Description:FIELD OF THE INVENTION
The present disclosure relates to a continuous electrochemical oxidizer for electrochemical conversion of aldehyde to acid.

BACKGROUND OF THE INVENTION
The background information herein below relates to the present disclosure but is not necessarily prior art.
Global warming, energy security and depleting fossil fuel reserves are key issues that directly or indirectly affect every nation of this world. To overcome or address these issues a strategic and sustainable step need to be taken by every decision-making body for better future. As a chemical engineer it is the duty to come out with novel and green approach for process industries to address the current ongoing issues. For this, the chemical engineers look for biomass.
The biomass is the key source to not only maintains the carbon cycle of the ecosystem but also to produce platform chemicals that are industrially important. There are various ways by which valorization of biomass can be done. Electrochemical process is one way by which biomass valorization can be done. Researchers have been working since years in the field of water splitting using application of electrical energy. In alkaline water splitting reaction, at cathode we get, high value industrial product, hydrogen that can be used as fuels but at anode side we get oxygen, which is not so of commercial value. Also the oxygen evolution reaction (OER) is kinetically sluggish causing much energy loss to produce products at anode and cathode.
Therefore, there is felt a need for a continuous electrochemical oxidizer for electrochemical conversion of aldehyde to acid which mitigates the drawbacks mentioned herein above or at least provides a useful alternative.

OBJECT OF THE INVENTION
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a continuous electrochemical oxidizer for electrochemical conversion of aldehyde to acid, which co-produce good amount of hydrogen.
Another object of the present disclosure is to provide a continuous electrochemical oxidizer for obtaining acid in good yield and better reactant conversion.
Yet another object of the present disclosure is to provide a continuous electrochemical oxidizer for obtaining acids with an environmental friendly method.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY OF THE INVENTION
The above drawbacks are overcome by replacing water splitting reaction in alkaline medium with biomass valorization reaction. In this furfural is used as a reactant for anodic reaction. Furfural is a versatile platform chemical derived from hydrolysis and dehydration of lignocellulosic biomass. Furfural undergoes electrochemical oxidation in alkaline medium using heterogeneous catalyst to produce 2-Furoic acid, which is a commercially important compound. 2-Furoic acid is commercially used as feedstock for organic synthesis and as intermediate to produce medicines, perfumes and esters. Furoic acid is also used to produce active pharmaceutical ingredients (API) like ceftiofur and prazosin. Based on research facts, the electrochemical conversion of furfural to 2-furoic acid is thermodynamically feasible and also kinetically fast compare to oxygen evolution reaction. Normally, in a continuous electrolyzer, the water splitting and oxygen evolution reaction takes place around 1.8 to 2.0 volt in alkaline medium. Based on these facts and information, a continuous electrochemical oxidizer is fabricated and performed the water splitting reaction to have hydrogen and oxygen evolution reaction at cathode and anode respectively. In the present invention, the applicant employed 3D modelling to fabricate continuous electrochemical oxidiser (CEO) that is inexpensive, effective, scalable, and user-friendly.
In an aspect, the present disclosure relates to a continuous electrochemical oxidizer for the electrochemical conversion of aldehyde to acid, wherein the continuous electrochemical oxidizer comprising:
a. an anode compartment comprising:
? an anode; and
? an anode solution comprising water, a first electrolyte, an aldehyde derived from lignocellulosic biomass,
b. a cathode compartment comprising:
? a cathode; and
? a cathode solution comprising water and a second electrolyte, and
c. an ion exchange membrane,
wherein the anode is pretreated nickel foam and the cathode is platinum sputtered nickel foam.
In another aspect, the present disclosure relates a process for obtaining an acid by electrochemical conversion of aldehyde derived from lignocellulosic biomass using a continuous electrochemical oxidizer as defined above.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The reactor of the present disclosure will now be described with the help of the accompanying drawings, in which:
Figure 1 illustrates a continuous electrochemical oxidizer assembly;
Figure 2 illustrates a schematic image of cylindrical structures engraved in a continuous electrochemical oxidizer;
Figure 3A illustrates a variation of furfural conversion and formation rate of 2-furoic acid with respect to different concentrations of furfural;
Figure 3B illustrates the yield and selectivity of 2-furoic acid at different concentrations of furfural;
Figure 4A illustrates the variation of furfural conversion and formation rate of 2-furoic acid with respect to different applied electric potential bias;
Figure 4B illustrates the yield and selectivity of 2-furoic acid at different applied electric potential bias;
Figure 5A illustrates the variation of furfural conversion and formation rate of 2-furoic acid with respect to different flow rates of electrolyte (1 M KOH); and
Figure 5B illustrates yield and selectivity of 2-furoic acid at different flow rates of electrolyte (1M KOH).
