Ovonic Battery Company, a subsidiary of Energy Conversion Devices (ECD Ovonics), has been awarded a $900,000 contract by Xcel Energy to support R&D of a new base-facilitated process for reforming renewable fuels, such as bioethanol and biomethanol, to produce hydrogen for use in fuel cells or engines.
This fundamentally new approach to hydrocarbon reforming dramatically reduces the required reaction temperature and avoids the generation of CO2 as a byproduct.
The reforming process can thereby become potentially simpler and cheaper (both in operating cost and capital investment); less energy-intensive; and cleaner. The program funded by Xcel will transfer this process from research to pilot level, examining the commercialization feasibility from both a technical and an economic perspective.
The Ovonic process, around which it has filed a number of patent applications, uses the chemical or electrochemical reactions of biofuels (or other biomass or carbonaceous materials—e.g., coal) with bases in which carbonate and/or bicarbonate compounds are produced as a by-product.
The process includes a carbonate or bicarbonate recycling process in which the carbonate or bicarbonate by-product is transformed to a base that can subsequently be further reacted with the feedstock to produce hydrogen.
Using a thermodynamic analysis, the Ovonic researchers determined that many hydrocarbons and oxygenated hydrocarbons react spontaneously with a base or basic aqueous solution to form hydrogen gas at less extreme conditions than those in steam reformation reactions.
In some of their work, the process led to the formation of hydrogen gas from a liquid phase reaction mixture, in some cases at room temperature, where hydrogen was the only gaseous product and thus was readily recoverable without the need for a gas phase separation step.
Furthermore, the reactions operate through the formation of carbonate ion or bicarbonate ion and thus avoid the production of the greenhouse gases CO and CO2.
In short, the inclusion of a base creates a new reaction pathway for the formation of hydrogen gas at lower temperatures than are needed for corresponding steam reformation processes and without the generation of CO2.
|Reactions for the Reforming of Ethanol (C2H5OH) into Hydrogen|
|Source: Ovonic Battery Company|
|(1)||C2H5OH(l) + 3H2O(l) → 6H2(g) + 2CO2(g)||23,950|
|(2)||C2H5OH(l) + 2OH-(aq) + 3H2O(l) → 6H2(g) +2HCO-(aq)||7,040|
|(3)||C2H5OH(l) + 4OH-(aq) + H2O(l) → 6H2(g) +2CO32-(aq)||-2,970|
As an example of the work, in the table above, reaction (1) represents the conventional reforming of ethanol and reactions (2) and (3) represent base-facilitated reformation reactions according to the Ovonic process.
Reactions (2) and (3) differ with respect to the relative amounts of hydroxide ion and ethanol.
Δ G is the Gibbs free energy of reaction for each of the reactions at standard conditions (25º C, 1 atmosphere and unit activity of reactants and products). Gibbs free energy is an indicator of the thermodynamic spontaneity of a chemical reaction. The more negative (or less positive) the Gibbs free energy is, the more spontaneous is the reaction.
The conventional reformation reaction (1) is a non-spontaneous reaction at standard conditions. The base-facilitated reformation reaction (2) is also non-spontaneous, but is more spontaneous than reaction (1) (and would become spontaneous at a lower temperature than reaction (1)).
Put another way, the first base-facilitated reaction is less non-spontaneous than the conventional reformation reaction. Further addition of base leads to a further decrease in the Gibbs free energy and ultimately provides a spontaneous reaction at standard conditions as exemplified by reaction (3) above.
The process can, in principle, be applied to a wide range of feedstocks, some of which will clearly perform better than others.
Xcel Energy is a major US electricity and natural gas company with regulated operations in 10 Western and Midwestern states. In terms of customers, it is the fourth largest combination natural gas and electricity company in the nation.
“Base-facilitated production of hydrogen from biomass”; US Patent Application 2005163704