REACTOR FOR ELECTROCHEMICAL SYNTHESIS

Abstract

A reactor (100) for electrochemical synthesis is proposed. The reactor (100) comprises a vessel (102) configured to receive a reaction mixture comprising an electrolytic medium and at least one reactant, at least a first electrode (108), and at least a second electrode (110). The first electrode (108) and the second electrode (110) are arranged within the vessel (102) and inter-penetrate one another without electrical contact. The first electrode (108) and/or the second electrode (110) are three dimensionally grid-shaped, the first electrode (108) and the second electrode (110) being arranged so as to allow and/or purposefully direct a flow of the reaction mixture therebetween. Further, a method for carrying out an electrochemical synthesis is pro-posed.

Claims

1.-13. (canceled)

14. A reactor for electrochemical synthesis, comprising a vessel configured to receive a reaction mixture comprising an electrolytic medium and at least one reactant, at least a first electrode, and at least a second electrode, the first electrode and the second electrode being arranged within the vessel and interpenetrating one another without electrical contact, wherein the first electrode and/or the second electrode are three dimensionally grid-shaped, the first electrode and the second electrode being arranged so as to allow and/or purposefully direct a flow of the reaction mixture therebetween.

15. The reactor according to claim 14, wherein the first electrode and the second electrode have an identical or different shape.

16. The reactor according to claim 14, wherein the first electrode and/or the second electrode are shaped in a regular or irregular pattern.

17. The reactor according to claim 14, wherein the first electrode and/or the second electrode are honeycomb-shaped.

18. The reactor according to claim 14, wherein the first electrode or the second electrode is comb-shaped.

19. The reactor according to claim 14, wherein the first electrode and the second electrode are made by an additive manufacturing method.

20. The reactor according to claim 14, wherein the first electrode and the second electrode are made at least partially of a material comprising metal, or wherein the first electrode and the second electrode are made at least partially of a material comprising plastics and/or polymer.

21. The reactor according to claim 14, wherein at least an outer surface layer of the first electrode and/or the second electrode comprises a material comprising at least one element selected from the group consisting of Pt, Pd, Ru, Ir, Ta, Ni, Ni-oxides, Au, Fe, Cr, Ag, Al, Ti, Mg, Mo, W, Cu, Sn, Zn, Cd, Pb, Pb-oxides, carbon allotropes, gas diffusion layers, any mixture and oxides thereof.

22. The reactor according to claim 14, wherein the vessel comprises a predetermined length, wherein the first electrode and the second electrode each comprise a length being in a range of 50% to 99% of the length of the vessel.

23. The reactor according to claim 14, wherein the vessel comprises a predetermined width, wherein the first electrode and the second electrode each comprise a width being in a range of 50% to 99% of the width of the vessel.

24. The reactor according to claim 14, wherein the vessel comprises at least one inlet for supplying the reaction mixture and at least one outlet for discharging the reaction mixture and/or its reaction products.

25. The reactor according to claim 14, further comprising a power source configured to apply a voltage or current to the first and second electrodes, wherein the first electrode and the second electrode each comprise at least one connection point connected to the power source.

26. Method for carrying out an electrochemical synthesis, comprising providing a reactor according to claim 14, supplying a reaction mixture comprising an electrolytic medium and at least one reactant to the vessel, and applying a predetermined voltage or current to the first electrode and second electrode.

Description

SHORT DESCRIPTION OF THE FIGURES

[0115] Further optional features and embodiments will be disclosed in more detail in the subsequent description of embodiments, preferably in conjunction with the dependent claims. Therein, the respective optional features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the preferred embodiments. The embodiments are schematically depicted in the Figures. Therein, identical reference numbers in these Figures refer to identical or functionally comparable elements.

[0116] In the Figures:

[0117] FIG. 1 shows a reactor according to the present invention, and

[0118] FIG. 2 shows an arrangement of the first and second electrodes.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0119] FIG. 1 shows a reactor 100 according to the present invention. The reactor 100 comprises a vessel 102 configured to receive a reaction mixture comprising an electrolytic medium and at least one reactant. The vessel 102 comprises a substantially cylindrical shape with a circular cross-section. For clarity reasons, a part of the cylindrical vessel wall defining the vessel interior is not illustrated. Particularly, the vessel 102 comprises at least one inlet 104 for supplying the reaction mixture and at least one outlet 106 for discharging the reaction mixture and/or its reaction products. The inlet 104 and the outlet 106 are located at opposite ends of the vessel 102 with respect to a cylinder axis of the cylindrical shape. Needless to say, the inlet 104 and the outlet 106 may be located at the same end of the vessel 102.

