Electrochemical process and apparatus for producing hydrogen

Abstract

An electrochemical process and apparatus for producing hydrogen and a dehydrogenated product from partial oxidation of an alcohol. The hydrogen may be utilised in a hydrogen fuel cell to generated electricity, e.g., to power a vehicle.

Description

ELECTROCHEMICAL PROCESS AND APPARATUS FOR PRODUCING HYDROGENTECHNICAL FIELD

[0001] The present invention relates to an electrochemical process and apparatus for producing hydrogen and a dehydrogenated product from partial oxidation of an alcohol. The hydrogen may be utilised in a hydrogen fuel cell to generated electricity, e.g., to power a vehicle.BACKGROUND ART

[0002] Increasing awareness about the environment effects of fossil fuels and resulting societal shift away from use of fossil fuels has driven the search for alternative clean fuel sources. A valuable alternative fuel is hydrogen. Hydrogen may be utilised in a fuel cell to generate clean energy by reacting hydrogen and oxygen in which the only by-product is water. However, hydrogen has disadvantages that have limited its widespread use. Hydrogen is a highly flammable gas that, due to its small atomic size, may permeate or leak through storage containers. Consequently, storage of hydrogen can be costly and dangerous. Further, generation of hydrogen can be energy intensive and produces pollution in itself, which reduces the viability of hydrogen as a clean energy source.

[0003] One solution that has been adopted is the use of liquid organic hydrogen carriers (LOHCs), such as toluene / methylcyclohexane. LOHCs may provide a stable source of hydrogen that is safe for storage and may generate hydrogen on demand by reaction with a catalyst. However, LOHCs are specialised chemicals that must be synthesised, potentially through wasteful processes. Further, when consumed in the generation of hydrogen, LOHCs create a by-product that must be regenerated or disposed of potentially leading to large volumes of by-product that must be transported and stored / disposed of.

[0004] Another alternative fuel source is direct alcohol fuel cells. A direct alcohol fuel cell utilises an alcohol, e.g. methanol or ethanol, in an electrochemical cell containing an anode and cathode to generate electricity. The alcohol and water react at the anode to produce carbon dioxide and electrons and protons. The protons are transported to the cathode where the protons react with oxygen to produce water. An advantage of thedirect alcohol fuel cells is that it uses alcohols that are low-cost and readily available as commodity chemicals, and the only liquid by-product is water. Direct alcohol fuel cells do, however, generate carbon dioxide. Additionally, direct alcohol fuel cells can suffer from a short life span due to the susceptibility of the cathode to, e.g., catalyst poisoning by the alcohol permeating from the anode to the cathode.

[0005] Accordingly, it is an object of the present invention to go some way to avoiding the above disadvantages; and / or to at least provide the public with a useful choice.

[0006] Other objects of the invention may become apparent from the following description which is given by way of example only.

[0007] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date.SUMMARY OF THE INVENTION

[0008] In a first aspect, the invention provides a process for preparing hydrogen from an alcohol, the process comprising:(a) providing an electrolyser comprising an electrochemical cell comprising: i. an anode comprising a partial oxidation catalyst, ii. a cathode comprising a reduction catalyst, and iii. a separator between the anode and the cathode;(b) contacting the anode with a mixture of the alcohol and water;(c) applying a voltage to the electrochemical cell such that the alcohol is partially oxidized at the anode to produce a product stream comprising a hydrogen precursor and a co-product stream comprising adehydrogenated product, and the product stream comprising the hydrogen precursor passes through the separator wherein the hydrogen precursor is converted to hydrogen at the cathode.

[0009] In a second aspect, the invention provides an apparatus for generating hydrogen from an alcohol, the apparatus comprising: a) an electrolyser comprising an electrochemical cell comprising a vessel divided by a separator into a first volume and a second volume, wherein: i. the first volume houses an anode comprising a partial oxidation catalyst capable of partially oxidizing a mixture of the alcohol and water to produce a product stream comprising a hydrogen precursor and co-product stream comprising a dehydrogenated product, and ii. the second volume houses a cathode comprising a reduction catalyst capable of converting the hydrogen precursor in the product stream to hydrogen;(a) an energy source for applying a voltage to the electrochemical cell.

[0010] In another aspect, the invention provides a process for generating electricity, the process comprising:(a) providing an electrolyser comprising an electrochemical cell comprising: i. an anode comprising a partial oxidation catalyst, ii. a cathode comprising a reduction catalyst, and iii. a separator between the anode and the cathode;(b) contacting the anode with a mixture of an alcohol and water;(c) applying a voltage to the electrochemical cell such that the alcohol is partially oxidized at the anode to produce a product stream comprising ahydrogen precursor and a co-product stream comprising a dehydrogenated product, and the product stream comprising the hydrogen precursor passes through the separator wherein the hydrogen precursor is converted to hydrogen at the cathode, wherein the voltage applied to the electrochemical cell is less than 1.2 V;(d) conveying the product stream comprising hydrogen to a fuel cell wherein the fuel cell converts the hydrogen to electricity and water.

[0011] In another aspect, the invention provides an apparatus for generating electricity, the apparatus comprising: a) an electrolyser comprising an electrochemical cell comprising a vessel divided by a separator into a first volume and a second volume, wherein: i. the first volume houses an anode comprising a partial oxidation catalyst capable of partially oxidizing a mixture of an alcohol and water to produce a product stream comprising a hydrogen precursor and a coproduct stream comprising a dehydrogenated product, and ii. the second volume houses a cathode comprising a reduction catalyst capable of converting the hydrogen precursor to hydrogen; b) an energy source for applying a voltage to the electrochemical cell, wherein the voltage to be applied to the electrochemical cell is less than about 1.2 V; wherein, in use, the product stream comprising the hydrogen from the second volume is conveyed to the fuel cell to produce electricity.

[0012] In another aspect, the invention provides a vehicle, the vehicle comprising: a) an electrolyser comprising an electrochemical cell comprising a vessel divided by a separator into a first volume and a second volume, wherein:i. the first volume houses an anode comprising a partial oxidation catalyst capable of partially oxidizing a mixture of an alcohol and water to produce a product stream comprising a hydrogen precursor and a coproduct stream comprising a dehydrogenated product, and ii. the second volume houses a cathode comprising a reduction catalyst capable of converting the hydrogen precursor to hydrogen; b) an energy source for applying a voltage to the electrochemical cell, wherein the voltage to be applied to the electrochemical cell is less than about 1.2 V; c) a fuel cell in fluid connection with the second volume; and d) a motor connected to the fuel cell; wherein, in use, the product stream comprising hydrogen from the second volume is conveyed to the fuel cell to produce electricity that is transmitted to the motor to drive the vehicle.

[0013] In another aspect, the invention provides a vehicle, the vehicle comprising: a) an electrolyser comprising an electrochemical cell comprising a vessel divided by a separator into a first volume and a second volume, wherein: i. the first volume houses an anode comprising a partial oxidation catalyst capable of partially oxidizing a mixture of an alcohol and water to produce a product stream comprising a hydrogen precursor and a coproduct stream comprising a dehydrogenated product, and ii. the second volume houses a cathode comprising a reduction catalyst capable of converting the hydrogen precursor to hydrogen;(b) an energy source for applying a voltage to the electrochemical cell, wherein the voltage to be applied to the electrochemical cell is less than about 1.2V; and(c) a combustion engine in fluid connection with the second volume; wherein, in use, the product stream comprising hydrogen from the second volume is conveyed to the combustion engine to drive the vehicle.

[0014] In another aspect, the invention provides a mobile apparatus for generating hydrogen from ethanol, the apparatus comprising: a) an electrolyser comprising an electrochemical cell comprising a vessel divided by a separator into a first volume and a second volume, wherein: i. the first volume houses an anode comprising a partial oxidation catalyst capable of partially oxidizing a mixture of the ethanol and water to produce a product stream comprising a hydrogen precursor and a coproduct stream comprising acetic acid, and ii. the second volume houses a cathode comprising a reduction catalyst capable of converting the hydrogen precursor to hydrogen; b) an energy source for applying a voltage to the electrochemical cell.

[0015] The following embodiments refer to any one or more of the above aspects.

[0016] The following embodiments and preferences may relate alone or in any combination of any two or more to any of the above aspects.

[0017] In some embodiments, the process further comprises the step of conveying the product stream comprising hydrogen to a fuel cell, wherein the fuel cell converts the hydrogen to electricity and water. In some embodiments, the electricity produced by the fuel cell is transmitted to a battery. In some embodiments, the electricity stored in the battery is used to drive the vehicle. In some embodiments, a combination of the electricity stored in the battery and the electricity directly from the fuel cell.

[0018] In some embodiments, a portion of the electricity produced in the fuel cell is used to apply a voltage to the electrochemical cell.

[0019] In some embodiments, the process is stationary. In some embodiments, the process is mobile.