LIST OF REFERENCE NUMERALS USED IN DETAILED DESCRIPTION AND DRAWING
A Anode compartment
B Gasket
C Anode catalyst
D Ion exchange membrane
E Cathode catalyst
F Gasket
G Cathode compartment

1 Anode inlet
2 Anode outlet
3 Cathode inlet
4 Cathode outlet
5 Cylindrical patterns
6 Screw holes

DETAILED DESCRIPTION OF THE INVENTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open-ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
In an aspect, the present disclosure relates to a continuous electrochemical oxidizer for the electrochemical conversion of aldehyde to acid, wherein said continuous electrochemical oxidizer comprises:
a. an anode compartment comprising:
? an anode; and
? an anode solution comprising water, a first electrolyte, an aldehyde derived from lignocellulosic biomass,
b. a cathode compartment comprising:
? a cathode; and
? a cathode solution comprising water and a second electrolyte, and
c. an ion exchange membrane,
wherein said anode is pretreated nickel foam and said cathode is platinum sputtered nickel foam.
In an embodiment, the aldehyde is heterocyclic aldehyde.
In another embodiment, the aldehyde is selected from the group consisting of furfural and 5-hydroxymethylfurfural.
In an embodiment, the acid is selected from the group consisting of heterocyclic acid.
In another embodiment, the acid is selected from the group consisting of 2-furoic acid, 2,5-furandicarboxylic acid, maleic acid, and succinic acid.
In an embodiment, the first electrolyte and the second electrolyte each independently selected from a group consisting of potassium hydroxide, sodium hydroxide, sodium perchlorate, borate buffer, phosphate buffer, and mixtures of two or more thereof.
In a preferred embodiment, the first electrolyte and the second electrolyte is potassium hydroxide.
In an embodiment, the ion exchange membrane is perfluorosulfonic acid (PFSA) membranes based on a PFSA/polytetrafluoroethylene (PTFE) copolymer.
The pretreated nickel foam is obtained by treating nickel foam with acid followed by with alcohol.
In an embodiment, the acid is selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and sulphuric acid and wherein the alcohol is selected from the group consisting of isopropyl alcohol, and ethanol.
Typically, the design of the continuous electrochemical oxidizer is symmetric.
The continuous electrochemical oxidizer has an overall size of 35 mm x 35 mm x 4 mm and an area measuring 25 mm x 25 mm has cylindrical structures embedded in the design. The cylindrical structure has a diameter of 1.0 mm and a curved surface area of 3.14 mm2.
The lateral surface from which the inlet and outlet pipe are extruded outward has an area of 128.34 mm2.
The other lateral surfaces that are smooth and do not have inlet or outlet openings have the perimeter of 78 mm.
The inlet and outlet measured 4.0 mm in diameter to control the electrolyte flow through the designed electrochemical oxidizer.
The outer opening of the inlet and outlet has an external perimeter of 15.7 mm.
The channel at the inlet and outlet for electrolyte flow through the embedded bed has an annular area of 351.5 mm2 and flow diameter of 2.5 mm.
The embedded depth of the flow channel between four cylindrical structures has an area of 6.28 mm2 and a perimeter of 16.14 mm.
The size of the continuous electrochemical oxidizer can be increased 4 times from the dimensions provided above.
The schematic of the experimental setup is depicted in Figure 1 and Figure 2. The continuous electrochemical oxidizer is assembled using two gold plated metallic plates, a platinum sputtered nickel foam that serve as the cathode (E), and a nickel foam that serves as the anode (C). Two gaskets (B and F) measuring 35 mm x 35 mm, each having a cut-out of 25 mm x 25 mm in the center is used to help prevent leaking. For ion transport across the electrochemical oxidizer, an ion exchange membrane (D - Nafion 117) is used (35 mm x 35 mm). The ion exchange membrane was purchased from the Fuel Cell Store. The continuous electrochemical oxidizer is assembled by tightening with screws and bolts.
The continuous electrochemical oxidizer has an overall size of 35 mm x 35 mm x 4 mm (Figure 1), and an area measuring 25 mm x 25 mm has cylindrical structures (5) embedded in the design. Each cylindrical structure has a diameter of 1.0 mm and a curved surface area of 3.14 mm2. The design pattern of a continuous electrochemical oxidizer is symmetric. The lateral surface, from which the inlet and outlet pipe is extruded outward, has an area of 128.34 mm2 and other lateral surfaces that are smooth and do not have inlet or outlet openings have a perimeter of 78 mm. The inlet and outlet measured 4.0 mm in diameter to control the electrolyte flow through the designed electrochemical oxidizer. The outer opening of the inlet and outlet has an external perimeter of 15.7 mm. The channel at the inlet and outlet for electrolyte flow through the embedded bed has an annular area of 351.5 mm2 and flow diameter of 2.5 mm. As can be seen in Figure 2, the embedded depth of the flow channel between four cylindrical structures has an area of 6.28 mm2 and a perimeter of 16.14 mm. This dimension is constant for each embedded flow channel between four cylindrical structures.

