On-site generation of clean, ultra-high pressure hydrogen via catalytic reforming of methanol and other alcohols

Abstract

A method for producing hydrogen includes a step of dehydrogenating an alcohol mixed with a metal hydroxide and / or metal oxide over a catalyst at a predetermined initial temperature and a predetermined initial pressure to produce gaseous H2 that is substantially free of gaseous CO2. Characteristically, the alcohol mixed with the metal hydroxide and / or metal oxide forms a metal hydroxide and / or metal oxide solution.

Description

ON-SITE GENERATION OF CLEAN, ULTRA-HIGH PRESSURE HYDROGEN VIACATALYTIC REFORMING OF METHANOL AND OTHER ALCOHOLSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application Serial No. 63 / 468,840 filed May 25, 2023, the disclosure of which is hereby incorporated in its(their) entirety by reference herein.TECHNICAL FIELD[0002| In at least one aspect, the present invention is related to methods for reforming alcohols.BACKGROUND

[0003] Over the past century, unparalleled industrial growth and an ever-increasing global population have led to an exponential surge in energy demands. At present, the world’s energy consumption has surpassed 1.7 x 105TWh annually, around 80% of which is still being supplied by burning fossil fuels such as coal, petroleum, and natural gas.1In addition to the long-term risk of exhausting these relatively vast, yet limited natural reserves, their combustion has led to the inevitable emission of CO2 and other greenhouse gases to the atmosphere in an unaccountable fashion. The increasing concentration of CO2 has by far outpaced the natural carbon cycle, leading to repercussions such as global warming, more unpredictable and extreme weather events, rise of sea levels, ocean acidification, and increasing loss of biodiversity among many other negative impacts.2'3In an effort to reach a united solution to carbon emissions and related challenges originating from the use of fossil energy, a rapid transition to carbon-neutral and renewable energy sources as well as the implementation of sustainable and circular technologies has been advocated.4'7However, renewable energy sources such as solar and wind often suffer from intermittency and hence, the development of energy storage / carrier technologies is vital for their wide-scale deployment.|0004] Drawing inspiration from nature and photosynthesis, the storage of renewable energy in chemical bonds has been investigated extensively for the development of energy carriers.8Hydrogen (H2), which holds the highest grlaavimetric energy density of 120 MJ kg’1, is considered a clean fuel producing only water upon combustion (Figure la). H2 generated with renewable energy by electrochemical water splitting is generally referred to as “green H2”.9Even though H2 is often recognized as an ideal renewable fuel candidate, it suffers from intrinsic challenges pertaining to its low volumetric energy density.10Limited industrial modes of H2 storage mostly include physical compression under very high pressures of 700 bar or at cryogenic temperatures. Due to its highly flammable and explosive nature, the storage and transportation of neat H2 is extremely challenging in terms of safety which has led to high capital intensity. Hence, chemical hydrogen carriers have been proposed as practical and efficient alternatives because they can facilitate a progressive transition to the so-called “hydrogen economy” that could utilize an already existing vast fossil fuel and refined hydrocarbon infrastructures.11In this regard, formic acid and methanol are of particular interest as both can propel the development of CO2 recycling technologies being products of the same, in parallel to the H2 economy.12’16

[0005] The use of formic acid (HCOOH) has been well explored for its catalytic decomposition to equivalents of H2 and CO2 with favorable energetics (AG° = -6.9 kcal moF1).17’22Yet, due to formic acid’s low H2 content (4.4 wt%), methanol (CH3OH) is more promising with a significantly higher H2 content of 12.6 wt% (higher than that of water).23’25In addition, methanol is an easy-to-handle liquid (B.P. 63 °C) that is convenient to store and transport. The H2 stored in methanol can be catalytically released (reforming) and further coupled with a fuel cell, referred to as reformed methanol fuel cell (RMFC).23However, conventional steam reforming of methanol is active only at high temperatures (>250 °C) due to relatively unfavorable thermodynamics (AG° = +0.6 kJ mol1) (Figure lb). Furthermore, the H2 produced by conventional reforming of methanol is a mixture with CO2 and small amounts of CO, which is not tolerated by the catalyst in the proton exchange membrane (PEM) based fuel cell catalysts even at very low concentrations of 10 ppm.19- 26

[0006] The desirable criteria that a viable methanol reformer should meet, at least in part, include: 1) rapid H2 generation on-demand at moderate temperatures; 2) clean and emission-free production of H2 (free of any CO / CO2); 3) safe and cost-effective; 4) easy to operate at scale; 4) highly efficient catalysis with high activities under low loading; and 5) meet the gravimetric H2 storage capacity recommended by US Department of Energy (4.5 wt%).8In 2013, a novel catalytic processwas identified independently in seminal studies by the groups of Beller and Giiitzmacher for low- temperature methanol dehydrogenation to 3H2 / CO2.27-28These reactions were enabled by Ru-based molecular catalysts under mild conditions (65-95 °C). Aqueous phase methanol dehydrogenation has since been explored further to understand the plausible mechanistic pathways and develop new catalysts with more favorable kinetics.29Notably, the addition of bases such as amines or metal hydroxides to the aqueous methanol solution proved effective in significantly lowering the residual CO2 concentration in the evolved gas mixture. CO2. which is a byproduct of the reforming reaction is effectively captured in situ by the base present.8, 29-31

[0007] A base-assisted methanol reformer that can produce a continuous stream of pure H2 and be directly fed into a PEM fuel cell is highly desired.25, 32Yet, to the best of our knowledge, an integrated low-temperature RMFC has yet to be demonstrated. Moreover, the generation of clean H2 under high pressures has not been reported to date, from methanol or any alternate H2 carrier.22, 33-36On-site H2 pressure generators or “chemical compressors” have wide applicability for the safer handling of H2 in th-fuelled vehicles, stationary power units, H2 refueling stations, and other applications. Currently, H2 compression is primarily achieved using mechanical compressors.37-38

[0008] Accordingly, there is a need for improved methods of storing and releasing H2.SUMMARY

[0009] In at least one aspect, a method for producing very high-purity H2 is provided.

[0010] In another aspect, a method for producing hydrogen includes a step of dehydrogenating an alcohol mixed with a metal hydroxide and / or metal oxide over a catalyst at a predetermined initial temperature and a predetermined initial pressure to produce gaseous H2 that is substantially free of gaseous CO2. Characteristically, the alcohol mixed with the metal hydroxide and / or metal oxide forms a metal hydroxide and / or metal oxide solution.

[0011] In another aspect, a method for producing hydrogen includes a step of dehydrogenating a methanol derivative mixed with a metal hydroxide and / or metal oxide over a catalyst at a predetermined initial temperature and a predetermined initial pressure to produce gaseous H2 that is substantially free of gaseous CO2.

[0012] In another aspect, a catalytic composition for use in hydrogen production includes a pincer-type ligand and a metal center wherein the metal is selected from ruthenium, iridium, iron, manganese, or cobalt.

[0013] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For a further understanding of the nature, objects, and advantages of the present disclosure, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:

[0015] FIGURES la, lb, and 1c. Introduction, a) methanol as a hydrogen carrier; b) conventional routes for CCh-to-methanol and methanol-reforming; and c) overall theme of the present study: low-temperature methanol-reforming for emission-free hydrogen generation.

[0016] FIGURE 2a. Schematic of a hydrogen generator.

[0017] FIGURE 2b. Schematic of a hydrogen generator providing hydrogen to a fuel cell.

