WO2009132381A1

WO2009132381A1 - A continuous system for production of hydrogen

Info

Publication number: WO2009132381A1
Application number: PCT/AU2009/000514
Authority: WO
Inventors: Neville Charles Stephenson; Geoffrey David Will
Original assignee: Alternative Energy International Ltd
Priority date: 2008-04-28
Filing date: 2009-04-23
Publication date: 2009-11-05

Abstract

A continuous system for the production of hydrogen by catalytic electrochemical decomposition of water and regeneration of the catalysts used in the production, the system including at least one reaction vessel containing a catalyst material, the at least one reaction vessel having at least one inlet and at least one outlet, the at least one reaction vessel operable in a production mode in which steam is input into the reaction vessel and product mixture is output and a regeneration mode in which gas including at least one global warming constituent is input into the reaction vessel and regeneration off gas is output, wherein once the system has reached operation conditions in the production mode, the input steam is heated prior to entry into the at least one reaction vessel by heat transfer with at least one of the product mixture or the regeneration off gas.

Description

A CONTINUOUS SYSTEM FOR PRODUCTION OF HYDROGEN

Field of the Invention.

The present invention relates to systems for the production of hydrogen and particularly to continuous system for the efficient reduction of steam to hydrogen and inorganic salts.

In this application, the term "catalyst" is used in a wide sense. Normally a catalyst remains unchanged in a chemical reaction and is used to facilitate their reaction. In this application, the "catalyst" used to dissociate water is itself initially involved in the chemistry and but can be regenerated to its original stoichiometry by processes described in this specification. The end result is the dissociation of water into its elemental components and the recovery of the catalyst material for reuse.

Background Art. Previous patent applications PCT/AU00/00446, and PCT/AU2004/001080, Australian Provisional Applications 2007903150 and 2008900212, describe electrochemical processes and equipment for the reduction of steam to hydrogen and the regeneration of the catalysts used in these processes, this providing a carbon-free pathway for the inexpensive production of hydrogen from water. The equipment described in Provisional Application 2007903150 involved a batch reactor wherein a pre-filled fuel canister is installed into the system to function as the reactor vessel until the iron based fuel material contained in the pre- filled canister is sufficiently exhausted. By provision of a pre-filled canister, the spent fuel canister can be removed and a replacement canister installed. The spent fuel canister is then connected to a reconstitution system for reconstitution of the fuel particles using for example, intermittent alternative energy sources. Australian Provisional Application 2008900212 describes a closed loop system for the regeneration of catalyst materials and provides a genuine carbon-free pathway for the storage and delivery of energy. It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country. Summary of the Invention.

The present invention is directed to a continuous system for the production of hydrogen, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

With the foregoing in view, the present invention in one form, resides broadly in a continuous system for the production of hydrogen by catalytic electrochemical decomposition of water and regeneration of the catalysts used in the production, the system including at least one reaction vessel containing a catalyst material, the at least one reaction vessel having at least one inlet and at least one outlet, the at least one reaction vessel operable in a production mode in which steam is input into the reaction vessel and product mixture is output and a regeneration mode in which gas including at least one global warming constituent is input into the reaction vessel and regeneration off gas is output, wherein once the system has reached operation conditions in the production mode, the input steam is heated prior to entry into the at least one reaction vessel by heat transfer with at least one of the product mixture or the regeneration off gas.

Whereas previous applications have described a batch reactor system where the spent fuel can be removed and regenerated using alternative energy sources, this specification describes a continuous feed system which not only provides a continuous supply of hydrogen by the electrochemical decomposition of steam, but also incorporates a regeneration chamber for the in situ reduction of the spent oxidants for their continued use in hydrogen production from steam.

Electrochemical decomposition of water is the only process for producing hydrogen that does not require an external energy input. These exothermic reactions utilize the energy incumbent in the oxidant, according to the following sample reaction system:-

Fe + 3/2 EbO → 1/2 Fe_* O_* + 3/2 ft OH - 49 KJ

Fe + 4/3 BO -> 1/3 Fe= 04 + 4/3 H_* OH - 50 KJ Thus, when 55.5 grams of iron converts to Fe* O* and H_^, 49KJ of heat is exothermed and 363KJ energy is stored in the hydrogen, a total of 412KJ.