[0020] In some embodiments, the process is carried out on a vehicle. In some embodiments, the vehicle is a land vehicle (e.g. a car, a truck or a train), a ship or an aircraft . In some embodiments, the vehicle a zero-emission vehicle.

[0021] In some embodiments, the electricity produced in the fuel cell is used to drive a motor of a vehicle.

[0022] In some embodiments, the process further comprises the step of conveying the product stream comprising hydrogen to a combustion engine to drive a vehicle.

[0023] In some embodiments, the co-product stream comprising the dehydrogenated product produced by the partial oxidation of an alcohol is used as a feedstock for a chemical process.

[0024] In some embodiments, the hydrogen precursor comprises protons. In some embodiments, the hydrogen precursor comprises water.

[0025] In some embodiments, the product stream comprising hydrogen is collected and then stored or distributed into a reticulation network.

[0026] In some embodiments, the co-product stream comprising the dehydrogenated product is removed from the electrolyser.

[0027] In some embodiments, the electrolyser is recharged by removing the dehydrogenated product from the electrolyser and charging the electrolyser with an alcohol.

[0028] In some embodiments, the voltage applied to the electrochemical cell is a low voltage. In some embodiments, the voltage applied to the electrochemical cell is from above 0 to about 1.5V. In some embodiments, the voltage applied at to the electrochemical cell is from above 0 to about 1.2V, optionally about 0.01 to 0.5 V, optionally about 0.05 to 0.2 V. In some embodiments, the voltage applied to theelectrochemical cell is less than about 1.0V. In some embodiments, the voltage applied to the electrochemical cell is less than about 0.8V.

[0029] In some embodiments, at least 95% of the alcohol consumed at the anode is converted to the dehydrogenated product. In some embodiments, at least 98% of the alcohol at the anode is converted to the dehydrogenated product.

[0030] In some embodiments, the process further comprises a step of separating the dehydrogenated product from the alcohol.

[0031] In some embodiments, the process further comprises a step of reducing the dehydrogenated product to regenerate the alcohol.

[0032] In some embodiments, the apparatus further comprises a fuel cell in fluid connection with the second volume, wherein the fuel cell is capable of converting the hydrogen to electricity and water. In some embodiments, the apparatus or vehicle comprises a battery connected to the fuel cell, wherein the battery is for storing electricity produced by the fuel cell.

[0033] In some embodiments, the apparatus is stationary. In some embodiments, the apparatus is mobile. In some embodiments, the apparatus is on a vehicle. In some embodiments, the vehicle is a land vehicle (e.g. a car, a truck or a train), a ship or an aircraft. In some embodiments, the vehicle is a zero-emission vehicle.

[0034] In some embodiments, the power generated by the fuel cell is used to drive the motor of a vehicle.

[0035] In some embodiments, the fuel cell is the energy source.

[0036] In some embodiments, the apparatus comprises a combustion engine in fluid connection with the second volume such that the product stream comprising hydrogen from the second volume may be conveyed to the combustion engine to drive the motor of a vehicle.

[0037] In some embodiments, the apparatus comprises a buffer tank between the second volume of the electrochemical cell and the fuel cell.

[0038] In some embodiments, the alcohol is a saturated alcohol. In some embodiments, the alcohol is a Ci-salcohol. In some embodiments, the alcohol is a Cisalcohol. In some embodiments, the alcohol is a Ci-salcohol. In some embodiments, the alcohol is methanol, ethanol, n-propanol, isopropanol, methylene glycol, ethylene glycol, propylene glycol, glycerol or a combination of any two or more thereof. In some embodiments, the alcohol is ethanol. In some embodiments, the alcohol is bioethanol.

[0039] In some embodiments, the alcohol is at least partially in vapour form. In some embodiments, the alcohol is substantially in vapour form.

[0040] In some embodiments, the electrochemical cell is operated at a temperature in a temperature range of about 0 to 250°C. In some embodiments, the electrochemical cell is operated at a temperature in a temperature range of about 0 to 150°C. In some embodiments, the electrochemical cell is operated at a temperature in a temperature range of about 50 to 250°C, 50 to 200°C, 50 to 150°C, 50 to 100°C, 80 to 250°C, 80 to 200°C, 80 to 150°C, 80 to 100°C, 100 to 250°C, 100 to 200°C, 100 to 150°C, 150 to 250°C or 150 to 200°C. In some embodiments, the electrochemical cell is operated at a temperature of about 55 to 110°C. In some embodiments, the electrochemical cell is operated at a temperature of about 150 to 200°C. In some embodiments, the electrochemical cell is operated at a temperature above about 50°C. In some embodiments, the electrochemical cell is operated at a temperature above about 60°C, 70°C, 80°C, 90°C or 100°C. In some embodiments, the electrochemical cell is operated at a temperature above about 150°C.

[0041] In some embodiments, the dehydrogenated product is a carboxylic acid, an aldehyde or a combination thereof. In some embodiments, the dehydrogenated product is a carboxylic acid. In some embodiments, the dehydrogenated product is acetic acid. In some embodiments, the dehydrogenated product is acetic acid, acetaldehyde or combination thereof.

[0042] In some embodiments, the co-product stream comprises at least about 80% of the dehydrogenated product. In some embodiments, the co-product stream comprises at least about 85%, 90, 95%, 98% or 99% of the dehydrogenated product. In some embodiments, the co-product stream comprises at least about 98% of the dehydrogenated product. In some embodiments, the co-product stream comprises at least about 99% of the dehydrogenated product. In some embodiments, the co-product stream comprises at least about 95% of a carboxylic acid, an aldehyde or a combination thereof. In some embodiments, the co-product stream comprises at least about 98% of a carboxylic acid, an aldehyde or a combination thereof. In some embodiments, the coproduct stream comprises at least about 99% of a carboxylic acid, an aldehyde or a combination thereof. In some embodiments, the co-product stream comprises at least about 95%, 98% or 99% of the carboxylic acid.

[0043] In some embodiments, the alcohol is a C1-3 alcohol and the co-product stream comprises at least about 80% of a C1-3 carboxylic acid, a C1-3 aldehyde or a combination thereof. In some embodiments, the alcohol is a C1-3 alcohol and the co-product stream comprises at least about 90% of a C1-3 carboxylic acid, a C1-3 aldehyde or a combination thereof. In some embodiments, the alcohol is a C1-3 alcohol and the co-product stream comprises at least about 95% of a C1-3 carboxylic acid, a C1-3 aldehyde or a combination thereof. In some embodiments, the alcohol is a C1-3 alcohol and the co-product stream comprises at least about 98% of a C1-3 carboxylic acid, a C1-3 aldehyde or a combination thereof. In some embodiments, the alcohol is a C1-3 alcohol and the co-product stream comprises at least about 98% of a C1-3 carboxylic acid, a C1-3 aldehyde or a combination thereof. In some embodiment, the alcohol is ethanol and the co-product stream comprises at least about 95% of acetic acid, acetaldehyde or combination thereof. In some embodiment, the alcohol is ethanol and the co-product stream comprises at least about 98% of acetic acid, acetaldehyde or combination thereof. In some embodiment, the alcohol is ethanol and the co-product stream comprises at least about 99% of acetic acid, acetaldehyde or combination thereof.

[0044] In some embodiments, the co-product stream consists of the dehydrogenated product, wherein the dehydrogenated product is a carboxylic acid, an aldehyde or acombination thereof. In some embodiments, the co-product stream consists essentially of the dehydrogenated product, wherein the dehydrogenated product is a carboxylic acid, an aldehyde or a combination thereof. In some embodiments, the co-product stream consists of the dehydrogenated product, wherein the dehydrogenated product is a carboxylic acid. In some embodiments, the co-product stream consists essentially of the dehydrogenated product, wherein the dehydrogenated product is a carboxylic acid.

[0045] In some embodiments, the product stream comprising hydrogen comprises about 2 vol% or less CO2. In some embodiments, the product stream comprising hydrogen comprises less than about 0.5 vol% CO2. In some embodiments, the product stream comprising hydrogen comprises less than 0.1 vol% CO2. In some embodiments, the product stream comprising hydrogen comprises less than 10 ppm CO. In some embodiments, the product stream comprising hydrogen comprises 2 vol% or less CO2 and less than 10 ppm CO.

[0046] In some embodiments, the separator is a porous, non-conductive material or an ionically conductive membrane. In some embodiments, the separator is a proton exchange membrane (PEM). In some embodiments, the PEM comprises a polybenzimidazole (PBI) polymer. In some embodiments, the PEM is a phosphoric acid doped PBI membrane or an ion-pair PBI membrane. In some embodiments, the separator is Nation. In some embodiments, the separator is an anion exchange membrane.

