DD287252A5 - PROCESS FOR THE CONVERSION OF PREPARED PRODUCTS OF TRIMETHYLOLPROPAN PRODUCTION TO TRIMETHYLOLPROPAN, DIMETHYLOLPROPAN AND OTHER PRODUCTS OF THE VALUE - Google Patents

Abstract

The invention relates to a process for the conversion of precursors of trimethylolpropane preparation to trimethylolpropane; Dimethylolpropane and other value-added products. Precursor fractions from the preparation of trimethylolpropane are converted by transesterification and transacetalization with methanol in the presence of a strongly acidic catalyst. Trimethylolpropane, dimethylolpropane or a valuable product fraction enriched in dimethylolpropane, the dimethylacetals of formaldehyde, n-butyraldehyde and alpha-ethylacrolein and methyl formate are obtained from the neutralized reaction mixture by multistage separation by distillation. The proposed procedure allows an increase in the yield of trimethylolpropane and the recovery of other usable products from a hitherto hardly chemically recycled waste fraction. {Trimethylolpropane; Forward Group; Rectification; Vacuum distillation; transesterification; transacetalization; methyl formate; Formaldehyde dimethyl acetal; n-Butyraldehyddimethylacetal; Ethyl acrolein dimethylacetal; Sulfuric acid; Separation}

Description

Field of application of the invention

The invention relates to a process for the conversion of precursors of trimethylolpropane preparation and serves to increase the overall yield of trimethylolpropane and to obtain further products of value.

Characterization of the known prior art Trimethylolpropane is a valuable intermediate for the production of coating resins, polyesters, polyurethanes, Plasticizers and synthetic lubricants. The preparation of trimethylolpropane is usually carried out by reacting n-butyraldehyde with formaldehyde in

aqueous solution in the presence of alkaline Kcndensationsmitteln, preferably calcium hydroxide or sodium hydroxide.

The starting aldehydes as well as the intermediates formed during the aldol condensation are very reactive,

therefore, in addition to the desired trimethylolpropane formation further reactions occur, leading to by-products of different structure. Although several methods have become known which have the objective of making appropriate measures to make the reaction so that high yields of trimethylolpropane are achieved and the

Proportion of by-products remains low, the by-product formation could be prevented in any case. Usually

In practice, trimethylolpropane yields of about 70 to 80% of theory are achieved.

The present after the trimethylolpropane synthesis reaction mixtures containing water, unreacted formaldehyde,

excess alkaline condensing agent, formate salts of the condensing agent used (calcium formate or

Sodium formate), trimethylolpropane and organic by-products. / The further workup of these reaction mixtures is carried out in a known manner iij a succession of several

technological stages. This includes:

Neutralization of the alkaline condensing agent by addition of an acid (organic acid, mineral acid, carbon dioxide);

- Separation of the excess formaldehyde;

- Separation of the formate salts, optionally present further inorganic constituents and the water of the target product trimethylolpropane and the organic by-products.

Different solutions are known for each of these processing stages. This gives a crude trimethylolpropane which, in addition to soluble residual amounts of formate salts and optionally further inorganic salts,

Impurities mainly contains the resulting in the trimethylolpropane synthesis and in the workup of the reaction mixtures of organic by-products.

The isolation of pure trimethylolpropane from this crude product is generally carried out by vacuum distillation. Apart from pure trimethylolpropane, a precursor fraction which contains the by-products which are more volatile than trimethylolpropane is obtained. In addition, a distillation residue is obtained which contains the by-products heavier than trimethylolpropane by-products and the residual fractions of formate salts and inorganic impurities contained in the crude product used in the vacuum distillation. The accumulating amounts of these by-products are considerable. According to the literature, in the recovery of 11 trimethylolpropane about 0.3t of organic by-products are obtained. These are usually about 40% lighter than trimethylolpropane volatile precursors and about 60% heavy as trimethylolpropane volatile products that arise as a vacuum distillation residue.

Since it is extremely difficult in practice to isolate individual constituents from the complicatedly composed, consisting of numerous components by-product mixtures and supply them to a material economy, these organic by-products of trimethylolpropane production are usually treated as waste products and utilized only as caloric.