When Fe_* O_* is reduced to iron, using, say, methane, the reaction proceeds as follows:- 1/2 Fe, O + 3/8 CH₄ → Fe + 3/8 CO + ³A HO OH +110.8KJ

Thus, 110.8KJ of energy is required, which is less than the 412KJ made available during the reduction of steam. It is to be noted that only 6 grams of methane are needed to reduce 80 grams of haematite to metallic iron. The basis of the present process is to pass biogas, or flue gas, through the catalyst material which have been used in electrochemical decomposition of water to produce hydrogen (whether a fixed bed of porous iron oxide, or iron oxide distributed on inert particles or in a proprietary, iron-based pellet form), to regenerate the catalyst material during which the reduction of the iron oxide occurs together with oxidation of the global warming components of the biogas. Upon completion of the process, the reaction vessel can then be flushed with high temperature steam which is reduced to hydrogen by the reduced oxides.

The two processes, namely hydrogen production and catalyst regeneration, can occur simultaneously in adjacent reaction vessels so that hydrogen production in one cylinder is accompanied by reduction of the iron oxides in the adjacent cylinder. There will therefore, normally be more than one reaction vessel provided in the system.

Each reaction vessel will normally have attendant pipework and controls to allow selective communication with desired inputs and outputs. For example, each reaction vessel will typically be capable of accepting inputs from a source of gas including greenhouse or global warming constituents whilst operating in the regeneration mode. A typical example of gases such as these are those expelled from a gasifier or power station. Gases which may be input to the reaction vessel during regeneration include carbon monoxide, hydrogen, carbon dioxide, water vapour, methane, any C_xH_y gas or depending upon the source, mixtures of these.

Appropriate conveying means may be provided in order to move the gas to, and through, the reaction vessel such as a fan, or blower for example.

Also dependent upon the source, the gas supplied during the regeneration mode of the system will typically be provided at an elevated temperature. Preferably, the input gas will be provided at the highest temperature possible during the regeneration mode, however the temperature may be adjusted to suit the conditions within the reaction vessel to optimise regeneration. An appropriate gas velocity will be provided through the reaction vessel, particularly if fluidisation of the catalyst material is required.

Normally the inlet to the or each reaction vessel will be provided with a valve assembly allowing the selective input of regeneration gas for the regeneration mode or saturated steam for the production mode.

Normally, the outlet from the or each reaction vessel will be provided with a valve assembly allowing direction of the regeneration off-gas to a first outlet from the system when operating in the regeneration mode or a hydrogen/steam mixture to post production finishing processes when operating in the production mode.

Typically, the regeneration off gas will be used to heat the steam/water which will then be introduced into a reaction vessel operating in the production mode.

This well preferably cool the regeneration off gas which may then be vented to the atmosphere. Appropriate conveying means will typically be provided such as a fan or blower or the like.

The hydrogen/steam mixture exiting any reaction vessels operating in the production mode is typically directed to postproduction finishing. Additionally, the hydrogen/steam mixture may be used to preheat steam/water for feed into a reaction vessel operating in the production mode. Typically, pre-heating of the feed steam/water using the hydrogen/steam mixture will occur prior to the preheating using the regeneration off gas. Typically, a heat exchanger is used for this purpose. One or more recycle streams may be provided.

As a result of the hydrogen/steam mixture being used to preheat the feed steam/water, the hydrogen/steam mixture exiting the heat exchanger will typically be of lower water content and higher hydrogen content than the mixture when it enters the heat exchanger. The exiting mixture is then typically passed through a gas scrubber to remove any undesirable gases which may remain in the product mixture, such as hydrogen sulphide, carbon monoxide, or carbon dioxide following which the finished hydrogen gas produced, is typically directed to a low- pressure hydrogen storage vessel.