[0047] In some embodiments, there is a fluid between the cathode and the separator. In some embodiments, there is an aqueous fluid between the cathode and the separator. In some embodiments, there is a fluid in the second volume. In some embodiments, there is an aqueous fluid in the second volume. In some embodiments, the aqueous fluid is water. In some embodiments, the alcohol and / or the aqueous fluid comprise an electrolyte. In some embodiments, the electrolyte is a potassium salt or a sodium salt. In some embodiments, the electrolyte is KCI or KOH. In some embodiments, the electrolyte is KOH.

[0048] In some embodiments, the anode comprises a partial oxidation catalyst. In some embodiments, the partial oxidation catalyst comprises a transition metal or a transitionmetal oxide. In some embodiments, the partial oxidation catalyst is a Pd catalyst, Pt catalyst, a Pt-Sn catalyst or a combination of two or more thereof. In some embodiments, the partial oxidation catalyst is embedded on a substate; optionally a carbon substrate, Ti substrate, a Ni substrate or a combination of two or more thereof; optionally, graphite, carbon black or carbon paper. In some embodiments, the substrate is a film, felt or foam, e.g. a Ni film, felt or foam. In some embodiments, the anode comprises 1 to 50 wt% of a partial oxidation catalyst, e.g., about 5 to 40 wt%, 10 to 30 wt%, 15 to 25 wt% or 20 wt%. In some embodiments, the partial oxidation catalyst is in the form of nanoparticles. In some embodiments, the partial oxidation catalyst is in the form of nanoparticles having an average particle size of about 1 to 10 nm. In some embodiments, the partial oxidation catalyst is in the form of a single atom catalyst.

[0049] In some embodiments, the anode is coated on the separator. In some embodiments the cathode is coated on the separator. In some embodiments, the anode and the cathode are coated on the separator. In some embodiments, the anode is coated on one side of the separator and the cathode is coated on an opposing side of the separator.

[0050] In some embodiments, the electrolyser comprises two or more of the electrochemical cells.

[0051] In some embodiments, the cathode comprises a reduction catalyst. In some embodiments, the reduction catalyst is a Pt catalyst, a Ni catalyst, Ru catalyst, a Fe catalyst or a combination of two or more thereof. In some embodiments, the reduction catalyst is embedded on a substate; optionally a carbon substrate; optionally, graphite, carbon black or carbon paper. In some embodiments, the reduction catalyst is in the form of a single atom catalyst.

[0052] In some embodiments, the electrochemical cell is operated at a pressure of from about 1 to 50 bar. In some embodiments, the electrochemical cell is operated at a pressure of from about 10 to 20 bar.

[0053] In some embodiments, the apparatus further comprises a first container for storing the alcohol, wherein the first container is in fluid communication with the first volume housing the anode.

[0054] In some embodiments, the apparatus further comprises: a first container for storing the alcohol, a second container for storing the water, and a third container for mixing the alcohol and the water, wherein the first container and second container are in fluid communication with the third container such that alcohol from the first container and water from the second container can be conveyed to the third container to form a mixture of the alcohol and water; and the third container is in fluid communication with the first volume.

[0055] In some embodiments, apparatus further comprises a fourth container for storing the dehydrogenated product in fluid communication with the first volume housing the anode.

[0056] In some embodiments, the apparatus comprises one or more pumps capable of pumping fluids from the storage containers to the electrolyser. In some embodiments, the apparatus comprises one or more pumps capable of pumping the alcohol from the first container and water from the second container to the third container. In some embodiments, the apparatus comprises one or more pumps capable of pumping the mixture of the alcohol and water from the third container to first housing of the electrolyser. In some embodiments, the apparatus comprises a pump capable of pumping the hydrogen from the electrolyser to the fuel cell.

[0057] In some embodiments, the apparatus comprises a control unit for controlling the one or more pumps.

[0058] In some embodiments, the first and / or the second housing of the electrochemical cell comprises a level sensor for detecting the amount of fluid in the first and / or second housing. In some embodiments, the fuel cell comprises a level sensor for detecting the amount of fluid in the fuel cell. In some embodiments, the first container comprises a level sensor for detecting the amount of fluid in the first container. In someembodiments, the second container comprises a level sensor for detecting the amount of fluid in the second container. In some embodiments, the third container comprises a level sensor for detecting the amount of fluid in the third container. In some embodiments, the electrochemical cell, fuel cell, first container, second container and / or third container comprise a level sensor for detecting the amount of fluid in the electrochemical cell, fuel cell, first container, second container and / or third container.

[0059] This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0060] In addition, where features or aspects of the invention are described in terms of Markush groups, those persons skilled in the art will appreciate that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0061] As used herein "(s)" following a noun means the plural and / or singular forms of the noun.

[0062] As used herein the term "and / or" means "and" or "or" or both.

[0063] The term "comprising" as used in this specification means "consisting at least in part of". When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

[0064] It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

[0065] Although the present invention is broadly as defined above, those persons skilled in the art will appreciate that the invention is not limited thereto and that the invention also includes embodiments of which the following description gives examples.BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The invention will now be described with reference to the Figures in which:

[0067] Figure 1 shows a diagram of use of a process according to the invention to generate electricity.

[0068] Figure 2 shows a blown-up CAD drawing of lab-scale electrochemical cell. For simplicity only one of the electrodes is shown.

[0069] Figure 3 shows a graph of current density vs cell voltage for the lab-scale electrolyser using a Pd / C anode and a Pt / C cathode.

[0070] Figure 4 shows a blown-up CAD drawing of a bench-scale electrochemical cell.

[0071] Figure 5 shows a graph of current vs time achieved in bench-scale ethanol electrolyser at cell voltages of 0.3, 0.4 and 0.5 V.

[0072] Figure 6 shows the activity of an electrochemical cell according to the invention as a function of cell voltage.

[0073] Figure 7 shows the faradaic efficiency (current selectivity) of an electrochemical cell according to the invention for acetic acid (left) and acetaldehyde (right) as a function of cell voltage.

[0074] Figure 8 shows acetic acid production rate in an electrochemical cell according to the invention as a function of cell voltage.

[0075] Figure 9 shows the activity of an electrochemical cell according to the invention as a function of cell temperature.

[0076] Figure 10 shows acetic acid current selectivity (left) and acetaldehyde current selectivity (right) in an electrochemical cell according to the invention as a function of cell temperature.

[0077] Figure 11 shows acetic acid production rate in an electrochemical cell according to the invention as a function of cell temperature.DETAILED DESCRIPTION OF THE INVENTION

[0078] Described herein is an electrochemical process for partially oxidising a mixture of an alcohol and water to produce a product stream comprising hydrogen and a coproduct stream comprising a dehydrogenated product. An example of this reaction may be represented by the following reactions (in which n is, e.g., 0 to 8):Anode reactionCH3(CH2)nOH + H2O -CH3(CH2)n-iCOOH + 4H++ 4e" (in acidic conditions) CH3(CH2)nOH + 4OH“ - CH3(CH2)n-iCOOH + 3H2O + 4e- (in alkaline conditions)Cathode reaction4H++ 4e“ -» 2H2(in acidic conditions)4H2O + 4e“ -» 4OH“ + 2H2(in alkaline conditions)Overall reaction (both acidic and alkaline conditions)CH3(CH2)nOH + H2O -CH3(CH2)n-iCOOH + 2H2.

[0079] The partial oxidation may be contrasted with full oxidation wherein the alcohol is fully oxidised to carbon dioxide or a carbonate. Selectivity for partial oxidation (vs full oxidation) is affected by various factors such as the choice of catalyst and voltage applied to the electrochemical cell. Generally, a lower voltage applied to the anode will favour the partial oxidation. Surprisingly, the inventors have discovered partial oxidation may beutilised to provide an efficient process for preparing hydrogen, particularly compared to full oxidation processes that are conventionally used in processes for generating hydrogen known in the art.

[0080] The alcohol functions as an organic hydrogen carrier which may be oxidised to produce hydrogen via a hydrogen precursor. The alcohol is an organic compound comprising one or more hydroxyl groups attached to an alkyl group. The alcohol may be a straight chain alcohol, such as n-propanol, or a branched alcohol, such as iso-propanol. In some embodiments, the alcohol is a Ci-salcohol. In some embodiments, the alcohol is a Ci-salcohol. Preferably, the alcohol is a Ci-salcohol, including but not limited to, methanol, ethanol, n-propanol, isopropanol, methylene glycol, ethylene glycol, propylene glycol, glycerol or a combination of any two or more thereof. In some embodiments, the alcohol is ethanol. In some embodiments, the alcohol is a biofuel derived from a biological source, such as bioethanol derived from, e.g., biomass. The alcohol may be supplied to the anode as a liquid, a vapour or a combination thereof.

