GB2459430A

GB2459430A - Production of hydrocarbons from carbon dioxide

Info

Publication number: GB2459430A
Application number: GB0724120A
Authority: GB
Inventors: Richard Stephen Cosmo Monkhouse
Original assignee: NEUTRAL CARBON Ltd
Current assignee: NEUTRAL CARBON Ltd
Priority date: 2007-12-10
Filing date: 2007-12-10
Publication date: 2009-10-28
Also published as: GB0724120D0

Abstract

This application describes a system for the generation of hydrocarbon fuels synthesised from carbon dioxide extracted from the atmosphere, by means of chemical and physical extraction of the carbon dioxide, followed by catalytic hydrogenation of the carbon dioxide using hydrogen generated by the electrolysis of water. The electrical energy for such a process is derived from renewable energy sources, such as concentrated solar power, wind, hydro and tidal energy. The fuel produced would be suitable for air, road or sea transport and is fully carbon neutral.

Description

Fuel Synthesis The present invention is directed towards a system for the generation of fuels from carbon dioxide, and in particular from carbon dioxide which has been extracted from the atmosphere.

There is a strong environmental need to find a less intrusive way of producing hydrocarbons for fuel, which does not have such a detrimental effect on the environment of the earth as is the case with existing fossil fuel based technology. In the last 40 years, the carbon dioxide concentration in the atmosphere has risen by around 35%. Approximately 60% of all of the carbon extracted from the ground (either in the form of coal, oil or gas) remains in the atmosphere after it has been combusted and this has resulted in a concentration increase from 280 ppm by volume to 380 ppm by volume.

It is thought by many that the increase in carbon dioxide concentration in the atmosphere affects climates and the planet is warming and we are noticing more abnormal weather conditions. With the predicted exponential growth of world energy use, there is an urgent need to find an alternative way of producing the hydrocarbon fuels, which are still required for transport worldwide, and particularly for air transport for which there is no viable alternative fuel One option is the use of biofuels, but the level of production required to meet the world's energy demands would use up too much of the world's arable land.

Alternative fuels for transport have has been proposed, but liquid hydrogen, for example, is impractical for many vehicles, as it cannot be kept from evaporating. Nuclear fuels have inherent dangers that have been seen, and the nuclear process again relies on a non-renewable source (uranium).

Hydrocarbons are excellent energy carriers and their use is widespread, but their production through the use of fossil fuels is damaging the planet and supplies will run out.

Traditionally, hydrocarbon fuels are generated from hydrocarbon and coal feedstock that has been taken from the ground and treated to generate the desired hydrocarbon chain length and product properties. These processes use up natural resources that take many centuries to generate. As the more readily accessible resources are used up, the cost of extracting the raw materials will increase and more areas of the earth will be disrupted. The resources will also ultimately run out so alternatives are needed.

It is therefore an object of the present invention to provide a process for the generation of hydrocarbon fuels without the disadvantages mentioned above.

According to the present invention there is provided a process for the production of hydrocarbons in which: carbon dioxide is removed from the air; hydrogen is produced by the electrolysis of water; and the carbon dioxide is hydrogenated with the hydrogen to form longer chain hydrocarbons, and wherein the process primarily uses a renewable energy source for power.

The renewable energy source may be selected from the group of solar, wind, hydro and tidal energy. These energy providers are entirely renewable and the selection of energy source will be dictated by the location of the processing plant. The renewable energy means may be solar power and may be harnessed by means of a photovoltaic cell, focussed solar collectors, or solar trough collectors. If solar power is used, the processing plant could be located in a desert region where there is a high mean solar energy that is readily available and which is away from the more densely populated developed regions. There is therefore the space to site the necessary solar collection area at an economic cost, as there is little or no ground rent for the otherwise unusable land.

Concentrated solar power or photovoltaic cells are preferred energy providers.

