WO2018163004A1

WO2018163004A1 - Hydrogen production from ethylene glycol under basic conditions

Info

Publication number: WO2018163004A1
Application number: PCT/IB2018/051161
Authority: WO
Inventors: Balamurugan VIDJAYACOUMAR; Khalid Al-Bahily; Sandro Gambarotta; Indira Thapa
Original assignee: Sabic Global Technologies B.V.
Priority date: 2017-03-08
Filing date: 2018-02-23
Publication date: 2018-09-13

Abstract

Disclosed is a method of producing hydrogen from monoethylene glycol. The method includes mixing an aqueous base, monoethylene glycol, and an iridium chloride (IrCl3) catalyst solubilized therein under conditions sufficient to produce hydrogen from the ethylene glycol present in the basic homogeneous aqueous solution.

Description

HYDROGEN PRODUCTION FROM ETHYLENE GLYCOL UNDER BASIC

CONDITIONS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/468,481 filed March 8, 2017, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

A. Field of the Invention

[0002] The invention generally concerns methods for producing hydrogen gas from monoethylene glycol. In particular, an aqueous basic homogeneous composition containing monoethylene glycol, an inorganic base, and an iridium halide catalyst can be used to produce hydrogen.

B. Description of Related Art

[0003] Hydrogen (H₂) can be used in a wide variety of industries, non-limiting examples of which include oil refining, ammonia production, and methanol production. Hydrogen can be produced using diverse resources including fossil fuels, such as natural gas and coal, nuclear energy, and other renewable energy sources, such as biomass, wind, solar, geothermal, and hydro-electric power. Conventional technology produces hydrogen from steam reforming of methane as shown in the equations (1) and (2) below. The major source of the methane is from natural gas.

CH₄ + H₂0→ CO + 3H₂ (1)

CO + H₂0→ C0₂ + H₂ (2)

Due to the depletion of fossil fuels, there is a necessity to find commercially viable alternative feedstocks to meet the growing demand for hydrogen production globally. [0004] Alternative processes for hydrogen production have been proposed. Examples include water-splitting, thermal dehydrogenation of formic acid, thermal dehydrogenation of amino-boranes, and catalytic dehydrogenation of small organic molecules (e.g., glycols), and the like.

[0005] With respect to catalytic dehydrogenation of small organic molecules to produce hydrogen, there have been some attempts to use ethylene glycol. Such attempts have been performed under heterogeneous catalysis conditions using supported catalyst materials, metal oxide catalysts, or metal nanoparticle catalysts or under homogeneous catalysis conditions using metal organic ligand complexes. Further such processes require additional materials and/or use high temperatures, thereby making the processes inefficient and difficult to scale- up for mass hydrogen gas production. By way of example, Japanese Patent Application Publication No. 2015-143161 to Kenichi et al. describes the dehydration of ethylene glycol using an Ir-bipyridine ligand complex in an aqueous solvent at 100 °C. U.S. Patent Application Publication NO. 2003/0099493 to Cortright et al. describes iridium supported on silica catalyst or a unsupported iridium metal foam in an aqueous solvent at 300 °C. Davidson et al. (Dalton Transactions, 2014, 43 : 11782) describes dehydrogenation of ethylene glycol at 400 °C using supported Pt, Ni, Rh catalysts.

[0006] As discussed, the current attempts to produce hydrogen from ethylene glycol use high temperatures, heterogeneous conditions, require the use expensive catalysts, and/or use catalysts that are labor intensive to manufacture or rely on complexing with organic ligands.

