DE2221691B2 - Process for the continuous production of p-benzoquinone - Google Patents

Description

3 4

is contaminated by benzene and discarded catechol by-product is consumed. This got to. These two processes also do not have a one-off effect in combination with the separation of the Schleigang found in technology. migen polymer in the anolyte circuit prevents the

The invention is based on the object of a build-up of by-product impurities in this

continuous process for the production 5 cycle. From the p-benzoquinone containing ben-

insoluble substances are also separated from p-benzoquinone by direct current electrolysis,

a dispersion of benzene in an aqueous acid. Preferably, at least part of the p-benzo

To create anolyte in at least one electrolysis, quinones by reacting the benzene phase with hydro-

in the case of contamination of the anolyte avoided and quinone converted into insoluble quinhydrone, the

worked under technically practical conditions io can be separated. In this way, the

will. The solution to this problem is based on the concentration of the p-benzoquinone in the circuit

Finding that the separation and the circulated benzene keep at a value below 1 g / liter,

leadership of the aqueous phase and the benzene phase of the resulting in lower losses in the anodic Oxi-

Anolyte is disrupted by a by-product. The dation leads. The one freed from slimy polymer

exact chemical composition of this anolyte anolyte as well as the benzene with reduced

product is unknown. However, it has the property of tem p-benzoquinone content, which is also

a polymeric compound is freed from slimy nature of polymer, are mixed and again

fineness. If the cells are returned to the anode compartment in flow mode,

Operate at a sufficiently linear speed! The method according to the invention is exhausted

this polymer from the cells into the anolyte or 20 not alone in the separation of solid secondary

in both the anolyte and the catholyte products from the anolyte. Neither the DT-PS 6 14 041

be dragged if porous diaphragms are used nor the US-PS 22 85 858 nor the DT-AS 11 01 171

will. If you put this slimy product in the give some hint, like that with the anodic

Benzene and / or anolyte circulating streams leaves, oxidation of benzene occurring difficulties

the concentration of this product increases as much as in a continuous technical process

that it acts as an emulsifier. This will be able to solve a, since so far p-benzoquinone in

effective separation of the aqueous anolyte phase and industrial scale only briefly anodically oxidized

the benzene phase practically impossible. Finally, see U d u ρ a et al., Op. a. O., ins-

the slimy product also causes retention special p. 50.

of the gases formed at the anode, causing malfunctions 30 Another unsolved problem in manufacture

in the separation of the gas from the liquid in the p-benzoquinone follows from the fact that

Anode circuit leads. The invention now proposes, first of all, in the anodic oxidation of benzene

the slimy polymeric material is formed as completely as possible phenol, which continues to o- and p-di-

is oxidized from the circulating aqueous hydroxybenzene. The o-dihydroxybenzene

Electrolyte as well as the circulated benzene 35 is undesirable in this process. Just that

to separate. p-Dihydroxybenzene converts to p-benzoquinone.

The invention thus provides a process o-Dihvdroxybenzol is under the process conditions

for the continuous production of p-Benzoquinone conditions further oxidized.

by direct current electrolysis of a dispersion of The benzene used in the process of the invention in an aqueous acidic anolyte in at least 4 ° electrolysis cells can either be with porous Diaeiner electrolysis cell, in which the cathode and phragmen or membranes, such as diaphragms are separated from the anode compartment by a diaphragm and filter fabric, or with non-porous diaphragms, separating the anolyte through the anode compartment and through which a catholyte is passed like cationic permselective diaphragms from the cathode compartment. Porous diaphragms, which are similar to the simple p-benzoquinone and sludge-like and gaseous membranes made from filter fabric, are more formidable by-products from the anolyte and considerably cheaper than the permselective diaphragms carry the aqueous acid analyte and not and can therefore for reasons of the Cost savings reacted benzene may be preferred together with. In the method of the invention, fresh benzene can be fed into the anode compartment, which is characterized by preventing clogging of the porous diaphragms by the fact that the anolyte is within 5 °. It could furthermore be found that the anode space is at a temperature of above advantageous if holding with porous diaphragms 20 to below 45 ⁰ C and the electrolysis is carried out at a without the oxygen-containing current density of above 5 A / dm ² carries out, the exhaust gases from the cathode containing the mixture continuously withdrawn from the exhaust gases from the anode and the hydrogen entdem anode compartment are mixed with gases containing benzene containing p-benzoquinone. When using porous slide phase and the aqueous acidic anolyte phase separates, in the electrolysis cells, the process of separating insoluble substances from the phases can at least be further improved by solids part of the p-benzoquinone from the benzene phase from the circulating catholyte removed in a known manner, the aqueous acid anolyte are. In this way, the polymeric phase with benzene reduced p-benzoquinone content 60 slimy substances, which are mixed through the porous diaphragm and returned to the anode compartment. get into the cathode compartment or in the cathode

