DE1205539B - Method for determining the end point of the hydrogenation of carbon-carbon multiple bonds in a liquid proton-containing phase - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07b

German class: 12 ο - 27

Number: 1205 539

File number: B 71842IV b / 12 ο

Filing date: May 10, 1963

Opening day: November 25, 1965

The hydrogenation of carbon-carbon multiple bonds is made by known processes in the liquid phase using metallic catalysts of the metals of Group VIII. Determination of the end point of hydrogenation that is particularly important in the case of selective hydrogenation of triple bonds to double bonds either by continuously measuring changes in volume, changes in pressure, when in use flowing hydrogen by the so-called contraction, which is defined as

Liters of input gas minus liters of end gas liters of input gas

100,

Procedure for determining the end point of the
Hydrogenation of carbon-carbon multiple bonds in a liquid proton-containing phase

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Fritz Beck,

Dr. Ludwig Schuster, Ludwigshafen / Rhine

or through continuous sampling and analysis.

All of these processes have the disadvantage that the end point of the hydrogenation is only reached can be determined much later than when actually reached. That is with proceedings, with which multiple bonds are hydrogenated to single bonds, usually not harmful, but poses in any case represents a loss of time and often leads to a waste of energy, since the shaking or Stirring devices, heating or cooling systems are still being operated at a point in time at which a Operation is no longer required. With selective hydrogenation of triple bonds to double bonds a hydrogenating treatment that goes beyond the end point of the hydrogenation is always with a loss of compounds with an olefinic double bond, d. H. with a reduction in selectivity, tied together. It has therefore become common practice to carry out these selective hydrogenations with less active, to carry out poisoned catalysts.

It has now been found that the end point of the hydrogenation of organic compounds with carbon-carbon multiple bonds, in the liquid proton-containing phase in the presence of finely divided metallic ones suspended in the hydrogenation mixture Catalysts without the disadvantages mentioned can be determined if one during the hydrogenation the time sequence of the electrochemical hydrogen reference voltage in the hydrogenation mixture on the catalyst measures and the maximum change in the reference voltage at the prevailing pH of the Hydrogenation mixture determined.

The maximum change in the hydrogen reference voltage after time represents a new one, which has not yet been achieved unknown, well definable and chronologically very precisely measurable variable for the end point of the hydrogenation represent.

The hydrogenation of the carbon-carbon multiple bond, that is, of triple and double bonds, is made according to methods known per se carried out as they are z. B. in "Η ο u b e η - W e y 1, Methods of Organic Chemistry", 4th edition, Vol. 4/2, pp. 283-295.

Examples of unsaturated compounds are: olefins, acetylenes, aralkyl compounds with olefinic or acetylenic side chains, cyclic mono- or polyunsaturated Hydrocarbons, olefin and acetylene alcohols, olefinically or acetylenically unsaturated carboxylic acids, likewise the derivatives of these alcohols or acids, e.g. B. esters, amides, anhydrides, and also unsaturated Ethers and unsaturated ketones.

Examples of the starting compounds mentioned are: butyne- (2), hexyne- (2), styrene, Phenylacetylene, cyclohexene, cyclooctadiene, allyl alcohol, Crotyl alcohol, propargyl alcohol, dimethylethinyl carbinol, 2-butynediol-1,4, tetramethylbutynediol, Ethyl crotonate, acetylenedicarboxylic acid, propargylic acid, mesityl oxide, dehydrolinalool, linalool.

The following catalysts can be used, for example: noble metals, in particular platinum, palladium, Iridium and ruthenium, also nickel, cobalt, iron, but also copper. The catalysts can also contain additives that increase or decrease their activity, e.g. B. zinc acetate, lead acetate, pyridine, Ammonia or triethanolamine. The catalysts can also be used on or unsupported will. Examples of known catalysts of this type are: platinum black, Palladium black, platinum on barium sulfate, on graphite or on asbestos, palladium on animal charcoal, Aluminum oxide, calcium carbonate, barium sulfate or silicon dioxide, colloidal platinum, colloidal palladium

