Steam reformation of n-hexane

Catalyst performance for steam reforming of n-hexane to produce CH4, CO, CO2, and H2 at 400° to 500°C was evaluated in a stainless steel reactor which has basically the same instrumentation used previously for oxidation catalyst studies (9, 12). The principal modifications consisted... 

The performance of several of the nickel and cobalt zeolite catalysts for steam reforming of n-hexane at 400°-500°C has been evaluated by short test runs with the reactor and the procedures described above (Table II). A Girdler reforming catalyst (G56) was tested under the same conditions as a comparative standard. All tests were conducted at a total pressure of 1 atm. Plateaus of sustained reforming activity were established within 1 hour. The cobalt catalysts lost essentially all reforming activity within 3 hours, presumably because of oxidation by steam. The space velocities reported are calculated in terms of theoretical hydrogen production based on the n-hexane injection rate and extent of conversion (Equation 2, Table II). The equation for the steam reforming of n-hexane with complete conversion to carbon dioxide is... 

Figure 6 Axial bed-tempcralure profiles and product gas composition comparison for steam reforming of n-hexane on the hybrid monolith and G-90C pellet bed. (From Ref. 8.)...

M. Flytzani-Stephanopoulos and G.E. Voecks, Autothermal Reforming of n-Tetradecane and Benzene Solutions of Naphthalene on Pellet Catalysts, and Steam Reforming of n-Hexane on Pellet and Monolithic Catalyst Beds, Final Report, DE-AI03-78ET-111326, pp. 74-119 (1980). 

Flytzani-Stephanopoulos, M. and Voeck, G.E. Autothermal reforming of n-tetradecane and benzene solutions of naphthalene on pellet catalysts, and steam reforming of n-hexane on Peppet and monolithic catalyst beds. U.S. DOE Report DE-AI03-78ET-11326, October 1980. 

Coke formation reactions reported above in VII may be more complex than realized previously. In very recent work on steam reforming of n-hexane, Bett, et al. (94) conclude that carbon formation may result from interaction of unreacted hexane and the products of secondary cracking reactions, or from unstable intermediates in the cracking process. A selection of other thoughts concerning the mechanism of coke formation in reforming on Ni would include the works of Whalley, et al. (95), Presland and Walker (96). and Renshaw, et al. (97). 

Wang and Gorte144 measured the differential rates of steam reforming of methane, ethane, n-butanc, n-hexane, 2-4-dimethylhexane, n-octane, cyclohexane,... 

Figure 2.12. Arrhenius plots for the steam reforming of methane, ethane, n-butane, /t-hexane, and benzene over Pd/Ce02 catalyst. Water partial pressure is lOOtorr. Adapted from Wang and Gorte.144...

Steam reforming was the primary reaction over these nickel catalysts. The presence of hydrocarbons (G2 to G5) which would indicate cracking reactions occurred to the extent of less than 10% in the reaction products. The presence of methane, which would indicate partial reforming, did not exceed 5% in the reaction products. There does not appear to be any significant difference in product selectivity for the n-hexane steam reforming reaction over nickel on the 2 quite different supports—zeolite vs. alumina. Carbonaceous residues accumulated in the case of all the nickel catalysts where reforming activity was sustained and the carbon deposition on the zeolite catalysts compared favorably with G56. 

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