For the purpose of recycling, it has already been proposed to obtain alpha-ethylacrolein by thermal cleavage of the by-products of the crude trimethylolpropane obtained by distillation. In this process, the feedstocks and the residues of the trimethylolpropane vacuum distillation are mixed and dried under continuous process by heating to 473 to 543K in liquid cleavage products (alpha-ethylacrolein, methanol, water, formaldehyde, n-butyraldehyde), gaseous decomposition products (carbon dioxide, carbon monoxide) and converted a flowable cleavage residue. A disadvantage of this procedure is that the alpha-ethylacrolein must be separated by distillation in additional technological stages of the remaining cleavage products, whereby its purification is quite expensive. Since the feedstreams are split only to a maximum of about 67%, especially the products of this boiling range are only used imperfectly in terms of material economy. If one also considers that both the by-products and residues of trimethylolpropane vacuum distillation contain considerable residual proportions of valuable trimethylolpropane which are converted to the less valuable alpha-ethylacrolein and the other low-quality fission products during the thermal cracking, recycling takes place according to the already proposed method economically unfavorable.

Object of the invention

The aim of the invention is to develop a process for the conversion of preproducts of the trimethylolpropane preparation, in which an increase in the yield of valuable product, trimethylolpropane, a production of dimethylolpropane and other valuable products is achieved and the overall economic efficiency the Trimelhylolpropan recovery is improved.

Presentation of the invention

Investigations to identify the structure of the products contained in the preprocess of the trimethylolpropane vacuum distillation have found that essentially the following types of sturctures occur:

Formic acid esters of trimethylolpropane such as trimethylolpropane monoformate (I), trimethylolpropane diformate (II) and trimethylolpropane orthoformate (III).

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(I) (M) (I I D

mixed acetal of formaldehyde with trimethylolpropane and methanol, trimethylolpropane-methanol formal (IV) CH ₀ OH

I ²

C ₀ H ^ -C-CH ₀ O-CH ₀ -OCH.

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CH ₂ OH

Trimethylolpropane cyclic acetals of different aldehydes with 1,3-dioxane structure wio trimethylolpropane formal (V), trimethylolpropane butyraldehyde acetal (VI), and trimethylolpropane ethylacrolein acetal (ViI)

C ₂ H ₅ -C.

\ r

CH ₂ OH (V)

C ₂ H ₅ -C

CH- (CH ₀ ) -CH, ι 2

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(Vl)

CH ₂ -O- C ₂ H ₅

H ₅ -C CH-C = CH,

CH ₂ -OH

(VII)

Trimethylolpropane monomethyl ether (VIII) and its cyclic acetal with formaldehyde, trimethylolpropane monomethyl ether formal (IX)

CH ₂ OCH ₃

CH ₂ OCH ₃

C ₀ H ₁₁ -C-CH ₀ OH

C ₂ H ₅ -C '

CH ₂ OH

, CH ₀ -O _x

CH ₂ -O '

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(VIII) (IX)

Formic acid esters of oimethyloipropane, dimothylolpropane monoformate (X) and dimothylolpropane diformate (XI)

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Dimethylolpropane '! XII) and its cyclic acetals dimethylolpropane-formal (XIII), dimethylolpropane-butyraldehyde-acetal (XIV) and dimethylolpropane-ethylacrolein-acetal (XV)

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- Further sturkture'l unidentified organic by-products. In addition, if necessary, small amounts of formaldehyde, methanol, n-butyraldehyde, alpha-ethylacrolein and water and always appreciable shares of the target product trimethylolpropane.

The proportions of the individual components may vary depending on the specific conditions and process steps in the trimethylolpropane synthesis and in the workup of the reaction mixtures in relatively wide Gronzen.

From the Zusammeniitellung of the identified constituents it is apparent that in the preliminary products of trimethylolpropane · vacuum distillation, the target product trimethylolpropane in free form and bound ester-like or acetal-like in high proportions and that a caloric use or a cleavage workup with the aim of obtaining alpha-ethylacrolein according to the known state of the art does not sufficiently take into account the valuable substance content of these substance mixtures.

