EP3481973A1

EP3481973A1 - Selective electrochemical hydrogenation of alkynes to alkenes

Info

Publication number: EP3481973A1
Application number: EP17758461.2A
Authority: EP
Inventors: Bernhard Schmid; Günter Schmid; Christian Reller
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2016-09-22
Filing date: 2017-08-16
Publication date: 2019-05-15
Anticipated expiration: 2037-08-16
Also published as: DE102016218230A1; WO2018054612A1; EP3481973B1; US20190276941A1; AU2017329370A1; AU2017329370B2; CN109790631A

Abstract

The invention relates to a method for the partial electrochemical hydrogenation of alkynes of chemical formula (I) to alkenes, (I) wherein R and R' are selected from inorganic and/or organic residues, wherein the compound of chemical formula (I) is hydrogenated on a copper-containing electrode. The invention further relates to the use of a copper-containing electrode for such partial electrochemical hydrogenation and to a device for performing the method.

Description

description

Selective electrochemical hydrogenation of alkynes to alkenes The present invention relates to a process for partiel ^¬ len electrochemical hydrogenation of alkynes by the chemical formula (I) to alkenes,

where R and R ^{A are} selected from inorganic and / or organic radicals,

wherein the compound of the chemical formula (I) is hydrogenated on a copper-containing electrode, the use of a copper-containing electrode for such a partial electrochemical hydrogenation, and an apparatus for carrying out the method.

The production of alkenes such as ethene or propene currently takes place mainly through the catalytic cleavage of

Crude oil (Naphta). An alternative approach is the partial hydrogenation of alkynes (eg ethyne). These can also be represented for example from coal or carbides and are therefore not dependent on crude oil. In classical hydrogenation, however, selectivity problems occur. Frequently, ^¬ fig over-reduction to the alkane take place. The necessary for the hydrogenation, hydrogen is also currently derived from coal gasification or steam reforming ^¬ and is therefore also associated with oil production.

The catalytic hydrogenation of alkynes has been achieved by special poisoned noble metal catalysts. An example of this is the Lindlar catalyst, which is a palladium catalyst poisoned with lead and quinoline. Another possibility is the "Birch analogue" The latter process is very expensive, but selective for E-alkenes, and new approaches to the production of hydrocarbons from, for example, carbon dioxide or carbon monoxide are emerging as part of the electrification of the chemical industry.

Electrification of the chemical industry means here, processes that are currently carried out by classical thermal processes or have not been possible to perform electro ^¬ chemically.

For example, the electrochemical hydrogenation of ethyne to ethene is known from X. Song, H. Du, Z. Liang, Z. Zhu, D. Duan, S. Liu, Int. J. Electrochem. Sei., 2013, 8,

From 6566 to 6573. However, the authors use here exclu ^¬ Lich electrodes made of the precious metal palladium, and the substrate selection is also limited to ethyne.

There is thus a need for simple and easily accessible processes for the preparation of alkynes from alkynes, which preferably take place without expensive noble metals. The inventors have found that partial reduction of alkynes can be performed by an electrochemical method using a Cu electrode in water-based electrolytes. In this case, the electrode can be designed both as a solid electrode and as a gas diffusion electrode. Due to the better substrate availability for Al ^¬ kine the latter is particularly suitable. The process according to the invention shows a high selectivity and activity, even for non-activated alkynes and for difficult substrates with electron-donating groups and / or steric hindrance. In a first aspect, the present invention relates to a process for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes,

wherein R and R ^{A are} selected from inorganic and / or organic radicals, wherein the compound of the chemical formula (I) is hydrogenated on a copper-containing electrode.

In addition, in a further aspect, the use of a copper-containing electrode for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes is disclosed,

wherein R and R ^{A are} selected from inorganic and / or organic radicals.

In addition, in yet another aspect of the present invention, an apparatus for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes is disclosed,

wherein R and R ^{x are} selected from inorganic and / or organic radicals, comprising:

An electrolysis cell (1) comprising a copper-containing Elect ^¬ rode, which is adapted to the alkyne to reduce the chemical ^¬ For mel (I) to alkene;

a source of the alkyne of the chemical formula (I) (3), which is designed to provide the alkyne of the chemical formula (I); and

a first feed means (2) for the alkyne of the chemical formula (I), which is adapted to supply the alkyne of chemi ^¬'s formula (I) from the source of the alkyne of chemical formula (I) of the electrolytic cell.

Further aspects of the present invention can be found in the dependent claims and the detailed description. The accompanying drawings are intended to illustrate embodiments of the present invention and to provide a further understanding thereof. In the context of the description, they serve to explain concepts and principles of the invention. Other embodiments and many of the advantages mentioned will become apparent with reference to the drawings.

The elements of the drawings are not necessarily to measure ^¬ scale shown to each other. Identical, functionally identical and identically acting elements, features and components are in the figures of the drawings, unless otherwise stated, each provided with the same reference numerals.

Figure 1 shows a schematic representation of the erfindungsge ^¬ MAESSEN device.

In a first aspect of the present invention, a process for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes is disclosed,

where R and R ^{A are} selected from inorganic and / or organic radicals,

wherein the compound of the chemical formula (I) is hydrogenated on a copper-containing electrode.

Alkynes are all chemical compounds which have a triple bond between 2 carbon atoms. The method is therefore not limited to ethyne but can be applied to other alkynes.

A general scheme of the electrochemical reaction of alkynes of the chemical formula I is as follows:

Ynerwünscht R ^"

All in Alken Aikan, where instead of the H ⁺ ions shown, it can also be D ⁺ ions, for example.

The good selectivity comes from the low

Reactivity of the resulting alkenes over the Elektrohyd- ration with Cu electrodes. In particular, electronically deactivated internal alkenes such as crotyl alcohol (trans-2-butenol) were inert to overreduction. The copper-containing electrode is not particularly limited and may include copper in addition to other components such as other metals and / or ceramics as a substrate, but may also be made of copper. It may also be chemically treated, for example for oxide formation. Likewise, it may be formed as a solid electrode or as a gas diffusion electrode. The better substrate availability for alkynes means that Tere, so the gas diffusion electrode particularly suitable, in particular for gaseous alkynes such as ethyne, propyne, 1-butyne or 2-butyne. Unlike palladium electrodes, the present copper-containing electrodes are much less expensive.

For example, a copper-containing

Electrode can be obtained by a layer comprising a Cu ⁺ / Cu-containing catalyst is deposited on a non-copper substrate, as described in DE 10 2015 203 245, or else by the layer on a copper substrate from ^¬ divorced.

The Cu ⁺ / Cu-containing catalyst is also referred to below as a copper / copper ion catalyst, copper catalyst or the like or simply as a catalyst, if not otherwise stated in the text, so these Be ^¬ handles in the context of to understand the present invention synonymous. Likewise, the non-copper substrate is also referred to simply as Sub ^¬ strat, so does not result from the text otherwise.

