Title of Invention

"A Process for the Preparation of Graphitic Nanofibers and Apparatus There for "

Abstract

The present invention relates to an apparatus and a process for the preparation of graphitic nanofibers to be used as hydrogen storage material through thermal cracking by passing acetylene gas, comprising the steps of creating vacuum by vacuum chamber in the silica tube placed in the heat resistance furnace, having catalyst placed in the ceramic boat; passivating the said catalyst by passing gases hydrogen and helium in the said silica tube at the desired pressure of 38-42 torr; heating the said catalyst material placed in the said silica tube at a temperature of 600-640 degrees C; passing acetylene gas prepared from the means to prepare the acetylene gas and hydrogen gas in the ratio of 2:1 at a pressure of 140-165 torr in the said silica tube to allow the thermal cracking of the said gases to produce carbon deposit, cooling the said furnace at a rate of 4-6 degrees per minute, removing the carbon deposit from the said silica tube, in the form of graphitic nanofibers.

Full Text

The subject application relates to the process for the preparation of graphitic nanofibre and apperatus therefor , through thermal cracking by using acetylene gas, to be used as hydrogen storage material The embodiment of the invention resides in the preparation of acetylene gas used in the thermal cracking and apparatus for the same. PRIOR ART The rapid depletion of natural resources and serious global environmental problems are connected with the overuse of fossil fuels. There is therefore a search for possible alternative sources of energy to replace fossil fuels. There are quite a number of primary energy sources available such as thermonuclear energy, nuclear reactors, solar energy, wind energy, hydropower, geothermal energy and the like. In contrast to the fossil fuels, in most cases, these energy sources can not be used directly, such as fuels for transportation and thus they must be converted into fuels necessitating a new energy carrier. In order to overcome the drawbacks, associated with the existing energy sources, hydrogen has been found to be an ideal fuel and versatile energy carrier. However, the problem of storage of hydrogen has persistently needs attention and in this regard carbon has been found to be the most suitable storage material for the storage of hydrogen. Due to the high surface area and abundant pore volume, porous carbon is considered to be the good absorbent. In case of conventional porous carbon, the hydrogen uptake is proportional to is surface area and pore volume, while the high hydrogen absorption capacity can be obtained at very low temperatures such as liquid nitrogen temperature. However, it has been found that in spite of their relatively small surface area and pore volume, carbon nanotubes and carbon nanofibers show very surprising high hydrogen storage capacity. In addition to the close shell carbon structure , graphitic nanotubules which get formed through wrapping of graphitic sheets so as to eliminate dangling bonds. The another carbon variant, which has been innovated, corresponds to the arrangement of graphitic network planes i around an axis. These graphitic planes are parallel/perpendicular/inclined (herring bone) to the fiber axis. These new carbon variants have been termed as graphitic nanofibers. The high hydrogen storage capacity have been found precisely highest in the graphitic nanofibers, which are achieved by the thermal cracking of hydrocarbon gas. However, it has been found that the actual hydrogen storage capacity depends upon the treatment imparted to graphitic nanofibers. • The main objective of the subject invention is to prepare the graphitic nanofibers having high hydrogen storage capacity. The graphitic nanofibers of the subject application are capable of storing hydrogen at densities much higher than the earlier material namely hydrides for example LaNi5H6, FeTiH^g and the like, where the storage capacity at ambient conditions are ~1.5wt.%. On the other hand, in Graphitic nanotubules and graphitic nanofibers, the storage capacity is ~ 10 to 15 wt.% and as high as -67% also. The graphitic nanofibers of the subject invention are prepared by the thermal cracking of carbon rich gas preferably acetylene gas. The graphitic nanofibers are prepared by the thermal cracking of the acetylene gas. The thermal cracking or decomposition was done by passing the gas in a silica tube having an inlet ports for the gases , hydrogen and helium. The presence of graphitic nanofibers has been confirmed by conducting the X-ray diffraction and more particularly transmission electron microscope technique (imaging and diffraction). For effective thermal cracking, the fine Ni and Cu were taken in a ceramic boat, placed in the said silica tube , acting as catalyst. The material in the ceramic boat is passivated by first creating the vacuum and then passing the hydrogen and helium gases into said silica tube. The catalyst passivation was achieved by heating the metal catalyst powder in hydrogen and helium gases at ambient conditions for one hour in the resistance heated furnace. The role of the catalyst