DE1087123B - Process and device for the continuous production of ª ‰ -alkoxycarboxylic acid esters - Google Patents

Description

GERMAN

The main patent 1,067,798 protects a process for the preparation of / J-alkoxycarboxylic acid esters in which ketenes and acetals are present in the presence of acidic fluorides of elements of III. to V group or of complex fluoric acids of elements of III. or Group V of the periodic system or mixtures of these compounds in amounts of about 0.1 to 10 weight percent, preferably 1.1 to 3.0 weight percent, based on the total weight of the reactants are reacted at -50 to + 150 ⁰ C. .

In the case of a discontinuous procedure, the reaction temperature is from about 0 to 10 ° C a catalyst concentration of about 1.5 to 2%, based on the total weight of the reactants, is required for complete conversion to achieve. When the catalyst concentration is reduced, however, the conversion decreases and part of the ketene becomes discharged from the apparatus with the exhaust gas and is thus lost to the reaction.

It has now been found that lowering the catalyst content has an advantageous effect on the reaction. The catalyst not only activates the reaction of ketone with acetal, but also has an undesirable effect also cleaving to the acetal. The alcohol produced in this side reaction is consumed part of the ketone, which is thereby withdrawn from the reaction with the acetal, and it is formed Alkyl acetate.

As a sodium alcoholate solution to neutralize the catalyst is used, its consumption depends on the catalyst concentration. If a lot of sodium alcoholate solution is used, it will get there larger amounts of alcohol in the crude product, which are difficult to separate in the case of using methylal azeotropic mixtures with excess methylal and that formed by methylal cleavage Give methyl acetate.

In the case of boron trifluoride, the catalyst concentration can be practically at continuous operation complete ketene absorption can be decreased if the reaction temperature is increased above 50 ° C. In this way, even with a lower catalyst concentration, there remains that for complete conversion required reaction speed obtained.

On the other hand, in the case of hexafluorophosphoric acid, the continuous procedure Do not lower the catalyst concentration by using a higher temperature, since the hexafluorophosphoric acid is quickly inactivated by the action of heat, so that on the contrary even a higher one Catalyst concentration must be applied.

Method and device
for continuous production
of / 3-alkoxycarboxylic acid esters

Addendum to patent 1,067,798

Applicant:

Wacker-Chemie G. mb H.,
Munich 22, Prinzregentenstr. 22nd

Dr. Eduard Enk, Dr. Fritz Knörr

and Dr. Hellmuth Spes, Burghausen (Obb.),

have been named as inventors.

It has now been found that even at low temperature in the presence of a small amount of catalyst a complete ketene turnover can be achieved if one implements the implementation at the same time Use of intensive cooling, a long contact time of the gas with the reaction liquid and using a small amount of fluid circulating through which the catalyst is removed from the reaction vessel before it is inactivated.

The cooling must be so effective that the temperature in the main reaction zone 0 ° C is not significant exceeds. This can only be achieved with relatively large cooling surfaces. It is however, it is important that the volume of liquid not be too large despite the large cooling surfaces required will. As a result of the inactivation of the catalyst, which also takes place at this temperature, care must be taken care must be taken that, if possible, only active catalyst is present in the reaction zone. this will achieved by keeping the amount of liquid circulating so small that the catalyst is already is removed from the reaction space prior to its inactivation.

With the usual washers, trickle towers or cooled reaction vessels it is necessary to fill these apparatuses required a large amount of liquid not to achieve the required short residence time. Therefore, the device shown schematically in the drawings I and II is used.

In order to achieve the longest possible contact time of the gas with the liquid, of which the amount depends on the absorbed ketene, the gas must not simply bubble through the reaction liquid. as the use of cooling

009 587/432

3 4

Snakes with small volume: proven by the instead of the apparatus described can, however

the gas flows together with the liquid. This can also be used any other apparatus which

At the same time, flow holds a liquid circulation the three conditions: very short residence time of the

Upright in the apparatus, liquid, relatively long contact time of the

A device that; ddn the just mentioned gas with the liquid and intensive cooling, in

requirements is shown in drawing I. unites.

The reaction space consists of two brine-cooled. The process allows the catalyst containers 1 and 2 with precisely known volumes, the concentration to a fraction of what it used to be a solegekühite 'pipe coil 3 lower the amount required together. At the same time the crowd will are connected. The line 4 serves as a circulation line io of the secondary profile resulting from methylal cleavage the reaction liquid, the upper container 2 is ductile methyl acetate reduced by 72%. The Kaas the line 6 with your exhaust gas cooler 7 and catalyzer amount accordingly is used for neutralization through an overflow line 5 - with the neutralization - only about a seventh of that for the discontinuous one vessel 11 connected. The condensate from the exhaust gas process required sodium methylate solution condenser 7 runs through the line 8 back into the demand 15.

container 2 back. The total volume of the two reac-. ·, ..

tion vessels including the pipe coil is thus Example 1

dimensioned that at a certain ketene and acetal the reaction vessel 1 is 100 g /? - methoxy

addition, the desired dwell time is reached. The propionic acid methyl ester, 8.8 g of 95% methylal and

Exhaust gas cooler 7 is filled through line 9 with the vinegar 20 0.27 g of hexafluorophosphoric acid. Then

acid tower 10 connected. The container 1 is filled with 138 g of ketene, 271 g of 95% methylene per hour.