It is not excluded that the non-copper substrate contains copper, as long as it does not consist essentially of copper. For example, the substrate can also be made of brass or brass. For example, the non-copper substrate comprises less than 60% by weight of copper, based on the total weight of the substrate, preferably less than 50% by weight, more preferably less than 40% by weight and particularly preferably less than 20% by weight of copper , example ^¬ as no copper.

In particular, all conductive substrates can be used in the production of such an electrode. Example ^¬, the substrate comprises at least one metal such as silver, gold, platinum, nickel, lead, titanium, nickel, iron, manganese, or chromium or their alloys such as stainless steels, and / or at least one non-metal such as carbon, Si, boron nitride (BN), boron-doped diamond, etc., and / or at least one conductive oxide such as indium tin oxide (ITO), aluminum zinc oxide (AZO), or fluorinated tin oxide (FTO), for example for manufacturing of photoelectrodes, and / or at least one polymer based on polyacetylene, polyethoxythiophene, polyaniline or polypyrrole for the preparation of polymer-based electrodes. The preparation of the CuVCu-containing catalyst can be carried out in various manners and is not particularly limited, and the various preparation processes of the CuVCu-containing catalyst can also be carried out on copper substrates.

For example, electro-reduction catalysts can be obtained when the catalyst is deposited in-situ on the electrode substrate. However, ex-situ deposition is not excluded according to the invention. The substrate here does not necessarily have to comprise copper or be copper, but may contain any conductive material, in particular also conductive oxides. Particularly preferably, the porous Substituted ^¬ staltungen of such an electrode in order to obtain gas diffusion electric ^¬ are.

Charge compensation in the Cu ⁺ / Cu-containing catalyst can take place by incorporation of anions in solution during production, for example hydroxide ions (OH ^- ), O 2 ^- , halide ions (halogen), for example fluoride, chloride, bromide, iodide, Sulfate, bicarbonate, carbonate or phosphates etc.

The copper-comprising layer can also be deposited from a solution comprising copper ions on the surface of the electrode. In accordance with certain embodiments, dendritic structures can be applied from solution in the coating, in which case no complete coating of the substrate has to be achieved, that is to say parts of the substrate are also removed. Strats can be visible. The coating of the substrate, as well as the structures of the catalyst, may in this case at ^¬ play, by means of scanning electron microscopy (SEM) or transmission electron microscopy (TEM) to be analyzed.

In the electrode, the substrate is not necessarily completeness, ^¬ dig covered by the coating. Here, the Bede ^¬ ckung the coating as a surface, for example, be 10 to 99, 9%, relative to the surface of the substrate, preferably 50 to 95%, more preferably 70 to 90%. For example, the substrate is only covered in such a way that the growth of the Katalysa ^¬ tors carried dendritic.

It can crystalline micro- to nanoporous systems for the Cu ⁺ / Cu-containing catalyst and / or those with a particularly high surface area, for example, more than 100 m ² / g, preferably ^¬ equal to or more than 500 m ² / g, on preferably equal to or more than 1000 m ² / g are obtained, wherein an addition of substances such as brighteners is not excluded. The CuVCu-containing catalyst in this case may have pores in a size of 10 nm to 100 ym, preferably from 50 nm to 50 ym, more preferably from 100 nm to 10 ym. Also, the Cu catalyst Cu-containing ⁺ / can dendritic struc ^¬ ren with fine structure, for example the distance between two dendrites which have a size of 1 to 100 nm preferably from 2 to 20 nm, more preferably 3 to 10 nm. The Be ^¬ For example, layering is porous. The Cu ⁺ / Cu-containing catalyst may be at least 40 wt.% Crystalline, based on the catalyst, more preferably at least 70 wt.%, Particularly preferably at least 80 wt.%, Where the Cu ⁺ / Cu containing catalyst and / or the coating may be crystalline.

The substrate can be porous, for example in order to be able to produce gas diffusion electrodes. The substrate may have pores in a size of 10 nm to 100 ym, preferably from 50 nm to 50 ym, more preferably from 100 nm to 10 ym. Due to the porous design of the non-copper substrate, or Also, a copper substrate, such as a Gasdif ^¬ fusion electrode, a good transport of a gaseous alkyne for Cu ⁺ / Cu-containing catalyst can be ensured and the efficiency of the electrolysis can be further improved. In particular, it can be ensured by a suitable pore size ei ^¬ ne targeted guidance to certain sections of the catalyst.

The concentration of Cu ⁺ in the porous copper catalyst layer / the coating comprising the catalyst Cu ⁺ / Cu-containing, for example, greater than 1 mol%, preferably greater than 5 mole%, more preferably more than 10 mol%, particular ^¬ DERS preferably greater than 20 mole%, and for example up to 99.9 mole%, based on the coating.

In the copper-containing electrode, the substrate may be porous. The substrate may in this case have pores in a size of 10 nm to 100 μm, preferably from 50 nm to 50 μm, more preferably from 100 nm to 10 μm. This is for example the case for preferred embodiments in which the electrode is a gas diffusion electrode.

In the copper-containing electrode at ^¬ the substrate comprises playing at least one metal such as silver, platinum, nickel, lead, titanium, nickel, iron, manganese or chromium or their alloys such as stainless steels, and / or at least one non-metal such as carbon, Si, boron nitride (BN), boron-doped Di ^¬ amant, etc., and / or at least one conductive oxide, such as indium tin oxide (ITO), aluminum zinc oxide (AZO), or fluorinated tin oxide (FTO) - for example for the production of photo ^¬ electrode, and / or at least one polymer based on polyacetylene, polyethoxythiophene, polyaniline or polypyrrole, such as in polymer-based electrodes. Also, copper alloys or mixtures of said materials with copper as well as substrates of copper or copper oxide are possible. According to certain embodiments, the coating is at least partially crystalline. According to certain forms of execution ^¬ catalyst Cu ⁺ / Cu-containing by weight is at least 40.% Crystalline, based on the catalyst, more preferably at least 70 wt.%, Particularly preferably at least 80 min ^¬ wt.%. According to certain embodiments, the Cu ⁺ / Cu-containing catalyst and / or the coating is crystalline. According to certain embodiments, the coating of the copper-containing electrode is microporous to nanoporous and / or has a particularly high surface area of, for example, more than 500 m ² / g, preferably equal to or greater than 800 m ² / g, more preferably equal to or greater than 1000 m ² / g. According to certain embodiments, the coating is therefore porous. The Cu ⁺ / Cu-containing catalyst may have pores in a size of 10 nm to 100 μm, preferably from 50 nm to 50 μm, more preferably from 100 nm to 10 μm. Also, the catalyst Cu ⁺ / Cu-containing can dendritic structures with a fine structure, for example the distance between two Dend ^¬ rites, having a size of 1 to 100 nm, preferably 2 to 20 nm, more preferably 3 to 10 nm.

