DE1568764C3 - Process for the simultaneous production of isoprene and an epoxy or an acrylate or an oxime - Google Patents

Description

1. Oxidation of isopentane to 2-methyl-2-hydroperoxybutane;

2. catalytic conversion of 2-methyl-2-hydroperoxybutane with

a) an olefinic compound under epoxidation conditions for the same or

b) with an acrolein to form an acrylic acid or an acrylate or

c) with a primary amine to form an oxime with simultaneous reduction of hydroperoxybutane to 2-methyl-2-hydroxybutane;

3. successive or simultaneous dehydration and dehydration of 2-methyl-2-hydroxybutane to isoprene and

4. Obtaining isoprene and the second products formed in the reaction.

The invention relates to a method for the simultaneous production of isoprene and an epoxy or an acrylate or an oxime.

Both isoprene and the other compounds mentioned above are of very great importance for technology. Isoprene is an important monomer that has extensive use in the manufacture of Synthetic rubber as well as numerous other uses finds. Epoxies, such as propylene oxide, are used on an extraordinarily large scale in the manufacture of various Polymeric surfactants and the like are used. Acry! Compounds are also used for Used in the manufacture of various polymers, and oximes are valuable in themselves and serve as starting materials for the production of other chemical compounds. Process for the production of such substances are already known. However, these leave the described ones above all with regard to economic production Substances to be desired, and the invention therefore aims to provide a more economical production process for the named connections are created.

From US-PS 29 67 897 it is known to produce isoprene from an isopentane, but none second valuable product is also produced. In contrast, the method according to the invention is based on Isopentane, which normally has only little value, and not only supplies with little effort the technically very popular isoprene, but also a valuable oxidation product, depending on the reducing agent used for the isopentane hydroperoxide produced as an intermediate may be an oxirane, an acrylic compound, or an oxime.

The method according to the invention of the type mentioned at the beginning is now characterized by the combination the following individual measures:

1. Oxidation of isopentane to 2-methyl-2-hydroperoxybutane;

2. catalytic conversion of 2-methyl-2-hydroperoxybutane with

a) an olefinic compound under epoxidation conditions for the same or

b) with an acrolein to form an acrylic acid or an acrylate or

c) with a primary amine to form an oxime with simultaneous reduction of the hydroperoxybutane to 2-methyl-2-hydroxybutane;

3. successive or simultaneous dehydration and dehydration of 2-methyl-2-hydroxybutane to isoprene and

4. Obtaining isoprene and the second products formed in the reaction.

The advantages that can be achieved according to the invention are evident. The one used as the starting product Isopentane, which is normally only of low value

ao sits and is extremely difficult to convert into isoprene, can be converted into a valuable connection transferred and at the same time to the generation of important and valuable technical Products used. Isopentane converted into the much more valuable tert-amyl alcohol is then expediently converted into the very valuable product isoprene. Between the different Stages of the process according to the invention there is an obvious and beneficial interaction, because one substance, which is difficult to convert directly into isoprene, is used to manufacture another valuable chemical compound is used and at the same time converted into a form, which is highly suitable for isoprene production.

In the following the invention is explained with reference to the embodiment shown in the drawing. In the oxidation zone 1, isopentane is oxidized with molecular oxygen to form isopentane hydroperoxide. The oxidation is carried out in the liquid phase generally at temperatures from 100 to 200 ^° C., preferably from 100 to 160 ^° C., and at pressures of about 7 to 56 atmospheres. Air, which can be diluted with inert gases, is preferably used as the source for molecular oxygen. But one can also use molecular oxygen from other sources. The oxidation is carried out under conditions which favor the formation of the hydroperoxide. The isopentane conversion per pass is preferably of the order of 10 to 50%. Various additives can be used to stabilize the system and to promote the production of the hydroperoxide.
The mixture of hydroperoxide and hydrocarbon is withdrawn from the oxidation zone 1 and passed into zone 2, in which the hydroperoxide is used to produce the valuable coproduct and to convert the hydroperoxide into tert-amyl alcohol with another substance, e.g. B. propylene, is converted catalytically.