In another aspect, the present disclosure relates to a process for obtaining an acid by electrochemical conversion of aldehyde derived from lignocellulosic biomass using a continuous electrochemical oxidizer as defined above.
In an embodiment, the aldehyde is furfural and the acid is 2-furoic acid.
The electrochemical reaction of furfural to 2-furoic acid at 1.85 V and 1 ml/min flow rate of said electrolyte results in 85.6% conversion of furfural and yields 72% of 2-furoic acid.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purposes only and not to be construed as limiting the scope of the disclosure. The following experiments can be scaled up to an industrial/commercial scale and the results obtained can be extrapolated to an industrial scale.
EXPERIMENTAL DETAILS
Experiment 1: Fabrication of continuous electrochemical oxidizer
The 3D model of the continuous electrochemical oxidizer was prepared using Creo parametric (8.0.3.0) software. The designs were then exported in the STL format to the Preform Software (version- 3.24.2), which is a powerful and flexible slicing software for Formlabs 3D printers. The appropriate orientation was determined with the help of the Preform software, and support structures were included in the design so that it could be successfully printed. After that, the designs were sent to the Formlabs Form for additive manufacturing. The prints were constructed one layer at a time by the Formlabs printer using a technique called low-force stereolithography. To print the devices, a transparent v4 resin was purchased and used. The 3D model of the continuous electrochemical oxidizer was printed at a speed of 100 microns per layer. According to the calculations, the area of the continuous electrochemical oxidizer that is electrochemically active is 6.25 cm2.
Catalyst Synthesis and Fabrication:
As an anode, porous nickel foam was used that was purchased from MTIKJ Group. To get rid of any form of organic impurities or surface oxides, nickel Foam was first treated with 1 M HCl, and then it was treated with isopropyl alcohol. The nickel foam was chopped into squares of 25 mm X 25 mm. Platinum was sputtered onto nickel foam to make the cathode by using DC sputtering. The base pressure was 1 x 10-6 mbar and the chamber pressure was set at 1 x 10-3 mbar. To improve the adherence of platinum, a sacrificial layer of titanium with a thickness of 20 nm was sputtered followed by 50 nm of platinum. The process was repeated on both sides of the nickel foam.
Assembly of continuous electrochemical oxidizer
The continuous electrochemical oxidizer was assembled using two gold-plated metallic plates, a platinum sputtered nickel foam that served as the cathode, and a nickel foam that served as the anode. Two gaskets measuring 35 mm x 35 mm, each having a cut-out of 25 mm x 25 mm in the center were used to help prevent leaking. For ion transport across the electrochemical oxidizer, an ion exchange membrane (Nafion 117) was used (35 mm x 35 mm). The continuous electrochemical oxidizer was assembled by tightening with screws and bolts.
The connection between the electrodes and the Potentiostat was accomplished by using titanium wires. When taking the readings for the experiment, Bio-Logic SAS, SP-150 Potentiostat was used. The catholyte used was 1 M KOH and anolyte was of varying concentration of furfural in 1 M KOH. Both furfural and potassium hydroxide pellets were purchased from Sigma Aldrich. Peristaltic pumps (miclins; PP 30 EX) were used to pump the electrolyte through the device at different flow rates.
For product identification (2-furoic acid), HPLC (Agilent Technologies, 1260 infinity) equipped with C18 Column (Zorbax 300 SB-C18; 4.6 mm x 150 mm x 3.5 µm) and diode-array detector was used. A 10% (v/v) acetonitrile and water containing 20 mM phosphoric acid was used as mobile phase at flow rate of 1 ml/min and 215 nm wavelength was used in HPLC detector.
Results:
Figure 3(A) and 3(B) study the conversion of furfural to 2-furoic acid and the rate of formation, yield, and selectivity of 2-furoic acid, respectively at the constant potential bias of 1.85 V and 1 ml/min of electrolyte flow rate. From the figures, it is evident that as the concentration of furfural increases from 5 mM to 50 mM, the percentage conversion of furfural increases from 62.3% to 85.6%. The rate of formation of 2-furoic acid increases from 27.8 µmol/h cm2 to 307 µmol/h cm2. The yield and selectivity do not increase linearly as the concentration of furfural is increased. When the concentration of furfural is increased from 5 mM to 25 mM, the yield of 2-furoic acid is up to 72%. At 5 mM concentration of furfural, selectivity of 2-furoic acid is around 93% but when concentration of furfural is increased to 50 mM, selectivity is reduced to 74.5%. At high concentrations of furfural (from 26 mM to 50 mM), there is a decreasing trend in yield and selectivity of 2-furoic acid. This decreasing trend in yield and selectivity of 2-Furoic acid is due to the concentration diffusion resistance of furfural on the catalyst surface.