It was therefore the object to chemically convert the precursors of trimethylolpropane Hersiellung in appropriate catfish and work up that the recovery of the originally contained trimethylolpropane and additional, formed in the chemical conversion trimethylolpropane amounts and other value products is possible. This object was achieved by a process for the conversion of Varlaufprodukten of rrimethylolpropan production to trimethylolpropane, dimethylolpropane and other value products under transesterification and Umacetalisierung the by-products contained erf ndungsgemäß in that the precursor product fraction with 0.6 to 5.0kg / kg of a low-boiling aliphatic alcohol and then mixed with 0.02 to 0.2 kg / kg of a strong acid and while maintaining a water content in the thus obtained mixture of 0.0 to 0.05kg / kg of a thermal treatment at a temperature of 293 to 343 K with a Residence time of 0.1 to 10 hours, then the acidic reaction mixture is neutralized by the addition of an alkaline substance and after workup trimethylolpropane, dimethylolpropane or a dimethylolpropane rich, nor shares of cyclischer ™ trimethylolpropane formal and other cyclic Aceta'en of Trimethylolpropane en thaltende value product fraction, which is used directly or for further conversion of the remaining cyclic acetals undergoes renewed transacetalization under harsher reaction conditions, and as woitere reaction products formic acid Alkylester, Formaldehyddialkylacetal and acetals of n-butyraldehyde and alpha-ethylacroleins with the low-boiling aliphatic alcohol in pure form or obtained as mixtures.

It is advantageous to use methanol as the low-boiling aliphatic alcohol. By using the particularly reactive in the transesterification and Umacetalisierung methanol, a rapid and running under mild conditions conversion can be achieved. Preferably, 2.0 to 3.0 kg / kg of the low boiling aliphatic alcohol is added.

As the catalytically active strong acid is advantageously used concentrated sulfuric acid. The preferred range for the acid addition in the first conversion step is 0.05 to 0.15 kg / kg, based on the feed fraction used. According to the invention, water in the mixture subjected to transesterification and transacetalization should be absent world-wide.

It is advantageous that the reaction temperature is adjusted during the thermal treatment so that the added

aliphatic alcohol is not distilled off from the reaction mixture. When methanol is the preferred

Reaction temperature at 303 to 333 K. The residence time in the first conversion step is preferably in the range of 0.5 to 3 hours. In the procedure according to the invention, those contained in the preliminary products of trimethylolpropane preparation Formic acid esters of trimethylolpropane or dimethylolpropane quantitatively transesterified to form Methyl formate and with release of equivalent proportions of the desired products trimethylolpropane and Dimethylol.

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(I)

Acetals with a chain-like structure, such as trimethylolpropane-methanol-formal (IV), are virtually quantitatively umacetallsiert.

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(IV)

Cyclic-structure acetals, such as trimethylolpropane-butyraldehyde-acetal (VI), trimethylolpropane-ethylacrolein-acetal (VII) and trimethylolpropane-formal (V), which are reported to be relatively stable to such transformations, are surprisingly found under the mild rencation conditions already partly transacetalized.

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The equilibration in the sense of a substantial formation of trimethylolpropane and dimethylolpropane is achieved in the novel procedure, without the measures commonly used in such reactions to influence the equilibration and thus the conversion in the desired direction, for example, continuously distilling off resulting, low-boiling reaction products, imperative are.

Under the mild working conditions to be used according to the invention, the transesterification and transacetalization proceed very gently, there are no noticeable side reactions taking place to form fission products which reduce the yield of products of value. Thus, a simple technological solution and a favorable operation in terms of energy consumption is made possible.

