DE1221621B - Process for the production of aqueous formaldehyde solutions - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07c

German class: 12 ο - 7/01

Number: 1221621

File number: F 43636IV b / 12 ο

Filing date: August 1, 1964

Opening day: July 28, 1966

. It is known that the heat generated in the formaldehyde production can be used in part to, for. B. the starting product, methyl alcohol, or water (if you are driving with the addition of steam) to evaporate and gently overheat. It is also known that this heat can be used to rectify a methyl alcohol-containing formaldehyde solution. It must be noted, however, that when both processes are coupled (evaporation of the starting products and rectification of the methyl alcohol-containing formaldehyde), additional steam and a large amount of cooling water are required under the otherwise usual conditions, since the larger amounts of heat in the condensation of formaldehyde and water at relatively low temperatures (below 90 ⁰ C) and are therefore difficult to recycle.

It is also known to use the waste heat from one device to heat another. from use is made of this fact in the method of the invention.

A process for the preparation of aqueous formaldehyde solutions by oxidation and dehydrogenation of methanol on silver contact in the presence of steam and preheated air at temperatures between 500 and 600 ⁰ C with incomplete methanol conversion has now been found, which is characterized in that the vaporous reaction mixture is simultaneously indirect generation of superheated steam ^{cools to about 100 0} C, the reaction gases with the condensate obtained in the further cooling and finally with water washes, the aqueous formaldehyde-methanol solution obtained using the resulting from the condensation and partially generated in the Superheated steam distilled heat in a vacuum column, and the methanol vapor obtained at the top of the column partly as reflux - with the addition of the methanol required for the reaction - gives up on the vacuum column, partly in vapor form after compression of the methanol vapor on the Reaction pressure of the methanol oxidation feeds, the compression taking place using a steam turbine, which is operated by means of the superheated steam generated by the hot reaction gases.

So it is the fresh methanol to be used in the process as a return to the working under vacuum Distillation column, which is used to separate the methanol from the formaldehyde solution, given and the methanol vapor leaving the column is compressed with a compressor and the reactor

Process for the preparation of aqueous
Formaldehyde solutions

Applicant:

Paint factories Bayer Aktiengesellschaft,

Leverkusen

Named as inventor:

Dr. Hans-Walther Brandt, Cologne-Flittard;

Dipl.-Ing. Jean-Philippe Darnand,

Cologne-Stammheim;

Dr. Raimund Wambach,

Dr. Hermann WoIz, Leverkusen

fed back. The compressor compressing the methanol vapor is operated with a steam turbine driven, which receives its steam from a steam generator, which with the overheating heat of the reaction gas leaving the reactor is heated, the water supplied to the steam generator is preheated with the formaldehyde solution draining off the column and the compressor cooler and the exhaust steam from the turbine is partly used for the reactor as reaction steam and the column as cover the residual heat is supplied.

This process enables both of the processes mentioned, i.e. evaporation and slight overheating of the starting products, as well as rectification of the methyl alcohol-containing Formaldehyde, to be carried out side by side without the need for additional steam will.

At the same time, this also leads to a reduction in the amount of cooling water.

Further advantages of the process are that it is carried out under vacuum at low temperatures Rectification of formaldehyde solutions containing methyl alcohol largely prevents formic acid formation is prevented. The figure shows an apparatus for carrying out the method. In the reactor 2 is the methanol-steam-air mixture coming from the mixing chamber is reacted with a silver catalyst. The hot reaction gases are cooled as quickly as possible in the coolers 3 and 4, in which at the same time steam is generated from the water flowing in through line 7 and this steam is superheated will. The water is in the heat exchangers 5

609 607/399

and 6 preheated. The steam is formed via line 8 (93%). The reaction gases leave the reactor

discharged. The now about 100 ⁰ C hot reaction port 2 with about 575 ° C and have approximately the following feed

Gases are converted into the condensation composition via line 9:

Stage 10 passed where some of the condensable pro- - _{about 2Q3} percent by volume formaldehyde

at high temperatures. are fluxed, which 5 _{about 34 7 percent by volume of water (steam} )

by pumping the condensate through line 11 _{about 41 2} percent by volume of inert gases (N ₂ , H ₂ , CO ₈ )

is accomplished with the pump 12. The resulting _{approximately 3 8} percent by volume methyl alcohol gaseous heat is via the heat exchanger 13 to the

Column 24 delivered. The still formaldehyde and you will be in coolers 3 and 4 down to about

In particular, methanol-containing exhaust gases from the condensate are cooled to 100 ° C. At the same time, however, 4

sation stage 10 are fed via line 15 into the from the heat exchangers 5 and 6

Condensation column 14 passed. Here, too, the heated water becomes water vapor of 30 ata and 230 ° C

Condensate circulated again with the pump 16 and generated in the heat exchanger 3 of 230

the heat generated in the cooler 17 is superheated by water at 400.degree. This steam is used to

cooling dissipated. The. Exhaust gases leave the turbine operation above and after expansion in the turbine

Written column 14 via line 18 and are used as a source of water vapor for the initial reaction

again in the absorption column 19 with the over mix.

