanol, 1, 2-cyclohexanedimethanol, diethylene glycol, 1, 2-transcyclopentanediol, 2, 4- pentanediol, styrene glycol being further preferred. Two or more of them may be used in combination.

Though the reason why a polyhydric alcohol is necessary in the invention is not absolutely clear, it is considered that when palladium starts in a divalent form such as chloride, and then forms a divalent peroxy complex as a new active component, and it is considered that alcohol makes an effective role for the induction of this active species. In addition to this role, it reacts with the formed aldehyde or ketone to form corresponding acetal or ketal, so that markedly high stability against the oxygen oxidation is secured in comparison with free aldehyde and ketone. Thus, it becomes possible to maintain selectivity of the product of interest at markedly high level.

When monohydric alcohols such as methanol, ethanol or propanol are used instead of polyhydric alcohols, the product is mainly an aldehyde or ketone compound, and formation of the corresponding acetal or ketal is extremely small. Since these free aldehyde and ketone are unstable in the presence of oxygen, they are successively oxidized so that the yield of intended aldehyde or ketone is not always high. Contrary to this, when polyhydric alcohols including divalent diols such as ethylene glycol, propylene glycol and butanediol are used, corresponding acetal or ketal can be obtained as the main product. Since the thus obtained acetal or ketal hardly undergoes successive oxidation under oxidation reaction conditions, yield of the aldehyde or ketone obtained by hydrolyzing the former is markedly high.

(Reaction conditions) According to the invention, the use of oxygen- containing gas is a necessary condition, but since there is a possibility that oxygen and an organic compound may form an explosive mixture at a certain temperature, under a certain pressure range and within a certain compositional range, it is necessary to avoid the danger.

The reaction will proceed if the partial pressure of oxygen is 0. 001 MPa or more, but the reaction rate becomes slow and the catalyst tends to be inactivated if the oxygen partial pressure is too low. In the invention, it is preferably from 0. 01 to 10 MPa and more preferably from 0. 05 to 5 MPa, but most preferable pressure is selected from the safety and economical points of view.

The reaction will proceed when the reaction temperature is 0°C or more, but since temperature- dependency of the reaction of the invention is large, more higher temperature is desirable. Though the reaction temperature is selected by taking formation conditions of explosive mixtures and increase in by-products due to radical auto-oxidation into consideration, but an economically significant reaction rate can be obtained within a temperature range of generally from 20 to 200°C, preferably from 40 to 180°C. Total pressure of the reaction may be a liquid phase holding pressure or more, but is generally from 0. 1 MPa to 20 MPa, preferably from 0. 1 MPa to 15 MPa. Also, the reaction time (residence time) is generally from 5 seconds to 20 hours, preferably from 10 seconds to 10 hours.

Concentration of the (a) palladium as a catalyst is within the range of from 0. 001 to 10% by weight, preferably from 0. 01 to 5% by weight, as [Pd2+] based on the total weight of reaction solution. Under high concentration condition, the reaction rate shows a different concentration-dependency from that under low concentration condition, and the catalytic efficiency tends to worsen, so that an efficient concentration is selected from the economical point of view.

Concentration of the (b) at least one metal M other than palladium belonging to the groups 8, 9, 10 and 14 of the periodic table can be described as its relative concentration to (a) palladium. That is, it can be selected within the range of generally 0. 1< [M]/ [Pd] <100 (molar ratio), preferably 0. 1< [M]/ [Pd] <10 (molar ratio).

The concentration if lower than this would entail a tendency of reducing the reaction rate and also a tendency of reducing the Pd precipitation inhibition effect as the principal effect of the metal (b). Also, its addition in too large amount may not inhibit the reaction itself but will cause a tendency of limiting its dissolving amount in the reaction system.