In one embodiment, the hydroperoxide in zone 2 is reacted with an olefin to form the olefin to convert into an oxirane compound and the hydroperoxide in tert-amyl alcohol.

The epoxidation with the aid of isopentane hydroperoxide is carried out in the presence of epoxidation catalysts carried out, the compounds of the following elements can be: Ti, V, Se, Cr, Zn,

3 4

Zr, Nb, Ta, Te, U, Mo, Ta, W and Re. The preferred ethylene, propylene, n-butylene, isobutylene, the pentenes,

Added catalysts are compounds of Mo, Ti, the methylpentenes, the n-hexenes, the octenes, the

V, W, Re, Se, Nb and Te. Dodecene, cyclohexene, methylcyclohexene, butadiene,

The amount of dissolved metal that is used as a catalyst in epoxystyrene, methylstyrene, vinyltoluene, vinylcyclohexene and dation can be converted into the phenylcyclohexenes. It is also possible to vary olefins within wide limits, but as a rule it is preferable to use substituents which, for example, halogen, oxygen, may advantageously contain at least 0.0001 mol and preferably sulfur. Such 0.002 to 0.03 mol per mol of hydroper-substituted olefins present are, for example, allyl alcohol, oxides to be used. It appears that amounts of more methallyl alcohol, cyclohexenol, diallyl ether, meal than 0.1 mol compared to smaller amounts do not offer any prophylactic methacrylate, methyl oleate, methyl vinyl ketone and parts, but amounts of up to 1 mol of allyl chloride can be used. According to the invention, more generally or more per mole of hydroperoxide can be used. All of the olefinic substances, including the olefinic catalyst, remain in the unsaturated polymer during the reaction. The reaction mixture is dissolved by known processes and can be epoxidized after removal, converted into epoxides, the reaction products from this again for the conversion lower olefins settlement can be used. Molyb- with about 3 or 4 carbon atoms which can be used in aliphatic Danish compounds include, for example, the orga chain epoxidized according to the invention. In particularly effective molybdenum salts, the oxides, for example Mo ₂ O ₃ , such olefins can be epoxidized according to the invention, MoO ₃ , molybdic acid, molybdenum fluoride, molybdenum phosphate, which are usually called -olefins or primary and sulfide. Molybdenum-containing hetero-olefins can also be designated. It is known that these use polyacids as well as their salts. Examples of primary olefins, e.g. B. propylene, butene-1, decene-1, this is phosphomolybdic acid and its Na-hexadecene-1 and the like. With the exception of ethylene trium and potassium salt. Likewise, it is much more difficult to epoxidize similar compounds than other or analogous compounds of the types of olefins described above. Use to such other substantially different metals as well as mixtures thereof. 25 more easily epoxidizable types of olefins belong

The catalytically active substances can, for example, be substituted for olefins, alkenes with internal epoxidation in the form of a compound or moderate unsaturation and cycloalkenes.
The ratio of olefinic! The substrate is soluble in the organic medium. Although the solubility in niche peroxy compounds during epoxidation depends to a certain extent on the type used in the individual case, it can vary over a wide range. In the general reaction medium from, but think as suitable one applies molar ratios of olefinic soluble substances for the purposes according to the invention with groups in the substrates to hydroperoxide in the, for example, hydrocarbon-soluble organometallic range from 0.5: 1 to 100: 1, expediently from 1 : 1 compounds with a solubility in methanol of up to 20: 1 and preferably from 2: 1 to 10: 1. A room temperature of at least 0.1 g per liter in 35 is also advantageous to take the reaction into account as much as possible. Exemplary soluble forms of high hydroperoxide conversion, preferably of catalytically active substances, include, inter alia, at least 50% and in particular at least 90%, the naphthenates, stearates, octoates and carbonyls. in conjunction with good selectivities.
You can also use various chelates, addition- When epoxidation, basic substances and enol salts, z. B. Acetoacetonate, 40 can be applied. Such basic substances are alkali uses. Individual and preferred catalytically active metal or alkaline earth metal compounds. Particularly the same compounds of this type are preferred for the purposes of the invention, the compounds of sodium, Kagemäßes purposes are the naphthenates and carbonyls Hum, lithium, calcium, magnesium, rubidium, of molybdenum, vanadium, titanium, tungsten, rhenium, cesium, strontium and barium. Ins-niobium, tantalum and selenium are used. Furthermore, Alkoxyverbin- 45 are special compounds that are found in the reaction dung, z. B. tetrabutyl titanate and other alkyl media are soluble, but insoluble titanates are also very suitable. Shapes usable and effective when in that

