United States Patent: 8524066

By way of introduction, and apology, this will be an overly-long report dealing with a relatively minor component of exhaust streams emanating from Coal-fired electric power generation plants,.

It will be the first of several, related and similar; and, we will explain further on why we feel compelled to address it. As will be seen in one or two reports to follow, there might be some very intriguing and synergistic ways in which it could be applied.

In our recent report, now accessible on the West Virginia Coal Association's web site via the link:

West Virginia Coal Association | : Saudi Arabia and CO2: The Rich Get Richer | Research & Development;

concerning, primarily, the news article: "SABIC Unit Plans World’s Largest CO2 Purification Plant",

it was disclosed how the Saudi Arabia Basic Industries Corporation, aka "SABIC", the largest company in the Middle East, had contracted with the German company, the Linde Group, the world's largest supplier of industrial gases, to collect the Carbon Dioxide emitted from several petroleum processing facilities/petrochemical plants, and to deliver that Carbon Dioxide to a factory to be constructed, where the CO2 would be consumed in "enhanced methanol and urea production".

We've previously documented, as in our report of:

West Virginia Coal Association | USDOE Converts Coal Exhaust into Fertilizer | Research & Development; concerning: "United States Patent 6,447,437 - Method for Reducing CO2, CO, NOx and SOx Emissions; 2002; Inventors: James Lee, TN, and Rongfu Li, China; Assignee: UT Battelle, LLC, Oak Ridge, TN; (USDOE Oak Ridge National Laboratory); Abstract: Industrial combustion facilities are integrated with greenhouse gas-solidifying fertilizer production reactions so that CO2, CO, NOx, and SOx emissions can be converted prior to emission into carbonate-containing fertilizers, mainly NH4HCO3 and/or (NH2)2CO, plus a small fraction of NH4NO3 and (NH4)2SO4. The invention enhances sequestration of CO2 into soil and the earth subsurface, reduces NO3 contamination of surface and groundwater, and stimulates photosynthetic fixation of CO2 from the atmosphere. The method for converting CO2, CO, NOx, and SOx emissions into fertilizers includes the step of collecting these materials from the emissions of industrial combustion facilities such as fossil fuel-powered energy sources and transporting the emissions to a reactor. In the reactor, the CO2, CO, N2, SOx, and/or NOx are converted into carbonate-containing fertilizers using H2, CH4, or NH3";

that, industrial exhaust gas CO2, in combination with Nitrogen Oxides, "NOx", as would be emitted together in Coal-fired power plant exhaust, i.e., "fossil fuel-powered energy sources", can be converted into Urea, one of the products Saudi Arabia intends to manufacture from CO2, with the chemical formula: "(NH2)2CO", also written as"CO(NH2)2"; and which, as taught by the University of Minnesota via:

Fertilizer Urea; is most commonly thought of as fertilizer.

And, perhaps surprisingly, as can be learned via:

Urea - Wikipedia, the free encyclopedia; wherein we're told, that: "For use in industry, urea is produced from synthetic ammonia and carbon dioxide";

Urea is already commonly made with Carbon Dioxide as a primary raw material, in combination with, as indicated in "United States Patent 6,447,437 - Method for Reducing CO2, CO, NOx and SOx Emissions", "ammonia", "NH3"; in reactions explained and illustrated by the recent:

"United States Patent: 8158824 - Process For The Production Of Urea From Ammonia and Carbon Dioxide; 2012; Assignee: Stamicarbon BV, The Netherlands; Abstract: Process for the production of urea from ammonia and carbon dioxide in a urea plant. Claims: Process for the production of urea from ammonia and carbon dioxide".

The above has some interesting implications relative to Coal utilization technologies other than electric power generation, as we'll address in at least one report to follow. Unfortunately, however, as it happens, the commercial production of ammonia often entails the emission of Carbon Dioxide, and, when Urea breaks down in the soil, making it's Nitrogen available for green plants to utilize, it releases it's bound Carbon Dioxide. That CO2 released by the breakdown of Urea might be counterbalanced by the uptake of CO2 by the green plants fertilized by the Urea; but, there are other ways in which Urea can be profitably utilized and consumed, ways which ensure that the Carbon Dioxide consumed in the synthesis of the Urea would remain permanently, chemically "sequestered".