[0081] The dehydrogenated product is a partial oxidation product of the alcohol. The dehydrogenated product is preferably a carboxylic derivative of the alcohol. For example, when the alcohol is ethanol, the dehydrogenated product may be acetic acid. Those persons skilled in the art will appreciate that depending on the conditions, e.g. at a basic pH, the carboxylic acid may instead exist as the corresponding acetate salt. As used herein, terms such as "carboxylic acid", "acetic acid" and other related terms are intended to describe the dehydrogenated product in the acid and acetate forms, as appropriate. The dehydrogenation product may include an aldehyde derivative of the alcohol. In some embodiments, the dehydrogenated product is a carboxylic acid, an aldehyde or a combination thereof.

[0082] Advantageously, the dehydrogenated product may be a valuable commodity product, such as acetic acid. Accordingly, in some embodiments, the invention provides a process for partially oxidising an alcohol to produce a dehydrogenated product, wherein the dehydrogenated product is a commodity product. Alternatively, in someembodiments, the dehydrogenated product is reduced back to the alcohol such that it may be reused as a liquid organic hydrogen carrier.

[0083] The hydrogen precursor is reduced to hydrogen at the cathode. The hydrogen precursor may be, e.g., a proton or water.

[0084] The oxidation process carried out by the electrolyser is selective for partial oxidation of the alcohol. Selectivity may be measured by the conversion of the alcohol to the dehydrogenated product. The electrolyser may achieve above 95% selectivity for partial oxidation of the alcohol, i.e. above 95% of the alcohol that is consumed at the anode is converted to the dehydrogenated product (on a mol% basis). Preferably, the electrolyser achieves above 98% selectivity for partial oxidation of the alcohol. Preferably, above 98% of the alcohol consumed at the anode is converted to the carboxylic acid (on a mol% basis).

[0085] The invention in another aspect may also be seen to comprise an electrochemical process for the production of a dehydrogenated product from an alcohol. The process comprising the steps of (i) contacting the alcohol with the anode and (ii) applying a voltage to the anode to partially oxidise the alcohol to produce the dehydrogenated product. In some embodiments, the alcohol is ethanol and the dehydrogenated product is acetic acid.

[0086] The electrochemical process of the aspects of the invention wherein the dehydrogenated product is reduced back to an alcohol.

[0087] The invention in another aspect may be seen to comprise an electrochemical process for the production of hydrogen from an alcohol. The process comprises the steps of (i) contacting the alcohol with the anode, (ii) applying a voltage to the anode to partially oxidise the alcohol to produce a hydrogen precursor, and (iii) reducing the hydrogen precursor to hydrogen at a cathode.

[0088] Also described is an apparatus for partially oxidising an alcohol to produce a product stream comprising hydrogen and a co-product stream comprising a dehydrogenated product. The apparatus comprises an electrolyser comprising anelectrochemical cell and an energy source for applying a voltage to the electrochemical cell. The electrochemical cell comprises a vessel divided by a separator into a first volume and a second volume. The first volume houses an anode comprising a partial oxidation catalyst capable of partially oxidizing a mixture of an alcohol and water to produce a partial dehydrogenation product and a hydrogen precursor. The second volume houses a cathode comprising a reduction catalyst capable of converting the hydrogen precursor to hydrogen.

[0089] The second volume comprising the cathode may be at a higher pressure than the first volume housing the anode. Without wishing to be bound by theory, it is believed protons pumping though the separator (e.g. a membrane) between the first volume and second volume may increase the pressure at the second volume, e.g., by acting like a compression stage.

[0090] The electrolyser may comprise a single electrochemical cell. Alternatively, the electrolyser may comprise two or more electrochemical cells, e.g., a stack of electrochemical cells.

[0091] An anode of the electrolyser comprises a partial oxidation catalyst. The term "partial oxidation catalyst" as used herein refers to any catalyst capable of partially oxidising the alcohol to produce a hydrogen precursor and a dehydrogenated product in an electrochemical cell. Preferably, the partial oxidation catalyst is a catalyst that is selective for partial oxidation under appropriate conditions (e.g. when a low voltage is applied to the anode). A person skilled in the art could select a suitable catalyst and appropriate conditions for achieving partial oxidation. Suitable catalysts include, but are not limited to a transition metal or a transition metal oxide, such as a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst. The anode may comprise the catalyst embedded on a substrate. Suitable substrates may include a carbon substrate (such as graphite, carbon black or carbon paper), a Ti substrate and / or a Ni substrate. The anode may comprise 1 to 50 wt% of the catalyst, e.g., about 5 to 40 wt%, 10 to 30 wt%, 15 to 25 wt% or 20 wt%. The catalyst may be in the form of nanoparticles, e.g. particles having an average particle size of about 1 to 10 nm. In some embodiments, the anode comprises Pdnanoparticles on carbon black. In some embodiments, the anode comprises 20 wt% Pd nanoparticles on carbon black. In some embodiments, the anode comprises Pt nanoparticles on carbon black. In some embodiments, the anode comprises 20 wt% Pt nanoparticles on carbon black. The partial oxidation catalyst may also be in the form of a single atom catalyst.

[0092] A cathode of the electrolyser comprises a reduction catalyst. The term "reduction catalyst" as used herein refers to any catalyst capable of reducing the hydrogen precursor to hydrogen. A person skilled in the art could select a suitable catalyst and conditions to reduce the hydrogen precursor to hydrogen. Suitable catalysts include, but are not limited to, a Pt catalyst, a Ni catalyst a Ru catalyst, a Fe catalyst or a combination of two or more thereof. The cathode may comprise the reduction catalyst embedded on a substrate. Suitable substrates may include a carbon substrate (such as graphite, carbon black or carbon paper), a Ti substrate and / or a Ni substrate. The reduction catalyst may be in the form of nanoparticle, e.g. particles having an average particle size of about 1 to 10 nm. The reduction catalyst may be in the form of a single atom catalyst.

[0093] In some embodiments, the partial oxidation catalyst is a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst and the reduction catalyst is a Pt catalyst, a Ni catalyst a Ru catalyst, a Fe catalyst or a combination of two or more thereof. In some embodiments, the anode comprises 1 to 50 wt% of the catalyst, e.g., about 5 to 40 wt%, preferably 10 to 30 wt%, more preferably 15 to 25 wt% of the partial oxidation catalyst, which is selected from a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst. In some embodiments, the anode comprises 1 to 50 wt% of the catalyst, e.g., about 5 to 40 wt%, preferably 10 to 30 wt%, more preferably 15 to 25 wt% of the partial oxidation catalyst, which is selected from a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst, wherein the catalyst is in the form of nanoparticle on a substrate, e.g. a carbon substrate such as carbon black. In some embodiments, the partial oxidation catalyst is embedded on substrate, e.g. a carbon substrate, preferably in the form of nanoparticles and the reduction catalyst is embedded on substrate, e.g. a carbon substrate, preferably in the form of nanoparticles.

[0094] The electrochemical cell comprises a separator between the anode and cathode. The separator functions to restrict flow of fluids between the anode and the cathode. Flow of fluids from the anode to the cathode, or vice versa, can reduce the efficiency of the process, e.g., exposing the cathode to the alcohol can lead to poisoning of the reducing catalyst and reduce the efficiency and lifespan of the catalyst. Ideally, only the hydrogen precursor produced at the anode may pass through the separator to react at the cathode. In some embodiments, the separator is a porous non-conductive membrane, such as Celgard microporous polymer. In some embodiments, the separator is an ionically- conductive membrane, such as a cation exchange membrane, an anion exchange membrane or a proton exchange membrane (PEM). Suitable ionically-conductive membranes include, but are not limited to, Nation, Piperion, Sustainion and Fumatech. In some embodiments, the PEM comprises a polybenzimidazole (PBI) polymer. In some embodiments, the PEM is a phosphoric acid doped PBI membrane or an ion-pair PBI membrane. Those persons skilled in the art will appreciate other conventional separators known in the art may be useful in the invention. Advantageously, an ionically conductive membrane may also function as the electrolyte removing the need for a further electrolyte. In some embodiments, there is a fluid between the separator and the cathode (e.g. in the second housing) to provide a medium for transporting the hydrogen precursor to the cathode. For example, when the separator is an anion exchange membrane, the electrochemical cell may comprise a fluid such as water or water vapour between the separator and the cathode. Advantageously, when the separator is a PEM, the hydrogen precursor (e.g. proton) may directly contact the cathode without the need for a fluid.

[0095] The electrochemical cell may be provided in the form of a layered cell. For example, the electrochemical cell may comprise an anode layer, e.g., carbon paper embedded with the partial oxidation catalyst, contacting one side of the separator and a cathode layer, e.g., carbon paper embedded with the reducing catalyst, contacting an opposing side of the separator. Alternatively, the electrochemical cell may comprise the anode, the cathode and the separator, wherein the partial oxidation catalyst of the anode is coated on a surface of the separator the reducing catalyst of the cathode is coated on an opposing surface of the separator. In the layered electrochemical cell, the separator is preferably a proton exchange membrane. The layered electrochemical cell may bepreferable in some embodiments, e.g., when providing a electrolyser comprising two or more electrochemical cells. In those embodiments, the electrolyser may comprise a stack of electrochemical cells.

