DE1202269B - Process for the preparation of 1,4-dimethylolcyclohexane - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C07c

German class: 12 ο -25

Number: 1202269

File number: E 21315IV b / 12 ο

Filing date: July 1, 1961

Opening day: October 7, 1965

The invention relates to a process for the production of l ^ -dimethylolcyclohexane from terephthalic acid dialkyl esters, in particular from dimethyl terephthalate.

l ^ -Dimethylolcyclohexane is an important starting material for the production of polyester fibers, such as those in the USA patent 2,901,466.

A one-step process for the production of l ^ -dimethylolcyclohexane from dialkyl terephthalate is not known.

Rather, it has always proven necessary to use 1,4-dimethylolcyclohexane in a discontinuous manner 2-step process to produce.

According to the US Pat. No. 2105,664 known process is firstly terephthalic acid diethyl ester in the presence of a first stage a nickel-kieselguhr catalyst hydrogenated to hexahydroterephthalic acid diethyl ester. After separation of the nickel catalyst, the hydrogenation product is then in a second stage in the presence of a Copper chromite catalyst reduced to 1,4-dimethylolcyclohexane.

It has now been shown that in order to obtain a satisfactory yield of 1,4-dimethylolcyclohexane to obtain the hydrogenation product obtained using a nickel catalyst, d. H. the Dialkyl hexahydroterephthalate carefully before reduction with the copper chromite catalyst clean, d. H. must distill in order to remove impurities, which the reduction of the hexahydroterephthalic acid dialkyl ester interfere with 1,4-dimethylolcyclohexane.

The use of a nickel-diatomaceous earth catalyst in the first stage of the process has heretofore been established regarded as the most advantageous way to produce 1,4-dimethylolcyclohexane. This results e.g. B. also from the German Auslegeschrift 1 072 620, in which the different behavior of Terephthalic acid on the one hand and terephthalic acid esters on the other hand is described in the hydrogenation. Thus, in German Auslegeschrift 1 072 620, an inert liquid is used for the hydrogenation of terephthalic acid Medium and a palladium or ruthenium catalyst are recommended for the hydrogenation of the terephthalic acid esters however, the use of a nickel catalyst is still indicated as being particularly suitable.

Surprisingly, however, it has now been found that the palladium catalysts known for the hydrogenation of terephthalic acid can also advantageously be used in a 2-stage process for the preparation of
1,4-dimethylolcyclohexane

Applicant:

Eastman Kodak Company,

Rochester, N. Y. (V. St. A.)

Representative:

Dr.-Ing. W. Wolff and H. Bartels, patent attorneys, Stuttgart 1, Lange Str. 51

Named as inventor:
George Alfred Akin,
Harrell Julian Lewis,
Toy Franklin Reid,
Kingsport, Tenn. (V. St. A.)

Claimed priority:

V. St. v. America July 18, 1960 (43 454) -

for the production of l ^ -dimethylolcyclohexane from Have dialkyl terephthalate used. It has been shown that the use of palladium catalysts in the hydrogenation of terephthalic acid dialkyl esters not only at favorable rates that were not suspected Yields, but that is a significant advantage compared to the previously known 2-stage process is achieved as the purification of the dialkyl hexahydroterephthalate of nickel traces is eliminated.

The invention therefore relates to a process for the preparation of 1,4-dimethylolcyclohexane by catalytic hydrogenation of a dialkyl terephthalate, in particular dimethyl terephthalate, to give a dialkyl hexahydroterephthalate, in particular dimethyl hexahydroterephthalate, at elevated temperatures ^{and reductions of up to about 400 °} C. and at elevated pressures of up to about 400 ° C. and at elevated pressures of up to 400 ° C. of the hydrogenation product with hydrogen in the presence of a copper chromite catalyst, which is characterized in that the dialkyl terephthalate is hydrogenated in the molten state in the first reaction stage in the presence of a palladium catalyst known as a hydrogenation catalyst and the hydrogenation product of the first reaction stage is continuously converted into the second reduction stage without intermediate purification .

