DE1240876B - Process for the production of trioxane - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

CO7d

German class: 12q-25

Number: 1240 876

File number: F 35838IV b / 12 q

Filing date: January 24, 1962

Opened on: May 24, 1967

The formation of trioxane in the distillation of acidified aqueous formaldehyde solutions has been around since known for a long time. According to U.S. Patent 2304080 Trioxane is produced from aqueous formaldehyde solutions in the presence of acids, with formaldehyde-containing Trioxane-water mixtures are distilled off. The low yields that can be achieved here can be increased by discontinuing the amounts of formaldehyde recovered from the distillate be returned to the distillation vessel.

Furthermore, US Pat. No. 2,347,447 describes a process for the preparation of trioxane, in which the formaldehyde-containing trioxane-water mixture is distilled off, while using a fractionating column. However, this fractionating column does not have a dephlegmator, rather, it is a column head with a reflux condenser attached, the

Process for the production of trioxane

Applicant:

Paint factories Bayer Aktiengesellschaft,
Leverkusen

Named as inventor:

Dr. Ernst-Ulrich Köcher, Leverkusen;

Dr. Gerhard Dankert, Cologne-Flittard;

Dr. Wolfgang von der Emden, Leverkusen;

Dipl.-Ing. Dieter Pinkwart, Cologne-Stammheim -

long operation of such a system any malfunctions, e.g. B. by paraformaldehyde separation, appear.

Tables I and Ia of Example 1 summarize the results obtained in comparative experiments. Experiment 1 of Table I as a comparative example to the process of the USA patent 2 304 080 was carried out and the considerable increase in the rate of reaction achieved compared to the known method.

Furthermore, it is particularly advantageous that the inventive method with a relatively Return is controllable. In this case, a low expenditure on apparatus for trioxane 20 is fully continuous relatively rich crude product obtained. can be carried out without

In this process, however, falls during the separation
of the trioxane from the crude product paraformaldehyde containing water and formaldehyde, which the
continuous execution of these procedures very 25
difficult. Furthermore, formaldehyde losses of at least 20%> occur in all previous processes
calculated on sales, on. Another disadvantage
of the previous processes is that the rate of formation of trioxane is quite low, looking for 2 to 20 under the same conditions, so that the process according to the invention can be used to obtain larger amounts of trioxane. The Trioxanaus either long times or large apparatuses let the progressiveness of the invention be required. clearly recognize according to the procedure.

There has now been a process for the production of According to a preferred embodiment of the

Trioxane by fractional distillation according to the invention is the separation of the 70 ⁰ / g aqueous formaldehyde solutions in counter-trioxane from the distillate, which generally contains water and formaldehyde in addition to waiting for acids and separation of the trioxane from trioxane, in the distillate found that the disadvantages of being carried out that the known processes that distill over do not have and that vapors before their condensation is characterized with a low that the distillation was in counter-boiling, water-immiscible solvents of 0.1 up to 2 moles of ammonia or a primary, secondary or tertiary aliphatic, aromatic mixed for the trioxane in liquid or vaporized form, the mixture condenses and the two phases formed thereby or heterocyclic amine or an acid amide are separated from one another, or acid imide and / or one polyvalent aiko- The aqueous phase that the beings tual portion of the hol with at least 3 carbon atoms or benzyl 45 over-distilled formaldehyde is then used for

alcohol or cyclohexanol or an aliphatic amino alcohol per liter of the reaction mixture carried out and wherein the amount of acid is such that the pH of the reaction mixture is below 2 lies.

The inventive method an improvement in the yield of trioxane and a

continuous implementation of the process fed back into the reaction, while from which the solvent and the trioxane-containing phase the trioxane as usual, preferably by distilling off of the solvent, is isolated.