Optionally, the energy obtained by means of the renewal source is used on location to run the processing plant, in particular the carbon dioxide extraction, the hydrogen electrolysis and the hydrogenation of the carbon dioxide to form longer chain hydrocarbons. Alternatively, the energy can be stored, for example in batteries, and transported to a further site where it can be used in the process of the present invention.

The carbon dioxide may be removed from the air by any suitable means.

Examples of processes include chemical processes using appropriate solvents or sorbents. Examples of possible chemical sorbents include sodium hydroxide solution, sodium carbonate solution, potassium carbonate solution, calcium hydroxide solution, methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA) and triethanolamine (TEA).

The use of chemical sorbents in this process requires low cost, low loss and low energy recycling of the sorbant, and the ability to maintain the water content of the air. An example of such a process may be found in US20061005 1274 where air is passed over solvent covered surfaces in a laminar flow to maximise the efficiency of the carbon dioxide capture from the air. The solvent is typically a hydroxide, for example sodium or potassium hydroxide.

Alternatively, physical processes could be used to harvest the carbon dioxide from the air. Examples of such processes include: pressurisation followed by expansion; the use of molecular sieves such as zeolites using temperature or electrical swing absorption; molecular membranes; or cryogenic separation.

The precise method used to extract the carbon dioxide from the air will be determined by the location of the processing plant and the properties of the air to be used as a feed.

The hydrogen is obtained from the water by means of electrolysis of water to produce a supply of hydrogen (for use in the plant) at the cathode and oxygen at the anode. This process is well known and may be greatly improved in efficiency by the use of electrolytes in the water and improved electrode materials as is known.

The carbon dioxide and hydrogen may be converted under moderate pressure, temperature, and under the action of a suitable catalyst to methanol and then with a second reaction vessel using the Fischer-Tropsch process to hydrocarbons of a selectable range of molecular weights. The choice of operating parameters (temperature, pressure, relative concentrations of feed materials, catalyst, residence time, etc) will affect the chain length and distribution of the hydrocarbons produced.

Hydrogenation of carbon dioxide directly to methane, and even octane can also be achieved using existing processes. For example, US6987134 discloses a process for converting carbon dioxide directly into octane using two catalysts (a salt in addition to the nickel hydrogenation catalyst). This process generates octane and water, and the water can naturally be recycled to the electrolysis stage as a feed to form hydrogen. Other hydrogenation processes may convert carbon dioxide to shorter chain hydrocarbons, for example propane or butane.

Again, the precise process used for the hydrogenation step will be selected to meet the specific criteria at each location including what hydrocarbons are required locally.

Each step of the process -harnessing of renewable energy, carbon dioxide removal from the air, hydrogen production by electrolysis of water, and hydrogenation of the carbon dioxide to longer chain hydrocarbons -may be optimised to maximise production and minimise waste. For example, operating parameters may be varied, including the selection of the most appropriate catalysts, to minimise waste heat as far as possible without seriously affecting the products generated. Direct solar heat would primarily be used to supply heat for the endothermic parts of the process such as the extraction of C02 from the sorbant and the hydrogenation of the carbon dioxide. It may also be possible to use heat exchange from the exothermic electrolysis process and from exothennic pressurisation stages.

Theoretical calculations may be run to show the efficacy of such a process. A pilot plant with a ten kilometre-wide solar collection square could produce an average of 5,000 MW. A typical current generating cost of a large scale concentrated solar power plant is around $0.10 -0.12 per kWhr.

If the chemical part of the conversion processes is for example, 50% efficient, then, with the electrical energy mentioned above, an output of 500,000 litres (3000 barrels') of refined petroleum-like hydrocarbon per hour could be produced at a cost of -$2 per litre. This could run about eighty 747 airliners in service.

The process of the present invention moves the generation of hydrocarbon fuels away from fossil fuels in the ground and pumping them into the atmosphere on combustion. In the present case, carbon is removed from the atmosphere to generate a carbon neutral process. The atmospheric level of carbon dioxide may therefore be controlled and stabilised.