509 690/480

3 4

To carry out the process of the invention, however, hydrogen can additionally be used if desired practically all of the usual palladium hydrogenation are introduced into the second reaction stage; even suitable for catalysts. A suitable palladium can be previously cooled hydrogen gas from any reactant catalyst contains, for example, about 0.25 to about tion stage can be returned to the same stage. 10 weight percent palladium on a dehydrated 5 It was found provided hydrogen in each or activated aluminum oxide, kieselguhr, active reaction stage is circulated that then carbon, dehydrated zirconia, dehydrated silica the best results are obtained when about

acid gel, chromium oxide, bentonite or asbestos carriers. 0.9 to about 1.8 kg hydrogen per 1.0 kg terephthalic

Dimethyl aluminum esters have been found to be particularly suitable as carriers in the first stage,

oxide and activated charcoal. The catalyst can io and about 1.0 to about 3 kg of hydrogen per kg of the from

in the form of tablets, granules or in the form of one exiting the first stage and entering the second stage

Fixed bed can be used. imported product. A part

The copper chromite catalysts can, for example, the cooled, crude product from each stage can be returned to the chromate salts concerned, such as basic copper ammonium stage, by decomposing complex copper in order to regulate the temperature; The reaction is your chromate, to be produced. Appropriately, nature after exothermic. Heat exchangers or other means of temperature control can be used to convert the catalyst in the form of tablets. Can also be used in the manufacture of the tablets. Both reaction stages water-soluble binders such as sodium silicate or are used within approximately the same temperature range and within the same pressure range. Barium oxide can also be operated as an active ingredient, as indicated above. That will be added in the second vator. Suitable catalysts are 1,4-dimethylolcyclohexane that accumulates in the stage with a copper content corresponding to 30 to collects. The methyl alcohol formed can be replaced by 80% CuO; a chromium content corresponding to 15 until distillation and condensation are removed. 55% Cr ₂ O ₃ and a barium content corresponding to 25 However, it was found that methyl-0 to 15% BaO present. alcohol serves to lower the melting point of the 1,4-di-

Catalyst tablets can reduce 2 to 25 weight methylolcyclohexane to such an extent that

Contains percentages of a water-soluble binder. this can be handled comfortably at normal temperature.

Water-insoluble foreign components, such as graphite, can become. The exhaust gas can be cleaned and put in

mold lubricants should be absent as much as possible. 30 the first stage, if desired, as pure water

It is desirable that the catalysts are recycled to such a substance.

Density tabletted that the average. In a modified embodiment of the side Crush resistance is greater than about finding, each of the two reaction stages is in two 2.27 kg. The tablet diameter can be about 1.6 mm or more divided into reaction zones or reactors, up to 12.7 mm with a comparable length. 35 The feed speed of the relevant

Experiments in which first a copper chromite dialkyl terephthalate was set so that the catalyst and then a palladium catalyst were used in the first zone of the first with a palladium catalyst, showed that the aromatic catalyst-operated reaction stage only a partial core was not attacked instead the wise hydrogenation takes place, and that the remaining ester groups bound to the aromatic nucleus 40 hydrogenation brought about by the palladium catalyst converted into CH ₂ OH groups and methyl alcohol, reaction in the second or the following zones with part of the unsaturated dialcohol in the case of continued The first reaction stage - operated with a palladium catalyst, the hydrogenation continues to give xylene and water - occurs. The second, was reduced, the water deactivating the copper chromite reaction catalyst operated with a copper chromite catalyst. If, on the other hand, a 45 stage is also divided into two or more mixed palladium-copper chromite catalysts in separate zones, with only a partial form of a catalyst bed being used, the result - the back on the copper chromite catalyst - water. If only one of the feed-in - reduction in the first zone is used, 1,4-dimethylolcyclohexane is found, and the reduction in the remaining one or the rest is not formed in any significant amounts. 50 zones continued and from the last zone the finished one

Although to carry out the 1,4-dimethylolcyclohexane according to the invention is removed. To the