Line 12 connected for ketene, while the Lei- IaI and 1.068 g of hexafluorophosphoric acid continuously

lines 13 for the catalyst and 14 for the acetal through lines 12, 13 and 14 are added. Of the

open into line 4. Reaction vessel 1 and coil 3 are

The device works as follows: Methylal is cooled in a cold bath to such an extent that

slight excess and ketene are in the presence of the temperature of the liquid in the reaction vessel 2

of the catalyst reacted with one another. Is -20 ° C. The volume of liquid in the

Before start-up, the reaction vessels 1 and 2 and the coil 3 is 90 cm ³ during the vessel up to the overflow with the reaction product ketene introduction up to the overflow. That filled through. Then ketene is continuously added through line 12, 30 to line 5 from vessel 2, catalyst through line 13 and methylal from ongoing reaction product in line 14 at the same time. The ketene bubbled sationsgef AESS 11 collected in which it triummethylatlösung with Nadurch the lower reaction vessel 1 into the pipe adjusted to a p _H 7 to 8 snake 3 and pulls the reaction liquid, which is on. The exhaust gas that lets the vessel 2 through the brine cooler 7 into the upper reaction container 2 and 35 in this way is free of ketene. The dwell time
through line 4 back into the lower reaction / _cm s liquid in vessel 1 and 2 '

container 1 arrives. The heat of reaction is greatest

partly free in the pipe coil 3 and from there can V ™ s end product per hour

simply discharged due to the large cooling surface takes about 13.5 minutes.

will. This heat exchange is carried out by the Zir- 40 During a test duration of 5 hours

effective support of the fluid flow. In the total admitted:

larger amounts of ketene is already in the lower reac- _rr , snnn / * c λο -κλ- ι \

* ". rQ η · 1 w ·· χ · j α j · j u - ketene 690.0 g (= 16.43 mol)

tiongfaß 1 releases so much heat that em- ",,,,,. ,, -., -.",. _{s H orir} ").," _n , -. · ■, (

fold jacket cooling no longer effective enough from- {{eifaylal (lOWoig) .. 1295.0 g (= 17.04 mol)

can be performed. In this case the 45 ^M ™ '*> ^{elost lm} ,, _n , _om ,, _n

Installation of cooling coils has been tried and tested, whereby by Ver- "Medial 67.0g (= 2.09MoI)

enlargement of the vessel 1 that is caused by the snakes

taken volume is compensated. This out o-M + h · '

management form of the vessel 1 of drawing I is in ^ viemoxypropion-

Drawing II shown. In this formula, 15 denotes the methyl ester of ₅ o soles ·· 100.0 g

charged cooling coils, 16 that with line 2 157.73 g

12 for ketene connected ketene inlet tube, the sodium methylate

lower end for better ketene distribution e.g. as a solution 45.6g (D = 0.9325;

Shower can be carried out, 17 the connection for 209.6 g / l Na CHO ₃ )

lines 4 and 18 connect to pipe coil 3. 55

The reaction product is obtained from the overflow. 2175 g of reaction product are obtained line 5 directly into the neutralization vessel 11 - 98.6% of the amount of ketene, methylal used, where it is obtained by adding sodium methylate solution to hexafluorophosphoric acid, / I-methoxypropionic acid the Ph 7 to 8 is set. The neutralization ester and sodium methylate solution. The catalyst can also by another neutralizing agent, the concentration is 0.264%. When working up such as sodium carbonate. of the reaction product by distillation

The exhaust gas coming from the exhaust gas cooler 7 will hold:

through line 9 into the _{2? 5 Q (= 361 mol) Mefh laI} (too-Wig) charged with acetic acid, corresponding

Directed scrubbing tower 10 and from there into the open ^ _starting ^^ _of ^ _{eing tzten} Methylais,

^g6 The advantage of this arrangement, in which cooler ^{5 195} ' ⁵ S (=? · ⁶ , ⁵ ^ ^Mo1 ) methyl acetate, correspondingly

^{and reaction space} are contracted, lies in ¹⁶ > ^{10 / a} > bez0 S ^{en on} introduced ketene,

the extremely low reaction volume with the same 40.0 g of methanol (from neutralization),

long contact time of the gas with the 1462.0 g (= 12.39 mol) ß-methoxypropionic acid

Liquid and intensive cooling. 70 methyl esters minus the 100 g used.