[0018] FIGURES 3a, 3b, 3c, 3d and 3e. Methanol reforming in a closed system, a) screening of Ru-based molecular catalysts, reaction conditions: CH3OH / H2O (10 mL, 9:1), KOH (80 mmol), catalyst loading (20 ppm.), stirring (800 rpm), T = 100 °C, t = 24 h; b) effect of reaction temperature, reaction conditions: CH3OH / H2O (30 mL, 9:1), KOH (240 mmol), C-4 (75 ppm.), stirring (800 rpm), t = 24 h; c) effect of altering the base, reaction conditions: CH3OH / H2O (30 mL, 9:1), OH" (240 mmol), C-4 (75 ppm.), stirring (800 rpm), T = 140 °C t = 24 h; d) effect of KOH content, reaction conditions: CH3OH / H2O (30 mL, 9:1), C-4 (75 ppm.), stirring (800 rpm), T = 140 °C, t = 24 h; e) effect of externally introduced H2 pressure, reaction conditions: CH3OH / H2O (30 mL, 9:1), KOH (240 mmol), C-4 (75 ppm.), stirring (800 rpm), T = 140 °C, t = 24 h. Pressures were measured with a piezoelectric pressure transducer. Calculation error ±5%.

[0019] FIGURE 4a and 4b. A wider library of homogeneous catalysts for methanol reforming screening.

[0020] FIGURE 5. A typical gas chromatography (GC) spectra of the gas mixture produced during alkaline methanol-reforming shows the sole presence of H2 and no CO / CO2.

[0021] FIGURE 6. Methanol reforming at 100 °C over extended periods, reaction conditions: CH3OH / H2O (30 mL, 9:1), KOH (240 mmol), C-4 (75 ppm.), stirring (800 rpm), t = 90 h.

[0022] FIGURE 7. Effect of reaction volume on H2 generation, reaction conditions: CH3OH / H2O (9:1), KOH (8 M), C-4 (75 ppm.), stirring (800 rpm), T - 140 °C, t - 90 h.

[0023] FIGURE 8. Effect of catalyst loading on H2 generation, reaction conditions: CH3OH / H2O (30 mL, 9:1), KOH (240 mmol), C-4 (75 ppm.), stirring (800 rpm), T = 140 °C, t = 24 h.

[0024] FIGURE 9. Effect on methanol content in the CH3OH / H2O reforming solution on H2 generation: total volume (10 mL), KOH (80 mmol), C-4 (20 ppm.), stirring (800 rpm), T = 100 °C, t = 24 h.

[0025] FIGURE 10. Generation of H2 at ultra-high pressures. Reaction conditions: CH3OH / H2O (9:1), C-4 (75 ppm.), stirring (800 rpm), T = 140 °C, t = 24 h, pressures measured with a piezoelectric pressure transducer. Calculation error ±5%.

[0026] FIGURE 11. Design setup of a realistic methanol reformer setup.

[0027] FIGURES 12a, 12b, 12c, 12d, 12e and 12f. Continuous hydrogen generation at ambient pressures, a) methanol reforming at 100 °C (Tset). reaction conditions: CH3OH / H2O (30 mL, 9:1), KOH (240 mmol), C-4 (75 ppm.), stirring (800 rpm), Tset = 100 °C, t = 12 h; b) effect of reaction temperature (Tset). reaction conditions: CH3OH / H2O (30 mL, 9:1), KOH (240 mmol), C-4 (75 ppm.), stirring (800 rpm), t = 12 h; c) and d) methanol-reforming for extended period (50 h) reaction conditions: CH30H(400 mL), H2O (50 mL), KOH (200 g), C-4 (50 pmol), stirring (800 rpm), Tset = 110-125 °C, t = 50 h; e) polarization curves with reformed methanol and commercial H2 f) constantcurrent hold of 2.5 A with reformed methanol and commercial H2, Fuel cell parameters: membrane (Nafion 211), electrode (4 cm2), anode (Pt on teflonized carbon paper, 0.5 mg / cm2), Cathode (Pt on teflonized carbon paper with microporous layer, 0.5 mg / cm2), gases humidified at 100 % RH, H2flow rate (40 ml / min), air flow rate (400 mL / min). Flow and volume measured with calibrated mass flow meter. Calculation error ±5%.

[0028] FIGURE 13. Representative H NMR spectra of the reaction mixture after hydrogenation of C-l residues of methanol-reforming in D2O.

[0029] FIGURES 14a and 14b. Catalytic dehydrogenation of different alcohols for H2 generation, reaction conditions: alcohol / H2O (30 mL, 9:1), KOH (240 mmol), C-4 (75 ppm.), stirring (800 rpm), T = 140 °C, t = 20 h. For equimolar, a correction factor was incorporated to assume equal moles of ethylene glycol and ethanol as compared to methanol (667 mmol).DETAILED DESCRIPTION

[0030] Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present invention, which constitute the best modes of practicing the invention presently known to the inventors. The Figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and / or as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0031] Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and / or use are to be understood as modified by the word "about" in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary; all R groups (e.g. Ri where i is an integer) include hydrogen, alkyl, lower alkyl, Ci-6 alkyl, C6-10 aryl, C6-io heteroaryl, -NO2, -NH2, -N(R’R”), -N(R’R”R”’)+L’, Cl, F, Br, -CF3, -CCI3, -CN, - SO3H, -PO3H2, -COOH, -CO2R’, -COR’, -CHO, -OH, -OR’, -O M+, -SO3’M+, -PO3M+, -C00 M+, -CF2H, -CF2R’, -CFH2, and -CFR’R” where R’, R” and R’” are Ci-10 alkyl or Ce-18 aryl groups; single letters (e.g., "n" or "o") are 1, 2, 3, 4, or 5; in the compounds disclosed herein including compounds described by formula or by name, a CH bond can be substituted with alkyl, lower alkyl, C1-6 alkyl, C&. 10 aryl, C6-io heteroaryl, -NO2, -NH2, -N(R’R”), -N(R’R”R”’)+L’, Cl, F, Br, -CF3, -CCI3, -CN, -SO3H, -PO3H2, -COOH, -CO2R’, -COR’, -CHO, -OH, -OR’, -O M+, -SO3M+, -PO3’M+, -C00 M+, -CF2H, - CF2R’, -CFH2, and -CFR’R” where R’, R” and R’” are C1-10 alkyl or Ce-is aryl groups, M+is a metal cation, and L~ is a negatively charged counterion; percent, "parts of," and ratio values are by weight; the term "polymer" includes "oligomer," "copolymer," "terpolymer," and the like; molecular weights provided for any polymers refers to weight average molecular weight unless otherwise indicated; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.

[0032] The term “alkyl” refers to C1-20 inclusive, linear (z.e., “straight-chain”), branched, saturated or at least partially and in some cases fully unsaturated (z.e., alkenyl and alkynyl) hydrocarbon chains, including for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, terTbutyl, pentyl, hexyl, octyl, ethenyl, propenyl, butenyl, pentenyl, hexenyl, octenyl, butadienyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, and allenyl groups. “Branched” refers to an alkyl group in which a lower alkyl group, such as methyl, ethyl or propyl, is attached to a linear alkyl chain. “Lower alkyl” refers to an alkyl group having 1 to about 8 carbon atoms (z.e., a C1-8 alkyl), e.g., 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms. “Higher alkyl” refers to an alkyl group having about 10 to about 20 carbon atoms, e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms.

[0033] It is also to be understood that this invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may, of course, vary.Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present invention and is not intended to be limiting in any way.

[0034] It must also be noted that, as used in the specification and the appended claims, the singular form "a," "an," and "the" comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.

[0035] The term “comprising” is synonymous with “including,” “having,” “containing,” or “characterized by.” These terms are inclusive and open-ended and do not exclude additional, unrecited elements or method steps.

[0036] The phrase “consisting of’ excludes any element, step, or ingredient not specified in the claim. When this phrase appeal’s in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[0037] The phrase “consisting essentially of’ limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

[0038] The phrase “composed of’ means “including” or “comprising.” Typically, this phrase is used to denote that an object is formed from a material.

