DE2052821C3 - Process for the production of 4-chloro-o-cresol - Google Patents

Description

The invention relates to a method / ur I Icr-.tcllunt · \ cm 4-chloro-o-cresol

It is known, for example, o-cresol with sulfuryl chloride in the presence of metal halides !! / u chlorinate Here one obtains as ί main product 4-chloro-o-cresol b / vv. 4-chloro-2-methylphenol with varying amounts of d-chloro-o-cresol and 4, r - dichloro-o-cresol. Sulfur dioxide and hydrogen chloride occur as gaseous reaction products.

The chlorination reaction is very natural in terms of the yield and quality of the 4-chloro-o-cresol. In addition, in the case of discontinuous \ experience, the amount of Rcaklion gas is produced within a very small temperature range. This enables the processing of the (lases. /. I). / ur recovery of SO ₂ as SO ₂ CI ₂ or in the case of exhaust gas cleaning in the sense of keeping the air clean. made much more difficult. 4 <i

I s has now been found. 1I.1U himself 4 - ('hlor-o-kresiiI by chlorination of n-cresol with sulfuryl chloride at lciiipcr.iiurcn from 10 to 70 C in the presence of a Make the catalytic converter loud if you can the (lilorierunj! in the presence of [isenpeniacarbonyl -15 as kalalysiior in an at least two-stage stirred tank cascade konlinuicrlicli performs.

The method is particularly advantageous in one three-stage stirred kettle cascade, with the Kcaklinnsgcmisch / ur completing the Reaction in the third stage of the stirred tank cascade heated to Icmpcralurcn from 50 to 130 ° C.

The erünilungsgemaße method has the advantage because the catalyst isene pentacarbonyl, which is in a liquid agglomerate state at room temperature, can be continuously cindosierl in a simple manner. In contrast to known processes, this is not necessary as a special process the production of a catalyst solution, as it is done, for example, by solution of aluminum alcoholal in anhydrous alcohol or of aluminum solate is known.

The procedure in a mchfsiuligctl Rülifkcsselkaskadc leads to a uniform amount of exhaust gas and thus to a trouble-free exhaust gas reduction.

The starting material is an oil, the water of which » content because of the disruptive effect of water on the isomer ratio of the chlorination products and /. Advantageous in order to avoid corrosion cracking should be less than 0.5 percent by weight, preferably less than 0.2 percent by weight.

For every mole of o-kresoi there is generally one equimolecular up to 1.2 times the molar amount of sulfuryl chloride used.

The chlorination of o-cresol is generally carried out in the temperature range between K) and 70.degree carried out. However, it is advantageous to use tighter temperatures to be observed. It is preferred to work in a range between 20 and 50 ° C.

The required amount of Lisenpeniacarbonyl generally fluctuates between 0.2 and 1.0, preferably between 0.3 and 0.7 percent by weight, based on on o-cresol used.

In a particularly preferred embodiment the process of the invention is carried out in a three-stage stirred tank cascade.

The liquid starting compounds o-Krc, -λ sulfuryl chloride and iron pentacarbonyl, preferably in a molar ratio of 1: 1.1: 0.01, are metered into the first stirred tank simultaneously and continuously. The o-cresol, which has a melting point ν η about 31 C. is heated to a temperature of about 40 to dt) C before the 1 m dosing. In the first stirred tank, the temperature is from 10 to 50 ° C., preferably in the temperature range from 20 to 30 ° C., and this temperature is maintained by cooling. With an average residence time of 4 to 24 hours, preferably of (1 to 12 hours. Between 80 and ') () "" de * introduced o-cresols are reacted in the first reaction chamber. The learning peraiureii are 10 to M) C higher than in the first stage. The dwell times are comparable to those in the first reactor. They are lower, the higher the temperature is selected. Temperatures of 25 to 70 C. preferably from 30 to 51) C maintained by supplying heat.

Per mole of 4-chloro-o-cresol, 1 mole of sulfur dioxide and 1 mole of hydrogen chloride form as exhaust gases Level free. It has also proven to be advantageous to complete the reaction further in a downstream third Rulirkesseliufe and, above all, to remove the remaining amounts of sulfur dioxide and hydrogen chloride from the reaction mixture. For this purpose, the reaction mixture is heated to temperatures of 50 ° to 130 ° C. and kept at this temperature for about an hour while stirring; B. bubbling a stream of nitrogen, need to be applied uiiil the yield to over ¹ JO ",, increased.

In a further advantageous embodiment of the process, the exhaust gas from all three boilers is usually recirculated in countercurrent via the first boiler in order to bring proportions of gaseous sulfuryl chloride back into solution ₍ before sulfur dioxide and hydrogen chloride are led out of the cascade. If necessary, the exhaust gas from all three stages be washed in a Ricscl column with the continuously flowing o-Krcsol.

The crude 4-chloro-o-cresol obtained with a C e *

hold of over 90 percent by weight can be based on usual Way, for example by fractional distillation, can be further purified.

The parts named in the following example are unless otherwise noted. Parts by weight.

example

A solution of 108 parts of o-cresol (water content 0.2 percent by weight) and 0.5 parts of hisenepentacarbonyl and 148.5 parts of sulfuryl chloride at the same time per hour continuously in the first stirred tank (1200 parts by volume) of a three-column stirred tank cascade metered.

A temperature of 25 C is maintained by cooling with brine or cold water. After a residence time of 11 hours, during which 85 "" of the o-cresol used have reacted and 80 "" of the total gas amount of sulfur dioxide and hydrogen chloride are evolved, the reaction mixture runs into the second, equally large stirred kettle! above, in which at glc rather dwell a temperature of 35 C is set by supplying heat «!. In the second stage, the chlorination is completed and more I0 "" off-gas are evolved.

In the third stirred tank (120 parts by volume) of the cascade, it is heated ^{to 1} JO to 100 C. With a residence time of 1 hour, the remaining H) "" of the expected total gas amount of sulfur dioxide and hydrogen chloride escape, which leave the cascade via the first stirred tank together with the exhaust gases on stage 1 and 2.

ίο After cooling down to 35 C it means that it is still liquid Crude product through a siphon into a receiver, in which by fractional distillation under reduced Pressure is worked up.

In the case of uninterrupted traffic, after reaching of the stationary state from the third A sample was taken from the stirred tank, which according to the gas chromatographic Analysis has the following composition:

2i> 6-chloro-ü-cresoI 5.5 ""

4,6-dichloro-o-cresoI 0.8 ""

4-chloro-o-cresoI 93.0 ""

o-cresol 0.5 ",,

Other 0.2 ",,

Claims (2)

Patent claims: 1. Process for the production of 4-chloro-o-kre · sol by chlorination \ on o-lcresol with sulfuryl chloride at temperatures of 10 to 70 C in the presence of a catalyst, characterized in that because the chlorination in the presence of iron penicarbonyl as a catalyst in an at least two-stage stirred tank cascade is carried out continuously. 2. The method according to claim 1, characterized in that the chlorination is carried out in a three-stage stirred tank cascade, wherein one the reaction mixture to complete the reaction in the third stage of the stirred tank cascade heated to temperatures from SO to 130 C.