Patent Application
20110162975
The planet Earth is currently plagued by two major problems having severe effects on it and its inhabitants, namely:
An object of this invention is to reduce these problems and thus improve the future of the world.
The increase in production of fossil fuel utilizing engines has resulted in excessive demand for crude oil in turn resulting in excessively high prices. The consumption of these fuels has increased the amount of carbon dioxide produced which has led to global warming. The absorbtion of carbon dioxide by trees and resulting release of oxygen has been debilitated by the removal of extensive forests. This imbalance has thrown and continues to cumulatively throw the world's ecology out of kilter.
Efforts to improve efficiencies of engines and reduce wastage of fossil fuel products have little chance of improving the situation because of exponentially growing populations and their aspirations. Other technologies are actively being sought.
Ways to address the problems mentioned above include:
It is an object of this invention to provide a process and apparatus which contributes to the above reductions and further provides a chemical raw material feedstock for the production of hydrocarbons, including fuels.
THIS invention relates to a process and apparatus for the production of hydrogen, oxygen and hydrocarbons from carbon dioxide and water.
A process for the production of hydrogen, oxygen and hydrocarbons from carbon dioxide and water includes the steps of:
The separation of positively charged hydrogen and carbon ions from negatively charged oxygen ions is conveniently achieved by the migration of negatively charged oxygen ions to the positive electrode and migration of positively charged hydrogen and carbon ions to the negative electrode.
The liquid state of steps (b), (c) and (d) may be achieved by conducting these steps in a chamber under high pressure and at a suitable temperature. For example, steps (b), (c) and (d) may be conducted in a chamber/s at a pressure of from 5.1 to 1000 atm, preferably from 5.1 atm to 200 atm, more preferably from 5.1 to 150 atm, most preferably 140 atm and a temperature above 0° C. to 500° C., preferably from 100° C. to 400° C.
The voltage applied across the positive electrode and the negative electrode in step (b) may be from 12 to 380v, preferably from 12 to 240v, more preferably from 12 to 120v, more preferably from 12 to 50v, most preferably 24v.
The direct current applied across the positive electrode and the negative electrode in step (b) may be 1-10 amp.
The carbon dioxide and water may be mixed at a volumetric ratio of 1:1 to 1:2.
In step (b), the electrolyte is preferably passed through a porous electrode so that ionization occurs under conditions of small porosity, with an average pore size from 0.1 micron to 1 mm, to effect high current density and higher ionization.
This invention also relates to an apparatus for the production of hydrogen, oxygen and hydrocarbons from carbon dioxide and water, the apparatus comprising:
The positive electrode and negative electrode are preferably located opposite one another within the reaction chamber.
Preferably, the positive electrode and negative electrode are porous with pores having an average size from 0.1 micron to 1 mm.
An agitator may be located in the reaction chamber between the positive electrode and negative electrode.
The reaction chamber may include at least one selectively permeable membrane located at or between the positive electrode and negative electrode.
The reaction chamber is adapted to operate at a pressure greater than or equal to 5.1 atm and a temperature above 0° C. to 500° C., typically from 100° C. to 400° C.
A hydrogen and hydrocarbon collection chamber is preferably located at the negative electrode and an oxygen collection chamber is preferably located at the positive electrode.
The hydrogen and hydrocarbon collection chamber is preferably adapted to receive hydrogen, hydrocarbons, hydrogen ions and carbon ions which have passed through pores in the negative electrode.
The oxygen collection chamber is preferably adapted to receive oxygen and oxygen ions which have passed through pores in the positive electrode.
The drawing is plan of a reactor according to an embodiment of the invention.
According to the present invention, a process for the production of hydrogen, oxygen and hydrocarbons from carbon dioxide and water includes the steps of:
Steps (b) and (c) of the process must be conducted with the reactants in the liquid state. This is because the ions need to migrate (move) through the liquid electrolyte to the relative electrodes and to obtain a high concentration of ions in close proximity to each other. The liquid state is typically achieved by conducting steps (b) and (c) under high pressure and at a suitable temperature. Conducting step (d) under high pressure is useful as the high pressure forces the nascent atoms into close proximity to enable them to form molecules.
The positive and negative electrodes are porous electrodes, with an average pore size from 0.1 micron to 1 mm, so that ions may pass through the electrodes and ionization occurs under conditions of small porosity, to effect high current density and higher ionization. Thus, the passage of the separated ions through the pores of the electrodes increases the degree of ionization.
The temperature of the electrolyte is used to control the pressure in the reaction chamber. The electrolyte exerts its vapour pressure according to its temperature. The temperature is thus controlled to provide the necessary pressure within the reactor at the required pressure to provide the pressure difference between the reaction chamber and the product chambers so that the ions are forced through the porous electrodes into product chambers where they link together to form atoms or molecules. For example, steps (b), (c) and (d) may be conducted in a chamber at a pressure of 5.1 atm and higher and a temperature of above 0° C. up to 400° C.