Through this combination of measures, i. H. form space, be continuously removed, and the

by working at high current density and ratio- both the catholyte and the anolyte can be relatively free of

moderately high temperature, a gas mixture will be held by the solids.

Anode developed mainly from carbon. 65 Since the electrolytic oxidation of benzene is strong

monoxide and carbon dioxide are formed; which takes place at the exothermic, it is desirable to

Oxygen formed in the anode will obviously operate in over-lysis cells at temperatures at which the

weighting amount for the oxidation of the undesired required cooling of the anolvts and / or catholvts

can still be carried out economically by heat exchange, which can be arranged in parallel in series, is to be supplied. There is continuously withdrawn therefore advantageous that the inventions are a p-benzoquinone-containing-making process according to the specified temperature benzene phase, namely the aqueous electrolyte, gas range, for example, at temperatures of 25 to 4O ⁰ C, and solids. The gases exist normally can be carried out. Although these are relatively wise from carbon dioxide, oxygen and some carbon-high temperatures apparently the formation of monoxide. The solid is a slimy polymer, favoring polymeric by-products as opposed to that formed during anodic oxidation. In order to operate at lower temperatures, phases will be separated from each other. Portions of the p-benzene through the other features of the process of the zoquinone-containing phase are mixed with benzene with the invention in connection with higher temperature, lower p-benzoquinone content and aqueous acidic do a contamination of the electrolysis cell, an electrolyte to a dispersion of the anolyte. Clogging of the diaphragms and an interruption The diaphragms that separate the electrolysis cells in the process due to the formation of solid anode spaces and cathode spaces can avoid substances in the anolyte and catholyte. from non-porous cation exchange membranes

Working at relatively high current densities in the 15 stand. If the electrolyte of the anolyte allows an aqueous process according to the invention to have a satisfactory acidity - which is preferred - the ion-exhibiting production rate and production exchange membrane should be able to generate hydrogen ions, based on the cost of the electrolytic cell. transferred to. If the catholyte holds p-benzoquinone, then non-porous diaphragms with a density of 7 to 20 amperes / dm ^{2 are desirable} However performed, and the As indicated above, the catholyte may be composed anolyte in the anode compartment at a temperature of from an aqueous electrolyte retained in the Wesent-25 to 4O ⁰ C. Under these conditions borrowed is free of p-benzoquinone.
consists of the gas escaping from the anode compartment. Porous diaphragms can also be used, a mixture mainly of carbon monoxide and as. These reduce the carbon dioxide carried in the cycle. The main amount of solid impurities on the anodes. Woven oxygen formed is used to oxidize the pyrocatechol formed as a filter cloth, but other byproducts are also used; Types of porous diaphragms for the process of see Fr. F ichter, J. Soc. Chem. Ind., Vol. 48 (1929), invention suitable.

