Non-toxic Low Cost Nitrogen Fixation by Titanium Dioxide


Dr. Glenn Miller within the University of Nevada Reno Department of Natural Resources and Environmental Science (NRES) focuses on the transport and transformation of organic and inorganic compounds. Dr. Miller’s lab has a long-term interest in the environmental photochemistry of organic compounds and recently is focusing on the photolysis of pesticides on soil surfaces and in the gas phase. They are also working on a variety of projects related to contamination from mining sites both from current precious metals mining sites and historic mines. Technology Summary: Nitrogen fixation is a process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3). Although the atmosphere is 78% nitrogen it is nutritionally unavailable because nitrogen molecules are held together by triple bonds. Atmospheric nitrogen does not easily react with other chemicals to form new compounds as it is relatively inert. Nitrogen Fixation frees up the nitrogen atoms to be used in other ways. Nitrogen must be “fixed” or converted through a natural or man-made process. Nitrogen is necessary to biosynthesize nucleotides for DNA and RNA and amino acids for proteins. It is important for agriculture the production of fertilizer and the production of explosives. Biological nitrogen fixation makes up about 65% of the world’s annual nitrogen fixation and industrially produced nitrogen fertilizers primarily produced by the Haber-Bosch process accounts for 25% of the total annual nitrogen fixation. The Haber-Bosch process is presently the only available non-biological technology that has been used commercially. The Haber-Bosch process has a relatively high operational cost operates at relatively high temperatures and pressures and depends on non-renewable and depleting sources of energy. The UNR nitrogen fixation process uses titanium dioxide (TiO2) a common soil constituent and a semi-conducting material that can be photo-chemically stimulated by light energy. It is relatively inexpensive and non-toxic making it safer to use than the catalysts typically used for the Haber-Bosch process. The nitrogen fixation system includes a nitrogen source such as air air with an enhanced nitrogen content or a pure nitrogen source mixed with oxygen. In a specific example the system includes a feed stream concentrator (configured to increase the nitrogen content of a nitrogen-containing feed stream). A reactor contains an amount of titanium dioxide and is fluidly coupled to the nitrogen source. The system includes a heater thermally coupled to the reactor. The reaction takes place using lower temperatures between 500 and 200o Celsius making it more efficient than traditional methods. The heater is configured to the heat catalyst in the reactor and a water supply is included in the system and is fluidly coupled to the reactor. The water supply is configured to provide water to wash reaction products from the titania catalyst. The system also includes a water removal system such as an evaporator a freeze dryer or a membrane water removal unit. In some implementations the system includes a water recycling unit and returns the water back to the water supply making the process renewable. Potential Applications: 1) Fertilizer: The majority of ammonia is used as fertilizers. When applied to soil it helps increase crop yields. About one third of agricultural nitrogen in the US is in the form of anhydrous ammonia and worldwide 110m tons are applied each year. 2) Precursor to nitrogenous compounds: Most synthetic nitrogen compounds are derived from ammonia. Cleaner: Ammonium hydroxide or household ammonia is a solution of ammonium in water. It is often used for cleaning ovens and other difficult cleaning tasks. Household ammonia ranges in concentration by weight from 5 to 10% ammonia. 3) Fermentation: Solutio


Inexpensive and non-toxic.

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