Process temperatures of up to 400 ⁰ C suitable purposes of temperature control can be part of the

are preferably temperatures of 150 from each zone of the first with palladium catalyst

up to 275 ⁰ C applied. operated reaction or hydrogenation stage

In one embodiment of the 55 flowing product according to the invention in the same zone or also in

Process is a reactor or one of these upstream zone or zones of the process for each stage

Reaction zone provided. In the process, the melted level will be returned. Corresponding

zener dimethyl terephthalate and hydrogen can also be part of the from each zone of the second

continuously into the first reactor or the first reaction operated with copper chromite catalyst

Introduced reaction zone in which the palladium 60 or reduction stage material flowing off into the

catalyst is located. The feed speed for the same zone or in one of these upstream

the terephthalic acid dimethyl ester is set in such a way, zone or zones of the same stage, to the tempe-

that a sufficient excess of hydrogen temperature to regulate, be recycled. The entire

in the one from the first reactor or the first into the first zone operated with palladium

Reaction mixture withdrawing reaction zone from material introduced in reaction stage - hereinafter

remains, which then in a likewise individual reactor - referred to as total charge - does not contain

or reaction zone of the second reaction stage, which is more than about 0.6, preferably 0.04 to 0.16 weight

4en containing copper chromite catalyst is transferred. parts of dialkyl terephthalate, based on 1.0

5 6

important part of the total load. Correspondingly, it is diverted and blown off into the atmosphere. Each holds the total charge of the first zone or the first absorber at a temperature of -75 ⁰ C the reactor is operated with a Kupferchromitkataly- and at a pressure of not more stages operated in the two reaction crystallizer second reaction stage corresponds used. Practically about 0.6 part by weight, preferably 0.04 to 5, of all of the gas stream in the gas stream is 0.16 part by weight of saturated diester per 1.0 of methane retained by any portion of the feed that escapes in the absorber. The fact that the amount of suitable adsorbent held, such as activated carbon, silica-hydrogenatable dialkyl terephthalate in the acid, activated aluminum oxide or calcium charge of the first zone is adsorbed with the palladium and sodium aluminum silicate. The catalyst-operated stage and the amount of i ° methane absorber leaving gas consists of practically reducible, saturated diester in the feed of pure hydrogen, which is then compressed to the first zone with the copper chromite catalyst and returned to the process, operated stage on the indicated level The procedure according to the invention is as follows

is kept, the amount of hydrogenatable ter- on the basis of preferred embodiments in phthalic acid dialkyl ester explained in the feed of the second * 5 individual.

Zone of the stage operated with palladium catalyst in FIG. 1 shows a two-step process,

and the amount of reducible saturated diester, each stage being only one reactor or one in the feed of the second zone which has a reaction zone. The first reactor contains Copper chromite catalyst operated stage also set the palladium catalyst and the second the copper. Thus the charge of the latter contains 20 chromite catalyst.

both zones usually on hydrogenatable terephthalic In Fig. 2 shows a two-step process,

dialkyl ester or reducible saturated di- in which four separate reaction zones or reactors ester no more than about 0.3 parts by weight of terephthalic are provided, and the first reaction stage of two acid dialkyl ester or saturated diester per 1.0 Ge charged with palladium catalyst and reactors Part of the feed to the reaction in question is the second reaction stage consisting of two with copper chromium zone, usually 0.02 to 0.08 parts by weight of tertiary catalyst charged reactors, dialkyl phthalate or saturated diester according to FIG. For example, 1 becomes more melted