Deis corresponds to a yield of 75.4%, based on the introduced ketene, and of 72.6%, based on methylal used.

The overall yield is accordingly 93.8%, based on methylal, and 91.5%, based on ketene.

If the lower reaction vessel is enlarged so much that the residence time of the liquid in the reactor takes place 13.5 minutes is 157 minutes, then after a short test duration despite the use of twice the amount of catalyst (0.527%) the ketene absorption is so poor that most of the Ketens escapes with the exhaust gas. If the amount of catalyst is increased four times (1.04%), so 11.3% of the ketene introduced is still lost with the exhaust gas.

Example 2

A reaction system (I ₁ 2 and 3 of drawing I) with a content of reaction ^{liquid of 3055 cm 3} during the ketene introduction, the lower reaction vessel 1 of which is provided with cooling coils as shown in drawing II, is initially filled with 3000 g / J-methoxypropionic acid methyl ester 300 g 95% methylal and 8.3 g hexafluorophosphoric acid charged.

Then 5310 g of ketene, 9800 g of 95% strength methylal and 40 g of hexafluorophosphoric acid are added continuously per hour over the course of 417 minutes. The temperature in the lower reaction vessel is -3 to + 1 ° C, in the upper -17 to -18 ° C. In the given time, a total of 36.92 kg (= 879.0 mol) of ketene, 68.5 kg of 95% Methylal, consisting of 65.070 kg (= 856 mol) of methylal and 3.430 kg (= 107.1 mol) of methanol, and 0.2863 kg of hexafluorophosphoric acid were added. The residence time is 12 minutes. The continuously overflowing reaction product is continuously neutralized, for which a total of 1330 cm ³ (= 1240 g) sodium methylate solution (209.6 g / l sodium methylate) are required. The total amount of substance used is thus 109.946 kg, the catalyst contained therein 0.261%.

The reaction product obtained is 109.9 kg, which is 99.9% of the amount used. That the Exhaust gas leaving the apparatus is free of ketones. Working up by distillation gives:

7 325 kg (= 96.4 mol) methylal (lOOVoig) = 11.27% of the methylais used,

1 154 kg (= 36.1 mol) of methanol (from the sodium methylate solution),

10100 kg (= 136.5 mol) methyl acetate = 15.52%, based on the introduced ketene,

88,000 kg or (after deducting the 3000 kg used) 85,000 kg / i-methoxypropionic acid methyl ester (= 720 mol), corresponding to a yield of 82.0%, based on the introduced ketene, and 84.1%, based on 100% Methylal.

The overall yield is thus 95.37%, based on methylal, and 97.52%, based on ketene.

If the inner cooling coils 15 of the lower reactor vessel (drawing II) in contrast to the described example is not cooled, the temperature in this vessel drops to 35 to 40 ° C below simultaneous browning of the reaction mixture. The reaction product running off has a strong smell Ketene, while a large part of the ketene is no longer absorbed at all and ends up in the exhaust gas. Even with the use of 2.05% catalyst, practically eight times the amount, it is among these Conditions not possible to achieve better ketene absorption.

Claims (7)

Patent claims: 1. Process for the preparation of / S-alkoxycarboxylic acid esters by reacting ketenes with acetals in the presence of fluorides of elements in the highest valence level of the IV. to V groups of the periodic table or of complex fluoric acids of elements the III. or V. Group of the Periodic Table or mixtures of these compounds according to Patent 1,067,798, characterized in that the reaction is carried out continuously with simultaneous Use of intensive cooling, a long contact time of the ketene with the Reaction liquid and the smallest possible amount of liquid through which the catalyst is removed from the reaction vessel before it is inactivated. 2. The method according to claim 1, characterized in that there is an amount of catalyst 0.01 to 1%, preferably from 0.1 to 0.6%, based on the amount of the end product, is used. 3. The method according to claim 1 and 2, characterized in that the reaction space continuously leaving the reaction mixture is continuously neutralized. 4. Apparatus for performing the method according to claim 1 to 3, consisting of a coil (3), which is connected to the reaction vessels (1 and 2). 5. Apparatus according to claim 4, consisting of a reaction vessel (1) which is provided with a supply line (12) provided for the Keten and through a line (4) into which the supply lines (13 and 14) open for the catalyst or the acetal, connected to the upper reaction vessel (2) is. 6. Apparatus according to claim 4 or 5, consisting of an upper reaction vessel (2), the through an exhaust line (6) and a return line (8) with a cooler (7) and through a Overflow line (5) is connected to a neutralization vessel (11). 7. Device according to one of claims 4 to 6, consisting of an exhaust gas cooler (7), the is connected by a line (9) to a washing tower (10) charged with acetic acid. 1 sheet of drawings