[0039] With respect to the terms “comprising,” “consisting of,” and “consisting essentially of,” where one of these three terms is used herein, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

[0040] It should also be appreciated that integer ranges explicitly include all intervening integers. For example, the integer range 1-10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Similarly, the range 1 to 100 includes 1, 2, 3, 4. . . . 97, 98, 99, 100. Similarly, when any range is called for, intervening numbers that are increments of the difference between the upper limit and the lower limit divided by 10 can be taken as alternative upper or lower limits. For example, if the range is 1.1.to 2.1 the following numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 can be selected as lower or upper limits. In the specific examples set forth herein, concentrations, temperature, and reaction conditions (e.g. pressure, pH, etc.) can be practiced with plus or minus 50 percent of the values indicated rounded to three significant figures. In a refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, etc.) can be practiced with plus or minus 30 percent of the values indicated rounded to three significant figures of the value provided in the examples. In another refinement, concentrations, temperature, and reaction conditions (e.g., pH, etc.) can be practiced with plus or minus 10 percent of the values indicated rounded to three significant figures of the value provided in the examples.

[0041] In the examples set forth herein, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 50 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In a refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 30 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples. In another refinement, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced with plus or minus 10 percent of the values indicated rounded to or truncated to two significant figures of the value provided in the examples.

[0042] Throughout this application, where publications are referenced, the disclosures of these publications in their entirety are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains.

[0043] The term “pressure reactor” refers to a reaction vessel designed to conduct chemical reactions under elevated pressure conditions. These reactors are commonly used in laboratory settings, as well as in industrial processes, to synthesize materials, test reactions, or conduct studies under specific conditions. In a refinement, a pressure reactor is a high-pressure reactor (e.g., 5 bar or more, absolute pressure).

[0044] The term “pincer ligand” refers to a ligand that includes a central aromatic ring flanked by two side arms that contain donor atoms. These side arms can be phosphines, amines, or other groupscapable of donating electrons to a metal center. The most common structure is a central aryl or heteroaryl ring (like pyridine) with two phosphine or amine groups attached to the ortho positions of the ring, forming a molecular claw that grasps a metal at three points.

[0045] The term “PNP ligand” refers to a type of pincer ligand in coordination chemistry that features phosphorus (P) and nitrogen (N) donor atoms arranged in a specific manner to stabilize a metal center. These ligands are typically tridentate usually with a central nitrogen atom flanked by two phosphorus atoms.

[0046] In at least one aspect, a method for producing hydrogen is provided. The method includes a step of dehydrogenating an alcohol mixed with a metal hydroxide and / or metal oxide over a catalyst at a predetermined initial temperature and a predetermined initial pressure to produce gaseous H2 that is substantially free of CO2 and substantially free of other gaseous carbon-containing products. To clarify, an alcohol can be mixed with a metal hydroxide, an alcohol can be mixed with a metal oxide, or an alcohol can be mixed with a combination of a metal hydroxide and a metal oxide. Collectively, the metal hydroxide and / or metal oxide can be referred to as “a metal base”). In this context, “substantially free” means that the gaseous products of the reaction include less than 2 mole percent gaseous CO2 and other gaseous carbon-containing products (i.e., the total of gaseous CO2 and other gaseous carbon-containing products is less than 2 % by volume). In a refinement, the gaseous products of the reaction include less than 10 % by volume, 5 % by volume, 4 % by volume, 3 % by volume, 2 % by volume, 1 % by volume, 0.5 % by volume, or 0. 1 % by volume gaseous CO2 and other gaseous carbon-containing products (i.e., the total of gaseous CO2 and other gaseous carbon- containing products is less than these values). Characteristically, the alcohol is mixed with the metal hydroxide and / or metal oxide to form a metal hydroxide and / or metal oxide solution. Advantageously, the alcohol and the metal hydroxide and / or metal oxide are present in a sufficient amount to develop a gauge pressure of at least 10 bar after the reaction.

[0047] In another aspect, the molar ratio of the alcohol to the metal hydroxide and / or metal oxide is from 10:1 to 18:1. In some refinements, the molar ratio of the alcohol to metal hydroxide and / or metal oxide is greater than about 1:1, 3:1, 4:1, 5:1, 10:1, 12:1, 15:1, or 20:1 and less than about100: 1 , 50: 1 , 40: 1 , 30: 1 , 25: 1 , or 22: 1. It should be appreciated that if both metal hydroxide and metal oxide are present these ratios are applicable to the total of metal hydroxide and metal oxide.

[0048] In another aspect, the alkali hydroxide and / or metal oxide is potassium hydroxide with a molar ratio of potassium hydroxide to the metal hydroxide and / or metal oxide from about 5 to 30. In some refinements, the molar ratio of the alcohol to the metal hydroxide and / or metal oxide is greater than about 1:1, 3:1, 4:1, 5:1, 10:1, 12:1, 15:1, or 20:1 and less than about 100:1, 50:1, 40:1, 30:1, 25:1, or 22: 1. It should be appreciated that if both metal hydroxide and metal oxide are present these ratios are applicable to the total of metal hydroxide and metal oxide.

[0049] In another aspect, the predetermined initial temperature is 0 to 300 degrees Celsius. In some refinements, the predetermined initial temperature is at least 0 °C, 10 °C, 20 °C, 30 °C, 50 °C, 70 °C, or 100 °C. In other refinements, the predetermined initial temperature is at most 300 °C, 250 °C, 220 °C, 200 °C, 180 °C, or 150 °C. Although the reaction temperature may change during the course of the reaction, typically, the reaction temperature will remain within these limits. Similarly, the predetermined initial pressure is a gauge pressure of 0 to 600 bar. In a refinement, the predetermined initial pressure is a gauge pressure of 0 to 100 bar. In some refinements, the predetermined initial pressure is a gauge pressure of at least 0 bar, 5 bar, 10 bar, 20 bar, 50 bar, 100 bar, 150 bar, or 200 bar. In other refinements, the predetermined initial pressure is a gauge pressure of at most 600 bar, 500 bar, 300 bar-, 200 bar, 100 bar, or 50 bar. Advantageously, during the course of the reaction, the pressure increases.

[0050] In another aspect, the hydrogen gas generated is produced at a gauge pressure greater than 10 bar. In some refinements, the hydrogen gas generated is produced at a gauge pressure greater than 0 bar, 1 bar, 2 bar, 5 bar, 10 bar, 20 bar, 50 bar, 100 bar, 150 bar, 200 bar, 250 bar, or 300 bar. In other variations, the hydrogen gas generated is produced at a gauge pressure of less than 1500 bar, 1200 bar, 1000 bar, 800 bar, 500 bar, 400 bar, 300 bar, 200 bar, or 100 bar. In another refinement, the hydrogen generated during the reaction is produced at a gauge pressure greater than 0 to 1000 bar without needing a mechanical compressor. In another refinement, the hydrogen generated is produced at a gauge pressure from 10 to 1000 bar. These pressures are realized without needing mechanical compression.

[0051] In another aspect, water is added to alcohol and a metal hydroxide and / or metal oxide solution. Typically, the water is present in an amount from 3 to 50 weight present of the combined weight of the water, the alcohol, the metal hydroxide and / or metal oxide, and the catalyst (i.e., the reaction mixture). In some refinements, the water is present in an amount of at least, 1, 2, 3, 5, 10, 15, 20 or 30 weight percent of the combined weight of the water, the alcohol, the metal hydroxide and / or metal oxide, and the catalyst and at most 60, 50, 45, 40, 35, or 30 weight percent of the combined weight of the water, the alcohol, the metal hydroxide and / or metal oxide, and the catalyst

[0052] In another aspect, the alcohol is a primary alcohol, a diol, a triol, a polyol, a polyethylene glycol, or combinations thereof. Examples of primary alcohols include, but are not limited to, methanol, ethanol, propanol, butanol, pentanol, and combinations thereof. Examples of diols include but are not limited to, ethylene glycol, 1,3-propan ediol, 1,4-butanediol, and mixtures thereof. In another refinement, the triol is glycerol. Therefore, in a refinement, the alcohol can be selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, glycol, 1,3- propanediol, 1,4-butanediol, glycerol, and combinations thereof.

[0053] In another aspect, the metal hydroxide is an alkali hydroxide or an alkaline earth metal hydroxide. Examples of alkali hydroxides include but are not limited to, sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, rubidium hydroxide, and mixtures thereof. Examples of alkaline earth metal hydroxides include but are not limited to, calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, and mixtures thereof.