1.0 part by weight of the feed of the relevant dimethyl terephthalate continuously by means of Zones. The exhaust gas from the second stage can be fed to a pump 10 through line 12 into line 14 be cleaned by pressing it over a suitable adsorbent 30, where it is treated with, as described below, and / or another suitable means is passed, recirculated hydrogen is combined, whereupon it as purified hydrogen at any one of the mixture of dimethyl terephthalate and Place of the reaction system is added again. Hydrogen then passes through a heat-die Cleaning is carried out gradually. The exchanger 16 in line 14 and occurs from there Exhaust gas first passes through a cooler to 35 from it into the reactor 18, which is filled with a palladium water, Methyl alcohol and other condensable catalyst is charged and the only reactor Remove vapors and then form a pre-first stage. Through the line 20 is warmer, where it is heated to 225 ° C to 425 ° C. He continuously pressed hydrogen into the reactor 18 then enters one of two existing methane and partially circulated via line 22 a, which are arranged so that it leads 40 alternately. Liquid material leaving reactor 18 can be used, and which serve the purpose of the im is continuously through the lines 24 and 26 Exhaust gas containing carbon oxide and hydrogen in a second with a copper chromite catalyst to be converted into methane and water. The methane-fed reactor 28 led to the only one Furnaces contain a nickel-containing or other second stage reactor. That from the suitable catalyst in fixed bed form and will be 45 liquid material emerging on its reactor at a temperature of 225 to 425 ° C and on ways to the reactor 28 with from the reactor 28 Pressures up to the working pressure of the reac- coming circulated hydrogen tion zones or reactors for the hydrogenation or combined, from the line 30 into the line 26 Reduction of the relevant terephthalic acid dialkyl entry. The liquid withdrawn from the reactor 18 esters operated. Metals of Group VIII of the Perio 50 material and those circulated in reactor 28 dic systems, such as iron, cobalt, ruthenium, go through after their union and hydrogen Rhodium, palladium, osmium, iridium, platinum are a heat sink before entering reactor 28 Catalysts suitable for nickel for the exchangers 32 Conversion of carbon monoxide with hydrogen to liquid material is through a line 31 in a Methane and water. In this case, the catalyst 55 separating device 33 can be drained from which the discharged through a line 36 in finely divided metallic form or in the form of gaseous fractions of a salt or compound are present, which become and liquid 1,4-dimethylolcyclohexane through do not interfere with the reaction, for example as chloride, a line 34 is withdrawn. The one from the two Carbonate, oxide, acetate or stearate. That which is returned to the Me reactors or in the circuit Thanofen leaving gas is cooled to all easily 60 conducted part of the hydrogen before it can be used to remove condensable fractions therefrom, and the primary liquid stream is combined, then Chilled to -75 ° C before being primed and chilled.

enters one of two methane absorbers, which according to FIG. 2 is terephthalic acid dimethyl

can also be operated alternately. Each individual ester continuously by means of a pump 38 through Methane absorber is periodically regenerated by pushing 65 a line 40 into a line 42, where it the pressure is reduced and the temperature is reduced to 100 with, as described below, returned 300 ° C is increased, with a stream of inert gas, such as material is combined. The resulting mixture Nitrogen, through the adsorbent contained therein is through a heat exchanger 44, which is in

