CS214596B1 - Process for producing di- to polyhydroxy compounds - Google Patents

Abstract

The invention relates to the field of organic technology. It solves the production of di-. to polyhydroxy compounds using alkaline earth hydroxides with a minimum need for cooling liquid. It can be used for the preparation of di-. to polyols, respectively. in condensation reactions with formaldehyde.

Description

The invention relates to the field of organic technology. Solves the production of di-. up to polyhydroxyluorin using alkaline earth hydroxides with minimal coolant demand. It can be used for the preparation of di-to polyols, respectively. in condensation reactions with formaldehyde.

SUMMARY OF THE INVENTION The present invention provides a process for producing di- to polyhydroxy compounds by reacting formaldehyde with aldehydes or ketones, in particular using alkaline earth hydroxides as a condensing agent, with a reduced need for heat removal.

Reaction. between formaldehyde and other aldehydes takes place at temperatures of 20 to 20 ° C. 40 ° C, whereby various methods of conducting the reaction are known. The reaction may take place e.g. by adding a basic catalyst to the mixture of aldehydes, adding both formaldehyde and higher aldehyde simultaneously to the aqueous alkali catalyst solution, or adding the higher aldehyde or ketone to the mixture of hydroxide and formaldehyde (Berlow E., Bart, RH,. JE: The Pentaerythritols, Reinhold Publ. Corp. New York 19.58; Walker JF: Eormaldehyde, Reinhold Publ. Corp., New York 1964), mainly raw materials in continuous systems are fed separately to the system. This scheme can be applied in both discontinuous and continuous systems. In most cases, it is ensured that the reaction product does not mix with different reactor residence times in continuous processes (German Pat. No. 1910,057, U.S. Pat. No. 2,790,836, Tal. Pat. No. 626,223, Franc, Pat. 1,251,470). The reactors are designed for this purpose in different ways, such as serpentine, tower type with mixing type of mixing and so on. Most of these systems work with homogeneous catalysts, most often sodium hydroxide, for reasons of simpler handling, but also because the catalyst does not catalyze formaldehyde side reactions.

A disadvantage of these systems is the increased formation of by-products e.g. formation of dipentaerythritol in the production of pentaerythritol increased demands on reactor design and heat dissipation. These disadvantages are addressed by MS. inventions which allow working with stirred reactors where heat removal is effected by the external circulation of the reaction mixture through a heat exchanger (Os. AO 170 615, CS AO 177 651). By application of the aforementioned author's certificates it is also possible to work with an alkaline earth catalyst in a continuous system, achieving high yields of the desired products as well as good heat dissipation.

The inconvenience of said reaction systems is the demand for heat dissipation, since in the summer months it is necessary to use a cooling station to cool the warmed circulating cooling water.

Research has shown that the reaction can be carried out with reduced heat dissipation, i.e. both cooling water and alkaline earth hydroxide, if the reaction is carried out according to the present invention.

According to the present invention, a process for the production of di- to polyhydroxy compounds by reacting formaldehyde with aldehydes and / or ketones, in particular using alkaline earth hydroxides as condensing agent, with reduced heat recovery needs, is effected preferably with an antifoam, sub-cooled to 10 to 40 ° C, preferably to 20 to 30 ° C, are fed into the reaction system, the average reaction time being 5 to 60 minutes, preferably 10 to 25 minutes and the temperature of the mixture at the outlet from the reaction system is 40 to 70 ° C, preferably 50 to 60 ° C.

The advantage of the preparation of the polyols according to the invention is the energy efficiency of the reaction system. Cooling water up to 25 ° C from an air cooling station can be used for heat removal. It does not require the cooling of 10 ° C or 15 ° C of hot water, which must be used in the prior art systems using alkaline earth hydroxides as condensing agent. In the process according to the invention, the feedstocks must be cooled to a temperature below 30 ° C before being fed to the suction side of the circulation pump via a cooler. This is especially the temperature of formaldehyde, respectively. dilution water, where e.g. condensate from the thickeners, the insulating part of the process. Moreover, raw materials stored, respectively. prepared in production generally do not reach this temperature. As an inhibitor of the internal condensation of formaldehyde, a compound of manganese, boron, iron or a mixture thereof is most preferably used, the dosing being suitable together with the formaldehyde, respectively. in dilution water. Before mixing formaldehyde with - the second aldehyde, respectively. ketone, it is advisable to prepare a mixture of formaldehyde with a condensing agent and dissipate the heat generated in the condenser so that the temperature of the mixture preferably does not exceed 30 ° C.

