Method for making single-wall carbon nanotubes using supported catalysts

• US 7,250,148 B2
• Filed: 07/30/2003
• Issued: 07/31/2007
• Est. Priority Date: 07/31/2002
• Status: Expired due to Fees

• Current Assignee: Unidym, Inc. (Wisepower Co., Ltd.)
• Original Assignee: Carbon Nanotechnologies, Inc. (Wisepower Co., Ltd.)
• Inventors: Smith, Kenneth A., Yang, Yuemei, Grosboll, Martin P.
• Primary Examiner(s): HENDRICKSON, STUART L
• Application Number:
  US10/630,054
• Publication Number:
  US 20050074392A1
• Time in Patent Office: 1,462 Days
• Field of Search: 423/447.3, 502/313, 502/316, 977/843
• US Class Current: 423/447.3
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 2202/02 Single-walled nanotubes
• CPC Class Codes: C01B 32/162 characterised by catalysts
• CPC Class Codes: Y10S 977/843 Gas phase catalytic growth, i.e. chemical vapor deposition

Abstract

A method for growing single-wall carbon nanotubes involves preparing a catalyst comprising catalytic metals, iron and molybdenum, and magnesium oxide support material and contacting the catalyst with a gaseous carbon-containing feedstock at a sufficient temperature and for a sufficient contact time to make single-wall carbon nanotubes. The weight ratio of iron and molybdenum can range from about 2 to 1 to about 10 to 1 and the metals loading up to about 10 wt % of the MgO. The catalyst can be sulfided. Methane is a suitable carbon-containing feedstock. The process can be conducted in batch, continuous or semi-continuous modes, in reactors, such as a transport reactor, fluidized bed reactor, moving bed reactors and combinations thereof. The process also includes making single-wall carbon nanotubes with catalysts comprising at least one Group VIB or Group VIIIB metal on supports such as magnesia, zirconia, silica, and alumina, where the catalyst is sulfided.

Claims

1. A method for producing single-wall carbon nanotubes, comprising:

(a) combusting a foaming agent and iron, molybdenum and magnesium oxide precursors to form a supported catalyst which is a solid solution; and

(b) contacting the catalyst with a gaseous stream comprising a carbon-containing feedstock at a sufficient temperature and for a contact time sufficient to make a carbon product comprising single-wall carbon nanotubes.

2. The method of claim 1 wherein iron and molybdenum are present in a weight ratio range from about 10 to 1 to about 2 to 1.

3. The method of claim 1 wherein the iron and molybdenum are present in a molar ratio range from about 20 to 1 to about 3 to 1.

4. The method of claim 1 wherein the catalytic metal is present on the magnesium oxide on a weight basis from about 0.5 wt % to at most about 10 wt % of the weight of the magnesium oxide.

5. The method of claim 1 wherein the iron precursor is selected from the group consisting of iron (III) nitrate, iron sulfite, iron sulfate, iron carbonate, iron acetate, iron citrate, iron gluconate, iron hexacyanoferrite, iron oxalate, tris(ethylenediamine) iron sulfate and combinations thereof.

6. The method of claim 1 wherein the iron precursor comprises iron (III) nitrate.

7. The method of claim 1 wherein the molybdenum precursor comprises ammonium heptamolybdate.

8. The method of claim 1 wherein the magnesium oxide precursor comprises magnesium nitrate.

9. The method of claim 1 wherein the combusting includes at least one compound selected from the group consisting of a citric acid, urea, glycine, hydrazine, sucrose, carbohydrazide, oxalyl dihydrazide, sugars, alcohols, and combinations thereof.

10. The method of claim 1 wherein the combusting includes citric acid.

11. The method of claim 1 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 150°

C. and about 1200°

C.

12. The method of claim 1 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 200°

C. and about 700°

C.

13. The method of claim 1 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 250°

C. and about 650°

C.

14. The method of claim 1 wherein the precursors are sprayed to form an aerosol prior to combustion.

15. The method of claim 1 wherein the combusting comprises contacting the precursors with a heated surface.

16. The method of claim 1 wherein the catalyst is exposed to a sulfur-containing compound.

17. The method of claim 16 wherein the sulfur-containing compound is selected from the group consisting of thiophene, hydrogen sulfide, a mercaptan and combinations thereof.