The principle reaction occurring during the process of the invention is:
CO2+2H2O→CH4+2O2
Similar reactions may occur to produce ethane (C2H6) and higher hydrocarbons. These reactions may be favoured by varying:
a) the molar quantities of feed H2O+CO2
b) agitation of the reaction electrolyte
c) reaction pressure and temperature; and
d) the porosity of the electrodes and/or membranes.
Despite the fact that the principle reaction:
(CO2+2H2O->CH4+2O2)
is thermodynamically unfavourable, continuous ionization can be maintained by the immediate and constant removal of the ions formed, in accordance with Le Chatelier's principle which favours restoration of equilibrium after removal of products.
Hydrogen ions/molecules and carbon ions/atoms are the basic building blocks of all hydrocarbons and may be converted into hydrocarbons (and polymeric hydrocarbons), such as fuels, using catalysts and/or other known methods. In the process of the invention, carbon and hydrogen ions are liberated/produced within the electrolyte and passed through pores in the negative electode. These carbon and hydrogen ions have a tendency to bond either with each other or themselves (or combinations) under certain conditions of pressure and temperature. By increasing the amount of hydrogen ions in proportion to the amounts of carbon ions the amount of bonding of hydrogen to carbon (forming methane and/or ethane and/or propane and/or butane, etc) can be varied. The more hydrogen ions which are ‘crowding’ carbon ions, the more carbon to hydrogen molecules will be formed and the less carbon and hydrogen molecules will be formed. These conditions are produced by (varying) the proportions of water which provides the hydrogen ions from a proportionately higher concentration of water in the reaction chamber. Agitation of the electrolyte also changes the proximity of the different ions to each other and thus the mixture of different molecules produced.
Semi-permeable membranes may be provided between the positive electrode and the negative electrode. The membranes may consist of porous materials such as sintered stainless steel, or carbon nanotubes for pores of smaller size. For example, the porosity of these membranes is selected to effect ‘filtering separation’ of the ions according to their size while ionized. The membranes may comprise the electrodes or be stronger than the material of the electrodes to provide physical strength support of the electrodes against the pressure difference on either side if the electrodes are made of ‘soft’ materials.
In a preferred form of the invention, the reaction conditions approximate the conditions under which the reactant will behave as a supercritical fluid exhibiting the properties of both liquids and gases. With reference to the below calculation, it is believed that a water and carbon dioxide stoichiometric mixture for the reaction below will act as a supercritical fluid at 185.281° C. and 14.007 Mpa (138.233 atm).
Reaction
CO2+2H2O→CH4+2O2
Use molar fractions for reaction proportions:
Since the supercritical conditions impart a state with no surface tension in the fluids, contact with the positive electrode and negative electrode will be enhanced reducing energy requirements. The transfer through the micropores of the membrane will also be facilitated as there will not be significant friction against the pore surfaces.
The ionization reaction may be enhanced by the use of a catalyst which may also function to reduce the propensity of the reaction mixture to form CO3 radicals. Sulphur-based catalysts maybe used, including minute quantities of sulphur or sulphur dioxide. These improve the electrolytic properties of the reactant medium.
Coal fired electricity production stations are prevalent throughout the world but a 1000-MW coal plant will produce and require the storage of about 50 million barrels of carbon dioxide a year to stop adding to the excess of carbon dioxide in the atmosphere and global warming. This is a preferable source of carbon dioxide for the process of the present invention. Alternatively, the carbon dioxide may be extracted from the atmosphere and liquefied prior to entering the chamber.
Oxygen produced by the process may be released to the atmosphere to further assist in redressing the imbalance of carbon dioxide in the atmosphere, or may be used for recombustion purposes.
With reference to the drawing, a reactor according to a first embodiment of the invention is indicated generally by the numeral 10. The reactor 10 comprises a reaction chamber 12 which is adapted to operate at a temperature up to or greater than or equal to 400° C. and with an internal pressure of greater than or equal to 5.1 atm. Controllable heating means (not shown) is provided for heating the reaction chamber 12. Carbon dioxide in the liquid phase and water in the liquid phase are supplied to the reaction chamber 12 from storage vessels 14 and 16, respectively. The storage vessels 14 and 16 feed carbon dioxide and water into the reaction chamber 16 by means of injection means (not shown). The carbon dioxide is fed in a liquid state under pressure exceeding 5.1 atm The water is fed under similar pressure. In an alternative form of the invention, the reactor 10 may include a pre-mixing chamber (not shown) interposed between the storage vessels 14 and 16 and the reaction chamber 12, in which the correct molar concentrations of carbon dioxide and water are established and the mixture is pressurized above 5.1 atm prior to injection into the reaction chamber 12. The pre-mixing chamber preferably also includes agitation means. Mixing means may also be provided within the reaction chamber 12 to assist with the mixing of carbon dioxide and water in the reaction chamber 12.