7 8

the line 42 is installed, results in a reactor 46 which serves to feed the amount of the reaction introduced, which is the first reactor of the reaction stage catalyzed with palladium-capable material in each of these two reactors. To regulate through. In this way, the heat and pressure generated in the hydraulic line 48 is continuously fed back to the reactor 46 with the recirculated, dredging or reduction of the hydrogen, supplemented into the purified hydrogen in question, introduced under 5 reactors. Terephthalic acid can be controlled. Pumps and valves can be used to control dimethyl ester, recycled material, and water to support or effect such control of the sub-material flow through reactor 46 along with. In the supply lines the product of the partial hydrogenation through each of the four reactors arranged heat line 50 into a closed container 52. A ία exchanger are used to regulate the temperature of the feed part of the liquid, exiting the reactor 46 of the respective reactors. By means of the material is continuously from the container 52-like heat exchanger can both excess heat dissipated through a line 54 by means of a pump 56 and the temperature of the material drawn and fed via line 42 to the fresh Tere reactors at the desired level phthalic acid dimethyl ester via line 40 to be maintained at 15 height. The fed terephthalate flows back into the reactor 46. The amount of acid dimethyl ester generally has a temperature of the circulated liquid material which is regulated below the desired reaction in such a way that overheating in the reactor 46 is temperature; therefore this serves to prevent the first one. The portion of the reactor of the first palladium catalyst leaving material that is not recycled, 20 driven stage recycled material that is continuously heated through a line 58 via a feedstock by mixing, heat exchanger 60 passed to a reactor 62, whereby at the same time the exothermic Hyd. H. the second reactor of the heat released by the palladium catalysis reaction is carried away by a fan-operated stage. That is made harmless from the reactor 62 or,
exiting material flows through a conduit 64 25 The following examples are intended to illustrate the process of leading to a conduit 66, where it is carried out with an invention.
Line 68 entering as described below. -I ₁
returned material combined or supplemented example
will. The combined streams of material pass each about 31.75 kg of molten, about 160 ° C warmer first a heat exchanger 70 and get 30 dimethyl terephthalate and 32.99 Nm ^{3 of} water from there into a reactor 72, ie the first reactor material of about 175 ° C and one Purity of 98.9 V or lumen percent operated with a copper chromite catalyst, the 0.86 volume second stage as impurities. The percent methane exiting from reactor 72, 0.23 percent by volume nitrogen and material flows through a line 74 to contain 0.001 percent by volume oxygen, were closed container 76 . 1, consisting of two 72 discharged liquid material, is continuously fed in series-connected reactors consisting of the container 76 through the line 68 by means of a hydrogenation unit. The pressure in the first pump 78 withdrawn and via line 66 together reactor was about 385 atmospheres and was a little lower with the material withdrawn from reactor 62 than the pressure in the second and last reactor. The returned to the reactor 72. Again, the 4 ° dimethyl terephthalate and hydrogen stream each recirculated amount is measured so that the heat generated in reactor 72 was combined with a stream of recirculated water, which was cooled down to such an extent that it can be controlled. That portion of the material discharged from reactor 72 at its temperature after being compressed to about 386 atmospheres in container 76 that was not about 175 ^° C. About 36 kg per hour were returned to reactor 72, hydrogen is continuously returned. The first reactor contained a palladium catalyst through line 80 over thermal. The palladium catalyst exchanger 82 passed into a reactor 84, ie essentially consisted of pressed aluminum, the second reactor of the second stage operated with copper chromite catalyst tablets of about 1.6 mm in diameter on the generator. About 0.5 weight percent palladium was loaded into the reactor. 84 leaving material, which consists mainly of 1,4-di-50 The product leaving the first reactor was methylolcyclohexane, passes through a line together with recycled hydrogen in the 86 in a separator 88, from which the liquid upper part of a second reactor is introduced . Hour-1,4-Dimethylolcyclohexane via line 90 off- Hch was taken about 77 kg of hydrogen in the second, while the exhaust gases were circulated through a reactor. In this case, the line 92 was cooled down in a gas cleaning system 55 as described above so that hydrogen was passed to Com-94, from the practically pure water pressure to about 386 atmospheres and mixing with the substance through a line 96 of the line 48 for the In the product coming from the first reactor, a first reactor 46 of the first with a palladium mixture ^{temperature of about 250 °} C. was established. The (fresh) second reactor entering the catalyst-operated stage contained approximately 90.7 kg of a copper-hydrogen feed. When using the in 60 chromite catalyst. In this reactor the FIG. 2, the ratio of reaction with formation of 1,4-dimethylolcyclohexane of the feed to reactor 46, i.e. the first, and methyl alcohol is brought to an end. Part of the entReactor of the first methyl alcohol with palladium catalyst was continued with the exhaust gas driven reaction stage and that of the reactor and could easily be separated therefrom by condensate 72, ie the first reactor of the second, with copper 65ation. 97 molprochromite catalyst-operated stage were converted into 1,4-dimethylolcyclohexane to the respective cent of the dimethyl terephthalate used, which was recycled and mixed with it. After Abso adjusted that a liquid-diluting effect separating the methanol, the exhaust gas contained about

9 10

93 percent by volume hydrogen, the remainder consisted of borrowed in the same and about 454 kg des

Nitrogen, oxygen, methane and carbon monoxide. liquid material emerging from the second reactor

A total of about 7.51 Nm ^{3 of} exhaust gas was produced per hour. rials returned to the second reactor every hour.

