WO2000015590A1 - Method for producing enol ethers - Google Patents

Abstract

The invention relates to a method for producing enol ethers of formula (I), by reacting alcohols of formula (II): R1OH and/or acetals or ketals of formula (III), in which R1 is an aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic rest, which can carry other substituents which do not react with acetylenes or allenes, and the rests R independently of each other represent hydrogen or aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic rests which can be joined such that they form a ring, and where m is 0 or 1, with acetylenes or allenes of formulas (IV) or (V) in the gaseous phase at elevated temperature in the presence of a heterogeneous catalyst containing zinc or cadmium together with silicon and oxygen, and by isolating the enol ethers of formula (I) by distillation.

Description

description

Process for the preparation of enol ethers

The invention relates to a process for the preparation of enol ethers by reacting alkynes or allenes with alcohols and with acetals or ketals which are able to form the enol ethers with elimination of alcohol, with an excess of alcohol being used and this excess and the acetal or Ketal returns.

Processes for the preparation of compounds of the formulas I and II are described in the unpublished German patent applications DE-A 19726666, DE-A 19726667 and DE-A 19726668

OR ¹

OR ¹

in denen R¹ Wasserstoff oder einen aliphatischen, cycloaliphatischen, araliphatischen, aromatischen oder heterocyclischen Rest bedeutet, wobei diese Reste weitere Substituenten, die nicht mit Acetylenen oder Allenen reagieren, tragen können und die

in which R ^{1 is} hydrogen or an aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radical, these radicals being able to carry further substituents which do not react with acetylenes or allenes and which

R independently of one another are hydrogen or aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radicals which can be linked to form a ring and m represents 0 or 1 by adding compounds of the formula III

R ⁱ OH III

to acetylenes or allenes of the formulas IV or V

R R

RC≡CRI ^V ^ _{C ==} = _C v,

RR where R ¹ and R have the meaning given above, in the gas phase at elevated temperature in the presence of a heterogeneous zinc or cadmium together with silicon and oxygen

Catalyst.

According to a modification of this method according to DE-A 19726667, which is likewise not prepublished, the by-products formed by reaction with the alcohols can also be obtained

React acetals or ketals of the formula II with the alkynes or allenes, 2 moles of enol ether being formed from one mole of alkyne or allen and one mole of acetal or ketal. Since the reaction takes place in the presence of the same catalyst, the acetal or ketal formed as a by-product can be returned to the alkyne or alien conversion.

This possibility of recycling is always desirable if there is no separate use of the acetals or ketals of the formula II.

It has now also been found that it is desirable, for safety reasons, to carry out the reaction in such a way that the alkyne or alien is virtually completely converted. This is only possible if you work with an excess of the alcohol used, with one mole of acetal or ketal in the feed corresponding to an additional mol of alcohol and recycling the unreacted alcohol and expediently also the acetal or ketal formed.

This object was achieved according to the invention with a combination of measures using a method for producing enol ethers of the formula I.

OR ¹

durch Umsetzung von Alkoholen der Formel II

by reacting alcohols of the formula II

RiOH II and / or

Acetals or ketals of the formula III

OR ¹

mit Acetylenen oder Allenen der Formeln IV bzw. V

with acetylenes or allenes of the formulas IV or V

in the gas phase at elevated temperature in the presence of a zinc or cadmium together with silicon and oxygen-containing heterogeneous catalyst and isolation of the enol ethers of the formula I by distillation, characterized in that

a) the reaction with a molar ratio of alcohol + acetal to alkyne and / or all is equal to or greater than 1 and is carried out in such a way that the stream leaving the reactor containing the enol ether of the formula I, excess alcohol of the formula II and acetal of the formula III is practically free of acetylenes or allenes (alkyne / allen conversion> 90%),

bl) the stream leaving the reactor is either subjected directly to a distillation with separation into an azeotrope consisting of enol ether I and alcohol II as the top product (which may also contain unreacted residues alkyne / allen), enol ether as intermediate boiler and acetal III as the bottom product and recycling the Top product and the bottom product into the reactor, with the proviso that the reaction conditions and the molar ratios of the reactor feed are selected such that the molar ratio of enol ether to alcohol in the reactor discharge is greater than the ratio of enol ether to alcohol in the azeotrope, or

