CS215217B1 - A method of complex catalyzed preparation of polyols - Google Patents

Abstract

The invention relates to a method for the complex-catalyzed preparation of polyols by base-catalyzed aldol condensation of carbonyl compounds with formaldehyde. The essence of the invention lies in the fact that at the beginning of the reaction, organic or inorganic redox inhibitors are simultaneously applied in an amount of 0.01 to 0.1% by weight of the formaldehyde used while continuously blowing the reaction solution with air or oxygen, and catalysts accelerating the conversion of unreacted formaldehyde to methanol and formic acid, preferably in an amount of 2% by weight of the input formaldehyde, which are applied in such a way that 1/3 is dosed into the reactor at the beginning of the aldol condensation and the remaining 2/3 are dosed after the main reaction is completed. Methyl blue, 2-methyl1, 4-naphthoquinane, potassium ferricyanide, manganese salts are preferably used as redox inhibitors. Metal salts or their compounds are preferably used as catalysts accelerating the conversion of unreacted formaldehyde to methanol and formic acid. The invention has application in the production of polyols.

Description

The application relates to a novel process for the preparation of polyols by aldol condensation, carbonyl compounds and formaldehyde in alkaline environments, and uses combinations of eukar formation inhibitors and catalysts to convert the convertible formyldehyde methanol and formic acid.

Although there is extensive scientific and patent literature for the preparation of aldol formaldehyde aldehyde condensates with higher aldehyde alcohols (HBJ Schurink: Pentaorythritol, Org. Syntheses, vol. 1, 2 ed., 425/1948: S. Berlpw, RH Barth, JB Show : The Pentaerythritola, Reinhold Publ. Co., 58 1958) and that some polyols belong to the basic industrial products of aldehyde chemistry, some negative elements in their technological manufacturing process have not been eliminated due to the complexity of the reaction. it is generally known that numerous polyols are prepared! basically catalyzed cross-linking aldol condensation of carbonyl compounds containing oG-hydrogens with formaldehyde by arduction of the resulting methylolcarbonyl compounds with formaldehyde in a subsequent crossed Cannizzar reaction. In these reactions, the most commonly used carbonyl compounds are lower aliphatic aldehydes such as acetaldehyde, n-butyraldehyde and isobutyraldehyde, with the resultant products being pentaerthritol, trimethylolethane, trimethylolpropane, and dimethylolpropane. Own or boxed Cannizzar reactions (TA Geisman: TJie Cannizzaro Reaction, Org. Reactions 2t 94 (1946) are used throughout these types of aldehyde condensations. In particular, the addition reaction of formaldehyde itself to form glycoldehyde, which induces a subsequent autocatalytic reaction, takes on a particular position. and a Idol reaction to form a diverse mixture of sugars (T. Mizuno, AH Weiss: Synthesis and Utilization of Formose Sugars, Adv. Carbohyd.

Chem. 29, 173 (1974). Alkaline sugars are highly unstable and undergo further alterations in further reactions to form colored products.

In conventional industrial production of penteerythritol and other related polyols, sodium hydroxide or calcium hydroxide are most commonly used as basic catalysts.

One of the major undesirable reactions, especially when using calcium hydroxide and an acocatalyst, is the reaction of formaldehyde itself to form sugars. Tgorba of sugars from formaldehyde in the process of producing polyols has many negative effects, such as decreasing its concentration and thereby decreasing the yield of polyols, improving the isolation of the desired products, forming chemically very heterogeneous syrups, which substantially negate the head isolation. products, reactions in subsequent post-treatment processes. There are known methods of using different inhibitors against the formation of carbohydrate syrups in the production of penteerythritol and other polyols. Some are based on the fact that the resulting glycoaldehyde does not bind to the complex (US Pat. 2,501,865 (1950)), thereby limiting its autocatalytic effect in the formation of sugars from formaldehyde. The landslide is reduced in the carbohydrate sulfur content of the reaction solution, but not prevented.

Absolutely effective inhibitor of carbohydrate syrup formation is the use of a suitable reoxide system according to AO 173988 in aldol condensations. It is based on the fact that the redox system used allows very rapid conversion of the resulting glycol aldehyde 215217 2 down to glycolic acid, thereby reliably protecting the formaldehyde present from the unwanted reaction or the sugar direction.

It is also generally known that in the preparation of polyols by aldol condensation of formaldehyde with a higher aliphatic aldehyde, the molar ratio of formaldehyde to the second aldehyde's eye is used is stoichiometric. By Import It is that by using an excess of formaldehyde, the yield of the main product calculated on the second aldehyde as well as the superior quality of the obtained pro-dock is increased.