[0120] The reactor 100 further comprises at least a first electrode 108 and at least a second electrode 110. The first electrode 108 and the second electrode 110 are arranged within the vessel 102. The reactor 100 may further comprise at least one support 111 configured to fix the first electrode 108 and the second electrode 110 at their position within the vessel 102. The support 111 may be provided at one or both ends of the electrodes 108, 110 within the vessel 102. The support 111 may be made from a material being not electrically conductive and being electrically isolating, respectively, such as polytetrafluoroethylene. Further, the first electrode 108 and the second electrode 110 interpenetrate one another. The first electrode 108 and the second electrode 110 are electrically insulated from one another. The first electrode 108 and the second electrode 110 are arranged so as to allow a flow of the reaction mixture therebetween. More particularly, the first electrode 108 and the second electrode 110 are arranged so as to direct a flow of the reaction mixture through the vessel 102.

[0121] FIG. 2 shows an arrangement of the first and second electrodes 108, 110. The first electrode 108 and the second electrode 110 have an identical shape. The first electrode 108 and the second electrode 110 are shaped in a regular pattern. The first electrode 108 comprises a plurality of first electrode portions 112 being angled with respect to one another. The second electrode 110 comprises a plurality of second electrode portions 114 being angled with respect to one another. The electrode portions 112, 114 respectively extend within planes different from one another. The electrode portions 112, 114 are respectively regularly angled with respect to one another. The electrode portions 112, 114 are angled with respect to one another at an angle in a range of 45° to 150° such as 120°. Thus, the first electrode 108 and the second electrode 110 are substantially three dimensionally grid-shaped. Particularly, the first electrode 108 and the second electrode 110 are substantially honeycomb-shaped or comprise honeycomb-shaped portions.

[0122] The specific shape of the first electrode 108 and the second electrode 110 respectively as a netting may be realized in that the first electrode 108 and the second electrode 110 are made by an additive manufacturing method such as 3D-printing. Particularly, the first electrode 108 and the second electrode 110 are made at least partially of a material comprising metal. The material of the first electrode 108 and/or the second electrode 110 may comprise at least one metal selected from the group consisting of Pt, Ta, Ni, Au, Fe, Ag, Al, Ti, Cu, any mixture and oxides thereof. Thus, the material of the first electrode 108 and/or the second electrode 110 may be steel, particularly, stainless steel, an alloy, particularly a Ni based alloy, a NiCu alloy and Bronze. The alloy may comprise metal alloy additives such as Cr, Co, Mg, V, Nb, Mo, Ti. Particular alloys applicable with the present disclosure are TiAl6V4, NiCr19NbMo or NiCr19NbMo. In addition, or alternatively, the alloy may comprise non-metal alloy additives such as carbon.

[0123] Preferably, the first electrode 108 and/or the second electrode 110 is made of steel, tool steel, high-grade steel such as 1.4404 according to EN 10027-2:1992-09, a Ni based alloy such as NiCr19NbMo, Monel (=2.4360 Ni based alloy Ni based alloy), a NiCu alloy having approximately 65% Ni, 33% CU and 2% Fe, brass having Zn up to 40% Zink, bronze having more than 60% Cu but without Zn, a NiAl alloy.

[0124] Alternatively, the first electrode 108 and/or the second electrode 110 may be made at least partially of a material comprising plastics and/or polymer. Basically, all plastic or polymer materials are usable which are suitable to form a filament for an additive manufacturing method such as 3D printing and having electrically conductive characteristics. The electrically conductive characteristics can be realized by electrically conductive additives such as carbon or graphite. Further, all plastic materials can be used that can be provided with a coating having electrically conductive characteristics.

[0125] Preferably, the first electrode 108 and/or the second electrode 110 is made of at least one plastic material selected from the group consisting of PLA (Polylactic Acid), ABS (Acrylonitrile butadiene), and ABS as basis for a coating, particularly a coating made of Ni.

[0126] At least an outer surface layer 116, 118 of the first electrode 108 and/or the second electrode 110 comprises a material comprising at least one element selected from the group consisting of Pt, Pd, Ru, Ir, Ta, Ni, Ni-oxides (incl. NiOOH), Au, Fe, Cr, Ag, Al, Ti, Mg, Mo, W, Cu, Sn, Zn, Cd, Pb, Pb-oxides, carbon allotropes (doped diamond, boron-doped diamond, glassy carbon, graphite, carbon nanotubes), gas diffusion layers, any mixture such as an alloy and oxides thereof.

