Patent Application
20110000198
We claim a filter and a process to synthesize carbon nanotubes from automotive engine exhaust waste. In one embodiment the filter is composed of iron plates that are polished prior to placement in the exhaust system. In another embodiment, metallic thin film made out of Fe, Al or Ni is deposited on metallic or nonmetallic layer and placed in the streamline of the exhaust waste. Minor modifications are required to current exhaust systems. The disclosed filter works on its own or in conjunction with other filtration systems. We further claim that the carbon nanotubes formed on the filter surface are recoverable and are utilized for many CNT applications.
This invention relates to a filter and method that converts automotive exhaust waist to carbon nanotubes.
Incomplete combustion, particularly in diesel engines, produces black carbon and many hydrocarbon gases that can contribute to global warming and potential health hazards.
Oxidation catalysts that convert hydrocarbon and carbon monoxide into carbon dioxide and water are known in the literature. Ceramic filters that are known for their efficiency to remove 90% of the particulates require 500° C. and oxygen rich exhaust condition. Filtration systems to capture particulates have been disclosed in prior art, see Nielsen et al. U.S. Pat. No. 5,167,765 and Surgiura et al. U.S. Pat. No. 5,755,963.
Filters that are disclosed in prior art do not teach the conversion of waste from automotive exhaust to commercially viable product such as carbon nanotubes as disclosed in this invention.
Before disclosing embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or being carried out in various ways.
As used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly indicates otherwise. Thus, for example, reference to “a filter” includes a mixture of two or more filters, and the like.
The invention describes a filter and a process that converts waist exhaust of automotive engines into carbon nanotubes. The aspects of the invention pertain to the filter material, treatment of the filter material, alignment of the filter material and process that yields the maximum amount of carbon nanotubes.
The filter material is made out of thin (less than 1 mm) thick iron metal, in a preferred embodiment the filter material is made out of pure iron sheets. In another embodiment the metallic filters are made of carbonated steal with low percentage of carbon. In yet another preferred embodiment, a thin layer of iron is posted on any polymeric or metallic sheets. This thin layer is produced by physical process known in the literature such as but not limited to pulse laser deposition or ablation processes.
In the event of using carbonated steel, or iron, a polishing scheme is needed to expose the iron grains on the surface. Such processes may not be needed for thin layer depositions as described before.
The filter material is placed in the path of the exhaust waste of an automotive engine. The filter material is preferably placed at an angle below 45° and most preferably below 15° measured from the streamline of the exhaust waste.
Localized heating of the filter material or its surrounding is required to activate the carbon nanotubes formation. Though a temperature in the range of 700° C. is preferred, temperatures as low as 200° C. showed carbon nanotubes formation. The efficiency of the tube formation is function of the filter angle and the temperature at the filter location.
The following examples are not to limit the scope of the invention but to illustrate the invention. A filter made out of polymeric structure was placed in the pathway of a diesel engine exhaust. The engine was allowed to run at normal operation condition for half an hour. The filter was recovered and evaluated using SEM.
A filter made out of carbonated steel was polished using techniques known in the literature. The surface was examined using optical microscopy. The grains were clearly shown. The filter was placed in the pathway of a diesel engine exhaust. The engine was allowed to run for half an hour under normal operation conditions. The filter was collected and examined using SEM.
A similar filter made out of carbonated steel was polished and placed in the pathway of the exhaust horizontally to the exhaust streamlines. The filter zone was heated using a gas burner. The diesel engine was allowed to run in normal condition for half an hour. The filter material was collected and examined using SEM.
A similar filter made out of carbonated steel was polished and placed in the pathway of the exhaust of a diesel engine at an angle of 5° to the streamlines of the exhaust. A diesel engine was allowed to run under normal operating conditions for half an hour. The filter location was heated using a gas burner. The filter was collected an examined using SEM.
The produced carbon nanotubes are purified by immersing the filter plate in a ionic liquid bath. The purification process using ionic liquids produces 95% purified carbon nanotubes. Without limitation to the composition, ionic liquids have the ability to dissolve carbonated materials other than carbon nanotubes leaving a highly purified carbon nanotube stock.