18. The method of claim 16 wherein the sulfur-containing compound comprises thiophene.

19. The method of claim 1 wherein the catalyst has a cross-sectional dimension of less than about 100 microns.

20. The method of claim 1 wherein the catalyst has a cross-sectional dimension of less than about 30 microns.

21. The method of claim 1 wherein the catalyst has a bulk density less than about 0.3 g/cm³.

22. The method of claim 1 wherein the catalyst has a bulk density less than about 0.1 g/cm³.

23. The method of claim 1 further comprising reducing the metal prior to the contacting step.

24. The method of claim 23 wherein the reducing is done with a reducing gas.

25. The method of claim 24 wherein the reducing gas comprises hydrogen.

26. The method of claim 1 wherein the metal is reduced during the contacting step.

27. The method of claim 1 wherein the temperature is in a range of about 500°

C. and about 1500°

C.

28. The method of claim 1 wherein the temperature is in the range of about 650°

C. and about 950°

C.

29. The method of claim 1 wherein the temperature is in the range of about 800°

C. and about 950°

C.

30. The method of claim 1 wherein the carbon-containing feedstock comprises a compound selected from the group consisting of methane, hydrocarbons, carbon monoxide and combinations thereof.

31. The method of claim 1 wherein the gaseous stream comprising the carbon-containing feedstock comprises methane.

32. The method of claim 1 further comprising mixing hydrogen with the gasesous stream comprising carbon-containing feedstock.

33. The method of claim 1 wherein the gaseous stream comprising the carbon-containing feedstock also comprises hydrogen.

34. The method of claim 1 wherein the gaseous stream comprising the carbon-containing feedstock comprises a mixture of methane and hydrogen.

35. The method of claim 1 wherein the contact time is in a range of about 0.1 seconds and about 60 minutes.

36. The method of claim 1 wherein the contact time is in a range of about 0.1 seconds and about 30 minutes.

37. The method of claim 1 wherein the contact time is in a range of about 10 seconds and about 10 minutes.

38. The method of claim 1 wherein the single-wall carbon nanotubes have diameters controlled by the contact time in the contacting step.

39. The method of claim 1 wherein the single-wall carbon nanotubes have lengths controlled by the contact time in the contacting step.

40. The method of claim 1 wherein the contacting is done at a pressure between about 0.1 atmospheres and about 200 atmospheres.

41. The method of claim 1 further comprising removing the catalyst from the carbon product with an acid.

42. The method of claim 41 wherein the acid is selected from the group consisting of citric acid, acetic acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid and combinations thereof.

43. The method of claim 41 wherein the acid comprises hydrochloric acid.

44. The method of claim 1 wherein at least about 50 wt % of carbon in the carbon product is single-wall carbon nanotubes.

45. The method of claim 1 wherein at least about 80 wt % of carbon in the product is single-wall carbon nanotubes.

46. The method of claim 1 wherein at least about 90 wt % of carbon in the product is single-wall carbon nanotubes.

47. The method of claim 1 wherein at least about 95 wt % of carbon in the product is single-wall carbon nanotubes.

48. The method of claim 1 wherein the catalyst is flowed through a transport reactor entrained in the gaseous stream comprising the carbon-containing feedstock.

49. The method of claim 48 wherein at least one other gaseous stream comprising the carbon-containing feedstock is introduced to the reactor at more than one inlet.

50. The method of claim 49 wherein the at least one other gaseous stream comprises hydrogen.

51. The method of claim 48 wherein the reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

52. The method of claim 48 wherein the reactor further comprises a solid-gas separator selected from the group consisting of a wet scrubber, a cyclone, an electrostatic precipitator, filter, and combinations thereof.

53. The method of claim 48 wherein a dispersing aid is used in the transport reactor.

54. The method of claim 53 wherein the dispersing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

55. The method of claim 1 wherein the catalyst is fluidized by the gaseous stream comprising the carbon-containing feedstock in a fluidized bed reactor.

56. The method of claim 55 wherein the fluidized bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

57. The method of claim 55 wherein a fluidizing aid is fluidized in the fluidized bed reactor.

58. The method of claim 57 wherein the catalyst and the carbon product are separated from the fluidizing aid by differential elutriation.

59. The method of claim 57 wherein the fluidizing aid exchanges heat with the catalyst.

60. The method of claim 57 wherein the fluidizing aid acts as a reactor wall scrubber.

61. The method of claim 57 wherein the fluidizing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

62. The method of claim 1 wherein the contacting occurs in a moving bed reactor, wherein the reactor has a moving bed comprising the catalyst and essentially-inert particles.

63. The method of claim 62 wherein the moving bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

64. The method of claim 62 wherein the gaseous stream comprising the carbon-containing feedstock is introduced into the reactor at more than one inlet.

65. The method of claim 62 wherein the essentially-inert particles comprise a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

66. The method of claim 62 wherein the essentially-inert particles are removed from the reactor, circulated and re-introduced to the reactor.