Claims

Claims 1. A process for the production of hydrocarbons in which: carbon dioxide is removed from the air; hydrogen is produced by the electrolysis of water; and the carbon dioxide is hydrogenated with the hydrogen to form longer chain hydrocarbons, and wherein the process primarily uses a renewable energy source.
2. A process as claimed in claim 1, in which the renewable energy is selected from solar, wind hydro and tidal energy.
3. A process as claimed in claim 2, in which the renewable energy is solar and is obtained by means of a photovoltaic cell, focussed solar collectors or solar trough collectors.
4. A process as claimed in any preceding claim, in which the carbon dioxide is removed from the air by means of chemical extraction 5. a process as claimed in claim 4, in which the chemical extraction uses one or more of the following chemicals as active agents sodium hydroxide, sodium carbonate hydrate, potassium carbonate solution, calcium hydroxide solution, sodium hydroxide solution, methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA) and triethanolamine (TEA).6. A process as claimed in any of claims 1 to 3 in which the carbon dioxide is removed from the air by means of physical extraction.7. A process as claimed in claim 6, in which the physical extraction is selected from the group of: pressunsation followed by expansion; the use of molecular sieves using temperature or electrical swing absorption; molecular membranes; and cryogenic separation.8. A process as claimed in any preceding claim, in which the hydrogenation step directly converts carbon dioxide to a hydrocarbon.9. A process as claimed in any one of claims 1 to 7, in which the carbon dioxide is first converted into methanol that is then further hydrogenated to a hydrocarbon.10. A process as claimed in any preceding claim, in which the hydrocarbon produced has a chain length of between 2 and 30 carbon atoms.11. Apparatus for the generation of a hydrocarbon fuel comprising: means for harnessing renewable energy; means for removing carbon dioxide from air; means for the electrolysis of water; and means for the hydrogenation of the carbon dioxide with the hydrogen.12. Apparatus as claimed in claim 11, in which the means for harnessing renewable energy comprise photovoltaic cells or concentrated solar power.AMENDMENTS TO THE CLAIMS HAVE BEEN MADE AS FOLLOWS: Claims 1. A process for the production of hydrocarbon fuels in which carbon dioxide is removed from the air, hydrogen is produced by the electrolysis of water; and the carbon dioxide is hydrogenated with the hydrogen to form hydrocarbons, and wherein the process primarily uses a renewable energy source selected from concentrated solar power, photovoltaic solar power, wind, hydro and tidal energy. The hydrocarbons produced would be suitable for fuel for air, road or sea transport and would, from an environmental perspective, be carbon neutral.2. A process as claimed in claim 1, in which the carbon dioxide is removed from the air by means of chemical extraction 3. A process as claimed in claim 2, in which the chemical extraction uses one or more of the following chemicals as active agents sodium hydroxide solution, sodium carbonate hydrate, potassium carbonate solution, calcium hydroxide solution, methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA) and triethanolamine (TEA). * ..4. A process as claimed in any of claims 1 to 3 in which the carbon dioxide is removed from the air by means of physical extraction. S.. * . . S. ISI....
5. A process as claimed in claim 4, in which the physical extraction is selected from the group of: pressurisation followed by expansion; the use of molecular sieves using temperature or electrical swing absorption; molecular membranes; and cryogenic separation.
6. A process as claimed in claim 1, in which the hydrogenation step directly converts carbon dioxide to a hydrocarbon.
7. A process as claimed in claim 1, in which the carbon dioxide is first converted into carbon monoxide or methanol that is then further hydrogenated to a hydrocarbon.
8. A process as claimed in any preceding claim, in which the hydrocarbon produced has a chain length of between 2 and 30 carbon atoms.
9. Apparatus for the generation of a hydrocarbon fuel comprising: means for harnessing renewable energy; means for removing carbon dioxide from air; means for the electrolysis of water; and means for the hydrogenation of the carbon dioxide with the hydrogen. *s. * S.
10. Apparatus as claimed in claim 9, in which the means for harnessing renewable energy comprise photovoltaic cells or concentrated solar power.*S S** S S *