As the reaction continued, about 95 mole percent of the amount used was initially used to achieve the optimum

male amount of the 5 terephthalic acid dimethyl ester in 1,4-dimethylolcyclo-

speed and the yield in each reactor converted into circular hexane and about 91 mol percent towards the end

run to be carried out hydrogen, each of the experiment, which lasted a total of 3 days,
the amount of which varies; so was the influence

the amount of circulating hydrogen Example 3
for an effective use of the two catalysts

The procedure was as in Example 1, but a higher yield was determined by varying the amount of hydrogen fed back instead of the hydrogen in each individual reactor. When the amount to circulate, the exhaust gas is converted into pure hydrogen by condensation of the extracted from the first reactor and in and adsorption and this recycled hydrogen to an amount 15 thereafter in the first reactor at a temperature of less than 0.9 kg per 1.0 kg of the recycled in the first 175 ° C. For this purpose, the reactor introduced dimethyl terephthalate exhaust gas was cooled to a temperature of about 5 ° C, was reduced, the yield of material hydrogenated by water vapor and methyl alcohol vapor therefrom decreased to an unsatisfactory amount, to condense. The liquid condensate was collected in a receptacle and a substantial part of the terephthalate used, and from time to time the acid dimethyl ester was drained off as a result of side reactions. The remaining gas was then wrecked. On the other hand, the amount of heat from the first in a preheater to approximately 300 ° C and extracted by reactor and in those returned about 13.6 kg of a nickel-containing, supported on 330 ⁰ C the hydrogen to over 1.8 kg per 1.0 kg The terephthalic acid dimethyl introduced into the first reactor and in a "methanizer" catalyst, where the carbon ester contained in the exhaust gas was increased, the rate of reaction with hydrogen to methane and water decreased considerably. Corresponding results were set. The gas withdrawn from the methanizer was obtained when the amount of hydrogen in the second reactor was cooled to about 2 ° C. in order to separate less than 1.0 kg of water of reaction for most of the cycle. The water collected in a receiver or more than 3.0 kg per 1.0 kg of the water collected by the first reactor 30 was drained from time to time, the liquid product transferred to the second reactor. The exhaust gas, which was now only a barely detectable product . It is not essential that each contained amount of carbon monoxide, returned hydrogen was cooled and then cooled to about -75 ° C and mixed in a material stream, as described in the present example, which is also cooled to about -75 ° C. The process was also conducted in ³⁵ , which carried out about 22.7 kg of a calcium aluminum adsorbent in such a way that it contained the adsorbent existing in the individual silicate, whereby hydrogen was practically fed back into the reactors separately from all methane as well as any nitrogen adiquid material present was introduced, were sorbed. Pure hydrogen remained, which also gave favorable results. contained only traces of oxygen and nitrogen. Also, after the experiment had run for a few hours, the gas under a pressure of 383 atmospheres, about 22.7 kg of fresh hydrogen was compressed to about 386 atmospheres and introduced into the first reactor in order to remove the returned to the reactor. The methane adsorbers in the first reactor, excess water, were switched off every 4 hours, ie while the substance and the one in the second reactor was in operation, the other was regenerated. In this example, an essentially complete yield of 1,4-dimethylolcyclohexane was retained. The conversion of dimethyl terephthalate in process was achieved with a degree of conversion of 1,4-dimethylolcyclohexane, the 60 mole percent being carried out when the pressure in the amount of the second reactor returned to the first reactor was decreased to about 50 atm, hydrogen about 45.4 kg hourly,
by removing the methanol from the 50

Hydrogen condenses and in this way Example4
Methanol concentration in the second reactor

has been reduced. If the procedure was otherwise followed as in Example 1, however, was

the same conditions as stated last, this time no hydrogen was circulated. It

was carried out, but without the methanol to 55 resulted in essentially complete hydrogenation

condense, less than 10 mole percent of the dimethyl terephthalate was reached; However