SUMMARY OF THE INVENTION

[0007] A discovery has been made that provides a solution to the aforementioned problems and inefficiencies associated with the generation of hydrogen from small organic molecules such as ethylene glycol. The discovery is premised on the use of a homogenous aqueous system that includes an aqueous basic solution having an iridium halide (IrX) catalyst and ethylene glycol (e.g., hydrated monoethylene glycol) solubilized in the basic solution. Hydrogen gas can be produced directly from monoethylene glycol at mild reaction conditions (e.g., from 80 °C to 200 °C, preferably from 100 °C to 160 °C, or more preferably between 110 to 130 °C). The system is oxygen-resilient, chemically robust, and energy efficient, thereby allowing for large scale hydrogen production to meet the ever increasing hydrogen gas demands of the chemical and petrochemical industries. Also, the catalysts used in the context of the present invention do not have to be complexed with organic ligands. In particular, the process of the present invention can (1) avoid the costs associated with conventional supported catalysts (2) be operated at reduced temperatures, (3) be a homogeneous catalytic system, (4) can limit or avoid the production of by-products such as methane, and/or (5) can avoid having to use catalyst— organic ligand complexes. Without wishing to be bound by theory, it is believed that enhanced efficiency of the system is due to the fact that the H₂ evolution occurs in the homogeneous phase of the reaction mixture with an iridium halide catalyst. [0008] In one aspect of the present invention, a method of producing hydrogen from monoethylene glycol is disclosed. The method can include obtaining a basic homogeneous aqueous solution that includes monoethylene glycol, a base, and an iridium halide (e.g., IrCh) catalyst solubilized therein and producing hydrogen (H2) gas from the ethylene glycol present in the homogeneous aqueous solution. In certain aspects, the iridium halide catalyst is not complexed with an organic ligand. The basic homogeneous aqueous solution can be obtained by adding the iridium halide catalyst to a basic solution that includes the monoethylene glycol and the base. The monoethylene glycol can be hydrated ethylene glycol, in a liquid form, or in a gaseous form, or a combination thereof. In some instances, the monoethylene glycol is obtained by ethylene oxide hydrolysis. The pH can be adjusted to a pH from 8 to 14, preferably 10 to 14, and most preferably 12 to 14 using an inorganic base (e.g., NaOH or KOH). The molar ratio of monoethylene glycol to base can be 15 : 1 to 2: 1, preferably 12: 1, or more preferably 10: 1. The molar ratio of monoethylene glycol to iridium halide can be 50: 1 to 50:0.1, preferably 25 :0.1, or more preferably 50:0.1. Without wishing to be bound by theory, it is believed that a hydroxide ion replaces the halide to form an iridium— hydroxyl bond, and the iridium-hydroxyl bond reacts with the monoethylene glycol to produce H2 gas. Formate and/or glycolate can also be produced and can be subsequently reacted to produce additional hydrogen and carbon dioxide. Notably, no, or substantially no, carbon dioxide or carbon monoxide is formed in certain aspects of the present invention. Methane can be produced in small amounts or substantially small amounts. Conditions for the production of hydrogen can include heating the aqueous solution. In some instances, the solution can be heated to a temperature of 80 °C and 200 °C, preferably between 100 °C and 160 °C, or more preferably between 1 10 °C and 130 °C until a sufficient amount of hydrogen is produced (e.g., 12 to 200 hours, preferably 72 to 168 hours). In some instances, the basic homogeneous solution can be exposed to electromagnetic radiation, preferably visible light or ultraviolet light, or both, to produce H2 from the monoethylene glycol.

[0009] In another aspect of the present invention, an aqueous composition capable of producing hydrogen (H2) gas from monoethylene glycol is described. The composition can include a molar ratio of monoethylene glycol to base of 15 : 1 to 2: 1, preferably 12: 1 , or more preferably 10: 1 and a molar ratio of monoethylene glycol to iridium halide can be 50: 1 to 50:0.1, preferably 25 :0.1, or more preferably 50:0.1. The composition can include sufficient base to make the pH of the composition basic. [0010] The term "homogeneous" is defined as a reaction equilibrium in which the catalyst(s), reactants, and products are all or substantially all in the same phase (e.g., the catalysts, reactants and products are dissolved or substantially dissolved in the basic aqueous medium). [0011] "Monoethylene glycol", "ethylene glycol", 1,3-ethanediol can be used interchangeably and all have the chemical formula of HO-CH2-CH2-OH.

[0012] The term "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0013] The term "substantially" and its variations are defined to include the ranges within 10%, within 5%, within 1%, or within 0.5%.