Pp. 325 to 329. The Contaminant By-products 30 In the process shown in FIG. 1 shown flow sheet

are continuously transformed into gaseous in the anode compartment in a simplified form the cross-section of an electrical

Compounds oxidized. The lysis cells 10 are shown at the same time. This usually includes

substances are removed from the circulating anolyte. several cells arranged in parallel, however

In the case of continuous, steady operation, the amounts that are electrically connected in series. The cells can

Oxygen content that emerges from the anode compartment can be constructed in a sandwich-like manner, each plate with

the gases normally below 25 percent by volume and with the exception of the end plate an anode compartment on the

can be kept below 10 percent by volume. one side and a cathode compartment on the other

In the following, the method of the invention is presented side by side. This is a bipolar electrical

Hand of the drawings explained. Circuit used. The anode and cathode

F i g. Fig. 1 shows a flow diagram of a preferred 40 rooms being interposed by one

Embodiment of the method of the invention; permselective diaphragm separated be porous

F i g. 2 shows diaphragms, such as plate-shaped diaphragms, taken in perspective and apart Representation of an electrolytic cell unit, then you can do this in the same way used in the method of the invention. For example, filters can; 45 fiberglass mats used as porous diaphragms

F i g. 3 shows a partial flow diagram of an embodiment,

of the anolyte circuit; The anode compartment of the electrolytic cell 10 is through

F i g. 4 shows a partial flow diagram of an embodiment of a conduit 11 with an elongated container 12

the electrolytic cell and the catholyte circuit; tied together. The container 12 serves as a storage container

F i g. 5 shows a partial flow diagram of an embodiment 50 for the liquid phases and as a gas-liquid

of the anolyte cycle. and liquid-liquid separators. The gas

In the method of the invention is preferably a phase which is normally a mixture of carbon

Power-transmitting diaphragm used to collect the dioxide, carbon monoxide and oxygen that is

The anode compartment and the cathode compartment of the electrolysis are located in the upper part of the container from which they are

cell to separate. This diaphragm can be perm- 55 pulled. The gases can through a

selective cationic exchange membrane or a condenser or a liquid trap are passed,

be porous diaphragm. to remove vaporized or entrained benzene

Far removed in performing the method of the invention. The liquids separate in the container 12

the benzene to be oxidized becomes with an aqueous phase by settling. The p-benzoquinone containing

Electrolytes converted into a dispersion, which is the 60 benzene phase above the aqueous

Anolyte represents a separate aqueous electrolyte, electrolyte. The aqueous electrolyte can, for example

which represents the catholyte, will be continuously through dilute aqueous sulfuric acid,

passed the cathode compartment. Both the anolyte and in the embodiment according to FIG. 1 will be the

Also the catholyte can be an aqueous, acidic electrolyte, polymeric substances and other insoluble substances which are in

and both can be produced from the same acidic 65 the anode compartment, with the liquid

Electrolytes. speed and gas phases transported into the container 12.

From the anode compartment of the electrolytic cell, which consists of The solids tend to follow the benzene phase,

There are several anode and cathode compartments, but they are also present in the aqueous phase.

Both the p-benzoquinone-containing benzene phase, gene meter and regulator, the phase ratio and which is separated in the container 12, as well as the transfer ratio can be selectively varied and in the aqueous phase are therefore maintained by slimy insoluble predetermined values.
Connections contaminated. A part of this connection- The stream T, which goes through the valve 20, transferred to fertilizer can accumulate at the interface between the benzene phase withdrawn to a device, benzene phase and the aqueous phase. in which the p-benzoquinone is removed and the benzene The polymeric solid compounds can be better accumulated at the interface for further use in the electrolysis process if it is recovered. This device is added in surface-active compounds to the F i g. 1 only indicated in general. Depending on which insoluble compound has been used to make the p-benzoquinone less wettable or less wettable by the benzene, the recycled benzene can promote separation from the aqueous phase. still contain some p-benzoquinone. In any case, parts of the acidic electrolyte phase that accumulate in the lower part of the container 12 is the amount of p-benzoquinone, which is much lower than the amount that accumulates in the benzene phase from the electrolyte by means of a pump 14 through a heating 15 lysis cell 10 is included. The benzene can be passed to example exchanger 13 to be distilled off the temperature wise, the solid p-benzo being controlled by cooling. The amount of the electrolyte quinone left, condensed and then returned is adjusted by valve 15. The pump 14 is guided. Fresh benzene can then possibly also lead parts of the electrolyte flow A through the flow B to supplement the filter 17 to the phase mixer 18. The filter 17 20 den.

removes the polymeric compounds and other The aqueous catholyte from the cathode compartment of the