The process product is suitable as a very pure starting material for the production of high-molecular

709 587/545

3 4

circular polyoxymethylene. Furthermore, it serves as a starting point

drawn solvent and must have as a source for the present pH value are suitable as

production of formaldehyde of the highest purity. Acids only those acids that are strongly dissociated in water,

As the starting material for 30 to 70% ig ^e wäß- example, the mineral acids and organic membered formaldehyde solutions used, the beispiels- 5 sulfonic acids, and Lewis acids such as sulfuric acid, from the in known manner by dehydration hydrochloric acid, phosphoric acid, perchloric acid, Borfluoroder oxidation Hydrogen formic acid, benzenesulfonic acid, p-toluenesulfonaldehyde or paraformaldehyde produced from methanol and a corresponding acid, alkanesulfonic acids and boron trifluoride.
the amount of water that has been obtained. The proportions of the components can be 50 to 70 percent by weight formaldehyde vary within wide limits. Used in hydro solutions. Presence of an appropriate amino compound

The embroidery to be used as amino compounds, the required amount of acid is naturally

Substance compounds contain at least one group higher than when using a corresponding one

pation of the general formula of alcohol, as part of the acid is used to neutralize the

15 base is consumed. In any case, the amount of acid must be

/ be so large that the pH of the reaction mixture

- N, is below 2. Appropriately, one comes

\ π / concentration of free acid of at least about

0.1 equivalent per liter of reaction mixture for

in which R and R 'are a hydrogen atom, an alkyl, 20 application, but they can easily have 1 equivalent

Aralkyl, aryl, acyl radical (including the sulfonyl per liter amount or exceed,

and carbaminyl radical), the radicals for carrying out the process according to the invention

can be the same or different. Furthermore, this is made up of formaldehyde, water, acid and

men organic nitrogen heterocycles with at least the basic compound to be used or the

a ring nitrogen into consideration, the additional 25 using alcohol existing reaction mixture

may contain further heteroatoms and are subjected to a distillation through a column. the

May be substituted on the ring and / or on the nitrogen. The way in which this distillation is carried out is

Instead of these amino compounds or in combination with optimal results, this is essential. Under application

nation with these, a polyhydric alcohol is also distilled in a packed column if selected

with at least 3 carbon atoms or benzyl 3 ° a suitable reflux ratio a trioxane

alcohol or cyclohexanol or aliphatic amino-water azeotrope, which is about under normal pressure

alcohols that boil two substituents on the amino group at 91.5 to 92.5 ° C and approximately 68% trioxane

can carry the meaning given above, in addition to 32% water and formaldehyde. Of the

used. The formaldehyde content of the distillate varies depending on the

Suitable nitrogen compounds are, for example, the formaldehyde concentration in the sump between

wise primary aliphatic and aromatic amines about 10 and 15% The execution of this azeotrope

like methylamine, ethylamine, isopropylamine, n-butyl distillation gains special importance through the

amine, cyclohexylamine, 2-ethylhexylamine, dodecyl- presence of the basic compound to be used

amine, aniline and its core substitution products or fertilize the alcohol in question in the reaction

such as the chloroanilines, toluidines, xylidines, anisidines, 4 ° mixture, where by increasing the formation

Anilinesulfonic acids and anilinecarboxylic acids as well as <x- speed of the trioxane a considerable reduction

or / 3-naphthylamine; Secondary generation of formaldehyde losses and, under certain circumstances, are also suitable

Amines such as diethylamine, dibutylamine and the N-Al reduce the formaldehyde concentration in the

kylaniline; tertiary amines such as trimethylamine, distillate is also effected.

Triethylamine, tributylamine, dimethyldodecylamine, 45 The process can be carried out batchwise or continuously. Dimethylaniline, diethylaniline are suitable and just as natural. In the case of discontinuous nitrogen heterocycles of the pyridine, pyrrole type, mode of operation, the distillate is cooled and the piperidines, pyrrolidine; morpholine and N-methylmorpholine may be separated from the specific heterocyclic aqueous fraction of the crystallized trioxane nitrogen bases. This can be done in the usual way by suction, N-methylpiperidine, triethylenediamine and 2,3-tri-5 ° centrifugation or by solvent exmethylene-3,4,5,6-tetrahydropyrimidine and melamine traction, eg. B. with methylene chloride and distilling off and called antipyrine. Aromatic and aliphatic solvents also occur. The obtained, low tables diamines such as the phenylenediamines and alkylene amounts of water and formaldehyde containing crude diamines, ζ. B. ethylenediamine, propylenediamine and trioxane can be used in this form.
1,6-diaminohexane can be used. In the case of continuous operation, several primary and secondary amines can also be used to carry out the process. In the acylated on nitrogen, z. B. be acetylated; 1 and 2 are exemplary substances, thioureas and N-sulfonyl compounds are suitable for the continuous production of trioxane or sulfonic acid amides, as shown in p-toluene.