[0096] The electrochemical cell may comprise an electrolyte chosen from those known to those persons skilled in the art. Electrolytes include acidic electrolytes, basic electrolytes, salt electrolytes and ionic liquid electrolytes. While a vast array of acids, bases, or ionic liquids can be used as electrolytes, electrochemical processes are affected by the choice of electrolytes and in particular, are different in basic vs acidic electrolytes. In some embodiments, the electrolyte is an aqueous solution comprising a salt, such as a potassium or sodium salt. In some embodiments, the potassium or sodium salt is a chloride or hydroxide salt. In some embodiments, the electrolyte is a 1-30 wt% aqueous salt solution, e.g., a 1-30 wt% aqueous KCI or KOH.

[0097] The voltage applied to the electrochemical cell is selected to favour partial oxidation of the alcohol (vs full oxidation). For this purpose, generally the voltage should be as low as possible. For example, from above 0 to about 1.5 V, from above 0 to about 1.2 V, about 0.01 to 0.5 V or about 0.05 to 0.2 V. In some embodiments, the voltage is less than 1.0 V. In some embodiments, the voltage is less than 0.8V. The preferred voltage applied to the electrochemical cell will also depend on the intended application. For example, when operated in combination with a fuel cell, the voltage applied to the anode should be lower than the output voltage of the fuel cell. Therefore, when combined with a fuel cell, the voltage applied to the electrochemical cell is preferably less than about 1.2V.

[0098] The operating conditions for the electrochemical cell may be selected according to the intended application and components of the system. Generally, the electrochemical cell is operated in a temperature range of about 0 to 250°C. For example, when the alcohol is supplied to the anode as a liquid, the electrochemical cell may be operated at a temperature of about 25 to 78°C. For example, when the alcohol is supplied to the anode as a vapour, the electrochemical cell may be operated at a temperature of about 55 to 110°C. The electrochemical cell may be operated at various temperature ranges, such as about 50 to 250°C, 50 to 200°C, 50 to 150°C, 50 to 100°C, 80 to 250°C, 80 to 200°C, 80 to150°C, 80 to 100°C, 100 to 250°C, 100 to 200°C, 100 to 150°C, 150 to 250°C or 150 to 200°C. In some embodiments, the electrochemical cell is operated at a temperature of about 55 to 110°C. In some embodiments, the electrochemical cell is operated at a temperature of about 150 to 200°C. In some embodiments, the electrochemical cell is operated at a temperature above about 50°C. In some embodiments, the electrochemical cell is operated at a temperature above about 60°C, 70°C, 80°C, 90°C or 100°C. In some embodiments, the electrochemical cell is operated at a temperature above about 150°C. Generally, the electrochemical cell is operated in at a pressure of about 1 to 50 bar. In some embodiments, the electrochemical cell is operated in at a pressure of about 10-20 bar.

[0099] In some embodiments, the electrochemical cell is operated at a voltage from above 0 to about 1.5 V, preferably from above 0 to about 1.2 V, more preferably about 0.01 to 0.5 V or about 0.05 to 0.2 V and a temperature in the range of 50 to 250°C, 50 to 200°C, 50 to 150°C, 50 to 100°C, 80 to 250°C, 80 to 200°C, 80 to 150°C, 80 to 100°C, 100 to 250°C, 100 to 200°C, 100 to 150°C, 150 to 250°C or 150 to 200°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 1.2 V and at a temperature of about 25 to 78°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 1.2 V and at a temperature of about 55 to 110°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 1.2 V and at a temperature of about 150 to 200°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 1.0 V and at a temperature of about 25 to 78°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 1.0 V and at a temperature of about 55 to 110°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 1.0 V and at a temperature of about 150 to 200°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 0.8 V and at a temperature of about 25 to 78°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 0.8 V and at a temperature of about 55 to 110°C. In some embodiments, the electrochemical cell is operated at a voltage less than about 0.8 V and at a temperature of about 150 to 200°C.

[0100] The electrochemical cell may be operated at a pH of 0 to 14. The preferred pH range may be selected based on various factors, such as the components of the system and desired hydrogenation product(s). For example, in some embodiments, the electrochemical cell comprises a Nation separator with no additional electrolyte and is operated at a pH of about 0 to 2. In some other embodiments, the electrochemical cell is operated at a pH of 7 or above to minimise formation of a condensation by-product of the dehydrogenated product (e.g. ethyl acetate when the alcohol is ethanol).

[0101] In some embodiments, the electrochemical cell comprises: i. an anode comprising a partial oxidation catalyst selected from a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst (preferably embedded on a substrate, e.g. a carbon substrate), ii. a cathode comprising a reduction catalyst selected from a Pt catalyst, a Ni catalyst a Ru catalyst, a Fe catalyst or a combination of two or more thereof(preferably embedded on a substrate, e.g. a carbon substrate), and iii. a separator between the anode and the cathode, wherein the separator is a PEM (preferably a PEM comprising a polybenzimidazole (PBI) polymer such as a phosphoric acid doped PBI membrane or an ion-pair PBI membrane).

[0102] In some embodiments, the electrochemical cell comprises: i. an anode comprising a partial oxidation catalyst selected from a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst (preferably embedded on a substrate, e.g. a carbon substrate), ii. a cathode comprising a reduction catalyst selected from a Pt catalyst, a Ni catalyst a Ru catalyst, a Fe catalyst or a combination of two or more thereof(preferably embedded on a substrate, e.g. a carbon substrate), andiii. a separator between the anode and the cathode, wherein the separator is a PEM (preferably a PEM comprising a polybenzimidazole (PBI) polymer such as a phosphoric acid doped PBI membrane or an ion-pairPBI membrane); and the electrochemical cell is operated at a voltage from above 0 to about 1.5 V, preferably from above 0 to about 1.2 V, more preferably about 0.01 to 0.5 V or about 0.05 to 0.2 V and a temperature in the range of 50 to 250°C, 50 to 200°C, 50 to 150°C, 50 to 100°C, 80 to 250°C, 80 to 200°C, 80 to 150°C, 80 to 100°C, 100 to 250°C, 100 to 200°C, 100 to 150°C, 150 to 250°C or 150 to 200°C.

[0103] In some embodiments, provided is a process for preparing hydrogen from an alcohol, the process comprising:(a) providing an electrolyser comprising an electrochemical cell comprising: i. an anode comprising a partial oxidation catalyst selected from a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst (preferably embedded on a substrate, e.g. a carbon substrate), ii. a cathode comprising a reduction catalyst selected from a Pt catalyst, a Ni catalyst a Ru catalyst, a Fe catalyst or a combination of two or more thereof (preferably embedded on a substrate, e.g. a carbon substrate), and iii. a separator between the anode and the cathode, wherein the separator is a PEM (preferably a PEM comprising a polybenzimidazole (PBI) polymer such as a phosphoric acid doped PBI membrane or an ion-pair PBI membrane);(b) contacting the anode with a mixture of the alcohol and water;(c) applying a voltage of less than about 1.5 V, preferably less than 1.0 V, more preferably less than about 0.8 V at a temperature in the range of 50 to250°C, to the electrochemical cell such that the alcohol is partially oxidized at the anode to produce a product stream comprising a hydrogen precursor and a co-product stream comprising a dehydrogenated product , and the product stream comprising the hydrogen precursor passes through the separator wherein the hydrogen precursor is converted to hydrogen at the cathode.

[0104] In some embodiments, provided is a process for preparing hydrogen from an alcohol, the process comprising:(d) providing an electrolyser comprising an electrochemical cell comprising: iv. an anode comprising a partial oxidation catalyst selected from a Pd catalyst, Pt catalyst, Ru catalyst and / or a Pt-Sn catalyst (preferably embedded on a substrate, e.g. a carbon substrate), v. a cathode comprising a reduction catalyst selected from a Pt catalyst, a Ni catalyst a Ru catalyst, a Fe catalyst or a combination of two or more thereof (preferably embedded on a substrate, e.g. a carbon substrate), and vi. a separator between the anode and the cathode, wherein the separator is a PEM (preferably a PEM comprising a polybenzimidazole (PBI) polymer such as a phosphoric acid doped PBI membrane or an ion-pair PBI membrane);(e) contacting the anode with a mixture of the alcohol and water;(f) applying a voltage of less than about 1.5 V, preferably less than 1.0 V, more preferably less than about 0.8 V at a temperature in the range of 50 to 250°C, to the electrochemical cell such that the alcohol is partially oxidized at the anode to produce a product stream comprising a hydrogen precursor and a co-product stream comprising a dehydrogenated product , and the product stream comprising the hydrogen precursor passes throughthe separator wherein the hydrogen precursor is converted to hydrogen at the cathode; and wherein, the co-product stream comprises at least about 80%, preferably at least about 85%, 90, 95%, 98% or 99%, of the dehydrogenated product and the dehydrogenated product is a carboxylic acid, an aldehyde or a combination thereof.