Solids, so that the current A, which the mixer 18 electrolytic cell 10 is in an elongated container 24

is supplied, is essentially free of solid transferred, which is used as a storage container and as a liquid

,, fabrics. The filter 17 can also be used in the cooling circuit for gas separators. The electrolyte, which is

, Γ, the aqueous electrolyte phase, as in FIG. 5 shown, 35 consists of dilute aqueous sulfuric acid,

: , to be ordered. Fresh water can flow Λ separates itself from the water generated at the cathode

,! ", are supplied to the gaseous compounds in the electrolytic cell 10, which mainly consist of

. ":", 'To replace used water. Hydrogen exist. The hydrogen can consist of the

The benzene phase containing p-benzoquinone will be removed from the top of the container 24 as exhaust gas.

_v i- _t j from the container 12 from a point above the 30 The aqueous electrolyte is from the lower part of the

'. [, _ Benzene-water interface withdrawn by means of a pump 19 container 24 by means of a pump 25 and

,,! _e deducted. When the slimy solid connection is passed through the heat exchanger 26 for cooling.

, ", _{c! i} not completely out of the benzene phase by settling. The pump 25 leads the catholyte into the electrolysis

" _Cn or by another method that works with the cell 10, whereby the current in the cooling and cell

_ni j _t container 12 has been removed, then 35 circuits through the valves 27 and 28 is controlled.

j ^. _r parts of the benzene-containing phase can be poured directly into fresh electrolyte solution, if necessary

^ _n the electrolytic cell 10 passed through a filter 22. Container 24 or any other location on the

^ j ₁ P Other parts of the circuit containing p-benzoquinone are fed.

. '., Benzene from the container 12 can by the In Fig. 2 is schematically a single cell

, Pump 19 in a p-benzoquinone removal device 40 shown, which is used for the method of the invention

device 23 are performed. The relative amounts of the turns can be made. The sandwich-like

direct circulating flow B and the flow T, the cell consists of the anode plate 100 and the

cathode plate 101 is used to remove the p-benzoquinone. Between the anode plate 100

adjusted by valves 20 and 21. The stream B and the cathode plate 101 are the cathode

', '] .. is filtered in filter 22 to remove any polymeric 45 denar spacer 102 and the anode spacer

To remove compounds or other solids, 103. The spacers 102 and 103 form the

_{rc> i} so that the benzene phase, which leads to the electrolysis cell 10 cathode and anode spaces, which are

. ρ is returned, is essentially free is separated by phragma 104. The anode compartment has

Ι · ,,, * solids. The stream T can also be filtered, preferably in the form of a winding passage

,,;,;. when he goes to the p-benzoquinone removal 50. The spacer 103 can, for example

- ,, device is performed, or a treatment for partitions or partitions 105 and 106 have the

.: ,,,, Removal of solids can be included in this stage- the anode in a series of interconnected

,. "_{; are} switched. After removing the largest part of the rooms or channels, divides one end of the

,. of the p-benzoquinone, the benzene stream T in the partition wall 105 with cross flow passages 107 and the

7_, container 12 is returned and thins from the 55 other end of the partition 106 with corresponding

-. '.' "Electrolysis cell 10 coming p-benzoquinone ent- transverse nut passages 108 is provided The anolyte

holding benzene. The benzene phase (stream B) and can then through an inlet line 109 in the upward

the aqueous electrolyte phase (stream A) are under current in a guide or dam part 110, the flow

the pump pressure in the feed end of the phase cuts 111 is introduced, and flows through

mixing and dispersing device 18 mixed and 60 the first subsections. The anolyte is then through

dispersed, and the resulting anolyte is the cross flow passages 107 in the section B again

led into the anode compartment of the electrolytic cell 10. and then through the cross-flow

; For the system shown, the phase relationship of the passage 108 can be in the sub-section C. After passage

Anolyte can be expressed as the volume of queuing of subsection C the anolyte flows through

Stream A divided by the volume of stream B, 65 the cutouts 111 of a guide or dam part 110 it

while the transfer ratio is the volume of the outlet line 112. The benzene electrolyte dispersion