Located within the reaction chamber 12, opposite one-another, are a positive electrode 18 and a negative electrode 20. The positive electrode 18 and negative electrode 20 are in the shape of discs, are made from sintered platinum and/or tightly rolled thin platinum sheets providing spaces of approximately 1 micron between the coils, and are porous with an average pore size of 1 micron. Located in front of the positive electrode 18 is a membrane 22, and in front of the negative electrode 20 is a membrane 24. The membranes 22 and 24 are made from sintered stainless steel and are porous, with an average pore size of 1 micron.
In an embodiment of the invention, the pores in a membrane 24 located in front of the negative electrode may be sized to be large enough to allow carbon and hydrogen ions to pass through, but too small to allow water and carbon dioxide molecules, and oxygen atoms, carbonate and hydroxyl ions (which are larger than carbon and hydrogen ions) to pass through. The pores in a membrane 22 located in front the positive electrode 18 may be sized to be large enough to allow oxygen ions to pass through, but too small to allow water and carbon dioxide molecules, and carbonate and hydroxyl ions (which are larger than oxygen ions) to pass.
Connection wires 26, encased and insulated from the remainder of the reactor in high temperature resistant mica, are attached to the positive electrode 18 and negative electrode 20 and are provided for passing a current across the positive electrode 18 and negative electrode 20 through the electrolyte. Pressure gauges 28 are provided to read the internal pressure within the reaction chamber 12.
Located next to the reaction chamber 12 and in fluid communication therewith are separation vessels 30 and 32 which are capable of withstanding high internal pressures of at least 5.1 atm. The separation vessels 30 and 32 are each provided with controllable heating means (not shown). The separation vessel 30 is connected to the reaction vessel 12 via a conduit 34 which enters the reaction vessel behind the membrane 24 and behind the negative electrode 20 so that fluid flowing from chamber 12 to chamber 30 must pass through the negative electrode 20. The separation vessel 32 is connected to the reaction vessel 12 via a conduit 36 which enters the reaction vessel behind the membrane 22 and behind the positive electrode 18 so that fluid flowing from chamber 12 to chamber 32 must pass through the positive electrode 18. Pressure gauges 28 are provided to read the internal pressure within the separation vessels 30 and 32.
In use, carbon dioxide and water in a 50/50 mixture by volume in the liquid phase are transferred from the storage vessels 14 and 16 into the reaction chamber 12 to provide an electrolytic liquid 38 in the reaction chamber. The liquid state of the electrolytic fluid 38 is maintained by maintaining suitable conditions of pressure and temperature within the reaction chamber 12, for example, a pressure of 5.1 atm and a temperature of 185° C. A direct voltage of 24 v is applied across the positive electrode 18 and negative electrode 20, which causes the formation of positive carbon and hydrogen ions, and negative oxygen ions in the electrolytic liquid 38, The carbon and hydrogen ions migrate through the electrolytic liquid 38 to the negative electrode 20, and the oxygen ions migrate to the positive electrode 18.
By way of a pressure differential between the reactor 12 and separation vessel 30, carbon and hydrogen ions pass through the pores in the membrane 24 and negative electrode 20 and into the separation vessel 30 where they join to generate hydrogen, hydrocarbons and carbon, and provide a hydrogen product 38 and a hydrocarbon product 40.
By way of a pressure differential between the reactor 12 and separation vessel 32, oxygen ions pass through the pores in the membrane 22 and positive 18 and into the separation vessel 32 where they join to generate a molecular oxygen product 42.
A permeable membrane which allows passage of oppositely charged ions from the common electrolyte mixture towards the positive electrode amd negative electrode through the membrane respectively and is adapted to maintain oppositely charged migrated ions apart, may be provided in the reaction chamber 12. If negative and positive charges are provided on each side of such a membrane, the oxygen ions will migrate to the positive side and the hydrogen and methane and hydrocarbons will migrate to the negative side of the membrane. Thus these components can be separated into different compartments using one or more membranes provided in the reaction chamber 12. To this end, it is preferable that the reaction chamber 12 (and the two electrodes) be divided into two compartments by a permeable or semi-permeable membrane. The reaction electrolyte in the two compartments would be oppositely charged.
1 atm=101,325 kPa
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008/06254 | Jul 2008 | ZA | national |
| 2008/06649 | Jul 2008 | ZA | national |
| 2008/07515 | Aug 2008 | ZA | national |
| 2008/10698 | Dec 2008 | ZA | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2009/053136 | 7/20/2009 | WO | 00 | 3/29/2011 |