The reaction mixture present after the conversion is neutralized and contains the products formed by transesterification and transacetalization formic acid methyl ester, formaldehyde dimethylacetal, n-butyraldehyde dimethyl acetal and alpha-ethylacrolein dimethylacetal, excess methanol, the products of value dimethylolpropane and trimethylolpropane, unreacted residual proportions of by-products of trimethylolpropane Herstollung (especially residual proportions of the cyclic acetals V, Vl and VII), and shares of inorganic salts from the neutralization of the mineral acid catalyst. It is separated by distillation separation of the low-boiling reaction products of methyl formate and dimethylformaldehyde dimethylacetal and the excess methanol in a known manner by distillation. In this case, according to the Siedelage first n-butyraldehyde dimethylacotal and alpha-ethylacrolein dimethylacetal, then rich in dimethylolpropane, still shares in cyclic! Trimethylolpropane formal (V) and other cyclic acetals of trimethylolpropane (Vl, VII) containing valuable product fraction and finally won trimethylolpropane. The rich in dimethylolpropane fraction can be used as Zusatzkompcnente for lubricants or work up to pure dimethylolpropane, which is a sought-after value-added product and can be used, inter alia, for the production of resins, paints, coatings and optoelectronic devices. If one still wants to eliminate the remaining portions of cyclic trimethylolpropane acetals and convert them into trimethylolpropane, this can be achieved according to the invention by subjecting this dimethylolpropane-rich fraction to further conversion of the remaining acetals to a new transacetalization under harsher reaction conditions. This second transacetalization step becomes advantageous with a use of 0.5 to 5.0 kg / kg of methanol, 0.02 to 0.2 kg / kg of sulfuric acid at temperatures in the range from 343 to 393 K with a residence time of 0.5 to 10 Hours operated, wherein the Formaldehvd dimethylacetal formally formed by Umacetalisierung of trimethylolpropane is continuously distilled off. After completion of the reaction, the acidic reaction mixture is neutralized and the remaining mixture in a known manner by distillation in formaldehyde · dimethylacetal. Separated methanol, n-butyraldehyde dimeihylacetal, alpha-ethylacrolein dimethylacetal, dimethylolpropane and trimethylolpropane. Preferably, the distillative separation of the neutralized reaction mixture from the second transacetalization can be carried out together with the neutralized reaction mixture from the first Umacetalisierungsstufe.

The conversion of the precursors of trimethylolpropane preparation with transesterification and transacetalization can advantageously also be carried out in combination with a transacetalization of by-products heavier than trimethylolpropane by-products, which are obtained as the residue of the trimethylolpropane vacuum distillation. The isolation of the trimethylolpropane additionally obtained by the process according to the invention leads to a marked increase in the overall yield of this valuable target product. The dimethylacetals of n-butyraldehyde and alpha-ethylacrolein are useful as a special solvent; they can also be converted to the aldehydes or to other derivatives of the aldehydes as needed. Methyl formate and formaldehyde dimethyl acetal are also valuable substances for which there are many possible uses. Thus, the process according to the invention for the conversion of precursor products of the trimethylolpropane preparation achieves a substantial standardization of the complex mixtures of substances and a conversion of previously scarcely used by-products into valuable, versatile materials.

The application of the process according to the invention is not necessarily limited to precursors from the trimethylolpropane vacuum distillation, it is also possible when using from other technological stages of trimethylolpropane production and processing (liquid-liquid extraction, recrystallization) derived by-product mixtures, if these contain the above-characterized structural types of by-products.

embodiments example 1

50 kg / h of an enriched with formic acid esters of trimethylolpropane precursor fraction from the vacuum distillation of crude trimethylolpropane with a composition according to the information in Table 1, Jen mixed with 100kg / h of methanol and with the addition of 3 kg / h of concentrated sulfuric acid (H ₂ SO ₄ content 0.98 kg / kg) at atmospheric pressure, 328K and 3 hours residence time in a stirred reactor. During this time gaseous about 2.65 kg / h of a largely consisting of formic acid methyl ester reaction product, which was condensed by cooling. After the indicated reaction time, the acidic reaction mixture was neutralized by addition of sodium hydroxide dissolved in methanol (NaOH concentration about 0.10 kg / kg), separated from the depositing inorganic salt and then distilled off in a continuous distillation column. The top product was a further 10.014 kg / h of methyl formate (boiling range 305-310K) and 1.351 kg / h of formaldehyde dimethyl acetal (boiling range 31Q-320K). As Geitenstromprodukt 113.170kg / h of methanol were recovered and returned to the stirred reactor. The bottom product of this column had the composition given in Table 2. It was further separated by multistage rectification.