Stream T divided by the volume of stream B. sion is continuously in contact with the

Through suitable control valves, flow and men- active surfaces of the anode 100, whereby the

! 509521 / 40C

9 10

anodic oxidation of benzene to p-benzoquinone in FIG. 4, the electrolytic cell 10 ' is designated because it is caused. the cell uses a porous diaphragm. In order to facilitate manufacture and to provide a maximum of this cell construction, the solids are removed before support for the diaphragm 104 , preferably from the aqueous catholyte phase outside, the cathode spacer 102 has the same 5 as the electrolytic cell. For example, a shape like the anode spacer 103, that is, the filter 29 in the circuit line downstream of the has the same partitions, cross flow passages pump 25 and above the line branching to and sliding or dams, and the downflow and valves 27 and 28 can be arranged will. The upward flow at the inlets and outlets filter 29 can also enter the cooling circuit alone is arranged in the same way. The catholyte can be placed through the heat exchanger 26, through an inlet line 113 into the cell and so for example between the valve 27 and the heat exchanger 26 through an outlet line 114 out of the cell. The filter can also pass into the cell. Anolyte circuit are arranged, namely at-In F i g. 3 is a modified embodiment, for example in the line between the valve 28 and the anolyte circuit according to FIG. 1 shown. The 15 of the electrolytic cell 10 '. The filter 29 can then in the same components of the circuit are effectively continuously provided with the fixed ones in the same reference numerals. The aqueous electrolytic catholyte by-products formed remove or lytphase in the container 12 ' circulates in the same way the by-products that are passed through the porous diaphragm as in the embodiment according to FIG. 1. The ab- the cell have been carried out
The change lies in the circulation of the p-benzo 20 in FIG. 5 is the modified embodiment of the quinone-containing benzene phase, which is shown from the Be of the anolyte circuit. In order to remove the heat container 12 ' by the pump 19' and prevent the exchanger from passing through the polymeric solids through a filter 22 ' in which the solids are contaminated, a filter can be removed in the cooling circuit materials. The entire clarified and run of the heat exchanger upstream of the purified benzene phase will be placed in the p-benzoquinone 25 heat exchanger 13 . Removal device 23 ' can thus be transferred. After min- example, a filter 17 in the feed line ^': least the majority of the p-benzoquinone has been removed to the heat exchanger between the valve 15, the benzene is to be attached with the essential and the heat exchanger. 13 \ reduced p-benzoquinone content by means of a. In this arrangement, the in FIG. 1 shown: Pump, not shown, passed through the valve 21 ' to 30 filter 17 between the valve 16 and the phase \ of the mixing device 18'. As omitted from mixer 18 or used in FIG. 3 can be seen, the regression is mixed up.

guided benzene, which consists of the stream B , with the In the process according to the invention, the elec-

■ I circulated aqueous phase, which from the trolyse cells in the temperature range of above 20

Current A exists, operated in the feed line to the mixing 35 to below 45 ° C. This means that the im

| device 18 '. The phase ratio of the anolyte circulated anolyte and preferably also the

is therefore the volume of current A divided by the circulating catholyte in this temperature

Volume of the stream B. The transfer ratio is range through controlled heat dissipation

.; 100 percent, with the stream T coming from the total through heat exchangers such as the

Benzene phase from the electrolytic cell 10 consists. 40 heat exchanger 13 in the anolyte circuit and / or

This arrangement has the advantage that very little is left to the heat exchanger 26 in the catholyte circuit.

p-Benzoquinone is circulated that will hold in one. A beneficial operating area for

previous passage through the electrolysis- the cells with respect to the liquid contained therein

cell 10 is formed. In those cases where the phases, such as the anolyte and the catholyte, is enclosed

?. p-Benzoquinone removal a precipitate from the 45 25 to 40 ⁰ C.