The mixing of the raw materials is suitable by means of a circulation pump, wherein the second aldehyde and / or ketone and formaldehyde with a condensing agent or separately are fed to the suction side of the pump and thence via a heat exchanger to one or more reactors. The reactor design requirements are not demanding. The reactors may be e.g. flow vessel equipped with a stirrer, but preferably upright cylinders, so that the sparingly soluble catalyst (using calcium hydroxide) is not deposited on the bottom of the vessel. To reduce settling, it is advisable to connect the reactor pump to the overflow of the previous reactor or to the reactor. of the mixer so that the pump partially sucks air into the reactor. Make drawn. the air did not cause foaming of the solutions, it is advisable either to separate or in one stream with the raw materials a defoamer. From the point of view of formaldehyde consumption, condensation agent, but also the possibility of formation of by-products, it is advantageous to choose piston flow vessels. Since the reaction takes place at temperatures of 30 to 60 ° C, the reaction time required depends on the type of aldehyde reactivity. ketone ranges from. 10 to 40 minutes, and the size and number of devices can be selected accordingly. It is advantageous to carry out the reaction according to the above process continuously, but of course, a batch-like reaction method is also possible. With the use of an inhibitor, it can be guaranteed that up to 60 ° C the condensation products of formaldehyde are not formed. It is advisable to use flow reactors with more or less prestige. The extension of the reaction time in the stirred reactor helps to form syrups. The reaction can be carried out without cooling during the reactions, with the raw materials being cooled below 30 ° C, or by increasing the amount of dilution water in the system. It is also possible to conduct the reaction with a higher concentration of raw materials, but in this case a portion of the heat of reaction is taken directly in the reactors or between the individual reactors to heat exchangers to remove the heat generated.

This method is more advantageous because less heat is needed to evaporate the water to isolate the product from the reaction solution.

The correctness of the reactions can be checked at the exit of the reactions by determining the condensates from formaldehyde alone, e.g. by the periodate method for vicinal dihydroxy compounds. Depending on the condensate content, it is possible to control the correctness of the reactions by adjusting the reaction temperature at the inlet or reactors, or by adjusting the concentration of the raw materials.

Energy saving as well as simple reactor design is the greatest advantage of the process of the present invention.

Particular processes for preparing polyols of the present invention are described in the Examples. which do not exhaust all possible combinations. EXAMPLE

The pentaerythritol is prepared in a thermally insulated reactor in that acetaldehyde is introduced into the mixture of formaldehyde, lime and the formaldehyde condensation inhibitor tempered to a certain temperature within 90 seconds. An aqueous mixture with a formaldehyde: acetaldehyde: calcium hydroxide molar ratio of 6: 1: 0.6, with a formaldehyde content of 13.7% by weight, is used as the feed.

The effect of the initial temperature of the mixture on the reaction time, the final temperature of the mixture and the yield of the reaction products is summarized in Table 1.

Table 1. Effect of initial pentaerythritol preparation parameters on product recovery. Manganese sulphate inhibitor in an amount of 0.0025 wt. of manganese on the shaft.

Number experiment initial temperature raw materials (° C) final temperature (° C) The reaction time (Min) Selectivity of product formation to acetaldehyde (%) PE DPE bis PEME £ PE 1 11.5 48,7 ‘ 17 76.5 2.2 2.7 81.3 2 ' 11.5 50.8 16 77.7 2.9 2.8 83.4 3 15.0 . .52,9 13 . 79.8 2.6 2.6 85.0 . 4 15.0 53.0 14 77.0 2.5 2.4 '81.9 5 15.0 53.4 15 80.2 : 2,5 2.6 85.3

PE - pentaerythritol

DPE. - dipentaerythritol bis PEME - bispentaerythritol monoformal. In addition, the tempered raw materials, in addition to acetaldehyde, are mixed and after stabilizing the temperature acetaldehyde is metered in, as in the first case. The results are summarized in Table 2.

Table 2. Effect of the initial temperature of the mixture on the final temperature of the reaction mixture and the selectivity of product formation to acetaldehyde.

Number experiment initial temperature mixtures (° C) Final mixture temperature (° C) Reaction. time (min) Selectivity of product formation to acetaldehyde (%) PE DPE bis PEME Σ.ΡΕ 1 15.3 47.0 19 . 77.0 3.4 2.2. 82.6 2 16.4 48.0 20.. 80.1 2.4 .2.5 85.0 3 20.0 51.7 15 80.0 . 2,6 ' 2.7  85.3 4 20.2 . 51.6 15 79.2 3.4 2.7 85.3 5 23.7 54.7 10 80.5 3.0 2.6 86.1 6 24.5 55.7 11 80.8 4.0 2.9. 87.7 . 7 29.65 60.7 7 80.8 3.9 2.8 87.5 8 30.5 61.5 8 81.0 3.8 2.8 . 87.6

In the next series of attempts. destroys the initial concentration of formaldehyde. When the initial concentration is reduced. % formaldehyde to 12.45 wt. the reaction temperature rises from an initial 30 ° C to 57 ° C, wherein the selectivity to acetaldehyde at the 9 minute period of acetaldehyde addition is 83.0% for pentaerythritol, 3.9% for dipontaerythritol and 2.7% for bispentaerythritol monoformal. The amount per technical product is 89.6%. In the case where the formaldehyde cohortation is reduced to 11% by weight. the initial temperature rises from 30 to 54 degrees with unchanged selectivity of acetaldehyde to pentaerythritol.

If the reaction is made without inhibitor, the temperature rises to 85 ° C, the product is dark brown with a sweet odor after. syrups and the yield of the technical product decreases by 10%. The isolated technical pentaerythritol is brown instead of snow white in the first case.