In this case, 0.160 kg / h of p.-butyraldehyde dimethylacet'jl (boiling range 385-390K), 1.246 kg / h of alpha-ethylacrolein · dimethylacetal (boiling range 403-408K), then 4.297 kg / h of a fraction were obtained, which in addition to dimethylolpropane mainly Trimethylolpropane formal and the cyclic acetals of trimethylolpropane with n-butyraldehyde or alpha-ethylacrolein contained (boiling range 360-383K at 0.27 to 0.4 kPa, composition of this fraction see Table 3). What remained was a residual proportion of sodium sulfate-containing trimethylolpropane concentrate (38.169 kg / h, calculated on a sodium sulfate-free basis). This concentrate was processed by further rectification under vacuum distillation of crude trimethylolpropane with little effort to trimerthylylpropane of high purity. The composition of the trimethylolpropane concentrate is given in Table 4.

Table 1: Composition of the conversion used in Example 1, enriched with formates of trimethylolpropane, Pre-product fraction (figures in kg / kg) Methanol 0.0119 kg / kg Water 0.0105 kg / kg Dimethylolpropane diformate (XI) 0.0110 kg / kg Dimethylolpropane monoformate (X) 0.0031 kg / kg Dimethylolpropane (XII) 0.0028 kg / kg Trimethylolpropane formal (V) 0.0492 kg / kg Trimethylolpropane monomethyl ether (VIII) 0.0026 kg / kg Trimethylolpropane butyraidehyde acetal (VI) 0.0098 kg / kg Trimethylolpropane-ethylacerolein-acetal (VII) 0.0697 kg / kg Trimethylolpropane-methanol formal (iV) 0.0561 kg / kg Trimethylolpropane monoformate (I) 0.3253 kg / kg Trimethylolpropane diformate (II) 0.0983 kg / kg Trimethylolpropane orthoformate (III) 0.1467 kg / kg

unidentified components 0.0035 kg / kg

Trimethylolpropane 0.1995 kg / kg Saponification number: 246.0 (mg KOH consumption per 1 g of substance)

Table 2: Composition of Example 1 after the conversion reaction and the separation of the light-sorbents Reaction products and de: Mc: h = .-. =! S available Stoffgnmkr.hns {data in kg / kg, based on sodium sulfate-free

Base)

Water 0.0366 kg / kg

n-butyraldehyde dimethyl acetal 0.0035 kg / kg

Ethylacrolein dimethyl acetal 0.0274 kg / kg Dimethylolpropane (XII) 0.0136 kg / kg Trimethyloipropan formal (V) 0.0475 kg / kg Trimethylolpropane monomethyl ether (VIII) 0.0029 kg / kg Trimethylolpropane butyraldehyde acetal (VI) 0.0052 kg / kg Trimethylolpropane-ethylacrolein-ecetal (VII) 0.0344 kg / kg

unidentified components 0.0038 kg / kg

Trimothylolpropane 0.8251 kg / kg Versoifungszahl: 0.3 (mg KOH consumption per 1 g of substance)

Table 3:

Composition of the fraction containing dimethylolpropane and cyclic trimethylolpropane-acetals according to Example 1 (data in kg / kg)

Dimethylolpropane (XII) 0.1443 kg / kg

Trimethyloipropan-formal (V) 0.4994 kg / kg

Trimethylolpropane monomethyl ether (VIII) 0.0098 kg / kg

Trimethylolpropane butyraldehyde acetal (VI) 0.0484 kg / kg

Trimethylolpropane-ethylacrolein-acetal (VII) 0.2911 kg / kg

not identified components 0.0070 kg / kg

Table 4:

Composition of the trimethylolpropane concentrate according to Example 1 (data in kg / kg based on sodium sulfate-free base)

Trimethyloipropan-formal (V) '0.0005 kg / kg

Trimethylolpropane monomethyl ether (VIII) 0.0023 kg / kg

Trimethylolpropane-butyraldehyde-acetal (VI) 0.0007 kg / kg

Trimethylolpropane-ethylacrolein-acetal (VII) 0.0083 kg / kg

unidentified components 0.0038 kg / kg

Trimethylolpropane 0.9844 kg / kg

The fraction containing dimethylolpropane and cyclic trimethylolpropane-acetals (Table 3) can be converted into products of value by transacetalization under more severe reaction conditions according to Example 2 to obtain further trimethylolpropane and dimethylacotalenes of formaldehyde, n-butyraldehyde and alpha-ethylacrolein.