The concentration of Cu ⁺ layer in the porous copper catalyst is, for example, greater than 1 mol%, preferably RESIZE ^¬ SSER than 5 mol%, more preferably more than 10 mol%, particularly preferably greater than 20 mole%, and up to 99, 9 Mol%, based on the coating. The coverage of the coating as a surface in the kupferhalti- gen electrode may, for example, 10 to 99, amounted to 9%, ^¬ be attracted to the surface of the substrate, preferably 50 to 95%, more preferably 70 to 90%. According to certain embodiments, the substrate is covered such that the growth of the catalyst is dendritic.

Alternatively or additionally, when the copper-containing electrode is formed as the gas diffusion electrode (GDE), the following Suitable features, such as for the gas diffusion electrode described in 102015215309.6.

A gas diffusion electrode as a copper-containing electrode comprises, for example, a preferably copper-containing carrier, preferably in the form of a sheet, and a first

Layer comprising at least copper and at least one Bin ^¬ , wherein the (first) layer hydrophilic and hydrophobic Po ^¬ ren and / or channels comprises, further comprising a second layer comprising copper and at least one binder, wherein the second layer is on the support and the first layer on the second layer, wherein the content of binder in the first layer is smaller than in the second layer. As hydrophobic water repellent is understood here. Hydro ^¬ phobic pores and / or channels are thus those which reject water. In particular, hydrophobic properties are associated with substances or molecules with nonpolar groups. In contrast, the ability to

Interaction with water and other polar substances understood.

The second layer, like the first layer, may comprise hydrophilic and / or hydrophobic pores and / or channels.

Also described is a gas diffusion electrode, comprising a, preferably copper-containing, carrier, preferably in the form of a sheet, and

a first layer comprising at least copper and at least one binder, the layer comprising hydrophilic and hydrophobic ^polymers and / or channels.

The hydrophilic and hydrophobic regions of the GDE can achieve a good three-phase relationship liquid, solid, gaseous. It can be found for example in the electrode to electric ^¬ lytseite hydrophobic channels or areas and hydrophilic Kanae ^¬ le or areas, wherein in the hydrophilic regions Ka low activity catalysts. Furthermore, inactive catalyst sites are located on the gas side. Particularly active centers are in Dreipha ^¬ sengebiet liquid, solid, gaseous. An ideal GDE has so-on with a maximum penetration of the bulk material with hydro ^¬ hydrophilic and hydrophobic channels to get as many three-phase ^¬ areas for active centers. In this respect, it is preferable to ensure that the first layer comprises hydrophilic and hydrophobic pores and / or channels.

By suitable adjustment of the first layer can be achieved that as many active catalyst centers are present in the gas diffusion electrode.

The carrier is not particularly limited as above, insofar as it is suitable for a gas diffusion electrode and is preferably copper-containing. For example, parallel wires can form a carrier in extreme cases. For example, the carrier is a sheet, more preferably a mesh, most preferably a copper mesh. As a result, both a sufficient mechanical stability and functionality as a gas diffusion electrode, for example, with regard to a high electrical conductivity can be ensured. The use of copper in the carrier can provide suitable conductivity and reduce the risk of introducing unwanted foreign metals. According Favor ^¬ th embodiments, therefore, the carrier consists of copper. A preferred copper-containing carrier is, according to certain embodiments, a copper mesh with a mesh width w of 0.3 mm <w <2.0 mm, preferably 0.5 mm <w <1.4 mm and a wire diameter x of 0.05 mm <x <0.5 mm, Favor 0.1 mm ^ x ^ 0.25 mm.

In addition, by making the first layer comprises copper, and a high electrical conductivity of the catalyst so-like, in particular in conjunction with a copper grid, a homogeneous potential distribution across the entire surface Elektrodenflä ^¬ (potential-dependent product selectivity) can be ensured. According to certain embodiments, the binder comprises a polymer, for example a hydrophilic and / or hydrophobic polymer, for example a hydrophobic polymer, in particular PTFE. In this way, a suitable adjustment of the hydrophobic pores or channels can be achieved. In particular, to produce the first layer of PTFE particles with a

Particle diameter between 5 and 95 ym, preferably used between 8 and 70 ym. Suitable PTFE powders include, for example, Dyneon® TF 9205 and Dyneon TF 1750. Suitable binder particles, for example, PTFE particles may at ^¬ play, be approximately spherical, for example sphe ^¬ driven, and can be prepared for example by Emulsionspolymerisati ^¬ on. In certain embodiments, the binder particles are free of surfactants. The particle size can be determined, for example, according to ISO 13321 or D4894-98a and can correspond, for example, to the manufacturer's instructions (eg TF 9205: medium

Particle size 8ym according to ISO 13321; TF 1750: medium

Particle size 25ym according to ASTM D4894-98a).

In addition, the first layer comprises at least copper, which may be present for example in the form of metallic copper and / or copper oxide and which acts as a catalyst center. Here, the first layer preferably contains metal ^¬ metallic copper in the oxidation state 0th

Also, the first layer may, for example, copper oxide contained ^¬ th, in particular CU ₂ O. The oxide can in this case contribute to stabilize the oxidation states of +1 of the copper and thus to obtain the selectivity for ethylene long-term stability. ^Under electrolysis conditions, it can be reduced to copper. For example, the first layer comprises at least 40 at. %

(Atomic percent), preferably at least 50 at.%, More preferably at least 60 at.% Copper, based on the layer. In addition, the first layer may also hold other promoters ent ^¬ which improve in cooperation with the copper, the specific catalytic activity of the GDE. For example, the first layer contains at least one metal oxide, preferably ZrÜ ₂ , Al ₂ O ₃ , CeÜ ₂ , Ce ₂ ≦ 03, ZnÜ ₂ , MgO; and / or at least one copper ^¬ rich intermetallic phase, preferably at least a Cu-rich phase, which is selected from the group of binary systems Cu-Al, Cu-Zr, Cu-Y, Cu-Hf, Cucé, Cu-Mg and the ternary systems Cu-Y-Al, Cu-Hf-Al, Cu-Zr-Al, Cu-Al-Mg, Cu-Al-Ce with Cu contents> 60 at .-%; and / or copper-containing

Perovskites and / or defect perovskite and / or perovskite related compounds, preferably YBa ₂ Cu307-s, wherein Ο δ ^ ^ Ι (corresponding YBa2Cu307- ₆ X _a), CaCu3 i ₄ 0I2,

Lai, 85Sro, 15CUO3, 930CI0, 053, (La, Sr) ₂ Cu0 ₄ . Preferred promoters here are the metal oxides.