Relative concentration of the halogen (c) to Pd is within the range of generally 1< [Cl and/or Br]/ [Pd] <100 (molar ratio) and preferably 0. 3< [C1 and/or Br]/ [Pd] <50 (molar ratio). Since there is a possibility of causing corrosion of the reactor material by water in the reactor under a high halogen concentration condition, it is desirable to select concentration of the halogen in such a level that the catalyst system functions within a level as low as possible. Also, a component containing a catalyst- derived halogen may be formed in some cases as a part of by-products, and in that case, it is desirable to supply the consumed halogen continuously or periodically in the form, e. g., of its metal salt.

The existing amount of polyhydric alcohols in the reaction system may be the theoretical amount (1 mole) based on olefin, but according to the invention, it is desirable to use also as a reaction solvent. It is within the range of generally from 1 to 99% by volume, preferably from 5 to 99% by volume, based on the total reaction volume. Also, amount of the polyhydric alcohol is generally from 1 to 100 moles, preferably from 2 to 50 moles, based on olefin. The existing amount of olefins in the reaction system can be selected within the range of generally from 1 to 99% by volume, preferably from 1 to 50% by volume.

When concentration of polyhydric alcohols is relatively low, namely when relative concentration of olefins is too high, it may entail a tendency of easily causing precipitation of palladium due to distribution of a part of the catalyst components into the olefin phase.

If the polyhydric alcohol concentration is too large, on the other hand, concentration of supplied olefin becomes relatively small and tends to entail low productivity and a difficulty in carrying out phase separation after the reaction. In such cases, it is possible to adjust relative concentrations of polyhydric alcohols and olefins and further improve phase separation characteristics, by adding an oxidation-inert third component to the reaction system.

According to the invention, it is possible to increase the activity and reactivity by further adding another component. For example, an additive agent having an effect to enhance the oxidation reaction, such as a copper compound or an alkali, alkaline earth or rare earth metal, may be added. Also, a method in which side reactions are inhibited by adding a radical trapping agent may be employed.

In a mass production process, particularly like the method for the production of cyclohexanone from cyclohexene among the reactions of the invention, efficient separation of certain impurities even in trace amounts is required when material balance in the total process is taken into consideration. For example, formation of impurities which are particularly hard to separate and have a possibility of exerting bad influences upon the product, such as cyclohexenone, cyclohexenol, chlorocyclohexanone and cyclohexenone ketal, should be controlled as small as possible.

The reaction of the invention can be carried out in accordance with the general oxidation reaction. When each component of the catalyst is present in the state of solution, the oxidation reaction can be effected using a batch reactor and by allowing olefins to contact with an oxygen-containing gas for a specified period of reaction time or using a continuous phase reactor and by continuously supplying an oxygen-containing gas and olefins. On the other hand, when the catalyst components of the invention are immobilized, the liquid phase reaction can be used, or a so-called trickle bed system can be employed in which the catalyst is packed in a fixing bed and corresponding olefins and oxygen are supplied as a liquid phase.

Regarding the supply of oxygen, a technique effective for dissolving oxygen in the reaction solution system, such as a technique in which the oxygen-containing gas is made into fine bubbles using mixing blades, a technique in which oxygen gas is made into fine bubbles by arranging baffle plates in the reactor or a technique in which the gas is sprayed into the system with a high linear velocity from a nozzle, can be employed.

(Treatment after oxidation reaction) The reaction product solution after oxidation reaction contains the material olefin, the ketal and/or acetal as the product, the catalyst components and the polyhydric alcohol. When the reaction product solution is under a pressurized condition, the pressure may be reduced by releasing it to a certain degree. When boiling points of the olefin and ketal and/or acetal in the reaction product solution are low greatly differing from that of the polyhydric alcohol solvent, these low boiling point components (olefin and ketal and/or acetal) can be separated directly from the reaction product solution by distillation. The polyhydric alcohol solution containing the catalyst components, obtained as bottoms of the distillation, can be recycled to the oxidation reaction step.