67. The method of claim 62 where the essentially-inert particles are regenerated after exiting the reactor.

68. The method of claim 62 wherein the essentially-inert particles are heated after exiting the reactor to produce essentially-inert heated particles.

69. The method of claim 67 wherein the essentially-inert heated particles are introduced into the reactor and exchange heat with the catalyst.

70. The method of claim 62 further comprising separating the catalyst and the carbon product from the essentially-inert particles.

71. The method of claim 70 wherein the separating is done by differential elutriation.

72. The method of claim 70 wherein the separating comprises a component selected from the group consisting of a cyclone, a classifier, a solid-gas separator, a disengaging section, a wet scrubber, a cyclone, an electrostatic precipitator, a filter and combinations thereof.

73. The method of claim 62 wherein the moving bed reactor is a counter-current moving bed reactor, wherein the counter-current moving bed reactor has a moving bed comprising the essentially-inert particles that move in a direction counter-current to flows of the catalyst and the gaseous stream comprising the carbon-containing feedstock.

74. The method of claim 62 wherein the moving bed reactor is a concurrent-flow moving bed reactor wherein the essentially-inert particles and the catalyst flow in the same direction.

75. The method of claim 74 wherein the gaseous stream comprising the carbon-containing feedstock, the essentially inert particles and the catalyst flow in the same direction.

76. The method of claim 74 wherein the gaseous stream comprising the carbon-containing feedstock flows in an opposite direction to movement of the essentially-inert particles and the catalyst.

77. A method for producing single-wall carbon nanotubes, comprising:

(a) combusting a foaming agent with precursors of catalytic metal comprising at least one metal from the group consisting of Group VIB and Group VIIIB and a support selected from the group consisting of oxides of aluminum, magnesium, silicon, zirconium and combinations thereof to form a catalyst;

(b) sulfiding the catalyst which is a solid solution; and

(c) contacting the catalyst with a gaseous stream comprising a carbon-containing feedstock at a sufficient temperature and for a contact time sufficient to make a carbon product comprising single-wall carbon nanotubes.

78. The method of claim 77 wherein the catalytic metal comprise Co and Mo.

79. The method of claim 77 wherein the support is magnesia.

80. The method of claim 77 wherein the foaming agent is selected from the group consisting of citric acid, urea, glycine, hydrazine, sucrose, carbohydrazide, oxalyl dihydrazide, sugars, alcohols, and combinations thereof.

81. The method of claim 80 wherein the foaming agent comprises citric acid.

82. The method of claim 77 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 150°

C. and about 1200°

C.

83. The method of claim 77 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 200°

C. and about 700°

C.

84. The method of claim 77 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 250°

C. and about 650°

C.

85. The method of claim 77 wherein the precursors are sprayed to form an aerosol prior to combustion.

86. The method of claim 77 wherein the combusting comprises contacting the precursors with a heated surface.

87. The method of claim 77 wherein the sulfiding is done by exposing the catalyst to a sulfur-containing compound selected from the group consisting of thiophene, hydrogen sulfide, a mercaptan and combinations thereof.

88. The method of claim 77 wherein the sulfiding is done prior to the contacting step.

89. The method of claim 77 wherein the sulfiding is done with the contacting step.

90. The method of claim 77 wherein the catalyst has a cross-sectional dimension of less than about 100 microns.

91. The method of claim 77 wherein the catalyst has a cross-sectional dimension of less than about 30 microns.

92. The method of claim 77 wherein the catalyst has a bulk density less than about 0.3 g/cm³.

93. The method of claim 77 wherein the catalyst has a bulk density less than about 0.1 g/cm³.

94. The method of claim 77 further comprising reducing the metal prior to the contacting step.

95. The method of claim 94 wherein the reducing is done with a reducing gas.

96. The method of claim 95 wherein the reducing gas comprises hydrogen.

97. The method of claim 77 wherein the metal is reduced during the contacting step.

98. The method of claim 77 wherein the temperature is in a range of about 500°

C. and about 1500°

C.

99. The method of claim 77 wherein the temperature is in the range of about 650°

C. and about 950°

C.

100. The method of claim 77 wherein the temperature is in the range of about 800°

C. and about 950°

C.

101. The method of claim 77 wherein the carbon-containing feedstock comprises a compound selected from the group consisting of methane, hydrocarbons, carbon monoxide and combinations thereof.

102. The method of claim 77 wherein the gaseous stream comprising the carbon-containing feedstock comprises methane.

103. The method of claim 77 further comprising mixing hydrogen with the gasesous stream comprising carbon-containing feedstock.