The metal oxide used is preferably water-insoluble, since ^{¬ can be used} with aqueous electrolytes in an electrolysis using Verwen ^¬ tion of the gas diffusion electrode according to the invention. Preferably, the metal oxides are not inert, but are intended to represent hydrophilic reaction centers that can serve for the provision of protons.

The promoters, in particular the metal oxide, can in this case promote the function and production of long-term stable electrocatalysts by stabilizing catalytically active Cu nanostructures. In this case, the structural promoters can reduce the high surface mobilities of the Cu nanostructures and thus their sintering tendency. The concept comes from the heterogeneous catalysis and is recognized ^¬ rich used within high temperature processes.

As promoters for the following electrochemical reduction of metal oxides can be used in particular, which can not be reduced to metals in the electrochemical window: Zr0 ₂ (E = -2,3V), A1 ₂ 0 ₃ (E = -2,4V), Ce0 ₂ (E = -2.3V), MgO (E = -2.5). It should be noted that the oxides mentioned are not added as additives, but part of the Catalyst itself are. The oxide met in addition to his radio ^¬ tion as a promoter also the feature copper in the oxidation state I to stabilize. Particularly preferred are for such gas diffusion electric ^¬ the metal oxide-copper catalyst structures which are produced as follows.

For the production of the metal oxides, according to certain embodiments, the precipitation can not be carried out in a pH-range between pH = 5.5-6.5 as described frequently, but in a range between 8.0-8.5, so that malachite does not precursor (Cu ₂ [(OH) ₂ I C0 ₃ ]), azurite (Cu ₃ (C0 ₃ ) 2 (OH) ₂ ) or

Aurichalzit (Zn, Cu) ₅ [(OH) ₆ 1 (C0 ₃ ) 2]) similar hydrate carbonates arise, but hydrotalcites

(CU6AI ₂ CO3 (OH) ₁ 6 .4 (H ₂ O)), which can be obtained in greater yield. Are also layered double (layered double hydroxides, LDHs) _X M ³⁺ _X (OH) _2] ^{q +} ^(Χ η q / n .yH ₂ 0 suitable, wherein M ¹⁺ = Li ^+, Na having a composition M ^{Z +!} _ ^+, K ^+, M ²⁺ = Ca ^2+, Mg ^2+, Cu ^2+, and M ³⁺ = ΑΙ, Υ, Τί, Hf, Ga. The entspre ^¬ sponding precursors may be prepared by co-dosage of a metal salt solution and a basic carbonate pH are precipitated controlled. A special feature of these materials is the presence of ultra-fine copper crystallites with egg ner size of 4-10 nm, which are stabilized struc ^¬ rell through the existing oxide.

After the precipitation, drying can be carried out with subsequent calcination in the 0 ₂ / Ar gas stream. The generated

Oxid precursors can also be connected directly in one

H2 / Ar gas flow can be reduced, whereby only the CU ₂ O or CuO is reduced to Cu and the oxide promoter is maintained. The activation step can also be done afterwards electrochemical ^¬ mixed. In order to improve the electrical conductivity of the applied layer prior to electrochemical activation, it is also possible to partially mix oxide precursors and activated precursors. In order to 0-10 wt.% Copper powder in similar particle size can be added to increase speed.

It is also not excluded that the finish is subjected ka- landrierte gas diffusion electrode of a subsequent Kalzi ^¬ discrimination / thermal treatment before the electro-chemical activation is performed.

Another possibility of producing suitable electrocatalysts is based on the approach of producing copper-rich intermetallic phases such as, for example, CusZr, CuioZr ₇ ,

Cu5iZri ₄ , which can be produced from the melt. ^Suitable ingots can subsequently be ground and completely or partially calcined in the O 2 / argon gas stream and converted into the oxide form. Of particular interest are the Cu-rich phases of the binary systems Cu-Al, Cu-Zr, Cu-Y, Cu-Hf, CuCe, Cu-Mg and the corresponding ternary systems with Cu contents> 60at%: CuYAl, CuHfAl, CuZrAl, CuAlMg, CuAICe. Copper-rich phases are, for example, E. Kneller, Y. Khan, U. Gorres, The Alloy System Copper zirconium, Part I. Phase Diagram and structural relations, Journal of Me ^¬ tallkunde 77 (1), pp 43-48, 1986 for Cu-Zr phases, from

Braunovic, M.; Konchits, V. V .; Myshkin, N.K .: Electrical contacts, fundamentals, applicationsand technology; CRC Press 2007 for Cu-Al Phases, from Petzoldt, F .; Bergmann, J.P .;

Schürer, R .; Schneider, 2013, 67 Metal, 504-507 (see, eg, Table 1) for Cu-Al phases, from Landolt-Börnstein - Group IV Physical Chemistry Volume 5d, 1994, pp 1-8 for Cu-Ga phases, and from PR Subramanian, D.E. Laughlin, Bulletin of Alloy Phase Diagrams, 1988, 9, 1, 51-56 discloses Cu-Hf phases.

TABLE 1 Copper-aluminum phases (taken from Petzoldt, F. Bergmann, J. P., Schürer, R. Schneider, 2013, 67 Metall, 504-507)

Phase Cu AI Hardness [HV] Spe. El. Wi¬

[Wt. %] [Wt. %] resistance [yQcm] Cu 100 0 100 1.75

20ι 80 20 1050 14.2

Cu ₉ Al ₄

Δ 78 22 180 13.4

Cu ₃ Al ₂

75 ₂ 75 25 624 12.2

Cu ₄ Al ₃

n ₂ CuAl 70 30 648 11.4

Θ CuAl ₂ 55 45 413 8.0

AI 0 100 60 2, 9

Also in these copper-rich intermetallic phases the content of copper is preferably greater than 40 at.%, Further be ^¬ vorzugt greater than 50 at.%, Particularly preferably greater than 60 At. %.

However, it is not excluded that the intermetallic ^¬ phases also contains non-metal elements such as oxygen, nitrogen, sulfur, selenium and / or phosphorus, so for example, oxides, sulfides, selenides, nirides and / or

Phosphides are included. For example, the intermetallic ^¬ intermetallic phases are partially oxidized.

Furthermore, the following copper-containing perovskite structures and / or defect perovskites and / or perovskite-related compounds can be used for electrocatalysts: YBa 2 Cu 3 O ₇ - ₆ , where Ο δ Ι, CaCu 3 Ti ₄ O 2,

Lai, 85Sro, i5, CUO3, 930CI0, 053, (La, Sr) ₂ Cu0 ₄ . Further, not be ^¬ is concluded that mixtures of these materials can be used for electrode preparation, or as needed subsequent calcination or activation steps Runaway ^¬ leads are.