Dimethyl terephthalate in 1,4-dimethylolcyclo- were less than 70 mol percent in 1,4-dimethylol-

converted to hexane. converted cyclohexane, apparently because of

_. . , “The elevated temperature.
_{Example2 6o}

The procedure was as in example 1, with fresh, example 5
highly active catalysts were used, however

This time, a part of the from each reactor was made. The procedure was as in Example 1, but was leaving product back into the same reactor - this time instead of the hydrogen in each one guided. The same flow rates were used to circulate the reactor through the exhaust gas conditions, temperatures and pressures as in example 1 condensation and adsorption as in example 3 applied and there were about 318 kg of the written off, cleaned and put into the first reactor in shape first reactor exiting liquid material hourly returned from purified hydrogen; aside from that

11 12

Some of the liquid from each reactor was made from chromium as Cr ₂ O ₃ ; 10.4 percent by weight of barium as material entering the same BaO reactor; 3.5 weight percent Na ₂ O and 9.5 weight recycled. The amount of SiO ₂ from each reactor. The average temperature in drawn and in the same reactor zurückge- third reactor was about 27O ⁰ C. The liquid material supplied from the in was such that 5 the third reactor was leaking product, less the feed of the first reactor 0.1 parts by weight of in the same reactor recirculated part, terephthalic acid dimethyl ester per 1.0 part by weight of the cooled to about 250 ° C and then contained in the fourth feed, and that the feed of the reactor introduced, which about 27.2 kg of the same second reactor at 1.4- Dimeth.ylolcyclohexan auf-Kupferchromitkatalysators contained. The reducible material durchschnittweisendem about 0.1 weight io Liehe temperature in this reactor was about 260 ⁰ C. portion of the corresponding saturated diester on emerging from the fourth and final reactor 1.0 part by weight of the respective feed contained. liquid product had the following composition:
A conversion of about 90 mole percent was found

achieved. Weight percent

B e i s o i e 1 6 l ^ -Cyclohexanedicarboxylic acid dimethyl ester 0.1

4-oxymethylcyclohexanecarboxylic acid methyl

In this example, a system as shown in FIG. 2 ^es if. ^r "YY", 'Y ",

shown, used. The first reactor of the first Re-1,4-dimethylcyclohexane 0.1

action stage had an internal diameter of 20 l-methyM-oxymethylcyclohexane 1,2

about 102 mm and the second reactor a through-l-methoxymethyl-4-oxymethylcyclohexane. 0.3

knife of about 61 mm. The first reactor of the second 1,4-dimethylolcyclohexane 68.0

Reaction stage had an internal diameter of methanol 29.6

about 152 mm and the second reactor a diameter other 0.1

knife of about 102 mm. 25th

Each about 31.8 kg of melted, about 16O ⁰ C was added a warm There about 97molprozentige Umwand-

Terephthalic acid dimethyl ester and 32.99 Nm ³ of water lung Terephthalsäuredimethylesters in 1,4-Distoff of about 175 ⁰ C and methylolcyclohexan achieved a purity of 98.9 Vo-. About lum percent of the waste gas was obtained every hour, 0.23 volume-7.01 Nm ^{3 as impurities.} This consisted of 93% by volume of nitrogen, 0.86% by volume of CH ₄ and 30% by volume of hydrogen, 1% by volume of nitrogen, containing 0.001% by volume of O ₂ . 15 volume percent carbon monoxide and direction introduced. The first two reactors contained 2.146 percent by volume of unidentified components, each had a palladium catalyst and after cleaning by condensation and adsorption, the two last reactors each had a copper chromite as described in Example 3, the exhaust gas was converted into a catalyst. The pressure in the first reactor was about an amount of about 5.66 Nm ³ per hour in the 385 atmospheres and was a little lower than the pressure recirculated in the first reactor.