Example 2

5.0 kg / h of a dimethylolpropane and cyclic trimethylolpropane-acetal-containing fraction according to Table 3 in Example 1 were reacted with 20.0 kg / h of methanol and with 0.750 kg / h of concentrated sulfuric acid with stirring at 363 K and the autogenous pressure. The formed formaldehyde dimethyl acetal was continuously distilled off from the reaction mixture via a column having sufficient separation performance. After 7 hours, the acidic reaction mixture was neutralized by the addition of sodium hydroxide dissolved in methanol (NaOH concentration about 0.10 kg / kg). The neutralized and separated from the deposited inorganic salt mixture was worked up by distillation in a known manner. In this case, 1.222 kg / h of formaldehyde dimethylacet ~> l, 0.900 kg / h of ethylacrolein dimethyl acetal and 0.140 kg / h of n-butyraldehyde dimethyl acetal were obtained. 23,850 kg / h of methanol were recovered and recirculated. The converted mixture after isolation of the dimethyl acetals had the composition shown in Table 5. The cyclic trimethylolpropane acetals were largely umacotalized under the harsher reaction conditions of this example, with additional amounts of the valuable target product trimethylolpropane being formed. Relatification can give a trimethylolpropane citrate having a similar composition to that of Example 1 (Table 4) which can be processed by introducing the vacuum distillation of crude trimethylolpropane to neat trimethylolpropane.

Table S:

Composition of the mixture obtained according to Example 2 (4.290 kg / h, based on sodium sulfate-free base) after separation of the dimethyl acetals formed (Angabon in kg / kg, based on sodium sulfate-free base)

Dimethylolpropane (XII) 0.1683 kg / kg

Trimethyloipropan formal (V) 0.0350 kg / kg

Trimethylolpropane monomethyl ether (VIII) 0.0121 kg / kg

Trimethylolpropane butyraldehyde acetal (VI) 0.0044 kg / kg

Trlmethylolpropane-ethylacrolein-acetal (VII) 0.0170 kg / kg

unidentified components 0.0082 kg / kg

Trimethylolpropane 0.7550 kg / kg

Example 3

A lead product fraction from de ^r vacuum distillation of crude trimethylolpropane with a composition as indicated in Table 6 was used in an amount of 50kg / kg with 150 kg / h of methanol and then 5 kg / h of concentrated sulfuric acid (H] SO ₄ content 0 , 98 kg / kg).

At a reaction time of 323 K, the acidic mixture was reacted at atmospheric pressure. During a residence time of 5 hours escaped about 1.45 kg / h of a largely bus formic acid methylesterbestohenden volatile reaction product, which was condensed by cooling.

After the indicated reaction time, the acidic reaction mixture was neutralized by the addition of sodium hydroxide dissolved in methanol (NaOH concentration about 0.10 kg / kg). The neutralized mixture was worked up analogously to the details in Example 1. A total of 3.932 kg / h of methyl formate and 2.695 kg / h of formaldehyde dimethyl acetal were obtained, and 10 l / kg of methanol were distilled off and recycled.

There remained 49.853 kg / h of a reaction mixture (based on natrlurnsulfatfreie base), were separated from the rectification by 0.673 kg / h of n-butyraldehyde dimethylocetal and 2.200 kg / h ^r 'vylacrolein dimethylacetal, as well as the water formed in the neutralization.

The remaining mixture was separated in a known manner by multistage rectification. This gave 21.906 kg / h of a dimethylolpropane-enriched product fraction and 22.514 kg / h (based on sodium sulfate-free basis) of a trimethylolpropane concentrate. The composition of the dimethylolpropane fraction is shown in Table 7, that of the trimethylolpropane concentrate in Table 8.

The trimethylolpropane concentrate can be processed to pure trimethylolpropane (included in the vacuum distillation of crude trimethylolpropane). The dimethylolpropane fraction can be used directly in the composition according to Table 7 for various fields of application. If one still wants to eliminate the cyclic trimethylolpropane acetals still present, this can be achieved in a further transacetalization stage according to Example 4.