As can be learned via:

Urea-formaldehyde - Wikipedia, the free encyclopedia; about  one "million metric tons of urea-formaldehyde" plastic resin "are produced every year", most of it going into resin-bonded "particleboard" and "fiberboard".

And, there are other plastic compounds, such as "Melamine", which, as can be learned via:

melamine (chemical compound) -- Encyclopedia Britannica; which tells us, that: "Modern commercial production of melamine typically employs urea as a starting material";

are made from CO2-recycling Urea. We'll note, as we were advised, that, the synthesis of Melamine from Urea results itself in the release of some of the bound Carbon Dioxide; but, as can be learned via:

Urea-melamine integration; that released Carbon Dioxide can be captured and recycled into the process.

There are other potentials, as well, as we'll document further on, but, herein we learn that the valuable Urea can be manufactured from Carbon Dioxide without the need for Ammonia, which causes the release of Carbon Dioxide in it's production; and, instead, can be synthesized from CO2 in combination with Nitrogen Oxides, "NOx", which Nitrogen Oxides are themselves, as indicated in the above-cited "United States Patent 6,447,437 - Method for Reducing CO2, CO, NOx and SOx Emissions", components, although not, as we'll elaborate further on, major components, of Coal-fired power plant exhaust streams.

As seen in excerpts from the initial link in this dispatch to the recent:

"United States Patent 8,524,066 - Electrochemical Production of Urea from NOx and Carbon Dioxide

Patent US8524066 - Electrochemical production of urea from NOx and carbon dioxide - Google Patents

Electrochemical production of urea from NOx and carbon dioxide - Liquid Light, Inc.

September 3, 2013

Inventors: Narayanappa Sivasankar, et. al., NJ

Assignee: Liquid Light Inc., NJ

Abstract: Methods and systems for electrochemical production of urea are disclosed. A method may include, but is not limited to, steps (A) to (B). Step (A) may introduce carbon dioxide and NOx to a solution of an electrolyte and a heterocyclic catalyst in an electrochemical cell. The divided electrochemical cell may include an anode in a first cell compartment and a cathode in a second cell compartment. The cathode may reduce the carbon dioxide and the NOx into a first sub-product and a second sub-product, respectively. Step (B) may combine the first sub-product and the second sub-product to produce urea.

Claims: A method for electrochemical production of urea, comprising:

(A) introducing carbon dioxide and a nitrogen oxide to a solution of an electrolyte and a heterocyclic catalyst in an electrochemical cell, wherein:

(i) said electrochemical cell including an anode in a first cell compartment and a cathode in a second cell compartment,

(ii) said cathode reducing said carbon dioxide into a first sub-product and reducing said nitrogen oxide into a second sub-product, and:

(iii) said heterocyclic catalyst includes (components specified); and:

(B) combining said first sub-product and said second sub-product to produce urea.

The method ... wherein said first sub-product is at least one of carbon monoxide or a reduced CO2 intermediate species, and wherein said second sub-product is at least one of ammonia or an ammonia-related intermediate compound.

(Note in the above that the Nitrogen Oxide is being electro-chemically reduced into "ammonia". That is the key step, since Urea synthesis can then proceed more or less in line with already-established practice, as in our introductory references, especially that concerning: "United States Patent 8,158,824 - Process For The Production Of Urea From Ammonia and Carbon Dioxide".)

The method ... wherein said cathode includes at least one of Al, Au, Ag, C, Cd, Co, Cr, Cu, Cu alloys, Ga, Hg, In, Mo, Nb, Ni, Ni alloys, Ni--Fe alloys, Sn, Sn alloys, Ti, V, W, Zn, elgiloy, Nichrome, austenitic steel, duplex steel, ferritic steel, martensitic steel, stainless steel, (etc.).

(A lot of things will work, in other words. This doesn't have to be that expensive to construct.)

The method ... wherein said electrical potential of said cathode ranges between approximately -0.5 volts to approximately -1.5 volts.

(The Claims specify alternative materials of construction to some extent, but, the upshot of it all is that Carbon Dioxide and Nitrogen Oxides can be electro-chemically reduced into more reactive "species" with very little, "-0.5 volts to approximately -1.5 volts", applied current. Such low currents, by the way, as we've noted in one or two previous reports, and as we will see in some reports to follow, can be generated by photovoltaics; and, a great deal of effort has been applied to designing solar-powered gas processing reactors for use in CO2 recycling processes like that disclosed herein.)