509 739/442

3 4

dium, platinum oxide, palladium oxide, Raney nickel, nary state of the transport of the molecular Raney cobalt, Raney iron, nickel on diatomaceous earth hydrogen adjusted to the catalyst surface or pumice stone. Since changes in this transport-For the hydrogenation of triple bonds and speed as strong changes in the Kata double bonds are preferred, the following Kata- S lysator reference voltage can have an effect. Used as measuring lysers: 0.2 to 5% palladium on electrode are usually gold or silver silicon dioxide, aluminum oxide or calcium carbon electrodes. The measuring electrode must not be natural, Raney nickel, 1% platinum on graphite. consist of the same material as the catalyst. The most important solvent is water. Calomel electrodes, if necessary with salt, acid or alkali additives, or silver-silver chloride electrodes are usually used as reference electrodes. The further into consideration, mixtures of water with orga- measuring device 3 is the electrodes used and niches, water-miscible solvents. Adapt it to the resistance in the circuit,
However, non-aqueous polar solutions can also be used. B. alcohols, ketones, lower ones in the course of a hydrogenation, in this case of fatty acids and cyclic ethers, especially metha- 15 2-butynediol- (1,4), using a palladium nol, ethanol, n- and iso-propanol, acetone In Figure 2, glacial acetic acid on alumina catalyst is tetrahydrofuran. Is the substrate itself a polar curve, together with the course of the hydrogenation liquid, such as e.g. B. in the case of the Dimethyläthinyl- shown speed. In Fig. 2, curve B, carbinols, at high substrate concentrations, the time course of the reference voltage can be used and / or completely without solvent. 2 ° of the hydrogenation rate for the hydrogenation of the measuring device used to display the catalyst reference voltage dimethylethinylcarbinol on a palladium catalyst (tube voltmeter or voltage converter on silicon dioxide, a, b and c voltage recorder) must have an input resistance, mark the beginning of the hydrogenation, the end of the is about a factor of 100 greater than the internal hydrogenation of the triple bond and the end resistance of the system. This requirement is easy for the hydrogenation of the double bond. To meet in both cases, since there is a large selection available commercially, the CsC bond to the C = C device with an input resistance of 10 ⁹ Ω bond is partially hydrogenated at time b , which results in a strong or more available that are adapted Shift of the reference voltage in negative Richan pH measurements with glass electrodes. Noticeable during processing.

Turning water or mixtures of water 30 The method shows particularly favorable results

with polar organic solvents is that in the selective hydrogenation of triple bonds

specific conductivity in the order of 10 ~ ⁶ to olefinic double bonds as well as in the selective

up to 10 ~ ⁷ S / cm, what can be measured with these devices tiven hydrogenation of compounds with several

already enough. An addition of electrolyte is naturally unsaturated bonds of various reactivity,

also here for a stable setting of the reference 35 You can then the hydrogenation very precisely at

voltage favorable. It is preferable to give electrolytes to stop the first hydrogenation stage. Further

with buffer effect too, e.g. B. ammonia or amines can even be used with such selective hydrogenations

and their salts, carboxylic acids and their salts very active (non-poisoned) catalysts through-

or strong acids, which then lead at the same time if the substance to be hydrogenated is so firmly attached

Stabilization of the pH value is achieved, but if 4 ° catalyst is adsorbed that a further hydration

The method can still be used even if the carbon-carbon double bond is created

pH in the solution is inhibited in the course of the hydrogenation during the first stage. This is

reaction shows a steady course, as this only z. B. the case when the compound to be hydrogenated

in a corresponding passage in the catalyst formation a carbon-carbon triple bond

reference voltage noticeable, but contains nothing at 45. In this case, however, it is particularly important

the sharp change in this measured variable at the end of the time of the termination of the reaction

point «of the hydrogenation reaction changes. recognize that after the disappearance of the CsC

The catalyst is used in finely suspended form. This inhibition disappears and the further-

The quantitative ratio ■ of the catalyst to the hydrogenation of the C = C bond with comparable

hydrogenating compound as well as the concentration 50 speed begins. In

of the compound to be hydrogenated, to the particular extent in each case, the proposed electrochemical

The solvents used are within the limits, such as the measuring method, even in those cases in which

they are known from prior art processes, the hydrogenation rate after the first stage

are. They are only slightly or not at all changes on the catalyst and substrate,

to vote. 55.