Note the heat of each reaction described above is at a reference temperature of 25⁰C and are less exothermic (or less endothermic in the case of FeO) at higher temperatures. At 25°C the reactions are slow and the nature of the oxide products varies according to the physical conditions.

Apart from the expected magnetite (Fe₃O₄) and hematite (Fe₂O₃) oxide forms, ferrous iron oxide an other forms such as iron hydroxides, for example Fe(OH)₃.xH₂0 may also form. The nature of the metallic products formed is typically dependant upon conditions such as wetness, operating temperature, operating pressure, time and the influence of contaminants in the feed iron. hi a single pass, roughly 25% of the steam will generally be converted to hydrogen, depending primarily on reaction temperature and extent of fuel conversion. Heat will also normally be liberated by the reactions, so that the product gas will be hotter than the reaction steam. This excess heat can be used to pre-heat the inlet steam or be retained in-system to maintain the temperature of the reactants.

The steam/hydrogen product mixture produced in the production mode is preferably partly cooled by exchange with the incoming reaction steam or water via a heat exchanger. The steam is condensed from the steam/hydrogen mixture in. Heat is transferred from the product mixture to deionised water which will preferably be provided in a lower part of each vessel, thereby generating the required steam and recycling enough heat to minimise the need for the addition of external heat. The condensate saturation temperature will be a function of the system pressure and thus is expected to increase up to approximately 150 - 180°C after the initial start-up period.

Condensed water vapour can be separated from the hydrogen product in a condensate separator and recycled to the steam generator via the condensate holding tank and condensate recycle pump. The controls in the condensate recycle system will normally influence how much condensate is recycled and to which part of the system generation circuit, thereby providing temperature control to the reactor vessel, which may otherwise tend towards thermal run-away.

The vapour condenser and steam generator are preferably integrated as a single (modular) unit operation. Typically, counter current heat exchange will occur between the hydrogen/steam mixture and the water/steam in the heat exchanger, hi this manner, the final condensing temperature can be minimised while preserving the heat in the system.

The product hydrogen gas passes on to the hydrogen holding tank for further use or treatment. The hydrogen is stored at the final system pressure, which will preferably not be greater than 1000 kPag. This product is deemed as "wet" because the dew point of the moisture will be not lower than the temperature of the tank, which will be influenced by the temperature of the gas coming from the condensate separator. In contrast, industrial hydrogen gas is typically expected to have a moisture dew point of somewhat less than -20°C.

The fuel will normally be iron particulate material. Other materials may be used for example a high surface area porous iron particulate. Reconstitution of reaction products

The chemical products produced at the catalyzed metallic surfaces are essentially oxides. These chemical products will generally be reconstituted in the present system in order to be at least partially recovered either for re-use in the system or for sale.

These (generally) insoluble compounds can be reduced to metal by a number of well known methods such as the formation of soluble salts, for example, nitrates and subsequent recovery by electrolysis. Commonly used industrial methods presently use carbon (coke) or organics such as methane. However, these systems are undesirable due to the formation of oxides of carbon which are a contributor to global warming.

Preferably, the thermal or electrochemical decomposition of the water for hydrogen production and the regeneration of the catalyst will take place in the same reaction vessel. The input of high energy steam will typically drive the decomposition reaction system(s) producing the hydrogen in a first direction and the input of the high temperature biogas or flue gas containing global warming constituents will typically drive the reaction system(s) in the opposite direction. The reaction vessel will therefore preferably be operable in a hydrogen production condition and a catalyst regeneration condition.

Normally, the operating conditions in the reaction vessel will be adjusted to maximise the hydrogen production in the production condition and to maximise the electrodeposition or regeneration of the catalyst material in the regeneration condition.

The catalyst will typically be an iron complex but may take other forms, such as transition metals, their complexes or suitable electro-positive and amphoteric elements. The invention is not limited to the type of catalyst which it is used to regenerate.

Brief Description of the Drawings.

Various embodiments of the invention will be described with reference to the following drawings, in which:

Figure 1 is a schematic unit process flow diagram of a continuous hydrogen steam-iron process according to a preferred aspect of the present invention.