For example, the catalyst particles comprising or consisting of copper, for example, copper particles used to prepare the GDE, have a uniformity

Particle size between 5 and 80 ym, preferably 10 to 50 ym, more preferably between 30 and 50 ym. Furthermore, the Catalyst particles preferably have a high purity without foreign ^¬ metal traces. By appropriate structuring, possibly with the aid of promoters, high selectivity and Langzeitsta ^¬ stability can be achieved.

Likewise, the promoters, for example the metal oxides, may have an appropriate particle size in the production.

To further adjust the porosity of the electrode, Cu powder aggregates having a particle diameter of 50 to

600 ym, preferably 100 to 450 ym, preferably 100-200 ym, supplied ^¬ give. The particle diameter of these additives is for example 1 / 3-1 / 10 of the total layer thickness of the layer. Instead of Cu, the addition may also be an inert material such as a metal oxide. As a result, an improved formation of pores or channels can be achieved.

According to certain embodiments, the first layer comprises less than 5 wt.%, More preferably less than 1 wt.%, And even more preferably no carbon- and / or carbon black-based, for example, conductive, filler with respect to the layer. In addition, the first layer according to ^certain embodiments does not contain any surface-active substances. In addition, according to certain embodiments, the first and / or second layer do not contain a sacrificial material, eg a sacrificial material with a release temperature of approximately below 275 ° C, eg below 300 ° C or below 350 ° C, in particular no pore former, which or more commonly wise in the production of electrodes using such a material at least partially in the electrode to ^¬ backward can.

Thus, only a (first) layer in the GDE is present, the content and proportion of binder, such as PTFE, may wt at ^¬ play 3-30.%, Preferably 3-20 wt.%, More before Trains t ^¬ 3-10 % By weight, even more preferably 3-7% by weight, based on the one (first) layer. The GDE described above further comprising a second layer of copper and at least one binder, wherein the two ^¬ th layer is located on the support and the first layer on the second layer, wherein the content of the binder in the first layer is smaller than in the second layer. Dane ^¬ Ben, the second layer coarser Cu or

Inertmaterialpartikel, for example, with

Particle diameters of 50 to 700 ym, preferably 100-450 ym include, in order to provide a suitable channel or pore structure ready ^¬ .

According to preferred embodiments, the second layer here comprises 3 to 30% by weight of binder, preferably 10 to 30% by weight of binder, more preferably 10 to 20% by weight of binder, preferably 10% by weight of binder, more preferably more than 10% by weight. and up to 20% by weight of binder, based on the second layer, and the first layer of 0-10% by weight of binder, eg 0.1 to 10% by weight of binder, preferably 1 to 10% by weight of binder, more preferably 1 to 7% by weight, even more preferably 3 to 7% by weight of binder, based on the first layer. The binder can be the same as in the first one

Be layer, such as PTFE. In addition, the Parti ^¬ kel, for the preparation of the second layer in accordance with certain embodiments of the first corresponding to those however also be different from this. The second layer is in this case a metal particle layer (metal particle layer, MPL), which un ^¬ terhalb the catalyst layer is (CL). By a Derar ^¬ term stratification highly hydrophobic regions in the MPL can be created and a catalyst layer with hydrophilic properties are generated selectively. Due to the highly hydrophobic nature of the MPL, undesired penetration of the electrolyte into the gas transport channels, ie flooding thereof, can also be prevented. According to certain embodiments, the second layer partially penetrates the first layer. This allows a good transition between the layers in terms of diffusion. In addition to the second layer, the GDE according to the invention may also have further layers, for example on the first layer and / or on the other side of the support.

To produce such a multilayered GDE, for example, a mixture for an MPL based on a highly conductive Cu mixture of dendritic Cu having particle sizes between 5-100 μm, preferably less than 50 μm and coarser Cu or inert material particles can be used

Particle sizes of 100-450 ym, preferably 100-200 ym, with ei ^¬ nem PTFE content of 3-30 wt.% Preferably 20 wt. ~ 6, in egg ner layer thickness of, for example, 0.5 mm on a Cu mesh with a mesh size of, for example, 1 mm (thickness, for example, 0.2-0, 6mm, eg 0.4 mm) are sieved and removed via a frame or squeegee. Corresponding dendritic copper may also be present in the first layer. Subsequently, a further Aufsieben the catalyst / PTFE mixture (CL), for example, with a PTFE content of 0.1-10 wt.%, And a smoothing or stripping, for example, over a 1 mm thick frame done, so that a total layer thickness (Hf) of 1 mm can be obtained. The thus pre-prepared layer may then one of calendar with a gap ^¬ width Ho = 0, 4-0, 7 mm, preferably from 0.5 to 0, 6mm, supplied to and off-rolled, so that a multi-layer gas diffusion electrode ^¬, as shown in Figure 3 is shown schematically, with a Cu network 8, an MPL 9 and a CL 10 can be obtained. By MPL better mechanical stability, ei ^¬ ne further reduction of the penetration of electrolyte and better conductivity, especially when using networks as carriers, can be achieved.

A stepwise production of the GDE by each sieving and rolling of each individual layer can lead to a lower adhesion between the layers and is therefore less preferred. The degree of fibrillation of the binder, for example PTFE, (structural parameter ζ) correlates directly with the applied shear rate, since the binder, for example a polymer, behaves as a shear-thinning (pseudoplastic) fluid upon swelling. After extrusion, the resulting layer has an elastic character due to the fibrillation. This structural change is irreversible, so that this effect can no longer be subsequently enhanced by further rolling, but the layer is damaged by the elastic behavior upon further action of shear forces. A particularly strong fibrillation can disadvantageously lead to a layer-side coiling of the electrode, so that too high contents of binder should be avoided.

For the gas diffusion electrode, it is advantageous to Besse ^¬ ren contacting nanoscale materials to coat the base layer, while maintaining a high porosity, a copper-PTFE as the second layer. The base layer can be characterized by a very high conductivity, for example 7 mOhm / cm or more, and preferably has a high porosity, for example of 50-70%, and a hydrophobic character. The binder content, for example PTFE, can be selected, for example, between 3-30% by weight, for example 10-30% by weight. The intermediate copper layer as the second layer can be catalytically active in the region of the overlap zone to the catalyst layer as the first layer itself, and serves in particular for better planar electrical connection of the electrocatalyst. Using this method, the required amount of catalyst can be reduced by a factor of 20-30.

Furthermore, the method of the two-layer structure offers the possibility of dispensing with binder materials as the first layer within the catalyst layer, as a result of which better electrical conductivity can be achieved. It can also handle very ductile or brittle powder Parti ^¬ kel. A subsequent activation of the electrochemical receive ^¬ NEN electrode may optionally be carried out, for example by chemical or electrochemical activation, and is not particularly limited. An electrochemical Aktvie ^¬ approximately procedure may lead to the conducting salt of the electrolyte cations (eg, KHC0 _3, K ₂ S0 ₄ NaHC0 _3, KBr, NaBr) to penetrate into the hydrophobic channels GDE and characterized hydrophilic regions are created.