The reference voltage is used in example 1, which is known per se
Way, e.g. B. with a measuring arrangement as described in In a 1-1 glass flask with a 35 mm F i g. 1 is played back. A measuring grid stirrer, a measuring electrode (gold or silver), electrode 1 is connected in a suitable manner against an electrolyte siphon to the reference electrode, a reference electrode 2 and the voltage is measured or funneled with a hydrogen feed and discharge and a drop of a conventional instrument 3 for adding the substrate is written continuously. Both electrodes are immersed in 4.5 g of a zinc-poisoned palladium catalyst, the liquid phase4. To create flawless sators (5% Pd on 7-Al ₂ O ₃ + 3% zinc acetate) in potential ratios at the measuring electrode, it is 500 ml of water, which is an addition of 7.5 g Trizweckweise, it directly with the catalyst suspen- 65 ethanolamine and Contains 1.5 g of acetic acid, submitted to the flow of sions (S). By suitable stirring.

5 6

directed. After 15 minutes, the catalyst with addition> iel 4
Hydrogen saturated, which is in the setting

a constant Wasserstoffgleichgewichtsbezugsspan- I _n a 500 ml glass flask as in Example 1 makes voltage of -678 mV noticeable (the reference is equipped described, 5 g of a trokspannung is kenen as well as in the now following arrival 5 Palladium catalyst (0.8% on SiO ₂ ), placed against the saturated calomel electrode and the vessel filled with hydrogen. Measure by). When adding 10.56 g of 2-butynediol (1,4) in a dropping funnel, a solution of 100 g of a concentrated aqueous solution takes place tetramethylbutynediol (1,4) in 125 ml of 0.05 normal within a few seconds methanolic sulfuric acid was added and the catalyst reference voltage in a positive direction. io hydrogenation reaction at 40 ⁰ C and a rotational speed it represents a value of -540 mV, which carried out the Gitterrührers of 600 U / min. Course of 3V ₂ hours steadily to -570 mV- The catalyst reference voltage falls in the course of decreases. After that a stronger change begins, 8 hours from -60 mV to -150 mV steadily. which reaches its maximum after 4 hours and 10 minutes. Then the time course of this measured variable shows

achieved. (^ - = 10 mV per minute at -630 mV). ^{15 shows} a much greater drop, which reaches its maximum value after 8 hours At ^r and 16 minutes (about 2 mV. At this point, an equimolar amount per minute is -165 mV). At this time hydrogen has been absorbed, ie the three-point is an equimolar amount of hydrogen on the multiple bond has been hydrogenated to the double bond. has been taken, ie, the C = C triple bond

_,. . , “20 of the molecule is selective for the C = C double bond

^Bei P ^iel been hydrogenated. ²

In the apparatus described in the example, if the same experiment is repeated with a

5 g of a palladium catalyst (5% on SiO ₂ ) in a thinner mixture of 70 g of tetramethylbutynediol

500 ml of 60% methanol, 7.5 g of triethanolamine and 160 ml of 0.05 normal methanolic sulfuric acid,

Containing 1.5 g of acetic acid, submitted. When adding 25 so, the hydrogenation rate is more than twice

from 15.4 g of linalool to the hydrogen-saturated one, and after 2 hours and 22 minutes it becomes

System, the catalyst reference voltage increases from the end point due to the steepest drop in the reference

-680 mV to about -300 mV, then in tension (about 3 mV per minute at -190 mV)

the progress of the hydrogenation is displayed within 46 minutes.

-550mV to drop continuously. After this 30th contribution> iel5
At this point, the reference voltage changes suddenly

stronger again and after 50 minutes it reaches the. In a flask with 500 ml contents, as in

steepest drop (35 mV per minute at -630 mV). Example 4 15 g of a dry palladium catalyst

At this point, an equimolar amount (0.8% Pd on CaCO ₃ , poisoned with 4.5% zinc acetate)