Line 20 washed incoming water. The 100 ° C hot reaction gases enter the two practical completely of methanol and formaldehyde or multi-stage condensation system 10, 14 a, in Free exhaust gases leave the column 19 via the 20 of the condensable products by indirect Line 22. The diluted condensate is exchanged with the heat with the circulating washing pump21 Draw liquid can be liquefied via the line 23 of the column 14.

leads. In the column 24, the rectification of the In a downstream absorption column 19 takes place

methanol-containing formaldehyde condensates of the colon are the residues still remaining in the inert gas

NEN 10 and 14 instead, the 25 and 26 gene formaldehyde and methyl alcohol with the addition of

flow in. The column 24 operates under reduced pressure to wash out water. Since in the first condenser

and is via the heat exchangers 13 and 27 (27 with sationsstufe 10 the condensation at fairly high

Exhaust steam from the turbine). That takes place in the head of the temperatures of 60 to 90 ° C, the

Column 24 accumulating methanol vapor is in the heat exchanger 13 via the resulting heat

Line 28 in the first stage of the compressor 29- 30 partial heating of the rectification column 24 can be used

leads and condenses in it, so that a part in the. This heat exchanger is located in the

Cooler 30 with normal water are liquefied lower third of the column, below the lower one

can. Between cooler 30 and 31 is via the inlet. The middle condensation column 14 as well

Line 32 that amount of methanol in gaseous form ent- the last absorption column 19 in which the small

taken, which is intended for conversion in reactor 2. 35 quantities of formaldehyde and mainly methyl

The cooler 31 is used for further cooling of the alcohol with an aqueous solution of formaldehyde

Return to the column with certain methanol cones and washed out with water are used to

densats. The remaining amount of methanol is completely removed from formaldehyde and methanol by fresh gas and the inert gas

to free methanol, which flows in via line 33, supplements. The resulting heat of condensation

and (cooled again in the cooler 34) via the 40 is discharged by water cooling. That the

Line 35 of column 24 was added at the top. The sorption column 19 leaving inert gas is up to

methanol-free formaldehyde leaves the column - traces of formaldehyde (less than 0.05 percent by volume)

sump via line 41 and is a part of the strainer and methyl alcohol freed.

In the column 24, the rectification of the takes place

Line 7 from the incoming water. The compressor 45 contains methyl alcohol formaldehyde at about 100 torr

29, which is necessary to place the methanol vapor in the and +70 to + 20 ° C. This creates education

Compressing lines 28 and 32 is carried out with one of by-products such. B. formic acid, far-

Steam turbine 36 driven, which avoided the overheated walking. The formaldehyde to be rectified

Steam via line 8 from the evaporator 3 and thus emerges from the condensation stage 10 through line 25

Superheater 4 refers. The 50 leaving the turbine as well as from the condensing stage 14 through line 26

Steam (through line 37) serves firstly as an additive in various places in the column 24 (since the

Reactor and flows to the mixing chamber 1. Second, the methyl alcohol content of both streams is different),

it is used to heat the column 24, the heat of which falls in the column head with the methyl alcohol vapor

Exchanger flows in via line 38. Third, temperatures of around 21 ⁰ C are used and with the

a part for preheating (with heat exchanger 39) 55 first stage of the compressor 29 to about 157 Torr

the air to be converted in the reactor 2, which compresses over and about 70 ° C. After the

Line 40 flows into the mixing chamber 1, methyl alcohol vapor in the cooler 30 from 70 to 30 ° C

needs. The process is carried out in that amount is withdrawn in gaseous form which is necessary for

the following example and on the basis of the figure implementation in the reactor is determined, and is therefore

explained in detail again. 60 with the second, third, fourth and fifth stages of the

. Compressor compressed to about 119 ⁰ C and 1.3 ata

Example _and give up. The methyl alcohol vapor of 119 ⁰ C and 1.3 ata is to be returned to the column in the correct amount of methyl alcohol is in the cooler 31 with

The presence of steam at 150 ° C and 1.3 ata 18 ° C cold water condenses completely. After adding

with preheated air on a silver catalyst 2 65 of methyl alcohol (which corresponds to the amount in the

at 550 to 600 ⁰ C converted to formaldehyde so that reactor 2 is converted) and further cooling

the methyl alcohol does not react 100%, so this liquid methyl alcohol serves as a return for

formaldehyde in very high yields (90 to column 24.

The column 24 is both - as already mentioned ■ - heated with the formaldehyde solution in the heat exchanger 13 and with 150 ^° C. steam of 1.3 ata (heat exchanger 27 which has left the turbine and is not intended for the conversion).

The amount of steam that is generated in the heat exchanger 4 and with which the turbine 36 is operated is like this large that they are used for heating the column 24 and for supplying the amount of water vapor intended for the reactor as well as sufficient to heat the air.

Claims (1)

Claim: Process for the preparation of aqueous formaldehyde solutions by oxidation and dehydration of methanol on the silver contact in the presence of water vapor and preheated air Temperatures between 500 and 600 ° C with incomplete methanol conversion, thereby characterized in that the vaporous reaction mixture with simultaneous indirect Generation of superheated steam to around 100 ° C cools, the reaction gases with the condensate obtained in the further cooling and finally washes with water, utilizing the aqueous formaldehyde-methanol solution obtained the resulting from the condensation and partly in the generated superheated water vapor distilled heat located in a vacuum column, and the at the top of the column obtained methanol vapor partly as reflux - with the addition of the required for the reaction Methanol ■ - gives up on the vacuum column, partly in vapor form after compression of the methanol vapor to the reaction pressure of the methanol oxidation, the compression taking place using a steam turbine which is operated by means of the superheated steam generated by the hot reaction gases. Considered publications:
German Patent No. 615,885;
German Auslegeschrift No. 1162 822;
E. Kirschbaum, Distilling and Rectification Technology, 1960, pp. 175 to 177. 1 sheet of drawings