[0054] In another aspect, metal oxide is an alkali metal oxide. In a refinement, the metal oxide is selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, calcium oxide, magnesium oxide, and cesium oxide.

[0055] In another aspect, the CO2 formed during the dehydrogenation reaction is captured by the metal hydroxide and / or metal oxide either in situ or in a separate step. In a refinement, the CO2 formed during the dehydrogenation reaction is captured by the metal hydroxide and / or metal oxide either in situ or in a separate step to produce hydrogen with a CO2 content of less than 10 % by volume, preferably less than 1 % by volume, and most preferably less than 0.1% by volume.

[0056] In another aspect, the CO2 formed during the dehydrogenation reaction is captured by the metal hydroxide and / or metal oxide either in situ or in a separate step to afford hydrogen with a CO content of less than 1 % by volume, preferably less than 0.1 % by volume, and most preferably less than 0.01% by volume.

[0057] In another aspect, the hydrogen produced includes less than 0.1% by volume of carbon- containing compounds. In a refinement, the hydrogen produced includes less than 0.01% by volume of carbon-containing compounds. In another refinement, the hydrogen produced includes less than 0.001% by volume of carbon-containing compounds. In still another refinement, the hydrogen produced is carbon-free.

[0058] In another aspect, the catalyst is a homogeneous catalyst. In a variation, the catalyst is a homogeneous catalyst composed of one or several ligands and a metallic center. In a refinement, the catalyst is a homogeneous catalyst selected from the group consisting of catalysts containing ruthenium, iridium, iron, manganese, or cobalt.

[0059] In another aspect, the catalyst is a homogeneous catalyst that includes metal (e.g., Ru) and a ligand framework. In a refinement, the homogeneous catalyst ligand framework is Macho-BH, PNPZPr, PNPfB“, PNP'>r, PNP®\ or PNPCv. (see, Figures 4a and 4b).

[0060] In another aspect, the catalyst is a homogeneous catalyst composed of a metal center and a pincer-type ligand. In a refinement, the pincer-type ligand is PNP type ligand.

[0061] In another aspect, the catalyst is a homogeneous catalyst immobilized on a surface by deposition, grafting, or any other immobilization method.

[0062] In another aspect, the catalyst is a heterogeneous catalyst. In a refinement, the catalyst is a heterogeneous catalyst system that includes a component selected from a group consisting of copper-based catalysts, indium-based catalysts, nickel-based, indium and nickel / gallium-based catalysts modified or not modified with other metals including lanthanides and / or precious metals, and combinations thereof.

[0063] In another aspect, heterogeneous catalysts for the reforming reaction may include (but are not limited to) copper-based catalysts (with additives and supports such as ZnO, Z1O2. MOFs, Ga, AI2O3, SiCh. TiCh), indium-based (ImCh / ZrC ), nickel-based (NiGa / AhCh, NiaGa / AhCh, NisGaa / AhCh), ruthenium, platinum, palladium based (Ru, Pt, Pd on various supports including silica, alumina, titania, zirconia, silica-alumina and carbon). Various promoters, such as precious metals (such as Pd, Pt, Rh, Ru) or lanthanides (such as La, Sm, Gd), can also be added to these heterogenous catalysts to improve selectivity and reactivity.

[0064] In another aspect, hydrogen produced is used in a fuel cell to generate electrical energy. In a refinement, the hydrogen produced is stored for later use at gauge pressures of 0 to 1000 bar. In another refinement, the hydrogen produced is stored for later use at gauge pressures of 0 to 600 bar. In another refinement, the hydrogen produced is stored for later use at gauge pressures of 0 to 300 bar. In another refinement, the hydrogen produced is stored for later use at gauge pressures of 10 to 1000 bar. In some refinements, the hydrogen produced is stored for later use at gauge pressures greater than 0 bar, 1 bar, 5 bar, 10 bar, 20 bar, or 50 bar and less than 1200 bar, 1000 bar, 800 bar, 600 bar, 300 bar, or 100 bar.

[0065] In another aspect, carbonate, and bicarbonate species produced during the dehydrogenation reaction are regenerated by hydrogenation to form back the alcohol and the metal hydroxide and / or metal oxide.

[0066] In another aspect, a method for producing hydrogen includes a step of dehydrogenating a methanol derivative in the presence of a metal hydroxide and / or metal oxide over a catalyst at a predetermined initial temperature and a predetermined initial pressure to produce H2 and CO2. In a refinement, the methanol derivative is selected from the group consisting of dimethyl ether, formaldehyde, paraformaldehyde, formalin, trioxane, formic acid, metal formate, alkyl formate, alkyl carbonates, and mixtures thereof. Details set forth above are also applicable to this variation.

[0067] Figures 2a and 2b depict a reactor for carrying out the method for producing hydrogen. Hydrogen generator 10 includes closed reaction vessel 12 configured to receive a catalyst from catalyst source 14 and a mixture of an alcohol and a metal hydroxide and / or metal oxide from alcohol source 18 and metal hydroxide source 20. Valves vl, v2, and v3 or other flow control devices can be used toregulate introduction of the catalyst, alcohol, or metal hydroxide and / or metal oxide Hydrogen generator 10 includes a temperature transducer 22 for monitoring the temperature (e.g., a thermometer) within the reaction vessel and a pressure transducer 24 for monitoring the pressure within the reaction vessel. Heater 24 for heating the reaction vessel to a predetermined initial temperature. The gaseous hydrogen can be provided from output 26 and controlled by valve v4. In a variation, hydrogen purification station 30 is used to remove any remaining CO2 from the formed gaseous H2. Hydrogen purification station 30 can deploy any number of techniques for purifying the ga and in particular, removing CO2. For example, Pressure Swing Adsorption (PSA) utilizes adsorbents like zeolites or activated carbons that capture impurities under high pressure, with the beds later depressurized to release the gases, making this method favored in scenarios requiring high-purity hydrogen. Membrane Separation employs the selective permeability of membranes, allowing CO2 and other impurities to pass through more readily than hydrogen, which is ideal for applications needing moderate -purity hydrogen. Amine Gas Treating, or amine scrubbing, involves passing the hydrogen through an amine solution that reacts with CO2 to form a stable compound, stripped later by heating, widely used across various industries for significant CO2 removal. Temperature Swing Adsorption (TSA) works similarly to PSA but uses temperature changes for regeneration, suitable when thermal energy is available and cost-effective. Cryogenic Separation leverages very low temperatures to separate gas components based on their condensation points, utilized where extreme hydrogen purity is necessary. Lastly, Molecular Sieves use synthetic zeolite materials with precise pore sizes for selective adsorption, often combined with other methods to achieve exceptionally high purity levels.

[0068] Still referring to 2b, hydrogen generator 10 can be used to provide H2 to a device 40. For example, device 40 can be a fuel cell that receives hydrogen from the hydrogen generator.

[0069] The following examples illustrate the various embodiments of the present invention. Those skilled in the art will recognize many variations that are within the spirit of the present invention and the scope of the claims.

[0070] Inspired by the foundations of homogeneous methanol dehydrogenation and our longterm vision for a functional methanol-based economy, we present herein a highly efficient, low- temperature methanol-reformer for emission-free H2 generation (Figure 1c). The two key reactants inour laboratory scale reformer, methanol and alkali hydroxides, readily generate H2 in the presence of a Ru-pincer based molecular catalyst at 100-140 °C. The system is emission-free and the H2 produced is of extremely high purity (>99.9 %). Under closed conditions, the catalytic system is efficient in generating H2 readily up to pressures of 144 bar. Under modified conditions, the H2 generation was effectively driven to remarkably high pressures of more than 450 bar, reproducibly demonstrating a novel chemical compression of H2. Furthermore, the integration of a low-temperature methanolreformer and PEM fuel cell was achieved for the first time. Under open conditions, our engineered reformer unit was able to produce a notably high volume of H2 (up to 140 L) with promising TONs of 1.2 x 105and a maximum TOF of 5,400 h"1. The clean H2 generated was simultaneously fed, without any purification, to the PEM fuel cell, which showed stable and continuous production of electric current for an extended period of over 27 h. Finally, the Ci-residues (carbonate / formate) of the reforming reaction were successfully converted reversibly back to methanol, indicating the potential application of the present system as a reversible H2 battery.