Figure 2 is a process flow diagram of a continuous hydrogen steam-iron process according to a further preferred aspect of the present invention. Figure 3 is a process flow diagram of a continuous hydrogen steam-iron process according to yet a further preferred aspect of the present invention. Detailed Description of the Preferred Embodiment. According to a particularly preferred embodiment, a continuous system for the production of hydrogen is provided. The preferred embodiment of the continuous system for the production of hydrogen by catalytic electrochemical decomposition of water and regeneration of the catalysts used in the production illustrated includes a pair of reactors 10 each containing a catalyst material. Each reactor has an lower inlet 12 and an upper outlet 13 and is operable in a production mode in which steam is input into a reactor and product mixture is output and a regeneration mode in which gas including global warming constituents is input into a second reactor and regeneration off gas is output. Therefore, according to the illustrated embodiment, one reactor is operating in each mode.

The two most important vessels in the preferred embodiment are the reactors 10 and the vapour condenser/steam generator 11. In this discussion, each of the reaction vessels is designated with reference numeral "10" with the distinction between them being their respective operating mode.

The reactors 10 are each pre-filled with an appropriate weight of particulate iron fuel. The inlet to each reactor is provided with a valve, V-I, V-2 allowing the a selective input regeneration gas for the regeneration mode, sourced from a gasifier 14 in the illustrated embodiment, or saturated steam for the production mode from the condenser 11. The outlet from each reaction vessel is provided with a valve V-3, V-4 allowing direction of the regeneration off-gas to a stack outlet from the system when operating in the regeneration mode or hydrogen/steam mixture post production finishing processes when operating in the production mode. According to the illustrated embodiment, the regeneration off gas is firstly mixed with combustion air used to heat the steam/water via the Heat Recovery Steam Generator (HRSG) 17, and the heated steam/water is then introduced into the reactor 10 operating in the production mode. This cools the regeneration off gas prior to venting to the atmosphere. Appropriate conveying means is provided such as a fan 16 or blower or the like.

The hydrogen/steam mixture exiting the reactor 1- operating in the production mode is typically directed to postproduction finishing. Additionally, the hydrogen/steam mixture may be used to preheat steam/water for feed into a reactor operating in the production mode prior to finishing. According to the illustrated embodiment, the condenser 11 is used for this purpose.

Due to the gas velocities in the reactors required to fluidise the bed of fuel particles, it is expected that there will be some level solids carry over. Any particulate carryover will generally be filtered out of the product gas by a sintered plate at the top of the reaction vessel. The plate is normally retained in a small lip in the top flange of the vessel and held down and sealed against the mating flange.

Fluidisation of the reactor bed will not only enhance the passage of the reaction steam through the bed, but helps to reduce short-circuiting, reduces the potential for particle agglomeration and typically assists in the removal of the reaction inhibiting oxide layer from partially reacted particles. The steam circuit of the system of the illustrated embodiment, that is the input side of reactors will operate at a higher pressure than the steam/hydrogen circuit or outlet side of the reactors, so any leaks will usually cause dilution of the product gas rather than hydrogen recycle into the reaction steam. If such a leak in severe enough it will eventually result in a reduction in steam supply to the reactor causing a loss of reactivity, either due to a loss of pressure differential and/or as a result of overloading the vapour condenser. Leakage events are to be determined from a loss of pressure differential between the steam/hydrogen circuit and the steam supply circuit. During startup, the reactor vessels can be purged with dry nitrogen or with the biogas or flue gas from the gasifier 14. This ensures that any air and moisture are displaced from the canister. As the steam supply heats up, and pressurizes the steam system, a mixture of nitrogen and steam enters the reactor via the steam inlet ports on the filter vessel. This mixing of dry nitrogen and steam is continued until the reaction temperature exceeds the saturation temperature of the reaction steam. Apart from eliminating explosion risks, this action reduces the risk of iron hydroxides forming and the presence of liquid water, as these may cause particle agglomeration and loss of reactive surface area. The steam sourced from the steam generator during startup is heated by two electric elements. One is immersed in the bottom of the vapour condenser/steam generator and generates saturated vapour, and the other is located in the top of the vapour condenser/steam generator to superheat the vapour as condensation is undesirable downstream of the steam generator. The steam can be recycled between the condenser and the steam generator until the steam is superheated in excess of 50° C. Electric heating continues until a minimum reaction steam temperature is achieved, namely approximately 450°C.