Also, when boiling points of the olefin and ketal and/or acetal are higher than that of the polyhydric alcohol solvent, an extraction solvent such as an organic solvent which forms two phase with the polyhydric alcohol is added, and two phase separation is carried out by extraction to separate the extraction solvent phase containing the olefin and ketal and/or acetal from the polyhydric alcohol phase containing the catalyst components. Thereafter, the olefin and ketal and/or acetal are recovered from the extraction solvent phase, and then the ketal and/or acetal can be taken out by distillation separation. The polyhydric alcohol phase containing the catalyst components can be recycled to the oxidation reaction step. In the two phase separation, when the extraction solvent side containing the olefin and ketal and/or acetal is contaminated with trace amounts of the catalyst components, the remaining amount of catalyst components in the extraction phase can be reduced to a negligible level by carrying out extraction of the extraction solvent phase twice or more with the polyhydric alcohol solvent. Also, it is possible to employ a technique in which the olefin and ketal and/or acetal are separated from the extraction solvent phase by distillation after the first two phase separation, thereby increasing the residual catalyst concentration in the extraction solvent phase to a certain degree, and then the extraction is carried out again.

In addition, water is formed in the reactor during the ketal formation by successive oxidation though slight.

It is desirable to remove the thus formed water from the reaction system as many as possible, but even then, when a halogen component such as Cl remains in the system, a possibility of its participation in the corrosion of reactor is large. Consequently, it is necessary to use a material having high resistance to a corrosive acid such as hydrogen chloride in necessary parts.

Materials such as glass, ceramics and Teflon can be used in a region where the reaction pressure is not so high, but in the case of high reaction pressure, it is desirable to use a vessel generally used as a corrosion- resistant reactor, namely a vessel made of an alloy such as a stainless alloy, particularly which is commonly called Hastelloy, an alloy containing titanium or an alloy containing zirconium, or a vessel in which these alloys are coated and adhered by compression to the surface.

Though the reactor has a particularly high possibility of undergoing corrosion, when a standing vessel and separation vessel are further arranged, these parts also have a high possibility of undergoing corrosion. In addition, in the case of the distillation of an oil phase containing the product, when the catalyst component is left, there is a possibility that the halogen component is concentrated, thus also having a high possibility of undergoing corrosion. It is desirable to use a corrosion- resistant material in these main containers and piping attached thereto, depending on the degree of possibility of corrosion within an economically acceptable range.

The polyhydric alcohols which are present in the reaction system as essential components are not completely inactive to the oxidation reaction. Also, though in extremely small amounts, some compounds formed by the successive oxidation of olefins have similar polarity to that of polyhydric alcohols. Thus, when a batch reaction is repeated for a prolonged period of time or in the case of a continuous reaction, certain components which are derived from the polyhydric alcohols and olefins but not necessarily desirable for the reaction are accumulated in the alcohol phase containing catalyst components. In order to operate the process stably, it is necessary to control the total material balance promptly. Consequently, it is necessary to supply new solution of catalyst materials by removing a part of the catalyst-containing polyhydric alcohol phase from the system, in response to the formation rate of these impurities and the formation rate of successively oxidized components. In that case, when the removing ratio of catalyst components removed from the system is large and the economical burden therefore is large, it is necessary to recover the catalyst components.

Its method is not limited, but a technique including removal of the organic matter, washing and recover of the metal components is effective.

Also, when an extraction solvent such as an organic solvent is recovered by distillation from the extraction solvent phase containing the two phase-separated product (ketal and/or acetal), accumulation of impurities may also occur in the same manner, and new extraction solvent can be supplied by removing a part of the old extraction solvent in this case too.

The ketal and/or acetals obtained by the invention are converted into corresponding ketones and/or aldehydes by carrying out hydrolysis in the presence of water and an acid. Examples of the acid which can be used in this case include mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, polyacids such as a heteropolyacid, and solid acids such as an ion exchange resin, zeolite and clay. The aldehydes and ketones of interest can be efficiently obtained by recovering water and polyhydric alcohols from the thus obtained reaction product solution rich in aldehydes and/or ketones and then separating and purifying the aldehydes and ketones as the intended compounds.

Also, the ketal and/or acetals obtained by the invention can be converted efficiently into corresponding alcohols by carrying out hydrogenation in the presence of water, a hydrogen source and a hydrogenation catalyst.