Includes benzene, for example by reacting with The method of the invention is preferably used in

Hydroquinone with the formation of quinhydrone, cell current densities can exceed 5 amperes / dm ²

the concentration of p-benzoquinone in the im carried out. Current densities of

Recycled benzene (stream B) below 1 gram 7 to 20 amps / dm ^{2 is} used. The practical upper one

-; per liter, while the concentration 50 limit of the current density has not been determined.

of the p-benzoquinone in the benzene phase apparently current densities up to 30 amps /

κ passage through the electrolytic cell 10 normal dm ² and higher can be used.

wise is at least twice that, ie 2 grams In the preferred embodiments of ver or more p-benzoquinone per liter of benzene. In order to achieve this method of the invention, in which the above greater increase in the p-benzoquinone concentration 55 specified technical features can be used in combination in a single pass through the electrolysis, the composition of the cell 10 , the length of the flow in the anode compartment The gases formed are adjusted so that the passage through the individual cells is increased so that they mainly consist of carbon monoxide and / or the individual cells can be so arranged carbon dioxide and small amounts of oxygen that a flow is achieved in series. 60 stand. For example, the oxygen content below this is particularly necessary when essentially all of the p-benzo cent is maintained in the 25 percent by volume, preferably below 10 percent by volume per isolation stage. In this way, additional quinone can be recovered from the benzene, such as by-product impurities, continuously as the benzene is separated from the anolyte by distillation, whereby the impurity becomes. 65 continuous to carbon dioxide and carbon

Modified embodiments of the circulatory monoxide are oxidized.

Guides of catholyte and anolyte in the process The anodes and cathodes can be made of lead foils

of the invention are shown in FIGS. 4 and 5 shown. or lead plates. The active surfaces

11 12

the anodes are converted into the flow diagram of FIG. 1 is similar. Dii lead oxide converted and then give a stable current density was at 13.5 ± 0.5 amps / dm ² and active anode. Lead dioxide surfaces can be made. The heat exchangers in the anolyte and catholyte circuits also formed with anodes made of lead alloys were operated in such a way that one or more conductive anodes coated with lead or an anolyte starting temperature from the electrolysis cell are lead alloys. It was maintained at around 30 ^° C. The phases can also be used with platinum electrodes or electrodes from the ratio in the anolyte to the electrolysis cell with another conductive metal or conductive 1 part by volume of the benzene phase to 4 parts by volume of the metal alloys. The cathode is aqueous electrolyte phase. The aqueous electrolyte is essentially inactive, and the surface is not modified during the io phase for the anolyte and the catholyte was in contact with the catholyte normally with the 10 weight percent sulfuric acid, ie, 10 weight electrolysis. As cathode material parts sulfuric acid were used for 100 parts of the aqueous can lead, platinum or other conductive metals or electrolyte solution. The pumping speed · metal alloys are used. th in the anolyte circuit were adjusted so that £

When using a sandwich-like cell, the anolyte flow rate through the elec

construction as in fig. 2, the trolysis cell can have a linear speed of 18 or

Spacers 102 and 103 both resulted from one art per second. The concentration of the p-Benzochi-

substance or some other material that is sub nons in the benzene phase of the anolyte, which is the cell

shows inert properties under the process conditions. was supplied was approximately 0.7 grams

This can be done with polypropylene or a similar synthetic 2 ° p-benzoquinone per liter of benzene. At the exit

fabric can be used. The diaphragms can approximate the concentration of the cell

be permselective ion exchange membranes containing 3 grams of p-benzoquinone per liter of benzene. The whole

the transfer or transfer of cations benzene phase generated by the cell

allow, such as the kationenaus- (after separation of the aqueous, the gas and

exchanger membranes, which in US-PS 31 93 480 as of the solid phases), the p-Benzoquinonent-

be written. Alternatively, diaphragms can be supplied with a removal stage in which the p-benzoquinone

used, which consist of filter cloth, such as containing benzene in contact with hydroquinone