Hydrogen has been absorbed, i.e. the final 35 submitted and the vessel filled with hydrogen. By

permanent double bond in the molecule is selective a dropping funnel is a mixture of 214.3 g

been hydrogenated. technical Dimethyläthinylcarbinolund 15 gaqueous

Example 3 ^% i§ ^e r ammonia solution added. The hydrogenation

is then carried out at 60 ° C and a speed of the grid in the apparatus 40 described in Example 1 stirrer of 1500 rpm. The catalyst is charged with 5 g of a palladium catalyst (4% on lysator reference voltage drops from -600 mV to SiO ₂ ) in 500 ml of isopropanol containing 2.5 g of sulfuric acid -650 mV in the course of 7 hours and 15 minutes. With the addition of 54 g of cycloocta, it decreases steadily. Then, a much stronger Ändedien- (l, 5) in the hydrogen-saturated system (at tion that after 7 hours and 21 minutes their maxi-4O ⁰ C and 600 revolutions of the stirrer per minute) reaches 45 paint value (11 mV per minute -750mV). the catalyst reference voltage rises from -270 mV. At this point in time the reaction is terminated to -170 mV. After hydrogenation for 1 hour at and the mixture was analyzed by gas chromatography to have an average hydrogenation rate of 178 ml of H ₂ (6-mK column, 125 ° C). It contains 0.0% dimethyl per minute, the reference voltage has steadily fallen to 210 mV äthinylcarbinol, 98.9% dimethylvinylcarbinol and has fallen. Then the reference voltage drops sharply; 5 ° 1.1% dimethylethyl carbinol, based on the after one hour and 10 minutes, a maximum initial content of dimethylethyl carbinol is reached.
pain value reached (5 mV per minute at —240 mV). Table 1 lists eight hydrogenation experiments with At this point in time an equimolar amount of hydrogen has been taken up from this substrate under various conditions, ie the one is compiled. The reaction is hydrogenated in each case in the steepness of the two double bonds in the molecule. and the reaction mixture is hydrogenated by gas chromatography and analyzed under the same conditions 16.4 g. A cyclohexene experiment is juxtaposed in each case; when the substrate is added with a normal or with a zinc-coated palladium catalyst, the catalyst reference voltage increases from -27OmV on a poisonous palladium catalyst. The selectivity is in -16OmV. After 43 minutes this value is about equally good in both cases, and the hydrogenation rate has steadily dropped to -20OmV. Then speed begins to change, but with the non-poisoned catalytic converter, the reference voltage is expected to change more sharply; after 43V ₂ Mi- according to much higher. Fig. 3 to 6 show the slots, a maximum value of 11 mV per course of the catalyst reference voltage is reached towards the end of the minute. At this point in time, an equivalent reaction for the last four experiments in Table 1 molar amount of hydrogen has been recorded. 65 again. Curve C in each case relates to the rate of hydrogenation is accordingly 105 ml using a gold measuring electrode and curve D to per minute at the beginning and slows down compared to the use of a silver measuring electrode. The point? End of hydrogenation steady. indicates the termination of the reaction.

Tem
pera
door
⁰ C Selective hydrogenation of dimethylethinylcarbinol among various to
Di-
methyl-
ethinyl
carbinol together
water Settlement
in Gev
Meth
anol des Re,
i literally
Iso-
prop-
anol action f
ocent
Tri-
ether
anol-
amine
buffer,
pH 8 semischs
At the
mo
niak S.
Ka
taly
sator catalyst Condition ι Together
settlement after
j he
ation
ogen
the
strat)
Di-
meth-
yi-
ethyl-
carb-
inol
7o 25th 7.7 87.4 - - 4.0 - 0.9 4% Pd on CaCO ₃ ,
Zn poisoned C.
Hydi
(rel
on
Sub
Tuesday
meth
yl-
vinyl-
carb-
inol
% 12.2 No. 25th Turn
number
of
Lattice
stir
rers
Per
Wed
groove 7.6 86.7 - - 3.9 - 1.8 4.5 ° / ₀ Pd on SiO ₂ Medium
Hydrogenation
swiftly
speed
during the
first stage
ml H ₂
per minute
per kg **) 87 3.8 1 25th 600 9.4 - 84.6 - 4.9 - 1.1 4% Pd on CaCO ₃ ,
Zn poisoned 100 96 8.0 2 25th 1200 9.3 - 83.7 - 4.8 - 2.2 4.5% Pd on SiO ₂ 110 91 5.0 3 60 600 47.0 *) 5.9 - 43.1 - 0.65 3.3 4% Pd on CaCO ₃ ,
Zn poisoned 440 94 1.8 4th 60 1200 47.0 *) 5.9 - 43.1 - 0.65 3.3 4% Pd on CaCO ₃ 1010 98.2 1.25 5 60 1000 87.7 *) 5.5 - - - 0.6 6.2 0.8% Pd on CaCO ₃ ,
Zn poisoned 327 98.7 1.1 6th 60 1000 87.7 *) 5.5 - - - 0.6 6.2 0.8% Pd on CaCO ₃ 560 98.9 2.8 7th 1500 690 97.2 8th 1500 1030