Examples of the hydrogen source include hydrogen, formalin and disodium borohydride (NaBH4), and examples of the hydrogenation catalyst include Raney Ni, Raney Co, an oxide containing Cu-Cr, a catalyst in which a group 8 metal such as Pd, Pt or Ru is carried on a carrier and a complex catalyst which uses a group 8 metal such as Ru, Pt or Pd as the central metal. The alcohols of interest can be efficiently obtained by recovering water and the acetal and/or ketal-formed alcohol from the reaction product solution which is obtained by hydrogenation and rich in alcohols and then separating and purifying the alcohols as the intended compounds.

The invention is described more illustratively by examples in the following, but the invention is not limited to these examples.

Examples EXAMPLE 1 A drum-shaped Pyrex reactor of 40 mm in inner diameter and 12 mm in height equipped with a magnetic bar and a gas-introducing tube was charged with 0. 1 mmol of Pd (CH3CN) 2Cl2, 0. 1 mmol of CUC12, 0. 1 mmol of FeCl3, 10 ml of ethylene glycol and 20 mmol of cyclohexene, the air was replaced with pure oxygen and then the reaction was carried out at 40°C for 5 hours under stirring. By adding an internal standard compound to the reaction solution, the product was analyzed by a gas chromatography. As a result, the cyclohexene conversion was 2. 5%, and cyclohexanone ketal was obtained with a yield of 2. 5%. TOF = 1. 0/hour. TOF means the formation rate of cyclohexanone and cyclohexanone ketal (mol) per 1 mol Pd per hour. In this case, only cyclohexanone ketal was formed.

Precipitation of palladium was not found in the solution after the reaction. Also, chlorocyclohexane was not formed.

EXAMPLE 2 The reaction was carried out in accordance with the procedure of Example 1, except that CuCl2 was not added.

As a result, the cyclohexene conversion was 2. 5%, and cyclohexanone ketal was obtained with a yield of 2. 5%. The TOF was 1. 0/hour. By-production of 1. 0 mol% chlorocyclohexane based on the cyclohexanone ketal was found. Precipitation of palladium was not found in the solution after the reaction.

COMPARATIVE EXAMPLE 1 The reaction was carried out in the same manner as described in Example 1, except that FeCl3 was not added.

As a result, the cyclohexene conversion was 2. 3%, the cyclohexanone ketal yield was 2. 3%, and the TOF was 0. 92/hour. After the reaction, reaction solution was turbid by fine black powder of Pd-black and precipitation of palladium was found on the bottom and the inner wall of the reactor.

Table 1 Pd Fe CHE Ketal TOF*** Remarks compd. compd. conv.* yield** Pd not precipitated, Example 1 0.1 mmol 0.1 mmol 0.1 mmol 2.5% 2.5% 1.0/hour chlorocyclohexane not formed Example 2 Pd not precipitated, 0.1 mmol 0.1 mmol not used 2.5% 2.5% 1.0/hour chlorocyclohexane formed Comparative Pd precipiated 0.1 mmol not used 0.1 mmol 2.3% 2.3% 0.92/hour Example 1 *: Cyclohexene conversion<BR> **: Cyclohexanone ketal yield<BR> ***: formation rate of cyclohexanone and cyclohexanone ketal per 1 mol Pd per hour By comparing Examples 1 and 2 with Comparative Example 1, it can be seen that precipitation of Pd is inhibited by the addition of Fe. It can be seen also that the formation of chlorocyclohexane is inhibited by further adding a copper compound.

EXAMPLE 3 A cylinder type Teflon beaker of 40 mm in inner diameter and 15 mm in height equipped with a magnetic stirrer was inserted into a SUS-316 autoclave having a withstand pressure of 100 kG and a size just fitted to the beaker, and the reaction was carried out at a reaction temperature of 80°C for 1 hour under an oxygen pressure of 7 kG using the same charging composition of Example 1. As a result, reaction product rates of cyclohexanone ketal/cyclohexanone = 24. 8 and cyclohexanone ketal/cyclohexenone = 26. 1 were obtained with the cyclohexene conversion of 30% and the TOF of 60/hour.