The temperature reaction medium that can be used in the epoxidation is dispersed. You can beituren depending on the reactivity, for example, compounds of organic acids such. B. and other properties of the individual system in 50 metal acetates, naphthenates, stearates, octoates and vary fairly wide limits. All-butyrate can be used. Furthermore, inorganic salts, commonly temperatures of about 20 to 200 ⁰ C, are useful z. Sodium carbonate, magnesium carbonate or Trimäßig of 0 to 15O ⁰ C and preferably from 50 to sodium phosphate suitable. To particularly preferred 120 ⁰ C, use. The reaction is carried out at pressurized types of metal salts, including, for example, nabeconditions sufficient to maintain trium naphthenate, potassium stearate and magnesium in a liquid phase. You can use carbonate. Also use alkali and alkaline earth hydroxides and subatmospheric pressures, usually oxides, e.g. B. NaOH, MgO, CaO, Ca (OH) ₂ and KOH, however, are pressures from about atmospheric pressure up to and alkoxides, e.g. B. sodium ethylate, potassium cumylate about 70 atmospheres most appropriate. and sodium phenate can be used.

Among the olefinically unsaturated substances that are in the 60 Furthermore, amides, z. B. NaNH ₂ , as well as quaternary

In the context of the process according to the invention, ammonium salts are suitably epoxidized. In general you can

include, for example, substituted and un- all alkali or alkaline earth compounds,

substituted aliphatic and alicyclic olefinic ones that react basic in water.

Compounds containing hydrocarbons, esters, Aiko- The basic substances are used in. of epoxidation

hole, ketones, ethers and the like. Preferably 65 in amounts of 0.05 to 10 mol, preferably of

are those compounds that are about 2 to 30 Koh- 0.25 to 3.0 mol and especially from 0.50 to

Use carbon atoms and preferably at least 3 carbons 1.50 moles per mole of epoxidation catalyst

have material atoms. Examples of such olefins are det. It was found that as a result of the

leadership of the basic compound in the reaction system significantly improved efficiencies in the Utilization of the organic hydroperoxides can be achieved in the epoxidation.

In other words, this means that a higher yield is obtained when the basic compounds are used of oxirane compound, based on the hydroperoxide consumed, is achieved. In addition, the Used hydroperoxide is reduced in a larger amount to alcohol instead of other undesirable products to pass over.

Furthermore, by using the basic substances, it is possible to obtain lower ratios of unsaturated To apply connection to hydroperoxide and thus the degree of conversion of the unsaturated compound while maintaining advantageously high reaction selectivities.

In a second embodiment, the hydroperoxide in zone 2 is mixed with a primary amine Formation of oxygen-containing amine derivatives, e.g. B. ketoximes, and implemented by tert-amyl alcohol. for the following conditions apply to this implementation:

Temperatures can vary quite widely depending on the reactivity and other properties of the other reactants. In general, it temperatures may range from about -10 to 175 ° C, preferably from 25 to 130 ° C and especially from 60 to HO ⁰ C, apply. During the reaction, pressure conditions are used which are sufficient to maintain a liquid reaction phase. While sub-atmospheric pressures can be used, pressures around atmospheric or slightly above are usually the most appropriate.

For the reaction, compounds of the following elements are used as catalysts: Ti, V, Cr, Se, Zr, Nb, Mo, Te, Ta, W, Re and U. These can be used as peracids or hydroxylation catalysts describe.

The amounts of the metal in solution and used as a catalyst for the reaction can be vary within wide limits, but it is usually expedient to at least 0.0001 mol and preferably 0.001 to 0.01 moles per mole of hydroperoxide present. It looks like, that amounts greater than about 0.1 mole offer no advantage over smaller amounts Reaction, the catalytically active substances remain dissolved in the reaction mixture and can after Removal of the reaction products from this mixture can be reused. The ratio of Hydroperoxide to amine is 0.01 to 10 moles, preferably 0.5 to 2 moles of hydroperoxide per mole Amine.