104. The method of claim 77 wherein the gaseous stream comprising the carbon-containing feedstock also comprises hydrogen.

105. The method of claim 77 wherein the gaseous stream comprising the carbon-containing feedstock comprises a mixture of methane and hydrogen.

106. The method of claim 77 wherein the contact time is in a range of about 0.1 seconds and about 60 minutes.

107. The method of claim 77 wherein the contact time is in a range of about 0.1 seconds and about 30 minutes.

108. The method of claim 77 wherein the contact time is in a range of about 10 seconds and about 10 minutes.

109. The method of claim 77 wherein the single-wall carbon nanotubes have diameters controlled by the contact time in the contacting step.

110. The method of claim 77 wherein the single-wall carbon nanotubes have lengths controlled by the contact time in the contacting step.

111. The method of claim 77 wherein the contacting is done at a pressure between about 0.1 atmospheres and about 200 atmospheres.

112. The method of claim 77 further comprising removing the catalyst from the carbon product with an acid.

113. The method of claim 112 wherein the acid is selected from the group consisting of citric acid, acetic acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid and combinations thereof.

114. The method of claim 112 wherein the acid comprises hydrochloric acid.

115. The method of claim 77 wherein at least about 50 wt % of carbon in the carbon product is single-wall carbon nanotubes.

116. The method of claim 77 wherein at least about 80 wt % of carbon in the product is single-wall carbon nanotubes.

117. The method of claim 77 wherein at least about 90 wt % of carbon in the product is single-wall carbon nanotubes.

118. The method of claim 77 wherein at least about 95 wt % of carbon in the product is single-wall carbon nanotubes.

119. The method of claim 77 wherein the catalyst is flowed through a transport reactor entrained in the gaseous stream comprising the carbon-containing feedstock.

120. The method of claim 119 wherein at least one other gaseous stream comprising the carbon-containing feedstock is introduced to the reactor at more than one inlet.

121. The method of claim 120 wherein the at least one other gaseous stream comprises hydrogen.

122. The method of claim 119 wherein the reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

123. The method of claim 119 wherein the reactor further comprises a solid-gas separator selected from the group consisting of a wet scrubber, a cyclone, an electrostatic precipitator, filter, and combinations thereof.

124. The method of claim 119 wherein a dispersing aid is used in the transport reactor.

125. The method of claim 124 wherein the dispersing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

126. The method of claim 77 wherein the catalyst is fluidized by the gaseous stream comprising the carbon-containing feedstock in a fluidized bed reactor.

127. The method of claim 126 wherein the fluidized bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

128. The method of claim 126 wherein a fluidizing aid is fluidized in the fluidized bed reactor.

129. The method of claim 128 wherein the catalyst and the carbon product are separated from the fluidizing aid by differential elutriation.

130. The method of claim 128 wherein the fluidizing aid exchanges heat with the catalyst.

131. The method of claim 128 wherein the fluidizing aid acts as a reactor wall scrubber.

132. The method of claim 128 wherein the fluidizing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

133. The method of claim 77 wherein the contacting occurs in a moving bed reactor, wherein the reactor has a moving bed comprising the catalyst and essentially-inert particles.

134. The method of claim 133 wherein the moving bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

135. The method of claim 133 wherein the gaseous stream comprising the carbon-containing feedstock is introduced into the reactor at more than one inlet.

136. The method of claim 133 wherein the essentially-inert particles comprise a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

137. The method of claim 133 wherein the essentially-inert particles are removed from the reactor, circulated and re-introduced to the reactor.

138. The method of claim 133 where the essentially-inert particles are regenerated after exiting the reactor.

139. The method of claim 133 wherein the essentially-inert particles are heated after exiting the reactor to produce essentially-inert heated particles.

140. The method of claim 133 wherein the essentially-inert heated particles are introduced into the reactor and exchange heat with the catalyst.

141. The method of claim 133 further comprising separating the catalyst and the carbon product from the essentially-inert particles.

142. The method of claim 141 wherein the separating is done by differential elutriation.

143. The method of claim 141 wherein the separating comprises a component selected from the group consisting of a cyclone, a classifier, a solid-gas separator, a disengaging section, a wet scrubber, a cyclone, an electrostatic precipitator, a filter and combinations thereof.

144. The method of claim 133 wherein the moving bed reactor is a counter-current moving bed reactor, wherein the counter-current moving bed reactor has a moving bed comprising the essentially-inert particles that move in a direction counter-current to flows of the catalyst and the gaseous stream comprising the carbon-containing feedstock.