[0014] The terms "inhibiting" or "reducing" or "preventing" or "avoiding" or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0015] The term "effective," as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0016] The use of the words "a" or "an" when used in conjunction with any of the terms "comprising," "including," "containing," or "having" in the claims, or the specification, may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0017] The words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0018] The methods of the present invention can "comprise," "consist essentially of," or "consist of particular ingredients, components, compositions, etc. disclosed throughout the specification. With respect to the transitional phase "consisting essentially of," in one non- limiting aspect, a basic and novel characteristic of the methods of the present invention are their abilities to produce hydrogen from ethylene glycol under basic conditions using an iridium halide catalyst.

[0019] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0021] FIG. 1 is a schematic of an embodiment of a reaction system of the present invention.

[0022] FIG. 2 is a graphical depiction of the dehydrogenation of monoethylene glycol using IrCh, in aqueous NaOH at 120 °C.

[0023] FIG. 3 is a graphical depiction of the products from the dehydrogenation of monoethylene glycol using IrCh, in aqueous NaOH at 120 °C.

[0024] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention provides for an efficient and scalable process for producing hydrogen gas from monoethylene glycol. The process includes mixing a homogeneous aqueous basic solution having an iridium halide catalyst (e.g., IrCh), monoethylene glycol, and a base and producing hydrogen gas from the ethylene glycol. As illustrated in non-limiting embodiments in the examples, this process allows for the efficient and scalable production of hydrogen gas. In certain instances, production of unwanted by-products such as methane can be avoided.

[0026] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections. A. Reactants and Medium for Production of Formate, Glycolate, and Hydrogen

1. Reactants

[0027] The reactants in the step of producing H₂, formate, and glycolate, can include monoethylene glycol in a gaseous form, a liquid form or a hydrated form. Monoethylene glycol is available from many commercial manufacturers, for example, Sigma Aldrich® (USA) or can be obtained from an ethylene oxide hydrolysis process. The basic reagent can include a metal hydroxide (MOH or M(OH)₂), where M is a alkali or alkaline earth metal. Non-limiting examples of alkali or alkaline earth metals include lithium, sodium, potassium, magnesium, calcium, and barium. In a preferred embodiment, the base is sodium hydroxide (NaOH). The molar ratio of small organic molecule (e.g., ethylene glycol) to base is 15: 1 to 2: 1, preferably 12: 1, or more preferably 10: 1 or 15: 1, 14: 1, 12: 1, 10: 1.2: 10: 1, 5: 1, 3 : 1, 2: 1, any range there between.

2. Catalyst

[0028] The catalyst of the present invention is an iridium halide catalyst. The halide can be a fluoride, bromide, chloride, iodide, or combinations thereof. In a preferred embodiment, the halide is chloride. The iridium can have a +3 valance state and can expand to higher valence states in situ {e.g., +4, +5, +6, and the like). In a preferred embodiment, the catalyst is IrCh. Iridium halides are available from many commercial manufacturers, for example, Sigma Aldrich® (USA). In certain instances, the catalyst is not complexed with an organic ligand prior to addition to the solution. In other instances, however, the catalyst can be complexed with an organic ligand. Non-limiting examples of organic ligands include aromatic compounds and derivatives thereof, bipyridine compounds and derivatives thereof, cyclopentadiene compounds and derivatives, petamethylcyclopentadienyl, cyclooctene and derivatives thereof, 1,5-cyclooctadiene, cyclohexyl and derivatives thereof, dimethylacetamide, N-N- dimehtylformamide, di acetyl acetonate anion (acac), butadiene, carboxylates, aminocarboxylate, and the like. 3. Medium

[0029] The production of hydrogen from monoethylene glycol can be performed in any type of medium that can solubilize the catalyst and reagents. In a preferred embodiment, the medium is water. Non-limiting examples of water include de-ionized water, salt water, river water, canal water, city canal water, combinations thereof, or the like.