Table 6: Composition of the precursor product fraction used in the conversion in Example 3 (data in kg / kg) Methanol 0.0054 kg / kg Water 0.0132 kg / kg Ethylacrolein 0.0024 kg / kg Dimethylolpropane formal (XIII) 0.0025 kg / kg Trimethylolpropane monomethyl ether formal (IX) 0.0025 kg / kg Dimethylolpropane-butyraldehyde acetal (XIV) 0.0085 kg / kg Dimethylolpropane-ethylacrolein-acetaKXV) 0.0076 kg / kg Dimethylolpropane diformate (XI) 0.0327 kg / kg Dimethylolpropane monoformate (X) 0.0562 kg / kg Dimethylolpropane (XII) 0.2754 kg / kg Trimethylolpropane formal (V) 0.0175 kg / kg Trimethylolpropane-butyraldehyde-acetal (VI) 0.0339 kg / kg Trimethylolpropane-ethylacrolein-acetal (VII) 0.1145 kg / kg Trimethylolpropane-methanol-formate (IV) 0.1207 kg / kg Trimethylolpropane monoformlate) 0.05l2kg / kg Trimethylolpropane orthoformate (III) 0.0231 kg / kg

unidentified components 0.0037 kg / kg

Trimethylolpropane 0.2290 kg / kg Saponification number: 72.3 (mg KOH consumption per 1 g of substance) Table 7: Composition of the dimethylolpropane fraction according to Example 3 (data in kg / kg) Dimethylolpropane formal (XIII) 0.0048 kg / kg Dimethylolpropane-butyraldehyde-acetal (XIV) 0.0095 kg / kg Dimethylolpropane-ethylacrolein-acetal (XV) 0.0082 kg / kg Dimethylolpropane (XII) 0.7911 kg / kg Trimethylolpropane formal (V) 0.0332 kg / kg Trimethylolpropane monomethyl ether (VIII) 0.0010 kg / kg Trimethylolpropane butyraldehyde acetal (VI) 0.0368 kg / kg Trimethylolpropane-ethylacrolein-acetal (VII) 0.1096 kg / kg

unidentified components 0.0058 kg / kg

Table 8:

, Composition of the Trimethylolpropane Concentrate According to Example 3 (Data in kg / kg, based on sodium sulfate-free basis)

Trimethylolpropane formal (V) 0.0027 kg / kg Trimethylolpropane monomethylethet (VIII) 0.0042 kg / kg Trimethylolpropane-butyraldehyde-acetal (VI) 0.0033 Kg / kg Trimethylolpropane-ethylacrolein-acetal (VII) 0.0205 kg / kg

unidentified components 0.0026 kg / kg

Trimethylolpropane 0.9667 kg / kg Example 4

25 kg / h of the obtained in Example 3 Dimothylolpropan fraction with a composition according to Table 7 were mixed with 50kg / h of methanol and then with 1.250kg / h of concentrated sulfuric acid (H ₂ SO ₄ content 0.98 kg / kg). The Umacetaliserung the cyclic Trimothylolpropan-Acoialo was carried out at 378 K under pressure, the resulting formaldehyde dimethyl acetal was separated from the reaction mixture. After 5 hours, the acidic mixture was neutralized, the precipitating inorganic salt was filtered off. Thereafter, the mixture was worked up by rectification in the manner already described in the preceding examples. 0.477kg / h of formaldohydedi-methylacetal, 0.740kg / h of n-butyraldehyde dimethyl acetal and 1.880kg / h of ethylacrolein dimethyl acetal were obtained. 57.264 kg / h of methanol was recovered and returned to the conversion stage.

The mixture after removal of the dimethyl acetals had the composition shown in Table 9. By rectification it was possible to obtain highly concentrated dimethylolpropane with a purity of more than 0.98 kg / kg. The resulting trimethylolpropane concentrate could be worked up in a known manner to pure trimethylolpropane.