fourth and final reactor. The molten te- The last-described procedure has been carried out in

rephthalic acid dimethyl ester stream was combined with a search carried out with a running time of different lengths, liquid, recirculated stream, which from 40, among other things, in an experiment with a running time of part of that emerging from the first reactor of more than 2 months. The catalyst activity left only product. This recirculated stream was little after. It has worked continuously, and cooled to a temperature of about 175 ⁰ C. In total, around 295 kg of liquid material per hour were returned to the first reactor at or near the temperatures indicated above during the entire duration of the experiment from the first reactor to the first reactor. The first reactor contained about 15.4 kg of the amount of hydrogenatable or reducible

Palladium catalyst with a content of about material in the feed of the reactors can be adjusted to 0.5 percent by weight of palladium, the pressed one, that the temperature rise in the aluminum oxide tablets of 1.6 mm diameter reactors ^{does not exceed about 50 0} C and was applied preferentially. The temperature in this reactor, within a range of about 10 to 35 ° C., averaged about 175 ° C. That is.

The product leaving the first reactor was reduced to H. predominantly hydrogen, can

cooled about 175 ° C before venting into the second reactor to the free atmosphere to enter a pressure difference between the first and the remaining about 6.8 kg of the same catalyst. To generate the average temperature in the last reactor 55 that, regardless of whether the second reactor for about 21O ⁰ C. was each reaction stage, one or more reactors upstream

The product emerging from the second reactor can be seen. This supports the transfer of the and about 477 kg of the one reactor recirculated from the third, the second reaction participant and the reaction products from the reactor downstream into the other or the next material was supported every hour after cooling to 236 ⁰ C 60 following. At appropriate places the feed is introduced into the upper part of the third reactor. pipes, pumps and valves can be used. This third reactor, ie the first reactor, is used to regulate the required pressure drop, the second with a copper chromite catalyst between the individual reactors,
The driven reaction stage contained about 63.5 kg of one. .

Copper chromite catalyst, as it is commercially available 65 B e ι s ρ 1 e 1 7

are available. The catalyst contained after- From terephthalic acid dibutyl ester was 1,4-dimen-

GONE annealing at 400 ⁰ C for approximately 33.2 thylolcyclohexan overall by the process described in Example 6 weight percent copper as CuO; 38.0 weight percent process produced. It was an excellent

Claims (1)

13 14 achieved almost complete conversion. The Re indicates that the terephthalic acid action product had the following composition: dialkyl ester in the molten state in the first reaction stage by weight in the presence of a palladium catalyst known as percent hydrogenation catalyst, dibutyl cyclohexanedicarboxylate .. 0.2 5 lysators hydrogenated and the hydrogenation product of l -OxymethyM-cyclohexanecarboxylic acid- first reaction stage is continuously converted into the second reduction stage 1,4-dimethylcyclohexane 0.2 without butyl ester 0.4 intermediate purification. l-methyl-4-oxymethylcyclohexane 1.5 2 · Process according to claim 1, characterized in that l-butoxymethyl-4-oxymethylcyclohexane ... 0.1 10 indicates that for each reaction stage at least 1,4-dimethylolcyclohexane 49.1 two Reaction zones are provided. n-butanol 48.2 3. The method according to claim 1 to 2, characterized in that other ingredients 0 * 3, that the liquid reaction product from the individual stages and / or the hydrogen .. 15 are partially circulated. Claims: 4 Method according to Claims 1 to 3, characterized 1. Process for the preparation of 1,4-dimethylol characterized in that to 1.0 kg of the in the first cyclohexane by catalytic hydrogenation of a reaction stage or the first reaction zone of the Terephthalic acid dialkyl ester, in particular of the first reaction stage introduced terephthalic rephthalic acid dimethyl ester, about 0.9 to 1.8 kg of recycled, dialkyl terephthalate, especially hexa previously cooled and compressed hydrogen hydroterephthalic acid dimethyl ester, can be used at increased levels. · Temperature up to 400 ° C and elevated pressures of 50 to about 500 at and reduction of the hydrogenation. Documents considered: Product with hydrogen in the presence of an as German Auslegeschrift No. 1 072 620; Copper chromite catalyst, thereby becoming U.S. Patent No. 2105,664. For this purpose, 1 sheet of drawings 509 690/480 9.65 © Bundesdruckerei Berlin