Suitable molybdenum compounds include, for example, the organic molybdenum salts, the oxides, e.g. B. Mo ₂ O ₃ , MoO ₂ , _{molybdic acid, MoO 3} , the molybdenum chlorides and oxychlorides, molybdenum fluoride, phosphate and sulfide. Furthermore, molybdenum-containing heteropolyacids and their salts, e.g. B. Phosphomolybdic acid and its sodium and potassium salt are suitable. Corresponding or analogous compounds of the other metals mentioned above can also be used.

It has been found that titanium compounds for this reaction are more unexpected and surprising Usability are. Titanium compounds are involved in the reaction of organic hydroperoxides Amines extremely effective.

You can use both inorganic and organic titanium compounds, with organic ones However, connections will produce much better results. The preferred titanium compounds are esters or salts of organic acids and are preferably derived from aliphatic or aromatic acids Alcohols and organic acids. Separate Examples are tetra-n-butyl titanate, din-butyl-di (2,6-tert-butyl-p-cresyl) titanate, n-butyl trioleoyl titanate, tetra-o-cresyl titanate, tetra-tert.-butyl titanate, Titanium naphthenate, titanium stearate, titanium ethylhexoate and titanium acetate. Inorganic compounds,

z. B. titanium tetrachloride are also suitable.

When using easily hydrolyzable titanium compounds it is advisable to remove the water of oxidation from the reaction zone during the reaction, for example as an azeotrope with benzene.

In practice, the catalytically active constituents can be in the form of a compound or mixture can be used which is initially soluble in the reaction medium. The solubility Although it depends to a certain extent on the reaction medium used in the individual case, it does come as suitable soluble substances for the invention Purposes hydrocarbon-soluble organometallic compounds with solubility in methanol at room temperature of at least 0.1 g per liter into consideration.

Exemplary soluble forms of the catalytically active substances are the naphthenates, stearates and octoates and carbonyls. Various chelates, addition compounds and enol salts, e.g. B. acetoacetonate, can also be used. Individual and preferred catalytic compounds of this type for the implementation according to the invention are the naphthenates and carbonyls of molybdenum, vanadium and Tungsten and especially the various titanium compounds.

The oxidation time depends on the conversion desired in each case. In conjunction with low Degrees of conversion and / or very active substances can be used very short reaction times. Usually reaction times of from about 1 minute up to 6 hours, and preferably from 5 minutes up to 2 hours.

The amines used are primary amines, with the amino group attached to a primary or secondary saturated carbon atoms may be bonded, and contain 1 to 20 carbon atoms and preferably 4 to 16 carbon atoms, e.g. B. benzylamine, isopropylamine, n-butylamine, cyclohexylamine, cyclooctylamine, Cyclododecylamine, amino-substituted saturated aliphatic groups that are cyclic or acyclic and may contain cyclic aryl or alkyl substituents.

The amine concentration in the reaction mixture can range from 5 to 60 percent by weight, preferably in the range of 5 to 15%.

The hydroperoxide concentration in the oxidation mixture is usually at the start of the reaction at 1% or above, however lower concentrations are effective and can be used will.

The reaction is expediently carried out practically in the absence of water. During the Relatively small amounts of water are permissible for implementation, but water is preferred

Excluded from the system during the main part of the implementation.

It is most advantageous to carry out the reaction in the presence of a solvent.

A preferred solvent or diluent is tert-butanol. However, you can also do others Alcohols e.g. B. tert-amyl alcohol, dimethylpropylcarbinol, Use methyl diethyl carbinol or dimethylphenyl carbinol. Primary or secondary alcohols, z. B. methanol, ethanol, n- or i-propanol, i- or n- or s-butanol and analogous pentanols or Hexanols are also suitable. Furthermore, one can use ether, e.g. B. diethyl ether, and ketones, e.g. B. Cyclohexanone, use. The 'lower aromatic hydrocarbons and the low-boiling chlorinated ones Hydrocarbons, e.g. B. chlorotoluene, are also suitable solvents.