145. The method of claim 133 wherein the moving bed reactor is a concurrent-flow moving bed reactor wherein the essentially-inert particles and the catalyst flow in the same direction.

146. The method of claim 145 wherein the gaseous stream comprising the carbon-containing feedstock, the essentially inert particles and the catalyst flow in the same direction.

147. The method of claim 146 wherein the gaseous stream comprising the carbon-containing feedstock flows in an opposite direction to movement of the essentially-inert particles and the catalyst.

148. A method for producing single-wall carbon nanotubes, comprising:

(a) combusting a foaming agent and precursors of cobalt oxide, molybdenum oxide and magnesium oxide to form a catalyst which is a solid solution;

(b) sulfiding the catalyst; and

(c) contacting the catalyst with a gaseous stream comprising a carbon-containing feedstock at a sufficient temperature and for a contact time sufficient to make a carbon product comprising single-wall carbon nanotubes.

149. The method of claim 148 wherein the foaming agent is selected from the group consisting of citric acid, urea, glycine, hydrazine, sucrose, carbohydrazide, oxalyl dihydrazide, sugars, alcohols, and combinations thereof.

150. The method of claim 148 wherein the foaming agent comprises citric acid.

151. The method of claim 148 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 150°

C. and about 1200°

C.

152. The method of claim 148 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 200°

C. and about 700°

C.

153. The method of claim 148 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 250°

C. and about 650°

C.

154. The method of claim 148 wherein the precursors are sprayed to form an aerosol prior to combustion.

155. The method of claim 148 wherein the combusting comprises contacting the precursors with a heated surface.

156. The method of claim 148 wherein the sulfiding is done by exposing the catalyst to a sulfur-containing compound selected from the group consisting of thiophene, hydrogen sulfide, a mercaptan and combinations thereof.

157. The method of claim 148 wherein the sulfiding is done prior to the contacting step.

158. The method of claim 148 wherein the sulfiding is done with the contacting step.

159. The method of claim 148 wherein the catalyst has a cross-sectional dimension of less than about 100 microns.

160. The method of claim 148 wherein the catalyst has a cross-sectional dimension of less than about 30 microns.

161. The method of claim 148 wherein the catalyst has a bulk density less than about 0.3 g/cm³.

162. The method of claim 148 wherein the catalyst has a bulk density less than about 0.1 g/cm³.

163. The method of claim 148 further comprising reducing the metal prior to the contacting step.

164. The method of claim 163 wherein the reducing is done with a reducing gas.

165. The method of claim 164 wherein the reducing gas comprises hydrogen.

166. The method of claim 148 wherein the metal is reduced during the contacting step.

167. The method of claim 148 wherein the temperature is in a range of about 500°

C. and about 1500°

C.

168. The method of claim 148 wherein the temperature is in the range of about 650°

C. and about 950°

C.

169. The method of claim 148 wherein the temperature is in the range of about 800°

C. and about 950°

C.

170. The method of claim 148 wherein the carbon-containing feedstock comprises a compound selected from the group consisting of methane, hydrocarbons, carbon monoxide and combinations thereof.

171. The method of claim 148 wherein the gaseous stream comprising the carbon-containing feedstock comprises methane.

172. The method of claim 148 further comprising mixing hydrogen with the gasesous stream comprising carbon-containing feedstock.

173. The method of claim 148 wherein the gaseous stream comprising the carbon-containing feedstock also comprises hydrogen.

174. The method of claim 148 wherein the gaseous stream comprising the carbon-containing feedstock comprises a mixture of methane and hydrogen.

175. The method of claim 148 wherein the contact time is in a range of about 0.1 seconds and about 60 minutes.

176. The method of claim 148 wherein the contact time is in a range of about 0.1 seconds and about 30 minutes.

177. The method of claim 148 wherein the contact time is in a range of about 10 seconds and about 10 minutes.

178. The method of claim 148 wherein the single-wall carbon nanotubes have diameters controlled by the contact time in the contacting step.

179. The method of claim 148 wherein the single-wall carbon nanotubes have lengths controlled by the contact time in the contacting step.

180. The method of claim 148 wherein the contacting is done at a pressure between about 0.1 atmospheres and about 200 atmospheres.

181. The method of claim 148 further comprising removing the catalyst from the carbon product with an acid.

182. The method of claim 181 wherein the acid is selected from the group consisting of citric acid, acetic acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid and combinations thereof.

183. The method of claim 181 wherein the acid comprises hydrochloric acid.

184. The method of claim 148 wherein at least about 50 wt % of carbon in the carbon product is single-wall carbon nanotubes.