After completion of the reaction, precipitation of Pd was not found.

EXAMPLE 4 The reaction was carried out in the same manner as described in Example 3, except that CuCl was not used. As a result, the cyclohexene conversion was 34% and the TOF was 67/hour. Chlorocyclohexane was formed in an amount of 1 mol% based on the ketal. After completion of the reaction, precipitation of Pd was not found.

COMPARATIVE EXAMPLE 2 The reaction was carried out in the same manner as described in Example 4, except that FeCl3 was not used and CuCl2 or CuCl was used in a predetermined amount. The results are shown in Table 2. Precipitation of Pd was found in all cases.

Table 2 Copper compound Cyclohexene conversion TOF* (/hour) CuCl (0. 1 mmol) 13. 5% 27 CUC12 (0. 1 mmol) 21. 0% 42 CuCl2 (0. 2 mmol) 45. 0% 90 * : formation rate of cyclohexanone and cyclohexanone ketal per 1 mol Pd per hour It can be seen from the above results that precipitation of Pd does not occur and the catalyst effectively functions when Fe is allowed to exist in the system, even if the oxygen concentration is increased and the cyclohexene conversion reaches a high level.

EXAMPLE 5 The reaction was carried out in the same manner as described in Example 1, except that a mixed solution of ethanol 5 ml + ethylene glycol 2. 5 g was used instead of ethylene glycol. As a result, the cyclohexene conversion was 22%, the (cyclohexanone + cyclohexanone ketal) yield was 21. 0%, the (cyclohexanone ketal + cyclohexanone) selectivity was 95% and the TOF was 8. 4/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 6 The reaction was carried out in the same manner as described in Example 1, except that a mixed solution of methanol 5 ml + ethylene glycol 2. 5 g was used instead of ethylene glycol. As a result, cyclohexanone ketal and cyclohexanone were obtained at a ratio of 17. 6, with the cyclohexene conversion of 10. 0%, the (cyclohexanone + cyclohexanone ketal) yield of 10. 0% and the TOF of 4. 0/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 7 The reaction was carried out in the same manner as described in Example 1, except that a mixed solution of 1, 4-butanediol 7. 5 g + ethylene glycol 2. 5 g was used instead of ethylene glycol. As a result, the cyclohexene conversion was 22% and the TOF was 8. 0/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 8 The reaction was carried out in the same manner as described in Example 1, except that 1, 3-propanediol was used instead of ethylene glycol. As a result, reaction products of cyclohexanone ketal/cyclohexanone = 2. 87 and cyclohexanone ketal/cyclohexenone = 16. 1 were obtained with the cyclohexene conversion of 16%. Regarding the (cyclohexanone + ketal) formation rate, the TOF was 6. 4/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 9 The reaction was carried out in the same manner as described in Example 1, except that 1, 4-butanediol was used instead of ethylene glycol. As a result, reaction products of cyclohexanone ketal/cyclohexanone = 0. 41 and cyclohexanone ketal/cyclohexenone = 4. 93 were obtained with the cyclohexene conversion of 27%. The (cyclohexanone + ketal) selectivity was 79% and the TOF was 8. 5/hour.

Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 10 The reaction was carried out in the same manner as described in Example 1, except that 2, 3-butanediol was used instead of ethylene glycol. As a result, the cyclohexene conversion was 7%, the (cyclohexanone ketal + cyclohexanone) selectivity was 91. 5% and the TOF was 2. 6/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 11 The reaction was carried out in the same manner as described in Example 1, except that 1, 2-cyclohexanediol was used instead of ethylene glycol. As a result, the cyclohexene conversion was 12%, cyclohexanone ketal/cyclohexanone was 3. 7, the (cyclohexanone ketal + cyclohexanone) selectivity was 90% and the TOF was 4. 3/hour. Precipitation of Pd was not found in the solution after the reaction.