sulfonic acid amide, phthalimide, acetanilide, benzanilide, 60 In FIG. 1 is a reminder equipped with a stirrer

oc- and y-pyridone, guanidine, dicyandiamide and action vessel 1 shown that the above

Sulfamic acid. Contains reaction mixture. Through line 2 is

As a polyhydric alcohol, for example, as much paraformaldehyde is added continuously as

Glycerine, 1,4-butylene glycol, diethylene glycol, tri- through the formation of trioxane and through losses

ethylene glycol. ^ 65 is consumed, so that in the reaction vessel 1 constantly

Suitable alkanolamines are, for example, ethanol, an approximately constant corresponding formaldehyde

amine, diethanolamine, triethanolamine and dibutanol concentration is maintained. The reaction

amine. mixture is heated to the boil. The fleeting

constituents distill through the packed column 3 and from there into the dephlegmator 4, which for a ensures sufficient reflux ratio in the column 3, so that an im at the top of the dephlegmator 4 essentially consisting of the trioxane-water azeotrope as well as smaller amounts of formaldehyde existing gaseous Mixture is removed, which reaches the condenser 7 via line 5 after in the line 5 has been admixed with methylene chloride. The methylene chloride can be vaporized directly fed from the column 19 via line 11 or condensed beforehand, possibly in a storage vessel collected and injected into line 5 in liquid form. From the condenser? flows that now liquid mixture in a separator 8, where it is in a specific heavier, from trioxane and methylene chloride existing and a specifically lighter one, consisting mainly of formaldehyde and water Phase separates. This aqueous phase now passes through an overflow 9 into a siphon-like blocking vessel 10, which in turn is directly connected to the reaction vessel 1 by an overflow. On this one The distilled water flows continuously into the path together with the unchanged formaldehyde Reaction vessel back. The separator 8 still carries a ventilation pipe at the top, which is for the Pressure equalization with the outside air takes care of the operation of the previously described part of the system permitted under increased or reduced pressure. The methylene chloride phase is at the bottom of the separator 8 continuously withdrawn in the amount in which it reproduces and the distillation column 19 supplied. Here the methylene chloride is distilled off and into the circuit via line 11 returned. At the bottom of the column 19, the crude trioxane is removed, which is then still in the usual Way can be cleaned.

The F i g. 2 shows a simplified embodiment of the system from FIG. 1. Here was on a dephlegmator waived. Otherwise, the reference numbers have the same meaning as in FIG. 1.6 a device for adding dropwise methylene chloride. The part of the plant in which the processing of the Trioxane-methylene chloride solution takes place, was not drawn. This can take place as in FIG. 1 or can also be carried out discontinuously. The absence of the dephlegmator brings the essentials The disadvantage is that at the top of the column 3 there is a very water-rich and formaldehyde-rich vapor stream emerges, the exact composition of which depends on the formaldehyde concentration in reaction vessel 1 and depends on the rate of distillation. The plant only works at a sufficiently low distillation speed reasonably satisfactory.

In both continuous embodiments, it is essential that the from the packed column 3 coming vapors before they are cooled with a low-boiling, water-immiscible solvent for trioxane are mixed. Methylene chloride is preferably used, but are other solvents, for example aliphatic or aromatic hydrocarbons, can also be used. the Use of the last-mentioned solvent requires a modification of the separator 8, since it then turns out to be specifically heavier phase separates the water-formaldehyde mixture on the bottom. By adding the solvent deposits of paraformaldehyde on the colder parts of the apparatus become practical completely prevented, which otherwise inevitably lead to blockages after a short period of operation the apparatus. For this reason, there is also a normal column head with a reflux condenser attached to regulate the reflux ratio in the Column 3 is unsuitable, while a dephlegmator as it is in the plant according to FIG. 1 is used, enables trouble-free operation.