If the oxime formed is to serve as a starting material for a further reaction, you can use the crude Use oxime. If the oxime is to be rearranged, an acid, e.g. B. Sulfuric acid, mix with the oxime and heat to make z. B. Cyclohexanone oxime in caprolactam convict.

It is an essential feature of the process according to the invention that one cyclohexylhydroxylamine and this can then be further oxidized with air to form the oxime. The manufacture of this product offers the advantage that only 1 mole of hydroperoxide is consumed in its production, while for production of the oxime 2 moles are required.

In a third embodiment of the method according to the invention, the hydroperoxide is in Zone 2 reacted with an unsaturated aldehyde, an unsaturated acid or an unsaturated Ester is formed and the hydroperoxide is converted into tertiary amyl alcohol.

The reaction of the isopentane hydroperoxide with the acrolein or methacrolein can be carried out in a solvent or diluents can be carried out. It is used for the production of the acid tert-amyl alcohol preferred, while for the direct preparation of the ester, if this is intended, a esterifying alcohol is used. In general, this last-mentioned alcohol is a primary or sometimes a secondary alcohol, preferably having 1 to 12 carbon atoms.

For the preparation of the acid, other alcohols, e.g. B. tert-butyl alcohol, dimethylpropylcarbinol, Methyl diethyl carbinol and dimethylphenyl carbinol can be used. One can also be primary or secondary Alcohols e.g. B. methanol, ethanol, n- or i-propanol, i- or n- or s-butanol and the corresponding Use pentanols or hexanols. To produce the acid, ethers, e.g. B. diethyl ether, Ketones e.g. B. acetone, or acids, e.g. B. acetic acid, as well as esters of such acids, e.g. B. methyl, Ethyl, propyl or butyl ester, suitable. You can also use lower aromatic hydrocarbons as well low-boiling chlorinated hydrocarbons, e.g. B. chlorotoluene, use. Also saturated hydrocarbons or even unsaturated hydrocarbons are suitable, e.g. B. Purified Butylenes, Hexylenes, Propylene trimers and tetramers or butylene dimers or trimers with appropriate pressures applied to keep the solvent in the liquid phase.

There are different catalysts for the conversion of hydroperoxide and unsaturated aldehyde can be used, but chromic acid is preferred for the preparation of the acid. Other catalysts are, for example, phosphomolybdic acid, tungsten chromic acid, selenium chromic acid, phosphorus vanadic acid and the like

For the direct production of the methyl ester from the aldehyde, the reaction is expedient in the Way carried out that the hydroperoxide or

ίο a hydroperoxide mixture together with one Redox agent to a solution of the oc, /? - ethylenically unsaturated Aldehyde in the appropriately chosen reactive medium, e.g. B. methanol, adds. Ferrous or ferric ions are particularly suitable redox agents and can be or ferric chloride or other soluble iron salts can be introduced to the reaction mixture. However, it can be used in place of or together with the Ferrous or ferric ions in the process according to the invention are other substances from the large number of known substances Use redox agents. Ions of other heavy metals, for example, are suitable as such redox agents, which can be present in different valency states, e.g. B. cobalt, manganese, copper, titanium, Chromium and vanadium ions.

In some cases, sodium bisulfite, 1-ascorbic acid, sodium formaldehyde sulfoxylate, the reducing sugars and similar substances can be used to reduce ions of higher valence. The reducing agent or the mixture of such agents is used in equivalent amounts or in an excess of, for example, up to about 10% of the amount stoichiometrically required for reducing the tert-butyl hydroperoxide. Instead of a stoichiometric amount of ferrous ions, a trace amount of a polyvalent metal, preferably ferrous or ferrous ions, can optionally be used in the process according to the invention, together with a stoichiometric amount of one of the reducing agents described above, which reduces the ferric ions to ferric ions to the extent that they are formed. In this procedure, ferric ions are the preferred promoters and are advantageously employed in amounts of from about 0.25 to about 1 equivalent per mole of hydroperoxide used. In any case, a temperature may be employed of from about -20 to about 15O ⁰ C, but in general, temperatures of from about 0 to about + preferable 2O ⁰ C, to restrict loss of aldehyde by evaporation or by side reactions to a minimum. The implementation time is not critical.