The process according to the invention is suitable for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes,

wherein R and R ^{A are} selected from inorganic and / or organic radicals.

In this case, the inorganic and / or organic radicals are not particularly limited, and the inorganic radicals may also comprise organic substructures, for example in adducts or complexes. Organic radicals according to certain embodiments comprise 1 to 100 C atoms, for example 1 to 40 C atoms, preferably 1 to 20 C atoms, for example 1 to 10, 1 to 6, 1 to 4, 1 to 2 C atoms or else also only 1 C atom. Suitable inorganic radicals are all inorganic radicals. Derivatives of inorganic radicals and / or substituted organic radicals are also suitable. Than ^¬ organic and / or organic radicals are, for example, -H, -D, -OH, -OR *, -SH, -SR *, -NH _2, -NR * R *, -COOH, -COOR *, -CHO , - COR *, -PH _2, -PR * R *, -F, -Cl, -Br, -I, -NO, -N0 _2, and substi ^{¬-substituted} or unsubstituted alkyl, alkenyl, alkynyl and aryl groups conceivable, wherein R * and R * likewise be ^¬ undesirables organic, for example having 1 to 100 carbon atoms, for example 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms, for example 1 - 10, 1 to 6, 1 to 4, 1 to 2 carbon atoms or but also only 1 C atom, or inorganic side chains, such as - H, -D, -OH, -SH, -NH ₂ , -COOH, -CHO, -PH ₂ , -F, -Cl, -Br, -I , -

NO, - O _2, as well as substituted or unsubstituted alkyl, alkenyl, alkynyl and aryl groups. Thus, all alkynes are suitable as starting materials of the process. It ^¬ NEN, compounds of the chemical formula (I) having two or more carbon-carbon triple bonds are partially hydrogenated Kgs consequently. However, according to certain embodiments, the compound of the chemical formula (I) has only one C-C triple bond, namely that shown in the chemical formula (I).

As partial hydrogenation here is the hydrogenation of

Alkyne, ie triple bond, to alkene, so double bond to understand. Electrochemical finds the reaction THROUGH USE of electricity, for example, in an electrolysis cell ^¬ instead.

According to certain embodiments, the inorganic and / or organic radicals R and R ^{x are} selected from substituted or unsubstituted alkyl, alkenyl, alkynyl and / or aryl radicals, preferably alkyl and / or aryl radicals, preferably from 1 to 40 carbon atoms. Atoms, preferably 1 to 20 C atoms, eg 1 to 10, 1 to 6, 1 to 4, 1 to 2 C atoms or even only 1 C atom, -H, -D, -OH, -OR * , -SH, -SR *, -NH ₂ , _NR * R *, -COOH, -COOR *, -CHO, -COR *, -PH ₂ , -PR * R *, -F, -Cl, -Br, -I, - NO, and -NO ₂ , where R * and R * represent organic and / or inorganic radicals, which are preferably selected from -H, - D, -OH, -SH, -NH ₂ , -COOH, - CHO, -PH ₂ , -F, -Cl, -Br, -I, -NO, - NO ₂ , as well as substituted or unsubstituted alkyl, alkenyl, alkynyl and aryl groups, preferably alkyl and / or aryl groups, with 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms, for example 1-10, 1 to 6, 1 to 4, 1 to 2 carbon atoms or else only 1 C atom. Suitable substituents for the substituted or unsubstituted alkyl, alkenyl, alkynyl and aryl groups or radicals are, for example, -D, -OH, -SH, -NH ₂ , -COOH, -CHO, -PH ₂ , - F, - Cl, -Br, -I, -NO, -NO _{2 in} question. So it can be func- side-chains such as -CH ₂ -OH or fluorinated alkyl and / or aryl radicals such as -CF ₃ .

If R and R ^{x are} each -H or -D, then the compound of the chemical formula (I) is the special case of ethyne. If either R or R is not both, -H or -D, the alkyne is called a terminal alkyne. For internal alkynes, neither R nor R ^{x is} -H or -D. In the case of terminal alkenes, the amount of charge used is preferably precisely controlled, since overhydration, albeit with poor efficiency, is possible. According to certain embodiments, due to this necessary control, neither R nor R ^{x is} -H or -D, so internal alkynes are hydrogenated. It has been found that electron-deficient and thus activated alkynes are less suitable for the process, since the desired alkenes are more reactive towards the hydrogenation of ^electrolytes . Therefore, less good selectivities can be achieved with electron-poor alkenes. Accordingly, according to the invention, preference is given to alkynes which do not carry electron-withdrawing radicals, for example -COOH, -COOR *, -CF ₃ (where R * is as defined above). Thus, according to certain embodiments, the alkyne of the chemical formula (I) has no electron withdrawing groups. According to certain embodiments, the elec- Ronen-withdrawing groups are selected from -COOH, -COOR *, and fluo ^¬ tured alkyl and / or aryl groups, preferably perfluorinated alkyl and / or aryl radicals as -CF. ₃

With regard to the efficiency of the process, preference is likewise given to alkynes which do not carry any functional groups which, in turn, can be converted by electroreduction. However, a simultaneous electro-reduction of a reducible side chain or a reducible radical is possible. Examples of such chain alkynes with a reducible side or a reducible rest are alkynes which func tional ^¬ groups such as -CHO, -COR *, -NO, or -NO ₂ or their carry side chains containing these residues. The reduction of aldehydes (-CHO), ketones (-COR *) and nitro compounds (- NO ₂ ) could be confirmed experimentally. From aldehydes (-CHO) and ketones (-COR *) alcohols (-CH ₂ -OH) or (-CHR * -OH) and from nitro compounds (-NO ₂ ) amines (-NH ₂ ) he ^¬ hold .

Thus, according to certain embodiments, the alkyne of the chemical formula (I) has no further reducible functional groups other than the triple bond. Particular preference is in the novel process gas ^¬ shaped or water-soluble / water-miscible alkynes, wherein ^¬ play, gaseous alkynes, alkyne of the chemical ^¬ For mel (I). Examples of such suitable compounds are ethyne,

Propyne, 1-butyne or 2-butyne, propargyl alcohol (2-propyne-1-ol) and 2-butyne-1-ol.

A good synergy has resulted in particular when using gaseous alkynes of the chemical formula (I) with a copper-containing gas diffusion electrode. According to certain embodiments, therefore, the copper-containing electrode is formed as a gas diffusion electrode, wherein the alkyne of the ^chemical formula ^¬ (I) is present in gaseous form.