b2) if the enol ether I and alcohol II do not form an azeotrope, the stream leaving the reactor is immediately subjected to a distillation, with separation into a top product consisting of enol ether I, uride into a bottom product consisting of acetal III and alcohol II and recycling of the bottom product into the Reactor, and / or

c) the stream leaving the reactor is subjected to a reaction on a suitable catalyst, for example an acidic ion exchanger at temperatures below 100 ° C., by converting the excess alcohol II with the enol ether I to the acetal III and separating the reaction mixture essentially freed from alcohol I by distillation the desired enol ether product and acetal III which is returned to the reactor. The conversion of alkynes or allenes with alcohols and / or acetals or ketals to enol ethers and the catalysts which are suitable for this purpose are known in detail from the cited publications. All of the measures specified there should apply here equally, so that reference is expressly made to these publications and they should be considered incorporated here. In summary, however, the reaction principle is again shown here using the example of the reaction of acetylene with ethanol and the type of catalysts used.

A) Reaction of acetylene with ethanol

OEt

HC ≡≡≡ CH + EtOH H ₂ C

H

OEt

HC = CH + 2 EtOH H ₃ C CH

OEt

B) Reaction of acetylene with the resulting diethylacetal

OEt OEt

HC CH H ₃ C CH 2 H ₂ C =

OEt H

Since the alcohol should now be used in excess, the overall reaction is shown schematically as follows:

In some cases, however, this reaction procedure has the problem that it is difficult to separate the reaction product into the components because of the formation of azeotropes with the vinyl ethers. According to the invention, this problem is solved in a simple manner with 2 equivalent methods A and B, it being possible for the two methods of operation to be combined with one another. Method A

As shown schematically in FIG. 1, acetylene is fed via line (1), the alcohol via line (2) and acetal which is recycled via line (6) into the reactor (R1), in which the gas phase reaction takes place on the zinc catalyst . A reaction mixture which contains the enol ether, excess alcohol, acetal, by-products and virtually no acetylene leaves the reactor (R1). This reaction mixture is passed either in the gaseous state or after condensation via line (3) into the second reactor (R ² ), where a reaction of the alcohol with the enol ether to form the .alpha Acetals takes place according to the equation exemplified for acetylene and ethanol: ^ OEt ^ OEt H ₂ C = C + EtOH _^ H ₃ CCH

H OEt

The conditions in the second reactor (R2) are chosen so that at the outlet of the reactor the acetal formation equilibrium is largely on the side of the acetal. This is the case if the reaction takes place at the lowest possible temperature, the highest possible partial pressure of the reagents or in the condensed phase. For example, at room temperature in the liquid phase, the equilibrium is almost entirely on the side of the acetal. Very little alcohol remains in equilibrium since the enol ether is in excess. The catalysts for this reaction are known per se and are acidic compounds in the broadest sense (for example Si0 ₂ , Al ₂ 0 ₃ , acidic ion exchangers, homogeneously dissolved Brønsted or Lewis acids).

The reaction mixture leaving the reactor (R2) via line (4) consists of enol ether, acetal and by-products and is practically free from alcohol and acetylene, so that the enol ether can be easily separated off. It is passed via line (4) into distillation D, where it is worked up into the enol ether product (5), by-products (7) and acetal (6) to be recycled. In order to ensure the stability of the products during the distillation, it may be expedient to add a neutralization after the reactor R2. Method B

B1) As shown schematically in FIG. 2, line (1) acetylene, line (2) the alcohol, line (6) recycled acetal and line (4) a recycled azeotrope of enol ether and alcohol into the reactor (R. ) fed in, in which the gas phase conversion takes place on the zinc catalysts. As in Method A, the reaction mixture leaving the reactor via line (3) consists of enol ether, acetal, alcohol and by-products and is practically free of acetylene. It is fed into the workup (D), in which a separation by distillation takes place. The top product (4) obtained is an azeotrope of enol ether and alcohol, the desired, practically alcohol-free enol ether product as intermediate boiler (5), the acetal (6) and by-products (7) from the bottom. The azeotrope (4) and the acetal (6) are returned to the reactor (R).