The following examples explain the process according to the invention. The quantities given relate to this to parts by weight.

example 1

In a 1-1 stirred apparatus with a 30 cm Raschig column attached, 315 parts of paraformaldehyde (95%) and 185 parts of water are placed in each case. Then, an acid and the amine to be used or the alcohol to be used are added to the mixture with stirring to 110 heated up to 120 ⁰ C bath temperature until a virtually clear solution has formed, and then as far higher heating that approximately at the head of the column Pass over 40 parts of distillate per hour. The distillate is condensed in a receiver cooled with ice-water. The composition of the distillate consists on average of 25% trioxane, 30% formaldehyde and 45% water. The trioxane is separated off by extraction with methylene chloride, shaking out the extract with a little sodium bisulfite solution, drying the extract and evaporating the methylene chloride.

In the following Table I are the when used corresponding amino compounds or alcohols in 19 experiments compared to that only in the presence an acid carried out experiment No. 1 compiled results obtained.

However, with the experimental setup given in this example, it is not possible to achieve a perfect Carry out azeotropic distillation, since the reflux ratio in the column is too low and practical is not adjustable.

H ₂ SO ₄
H ₂ SO ₄
H ₂ SO ₄
H ₂ SO ₄
H ₂ SO ₄
H ₂ SO ₄ acid Table I. Oxy compound Trioxane yield in%
of sales*) attempt
No. 1 mole percent **)
1.5 mole percent
2 mole percent
2 mole percent
2 mole percent
2 mole percent Amino or 1 mole percent
1 mole percent
1 mole percent
1 mole percent
1 mole percent 54.1
85.3
100.0
78.1
89.4
75.0 1
2
3
4th
5
6th without
Piperidine
Piperidine
Pyridine
aniline
ammonia

See footnotes at the end of the table.

I 240 876

Table I (continued)

attempt
No. H ₂ SO ₄ acid 7th H ₂ SO ₄ 2 mole percent 8th H ₂ SO ₄ 2 mole percent 9 H ₂ SO ₄ 2 mole percent 10 H ₂ SO ₄ 2 mole percent 11 H ₂ SO ₄ 2 mole percent 12th H ₂ SO ₄ 1 mole percent 13th p-TSS ***) 1 mole percent 14th p-TSS 2 mole percent 15th p-TSS 2 mole percent 16 H ₂ SO ₄ 2 mole percent 17th H ₂ SO ₄ 2 mole percent 18th p-TSS 2 mole percent 19th H ₂ SO ₄ 1 mole percent 20th 2 mole percent

Tnoxane yield in% / xy connection of sales *) 1 mole percent 83.2 1 mole percent 66.8 1 mole percent 73.8 1 mole percent 74.4 1 mole percent 69.7 1 mole percent 73.2 1 mole percent 75.1 1 mole percent 89.7 1 mole percent 74.0 1 mole percent 79.5 1 mole percent 78.0 1 mole percent 80.4 1 mole percent 77.8 1 mole percent 80.3

urea

Guanidine sulfate

Dimethylaniline

Triethylamine

Phthalimide

Aniline-2-sulfonic acid

Anthranilic acid

aniline

p-toluidine

p-chloroaniline

Benzyl alcohol

p-toluenesulfamide

p-toluenesulfamide

Cyclohexanol

*) Based on formaldehyde consumed. **) Based on the formaldehyde used. ***) p-toluenesulfonic acid.

Furthermore, attempts were made according to the stick patent specification to be used in the USA.- inventive method 2,347,447 in the example described substance or oxy compounds was worked. the method, compared to this results obtained are in the following Ta method without and in the presence of those summarized after the erbelle Ia.

acid Table Ia Formaldehyde loss
in% of sales Trioxane
yield
% attempt
No. H ₂ SO ₄ 1 mole percent
H ₂ SO ₄ 1.5 mole percent
H ₂ SO ₄ 2 mole percent
H ₂ SO ₄ 2 mole percent
p-TSS 3 mole percent Amino or oxy compound 20th
12.3
9.2
14.3
7.4 80
87.7
90.8
85.7
92.6 1
2
5
6th
28 without
(according to U.S. Patent 2,347,447)
Piperidine 1 mole percent
Aniline 1 mole percent
Ammonia 1 mole percent
Triethanolamine 1 mole percent

The experiments show that in the process according to the invention, the trioxane yield is significantly greater and the formaldehyde loss is considerably less than in the known process.