The reaction can also be carried out in such a way that one isopentane hydroperoxide or a mixture containing isopentane hydroperoxide and a redox agent to form a solution of an aldehyde, z. B. a «, / S-ethylenically unsaturated aldehyde, in a suitable reactive primary or secondary alkanol, e.g. B. methanol, ethanol or another non-tertiary alcohol with up to about 12 carbon atoms in the molecule. Ferro or Ferric ions are preferred redox agents and can be obtained by adding ferrous or ferric chloride or other soluble iron salts can be introduced to the reaction mixture. Chlorides and bromides are the preferred salts. Examples of other known redox agents that act in place of or together with the ferrous or ferric ions in the invention

609 647/34

according to methods can be used are cobalt, manganese, tin, cerium, nickel, lead, titanium, Chromium and vanadium ions present in solution or mixtures thereof. These metals have the following Ordinal numbers: 22 to 28, 50, 58 to 82.

The redox agent or mixtures of redox agents can with respect to the hydroperoxide in stoichiometric amounts or in excess, for example up to about twice that amount can be used. However, they are also less than stoichiometric amounts are effective and generally preferred. Generally one uses at least 0.05 equivalent of redox agent per equivalent of hydroperoxide. An appropriate range is 0.1 to 1 equivalent of redox agent per equivalent of hydroperoxide. Compared to the way of working using cupriions, in this case it can be due to the low. Quantities spoken of a conversion carried out with catalytic quantities will.

The redox agents can be in any of their valence states. For example, both achieved equally good results with both ferrous and ferric chloride. In some cases it is an acidic The environment is favorable, which can then be achieved by adding a small amount of sulfuric or hydrochloric acid or another strong acid can be adjusted to the reaction mixture. One can also use a redox couple, e.g. B. Ferro-ferric ions or cobalto-cobalti ions or a mixed couple, e.g. Use e.g. cobalto ferric ions or mangano stanni ions.

Chloride and Bromide.sare preferred when performing this procedure for the preparation of However, esters can be used compounds which contain other anions. These give similar anions Results as given in the examples. Iron halides or mixtures thereof are preferred.

For the direct production of the ester one can use the aldehyde, the. Hydroperoxide, the alkanol, e.g. B. Methanol, and chromic acid (or phosphomolybdic acid, tungsten chromic acid, selenium chromic acid, phosphorus vanadic acid, or the like).

The concentration of the aldehyde or acrolein in the reaction mixture can range from 1 to 50 percent by weight, preferably 10 to 20 percent by weight. The reaction temperature may be -50 to + 15O ⁰ C, suitably 0 to 100 ° C be, and is preferably in the range of room temperature or slightly below up to about 60 ° C. It can be atmospheric pressure or below, or overlying pressures and reaction times of 10 Use for minutes to 6 hours, preferably 0.5 to 3 hours. A reaction time of one hour is suitable for many reactions.

The ratio of hydroperoxide to aldehyde is in the range from 0.1 to 2 mol, preferably from 0.5 to 1.0 mole, per mole of the acrolein.

The process according to the invention can be carried out batchwise, intermittently or continuously. A continuous reaction can take place in an elongated reaction zone, e.g. B. a pipe or Tower or in a plurality of reactors connected in series, and the hydroperoxide can be added at intervals along the path of the flowing solution or mixture.

If you want to prepare a methacrylic acid ester from the acid, you can the reaction mixture add appropriate alcohol. The reaction mixture containing the added alcohol, e.g. B. methanol, contains, is heated to carry out the esterification and to remove the water formed. then the mixture can be separated into individual fractions by distillation. Included in the mix Catalyst remains in the residue and can be recovered and returned to the oxidation stage be used. Other ways of working are also possible.

ίο The reaction mixture from zone 2 is in the Separation zone 3 introduced, in which the mixture is broken down into its constituent parts by appropriate distillation steps is dismantled. As can be seen from the drawing, the coproduct is withdrawn via line 4.