According to certain embodiments, the hydrogenation is carried out with a proton donor selected from water and alcohols having 1 to 20 C atoms, preferably water and alcohols having 1 to 12, eg 1 to 6 or 1 to 4 C atoms, more preferably Water. The water may in this case also be partially or completely deuterated, ie include as HDO or D ₂ O, or else tritium, for example in the production of radioactive markers. Although an electrolyte which can be used in the method of the present invention is not particularly limited, an aqueous electrolyte is thus advantageously used. In addition, any conductive salts and / or ionic liquid be used. Also, mixtures of water with inert organic solvents such as 1,4-dioxane can be used to improve substrate solubility.

In a further aspect, the present invention relates to the use of a copper-containing electrode for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes,

wherein R and R ^{A are} selected from inorganic and / or organic radicals.

The copper-containing electrode in this case corresponds to that which has been described in connection with the method according to the invention.

Furthermore, the present invention relates to a device for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes,

wherein R and R ^{A are} selected from inorganic and / or organic radicals, comprising an electrolytic cell (1) comprising a copper-containing Elekt ^¬ rode, which is adapted to reduce the alkyne of the chemical For ^¬ mel (I) to alkene;

a source of the alkyne of the chemical formula (I) (3), which is designed to provide the alkyne of the chemical formula (I) be ^¬ ; and a first feed means (2) for the alkyne of the chemical formula (I), which is adapted to supply the alkyne of chemi ^¬'s formula (I) from the source of the alkyne of chemical formula (I) of the electrolytic cell.

In this case, the electrolytic cell is not particularly limited insofar as it has the copper-containing electrode which may correspond to that in the method according to the invention. In particular, the inventive method can be carried out with the device according to the invention. In this case, the copper-containing electrode can act as a cathode. The further Be ^¬ constituents of the electrolytic cell as the anode, possibly the membrane, power source, etc. are not particularly limited, such as not their arrangement.

Examples of a possible cell arrangement are as follows.

A cathode compartment II can be designed such that a

Catholyte is supplied from below and then leaves the Ka ^¬ method space II upwards. Alternatively, the catholyte may be supplied from above but, as for example in case ^¬ film-electrodes. At the anode A, which is electrically connected to the cathode K by means of a current source for providing the voltage for the electrolysis, the oxidation of a substance takes place in an anode space I, which is supplied from below, for example with an anolyte the anolyte leaves with the product of the oxidation then the anode compartment. Anode space and cathode space can be separated by a membrane M. In such a 3-chamber structure as in other constructions, a reaction gas such as an alkyne of the chemical formula (I) may be replaced by a

Gas diffusion electrode can be promoted as a cathode in the cathode compartment II for reduction. Embodiments with a porous anode are also conceivable. Rooms I and II can be separated by a membrane M as described.

In contrast, in the PEM (proton or ion exchanger membrane) construction, a cathode K, for example a gas diffuser, is located. sion electrode, and an anode A directly to the membrane M, where ^{¬ is} separated by the anode compartment I from the cathode compartment II.

Mixed forms of these cell structures are conceivable, in which a structure may be provided with a Gasdif ^¬ fusion electrode provided for example catholyte which is not connected to the membrane, whereas the anode may be due to the membrane on anolyte. Of course, other hybrid forms or other embodiments of the exemplified electrode spaces are conceivable.

Also conceivable are embodiments without membrane. According to certain embodiments, the cathode side

Electrolyte and the anode-side electrolyte thus be identical, and the electrolysis cell / electrolysis unit can do without membrane. However, it is not excluded that the electrolysis cell in such embodiments has a membrane ^¬ ran, but this is ver ^¬ connected with additional effort in terms of the membrane as well as the applied voltage. Catholyte and anolyte can be mixed again optional and outside the electric ^¬ lysezelle.

If present, the membrane can also be multi-layered, so that separate feeds of anolyte or catholyte are made possible. Separation effects in aqueous electric ^¬ LYTEN achieved for example by the hydrophobicity of intermediate layers ^¬. Nevertheless, conductivity can be ensured if conductive groups are integrated in such separation layers. The membrane may be an ion-conducting membrane, or a separator, which causes only a mechanical separation and is permeable to cations and anions.

By using a gas diffusion electrode, it is mög ^¬ Lich to establish a three-phase electrode. For example, a gas can be guided from behind to the front side of the electrically active electrode to carry out an electrically ^¬ chemical reaction there. According to certain embodiments, the gas diffusion electrode may also only to be traversed, ie a gas such as the alkyne of the chemical formula (I) is passed past the rear side of the gas diffusion electrode in relation to the electrolyte, wherein the gas can then penetrate through the pores of the gas diffusion electrode and the product can be discharged behind. Preferably, the gas flow during the backflow is reversed to the flow of

Electrolytes, so that any squeezed liquid can be transported from ^¬ . By a sufficient porosity of the gas diffusion electrode so two modes of operation are possible: A cell variant made ^¬ light direct active flow through the GDE with a gas. The resulting products are made by the

Katholytausgang removed from the electrolysis cell and can be separated from the liquid electrolyte in a subsequent phase separator. The second cell variant describes a mode of operation in which the gas flows in the rear region of the GDE through an adapted gas pressure. The gas pressure should be chosen so that it is equal to the hydrostatic pressure of the electrolyte in the cell, so that no electrolyte is pushed through.

Further, in order to prevent passage of electrolyte through the gas diffusion electrode ^¬, a film can be deposited on the side remote from the electrolyte side of the gas diffusion electrode to prevent the electrolyte on conversion to gas. The film may in this case be suitably provided and is, for example, hydrophobic. In certain embodiments, the electrolytic cell on a diaphragm which separates the cathode chamber and the anode chamber of the electrolytic cell to prevent a mixing of the electric ^¬ LYTEN. The membrane is not particularly limited here, as long as it separates the cathode space and the anode space. In particular, it essentially prevents one

Conversion of the resulting at cathode and / or anode gases to the anode or cathode compartment. A preferred membrane is an ion exchange membrane, for example polymer based. Next Polymer membranes can also be used ceramic membranes.

Likewise, the material of the anode is not particularly limited and depends primarily on the desired reaction. Exemplary anode materials include platinum or platinum alloys, palladium or palladium alloys, and glassy carbon. Other anode materials are also conductive Oxi ^¬ de such as doped or undoped Ti0 _2, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), iridium oxide, etc. If necessary, these catalytic acti ^¬ ven compounds may be deposited on the surface even in thin-film technology, for example on a titanium carrier. Besides, the source of the alkyne of the chemical formula (I) and a first feeding means (2) of the alkyne of the chemical formula (I) are not particularly limited. The alkyne of the chemical formula (I) may be derived for example from a pre ^¬ storage container or other container as well as of a sepa- rate reactor, etc. as a source. As a first feeder, for example, pipes, hoses, etc. are used. In particular, the source of the alkyne of the chemical formula (I) and the first feed means (2) of the alkyne of the chemical formula (I) are adapted to the particular alkyne with respect to the materials used so that they are not affected by the alkyne of the chemical formula ( I) are attacked.