Example 2

In this example, the procedure is as in Example 1, but a Raschig column is installed at the top Dephlegmator connected, in which part of the vapors distilling off is condensed. The rest The portion of the distillate is taken off at the head of the dephlegmator at 92.5 to 94 ° C.

Approach: As in example 1.

The amino compound is 0.2 mol of aniline and the acid is 0.3 mol of p-toluenesulfonic acid per 10 mol Formaldehyde used.

About 30 parts of distillate are obtained per hour, which contains 68% trioxane, 18% water and 14% Contains formaldehyde. The trioxane yield is 93.4% of sales.

In a parallel experiment, which only in the presence of 0.1 mol of sulfuric acid per 10 mol of formaldehyde is carried out, the trioxane yield is 76.8% of the conversion.

Example 3

In the apparatus shown in FIG. 2, continuous tests lasting from 30 to 70 hours are carried out carried out, a solution of 315 parts of p-formaldehyde (95%) and 185 parts of water with the addition the amount of acid and amino or oxy compound indicated in Table II is heated to the boil and the rate of distillation at the top of the column 3 is about 40 parts per hour. In the outgoing vapors from the column 3 is an equal amount of methylene chloride from the storage vessel added dropwise, then the outgoing mixture in the condenser? condenses, then the liquid mixture brought into the separator 8 and there the organic trioxane-methylene chloride phase from the Formaldehyde-water phase separated, the latter with a content of 35 to 38% formaldehyde through the line 9 is returned to the reaction vessel via the blocking vessel 10. The trioxane phase becomes the trioxane is separated off in the customary manner by distillation.

The results obtained by this method in various experiments are summarized in Table II.

Table II

10

attempt
No. p-TSS *) acid Amino or oxy compound 1 mole percent 3,4,5,6-tetrahydro- 1 mole percent Triox
g / h booty
% of sales Formaldehyde loss
in% of the stake 1 p-TSS 0.5 mole percent without 1 mole percent pyrimidine 1 mole percent 4.9 72.3 14.8 2 p-TSS 1.5 mole percent aniline 1 mole percent Piperidine 1 mole percent 8.92 95.2 2.53 3 H ₂ SO ₄ 1.5 mole percent Pyridine 0.1 mole percent Diethylene glycol 9.33 91.7 4.62 4th H ₂ SO ₄ 1.5 mole percent aniline Triethanolamine 10.05 89.0 7.07 5 1.5 mole percent 2,3-trimethylene 9.57 87.5 6.97 p-TSS 6th p-TSS 0.5 mole percent 12.4 91.5 4.52 7th p-TSS 1.0 mole percent 9.45 91.2 5.1 8th 2.0 mole percent 10.3 100.0 -

*) p-toluenesulfonic acid.

From Table II it can be seen that in the case of the invention ao according to the method a considerable increase in the rate of reaction is achieved and the pro Hour obtained yield of trioxane is significantly higher than if without the amino or alcohol compounds in question is being worked on. In addition, the formaldehyde losses are significantly lower.

Claims (2)

Patent claims: 1. Process for the preparation of trioxane by fractional distillation of 30 to 70% aqueous Formaldehyde solutions in the presence of acids and separation of the trioxane from the distillate, characterized in that the distillation in the presence of 0.1 to 2MoI Ammonia or a primary, secondary or tertiary aliphatic, aromatic or heterocyclic Amine or an acid amide or acid imide and / or a polyhydric alcohol with at least 3 carbon atoms or benzyl alcohol or cyclohexanol or an aliphatic Performs amino alcohols per liter of the reaction mixture and the amount of acid measured becomes that the pH of the reaction mixture is below 2. 2. The method according to claim 1, characterized in that that the separation of the trioxane from the distillate is carried out continuously with the aid of a Water-immiscible low-boiling solvent for the trioxane carries out, wherein this solvent in liquid or vaporized form mixed with the over-distilling vapors, the distillate condenses and the two phases forming in the condensate from each other are separated, with the containing most of the formaldehyde distilled over aqueous phase is returned to the reaction vessel and from the other phase the trioxane in Is isolated in the usual way. Considered publications:
U.S. Patent Nos. 2,304,080, 2,347,447. 1 sheet of drawings 709 587/545 5.67