in the preparation of graphitic nanofibers is in the formation of solid solution of .carbon in the metal catalyst followed by diffusion of carbon formation of graphitic nanofibers. The cracking was carried out in the stationary mode. The thermal cracking of the gas was achieved by heating in the pressure of Ni and Cu catalyst powders. The tube was then allowed to cool and carbon deposited near the tube regions is flushed with a mixture of helium gas and fresh air, before finally collecting the carbon deposits. The embodiment of the invention resides in the process for the preparation of graphitic nanofibers to be used as hydrogen storage material through thermal cracking by passing acetylene gas, comprising the steps of, creating vacuum in the silica tube placed in the heat resistance furnace having catalyst in it, passivating the said catalyst by passing gases 8-12 % each of hydrogen and helium in the said silica tube at a pressure of 38-42 torr; heating the said catalyst material placed in the said silica tube at a temperature of 600-640 degrees C; passing acetylene gas and hydrogen gas in the ratio of 2:1 at a pressure of 140-165 torr in the said silica tube to allow the thermal cracking of the said gases to produce carbon deposit; cooling the said furnace at a rate of 4-6 degrees per minute, removing the carbon deposit from the said silica tube, in the form of graphitic nanofibers. The catalyst used in the subject application is Ni and cobalt in the ratio of 98% : 2%, having the particle size of said Ni from 0.2 to 0.5µm and said cobalt from 0.20-0.27µm, specifically, the particle size of the said Ni is 0.4µm and said cobalt is 0.25µm. The said acetylene gas is prepared by reacting the calcium carbide with water in a container. The another embodiment of the present invention resides in the apparatus for the preparation of graphitic nanofibers to be used as hydrogen storage material through thermal cracking by passing acetylene gas, comprising a means to prepare the said acetylene gas, a heat resistance furnace, a silica tube placed in the said heat resistance furnace, means to create vacuum in the said silica tube, a container containing catalyst placed in the said silica tube, means to close the said silica tube, a multi inlet glass knob having a single outlet connected to the said means closing the said silica tube, a heating means to heat the said silica tube, a barometer to maintain the desired pressure of the said gases having its inlets connected to the outlets of cylinders containing hydrogen gas and helium gas, and to the said means for preparing the said acetylene gas, means controlling the flow of gases from the said cylinders containing hydrogen gas, helium gas and the acetylene gas, the plurality of gas flow meters provided at the outlet of the barometer to control the flow of the said gases, a connecting tube connecting the barometer with the outlet of the said glass knob. The said means to prepare the acetylene gas comprises a container having an opening for the insertion of the tube, a vessel provided at the inlet of the said container, a cascade of interconnected vessels preferably three provided adjacent to the container, wherein the first vessel is connected to the said opening of the said container and the outlet of the said third vessel connected to the inlet of the said barometer. The said means to create the vacuum in the said silica tube is the vacuum chamber and the means to close the said silica tube is a cork having a hole for the insertion of the outlet of said glass knob. The means to control the flow of gases are valves connected at the outlets of cylinders containing said hydrogen gas, helium gas and said acetylene gas. The said connecting means connecting the barometer and the outlet of the said glass knob is a rubber tube and the said container containing the catalyst is ceramic boat. Accordingly, the present invention relates to a process for the preparation of graphitic nanofibers to be used as hydrogen storage material through thermal cracking by passing acetylene .gas, comprising the steps of: creating vacuum in the silica tube placed in the heat resistance furnace, having catalyst in it; passivating the said catalyst by passing gases 8-12 % each of hydrogen and helium in the said silica tube at a pressure of 38-42 torr; heating the said catalyst material placed in the said silica tube at a temperature of 600-640 degrees C; passing acetylene gas and hydrogen gas in the ratio of 2:1 at a pressure of 140-165 torr in the said silica tube to allow the thermal cracking of the said gases to produce carbon deposit; cooling the said furnace at a rate of 4-6 degrees per minute, removing the carbon deposit from the said silica tube, in the form of graphitic nanofibers. The present invention also relates to an apparatus for the preparation of graphitic nanofibers to be used as hydrogen storage material through thermal cracking by passing acetylene gas, as claimed in claim 1, comprising a means to prepare the said acetylene gas, a heat resistance furnace, a silica tube placed in the said heat resistance furnace, means to create vacuum in the said silica tube, a container containing catalyst placed