[0071] 1. Catalytic reforming of methanol under alkaline conditions

[0072] 1.1. Methanol reforming in a closed system

[0073] For H2 generation under pressures, the reaction was performed in a pressure vessel (Parr reactor) simply using a mixture of CH3OH / H2O (9:1) and KOH (a model metal hydroxide) in the presence of a catalyst. In a typical set-up, the pressure generated in the headspace was monitored throughout the reaction, and for reasonable comparison, the reported pressures are the ones after the reactor was cooled back to room temperature after the reforming reaction unless specifically stated otherwise. Efficient reforming of methanol or any other alcohol in a closed system is particularly challenging given that the accumulation of gaseous products in the reactive space can inhibit the forward reaction and arrest the catalyst in a reversible state.29However, we observed that the addition of a strong base, such as an alkali hydroxide, has driven the reaction thermodynamically (i.e., increased exothermicity). In addition to the H2 generation reaction, we observed a parasitic reaction, where trace amounts of a glycol solvent oxidized in the presence of a base even under 80 bar of H2. These results have inspired us to study the yet unexplored chemistry of methanol-reforming in a closed system.39"41

[0074] Among the different molecular catalysts identified for the dehydrogenation of methanol and other alcohols, the family of pincer-based metal complexes was found to be promising for the reforming of methanol under alkaline conditions. The pincer-based metal complexes are composed of a pincer ligand and a metallic center / complex. The pincer ligands in these pincer-based metal complexes are chelating agents that bind tightly to three adjacent coplanar sites of a metal complex. The pincer ligands can be of the ECE type (E = N, P), the ENE type (E = C, S, Se, P, N), the YNX type (Y = C, N, O, and X = N, O, S) or the PCN type. The pincer ligand can, for example, be of the PNP, PNN, PCP, NCN, CNC, SNS, NNN, PCN, and ONS type. In particular, PNP-pincer based metal complexes were found to be promising, especially when the pH of the system is neutral or basic.42'45Besides pincer ligands, other chelating agents could also be used in combination with a metallic center in metal complexes adapted for the reforming of methanol under alkaline conditions.

[0075] Under our preliminary reaction conditions at 100 °C, a library of catalysts was screened (Figure 3a). Advantageously, the Ru-PNP catalysts (C-l to C-6) were indeed effective in generating pressures (50-150 psi) from a solution of KOH in CH3OH / H2O due to gases generated inside the reactor. When the gas phase was analyzed for composition via gas chromatography (GC), only a single peak for H2 was detected, indicating that the gas phase was composed of a very high purity H2 ( >99.9% (Figure 5). Notably, no CO and CO2 traces were detected suggesting that none of the oxidized C-l products were present in the gas phase. When a scaled-up reaction (30 m ) was carried out, Ru- PNP'Pr(C-4) catalyzed the reaction to generate a notable pressure of 485 psi (33 bar) corresponding to 3.3 L of clean H2. As depicted in Table 1, the base plays two essential roles: a) a CO2 scavenger, making the system emission-free, and b) an effective promoter, driving the rate of H2 generation by a factor of more than 100 when compared to a reaction in the absence of the base. The reforming reaction is also expected to be active in the presence of a broad array of homogeneous catalysts and, in particular', pincer-type catalysts such as the ones depicted in Figure 4. The metal center in these homogeneous catalysts can be a transition metal or a metal selected from the lanthanide series. Ruthenium, manganese, cobalt, and iron are, for example, suited for the preparation of homogeneous catalysts for the reforming reaction described herein. Furthermore, the homogeneous catalysts for the reforming reaction can be immobilized on a support or surface by deposition, grafting or any other known immobilization method by a person having just ordinary skills in the art.

[0076] The reforming reaction is also active in the presence of various heterogeneous reforming catalyst systems. In one aspect, heterogeneous reforming catalyst systems include a component selected from the group consisting of copper-based catalysts, indium-based catalysts, nickel-based, indium, and nickel / gallium-based catalysts modified with lanthanides and / or precious metals, and combinations thereof. In a refinement, the heterogeneous catalyst system includes catalysts containing Cu, Zn and alumina.

[0077] Table 1. Control studies to validate the role of the baseaaReaction conditions: CH3OH / H2O (30 mL, 9:1), C-4 (50 pmol), stirring (800 rpm), t = 24 h.bmeasured with piezoelectric pressure transducer. Calculation error ±5%.

[0078] In light of these encouraging initial results, the reaction profile at different temperatures was explored (Figure 3b). While the maximum achievable internal temperatures in the previous open system studies were the reflux temperatures of the liquid mixture (generally below 100 °C), a closed system appeared advantageous to increase the internal temperatures to higher ranges and obtain better performance. Indeed, when the reaction temperature was increased from 100 °C to 120 °C, the catalysis improved significantly, and a high H2 pressure of 90 bar was achieved, corresponding to 9 L of H2, almost tripling from the 3.3 L at 100 °C. Ramping the temperatures further led to a relatively small increase with the final pressures of 100 bar for a reaction at 140 °C and 106 bar for 160 °C, respectively. The saturation in the pressures points toward the limited availability of the base and methanol in these cases. Expectedly, varying the temperature had a prominent effect on the reaction rates, as evident in Figure 3b. While 17% of the reaction was complete in the first 2 h of heating at 100 °C (rate2h = 0.7 psi min'1), the yield rose sharply to 74% at 140 °C with a rate of 9.1 psi min'1. In fact, 75% of the final H2 pressure was generated within the first hour of the reaction at 160 °C. To note, a similar high H2 pressure of 84 bar was obtained even at 100 °C, albeit over an extended period of 90 h (Figure 6). Interestingly, analysis of the headspace prior to heating the reactor also showed a clean H2 peak in GC, suggesting that the catalysis was already active at room temperature, althoughthe reaction rate was too slow for quantification. The reaction temperature for the reforming reaction can be varied between a temperature of about 0 to 300 degrees Celsius.

[0079] Next, the effect of altering the base on the methanol-reforming reaction was investigated (Figure 3c). With LiOH and NaOH, H2 pressures of 92 bar and 93 bar were achieved, respectively, which were comparable to the ones with KOH. Even Ca(OH)2 was active in H2 generation but led to a much lower pressure of 23.5 bar. Importantly, LiOH (23.9 g mol'1) and NaOH (40.0 g mol'1) have lower equivalent masses than KOH (56.1 g mol'1) and hence, provide significant gravimetric advantages in developing a viable H storage system. With LiOH, a significant working H2 capacity of 5.7 wt% was achieved with a weight efficiency increased by a factor of 1.5 relative to that with KOH. On the other hand, a NaOH-based system can provide cost-effectiveness due to its substantially lower commercial prices. Besides LiOH, NaOH, KOH, and Ca(OH)2, any other metal hydroxide such as cesium hydroxide, rubidium hydroxide, magnesium hydroxide, strontium hydroxide, and barium hydroxide can be used for the reforming reaction described herein.

[0080] Furthermore, the base content in the reformer had a pronounced impact on the H2 pressure generated. As shown in Figure 3d, the H2 pressure grew rapidly from 79 bar’ with 180 mmol of KOH to 146 bar with 360 mmol KOH with an overall linear trend. These observations underline the chemical compression of H2 achieved practically with the present system where ~15 L of H2 can be generated from a working volume of 30 inL, which is less than 2% of the volume of the gas generated and hence, achieve a compression factor of 540. To further explore the factors affecting the H2 generation in a closed system, H2 was introduced in the reactor at different pressures before the start of the reforming reaction (Figure 3c). Interestingly, the addition of external pressure had minimal effect on the pressure generated by the reformer, which remained stable even upon introducing 50 bar of H2 (net pressure = 148 bar). This is a strong indication that a) the catalysis is equally efficient at high pressures and b) the present reformers have the potential as multiple stacked units to generate a much higher cumulative H2 pressure. Other parameters, including CH3OH / H2O ratios (Figure 9), and reaction volume (Figure 7) and catalyst loading (Figure 8), were also investigated.