Tertiary amyl alcohol is removed via line 5 and introduced into dehydration zone 6. Although the separation zone 3 is only shown schematically, this zone preferably consists of a number of distillation columns. The unreacted portion of the starting materials is recovered in these columns and fed back into the process (not shown). The catalyst is also recovered and recycled.
In zone 6, the tert-amyl alcohol is dehydrated to isopentene. One can, for example, the following conditions apply in the dehydration: temperatures in the range of 100 to 35O ⁰ C, preferably from 150 to 25O ⁰ C, pressures from atmospheric up to about 3.5 atm and catalysts, such as. B. aluminum oxide, titanium oxide, silicon dioxide, MgO, ZnO and ThO ₂ .

The isopentene formed is fed into the dehydrogenation zone 7 and there dehydrogenated to isoprene. In the dehydrogenation, for example, temperatures from 500 to 800 ⁰ C, preferably from 600 to 700 ⁰ C, pressures from 0.35 to 3.5 atmospheres, preferably from 1.05 to 2.1 atmospheres, and catalysts such as. B. Cr ₂ O ₃ , Fe ₂ O ₃ , ZnO, CoO and mixtures thereof are used.

The reaction mixture emerging from the dehydrogenation zone is fractionated in zone 8, and isoprene is obtained as a product.

The tertiary amyl alcohol can also be dehydrated and dehydrated at the same time subject, producing isoprene directly.

The following examples illustrate the invention without restricting it. _: .

Examples
Oxidation of isopentane

Isopentane, containing 0.4 weight percent Butylhydrpperoxyd as initiator, is oxidized with 10% O ₂ at 14O ⁰ C and 35 atm 3.7 hours hours in a steel autoclave. The degree of conversion is 25% ■■ and the. Selectivity to hydroperoxide 50%. To remove the unreacted isopentane, the reaction mixture is distilled at atmospheric pressure, 52 percent by weight of isopentane hydroperoxide in mainly tert-amyl alcohol remaining as the bottom fraction.

Epoxidation

A mixture of 100 g of the concentrate described above (0.5 mole hydroperoxide), 168 g (4 moles) of propylene and 1.0 g of molybdenum naphthenate with 5% Mo is heated in a pressure vessel for 2 hours at 10O ⁰ C. Then the reaction mixture

into a 5-tray column with a re-nut ratio of 5: 1 and at atmospheric pressure for recovery of propylene, propylene oxide and tert-amyl alcohol, as indicated in the table below, distilled.

Fraction head temperature amount
⁰ C g

Main ingredient

-46 to -30 150.0

-30 to 33 1.4

33 to 36 22.0

36 to 90 2.1

90 to 96 4.0

Propylene propylene oxide

Methyl isopropyl ketone

of aqueous acetone in the amount of 2 parts by volume of aqueous acetone per part of hydrocarbon feed. Isoprene mixed with solvent is drawn off as a vaporous product in a side stream. The isoprene is separated from this stream by extracting the solvent with water.

Oxidation of isopentenes

Part of the isopentenes that is 50 parts per million

ίο contains cobalt as naphthenate, is ^{oxidized with air at 13O 0} C and 35 atü. At 10% conversion, the selectivity to epoxies is 55%. The epoxides are separated by distillation in a 5-tray column at atmospheric pressure and a reflux ratio of 5: 1.

96 to 103 84.0 tert-amyl alcohol fraction

The yield of propylene oxide - based on the hydroperoxide - is 78%, and the hydroperoxide conversion is practically quantitative.

The ketone is hydrogenated over a copper chromite catalyst at 3.5 atmospheres and 150 ^° C., and the alcohol formed is combined with the tert-amyl alcohol.

Head temperature weight percent of
feed

⁰ C

Main ingredient

1. 2. 3. 25 30 to 40
40 to 70
70 to 83
Residue

87.0
0.5
6.0
6.5

Isopentenes
Epoxies

Dehydration

The mixed alcohols are dehydrated in the vapor phase over alumina at 25O ⁰ C, atmospheric pressure and a liquid volume-related space velocity of Figure 1. The conversion is 95% and the selectivity to isopentenes is 98%.