in the said silica tube, means as herein described to close the said silica tube, a multi inlet glass knob having a single outlet connected to the said means closing the said silica tube, a heating means as herein described to heat the said silica tube, a barometer to maintain the desired pressure of the said gases having its inlets connected to the outlets of cylinders containing hydrogen gas and helium gas, and to the said means for preparing the said acetylene gas, means as herein described controlling the flow of gases from the said cylinders containing hydrogen gas, helium gas and the acetylene gas, the plurality of. gas flow meters provided at the outlet of the barometer to control the flow of the said gases, a connecting tube connecting the barometer with the outlet of the said glass knob. The subject application . may better be understood with reference to accompanying drawings, which are for illustrative purposes, explaining the invention in the best possible ways. Hence, the same should not be construed to restrict the scope of the application. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1-3 depicts the various stages involved in the process for the preparation of graphitic nanofibers and apparatus used for the preparation of the same; Figure 4 depicts the X-ray diffractogram of the graphitic nanofibers prepared through the thermal cracking of acetylene gas; Figure 5 depicts the scanning electron micrograph of graphitic nanofibers prepared through the thermal cracking of acetylene gas; Figure 6 depicts the transmission electron micrograph of graphitic nanofibers; Figure 7 depicts the diffraction electron micrograph of graphitic nanofibers. DETAILED DESCRIPTION OF THE INVENTION In the subject invention, the acetylene gas is prepared by using an improved apparatus comprising a container (13) or vessel made up of metal, preferably steel having an inlet for the insertion of the tube. A small vessel (11) is provided at the opening of the container (13) or vessel, as shown in figure 2. The vessel (13) is filled with water (12) at 2/3rd level.The calcium carbide stones (CaC2) are placed in the small vessel (11) in the amount of from 220-270 grams. The calcium carbide stones may be placed in the container (13) also. A cascade of vessels, preferably three vessels are provided adjacent to the container, paced one over the other. The inlet of the container is connected to first vessel (16). The gas from the container (13) is passed in the first vessel (16). The vessel (16) is filled with water. The gas from the vessel (16) is then passed to second vessel (15), which is again filled with water and finally enters the third vessel (14), which is half filled with water. The outlet of the third vessel (14) is connected to the barometer (17). The outlet of the third vessel (14) is provided with a valve to allow the gas to be passed to the barometer (17) to create a pressure of 52.63mbar. The apparatus used in the preparation of graphitic nanofibers comprises a silica tube (2) having inlet ports for the gases, which is placed in the resistance heated furnace (4) as shown in figure 1. A ceramic boat (3) having cobalt-Nickel catalyst is placed in the said silica tube (2). A vacuum unit (1) is provided to create the vacuum in the said silica tube (2). A cork (9) is provided at one end of the said silica tube(2) and a glass knob (10) is provided for the inletting of plurality of gases in the said silica tube (2) through the said cork (9). The barometer is provided to maintain the desired pressure. The outlet of the vacuum unit (1) is connected to the inlet of said silica tube (2) at the glass knob (10), through the said rubber cork (9). The silica tube (2) used in the subject application is having a length of 70-80cm and a diameter of 1-3cm. The size of the inlet ports is from 2mm-4mm diameter and a length of 1-3mm for the insertion of hydrogen and helium gases. In the process for the preparation of graphitic nanofibers through thermal cracking, it comprises, placing the silica tube (2) in the resistance heated furnace (4) as shown in figure 1. The cobalt-Nickel catalyst is placed in the said ceramic boat (3) and vacuum is created in the said silica tube (2) by vacuum unit (1). The silica tube (2) is placed in the stationary mode. The plurality of gases are inletted in the said silica tube (2)through the glass knob. The vacuum is created in the silica tube (2) at a pressure of 10"3 torr. The 10% of hydrogen gas is passed in the said silica tube (2) at a pressure of 40 torr, followed by the passing of helium gas at the same pressure. The catalyst passivation is achieved by heating the metal catalyst powder in Hydrogen and Helium gases at ambient conditions for one hour in the said resistance heated furnace((4). The particle size of the catalyst having size of Ni 0.2 to 0.5µm and cobalt 0.20-0.27µm. The acetylene gas prepared as discussed with reference to figure 2, is passed through the barometer along with the hydrogen gas in the ratio of 2:1 to the silica tube at a pressure of 160torr. The cracking is carried out in the stationary mode. The thermal cracking of the gas is achieved by heating these in the presence of Ni (98%) and