COMPARATIVE EXAMPLE 3 The reaction was carried out in the same manner as described in Example 1, except that ethanol was used instead of ethylene glycol. As a result, the cyclohexene conversion was 35% and the cyclohexanone yield was 17%.

The selectivity of cyclohexanone was 51%. Precipitation of palladium was not found on the inner wall of the reactor.

Cyclohexanone acetal was not formed.

Results of Examples 5 to 11 and Comparative Example 3 are shown in the following Table 3, together with the results of Example 1.

Table 3 CHN Alcohols TOF** Remarks ketal/CHN* no Pd ethylene glycol precipitation, Ex. 1 100 1. 0/h (EG) 10 ml no chlorocyclohexane ethanol 5 ml + Ex. 5 >10 8. 4/h no Pd precipitation EG 2. 5 g methanol 5 ml + Ex. 6 17. 6 4. 0/h no Pd precipitation EG 2. 5 g 1, 4-butanediol Ex. 7 (BG) 7. 5 g + >10 8. 0/h no Pd precipitation EG 2. 5 g 1, 3-propanediol Ex. 8 2. 87 6. 4/h no Pd precipitation 10 ml 1, 4-butanediol Ex. 9 0. 41 8. 5/h no Pd precipitation (BG) 10 ml Ex. 2, 3-butanediol 5-10 2. 6/h no Pd precipitation 10 10 ml Ex. 1, 2-cyclohexane- 3. 7 4. 3/h no Pd precipitation 11 diol 10 ml no Pd Comp. ethanol 10 ml 0 6. 8/h precipitation, Ex. 3 no ketal formation * : Cyclohexanone ketal/cyclohexanone ** : formation rate of cyclohexanone and cyclohexanone ketal per 1 mol Pd per hour By the comparison of Examples 1 and 5 to 11 with Comparative Example 3, it can be seen that CHN ketal is formed when a polyhydric alcohol is present. Since CHN ketal hardly undergoes successive oxidation in the reaction system in comparison with CHN, it is desirable for the (CHN + CHN ketal) selectivity that a product having large CHN ketal/CHN ratio is obtained.

EXAMPLE 12 The reaction was carried out in the same manner as described in Example 7, except that Pd (BzCN) 2Cl2 was used instead of Pd (CH3CN) 2Cl2. As a result, the cyclohexene conversion was 5% and the TOF was 2/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 13 The reaction was carried out in the same manner as described in Example 7, except that PdCl2 was used instead of Pd (CH3CN) 2Cl2. As a result, the cyclohexene conversion was 4% and the TOF was 1. 6/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 14 A cylinder type Teflon beaker of 40 mm in inner diameter and 15 mm in height equipped with a magnetic stirrer was inserted into a SUS-316 autoclave having a withstand pressure of 100 kG and a size just fitted to the beaker, and the reaction was carried out at a reaction temperature of 70, 80, 90 or 100°C for 1 hour under an oxygen pressure of 7 kG using the same charging composition of Example 1. Precipitation of Pd was not found in the solution after the reaction. The results are shown in Table 4. It can be seen that the reaction rate largely depends on the reaction temperature and oxygen pressure.

Table 4 Reaction Cyclohexene Ketal/Ketal/ Temperature TOF* conversion cyclohexanone cyclohexenone (0c) 70 21% 42 >40 >1000 80 30% 58 24. 8 26. 1 90 50% 93 28. 5 12. 3 100 58% 110 18. 3 15. 7 * : formation rate of cyclohexanone and cyclohexanone ketal per 1 mol Pd per hour EXAMPLE 15 The reaction was carried out in the same manner as described in Example 14, except that a mixture of ethylene glycol 2. 5 g + 1, 4-butanediol 7. 5 g was used as the reaction solvent and the reaction temperature was 40, 60, 80 or 90°C. Precipitation of Pd was not found in the solution after the reaction. The results are shown in Table 5.