The method ... wherein combining said first sub-product and said second sub-product includes combining said first sub-product and said second sub-product in said electrochemical cell to produce urea. 

The method ... wherein said cathode includes a first cathode material for reducing said carbon dioxide and a second material for reducing said nitrogen oxide.


Background and Field: The present disclosure generally relates to the field of chemical reduction, and more particularly to a method and/or apparatus for implementing electrochemical production of urea from NOx and carbon dioxide. 

The combustion of fossil fuels in activities such as electricity generation, transportation, and manufacturing produces billions of tons of carbon dioxide annually.  

A mechanism for mitigating emissions is to convert carbon dioxide into economically valuable materials such as fuels and industrial chemicals. If the carbon dioxide is converted using energy from renewable sources, both mitigation of carbon dioxide emissions and conversion of renewable energy into a chemical form that can be stored for later use will be possible.


Urea is an important fertilizer and industrial chemical used around the world. Industrially, urea is synthesized from carbon dioxide and ammonia at temperatures between 150 to 210 degrees Celsius and pressures of 120 to 400 atmospheres. Ammonia is typically produced from hydrogen and nitrogen at relatively high temperatures and pressures.
The overall process of industrially synthesizing urea requires a large amount of energy, which generally comes from natural gas. The combustion of natural gas contributes to the concentration of carbon dioxide in the atmosphere and thus, global climate change.

Summary: A method for electrochemical production of urea may include, but is not limited to, steps (A) to (B). Step (A) may introduce carbon dioxide and NOx to a solution of an electrolyte and a heterocyclic catalyst in an electrochemical cell. The electrochemical cell may include an anode in a first cell compartment and a cathode in a second cell compartment. The cathode may reduce the carbon dioxide to a first sub-product and the NOx to a second sub-product. Step (B) may combine the first sub-product and the second sub-product to produce urea. 

A system for electrochemical production of urea may include, but is not limited to, an electrochemical cell, a carbon dioxide source, a NOx source, and an energy source.

In accordance with some embodiments of the present invention, an electrochemical system is provided that generally allows carbon dioxide and NOx to be converted to urea. In some embodiments, the energy used by the system may be generated from an alternative energy source to avoid generation of additional carbon dioxide through combustion of fossil fuels. 

Some embodiments of the present invention thus relate to environmentally beneficial methods for reducing carbon dioxide.

Carbon dioxide may be photochemically or electrochemically reduced to carbon monoxide or other reduced CO2 intermediates, and NOx may be photochemically or electrochemically reduced to ammonia or an ammonia-like intermediate compound. The carbon monoxide and the ammonia or ammonia-like compound may combine to form urea as a product of the system.

The electrical energy for the electrochemical reduction of carbon dioxide may come from ... alternatives (e.g., hydroelectric, wind, solar power, geothermal, etc.), from a solar cell, or other nonfossil fuel source of electricity, provided that the electrical source supply at least approximately 1.5 volts across the cell. Other voltage values may be adjusted depending on the internal resistance of the cell employed. 

Advantageously, the carbon dioxide may be obtained from any source (e.g., an exhaust stream from fossil-fuel burning power or industrial plants, from geothermal or natural gas wells or the atmosphere itself). Most suitably, the carbon dioxide may be obtained from concentrated point sources of generation prior to being released into the atmosphere. For example, high concentration carbon dioxide sources may frequently accompany natural gas in amounts of 5% to 50%, exist in flue gases of fossil fuel (e.g., coal, natural gas, oil, etc.) burning power plants, and nearly pure carbon dioxide may be exhausted from cement factories and from fermenters used for industrial fermentation of ethanol. Certain geothermal steams may also contain significant amounts of carbon dioxide. The carbon dioxide emissions from varied industries, including geothermal wells, may be captured on-site. Separation of the carbon dioxide from such exhausts is known. Thus, the capture and use of existing atmospheric carbon dioxide in accordance with some embodiments of the present invention generally allow the carbon dioxide to be a renewable and unlimited source of carbon.

In the process described, water may be oxidized (or split) to protons and oxygen at the anode while the carbon dioxide is reduced to carbon monoxide or a CO2-derived intermediate species at the cathode and the NOx is reduced to ammonia or an ammonia-like intermediate compound at the cathode. The electrolyte in the cell may use water as a solvent with any salts that are water soluble and with a pyridine or pyridine-derived catalyst
Carbon dioxide and NOx may be efficiently converted to value-added products, using either a minimum of electricity (that may be generated from an alternate energy source) or directly using visible light. Some processes described (herein) may generate urea useful for chemical processes. Moreover, the catalysts for the processes may be substituents-sensitive and provide for selectivity of the value-added products. 