Filter cloths made of synthetic plastic fibers. The resulting quinhydron lower

for example polyester fibers. hit and excess hydroquinone were through

The anode electrolyte and the cathode electrolyte 3 ° filtration separated from the supernatant benzene, can consist of at least 5 percent by weight and preferred The benzene obtained thereby contained about 0.7 grams of at least 10 percent by weight aqueous p-benzoquinone per liter of benzene and was composed of the sulfuric acid. Concentrations of 10 to procedure pumped back. After the benzene was also 25 percent by weight consumed, fresh benzene became that used in practicing the process of the invention. Benzene in the cycle can be added, and other organic or inorganic water can also be used, if necessary, and acids such as phosphoric acid can be used in the cycle. Phosphorus-guided aqueous electrolyte was added. The in the phosphoric acid is a good electrolyte, since it has a little less anode space formed gas. The following corrosive effects on metals than sulfuric acid. In the setting: 80% CO ₂ , 10% CO and 10% (or less) anolyte can be the volume ratio of benzene to 4 ° O ₂ .

aqueous phase in operation from 0.01: 1 to 1.0: 1 B e i s ρ i e 1 2

lie. In the case of continuous operation, the p-Benzo- _A continuous process has been established in accordance with

quinone concentration in the anolyte, as carried out by the cell Example 1, with the exception that the

my range of 0.5 to 80 grams of cationic permselective diaphragms from the

p-benzoquinone per liter of benzene. The linear 45 electrolytic cells are removed and replaced by porous diaphragm

The speed of the benzene electrolyte dispersion (which the _men replaced.

Anolyte) through the anode chamber should be at least _{shing le he} h of a vinyl chloride-acrylonitrile copoly-

at 3 cm and preferably bt \ least 9 cm per merisat used. The catholyte circuit was then

Second lie. The upper limit of the linear _{according to} FIG. 4, with a filter 29 in speed is not critical. A typical 50 _each circulation line was used, so that the im

Operating range is 15 to 60 cm per second. Circulated aqueous electrolyte was devoid of

A cell for the method according to the invention solids,

can have the following specifications: B e i s t> i e 1 3

Element thicknesses (each) _,. ,. ··, ■, -w _ »i_ -o aj iir « i_ j -> tic ν ί ir 55 A continuous process according to anodes / cathodes .... 3.175 to 6.35 mm example 1 or 2 was carried out using spacers (anode / _aq £ _ger Ils phosphoric acid electrolyte in the anode Kathodente. Ie) from 1.587 to 12.7 mm _KRDS, onzentrationsbereich _{in The} ^ is 10 to

Diaphragms 0.508 to 1.290 cm _{ω weight percent} p _hos p _horsäur e, wherein a 30ge-

to ^e Ka7ho ^e de ^a ) *. ° ... °. ° 0.508 to 2.032 cm ⁶ ° ™ real percent phosphoric acid is particularly advantageous

a j λ. Delivers results.

Anode compartment (preferred _{volume for the compounds could be determined}

^Large) ° ' ^{254 to} °' ^{762 cm} the polymeric solids produced in the cells in

The examples illustrate the invention. advantageously by filtration from the im

d · · 1 1 65 circulating streams could be removed.

Example ί _Dje E _nt f _{ernung de} r solids may, for example

A continuous process was also used, including centrifuging, decanting or sedimentation.

corresponding to the flow diagram of FIG. 3 performed, mentation can be achieved.

For this purpose 3 sheets of drawings

s? i.

1 ■ ·. ■■■ ·

Claims (2)