Figures 4(A) and 4(B) show the performance of continuous electrochemical oxidizer in terms of conversion of reactant and formation of desired product. As applied electric potential bias increases from 1.45 V to 1.95 V, the conversion of furfural increases from 44.7% to 86% and the rate of formation of 2-furoic acid increases from 34.8 µmol/h cm2 to 309.4 µmol/h cm2. Thus, it is clearly evident that as applied electric potential bias is increased, the yield and selectivity of 2-furoic acid is also increased. Maximum yield found is 64.4% at 1.95 V and as high as 75% selectivity is achieved at 50 mM concentration of furfural and 1.95 V.
Figures 5(A) and 5(B) show the performance of continuous electrochemical oxidizer in terms of conversion of reactant and formation of desired product. As flow rate of electrolyte (1 M KOH) increases from 0.5 ml/min to 4.0 ml/min, the conversion of furfural decreases from 95.7% to 58% and rate of formation of 2-furoic acid increases from 124.3 µmol/h cm2 to 618 µmol/h cm2 at 1.85 V. Thus, it is evident that as flow rate of electrolyte (1 M KOH) is increased, the yield and selectivity of 2-furoic acid is also increased up to flow rate of 1 ml/min. But as the flow rate is further increased from 1 ml/min to 4 ml/min the yield and selectivity of 2-furoic acid is lowered. This fall in yield and selectivity of 2-furoic acid is due to less residence time available for intermediates formed during the reaction to get converted into 2-furoic acid. The maximum yield found is 63.7% and as high as 75% selectivity of 2-furoic acid is achieved at 50 mM furfural, 1.85 V and 1 ml/min flow rate of electrolyte.

TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a continuous electrochemical oxidizer for electrochemical conversion of aldehyde to acid, which:
? results in the economical production of good amounts of hydrogen.
? results in the simultaneous production of clean hydrogen from the aldehyde electrolysis, that can be utilized as fuel for electrical vehicles operated on fuel cells.
? produces acid in good yield and better reactant conversion
? produces acid with an environmentally friendly method.
? is energy efficient.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. , Claims:WE CLAIM:
1. A continuous electrochemical oxidizer for electrochemical conversion of aldehyde to acid, wherein said continuous electrochemical oxidizer comprises:
a. an anode compartment comprising:
? an anode; and
? an anode solution comprising water, a first electrolyte, an aldehyde derived from lignocellulosic biomass,
b. a cathode compartment comprising:
? a cathode; and
? a cathode solution comprising water and a second electrolyte, and
c. an ion exchange membrane,
wherein said anode is pretreated nickel foam and said cathode is platinum sputtered nickel foam.
2. The continuous electrochemical oxidizer as claimed in claim 1, wherein said aldehyde is heterocyclic aldehyde.
3. The continuous electrochemical oxidizer as claimed in claims 1 and 2, wherein said aldehyde is selected from the group consisting of furfural and 5-hydroxymethylfurfural.
4. The continuous electrochemical oxidizer as claimed in claim 1, wherein said acid is heterocyclic acid.
5. The continuous electrochemical oxidizer as claimed in claims 1 and 4, wherein said acid is selected from the group consisting of 2-furoic acid, 2,5-furandicarboxylic acid, maleic acid, and succinic acid.
6. The continuous electrochemical oxidizer as claimed in claim 1, wherein the design of said continuous electrochemical oxidizer is symmetric.
7. The continuous electrochemical oxidizer as claimed in claim 1, wherein said continuous electrochemical oxidizer has an overall size of 35 mm x 35 mm x 4 mm and an area measuring 25 mm x 25 mm has cylindrical structures embedded in the design.
8. The continuous electrochemical oxidizer as claimed in claim 12, wherein said cylindrical structure has a diameter of 1.0 mm and curved surface area of 3.14 mm2.
9. The continuous electrochemical oxidizer as claimed in claim 1, wherein said lateral surface from which the inlet and outlet pipe are extruded outward has an area of 128.34 mm2.
10. The continuous electrochemical oxidizer as claimed in claim 1, wherein the other lateral surfaces that are smooth and do not have inlet or outlet openings have a perimeter of 78 mm.