The material emerging from the dehydration stage is placed in a 5-floor distillation device distilled at a reflux ratio of 2: 1, and the products are recovered as follows

Fraction head temperature

Weight percent of the charge

Main ingredient

40

1. to 30 0.5 -

2. 30 to 40 74.0 isopentenes

3rd residue 25.5 not converted

Delter alcohol, water and non-volatile substances

Dehydration of the isopentenes

The catalyst consists of 78.5 MgO, 20 Fe ₂ O ₃ , 5 CuO and 5 K ₂ O (parts by weight). The following operating conditions are used:

Feed rate (parts by volume) Hydrocarbon vapor (normal conditions) per part by volume of catalyst and hour 476

Parts by volume of steam / parts by volume K. W 7/1 ^6c

Temperature, ⁰ C 649

Degree of conversion 42%

Selectivity to isoprene 65%

The material withdrawn from the dehydrogenation stage is subjected to an extractive distillation to separate isoprene. Is distilled in a column 50bödigen at 1.75 atm using the epoxides are dehydrated over a Thoriumoxydkatalysator at 400 ⁰ C and a related liquid volume hourly space velocity of 0.3. The degree of conversion of the epoxy is 100%, and the analysis of the reaction mixture shows an isoprene yield of 47%. The reaction mixture withdrawn is distilled in a 20-tray column at a reflux ratio of 10: 1 and at atmospheric pressure. At a head temperature of 33 to 36 ° C, isoprene is recovered as product in an amount of 35% of the charge.

Oxidation of primary amines

A solution of 19.8 g (0.2 mol) of cyclohexylamine in 112 g of benzene containing 0.002 mol of tetra-n-butyl titanate is refluxed using an overhead condenser and water separator. 20.0 g of the hydroperoxide concentrate described above (hydroperoxide content 0.1 mol) was added over a period of 10 minutes. When the addition is complete, the mixture obtained is heated under reflux for a further hour at 82 ° C. On the basis of the gas chromatographic analysis, the reaction mixture contains 0.036 mol of cyclohexanone oxime, which corresponds to a product yield of 72%, based on the hydroperoxide. The hydroperoxide conversion is 100%. The reaction mixture obtained is used to separate the various Product fractions distilled. The distillation takes place in a 10-bottom column at one Reflux ratio of 5: 1 and at atmospheric pressure.

fraction Head temperature Weight composition ⁰ C G 1. 79 to 82 96 benzene 2. 82 to 103 17.5 C ₅ alcohols and Ketones 3. 103 to 130 1.5 - 4th 130 to 136 14.5 Cyclohexylamine

The residue, which contains the oxime, is at 5 mm Hg distilled to separate the oxime overhead as a product.

Oxidation of methacrolein

A solution of 7.5 g of methacrolein (0.107 mol), 17.3 g of the hydroperoxide concentrate described above (hydroperoxide content 0.086 mol) and 0.25 g of Cr ₂ O ₃ in 35 g of anhydrous tert-butanol is heated at 45 ° C. for 4 hours implemented. The hydroperoxide conversion is 91%. Analysis of the reaction mixture shows that 74% of the methacrolein has been converted with a selectivity to methacrylic acid of 52%. To separate the constituents, the reaction mixture is fractionally distilled and the mixture

of methylpentanols is converted into isoprene in the manner described above. The distillation takes place in a 5-tray column at atmospheric pressure. At 50 to 53 ° C are 1.9 g of methacrolein and at 82-83 ⁰ C. tert-butanol is obtained. The bottom fraction is extracted with 100 ml of 5% strength aqueous NaHCOg solution. The aqueous phase is acidified with HCl, extracted with ether and the ether evaporated, leaving 4.9 residue and 3.5 g methacrylic acid

ίο included, lagging behind. 1 in a 5bödigen column and cuts at 100 to 104 ⁰ C, a fraction out, which mainly consists (13 g) in tert-amyl alcohol: The organic phase during the extraction with bicarbonate is distilled at atmospheric pressure and a reflux ratio of third

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Claims (1)

Claim: Process for the simultaneous production of isoprene and an epoxy or an acrylate or an oxime, characterized by the combination of the following individual measures :