In US-PS 2130151 a method for claims: Production of p-benzoquinone with an open electrolysis cell (without diaphragm) is described, be 1. Process for continuous production in which the p-benzoquinone ai formed at the anode is transferred from p-benzoquinone to the cathode by direct current electrolysis 5 and is reduced there to hydroclanoi a dispersion of benzene iii an aqueous. The process has not found its way into technology with acidic anolyte in at least one electrolytic cell. If the process were carried out as described, in which the cathode and anode compartments were carried out through one, there was a risk that the diaphragm would be separated and the oxygen formed at the anode would be separated by the anode mixing; space the anolyte and a catholyte is passed through the cathode space with the hydrogen formed at the cathode, separating the p-benzo-oxyhydrogen gas. It can also be assumed that be; quinones and sludge-like and gaseous this process of the production of p-Benzoquinoc by-products from the anolyte and recycle and hydroquinone in an open cell insoluble of the aqueous acidic anolyte and the unreversed quinhydrone is formed, which leads to other process- »eten benzene optionally together with 15 technical difficulties. It is carried out, fresh benzene in the anode compartment, characterized in that the electrolyte is contaminated by oxidation products of the anolyte benzene, which dissolve in the electrolyte inside the anode compartment at a temperature which must then be discarded. Furthermore, the temperature must be kept from above 20 to below 45 ° C. and the electrolysis of the cell must be stopped and cleaned at a current density of above ao at intervals of about 24 hours. 5 A / dm ² carries out that from the anode compartment also that described in DT-PS 117 251 (1899) continuously withdrawn mixture of gases, process for the production of p-benzoquinone by the benzene phase containing p-benzoquinone and anodic oxidation of benzene in dilute Schweder The aqueous acidic anolyte phase separates, insoluble acidic acid with a rotating lead anode has no inlet Separating substances from the phases, at least one as found in technology. Under the procedural part of the p-benzoquinone from the benzene phase in conditions form by-products, in particular known manner separates the aqueous anolyte succinic acid, if without, and maleic acid, if phase with benzene-reduced p-benzoquinone with a diaphragm. It also forms mixed content and returned to the anode compartment - after a few hours a gas, water and leads. 30 benzene existing voluminous sludge, which with 2. The method according to claim 1, characterized in that the disruptive formation of solid by-products is characterized in that the electrolysis is related to a current. The result is an extremely stable density of 7 to 20 A / dm ² and the foam, the further treatment of which offers considerable tech anolyte in the anode compartment at a temperature niche difficulties; see R. Kempf, holds ^{from 25 to 40 ° C.} 35 Journal f. Prakt. Chemie [2], Vol. 83 (1911), p. 329 to 394. DT-PS 6 14 041 describes a process for the production of p-benzocliinone by anodic oxidation of benzene in an open cell (without di- It has long been known that the anodic 40 phragma) describes the difficulties of the Oxidation of benzene p-benzoquinone is formed. Want to avoid the Kempf proceedings. One weird Anodic oxidation of benzene has been intensely both rising anode is theoretically above the cathode as well as in the hope of a prak- ing, and the benzene is by a fine-pored table application examined; see e.g. B. Seyewetz filter immersed in the electrolyte below the anode. and Niodon, Bull. Soc. Chem. France (4), vol. 33 45 leads. The fine droplets of benzene flow up- (1923), P. 449 to 456, and K. S. U d u ρ a downward and along the bottom of the anode and et al., Bull. Acad. Polonaise Sciences, Vol. IX, No. 2 collect on the aqueous phase and are of (1961), pp. 45 to 50. When the electrolysis cells are in operation, they are returned to the circuit there. That evolves at the anode oxygen and at the drive points all in connection with the US-PS Cathode hydrogen, the disadvantages described in the mixture of oxyhydrogen 50 21 30 151. This too result. Therefore, up to now the general method has not found its way into technology used where the anode and cords. method space by a diaphragm from a porous In US-PS 13 22 580 and 22 85 858 VerMaterial was separated. Mostly, in the reports for the production of p-benzoquinone from tests, discontinuously working cells 55 benzene in electrolysis cells were described that were also used; however, cells of the through-porous diaphragm are also equipped. Fiußtyps known in US-PS, see DT-AS 1102171 and 1101436. 13 22 580 is introduced at a current density of 0.5 Am-The published results were for the pere / dm ² and at an anolyte temperature below 12 ° C of the procedure in the technology did not work. The formation of solid impurities is encouraging. As far as is known, no Vcr-60 has not yet been described; However, it can be seen that the drive for the production of p-benzoquinone by low current density and the anodic oxidation of benzene for cooling the anolyte have been described, required expenditure for a technical process that was developed beyond the laboratory stage for the production of p-benzoquinone became uneconomical . Udupa et al., Op. Cit., Come to the are. In US-PS 22 85 858, that the oxidation only during a 65 Anolyttemperaturen from 25 to 3O ⁰ C proceeds well, and a short period of electrolysis and current density of 2.4 Amp / dm ² is being worked at higher end, it However, if the electrolysis continues, the formation of p-benzo is indicated that under these conditions quinone decreases. the acid anolyte by oxidation products