To achieve shutdown, all external heating is shut down and the reaction steam is quenched to approximately 250°C using an attemperation control system, until the reactor temperature falls below approximately 320°C. At this point, a steam bypass valve can be opened to divert the steam away from the reactor and all remaining cooling/purging of the reactor vessel can be completed with nitrogen.

As stated above, the other important process steps in the system is the vapour condenser and steam generation heat exchanger steps which are illustrated in Figure 1.

The steam/hydrogen product gas is preferably partly cooled by exchange with the feedwater via heat exchanger arrangement. The steam is condensed from the steam/hydrogen mixture prior to storage of the produced hydrogen. Heat is transferred from steam in the product mixture initially to the feed, deionised water thereby generating the required steam and recycling enough heat to minimise the need for the addition of external heat into the system. The condensate saturation temperature will be a function of the system pressure and thus is expected to increase up to approximately 150 - 180⁰C after the initial start-up period. Condensed water vapour is separated from the hydrogen product in the condenser/separator and may be recycled to the steam generator via a condensate holding tank and condensate recycle pump (not shown). The controls in the condensate recycle system influence how much condensate is recycled and to which part of the system generation circuit, thereby providing temperature control to the reactor vessels, which may otherwise tend towards thermal run-away.

Typically, counter current heat exchange will occur between the hydrogen/steam mixture and the water/steam in the condenser/separator. In this manner, the final condensing temperature can be minimised while preserving the heat in the system.

The product hydrogen gas passes through a gas scrubber 18 to separate undesirable gas constituents such as hydrogen sulfide (H₂S), carbon monoxide (CO) and carbon dioxide (CO₂) prior to passing on to the low pressure hydrogen storage 19.

The hydrogen is stored at the final system pressure, which will preferably not be greater than 1000 kPag. This product is deemed as "wet" because the dew point of the moisture will be not lower than the temperature of the tank, which will be influenced by the temperature of the gas coming from the condensate separator. In contrast, industrial hydrogen gas is typically expected to have a moisture dew point of somewhat less than -2O⁰C. The cooling of the steam/hydrogen mixture causes condensation of the steam vapour until the saturation temperature at that operating pressure is reached. For a 1000 kPag operating pressure, this is approximately 184⁰C. The condensate is preferably returned to the condenser/separator by the condensate return pump. Retention of condensate is used as a secondary means to control the reactor temperature, that is, retaining condensate will result in increased steam flow as the condenser water level falls and the temperature rises.

The primary means for temperature control in the reaction is through the removal of condensate to the reaction steam, that is steam attemperation by progressively diverting the condensate to a spray nozzle installed in the vapour condenser/steam generator. The final steam temperature exiting the vapour condenser/steam generator is monitored to ensure it does not fall below 250°C in order to avoid condensate droplet formation. It is important that the system is operated so that it does not result in large thermal shocks, hence the maximum condensate flow is limited through appropriate pipe size selection and the configuration and operation of the automatic control system.

Electric heating elements in both upper and lower sections of the condenser/separator may be provided for use in start-up. The lower elements generate saturated steam that the other element then superheats.

The use of an electric heating system for start-up allows more precise control of heating rates and peak component temperatures. To some degree this is inherently managed through the appropriate sizing of the heating elements. For example, using a 3,200 W lower element and a 1200 W upper element limits the maximum thermal ramp up rate to 4.4 kW.

During startup, and to a lesser extent during shutdown, it is important not to allow condensation to occur inside the reactor or downstream of the reactor, as liquid water may not pass through the filter elements at the necessary rate and entrained water droplets traveling at high velocity may also cause damage to the components. The presence of liquid water may also cause the development of hydroxides or corrosion products that may adversely affect both the vessel and the filter elements. Hence, the steam is initially recirculated through the condenser during startup. During this time, the reactor can also be electrically heated. Once the two vessels have been heated to approximately 220°C, steam is allowed to pass to the reactor to continue the heating sequence.