185. The method of claim 148 wherein at least about 80 wt % of carbon in the product is single-wall carbon nanotubes.

186. The method of claim 148 wherein at least about 90 wt % of carbon in the product is single-wall carbon nanotubes.

187. The method of claim 148 wherein at least about 95 wt % of carbon in the product is single-wall carbon nanotubes.

188. The method of claim 148 wherein the catalyst is flowed through a transport reactor entrained in the gaseous stream comprising the carbon-containing feedstock.

189. The method of claim 188 wherein at least one other gaseous stream comprising the carbon-containing feedstock is introduced to the reactor at more than one inlet.

190. The method of claim 189 wherein the at least one other gaseous stream comprises hydrogen.

191. The method of claim 188 wherein the reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

192. The method of claim 188 wherein the reactor further comprises a solid-gas separator selected from the group consisting of a wet scrubber, a cyclone, an electrostatic precipitator, filter, and combinations thereof.

193. The method of claim 188 wherein a dispersing aid is used in the transport reactor.

194. The method of claim 193 wherein the dispersing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

195. The method of claim 148 wherein the catalyst is fluidized by the gaseous stream comprising the carbon-containing feedstock in a fluidized bed reactor.

196. The method of claim 195 wherein the fluidized bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

197. The method of claim 195 wherein a fluidizing aid is fluidized in the fluidized bed reactor.

198. The method of claim 197 wherein the catalyst and the carbon product are separated from the fluidizing aid by differential elutriation.

199. The method of claim 197 wherein the fluidizing aid exchanges heat with the catalyst.

200. The method of claim 197 wherein the fluidizing aid acts as a reactor wall scrubber.

201. The method of claim 197 wherein the fluidizing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

202. The method of claim 148 wherein the contacting occurs in a moving bed reactor, wherein the reactor has a moving bed comprising the catalyst and essentially-inert particles.

203. The method of claim 202 wherein the moving bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

204. The method of claim 202 wherein the gaseous stream comprising the carbon-containing feedstock is introduced into the reactor at more than one inlet.

205. The method of claim 202 wherein the essentially-inert particles comprise a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

206. The method of claim 202 wherein the essentially-inert particles are removed from the reactor, circulated and re-introduced to the reactor.

207. The method of claim 202 where the essentially-inert particles are regenerated after exiting the reactor.

208. The method of claim 202 wherein the essentially-inert particles are heated after exiting the reactor to produce essentially-inert heated particles.

209. The method of claim 202 wherein the essentially-inert heated particles are introduced into the reactor and exchange heat with the catalyst.

210. The method of claim 202 further comprising separating the catalyst and the carbon product from the essentially-inert particles.

211. The method of claim 210 wherein the separating is done by differential elutriation.

212. The method of claim 210 wherein the separating comprises a component selected from the group consisting of a cyclone, a classifier, a solid-gas separator, a disengaging section, a wet scrubber, a cyclone, an electrostatic precipitator, a filter and combinations thereof.

213. The method of claim 202 wherein the moving bed reactor is a counter-current moving bed reactor, wherein the counter-current moving bed reactor has a moving bed comprising the essentially-inert particles that move in a direction counter-current to flows of the catalyst and the gaseous stream comprising the carbon-containing feedstock.

214. The method of claim 202 wherein the moving bed reactor is a concurrent-flow moving bed reactor wherein the essentially-inert particles and the catalyst flow in the same direction.

215. The method of claim 214 wherein the gaseous stream comprising the carbon-containing feedstock, the essentially inert particles and the catalyst flow in the same direction.

216. The method of claim 214 wherein the gaseous stream comprising the carbon-containing feedstock flows in an opposite direction to movement of the essentially-inert particles and the catalyst.

217. A method for producing carbon nanotubes, comprising:

(a) combusting a foaming agent, precursors of at least one catalytic metal selected from the group selected from Group VIIIB metal precursors, Group VIB metal precursors, and combinations thereof, and refractory material precursors to form a supported catalyst which is a solid solution; and

(b) contacting the catalyst with a gaseous stream comprising a carbon-containing feedstock at a sufficient temperature and for a contact time sufficient to make a carbon product comprising carbon nanotubes.

218. The method of claim 217 wherein the carbon nanotubes are selected from the group consisting of multiwall carbon nanotubes, single-wall carbon nanotubes and a combination thereof.

219. The method of claim 217 wherein the catalytic metal comprises metals from both Group VIIIB and Group VIB and wherein the Group VIIIB metal and the Group VIB metal have a weight ratio in the range of about 10 to 1 to about 2 to 1.