[0081] 1.2. Ultra-high pressure (UHP) generation.

[0082] The methanol-reformer demonstrated vide supra can efficiently generate pure H2 in the pressure range of 100-150 bar, which is at par with the pressures generally available with commercial H2 cylinders and satisfies the requirements of regular applications, with a major advantage of safe and convenient transportation. In addition, certain applications, such as storage and transportation in H2- fuelled vehicles and refueling stations, use higher H2 pressures to obtain better volumetric energy densities. At present, these sectors use specialized carbon composite tanks to store H2 in the pressure range of 250-700 bar or higher. When compared to such high-risk storage modes over a long period, alternate methods of generating the H2 pressure on-demand are highly desired. Hence, we explored further the present methanol-reformer to test its ability to generate H2 at even higher pressures. For this, the experimental setup was modified with a smaller volume reactor rated to hold higher pressures with a smaller volume (Figure 2a).

[0083] As discussed previously, we noted that the Hi pressures can be increased significantly by manipulating a couple of parameters: a) base content (Figure 3d) relative headspace volume (Figure 7). When the reforming reaction with 30 mL CH3OH / H2O and 240 mmol KOH was repeated in the new reactor at 140 °C (Figure 10), the Hi pressure increased from 100 bar (with -100 mL headspace) to 162 bar (with -60 mL headspace). Progressively increasing the base content to 420 mmol resulted in a pressure generation of 241 bar (304 bar at 140 °C). Finally, a slight increase in the reaction scale (40 mL) drove the reaction to a promising ultra-high pressure (UHP) of 456 bar (6703 psi) at 140 °C and 362 bar (5321 psi) at room temperature. While the safety guidelines of our reactors and laboratory facilities limited us to the reported pressure ranges, our optimization studies allow us to reasonably project that the reformer can be further modified to achieve pressures of 690 bar (10,000 psi) or higher as per the application needs.

[0084] 1.3. Methanol reforming at ambient pressures.

[0085] Following the promising Hi generation achieved under closed conditions, the catalytic system was also assessed while operating under open conditions with a vision to obtain continuous evolution of high-purity H2 and tandem flow into an H2 / air fuel cell. In 2013, Beller and co-workers found a stable homogeneous catalytic system that produced over 7 L of H2 from CH3OH under reflux over 24 days with a notable catalytic activity (TOFmax > 2500).28Since then, the catalysis for aqueousphase methanol dehydrogenation has been well studied under ambient pressures. However, the development of these fundamental catalytic systems toward a realistic reformer at scale has remained unexplored.8Hence, in contrast to the conventionally used setup using glass vessels, condensers, and burettes, a more safe, adjustable, easy-to-operate, and industrially viable model was proposed. For this, a completely metallic unit was engineered as shown in Figure 11, by modifying the head of the original Parr reactor (135 mL), which was then connected to a metallic water condenser followed by a check valve set to 10 psi (to maintain positive flow). The H2 flows and volumes were conveniently monitored using a mass flow meter (MFM).

[0086] At first, the reactor model was validated by heating a 30 mL solution of CH3OH / H2O and KOH in the presence of 50 pmol (75 ppm.) C-4 (Figure 12a). While the hotplate was set to 100 °C (Tset), the temperature of the reaction mixture was within 90-95 °C (Tint). Simultaneously, a continuous generation of clean H was achieved, with a high purity of > 99.9% as verified via GC. Over an initial period of 2 h, more than 2.7 L of H2 was generated with a steady average flow of 22 ml min’1. Overall, the reformer was run for 12 h, which generated a cumulative volume of 11.5 L of H2 with notable catalytic turnovers (TON = 9494 and TOFavg= 1025 h’1). At this point, the reaction reached saturation with a negligible flow of < 1 mL min’1and the Tint dropped to 75 °C. While the extent of the reaction remained unperturbed, the rates could be improved by a moderate increase in the temperature (Tset). Compared to 2.7 L at 100 °C, a significantly higher volume of ~4.4 L of H2 (flowavg = 37 mL min’1) was obtained at 110 °C within 2 h, which was further increased to 7.4 L H2 (flowavg = 62 mL min’1) at 120 °C with a notable TOF2h of 3020 h’1(Figure 12b). When the catalyst loading was halved (38 ppm.) in the reaction at 120 °C, ~5 L of H2 was generated in 2h with a TOF211 of 4080. On the other hand, an increase in catalyst loading to 112 ppm. led to a comparable H2 volume (7.35 L, TOF2h = 1940). However, the open reforming system proved to be more dynamic than the closed system and hence, increasing the temperature further to 130-140 °C proved detrimental to the H2 generation, plausibly due to an increased fraction of methanol in the vapor phase.

[0087] 1.4. A realistic methanol reformer at scale.

[0088] Guided by our understanding of the methanol-reforming system thus far, a scaled-up reforming reaction was operated for continuous generation of H over an extended period. This is keyto establishing the long-term stability and activity of the reforming catalyst as well as to demonstrate a steady integrated reformed methanol fuel cell (I-RMFC). For this, a 600 mL reactor was charged with 300 mL CH3OH, 40 mL H2O, and 150 g KOH in the presence of 50 pmol C-4 (Figure 12c). When heated to Tset = 110 °C, the reforming proceeded with a very high rate of reaction (TOFmax > 5400, Figure 12d) with an initial flow of up to 120 ml min-1. For over 20 h, the H2 flow continued to be steady (> 40 mL min-1) as the Tset was gradually increased to 125 °C. A total H2 volume of 110 L was generated after 30 h. As the reactants were consumed, 100 mL CH3OH, 10 mL H2O, and 50 g KOH was freshly introduced in the remaining solution containing the catalyst, and the reaction was run for an additional 20 h. Overall, the scaled-up reaction produced -140 L of H2 and a remarkably stable catalytic performance resulted in one of the highest ever cumulative TON of > 115,000 and TOFavg of 2300 over 50 h for homogeneous methanol reforming.

[0089] 1.5. Emission-free integrated reformed methanol fuel cell (I-RMFC).

[0090] H2 fuel cells have been recognized as one of the most promising technologies in the overall development of clean energy and sustainable ecosystems.46In this regard, RMFCs have gained much attention due to their high efficiencies and overall operating flexibility.47Conventional RMFC units often include a steam reformer of methanol at high temperatures, and a H2 purifier preceding the fuel cell setup. With our goal of developing a novel low-temperature and emission-free RMFC, a PEM fuel cell unit was assembled and placed directly at the outlet of the methanol-reformer. To demonstrate the tandem generation of H and electrical power, the open reforming system was chosen. As the proof-of-concept trial, the H2 generated from a small-scale (30 mL) reforming reaction was flowed at without any purification step first through a humidifier and then directly through the anode side of the fuel cell while the cathode side of the fuel cell was fed with either humified air or O2. The fuel cell performance was tested via polarization curve measurements (Figure 12e) using the H2 obtained by methanol-reforming and was found analogous to the one with the benchmark ultra-high-purity commercial H2 as the anode feed. The Fh / air fuel cell was also tested at a constant current (I = 2.5 A) and a stable cell voltage (0.55 V) was observed over 1 h.

[0091] Following this, the I-RMFC was tested for its durability over an extended duration. The scaled-up reforming unit (with 300 mL CH3OH) established earlier in this study with a steady H2 flowwas highly suited to be coupled to the Hi / air fuel cell. Hence in a separate extended run, the I-RMFC was operated continuously for over 27 h and a stable average voltage of 0.54 V was maintained (at constant I = 2.5 A), which was also very close to the values obtained in a run with commercially obtained pure H2 gas (Figure 121). During this period, -65 L H2 (produced from methanol reforming) was consumed in the fuel cell, demonstrating efficient and continuous conversion of chemical energy to electricity. In addition to validating the robustness of the I-RMFC over an extended period, the consistent cell output also indicates that the cell continued to be mostly unaffected by any trace CO, if any, in the stream.