Furthermore, the formaldehyde content of the solution after neutralization is in the first case 5.7% by weight, which can be obtained by pressure rectification, possibly by steam distillation, while in the second case the solution does not contain formaldehyde. . . ·

Example 2

The preparation of 1,1,1-trimethylolpropanol (2,2-dihydroxymethyl-1-butanol) is carried out in the presence of calcium hydroxide in three cylindrical jacketed reactors. The reactor diameter is 3 cm, height 50 cm. At a rate of 35 cm ² per minute, the reaction mixture contains 18 wt. % of formaldehyde in the feed and the molar ratio of formaldehyde-n-butyraldehyde-lime is 3.5: 1: 0.6, 85% yield on n-butyraldehyde is obtained. In this case, the initial reaction temperature with the addition of 0.0065 wt. the manganese formate in the feed is at the inlet of the first reactor 30 ° C at the outlet of the last reactor 50 ° C. The cooling water temperature is 25 ° C. The solution is neutralized after neutralization. If the formaldehyde internal condensation inhibitor is not used, the temperature after 3 reactors reaches 70 ° C and the product is brown after neutralization. The yield will decrease by 13%.

EXAMPLE 1 a d 3

In the apparatus of Example 2, 2,2,6,6-tetrahydroxymethyl-1-cyclohexanol is prepared by condensing cyclohexanone with formaldehyde. When using a molar ratio of 6: 1: 0.7 - formaldehyde-cyclohexanone-calcium hydride and a concentration of 15 wt. of formaldehyde to the reaction solution using 0.01% manganese sulfate provides 80% selectivity for the desired product. Subtle yields are obtained using 0.02% ferrous sulfate or 0.05% sodium tetraborate. Without the use of inhibitors, the product yield drops by 13%.

Claims (3)

In the next series of experiments. it destroys the initial concentration of formaldehyde. In the destruction of the initial concentration. to 12.45% by weight, the reaction temperature rises from an initial 30 ° C to 57 ° C, while the selectivity to acetaldehyde at 9 minutes for the start of acetaldehyde addition is 83.0% for pentaerythritol, 3.9% for dipontaerythritol and 2.7% % to biosentium triolmonoform. The amount for the technical product is 89.6%. If the formaldehyde concentration is reduced to 11% by weight. the initial temperature rises from 30 to 54 degrees with unchanged acetaldehyde selectivity to pentaerythritol. If the reaction is carried out without inhibitor, the temperature rises to 85 ° C, the product is dark brown with a sweet odor. the syrup and yield technology will drop by 10%. The isolated technical pentaerythritol is brown instead of the wild-type in the first case. In addition, the formaldehyde content of the solution is poneutralized. it is in the first case 5.7% by weight, which can be obtained by pressure rectification, optionally by steam distillation, while in the latter case the solution does not contain formaldehyde. . . Example 2 Preparation of 1,1,1-trimethylolpropia (2,2-dihydroxymethyl-1-butanol) is carried out in the presence of calcium hydroxide in three cylindrical reactors. The reactor diameter is 3 cm, height 50 cm. When the reaction mixture is dosed at 35 cm 2 for a minute, the mixture contains 18% by weight of formaldehyde in the feed and the molar ratio of formal-dehyd - n-butyraldehyde-lime is 3.5: 1: 0, 6, reaches 85% yields on n-butyraldehyde. The initial reaction temperature with the addition of 0.0065 wt. the manganese formate is fed to the first reactor at 30 ° C to the outlet of the last 50 ° C reactor. Cooling water temperature is 25 ° C. The neutralization solution is cloudy. If no formaldehyde intracondensation inhibitor is used, the temperature after 3 reactors reaches 70 ° C and the product is neutral after neutralization. Example 1 and d 3 In the apparatus of Example 2, 2,2,6,6-tetrahydroxymethyl-1-cyclohexanol is prepared by condensation of cyclohexanone with formaldehyde. Using a 6: 1: 0.7 molar ratio of formaldehyde-cyclohexanone calcium hydroxide and a concentration of 15 wt. of formaldehyde to the reaction solution using 0.01% manganese sulfate afforded 80% selectivity to the desired product. Similar extracts are obtained using 0.02% ferrous sulfate or 0.05% sodium tetraborate. Without the use of inhibitors, the product yields will drop by 13%. BACKGROUND OF THE INVENTION A process for the production of di- to polyhydroxy compounds by reacting formaldehyde with aldehydes and / or ketones, in particular using alkaline earth hydroxides as a condensing agent with a devastated need for reaction heat, characterized in that the raw materials or mixtures thereof together with the formaldehyde condensation inhibitor OF THE INVENTION preferred with defoamer, supercooled to 10 to 40 ° C, preferably to 20 to 30 ° C, are brought into the reaction system, the average reaction time being 5 to 60 minutes, preferably 10 to 25 minutes, and the temperature of the mixture leaving the reaction system is 40 to 70 ° C, preferably 50 to 60 ° C. Tisk 51/84