[0127] Preferably, the outer surface layer 116, 118 is made of Pt, Pd, Ru such as Ru composites, Ni, Ni-oxides (incl. NiOOH), Au, Ag, Al, carbon allotropes (doped diamond, boron-doped diamond, graphite, carbon nanotubes), Pb, Pb-oxides, Cr, Cu, Sn, Zn, Cd. With other words, an outer surface layer 116 of the first electrode 108 comprises a material comprising graphite and/or Nickel. In addition or alternatively, an outer surface layer 118 of the second electrode 110 comprises a material comprising graphite and/or Nickel. The outer surface layer 116, 118 is a coating.

[0128] Referring back to FIG. 1, the vessel 102 comprises a predetermined length 120. The first electrode 108 and the second electrode 110 each comprise a length 122, 124 being in a range of 50% to 99% of the length 120 of the vessel 102 such as 85%. With other words, the first electrode 108 comprises a length 124 being in a range of 50% to 99% of the length 120 of the vessel 102 and the second electrode 110 comprises a length 124 being in a range of 50% to 99% of the length 120 of the vessel 102. The vessel 102 comprises a predetermined width 126. The first electrode 108 and the second electrode 110 each comprise a width 128, 130 being in a range of 50% to 99% of the width 126 of the vessel 102 such as 85%. With other words, the first electrode 108 comprises a width 128 being in a range of 50% to 99% of the width 126 of the vessel 102 and the second electrode 110 comprises a width 130 being in a range of 50% to 99% of the width 126 of the vessel 102.

[0129] As is further shown in FIG. 1, the reactor 100 further comprises a pump 132 configured to provide a predetermined flow of the reaction mixture through the vessel 102. The reactor 100 further comprises a power source 134 configured to apply a voltage or current to the first and second electrodes 108, 110. For this purpose, the first electrode 108 and the second electrode 110 each comprise at least connection point 136, 138 connected to the power source 134. With other words, the first electrode 108 comprises a connection point 136 connected to the power source 134 and the second electrode comprises a connection point 138 connected to the power source 134. The first electrode 108 and the second electrode 110 are supplied with current or voltage such that the first electrode 108 operates as anode and the second electrode 110 operates as cathode.

[0130] The reactor 100 may be modified as follows. The first electrode 108 and the second electrode 110 may have a different shape. The first electrode 108 and/or the second electrode 110 may be shaped in an irregular pattern. The first electrode 108 or the second electrode 110 may be two dimensionally grid-shaped. The first electrode 108 or the second electrode 110 may be comb-shaped. The vessel 102 may have a cylindrical shape with an oval, elliptical polygonal or polygonal with rounded edges cross-section.

[0131] The operation and method for carrying out an electrochemical synthesis will be explained in further detail hereinafter. The reactor 100 as described above is provided. A reaction mixture comprising an electrolytic medium and at least one reactant is supplied to the vessel 102 via the inlet 104. A flow of the reaction mixture through the vessel 102 is provided by means of the pump 132. The reaction mixture may be circulated through the vessel 102. The flow may be continuous or in a pulsed manner. Further, a predetermined voltage or current is applied to the first electrode 108 and second electrode 110 by means of the power source 134. The voltage or current applied to the first electrode 108 and the second electrode 110 is adapted to the type of reactant and/or the type of intended electrochemical reaction. Thereby, the electrosynthesis of the reactant takes place when contacting the first and second electrodes 108, 110. The reaction mixture and/or its reaction products are discharged from the vessel 102 via the outlet 106 after a predetermined time, for example after a predetermined amount of reaction products are synthesized. Basically, the method may be carried out in a continuous or batch manner.

[0132] Hereinafter, a non-limiting more detailed example of an operation of the reactor for electrochemical synthesis is given.

Example 1

[0133] Starting position: [0134] The electrochemical oxidation of 5-(Hydroxymethyl)furfural (1) (HMF) to 2,5-furanedicarboxylic acid (2) can be achieved in an aqueous electrolyte at basic pH. [0135] The synthesis follows a published protocol and is best carried out on Ni-oxide-hydroxide (NiOOH) catalytic anodes. [0136] Due to the oxidation directly on the electrode surface, the overall active surface area of the catalytic anode plays a crucial role for achievable space-time-yields.

##STR00001## [0137] The reaction yield and stability of pre-formed catalytic NiOOH surfaces is best on high surface area nickel electrodes like Ni-foam or Ni-net. [0138] Construction of flow-through continuous electrochemical cells with significant production capacities, utilizing these porous materials would require multi-stacking of thin Ni-foam or Ni-net, since only low penetration depths of the electric field are possible for thick porous electrodes. These stacking procedures result in complex electric contacting requirements and physical stabilization efforts to eliminate short circuits.