[0092] 1.6. Recharging the hydrogen battery.

[0093] Once the th is generated, the spent or “th-lean” species can potentially be converted (or hydrogenated) back to the “Fh-rich” fuel, resulting in a rechargeable hydrogen storage media or an “th battery”. Such reversible systems are quite rare in literature, especially for methanol.8'13, 18, 30‘31, 48Methanol-based reversible f storage was demonstrated earlier by our group and later by Liu et al.; however, only when using amines as bases. To date, demonstrating a reversible alkaline methanol reforming system continues to be a highly challenging frontier. This is primarily due to the relative inertness of carbonate / formate salts toward catalytic hydrogenation and the thermodynamically uphill conversion to methanol.

[0094] Recently, we developed a protocol wherein compounds analogous to metal carbonates were converted to methanol efficiently using ethylene glycol as the mediator and catalyst C-2.39Hence, within the limited scope of this study, we briefly investigated the possibility of hydrogenating the C-l residues (primarily containing potassium formate and some potassium carbonate) obtained after the methanol-reforming reaction is completed. A small fraction (1 g, carbon content -11 mmol) of the dried residue was dissolved in ethylene glycol and subjected to hydrogenation with 70 bar of H2 and 50 pmol of C-2 (Table 2). After a reaction at 120 °C over 60 h, 10.1 mmol CH3OH was produced, substantiating that the present system is potentially rechargeable. The metal carbonate and metal bicarbonate species produced from the metal hydroxide during the reforming reaction can thus be regenerated by hydrogenation to form back the alcohol and alkali metal hydroxide.

[0095] Table 2. Attempted hydrogenation of the C-l residues obtained from methanolreforming21

[0096] aReaction conditions: reactant sample (1 g), C-2 (50 pmol), stirring (800 rpm), ethylene glycol (20 mL), H2 (70 bar).byields determined via!H NMR using an internal standard. Calculation error ±5%.

[0097] 1.7. Comparing reforming of methanol with other alcohols

[0098] To validate the selection of methanol over other alcohols for reforming and H2 generation, the catalytic dehydrogenation of ethylene glycol and ethanol was performed and compared to that of methanol. For this, an equal volume (27 mL) of the alcohol, 3 mL water, and 240 mmol of KOH were activated in the presence of C-4 (50 pmol). The generation of H2 underpressure was plotted as shown in (Figure 14). It is quite evident that the rate of H2 pressures obtained with ethanol and ethylene glycol are comparable but significantly lower than that with methanol, even after including a correction factor to compare in equimolar terms. Although the H2 pressures obtained were lower, any alcohol can be used in the reforming reaction described herein to obtain hydrogen. In addition to alcohols, derivatives of alcohols such as dimethyl ether, formaldehyde, paraformaldehyde, formalin, trioxane, formic acid, metal formate, alkyl formate, and alkyl carbonates can also be reformed in a metal hydroxide solution over a catalyst to obtain hydrogen.

[0099] 2. Conclusion

[0100] In conclusion, a realistic, highly efficient and low-temperature methanol reformer has been developed for rapid and clean H2 generation, based on the fundamental concept of catalytic methanol dehydrogenation. The reaction mixture is comprised of the key reactants: methanol and alkali hydroxide. In a novel closed reforming system, even a small-scale reaction generated high pressures of H2 up to 150 bar on-demand, which is in the range of most commercial H2 tanks and cylinders. Notably, almost 80% of the H2 pressure is reached within the first two hours of the reaction,exhibiting remarkable reaction rates, especially under thermodynamically unfavorable closed conditions. Furthermore, higher pressure requirements were achieved with minor modifications to the operating parameters and scale, which translated into a rare realization of ultra-high pressure H2 of more than 450 bar. These high pressures / volumes of H2 were generated from a working reaction volume, which was as low as 2% of those, emphasizing the major advantages of this methanol-based system as a “chemical compressor” of H2 in terms of convenience, safety, as well as cost-effectiveness.

[0101] In parallel, the low-temperature methanol reformer can be operated in open conditions near atmospheric pressure. The rapid evolution of clean H2 with flow rates of 50-120 mL min'1and a net volume of >11 L was observed with no traces of CO2 and CO as contaminants. The reformer was readily scaled-up to continuously produce clean H2 from 400 mL CH3OH and 200 g KOH with notably stable and high catalytic activities with only 5 ppm catalyst loading. Hence, a cumulative H2 volume of 140 L, TON of 1.2 x 105and a maximum TOF of >5400 h'1were achieved, which was, to our knowledge, is the highest TOF to date for homogeneous reforming at scale. These promising results prompted the first demonstration of a low temperature and emission-free “integrated RMFC” which showed continuous and stable performance (V = 0.55 V at A= 2.5 A) for over 27 h when the H2 from the reformer was directly fed to the fuel cell without any additional purification. Finally, the potential of the present methanol system as a reversible H2 carrier was validated by successfully converting back the C-l residues from the reforming step to methanol by “recharging” the system with H2. The present research is geared towards developing more cost-effective and heterogenized catalysts as well as an ideal “one-pot H2 battery.”. We believe that the present system satisfies the key parameters of an ideal H2 carrier. In addition, it provides the fundamental steps to a functional and industrially viable “on-board” H2 generator which could stimulate the replacement of current hazardous H2 storage and transportation methods. The demand for safer and greener hydrogen-fueled vehicles is well- documented. Moreover, the synergy of the present system with renewable and sustainable fuel technologies can also help (in the long run) in reducing humankind’s carbon footprint across the globe.

[0102] 3. Experimental Methods

[0103] 3.1. Materials and methods

[0104] All experiments were earned out under an inert atmosphere (with N2 or Ar) using standard Schlenk techniques with the exclusion of moisture unless otherwise stated. Complexes Ru- Macho (C-l, Strem Chemicals, 98%), Ru-Macho-BH (C-2, Strem Chemicals, 98%), RuHClPNP'Pr(CO) (C-4, Strem Chemicals, 98%), RuHClPNP^'(CO) (C-5, Strem Chemicals, 98%) and RiiHCIPNPc'(CO) (C-5, Strem Chemicals, 98%) were used as received without further purification. RuHClPNAfeP / i(CO) (C-3) was prepared following a reported procedure.49All catalysts were weighed inside an argon filled glove box. Lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide were purchased from commercial sources and used without further purification. Methanol (DriSolv) and DI water were sparged with N2 for 1 h prior to use.1H and13C NMR spectra were recorded on 400 or 500 MHz, Varian NMR spectrometers. ’H and13C NMR chemical shifts were determined relative to the residual solvent signals. H2 (Gilmore, ultra-high pure grade 5.0) was used without further purification. Figure 13 provided representative1H NMR spectra of the reaction mixture after hydrogenation of C-l residues of methanol-reforming in D2O.

[0105] 3.2. Standard procedure for methanol reforming in closed conditions

[0106] In a nitrogen-filled chamber, the pre-weighed amount of base, catalyst, methanol and water were added to the Monel Parr reactor equipped with a magnetic stir bar, thermocouple and piezoelectric pressure transducer. The reaction mixture was then placed in a preheated aluminum block and was stirred at 800 rpm. The internal temperature of the reaction mixture and pressure generated in the reactor were monitored through Lab VIEW software. After heating for a given amount of time, the reactor was cooled down to room temperature. The gas generated was partly collected in an airtight bag and was analyzed by GC whereas the remaining gas was slowly released.

[0107] 3.3. Standard procedure for methanol reforming at ambient pressure

[0108] The methanol-reformer was assembled as depicted in Figure 11. In a nitrogen-fdled chamber, the pre- weighed amount of base, catalyst, methanol and water were mixed and added to the Monel Parr reactor equipped with a magnetic stir bar. The reactor was then placed in an aluminum block and was stirred at 800 rpm. The reactor was attached to a water condenser and the accompanying assembly. The hotplate was heated to the desired temperature (Tset) and the internal temperature (Tint) was monitored using a thermocouple inserted in the thermowell of the reactor. The pressure releasevalve was adjusted to 10 psi. The evolution of the H2 gas was monitored using a calibrated mass flow meter (MFM) connected to the LabVIEW software. A fraction of the evolved gas was analyzed by GC at regular- intervals.