Table 9: Composition of the dimethylolpropane fraction boiled according to Example 4 (23.630 kg / h, based on sodium sulfate-free Base) after separation of the dimethyl acetals formed (data in kg / kg, based on sodium sulfate-free base) Dirnethylol propane butyraldehyde acetal (XIV) 0.0002 kg / kg Dimethylolpropane-ethylacroleln-acetaKXV) · 0.0003 kg / kg Oimethylolpropane (XIII) 0.8532 kg / kg Trimethy loipropan-formal (V) 0.0018 kg / kg Trimethylolpropane monomethyl ether (VIII) 0.0011 kg / kg Trimethylolpropane-butyraldehyde-acetal (VI) 0.0008 kg / kg Trimethylolpropane-ethylacrolein-acetal (VII) 0.0035 kg / kg

unidentified components 0.0059 kg / kg

Trimethylolpropane 0.1332 kg / kg It can be seen from the examples that the precursor product fractions in the treatment according to the invention are undulating Conversion of the esters and acetals of the polyols dimethylolpropane and trimethylolpropane and forming the valuable Polyols react. If proportions of free aldehydes or free carboxylic acids are contained in the feed product fractions, they are

also converted into Dimothylacetale or in carboxylic acid methyl ester.

One thus achieves a far-reaching formation of high-grade products from previously hardly chemically used waste products.

Claims (11)

1. A process for the conversion of precursors of trimethylolpropane production to trimethylolpropane, dimethylolpropane and other value products with transesterification and Umacetalisierung the by-products contained, dr-Jurch characterized in that the precursor product fraction with 0.3 to 5.0 kg / kg of a low-boiling aliphatic alcohol and then mixed with 0.02 to 0.2 kg / kg of a strong acid and while maintaining a water content in the thus obtained mixture of 0.0 to 0.05 kg / kg of a thermal treatment at a temperature of 293 to 343 K with a Residence time of 0.1 to 10 hours, then the acidic reaction mixture is neutralized by the addition of an alkaline substance and after workup trimethylolpropane, dimethylolpropane or a rich in dimethylolpropane, still proportions of cyclic trimethylolpropane formal and other cyclic acetals of trimethylolpropane containing value-product fraction , the it is used directly or for further conversion of the remaining cyclic acetals undergoes renewed transacetalization under harsher reaction conditions, and obtained as further reaction products alkyl formate, Formaldehyddlalkylacetal and acetals of n-butylraldehyde and alpha-ethylacroleins with the low-boiling aliphatic alcohol in pure form or as mixtures become. 2. The method according to claim 1, characterized in that methanol is mixed as a low-boiling aliphatic alcohol. 3. Process according to claims 1 and 2, characterized in that 2.0 to 3.0 kg / kg of low-boiling aliphatic alcohol are added. 4. Process according to claims 1 to 3, characterized in that sulfuric acid is added as a strong acid. 5. Process according to claims 1 to 4, characterized in that 0.05 to 0.15 kg / kg sulfuric acid are mixed. 6. Process according to claims 1 to 5, characterized in that the thermal treatment is carried out at a temperature of 330 to 333 K. 7. Process according to claims 1 to 6, characterized in that the thermal treatment takes place at a residence time of 0.5 to 3 hours. 8. Process according to claims 1 to 7, characterized in that the workup of the neutralized reaction mixture with recovery and recycling of the excess aliphatic alcohol and the isolation of the reaction products in pure form or in the form of mixtures by distillation. 9. The method according to claim 1, characterized in that the rich in dimethylolpropane, still proportions of cyclic trimethylolpropane formal and other cyclic acetals of trimethylolpropane containing valuable product fraction for further conversion of the remaining acetals in an additional conversion stage with 0.5 to 5.0 kg / kg of the low-boiling aliphatic alcohol and 0.02 to 0.2 kg / kg of the strong acid mixed and by thermal treatment at a temperature of 343 to 393 K and the autogenous pressure with a residence time of 0.5 to 10 hours umacetalisiert and then the acidic reaction mixture is neutralized and worked up by distillation. 10. The method according to claims 1 and 9, characterized in that the distillative separation of the neutralized reaction mixture from the second conversion stage gemoinsam carried out with the neutralized reaction mixture from the first conversion stage. 11. The method according to claim 1, characterized in that the conversion of the precursors of trimethylolpropane Hfirstellung under transesterification and Umacetalisierung in combination with a Umacetalisierung of heavier than trimethylolpropane volatile by-products obtained as the residue of the trimethylolpropane vacuum distillation, is performed.