Table 5 Reaction Cyclohexene Ketal/Ketal/ Temperature TOF* conversion cyclohexanone cyclohexenone (°C) 40 4% 8 5. 3 12. 5 60 13% 24 2. 6 8. 0 80 46% 84 2. 3 7. 2 90 87% 154 1. 1 3. 7 * : formation rate of cyclohexanone and cyclohexanone ketal per 1 mol Pd per hour It can be seen that the reaction rate is rapidly increased as the reaction temperature increases.

EXAMPLE 16 The reaction of Example 14 was carried out, except that the reaction temperature was fixed to 80°C and the charging amount of cyclohexene was changed. Precipitation of Pd was not found in the solution after the reaction.

The results are shown in Table 6.

Table 6 Cyclo-Cyclo-Ketal/Ketal/ Reaction TOF* hexene hexene Cyclo-Cyclo- time (/h) /Pdconv. hexanone hexenone 200 1. 0 26% 50 24. 8 26. 1 3. 0 70.5% 43 11. 7 10. 4 400 1. 0 37% 47 27. 6 19. 0 3. 0 60% 37 17. 2 11. 9 * : formation rate of cyclohexanone and cyclohexanone ketal per 1 mol Pd per hour EXAMPLE 17 The reaction of Example 15 was carried out, except that the reaction temperature was fixed to 90°C and the charging amount of each of Pd, Cu and Fe was fixed to 0. 025 mmol. As a result, the cyclohexene conversion was 58%, the TOF value was 425/hour, the cyclohexanone ketal/cyclohexanone ratio was 4. 4 and the cyclohexanone ketal/cyclohexenone ratio was 8. 5. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 18 The same oxidation reaction of Example 3 was carried out, except that FeCl3 was changed to the co-catalysts shown in Table 7. As a result, the product was mostly cyclohexanone ketal. The TOF values are shown in Table 7.

Table 7 Pd black Co-catalyst TOF/hour precipitation _ Example 3 Fecal3 60 no Example 18 RuCl3 70 slight Cods 57 slight Sn (acac) 2Br2 27 no Ni (acac) 2 4 no acac : acetylacetonate EXAMPLE 19 A cylinder type Teflon beaker of 40 mm in inner diameter and 15 mm in height equipped with a magnetic stirrer was inserted into a SUS-316 autoclave having a withstand pressure of 100 kG and a size just fitted to the beaker, and the reaction was carried out at a reaction temperature of 80°C under an oxygen pressure of 7 kG using the same charging composition of Example 1 and adding 20 mmol of styrene. After 1 hour of the reaction, the contents were taken out and analyzed by GC. As a result, the TOF value was 154/hour, the EG acetal compound selectivity of phenylacetaldehyde was 54%, the EG ketal compound selectivity of acetophenone was 11% and the (phenylacetaldehyde + acetophenone) selectivity was 25%.

Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 20 The reaction was carried out in the same manner as described in Example 19, except that a-methylstyrene was used instead of styrene. As a result, the TOF value was 54/hour, and only 2-phenylpropylaldehyde and its EG acetal compound were formed. The acetal/aldehyde ratio was 2. 5.

Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 21 The reaction was carried out in the same manner as described in Example 19, except that 3, 4- dihydronaphthalene was used instead of styrene. As a result, the TOF value was 90/hour. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 22 The reaction was carried out in the same manner as described in Example 19, except that 1-octene was used instead of styrene. As a result, the TOF value was 46/hour, the (ketal compound + acetal compound) selectivity was 70%, and a ketal compound of corresponding ketone compound of the octene in which the double bond was shifted was mainly obtained. Precipitation of Pd was not found in the solution after the reaction.

EXAMPLE 23 The reaction was carried out in the same manner as described in Example 22, except that 2-octene was used instead of 1-octene. As a result, the TOF value was 40/hour and the (ketal compound + acetal compound) selectivity was 84%. Distribution of the formed products was the same as the case of Example 22. Precipitation of Pd was not found in the solution after the reaction.

