Integrated processes for generating carbon monoxide for carbon nanomaterial production

Abstract

The integrated processes of the dry reforming or partial oxidation upstream of the carbon nanotube-producing reactor are described allowing the carbon monoxide to be produced on an as-needed basis, negating the need to transport carbon monoxide to the production site or store large quantities of carbon monoxide on-site. The apparatuses allowing to carry out such integrated processes are also provided. Carbon dioxide emissions may be eliminated from the carbon nanotube production process. This may be achieved by recycling the carbon dioxide byproduct and mixing it with the feed to the partial oxidation process.

1 . A process for producing carbon nanotubes comprising:
 (a) combining a hydrocarbon stream, a carbon dioxide stream and an oxygen stream to form a combined stream and, in a conversion reactor, subjecting the hydrocarbon in the combined stream to a process of conversion to form a converted gas stream comprising hydrogen, carbon monoxide, carbon dioxide, and an unreacted portion of oxygen;   (b) removing the unreacted portion of oxygen from the converted gas stream by subjecting the converted gas stream to deoxidation to produce a deoxygenated gas stream comprising the hydrogen, the carbon monoxide, and the carbon dioxide;   (c) separating the hydrogen from the deoxygenated gas stream to form a principal stream, and a by-product stream, wherein the principal stream comprises the carbon monoxide and the carbon dioxide, and the by-product stream comprises the hydrogen;   (d) directing the principal stream to a nanocarbon tube production unit to obtain the carbon nanotubes and the carbon dioxide stream; and   (e) recycling the carbon dioxide by directing the carbon dioxide stream to the conversion reactor.   
     
     
         2 . The process of  claim 1 , further comprising utilizing the by-product stream. 
     
     
         3 . The process of  claim 2 , wherein the step of utilizing the by-product stream comprises recycling the hydrogen by directing the by-product stream to the conversion reactor. 
     
     
         4 . The process of  claim 2 , wherein the step of utilizing the by-product stream comprises exporting the hydrogen as fuel. 
     
     
         5 . The process of  claim 1 , wherein the step of removing the unreacted portion of oxygen is carried out in a deoxidation apparatus. 
     
     
         6 . The process of  claim 1 , wherein the step of separating the hydrogen from the deoxygenated gas stream is carried out in at least a one stage membrane separator. 
     
     
         7 . The process of  claim 6 , wherein the membrane separator comprises at least two stages. 
     
     
         8 . The process of  claim 6 , wherein the membrane separator includes at least one membrane comprising a layer of an inorganic material deposited on a porous amorphous substrate. 
     
     
         9 . The process of  claim 8 , wherein the inorganic material comprises a layer of silicon dioxide. 
     
     
         10 . The process of  claim 9 , wherein the layer of silicon dioxide is formed by chemical vapor deposition. 
     
     
         11 . The process of  claim 8 , wherein the porous amorphous substrate comprises alumina. 
     
     
         12 . The process of  claim 8 , wherein the porous amorphous substrate comprises pores having diameter between about 5 and about 10 nanometers. 
     
     
         13 . The process of  claim 1  wherein the process of conversion includes catalytic reforming of the hydrocarbon. 
     
     
         14 . The process of  claim 13 , wherein the catalytic reforming is carried out in the presence of a catalyst comprising a metal selected from the group consisting of nickel, platinum, palladium, and rhodium. 
     
     
         15 . The process of  claim 13 , wherein the process of conversion is carried at a temperature between about 700° C. and about 1,400° C. 
     
     
         16 . The process of  claim 13 , wherein the process of conversion is carried at a pressure up to about 150 atmospheres. 
     
     
         17 . The process of  claim 1 , wherein the hydrocarbon is methane. 
     
     
         18 . An apparatus for producing carbon nanotubes comprising:
 (a) a conversion reactor that converts a mixture of a hydrocarbon(s), carbon dioxide and oxygen into a converted gas stream comprising hydrogen, carbon monoxide, carbon dioxide, and an unreacted portion of oxygen;   (b) a deoxidation unit, in fluid communication with the conversion reactor, wherein the deoxidation unit removes the unreacted portion of oxygen from the converted gas stream and produces a deoxygenated gas stream comprising the hydrogen, the carbon monoxide, and the carbon dioxide;   (c) at least a one stage membrane separator, in fluid communication with the deoxidation unit, wherein the membrane separator separates the hydrogen from the deoxygenated gas stream and forms a principal stream and a by-product stream, wherein the principal stream comprises the carbon monoxide and the carbon dioxide, and the by-product stream comprises the hydrogen;   (d) a nano-carbon tube production unit, in fluid communication with the membrane separator, wherein the nano-carbon tube production unit produces carbon nanotubes and the carbon dioxide stream; and   (e) a carbon monoxide recycling device, in fluid communication with the nano-carbon tube production unit, that directs the carbon dioxide stream to the conversion reactor.   
     
     
         19 . The apparatus of  claim 18 , wherein the membrane separator comprises at least two stages. 
     
     
         20 . The apparatus of  claim 19 , wherein the membrane separator includes at least one membrane comprising a layer of an inorganic material deposited on a porous amorphous substrate. 
     
     
         21 . The apparatus of  claim 20 , wherein the inorganic material comprises a layer of silicon dioxide. 
     
     
         22 . The apparatus of  claim 21 , wherein the layer of silicon dioxide is formed by chemical vapor deposition. 
     
     
         23 . The apparatus of  claim 20 , wherein the porous amorphous substrate comprises alumina. 
     
     
         24 . The apparatus of  claim 20 , wherein the porous amorphous substrate comprises pores having diameter between about 5 and about 10 nanometers. 
     
     
         25 . The apparatus of  claim 20 , further comprising means for exporting the hydrogen.