B2) If the enol ether I and alcohol II do not form an azeotrope, in many cases according to FIG. 3, the stream 3 leaving the reactor can be subjected directly to a distillation in column D with separation into a top product (5) consisting of enol ether and one off Bottom product (6) consisting of acetal and alcohol, which is introduced into the reactor together with alkyne / allen (1) and alcohol (2).

In both methods, the molar ratio of free alcohol + acetal to acetylene is chosen to be equal to or greater than 1, preferably 1: 1 to 5 to 1 and in particular 1 to 1 to 2 to 1, with method (B) being an additional condition that the molar ratio of enol ether to alcohol in the reaction discharge is greater than the molar ratio of enol ether to alcohol in the azeotrope, preferably 1.01 to 100 times larger, and in particular 2 to 100 times larger.

The acetylenes and allenes used are primarily the technically easily accessible acetylenes and / or allenes having 2 or 3 to 8 carbon atoms, and in particular acetylene, methylacetylene or allene or mixtures thereof, for example as they come from a C ₃ stream of one Steam crackers can be isolated.

However, the procedure according to the invention is particularly advantageous for the use of pure acetylene. Alcohols R ¹ 0H are aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic alcohols

Consideration. In general, however, low molecular weight aliphatic alcohols, in particular alkanols or alkanediols with 1 to 8, preferably 1 to 6, carbon atoms are used. Are in detail

Methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert. -Butanol, pentanol, isopentanol, ethylhexanol, ethylene glycol, propylene glycol -1, 2 and -1.3, butanediol -1, 4 and hexanediol-1,6 and especially methanol, ethanol and butanol.

The alcohols and ketals or acetals are reacted with the acetylenes or allenes in the presence of the heterogeneous zinc or cadmium and silicon and oxygen-containing catalyst in the gas phase either over a fixed bed or in a fluidized bed at temperatures from 50 to 400 ° C, preferably 100 to 250 ° C and particularly preferably 120 to 200 ° C and pressures of 0.1 to 50 bar, in particular 0.8 to 20 bar and particularly preferably 0.9 to 10 bar (all pressures based on the Sum of the partial pressures of the educts).

If necessary, the reaction mixture can be diluted with inert gases such as nitrogen, argon, low molecular weight alkanes or olefins for reasons of operational safety and better heat dissipation.

As zinc or cadmium as well as silicon and oxygen-containing catalysts cadmium silicates and preferably zinc silicates come into consideration, e.g. Silicates selected from the group consisting of (a) X-ray amorphous zinc silicate or cadmium silicate, produced by impregnating a silica carrier with a zinc or cadmium salt,

(b) crystalline zinc silicate with essentially the composition and structure of the hemimorphite of the formula ZnSi ₂ 0 ₇ (OH) ₂ -H0, where the zinc can be present in an up to 25% excess or less, based on the stoichiometric composition, and /or

(c) essentially X-ray amorphous zinc silicate, prepared by precipitation in aqueous solution from a soluble silicon and zinc compound, the formula V

Zn _a Si _c O _{a + 2c} - _{0, 5e} (OH) _s ^• f H ₂ 0 V,

in which e means the values 0 to the sum of 2a + 4c, the ratio a / c is 1 to 3.5 and f / a is 0 to 200. (a) X-ray amorphous zinc silicate or cadmium silicate catalysts are, for example, loaded with an amorphous silica

Zinc salt or cadmium salt and formation of the catalyst obtained by a thermal treatment.

The Si0 carrier is at least predominantly amorphous, has one

BET surface area between 10 and 1500 m / g, particularly preferred

100 to 500 m ² / g, a water absorption capacity of 0.1 to

2 ml / g, particularly preferably from 0.7 to 1.3 ml / g and can be used as a powder or as a finished molded article.

The carrier can also be calcined before impregnation.

However, the carrier is preferably not calcined.

A zinc-soluble or cadmium compound is a compound which is soluble in a suitable solvent. Zinc (II) salts are preferably used, which are soluble in water or aqueous ammonia or alcohols, preferably lower alcohols, and whose decomposition temperature is below 400 ° C. to 500 ° C.

An ammonia-alkaline zinc (II) acetate solution is particularly preferably used for the impregnation. In some cases, it has proven advantageous to carry out the loading with zinc in several successive impregnation steps.