Cobalt (2%) catalyst powders at 600-640 °C for two hours in resistance heated furnace (4) as shown in figure 2. The silica tube (2) was then allowed to cool at a rate of 5°C /minute. At this stage the carbon deposits near the silica tube (2) regions where catalyst powders were located could be seen. The carbon deposit is flushed with the 2% helium and fresh air as shown in figure (3), before collecting the said deposit material. After collecting the said deposited material , the same was characterized through x-ray diffractometer and scanning electron microscopy and finally the same was characterized through electron microscopy techniques, results whereof are shown in figures 4-7. The subject application is a statement of invention, where various alterations and modifications are possible without deviating from the scope of the application, hence the same should not be construed to restrict the scope of the application. WE CLAIM: 1. A process for the preparation of graphitic nanofibers to be used as hydrogen storage material through thermal cracking by passing acetylene .gas, comprising the steps of: creating vacuum in the silica tube placed in the heat resistance furnace, having catalyst in it; passivating the said catalyst by passing gases 8-12 % each of hydrogen and helium in the said silica tube at a pressure of 38-42 torr; heating the said catalyst material placed in the said silica tube at a temperature of 600-640 degrees C; passing acetylene gas and hydrogen gas in the ratio of 2:1 at a pressure of 140-165 torr in the said silica tube to allow the thermal cracking of the said gases to produce carbon deposit; cooling the said furnace at a rate of 4-6 degrees per minute, removing the carbon deposit from the said silica tube, in the form of graphitic nanofibers. 2 The process as claimed in claim 1, wherein the said catalyst used is Ni and copper. 3 The process as claimed in claim 2, wherein the ratio of said Ni and copper is 98% and 2%. 4 The process as claimed in claim 1, wherein the particle size of the said Ni is 0.2 to 0.5µm and said copper 0.20-0.27µm. 5 The process as claimed in claim 4, wherein the particle size of the said Ni is 0.4µm and said copper 0.25µm. 6 The process as claimed in claim 1, wherein the said acetylene gas is prepared by reacting the calcium carbide with water in a container. 7 An apparatus for the preparation of graphitic nanofibers to be used as hydrogen storage material through thermal cracking by passing acetylene gas through a vacuum silica tube comprising a means as herein described to prepare the said acetylene gas, a heat resistance furnace, a silica tube placed in the said heat resistance furnace, a vacuum chamber connected to the said silica tube to create vacuum, a container containing catalyst placed in the said silica tube, means as herein described to close the said silica tube, a multi inlet glass knob having a single outlet connected to a cork closing the said silica tube, a heating means as herein described to heat the said silica tube, a barometer to maintain the desired pressure of the said gases having its inlets connected to the outlets of cylinders containing hydrogen gas and helium gas, and to the said means for preparing the said acetylene gas, means as herein described controlling the flow of gases from the said cylinders containing hydrogen gas, helium gas and the acetylene gas, the plurality of gas flow meters provided at the outlet of the barometer to control the flow of the said gases, a connecting tube connecting the barometer with the outlet of the said glass knob. 8 An apparatus as claimed in claim 7, wherein the said means to prepare the acetylene gas comprises a container having an opening for the insertion of the tube, a vessel provided at the inlet of the said container, a cascade of interconnected vessels, preferably three, provided adjacent to the container, wherein the first vessel is connected to the said opening of the said container and the outlet of the said third vessel connected to the inlet of the said barometer. 9 An apparatus as claimed in claim 7, wherein the said means to control the flow of gases are valves connected at the outlets of cylinders containing said hydrogen gas, helium gas and said acetylene gas. 10 An apparatus as claimed in claim 7, wherein the said connecting means connecting the barometer and the outlet of the said glass knob is a rubber tube. 11 An apparatus as claimed in claim 7, wherein the said container containing the catalyst is ceramic boat. 12 A process for the preparation of graphitic nanofibers substantially as herein before described with reference to the accompanying drawings 13 An apparatus for the preparation of graphitic nanofibers substantially as herein before described with reference to the accompanying drawings.

Documents:

888-del-2001-abstract.pdf

888-del-2001-claims.pdf

888-del-2001-complete specification (granted).pdf

888-del-2001-correspondence-others.pdf

888-del-2001-correspondence-po.pdf

888-del-2001-description (complete).pdf

888-del-2001-drawings.pdf

888-del-2001-form-1.pdf

888-del-2001-form-13.pdf

888-del-2001-form-19.pdf

888-del-2001-form-2.pdf

888-del-2001-form-26.pdf

888-del-2001-form-3.pdf