Sak nepr. in the production of pentaerythritol, the molar ratio of formaldehyde to acetaldehyde used is greater than 4. Usually, 4.5-5 moles of formaldehyde per mole of acetaldehyde are used. Upon completion of the reaction, the unreacted formaldehyde is removed most easily by autocatalytic route to sugar, or methanol and formic acid are performed in-house using the Cannizzar reaction. (US Pat. 2,206,397, (1940)); Procedures are known where excess formaldehyde is removed by pressure distillation, which is expensive (Brit. Pat. 757, 564 (1956)). This method is exclusive to processes where high excess formaldehyde (10-15 moles) is used. In processes with an excess of up to 1 mole of formaldehyde, it is expedient to remove formaldehyde by catalyzing the Cannizzar reaction. When the glycosyldehydrogenation inhibitors are applied to the complex (e.g., boric acid), due to insufficient inhibition, the permeable formaldehyde is first autocatatically made into sugars before being transferred to methanol and formic acid by the Cannizza reaction.

These shortcomings are solved by a new proposed process for the production of polyols by aldol condensation of selected carbonyl compounds which reliably prevents sugars and converted by reacted formaldehyde catalyzed by Cannizzar reaction to methanol and formic acid.

The present invention is based on the fact that it simultaneously administers inhibitors with the preference of known formaldehyde-protecting redox systems from the autocatalytic reaction to sugars and metal-containing catalysts and its compound accelerating the conversion of unreacted formaldehyde to methanol and formic acid.

However, the choice and function of the metal catalysts used to accelerate the Cannizzar reaction to remove unnecessary formaldehyde from the reaction melt is more desirable.

A more detailed study of the rates of the Cannizzar reaction of formaldehyde in the reaction solutions after the preparation of the polyols revealed that the rate of the Cannizzar reaction is predominantly due to the composition of the reaction effluent and also to the metal catalyst. Reaction solutions with the same excess formaldehyde content have been shown to be removed by said reaction with the same excess formaldehyde content with the same catalyst at a very different time. This suggests that the reaction solution, e.g., after the preparation of peneterythritol, does not always contain the same amount of undesirable products that reduce catalyst activity.

We have also unequivocally confirmed that the rapid reaction of formaldehyde in the reaction solution is also dependent on the type of salt anion in which the catalyst is added. For example, if different salts of a divalent medium are used as the catalyst, at 3 215217 2+ Cu concentrations, the Cannizzar reaction of formaldehyde Cu (NO-j) 2, then copper oxalate CuO and CoSo 4 is the most accelerated. It is also possible to use a powdered metal sword with substantial catalysis efficiency.

It is also important to note that it is expedient to add catalysts to accelerate the Cannizzar reaction of formaldehyde by adding brown to the beginning of the aldol condensate. This gives the reaction solutions which are essential to catalytically remove formaldehyde as the catalyst batch after the reaction is complete! polyol formation.

Obviously, it depends on the reaction conditions and the rate of addition of acetaldehyde around the Cu catalyst, respectively. its compounds can be applied from the beginning of the aldol condensation. Optimally, the amount was shown to be about 0.2-1.0 g per liter of reaction solution. Larger doses are undesirable because formaldehyde may drop. it is expedient to add violet purple to the catalyst after the end of the main reactions; in the reaction solution of the end-of-reaction products only unreacted formaldehyde is already present. Generally, it is expedient to add 2/3 of the total amount of catalyst to the reactor at the beginning of 1/3 and after the end of the main reactions.

The catalyst can be recycled to the first stage of condensation after completion of the reaction.

The main advantages of the proposed process for preparing polyols are that: - it allows all types of aldol condensation of formaldehyde-catalysed bases to be carried out in such a way that sugars are avoided, - syrupy-like after major product isolation is more homogeneous from chemical point of view and therefore easier to use for further processing, - by combining inhibitor and Cu-catalysts, the efficiency of the main reaction is improved by 5-7%, - practical yields of 10-15% are considered due to the easier isolation of the main products.