If the carrier is used as a powder, the catalyst can be brought into the desired shape by shaping (e.g. by mixing, kneading and extruding or tableting).

In order to increase the pore volume, pore formers may be added (for example, superabsorbents as Lutexal ^® P (from BASF Ludwigshafen) or Walocel® (methyl - cellulose / synthetic resin -combination, Wolff, Walsrode)) at the molding.

Alternatively, another carrier, for example A1 ₂ 0 ₃ , can also be impregnated with a silicon oxide precursor compound (for example Si (0R)) and with a zinc salt or cadmium salt.

The zinc or cadmium loading can vary within wide limits. Typical values for an uncalcified precatalyst which has been prepared by impregnating an SiO ₂ support with a zinc salt or cadmium salt are, for example, between 1 and 60% by weight, Zn or Cd preferably between 7 and 30% by weight. Contents between 10 and 25% by weight (calculated in each case as ZnO or CdO) are particularly preferred. The precatalyst can also be doped with other elements preferably with alkali, alkaline earth or transition metals.

Furthermore, the catalytically active component can contain up to

80, preferably up to 50 and in particular up to 20 mol percent, may also be doped with further metals, selected from group (A) consisting of beryllium, magnesium,

Calcium, strontium, barium, manganese, iron, cobalt, nickel and copper and group (B), consisting of titanium, zirconium,

Hafnium, germanium, tin and lead, the elements of which

Group (A) partly replace zinc or cadmium and the elements of group (B) partly silicon.

The precatalyst can then be calcined at a temperature of at most 600 ° C., in particular between 80 and 300 ° C., in air or under an inert gas. The calcination between 120 and 250 ° C. in air is particularly preferred.

After the preparation of the generally catalytically inactive precatalyst, by applying a zinc or cadmium compound to a silicon oxide support, a formation is preferably carried out in which the actual active phase is formed above all on the surface of the catalyst. This solid-state reaction is promoted by the presence of water, alcohols, preferably lower alcohols or carboxylic acids, preferably lower carboxylic acids and is therefore advantageously carried out by heating the precatalyst at a temperature between 50 and 400 ° C. in an atmosphere containing water or alcohol. The reaction is preferably carried out between 100 and 250 ° C. in a gas mixture containing water or methanol. It is particularly preferred to carry out the reaction between 120 and 200 ° C. with a gas mixture containing methanol directly in the reactor in which the reaction with the alkyne or allen is to take place later. If a precatalyst based on zinc acetate is assumed, it is very easy to determine when the solid-state reaction has ended, since at this point there is almost no methyl acetate in the exhaust gas. In some cases it has proven to be advantageous to apply a mixture of methanol with alkyne and / or all and possibly also other components (such as hydrocarbons) to the precatalyst to form the active phase under reaction conditions. The formation of the active layer is caused by the increase in alkyne or alien conversion (after about 5 to 30 minutes, depending on the temperature), by the increase in selectivity (after 10 to 300 minutes, depending on the temperature) and by the decay the concentration of methyl acetate in the exhaust gas. A steady state (with high alkyne or alien conversions) and a high one Selectivity is dependent on the temperature after about 2 to

Reached 20 hours.

The corresponding mercury silicates can also be produced, but are less technically and ecologically less suitable.

(b) Hemimorphite as a catalyst

Hemimorphite is a zinc silicate of the formula Zn Si ₂ 0 ₇ (OH) ₂ ^• H0. However, not only pure hemimorphite, but generally heterogeneous catalysts are suitable for the reaction according to the invention, which at least predominantly contain zinc silicate with the structure of the hemimorphite of the formula Zn Si 0 ₇ (OH) _2-2y O _y ^• x H ₂ 0, where x and y stand for the values 0 to 1.

The production of hemimorphite is known from the literature. It can take place under normal conditions or hydrothermal conditions. Hemimorphite is preferably used, as is obtained according to the process described in DE-A 19726670.

(c) X-ray amorphous zinc silicate catalyst

It has been found that an essentially X-ray amorphous product with improved catalytic properties is obtained under the same hemimorphite production conditions but with a shorter reaction time as a precursor for the production of a crystalline hemimorphite.