[0105] Alternatively, the electrolyser may operate in combination with a power generating device for converting the hydrogen to power, e.g. a combustion engine or fuel cell. According, in some embodiments, at least a portion of the product stream comprising hydrogen may be conveyed to a combustion engine. The combustion engine may be for powering a vehicle, such as a car, ship, train or plane.

[0106] In some embodiments, at least a portion of the product stream comprising hydrogen produced in the electrolyser is conveyed to a fuel cell in which the hydrogen is converted to electricity and water. A conventional fuel cell comprises a hydrogen oxidation anode, in which hydrogen may be oxidized to protons, and a hydrogen-evolution cathode in which the protons are combined with oxygen (or air) to generate electricity. The combination of electrolyser and fuel cell provides a closed system for producing hydrogen and converting the hydrogen to electricity (i.e. the hydrogen produced in the electrolyser is utilised directly within the system). Accordingly, the combination of electrolyser and fuel cell may be utilised in mobile applications, e.g. for powering a vehicle wherein the vehicle is fuelled by the alcohol. For this purpose, vehicle may be refuelled by replenishing the alcohol consumed by in the electrolyser. Alternatively, the combination of electrolyser and fuel cell may be utilised in stationary applications. Advantageously, producing hydrogen in a separate component (the electrolyser) from the fuel cell reduces poisoning of the fuel cell cathode, e.g. by the alcohol, compared to direct ethanol fuel cells.

[0107] In some embodiments, the fuel cell is a single cell. In some other embodiments, the fuel cell is two or more cells operating in series, e.g., a stack of fuel cells.

[0108] The electrolyser may be directly connected to fuel cell. Alternatively, there may be an intermediate component between the electrolyser and the fuel cell, e.g. a gas cleaner. Some or all of the electricity produced by the fuel cell may be transmitted to operate the electrolyser. Advantageously, in those embodiments, the electrolyser and fuel cell combination may be self-sufficient. In those embodiments in which all of the electricity produced by the fuel cell is transmitted to the electrolyser, the remaining hydrogen may be conveyed to a tank for transport or storage or conveyed to a separate device for converting the hydrogen to power. In some embodiments, at least a portion of the product stream comprising hydrogen may be conveyed to multiple fuel cells, e.g., a small fuel cell for powering the electrolyser and a larger fuel cell for producing electricity for external applications.

[0109] The electrolyser cell and fuel cell may be provided as separate cells. In these embodiments, the electrolyser cell and the fuel cell may be operated separately such that a voltage is applied independently to each cell. For example, a voltage may be applied to the electrolyser cell to produce hydrogen at the cathode, that is conveyed from the electrolyser cell to the fuel cell. A separate voltage is applied to the fuel cell to convert the hydrogen to protons,

[0110] Alternatively, the electrolyser and fuel cell may be provided as a combined cell. In these embodiments, the electrolyser cell and the fuel cell may be operated in series such that a voltage is applied across both the electrolyser cell and the fuel cell. The electrolyser cell and fuel cell may share an electrode wherein the cathode of the electrolyser also functions as the anode of the fuel cell. In some embodiments, the shared electrode is a porous electrode. For example, the shared electrode may be a porous material, such as carbon paper or carbon cloth, comprising a reduction catalyst on the electrolyser side and a hydrogen oxidation catalyst on the fuel cell side. In use, protons generated at the electrolyser anode are reduced to hydrogen in contact with the reduction catalyst of the shared electrode. The hydrogen then passes through the shared electrode and is converted to protons in contact with the hydrogen oxidation catalyst of the shared electrode. Advantageously, the shared electrode allows diffusion of hydrogen from the electrolyser side to the fuel cell side. Preferably, the shared electrode allows selectivediffusion of hydrogen only from the electrolyser side to the fuel cell side, i.e., essentially filtering the hydrogen between the electrolyser cell and the fuel cell. An advantage of providing the electrolyser and fuel cell as a combined cell is potential design efficiencies, e.g. by reducing number of components in the system (such as reducing the number of end plates), and / or integrating elements such as heating and fluid transport.

[0111] The electrolyser and fuel cell may be provided in a stack of alternating cells each "unit" containing an alcohol oxidation anode, a shared or discrete hydrogen reduction / oxidation electrode(s), and an oxygen reduction cathode. Again, an advantage of providing the electrolyser and fuel cell as a combined cell is design efficiencies e.g. by reducing number of components in the system (such as reducing the number of end plates), and / or integrating elements such as heating and fluid transport.

[0112] In some embodiments, provided is a single-stack electrochemical apparatus comprising of: a) an ethanol oxidation anode configured to partially oxidize ethanol in the presence of water to produce acetic acid, protons, and electrons; b) at least one proton exchange membrane adjacent to the ethanol anode; c) a porous electrode with a hydrogen-evolution electrocatalytic cathode on a first side facing the ethanol anode, and a hydrogen-oxidation electrocatalyst anode on a second side facing the oxygen reduction cathode, so that hydrogen formed on the first side is consumed on the second side.

[0113] The electricity produced by the fuel cell may be used for powering a vehicle, such as a land vehicle (e.g. a car truck or train), ship or aircraft. In some embodiments, the fuel cell may be used for driving the motor of the vehicle. Preferably, the outlet pressure from the electrolyser is higher than the fuel cell inlet pressure. For example, the outlet pressure from the electrolyser may be about 2 to 10 bar higher than the fuel cell inlet pressure. In some embodiments, the apparatus further comprises a hydrogen buffer volume between the electrolyser and fuel cell. The buffer volume is a space in which hydrogen may collect before entering the fuel cell. The size of the buffer volume may beselected depending on the system requirements, e.g., the rate of hydrogen production in the electrolyser versus hydrogen consumption by the fuel cell. For example, a minimal buffer volume may be necessary if the rate of hydrogen product is similar to the rate of hydrogen consumption, while a larger buffer volume (or buffer tank) may be useful if there is a significant different between the rate of hydrogen production versus consumption. The purpose of the buffer volume is to ensure constant flow of hydrogen to the fuel cell. Additionally or alternatively, the electricity produced by the fuel cell may be transmitted to a battery for later use.

[0114] Accordingly, in some embodiments, the apparatus comprises the electrolyser in fluid connection with a fuel cell. In some embodiments, the apparatus further comprises a battery for storage of the electricity produced by the fuel cell.

[0115] Use of an apparatus according to the invention in an electric vehicle is shown in figure 1. In this figure, a feed stream 102 (liquid fuel) is conveyed to an electrolyser 300 (dehydrogenator) to produce a product stream comprising 104 comprising hydrogen and a co-product stream 106 comprising a dehydrogenated product. The product stream 104 produced in the electrolyser 300 is conveyed to a fuel cell 500, which produces electricity to drive a vehicle. Optionally, a portion of the electricity produced by the fuel cell 500 may be transmitted back to the electrolyser 300 to drive the electrochemical process. In this example, the fuel cell 500 also produces heat and water that, optionally, may be utilised by the electrolyser 300.

[0116] The apparatus may comprise containers (e.g. tanks) for storing fluids to be used in the apparatus and / or fluids produced by the apparatus. For example, the apparatus may comprise a first container for storing the alcohol and / or a second container for storing water. The apparatus may further comprise a third container for mixing the alcohol and water before addition to the electrolyser. In these embodiments, the first and second container are in fluid connection with the third container and the third container is in fluid connection with the first housing of the electrochemical cell. Alternatively, the alcohol and water may be conveyed directed to the electrolyser. In these embodiments, the first and second containers are in fluid connection with the first housing of the electrochemical cell.The apparatus may comprise a container for storage of the dehydrogenated product produced by the electrolyser. Those persons skilled in the art will appreciate the first, second, third and fourth containers as described above are exemplary. Other configurations of storage containers are within the scope of the invention, e.g., the use of multiple containers for each component. Containers suitable for use in the apparatus may be selected depending on the intended function, e.g., whether the container is for shortterm or longer term storage, mobile or stationary applications and the required volume.

[0117] Fluids in the apparatus may be conveyed around the apparatus with conventional means, e.g. pumps. For example, the apparatus may comprise one or more pumps located between the containers, electrolyser and / or fuel cell. In some embodiments, the alcohol stored in the first container and water stored in the second container are pumped to the third container, then the mixture is pumped from the third container to the first housing of the electrochemical cell.

[0118] The apparatus may further comprise a control unit for controlling the one or more pumps. The function of the control unit is to increase, decrease or stop the flow of fluids among components in the apparatus as required. For example, flow of the mixture of alcohol and water into the electrolyser may be modulated depending on the rate in which the mixture is consumed by the electrolyser. Accordingly, the control unit may be operated in combination with sensors in the apparatus. For example, the first and / or second housings of the electrochemical cell may comprise level sensors to detect the amount of fluid in each housing. The first, second, third and / or fourth containers may also comprise level sensors to detect the amount of fluid in each container. Flow sensors may also be used to detect the rate of flow of a fluid between components. Sensors may also be useful independent of a control unit to monitor the apparatus, e.g., to monitor if amount of the alcohol and / or water in the apparatus is low and must be refilled.