[0139] Application of the reactor 100 according to the present invention:

[0140] Metal printing of 3D interpenetrating electrodes as described above can be used to overcome these limitations. [0141] Interpenetrating structures can be printed via Selective Laser Melting of stainless steel in a 3D printer. [0142] The structural motif comprises of one regularly shaped grid electrode, which is interpenetrated regularly by a second non-touching electrode of any shape. Used design motif is depicted in FIGS. 1 and 2. [0143] The stainless-steel grid is pretreated with aqueous HCl for surface cleaning and subsequently exposed to an electroless Ni plating solution to obtain a smooth uniform Ni surface. (as described in Nickel Plating on Steel by Chemical Reduction”, Abner Brenner and Grace E. Riddell published in Part of Journal of Research of the National Bureau of Standards, Research Paper RP 1725, Volume 37, July 1946) [0144] Direct utilization of the stainless-steel electrode is also possible but requires repetitive use under the following reaction conditions to show similar performance to Ni plated electrodes. [0145] The obtained Ni electrode is activated in the literature known procedure for NiOOH formation on Ni electrodes. [0146] The activated electrode can be directly used in flow through cell systems. [0147] 3D printing of the interpenetrated structure allows occupation of the full cell volume with electrocatalytic NiOOH. [0148] The regularly interpenetrated structure ensures a constant electric field and therefore constant catalytic activity throughout the entire cell volume.

[0149] General Experimental Procedure:

[0150] The 3D printed structures were subjected to electroless Ni plating. For this purpose the electrode was subjected to aqueous HCl (15% aq.) for 5 minutes and exposed to a electroless Ni plating solution according to the literature described in “Nickel Plating on Steel by Chemical Reduction, Abner Brenner and Grace E. Riddell” published in Part of Journal of Research of the National Bureau of Standards, Research Paper RP 1725, Volume 37, July 1946. The Ni plated electrode was activated to NiOOH surface by a standard procedure as disclosed in “Oxidation of alcohols by electrochemically regenerated nickel oxide hydroxide. Selective oxidation of hydroxysteroids” Johann Kaulen and Hans-J. Schäfer published in Tetrahedron Vol. 38 No. 22. pp. 3299 to 3308, 1982 to obtain a catalytically active surface.

[0151] Preparation of Main Electrolyte:

[0152] A buffer solution containing K.sub.2HPO.sub.4 (34.84 g, 0.2 mol) in 400 mL water was adjusted to pH 12 by addition of 30% aqueous KOH and finally diluted to a total volume of 500 mL.

[0153] Procedure for Electrochemical Conversion:

[0154] HMF (1.11 g, 8.8 mmol) was dissolved in 110 g of the main electrolyte buffer solution to give the final reaction mixture. The electrochemical cell, containing the 3D printed electrodes, was filled with this solution and a current of 400 mA was applied until 10-12 F passed the solution. The reaction was carried out at room temperature. The electrolyte was circulated with a speed of 1.2 L/min. After the electrolysis was finished, the resulting solution was cooled below 9° C. and acidified to pH 0.3 with aqueous HCl, keeping the temperature at 9° C. or below. Resulting precipitate was stirred for 10 minutes. The solid was filtered and washed with cold water (2 times, 15 mL). The solid was again suspended in 15 mL water, cooled below 9° C. and further acidified to pH 0 by aqueous HCl and stirred for 10 minutes to obtain high purity product. The resulting precipitate was again filtered and washed two times with 15 mL water. The solid was dried at 80° C. to obtain pure 2,5-furanedicarboxylic acid.

CITED LITERATURE

[0155] “Nickel Plating on Steel by Chemical Reduction”, Abner Brenner and Grace E. Riddel” published in Part of Journal of Research of the National Bureau of Standards, Research Paper RP 1725, Volume 37, July 1946 [0156] “Oxidation of alcohols by electrochemically regenerated nickel oxide hydroxide. Selective oxidation of hydroxysteroids” Johann Kaulen and Hans-J. Schäfer published in Tetrahedron Vol. No. 22. pp. 3299 to 3308, 1982

LIST OF REFERENCE NUMBERS

[0157] 100 reactor [0158] 102 vessel [0159] 104 inlet [0160] 106 outlet [0161] 108 first electrode [0162] 110 second electrode [0163] 111 support [0164] 112 first electrode portion [0165] 114 second electrode portion [0166] 116 outer surface layer [0167] 118 outer surface layer [0168] 120 length [0169] 122 length [0170] 124 length [0171] 126 width [0172] 128 width [0173] 130 width [0174] 132 pump [0175] 134 power source [0176] 136 connection point [0177] 138 connection point