For this, e.g. an aqueous suspension of an alkali or alkaline earth silicate with an aqueous solution of a zinc salt

a) Temperatures from 20 ° C, preferably 50 ° C to the boiling point of the resulting aqueous suspension

b) a pH of 4 to 9.5, preferably at a pH near the neutral point,

c) and such proportions of alkali silicate and zinc salt implemented that the conditions of formula VI are met and d) such a dwell time is observed that crystallization of the zinc silicate does not yet occur to a considerable extent.

The essentially X-ray amorphous zinc silicate thus obtainable contains Zn ²⁺ , Si ⁴⁺ and O ² "ions; in addition, the compound can contain OH ions and water of hydration. The Zn / Si ratio is 0.3 to 5, preferably 1 to 2.7, particularly preferably 2 to 2.3 and very particularly preferably 2.

The amorphous zinc silicate precipitation catalyst to be used according to the invention can also be doped with up to 80, preferably up to 50 and in particular up to 20 mol percent with further metals selected from group (A) consisting of beryllium, magnesium, calcium, strontium, Barium, manganese, iron, cobalt, nickel, copper, cadmium and mercury and group (B) consisting of titanium, zirconium, hafnium, germanium, tin and lead, the elements of group (A) being partly zinc and the elements of Group (B) partially replace silicon in the hemimorphite structure.

Examples

example 1

a) Production of ethyl vinyl ether in a tubular reactor

In a tubular reactor (length: 6 m, diameter: 6 mm), a zinc silicate catalyst (produced by impregnating spherical (0 3-5 mm) SiO shaped bodies with ammoniacal zinc acetate solution - Zn content, calculated as ZnO: 20 wt .-%) acetylene, ethanol and 1, 1-diethoxyethane with a load of 0.5 kg-m ^"2 -s ^_1 at a temperature of 160 ° C and normal pressure. The alcohol and the acetal were evaporated in front of the reactor and The gas mixture was quantitatively analyzed by means of online gas chromatography and then condensed at -10 ° C. The amounts and composition of the product mixture are summarized in Table 1. The selectivity to ethyl vinyl ether was 98% ( regarding ethanol + 1, 1-diethoxyethane). Table 1

bl) acetalization of the reactor discharge

0.1 ml of p-toluenesulfonic acid was added to 100 ml of the condensed constituents of the reactor discharge from Example 1 (a) and the mixture was stirred at room temperature for 5 min. Then it was neutralized with 1 g of potassium carbonate. The compositions (determined by gas chromatography) before and after the acetalization are shown in Table 2.

Table 2

b2) Acetalization with an acidic ion exchanger

The reaction discharge from Example 1 (a) was passed through a tube reactor made of glass (400 mm long, diameter 28 mm) cooled to 0 ° C. The reactor was filled from bottom to top as follows: first in a heat exchange section of approx. 8 cm height with metal Raschig rings, above it the acidic ion exchanger (Amberlyst 15.8 cm), then a basic ion exchanger (Amberlyst A21, 10 cm) and finally another inert pack (eg glass balls) to fill the column. 10 ml / min (corresponds to approx. 0.5 min residence time on the acidic ion exchanger) of the mixture from example la) were passed through the reactor. The composition before and after the reactor is given in Table 3: Table 3

c) distillation of the acetalization mixture and recycling of the acetal to the reactor

500 ml of the reactor discharge according to (b1) were separated by distillation on a packed column. 320 g of ethyl vinyl ether with a purity of 99.9% were obtained. The reactor sump was returned to the stage 1) reactor.

500 g of the reactor discharge according to (b2) were separated by distillation on a packed column (1.5 m wire mesh rings, 5 mm in diameter). 320 g of ethyl vinyl ether with a purity of 99.9% were obtained. The reactor bottom (about 170 g) was returned to the stage la reactor.

Example 2

The discharge from Example la) was separated in a column (1.5 m, wire mesh rings, 5 mm in diameter) at a reflux ratio of 2: 1. 222 g of ethyl vinyl ether with a purity of> 99.9% were obtained from 300 g (bp. 35 ° C.). The residue contained ethanol and acetal in a ratio of 49.5 to 50.5 and was returned to the reactor of stage la).