[0119] The product stream comprising hydrogen produced in the electrolyser may be convey to a storage tank for transport or storage. Accordingly, in some embodiments, the apparatus comprises a fifth container for storing the hydrogen, wherein the fifth container is in fluid connection with the electrolyser.

[0120] As discussed above, preferably the amount of contaminants in the product stream comprising hydrogen from the electrolyser is minimised. For some applications, the product stream produced by the electrolyser may be cleaned, e.g. to further reduce contaminants such as carbon dioxide or ethanol, before being conveyed to the power generating device. Accordingly, the apparatus may further comprise a gas cleaner between the electrolyser and power generating device. Preferably, the product stream conveyed to the fuel cell comprises less than about 2 ppm CO2 and / or less than about 0.2 ppm CO. Advantageously, particularly compared with full oxidation process for generating hydrogen, the process of the present invention may provide a product stream comprising hydrogen comprising sufficiently low levels of CO2 and / or CO that purification is not required before use, or less purification is required compared to a full oxidation process.

[0121] The apparatus comprises an energy source for applying a voltage to the electrolyser (i.e. to the electrochemical cell or cells). When the electrolyser is operated in combination with a fuel cell that transmits electricity back to the electrolyser, the energy source may function as a "starter" to initiate operation of the process. In some embodiments, the battery is used as the energy source to apply a voltage to the electrolyser.

[0122] In some embodiment, the process is a stationary plant for producing the dehydrogenated product, e.g., a commodity product.

[0123] The apparatus may be a mobile unit. For example, the electrolyser may be operated with a power generating device, e.g. a combustion engine or fuel cell, to convert the hydrogen to power the vehicle, e.g., drive the motor. In some embodiments, the vehicle is a zero-emission vehicle, such as a zero emission car. For this purpose, the dehydrogenated product (and any other by products) may be removed from the electrolyser and the electrolyser recharged with an alcohol to refuel the process.Additionally or alternatively, the apparatus may be a mobile plant for producing hydrogen and / or a dehydrogenated product.

[0124] The following non-limiting examples are provided to illustrate the present invention and in no way limit the scope thereof.EXAMPLESExample 1

[0125] The performance of a lab scale electrochemical ethanol electrolyser was tested using a Pd / C anode catalyst and a Pt / C cathode catalyst. Figure 2 shows a blown-up CAD drawing of a lab-scale electrochemical cell. For simplicity only one of the electrodes is shown. The electrochemical cell 302 has a endplates 304 with flow channels 306. Between the endplates 304 is an electrode 308 / 310 (i.e. anode 308 or cathode 310), in this example a catalyst coated carbon paper electrode. The catalyst coated carbon paper electrode 308 / 310 abuts a membrane 312, in this example a Celgard membrane, which abuts a gasket 314.

[0126] 40%wt EtOH and 10%wt KOH in water was fed to the anode and 10%wt KOH in water was fed to the cathode. The anode and cathode catalyst were spray coated onto carbon paper (SpectraCarb 2050A-1535, 0.380 mm thick) to achieve a loading of 5 mg / cm2catalyst for both the anode and cathode. Both anode and catalysts contained 20 wt% metal. The catalytic electrode layers contained 10wt% Nation as a binder. The anode and cathodes (both electrodes were 1.8 x 1.8 cm in size) were assembled into the lab cell using Celgard 2400 (a Microporous polypropylene Membrane) as a separator between the anode and cathode. The cell was operated at 24.5°C and the cell voltage was scanned from 0.2 V to 1.5 V at 20 mV / s and the current measured using a Gamry Reference 3000 potentiostat (Figure 3). The results show that at 0.5 V, a significant current density flows (approx. 75 mA / cm2) corresponding to the dehydrogenation of ethanol at the anode and the formation of hydrogen at the cathode. As the cell voltage increases, the current density drops around 1.4 V due to the passivation of the anode catalyst (palladium oxide formation), where it is no longer active for ethanol oxidation. While this shows that operating continuously at or above 1.4 V is not possible, the palladium oxidation also cleans and reactivates the catalyst by removing adsorbed poisons from the ethanol dehydrogenation reaction. Thus periodic steps from low voltage to high voltage can be beneficial to enhance overall performance.Example 2

[0127] Hydrogen was successfully produced in a bench-scale electrochemical ethanol electrolyser. Figure 4 shows a blown-up CAD drawing of a bench scale electrochemical cell. The cell is a layer configuration with sequence of layers in the order of an end plate 316, gasket 314, a current collector and flow distribution place 318, a gasket 314, an anode electrode 308 (catalyst coated carbon paper electrode) and a membrane 312 (Celgard membrane) to form the anode cell (i.e. volume housing the anode). This sequence of layers is mirrored with cathode electrode 310 to form the cathode cell (i.e. volume housing the cathode).

[0128] The cell used 5 mg / cm220wt% Pd / C on carbon paper (SpectraCarb 2050A-1535, 0.380 mm thick) as the anode and 1 mg / cm2 Pt loading on carbon paper (Toray TGP-H- 90) as the cathode. 40%wt EtOH and 10%wt KOH was recirculated through both the anode and cathode at temperature of 50°C. The anode and cathode were both 100 x 100 mm in size and were separated from each other using a Celgard 2400 microporous polypropylene membrane. The cell voltage held at 0.3, 0.4 and 0.5 V for 100s each and the total current measured using a Corrtest CS350M EIS Potentiostat / Galvanostat coupled with a CS2020B booster (Figure 5). The current was found to be stable at each voltage and shows that the hydrogen production rate increases with increasing cell voltage.Example 3

[0129] Experiments were performed to understand the impact of cell voltage and temperature on the activity (mean current density in mA cm'2) and selectivity for liquid products of an electrochemical cell according to the invention. The experiments were performed in the high temperature PEM setup which has SS316 end plates, impregnated graphite cell plates and Teflon gaskets to provide sealing and electrical insulating properties.

[0130] For the temperature sweep experiments, the cell voltage was held at 0.5 V and the temperature was held at 140°C, 160°C, 180°C and 200°C for 60 minutes at each temperature.

[0131] In the cell voltage sweep experiments, the temperature was set to 160 °C and the cell voltage was varied over 0.3 V, 0.35 V, 0.4 V, 0.45 V, 0.5 V, 0.6 V, 0.7 V and 0.8 V for 60 minutes each.

[0132] The membrane electrode assembly consisted of 3 mg cm'240% PtRu / C (1:1 Pt:Ru) on MB-30 carbon paper with 20wt% Teflon binder present in the catalyst layer as both the anode and cathode. The membrane was Advent's Ion Pair membrane. The total active electrode area was 4.4 cm2.

[0133] The reactant feed consisted of 2 M ethanol that was pumped at 0.5 ml min-1and recirculated.

[0134] As shown in Figure 6, activity increased with cell voltage up until 0.7 V where the activity began to drop. The decrease in activity at a high voltage was possibly caused by potential-induced catalyst poisoning at the higher voltages. Interestingly the acetic acid selectivity increased significantly with cell voltage, while selectivity for the acetaldehyde reached a minimum at 0.6 V - ignoring the outlier at 0.35 V (see Figures 7). A maximum acetic acid production rate was achieved at a cell voltage of 0.7 V (see Figure 8).

[0135] The electrochemical cell activity was found to be strongly dependent on temperature with activity increasing with increasing temperature (see Figure 9). However, acetic acid selectivity decreased slightly with increasing temperature until 200 °C where it plateaued (see Figure 10). As shown in Figure 10, acetaldehyde selectivity increased until 160°C then decreased until 200 °C. Although the acetic acid selectivity was observed to decrease at higher temperatures, the high dependence of activity on temperature means the acetic acid production rate was positively linked to cell temperature (see Figure 11).

[0136] It is not the intention to limit the scope of the invention to the abovementioned examples only. As would be appreciated by a skilled person in the art, many variations arepossible without departing from the scope of the invention as set out in the accompanying claims.

Claims

CLAIMS1. A process for preparing hydrogen from an alcohol, the process comprising:(a) providing an electrolyser comprising an electrochemical cell comprising: i. an anode comprising a partial oxidation catalyst, ii. a cathode comprising a reduction catalyst, and iii. a separator between the anode and the cathode;(b) contacting the anode with a mixture of the alcohol and water;(c) applying a voltage to the electrochemical cell such that the alcohol is partially oxidized at the anode to produce a product stream comprising a hydrogen precursor and a co-product stream comprising a dehydrogenated product, and the product stream comprising the hydrogen precursor passes through the separator wherein the hydrogen precursor is converted to hydrogen at the cathode.