As the system ramps up, the combination of increased condenser temperature and hydrogen formation reactions will result in the system pressure rising until the operating pressure of 1000 kPa is achieved.

The embodiments of the present invention illustrated in Figure 2 and Figure 3, more complete plant flow diagrams. A pair of alternatives are illustrated in Figure 2 and Figure 3. In particular, the alternatives illustrated basically differ due to the position of valves V-1201 to V-1204.

As illustrated, the first alternative, illustrated in Figure 2 has valves V- 1201 to V-1204 positioned after the solid precipitator rather than directly after the reactor as is illustrated in the second alternative, in Figure 3. The first alternative is more preferred of the two options as valves V-1201 to V-1204 may be damaged in the second alternative and by solid particles fluidised in the reactor/mixer and carried out of the exit by the gas. A list of the major components, the description, and other salient information before the alternatives illustrated in Figure 2 and Figure 3 is as follows:

In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

Claims

Claim

1. A continuous system for the production of hydrogen by catalytic electrochemical decomposition of water and regeneration of the catalysts used in the production, the system including at least one reaction vessel containing a catalyst material, the at least one reaction vessel having at least one inlet and at least one outlet, the at least one reaction vessel operable in a production mode in which steam is input into the reaction vessel and product mixture is output and a regeneration mode in which gas including at least one global warming constituent is input into the reaction vessel and regeneration off gas is output, wherein once the system has reached operation conditions in the production mode, the input steam is heated prior to entry into the at least one reaction vessel by heat transfer with at least one of the product mixture or the regeneration off gas.

2. A continuous system for the production of hydrogen as claimed in claim 1 wherein the gas used in the regeneration mode is biogas, or flue gas,

3. A continuous system for the production of hydrogen as claimed in claim 1 or claim 2 wherein each reaction vessel contains a bed of porous metal oxide, metal oxide distributed on inert particles or metal-based pellet form.

4. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein at least a pair of reactor vessels is provided one operating in hydrogen production mode and one operating in catalyst regeneration mode simultaneously.

5. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein the gas supplied during the regeneration mode of the system is provided at an elevated temperature.

6. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein an appropriate gas velocity is provided through the reaction vessel to fluidise the bed of the catalyst material.

7. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein the regeneration off gas is used to heat the steam/water prior to introduction into a reaction vessel operating in the production mode.

8. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein the product mixture is used to preheat steam/water for feed into a reaction vessel operating in the production mode.

9. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein the catalyst material is oxidised in the production mode to form oxide products, the particular type of which is optimised by adjusting any one or more of wetness, operating temperature, operating pressure, time and the influence of contaminants in the feed catalyst material.

10. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein a portion of the heat liberated when in the production mode and a portion of which is retained in-system to maintain the temperature of the reactants.

11. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein water is provided in a lower part of each reaction vessel, thereby generating the required steam by absorbing heat from the reactions in the vessel in the production mode and recycling enough heat to minimise the need for the addition of external heat to the reaction vessel.

12. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein a vapour condenser and steam generator are provided integrated as a single (modular) unit operation.

13. A continuous system for the production of hydrogen as claimed in claim 12 wherein counter current heat exchange occurs between the product mixture and the intlet water/steam in the vapour condenser and steam generator.

14. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein the product mixture undergoes separation to isolate the hydrogen gas which is stored at the final system pressure.

15. A continuous system for the production of hydrogen as claimed in claim 4 wherein each reaction vessel is operable in a hydrogen production condition and a catalyst regeneration condition.

16. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein operating conditions in each reaction vessel are adjusted to maximise the hydrogen production in the production condition and to maximise the electrodeposition or regeneration of the catalyst material in the regeneration condition.

17. A continuous system for the production of hydrogen as claimed in any one of the preceding claims wherein the catalyst material is chosen from the group of iron complexes, transition metals, transition metal complexes, electro-positive and amphoteric elements.