Example 3

a) Production of isobutyl vinyl ether in the gas phase

In a tubular reactor (length: 6 m, diameter: 6 mm), a zinc silicate catalyst (produced by impregnation of spherical (0 3-5 mm) SiO shaped bodies with ammoniacal zinc acetate solution, Zn content, calculated as ZnO: 20 wt . -%) Acetylene, isobutanol and 1, 1-di-iso-butoxy-ethane with a load of 0.1 kg-m ^ -s ^{"1 implemented} at a temperature of 160 ° C and normal pressure. The alcohol and the acetal were evaporated in front of the reactor and passed into the reactor in gaseous form with the acetylene. The escaping gas mixture was analyzed quantitatively by means of online gas chromatography and then condensed at -10 ° C. The amount and composition of the product mixture are summarized in Table 6. The selectivity for isobutyl vinyl ether was 98% (with respect to i-butanol + 1, 1-di-iso-butoxyethane).

Table 6

b) Acetalisierung des Reaktoraustrages aus 3 (a)

b) acetalization of the reactor discharge from 3 (a)

0.1 ml of p-toluenesulfonic acid was added to 100 ml of the condensed constituents of the reactor discharge from 3 (a) and the mixture was stirred at room temperature for 5 min. Then it was neutralized with 1 g of calcium carbonate. The compositions (determined by gas chromatography) before and after the acetalization are shown in Table 7.

Table 7

c) distillation of the acetalization mixture and recycling of the acetal in the reactor

500 g of the reactor discharge according to Example 3b were separated by distillation on a packed column (1.5 m, wire mesh rings, 5 mm in diameter). 355 g of isobutyl vinyl ether with a purity of 99.9% were obtained. The reactor bottom (138 g) was returned to the stage 3a) reactor.

Claims

claims 1. Process for the preparation of enol ethers of the formula I. OR ¹

by reacting alcohols of the formula II RiOH II and / or Acetals or ketals of the formula III OR ¹

in which R ^{1 is} an aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radical, these radicals can carry further substituents which do not react with acetylenes or allenes and the radicals R independently of one another are hydrogen, or aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radicals which can be linked to form a ring and m represents 0 or 1, with acetylenes and / or allenes of the formulas IV and V

in the gas phase at elevated temperature in the presence of a zinc or cadmium together with silicon and oxygen-containing heterogeneous catalyst and isolation of the enol ethers of the formula I by distillation, characterized in that a) implementation with a molar ratio of alcohol + Acetal to alkyne and / or allen equal to or greater than 1 and carried out in such a way that the stream leaving the reactor containing the enol ether of formula I, excess alcohol of formula II and acetal of formula III is practically free of acetylenes or or allenes, b ¹ ) the stream leaving the reactor is either subjected directly to a distillation with separation into an azeotrope consisting of enol ether I and alcohol II as the top product (which may also contain unreacted residues alkyne / allen), enol ether as intermediate boiler and acetal III as the bottom product and Returning the top product and the bottom product into the reactor, with the proviso that the reaction conditions and the molar ratios of the reactor feed are selected such that the molar ratio of enol ether to alcohol in the reactor discharge is greater than the ratio of enol ether to alcohol in the azeotrope, or b ² ) if the enol ether I and alcohol II do not form an azeotrope, the stream leaving the reactor is subjected directly to a distillation, being separated into a top product consisting of enol ether I and a bottom product consisting of acetal III and alcohol II and Returning the bottom product to the reactor, and / or c) the stream leaving the reactor is subjected to a reaction on a catalyst suitable for the acetalization at temperatures below 100 ° C., converting the excess alcohol II with the enol ether I to the acetal III and separating the reaction mixture, which is essentially freed from alcohol I, into the enol ether product by distillation and acetal III, which is returned to the reactor. 2 ^" . Process according to claim 1, characterized in that propyne, propadiene or mixtures thereof are used as alkyne and / or all. 3. The method according to claim 1, characterized in that acetylene is used as alkene. 4. The method according to claim 1, characterized in that the alcohols R ¹ OH alkanols or alkanediols with 1 to 8 carbon atoms used. Process according to Claim 1, characterized in that alkanols or alkanediols selected from the group consisting of methanol, ethanol, propanol, butanol, isobutanol, ethylhexanol, ethylene glycol, propylene glycol -1, 2, propylene glycol -1,3 and 1, -butanediol are used .