71
Steam Gasification and Reforming Technologies
amounts of carbon monoxide reduces the hydrogen yield and it also requires complex
gas cleanup process. Overall, ethanol is still one of the best raw materials for steam
reforming to produce hydrogen.
An extensive number of studies to develop different types of catalysts for ethanol
steam reforming have been reported in the literature [109–116]. Mas et al. [109] used
Ni(III)–Al(III) lamellar double hydroxide as catalyst precursor. They developed a
Langmuir–Hinshelwood type of kinetic model for steam reforming of ethanol for
this catalyst. A general model was found to be valid for a wide range of water/ethanol
feed ratio and temperatures. Biswas and Kunzru [110] examined the effects of copper, cobalt, and calcium doping on Ni–CeO 2 –ZrO 2 catalysts for steam reforming
of ethanol. The data were obtained in the temperature range of 400°C–650°C. The
nickel loading was kept fixed at 30 wt%, whereas Cu and Co loading was varied from
2 to 10 wt% and Ca loading was varied from 5 to 15 wt%. For Cu- and Ca-doped catalysts, the activity increased significantly; however, Co-doped catalysts showed poor
activity. The catalyst activity was in the order: Ni > NiCu 5 > NiCa 15 > NiCo 5 . For
steam reforming reaction, the highest hydrogen yield was obtained on the undoped
catalyst at 600°C. With calcium doping, in the temperature range of 400°C–550°C,
higher hydrogen yield was obtained compared to those for undoped catalysts. Akdim
et al. [111] compared the steam reforming of non-noble metal (Ni–Cu) with noble
metals (Rh or Ir) supported over neutral SiO 2 , amphoteric Al 2 O 3 , and redox CeO 2 .
The data showed that for each domain of temperature, quite different mechanistic
routes were governing for the three tested systems. The data suggested some methods that improved the catalyst formula for the steam reforming of ethanol. Finally,
the effect of support on catalytic behavior of nickel catalysts in the steam reforming
of ethanol for hydrogen production was investigated by Fajardo et al. [112]. They
studied Al 2 O 3 -, MgO-, SiO 2 -, and ZnO-supported nickel catalysts and showed that
the catalyst behavior can be influenced by the experimental conditions and chemical
composition of the catalysts.
The steam reforming of ethanol by different types of Co catalysts was investigated
by Sekine et al. [113], Song et al. [115], and He et al. [116]. Sekine et al. [113] examined steam reforming of ethanol over Co/SrTiO 3 with an addition of another metal:
Pt, Pd, Rh, Cr, Cu, or Fe. Ethanol conversion and H 2 yield improved significantly by
adding Fe and Rh at 823 K; however, Rh addition promoted CH 4 formation. Within
Fe loading of 0.33–1.33 mol%, Fe addition increased the selectivity of steam reforming of ethanol. The addition of Fe on Co/SiO 2 catalyst was not very effective. High
activity of Fe/Co/SrTiO 3 catalyst came from interaction among Fe, Co, and SrTiO 3 .
Song et al. [115] showed that the use of novel synthesis methods such as solvothermal
decomposition, colloidal crystal templating, and reverse microemulsion to prepare
CeO 2 -supported Co catalysts gave better performance than the catalysts prepared
using conventional incipient wetness impregnation method for ethanol steam reforming. The improvement can be attributed to a better cobalt dispersion and a better
Co–CeO 2 interaction for the catalysts prepared using these novel methods. He et al.
[116] examined a series of Co–Ni catalysts prepared from HT-like materials by coprecipitation for steam reforming of ethanol. The results showed that the particle
size and reducibility of the Co–Ni catalysts are influenced by the degree of formation of HT-like structure and increasing Co content. All catalysts were active and