Illustratively, the application of inhibitors and CU-catalysts in the preparation of polyols in the following cases, which are not exhaustive and provide only basic information on the reaction parameters and properties of the products obtained. Example 1

1.5 kg of formaldehyde and 0.65 kg of Ca (OH) 2 in the form of lime milk with the required amount of water are metered into a 20 l reactor so that the total volume of the reaction solution of 1-dehydroxy and calcium milk is 7.5 l. 0.5 g of methylene blue and 5 g of CuNo 2 soluble in small amounts of water are added with permanent air blowing, and after addition of both reagents, acetaldehyde is added in a quantity of 0.44 kg diluted with water to a total volume of 7.5 L. The gelling takes 30 minutes in such a way that 40 l, 2.5 l in the second 10 minutes, and 1.0 l of acetaldehyde are added in the first 10 minutes. to 37 ° C and gradually increases to 40-45 ° C at which temperature the reaction mixture is maintained by cooling After completion of the acetaldehyde addition, the reaction mixture is allowed to return to 1 minute, after which 25 g of CuNo-i and reaction temperature are added will increase to 50 4 215 217 C at which temperature the reaction mixture is maintained takdlho, when unreacted formaldehyde is quantified and converted to an acid and methanol. Formic '. It takes about 30-35 minutes to δο react the reaction by neutralizing the Ca (OH) 2 present with formic acid. The Cu catalyst is filtered off or centrifuged and returned to a new experiment after regeneration. It is also possible to separate the Cu catalyst together with the excess, unreacted calcium hydroxide, and, after separating the mixture in a 1: 2 ratio, to return to the new process described above. The filtrate is spontaneously separated by one of the known methods for isolating pentaerythritol, yielding about 1.22 kg of penta and dipentaerythritol, i.e. 90% yield on acetaldehyde. The crude product contained 5.5% dipentaerythritol.

A 0.20 kg syrup residue was light and did not contain any carbohydrate products that could be formed by basic transformation from the carbohydrates. Example 2

The procedure of Example 1, with the exception that the CuNo 2 catalyst as catalyst is used with copper oxide in an amount of 10 g at the start of the reaction and 20 g after addition of acetaldehyde. The yield of penta- and dipentaerythritol was 88% by weight of acetaldehyde.

The reaction time to convert unreacted formaldehyde to methanol and formic acid increased from 35 to 50 minutes. Example 3

The procedure of Example 1 except that powdered honey was used instead of CuNo 2 as a catalyst. The yield of penta- and dipentaerythritol was 86%, and the time to remove unreacted formaldehyde was increased to 70 minutes. Example 4

The procedure of Example 1, except that copper oxide (10 + 20 g) was used as the catalyst instead of Cu. The yield of penta- and dipentaerythritol was 86% for acetaldehyde, and the post-discharge time for removal of unreacted formaldehyde is 20-25 minutes. Example 5

Add Q, 70 kg of formaldehyde to a 15 L reactor and make up with lime milk containing 0.47 kg of Ca (OH) 2 and an amount of water to give a total reaction volume of 9 L. 5 g of methylene blue and 10 g of CuNo 2 soluble in a small volume of water.

After addition of the catalysts, 0.71 kg of freshly distilled isobutyraldehyde was added at such a rate that the addition was completed in 3 minutes. The urea temperature of the reaction mixture rises up to 45 ° C at which temperature the addition of isobutyraldehyde is complete with cooling. Thereafter, 20 g of CuNo-4 are added and the reaction mixture is maintained at 50 ° C until the unreacted formaldehyde is quantitatively converted to methanol and formic acid, which lasts about 3 minutes. Furthermore, the known process for the isolation of dimethylpropane as the main product by known methods is followed. The yield of dimatylolpropane was 101 kg i.e. 97% h and isobutyraldehyde. 2.5 kg of syrupy syrup contains no sugars.

The invention is widely used in all technological processes for the production of polyols, which are the basis of the paint industry. preparing some types of resins.

Claims (3)

OBJECT OF THE INVENTION 1. A process for the complexly catalyzed preparation of polyols by the base-catalyzed aldol condensation of carbonyl compounds with formaldehyde, characterized in that at the same time organic or inorganic redox inhibitors, sufficiently stable and mobile in an alkaline medium, protect the formaldehyde from autocatalytic reaction on sugar. 0.01 to 0.1% by weight of the formaldehyde used in the continuous purge of the reaction solution with air or oxygen and catalysts to facilitate the conversion of unreacted formaldehyde to methanol and formic acid, preferably in an amount of 2% by weight of the formaldehyde feed, which is applied such that at the beginning of the aldol condensation, 1/3 is fed into the reactor and the remaining 2/3 is fed after the completion of the main reaction. Method according to claim 1, characterized in that methyl blue, 2-methyl-1,4-naphthoquinone, potassium ferrocyanide, manganese salts are preferably used as redox inhibitors. 3. The process of claim 1, wherein the catalysts accelerating unreacted formaldehyde to methanol and formic acid are preferably metallic copper or its compounds.