220. The method of claim 217 wherein the catalytic metal comprises metals from both Group VIIIB and Group VIB and wherein the Group VIIIB metal and the Group VIB metal have a molar ratio in the range of about 20 to 1 to about 3 to 1.

221. The method of claim 217 wherein the catalytic metal is are present on the refractory particles at a loading in the range of about 0.5 wt % and about 10 wt % of the weight of the refractory material.

222. The method of claim 217 wherein the Group VIIIB metal precursor is selected from a Group VIIIB-containing compound wherein the compound is selected the group consisting of a nitrate, a sulfite, a sulfate, a carbonate, an acetate, a citrate, a gluconate, a hexacyanoferrite, an oxalate, a tris(ethylenediamine) sulfate and combinations thereof.

223. The method of claim 217 wherein the Group VIB metal precursor is a Group VI-containing compound wherein the compound is an ammonium compound.

224. The method of claim 217 wherein the refractory material precursor is a nitrate compound.

225. The method of claim 217 wherein the foaming agent is selected from the group consisting of citric acid, urea, glycine, hydrazine, sucrose, carbohydrazide, oxalyl dihydrazide, sugars, alcohols, and combinations thereof.

226. The method of claim 217 wherein the foaming agent comprises citric acid.

227. The method of claim 217 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 150°

C. and about 1200°

C.

228. The method of claim 217 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 200°

C. and about 700°

C.

229. The method of claim 217 wherein the combusting is conducted by exposing the precursors to temperatures in the range of about 250°

C. and about 650°

C.

230. The method of claim 217 wherein the precursors are sprayed to form an aerosol prior to combustion.

231. The method of claim 217 wherein the combusting comprises contacting the precursors with a heated surface.

232. The method of claim 217 further comprising sulfiding the catalyst wherein the catalyst is exposed to a sulfur-containing compound.

233. The method of claim 232 wherein the sulfur-containing compound is selected from the group consisting of thiophene, hydrogen sulfide, a mercaptan and combinations thereof.

234. The method of claim 232 wherein the sulfur-containing compound comprises thiophene.

235. The method of claim 232 wherein the sulfiding is done prior to the contacting step.

236. The method of claim 232 wherein the sulfiding is done with the contacting step.

237. The method of claim 217 wherein the catalyst has a cross-sectional dimension of less than about 100 microns.

238. The method of claim 217 wherein the catalyst has a cross-sectional dimension of less than about 30 microns.

239. The method of claim 217 wherein the catalyst has a bulk density less than about 0.3 g/cm³.

240. The method of claim 217 wherein the catalyst has a bulk density less than about 0.1 g/cm³.

241. The method of claim 217 further comprising reducing the metal prior to the contacting step.

242. The method of claim 241 wherein the reducing is done with a reducing gas.

243. The method of claim 242 wherein the reducing gas comprises hydrogen.

244. The method of claim 217 wherein the metal is reduced during the contacting step.

245. The method of claim 217 wherein the temperature is in a range of about 500°

C. and about 1500°

C.

246. The method of claim 217 wherein the temperature is in the range of about 650°

C. and about 950°

C.

247. The method of claim 217 wherein the temperature is in the range of about 800°

C. and about 950°

C.

248. The method of claim 217 wherein the carbon-containing feedstock comprises a compound selected from the group consisting of methane, hydrocarbons, carbon monoxide and combinations thereof.

249. The method of claim 217 wherein the gaseous stream comprising the carbon-containing feedstock comprises methane.

250. The method of claim 217 further comprising mixing hydrogen with the gasesous stream comprising carbon-containing feedstock.

251. The method of claim 217 wherein the gaseous stream comprising the carbon-containing feedstock also comprises hydrogen.

252. The method of claim 217 wherein the gaseous stream comprising the carbon-containing feedstock comprises a mixture of methane and hydrogen.

253. The method of claim 217 further comprising mixing an oxidizing gas with gaseous stream comprising the carbon-containing feedstock.

254. The method of claim 253 wherein the oxidizing gas is selected from the group consisting of oxygen, water vapor, carbon dioxide and combinations thereof.

255. The method of claim 217 wherein the contact time is in a range of about 0.1 seconds and about 60 minutes.

256. The method of claim 217 wherein the contact time is in a range of about 0.1 seconds and about 30 minutes.

257. The method of claim 217 wherein the contact time is in a range of about 10 seconds and about 10 minutes.

258. The method of claim 217 wherein the single-wall carbon nanotubes have diameters controlled by the contact time in the contacting step.