Examples 6 to 9

*) Technical dimethylethinylcarbinol.

**) Hydrogenation rate, based on 1 kg of reaction mixture.

35 after purging with nitrogen and hydrogen hydrogen to the pressure given in the table below

The hydrogenations are forced into a 35 liter autoclave. Immediately after starting the Made of stainless steel. The vessel is equipped with a stirrer, the hydrogen uptake begins. The fast-moving ones The lattice stirrer for a more intensive temperature rises from around 20 ° to 50 ° C and is through mixture of the liquid with the gaseous phase 40 external cooling is kept at this temperature, Mistake. ■ The electrochemical hydrogen reference voltage

To measure the electrochemical hydrogen rises by leaps and bounds to a certain height and holds The reference voltage on the powdery catalyst is then approximately constant until saturation an electrode made of sheet gold is used, which converts the triple bond to the double bond. Short is connected to a calomel electrode. Both 45 before the tension continues to rise, slowly at first, Electrodes are pressure-tight thanks to the autoclave lid then faster and faster. The green is guided from the curves. A millivolt recorder registers the voltage curve.

17.35 kg of technical 1,4-butynediol solution (33%) are poured into the pressure vessel and adjusted to a pH of 7.5 with 50% concentrated ammonia solution. After adding 1.5 kg of the catalyst (0.2 Pd on 7-Al ₂ O ₃ , 2 to 3% Zn)

The most recent time to stop the hydrogenation can be seen. One breaks expediently at the moment of strongest voltage change.

For analysis, a small part of the solution is sucked off from the catalyst and from the water in a vacuum freed. The residue is examined by gas chromatography. The percentages are area percentages.

Table 2

No Temperature pressure recording Duration in mV
lowest tension
(Modification) mV / min
at the end Composition of
Residue (%) Butenediol Butanediol yield
o / "Her ⁰ C atü Liters of H ₂ Minutes 503 mV
maximum 10 Butynediol 100 theory 6th 45 5 1750 115 546 552 33 _ 100 - 97 ■ 7 45 8th 1845 75 525 605 20th - 100 - 96.5 8th 50 6th 2140 110 512 584 12th - 100 - 96.0 9 60 6th 2500 90 553 - 96.5

B is ρ ie 1 10 ^ 5 _{g of} acetic acid, submitted. When adding

In the apparatus described in Example! 65 46.5 g of phenylacetylene are converted into hydrogen-saturated Ge-15 g of a 0.8% palladium catalyst on calcium carbonate, which is poisoned with 5% zinc acetate,
in 500 ml of methanol, the 5.4 g of triethanolamine and

mixed at 35 ° C. and a stirring speed of 650 rpm, the catalyst reference voltage increases from -674 mV to -430 mV. Over the course of 50 minutes

this value hardly changes at an average hydrogenation rate of 190 ml per minute. Then the reference voltage begins to drop steeply, reaching a maximum value of 100 mV per minute after 52.5 minutes. At this point, an equimolar amount of hydrogen has been taken up. If the experiment is repeated with a different metallic catalyst, namely 10 g of Raney nickel, the catalyst reference voltage increases from -663 mV to -600 mV after the addition of the substrate. After 80 minutes, a stronger change begins to be noticeable at -610 mV, which reaches a maximum value of 17 mV per minute _{after 84V for 2 minutes.} At this point an equimolar amount of hydrogen has been taken up; the hydrogenation rate was initially 220 ml per minute and had dropped to 110 ml per minute after 80 minutes.