B. Generation of Hydrogen

[0030] As illustrated in the Examples section, hydrogen can be produced by mixing an aqueous composition having a basic pH, monoethylene glycol, and an iridium halide catalyst. In preferred instances, the catalyst and the monoethylene glycol are partially or fully solubilized within the aqueous composition. FIG. 1 is a schematic of an embodiment of a reaction system 100 for producing hydrogen and optionally, formate and glycolate, from ethylene glycol. System 100 includes reactor 102, aqueous mixture 104, and mixer 106. Reactor 102 can be transparent, translucent, or opaque. The aqueous homogeneous mixture 104 can include the aqueous ethylene glycol, iridium halide catalyst, and a base described throughout the specification. Mixer 106 can agitate the mixture to assist in dissolution of the ethylene glycol, iridium halide catalyst, and base. The iridium halide catalyst can be used to catalyze the production of hydrogen, formate and glycolate from the ethylene glycol as shown in reaction pathway below:

Glycolate Basic aqueous homogeneous mixture 104 can be heated to heated to a temperature between 80 °C and 200 °C, preferably between 100 °C and 160 °C, or more preferably between 110 °C and 130 °C, or 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, 155 °C, 160 °C, 165 °C, 170 °C, 180 °C, 185 °C, 190 °C, 195 °C, 200 °C, or any value or range there between until a sufficient amount of hydrogen is generated or the ethylene glycol is sufficiently depleted. For example, basic aqueous homogeneous mixture 104 can be heated at the desired temperature of 12 to 200 hours, 50 to 180 hours, 72 to 168 hours, or 90 to 150 hours. In some embodiments, ethylene glycol is continuously fed to reactor 102. In some embodiments, the solution can be irradiated with electromagnetic radiation, preferably visible light or ultraviolet light, or both. [0031] Without wishing to be bound by the theory, it is believed that the production of hydrogen occurs in the homogeneous phase of the aqueous mixture. The spent iridium halide catalyst can precipitate or be precipitated from the solution by changing the pH of the solution (e.g., addition of base to increase the pH of the solution). The resulting precipitate can be removed, or substantially removed, through known solid/liquid filtration methods (e.g., centrifugation, filtration, gravity settling, etc.). In some embodiments, the iridium halide catalyst is not removed or is partially removed from the solution. The formate (or formic acid), or glycolate (or glycolic acid), which can also be dissolved in the solution, can then be used as a carbon source for production of other compounds (e.g., oxalates and/or more monoethylene glycol).

[0032] Notably, and in one non-limiting embodiment, no carbon dioxide, carbon monoxide, or methane is formed during the production of hydrogen and, optionally formate and/or glycolate. Thus, the process can be considered a "green" process. Further, the efficiency of system 100 allows for one to use ethylene glycol as a hydrogen storage agent and formate and/or glycolate as carbon sources for homologation reactions. This solves some of the current problems in the hydrogen production industry relating to the transport or storage of hydrogen gas.

EXAMPLES

[0033] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.

Materials and Product Analysis [0034] Materials. Monoethylene glycol was purchased from Sigma-Aldrich® (Canada) and iridium chloride was purchased from Strem Chemicals (USA). Chemicals were used without further purification. If not specifically mentioned, all reactions were carried out in deionized water without degassing or other modifications.

[0035] Product Analysis. Gas identification and detection was carried out with an Agilent 7820 A GC equipped with a thermal conductivity detector (GC-TCD), using an Agilent GS-Carbon Plot column for (CO2) or Agilent HP-Molesieve column (for all other gases). Reaction mixtures were analyzed by Bruker Avance II spectrometer at 400 MHz for ¾ and 100 MHz for C using 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid sodium salt (98 atom % D, Sigma Aldrich®) as a reference standard for quantitation of the products in D2O (99.9 atom % D, Sigma Aldrich®).

Example 1

(Production of Hydrogen from Monoethylene Glycol)

[0036] Monoethylene glycol (MEG, 15 mL, 268 mmol) was charged into a 100 mL round bottom flask fitted with a condenser and diluted with water (35 mL) and NaOH (lg) was added. The IrCb catalyst (150 mg, 0.5 mmol) was added and the resultant solution was heated to 120 °C reflux with a water condenser for up to 192 h. The IrCb catalyst was not complexed with an organic ligand. Gas produced from the reaction was collected in a cylinder and analyzed by GC-TCD while the resulting reaction mixture was analyzed by MR. The millimolar amounts of monoethylene glycol, hydrogen, methane, sodium formate, sodium glycolate produced over time is listed in Table 1.