Specific process conditions may be established that maximize the carbon dioxide and NOx conversion to specific chemicals beyond urea.

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Although the Disclosure is clear about where we might obtain Carbon Dioxide, i.e., "high concentration carbon dioxide sources may frequently accompany natural gas in amounts of 5% to 50%, exist in flue gases of fossil fuel (e.g., coal, natural gas, oil, etc.) burning power plants, and nearly pure carbon dioxide may be exhausted from cement factories and from fermenters used for industrial fermentation of ethanol", it's less clear about where we might obtain the Nitrogen Oxides, NOx.

However, as can be learned via:

NOx - Wikipedia, the free encyclopedia; and: Fossil fuel combustion flue gases;

NOx is a component, although, it might surprise you to learn, a pretty minor one, in terms of relative volumes, of Coal-fired power plant exhaust gas; making up, depending on both the type of boiler utilized and the grade of Coal being combsuted, maybe only three percent of exhaust gas volume, most of which, like our atmosphere, consists of molecular Nitrogen, N2.

If we read the literature correctly, agricultural industry, perhaps counter-intuitively, accounts for the bulk of NOx emissions arising from human activities. And, in point of fact, there might not be enough NOx in any one Coal-fired power plant's exhaust to make capturing it and converting it into Urea a worthwhile proposition as a practical, commercial matter.

Again however, and, it's a big however, as can be learned via:

Air Transport | US EPA; concerning the heavily-litigated "Cross-State Air Pollution Rule" (CSPAR)", the emission of Nitrogen Oxides from Coal-fired power plants has become a, perhaps unwarrantedly-outsized,  concern, and, whether it makes sense or not to do so, will have to be dealt with.

On the other hand, if we're already collecting the Carbon Dioxide, perhaps for use in a process like that described in our report of:

West Virginia Coal Association | Penn State May 14, 2013, CO2 to Methane | Research & Development; concerning: "United States Patent 8,440,438 - Electromethanogenic Reactor and Processes for Methane Production; May 14, 2013; Assignee: The Penn State Research Foundation, University Park, PA; Biological processes for producing methane gas and capturing carbon from carbon dioxide are provided according to embodiments of the present invention which include providing an electromethanogenic reactor having an anode, a cathode and a plurality of methanogenic microorganisms disposed on the cathode. Electrons and carbon dioxide are provided to the plurality of methanogenic microorganisms disposed on the cathode. The methanogenic microorganisms reduce the carbon dioxide to produce methane gas, even in the absence of hydrogen and/or organic carbon sources";

to manufacture a substitute natural gas, Methane, and thus forestall some of the contention over environmental damage caused by fracking for shale gas, or, as seen in:

West Virginia Coal Association | August 13, 2013 Power Plant CO2 to High-Octane Gasoline | Research & Development; concerning: "US Patent 8,506,910 - Process and System for Producing Liquid Fuel from Carbon Dioxide and Water; 2013; Assignee: CRI Ehf, Iceland; Abstract: A process and system for producing high octane fuel from carbon dioxide and water is disclosed. The feedstock for the production line is industrial carbon dioxide and water, which may be of lower quality. The end product can be high octane gasoline, high cetane diesel or other liquid hydrocarbon mixtures suitable for driving conventional combustion engines or hydrocarbons suitable for further industrial processing or commercial use. Products, such as dimethyl ether or methanol may also be withdrawn from the production line";

to manufacture "high octane gasoline", and thus forestall the environmental, and human, ravages of yet another OPEC-related Middle East or Arabian war; then, maybe, it might make sense to use utilize a small amount of that CO2 to convert, via the process of our subject, "US Patent 8,524,066 - Electrochemical Production of Urea from NOx and Carbon Dioxide", the Nitrogen Oxides we might be forced by law to collect from our Coal-fired power plant exhaust in any case, into a relatively small amount of Urea, perhaps for use, if nothing else, as a fertilizer in the flower garden out at the main road entrance to the power plant.

But, as we indicated in our opening statements in this dispatch, there are other, perhaps much more intriguing, options for the use of Coal exhaust-based Urea, as well, which we will address in at least one report to follow.


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