In addition, in the device according to the invention further feeding devices, e.g. be provided for electrolyte, discharge devices, pumps, heating and / or cooling devices, etc.

According to certain embodiments, the copper-containing electrode is designed as a gas diffusion electrode, wherein the first feed device (2) for the alkyne of the chemical formula (I) feeds the alkyne of the chemical formula (I) of the Gasdiffusi ^¬ onselektrode. The above embodiments, refinements and developments can, if appropriate, be combined with one another as desired. Further possible refinements, developments and implementations of the invention also include combinations of features of the invention which have not been explicitly mentioned above or described below with regard to the exemplary embodiments. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.

The invention will be illustrated below with reference to some exemplary embodiments, but not the latter

restrict.

Examples

The four following embodiments were performed in an H cell. A 2 cm ² solid Cu electrode was used, which was coated with high purity Cu from a CuSC ^ solution. A constant current of 30 mA was applied. As the electrolyte, KBr was USAGE ^¬ det 0. IM aqueous. In order to avoid influences from the anode, the ano ^¬ denraum was separated by a Nafion N 117 membrane.

Example 1: Reduction of ethyne:

After a 10 minute run-in period, purging the cell with argon, a stream of 7.7 ml / min of ethyne was passed through the cell. This resulted in a current efficiency of 60% for the reduction of ethyne to ethene. Overreduction to ethane occurred with a maximum current efficiency of 1.5%. The rest of the river led to emergence of what ^¬ serstoff. The total conversion of the gas stream was about 1.5%.

Example 2: Reduction of propargyl alcohol:

The cell was purged with argon throughout the experiment. After a 10 minute break-in period was Propargyl alcohol (32 μΐ, 0.55 mmol) the electrolyte ^{¬ added} . Based on this weight results in a

Equivalent charge of 3.7 F / mol (2 F / mol required). Despite the significant charge surplus, only traces of propanol appeared. Sales of propargyl alcohol to allyl alcohol executed ^¬ gen was complete. At the initial concentration of 0.1 M propargyl alcohol also no more hydrogen evolution occurred. The current efficiency for the conversion of propargyl alcohol to allyl alcohol is therefore well above 90% at high concentrations.

Example 3: Reduction of 1-butyn-1-ol: The cell was purged with argon throughout the experiment. After a 10 minute run-in phase, butyn-1-ol (32 μΐ, 0.43 mmol) was added to the electrolyte. The imple ^¬ Zung Butin-l-ol to crotyl alcohol was complete. The initial current efficiency is over 90%. Despite a used equivalent charge of 4.8 F / mol (2 F / mol required), no overreduction to n-butanol was observed.

Comparative Example 1 Reduction of Allyl Alcohol: The cell was purged with argon throughout the experiment. After a 10 minute run-in, allyl alcohol (32 μΐ, 0.47 mmol) was added. In contrast to the alkynes, neither high current yields nor high sales were observed. After an equivalent charge of 4.4 F / mol only a conversion of 34% could be determined.

Comparative Example 2 Reduction of Potassium Fumarate

The cell was purged with argon throughout the experiment. After a 10 minute break-in period were

Fumaric acid (58.7 mg, 0.51 mmol) and KOH (200 μM 5M, lmmol) were added. The conversion to potassium succinate after a Equivalence charge of 4.1 F / mol was complete. The initial current efficiency was over 90%.

Using a gas diffusion electrode, the results of an electrohydrogenation of ethyne on a solid Cu electrode and 15mA / cm ² at a current density of 170mA / cm ^{2 could} be readjusted.

The reactions resulting from the examples are thus as follows:

Ethin One Elten nbht

Crolyl-Alfc n-butanol

The good selectivity is shown here about through the ge ^¬ rings reactivity to the Elektrohydrierung with copper electrodes. Electronically deactivated internal alkenes such as crotyl alcohol were inert to Überredukti ^¬ on. In the experiments it has been shown that the erfindungsge ^¬ Permitted process exhibits a high selectivity and activity.

Acetylene, propargyl alcohol and 2-butyne-l-ol were evaluated as Substra ^¬ te. None of the 3 substrates is considered to be activated, which underlines the high activity of the catalytic process. Propargyl alcohol and 2-butyn-1-ol are known as to consider difficult substrates, since both carry electron-donating ^¬ substituents. In addition, 2-butyn-1-ol is an internal alkyne that is also sterically hindered. The alkyne hydrogenation described here can be used in addition to

high-volume compounds are also used for the electro-organic synthesis of specialty chemicals such as drugs or feed additives.

Claims

claims

1. A process for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes,

where R and R ^{A are} selected from inorganic and / or organic radicals,

2. The method of claim 1, wherein the inorganic and / or organic radical is selected from -H, -D, substituted ^¬ or unsubstituted alkyl, alkenyl, alkynyl and / or aryl radicals, -OH, -OR *, - SH, -SR *, -NH ₂ , -NR * R *, -COOH, -COOR *, -CHO, -COR *, -PH ₂ , -PR * R *, -F, -Cl, -Br, - I, -NO, and -NO2, where R * and R * represent organic and / or inorganic radicals.

3. The method of claim 1 or 2, wherein neither R nor R ^{A are} -H or -D.

4. The method according to any one of the preceding claims, wherein the alkyne of the chemical formula (I) has no electron-withdrawing radicals.

5. The method of claim 4, wherein the electron-withdrawing radicals are selected from -COOH, -COOR *, and fluorinated Al ^¬ kyl- and / or aryl radicals.

A process according to any one of the preceding claims wherein the alkyne of the chemical formula (I) has no further reducible functional groups other than the triple bond.

A process according to any one of the preceding claims, wherein the hydrogenation is carried out with a proton donor selected from water and alcohols having 1 to 20 carbon atoms.

8. The method according to any one of the preceding claims, wherein the copper-containing electrode is formed as a gas diffusion electrode ^¬ , wherein the alkyne of the chemical formula (I) is present in gas ^¬ form.

9. Use of a copper-containing electrode for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes,

wherein R and R ^{A are} selected from inorganic and / or organic radicals.

10. Apparatus for the partial electrochemical hydrogenation of alkynes of the chemical formula (I) to alkenes,

11. The device according to claim 10, wherein the copper-containing electrode is formed as a gas diffusion electrode, wherein the first supply means (2) for the alkyne of the chemical formula (I), the alkyne of the chemical formula (I) of the Gasdiffu- sionselektrode supplies.