Table 1

FIG. 2 is a graphical depiction of the results listed in Table 1. FIG. 3 is a graphical depiction of the products listed in Table 1. As determined from the data, hydrogen can be produced from a homogeneous basic composition of an iridium halide catalyst and ethylene glycol.

Claims

1. A method of producing hydrogen gas (H2) from monoethylene glycol, the method comprising:

obtaining a basic homogenous aqueous solution comprising monoethylene glycol, a base, and an iridium halide catalyst solubilized therein; and

producing H2 from the monoethylene glycol present in the basic homogeneous aqueous solution.

2. The method of claim 1, wherein the iridium halide catalyst is IrCh.

3. The method of any one of claims 1 to 2, wherein the basic homogenous aqueous composition is obtained by adding the iridium halide catalyst to a basic solution comprising the monoethylene glycol and the base.

4. The method of any preceding claim, wherein the base is a metal hydroxide, preferably sodium hydroxide (NaOH).

5. The method of any preceding claim, wherein the basic homogenous aqueous solution has a pH from 8 to 14, preferably 10 to 14, and most preferably 12 to 14.

6. The method of any preceding claim, further comprising heating basic homogenous aqueous solution to produce H2 from the monoethylene glycol.

7. The method of claim 6, wherein the basic homogenous aqueous solution is heated to a temperature between 80 °C and 200 °C, preferably between 100 °C and 160 °C, or more preferably between 110 °C and 130 °C.

8. The method of any preceding claim, further comprising exposing the basic homogeneous aqueous solution to electromagnetic radiation, preferably visible light or ultraviolet light, or both, to produce H2 from the monoethylene glycol.

9. The method of any preceding claim, wherein the basic homogenous aqueous solution reacts to produce H2 for 12 to 200 hours, preferably 72 to 168 hours

10. The method of any preceding claim, wherein the basic homogenous aqueous solution comprises a molar ratio of monoethylene glycol to base of 10: 1 to 2: 1, preferably 10: 1.2, or more preferably 10: 1.

11. The method of any preceding claim, wherein the basic homogenous aqueous solution comprises a molar ratio of monoethylene glycol to iridium halide of 50: 1 preferably 25:0.1, or more preferably 50:0.1.

12. The method of any preceding claim, wherein methane (CH₄), a formate, and a glycolate are also produced.

13. The method of any preceding claim, wherein the monoethylene glycol used in the method is obtained by ethylene oxide hydrolysis.

14. The method of any preceding claim, wherein the monoethylene glycol is in a liquid form.

15. A basic homogeneous aqueous solution comprising monoethylene glycol, a base, and an iridium halide catalyst solubilized therein.

16. The basic homogeneous aqueous solution of claim 15, wherein the iridium halide catalyst is IrCh.

17. The basic homogeneous aqueous solution of any one of claims 15 to 16, wherein the base is a metal hydroxide, preferably sodium hydroxide (NaOH).

18. The basic homogeneous aqueous solution of any one of claims 15 to 17, wherein the basic homogeneous aqueous solution has a pH from 8 to 14, preferably 10 to 14, and most preferably 12 to 14.

19. The basic homogeneous aqueous solution of any one of claims 15 to 18, wherein the basic homogenous aqueous solution has a temperature between 80 °C and 200 °C, preferably between 100 °C and 160 °C, or more preferably between 110 °C and 130 °C.

20. The basic homogeneous aqueous solution of any one of claims 14 to 19, comprising:

(a) a molar ratio of monoethylene glycol to base of 15: 1, preferably 12: 1, or more preferably 10: 1; and/or

(b) a molar ratio of monoethylene glycol to iridium halide of 50: 1, preferably 25:0.01, or more preferably 50:0.1.