2. The process of claim 1, wherein the voltage applied to the electrochemical cell is above 0 to about 1.5V; optionally, above 0 to about 1.2V, about 0.01 to 0.5 V, or about 0.05 to 0.2 V; optionally, wherein the voltage applied to the electrochemical cell is less than about 1.0V or less than about 0.8V.

3. The process of claim 1 or 2, wherein the process further comprises the step of conveying the hydrogen to a fuel cell, wherein the fuel cell converts the hydrogen to electricity and water.

4. The process of claim 3, wherein the electricity produced in the fuel cell is used to drive a motor of a vehicle; optionally wherein the vehicle is land vehicle (e.g. a car, a truck or a train), a ship or an aircraft.

5. The process of claim 3 or 4, wherein a portion of the electricity produced by the fuel cell is transmitted to a battery.

6. The process of any one of claims 3 to 5, wherein a portion of the electricity produced in the fuel cell is used to apply a voltage to the electrochemical cell.

7. The process of any one of claims 1 to 6, wherein the co-product stream comprises at least about 80% of the dehydrogenated product; optionally at least about 85%, 90, 95%, 98% or 99% of the dehydrogenated product.

8. The process of any one of claims 1 to 7, wherein the co-product stream comprises at least about 80% of the dehydrogenated product and the dehydrogenated product is a carboxylic acid, an aldehyde or a combination thereof.

9. The process of any one of claims 1 to 8, wherein the co-product stream comprises at least about 95% of the dehydrogenated product and the dehydrogenated product is a carboxylic acid, an aldehyde or a combination thereof.

10. The process of any one of claims 1 to 9, wherein the electrochemical cell is operated at a temperature in a temperature range of about 0 to 250°C; optionally in a temperature range of about 50 to 250°C, 50 to 200°C, 50 to 150°C, 50 to 100°C, 80 to 250°C, 80 to 200°C, 80 to 150°C, 80 to 100°C, 100 to 250°C, 100 to 200°C, 100 to 150°C, 150 to 250°C or 150 to 200°C.

11. An apparatus for generating hydrogen from an alcohol, the apparatus comprising:(a) an electrolyser comprising an electrochemical cell comprising a vessel divided by a separator into a first volume and a second volume, wherein: i. the first volume houses an anode comprising a partial oxidation catalyst capable of partially oxidizing a mixture of the alcohol and water to produce a product stream comprising hydrogen and a co-product stream comprising a dehydrogenated product, and ii. the second volume houses a cathode comprising a reduction catalyst capable of converting the hydrogen precursor in the product stream to hydrogen;(b) an energy source for applying a voltage to the electrochemical cell.

12. The apparatus of claim 11, wherein the voltage to be applied to the electrochemical cell is above 0 to about 1.5V; optionally, above 0 to about 1.2V, about 0.01 to 0.5 V, or from about 0.05 to 0.2 V; optionally, wherein the voltage applied to the electrochemical cell is less than about 1.0V or less than about 0.8V.

13. The apparatus of claim 11 or 12, wherein the apparatus further comprises a fuel cell in fluid connection with the second volume, wherein the fuel cell is capable of converting the hydrogen to electricity and water.

14. The apparatus of claim 13, wherein the comprises a battery connected to the fuel cell, wherein the battery is for storing electricity produced by the fuel cell.

15. The apparatus of any one of claims 11 to 14, wherein the apparatus is on a vehicle; optionally wherein the vehicle is a land vehicle (e.g. a car, a truck or a train), a ship or an aircraft.

16. The apparatus of claim 15, wherein the fuel cell is connected to a motor configured to drive the vehicle such that electricity produced by the fuel cell can be transmitted to the motor to drive the vehicle.

17. The apparatus of any one of claims 11 to 16, wherein the apparatus comprises a buffer tank between the second volume of the electrochemical cell and the fuel cell.

18. The apparatus of any one of claims 11 to 17, wherein the apparatus further comprises: a first container for storing the alcohol, a second container for storing the water, and a third container for mixing the alcohol and the water, wherein the first container and second container are in fluid communication with the third container such that alcohol from the first container and water from the second container can be conveyed to the third container to form a mixture of the alcohol and water; and the third container is in fluid communication with the first volume.

19. The apparatus of any one of claims 11 to 18, wherein the apparatus further comprises a fourth container for storing the dehydrogenated product in fluid communication with the first volume housing the anode.

20. The apparatus of claim 18 or 19, wherein the apparatus comprises one or more pumps capable of pumping fluids from the storage containers to the electrolyser; optionally wherein the apparatus comprises one or more pumps capable of pumping the alcohol from the first container and water from the second container to the third container; optionally wherein the apparatus comprises one or more pumps capable of pumping the mixture of the alcohol and water from the third container to first housing of the electrolyser; optionally, wherein the apparatus comprises a pump capable of pumping the hydrogen from the electrolyser to the fuel cell.

21. The apparatus of claim 20, wherein the apparatus comprises a control unit for controlling the one or more pumps.

22. The process of any one of claims 1 to 10, or the apparatus of any one of claims 11 to 21, wherein the alcohol is a saturated alcohol; optionally, wherein the alcohol is a Ci-salcohol; optionally, wherein the alcohol is a Ci-salcohol; optionally, wherein the alcohol is a Ci-salcohol; preferably, wherein the alcohol is methanol, ethanol, n- propanol, isopropanol, methylene glycol, ethylene glycol, propylene glycol, glycerol or a combination of any two or more thereof; more preferably, wherein the alcohol is ethanol.

23. The process of any one of claims 1 to 10 and 22, or the apparatus of any one of claims 11to 22, wherein the alcohol is at least partially in vapour form; optionally, wherein the alcohol is substantially in vapour form.

24. The process of any one of claims 1 to 10, 22 and 23, or the apparatus of any one of claims 11 to 23, wherein the dehydrogenated product is a carboxylic acid.

25. The process of any one of claims 1 to 10 and 22 to 24, or the apparatus of any one of claims 11 to 24, wherein the separator is a porous, non-conductive material oran ionically conductive membrane; optionally, wherein the separator is an anion exchange membrane; preferably, wherein the separator is a proton exchange membrane, such as Nation.

26. The process or apparatus of claim 25, wherein separate is a proton exchange membrane comprising a polybenzimidazole (PBI) polymer, such as a phosphoric acid doped PBI membrane or an ion-pair PBI membrane.

27. The process of any one of claims 1 to 10 and 22 to 26, or the apparatus of any one of claims 11 to 26, wherein there is a fluid between the cathode and the separator; optionally, wherein there is an aqueous fluid between the cathode and the separator; optionally, wherein the alcohol and / or the aqueous fluid comprise an electrolyte; optionally wherein, the electrolyte is a potassium salt (such as KOH) or a sodium salt.

28. The process of any one of claims 1 to 10 and 22 to 27, or the apparatus of any one of claims 11 to 27, wherein the partial oxidation catalyst comprises a transition metal or a transition metal oxide; optionally, wherein the partial oxidation catalyst is a Pd catalyst, Pt catalyst, a Pt-Sn catalyst or a combination of two or more thereof.

29. The process of any one of claims 1 to 10 and 22 to 28, or the apparatus of any one of claims 11 to 28, wherein the partial oxidation catalyst is embedded on a substate; optionally a carbon substrate, Ti substrate, a Ni substrate or a combination of two or more thereof; optionally, graphite, carbon black or carbon paper.

30. The process of any one of claims 1 to 10 and 22 to 29, or the apparatus of any one of claims 11 to 29, wherein the anode comprises 1 to 50 wt% of a partial oxidation catalyst; optionally, about 5 to 40 wt%, 10 to 30 wt%, 15 to 25 wt% or 20 wt%; optionally, wherein the partial oxidation catalyst is in the form of nanoparticles; optionally, wherein the partial oxidation catalyst is in the form of nanoparticleshaving an average particle size of about 1 to 10 nm; optionally wherein the partial oxidation catalyst is in the form of a single atom catalyst.

31. The process of any one of claims 1 to 10 and 22 to 30, or the apparatus of any one of claims 11 to 30, wherein the anode is coated on one side of the separator and the cathode is coated on an opposing side of the separator.

32. The process of any one of claims 1 to 10 and 22 to 31, or the apparatus of any one of claims 11 to 31, wherein the electrolyser comprises two or more of the electrochemical cells.

33. The process of any one of claims 1 to 10 and 22 to 32, or the apparatus of any one of claims 11 to 32, wherein the reduction catalyst is a Pt catalyst, a Ni catalyst, Ru catalyst, a Fe catalyst or a combination of two or more thereof; optionally, wherein the reduction catalyst is embedded on a substate; optionally a carbon substrate; optionally, graphite, carbon black or carbon paper; optionally wherein the reduction catalyst is in the form of a single atom catalyst.

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