(Examples of the use of mixed material of cyclohexene and benzene) EXAMPLE 24 A cylinder type Teflon beaker of 40 mm in inner diameter and 15 mm in height equipped with a magnetic stirrer was inserted into a SUS-316 autoclave having a withstand pressure of 100 kG and a size just fitted to the beaker and, with an assumption of the case of the coexistence of benzene, charged with 2. 2 g of benzene, 2 g of cyclohexene, 0. 3 mmol of Pd (CH3CN) 2Cl2, 0. 3 mmol of CuCl2, 0. 3 mmol of FeCl3 and 6. 2 g of 1, 4-butanediol. The reaction was carried out at a reaction temperature of 70°C and under various oxygen pressures described in the following table. The main product other than cyclohexanone and cyclohexanone ketal was cyclohexenone. The results are shown in Table 8.

Table 8 Oxygen Reaction time Cyclohexene pressure Selectivity (%) (min) conversion (%) (kG) 4 24 63 71 5 20 67 72 6 22 68 77 7 24 62 84 8 9 72 70 9 11 85 74 Selectivity = cyclohexanone + cyclohexanone ketal EXAMPLE 25 The same reaction apparatus of Example 24 was used and, with an assumption of the case of the coexistence of benzene, charged with 2. 2 g of benzene, 2 g of cyclohexene, 0. 6 mmol of Pd (CH3CN) 2Cl2, 0. 6 mmol of CuCl2, 0. 6 mmol of FeCl3 and 6. 2 g of 1, 4-butanediol. The reaction was carried out under an oxygen pressure of 7 kG and at various reaction temperatures described in the following table. The main product other than cyclohexanone and cyclohexanone ketal was cyclohexenone. The results are shown in Table 9.

Table 9 Reaction Reaction time Cyclohexene Selectivity (%) temp. (°C) (min) conversion (%) 70 8 80 70 65 11 75 76 60 28 72 79 Selectivity = cyclohexanone + cyclohexanone ketal EXAMPLE 26 The same reaction apparatus of Example 24 was used and, with an assumption of the case of the coexistence of benzene, charged with 1. 1 g of benzene, 1 g of cyclohexene, 0. 3 mmol of Pd (CH3CN) 2Cl2, 0. 3 mmol of CuCl2, 0. 3 mmol of FeCl3 and 6. 2 g of 1, 4-butanediol. The reaction was carried out at a reaction temperature of 80°C for 3. 5 minuets under an oxygen pressure of 7 kG. As a result, conversion of cyclohexene was 92%, selectivity of cyclohexanone and cyclohexanone ketal was 70%. The main product other than cyclohexanone and cyclohexanone ketal was cyclohexenone.

EXAMPLE 27 Materials and catalyst components were charged into the reaction apparatus in the same manner as described in Example 24, except that 1, 2-cyclohexanedimethanol was used instead of 1, 4-butanediol. The reaction was carried out at a reaction temperature of 70°C for 32 minuets under an oxygen pressure of 7 kG. As a result, conversion of cyclohexene was 52% and selectivity of cyclohexanone and cyclohexanone ketal was 84%. The cyclohexanone ketal/cyclohexanone ratio was 3.

EXAMPLE 28 Materials and catalyst components were charged into the reaction apparatus in the same manner as described in Example 27, except that 2. 3 g of 1, 2-cyclohexanedimethanol and 3. 9 g of 1, 4-cyclohexanedimethanol were used instead of 6. 2 g of 1, 2-cyclohexanedimethanol. The reaction was carried out at a reaction temperature of 70°C for 20 minuets under an oxygen pressure of 7 kg. As a result, conversion of cyclohexene was 70% and selectivity of cyclohexanone and cyclohexanone ketal was 63%. The cyclohexanone ketal/cyclohexanone ratio was 1.

Industrial applicability According to the invention, it becomes possible to produce ketal and/or acetal from olefins with a high conversion rate and a high selectivity, while inhibiting precipitation of Pd component, so that its industrial availability is high.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

This application is based on Japanese patent application No. 2000-125535 filed on April 26, 2000, the entire contents thereof being hereby incorporated by reference.