Example 11

In the apparatus described in Example 1, 10 g of a 0.8 ° / _o by weight palladium catalyst on silica in 500 ml of methanol, 3.5 g acetic acid and 1.5 g of sodium acetate containing presented. When 25 g of acetylacetylene are added to the hydrogen-saturated mixture at 30 ° C. and the stirrer rotates at 650 rpm, the catalyst reference voltage increases from -618 mV to -525 mV. After 170 minutes this value has hardly changed (-52OmV). Now a stronger change begins in a positive direction, which after 182 minutes reaches a ίο maximum value of 100 mV per minute. At this point, an equimolar amount of hydrogen has been taken up. The hydrogenation rate is 28 ml per minute at the beginning and increases to 84 ml per minute at the end.

Example 12

In the apparatus described in Example 1

5 g of a 4.5% palladium catalyst are applied

so silicon dioxide in 500 ml of glacial acetic acid as a solvent, containing 20 g of sodium acetate, submitted. With the addition of 25 g of farnesyl acetone

(CH ₃ - CO - CH ₂ - CH ₂ - CH = C - CH ₂ - CH ₂ - CH = C - CH ₂ - CH ₂ - CH = C - CH ₃ )

CH ₃

to the hydrogen-saturated mixture at 25 ° C and a speed of the stirrer of 600 rev / min increases with it Catalyst reference voltage taken from a silver probe from -336 mV to -282 mV. To For 105 minutes the value has changed steadily up to a level of -300 mV. The mean rate of hydrogenation is therefore 20 ml per minute. Now the hydrogenation begins to slow down will; at the same time, the catalyst reference voltage changes more quickly and occurs after 115 minutes a maximum value of 2 mV per minute. At this point is an equimolar amount Hydrogen has been absorbed.

Example 13

In the apparatus described in Example 1, 12 g of a 5% palladium catalyst on aluminum oxide in 500 ml of water containing 1.5 g of sulfuric acid (100%) are initially introduced. On addition of 16.1 g of acetylene dicarboxylic acid to hydrogen-saturated mixture at 40 ⁰ C and a stirrer speed of 650 rev / min, the catalyst reference voltage rising from -394 mV to -130 mV. After 120 minutes it is still -160 mV. Then a stronger change begins, reaching a maximum value of 40 mV per minute after 136 minutes. At this point, an equimolar amount of hydrogen has been taken up. The hydrogenation rate is 20 ml per minute at the beginning and is close to the end point at 28 ml per minute.

Example 14

In the apparatus described in Example 1, 5 g of a 4% palladium catalyst on calcium carbonate in 500 ml of 50 percent by volume of methanol containing 6 g of triethanolamine and 1.5 g of acetic acid are initially introduced. When adding 25.5 g of acetylenedicarboxylic acid diethyl ester to the hydrogen-saturated mixture CH ₃

CH ₃

(at 25 ⁰ C and 600 revolutions of the stirrer per minute) the catalyst reference voltage increases from -700 mV to -566 mV. The initial hydrogenation rate is 95 ml per minute and has increased to 120 ml per minute after 27 minutes. During this time, the catalytic converter reference voltage changed steadily and reached a value of - 588 mV. Now begins a stronger change in the direction of the reversible hydrogen reference voltage, which reaches a maximum value of 26 mV per minute after 32 minutes. At this point, an equimolar amount of hydrogen has been taken up.

Claims (4)

Patent claims: 1. Method for determining the end point of the hydrogenation of organic compounds with Carbon-carbon multiple bonds in a liquid proton-containing phase in the presence of finely divided metallic catalysts suspended in the hydrogenation mixture, thereby characterized in that the time course of the electrochemical during the hydrogenation Measures hydrogen reference voltage in the hydrogenation mixture on the catalyst and the maximum Change in reference voltage with time at the prevailing pH of the hydrogenation mixture determined. 2. Method for determining the end point of hydrogenation of carbon-carbon multiple bonds according to claim 1, characterized in that it is used in the partial hydrogenation of acetylene compounds or of compounds with multiple double bonds. Considered publications:
Houben-Weyl, Methods of Organic Chemistry, 4th edition, Vol. III, Part 2, pp. 139ff. For this purpose 2 sheets of drawings 509 739/442 11.65 © Bundesdruckerei Berlin