259. The method of claim 217 wherein the single-wall carbon nanotubes have lengths controlled by the contact time in the contacting step.

260. The method of claim 217 wherein the contacting is done at a pressure between about 0.1 atmospheres and about 197 atmospheres.

261. The method of claim 217 further comprising removing the catalyst from the carbon product with an acid.

262. The method of claim 261 wherein the acid is selected from the group consisting of citric acid, acetic acid, nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid and combinations thereof.

263. The method of claim 261 wherein the acid comprises hydrochloric acid.

264. The method of claim 217 wherein at least about 50 wt % of carbon in the carbon product is single-wall carbon nanotubes.

265. The method of claim 217 wherein at least about 80 wt % of carbon in the product is single-wall carbon nanotubes.

266. The method of claim 217 wherein at least about 90 wt % of carbon in the product is single-wall carbon nanotubes.

267. The method of claim 217 wherein at least about 95 wt % of carbon in the product is single-wall carbon nanotubes.

268. The method of claim 217 wherein the catalyst is flowed through a transport reactor entrained in the gaseous stream comprising the carbon-containing feedstock.

269. The method of claim 268 wherein at least one other gaseous stream comprising the carbon-containing feedstock is introduced to the reactor at more than one inlet.

270. The method of claim 269 wherein the at least one other gaseous stream comprises hydrogen.

271. The method of claim 268 wherein the reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

272. The method of claim 268 wherein the reactor further comprises a solid-gas separator selected from the group consisting of a wet scrubber, a cyclone, an electrostatic precipitator, filter, and combinations thereof.

273. The method of claim 268 wherein a dispersing aid is used in the transport reactor.

274. The method of claim 273 wherein the dispersing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

275. The method of claim 217 wherein the catalyst is fluidized by the gaseous stream comprising the carbon-containing feedstock in a fluidized bed reactor.

276. The method of claim 275 wherein the fluidized bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

277. The method of claim 275 wherein a fluidizing aid is fluidized in the fluidized bed reactor.

278. The method of claim 277 wherein the catalyst and the carbon product are separated from the fluidizing aid by differential elutriation.

279. The method of claim 277 wherein the fluidizing aid exchanges heat with the catalyst.

280. The method of claim 277 wherein the fluidizing aid acts as a reactor wall scrubber.

281. The method of claim 277 wherein the fluidizing aid is a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

282. The method of claim 217 wherein the contacting occurs in a moving bed reactor, wherein the reactor has a moving bed comprising the catalyst and essentially-inert particles.

283. The method of claim 282 wherein the moving bed reactor comprises more than one zone wherein each zone is capable of maintaining a different set of reaction conditions.

284. The method of claim 282 wherein the gaseous stream comprising the carbon-containing feedstock is introduced into the reactor at more than one inlet.

285. The method of claim 282 wherein the essentially-inert particles comprise a material selected from the group consisting of metal oxide particles, sand, quartz beads, ceramic particles, refractory material and combinations thereof.

286. The method of claim 282 wherein the essentially-inert particles are removed from the reactor, circulated and re-introduced to the reactor.

287. The method of claim 282 where the essentially-inert particles are regenerated after exiting the reactor.

288. The method of claim 282 wherein the essentially-inert particles are heated after exiting the reactor to produce essentially-inert heated particles.

289. The method of claim 282 wherein the essentially-inert heated particles are introduced into the reactor and exchange heat with the catalyst.

290. The method of claim 282 further comprising separating the catalyst and the carbon product from the essentially-inert particles.

291. The method of claim 290 wherein the separating is done by differential elutriation.

292. The method of claim 290 wherein the separating comprises a component selected from the group consisting of a cyclone, a classifier, a solid-gas separator, a disengaging section, a wet scrubber, a cyclone, an electrostatic precipitator, a filter and combinations thereof.

293. The method of claim 282 wherein the moving bed reactor is a counter-current moving bed reactor, wherein the counter-current moving bed reactor has a moving bed comprising the essentially-inert particles that move in a direction counter-current to flows of the catalyst and the gaseous stream comprising the carbon-containing feedstock.

294. The method of claim 282 wherein the moving bed reactor is a concurrent-flow moving bed reactor wherein the essentially-inert particles and the catalyst flow in the same direction.

295. The method of claim 294 wherein the gaseous stream comprising the carbon-containing feedstock, the essentially inert particles and the catalyst flow in the same direction.

296. The method of claim 294 wherein the gaseous stream comprising the carbon-containing feedstock flows in an opposite direction to movement of the essentially-inert particles and the catalyst.