[0109] 3.4. Membrane electrode assembly (MEA) fabrication

[0110] Catalyst inks were made from 12 mg of Pt black, 3 mg of Vulcan XC72R, 750 mg of Millipore water, 75 mg of 5 wt% Nafion solution and 75 mg of isopropyl alcohol. The ink was sonicated and then painted onto a 4 cm2Toray Carbon Paper electrode (E-TEK, TGH-060, 10% wet proofing) for the anode and 4 cm2Toray Carbon Paper with a microporous layer (Sigracet 22BB) for the cathode. The catalyst inks were applied until a platinum loading of 0.5 mg / cm2was obtained. The electrodes were then dried in an oven at 110 °C. The membrane electrode assembly was prepared with Nafion-211 membrane and sandwiched between the cathode and anode and hot pressed at 140 °C for 5 min at 500 lbs.

[0111] 3.5. Reformed Methanol Fuel Cell (RMFC) Measurements

[0112] The fuel cell polarization measurements were performed using a Fuel Cell Test System 89OB (Schribner Associated). Prior to experiments the MEA was subject to a break-in or conditioning procedure similar to previously reported procedures, where several constant voltage experiments were conducted at 80 °C with oxygen and at 40 °C with air. The MEAs were then tested at 60 °C after the break-in procedure. Humidified hydrogen (from a cylinder or the coupled methanol reformer) flowed through the anode compartment at 40 mL / min at 85 °C, while humidified oxygen or air flowed through the cathode compartment at 100 or 400 mL / min, respectively, at 85 °C with relative humidity of 100%.

[0113] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.

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Claims

WHAT IS CLAIMED IS:

1. A method for producing hydrogen comprising: dehydrogenating an alcohol mixed with a metal hydroxide and / or metal oxide over a catalyst in a closed pressure reactor at a predetermined initial temperature and a predetermined initial pressure by a dehydrogenation reaction to produce gaseous H2 that is substantially free of gaseous CO2, the alcohol being mixed with the metal hydroxide and / or metal oxide to form a metal hydroxide and / or metal oxide solution, wherein the alcohol and metal hydroxide and / or metal oxide are present in a sufficient amount to develop a gauge pressure of at least 10 bar after reaction.

2. The method of claim 1, wherein a molar ratio of the alcohol to metal hydroxide and / or metal oxide is from 10 to 18.

3. The method of claim 1, wherein the alcohol is a primary alcohol, a diol, a triol, a polyol, a polyethylene glycol, or mixtures thereof.

4. The method of claim 3, wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol, glycol, 1,3-propanediol, 1,4-butanediol, glycerol, and combinations thereof.

5. The method of claim 1, wherein the metal hydroxide is an alkali hydroxide or an alkaline earth metal hydroxide.

6. The method of claim 5, wherein the alkali hydroxide is selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, rubidium hydroxide, and mixtures thereof.

7. The method of claim 6, wherein the alkali hydroxide and / or metal oxide is potassium hydroxide with a molar ratio of potassium hydroxide to metal hydroxide and / or metal oxide is from about 5 to 30.

8. The method of claim 5, wherein the alkaline earth metal hydroxide is selected from the group consisting of calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, and mixtures thereof.

9. The method of claim 1, wherein the metal hydroxide and / or metal oxide solution further includes water.

10. The method of claim 1, wherein the predetermined initial temperature is 0 to 300 degree Celsius.

11. The method of claim 1 , wherein the CO2 formed during the dehydrogenation reaction is captured by the metal hydroxide and / or metal oxide cither in-situ or in a separate step.

12. The method of claim 1, wherein the CO2 formed during the dehydrogenation reaction is captured in situ by the metal hydroxide and / or metal oxide to produce hydrogen with a CO2 content of less than 2 % by volume.

13. The method of claim 1, wherein residual CO2 formed during the dehydrogenation reaction is captured in a separate step to afford hydrogen with a CO content of less than 1 % by volume.

14. The method of claim 1, wherein the hydrogen produced includes less than 0.1% by volume of carbon-containing compounds.

15. The method of claim 1, wherein the hydrogen produced is substantially carbon free.

16. The method of claim 1, wherein the hydrogen generated produces a gauge pressure from 10 to 1000 bar17. The method of claim 1, wherein the hydrogen generated produces a gauge pressure greater than 50 bar.

18. The method of claim 1, wherein the hydrogen generated produces a gauge pressure greater than 100 bar.

19. The method of claim 1, wherein the hydrogen generated produces a gauge pressure greater than 10 bar without needing a mechanical compressor.

20. The method of claim 1, wherein the hydrogen generated produces a gauge pressure greater than 50 bar without needing a mechanical compressor.

21. The method of claim 1, wherein the catalyst is a homogeneous catalyst.

22. The method of claim 1, wherein the catalyst is a homogeneous catalyst including one or several ligands and a metallic center.

23. The method of claim 1, wherein the catalyst is a homogeneous catalyst selected from the group consisting of catalysts that include ruthenium, iridium, iron, manganese, or cobalt.

24. The method of claim 1, wherein the catalyst is a homogeneous catalyst that includes a ligand framework.

25. The method of claim 24, wherein the homogeneous catalyst ligand framework is Macho-BH, PNPZPr, PNP,p". PNPZPr, PNP^“, or PNPCv.

26. The method of claim 1, wherein the catalyst is a homogeneous catalyst including metal center and a pincer-type ligand.

27. The method of claim 26, wherein the pincer-type ligand is PNP type ligand.

28. The method of claim 1, wherein the catalyst is a homogeneous catalyst immobilized on a surface by deposition, grafting, or any other immobilization method.

29. The method of claim 1, wherein the catalyst is a heterogeneous catalyst.

30. The method of claim 1, wherein the catalyst is a heterogeneous catalyst system including a component selected from a group consisting of copper-based catalysts, indium-based catalysts, nickel-based, indium and nickel / gallium-based catalysts modified or not modified with other metals including lanthanides and / or precious metals, and combinations thereof.

31. The method of claim 1, wherein the hydrogen produced is used in a fuel cell to generate electrical energy.

32. The method of claim 1, wherein the hydrogen produced is stored for later use at gauge pressures of 0 to 300 bar.

33. The method of claim 1, wherein the hydrogen produced is stored for later use at gauge pressures of 10 to 1000 bar.

34. The method of claim 1, wherein carbonate and bicarbonate species produced during the dehydrogenation reaction are regenerated by hydrogenation to form back the alcohol and metal hydroxide and / or metal oxide.

35. A method for producing hydrogen comprising: dehydrogenating a methanol derivative mixed with a metal hydroxide and / or metal oxide over a catalyst at a predetermined initial temperature and a predetermined initial pressure to produce gaseous H2 that is substantially free of gaseous CO2.

36. The method of claim 35, wherein the methanol derivative is selected from the group consisting of dimethyl ether, formaldehyde, paraformaldehyde, formalin, trioxane, formic acid, metal formate, alkyl formate, alkyl carbonates, and mixtures thereof.

37. The method of claim 1, wherein the predetermined initial pressure is a gauge pressure from 0 to 600 bar.

38. A hydrogen generator comprising: a closed reaction vessel configured to receive a catalyst and a mixture of an alcohol and a metal hydroxide and / or metal oxide; a temperature transducer for monitoring the temperature within the reaction vessel; a pressure transducer for monitoring the pressure within the reaction vessel; and a heater for heating the reaction vessel to a predetermined initial temperature.

39. The hydrogen generator of claim 38, wherein the reaction vessel is configured to operate at a gauge pressure up to 2000 bar.

40. The hydrogen generator of claim 38, wherein the catalyst is immobilized on a support within the reaction vessel.

41. A fuel cell system, comprising: a hydrogen generator as claimed in claim any of claims 37 to 39; and a fuel cell configured to receive hydrogen produced by the hydrogen generator.

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